Inligting

'n Vraag oor dicumarol

'n Vraag oor dicumarol



We are searching data for your request:

Forums and discussions:
Manuals and reference books:
Data from registers:
Wait the end of the search in all databases.
Upon completion, a link will appear to access the found materials.

Ek weet dat dicumarol in muwwe soetklawer ontdek is, aangesien dit bloeding by beeste veroorsaak het, maar as iemand trombo-emboliese afwykings gehad het wat onbeheerde trombose veroorsaak, sal dit goed wees om muf soetklawer te eet (in die geval van afwesigheid van enige manier van die moderne lewe), veral dat bevat dit ander mikroörganismes?


Bestudeer maklike vrae en antwoorde oor bloed

Bloed is 'n middel van stofvervoer deur die liggaam. Bloed versprei voedingstowwe, suurstof, hormone, teenliggaampies en selle wat in verdediging spesialiseer na weefsels en versamel afval soos stikstofafval en koolstofdioksied daaruit.

Die komponente van bloed

Meer bytgrootte V&As hieronder

2. Watter elemente bestaan ​​uit bloed?

Bloed word gemaak van 'n vloeistof en 'n sellulêre gedeelte. Die vloeistofdeel word plasma genoem en bevat verskeie stowwe, insluitend proteïene, lipiede, koolhidrate en minerale soute. Die sellulêre komponente van bloed staan ​​ook bekend as bloedliggaampies en dit sluit in eritrosiete (rooibloedselle), leukosiete en bloedplaatjies.

Kies enige vraag om dit op FB of Twitter te deel

Kies (of dubbelklik) net 'n vraag om te deel. Daag jou Facebook- en Twitter-vriende uit.

Hematopoïese, beenmurg en stamselle

3. Wat is hematopoiese?

Hematopoïese is die vorming van bloedselle en die ander elemente waaruit bloed bestaan.

4. Waar vind hematopoïese plaas?

Hematopoïese vind plaas in die beenmurg (hoofsaaklik binne plat bene), waar eritrosiete, leukosiete en bloedplaatjies gemaak word en in limfoïede weefsel, wat verantwoordelik is vir die rypwording van leukosiete en wat in die timus, milt en limfknope voorkom.

5. In watter bene kan beenmurg hoofsaaklik gevind word? Is beenmurg van beenweefsel gemaak?

Beenmurg kan hoofsaaklik gevind word in die interne holtes van plat bene, soos werwels, die ribbes, die skouerblaaie, die borsbeen en die heupe.

Beenmurg word nie van beenweefsel gemaak nie, hoewel dit net soos beenweefsel 'n bindweefsel is.

6. Wat is bloedstamselle?

Stamselle is ongedifferensieerde selle wat in staat is om te differensieer na ander tipes gespesialiseerde selle.

Die stamselle van die beenmurg produseer gedifferensieerde bloedselle. Afhangende van stimuli van spesifieke groeifaktore, word stamselle verander in rooibloedselle, leukosiete en megakariosiete (die selle wat bloedplaatjies vorm). Navorsing toon dat die stamselle van die beenmurg ook in spier-, senuwee- en lewerselle kan differensieer.

Rooibloedselle en hemoglobien

7. Wat is die ander name vir eritrosiete? Wat is die funksie van hierdie selle?

Eritrosiete staan ​​ook bekend as rooibloedselle (RBC's) of rooibloedselle. Rooibloedselle is verantwoordelik vir die vervoer van suurstof van die longe na weefsels.

8. Wat is die naam van die molekule in rooibloedselle wat suurstof vervoer?

Die respiratoriese pigment van rooibloedselle word hemoglobien genoem.

9. Wat is die molekulêre samestelling van hemoglobien? Hang die funksionaliteit van hemoglobien as 'n proteïen af ​​van die tersiêre of kwaternêre struktuur daarvan?

Hemoglobien is 'n molekule wat bestaan ​​uit vier polipeptiedkettings, elk gebind aan 'n ysterbevattende molekulêre groep wat 'n heemgroep genoem word. Daarom bevat die molekule vier polipeptiedkettings en vier heemgroepe.

As 'n proteïen wat uit polipeptiedkettings bestaan, hang die funksionaliteit van hemoglobien af ​​van die integriteit van sy kwaternêre struktuur.

10. Wat is gemiddeld die lewensduur van 'n rooibloedsel? Waar word hulle vernietig? Waarheen gaan heemgroepe na die vernietiging van hemoglobienmolekules?

Rooibloedselle leef gemiddeld vir ongeveer 120 dae. Die milt is die hooforgaan waar ou rooibloedselle vernietig word.

Tydens die vernietiging van rooibloedselle verander die heemgroepe in bilirubien en hierdie stof word dan deur die lewer gevang en later na die ingewande uitgeskei as 'n deel van gal.

11. Wat is die funksies van die milt? Waarom kan mense nog leef na 'n totale splenektomie (chirurgiese verwydering van die milt)?

Die milt het baie funksies: dit neem deel aan die vernietiging van ou rooibloedselle daarin gespesialiseerde leukosiete word volwasse dit help om die hematopoietiese weefsel van beenmurg te regenereer wanneer nodig en dit kan optree as 'n sponsagtige orgaan om bloed in sirkulasie te behou of vry te stel. .

Dit is nie onmoontlik om na 'n totale splenektomie te lewe nie, want geen van die funksies van die milt is beide lewensbelangrik en eksklusief vir hierdie orgaan nie.

Bloedarmoede verduidelik

12. Wat is bloedarmoede? Wat is die vier hooftipes anemie?

Bloedarmoede is 'n lae konsentrasie hemoglobien in die bloed.

Die vier hooftipes bloedarmoede is voedingstoftekortanemie, bloedarmoede wat veroorsaak word deur bloedverlies, hemolitiese anemie en aplastiese anemie.

Voedingstoftekortanemie word veroorsaak deur 'n dieettekort aan fundamentele voedingstowwe wat nodig is vir die produksie of funksionering van rooibloedselle, soos yster (ystertekortanemie), vitamien B12 en foliensuur.

Bloedarmoede wat deur bloedverlies veroorsaak word, kom voor in hemorragiese toestande of in siektes soos peptiese ulserasies en haakwurmsiekte.

Hemolitiese anemie word veroorsaak deur die oormatige vernietiging van rooibloedselle, byvoorbeeld in siektes soos malaria of in hipervolemiese toestande (oormatige water in bloed wat lisis van rooibloedselle veroorsaak).

Aplastiese anemie kom voor as gevolg van tekorte in hematopoïese en kom voor wanneer beenmurg beseer word deur kanker van ander weefsels (metastase), deur outo-immuun siektes, deur dwelmvergiftiging (soos sulfa-middels en antikonvulsante) of deur chemiese stowwe (soos benseen, insekdoders, verf). , onkruiddoders en oplosmiddels in die algemeen). Sommige genetiese siektes beïnvloed ook beenmurg, wat aplastiese anemie veroorsaak.

Witbloedselle

13. Wat is die verskil tussen wit en rooibloedselle? Wat is leukosiete?

Rooibloedselle word eritrosiete genoem en witbloedselle word leukosiete genoem.

Leukosiete is selle wat gespesialiseer is in die verdediging van die liggaam teen vreemde middels en is deel van die immuunstelsel.

14. Wat is die verskillende tipes leukosiete en hoe word hulle in granulosiete en agranulosiete geklassifiseer?

Die tipes leukosiete is limfosiete, monosiete, neutrofiele, eosinofiele en basofiele. Granulosiete is dié met 'n sitoplasma wat korrels bevat (wanneer dit onder elektronmikroskopie bekyk word): neutrofiele, eosinofiele en basofiele is granulosiete. Agranulosiete is die ander leukosiete: limfosiete en monosiete.

15. Wat is die generiese funksie van leukosiete? Wat is leukositose en leukopenie?

Die generiese funksie van leukosiete is om deel te neem aan die verdediging van die liggaam teen vreemde middels wat dit binnedring of binne die liggaam geproduseer word.

Leukositose en leukopenie is kliniese toestande waarin 'n bloedmonster 'n abnormale aantal leukosiete bevat. Wanneer die leukosiettelling in 'n bloedmonster bo die normale vlak vir die individu is, word dit leukositose genoem. Wanneer die leukosiettelling laer is as die verwagte normale vlak, word dit leukopenie genoem. Die vermenigvuldiging van hierdie verdedigingselle, leukositose, vind gewoonlik plaas wanneer die liggaam aan infeksies of kanker van hierdie selle ly. 'n Lae telling van hierdie verdedigingselle, of leukopenie, kom voor wanneer sommige siektes, soos VIGS, die selle aanval of wanneer immuunonderdrukkende middels gebruik word.

Oor die algemeen gebruik die liggaam leukositose as 'n verdedigingsreaksie wanneer dit aansteeklike of patogene middels in die gesig staar. Die kliniese toestand van leukositose is dus 'n teken van infeksie. Leukopenie vind plaas wanneer daar 'n tekort in die produksie is (byvoorbeeld in beenmurgsiektes) of oormatige vernietiging van leukosiete (byvoorbeeld in die geval van MIV-infeksie).

Bloedplaatjies en hemostase

16. Wat word die meganismes genoem om bloeding te bevat?

Die fisiologiese meganismes om bloeding te bevat (een daarvan is bloedstolling) word generies genoem hemostase, of hemostatiese prosesse.

17. Hoe word bloedplaatjies gevorm? Wat is die funksie van bloedplaatjies? Wat is die kliniese gevolge van die toestand bekend as trombositopenie?

Bloedplaatjies, ook bekend as trombosiete, is fragmente van groot beenmurgselle wat megakariosiete genoem word. Deur hul eienskappe van samevoeging en kleefvermoë is hulle direk betrokke by bloedstolling en stel stowwe vry wat ander hemostatiese prosesse aktiveer.

Trombositopenie is 'n kliniese toestand waarin die bloedplaatjietelling van 'n individu laer as normaal is. In hierdie situasie word die persoon vatbaar vir bloeding.

Die stollingskaskade

18. Hoe weet die liggaam dat die stollingsproses moet begin?

Wanneer weefselwond besering aan 'n bloedvat bevat, stel die plaatjies en endoteelselle van die wand van die beskadigde vaartuig stowwe (onderskeidelik bloedplaatjiefaktore en weefselfaktore) vry wat die stollingsproses veroorsaak.

19. Hoe kan die bloedstolling (stollings) proses beskryf word?

Bloedstolling behels 'n reeks chemiese reaksies waarvan die produkte ensieme is wat die daaropvolgende reaksies kataliseer (dit is hoekom stollingsreaksies kaskadereaksies genoem word). In die plasma verander tromboplastinogeen in tromboplastien, 'n reaksie wat veroorsaak word deur weefsel- en bloedplaatjiefaktore wat vrygestel word na 'n besering aan 'n bloedvat. Saam met kalsiumione kataliseer tromboplastien dan die transformasie van protrombien in trombien. Trombien kataliseer dan 'n reaksie wat fibrien uit fibrinogeen produseer. Fibrien, as 'n onoplosbare stof, vorm 'n netwerk wat rooibloedselle en bloedplaatjies vasvang en sodoende die bloedklont vorm en die bloeding bevat.

20. Wat is stollingsfaktore?

Stollingsfaktore is stowwe (ensieme, koënsieme, reagense) wat nodig is vir die stollingsproses om te gebeur. Benewens die snellerfaktore en reagense wat reeds beskryf is (weefsel- en bloedplaatjiefaktore, tromplastinogeen, protrombien, fibrinogeen, kalsiumione), neem ander stowwe deel aan die bloedstollingsproses as stollingsfaktore. Een hiervan is faktor VIII, waarvan die tekort hemofilie A veroorsaak, en 'n ander faktor IX, waarvan die tekort hemofilie B veroorsaak.

21. In watter orgaan word die meeste van die stollingsfaktore geproduseer? Wat is die rol van vitamien K in bloedstolling?

Die meeste stollingsfaktore word in die lewer geproduseer.

Vitamien K neem deel aan die aktivering van verskeie stollingsfaktore en is noodsaaklik vir die behoorlike funksionering van bloedstolling.

Hemofilie verduidelik

22. Wat is faktor VIII? Wat is die genetiese siekte waarin hierdie faktor afwesig is?

Faktor VIII het die funksie om faktor X te aktiveer, wat op sy beurt nodig is vir die transformasie van protrombien in trombien tydens die stollingskaskade. Hemofilie A is die X-gekoppelde genetiese siekte waarin die individu nie faktor VIII produseer nie en as gevolg daarvan meer vatbaar is vir ernstige bloeding.

23. Hoe word hemofilie behandel? Hoekom is hemofilie skaars by vroue?

Hemofilie word medies behandel met die toediening van faktor VIII, in die geval van hemofilie A, of van faktor IX, in die geval van hemofilie B, deur middel van bloed of vars bevrore plasma-oortappings.

Beide hemofilie A of B is X-gekoppelde resessiewe siektes. Vir 'n meisie om hemofiel te wees, is dit nodig dat albei haar X-chromosome aangetas word, terwyl seuns, wat net een X-chromosoom het, makliker aangetas word. ’n Meisie met net een aangetaste chromosoom vertoon nie die siekte nie, aangesien die normale geen van die onaangeraakte X-chromosoom die stollingsfaktor produseer.

24. Wat is die epidemiologiese assosiasie tussen hemofilie en MIV-infeksie?

Aangesien hemofiele pasiënte gereelde oortappings van stollingsfaktore (VIII of IX) benodig, is hulle meer vatbaar vir kontaminasie deur aansteeklike middels wat teenwoordig is in die bloed waaruit die oorgeplante elemente kom. In die verlede het bloedbanke gewoonlik nie MIV-opsporingstoetse uitgevoer nie en baie hemofiele pasiënte het met die virus besmet geraak.

Antistolling en fibrinolise

25. Wat is antikoagulante? Wat is die praktiese toepassings van antikoagulante, soos heparien, in Geneeskunde?

Antistolmiddels is stowwe wat stollingsreaksies blokkeer en dus die stollingsproses stop. Gewoonlik sirkuleer antikoagulante in die plasma, aangesien bloed onder normale toestande vloeibaar gehou moet word.

In Geneeskunde word antikoagulante soos heparien gebruik in operasies waarin weefselbeserings wat deur chirurgie veroorsaak word, ongewenste sistemiese bloedstolling kan veroorsaak. Hulle word ook gebruik om die vorming van trombose in die bloedvate van pasiënte te vermy wat 'n verhoogde risiko vir trombose het.

26. Wat is dikumarol? Wat is die rol van hierdie stof in die stollingsproses en wat is 'n paar voorbeelde van die toksisiteit daarvan?

Dicoumarol is 'n antistolmiddel. As gevolg van sy molekulêre struktuur kompeteer dikumarol met vitamien K om aan substrate te bind, wat die vorming van stollingsfaktore blokkeer en die produksie van protrombien onderbreek. Dicoumarol word in sommige ontbindende groente aangetref en kan ernstige interne bloeding veroorsaak wanneer daardie groente per ongeluk ingeneem word. Kumariniese antikoagulante kan nie tydens swangerskap toegedien word nie, aangesien hulle die plasentale versperring verbysteek en fetale bloeding kan veroorsaak.

27. Streptokinase is 'n stof wat gebruik word in die behandeling van akute miokardiale infarksie. Wat is die funksie van hierdie stof?

Stowwe bekend as fibrinolitika, soos streptokinase en urokinase, kan trombi vernietig (klonte wat in bloedvate, kapillêre of binne die kamers van die hart gevorm word) en word gebruik in die behandeling van obstruksies van die kransslagare of ander bloedvate.

Streptokinase vernietig die fibriennetwerk en los gevolglik die trombotiese klont op. Sy naam is afgelei van die bakterieë wat dit produseer, streptokokke.


Opstel-inhoud:

  1. Opstel oor die inleiding tot bloedstolling
  2. Opstel oor die metodes om bloedstolling te bepaal
  3. Opstel oor die belangrikheid van bloedstolling
  4. Opstel oor die meganisme van bloedstolling
  5. Opstel oor die faktore wat bloedstolling beïnvloed
  6. Opstel oor die siektes wat voorkom as gevolg van bloedstolling
  7. Opstel oor die natuurlike inhibeerders van bloedstolling
  8. Opstel oor die faktore wat bloedstolling voorkom en bespoedig

Opstel # 1. Inleiding tot bloedstolling:

Wanneer bloed gestort word, verloor dit binne 'n paar minute sy vloeibaarheid en sit in 'n halfvaste jellie. Hierdie verskynsel word bloedstolling of stolling genoem. By verdere aanhou trek die klont terug na 'n kleiner volume en druk 'n helder strooikleurige vloeistof uit, wat die serum genoem word. Serum sal nie meer stol nie.

Wanneer die proses van bloedstolling onder die ultra-mikroskoop bestudeer word, word gesien dat klein korrels aanvanklik verskyn, dikwels naby 'n klomp disintegrerende bloedplaatjies. Hierdie korrels sluit saam om naalde te vorm, wat weer met mekaar verenig om lang drade oor die hele bloedmassa te vorm. Hierdie drade kruis mekaar en vorm 'n soort netwerk, in die maas waarvan die rooi en wit selle verstrengel raak. Die klont trek geleidelik terug en serum skei uit.

Daar moet kennis geneem word dat bloedstolling die eienskap van plasma alleen is. Die rooi en wit selle neem nie daaraan deel nie. Hulle word net in die maas van die klont vasgevang en word daardeur verwyder. Dit is as gevolg van hierdie feit dat die stolsel 'n rooi kleur het, en die serum 'n helder nie-sellulêre vloeistof is. Bloedplaatjies neem deel aan die proses.

Normale stollingstyd:

Gemeet volgens die metode van Lee en White is dit 6 tot 17 minute in glasbuis en 19 tot 60 minute in gesilikoniseerde buis.

Opstel # 2. Metodes om bloedstolling te bepaal:

i. Kapillêre glasbuis metode:

Hierdie metode word gewoonlik as 'n bedkantprosedure aangeneem. Die vinger word geprik en die bloed word in 'n kapillêre glasbuis van ongeveer 15 cm (6 duim) lank laat vloei. 'n Klein bietjie van die glasbuis word elke vyftien sekondes versigtig afgebreek totdat 'n fyn draadjie gestolde bloed verskyn terwyl die buis gebreek word. Die tydperk tussen die voorkoms van bloed in die vinger en die vorming van hierdie draad word as die bloedstollingstyd geneem. Die gemiddelde tyd, volgens hierdie metode, is 3-4 minute.

ii. Wright’s koagulometer:

Die beginsel is dieselfde as hierbo. Bloed word toegelaat om in 'n dosyn kapillêre buise van gelyke kaliber te vloei. Die buise word aan beide kante verseël en in 'n waterbad van 37°C geplaas. Na 4 minute word die eerste buis (die buis wat eers met bloed gevul is) uit die waterbad gehaal, die punte word gebreek en die bloed binne-in word in water uitgestoot. Dieselfde prosedure word met al die ander buise met tussenposes van 30 sekondes herhaal. Wanneer die bloed wat uit 'n spesifieke buis verdryf word die vorm van 'n wurmagtige klont het, word die eindpunt bereik.

iii. Metode van Lee en White:

1 ml bloed word met 'n droë spuit uit 'n aar getrek en in twee skoon proefbuise, 8 mm in deursnee, geplaas. Die buise word toegemaak met 'n rubberprop. 5 minute na die onttrekking van die bloed op die manier wat beskryf is, word die eerste buis liggies 45 grade gekantel met een minuut tussenposes totdat dit 180 grade omgekeer kan word sonder dat bloed vloei.

Hierdie tyd word aangeteken en dieselfde prosedure word met die tweede buis herhaal. Aangesien hantering stolling bevoordeel, word die tyd vir die tweede buis geneem as die ware bloedstollingstyd aangesien dit minder as die eerste buis gekantel is.

Normale gemiddelde is 3,25 minute, die reeks is 2-5 minute. Dit word gewoonlik bepaal deur Duke’s metode. Die lobule van die oor word deurboor en die tyd word aangeteken. Die bloed wat uitvloei, word elke halfminuut met 'n stukkie filtreerpapier opgevee totdat bloeding ophou. Dit dui die eindpunt aan.

Protrombientyd (vinnig):

'n Geskatte protrombientyd is gewoonlik 11 tot 16 sekondes. Wanneer weefselekstrak (tromboplastien) en kalsiumchloried in 'n optimum hoeveelheid gemeng (toegevoeg) word by bloed met normale fibrinogeeninhoud, kan die enigste faktor wat 'n onvoldoende konsentrasie protrombien het, die stollingstyd verander.

As die protrombien verminder word, neem die bloedstollingstyd toe. Hierdie toets is 'n kwantitatiewe een vir protrombien in bloed gebaseer op die bloedstollingstyd van geoksaleerde bloedplasma in die teenwoordigheid van weefselekstrak (tromboplastien) en kalsiumchloried.

In elke laboratorium word gewoonlik 'n kromme van protrombienkonsentrasie in die bloed tot die protrombientyd geteken vir die evaluering van die protrombientyd. Die enigste voorsorgmaatreël is dat bloed wat van die pasiënt verwyder word onmiddellik geoksaleer word sodat geen van die protrombien in trombien omgeskakel kan word nie.

In 'n proefbuis word 0,2 ml kommersiële tromboplastien wat kalsium bevat by 37°C gehou. Na 30 sekondes word 0,1 ml plasma vinnig vanaf 'n pipet bygevoeg, en 'n stophorlosie word gelyktydig begin. Die buis word in die waterbad gehou en word voortdurend maar liggies vir 10 sekondes geskud. Dan in helder direkte beligting word die buis een keer per sekonde voortdurend van vertikale tot byna horisontale posisie gekantel totdat 'n jel verskyn.

Dit is die eindpunt. 'n Waarde van 11 tot 16 sekondes is bevredigend, maar die toets moet altyd in duplikaat uitgevoer word.

Opstel # 3. Belangrikheid van bloedstolling:

Die verskynsel van stolling is van enorme fisiologiese belang. Die doel daarvan is om verdere bloeding te stop. Wanneer bloeding voorkom, koaguleer die gestorte bloed en die bloedvate word deur die klont verstop.

Die terugtrekking van die klont druk die gebarste vate verder saam en sodoende word bloeding gestop.

Opstel # 4. Meganisme van bloedstolling:

Reeds in 1904 het Morawitz die basiese feite oor die meganisme van bloedstolling op die volgende manier beskryf. Wanneer bloed gestort word, disintegreer die bloedplaatjies (deur in kontak te kom met ruwe water-nat-tafeloppervlak), en maak tromboplastien vry.

Sekere hoeveelheid tromboplastien word ook afgelei van die beskadigde weefsels van die beseerde plek. Tromboplastien omskep protrombien in trombien met behulp van kalsiumione en trombien tree in wisselwerking -met fibrinogeen wat fibrien vorm.

Dit is die klont. Hierdie teorie kan in die volgende stappe opgesom word:

Protrombien + Kalsiumioon + Fibrinogeen → Nul

Na bloedvergieting:

1. Tromboplastien + Protrombien + Kalsiumioon → Trombien

2. Trombien + Fibrinogeen → Fibrien (klont).

Sedert 1940 het navorsingswerk aangedui dat die stollingsmeganisme 'n komplekse proses is. In 1954 is 'n Inter­nasionale Komitee gestig. Die komitee het van tyd tot tyd 'n internasionale nomenklatuurstelsel voorgestel met die verskyning van nuwe faktore.

Opstel # 5. Faktore wat bloedstolling beïnvloed:

Faktor I of Fibrinogeen:

Dit is globulien van aard, maar het 'n baie groter molekule as serumglobulien. Die molekulêre gewig is ongeveer 330 000. Dit word by ongeveer 56°C gestol en presipiteer deur een vyfde versadiging met ammoniumsulfaat en versadiging met NaCl. Dit word van ander plasmaproteïene onderskei deur sy eienskap van stolling, waartydens fibrinogeen in fibrien omgeskakel word.

Faktor II of Protrombiene:

Dit is proteïen van aard en teenwoordig in normale plasma. Dit het 'n molekulêre gewig van ongeveer 62 700. Dit is baie labiel in waterige oplossing en word geïnaktiveer deur sure by pH 4.8, deur alkali by pH 10.0 en deur hitte by 60°C maar is onbepaald stabiel wanneer dit uit die bevrore toestand gedroog word. In geoksaleerde plasma word twee vorme van protrombien gevind ‘A’ en ‘B’.

Die A’ vorm word vernietig deur suurstof en is hitte-labiel. Die ‘B’ vorm is verwyderbaar deur aluminiumhidroksied. In normale plasma bly die twee vorme verenig as kalsiumverbinding. Wanneer oksalaat bygevoeg word, word kalsium verwyder en die twee komponente word geskei.

Dit kan soos volg geïsoleer word:

As die pH van plasma op 5,3 aangepas word, word beide protrombien en globulien neerslag. Protrombien word opgelos deur die presipitaat met verdunde kalsiumbikarbonaat te behandel. Na filtrasie word die pH van die filtraat weer na 5.3 aangepas wanneer protrombien uitskei. In hierdie vorm is dit 'n wit poeier, onoplosbaar in water en bly gekombineer met 'n proteïen. 100 ml plasma bevat 40 mgm van hierdie stof.

Die protrombienaktiwiteit van bloed word gemeet aan die stollingstyd van herverkalkte geoksaleerde plasma, waarby weefselemulsie gevoeg is. In menslike onderwerp is die gemiddelde ‘protrombientyd’ 12 sekondes. Protrombientyd sal langer wees in 'n tekort aan faktor V of faktor VII of Stuart faktor. Protrombien word in die lewer vervaardig. Vitamien K is noodsaaklik vir die vorming van protrombien. Tydens stolling word protrombien in trombien omgeskakel.

Faktor III of tromboplastien:

Dit is afgelei van twee bronne:

1. Intrinsiek in die plasma:

Intrinsieke tromboplastien word in die plasma gevorm as gevolg van interaksie tussen verskillende plasmafaktore, bv. Hageman faktor of faktor XII, PTA of faktor XI, Kersfees faktor of faktor IX, antihemofiele globulien of faktor VIII, kalsiumione, faktor V en faktor X.

Protrombien word omgeskakel na trombien met behulp van intrinsieke tromboplastien in teenwoordigheid van kalsiumione. Daar moet kennis geneem word dat bloed wat normaalweg deur die bloedsomloopstelsel vloei nie sal stol nie. Maar as die oppervlak van die bloedvat weens enige rede grof word, sal bloed stol selfs sonder die byvoeging van weefselekstrak (ekstrinsieke tromboplastien).

2. Ekstrinsieke of Weefseltromboplastien:

Dit word gevorm uit verskillende weefsels, bv. ekstrakte van brein, longe, ens., as gevolg van besering. So lank was dit bekend dat protrombien in trombien omgeskakel is met behulp van kal&siumione en tromboplastien wat uit beskadigde weefsels vrygestel is. Maar onlangs is gevind dat verskeie plasmafaktore, bv. faktor VII of prokonvertien, benodig word vir sulke omskakeling en die proses word ekstrinsieke tromboplastienvorming genoem.

Faktor IV of Kalsium:

Ioniese kalsium help baie met bloedstolling deur op te tree as 'n kofaktor in die bloedstollingsproses. Dit is noodsaaklik vir die vorming van beide intrinsieke en ekstrinsieke tromboplastiene en ook vir die omskakeling van protrombien in trombien.

Faktor V of Labiele Faktorversneller Globulien of Proaccelerin:

Hierdie faktor is nodig vir die volledige omskakeling van protrombien in trombien deur die ekstrinsieke of intrinsieke tromboplastien. Dit is 'n proteïen, hitte-labiel en word binne 'n halfuur by 56°C geaktiveer of deur die pH tot 10,5 te verhoog. Dit is teenwoordig in plasma, maar word opgebruik tydens stolling.

Faktor VI of Accelerin:

Hierdie faktor is 'n hipotetiese aktiveringsproduk van proaccelerin (faktor V).

Faktor VII of Stabiele Faktor of Proconvertin:

Hierdie faktor is teenwoordig in plasma en word nie tydens stolling opgebruik nie. Dit is hittebestendig en kan temperature tot 56°C weerstaan. Dit is 'n proteïen en bly geassosieer met protrombien. Dit versnel ekstrinsieke of weefseltromboplas- en sjitienvorming, wat geaktiveer word deur ekstrak wat uit beskadigde weefsel vrygestel word. Die vorming daarvan word vertraag na toediening van Dicoumarin en in 'n tekort aan vitamien K. Tydens bloedstolling word prokonvertien verander in omskakeling.

Faktor VIII of antihemofiele faktor (AHF) of antihemofiele globulien (AHG) of plaatjie kofaktor I:

Hierdie faktor help met die vorming van intrinsieke tromboplastien en intrinsieke protrombienomskakeling. Dit is aanhoudend in die plasma en verdwyn wanneer die bloed stol. Dit is proteïen van aard en bly in noue assosiasie met fibrinogeen. Hierdie faktor is antihemofiel. In Hemofilie (bloeding se siekte) is die defek nie in die bloedplaatjies nie, maar dit is te wyte aan die afwesigheid van hierdie faktor wat help met die afbreek van bloedplaatjies en die vrystelling van bloedplaatjie kofaktor I of tromboplastien faktor.

Die tekort aan AHG wat lei tot klassieke hemofilie by die mannetjie word oorgedra as 'n geslagsgekoppelde resessiewe eienskap. Die liggaam slaag nie daarin om hierdie noodsaaklike globulien te sintetiseer nie as gevolg van die afwesigheid van die spesifieke ensiem wat deur die mutante geen beheer word. Dit word op bariumsulfaat geadsorbeer en het 'n molekulêre gewig groter as 200 000.

Faktor IX of Kersfeesfaktor of Plasma tromboplastienkomponent (PTC) of plaatjie-kofaktor II:

Hierdie faktor is nodig vir intrinsieke tromboplastienvorming. Afwesigheid van hierdie faktor lei tot 'n siektestimulerende hemofilie bekend as hemofilie C en word as 'n geslagsgekoppelde resessief by die man oorgedra. Dit word deur aluminiumhidroksied geadsorbeer, is labiel vir hitte, maar is relatief stabiel tydens berging. Dit word neergeslaan deur 59 persent ammoniumsulfaat. Hierdie tipe siekte is die eerste keer gevind in 'n pasiënt genaamd Kersfees en vandaar die naam Kersfeesfaktor. Hierdie faktor word nie tydens stolling opgebruik nie.

Faktor X of Stuart Factor:

In 1959 is die internasionale nomenklatuur aan hierdie faktor gegee. Chemies het dit baie van die eienskappe soortgelyk aan dié van faktor VII. Die sintese daarvan word ook vertraag na toediening van Dicoumarin. Afwesigheid van hierdie faktor lei tot ligte hemorragiese diatese. Dit is stabiel in kamertemperatuur, maar vernietig vinnig by 56°C in serum.

Faktor XI of Plasma Tromboplastien Antesedent (PTA):

Dit word geaktiveer deur aktiewe Hageman-faktor, en lei uiteindelik tot die vorming van trombien. Tekort hieraan veroorsaak ligte bloedingneigings van hemofiloïed D tipe en word as 'n geslagsgekoppelde dominant na beide geslagte oorgedra.

Faktor XII of Hageman of Oppervlaktefaktor:

Dit is proteïen van aard. Onaktiewe vorm word geaktiveer op oppervlakkontak. Dit aktiveer op sy beurt die proteïenverdelende ensiem kallikreïen om plasmakiniene te produseer. Die gevolglike effekte is verhoogde vaskulêre deurlaatbaarheid en dilatasie van bloedvate.

Faktor XIII of Fibrien-stabiliserende of Laki-Lorand faktor (LLF):

Die aktiewe vorm saam met Ca++ skakel sagte fibrienklont om na 'n soliede, veselagtige een. Die werking daarvan verminder ook die oplosbaarheid van die klont in ureumsol. Persone met aangebore misvorming van LLF ly aan swak wondgenesing.

Rol van trombien:

Trombien is 'n homogene glikopro en sjietïen met molekulêre gewig 40 000 wat as 'n proteïenase optree. Dit outokataliseer sy eie vir&shimasie deur plasma Ac-globu­lin om te skakel in die aktiewe serum Ac-globulien en deur bloedplaatjies te labiliseer om tromboplastiengenerering te versnel en vasokonstriktors vry te stel. Dit verdeel slegs vier pep­tide-bindings in die omskakeling van fibrino­gen na fibrien en dit is almal bindings tussen arginien- en glisienreste.

Rol van fosfolipied:

Fosfolipiedkefalien (kefalien) help met die vorming van protrombinase. In die intrinsieke stelsel is dit in die plaatjie faktor 3 en in die ekstrinsieke een in weefsel tromboplastien.

Rol van Proteïen:

Bloedstollingsfaktore, van V tot XII, is plasmaproteïene meestal β-globuliene. 'n Paar van hulle is egter óf α-globulien óf ϒ-globulien.

Die behoeftes vir bydrae van baie stollingsfaktore is betrokke by die bloedstollingsproses. Maar die plasma proteïen stollingsfaktore wissel gewoonlik in pare. As gevolg van hierdie interaksie word elkeen van die stollingsfaktore weer van 'n onaktiewe vorm na 'n aktiewe een omgeskakel.

Aangesien al die stollingsfaktore nie veronderstel is om ensiemaksies te besit nie, word hierdie omskakeling van ensieme van 'n onaktiewe vorm na 'n aktiewe een tog in die volgorde van werking van stollingsfaktore geïnisieer. Die proses van intrinsieke en ekstrinsieke sisteme is skematies in Fig. 4.3 getoon.

Davie en Ratnoff (1965) het voorgestel wat 'n ‘watervalvolgordehipotese’ genoem is om die opeenvolging van gebeure wat in die bloedstolling plaasvind, te verduidelik. Elke proteïenkoagulasiefaktor bestaan ​​in die plasma in 'n onaktiewe (pro-ensiem) vorm en word opeenvolgend geaktiveer totdat uiteindelik trombien gevorm word wat dan fibrinogeen in fibrien omskakel.

Macfarlane het 'n skema van bloedstolling voorgestel wat 'n ensiemkaskade genoem word wat baie soortgelyk is aan die ‘waterfall’-skema (Fig. 4.4) van Davie en Ratnoff.

Klont terugtrekking:

Gewoonlik trek bloedklont terug tot ongeveer die helfte van sy aanvanklike volume binne 20 tot 24 uur. Wanneer bloed gestort word, vorm fibriene 'n netwerkagtige struktuur. Die bloedplaatjies kleef aan hierdie fibriennetwerke en vorm knope. Die fibrienraamwerk word dan gedraai en verkort, en klontintrekking vind plaas.

Opstel # 6. Siektes wat voorkom as gevolg van gebreke in bloedstolling:

Gebrek aan fibrinogeen of faktor I:

Afibrinogenemie of fibrinogeenopenie is 'n seldsame aangebore siekte as gevolg van 'n gebrek aan fibrinogeen. Soms word dit tydens abnormale swangerskap gevind.

As gevolg van vermindering van protrombien of faktor II:

Vitamien K help met die vorming van protrombien in die lewer. Vitamien K is 'n naftokinoonderivaat. Dit word uit die dunderm geabsorbeer in die teenwoordigheid van galsoute. In die lewer help dit met die sintese van protrombien en faktor VII of stabiele faktor of prokonvertien.

In die lewersiekte, bv. Sirrose van die lewer, kwaadaardige siekte van die lewer, ens., is daar 'n afname in sintese van protrombien in die lewer. By Obstruktiewe geelsug as gevolg van afwesigheid van galsoute, word vitamien K nie geabsorbeer nie. As gevolg van 'n gebrek aan vitamien K, word sintese van protrombien en faktor VII verminder. Protrombientyd word verleng en bloeding kom dikwels voor.

As gevolg van 'n gebrek aan AHG of Faktor VIII-hemofilie:

Dit is 'n siekte wat by mans voorkom, maar deur wyfies oorgedra word. Die bloedstollingstyd is abnormaal verleng. Daar is 'n neiging om ernstig te bloei na onbenullige beserings. Die knie- of elmbooggewrig kan met bloed uitgerek word. Die bloedplaatjietelling bly normaal. Daar is 'n gebrek aan faktor VIII of antihemofiele globulien (AHG). Blood transfusion temporarily supplies AHG and stops bleeding.

Sometimes it has been observed that if bloods taken from two subjects are mixed together, coagulation time is normal although the blood coagulation time of each individual subject has got prolonged blood coagulation time. From this it has been assumed that there are two types of haemophilic subjects, one lacking in AHG and another lacking factor IX or Christmas factor or PTC.

Due to Diminution of Factors V, VII and IX-Psedohaemophilia:

In this disease there is congenital deficiency of factors V, VII and IX. The haemorrhagic condition stimulates haemophilia.

Essay # 7. Natural Inhibitors of Blood Coagulation:

To maintain blood in a fluid state in the normal condition, retarding influences coexist with positive coagula­tion-inducing -factors in the circulating blood.

Some of the ingrained safeguards against intravascular clotting are:

(a) The relative slowness of thrombin production,

(b) The unbroken continuity of the vascular endothelium and

(c) Removal of clotting intermediates by the R. E. cells. Besides these, other definite inhibitors of coagula­tion are present.

Antithrombin activities remove thrombin from blood. Antithrombin I is the thrombin-adsorbing effect of fibrin but whether it plays a role in normal blood coagulation is unknown. Antithrombin II is a factor which acts jointly with heparin. Antithrombin III is the so-called physiological antithrombin because it is present naturally and inactivates thrombin progressively. Heparin is described separately below. Antithromboplastins are present in normal blood, and one or more circulating antithromboplastins are claimed to be present.

Intravascular Clotting or Thrombosis:

It is a clot formed inside the blood vessels. Thrombus is formed due to slowing of circulation and damage of the vascular endothelium. Atheromatous patches occur in blood vessels and the vascular endothelium is damaged in some abnormal conditions. Masses of platelets are deposited in the damaged endothelium. Filaments of fibrin form also a network in this region. The platelets liberate thromboplastin.

The fibrin, entangled in the lamellae of platelets, forms the thrombus or clot. Intravascular thrombosis sometimes occurs in coronary and cerebral vessels which are called coronary thrombosis and cerebral thrombosis respectively. After surgical operations, etc., thrombosis may occur in big veins.

At first it was isolated from liver by McLean in Howell’s laboratory, hence the name. Subsequently, it has been extracted from many tissues in the body. It is anticoagulant, in vivo and in vitro. One unit of heparin is defined as the quantity of material which will prevent the clotting of 1ml of cat’s blood for 24 hours when kept in cold. Chemically it is mucoitin polysulphuric acid.

Mucoitin is a polysaccharide, composed of glucosamine, glucuronic acid and esterified sulphuric acid forming an ester with molecular weight of about 17,000. It has been shown that any substance with a high molecular weight, and being composed of polysaccharides and several SO4 groups, can act as an anticoagulant. Hirudin, found in cervical glands of the common medicinal leech (Hirudo), is a compound of this nature. Heparin is normally secreted by the mast cells.

These cells are found in blood to about 1%. They remain scattered throughout the reticulo-endothelial system and found abundantly along the course of many blood vessels, such as those of liver. Sometimes they replace the intima of the blood vessels. These cells are found to contain granules which are supposed to be the precursors of heparin.

It is doubtful whether heparin is present in normal blood in any appreciable amount and as such it probably takes no part in preventing intravascular clotting normally. Heparin helps to maintain the normal fluidity of the blood within the vascular bed. It inhibits the transformation of prothrombin to thrombin when accompanied by a plasma cofactor albumin X and neutralises the action of thrombin on fibrinogen.

iii. Fibrinolise:

Clotted blood if kept sterile remains intact for several weeks. But if it is not kept sterile the clot breaks up. This fibrin breakdown in the clot is known as fibrinolysis and is brought about by a proteolytic enzyme in the plasma known as plasmin or fibrinolysin.

The precursor of the enzyme plasminogen (also known as profibrinolysin) is activated to plasmin by activators present in tissues, serum, urine and some bacteria. Normally fibrinolysis is prevented by the presence of another substance in the blood known as antiplasmin which remains attached to the plasma albumin.

Essay # 8. Factors Preventing and Hastening Blood Coagulation:

i. By lowering temperature, blood coagulation can be prevented.

ii. By avoiding contact with water-wettable surface and injured tissues. This prevents thrombokinase action. When blood is collected in a tube coated with paraffin, the surface not being water-wettable, the platelets will not break down and coagulation will not take place.

iii. Removal of calcium ions:

This is the commonest practice in clinical laboratories. This is done by adding citrates or oxalates of Na or K. Sodium fluoride (0.3% solution) is also used,

(b) By For­mation of a Complex Compound:

The substances used are di- and trisodium citrate and ethylene diamine tetra acetate (EDTA).

iv. Precipitation of Fibrinogen:

By adding various salt solutions in adequate amounts. When blood is mixed with one quarter of its volume of magnesium sulphate or with an equal volume of half saturated sodium sulphate solution, clotting is prevented.

v. By the Addition of Substances of Biological Origin:

Simple proteins found in some fish.

When it is injected into the veins, the coagulability of blood is reduced. [But peptone does not prevent the blood coagulation of a sample of blood in vitro]. Extracts of cray fish and nussels act in somewhat similar manner. They act by increasing secretion of heparin by the mast cells.

Mucoitin-polysulphuric acid produced by mast cells.

Hirudin (Leech extract) and the venom of certain snake. Heparin, hirudin and venom inhibit blood coagulation by inhibiting activation of prothrombin and thrombin fibrinogen reaction.

Same as heparin and hirudin.

f. Dicoitmarin or Dicoumarol:

It is chemically related to the naphthoquinone derivative. It is antagonist to vitamin K. It inhibits the synthesis of prothrombin in the liver by preventing the action of vitamin K. Dicoumarol lowers the plasma prothrombin level and depresses the activity of factor VII.

Action similar to that of dicoumarol. Its action is quick and depresses the activity of factor VII more than prothrombin.

vi. By adding azo dyes and synthetic products:

Chicago blue, trypan red, trypan blue act as anticoagulants both in vivo and in vitro.

Factors Hastening Blood Coagulation:

ii. Contact with water-wet table surface and contact with rough surface.

iii. Additions of foreign bodies into, a sample of blood (vide ‘Defibrinated blood’).

v. Addition of thromboplastin.

vi. Vitamin K injection or oral administration in high doses increases the prothrombin content of blood and increases the coagulability.

vii. Addition of calcium chloride, both in vivo and in vitro.

viii. Adrenaline injection produces constriction of blood vessels and helps in haemostatis mechanism.


1. Historical Review of Vitamin K:

Dam discovered this vitamin after studying haemorrhagic disease in chickens between the years 1930 and 1933.

2. Chemical Structure of Vitamin K:

It is a naphthoquinone derivative.

It is reported that more than one member of the K family, such as K1 K2 etc., are synthesised by green plants and bacteria. The artificially synthetic product (menadione), 2-methyl-1, 4- naphthoquinone (K3) without any side chain is 3 times more potent than the natural variety.

Two naturally-occurring vitamins K are vitamin K1 (phylloquinone, phytonadione) having a phytyl chain attached at position 3 of menadione nucleus, and vitamin K2 (flavinoquinone, farnoquinone) having a difarnesyl chain attached at position 3. Activity is apparently related to the presence of methyl group at 2 positions in the quinonoid ring. Synthetic vitamin K is called vitamin K3 (commercially menadione).

3. Properties of Vitamin K:

It is fat-soluble, heat stable, and can stand cooking. Vitamin K1 is yellow viscid oil, but vitamin K2 is a yellow, crystalline solid. The K vitamins are readily destroyed by light, alkali and alcohol.

4. Distribution of Vitamin K:

Vegetable sources are rich, such as cabbage, spin­ach, alfalfa, tomato, soya-bean, etc. It is absorbed from the in­testine with the help of bile salts. Most putrefied animals and plants contain considerable amount of vitamin K. It has also been produced synthetically.

Under normal circumstances, adequate amounts are synthesised by normal intestinal bacteria. Excessive amount of vitamin A administra­tion in certain species produces interference with bacterial synthesis of vitamin K in the intestine producing prothrombinaemia and haemorrhagic manifestations.

5. Functions of Vitamin K:

It helps to maintain the formation of normal prothrombin and factor VII in the blood and thus takes part in normal coagulation. It has been postulated that vitamin K acts as the prosthetic group to an apoenzyme to produce a holoenzyme which is involved in the clotting reactions. Prothrombin and factor VII are formed in the liver.

The principal overall effect of vitamin K is to shorten the prothrombin time. It is also postulated that vitamin K1 is an essential component of phosphorylation in both the processes of photosynthesis in green plants and animal tissues, as a cofactor necessary in oxidative phosphorylation. Loss of activity of vitamin K by ultra-violet radiation impairs oxidative phosphorylation in the mitochondria.

Bile salts are necessary for the absorption of vitamin K. In jaundice and in certain diseases of liver, when the bile secretion is defective, vitamin K fails to be absorbed resulting haemorrhages. Hepatic disease also produces hypoprothrombinaemia which is corrected by vitamin K administration. The haemorrhagic disease in the new-born is believed to be due to lack of vitamin K, since vitamin K deficiency in the new-born is due to absence of bacteria in their gut. An important therapeutic use of vitamin K is as an antidote to the anticoagu­lant drugs such as dicumarol.

6. Deficiency of Vitamin K:

Defective blood coagulation and haemorrhages.

7. Daily Requirement of Vitamin K:

Normal mixed diet supplies this vitamin in adequate amount. In the treatment of haemorrhagic diseases pro­duced as a result of vitamin K deficiency, 5 mgm is given either orally or by injection. It is believed that in adults, quite a good amount of vitamin K is synthesised by the bacteria in the gut.


BLOOD CLOTTING (HAEMOSTASIS)

The clot or coagulam is a dark -reddish-brown ‘scum’ formed mainly by a network of threads in which dead or damaged blood elements are trapped.

  • It is the property of plasma.
  • Normal blood clotting time is 3−10 min.
  • The clot inside the blood vessels is called a thrombus. A moving thrombus is called embolus.
  • In haemophilia (a sex-linked disease) the blood clotting is delayed.
  • According to Macferlane hypothesis, there are 13−factors responsible for blood clotting (or coagulation). The 4−factors are primary and 9−factors are accessory for this process.
  1. Fibrinogeen
  2. Protrombien
  3. Thromboplastin (Thrombokinase)
  4. Calcium ions

Accessory factors

(V) Labile factor (Proaccelerin) − It helps incomplete conversion of prothrombin into thrombin.

(VI) No separate entity, hence No specific name (existence doubtful).

(VII) Stable factor (Proconvertin) − It accelerates the formation of active
thromboplastin.

(VIII) Anti−haemophilic globulin (AHG)− The absence of this factor delays blood clotting causing Haemophilia−A. This type of haemophilia is most common (80%).

(IX) Plasma thromboplastin co−factor (PTC)− The deficiency of this factor causes Haemophilia−B. Approximately 20% of haemophilic patients have this type of haemophilia. The IX factor is also known as Christmas factor and Haemophilia
B is known as ‘Christmas disease’.

(X) Stuart Prower factor− It helps in the conversion of prothrombin into thrombin.

(XI) Plasma thromboplastin antecedent (PTA)− It activates the inactive christmas factor. The deficiency of this causes a rare type of bleeder-disease, called
Haemophilia -C.

(XII) Hageman’s factor or Glass factor − It converts inactive PTA into active form. It also dilates blood vessels for increasing their permeability.

(XIII) Fibrin stabilizing factor− It causes polymerization of soluble fibrin into insoluble fibrin and also inhibits depolymerization.


KORREKTE ANTWOORDE

The p53 protein is a transcription factor that is able to suppress malignant transformation of cells by several mechanisms. It induces 1) proteins involved in DNA repair to eliminate DNA damage 2) cyclin-dependent kinase (Cdk) inhibitors to evoke quiescence (Go phase) and 3) pro-apoptotic proteins to kill cells with unrepairable DNA damage (MCQ1: B). The actin gene is not among those genes regulated by p53 (compare samples 2 to 5 in Fig. 1 MCQ2: B). The E6 oncoprotein is able to down-regulate p53 (compare samples 2 and 4 in Fig. 1), and this anti-apoptotic effect contributes to the oncogenic action of papillomaviruses (MCQ3: B). NQ01 prevents the effect of E6 (compare samples 3, 4, and 5 in Fig. 1), but possible complex formation between these two proteins was not analyzed in this experiment (MCQ4: C).

γ-Irradiation causes DNA damage and thereby increases the level of p53 in p53-positive cells (compare samples 1 and 4 in Fig. 2). The effect of dicoumarol and radicicol indicates that both NQ01 and Hsp90 is involved in the mediation of this effect (compare samples 4, 5, and 6 in Fig. 2). Both proteins are, thus, involved in DNA-damage-stimulated signaling processes leading to p53 induction (MCQ5: D). DNA repair (MCQ6: D) and inhibition of the cell cycle by blocking the phosphorylation of retinoblastoma protein by cyclin-dependent kinases (MCQ7: D, MCQ8: D, MCQ9: D). These experiments suggest that the inhibition of Hsp90 is unlikely to stop malignant cell proliferation in p53-positive myeloid leukemia patients (MCQ10: E).

Western blot analysis of human colon carcinoma cells transfected with p53, NQO1, and E6 cDNAs (for details see the text).

The effect of γ-irradiation, dicoumarol, and radicicol treatment on myeloid leukemia cells (details in the text).


Note the following:
(a) Vel (b) Fagosiete
(c) B-cells (d) Inflammasie
(e) Teenliggaampies (f) T-cells
(g) Koors (h) Antimicrobial proteins
(i). NK-cells (j) Secretions
Identify the factors involved in 2nd line of defense.

Assertion: Cancer cells are virtually immortal until the body in which they resides dies.

Rede: Cancer is caused by damage to genes regulating the cell division cycle.


Materiale En Metodes

Sel Kultuur

Rat basophilic leukemia (RBL)-2H3 cells were grown in DME supplemented with 16% FCS and 1 mM l -glutamine. CHO cells were cultured in DME supplemented with 10% FCS.

Antibodies and Other Reagents

NAD + , NADP + , NADH, BFA, and GAPDH from skeletal rabbit muscles were obtained from Sigma Chemical Co. (St. Louis, MO). Tissue culture materials were from GIBCO BRL (Grand Island, NY) and Seromed (Berlin, Germany). GTP and ATP were from Boehringer Mannheim (Mannheim, Germany). Rabbit anti–α-mannosidase II (Man II) antibody was provided by K. Moremen (University of Georgia, Athens, GA), and a rabbit anti–β-COP antibody by J. Donaldson and J. Lippincott-Schwartz (National Institutes of Health, Bethesda, MD). All other chemicals were obtained from commercial sources at the highest available purity. BFA was stored at −20°C in stock solutions in DMSO. Dicumarol was prepared before use as an aqueous solution.

Cell Permeabilization

RBL (grown in glass chamber slides) were placed on ice and immediately washed with the permeabilization buffer (PB: 25 mM Hepes-Koh, pH 6.95, 125 mM KOAc, 2.5 mM Mg[OAc]2, 10 mM glucose, 1 mM DTT, 1 mM EGTA, and 0.5 μM taxol). Cells were then incubated with 3 U/ml of streptolycin O (SLO) (Biomerieux, Marcy l'Etoile, France), previously activated for 5 min at room temperature in PB for 8 min on ice. Unbound SLO was removed and cell monolayer was washed with cold PB, and then treated with permeabilization buffer supplemented with 1 mg/ml rat brain cytosol, 1 mM ATP, 250 μM UTP, 2 mM creatine phosphate, 7.3 U/ml creatine phosphokinase at 37°C for between 20-30 min (in the presence of the indicated treatments). To check the extent of permeabilization, cells were stained with Trypan blue (and propidium iodide) and the leakage of the cytosolic enzyme lactic dehydrogenase was measured. With the adopted schedule of SLO treatment, 95% of cells were stained with Trypan blue or propidium iodide and >80% of the lactic dehydrogenase activity was recovered in the supernatant of the permeabilized cell monolayer. Rat brain cytosol was prepared according to Malhotra et al. (1989).

BFA-dependent ADP-Ribosylation

ADP-Ribosylation in Permeabilized Cells.

RBL cells were plated in 24-well plates and used after 24 h at 90% confluency (300,000 cells/well per 250 μl). They were permeabilized as described above and then exposed for 20 or 60 min to PB containing 500 μM tymidine, 30 μM 32 P-NAD + (3 μCi/sample) and, where specified, BFA. At the end of the incubations the supernatant and the cell proteins were precipitated with 10% TCA, dissolved in sample buffer, and separated on SDS-PAGE. The radioactivity bound to BARS-50 and GAPDH was evaluated by fluorography.

ADP-Ribosylation of Cytosol.

Cytosol and membranes were prepared from rat brain as described (De Matteis et al., 1994). Cytosol (10 mg/ml) and salt-washed membranes (2 mg/ml) were incubated in the presence or absence of 200 μM NAD + or 100 μM BFA or both for 60 min at 37°C. Under these experimental conditions the ADP-ribosylation of BARS-50 (evaluated in parallel experiments run in the presence of 32 P-NAD + ) was maximal (>90%), whereas that of GAPDH was only partial (3–4%). No other proteins were detectably ADP-ribosylated by BFA (see Fig. 3). At the end of the incubation the samples were centrifuged at 100,000 g for 60 min and then the supernatants (cytosol) were dialyzed for 16 h at 4°C and used in immunofluorescence experiments in permeabilized cells as described below.

Immunofluorescence and Lectin Staining

Intact or permeabilized RBL cells were fixed in 4% paraformaldehyde in PBS at room temperature for 10 min, quenched in 10 mM NH4Cl for 10 min, washed in PBS, and permeabilized with 0.05% saponin, 0.2% BSA in PBS for 30 min at room temperature. The cells were stained with FITC-conjugated helix pomatia lectin (100 μg/ml in PBS containing 0.2% BSA) for 45 min or incubated with primary antibody for 1 h at room temperature, washed thoroughly with PBS, and incubated with specific FITC-, TRITC-, or Cy3-conjugated secondary antibody for 30 min at room temperature. After thorough washing, slides were mounted in Mowiol 4-88 (Calbiochem-Novabiochem, La Jolla, CA) and examined using a microscope equipped with a Plan-Neofluar 40× objective (Axiophot Carl Zeiss, Thornwood, NY). RBL or CHO cells grown in glass chamber slides (Nunc, Roskilde, Denmark intact or permeabilized as described above), were fixed in 4% paraformaldehyde in PBS (pH 7.4) at room temperature for 10 min, quenced in 10 mM NH4Cl for 10 min and then washed in PBS and permeabilized with 0.05% saponin, 0.2% BSA in PBS for 30 min at room temperature. Cells were stained with FITC-conjugated helix pomatia lectin (100 μg/ml in PBS containing 0.2% BSA) for 45 min or incubated with primary antibody for 1 h at room temperature, washed thoroughly with PBS and incubated with specific FITC-, TRITC-, or Cy3-conjuagted secondary antibody for 30 min at room temperative as described earlier (Buccione et al., 1996).

Electron Microscopy

Cells were fixed with 2% glutaraldehyde in PBS (pH 7.4), postfixed with reduced osmium (1% of OsO4 and 1.5% of potassium ferrocianide in 0.1 M cacodilate buffer, pH 7.4), and embedded in Epon 812 as described earlier (Buccione et al., 1996).

Preparation of BARS-50–enriched Cytosolic Fractions

Rat brain cytosol (Malhotra et al., 1989) was precipitated with 35% saturated (NH4)2SO4. The precipitate was dissolved in 25 mM Hepes, pH 8.0, containing 5% glycerol, 0.5 M (NH4)2SO4 and 1 mM DTT (buffer A) and applied to a phenyl sepharose HP column (Pharmacia Biotech, Piscataway, NJ) equilibrated with buffer A. Proteins were eluted with a linear gradient of buffer A minus (NH4)2SO4. The fractions containing BARS-50 were identified by the BFA-dependent ADP-ribosylation assay (De Matteis et al., 1994). These fractions (containing a 45-fold enriched BARS-50 and no GAPDH) were concentrated and dialyzed against buffer B (25 mM Hepes, pH 7.2, 50 mM K, and 1 mM Mg acetate) overnight. The final protein concentration was 2–3 mg/ml.


12th Class Biology Genetics Multiple Allelism

More than two alternative forms (alleles) of a gene in a population occupying the same locus on a chromosome or its homologue are known as multiple alleles.

Characteristics of multiple allelism

(a) There are more than two alleles of the same genes.

(b) All multiple alleles occupy the corresponding loci in the homologous chromosomes.

(c) A chromosome or a gamete has only one allele of the group.

(d) Any one individual contains only two of the different alleles of a gene, one on each chromosome of the homologous pair carrying that gene.

(e) Multiple alleles express different alternative of a single trait.

(f) Different alleles may show codominance, dominance-recessive behaviour or incomplete dominance among themselves.

(g) Multiple alleles confirm to the Mendelian pattern of inheritance.

Examples of multiple allelism : A well known example of a trait determined by multiple alleles is the blood groups in man and skin colour. Other example are eye colour in Drosophila, colour of wheat kernel, corolla length in Nicotiana, Coat colour in Cattle etc.

Blood groups in man

Blood proteins : According to Karl landsteiner (1900) a Nobel prize winner, blood contains two types of proteinous substances due to which agglutinations occurs.

(1) Agglutinogen or antigen : It is a protein found on the cell membrane of RBC&rsquos.

(2) Agglutinin or antibody : This the other proteinous substance, found in the plasma of the blood.

Whenever the blood of a person receives the foreign proteins (antigen) his blood plasma starts forming the antibodies in order to neutralize the foreign antigens.

Agglutinations : Two types of antigens are found on the surface of red blood corpuscles of man, antigen A and B. To react against these antigens two types of antibodies are found in the blood plasma which are accordingly known as antibody &ndash anti-A or a en anti-B or b. Agglutination takes place only when antigeen A en antibody a occur together or antigen B en antibody b are present in the blood.

Under such condition antibody a reageer met antigeen A and makes it highly sticky. Similarly antigen B in presence of antibody b become highly sticky with the result RBC&rsquos containing these antigens clump to form a bunch causing blockage of the capillaries. Agglutination in blood is therefore antigen-antibody reaction.

Types of blood groups

ABO blood group : Landsteiner divided human population into four groups based on the presence of antigens found in their red blood corpuscles. Each group represented a blood group. Thus there are four types of blood groups viz. A, B, AB and O. He observed that there was a reciprocal relationship between antigen and antibody according to which a person has antibodies for those antigens which he does not possess.

Blood groups of man with antigen and antibodies

Type of blood group

% in society

M, N blood group : K. Landsteiner and A.S. Wiener discovered that antigen M,N or both MN are also found on the surface of red blood corpuscles of human beings. No antibodies are however formed in the blood plasma for these antigens.

In this way when blood with M group is injected in rabbit it will produce antibodies in the blood serum which will bring about agglutination with blood group M and MN but not with blood of N group. In the same way on injecting blood of N group into the rabbit it will bring about agglutination with blood group N and MN and not with blood having blood group M.

Blood transfusion

Blood transfusion is best done in the persons of same blood group. At the same time it is possible to know in which different blood groups the blood transfusion can be made possible.

Persons with blood group AB are called universal recipients because both antigens A and B are found in their blood and the two antibodies &lsquoa&rsquo and &lsquob&rsquo are absent. Therefore, such persons can receive blood of all the blood groups.

In the same way persons who have blood group [<^<>>]are universal donors as they lack both the antigens and [R<^<>>] person can donate to Rh + person as well as Rh &ndash person but Rh + person cannot donate blood to Rh &ndash person. But at the same time such persons can not be given the blood of any other blood group except blood group O because their blood possesses both the antibodies &lsquoa&rsquo and &lsquob&rsquo. Persons belonging to blood group A and B contain only one antigen and one antibody against it, in their blood. Such persons can therefore receive blood either of the blood group of their own or the blood group O.

A place where blood of different blood groups is safely stored in bottles for emergency use, is called blood bank. Blood after proper testing is stored in a sealed bottle at a definite temperature [(4<>^circ -6<>^circ c)] to be preserved for a definite time period.

Artificial anticoagulants are used to prevent blood clotting in the blood banks. These anticoagulants are added to the blood preserved in bottle. Such anticoagulants include sodium citrate, double oxalates (sodium and ammonium), dicumarol and EDTA (ethylene diamine tetra acetic acid). The whole blood in this way can be stored for a maximum period of 21 days.

Inheritance of blood groups

Blood groups in human are inheritable trait and are inherited from parents to offsprings on the basis of Mendel&rsquos Laws. Blood group inheritance depends on genes received from parents. Genes controlling blood group in man are three instead of two and are called multiple alleles. All these three genes or alleles are located on the same locus on homologous chromosomes. A person can have only two of these three genes at a time which may be either similar or dissimilar in nature. These genes control the production of blood group/antigens in the offspring. The gene which produces antigen A is denoted by [<^>,] gene for antigen B by [<^>] and the gene for the absence of both antigens by [<^>.]it is customary to use the letter I (Isohaemagglutinogen) as a basic symbol for the gene at a locus. Based on this, six genotypes are possible for four blood groups in human population.


Chemical Biology, Protein Engineering Led to Targeted HBV Treatment Advances

Two key aspects of the HBV lifecycle vital to the development of chronic infections are the creation of a viral minichromosome in the form of cccDNA and the expression of the regulatory HBx protein.

Responsible for nearly half of all cases of hepatocellular carcinoma, chronic hepatitis B virus (HBV) is a worldwide concern and a major public health problem. Through rigorous research, investigators have identified 2 key aspects of the HBV lifecycle essential to the development of chronic infections: the establishment of a viral minichromosome in the form of covalently closed circular (ccc) DNA and the expression of the regulatory hepatitis B virus X (HBx) protein.

Researchers penned an overview of recent advances in the scientific understanding of cccDNA and the mechanistic and functional roles of HBx in a recent article in ACS Infectious Diseases.

Related Articles

cccDNA Overview

According to researchers, the successful establishment of cccDNA is “critical” for HBV replication. Despite this, the specific host mechanisms that act to convert relaxed circular (rc) DNA into cccDNA are poorly understood.

Scientific advances have allowed researchers to begin identification of the roles played by various host enzymes in cccDNA generation, either through rationally testing the enzymes involved in DNA metabolism or by RNA silencing. Additional research has identified similarities between the antisense strand of rcDNA structure and 5′ flap structures, formed during Okazaki fragment maturation, as a contributor to the formation of cccDNA, and RNA silencing screening studies also identified several DNA polymerases — α, η, κ, and λ — that mediate cccDNA establishment.

Taken together with the recent confirmation of DNA ligases I and III as crucial in converting rcDNA to cccDNA and the identification the role of topoisomerase 1 and 2 in cccDNA synthesis, these factors may represent a novel therapeutic avenue for the treatment of chronic HBV infection, according to the researchers.

Further biochemical and biophysical studies are required to define the role of cccDNA-bound hepatitis B core antigen, which would prove “invaluable” for the study of both cccDNA and HBx.

HBx Overview

HBx is the primary effector protein encoded by HBV. Although numerous human proteins have been identified as potential interactors with HBx, “relatively few” of these interactions have known functional outcomes, representative of the ambiguity that surrounds the poorly understood structure of the protein.

Within the nucleus, HBx performs dual roles: redirecting host transcription factors, including p53, NF-κB, and CREB, to change the expression of a “wide variety of gene families,” and initiating virus replication via the stimulating transcription of cccDNA. Although HBx is critical for both cccDNA transcription and the development of viremia in vivo, the HBx protein itself is not packaged in the mature virion. According to the researchers, this raises the question of how, during initial HBV infection, HBx can be expressed without being already present in the cell.

“Current theories propose that HBx may be transcribed from rcDNA or dslDNA before or during conversion into cccDNA, though one recent report identified HBx mRNA in both cell culture derived virus preparations and HBV patient plasma, suggesting that it may indeed be packaged into the virion,” the researchers noted.

Yael David, PhD, and colleagues went on to describe the more well-known HBx functions and regulatory mechanisms.

HBx and CRL4. Until recently, the structural basis and functional significance for the interaction between HBx and damaged DNA-binding protein 1 (DDB1) was unknown however, research has found that DDB1 works as an obligate adaptor protein for the cullin-RING ligase 4 (CRL4) E3 ligase complex. Later proteomic studies identified the HBx-mediated degradation of the structural maintenance of chromosomes. More targeted in vitro and cell-based studies are needed.

HBx and chromatin modifications. According to the researchers, decades of study have illustrated that HBx is able to redirect the cellular machinery responsible for the erasure or deposition of histone posttranslational modifications, to produce the active chromatin landscape on cccDNA. Specific chromatin immunoprecipitation-based studies found that, within HBx-deficient infections, there was an “increased occupancy of the histone deacetylases Sirt1 and HDAC1” on cccDNA. This suggests that HBx may either outcompete for binding sites or mediate their degradation. Ultimately, the ability of HBx to recruit diverse proteins to cccDNA “raises questions about the mechanism by which it mediates such interactions.”

Posttranslational modifications of HBx. To modulate its functions, HBx itself is posttranslationally modified, adding an additional layer of complexity to HBx biology and regulation. Recent studies have described the biochemical roles for both HBx posttranslational modifications and the enzymes that deposit them, which may eventually provide insight into so-called novel pathways to indirectly target the HBx function. In the future, a more detailed analysis of HBx structure and posttranslational modifications in vivo will be required, allowing future in vitrostudies to use more physiologically relevant conditions.

Advances in HBx and cccDNA-Targeting Treatments

To date, a significant body of work has highlighted the relative importance of both cccDNA and HBx in HBV replication and in the persistence of chronic infection. In this vein, recent studies have reported a variety of approaches that can target viral elements through the use of small molecule or biologic tools. Methods range from rationally targeted approaches, backed by established and recently developed methodologies, to “target-agnostic high-throughput screens.”

Current genome editing methods allow for the “relatively facile, locus-specific” generation of double-stranded DNA breaks. This generation led to theories suggesting that a similar approach could be used to target cccDNA for degradation. Several independent groups reported relative successes, but barriers still remain that prevent the clinical use of this approach — specifically, the lack of clinical trials surrounding the practice of gene-editing therapy.

Hepatitis B virus has a 10-fold higher mutation rate compared with conventional DNA viruses as a result, resistance mutations may rapidly rise in conjunction with strong selective pressure. In addition, an approximately 8% sequence divergence at the DNA level may make it difficult for researchers to development a therapy capable of targeting each HBV genotype. Perhaps most importantly, though, is that the generation of a double-stranded DNA break in cccDNA would result in the generation of dslDNA, which could lead to genome integration by host DNA and the promotion of oncogenesis.

Despite these potential pitfalls, genome editing remains an attractive approach, useful in both research and in the clinic setting.

The lifecycle of HBV is complex, creating a challenging environment for study however, this complexity also opens up several pathways that may be adapted for use within high-throughput screening approaches. Multiple recent studies have reported successes through promising screening approaches, several of which specifically targeted HBx functions or restricted cccDNA expression.

One example was the identification of a high-throughput screening that advantageously leveraged the documented role of HBx in inhibiting certain RNA silencing pathways. Using a computational model to generate a 3-dimensional structural model of HBx, investigators identified potential binders, which were then used to screen for the reversal of HBx-mediated RNA silencing suppression. One compound, dubbed “IR415,” was generated additional studies will be necessary to determine whether IR415 disrupts any other aspects of HBx function.

Even more recently, researchers identified another HBx targeting molecule using a split luciferase screening assay. Nitazoxanide, a broad-spectrum, anti-infective agent used typically to treat parasitic infections was identified as a potential disruptor. Future studies should examine this interaction.

Most recently, investigators reported a chemical screen used to identify inhibitors of episomal DNA expression. Dicoumarol, a small molecule, was shown to decrease episomal DNA expression, which was validated using HBV-infected primary human hepatocytes. A dose-dependent depletion of cccDNA was observed, suggesting that dicoumarol may be the basis for future drug development.

Looking Forward: Future Perspectives in HBV

The use of interdisciplinary techniques, in particular, have led to significant advances in the understanding of cccDNA establishment and regulation, as well as the mechanisms of HBx function however, questions still remain regarding these “key components” of HBV.

One difficulty in the study of HBx is the scarcity of methods used to manipulate or modulate native HBx within the context of an active HBV infection however, the use of small molecules as described may represent a unique opportunity to chemically address these methodological challenges. Similarly, the use of protein engineering strategies to better study HBx both in vivo and in vitro should be developed protein fusion methods have been reported in the literature, but efforts must continue to build on this process.

Despite significant progress in identifying the elements involved in the establishment and repair of cccDNA, structural and regulatory component details remain “enigmatic,” according to the authors. Recent efforts have been made to characterize the landscape of post-translational modifications of cccDNA, but many of these efforts rely on chromatin immunoprecipitationplus next-generation DNA sequencing, which has several shortcomings — availability, inherent target bias, and relatively low throughput among them.

Finally, the development of increasingly sophisticated methods to study chromatin biology in HBV-susceptible cell lines may establish a platform allowing for the interrogation of key biochemical questions regarding cccDNA. Specifically, the development of a method for the reconstruction of a cccDNA model for use in in vitro biochemical and biophysical studies might provide “crucial insight into the mechanisms behind recognition and recruitment of host factors onto cccDNA,” the researchers noted.

“Continued efforts in recent years have revealed critical details about the cccDNA life cycle and the HBx function that may potentially serve as the basis for novel therapeutic approaches,” David and colleagues concluded. “[O]ngoing research is needed to further build upon these advances. Chemical biologic and protein engineering techniques are perfectly poised to fully illuminate these two cryptic yet indispensable components of chronic HBV infection.”


Life Sciences Questions and Answers – Respiration – 2

This set of Life Sciences Questions and Answers for Freshers focuses on “Respiration – 2”.

1. What is Respirasome?
a) The supramolecular complex of complex I, II, and III
b) Respiratory center of the body
c) Complex III and IV of the electron transport chain
d) The intermediate complex formed during oxidative phosphorylation
View Answer

2. FeS and FAD are the prosthetic groups of ______
a) Complex I
b) Complex II
c) Complex III
d) Complex IV
View Answer

3. Mark the INCORRECT statement about Coenzyme Q?
a) It shows ubiquitous in nature
b) It is also known as ubiquinone
c) Q refers to the quinone chemical group
d) It has a protein bound prosthetic group
View Answer

4. Out of the following, which one is not the inhibitor of the electron transport chain?
a) Rotenone
b) Antimycin A
c) Cyanide
d) Malonate
View Answer

5. Name the physiological uncoupler which stops ATP synthesis.
a) 2, 4-dinitrophenol
b) Dicoumarol
c) FCCP
d) Thermogenin
View Answer

6. What is the total yield of ATP from complete oxidation of one molecule of glucose?
a) 32
b) 10
c) 8
d) 40
View Answer

7. Fermentation is similar to anaerobic respiration.
a) True
b) False
View Answer

8. What is the Cori cycle?
a) Glyoxylate cycle
b) Gluconeogenesis
c) Lactic acid cycle
d) Citric acid cycle
View Answer

9. Which of the following is CORRECT for the Pasteur Effect?
a) Utilization of glucose for fermentation
b) Increased glucose consumption by yeast in anaerobic condition
c) Fermentation favors aerobic condition more than anaerobic
d) Increased consumption of glucose by yeast in aerobic condition
View Answer

10. What is the Warburg effect?
a) Shows increased glycolysis in Cancer cell
b) Disease caused by pesticide
c) Blockage of ATP synthesis
d) Inhibitor of glycolysis
View Answer

11. Mark the correct equation for Respiratory quotient?
a) RQ = O2 produced/Co2 verteer
b) RQ = Co2 produced/ O2 verteer
c) RQ = H2O produced/ Co2 verteer
d) RQ = H2O produced/ O2 verteer
View Answer

Sanfoundry Global Education & Learning Series – Life Sciences.

Participate in the Sanfoundry Certification contest to get free Certificate of Merit. Join our social networks below and stay updated with latest contests, videos, internships and jobs!


Kyk die video: Zadruga 5 - Car i Dalila zanemeli na pitanje o izolaciji -. (September 2022).