Tarihin ƙirƙirar ka'idar Hayflick
Leonard Hayflick (an haife shi a ranar 20 ga Mayu, 1928 a Philadelphia), farfesa a fannin jikin mutum a Jami'ar California a San Francisco, ya haɓaka ka'idar sa yayin da yake aiki a Cibiyar Wistar da ke Philadelphia, Pennsylvania, a 1965. Frank MacFarlane Burnet ya sanya wa wannan ka'idar sunan Hayflick a cikin Littafinsa mai suna Internal Mutagenesis, wanda aka buga a shekarar 1974. Ma’anar ka’idar Hayflick ya taimaka wa masana kimiyya su yi nazarin illolin tsufan tantanin halitta a jikin dan’adam, ci gaban tantanin halitta tun daga matakin amfrayo zuwa mutuwa, gami da tasirin rage tsawon karshen chromosomes da ake kira. telomeres.
A cikin 1961, Hayflick ya fara aiki a Cibiyar Wistar, inda ya lura ta hanyar lura cewa sel ’yan adam ba sa rarraba har abada. Hayflick da Paul Moorehead sun bayyana wannan al'amari a cikin wani littafi mai suna Serial Cultivation of Human Diploid Cell Strains. Aikin Hayflick a cibiyar Wistar an yi niyya ne don samar da maganin gina jiki ga masana kimiyya da suka gudanar da gwaje-gwaje a cibiyar, amma a lokaci guda Hayflick ya tsunduma cikin binciken nasa kan illar ƙwayoyin cuta a cikin sel. A cikin 1965, Hayflick ya yi karin bayani kan manufar iyakacin Hayflick a cikin wani littafi guda daya mai suna "Ikantaccen Rayuwar Kwayoyin Diploid na Dan Adam a cikin Muhalli na wucin gadi".
Hayflick ya zo ga ƙarshe cewa tantanin halitta zai iya kammala mitosis, watau tsarin haifuwa ta hanyar rarraba, kawai sau arba'in zuwa sittin, bayan haka mutuwa ta faru. Wannan ƙarshe ya shafi kowane nau'in sel, na manya ko ƙwayoyin cuta. Hayflick ya gabatar da hasashe bisa ga mafi ƙarancin ikon kwafin kwayar halitta yana da alaƙa da tsufa kuma, don haka, tare da tsarin tsufa na jikin ɗan adam.
A cikin 1974, Hayflick ya haɗu tare da kafa Cibiyar Nationalasa kan tsufa a Bethesda, Maryland.
Wannan cibiyar reshe ne na Cibiyar Kiwon Lafiya ta Amurka. A cikin 1982, Hayflick kuma ya zama mataimakin shugaban kungiyar American Society for Gerontology, wanda aka kafa a 1945 a New York. Daga baya, Hayflick ya yi aiki don yada ka'idarsa kuma ya karyata ka'idar Carrel na rashin mutuwa.
Karyata ka'idar Carrel
Alexis Carrel, wani likitan fiɗa na Faransa wanda ya yi aiki tare da nama na zuciya na kaji a farkon karni na ashirin, ya yi imanin cewa kwayoyin halitta zasu iya haifuwa har abada ta hanyar rarrabawa. Carrel ya yi iƙirarin cewa ya iya cimma rabon ƙwayoyin zuciya na kaji a cikin matsakaicin abinci mai gina jiki - wannan tsari ya ci gaba har fiye da shekaru ashirin. Gwaje-gwajen da ya yi da naman zuciya na kaji sun ƙarfafa ka'idar rarraba tantanin halitta mara iyaka. Masana kimiyya sun yi ƙoƙari su sake maimaita aikin Carrel, amma gwaje-gwajen su ba su tabbatar da "gano" na Carrel ba.
Sukar ka'idar Hayflick
A cikin 1990s, wasu masana kimiyya, irin su Harry Rubin a Jami'ar California a Berkeley, sun bayyana cewa iyakar Hayflick ya shafi ƙwayoyin da suka lalace kawai. Rubin ya ba da shawarar cewa lalacewar tantanin halitta na iya haifar da lalacewa ta hanyar ƙwayoyin da ke cikin wani yanayi daban da na asali a cikin jiki, ko kuma ta hanyar masana kimiyya suna fallasa ƙwayoyin da ke cikin lab.
Ci gaba da bincike kan lamarin tsufa
Duk da sukar da ake yi, wasu masana kimiyya sun yi amfani da ka'idar Hayflick a matsayin tushen ci gaba da bincike kan al'amuran tsufa na salula, musamman ma telomeres, wanda shine sassan ƙarshe na chromosomes. Telomeres suna kare chromosomes kuma suna rage maye gurbi a cikin DNA. A cikin 1973, masanin kimiyyar Rasha A. Olovnikov ya yi amfani da ka'idar Hayflick na mutuwar tantanin halitta a cikin bincikensa na ƙarshen chromosomes waɗanda ba sa haifuwa da kansu yayin mitosis. A cewar Olovnikov, tsarin rarraba tantanin halitta yana ƙare da zaran tantanin halitta ba zai iya sake haifar da ƙarshen chromosomes ba.
Bayan shekara guda, a cikin 1974, Burnet ya kira ka'idar Hayflick da Hayflick iyaka, ta amfani da wannan sunan a cikin takardarsa, Mutagenesis na ciki. A cikin zuciyar aikin Burnet shine tunanin cewa tsufa wani abu ne na zahiri da ke cikin sel na nau'ikan rayuwa daban-daban, kuma aikinsu mai mahimmanci yayi daidai da ka'idar da aka sani da iyakacin Hayflick, wanda ke kafa lokacin mutuwar kwayoyin halitta.
Elizabeth Blackburn ta Jami'ar San Francisco da abokin aikinta Jack Szostak na Makarantar Kiwon Lafiya ta Harvard a Boston, Massachusetts, sun juya zuwa ka'idar Hayflick iyaka a cikin nazarinsu na tsarin telomeres a 1982 lokacin da suka sami nasarar cloning da ware telomeres.
A cikin 1989, Greider da Blackburn sun ɗauki mataki na gaba don nazarin abin da ke faruwa na tsufa ta tantanin halitta ta hanyar gano wani enzyme mai suna telomerase (wani enzyme daga rukuni na masu canja wuri wanda ke sarrafa girman, lamba da nucleotide abun da ke ciki na chromosome telomeres). Greider da Blackburn sun gano cewa kasancewar telomerase yana taimakawa ƙwayoyin jikin su guje wa shirin mutuwa.
A cikin 2009, Blackburn, D. Szostak da K. Greider sun sami lambar yabo ta Nobel a fannin ilimin halittar jiki ko magani tare da kalmar "saboda gano hanyoyin kariya na chromosomes ta hanyar telomeres da enzyme telomerase." Binciken su ya dogara ne akan iyakar Hayflick.