كتاب Encyclopedia of Physical Science and Technology - Molecular Biology-Elsevier

immature and autoreactive T cells, Wolffian and Mullerian duct regression during sexual development, tumor regression, and in elimination of virus-infected cells. Furthermore, it has been suggested that apoptosis occurs in many diseases such as cancer, fulminant hepatitis, acquired immune deficiency syndrome (AIDS), diabetes mellitus, and neurodegenerative disorders such as Alzheimer’s disease and prion disease. Growth and differentiation of cells are strictly regulated by factors such as cytokines and low-molecular-weight compounds such as steroid hormones. These factors are generally bound to the corresponding receptors in order to transduce the appropriate cell signals, to promote growth and differentiation. On the other hand, apoptotic cell death is aggressively controlled by a number of polypeptides, so-called death factors exposed at the cell surface or circulating in the body as soluble factors in some situations. Growth and differentiation factors act via transcriptional regulation through the activation of a series of protein kinases. On the other hand, death factors execute apoptosis through the activation of caspases, and many proteins essential for cell survival are degraded by these activated caspases. It is currently believed that apoptotic death is due to the degradation of many functional proteins by caspases. Cell-free systems for the study of apoptosis have been established and facilitate our understanding of the underlying molecular mechanisms. Several factors involved in apoptotic pathways have been identified and part of these pathways has been revealed by biochemical approaches based on cell-free apoptosis system. Regulatory mechanisms for apoptosis include: the CED-3/caspase family proteases and CED-4/Apaf-1 family which act as executors of apoptosis; CED-9/Bcl-2 family (including antiapoptotic and pro-apoptotic factors) which act as regulators of apoptosis, and many factors which contribute to apoptotic morphological changes have been identified. Here, I shall focus on the currently proposed molecular mechanisms of death receptor activity and caspase activation. Moreover, I will also discuss the DNase responsible for apoptotic DNA fragmentation, both in vitro and in vivo, and finally the mechanism by which apoptotic cells are cleared.
كاتب غير معروف - يشمل يركن (كاتب غير معروف) كل الكتب التي لا يعرف مؤلفيها، حيث أن العمل في شيء بالشكل المجهول هو التدخل بشكل شخصي دون استخدام اسم محدد أو التعريف عن الهوية، وتشير حالة "غير معروف" أو "المجهول" عادة إلى حالة شخص ما بدون معرفة عامة لشخصيته أو لمعلومات تحدد هويته. هناك العديد من الأسباب التي يختار من أجلها شخص ما إخفاء شخصيته أو أن يصبح مجهولا. يكون بعض تلك الأسباب قانونيا أو اجتماعيا، مثل إجراء الأعمال الخيرية أو دفع التبرعات بشكل مجهول، حيث يرغب بعض من المتبرعين بعدم الإشارة إلى تبرعاتهم بأي شكل يرتبط بشخصهم. كما أن من يتعرض أو قد يتعرض للتهديد من قبل طرف ما يميل إلى إخفاء هويته، مثل الشهود في محاكمات الجرائم، أو الاتصال بشكل مجهول بالسلطات للإدلاء بمعلومات تفيد مسار التحقيق في القضايا العالقة. كما أن المجرمين بشكل عام يحاولون إبقاء أنفسهم مجهولي الهوية سواء من أجل منع إشهار حقيقة ارتكابهم للجريمة أو لتجنب القبض عليهم.
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