Ateeq Bushra, Farah M Abul, Ahmad Waseem
Gene-Tox Laboratory, Section of Genetics, Department of Zoology, Aligarh Muslim University, Aligarh-202002, India.
Life Sci. 2006 Jan 25;78(9):977-86. doi: 10.1016/j.lfs.2005.06.008. Epub 2005 Aug 30.
Apoptosis or programmed cell death is characterized morphologically by chromatin condensation, cell shrinkage, fragmentation of the nucleus and cytoplasm, and consequently formation of apoptotic bodies. It has also been best characterized by the cleavage of DNA into nucleosomal size fragments of 180-200 bp or multiples of the same. Contrary to this, under extreme conditions, the cells were found to show adaptive response to apoptosis and unable to regulate their own death; necrosis is therefore predominantly observed. In the present study, we showed induction of apoptosis in Clarias batrachus due to sublethal concentration of 2,4-D and butachlor at multiple exposure time. The first phase of the study involved light microscopy (LM) and transmission electron microscopy (TEM) for ultrastructural abnormalities of the germinal tissues. While, in the second phase of the study, DNA degradation of blood and hepatic tissue was resolved on agarose gel electrophoresis. In histopathological studies, large numbers of stage II oocytes were noted for nuclear blebbing irrespective of the test chemical. Some of the butachlor-exposed oocytes showed vacuolation and electron dense cytoplasm along with thickened nuclear envelope, having close association with the lysosomes on the cytoplasmic side. Some oocytes undergo nuclear blebbing having inner dense core and translucent cytoplasm. Leydig cells were slightly hypertrophied and few appeared pycnotic, a process involving necrotic changes in which the cell nuclei were characterized by rounding up and condensation resulting in hyperchromatic staining or pycnosis. In testicular tissue, spermatogonial nuclei had irregular large clumps of heterochromatin adjoining the nuclear membrane indicating initial stage of apoptotic cell death. Electrophoretic separation resulted in a ladder pattern of blood DNA and smear like pattern of hepatic DNA. These results indicate that the above herbicides are able to induce apoptosis both at molecular as well as cytological level. A reference dose or safety factor approach to calculate risk of human exposure to both chemicals is still awaited.
细胞凋亡或程序性细胞死亡在形态学上的特征是染色质浓缩、细胞皱缩、细胞核和细胞质碎片化，进而形成凋亡小体。它的最佳特征还在于DNA被切割成180 - 200 bp的核小体大小片段或其倍数。与此相反，在极端条件下，发现细胞对细胞凋亡表现出适应性反应且无法调节自身死亡；因此主要观察到坏死现象。在本研究中，我们表明，在多次暴露时间下，2,4 - D和丁草胺的亚致死浓度会诱导胡子鲶细胞凋亡。研究的第一阶段涉及光学显微镜（LM）和透射电子显微镜（TEM），以观察生殖组织的超微结构异常。而在研究的第二阶段，通过琼脂糖凝胶电泳解析血液和肝脏组织的DNA降解情况。在组织病理学研究中，无论测试化学品如何，都观察到大量II期卵母细胞出现核泡化。一些暴露于丁草胺的卵母细胞出现空泡化和电子致密的细胞质，同时核膜增厚，在细胞质一侧与溶酶体紧密相连。一些卵母细胞经历核泡化，具有内部致密核心和半透明细胞质。睾丸间质细胞略有肥大，少数出现核固缩，这一过程涉及坏死变化，其中细胞核的特征是变圆和浓缩，导致染色质深染或核固缩。在睾丸组织中，精原细胞核有不规则的大团异染色质毗邻核膜，表明细胞凋亡死亡的初始阶段。电泳分离结果显示血液DNA呈梯状模式，肝脏DNA呈涂片状模式。这些结果表明，上述除草剂能够在分子和细胞学水平上诱导细胞凋亡。目前仍在等待通过参考剂量或安全系数方法来计算人类接触这两种化学品的风险。
