Glasø M, Wetteland P
Electron Microscopical Laboratory, University of Oslo, Norway.
APMIS. 1990 Aug;98(8):695-712. doi: 10.1111/j.1699-0463.1990.tb04990.x.
Ultrastructural morphometric characteristics of basal keratinocytes in hairless mouse epidermis were analyzed statistically. The following variables were assessed: (i) low versus physiological osmolality during fixation, (ii) alterations induced by a 2-stage carcinogenesis regimen using DMBA and TPA, (iii) criteria for a cell being dark versus being clear, (iv) inter-observer variation. The results show that with low fixation osmolality most basal cells swell and become electron lucent. The few cells which apparently do not swell stand out as shrunken electron dense dark cells. Morphometrically they are more differentiated than clear cells, but do share many features with the basal cell type which appears after fixation in a buffer of physiological osmolality. Iso-osmolality during fixation seems to induce a homogeneous basal cell population of relatively electron dense cells without typical dark and clear elements. Treatment with DMBA/TPA induces not only intercellular edema and reduced desmosomal contacts, but causes injury to the plasma membrane leading to hydropic changes in the cells. This general intra- and intercellular DMBA/TPA induced hydration might induce secondary compression of some of the cells, leading to an increased number of compressed dark cells. It is, however, only after fixation in low buffer osmolality that these effects of DMBA/TPA are statistically significant and clearly observable. The inter-person variation was, apart from a few instances, either not statistically significant or did not interfere with the other effects. We did not find clear arguments in favor of the view that dark cells are primitive epidermal stem cells. They seem only to reflect non-specific toxic effects of tumor promoters, which appear only under certain fixation conditions, that have been used by most authors. The results suggest that dark and clear cells are mainly a consequence of the degree of cellular hydration.
对无毛小鼠表皮基底角质形成细胞的超微结构形态特征进行了统计分析。评估了以下变量：（i）固定过程中的低渗与生理渗透压，（ii）使用二甲基苯并蒽（DMBA）和十四酰佛波醇乙酸酯（TPA）的两阶段致癌方案诱导的变化，（iii）细胞深色与浅色的标准，（iv）观察者间差异。结果表明，在低固定渗透压下，大多数基底细胞肿胀并变得电子透明。少数明显未肿胀的细胞表现为收缩的电子致密深色细胞。从形态计量学角度来看，它们比透明细胞分化程度更高，但确实与在生理渗透压缓冲液中固定后出现的基底细胞类型有许多共同特征。固定过程中的等渗似乎诱导了相对电子致密的细胞组成的均匀基底细胞群体，没有典型的深色和浅色成分。用DMBA/TPA处理不仅会诱导细胞间水肿和桥粒接触减少，还会导致质膜损伤，从而导致细胞出现水样变化。这种DMBA/TPA诱导的细胞内和细胞间普遍水合作用可能会导致一些细胞的继发性压缩，导致压缩深色细胞数量增加。然而，只有在低缓冲渗透压下固定后，DMBA/TPA的这些作用才具有统计学意义且清晰可见。除了少数情况外，观察者间差异要么没有统计学意义，要么不干扰其他效应。我们没有找到明确的论据支持深色细胞是原始表皮干细胞的观点。它们似乎只是反映了肿瘤启动子的非特异性毒性作用，这种作用仅在大多数作者使用的某些固定条件下才会出现。结果表明，深色细胞和浅色细胞主要是细胞水合程度的结果。
