Using histochemical procedures to reveal the presence of nucleoside diphosphatase (NDPase), thiamine pyrophosphatase (TPPase) and acid phosphatase (AcPase), we investigated the appearance, distribution and ultrastructure of amoeboid and microglial cells in the cerebral hemispheres of chick embryos and young chicks, in order to elucidate the relationship between these two cell populations. On day 6 of incubation, a few round cells exhibiting NDPase, TPPase and AcPase activity were first detected in the thin mantle layer of the cerebral hemisphere. In the corpus striatum, these round cells increased rapidly in abundance until day 13 of incubation, after which their numbers gradually decreased, so that, on day 19 of incubation, they had entirely disappeared. Between day 10 and day 17 or 18 of incubation, round cells were located mainly in the zone of the mantle layer closest to the lumen. On day 10 of incubation, NDPase-, TPPase- and AcPase-positive cells that had a few short cytoplasmic processes (poorly ramified cells) were detected in the intermediate and basal zones of mantle layer. They increased in abundance until day 17 or 18 of incubation and thereafter rapidly decreased in number. Round and poorly ramified cells exhibited NDPase activity on their plasma membranes and in their cytoplasmic vacuoles, with TPPase and AcPase activity being localized within their vacuoles. On day 19 of incubation, NDPase- and TPPase-positive cells with long, well-ramified cytoplasmic processes (well-ramified cells) were observed in the corpus striatum, these being mainly localized in the basal zone. After hatching, these cells increased rapidly in abundance and were distributed throughout the corpus striatum.(ABSTRACT TRUNCATED AT 250 WORDS)
Interactions of pancreatic islets and islet-associated mononuclear cells (IAMCs) from the nonobese diabetic (NOD) mouse were morphologically investigated. To obtain IAMCs, pancreatic islets isolated from adult NOD mice were cultured for 7 days with interleukin 2. Noted by light microscopy, interactions between IAMCs and freshly isolated islets from young NOD mice began 30 min after the initiation of the coculture, and 6 h later, normal cellular array of the islets was lost. By electron microscopy, most IAMCs had low nucleus-cytoplasm ratio, the nucleus was notched and exhibited condensed chromatin along the nuclear membrane, and well-developed Golgi complexes and several mitochondria were distributed in the cytoplasm. These IAMCs adhered to beta-cells, but not to alpha- or delta-cells, with their pseudopods and caused cytolysis of beta-cells. Immunohistochemical study with antibodies specific for pancreatic hormones demonstrated that only cells reacting with anti-insulin antibody were selectively lost as the incubation time proceeded. Electron immunohistochemistry by immunogold technique showed that effector cells in IAMCs reacted with anti-CD8 (Lyt-2) antibody, but not anti-CD4 (L3T4) or anti-asialogangliosideM1 antibody. In addition, the concentration of pancreatic hormones in the culture medium, used as a marker of cytolysis, also demonstrated that insulin was significantly increased after 6 h of culture, whereas glucagon and somatostatin were not. These results suggest that CD8+ cytotoxic T lymphocytes are involved in the selective destruction of pancreatic beta-cells in the NOD mouse.
By using a whole-embryo culture technique (New 1978), the effects of oxygen concentration (5%, 20% and 95% oxygen) on embryonic development in the rat were investigated by light and electron microscopy. The best embryonic development occurred when the 9.5-day-old embryos were cultured for 24 h with 5% oxygen, and the 10.5-day-old embryos with 20% oxygen (optimum oxygen concentration). When the 9.5- and 10.5-day-old embryos were cultured for 24 h with too little or too much oxygen, retardation of the embryonic growth and abnormal development was observed. Using light microscopy, numerous degenerating cells, exhibiting granular deposits in the cytoplasm, were seen, but the distribution of the degenerating cells was quite different between the two groups. With electron microscopy, the most striking feature of the degenerating cells in the embryos cultured with too little oxygen, was the extreme swelling of the mitochondria without any morphological alterations of the nucleus or the other cell organelles. On the other hand, the characteristic feature of the degenerating cells in the embryos exposed to too much oxygen, was the formation of phagolysosomes in the cytoplasm. Morphological alterations of the nucleus or mitochondria were not evident. In the present study, the possible teratogenic mechanism of too much or too little oxygen in the whole-embryo culture of the rat embryo is discussed.
The myotome of early chick embryos was investigated histochemically by means of the acetylcholinesterase (AChE) reaction. Light-microscopically, at the cervical level, the myotome was first recognized and AChE activity demonstrated at stage 13 (2-day-old embryo). Subsequently, the myotome elongated ventro-laterally along the inner surface of the dermomyotome and reached the ventro-lateral end of the dermomyotome at stage 17 to 18 (3 day-old embryo). AChE activity in the myotome showed subsequent increase in intensity during the course of development. The myotome consisted mainly of AChE-positive cells displaying enzymatic activity along the nuclear membrane and within the cytoplasm. In contrast, almost all cells of the dermomyotome and the interstitial cells were AChE-negative. Electron-microscopically, the myotome cells of the 2 day-old embryo and the cells in the dorso-medial portion of the myotome of the 3 day-old embryo were morphologically undifferentiated; AChE activity was detected in the nuclear envelope and in single short profiles of the endoplasmic reticulum (ER). On the other hand, in the 3 day-old embryo the cells in the ventro-lateral portion of the myotome showed AChE activity in the nuclear envelope, numerous profiles of the ER and some Golgi complexes. These AChE-positive cells were regarded as developing myogenic cells based on their morphological characteristics. The present findings indicate (i) that the appearance of AChE activity in the cytoplasm is the first sign of the differentiation of myogenic cells, and (ii) that in these myogenic cells the increase in AChE activity is based on the development of the ER.
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