PubMed · 707562
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J L Haynes. 1978. Stem cells.. https://pubmed.ncbi.nlm.nih.gov/707562/
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Estimates of total number of different neuron and glial cell types in the dentate nuclei and the four major regions of the human cerebellum were obtained by new stereological methods. With the optical disector and Cavalieri methods, the total number of neurons and glial cells in the human cerebellum of five elderly men was estimated to be 105,000 x 10(6) (coefficient of variation, CV = 0.13). Of this total, the granule cells comprised 101,000 x 10(6) (CV = 0.13) and the Purkinje cells comprised 30.5 x 10(6) (CV = 0.13) of the neurons. The mean of the total number of neurons in the dentate nucleus was 5.01 x 10(6) (CV = 0.28). The average surface area of the human cerebellum was estimated to be 1160 cm2 (CV = 0.29). The rationale for the different sampling schemes used to quantify the various cell types is described.
The receptors for tumor necrosis factor (TNF) exist in cell-associated as well as soluble forms, both binding specifically to TNF. Since the soluble forms of TNF receptors (sTNF-Rs) can compete with the cell-associated TNF receptors for TNF, it was suggested that they function as inhibitors of TNF activity; at high concentrations, the sTNF-Rs indeed inhibit TNF effects. However, we report here that in the presence of low concentrations of the sTNF-Rs, effects of TNF whose induction depend on prolonged treatment with this cytokine are augmented, reflecting an attenuation by the sTNF-Rs of spontaneous TNF activity decay. Evidence that this stabilization of TNF activity by the sTNF-Rs follows from stabilization of TNF structure within the complexes that TNF forms with the sTNF-Rs is presented here, suggesting that the sTNF-Rs can affect TNF activity not only by interfering with its binding to cells but also by stabilizing its structure and preserving its activity, thus augmenting some of its effects.
The well-known mitogenic effects of TSH observed in vivo on the thyroid are not always reproducible of human thyroid cells in vitro where conflicting results have been obtained. In order to clarify this issue, we have used primary cultures of human thyroid cells obtained from normal tissue and maintained in serum-free medium for several days. In this in vitro model we have studied the effect of TSH on growth by measuring three different parameters: [3H]-thymidine incorporation, cell counts, and DNA measurement. Monolayer cultures were plated at both low and high cell density (2 x 10(4) and 8 x 10(4) cells/25 mm well, respectively). Although at either cell density cultures were equally able to functionally respond to TSH in terms of cAMP accumulation a significant growth response to TSH was observed only in low density cultures. In high density cultures TSH had an antimitogenic effect. Moreover, TSH potentiated the mitogenic effect of insulin only in low density cultures. In contrast to TSH, FCS induced a similar proliferative response at both high and low cell density. Following TSH stimulation, cAMP content was always increased, paralleling the effect of growth in low density but not in high density cultures. The cAMP analogues dibutyryl-cAMP and 8-bromo-cAMP, as well as cholera toxin and forskolin, did not mimic the mitogenic effect of TSH but had an antiproliferative effect. In addition, these agents blunted the proliferative effect of insulin. These data suggest that in thyroid cells TSH is able to elicit both a mitogenic and an antimitogenic effect depending on the environmental conditions such as cell density.(ABSTRACT TRUNCATED AT 250 WORDS)