We report data on the structural and functional characterization of the 5 H flanking region of the human mitochondrial glycerol-3-phosphate dehydrogenase (mtGPDH) gene. We found two regions upstream of 5 H -untranslated sequences exhibiting promoter activity in transient transfection assays. Transcription start sites and potential regulatory sites in both promoter regions were defined. The proximal promoter was approximately sevenfold more active than the distal one in most cell lines, but it was only twice as active in a neuroblastoma cell line. These observations seem to indicate that the rate of transcription, as well as the tissue-specific expression of the human mtGPDH gene, is the result of a combinatorial effect of transcription factors on at least two promoters. 3,5,3H -Triiodothyronine failed to alter the transcriptional activity of human mtGPDH promoter(s) constructs in transient transfection assays. Although this finding seems to be in conflict with the reported effect of 3,5,3Htriiodothyronine in rodents, it is consistent with our observation of 3,5,3H -triiodothyronine stimulation of mtGPDH activity in primary cultures of rat adipocytes, but not human cultured adipocytes, suggesting distinct regulation of this gene in both species.

Light microscopy of stained (protargol, Feulgen, aceto‐orcein, methyl green‐pyronin) specimens of Onychodromus acuminatus during excystment shows that the macronucleus appears during the first hour as a warped ribbon with variable density and width and with sharpened ends. One extraordinary point that reaches the cortex is frequently seen in front of a small granule where the bundle of positioning fibers arises. The macronucleus returns to its previous form, with rounded edges, at the end of cortical morphogenesis, and later divides twice. Some details of cortical morphogenesis during the excystment process are discussed.

SYNOPSIS By using the split‐pair method autogamy was induced in Stylonychia mytilus Ehrenberg and S. muscorum Kahl, and the process was thoroly studied in the former. The pairs split early in conjugation continued the process as autogamonts and never united again altho they were placed in the same depression slide. The pattern of nuclear behavior during autogamy closely resembles that reported for conjugation. The fusion of pronuclei at metaphase is usually observed, but it occasionally fails and the stationary pronucleus appears to continue its development as a hemicaryon. The macronuclear anlage and the definitive micronuclei differentiate from particular products of the 3rd postgamic division.

No abstract

No abstract