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Biomedical subjects

T Joseph

Publications and source records attributed to T Joseph.

At least 127 records · Page 7Linked to original sources
PubMed1981

Precursor Forms of Pea Vicilin Subunits: MODIFICATION BY MICROSOMAL MEMBRANES DURING CELL-FREE TRANSLATION.

Polyribosomal RNA isolated from pea cotyledons at various developmental stages programmed the cell-free synthesis of polypeptides which were recognized by antibodies specific for pea storage proteins. There were quantitative and qualitative changes in the template activity during seed maturation. Most of the polysomal RNA was associated with the membrane fraction, and all of the template for storage protein occurred in this fraction. Using RNA from a stage of seed maturation at which the synthesis of the high-molecular weight vicilin polypeptides predominate, it was found that the major translation products, although antigenically recognizable as storage protein, did not coincide with the authentic vicillin polypeptides on denaturing polyacrylamide gels. The addition during translation of microsomal membranes from dog pancreas or pea cotyledons resulted in the appearance of new polypeptides which did coincide with some of the authentic vicilin polypeptides (in the apparent molecular weight regions of 75,000 and 50,000) and were antigenically recognizable as storage protein. Other translation products related to storage protein were not visibly altered in their electrophoretic mobility by the addition of membranes. Microsomal membranes treated with Triton X-100 were not effective in modifying the cell-free products. The modified vicilin polypeptides and at least two other translation products were protected from proteolytic degradation, suggesting that they were sequestered within microsomal vesicles. Thus, these storage protein components may be synthesized by a mechanism analogous to that described for membrane and secretory proteins (Blobel G, B Dobberstein 1975 J Cell Biol 67: 835-851).

Journal Article↗
PubMed1976

The development of adrenocorticotrophin-sensitive adenylate cyclase activity in the foetal rabbit adrenal: a correlated biochemical and morphological study.

Proliferation of the smooth endoplasmic reticulum, the site of some hydroxylating steroidogenic enzymes in foetal adrenocortical cells, is the first major change in the process of their differentiation into steroidogenic tissue. This was observed in our ultrastructural studies on foetal rabbit adrenals to begin at about day 19 of development. Morphological changes in the mitochondria, the site of production of other steroidogenic enzymes, occurred at about day 24. The elongated or rod-shaped forms of the earlier stages became flattened and rounded by this time, while the cristae were transformed from a flattened lamellar type of the earlier stages to the tubulo-vesicular form of the adult. Other changes observed included an increase in microvilli and in cell size, with a concomitant increase in thickness of the gland. Adenylate cyclase activity in foetal adrenal homogenates was assessed in response to sodium fluoride (NaF) and ACTH. All preparations responded to NaF. While good responses to ACTH were observed at days 24, 27, 28 and in the neonate, there was a lack of any significant response in the day 19 gland. Foetal ACTH was depressed by administration of cortisol, and the effects of this treatment on both the morphological changes and adenylate cyclase activity was reassessed. The response of foetal adrenals to ACTH was depressed by this treatment and differentiation of the mitochondria was arrested. These results suggest a circumscribed period for the development of ACTH-sensitive adenylate cyclase coinciding with the time at which final differentiation of the mitochondria is completed. Furthermore, both the differentiation of the mitochondria and the development of ACTH-sensitive adenylate cyclase in the foetal adrenal may be dependent on foetal ACTH secretion.

Adenylyl Cyclases↗