Further studies on chromocentres and their implications in regeneration

Previous investigations using a number of invertebrates, as well as regenerative tissues/organs of various vertebrates, have promulgated the hypothesis that heterochromatin, in the form of nuclear chromocentres, is correlated with the ability to regenerate. In order to test the universality of this hypothesis, cells from a variety of additional animals were examined for the presence of nuclear chromocentres. In accordance with the hypothesis, cells from these organisms contained numerous chromocentres. Evidence indicates that chromocentres, double minute chromosomes, chromosome 'dots', and telomeres may be different forms of the same heterochromatin entity.     

Further studies on the oscillatory rate of hemoglobin synthesis in rabbit reticulocytes

The rate of hemoglobin synthesis in rabbit reticulocytes was found to be oscillatory after synchronization of the reticulocytes by precooling at 0 °C. Both α and β chains are synthesized in an oscillatory manner and in phase after synchronization. Experiments designed to study the effect of cooling on the polyribosomes showed a slowly proceeding shift in the polyribosome profile in favor of monosome formation. This shift proved to be reversible. After rapidly warming cooled reticulocytes, the original polyribosome profile was restored within 40–120 sec.     

Further studies on the gangliosidic nature of the cholinergic-specific antigen, Chol-1

The antigen designated as Chol-1 beta, detected by an antiserum specific for cholinergic neurons, has been purified to homogeneity from ganglioside mixtures extracted from Torpedo electric organ and pig brain. The final products from the two sources behaved identically in a wide range of tests and gave coincident immunopositive and Ehrlich-positive spots after thin layer chromatography in seven different solvent systems; they were thus considered to be identical and to constitute a single, pure chemical species. Gas-chromatographic analysis revealed the presence of long-chain bases, glucose, galactose, N-acetylgalactosamine, and sialic acid in integral molar ratios of 1:1:2:1:3; the compound's reactivity to cholera toxin after Vibrio cholerae sialidase treatment on thin layer chromatography and the recovery of GM1 as sole product of exhaustive sialidase treatment identified it as a member of the gangliotetrahexosyl series. From the products of partial enzymatic desialylation and treatment with beta-galactosidase and a comparison of the compound's immunoreactivity to anti-Chol-1 antisera with that of other trisialogangliosides of defined molecular structure, we were able to assign a disialosyl residue alpha-Neu5Ac-(2----8)-alpha-Neu5Ac-(2----3)- to the inner galactose, and we suggest GalNAc as a possible site of linkage of the third sialic acid.     

Further studies on the rabbit erythroid cell plasma membrane transferrin receptor

Studies reproted here indicate that a major cell surface glycoprotein of the rabbit bone marrow erythroid cell may be involved in binding transferrin. The glycoprotein has an apparent molecular weight of 18,000. It is suggested that bone marrow erythroid cells may provide an invaluable source of the red cell membrane transferrin receptor for future studies.     

Further studies on the relationship of adrenal and gonadal steroids in pubertal development in female rats.

Surgical adrenalectomy or the administration of aminoglutethimide, corticosterone (B), and androstenedione (delta 4) to the immature female rat had no effect on the timing of vaginal membrane opening. Dehydroepiandrosterone (DHA) and estrone (E1) significantly hastened vaginal patency. Aminoglutethimide increased pituitary LH content while FSH content was decreased. An anti-17 beta-E2 antibody increased pituitary LH content and plasma concentration suggesting enhanced synthesis and release of LH. Pituitary FSH content was unaltered while plasma FSH decreased. Aminoglutethimide increased adrenal and ovarian but not pituitary weight while the antibody had no effect. Since little DHA is present in rat plasma and adrenal and since only estrogens have any effect on the onset of puberty, it is likely that the adrenal is not directly involved in pubertal development in the female rat.     

Comparative studies on the nature of purified cytomembranes of the rabbit parotid gland

Synopsis Centrifugation procedures have been evolved for isolating purified samples of rough endoplasmic reticulum, Golgi, zymogen granule and plasmalemmal membranes from homogenates of rabbit parotid gland tissue. The purification process was monitored using morphometry and enzyme and chemical marker assays.The membrane preparations were analysed by sodium dodecylsuphate (SDS) polyacrylamide gel electrophoresis, quantitative phospholipid thin layer chromatography and by enrichment studies. The results were used to evaluate various possible general models for the behaviour of membranes during the secretory cycle of parotid acinar cells.