AMP photophosphorylation and binding by chloroplasts

Stoichiometric amounts of chloroplast thylakoids photophosphorylate free AMP to tightly bound ADP. Free ADP is a poor competitor for this AMP photoreaction, which saturates below 16 micronAMP. The inhibitor, diadenosine pentaphosphate, abolishes AMP photophosphorylation, and inhibits dark ADP binding. Taken together, these data imply that this photoreaction involves the high affinity nucleotide binding site(s) of chloroplast coupling factor CF1, and that little mixing with free nucleotides occurs.     

Industrial toxicology of metals of the platinum group

Metals of the platinum group have found important application in technology and industry. Compounds of these metals display a broad spectrum of toxic effects on the organism. In persons dealing with them in the production, they induce allergic occupational diseases of the respiratory passages, dermatoses, affections of the eyes. Their resorptive chronic effect in experiment is characterized by reduction in the body mass of the animals and the content of haemoglobin in the blood, by disturbances of the protein-synthesizing function of the liver, decreased cholinesterase activity in the blood, impaired carbohydrate and lipid metabolism, reduced concentrating capacity of the liver, development of glomerulonephritis. Platinum and platinoids irritate mucous membranes and skin. They penetrate the organism through intact skin. Data on the distribution of the metals in the organs and on their elimination from the organism are reported. Toxicity of the metals of the platinum group is correlated with valence of the compounds and with electron structure. MAC for milling and condensation aerosols of poorly soluble compounds (metal and its oxides) are recommended at 0.1 mg/m3. For aerosols of all soluble compounds of platinum and platinoids, MAC of 0.001 mg/m3 are recommended.     

Nonspecific and antigen-specific adhesiveness of circulating lymphocytes in dysentery patients undergoing combined therapy using thymalin and indomethacin

Nonspecific adhesiveness of lymphocytes to polyacrylonitrile fiber and the antigen-specific adhesiveness of T-lymphocytes to Shigella flexneri pellicular immunosorbent have been studied in dysentery patients. Short courses of treatment with indomethacin, but not with thymalin (the preparation of thymic hormones), used for immunomodulation, have accelerated the normalization of nonspecific lymphocyte adhesiveness during regression of the disease, while indomethacin, in contrast to thymalin, inhibits antigen-specific T-lymphocyte adhesiveness which increases with the development of immune response.     

Glucocorticoid-mediated degradation of DNA in thymocytes of rats with transplantable Zajdela ascites hepatoma

Tumour growth was shown to be associated with DNA breakdown in thymocytes of rats bearing Zajdela ascites hepatomas. The tumour action on the thymus is mediated through adrenal glands since bilateral adrenalectomy completely prevents DNA breakdown in thymocytes. Using Southern hybridization of DNA genome with probes for histone, ribosomal and heat shock gene (hsp 70), it was shown that the degradation products of specific DNA sequences are as heterogenous as those of total DNA, although marked differences in appearance of nucleosomal ladder were seen. These data were interpreted to indicate different patterns of DNA breakdown in dying thymocytes. DNA breakdown in thymocytes in vivo and in isolated rat liver nuclei in vitro seems to proceed by similar mechanisms.     

Saturation-transfer electron spin resonance studies on the mobility of spin-labeled sodium and potassium ion activated adenosinetriphosphatase in membranes from Squalus acanthias

The sodium and potassium ion activated adenosinetriphosphatase [(Na+,K+)-ATPase] in membranous preparations from Squalus acanthias has been spin-labeled on sulfhydryl groups after prelabeling with N-ethylmaleimide. Saturation-transfer electron spin resonance spectroscopy has been used to study the rotational motions of the labeled protein on the microsecond time scale. Effective rotational correlation times deduced from the diagnostic line-height ratios in the second-harmonic, 90 degrees out-of-phase (V2') spectra are much larger than those deduced from the spectral integrals, indicating the presence of large-scale segmental motions, in addition to rotation of the protein as a whole. Experiments involving controlled cross-linking of the protein by glutaraldehyde, as well as measurements of the line broadening of the conventional electron spin resonance spectra, support this interpretation. Both the spectral integrals and diagnostic line-height ratios are found to increase irreversibly with time on incubation at temperatures greater than 20 degrees C, corresponding to a decrease in the segmental motion of the protein and probably also in the overall protein rotation. The native enzyme displays a marked nonlinearity in the Arrhenius temperature dependence of the activity at temperatures above 20 degrees C, and the activity decreases with a half-life of ca. 70 min on incubation at 37 degrees C (but not on incubation at low temperature), paralleling the time- and temperature-dependent changes in the saturation-transfer spectra of the labeled protein. Both of these observations suggest that the changes observed in the molecular dynamics could correspond to functional properties of the protein.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ultrastructural studies of endocrine-like cells in the fundic gastric mucosa of the bullfrog,Rana catesbeiana

Summary This study is concerned with electron-microscopic observations on endocrine or paracrine cells in the fundic gastric mucosa of the bullfrog. Also, an attempt was made to identify the histamine-releasing cells involved in the secretagogue response. At least three distinct endocrine-like cell types were found. The classification is based on the appearance of secretory granules and other organelles, and the relationship of endocrine-like cells with other cells in the tissue. The amphibian endocrine-like cells resemble the ECL, D and EC cells of mammals. Type-I (ECL) cells showed degranulation after repeated stimulation with tetragastrin (TG), acetylcholine (ACh) and K⁺ depolarizing solution, all of which release histamine.     

Ontogenesis of TRH mRNA in the rat pancreas

The rapid changes in TRH levels in the rat pancreas during the neonatal period make this organ an interesting model for the study of the regulation of TRH biosynthesis. Pancreatic RNAs were isolated by the guanidinium thiocyanate method and layered onto CsCl cushion. Northern blot preparations were hybridized with 32P labeled TRH cDNA probe. Pancreatic TRH mRNA was first detected in 19-day old fetuses and reached the highest level on day 0, then decreased, being barely detectable 14 days after birth. The neonatal injection of streptozotocin induced a dramatic drop of TRH mRNA levels 24 hours later. This result suggests that the peculiar evolution of TRH level in pancreas is partly due to the evolution of the expression of the TRH gene.     

R-factor from the natural strain of Salmonella derby carrying a DNA-polymerase gene

A R-factor which determines multiple stability to antibiotics (Cm, Pn, Sm) was found in a Salmonella derby strain isolated from the clinical material. The plasmid was eliminated by treatment with ethidium bromide; the DNA-polymerase activity in the antibiotic-sensitive derivatives measured under conditions optimal for DNA-polymerase I from E. coli was found to be decreased 10-50-fold. Plasmid DNA of S. derby K89 was fractionated by electrophoresis in agarose gel; individual zones I-IV were obtained, using a preparative technique. Upon transformation of S. derby K82 pol- cells, only plasmid DNA in zone II (designed as pSD Cm pol) gave Cm-resistant transformants, in which the DNA-polymerase activity decreased to the normal level. The experimental results pont to the binding of the DNA-polymerase gene to the S. derby plasmid.     

Development of genetic research in the USSR

Two periods of the development of genetic research in the USSR with reference to its current trends of plant and animal genetics, cytogenetics, and molecular genetics are reviewed. A short list of priority areas is established: the maintenance and use of unique gene pools of plants and animals; the domestication of animals and cultivation of new plants; the development of programmes for mathematical treatment of genetic data banks. It is suggested to consider them within the framework of international projects. The idea is to promote the collaborative efforts of scientists on an international scale.