Re-examination of the subcellular localization of thyroxine 5''-deiodination in rat liver.

We describe the existence of at least two thyroxine 5'-deiodinases in rat liver. They co-fractionate with NADPH-cytochrome c reductase, the marker enzyme for membranes of the endoplasmic reticulum. Subcellular-localization studies of the most active microsomal thyroxine 5'-deiodinase were performed under substrate saturation and at optimal pH 6.8. This enzyme was a Km(app.) of about 3 microM-thyroxine and a Vmax. of about 8 ng of tri-iodothyronine/min per mg of protein. Our study confirms in part the earlier reports of microsomal localization of thyroxine 5'-deiodination. However, this process is not mediated by only a single enzyme.     

The nucleotide sequence of tRNA tyrosine from the fission yeast Schizosaccharomyces pombe.

The sequence of tRNA tyrosine from the fission yeast Schizosaccharomyces pombe is pCUCCUGAUm1 GGUG psi AGDDGGDDAUCACACor (psi) CCGGUG psi Ai6 AACCGGUUGm7 GUm5C GCUAGT psi CGm1 AUUCUGGUCAGGAGACCAOH. This sequence differs in 30 nucleotides from the tRNA-Tyr seqence of the budding yeast Saccharomyces cerevisiae. It has a unique anticodon stem of only four GC base pairs. The normal fifth pair position of nucleotide 28-44 is occupied by a C-U and in 20% of the tRNA-Tyr molecules it is psi-U. This unusual feature and its implications are considered in the discussion.     

Properties of a Candida albicans strain possessing an increased sensitivity to polyene antibiotics]

Characteristics of a mutant of the yeast-like fungus Candida albicans with increased sensitivity to amphotericin B, levorin and nystatin is presented. Increased sensitivity to the polyens in the isolate must be associated with changes in the cell wall and/or with decreased total viability of the strain. The following factors were in favour of this: presence of significant amounts of pseudomycelial cells with thinner cell walls as compared to the yeast cells in the population of the mutant strain; a higher rate of potassium liberation from the cells of the mutant strain in the presence of amphotericin B; a lower growth rate of the mutant strain on solid and liquid media; an increased death rate of the cells in the intact culture of the mutant strain as compared to the initial strain; absence of changes in the absorption spectrum of sterols isolated from the cells of the mutant strain as compared to the initial culture.     

Antiviral activity of the complexes obtained at different ratios of complementary homopolyribonucleotides

Antiviral activity of the complexes of synthetic polyribonucleotides, i.e. poly (I).poly (C) and poly (G).poly (C) obtained at non-equimolar ratios of homopolymers was studied. The system of chick embryon fibroblasts and horse Venezuellan eguine encephalitis virus served as the model. It was shown that the active and stable complexes poly (I).poly (C) and poly (G).poly (C) were formed at some excess of poly (C), i.e. at the ratio of poly G) or poly (I) to poly (C) equal to 40/60 to 20/80 molar per cent. The role of the excessive poly (C) in formation of the stable secondary structure of the nucleotide complexes and its significance as one of the means for affecting the fine structure of double-stranded RNA were discussed.     

Biological method of identifying antibiotic substances at an early screening stage

A biological method was used in addition to the chemical methods of identification in the screening programme of new antibiotics. The method consists of evaluation of the effect of the crude antibiotic preparations on microbial forms resistant to various antibiotics. The efficiency of the biological method is shown. It provides more complete and rapid characterization of the properties of the new antibiotics and their rough identification at early screening stages.     

Change in the adrenal cortex of rats in stress after hypophysectomy, thyroidectomy and castration

To elucidate factors producing destructive changes in the adrenal cortex under severe stress, the following experiments were performed: 1) severe combined stress (KC) including unilateral adrenalectomy and fixation in supin position for 24 h (control group); 2)hypophysectomy KC; 3) thyroidectomy KC; 4) bilateral orchiectomy KC; 5) injection of vitamine "E" for 14 days + KC. The adrenals were studied by a complex of morphometrical and histochemical methods. Hypophysectomy prevented estructive changes in the adrenal cortex under KC. This effect was not connected with hypofunction of the thyroid gland and the testes, as their excision (in rats without hypophysectomy) did not prevent the development of necrobiotic changes in the adrenal cortex. A suggestion is made on a "corticolytic" effect of ACTH which reveals itself under severe stress. Destruction of adrenocorticocytes is supposed to result from activation of peroxide oxidation of lipids. This is indirectly supported by a large number of lipofuscin containing cells, by decrease in the activity of alkaline phosphatase and ATPh-ase, by activation of acid phosphatase and also by decreasing alterative phenomena at the injection of vitamine "E".     

Transport noise in membranes. Current and voltage fluctuations at equilibrium

A formulism is described for the treatment of noise resulting from the transport of ions in channels containing an arbitrary number of activation energy barriers. The analysis is based on Nyquist's theorem and is therefore restricted to fluctuations around the equilibrium state. Within this limit the spectral intensities of current and voltage noise are given by the frequency-dependent admittance, which in turn is closely linked to the relaxation-time spectrum of the transport system. Explicit expressions for the spectral intensity of current noise are derived for channels with two and three energy barriers. The analysis may be used to predict the spectral intensity of noise from the gating system in nerve.     

Structures and fatty acid compositions of neutral glycosphingolipids of human plasma

Major neutral glycosphingolipids were isolated from human plasma and their structures and fatty acid compositions studied. The four neutral glycosphingolipids of plasma were characterized as Glc beta(1 leads to 1)ceramide, Gal beta(1 leads to 1)- ceramide, Gal beta(1 leads to 4) Glc beta (1 leads to 1)ceramide, Gal alpha(1 leads to 4) Gal beta(1 leads to 4) Glc beta(1 leads to 1)ceramide and GalNAc beta(1 leads to 3) Gal (1 leads to 4) Gal (1 leads to 4) Glc beta(1 leads to 1)-ceramide. The glycosphingolipids contained mostly short chain fatty acids of which most prominent was C16. Erythrocyte glucosylceramide and lactosylceramide exhibited similar fatty acid compositions as their plasma counterparts. Triglycosylceramide and globoside of erythrocytes contained almost exclusively long-chain fatty acids. In lactosylceramide obtained from "p" erythrocytes, an accumulation of long-chain fatty acids was found; this accumulation was not observed, however, in lactosylceramide isolated from "p" plasma. It was concluded that plasma and erythrocyte glycosphingolipids are synthesized at separate sites where short- and long-chain fatty acids, respectively, are available. Plasma and erythrocyte glucosylceramide, and probably a fraction of lactosylceramide, exchange between plasma and erythrocyte pools. The latter conclusion is discussed in the light of the relative roles of carbohydrate and lipid moieties of the glycosphingolipids in maintaining their association with erythrocyte membranes.