Regulation of rat hepatic stearoyl coenzyme A desaturase. The roles of insulin and carbohydrate.

The rat hepatic stearoyl-CoA desaturation decreased by 3.7-fold in streptozotocin-induced diabetes. Insulin treatment of diabetic rats increased the enzyme activity by 7-fold. In marked contrast to glucose administration, fructose feeding in diabetic rats resulted in 20-fold stimulation of stearoyl-CoA desaturation, although both carbohydrates stimulated stearoyl-CoA desaturation in normal rats. Measurement of the microsomal electron transfer components showed no significant changes in the NADH-cytochrome b5 reductase activity or in the concentration of cytochrome b5. However, the activity of the terminal desaturase changed in a parallel fashion as the amount of terminal desaturase reflect changes in the overall desaturation. Supplementation of various microsomes with the saturating amount of purified terminal desaturase resulted in the formation of similar amounts of catalytically active complex and increased the stearoyl-CoA desaturation to the same level suggesting that the changes in the amount of terminal desaturase reflect changes in the overall desaturation. The results support the suggestion that both insulin and the intermediates of carbohydrate metabolism are involved in the regulation of terminal desaturase.     

E.s.r. of spin-trapped radicals in aqueous solutions of peptides. Reactions of the hydroxyl radical.

The reactions of hydroxyl radicals with 30 dipeptides and several larger peptides were studied in aqueous solutions. The OH radicals were generated by U.V. photolysis of H2O2. The short-lived peptide radicals were spin-trapped using t-nitrosobutane and identified by e.s.r. For dipeptides containing the amino terminal residues glycine, alanine and phenylalanine, abstraction of the hydrogen from the carbon adjacent to the peptide nitrogen was the major process leading to the spin-adducts. Such radicals will be referred to as backbone radicals. Dipeptides with a carbonyl terminal serine residue and also glycylglutamic acid form both backbone and side-chain radicals, with the latter being formed in larger quantities. For dipeptides, side-chain radicals were detected on either the carboxyl or amino terminal residues of both. The effect of pD on the e.s.r. sectrum of the spin-adducts of glycylglycine was studied and the pK of the carboxyl group of this radical was determined to be 2.5. For (Ala)3 and (Ala)n, with an average value of n = 1800, backbone and minor side-chain radicals were observed. For ribonucleases-S-peptide, containing 20 amino acid residues, both backbone and side-chain radicals were detected.     

The Role of Fluoride in Montmorillonite-Catalyzed RNA Synthesis

The montmorillonite-catalyzed reactions of the 5′-phosphorimidazolide of adenosine in the presence of fluoride were investigated to complete our study on the effect of salts on this type of reaction. Both anions and cations have been found to influence the oligomerization reactions of the activated nucleotides, being used here as a model system for pre-biotic RNA synthesis. However, in total contrast to the behavior of the activated nucleotides in the presence of montmorillonite and other salts, alkali metal fluorides did not yield any detectable oligomerization products except in very dilute (<0.005 M) solutions of fluoride. Instead, 5′-phosphorofluoridates were formed. Their identity was confirmed by a combination of HPLC, mass spectrometry, synthesis, and NMR.     

Phosphocaveolin-1 is a mechanotransducer that induces caveola biogenesis via Egr1 transcriptional regulation

Maintenance of epithelial cell adhesion is crucial for epidermal morphogenesis and homeostasis and relies predominantly on the interaction of keratins with desmosomes. Although the importance of desmosomes to epidermal coherence and keratin organization is well established, the significance of keratins in desmosome organization has not been fully resolved. Here, we report that keratinocytes lacking all keratins show elevated, PKC-α–mediated desmoplakin phosphorylation and subsequent destabilization of desmosomes. We find that PKC-α activity is regulated by Rack1–keratin interaction. Without keratins, desmosomes assemble but are endocytosed at accelerated rates, rendering epithelial sheets highly susceptible to mechanical stress. Re-expression of the keratin pair K5/14, inhibition of PKC-α activity, or blocking of endocytosis reconstituted both desmosome localization at the plasma membrane and epithelial adhesion. Our findings identify a hitherto unknown mechanism by which keratins control intercellular adhesion, with potential implications for tumor invasion and keratinopathies, settings in which diminished cell adhesion facilitates tissue fragility and neoplastic growth.     

Thermal enhancement of the effectiveness of gamma radiation for induction of reproductive death in cultured mammalian cells.

The induction by gamma radiation of reproductive death in cultured cells derived from a rat ureter carcinoma (RUC-2) and from Chinese-hamster lung tissue (CH-V79) was shown to be enhanced by hyperthermic treatments at 41, 43 and 45 degrees C. The degree of enhancement was found to depend on the line of cells studied, the temperature employed and the level of damage considered. The influence of accumulating sublethal damage was decreased by hyperthermia, and the final slope of the radiation survival curve was increased. The degree of enhancement of lethal damage was found to depend on the time interval between the heat treatment and irradiation, especially at 41 degrees C.     

A Comprehensive Review of Animal Models for Coronaviruses: SARS-CoV-2, SARS-CoV,and MERS-CoV

The recent outbreak of coronavirus disease(COVID-19) caused by the novel severe acute respiratory syndrome coronavirus 2(SARS-CoV-2) has already affected a large population of the world. SARS-CoV-2 belongs to the same family of severe acute respiratory syndrome coronavirus(SARS-CoV) and Middle East respiratory syndrome coronavirus(MERSCoV). COVID-19 has a complex pathology involving severe acute respiratory infection, hyper-immune response, and coagulopathy. At present, there is no therapeutic drug or vaccine approved for the disease. There is an urgent need for an ideal animal model that can reflect clinical symptoms and underlying etiopathogenesis similar to COVID-19 patients which can be further used for evaluation of underlying mechanisms, potential vaccines, and therapeutic strategies. The current review provides a paramount insight into the available animal models of SARS-CoV-2, SARS-CoV, and MERS-CoV for the management of the diseases.