Recent advances in cellular effects of fluoride: an update on its signalling pathway and targeted therapeutic approaches

Molecular Biology Reports - Fluoride is a natural element essential in minute quantities in human’s to maintain dental and skeletal health. However, the disease fluorosis manifests itself due...     

Quaternary variations in the structural assembly of N‐acetylglucosamine‐6‐phosphate deacetylase from Pasteurella multocida

N‐acetylglucosamine 6‐phosphate deacetylase (NagA) catalyzes the conversion of N‐acetylglucosamine‐6‐phosphate to glucosamine‐6‐phosphate in amino sugar catabolism. This conversion is an essential step in the catabolism of sialic acid in several pathogenic bacteria, including Pasteurella multocida, and thus NagA is identified as a potential drug target. Here, we report the unique structural features of NagA from P. multocida (PmNagA) resolved to 1.95 Å. PmNagA displays an altered quaternary architecture with unique interface interactions compared to its close homolog, the Escherichia coli NagA (EcNagA). We confirmed that the altered quaternary structure is not a crystallographic artifact using single particle electron cryo‐microscopy. Analysis of the determined crystal structure reveals a set of hot‐spot residues involved in novel interactions at the dimer‐dimer interface. PmNagA binds to one Zn²⁺ ion in the active site and demonstrates kinetic parameters comparable to other bacterial homologs. Kinetic studies reveal that at high substrate concentrations (~10‐fold the K_M), the tetrameric PmNagA displays hysteresis similar to its distant neighbor, the dimeric Staphylococcus aureus NagA (SaNagA). Our findings provide key information on structural and functional properties of NagA in P. multocida that could be utilized to design novel antibacterials.     

Proteolytic activity and nitrogen transfer in maize seeds during imbibition

Ethanol-soluble and insoluble nitrogen and protease activity in maize seeds during imbibition period of 6 to 60 h at 30 ± 2 °C were determined both in light and in the dark. In light, soluble and insoluble nitrogen in the embryo were similar to that in the dark. But the increase in soluble nitrogen in the endosperm up to 38 h was higher in light than in the dark. Decrease in insoluble nitrogen was correlated with increase in soluble nitrogen, the level always being higher in the dark. Light increased protease activity also in the endosperm. Among various light qualities, red light was most effective in inducing proteolysis, and loss of nitrogen from the endosperm. Further, the growth and organic nitrogen of primary leaves from seedlings raised from light pretreated seeds were better than those from dark pretreated ones.     

Alteration of pial vessel responses to blood pressure changes in rats after hypoxia

Previous studies in newborn lamb have shown impairment of cerebral blood flow autoregulation after hypoxia followed by reoxygenation. The present study was done to see if such a phenomenon existed in the adult rat and if it could be demonstrated at the level of the pial arterioles. Using an open cranial window preparation, we assessed the changes in pial vessel diameter during blood pressure alterations induced by hemorrhage and reinfusion of blood, before and after 30 s of hypoxia, in 15 male Sprague-Dawley rats. Mean diameters of pial arteries in the study group of rats were 128 +/- 54 microns before hypoxia and 141 +/- 61 microns after normoxia following hypoxia. The corresponding diameters in rats serving as time controls were 136 +/- 52 and 138 +/- 52 microns. Slopes of pial vessel diameters as a function of mean arterial blood pressures decreased significantly (p less than 0.05) after hypoxia from -0.86 +/- 0.45 to 0.03 +/- 0.66 (mean +/- SD). In the control rats not subjected to hypoxia, the slopes remained unchanged over a similar time period (-0.60 +/- 0.16 and -0.42 +/- 0.19). The negative slopes indicate that pial vessels dilate during hypotension and constrict during hypertension. Such vascular responses may play a role in autoregulation of cerebral blood flow. We found that a relatively brief period of hypoxia can cause a long-lasting impairment of vascular responses even after restoration of normoxia. These findings are consistent with a previous report of persistent impairment of cerebral blood flow autoregulation after a brief period of hypoxia.     

A Rapid Method for Isolating Mutants of Bacillus subtilis Producing Increased or Decreased Amounts of the Antibiotic, Mycobacillin

S ummary : A simple, rapid and efficient technique is described for the isolation of mutants of Bacillus subtilis in which the synthesis of mycobacillin, an antifungal antibiotic, is blocked. Suspensions of a chosen culture were subjected to ultraviolet radiation and then plated; colonies failing to produce antibiotic were located by flooding the incubated plates with agar seeded with sensitive fungi such as Candida albicans and Aspergillus niger . The method is also applicable for the isolation of high potency strains.     

Identification of a QTL for Adipocyte Volume and of Shared Genetic Effects with Aspartate Aminotransferase

Plasma levels of aspartate aminotransferase (AST), a liver enzyme, are elevated in patients with visceral obesity. This study examined whether adipocyte volume is under the influence of genetic factors and evaluated its genetic correlations with AST. Fasting plasma levels of 344 pedigreed baboons from the Southwest National Primate Research Center in San Antonio, TX, USA, were assayed for AST. Adipocyte volume was measured using biopsies of omental adipose tissue. Adipocyte volume, body weight, and plasma AST were heritable. Genetic correlations between the measured adiposity-related phenotypes and AST were significant. A quantitative trait locus (LOD score 3.2) for adipocyte volume was identified on the baboon homolog of human chromosome 6 near marker D6S1028. These results suggest that omental adipocyte volume is under genetic regulation and that shared genetic factors influence adiposity-associated traits and AST.     

Separation of Reticuloendotheliosis Virus from Avian Tumor Viruses

Velocity sedimentation and isopycnic density gradient centrifugation indicate that reticuloendotheliosis virus has a different mass and buoyant density than members of the avian tumor virus group. The group-specific antigen of the avian tumor virus group was not detected in concentrated and purified reticuloendotheliosis virus preparations.