Impact of host proteases on reovirus infection in the respiratory tract

Virion uncoating is an essential early event in reovirus infection. In natural enteric infections, rapid proteolytic uncoating of virions is mediated by pancreatic serine proteases. The proteases that promote reovirus disassembly and cell entry in the respiratory tract remain unknown. In this report, we show that endogenous respiratory and inflammatory proteases can promote reovirus infection in vitro and that preexisting inflammation augments in vivo infection in the murine respiratory tract.     

The PP-fold solution structure of human polypeptide YY and human PYY3-36 as determined by NMR

PYY3-36 is a biopharmaceutical antiobesity agent under development as well as an endogenous satiety hormone, which is generated by dipeptidyl peptidase-IV digestion of polypetide YY (PYY), and in contrast to the parent hormone, PYY is highly selective for the Y2 versus the Y1 receptor. NMR analysis revealed a highly ordered, back-folded structure for human PYY in aqueous solution similar to the classical PP-fold structure of pancreatic polypeptide. The NMR analysis of PYY3-36 also showed a folded structure resembling a PP-fold, which however was characterized by far fewer long distance NOEs than the PP-fold observed in the full-length peptide. This suggests that either a conformational change has occurred in the N-terminal segment of PYY3-36 or that this segments is characterized by larger dynamics. The study supports the notion that the PP-fold is crucial for establishing simultaneous interactions with two subsites in the receptor for binding of, respectively, the N- and C-terminal ends of PYY. The Y2 receptor only requires recognition of the C-terminal segment of the molecule as displayed by the Y2 selective PYY3-36.     

PYY(3-36) reduces food intake and body weight and improves insulin sensitivity in rodent models of diet-induced obesity

The gut hormone peptide YY (PYY) was recently proposed to comprise an endogenous satiety factor. We have studied acute anorectic functions of PYY(3-36) in mice and rats, as well as metabolic effects of chronic PYY(3-36) administration to diet-induced obese (DIO) mice and rats. A single intraperitoneal injection of PYY(3-36) inhibited food intake in mice, but not in rats. We next investigated the effects of increasing doses (100, 300, and 1,000 microg.kg-1.day-1) of PYY(3-36) administered subcutaneously via osmotic minipumps on food intake and body weight in DIO C57BL/6J mice. Whereas only the highest dose (1,000 microg.kg-1.day-1) of PYY(3-36) significantly reduced food intake over the first 3 days, body weight gain was dose dependently reduced, and on day 28 the group treated with 1,000 microg.kg-1.day-1 PYY(3-36) weighed approximately 10% less than the vehicle-treated group. Mesenteric, epididymal, retroperitoneal, and inguinal fat pad weight was dose dependently reduced. Subcutaneous administration of PYY(3-36) (250 and 1,000 microg.kg-1.day-1) for 28 days reduced body weight and improved glycemic control in glucose-intolerant DIO rats. Neither 250 nor 1,000 microg/kg PYY(3-36) elicited a conditioned taste aversion in male rats.     

Cavitation caused by mechanical heart valve prostheses--a review

Heart valve dysfunction often necessitates surgical implantation of a mechanical heart valve (MHV). Although implantation of a MHV is a life-saving procedure, the patient still faces potentially complications such as thromboembolic events and material failure. These complications may be caused by cavitation, which can occur during valve closure. Cavitation is an erosive phenomenon that can be generated in fluids when the pressure locally drops below the vapor pressure. This paper reviews the literature on cavitation and MHVs and particular features of the valve and closing conditions that potentially increase the intensity of cavitation. Techniques for detecting cavitation will be discussed. Of these, an acoustic approach will be emphasized, since it is currently the only technique able to detect and quantify cavitation in vivo.     

Cellular changes in early development of regenerating thin cell layer-explants of rapeseed analyzed by light and electron microscopy

Cellular changes in thin cell layer (TCL) explants of stem origin of Brassica napus L. cv. Vega were studied from 0 to 15 day by light and transmission electron microscopy. Apical and basal ends of the old explants were analysed separately. Quantitative and qualitative analyses showed that during the first culture day the parenchyma cells enlarged significantly as did the cytoplasm/vacuole ratio. The cytoplasm contained increased rough endoplasmic reticulum (RER), polysomes and dictyosomes associated with both coated and uncoated vesicles. The cell enlargement continued during the first 5 days of culture. The structural organization of the cell wall became somewhat loose and inhomogeneous. Parenchyma in the basal end divided frequently, resulting in several centres of division, while cell division in apical cells was less frequent and cells there remained enlarged. Starch accumulation started on the first day and increased until the third day. i. e. until cell divisions became more frequent. The starch content of dividing cells gradually decreased and starch was almost totally lacking in 15-day-old explants. Starch grains remained numerous, however, in the large non-dividing apical cells, except in those cells adjacent to the medium. Cell divisions started close to medium in explants containing vascular tissue, but closer to the epidermis in the explants without vascular tissue.
The results show how rapid (one day) striking changes in the cells take place and suggest that optimal hormone concentration and intertissue relations between epidermis and parenchyma and between parenchyma and vascular tissues as well as intercellular relations among parenchyma cells determine the first cell division sites and planes in the explants. Although the cells change from elongated to spheroid, their original polarity remains as evidenced by the formation of more numerous basal shoot primordia than in apical shoot primordia.     

Evidence for a novel glycinamide ribonucleotide transformylase in Escherichia coli.

We demonstrate here that Escherichia coli synthesizes two different glycinamide ribonucleotide (GAR) transformylases, both catalyzing the third step in the purine biosynthetic pathway. One is coded for by the previously described purN gene (GAR transformylase N), and a second, hitherto unknown, enzyme is encoded by the purT gene (GAR transformylase T). Mutants defective in the synthesis of the purN- and the purT-encoded enzymes were isolated. Only strains defective in both genes require an exogenous purine source for growth. Our results suggest that both enzymes may function to ensure normal purine biosynthesis. Determination of GAR transformylase T activity in vitro required formate as the C1 donor. Growth of purN mutants was inhibited by glycine. Under these conditions GAR accumulated. Addition of purine compounds or formate prevented growth inhibition. The regulation of the level of GAR transformylase T is controlled by the PurR protein and hypoxanthine.