Changes in the thymus of peripubertal rats induced by centrally applied somatostatin-28

The aim of this study was to investigate the effects of centrally applied somatostatin-28 on morphometric characteristics of the thymus, the thymocyte subpopulations, as well as, on apoptosis and phases of cell cycle in thymocytes. For this purpose, peripubertal male rats were cannulated intracerebroventriculary and treated with repeated, nanomolar concentrations of somatostatin-28 (experimental group) or saline (control group). Animals were sacrificed and their thymuses were used for the analysis of thymocyte subpopulations, cell cycle and apoptosis by flow cytometry and for the evaluation of morphometric parameters by stereological analysis. Our results showed that somatostatin-28 caused decrease of the thymic mass and volume, as well as total thymocytes number. Stereological analysis revealed volume decrease of thymic cortex and medulla accompanied with cellularity decrease. Somatostatin in the deeper cortex decreased the number of thymocytes, per volume unit, while in outer cortex raised their number. A significant increase in the percentage of double-negative and both single-positive thymocyte subpopulations, in parallel with a diminished percentage of double-positive cells was found. The cellularity of double-positive and single-positive thymocyte subpopulations was decreased. Somatostatin-28 treatment augmented the percentage of apoptotic cells, while the percentage of the cells represented in phases of cell cycle was reduced. These results suggest that somatostatin-28 induce thymus hypotrophy as result of decreasing cortex and medulla volume and cellularity. Changes in the percentage and cellularity of thymocyte subpopulations and numerical density of thymocytes in outer and deeper cortex, indicate that somatostatin-28 evoked disturbance in transition of double-negative to double-positive thymocytes.     

Physiological and biochemical characterization of AnNitA, the Aspergillus nidulans high-affinity nitrite transporter

High-affinity nitrite influx into mycelia of Aspergillus nidulans has been characterized by use of (13)NO(2)(-), giving average K(m) and V(max) values of 48 ± 8 μM and 228 ± 49 nmol mg(-1) dry weight (DW) h(-1), respectively. Kinetic analysis of a plot that included an additional large number of low-concentration fluxes gave an excellent monophasic fit (r(2) = 0.96), with no indication of sigmoidal kinetics. Two-dimensional (2D) and three-dimensional (3D) models of AnNitA are presented, and the possible roles of conserved asparagine residues N122 (transmembrane domain 3 ]Tm 3]), N173 (Tm 4), N214 (Tm 5), and N246 (Tm 6) are discussed.     

Regulation of inducible nitric oxide synthase activity/expression in rat hearts from ghrelin-treated rats

The purpose of this study was to examine the effects of ghrelin on protein kinase B (Akt) and mitogen-activated protein kinase p42/44 (ERK1/2) activation as well as ghrelin effects on inducible nitric oxide (NO) synthase (iNOS; for gene Nos2) activity/expression in rat hearts. Male Wistar rats were treated with ghrelin (0.3 nmol/5 μl) or an equal volume of phosphate-buffered saline, injected every 24 h into the lateral cerebral ventricle for 5 days and 2 h after the last treatment the animals were sacrificed. Serum NO, L-arginine (L-Arg), and arginase activity were measured spectrophotometrically. For phosphorylation of Akt, ERK1/2, and iNOS protein expression, Western blot method was used. The expression of Nos2 mRNA was measured by the quantitative real-time polymerase chain reaction (qRT-PCR). Treatment with ghrelin significantly increased NO production in serum by 1.4-fold compared with control. The concentration of L-Arg was significantly higher in ghrelin-treated rats than in control while arginase activity was significantly lower in ghrelin-treated than in control hearts. Ghrelin treatment increased phosphorylation of Akt by 1.9-fold and ERK1/2 by 1.6-fold and increased iNOS expression by 2.5-fold compared with control. In addition, ghrelin treatment increased Nos2 gene expression by 2.2-fold as determined by qRT-PCR. These results indicate that ghrelin regulation of iNOS expression/activity is mediated via Akt/ERK1/2 signaling pathway. These results may be relevant to understanding molecular mechanisms underlying direct cardiovascular actions of ghrelin.     

Immobilization of lipase from Candida rugosa on Sepabeads(®): the effect of lipase oxidation by periodates

The objective of this paper was the investigation of a suitable Sepabeads^? support and method for immobilization of lipase from Candida rugosa. Three different supports were used, two with amino groups, (Sepabeads^? EC-EA and Sepabeads^? EC-HA), differing in spacer length (two and six carbons, respectively) and one with epoxy group (Sepabeads^? EC-EP). Lipase immobilization was carried out by two conventional methods (via epoxy groups and via glutaraldehyde), and with periodate method for modification of lipase. The results of activity assays showed that lipase retained 94.8% or 87.6% of activity after immobilization via epoxy groups or with periodate method, respectively, while glutaraldehyde method was inferior with only 12.7% of retention. The immobilization of lipase, previously modified by periodate oxidation, via amino groups has proven to be more efficient than direct immobilization of lipase via epoxy groups. In such a way immobilized enzyme exhibited higher activity at high reaction temperatures and higher thermal stability.     

Immobilization of lipase from Candida rugosa on Eupergit C supports by covalent attachment

The present study compares the results of three different covalent immobilization methods employed for immobilization of lipase from Candida rugosa on Eupergit^® C supports with respect to enzyme loadings, activities and coupling yields. It seems that method yielding the highest activity retention of 43.3% is based on coupling lipase via its carbohydrate moiety previously modified by periodate oxidation. Study of thermal deactivation kinetics at three temperatures (37, 50 and 75 °C) revealed that the immobilization method also produces an appreciable stabilization of the biocatalyst, changing its thermal deactivation profile. By comparison of the t_1/2 values obtained at 75 °C, it can be concluded that the lipase immobilized via carbohydrate moiety was almost 2-fold more stable than conventionally immobilized one and 18-fold than free lipase. The immobilization procedure developed is quite simple, and easily reproduced, and provides a promising solution for application of lipase in aqueous and microaqueous reaction system.     

Apatite formation on nanomaterial calcium phosphate/poly-DL-lactide-co-glycolide in simulated body fluid

Simulated body fluid (SBF) is an artificial fluid which has ionic composition and ionic concentration similar to human blood plasma. Purpose: This paper compares the interaction between the nanomaterial containing calcium phosphate/poly-dl-lactide-co-glycolide (N-CP/PLGA) and SBF, in order to investigate whether and to what extent inorganic ionic composition of human blood plasma leads to the aforementioned changes in the material. Methods: N-CP/PLGA was incubated for 1, 2, 3, and 5 weeks in SBF. The surface of the material was analyzed on SEM-EDS and FTIR spectrometer, while SBF was subjected to pH and electrical conductivity measurement. Results: Our results indicate that dissolution of the polymer component of the material N-CP/PLGA and precipitation of the material similar to hydroxyapatite on its surface are based on the morphologic changes seen in this material. Conclusions: The mechanism of the apatite formation on the bioceramic surface was intensively studied and was considered crucial in designing the new biomaterials. The results obtained in this work indicate that N-CP/PLGA may be a good candidate for application to bone regeneration.