Effect of high level section of the spinal cord on the cyclic AMP system in rat liver

The effect of high level section of the spinal cord upon the hepatic cyclic AMP system was investigated in the rat. We report that transection of the spinal cord dramatically decreases the basal level of cyclic AMP from 0.88 nmol/g liver to 0.36 nmol/g at 1 h and to 0.20 nmol/g at 4 h. This was not due to increased activity of cyclic AMP phosphodiesterase or to decreased activity of basal adenylate cyclase. The sensitivity of adenylate cyclase to its usual effectors in vitro was not impaired. It is proposed that the lowering of liver cyclic AMP below its basal level after high level section of the spinal cord is due to decreased levels of hepatic catecholamines and/or plasma glucagon.     

Immunity indices during the vaccinal therapy of protracted forms of dysentery in children

The results obtained in the study of the dynamics of systemic and local immunity characteristics in children with prolonged and chronic dysentery under the influence of vaccinal therapy are presented. The vaccine, containing soluble antigenic complexes isolated from Shigella sonnei cells by disintegration with hydroxylamine, was introduced intrarectally in doses of 2-4 mg. The course of treatment consisted of 5-6 administrations. The vaccinal therapy resulted in an increase in the level of immunoglobulins and the titer of specific antibodies, particularly IgA, in sera and fecal filtrates. These data coincided with an increase in the number of IgA-producing cells in bioptic samples of the mucous membrane of the large intestine. The vaccinal therapy contributed to the cessation of the release of bacteria in 82.5% of the patients.     

Characterization of the Munc13-calmodulin interaction by photoaffinity labeling

Sensing of and response to transient increases in the residual presynaptic Ca2+ levels are important adaptive mechanisms that define the short-term plasticity characteristics of neurons. Due to their essential function in synaptic vesicle priming and in the modulation of synaptic strength, Munc13 proteins have emerged as key regulators of these adaptive mechanisms. Indeed, Munc13-1 and ubMunc13-2 contain a conserved calmodulin (CaM) binding site and the Ca2+ -dependent interaction of these Munc13 isoforms with CaM constitutes a molecular mechanism that transduces residual Ca2+ signaling to the synaptic exocytotic machinery. Here, we used Munc13-derived model peptides in photoaffinity labeling (PAL) experiments to demonstrate the stoichiometric and Ca2+ -dependent CaM binding of the other members of the Munc13 family, bMunc13-2 and Munc13-3, via structurally distinct non-conserved binding sites. A PAL-based Ca2+ titration assay revealed that all Munc13 isoforms can form a complex with CaM already at low Ca2+ concentrations just above resting levels, underscoring the Ca2+ sensor/effector function of this interaction in short-term synaptic plasticity phenomena.     

Morphological variation of the <Emphasis Type="Italic">Caloneis schumanniana</Emphasis> species complex (Bacillariophyceae) from different environmental conditions in North American streams

The aim of the present study is to test by molecular DNA data a hypothesis concerned to speciation by allopatry occurring in Mimagoniates microlepis, associated to the Serra do Mar mountain chain (Atlantic Rain Forest hotspot) in Southern Brazil. Overall genetic diversity and mean genetic distances were high, demonstrating both good conservation status and genetic differentiation. Neighbor-Joining (NJ) and parsimony analyses, together with population genetic parameters (Φ_ST, N_m, G_ST, and AMOVA), identified two main vicariant genetic/evolutionary stocks dividing the upper Iguaçu River samples from those of the coastal plains. Other well-supported intrinsic monophyletic clades were also identified, suggesting fast and remarkable speciation processes. In addition, the genetic, evolutionary, geographic, and phylogeographic evidences reinforced an occurring species complex. Moreover, these evolutionarily significant units (species complex) seem to be inside four natural biogeographic areas. Thus, the genesis and evolution of the Serra do Mar complex might be associated to diversification processes of M. microlepis. Such a consideration suggests that the areas including the upper Iguaçu River and the coastal plains of the states of São Paulo, Paraná, and Santa Catarina require distinct conservation policies involving one of the global biodiversity hotspots, namely, the Brazilian Atlantic Rain Forest.     

Comparative Pathogenesis of an Avian H5N2 and a Swine H1N1 Influenza Virus in Pigs

Pigs are considered intermediate hosts for the transmission of avian influenza viruses (AIVs) to humans but the basic organ pathogenesis of AIVs in pigs has been barely studied. We have used 42 four-week-old influenza naive pigs and two different inoculation routes (intranasal and intratracheal) to compare the pathogenesis of a low pathogenic (LP) H5N2 AIV with that of an H1N1 swine influenza virus. The respiratory tract and selected extra-respiratory tissues were examined for virus replication by titration, immunofluorescence and RT-PCR throughout the course of infection. Both viruses caused a productive infection of the entire respiratory tract and epithelial cells in the lungs were the major target. Compared to the swine virus, the AIV produced lower virus titers and fewer antigen positive cells at all levels of the respiratory tract. The respiratory part of the nasal mucosa in particular showed only rare AIV positive cells and this was associated with reduced nasal shedding of the avian compared to the swine virus. The titers and distribution of the AIV varied extremely between individual pigs and were strongly affected by the route of inoculation. Gross lung lesions and clinical signs were milder with the avian than with the swine virus, corresponding with lower viral loads in the lungs. The brainstem was the single extra-respiratory tissue found positive for virus and viral RNA with both viruses. Our data do not reject the theory of the pig as an intermediate host for AIVs, but they suggest that AIVs need to undergo genetic changes to establish full replication potential in pigs. From a biomedical perspective, experimental LP H5 AIV infection of pigs may be useful to examine heterologous protection provided by H5 vaccines or other immunization strategies, as well as for further studies on the molecular pathogenesis and neurotropism of AIVs in mammals.     

Utility of surface-supported bilayers in studies of transmembrane helix dimerization

This review focuses on the methods that are available to study transmembrane (TM) helix dimerization in membrane-like environments (either bacterial membranes or lipid bilayers, as mimics of the eukaryotic cellular membrane), with an emphasis on the utility of surface-supported bilayers in such studies.     

Glycan structures and antiviral effect of the structural subunit RvH2 of Rapana hemocyanin

Molluscan hemocyanins are very large biological macromolecules and they act as oxygen-transporting glycoproteins. Most of them are glycoproteins with molecular mass around 9000 kDa. The oligosaccharide structures of the structural subunit RvH2 of Rapana venosa hemocyanin (RvH) were studied by sequence analysis of glycans using MALDI-TOF-MS and tandem mass spectrometry on a Q-Trap mass spectrometer after enzymatical liberation of the N-glycans from the polypeptides. Our study revealed a highly heterogeneous mixture of glycans of the compositions Hex_0-9 HexNAc_2-4 Hex_0-3 Pent_0-3 Fuc_0-3. A novel type of N-glycan, with an internal fucose residue connecting one GalNAc(β1-2) and one hexuronic acid, was detected, as also occurs in subunit RvH1. A glycan with the same structure but with two deoxyhexose residues was observed as a doubly charged ion. Antiviral effects of the native molecules of RvH and also of Helix lucorum hemocyanin (HlH), of their structural subunits, and of the glycosylated functional unit RvH2-e and the non-glycosylated unit RvH2-c on HSV virus type 1 were investigated. Only glycosylated FU RvH2-e exhibits this antiviral activity. The carbohydrate chains of the FU are likely to interact with specific regions of glycoproteins of HSV, through van der Waals interactions in general or with certain amino acid residues in particular. Several clusters of these residues can be identified on the surface of RvH2-e.     

<Emphasis Type="Italic">In vitro</Emphasis> culture of <Emphasis Type="Italic">Hypericum rumeliacum</Emphasis> Boiss. and production of phenolics and flavonoids

The Balkan endemic species, Hypericum rumeliacum, Guttiferae was introduced in vitro for the first time with the aim to study the type of morphogenetic response to plant growth regulators and ability to produce phenolics and flavonoid compounds. The morphoregulatory effect of 2,4-dichlorophenoxyacetic acid (2,4-D), 1-naphtaleneacetic acid (NAA), 6-benzyladenine (BA) and combination of BA with NAA in Murashige–Skoog's basal medium on leaf lamina, internode stem segment, stem node and root cuttings was studied. Histological analysis of the structures regenerated from the primary explants proved the presence of both, embryoids and meristemoids. The node explants cultivated on BA-supplemented medium were the most favourable for regeneration through meristemoids. Therefore a double-stage culture approach, allowing an effective multiplication of large quantities of plant shoots in vitro along with maintenance of the biosynthetic capacity of the culture was developed. It comprised one subculture of three-nodal stem explants derived from the stock shoot cultures on MS medium supplemented with 0.2 mg/l BA followed by subculture of the induced multiple shoots on cytokinin-free MS medium. Determination of the total phenolics and flavonoids showed that the decrease of the levels of these secondary metabolites is transitional, as the exclusionof BA from the medium resulted in an increase of their total content.     

Development of an HPLC method for the determination of nifedipine in human plasma by solid-phase extraction

Nifedipine, a dihydropyridine calcium channel antagonist, is widely used in the treatment of hypertension and other cardiovascular disorders. A selective, sensitive and accurate high-performance liquid chromatographic method has been developed, validated and applied for determination of nifedipine in human plasma samples. A series of studies were conducted in order to investigate the effects of mobile phase composition, buffer concentration, mobile phase pH and concentration of organic modifiers, and to develop a convenient and easy-to-use method for quantitative analysis of nifedipine. The method involves solid-phase extraction on C18 cartridges. The chromatographic separation was accomplished on a Lichrocart Lichrospher 60 RP selectB column with a mobile phase composed of 0.020 mol/L KH2PO4 (pH 4.8) and acetonitrile (42:58, v/v). UV detection was set at 240 nm. The calibration curve was linear in the concentration range of 5.0-200.0 ng/mL for nifedipine in plasma and the limit of quantification was 5.0 ng/mL.