Reversible change in thiol redox status of the insulin receptor alpha-subunit in intact cells

In this study, we used maleimidobutyrylbiocytin to examine possible alteration that may occur in the redox state of the insulin receptor (IR) sulfhydryl groups in response to reduced glutathione (GSH) or N-acetyl-L-cysteine (NAC). Short-term treatment of intact cells expressing large numbers of IR with GSH or NAC led to a rapid and reversible reduction of IR alpha-subunit disulfides, without affecting the receptor beta-subunit thiol reactivity. The overall integrity of the oligomeric structure of IR was maintained, indicating that neither class I nor class II disulfides were targeted by these agents. Similar findings were obtained in cells transfected with IR mutants lacking cysteine524, one of the class I disulfides that link the two IR alpha-subunits. Membrane-associated thiols did not participate in GSH- or NAC-mediated reduction of IR alpha-subunit disulfides. No difference in insulin binding was observed in GSH-treated cells; however, ligand-mediated increases in IR autophosphorylation, tyrosine phosphorylation of cellular substrates, and dual phosphorylation of the downstream target mitogen-activated protein kinase were inhibited at concentrations of GSH (10 mM or greater) that yielded a significant increase in IR alpha-subunit thiol reactivity. GSH did not affect IR signaling in the absence of insulin. Our results provide the first evidence that the IR alpha-subunit contains a select group of disulfides whose redox status can be rapidly altered by the reducing agents GSH and NAC.     

Successful immunotherapy with matrix metalloproteinase-derived peptides in adjuvant arthritis depends on the timing of peptide administration

We have recently found that matrix metalloproteinases (MMPs) are targets for T-cell and B-cell reactivity in experimental arthritis. In the present article, we investigate whether modulation of MMP-specific T-cell responses could influence the course of adjuvant arthritis (AA). Lewis rats were treated nasally with MMP peptides prior to or after AA induction. Administration of the MMP-10 or the MMP-16 peptide prior to AA induction reduced the arthritic symptoms. In contrast, administration of the MMP-10 peptide after AA induction aggravated the arthritic symptoms. The present study shows the possible usefulness of MMP peptides for immunotherapy. However, a clear understanding of proper timing of peptide administration is crucial for the development of such therapies.     

A comparison of the immune response induced by DNA or by an inactivated vaccine against tick-borne encephalitis

BALB/c mice were immunized with recombinant plasmid DNA pSVK3-ENS1 and pcDNAI-NS3 containing, respectively, genes E-NS1 and NS3 of tick-borne encephalitis (TBE) virus. Antibodies to TBE virus proteins were detected in the blood sera of the immunized animals by the method of the enzyme immunoassay. Though the titers of virus-specific antibodies in the sera of mice immunized with protein vaccines exceeded those registered after immunization with DNA vaccines, essential protective immunity was observed after the use of both vaccines.     

The circadian dynamics of the attacks of the synanthropic population of Culex pipiens molestus mosquitoes at the Staraia Russa Health Resort

The diurnal biting activity of Culex pipiens molestus in rooms of populated houses was studied in August 1998. The highest activity was recorded at 3.00-4.00 a. m., when 25-30 females attacked one volunteer rer 10 minutes.     

Effects of medium viscosity on kinetics of the enzymatic reaction catalyzed by bacterial RNase

Effects of medium viscosity on kinetic parameters of poly(U) hydrolysis catalyzed by RNase from Bac. intermedius 7P (binase) were studied in solutions of sucrose (4-50 wt. %) and glycerol (35-62 wt. %) in Tris--sodium acetate buffer (pH 7.5) at 25 degreesC. The rate constant of reaction kcat was practically unchanged over a wide range of viscosities (1-15 cP for sucrose and 2.5-3 cP for glycerol). In glycerol solutions, kcat slightly increased with viscosity increase from 4 to 10 cP. Addition of NaCl to the buffer medium resulted in an inhibitory effect of Na+ on kcat, prevented by 50% sucrose or 60% glycerol. It is concluded that binase-catalyzed poly(U) cleavage occurs through a "tense"-substrate mechanism, similarly to reactions catalyzed by alpha-chymotrypsin, trypsin, and laccase.     

Granule-bound starch synthase: structure, function, and phylogenetic utility

Interest in the use of low-copy nuclear genes for phylogenetic analyses of plants has grown rapidly, because highly repetitive genes such as those commonly used are limited in number. Furthermore, because low- copy genes are subject to different evolutionary processes than are plastid genes or highly repetitive nuclear markers, they provide a valuable source of independent phylogenetic evidence. The gene for granule-bound starch synthase (GBSSI or waxy) exists in a single copy in nearly all plants examined so far. Our study of GBSSI had three parts: (1) Amino acid sequences were compared across a broad taxonomic range, including grasses, four dicotyledons, and the microbial homologs of GBSSI. Inferred structural information was used to aid in the alignment of these very divergent sequences. The informed alignments highlight amino acids that are conserved across all sequences, and demonstrate that structural motifs can be highly conserved in spite of marked divergence in amino acid sequence. (2) Maximum-likelihood (ML) analyses were used to examine exon sequence evolution throughout grasses. Differences in probabilities among substitution types and marked among-site rate variation contributed to the observed pattern of variation. Of the parameters examined in our set of likelihood models, the inclusion of among-site rate variation following a gamma distribution caused the greatest improvement in likelihood score. (3) We performed cladistic parsimony analyses of GBSSI sequences throughout grasses, within tribes, and within genera to examine the phylogenetic utility of the gene. Introns provide useful information among very closely related species, but quickly become difficult to align among more divergent taxa. Exons are variable enough to provide extensive resolution within the family, but with low bootstrap support. The combined results of amino acid sequence comparisons, maximum-likelihood analyses, and phylogenetic studies underscore factors that might affect phylogenetic reconstruction. In this case, accommodation of the variable rate of evolution among sites might be the first step in maximizing the phylogenetic utility of GBSSI.      

A study of the catalytic properties of the nitrile hydratase immobilized on aluminum oxides and carbon-containing adsorbents

The nitrile hydratase isolated from Rhodococcus ruber strain gt1, displaying a high nitrile hydratase activity, was immobilized on unmodified aluminum oxides and carbon-containing adsorbents, including the carbon support Sibunit. The activity and operational stability of the immobilized nitrile hydratase were studied in the reaction of acrylonitrile transformation into acrylamide. It was demonstrated that an increase in the carbon content in the support led to an increase in the amount of adsorbed enzyme and, concurrently, to a decrease in its activity. The nitrile hydratase immobilized on Sibunit and carbon-containing aluminum α-oxide having a “crust” structure displayed the highest operational stability in acrylonitrile hydration. It was shown that the thermostability of adsorbed nitrile hydratase increased by one order of magnitude.     

Effect of Pristine Multi-Walled Carbon Nanotubes on Formation and Degradation of Bacterial Biofilms

Microbiology - The effect of pristine multi-walled carbon nanotubes (MWCNT) on the biofilms of gram-negative bacteria, typical members of the activated sludge community, and gram-positive...