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S Rybak

Publications and source records attributed to S Rybak.

11 recordsLinked to original sources
PubMed1999

Single-chain variable fragments selected on the 57-76 p21Ras neutralising epitope from phage antibody libraries recognise the parental protein.

Phage antibodies have been widely prospected as an alternative to the use of monoclonal antibodies prepared by traditional means. Many monoclonal antibodies prepared against peptides are able to recognise the native proteins from which they were derived. Here we show that the same is also true for phage antibodies. We have selected a number of single-chain variable fragments (scFv) from a large phage scFv library against a peptide from the switch region II of p21Ras. This peptide is known to reside in a mobile area of the native protein and is the epitope of a well characterised monoclonal antibody. Selected scFvs were able to recognise native p21Ras in both ELISA and Western blots, indicating that peptides are also likely to be very useful in selecting from phage antibody libraries.

Amino Acid Sequence↗
PubMed1998

Pretreatment with intraventricular aurintricarboxylic acid decreases infarct size by inhibiting apoptosis following transient global ischemia in gerbils.

The goal of this study was to determine whether aurintricarboxylic acid (ATA), an endonuclease inhibitor known to inhibit apoptosis, could ameliorate cell damage in a gerbil model of transient ischemia. Transient ischemia was induced in gerbils by bilateral carotid artery occlusion for a period of 5 minutes. Four micrograms of ATA was administered intraventricularly 1 hour before ischemia, and the brains were assessed histologically 1 week later to quantitate cell loss in the vulnerable CA-1 subsector of the hippocampus. In a separate set of experiments, 4 microg of ATA was administered intraventricularly 1 hour before ischemia and the brains were assessed for evidence of DNA fragmentation by the TUNEL method. There was only a 16% cell loss compared with nonischemic controls in animals pretreated with ATA that was significantly less (p < 0.05) than the 48% cell loss in animals pretreated with saline alone. TUNEL-positive cells were first evident at 3 days and were still present at 7 days subsequent to ischemia. Maximal staining occurred at 4 days. Pretreatment with ATA virtually eliminated TUNEL staining at 4 days. These results support the hypothesis that the delayed cell death secondary to transient ischemia is, in part, apoptotic. Furthermore, ATA afforded significant neuronal protection and prevented DNA fragmentation.

Animals↗
PubMed1996

Central and peripheral neurochemical alterations and immune effects of prenatal ethanol exposure in rats.

In contrast to the well known effects of prenatal ethanol exposure on the central nervous system, data about its peripheral effects are scarce. Here, Sprague Dawley rats were fed a liquid diet (gestational days 0-20) containing 36% ethanol-derived calories (EDCs, group H) or were pair-fed with 18% EDCs (group L) or 0% EDCs (group C). On postnatal day 20, one male and one female from each of 10 litters per group were killed. Norepinephrine (NE) was analyzed in the frontal cortex, spleen and thymus, and dopamine, 5-hydroxytryptamine (serotonin, 5-HT) and their metabolites 3,4-dihydroxyphenylacetic acid, homevanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) were analyzed in the striatum by high-performance liquid chromatography with electrochemical detection. Lymphocyte subpopulations in the spleen and thymus were also assessed in half of these litters. Significant decreases in splenic NE concentration were seen in both sexes of group H (males 27%, females 28%). Decreases in striatal 5-HT and 5-HIAA of group H subjects appeared to be sex specific (only females were significantly affected: 23% decrease in 5-HT, 37% decrease in 5-HIAA). Pronounced, dose-dependent reductions in T cell percentages were observed in both the thymus and spleen. Splenic CD8+ and CD4+ cell percentages were positively correlated with the splenic NE concentrations. It is concluded that the decreases seen in splenic T cell percentages subsequent to prenatal ethanol exposure may be caused, at least partially, by impaired noradrenergic control of this organ.

Animals↗
PubMed1983

Gangliosides stimulate neurite outgrowth and induce tubulin mRNA accumulation in neural cells.

Morphological changes observed in a somatic neurohybrid clonal cell line SB21B1 are accompanied by a 9 fold increase in the expression of mRNA sequences for tubulin 14 days following the addition of various brain gangliosides to the culture medium. Upon removal of gangliosides, the expression of the tubulin message is restored to near basal levels. Actin mRNA sequences expression is not changed under these experimental conditions. This report documents for the first time, the involvement of gangliosides in the regulation of cellular gene expression for tubulin sequences by a mechanism which may be distinct from that of dibutyryl cyclic-AMP.

Actins↗
PubMed1983

The interaction of gamma-aminobutiric acid with hydrated Ca2+ and Mg2+. A pseudopotential ab initio study.

As a continuation of a previous work we consider the interaction of Mg2+ and Ca2+ with a neurotransmitter, gamma-aminobutiric acid (GABA). The purpose is twofold, to determine if there is a direct interaction of Ca2+ with the amino acid, which could have some biological relevance, and to find out if such a hypothesis can account for the different role of Ca2+ and Mg2+ on the amino acid's release. We performed ab initio pseudopotential studies of the GABA-ion complex in the presence of the first hydration shell around the interaction's region. We calculated the interaction energy of the hydrated complex by means of a many-body expansion up to three-body terms. We found out that the three-body terms in systems involving the divalent ion have a considerable value and seems to be of a different character for Mg2+ and Ca2+. We found out that the three-body terms are responsible for the observed difference between the coordination properties of Mg2+ and Ca2+ and can lead to a difference in the aminoacid interaction with each ion. The hypothesis of a gamma-aminobutiric acid-Ca2+ complex, that facilitates the aminoacid release has been substantiated. The reasons for the different effect of Ca2+ and Mg2+ has been envisaged but not clearly established.

Calcium↗
PubMed1983

Biphasic regulation by dibutyryl cyclic AMP of tubulin and actin mRNA levels in neuroblastoma cells.

Blot hybridization analysis that used labeled tubulin cDNA probes revealed that N6,O2'-dibutyryladenosine 3',5'-cyclic monophosphate [dibutyryl cyclic AMP (Bt2cAMP)] initially increases and later decreases the level of tubulin mRNA in a neuroblastoma-glioma hybrid cell line as well as in the parent cells. A significant increase in tubulin mRNA sequences is already evident 1 hr after the addition of Bt2cAMP to the neuroblastoma cells, and a maximal induction of 2-fold is seen after 12 hr. Continued treatment with Bt2cAMP for 4 days results in a down-regulation of the initial tubulin mRNA level independently of cell density. In the glioma cells Bt2cAMP also rapidly increases the level of tubulin mRNA sequences, reaching a maximum within 6 hr. However, in these cells the subsequent decrease in tubulin mRNA content depends on the culture's phase of growth: cells at the logarithmic growth phase do not down-regulate the tubulin mRNA content even after prolonged treatment with Bt2cAMP, whereas confluent cells do. The hybrid cell line manifests intermediate characteristics in Bt2cAMP regulation of tubulin mRNA level. The time course of induction and down-regulation of tubulin mRNA content observed in the hybrid cells is similar to that of the parent neuroblastoma, whereas the sensitivity to induction is glioma-like and is 8-fold over the initial level. Blot hybridization with labeled actin cDNA probes showed a similar but not identical induction of actin mRNA synthesis with the hybrid and glioma cells, whereas no significant change was observed with the neuroblastoma cells. Moreover, prolonged treatment with Bt2cAMP of all these cell lines did not result in down-regulation of actin mRNA sequences below the initial control value. It was also observed that the level of tubulin sequences in mRNA isolated from 12-day-old rat brain was higher than that in the newborn brain. However, at an age of 30 days, the level of tubulin sequences decreases to about 75% of the newborn level.

Actins↗