Alterations in Glutamate Transporter Protein Levels in Kindling-Induced Epilepsy

Abstract: There is increasing evidence that levels of glutamate are elevated in certain brain regions immediately prior to and during induction and propagation of seizures. Modulation of high-affinity glutamate uptake is a potential mechanism responsible for the elevated levels observed with seizures. To date, three distinct Na⁺-dependent glutamate transporters have been cloned from rat and rabbit: GLT-1, GLAST, and EAAC-1. We performed a series of experiments to determine whether levels of these transporters are altered in amygdala-kindled rats. Levels of GLT-1, GLAST, and EAAC-1 were examined in three brain regions (hippocampus, piriform cortex/amygdala, and limbic forebrain) by quantitative immunoblotting using subtype-specific antibodies. GLAST protein was down-regulated in the piriform cortex/amygdala region of kindled rats as early as 24 h after one stage 3 seizure and persisting through multiple stage 5 seizures. In contrast, kindling induced an increase in EAAC-1 levels in piriform cortex/amygdala and hippocampus once the animals had reached the stage 5 level. No changes in GLT-1 were observed in any region examined. Changes in transporter levels could contribute to the changes in glutamate levels seen with kindling.     

Crystallization of the complex of human IFN-γ and the extracellular domain of the IFN-γ receptor

A complex of human interferon-γ (IFN- γ) with the soluble extracellular domain of the IFN- γ receptor α-chain (IFN-γ-R) has been crystallised. Crystals of the complex were grown using PEG 4000 as the precipitating agent in the presence of β-octyl glucoside. The receptor-ligand complex crystallizes in a monoclinic space group and diffracts to about 3.0 Å resolution. Isomorphous crystals have been obtained with complex containing selenomethionine and cysteine mutants of IFN-γ, which may facilitate the ongoing X-ray structure determination. © 1995 Wiley-Liss, Inc.     

Accumulation of the isolated carboxy-terminal domain of histone H1 in the Xenopus oocyte nucleus

Histone H1 accumulates in the nucleus after injection into the cytoplasm of Xenopus oocytes. A proteolytic fragment of 89 amino acids encompassing the carboxy-terminal domain also accumulates in the nucleus. Lysine, alanine and proline compose 84% of this domain. Accumulation is not due solely to the high lysine content since poly-L-lysine does not accumulate in the nucleus when injected into the cytoplasm of Xenopus oocytes. Proteolytic fragments encompassing other domains of the molecule are degraded in the oocyte after injection. In these instances degradation is more rapid in the cytoplasm than in the nucleus giving the false impression of accumulation in the nucleus, an artefact which is likely to confuse other studies of protein migration. Susceptibility to rapid degradation is a dominant feature, thus the globular domain destabilises the contiguous carboxy-terminal domain. The properties of the carboxy-terminal domain of H1 and the possible involvement of the amino acids lysine, proline and alanine in migration are discussed and compared with those of a domain that specifies migration of nucleoplasmin into the oocyte nucleus.     

The turnover of chlorophyll in greening wheat leaves

A method for the estimation of chlorophyll turnover in wheat leaves is presented. This is based on the inhibition of chlorophyll synthesis by treatment of the cut leaves with laevulinic acid (LA), a competitive inhibitor of δ-aminolaevulinic acid dehydratase. The turnover of chlorophyll in young, greening leaves, given short periods of light was a relatively rapid process. However, in seedlings exposed to light for longer periods the turnover became progressively slower, and was measured in days rather than hours.     

Binding of protein chemotactic factors to the surfaces of neutrophil leukocytes and its modification with lipid-specific bacterial toxins

Summary The binding to neutrophil leukocytes of human serum albumin (HSA), which is chemokinetic for leukocytes, i.e. influences their rate of locomotion, and of alkali-denatured HSA, which is chemotactic for leukocytes, i.e. influences their direction of locomotion, was studied. Native serum albumin showed low affinity binding to the neutrophil surface. Denatured serum albumin showed saturable binding with a K_a of approximately 10⁶ litres per mole to about 10⁶ binding sites per cell. Another protein chemotactic factor, _s-casein, gave similar binding. These results exclude that chemotactic reactions to denatured proteins are mediated in a completely non-specific manner and suggest the presence on the cell of a restricted number of defined recognition sites. Binding was reduced following treatment of the cells with either of two lipid-specific bacterial toxins, perfringolysin, the -toxin of Clostridium perfringens, an oxygen-labile cholesterol-specific toxin, and Staphylococcus aureus Sphingomyelinase C. Both have previously been shown to reduce chemotactic reactions and both were used at doses which did not reduce cell viability. These results suggest an important, and possibly direct, role for membrane lipid in the binding sites for chemotactic factors. Visual analysis of the behaviour of perfringolysin-treated neutrophils showed that these cells were still capable of chemotactic locomotion. The cells appeared to be less efficient than normal in detecting chemotactic gradients only when at a distance from the gradient source, a finding which is consistent with reduced binding of the chemotactic factor to the cell surface.     

Factors affecting tissue nutrient concentrations in aCarex meadow

Summary The influence of community and edaphic variables on tissue nutrient concentration was assessed for seven species on aCarex wetland in southern Quebec, Canada.Potassium and sodium tissue levels were considerably higher and Ca and Mg 35% lower than in a deciduous forest. Macronutrient concentrations decreased in the order K>N>Ca>Mg>Na>P. Micronutrient concentrations (Fe>Mn>Zn>Cu) ranged from 0.038–0.005 mg/g. This was 2–3 times less abundant than in an adjacentScirpus wetland. Inter-species coefficient of variation in N, P and K was low (14%) compared to variation in Ca, Mg, and the micronutrients (35%).Principal components analysis of interrelations between tissue elements indicated a clear distinction between N, P, K, Cu, Mn, and Zn levels and ash, Ca, Mg, Na, and Fe levels on the first component. This difference related closely to water depth and fire incidence. The coincidence of burning with water depth and the period of maximum snowmelt and runoff in the Spring suggested the loss of N, P, K, Cu, Mn and Zn by volotilization, runoff, or leaching.Stem density was the most important parameter influencing tissue N, P, and K concentrations whereas soil nitrogen levels were important in ash, Ca, and Mg concentrations. Water depth was the most important variable in the case of Cu, Fe, Mn, Na and Zn levels. Typha angustifolia had the highest level of total nutrients in green tissue,Carex lanuginosa the lowest. Principal components analysis indicated soil nitrogen, water depth, and soil potassium levels, in that order, were the three most important variables influencing the patterns of tissue element variation among species.Potassium and sodium levels in 1-year old litter were 11% and 0.4% compared to concentrations in green tissue. Iron and manganese, both subject to oxidation and adsorption to litter at the soil surface, were distinctly higher (2247% and 199%) in litter than green tissue. Concentrations of these and other elements in litter were consistent with results reported in literature and indicated litter was especially active as a site of cation exchange in the system.     

ABO and Rh blood groups in relation to sex ratio, mean number and mortality of sibs.

Data are presented on the sex ratio, mean number and mortality of the sibs of 17,060 schoolchildren, and on the sex ratio and mean number of the sibs of 5,785 blood donors, in relation to the children's and donors' sex and ABO and Rh blood groups. The sex ratio is significantly higher for the sibs of AB + B than for those of A + O schoolboys, and for the sibs of Rh-negative than for those of Rh-positive male blood donors, but in both cases the mean number of sibs is exactly the same for the first-mentioned as for the second-mentioned category.     

Anti-idiotypic antibody response to monoclonal anti-CD4 preparations in nonhuman primate species.

A series of mouse monoclonal anti-CD4 preparations was characterized for the ability to recognize overlapping epitopes on CD4 and to inhibit HIV/simian immunodeficiency virus (SIV) syncytium formation. Based on this characterization, mAb able to recognize CD4 epitopes overlapping the HIV binding site were selected and used to immunize nonhuman primates to elicit the production of specific anti-Id antibodies. Five baboons and five rhesus monkeys were immunized with either individual or a cocktail consisting of several monoclonal anti-CD4 preparations. All the nonhuman primates produced specific anti-Id that recognized either private or cross-reactive Id depending on the monoclonal anti-CD4 used to generate the anti-Id response. Inhibition assays were performed to ascertain the ability of: 1) soluble CD4 to inhibit the Id-anti-Id reaction and 2) the various anti-Id to inhibit the CD4-monoclonal anti-CD4 reaction. These studies demonstrated that some of the anti-Id recognized a cross-reactive Id that was associated with the Ag-combining site. In addition, some of the anti-Id weakly recognized SIV gp120 by Western blot analysis. These studies may be useful in designing experiments that may lead to a better understanding of the CD4-HIV gp120 interaction and to the production of Id and/or anti-Id reagents that might be used to manipulate this virus-receptor interaction.