Carrier mediated GABA translocation into rat brain mitochondria

GABA added to rat brain mitochondria causes oxidation of intramitochondrial NAD(P)H as well as inducing glutamate efflux from the mitochondrial matrix. The rate of NAD(P)H oxidation shows saturation characteristics, depends on GABA transport across the mitochondrial membrane and is inhibited by non-penetrant compounds and by the metal-complexing agent bathophenanthroline. These results show the existence of a specific GABA carrier. Inhibition studies strongly suggest the existence of two separate binding sites, namely the GABA binding site and the dicarboxylates binding site, as well as suggest the presence of a metal ion (ions) at GABA binding site. The occurrence of a GABA/GLUTAMATE antiport is proposed which allows a cyclical route to account for GABA synthesis and degradation in brain.     

Copper distribution in the normal human brain

Copper concentration was determined in samples from 38 areas of 7 normal human brains. The grey matter contained higher concentrations of copper than the white matter. Identical areas of the grey and white matter of the cerebral cortex showed significant differences between individuals. In the caudate nucleus the highest concentrations of copper were found in the tail followed by the body and the head, respectively. A negative linear regression between age and brain copper levels was demonstrated.     

Role of H-2 antigens in the host response to methylcholanthrene-induced tumors

H-2 loss variant sublines of a sarcoma (M-AS), induced by methylcholanthrene in an (A × A.SW)F₁ mouse, were used to study the role of the MHC products in the recognition of MC-TSTA. The two reciprocal variant sublines (M-A and M-S) were found to express the TSTA of the original tumor as shown by cross-reactions in graft rejection experiments performed in (A × A.SW)F₁ mice. In the A/Sn and A.SW mice the presence of the reciprocal parental H-2 antigens on the immunizing cells decreased the response against the tumor antigens. An admixture of lymphocytes derived from hyperimmune mice inhibited the outgrowth of the tumor cells. The growth inhibition was mediated by T cells and was H-2 restricted. Cells derived from hyperimmune syngeneic mice inhibited the outgrowth of the variant subline used for immunization but had no effect on the reciprocal variant subline.     

Steroidogenesis in isolated adrenocortical cells. Correlation with receptor-bound adenosine 3′:5′-cyclic monophosphate

Because several groups have recently questioned a mediating role for cyclic AMP in adrenocortical steroidogenesis, we analysed the problem in more detail by measuring three different cyclic AMP pools in cells isolated from decapsulated rat adrenals. Extra-cellular, total intracellular and bound intracellular cyclic AMP were determined by radioimmunoassay in comparison with corticosterone production induced by low corticotropin concentrations. The increase in extracellular and total intracellular cyclic AMP with low corticotropin concentrations was dependent on the presence of a phosphodiesterase inhibitor and short incubation times. Bound intracellular cyclic AMP was less dependent on these two parameters. In unstimulated cells cyclic AMP bound to its receptor represents only a small fraction of the total intracellular cyclic AMP. After stimulation by a concentration of corticotropin around the threshold for corticosterone production, an increase in bound cyclic AMP was observed which correlated very well with steroidogenesis both temporally and with respect to corticotropin concentration. This finding was complemented by measuring a concomitant decrease in free receptor sites. Full occupancy of the receptors was not necessary for maximal steroidogenesis. Binding kinetics of cyclic [(3)H]AMP in concentrations equivalent to the intracellular cyclic AMP concentration suggest the presence of at least three different intracellular cyclic AMP pools. These observations are in agreement with a possible role for cyclic AMP as a mediator of acute steroidogenesis induced by low corticotropin concentrations.     

Streptococcus pneumoniae type 3 encodes a protein highly similar to the human glutamate decarboxylase (GAD65)

Abstract A 2.5-kb Sca I fragment of the type 3 pneumococcal strain 406 DNA containing a 1425-nucleotide open reading frame ( gadA ) and encoding a 475-amino acid protein ( M _rmr 54427) was characterised. The gene gadA was expressed in Salmonella typhimurium . Pulsed-field gel electrophoresis and Southern blotting analysis of DNAs prepared from several pneumococcal serotypes showed that only those clinical isolates belonging to serotype 3 harbour the gadA gene. Sequence comparison of GadA with proteins included in the data banks revealed the highest similarity with human glutamate decarboxylase (GAD₆₅) (59% similarity, 28% identity). Auto-antibodies to GAD₆₅ have been associated with the onset of insulin-dependent diabetes mellitus. Interestingly, several epitopes of GAD₆₅ that have been identified as immunodominant are particularly well conserved in the pneumococcal GadA.     

Autolysins are direct involved in the bactericidal effect caused by penicillin in wild type and in tolerant pneumococci

The two pneumococcal autolytic enzymes (an N-acetylmuramoyl-L-alanine amidase and an endo-beta-1,4-N-acetylglucosaminidase) are directly involved in the penicillin-induced killing of Streptococcus pneumoniae. The activity of these lytic enzymes was efficiently controlled in tolerant mutants under physiological conditions.     

Autoimmune syndrome after induction of neonatal tolerance to alloantigens: effects of in vivo treatment with anti-T cell subset monoclonal antibodies

BALB/c (H-2d) mice rendered tolerant to h-2b alloantigens by neonatal injection of semiallogeneic (C57BL/6 X BALB/c)F1 spleen cells develop autoimmune features due to an abnormal activation of persisting F1 donor B cells. The role of T cells in this autoimmune syndrome was studied by in vivo treatment of tolerant mice with anti-L3T4(GK-1.5) or anti-Ly-2 (H-35-17.2) monoclonal antibodies. The treatment of tolerant mice from day 2 to day 21 of life with anti-L3T4 MAb completely prevented the occurrence of circulating immune complexes of anti-ssDNA anti-Sm and anti-hapten (FITC) IgG antibodies as well as the glomerular deposition of Ig that were usually seen in untreated tolerant mice. This effect persisted for at least 6 wk after stopping this treatment. When the injections of anti-L3T4 MAb were delayed until day 15 of life, a very significant decrease of the autoimmune manifestations was still observed. Treatment of tolerant mice with anti-Ly-2 MAb during the same period had no effects on the autoimmune disease as compared with untreated tolerant mice. No effects on the maintenance of tolerance vs H-2b alloantigens were observed after treatment with anti-L3T4 MAb, as followed by the decrease of CTL and CTL-p alloreactivity and by the persistence of F1 donor B cells, indicated by the presence of Ig bearing the Ighb donor allotype. These results suggest the existence of interactions between L3T4+ T cells and persisting autoreactive B cells from F1 donor origin in the development of the autoimmune syndrome after neonatal induction of transplantation tolerance.     

Genome Sequences of Burkholderia sp. Strains CCGE1002 and H160, Isolated from Legume Nodules in Mexico and Brazil

The genome sequences of Burkholderia sp. strains CCGE1002 from Mexico and H160 from Brazil, isolated from legume nodules, are reported. Their gene contents in relation to plant-microbe interactions and xenobiotic degradation are discussed.