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Biomedical subjects

B Schmitt

Publications and source records attributed to B Schmitt.

At least 19 recordsLinked to original sources
PubMed1992

Glutamate receptors of Drosophila melanogaster: cloning of a kainate-selective subunit expressed in the central nervous system.

We report the isolation and functional characterization of cDNAs encoding a Drosophila kainate-selective glutamate receptor. The deduced mature 964-residue protein (DGluR-I) is 108,482 Da and exhibits significant homology to mammalian glutamate receptor subunits. Injection of DGluR-I cRNA into Xenopus oocytes generated kainate-operated ion channels which were blocked by the selective non-N-methyl-D-aspartate receptor antagonist 6-cyano-7-nitro-quinoxaline-2,3-dione and philanthotoxin. DGluR-I transcripts are differentially expressed during Drosophila development and, in late embryogenesis, accumulate in the central nervous system.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1992

Cortical visual impairment following bacterial meningitis: magnetic resonance imaging and visual evoked potentials findings in two cases.

Cortical visual impairment (CVI) following bacterial meningitis is a very uncommon complication. Two children with CVI following bacterial meningitis are reported. Bacterial agents were Haemophilus influenzae type B in one and meningococci in the other child. Both children showed only insufficient recovery from CVI, mental retardation and residual neurological symptoms. Flash visual evoked potentials (VEP) showed preserved cortical response at onset of CVI. Re-evaluations several months later showed significantly reduced amplitudes, but normal latencies for P100. Thus, flash VEP does not allow prediction of visual outcome. MRI results have not been reported before. MRI at onset of diagnosis showed occipital parenchymal irregularities with enlarged sulci and subarachnoid spaces. Follow up MRI 15 months after onset of CVI in one patient showed marked atrophy of the occipital cortex, hyperintensities of the cortical white matter and no visible optic radiation. The MRI findings indicate hypoxic-ischaemic lesions in the border zone between the distribution of the great cerebral arteries.

Blindness↗
PubMed1992

Primary structure and alternative splice variants of gephyrin, a putative glycine receptor-tubulin linker protein.

A 93 kd polypeptide associated with the mammalian inhibitory glycine receptor (GlyR) is localized at central synapses and binds with high affinity to polymerized tubulin. This protein, named gephyrin (from the Greek gamma epsilon phi upsilon rho alpha, bridge), is thought to anchor the GlyR to subsynaptic microtubules. Here we report its primary structure deduced from cDNA and show that corresponding transcripts are found in all rat tissues examined. In brain, at least five different gephyrin mRNAs are generated by alternative splicing. Expression of gephyrin cDNAs in 293 kidney cells yields polypeptides reactive with a gephyrin-specific antibody, which coprecipitate with polymerized tubulin. Thus, gephyrin may define a novel type of microtubule-associated protein involved in membrane protein-cytoskeleton interactions.

Amino Acid Sequence↗
PubMed1992

Reconstruction of the arteria carotis communis in newborn following extracorporeal membrane oxygenation (ECMO).

With the help of ECMO it is possible to save the lives of newborn infants suffering from severe respiratory distress syndrome not responding to conservative treatment. Using Bartlett's classic venous-arterial perfusion technique in ECMO the right arteria carotis communis had to be sacrificed. Thus, despite the life-saving character of this new method, the ligation of the carotid with all its possible complications had often been a major argument against using this therapy. We are now therefore trying to reconstruct the arteria carotis after decannulating the vessel after extracorporeal membrane oxygenation. In our 8 cases so far, post-op examinations showed no obstruction of blood flow in the vessel. No neurological deficiencies were recorded.

Anastomosis, Surgical↗
PubMed1992

EEG and evoked potentials in HIV-infected children.

Forty-seven HIV-seropositive children were investigated by EEG and evoked potentials (BAEP, SEP). Twenty-three children were symptomatic (P2), 8 seropositive without symptoms (P1), and 16 children were less than 15 months of age (P0). Some of them were investigated at different stages of HIV infection. During the neonatal period, 7 newborns of drug-addicted mothers had seizures and frequent spikes and sharp waves in their EEGs. Among (P2) children 6/23 showed background slowing and 1 had rhythmic theta activity (6 with and 1 without neurological symptoms). In BAEP, bilateral prolonged interpeak latencies (IPL) were found in 1 child with severe AIDS encephalopathy. Side differences greater than or equal to 0.4 ms in IPL were seen in 2 (P2), 1 without and 1 with neurological symptoms. A late onset was seen in 2 (P1) and 4 (P2) children. Median SEPs were normal in 24/26 patients; N20/N13 amplitude ratio was reduced in 2 (P1) patients. EEG and BAEP revealed nonspecific abnormal features in HIV encephalopathy. The the progression of the disease. However, also in the symptomatic group, normal results of EEG and BAEP dominated. SEP in the symptomatic group revealed only normal values. For monitoring the effectiveness of AZT treatment in HIV encephalopathy, EEG seems to be a relevant investigation; for evoked potentials more data and experience are needed.

AIDS Dementia Complex↗
PubMed1991

The 93-kDa glycine receptor-associated protein binds to tubulin.

A peripheral membrane protein with a relative molecular mass of 93,000 Da is associated with cytoplasmic domains of the inhibitory glycine receptor of mammalian spinal cord. Here, evidence is given that this 93-kDa protein binds to polymerized tubulin. First, tubulin cofractionated with the 93-kDa protein upon affinity purification of the glycine receptor. Second, tubulin bound to the isolated 93-kDa protein in an overlay procedure. Third, in assays containing the purified glycine receptor, the 93-kDa protein as well as the glycine receptor alpha and beta subunits coassembled with tubulin and microtubules. The interaction of the 93-kDa protein with tubulin displayed high affinity (KD approximately 2.5 nM) and significant cooperativity (Hill coefficient approximately 2.1) and approached a stoichiometry of approximately 1:4 under saturating conditions. These data suggest that the 93-kDa protein anchors the glycine receptor at postsynaptic sites via binding to subsynaptic tubulin.

Animals↗
PubMed1991

Molecular cloning of an invertebrate glutamate receptor subunit expressed in Drosophila muscle.

Insects and other invertebrates use glutamate as a neurotransmitter in the central nervous system and at the neuromuscular junction. A complementary DNA from Drosophila melanogaster, designated DGluR-II, has been isolated that encodes a distant homolog of the cloned mammalian ionotropic glutamate receptor family and is expressed in somatic muscle tissue of Drosophila embryos. Electrophysiological recordings made in Xenopus oocytes that express DGluR-II revealed depolarizing responses to L-glutamate and L-aspartate but low sensitivity to quisqualate, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA), and kainate. The DGluR-II protein may represent a distinct glutamate receptor subtype, which shares its structural design with other members of the ionotropic glutamate receptor family.

Amino Acid Sequence↗
PubMed1991

Kinetics of the specific binding of a second RNA polymerase to the standard bacterial-transposon-Tn3 bla promoter complex.

It was shown previously, that at moderate excess of RNA polymerase (RNAP) relative to DNA, the complex of the bla promoter from bacterial transposon Tn3 with RNAP is locked in an inactive, heparin-resistant, isomeric state which is not that of the 'open' complex. This 1:1 isomer can accommodate a second RNAP, which becomes tightly and specifically bound just upstream of the first RNAP [Duval-Valentin & Reiss (1990) Mol. Microbiol. 4, 1465-1475]. Both the resulting 2:1 complex and its antecedent 1:1 complex formed at excess of RNAP are immediately and permanently inhibited for transcription initiation. Using the gel-retardation technique, we investigate here the kinetics of formation and decay of the 2:1 complex under various experimental conditions. The data are consistent with pseudo-first-order kinetics at moderate excess of RNAP. The salt-dependence of rate and equilibrium constants has been analysed within the framework of the theoretical model described by Lohman, Dehaseth & Record [(1978) Biophys. Chem. 8, 281-294]. It was found that the salt-dependence is consistent with the existence of a transient intermediate during formation of the 2:1 complex, which forms rapidly on the time scale of its isomerization to the final 2:1 complex. The intermediate is characterized by the release of about seven cations from the 1:1 complex, one additional cation being released upon its final isomerization. Formation of the 2:1 complex at high excess of RNAP becomes inhibited, probably as a result of a 'bumping' effect of the complex by the enzyme, also observed with several other promoters. We conclude that formation of the 2:1 complex closely mimics that of the standard 1:1 complex, except that the final isomerization step to an 'open' complex is lacking. A mechanism of the formation of the 2:1 complex and of its role in transcription regulation of constitutive promoter by RNAP is proposed.

DNA Transposable Elements↗
PubMed1991

Alternative splicing generates two variants of the alpha 1 subunit of the inhibitory glycine receptor.

The inhibitory glycine receptor (GlyR) in mammalian spinal cord displays pharmacological and molecular heterogeneity of its strychnine binding alpha subunit. Here, cDNAs were isolated which encode a variant (alpha ins 1) of the rat GlyR alpha 1 subunit that contains eight additional amino acids in its putative cytoplasmic domain. Analysis of the corresponding genomic sequence showed that alpha ins 1 transcripts result from alternative splice acceptor site selection. S1 nuclease protection experiments, Northern blot analysis, and RNA amplification by polymerase chain reaction revealed alpha 1 and alpha ins 1 mRNA in postnatal spinal cord, but not in other brain regions. Expression of synthetic alpha ins 1 RNA in Xenopus oocytes generated glycine-gated strychnine-sensitive chloride channels. These data indicate that alternative splicing contributes to GlyR alpha subunit heterogeneity in the mammalian central nervous system.

Amino Acid Sequence↗
PubMed1991

Chromosomal translocation detected by bcl-1 and bcl-2 rearrangement in low-grade B-cell lymphomas in a European population.

Twenty-nine cases of non-Hodgkin's lymphoma of low-grade malignancy in a European population were investigated for the presence of bcl-2 and bcl-1 gene rearrangement. The cases were classified according to the Kiel classification. It was shown that bcl-2 gene rearrangements were exclusively confined to centroblastic-centrocytic lymphomas. bcl-1 rearrangements were found in two cases of chronic lymphocytic leukaemia. As the chromosomal translocation t(14;18) is reported to occur in up to 85% of follicular lymphomas, our results provide additional evidence that the differentiation of low-grade B-cell lymphomas according to the Kiel classification defines biologically distinct entities.

Chromosomes, Human, Pair 14↗
PubMed1991

How to build a glycinergic postsynaptic membrane.

The inhibitory glycine receptor (GlyR) is a ligand-gated chloride channel protein found at many synapses of the mammalian central nervous system. During development, distinct isoforms of the GlyR are generated by the sequential expression of different alpha subunit variants. The appearance of adult-type GlyRs in spinal cord is accompanied by the accumulation of a 93 x 10(3) Mr receptor-associated peripheral membrane protein. The latter has been localized at the cytoplasmic face of glycinergic postsynaptic membranes and is thought to anchor GlyRs beneath glycinergic nerve terminals. The 93 x 10(3) Mr protein binds with high affinity to polymerized tubulin, suggesting that it functions as a receptor-microtubule linking component. Our data suggest that the interaction of developmentally regulated receptor isoforms with specialized microtubule-associated proteins represents a crucial step in the assembly of postsynaptic receptor matrices.

Animals↗
PubMed1990

Heterogeneity of Drosophila nicotinic acetylcholine receptors: SAD, a novel developmentally regulated alpha-subunit.

Two genes, ard and als, are known to encode subunits of the nicotinic acetylcholine receptor (nAChR) in Drosophila. Here we describe the isolation of cDNA clones encoding a novel member (SAD, or alpha 2) of this receptor protein family. The deduced amino acid sequence displays high homology to the ALS protein and shares structural features with ligand binding nAChR alpha-subunits. Sad transcripts accumulate during major periods of neuronal differentiation and, in embryos, are localized in the central nervous system. Expression of SAD cRNA in Xenopus oocytes generates cation channels that are gated by nicotine. These data indicate heterogeneity of nAChRs in Drosophila.

Amino Acid Sequence↗
PubMed1979

[Leydig cell tumor of the ovary (biologic (in vivo and in vitro) and ultrastructural study) (author's transl)].

The authors present the case of a young hirsute woman of 28 years old. Urinary 17 KS were very increased without DHA, but with androsterone, etiocholanolone and 11 oxy 17 Ketosteroids. Androstenedione and testosterone plasmatic levels were very high and per operative selective ovarian vein catheterization showed a direct production of these potent androgens. In vitro study of the tumor allowed to obtain same results. Light and electron microscopic study showed a Leydig cell tumor of left ovary.

17-Ketosteroids↗
PubMed1978

On the peripheral location of the Y chromosome.

The location of the Y chromosome in metaphase spreads is studied in groups of (a) 96 normal males, (b) 17 Down's syndrome patients, and (c) 51 patients with Klinefelter's syndrome. The position of the Y is scored as either peripheral or nonperipheral using several of the traditional definitions found in the literature. It is shown that contradictory results may be obtained depending on the particular definition employed and that none of the available definitions capture the essence of the meaning of 'peripheral'. Therefore a new, standardized definition is introduced-one that applies to both circular and noncircular spreads. Using this new definition, we find definite intergroup variability. The Y is peripheral in normal males, but not in either the Down's or Klinefelter's samples.

Adolescent↗
PubMed1978

[Bioavailability of Ce-Ferro forte. Comparative iron load test (author's transl)].

The intraindividual relative bioavailability of three oral iron preparations was investigated in 9 male and 3 female healthy volunteers. After an overnight fast each of the volunteers took 110 mg Fe++ in a weak gelatine capsule soluble within the duodenum (Ce-Ferro forte) or 105 mg and 100 mg Fe++ respectively in commercial preparations. Care was taken that a 3 days interval took place between the investigations. Before taking and 1/2, 1, 2, 4, 6, 8 and 12 hrs. after taking the iron capsule, blood was withdrawn into heparinized test tubes and plasma iron concentrations were determined using an atomic absorption spectrophotometer. After taking Fe++ sulfate in a weak gelatine capsule (A), the mean plasma iron increased significantly higher in comparison to preparation B in the 2nd and in the 4th hour and in comparison to preparation C in the 1st hour. The area under curve of iron increase was 531 +/- 329 (SD) after A, 415 +/- 327 And 414 +/- 390 after B and C respectively without significant changes. From these data was concluded that Fe++ sulfate in a duodenal soluble weak gelatine capsule has a beter bioavailability than the 2 other preparations investigated.

Administration, Oral↗