Search PubMed⌕ Search

Biomedical subjects

T Schuster

Publications and source records attributed to T Schuster.

At least 73 records · Page 4Linked to original sources
PubMed1994

Decrease of gap junction number in the rat neural tube between ED 11 and ED 15.

The apical regions of neuroepithelial cells of 11 and 15 day-old rat embryos were found to be interconnected near their luminal surface by extended junctional complexes, consisting of tight junctions and desmosome-like contacts. On the 11th and 12th embryonal day, small gap junction cell contacts occur in the juxtaluminal region of the neural tube. Besides these intercellular gap junctions, annulated gap junctions, located intracellularly, were also detected at this developmental stage. The latter type is thought to originate from intercellular gap junctions by an invagination process in the course of degradation of extended contacts which exist between neuroepithelial cells in earlier developmental phases. The decrease of gap junction number by the 14th and 15th embryonal day could be correlated with processes of cellular development and differentiation.

Animals↗
PubMed1993

Synaptophysin and synaptoporin expression in the developing rat olfactory system.

The expressions of two closely related synaptic vesicle antigens synaptophysin and synaptoporin were examined in the olfactory system of the adult rat and during pre- and postnatal development. In the adult, immunocytochemistry showed that the continuously regenerating olfactory receptor neurons (primary neurons) produce both synaptophysin and synaptoporin which were localized in the cell bodies of the receptor neurons in the olfactory epithelium, their dendrites, axonal processes in the olfactory nerve and their terminals in the olfactory bulb glomeruli. Furthermore, ultrastructural analysis revealed synaptophysin- and synaptoporin-immunoreactivities associated with synaptic vesicles in most olfactory receptor axonal terminals impinging on dendrites of the mitral and tufted neurons (secondary neurons in the olfactory bulb circuitry) in the olfactory glomeruli. In like manner, tufted neurons, granule and periglomerular neurons (interneurons in the olfactory bulb circuitry) express both synaptophysin and synaptoporin. In contrast, mitral neurons expressed only the synaptophysin antigen which was likewise associated with mitral axonal terminals in their target the olfactory cortex. The patterns of synaptophysin and synaptoporin expressions in mitral neurons (synaptophysin only) and tufted neurons (synaptophysin and synaptoporin) were similar in prenatal, postnatal and adult rats as revealed by immunocytochemistry and in situ hybridization. However, the biosynthesis of synaptophysin and synaptoporin by granule and periglomerular neurons, olfactory bulb interneurons, occurred mainly postnatally.

Animals↗
PubMed1993

Identification of a gene encoding a novel zinc finger protein in Saccharomyces cerevisiae.

In the course of a comprehensive genomic screen for cell cycle regulated genes in the yeast Saccharomyces cerevisiae (Price et al., 1991) we identified and characterized a transcriptional unit encoding a putative zinc finger protein named FZF1 (EMBL accession number: X67787). This gene encodes a protein containing five zinc fingers of the Cys2His2 class, three of which are positioned in tandem at the N-terminus. The fourth and fifth finger follow after an interruption of 61 and 66 amino acids, respectively. While FZF1 is constitutively expressed at a very low level, its deletion is not essential for growth. Its similarity with known transcription factors, however, suggests that the FZF1 gene product may serve as a transcription factor in yeast.

Amino Acid Sequence↗
PubMed1993

Psychometric properties of a cognitive measure of personality disorders.

This study evaluated the internal consistency, 1-month test-retest reliability, and validity of a cognitive measure of personality disorders, the Belief Questionnaire (BQ; Beck, 1990). A large, nonclinical sample of college undergraduates completed the BQ, the MMPI-Personality Disorder scales (MMPI-PD; Morey, Waugh, & Blashfield, 1985), and the Personality Diagnostic Questionnaire-Revised (PDQ-R; Hyler & Rieder, 1987) at two times separated by 1 month. Results indicated high internal consistency and test-retest reliability for the BQ subscales. Validity results, however, were not so strong. The BQ scales were highly positively intercorrelated, and only moderate correspondence between BQ scores and corresponding scores from the MMPI-PD and PDQ-R was found.

Adolescent↗
PubMed1992

Differentially regulated malate synthase genes participate in carbon and nitrogen metabolism of S. cerevisiae.

We have isolated a second gene (MLS1), which in addition to DAL7, encodes malate synthase from S. cerevisiae. Expression of the two genes is specific for their physiological roles in carbon and nitrogen metabolism. Expression of MLS1, which participates in the utilization of non-fermentable carbon sources, is sensitive to carbon catabolite repression, but nearly insensitive to nitrogen catabolite repression. DAL7, which participates in catabolism of the nitrogenous compound allantoin, is insensitive to carbon catabolite repression, but highly sensitive to nitrogen catabolite repression. Results obtained with null mutations in these genes suggest that S. cerevisiae contains at least one and perhaps two additional malate synthase genes.

Amidine-Lyases↗
PubMed1992

DIT101 (CSD2, CAL1), a cell cycle-regulated yeast gene required for synthesis of chitin in cell walls and chitosan in spore walls.

A mutant screen has been designed to isolate mutants in Saccharomyces cerevisiae deficient in spore wall dityrosine. As shown by electron microscopy, most of the mutant spores lacked only the outermost, dityrosine-rich layer of the spore wall. Mutant dit101, however, was additionally lacking the chitosan layer of the spore wall. Chemical measurements showed that this mutant does not synthesize chitosan during sporulation. The mutant spores were viable but sensitive to lytic enzymes (glusulase or zymolyase). Unlike most of the dit-mutants, dit101 did show a distinctive phenotype in vegetative cells: they grew normally but contained very little chitin and were therefore resistant to the toxic chitin-binding dye, Calcofluor White. The cells showed barely detectable staining of the walls with Calcofluor White or primulin. The decrease in the amount of chitin in vegetative cells and the absence of chitosan in spores suggested that the mutant dit101 could be defective in a chitin synthase. Indeed, a genomic yeast clone harboring the gene, CSD2, sharing significant sequence similarity with yeast chitin synthases I and II (C. E. Bulawa (1992), Mol. Cell. Biol. 12, 1764-1776), complemented our mutant and was shown to correspond to the chromosomal locus of dit101. Thus, the mutations dit101 and csd2 (and probably also call; M. H. Valdivieso et al., (1991), J. Cell Biol. 114, 101-109) were shown to be allelic. The gene was mapped to chromosome II and was located about 3 kb distal of GAL1. Using this DNA clone, a transcript of about 3500-4000 nucleotides was detected. Comparing RNA isolated from vegetative cells and from sporulating cells at different times throughout the sporulation process, no significant differences in DIT101 transcript levels could be detected indicating absence of sporulation-specific transcriptional regulation. However, the amount of DIT101 transcript changed significantly at different stages of the mitotic cell cycle, peaking after septum formation, but before cytokinesis. As most of the chitin synthesis of vegetative cells occurs at this stage of the cell division cycle, chitin synthesis mediated by DIT101 could be primarily regulated at the level of transcription in vegetatively growing cells.

Cell Cycle↗
PubMed1992

Meiotic chromosome condensation and pairing in Saccharomyces cerevisiae studied by chromosome painting.

Non-isotopic high resolution in situ hybridization was applied to cytological preparations of sporulating yeast cells. Ribosomal DNA (rDNA) and chromosome V-specific recombinant lambda clones were used to tag individual chromosomes and chromosome subregions. This allowed the study of chromosome behaviour during early meiotic prophase. It was found that chromatin becomes condensed and homologous DNA sequences then appear to become aligned prior to synaptonemal complex formation.

Chromosome Banding↗
PubMed1992

Identification of a new set of cell cycle-regulatory genes that regulate S-phase transcription of histone genes in Saccharomyces cerevisiae.

Histone mRNA synthesis is tightly regulated to S phase of the yeast Saccharomyces cerevisiae cell cycle as a result of transcriptional and posttranscriptional controls. Moreover, histone gene transcription decreases rapidly if DNA replication is inhibited by hydroxyurea or if cells are arrested in G1 by the mating pheromone alpha-factor. To identify the transcriptional controls responsible for cycle-specific histone mRNA synthesis, we have developed a selection for mutations which disrupt this process. Using this approach, we have isolated five mutants (hpc1, hpc2, hpc3, hpc4, and hpc5) in which cell cycle regulation of histone gene transcription is altered. All of these mutations are recessive and belong to separate complementation groups. Of these, only one (hpc1) falls in one of the three complementation groups identified previously by other means (M. A. Osley and D. Lycan, Mol. Cell. Biol. 7:4204-4210, 1987), indicating that at least seven different genes are involved in the cell cycle-specific regulation of histone gene transcription. hpc4 is unique in that derepression occurs only in the presence of hydroxyurea but not alpha-factor, suggesting that at least one of the regulatory factors is specific to histone gene transcription after DNA replication is blocked. One of the hpc mutations (hpc2) suppresses delta insertion mutations in the HIS4 and LYS2 loci. This effect allowed the cloning and sequence analysis of HPC2, which encodes a 67.5-kDa, highly charged basic protein.

Amino Acid Sequence↗
PubMed1992

[Morphometric-stereological study of hippocampal long term potentiation with special consideration of the analysis of variance with two-way hierarchical classification].

Regarding the hippocampal formation and especially the external two thirds of it's dentate molecular layer a lot of possible morphological changes after long-term potentiation (LTP) have been described in literature. The present morphometric-stereological study of vesicles in axo-spino-dendritic synapses of the inner third of the molecular layer was done under the aspect of heterosynaptic influences following LTP. Because of the hierarchical link of the three analytic levels (test-group, animal, synapse), for statistical interpretation we used the analysis of variance with two-way hierarchical classification. Between the 3 groups (passive control, active control, LTP-group) we found no significant differences. Because of the great differences between the vesicles even within a single synapse we subsequently investigated the middle third of the molecular layer, i.e. the terminal area of the stimulated perforant path. No differences between the three groups we found here either. There was no confirmation for the expected greater homogenization of the synapses based on the uniform input. As a result of this study pure morphological studies without selective staining of specific population of synapses are considered inadvisable. Only with the help of selective staining in the area of the synapses possible differences between the groups may be found.

Analysis of Variance↗
PubMed1991

A general approach to the isolation of cell cycle-regulated genes in the budding yeast, Saccharomyces cerevisiae.

We describe a general approach to the isolation of cell cycle-dependently regulated transcripts in Saccharomyces cerevisiae. This approach is based on the physical identification of cell cycle-regulated transcripts by Northern hybridization using as probes yeast DNA isolated from an ordered S. cerevisiae genomic library. The purpose of this is twofold; first, to assess the importance of transcriptional regulation in cell cycle control; and second, to identify novel genes that may have important roles in the eukaryotic cell cycle. We report the isolation of two previously uncharacterized genes that are transcribed at points in the cell cycle to which specific transcriptional activation has not been assigned: namely, mitosis and early G1 phase. It is argued that these transcripts serve as important landmarks for cell cycle events that are not readily distinguished by either morphological or cytological criteria. The cell cycle-dependent transcription of the RNR1 and CLN1 genes is also described and the implications for cell cycle control, in G1, are discussed with reference to these two genes.

Blotting, Northern↗
PubMed1991

The role of CDC28 and cyclins during mitosis in the budding yeast S. cerevisiae.

cdc28-1N is a conditional allele that has normal G1 (Start) function but confers a mitotic defect. We have isolated seven genes that in high dosage suppress the growth defect of cdc28-1N cells but not of Start-defective cdc28-4 cells. Three of these (CLB1, CLB2, and CLB4) encode proteins strongly homologous to G2-specific B-type cyclins. Another gene, CLB3, was cloned using PCR, CLB1 and CLB2 encode a pair of closely related proteins; CLB3 and CLB4 encode a second pair. Neither CLB1 nor CLB2 is essential; however, disruption of both is lethal and causes a mitotic defect. Furthermore, the double mutant cdc28-1N clb2::LEU2 is nonviable, whereas cdc28-4 clb2::LEU2 is viable, suggesting that the cdc28-1N protein may be defective in its interaction with B-type cyclins. Our results are consistent with CDC28 function being required in both G1 and mitosis. Its mitotic role, we believe, involves interaction with a family of at least four G2-specific cyclins.

Alleles↗
PubMed1991

Tracheal stenosis by innominate artery compression in infants: surgical treatment in 35 cases.

This is a report on 35 cases of innominate artery compression of the trachea and its surgical correction by means of aortotruncopexy. Diagnostic procedures of choice were tracheoscopy and magnetic resonance imaging, which offers representative images of inspiration and expiration, shows the anatomical relations between aortic arch and trachea and reveals the extent of tracheal compression. Surgical treatment is indicated if narrowing of the tracheal lumen exceeds 70%. By fixation of the aortic arch and the proximal innominate artery to the back of the sternum, tracheal compression is relieved. There was no unsuccessful operation in the 35 children. One late death occurred from cardiac failure, unrelated to tracheal compression.

Aorta, Thoracic↗
PubMed1991

Heterosynaptic changes in number and shape of the transmission zones of axo-spino-dendritic synapses in the central nervous system following long-term potentiation.

Regarding the hippocampal formation and especially the external two thirds of it's dentate molecular layer a lot of possible morphological changes after long-term potentiation (LTP) have been described in literature. The present morphometric-stereological study of axo-spino-dendritic synapses from the inner third of the molecular layer was done under the aspect of heterosynaptic influences following LTP. We were looking for differences in the number of transmission zones, in the total length of the transmission zone and in the qualitative shape of the single transmission membrane. Because of the hierarchical link of the three analytic levels (test-group, animal, synapse), for statistical interpretation we used the analysis of variance with two-way hierarchical classification. We detected large differences between the single synapses but not significant differences between the 3 groups (passive control, active control, LTP-group). Our quantitative studies showed the same results also in the middle third of the molecular layer (Grabs et al. 1991). Pure morphological studies should be done under selective staining of specified population of synapses to differ in stimulated and non-stimulated synapses. Only with the help of selective staining in the area of the synapses possible differences between the groups may be found.

Animals↗
PubMed1991

Annulated gap junctions in the rat neural tube.

Annulated gap junctions have been studied electron microscopically in normal rat embryo neural tube on day 12 of gestation. Localization, size and content of annulated gap junctions were characterized. Like in other tissues annulated gap junctions are thought to be involved in a degradation cycle of gap junctions.

Animals↗