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Biomedical subjects

W Schmid

Publications and source records attributed to W Schmid.

At least 73 records · Page 4Linked to original sources
PubMed1993

Ultrasound screening for chromosomal anomalies in the first trimester of pregnancy.

For the last 6 years, sonographic signs for excessive fluid accumulation in the backs of 10- to 12-week-old fetuses have been looked for prior to transabdominal chorionic biopsy. In 1400 pregnancies, subsequent karyotype analyses revealed 28 cases of Down syndrome. In 15 (= 54 per cent), a large fluid cushion over most of the back had been documented at the time of biopsy. Only a few chromosomally normal fetuses with the same peculiarity were observed. The cushion was also present in fetuses with trisomies 18 and 13, and in Turner syndrome. Systematic first-trimester screening for nuchal fluid accumulation seems to be a recommended method for the detection of Down syndrome and other chromosome anomalies in young pregnant women at low risk. It compares favourably with current methods of maternal serum screening performed at 16-18 weeks which require a higher number of invasive procedures.

Chromosome Aberrations↗
PubMed1993

The ERE-like sequence from the promoter region of the testis specific hsp70-related gene is not estrogen responsive.

The 5'flanking region of the hsp70-related gene which is specifically expressed in rat and mouse spermatocytes contains the GGTCAnnnCGACC sequence closely resembling the palindromic consensus ERE (estrogen responsive element, GGTCAnnnTGACC). We used a transient expression assay to study whether this ERE-like sequence can transfer estrogen responsiveness either to heterologous or homologous promoters linked to a reporter CAT gene. We found that the GGTCAnnnCGACC sequence either as an isolated element or in its natural sequence context does not respond to hormone stimulation in MCF-7 and Fe33 cells. This observation points to the importance of the T-nucleotide in a right half-palindrome of ERE for ligand-dependent activation of transcription.

Animals↗
PubMed1993

Expression of the mouse glucocorticoid receptor and its role during development.

Genes encoding enzymes involved in gluconeogenesis are activated in liver shortly after birth by the synergistic effect of glucagon and glucocorticoids. This induction is achieved by the synergistic action of hormone responsive and liver-specific enhancer elements. In the case of glucocorticoids, this enhancer is composed of a glucocorticoid-response element (GRE) and a number of cell-specific hepatocyte nuclear factor 3 (HNF-3) binding sites. The GRE binds the ligand-activated glucocorticoid receptor (GR) which is ubiquitously expressed and the HNF-3 element binds a cell-specific protein factor. To further understand the role of cell-specific glucocorticoid signalling in the perinatal period and earlier during development we have studied the expression of the mouse GR gene. The gene has been cloned and fully characterized. Expression of the gene is controlled by at least three promoters, one of which is only active in T-lymphocytes. Expression of GR mRNA has been detected back to day 9.5 of mouse development. The role of GR during mouse development has been further analysed by disruption of the GR gene in vivo by homologous recombination in mouse embryonic stem cells.

Animals↗
PubMed1992

[Molecular genetics diagnosis of Steinert's myotonic dystrophy].

Myotonic dystrophy (DM) is the most common neuromuscular disease with adult onset (incidence 1 in 8000). The biochemical basis of this autosomal dominantly inherited disease is still unknown. The most striking features are myotonia and progressive muscular wasting. There is high variability of disease severity in patients from different families, but also within the same family. For practical reasons three subtypes can be defined: The classical adult onset form of the disease, a mild form with late onset and/or very moderate symptoms, eg. cataracts only, and the most severe congenital form which is transmitted by affected females. Furthermore, the progression of DM in affected families may exhibit an increase in the severity of the disease in successive generations. This observation is called anticipation. Very recently the DM gene has been cloned and an unstable DNA sequence specific for the disease has been characterized. Detection of an enlarged DNA fragment due to the expansion of a trinucleotide (CTG) repeat within the DM gene can be used for direct DNA diagnosis in affected individuals and persons at risk. Furthermore, there is a strong correlation between the length of fragment expansion and the degree of disease severity in gene carriers. We report here our preliminary results of the investigation of over 70 patients and demonstrate the clinical usefulness of this new method by the findings in three families.

Adult↗
PubMed1992

The transcription factor CREB, but not immediate-early gene encoded proteins, is expressed in activated microglia of lumbar spinal cord following sciatic nerve transection in the rat.

Expression of CREB, JUN, FOS and KROX-24 proteins was investigated in glial cells of the lumbar spinal cord. In untreated rats, CREB, c-JUN and JUN D were present in glial cells of the ventral and dorsal horn. Following sciatic nerve transection, the number of CREB immunoreactive glial cells increased in both the ipsilateral ventral and dorsal horns between 24 h and 48 h, reached a maximum after 5 days and returned to control levels after 20 days. Counterstaining with Cresyl violet, a general stain of cells, revealed that the increase of CREB positive glial cells was congruent with the increase of the number of glial cells. Staining with GFAP, a marker for astrocytes, showed an increase in intensity of labelling but no change in number of GFAP labelled cells. This indicates a constitutive expression of CREB in activated microglia. The number of glial cells labelled by c-JUN and JUN D did not change, and glial cells were not labelled by FOS and KROX-24 proteins following sciatic nerve transection. These findings demonstrate that proliferation and differentiation of glial cells in vivo can occur in absence of JUN, FOS and KROX proteins.

Animals↗
PubMed1992

At least three promoters direct expression of the mouse glucocorticoid receptor gene.

We have characterized the gene for the mouse glucocorticoid receptor. The gene spans approximately 110 kilobases, and glucocorticoid receptor transcripts are assembled from nine exons. Expression of the gene is controlled by at least three promoters, resulting in glucocorticoid receptor transcripts with different 5' nontranslated exons. One promoter is cell-specific, found to be active only in T lymphocytes. The other two promoters are active to various degrees in all cell lines and tissues so far analyzed and are located in a CpG island. The promoter activities are accompanied by DNase I hypersensitivity sites in chromatin. In contrast to a conservation of exon-intron structure, differences in promoter organization suggest a divergence between the evolution of regulatory and coding regions among members of the steroid receptor super-family.

Animals↗
PubMed1992

Use of sialic acid analogues to define functional groups involved in binding to the influenza virus hemagglutinin.

The initial step of influenza infection is binding of the virus particles via their hemagglutinin to cell-surface sialic acids. This study was initiated to elucidate the functional groups of the nine-carbon sialic acid molecule which interact with the hemagglutinin and contribute to the affinity of this sugar to the protein. In order to address this question, synthetic sialic acid analogues were tested in a virus adsorption inhibition assay for their inhibitory potency. Modifications in three regions of the sialic acid molecule were evaluated: the glycerol side chain (C7-C9), the N-acetyl group at C5, and the carboxy group (C1). In the glycerol side chain, the hydroxy groups at C7 and C8 appear to be important for binding through hydrogen bonds, whereas the hydroxyl at C9 does not appear to be involved. The N-acetyl group is critical for the interaction of sialic acid with the hemagglutinin. The results suggest that its contribution is mediated through hydrophobic interactions of the methyl group. Finally, the orientation of the carboxy group is essential for the binding of sialic acid to the hemagglutinin. The information gained in this study will be useful in developing novel compounds which bind more avidly to the influenza virus hemagglutinin. Such a strategy may contribute to the design of new anti-influenza drugs.

Binding Sites↗
PubMed1992

Phosphorylation of CREB affects its binding to high and low affinity sites: implications for cAMP induced gene transcription.

Cyclic AMP treatment of hepatoma cells leads to increased protein binding at the cyclic AMP response element (CRE) of the tyrosine aminotransferase (TAT) gene in vivo, as revealed by genomic footprinting, whereas no increase is observed at the CRE of the phosphoenolpyruvate carboxykinase (PEPCK) gene. Several criteria establish that the 43 kDa CREB protein is interacting with both of these sites. Two classes of CRE with different affinity for CREB are described. One class, including the TATCRE, is characterized by asymmetric and weak binding sites (CGTCA), whereas the second class containing symmetrical TGACGTCA sites shows a much higher binding affinity for CREB. Both classes show an increase in binding after phosphorylation of CREB by protein kinase A (PKA). An in vivo phosphorylation-dependent change in binding of CREB increases the occupancy of weak binding sites used for transactivation, such as the TATCRE, while high affinity sites may have constitutive binding of transcriptionally active and inactive CREB dimers, as demonstrated by in vivo footprinting at the PEPCK CRE. Thus, lower basal level and higher relative stimulation of transcription by cyclic AMP through low affinity CREs should result, allowing finely tuned control of gene activation.

Amino Acid Sequence↗
PubMed1992

The transcription factors c-JUN, JUN D and CREB, but not FOS and KROX-24, are differentially regulated in axotomized neurons following transection of rat sciatic nerve.

In adult rats, expression of c-JUN, JUN B, JUN D, c-FOS, FOS B, KROX-24 and CREB proteins was investigated by immunocytochemistry in L4 and L5 dorsal root ganglia and lumbar spinal cord for up to 300 days following transection of the left sciatic nerve. In dorsal root ganglia, expressions of c-JUN and JUN D were increased 10 h and 15 h after sciatic nerve transection, respectively. c-JUN was still at an elevated level after 300 days predominantly in small diameter neurons, whereas JUN D had declined to control levels after 100 days. In contrast to the JUN proteins, expression of CREB showed a delayed onset after 10 days and reached a maximum between 70 and 150 days. In motoneurons, expression of c-JUN and JUN D was increased 15 h and 25 h after sciatic nerve transection, respectively. Expression of c-JUN remained increased after 150 days, whereas JUN D had declined to control levels after 70 days. In contrast, expression of CREB declined within 30 h in axotomized motoneurons and remained on a reduced level for up to 150 days. JUN B, c-FOS, FOS B and KROX-24 were not induced either following axotomy or following a repeated nerve crush. Sciatic nerve transection including the surgical procedure transynaptically provoked a transient expression of all JUN, FOS and KROX-24 proteins in neurons of spinal dorsal horn which disappeared after 5 days except the expression of JUN D which lasted for up to 20 days. In contrast, CREB immunoreactivity was not at all altered in neurons of spinal dorsal horn. In untreated animals, CREB and to a lesser extent JUN D showed an ubiquitous expression in neurons and glia cells of spinal cord, whereas expression of c-JUN and a weak expression of FOS B were restricted to motoneurons. In neurons of the dorsal root ganglia, a basal expression was found for c-JUN, JUN D and CREB and, at a low level, for FOS B and KROX-24. c-JUN and JUN D were colocalized with CREB in many cells such as interneurons, motoneurons, dorsal root ganglion cells and glial cells indicating the possibility for both the control of c-jun and jun D expression by CREB and the competition of JUN and CREB proteins for CRE consensus sequences.

Animals↗
PubMed1992

The ERE-like sequence from the promoter region of the testis specific hsp70-related gene is not estrogen responsive.

The 5'flanking region of the hsp70-related gene which is specifically expressed in rat and mouse spermatocytes contains the GGTCAnnnCGACC sequence closely resembling the palindromic consensus ERE (estrogen responsive element, GGTCAnnnTGACC). We used a transient expression assay to study whether this ERE-like sequence can transfer estrogen responsiveness either to heterologous or homologous promoters linked to a reporter CAT gene. We found that the GGTCAnnnCGACC sequence either as an isolated element or in its natural sequence context does not respond to hormone stimulation in MCF-7 and Fe33 cells. This observation points to the importance of the T-nucleotide in a right half-palindrome of ERE for ligand-dependent activation of transcription.

Animals↗
PubMed1992

[Noninvasive screening for chromosome abnormalities in young pregnant patients].

Two thirds of the patients with Down's syndrome are born by women below 35 years of age. An extension of invasive prenatal diagnosis to these women is problematical due to the operative risks and the relatively high costs. Therefore, non-invasive screening methods are sought, apt to identify groups at high risk. Biochemical screening methods applied at 16 weeks of pregnancy (triple test) and the new first trimester tests are discussed. Ultrasound screening at 10 to 12 weeks is dealt with in more detail. A large fluid cushion over most of the back was documented not only in most cases of trisomy 21 but in trisomies 18 and 13 and in Turner's syndrome as well. Only few chromosomally normal fetuses with the same peculiarity were observed. Systematic first trimester screening for nuchal fluid accumulation seems to be a recommendable method for the detection of chromosome anomalies. It compares favourably with current methods of maternal serum screening performed at 16-18 weeks which require a manyfold higher number of invasive procedures.

Amniocentesis↗
PubMed1991

[Neurofibromatosis Type 1: genetic studies with DNA markers in 38 families].

To establish preclinical DNA-diagnosis of neurofibromatosis type 1 (NF1) in familial cases we have investigated 38 families segregating for the disease. The families were tested with 6 polymorphic DNA markers from the chromosome region 17p11.1-q11.2. Two-thirds of the families were informative for flanking markers. An informative situation was achieved for 33 out of 40 individuals at risk (i.e. first degree relatives): 30 cases were diagnosed as noncarriers of the mutated gene, and three clinically normal individuals (including an adult and two children aged three and six respectively) were found to carry the risk haplotype. The remaining 7 persons at risk could not be typed unequivocally due to non-informative markers or recombination events. In 5 families with healthy grandparents the origin of the mutation could be traced back to the grandfather's germ cells. Despite the recent cloning and initial characterization of parts of NF1 gene, studies using linked and eventually intragenic DNA markers will continue to be of great value for genetic counselling. Such analyses allow highly accurate preclinical and prenatal diagnosis in close relatives of familial cases.

Adolescent↗
PubMed1991

A 48,XXY,+21 Down syndrome patient with additional paternal X and maternal 21.

The origin of meiotic nondisjunction of the extra chromosomes X and 21 was studied in a patient with the karyotype 48,XXY,+21 using DNA polymorphisms. The extra chromosome X was the result of paternal first meiotic nondisjunction of X and Y. The extra chromosome 21 was derived from the mother. The meiotic error in the mother most probably occurred in meiosis II. Thus, this is a combination caused by the chance occurrence of two independent events.

Aneuploidy↗
PubMed1991

A computer-based assessment of structural and displacement asymmetries of the mandible.

The purpose of this article was to assess and quantify the different components that can lead to mandibular asymmetry in a person during or at the end of growth and to investigate the extent to which improvement can be obtained in the different situations. Three boys and 17 girls, 8 to 21 years of age, with facial asymmetry and chin deviation were selected. Posteroanterior cephalometric radiographs were taken in intercuspal position. On each radiograph, three mandibular points (menton, gonion or antegonion, and articular point) were selected to define a mandibular area. A vertical axis of reference was also determined. Computer-aided design was employed to develop two systems (A and B) to assess a symmetry degree of the mandible. With system A, the left mandibular area was rotated around the vertical axis of reference, and the degree of the superimposition between the left and right areas was plotted. With system B, the left area was rotated around an axis that ran through menton and was perpendicular to a line connecting the two articular points of the mandible. Also, in this case, the degree of superimposition between the two areas was plotted. With system A, the degree of superimposition was a function of mandibular position and mandibular symmetry. With system B, it was a function of mandibular symmetry only. Thus through comparative examination of the data, assessment of displacement asymmetry and structural asymmetry was possible. In two patients, only displacement asymmetry was present, whereas 14 patients showed various features of structural asymmetry. The patients were treated with orthopedic splints to keep the mandible in a position of symmetry. Orthodontic treatment followed so that the intercuspal position would finally coincide with the position of symmetry. Computer-aided design analysis was performed again after a mean observation period of 41.1 months. In 11 patients an improvement in symmetry was observed with both systems. The patients in whom no improvement of structural asymmetry was observed showed a relatively high degree of symmetry at the beginning or had a considerably higher age than the mean age of the whole group. The clinical implications of the data are discussed.

Adolescent↗
PubMed1991

CMP-N-acetylneuraminic acid synthetase of Escherichia coli: high level expression, purification and use in the enzymatic synthesis of CMP-N-acetylneuraminic acid and CMP-neuraminic acid derivatives.

The gene encoding CMP-N-acetylneuraminic acid (CMP-NeuAc) synthetase (EC 2.7.7.43) in Escherichia coli serotype O7 K1 was isolated and overexpressed in E.coli W3110. Maximum expression of 8-10% of the soluble E.coli protein was achieved by placing the gene with an engineered 5'-terminus and Shine-Dalgarno sequence into a pKK223 vector derivative behind the tac promoter. The overexpressed synthetase was purified to greater than 95% homogeneity in a single step by chromatography on high titre Orange A Matrex dye resin. Enzyme purified by this method was used directly for the synthesis of CMP-NeuAc and derivatives. The enzymatic synthesis of CMP-NeuAc was carried out on a multigram scale using equimolar CTP and N-acetylneuraminic acid as substrates. The resultant CMP-NeuAc, isolated as its disodium salt by ethanol precipitation, was prepared in an overall yield of 94% and was judged to be greater than 95% pure by 1H NMR analysis. N-Carbomethoxyneuraminic acid and N-carbobenzyloxyneuraminic acid were also found to be substrates of the enzyme; 5-azidoneuraminic acid was not a substrate of the enzyme. N-Carbomethoxyneuraminic acid was coupled to CMP at a rate similar to that observed with NeuAc, whereas N-carbobenzyloxyneuraminic acid was coupled greater than 100-fold more slowly. The high level of expression achieved with the E.coli synthetase, together with the high degree of purity readily obtainable from crude cell extracts, make the recombinant bacterial enzyme the preferred catalyst for the enzymatic synthesis of CMP-N-acetylneuraminic acid.

Amino Acid Sequence↗
PubMed1990

Two genetically defined trans-acting loci coordinately regulate overlapping sets of liver-specific genes.

Mice homozygous for deletions around the albino locus fail to activate expression of a set of neonatal liver functions and die shortly after birth. This phenotype is thought to result from the loss of a positive transacting factor, denoted alf, in deletion homozygotes. Using differential cDNA screening, we isolated and characterized genes whose cell type-specific transcription is affected by alf and found as a common feature that expression of these genes is induced by glucocorticoids and cAMP. Surprisingly, a subset of these alf-responsive genes is negatively controlled by the tissue-specific extinguisher locus Tse-1. Administration of glucocorticoids and cAMP leads to reversal of Tse-1-mediated extinction of these genes. These results show that two trans-acting factors coordinately regulate expression of overlapping sets of liver-specific genes. We suggest that both the lethal phenotype and the extinguished state result from interference with hormone signal transduction.

Animals↗