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Biomedical subjects

K Mann

Publications and source records attributed to K Mann.

At least 199 records · Page 11Linked to original sources
PubMed1998

[Subtotal retroperitoneoscopic adrenal gland resection--an alternative to adrenalectomy?].

Primary adrenal tumors were removed in 24 patients by the posterior retroperitoneoscopic approach, maintaining tumor-free parts of the ipsilateral adrenal gland. These partial adrenal resections did not cause a significantly different operating time or blood loss compared to 58 complete adrenalectomies performed during the same period. All 20 patients with hormonally active tumors are biochemically and clinically cured (mean follow-up 18 months). In selected cases the retroperitoneoscopic subtotal adrenal gland resection is a safe procedure, which can potentially maintain the function of the adrenal gland's cortex.

Adrenal Gland Neoplasms↗
PubMed1997

Cloning, sequencing, crystallization and X-ray structure of glutathione S-transferase-III from Zea mays var. mutin: a leading enzyme in detoxification of maize herbicides.

Glutathione S-transferases (GSTs) are enzymes that inactivate toxic compounds by conjugation with glutathione and are involved in resistance towards drugs, antibiotics, insecticides and herbicides. Their ability to confer herbicide tolerance in plants provides a tool to control weeds in a wide variety of agronomic crops. GST-III was prepared from Zea mays var. mutin and its amino acid sequence was determined from two sets of peptides obtained by cleavage with endoprotease Asp-N and with trypsin, respectively. Recombinant GST-III was prepared by extraction of mRNA from plant tissue, transcription into cDNA, amplification by PCR and expression. It was crystallized and the crystal structure of the unligated form was determined at 2.2 A resolution. The enzyme forms a GST-typical dimer with one subunit consisting of 220 residues. Each subunit is formed of two distinct domains, an N-terminal domain consisting of a beta-sheet flanked by two helices, and a C-terminal domain, entirely helical. The dimeric molecule is globular with a large cleft between the two subunits. The amino acid sequence of GST-III and its cDNA sequence determined here show differences from sequences published earlier.

Amino Acid Sequence↗
PubMed1997

Intra- and interhemispheric electroencephalogram coherence in siblings discordant for schizophrenia and healthy volunteers.

Former studies had pointed to an increased electroencephalogram (EEG) coherence in schizophrenics, but it remained unsolved whether this deviation represents the premorbid state or is only a consequence of the current or previous schizophrenic episodes. To clarify this question, we tested the hypothesis that subjects at elevated risk also reveal higher coherences compared to healthy controls. For that, intra- and interhemispheric EEG coherences were investigated in untreated schizophrenics, their healthy siblings, and healthy controls. Differences were only found regarding the intrahemispheric coherences. Both in schizophrenics and, even though to a lesser degree, in their siblings significantly higher coherence estimates were found compared to the control group. The results are in accordance with the assumption that schizophrenia is predominantly a neurodevelopmental disease. Increased coherence might be assumed to be a vulnerability marker for schizophrenia reflecting maldevelopment of the brain before onset of the disorder.

Adult↗
PubMed1997

[Incidence, clinical picture and treatment of hypothyroid coma. Results of a survey].

BACKGROUND: Myxedema coma is a severe life-threatening clinical state with a high mortality rate. Very often symptoms are masked because of concurrent illnesses. There are no data available about the incidence and prevalence of this disease. Therefore we conducted a survey in the Federal Republic of Germany between 1993 and 1995 by a questionnaire on the occurrence of myxedema coma. METHODS: Questionnaires were mailed to 800 departments of medicine. RESULTS: We received 168 questionnaires for further evaluation. Among those, 24 patients were classified as myxedema coma, but according to clinical data we could reclassify 12 patients as myxedema coma and 12 patients as severely hypothyroid but without coma. The mean age of the patients was 73 years. The etiology was Hashimoto's thyroiditis in 16 patients (67%), in 15 patients the thyroid disease was unknown. In 6 patients thyroid hormone therapy was withdrawn after thyroid surgery. One patient became hypothyroid after radioiodine therapy and 1 patient had secondary hypothyroidism. 19 of the 24 patients received i.v. thyroxine therapy and 11 patients received corticosteroids additionally. Six patients (25%) died. CONCLUSION: These data emphasize that myxedema coma is a rare disease (24 patients within two years in Germany) occurring especially in older patients and is associated with a high mortality rate also in non-comatose patients. In the majority of the patients myxedema coma was the first manifestation of thyroid disease.

Aged↗
PubMed1997

Structural and functional characterization of the extracellular calcium-binding protein BM-40/secreted protein, acidic, rich in cysteine/osteonectin from the nematode Caenorhabditis elegans.

Caenorhabditis elegans BM-40 (positions 19-264) and its extracellular calcium-binding domain (positions 139-264) were obtained in recombinant form from human kidney cells using an episomal expression vector. The purified proteins showed single bands of 33 kDa [BM-40-(19-264)-peptide] or 14 kDa [BM-40-(139-264)-peptide] on electrophoresis, contained internal disulfide bonds and a helices and were relatively resistant to matrix metalloproteinases. Hexosamine analysis indicated substitution by one N-linked and two O-linked oligosaccharides and recombinant BM-40 was indistinguishable in its immunological epitopes from nematode tissue-derived BM-40, suggesting that it was obtained in native form. Both recombinant C. elegans proteins showed a distinct binding activity for human collagens I and IV in solid-phase and surface-plasmon-resonance assays with an affinity (Kd = 1-2 microM), comparable to that of mammalian BM-40. However, calcium-binding studies revealed only a low-affinity site (Kd = 6.2 mM) and failed to show the characteristic conformational change upon addition of EDTA. These and a few other differences are apparently due to two extra disulfide bonds and two deletions/insertions in C. elegans BM-40 and can be partly interpreted from the X-ray structure of a large part of human BM-40. The immunological assays available and the predictions of the location of the collagen-binding epitope should facilitate a molecular and genetic approach to understand the function of BM-40 in the development of C. elegans.

Amino Acid Sequence↗
PubMed1997

Dimer model for the microfibrillar protein fibulin-2 and identification of the connecting disulfide bridge.

Fibulin-2 is a novel extracellular matrix protein frequently found in close association with microfibrils containing either fibronectin or fibrillin. The entire protein and its predicted domains were obtained as recombinant products and examined by ultracentrifugation and electron microscopy. This demonstrated a disulfide-linked homodimer of 175 kDa subunits. Partial reduction to monomers identified specifically an odd Cys574 residue responsible for dimer formation in one of three anaphylatoxin-like modules that constitute the central globular domain I (13 kDa) of fibulin-2. Furthermore, a Cys574-Ser mutation abolished disulfide connection but not non-covalent dimerization of fibulin-2. The C-terminal region (85 kDa) was shown to represent a 35-nm-long rod consisting of 11 calcium-binding EGF-like modules (domain II) and a small terminal globe (domain III). The unique N-terminal domain N (55 kDa) was also rod-shaped (approximately 38 nm) and rich in galactosamine indicating extensive O-glycosylation. A dimer model is proposed indicating mainly a rod-like shape of 80 nm length based on an anti-parallel association of two subunits through their domains I. This model also implies alignment of domains II and N between different subunits. This was demonstrated by surface plasmon resonance assay which showed a distinct interaction between domains N and II with a Kd of approximately 0.7 microM.

Amino Acid Sequence↗
PubMed1997

Significant changes in thyroid hormone parameters after a four week recreation period at the North Sea without alterations of iodine intake.

UNLABELLED: Many studies have been carried out evaluating thyroid hormone parameters in patients suffering from various illnessess. However data on thyroid function after a recreation period are missing. Therefore we evaluated thyroid hormone parameters in 178 patients (mostly suffering from chronic obstructive lung disease) undergoing a four week recreation period in a health spa on the island Borkum at the North Sea. We observed a subtle, but significant increase in basal TSH concentrations from 1.20 mU/l (median) to 1.50 mU/l; (p<0. 001) and a fall in T4 values from 97.5 +/- 17.7 nmol/l (mean +/- SD) to 90.3 +/- 17.0 (p<0.001) and T3 from 2.21 +/- 0.33 nmol/l to 2.09 +/- 0.33 (p<0.001). However no increase in iodine intake occurred during the four weeks: median iodine excretion 61 microg iodine/g creatinine at the beginning vs 65 microg iodine/g creatinine at the end. IN CONCLUSION: a recreation period at the North Sea is associated with subtle but significant changes in thyroid hormone parameters. However no increase in iodine intake occurs during the four week observation period.

Adult↗
PubMed1997

Drosophila laminin binds to mammalian nidogen and to heparan sulfate proteoglycan.

A Drosophila laminin that has the chain composition alpha5 beta1 gamma1, relative to mammalian laminins, bound human and mouse nidogen almost as strongly as mouse laminin-1 (alpha1 beta1 gamma1) in solid-phase assays, and had only a fourfold lower affinity in a radioligand competition test. This is due to a short, highly conserved sequence that occurs in both laminin gamma1 chains and which binds nidogen. When the single conservative amino acid difference between the two sequences (Tyr-->His) was introduced into the mouse laminin binding module gamma1 III4 it failed to cause any change of binding. A high affinity between Drosophila laminin and mouse nidogen resulted in the formation of a stable complex in solution. Drosophila laminin also bound to the mouse heparan sulfate proteoglycan perlecan and the formation of this complex was inhibited by heparin, but not by chondroitin sulfate. In addition, a weaker connection between the core protein of mouse perlecan and Drosophila laminin can be mediated through nidogen. Elastase and other proteases degraded Drosophila laminin to a restricted number of larger fragments (40-300 kDa), almost all of which were bound to a heparin affinity column. Three fragments could be displaced at low salt concentration and were derived from the short arms of the Drosophila laminin, as shown by sequence analysis. A more strongly bound 50-kDa fragment apparently comprised the globular domains LG2 and LG3 derived from the C-terminal part of its alpha chain. Therefore, Drosophila laminin and mouse laminin-1 differ in certain aspects of protease stability and heparin-binding sites that, in part, can be attributed to their different alpha chains. The data suggest the existence of a nidogen analog and heparan sulfate proteoglycans in Drosophila, which remain to be identified.

Animals↗
PubMed1997

Limited cleavage of extracellular matrix protein BM-40 by matrix metalloproteinases increases its affinity for collagens.

The 33-kDa matrix protein BM-40 (SPARC, osteonectin) consists of an acidic N-terminal domain I, a central cysteine-rich follistatin-like module, and a C-terminal extracellular calcium-binding (EC) module. Previous studies attributed collagen IV and high affinity calcium binding of BM-40 to its EC module, which was shown by x-ray crystallography to consist of an EF-hand pair surrounded by several alpha-helical and loop segments. This module was now shown by surface plasmon resonance assay to bind with similar affinities to collagens I, III, and V. Cleavage of recombinant BM-40 and its EC module by collagenase-3, gelatinases A and B, matrilysin, and stromelysin-1 showed similar fragment patterns, whereas collagenase-1 was inactive. Some differences were, however, observed in cleavage rates and the preference of certain cleavage sites. Edman degradation of fragments demonstrated only three to four major cleavage sites in the central region of domain I and a single uniform cleavage in helix C of the EC module. Cleavage is accompanied by a 7-20-fold increase in binding activity for collagens I, IV, and V but revealed only small effects on calcium-dependent alpha-helical changes in the EC module. The data were interpreted to indicate that helix C cleavage is mainly responsible for enhancing collagen affinity by exposing the underlying helix A of the EC module. A similar activation may also occur in situ as indicated previously for tissue-derived BM-40.

Amino Acid Sequence↗
PubMed1997

Recombinant expression and isolation of human L-arginine:glycine amidinotransferase and identification of its active-site cysteine residue.

Creatine and its phosphorylated form play a central role in the energy metabolism of muscle and nerve tissues. l-Arginine:glycine amidinotransferase (AT) catalyses the committed step in the formation of creatine. The mitochondrial and cytosolic forms of the enzyme are believed to derive from the same gene by alternative splicing. We have expressed recombinant human AT in Escherichia coli with two different N-termini, resembling the longest two forms of the enzyme that we had isolated recently from porcine kidney mitochondria as a mixture. The enzymes were expressed with N-terminal histidine tags followed by factor Xa-cleavage sites. We established a new method for the removal of N-terminal fusion peptides by means of an immobilized snake venom prothrombin activator. We identified cysteine-407 as the active-site residue of AT by radioactive labelling and isolation of labelled peptides, and by site-directed mutagenesis of the protein.

Amidinotransferases↗
PubMed1997

Redox state regulates binding of p53 to sequence-specific DNA, but not to non-specific or mismatched DNA.

Redox modulation of wild-type p53 plays a role in sequence-specific DNA binding in vitro . Reduction produces a DNA-binding form of the protein while oxidation produces a non-DNA-binding form. Primer extension analysis reveals that increasing concentrations of reduced p53 result in enhanced protection of the consensus sequence, while increasing concentrations of oxidized p53 confer minimal protection of the consensus sequence. DNA binding by oxidized p53 is, therefore, not sequence-specific. In contrast, there is no observable difference in the binding of oxidized p53 and reduced p53 to double-stranded non-specific or mismatched DNA in gel mobility shift assays. Both forms of p53 bind equally well, suggesting that redox modulation of p53 does not play a role in its binding to non-specific or mismatched DNA. In view of the in vitro evidence that redox state influences the sequence-specific DNA-binding of p53, we have examined the effect of oxidative stress on the in vivo ability of p53 to bind to and transactivate PG13-CAT, a reporter construct containing multiple copies of the p53 consensus binding site linked to the chloramphenicol acetyltransferase gene. Hydrogen peroxide treatment of cells cotransfected with p53 results in a marked decrease in CAT activity, suggesting that oxidation of p53 decreases the ability of the protein to bind to consensus DNA and transactivate target genes in vivo.

Animals↗
PubMed1997

Characterization of recombinant perlecan domain I and its substitution by glycosaminoglycans and oligosaccharides.

Recombinant mouse perlecan domain 1(173 residues) was produced in transfected embryonic kidney cells and purified from the culture medium on DEAE-cellulose. It was shown to be modified by glycosaminoglycans and could be partially separated into two protein pools which were either substituted with heparan sulfate (fragment IA) or, to a smaller extent (20%), with chondroitin/dermatan sulfate or a mixture of both glycosaminoglycans (fragment IB). The average molecular mass of the glycosaminoglycans was about 8-10 kDa and, thus, smaller than in tissue-derived perlecans. Sequence and carbohydrate analyses localized the heparan sulfate attachment site to three Ser residues within SGD consensus sequences. Furthermore, the N-terminal part of fragment IA contained six Thr/Ser residues substituted by branched galactosamine-containing oligosaccharides and an N-substituted Asn residue. Fragment I was also shown to contain unique immunological epitopes which are not dependent on glycosaminoglycans and are shared by tissue-derived perlecan. Circular dichroism demonstrated a distinct alpha helix (20%) and beta structure (60%) in fragment IA, consistent with predictions of a novel SEA protein module located in the C-terminal part of domain I.

Amino Acid Sequence↗
PubMed1997

Identification of bovine zona pellucida glycoproteins.

Despite the economical importance of in vitro gamete technologies in cattle, only little is known about the molecular mechanisms of binding of spermatozoa to the zona pellucida (ZP) of the oocyte. The aim of the present work was to identify proteins from the bovine zona pellucida (bZP) and to investigate which bZP proteins play a role in sperm-egg binding. High resolution 2-dimensional polyacrylamide gel electrophoresis of bZP proteins under reducing conditions showed that the bovine ZP could be separated into 4 glycoprotein spots, provisionally named bZP1, bZP2, bZP3, and bZP4, with different molecular masses and isoelectrical points. The N-terminal amino acid sequence of bZP1, bZP2, and bZP4 could be determined. The N-terminal amino acid sequences of bZP1 and bZP4 were identical and were homologous to that of pZP4. Comparison of our data to that of Noguchi et al., 1994 (Biochim Biophys Acta 1201:7-14) revealed that bZP2 and bZP4 are fragments of bZP1. Immunoblot analysis showed that, respectively, anti-porcine-ZP3alpha and -ZP3beta antibodies recognized 2 distinct regions of the bZP3 spot. Both antibodies inhibited sperm-egg binding in the bovine. We conclude that the bovine ZP consists of 3 proteins that correspond by size, N-terminal amino acid sequence, and antigenic determinants of pZP1, pZP3alpha, and pZP3beta, respectively, that are encoded by the porcine ZPA, ZPB, and ZPC genes (Harris et al., 1994: J Seq Map 4:6331-393), respectively.

Animals↗
PubMed1997

Retinal GFAP and bFGF expression after multiple argon laser photocoagulation injuries assessed by both immunoreactivity and mRNA levels.

The expression of GFAP and bFGF after retinal photocoagulation injury in the rat was assessed by immunocytochemistry and reverse transcriptase PCR. Beta-actin mRNA expression was unaltered after injury and was therefore a good control for the quality of the RNA samples and the PCR reaction. GFAP mRNA increased from undetectable levels in normal retina to relatively high levels at 24 and 48 hr after injury, returning to barely detectable levels at 3 and 7 days. Müller cell GFAP immunoreactivity was elevated by 24 hr, stronger by 48 hr and persisted for 30-45 days. Thus, the expression of GFAP immunoreactivity after photocoagulation was due to new protein synthesis but the mRNA, and therefore the stimulus, was only present for a few days. This indicates that the GFAP protein in Müller cells has a long lifetime similar to that of astrocytes despite different gene control elements. bFGF is a possible stimulus for Müller GFAP expression because Müller cells have bFGF receptors. bFGF mRNA was detectable in normal, 24 and 48 hr retinas but decreased to undetectable levels (even after 35 cycles of PCR) at three days after injury and had only partly recovered by 7 days. Immunocytochemistry demonstrated a rapid change in localization of bFGF at the lesion sites early after lesion. At 2-3 days bFGF in blood vessels was markedly increased while at 7 days there was an increase around the photoreceptors flanking each lesion. These shifts in bFGF localization were too late to be a stimulus for the widespread upregulation of GFAP expression by Müller cells. The reduction in bFGF mRNA at three days was unexpected as studies of brain injury generally show a longer lasting elevation of bFGF expression. Therefore it is likely that bFGF expression is controlled by different mechanisms in the retina compared to the brain. However, a reduction in bFGF synthesis after photocoagulation is consistent with the anti-angiogenic effect of laser photocoagulation in diabetic retinopathy.

Actins↗
PubMed1997

Recombinant and tissue-derived mouse BM-40 bind to several collagen types and have increased affinities after proteolytic activation.

The calcium-binding extracellular matrix protein BM-40 was obtained as a mouse cDNA product from a stably transfected kidney cell clone. Electrophoresis and N-terminal sequence analysis demonstrated absence of the proteolytic processing previously observed for a mouse tumour-derived BM-40. Yet the two forms of BM-40 were very similar in their CD spectra, their calcium-dependent change in alpha helix content and their immunological epitopes. In surface plasmon resonance assays, recombinant mouse BM-40 showed distinct binding to the triple-helical domains of collagens I, II, III, IV and V with Kd = 1-4 microM but no binding to collagen VI. These interactions were abolished in the presence of EDTA. Tissue-derived mouse BM-40, however, bound collagens I and IV with Kd = 0.1-0.2 microM. Activation of collagen binding to give a similar Kd could be achieved for recombinant mouse BM-40 by treatment with the matrix metalloproteinase collagenase-3. The major cleavage site was located in helix C of the extracellular calcium-binding module of BM-40 and other less prominent cleavages occurred close to the N-terminus. The sensitive helix C site was just one residue away from that sensitive to endogenous tissue proteolysis, suggesting that cleavage could be a physiological mechanism to modulate collagen binding.

3T3 Cells↗
PubMed1997

[Dependency outcome of alcohol-dependent patients after inpatient detoxification and motivation treatment].

In addition to psychiatric outpatient treatment, the detoxification of alcoholics in psychiatric hospitals is an important link between medical detoxification and psychosocial inpatient treatment aiming at abstinence. Integrated models of inpatient detoxification and motivation therapy focus on improvement of the motivation of patients towards further treatment of their alcoholism and towards abstinence. In our study 529 alcoholics underwent such treatment lasting between 2 to 3 weeks. A total of 469 patients (89%) were followed up after 8 months; 242 alcoholics (52% of the follow-up sample; 46% of the whole sample) achieved the treatment goal and started further treatment, mainly as inpatients. Fifty-four of these patients relapsed before they started further alcoholism treatment, but achieved abstinence afterwards; 60 (25%) of these 242 patients relapsed after the specific alcoholism therapy; 227 alcoholics did not start further treatment after the initial detoxification and motivation therapy. In this subpopulation, 113 (50%) relapsed during the follow-up period. Although this is not a controlled study, it can be concluded that integrated inpatient detoxification and motivation therapy has positive effects on the treatment behavior of alcoholic patients and enhances the probability of further abstinence.

Adult↗
PubMed1997

Analysis of sleep EEG microstructure in subchronic paroxetine treatment of healthy subjects.

Paroxetine is a selective and potent serotonin reuptake inhibitor and its efficacy for the treatment of depression has been proven. Under acute and subchronical treatment regimens, disturbances of the regular sleep pattern are a reported side effect of the drug. The present study was therefore performed to investigate the impact of subchronic treatment with the selective serotonin reuptake inhibitor paroxetine on the microstructure of the sleep EEG. The study especially addressed the question of subchronic effects of paroxetine medication (30 mg/day) in eight healthy male volunteers in a double blind, placebo-controlled crossover design. Conventional sleep EEG parameters and a spectral power analysis for different sleep stages after 4 weeks of treatment were computed. Additionally, the correlation of certain EEG rhythms across the night was calculated in order to detect subtle dynamical EEG alterations, not necessarily obvious when regarding conventional EEG analysis. Although we could not detect any alterations of the spectral power values in certain frequency bands either during NREM nor during REM sleep following subchronic paroxetine medication, the dynamical EEG attributes across the night revealed a significant enhancement of the correlation between certain EEG rhythms mainly during NREM sleep.

Adult↗