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Biomedical subjects

K Wolf

Publications and source records attributed to K Wolf.

At least 73 records · Page 4Linked to original sources
PubMed1999

A novel group-II intron in the cox1 gene of the fission yeast Schizosaccharomyces pombe is inserted in the same codon as the mobile group-II intron aI2 in the Saccharomyces cerevisiae cox1 homologue.

We describe herein a large group-II intron which is inserted in the mitochondrial cox1 gene of the Schizosaccharomyces pombe strain EF2. The intron RNA consists of 2492 nucleotides which can be folded into a secondary structure with all the expected sequence motifs of subgroup-IIA1 introns (Michel et al. 1989). Determination of the exact splice point revealed that the intron is inserted in the same codon, but 1 bp downstream, as the mobile intron aI2 in the Saccharomyces cerevisiae cox1 homologue. A total of nine nucleotide changes was observed around the insertion site of the intron in the cox1 gene of strain EF2 compared with the reference strain ade7-50h(-). Seven of these changes are clustered within the 51 bp upstream of the splice point. Only one sequence deviation was found in the downstream exon. The intron is capable of splicing despite the fact that both the EBS1/IBS1 and the EBS2/IBS2 sequence motifs, thought to be necessary for correct splicing, extend over 5 instead of 6 bp. The maturase, endonuclease and reverse transcriptase domains of the putative protein encoded by the newly described S. pombe group-II intron were not closer to those encoded by the other two, cobI and cox2I, S. pombe group-II introns than to the group-II intron-encoded proteins in Allomyces, Marchantia, Podospora and Saccharomyces.

Amino Acid Sequence↗
PubMed1999

The effect of wind direction on the observed size distribution of particle adsorbed polycyclic aromatic hydrocarbons on an inner city sampling site.

An investigation of the variability in the size distribution of particle adsorbed polycyclic aromatic hydrocarbons (PAHs) on an inner city sampling site showed differences depending on the wind direction. Particle size distributions of PAHs from outdoor air sampling were measured in Munich from 1994 to 1997. The sampling site is located northeast of a crossing with heavy traffic and southwest of a large inner city park. Depending on the wind direction, three different size distributions of particle adsorbed PAHs were observed. The maximum PAH concentration on very small particles (geometric mean diameter 75 nm) was observed with wind from west to southwest coming directly from the crossing area or the roads with heavy traffic. The maximum PAH concentration on particles with geometric mean diameter of 260 nm was found on days with wind from the built-up area north of the sampling site. On particles with geometric mean diameter of 920 nm the maximum PAH concentration was found on days with main wind directions from northeast to east. On these days the wind is blowing from the direction of the city park nearby. The distribution of particle adsorbed PAHs within different particle size classes is substantially influenced by the distance of the sampling site from strong sources of PAH loaded particulate matter.

Cities↗
PubMed1999

Functional hierarchy of simultaneously expressed adhesion receptors: integrin alpha2beta1 but not CD44 mediates MV3 melanoma cell migration and matrix reorganization within three-dimensional hyaluronan-containing collagen matrices.

Haptokinetic cell migration across surfaces is mediated by adhesion receptors including beta1 integrins and CD44 providing adhesion to extracellular matrix (ECM) ligands such as collagen and hyaluronan (HA), respectively. Little is known, however, about how such different receptor systems synergize for cell migration through three-dimensionally (3-D) interconnected ECM ligands. In highly motile human MV3 melanoma cells, both beta1 integrins and CD44 are abundantly expressed, support migration across collagen and HA, respectively, and are deposited upon migration, whereas only beta1 integrins but not CD44 redistribute to focal adhesions. In 3-D collagen lattices in the presence or absence of HA and cross-linking chondroitin sulfate, MV3 cell migration and associated functions such as polarization and matrix reorganization were blocked by anti-beta1 and anti-alpha2 integrin mAbs, whereas mAbs blocking CD44, alpha3, alpha5, alpha6, or alphav integrins showed no effect. With use of highly sensitive time-lapse videomicroscopy and computer-assisted cell tracking techniques, promigratory functions of CD44 were excluded. 1) Addition of HA did not increase the migratory cell population or its migration velocity, 2) blocking of the HA-binding Hermes-1 epitope did not affect migration, and 3) impaired migration after blocking or activation of beta1 integrins was not restored via CD44. Because alpha2beta1-mediated migration was neither synergized nor replaced by CD44-HA interactions, we conclude that the biophysical properties of 3-D multicomponent ECM impose more restricted molecular functions of adhesion receptors, thereby differing from haptokinetic migration across surfaces.

Antibodies, Monoclonal↗
PubMed1999

Effect of azithromycin plus rifampin versus that of azithromycin alone on the eradication of Chlamydia pneumoniae from lung tissue in experimental pneumonitis.

Azithromycin, doxycycline, and rifampin, alone or in combination, were tested in vitro against Chlamydia pneumoniae AR-39. The combination of azithromycin plus rifampin showed the strongest activity and produced higher rates of eradication of C. pneumoniae from lung tissues than azithromycin alone in experimental mouse pneumonitis.

Animals↗
PubMed1999

Inhibition of the renin-angiotensin system upregulates cyclooxygenase-2 expression in the macula densa.

The expression of cyclooxygenase 2 (COX-2) in the late thick ascending limb, including the macula densa, is found to be upregulated in an activated renin-angiotensin system. How this upregulation is managed is not yet known. We therefore considered the possibility that the stimulation of COX-2 expression is triggered by the activation of the renin-angiotensin system. For this purpose, we treated male Sprague-Dawley rats with the angiotensin I-converting enzyme inhibitor ramipril (10 mg/kg per day), the angiotensin II type 1 (AT(1)) receptor blocker losartan (30 mg/kg per day), and the angiotensin II type 2 (AT(2)) receptor blocker PD123319 (6 mg/kg per day) for 4 days. We determined the expression of COX-2 mRNA and protein in the renal cortex. We found that ramipril and the AT(1) receptor blocker losartan increased COX-2 mRNA and COX-2 immunoreactivity in the macula densa approximately 4-fold, whereas the AT(2) blocker PD123319 showed no effect. A low-salt diet (0.02% wt/wt) stimulated COX-2 expression in the kidney cortex <2-fold. The combination of a low-salt diet with ramipril led to a further increase of COX-2 mRNA and COX-2 immunoreactivity compared with low salt or ramipril alone. These data indicate that endogenous angiotensin II apparently inhibits COX-2 expression in the macula densa via AT(1) receptors and can therefore not account for the stimulation of COX-2 expression associated with an activated renin-angiotensin system. Because macula densa-derived prostaglandins are considered stimulators of renin secretion and renin synthesis, inhibition of macula densa COX-2 by angiotensin II could form a novel indirect negative feedback control of the renin system.

Angiotensin II↗
PubMed1998

Mosaic structure of the cox2 gene in the petite negative yeast Schizosaccharomyces pombe: a group II intron is inserted at the same location as the otherwise unrelated group II introns in the mitochondria of higher plants.

In contrast to homologous genes in other fungal mitochondrial genomes, the gene encoding subunit 2 of cytochrome oxidase (cox2) in several Schizosaccharomyces pombe strains contains a large group II intron. Its 2436 nucleotides can be folded into a typical group II intron secondary structure, possessing all the expected sequence motifs for subgroup IIA1 (Michel et al., 1989). This intron is remarkable for the following reasons: (i) Five nucleotide changes were observed compared with the continuous form of the cox2 gene in the reference strain 50 at the 3'-exon sequence, but not in the 5'-exon. (ii) One of these changes occurred at the splice point leading to a serine instead of a threonine residue in the deduced cox2 polypeptide. In all cases, the alterations resulted in the replacement of more frequently used codons by rare ones. (iii) Although the intron is able to undergo splicing, the sequence motifs thought to be necessary for interaction between the 5'-exon and the intron during the splicing process (the EBS1/IBS1 as well as the EBS2/IBS2 pairings) are unusual. (iv) The intron is inserted at the same location in the cox2 gene as the otherwise unrelated intron from higher plants.

Alleles↗
PubMed1998

Relocation of urf a from the mitochondrion to the nucleus cures the mitochondrial mutator phenotype in the fission yeast Schizosaccharomyces pombe.

In previous papers we have reported the characterisation of mitochondrial mutator mutants of Schizosaccharomzyces pombe. In contrast to nuclear mutator mutants known from other eucaryotes, this mutator phenotype correlates with mutations in an unassigned open reading frame (urf a) in the mitochondrial genome. Since an efficient biolistic transformation system for fission yeast mitochondria is not yet available, we relocated the mitochondrial urf a gene to the nucleus. As host strain for the ectopic expression, we used the nonsense mutant ana(r)-6, which carries a premature stop codon in the urf a gene. The phenotype of this mutant is characterised by continuous segregation of progeny giving rise to fully respiration competent colonies, colonies that show moderate growth on glycerol and a fraction of colonies that are unable to grow on glycerol. The phenotype of this mutant provides an excellent tool with which to study the effects on the mutator phenotype of ectopic expression of the urf a gene. Since a UGA codon encoding tryptophan is present in the original mitochondrial gene, we constructed two types of expression cassettes containing either the mitochondrial version of the urf a gene (mt-urf a) or a standard genetic code version (nc-urf a; UGA replaced by UGG) fused to the N-terminal import leader sequence of the cox4 gene of Saccharomyces cerevisiae. We show that the expression of the mt-urf a gene in its new location is able to cure, at least in part, the phenotype of mutant ana(r)-6, whereas the expression of the nc-urf a gene completely restores the wild-type (non-mutator) phenotype. The significant similarity of the urf a gene to the mitochondrial var1 gene of S. cerevisiae and homologous genes in other yeasts suggests that the urf a gene product might be a ribosomal protein with a dual function in protein synthesis and maintenance of mitochondrial DNA integrity.

Amino Acid Sequence↗
PubMed1998

Vascular remodeling and growth factor gene expression in the rat lung during hypoxia.

Recent studies suggest that the vasoactive peptides endothelin-1 and -3 and the mitogens VEGF and PDGF-A and -B could be involved in the pathogenesis of hypoxic pulmonary hypertension. We were interested to investigate whether these peptides could also be involved in the vascular remodeling occurring during chronic hypoxia (10% oxygen; 1 and 3 weeks) in the rat. Hypoxia increased significantly systolic right ventricular pressure and typical morphological signs of vascular remodeling were found. This was accompanied by increased ET-1 and the ET-3 mRNA expression after acute (6 h; P < 0.05) and chronic hypoxia of 1 (P < 0.05) and 3 weeks (P < 0.05). In contrast, we found no effects of hypoxia on the gene expression of VEGF and PDGF-A and -B in the lung. Our findings indicate that ET-3 in addition to ET-1 could be involved in the process of hypoxia-induced vascular remodeling, whereas it appears less likely that the mitogens VEGF and PDGF-A and -B are essentially involved in the pathogenesis of hypoxic pulmonary hypertension.

Animals↗
PubMed1998

Identification of a protein essential for replication of porcine circovirus.

The largest open reading frame of porcine circovirus (ORF 4) encodes a protein of 312 amino acids. The predicted gene product of ORF 4 shows similarities to Rep proteins of other plant circoviruses and geminiviruses. Three motifs have been identified that are characteristic for proteins involved in rolling circle replication and the consensus sequence for a putative dNTP-binding box (GKS) has been found. In this paper, experimental evidence is presented which indicates that ORF 4 encodes the replication protein of porcine circovirus. After cloning of the ORF 4 gene product, it was supplied in trans in a transient replication assay. The ORF 4 gene product promoted the replication of plasmid pOP11, which carries the origin of DNA replication of porcine circovirus. Since pOP11 itself is unable to replicate in virus-free porcine kidney cells, the ORF 4 gene product must be essential for replication of porcine circovirus.

Amino Acid Sequence↗
PubMed1998

Crohn's disease masquerading as aphthous ulcers.

Although intraoral involvement in Crohn's disease (CD) is observed in only approximately 9% of cases, oral inflammation precedes intestinal symptoms of CD in about 60% of these patients. We describe a 20-year-old male with recurrent, painful, intraoral lesions who presented no other signs of systemic disease apart from severe loss of body weight. From the routinely screened serological parameters only the erythrocyte sedimentation rate and the acute phase reactants were elevated. A biopsy from the vestibular mucosa revealed a dense mononuclear infiltrate and, focally, small noncaseating granulomas suggestive of CD. Gastrointestinal endoscopy was performed showing mucosal involvement reaching from the esophagus to the descending colon. The diagnosis of active CD was confirmed by histopathology of intestinal biopsy specimens. As oral lesions are sometimes treated without a definite diagnosis, we emphasize the need to search for underlying systemic illness in the differential diagnosis of recurrent inflammatory lesions of the oral cavity.

Adult↗
PubMed1998

PET and SPECT in medically non-refractory complex partial seizures. Temporal asymmetries of glucose consumption, benzodiazepine receptor density, and blood flow.

AIM: In contrast to medically refractory complex partial seizures (CPS), only limited knowledge exists on cerebral perfusion and metabolism in medically non-refractory CPS. The aim of this study was to investigate the frequency of temporal asymmetries in regional cerebral glucose consumption (rCMRGlc), regional cerebral blood flow (rCBF), and regional cerebral benzodiazepine receptor density (BRD) in this group of patients. METHODS: The study included 49 patients with medically non-refractory cryptogenic CPS (age: 36.0 +/- 16.1 years). rCMRGlc was studied with F-18-FDG-PET (FDG), rCBF with Tc-99m-ECD-SPECT (ECD), and BRD with l-123-iomazenil-SPECT (IMZ). All studies were performed interictally and within four weeks in each patient. Duration of epilepsy ranged from 0.1 to 42 years (median 4.0 years). SPECT was performed with the triple-headed SPECT camera Multispect 3, PET with the PET camera ECAT EXACT 47. Using linear profiles, glucose consumption, as well as uptake of ECD and IMZ, were measured in four temporal regions of interest (ROIs), and asymmetry indices were calculated (ASY). The results were compared to 95% confidence intervals determined in control subjects. RESULTS: Thirty-five of the 49 (71%) patients had at least one significantly elevated ASY; temporal rCMRGlc was asymmetrical in 41% of the patients, temporal BRD in 29%, and temporal rCBF in 24%. One patient had an asymmetry of all three variables, two of temporal rCMRGlc and BRD, three of temporal rCMRGlc and rCBF, and another four of rCBF and BRD. Fourteen patients had an isolated temporal asymmetry in rCMRGlc, seven in BRD, and four in rCBF. A discrepancy in lateralization between the three modalities was not observed. CONCLUSION: The majority of patients with medically non-refractory CPS have focal abnormalities of blood flow and metabolism in their temporal lobe. In this group of patients, FDG-PET demonstrates abnormalities with the highest frequency of the three modalities studied, followed by IMZ-SPECT, and ECD-SPECT.

Adolescent↗
PubMed1997

Nitric oxide synthase isoform III gene expression in rat liver is up-regulated by lipopolysaccharide and lipoteichoic acid.

This study was done to investigate the influence of Gram-negative and Gram-positive sepsis on the expression of the three isoforms of nitric oxide synthase (NOS) gene in rat liver and kidney. Male Sprague-Dawley rats were treated with lipopolysaccharide (LPS, 10 mg/kg i.v.) as an in vivo model for Gram-negative sepsis or lipoteichoic acid (LTA, 10 mg/kg i.v.) as an in vivo model for Gram-positive sepsis. Animals were killed 12 h and 24 h after i.v. treatment. NOS mRNA of the three isoforms was determined by RNase protection assay. NOS II gene expression was strongly induced after LPS or LTA treatment in rat liver and kidney, indicating the efficacy of this treatment to induce sepsis. We found no change of NOS I gene expression after LPS or LTA injection in rat liver and kidney. NOS III gene expression was increased about 8-fold 12 h and about 5-fold 24 h after induction of sepsis in the rat liver whereas in the kidney there was no significant increase in NOS III gene expression. After correction for length NOS III mRNA was about 4- and 40-fold more abundant 12 h and 24 h after LPS treatment than NOS II mRNA in the liver, respectively. Twelve and 24 h after LTA treatment NOS III mRNA was about 18- and 140-fold more abundant than NOS II in the liver. These findings suggest that NOS III is an even more potent source of NO than NOS II in the liver after stimulation with LPS or LTA.

Animals↗
PubMed1997

[Value of imaging methods in trauma surgery].

Radiography is still the basic imaging method in traumatology and orthopedics. However, technical improvements and new imaging modalities may partially replace the conventional diagnostic imaging strategies. This review describes actual indications of x-ray examination, computed tomography (CT), ultrasonography and magnetic resonance imaging (MRI). New developments and future aspects in digital radiology, CT and MRI, two- and three-dimensional reconstruction techniques and image guided therapies are demonstrated.

Diagnostic Imaging↗
PubMed1997

Correlation of resistance to the alkaloid lycorine with the degree of suppressiveness in petite mutants of Saccharomyces cerevisiae.

In previous papers (Del Giudice et al. Curr Genet 8:493-497, 1984; Massardo et al. Curr Genet 17:455-457, 1985) we have shown that strains of Saccharomyces cerevisiae that are devoid of mitochondrial DNA (rhoo) are resistant to the alkaloid lycorine isolated from Amaryllis plants, whereas strains containing mitochondrial DNA (rho-, mit-, or rho+) are sensitive to this drug. In addition, we were able to show that the so-called hypersuppressive petites, whose mitochondrial genomes consist of short regions of DNA containing an ori sequence,show intermediate resistance. In this paper, we demonstrate that the degree of suppressiveness of a rho- mutant correlates with the degree of resistance to lycorine.

Alkaloids↗
PubMed1997

Hypoxia and cobalt stimulate vascular endothelial growth factor receptor gene expression in rats.

This study aimed to examine the influence of acute tissue hypo-oxygenation on the expression of the vascular endothelial growth factor (VEGF) receptor genes. To this end male Sprague-Dawley rats were exposed to different hypoxic conditions such as 10% or 8% oxygen, 0.1% carbon monoxide and cobalt chloride (60 mg/kg) for 6 h and the abundance of flt-1, flt-4 and flk-1 mRNA in lungs and livers was determined by RNase protection assay. The relative proportions of flt-1, flt-4 and flk-1 were 10:2.5:1 and 10:10:2 in normoxic lungs and livers, respectively. It was found that 8% but not 10% oxygen increased flt-1 mRNA two- to three-fold in both organs, whilst flt-4 and flk-1 mRNA were not changed by acute inspiratory hypoxia. Carbon monoxide inhalation also increased flt-1 mRNA but not flt-4 or flk-1 mRNA in both organs. Subcutaneous cobalt administration increased flt-1 mRNA in the livers only, whilst flt-4 and flk-1 mRNA remained unchanged. These findings show that acute tissue hypo-oxygenation is a rather selective stimulus for flt-1 gene expression. The efficiency of the different manoeuvres applied to stimulate flt-1 gene expression is rather similar to the stimulation of erythropoietin gene expression. It is not unreasonable to assume, therefore, that the oxygen-dependent regulation of both genes at the cellular level has significant similarities.

Animals↗
PubMed1997

Influence of salt intake on atrial natriuretic peptide gene expression in rats.

Mammalian atrial cardiocytes produce and secrete a peptide hormone called atrial natriuretic peptide (ANP), which causes diuresis, natriuresis, a decrease of blood pressure and inhibition of smooth muscle contraction, renin and aldosterone release. Despite a variety of investigations, the influence of salt intake on the transcriptional regulation and the circulating levels of ANP is still not clear. This study sought to examine the influence of different levels of long-term dietary salt intake on the expression of the ANP gene in different regions of the rat heart. To this end male Sprague-Dawley rats were fed either a high-salt (4% saline chow) or a low-salt (0.02% saline chow) diet for 5, 10 or 20 days. Another group had access to normal chow and received 1% NaC1 as a drinking solution for 10 days. During the experiment sodium and chloride uptake via food or drinking solutions was monitored and sodium and chloride excreted in the urine was determined. ANP mRNA levels in the atria and the ventricles were assayed. We found that no form of the different salt diets had influence on cardiac ANP mRNA levels at any of the times examined though excretion rates of sodium and chloride differed by a factor of 200. Also plasma immunoreactive ANP remained unaltered. At the same time plasma renin activities were markedly increased in rats fed a low-salt diet and substantially suppressed in rats fed a high-salt diet, suggesting the efficacy of the salt diet. Our findings suggest that ANP gene expression and secretion of the active hormone are probably not involved in salt balance during chronic salt loading given by dietary food or by 1% NaCl in the drinking water.

Animals↗