Biomedical subjects

A Völker

Publications and source records attributed to A Völker.

At least 19 recordsLinked to original sources

PubMed2001

A comprehensive two-dimensional map of cytosolic proteins of Bacillus subtilis.

Proteomics relying on two-dimensional (2-D) gel electrophoresis of proteins followed by spot identification with mass spectrometry is an excellent experimental tool for physiological studies opening a new perspective for understanding overall cell physiology. This is the intriguing outcome of a method introduced by Klose and O'Farrell independently 25 years ago. Physiological proteomics requires a 2-D reference map on which most of the main proteins were identified. In this paper, we present such a reference map with more than 300 entries for Bacillus subtilis proteins with an isoelectric point (pI) between 4 and 7. The most abundant proteins of exponentially growing cells were compiled and shown to perform mainly housekeeping functions in glycolysis, tricarboxylic acid cycle (TCC), amino acid biosynthesis and translation as well as protein quality control. Furthermore, putative post-translational modifications were shown at a large scale, with 47 proteins in total forming more than one spot. In a few selected cases evidence for phosphorylation of these proteins is presented. The proteome analysis in the standard pI range was complemented by either stretching the most crowded regions in a narrow pH gradient 4.5-5.5, or by adding other fractions of the total B. subtilis proteome such as alkaline proteins as well as extracellular proteins. A big challenge for future studies is to provide an experimental protocol covering the fraction of intrinsic membrane proteins that almost totally escaped detection by the experimental procedure used in this study.

Bacillus subtilis↗

PubMed2001

Cell cycle-independent expression of the Arabidopsis cytokinesis-specific syntaxin KNOLLE results in mistargeting to the plasma membrane and is not sufficient for cytokinesis.

The Arabidopsis KNOLLE gene encodes a cytokinesis-specific syntaxin that localises to the plane of division and mediates cell-plate formation. KNOLLE mRNA and protein expression is tightly regulated during the cell cycle. To explore the significance of this regulation, we expressed KNOLLE protein under the control of two constitutive promoters, the flower-specific AP3 and the cauliflower mosaic virus 35S promoter. The transgenic plants developed normally, although KNOLLE mRNA and protein accumulated to high levels in non-proliferating cells and protein was incorporated into membranes. Immunolocalisation studies in transgenic seedling roots revealed mistargeting of KNOLLE protein to the plasma membrane in tip-growing root hairs and in expanding root cells, whereas no mislocalisation was observed in proliferating cells. By comparative in situ hybridisation to embryo sections, the 35S promoter yielded, relative to the endogenous KNOLLE promoter, low levels of KNOLLE mRNA accumulation in proliferating cells that were insufficient to rescue cytokinesis-defective knolle mutant embryos. Our results suggest that in wild type, strong expression of KNOLLE protein during M phase is necessary to ensure efficient vesicle fusion during cytokinesis.

Arabidopsis↗

PubMed1998

Nonnative proteins induce expression of the Bacillus subtilis CIRCE regulon.

The chaperone-encoding groESL and dnaK operons constitute the CIRCE regulon of Bacillus subtilis. Both operons are under negative control of the repressor protein HrcA, which interacts with the CIRCE operator and whose activity is modulated by the GroESL chaperone machine. In this report, we demonstrate that induction of the CIRCE regulon can also be accomplished by ethanol stress and puromycin. Introduction of the hrcA gene and a transcriptional fusion under the control of the CIRCE operator into Escherichia coli allowed induction of this fusion by heat shock, ethanol stress, and overproduction of GroESL substrates. The expression level of this hrcA-bgaB fusion inversely correlated with the amount of GroE machinery present in the cells. Therefore, all inducing conditions seem to lead to induction via titration of the GroE chaperonins by the increased level of nonnative proteins formed. Puromycin treatment failed to induce the sigmaB-dependent general stress regulon, indicating that nonnative proteins in general do not trigger this response. Reconstitution of HrcA-dependent heat shock regulation of B. subtilis in E. coli and complementation of E. coli groESL mutants by B. subtilis groESL indicate that the GroE chaperonin systems of the two bacterial species are functionally exchangeable.

Bacillus subtilis↗

PubMed1997

Studies on spontaneous promoter-up mutations in the transcriptional activator-encoding gene phIR and their effects on the degradation of phenol in Escherichia coli and Pseudomonas putida.

The activator-encoding gene phlR was identified upstream of the plasmid-encoded operon for phenol degradation in Pseudomonas putida strain H by cassette mutagenesis and DNA sequence analysis. The deduced amino acid sequence of PHLR shows high homology to DmpR of P. putida sp. CF600 and to the chromosomally encoded PhhR of P. putida P35X reported previously. Trans-activation of phenol degradation was observed when phlR was overexpressed in a phlR insertion mutant. Transconjugants of Escherichia coli carrying pPGH11, which contains the complete set of phl genes, are unable to grow on phenol as carbon source. However, two types of mutants were selected for further characterization that were able to metabolize phenol as sole source of carbon and energy. In both types of mutants enhanced expression of phlR is responsible for the Phl+ phenotype. In type I (pPGH13) a deletion of 1 bp made the -35 region and the spacing between the -35 and -10 regions of the phlR promoter more similar to the consensus structure. In type II (pPGH14) a duplication of the phlR 5' region was identified that includes part of the -35 motif and reduces the spacing between the -35 and -10 regions. In addition, due to the duplication of part of phlR, the distance from the phlR promoter to the catabolic phl operon is increased. Different transcriptional start sites have been identified by primer extension analysis in clones harboring pPGH14 or the wild type phlR. Quantitative primer extension analysis revealed that the greatest amount of phlR transcript is expressed from the partial, phlR duplication. Growth on phenol and phenol hydroxylase activity reflect the high level of phlR transcript in E. coli transconjugants. Overexpression of PhlR was also observed when pPGH14 was transferred into P. putida, and results in earlier induction of the phenol degradation operon relative to the wild-type strain.

Bacterial Proteins↗

PubMed1996

Functional relevance of anaerobic metabolism in the isolated respiratory network of newborn rats.

Respiratory (C3-C5) activity and extracellular K+, pH and Ca2+ (aKe, pHe, [Ca]e, respectively) in the ventral respiratory group (VRG) were measured in vitro. In brainstem-spinal cord preparations from 0- to 1-day-old rats, lowering of bath glucose content from 30 to 10 mM for 1 h did not affect aKe or rhythmic activity. In preparations from 2- to 3-day-old animals, however, an aKe rise by about 1 mM and disturbance of rhythm occurred after a delay of 50 min. Glucose-free saline resulted, after about 30 min, in reversible blockade of respiratory rhythm and an aKe rise by more than 8 mM, whereas pHe remained unaffected. Exposure to anoxia for 30 min after 1 h of pre-incubation in 10 mM glucose led to a progressive rise of aKe, and a fall of [Ca]e. The concomitant suppression of rhythm was irreversible in preparations from 2- to 3-day-old animals. Similar effects on aKe and [Ca]e and irreversible blockade of rhythm were revealed during anoxia in glucose-free solution, or by addition of 2-5 mM iodoacetate to oxygenated or hypoxic solutions. Iodoacetate led to a slow increase of pHe by more than 0.2 pH units, which was accelerated by anoxia. Our findings show that normal respiratory network functions in the en bloc medulla, in particular from rats older than 1 day, depend on high bath glucose levels, necessary for effective utilization of anaerobic metabolism.

Acidosis↗

PubMed1995

Anoxic disturbance of the isolated respiratory network of neonatal rats.

Tissue oxygen (PO2), K+ (aKe), pH (pHe) and Ca2+ ([Ca2+]e) were measured in the region of the ventral respiratory group (VRG) in the in vitro brainstem-spinal cord preparation of neonatal rats. During tissue anoxia, elicited by superfusion of N2-gassed solutions, an initial increase in the frequency of respiratory activity, lasting between 2 and 12 min, turned into a frequency depression. During anoxia periods of up to 60 min, respiratory activity persisted in solutions containing CO2/bicarbonate, whereas a complete blockade was observed after 15-25 min in N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid- (Hepes)-buffered salines. After such anoxic apnea, respiratory rhythmicity could be reactivated by superfusion of hypoxic, CO2/bicarbonate-buffered solutions. In both types of hypoxic solutions, aKe increased by maximally 1.5 mM, whereas an initial increase of pHe by up to 0.05 pH units turned, after 2-4 min, into an acidification which could exceed 0.5 pH units. In contrast, [Ca2+]e remained unaffected by anoxia. Addition of 2-5 mM cyanide (CN-) to oxygenated Hepes-buffered saline evoked an increase in PO2 in the VRG from 100 to more than 300 mmHg. The effects of CN- on respiratory activity, aKe and pHe were almost identical to those during anoxia. In oxygenated, CO2/bicarbonate-free solutions of different pH, however, an increase in pHe in the VRG led to a decrease in respiratory frequency, whereas a fall of pHe produced a frequency acceleration. A rise of aKe in the VRG by more than 2 mM as induced by superfusion of a 7 mM K+ solution led to a sustained increase of respiratory frequency. The results indicate that blockade of aerobic metabolism does not severely perturb K+ and Ca2+ homeostasis and that the biphasic response to anoxia is not directly related to the observed changes in PO2, aKe, pHe, or [Ca2+]e. In the respiratory network of neonatal mammals, CO2 might provide a stimulus for long-term maintenance of respiratory activity under oxygen depletion.

Animals↗

PubMed1994

Anoxia induced functional inactivation of neonatal respiratory neurones in vitro.

In the isolated brain stem-spinal cord preparation of neonatal rats, respiratory (C4) activity persisted at reduced frequency during tissue anoxia. In seven biphasic expiratory (Bi-E) and in 12 of 22 inspiratory (Insp) neurones, recorded with the 'blind' patch-clamp technique, anoxia evoked a persistent hyperpolarization by up to 16 mV whereas membrane potential of the remaining Insp neurones depolarized slightly or remained unaffected. Respiration-related synaptic potentials and action potential discharges were blocked in all Bi-E and in about 50% of the Insp neurones, whereas rhythmic activity persisted in the other cells. The results indicate that a major population of neonatal respiratory neurones is functionally inactivated during anoxia. This mechanism might contribute to the anoxia tolerance of the immature brain.

Animals↗

PubMed1994

Analysis of the induction of general stress proteins of Bacillus subtilis.

In Bacillus subtilis stress proteins are induced in response to different environmental conditions such as heat shock, salt stress, glucose and oxygen limitation or oxidative stress. These stress proteins have been previously grouped into general stress proteins (Gsps) and heat-specific stress proteins (Hsps). In this investigation the N-terminal sequences of 13 stress proteins of B. subtilis were determined. The quantification of the mRNA and the analysis of the protein synthesis pattern support the initial hypothesis that the chaperones DnaK and GroEL are Hsps in B. subtilis. In contrast, the recently described proteins GsiB, Ctc and RsbW belong to a class of Gsps that are induced by various stresses including heat shock. The main part of the Gsps described in this study failed to be induced in the sigB deletion mutant ML6 in response to heat shock. However, all the five Hsps were induced in this mutant in response to heat shock. These data indicate that SigB plays a crucial role in the induction of general stress genes, but is dispensable for the induction of Hsps.

Amino Acid Sequence↗

PubMed1994

Primary eosinophilic granuloma of the oculomotor nerve. Case report.

The authors report the occurrence of primary eosinophilic granuloma of the oculomotor nerve without osseous involvement in a 68-year-old man. Histopathological and neuroradiological findings are discussed. This case demonstrates that eosinophilic granuloma should be included in the differential diagnosis of tumor in which cranial nerves are involved.

Aged↗

PubMed1993

[250 years ago: the origin of electrotherapy exemplified by Halle].

Experiments started in 1743 by a working group at the university of Halle marked the beginning of efforts to incorporate electricity into clinical therapy. Very soon this resulted in knowledge that was also taken up elsewhere, leading to a period of intensive research. The creative suggestions that originated in Halle were authored, among others, by Johann Gottlob Krüger, Christian Gottlieb Kratzenstein and Johann Joachim Lange. Their experimental and clinical findings were accompanied by deliberations on the mechanism of action of electrotherapy on which they reported in detail. Due to adverse circumstances this initially leading position occupied by Halle faded out already shortly after the middle of the century.

Electric Stimulation Therapy↗

PubMed1992

Developmental changes in the hypoxia tolerance of the in vitro respiratory network of rats.

The functional relation between respiratory activity, extracellular potassium activity (aKe) and tissue oxygen pressure (pO2) was analyzed in vitro in the ventral respiratory group (VRG) of the neonatal brainstem-spinal cord (NB) and the perfused adult brainstem (AB) of rats. In the AB, an aKe increase of up to 35 mM and a reversible blockade of respiratory activity occurred during anoxia periods of 5-10 min. In the NB, respiratory activity persisted during a 60 min anoxia in CO2/HCO3(-)-buffered solutions and aKe increased by less than 1.5 mM. In both preparations, inhibition of glycolysis by iodoacetate led to an irreversible blockade of respiratory rhythm and a delayed increase of aKe by more than 15 mM. We conclude that anaerobic metabolism is sufficient for the maintenance of respiratory activity and potassium homeostasis in the brainstem of the neonatal rat, but not of the adult.

Aging↗

PubMed1992

Scanning electron microscopic study of denervated and reinnervated intrafusal muscle fibers in rats.

Isolated muscle spindles from lower lumbrical muscles of rats were used to study the 3-dimensional organization of intrafusal structures by scanning electron microscopy following (a) complete denervation, (b) reinnervation after a single crush lesion of the sciatic nerve, or (c) reinnervation after transection and immediate suture of this nerve. One week after complete denervation, previous sites of intrafusal motor endplates were transformed into sarcolemmal ovoid bulges. These bulges persisted in denervated muscle spindles up to 12 weeks. Regenerated motor nerve endings were detected on intrafusal muscle fibers 1 month, and thereafter following sciatic nerve crush injuries, and 3 months and later following transection and suture of the nerve. Furthermore, 3 different types of subsynaptic areas of motor nerve terminals were observed. The scanning electron microscopic technique also allowed visualization of splitting and fusion of intrafusal muscle fibers. The findings are discussed in view of their possible functional implications.

Animals↗

PubMed1992

[Mining medicine in the 18th century. On the 250th anniversary of the birthday of Ignaz von Born (1742-1791)].

Ignaz von Born (1742-1791) improved several technical and methodical approaches to mining and was thus instrumental in creating the prerequisites for reducing certain professional miner's diseases. Among these diseases, lead or saturnine poisoning (colica saturnina) caused by lead monoxide PbO, also known as litharge, was much dreaded (a 17th-century physician from Goslar wrote a treatise on "Lithargyrii fumo noxio morbifico, vulgo dicto 'pit cat'"); a miner's disease associated with phthisis and pareses of a then unknown etiology; and in some cases even with hookworm disease that was much later recognised as yet another professional disease of miners. During this era a new professional image of a mining engineering physician developed, with several of these doctors trying to go beyond merely curative measures: they aimed at achieving meaningful prevention that involved standard measures and behavioural patterns on the one hand and improvements in the professional mining procedure on the other.

History, 18th Century↗

PubMed1992

[In memory of Hermann Jastrowitz (1882-1943)].

The 50th anniversary of the infamous "Wannsee Conference" that was held on 20 January 1942 at Berlin prompts us to recall the memory of the life and achievements of physicians who were the victims of the measures that had been decreed during that conference-physicians who made medical history both during their lifetime and by the fate they endured. One of these was the Jewish physician Hermann Jastrowitz, whose meritorious achievements for the benefit of the Outpatient Division and Hospital of the Department of Medicine of the University of Halle have been practically completely documented and reconstructed from university and other records.

Germany↗

PubMed1992

[Christian Gottlieb Selle (1748-1800), the last private physician of Friedrich the Great].

Among the physicians in ordinary to Frederick the Great Christian Gottlieb Selle ranks chronologically in the last place. In the course of his professional life the physician who graduated in Halle in 1770 was promoted to head positions in the Prussian public health organization and medical care of Berlin. His expertise for a new Halle education model inaugurated the era of the Halle Schola clinica in 1787.

Famous Persons↗

PubMed1992

[The Schaarschmid brothers. On the 200th anniversary of the death of August Schaarschmid (1720-1791)].

The 200th anniversary of the death of August Schaarschmid is the occasion to remember the life and work of this university teacher in connection with life and work of his brother Samuel Schaarschmid. The two temporarily taught at the Berlin Collegium medico-chirurgicum and in the Prussian capital they above all worked in the field of the surgical training. Later on August Schaarschmid changed to the Mecklenburg Academy of Bützow. The edition of a wide-spread special periodical as well as of a series of much used teaching tables belongs to the lasting merits of the brothers Schaarschmid whose eventful fate should be described here.

Germany↗

PubMed1991

[Not Available].

Explore the source record for details and available documents.

Germany↗

PubMed1991

[A viatorium medico-historicum. VI. Historical highlights in university cities of the Saxony-Anhalt area].

This part of a viatorium medico-historicum dealing with the region of Saxony-Anhalt, which finishes the series of contributions, leads into the cities and towns of the country where colleges are located. Thereby points of memory and recollection from the history of medicine, pharmaceutics and natural sciences were written down. Briefly entered were life and work of personalities, in whom life and work are connected with the facts mentioned.

Education, Medical↗