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Biomedical subjects

G Werner

Publications and source records attributed to G Werner.

At least 55 records · Page 3Linked to original sources
PubMed1997

Arrangement of the vanA gene cluster in enterococci of different ecological origin.

Glycopeptide-resistant enterococci (vanA) isolated from infections in humans, from non-hospitalized humans, from sewage, from animal feces and from meat products in Germany (20 Enterococcus faecium and one Enterococcus hirae) were investigated for the arrangement of the genes in the vanA gene cluster by means of overlapping PCR with five primer pairs. In 20 of these strains, the vanA gene clusters were uniform which suggests a horizontal spread among different ecosystems. In one clinical isolate a rearrangement was detected in the vanY-vanZ region.

Animals↗
PubMed1996

Determination of metal ions by ion chromatography with precolumn electrochemical preconcentration.

The determination of heavy metals in concentrations less than 10(-6) mol/L by ion chromatography with conductivity detection requires a preconcentration step. Therefore, a special electrochemical equipment and method was developed for the on-line preconcentration of the divalent metals Ni, Co, Zn and Cd and their subsequent ion chromatographic determination. The loop of the injection valve of an ion chromatograph was replaced by an electrochemical flow-through-cell with a gold working electrode, a platinum auxiliary electrode and a silver/silver sulphate reference electrode. The preconcentration step consists of the deposition of the reduced metals on the electrode surface during a continuous pumping of the sample solution through the cell. After switching of the mobile phase through the cell, the analytes are injected after their reoxidation directly into the mobile phase. A new preconcentration step is simultaneously possible during the actual chromatographic run. An effective separation of the analytes from the matrix is also possible with the proposed system. A maximum of metal ion accumulation was obtained after 120 min in the galvanostatic mode on a gold tube electrode. The detection limits for Co(II), Ni(II), Zn(II) and Cd(II) were improved by a factor of 7.7, 10.4, 11.2, 14.0, respectively, and were in the 0.1 micromol/L concentration range with a RSD of 2-6%. The accumulation of metal ions was disturbed in the presence of Cr(III).

Journal Article↗
PubMed1996

Determination of cyanide in microsamples by means of capillary flow injection analysis with amperometric detection.

A new approach for determining cyanide in microsamples is described. The method is based on capillary flow injection analysis (CFIA) with amperometric detection. The sensing electrode is a silver-plated microdisk electrode, where cyanide can react under formation of a dicyanoargentate complex. A remarkably low mass detection limit of 231 fmol cyanide is obtained for an injection volume of 60 nl. The sample throughput of the CFIA-arrangement is comparable with a conventional sized FIA-system. A practical application is given by analyzing the cyanide (amygdalin) concentration in apple kernels.

Journal Article↗
PubMed1996

Amperometric carbohydrate detection in flow systems by means of a bismuth modified platinum electrode.

Bismuth modified platinum electrodes are used for constant-potential amperometric determination of carbohydrates in flow systems. The monitored response is stable and reproducible over more than two days. An attempt is made to gain more detailed information about the characteristics of the modified layer by electrochemical methods and X-ray photoelectron spectroscopy. The response proved to be linear over the investigated concentration range (1.1-1200 micromol/L) and detection limits for glucose and fructose were found to be 1.1 micromol/L.

Journal Article↗
PubMed1996

Cardiac microembolism: prevalence and clinical outcome.

High intensity transient signals (HITS) have been identified ultrasonically in patients with extracranial vascular or cardiac disease and are suggestive of microembolic material. We studied the prevalence of these signals in 60 patients with increased risk for cardioembolic stroke and in a control group of 20 subjects. Patient groups (n = 20) were characterized by either non-rheumatic atrial fibrillation (AFIB) (I) or a history of prosthetic valve surgery with AFIB (II) or without AFIB (III). Embolic signals were not seen in the control group. In group I, 3 patients (15%) demonstrated HITS, in groups II and III 10 patients (50%). Microembolic signals in patients with prosthetic heart valves (II, III) had a higher signal intensity, indicating different embolic material. There was no correlation of microembolic signals with the anticoagulant treatment or the position of the prosthetic valve. HITS were found in 1/9 (11%) of the patients with a bioprosthetic valve as compared to 19/31 (61%) with a mechanical valve. After 6-12 months, 1 of 12 HITS positive patients had experienced a stroke and 2 had died. None of the 28 patients without HITS had suffered a stroke, 2 had died. Microembolic signals are frequent events in patients with mechanical prosthetic valves. In these patients they do not appear to be a major prognostic factor for an impending cardioembolic stroke.

Aged↗
PubMed1996

The bicyclams, a new class of potent human immunodeficiency virus inhibitors, block viral entry after binding.

The bicyclams represent a new class of highly potent and selective HIV inhibitors. Time-of-addition experiments have previously shown that these compounds interfere with an early event in the viral replicative cycle. Additional experiments have now been carried out in order to investigate in more detail the mechanism of action of these promising compounds. As described in this paper, PCR experiments revealed that no viral DNA was formed following viral infection, thus confining the target(s) of action of the bicyclams to an early stage of HIV infection. An assay, using pseudotype virions containing the envelope of HIV-1 and the genome of a plaque-forming virus (Cocal Virus), pointed to viral entry as the main target of the bicyclams. HIV-1 strains resistant to two prototype bicyclams, JM2763 and SID791 (JM3100), were raised. Results obtained with SID791 with respect to syncytium formation induced by SID791-sensitive and -resistant HIV-1 strains and the cross-resistance observed for dextran sulfate, suggest inhibition of binding and/or fusion as a plausible target of SID791. Additional experiments enabled us to exclude SID791 and JM2763 as binding inhibitors and to conclude that bicyclams block the entry of cell-bound virus. Furthermore, a monoclonal antibody recognising the V3 loop of wild-type gp120 did not bind to this region in the two bicyclam-resistant strains. Our results point to gp120 as a possible target for the HIV-inhibitory effects of the bicyclams.

Antibodies, Monoclonal↗
PubMed1996

Focal neurologic deficits in infective endocarditis and other septic diseases.

INTRODUCTION: Focal neurologic deficits in sepsis frequently result from parenchymal lesions due to cerebral embolism. The aim of this study was to characterize clinical, laboratory and radiologic patterns of those patients. PATIENTS AND METHODS: Medical records of 30 patients with focal neurologic symptoms during sepsis were analyzed retrospectively. RESULTS: 24 patients (22 with infective endocarditis) had ischemic stroke. Cerebrospinal fluid (CSF) analyses revealed inflammation in 11 of 12 patients. Patients who died (11/24) suffered more frequently from secondary intracerebral hemorrhage (p = 0.0031), which was significantly associated with intravenous high-dose anticoagulation (p = 0.0059). Six patients had slowly progressive focal neurologic deficits without evidence for stroke. All showed CSF inflammation and three developed multiple cerebral abscesses. CONCLUSIONS: There are two distinctive groups of patients with focal neurologic deficits during sepsis. One presents with stroke and CNS inflammation (septic embolic focal encephalitis). The other group develops slowly progressive focal neurologic deficits and sometimes multiple cerebral abscesses (septic metastatic focal encephalitis).

Adult↗
PubMed1996

The molecular target of bicyclams, potent inhibitors of human immunodeficiency virus replication.

Bicyclams are a novel class of antiviral compounds which act as potent and selective inhibitors of the replication of human immunodeficiency virus type 1 (HIV-1) and HIV-2. They block an early step in the viral life cycle following adsorption to the CD4 receptor and preceding reverse transcription. To identify the molecular target of these compounds, we genetically analyzed variants of the HIV-1 molecular clone NL4-3, which developed resistance against two structurally related bicyclams, JM2763 and the more potent SID791. The resistant strains were obtained after long-term passaging in MT-4 cells in the presence of progressively increasing compound concentrations. Recombinants between selected genes of the resistant strains and the parental NL4-3 provirus were generated by adapting the marker rescue technique to MT-4 cells. The bicyclam-resistant phenotype was rescued by transferring the envelope gp120 gene of bicyclam-resistant virus into the NL4-3 parental genetic background. In the gp120 genes of the resistant strains, we identified several mutations leading to amino acid substitutions in the V3 loop. Furthermore, two substitutions of highly conserved amino acids in close proximity to the disulfide bridges of the V3 and V4 loops were found in both SID791- and JM2763-resistant strains. Additional mutations in regions encoding V3, C4, V5, and C5 were present in SID791-resistant viruses. Recombination experiments with overlapping parts of the envelope gene indicated that most, if not all, of the mutations were necessary to develop the fully SID791 resistant phenotype. The mutations in the C-terminal part of gp120 downstream of the V3 loop sequence conferred partial resistance to JM2763 but did not significantly decrease susceptibility to SID791. The genetic data and the biological properties of the resistant viruses point to inhibition of entry and fusion as the mode of action of the HIV-inhibitory bicyclams. A possible mechanism of binding of bicyclams to gp120 leading to inhibition of unfolding of gp120 and its shedding from the gp41 fusion domain is discussed.

Amino Acid Sequence↗
PubMed1996

Alternative tertiary care pathways for a rural Department of Veterans Affairs Medical Center.

This study addresses the cost of rural health care delivery where veterans do not have ready access to tertiary Department of Veterans Affairs Medical Centers (VAMCs) but where local community health care is available. The study sample was 209 patients referred for tertiary care to a VAMC 50 miles distant from the referring rural VAMC. The cost of tertiary referral VAMC care was retrospectively compared with the cost had the patients received the tertiary care in the local community hospital located in the immediate vicinity. In addition, the cost of travel resulting from the remote access was also computed. Findings indicate that a savings of +309,293 could have been obtained had a local community hospital provided the tertiary care utilizing the Health Care Financing Administration Medicare rate. Data generated by the methodology of this study are expected to provide a baseline for policy decisions relating to alternative pathways for tertiary care in the Department of Veterans Affairs.

Cost Savings↗
PubMed1995

Lipids of fish parasites and their hosts: fatty acid fingerprints of four species of acanthocephalans and of their hosts' intestinal tissues.

The fatty acid fingerprints of total lipid extracts from the four fish parasites Acanthocephalus lucii, Neoechinorhynchus rutili, Paratenuisentis ambiguus, and Pomphorhynchus laevis were investigated by capillary gas-liquid chromatography (GLC). The fatty acid patterns of the parasites were compared with those of their respective host tissue, viz., intestinal tract tissue of infected perch, brown trout, eel, and chub. The highly complex gas chromatograms revealed significant differences not only between parasite and host tissue but also between the parasites themselves. For instance, all the parasites contained much more eicosapentaenoic acid (20:5n-3) than did the respective fish intestinal tissue. Differences were also observed between the presoma and metasoma of Pomphorhynchus laevis.

Acanthocephala↗
PubMed1995

Mode of action of SDZ NIM 811, a nonimmunosuppressive cyclosporin A analog with activity against human immunodeficiency virus type 1 (HIV-1): interference with early and late events in HIV-1 replication.

SDZ NIM 811 is a cyclosporin A analog that is completely devoid of immunosuppressive capacity but exhibits potent and selective anti-human immunodeficiency virus type 1 (HIV-1) activity. The mechanism of action of SDZ NIM 811 is clearly different from those of all other anti-HIV agents described so far. In cell-free assays, it is not an inhibitor of reverse transcriptase, protease, integrase, and it does not interfere with Rev or Tat function. SDZ NIM 811 does not down-regulate CD4 or inhibit fusion between infected and uninfected, CD4-expressing cells. p24 production from chronically HIV-infected cells is not impaired either. To elucidate the mode of action of SDZ NIM 811, we performed DNA PCR analysis in HIV-1 IIIB-infected MT4 cells in one cycle of virus replication. The effects of SDZ NIM 811 on the kinetics of viral DNA synthesis, appearance of two-long terminal repeat circles (2-LTR circles), and integration of DNA were studied. SDZ NIM 811 inhibited 2-LTR circle formation in a concentration-dependent manner, which is indicative of nuclear localization of preintegration complexes. Half-maximal inhibition was achieved at 0.17 microgram/ml; this concentration is close to the 50% inhibitory concentrations (0.01 to 0.2 microgram/ml) for viral growth inhibition. As expected, integration of proviral DNA into cellular DNA was also inhibited by SDZ NIM 811. Analysis of the viral particles produced by SDZ NIM 811-treated, chronically infected cells revealed amounts of capsid proteins, reverse transcriptase activity, and viral RNA comparable to those of the untreated control. However, these particles showed a dose-dependent reduction in infectivity (50% inhibitory concentration of 0.028 microgram/ml) which indicates that the assembly process is also impaired by SDZ NIM 811. Gag proteins are postulated to play a role not only in assembly but also in early steps of viral replication, e.g., nuclear localization of the preintegration complex. Recently, it was reported that HIV-1 Gag protein binds to cyclophilin A, the intracellular receptor for cyclosporin A. Interference with Gag-cyclophilin interaction may be the molecular basis for the antiviral activity of cyclosporin A and its analogs.

Antiviral Agents↗
PubMed1995

Immunocytochemical localization of histone H4 in the chromatoid body of rat spermatids.

Histone H4 could be localized in rat spermatids using immunocytochemistry with a monoclonal histone-H4-antibody (IgM mouse) in combination with a goat-anti-mouse-antibody labeled with 6 nm gold particles. Label was found in spermatids from step 2 to step 9 in the nucleus predominantly near its envelope and in the electron-dense material of the chromatoid body. In later spermatids, where the chromatoid body had disappeared, gold particles were still seen in the nucleus but now evenly distributed over the condensed chromatin. In the controls without primary antibody both the nucleus and the chromatoid body were unlabeled. The results suggest that the chromatoid body might play a role in the nuclear protein transition during spermiogenesis.

Animals↗
PubMed1994

Calcium signalling in individual T-cells measured by confocal microscopy.

Laser-scanning confocal microscopy was used in conjunction with a highly fluorescent Ca2+ indicator fluo-3 to visualize real-time alterations in the intracellular Ca2+ concentration ([Ca2+]i) in individual living Jurkat T-cells during the first minutes of activation by phytohaemagglutinin (PHA) at the physiological temperature (37 degrees C). With a delay of 30-120 s, PHA induced a strong [Ca2+]i peak in the micromolar range (1-3 microM). The rise in [Ca2+]i lasted for 1-2 minutes, and was followed by a sustained plateau of elevated [Ca2+]i in the 0.2-0.5 microM range. Some cells (10-20%) responded with additional asynchronous 0.5-1.5 microM peaks during the plateau phase. These oscillations continued for 10-20 minutes. The spans of the peaks ranged from 30 to 100 s, intervals between peaks varied from 60 to 300 s. It was shown that the initial [Ca2+]i peak was associated with Ca2+ mobilisation from internal sources, whereas the plateau was maintained by an influx of Ca2+ from external medium. In K(+)-rich medium or in the presence of quinine, a K+ channel blocker, no secondary response to PHA-activation characterised by an elevated plateau was observed. The data suggest that the Ca2+ influx was dependent on the membrane potential and/or the extracellular K(+)-concentration. Optical sectioning showed that the intracellular Ca2+ distributed almost homogeneously throughout the cell volume both in control and in PHA-stimulated cells including those exhibiting Ca2+ oscillations. This suggests that Ca2+ signals are localized not only in cytoplasm at the cell plasma membrane but can be also transferred directly into the nucleus.

Aniline Compounds↗
PubMed1993

Construction of concepts by the nervous system: from neurons to cognition.

Neurophysiological studies have recently identified a pattern of synchronized slow-wave activity in the visual cortex which characteristically encompasses groups of neurons activated by similar or closely related stimulus attributes. This slow-wave activity appears to tag clusters of neurons to form aggregates representing in their totality more complex, higher-order stimulus attributes across disparate positions in the cortical representation. The notion is advanced that the function of these aggregates is analogous to that ascribed to the subsymbolic computational level in connectionist networks. On this basis, the argument is presented that the synchronized cortical activity is an important aspect of the construction of symbolic representation by the nervous system and, thus, a step from neural information processing to the symbolic processes stipulated by classical cognitivism.

Animals↗
PubMed1993

Trace metal determination in tears by anodic stripping voltammetry in a capillary flow injection system.

The adaptation of a fused silica capillary system to flow injection is described. The incorporated electrochemical cell, consisting of a microelectrode arrangement, is demonstrated to be well suited for conductivity and voltammetric measurements. Microanalytical studies with injection volumes within the nanolitre range were performed. Analytical characteristics of the method, such as accuracy, precision, sensitivity and limit of detection, are discussed. By using capillary flow injection, tear samples were investigated with respect to conductivity and trace-metal concentration. The last was performed via anodic stripping voltammetry at mercury-coated platinum microdisc electrodes. Lead, cadmium and copper were found to be present at concentrations in the lower microgram l-1 range.

Child↗
PubMed1993

Ultrastructural localization of wheat germ agglutinin binding sites on the sperm surface of water buffalo (Bubalus bubalis). A fracture label study.

In the present study we have examined the plasma membrane surface organization employing fluorescein isothiocyanate linked wheat germ agglutinin (WGA) of the cauda epididymal and ejaculated spermatozoa of water buffalo. Intramembrane particle distribution pattern in the various segments of the spermatozoa has also been observed. WGA-ovomucoid gold has been used to study the distribution of sialoproteins on the sperm surface. With fracture label, WGA receptor sites have been identified on the fractured membrane halves of the sperm plasma membrane overlying the acrosome as well as the middle piece and the principle piece.

Acrosome↗
PubMed1993

Spectroscopic and microscopic studies of buffalo-bull (Bubalus bubalis) spermatozoa.

We have examined the epididymal (caput, corpus and cauda) and ejaculated spermatozoa of bufallo-bull (Bubalus bubalis) employing microscopic and spectroscopic techniques. Fluorescein isothiocyanate conjugated lectins namely concanavalin A (Con A), Dolichos biflorus (DBA), Maclura pomifera (MPA), peanut agglutinin (PNA), soybean agglutinin (SBA) and wheat germ agglutinin (WGA) were used to study the changes in the sperm surface carbohydrate make up as the spermatozoa mature. Quantitative analysis of the lectin binding was made flow cytometrically. 31P-NMR (nuclear magnetic resonance) spectra of the sperms obtained from different regions (head, body and tail) of the epididymis and of the ejaculate were analyzed to assess their metabolic activity. And the kinetics of spin label reduction of these samples was monitored with ESR (electron spin resonance) spectroscopy. These observations are supplemented with the electron microscopic (SEM and TEM) examination of the epididymal and ejaculated spermatozoa.

Animals↗