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Biomedical subjects

W Fischer

Publications and source records attributed to W Fischer.

At least 73 records · Page 4Linked to original sources
PubMed1998

Uptake and incorporation of choline and ethanolamine into lipoteichoic acid and teichoic acid by the choline-independent mutant JY2190 of Streptococcus pneumoniae.

Lipoteichoic acid- and teichoic acid-containing muropeptides were isolated from choline- or ethanolamine-grown cells of the choline-independent mutant JY2190 of Streptococcus pneumoniae. Choline was taken up and incorporated into lipoteichoic acid and teichoic acid with 81% efficiency, compared with the parent strain Rx1. With similar efficiency, ethanolamine was incorporated. Accordingly, the mutant is a valuable tool for identifying the individual genes encoding the enzymes of choline utilisation, because any of these genes can be deleted without affecting viability and growth rate.

Choline↗
PubMed1998

Characterization of the extracellular ligand-binding domain of the type II activin receptor.

The binding of a ligand to cell surface receptors initiates a cascade of intracellular signals that generate responses to the external stimuli. Thus, this event plays a pivotal role in the mechanism of transmembrane signaling. Activin is a member of a cytokine family that is involved in diverse biological processes. To study the structural basis that underlies the transmembrane signaling mechanism, we have overexpressed the soluble extracellular domain of the type II activin receptor from mouse (ActRII-ECD). We used the methylotrophic yeast Pichia pastoris as an expression host to produce a large quantity of ActRII-ECD. Expression was carried out in a fermentor with a typical yield of 10 mg of pure ActRII-ECD from a liter of growth media. Biological function was confirmed by the ability to decrease the activin-stimulated release of FSH from cultured rat pituitary cells in addition to several activin-binding assays, including native gel shift and chemical cross-linking. The glycosylation on ActRII-ECD was shown to be dispensable for high-affinity activin binding, and nonnatural sugars from the yeast expression host did not interfere with binding, indicating that the binding of activin is not sensitive to the environment near the two positions of N-linked glycosylation. Analytical ultracentrifugation of the complex between activin A and ActRII-ECD reveals that two receptors associate with one activin A dimer, consistent with results from chemical cross-linking experiments.

Activin Receptors↗
PubMed1998

Static magnetic resonance imaging of the pelvic floor muscle morphology in women with stress urinary incontinence and pelvic prolapse.

In a study, the magnetic resonance imaging (MRI) findings of 69 women were analyzed to define the typical MRI appearance of the pelvic floor musculature in healthy subjects (n = 20) and women with urinary incontinence (UI) and/or genitourinary prolapse (GP) (n = 49). The following parameters were determined: thickness and signal intensity of the levator muscles on each side, distance between the urethra and symphysis, diameter of the proximal urethra, and thickness and configuration of the anterior vaginal wall. These parameters were correlated with the patients' age and parity, urodynamic parameters, and the clinical assessment of the pelvic floor. In contrast to healthy subjects, the frequent findings in women with UI and/or GP are higher signal intensity of the levator muscles (p < 0.05) and loss of the hammock-like configuration of the vagina (p < 0.01). On static MRI, the morphometry of the levator musculature identified no findings typical of either UI or GP. Analysis of MRI combined with patients' parity suggests that the severity of damage to the pelvic floor at delivery is determined by the traumatic event as such and not by the number of deliveries. Urethral diameter, distance of the symphysis to the urethra, and vaginal wall thickness cannot distinguish between controls and women with UI and/or GP. Urodynamic and functional clinical parameters do not correlate with the changes in the pelvic floor musculature demonstrated by static MRI. Although morphological changes in UI and/or GP can be demonstrated by MRI, they can be assigned a pathogenic role only if clinical symptoms are present.

Adolescent↗
PubMed1998

Rebound insomnia after hypnotic withdrawal in insomniac outpatients.

The effect of abrupt medication withdrawal (no-pill discontinuation) was investigated in 1507 insomniacs using the patients' self-ratings on visual analogue scales. Drug discontinuation followed a 28-day treatment period with either 7.5 mg zopiclone, 0.25 mg triazolam, 1.0 mg flunitrazepam, or placebo in a randomized, double-blind, parallel group, multicenter study in private practice. Deterioration below individual pretreatment values (no-pill baseline) in at least one of three subjective parameters of sleep quality (sleep latency, total sleep time, nocturnal awakenings) and three parameters of daytime well-being (morning freshness, daytime tiredness, anxiety) were defined as rebound. The number of patients with rebound (rebound rate) was analyzed for every day of a 2-week posttreatment period. The overall rebound rate was higher in the placebo group (p < or = 0.001) than in each group treated with active drugs. Rebound rates affecting sleep quality were higher for placebo than for zopiclone (p < or = 0.001) and for flunitrazepam (p < or = 0.05). Rebound rates were smaller for zopiclone (p < or = 0.001) and flunitrazepam (p < or = 0.01) than for triazolam. Rebound in at least one item per day appeared in 21.5% (sleep quality) and 25.5% (daytime well-being) of the patients. Rebound decreased with increasing numbers of items of sleep quality or daytime well-being. Patients who did not respond to treatment showed higher rebound rates than those who were treatment responders (p < or = 0.001). Concerning treatment nonresponders, highest rebound was seen in the placebo group, whereas rebound was lowest in placebo responders. These results show that pill discontinuation itself may worsen sleep and daytime well-being in the sense of a rebound phenomenon. Furthermore, the number of patients with rebound remained at a high and varying level during the whole posttreatment period. This result indicates that a deterioration of sleep after drug withdrawal is not apparent during a few days but may last for longer periods in some patients and is modified by marked night-to-night variations.

Adolescent↗
PubMed1998

Effect of clobenpropit, a centrally acting histamine H3-receptor antagonist, on electroshock- and pentylenetetrazol-induced seizures in mice.

The anticonvulsant activity of clobenpropit, an isothiourea derivative of histamine and potent H3-receptor antagonist, was investigated in two representative seizure models in mice. In the maximal electroshock seizure threshold test, clobenpropit dose-dependently raised the electroconvulsive threshold for tonic (hindlimb extension) seizures, but a significant increase of about 15% was determined only at the high dose of 40 mg/kg i.p. The protective action of this drug was reduced by immepip and (R)-alpha-methylhistamine, selective H3-receptor agonists. In co-medication with two standard antiepileptics, clobenpropit (20 and 40 mg/kg) significantly increased the anticonvulsant effectiveness of carbamazepine and tended to increase the effectiveness of valproate. Additional studies indicated that the high dose of clobenpropit also significantly enhanced the plasma carbamazepine concentration. One the other hand, in the s.c. PTZ seizure threshold test clobenpropit revealed no protective effects. In the rotarod ataxia test, impaired motor function was observed at 80 mg/kg clobenpropit. In conclusion, the present findings indicated no pronounced anticonvulsant effects of clobenpropit against generalized tonic as well as clonic seizures.

Animals↗
PubMed1998

Influence of ethanol on the pentylenetetrazol-induced kindling in rats.

The effects of ethanol on the development of pentylenetetrazol (PTZ)-kindling as well as on fully PTZ-kindled convulsions in rats were investigated. Ethanol (0.5, 1.0 and 1.5 g/kg i.p.) administered 15 min prior to each PTZ-injection (35 mg/kg i.p.; 3 times/week) significantly inhibited the progressive seizure development compared to saline-treated controls. For the higher doses of ethanol the kindling process was restricted to seizure stages of 1 or 2. Tolerance to this antiepileptogenic action did not occur even after 20 PTZ-stimulations. In a second series of experiments, 0.5 g/kg ethanol administered 10h before each PTZ-injection facilitated the rate of kindling development after 7 to 10 PTZ-injections, while the higher doses of ethanol did not modulate or even slightly reduced the seizure development. In a third test, intermittent administration of a high dose of ethanol (2 g/kg p.o.; twice daily for 6 days) before the kindling procedure (0.5 g/kg i.p. ethanol 10h prior to each PTZ-injection), significantly intensified the kindling development. In addition, studies with fully PTZ-kindled rats demonstrated that ethanol (0.1 to 1.5 g/kg i.p.), given 15 min prior or 2 min after PTZ, reduced the seizure severity in a dose-dependent manner. In conclusion, the present findings provide evidence for pronounced antiepileptogenic and anticonvulsant effects of ethanol after acute application, whereas repeated administration of high doses with longer withdrawal periods leads to proconvulsant actions, possible mediated via neuroadaptive changes in NMDA and/or GABA(A) receptor-related mechanisms.

Animals↗
PubMed1998

D-Alanylcardiolipin, a major component of the unique lipid pattern of Vagococcus fluvialis.

Motile group N streptococci, classified as Vagococcus fluvialis, have been isolated from cows' udders, human and animal feces, river water, and seawater. They possess an unusual membrane lipid and fatty acid pattern. We isolated and characterized 13 polar lipids, 8 of them also found in other gram-positive bacteria: mono- and dihexosyldiacylglycerol, an acylated and a glycerophosphate-substituted derivative of the latter, cardiolipin, phosphatidylglycerol, D-alanylphosphatidylglycerol, and L-lysylphosphatidylglycerol. Besides them, we characterized two rare compounds, bis(acylglycero)phosphate and alpha-D-glucopyranosylcardiolipin, and two compounds so far not detected in nature, D-alanylbis(acylglycero)phosphate and D-alanylcardiolipin. The concomitant occurrence of four aminoacyl phospholipids in one organism is another unique finding. Substituted cardiolipins represent a novel lipid class: in vagococci, D-alanylcardiolipin is a major membrane lipid component, contributing 11 and 26 mol% of total lipids in the exponential and stationary phases of growth, respectively. The vagococcal lipids contain even-numbered straight-chain saturated and cis-monounsaturated fatty acids, but the cis-monoenic acids belong to the omega-9 series and not the omega-7 series, found in enterococci, lactococci, and streptococci.

Cardiolipins↗
PubMed1998

Generation and properties of a Streptococcus pneumoniae mutant which does not require choline or analogs for growth.

A mutant (JY2190) of Streptococcus pneumoniae Rx1 which had acquired the ability to grow in the absence of choline and analogs was isolated. Lipoteichoic acid (LTA) and wall teichoic acid (TA) isolated from the mutant were free of phosphocholine and other phosphorylated amino alcohols. Both polymers showed an unaltered chain structure and, in the case of LTA, an unchanged glycolipid anchor. The cell wall composition was also not altered except that, due to the lack of phosphocholine, the phosphate content of cell walls was half that of the parent strain. Isolated cell walls of the mutant were resistant to hydrolysis by pneumococcal autolysin (N-acetylmuramyl-L-alanine amidase) but were cleaved by the muramidases CPL and cellosyl. The lack of active autolysin in the mutant cells became apparent by impaired cell separation at the end of cell division and by resistance against stationary-phase and penicillin-induced lysis. As a result of the absence of choline in the LTA, pneumococcal surface protein A (PspA) was no longer retained on the cytoplasmic membrane. During growth in the presence of choline, which was incorporated as phosphocholine into LTA and TA, the mutant cells separated normally, did not release PspA, and became penicillin sensitive. However, even under these conditions, they did not lyse in the stationary phase, and they showed poor reactivity with antibody to phosphocholine and an increased release of C-polysaccharide from the cell. In contrast to ethanolamine-grown parent cells (A. Tomasz, Proc. Natl. Acad. Sci. USA 59:86-93, 1968), the choline-free mutant cells retained the capability to undergo genetic transformation but, compared to Rx1, with lower frequency and at an earlier stage of growth. The properties of the mutant could be transferred to the parent strain by DNA of the mutant.

Carbohydrate Sequence↗
PubMed1998

Laparoscopic staging of gastric cancer is safe and affects treatment strategy.

The accuracy of laparoscopic staging has been documented, but its safety and impact on clinical decision making are less clear. In a prospective series of 64 patients referred to a single consultant, laparoscopy was performed in 49, after exclusion of patients unlikely to derive benefit from laparoscopic staging. The prelaparoscopy treatment plan was altered in 17 (34%). Laparoscopy detected 11 cases of peritoneal and four cases of liver metastasis, of which nine and two, respectively, were not detected by CT scan. Laparoscopy was useful in assessing fitness for major surgery, the planned extent of which was reduced in five cases as a result. Port site metastasis occurred in one case of stage IVB cancer, in conjunction with widespread progressive disease. Laparoscopic staging is recommended in gastric cancer, since it causes important changes to the management plan in one-third of cases, and the risks of port site metastasis appear low.

Adenocarcinoma↗
PubMed1998

alpha-d-glucopyranosyl-, d-alanyl- and l-lysylcardiolipin from gram-positive bacteria: analysis by fast atom bombardment mass spectrometry.

Cardiolipin species substituted on O2 of the middle glycerol moiety with alpha-d-glucopyranosyl, d-alanyl and l-lysyl residues were isolated from different gram-positive bacteria. There respective structures were elucidated by positive and negative mode fast atom bombardment mass spectrometry. The structural heterogeneity due to different fatty acid combinations was documented by up to seven molecular ions. General structural features were derived from diagnostic fragment ions, generated by single cleavage at the phosphodiester moieties in both positive and negative ion mode. A diagnostically important fragment ion for d-alanylcardiolipin was observed in the positive ion mode. It arose from double cleavage of the phosphodiester moieties yielding [NaH(Na) PO4-CH2.CH(OCO.CHNH2.CH3) CH2+]+. The fatty acid combinations in the phosphatidyl and diacylglycerol ions make it possible to recognize whether saturated and unsaturated fatty acids were selectively or randomly distributed on the two positions of the glycerol moieties. Molecular structures of cardiolipins, derived from mass spectrometric experiments, are in full agreement with those, elucidated by classical chemical analyses.

Cardiolipins↗
PubMed1997

Small-angle X-ray scattering analysis of pneumococcal lipoteichoic acid phase structure.

X-Ray-scattering analysis was performed on micelles of lipoteichoic acid from Streptococcus pneumoniae. This lipoteichoic acid differs from poly(glycerophosphate) and poly(glycosylglycerophosphate) lipoteichoic acids by a unique positively charged diacylglyceroglycolipid anchor and a complex structure of the hydrophilic chain which is composed of zwitterionic tetrasaccharide ribitol phosphate repeats each carrying two zwitterionic phosphocholine substituents. The size distribution of the lipoteichoic acid micelles was sufficiently homogenous to determine their size and some related molecular parameters by small-angle scattering analysis. Nearly independent on the ionic strength of the aqueous dispersion, an average micelle contained about 150 lipoteichoic acid molecules arranged in a spherical assembly with a diameter of about 23 nm, whereby the hydrophilic region occupied an outer shell of about 8.5 nm thickness. Taken this as the average chain length of LTA in the micelle and 7.2 repeats per chain, each repeat contributed about 1.2 nm to the thickness of the hydrophilic shell as compared to 2.4 nm for a fully extended chain conformation and 1.1 nm estimated for a more helical arrangement [Klein, R. A., Hartmann, R., Egge, H., Behr, T. & Fischer, W. (1994) Carbohydr. Res. 256, 189-222]. A comparison with the micelle of poly(glycerophosphate) lipoteichoic acid of Staphylococcus aureus suggests that the supramolecular structure is largely independent of the structure of the hydrophilic chain and solely dictated by the small cross-sectional area of the diacylglycerol moiety common to all lipoteichoic acids and lipoglycans of gram-positive bacteria.

Carbohydrate Sequence↗
PubMed1997

Anti-human kappa opioid receptor antibodies: characterization of site-directed neutralizing antibodies specific for a peptide kappa R(33-52) derived from the predicted amino terminal region of the human kappa receptor.

Site-directed polyclonal Abs specific for a synthetic peptide with sequence homology to the predicted N-terminal sequence of the human kappa opioid receptor [anti-kappa R-(33-52)] are capable of binding to normal human cells and cell lines expressing mRNA specific for the human kappa receptor. Flow cytometric analysis of 1) a neuronal cell line (NT2), 2) blood-derived CD14+ monocytes, 3) monocyte-like cell lines (U937 and THP 1), 4) blood-derived CD3+ T cells and a T cell line, and 5) human B cell lines bound anti-kappa R-(33-52) in a specific manner. Anti-kappa R-(33-52) was also found to specifically neutralize the immunosuppressive activities associated with the kappa R-selective agonist U50,488H. This antiserum was found to block U50,488H-mediated inhibition of 1) Staphylococcus aureus Cowen strain I-induced B and T lymphocyte proliferation, 2) PHA-induced T lymphocyte proliferation, and 3) S. aureus Cowen strain I-induced IgG production. However, this antiserum failed to neutralize mu R-selective agonist (Tyr-D-Ala-Gly-NMe-Phe-Gly-ol)-mediated suppression of IgG synthesis. Finally, the kappa R-selective antagonist nor-binaltorphimine hydrochloride inhibits the binding of anti-kappa R-(33-52) to the U937 cell line. These results suggest that anti-kappa R-(33-52) specifically interacts with the human kappa R molecule. Studies conducted with anti-kappa R-(33-52) indicated that this antiserum effectively blocked U50,488H-mediated immunosuppression, but by itself did not enhance or suppress lymphocyte activation. These data suggest that anti-kappa R-(33-52) 1) does not interact with the effector binding site of the receptor, but sterically interferes with U50,488H binding to the receptor; and/or 2) the antiserum interacts with a secondary binding site that is important for ligand binding, but may not be involved in signal transduction.

Adult↗
PubMed1997

Evaluating a primary prevention program in a multicultural population: the importance of representations of back pain.

OBJECTIVE: This study was carried out during 4 years of longitudinal research assessing back pain problems and the impact of a back pain primary prevention program on the employees of a food and non-food chain store. The impact of the teaching program was reevaluated in a secondary analysis, taking into account subjects' prior representations of back pain. METHODS: Subjects were grouped according to their cultural origins and socioprofessional levels. Their representations were assessed by means of open questions before and after the teaching program. RESULTS: The teaching program reinforced pre-existing representations in those participants socioculturally nearest the teachers; it had a weak or even disturbing impact on those furthest removed from the teachers in sociocultural terms. CONCLUSION: The differential impact of the teaching program in this study indicates that participants' prior representation play a role in the outcome of a Back School teaching program. Thus, the participants' representations should be taken into account when designing the program and when assessing participants' suitability for such programs, their adherence, and the outcome.

Back Pain↗
PubMed1997

Effect of lipoteichoic acid on thermotropic membrane properties.

Lipoteichoic acid, diglucosyldiacylglycerol, and phosphatidylglycerol isolated from Staphylococcus aureus were embedded in dipalmitoylglycerophosphoglycerol vesicles, and their thermotropic influence on this matrix was studied by differential scanning calorimetry. The natural fatty acids of phosphatidylglycerol effected peak broadening and a decrease in molar heat capacity. These effects were more pronounced with the glycolipid, which also increased the main transition temperature. With the lipoteichoic acid mixtures, two broad main transition peaks were observed, possibly due to different levels of lipoteichoic acid in vesicles. Both peaks showed a further upshift in transition temperatures and a pronounced decrease in molar heat capacity. Since the diacylglycerol moieties of all three amphiphiles were practically identical, the differences in the thermotropic effects have to be ascribed to the different structures of the head groups. Diglucosyldiacylglycerol is proposed to exert an additional effect by hydrogen bonding the hydroxyls of the sugar rings to their phospholipid neighbors. The stronger effect of lipoteichoic acid points to dynamic interactions of the long hydrophilic chain with the vesicle surface, which stabilize the membrane structure.

Calorimetry, Differential Scanning↗
PubMed1997

Pelvic floor findings in urinary incontinence--results of conditioning using vaginal cones.

BACKGROUND: Conservative treatment of urinary incontinence (UI) may be more reliable if it is associated with improved testing of pelvic floor function. The results of cone training in patients and healthy controls are compared. METHODS: Voluntary contractions of pelvic floor muscles in 16 women with genuine stress incontinence, 14 with mixed stress/urge incontinence, and eight healthy controls were assessed by digital transvaginal palpation, manometry, and inspection using the so-called speculum-lift test. In addition, the capability to hold vaginal cones was investigated. All examinations were done before and after four-week cone training (Femcon 20-70 g). RESULTS: Prior to cone training, no pelvic floor response was recordable from eight women (27%) by palpation and from seven women (23%) by inspection. After training, contractions were restored in all women. The best post-training results were obtained by palpation (27 positive responses), followed by manometry (25 women, 83%), and speculum-lift test (13 women, 43%). The capability to hold vaginal cones was also improved. Initial weights in 15 UI patients (50%) were lower (cone No. 1-2) than in eight healthy women (cone No. 5). Average contractility increased from 5 to 9.7 mmHg in patients and from 17.5 to 23.1 mmHg in healthy women. Twenty-four patients (80%) were cured (57%) or improved (23%). Twenty-six asked for continuation of cone training. CONCLUSIONS: Pelvic floor conditioning with vaginal cones is a good alternative to poor acceptance or insufficient availability of conventional exercises.

Adult↗
PubMed1996

Long-term functional recovery from age-induced spatial memory impairments by nerve growth factor gene transfer to the rat basal forebrain.

Nerve growth factor (NGF) stimulates functional recovery from cognitive impairments associated with aging, either when administered as a purified protein or by means of gene transfer to the basal forebrain. Because gene transfer procedures need to be tested in long-term experimental paradigms to assess their in vivo efficiency, we have used ex vivo experimental gene therapy to provide local delivery of NGF to the aged rat brain over a period of 2.5 months by transplanting immortalized central nervous system-derived neural stem cells genetically engineered to secrete NGF. By grafting them at two independent locations in the basal forebrain, medial septum and nucleus basalis magnocellularis, we show that functional recovery as assessed in the Morris water maze can be achieved by neurotrophic stimulation of any of these cholinergic cell groups. Moreover, the cholinergic neurons in the grafted regions showed a hypertrophic response resulting in a reversal of the age-associated atrophy seen in the learning-impaired aged control rats. Long-term expression of the transgene lead to an increased NGF tissue content (as determined by NGF-ELISA) in the transplanted regions up to at least 10 weeks after grafting. We conclude that the gene transfer procedure used here is efficient to provide the brain with a long-lasting local supply of exogenous NGF, induces long-term functional recovery of cognitive functions, and that independent trophic stimulation of the medial septum or nucleus basalis magnocellularis has similar consequences at the behavioral level.

Aging↗
PubMed1996

Microheterogeneity of the hydrophobic and hydrophilic part of the glycosylphosphatidylinositol anchor of alkaline phosphatase from calf intestine.

Digestion of calf intestine alkaline phosphatase with pronase and subsequent dephosphorylation of the released peptidyl-(Etn-P)2-glycosyl-PtdIns with HF generated 8 glycosyl-Ins species the largest of which (G1 and G2) have the following proposed structures: [sequence: see text] G3 and G5 are lower homologues of G1 and G2, respectively, being one alpha 1-2 linked mannopyranosyl residue shorter. G4 is analogous to G2 lacking the N-acetylgalactosaminyl residue and G6 is the next lower homologue of G4. Most of G4 and G6 occur substituted with a palmitoyl (G4, G6) or a myristoyl residue (G6) probably attached to the inositol moiety. Thus, the basic ManxGlc-Ins species are either substituted with an N-acetylgalactosaminyl residue or a fatty acid ester. The structures were deduced from compositional analysis, molecular-mass determination by matrix-assisted laser desorption MS, sequential hydrolysis with appropriate exoglycosidases and treatment with CrO3. Purification of the glycosylinositol species was achieved by a novel reverse-phase HPLC technique using fluorescent fluoren-9-yl-methoxy-carbonyl (Fmoc) derivatives. These stable derivatives were susceptible to hydrolysis with exoglycosidases which allowed sequential cleavages to be carried out and kinetics to be followed at the picomole level. We observed recently that native alkaline phosphatase separates on octyl-Sepharose into four distinct fractions of increasing hydrophobicity (F1-F4). Here we show that all four fractions contain G1-G6. The acylated species G4 and G6 were restricted to F2 and F4 which had been shown earlier to contain, on average, 2.5 and 3 fatty acid residues/subunit, respectively. In all four fractions the diradylglycerol moiety was predominantly diacylglycerol, alkylacylglycerol being less than 10% which is in contrast to most glycosyl-PtdIns--anchored proteins of mammalian origin.

Acetylgalactosamine↗