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Biomedical subjects

W Fischer

Publications and source records attributed to W Fischer.

At least 91 records · Page 5Linked to original sources
PubMed1996

The aqueous solution structure of a lipoteichoic acid from Streptococcus pneumoniae strain R6 containing 2,4-diamino-2,4,6-trideoxy-galactose: evidence for conformational mobility of the galactopyranose ring.

The 2D-NOESY spectra for the per-N-acetylated and the native lipoteichoic acid (LTA) oligomer from Streptococcus pneumoniae strain R6 clearly indicate a difference in conformation of the 2,4,6-trideoxy-galactopyranose ring. Whereas the 2,4-N-acetylated Gal24N adopts the usual 4C1 chair conformation, the native 2-N-acetyl-4-amino Gal24N exhibits conformational mobility with comparable populations in the 4C1 chair and 5S1 skew conformations, as determined using MD simulation for the partial trisaccharide Me-beta-D-Glc6P-(1-->3)-alpha-D-Gal24N-[6-PC]-(1-->4)-alpha- D-galNAc and from the intra-ring NOE effects. 31P-NMR spectra point to a strong electrostatic or hydrogen-bonding interaction between the free 4-NH2 group on the Gal24N and the negatively charged diester phosphate group between adjacent pentasaccharide repeating-units [Ribitol-(5-->6)-beta-D-Glc6P]. Molecular modelling and MD simulation experiments confirmed that such an interaction was feasible with the Gal24N galactopyranose ring in the inverted B1.4 or skew 5S1 conformation.

Acetylgalactosamine↗
PubMed1996

Postpartum pelvic floor conditioning using vaginal cones: not only for prophylaxis against urinary incontinence and descensus.

Seventy-one women were examined 6-8 weeks after spontaneous delivery by pelvic floor (PF) palpation, inspection, manometry and gravimetry. Re-examination was performed in the same way after 4-6 weeks of daily cone training. Control groups included 20 women prior to and after conventional puerperal exercises, and 8 nulliparae prior to and after the same cone training, using a five-cone set. The number of puerperae not capable of voluntary PF contraction declined from 34% before to 6% after training. Optimum initial and post-training responses were exhibited by all nulliparae. Differences between cone and conventional exercise groups were of minor importance. Contractility increased from 5 to 10 mmHg on average in puerperae and from 15 mmHg to 21 mmHg in nulliparae. Cone nos. 1-3 were most frequently required at the beginning of training, and nos. 3-5 towards the end. Cone training works well as an alternative or complement to conventional postpartum exercises, and may therefore be recommended especially to puerperae who are not capable of holding vaginal cones of 20-70 g 6 weeks after delivery.

Adult↗
PubMed1996

Thin-layer chromatographic analysis of phenols on TLC aluminium sheets RP-18 F(254s).

The thin-layer chromatographic properties of phenolic compounds on TLC aluminium sheets RP-18 have been investigated in different eluent systems. Moreover, a method for the qualitative and quantitative thin-layer chromatographic determination of pentachlorophenol (PCP) in leather goods has been developed. This procedure includes sample preparation by solid phase extraction (SPE) using LiChrolut(R) EN columns.

Journal Article↗
PubMed1996

Stress measurement in alumina scales on high temperature alloys using X-ray stress evaluation and laser Raman spectroscopy.

The effect of silicon and titanium on the spallation resistance of alumina scales grown on NiCrAlY-type alloys has been investigated using model alloys with different additions of Si or Ti. For this purpose cyclic oxidation experiments have been carried out at temperatures between 950 and 1100 degrees C. After various times stresses in selected Si-doped samples have been determined by X-ray stress evaluation (XSE) at ambient temperature. The compressive stresses in the scales have been found to increase with an increasing oxidation time tending to become constant for long times. The development of stress is affected by the presence of Si. Laser Raman spectroscopy (LRS) has been calibrated for strain measurement using XSE results. Then LRS has been applied for strain measurement at higher temperatures.

Journal Article↗
PubMed1996

D-alanine deprivation of Bacillus subtilis teichoic acids is without effect on cell growth and morphology but affects the autolytic activity.

Using insertional inactivation of the different genes of the dlt operon in Bacillus subtilis, we searched for metabolic and morphological changes caused by D-alanine ester deprivation of lipoteichoic acid and wall teichoic acid. There were no alterations of cell growth, basic metabolism, cellular content of phosphorus-containing compounds, ultrastructure, cell separation, and surface charge. The only alteration observed was an enhancement of endogenous and beta-lactam-induced cell lysis. Since this enhancement is doubtless correlated with the D-alanine ester deprivation of the teichoic acids, the present view based on in vitro experiments, that negatively charged LTA is inhibitory to autolysins, may be questioned. We propose that negatively charged lipoteichoic acid and/or wall teichoic acid serve in vivo to fix the cationic autolysins within the cell wall-membrane complex by electrostatic interaction. Positively charged D-alanine ester substituents decrease the binding capacity of the teichoic acids for autolysins by charge compensation.

Alanine↗
PubMed1996

Penicillin tolerance and modification of lipoteichoic acid associated with expression of vancomycin resistance in VanB-type Enterococcus faecium D366.

Induction of vancomycin resistance in Enterococcus faecium D366, which exhibits a VanB-type resistance, as well as its constitutive expression in MT9, a derivative of D366, was associated with penicillin tolerance as shown by decreased lysis and killing of the cells. This phenomenon was linked neither to decreased expression of the different autolysins nor to their decreased lytic activity on the different cell walls. The only change observed was that almost twice the normal amount of D-alanine was attached to the lipoteichoic acid.

Anti-Bacterial Agents↗
PubMed1996

Interactions of human mannose-binding protein with lipoteichoic acids.

We explored the interaction of human recombinant mannose-binding protein and lipoteichoic acids (LTAs) by enzyme-linked immunosorbent assay. The best ligand was Micrococcus luteus lipomannan, followed by Enterococcus spp. LTA containing mono-, di-, and oligoglucosyl substituents. LTAs lacking terminal sugars (those of Streptococcus pyogenes and Staphylococcus aureus) or containing galactosyl substituents (those of Listeria spp. and Lactococcus spp.) were poor ligands. These results are consistent with known structural requirements for binding through the mannose-binding protein carbohydrate recognition domain.

Acute-Phase Proteins↗
PubMed1996

Influence of lipoteichoic acid structure on recognition by the macrophage scavenger receptor.

Lipoteichoic acids (LTAs) belong to the immunostimulatory class of molecules of gram-positive bacteria (GPB). Previous investigations showed that the macrophage scavenger receptor (SR), a glycosylated trimeric transmembrane protein, binds directly to many GPB, possibly via LTA. SR binding to other ligands is dependent upon the spatial characteristics of the repeating negative charge of the ligand. We therefore investigated SR recognition of LTA species with various charge densities and distributions by determining the capacity of these LTAs to compete with the binding of metabolically labeled SR to beads coated with the known SR ligand polyguanylic acid. Staphylococcus aureus LTA, a classical LTA type (unbranched 1,3-linked polyglycerophosphate chain covalently bound to a membrane diacylglyceroglycolipid), had a 50% inhibitory concentration (IC50) for inhibition of SR binding of 0.84 microg/ml. When the S. aureus LTA was rendered more negatively charged by removal of ester-linked alanine from the polyglycerophosphate backbone, the IC50 dropped to 0.23 microg/ml. Other polyglycerophosphate LTAs from Enterococcus faecalis, Enterococcus faecium, Enterococcus hirae, Listeria monocytogenes, Listeria welshimeri, and Streptococcus sanguis showed IC50S of 0.5 to 2.1 microg/ml, supporting the role of negative charge in binding to SR. Accordingly, the zwitterionic LTA of Streptococcus pneumoniae and Clostridium innocuum LTA substituted with positively charged sugar residues had no binding capacity. Monoglycerophosphate branches, but not succinyl ester, affected binding of lipoglycans. The data presented above parallel the previous findings for whole organisms and support the role of surface-associated LTA as a major ligand of GPB for binding to SR. Whether binding of LTA and whole GPB to macrophages initiates uptake and degradation or results in signal transduction remains to be determined.

Animals↗
PubMed1996

The intercellular adhesin involved in biofilm accumulation of Staphylococcus epidermidis is a linear beta-1,6-linked glucosaminoglycan: purification and structural analysis.

The primary attachment to polymer surfaces followed by accumulation in multilayered cell clusters leads to biofilm production of Staphylococcus epidermidis, which is thought to contribute to virulence in biomaterial-related infections. We purified a specific polysaccharide antigen of biofilm-producing S. epidermidis 1457 and RP62A, which was recently shown to have a function in the accumulative phase of biofilm production by mediating intercellular adhesion (D. Mack, M. Nedelmann, A. Krokotsch, A. Schwarzkopf, J. Heesemann, and R. Laufs, Infect. Immun. 62:3244-3253, 1994). Following Sephadex G-200 gel filtration, this antigen was separated by Q-Sepharose chromatography into a major polysaccharide, polysaccharide I (> 80%), which did not bind to Q-Sepharose, and a minor polysaccharide, polysaccharide II (< 20%), which was moderately anionic. As shown by chemical analyses and nuclear magnetic resonance spectroscopy, polysaccharide I is a linear homoglycan of at least 130 beta-1,6-linked 2-deoxy-2-amino-D-glucopyranosyl residues. On average, 80 to 85% of them are N acetylated; the rest are non-N-acetylating and positively charged. Chain cleavage by deamination with HNO2 revealed a more or less random distribution of the non-N-acetylated glucosaminyl residues, with some prevalence of glucosaminyl-rich sequences. Cation-exchange chromatography separated molecular species whose content of non-N-acetylated glucosaminyl residues varied between 2 and 26%. Polysaccharide II is structurally related to polysaccharide I but has a lower content of non-N-acetylated D-glucosaminyl residues and contains phosphate and ester-linked succinate, rendering it anionic. Enzyme-linked immunosorbent assay inhibition with various monosaccharides revealed the beta-anomeric form and the acetylated amino group of the D-glucosaminyl residues as important for reactivity with the specific antiserum. The unbranched polysaccharide structure favors long-range contacts and interactions between polysaccharide strands and the cell wall and/or lectin-like proteins, leading to intercellular adhesion and biofilm accumulation. The structure of the polysaccharide is, so far, considered to be unique and, according to its function, is referred to as S. epidermidis polysaccharide intercellular adhesin (PIA).

Acetylglucosamine↗
PubMed1996

[Pelvic floor conditioning with vaginal weights--post partum and in urinary incontinence].

To check on the efficacy of cone training 71 women were thoroughly examined six to eight weeks after spontaneous deliveries at various risk levels. Their pelvic floor was examined by palpation, inspection, manometry and gravimetry. All of them were re-examined in the same way after four to six weeks of daily cone training. Thirty women with moderate genuine stress incontinence (16) or stress/urge incontinence (14) were evaluated by the same procedure, independent of gestation. A control group included 20 women prior to and after conventional puerperal pelvic floor exercises and eight nulliparae of the same age prior to and after the same cone training, using a five-cone set. The number of puerperae not capable of voluntary pelvic floor contraction declined from 34 % before to 6 % after training. Optimum initial and posttraining responses, on the other hand, were exhibited by all nulliparae. Differences in childbirth risk for pelvic floor damage played a less important role than childbirth proper. Training related differences were of minor importance, as well, between cone and conventional exercise groups. Notwithstanding different initial values, all puerperae increased their contractility to 10 mm Hg on average, while the increase accomplished by nulliparae was from 15 mm Hg to 21 mm Hg. Cone Nos. 1-3 (20.0-45.0g) were most frequently required at the beginning of training and Nos. 3-5 (45.0-70.0 g) towards the end, for an average increase by one or two cone numbers. 25 % of the cone women and 35 % of the conventional exercise probands failed to complete the training, which was indicative of limited patient compliance after delivery. A positive correlation was found to exist between motivation and training success. Cone training also had positive effects on sexuality. It has proved to work well alternatively or complementary to conventional postpartum exercises and, therefore, may be recommended to all women who are not capable of holding with their pelvic floor vaginal cones of 20-70 g in the postpartum period. In women with urinary incontinence (UI) no pelvic floor response was recordable, prior to training, from five women (17 %). Response was not even recorded from eight women (21 %) by palpation. After training, the capability of voluntary and reflex contraction of pelvic floor muscles was restored in all women. The best post-training result was obtained from palpation (27 positive responses). Manometry and capability of the pelvic floor to hold vaginal cones were other suitable methods in this context: in 15 women (50 %) cone weights were extremely low at the beginning of treatment (Cone no. 1-2), while after treatment 19 women (63 %) held cones up to Nos. 4-5. All healthy women of the control group started with Cone No. 5. In conformity with postpartum groups average increase in pelvic floor contractility was from 5 mm to 10 mm Hg in UI patients. Twenty-four women (80 %) were cured from UI (57 %) or were improved (23 %). Twenty-six women asked for continuation of cone training. Pelvic floor conditioning, using vaginal cones, is a good alternative to poor acceptance or insufficient availability of conventional pelvic floor exercises in conservative treatment of urinary incontinence and descensus.

Adult↗
PubMed1996

The role of congruence between patient and therapist in chronic low back pain patients.

OBJECTIVE: To determine the role of congruence in the perception of the evolution of back pain during treatment and in the expectations about the future of back pain problems. Congruence was defined as the agreement between patient and therapist on various aspects of back pain problems and of treatment. DESIGN: Semistructured interviews at the beginning and the end of treatment. SUBJECTS: Seventy-one back pain patients and their therapists (6 chiropractors and 6 rheumatologists). MAIN OUTCOME MEASURES: Synthesized index of congruence based on 24 questions asked of both the patient and his/her therapist. RESULTS: The distribution of the congruence scores indicated a high level of congruence in 39.4% of the cases, an average level in 35.2% and a low level in 25.4%. The results demonstrated that congruence was significantly associated with the perception of an improvement in back pain. This positive perception was nevertheless associated with the expectation of persistence or recurrence of the back pain problem in the future. Noncongruence was correlated with the patient's estimation of a less favorable evolution of the back pain problem during the treatment and with a major difficulty for both the therapist and the patient to express clear expectations about the future of the patient's back pain problem. CONCLUSIONS: Congruence mainly reflects an agreement that the treatment is aimed at the management of a long-term condition rather than at the resolution of the back pain problem. Congruent patients seem to accept living with their back problems, a position shared by their therapists, whereas noncongruent patients do not seem to share this conception of back pain.

Adult↗
PubMed1995

The 94- to 97-kDa mouse macrophage membrane protein that recognizes oxidized low density lipoprotein and phosphatidylserine-rich liposomes is identical to macrosialin, the mouse homologue of human CD68.

We have previously reported the partial purification of a 94- to 97-kDa plasma membrane protein from mouse peritoneal macrophages that binds oxidatively modified low density lipoprotein (OxLDL) and phosphatidylserine-rich liposomes. We have now identified that protein as macrosialin, a previously cloned macrophage-restricted membrane protein in the lysosomal-associated membrane protein family (mouse homologue of human CD68). Early in the course of purification of the 94- to 97-kDa protein, a new OxLDL-binding band at 190-200 kDa appeared and copurified with the 94- to 97-kDa protein. The HPLC pattern of tryptic peptides from this higher molecular mass ligand-binding band closely matched that derived from the 94- to 97-kDa band. Specifically, the same three macrosialin-derived tryptic peptides (9, 9, and 15 residues) were present in the purified 94- to 97-kDa band and in the 190- to 200-kDa band and antisera raised against peptide sequences in macrosialin recognized both bands. An antiserum against macrosialin precipitated most of the 94- to 97-kDa OxLDL-binding material. We conclude that the binding of OxLDL to mouse macrophage membranes is in part attributable to macrosialin. Our previous studies show that OxLDL competes with oxidized red blood cells and with apoptotic thymocytes for binding to mouse peritoneal macrophages. Whether macrosialin plays a role in recognition of OxLDL and oxidatively damaged cells by intact macrophages remains uncertain.

Amino Acid Sequence↗
PubMed1995

Incorporation of D-alanine into lipoteichoic acid and wall teichoic acid in Bacillus subtilis. Identification of genes and regulation.

The Bacillus subtilis dlt operon (D-alanyl-lipoteichoic acid) is responsible for D-alanine esterification of both lipoteichoic acid (LTA) and wall teichoic acid (WTA). The dlt operon contains five genes, dltA-dltE. Insertional inactivation of dltA-dltD results in complete absence of D-alanine from both LTA and WTA. Based on protein sequence similarity with the Lactobacillus casei dlt gene products (Heaton, M. P., and Neuhaus, F. C. (1992) J. Bacteriol. 174, 4707-4717), we propose that dltA encodes the D-alanine-D-alanyl carrier protein ligase (Dcl) and dltC the D-alanyl carrier protein (Dcp). We further hypothesize that the products of dltB and dltD are concerned with the transport of activated D-alanine through the membrane and the final incorporation of D-alanine into LTA. The hydropathy profiles of the dltB and dltD gene products suggest a transmembrane location for the former and an amino-terminal signal peptide for the latter. The incorporation of D-alanine into LTA and WTA did not separate in any of the mutants studied which indicates that either one and the same enzyme is responsible for D-alanine incorporation into both polymers or a separate enzyme, encoded outside the dlt operon, transfers the D-alanyl residues from LTA to WTA (Haas, R., Koch, H.-U., and Fischer, W. (1984) FEMS Microbiol. Lett. 21, 27-31). Inactivation of dltE has no effect on D-alanine ester content of both LTA and WTA, and at present we cannot propose any function for its gene product. Transcription analysis shows that the dlt operon is transcribed from a sigma D-dependent promoter and follows the pattern of transcription of genes belonging to the sigma D regulon. However, the turn off of transcription observed before sporulation starts seems to be dependent on the Spo0A and AbrB sporulation proteins and results in a D-alanine-free purely anionic LTA in the spore membrane. The dlt operon is dispensable for cell growth; its inactivation does not affect cell growth or morphology as described for L. casei.

Alanine↗
PubMed1995

Reversal of age-dependent cognitive impairments and cholinergic neuron atrophy by NGF-secreting neural progenitors grafted to the basal forebrain.

A highly NGF-secreting cell line was generated by retroviral transduction of a conditionally immortalized CNS-derived neural progenitor cell line. After transplantation to the nucleus basalis magnocellularis (NBM), the cells continue to express the NGF transgene for at least 10 weeks, producing sufficient NGF to reverse cholinergic neuron atrophy in aged rats and induce cellular hypertrophy in young rats. In cognitively impaired aged rats, transplants of the NGF-secreting cells placed either in the NBM and septum or in only the NBM induced a near-complete reversal of the spatial learning impairment. This was accompanied by a normalization of the size of the cholinergic neurons in the grafted areas. The results demonstrate that locally increased supply of NGF to the basal forebrain cholinergic nuclei has a significant impact on cognitive function and support the usefulness of neural progenitor cells for a long-term localized delivery of neurotrophins to the CNS.

Age Factors↗