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Biomedical subjects

W Breuer

Publications and source records attributed to W Breuer.

69 records · Page 4Linked to original sources
PubMed1991

Dermal metabolism of 4-nitrophenol and 4-nitroanisole in single-pass perfused rabbit ears.

1. 4-Nitrophenol and 4-nitroanisole were applied either dermally or arterially to isolated rabbit ears perfused under single-pass conditions with protein-free buffer solution. 2. 4-Nitroanisole yielded only phase II metabolites of 4-nitrophenol. 3. The apparent Vmax values for 4-nitrophenol glucuronidation and sulphation were about 20 pmol and 10 pmol/min per cm2, respectively. 4. The difference in apparent Km between dermal and arterial drug application is a measure of first-pass metabolism by the epidermal layer. 5. The amount of 4-nitrophenyl conjugate detected after 4-nitroanisole administration was assumed to represent O-dealkylation of 4-nitroanisole; the capacity of this reaction was one order of magnitude lower than the direct conjugation of 4-nitrophenol.

Administration, Cutaneous↗
PubMed1990

Reconstitution of a kidney chloride channel and its identification by covalent labeling.

The basolateral membrane of the thick ascending loop of Henle (TALH) of the mammalian kidney is characterized by its high content of Na+/K(+)-ATPase and a Cl- conductance, which function in parallel in salt reabsorption. In order to reconstitute the Cl- channels, TALH membrane vesicles were solubilized in 1% sodium cholate in buffer containing 200 mM KCl, followed by dilution with soybean lipids (final ratio of protein/detergent/lipid of 1:3:15 in mg) and removal of the detergent by gel filtration on Sephadex G-50. Cl- channel activity in the liposomes was determined by a 36Cl- uptake assay where the accumulation of the radioactive tracer against its chemical gradient is driven by the membrane potential (positive inside) generated by an outward Cl- gradient. The 36Cl- uptake by the KCl-loaded liposomes was dependent on the inclusion of membrane protein and was abolished by valinomycin, indicating the involvement of a conductive pathway. It was also inhibited by 36% by 100 microM 4,4'-diisothiocyanostilbene-2,2'-disulfonate (DIDS) and 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB). Solubilization of the Cl- channels in cholate was optimal in the presence of 200 mm KCl, but was found to decrease markedly at low ionic strength. SDS-PAGE analysis of the proteins extracted by cholate at high and low salt concentrations showed that the Cl- channel-containing high KCl extract was enriched in the 96 and 55 kDa alpha- and beta-subunits of the Na+/K(+)-ATPase (the major proteins in the membrane preparation) and several minor protein bands. Treatment of the membrane vesicles with the radioactive analogue of DIDS, [3H]2DIDS, labeled primarily a 65 and a 31 kDa protein. The solubilization of the 31 kDa protein by cholate depended markedly on the ionic strength and thus paralleled the solubilization pattern of Cl- channel activity. Furthermore, the labeling of the 31 kDa protein was prevented by nonradioactive DIDS and by NPPB but not by other compounds, indicating that it may be a Cl- channel component.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1989

Inhibition of prostaglandin E2 synthesis by a blocker of epithelial chloride channels.

Arginine-vasopressin (AVP) elicits a variety of responses in cultured rat mesangial cells, among them stimulation of prostaglandin biosynthesis and activation of Cl- channels. AVP produced an 11-fold increase over basal levels in prostaglandin E2 release from cultured mesangial cells. This response was completely inhibited by 25 microM indomethacin and 82 +/- 5% inhibited by 25 microM 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB) which is a potent blocker of epithelial Cl- channels. The IC50 for NPPB inhibition of prostaglandin E2 release was 8 microM. Indomethacin and NPPB at 25 microM also inhibited AVP-stimulated cellular accumulation of prostaglandin E2 by 98% and 79 +/- 7% respectively. The inhibitory effect of NPPB was not due to interference with the cellular response to AVP since at 50 microM it did not block AVP-stimulated release of arachidonate metabolites from cells metabolically labeled with [3H]-arachidonic acid. It is suggested that NPPB inhibition of prostaglandin E2 synthesis is at the cyclooxygenase level on the basis of its structural similarity to the fenamic acid type of cyclooxygenase inhibitors.

Animals↗
PubMed1989

Postnatal development of lectin binding sites in the rat ventral prostate.

Five Fluorescein-isothiocyanate (FITC)-labelled lectins were used to study the postnatal development of carbohydrate constituents in the rat ventral prostate: Concanavalin A (Con A), wheat germ agglutinin (WGA), peanut agglutinin (PNA), Dolichos biflorus agglutinin (DBA) and Ricinus communis agglutinin I (RCA-I). With all the lectins tested, except RCA-I, specific binding sites could be shown for every stage of differentiation in the glandular epithelium. Binding sites for Con A, WGA, PNA and DBA were found from day 10 to 13 post partum onwards. Each lectin showed a characteristic localization. Binding sites for the lectins used changed to different extents during the following two weeks. After the 24th day post partum no further changes in the lectin binding pattern could be found. The development of the lectin binding properties showed that the changes in carbohydrate-containing constituents of the prostate correlate with the beginning of prostatic secretion and to prostatic epithelial differentiation. In the periacinar stroma the development of the lectin binding pattern was similar to that in the glandular epithelium. The changes of stromal binding sites for Con A and WGA during epithelial differentiation may reflect the changes of epithelial-stromal interactions in the prostate.

Animals↗
PubMed1989

Characterization of chloride channels in membrane vesicles from the kidney outer medulla.

The basolateral membrane of the thick ascending loop of Henle (TALH) of the mammalian kidney is highly enriched in Na+/K+ ATPase and has been shown by electrophysiological methods to be highly conductive to Cl-. In order to study the Cl- conductive pathways, membrane vesicles were isolated from the TALH-containing region of the porcine kidney, the red outer medulla, and Cl- channel activity was determined by a 36Cl uptake assay where the uptake of the radioactive tracer is driven by the membrane potential (positive inside) generated by an outward Cl- gradient. The accumulation of 36Cl- inside the vesicles was found to be dependent on the intravesicular Cl- concentration and was abolished by clamping the membrane potential with valinomycin. The latter finding indicated the involvement of conductive pathways. Cl- channel activity was also observed using a fluorescent potential-sensitive carbocyanine dye, which detected a diffusion potential induced by an imposed inward Cl- gradient. The anion selectivity of the channels was Cl- greater than NO3- = I- much greater than gluconate. Among the Cl- transport inhibitors tested, 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPAB), 4,4'-diisothiocyano-stilbene-2,2'-disulfonate (DIDS), and diphenylamine-2-carboxylate (DPC) showed IC50 of 110, 200 and 550 microM, respectively. Inhibition of 36Cl uptake by NPPAB and two other structural analogues was fully reversible, whereas that by DIDS was not. The nonreactive analogue of DIDS, 4,4'-dinitrostilbene-2,2'-disulfonate (DNDS), was considerably less inhibitory than DIDS (25% inhibition at 200 microM). The irreversible inhibition by DIDS was prevented by NPPAB, whereas DPC was ineffective, consistent with its low inhibitory potency.(ABSTRACT TRUNCATED AT 250 WORDS)

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1981

Identification of endogenous binding proteins for the lectin discoidin-I in Dictyostelium discoideum.

Recent biochemical and genetic evidence has shown that the endogenous lectin discoidin-I is involved in intercellular adhesion during development of the cellular slime mold Dictyostelium discoideum. We have prepared discoidin-I affinity columns and used them to isolate the lectin receptors. By using the cell surface radioiodination method, 11 discoidin-I binding proteins were identified in wild-type NC4 cells by gel electrophoresis, with apparent molecular weights of 95,000, 85,000, 78,000, 72,000, 60,000, 33,000, 31,000, 28,000, 25,000, 21,000, and 15,000. Only three (gp33, gp31, and gp28) were under developmental regulation. The amount of gp31 increased 8- to 10-fold during aggregation, and it was the predominant discoidin-I binding protein synthesized at the aggregation stage. Discoidin-I binding proteins derived from aggregation stage cells were potent inhibitors of discoidin-I in a hemagglutination assay in vitro. The same preparation was found to promote aggregation of cells bearing discoidin-I on the surface, suggesting a multivalent interaction.

Carrier Proteins↗
PubMed1980

[Surgical treatment of endometriosis of the large intestine (author's transl)].

Endometriosis is a sufficiently common disease that should always be considered in the differential diagnosis of colon lesions in women of child bearing age. Six selected cases illustrate problems of diagnosis and management of endometriosis of the colon. Characteristics of colon endometriosis are typical large-bowel symptoms such as colicky pains and hemorrhage usually situated in the sigmoid and rectosigmoid region, extramucosal radiologic appearance of a marked smooth-walled stenosis, and the difficult endoscopic and histological preoperative diagnosis. Suspected malignancy and the presence of the symptoms of a colon lesion are indications for bowel resection, which is an effective form of therapy.

Adult↗
PubMed1978

Asymmetry of the red cell anion exchange system. Different mechanisms of reversible inhibition by N-(4-azido-2-nitrophenyl)-2-aminoethylsulfonate (NAP-taurine) at the inside and outside of the membrane.

In the dark, the photoaffinity reagent, N-(4-azido-2-nitrophenyl)-2-aminoethylsulfonate (NAP-taurine), acts as a reversible inhibitor of red cell anion exchange when it is present either within the cell or in the external solution. A detailed analysis of the inhibition kinetics, however, reveals substantial differences in the responses to the probe at the two sides of the membrane. On the inside of the cell, NAP-taurine is a relatively low affinity inhibitor of chloride exchange (Ki = 370 microM). Both the effects of chloride on NAP-taurine inhibition and the affinity of NAP-taurine for the system as a substrate are consistent with the concept that internal NAP-taurine competes with chloride for the substrate site of the anion exchange system. External NAP-taurine, on the other hand, is a far more potent inhibitor of chloride exchange (Ki = 20 microM). It acts at a site of considerably lower affinity for chloride than the substrate site, probably the modifier site, at which halide anions are reported to cause a noncompetitive inhibition of chloride transport. NAP-taurine therefore seems to interact preferentially with either the substrate or modifier site of the transport system, depending on the side of the membrane at which it is present. It is suggested that the modifier site is accessible to NAP-taurine only from the outside whereas the transport site may be accessible from either side.

Binding Sites↗
PubMed1978

N-(4-azido-2-nitrophenyl)-2-aminoethylsulfonate (NAP-taurine) as a photoaffinity probe for identifying membrane components containing the modifier site of the human red blood cell anion exchange system.

Exposure of cells to intense light with the photoactivatable reagent, N-(4-azido-2-nitrophenyl)-2-aminoethylsulfonate (NAP-taurine), present in the external medium results in irreversible inhibition of chloride or sulfate exchange. This irreversible inhibition seems to result from covalent reaction with the same sites to which NAP-taurine binds reversibly in the dark. As shown in the preceding paper, high chloride concentrations decrease the reversible inhibition by NAP-taurine in the dark, in a manner suggesting that NAP-taurine and chloride compete for the modifier site of the anion transport system. In a similar fashion, high chloride concentrations in the medium during exposure to light cause a decrease in both the irreversible binding of NAP-taurine to the membrane and the inhibition of chloride exchange. Most of the chloride-sensitive irreversibly bound NAP-taurine is found in the 95,000 dalton polypeptide known as band 3 and, after pronase treatment of intact cells, in the 65,000 dalton fragment of this protein produced by proteolytic cleavage. After chymotrypsin treatment of ghosts, the NAP-taurine is localized in the 17,000 dalton transmembrane portion of this fragment. Although the possible involvement of minor labeled proteins cannot be rigorously excluded, the modifier site labeled by external NAP-taurine appears, therefore, to be located in the same portion of the 95,000 dalton polypeptide as is the transport site.

Affinity Labels↗
PubMed1977

Synthesis of tritiated 4,4'-diisothiocyano-2,2'-stilbene disulfonic acid ([3H]DIDS) and its covalent reaction with sites related to anion transport in human red blood cells.

The potent and specific inhibitor of anion permeability, 4,4'-diisothicyanostilbene-2,2'-disulfonic acid (DIDS) was synthesized in tritiated form ([3H]DIDS) from tritiated 5-nitrotoluene-o-sulfonic acid. Its reactions with and effects on red blood cells were compared with those of a reduced form ([3H]H2DIDS), previously used as a tracer for DIDS. The rate of covalent reaction of [3H]DIDS was substantially faster than that of [3H]H2DIDS at all temperatures tested. With both agents, the rate of reaction was increased in alkaline media, although the response occurred at a lower pH with [3H]DIDS. On the other hand, the relationship of irreversible membrane binding to the degree of inhibition of sulfate fluxes was linear and virtually the same for both agents, with 100% inhibition associated with the binding of approximately 1.2 X 10(6) molecules per cell. About 90% of the binding for each probe was to a particular membrane protein, known as band 3, equivalent to about 1 mole of agent per mole of protein.

Anions↗
PubMed1976

The interaction of an anionic photoreactive probe with the anion transport system of the human red blood cell.

N-(4-azido-2-nitrophenyl)-2-aminoethyl[35S]sulfonate is employed as a photoreactive probe for the anion transport system in the human erythrocyte. In the dark and at 37 degrees C the probe penetrates the membrane via a pathway sensitive to specific inhibitors of anion permeability. It reversibly inhibits sulfate and chloride fluxes but the inhibition is reduced by higher concentrations of sulfate. Upon photolysis to produce a reactive nitrene (at 0 degrees C to minimize penetration), the probe inhibition of anion permeability. Under appropriate conditions the degree of inhibition after photoactivation (irreversible) is almost the same as that in the dark (reversible). The binding sites for the radioactive probe are largely found in proteins of 95 000 apparent molecular weight (band 3). After pronase treatment of the labelled cells, most of the probe is found in a 65 000 molecular weight segment derived from the 95 000 molecular weight protein. In this respect the photoreactive probe resembles another potent irreversible inhibitor of anion transport, 4, 4'-diisothiocyano-2, 2' stilbene disulfonate. In fact, most of the binding sites for each probe are common to both. Thus, in the dark, the azido derivative protects the anion system from inhibition by DIDS and substantially reduces the binding of DIDS to band 3 protein. Conversely, pretreatment with DIDS substantially reduces the binding of the photoreactive probe to the same protein. The fact that an apparent substrate for the anion permeation system competes for binding sites with a specific non-penetrating inhibitor of anion permeability suggests that the inhibitory and transport sites may be closely related and implicates the 95 000 molecular weight protein as the element of the anion transport system which contains the substrate binding site.

Biological Transport↗
PubMed1975

Pyridoxal phosphate. An anionic probe for protein amino groups exposed on the outer and inner surfaces of intact human red blood cells.

Pyridoxal phosphate is a potent probe for exploring the "sidedness" of proteins in the membrane of the intact red blood cell. It reacts with amino groups with a high degree of specificity, forming a Schiff's base that can be fixed as an irreversible bond upon reduction with NaBH4; its binding site can be identified by use of [3-H]pyridoxal phosphate or NaB3-H4; it can be used as a surface probe under conditions of minimal penetration, or it can be used as a probe for proteins on the inside of the membrane under conditions of substantial uptake. Pyridoxal phosphate uptake involves a rapid and a slow component. The former represents the binding to the outer surface of the membrane; it is not substantially affected by pH and temperature, but is reduced considerably by pretreatment of cells by 4,4-diisothiocyano-2,2-stilbenedisulfonic acid, a specific inhibitor of anion transport. The slow component represents penetration into the cell; it is blocked by high pH, low temperature, or pretreatment with the disulfonic stilbene. Pyridoxal phosphate itself is also an effective and specific inhibitor of the permeation of other anions. Under conditions of minimal uptake, the only labeled proteins are three glycoproteins and a protein of apparent molecular weight 95,000. Under conditions of substantial uptake into the cell, the other major protein bands seen by staining on acrylamide gels after electrophoresis are labeled. It is concluded that virtually all of the major membrane proteins interact with pyridoxal phosphate from one side of the membrane or the other. The differences in labeling under conditions of minimal or maximal uptake can, therefore, be attributed to the sidedness in the distribution of the membrane proteins rather than to differences in their reactivity.

Amino Acids↗
PubMed1975

A comparison of intact human red blood cells and resealed and leaky ghosts with respect to their interactions with surface labelling agents and proteolytic enzymes.

Resealed ghosts and intact red blood cells were directly compared with respect to their interactions with surface proteins by 4.4'-diisothiocyano-2,2'-stilbene disulfonic acid (DIDS) and by pyridoxal phosphate-borohydride (as seen after sodium dodecylsulfate/acrylamide gel electrophoresis) was substantially the same in cells and resealed ghosts under conditions in which a relatively small change would be apparent. In each membrane system, DIDS labels a protein component of apparent molecular weight 95 000 and pyridoxal phosphate labels the same protein plus three glucoprotein components. The sensitivity of surface proteins and of DIDS and pyridoxal phosphate-labelled sites to pronase was also similar in the cells and resealed ghosts. The glycoproteins were digested, in each case, and the 95 000 (molecular weight) protein was largely split into two proteins of apparent molecular weights 65 000 and 35 000, with both portions containing DIDS and pyridoxal phosphate in the presence of hemoglobin was similar to the labelling of intact cells, provided that the pyridoxal phosphate was present on both the outside and inside of the cells. Virtually all of the major protein components visible by staining on acrylamide gels were labelled. It is concluded that none of the probes could detect any substantial differences in reactivity of proteins of the outer surface of the membrane protein conformation or arrangement occur as a consequence of lysis and resealing of ghosts, that are detectable by the reported procedures.

Blood Proteins↗
PubMedDate not supplied

Effects of a health promotion program on sustaining health behaviors in older adults.

BACKGROUND: Controversy exists regarding the optimal way to provide health promotion education to the elderly. This prospective randomized study evaluated the effectiveness of individualized assessment and counseling coupled with the receipt of a written health plan on client adherence to health behavior recommendations. METHODS: Two hundred thirty-seven ethnically diverse and predominantly low-income adults 60 and older, participating for the first time in an established statewide public health prevention program delivered in both rural and urban clinics, were recruited and randomly assigned to treatment and control groups. All participants received a standardized assessment that included a health history, nutrition assessment, and limited physical exam from a public health nurse. The treatment group additionally received a written personal health plan and individualized counseling to support implementation of the plan. Both groups were interviewed after one year to determine their adherence to the original recommendations. RESULTS: Seventeen preventive services and health behaviors were evaluated. There were no statistically significant differences between the groups on health care use and previous health behaviors at baseline. Using logistic regression and controlling for socioeconomic and demographic variables, we found that the treatment group that received a personal health plan and counseling completed significantly more preventive referrals and health behavior changes (P < .001). CONCLUSIONS: A client-centered planning process with supportive counseling by public health nurses, combined with health plans provided to clients, can significantly increase the prevention measures taken by older adults.

Aged↗