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Biomedical subjects

M Wagener

Publications and source records attributed to M Wagener.

32 records · Page 2Linked to original sources
PubMed1996

Expression cloning and functional characterization of the kidney cortex high-affinity proton-coupled peptide transporter.

The presence of a proton-coupled electrogenic high-affinity peptide transporter in the apical membrane of tubular cells has been demonstrated by microperfusion studies and by use of brush border membrane vesicles. The transporter mediates tubular uptake of filtered di- and tripeptides and aminocephalosporin antibiotics. We have used expression cloning in Xenopus laevis oocytes for identification and characterization of the renal high-affinity peptide transporter. Injection of poly(A)+ RNA isolated from rabbit kidney cortex into oocytes resulted in expression of a pH-dependent transport activity for the aminocephalosporin antibiotic cefadroxil. After size fractionation of poly(A)+ RNA the transport activity was identified in the 3.0- to 5.0-kb fractions, which were used for construction of a cDNA library. The library was screened for expression of cefadroxil transport after injection of complementary RNA synthesized in vitro from different pools of clones. A single clone (rPepT2) was isolated that stimulated cefadroxil uptake into oocytes approximately 70-fold at a pH of 6.0. Kinetic analysis of cefadroxil uptake expressed by the transporter's complementary RNA showed a single saturable high-affinity transport system shared by dipeptides, tripeptides, and selected amino-beta-lactam antibiotics. Electrophysiological studies established that the transport activity is electrogenic and affected by membrane potential. Sequencing of the cDNA predicts a protein of 729 amino acids with 12 membrane-spanning domains. Although there is a significant amino acid sequence identity (47%) to the recently cloned peptide transporters from rabbit and human small intestine, the renal transporter shows distinct structural and functional differences.

Amino Acid Sequence↗
PubMed1996

The peptide-based thrombin inhibitor CRC 220 is a new substrate of the basolateral rat liver organic anion-transporting polypeptide.

The peptidomimetic thrombin inhibitor CRC 220, 4-methoxy-2,3,6-trimethylphenylsulfonyl-L-aspartyl-D-4-amidinop henylalanyl- piperidide, is taken up into isolated rat hepatocytes through active, carrier-mediated transport. This uptake is inhibited by bile acids. Functional expression in Xenopus laevis oocytes was performed to identify the transport system responsible for the hepatocellular CRC 220 uptake. Injection of poly(A)+RNA in X. laevis oocytes resulted in a two- to three-times higher uptake of CRC 220, compared with uninjected or water-injected control oocytes. Taurocholate (200 mumol/L) inhibited this uptake completely. No uptake of the peptidomimetic thrombin inhibitor was observed, when X. laevis oocytes were injected with complementary RNA (cRNA) encoding either the cloned rat liver Na(+)-dependent taurocholate transporter Ntcp, the renal oligopeptide carrier rhaPT or the intestinal oligopeptide transporter PepT1. However, after injection of cRNA of the cloned rat liver Na(+)-independent organic anion transporting polypeptide oatp, a specific and saturable CRC 220 uptake was observed (Michaelis-Menten constant 29.5 mumol/L). Cis-inhibition with known oatp-substrates, e.g., 20 mumol/L Bromsulphalein (BSP), 2007 mumol/L taurocholate and 2007 mumol/L cholate, occurred in oatp-expressing X. laevis oocytes, whereas substrates of the two peptide carriers as well as dipeptide- and single-amino acid constituents of the thrombin inhibitor itself lacked any significant inhibitory effects. These data show that the modified dipeptide CRC 220 is a highly selective substrate of the organic anion transporting polypeptide oatp in the basolateral plasma membrane of rat hepatocytes.

Animals↗
PubMed1996

The comparison of geometric and electronic properties of molecular surfaces by neural networks: application to the analysis of corticosteroid-binding globulin activity of steroids.

It is shown how a self-organizing neural network such as the one introduced by Kohonen can be used to analyze features of molecular surfaces, such as shape and the molecular electrostatic potential. On the one hand, two-dimensional maps of molecular surface properties can be generated and used for the comparison of a set of molecules. On the other hand, the surface geometry of one molecule can be stored in a network and this network can be used as a template for the analysis of the shape of various other molecules. The application of these techniques to a series of steroids exhibiting a range of binding activities to the corticosteroid-binding globulin receptor allows one to pinpoint the essential features necessary for biological activity.

Drug Design↗
PubMed1996

Comparison of structurally different allosteric modulators of muscarinic receptors by self-organizing neural networks.

Similarities in the molecular structure and surface properties of the allosteric modulators of muscarinic receptors, alcuronium, gallamine, tubocurarine, and the hexamethonium compound W84, a well-known pharmacological tool, are explored. The analysis of the molecular electrostatic potential (MEP) as well as of the shape of the molecular surface is performed by self-organizing neural networks. A distorted sandwich conformation of W84 is suggested to be the active form. The importance of the MEP for binding of these compounds could be established.

Alcuronium↗
PubMed1996

Determinants of compliance with antiretroviral therapy in patients with human immunodeficiency virus: prospective assessment with implications for enhancing compliance.

Non-compliance with therapy is a significant problem, particularly when the disease process is chronic and therapeutic regimens are employed for prolonged periods. We assessed the prevalence and variables associated with compliance with antiretroviral therapy in patients with human immunodeficiency virus infection, by means of a longitudinal observational study of 46 patients aged 23 to 68 years, with human immunodeficiency virus infection, followed at the Pittsburgh VA Medical Center. Data on demographics, medical status, physical functioning (Karnofsky performance scores), CD4 lymphocyte count, depression (Beck depression inventory), coping (inventory of coping with illness scale scores), and psychological and emotional stress (profile of mood states scale scores), were prospectively assessed on all patients at baseline and every 6 months. Compliance was assessed at 6 and 12 months: patients taking > or = 80% of antiretroviral therapy were considered compliant. Overall, 63% of patients were compliant with antiretroviral therapy. Age, education, employment, religious support, and perceived quality of life did not correlate with compliance. By univariate analysis, lack of prior intravenous drug use was significantly associated with compliance (p = 0.01). Compliant patients had significantly better adaptive coping (p = 0.03), and less depression (p = 0.04). By multivariate analysis, black race was significantly associated with non-compliance independent of intravenous drug use and educational status. History of prior opportunistic infection (which presumably heightens the perceived severity of illness) (p = 0.02), and lesser psychological disturbance scores (p = 0.02) were associated with compliance. Compliance was observed despite the greater number of prescription medications taken by compliant patients (p = 0.04). At 12 months, Karnofsky scores were better in compliant patients (p = 0.02), although mortality was not different. Besides identifying predictors of compliance, our data suggest that symptoms of depression and psychological stress be sought in patients with non-adherence.

Activities of Daily Living↗
PubMed1995

Variation of the oxime function of bispyridinium-type allosteric modulators of M2-cholinoceptors.

The bisbenzylether of the bispyridinium oxime, DUO 3-O (4,4'-Bis-[(2,6-dichlorobenzyloxyimino)-methyl]-1,1'-propane-1,3- diyl-bispyridinium dibromide), has been found to stabilize the antagonist binding to the M2-cholinoceptors which is indicative of an allosteric action. The oxygen of the oxime group was replaced with a nitrogen and a CH2-group leading to DUO 3-N and 3-C, respectively. The allosteric potency of the compounds was characterized by the concentrations which retarded the rate of dissociation of [3H]N-methyl-scopolamine from porcine cardiac cholinoceptors by a factor of 2 (EC50). The hydrazone derivative DUO 3-N was found to be the most active compound (ED50 = 2.7 microM) exceeding in activity DUO 3-O by a factor of 1.6 and DUO 3-C by a factor of 5. No correlation was found between the lipophilicity, determined as octanol/water partition coefficient, and the allosteric potency. The distribution of charges in the molecules was calculated by means of PEOE and displayed as Kohonen maps: The calculations exhibit a shift of the positive charge in the pyridinium ring from the nitrogen to the carbon atom in para-position when going from DUO 3-C to 3-O and 3-N. This shift parallels the rank order of the allosteric potency. From these results the conclusion has been drawn that the between distance the terminal ring-system and the positive charge is pivotal for the interaction of the allosteric modulators with the receptor protein.

Allosteric Regulation↗
PubMed1994

Infectious complications in liver transplant recipients on tacrolimus. Prospective analysis of 88 consecutive liver transplants.

This prospective study characterizes the incidence, etiology, timing, risk factors, and outcome of the infectious complications after 88 consecutive liver transplantations in 79 patients receiving tacrolimus (FK506) as primary immunosuppression with a median follow-up of 880 days. Infections occurred in 59% (47/79) of the patients, and 39% had major infections. Of the major infections, 55% were bacterial, 22% were viral, and 22% were fungal. Bacteremia accounted for 30% of major bacterial infections. Sixty percent of bacteremias occurring within the first 3 months were catheter related, while 75% of those occurring more than 3 months after transplant were of a biliary source. Patients with recurrent hepatitis C virus hepatitis and patients requiring dialysis after transplant had a significantly higher rate of infections as compared with other patients. Overall mortality was 18%, and 29% of all deaths were associated with infection. Only invasive aspergillosis was associated with infectious mortality. Our data suggest that the potent immunosuppressive agent FK506 is not associated with a higher incidence of infectious complications as compared with previous studies using CsA.

Adult↗
PubMed1991

Use of ciprofloxacin versus use of aminoglycosides for therapy of complicated urinary tract infection: prospective, randomized clinical and pharmacokinetic study.

The efficacy of oral ciprofloxacin was compared with that of parenteral aminoglycoside for therapy of complicated urinary tract infection in a prospective randomized trial. The setting was a chronic-care Veterans Administration facility in which long-term bladder catheterization and resistant bacteria were common. Sixty-five consecutive patients were stratified for presence and type of bladder catheter, the presence of Providencia and Pseudomonas aeruginosa organisms versus other urinary pathogens, and renal dysfunction. A pharmacokinetic study of ciprofloxacin concentrations in serum and urine was performed with selected patients. Urinary catheters were present in 94%. All patients were symptomatic, and 58.5% had fever. Ciprofloxacin, 500 mg every 12 h orally, was compared with parenteral aminoglycoside for 7 to 10 days. Clinical response, defined by resolution of symptoms and fever at 5 to 9 days posttherapy (short-term) and 28 to 30 days posttherapy (long-term), was essentially identical for both treatment groups. Bacteriologic response, defined by sterile urine cultures, showed that ciprofloxacin was significantly more efficacious (P = 0.0005) than aminoglycoside at 5 to 9 days posttherapy. However, by 28 to 30 days, the response rate was essentially identical. Emergence of resistance to the study antibiotic was seen in 62 and 70% of those who did not show a bacteriological response and were receiving ciprofloxacin and aminoglycosides, respectively. Concentrations of ciprofloxacin and aminoglycoside in the urine substantially exceeded the MIC for the urinary pathogens isolated, although these concentrations did not correlate with short-term bacteriologic response for either antibiotic. Ciprofloxacin was efficacious in complicated urinary tract infection compared with the current standard of parenteral aminoglycoside among catheterized patients with relatively resistant bacteria.

Administration, Oral↗
PubMed1990

Aural irrigation with water: a potential pathogenic mechanism for inducing malignant external otitis?

We hypothesized that the forcible introduction of water containing Pseudomonas aeruginosa into the ear canal of a susceptible host (an elderly diabetic with cutaneous hypoperfusion secondary to microangiopathy) was the inciting factor in the development of malignant external otitis. Tap water irrigation of the ears by a physician preceded the onset of symptoms in 61.5% (8/13) of cases of malignant external otitis. Two control subjects with known diabetes mellitus were matched for each patient by sex and age. Both groups were questioned on the nature and degree of aural water exposure, as well as history of ear disease. There were no significant differences between 13 patients and 26 control subjects for presence of ear disease (hearing loss, chronic infection, prior operations), swimming, showering, bathing, frequency of ear cleaning, or method of ear cleaning (washcloth, cotton applicator). Patients with malignant external otitis had a statistically significant higher incidence of aural irrigation with tap water when compared with control subjects. We suggest that a substantial number of cases of malignant external otitis may be iatrogenic.

Aged↗
PubMed1986

Staphylococcus aureus nasal carriage and infection in patients on hemodialysis. Efficacy of antibiotic prophylaxis.

We conducted a five-year prospective controlled study of prophylaxis of Staphylococcus aureus nasal carriage and infection among patients in a hemodialysis unit. Carriers tended to have chronic colonization with a single phage type. S. aureus infections occurred significantly more frequently in carriers than in noncarriers and, in 93 percent of the infected carriers, were caused by the same phage type as that carried in the nares. Neither intravenous vancomycin nor topical bacitracin was found to be efficacious in eradicating nasal carriage. However, oral rifampin given for five days decreased S. aureus carriage over a one-month follow-up period, but within three months colonization of the nares recurred in most carriers, often with an S. aureus of the original phage type. Carriers were then randomly assigned to receive either rifampin or no prophylaxis. Rifampin was readministered at three-month intervals if culture of the anterior nares yielded S. aureus. Infections with S. aureus occurred significantly more frequently in carriers given no prophylaxis than in those given a full course of rifampin. S. aureus resistant to rifampin was isolated from the anterior nares of four patients, but these isolates were not implicated in any infections. The incidence of infection at the dialysis access site, skin, and soft tissue of patients on hemodialysis can be decreased by interventions directed at nasal carriage of S. aureus.

Administration, Intranasal↗
PubMed1984

[High-dose thalamonal-rohypnol for premedication. A randomized double-blind study].

The combination of fentanyl and droperidol, Innovar, was compared to flunitrazepam (1-2 mg) in a higher dosage (2.5-5 ml) for i.m. premedication. We measured psychological (ESB) and physiological (blood pressure, heart rate, p.cortisol) stress parameters before and after premedication. Side effects were registered. The day after surgery the patients were asked about the quality of premedication. Flunitrazepam reduced anxiety; Innovar did not. After Innovar the feeling of weakness increased significantly compared to flunitrazepam. Two patients panicked and refused operation. Other severe side effects were not observed. There were slight advantages for flunitrazepam on physiological stress. Patients were more satisfied with flunitrazepam than with Innovar premedication. The results show that Innovar also in a higher dosage cannot be recommended for premedication.

Adolescent↗
PubMedDate not supplied

Locating biologically active compounds in medium-sized heterogeneous datasets by topological autocorrelation vectors: dopamine and benzodiazepine agonists.

Electronic properties located on the atoms of a molecule such as partial atomic charges as well as electronegativity and polarizability values are encoded by an autocorrelation vector accounting for the constitution of a molecule. This encoding procedure is able to distinguish between compounds being dopamine agonists and those being benzodiazepine receptor agonists even after projection into a two-dimensional self-organizing network. The two types of compounds can still be distinguished if they are buried in a dataset of 8323 compounds of a chemical supplier catalog comprising a wide structural variety. The maps obtained by this sequence of events, calculation of empirical physicochemical effects, encoding in a topological autocorrelation vector, and projection by a self-organizing neural network, can thus be used for searching for structural similarity, and, in particular, for finding new lead structures with biological activity.

Databases, Factual↗
PubMedDate not supplied

Superposition of three-dimensional chemical structures allowing for conformational flexibility by a hybrid method.

The superposition of three-dimensional structures is the first task in the evaluation of the largest common three-dimensional substructure of a set of molecules. This is an important step in the identification of a pharmacophoric pattern for molecules that bind to the same receptor. The superposition method described here combines a genetic algorithm with a numerical optimization method. A major goal is to adequately address the conformational flexibility of ligand molecules. The genetic algorithm optimizes in a nondeterministic process the size and the geometric fit of the substructures. The geometric fit is further improved by changing torsional angles combining the genetic algorithm and the directed tweak method. This directed tweak method is based on a numerical quasi-Newton optimization method. Only one starting conformation per molecule is necessary. Molecules having several rotatable bonds and quite different initial conformations are modified to find large structural similarities. A set of angiotensin II antagonists is investigated to illustrate the performance of the method.

Algorithms↗