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Biomedical subjects

R Mayer

Publications and source records attributed to R Mayer.

At least 19 recordsLinked to original sources
PubMed1992

Labeled proteinase inhibitors: versatile tools for the characterization of serine proteinases in solid-phase assays.

Peptidyl chloromethyl ketones were used for the specific labeling of proteinases by attaching a biotin group to the N-terminal end of the peptide. Such labeled peptide inhibitors allowed the detection and quantitation of proteolytic enzymes immobilized on the plastic surface of a microtiter plate, as well as on nitrocellulose. The validity of these solid-phase assays was demonstrated using subtilisin Carlsberg as a model enzyme and biotinyl-epsilon-aminocaproyl-L-alanyl-L-alanyl-L-propyl-L-phenylal++ + anyl- chloromethyl ketone as a specific reagent. In addition to being usable for the screening of a particular proteinase in a large number of samples, these assays can be adapted for the analysis of specific proteolytic enzyme present in complex mixtures.

Amino Acid Sequence↗
PubMed1992

Family therapy in general practice: views of referrers and clients.

Family therapy is being used in a variety of settings, including general practice. To assess the views as to the effectiveness and acceptability of a family therapy clinic in a north London surgery, questionnaires were given to general practitioners referring patients, and to clients. Replies were received from seven doctors and 20 clients, representing 11 families. There was a high level of satisfaction among general practitioners referring patients. The clinic proved to be highly acceptable for clients, with 90% agreeing that it was easier to attend a clinic at the practice than at a hospital; and only one patient thought that knowing the general practitioner worked in the practice made it harder to talk openly. Eighty per cent of patients felt the problem had improved at the time of follow up. Where the problem had not improved, 60% felt that they were dealing with it better. Almost all of the patients felt that the family therapy clinic should become a permanent part of local services. The family therapy clinic in general practice has been shown to be effective and popular with users of the service.

Adolescent↗
PubMed1992

Secretion of macrophage cytotoxic factors induced by new desmuramyl acylpseudopeptide analogs of muramyl dipeptide.

Sixteen desmuramyl analogs of muramyl dipeptide (MDP) were tested for their abilities to stimulate cytotoxic factor secretion by mouse peritoneal macrophages. Among them, the pseudohexapeptide Boc-Gly psi [CH2O]-D-Ala-Ala-D-Glu[Lys(H-Gly)NHEt]-NH2 appeared to be four times more effective than MDP. From this study, the D configuration of the pseudo-alanyl (or lactyl) residue appears to be essential for activity.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1991

Water-soluble macromolecular fluorogenic substrates for assaying proteinases: determination of pancreatic elastase activity.

Water-soluble macromolecular fluorogenic substrates were synthesized in order to develop an easy specific proteinase assay. The validity of this method was tested with porcine pancreatic elastase by using its specific peptidic substrate Ala-Ala-Pro-Ala linked to a hydrosoluble polymer. The octapeptidic sequence FTC-epsilon Aca-Ala-Ala-Pro-Ala-Gly-Gly-Gly was linked to a water-soluble and neutral poly-L-lysine derivative. The aminocaproyl residue and the triglycyl sequence were added in order to improve the stability of the substrate, and the accessibility of the specific sequence Ala-Ala-Pro-Ala to elastase, respectively. The assay is based on the quantitative precipitation of the polymeric substrate in isopropanol while the released soluble fluorescent peptidic moiety is fluorometrically titrated in the supernatant.

Amino Acid Sequence↗
PubMed1991

beta-Furfuryl-beta-glucoside. An endogenous activator of higher plant UDP-glucose: (1----3)-beta-glucan synthase.

We have recently established the existence of endogenous activators of higher plant UDP-glucose: (1----3)-beta-glucan synthase (Callaghan, T., Ross, P., Weinberger-Ohana, P., and Benziman, M. (1988) Plant Physiol. 86, 1099-1103). Here we report the purification and chemical analysis of the most abundant and specific compound, termed Activator I, isolated from Vigna radiata. This compound was extensively purified by a multistep procedure which yielded 0.1 mg of purified activator/g of fresh tissue. Enzyme digestion, neutral sugar analysis, GC/MS of permethylated derivatives, and NMR analysis of native Activator I indicated that the compound contains a single beta-linked glucosyl residue. High resolution FAB-MS indicated an elemental composition of C11H16O7 (Mr = 260), with a calculated Mr of 98 for the aglycone. 13C, DEPT, and COSY NMR spectra showed that the aglycone molecule is an oxygen heterocycle of 5 carbons, consistent with a structure of beta-furfuryl alcohol. Comparison of IR and GC/EI-MS spectra of authentic beta-furfuryl alcohol with native aglycone confirmed the conclusion that Activator I is beta-furfuryl-beta-glucoside. Chemically synthesized beta-furfuryl-beta-glucoside has identical chemical properties and biological activity when compared with the purified endogenous activator (Ka = 50 microM).

Enzyme Activation↗
PubMed1991

Polypeptide composition of bacterial cyclic diguanylic acid-dependent cellulose synthase and the occurrence of immunologically crossreacting proteins in higher plants.

To comprehend the catalytic and regulatory mechanism of the cyclic diguanylic acid (c-di-GMP)-dependent cellulose synthase of Acetobacter xylinum and its relatedness to similar enzymes in other organisms, the structure of this enzyme was analyzed at the polypeptide level. The enzyme, purified 350-fold by enzyme-product entrapment, contains three major peptides (90, 67, and 54 kDa), which, based on direct photoaffinity and immunochemical labeling and amino acid sequence analysis, are constituents of the native cellulose synthase. Labeling of purified synthase with either [32P]c-di-GMP or [alpha-32P]UDP-glucose indicates that activator- and substrate-specific binding sites are most closely associated with the 67- and 54-kDa peptides, respectively, whereas marginal photolabeling is detected in the 90-kDa peptide. However, antibodies raised against a protein derived from the cellulose synthase structural gene (bcsB) specifically label all three peptides. Further, the N-terminal amino acid sequences determined for the 90- and 67-kDa peptides share a high degree of homology with the amino acid sequence deduced from the gene. We suggest that the structurally related 67- and 54-kDa peptides are fragments proteolytically derived from the 90-kDa peptide encoded by bcsB. The anti-cellulose synthase antibodies crossreact with a similar set of peptides derived from other cellulose-producing microorganisms and plants such as Agrobacterium tumefaciens, Rhizobium leguminosarum, mung bean, peas, barley, and cotton. The occurrence of such cellulose synthase-like structures in plant species suggests that a common enzymatic mechanism for cellulose biogenesis is employed throughout nature.

Affinity Labels↗
PubMed1991

Hydrosoluble fluorogenic substrates for plasmin.

New hydrosoluble fluorogenic substrates for plasmin gluconoylpeptidyl-3-amido-9-ethylcarbazole were synthesized. The substitution of the N-terminal end of the peptides by a gluconoyl group prevents the substrates from aminopeptidase degradation and highly increases their hydrosolubility. The substitution of the peptide C-terminal end by a 3-amino-9-ethylcarbazole group leads to substrates suitable for direct fluorometric assay of plasmin present in cell supernatants or in cell lysates. On the basis of the kinetic parameters of the substrate hydrolysis by plasmin, it was found that D amino acids in the P2 position decrease systematically the kinetic constants of the substrates. The L configuration of the P2 amino acid appears therefore as essential in optimum substrates for plasmin.

Amino Acid Sequence↗
PubMed1991

Neuromuscular blockade significantly decreases systemic oxygen consumption during hypothermic cardiopulmonary bypass.

The design limits of cardiopulmonary bypass (CPB) equipment and the performance characteristics of membrane oxygenators may place the patient with a very large body surface area at risk for incurring an oxygen debt during CPB. The influence of resting muscle tone on systemic oxygen consumption (VO2) during hypothermic (25 to 28 degrees C) nonpulsatile CPB was calculated using the Fick equation prior to, and following, neuromuscular blockade (pancuronium, 0.15 mg/kg, n = 10; or succinylcholine, 1.5 mg/kg, n = 7). During hypothermic CPB, initial VO2 was 70 +/- 30 mL/min/m2, which was significantly reduced (by 30%) to 49 +/- 13 mL/min/m2 after onset of neuromuscular blockade, with a concomitant increase in mixed venous O2 saturation from 73% +/- 18% to 83% +/- 14%. Choice of muscle relaxant did not influence the change in VO2. With succinylcholine there was a return of VO2 to control values with recovery of neuromuscular function. This study demonstrates that in the unconscious and unmoving patient during hypothermic CPB, administration of muscle relaxants to achieve complete neuromuscular blockade can significantly reduce systemic oxygen consumption.

Anesthesia, Intravenous↗
PubMed1991

Peptide derivatives specific for a Plasmodium falciparum proteinase inhibit the human erythrocyte invasion by merozoites.

A specific proteinase of P. falciparum merozoites has been detected by using hydrosoluble fluorogenic peptidic substrates synthesized by classical peptide chemistry; their N-terminal end was acylated by a gluconoyl group that protects them from aminopeptidase degradation and increases their hydrosolubility, and their carboxylic end was substituted by a 3-amino-9-ethylcarbazole group. The sequence Val-Leu-Gly-Lys was found to be the most specific substrate. On this basis, reversible peptidic inhibitors were synthesized by substituting the C-terminal lysyl residue, at the proteolytic site, by different alkylamines and amino alcohols. The activity of these compounds, studied on the P. falciparum proteinase and in in vitro cultures, strongly suggests a specific effect of this peptidic sequence on the reinvasion process. The peptidic inhibitors do not impair the release of merozoites from schizonts, but selectively inhibit the invasion step leading to the formation of rings. Although the natural target of this enzyme is not yet known, these specific peptide inhibitors could lead to a new antimalarial approach.

Amino Acid Sequence↗
PubMed1991

[Triterpene saponins from the Chinese drug "Daxueteng" (Caulis sargentodoxae)].

From the chinese drug "Daxueteng" (Caulis Sargentodoxae: Sargentodoxa cuneata (Oliv.) Rehd. et Wils.; syn. Holboellia cuneata Oliv.) (Sargentodoxaceae), catechin and two known triterpene saponins, rosamultin (7) and kajiichigoside F1 (8) have been isolated. Some hitherto unknown reaction products of the saponins are described. Both 7 and 8 show haemolytic and in vitro antiviral activity.

Antiviral Agents↗
PubMed1991

Site-directed serology using synthetic oligopeptides representing the C-terminus of the external glycoproteins of HIV-1, HIV-2, or SIVmac may distinguish subtypes among primate lentiviruses.

In this study the presence of a highly immunogenic domain located at the C-terminus of the external glycoproteins (EGP) of human and simian immunodeficiency viruses (HIV-1, HIV-2, and SIVMAC) is shown using synthetic oligopeptides as antigens in enzyme immunoassays. This epitope is probably located within the last 13 and 15 residues of the EGP of HIV-1 and HIV-2, respectively. The C terminal epitope of the EGP of SIVMAC may involve residues located more upstream. Among the HIV-2/SIV serotype, we observed that the reactivity to the C-terminal epitope of gp120 was dependent of both species and geographical origin of the samples tested. It seems that this gp 120 C-terminal epitope could distinguish subtypes among the HIV-2/SIV serotype. Further studies, using site-directed enzyme immunoassays with synthetic peptides representing the C-terminus of the EGP derived from a wide variety of HIV2/SIV strains must be performed to confirm this observation. These kinds of assays may constitute important tools for use in seroepidemiological studies and broaden our understanding of the distribution and phylogenetic relationship of primate lentiviruses.

Amino Acid Sequence↗
PubMed1991

Prophylaxis of bacterial infections with ciprofloxacin in patients undergoing bone marrow transplantation.

Twenty-six oncology patients, 25 of whom received bone marrow transplants, were enrolled in a prospective, randomized, double-blinded, placebo-controlled trial assessing the efficacy of ciprofloxacin, 750 mg p.o. b.i.d., for preventing bacterial infections during prolonged neutropenia. Treatment was begun within 48 hr of initiation of chemotherapy and continued until the absolute granulocyte count recovered to greater than or equal to 500/microliters, or until the onset of fever (greater than or equal to 38.3 degrees C). Seven evaluable subjects received ciprofloxacin, and 11 received placebo. Risk factors for infection were comparable in both groups. Fever occurred in all study subjects, but onset was delayed in ciprofloxacin recipients (median = 6 days after the fall of the absolute granulocyte count to less than or equal to 500/microliters vs. 3 days for placebo recipients, P = 0.01). No clinically or microbiologically documented infections occurred in ciprofloxacin recipients vs. 10 infections in placebo recipients (5 bacteremias, 4 skin/soft tissue infections, 1 urinary tract infection, P = 0.0003). Ciprofloxacin recipients required fewer days of therapeutic antimicrobials (median: 28 antibiotic-days vs. 49, P0.02). The bioavailability of ciprofloxacin appeared comparable to that found in previously published studies of normal volunteers and patients not receiving chemotherapy. Adverse effects and colonization by ciprofloxacin-resistant microorganisms were monitored, but the sample sizes were too small to permit meaningful conclusions about these safety parameters. Ciprofloxacin appears to be effective for preventing bacterial infections in neutropenic patients. Additional trials are needed to establish the optimal dose of ciprofloxacin and to compare its safety and efficacy with those of currently used prophylactic regimens.

Adult↗
PubMed1991

Evidence for a cyclic diguanylic acid-dependent cellulose synthase in plants.

Because numerous attempts to detect an activity for a cellulose synthase in plants have failed, we have taken a different approach toward detecting polypeptides involved in this process. The uniqueness of the structure and function of cyclic diguanylic acid (c-di-GMP) as an activator of the cellulose synthase of the bacterium Acetobacter xylinum makes it an attractive probe to use in a search for a c-di-GMP receptor that might be involved in the process in plants. Direct photolabeling with 32P-c-di-GMP has been used, therefore, to identify in plants two membrane polypeptides of 83 and 48 kD derived from cotton fibers that possess properties consistent with their being components of a c-di-GMP-dependent cellulose synthase. Based upon several criteria, the 48-kD species is proposed to be derived by proteolytic cleavage of the 83-kD polypeptide. Both polypeptides bind c-di-GMP with high affinity and specificity and show antigenic relatedness to the bacterial cellulose synthase, and the N-terminal sequence of the 48-kD polypeptide also indicates relatedness to the bacterial synthase. Ability to detect both cotton fiber polypeptides by photolabeling increases markedly in extracts derived from fibers entering the active phase of secondary wall cellulose synthesis. These results provide a basis for future work aimed at identifying and characterizing genes involved in cellulose synthesis in plants.

Acetobacter↗
PubMed1991

Cellulose biosynthesis and function in bacteria.

The current model of cellulose biogenesis in plants, as well as bacteria, holds that the membranous cellulose synthase complex polymerizes glucose moieties from UDP-Glc into beta-1,4-glucan chains which give rise to rigid crystalline fibrils upon extrusion at the outer surface of the cell. The distinct arrangement and degree of association of the polymerizing enzyme units presumably govern extracellular chain assembly in addition to the pattern and width of cellulose fibril deposition. Most evident for Acetobacter xylinum, polymerization and assembly appear to be tightly coupled. To date, only bacteria have been effectively studied at the biochemical and genetic levels. In A. xylinum, the cellulose synthase, composed of at least two structurally similar but functionally distinct subunits, is subject to a multicomponent regulatory system. Regulation is based on the novel nucleotide cyclic diguanylic acid, a positive allosteric effector, and the regulatory enzymes maintaining its intracellular turnover: diguanylate cyclase and Ca2(+)-sensitive bis-(3',5')-cyclic diguanylic acid (c-di-GMP) phosphodiesterase. Four genes have been isolated from A. xylinum which constitute the operon for cellulose synthesis. The second gene encodes the catalytic subunit of cellulose synthase; the functions of the other three gene products are still unknown. Exclusively an extracellular product, bacterial cellulose appears to fulfill diverse biological roles within the natural habitat, conferring mechanical, chemical, and physiological protection in A. xylinum and Sarcina ventriculi or facilitating cell adhesion during symbiotic or infectious interactions in Rhizobium and Agrobacterium species. A. xylinum is proving to be most amenable for industrial purposes, allowing the unique features of bacterial cellulose to be exploited for novel product applications.

Bacteria↗