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Biomedical subjects

R M Richards

Publications and source records attributed to R M Richards.

At least 37 records · Page 2Linked to original sources
PubMed1994

Capillary zone electrophoresis assay of the uridine diphosphate N-acetylmuramyl peptide precursors and the disaccharide pentapeptide derivative of bacterial cell wall peptidoglycan.

Uridine diphosphate N-acetylmuramyl peptide (EDP-MurNac) precursors and disaccharide pentapeptide of bacterial cell wall peptidoglycan were extracted from Enterobacter colacae cells and examined by capillary zone electrophoresis. Five UDP-MurNac derivatives with dibromopropamidine isethionate as the internal standard, and disaccharide pentapeptide with pyrimethamine as the internal standard, were successfully and rapidly analysed by using a fused-silica capillary and sodium phosphate buffer in methanol as the organic modifier at appropriate pH. Accurate quantitation was also achieved. The method provides the potential to investigate quantitatively the effect of antibacterials on the biosynthesis of peptidoglycan and to determine the relative cellular concentrations of the murein precursors within the cell cycle.

Cell Cycle↗
PubMed1994

A triterpene from Rubus pinfaensis.

A new pentacyclic triterpene, pinfaensin, was isolated from the roots of Rubus pinfaensis and the structure elucidated by 13C NMR methods. This triterpene, a glycoside of pinfaensic acid (glucosyl 23-formyl-2 alpha,3 beta,19 alpha-trihydroxyurs-12-en-28-oate), in order to achieve purification and characterization, was hydrolysed to previously unreported pinfaensic acid which on acetylation and methylation gave methyl diacetoxypinfaensate (methyl 2 alpha,3 beta-diacetoxy-23-formyl-19 alpha-hydroxyurs-12-en-28-oate).

Carbohydrate Sequence↗
PubMed1994

Study of the mutual effects of sulphadiazine and ciprofloxacin on their uptakes by Pseudomonas aeruginosa.

A high-performance liquid chromatography (HPLC) assay was developed for ciprofloxacin and sulphadiazine in Isosensitest broth. Combining the HPLC assay with cell dry-weight determinations indicated that both compounds were able to enhance the uptake of the other by log phase Pseudomonas aeruginosa cultured in the presence of the compounds. It is hypothesized that the increased bacterial uptakes are the reason for the enhanced antibacterial activity previously reported for combinations of ciprofloxacin and sulphadiazine.

Chromatography, High Pressure Liquid↗
PubMed1993

Investigation of cell envelope damage to Pseudomonas aeruginosa and Enterobacter cloacae by dibromopropamidine isethionate.

Electron micrographs of log-phase Pseudomonas aeruginosa and Enterobacter cloacae cultured for 4 h in the presence of subinhibitory concentrations of dibromopropamidine isethionate indicate that this antibacterial agent can cause marked damage to the cell envelope structures of both species. This result provides an explanation of how dibromopropamidine can enhance the uptake and thus the activity of a second antibacterial agent used in combination with it.

Anti-Bacterial Agents↗
PubMed1993

In vitro evaluation of the antimicrobial activities of selected lozenges.

The in vitro antimicrobial activities of 10 lozenges (Merothol, Merocets, Merocaine, Strepsils (two varieties), Dequacaine, Dequacets, Zensyls, Tyrozets, and Labosept) were determined by use of a microtiter counting method with Streptococcus pyogenes, Staphylococcus aureus, and Candida albicans as the test organisms. Merothol, Merocets, Merocaine, and both Strepsils formulations all reduced the counts of both S. aureus and S. pyogenes suspensions by approximately 6 log cycles within 5 and 20 min, respectively. Merothol, Merocets, and Merocaine also caused a reduction in the counts of the C. albicans suspension approximately 5 log cycles within 40 min, but no other lozenge formulation showed rapid and marked activity against C. albicans. Dequacaine and Dequacets showed marked but much slower activities against this yeast. Zensyls caused an approximately 6-log-cycle reduction in bacterial counts within 40 min, and Dequacaine, Dequacets, and Tyrozets showed marked but slower antibacterial activities. This work confirmed by a statistically sound in vitro method the in vivo antibacterial activities reported for Merothol, Merocets, and Merocaine, demonstrated equivalent antibacterial activities for Strepsils, and indicated that Merothol, Merocets, and Merocaine also showed marked activities against C. albicans.

Administration, Oral↗
PubMed1993

The effects of student nurse community mental health placements on sufferers of mental health problems in the community.

The effects which student nurses have on the care of clients with mental health problems in the community is an area which has seldom been studied. With the closure of large psychiatric hospitals and the rise in community placements as part of Project 2000, an increasing number of students are being placed in the community. The study gathers data from clients attending five self-help/support groups in the North Derbyshire area of England. Analysis of the data challenges assumptions generally held by community psychiatric nurses (CPNs) that the presence of a third person, e.g. student/visitor, during a CPN home visit to the client is detrimental to the therapeutic interaction between the CPN and the client. The findings are inconclusive but suggest that some client groups (possibly those with long-term mental health problems) may find the presence of a student during a CPN visit facilitative. The study raises the issue of the student nurse/patient power relationship within a support group. Findings suggest that membership of a support group is empowering to the client and illustrates that clients in the community have greater control over the involvement of student nurses in their care than patients in hospital. Groups within the sample expressed a unanimous view that student nurse placements should be long enough to allow therapeutic nurse/client relationships to develop. This is in direct contrast to the current Project 2000 Common Foundation Programme approach of short observational non-institutional placements.

Attitude to Health↗
PubMed1993

An electronmicroscope study of the effect of sulphadiazine and trimethoprim on Enterobacter cloacae.

Electronmicroscopy of thin sections of log phase cells of Enterobacter cloacae NCTC 10005 grown for 4 h in the presence of sulphadiazine 250 micrograms/ml, trimethoprim 12.5 microliters/ml or the combination of sulphadiazine 250 micrograms/ml plus trimethoprim 12.5 micrograms/ml indicated that both agents caused marked morphological damage even though the MIC of sulphadiazine for the E. cloacae strain was > 3000 micrograms/ml. The damage took the form of electron-transparent areas devoid of ribosomes in the cytoplasm and detachment of the outer membrane. The latter was most marked with trimethoprim, which also caused damage to the cytoplasmic membrane. It is postulated that the synthesis of the peptidoglycan layer was affected by the antimetabolites since the morphological effects were strikingly similar to those caused by treatment of E. cloacae with disodium edetate plus lysozyme. Viable counts of cultures undergoing the same treatments as those prepared for electronmicroscopy indicated that although sulphadiazine merely partially inhibited growth it nevertheless enhanced the bactericidal action of trimethoprim over a 5-h period.

Cell Membrane↗
PubMed1993

Investigation of synergism between combinations of ciprofloxacin, polymyxin, sulphadiazine and p-aminobenzoic acid.

Subinhibitory concentrations of combinations of any two of ciprofloxacin, colistin (or polymyxin B), sodium sulphadiazine and p-aminobenzoic acid were shown by checkerboard minimum inhibitory concentration determinations to have synergistic inhibitory activity against Pseudomonas aeruginosa and to have either synergistic or additive activity against Staphylococcus aureus. In addition, sulphadiazine plus either ciprofloxacin or polymyxin showed markedly enhanced killing activity against both P. aeruginosa and S. aureus. p-Aminobenzoic acid plus either ciprofloxacin or polymyxin also demonstrated enhanced killing activity against P. aeruginosa but these combinations were less effective in enhancing activity against S. aureus. Ciprofloxacin in combination with polymyxin had a marked synergistic effect against P. aeruginosa but only a slight synergistic effect against S. aureus. These findings indicate a potential usefulness for the synergistic combinations against P. aeruginosa and S. aureus in the clinical situation; that is, they indicate an extended role for sulphonamides and support a potential role for p-aminobenzoic acid as enhancers of the activity of primary antibacterial agents such as ciprofloxacin and polymyxin. We suggest that for a second antibacterial to enhance the activity of ciprofloxacin, it may be necessary for the second antibacterial to increase cell permeability so increasing bacterial uptake of ciprofloxacin.

4-Aminobenzoic Acid↗
PubMed1993

Effects on cell morphology of growing Pseudomonas aeruginosa, Enterobacter cloacae and Staphylococcus aureus in subinhibitory concentrations of p-aminobenzoic acid.

Light microscopy and electron microscopy studies with Enterobacter cloacae, Pseudomonas aeruginosa and Staphylococcus aureus grown in the presence of subinhibitory concentrations of p-aminobenzoic acid indicate that p-aminobenzoic acid may have a direct or indirect effect on the cell walls. The morphological effects of p-aminobenzoic acid varied with different bacterial species. E. cloacae grown in the presence of p-aminobenzoic acid produced filaments while P. aeruginosa cells were elongated and had thicker peripheral cell walls. S. aureus had increased overall cell size and thicker transverse cell walls.

4-Aminobenzoic Acid↗
PubMed1991

An evaluation of the antibacterial activities of combinations of sulfonamides, trimethoprim, dibromopropamidine, and silver nitrate compared with their uptakes by selected bacteria.

Modifications of antibacterial activity have been demonstrated using combinations of two antibacterials from trimethoprim, sulfonamides (sulfadiazine, sulfamerazine, and silver sulfadiazine), silver nitrate, and dibromopropamidine isethionate, either formulated in a cream base or dissolved in peptone water. The creams were evaluated using the agar cup diffusion method in isosensitest agar. The peptone water solutions provided fractional inhibitory concentrations for combinations of the antibacterial substances. The test organisms were Pseudomonas aeruginosa, Enterobacter cloacae, and Staphylococcus aureus. Bacterial uptakes of antibacterial combinations, determined by either an HPLC assay method or an atomic absorption method, combined with dry cell weight determinations, indicated that enhancement of activity of the antibacterial combinations against P. aeruginosa (two strains) and E. cloacae were related to marked increases in the bacterial uptake of the chemical agents. Decreases in activity were related to decreased uptake of either dibromopropamidine and/or silver ions. The effect of the trimethoprim and the sulfonamides was shown to depend on their effect on bacterial folate synthesis. It is suggested that partial blockade of the folate synthetic pathway leads to an effect on cell permeability which results in increased uptake of antibacterials. Dibromopropamidine isethionate also has an effect on cell permeability which produces an increased bacterial uptake of a second antibacterial present in the medium. These findings provide further explanation of how subinhibitory concentrations of trimethoprim and sulfonamide combinations are synergistic against a wide range of bacteria even when certain bacteria are resistant to either member of the combination.

Bacteria↗
PubMed1986

Structure and activity of recombinant human interferon-gamma analogs.

We have prepared interferon-gamma (IFN-gamma) analogs to study the structural role of particular amino acids in relation to their effects on antiviral activity. Three IFN-gamma analogs were prepared on the basis of predicted secondary structure. In two of the analogs, [Gln25]IFN-gamma and [Thr45]IFN-gamma, changes were made at residue 25 (Asn to Gln) and at residue 45 (Met to Thr), respectively. [Gln25Lys78]IFN-gamma had two changes, at residue 25 (Asn to Gln) and residue 78 (Asn to Lys). Another analog, [Cys-Tyr-Cys]IFN-gamma, incorporated Cys-Tyr-Cys at the amino terminus. Comparison of the structure and activity of these analogs with that of the natural sequence protein suggested that residues 25 and 78 are at the protein surface and play an important role in antiviral activity. The residue at position 45 was found to be important for maintaining the protein structure, as assessed by circular dichroism spectroscopy. The addition of Cys-Tyr-Cys resulted in a small perturbation of protein structure and a small decrease in antiviral activity.

Amino Acid Sequence↗
PubMed1984

An in-vitro model of intracellular bacterial infection using the murine macrophage cell line J774.2.

A simple model of intracellular bacterial infection based on the ability of the macrophage cell line J774.2 to phagocytose Escherichia coli in a reproducible manner is described. Viable counting of intracellular bacteria and microscopic examination of infected macrophage cultures after treatment with fluorescent E. coli antibody showed that the bacteria multiplied within the J774.2 cells. Viable intracellular bacteria may be used to study the activity of bactericidal and bacteriostatic drugs within the macrophage. The low apparent intracellular bactericidal activity of streptomycin, which was time- and concentration-dependent, accords with a low permeability of the J774.2 macrophages to this antibiotic. An exclusively intracellular infection could be achieved by inactivation of non-phagocytosed extracellular bacteria by streptomycin treatment of infected macrophage cultures. Under appropriate conditions intracellular bacterial viability was unaffected.

Animals↗
PubMed1984

Quantification of uptake of liposomal carboxyfluorescein by professional phagocytes in-vitro. A flow microfluorimetric study on the J774 murine macrophage cell line.

Unilamellar egg phosphatidylcholine/cholesterol liposomes containing carboxyfluorescein were prepared by an ether injection method. The ability of cells of the J774.2 murine macrophage cell line to incorporate the liposomal fluorophore during incubation at 37 degrees C was measured by flow microfluorimetry. Liposomes incorporating additional phosphatidylserine or phosphatidic acid were taken up much more avidly than those lacking these phospholipids and the greatest uptake of carboxyfluorescein was observed with the phosphatidylserine species. Calculation of the number of liposomes taken up, greater than or equal to 0.2% of the number given, showed that this was an inefficient process. However these uptake data support previous findings based on the intracellular bactericidal activity of liposomal antibiotics determined in an identical in-vitro system.

Animals↗
PubMed1984

Effect of silver on whole cells and spheroplasts of a silver resistant Pseudomonas aeruginosa.

Electron micrographs of a silver resistant strain of Pseudomonas aeruginosa grown in the presence of 50 micrograms/ml Ag+ indicate that the surviving cells are resistant at the level of the cytoplasmic membrane. Spheroplasts of the resistant strain were not lysed by 1 h contact with 8 micrograms/ml Ag+, but were 36% and 22% lysed by 1 h contact with 20 micrograms/ml chlorhexidine and 40 micrograms/ml polysorbate 80, respectively. Spheroplasts of a silver sensitive strain of P. aeruginosa were lysed by 22% on contact with 1 microgram/ml Ag+ for 1 h.

Cell Membrane↗
PubMed1983

Enhanced activity of streptomycin and chloramphenicol against intracellular Escherichia coli in the J774 macrophage cell line mediated by liposome delivery.

Streptomycin and chloramphenicol were entrapped within large neutral or anionic unilamellar vesicles of egg phosphatidylcholine prepared by an ether injection method. Both antibiotics in liposomal form were inactive against Escherichia coli in a simple tube dilution assay. A comparison was made of the activities of the free and liposomal forms of the antibiotics against E. coli located within the macrophages of the J774.2 murine cell line. The apparent intracellular antibacterial activity of both antibiotics was increased more than 10-fold by entrapment in neutral liposomes and in the case of chloramphenicol in anionic liposomes containing phosphatidylserine. Anionic liposomes containing phosphatidic acid were much less effective carriers than neutral liposomes for either antibiotic in this in vitro system. Incubation at 4 degrees C of cells with liposomes containing antibiotic or carboxyfluorescein inhibited intracellular antibacterial activity and cell-associated fluorescence. The high intracellular activity of the liposomal antibiotics is consistent with their phagocytic uptake by the macrophages followed by intracellular liposomal degradation and antibiotic release. Liposomal modification of cellular uptake and intracellular distribution of antibiotics may be used to extend the activity of existing and new agents against intracellular infection of the reticuloendothelial system.

Animals↗
PubMed1981

Electron microscope study of the effect of benzalkonium, chlorhexidine and polymyxin on Pseudomonas cepacia.

Electron micrographs of Pseudomonas cepacia cell grown in nutrient broth show an external membrane which is distinctly wavy, when compared with similar preparations of Pseudomonas aeruginosa, and which is not affected by growing in the presence of broth containing benzalkonium (10 microgram/ml), chlorhexidine (10 microgram/ml) or polymyxin (25 units/ml). Both benzalkonium (10 microgram/ml) and chlorhexidine (10 microgram/ml) damage the cytoplasmic membrane of P. cepacia cell grown in the presence of the chemicals. Contrasts are shown between the effect of polymyxin (chlorhexidine and benzalkonium) on the outer membrane of P. cepacia and P. aeruginosa.

Benzalkonium Compounds↗