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Biomedical subjects

R J Stretton

Publications and source records attributed to R J Stretton.

At least 19 recordsLinked to original sources
PubMed1990

Effects of octenidine and pirtenidine on adhesion of Candida species to human buccal epithelial cells in vitro.

Adherence of Candida spp. to buccal epithelial cells in vitro was significantly reduced after both short- and long-term periods of yeast exposure to sub-inhibitory concentrations of octenidine and pirtenidine. In addition, the pretreatment of either Candida or the epithelial cells or both with the drugs reduced adherence, this being greatest when both types of cells were pretreated. No difference in adherence to buccal epithelial cells was observed between yeast from stationary or exponential phases and the drugs were effective in reducing the adherence of cells from either growth phase. The drugs also inhibited germ-tube formation, which might contribute to their effects on adherence as far as C. albicans is concerned.

Aminopyridines↗
PubMed1990

Crude oil and hydrocarbon-degrading strains of Rhodococcus rhodochrous isolated from soil and marine environments in Kuwait.

Soil and marine samples collected from different localities in Kuwait were screened for microorganisms capable of oil degradation. Both fungi and bacteria were isolated. The fungal flora consisted of Aspergillus terreus, A. sulphureus, Mucor globosus, Fusarium sp. and Penicillum citrinum. Mucor globosus was the most active oil degrading fungus isolated. Bacterial isolates included Bacillus spp. Enterobacteriaceae, Pseudomonas spp., Nocardia spp., Streptomyces spp.,and Rhodococcus spp. Among these Rhodococcus strains were the most efficient in oil degradation and, relatively speaking, the most abundant. Bacterial and fungal isolates differed in their ability to degrade crude oil, with Rhodococcus isolates being more active that fungin in n-alkane biodegradation, particularly in the case of R. rhodochrous. In addition to medium chain n-alkanes, fungi utilized one or more of the aromatic hydrocarbons studied, while bacteria failed to do so. R. rhodochorous KUCC 8801 was shown by GLC and post-growth studies to be more efficient in oil degradation than isolates known to be active oil degraders.

Journal Article↗
PubMed1990

Growth of Candida albicans on hydrocarbons: influence on lipids and sterols.

Candida albicans KTCC 89062 an isolate from a crude oil polluted soil sample in Kuwait grew adequately on n-alkanes with only 12 to 20 carbon chains but not on aromatic hydrocarbons. This isolate grew on glucose better than on any of the alkanes. Alkane-grown cells contained higher proportions of total lipids than glucose-grown cells, and the total lipid content was directly proportional to the alkane chain length. The sterol content also increased in alkane-grown cells; the highest level was with C12 as substrate and progressively lower sterol levels were obtained as the carbon chain length increased. The phospholipid:sterol ratio decreased when the cells were grown on alkanes as compared with glucose grown cells. The ratio of unsaturated:saturated fatty acids was higher in alkane than glucose grown cells and decreased progressively from C12 to C20 as substrates. Growth on alkanes but not on glucose was associated with pseudohyphal formation.

Alkanes↗
PubMed1989

In vitro studies of haemolysis by some staphylococci grown in chemically defined media.

Staphylococcus aureus (five strains) and Staph. epidermidis (one strain) have been evaluated for comparative growth and haemolysin titre in both brain heart infusion (BHI) and in developed, nutritionally adequate, chemically defined media (CDMs) varying only in amino acid composition. The ability to show a particular haemolytic profile was strain-dependent and the haemolytic titre (HU50/ml) was both strain- and medium-dependent. Highest titres of both alpha and beta type haemolysins were obtained in BHI. Maximum titres were in general detected in the late exponential phase in both CDMs and BHI. Titres declined during the stationary phase in CDMs. Staphylococcus epidermidis produced a delta-type haemolysis profile on BHI-based blood agars, but only rabbit blood was sensitive in agars based on a developed, chemically defined medium (CDM/A; 13 amino acids) in which all six staphylococci grew. The addition of yeast extract to CDM/A increased alpha haemolysin titre, but suppressed beta haemolysin formation; beta haemolysin was, however, detected in yeast extract/phosphate-buffered saline. Strain Wood 46 degraded haemoglobin, but only in (initially) whole blood; red blood cell-free haemoglobin-rich plates (BHI) were unaffected during growth. A novel haemolytic profile is described for Staph. aureus NCTC 8532 growing on blood agars based on CDM/A and may relate to the production of methaemoglobin during haemolysis.

Amino Acids↗
PubMed1989

Effects of sub-inhibitory concentrations of antifungal agents on adherence of Candida spp. to buccal epithelial cells in vitro.

The adherence of three Candida spp. to human buccal epithelial cells following treatment of the yeast with subinhibitory concentrations of amphotericin B, nystatin, miconazole nitrate and 5-fluorocytosine was investigated in vitro. Preincubation of C. albicans, C. tropicalis or C. kefyr with these antifungals inhibited their adherence to varying degrees (reduction between 17% and 78% of the control value). Pretreatment of yeast for a short period (1 h) had less effect on adhesion than pretreatment for a long period (24h). Furthermore, treating C. albicans with a combination of amphotericin B plus 5-fluorocytosine, both at 1/8 MIC level, led to stronger adherence inhibition than that obtained for yeast pretreated with either one alone at 1/4 MIC levels. Exposure of C. albicans to antifungals affected the outer cell envelope, as observed by scanning electron microscopy, it also suppressed germination significantly, again to a different extent depending on the antifungal used. Compared with the control grown yeasts, an increase in the excretion of extracellular polymer into the supernatant of yeast cultured with various antifungals was observed. Chemical composition of this material showed that it is mannoprotein in nature containing hexoses (85-90%) and protein (7-9%). Mannose was the major sugar making about 87% of the total carbohydrates. Our results suggest that antifungals, at sub-inhibitory concentrations, have multiple effects on Candida and point to the possibility of using these drugs in the prophylaxis against candidosis.

Antifungal Agents↗
PubMed1988

The influence of pyrithione on the growth of micro-organisms.

Pyrithione was active against a range of micro-organisms, the most resistant being Gram-negative bacteria. The growth curves for Klebsiella pneumoniae and Bacillus licheniformis showed a drug-dependent lag phase. Candida albicans grew with a drug-dependent growth rate. EDTA antagonized the effects of pyrithione.

Bacillus cereus↗
PubMed1987

Experimentally induced Bacteroides infections in the rabbit.

Rabbits were infected with Bacteroides fragilis, B. macacae and B. gingivalis in monoinfection, mixed Bacteroides infection, and mixed infection of B. gingivalis with Streptococcus faecalis, Escherichia coli and Clostridium sporogenes. Monoinfection gave rise to localised, nodular abscesses at cell levels greater than 0.5 X 10(5) cfu ml-1, the severity of which was dose related. Mixed infections including B. gingivalis caused severe spreading lesions and affected organs distant from the injection site. Histopathological studies indicate an inflammatory response with gas vacuolation and local necrosis.

Animals↗
PubMed1987

Aspects of the effect of bile salts on Candida albicans.

Cholic acid, chenodeoxycholic acid, deoxycholic acid, glycocholic acid, glycodeoxycholic acid, hyodeoxycholic acid and lithocholic acid as their sodium salts, were fungistatic to the growth of Candida albicans. Of the compounds tested, cholic acid, deoxycholic acid and chenodeoxycholic acid were the most active. In combination with other antifungal agents only cholic acid exhibited synergism with amphotericin B, whilst the imidazole antifungal agents inhibited the action of the bile salts. The bile salt minimal inhibitory concentrations were close to the critical micelle concentrations. Even though the compounds are surface active they did not cause loss of intracellular K+ and were without effect on oxygen consumption. The bile salts, particularly cholic acid, produced morphological changes that gave rise to swollen cells.

Amphotericin B↗
PubMed1985

The influence of incubation time and medium composition on fatty acid production by some Bacteroides species.

Thirteen strains (eleven species) of Bacteroides have been examined for the production of short chain fatty acids (SCFAs). Two media, cooked meat glucose (CMG) and peptone yeast glucose (PYG) were examined quantitatively by gas liquid chromatography (glc) after anaerobic incubation at 37 degrees C for up to 7 days. Growth and medium pH were monitored in PYG for two species. The SCFA profile was established after 12 h and the amount of acids produced was greater in CMG than in PYG; both CMG and PYG contained SCFAs prior to inoculation. Maximum acid production and lowering of pH appear to coincide with the stationary phase of growth. Results are discussed in terms of a standardized approach to the identification of anaerobic bacteria.

Bacteroides↗
PubMed1983

The influence of growth in the presence of antibiotics on the lipid composition of Salmonella typhimurium.

The lipid content of Salmonella typhimurium was examined after growth in the presence of benzylpenicillin, ampicillin, mecillinam and tetracycline in nutrient broth and a defined medium with either glucose, acetate or glycerol as the sole carbon source. The total lipid content was not changed significantly but the level of palmitoleic acid was higher in antibiotic treated cells with the level of C17 delta being lower. The level of phospholipids was increased slightly in antibiotic treated cells, with phosphatidylserine and diphosphatidyl glycerol being the most affected. The results are discussed in terms of antibiotic resistance and mode of action of the beta-lactam antibiotics.

Anti-Bacterial Agents↗
PubMed1983

Ampicillin induced septum formation in Bacillus cereus.

Cells of Bacillus cereus grown in the presence of subinhibitory concentrations of ampicillin at either 30 degrees or 45 degrees C exhibited an increase in the numbers of centres of septum formation per unit cell length. Under identical conditions of cultivation, cells of Escherichia coli grew as aseptate filaments. In general, untreated B. cereus cells grown at 45 degrees C were longer than those grown at 30 degrees C. The strain of E. coli used was unaffected in terms of filamentation by elevated growth temperature. Results are discussed in terms of the presence and availability of penicillin binding proteins and autolysins involved in cell growth, division and separation.

Ampicillin↗
PubMed1981

Aspects of the antibacterial action of diphenyliodonium chloride.

Diphenyliodonium chloride was found to be a broad spectrum antimicrobial agent and its activity was affected by pH and inoculum size. Its uptake by bacterial cells was Langmuirian, and it caused loss of intracellular material. Aerobic glucose metabolism and dehydrogenase activity were inhibited. Low concentrations of the drug affected the membrane-bound ATPase and K transport in Streptococcus faecalis.

Adenosine Triphosphatases↗
PubMed1981

Studies on the antibacterial activity of phanquone: effect on metabolic activities of Escherichia coli and Staphylococcus aureus.

Phanquone partically inhibited oxygen consumption by Escherichia coli and Staphylococcus aureus; its effect was more pronounced when succinate, rather than glucose, was used as an energy source. It also inhibited dehydrogenase activities when estimated by the TTC method with succinate, lactate or malate as substrate, but not with glucose or pyruvate. The uptake of 32 P-phosphate, 14C-glutamate and, to a lesser extent, 14C-proline was retarded in its presence. Both E. coli and S. aureus took up Phanquone in a Langmuirian fashion. Leakage of intracellular 32P-containing compounds was not observed even when high concentrations of Phanquone were used.

Amino Acids↗
PubMed1981

Effect of growth medium on the lipid composition of log and stationary phase cultures of Salmonella typhimurium.

The lipid content of Salmonella typhimurium was not significantly influenced by the carbon source present in the growth medium. The principal fatty acid was palmitic acid. Significant levels of palmitoleic acid were found in log phase cultures, and this was replaced by a C17 delta fatty acid in the stationary phase. The other fatty acids present in significant quantities were lauric, myristic, cis-vaccenic and linoleic acids. The phospholipids present were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidic acid and phosphatidylserine.

Culture Media↗
PubMed1980

Steroidal alpha-methylene delta-lactones as potential antitumor agents.

Four novel steroidal alpha-methylene delta-lactones have been synthesized and shown to be active against human nasopharyngeal carcinoma (KB) cells in culture. The syntheses involved the use of known alpha-methylenation procedures. In addition, the lactone 6 was directly methylenated by reaction with CH2O/KOH or Et2NH/CH2O/Et2NH.HCl. The formation of a cysteine adduct (15) with the alpha-methylene lactone 10 is reported.

Antineoplastic Agents↗