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Biomedical subjects

R D Cooper

Publications and source records attributed to R D Cooper.

At least 55 records · Page 3Linked to original sources
PubMed1996

Reductive alkylation of glycopeptide antibiotics: synthesis and antibacterial activity.

Reductive alkylation of the A82846 family of glycopeptide antibiotics has the potential of producing seven products. N-Alkylation of the disaccharide amino function can be accomplished selectively, and offers the greatest increase in antibacterial activity. Products resulting from N-alkylation of LY264826 (A82846B) provide the most potent derivatives as compared to other members of this class of antibiotics. Two of these derivatives, LY307599 and LY333328 are approximately 500 times more active than vancomycin against vancomycin-resistant enterococci.

Alkylation↗
PubMed1996

Distribution of anopheline mosquitoes in northern Australia.

Using carbon-dioxide-baited light traps and larval sampling, anopheline mosquitoes were collected from 620 sites in northern Australia. Twelve species were recorded. Anopheles annulipes s. l. (335 sites). An. bancroftii (181 sites), An. meraukensis (162 sites), An. farauti s. s. (133 sites), An. farauti 3 (93 sites), An. amictus (93 sites), An. hilli (88 sites), An. novaguinensis (70 sites), and An. farauti 2 (67 sites) were common and widespread throughout the region, while An. powelli (5 sites), An. stigmaticus (2 sites), and An. colledgei (1 site) were rarely collected. At the time of the surveys the distribution of these species was not limited by the availability of oviposition sites.

Animals↗
PubMed1995

Activities of the semisynthetic glycopeptide LY191145 against vancomycin-resistant enterococci and other gram-positive bacteria.

LY191145 is the prototype of a series of compounds with activities against vancomycin-resistant enterococci derived by modification of the glycopeptide antibiotic LY264826. LY191145 had MICs for vancomycin- and teicoplanin-resistant enterococci of < or = 4 micrograms/ml for 50% of isolates and < or = 16 micrograms/ml for 90% of isolates. Its MICs for vancomycin-resistant, teicoplanin-susceptible enterococci were 1 to 8 micrograms/ml. LY191145 retains the potent activities of its parent compound against staphylococci and streptococci. In vivo studies in a mouse infection model confirmed these activities. This compound indicates the potential of semisynthetic glycopeptides as agents against antibiotic-resistant gram-positive bacteria.

Animals↗
PubMed1995

Distribution of members of the Anopheles farauti complex in the northern territory of Australia.

The distribution of members of the Anopheles farauti complex was studied in the Northern Territory of Australia during 3 surveys conducted in 1988, 1989, and 1990. At the time of these surveys An. farauti s.l. was common north of 15 degrees S along the coast and up to 50 km inland. The sibling species An. farauti 1, An. farauti 2, and An. farauti 3 were identified from 126 adult and larval collections using allozyme electrophoresis and species-specific DNA probes. Anopheles farauti 1 was the most abundant species along the coast and was found in 45% of collections. Anopheles farauti 2 had a more restricted range, occurring in 12% of collections on the east coast and in the central area of the survey region. Anopheles farauti 3 had the widest distribution of the 3 species, occurring on the coast and throughout the coastal plain up to 100 km inland. It was found in 43% of the collection sites. The distribution of the 3 sibling species is discussed with regard to the possibility of malaria transmission in the area.

Animals↗
PubMed1995

Susceptibility of Guyanan Saimiri monkeys to a chloroquine-sensitive and a chloroquine-resistant strain of Plasmodium vivax from Papua New Guinea.

Attempts were made to infect splenectomized Guyanan Saimiri sciureus monkeys with the following Papua New Guinean strains of Plasmodium vivax: AMRU-1, a chloroquine-resistant strain; and AMRU-2, a chloroquine-sensitive strain. Inoculation of 7 monkeys with the AMRU-1 strain, 4 using blood-stage parasites and 3 using sporozoites, all failed to produce infections. Inoculation of 4 monkeys with the AMRU-2 strain, 3 using blood-stage parasites and 1 using sporozoites, were all successful in establishing infections. The results suggest that Guyanan Saimiri are refractory to infection with the AMRU-1 strain. If refractoriness occurs in other species and subspecies of Saimiri monkeys, then studies on the AMRU-1 strain of P. vivax may be restricted to work using Aotus monkeys.

Animals↗
PubMed1994

Studies of a chloroquine-resistant strain of Plasmodium vivax from Papua New Guinea in Aotus and Anopheles farauti s.l.

AMRU-1, a chloroquine-resistant strain of Plasmodium vivax from Papua New Guinea, was established in Aotus monkeys as a potential model for chemotherapeutic studies. The course of infection in 16 untreated, splenectomized, Colombian, and Panamanian animals was reasonably reproducible with parasitemias being maintained above 1,000/mm3 for an average of 13.7 days. Moderate to high parasitemias (1,200-68,800/mm3) were recorded in these monkeys, with a mean maximum parasitemia of 20,587.5/mm3. The sibling species Anopheles farauti 1, A. farauti 2, and A. farauti 3 were infected with gametocytes of this strain; these gametocytes completed the sporogonic phase, producing sporozoites that were infective to Aotus monkeys. Maximum infections in mosquitoes occurred 3-4 days prior to the peak parasitemia in the monkeys. Using these 3 species of Anopheles, sporozoite-induced infections were obtained in monkeys in 9 of 15 attempts with an average prepatent period of 32 days. The findings show that a suitable model system could be developed to assess the activity of antimalarial drugs against the blood stages and possibly the liver stages of the AMRU-1 strain.

Animals↗
PubMed1993

The enzymes involved in biosynthesis of penicillin and cephalosporin; their structure and function.

The biosynthetic pathway resulting in the penicillins and cephalosporins contains two Fe2+ oxidase enzymes which are responsible for the conversion of alpha-aminoadipoyl-L-cysteinyl-D-valine into isopenicillin N and penicillin N into deacetoxycephalosporin C. We will discuss the studies delineating the ligand binding of these enzymes and present a possible secondary structure.

Amino Acid Sequence↗
PubMed1993

Audit of near patient cholesterol testing in occupational health clinics.

An audit of near patient cholesterol testing was carried out in occupational health clinics. The aims were to examine the statistical agreement between Reflotron and laboratory measurements of blood cholesterol and to formulate a policy for the use of Reflotrons in cholesterol testing. Three hundred and fifty-two staff members attending occupational health clinics over a period of 10 months had blood taken for both Reflotron and laboratory measurements. The correlation between the two methods was 0.95. The Reflotron had a negative bias compared to the laboratory, with the mean difference between the two methods of measurement being -0.21 mmol/l (95 per cent confidence interval -0.18 to -0.25 mmol/l). Despite the high correlation coefficient and small mean difference, the scatter of Reflotron-laboratory differences was broad, with 95 per cent of the differences lying in the range of 0.95 mmol/l below to 0.52 mmol/l above the laboratory result. For Reflotron results of 5.50 mmol/l and greater, the sensitivity and specificity of the Reflotron in detecting subjects with laboratory cholesterol levels greater than 6.5 mmol/l were 100 per cent and 70 per cent respectively. The laboratory participated in two external quality assessment schemes for cholesterol testing during the course of the audit and all the results of these fell within the acceptable limits. The audit demonstrated that the Reflotron was too imprecise to be used to give accurate measurements of blood cholesterol. However, providing a suitable Reflotron result above which patients were sent for confirmatory laboratory testing was selected, it was an acceptable screening device in the detection of hypercholesterolaemia. Other Reflotron users should consider carrying out similar audits.

Ambulatory Care Facilities↗
PubMed1991

The Anopheles punctulatus complex: DNA probes for identifying the Australian species using isotopic, chromogenic, and chemiluminescence detection systems.

Isotopic and enzyme-labeled species-specific DNA probes were made for the three known members of the Anopheles punctulatus complex of mosquitoes in Australia (Anopheles farauti Nos. 1, 2, and 3). Species-specific probes were selected by screening total genomic libraries made from the DNA of individual species with 32P-labeled DNA of homologous and heterologous mosquito species. The 32P-labeled probes for A. farauti Nos. 1 and 2 can detect less than 0.2 ng of DNA while the 32P-labeled probe for A. farauti No. 3 has a sensitivity of 1.25 ng of DNA. Probes were then enzyme labeled for chromogenic and chemiluminescence detection and compared to isotopic detection using 32P-labeled probes. Sequences of the probe repeat regions are presented. Species identifications can be made from dot blots or squashes of freshly killed mosquitoes or mosquitoes stored frozen, dried, and held at room temperature or fixed in isopropanol or ethanol with isotopic, chromogenic, or chemiluminescence detection systems. The use of nonisotopic detection systems will enable laboratories with minimal facilities to identify important regional vectors.

Alkaline Phosphatase↗
PubMed1990

Distribution of the sibling species of Anopheles farauti in the Cape York Peninsula, northern Queensland, Australia.

The sibling species of Anopheles farauti s.l. were collected in larval and adult surveys from 34 localities on Cape York Peninsula and were identified by isoenzyme electrophoresis. The most common species near the coast was An. farauti 1 which was often found breeding within 100 m of the sea in either brackish or freshwater habitats. Larvae of the other 2 species were not found in brackish water which accords with previous laboratory observations of their lower salinity tolerance. Anopheles farauti 2 appears to have the widest distribution of the 3 sibling species on Cape York Peninsula as it was common in both coastal and inland localities. Anopheles farauti 3 was rarely found near the coast. In one locality at Lockhart River near the east coast of the peninsula larvae of the 3 species were found together in a small muddy creek.

Animals↗
PubMed1988

Oral absorption of cephalosporin antibiotics. 1. Synthesis, biological properties, and oral bioavailability of 7-(arylacetamido)-3-chloro cephalosporins in animals.

A number of 7-(arylacetamido)-3-substituted cephalosporins were prepared and tested in animals for oral absorbability. Bioavailability in mice, rats, dogs, and monkeys was determined after oral or parenteral administration. Oral bioavailability of five compounds selected for more intensive study was generally higher than that of penicillin V in all species tested. The results of ED50 testing against experimental infections in mice generally supported the bioavailability studies. Antibiotic activities were evaluated against Gram-positive and Gram-negative organisms with some derivatives expressing in vitro activity similar to cefaclor. The plasma half-life in rats was relatively short and the plasma curves were strongly influenced by probenecid, indicating rapid renal secretion. Some 7-(arylacetamido)-3-chloro cephalosporins are orally absorbed in animals to a greater extent than penicillin V, and antibacterial agent of proven clinical utility.

Administration, Oral↗
PubMed1987

Effectiveness of controlled-release personal-use arthropod repellents and permethrin-impregnated clothing in the field.

Two topical controlled-release personal-use arthropod repellent formulations of diethyl methylbenzamide (deet) and permethrin-impregnated clothing were tested on human volunteers in a tropical rain forest near Innisfail, Queensland, Australia. The field trials were arranged in a four-way factorial design which compared fabric types, permethrin treatment and repellent treatments over a 14-hour test period. An analysis of variance with each factor treated as a fixed effect indicated that treatment of the clothing with permethrin and use of topical repellents were effective in preventing bites. The controlled release formulations were not significantly better than the current U.S. Army formulation of deet under field conditions. The repellent formulations and the permethrin-treated clothing used as one system provided better protection than the repellent formulations or permethrin-treated clothing used separately.

Administration, Cutaneous↗
PubMed1985

Orally absorbable cephalosporin antibiotics. 1. Structure-activity relationships of benzothienyl- and naphthylglycine derivatives of 7-aminodeacetoxycephalosporanic acid.

A structure-activity relationship study of a number of orally absorbed cephalosporins together with their syntheses is described. These new cephalosporins are benzothienyl- and naphthylglycine derivatives of 7-aminodeacetoxycephalosporanic acid. Several different synthetic methods for the glycine side chains, their protection, and the final acylations are reported. Several of these analogues were more active than cephalexin both in vitro and in vivo against commonly encountered Gram-positive bacteria. (R)-7-(3-Benzothienylglycylamido)-3-methyl-3-cephem-4-carboxylic acid (1R) has emerged as a potent antibacterial agent and is currently undergoing preclinical evaluation.

Administration, Oral↗