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Biomedical subjects

M Warren

Publications and source records attributed to M Warren.

140 records · Page 8Linked to original sources
PubMed1965

Anopheles balabacensis balabacensis identified as vector of simian malaria in Malaysia.

The mosquito Anopheles balabacensis balabacensis has been identified as a natural vector of at least two species of simian malaria in the monsoon forests of the northern Malay States. This mosquito is also a serious vector of human malaria from Viet Nam to northern Malaya. This is the first report of a mosquito which transmits both human and simian malaria in nature.

Animals↗
PubMedDate not supplied

The quartz crystal microbalance as a continuous monitoring tool for the study of endothelial cell surface attachment and growth.

The quartz crystal microbalance (QCM) was used to monitor endothelial cell (EC) adhesion on the gold surface of an oscillating quartz crystal contained in a QCM device. A number of parameters were investigated. First, we observed differential QCM O-ring toxicities for ECs. Second, appropriate conditions for cell culture and QCM cell environment were identified that can eliminate large-scale frequency oscillations in the measurements. These artifacts are not due to added cells but originate in the time-dependent evaporation of water. Having eliminated these artifacts, we then demonstrated that the measured steady-state crystal frequency shift, Delta f, and motional resistance shift, DeltaR, were determined by the number of firmly attached ECs requiring trypsinization from the crystal surface. Last, following steady-state attachment of ECs, the EC growth stimulation by fibroblast growth factor was monitored in a continuous fashion by measuring f and R values over a 72 h. period. We observed the Delta f values to increase in a way that reflected the increase in EC number bound to the QCM surface. Following addition of ECs to the QCM, the time-dependent increase in DeltaR can be interpreted in terms of increase by the ECs of the energy dissipation properties of the solution at the solution-gold surface interface. This effect is due to their rapid surface attachment and the elaboration of their cytoskeletal properties. These results indicate that the QCM technique can be used for the study of EC attachment and growth and suggest its potential for the real time study of per unit surface area cell mass distribution dynamics and viscoelastic properties and the cells' responses to stresses or perturbations brought about using biologically active molecules.

Animals↗
PubMedDate not supplied

Homology between Streptomyces genes coding for synthesis of different polyketides used to clone antibiotic biosynthetic genes.

Many important antibiotics such as tetracyclines, erythromycin, adriamycin, monensin, rifamycin and avermectins are polyketides. In their biosynthesis, multifunctional synthases catalyse iterated condensation of thio-esters derived from acetate, propionate or butyrate to yield aliphatic chains of varying length and carrying different alkyl substituents. Subsequent modifications, including aromatic or macrolide ring closure or specific methylations or glycosylations, generate further chemical diversity. It has been suggested that, if different polyketide synthases had a common evolutionary origin, cloned DNA coding for one synthase might be used as a hybridization probe for the isolation of others. We show here that this is indeed possible. Study of a range of such synthase genes and their products should help to elucidate what determines the choice and order of condensation of different residues in polyketide assembly, and might yield, by in vitro recombination or mutagenesis, synthase genes capable of producing novel antibiotics. Moreover, because genes for entire antibiotic pathways are usually clustered in Streptomyces, cloned polyketide synthase genes are valuable in giving access to groups of linked biosynthetic genes.

Anthraquinones↗
PubMedDate not supplied

Selective primary health care. XXIV. Malaria.

The eradication of malaria remains an elusive goal in many tropical and subtropical countries, even though methods are available that, if used correctly, will permit control of the disease in most area. These methods include chemotherapy directed against the parasite in the human host and such antivector techniques as a reduction of mosquito breeding sites and an attack on the aquatic and adult stages of mosquitoes. The direction of a malaria control program requires a detailed understanding of malaria epidemiology and control measures as well as flexibility in their application to different epidemiologic situations. In most developing countries, the success of a malaria control effort will depend on a well-functioning primary health care system and active community participation in control activities.

Antimalarials↗
PubMedDate not supplied

Vasomotor symptom relief by soy isoflavone extract tablets in postmenopausal women: a multicenter, double-blind, randomized, placebo-controlled study.

OBJECTIVE: To determine the safety and efficacy of an oral soy isoflavone extract for relief of menopausal hot flushes. DESIGN: This was a double-blind, randomized, parallel group, outpatient, multicenter (15 sites) study. A total of 177 postmenopausal women (mean age = 55 years) who were experiencing five or more hot flushes per day were randomized to receive either soy isoflavone extract (total of 50 mg genistin and daidzin per day) or placebo. Physical examinations and endometrial and biochemical evaluations were performed upon admission and completion. Body weight, symptoms, and safety were evaluated at all visits. RESULTS: Relief of vasomotor symptoms was observed in both groups. Decreases in the incidence and severity of hot flushes occurred as soon as 2 weeks in the soy group, whereas the placebo group experienced no relief for the first 4 weeks. Differences between evaluable subjects in both groups were statistically significant over 6 weeks (p = 0.03). Over 12 weeks, between-group differences approached significance (p = 0.08). Endometrial thickness evaluated by ultrasound, lipoproteins, bone markers, sex hormone-binding globulin and follicle-stimulating hormone, and vaginal cytology did not change in either group. CONCLUSIONS: Soy isoflavone extract was effective in reducing frequency and severity of flushes and did not stimulate the endometrium. Soy isoflavone extracts provide an attractive addition to the choices available for relief of hot flushes.

Double-Blind Method↗
PubMedDate not supplied

Physicochemical and bacteriological assessment of water quality at the Ross Barnett reservoir in central Mississippi.

The Ross Barnett Reservoir serves as a source of water supply for the city of Jackson, Mississippi, U.S.A. and is an important site for recreational activities for many residents of Mississippi counties. A broad spectrum of illness is associated with water-contact activities like bathing and swimming in recreational waters. In the present research, we assessed the bacteriological quality of water in the Ross Barnett Reservoir and compared the levels of bacteria with the recommended criteria for public health protection. From June 12, 1999 to October 2, 1999, we collected water samples weekly from two different sites in the reservoir and tested them for the following bacteriological parameters: heterotrophic plate counts, total coliforms, fecal coliforms, and fecal streptococci. The samples were also tested for basic physical and chemical characteristics of water. The results of the study indicate that the respective mean concentrations of bacteria (colony forming units per 100 mL of water) in water samples collected from the reservoir were 5.6 x 10(6)+/-1.5 x 10(6) (heterotrophic plate counts), 4.5 x 10(4) +/- 5.3 x 10(4) (total coliforms), 5.0 x 10(2) +/- 1.6 x 10(2) (fecal coliforms), and 9.1x10(1)+/-7.3x10(1) (fecal streptococci). The values of all physical and chemical parameters were at acceptable levels. The bacterial densities, however, often exceeded federal/state guidelines by several orders of magnitude, raising considerable public health concerns. Steps should therefore be taken to develop and implement strategies to improve the water quality and to reduce or eliminate the potential health risks associated with water-contact activities in the Ross Barnett Reservoir.

Enterobacteriaceae↗
PubMedDate not supplied

The effect of glucose, insulin and dexamethasone upon 7-ethoxycoumarin O-deethylase activity of adult rat hepatocytes in primary culture.

The influence of glucose, insulin and/or dexamethasone on the 7-ethoxycoumarin O-deethylase activity of rat hepatocytes in primary culture was investigated. The addition of extra glucose to the medium attenuated the fall in enzyme activity observed during the first 24 h in culture, this effect being dose-dependent. The inclusion of insulin further enhanced this effect, but glucose + insulin did not prevent the decrease in enzyme activity in the subsequent 48 h. The inclusion of dexamethasone, alone or in combination with glucose + insulin, also attentuated the initial decline in enzyme activity. After 24 h in culture, the enzyme activity increased such that after 72 h in culture, the activity was greater than that measured in the freshly isolated cells.

7-Alkoxycoumarin O-Dealkylase↗
PubMedDate not supplied

Plasmodium coatneyi: observations on periodicity, mosquito infection, and transmission to Macaca mulatta monkeys.

Plasmodium coatneyi has adapted well to experimental studies with Macaca mulatta monkeys and Anopheles dirus mosquitoes. Studies were made to determine 1) the course of asexual parasitemia, 2) periods when infective gametocytes were produced, 3) the laboratory-reared mosquitoes susceptible to infection, 4) the mosquito most capable of transmitting the infection to monkeys via bite, 5) the pattern of recrudescence, and 6) the prepatent periods following the bites of infected An. dirus mosquitoes. The period when infective gametocytes are produced is concentrated primarily in the first week when parasitemia exceeds 1,000/microl. Mosquitoes were more heavily infected on days when the asexual parasite counts were highest. Gametocyte counts were generally low. Mature forms of the parasite markedly sequestered giving a pattern of high-low periodicity. Anopheles dirus and An. freeborni mosquitoes were nearly equal in terms of their ability to support oocyst development. Other species (An. stephensi, An. maculatus, and An. gambiae.) were less supportive. High sporozoite densities in the salivary glands were frequently produced in An. dirus and sporozoite transmission was obtained via the bites of these mosquitoes after 12-18 days of extrinsic incubation. Prepatent periods ranged from 10 to 15 days. The presence of frequent parasitic recrudescences suggests mechanisms similar to that seen in human infections with P. falciparum. It is proposed that P. coatneyi in M. mulatta monkeys can be a suitable model for studies on cerebral pathology, vaccine efficacy, and the testing of antimalarial drugs.

Animals↗