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Biomedical subjects

N Hill

Publications and source records attributed to N Hill.

At least 55 records · Page 3Linked to original sources
PubMed1991

Trial of pyrethroid impregnated bednets in an area of Tanzania holoendemic for malaria. Part 2. Effects on the malaria vector population.

The malaria vector population consisted mainly of Anopheles gambiae s.s. with a small contribution from An. funestus and An. rivulorum. The mosquitoes coming to bite in bedrooms were monitored with light traps set beside untreated bednets. When impregnated bednets were provided for all the other beds in a village the Anopheles populations declined but the Culex quinquefasciatus populations were unaffected. The survival of An. gambiae (as measured by the mean number of ovarian dilatations) and the sporozoite rate declined following introduction of the nets and the estimated sporozoite inoculation rates into people not under their nets declined by more than 90%. The net introductions caused sharp declines in the number of mosquitoes resting indoors, but the evidence was inconclusive regarding diversion to outdoor resting, animal biting, earlier biting or outdoor biting. DDT spraying greatly reduced the Anopheles populations.

Animals↗
PubMed1990

Amplification and analysis of human DNA present in mosquito bloodmeals.

DNA fingerprinting should permit the identification of individual human hosts of haematophagous arthropods, providing epidemiologically useful information, for example, the biting rates on different people and the impact of insecticide-impregnated bednets. Investigations reported here demonstrate that it is possible to extract, amplify and fingerprint human DNA from the bloodmeals of individual female Anopheles gambiae mosquitoes kept at 24 degrees C for up to 10-15 h post-ingestion.

Animals↗
PubMed1989

Kinetics of pulmonary platelet deposition and clearance during thrombin-induced microembolism in rabbits.

Using 111In-labeled autologous platelets, we studied the kinetics of pulmonary platelet deposition and clearance in relation to hemodynamic and structural events during thrombin-induced pulmonary microembolism in rabbits. Autologous platelets were radiolabeled and returned to animals prior to infusion of thrombin (100 units/kg over 15 min) (n = 20) or saline (n = 6). All animals were pretreated with tranexamic acid, an inhibitor of fibrinolysis. Thrombin-treated animals manifested progressive increases in mean pulmonary platelet activity, reaching a maximum of 38% above baseline (p less than .0001), whereas no change was observed in saline-treated controls. Animals that died during, or immediately following, thrombin infusion manifested significantly greater increases in pulmonary platelet uptake (mean 1.55 +/- 0.47 times baseline), compared to surviving animals (1.14 +/- 0.16; p less than .05 survivors vs. nonsurvivors). In surviving animals, following cessation of thrombin, pulmonary platelet activity cleared gradually, with a half-time of approximately 12 min. Thrombin reduced circulating platelet counts (p less than .001), increased mean pulmonary artery pressure (13 +/- 3 mm Hg to 18 +/- 6 mm Hg; p less than .0001), and reduced mean systemic arterial pressure (55 +/- 10 mm Hg to 44 +/- 7 mm Hg; p less than .001). The time courses of these events approximated that of thrombin-induced pulmonary platelet uptake. Furthermore, the increase in pulmonary artery pressure occurred predominantly in the group of animals in which the increase in pulmonary radiolabeled platelet activity exceeded the median value of 20%. Postmortem histology showed extensive pulmonary thrombus extending from small arterial to capillary levels in animals that died during, or immediately following, thrombin infusion, but not in surviving animals. Our findings suggest that platelet aggregation plays an important role in the pathogenesis of hemodynamic change following thrombin-induced pulmonary embolization.

Animals↗
PubMed1988

Nifedipine in chronic cor pulmonale: acute and relatively long-term effects.

After 20 mg sublingual nifedipine in 12 men with clinical stable chronic cor pulmonale the mean arterial pressure and systemic vascular resistance fell, cardiac index rose, and mean pulmonary arterial (Ppa) and wedge (Ppaw) pressures, right atrial pressure, and PaO2 remained unchanged. After 20 mg orally every 6 hours for 24 hours in 11 patients, the mean arterial pressure fell further, systemic vascular resistance remained low, and the cardiac index returned to baseline, whereas the Ppa and Ppaw decreased, but the pulmonary vascular driving pressure (Ppa-Ppaw), right atrial pressure, PaO2, and spirometry and ejection fractions remained unchanged. Of eight patients receiving maintenance therapy four developed untoward side effects in 1 to 3 weeks and one was noncompliant. The remaining three patients evaluated at 6 weeks failed to improve and had unchanged resting hemodynamics. Thus in the absence of a potentially reversible hypoxic pulmonary hypertension, nifedipine may not improve pulmonary arterial pressure and cardiac function in clinically stable patients with cor pulmonale.

Administration, Sublingual↗
PubMed1987

The relative efficacy of repellents against mosquito vectors of disease.

Laboratory tests of insect repellents by various different methods showed that An.stephensi Liston was consistently more susceptible than An.gambiae Giles, An.albimanus Wiedemann or An.pulcherrimus Theobald. The six repellents tested were di-ethyl toluamide (deet), di-methyl phthalate (DMP), ethyl-hexanediol, permethrin, citronella and cedarwood oil. Testing systems in which the mosquitoes were presented with a choice gave consistently lower ED50 values than when there was no choice, i.e. the standards of tolerance are not absolute but depend on the options available. In field tests in an experimental hut a curtain with a high dose of di-ethyl toluamide (deet) reduced biting in the hut but had to be re-impregnated frequently. Deet-impregnated anklets gave about 84% protection against Culex quinquefasciatus Say for 80 days after one impregnation, in a trial in which the anklets were brought out of sealed storage and tested for 2 h nightly. Similar protection was found against An.funestus Giles but the protection against An.gambiae s.l., An. coustani Laveran and Mansonia spp. was not as good. There were highly significant differences between the four collectors' mosquito attractiveness but this varied highly significantly between the mosquito species.

Animals↗
PubMed1984

Enoxacin-induced alteration of susceptibility of pneumococci and Pseudomonas to phagocytosis by human polymorphonuclear leukocytes.

This report examines the effects of exposure to enoxacin on interactions of bacteria and neutrophils. Pretreatment of Streptococcus pneumoniae and Pseudomonas aeruginosa with x 1/2 to x4 the MIC of enoxacin had no enhancing effect upon phagocytic killing when the antibiotic was not present. Phagocytic killing was synergistically enhanced when enoxacin was continually present although this was not manifested in increased phagocytosis. The enhanced killing was abrogated by disruption of bacterial opsonization, internalization and intraleukocytic killing processes of polymorphonuclear leukocytes. These observations indicate that the synergistic killing of Str. pneumoniae and Ps. aeruginosa by enoxacin and human neutrophils is due to enhanced intracellular killing and not an increase in phagocytosis.

Blood Bactericidal Activity↗
PubMed1983

Acute effects of captopril on cardiopulmonary hemodynamics and renin-angiotensin-aldosterone and bradykinin profile in hypertension.

Hemodynamic variables were measured and plasma renin activity (PRA), angiotensin II (AII), aldosterone, and bradykinin assays performed in 21 hypertensive men on regular diet and thiazide diuretics before and 60 to 90 minutes after 25 mg oral captopril. Heart rate, right and left ventricular filling pressures, mean cardiac index (CI), and pulmonary vascular resistance (PVR) remained unchanged. The mean intra-arterial pressure (MAP) fell from 140 +/- 5 to 116 +/- 6 mm Hg (p less than 0.001) correlating with reduction of systemic vascular resistance (SVR) (r = 0.87, p less than 0.001), control PRA (r = 0.59, p less than 0.01), and All levels (r = 0.72, p less than 0.005) but not with control bradykinin or its postcaptopril rise (p less than 0.01). The fall in SVR correlated with reduction in plasma All (r = 0.80, p less than 0.001) and aldosterone concentrations (r = 0.53, p less than 0.05). Of four patients (19%) with precipitous fall in MAP after captopril, three needed volume expansion for circulatory support. We conclude: (1) All reduction by captpril and not bradykinin potentiation explains most of the agent's hemodynamic response in hypertensive circulation, (2) endogenous All may have a supportive role for SVR and possibly for CI but not for PVR, and (3) extra precaution is warranted while captopril is being started in patients taking diuretics.

Adult↗
PubMed1977

Changes in the immunocompetence and surface markers of lymphocytes in stored blood.

Changes in lymphocyte responses to mitogens and other lymphocyte markers were studied during a 14-day period of storage of blood at 4 degrees C and 22 degrees C in plastic bags. The following tests were done: (a) absolute lymphocyte and neutrophil counts, (b) blastogenic response to PHA, PWM, Con-A, and LPS and (c) determination of T and B cells using E-rosette and EAC-rosette techniques. The neutrophils disappeared rapidly at 22 degrees C. The absolute lymphocyte count doubled in a week. The responses to PHA, PWM, and Con-A declined rapidly and were absent by the 6th day. The response to LPS disappeared on day 14. The ability to form E-rosettes and EAC-rosettes was lost by days 4 and 6, respectively. The results obtained at 4 degrees C were similar except that these changes were delayed varying from 1-7 days.

B-Lymphocytes↗
PubMed1976

Epidemiology of an outbreak of head lice in Georgia.

An outbreak of head lice infestation (pediculosis) occurred in elementary school children in Barrow County, Georgia, in January 1974. An investigation was initiated to define the magnitude of the outbreak, determine factors that contribute to transmission, and disseminate information on control. All elementary school children in the county were examined for head lice and answered a questionnaire. Fifty-three (3%) of 1,783 white pupils were infested, but none of the 500 black pupils was infested. Distribution of infestation in the white pupils was influenced by grade, bed-sharing, socioeconomic status, infestation of other family members, crowding in the home, and family size; distribution was not influenced by hair length or the sex of the pupil. Recommendations for control based on the results of the investigation included procedures for identifying and processing cases, distributing free pediculicides, continuing surveillance, educating school personnel and parents on how to control the parasite.

Animals↗