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Biomedical subjects

R Luke

Publications and source records attributed to R Luke.

17 recordsLinked to original sources
PubMed1999

Influence of crystal orientation on oxygen analysis in NiO with energy dispersive X-ray analysis

Characteristic X-ray spectra of stoichiometric NiO were investigated by EDX. Peak intensities of Ni-Kalpha and O-Kalpha are determined for several zone axes and also off-axis specimen orientations. The intensity ratios depend strongly on specimen orientation, resulting in errors of up to 30% in concentration analysis. Based on Bloch wave calculations, the dependence on the zone axis is explained qualitatively by the ordered structure of NiO, assuming the atoms to be ideal point scatterers. However, in order to get a quantitative description this simple model is not sufficient: the spatial structure of the electron shells must also be considered.

Journal Article↗
PubMed1995

Comparison of echocardiographic variables between type I diabetics and normal controls.

This report compares echocardiographic estimates of systolic and diastolic function and ventricular dimensions in type I diabetics and normal controls. A random sample of 60 diabetics selected from a central hospital diabetic clinic was compared with a sample of 40 nondiabetic controls, and matched to the diabetics by age, gender, and blood pressure. Simple comparisons showed that diabetics had a higher mean resting heart rate (HR) (p < 0.001) and a slower diastolic early filling phase (maximal rate of increase in left ventricular dimension in early diastole [v/dtmax], p = 0.08; time from end-systole until dv/dtmax [ES-dv/dtmax], p = 0.03), which were explained by differences in HR and other factors. Resting HR was significantly associated with several echocardiographic variables, but the slope relating resting HR to ventricular dimension was more negative in diabetics than in controls (end-diastolic diameter, p < 0.008; end-systolic diameter, p < 0.005), and the ratio of systolic to diastolic duration was significantly (p < 0.01) less positive in diabetics. The association of resting HR to duration of isovolumic diastole was positive in diabetics and negative in controls (p < 0.02). Among diabetics, those with higher resting HR had more retinopathy (p < 0.05), microalbuminuria (p < 0.05), smaller ventricles (p < 0.01), and longer isovolumic diastole (p < 0.05). Poorer diabetic control was associated with poorer systolic (fractional shortening, p < 0.05) and diastolic (dv/dtmax, p < 0.05; ES-dv/dtmax, p < 0.05) function.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Observations on strongyloidiasis in Queensland aboriginal communities.

OBJECTIVE: To report the prevalence and distribution of infections with the parasitic nematode Strongyloides stercoralis in the Aboriginal and Torres Strait Islander communities of Queensland. DESIGN: A 20-year retrospective survey of computerised data and selected files from the former Aboriginal Health Programme (AHP) of the State Health Department of Queensland, based on cases diagnosed by the microscopic examination of preserved faecal specimens. Findings were compared with figures published in annual reports. STUDY POPULATION: Children under 15 years of age from 122 Aboriginal and Torres Strait Islander communities. RESULTS: Numbers of specimens examined varied widely according to time and place, as did detected infection rates. In 32,145 faecal samples examined by AHP microscopists during 1972-1991 the overall infection prevalence was 1.97%. Strongyloides larvae were found in only 52 of 122 communities. The parasite was absent from many small, southern inland communities, and the prevalence of infection increased in northern regions with summer wet seasons. On average, it was highest in Doomadgee (12%), where a peak prevalence of 27.5% (92/334 children examined) was detected in a wet season survey. Some infections resolved spontaneously, while others persisted for more than four years. At Gununa (Mornington Island), the prevalence fell from 26.2% to below 7% after thiabendazole treatment of most infected children, and remained at this level for at least four years. Single stool examinations by experienced microscopists may have failed to diagnose at least 26% of infected cases. The records give no indication of the clinical impact of strongyloidiasis. CONCLUSIONS: Strongyloidiasis is well established in many Aboriginal communities of north-eastern Australia. Children appear to be the major reservoirs of infection; the prevalence in adults is probably much lower. Failing improvements in community sanitation and hygiene, it may be possible to reduce significantly, if not eradicate, the infection by selectively treating diagnosed children with thiabendazole.

Adolescent↗
PubMed1992

Isosporiasis in the aboriginal population of Queensland.

OBJECTIVE: To report on the endemicity of Isospora belli in Queensland. DESIGN: A 10-year retrospective survey of data from routine parasitological surveillance of Queensland Aboriginal communities, by microscopic examination of preserved faecal specimens. SETTING: The Aboriginal Health Programme of the Queensland Department of Health and Medical Services. POPULATION: Children under 15 years of age from all the Aboriginal communities of Queensland. RESULTS: Oocysts of I. belli were detected in 33 (0.2%) of a total of 17,642 faecal samples examined. CONCLUSION: Isosporiasis is endemic in the Queensland Aboriginal population. It is likely to be more common than indicated, because the infection is difficult to diagnose, and the techniques used to identify the organism were not particularly sensitive. It is predicted that isosporiasis will be recognised with increasing frequency as a cause of diarrhoea in Aboriginal and white Australians who develop AIDS.

Adolescent↗
PubMed1990

Endocarditis in the 80s in a general hospital in Auckland, New Zealand.

The clinical and investigative features of 102 episodes of infective endocarditis were analysed retrospectively. The most frequent presenting symptoms (malaise, fever, sweats, myalgia, weight loss) were non-specific. Fever, cardiac murmur, tachycardia, vascular phenomena and a change in mental state were the most common physical signs at admission. Anaemia was present in half the episodes and renal and liver dysfunction in about one-third. Streptococci (61) and staphylococci (31) were the causative organisms in all but 10 episodes. The commonest predisposing factors were underlying cardiac disease (52 per cent) and a preceding focus of infection (14.6 per cent). Left ventricular failure (33 per cent) and focal neurological disease (29 per cent) occurred frequently. Valvular surgery was performed in 20 episodes, with two in-hospital deaths. Overall hospital mortality was 27.5 per cent and death was most commonly neurological (11/28). A higher mortality was associated with elevated total white blood count, microscopic haematuria, renal or liver dysfunction at admission, S. aureus endocarditis, the development of left ventricular failure or focal neurological disease, age greater than or equal to 60 years and persistence of fever after one week of antibiotic therapy. The absence of both renal dysfunction at admission and subsequent microscopic haematuria identified a group with a very low hospital mortality (4.7 per cent). The three-year mortality of the entire group was 43.5 per cent.

Adult↗
PubMed1987

Hemodynamic effects of intermittent transdermal nitroglycerin in chronic congestive heart failure.

The hemodynamic effects of intermittent and continuous treatment with transdermal nitroglycerin, 10 mg/24 hours, were compared in 10 patients with chronic congestive heart failure (CHF). Eight patients responded to initial application with more than a 20% reduction in mean pulmonary artery wedge pressure. Cardiac index increased from a control value of 2.1 +/- 0.5 to 2.4 +/- 0.6 liters/min/m2 at 2 hours (p less than 0.05) and mean pulmonary wedge pressure was reduced from 22 +/- 5 to 16 +/- 6 mm Hg (p less than 0.01). The 2 nonresponders had the largest left ventricular volumes on 2-dimensional echocardiograms. Responders were randomized to intermittent (16 hours/day) or continuous (24 hours/day) treatment for 1 month followed by a month of the alternate treatment. After 1 month of intermittent treatment, the hemodynamic response after reapplication was similar to the initial response. After another month of continuous treatment, hemodynamic values 24 hours after application were similar to initial control values and there was no change after removal and reapplication. Thus, the moderate vasodilator effect of transdermal nitroglycerin in CHF is maintained with intermittent treatment, whereas tolerance develops with continuous treatment.

Administration, Cutaneous↗
PubMed1987

Transdermal nitroglycerin in angina pectoris: efficacy of intermittent application.

Continuous application of transdermal nitroglycerin appears to result in tolerance to the antianginal effect. In a double-blind study the effects of continuous (24 h/day) and intermittent (16 h/day) application of transdermal nitroglycerin in a dosage of 10 mg/day were compared with the effects of placebo in 12 patients with chronic stable angina receiving treatment with beta-adrenergic blocking or calcium channel blocking agents. Exercise performance was assessed 2 to 4 hours after initial application and after 1 week of each treatment given in random order with a 3 day interval between treatments. Exercise time to onset of angina, total exercise duration and time to 1 mm ST segment depression were all significantly increased after initial application during the continuous and intermittent treatment periods. These increases were maintained after 1 week of intermittent but not continuous treatment. Thus the benefit of initial application of transdermal nitroglycerin is maintained with intermittent treatment and a daily nitrate-free interval, whereas tolerance to antianginal effect occurs with continuous treatment.

Administration, Cutaneous↗
PubMed1974

Effect of acute and chronic calcium administration on plasma renin.

To evaluate the effect of Ca(++) on renin release, plasma renin activity (PRA) was measured after acute and chronic Ca(++) administration. 1% CaCl(2) was infused into one renal artery of 10 anesthetized dogs (0.3 mg/kg/min). The excreted fraction of filtered calcium (EF(ca++)) and EF(Na+) from the infused kidney were elevated (P < 0.04) during three successive 15-min infusion periods. Serum calcium concentration was significantly elevated (P < 0.001). Creatinine clearance, systemic arterial pressure, and renal blood flow did not change (P > 0.10). Compared to control (45 ng/ml/h+/-5.2 SE), renal venous PRA was suppressed (P < 0.0001) after infusion of Ca(++) for 15, 30, and 45 min (20 ng/ml/h+/-4.6, 16 ng/ml/h+/-4.0, and 13 ng/ml/h+/-2.7, respectively). 15 and 30-min after infusion, PRA did not differ from control (P > 0.20). Chronic Ca(++) loading was achieved in Sprague-Dawley rats by replacing drinking water with 1% CaCl(2) for 17 days. At sacrifice, serum Ca(++), Na(+), and K(+) of controls (n = 12) did not differ (P > 0.60) from Ca(++)-loaded rats (n = 12). Ca(++) excretion (467 mueq/24 h+/-51) was elevated (P < 0.001) compared to controls (85 mueq/24 h+/-12). PRA (8.6 ng/ml/h+/-1.4) and renal renin content of Ca(++)-loaded rats did not differ from controls (P > 0.80). However, after 8 days of sodium deprivation, both PRA and renal renin content of calcium-loaded animals were significantly lower than the respective values in pair-fed controls (P < 0.005). During the period of sodium deprivation, calcium-drinking animals were in greater negative sodium balance than controls (P < 0.005). The data are consistent with the hypothesis that acute and chronic calcium administration inhibit renin secretion.

Animals↗
PubMedDate not supplied

Intestinal parasites in Zambian patients with AIDS.

Previous studies have found a high prevalence of Isospora belli and Cryptosporidium parvum infections in African acquired immune deficiency syndrome (AIDS) patients with chronic diarrhoea. We aimed to determine the prevalence of gastrointestinal parasite in AIDS patients in hospital, not only those with diarrhoea, and to compare them with the general community. Clinically diagnosed AIDS patients in a Zambian teaching hospital were interviewed and examined, and stool specimens were studied for parasite infection. A control group was recruited from adults in a township near Lusaka. Of 90 AIDS patients (58% male), 50 (56%) had chronic diarrhoea and 9 (10%) had diarrhoea of shorter duration. In the control group (105 adults; 85% female), only one complained of diarrhoea. A variety of intestinal protozoa and helminths was found in 57% of AIDS patients and 88% of the community members. Isosporiasis was detected in 7, and cryptosporidiosis in 2, AIDS patients, all with diarrhoea, but not in any control. Strongyloides was found in 2 AIDS patients with diarrhoea and one community resident. Hospital patients with AIDS had fewer Entamoeba coli and E. histolytica infections, probably because of previous chemotherapy. We conclude that AIDS predisposes to isosporiasis and cryptosporidiosis, but not to infection with extracellular intestinal parasites, such as Entamoeba species, Blastocystis, Chilomastix, Endolimax, Ascaris and Necator.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Diagnosis by faecal culture of Dientamoeba fragilis infections in Australian patients with diarrhoea.

This paper reports the first survey in Australia to use faecal culture to detect Dientamoeba fragilis in patients with diarrhoea. Of 3 different protozoal culture media evaluated on a case of known infection, modified Boeck & Drbohlav's medium was the most suitable. The organism could be grown from faeces stored for up to 24 h at room temperature, but for only 10 h at 4 degrees C. Culture was then used, in combination with microscopy of smears fixed with polyvinyl alcohol and trichrome-stained, to examine single stool specimens from 260 consecutive patients with diarrhoea in the city of Brisbane. D. fragilis was detected in 4 (1.5%) specimens, only 2 of which were positive by microscopy. Other protozoa were found in 36 (13.8%) specimens: Blastocystis hominis in 28 (10.8%), Giardia duodenalis in 4 (1.5%), Endolimax nana in 3 (1.2%), and Entamoeba coli in one (0.4%). One strain of Dientamoeba was cryopreserved in liquid nitrogen and recultured successfully 10 d later. Culture was more sensitive than microscopy in diagnosing D. fragilis infection and the organism, of dubious pathogenicity, was not common in patients with diarrhoea in this community. Prevalence surveys of intestinal protozoan infections should use faecal culture, and specimens should be less than 12 h old and not refrigerated. Dientamoeba strains isolated by culture can be cryopreserved.

Animals↗