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Biomedical subjects

J Ritchie

Publications and source records attributed to J Ritchie.

At least 73 records · Page 4Linked to original sources
PubMed1990

Determination of plasma dexamethasone by chemical oxidation and electron capture negative ionization mass spectrometry.

A quantitative assay for dexamethasone in human plasma is described as based on methodology employing electron capture negative ionization mass spectrometry (ECNI/MS). The unique feature of this assay is the sample preparation involving chemical oxidation which transforms dexamethasone to a highly electrophilic species while not significantly affecting the electrophilic character of the biochemical matrix, thereby permitting selective and sensitive detection of the analyte. Optimized chemical procedures and instrumental parameters are described for the detection of oxidized dexamethasone. Finally, the newly developed methodology, based on gas chromatography/mass spectrometry (GC/MS) with ECNI, is evaluated by comparison with a conventional GC/MS assay using electron impact of an 11,17,21-tris-trimethylsilyl ether 20-enol-trimethylsilyl ether derivative of dexamethasone and with a radioimmunoassay in the analysis of pooled samples of human plasma containing widely varying concentrations of the drug as obtained from patients at different stages of the dexamethasone suppression test.

Dexamethasone↗
PubMed1988

Eating attitudes and behaviours of a sample of university students.

A sample of 213 first year psychology students at the University of Waikato (139 women, 74 men) completed a questionnaire on eating attitudes and behaviours. The women students were significantly more likely than the men to erroneously believe themselves to be overweight, to feel dissatisfied with their present weight and to go on diets. Fourteen percent of the women, but only 1% of the men scored more than 30 on the eating attitudes test, a score believed to be indicative of potential eating disorder. The social pressures which result in women's unrealistic expectations of their body size are discussed.

Adult↗
PubMed1987

Effects of gamma-interferon on the endocrine system: results from a phase I study.

Interferon causes profound biological changes when given to patients with cancer and many of these could not be predicted from in vitro or animal model systems. We documented significant changes in hormonal levels for a group of 18 patients who were participants in a Phase I gamma-interferon trial. Adrenocorticotropic hormone, cortisol, and growth hormone were all significantly elevated 2 h after treatment with gamma-interferon, with cortisol and adrenocorticotropic hormone returning to base line by 24 h. A placebo group failed to show this change, suggesting a specific interferon effect. Possible mechanisms for these findings and implications for the use of interferons are discussed.

Adrenocorticotropic Hormone↗
PubMed1987

Children's knowledge of the health risks of smoking.

One thousand, two hundred and fifty-four intermediate and secondary school students ranging in age from 10 to 16 were questioned, as part of a larger study on their knowledge of the health risks of smoking. Though they were well aware of some of the specific ill effects of smoking including its relationship to lung cancer and the danger to the fetus during pregnancy, very few (12% of girls and 14% of boys) knew that smoking causes more deaths in New Zealand than road accidents. Existing health education programmes have clearly failed to teach young people about the potentially fatal effects of smoking.

Adolescent↗
PubMed1987

Estimation of myocardial infarct size by electrocardiographic and radionuclide techniques.

The Western Washington Intravenous Streptokinase in Acute Myocardial Infarction Trial was a randomized, experimental, multicenter clinical study comparing intravenous streptokinase therapy to conventional therapy of acute myocardial infarction. Myocardial infarct size was estimated by spatial vectorcardiography in 93 patients in the treatment group and 80 patients in the control group eight weeks post MI. The estimated infarct size for the treated group was smaller: 16 +/- 10% MI vs. 20 +/- 9% MI for the control group, P = 0.01. Four independent techniques to estimate infarct size were prospectively compared within the same day: Cowan's spatial VCG; the Selvestor/Wagner QRS score; 99m technetium synchronized ejection fractions and 201-Thallium Tomography. There was strong correlation between the two ECG techniques (r = 0.88) and between the two radionuclide techniques (r = 0.77). Statistically significant correlations (P = 0.0001) were described, respectively, among the four techniques, but the correlations were not clinically strong between electrocardiographic and radionuclide techniques: IAD vs. EF, r = -0.41; IAD vs. 201-Tl, r = 0.50; QRS Score vs. EF, r = -0.49; QRS Score vs. 201-Tl, r = 0.58.

Clinical Trials as Topic↗
PubMed1986

Alterations in corticotropin-releasing factor-like immunoreactivity in discrete rat brain regions after acute and chronic stress.

Corticotropin releasing factor (CRF) may regulate endocrine, autonomic, and behavioral responses to stress. Evidence indicates that CRF-like immunoreactivity (CRF-LI) is widely distributed throughout the CNS. In this study, the distribution of CRF-LI was determined in 36 rat brain regions by combined radioimmunoassay-micropunch dissection techniques and the effect of stress on CRF-LI was investigated, using a chronic stress model that induces endocrine changes in rats similar to those seen in depressed humans. A control group of rats was handled daily. An acute stress group was subjected to 3 hr of immobilization at 4 degrees C, while a chronic stress group was exposed to unpredictable stressors. Thirty-six brain regions were microdissected by the technique of Palkovits and assayed for CRF-LI, using a specific antiserum to ovine CRF. CRF-LI was detected in most regions. In controls, the highest concentrations were found in the arcuate nucleus/median eminence, the hypothalamic paraventricular (PVN) nucleus, and the periventricular nucleus. The next highest levels were found in the raphe nuclei and dorsal vagal complex. CRF-LI was well represented in the locus coeruleus (LC); in the central, cortical, and medial amygdaloid nuclei; and in the bed nucleus of the stria terminalis. Low concentrations occurred in the hippocampus and cerebrocortical regions. Appreciable concentrations were detected in midbrain and brain stem regions. Acute stress reduced CRF-LI in the arcuate nucleus/median eminence (ME) (by 52%) and in the median preoptic (MPO) nucleus (by 32%) and doubled its concentration in the locus coeruleus.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1983

The genetic control of sparteine and debrisoquine metabolism in man with new methods of analysing bimodal distributions.

Debrisoquine and sparteine tests were carried out in 215 random white British subjects. There is a high degree of correlation between the urinary 'metabolic ratios' of the two drugs. New mathematical techniques have been developed (1) to define phenotypes and (2) to identify the genotypes within the dominant phenotype. The members of 15 families were tested with both debrisoquine and sparteine. The results indicate that persons who are 'poor metabolisers' of sparteine are also 'poor metabolisers' of debrisoquine and are autosomal Mendelian recessives.

Adult↗
PubMed1983

The effect of pulmonary hypertension on systolic function of the right ventricle.

This study sought to determine if the right ventricular ejection fraction (RVEF) could be used to diagnose pulmonary hypertension noninvasively. The right ventricular ejection fraction was measured with gated blood pool radionuclide ventriculography and compared to hemodynamic measurements made within 48 hours in 57 subjects. There was a significant inverse relationship between the RVEF and pulmonary artery pressure (r = .57, p less than .001) and the sensitivity of RVEF greater than .45 in diagnosing pulmonary hypertension was .76. Other significant determinants of right ventricular function, including right coronary disease, left ventricular function and tricuspid regurgitation, were also considered.

Cardiac Output↗
PubMed1982

The normal right ventricular response to supine exercise.

Nine normal, healthy young males performed graded, maximal supine bicycle exercise with monitoring of hemodynamic and gated blood pool parameters. Right ventricular ejection fraction (RVEF) was greater than 0.45 in all acquisitions at rest (mean +/- SD = 0.53 +/- 0.05) and increased greater than 0.05 in all subjects with maximal exercise (mean +/- SD = 0.69 +/- 0.06 at stage 4). There was a very close correspondence between RV and LV stroke counts from the radionuclide angiograms at rest and all exercise levels in all patients. Cardiac output changes by radionuclide data from the RV correlated closely with those obtained by the Fick technique. Multivariate analysis of RVEF vs pulmonary artery pressure, total pulmonary resistance, and heart rate showed that RVEF was inversely related to total pulmonary resistance in these patients (n = 43 acquisitions, r = 0.61, RVEF = 0.75 -- 0.001 TPR in dynes-sec/cm5 Sy.x = 0.07) and positively related to heart rate (n = 43, 4 = 0.78, RVEF = 0.34 + 0.0025 x HR Sy.x = 0.05). RVEF was not significantly related to the other hemodynamic parameters. These results suggest that in normal subjects RV systolic function is afterload-dependent and that total pulmonary resistance may be a suitable afterload index. The results emphasize that heart rate must be considered when comparing RVEF changes.

Adult↗