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Biomedical subjects

R McDonald

Publications and source records attributed to R McDonald.

At least 19 recordsLinked to original sources
PubMed1992

Diagnosis of myocardial contusion. Quantitative analysis of single photon emission computed tomographic scans.

Prior studies from our institution have shown that single photon emission computed tomography is sensitive (100%) in predicting patients at risk for serious arrhythmias. However, the positive predictive value is low (15% to 20%). The purpose of this study was to determine if quantitative analysis of single photon emission computed tomographic defects could improve predictive value. One hundred seventy-five patients with positive single photon emission computed tomographic scans were studied. One hundred two patients developed arrhythmias, 42 of which were ventricular. Arrhythmias were associated with all defect loci and all defect sizes. The incidence of arrhythmias did increase with increasing size. Patients were at risk for arrhythmias up to 72 hours after trauma. The value of single photon emission computed tomography is its ability to predict patients at risk for arrhythmias. This study shows that any single photon emission computed tomographic defect, regardless of location or size, is a significant predictor of arrhythmias.

Adolescent↗
PubMed1991

Inhibition of trypsin by t-butyloxycarbonyl-alpha-aza-(4-aminophenyl)alanine phenyl ester.

t-Butyloxycarbonyl-alpha-aza-(4-aminophenyl)alanine phenyl ester (III: R = NH2) has been synthesized. The rate of inhibition of trypsin (EC 3.4.21.4) by this compound (due to acylation followed by slower deacylation) shows a marked pH maximum at approximately 6. The shape of the pH-rate curve is discussed in terms of (i) the normal pH-activity curve of trypsin reacting with a charged substrate, i.e. the protonated form of the amino compound, (ii) the deprotonation of the 4-amino group with pKa 4.3, and (iii) the lower rate of reaction of the enzyme with the uncharged, deprotonated form of the ester.

Amino Acids, Diamino↗
PubMed1991

Nutrient intake of low-income Southeast Asian pregnant women.

Dietary nutrient intakes of 91 Cambodian, 37 Laotian, and 59 Vietnamese low-income pregnant women attending a university teaching hospital outpatient clinic in Southern California were measured. The nutrient intakes of the Southeast Asian groups were compared with one another as well as with the intakes of a group of 165 low-income non-Southeast Asian pregnant women of similar height, weight, and age from the same outpatient clinic population. Computerized analysis of the 24-hour recall data showed that there were few differences in nutrient intake between the Southeast Asian groups, except that the Cambodian group consumed significantly less fat, riboflavin, vitamin D, and calcium than the Vietnamese group. However, there were a number of differences between the nutrient intakes of the Southeast Asian groups and those of the non-Southeast Asian group. These included significantly lower intakes of fat, riboflavin, folate, vitamins D and E, calcium, phosphorus, potassium, and magnesium and significantly higher intakes of thiamin, niacin, sodium, and selenium. These findings suggest that low-income Southeast Asian pregnant women have some good dietary habits that dietitians need to reinforce and other dietary habits that need improvement.

Adult↗
PubMed1990

Characteristics of participants at baseline in the Treatment of Mild Hypertension Study (TOMHS).

The Treatment of Mild Hypertension Study (TOMHS) is a randomized, double-blind clinical trial currently being conducted to compare the effects of nonpharmacologic therapy alone with those of 1 of 5 active drug regimens combined with nonpharmacologic therapy, for long-term management of patients with mild hypertension. Six classes of drugs were studied: (1) acebutolol (beta blocker), (2) amlodipine (calcium antagonist), (3) chlorthalidone (diuretic), (4) doxazosin (alpha 1 antagonist), (5) enalapril (angiotensin-converting enzyme inhibitor) and (6) placebo. All participants received nutritional-hygienic advice to reduce weight and sodium and alcohol intakes and to increase physical activity. End points include blood pressure change, side effects and quality-of-life indices; incidence of electrocardiographic and echocardiographic abnormalities; and incidence of cardiovascular clinical events, including death, among participants receiving drugs as first-step treatment as well as nonpharmacologic treatment compared with incidence among those participants randomized to nonpharmacologic treatment only as the initial step.

Aged↗
PubMed1990

Palliative radiation therapy for Kaposi's sarcoma in patients with AIDS.

Kaposi's sarcoma is a common manifestation of AIDS, particularly in young male homosexual patients. Between 1987 and 1988, eight patients with Epidemic Kaposi's sarcoma received palliative radiation therapy. The authors' experience indicates that radiation therapy can provide good to excellent palliation for skin and oropharyngeal lesions.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Persistently low natural killer cell activity in normal adults: immunological, hormonal and mood correlates.

This current study is concerned with the identification of the incidence of persistently low natural killer (NK) cell activity in an essentially healthy population of young adults, and the characterization of the psychological profile associated with this pattern of NK activity. Eighty-eight individuals, between the ages of 18 and 44 years, were accrued to this project. Subjects were tested serially, at baseline induction into the study, and at 2 and 4 weeks follow-up. Baseline assessment included a complete physical examination and laboratory work-up in order to exclude anyone ill at the time of enrollment, and to have complete physical status information on all subjects at the time of accrual. NK activity, urinary catecholamine levels and psychological status were also assessed at baseline, and at the specified follow-up intervals. Individuals with low NK activity were operationally defined as those having NK function either below the group mean, or below the group lowest quartile, at baseline and at two follow-up assessments. Results showed that in both univariate analyses, as well as in logistic regression models, age and the perception of environmental stressors or 'hassles' predicted persistently low NK activity. Younger subjects, who perceived environmental events to which they were exposed as more serious in nature, were more likely to exhibit a persistently low NK profile over time than older individuals who perceived daily events as less important to them.

Adult↗
PubMed1988

Iron, zinc and magnesium nutrition and athletic performance.

During the last decade there has been considerable interest in the idea that dietary trace elements supplementation can result in an improvement in athletic performance. The current paper discusses this idea as it relates to 3 elements: iron, zinc and magnesium. Emphasis has been placed on examining the implicit assumptions underlying the idea that mineral supplements help the athlete. These assumptions include the beliefs that the athlete has a higher than normal requirement for minerals; that the athlete consumes a diet inadequate in these minerals; and that a marginal deficiency of these elements has a direct effect on athletic performance. Evidence is presented that both iron deficiency and magnesium deficiency can result in a significant reduction in exercise performance; however, the biochemical lesions underlying the reductions in exercise performance have not been identified. There is evidence that dietary magnesium intake may be suboptimal in some individuals, thus dietary supplementation of this element may be useful in some population groups. Excessive magnesium supplementation is not thought to be a serious health problem. Similar to magnesium dietary iron supplements can improve athletic performance in individuals severely deficient in this element. However, few studies have documented a need for iron supplements in healthy athletes. If iron supplements are used, it is important that the level of supplementation is not excessive, as excess iron in the diet can result in an induced zinc deficiency. In marked contrast to iron and magnesium, there is little evidence for the idea that zinc deficiency influences exercise performance in humans. Despite this fact, zinc supplements have been widely advocated for the athlete, as it is known that intense exercise can result in changes in zinc metabolism. If zinc supplements are used, it is important that they are not excessive, as excess zinc in the diet can result in a secondary copper deficiency.

Humans↗
PubMed1986

Age-related differences in the bone mineralization pattern of rats following exercise.

The effect of 12 weeks of treadmill exercise on the mineralization of trabecular and cortical bone was studied in rats 7, 14, and 19 months of age. Bone mineralization was evaluated by measuring concentrations of Ca, Mg, and hydroxyproline as well as uptake of 45Ca concentration in the femur, humerus, rib and calvaria. The 7- and 14-month-old rats increased mineralization in those cortical bones directly involved in exercise. The 19-month animal responded to exercise by increasing mineralization in all bones examined, including the nonweight bearing trabecular calvaria and cortical rib. From these data, it is apparent that the older animals undergo a total skeletal mineralization in response to exercise compared with local adaptation in the younger animal. Further, we provide evidence to support the use of the rat as a model in which to study mammalian bone physiology during the aging process.

Aging↗
PubMed1986

Identical twins discordant for presenile dementia of the Alzheimer type.

In genetically proven identical female twins, discordant for presenile dementia of the Alzheimer type, the affected twin began to dement at the age of 49, and died 15 years later; the diagnosis was confirmed at post-mortem. The surviving twin remains clinically unaffected 20 years after the onset of dementia in her sister. Environmental aetiological factors are postulated to account for this discordance.

Alzheimer Disease↗
PubMed1986

Ketoconazole-induced changes in selected canine hormone concentrations.

The effects of administering ketoconazole at a high dosage (30 mg/kg of body weight/day) and at a low dosage (10 mg/kg/day) on steroidogenesis in the dog were compared. Ketoconazole significantly suppressed basal plasma cortisol concentrations (P = 0.001), cortisol responsiveness to ACTH (P = 0.002 to 0.005), and serum testosterone concentrations (P = 0.0005). The data indicated a rebound effect after ketoconazole treatment was stopped and that testosterone suppression was being overridden at lower ketoconazole doses. Plasma 17-alpha-hydroxyprogesterone concentrations (P = 0.0005) and serum progesterone concentrations (P = 0.014 to 0.003) were significantly increased during ketoconazole treatment. Aldosterone, 11-desoxycortisol, and 17-beta-estradiol concentrations did not change significantly during ketoconazole treatment.

17-alpha-Hydroxyprogesterone↗
PubMed1985

Systolic Hypertension in the Elderly Program (SHEP): antihypertensive efficacy of chlorthalidone.

The Systolic Hypertension in the Elderly Program (SHEP) is a randomized, blinded test of the efficacy of antihypertensive drug treatment. In a large feasibility trial, 551 men and women who had isolated systolic hypertension and were at least 60 years old received chlorthalidone (25 to 50 mg/day) or matching placebo as the step I drug. After 1 year, 83% of the chlorthalidone group and 80% of the placebo group were still taking SHEP medications. Of those still taking chlorthalidone, 88% had reached goal blood pressure (BP) without requiring a step II drug, and most had responded to the lower dose (25 mg/day). The BP response was similar in all age, sex and race subgroups, with an overall mean difference between randomized groups of 17 mm Hg for systolic BP (p less than 0.001) and 6 mm Hg for diastolic BP (p less than 0.001). The only common adverse effects were asymptomatic changes in the serum levels of potassium (0.5 mEq/liter lower in the chlorthalidone group, p less than 0.001), uric acid (0.9 mg/dl higher, p less than 0.001) and creatinine (0.08 mg/dl higher, p = 0.02). This study indicates that chlorthalidone is effective for lowering BP in elderly patients with systolic hypertension and sets the stage for a larger trial of the effects of such treatment on the incidence of cardiovascular disease.

Aged↗
PubMed1979

Chlorambucil therapy in childhood nephrotic syndrome.

Chlorambucil (Leukeran), a cytotoxic agent, was administered to 13 children with the nephrotic syndrome who had responded to steroid therapy, but frequently relapsed. In all patients corticosteroid therapy had become unsatisfactory. Eleven patients have so far remained in remission for an average follow-up period of 31 months since chlorambucil therapy. No side-effects of therapy were observed in this study, but several grave complications of high-dosage therapy have been reported in the recent literature. A dose of 0.2 mg/kg/d for 8 weeks should not be exceeded.

Adolescent↗
PubMed1978

Interaction of cromolyn sodium in aqueous solution with magnesium ions.

The interaction of the antiasthmatic drug cromolyn sodium with Mg2+ ions in solution was studied. Selective ion electrode and torsion viscometer measurements were used to establish the degree of interaction. At the concentrations studied, the cromolyn ion had no more affinity for Mg2+ than SO42-. However, thixotropic gels were formed between 4 X 10(-2) M cromolyn sodium and 4 X 10(-4) Mg2+. At lower concentrations of Mg2+, viscosity still increased significantly. However, when the cromolyn concentration was lowered, the increase in viscosity was much less marked.

Chemical Phenomena↗
PubMed1977

Register of cases of subacute sclerosing panencephalitis (SSPE) in Southern Africa.

An analysis of cases of subacute sclerosing panencephalitis (SSPE) in Southern Africa to the end of 1976 is presented. In the 2 years since the last report in 1975, 15 new cases have been added to the register. Seven patients from the Cape Province were investigated in Groote Schuur and Red Cross War Memorial Children's Hospitals in Cape Town and a recent postal survey revealed 6 cases in the Transvaal and 1 each from South West Africa and Rhodesia. This analysis indicates that the high incidence and temporal clustering of cases in the Cape Province is continuing, and that the relatively constant annual number of cases in the Transvaal and the apparent absence of the disease in Natal and the Orange Free State are being maintained.

Adolescent↗
PubMed1977

Oral and intravenous propranolol during exercise.

The intrinsic sinoatrial (SA) rate at rest and during exercise was measured in 5 normal male subjects after prolonged oral and acute intravenous administration of propranolol and atropine. At rest, the intrinsic SA rate was similar after both oral and intravenous propranolol. At the higher levels of power output on a cycle ergometer, cardiac rate was slower after oral than after intravenous propranolol. When the intravenous study was repeated with the use of an additional dose of propranolol, cardiac rate was lower at comparable levels of power output, but not as low as that after oral propanolol. Differences in responses were interpreted as reflecting varying degrees of beta blockade, the most complete being that after prolonged oral propranolol administration of 320 mg daily. The intravenous dose of propranolol usually used to obtain the "pharmacologically isolated heart" at rest is too small to induce full beta blockade in exercise.

Administration, Oral↗