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Biomedical subjects

S Whittaker

Publications and source records attributed to S Whittaker.

84 records · Page 5Linked to original sources
PubMed1987

Variations in mortality of the coloured, white and Asian population groups in the RSA, 1978-1982. Part II. Cerebrovascular disease.

An analysis was undertaken of mortality from cerebrovascular disease in the RSA between 1978 and 1982 in whites, coloureds and Asians. This article details the age-specific mortality rates for each group and also comparisons between groups based on age-standardised mortality rates. Marked differences are seen between the various population groups, the rates for Asians and coloureds (particularly females) far exceeding that for whites. Comparison of these data with those published previously by Wyndham suggest that while mortality from this cause may be falling among whites and Asians, the rate is remaining relatively static in the coloured population.

Adult↗
PubMed1987

Variations in mortality of the coloured white and Asian population groups in the RSA, 1978-1982. Part III. Rheumatic heart disease.

An analysis was undertaken of mortality from rheumatic heart disease in the RSA between 1978 and 1982 in whites, coloureds and Asians. This article details the age-specific mortality rates (MRs) for each group and also comparisons between groups based on age-standardised MRs. The rates for Asians and coloureds markedly exceed those for whites, particularly in the lower age groups (under 45 years).

Adolescent↗
PubMed1986

Cardiogenic shock without a critically raised left ventricular end diastolic pressure: management and outcome in eighteen patients.

Eighteen patients in whom shock developed after acute myocardial infarction are described. There was electrocardiographic evidence of acute inferior infarction in 11, of inferolateral infarction in three, and of anteroseptal infarction in four. In all cases the right atrial pressure was the same as or exceeded the end expiratory pulmonary artery wedge pressure. Plasma volume expansion of 100-2500 ml was needed to produce an optimum pulmonary artery wedge pressure. Eleven patients needed additional inotropic support with dopamine. Despite the absence of a critical increase in pulmonary artery wedge pressure, potential or actual hypoxia was almost always present. Six patients needed endotracheal intubation and mechanical ventilation because they had severe hypoxia that was unresponsive to supplemental inspired oxygen. Life threatening arrhythmias were also common (ventricular fibrillation in seven patients and complete heart block in four). Five patients died. All surviving patients are well and only one requires treatment for heart failure.

Aged↗
PubMed1982

Reinforcement contingencies and signal detection.

Pigeons were trained to discriminate temporal stimuli in a discrete-trial signal-detection procedure. Pecks to one side key were reinforced intermittently after exposure to one duration, and pecks to the other side key were reinforced intermittently after exposure to a different duration. In Experiment I, the allocation of reinforcers was varied systematically for correct responses and for errors, using a procedure that controlled the obtained numbers of reinforcers. When reinforcers were allocated symmetrically, the level of discrimination decreased as the proportion of reinforcers for errors increased. When reinforcers were allocated asymmetrically, the decrease in discrimination was less systematic. Bias toward one or the other side key roughly matched the ratio of reinforcers obtained by pecks at those keys, independent of the level of discrimination. In Experiment II, the overall rate of reinforcement for correct responses was varied both within and between experimental conditions. The level of discrimination was positively related to the overall rate of reinforcement. The discrimination data of both experiments were interpreted in relation to the contingencies of reinforcement and nonreinforcement, characterized by the average difference in reinforcement probability for correct responses and errors.

Animals↗
PubMed1978

Contrast and induction in multiple schedules of discrete-trial concurrent reinforcement.

Three pigeons were exposed to two-key discrete-trial concurrent schedules of reinforcement. Red and white key colors alternated irregularly and the assignment of reinforcers depended on key color. The red-key schedules were held constant, with the scheduled relative frequency of reinforcement for left-key pecks set at 0.75, while the white-key schedules varied. When the location of white-key reinforcement was changed from one side to the other, while its overall frequency was constant, red-key choices shifted in the same direction as white-key choices, an induction effect. When the overall frequency of white-key reinforcement was changed while its location remained constant, red key choices shifted in a direction opposite to white-key choices, a contrast effect. Both induction and contrast effects were clearer when the overall frequency of red-key reinforcement was reduced. These data demonstrate that the allocation of responding may exhibit schedule interaction effects similar to those commonly reported for response rate.

Journal Article↗
PubMedDate not supplied

What is subjective global assessment of nutritional status?

Presented and described in detail is a clinical technique called subjective global assessment (SGA), which assesses nutritional status based on features of the history and physical examination. Illustrative cases are presented. To clarify further the nature of the SGA, the method was applied before gastrointestinal surgery to 202 hospitalized patients. The primary aim of the study was to determine the extent to which our clinician's SGA ratings were influenced by the individual clinical variables on which the clinicians were taught to base their assessments. Virtually all of these variables were significantly related to SGA class. Multivariate analysis showed that ratings were most affected by loss of subcutaneous tissue, muscle wasting, and weight loss. A high degree of interobserver agreement was found (kappa = 0.78, 95% confidence interval 0.624 to 0.944, p less than 0.001). We conclude that SGA can easily be taught to a variety of clinicians (residents, nurses), and that this technique is reproducible.

Humans↗
PubMedDate not supplied

Sun and skin cancer.

Ultraviolet light is the most common carcinogen to which man is exposed and it is responsible for both the initiation and promotion of skin cancer as shown by mutations of tumour supressor genes controlling the cell cycle. Apart from its effects on skin carcinogenesis, it is also responsible for premature skin ageing, cataracts, sunburn and immunosupression.

Causality↗