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Biomedical subjects

S Bull

Publications and source records attributed to S Bull.

9 recordsLinked to original sources
PubMed1992

The common cold, pattern sensitivity and contrast sensitivity.

Results from two studies involving challenge with respiratory syncytial viruses showed that volunteers who developed colds were more sensitive to a visually distracting pattern presented prior to virus challenge than were volunteers who did not get a cold. Volunteers with sub-clinical infections reported more illusions after virus challenge than they had done before, whereas uninfected volunteers and those with colds tended to report fewer illusions on the second test. These effects did not occur when volunteers were challenged with either a coronavirus or rhinovirus. Overall, the results confirm that behavioural measures may be related to susceptibility to subsequent illness, and that viral infections may influence visual perception. They also show that the effects vary according to the nature of the infecting agent, which agrees with results from studies looking at other aspects of behaviour.

Adolescent↗
PubMed1990

Expression of ras oncogene leads to down-regulation of protein kinase C.

The effect of mutated c-Ha-ras expression on Ca2+ and phospholipid-dependent protein kinase C (PKC) activity during the process of transformation was analysed using an inducible metallothionein-ras hybrid oncogene system. A close correlation was found between the timing of ras expression and the loss of PKC enzymatic activity measured in a cell-free system. Examination of the subcellular distribution of the enzyme in inducible and constitutive ras-transformants revealed that expression of ras was associated with an apparent translocation of PKC to the plasma membrane concomitant with down-regulation of PKC enzymatic activity in particulate as well as cytosolic fractions. Quantitation of PKC protein utilizing a PKC-specific antiserum showed that ras expression was associated with a decrease in the total amount of PKC protein present in the cell. We conclude that transformation by c-Ha-ras is accompanied by down-regulation of PKC activity and that the basis of this effect may, to a large extent, lie in the down-regulation of the amount of PKC protein.

Animals↗
PubMed1988

Role of atrial natriuretic peptide in the natriuretic response to central volume expansion induced by head-out water immersion in sodium-retaining cirrhotic subjects.

PURPOSE: It is possible that abnormalities in atrial natriuretic peptide may be involved in the pathogenesis of sodium retention in edema states. We performed a study in a group of 12 sodium-retaining cirrhotic subjects to determine the role of this peptide in mediating differences in the natriuretic response to central volume expansion induced by head-out water immersion. PATIENTS AND METHODS: Each patient was maintained for seven days on a 20-mmol sodium intake, and then studied on both control and immersion days. On each day, measurements of the following were obtained: plasma atrial natriuretic peptide, hematocrit, electrolytes, creatinine, plasma renin activity, serum aldosterone, urinary cyclic guanosine monophosphate (cGMP), blood pressure, and pulse rate. RESULTS: In six subjects, immersion resulted in a marked natriuresis sufficient to induce negative sodium balance by the third hour, and these subjects were termed "responders." In these six patients, baseline pre-immersion levels of plasma renin activity and serum aldosterone were all below 3 ng/liter/second and 4 nmol/liter, respectively. In the other six subjects, the natriuretic response to immersion was markedly blunted and insufficient to induce negative sodium balance, and these subjects were termed "non-responders." In these subjects, baseline pre-immersion levels of plasma renin activity and aldosterone were all above 3.5 ng/liter/second and 5 nmol/liter, respectively, and were significantly elevated compared with the responders, and compared with the normal range for control subjects consuming the same sodium intake. In both groups of cirrhotic subjects, baseline levels of plasma atrial natriuretic peptide and cGMP excretion were significantly and comparably elevated compared with the normal range for control subjects ingesting the same sodium intake. Despite the marked difference in the natriuretic response to immersion in both responders and non-responders, there was a significant and comparable further elevation of plasma atrial natriuretic peptide and urinary cGMP excretion during immersion, compared with the control day. CONCLUSION: These results suggest that the relative resistance to the natriuretic action of atrial natriuretic peptide in the non-responders compared with the responders is mediated by anti-natriuretic factors acting at a level parallel with or beyond atrial natriuretic peptide release or coupling to its cGMP-linked receptors.

Adult↗
PubMed1987

A prospective evaluation of magnetic resonance imaging, computed tomography, and mediastinoscopy in the preoperative assessment of mediastinal node status in bronchogenic carcinoma.

Computed tomography, magnetic resonance imaging, chest roentgenography, and mediastinoscopy were compared prospectively as staging modalities to assess mediastinal node status in 84 patients with presumed operable bronchogenic carcinoma. Computed tomography was associated with a sensitivity of 71.0%, a specificity of 87.7% and an overall accuracy of 82.1%. Magnetic resonance imaging did not provide any advantage over computed tomography in the assessment of mediastinal node status. The accuracy of computed tomography was not dependent on cell type of the primary tumor. Although chest roentgenography had a sensitivity of 80.7%, the overall accuracy of 57.1% was unacceptably low. The sensitivity (87.1%), specificity (100%), positive (100%) and negative (93.0%) predictive values, and accuracy (95.2%) of mediastinoscopy exceeded those observed with all other modalities. We continue to recommend mediastinoscopy as the most accurate staging investigation in the routine management of patients with bronchogenic carcinoma.

Carcinoma, Bronchogenic↗
PubMed1986

Preventable causes of death versus infant mortality as an indicator of the quality of health services.

We have made a preliminary comparison of infant mortality with the preventable causes of death proposed by Rutstein and colleagues, as indicators of the quality of health care. Two analyses were carried out. The first analysis compared the correlations of infant mortality and of the preventable deaths with four health service variables in 17 developed countries. Infant mortality was more highly correlated with the health service variables and less highly correlated with per capita income in comparison with the preventable deaths. The second analysis examined correlations of the two mortality indicators with variables reflecting the quality of general practitioner training in England. Here again, infant mortality appeared to be more sensitive, although reasons for regarding this result with caution are emphasized. Suggestions are made for further research on the concept of preventable mortality as a health outcome indicator.

Adolescent↗
PubMed1984

A comparison of plans for hypertension screening.

Correcting to the work by Donner and Bull [1], it is reported that, in the setting they considered, screening plans based on the mean have higher power (probability of identifying a true hypertensive) than screening plans based on the minimum. However, for any reasonable size (probability of a false diagnosis of hypertension) the powers of the two plans are close.

Blood Pressure Determination↗
PubMed1984

Testing the effect of sex differences on sib-sib correlations.

Procedures for testing the effect of sex differences on sib-sib correlations are studied. It is demonstrated that a simple procedure for testing the equality of a pair of brother-brother and sister-sister correlations (the modified Z test) is comparable in power to the likelihood ratio test in moderately large samples drawn from sibship-size distributions that are likely to occur in practice. In small samples, the modified Z test is preferable to the likelihood ratio test, since the latter tends to be anti-conservative.

Biometry↗
PubMed1983

Inferences concerning a common intraclass correlation coefficient.

The maximum likelihood estimator, rhoM, of a common intraclass correlation, rho, is derived in two independent samples drawn from multivariate normal populations. A likelihood ratio statistic for testing the assumption of a common rho is also derived and examples are given. Comparisons are made with a procedure based on Fisher's transformation.

Models, Theoretical↗