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Biomedical subjects

D R Williams

Publications and source records attributed to D R Williams.

At least 199 records · Page 11Linked to original sources
PubMed1988

Outbreaks of classical swine fever in Great Britain in 1986.

Classical swine fever was confirmed in 10 herds in Britain between April 10 and June 25, 1986 and typical acute disease was seen in nine of them. Serological evidence of exposure to classical swine fever virus was found in a further seven herds which, together with another nine, were slaughtered as dangerous contacts. Altogether 7781 pigs in 26 herds were slaughtered at a cost of 450,101 pounds for compensation alone. In order to detect subclinical disease, the majority of traced herds were blood sampled as well as inspected. A total of 119,169 pigs were inspected in 506 herds and 8302 blood samples were collected. Three primary outbreaks were identified, all attributed to the feeding of unprocessed waste food containing imported pig meat products. There was no spread of disease from two of these primary outbreaks.

Acute Disease↗
PubMed1988

Team management of the elderly patient with hip fracture.

The management of 200 consecutive patients with hip fracture by a joint hospital and community team in Peterborough has shown that over half the patients could be discharged considerably earlier than is usual. The patients are cared for at home by the hospital-at-home nursing service and generally need much less nursing care than patients treated conventionally. In the first 10 months of the scheme 733 inpatient bed-days were saved and the average hospital stay of patients discharged home was reduced from 22.0 to 14.6 days.

Aged↗
PubMed1988

Topography of the foveal cone mosaic in the living human eye.

Interference fringes whose spatial frequency exceeds the resolution limit form visible moiré patterns with the foveal cone mosaic. This paper describes a model of foveal cone sampling that shows how these moiré patterns depend on the spatial frequency and orientation of an interference fringe imaged on a triangular lattice of cones. The model is tested with two psychophysical experiments. The first experiment shows that the behavior of the moiré patterns is quantitatively consistent with anatomical estimates of cone spacing across the human fovea. These patterns provide a psychophysical method for measuring cone spacing within 1.75 deg of the foveal center. In some observers, cone spacing is larger in a horizontal direction than in a vertical direction at any particular location within the fovea. The second experiment shows that the behavior of the moiré patterns is consistent with the triangular packing of foveal cones observed anatomically, and allows the orientation of the cone mosaic to be determined at the foveal center. These observations demonstrate the rich information that methods based on aliasing can provide about the topography of foveal cones in the living human eye.

Adult↗
PubMed1988

Carbon dioxide elimination during total cardiopulmonary bypass in infants and children.

The authors measured the rate of carbon dioxide elimination (VCO2) in 25 pediatric patients (age 2 days to 9 yr) during total cardiopulmonary bypass at average venous blood temperatures ranging from 19.5 to 35.9 degrees C. A multiplexed mass spectrometer was connected to the gas inlet and exhaust ports of the bubble oxygenator, and the gas-phase Fick principle was used to determine VCO2. A curvilinear relationship was found between log VCO2 and venous blood temperature, and a quadratic regression equation (r2 = 0.74) was fit to the data. Q10 (the ratio of VCO2 before and after a 10 degree C temperature change) was estimated to be 2.7 or 3.0, depending on the analytic method used. Venous blood temperature as a predictor variable explained a greater proportion of the variability of log VCO2 than did nasopharyngeal or rectal temperatures. Analysis of covariance revealed that total circulatory arrest during bypass (utilized in 10 patients for 34 +/- 4 min, mean +/- SEM) affected the relationship of venous blood temperature with log VCO2, by increasing the y-intercept (P = .008) but not the slope. These data, with associated 95% prediction intervals, define the expected CO2 elimination rates at various temperatures during standard bypass conditions in our patients. Real-time measurement of VCO2 using mass spectrometry can be a useful routine monitor during CPB that may help to assess patient metabolic function, adequacy of perfusion, and oxygenator performance.

Blood Physiological Phenomena↗
PubMed1988

Central venous catheter stiffness and its relation to vascular perforation.

Delayed central venous perforation is an uncommon but serious complication of central venous catheter insertion. An increase in catheter stiffness may have been responsible for our association of venous perforation with use of a guidewire insertion technique. A bench model was used to investigate the stiffness characteristics of thirty-four different types of catheters. The initial stiffness is poorly described by material or catheter gauge. A large range of values is seen between apparently similar catheters--the 16 gauge polyethylene catheter associated with two perforations at our institution had an initial stiffness value 7.5 Nm2 X 10(-5) at 37 degrees C in comparison with our previous standard--the 16 gauge Deseret Intracath with an initial stiffness of 2 Nm2 X 10(-5). Multilumen catheters had a similar range of stiffness to single lumen catheters, while paediatric catheters in general were less stiff. Dialysis catheters were up to five times as stiff as the stiffest central venous catheter. Stiffness decayed at a rate and to an extent which differed from catheter to catheter. Absorption of water by the catheter appears to be one factor involved in stress relaxation.

Aged↗
PubMed1988

LL-F28249 antibiotic complex: a new family of antiparasitic macrocyclic lactones. Isolation, characterization and structures of LL-F28249 alpha, beta, gamma, lambda.

A new family of antiparasitic macrolides has been isolated from Streptomyces cyaneogriseus sp. noncyanogenus. The compounds, designated LL-F28249 alpha, beta, gamma and lambda, possess potent antiparasitic activity. The isolation, purification and structure determination by spectroscopic methods are presented.

Anti-Bacterial Agents↗
PubMed1987

Diabetes and glucose tolerance in New South Wales coastal Aborigines: possible effects of non-Aboriginal genetic admixture.

A survey of adults living in two predominantly Aboriginal communities in eastern New South Wales revealed a crude prevalence of clinically diagnosed diabetes of 6.7% in Aboriginals. 1.4% of Aboriginal subjects investigated with 75 g oral glucose tolerance tests were found to have previously undiagnosed diabetes, and 2.8% had impaired glucose tolerance. 53% of women and 27% of men were obese as judged by body mass index. The age-sex standardised prevalence of diabetes in Aboriginals (previously diagnosed and newly detected) was 7.8%, which is substantially lower than the 15.6% prevalence found in the Aboriginal population of Bourke (central New South Wales). HLA antigen studies on these same individuals suggest approximately 60% genetic admixture from non-Aboriginal sources. Insulin response to oral glucose and mean body mass index were both related to non-Aboriginal genetic admixture with higher values in Aboriginal subjects than in their non-Aboriginal neighbours, and highest values were found in those with no detectable non-Aboriginal HLA haplotypes. The extent of genetic admixture in these communities may partly explain the lower prevalence of diabetes when compared with that found in the Aboriginal population of Bourke.

Adolescent↗
PubMed1987

Observations on the incidence of herds with non-visible lesioned tuberculin test reactors in south-west England.

The herd incidence of confirmed Mycobacterium bovis infection in cattle in the south-west of England has been approximately ten times that of the remainder of England and Wales; this greater incidence has been attributed to infection from badgers. The incidence of herds with only non-visible lesioned tuberculin test reactors, from which M. bovis was not isolated, has also remained higher in the south-west region. The incidences of these latter unconfirmed incidents were compared in parishes in the south-west region in which M. bovis in cattle had been confirmed, and those where M. bovis had not been confirmed, for the period 1979-83. This analysis was carried out both for those parishes in which herds had been subjected to annual tuberculin testing and for those subjected to biennial tuberculin testing. The incidence of unconfirmed incidents was significantly higher in parishes in which confirmed incidents had occurred, and this difference was found in both the annual and biennially tested parishes. The relative risks for the incidence of unconfirmed incidents in annually and biennially tested parishes were 1.89 and 2.56, respectively. The incidence of unconfirmed incidents in biennially tested parishes was lower than in annually tested parishes. The incidence of non-specific tuberculin test reactor herds was estimated from tuberculin test results in the eastern region of England during a period when tuberculosis was not confirmed in cattle. A comparison of this incidence and that of unconfirmed incidents in the south-west region suggests that approximately 70% of the unconfirmed incidents in the south-west were related to exposure to M. bovis. The results of the analyses indicate that unconfirmed incidents cannot be completely ignored in epidemiological analyses and studies of bovine tuberculosis in the problem areas of the south-west region of England.

Animals↗
PubMed1987

A rationale for the management of advanced tooth wear (ATW).

An approach to the treatment of patients with significant loss of tooth tissue is presented. Alternative treatment modes are discussed and the possible outcome of treatment considered. Guidelines are offered for the management of such cases including a flow-chart concerning the use of temporary appliances.

Crowns↗
PubMed1987

A retrospective review of adenocarcinoma-in-situ and glandular atypia of the uterine cervix.

Between 1978 and 1985, 19 cases of adenocarcinoma-in-situ and 12 cases of glandular atypia have been identified at the Birmingham and Midland Hospital for Women. In 19 cases an associated dysplastic squamous element was identified, 20 of 28 pre-diagnosis smears correctly predicted a glandular lesion, 5 of 17 colposcopically directed biopsies predicted the findings in a larger biopsy (cone biopsy or hysterectomy). Colposcopy provided no additional information with regard to diagnosis. Twelve of 13 patients managed by cone biopsy and 16 of 17 by abdominal hysterectomy have been treated successfully as defined by subsequent normal cytology.

Adenocarcinoma↗
PubMed1987

Psychophysical estimate of extrafoveal cone spacing.

In the extrafoveal retina, interference fringes at spatial frequencies higher than the resolution limit look like two-dimensional spatial noise, the origin of which has not been firmly established. We show that over a limited range of high spatial frequencies this noise takes on a striated appearance, with the striations running perpendicular to the true fringe orientation. A model of cone aliasing based on anatomical measurements of extrafoveal cone position predicts that this orientation reversal should occur when the period of the interference fringe roughly equals the spacing between cones, i.e., when the fringe spatial frequency is about twice the cone Nyquist frequency. Psychophysical measurements of the orientation reversal at retinal eccentricities from 0.75 to 10 deg are in quantitative agreement with this prediction. This agreement implies that at least part of the spatial noise observed under these conditions results from aliasing by the cone mosaic. The orientation reversal provides a psychophysical method for estimating spacing in less regular mosaics, complementing another psychophysical technique for measuring spacing in the more regular mosaic of foveal cones [D.R. Williams, Vision Res. 25, 195 (1985); Vision Res. (submitted)].

Animals↗
PubMed1987

Cone spacing and the visual resolution limit.

It is commonly assumed that the visual resolution limit must be equal to or less than the Nyquist frequency of the cone mosaic. However, under some conditions, observers can see fine patterns at the correct orientation when viewing interference fringes with spatial frequencies that are as much as about 1.5 times higher than the nominal Nyquist frequency of the underlying cone mosaic. The existence of this visual ability demands a closer scrutiny of the sampling effects of the cone mosaic and the information that is sufficient for an observer to resolve a sinusoidal grating. The Nyquist frequency specifies which images can be reconstructed without aliasing by an imaging system that samples discretely. However, it is not a theoretical upper bound for psychophysical measures of visual resolution because the observer's criteria for resolving sinusoidal gratings are less stringent than the criteria specified by the sampling theorem for perfect, alias-free image reconstruction.

Humans↗