Biomedical subjects
Publications and source records attributed to D R Williams.
Nineteen pigs in a 500 sow herd died from anthrax over a period of 95 days. This paper describes some of the problems encountered and how they were dealt with, including the risks to public health, the disposal of slurry and the cleansing and disinfection of the premises after the herd was slaughtered.
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A complete description of the loss of contrast sensitivity at high spatial frequencies requires an estimate of the role of eye movements, which could blur fine detail. We describe a new technique to isolate their effect. Observers viewed either a 100 c/deg interference fringe, which the cone mosaic aliased to a low frequency zebra stripe, or an artificial zebra stripe. The real and artificial zebra stripes have similar spatial patterns, but differ in the temporal modulation produced by eye movements. Contrast threshold was measured as a function of duration for both stimuli flashed in the dark. The ratio of the contrast thresholds for the real and artificial zebra stripes with long durations, when eye movements could have a differential effect, is always within a factor of two or so of the ratio for 1 msec flashes, when eye movements are eliminated. These results support the view that eye movements are only a minor source of image degradation even at very high spatial frequencies, and provide no support for the view that they improve high resolution tasks.
Although spatial aliasing by the extrafoveal retina can occur under natural viewing conditions, it does not commonly disturb our vision. One possible explanation for this is that real scenes do not have sufficient power in the high frequencies to produce aliasing. We examined whether aliasing distorted the appearance of a high contrast edge, which is a common stimulus in the environment. Observers made a two-interval forced-choice discrimination between low-pass filtered and unfiltered edges at 0, 10, 20, and 40 deg eccentricity. This discrimination could be made only when frequency components were removed below both the cone and ganglion cell Nyquist frequencies at each eccentricity. Since supra-Nyquist frequency components could not be detected in edges, they are incapable of producing aliasing.
An intensive nonlinearity in the visual system can produce distortion products, or difference frequency gratings, when observers view two high contrast, high spatial frequency interference fringes of slightly different frequency or orientation added together at the retina. These distortion products are visible even when the two fringes imaged on the retina are above the resolution limit. Our experiments take advantage of this nonlinearity to measure the spatial filtering in the visual system following the formation of the retinal image, but preceding the site of the nonlinearity. The point spread function corresponding to this spatial filter is so small that it can be entirely explained by light integration within the apertures of foveal and parafoveal cones. The small size of this point spread function implies that (1) laser interferometry avoids contrast losses inherent in the eye's optics at spatial frequencies as high as 130 c/deg, (2) retinal scatter causes negligible image degradation in the fovea and parafoveal retina, (3) eye movements have little or no effect on contrast sensitivity to the distortion product and (4) that there is no neural spatial summation in the visual system prior to the site of the nonlinearity. Distortion products could also be observed when a bright interference fringe was briefly flashed on the fovea and a test interference fringe was viewed through the resulting afterimage. Measurements of the point spread function at stages in the visual system that precede the generation of this distortion product were similar to those obtained with simultaneous presentation of the two fringes, implying that the aftereffect of light adaptation is extremely local, no larger than the dimensions of single cones.
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As part of a District-based audit of diabetes care all attendances (of diabetic and non-diabetic patients) at a local Accident and Emergency department were monitored over a 3-month period. A total of 9505 attendances took place of which 62 (0.7%) were by people with diabetes. This was no different from the expected number of attendances (61.5) based on the rates seen in non-diabetic individuals. Of these 62 attendances, 20 (by 15 individuals) were directly related to diabetes (hypoglycaemia 17, hyperglycaemia 1, for supplies of insulin or equipment 2). When these diabetes-specific attendances were removed from the total, the number of attendances (42) was significantly (p = 0.004) less than that expected. Diabetic males aged 0-19 years attended significantly more often than non-diabetic individuals of the same age but this excess was solely attributable to diabetes.
The prevalence of Type 2 (non-insulin-dependent) diabetes in different South Asian (Asian) communities was compared during the Coventry Diabetes Study, a cross-sectional house to house screening programme for diabetes. Screening was by capillary whole blood glucose measurement with oral glucose tolerance tests when concentrations were greater than or equal to 6.0 mmol l-1 within 2 h of a meal or greater than or equal to 5.0 mmol l-1 2 h or more after a meal and a random 10% of others. Of the 4395 resident Asians, 94% were represented by five communities: Punjabi Sikhs, Punjabi Hindus, Gujerati Moslems, Gujerati Hindus, and Pakistani Moslems. Response to screening was 77-89% and to glucose tolerance test was 59-79%. Differences in anthropometry, socioeconomic circumstances, and migratory patterns were found, but all groups had a higher prevalence of Type 2 diabetes than Europeans. Gujerati Moslems had the highest age-adjusted prevalence (per 1000) of Type 2 diabetes (males: 160 (95% CI 107-228), females: 204 (95% CI 144-283)) when compared with the other Asian groups (males: Punjabi Sikhs 89(72-110), Pakistani Moslems 91(67-120), Gujerati Hindus 84(57-120), Punjabi Hindu 113(74-171); females: Punjabi Sikhs 75(60-94), Pakistani Moslems 103(78-133), Gujerati Hindus 88(62-122), Punjabi Hindu 116(77-174)). That all the Asian groups had a high prevalence of diabetes, in spite of their known dietary, cultural, and socioeconomic differences, suggests that the Asian predisposition to Type 2 diabetes is inherited although environmental factors may be necessary for this to be expressed.
A working group was established in order to suggest the process and outcome variables most appropriate for the continuing audit of diabetes services. The proposed audit is being piloted in hospitals in selected United Kingdom Health Districts. The main process and outcome measures suggested are: waiting and consultation times; missed or cancelled appointments; information given to patients and the primary care team; knowledge of diabetes and risks of smoking; recording of key examinations and investigations, i.e. levels of glycosylated haemoglobin (or equivalent), serum cholesterol, body mass index, blood pressure, albumin excretion rate, presence and extent of retinopathy, history of coronary artery, cerebrovascular or peripheral vascular disease; history of severe hypoglycaemia; presence of foot problems; psychological well-being; patient satisfaction; admission rates and hospital bed days for hyperglycaemic and other diabetes related emergencies.
OBJECTIVE: To assess the efficacy of cervical conization as primary management of cervical intraepithelial glandular neoplasia (CIGN). DESIGN: A multicentre prospective cohort study. SETTING: CRC Clinical Trials Unit, Birmingham. SUBJECTS: 84 women registered with the Unit between May 1986 and January 1989. After excluding 33 women, 51 who had been managed in accordance with the described protocol and had the presence of CIGN confirmed by central review of diagnostic histopathological material were included in the study. INTERVENTION/PROTOCOL: Women with CIGN diagnosed on a cervical cone specimen were managed in accordance with a specific protocol: (a) women with negative cone margins were managed conservatively and followed up with regular cervical cytological and colposcopic examinations; (b) women with involved cone margins were managed by hysterectomy. MAIN OUTCOME MEASURES: Presence or absence of CIGN at cone margins, results of cervical cytological examinations following conization, results of histopathological assessment of any surgical specimens taken after initial cone biopsy. RESULTS: Of the 51 women with confirmed CIGN, managed by conization, 14 (27%) were aged 30 or less and 15 (29%) were nulliparous. Thirty five women who had a cone biopsy showing margins free of CIGN have been managed by conization alone. After a median follow-up period of 12 months there is no apparent residual CIGN or invasive disease in this group. Thirteen women have had further surgical procedures (according to protocol) and two have had a hysterectomy for benign gynaecological disorders. Eight further procedures were carried out because the original cone biopsy had margins involved with CIGN, and only one of them was found to have residual CIGN. The other five procedures were carried out solely because of abnormal cytology, only one of them had a diagnosis of CIN 1. A total of 10 women had cytological abnormality following cone biopsy, one had CIGN, one had CIN 1 and a third had CIN 3. CONCLUSIONS: Our preliminary data suggests that when a diagnosis of CIGN is made upon a cone biopsy, further surgery is unnecessary in those women in whom the margins of the cone specimen are free of disease. Cytological and colposcopic follow up, including cytological sampling of the endocervical canal, is recommended for these women.
Four adult patients with at least 8 teeth that had attachment loss of 5 to 10 mm which bled on probing were included in this study. Polymeric tetracycline (TCN) containing fibers were placed and left in the pockets for a period of 10 days. Plasma samples were collected at baseline, 1 hour, 3 hours, 3 days, and 10 days after fiber placement. The mean length of fiber used averaged 187 cm with a range of 160 to 222 cm. The maximum TCN dose per patient averaged 105 mg with a range of 91 to 126 mg producing no detectable serum level greater than 0.1 micrograms/ml. This level was found in 3 of the 4 subjects at 3 hours after fiber placement and in 1 subject at 3 days after fiber placement. Transient and insignificant levels of TCN became available systemically shortly after the placement of multiple fibers. The dose of TCN in each patient was well tolerated and was not associated with any serious adverse effects.
This review summarizes current knowledge about the social sources of differences in blood pressure between blacks and whites in the United States. Genetic variables may play some role in explaining black-white differences in blood pressure, but social factors are more important than genetic ones. I review evidence linking stress, social integration, coping styles, and health behavior (including obesity) to high blood pressure, emphasizing that the distribution of these risk factors is shaped by larger social structures and processes. Effective efforts to reduce stress and improve health practices must not focus only on the individual but must seek to alter the social, economic, and political structures and arrangements that produce disease.
Records of anticoagulation for cardiopulmonary bypass from 58 patients who underwent elective coronary artery revascularization were analyzed to determine whether the harvesting of autologous platelet-rich plasma produces heparin resistance. The effect of preoperative heparin therapy on anticoagulation for cardiopulmonary bypass after harvesting of platelet-rich plasma was also evaluated. Patients were grouped by presence of preoperative heparin therapy and type of blood component harvested before cardiopulmonary bypass, including platelet-rich plasma, autologous whole blood, both, or neither. The dose of heparin required to initiate and to maintain anticoagulation for cardiopulmonary bypass was determined for each patient, and the groups were compared by two-way analysis of variance. Significantly more heparin was required to maintain anticoagulation for cardiopulmonary bypass in the platelet-rich plasma group than in the groups receiving autologous whole blood or no blood products. More heparin was also required to initiate and to maintain anticoagulation for cardiopulmonary bypass after preoperative heparin therapy. These results reinforce the concept that anticoagulation during cardiopulmonary bypass must be carefully monitored, and increased vigilance may be warranted in patients after harvesting of platelet-rich plasma.
This paper examines the association between marital status and psychiatric disorder for Blacks and explores the extent to which these patterns differ from those for Whites. Widowed and separated/divorced Black males and females have higher rates of disorder than the married; never-married Blacks do not have an elevated risk of psychiatric illness. The association between marital status and disorder for White males is similar and stronger than that observed for Blacks. For White women, the separated/divorced have a higher risk of disorder than the married, and unmarried White females have higher rates of the substance abuse disorders, but lower rates of the anxiety disorder than the married. Across all marital status groups, Black males and White males have higher rates of disorder (except for depression), than females. A complex pattern emerges when gender differences in the relative rates of disorder for unmarried Blacks compared to married Blacks are considered. Separated/divorced Black men, widowed Black women, and never-married Black men are worse off than their respective peers. Except for the separated/divorced, opposite patterns are evident for Whites. Directions for further research are outlined.
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In a prospective study concerning the pathogenesis of impaired glucose tolerance and Type 2 (non-insulin-dependent) diabetes mellitus, 346 subjects with no clinical history of diabetes were given a standard 75 g oral glucose tolerance test. The expected positive associations between 120-min plasma glucose concentration and age and body mass index were observed in both sexes and between 120-min plasma glucose and waist/hip ratio in male subjects. An unexpected negative correlation was found between 120-min plasma glucose and height in both sexes (r = -0.23, (95% confidence interval, -0.38 - -0.07) p less than 0.007 for male subjects and r = -0.24, (-0.37 - -0.11) p less than 0.006 for female subjects). These negative associations with height remained significant after controlling for age and body mass index in male subjects but not in female subjects. In the latter a highly significant negative relationship of height with age was recorded (r = -0.33, (-0.45 - -0.20) p less than 0.0001). Comparison between individuals with impaired glucose tolerance and control subjects matched for sex, age and body mass index showed that subjects with impaired glucose tolerance are significantly shorter. Mean (+/- SEM) height in the male subjects with impaired glucose tolerance (n = 29) was 173.4 +/- 1.1 cm vs 176.9 +/- 1.3 cm in control subjects, p = 0.02. In the female subjects (n = 39) mean (+/- SEM) height was 159.4 +/- 1.0 cm vs 162.4 +/- 1.0 cm in control subjects, p = 0.02. The negative relationship between height and glucose tolerance is a new epidemiological observation which has not been previously reported.(ABSTRACT TRUNCATED AT 250 WORDS)
Tongue-based flaps have proved to be satisfactory for closing palatal defects. The bulk of grafted tissue, however, may present problems for the prosthodontist in construction of removable partial dentures. These problems include lack of space and denture support and physical properties of the graft. Careful design of the denture is needed to optimize available space and support. An impression technique that allows differential loading of parts of the oral mucosa is described.