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Biomedical subjects

D R Thomas

Publications and source records attributed to D R Thomas.

At least 19 recordsLinked to original sources
PubMed1995

Preoperative assessment of older adults.

Caring for older patients who need surgery presents challenging medical situations. The clinical paradigm involves identifying coexisting disease, defining the urgency of the intervention, and predicting postoperative complications based on the type of surgery planned. The prime function of the medical consultant is searching for correctable medical conditions. The consultant must carefully identify coexisting and comorbid conditions. Emergency surgery should be avoided, if possible, by elective planning. The risk of surgery varies with the procedure. Non-body cavity surgery, with the exception of hip fracture repair, is usually tolerated well. Age is a risk factor for surgery, but coexisting disease is more important than age alone. The net effect of improvements in surgical outcome advances the age at which surgical risk becomes prohibitive.

Age Factors↗
PubMed1995

The risk of acquiring Q fever on farms: a seroepidemiological study.

OBJECTIVES: To determine the occupational risk of Q fever. DESIGN: Cohort study. SETTING: Community: five English local authority districts. SUBJECTS AND METHODS: Prevalence and incidence of immunoglobulin G (IgG) specific antibody to Coxiella burnetii phase II antigen was measured in a representative (study) cohort of farm workers in the United Kingdom, and detailed exposure data were collected. Also seroprevalence of Q fever in a (control) cohort of police and emergency service personnel was measured. RESULTS: Prevalence was significantly (P < 0.01) higher in the study cohort (105/385 v 43/395). During the first 12 month period after enrollment no seroconversions were found (upper 95% confidence limit: 1318/100,000/year). During the second 12 month period after enrollment two seroconversions were found, equalling an incidence of 813/100,000/year (95% confidence interval (95% CI) 98-2937/100,000/year). No association was found between seroprevalence and age. In the study cohort, extent of total contact with farm animals seemed more important than exposure to any specific animal: full time employees were more than four times more likely to be antibody positive than part time employees (P < 0.05). Exposure to cattle, but not sheep, goats, cats, raw milk, and hay (all reported sources of Q fever) was associated with being positive to Coxiella burnetii IgG by univariate analysis but this association was not independent of total farm animal contact. CONCLUSIONS: The risk of Q fever on livestock farms is related to contact with the farm environment rather than any specific animal exposure. The absence of an increasing prevalence with age suggests that exposure may occur as clusters in space and time (outbreaks).

Adolescent↗
PubMed1995

Prevention and rehabilitation of overuse injuries of the elbow.

Rehabilitation from injury and prevention of injury are terms that describe differing aspects of the same challenge. The clinician must be continually aware of the principles of rehabilitation and their order of priority (prevent further damage, restore motion, restore strength, reestablish coordination) while supervising patients' progress toward their goals. If patients are made aware of these principles at an early stage, and taught to take as much responsibility as possible for their own rehabilitative course, they will be more likely to reach their own ideal compromise of safety and speed of progress. In addition to helping with rehabilitation from injury, knowledge and self-awareness that patients obtain during this process may help in the prevention of future injuries.

Cumulative Trauma Disorders↗
PubMed1992

Salivary testosterone levels and major depressive illness in men.

Studies of testosterone levels in patients with major depressive illness have produced varying results, plasma levels usually being reported. Saliva levels reflect 'free' plasma testosterone, and a pilot study of 11 men with major depression with melancholia, who underwent a standard dexamethasone suppression test, is described. There were no significant differences in testosterone levels compared with an age-matched control group. In the patient group, pre-dexamethasone levels correlated significantly and negatively with depression ratings on the 21-item Hamilton and the Montgomery and Asberg depression scales, and also with state anxiety measured on the Spielberger scale.

Adult↗
PubMed1992

Performance of Polypay, Coopworth, and crossbred ewes: II. Survival and cumulative lamb and wool production over 4 years.

Six ewe genotypes, generated by mating Coopworth (C), Polypay (P), and Suffolk (S) rams to P and Coopworth-type (Ct) ewes, were exposed to Hampshire rams for spring lambing from 1987 through 1990. Data from 1,013 exposures and 973 resultant lambings were used to analyze reproductive traits and cumulative ewe productivity over 4 yr. Ewe body and fleece weights were also analyzed. Ewes from S sires weaned the heaviest lambs and ewes from P sires weaned the largest number of lambs, resulting in similar total weight of lamb weaned per ewe mated. Coopworth-sired ewes weaned the least total weight of lamb per ewe mated. Ewes weaning twins produced 54% more total litter weight per ewe than those weaning singles. Annual ewe survival averaged 95%, ranging from 93% for S x P and C x P ewes to 97% for P x Ct and C x Ct ewes. When cumulative number and weight of lamb produced was assessed on the basis of all ewes starting the trial, P-sired ewes were highest, followed in order by daughters of S and C sires. Suffolk-sired ewes (67 kg) were 13% heavier than daughters of P rams and 19% heavier than daughters of C rams. Adjustment of lamb production for ewe metabolic body size resulted in C-sired ewes being more efficient than the heavier S-sired ewes. Coopworth-sired ewes produced 32% more wool than ewes sired by the other two breeds. Differences in wool production between ewes weaning one or two lambs were small.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

A comparison of generalization functions and frame of reference effects in different training paradigms.

Six experiments were carried out to compare go/no-go and choice paradigms for studying the effects of intradimensional discrimination training on subsequent measures of stimulus generalization in human subjects. Specifically, the purpose was to compare the two paradigms as means of investigating generalization gradient forms and frame of reference effects. In Experiment 1, the stimulus dimension was visual intensity (brightness); in Experiment 2, it was line orientation (line-angle stimuli). After learning to respond (or to respond "right") to stimulus value (SV) 4 and not to respond (or to respond "left") to SV2 (in Experiment 1) or SV1 (in Experiment 2), the subjects were tested for generalization (recognition) with an asymmetrical set of values ranging from SV1 to SV11. Go/no-go training produced peaked gradients, whereas choice training produced sigmoid gradients. The asymmetrical testing resulted in a gradual shift of the peak of responding (go/no-go group) or in the point of subjective indifference (PSI; choice group) toward the central value of the test series; thus, both paradigms revealed a frame of reference effect. The results were comparable for the quantitative (intensity) and the qualitative (line-angle) stimulus dimensions. Experiment 3 compared the go/no-go procedure with a yes/no procedure in which subjects responded "right" to SV4 and "left" to all other intensities and found no differences between these procedures. Thus the difference in gradient forms in go/no as opposed to (traditional) choice paradigms depends on whether one or two target stimuli are used in training. In Experiment 4, in which visual intensity was used, the shift in the PSI following choice training varied positively with the range of asymmetrical test stimuli employed. In Experiment 5, also with visual intensity, the magnitude of the peak shift following go/no-go training varied as a function of overrepresenting a high or a low stimulus value during generalization testing. Experiment 6, with line angles, showed that the PSI following choice training varies in a similar way. The frame of reference effects obtained in these experiments are consistent with an adaptation-level model.

Discrimination Learning↗
PubMed1991

The epidemiology of Nematodirus battus--is it changing?

Natural populations of 3rd-stage Nematodirus battus larvae were present on pastures in North Wales throughout the year; highest numbers were present in late spring, with smaller peaks occurring in autumn. Inter-site variation was observed in the timing and magnitude of these peaks. Hatching on experimental plots occurred 2 months to 2 years following deposition of eggs. Intraspecfic and inter-site variation occurred in the timing, and inter-site variation occurred in the magnitude, of the mass hatch on upland and lowland experimental plots. Arrested 4th-stage N. battus were recovered from Welsh Mountain lambs. Percentage arrest and number of arrested worms was greatest during winter and early spring. The prevalence and intensity of N. battus infection in 1-, 2- and 3-year-old Welsh Mountain ewes was low. The plasticity exhibited in the parasite's life-history is discussed in relation to potential changes in the epidemiology of nematodiriasis.

Animals↗
PubMed1991

Peak shift revisited: a test of alternative interpretations.

In Experiment 1, 2 groups of human subjects were trained to respond to 1 of 2 light intensity stimuli, S2 or S4, and then were tested for generalization with a randomized series of increasing values from S1 to S11. Both groups, including the group trained to respond to dimmer value, showed peak shifts to a brighter more centrally located test stimulus. In Experiment 2, which used line angle stimuli, both the size of the difference between S+ and S- and the range of test stimuli that extended beyond S+ were varied. The larger the S(+)-S- separation and the larger the range, the greater was the peak shift obtained. In Experiment 3, training involved an S- (line angle) surrounded by 2 S+ values with testing symmetrical about the training values and covering either a narrow or a wide range. The wide range produced greater peak shifts in both directions from S-. All 3 experiments support an adaptation-level interpretation of intradimensional discrimination learning and generalization test performance in human subjects. Related work with animals suggests the presence of similar processes.

Adult↗
PubMed1990

Postantibiotic colonization with Clostridium difficile in nursing home patients.

Clostridium difficile causes pseudomembranous colitis and is responsible for 20% to 25% of cases of postantibiotic diarrhea. In an earlier study, nursing-home patients with C. difficile infection were noted to have a high mortality rate. Because most of these infected patients had been treated with antibiotics, it was not clear whether this high mortality rate was associated with C. difficile infection or simply with antibiotic treatment. A prospective study was carried out to determine the rate of postantibiotic C. difficile colonization and risk factors for infection in patients in a 233-bed long-term care facility, as well as to determine whether C. difficile infection is associated with increased mortality. During a six-month period 150 courses of antibiotics were prescribed for 108 patients. Stool specimens were collected from 36 (33%) patients following the first course of antibiotic treatment, and 12 (33%) were infected with C. difficile. Risk factors for infection included ward location and stool incontinence. Age, body-mass index less than or equal to 18 kg/m2, and diagnoses of dementia and pressure scores tended to be associated with infection, but not significantly. Early mortality rates did not differ, but 12-month mortality for the infected patients was higher (83% vs 50%, P = .05). Therefore, we conclude that postantibiotic C. difficile infection serves as a marker of death in nursing-home patients, one that can be differentiated from the risk of antibiotic treatment alone. This increased death rate may be related in part to clinically unrecognized pseudomembranous colitis or, alternatively, to absorption of C. difficile toxins or even endotoxin from the gut lumen into the systemic circulation.

Adult↗
PubMed1989

Protein-losing enteropathy associated with Clostridium difficile infection.

A commercially available radial immunodiffusion assay was used to measure serum alpha-1-antitrypsin levels in stool samples from subjects aged over 60 years as a marker of protein-losing enteropathy. alpha 1-antitrypsin was found in all of 12 patients with colonoscopy-confirmed pseudomembranous colitis, 6 of 14 (43%) patients with Clostridium difficile diarrhoea without pseudomembranes, 6 of 12 (50%) nursing-home patients culture-positive for Cl difficile but negative for its cytotoxin, and none of 15 healthy control subjects. It is concluded that serum protein loss into the gastrointestinal tract can occur as a result of Cl difficile infection, that its presence correlates with the severity of disease, and that it may occur even in the absence of diarrhoea. The diagnosis of protein-losing enteropathy should be considered for all patients with Cl difficile infection, particularly elderly nursing-home patients, in whom the risk of Cl difficile disease and the frequency of severe malnutrition are high.

Adolescent↗
PubMed1989

Differential diagnosis of dementing diseases.

The prevalence of dementia in the aging population is reaching epidemic proportions. Normal aging alone does not result in intellectual decline. The author observes that the clinical presentation of cognitive dysfunction involves a complex array of differential diagnoses, illustrated by the first six months' experience in the UMC Geriatric Assessment Clinic. He notes that dementias may be grouped into static, reversible, or progressive types, and he outlines a classification system for dementing illnesses as an aid in clinical evaluation.

Aged↗
PubMed1988

Peripheral serotoninergic receptor sensitivity in senile dementia of the Alzheimer type.

Platelet aggregation induced by 5-hydroxytryptamine (5-HT) was used as a measure of the functional responsiveness of peripheral 5-HT receptors in controls and drug-free patients suffering from senile dementia of Alzheimer type (SDAT). No significantly different aggregatory response (5-HT/ADP ratio) was noted between the two groups of subjects. If the receptor mediating this response is a 5-HT2 receptor, there is no evidence to suggest that the functional activity of this system is abnormal in SDAT.

Aged↗