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Biomedical subjects

D R Thomas

Publications and source records attributed to D R Thomas.

At least 91 records · Page 5Linked to original sources
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

Does conditional discrimination learning by pigeons necessarily involve hierarchical relationships?

Four experiments demonstrate that when putative conditional and discriminative cues are presented simultaneously in the single reversal procedure, it is not possible to ascribe a uniquely conditional or uniquely discriminative function to either of the cues. In Experiment 1, pigeons were trained to respond to a blue key and not to a red key while the houselight was on; then in a different session they learned the reversal of this discrimination with the houselight off (single reversal). Separate groups were tested for color generalization with houselight conditions alternating in blocks of trials or for houselight intensity generalization with blue and red key colors alternating in blocks of trials. Both test procedures revealed a conditional relationship between houselight and key color conditions. Experiment 2 produced the same result following training in which the key colors were held constant across training sessions while the houselight and no houselight conditions varied within sessions. In Experiment 3, separate groups were trained with the two procedures but were tested with randomly ordered combinations of key colors and houselight intensities. The two groups yielded indistinguishable bidimensional generalization gradients with peaks at both previously reinforced stimulus combinations. In Experiment 4 the subjects were switched from one of these training procedures to the other with no decrement in their discriminative performance. We conclude that for successive discriminations between conditional- and discriminative-stimulus combinations, the notion of a hierarchical relation between conditional and discriminative stimuli must be extended to include a symmetrical relationship or the notion should be abandoned altogether.

Journal Article↗
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↗
PubMed1988

Fifteen-year interval spirometric evaluation of the Oregon predictive equations.

The 1969 Oregon spirometric predictive equations were evaluated by retesting 199 of the 988 original sample population after 15 years. The 1969 data were used to test for sample bias between the retested and not-retested groups. There was no significant difference in mean values for age, height, or test results except for a five-year age difference in men. Regression analysis of residuals and the differences between calculated and predicted values of annual decrements of FVC, FEV1, and FEF25-75% on age revealed no statistically significant age trend. Although residual means were statistically significant for FVC and FEV1 for men and FVC and FEF25-75% for women, the differences between calculated and predicted annual decrements were significant only for women in FEF25-75%. Although group performance was accurately predicted for most tests, test SDs and SEMs demonstrated considerable individual variation. Lower limits of normality are suggested to assist in evaluating previously-tested patients.

Adult↗
PubMed1988

Assessment and management of agitation in the elderly.

The management of agitated behavior in the elderly represents one of the major challenges in geriatric medicine. Inappropriate verbal, vocal, or motor activity often results in problem behavior that burdens caregivers or nursing home staff. A careful differential diagnostic approach to agitated behavior is imperative to avoid misdiagnosis. The misuse of psychoactive drugs often begins with an unclear idea of the underlying pathophysiology. Treatment should be combined with an explicit establishment of therapeutic goals and a precise understanding of the pharmacological profiles of commonly used drugs.

Aged↗
PubMed1987

Biochemical effects of the antidepressant paroxetine, a specific 5-hydroxytryptamine uptake inhibitor.

Paroxetine was shown to be a potent (Ki = 1.1 nM) and specific inhibitor of [3H]-5-hydroxytryptamine (5-HT) uptake into rat cortical and hypothalamic synaptosomes in vitro. Lineweaver-Burk kinetic analysis determined that this inhibition was competitive in nature, implying a direct interaction with the 5-HT uptake transporter complex. Oral administration of paroxetine produced a dose-related inhibition of [3H]-5-HT uptake (ED50 = 1.9 mg/kg) into rat hypothalamic synaptosomes ex vivo with little effect on [3H]-l-noradrenaline (NA) uptake (ED50 greater than 30 mg/kg). This selectivity for 5-HT uptake was maintained after oral dosing for 14 days. Paroxetine (ED50 1-3 mg/kg PO) prevented the 5-HT depleting effect of p-chloroamphetamine (PCA) in rat brain, demonstrating 5-HT uptake blockade in vivo. Radioligand binding techniques in rat brain in vitro showed that paroxetine has little affinity for alpha 1, alpha 2 or beta adrenoceptors, dopamine (D2), 5-HT1, 5-HT2 or histamine (H1) receptors at concentrations below 1000 nM. Paroxetine demonstrated weak affinity for muscarinic receptors (Ki = 89 nM) but was at least 15 fold weaker than amitriptyline (Ki = 5.1 nM). Paroxetine, therefore, provides a useful pharmacological tool for investigating 5-HT systems and furthermore should be an antidepressant with reduced tricyclic-like side-effects.

Animals↗
PubMed1987

Teaching medical decision analysis: the hepatitis B vaccine.

The process of formal decision analysis is illustrated by using the case of the hepatitis B vaccine in a computer program designed to teach both subjects to medical students. The software presents the medical facts, determines personal risks, allows input of personal values and calculates utilities for the various branches of the decision tree. There are three possible choices: vaccinate; screen first for antibodies against the hepatitis B virus and vaccinate only if negative; and wait (do not vaccinate). The decision with the utility of the highest numerical value is assumed to be the best under the given set of circumstances. Unlike commercial packages, this software contains the information internally and does not require that the user be familiar with either medical decision analysis or with the medical aspects of hepatitis. The program is available for PC's.

Decision Making, Computer-Assisted↗
PubMed1987

Physician awareness of cost under prospective reimbursement systems.

The failure of some strategies to reduce physician use of costly hospital services has been attributed in part to retrospective reimbursement systems. However, anticipation of changes in the reimbursement structure has led to speculation that a different environment might lead to increased cost awareness by physicians. To measure the impact of prospective reimbursement systems on physician awareness of cost, the authors surveyed 46 medicine residents and faculty at a medical center. Data show that only 34% were able to correctly estimate common charges and 24% less common charges. In the early stages of prospective reimbursement, there has been no increased physician awareness of cost.

Cost Control↗
PubMed1987

Thyroid status in senile dementia of the Alzheimer type (SDAT).

Thyroid function was investigated in a group of 21 patients with severe senile dementia of the Alzheimer type (SDAT) and in a group of 17 age and sex matched normal controls. Free thyroid hormone levels (triiodothyronine (T3) and thyroxine (T4) were measured, as were also the thyrotrophin (TSH), prolactin (PRL) and growth hormone (GH) responses to thyrotrophin releasing hormone (TRH)). When compared to controls, patients demonstrated a significantly lower free T3 value (but not free T4), a blunted TSH response to TRH, slightly elevated basal PRL and GH values and a small GH response to TRH. However, all differences were small in biological terms and were within the laboratory's normal range. This emphasizes the relative normality of neuroendocrine function, particularly thyroid status, in SDAT.

Aged↗