Biomedical subjects

R J Barrett

Publications and source records attributed to R J Barrett.

152 records · Page 9Linked to original sources

PubMedDate not supplied

Effects of pyrithiamin and oxythiamin on acetylcholine levels and utilization in rat brain.

Regional cerebral acetylcholine (ACh) levels and utilization rate were assessed in vivo in rats rendered thiamin deficient using the thiamin antagonists pyrithiamin or oxythiamin. ACh levels were significantly reduced in all brain regions of pyrithiamin treated rats and in the medulla-pons and striatum of oxythiamin treated rats compared to controls. ACh utilization was significantly reduced in the midbrain, striatum and hippocampus of pyrithiamin treated rats, but was reduced only in the striatum of oxythiamin treated rats compared to controls. Thus, there are some reductions in ACh levels and utilization that are unique to pyrithiamin induced deficiency and as such are distinct from oxythiamin/undernutrition related reductions. Since only pyrithiamin produces neurological symptoms, its unique ACh effects may be related to these symptoms.

Acetylcholine↗

PubMedDate not supplied

Effects of training dose on amphetamine drug discrimination: dose-response functions and generalization to cocaine.

Rats were trained to discriminate one of three doses of amphetamine (AM), 0.5, 1, or 2 mg/kg, from vehicle (VEH) in a two-lever, food-reinforced, drug-discrimination task. The purpose of the study was to investigate the nature of the shift of the dose-response curve and generalization to cocaine (COC) as a function of training dose. In order to preclude potential differences among the groups in stimulus control, the three training-dose groups were required to perform the discrimination at high and equivalent levels of accuracy. The shift of the dose-response functions to the right as a function of increasing training dose was not parallel. The slope decreased as training dose increased. There was a dose-dependent increase in AM lever responding to test doses of COC that tended to be affected by training dose. The results suggest that proper evaluation of training-dose effects requires that groups be trained to equivalent levels of stimulus control.

Amphetamine↗

PubMedDate not supplied

Collective danger and individual risk: cultural perspectives on the hazards of medical research.

Changes in medical research ethics in the past two decades have made the communication of risk to potential participants a legal imperative. Using ethnographic data from two different cultures, we examine the hazards associated with medical research in relation to the respective societal contexts that imbue them with meaning. The Iban, a Dayak people indigenous to Borneo, perceive the hazards of participating in research in terms of danger to the collective. In Australia they are construed in terms of risk to individuals. Risk in medical research is one manifestation of a broader notion of 'risk' that is constitutive of the research enterprise itself and, we argue, fundamental to post-industrial society.

Australia↗

PubMedDate not supplied

Use of a retained urethral catheter in three dogs with prostatic neoplasia.

Percutaneous nephrostomy catheters modified by cutting off the tubing connectors were implanted in three dogs with prostatic neoplasia to relieve or prevent stranguria. One catheter was implanted with a guide wire through a perineal urethrotomy, and two catheters were implanted via celiotomy and cystotomy. Morbidity and complications were minimal. Inflammation of the abdominal incision was present from day 4 to day 8 in the dogs with celiotomy. Urinary incontinence was continuous in one dog and intermittent in two dogs. Hematuria occurred in two dogs. The retained urethral catheter was a suitable palliative treatment for urethral obstruction in three dogs with prostatic neoplasia.

Adenocarcinoma↗

PubMedDate not supplied

Discrimination of serotonergic drugs is unaltered in rats prenatally exposed to ethanol.

Pregnant rats were administered intragastrically 4.0 g/kg of ethanol (31.6% v/v) two times per diem on days 10-14 of gestation. A second group of pregnant rats were pair-fed to the ethanol treated group and placebo intubated, while a third group was not intubated. Prenatal ethanol exposure resulted in both reduced birth weight, weaning weight, and percent of pups surviving from birth to weaning. The treatment did not, however, affect the number of pups delivered. Two male pups approximately 60 days old were randomly selected from each litter for testing in a 2-lever drug discrimination task. One pup was trained to discriminate quipazine (3.0 mg/kg) from saline, while the second was trained to discriminate 5-HTP (30.0 mg/kg) + Ro4-4602, a peripheral decarboxylase inhibitor, from saline. Following acquisition, discrimination behavior was shown to be both dose and time dependent. None of these behavioral measures were altered by prenatal ethanol exposure.

5-Hydroxytryptophan↗

PubMedDate not supplied

After treatment ends: neutral time.

For persons diagnosed with cancer, the remission period may be marked by increased anxiety and distress. While the medical team may view remission as an eagerly anticipated milestone, the decreased medical surveillance during this time can cause a heightened fear of recurrence for the patient. One author has called this period of remission "neutral time," a time characterized by uncertainty. The safety signal hypothesis, developed by Martin Seligman, may help to explain the anxiety experienced by some patients during the remission period. Because cancer is frequently a silent disease with no overt symptoms, patients in remission often have no safety signal to indicate that the disease will not return. A case study is presented and discussed in light of these two concepts.

Anxiety↗

PubMedDate not supplied

Endometrial cancer risk in relation to serum lipids and lipoprotein levels.

Blood lipids are useful biochemical indicators for assessing the risk of a number of chronic diseases, particularly those associated with obesity. In a multicenter case-control study that included 256 cases and 185 controls less than 75 years old, we studied the risk of endometrial cancer in relation to serum cholesterol, low density lipoprotein cholesterol, high density lipoprotein cholesterol, and triglycerides. Contrary to expectation, blood lipids were, in general, lower among cases compared with controls. The effects of low blood lipids, specifically cholesterol and low density lipoprotein cholesterol, were limited to older women (> or = 55 years). Risk of the disease in this subgroup of 177 cases and 110 controls was increased 3-4-fold among those with the lowest cholesterol or low density lipoprotein cholesterol values. For example, after adjustment for age, education, smoking status, obesity, and body fat distribution, the relative risks of endometrial cancer across decreasing quartiles of serum cholesterol were 1.0, 2.5, 2.4, and 4.2 (P for trend < 0.01). We examined blood lipid levels by disease stage. The low lipid values of older cases did not appear to be a consequence of the disease. While we cannot rule out the possibility that hypocholesterolemia is a predisposing factor for endometrial cancer, there is no obvious biological explanation for the inverse association.

Adult↗

PubMedDate not supplied

Relation of endometrial cancer risk to past and contemporary body size and body fat distribution.

In a multicenter case-control study that included 403 cases and 297 controls, we examined the relation of past and contemporary body size, including body fat distribution, to the risk of endometrial cancer. The relative contributions of past and contemporary body size were assessed by examining weight and height histories provided by the subjects. Anthropometric indicators thought to reflect early environmental influences (e.g., height and sitting height), current weight, and fat distribution patterns were measured directly. Height was not a risk factor for endometrial cancer, but inexplicably, sitting height was inversely associated with risk. Weight during early adulthood appeared to be directly related to disease risk, but the association was explained by contemporary weight and thus weight gain during adulthood. While contemporary weight was associated with risk of endometrial cancer, the effect was restricted to those in the top quartile. Women whose measured weight at interview exceeded 78 kg had 2.3 times the risk of those weighing less than 58 kg (95% confidence interval, 1.4 to 3.7). Upper-body obesity (waist-to-thigh circumference ratio) was a risk factor independent of body weight. After adjustment for weight, the relative risks of endometrial cancer across increasing quartiles of upper-body obesity were 1.0, 1.5, 1.8, and 2.6 (P for trend < 0.001). These data indicate that both obesity and the distribution of adipose tissue accumulated during adult life increase endometrial cancer risk substantially.

Adipose Tissue↗