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Biomedical subjects

E A Thomas

Publications and source records attributed to E A Thomas.

At least 19 recordsLinked to original sources
PubMed1992

Erythrocyte metallothionein response to dietary zinc in humans.

The response of erythrocyte metallothionein to dietary zinc in human subjects was evaluated in a controlled metabolic protocol including standard indices of zinc status. Fifteen male subjects, age 27 +/- 3.6 y, participated in a 90-d, four-phase study consisting of acclimation (7 d; 15 mg Zn/d), treatment (6 wk; either 3.2, 7.2 or 15.2 mg Zn/d), depletion (12 d; 0.55 mg Zn/d) and supplementation (30 d; self-selected diet plus 50 mg Zn/d) phases. During the treatment phase erythrocyte metallothionein decreased in the group fed 3.2 mg Zn/d. Erythrocyte metallothionein decreased during the depletion phase (46 +/- 10%) to below the normal concentration in all groups and increased in the supplementation phase. Plasma zinc concentration decreased in the group fed 3.2 mg Zn/d during the treatment phase relative to the acclimation phase. Erythrocyte zinc decreased in all groups during the depletion phase relative to the treatment phase, and then increased during the supplementation phase. These data suggest that erythrocyte metallothionein can be used as a measure of status in severe zinc depletion and that comparing the change in erythrocyte metallothionein over a 6-wk period can differentiate between low and adequate levels of dietary zinc intake.

Adult↗
PubMed1992

Conversion of N-(2-chloroethyl)-4-piperidinyl diphenylacetate (4-DAMP mustard) to an aziridinium ion and its interaction with muscarinic receptors in various tissues.

A 2-chloroethylamine derivative [N-(2-chloroethyl)-4-piperidinyl diphenylacetate (4-DAMP mustard)] of the selective muscarinic antagonist N,N-dimethyl-4-piperidinyl diphenylacetate (4-DAMP) was synthesized, and its conversion to an aziridinium ion and interaction with muscarinic receptors was investigated. When dissolved in aqueous solution at pH 7.4 and 37 degrees, 4-DAMP mustard released an equivalent amount of chloride. The release of chloride was consistent with a first-order process having a half-time of 5.7 min. The aziridinium ion reached a peak concentration at 32 min, corresponding to 75% of the initial concentration of 4-DAMP mustard. When homogenates of rat brain, heart, and submaxillary gland were incubated with 4-DAMP mustard (9 nM) for 1 hr, washed extensively, and then assayed for muscarinic receptor binding properties, a 56% decrease in the binding capacity of N-[3H]methylscopolamine in the heart and brain and a 71% decrease in the gland were observed, without a significant change in the dissociation constants. The affinity of 4-DAMP mustard and its transformation products for muscarinic receptors was determined in competitive binding experiments with N-[3H] methylscopolamine, and the results show that the aziridinium ion of 4-DAMP mustard was the most potent form, compared with the parent 2-chloroethylamine (4-DAMP mustard) and the alcoholic hydrolysis product. The rates of receptor alkylation by 4-DAMP mustard were measured in the rat heart and gland. Virtually no alkylation (less than 1%) occurred in the heart at a 4-DAMP mustard concentration of 1.6 nM, after 30 min, whereas almost 50% alkylation was observed in the gland under the same conditions. Almost complete alkylation of receptors in the gland could be achieved at a 4-DAMP mustard concentration of 200 nM, after 1 hr. Treatment of the isolated rat ileum with 4-DAMP mustard caused an irreversible blockade of contractions elicited by the muscarinic agonist oxotremorine-M, and this blockade persisted after extensive washing. The results presented here show that 4-DAMP mustard forms an aziridinium ion that binds irreversibly to muscarinic receptors and exhibits selectivity for M3, compared with M2 muscarinic receptors.

Alkylation↗
PubMed1991

The role of ultrasound in the early diagnosis and management of heterotopic bone formation.

Heterotopic bone formation (HBF) is one of the many causes of painful limb swelling and is well recognized as posing clinical, radiological, and pathological diagnostic difficulties. We have evaluated the use of sonography to determine its role in reaching a diagnosis at a time when symptoms are maximal and the radiological diagnostic features absent. Serial ultrasound examination identified unique 'zone phenomea' in a heterogeneous group of eight patients before the classic radiological features appeared. The zone transformation matches the evolution and maturation process described pathologically and forms the basis of an early definitive diagnosis in all cases. The sonographic features are specific for the condition, unlike the scintigraphic appearances. Although CT confirms the peripheral location of the calcification, the low cost, safety, and general availability of ultrasound scanning make it the optimum imaging method for diagnosing and monitoring heterotopic bone formation.

Adult↗
PubMed1990

Duplex ultrasound of the abdominal aorta--a neglected tool in aortic dissection.

The use of duplex ultrasound for the diagnosis and assessment of abdominal aortic dissection and visceral arterial involvement is discussed. Ultrasound is simple and non-invasive and may be superior to aortography in diagnosis; it should be performed after ultrasound assessment of the aortic root. It also provides an effective means of follow-up evaluation if conservative treatment is employed. Three cases are discussed in whom there was no operative intervention. In one case, aortography failed to make a positive diagnosis of aortic dissection. The diagnosis was made by ultrasound in all three cases, one of whom was found subsequently to have Marfan's syndrome.

Adult↗
PubMed1989

Nucleoid halo expansion indirectly measures DNA damage in single cells.

A simple test has been developed that measures how much DNA damage has occurred in a single mammalian cell. The procedure is based on the microscopic examination of "halos" of nucleoids that adhere to coverslips. Nucleoids are produced by flowing salt solutions containing detergents over the attached cells. The nucleoid halos are thought to be a tangle of loops of free DNA that emanate from the remnants of the nucleus. When visualized by staining with ethidium bromide the nucleoid halos first expand, and then contract as the concentration of ethidium increases. Exposure of nucleoids to very low levels of DNA chain-breaking treatments results in the incremental expansion of the halos to a maximum of 15 microns or more. Our assay is based upon quantitating the degree of halo expansion. If intact cells are exposed to DNA-damaging treatments, then allowed increasing periods of post-treatment growth before forming nucleoids, the DNA repair processes result first in expanded and then in contracted halos. By admixing a supercoiled plasma DNA of known length (38 kb) to nucleoids with contracted halos, the fractional halo expansion and the fraction of surviving plasmid supercoils can be measured from the same solution. Use of photodynamic DNA damage showed that the halo expansion was 11.6 times more sensitive than plasmid relaxation. Use of gamma-irradiation showed that the halo expansion was 3.6 times more sensitive than plasmid relaxation. The latter value demonstrates that one break per 137,000 bp results in the expansion of the halos to 63% of their maximal value. We estimate that this method will detect about 5000 breaks per nucleus containing 5 x 10(9) bp.

Animals↗
PubMed1987

Behavior-dependent contexts for repeated plays of the Prisoner's Dilemma: II. Dynamical aspects of the evolution of cooperation.

Iterated Prisoner's Dilemma models are proposed in which, at any trial, the probability of staying in the game depends on the outcome of the previous trial. If a player's choice depends on its own play (cooperate or defect) at the previous trial, it becomes possible for cooperative strategies to increase when rare in a population of egoists. A dynamic analysis is used to demonstrate that stable polymorphisms may result, and may involve more strategies than just Tit-for-Tat and all-Defect. The tendency for clustering among like strategists to enhance their initial increase when rare is also explored dynamically.

Behavior↗
PubMed1987

The accuracy of digital subtraction angiography for the quantification of atherosclerosis.

Digital subtraction angiography (DSA) allows the degree of arterial patency or stenosis to be rapidly quantified. We have assessed the accuracy with which a single-plane DSA system is able to quantify area patency by densitometric and geometric methods. Arterial phantoms were designed to test for systematic error; intra-arterial DSA images of critical lesions of the carotid bifurcation and the lower abdominal and peripheral vessels were used to determine intra- and interobserver reproducibility. The densitometric method, which was more accurate than the geometric method, had a mean systematic error of up to 4% and a mean intra-observer variability of about 15% (coefficient of variation). We have identified the principal sources of inaccuracy and ways in which it may be reduced.

Arteriosclerosis↗
PubMed1986

Strategic deworming for spring-calving beef cow/calf herds.

Strategic application of an anthelmintic was tested during the 1982 grazing season as part of the continued study of the epidemiology of beef cattle parasitism in central Missouri. Forty Hereford and Hereford X Simmental cow/calf pairs were assigned to 2 treatment groups. The 20 cow/calf pairs in group 1 were nonmedicated controls. After calving in mid-March, the 20 cows in group 2 were drenched with a 10% suspension of the anthelmintic fenbendazole (10 mg/kg of body weight). Ten cow/calf pairs were placed on each of four 20-acre fescue or orchard grass pastures in mid-May. Cows and calves in treatment group 2 were drenched with the 10% fenbendazole suspension (5 mg/kg) in mid-July. Body weights and fecal specimens were obtained monthly. Nematode egg counts in cow and calf fecal specimens collected monthly were significantly (P less than 0.05) lower in treatment group 2 than in treatment group 1. Numbers of larvae cultured for speciation revealed that Ostertagia ostertagi was the predominant nematode species. Developmental arrest of O ostertagi was found to be significantly (P less than 0.05) greater than zero from mid-May to mid-July. An important significant difference (P less than 0.01) was shown in body weights of calves, with the calves in treatment group 2 having a higher mean weight gain of 22.5 kg in adjusted 205-day weaning weights, and a higher mean daily gain of 0.11 kg. Weight maintenance of cows was not affected significantly by anthelmintic treatment. Nematode egg counts in monthly cow and calf fecal specimens were not significantly different between those animals on different pastures.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Training in geropsychology at the doctoral level: 1984.

To study type and amount of training in geropsychology available to students in APA-approved doctoral programs in clinical and counseling psychology, a questionnaire was mailed to all such programs in 1984. Response rate was 71 of 132 (59%) for clinical programs and 27 of 37 (73%) for counseling programs. Very little difference was found between responses of clinical and counseling programs and between this 1984 survey and one conducted in 1975-76. There seems to be a very small increase in training opportunities for psychology students in geropsychology in 1984 at the doctoral level.

Education, Graduate↗
PubMed1985

Maggot control.

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Air Pressure↗