PubMed Health⌕ Search

Biomedical subjects

A D Williams

Publications and source records attributed to A D Williams.

At least 19 recordsLinked to original sources
PubMed1994

A computer simulation for learning about the physiological response to exercise.

An interactive computer program written for IBM-compatible microcomputers, which simulates the physiological response to graded exercise in healthy individuals, is described. The program presents high-resolution graphic data (heart rate, pulmonary ventilation, oxygen consumption, and blood lactate concentration) in a form comparable to that of a chart recorder display. Data are derived from an empirical model that allows users to select certain parameters of the subject they wish to investigate, including sex, age, height, weight, and level of training. Measurements may be taken directly from the monitor screen by use of the cross-hair cursor facility provided. The program has been positively evaluated in use by undergraduate students and shown to be an effective teaching aid. The potential use of the software in light of these findings is discussed.

Adolescent↗
PubMed1990

Hyperlipidaemia and atherogenesis.

Hyperlipidaemia has become generally accepted as a cause of coronary artery atherosclerosis, arterial occlusion and subsequent myocardial infarction. This may be true in a few people with lipid intolerance, but for the majority, hyperlipidaemia represents a normal physiological response to another pathological process. One such disease process involves the vessel wall, which appears to suffer injury. The cause of the injury may be associated with abnormal movement in the wall and this in turn can be provoked by stress. A hypothesis encompassing these observations is proposed. It would therefore appear that hyperlipidaemia is not a cause of arterial disease, but as part of normal homeostasis, it can be a risk indicator. It is dangerous to consider hyperlipidaemia as a cause of myocardial infarction as this leads to inappropriate treatment. The lowering of cholesterol and low density lipoproteins (LDL) by any means other than sensible dieting may be likened to attempts to lower elevated white blood cell counts in cases of bacterial pneumonia, without treating the pneumonia.

Arteriosclerosis↗
PubMed1981

Heterogeneity of the rabbit collecting tubule: localization of mineralocorticoid hormone action to the cortical portion.

This study was designed to examine the sodium, potassium, and chloride transport rates across the cortical and outer medullary collecting tubule and to localize the action of mineralocorticoid hormone. Rabbit collecting tubules were dissected from the cortex (CCT), the outer stripe of the outer medulla (OMCT0), or the inner stripe of the outer medulla (OMCTi). From normal rabbits, the transepithelial voltage was -20.8 +/- 2.7 mV in CCT, -4.2 +/- 1.4 mV in OMCT0, and +10.6 +/- 2.3 mV in OMCTi. From DOCA-treated rabbits, only the CCT voltage was different (-42.9 mV). Net sodium absorption across the CCT increased ith DOCA-treatment from 23 +/- 5 to 54 +/- 8 pEq . mm-1 . min-1, whereas net potassium secretion increased from 15 +/- 2 to 43 +/- 5 pEq . min-1 . min-1. Net chloride absorption was significant only in DOCA-treated rabbits. The OMCTi, in contrast, displayed no net transport of sodium, potassium, or chloride and had a lower rate coefficient for sodium efflux than did the CCT. DOCA treatment had no effect on any transport rate measured in this segment. The OMCT0 has small potassium secretion, which did not increase with DOCA treatment. The collecting tubule is heterogeneous along its length with respect to ion transport. Mineralocorticoid-hormone-sensitive sodium absorption is present predominantly, if not exclusively, in the cortical collecting tubule.

Animals↗
PubMed1980

Echinobothrium bonasum sp. n., a new cestode from the cownose ray, rhinoptera bonasus (Mitchill 1815), in the western North Atlantic.

Echinobothrium bonasum sp. n. is described from the cownose ray, Rhinoptera bonasus (Mitchill), taken in Atlantic coastal waters of Chesapeake Bay, Virginia, and off Sakonnet Point, Rhode Island. This species can be distinguished from all others by the following combination of characters: 14 hooklets armature of 11 large hooks, six in the anterior row and five in the posterior row, flanked by 12 to 14 hooklets per side; 24 to 25 spines per row on the cephalic peduncle; 24 to 31 testes per segment, and, wide vitelline bands that overlap the testicular field.

Animals↗
PubMed1977

Quantitative histochemical studies of the hypothalamus enzymes of acetylcholine metabolism.

The quantitative histochemical distribution of acetylcholinesterase and choline acetyltransferase activity has been measured in individual hypothalamic nuclei and median eminence, as well as in entire hypothalamic sections by a mapping technique. There was an 18-fold range of nuclear choline acetyltransferase activity with highest activities in the lateral preoptic nucleus and median eminence. There was a nine-fold range of nuclear acetylcholinesterase activity with highest activities in the lateral preoptic and magnocellular nuclei and lowest activity in the median eminence. The substantial gradients of choline acetyltransferase activity found in the hypothalamus indicate the importance of using a technique that provides an objective, permanent record of contiguous sample locations thereby allowing detailed analysis of tissue areas using, but not dependent on, anatomical boundaries.

Acetylcholinesterase↗
PubMed1977

Glucose and 3-O-methylglucose protection against alloxan poisoning of pancreatic alpha and beta cells.

Alloxan infused into the isolated perfused rat pancreas caused transient insulin secretion release. Alloxan poisoning also prevented subsequent induction of glucose-mediated unsulin release and also prevented the inhibition of glucagon release by glucose. Glucose or 3-O-methylglucose infused simultaneously with alloxan protected the alpha- and beta-cell, allowing subsequent glucose inhibition of glucagon secretion and stimulation of insulin release. The above alloxan effects were dose-related, the alpha-cell being one fourth as sensitive to alloxan as the beta-cell. The data indicate that (1) alloxan and glucose suppression of amino-acid-stimulated glucagon secretion is independent of concomitant insulin secretion; (2) alloxan, like glucose, affects alpha-and beta-cells directly, stimulating the beta-cell and inhibiting the alpha-cell; and (3) alloxan acts on a glucoreceptor system with comparable physicochemical characteristics common to both cell types.

Alloxan↗
PubMed1977

Measuring the impact of child mortality on fertility: a methodological note.

Recent studies of the impact of child mortality on children ever born have used the "replacement factor" to measure mortality. When microlevel data are used, however, use of the replacement factor (or other variables which are nonlinear in the family's experienced child mortality rate) yields biased coefficients. An alternative model suggests a sequential, rather than a static, decision-making process to relate the decision to have an additional child to the reproductive experience to date. In this case, unbiased coefficients are obtained if the functional form is correctly specified. In the abscence of a priori knowledge of the functional form, it is difficult to untangle true effects from spurious ones.

Child↗
PubMed1975

Fast and slow axoplasmic flow in sciatic nerve of diabetic rats.

Accumulation of acetylcholinesterase (AChE) and choline acetylase (ChAc) activities proximal to a tie placed on the sciatic nerve was measured in control, untreated diabetic, and insulin-treated diabetic rats. In the diabetic animals AChE accumulation was reduced by about 20% and ChAc accumulation by about 40%. Insulin treatment eliminated the impairment. It remains an open question whether these reversible functional changes in rat have any counterpart in the diabetic neuropathy of man.

Acetylcholinesterase↗