Search PubMed⌕ Search

Biomedical subjects

K J Collins

Publications and source records attributed to K J Collins.

At least 19 recordsLinked to original sources
PubMed1992

Immunohistochemical, morphological and functional changes in the peripheral sudomotor neuro-effector system in elderly people.

Age-related changes in the human peripheral sudomotor neuro-effector system have been investigated in six 80-year-olds and six young adults. Histochemical and immunohistochemical studies on forearm skin biopsies showed diminished vasoactive intestinal polypeptide (VIP) and calcitonin gene related peptide (CGRP)-like immunoreactivity and a virtual absence of acetylcholinesterase in the elderly sudomotor nerve endings compared to the young. Reduced size of nerve bundles and decreased density of sympathetic nerve endings adjacent to the sweat glands of old people were shown by the neuronal marker, protein gene product (PGP 9.5), and by electron microscopy. Image analysis techniques were also used to demonstrate a marked regression in secretory coil size with age. Functional decrements accompanying the neurochemical and morphological changes in the neuro-effector system were measured in ten 80-year-olds by local quantitative nicotine axon reflex responses and compared with 12 young adults. These studies demonstrate marked regressive changes in both the nerve endings and target cells in old age and appear to express a significant loss of vigour in trophic interactions.

Acetylcholinesterase↗
PubMed1991

Age-related changes in autonomic control: the use of beta blockers in the treatment of hypertension.

Functional decrements in autonomic control and reflex activity in the elderly resemble the effects of beta-adrenoreceptor blockade. This arises partly from an age-related decrease in intrinsic beta-adrenoreceptor sensitivity and partly from effector changes associated with degenerative processes such as arteriosclerosis. In the elderly, compensatory adjustments in cardiovascular control result from both sympathetic and parasympathetic dysfunction. The characteristics of aging in autonomic nervous control are examined in relation to the treatment of essential hypertension by beta blockers in the elderly. Increased cardiac output with exercise depends more on increased intracardiac volume than on sympathetic modulation of heart rate in older people. Baroreceptor-dependent and renin blood pressure responses are diminished. The cold pressor response, which is found to be greater in the elderly than in young adults, is abolished by alpha and not beta blockers. Blood viscosity and blood platelets also increase in moderately cold conditions, and a beta blocker with vasodilator and antiplatelet activity may therefore be useful. Trigeminal cardiorespiratory reflex responses to facial cooling evoke a higher blood pressure but smaller bradycardia in old people. These constraints of autonomic nerve function on the use of beta blockers for treating hypertension are imposed on a background of altered drug pharmacokinetics and pharmacodynamics in the elderly.

Adrenergic beta-Antagonists↗
PubMed1990

Acute respiratory failure precipitated by general anesthesia in Leigh's syndrome.

Three patients with Leigh's syndrome developed respiratory failure following general anesthesia. Although all three had respiratory symptoms prior to the anesthetic, the diagnosis was not suspected at the time of the procedure in two of the children. We reviewed the case notes of 16 other patients with Leigh's syndrome. Eight had received anesthetic agents without incident. Although the majority subsequently developed respiratory abnormalities and died with respiratory failure, this problem was not evident at the time of anesthesia. In the presence of respiratory abnormalities, general anesthesia carries significant risks in Leigh's syndrome.

Anesthesia, General↗
PubMed1990

Oxylog studies of energy expenditure and schistosomiasis in the Sudan.

The effects of varying intensities of S. mansoni infection on physical work performance in agricultural tasks were studied in 269 male farmers living in the highly endemic Gezira area of the Sudan. The subjects were in the age range 18-50 years, and they were subdivided into four infection groups: non-infected (passing no S. mansoni eggs in their faeces), lightly infected (egg excretion 1-499), moderately infected (egg excretion 500-999), and heavily infected (egg excretion 1000+ eggs g-1 faeces). The Oxylog, a portable oxygen analyser, was used to measure energy expenditure throughout the field studies. The investigations showed that heavy S. mansoni infection significantly lowered oxygen intake by 20-30% during agricultural work tasks. There was a clear relationship between the intensity of S. mansoni infection and both the aerobic power output and morbidity in those populations. Anti-schistosomal treatment (praziquantel) given over a period of 1 year produced a marked improvement in working capacity and reduced morbidity.

Adult↗
PubMed1987

Effect of cortical kindling on [3H]D-aspartate uptake and glutamate metabolism in rats.

The effects of cortical kindling in rats on [3H]D-aspartate uptake and on glutaminase and glutamine synthetase activities has been studied. The high affinity uptake of [3H]D-aspartate in control cortical tissue (Km approximately 2 microM) was undetectable in the kindled tissue, whilst the enzyme activities were unchanged. A loss of the high-affinity uptake sites for excitatory amino acids may be a contributing factor to the kindling phenomenon.

Animals↗
PubMed1987

Energy expenditure of agricultural workers in an area of endemic schistosomiasis in the Sudan.

Indices of physiological performance in the field under natural working conditions were measured in 46 Sudanese Gezira villagers and related to exercise performance under controlled laboratory conditions. The effect of Schistosoma mansoni infection on energy expenditure in the field was also investigated. A highly significant positive association between the maximal aerobic power output (VO2 max) measured in the laboratory with energy expenditure in the field (r = + 0.51, p less than 0.001) and with changes in body weight during work (r = 0.41, p less than 0.01) was found. The villagers' energy expenditure in field work amounted to 25-28 KJ/min, which corresponded to more than 50% of their predicted VO2 max. They maintained that relative work level for more than an hour. The differences in energy expenditure between moderately infected and non-infected villagers with schistosomiasis did not attain statistical significance but the number of non-infected subjects on which the comparison was based was small.

Adolescent↗
PubMed1987

Effects of cold on old people.

Increased morbidity and mortality from cardiovascular and respiratory disease in the elderly is strongly associated with cold winters in Britain. Though there is often impairment of thermoregulation in old people, deaths from hypothermia are proportionally small. Recent physiological investigations on the effects of cold in the elderly may help to explain the causes of excess winter deaths.

Aged↗
PubMed1986

Quantitative studies of N-methyl-D-aspartate, 2-amino-5-phosphonovalerate and cis-2,3-piperidine dicarboxylate interactions on the neonatal rat spinal cord in vitro.

The interactions between N-methyl-D-aspartate (NMDA), (+/-)2-amino-5-phosphonovalerate (2AP5) and (+/-)cis-2.3-piperidine dicarboxylate (cis-PDA) were examined quantitatively in the neonatal rat spinal cord in vitro. NMDA and cis-PDA evoked concentration-dependent motoneuronal depolarizations. The maximal cis-PDA-evoked response was approximately 60% of that evoked by NMDA. When applied in combination with fixed concentrations of cis-PDA, NMDA evoked concentration-dependent depolarizations superimposed upon the basal cis-PDA-evoked depolarizations, the dose-response curve for which intercepted the control dose-response curve and was subsequently moved to the right compared with the control curve. 2AP5 shifted the NMDA dose-response curves to the right and Schild regression analysis gave a pKB of 5.0 with a slope of 1.00. 2AP5 also moved the cis-PDA dose-response-curve (apparent KB 3.1 X 10(-5) M) to the right and abolished the cis-PDA component of the NMDA + cis-DPA dose-response curve. These results are consistent with the predictions of drug-receptor theory for the interactions of a full agonist (NMDA), competitive antagonist (2AP5) and partial agonist (cis-PDA) and represent further evidence for a population of excitatory amino acid receptors for which NMDA is a selective agonist.

2-Amino-5-phosphonovalerate↗
PubMed1986

Low indoor temperatures and morbidity in the elderly.

Low ambient temperatures are particularly harmful to the elderly and in the winter in the UK temperatures in some dwellings may fall to 6 degrees C. The World Health Organization recommends a minimal indoor temperature of 18 degrees C and a 2-3 degrees C warmer minimal temperature for rooms occupied by sedentary elderly, young children and the handicapped. Below 16 degrees C, resistance to respiratory infections may be diminished. Both low and high relative humidities promote respiratory illnesses. At temperatures below 12 degrees C, cold extremities and slight lowering of core temperature can induce short-term increases in blood pressure. Raised blood pressure and increased blood viscosity in moderate cold may be important causal factors in the increased winter morbidity and mortality due to heart attacks and strokes. Deep body temperature does not usually fall until resting clothed elderly people are exposed for two or more hours to an ambient temperature of 9 degrees C or below. Statistics available for the UK population do not support the view that there are large numbers of elderly people suffering from clinical hypothermia, though there may be a larger number in whom hypothermia is undiagnosed when the condition occurs secondary to other disorders.

Aged↗
PubMed1985

Effects of age on body temperature and blood pressure in cold environments.

Mean deep body temperature fell by 0.4 +/- 0.1 (SD) degrees C in five sedentary, clothed 63-70 year old men and by 0.1 +/- 0.1 degrees C in four young adults after 2 h exposure in still air at 6 degrees C (P less than 0.001). The mean increase in systolic and diastolic pressure was significantly greater (P less than 0.002) in the older subjects (24 +/- 4 mmHg systolic, 13 +/- 4 mmHg diastolic) than in the young (14 +/- 6 mmHg systolic, 7 +/- 3 mmHg diastolic) after 2 h at 6 degrees C. A small rise in blood pressure occurred in the older men at 12 degrees C, but there was no increase in either group at 15 degrees C. The association of variables is particularly marked between systolic blood pressure and core temperature changes at 6 degrees C. There were no appreciable cold-adaptive changes in blood pressure or thermoregulatory responses after 7-10 days repeated exposure to 6 degrees C for 4 h each day. Blood pressure elevation in the cold was slower but more marked in the older men. These changes in blood pressure may provide a possible basis for delineating low domestic limiting temperature conditions.

Adolescent↗
PubMed1985

Headache.

Explore the source record for details and available documents.

Adolescent↗
PubMed1979

Secretion and metabolism of cortisol and aldosterone during controlled hyperthermia.

1. The rates of secretion and metabolic clearance of cortisol and aldosterone in response to passive heating have been investigated in fifteen young men by the controlled hyperthermia technique combined with continuous I.V. infusion of [14C]cortisol and [3H]aldosterone. 2. During a 1 hr period of elevation of deep body temperature to 38.0 degrees C mean hepatic blood flow measured by indocyanine green clearance decreased by more than 25% compared with normothermic condition. 3. The pattern of response in hyperthermia involved decreasing plasma specific activities indicating increased adrenal secretion of both cortisol and aldosterone. 4. Aldosterone metabolic clearance rate usually decreased in hyperthermia when there was little change in the clearance rate of cortisol, but an increased aldosterone clearance rate was observed when there were significant increases in the clearance rate of cortisol. A contributing factor to elevation of plasma aldosterone concentration in the heat is the reduction in hepatic blood flow which reduces aldosterone metabolic clearance rate. 5. Suppression of the thermally induced rise in plasma cortisol concentration by dexamethasone was associated with a decrease in aldosterone clearance rate which may reflect increased availability of aldosterone-binding plasma protein. 6. Marked rises in plasma cortisol were always accompanied by simultaneous rises in aldosterone, but rises in aldosterone sometimes occurred in the absence of a rise in cortisol. We therefore suggest that ACTH stimulation plays an important, but not exclusive, role in the stimulation of aldosterone secretion during hyperthermia.

Aldosterone↗
PubMed1977

Accidental hypothermia and impaired temperature homoeostasis in the elderly.

A longitudinal study of the age-related decline in thermoregulatory capacity was made in 47 elderly people to try to identify those at risk from spontaneous hypothermia. During the winters of 1971-2 and 1975-6 environmental and body temperature profiles were obtained in the home, and thermoregulatory function was investigated by cooling and warming tests. Environmental temperature and socioeconomic conditions had not changed but the body core-shell temperature gradients were smaller in 1976, indicating progressive thermoregulatory impairment. People at risk of developing hypothermia also seem to have low resting peripheral blood flows, a nonconstrictor pattern of vasomotor response to cold, and a higher incidence of orthostatic hypotension.

Aged↗
PubMed1976

Energy expenditure and physiological performance of Sudanese cane cutters.

The thermal and exercise tolerances of 165 Sudanese cane cutters were measured in the laboratory and related to work performance and productivity in the cane fields. The results showed that the amount of cane cut per minute in the field was significantly correlated with changes in body weight (r = +0-53) during the third hour of work, aerobic energy expenditure (r = + 0-43), and cardiac frequency during work. These variables in turn were associated with predicted maximal power output (VO2 max) measured in the laboratory. The average energy expenditure during cane cutting was 1-66 +/- 0-33 1/min-1 (34-9 kJ/min-1) which represents approximately 60% of the workers predicted VO2 max. This rate of energy expenditure was sustained in the cane fields for at least three hours without significant pauses for rest. The sweat losses measured in 32 cane cutters during the two and three hours of work averaged 637 +/- 221 and 770 +/- 282 g/h-1 respectively, while the mean urine temperature immediately on cessation of effort was 37-74 +/- 0-46 degrees C. Despite the additional environmental heat load of the tropics, it would seem that cane cutters performing a self-paced task demanding heavy physical effort, are able to sustain work levels well in excess of those recommended for most European factory workers without obvious signs of fatigue or heat stress.

Adult↗