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Biomedical subjects

D Robertshaw

Publications and source records attributed to D Robertshaw.

14 recordsLinked to original sources
PubMed1992

Determination of maximal oxygen consumption in exercising pregnant sheep.

Previous work with pregnant ewes has shown that acute bouts of exercise may cause changes in plasma hormone concentrations, blood flow distribution, and maternal and fetal temperatures. However, most of these studies do not quantify the chosen exercise intensity through measurement of oxygen consumption (VO2). Therefore the purpose of this study was to statistically model the VO2 response of pregnant sheep to treadmill (TM) exercise to determine the exercise intensities (% maximal VO2) of previous studies. Ewes with either single (n = 9) or twin (n = 5) fetuses were studied from 100 to 130 days of gestation. After 1-2 wk of TM habituation, maximal VO2 (VO2max) was determined by measurements of VO2 (open flow-through method) and blood lactate concentration. VO2 was measured as a function of TM incline (0, 3, 5, and 7 degree) and speed (0.8-3.4 m/s). VO2max averaged 57 +/- 7 (SD) ml.min-1.kg-1, and peak lactate concentration during exercise averaged 22 +/- 2 mmol/l. The relationship between VO2 (ml.min-1.kg-1) and incline (INC) and speed (SP) [VO2 = 0.70(INC) + 13.95(SP) + 1.07(INC x SP) - 1.18] was linear (r2 = 0.94). Our findings suggest that most previous research used exercise intensities less than 60% VO2max and indicate the need for further research that examines the effect of exercise during pregnancy at levels greater than 60% VO2max.

Animals↗
PubMed1991

Direct referral hearing aid provision in the over sixties age group.

A prospective study was designed in which General Practitioners were issued with a standard referral letter for hearing aid provision. Unknown to the General Practitioner an independent otolaryngologist assessment was obtained at the time of first attendance. Three hundred consecutive patients selected by General Practitioners applying these guidelines were seen in a designated hearing aid clinic staffed by audiological technicians of senior grade or above. Referral pro formata were incomplete in 75 patients who were not assessed. Ninety-four patients (31 per cent) (95 per cent confidence interval 29-36 per cent) were accepted by the audiologist. Obstructing wax was the most common criterion failed. Clinical agreement between audiologist and otolaryngologist was 57 per cent greater than chance. None of the cases of clinical disagreement altered treatment. A direct referral system as proposed could have processed only 31 per cent of 300 referrals. However, experienced technical staff reliably detected otological pathology and with aural toilet facilities 91 per cent of 225 patients (confidence interval 88-94 per cent) were aided.

Aged↗
PubMed1990

Influence of dehydration and watering on camel red cell size: a scanning electron microscopic study.

Three young female camels were subjected to an eleven day period of dehydration followed by a single large drink. Blood haematocrit and plasma protein concentration were monitored regularly during dehydration and for 48 h following watering. Blood samples were taken at regular intervals, before and after watering, and prepared for scanning electron microscopy (SEM) for analysis of red cell size and shape. Plasma protein concentration did not change rapidly on watering implying that the camel has homeostatic mechanisms which regulate plasma osmolarity by controlling the rate at which large volumes of water are absorbed on drinking. By SEM, camel red cells were elliptical in shape with mean surface dimensions of 6.5 microns x 4.0 microns with an estimated minimum thickness at mid point of 0.95 microns: neither their shape constant nor size changed on dehydration or watering corroborating the absence of major and rapid changes in osmolarity.

Animals↗
PubMed1990

Cold-induced changes in breathing pattern as a strategy to reduce respiratory heat loss.

Thermoregulatory benefits of cold-induced changes in breathing pattern and mechanism(s) by which cold induces hypoventilation were investigated using male Holstein calves (1-3 mo old). Effects of ambient temperatures (Ta) between 4 and 18 degrees C on ventilatory parameters and respiratory heat loss (RHL) were determined in four calves. As Ta decreased, respiratory frequency decreased 29%, tidal volume increased 35%, total ventilation and RHL did not change, and the percentage of metabolic rate attributed to RHL decreased 26%. Total ventilation was stimulated by increasing inspired CO2 in six calves (Ta 4-6 degrees C), and a positive relationship existed between respiratory frequency and expired air temperature. Therefore, cold-exposed calves conserve respiratory heat by decreasing expired air temperature and dead space ventilation. Compared with thermoneutral exposure (16-18 degrees C), hypoventilation was induced by airway cold exposure (4-6 degrees C) alone and by exposing the body but not the airways to cold. Blocking nasal thermoreceptors with topical lidocaine during airway cold exposure prevented the ventilatory response but did not lower hypothalamic temperature. Hypothalamic cooling (Ta 16-18 degrees C) did not produce a ventilatory response. Thus, airway temperature but not hypothalamic temperature appears to control ventilation in cold-exposed calves.

Acclimatization↗
PubMed1990

Effect of bilateral splanchnic nerve section on adrenal function in the ovine fetus.

The effect of bilateral splanchnic nerve (SPLX) section in fetal sheep [116-121 days gestational age (dGA)] on subsequent adrenocortical function was investigated. Fetal cortisol release was stimulated by 1) ACTH-(1-24) administration (100 ng/min for 15 min) at 126-129 and at 132-135 dGA, and 2) nitroprusside-induced hypotension (50% reduction in fetal arterial blood pressure for 10 min) at 129-132 and 136-139 dGA. No differences were observed between SPLX and control fetuses (CONT) in basal arterial plasma concentrations of cortisol from 126-141 dGA. A significant effect of fetal age on basal cortisol was observed in both SPLX and CONT fetuses from 126-141 dGA. A significant (P less than or equal to 0.05) increase in fetal arterial concentrations of cortisol was achieved by ACTH-(1-24) infusion in SPLX and CONT and did not differ between groups at either 126-129 or 132-135 dGA. Hypotension induced a significant increase in fetal plasma cortisol concentrations in SPLX and CONT fetuses (P less than or equal to 0.05). SPLX fetuses secreted significantly less cortisol in response to hypotension than CONT fetuses at both 129-132 and 136-139 dGA (P less than 0.05). Fetal arterial plasma concentrations of immunoreactive ACTH in response to hypotension were not different between CONT and SPLX fetuses. We estimated the half-life of endogenous fetal plasma cortisol after both hypotension and infusion of ACTH-(1-24). There were no differences between either method of inducing cortisol release on the endogenous cortisol half-life, nor were any differences in cortisol half-life observed between SPLX and CONT. At 136-139 dGA the adrenomedullary response to hypotension was abolished in SPLX, confirming completeness of denervation. In conclusion, the splanchnic nerves do not appear to be involved in the normal increase in basal fetal plasma cortisol observed in late gestation in fetal sheep. However, splanchnic nerve modulation of secretion of cortisol in response to stress may be involved in the increased fetal adrenal sensitivity to stress observed late in gestation.

Adrenal Glands↗
PubMed1989

Brain cooling and respiratory heat exchange in camels during rest and exercise.

Respiration in relation to brain temperature (Tb) and body temperature (Tc) were investigated in two camels at rest and one during exercise (running at 10 km/h). The animals were subjected to natural ambient conditions (day: 25-30 degrees C, relative humidity (RH) about 65%; night: 15-20 degrees C, RH approx. 90%). They were studied when fully hydrated and during progressive dehydration by up to 15% of initial weight. At low Tc (less than 38 degrees C) Tb greater than Tc by approximately 0.2 degrees C, at higher Tc significant brain cooling was observed by as much as 1.5 degrees C during exercise. Minute ventilation (VE) and respiratory rate (f) increased with Tc such that tidal volume was constant and similar at rest and during exercise (Tc-Tb) increased linearly with f and hence VE. The cooling, dependent on turbinate heat exchange was related to certain features of the air flow pattern and f which have also been described in other large mammals.

Animals↗
PubMed1989

A system for accelerated provision of hearing aids to residents of homes for the elderly.

A study was undertaken to detect undiagnosed deafness in elderly people, living in Part III Residential Homes in North Tees, South Tees and Hartlepool Health Districts, to provide hearing aids and to estimate the subsequent success in rehabilitation. The residents were referred by the senior staff in the homes and assessed by a doctor and audiology technician in a domiciliary setting. Those found to have a significant hearing impairment were prescribed hearing aids without formal pure tone audiometry. A pilot study compared the method of hearing evaluation employed with such conventional testing. Six months after fitting, the degree of compliance with aiding was assessed. The results show a significant level of undiagnosed deafness in the community and, with this method of provision, an acceptance rate of 41.2 per cent of those recommended for aiding at six months which is higher than suggested by previous similar studies of this population.

Aged↗
PubMed1979

Hyperhidrosis and the sympatho-adrenal system.

Some disorders in which excessive sweating, hyperhidrosis, is a symptom are also characterized by increased sympatho-adrenal activity. Such disorders are hypotension, hypoglycemia, pheochromocytoma and hyperthyroidism. Sweat glands are controlled by a cholinergic innervation but can also be stimulated by adrenergic agents whose effects can be blocked by both alpha- and beta-receptor blocking drugs. An adrenergic innervation has also been demonstrated. There is evidence that the adrenergic component of sweating particularly secretion of the adrenal medulla, is responsible for the enhancement of sweating during exercise but not for the hyperhidrosis present in these disorders since sweating in these circumstances can be effectively blocked by cholinergic blocking compounds. Cutaneous vasoconstriction due to elevated plasma catecholamines reduces the rate of evaporation of sweat and allows sweat to accumulate on the skin. It is suggested that in the case of hypotension and insulin hypoglycemia sweating results from general sympathetic stimulation and that adrenal medullary hormones are not an essential component of the response. Hyperhidrosis in pheochromocytoma may be due to central activation of heat loss mechanisms resulting from the passage of plasma catecholamines across the blood-brain barrier combined with increased thermogenesis and cutaneous vasoconstriction. The hyperhidrosis of hyperthyroidism is probably due to increased thermogenesis.

Adrenal Gland Neoplasms↗
PubMed1978

Influence of diet on leg uptake of glucose during heavy exercise.

Four young men each performed three treadmill walks to exhaustion at 70% of their respective O2 uptake maxima. Each walk followed 3 days consumption of either a normal mixed (M), high fat and protein (F-P), or high carbohydrate (CHO) diet. The fractional use of carbohydrates for energy during the initial 1/2-hr of work was significantly reduced following the F-P diet as compared with the M or CHO diets (P less than 0.005), averaging 38.2% (F-P), 69.9% (M), and 71.9 (CHO). Carbohydrates energy production was negatively correlated with blood levels of both free fatty acids ( r = -0.62, P less than 0.05) and beta-OH-butyrate (r = - 0.79, P less than 0.005). Work time to exhaustion was closely correlated with the fractional usage of carbohydrates for energy (r = 0.86, P less than 0.001). The femoral arteriovenous blood glucose difference was directly related to the pre-work dietary carbohydrate fraction, with the 30-min work means 0.25 mM (F-P), 0.34 mM (M), and 0.52 mM (CHO). Estimation of leg arteriovenous O2 difference indicated that leg uptake of blood-borne glucose provided approximately 23 +/- 10% (F-P), 30 +/- 8% (M), and 46 +/- 13% (CHO) of the legs' aerobic substrate during the first 30 min of work. These results provide further evidence for the shift from noncarbohydrate to carbohydrate energy sources during exercise as the carbohydrate fraction of the diet is elevated.

Adult↗
PubMed1977

Effect of lipid solvents on cutaneous moisture loss.

Application of various lipid solvents and dimethyl sulphoxide to the skin of cattle, sheep, eland and African buffalo exposed to an air temperature of 20 degrees C caused an increase in cutaneous moisture loss. The effect did not occur after exposure to an air temperature of 40 degrees C or after adrenaline administration. Blockage of sweating by either bethanidine or phenoxybenzamine did not affect the response. Camel, donkey, dog and man showed no increase in cutaneous moisture loss after lipid solvent application to the skin. It is concluded that lipid solvents directly stimulate the secretory cells of the sweat glands of members of the family Bovidae and that this is not due to the release of transmitter substance nor to stimulation of adrenergic receptors, but is due to direct stimulation of the sweat glands themselves.

Animals↗