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Biomedical subjects

R A Little

Publications and source records attributed to R A Little.

At least 109 records · Page 6Linked to original sources
PubMed1984

Effect of limb ischaemia on blood pressure and the blood pressure-heart rate reflex in the rat.

The effects of bilateral hind-limb ischaemia on blood pressure and on the blood pressure-heart rate reflex have been studied in the rat. Limb ischaemia increased blood pressure and decreased the elevation and slope of the regression line describing the relationship between heart period (H.P.) and mean arterial pressure (M.A.P.). Nociceptive afferents from muscle receptors using long fibre tracts in the anterolateral part of the spinal cord seem to be responsible for the changes seen. The changes in the blood pressure-heart rate reflex were mediated by a combination of vagal inhibition and sympathetic activation. The efferent pathway for the pressor effect was in the sympathetic outflow. Central catecholaminergic neurones were involved in the pressor effect of limb ischaemia but not in the changes in the blood pressure-heart rate reflex. Electrolytic lesions in the posterior hypothalamus attenuated the inhibition of the reflex and it is suggested that neurones in the defence area may be activated by limb ischaemia. The interaction between limb ischaemia and the H.P.-M.A.P. relationship was not affected by opioid antagonists. After the period of ischaemia there was an increase in the elevation of the regression line describing the relationship between H.P. and M.A.P. which was secondary to the fall in body temperature characteristic of this phase of the response to injury.

Afferent Pathways↗
PubMed1984

The effects of minor and moderately severe accidental chest injuries on pulmonary function in man.

Pulmonary function has been measured at intervals after direct chest injuries of mild and moderate severity in 46 patients. Ventilatory capacity (e.g. FEV1) and vital capacity were reduced and the residual volume was increased. Total lung capacity and alveolar volume were also reduced and as a result total pulmonary diffusing capacity (transfer factor) was decreased, however, the remaining lung had a normal diffusion coefficient. Intercostal nerve block at the fracture site did not improve ventilatory capacity although marked pain relief was achieved. Recovery was slower in those patients not admitted to hospital than in the more seriously injured patients who were admitted. It is suggested that more attention should be paid to the outpatient follow-up of such patients, perhaps paying particular attention to physiotherapy.

Accidents↗
PubMed1983

The effect of sepsis on the oxidation of carbohydrate and fat.

Oxidative metabolism has been studied by indirect calorimetry in 27 patients with sepsis and in 7 non-septic patients while they were all receiving total parenteral nutrition. Glucose oxidation was reduced in the septic patients and fat oxidation continued despite the infusion of an excess of glucose. The extent of these changes depended on the severity of the septic state as measured by the scoring system described in the preceding paper. The mechanism of these changes is not known. They were not related to an elevation of the plasma nonesterified fatty acid concentration. Alterations must have occurred in the way fat was taken up and metabolized by the cells. Here insulin resistance and the highly significant positive relationship found between the plasma cortisol concentration and the sepsis score might be important.

Adult↗
PubMed1983

Fat metabolism in elderly patients with severe hypothermia.

Elderly patients with accidental hypothermia (core temperatures 25.0-35.5 degrees C) have been studied to determine the effect of low temperature on energy metabolism. The respiratory exchange ratios were low (median 0.75). Concentrations of plasma glycerol, non-esterified fatty acids and ketone bodies were high, and, except in the case of glycerol, rose with the duration of the hypothermia. Plasma glucose concentrations were often high but extremely variable. Arteriovenous differences across the forearm showed net release of glycerol and extraction of ketone bodies. Despite the hypothermia the mean extraction ratios for acetoacetate and 3-hydroxybutyrate were very similar to published values in normal, fasting, euthermic subjects. It was concluded that, in agreement with other work showing inhibition of glucose utilization at low temperature, fat is the main fuel used at very low body temperatures.

3-Hydroxybutyric Acid↗
PubMed1983

Immunoglobulin-complexed aspartate aminotransferase.

We report two cases of unexplained, isolated, persistently increased aspartate aminotransferase activity in serum. In the first patient, this lasted for 10 years and prompted multiple hospitalizations and medical/surgical consultations. For patient two, the abnormal enzyme activity resulted in hospitalization for further evaluation of possible heart disease. In spite of extensive investigation to determine the possible reason for the abnormality, no clear clinical cause was ever discovered in either patient. Electrophoretic and immunologic evidence indicates that the enzyme was complexed to IgG in the serum of both individuals. Recognition that this complex is probably benign may obviate other patients having to undergo unnecessary hospitalization, anxiety, and expense.

Aspartate Aminotransferases↗
PubMed1983

Effect of injury on the reflex control of pulse rate in man.

The changes in pulse rate elicited by a Valsalva maneuver, a maximal inspiration and a passive head-up tilt, have been measured in patients within a few hours of limb injury before definitive treatment and in control subjects. The injuries were of minor or moderate severity. In all those tested in the Valsalva maneuver, the pulse rate increased during phase 2 and decreased during phase 4 of the response, and both changes were directly related to the initial pulse rate. In controls the increase in pulse rate during phase 2 was greater when the maneuver was performed at 40 mm Hg than at 20 mm Hg, but after injury this difference was not seen and the increases at 20 mmHg and at 40 mm Hg were the same as in controls at 20 mm Hg. The bradycardia during phase 4 was less in injured patients than in controls. The responses returned to normal during recovery. The increase in pulse rate during a maximal inspiration was not affected by injury. When the controls were given a head-up tilt the pulse rate increased, the rise depending on the angle of the tilt. A proportion of the injured patients, which increased with the severity of the injury, did not show this response, for the pulse rate decreased at the higher angles of tilt.

Adolescent↗
PubMed1982

The effect of naloxone on some neuroendocrine responses to limb ischaemia.

The finding that naloxone reverses the arterial hypotension produced by bacterial endotoxin in the rat was confirmed and the effect of naloxone on the responses to another form of injury, limb ischaemia was studied. Naloxone had no effect on the fall in blood pressure and colon temperature or on behaviour and survival after bilateral hind-limb ischaemia. The ambient temperature threshold for the onset of shivering was depressed by limb ischaemia as in untreated rats. The increases in the plasma concentrations of glucose and corticosterone and the decrease in that of prolactin after limb ischaemia were unaltered by naloxone. In control rats naloxone reduced the ambient temperature threshold for the onset of shivering and the plasma prolactin concentration. It is concluded that the endogenous opioids do not play a very significant part in the responses to ischaemic limb trauma.

Animals↗
PubMed1981

Body temperature after accidental injury.

Core and mean skin temperatures have been measured in 82 patients shortly after accidental injuries of different severity in order to study the effects of injury on thermoregulation. Skin temperature fell after injury and core temperature also when the injury was severe. After severe injuries both core and mean body temperatures were negatively related to the severity of the injury, measured by the Injury Severity Score. The fall in skin temperature was attributed to vasoconstriction and that in core temperature to decreased heat production due to reduced oxygen transport to the tissues. These changes in temperature should have stimulated shivering which was not observed in the severely injured. This suggests that thermoregulation is affected after injury, and possible mechanisms are discussed.

Accidents↗
PubMed1981

The acute toxicity of some organolead and organotin compounds in the rat, with particular reference to a gastric lesion.

The acute toxicity of triphenyl, tributyl and dibutyllead in the rat appears to result from their irritating properties to membranes regardless of their route of administration. A more detailed examination of their oral toxicity has shown that a single dose inhibits gastric emptying with resulting fluid distension. A similar effect was observed with a number of other organolead and organotin compounds. Analysis of gastric fluid from pyloric ligated rats following an oral organolead dose showed increased concentrations of Na+ and glucose and decreased concentrations of H+ and K+. Dilation of the gastric mucosal microcirculation was also observed along with desquamation of surface mucous cells which resulted in shallow erosions of the upper portions of the gastric glands. It is suggested that oral dosing with a number of organoleads and, possibly, organotins has an effect on mucosal membranes that results in erosion of the gastric mucosa and increases permeability of the mucosal microcirculation. This would allow leakage of plasma constituents into interstitial fluid and ultimately the gastric lumen with back-diffusion of H+ into the gastric mucosa. Such a lesion would impair gastric function and reduce normal food and water consumption. The starvation and dehydration may then be the important factors for death that follows oral dosing with organolead and organotin compounds.

Animals↗
PubMed1981

Substrate oxidation shortly after accidental injury in man.

1. Oxidative metabolism have been studied by indirect calorimetry in 42 patients within the first 6 h after accidental injury. 2. The level of energy expenditure bore no relationship to the severity of the injury and varied more widely from patient to patient than in normal subjects. 3. After minor and moderate injuries the respiratory exchange ratio (mean 0 . 86) was not different from that in normal subjects on a mixed diet. After severe injuries the ratio (mean 0 . 78) was significantly lower (P less than 0 . 005), indicating that the main substrate for oxidation in these patients was fat, despite their hyperglycaemia.

Adolescent↗
PubMed1981

Arterial baroreceptor reflex function during elevation on intracranial pressure.

The ability of the arterial baroreceptor reflex to buffer the blood pressure responses elicited by increasing the intracranial pressure (ICP) has been studied in chloralose anesthetized cats. Standardized elevations of ICP induced pressor responses of similar magnitude irrespective of whether the baroreceptor inhibitory activity was high or vey low. When ICP was elevated baroreceptor activation induced a reflex reduction of flow resistance and blood pressure, but never to the same levels obtained when ICP was normal. Thus when ICP was elevated there was an upward displacement of the curve relating carotid sinus pressure to mean arterial blood pressure.

Animals↗
PubMed1981

Spontaneous periodic hypothermia with lipoma of the corpus callosum.

A patient with spontaneous periodic hypothermia who had both a lipoma and agenesis of the corpus callosum is described. Spontaneous periodic hypothermia associated with corpus callosum abnormalities is a distinct entity and although the mechanism underlying the hypothermic episodes is unexplained, the term "diencephalic autonomic epilepsy" does not seem appropriate.

Adult↗
PubMed1980

Effect of changes in baroreceptor input on the intensity of shivering in the anaesthetised cat.

1. Shivering in the barbitone-anaesthetised cat exposed to a lowered ambient temperature was reduced by transient haemorrhagic or drug induced hypotension such that there was a positive correlation between mean arterial blood pressure and the intensity of shivering. 2. Shivering which had been reduced by haemorrhage could be restored by the reinfusion of blood, centripetal stimulation of a buffer nerve or by the intravenous administration of methoxamine. 3. The intensity of shivering was increased by the intravenous injection of methoxamine and by stimulation of a buffer nerve, although the latter response was attenuated by intact buffer nerves. 4. There was a marked variation in the importance of the different buffer nerves in maintaining shivering. 5. Shivering was abolished by deafferentation of the baroreceptors and although it could be restored by electrical stimulation of a buffer nerve methoxamine was then without effect. 6. A prolonged period (90-120 min) of hypotension (50-60 mm Hg) impaired the ability to shiver even after the hypovolaemia and hypotension had been corrected.

Animals↗
PubMed1980

Metabolic aspects of hypothermia in the elderly.

1. Plasma concentrations of glucose, lactate, amino acids, non-esterified fatty acids, glycerol, ketone bodies, insulin and cortisol were measured in 43 elderly patients with hypothermia. In 15 of these patients forearm arteriovenous differences were also measured. Core temperatures ranged from 25.9 to 35.5 degrees C. 2. The metabolic state was of mobilization of glycogen and triacylglycerol stores, with high plasma concentrations of lactate and lipid metabolites. The plasma concentration of glucose was raised in those with hypothermia of a short duration (less than 6 h). In other patients it was low in those with core temperatures around 30 degrees C, but below this temperature it was variable and often high. Concentrations of other metabolites or hormones were not related to core temperature. 3. Plasma concentrations of cortisol were high and positively correlated with those of lactate and glycerol, suggesting active involvement in stimulation of muscle glycogenolysis and of lipolysis. 4. Plasma concentrations of insulin ranged from very low to very high and appeared to depend on the concentrations of both glucose and alanine. 5. Arteriovenous differences were generally small. There was peripheral release of lactate and of amino acids but no overall peripheral uptake of glucose. In nine out of 15 patients there was a significant peripheral release of glucose.

Aged↗
PubMed1980

Changes in cardiac output and its distribution after non-haemorrhagic injury in the rat.

In the unanaesthetized rat cardiac output, measured by a thermodilution technique, fell rapidly following a 4h period of bilateral hind-limb ischaemia. There was a significant positive correlation between body temperature and total cardiac output after injury. There were also striking changes in the distribution of cardiac output; for example, hepatic artery flow was markedly increased, whereas splanchnic flow fell passively with the reduction in cardiac output. There were suggestions of regional differences in the reduction of blood flow within the brain.

Animals↗