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Biomedical subjects

R A Little

Publications and source records attributed to R A Little.

At least 127 records · Page 7Linked to original sources
PubMed1980

Protein metabolism after unilateral femoral fracture in the rat, and comparison with sham operation.

Urinary excretion of nitrogen, creatinine and N tau-methylhistidine were measured in the rat after unilateral femoral fracture or sham operation. Increased urinary nitrogen excretion occurred in both groups of rats. Cumulative excretion of both nitrogen and N tau-methylhistidine was slightly greater after femoral fracture than after sham operation and this difference agreed quantitatively with loss of muscle protein from the limb with fracture. Sham operation caused no local effect on muscle-protein content and no differences were seen in muscle-protein content between the uninjured hind limb of rats with femoral fracture and either hind limb of sham-operated rats. It was concluded that bone fracture per se does not contribute significantly to the increased urinary nitrogen excretion seen after femoral fracture in the rat; similar changes are produced by equivalent sham operation and any difference between the effects of the two procedures represents local muscle wasting, probably due to disue of the fractured leg.

Animals↗
PubMed1979

A sequential study of changes in the brain and cerebrospinal fluid of the rat following triethyltin poisoning.

Following a single intravenous (i.v.) injection of triethyltin (10 mg/kg) in rats, vacuoles appeared in the myelin sheath within 3 h and they progressively increased in size between 6 and 24 h. Their development was closely correlated with a progressive increase in water, sodium, and chloride content of the brain, and of cerebrospinal fluid (CSF) pressure. Oedema was more extensive in tissues consisting predominantly of white matter rather than grey matter. The sustained increase in CSF pressure did not precede the development of lesions and was the result of, rather than the cause of, brain oedema and swelling. These findings indicate that triethyltin has a direct effect on the myelin sheath.

Animals↗
PubMed1979

Effects of non-haemorrhagic injury on the cardiovascular response to tilting in the rat.

In the unanaesthetized uninjured rat a head-up tilt elicited a pressor response, the magnitude of which was directly related to the angle of tilt. The pressor response was reduced by a 4 h period of bilateral hind-limb ischaemia and by a non-fatal scald, although the slope of the regression line relating percentage rise in mean arterial blood pressure to the angle of tilt was unaltered. The degree of impairment of the response was directly related to the severity of the injury. In the uninjured rat there was a sigmoid relationship between the angle of tilt and the mean heart rate during the tilt. No relationship could be demonstrated between angle of tilt and heart rate in the injured rats.

Animals↗
PubMed1978

H2-receptors and traumatic oedema.

The effects of the H2-antagonists, metiamide and cimetidine, on the oedema following limb ischaemia or scald have been investigated in two strains of rat. No inhibition of oedema formation was found except when large doses of cimetidine were given before scalding. This effect was attributed to the fall in body temperature. Our results do not support the view that H2-receptors are concerned in the vascular response to injury.

Animals↗
PubMed1978

Constitutional factors and the local and general responses to injury.

The different constitutional factors which may affect the response to injury and the problems which must be considered in evaluating any injury model are discussed. Species, age, sex, nutrition and the presence of disease are discussed in relation to an injury model based on hind limb ischaemia, with reference to the extensive literature.

Aging↗
PubMed1978

Effect of streptozotocin-diabetes on the local and general responses to injury in the rat.

1. The effects of streptozotocin-diabetes on the local and general responses to a 4 h period of bilateral hind-limb ischaemia in the rat have been investigated. The rats were injured 48 h after the intravenous injection of the streptozotocin. 2. Less fluid was lost from the circulation into the injured limbs after injury in the diabetic rats and this was directly related to the severity of the diabetes, but could not be explained by dehydration. However, when the diabetic and nondiabetic injured rats were considered together there was significant negative correlation between either plasma osmolality or plasma glucose concentration and water content in the injured hind limb. 3. The relationship between plasma glucose concentration and plasma osmolality was changed by injury such that, particularly in the injured diabetic rats, plasma osmolality at a given glucose concentration was higher than that predicted from the relationship betweeen these variables in the uninjured rat.

Animals↗
PubMed1978

Effects of inhibition of adrenal steroidogenesis on compensation of fluid loss and on survivial after limb ischaemia in the rat.

In rats injected with a specific inhibitor of adrenal steroidogenesis, 4alpha,5-epoxy-17beta-hydroxy-3-oxo-5alpha-androstane-2alpha-carbonitrile (WIN 24 540), the increase in the concentration of corticosterone in the plasma caused by bilateral hind-limb ischaemia was greatly reduced. The lethality of this injury was increased. Fluid loss into the hind limbs was unaltered but the compensatory movement of fluid into the plasma was imparied. The hyperglycaemia that occurred after the injury was markedly reduced by WIN 24 540, but this was probably unrelated to the poorer compensation of fluid loss as there was no corresponding fall in plasma osmolality. The effects of injecting WIN 24 540 could be completely reversed by the simultaneous injection of corticosterone, so as to restore the rise in its concentration in the plasma. We conclude that the adrenal cortex plays an active part in the early circulatory and metabolic responses to injury, in contrast to its reportedly permissive role in the later catabolic phase.

Adrenal Cortex↗
PubMed1977

Measuring the severity of injury.

The injury severity score as a method for measuring the severity of injury has been found useful for epidemiological and metabolic research. Comparison with plasma cortisol concentrations confirmed that the method could distinguish between minor and moderate injuries. Before using the method one must decide on the need to weight the score for age. This is necessary when studying some relationships--for example, mortality and severity--but not others--for example, plasma cortisol concentration and severity.

Adolescent↗
PubMed1976

Role of tissue fluid hyperosmolality in the pathogenesis of post-traumatic fluid loss.

The changes in interstitial fluid osmolality in the injured tissues during and after bilateral hind-limb ischaemia have been studied in young rabbits. There was a marked tissue fluid hyperosmolality which was directly related to the period of ischaemia. The increase in osmolality could be attributed to increases in lactate and potassium concentration. The interstitial fluid hyperosmolality disappeared rapidly after restoration of the circulation to the hind-limbs and would therefore only be of importance in the earliest stages of the pathogenesis of post-ischaemic fluid loss. Although the tissue fluid hyperosmolality is so short-lasting 56% of the fluid loss, measured 1 h after a 4-h period of ischaemia, occurs during the first 10 min following removal of the tourniquets. The lactate concentration in ischaemic skeletal muscle of the newborn rabbit was higher than that in the older animal and if this is reflected in an increased tissue fluid hyperosmolality it may be a factor in the greater post-ischaemic fluid loss characteristic of the neonate.

Age Factors↗
PubMed1975

Experimental studies on the pathophysiological responses of the newborn to injury.

Experimental studies are reviewed which show that there are significant differences with age in both the local and general responses to injury. The results seem to confirm the belief in the striking ability of the newborn to withstand injury and suggest that one important aspect of this resistance is an increased ability to compensate circulatory hypovolaemia.

Age Factors↗
PubMed1974

The compensation of post-traumatic oedema in the rabbit at different ages.

1. The compensation of fluid loss from the circulation after an LD(50) period of bilateral hind-limb ischaemia in a thermoneutral environment has been studied in the rabbit from birth until young adulthood.2. The fluid loss from the circulation was calculated from the increase in the great vessel haematocrit value as the red cell volume and F(cells) were unchanged after limb ischaemia. This ;apparent' fluid loss was compared with the ;actual' fluid loss calculated from the increase in water content of the injured limbs.3. The 0- to 1-day-old rabbit was better able to restore fluid, and protein, to the circulation than the older animal and suffered a smaller percentage reduction in arterial blood pressure after an LD(50) period of ischaemia.4. The better compensation of post-traumatic fluid loss during the first 48 hr of life may be explained by the high capillary filtration coefficient and the post-traumatic increase in plasma protein osmotic pressure found at that age.5. The more efficient restoration of the plasma volume by the 0- to 1-day-old rabbit may account for the increased ability to withstand post-traumatic fluid loss at that age.

Age Factors↗