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Biomedical subjects

D E Ray

Publications and source records attributed to D E Ray.

At least 73 records · Page 4Linked to original sources
PubMed1982

Changes in brain blood flow associated with deltamethrin-induced choreoathetosis in the rat.

Deltamethrin is a pyrethroid insecticide which produces reversible motor symptoms in mammals involving facial movements, progressive incoordination, and choreoathetosis. These symptoms were found to be preceded and accompanied by increases in blood flow in the caudate nucleus and cerebral cortex of conscious rats. Blood flow, measured by the hydrogen polarography method, showed a 2.8-3.8 fold increase in the caudate nucleus and a 1.9-2.6 increase in the cortex after intraperitoneal deltamethrin. The increase in caudate blood flow provided an early and sensitive indicator of the development of motor symptoms, and preceded development of EEG spike discharges. A different pattern of motor symptoms consisting largely of tremor with no choreoathetosis was produced for comparison using another pyrethroid, cismethrin. This, whilst producing a similar increase in cortical flow, did not produce the disproportionate increase in caudate flow characteristic of deltamethrin. Although the actions of deltamethrin were shown not to be restricted to the extrapyramidal system, the selectivity of the blood flow increases, and the nature of the symptoms produced show deltamethrin to be a useful tool for the production of experimental extrapyramidal motor hyperactivity.

Animals↗
PubMed1982

Studied on cerebellar haem metabolism in the rat in vivo.

Rats were injected intraventricularly with 5-amino[4-14C]laevulinate and the radioactivity recovered in the total cerebellum homogenate and in its haem and porphyrin fractions was determined in time. Two phases could be distinguished in the decline of haem radioactivity, suggesting labelling of at least two pools of widely different turnover rates. Succinyl acetone, when injected intraventricularly, caused a marked and long-lasting inhibition of cerebellar 5-aminolaevulinate dehydratase activity and a corresponding inhibition of the incorporation of [14C]5-aminolaevulinate into cerebellar haem in vivo. Inhibition of cerebellar haem biosynthesis by succinylacetone was followed by stimulation of the first enzyme of the pathway, 5-aminolaevulinate synthase, whereas intraventricular injection of haematin led to a significant depression of the activity of the enzyme. This suggested that the cerebellar 5-aminolaevulinate synthetase is regulated by haem through a negative feedback mechanism. Rats given repeated doses of succinylacetone, so as to maintain 80% inhibition of their cerebellar 5-aminolaevulinate dehydratase activity for 5 days, failed to exhibit any obvious symptoms of toxicity but became more sensitive to the neurotoxic effects of large intraventricular doses of 5-aminolaevulinate.

5-Aminolevulinate Synthetase↗
PubMed1981

A study of the kinetic behaviour of glucose based on simultaneous estimates of influx and phosphorylation in brain regions of rats in different physiological states.

Results from the application of a procedure that allows simultaneous estimation of the rates of glucose transport from blood and of glucose phosphorylation in discrete regions of the brain are given for groups of rats displaying chemically induced motor disturbances. The procedure is based on sequential injections of [14C]- and [3H]-2-deoxyglucose followed a few minutes later by focused microwave irradiation to the head. Control conscious rats were used and rats displaying either whole body tremors, hind-limb rigidity or choreoathetotic movements induced by synthetic pyrethroid compounds. For individual rats estimates of 5 parameters were obtained in up to 16 brain regions. In addition brain tissue and plasma glucose concentrations were determined. The 5 parameters were: (1) rate of total glucose influx from plasma; (2) rate of glucose phosphorylation (equivalent to net influx); (3) rate of glucose efflux; (4) half-life of free glucose in brain; and (5) PS-product expressed as the ratio of the rate of glucose influx to plasma glucose concentration. For each parameter significant differences between regions were found in all groups of animals including conscious controls. The mean values for the somatosensory cortex of control rats were parameter: (1) 2.02 mumol/g/min; (2) 1.11 mumol/g/min; (3) 0.91 mumol/g/min; (4) 0.94 min; and (5) 0.196 ml/g/min. A high correlation was observed between the rate of total glucose influx and the rate of glucose phosphorylation for all brain regions in all groups of rats. This finding is discussed in terms of a synchronized regulatory mechanism on the glucose transport carrier of capillary endothelial cells and on the functional hexokinase Vmax activity within brain cells.

Animals↗
PubMed1981

Electroencephalographic and evoked response correlates of trimethyltin induced neuronal damage in the rat hippocampus.

Trimethyltin produces localized neuronal damage in the rat hippocampus, amygdala and pyriform cortex when given systemically. In the present study the behavioural, electroencephalographic and auditory evoked responses of conscious rats were followed over an 11 day period after oral administration of trimethyltin. An early increase in hippocampal and, to a lesser extent, neocortical evoked response was seen, this preceding the behavioural symptoms. Development of symptoms (hyperactivity, tremor and fear) was accompanied by an increase in the incidence of theta rhythm in the electroencephalogram (EEG). Finally a fall in hippocampal evoked response and theta incidence was seen. It is suggested that a phase of neuronal excitability precedes neuronal damage, and that this is more pronounced in the hippocampus than in areas not developing subsequent neuronal loss.

Animals↗
PubMed1980

Estrous response of early postpartum beef heifers to progesterone and estradiol-17beta during restricted dietary energy.

A study was conducted to determine reproductive response of primiparous beef heifers to an ovulation induction regimen during restricted dietary energy intake. Thirty-seven Barzona x Hereford heifers, maintained under drylot conditions, were utilized. Heifers were restricted in TDN on a pen basis to approximately 50% of N.R.C. recommendations for the first 90 days postpartum, then received 120% for 80 days thereafter. All animals received control injections (C) or 30 mg progesterone on day 15 postpartum followed in 48 hours by 2 mg estradiol-17beta (PE). Treated heifers not ovulating at first treatment and/or not cycling, were re-treated at 60 day postpartum, with non-cycling C heifers receiving control injections. Intact fertile bulls were maintained with the heifers from day 1 to 170 days postpartum, with visual observations for signs of estrus and breeding activity conducted twice daily during this period. At first treatment, seven of 18 heifers ovulated, one conceived and four continued to cycle. At second treatment, three of 13 conceived and seven returned to a synchronized estrus 15 to 21 days later. Although intervals to first estrous behavior and estrus favored PE heifers (P< .05), by 90 and 170 days postpartum no advantage in interval to conception or number conceiving was observed.

Journal Article↗
PubMed1980

Selective inhibition of thermogenesis by tributyl S,S,S,-phosphorotrithioate (DEF).

1 Rats and mice given tributyl S,S,S,-phosphorotrithioate (DEF) showed large dose-related falls in body temperature which lasted several hours to several days at environmental temperatures below thermoneutrality (30 to 31 degrees C). 2 DEF produced only mild sedation and a remarkable degree of motor control was retained even when body temperatures fell below 30 degrees C. At the dose producing maximal hypothermia only 2% of rats died within the first 24 h, although prolonged hypothermia was usually lethal. 3 Hypothermia was associated with a complete block of cold-induced thermogenesis, with relatively little effect on basal metabolism at thermoneutrality. 4 Heat conservation mechanisms (peripheral vasoconstriction and piloerection) appeared to be unaffected by DEF and retained their usual temperature thresholds. 5 Adrenal catecholamine secretion in response to handling or acute cold exposure was normal in DEF-treated rats but the fall in body temperature could be markedly reduced by large intraperitoneal injections of noradrenaline, although not atropine. The increase in oxygen consumption produced by injected catecholamines was also unaffected by DEF treatment. 6 It is concluded that the block of cold-induced thermogenesis probably results from a lack of catecholamine release at the tissue level. That this is likely to be mediated at a peripheral site is suggested by the lack of effect of intracerebroventricular DEF.

Animals↗
PubMed1977

Inert gas narcosis.

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Anesthesia, General↗
PubMed1977

Influence of systemic factors on hyperbaric oxygen toxicity in the rat visual system.

The electroretinogram (ERG) was measured in lightly anaesthetised rats exposed to 4-7 atm O2 until death. An initial increase and later decrease in amplitude with increase in latency was seen which, although not consistently related to the appearance of seizures characteristically seen above 4.5 atm 02, appeared closely linked to systemic factors. A fall in respiration rate always preceded the fall of the ERG, and apnoea preceded ERG extinction. When blood pressure and ERG were measured in two comparable groups of rats exposed to 5.76 atm O2, both records showed similar time courses. The cerebral visual evoked response (VER) was measured at 5.76 atm O2 simultaneously with the ERG. The later VER waves showed a degree of enhancement at the time of seizures, but otherwise amplitude and waveform were maintained until late in toxicity. EEG spiking gave the earliest indication of toxicity, and it is concluded that the primary projection to the rat visual cortex is comparatively resistant to high-pressure oxygen.

Animals↗