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M A Simmonds

Publications and source records attributed to M A Simmonds.

102 records · Page 6Linked to original sources
PubMed1970

Central effects of 6-hydroxydopamine on the body temperature of the rat.

1. Rats which had been pretreated with intraventricular injections of 6-hydroxydopamine (6-OHDA) to cause a selective depletion of brain noradrenaline (NA) to 20.7% of control brain NA and brain dopamine (DA) to 34.6% of control brain DA retained an unimpaired ability to regulate their body temperatures on exposure to heat or cold. This is discussed in relation to the possible role of brain NA in the central control of body temperature.2. Intraventricular injections of 6-OHDA in normal rats at room temperature caused an acute, dose dependent hypothermia of up to 4.5 degrees C which lasted for 4-5 hours. Depletion of brain NA and DA by prior treatment with 6-OHDA markedly reduced the hypothermic response to a subsequent dose of 6-OHDA. Selective depletion of brain NA without affecting brain DA did not reduce the response to 6-OHDA. The acute hypothermic response to 6-OHDA, may therefore, be related to a release of DA in the brain.

Animals↗
PubMed1970

Effect of environmental temperature on the turnover of 5-hydroxytryptamine in various areas of rat brain.

1. Rats were exposed to environmental temperatures of 9, 24 or 32 degrees C and the turnover of 5-hydroxytryptamine (5-HT) was estimated in various areas of brain by two different methods in separate series of experiments. In the first method, small amounts of tritium labelled 5-HT, [(3)H]5-HT, were injected into the c.s.f. in order to label radioactively the endogenous 5-HT in the brain. The rates of disappearance of [(3)H]5-HT from discrete areas of brain were taken as indices of the rates of turnover of endogenous 5-HT in these areas. In the second method, the rate of accumulation of endogenous 5-HT after inhibition of monoamine oxidase by pargyline was taken as an estimate of 5-HT turnover.2. The results obtained by each method were in agreement. The turnover of 5-HT increased with increasing environmental temperature from 9 to 32 degrees C in specific brain areas. During the first hour of exposure to 32 degrees C, the turnover of 5-HT increased in the preoptic area, hypothalamus and cortex + hippocampus, but not in striatum or midbrain. During the subsequent 2 hr at 32 degrees C, however, the turnover of 5-HT in the preoptic area and hypothalamus fell while that in the striatum showed a delayed rise.3. It is concluded that 5-HT is involved in several different cerebral pathways which increase their activity upon exposure of the rat to heat. These pathways are not located exclusively in the preoptic area and hypothalamus.

Animals↗
PubMed1969

Thermoregulation: effects of environmental temperature on turnover of hypothalamic norepinephrine.

The hypothesis that norepinephrine is a transmitter in the temperature regulating center of the hypothalamus is based on observations of changes in the rectal temperatures of animals after injections of norepinephrine into the hypothalamus. By introducing tritiated norepinephrine as a label into the endogenous norepinephrine stores in the brain and then measuring the disappearance of tritiated norepinephrine from discrete areas, one can monitor the activity of norepinephrine-containing neurons in those areas. In the rat exposed to heat, the turnover of endogenous norepinephrine appears to be increased selectively in the hypothalamus, whereas exposure to cold has no effect.

Animals↗
PubMed1969

Effect of environmental temperature on the turnover of noradrenaline in hypothalamus and other areas of rat brain.

1. The hypothesis that noradrenaline (NA) may be a transmitter in the temperature regulating centre in the hypothalamus is based on the changes in rectal temperature induced by injection of large doses of NA into the brain. As an alternative approach, the effect of environmental temperature on the rate of turnover of endogenous NA in the hypothalamus has been studied.2. Small amounts of tritium labelled noradrenaline [(3)H]NA were injected into the c.s.f. of rats in order to label radioactively the endogenous NA in the brain. The rats were then exposed to environmental temperatures of 9, 17, 24 and 32 degrees C. The rates of disappearance of [(3)H]NA from discrete areas of brain were taken as indices of the rates of turnover of endogenous NA in those areas.3. The rate of disappearance of [(3)H]NA from the hypothalamus was three times as fast at 9 and 32 degrees C as at 17 or 24 degrees C. There were no such significant differences from the pre-optic area or ;rest of brain' (whole brain minus hypothalamus, pre-optic area, cerebellum and medulla).4. The endogenous concentrations of NA were not altered by the experimental procedures in any of the areas of brain studied.5. The rats maintained normal rectal temperatures at environmental temperatures of 9, 17 and 24 degrees C but became 2.8 degrees C hyperthermic at 32 degrees C.6. It is concluded that mild conditions of both heat and cold resulted in an increased turnover of NA in specific nerve terminals in the hypothalamus. Since the rats were thermoregulating normally, the nerve terminals involved are regarded as forming a part of the central temperature regulating centre.

Animals↗
PubMedDate not supplied

Studies of the recovery and the cost of low-glycerol cryopreserved human red blood cells.

Red blood cells were equilibrated with 28 per cent (v/v) glycerol and 3 per cent mannitol in 0.65 g/100 ml sodium chloride. The units were frozen by immersion into liquid nitrogen and stored at -160 C. After thawing, they were reconstituted and washed using the IBM 2991 Blood Cell Processor. Freeze-thaw rate curves, the effect of thawing techniques, the effect of varying postthaw washing and processing techniques, estimates of red blood cell losses because of hemolysis, and in vitro recovery were determined. In vivo recovery was determined by 51Cr techniques 24 hours after infusion and Ashby survivals and subsequent life span were measured. Metabolic, scanning electronmicroscopy, cost estimates and quality control studies were done on the reconsituted red blood cells. Recipients were evaluated before and after transfusion for metabolic erythrocyte characteristics and for evidence of hemolysis. The modified method requires less wash solution and less technician time than does the standard low-glycerol method. Two units for the same recipient could be passed through the IBM software with no alteration of cell survival or loss. Revision of the IBM 2991 processing procedure provided excellent recovery of viable previously frozen red blood cells at probably a lower cost.

Blood Preservation↗