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Biomedical subjects

K E Cooper

Publications and source records attributed to K E Cooper.

At least 73 records · Page 4Linked to original sources
PubMed1980

Modification of thermoregulatory responses in rabbits reared at elevated environmental temperatures.

1. Pregnant New Zealand white rabbits were kept from 14 days pre-partum at an environmental temperature of 33 degrees C, and their offspring were reared at this temperature. 2. In response to a 4 hr cold exposure, animals (aged 90-180 days) raised in this way showed significant drops in colonic temperature (-2.7 +/- 0.5 degrees C) while control animals reared at 20 degrees C did not (+0.05 +/- 0.1 degrees C). 3. A reduced, monophasic endotoxin fever was observed in animals reared at 33 degrees C, while a normal biphasic fever was seen in rabbits originally reared at 20 degrees C and subsequently acclimated to 33 degrees C. 4. A greatly reduced temperature response to intravenous infusion of noradrenaline was also found in animals raised at 33 degrees C. 5. It is proposed that thermal afferent input during early life may play an important role in the development of the thermoregulatory system.

Acclimatization↗
PubMed1980

Convulsive and hypothermic effects of vasopressin in the brain of the rat.

Arginine vasopressin (AVP) was administered into the lateral cerebral ventricles of rats to assess its effects when given directly into the brain. AVP (1.0 microgram) caused an immediate sharp decrease in body temperature. Behaviorally, AVP caused short pauses of immobility and staring upon the first injection but the same dose caused myoclonic-myotonic convulsions upon the second injection 2 days later. Thereafter, as little as 10 ng of AVP caused seizures.

Animals↗
PubMed1980

Vasopressin increases the central nervous system suppressive control over gill reflex behaviours and associated neural activity in Aplysia.

Exposure of the abdominal ganglion of Aplysia to arginine vasopressin (10(-12) M) reduces the amplitude of the gill withdrawal reflex, accelerates its rate of habituation, and causes a concomitant decrease in the number of action potentials evoked in gill motor neuron L7. The effects of vasopressin on both the reflex and the concomitant neural activity evoked in L7 were completely reversible. Vasopressin did not affect the passive membrane properties of L7. The results indicate that a vertebrate neurohypophyseal hormone can affect behavioural responses as well as modify the synaptic efficacy of the reflex pathway.

Animals↗
PubMed1979

Evidence supporting a role for endogenous vasopressin in natural suppression of fever in the sheep.

1. The antipyretic effect of arginine vasopressin (AVP) introduced into the brain by push-pull perfusion was investigated in the sheep. 2. Control perfusions with sucrose solutions had no effect on fevers induced by a bacterial endotoxin. Sucrose solutions containing AVP (4.0 microgram/ml.) perfused at 40 microliter./min had significant antipyretic activity, reducing the two peaks of the fever but had no effect on resting body temperature. 3. Loci in which AVP induced antipyresis were limited to the septal region about 2-3 mm anterior to the anterior commissure. 4. The amounts of AVP in perfusates from the septal region correlated negatively with changes in body temperature. 5. AVP administered I.V. did not lower fever. 6. AVP plasma levels correlated negatively with fever magnitude following premature birth induced by dexamethasone.

Animals↗
PubMed1979

Sensitivity of hypothalamic sites to salicylate and prostaglandin.

This study was designed to determine the dose of salicylate necessary to produce substantial antipyresis, and to determine the relationship between the response to salicylate and prostaglandin infused into the same region of the preoptic area of the rabbit. The effect of preoptic infusions of three doses of sodium salicylate, or a control solution, on the fever produced by an intravenous injection of endogenous pyrogen was measured. The pyrogenic response to prostaglandin E1 injected into the same preoptic sites in the same rabbits was also monitored. The results showed that the 50 microgram/microL per hour dose of salicylate did not produce significant antipyresis but that the 100 and 200 microgram/microL per hour doses did. The results also showed a significant correlation between the magnitude of fever produced by prostaglandin E1 and the magnitude of antipyresis produced by sodium salicylate at a particular site. Those sites at which infusion of salicylate produced the most effective antipyresis were also the ones at which prostaglandin E1 produced the largest fevers.

Animals↗
PubMed1979

Development of fever in the newborn lamb.

Newborn lambs do not become febrile in response to intravenous (iv) bacterial endotoxin in moderate doses. Newborn lambs were tested to see if they could become febrile to large doses of endotoxin or to endogenous pyrogen. At 5 h of age lambs do not become febrile to relatively large doses of endotoxin or to endogenous pyrogen, but rather become hypothermic. At 32 h and all subsequent times, fevers could be elicited. Onset time of fevers in lambs was short initially and gradually lengthened over 9 days, at which time it was similar to the onset time of the adult fever. With respect to the febrile response, newborn lambs showed varying degrees of tolerance after 10 days of daily injections of endotoxin, as compared to the ewe which becomes tolerant in 2 or 3 days.

Aging↗
PubMed1979

Ontogeny of fever.

The newborn of the sheep and the guinea pig are refractory to bacterial pyrogen. The newborn lamb does not get fever and the newborn guinea pig only gets fever to large doses of intravenous bacterial endotoxin. It would appear that the lack of febrile response to endotoxin occurs beyond the stage of production of endogenous pyrogen and may represent either an immaturity of the brain mechanisms for heat production and heat conservation, which are driven by endogenous pyrogen, or, as evidence is presented, there may be a circulating endogenous antipyretic substance present in the circulation of the newborn lamb and there is evidence that such a substance is present in the circulation of the ewe close to term. Possible relevance of these findings to lack of fever in the infected human neonate is discussed.

Animals↗
PubMed1978

Imparied thermoregulation in pregnant rabbits at term.

Pregnant and nonpregnant female rabbits were placed in hot (33 degrees C) and cold (3 degrees C) environments and their core temperatures measured. Pregnant rabbits during the 3 days before giving birth were less able to maintain normal body temperatures in thermally adverse environments than were nonpregnant rabbits. This alteration in thermoregulatory ability may permit an environmental temperature change that is not dangerous to nonpregnant rabbits to be potentially harmful or lethal to both mother and offspring.

Animals↗
PubMed1978

Perfusions of the posterior hypothalamus of cats with various ions and saccharides: effects on body temperature.

Alterations of the ionic constituents of solutions perfused through the tissue of the posterior hypothalamic region in conscious cats elicited changes in body temperatures. Increasing the (Ca2+) to (Na+) ratio of the perfusion solution elicited falls in body temperature which were accompanied by changes in posture and vasomotor tone which assisted the heat loss. The magnitude of the fall was dependent on the ratio of (Ca2+) to (Na+) and was not related to the osmolarity of perfusion solution. The addition of dextrose to the perfusion solution attenuated or abolished the response produced by an increase in the (Ca2+) to (Na+) ratio. This dextrose effect could be attributed to its role as an energy substrate. These data are consistent with and extend previous suggestions that the set point for body temperature may be dependent on the inherent ratio of the ionic constituents of the posterior hypothalamic area. Further, they suggest that these ionically induced alterations can be overriden by increasing the available energy substrate.

Animals↗
PubMed1978

The effect of clothing on the initial ventilatory responses during cold-water immersion.

The effect of clothing on ventilatory responses during cold-water immersion was studied. Subjects were immersed in water at 13.9 degrees C on two occasions wearing either a bathing suit only or clothed with jacket, shirt, pants, and sports shoes. It was found that the initial gasp and subsequent minutes of expired ventilation were significantly attenuated, whereas the changes in end-tidal PCO2 were only significantly different for the 2nd and 3rd min of the immersion. It would appear that the use of clothing may prove beneficial during the first few minutes of a cold-water immersion by decreasing the powerful drive to increased respiration.

Clothing↗
PubMed1978

The relationship of deep and surface skin temperatures to the ventilatory responses elicited during cold water immersion.

Subjects were immersed for 10 min in water at 14.5 degrees C, after exposure either to ambient temperature or sauna heating. During the immersions, total ventilation, end-tidal PCO2, the mean of three surface skin temperatures, and deep skin temperatures were measured. There was a statistically significant correlation between the rate of change of deep skin temperature and the initial ventilatory responses evoked during both cold water immersions. After the sauna heating and cold water exposure, the temperature gradient through the skin appeared to be related to the ventilatory response. There was no significant correlation between the rate of change of mean surface skin temperature and the ventilatory response. The results suggest that the primary drive to increased ventilation during cold water immersion is the rate of change of deep skin temperature.

Adult↗
PubMed1978

Alcohol and respiratory and body temperature changes during tepid water immersion.

Resting subjects were immersed for 30 min in water at 22 and 30 degrees C after drinking alcohol. Total ventilation, end-tidal PCO2, rectal temperature, aural temperature, mean skin temperature, heart rate, and oxygen consumption were recorded during the experiments. Blood samples taken before the immersion period were analyzed by gas-liquid chromatography. The mean blood alcohol levels were 82.50 +/- 9.93 mg.(100 ml)-1 and 100.6 +/- 12.64 mg (100 ml)-1 for the immersions at 22 and 30 degrees C, respectively. There was no significant change in body temperature measured aurally or rectally, mean surface skin temperature, or heart rate at either water temperature tested. Total expired ventilation was significantly attenuated for the last 15 min of the immersion at 22 degrees C, after alcohol consumption as compared to the ventilation change in water at 22 degrees C without ethanol. This response was not consistently significantly altered during immersion in water at 30 degrees C. It is evident that during a 30-min immersion in tepid water with a high blood alcohol level, body heat loss is not affected but some changes in ventilation do occur.

Body Temperature↗