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R Refinetti

Publications and source records attributed to R Refinetti.

At least 55 records · Page 3Linked to original sources
PubMed1991

A prolegomenon to the study of graduate research training.

Academic physiologists are both teachers and researchers. As a teacher the physiologist has two main tasks, to teach courses and to supervise graduate student research. It is argued that these two tasks involve different pedagogic strategies and therefore should not be confounded with one another. The physiologist who acts as a teacher in a situation of research advising will be an inappropriate advisor and will provide the student with inappropriate research training. When performing the task of graduate advisor, the physiologist should maintain a liberal attitude that fosters the graduate student's research education.

Education, Graduate↗
PubMed1990

Peripheral nervous control of cold-induced reduction in the respiratory quotient of the rat.

Cold-exposed rats show a reduction in the respiratory quotient which is indicative of a relative shift from carbohydrates to lipids as substrates for oxidative metabolism. In the present study, the effects of food deprivation and cold exposure on the respiratory quotient were observed. In addition, the involvement of the three main branches of the peripheral nervous system (sympathetic, parasympathetic, and somatic) was investigated by means of synaptic blockade with propranolol, atropine, and quinine, respectively. Both propranolol and quinine blocked the cold-induced decrease in respiratory quotient and increase in heat production, whereas atropine had only minor and very brief effects. It is concluded that both the sympathetic and somatic branches are involved in the metabolic changes associated with cold-induced thermogenesis and that the increase in metabolic heat production involves a shift from carbohydrate to lipid utilization irrespective of which of the two branches is activated.

Animals↗
PubMed1990

Retrieval performance in online search in thermal physiology.

Documents on four topics in thermal physiology were searched for in both BIOSIS and MEDLINE using both natural language and standard index words. The search by natural language retrieved more relevant documents than the search by standard index words in both databases. Overall, more relevant documents were retrieved in MEDLINE than in BIOSIS. Even in MEDLINE, however, only about 40% of the total existing documents (as estimated by an expert in thermal physiology) were retrieved.

MEDLARS↗
PubMed1990

Body temperature rhythms, cold tolerance, and fever in young and old rats of both genders.

The circadian rhythm of body temperature (CTR) of male and female rats living at 23 degrees C, as well as their body temperature response to a yeast injection or to a 2-h exposure to 0 degree C, was investigated by telemetry. Young rats had a clear CTR with a mean nocturnal peak of 38.0 +/- 0.1 degree C and diurnal trough of 36.2 +/- 0.1 degree C. Older rats, starting at about 18 months of age, tended to have poor (that is, lower amplitude) rhythms. Mean daily body temperature was 37.1 +/- 0.2 degree C at all ages. After exposure to the cold, the body temperature of young rats, old rats with a strong CTR, and old rats with a poor CTR changed in the ranges of -0.3 to +1.5 degree C, -3.1 to +0.7 degree C, and -5.2 to +0.4 degree C, respectively. This indicates that old animals, especially but not exclusively those with poor CTRs, are less resistant to cold stress. On the other hand, the capacity to develop a fever in response to a yeast injection was equivalent in the three groups of animals, although females had a smaller response than males. It is concluded that the process of aging does not have a generalized debilitating effect on temperature regulation in rats. Rather, aging seems to affect individual components of the thermoregulatory system differentially.

Acclimatization↗
PubMed1989

Online coverage of the literature on thermal physiology.

Online searches for research topics in thermal physiology usually do not retrieve more than 40% of the existing publications. In order to determine whether this low retrieval rate is due to deficient coverage of the literature or to problems in storage and retrieval of information, a list of 25 major papers, 25 minor papers and 15 obscure papers on thermal physiology was compiled. The 65 documents were searched online in the MEDLINE database. Retrieval rate was more than 60% for obscure papers, 80% for minor papers, and 90% for major papers. It is concluded that MEDLINE has an appropriate coverage of the literature on thermal physiology and that the low retrieval rate in online searches is due mostly to problems in information processing.

Animals↗
PubMed1989

Computation of the effective body mass for metabolic studies of lean and obese rats.

The whole-animal metabolic rates of lean and obese rats cannot be directly compared because obese rats have much greater body mass than lean rats. Expressing the results as metabolic rate per unit of body mass is also not satisfactory because lean and obese rats of the same size have different body compositions. To make possible comparisons between the two types of rats, metabolic rate must be expressed per unit of effective body mass. Effective body mass for lean and obese Zucker rats can be calculated as 1.00 M0.75 and 0.82 M0.75, respectively, where M is the mass of the animal.

Animals↗
PubMed1989

Respiratory gaseous exchange in the Zucker rat.

Measurements were made of the oxygen consumption and carbon dioxide production of lean and obese Zucker rats ranging from 4 to 400 days of age. As expected, O2 consumption per animal increased with age and was higher in obese than in lean rats. However, O2 consumption was lower in obese animals when expressed per unit of metabolic body mass. Age per se did not influence the respiratory quotient (R), but obese animals had consistently higher Rs than lean animals. These results confirm and extend previous findings described in the literature.

Aging↗
PubMed1989

Thermopreferendum of the rat: inter- and intra-subject variabilities.

The thermopreferendum of male hooded rats was studied in a temporal thermal gradient. The preferred ambient temperature was found to be approximately 19 degrees C. In addition to the thermopreferendum, three other physiological functions (resting body temperature, daily food intake, and daily ambulatory activity) were each measured in eight rats for 8 days. Overall variability of the thermopreferendum data was higher than that of body temperature and food intake data but lower than the variability of ambulatory activity data. Coefficients of inter- and intrasubject variabilities were computed for each of the four variables. Inter-subject variability was equivalent in all variables, but intrasubject variability was smaller for thermopreferendum and activity than for food intake and core temperature. The thermopreferendum of 19 degrees C is consistent with previously published results but inconsistent with the available data on the thermoneutral zone of the rat (27-28 degrees C). The cause of this inconsistency remains to be determined.

Animals↗
PubMed1989

Effect of ambient temperature on respiratory quotient of lean and obese Zucker rats.

O2 consumption and CO2 production were measured in lean and obese Zucker rats under these conditions: thermal neutrality (acclimation and test at 25 degrees C), acute cold (acclimation to 25 degrees C and test at 15 degrees C), and chronic cold (acclimation and test at 15 degrees C). The respiratory quotient (RQ) of ad libitum-fed animals was 0.92 at neutrality, 0.87 at acute cold, and 0.77 at chronic cold. Lean and obese animals had comparable RQs under the three conditions. These results confirm previous investigations on the effect of ambient temperature on gaseous exchange in rats but fail to demonstrate a difference in substrate utilization in the metabolism of lean and obese Zucker rats.

Animals↗
PubMed1989

Magnitude estimation of warmth: intra- and intersubject variability.

Fifty-two subjects, both male and female, 18 to 62 years old, were asked to hold a metal bar maintained at different temperatures (33 degrees to 42 degrees C), and to estimate the magnitude of the resulting thermal sensation. On the average, the estimates were linearly related to the stimulus temperature, although most individual subjects either under- or overestimated middle-range values. Intersubject variability, which was twice as large as intrasubject variability, could not be accounted for by gender, age, or body-temperature differences.

Adolescent↗
PubMed1989

Body size and metabolic rate in the laboratory rat.

When the basal metabolic rates of living beings from different species are compared, a relationship between metabolic rate (M) and body size (S) can be identified as follows: M = a Sb, where b is close to 3/4. The present study investigated whether the same relationship applies within a species. In the laboratory rat, Rattus norvegicus, it was found that b can vary considerably from one sample of animals to another. The value of b was also affected by the activity level of the animals, but not by moderate cold exposure. The best estimate for the basal intraspecific b in the rat may be closer to 2/3 than to 3/4, but the variability of the experimental data prevent a definite conclusion at this point. Further research is necessary to explain the variability between different samples of rats.

Animals↗
PubMed1988

Absence of metabolic acclimation to cycling temperature conditions in the goldfish.

Studies of whole organism metabolism have failed to confirm an effect of cyclic acclimation in fish while studies at the hematological level show clear changes due to cyclic thermal regimes. To reevaluate the effect of cycling temperatures on fish metabolism, oxygen consumption was measured in goldfish acclimated to either a constant temperature (28 degrees C) or a diurnal sinewave cycle (20-36 degrees C). Fish from both acclimation conditions were tested at one of three temperatures (20, 28, 36 degrees C). Oxygen consumption increased with temperature but did so independently of the acclimation regime. Thus, cyclic acclimation did not alter metabolic sensitivity.

Acclimatization↗
PubMed1988

Effects of food temperature and ambient temperature during a meal on food intake in the rat.

Rats kept either at thermoneutrality (29 degrees C) or in the cold (19 degrees C) were fed either at thermoneutrality or in the cold. Rats kept in the cold ingested consistently more food than rats kept at thermoneutrality. Also, independently of nature temperature, rats fed in the cold ingested more food than rats fed at thermoneutrality. There was no interaction between nurture temperature and meal temperature. In a second experiment, rats kept at thermoneutrality were fed food pellets previously warmed or cooled to 12, 29, or 48 degrees C. Food temperature per se had no significant effect on food intake.

Animals↗
PubMed1987

A reevaluation of the role of the lateral hypothalamus in behavioral temperature regulation.

Rats exposed to the cold (-9 degrees C) were trained to depress a lever to obtain pulses of infrared heat. Half of the animals received bilateral electrolytic lesions of the lateral hypothalamus and half were sham operated. Lesioned and control animals performed similarly postoperatively and responded appropriately to changes in reward duration and intensity. Thus, lateral hypothalamic lesions do not impair behavioral thermoregulation. Despite normal behavioral heat intake, body temperature of the lesioned rats fell significantly during the sessions, which can be attributed to an impairment in metabolic heat production due to the lesions.

Animals↗
PubMed1986

Effects of lateral hypothalamic lesions on thermoregulation in the rat.

The effects of bilateral lesions in the lateral hypothalamus (LH) of the rat on several thermoregulatory and non-thermoregulatory variables were studied. In agreement with the literature, a reduction in food and water intake and in body mass were observed in the experimental animals but not in the operated controls. Rectal temperature and metabolism increased for a few hours after the lesion, decreased below pre-lesion level for a day or two, and finally returned to baseline level. The increase in rectal temperature during a 1-hr exposure to 5 degrees C was accentuated in the control but not in the experimental subjects. An improvement in operant thermoregulatory behavior, measured by nose-poke and lever-press responses, was observed in most LH-lesioned animals. Thermal preference in a gradient, two measures of general activity, and light avoidance were not affected by the lesions. The post-lesion improvement in operant thermoregulatory behavior does not support the view of the LH as a necessary locus for the integration of behavioral thermoregulatory responses.

Animals↗
PubMed1986

Effects of anterior and posterior hypothalamic temperature changes on thermoregulation in the rat.

Metabolic heat production and operant thermoregulatory behavior were studied in rats with thermodes implanted into the anterior and posterior hypothalamus. Metabolism was found to be inversely related to anterior hypothalamic temperature (between 32 and 42 degrees C) and not related to posterior hypothalamic temperature. Behavior, on the other hand, was found to be inversely related to both anterior and posterior hypothalamic temperature. Therefore, temperature changes in the anterior hypothalamus affect both autonomic and behavioral thermoregulation, whereas temperature changes in the posterior hypothalamus affect only behavioral thermoregulation.

Animals↗