Biomedical subjects

R Bertin

Publications and source records attributed to R Bertin.

At least 37 records · Page 2Linked to original sources

PubMed1994

[Functional exploration of brown adipose tissue using beta3 agonists].

In view to utilize beta 3 adrenoceptor agonists for the investigation of body lipid metabolism, a study of the effects of BRL 37344 on the functional activity of the brown adipose tissue was performed in the Rat. It is known that this tissue is the principal site of heat production for nonshivering thermogenesis mainly due to the oxidation of fatty acids under the control of norepinephrine (NA) released from the sympathetic nervous system. In order to stimulate the activity of the tissue, rats were reared at 16 degrees C. When they were one month old, they were divided in two groups; one group received a surgical sympathectomy of the interscapular brown adipose tissue (TABI) (S group); the other group was sham-operated (T group). The resting metabolism was estimated by the continuous measurement of O2 consumption and CO2 release, at an ambient temperature of 25 degrees C. The animal capacity for nonshivering thermogenesis was determined by increased O2 consumption following i.p. administration of NA or BRL 37344. In the S group a large decrease in TABI NA content and a decrease in resting metabolism were observed. In both groups VO2 was increased by the two drugs; the increase was linearly related to the dose of BRL (between 2.5 to 10 micrograms/kg); but it was 3 times as high in the T group as in the S group. Moreover, the effect of BRL was 40 fold greater than the effect of NA. These results seem to indicate that, in cold reared rats, a part of nonshivering thermogenesis may be mediated by the beta 3 receptors of the brown fat. It may be concluded that the rats born in cold conditions are good models to study the role of beta 3 receptors in the energetic activity of this tissue very profuse in infant but not in adult man.

Adipose Tissue, Brown↗

PubMed1993

[Surgery of the foot in equinus deformity in hemiplegic adults].

The authors report the results of surgical treatment of the equinus deformity of the foot in adult hemiplegia performed on 23 patients with a long term follow-up for 20 of them. Surgical treatment required two phases. Firstly, a spasticity correction by scopiform neurotomy of the posterior tibial nerve: this operation had to be done 14 times because of the importance of the spasticity. Secondly, a phase of truly orthopaedic surgery which involved successively, a treatment of the equinus deformity by lengthening of the Achilles tendon, a restoration of the dorsal flexion by anterior muscle transfer and some complementary operations on the forefoot. An astragalo-scaphoid arthrodesis was associated in the 13 most recent cases. Results were subjectively judged very good or good for 17 patients. Objectively, walking appliances have been reduced, gait was more secure and a greater autonomy has been reached. However, the goals of this surgery are limited as it has no incidence on central interferent lesions and neuropsychological troubles resulting from brain damage. The quality of the result is, in other respects, conditional upon the gait pattern of the whole limb, particularly upon the importance of the flexion of the knee during the step cycle.

Achilles Tendon↗

PubMed1993

Postnatal development of nonshivering thermogenesis in rats: effects of rearing temperature.

A comparative chronological study (from 1 to 33 days post partum) was performed to establish the capacity for nonshivering thermogenesis (NST) in rats born and reared at 28 degrees C and at 16 degrees C. The resting metabolism measured at 33 degrees C was higher in the 16 degrees C rats than in the 28 degrees C rats from the 3rd day. When expressed per weight or per surface area units it was higher in 16 degrees C pups than in 28 degrees C pups until the end of the 3rd week. In fact the resting metabolism was significantly proportional to different powers of weight (W0.67 at 16 degrees C and W0.75 at 28 degrees C) during the suckling period. At birth, respiratory quotient (RQ) was the same in both groups (0.70); it increased slowly to the end of the 3rd week (about 0.80). During the 3rd week RQ was lower in 16 degrees C rats than in 28 degrees C animals. This indicates that 16 degrees C rats are more dependent on the milk supplied by their mother. After weaning there were no differences in RQ values (0.90). Rectal temperature was low in both groups on day 1 (about 32 degrees C). It increased until weaning when it stabilized at 37 degrees C. From day 1 to day 18, it was significantly lower in cold reared rats. The capacity for NST was measured by investigating the effect of an injection of norepinephrine (NE) on the metabolic rate at 33 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗

PubMed1991

Effects of the rearing temperature on the temporal feeding pattern of the staggerer mutant mouse.

The temporal feeding pattern of the staggerer mutant mouse was tested under two thermal rearing conditions, 28 degrees C and 22 degrees C, and compared to that of the normal mouse. At a temperature of 28 degrees C, the mutants were observed to eat more than the normal mice did although they showed a drastic body weight deficit. At 22 degrees C, this peculiarity was still observed, but with an altered feeding pattern, wherein the mutants ate as much during both the dark and light phases.

Animals↗

PubMed1991

Catecholamine turnover in heart and adrenals of young rats: effects of rearing temperature.

1. A comparative chronological study (from birth to one month of age) was performed to establish the levels and turnover rates of catecholamines in the heart and adrenals of rats born and reared at 28 and 16 degrees C. 2. In the heart, cold induced marked increases of the norepinephrine level and turnover rate only from the second week of age. 3. In the adrenals there was considerable early stimulation of epinephrine production, but only in 28 degrees C rats. 4. The differences observed in the stimulation of the sympathetic nervous system according to the rearing temperature are possibly due to the behavior of the mother in warming the pups.

Adrenal Glands↗

PubMed1991

Serotonin content of the interscapular brown adipose tissue of growing rats.

In brown fat of newborn rats the serotonin (5HT) content is high during the first five days of life. This may play a part in the lipid repletion of the tissue, lipids being the main fuel for nonshivering thermogenesis. Subsequently 5HT increases more in young rats reared at 16 degrees C than in those reared at 28 degrees C but to a lesser extent than norepinephrine (NE) content. A possible role of 5HT in thermoregulation of the rat during the early postnatal period is discussed.

Adipose Tissue↗

PubMed1991

Adipose tissue lipolytic activity and urinary catecholamine excretion in cold-acclimated piglets.

This study was designed to investigate the effect of chronic cold exposure (12 degrees C for 3 weeks) on catecholamine production and noradrenaline-induced lipolytic rate to further describe thermoregulatory mechanisms in 5- to 8-week-old pigs. Lipolytic activity in white adipose tissue was assessed in vitro while catecholamine production was estimated by measuring noradrenaline, adrenaline, and dopamine levels in 24-h urine samples. Animals were fed ad libitum and food intake was 20% greater in the cold. In control piglets maintained in a 23 degrees C environment, the addition of increasing amounts of noradrenaline (10(-6), 10(-5), 10(-4) M) stimulates lipolysis (p less than 0.05) and enhances the basal lipolytic rate (5.4 mu equiv. fatty acids.120 min-1.g-1 tissue) by 2.5-, 2.7-, and 3.9-fold, respectively. Three weeks of cold acclimation had no effect on basal lipolytic rate but increased significantly noradrenaline responsiveness: incubation of subcutaneous white fat in the presence of 10(-4) M noradrenaline does increase the basal lipolytic rate by sixfold. Noradrenaline effects were maximally activated by theophylline. Daily dopamine and noradrenaline excretions (3-10 micrograms/24 h) were increased significantly (up to eightfold) after 10 days of cold acclimation. By contrast, adrenaline excretion was quite low (0.6-1.6 micrograms/24 h) and showed no significant variation with time. It is likely that these hormonal and biochemical modifications play a prominent part in the mechanism of cold acclimation in the piglet. Their significance in the development of shivering and nonshivering thermogenesis is discussed in relation to the supply of energy substrates to the fatty acid utilizing tissues and to the possible uncoupling effect of free fatty acids.

Acclimatization↗

PubMed1991

Are adrenal catecholamines involved in the enhancement of aldosterone production in cold acclimated rats?

In order to determine the possible role of adrenal catecholamines in the enhancement of aldosterone production in cold acclimated rats, dopamine (DA), noradrenaline (NA) and adrenaline (A) contents of adrenals were investigated in cold acclimated (or not), hypophysectomized (or not) rats. The DA content, DA being an inhibitor of aldosterone synthesis, increased in hypophysectomized rats and remained unchanged in sham-operated ones following cold exposure. The NA and A contents, these being, in vitro, stimulators of aldosterone production did not increase, in either group of cold acclimated rats. It is concluded that adrenal catecholamines do not seem to be implicated in the enhancement of aldosterone production.

Acclimatization↗

PubMed1990

Effects of cold acclimation on the energetic metabolism of the staggerer mutant mouse.

Staggerer mutant mice are lean despite their hyperphagia. Brown adipose tissue activity may be implicated in this phenomenon. The aim of this work is to determine the energetic metabolism and to detail some characteristics of the brown adipose tissue of Staggerer mutant mice born and reared either at 28 degrees C (within the thermoneutral zone) or 22 degrees C (cold temperature) compared to nonmutant control mice. In mutant mice reared at thermoneutrality the resting metabolism was found to be higher than that of controls, and further the activity of the brown adipose tissue increased as indicated in relative mass, composition and cytochrome oxydase activity. A stimulatory effect of cold exposure was observed in both mutant and nonmutant mice. It is suggested that Staggerer mice may provide a good model for the study of the cold-induced or diet-induced mechanisms of brown fat stimulation.

Acclimatization↗

PubMed1990

Norepinephrine turnover in brown adipose tissue of young rats: effects of rearing temperature.

Brown adipose tissue (BAT) has an important role in the thermogenesis of newborn mammals and cold-acclimated rodents. Heat production within the tissue is regulated by the sympathetic nervous system (SNS) via norepinephrine (NE) release. As only little is known of the progressive role of SNS during the developmental period, NE content and turnover were determined in BAT of infant rats 1-33 days of age. The dams and the pups were kept at either 28 or 16 degrees C. It was observed that the NE level in the tissue and the mediator turnover had an almost parallel evolution during the experimental period. In the first week of life, level and turnover of NE were higher in the 28 degrees C group than in the 16 degrees C group. During the second week, the level remained constant in rats kept at 28 degrees C, but the NE turnover slightly decreased. In contrast, a large increase of both parameters was observed in rats kept at 16 degrees C. Then a decrease occurred in both groups until weaning. Subsequently the values remained almost constant. It must be noted that, from the end of the first week, NE content and turnover were always significantly higher in the 16 degrees C group than in the 28 degrees C group. At the end of the first month, the level was 50% higher in cold-acclimated rats and turnover was four times as high as in controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗

PubMed1990

Thermogenic capacity of the brown adipose tissue of developing rats; effects of rearing temperature.

A chronological study was performed to investigate the postnatal development of the thermogenic capacity of the brown adipose tissue (BAT) comparing rats born and reared at 16 degrees C (cold) or 28 degrees C (control). Mitochondrial mass, cytochrome-c-oxidase activity (index of oxidative capacity) and GDP binding to mitochondria (uncoupling test) were investigated in rats from 1 to 33 days of age. Specific cytochrome-c-oxidase activity was the same in both groups during the first week, then increased in the cold group and decreased in controls; from the 9th day it was always twice as high in the former as in the latter. Specific binding of GDP to mitochondrial proteins remained almost constant in control rats during the first week contrasting with a rapid increase in that for cold rats. Afterwards it decreased in both groups until weaning but remained five times as high in cold rats as in control rats. As growth of BAT is faster and mitochondrial content greater in cold reared rats, the capacity of the tissue for thermogenesis appeared to be greatly temperature dependent soon after birth and during the entire suckling period. However the mechanisms of this stimulation remain to be elucidated.

Adipose Tissue, Brown↗

PubMed1990

[Osteosynthesis of radial head fractures in adults].

The authors report their experience and the results of internal fixation of radial head fractures in adults. They studied type 2 and type 3 fractures of Mason classification. Results were appraised with criteria of Radin and Riseborough. They found a rate of 80 per cent of objectively good or fair results. Fractures with one fragment (type 2) and without associated lesions (like sprain or dislocation of elbow) had the best results which depended of the quality of internal fixation. The series reported in the literature using the same operative technique are comparable. The results are equal or better than head resection with or without arthroplasty. Internal fixation is considered as the best operative technique for displaced fractures in adults. Reduction must be perfect. Head resection must be considered per-operatively if a perfect reduction is technically impossible to achieve.

Adolescent↗

PubMed1989

Evidence for a cold-induced aldosterone stimulation in the rat.

This study was undertaken to determine the secretion of aldosterone by male Long-Evans rats acclimated for six weeks to moderate cold (15 C), in comparison with rats maintained at thermo-neutral temperature (28 C). The following determinations were made: corticosteroids in plasma and adrenals, PRA, and hydromineral balance. Cold acclimation highly increased the plasma and adrenal levels of aldosterone and corticosterone. The cold stimulation of aldosterone was induced neither by the renin-angiotensin system, nor by alterations of hydromineral balance: PRA, plasma sodium and potassium concentrations, blood hematocrit, and hydromineral balance at 15 C and 28 C did not differ. Moreover this stimulation was induced neither by ACTH, nor by any other hypophyseal factors, since plasma aldosterone levels remained high in hypophysectomized rats. This study provides evidence of an aldosterone stimulation which appeared during moderate cold acclimation; the origin of this stimulation must be investigated.

Adrenal Glands↗

PubMed1987

Some regulatory aspects of thermogenesis in cold-exposed piglets.

1. Thermoregulatory mechanisms were studied in weaned piglets fed ad libitum for 3 weeks at 12 or 23 degrees C. 2. Cold-adapted pigs maintained a growth rate and a carcass composition similar to the control ones, while increasing food intake by 20% (P less than 0.05). 3. Lipoprotein lipase activity was increased (P less than 0.05) by cold exposure in white adipose tissue (WAT) and heart. A large enhancement of lipogenesis was observed in WAT and to a lesser extent in the liver while WAT composition did not change significantly in the cold. 4. Cytochrome oxydase activity was increased in liver (30%), perirenal fat (40%) and interscapular muscle (75%) of cold-exposed pigs. 5. Plasma levels of thyroid hormones (TSH, T3, T4) were increased in the cold. 6. Mechanisms and locations of heat production are discussed.

Acclimatization↗

PubMed1985

Effects of cold acclimation on the activity of lipoprotein lipase in adipose tissues of genetically obese Zucker rats.

The activity of lipoprotein lipase (LPL) was studied in interscapilar brown adipose tissue (BAT), epididymal white adipose tissue (WAT) and in the heart of lean and obese adult Zucker rats maintained at 22 degrees C or adapted to cold (10 degrees C). In WAT the specific activity per gram of tissue was lower in obese than in lean rats but the total activity within the tissue was three-fold higher. Cold acclimation did not modify total activity in either lean or obese rats. In BAT, but not in the heart, both specific and total activities were lower in obese than in lean animals. They were enhanced in both tissues following cold acclimation. Six-hour fasting led to a decrease in specific activity in WAT of lean rats but had no effect in obese animals; an increase was observed in BAT and heart of both genotypes. Insulin administration has no effect on activities in WAT in either 22 or 10 degrees C adapted obese rats. Norepinephrine administration stimulates LPL activity in BAT and heart of all groups. It is concluded that the lack of development of obesity previously observed in obese rats following cold acclimation is not due to a decreased capacity of lipid uptake by WAT. It might in part be due to an increased lipid oxidation in BAT.

Acclimatization↗

PubMed1984

[Effect of cold adaptation on the feeding behavior of genetically obese Zucker rats].

A diurnal hyperphagia is certainly the main factor of adiposity in the genetically obese Zucker fa/fa rat. In a previous experiment it was observed that cold-acclimatization suppressed hyperphagia and stopped the increase in obesity. In this work, the chronology of modification in the feeding pattern is studied during the first month of cold exposure (10 degrees C). The main cold-induced modifications are observed after 2 weeks of cold exposure. Possibly the decrease in metabolic efficiency of food could parallel the cold-induced enhancement of energetic capacity of brown adipose tissue which has been described elsewhere. This tissue could play a role in the obesity of the Zucker rat.

Acclimatization↗

PubMed1983

Effects of cold acclimation on the feeding pattern and energetic metabolism of genetically obese Zucker rats.

1. The feeding pattern, growth rate and energetic metabolism were studied in obese Zucker rats of 5-12 weeks of age kept at ambient temperatures of 22 or 10 degrees C. 2. During this period, the increment in obesity of the 22 degrees C-exposed animal was found to be due to diurnal hyperphagia and not to a lowered resting metabolism. 3. In the 10 degrees C-exposed rat the development of non-shivering thermogenesis associated with a lack of enhancement of food intake leads to prevent the obesity.

Acclimatization↗

PubMed1983

In vivo effects of indomethacin and cyclophosphamide on CFU-GM proliferation and cyclic nucleotide levels in bone marrow of mice.

The effects of indomethacin (6 mg/kg daily, orally, for 4 days) or cyclophosphamide (150 mg/kg, a single dose, intraperitoneally) on myelopoiesis were studied in mice. A hyperplasia of the committed stem cell compartment (rise in the recognizable myeloid precursors, increase of both colony forming capacity and number of CFU-GM in S-phase) associated to an increase of cyclic AMP and GMP amounts in bone marrow cells of treated mice were observed. These results suggest a possible relationship between the in vitro enhancement of proliferative activity of CFU-GM and the in vivo increase of both cyclic nucleotide levels in medullary environment.

Animals↗