Biomedical subjects

Y Cherel

Publications and source records attributed to Y Cherel.

At least 37 records · Page 2Linked to original sources

PubMed1995

Protein and lipid utilization during fasting with shallow and deep hypothermia in the European hedgehog (Erinaceus europaeus).

We investigated whether the relative contributions of body protein and lipid reserves differ according to the level of energy expenditure in fasting animals. Protein and lipid utilization was therefore quantified and compared in hedgehogs which fasted with shallow and deep hypothermia, i.e. by exposure at 5 or 20 degrees C ambient temperature. Body composition was determined for every 150-g decrease in mass throughout the experiment, allowing the calculation of regression lines between body mass (independent variable, x) and body composition (dependent variable, y: water, protein, neutral lipids, phospholipids and cholesterol). There were highly significant (P < 0.001) linear decreases in all body components with decreasing body mass in both groups of hedgehogs. Neutral lipids were the main component of the total body mass loss (54%) in fasted animals with shallow and deep hypothermia, percentages of water (26-30%) and protein (10-11%) being lower, and those of phospholipid and cholesterol negligible (< 0.5%). In spite of different levels in energy expenditure (2.54 and 1.07 W.kg-1 in shallow- and deep-hypothermal fasting hedgehogs, respectively), the energy sources were identical in both groups, neutral lipid being the main fuel (91-92%) and body protein accounting for the remainder (8-9%). Prolonged fasting with shallow and deep hypothermia were marked by low alaninemia and glycemia, while plasma free fatty acids and beta-hydroxybutyrate were elevated.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Involvement of corticosterone in the fasting-induced rise in protein utilization and locomotor activity.

During fasting, most of the energy is derived from lipids whereas proteins are efficiently spared. However, there is a late rise in net protein utilization. Fasting is also associated with an increase in locomotor activity. Because the plasma corticosterone level increases concomitantly with these metabolic and behavioral changes, the involvement of corticosterone has been hypothesized. To test this, the net protein utilization and locomotor activity were investigated in fasted adrenalectomized (Adx) rats, with or without replacement with corticosterone, and in fasted intact rats treated with RU486, an antagonist of type II glucocorticoid receptors. During the phase of fasting characterized by protein sparing, urine nitrogen loss was further reduced in Adx rats and in RU486-treated controls compared with intact rats and with Adx rats with corticosterone replacement: this indicates a catabolic effect of corticosterone through type II receptors. In the last phase of fasting, the rise in net protein breakdown was suppressed in Adx rats and restored by corticosterone replacement. The increase in locomotor activity induced by fasting in controls was suppressed in Adx and restored by corticosterone replacement. This rise in running activity was still present in RU486-treated rats. In conclusion, this study shows that corticosterone plays a critical role in the changes of both protein catabolism and locomotor activity during prolonged fasting.

Adipose Tissue↗

PubMed1995

Histopathological alterations of turkey skeletal muscle observed at the slaughterhouse.

1. Six leg muscles (iliotibialis cranialis, iliotibialis lateralis, flexor cruris lateralis pars pelvica, gastrocnemius lateralis, gastrocnemius medialis and puboischiofemoralis medialis) were collected immediately after slaughter from each of 200 randomly selected male commercial turkeys. 2. Among these 1,200 samples processed for histology and examined in cross-sections, 9.4% exhibited fibre splitting and 9% intrafascicular adipose tissue infiltration. 3. Gastrocnemius medialis muscles were more often affected than other muscles (P < 0.05), with 33% showing isolated necrotic fibres. There were rarely more than 5 necrotic cells out of roughly 4000 cells per sample. 4. Twelve percent of samples showed a high incidence of hypercontracted fibres, 63% a medium incidence (less than 8% present) and 24% none. Hypercontraction was more frequent in puboischiofemoralis medialis muscles (P < 0.05).

Abattoirs↗

PubMed1994

Effect of fasting and thyroidectomy on cysteine proteinase activities in liver and muscle.

Prolonged starvation mimics chronic negative nitrogen balance observed in many physiopathological situations. During starvation, an initial decrease in protein utilization (phase I) is followed by a long period of protein sparing (phase II) that ends with a marked rise in nitrogen excretion (phase III). Variations in protein metabolism during starvation are determined by changes in protein synthesis and degradation rates (Cherel, Y., Attaix, D. Rosolowska-Huszcz, D., Belkhou, R., Robin, J.P., Arnal, M. and Le Maho, Y. (1991) Clin. Sci. 81, 611-619), but little information is available on expression of proteolytic systems. In this study, cathepsin B, H and L activities were compared in hindlimb muscles and liver at various phases of starvation in thyroidectomized and sham-operated rats. In muscle, cathepsin activities fell from the fed state to phase II, which suggests that cathepsins may play a role in the curtailment of muscle proteolysis during protein sparing phase. This decrease of muscle cathepsin activities was reproduced by thyroidectomy alone. In contrast, liver cathepsin B and H activities fell during starvation, but were not affected by thyroidectomy alone. Liver cathepsin L decreased only during starvation in thyroidectomized animals. These observations emphasize that different mechanisms modulate cathepsin expression in skeletal muscle and liver.

Animals↗

PubMed1994

Energy and protein requirements for molt in the king penguin Aptenodytes patagonicus.

Adult king penguins annually fast ashore for 1 mo for molting. By the end of molt, they have lost 44% of their prefasting body mass. About 18% of new feather synthesis occurs at sea, thus reducing both nutrient requirement and fasting duration. Plumage synthesis continues during the first 3 wk of fasting. Loss of old feathers occurs between day 12 and day 21 of the molt, and it is associated with a peak in daily body mass loss. The dry mass of epidermal structure synthesized during molt is 395 g. Body composition analysis indicates that fat oxidation accounts for 85% of total energy expenditure. The proportion for protein is 15%, a value twofold higher than during the breeding (nonmolting) fast. The mean energy expenditure is also 21% higher during the molting fast (3.04 W/kg). Compared with other birds, the energetic cost of feather synthesis is the lowest in king penguins (85 kJ/g) and consequently the energetic efficiency is the highest (25%). Changes in tissue composition during molt show that integument is the main lipid source (72% of the lipid loss) and thus the main source of energy (61% of the total energy expenditure). The integument and the pectoral muscles play a major role in molting protein metabolism, providing 20 and 57%, respectively, of the total protein needs for feather synthesis and/or energy expenditure. This result emphasizes the role of integument as a protein source, because the large premolting muscle hypertrophy is not sufficient to account for the totality of the protein cost of molt.

Adult↗

PubMed1994

Comparison of postnatal development of anterior latissimus dorsi (ALD) muscle in heavy- and light-weight strains of turkey (Meleagris gallopavo).

ALD muscle development was studied from day 2 to week 15 in males of two turkey strains. At 15 weeks, the heavy-weight (HW) strain weighted 2.2 times as much as the light-weight strain (LW). Morphometric and immunocytochemical analysis showed the presence of small fibers in HW ALD muscle which simultaneously accumulated ventricular and embryonic fast myosin heavy chain isoforms. The appearance of these nascent myofibers suggests that hyperplasia contributes to the growth of HW ALD muscle.

Age Factors↗

PubMed1993

Histology and histomorphometry of the tibial diaphyseal growth in two turkey strains during the first six weeks after hatching.

The comparative cortical growth of the tibio-tarsus was studied during the first six weeks after hatching in two turkey strains, a light and a heavy one. At one day post-hatching the cortical appeared to be constituted in both strains of an embryonic non-active fibrous bone tissue which had completely disappeared at one week. On and after one week the cortex was constituted of a fibrolamellar adult bone tissue elaborated on the periosteal part of the cortex. Its vascular pattern depended on the strain and on the thickness of the cortical faces. The histomorphometric studies showed that the growth in thickness was earlier and faster in the heavy strain with a Total Diaphyseal Surface twice larger at 6 weeks but a Diaphyseal Cortical Ratio not significantly different since 3 weeks of age.

Animals↗

PubMed1993

[Comparative study of the diaphyseal osseous growth of the tibia between 3 and 12 weeks in 2 strains of turkey: histological and histomorphometric aspects].

The comparative cortical growth of the tibiotarsus was studied in 2 turkey strains, one light, one heavy, between 3 and 12 weeks of age, using histological and histomorphometrical methods. The growth in thickness started earlier and was much faster and larger in the heavier turkey strain. The early ovoid shape of the cortex of the heavier strain and the difference between the thickness of the narrow and the thick cortical faces seemed to be related to the action of strong mechanical strains. Nevertheless the diaphyseal cortical ratio remained not significantly different in the 2 strains from the age of 3 weeks. The light strain exhibited during all the studied periods indicated a more variable mineral apposition rate and earlier and more extensive bone remodelling phenomena. Most of the growth in thickness parameters were significantly higher in the heavier strain when turkeys of the 2 strains were compared at an equivalent weight.

Age Factors↗

PubMed1992

Relationships between lipid availability and protein utilization during prolonged fasting.

Mammals and birds adapt to prolonged fasting by mobilizing fat stores and minimizing protein loss. This strategy ends with an increase in protein utilization associated with behavioural changes promoting food foraging. Using the Zucker rat as a model, we have investigated the effect of severe obesity on this pattern of protein loss during long-term fasting. Two interactions between the initial adiposity and protein utilization were found. First, protein conservation was more effective in obese than in lean rats: fatty rats had a three times lower daily nitrogen excretion and proportion of energy expenditure deriving from proteins, and a lower daily protein loss in various muscles. This phase of protein sparing is moreover nine times longer in the fatty rats. Second, obese animals did not show the late increase in nitrogen excretion that occurred in their lean littermates. Total body protein loss during starvation was larger in fatty rats (57% versus 29%) and, accordingly, total protein loss was greater in their muscles. At the end of the experiment, lean and obese rats had lost 98% and 82%, respectively, of their initial lipid reserves, and fatty rats still had an obese body composition. These results support the hypothesis that in severely obese humans and animals a lethal cumulative protein loss is reached long before the exhaustion of fat stores, while the phase of protein conservation is still continuing. In contrast, in lean rats, survival of fasting seems to depend on the availability of lipid fuels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗

PubMed1992

Stress in birds due to routine handling and a technique to avoid it.

The stress that might result in animals from the routine handling that most experimental studies involve, e.g., weighing, injecting, and blood sampling, is usually assumed to be minimal when the animals look quiet. However, the intensity of this stress remains largely ignored. We have developed a system that allows blood samples to be taken from freely behaving geese without entering the animal room. In these entirely undisturbed geese, the humoral indexes of stress, i.e., blood levels of catecholamines, corticosterone, and lactate, were as low or even lower than the lowest values previously reported for birds. Remarkably, the mean basal values for epinephrine and norepinephrine were 90-fold and 5-fold, respectively, below the lowest values in the literature. Stress-induced variations in pH that would have concealed detection of nutrition-induced changes in pH were eliminated. In contrast, even though the birds looked quiet during a short 5-min routine handling procedure, to which they had been accustomed for weeks, there was a dramatic increase in the level of humoral indexes of stress. These increased severalfold within only 2 min, and the return to initial values could take up to 1 h. Acid-base balance was also disrupted. Thus, in studies on animals, the absence of stress cannot be deduced from only behavioral observations. Only a system for taking blood without human interference may enable stress-free investigations.

Adaptation, Psychological↗

PubMed1992

[Histomorphometric study of the superficial pectoral muscle of the turkey. Relationship with the meat discoloration syndrome].

Scallop discoloration affects about 30% of turkey carcasses, causing important economic losses. Histological and histomorphometric analyses of the superficial pectoral muscle were performed in order to show distinctive aspects of discolored scallops and predictive criteria for the phenomenon. Pectoral muscles of live male turkeys were biopsied 8 d before slaughter. Twenty four h after slaughtering, the same animals were classified into 2 distinctive classes by reflectometry (pale and dark muscles) and muscle samples were collected in each group. Superficial pectoral muscle was totally composed of type IIB, fast switch and glycolytic fibers. Pale and dark muscles exhibited no significant differences 8 d before slaughtering, but glycogen level was higher in pale muscles 24 h after slaughtering. These results do not support the current hypothesis of accelerated glycolysis and low ultimate pH to explain the meat discoloration syndrome in turkeys.

Animals↗

PubMed1991

Brief fasting decreases protein synthesis in the brain of adult rats.

The influence of starvation on protein synthesis in the adult rat brain was studied in vivo by an intravenous injection of a flooding dose of unlabeled valine including a tracer dose of L-[3,4(n)-3H]valine. Brief starvation (24 hours) induced a 20% decline in fractional and absolute rates of brain protein synthesis. This decline resulted from a 20% decrease in the efficiency of protein synthesis (microgram protein synthesized per day per microgram RNA) whereas the capacity for protein synthesis (microgram RNA per mg protein) was maintained. Prolonged starvation (5 days) was marked by no further significant changes in the fractional rate, absolute rate and efficiency of protein synthesis, whereas the capacity for protein synthesis decreased slightly. The relative contribution of brain to whole-body protein synthesis increased during fasting, and neither the protein nor the RNA brain content did change during the experiment. These results clearly indicate that brain proteins are spared in response to brief and prolonged food deprivation, and that brain protein synthesis is very sensitive to short-term fasting.

Animals↗

PubMed1991

Refeeding after the late increase in nitrogen excretion during prolonged fasting in the rat.

Recovery of body mass, food intake and body composition was studied in the laboratory rat after the late increase in nitrogen excretion that characterizes prolonged fasting in mammals and birds. The rats lost 43% of their body mass during 13 days of food deprivation. They all regained their prefasting body mass within a shorter period of 11 days of refeeding. These results confirm that the late increase in nitrogen excretion in rats, as in spontaneously fasting birds, is reversible and is a part of the physiological adaptations to long-term food deprivation. Water intake of the rats continuously decreased during fasting, and the animals virtually stopped drinking as protein utilization increased. On refeeding, changes in water intake paralleled those in food intake. The refed rats progressively increased their daily food intake, that was always higher than the prefasting value (8.0-10.4 vs. 6.7% of body mass). The comparison of organ weights between fed and ad lib refed rats of similar body weight indicates that muscle mass was regained earlier than body fat during refeeding. The laboratory rat therefore appears to be a good experimental model to investigate the metabolic and behavioural changes that occur during spontaneous anorexia and refeeding in wild animals.

Animals↗

PubMed1991

Whole-body and tissue protein synthesis during brief and prolonged fasting in the rat.

1. Little information is currently available on protein turnover during chronic protein loss situations. We have thus measured the whole-body and tissue protein fractional synthesis rates (ks), the whole-body fractional protein degradation rate (kd), the capacity for protein synthesis (Cs) and the efficiency of protein synthesis (kRNA) in vivo in fed and fasted (1, 5 and about 9 days) 400 g rats. 2. One day of starvation resulted in a reduced ks and an increased kd in the whole body. ks was selectively depressed in skeletal muscles, mainly owing to a reduced kRNA, and was not modified in heart, liver and skin. The contribution of skin to whole-body protein synthesis increased by 39%. 3. During the phase of protein sparing (5 days of fasting), kd in the whole body decreased below the control fed level. ks in skeletal muscles was sustained because kRNA was restored to 82-98% of the control value. 4. Rats were in a protein-wasting phase after 9 days of starvation. kd in the whole body did not increase and was actually 78% of the value observed in fed animals. By contrast, ks in the whole body and tissues decreased to 14-34% of the control values, owing to reductions in both Cs and kRNA. Whatever the duration of the fast, the contribution of the skin to whole-body protein synthesis largely exceeded that of skeletal muscle. 5. The present findings suggest that the main goal in the treatment of chronic protein loss should be to sustain protein synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

[Tibial dyschondroplasia in meat turkeys: morphometric study of its relationship with lameness].

The tibiotarsal bones from 1,084 15-week-old growing commercial male turkeys, half of which clinically lame, were examined for dyschondroplasia. Lesions were a cone of retained cartilage, confined to the postero-medial area of the proximal metaphysis of the tibiotarsus. Dense woven bone was present around the largest lesions associated with thickening of the diaphyseal cortex below the lesion. Length of abnormal cartilage varied from 0.1 cm to 5.3 cm. Width never exceeded 2.9 cm. Half of the affected turkeys showed unilateral localization of dyschondroplastic lesions. The percentage of damaged tibias was 54 per cent and the percentage of affected turkeys was more than 70 per cent. The incidence of dyschondroplasia was the same in lame and clinically healthy turkeys but, on average, lame turkeys exhibited longer lesions than clinically normal birds. The tibias of lame turkeys were more curved than the tibias of healthy ones as well in the anterio-posterior projection as in the latero-medial one. The latero-medial projection of incurvation was correlated with the length of dyschondroplastic lesions.

Animals↗

PubMed1988

Early changes in plasma hormones and metabolites during fasting in king penguin chicks.

Chicks of the king penguin (Aptenodytes patagonica) can tolerate a fast of 4-6 months during the subantarctic winter. The aim of this work was to study their initial response to food deprivation. Nine chicks were starved for 18 days. Two phases of starvation were defined according to changes in the specific daily loss in body mass: it decreased by 92% in phase I (6.6 +/- 0.3 days) and remained steady and low in phase II. Phase I was marked by a large decline in protein utilization, indicated by decreases in plasma levels of alanine (58%), uric acid (89%) and urea (76%) together with a decrease in circulating corticosterone (60%) and thyroxine (75%). In phase I, plasma insulin concentration decreased (61%) in some birds, but did not change in others; plasma pancreatic glucagon was stable whereas gut-glucagon decreased by 75%. Free fatty acids and beta-hydroxybutyrate concentrations gradually rose during the fast to 5 to 6 times pre-fast levels. Glycemia remained unchanged. Phase II was characterized by no change in plasma concentrations of protein-derived metabolites and by no or little change in circulating hormone levels. From comparison with previous data, we conclude that there are similar early adjustments to food deprivation in king penguin chick, rat and man: (1) a decrease in resting metabolic rate, (2) a decrease in protein utilization, and (3) mobilization of fat stores. The key adaptations to long-term fasting in these species are therefore effectiveness in protein sparing and ability to prolong this situation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

Plasma hormone levels in relation to lipid and protein metabolism during prolonged fasting in king penguin chicks.

Chicks of king penguin (Aptenodytes patagonica), while only 3-4 months old, tolerate 4-6 months of fasting when they are abandoned by their parents during the subantarctic winter. The body mass of nine chicks, which were followed during this natural winter fast, was 13.1 kg at capture and 3.4 kg after 150 days of fasting, a 74% decrease. The longer phase II (129 days) was marked by lipid mobilization and protein sparing, as indicated by a continuous increase in plasma levels of free fatty acids, glycerol, and beta-hydroxybutyrate, whereas plasma alanine, uric acid, and urea remained stable at low values. In phase III, by contrast, plasma concentrations of lipid-derived metabolites decreased, while plasma alanine, uric acid, and urea increased markedly, indicating an increase in protein utilization. Plasma insulin concentration did not significantly change during either phase II or phase III. Plasma glucagon remained constant during phase II and at the beginning of phase III but increased 2.6 times afterward. Plasma corticosterone increased only slightly during the first 4 months of the fast but reached very high values at the end of phase II and the beginning of phase III (4.7 times basal values); moreover, it further increased 3.1 times before phase III was stopped. Altogether, these data accord with the idea that the outstanding resistance of king penguin chicks to starvation is due to the ability to extensively prolong the situation of protein sparing, which seems to require the maintenance of low plasma concentrations of corticosterone and insulin for up to 4 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

In vivo glucose utilization in rat tissues during the three phases of starvation.

Three phases of starvation have been described from changes in protein and lipid utilization in birds and mammals. In the present study, tissue glucose utilization was measured in vivo during these three phases, using a 2-deoxy-[1-3H]glucose technique in the anesthetized rat. According to this technique, the term glucose utilization therefore refers to transport and phosphorylation of glucose in tissues, ie, whatever is the fate of glucose. Whole-body glucose turnover rate, which was determined by a continuous infusion of [3-3H]glucose, decreased by 40% during the first two days of starvation (phase 1); it did not change thereafter, neither in the protein-sparing phase 2 nor in phase 3, which is marked by an increase in net protein breakdown. Two days of starvation caused a marked decrease in the glucose utilization in skeletal muscles; this decrease was higher in oxidative muscles (65% in diaphragm, 66% in soleus) than in glycolytic muscles (31% in extensor digitorum longus, 34% in epitrochlearis). Glucose utilization also decreased in heart atria (75%), heart ventricles (93%), and white adipose tissue (54%); by contrast, there was a two-fold increase in glucose utilization in brown adipose tissue and no change in brain and skin. No variations were observed in glucose utilization in any of the tissues from phase 1 to phase 2. However, phase 3 was marked by a decrease in glucose utilization in extensor digitorum longus (45%), brown adipose tissue (76%), brain (29%), and skin (40%), whereas there was a 2.3- and 3.4-fold increase in glucose utilization in diaphragm and heart ventricles, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗