Alain Fréminet

Behavioral, Ventilatory, and Metabolic Responses to Severe Hypoxia and Subsequent Recovery of the Hypogean Niphargus rhenorhodanensis and the Epigean Gammarus fossarum (Crustacea: Amphipoda)

Two aquatic amphipod crustaceans were investigated: Niphargus rhenorhodanensis (a hypogean species, which has to cope with severe hypoxic conditions during about 6 mo per year during the hydrological cycle) and Gammarus fossarum (an epigean species, which lives continuously in well-oxygenated water). The lethal times for 50% of the population (LT50) for these closely) related species were 46. 7 and 6.3 h, respectively, in very severe hypoxia (<0.2 Torr) at 11°C. Therefore, the aim of this study was to examine some possible reasons why the subterranean Niphargus survived severe hypoxia longer than Gammarus and numerous other epigean crustaceans. During severe hypoxia Niphargus reduced its energetic expenditures compared with Gammarus. This reduction was associated with changes in locomotion and ventilation. In both species, anaerobic metabolism was fueled in severe hypoxia by the breakdown of glycogen and arginine phosphate. In Niphargus, however glutamate was also utilized. This resulted in the production of l-lactate as the major end product in both species. Alanine was found to be a minor end product in Gammarus, while alanine and succinate were found to be the minor end products in Niphargus. Compared to Gammarus, and to most other epigean crustaceans, Niphargus showed high amounts of stored glycogen and arginine phosphate. During severe hypoxia, both organisms excreted lactate into the medium, which is unusual for crustaceans. The differences in the stores of phosphagen and glycogen, and in behavioral and ventilatory responses, are probably the main reasons for their different resistance to severe hypoxia. During recovery, both species displayed a characteristic hyperventilation and their metabolism was predominantly aerobic. Gammarus excreted a great part of the lactate accumulated during severe hypoxia, whereas Niphargus remetabolized it, the latter possessing a higher glyconeogenesis capacity from lactate. After 24 h recovery, energy charge in both amphiods was not completely restored, and only Niphargus showed a total removal of the accumulated end products. Niphargus showed a faster replenishment of ATP concentration.

Behavioral, Ventilatory, and Metabolic Responses of the Hypogean Amphipod Niphargus virei and the Epigean Isopod Asellus aquaticus to Severe Hypoxia and Subsequent Recovery

The locomotory and ventilatory activities and the intermediary and energy metabolism modifications of the hypogean amphipod Niphargus virei and the epigean isopod Asellus aquaticus were compared during severe hypoxia (<0.03 kPa) and subsequent recovery. The aims of this study were (1) to determine why the subterranean species displayed a greater tolerance of hypoxia than A. aquaticus and numerous other epigean crustaceans, (2) to confirm previous results obtained with the hypogean amphipod Niphargus rhenorhodanensis and the epigean amphipod Gammarus fossarum, (3) to provide an interspecific comparison of epigean species in order to see if responses showed by epigean amphipods during hypoxia and recovery can be extended to epigean isopods, and (4) to better understand the ecological problems of the hypogean organisms survival and perennation in subterranean habitats. Both organisms responded to long-term experimental severe hypoxia with classical anaerobic metabolism, characterized by a decrease in ATP and phosphagen, the use of glycogen and glutamate, and the accumulation of lactate (with some alanine). In addition, some accumulation of succinate was found in N. virei. Lactate (and succinate for N. virei) was also largely excreted by both amphipods, which is unusual for the crustacea in general Compared with A. aquaticus and most other epigean crustaceans, N. virei showed large amounts of stored glycogen and arginine phosphate. These differences in glycogen and phosphagen stores, and the ability to reduce glycolytic flux and energetic expenditures linked to locomotion and ventilation, extended the survival of hypogean crustaceans under experimental anaerobiosis (LT50 was 52.1 h for N. virei and 19. 7 h for A. aquaticus during severe hypoxia at 11° C). During recovery, both species displayed characteristic hyperventilation, slow locomotory activity, and predominantly aerobic metabolism. Asellus aquaticus excreted a large part of the lactate accumulated during severe hypoxia, whereas N. virei remetabolized it, as it had a higher lactate-derived glyconeogenesis capacity. The disposal of endproducts and replenishing of glycogen, ATP, and phosphagen required more than 24 h for both organisms. Niphargus virei showed a faster and more complete replenishment of ATP and arginine phosphate levels than A. aquaticus. Data concerning locomotory, ventilatory, and metabolic responses to hypoxia and subsequent recovery in N. virei and A. aquaticus are similar to those obtained with N. rhenorhodanensis and G. fossarum.

Determination of glucose turnover in sea bass Dicentrarchus labrax. comparative aspects of glucose utilization

1. Parameters of in vivo glucose utilization by sea bass (132 +/- 6 g, mean +/- SEM) acclimated at 15 degrees C in sea-water were measured after single injection of labelled glucose. 2. Glucose turnover rate (RG; mumol . min-1 . kg-1) was found to be 0.55-065 (2-3H glucose) and 0.34 +/- 0.42 (U14C glucose). 3. Glucose transit time was 443-449 min, glucose mass 233-261 mumol . kg-1, and glucose recycling 37%. 4. Oxygen consumption (MO2) amounted to 94 +/- 6.2 mumol . min-1 . kg-1. 5. The comparison with other fish species, mammals and birds, taking into account body size, temperature, diet, exercise, in poikilotherms and homeotherms leads to the calculation of a glucose turnover index (RGI = RG x 6 x 100 x MO2(-1)). 6. Value of this, generally lower in ectotherm teleosts (2-9), than in endotherms: mammals, birds and thunidae (22-60), confirms the minor quantitative importance of glucose in the metabolism of most fish.

Effect of fasting on glucose, lactate and alanine turnover in rats and guinea-pigs

-1. Blood glucose and lactate levels were comparable in fed rats and guinea-pigs but blood alanine was three times higher in rats than in guinea-pigs. 2. After a 48 hr fasting period blood concentration and turnover rates of glucose, lactate and alanine decreased in rats. 3. After a 48 hr fasting period blood concentration and turnover rates of glucose and lactate did not vary in guinea-pigs whereas blood alanine and alanine turnover increased. 4. Increased availability of glucose precursors and a better efficiency of gluconeogenic processes in fasted guinea-pigs compared to fasted rats may explain in part the different variation of blood glucose and glucose turnover rate during starvation in the two species.

Carbohydrate and amino acid metabolism during acute hypoxia in rats: blood and heart metabolites

1. 1. Metabolic response of rats to acute hypoxia in vivo was studied by measuring glycogen store, blood and heart metabolites after a 30 min exposition to a 5% O2-95% N2 gas mixture. 2. 2. The hypoxic test induced decrease of glycogen content of 47, 20 and 85% in the liver, muscle and heart, respectively. 3. 3. Glucose, lactate, alanine and succinate were increased by 65, 310, 100 and 580% respectively in blood from control as compared with hypoxic animals. 4. 4. Creatine-phosphate and ATP content in the heart was decreased by 92 and 45% respectively, whereas ADP and AMP did not change after hypoxia. 5. 5. Hypoxia induced an increase of lactate (680%), pyruvate (105%), citrate (105%), succinate (152%), malate (544%) and alanine (273%), and a decrease of α-keto-glutarate (30%), glutamate (55%) and aspartate (55%) in the myocardium. 6. 6. These data demonstrate the simultaneous utilization of carbohydrates and amino acids in response to oxygen deprivation in a strictly aerobic species. However ATP production arising from amino acid fermentation appears of minor quantitative importance compared with that of glycogenolysis and glycolysis. In the discussion, the possible role of these reactions is examined and the results of the present study are compared with those obtained in other organs and other species.

Comparison of glycogen store in rats and guinea-pigs: Effects of anaesthesia, fasting and re-feeding

Abstract 1. 1. Glycogen contents in the liver, muscle, heart and carcass were determined in rats (R) and guinea pigs (GP). The animals of the same initial body weight (400 g) were studied in five conditions: fed or normal (N) after 24 (F 24), 48 (F 48), 96 (F 96) hr of fast and after 24 hr of renutrition following 96 hr of fast (FR). 2. 2. Preliminary experiments were carried out to ascertain the experimental procedure. The less detrimental anaesthetic procedure was found to be ether in rats and nembutal in guinea pigs. 3. 3. In fed conditions, liver glycogen content was comparable in the two species (R = 73.7 ± 4.8; GP = 74.7 ± 11.5 mg.g −1 ) but hepatic store was larger in GP than in R (3584 ± 676 vs 2854 ± 231 mg.kg −1 BW) due to higher liver weight in GP than in R. Hepatic glycogen was totally exhausted in F 24 and remained low in F 48 and F 96. Hepatic glycogen was larger in FR than in control conditions (R:4000 ± 509; GP 3773 ± 663 mg.kg −1 BW). 4. 4. In fed conditions, the content of glycogen, in the anterior muscles of the thigh was 2.3 times higher in GP than in R (16.6 ± 0.9 vs 7.2 ± 1.2 mg.g −1 ). The utilization during fasting was more progressive and important in GP (F 24:10.3; F 24:8.9; F 96:6.8 mg.g −1 ) than in R (F 24:4.9; F 48:4.3; F 96:3.8 mg.g −1 ). In FR groups, muscular glycogen content was 28% higher than in control group in R but remained 29% lower than in control group in GP. 5. 5. In fed conditions, myocardial glycogen was 1.5 times higher in GP than in R (7.8 ± 1.2 vs 5.1 ± 0.6 mg.g −1 ). It was increased during fasting in R (F 24:6.7; F 48:7.4; F 96:8.7 mg.g −1 ) whereas it was decreased in FR conditions (4.1 mg.g −1 ). In GP after a decrease in F 24 (6.8 mg.g −1 ), myocardial glycogen was increased at F 48 (8.7 mg.g −1 ) and F 96 (10.1 mg.g −1 ) and was below control values in FR group (6.2 mg.g −1 ). 6. 6. In fed conditions carcass glycogen was higher in GP than in R (3287 ± 231 vs 2229 ± 288 mg.kg −1 BW). This parameter decreased during fasting in the two species (R: F24:1411; F 48:1035; F 96:798. GP: F 24:2283; F 48:1847; F96:1322 mg.kg −1 BW). In FR conditions, carcass glycogen was comparable to control conditions in R (2354 ± 180 mg.kg −1 BW) but remained low in GP (2520 ± 208 mg.kg −1 BW).

Comparison of glycogen stores in 3- and 7-month-old lean and obese zucker rats under fed and fasted conditions☆

Glycogen content (mg/g) and stores (mg) were determined in 3- and 7-month-old obese and lean Zucker rats, under fed and fasted (48 hr) conditions. Hepatic content was higher in fed obese than in lean rats (3 months: 90 vs 70; 7 months: 107 vs 74); it was exhausted after fasting in lean but decreased by 56% in obese rats. Muscle content in fed obese and lean animals did not differ; it decreased comparably after fasting. Myocardial content was higher in fed obese than lean rats (3 months: 7.2 vs 3.6; 7 months: 7.5 vs 6.3); it was enhanced with fasting (10.0 vs 7.5). Total glycogen stores were higher in obese than in lean animals (3 months: 2500 vs 1400; 7 months: 4000 vs 2000) because of the hepatic store. The discussion includes a comparison with available data, taking into account methodological aspects, lipid stores and the FFA/carbohydrate interrelationship.

Effect of cold ambient temperature on glucose and alanine turnover in dogs

AbstractThe metabolic effects of acute cold exposure were examined in dogs exposed to either+25° C (TaN) or−21°C (TaC). Simultaneous infusion ofd-3-3H glucose and U−14C alanine was used to measure glucose (R Glu) and alanine carbon (R Ala) turnover rates. At the two ambient temperatures the animals remained normothermic and normoglycemic throughout the experiments. Cold exposure provoked a significant increase

Comparison of glycogen store in two strains of rat and guinea-pig under fed and fasted conditions

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