Modification Of Energy Metabolism Research Articles

Comparative responses to severe hypoxia and subsequent recovery in closely related amphipod populations (Gammarus minus) from cave and surface habitats

The locomotory and ventilatory activities, oxygen consumption, and the intermediary and energy metabolism modifications of a spring and a cave population of the aquatic amphipod crustacean Gammarus minus were investigated in normoxia, severe hypoxia (\(P_{{\text{O}}_{\text{2}} } \) < 0.03 kPa) and subsequent recovery. The aims of this study were to compare (1) the reactions of both populations to these experimental conditions, (2) these results with those obtained on the hypogean amphipod Niphargus, and (3) the degree of adaptation to hypoxia showed by both populations of G. minus. Despite their different origins, both populations of G. minus presented identical responses in all experimental conditions. The lethal time for 50% of the population was about 6 h, and the oxygen consumption about 44 μmol O2/g dw per h in normoxic conditions. The metabolic effects of severe hypoxia and subsequent recovery were significant compared to normoxic conditions, but also similar between both populations for alanine, arginine phosphate, ATP, glycogen and lactate levels. This study (i) underlines the statement that a high resistance to lack of oxygen is not universally found in subterranean organisms, but is more related to oxygen availability and/or to the energetic state of each subterranean ecosystem, and (ii) highlight the diversity of adaptive responses to an environmental constraint expressed by hypogean crustaceans.

Locomotory, ventilatory and metabolic responses of the subterranean Stenasellus virei (Crustacea, Isopoda) to severe hypoxia and subsequent recovery

The locomotory and ventilatory activities and the intermediary and energy metabolism modifications of the hypogean aquatic isopod crustacean Stenasellus virei were investigated in severe hypoxia (Po 2 < 0.03 kPa) and subsequent recovery. The aims of this study were i) to determine why the subterranean species displayed a greater tolerance of hypoxia than numerous other epigean crustaceans, ii) to confirm previous results obtained with four hypogean and epigean crustaceans, iii) to compare the responses to severe hypoxia in hypogean amphipods and isopods, and iv) to better understand the ecological problems of the hypogean organisms survival in subterranean habitats. S. virei responded to experimental long-term, severe hypoxia with classical anaerobic metabolism mainly characterized by a decrease in adenosine triphosphate (ATP) and phosphagen, utilization of glycogen and glutamate, and accumulation of lactate and alanine. Lactate was also largely excreted by this organism, which is unusual for crustaceans in general. Compared to most other epigean crustaceans, the isopod S. virei showed high amounts of stored glycogen and arginine phosphate. These differences in glycogen and phosphagen stores, and the ability to reduce energetic expenditures linked to locomotion and ventilation, extended the survival of S. virei under experimental anaerobiosis. During recovery, the isopod S. virei showed a higher capacity for glyconeogenesis from lactate and a faster and total replenishment of ATP and arginine phosphate levels than epigean crustaceans. Data concerning responses to hypoxia and subsequent recovery in S. virei are similar to those previously obtained with two other hypogean amphipods, except that this isopod did not synthesize succinate in anaerobiosis.

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 organism's 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 an...

Changes in microregional perfusion, oxygenation, ATP and lactate distribution in subcutaneous rat tumours upon water-filtered IR-A hyperthermia.

The effect of hyperthermia on microcirculatory and metabolic parameters in s.c. DS-sarcomas of different sizes on the hind foot dorsum of SD-rats was investigated. Hyperthermia was carried out using a novel water-filtered, infrared-A radiation technique. Heating was performed at a rate of 0.5 degrees C/min until 44 degrees C was achieved in the tumour centre, which was maintained for 60 min. Using a multichannel laser Doppler flowmeter, red blood cell flux could be assessed continuously and at several sites within the tumour tissue simultaneously. Substantial inter-site variations in laser Doppler flux (LDF) were observed during hyperthermia which were independent of tumour size, site of measurement, and temperature at the site of measurement, indicating that single site measurements of tumour LDF are poor predictors of the mean response of a tumour to hyperthermia. When mean LDF was considered, decreases in red blood cell fluxes occurred that were more pronounced the greater the tumour volume. In no case was vascular stasis observed. Hyperthermia did not affect tumour oxygenation substantially. Microregional and global assessment of lactate and ATP concentrations demonstrated increased lactate and decreased ATP levels following hyperthermia. Tumour glucose levels were increased following hyperthermia, possibly due to an enlarged distribution space resulting from development of interstitial oedema. Changes in lactate and ATP levels and the lack of changes in tumour oxygenation suggest a modification of energy metabolism following hyperthermia in the form of increased ATP hydrolysis, intensified glycolysis and impaired oxidative phosphorylation.

Modification of energy metabolism by the presence of the gut microflora in the chicken

Whether the association with gut microflora modifies the energy metabolism of chickens was investigated by varying the metabolizable energy consumption level from zero to above the maintenance requirement in the germ-free and conventional states. Single comb White Leghorn chicks were either fasted for 3 d (Expt 1), or fed for 6 d at a fixed daily meal intake of 2, 5 or 8 g/d (Expt 2), or 5, 10 or 15 g/d (Expt 3). Changes in carcass energy deposition and heat production indicated that when no dietary energy was available the presence of the gut microflora could benefit the birds by reducing energy losses, whereas when dietary energy was supplied the efficiency of energy utilization was reduced by the presence of the gut microflora. It was concluded, therefore, that the heavy burden of the gut microflora modifies energy metabolism by exerting a buffering or a counter-productive action on the energy utilization of the chicken.

Modification of Energy Metabolism and Radiation Response of a Murine Tumor by Changes in Nitric Oxide Availability

The nitric oxide donor, SIN-1 and nitric oxide synthase inhibitor, nitro-L-arginine were examined for their effects on energy metabolism using 31P magnetic resonance spectroscopy, and on radiation sensitivity in the transplantable murine tumour, SCCVII/Ha. SIN-1 at 2 mg/kg i.v. reduced Pi/total by 40-50% within 10 min and increased X-ray sensitivity 3 fold, consistent with increased tumour oxygenation. Nitro-L-arginine at 10 mg/kg i.v. increased Pi/total by 250% at 45 min and was maintained for at least 2 hr. Nitro-L-arginine also increased radiation resistance 3-5 fold, consistent with the induction of tumour hypoxia. The results indicate that tumour energy metabolism may be altered through drug induced modification of nitric oxide availability, and that these changes are sufficient to modify tumour sensitivity to X-rays.

Reversible intracellular ATP changes in intact rat spermatozoa and effects on flagellar sperm movement

The initiation of motility and modification of energy metabolism of rat caudal epididymal spermatozoa can be induced by dilution in a saline medium. We have investigated in these cells the relationships between the energy reserve (sperm ATP content measured by bioluminescence) and flagellar movement (high speed videomicrography, 200 frames/sec). A steady state was observed in sperm ATP content, progressive velocity (Vp) and flagellar beat frequency (F) with sperm dilution in a medium with glucose, lactate, pyruvate and acetate substrates after 30 minutes of incubation. Without these substrates, changes in metabolic pathways occurred immediately and initially disturbed the relationship between ATP levels and F, suggesting differences in motility initiation when energy is from an endogenous origin via mitochondrial oxidative phosphorylation. This "energy crisis" was reversed by the addition of substrates to the medium. The three-dimensional flagellar movement observed in the presence of substrates quickly became two-dimensional in their absence. The flagellar beat envelope became more splayed, the mean amplitude of lateral head displacement increased and F decreased. The resulting high flagellar beat efficiency can be compared to that observed during hyperactivation which is a physiological event related to a fall in intracellular ATP level. In both media, the displacement of the flagellum in relation to the wave axis varied sinusoidally. The sine period increased with time when the spermatozoa were incubated in the medium without substrates. These results suggest a gradual slowing-down of the velocity of wave formation in the proximal part of the flagellum.

Scanning microfluorometric measurement of cell constituents. Principles of the method and its application to the determination of NAD content and redox state of XTH-2 cells in culture.

The scanning of fluorescence of a cell culture along a path several milimeters long, gives a series of signals, which allow calculation of the fluorescence emitted per cell. The emission at 450 +/- 10 nm, excited at 360 nm, provides a measure of NADH (and NADPH) per cell. Combination of this method with modifications in energy metabolism, allows determination in the same sample of total NAD content, of NAD redox state, content of NAD in the mitochondria and content of NAD plus NADP in the cytoplasm. The method can be extended to measure other cellular constituents by labelling with fluorescent markers, e.g. antibodies.

MR-tomography and -spectroscopy of skeletal muscles using high magnetic field strengths

Intact as well as neuromuscular affected skeletal muscles can be precisely analysed by MR tomography with high magnetic field strengths. The substitution of muscle by adipose tissue under atrophic conditions is seen most clearly in fat images, while the morphology of small structures is predominantly shown by water images. The aim of in-vivo spectroscopy is an identification and quantification of metabolites. A relative increase in the amount of adipose tissue within atrophic muscles was confirmed by the 1-H spectrum. As concluded from 13-C and 31-P spectra there was neither a change in adipose tissue composition nor a modification of energy metabolism.

Modifications in energy metabolism during the development of chick glial cells and neurons in culture.

Developmental changes in lactate dehydrogenase (LDH), enolase, hexokinase (HK), malate dehydrogenase (MDH), and glutamate dehydrogenase (GDH) activities were measured in cultures of pure neurons and glial cells prepared from brains of chick embryos (8 day-old for neurons, 14 day-old for glial cells) as a function of cellular development with time in culture. The modifications observed in culture were compared to those measured in brain extracts during the development of the nervous tissue in the chick embryo and during the post-hatching period. A significant increase of MDH, GDH, LDH, and enolase activities are observed in neurons between 3 and 6 days of culture, whereas simultaneously a decrease of HK values occurs. In the embryonic brain between 11 and 14 days of incubation, which would correspond for the neuronal cultures to day 3 through 6, modifications of MDH, GDH, HK, and enolase levels are similar to those observed in neurons in culture. Only the increase of LDH activity is less pronounced in vivo than in cultivated cells. The evolution of the tested enzymatic activities in the brain of the chick during the period between 7 days before and 10 days after hatching is quite similar to that observed in cultivated glial cells (prepared from 14 day-old embryos) between 6 and 18 days of culture. All tested activities increased in comparable proportions. The modifications of the enzymatic profile indicate that some maturation phenomena affecting energy metabolism of neuronal and glial elements in culture, are quite similar to those occuring in the total nervous tissue. A relationship between the development of the energy metabolism of the brain and differentiation processes affecting neuroblasts and the glial-forming cells is discussed.

Energy metabolism and hormonal profile in children with edematous protein-calorie malnutrition

Modifications in energy metabolism and endocrine homeostasis (plasma insulin and growth hormone values, glucose and free fatty acid levels, serum thyroxine and TSH, free thyroxine index, and urinary catecholamines) were investigated in eight children with edematous protein-calorie malnutrition. Caloric expenditure was low at admission and correlated linearly with increased caloric intake throughout the study. The hormonal changes at admission were characterized by a negligible insulin response to intravenous arginine or glucose and by markedly elevated growth hormone levels which were neither increased by arginine nor suppressed by intravenous glucose. Serum thyroxine values were low, but free thyroxine index and serum TSH levels were within normal limits. At admission to the study, 24-hour urinary excretion of dopamine and norepinephrine was relatively reduced in relation to the excretion of epinephrine. All these modifications were corrected at time of the recovery study. It is suggested that in edematous protein-calorie malnutrition, insulin acts as the primary regulator of peripheral fuel release and that the high, nonsuppressible growth hormone levels may form part of an important homeostatic mechanism to provide substrates for brain metabolism via lipolysis.

EFFECOF TRIAMCINOLONE ADMINISTRATION ON CORTICOSTEROID METABOLISM IN THE LIVER.

Despite evidence that thyroidal activity, gonadal hormones and food intake can modify steroidal metabolism in the liver, the regulatory mechanisms involved are not clear. These studies suggest that a modification of energy metabolism can influence the corticosteroid metabolism. Corticosteroids, through their stimulation of hepatic carbohydrate synthesis, can modify energy metabolism. Therefore, the influence of corticosteroids upon the Δ4-3-ketosteroid reductase activity in the liver has been investigated in male rats and hamsters. Cortisol 1,2-3H was incubated with liver slices from animals treated with triamcinolone and from untreated controls. In the intact and adrenalectomized animals, treatment caused an elevation in both the steroid reducing capacity and the glycogen content. Similarly, feeding increased the reduction of cortisol in both intact and adrenalectomized animals. Thus, this increased rate of reduction of corticosteroids in the liver caused by the administration of triamcinolone could be s...