Stimulation by D-glucose of mitochondrial respiration

Summary D-glucose increases O₂ uptake by cerebellum mitochondria. This effect is abolished by D-glucose-6-phosphate and D-mannoheptulose. It is proposed that the phosphorylation of D-glucose as catalyzed by bound hexokinase directly affects mitochondrial respiration.     

Inhibition of nuclear and mitochondrial respiration by arsenite

Résumé La respiration des noyaux isolés du thymus de rat est inhibée par l'arsénite à une concentration 10 fois supérieure à celle qui inhibe la respiration mitochondriale. Ce fait suggère, une difficulté de pénétration à travers la membrane nucleaire et ne rend pas compte de la différence entre le méchanisme de la phosphorylation oxydative des noyaux et celle des mitochondria.     

Stimulation of the respiration of polymorphonuclear leucocytes by antileucocyte antibodies

Riassunto Gli anticorpi antileucociti provocano una marcata stimolazione della respirazione, rotenone, Antimicina A e cianuro insensibile, ed una aumentata attività del ciclo degli esosomonofosfati nei leucociti di cavia.     

Different effects of D-glucose anomers for respiration of bacterial germinated spores

Summary Effects of - or -D-glucose on the respiration of germinated spores (only germinated spores not including swollen spores and elongated spores) ofBacillus subtilis andB. megaterium were studied. In our conditions, net amount of oxygen consumed by 10¹⁰ germinated spores ofB. subtilis per min after addition of - or -D-glucose was 1.6 g or 6.6 g (/=4.13), while that byB. megaterium was 4.5 g or 6.8 g (/=1.51), respectively. However, the net amounts of oxygen consumed by 10¹⁰ vegetative cells per min after addition of - or -D-glucose were identical, forB. subtilis in both cases 443.0 g and forB. megaterium in both cases 604.4 g.     

Different effects of D-glucose anomers for respiration of bacterial germinated spores.

Effects of alpha- or beta-D-glucose on the respiration of germinated spores (only germinated spores not including swollen spores and elongated spores) of Bacillus subtilis and B. megaterium were studied. In our conditions, net amount of oxygen consumed by 10(10) germinated spores of B. subtilis per min after addition of alpha- or beta-D-glucose was 1.6 microgram or 6.6 microgram (beta/alpha = 4.13), while that by B.megaterium was 4.5 microgram of 6.8 microgram (beta/alpha = 1.51), respectively. However, the net amounts of oxygen consumed by 10(10) vegetative cells per min after addition of alpha- or beta-D-glucose were identical, for B.subtillis in both cases 443.0 microgram and for B.megaterium in both cases 604.4 microgram.     

The effect of camphor on mitochondrial respiration

Summary Camphor at <8 moles/mg protein reduced the rate of oxygen consumption by rat liver mitochondria. The effect occurs only with NAD⁺-linked substrates. Succinate linked respiration was inhibited but this appears to be caused by some conversion of succinate to malate. At higher levels, camphor increases oxygen consumption with succinate substrate, by uncoupling at site II.Acknowledgment. D.F.G.-C. is grateful to the New Zealand Cancer Society (Wellington Branch), for financial support. We thank Mrs E. Dye for technical assistance and Dr W. Jordan for valuable discussions.     

Phytanic acid impairs mitochondrial respiration through protonophoric action

Refsum disease is a rare, inherited neurodegenerative disorder characterized by accumulation of the dietary branched-chain fatty acid phytanic acid in plasma and tissues caused by a defect in the alphaoxidation pathway. The accumulation of phytanic acid is believed to be the main pathophysiological cause of the disease. However, the exact mechanism(s) by which phytanic acid exerts its toxicity have not been resolved. In this study, the effect of phytanic acid on mitochondrial respiration was investigated. The results show that in digitonin-permeabilized fibroblasts, phytanic acid decreases ATP synthesis, whereas substrate oxidation per se is not affected. Importantly, studies in intact fibroblasts revealed that phytanic acid decreases both the mitochondrial membrane potential and NAD(P)H autofluorescence. Taken together, the results described here show that unesterified phytanic acid exerts its toxic effect mainly through its protonophoric action, at least in human skin fibroblasts. Received 4 August 2007; received after revision 26 September 2007; accepted 10 October 2007 J. C. Komen, F. Distelmaier: These authors contributed equally to this work.     

Uptake of D-glucose anomers by rat retina

Summary Uptake ofd-glucose anomers by isolated rat retina was studied. After 3 min incubation at 37°C in the presence of or anomer (750 g/ml), a significantly greater uptake (1.32 mg/g wet tissue) of -anomer was observed compared with that of -d-glucose (1.11 mg/g wet tissue). This result and other data suggest that the carrier ford-glucose transport in the retina prefers the -anomer stereospecifically.Acknowledgment. The authors are grateful to Mr S. Suzuki for his technical assistance.     

GMP-stimulation of the cyanide-insensitive mitochondrial respiration in heat-shocked conidia ofNeurospora crassa

Summary In mitochondria of heat-shocked conidia ofNeurospora exogenous NADH and succinate were oxidized mainly via the alternative, hydroxamate-sensitive pathway (70%) and only 30% via the cytochromic, cyanide-sensitive pathway which was predominant in untreated conidia; the alternative oxidase pathway was markedly stimulated by guanosine 5-monophosphate (GMP).We are grateful to Mrs A. Cattaneo for her skillful technical assistance.     

GMP-stimulation of the cyanide-insensitive mitochondrial respiration in heat-shocked conidia of Neurospora crassa

In mitochondria of heat-shocked conidia of Neurospora exogenous NADH and succinate were oxidized mainly via the alternative, hydroxamate-sensitive pathway (70%) and only 30% via the cytochromic, cyanide-sensitive pathway which was predominant in untreated conidia; the alternative oxidase pathway was markedly stimulated by guanosine 5'-monophosphate (GMP).     

Stimulation of pyruvate carboxylation by gastric secretagogues

Pyruvate carboxylation was stimulated by 2 gastric secretagogues, histamine and dibutyryl cyclic AMP, and by butyrate. Thiocyanate, an inhibitor of acid secretion, produced a slight decrease. Avidin significantly reduced acid secretion and this effect was overcome by biotin and oxalacetate. The results suggest that carboxylation of pyruvate is one of the reactions controlling oxidative metabolism and acid secretion in toad gastric mucosa.     

Stimulation of pyruvate carboxylation by gastric secretagogues

Summary Pyruvate carboxylation was stimulated by 2 gastric secretagogues, histamine and dibutyryl cyclic AMP, and by butyrate. Thiocyanate, an inhibitor of acid secretion, produced a slight decrease. Avidin significantly reduced acid secretion and this effect was overcome by biotin and oxalacetate. The results suggest that carboxylation of pyruvate is one of the reactions controlling oxidative metabolism and acid secretion in toad gastric mucosa.This investigation was supported by Consejo de Desarrollo Científico y Humanístico de la Universidad del Zulia, and by CONICIT Grant S1-0455.     

Stimulation of sporulation ofClostridium perfringens by papaverine

Summary Papaverine induced sporulation inClostridium perfringens, strains FD-1 and PS52; growth was markedly slowed under these conditions. Papaverine induced sporulation in the presence of glucose, a sporulation repressor, although increasing glucose concentrations overcame the papaverine effect. Papaverine induced sporulation of strain FD-1 more effectively than did theophylline.The author wishes to thank Mrs P.A. Thompson for excellent technical assistance.     

Stimulation of polydnavirus replication by 20-hydroxyecdysone

During oviposition the endoparasitic waspCampoletis sonorensis, introduces a polydnavirus into parasitized insects where viral gene expression is required for endoparasite survival. The polydnavirus is integrated into wasp chromosomal DNA and replicates only in the ovary. Ecdysteroids regulate the developmental expression of many insect genes and may regulate polydnavirus replication. Direct verification of viral replication was performed by dot blot hybridization and by amplifying DNA sequences containing the viral integration site; this junction fragment cannot be amplified from integrated virus. Thoracic ligations and in vitro ecdysteroid treatments of wasp ovaries support the hypothesis that polydnavirus DNA replication is regulated by ecdysteroid during parasite development.     

Seasonal changes in the critical arousal temperature of the marsupialSminthopsis crassicaudata correlate with the thermal transition in mitochondrial respiration

Summary During periods of torporSminthopsis crassicaudata, a dasyurid marsupial, regulated its body temperature above about 16.3°C in summer and 13.0°C in winter. Animals with lower body temperatures were unable to arouse. Liver, heart and brain mitohondrial succinate:cytochrome c reductase showed a thermal transition at 16°C in summer and at 12.5°C in winter. Thus the lowest regulated body temperature was just above the temperature where changes were detected in mitochondrial respiration.Acknowledgments. This work was supported by a Flinders University Research Scholarship Award to F. Geiser. We thank Prof. J. H. Bennett for the supply of animals and M. O'Driscoll for the animal maintenance.     

Stimulation of polydnavirus replication by 20-hydroxyecdysone.

During oviposition the endoparasitic wasp Campoletis sonorensis, introduces a polydnavirus into parasitized insects where viral gene expression is required for endoparasite survival. The polydnavirus is integrated into wasp chromosomal DNA and replicates only in the ovary. Ecdysteroids regulate the developmental expression of many insect genes and may regulate polydnavirus replication. Direct verification of viral replication was performed by dot blot hybridization and by amplifying DNA sequences containing the viral integration site; this 'junction' fragment cannot be amplified from integrated virus. Thoracic ligations and in vitro ecdysteroid treatments of wasp ovaries support the hypothesis that polydnavirus DNA replication is regulated by ecdysteroid during parasite development.