Effect of 2,4-dinitrophenol on the hypometabolic response to hypoxia of conscious adult rats

Saiki, Chikako, and Jacopo P. Mortola. Effect of2,4-dinitrophenol on the hypometabolic response to hypoxia of conscious adult rats. J. Appl. Physiol. 83(2):537-542, 1997.During acute hypoxia, a hypometabolic response iscommonly observed in many newborn and adult mammalian species. Wehypothesized that, if hypoxic hypometabolism were entirely a regulatedresponse with no limitation in O₂availability, pharmacological uncoupling of the oxidativephosphorylation should raise O₂consumption(O₂) bysimilar amounts in hypoxia and normoxia. Metabolic, ventilatory, andcardiovascular measurements were collected from conscious rats in airand in hypoxia, both before and after intravenous injection of themitochondrial uncoupler 2,4-dinitrophenol (DNP). In hypoxia (10%O₂ breathing, 60% arterialO₂ saturation),O₂, as measured by anopen-flow technique, was less than in normoxia (~80%). SuccessiveDNP injections (6 mg/kg, 4 times) progressively increasedO₂ in both normoxia andhypoxia by similar amounts. Body temperature slightly increased innormoxia, whereas it did not change in hypoxia. The DNP-stimulatedO₂ during hypoxia couldeven exceed the control normoxic value. A single DNP injection (17 mg/kg iv) had a similar metabolic effect; it also resulted inhypotension and a drop in systemic vascular resistance. We concludethat pharmacological stimulation ofO₂ counteracts theO₂ drop determined byhypoxia and stimulates O₂not dissimilarly from normoxia. Hypoxic hypometabolism is likely toreflect a regulated process of depression of thermogenesis, with nolimitation in cellular O₂availability.

     

Origin of the central cells of erythroblastic islands in fetal mouse liver: ultrahistochemical studies of membrane-bound glycoconjugates

 To clarify the origin of the central cells in hepatic erythroblastic islands, glycoconjugates on the surface of cellular constituents in fetal mice liver were ultrahistochemically examined using lectin staining. At 11 days of gestation, the cells derived from mesenchyme in fetal liver, including sinusoidal macrophages, endothelial cells, and erythropoietic cells, bound Griffonia simplicifolia isoagglutinin I-B4 (GS-I-B4), but hepatocytes lacked binding sites for the isolectin. Scavenger macrophages in the hepatic cords at 13 days of gestation and the central cells in the erythroblastic islands at 15 days of gestation also bound GS-I-B4. Hepatocytes, however, exhibited no GS-I-B4 binding site at any gestational day. At 11 days of gestation, none of the cells in fetal liver had binding sites for soybean agglutinin (SBA), but cells derived from mesenchyme acquired these binding sites at 13 days of gestation. The central cells in the erythroblastic islands also bound SBA, but hepatocytes did not bind the lectin at all. The central cells in the erythroblastic islands can be considered to belong to a mesenchymal cell lineage, and primitive sinusoidal macrophages at 11 days of gestation are possible precursors of these central cells. Accepted: 22 January 1997     

GABA, Glutamic Acid Decarboxylase, and GABA Transaminase Levels in the Myenteric Plexus in the Intestine of Humans and Other Mammals

Abstract: Regional distribution of endogenous γ- aminobutyric acid (GABA), its synthesizing enzyme, glutamic acid decarboxylase (GAD), and metabolic enzyme, GABA transaminase (GABA-T), were determined in the intestinal tract of guinea pigs and cats and the findings compared with the number of ganglion cells in Auerbach's plexus. There were positive correlations among the GABA contents and the numbers of neural cells of the plexus. The precise localization of GABA and GAD in individual layers (mucosa, circular and longitudinal muscles, and Auerbach's plexus) in the human and cat colon was also determined. The endogenous GABA contents and GAD activity were the highest in Auerbach's plexus in tissues of both species. These results indicate that GABA is synthesized and localized in Auerbach's plexus and probably plays a significant role in the enteric nervous system.     

A rapid sensitive method for the determination of ascorbic acid in the excess of 2,6-dichlorophenolindophenol using a stopped-flow apparatus

A rapid and sensitive method termed “time difference analysis” for the determination of reduced ascorbic acid even in the presence of excess triose reductone has been developed by using a stopped-flow apparatus in excess 2,6-dichlorophenolindophenol. The lowest limit of the concentration of ascorbic acid was about 2 × 10^?7m. A single stopped-flow trace can be used for both qualitative and quantitative analysis of ascorbic acid. The contamination of triose reductone, which disturbs the analysis in the ordinary static measurement, can be safely distinguished because of the sluggishness of the reaction.     

Comparison of R- and S-form lipopolysaccharides fractionated from Escherichia coli UKT-B lipopolysaccharide in pyrogen and Limulus tests

Different LPS was shown to have a relatively different proportion of O-specific chain-less (R-form) LPS by polyacrylamide gel electrophoresis (PAGE) with sodium deoxycholate (DOC). By using DOC-PAGE, S-form LPS having O-chain with approximately 11 repeating units on average (S-Fr) and O-chain-less LPS (R-Fr) were separated from Escherichia coli UKT-B S-form LPS. Significantly stronger pyrogenicity was observed in R-Fr than in S-Fr when measured on the weight basis. Similar result was observed in Limulus test. Comparing biological activities of different S-form LPS, attention should be given to the amounts of co-existing R-form LPS.     

Ultrastructural observations of mitochondrial morphology through the life cycle of the brown alga,Mutiomo cylindricus (Cutleriaceae,Tilopteridales)

Protoplasma - Mitochondrial morphology varies according to development and the physiological conditions of the cell. Here, we performed electron tomography using serial sections to analyze the...     

Effects of lighting environment on the degeneration of retinal ganglion cells in glutamate/aspartate transporter deficient mice,a mouse model of normal tension glaucoma

Lighting conditions may affect the development of retinal degenerative diseases such as macular degeneration. In this study, to determine whether the lighting environment affects the progression of degeneration of retinal ganglion cells (RGCs), we examined glutamate/aspartate transporter (GLAST) heterozygous (GLAST^+/-) mice, a mouse model of normal tension glaucoma. GLAST^+/- mice were reared under a 12-h light-dark cycle (Light/Dark) or complete darkness (Dark/Dark) condition after birth. The total RGC number in the Dark/Dark group was significantly decreased compared with the Light/Dark group at 3 weeks old, while the number of osteopontin-positive αRGCs were similar in both groups. At 6 and 12 weeks old, the total RGC number were not significantly different in both conditions. In addition, the retinal function examined by multifocal electroretinogram were similar at 12 weeks old. These results suggest that lighting conditions may regulate the progression of RGC degeneration in some types of glaucoma.