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L Mela-Riker

Publications and source records attributed to L Mela-Riker.

12 recordsLinked to original sources
PubMed1992

Chronic hyperdynamic sepsis in the rat. II. Characterization of liver and muscle energy metabolism.

Sepsis was induced in male rats by injections of live Escherichia coli No. 4 (or E. coli No. 3) and Bacteroides fragilis organisms into a preformed subcutaneous abscess. Body weight, food and water intake, and cardiac output were measured daily. After 1, 2, or 3 weeks, animals were sacrificed, and blood, liver, and muscle were collected for measurements of plasma glucose and carnitine, mitochondrial respiratory activity, mitochondrial cytochrome concentrations, and tissue adenine nucleotides. Compared with sham controls, no significant differences were found in state 3 respiratory activities of liver mitochondria isolated from rats with moderate (no weight loss, cardiac output increased to 150% of control) or severe (0.5% weight loss/day, cardiac output increased to 200% of control) sepsis at any time. After 1 week of severe, but not moderate, sepsis, pyruvate-supported respiration in muscle mitochondria was significantly decreased, while branched-chain ketoacid and beta-hydroxybutyrate-supported respiration remained unchanged. After 2 weeks of severe, but not moderate, sepsis, beta-hydroxybutyrate and branched-chain ketoacid oxidation increased severalfold; pyruvate utilization remained depressed. Severe or moderate sepsis did not uncouple mitochondrial respiration at any time. Total muscle carnitine concentration was significantly decreased after long-term but not short-term severe sepsis. Severe short-term sepsis caused a significant increase in liver short-chain acyl and total carnitines. Muscle energy charge was unaltered by either moderate or severe sepsis. These results represent the first demonstration of sepsis-induced fuel shifts at the mitochondrial level in muscle: Severe hyperdynamic sepsis is characterized by the reduced ability of muscle mitochondria to utilize pyruvate with a simultaneous increase in branched-chain ketoacid and ketone body utilization. These changes were not observed in liver mitochondria.

Adenine Nucleotides↗
PubMed1989

Potential role of mitochondrial calcium metabolism during reperfusion injury.

Ischemia-reperfusion injury has been associated with intracellular H2O2 and superoxide radical production from accumulated hypoxanthine (HX) and xanthine oxidase (XO). The effect of H2O2 and superoxide radical on mitochondrial Ca2+ efflux was characterized in isolated renal mitochondria using a HX-XO system. Mitochondria were suspended in buffered medium containing 200 microM HX. Extramitochondrial Ca2+ was monitored kinetically at 660-685 nm using the Ca2+ indicator arsenazo III. After preloading mitochondria with 18-25 nmol Ca2+/mg protein, addition of XO to the medium caused a rapid oxidation of mitochondrial NAD(P)H followed by Ca2+ release. Ca2+ efflux was attributed to mitochondrial metabolism of H2O2 because efflux could be prevented with catalase but not superoxide dismutase. The Ca2+ efflux rate (r = 0.995) and lag time to Ca2+ efflux (r = 0.987) both correlate well with the NAD(P)H oxidation rate. Exogenous ATP prevents Ca2+ efflux in a dose-dependent fashion (Km = 35 microM ATP) without affecting NAD(P)H oxidation; ATP plus oligomycin, however, had no effect. The protective effect of ATP on Ca2+ efflux was diminished by ruthenium red (RR). XO-induced Ca2+ efflux increased state 4 respiration 148% via a futile Ca2+ cycle involving the Ca2+ uniport. The increase in state 4 respiration could be reversed with RR (alpha less than 0.001) or ATP (alpha less than 0.01); ATP plus oligomycin, however, had no effect. The results are discussed in relation to the oxygen free radical theory of reperfusion injury.

Animals↗
PubMed1989

Perinatal development of heart, kidney, and liver mitochondrial antioxidant defense.

Development of the mitochondrial antioxidant defense system was studied to assess its potential role in the newborn mammal's tolerance to oxidative challenge and to gain insight into the fetal adaptation to a relatively hyperoxic adult environment. Isolated heart, kidney, and liver mitochondria from fetal, newborn, and adult guinea pigs were used. In situ function of the antioxidant enzymes was estimated in mitochondrial suspensions after the addition to selenite or tert-butyl hydroperoxide by determining NAD(P)H oxidation rates spectrophotometrically at 340-375 nm. Kidney and liver mitochondria from newborn animals were less susceptible to selenite and tert-butyl hydroperoxide-induced NAD(P)H oxidation. The pattern of change, however, varied widely with tissue type. Kidney mitochondria displayed the largest change with a 3- to 4-fold increase in rate from the fetal to adult period. NAD(P)H oxidation rates in intact mitochondria did not correlate consistently with glutathione reductase and peroxidase activities in sonicated mitochondria suggesting in situ regulation by other endogenous factors. Immediately after birth, mitochondrial glutathione reductase and peroxidase activities dropped 38-50% and 50-70%, respectively, in all tissues studied. Total glutathione content of heart and liver mitochondria did not change with age. Adult kidney mitochondrial glutathione, however, declined to 24% of fetal values. Mitochondrial superoxide dismutase activity increased 150-300% from the fetal to the adult period in all tissues studied. Perinatal changes in the mitochondrial antioxidant system and their relationship to mitochondrial calcium metabolism are discussed in terms of the newborn's resistance to oxidative stress.

Animals↗
PubMed1989

Parallel changes in brain tissue blood flow and mitochondrial function during and after 30 minutes of bilateral forebrain ischemia in the gerbil.

Forebrain ischemia was induced in Mongolian gerbils by bilateral occlusion of the common carotid arteries for 30 minutes. These animals do not have a complete circulus arteriosus Willisii. Mitochondria were prepared from the forebrain tissue at the end of the 30 minutes occlusion period as well as at different time points after the release of the occlusion. Tissue blood flow in the forebrain was also determined by measuring the brain tissue accumulation of 14C-iodoantipyrine. Tissue blood flow in the forebrain decreased from a control level of 1.43 +/- 0.03 ml/min/gr to 0.13 +/- 0.03 ml/min/gr by the 30th minute of ischemia, increased to 1.12 +/- 0.25 ml/min/gr after 5 minutes of reflow, but decreased again to 0.41 +/- 0.07 ml/min/gr after 1 1/2 hours of reflow. Oxygen consumption rate of mitochondria prepared from the forebrain (glutamate + malate as substrates in the presence of ADP) was 98 +/- 13 nmoles O2/min/mg protein in control animals, decreased to 61 +/- 9 nmoles O2/min/mg protein after 30 minutes of occlusion, recovered to 106 +/- 9 nmoles O2/min/mg protein during the first 30 minutes of reperfusion. During extended reperfusion, mitochondrial respiratory activity declined reaching 20 +/- 5 nmoles O2/min/mg protein after 5 1/2 hours of reperfusion. Respiratory control ratio of the mitochondria (relative increase of respiration upon addition of ADP) was 9.2 +/- 1.3 in control animals, 7.0 +/- 1.5 after 30 minutes of carotid occlusion, 9.0 +/- 1.2 after 30 minutes of reperfusion, and 5.8 +/- 0.8 after 5 1/2 hours of reperfusion. Superoxide dismutase activity of the forebrain mitochondria was 5.10 +/- 0.7 I.U./mg protein in control animals, decreased to 3.3 +/- 1.6 I.U./mg protein after 30 minutes of occlusion and remained at this level throughout the reperfusion period. These data confirm earlier reports that deterioration of mitochondrial function may contribute to the development of ischemic and post-ischemic brain tissue damage. It also appears possible that postischemic damage of mitochondrial function develops secondary to postischemic deterioration of tissue blood flow.

Animals↗
PubMed1988

Chronic hyperdynamic sepsis in the rat: I. Characterization of the animal model.

We describe a new rat model of chronic hyperdynamic sepsis. After control values for weight gain, and food and water intake of each animal were obtained over a 5-day period, male Sprague-Dawley rats weighing 370-425 g were anesthetized, catheterized to allow chronic cardiac-output measurements, and a sterile subcutaneous cavity was formed over the flank area. The animals were allowed a 3-4 day postoperative recovery period. Body weight, food and water intake, and cardiac output were measured daily. Frequent blood samples were withdrawn for bacterial cultures and white cell counts (WBC). On the third and, in some cases, the fourth postoperative day, the subcutaneous cavity was inoculated with 10(9) colony-forming units of Escherichia coli and Bacteroides fragilis. The resulting sepsis was characterized by loss of body weight in spite of normal food and water intake, increased cardiac output, increased WBC, intermittent bacteremia, decreased muscle mass, and decreased cross-sectional area of skeletal muscle myofibrils. Two levels of septic response emerged--moderate and severe. Based on the above-mentioned measurements, it was possible to categorize all long-term septic animals into these two groups. Both groups exhibited cardiac-output, body-weight, and WBC data significantly different from sham controls. Repeated inoculations of the subcutaneous abscess initiated on the third postoperative day resulted in moderate sepsis with no long-term mortality, severe sepsis with 23% mortality over a 3-week period, or a 100% mortality within 4 days, depending on the virulence of the E. coli organisms used. The new model is ideally suited for pathophysiologic studies of sustained, hyperdynamic sepsis.

Animals↗
PubMed1987

Selenite-induced NAD(P)H oxidation and calcium release in isolated mitochondria: relationship to in vivo toxicity.

The effects of selenite on the mitochondrial NAD(P)H/NAD(P) ratio and calcium pool are described. Small quantities of selenite can 1) oxidize mitochondrial NAD(P)H and 2) induce calcium release from isolated mitochondria. Reduced NAD(P)H within intact mitochondria was monitored kinetically using the wavelength pair, 340-375 nm. NAD(P)H oxidation rates at various concentrations of selenite were calculated. Mitochondria from older animals can oxidize NAD(P)H faster than those of younger animals; maximum selenite-induced oxidation rates correlate well with age of the animal in both kidney (r = 0.920) and liver (r = 0.839) mitochondria, the oxidation rates in the adult (liver 15.4, kidney 34.8 nmol/min/mg of protein) being 3-5 times the rates in the 1- to 2-day-old newborn (liver 2.8, kidney 10.3 nmol/min/mg protein). Calcium fluxes within mitochondrial suspensions were monitored kinetically using the calcium indicator, Arsenazo III, and the wavelength pair, 660-685 nm. Susceptibility to selenite-induced calcium release is age dependent, the mitochondria of older animals being more susceptible. Incubation time required to induce calcium release was 77 +/- 30 sec in the adult compared to 406 +/- 25 sec at the age of 0-4 days in the newborn. The bimodal toxic manifestations of selenite in vivo are discussed in view of the age-dependent differences in selenite metabolism at the cellular level.

Aging↗
PubMed1985

DMSO effects on synaptic facilitation and calcium dependence in bullfrog sympathetic ganglion.

Synaptic transmission in the bullfrog sympathetic ganglion was studied by means of extra- and intracellular recordings. DMSO (3-10%) caused a single orthodromic stimulus to generate a brief burst of repetitive postganglionic discharges. DMSO also partially reversed a preexisting transmission failure in low Ca2+ medium. Ganglia were exposed to gradual reductions in extracellular Ca2+, in the absence and in the presence of DMSO. The recorded amplitude of the postganglionic compound action potential (CAP) was plotted as a function of Ca2+ concentration. In the absence of DMSO transmission failed progressively as Ca2+ was reduced from 1.8 to 0.47 mM but DMSO (3% and 10%) shifted the curve of transmission failure to the left (lower Ca2+ concentration). DMSO inhibits ganglion cholinesterase activity, but this is not the mechanism of its facilitatory effect on Ca2+ entry, since physostigmine did not shift the curve of transmission failure in low Ca2+ to the left. The data suggest that DMSO maintained transmitter release in low Ca2+ by a direct, nonspecific enhancement of Ca2+ influx into the presynaptic nerve terminal.

Animals↗
PubMed1984

Mitochondrial function in shock.

Studies utilizing animal models of circulatory shock have revealed mitochondrial structural and functional damage in the liver, kidney, and brain. Adenosine triphosphate (ATP) synthesis and calcium transport rates of these mitochondria decline significantly during circulatory shock. The specific enzyme functions affected deleteriously by low flow states are the ATP synthetase, adenine nucleotide translocase, and carrier-mediated calcium transport. Other cellular alterations that possibly are responsible for, or are related to, the shock-induced mitochondrial deterioration are discussed. Differences in the mitochondrial responses to endotoxemia and hyperdynamic sepsis are described. Data are presented on the beneficial effects of early glucocorticoid treatment in prevention of mitochondrial functional deterioration during endotoxemia.

Adenosine Triphosphate↗