PubMed Health⌕ Search

Biomedical subjects

T C Vary

Publications and source records attributed to T C Vary.

At least 19 recordsLinked to original sources
PubMed1992

Age-dependent decrease in the amount of eukaryotic initiation factor 2 in various rat tissues.

Recent studies have suggested that the decline in protein synthesis that occurs in rat liver and brain during development and aging is associated with a decrease in the activity of eukaryotic initiation factor 2 (eIF-2). One way in which eIF-2 activity could be decreased in tissue extracts would be through a decrease in the activity of the GDP exchange factor, eIF-2B. In the present study, the activity of eIF-2B was measured in tissue extracts and was found to be less in older than in younger rats. Thus a decrease in eIF-2B activity could account for part of the decrease in protein synthesis that occurs during aging. Another way in which eIF-2 activity could be decreased would be through a decrease in amount of the protein. Therefore the amount of eIF-2 in various tissues was quantified by protein immunoblot analysis. We found that the amount of eIF-2 relative to total protein tended to fall with increasing age. Furthermore, eIF-2 content was directly proportional to the rate of protein synthesis in the tissues examined. Finally, slot-blot analysis of polyadenylated RNA revealed no significant change in the relative abundance of eIF-2 alpha mRNA with age. The last-mentioned experiments suggest that the synthesis of eIF-2 may be regulated through changes in the deficiency of translation of eIF-2 alpha mRNA rather than through changes in gene transcription.

Aging↗
PubMed1992

Effects of recombinant monokines on hepatic pyruvate dehydrogenase, pyruvate dehydrogenase kinase, lipogenesis de novo and plasma triacylglycerols. Abolition by prior fasting.

1. The effects of recombinant human tumour necrosis factor alpha (TNF) and murine interleukin-1 alpha (IL-1) on the activation state of the hepatic pyruvate dehydrogenase complex (PDHa), the activity of mitochondrial PDH kinase, hepatic lipogenesis de novo and plasma triacylglycerol (TG) concentrations were studied. 2. Monokine effects depended upon prior nutritional state. In rats fasted for 20 h or 45 h before monokine administration and refeeding (orally or with intravenous glucose), PDHa, TG and hepatic lipogenesis were not increased. In rats fed ad libitum, treatment with TNF plus IL-1 increased the contribution of hepatic lipogenesis to circulating TG to 550% of control values (P = 0.03) and plasma TG concentrations to 159% (P = 0.02), whereas PDHa increased slightly to 120% (P = 0.02) and liver glycogen content fell to 45.8% (P = 0.05) of control values. 3. Intrinsic hepatic PDH kinase activity was not changed by monokine treatment in rats fed ad libitum. 4. The increased lipogenesis de novo showed no correlation (r2 = 0.05, not significant) with hepatic PDHa in individual animals fed ad libitum. 5. In conclusion, these results suggest that monokines increase pyruvate flux through hepatic PDH in vivo in rats fed ad libitum primarily by mechanisms other than covalent modification of PDH. Prior nutritional status exerts a permissive effect for monokine stimulation of PDHa and lipogenesis, consistent with a substrate-mediated action, but the mechanism of this permissive effect remains uncertain.

Animals↗
PubMed1992

Regulation of hepatic protein synthesis in chronic inflammation and sepsis.

The regulation of protein synthesis was determined in livers from control, sterile inflammatory, and septic animals. Total liver protein was increased in both sterile inflammation and sepsis. The rate of protein synthesis in vivo was measured by the incorporation of [3H]phenylalanine into liver proteins in a chronic (5 day) intra-abdominal abscess model. Both sterile inflammation and sepsis increased total hepatic protein synthesis approximately twofold. Perfused liver studies demonstrated that the increased protein synthesis rate in vivo resulted from a stimulation in the synthesis of both secreted and nonsecreted proteins. The total hepatic RNA content was increased 40% only in sterile inflammation, whereas the translational efficiency was increased twofold only in sepsis. The increase in translational efficiency was accompanied by decreases in the amount of free 40S and 60S ribosomal subunits in sepsis. Rates of peptide-chain elongation in vivo were increased 40% in both sterile inflammation and sepsis. These results demonstrate that sepsis induces changes in the regulation of hepatic protein synthesis that are independent of the general inflammatory response. In sterile inflammation, the increase in protein synthesis occurs by a combination of increased capacity and translational efficiency, while in sepsis, the mechanism responsible for accelerated protein synthesis is an increased translational efficiency.

Animals↗
PubMed1992

Sepsis-induced changes in protein synthesis: differential effects on fast- and slow-twitch muscles.

Sepsis is associated with severe muscle wasting. Mechanisms responsible for sepsis-induced alterations in muscle protein metabolism were investigated in vivo and compared with changes induced by nonseptic inflammation. The rate of protein synthesis in mixed hindlimb muscles was not altered in inflammation but was inhibited 50% in sepsis. This inhibition did not result from a decreased RNA content. Instead, the translational efficiency was significantly reduced by 50% in skeletal muscle of septic animals compared with control. The effect of sepsis to lower the rate of protein synthesis was further examined using individual muscles containing different fiber types. Both the protein concentration and protein synthetic rate in fast-twitch muscles were reduced by sepsis, whereas neither of these parameters was affected in slow-twitch muscles or heart. The decreased translational efficiency did not result from a change in the rate of peptide-chain elongation. Instead, the sepsis-induced inhibition of protein synthesis resulted from a restraint in peptide-chain initiation because sepsis caused a 1.6-fold increase in free ribosomal subunits. Overall, sepsis, but not inflammation, caused an inhibition of protein synthesis primarily in muscles composed of fast-twitch fibers. The mechanism involved in the reduced rates of protein synthesis in muscles resulted from an inhibition of peptide-chain initiation, with no change in peptide-chain elongation.

Abscess↗
PubMed1991

Intravascular plastic catheters. How they potentiate tumor necrosis factor release and exacerbate complications associated with sepsis.

We tested the hypothesis that long-term intravascular cannulation exacerbates the harmful effects of an infectious challenge. Four groups of rats were initially studied: rats without intravascular catheters or infection (group 1), rats without catheters with a polymicrobial infection (group 2), rats with catheters but no infection (group 3), and rats with catheters and infection (group 4). Infected animals had an increased mortality and generated a significantly increased tumor necrosis factor response compared with noninfected animals. Animals with catheters and infection generated far less cardiac output than animals from the other three groups. No histologic changes differentiated the four groups. Therefore, the presence of a sterile intravascular catheter significantly increases cardiac dysfunction and mortality rates in rats with chronic bacteremia. These results suggest that intravascular plastic catheters potentiate the destructive cascade of events produced by the host in response to bacteremia.

Abscess↗
PubMed1991

Oxygen debt and metabolic acidemia as quantitative predictors of mortality and the severity of the ischemic insult in hemorrhagic shock.

BACKGROUND AND METHODS: An experimental canine model of hemorrhagic, hypovolemic shock is described that uses oxygen debt and its metabolic consequences of lactic acidemia and metabolic base deficit as independent variables for the prediction of probability of death. RESULTS: Lactic acidemia and metabolic base deficit are compared with the conventional hemodynamic variables of BP and cardiac output (Qt) as predictors of outcome and are shown to be superior using a modified Kaplan-Meier probability statistic. The LD50 for oxygen debt is shown to be 113.5 mL/kg, 12.9 mmol/L for lactate, and -18.8 mmol/L for base excess (BE). Comparison is made between the ability of Qt, BP, shed blood, BE, and lactate to predict oxygen debt. CONCLUSIONS: Of the single-variable predictors, BE shows the highest explained variability. However, a combined prediction from both lactate and BE appears superior to the use of either alone. Using this regression to compute the oxygen debt, it is possible to estimate accurately the actual level of oxygen debt from the BE and lactate values obtained during hemorrhagic hypovolemia. From serial determinations over time of the increase in these biochemical variables above the oxygen debt baseline, it is possible to estimate the rate of oxygen debt accumulation and the time remaining until the LD50 will be reached as indicators of the severity of the total body ischemia resulting from hemorrhagic shock.

Acid-Base Equilibrium↗
PubMed1991

Increased pyruvate dehydrogenase kinase activity in response to sepsis.

The effect of sterile inflammation and sepsis on the proportion of active pyruvate dehydrogenase complex (PDH) in mitochondria isolated from skeletal muscle has been investigated. The proportion of active PDH in mitochondria isolated from septic animals was significantly reduced compared with control under all incubation conditions examined, even in the presence of inhibitors of the PDH kinase. There was no significant difference between control and sterile inflammation in any of the incubations examined. The rate constant for ATP-dependent inactivation of the PDH complex in mitochondrial extracts from control animals was -0.42 min-1 (r = 0.993; P less than 0.001) and was not altered in mitochondrial extracts from sterile inflammatory animals (-0.43 min-1; r = 0.999; P less than 0.001). However, rate constants for inactivation in septic animals was significantly increased over twofold to -1.08 min-1 (r = 0.987; P less than 0.001) (P less than 0.001 vs. control or sterile inflammation). In the presence of inhibitors of the PDH kinase reaction (2.5 mM pyruvate or 1 mM dichloroacetate), inactivation of PDH after addition of ATP was significantly greater in mitochondrial extracts from septic than either control or sterile inflammatory animals. These results suggest that sepsis, but not sterile inflammation, induces a stable factor in skeletal muscle mitochondria that increased PDH kinase activity.

Animals↗
PubMed1989

Effect of dichloroacetate on plasma and hepatic amino acids in sterile inflammation and sepsis.

The effect of sterile inflammation and chronic sepsis on the plasma and hepatic free amino acid concentrations was determined. Relative to control animals, only minor alterations in the plasma amino acid concentrations were observed in sterile inflammation and sepsis. In liver, concentrations of alanine, serine, threonine, asparagine, proline, and glycine were significantly increased to the same extent in sterile inflammation and sepsis, while hepatic glutamine concentrations were significantly decreased. Compared with sterile inflammation, the branched-chain amino acid concentrations were depressed in the liver of septic animals. Following administration of dichloroacetate, hepatic alanine concentrations were significantly reduced more than threefold in each of the conditions examined; in contrast, significant increases in hepatic concentrations of threonine, glycine, glutamine, glutamate, histidine, and proline were observed. Also following administration of dichloroacetate, the branched-chain amino acid concentrations were all significantly elevated in each of the conditions examined, and plasma alanine concentrations were significantly decreased, while those of glutamine and glycine were significantly increased. These results demonstrate that there is a disassociation between the plasma and hepatic concentration of free amino acids in sterile inflammation and sepsis. Furthermore, the results demonstrate that some of the alterations in hepatic amino acid metabolism may be reversed pharmacologically by dichloroacetate.

Abscess↗
PubMed1989

Role of anaerobic bacteria in intra-abdominal septic abscesses in mediating septic control of skeletal muscle glucose oxidation and lactic acidemia.

Altered glucose metabolism and lactic acidemia are features of Gram-negative polymicrobial abscesses, but the relationship between carbohydrate metabolism and the aerobic or anaerobic organisms is unclear. Since reductions in the % active pyruvate dehydrogenase complex (PDHa) limits glucose oxidation in sepsis, the effect of a 7-day monoclonal (E. coli or B. fragilis) vs. biclonal (E. coli + B. fragilis) intra-abdominal abscess (IA) on PDHa and lactate concentrations in skeletal muscle (SM) and plasma was studied in rats. A chronic IA was created by the intraperitoneal introduction of a sterile rat fecal-agar pellet (1.5 ml) inoculated with a known bacterial flora [sterile (S); E. coli 10(6) CFU/ml (EC); B. fragilis 10(8) CFU/ml (BF); E. coli 10(3) CFU/ml + B. fragilis 10(4) CFU/ml (ECLBF); E. coli 10(3) CFU/ml + B. fragilis 10(8) CFU/ml (ECHBF)]. Neither SM PDHa nor SM nor plasma lactate were altered from control in animals with either sterile (S) or E. coli (EC) monoclonal IA, but SM PDHa was significantly (p less than 0.001) reduced and SM lactate increased (p less than 0.05) in rats with B. fragilis 10(8)/ml (BF) monoclonal IA. In biclonal IA, the effect of sepsis on SM PDHa depended on the concentration of B. fragilis in the IA fluid (ECLBF = 10(4) CFU/ml vs. ECHBF = 10(8) CFU/ml) since the E. coli were constant (10(3) CFU/ml). At the lower B. fragilis IA concentration (ECLBF), the SM PDHa was not different from control. However, when the IA B. fragilis concentration was increased to 10(8) CFU/ml (ECHBF), the SM PDHa was significantly (p less than 0.001) decreased relative to control. A decreased muscle PDHa was always associated with elevated SM and plasma lactate concentrations. These results suggest that IA which permit a threshold of relatively nonlethal (BF = 0% mortality) anaerobic B. fragilis (greater than or equal to 10(8) CFU/ml) to enter the circulation are more important in altering metabolic control of skeletal muscle glucose oxidation and in producing lactic acidemia than are IA with only aerobic E. coli. However, in biclonal intra-abdominal abscesses, B. fragilis potentiated the early mortality from E. coli (EC = 6% vs. ECHBF = 37% mortality), suggesting that the metabolic effect of the B. fragilis-induced lactic acidemia is synergistic with the direct toxic effects of the E. coli.

Abdomen↗
PubMed1989

Pharmacologic modulation of increased release of gluconeogenic precursors from extra-splanchnic organs in sepsis.

The effect of sterile inflammation and sepsis on the release of lactate and amino acids by peripheral tissues was investigated by removing the splanchnic organs (liver and small intestines) from the circulation and monitoring changes in plasma substrates for 30 min. Functional hepatectomy was performed in rats 5-7 days following the intraperitoneal introduction of a fecal-agar pellet (1.5 ml) [sterile vs. Bacteriodes fragilis (10(8) CFU) + E. coli (10(3) CFU)]. Following functional hepatectomy, dichloroacetate, an activator of the pyruvate dehydrogenase complex, significantly inhibited both lactate and alanine release. L-cycloserine, an inhibitor of alanine aminotransferase, significantly (P less than .05) reduced alanine following hepatectomy. Methionine sulfoximine, an inhibitor of glutamine synthetase, significantly (P less than .005) decreased glutamine accumulation following functional hepatectomy in each of the conditions examined. Treatment with each of these drugs abolished the differences between control and sepsis following hepatectomy. These results demonstrate that alterations in the amino acid profiles during sepsis may be modulated in peripheral organs pharmacologically by utilizing known inhibitors of critical regulatory enzymes.

Alanine↗
PubMed1989

Role of extra-splanchnic organs in the metabolic response to sepsis: effect of insulin.

The effect of sterile inflammation and sepsis on the release of lactate and amino acids by peripheral tissues was investigated in rats by removing the splanchnic organs (liver + small intestines) from the circulation and monitoring changes in blood metabolites over 30 min. Functional hepatectomy was performed in rats 5-7 days following the intraperitoneal introduction of a fecal-agar pellet (sterile vs. Bacteroides fragilis + E. coli). Lactate was significantly (P less than .05) increased in each of the conditions following hepatectomy but was raised to a significantly greater extent in sepsis (P less than .05). A similar response was observed for glutamine while alanine was only significantly (P less than .05) increased in sepsis following hepatectomy. Branched chain amino acids (BCAA) showed differential changes in sepsis compared to control. In control and sterile inflammation, functional hepatectomy was associated with significant decreases (P less than .05) in BCAA. In sepsis, BCAA were not decreased following hepatectomy and were significantly (P less than .05) elevated relative to control or sterile inflammation. Phenylalanine concentrations were not altered in control or sterile inflammation but were significantly elevated in sepsis (P less than .05). Insulin attenuated the accumulation of lactate and amino acids in fed control animals, following functional hepatectomy. However, in septic animals, insulin failed to prevent the rise in plasma lactate following hepatectomy.

Alanine↗
PubMed1988

Inhibition of skeletal muscle protein synthesis in septic intra-abdominal abscess.

Chronic sepsis is always associated with profound wasting leading to increased release of amino acids from skeletal muscle. Net protein catabolism may be due to decreased rate of synthesis, increased rate of degradation, or both. To determine whether protein synthesis is altered in chronic sepsis, the rate of protein synthesis in vivo was estimated by measuring the incorporation of [3H]-phenylalanine in skeletal muscle protein in a chronic (5-day) septic rat model induced by creation of a stable intra-abdominal abscess using an E. coli + B. fragilis-infected sterile fecal-agar pellet as foreign body nidus. Septic rats failed to gain weight at rates similar to control animals, therefore control animals were weight matched to the septic animals. The skeletal muscle protein content in septic animals was significantly reduced relative to control animals (0.18 +/- 0.01 vs. 0.21 +/- 0.01 mg protein/gm wet wt; p less than 0.02). The rate of incorporation of [3H]-phenylalanine into skeletal muscle protein from control animals was 39 +/- 4 nmole/gm wet wt/hr or a fractional synthetic rate of 5.2 +/- 0.5%/day. In contrast to control animals, the fractional synthetic rate in septic animals (2.6 +/- 0.2%/day) was reduced by 50% compared to control animals (p less than 0.005). The decreased rate of protein synthesis in sepsis was not due to an energy deficit, as high-energy phosphates and ATP/ADP ratio were not altered. This decrease in protein synthesis occurred even though septic animals consumed as much food as control animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdomen↗
PubMed1988

Metabolic effects of partial reversal of pyruvate dehydrogenase activity by dichloroacetate in sepsis.

The metabolic effects of dichloroacetate on carbohydrate metabolism were investigated in normal fed, sterile inflammatory, and chronic septic animals. Chronic sepsis, but not sterile inflammation, was associated with elevated plasma, liver, and skeletal muscle lactate concentrations. Sodium dichloroacetate significantly reduced both plasma and intracellular pyruvate and lactate concentrations in all conditions examined, while plasma glucose concentrations remained unchanged. Decreased tissue metabolite concentrations were associated with a significantly increased active pyruvate dehydrogenase complex in liver and skeletal muscle in each of the conditions examined. In liver, dichloroacetate fully activated (greater than 85%) the pyruvate dehydrogenase complex under all conditions. In skeletal muscle from chronic septic animals, the dichloroacetate-induced increases in active pyruvate dehydrogenase were significantly less than those observed in non-septic animals. The data suggest that although dichloroacetate can partially reverse the sepsis-induced effects on skeletal muscle pyruvate dehydrogenase activity, there may be additional regulatory factors in skeletal muscle from septic animals. The dichloroacetate stimulation of the pyruvate dehydrogenase activity may provide a pharmacological method for reducing the elevated lactate concentrations observed in chronic severe sepsis.

Abscess↗
PubMed1988

Pharmacological reversal of abnormal glucose regulation, BCAA utilization, and muscle catabolism in sepsis by dichloroacetate.

Sepsis has been shown to decrease skeletal muscle glucose oxidation by inhibiting the pyruvate dehydrogenase activity (PDHa) and to increase proteolysis and use of branched-chain amino acids (BCAA). The effects of dichloroacetate (DCA), which reverses PDHa inhibition, were studied in skeletal muscle from a septic (S) rat model of intra-abdominal abscess (E. coli + B. fragilis) and compared to control (C) and sterile inflammatory abscess (I) animals. In one set of S, I, and C animals, DCA (1 mmol/kg) was injected intraperitoneally at 0, 30, and 60 min. Septic, but not I, rats had a twofold increase in skeletal muscle lactate concentrations over C, but no changes in pyruvate. After DCA, both lactate and pyruvate were reduced (p less than 0.001) to same level in S, I, and C. Skeletal muscle alanine was increased in S compared to I or C, but after DCA was reduced threefold in C, S, and I (p less than 0.001) suggesting that alanine synthesis may be impaired due to decreased pyruvate availability. Like alanine, skeletal muscle BCAA were increased in S compared to C, but not altered in I. Following DCA, BCAA levels in muscle from S were reduced (p less than 0.001) to values seen in C or I. Muscle phenylalanine content was significantly elevated in S (p less than 0.05) compared to C or I, but was reduced (p less than 0.05) after DCA in S but not in C or I. Decreased muscle phenylalanine associated with lowered BCAA suggests DCA may decrease septic muscle protein catabolism and/or enhance protein synthesis. Coupled with an increased PDHa and reduced lactate levels, this suggests that DCA may reverse the excess muscle catabolism and BCAA dependence of sepsis by increasing glucose and lactate oxidation and may be a useful therapeutic modality.

Acetates↗
PubMed1987

Advanced signal-processing method for the detection, localization, and quantification of acute myocardial ischemia.

In this study of a canine heart model of localized reversible ischemia, a computer-based single-processing method is developed to detect and localize the epicardial projections of ischemic myocardial electrocardiograms (ECGs) during the cardiac activation, rather than the repolarization, phase. This is done by transforming ECG signals from an epicardial sensor array into the multichannel spectral domain and identifying three decision variables: (1) the frequency in hertz of the spectral peak (f0), its frequency band width 50% below the peak value (w0), and the maximum eigenvalue difference of the ECG signal's autocorrelation matrix (e0). With use of the histograms of the f0, w0, and e0 parameters of 3256 ECGs from normal and 957 from ischemic areas of myocardium obtained from 12 dogs, it was possible to predict ischemia in a new test group of nine animals from a Neyman-Pearson (NP) test in which the threshold probabilities of detecting ischemia for each decision variable are compared with those of detecting normality. Quantification of each sensor area by the NP tests revealed that, compared with the control, ECG spectra with decreased F0 and w0 and increased e0 relative to their respective thresholds had increased myocardial lactate (p less than 0.01), decreased adenosine triphosphate (ATP) (p less than 0.05), and reduced creatine phosphate (p less than 0.01). Prediction of f0 (p less than 0.0006) as a continuous variable could be obtained from the regression of the myocardial levels of ATP plus creatine phosphate, which demonstrated that this decision variable appears to directly reflect myocardial energetics. It appears that an advanced signal-processing method for ECG array data can be used to detect, localize, and quantify reversible myocardial ischemia.

Adenosine Triphosphate↗
PubMed1986

Modulation of pyruvate dehydrogenase kinase activity in cultured hepatocytes by glucagon and n-octanoate.

The activity of pyruvate dehydrogenase kinase in extracts of mitochondria from rat hepatocytes cultured for 21 h in medium 199 was increased 2.5-fold by the presence of 55 nM-glucagon and 1 mM-sodium n-octanoate in the culture medium. The change was comparable with that induced in vivo by 48 h starvation. The potential contribution of branched-chain complex to estimates of PDH-complex activity in rat liver mitochondria has been defined.

Animals↗