Peroxisomal fatty acid oxidation capacity is more resistant to ischaemic and reperfusion injury than mitochondrial fatty acid oxidation capacity in feline hearts

Mitotic recombination induced by six alkylating agents has been studied in the wing-spot test of Drosophila melanogaster. The model mutagens chosen have different models of action at the DNA level. These are: the direct-acting small alkylating agent methylmethanesulfonate (MMS), the small promutagens N-dimethylnitrosamine (DMN) and N-diethylnitrosamine (DEN), the bifunctional cross-linking alkylating agents mitomycin C (MMC), chlorambucil (CLA) and monocrotaline (MCT). Flies of the standard cross (flr3 / TM3, Bds females and mwh males) were used to produce the larvae to be treated. Three-day old Drosophila larvae were exposed by chronic feeding for 48 h to three different concentrations of all six alkylating agents. Acute feeding for only 2 h was used in addition with DEN and MMC. Wings of the marker-heterozygous (mwh+ / + flr3) as well as of the balancer-heterozygous (mwh+ / TM3, Bds) progeny were analysed. The ranking of the compounds with respect to their genotoxic potency, based on mwh clone formation frequency in marker-heterozygous wings was: MMS > MNC > DMN > CLA approximately MCT > DEN. The ranking with respect to the induction of twin spots, which are produced by mitotic recombination exclusively, was: MMS > DMN > MMC > MCT > CLA > DEN. The quantitative determination of recombinagenic activity, based on mwh clone formation frequencies obtained in both types of wings, gave the following values: MMS, 93%; MCT, 87%; CLA, 80%; MMC, 73%; DMN, 67%; DEN, 22%. A clear relationship exists between the extent of N-alkylation of DNA and the efficiency of the monofunctional agents MMS and DMN as well of the bifunctional agents MCT, CLA and MMC to induce mitotic recombination. This contrasts with the ethylation of base oxygen atoms and the resulting lower efficiency of DEN to produce mitotic recombination.     

Effects of fatty acid oxidation on glucose utilization by isolated hepatocytes

We have studied the inhibitory action of long- and short-chain fatty acids on hepatic glucose utilization in hepatocytes isolated from fasted rats. The rates of hepatic glucose phosphorylation and glycolysis were determined from the tritiated products of [2-3H] and [6-3H]glucose metabolism, respectively. The difference between these was taken as an estimate of the 'cycling' between glucose and glucose-6-phosphate. In the presence of 40 mM glucose this cycling was estimated at 0.68 mumol/min/g wet wt. Glucose phosphorylation was unaffected during palmitate and hexanoate oxidation to ketone bodies but glycolysis was inhibited. The rate of glucose cycling was increased during this phase to 1.25 mumol/min/g. Following the complete metabolism of the fatty acids, glycolysis was reinstated and cycling rates returned to control levels. Hepatic glucose cycling appears to be an important component of the glucose/fatty acid cycle.     

Glutathione disulfide as an index of oxidative stress during postischemic reperfusion in isolated rat hearts

Junctional sequences of immunoglobulin (Ig)/T-cell receptor (TCR) gene rearrangements are used as patient-specific PCR targets for the detection of minimal residual disease (MRD) in acute lymphoblastic leukaemias (ALLs). Clonal evolution of gene rearrangements is a major pitfall of this strategy. Using high-resolution PCR-based analyses (including denaturing gel electrophoresis and single-stranded conformation polymorphism (SSCP)) we have compared Ig/TCR gene rearrangements at presentation and relapse in a series of ALLs. These methods allow an unambigous comparison of rearrangements taking into account junctional size and nucleotide sequence information and allow a precise assessment of the clonal evolution. V gamma-J gamma and V delta 1-J delta 1 rearrangements were analysed in 12 T-ALLs. VH-JH, V gamma-J gamma, V delta 2-D delta 3 and, in selected cases, DH-JH rearrangements were studied in 14 B-lineage ALLs. Clonal evolution, regarding major rearrangements, occurs for at least one of these loci in 2/12 T-ALLs and in 5/14 B-lineage ALLs. Clonal evolution is more marked for minor rearrangements than for major ones. As shown using SSCP analysis, rearrangements observed at relapse are sometimes found in minor clones at presentation which are therefore selected in vivo by a proliferative advantage. These data, as well as those from the available literature, suggest the use of at least two patient-specific probes to detect MRD in ALLs. A general strategy including selected Ig/TCR rearrangements and chromosomal abnormalities as PCR targets is proposed.     

Dexamethasone-induced impairment in skeletal muscle glucose transport is not reversed by inhibition of free fatty acid oxidation

Our previous studies suggested a possible role for the glucose-free fatty acid (FFA) cycle, ie, preferential utilization of FFA by muscle at the expense of glucose, in dexamethasone (DEX)-induced insulin resistance. To determine whether this resistance could be reversed by inhibiting FFA utilization, we used etomoxir, a potent inhibitor of mitochondrial FFA oxidation. Male Sprague-Dawley rats were injected subcutaneously with 1 mg/kg DEX or the vehicle every other day for 10 days, and half of each group was administered 10 mg/kg etomoxir by gavage once per day and 1 hour before the experiment. As expected, etomoxir treatment increased serum FFA levels and inhibited FFA oxidation by diaphragm in vitro. Administration of etomoxir decreased serum glucose and insulin concentrations under basal conditions in both control and DEX-treated animals, implying enhanced insulin sensitivity. DEX treatment significantly increased endogenous glucose production and decreased whole-body glucose disposal, as well as 2-deoxyglucose (2-DG) uptake by skeletal muscle during euglycemic-hyperinsulinemic clamps. Administration of etomoxir led to small but significant increases in glucose disposal rates of both control (14%) and DEX (23%) groups, but had no effect on residual endogenous glucose production. Thus, DEX-induced insulin resistance was marginally ameliorated but not completely reversed by etomoxir. Depressed 2-DG uptake by individual muscle tissues observed in the present study in conjunction with the absence of free intracellular glucose in muscle tissue following glucose-insulin infusion strongly suggests that the primary defect in glucose metabolism is at the level of transport. Neither overall abundance of the insulin-sensitive glucose transporter (GLUT-4) in skeletal muscle nor its distribution between intracellular stores and plasma membrane were modified by DEX treatment, either, under basal conditions or in response to acute insulin stimulus. These results suggest a defect(s) in the inherent activity of plasma membrane-bound GLUT-4 as the likely mechanism for DEX-induced insulin resistance.     

Regulation of tumour cell fatty acid oxidation by n-6 polyunsaturated fatty acids

The aim of this study was to evaluate acute effects of ethyl tert-butyl ether (ETBE) in man after short-term exposure. ETBE may in the future replace methyl tert-butyl ether, a widely used oxygenate in unleaded gasoline. Eight healthy male volunteers were exposed to ETBE vapor for 2 h at four levels (0, 5, 25, and 50 ppm) during light physical exercise. The subjects rated irritative symptoms, discomfort, and central nervous system effects in a questionnaire. Ocular (eye redness, tear film break-up time, conjunctival epithelial damage, and blinking frequency), nasal (acoustic rhinometry and analysis of inflammatory markers and cells in nasal lavage fluid), and pulmonary (peak expiratory flow, forced expiratory volume in 1 s, forced vital capacity, vital capacity, and transfer factor) measurements were performed. Significantly increased ratings of solvent smell (p = 0.001, repeated-measures ANOVA) were seen during exposures and correlated to exposure levels. Furthermore, significantly elevated ratings of discomfort in throat and airways were seen during and after 50 ppm compared to the control exposure (p = 0.02). Increased nasal swelling (p = 0.001) and blinking frequency (p = 0.01) were noted at all exposure levels, but their magnitudes were not related to exposure levels. A slightly impaired pulmonary function was seen at 25 and 50 ppm, since forced vital capacity (p = 0.02) and vital capacity (p = 0.04) differed significantly from the clean air exposure. Although the impairments seemed to fall within normal inter- and intraindividual variation and have no clinical relevance as such, it cannot be excluded that other individuals may react more severely than eight healthy male volunteers in this study.     

Effect of emeriamine, an inhibitor of fatty acid oxidation, on metabolic fate of a geometrical isomer of linoleic acid in perfused rat liver

Recent functional imaging studies have begun to identify the neural correlates of emotion in healthy volunteers. However, studies to date have not differentially addressed the brain areas associated with the perception, experience, or expression of emotion during emotional arousal. To explore the neural correlates of emotional experience, we used positron emission tomography (PET) and 15-water to measure cerebral blood flow (CBF) in 12 healthy women during film- and recall-induced emotion and correlated CBF changes attributable to emotion with subjects' scores on the Levels of Emotional Awareness Scale (LEAS), a measure of individual differences in the capacity to experience emotion in a differentiated and complex way. A conjunction analysis revealed that the correlations between LEAS and CBF during film- and recall-induced emotion overlapped significantly (z = 3.74, p < 0. 001) in Brodmann's area 24 of the anterior cingulate cortex (ACC). This finding suggests that individual differences in the ability to accurately detect emotional signals interoceptively or exteroceptively may at least in part be a function of the degree to which the ACC participates in the experiential processing and response to emotion cues. To the extent that this finding is consistent with the functions of the ACC involving attention and response selection, it suggests that this neural correlate of conscious emotional experience is not exclusive to emotion.     

Induction by leptin of uncoupling protein-2 and enzymes of fatty acid oxidation

We have studied mechanisms by which leptin overexpression, which reduces body weight via anorexic and thermogenic actions, induces triglyceride depletion in adipocytes and nonadipocytes. Here we show that leptin alters in pancreatic islets the mRNA of the genes encoding enzymes of free fatty acid metabolism and uncoupling protein-2 (UCP-2). In animals infused with a recombinant adenovirus containing the leptin cDNA, the levels of mRNAs encoding enzymes of mitochondrial and peroxisomal oxidation rose 2- to 3-fold, whereas mRNA encoding an enzyme of esterification declined in islets from hyperleptinemic rats. Islet UCP-2 mRNA rose 6-fold. All in vivo changes occurred in vitro in normal islets cultured with recombinant leptin, indicating direct extraneural effects. Leptin overexpression increased UCP-2 mRNA by more than 10-fold in epididymal, retroperitoneal, and subcutaneous fat tissue of normal, but not of leptin-receptor-defective obese rats. By directly regulating the expression of enzymes of free fatty acid metabolism and of UCP-2, leptin controls intracellular triglyceride content of certain nonadipocytes, as well as adipocytes.     

Protective effect of amiloride against reperfusion damage as evidenced by inhibition of accumulation of free fatty acids in working rat hearts

To examine whether amiloride protects against ischemia-induced or reperfusion-induced damage to the heart, mechanical and metabolic studies were performed in the isolated, working rat heart. Ischemia decreased both mechanical function and the tissue levels of high-energy phosphates and increased the tissue levels of free fatty acids (FFAs). Reperfusion restored the levels of high-energy phosphates but further increased FFA accumulation. For this reason, accumulation of FFAs was used as an indicator of both ischemia-induced and reperfusion-induced damage. Drugs were added to the perfusion solution 5 min before ischemia until the end of ischemia (pre) or until 10 min after reperfusion (pre + post). Diltiazem (1 or 5 mumol/L pre) decreased the mechanical function of the non-ischemic heart and attenuated both ischemia-induced and reperfusion-induced accumulation of FFAs. Amiloride (50 mumol/L pre) did not affect the mechanical function of the non-ischemic heart or attenuate ischemia-induced or reperfusion-induced FFA accumulation effectively. However, amiloride (50 mumol/L pre + post) did markedly attenuate the reperfusion-induced accumulation of FFAs. In conclusion, diltiazem attenuates both ischemia-induced and reperfusion-induced myocardial damage, probably through its energy-sparing effect as a result of a decrease in mechanical function before ischemia. In contrast, amiloride attenuates only the reperfusion-induced myocardial damage through mechanisms other than the energy-sparing effect.     

Inhibition of (Na/K)-ATPase by NFE induces an increase in mechanical activity of perfused guinea-pig heart

The effect of 1-(5-nitro-2-furyl)-2-(phenylsulfonyl)-2-(furylcarbonyl)- ethylene (NFE) on stimulation of (Na/K)-ATPase by sodium and potassium ions was tested in isolated, partially purified sarcolemmal preparation from guinea-pig hearts. NFE inhibited competitively the stimulation of the enzyme by increasing concentrations of potassium. This inhibition was characterized by a significant (p < 0.001) increase of the K0.5 value, a considerable decrease of the Hill's cooperativity constant n as well as by an insignificant diminution of the Vmax value. Contrary to the effect on stimulation by potassium, NFE inhibited non-competitively the stimulation of the ATPase by sodium ions with a significant (p < 0.001) depression of Vmax but without any considerable effect on the K0.5 and n values. These results indicated that NFE may interact with the molecule of (Na/K)-ATPase in a locus close to or identical with the potassium binding site of the enzyme, i.e., in a similar mode as it was well documented for ouabain. This possibility was strongly supported by the finding that NFE administered at the concentration of 0.1 mumol/l in the perfusion medium increased significantly (p < 0.01) the mechanical activity of isolated perfused guinea-pig heart (Langendorff preparation). Nevertheless, it also caused some adverse effects such as a slight increase in coronary flow resistance and in heart rate as well as in the left ventricular end-diastolic pressure.(ABSTRACT TRUNCATED AT 250 WORDS)     

Inhibiting effects of mixtures of alpha-tocopherol with beta-carotene or vitamin A during oxidation of polyunsaturated fatty acid esters]

Use of sodium sulfite to reduce nitrogenous contamination in fiber analysis was evaluated. The effects of sodium sulfite on analytical accuracy and precision were examined for amylase-treated neutral detergent fiber (aNDF), sequentially determined acid detergent fiber (sADF), and acid detergent lignin (sADL) in animal feeds. In one experiment, 0.5 g sodium sulfite was added per sample during neutral detergent (ND) extraction. The treatment consistently reduced aNDF, sADF, and sADL values of 180 alfalfa samples and improved precision (decreased within-sample variance of replicated analyses). The greatest effect was on precision of sADL analysis, with within-sample variance reduced by more than 50%. In a second experiment, 24 animal feeds were analyzed for a aNDF, sADF, and sADL with and without addition of 0.5 g sodium sulfite per sample during ND extraction. Nitrogen contents of the recovered fiber fractions were determined. Sodium sulfite reduced fiber and lignin values and decreased nitrogen concentration in residues. Within-sample variance was lower in all analyses. In a third experiment, 23 animal feeds were analyzed for aNDF with sodium sulfite at 0, 0.25, 0.5, and 1.0 g per sample. Average aNDF of feeds was reduced by each additional increment of sodium sulfite; however, 1.0 g sodium sulfite resulted in only a slight reduction in aNDF compared with 0.5 g. Therefore, 0.5 g sodium sulfite per sample should be added to samples prior to aNDF analysis.     

Effects of chronic ethanol consumption on extramitochondrial fatty acid oxidation and ethanol metabolism by rat kidney

1. We evaluated the effects of chronic ethanol consumption on microsomal and peroxisomal fatty acid oxidation and on ethanol oxidation by the kidney. 2. When mature rats were fed 20% ethanol for 10 weeks, an increase in alcohol dehydrogenase and catalase activities were observed in the kidney. 3. Renal microsomal and peroxisomal oxidation of fatty acids also increased by the treatment, but total cytochrome P450 content did not. 4. We concluded that chronic ethanol consumption results in an increased extramitochondrial disposition of fatty acids and ethanol oxidation by the kidney.     

Effects of chronic angiotensin-converting enzyme inhibition on left ventricular and myocyte structure and function during recovery from chronic rapid pacing

LV and myocyte function and angiotensin converting enzyme (ACE) activity with ACE inhibitor (ACEI) treatment were examined in four groups of dogs (n = 6 each): (1) control; (2) with 4 weeks of recovery from chronic rapid pacing (REC: 216 beats/min), (3) ACEI for the first 14 days of REC (ACEI--14), and (4) ACEI for 28 days of REC (ACEI--28). Three additional control dogs were administered ACEI for 28 days. LV mass increased with REC compared to control (146 +/- 6 v 92 +/- 3 g, P < 0.05), was unaffected with ACEI--14, and was decreased with ACEI--28 compared to REC (111 +/- 8 g, P < 0.05). Myocyte function was decreased in REC compared to controls (43 +/- 3 v 63 +/- 3 microns/s, P < 0.05) and was similarly reduced with ACEI--14. However, with ACEI--28, myocyte shortening velocity was increased compared to REC (56 +/- 1 microns/s, P < 0.05). Myocyte beta-adrenergic response was decreased with REC and ACEI--14 compared to controls (53 +/- 9 and 57 +/- 14, respectively v 127 +/- 14 microns/s, P < 0.05). ACEI--28 resulted in a normalization of myocyte beta-adrenergic responsiveness (108 +/- 3 microns/s). LV myocardial ACE activity increased in REC compared to control (5.82 +/- 0.21 v 3.51 +/- 0.15 nmol/mg/min, P < 0.05). With ACEI--14 or ACEI--28, myocardial ACE activity was decreased compared to REC (4.16 +/- 0.06 and 4.08 +/- 0.23 nmol/mg/min; P < 0.05). In control dogs administered ACEI, there were no differences in any of these parameters compared to controls. The unique findings in this study were: (1) effects of ACEI treatment in this model of LV hypertrophy were time dependent with respect to LV mass and LV and myocyte function; and (2) the effect of ACEI treatment on the degree of LV hypertrophy appears to not be solely due modulation of myocardial ACE activity.     

Induction of lipid peroxidation during heavy metal stress in Saccharomyces cerevisiae and influence of plasma membrane fatty acid unsaturation

The degree of plasma membrane fatty acid unsaturation and the copper sensitivity of Saccharomyces cerevisiae are closely correlated. Our objective was to determine whether these effects could be accounted for by differential metal induction of lipid peroxidation. S. cerevisiae S150-2B was enriched with the polyunsaturated fatty acids (PUFAs) linoleate (18:2) and linolenate (18:3) by growth in 18:2- or 18:3-supplemented medium. Potassium efflux and colony count data indicated that sensitivity to both copper (redox active) and cadmium (redox inactive) was increased in 18:2-supplemented cells and particularly in 18:3-supplemented cells. Copper- and cadmium-induced lipid peroxidation was rapid and associated with a decline in plasma membrane lipid order, detected by fluorescence depolarization measurements with the membrane probe trimethylammonium diphenylhexatriene. Levels of thiobarbituric acid-reactive substances (lipid peroxidation products) were up to twofold higher in 18:2-supplemented cells than in unsupplemented cells following metal addition, although this difference was reduced with prolonged incubation up to 3 h. Conjugated-diene levels in metal-exposed cells also increased with both the concentration of copper or cadmium and the degree of cellular fatty acid unsaturation; maximal levels were evident in 18:3-supplemented cells. The results demonstrate heavy metal-induced lipid peroxidation in a microorganism for the first time and indicate that the metal sensitivity of PUFA-enriched S. cerevisiae may be attributable to elevated levels of lipid peroxidation in these cells.     

Modulation of peroxisomal and microsomal fatty acid oxidation by acetone. A comparative study between liver and kidney

Using an immunoelectron microscopic technique, we demonstrated the distinctive localization of L-selectin, alphaL and beta2 integrins (LFA-1) on lymphocytes adhering to high endothelial venules (HEVs) of peripheral lymph nodes. Immunogold staining clearly demonstrated the preferential localization of L-selectin on the faintly adherent microvilli to endothelial surfaces. Often, the particles of L-selectin were found around those microvilli with a dispersed distribution. Examination by antibody-coated latex beads showed that the localization of L-selectin was not restricted to the lymphocyte surface but also found on endothelial cells. These data suggest the molecular shedding from lymphocytes and its transfer to the HEV surface as the 'molecular footprints' of rolling cells. Concomitant with the dispersion of L-selectin, the gold particles of alphaL, and beta2 integrins showed significant capping and clustering images on the adherent border of lymphocytes. This redistribution of LFA-1 may be important for inducing the transition of the molecule into the active state to facilitate effective binding to its endothelial ligands. These morphological findings revealed the characteristic behavior of L-selectin and LFA-1 on lymphocytes, and they confirm their respective molecular roles in the current adhesion cascade model between lymphocytes and HEVs.     

Supplementation of coconut oil from different sources to the diet induces cellular damage and rapid changes in fatty acid composition of chick liver and hepatic mitochondria

PURPOSE OF THE STUDY: Impaction in pertrochanteric fracture sites is a well known phenomenon; the screw-plate system is designed to stabilise the fracture. Although easier to use, the risk with the nail-plate system is postoperative penetration of the nail into the joint. The present study was conducted to determine the exact conditions of the impaction, and to identify possible ways to improve the nail-plate system. MATERIAL-METHOD: The study included 129 cases of pertrochanteric fracture, excluding sub-trochanteric fractures. All fractures were fixed with a 130 degrees angulated nail-plate. In all cases, consolidation was uneventful after 8 to a 12 weeks. The anatomical type of fracture, i.e. stable or unstable, was determined according to the size of the intermediary fragment, including the trochanter minor. The displacement was measured as the difference between the length of the nail and the length of the femoral head and neck measured along the axis of the femoral neck. The parameters examined were: fracture stability degree, bony mineralisation (Singh Index), nail length, femoral neck, length nail position in the femoral head, and above all, fracture reduction. All these parameters were computerised and compared using Stat View statistics software. RESULTS: Impaction was observed in 43 per cent of cases. Among these, 25 per cent were rated as slight (1 to 5 mm), 18 per cent as moderate (over 5 mm) and 9 per cent as marked (10 to 25 mm). Impaction was associated with demineralisation of the bone tissue (p = 0.001). The anatomical classification of the fracture was not a determining factor (p = 0.19), as marked displacements were also recorded in stable fractures. A posterior and inferior position of the intramedullary nail in the femoral head is one of displacement determining factors (p = 0.004, two-sided 1 test). Valgus over-correction is the most important factor, especially when it is associated with bony demineralisation (p = 0.02) and an inadequately centred intramedullary pin (p = 0.02). Shorter the femoral neck, and shorter the nail, greater was the frequency of nail articular penetration. DISCUSSION: The risk of articular penetration therefore reaches 15 per cent in petrochanteric fractures repaired with a nail plate, set at an angle of 130 degrees. A short neck, a cervicodiaphyseal angle superior to 140 degrees, and demineralisation are the three determining parameters. Stable or unstable fracture has in fact little effect on displacement incidence, and therefore does not, on its own, warrant the use of a prosthesis in comminuted fractures. The authors compared their results to literature on progressive sliding system: the incidence of complications associated with this type of fracture treatment is identical, but the determining parameters are different. CONCLUSION: The study shows that the nail-plate is efficient and provides simple and solid fracture fixation. However, this osteosynthesis material needs to be modified in order to improve its fixation in the femoral head.     

Comparison of myocardial contrast echocardiography and low-dose dobutamine stress echocardiography in predicting recovery of left ventricular function after coronary revascularization in chronic ischemic heart disease

BACKGROUND: Dobutamine stress echocardiography (DSE) and myocardial contrast echocardiography (MCE) can predict recovery of left ventricular function after myocardial infarction. DSE also has been shown to predict left ventricular functional recovery after revascularization in chronic ischemic heart disease, whereas MCE has not been evaluated in such patients. This study was performed to compare DSE and MCE in the prediction of left ventricular functional recovery after revascularization in patients with chronic ischemic heart disease. METHODS AND RESULTS: MCE and DSE were performed in 35 patients with chronic coronary artery disease and significant wall motion abnormalities (mean ejection fraction, 0.36 +/- 0.09). Regional wall motion was scored by use of a 16-segment model wherein 1 = normal or hyperkinetic, 2 = hypokinetic, 3 = akinetic, and 4 = dyskinetic. Each segment was evaluated for contractile reserve by DSE and perfusion by MCE. Revascularization (coronary artery bypass graft [n = 13] and percutaneous transluminal coronary angioplasty [n = 10]) was successful in 23 patients. Follow-up echocardiograms were done to assess wall motion 30 to 60 days later. In 238 segments with resting wall motion abnormalities, perfusion was more likely to present than contractile reserve (97% versus 91%, P < .02). Revascularization resulted in functional recovery in 77 of 95 hypokinetic segments (81%) but only 18 of 57 akinetic segments (32%, P < .0001). DSE and MCE were not significantly different in predicting functional recovery of hypokinetic segments. In akinetic segments, DSE and MCE had similar sensitivities (89% versus 94%, respectively) and negative predictive values (93% and 97%, respectively) in predicting functional recovery. However, DSE had a higher specificity (92% versus 67%, P < .02) and positive predictive value (85% versus 55%, P < .02) than MCE in predicting functional recovery. CONCLUSIONS: Both contractile reserve by DSE and perfusion by MCE are predictive of functional recovery in hypokinetic segments after coronary revascularization in patients with chronic coronary revascularization in patients with chronic coronary artery disease. In akinetic segments, myocardial perfusion by MCE may exist in segments that do not recover contractile function after revascularization. Thus, contractile reserve during low-dose dobutamine infusion is a better predictor of functional recovery after revascularization in akinetic segments than perfusion.     

Carnitine acetyltransferase is not a cytosolic enzyme in rat heart and therefore cannot function in the energy-linked regulation of cardiac fatty acid oxidation

The subcellular location of cardiac carnitine acetyltransferase (CAT) was investigated by measuring the release of carnitine acetyltransferase and of marker enzymes from isolated rat myocytes permeabilized with digitonin. Additionally, the carnitine acetyltransferase activity exposed to the cytosolic compartment was quantified. The results indicate that soluble acetyl transferase is not present in the cytosol, and that only 5% of the cellular carnitine acetyltransferase activity is positioned to catalyse the formation of cytosolic acetyl coenzyme A. This situation makes it unlikely that the energy-linked regulation of cardiac fatty acid oxidation proceeds by mechanisms which require the conversion of acetylcarnitine to acetyl coenzyme A in the cytosol.     

Inactivation and conformational changes of fatty acid synthase from chicken liver during unfolding by sodium dodecyl sulfate

Fatty acid synthase is an important enzyme participating in energy metabolism in vivo. The inactivation and conformational changes of the multifunctional fatty acid synthase from chicken liver in SDS solutions have been studied. The results show that the denaturation of this multifunctional enzyme by SDS occurred in three stages. At low concentrations of SDS (less than 0.15 mM) the enzyme was completely inactivated with regard to the overall reaction. For each component of the enzyme, the loss of activity occurred at higher concentrations of SDS. Significant conformational changes (as indicated by the changes of the intrinsic fluorescence emission and the ultraviolet difference spectra) occurred at higher concentrations of SDS. Increasing the SDS concentration caused only slight changes of the CD spectra, indicating that SDS had no significant effect on the secondary structure of the enzyme. The results suggest that the active sites of the multifunctional fatty acid synthase display more conformational flexibility than the enzyme molecule as a whole.     

Sugar composition of dietary fibre and short-chain fatty acid production during in vitro fermentation by human bacteria

The aim of the present study was to assess the relationship between the disappearance of dietary fibre sugars and the production of individual short-chain fatty acids (SCFA). The bacterial degradation of five dietary fibres whose sugars were quantified was investigated in vitro using a human faecal inoculum. Involvement of the main fibre sugars in SCFA production was evaluated by a stepwise multiple linear regression. The results show first that the nature and chiefly the associations between the fibre sugars were key variables in the fermentability. Second, the nature and the amounts of SCFA produced were closely related to the in vitro fermentation of the main sugars available: uronic acids seemed to be principally involved in the production of acetic acid whereas the production of propionic acid could be promoted by the fermentation of glucose and, to a lesser extent, by that of xylose and arabinose. Xylose tended to have a greater impact than uronic acids and glucose on the production of butyric acid. Thus, it would be possible to predict which SCFA could be specifically produced during the fermentation of a fibre, as far as the chemical composition and structure of this fibre are known.