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Biomedical subjects

C Guarnieri

Publications and source records attributed to C Guarnieri.

At least 55 records · Page 3Linked to original sources
PubMed1993

Incorporation of [14C]hypoxanthine into cardiac adenine nucleotides: effect of aging and post-ischemic reperfusion.

In order to investigate whether the 'hypoxanthine salvage' pathway of the cardiac muscle is modified with age, we aerobically perfused isolated hearts of 4-month- and 22-month-old male Wistar rats for 20 min with 0.18 microM [14C]hypoxanthine. A second group of hearts was subjected to a 30-min ischemic perfusion (95% reduction of the coronary flow), followed by 20 min of reperfusion. In this last 20 min, the perfusate contained the same concentration of [14C]hypoxanthine used under the aerobic condition. After 20 min of aerobic perfusion the myocardial levels of ATP were significantly lower (15%) in aged than young rat hearts, whilst no age-related differences were observed at the end of the reperfusion. In the young rats the incorporation of the isotope into ATP, ADP, and AMP was significantly higher (192%, 226%, and 300%, respectively), after 20 min of reperfusion with respect to the aerobic values. On the contrary, in the aged hearts, no significant change in the rate of [14C]-incorporation into ATP was observed during reperfusion, despite an increase of the [14C]-incorporation into ADP and AMP. Moreover, the content of each labeled adenine nucleotide was significantly higher in aged than young hearts at the end of the aerobic period, whereas the incorporation of the labeled hypoxanthine was not affected by age after 20 min of reperfusion. The release of uric acid into coronary effluents was greater (50%) in aged than young rats during the reperfusion period, but no age-dependent differences in the isotope incorporation into uric acid were observed. These data indicate that in the aged rat heart, perfused under aerobic conditions, there is an increased incorporation of hypoxanthine into ATP, although it does not further increase during postischemic reperfusion.

Adenine Nucleotides↗
PubMed1993

Age-dependent differences of ATP breakdown and ATP-catabolite release in ischemic and reperfused hearts.

The hearts of young (6 months) and aged (24 months) rats, paced at a frequency of 300 bpm, were perfused by the Langendorff technique and subjected to: 20 min of equilibration perfusion, 30 min of global ischemia (95% reduction of the coronary flow) and 20 min of reperfusion. The control group was equilibrated for 20 min and then aerobically perfused for 50 min. After 20 min of stabilization, ATP and ADP levels and the adenine nucleotide pool were significantly higher in young than aged hearts (15% increase), but no modifications were found between the two age groups after 50 min of aerobic perfusion. Even the energy charge did not change under aerobic conditions. At the end of the ischemic period the levels of ATP and ADP decreased to a similar extent in young and aged hearts. After 20 min of reperfusion the myocardial level of ATP remained lower in comparison to the preischemic and control values in both age groups. At the end of the reperfusion there was a decrease in energy charge and creatine phosphate levels in the aged group in respect to the young group. The concentrations of adenosine, hypoxanthine and xanthine in coronary effluents did not change during ischemia and reperfusion irrespective of the age of the animals. On the contrary, the release of uric acid during ischemia and reperfusion was greater in aged than young hearts (90% increase). Moreover, the level of inosine in perfusates during the ischemic period was significantly lower in the 24-month-old group (30% decrease). These results are in accordance with the increased purine nucleoside phosphorylase activity and the decreased hypoxanthine phosphorybosyl-transferase activity found in the myocardium of the aged vs. young rats at the end of the reperfusion period. These data indicate that in the aged rat hearts, when exposed to ischemic and reperfusion conditions, there is a modification of purine breakdown which leads to a greater production of uric acid in respect to that found in young hearts.

Adenosine Diphosphate↗
PubMed1993

Effect of age on phosphorylated compounds and mechanical activity of isolated rat heart: a 31P-NMR study.

OBJECTIVE: The aim was to test the hypothesis that aging may change the function and energetics of isolated hearts subjected to an increased work load induced by varying the calcium concentration ([Ca2+]) in the perfusion fluid from 0.5 to 1.0, 1.5, or 2.0 mM. METHODS: Female Wistar rats aged 4, 12-14, and 22-24 months were used. Their hearts were perfused through the aorta and changes in myocardial phosphorylated compound concentration were measured by means of 31P-nuclear magnetic resonance spectroscopy and biochemical analysis. Myocardial contractility was measured in situ in closed heart anaesthetised animals and was followed in vitro during perfusion. RESULTS: The contractile indices measured in situ revealed a decrease with aging of the left ventricular developed pressure and dP/dtmax, while heart rate did not show any significant difference. In all age groups the stepwise increase in [Ca2+] caused a graded increase in left ventricular pressure in the perfused hearts. In aged rats, the left ventricular pressure associated with the different concentrations of Ca2+ was significantly lower than in young rats. In all three groups the myocardial content of inorganic phosphorus (Pi) increased in response to a rise in [Ca2+] and left ventricular pressure. The ATP content of the hearts remained constant in all three groups at each value of [Ca2+] induced left ventricular pressure. However, both ATP and total adenine nucleotide contents of the hearts were lower in aged rats. When the alteration in Pi due to each increase in [Ca2+] was expressed in relation to the rise in left ventricular developed pressure, this relationship was not significantly different in the three groups of hearts. CONCLUSIONS: The reduced mechanical activity of aged rat hearts is not due to a diminished efficiency of the mechanisms transferring high energy phosphates.

Adenosine Triphosphate↗
PubMed1993

Effect of trimetazidine on mitochondrial function and oxidative damage during reperfusion of ischemic hypertrophied rat myocardium.

The mitochondria harvested at the end of perfusion of control hearts and assayed for respiratory activity had a better function after ischemia and reperfusion following trimetazidine injection when glutamate was used as substrate. The protective effect of trimetazidine was enhanced when the mitochondria were isolated from hypertrophied perfused rat hearts. In fact the drug improved both the RCI and QO2 parameters with glutamate or succinate as substrates and raised the glutamate-induced QO2 value of mitochondria extracted from the hypertrophied heart perfused in aerobic conditions. In the aerobically perfused heart trimetazidine did not change either the levels of tissue malondialdehyde and lipofuscin, or the rate of mitochondrial O.2 generation while it reduced the O.2 formation and malondialdehyde content in the hypertrophied heart. After ischemia and reperfusion, the drug reproduced these protective effects in the hypertrophied hearts and reduced the level of tissue malondialdehyde in control hearts. The protective effect of trimetazidine against MDA formation was dose-dependent, being more evident at a higher dose (10 mumol/l). Preincubation of rat heart mitochondria with 0.1-10 mumol/l trimetazidine did not affect NADH oxidase, NADH dehydrogenase and NADH-cytochrome c reductase, succinate oxidase and cytochrome c oxidase activities. These results indicate that trimetazidine injected into isolated rat hearts protects against the damage induced on cardiac energetics and oxidative injuries by moderate ischemia and reperfusion stress, particularly in monocrotaline-induced hypertrophy in the rat heart. We suggest that trimetazidine reduces the formation of oxidative damage by preserving cardiac mitochondrial function.

Animals↗
PubMed1993

Prevention of reperfusion syndrome in acute muscular ischaemia with free radical scavengers and membrane-protecting compounds: an experimental study.

The prevention of oxidant-induced damage following reperfusion was experimentally evaluated. Two pharmacological regimens containing different combinations of antioxidant factors and membrane-stabilizing compounds, such as alpha-tocopherol (vitamin E), methionine, dexamethasone, mannitol and cysteine, were administered. The reduced/oxidized glutathione (GSH/GSSG) ratio in muscle was used to evaluate oxidative stress. Ischaemia was induced by occluding the aorta and the inferior vena cava with an irrigation-occlusion catheter. After 4 h of ischaemia, five sheep were reperfused without any treatment (control group) and five treated with an endoaortic bolus administered at declamping (treatment 1). In five other sheep, treatment started during ischaemia (treatment 2). Ischaemia and, in particular, reperfusion significantly reduced the muscle GSH content, compared with the basal value in the control group; thus the GSH/GSSG ratio decreased significantly in the control group from 10.5(2.2) (mean(s.e.) basal value) to 0.687(0.3) at reperfusion (P < 0.009). Both treatments 1 and 2 significantly prevented a reduction in GSH content induced by reperfusion following ischaemia; the GSH/GSSG ratio (10.5(2.2) basal value) increased to 19.67(4.6) with reperfusion in the treatment group 1, mainly because of a lower decrease of GSH and a lower level of GSSG while it did not change in treatment group 2 (10.7(5.0)). Levels of creatine phosphokinase did not change in the treated groups, although they increased significantly in the control group (P < 0.006). Although oxidative stress is not the only cause of damage in revascularization, this study confirms the protective ability of treatment with free radical scavengers and membrane-stabilizing compounds.

Animals↗
PubMed1993

Effect of glutathione monoethyl ester on glutathione level and cardiac energetics in reperfused pig heart.

The GSH level in myocardial tissue represents an important defense mechanism against oxygen toxicity. Since the ischemia-induced depletion of GSH might favour the cytotoxicity of oxygen-derived free radicals produced during reperfusion, we assessed the effects of the GSH donor, glutathione monoethylester, in anaesthetized pigs subjected to 90 minutes of coronary occlusion followed by 30 minutes reperfusion. The drug was infused intracoronarily at a dose of 1 mg/ml (0.5 ml/min) throughout the experimental period. After coronary occlusion and reperfusion, we found a decrease in GSH, ADP, ATP and phosphocreatine levels in reperfused compared with non-ischemic tissue. Less evident were the differences in mitochondrial function, there being only a reduction in the reperfused tissue of the respiratory control index and state 3 respiration values when pyruvate was used as substrate. The infusion with glutathione monoethylester decreased the depletion of tissue GSH and improved the GSH/GSSG ratio, particularly in the non-ischemic tissue. Moreover, the drug decreased the mitochondrial dysfunction at the level of pyruvate utilization and partially prevented the fall in ATP in the reperfused tissue. This study confirms a possible protective effect of glutathione monoethylester in the prevention of reperfusion-induced myocardial damage.

Adenosine Diphosphate↗
PubMed1993

Age-related changes in cardiac mitochondrial energetics under the influence of calcium in rat.

Mitochondria extracted from the hearts of Wistar rats aged 6 and 24 months showed similar values for the respiratory control index (RCI), state 3 oxygen consumption (QO2) and ADP/O measured using glutamate or succinate as substrates; with the exception that the QO2 of the aged rats was lower than that of the young rats in the presence of glutamate. The consumption of O2 induced by 2-oxoglutarate and ADP was similar in both age groups. Concentrations of external free Ca2+ ranging from 0.2 to 0.8 microM produced an increase in O2 consumption and ATP formation in the young mitochondria, with a maximum effect at 0.2 microM external free Ca2+. Little or no change in O2 consumption and ATP formation was evident in aged mitochondria following incubations in concentrations of external free Ca2+ ranging from 0.2 to 0.8 microM. The continuous rate of formation of ATP, measured in the presence of 0.2 microM external free Ca2+ using a luminescence method, confirmed the previous results. This study indicates that the cardiac mitochondrial phosphorylating system of aged rats is poorly sensitive to variations in external free calcium.

Adenosine Triphosphate↗
PubMed1993

Prodynorphin mRNA is synthesized in adult cultured rat ventricular cardiomyocytes.

In the myocardial cell, stimulation of the K opioid receptor is involved in the modulation of cytosolic calcium and pH homeostasis, as well as in the regulation of myofilament responsiveness to calcium. In the present study, we found that prodynorphin mRNA, which encodes for the synthesis of a common precursor of opioid peptides interacting with K sites, is synthesized both in atrial and ventricular tissue of the rat heart. In adult cultured rat ventricular cardiomyocytes, the level of prodynorphin mRNA did not differ from that detected in the original ventricular tissue. This finding indicates that the myocardial cell is a source for prodynorphin gene expression and has the potential for an intrinsic synthesis of dynorphin-related peptides.

Animals↗
PubMed1992

Mitochondrial production of oxygen free radicals in the heart muscle during the life span of the rat: peak at middle age.

Mitochondria extracted from Wistar rat hearts at 3, 14-18 and 24 months of age showed no change in state 3-mitochondrial respiration measured in the presence of glutamate or succinate. Again no changes were found in the SMP-O2- production at the level of the rotenone-inhibited region, whilst at the level of the antimycin-inhibited region there was a marked increase in O2- production in the group of 14-18-month-old rats. In the same age period, the production of mitochondrial H2O2 supported by glutamate or succinate and the level of GSSG increased in comparison to the young group, accompanied by a decrease in the GSH level. Mitochondrial TBARS levels did not change during a life span, while a progressive accumulation in the mitochondrial lipofuscin content with age was measured.

Aging↗
PubMed1992

Superinduction of ornithine decarboxylase by halogenated ribofuranosylbenzimidazoles.

1. The effect of dichlororibofuranosylbenzimidazole (DiCl-RB), an inhibitor of hnRNA synthesis and casein kinase-2 activity, on ornithine decarboxylase (ODC) was investigated in a difluoromethylornithine (DFMO) resistant, ODC overproducing cell line. 2. In cells growing in the absence of DFMO, DiCl-RB provoked a marked, but transient increase in ODC activity and immunoreactive ODC content. 3. The ODC response to DiCl-RB was prevented by cycloheximide and was not due to stabilization of the enzyme. 4. The dibromo derivative analogue (DiBr-RB) exerted similar effects on ODC, but was effective at lower concentrations. 5. The halogenated ribofuranosylbenzimidazoles were ineffective in cells growing in the presence of DFMO and containing higher levels of ODC protein.

Animals↗
PubMed1992

Spontaneous superoxide generation by polymorphonuclear leukocytes isolated from patients with stable angina after physical exercise.

The activation of circulating polymorphonuclear leukocytes was determined in terms of O2.- generation and elastase release in patients with stable angina (n = 12) and in control subjects (n = 8) after maximal physical exercise and after a 15-min recovery. There was no spontaneous O2.- formation under basal conditions in both groups of patients. On the contrary, there was significant formation of O2.- (p < 0.001) from patients with stable angina measured directly after exercise, along with a slight spontaneous O2.- formation in control subjects (p < 0.05). After recovery, the spontaneous polymorphonuclear leukocyte-O2.- formation decreased but was still present in the patients with stable angina, while in the healthy subjects these values returned to resting levels. The activation of polymorphonuclear leukocytes with phorbol 12-myristate 13-acetate enhanced O2.- formation both in healthy subjects and in patients with stable angina, with a lesser effect in the latter. Moreover, no differences were observed in polymorphonuclear leukocyte-stimulated O2.- formation during the protocol, both in the angina stable patients and healthy subjects. No changes were found in plasma elastase levels among stable angina patients nor in control subjects as a consequence of exercise or recovery. This study indicates there is an early activation of circulating polymorphonuclear leukocytes in terms of O2.- production in stable angina patients during maximal exercise, which is still present after a 15-min recovery. Such activation occurs without elastase release. However, in healthy subjects maximal exercise resulted in very little increase in neutrophil activation.

Angina Pectoris↗
PubMed1992

Local haemofiltration with free radical scavenger treatment during revascularisation of severe muscular ischaemia induced in sheep limbs.

Many treatments have been proposed for the prevention of the revascularisation syndrome following embolectomy or thrombectomy in patients with severe ischaemia. These include the administration of diuretics, bicarbonate, buffer solutions, free radical scavengers, washing out the venous blood from the ischaemic leg, or systemic dialysis. The aim of our study was to investigate the effect of combining haemofiltration with a treatment using compound oxy-radical scavengers in order to prevent or to reduce the appearance of the revascularisation syndrome. The study was performed on 13 sheep. Eight animals underwent 4 h of aortic and vena cava occlusion using irrigation-occlusion catheters, followed by normal reperfusion (control group). Five sheep underwent the same period of ischaemia, followed by 1 h of local haemofiltration and re-oxygenation and 2 h of normal revascularisation. The priming solution for the ECC circuit consisted of 500 ml of 20% mannitol and 500 ml of 18/1000 HCO3- contained: superoxide dismutase (150,000 I.U.), methylprednisolone, 1 g, and heparin, 10,000 I.U. After the 3rd h of ischaemia, 2.1 g of acetate alpha-tocopherol (30 mg kg-1) were injected i.m. The treatment produced good protection against oxidative stress, shown by an increase in the glutathione ratio (GSH/GSSG), and reduced muscular damage, confirmed by a moderate increase in creatine phosphokinase (CPK) levels (significantly higher in the control group). Diuresis was significantly higher in the treated group, and the acid-basic and potassium balance returned to normal more rapidly. Our data suggest that this combined treatment could be effective in the prevention of the ischaemia-reperfusion syndrome.

Animals↗
PubMed1992

Kappa and delta opioid receptor stimulation affects cardiac myocyte function and Ca2+ release from an intracellular pool in myocytes and neurons.

We investigated the effects of mu, delta, and kappa opioid receptor stimulation on the contractile properties and cytosolic Ca2+ (Cai) of adult rat left ventricular myocytes. Cells were field-stimulated at 1 Hz in 1.5 mM bathing Ca2+ at 23 degrees C. The mu-agonist [D-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin (10(-5) M) had no effect on the twitch. The delta-agonists methionine enkephalin and leucine enkephalin (10(-10) to 10(-6) M) and the kappa-agonist (trans-(dl)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclo-hexyl]- benzeneacetamide)methanesulfonate hydrate (U-50,488H; 10(-7) to 2 x 10(-5) M) had a concentration-dependent negative inotropic action. The sustained decrease in twitch amplitude due to U-50,488H was preceded by a transient increase in contraction. The effects of delta- and kappa-receptor stimulation were antagonized by naloxone and (-)-N-(3-furyl-methyl)-alpha-normetazocine methanesulfonate, respectively. In myocytes loaded with the Ca2+ probe indo-1, the effects of leucine enkephalin (10(-8) M) and U-50,488H (10(-5) M) on the twitch were associated with similar directional changes in the Cai transient. Myofilament responsiveness to Ca2+ was assessed by the relation between twitch amplitude and systolic indo-1 transient. Leucine enkephalin (10(-8) M) had no effect, whereas U-50,488H (10(-5) M) increased myofilament responsiveness to Ca2+. We subsequently tested the hypothesis that delta and kappa opioid receptor stimulation may cause sarcoplasmic reticulum Ca2+ depletion. The sarcoplasmic reticulum Ca2+ content in myocytes and in a caffeine-sensitive intracellular Ca2+ store in neurons was probed in the absence of electrical stimulation via the rapid addition of a high concentration of caffeine from a patch pipette above the cell. U-50,488H and leucine enkephalin slowly increased Cai or caused Cai oscillations and eventually abolished the caffeine-triggered Cai transient. These effects occurred in both myocytes and neuroblastoma-2a cells. In cardiac myocyte suspensions U-50,488H and leucine enkephalin both caused a rapid and sustained increase in inositol 1,4,5-trisphosphate. Thus, delta and kappa but not mu opioids have a negative inotropic action due to a decreased Cai transient. The decreased twitch amplitude due to kappa-receptor stimulation is preceded by a transient increase in contractility, and it occurs despite an enhanced myofilament responsiveness to Ca2+. The effects of delta and kappa opioids appear coupled to phosphatidylinositol turnover and, at least in part, may be due to sarcoplasmic reticulum Ca2+ depletion.(ABSTRACT TRUNCATED AT 400 WORDS)

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1992

[A 31P-NMR spectroscopic study of the changes in energy metabolism induced by cardiac ischemia and reperfusion in rats of different ages].

In order to investigate the energetic status of the aged heart during ischemia and reperfusion we perfused female Wistar rats 6, 12 and 24 month old. The hearts were subjected to 15 min of global total ischemia plus 30 min of reperfusion. NMR spectra were collected during the entire experimental period to have the in vivo monitoring of the changes in intracellular pH and intracellular ATP, PCr and Pi contents. In the first 8 min of ischemia the fall of pH was similar in the 3 groups of rats, while at the end of the ischemic period the young rat hearts showed an intracellular pH significantly lower than aged rat hearts. At the end of reperfusion, ATP and PCr contents appeared significantly higher in the adult and aged hearts as compared to the young. The Pi content, on the contrary, was significantly lower in aged than young rat hearts. We suggest that the hearts of adult and aged animals, at the end of reperfusion, showed larger energetic recovery, in our experimental conditions of brief ischemia, than young hearts.

Aging↗
PubMed1991

Comparison between alpha-adrenergic- and K-opioidergic-mediated inositol (1,4,5)P3/inositol (1,3,4,5) P4 formation in adult cultured rat ventricular cardiomyocytes.

In adult cultured rat ventricular cardiac myocytes, both the alpha-adrenergic agonist phenylephrine and the selective kappa opioid receptor ligand U-50, 488H affected phosphoinositide turnover. Phenylephrine, over a time course of 10 min, caused a transient increase in Ins(1,4,5)P3 which peaked at 1 min and had returned to control at 2 min. In addition, phenylephrine produced a progressive and sustained increase in the formation of Ins (1,3,4,5)P4 which achieved a plateau after 5 min of exposure to the agonist. U-50,488H induced an increase in Ins(1,4,5)P3 which peaked at 1 min at a level significantly higher than that due to phenylephrine and was still elevated after 10 min exposure to the kappa opioid receptor agonist. In addition, U-50,488H caused a sustained increase in Ins(1,3,4,5)P4 which was comparable to that due to phenylephrine. The stimulatory effects produced by phenylephrine and U-50,488H were receptor-mediated events, since they were fully antagonized by their respective antagonists, phentolamine or Mr-1452.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1991

Reduced neutrophil superoxide generation and plasma lipoperoxide levels in pigs fed with cod liver oil.

Circulating neutrophils, isolated from pigs fed for 8 weeks with a diet supplemented with CLO, had an accentuated n-3 fatty acid incorporation into the plasma membrane, as evidenced by an approximately four-fold greater n-3/n-6 ratio as compared with the control diet group. Moreover, the neutrophils of the CLO fed pigs produced less superoxide when stimulated with PMA or f-MLP, as well as showing a more prolonged latency period before O2(-)-generation. In the plasma of pigs fed with CLO there were higher levels of thiobarbituric reactive material and lipofuscin, while the content of GSSG was similar in both dietary groups. The results of this study indicate that dietary supplementation with CLO reduces the activation of circulating neutrophils and favours the presence in the plasma of lipoperoxides.

Animals↗
PubMed1991

Scavenger effect of sulfasalazine, 5-aminosalicylic acid, and olsalazine on superoxide radical generation.

The in vitro antioxidant capacity of sulfasalazine (SASP), its metabolites (SP, 5-ASA), and olsalazine (OAZ), was studied by evaluating their effects on superoxide (O2-.) production. Assay systems were the xanthine-xanthine oxidase (X/XOD) reaction and phorbol myristate acetate (PMA)-activated polymorphonuclear leukocytes (PMNs), using the cytochrome c (cyt-c) reduction assay and a luminol-dependent chemiluminescence method. 5-ASA, SASP, and OAZ showed a dose-dependent scavenger effect in both O2-. generating systems, 5-ASA being the most powerful (greater than 50% of inhibition in the PMNs system and greater than 70% in the X/XOD system at 10 microM concentration). SP had an inhibitory effect only in the PMNs system but did not modify the activity of xanthine oxidase, thus excluding a scavenger action. These data suggest that the scavenger effect of 5-ASA, SASP, and OAZ may be an important mechanism of action.

Aminosalicylic Acids↗