Biomedical subjects

C M Caldarera

Publications and source records attributed to C M Caldarera.

At least 19 recordsLinked to original sources

PubMed1992

Ornithine decarboxylase and ornithine decarboxylase-inhibiting activity in rat thymocytes.

Isolation of thymocytes from rat thymus resulted in the disappearance of the high activity of ornithine decarboxylase (ODC) that characterizes the thymus of young rats, together with the appearance of an antizyme-like ODC inhibiting activity, which showed a chromatographic profile that resembled that of dexamethasone-treated rat thymus. Omission of serum or addition of dexamethasone or spermidine did not affect appreciably the extent of the antizyme-like activity. On the other hand, a variety of hormonal effectors, i.e. insulin, glucagon, adrenalin and T3, as well as the phorbol ester, PMA or the mitogen, concanavalin A (Con A) induced ODC activity in cultured thymocytes together with the disappearance of the antizyme-like activity. A paradoxical, transient induction of ODC was caused by the transcriptional inhibitor, actinomycin D. Complexed ODC was detected in rat thymus, but not in thymocytes, either quiescent or stimulated by mitogens. These results indicate that thymic lymphocytes can express either ODC activity or its inhibitor depending on the hormonal and proliferative status of the cells.

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

Polyamine plasma levels and liver regeneration following partial hepatic resection in man.

Polyamines (putrescine, spermidine, and spermine) are widely distributed in animal and vegetal tissues, where their intracellular concentration strictly correlates with normal and pathological cell growth and protein synthesis. By means of a sensitive HPLC technique, the fasting plasma concentrations of polyamines were measured serially in 11 patients who underwent partial hepatic resection because of focal liver lesions. Samples were obtained before surgery and over the next 6 months, during hepatic regeneration. Liver volume was also measured by ultrasound on the basis of the 3 maximum diameters of the liver. From 2 to 4 weeks after surgery, plasma putrescine increased by a maximum of 78%, and spermidine by approximately 50%. No changes were observed in spermine levels. The spermidine/spermine ratio nearly doubled during liver regeneration. The volume of the liver decrease from 1505 [SD 236] ml to 743 [151] ml after resection, and returned to nearly normal values after 6 months (1231 [100] ml, p < 0.05 vs. basal values). The liver regeneration rate was highest 2-4 weeks after resection, and declined thereafter, when prevailing polyamine concentrations returned to normal. These data show that liver regeneration is accompanied by a significant increase in fasting putrescine and spermidine concentrations, which might be biochemical signals of active liver cell regeneration.

Adult↗

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↗

PubMed1992

[Coenzyme Q9 biosynthesis in the aging myocardium after ischemia and reperfusion].

The purpose of the present study was to evaluate the biosynthesis of coenzyme Q9 (CoQ9) in isolated and perfused young (6 months) and aged (24 months) rat hearts, either under aerobic perfusion condition or during postischemic reperfusion. The young and aged hearts have been divided into 2 groups: Group A, aerobic perfusion for 60 min with recirculating Krebs-Henseleit solution, containing 0.8 microM p-OH-[U-14C]benzoate plus 2.5 mM mevalonlactone; Group B, severe ischemic perfusion for 30 min, followed by 60 min of reperfusion under the same experimental condition of Group A. At the end of the reperfusion the mitochondrial content of CoQ9 was lower in young than aged rat hearts (p < 0.01). In Group A the incorporation of the labeled precursor into mitochondrial CoQ9 was greater in the hearts of aged than young rats (p < 0.01); on the contrary, in Group B this incorporation was significantly reduced in aged than in young rats (p < 0.05). Thus, it is possible that, in the aged rat heart, the higher activity of CoQ9 biosynthesis is related to an elevated turnover of the coenzyme due to the aging process; moreover, this activity is partially reduced by an ischemic-reperfusion stress.

Aerobiosis↗

PubMed1992

[Variations in the functionality of cardiac adenyl cyclase as a function of age].

The metabolic and functional activity of the heart closely depends on cAMP and therefore on the integrity of adenylate cyclase (AC) system. Alterations of this signal transduction system might be co-responsible for the impairment of cardiac performance observed with aging. Evidence is here provided that basal activity of cardiac membrane-bound (48,000 x g) AC significantly declines with the age of the rat (1, 12, 24 month-old). This is accompanied with the decrease of cAMP content, which leads to the fall of cAMP/cGMP molar ratio a possible final determinant of cardiac performance. Kinetic analyses indicate that aging is associated with a net increase of the Km of a cardiac AC, while the Vmax is unaffected. Besides, the response in vitro of AC from 24-month-old heart to the inhibitor spermine or a different stimulants, such as Gpp (NH) p, isoproterenol, PGE1 or forskolin, is significantly lower than that of AC from 1 month-old one. The suggestion is made that aging causes an impairment in the capability of the catalytic moiety of cardiac AC to make functional complexes with activated guanine nucleotide binding proteins.

Adenylyl Cyclases↗

PubMed1992

Induction of ornithine decarboxylase by transcriptional inhibitors in quiescent thymocytes.

The transcriptional inhibitors actinomycin D and dichlororibofuranosylbenzimidazole induced ornithine decarboxylase activity in isolated, quiescent thymocytes, which otherwise did not show detectable levels of the enzyme. This paradoxical induction was transient and dependent on the presence of serum and continuous protein synthesis. However, alpha-amanitin, another inhibitor of transcription, did not affect ornithine decarboxylase activity. Dichlororibofuranosylbenzimidazole and actinomycin D were unable to enhance the activity of spermidine acetyltransferase or S-adenosyl-methionine decarboxylase, which are other inducible and short-lived enzymes involved in the metabolism of polyamines.

Animals↗

PubMed1992

Biochemical correlates with myocardial aging.

Both contraction and relaxation times are prolonged in cardiac muscle of senescent animals. This is in part explained by an alteration of excitation-contraction coupling due to an increased duration of the action potential, reduced biosynthesis of the Ca(2+)-stimulated ATPase pump of sarcoplasmic reticulum, and prevalence of the V3 isoform of myosin with slow ATPase activity. The response to catecholamine decreases with aging because of a defective transmission of alpha and beta adrenergic stimulation mediated respectively by phosphoinositide hydrolysis and adenylate cyclase. Cardiac energetics is also impaired in the aged myocardium, since ATP and creatine phosphate levels are reduced by about 20%. This reduction seems in part the consequence of defective mitochondrial function, especially in fatty acid oxidation and ATP translocation to the cytoplasm. In this paper we have discussed the possibility that oxygen free radicals may be a cause of myocardial senescence, by damaging the nuclear and mitochondrial genomes as well as membranes and other cellular components.

Aging↗

PubMed1991

[The inhibitory effect of magnesium on mitochondrial calcium uptake in ischemic and reperfused rat hearts].

Several studies suggest that the protection exerted by Mg2+ on the reperfused myocardium may be mostly due to its competitive effect with respect to Ca2+. The aim of this research was to evaluate the inhibitory action of Mg2+ on mitochondrial Ca2+ uptake in the reperfused myocardium. Hearts of male Wistar rats (250-300 g) were isolated and perfused by the Langendorff technique. Aerobic control hearts (n = 6) were perfused with a constant flow of 10 ml/min/g for 65 min. In a second group (n = 6) the hearts were aerobically equilibrated for 20 min, then subjected to 30 min of ischemia (98% reduction of coronary flow) and subsequently reperfused for 15 min at the same preischemic flow. The hearts of both groups were electrically stimulated at 300 b/min. Then, the hearts were pooled in groups of 2 each and homogenized for the isolation of mitochondria. One part of mitochondrial suspension was used to evaluate the respiratory function by a polarographic technique. The remaining part was incubated with fura-2/AM for 10 min at 30 degrees C in order to determine the kinetics of Ca2+ transport within mitochondria in the presence of succinate as substrate. Ca2+ uptake was reduced in the mitochondria of reperfused hearts with respect to control, particularly in the presence of elevated extramitochondrial Ca2+ concentrations (greater than 10 nM). On the contrary the initial rate of Ca2+ uptake was increased in the reperfused mitochondria.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

[The biochemical bases of cardiovascular aging].

The majority of reports concerning the performance of senescent heart in both human and animal models states that, at rest, most hemodynamic parameters are substantially unchanged during aging, with the exception of a prolongation of left ventricular ejection time and a decrease in the early diastolic filling rate. A biochemical rationale for the increased early diastolic filling time with age seems to be the enhanced stiffness of left ventricular wall due to either myocardial hypertrophy or collagen tissue accumulation. The prolonged time of contraction and the inadequate response to stress of cardiac muscle in elderly subjects may be the consequence of changes in different steps of the excitation-contraction coupling, namely altered intracellular calcium homeostasis, reduced availability of highly energetic compounds, and impaired response to adrenergic stimulation. These defects can cause major hemodynamic changes when the heart is subjected to volume or pressure overload. In fact, during exercise, elderly subjects can reach a maximal heart rate slower than that of younger people. The possibility that the toxicity of oxygen reactive forms may provoke some age-related myocardial lesions such as structural alteration of membranes and enzyme inactivation is very attractive but the linkage between the most functional perturbations of aged hearts and peroxidative stress remains to be clarified.

Aging↗

PubMed1990

Effect of ATP depletion and phenanthroline on the spermidine-mediated decay of ornithine decarboxylase in erythroleukemia cells.

Addition of spermidine to Friend erythroleukemia cells caused a rapid decay of ornithine decarboxylase (ODC) activity and the accumulation of a ODC-antizyme complex. The induction of antizyme only partially accounted for the decrease of ODC activity by a direct inhibition of the enzyme. However, the antizyme induction was accompanied by a marked reduction of the half-life of ODC. Shift of the cells to an ATP-depleting medium prevented the spermidine-elicited decay of ODC activity as well as the accumulation of ODC-antizyme complex. However, ODC appeared to be stabilized even when ATP depletion was performed 40 min after spermidine addition, in the presence of high levels of antizyme. Similar results were obtained by treating the cells with phenanthroline, a heavy metal chelator and protease inhibitor. These findings indicate that ATP and some metalloprotease(s) may be involved in the degradation pathway of ODC, even in the presence of high levels of polyamines.

Adenosine Triphosphate↗

PubMed1990

Mitochondrial function and superoxide generation from submitochondrial particles of aged rat hearts.

A decrease in heart function with ageing might be related to an impairment of mitochondrial function, since these organelles produce the greatest fraction of ATP in the myocyte. Mitochondria extracted from Wistar rat hearts at 3, 14, 18 and 24 months of age were employed to evaluate the changes of the respiratory activity during lifetime. A slight decrease of the respiratory rate (QO2) was observed in the 14 month group with respect to the 3 month group when succinate was used as substrate, whereas the respiratory control index (RCI) in the presence of glutamate or succinate increased in the 24 month group. The latter result may be related to a condition of moderate hypertrophy that generally occurs in the ageing heart. Submitochondrial particles (SMP) were also prepared to study the superoxide radicals (O2-) production at the level of rotenone or antimycin-inhibited regions of the respiratory chain. A strong elevation in the O2- generation was observed in the antimycin-inhibited region at 14 months of age; on the contrary, the rate of O2- production remained unchanged in the 24 month group in comparison to the youngest group. These observations correlate well with the enhanced tissue level of oxidized glutathione that was observed at 14 and 18 months of age. The products of lipid peroxidation (TBARS) did not change in the rat heart at any of the ages measured, whereas the levels of fluorescent substances progressively increased beginning from 18 months of age, with a greater extent in the mitochondrial compartment. The present study suggests that age does not substantially affect mitochondrial respiration and energy output in the rat heart, while a greater production by cardiac mitochondria of superoxide anions in the adult rats (14 months) might accelerate the fluorescent pigment formation.

Aging↗

PubMed1990

Calcium stimulates opioid receptor agonism in rat cardiac sarcolemma.

We have found that calcium stimulates, in a dose-dependent manner, the binding of opioid to kappa and delta receptors in sarcolemma from rat's ventricles isolated by hypotonic lithium bromide shock. Opioid binding was measured using [3H]-diprenorphine as a radioligand. The delta-selective agonist [D-Ala2, D-Leu5]-enkephalin and the kappa-selective agonist U-50, 488H both inhibited control and Ca(2+)-stimulated [3H]-diprenorphine binding to the sarcolemma, whereas [D-Ala2,MePhe4,Gly-(ol)5]-enkephalin was ineffective. The stimulatory effect of calcium increased the maximal binding capacity without affecting the affinity of the receptor for the ligand.

Animals↗

PubMed1990

Receptors for atrial natriuretic factor in cardiomyocytes and aortic smooth muscle.

The aim of this work was to investigate whether specific receptors for atrial natriuretic factor (ANF) are present in ventricular cardiomyocytes and aortic smooth muscle membranes. 125I-ANF was employed to test the binding of the radioligand to isolated rat cardiomyocytes. Calcium-tolerant ventricular cardiomyocytes were obtained by retrograde perfusion with collagenase. 125I-ANF binding to cardiomyocytes was highly specific (70-80%) with a KD value of 72.6 pM and a Bmax of 9.37 fmol/mg protein. In other studies, 125I-ANF binding was investigated with a membrane preparation obtained from calf thoracic aorta, from which the endothelium had been previously stripped off. In this preparation too the interaction of 125I-ANF (70-80%) was highly specific, with a KD value of 70.4 pM and a Bmax of 8.78 fmol/mg protein. These results suggest that specific receptors to atrial natriuretic factor are present both in isolated rat cardiomyocytes and in the smooth muscle of calf thoracic aorta. This second observation is in agreement with the hypothesis that the vasodilator effect of atrial natriuretic factor is due to a direct interaction between this peptide and vascular smooth muscle cells.

Animals↗

PubMed1990

Changes in myocardial mitochondrial respiration after ligation of the coronary artery in pigs.

After ligation of the left coronary artery, porcine cardiac mitochondria were isolated by homogenizing the tissue and treating the myofibrillar pellet with nagarse. When compared with unligated controls, the ischemic myocardium showed decreases in phosphocreatine (to 41%), ATP (to 56%) and in the mitochondrial respiratory control index (to 69% and 78% as measured with glutamate and succinate respectively). No changes were found in the corresponding P/O ratios. Similar results were obtained upon separation of the mitochondria into two main fractions by a density gradient technique, though only one of these fractions showed a fall in succinate-supported respiration. The results suggest that ischemia decreases the NADH-dehydrogenase activity of cardiac mitochondria.

Adenosine Diphosphate↗

PubMed1990

Influence of age on oxidative damage in mitochondria of ischemic and reperfused rat hearts.

Hearts from rats aged 3 months and 24 months respectively were isolated and subjected to a brief ischemia. The extent of myocardial injury, measured by release of creatine phosphokinase into coronary effluents and by developed tension, was greater in the young rats than in the old when compared with their corresponding non-ischemic controls. The amount of peroxidation, measured in the isolated mitochondria using the malondialdehyde method, was also greater in the younger rats. In contrast, when mitochondria from non-ischemic hearts were incubated for 20 minutes in a medium containing FeCl3, NADPH and ADP, known to generate hydroxyl radicals, significant peroxidation (together with a decrease in respiratory control indices) was obtained only from mitochondria isolated from the older rats. If, as the in vitro results suggest, the mitochondria of the old rats are not less sensitive to peroxidative attack, the difference between the effects of ischemia in the two age groups may be due to a lower rate of formation of reactive species of oxygen or to a greater anti-oxidative cytosolic capacity in the hearts of older rats. Alternatively, the overall oxidative stress following ischemia may be due to the effects of different radicals which target different parts of the mitochondrial membrane.

Aging↗

PubMed1989

Opioid receptors in rat cardiac sarcolemma: effect of phenylephrine and isoproterenol.

The present study demonstrates the presence of opioid receptors in the rat cardiac sarcolemma isolated by the hypotonic LiBr-shock procedure. Opioid binding was measured by using [3H]U69 593, [3H](2-D-penicillamine,5-D-penicillamine)enkephalin ([3H]DPDPE) or [3H][D-Ala2,MePhe4,Gly-(ol)5]enkephalin ([3H]DAGO) as selective radioligands for K, delta and mu opioid receptors, respectively. Both the K- and delta-selective ligands exhibited highly specific (75-86%) binding, saturable at a concentration of about 20 nM. No specific binding for the selective agonist DAGO was observed. A marked increase in both [3H]U69 593 and [3H]DPDPE binding was observed after incubation of the sarcolemma with the alpha-adrenoceptor agonist phenylephrine or with the beta-adrenoceptor agonist isoproterenol. These stimulatory effects were associated with an increase in the Bmax values, a decrease in the Kd values, and were completely antagonized by the respective antagonists phentolamine and propranolol.

Analgesics↗