Biomedical subjects

L Cavallini

Publications and source records attributed to L Cavallini.

At least 19 recordsLinked to original sources

PubMed1992

Fructose-1,6-diphosphate inhibits platelet activation.

Fructose-1,6-diphosphate (FDP) is a physiological product which exhibits pharmacological properties. This study shows that FDP (1-3 mM) inhibits platelet aggregation induced by the agonists thrombin, vasopressin, platelet activating factor, ADP, adrenaline, arachidonate and the stable thromboxane analogue U 44069. Thrombin-promoted ATP secretion and cytosolic Ca2+ rise are also drastically inhibited by FDP, which decreases, although to a lesser extent, the protein kinase C-dependent phosphorylation of the 47 kDa protein. The inhibition on thrombin-induced aggregation is shared, albeit less efficiently, by glucose-1,6-diphosphate and fructose-2,6-diphosphate but not by other phosphorylated monosaccharides (fructose-1:2 cyclic,6-diphosphate, glucose-1- and glucose-6-phosphate, fructose-1- and fructose-6-phosphate, mannose-6-phosphate and 5-phosphoryl ribose-1-pyrophosphate). FDP does not affect platelet activation induced by the protein kinase C activators dioctanoylglycerol or phorbol 12-myristate 13-acetate. No increase of cAMP concentration is observed in FDP-treated platelets. Altogether, these results indicate that FDP inhibits platelet activation at a level preceding phospholipase C. The data are consistent with a general inhibitory action of FDP on signal transmission.

Adenosine Triphosphate↗

PubMed1992

Inhibition of thrombin-induced platelet activation by dioctanoylglycerol pretreatment is not correlated with the 47 kDa protein phosphorylation.

The effect of platelet pretreatment with moderate amounts of 1,2-dioctanoylglycerol on subsequent thrombin-induced activation and its correlation with the degree of protein phosphorylation is studied. Protein kinase C preactivation (treatment with 1 microM dioctanoylglycerol for 20 min) significantly reduces thrombin-promoted platelet aggregation, cytosolic calcium-rise, ATP-secretion and, albeit to a lesser extent, protein phosphorylation. Exposure of platelets to dioctanoylglycerol brings about a transient phosphorylation of a 47 kDa protein and a slight but more persistent phosphorylation of proteins of approximate molecular mass 26 and 68 kDa. It is hypothesized that the latter phosphoproteins are responsible for the inhibition of the thrombin-promoted platelet activation. Agonist-evoked aggregation is more affected by a long (20 min) rather than a short (1 min) pretreatment with dioctanoylglycerol, showing no correlation with the phosphorylation of the major substrates of protein kinase C.

Adenosine Triphosphate↗

PubMed1992

[Is it possible to improve the nutritional status of dialysis patients?].

It is well known that hemodialyzed patients show a protein-calorie malnutrition (PCM) due to several factors: dialytic and/or biologic age, diet, hormonal status, amino acid loss. The nutritional status of 44 HD patients was quarterly evaluated from september '87 to may '90 (32 months) and ten of them (5 M, 5 F) were treated by means of L-carnitine (6 g/ev/week) from september '88 to may '90. In the 5 treated males a net gain (+ 80 g/month) of the muscle mass was observed while the 5 treated females showed a low increase of fats. This trend was different (even though not significantly different) from that observed in the untreated group, in which a muscle mass loss and a fat increase was the rule.

Aged↗

PubMed1991

A procedure allowing measurement of cytosolic Ca2+ in rat platelets. Inhibition of a plasma lipoprotein on fura 2-AM loading.

Loading of the fluorescent Ca2+ probe fura 2 in rat platelets is highly inhibited by a plasmatic factor that is removed by gel filtration through a Sepharose C-2B column. Rat plasma also inhibits fura 2 loading in human platelets. The inhibitory effect is abolished by perchloric acid-deproteinization or heat denaturation of plasma suggesting a proteic nature of the inhibitory compound. Indeed the 10,000 x g supernatant of the heat denaturated plasma shows a positive effect on fura 2 accumulation, most likely by partially inhibiting its cellular effux. These effects are only negligibly shown by the corresponding fractions of human plasma. Results obtained by fractionation of rat plasma proteins by means of ion exchange DEAE Sepharose C-6B chromatography and ultracentrifugation through high density saline solutions indicate that the inhibition of cellular fura 2 loading is due to the HDL fraction of rat plasma.

Animals↗

PubMed1991

Platelet responses promoted by the activation of protein kinase C or the increase of cytosolic Ca2+ are potentiated by adrenaline. Effects of cAMP and staurosporine.

We studied the action of the alpha 2 adrenergic agonist adrenaline on the platelet responses evoked by the activation of protein kinase C or by the ionophore induced increase of cytosolic Ca2+. Both the phorbol ester and ionomycin-induced aggregation are strongly potentiated by adrenaline which per se does not behave as an activating agonist. The potentiation by adrenaline is observed both when added before and after the aggregating agent; in the latter case the effect increases on increasing the delay of adrenaline addition. Adrenaline also reverses the inhibition by cAMP of the PMA (or ionomycin) induced aggregation. It also has a strong potentiating effect (over 100%) on the phorbol ester induced ATP secretion and a weaker effect on the secretion induced by ionomycin. The effect on secretion is visible only when adrenaline is added prior to the stimulus. The inhibition by cAMP of the PMA or ionomycin induced secretion is also counteracted by adrenaline. In no case adrenaline modifies the pattern of platelet phosphoproteins. Ionomycin induces some platelet aggregation also in the presence of the protein kinase inhibitor staurosporine; also this phosphoprotein independent aggregation is strongly stimulated by adrenaline.

Alkaloids↗

PubMed1990

The action of the glutathione transferase substrate, 1-chloro-2,4-dinitrobenzene on synaptosomal glutathione content and the release of hydrogen peroxide.

We studied the action of the glutathione transferase substrate, 1-chloro-2,4-dinitrobenzene (CDNB) on the synaptosomal production of H2O2. We found that CDNB (30-40 microM) readily depletes the cytosolic glutathione but is almost without effect on the mitochondrial fraction. The depletion of the cytosolic glutathione induced by CDNB affords the detection in the extracellular space of H2O2 produced intrasynaptosomally upon increasing the cytosolic Ca2+ concentration that is otherwise destroyed by glutathione peroxidase. Higher concentrations of CDNB induce a H2O2 production which is not related to the glutathione content. This H2O2 is of mitochondrial origin and requires that NAD be reduced. The primary product of the mitochondrial CD-NB-dependent oxygen reduction is at least in part the superoxide anion.

Animals↗

PubMed1990

Effects of prolactin on the morphology and function of rat Leydig cells: short-term versus long-term administration.

The bolus administration of prolactin (PRL) to adult rats did not cause any apparent change in the basal and luteinizing hormone (LH)-stimulated blood levels of testosterone (as estimated by radioimmune assay). Prolonged PRL infusion did not affect either basal testosterone plasma concentration or the morphology of Leydig cells (as evaluated by electron microscopy and stereology). Conversely, prolonged PRL treatment notably increased the gonadotrophic effects of chronic LH administration; this mainly consisted of a rise in the blood concentration of testosterone and a conspicuous hypertrophy of Leydig cells. The LH-induced increase in the volume of Leydig cells was the result of an increase in the volumes of all the organelles involved in steroid synthesis (i.e., smooth endoplasmic reticulum, peroxisomes and mitochondria). However, the trophic effects of PRL infusion exclusively concerned smooth endoplasmic reticulum and peroxisomes. In the light of these findings, the hypothesis is advanced that the mechanism underlying the gonadotrophic action of PRL involves an enhancement of the endogenous cholesterol synthesis, which could provide an abundance of precursors for testosterone synthesis, the post-cholesterol steps of which, in turn, would be exclusively controlled by LH.

Animals↗

PubMed1990

Effects of prolonged cyclosporine-A treatment on the Leydig cells of the rat testis.

The effects of a prolonged (30-day) treatment with daily therapeutical doses of cyclosporin A (CAS) (20 mg/kg) on testicular Leydig cells were studied in adult rats. CSA administration provoked a significant decrease in both basal and human chorionic gonadotropin (hCG)-stimulated testosterone concentration in the peripheral blood without affecting the volume of the testes or the interstitial space. However, there was conspicuous atrophy of the Leydig cells, due mainly to a decrease in mitochondria and smooth endoplasmic reticulum, the organelles containing the enzymes of testosterone synthesis. Lipid droplets, in which cholesterol is stored, were notably increased. The nuclear volume and the surface area per cell of rough endoplasmic reticulum fell significantly in Leydig cells of CAS-treated animals. In light of these findings, it is concluded that CSA inhibits the growth and steroidogenic capacity of rat Leydig cells, probably by depressing their protein synthesis. Whether the mechanism underlying the action of CSA on Leydig cells is only indirect, by blockade of hypophyseal gonadotropin release, or also direct is unsettled and requires further investigation.

Animals↗

PubMed1990

The protective action of pyruvate on recovery of ischemic rat heart: comparison with other oxidizable substrates.

The recovery of both contractile performance and metabolic response of rat heart following 1 h of ischemia after equilibration with glucose + insulin (glucose-ischemia) or with pyruvate (pyruvate-ischemia), was tested in normoxic reperfusion in the presence of glucose + insulin, pyruvate, lactate or acetate. In glucose-ischemia only the reperfusion with pyruvate results in a complete recovery of the contractile force (left ventricular pressure, LVP) (170%) and good recovery of high energy phosphate compounds. Lower LVP and tissue energy charge were found in glucose reperfusion and even less in lactate and acetate reperfusion. Disappearance of the IMP accumulated during ischemia is evident only in the pyruvate reperfusion indicating a higher metabolic recovery. On the contrary in pyruvate-ischemia all types of reperfusion tested were effective in reactivating the contractile force (although acetate to a lesser extent); the contractile activity was accompanied by a good recovery of phosphocreatine, ATP, energy charge and by the decrease of IMP. Large decreases of adenine nucleotides and NADP and lower decreases of NAD are observed during ischemia/reperfusion in both systems. Pyruvate-ischemia is quite similar to, if not worse than glucose-ischemia, for all the metabolic parameters considered, but not worse for the possibility of recovery. Some specific effect of pyruvate should be exerted during the ischemic phase. The mechanism of pyruvate protection is discussed in relationship to: (i) the possible activation of pyruvate dehydrogenase, (ii) the activation of NADPH-dependent peroxide scavenging systems, (iii) the direct scavenging action of pyruvate on H2O2.

Acetates↗

PubMed1990

Morphology and functional responses of isolated zona glomerulosa cells of streptozotocin-induced diabetic rats.

Streptozotocin-induced diabetes significantly decreased plasma aldosterone concentration in rats whose renin-angiotensin system had been pharmacologically interrupted. Isolated zona glomerulosa cells showed a marked atrophy, coupled with a reduced basal secretion of aldosterone and corticosterone. The secretory response to the three main physiological stimuli (ACTH, angiotensin II and potassium) was also notably impaired. The hypothesis is advanced that the chronic lack of insulin may directly impair the growth and steroidogenic capacity of rat adrenal zona glomerulosa.

Adrenocorticotropic Hormone↗

PubMed1990

Effects of prolonged administration of lovastatin, an inhibitor of cholesterol synthesis, on the morphology and function of rat Leydig cells.

We examined the effects of a prolonged treatment with lovastatin, a potent competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, on the morphology and function of rat Leydig cells. Twenty-four h after the first lovastatin injection, no conspicuous ultrastructural changes were found, but isolated Leydig cells showed a notable reduction in their basal and HCG-stimulated testosterone production. By prolonging lovastatin administration (daily injections for 3 and 5 days), Leydig cells progressively recovered their secretory activity, and this was associated with a striking proliferation of smooth endoplasmic reticulum and peroxisomes. The hypothesis is discussed that these morphologic changes are the counterpart of an enhanced newly synthesis of HMG-CoA reductase, that is the expression of a compensatory response of Leydig cells aimed at maintaining an adequate production of cholesterol (i.e. testosterone precursors) in spite of the chronic competitive inhibition of HMG-CoA reductase by lovastatin.

Animals↗

PubMed1990

Cardiovascular stability during the haemodialysis session: relationship between modelling and impedance parameters.

The percentage of body water, if calculated from impedance, was found to be significantly different from the classic 58%. This supports the view that the evaluation of the dialytic efficiency should be, in the near future, carried out on the basis of a 'two-pool' model instead of the old 'one-pool'. The serial collection of data during a dialytic session supported the hypothesis that, 90 min after the start or, in general, after a body-water loss of about 5%-6%, some fundamental changes in measured indexes (phase angle, systolic pressure, body volumes, correlation matrix) usually appear. Large-scale research, based on an RS 232 interface connected to a computerised program, will probably help in clarifying whether some major intra-dialytic phenomena could in the near future be easily and automatically predicted.

Body Water↗

PubMed1990

Lipid droplets in the secretory response of Leydig cells of normal and hCG-treated rats.

Prolonged (7-day) hCG infusion caused a remarkable hypertrophy of rat Leydig cells, coupled with a notable enhancement of their basal and stimulated testosterone production in vitro. It also provoked a conspicuous accumulation of lipid droplets in the cytoplasm of hypertrophic cells. The administration of 4-aminopyrazolo-pyrimidine (4APP), at a dose causing a significant hypocholesterolaemia, did not affect the morphology and function of Leydig cells in normal rats. Conversely, in chronically hCG-infused animals, 4APP reversed lipid-droplet accumulation and significantly depressed stimulated testosterone production. The following conclusions are drawn: 1) chronic hCG treatment enhances the ability of rat Leydig cells to take-up exogenous cholesterol from circulating lipoproteins, and to store it in lipid droplets as a reserve material; 2) lipid-droplet stored cholesterol is employed only in the case of intense acute stimulation, since, under basal conditions, endogenous cholesterol synthesis is able to meet the requirements for testosterone production alone.

Adenine↗

PubMed1989

Further purification and characterization of the succinyl-CoA:3-hydroxy-3-methylglutarate coenzyme A transferase from rat-liver mitochondria.

Succinyl-CoA:3-hydroxy-3-methylglutarate coenzyme A transferase, previously identified in rat-liver mitochondria (Deana et al. (1981), Biochim. Biophys. Acta 662, 119-124), was purified to near homogeneity and further characterized. After the last purification steps consisting of Ultrogel AcA-44 filtration and agarose-hexane-coenzyme A chromatography, the enzyme was apparently tetrameric with a mass of 48-52 kDa determined by gel filtration on Sephadex G-75, ultracentrifugation through a sucrose gradient and SDS-gel electrophoresis. By means of a HPLC technique developed for measuring the CoA esters we could determine the enzyme activity in both forward and reverse directions and show that the kinetic constants, i.e., Km of reactants and Vmax, are not too different for the two reactions. Double-reciprocal plots of the enzyme velocities versus the concentration of one substrate at different fixed concentrations of the other substrate gave families of straight lines converging below the substrate-abscissa for both forward and backward reactions, indicating a kinetic mechanism of rapid equilibrium random Bi-Bi type. The competitive inhibition of the product succinate with respect to both reactants, 3-hydroxy-3-methylglutarate and succinyl-CoA, as well as the Haldane relationships are consistent with this conclusion. An inhibitory effect on CoA transferase activity by acetate, acetoacetate, acetyl-CoA, acetoacetyl-CoA, coenzyme A, carnitine, ZnCl2 and high concentrations of the monovalent anions ClO4-, F-, I- and Cl- was also found.

Animals↗

PubMed1989

Generation of hydrogen peroxide by cerebral-cortex synaptosomes. Stimulation by ionomycin and plasma-membrane depolarization.

Guinea-pig cerebral cortex synaptosomes steadily release H2O2 into the suspending medium, at the rate of 20-30 pmol min-1 mg protein-1. A transient increase of the H2O2 release is induced by the addition of 1 mM Ca2+, which declines within 60-90 s to a rate identical or slightly higher than that before Ca2+. The extra H2O2 following Ca2+ addition varies between 40-100 pmol/mg protein and is insensitive to verapamil. The H2O2 release increases strongly (up to 250 pmol min-1 mg-1) upon depletion of the synaptosomal glutathione by treatment with 1-chloro-2,4-dinitrobenzene, a substrate for glutathione transferase. This treatment however has no effect on the Ca2+-induced H2O2 transient. In these treated synaptosomes a further increase of the output of H2O2 is rapidly induced upon addition of the Ca2+ ionophore ionomycin. This increase (about 100 pmol min-1 mg-1) lasts several minutes and requires the presence of Ca2+. A similar, though less pronounced increased H2O2 release is obtained (also in the absence of Ca2+) upon depolarization of the synaptosomal plasma membrane with KCl or with veratridine.

Animals↗

PubMed1989

Stereological and functional investigations on isolated adrenocortical cells: zona fasciculata/reticularis cells of chronically ACTH-treated rats.

The morphology and function of isolated inner (zona fasciculata/reticularis) adrenocortical cells of rats pretreated with ACTH for 3, 6, 9 or 12 days were investigated. ACTH treatment induced a notable time-dependent enhancement in the steroidogenic capacity (corticosterone production) and growth of inner cells. The volumes of cells, mitochondrial compartment, membrane space [the cellular space occupied by smooth endoplasmic reticulum (SER) membranes] and lipid-droplet compartment, as well as the surface area of mitochondrial cristae and SER tubules, were increased in relation to the duration of ACTH pretreatment, and showed a highly significant positive linear correlation with both basal and stimulated corticosterone production. The acute exposure of isolated cells to ACTH provoked a striking lipid-droplet depletion, the extent of which was linearly and positively correlated with stimulated corticosterone secretion. The hypertrophy of the mitochondrial compartment and SER are interpreted as the morphological counterpart of the enhanced steroidogenic capacity of inner adrenocortical cells, inasmuch as the enzymes of steroid synthesis are located in these two organelles, and it is well known that chronic ACTH exposure stimulates the de novo synthesis of many of them in vivo. The rise in the number of lipid droplets, in which cholesterol is stored, is interpreted as being due to the fact that, under chronic ACTH treatment, the processes leading to cholesterol accumulation in adrenocortical cells (exogenous uptake and endogenous synthesis) exceed those of its utilization in basal steroid secretion. Cholesterol accumulated in lipid droplets as a reserve material may be rapidly utilized after acute ACTH exposure to meet the needs of the enhanced steroidogenic capacity of adrenocortical cells.

Adrenal Cortex↗

PubMed1989

Effect of L-carnitine and L-aminocarnitine on calcium transport, motility, and enzyme release from ejaculated bovine spermatozoa.

Experiments were performed to further elucidate the role of gamma-amino-beta-hydroxybutyric acid trimethylbetaine (carnitine) on the metabolism and functions of spermatozoa. Addition of 20 mM L-carnitine to suspensions of ejaculated bovine spermatozoa resulted in an increase of cellular calcium transport, whereas 20 mM L-aminocarnitine (an inhibitor of carnitine palmitoyltransferase) caused an inhibition of this process. Both L-carnitine and L-aminocarnitine inhibited the progressive motility of spermatozoa, and the oxygen consumption as well as the release of the enzymes hyaluronidase and glutamate-oxaloacetate transaminase from spermatozoa. Labeled carnitine was rapidly taken up by spermatozoa by a process strongly dependent on temperature and extracellular concentration of carnitine. It is concluded that the effects produced by high concentrations of carnitine or aminocarnitine are mainly due to interactions of these compounds with the cellular membranes of spermatozoa.

Acyltransferases↗

PubMed1989

A morphometric study of the reversal of ACTH-induced hypertrophy of rat adrenocortical cells after cessation of treatment.

The effect of a prolonged (7-day) ACTH administration on rat zona fasciculata cells and its reversal after cessation of treatment was investigated by morphometry. ACTH treatment caused a notable cell hypertrophy, which was mainly due to the increase in the volume of the mitochondrial compartment and to smooth endoplasmic reticulum (SER) proliferation, and a conspicuous rise in the basal level of corticosterone. After cessation of ACTH administration, rat zona fasciculata cells underwent a time-dependent atrophy, so that after 5 days they resembled those of control animals, and the blood concentration of corticosterone reverted to the base-line value. The cell atrophy was provoked by the decrease in the volumes of the mitochondrial compartment and SER, and was associated with a striking time-dependent accumulation of dense bodies. Stereology demonstrated that during the first two days after ACTH withdrawal the decrease of SER prevailed over that of the mitochondrial compartment, while the reverse occurred during the remaining three days. The increase in the volume of dense-body compartment, though largely due to the accumulation of residual bodies, was mainly coupled with a rise in the volume of the microautophagic-vacuole compartment during the first two days after ACTH cessation and with an increase in that of the macroautophagic-vacuole compartment during the following three days. The hypothesis is advanced that both micro- and macroautophagy play a role in the reversal of ACTH-induced hypertrophy of rat zona fasciculata cells after cessation of treatment, the first process being mainly involved in the elimination of SER, and the second one in the degradation of mitochondria.

Adrenocorticotropic Hormone↗