Biomedical subjects

G Ronca

Publications and source records attributed to G Ronca.

At least 19 recordsLinked to original sources

PubMed2003

Relationship between iron and protein content of dishes and polyphenol content in accompanying wines.

The traditional combination of wines and dishes is highly complex, elaborated and refined. The aim of this study was to investigate the possible relationship between the chemical composition of wines and dishes that determines their combination. We determined the content of total polyphenols in 56 wines. The content of total proteins, total lipids, kilocalories, sodium, potassium, calcium, copper and zinc were determined in 44 raw foods and 44 dishes. Nine gourmets independently chose three wines for each food. We correlated the content of the chemical constituents of foods with the phenol content of wines combined with each food by the gourmets. A significant positive correlation was obtained between the phenol content of wines and iron (r = 0.81, p < 0.0001) and total protein content (r = 0.66, p < 0.0001) of foods. Nine gourmets composing a second panel chose three wines for each dish. A significant positive correlation was also obtained between the phenol content of wines and iron (r = 0.69, p < 0.0001), total protein (r = 0.50, p < 0.0006) and potassium (r = 0.45, p < 0.002) in dishes combined with wines by the second panel of gourmets. Plant phenols decrease the intestinal absorption of iron and have antioxidant activity in the intestinal tract and elsewhere in the body. These positive effects compensate the negative antinutritional activity toward protein digestion. The traditional combination of wines and dishes appears to be very favorable since wines poor in phenols are combined with dishes poor in iron and/or proteins to minimize their possible antinutritional effects, while phenol-rich wines are combined with dishes rich in iron to decrease iron absorption and prandial peroxidative stress.

Carbohydrates↗

PubMed2002

Effect of lecithin on epicutaneous absorption of diclofenac epolamine.

The epicutaneous application of nonsteroidal antiinflammatory drugs in localized rheumatic diseases results in a highly targeted antiinflammatory action and is associated with reduced systemic effects. The new diclofenac epolamine (DHEP) salt is much more soluble both in water and in lipid solvent than other diclofenac salts. The pharmaceutical addition of lecithin to DHEP leads to the formation of mixed micelles with high affinity to the cellular component, which guarantees the absorption of the active ingredient. We performed a bioavailability randomized, cross-over study to compare the plasma profiles of diclofenamic acid after repeated epicutaneous administration of the new topical formulation with those of the marketed DHEP formulation without lecithin. Based on a randomization list, 12 healthy volunteers were asked to apply one of the two formulations twice a day for 10 consecutive days. The other formulation was given after a washout period of 1 week. Blood samples were collected before the morning epicutaneous dose on days 1, 3, 5 and 8 of treatment and on day 10 at different sampling times until 24 h after the application. The pharmacokinetic analysis showed a significantly higher plasma concentration of diclofenamic acid after the application of DHEP lecithin, which indicates a better saturation of the subcutaneous tissues underlying the application site. This also indicates increased local availability of the active principle. In conclusion, the new DHEP formulation with lecithin should have a therapeutic advantage compared with the formulation without lecithin, even in cases of short- to medium-term treatments.

Adjuvants, Pharmaceutic↗

PubMed2000

Protection of ischemic rat heart by dantrolene, an antagonist of the sarcoplasmic reticulum calcium release channel.

Cytosolic Ca2+ overload plays a major role in the development of irreversible injury during myocardial ischemia. Such overload is due at least in part to the release of Ca2+ from the sarcoplasmic reticulum. Therefore, we investigated whether dantrolene, a blocker of the sarcoplasmic reticulum Ca2+ release channel, may protect from ischemic injury. In binding experiments, we determined the effect of dantrolene on [3H]-ryanodine binding in rat cardiac tissue. In perfusion experiments, isolated rat hearts were perfused for 20 min in the working mode, in the presence of 0-45 microM dantrolene. The hearts were then subjected to 30 min of global ischemia and 120 min of retrograde reperfusion. Tissue injury was evaluated on the basis of triphenyltetrazolium chloride (TTC) staining and LDH release. The binding experiments showed that dantrolene displaced 4 nM [3H]-ryanodine with IC50 of 34 microM. In the perfusion experiments, tissue necrosis (i.e., TTC-negative tissue) averaged 28.3 +/- 1.6% of the ventricular mass under control conditions. Dantrolene was protective at micromolar concentrations: tissue necrosis decreased to 21.4 +/- 1.0% and 8.4 +/- 1.4% with 1 microM and 45 microM dantrolene, respectively (P < 0.05 and P < 0.01). Similar results were obtained with regard to LDH release. At low concentrations (up to 4 microM), dantrolene did not produce any significant hemodynamic effect, except for a slight increase in coronary flow, whereas at higher concentration a negative inotropic effect was apparent. In conclusion, dantrolene reduced ischemic injury even at concentrations that did not affect contractile performance. Modulation of sarcoplasmic reticulum Ca2+ release might represent a new cardioprotective strategy.

Animals↗

PubMed2000

A novel mutation in the pendrin gene associated with Pendred's syndrome.

OBJECTIVE: Pendred's syndrome is an autosomal recessive disorder characterized by goitre, sensorineural deafness and iodide organification defect. It is one of the most frequent causes of congenital deafness, accounting for about 10% of hereditary hearing loss. It is caused by mutations in the pendrin (PDS) gene, a 21 exon gene located on chromosome 7. The aim of this study was to examine an Italian family affected with Pendred's syndrome at the molecular level. PATIENTS: Thirteen subjects belonging to a family from Southern Italy were evaluated for the clinical and genetic features of Pendred's syndrome. MEASUREMENTS: Exons 2-21 of the PDS gene were amplified from peripheral leucocytes by the polymerase chain reaction; mutation analysis was performed by single strand conformation polymorphism, direct sequencing and restriction analysis. RESULTS: The index patient had the classical triad of the syndrome and harboured two mutations in the PDS gene in the form of compound heterozygosity. He was found to be heterozygous for a cytosine to adenosine mutation at nucleotide 1523 in exon 13 and for a IVS 1001 + 1G --> A mutation. The former is a novel mutation which results in a change of 508 threonine to asparagine in the putative eleventh transmembrane domain. The latter mutation in the donor splice site has already been described in other patients and is thought to lead to aberrant splicing and premature protein truncation. Three subjects who were heterozygous for one mutation had normal phenotypes. Two subjects had sensorineural deafness and were heterozygous for a single mutation. Goitre was found only in patients with Pendred's syndrome and was absent in all other individuals, albeit residing in an iodine-deficient area. CONCLUSIONS: We have identified a novel mutation in the pendrin gene causing Pendred's syndrome, and confirm that molecular analysis is a useful tool for a definitive diagnosis. This is particularly relevant in cases such as in the subjects of our family in which the clinical features might be misleading and other genetics factors might be responsible for deafness.

Adult↗

PubMed1999

Effect of resveratrol and some other natural compounds on tyrosine kinase activity and on cytolysis.

Resveratrol is a phytoalexin with several biological and pharmacological activities including the "French paradox". We investigated the effect of resveratrol on cytolytic activity by oxygen reactive species and on soluble and particulate tyrosine kinases from human placenta and human prostatic adenoma. These effects were compared with those of piceatannol, quercetin, catechin and epicatechin. Fifty percent of erythrocyte lysis due to H2O2-lactoperoxidase-KI incubation, in which I3-, OI- and oxygen singlet are produced, was obtained after 22 +/- 7 (SD) min in the absence of the tested compounds. The 50% lysis was obtained after 66 +/- 15, 129 +/- 35, 196 +/- 21, 240 +/- 63 and 420 +/- 80 min with 40 microM piceatannol, quercetin, resveratrol, epicatechin and catechin respectively. Protection was concentration dependent. The assay of tyrosine kinase activity was performed using two different substrates as follows: substrate A corresponded to the sequence 1-17 of gastrin, and substrate B to sequence 6-20 of cell division kinase p34cdc2. In all experiments, initial velocity was measured. When assayed with both substrates, tyrosine kinase activities from particulate and cytosolic fractions of placenta were more inhibited by piceatannol and quercetin. Resveratrol significantly inhibited the particulate fraction and the cytosolic fraction respectively when substrates A and B were employed: Catechin acted as an inhibitor with substrate A and particulate fraction while in the other experimental conditions it acted as an activator. Resveratrol inhibited the tyrosine kinase of particulate and cytosolic fractions of prostatic adenoma assayed with substrate A and B.

Anti-Infective Agents↗

PubMed1998

Sulfhydryl redox state affects susceptibility to ischemia and sarcoplasmic reticulum Ca2+ release in rat heart. Implications for ischemic preconditioning.

We investigated the effect of sulfhydryl and disulfide reagents on ischemic preconditioning and on sarcoplasmic reticulum Ca2+ release. Isolated working rat hearts were subjected to ischemic preconditioning (three 3-minute periods of global ischemia) or to control aerobic perfusion, which was followed by 30 minutes of global ischemia and 120 minutes of retrograde reperfusion. Necrosis was evaluated on the basis of lactate dehydrogenase release and triphenyltetrazolium chloride staining. In parallel experiments, sarcoplasmic reticulum Ca2+ release and [3H]-ryanodine binding were determined before the sustained ischemia. Ischemic preconditioning was associated with protection versus ischemic injury, decreased Ca2+ release and reduced [3H]-ryanodine binding. The disulfide reducing agent dithiothreitol (1 mmol/L) removed the protection provided by ischemic preconditioning, if added to the perfusion buffer either before or after the preconditioning procedure. In preconditioned hearts, dithiothreitol increased sarcoplasmic reticulum Ca2+ release and ryanodine binding, whereas in control hearts it had no effect on either tissue injury or sarcoplasmic reticulum function. Perfusion of control hearts with the sulfhydryl blocking agents 4,4'-dithiodipyridine (25 micromol/L) and N-ethylmaleimide (16 micromol/L) increased the resistance to ischemia and reduced sarcoplasmic reticulum Ca2+ release and [3H]-ryanodine binding. These effects were not additive with those induced by preconditioning. Sulfhydryl and disulfide reagents produced similar effects on Ca2+ release and [3H]-ryanodine binding if added in vitro to preparations obtained from control and preconditioned hearts. We conclude that ischemic preconditioning is associated with the oxidation of sulfhydryl groups involved in the modulation of sarcoplasmic reticulum Ca2+ release.

Animals↗

PubMed1998

Anti-inflammatory activity of chondroitin sulfate.

The pharmacokinetics of chondroitin sulfate (CS, Condrosulf, IBSA, Lugano, Switzerland) were investigated in rats and in healthy volunteers using CS tritiated at the reducing end and CS labeled with 131I or 99mTc respectively. A rapid absorption of orally administered CS is observed in rats and in humans when the drug is dissolved in water. Lower and delayed absorption is observed when CS is administered in gastroresistant capsules. The absolute bio-availability is 15 and 12% for rats and humans respectively. The CS shows a tropism for cartilagineous tissues in rats and for knee tissues in humans as demonstrated by scintigraphic analysis with 99mTc-CS. Monomers, oligo and polysaccharides produced by enzymatic hydrolysis of CS appear in the blood and tissues together with native CS. The effects of partially depolymerized (m.m. 3 to 15 kD) and desulfated fractions on human leukocytes were investigated. CS and its fractions inhibit the directional chemotaxis induced by zymosan-activated serum, are able to decrease the phagocytosis and the release of lysozyme induced by zymosan and to protect the plasma membrane from oxygen reactive species. In rats the oral administration of CS significantly decreases granuloma formation due to sponge implants and cell migration and lysosomal enzyme release in carrageenan pleurisy. Compared with nonsteroidal anti-inflammatory drugs (indomethacin, ibuprofen), CS appears to be more effective on cellular events of inflammation than on edema formation. It is noteworthy that CS is devoid of dangerous effects on the stomach, platelets and kidneys. In synovial fluid of patients requiring joint aspiration, treated orally for 10 days with CS (800 mg/day) the hyaluronate concentration and the intrinsic viscosity significantly increased, while collagenolytic activity, phospholipase A2 and N-acetylglucosaminidase (NAG) decreased. These results give an insight into the mechanism of the anti-inflammatory and chondroprotective actions demonstrated by this drug in a number of clinical trials in patients with osteoarthritis.

Administration, Oral↗

PubMed1996

Sarcoplasmic reticulum calcium uptake in human myocardium subjected to ischemia and reperfusion during cardiac surgery.

We evaluated the effect of ischemia and reperfusion on sarcoplasmic reticulum Ca uptake in patients subjected to cardiac surgery. Our series included 16 patients (seven female, nine male, age 63 +/- 2 years): five were subjected to aortic valve replacement, five to aortic and mitral valve replacement, six to coronary artery bypass graft. In each case no clinical, electrocardiographic or echocardiographic evidence of perioperative infarction was observed. Biopsies were obtained from the right atrium of each patient before starting extracorporeal circulation, and after the recovery of spontaneous contractile activity, i.e. after cardioplegia-ischemia-reperfusion. The tissue was homogenized, and oxalate-supported Ca uptake, which represents sarcoplasmic reticulum Ca uptake, was measured in the unfractionated homogenate. The assay was performed under basal conditions and in the presence of 900 microM ryanodine, in order to block sarcoplasmic reticulum Ca release channels. Under basal conditions at pCa = 5.85 the rate of sarcoplasmic reticulum Ca uptake averaged 4.76 +/- 0.37 nmol/min per mg of protein in the pre-ischemic samples, and decreased significantly in the post-ischemic samples (3.09 +/- 0.29 nmol/min per mg, P < 0.01). A significant decrease of Ca uptake after ischemia and reperfusion was observed also in the presence of ryanodine (3.53 +/- 0.48 nmol/min per mg) compared to pre-ischemic values (5.98 +/- 0.56 nmol/min per mg, P < 0.01). Additional experiments showed no change in the Ca sensitivity of Ca uptake in the postischemic samples (Kca = 0.48 +/- 0.02 microM, no significant difference after ischemia and reperfusion). In conclusion, active sarcoplasmic reticulum Ca transport was impaired in human atrial myocardium after reversible ischemia and reperfusion.

Aged↗

PubMed1995

Interaction between gallopamil and cardiac ryanodine receptors.

1. In a sarcoplasmic reticulum fraction obtained from rat hearts, the analysis of equilibrium [3H]-ryanodine binding showed high and low affinity sites (KD = 1.3 nM and 2.8 microM, Bmax = 2.2 pmol mg-1 and 27.8 pmol mg-1). The dissociation rate constant increased at 1 microM vs 4 nM [3H]-ryanodine concentration, and micromolar ryanodine slowed the dissociation of nanomolar ryanodine. 2. The binding of 4 nM [3H]-ryanodine was not affected by gallopamil, while the binding of 100 nM to 18 microM [3H]-ryanodine was partly displaced. Data analysis suggested that gallopamil inhibited low affinity [3H]-ryanodine binding, with IC50 in the micromolar range. 3. Gallopamil decreased the dissociation rate constant of 1 microM [3H]-ryanodine. While gallopamil alone did not affect the dissociation of 4 nM [3H]-ryanodine, gallopamil and micromolar ryanodine slowed it to a greater extent than micromolar ryanodine alone. 4. Our results are consistent with the hypothesis that the ryanodine receptor is a negatively cooperative oligomer, which undergoes a sequential alteration after ryanodine binding. Gallopamil has complex actions: it inhibits ryanodine binding to its low affinity site(s), and probably modulates the cooperativity of ryanodine binding and/or the transition to a receptor state characterized by slow ryanodine dissociation. These molecular actions could account for the previously reported effect of gallopamil on the sarcoplasmic reticulum calcium release channel.

Animals↗

PubMed1995

Postischemic changes in cardiac sarcoplasmic reticulum Ca2+ channels. A possible mechanism of ischemic preconditioning.

We investigated the modifications of cardiac ryanodine receptors/sarcoplasmic reticulum Ca2+ release channels occurring in ischemic preconditioning. In an isolated rat heart model, the injury produced by 30 minutes of global ischemia was reduced by preexposure to three 3-minute periods of global ischemia (preconditioning ischemia). The protection was still present 120 minutes after preconditioning ischemia but disappeared after 240 minutes. Three 1-minute periods of global ischemia did not provide any protection. In the crude homogenate obtained from ventricular myocardium, the density of [3H]ryanodine binding sites averaged 372 +/- 18 fmol/mg of protein in the control condition, decreased 5 minutes after preconditioning ischemia (290 +/- 15 fmol/mg, P < .01), was still significantly reduced after 120 minutes (298 +/- 17 fmol/mg, P < .05), and recovered after 240 minutes (341 +/- 21 fmol/mg). Three 1-minute periods of ischemia did not produce any change in ryanodine binding. The Kd for ryanodine (1.5 +/- 0.3 nmol/L) was unchanged in all cases. In parallel experiments, the crude homogenate or a microsomal fraction was passively loaded with 45Ca, and Ca(2+)-induced Ca2+ release was studied by the quick filtration technique. In both preparations, the rate constant of Ca(2+)-induced Ca2+ release decreased 5 and 120 minutes after preconditioning ischemia (homogenate values: 19.7 +/- 1.4 and 18.9 +/- 0.9 s-1 vs a control value of 25.4 +/- 1.7 s-1, P < .05 in both cases) and recovered after 240 minutes (23.0 +/- 1.9 s-1). The Ca2+ dependence of Ca(2+)-induced Ca2+ release was not affected by preconditioning ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

PubMed1995

Effect of L-propionyl carnitine on some properties of erythrocytes and leukocytes of alcohol abusers.

The effect of L-propionyl carnitine, the carnitine derivative utilized as a more effective drug for membrane protection, on Na-K ATPase activity of erythrocyte ghosts of alcohol-dependent patients and blood donors has been investigated. The effect of L-propionyl carnitine on leukocyte chemotaxis and cytochrome c reduction, a measure of superoxide ion production was also studied. It has been in fact observed that alcohol is immunotoxic on both the non-specific and the specific immune response. In alcohol-dependent erythrocytes, a significant higher value of the 1H-NMR spin lattice relaxation time (T1) was observed as compared to blood-donor erythrocytes. The in-vitro addition of ethanol increases the T1 values of blood donor erythrocytes, whereas it is without effect on the T1 value of alcohol-dependent erythrocytes. The Na-K ATPase activity is higher in alcohol-dependent erythrocyte ghosts as compared to blood-donor ghosts. A non-significant increase of the Na-K ATPase activity of blood-donor ghosts was observed with the increasing of L-propionyl carnitine concentrations (from 0.2 to 5.0 mM), whereas the Na-K ATPase activity of alcohol-dependent ghosts decreases. From these combined effects the differences of Na-K ATPase activity progressively decrease with the increasing of L-propionyl carnitine concentration, and no significant differences are observed between the two groups at L-propionyl carnitine concentrations higher than 0.5 mM. The in-vitro addition of ethanol increases the enzyme activity to a greater extent in blood-donor ghosts as compared to alcohol-dependent ghosts. This in-vitro activation by ethanol is decreased by the addition of L-propionyl carnitine. The chemotaxis induced by N-formyl-methionyl-leucylphenylalanine and the superoxide anion production stimulated by zymosan is significantly lower in alcohol-dependent neutrophils. L-Propionyl carnitine increases, in a dose-dependent way, both chemotaxis and superoxide anion production of alcohol-dependent neutrophils, and no significant difference was observed between the two groups at 5 mM L-propionyl carnitine. These experimental results suggest that L-propionyl carnitine administration may be useful for reducing some acute and chronic damages due to alcohol ingestion. The protective and modulatory actions of L-propionyl carnitine may be even more evident in cells and tissues different from those investigated in this study and in which ethanol determines several biochemical damages.

Alcoholism↗

PubMed1995

Biochemical and pharmacokinetic aspects of oral treatment with chondroitin sulfate.

Chondroitin sulfate (Condrosulf) was characterized for structure, physiochemical properties and purity. This glycosaminoglycan has a relative molecular mass of about 14,000, a sulfate-to-carboxyl ratio of 0.95 due to the high percentage of monosulfated disaccharides (38% 6-monosulfate and 55% 4-monosulfate) and a low amount of disulfated disaccharides (1.1%) inside the polysaccharide chains. No other glycosaminoglycans were detected in the preparation. Chondroitin sulfate was labelled by reduction with sodium 3H-borohydride and administered by oral route in the rat and dog. More than 70% of radioactivity was absorbed and found in urine and tissues. The plasma radioactivity was fractionated by size-exclusion chromatography in three fractions: radioactivity associated with high, intermediate and low molecular mass compounds. The peak value of the concentration of high molecular mass radioactivity compounds in plasma was reached after 1.6 and 2.1 h for the rat and dog, respectively. After 36 h the high molecular mass radioactivity compounds were still present in plasma of dog and rat. After 24 h radioactivity was higher in the intestine, liver, kidneys, synovial fluid and cartilage than in other tissues. Condroitin sulfate was orally administered to man (healthy volunteer) in a single daily dose of 0.8 g and in two daily doses of 0.4 g. The results showed that both forms of administration determined a significant increase of plasma concentration of chondroitin sulfate as compared with predose value over a full 24 h period. Elimination constant values and tmax (of the first administration in the case of fractionated dose) were almost the same for the two administrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

Are dihydropyridine receptors downregulated in the ischemic myocardium?

OBJECTIVE: We investigated the effect of ischemia on cardiac dihydropyridine receptors, which correspond to L-type sarcolemmal calcium channels. METHODS: Isolated working rat hearts were perfused aerobically for 10 min, and then subjected to 10-60 min of global ischemia. Control hearts were perfused aerobically for 30 min. [3H]PN 200-110 binding was measured in the unfractionated homogenate, in a crude membrane preparation and in a microsomal fraction. RESULTS: In the homogenate obtained from control hearts, the Kd and Bmax averaged 0.23 +/- 0.05 nM and 84 +/- 4 fmol/mg protein, respectively, and ischemia did not produce any significant change in these variables. Similar results were obtained in the crude membrane preparation (Kd = 0.29 +/- 0.08 nM, Bmax = 113 +/- 7 fmol/mg, yield of binding sites = 98 +/- 6%, no significant change in these variables during ischemia). On the contrary, in the microsomal fraction, the Bmax for [3H]PN 200-110 decreased after ischemia (115 +/- 15 fmol/mg after 20 min of ischemia vs. 190 +/- 34 fmol/mg in the control condition, P < 0.05), without any change in the Kd. In this fraction, the yield for PN 200-110 binding sites was 4.7 +/- 0.6% in the control condition and 2.8 +/- 0.5% after ischemia (P < 0.05). The yield of other sarcolemmal markers such as [3H]quinuclidinyl benzylate and [3H]ouabain binding sites was not reduced in the microsomal fraction obtained ischemic hearts. CONCLUSIONS: The total number of cardiac dihydropyridine binding sites was not downregulated during ischemia, although their distribution after tissue fractionation was slightly modified, possibly reflecting receptor redistribution between different subcellular pools.

Animals↗

PubMed1994

Effects of glycosaminoglycans on U-937 leukemia cell proliferation and differentiation: structure-function relationship.

Glycosaminoglycans (heparins, dermatan sulfate, chondroitin sulfate) with different structures and physicochemical properties were evaluated for their capacity to influence proliferation and differentiation of U-937 cell line. The contrasting and specific effects of glycosaminoglycans (depending on their structures and properties) on a leukemia cell line could help explain the regulation of proliferative and/or differentiative processes of hematopoietic cells in order to clarify the control of development and differentiation of hematopoietic progenitor cells by bone marrow extracellular matrix. Heparin from beef intestinal mucosa, heparan sulfate from beef spleen, dermatan sulfate from beef intestinal mucosa, and chondroitin sulfate from bovine trachea were extracted and purified, and their purity, structures, and physicochemical properties were evaluated. Fast-moving heparin was obtained by its selective precipitation as barium salt, and partially desulfated and re-N-sulfated heparin was produced by chemical modifications. Different glycosaminoglycans were tested to evaluate their effects on proliferation and differentiation processes of a monoblastic leukemia cell line (U-937). Heparin and derivatives (from 0.1 to 100 micrograms/ml) inhibit cell proliferation; heparan sulfate does not produce modifications, while chondroitin sulfate and dermatan sulfate (from 0.01 to 100 micrograms/ml) significantly stimulate cell growth. Cell differentiation was evaluated by cytoenzymatic determination of alpha-naphthyl butyrate esterase and by fluorescein-labeled anti-HLA-DR, anti-CD11b, and anti-CD14 antibodies. Nitro blue tetrazolium reduction and phagocytosis were also evaluated. Heparin and derivatives significantly increase U-937 differentiation. Heparin sulfate has no effect, while chondroitin sulfate and, to a lesser extent, dermatan sulfate, induce a strong decrease of differentiative markers. The regulation of U-937 cell properties appears to be related to charge density and to the amount of N-sulfate and N-acetyl groups. In particular, glycosaminoglycans with lower sulfate-to-carboxyl ratios and N-sulfate group percentages (chondroitin sulfate and dermatan sulfate) stimulate proliferation and produce a decrease of differentiative markers; on the contrary, polysaccharides with high charge density and N-sulfate group amounts (heparin and derivatives) inhibit U-937 proliferation and induce terminal differentiation. A previous paper (N. Volpi, L. Bolognani, A. Conte, and M. Petrini, (1993) Leukemia Res. 17, 789-798) demonstrates dissimilar effects on U-937 cells by chondroitin sulfates with different structures and physicochemical properties. In this study we confirm the importance of glycosaminoglycan structures and physicochemical properties in regulating cell functions. Possible mechanisms of action are discussed.

Animals↗

PubMed1994

Effect of ischemia and reperfusion on cardiac ryanodine receptors--sarcoplasmic reticulum Ca2+ channels.

We investigated the effect of ischemia and reperfusion on the cardiac ryanodine receptor, which corresponds to the sarcoplasmic reticulum Ca2+ channel. Isolated working rat hearts were subjected to 10 to 30 minutes of global ischemia, followed or not by reperfusion. Ischemia produced significant reduction in the density of high-affinity 3H-ryanodine binding sites, determined either in whole-heart homogenate (Bmax, 220 +/- 22, 203 +/- 12, and 228 +/- 14 fmol/mg protein after 10, 20, and 30 minutes of ischemia versus 298 +/- 18 fmol/mg protein in the control condition; P < .01) or in a fraction enriched in sarcoplasmic reticulum (Bmax, 1.08 +/- 0.15 pmol/mg protein after 20 minutes of ischemia versus 1.69 +/- 0.08 pmol/mg protein in the control condition; P < .01). The Kd (1.5 +/- 0.1 nmol/L) and the Ca2+ dependence of high-affinity 3H-ryanodine binding were not affected by ischemia. The density of low-affinity 3H-ryanodine binding sites was also reduced after 20 minutes of ischemia (14.0 +/- 2.3 versus 34.0 +/- 8.2 pmol/mg protein in the sarcoplasmic reticulum fraction, P < .05), without significant changes in Kd (4.7 +/- 1.2 versus 2.4 +/- 1.0 mumol/L). All these changes persisted after 20 minutes of reperfusion. Analysis of tissue fractions showed that 55% of the ryanodine binding sites were retained in the pellet of a low-speed centrifugation ("nuclear pellet") and that the effects of ischemia concerned only the receptors released in the supernatant ("postnuclear supernatant"). In parallel experiments, we evaluated the effect of ryanodine on oxalate-supported Ca2+ uptake, which represents sarcoplasmic reticulum Ca2+ uptake. As expected, we found that high concentrations of ryanodine stimulated Ca2+ uptake, owing to channel blockade. The response to 900 mumol/L ryanodine was slightly reduced in crude homogenate and significantly reduced in postnuclear supernatant obtained from ischemic hearts. In conclusion, the number of ryanodine receptors is reduced after ischemia; this effect concerns a subpopulation of the receptors, persists after reperfusion, and might contribute to modify sarcoplasmic reticulum function.

Animals↗

PubMed1994

L-propionyl carnitine protects erythrocytes and low density lipoproteins against peroxidation.

The effects of peroxidation on the erythrocytes of rats orally treated with L-propionyl carnitine for 15 days (50 mg/kg/day) were investigated. Peroxidation was produced by incubating the cells in the presence of the cytotoxic system: lactoperoxidase-hydrogen peroxide and iodide ions. Lysis of erythrocytes was evaluated by measuring the turbidity following the decrease in absorbance at 600 nm. The 50% of erythrocyte lysis of untreated animals was observed after 16 min and in about 30 min all the cells were lysed. With L-propionyl carnitine-treated rat erythrocytes the time at which 50% of lysis was observed increased to 23 min. L-propionyl carnitine also exerted its protective effect in vitro when incubated with untreated rat erythrocytes or human erythrocytes in the presence of the cytolytic system. The presence of L-propionyl carnitine in the incubation mixture markedly decreased the malonaldehyde formation. The protection was concentration-dependent. To establish if L-propionyl carnitine protects from oxygen reactive species or is able to stabilize the damaged membranes, a latent damage was produced by incubating the erythrocytes with the cytolytic system for a few minutes. The cells were then removed and suspended in buffered saline in the absence or in the presence of different L-propionyl carnitine concentrations. L-propionyl carnitine decreased the velocity of lysis of damaged erythrocytes. These data suggest that L-propionyl carnitine protects erythrocytes from oxygen reactive species and also stabilizes the damaged membrane probably by specific binding with protein and/or phospholipid domains. Low density lipoproteins (LDLs) from human blood were peroxidized by exposure to Cu2+ ions in the presence of various L-propionyl carnitine concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Reversing of chlorambucil resistance by ethacrynic acid in a B-CLL patient.

We evaluated the reversing activity of ethacrynic acid in a B-CLL patient resistant to chlorambucil. The glutathione S-transferase (GST) activity, measured in peripheral blood lymphocytes, resulted extremely elevated. Ethacrynic acid, at pharmacological concentrations, partially reversed chlorambucil resistance and this result appeared related to the increased GST levels.

Aged↗

PubMed1993

Activity of different revertant agents on multidrug resistance: in vitro evaluation of their combination.

The revertant activity of different compounds has been assayed on a multidrug-resistant human breast-cancer cell line (MCF 7/Dx). The calcium-channel blocker nicardipine showed the higher revertant ability when compared to cefoperazone or cyclosporin A at concentrations close to the pharmacological range. Interestingly, nicardipine was able to increase the revertant activities of both cefoperazone and cyclosporin A, but these latter were not able to enhance each other over a plateau. However, a limit of about 70% of growth inhibition of the line cultured in the presence of 60 microM doxorubicin seems to be insuperable at the concentrations employed. The combination of the three drugs brings the concentrations of drugs to the point at which the maximum possible inhibition is reached in the pharmacological range, but the complete reversion of chemoresistance is not reached when the doxorubicin is added at the concentration capable of reducing the cell proliferation by 50%.

ATP Binding Cassette Transporter, Subfamily B, Mem↗