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Biomedical subjects

L Palmieri

Publications and source records attributed to L Palmieri.

At least 37 records · Page 2Linked to original sources
PubMed1999

Light-scattering study of a supercooled epoxy resin.

The dynamics of the fragile glass-forming liquid diglycidyl ether of bisphenol-A was studied by depolarized Rayleigh-Brillouin light-scattering and photon correlation spectroscopy above the glass transition, in the temperature range from 261 to 473 K and in the frequency range from 1 Hz to 300 GHz. The structural (alpha-) relaxation process was revealed and no signature of the secondary relaxation previously evidenced by dielectric spectroscopy at about 0.1 GHz was observed. The characteristic time of the alpha process differs from that determined by dielectric spectroscopy of an amount, which increases with increasing temperature. The relaxation times were compared with viscosity data to test the predictions of the classic Stokes-Einstein-Debye model. The tau proportional, variant eta behavior was verified for dielectric data, while a fractional power law of viscosity tau proportional, variant eta(0.89) was obtained for light-scattering relaxation times, extending over more than seven decades in viscosity and time. This deviation of light scattering from viscosity data could be interpreted in terms of cooperative motion in the supercooled liquid with a characteristic length xi(a) proportional, variant(T-T0)(-v) where T(0)=229 K is the Vogel temperature and v is close to 2 / 3 which is consistent with the prediction of the fluctuation theory of glass transition.

Journal Article↗
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↗
PubMed1999

[Cardiovascular risk and social classes: a comparison between adult female populations in rural and urban areas].

The distribution of cardiovascular risk factors and the prevalence of several risk conditions are analysed in two female cohorts in southern-central Italy, one living in an urban area (the city of Naples) and the other in a rural area (the province of Latina). Analysis of different social classes identified through the level of education was also performed. The distribution of risk factors is different in the two areas (body mass index, systolic and diastolic blood pressure are higher in the province of Latina, while serum total and HDL cholesterol are higher in Naples) as well as the prevalence of several risk conditions (the prevalence of hypertension is higher in the province of Latina, whereas hypercholesterolemia and smoking are more prevalent in Naples). Cardiovascular risk factors are unevenly distributed in the different social classes: body mass index and systolic and diastolic blood pressure decrease as the educational level increases in both cohorts; in the city of Naples, serum total and HDL cholesterol increase with the increase in educational level. An awareness of these differences is crucial to targeting primary prevention campaigns in specific social classes.

Adult↗
PubMed1998

The sequence, bacterial expression, and functional reconstitution of the rat mitochondrial dicarboxylate transporter cloned via distant homologs in yeast and Caenorhabditis elegans.

The dicarboxylate carrier (DIC) belongs to a family of transport proteins found in the inner mitochondrial membranes. The biochemical properties of the mammalian protein have been characterized, but the protein is not abundant. It is difficult to purify and had not been sequenced. We have used the sequence of the distantly related yeast DIC to identify a related protein encoded in the genome of Caenorhabditis elegans. Then, related murine expressed sequence tags were identified with the worm sequence, and the murine sequence was used to isolate the cDNA for the rat homolog. The sequences of the worm and rat proteins have features characteristic of the family of mitochondrial transport proteins. Both proteins were expressed in bacteria and reconstituted into phospholipid vesicles where their transport characteristics closely resembled those of whole rat mitochondria and of the rat DIC reconstituted into vesicles. As expected from the role of the DIC in gluconeogenesis and ureogenesis, its transcripts were detected in rat liver and kidney, but unexpectedly, they were also detected in rat heart and brain tissues where the protein may fulfill other roles, possibly in supplying substrates to the Krebs cycle.

Amino Acid Sequence↗
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↗
PubMed1998

Kinetics of the reconstituted tricarboxylate carrier from eel liver mitochondria.

The tricarboxylate carrier from eel liver mitochondria was purified by chromatography on hydroxyapatite and Matrix Gel Blue B and reconstituted into liposomes by removal of the detergent with Amberlite. Optimal transport activity was obtained by using a phospholipid concentration of 11.5 mg/ml, a Triton X- 114/phospholipid ratio of 0.9, and ten passages through the same Amberlite column. The activity of the carrier was influenced by the phospholipid composition of the liposomes, being increased by cardiolipin and phosphatidylethanolamine and decreased by phosphatidylinositol. The reconstituted tricarboxylate carrier catalyzed a first-order reaction of citrate/citrate or citrate/malate exchange. The maximum transport rate of external [14C]citrate was 9.0 mmol/min per g of tricarboxylate carrier protein at 25 degrees C and this value was virtually independent of the type of substrate present in the external or internal space of the liposomes. The half-saturation constant (Km) was 62 microM for citrate and 541 microM for malate. The activation energy of the citrate/citrate exchange reaction was 74 kJ/mol from 5 to 19 degrees C and 31 kJ/mol from 19 to 35 degrees C. The rate of the exchange had an external pH optimum of 8.

Anguilla↗
PubMed1997

Identification of the yeast ACR1 gene product as a succinate-fumarate transporter essential for growth on ethanol or acetate.

The protein encoded by the ACR1 gene in Saccharomyces cerevisiae belongs to a family of 35 related membrane proteins that are encoded in the fungal genome. Some of them are known to transport various substrates and products across the inner membranes of mitochondria, but the functions of 28 members of the family are unknown. The yeast ACR1 gene was introduced into Escherichia coli on an expression plasmid. The protein was over-produced as inclusion bodies, which were purified and solubilised in the presence of sarkosyl. The solubilised protein was reconstituted into liposomes and shown to transport fumarate and succinate. Its physiological role in S. cerevisiae is probably to transport cytoplasmic succinate, derived from isocitrate by the action of isocitrate lyase in the cytosol, into the mitochondrial matrix in exchange for fumarate. This exchange activity and the subsequent conversion of fumarate to oxaloacetate in the cytosol would be essential for the growth of S. cerevisiae on ethanol or acetate as the sole carbon source.

Acetates↗
PubMed1997

Identification of the yeast ARG-11 gene as a mitochondrial ornithine carrier involved in arginine biosynthesis.

The ARG-11 gene in Saccharomyces cerevisiae encodes a protein with the characteristic features of a family of 35 related membrane proteins that are encoded in the fungal genome. Some of them are known to transport various substrates and products across the inner membranes of mitochondria, but the functions of 29 members of the family are unknown. The yeast ARG-11 protein has been over-produced as inclusion bodies in Escherichia coli. It has been solubilized in the presence of sarkosyl, re-constituted into liposomes and shown to transport ornithine in exchange for protons. Its main physiological role is probably to take ornithine synthesized from glutamate in the mitochondrial matrix to the cytosol where it is converted to arginine.

Amino Acid Transport Systems, Basic↗
PubMed1996

Identification by bacterial expression and functional reconstitution of the yeast genomic sequence encoding the mitochondrial dicarboxylate carrier protein.

The inner membranes of mitochondria contain a family of transport proteins of related sequence and structure. The DNA sequence of the genome of Saccharomyces cerevisiae encodes at least 35 members of this family. Three of them can be recognised as known isoforms of the ADP-ATP translocase and two others as the phosphate and citrate carriers. The transport functions of the remainder cannot be identified with certainty. One of them, encoded on yeast chromosome xii, shows a fairly close sequence relationship to the known sequence of the bovine mitochondrial oxoglutarate-malate carrier. The yeast protein has been obtained by over-expression in Escherichia coli, reconstituted into phospholipid vesicles and shown to have transport properties characteristic of the mitochondrial carrier for dicarboxylate ions, such as malate, and also phosphate, previously biochemically characterised, but not sequenced, from both mammalian and yeast mitochondria. This is the first example of the biochemical identification of an unknown membrane protein encoded in the yeast genome since the completion of the genomic sequence.

Carrier Proteins↗
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↗
PubMed1994

Kinetic characterization of the reconstituted ornithine carrier from rat liver mitochondria.

The ornithine carrier was purified from rat liver mitochondria and reconstituted into liposomes by removing the detergent from mixed micelles by hydrophobic chromatography on Amberlite XAD-2. The efficiency of reconstitution was optimized with respect to the concentration of protein and phospholipid, the Triton X-100/phospholipid ratio, the Amberlite/detergent ratio and the number of passages through a single Amberlite column. The activity of the carrier was influenced by the phospholipid composition of the liposomes, increasing in the presence of acidic phospholipids and decreasing in the presence of dioleoylphosphatidylcholine. In the reconstituted system the incorporated ornithine carrier catalyzed a first-order reaction of ornithine/ornithine or ornithine/citrulline exchange. The maximum transport rate of external [14C]ornithine was 3.2 mmol/min per g protein at 25 degrees C. This value was independent of the type of substrate present at the external or internal space of the liposomes (ornithine, citrulline and lysine). The half-saturation constant (Km) was 0.16 mM for ornithine, 1.2 mM for lysine and 3.6 mM for citrulline. The activation energy of the ornithine/ornithine exchange reaction was 89 kJ/mol. The rate of exchange had a pH optimum at 8 and was inhibited by cations.

Animals↗
PubMed1994

Effect of L-propionyl carnitine on in-vitro membrane alteration of sickle-cell anaemia erythrocytes.

Sickle-cell anaemia erythrocytes are under oxidative stress which contributes to some of the reversible and irreversible modifications observed in these cells. L-Propionyl carnitine, which protects myocardium, endothelium and erythrocytes from peroxidative damages and is able to stabilize damaged cell membranes, is also able to decrease the formation of thiobarbituric acid reactive substances which are produced by incubating erythrocytes with hydrogen peroxide in the presence of atmospheric oxygen or 95% N2-5% CO2 mixture. In these experimental conditions the increase of thiobarbituric-acid-reactive substances is significantly lower at 5 mM and 10 mM L-propionyl-carnitine concentrations. The formation of irreversibly sickled cells induced by 24-h incubation of sickle-cell anaemia erythrocytes under 95% N2-5% CO2 mixture is significantly decreased in the presence of 1 mM or higher L-propionyl-carnitine concentrations. The percent filtration of sickle red blood cells through micropore filters is significantly decreased at oxygen tensions between 20 and 40 mmHg. These in-vitro observations suggest that L-propionyl carnitine may be beneficial in maintaining the normal shape of sickle-cell anaemia erythrocytes at low oxygen tension and in decreasing the peroxidative damages which accumulate during the life of red blood cells.

Anemia, Sickle Cell↗
PubMed1994

Protection of beta-thalassaemic erythrocytes from oxidative stress by propionyl carnitine.

Susceptibility to oxidative stress is increased in erythrocytes of patients with beta-thalassaemia due to the free alpha-chain pool and to the excess of iron. We have investigated the effect of L-propionylcarnitine concentrations on oxidative stress determined by lactoperoxidase-hydrogen peroxide-iodide and by xanthine oxidase-acetaldehyde on erythrocytes of patients with beta-thalassaemia (major and intermedia). L-propionyl carnitine protects the erythrocytes from oxidative stress as measured by cell lysis. The protection is concentration-dependent. L-propionyl carnitine also stabilizes the cell membranes in which a latent peroxidative damage has been produced. These data suggest that L-propionyl carnitine may prove beneficial in protecting in vivo patients in which peroxidative damage of cell structure is increased as in the case of beta-thalassaemic patients.

Adult↗
PubMed1994

Renal excretion of ascorbic acid in insulin dependent diabetes mellitus.

Serum ascorbic acid (AA) is reduced in diabetic patients. Aim of this study was 1) to verify whether such a decrease might be due to an altered urinary excretion of AA, and 2) whether this latter was modified in presence of early diabetic nephropathy with microalbuminuria (albumin excretion rate [AER] > 20 micrograms/min) in a group of 21 patients affected by insulin-dependent (type 1) diabetes mellitus (IDDM) as compared with 13 healthy controls matched for sex, age, dietary AA intake, and creatinine clearance per 1.73 m2 (CCl). Mean serum AA (+/- SD) was lower in diabetics (40.3 +/- 14 microM/l) than in controls (85.1 +/- 23.5 microM/l; p = 0.0001) and there was no difference between serum AA of patients with or without microalbuminuria. Urinary excretion of AA to creatinine x 100 (UAA/Cr) was higher in micro- (n = 6; 4.6 +/- 1.7) as compared to normoalbuminurics (n = 15; 1.6 +/- 0.9) or controls (1.5 +/- 1.2; p = 0.0001). For values exceeding renal threshold of tubular AA reabsorption (39 microM) the regression line of serum AA to UAA/Cr was significantly (p = 0.001) steeper in diabetics than in controls, suggesting an impaired tubular reabsorption of filtered AA in IDDM. The ratio of AA clearance to CCl was moreover related to AER (r = 0.48; p = 0.03) and to blood glucose (r = 0.51; p = 0.01), being unrelated to uric acid clearance, glycosuria and to urinary excretion of both alanine aminopeptidase and N-acetyl-beta-glucosaminidase.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗