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Biomedical subjects

G Palma

Publications and source records attributed to G Palma.

At least 19 recordsLinked to original sources
PubMed2006

Temperature dependence of universal fluctuations in the two-dimensional harmonic XY model.

We compute exact analytical expressions for the skewness and kurtosis in the two-dimensional harmonic XY model. These quantities correspond to the third and fourth normalized moments of the probability density function (PDF) of the magnetization of the model. From their behavior, we conclude that they depend explicitly on the system temperature even in the thermodynamic limit, and hence the PDF itself must depend on it. Our results correct the hypothesis called universal fluctuations, they confirm and extend previous results which showed a T dependence of the PDF, including perturbative expansions within the XY model up to first order in temperature.

Journal Article↗
PubMed2005

Corrections to universal fluctuations in correlated systems: the two-dimensional XY model.

Generalized universality, as recently proposed, postulates a universal non-Gaussian form of the probability density function (PDF) of certain global observables for a wide class of highly correlated systems of finite volume N. Studying the two-dimensional XY model, we link its validity to renormalization group properties. It would be valid if there were a single dimension 0 operator, but the actual existence of several such operators leads to T-dependent corrections. The PDF is the Fourier transform of the partition function Z(q) of an auxiliary theory which differs by a dimension 0 perturbation with a very small imaginary coefficient iq/N from a theory which is asymptotically free in the infrared. We compute the PDF from a systematic loop expansion of ln Z(q).

Journal Article↗
PubMed2003

On the species specificity of sperm binding and sperm penetration of the zona pellucida.

Sperm binding and sperm penetration of the zona pellucida (zp) are regarded as species-specific. In this investigation, the interactions between bovine oocytes and porcine, respectively, equine spermatozoa have been studied under in vitro conditions and compared with the normal in vitro fertilization of bovine oocytes by bovine sperm. Surprisingly, many of the heterologous spermatozoa adhered firmly to the bovine oocytes and could not be removed by intense washing. On average, more than 100 boar or equine spermatozoa were bound to the zp of bovine oocytes. Electron microscopic studies clearly demonstrated that porcine sperm attached to the zona and underwent the acrosome reaction. Equine spermatozoa displayed a similar binding affinity, but unlike the porcine spermatozoa even penetrated the zp and were taken up into the oocyte after a longer period of co-incubation. Considering these new results the dogma of a strict species specificity of sperm zona interactions under in vitro conditions has to be reconsidered.

Acrosome↗
PubMed2003

Repair of pulmonary artery sling by reimplantation without cardiopulmonary bypass.

A 20-month-old girl successfully underwent repair of pulmonary artery sling through a median sternotomy by division of the left pulmonary artery and its reimplantation into the main pulmonary artery without cardiopulmonary bypass or tracheal reconstruction. The patient is doing well on 18 months follow-up with unobstructed pulmonary blood flow and dramatic reduction of tracheal stenosis. Simple repair of pulmonary artery sling is feasible with good results in selected cases without tracheomalacia.

Abnormalities, Multiple↗
PubMed2002

Finite size scaling in the two-dimensional XY model and generalized universality.

In recent works [S. T. Bramwell, P. C. W. Holdsworth, and J.-F. Pinton, Nature (London) 396, 552 (1998); S. T. Bramwell et al., Phys. Rev. Lett. 84, 3744 (2000)], a generalized universality has been proposed, linking phenomena as dissimilar as two-dimensional (2D) magnetism and turbulence. To test these ideas, we performed Monte Carlo simulations of the 2D XY model. We found that the shape of the probability distribution function for the magnetization M is non-Gaussian and independent of the system size-in the range of the lattice sizes studied-below the Kosterlitz-Thoules temperature. However, our results suggest that in the full 2D XY model the shape of these distributions has a slight dependence on temperature-for finite volume-below the lattice-shifted critical temperature T*(L). This behavior can be explained by using renormalization group arguments and an extended finite-size scaling analysis, and by the existence of bounds for M.

Journal Article↗
PubMed2001

Functional morphology of the zona pellucida.

The zona pellucida (ZP) is an extracellular matrix surrounding the oocyte and the early embryo that exerts several important functions during fertilization and early embryonic development. The ZP of most mammalian species is composed of three major glycoproteins that show considerable heterogeneity due to extensive post-translational modifications. Sodium dodecyl sulphate polyacrylamide gel electrophoresis of the ZP reveals three to four glycoproteins which have been nominated ZPI. ZP2, ZP3 and ZP4. As cloning and characterization of the ZP genes of a variety of mammalian species including domestic animals show a high homology, three classes of ZP genes, ZPA, ZPB and ZPC can be discerned. The corresponding proteins were named ZPA, ZPB and ZPC. Whereas in the mouse ZPB is the primary sperm receptor. the situation is more complicated in other species. For instance, in the pig ZPA has been shown to possess receptor activity. Interaction between gametes during fertilization is at least in part regulated by carbohydrate moieties of the ZP and carbohydrate-binding proteins of the sperm surface. In domestic animals zona proteins are expressed in both the oocyte and granulosa cells in a stage-specific pattern and may play a role in granulosa cell differentiation. The role of ZP glycoproteins in immunocontraception is briefly discussed.

Animals↗
PubMed2000

Activity enhancement by the support in the hydrogenation of C=C bonds over polymer-supported palladium catalysts

Four synthetic ion-exchange resins (AH, BH, CH, DH) of different hydrophilic/hydrophobic properties were used as supports for heterogeneous palladium catalysts (A, B, C, D). The resins contained styrene (STY) and 2-(methacryloxy)ethylsulfonic acid (MESA) as the comonomers. Either divinylbenzene (DVB: CH, DH resins) or N,N'-methylenebisacrylamide (MBAA: AH, BH resins) were used as the cross-linker. AH contained also N,N-dimethylacrylamide (DMAA) as the third comonomer. The catalysts (Pd 0.25-0.45% w/w) were obtained by ion-exchanging the acidic forms of the resins with [Pd(OAc)2] and reducing palladium(II) with excess sodium borohydride. The use of NaBH4 also ensured the neutralization of the acidic sites of the supports. No effect of the hydrophilic/hydrophobic properties of the supports was observed in the hydrogenation of cyclohexene and 2-cyclohexen-1-one in methanol, at 25 degrees C and 0.5, 1, and 1.5 MPa, respectively. However, catalysts A and B, containing amido groups provided by either DMAA or MBAA, proved to be more active than C and D. The observed activity enhancement was directly proportional to the nitrogen/ palladium molar ratio in the catalysts. This finding suggests that amido groups promote palladium through a direct interaction with the metal surface.

Journal Article↗
PubMed1999

[Late traumatic rupture of the chordae tendineae].

A rare case of traumatic rupture of chordae tendineae with tricuspid regurgitation is described. The rupture occurred later trauma, with an unusual mechanism, in fact it has been produced by the strangling of valvular apparatus. This strangling occurred because heart's displacement in left thorax trough a pleural-pericardial window caused by trauma.

Accidents, Traffic↗
PubMed1999

Amperometric biosensor involving covalent immobilization of choline oxidase and butyrylcholinesterase on a methacrylate-vinylene carbonate co-polymer.

A two-enzyme sensor for the determination of choline esters was prepared by the covalent co-immobilization of choline oxidase and butyrylcholinesterase on polymer membranes, obtained by radiation-induced co-polymerization of 2-hydroxyethylmethacrylate and vinylene carbonate at low temperature. The enzyme-modified membrane was applied to a platinum electrode and the determination of substrates was based on the electrochemical detection of enzymically generated H2O2. The analytical characteristics of this sensor, including the optimization of immobilization procedures, calibration curves for different substrates, pH and temperature effects and stability, are described.

Alcohol Oxidoreductases↗
PubMed1998

Differential expression of ZPC in the bovine ovary, oocyte, and embryo.

Using nonradioactive in situ hybridization (ISH), the mRNA encoding the zona glycoprotein bZPC was localized in bovine ovaries, oocytes, and embryos. In the ovary, the distribution of the mRNA was correlated with the developmental stage of the follicle. Whereas in primordial and primary follicles the mRNA was predominantly seen in the oocyte, it was found in both the oocyte and the follicle cells of secondary and tertiary follicles. In 2-day-old embryos produced by in vitro fertilization (IVF), no mRNA encoding ZPC could be demonstrated. Immunoblotting using monospecific polyclonal antibodies against porcine ZPC revealed a distinct band at a molecular weight of 47 kD in the ovarian cortex of cows, calves, and fetuses as well as in bovine follicle cells. Immunohistochemistry using the ZPC antibody displayed a strong signal in the zona pellucida of bovine oocytes and 2- to 6-day-old embryos as well as in the follicle cells. Our results show that during follicular development bovine ZPC is synthesized by the oocyte of the primary follicle and by both the oocyte and the follicle cells of the secondary and tertiary follicle. After fertilization, the synthesis of the zona protein is finished.

Animals↗
PubMed1998

Covalently immobilized choline oxidase and cholinesterases on a methacrylate copolymer for disposable membrane biosensors.

Bienzymatic sensors for the determination of esters of choline were prepared by covalent co-immobilization of cholinesterases and choline oxidase on polymer membranes, obtained by radiation-induced copolymerization of 2-hydroxyethyl methacrylate and glycidyl methacrylate at low temperature. Optimization of the covalent attachment of choline oxidase and acetyl- or butyrylcholinesterase to copolymer was explored. The enzyme-modified polymers were applied on platinum electrodes to form amperometric sensors, based on the electrochemical detection of enzymatically developed hydrogen peroxide. Acetyl-, acetylthio-, butyryl-, and butyrylthiocholine contents in standard solutions were measured, and linear calibration curves were determined. Temperature and pH effects on the electrochemical response are described.

Alcohol Oxidoreductases↗
PubMed1998

Topography of growth hormone receptor expression in the bovine embryo.

Using in situ hybridization, mRNA encoding the growth hormone receptor (GHR) was localized in preimplantation embryos produced by in vitro fertilization (IVF) as well as in 30- to 70-day-old bovine embryos. In IVF embryos the transcript of GHR was demonstrated in the inner cell mass of 8-day-old blastocysts. In 30-day-old embryos, the mesonephros was the first organ to express the mRNA of GHR. In 40-day-old embryos, the transcript was found in the neurones of the spinal ganglions, the splanchnic nerves and the motoneurones of the spinal cord, in the vascular endothelium, and in the developing striated muscle tissue. Colocalization of the protein by immunohistochemistry showed an identical distribution pattern of GHR in 30- to 70-day-old embryos.

Animals↗
PubMed1997

Dipyridamole-induced ischemia as a prognostic marker of future adverse cardiac events in adult patients with hypertrophic cardiomyopathy. Echo Persantine Italian Cooperative (EPIC) Study Group, Subproject Hypertrophic Cardiomyopathy.

BACKGROUND: Myocardial ischemia may play a role in the natural history of hypertrophic cardiomyopathy (HCM). To assess the relative prevalence and the prognostic value of dipyridamole-induced ischemia, 79 patients with HCM and without concomitant coronary artery disease (53 men; mean age, 46+/-15 years) underwent a high-dose (up to 0.84 mg/kg over 10 minutes) dipyridamole test with 12-lead ECG and two-dimensional echo monitoring and were followed up for a mean of 6 years. METHODS AND RESULTS: Twenty-nine patients (37%) showed ECG (ie, ST depression > or = 2 mV) signs of myocardial ischemia during dipyridamole test (group 1), whereas 50 (63%) had a negative test (group 2). No patient had transient wall motion abnormalities during the dipyridamole test. During the follow-up, 16 events (ie, left ventricular or atrial enlargement, unstable angina, syncope, atrial fibrillation, and bundle-branch block) occurred in 29 patients in group 1 and 5 in 50 patients in group 2 (55% versus 10%, P<.001). Patients with a positive dipyridamole test showed worse 72-month event-free survival rates compared with patients with a negative test (36.2% versus 84.2%, P<.001). A forward stepwise event-free survival analysis identified dipyridamole test positivity by ECG criteria (chi2=19.7, P=.0001), rest gradient (chi2=11.3, P=.0008), and age (chi2=4.1; P=.0413) as independent and additive predictors of subsequent events. CONCLUSIONS: ECG signs of myocardial ischemia elicited by dipyridamole are frequent in patients with HCM and identify patients at higher risk of cardiac events, suggesting a potentially important pathogenetic role of inducible myocardial ischemia in determining adverse cardiac events in these patients.

Adult↗
PubMed1995

Peripheral nerve repair using a poly(organo)phosphazene tubular prosthesis.

Nerve regeneration experiments were carried out using tubular nerve guides of poly[(ethylalanato)1.4(imidazolyl)0.6phosphazene] (PEIP). By means of in vivo tests, this polymer was found to be biodegradable and transformed into harmless products. The tubular nerve guides were prepared by deposition of the dissolved polymer on a glass capillary tube, followed by evaporation of the solvent (methylene dichloride). After transectioning, rat sciatic nerve stumps were immediately sutured into the ends of 10-mm-long polymer tubes. On removal of the prosthesis, after implantation for 45 d, a tissue cable was found bridging the nerve stumps in all cases. Histological analysis revealed that the tissue cable was essentially composed of a regenerated nerve fibre bundle. A parallel series of experiments was undertaken to compare the use of silicone tubes that are not biodegradable and are most frequently used for studies of nerve regeneration with tubulization techniques. The advantages of biodegradable PEIP tubular nerve guides used for peripheral nerve repair are discussed.

Animals↗
PubMed1994

Radiation grafting of hydrophilic monomers onto poly[bis(trifluoroethoxy)phosphazene].

The hydrophilic monomers dimethylacrylamide (DMAA) and acrylamide (AAm) were radiation grafted onto poly[bis-(trifluoroethoxy)phosphazene] (PTFP) for biocompatibility enhancement through direct irradiation of the polymer films immersed in monomer-solvent mixtures, and the progress of grafting was followed up to a large monomer depletion. The water absorption of the samples was found to increase as the amount of the grafted chains increased. The grafted chains, mainly confined in the film surface at high dose rates, progressively extend to the interior of the sample as the dose rate decreases. In the grafted samples the ultimate mechanical properties epsilon r and sigma r were essentially preserved. The in vivo tests indicated an enhancement of surface biocompatibility in the PTFP-g-AAm samples and not in the PTFP-g-DMAA samples.

Absorption↗
PubMed1994

Technetium-99m methoxy isobutyl isonitrile simultaneous evaluation of ventricular function and myocardial perfusion in patients with congenital heart disease.

The authors evaluated the clinical applications of Tc-99m methoxy isobutyl isonitrile (MIBI) in the simultaneous assessment of ventricular function and myocardial perfusion in patients with congenital heart disease. Global ventricular function was assessed by first-pass ECG gated study. Myocardial perfusion was evaluated on images performed 1 hour after the injection of the tracer. Regional wall motion and systolic thickening were assessed by gated study acquired after the perfusion study. Two young patients were studied after a surgical Glenn procedure. The first patient, with a history of transposition of the great vessels and univentricular heart, had an ejection fraction of 44%. The left ventricle was dilated and the right ventricle was not appreciable. The septal and inferoapical regions showed reduced perfusion and reduced systolic thickening. The second patient, with a history of pulmonary atresia, septal defect and left ventricular hypoplasia, had a right ventricular ejection fraction of 37%. Regional wall motion, systolic thickening, and myocardial perfusion were normal. The right ventricle was hypertrophic and larger than the left ventricle. Thus, a single injection of Tc-99m MIBI allows noninvasive simultaneous assessment of global and regional ventricular function and myocardial perfusion in young patients with complicated congenital heart disease.

Child, Preschool↗
PubMed1993

Polyphosphazenes as biomaterials: surface modification of poly(bis(trifluoroethoxy)phosphazene) with polyethylene glycols.

Investigations were carried out on the metathetical exchange reaction between the -O-CH2CF3 moieties of poly(bis(trifluoroethoxy)phosphazene) (PTFP), in the state of slightly swollen films, and the alkoxide ions derived from methoxypolyethylene glycol (MPEG) of molecular mass ranging from 350 to 5000 g/mol. The substitution of these hydrophilic chains, mostly confined to thin surface layers, was revealed by means of optical microscopy and scanning electron microscopy observations, surface elemental analysis by energy-dispersive X-ray analysis (EDXA), FTIR-ATR analysis and water contact angle measurements. The surface biocompatibility was enhanced in all cases, whilst the mechanical properties of the original PTFP films were substantially retained in the modified samples exhibiting low substitutions. Such samples were obtained especially when the metathetical reaction was carried out with MPEG5000.

Animals↗