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Biomedical subjects

M Scarpa

Publications and source records attributed to M Scarpa.

At least 55 records · Page 3Linked to original sources
PubMed1995

Parkinson's disease affects automatic and spares intentional verbal learning. A stochastic approach to explicit learning processes.

We studied word list and paired associates learning in patients with idiopathic Parkinson's disease and normal controls by means of a two-stage stochastic model, which allows independent measurements of encoding, storage and retrieval abilities. We preliminarily ascertained that the model components were both sufficient and necessary to account for the overall performance of the subjects, and then compared the learning abilities between the two groups. Parkinson's disease patients were selectively impaired in identifying well-known engrams, for which learning is superfluous, and in automatic retrieval, namely in abilities that do not need attentional effort. By contrast, they were unimpaired in encoding and intentional retrieval, which require a purposeful effort. The automatic-voluntary dissociation of Parkinson's disease patients' motor behaviour is, therefore, paralleled by some features of their memory performance.

Aged↗
PubMed1995

Covert visuospatial attentional mechanisms in Parkinson's disease.

Orienting and focusing of attention were assessed in 32 Parkinson's disease and 32 control subjects. No differences were found in the covert orienting of attention, suggesting that the Parkinson's disease subjects of the current study were not impaired in the ability to orient attention towards an expected source of stimulation. However, with the process of modulating the attentional focus or of managing more than one attentional task, dysfunction in Parkinson's disease subjects became apparent. The observed results are explained in terms of deficits in the relationship between task-related distribution of attentional resources and time efficiency of processing.

Attention↗
PubMed1994

Electrostatic control of oxidative deamination catalysed by bovine serum amine oxidase.

The ionic-strength-dependence of steady-state kinetic parameters (kc and Km') for non-biogenic (benzylamine, butylamine) and biogenic (spermine, spermidine) amines has been measured in the bovine serum amine oxidase reaction. The catalytic rate constant (kc) values are similar (0.9-2.5 s-1) for all the substrates studied and are almost constant over the experimental ionic strength range (24-155 mM). In contrast, Km' values are in the range 6-2300 microM and undergo a 4-12-fold increase with increasing ionic strength, parallelled by a decrease in catalytic efficiency. From an analysis of the kc and Km' values and their dependence on ionic strength, we conclude that more than one negative site is involved in the binding of these amines and that the relative dielectric constant of the binding site is lower than that of aqueous solutions.

Amine Oxidase (Copper-Containing)↗
PubMed1994

Perturbation of a prehension movement in Parkinson's disease.

Movement kinematics of the transport and manipulation components of a double-step prehension task were studied in eight Parkinson patients and eight control subjects. The aims were to (a) assess the effects of a spatial perturbation upon the movement for the two groups and (b) add data to the controversy about the damage/preservation of predictive behaviour in Parkinson patients. The results showed: (a) Both groups are able to preprogram a movement. (b) In both groups, the perturbation results in an anticipation of all kinematic parameters, both of the transport and manipulation components. (c) Parkinson patients, when adopting a predictive behavior, show a delay between the beginning of the two components, and thus activate them in sequence rather than simultaneously. This delay is significantly reduced by the perturbation, indicating that Parkinson patients, when using a responsive behavior, can recouple the two motor components.

Aged↗
PubMed1994

A sensitive spectrophotometry-based method for the determination of the rate of hydrogen peroxide generation in biological systems.

A new sensitive spectrophotometric method for the determination of the rate of hydrogen peroxide generation in biological systems has been developed. This method is based on the measurement of the oxidation rate of reduced cytochrome c by H2O2 in the presence of a mediator and permits the detection of H2O2 generation rates as low as 60 nM min-1. The solution of the differential equations of the kinetic process permitted the calculation of the kinetic rate constants and assessment of the conditions required to measure the hydrogen peroxide generation rate.

Amine Oxidase (Copper-Containing)↗
PubMed1994

Antiretroviral activity of furocoumarins plus UVA light detected by a replication-defective retrovirus.

The replication defective retrovirus, pXM5(N2), was used for an easy, safe and reproducible test for the screening of furocoumarins with antiretroviral activity. High titer viral supernatants have been photomodified by UVA light (20 kJ m-2) in the presence of different concentrations of two psolarens (8-methoxypsoralen, 8-MOP and 4,5',8-trimethylpsoralen, TMP) and one angelicin (4,6,4'-trimethylangelicin, TMA). At low concentrations (100-250 ng ml-1) 8-MOP and TMA did not show any significant antiviral activity, while TMP demonstrated a reduction of virus infectivity by one log at 250 ng ml-1. At the highest concentration (5 micrograms ml-1), TMA and TMP reduced the virus titer by one and more than two logs, respectively, being, therefore, two and four times more active than 8-MOP. The most active compound, TMP, was further tested on HIV-1 viral supernatants. Total inactivation of the HIV-1 (200 SFU) was obtained in the presence of 1 microgram ml-1 of TMP and 20 kJ m-2 of UVA light. Our results support the validity of the N2 system to detect the antiretroviral activity of furocoumarins and suggest the potential of TMP in combination with UVA light against HIV-1.

3T3 Cells↗
PubMed1994

Gene transfer in regenerating muscle.

We have compared the efficiency of direct gene transfer in normal and regenerating rat skeletal muscle. Muscle necrosis and regeneration was induced by intramuscular injection of bupivacaine in the soleus muscle of adult rats. Plasmids containing beta-galactosidase (beta-gal) or chloramphenicol acetyltransferase (CAT) genes driven by viral promoters were injected 3 days after bupivacaine treatment into the regenerating and the contralateral uninjured muscles. Expression of CAT activity was > 80-fold higher in regenerating compared to control muscles at 7 days post-transfection, but decreased at 30 and 60 days. Southern blot analysis showed that the predominant form of CAT DNA was episomal in transfected muscles; however, CAT activity measurements performed on the same transfected muscles showed no precise correlation between enzymatic activity and amount of plasmid DNA. Expression of beta-gal was detected in numerous regenerating fibers of the injured soleus muscles at 7 days post-transfection; in contrast, only rare positive fibers were found in control muscles. Focal infiltrates of mononuclear cells, which surround and invade selectively beta-gal-positive fiber segments, were observed at 30 days post-transfection, suggesting that immune mechanisms are implicated in the progressive loss of transgenes with time. The finding that regenerating muscle fibers display a higher efficiency of transfection may be relevant to gene therapy of Duchenne muscular dystrophy, because regenerating fibers are numerous in the early stages of the disease.

Animals↗
PubMed1993

Uptake and life time of fluoride ion in rats by 19F-NMR.

19F nuclear magnetic resonance (NMR) was utilized to obtain information on the uptake and half-life time of fluoride ion in rats. Changes in tissue fluoride level after acute loading were monitored over time in blood and tissue homogenates obtained from liver and brain. The rate of fluoride elimination from various tissues was roughly similar, following in all cases a first-order kinetic rate law. The F- concentration in brain was about 20% of that found in liver, indicating a reduced fluoride diffusion across the blood-brain barrier. In vivo F- spectra were obtained in rat brain in few minutes with a good signal-to-noise ratio; this confirms the possibility of extending the use of F- as a probe of biomolecules to in vivo applications.

Animals↗
PubMed1992

Effect of phosphate ion on the activity of bovine plasma amine oxidase.

The system bovine plasma amine oxidase-polyamine-phosphate ion was investigated by activity measurements and 31P NMR spectroscopy. Lineweaver-Burk plots showed that phosphate ion, under physiological conditions, is an apparent competitive inhibitor of bovine plasma amine oxidase. While NMR measurements of the T1 of 31P do not suggest the binding of phosphate to/or near the paramagnetic Cu(II) sites of bovine plasma amine oxidase, the chemical shift dependence of 31P on spermidine concentration indicates the formation of a spermidine-phosphate complex. The value of the dissociation constant of this complex was found 18.5 +/- 1.4 mM, at pH 7.2, by NMR, in good agreement with the value 17.0 +/- 0.8 mM calculated from activity measurements, assuming the enzyme activity is proportional to the free amine concentration, under second order conditions. Our data suggest that the decrease of the free spermidine, due to the binding of phosphate ion, is responsible of the observed inhibition of bovine plasma amine oxidase.

Amine Oxidase (Copper-Containing)↗
PubMed1992

Temporal coupling between transport and grasp components during prehension movements: effects of visual perturbation.

The temporal coupling between the transport and grasp components of prehension movements was investigated through two experiments. In Experiment 1, six normal subjects were required to reach and grasp each of three spheres located at three different distances (Blocked trials). In Experiment 2, a visual perturbation paradigm was used in which the location of the object to be reached and grasped could change at the beginning of arm movement (Perturbed trials). The same subjects participated in both experiments. Kinematics of wrist trajectory (transport component) and of distance between thumb and index finger (grasp component) were analyzed. The results of Experiment 1 showed that the two components could be temporally coupled during their time course. In Experiment 2, the visual perturbation affected both the components, but different times were required by each component to reorganize the movement towards the new target. These different times caused the decoupling of those events that appeared synchronized in Experiment 1. Finally, evidence was found to suggest that planning of grip formation takes into account not only the perceived characteristics of the object, but also the time planned by the transport component to reach the object.

Acceleration↗
PubMed1992

ATP-stimulated glutamate-dependent calcium uptake by rat synaptosomes.

The entry of Ca2+ in rat synaptosomes was followed with a Ca(2+)-selective electrode. Extracellular ATP is necessary for the entry which is a function of synaptosomal protein, free Ca2+ and glutamate concentrations. Ketamine, glycine and kainate have negligible effect while quisqualate slightly inhibits the uptake of Ca2+ in the presence of glutamate. The added ATP is hydrolyzed by the synaptosomes through an ouabain-insensitive ecto-ATPase affected by the presence of Ca2+, glutamate and, to a slight extent, NMDA.

Adenosine Triphosphate↗
PubMed1992

Added ATP influences some responses of rat synaptosomes to glutamate.

ATP added externally to rat synaptosomes activated uptake of both Ca2+ and glutamate which was partially accounted for by the uptake phenomena of synaptic vesicles and mitochondria, as shown by using specific inhibitors of the latter. Increasing concentrations of glutamate stimulated Ca2+ entry linearly, as shown by using 45Ca or a Ca-specific electrode. The processes of glutamate and Ca2+ uptake shared some common features and their ATP-dependence may be correlated with an ouabain-insensitive synaptosomal ectonucleotidase activity measured by a 31P-NMR or a luminometric technique. The ATP hydrolysis catalysed by the synaptosomes was activated by both Ca2+ and glutamate. The present synaptosomal activities may represent a model for studying the modulatory effects of ATP on the glutamatergic neurotransmission.

Adenosine Triphosphate↗
PubMed1992

Screening for cystic fibrosis gene mutations by multiplex DNA amplification.

We have developed a simple rapid DNA screening test that allows us simultaneously to analyze seven CF mutations (delta F508, R347P, S549N, G551D, R553X, R334W, 444delA) that together account for about 60% of all CF mutations in the Italian population. It consists of three steps: multiplex polymerase chain reaction (PCR) amplification of exons 4, 7, 10 and 11; restriction endonuclease digestion of the PCR products; and vertical polyacrylamide gel electrophoresis analysis. We have used our multiplex assay for analyzing 15 CF chromosomes (non delta F508) and have found 3 cases of the R553X mutation; the latter have been confirmed by amplification and digestion of exon 11.

Amino Acid Sequence↗
PubMed1992

A model-based study of learning and memory following transient global amnesia attacks.

Verbal learning and forgetting were studied in patients one month after an episode of Transient Global Amnesia and in normal control subjects by means of a two-stage stochastic model, which allows independent measurements of encoding, storage and forgetting. We preliminarily ascertained both the necessity and the sufficiency of the model to account for several performance scores of the two experimental groups, and then compared the learning and forgetting functions between groups. In spite of the analytical power of the statistical method adopted. Transient Global Amnesia was not found to entail persistent impairment of encoding and storage, as well as of retaining memory traces and retrieval algorhythm.

Cerebral Cortex↗
PubMed1991

Influence of different types of grasping on the transport component of prehension movements.

The main aim of the present study was to clarify whether different types of grasping may affect the transport component of prehension movements. To this purpose two experiments were carried out. In the first experiment the kinematics of arm movements (transport and manipulation components) were studied in eight normal subjects instructed to reach and grasp different objects located either 20 or 30 cm from their hand. The objects employed required two different types of grip: prehension with the whole hand and prehension with the index finger and the thumb (precision grip). In the second experiment subjects were instructed to point to the same objects employed in the first experiment. This experiment served as a control for the precision requirements related to the object size. The results showed that, once the precision requirements were taken into account, the transport component remained unmodified with the different types of grip. The time course of the manipulation component and its temporal relations with the transport component changed with the type of grasping. The maximal hand aperture was reached earlier in the precision grip than in the whole hand prehension and the temporal coupling with the transport component was weaker in the former condition than in the latter. The data are interpreted as further evidence in favour of independence between the transport and the manipulation "channels".

Adolescent↗
PubMed1991

Characterization of recombinant helper retroviruses from Moloney-based vectors in ecotropic and amphotropic packaging cell lines.

We have characterized the recombinant replication-competent retrovirus (RCV) arising from p delta N2-derived vectors in the packaging cell lines psi 2 (ecotropic) and PA317 (amphotropic). Detailed restriction patterns and sequence of the envelope region of these RCVs has indicated that they arose from recombination events between the virus plasmids used to create the packaging cell line and the vectors. There was no evidence of recombination involving endogenous murine retroviral sequences in the packaging cell line or in transduced hematopoietic cells. In addition, we have confirmed that the mutation of the start codon of the pXM5(N2) derivatives gag+ sequence drastically decreased the occurrence of RCV production. These results offer encouragement that the risk of RCV production can be adequately decreased in gene therapy applications of defective retrovirus vectors.

Adenosine Deaminase↗
PubMed1991

Gene transfer of adenosine deaminase into primitive human hematopoietic progenitor cells.

The inherited deficiency in adenosine deaminase (ADA), which results in severe combined immunodeficiency, is generally regarded as an optimal model for the development of human somatic gene therapy. The ideal target for the correction of ADA deficiency and other lympho-hematopoietic disorders would be the hematopoietic stem cell. We have used a combination of recombinant human interleukins-3 and -6 to stimulate the proliferation of primitive human hematopoietic progenitor cells during a period of co-cultivation with irradiated cells producing high titers of an ADA-transducing retroviral vector packaged in amphotropic particles. In a series of nine experiments, an average of 83% of the clonogenic progenitors (CFU-E and CFU-GM) were found to have acquired the transferred sequence as determined by polymerase chain reaction analysis. In addition, in two experiments, 24-44% of the clonogenic progenitors derived from long-term myeloid cultures 9 weeks post-transduction were found to contain vector sequence. The latter cells are derived from so-called "long-term culture-initiating cells" (LTC-IC), which are primitive cells probably related to hematopoietic stem cells. Moreover, the transduced ADA enzyme was found to be expressed in both normal and ADA-deficient erythroid colonies, and in the nonadherent cells of long-term bone marrow culture for at least 2 weeks at levels that approximate the endogenous ADA levels of normal erythroid cells. These results indicate that the ADA coding sequence can efficiently be introduced by retroviral gene transfer into both committed and primitive human hematopoietic progenitor cells, and that this will result in adequate expression of the transduced enzyme in the progeny of committed hematopoietic progenitors.

Adenosine Deaminase↗