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Biomedical subjects

F Rossi

Publications and source records attributed to F Rossi.

At least 343 records · Page 19Linked to original sources
PubMed1995

Target neuron controls the integrity of afferent axon phenotype: a study on the Purkinje cell-climbing fiber system in cerebellar mutant mice.

The effects of target loss on adult axonal arbors were investigated by comparing the morphological changes of adult climbing fibers in several mutant mouse strains where Purkinje cells slowly degenerate (namely, Lurcher, nervous, Purkinje cell degeneration, and tambaleante), with those occurring after a fast Purkinje cell death induced by mechanical lesions of the adult mouse cerebellum. In each of the different mutations, Purkinje cells displayed distinctive structural modifications. However, a set of regressive changes common to all strains could be disclosed, mostly dendritic atrophy and a progressive axonal retraction with the hypertrophy of recurrent collaterals. Climbing fibers that contacted such degenerating neurons also showed abnormal morphological features, consisting in the presence of extensive perisomatic plexuses, whereas peridendritic branches were atrophic or absent. In Lurcher mice, target-deprived climbing fibers were strictly confined around the granular-molecular layer interface and never penetrated into the molecular layer. Similar terminal plexuses at the level of the former Purkinje cell layer were observed in the other mutants. However, in the latter cases, atrophic terminal arbors were also present in the molecular layer, being confined to the deep portions in nervous, while spanning its whole extent in Purkinje cell degeneration and tambaleante mice. Following mechanical lesions, atrophic target-deprived climbing fibers were exclusively located in the molecular layer. In addition, some of the Purkinje cells that survived after the injury displayed regressive modifications similar to those observed in mutant mice, and their climbing fibers were characterized by perisomatic plexuses. These results show that the normal relationship between the climbing fiber and its Purkinje cell is already disrupted during the slow degeneration of the target neuron. As a consequence, the phenotypic pattern of target-deprived climbing fibers reflects the preceding interactions with their postsynaptic neurons and it is determined by the onset time and progression rate of Purkinje cell degeneration.

Afferent Pathways↗
PubMed1995

Effects of RO 5-4864 and PK 11195 on guinea pig trachea.

Previous reports have suggested a role played by peripheral benzodiazepine receptors (PBZ) in the regulation of calcium. The aid of this investigation was to evaluate the effects of Ro 5-4864 (PBZ agonist) and PK11195 (PBZ antagonist) in guinea pig trachea and their possible role in the regulation of calcium. Ro 5-4864 and PK 11195 showed spasmolytic effects on the contraction curve induced by acetylcholine. Moreover, Ro 5-4864, PK 11195 and diltiazem (a Ca2+ -antagonistic drug) shifted to the right the contraction curves induced by acetylcholine, potassium chloride (KCl), calcium chloride (CaCl2), or by Bay K 8644. These results demonstrate that the benzodiazepines and their antagonists may exhibit Ca2+ -antagonistic activity. Ro 5-4864 and PK 11195 may exert this effect at a site that is a component of, or is associated with, voltage operated calcium channels (VOC).

Acetylcholine↗
PubMed1994

Vasomotor reactivity and catecholamine, arginine vasopressin plasma levels during ageing and development in rats.

Vascular reactivity, heart rate responses to vasoconstrictor and/or vasodilatator agents and catecholamine and arginine vasopressin turnover were studied in normotensive Wistar Kyoto (WKY), spontaneously hypertensive (SHR), normolipemic Brown Norway (BN) and spontaneously hyperlipemic Yoshida (YOS) anaesthetized rats at 2, 6 and 18 months of age. In this study, we investigated whether ageing and development could affect cardiovascular reactivity to vasoactive substances and catecholamine and arginine vasopressin turnover. No significant changes in the pressor responses to noradrenaline and to carotid sinus baroreceptor stimulation were observed nor were there significant alterations in reflex tachycardia and bradycardia. Arginine vasopressin plasma levels also did not change with ageing and development. On the other hand, the hypotensive responses to isoprenaline decreased in old rats, acetylcholine relaxation effect increased with ageing and development in some rat strains (BN and YOS) and catecholamine plasma levels increased with ageing and development. Our results indicate that during ageing and development, vascular responsiveness to vasoconstrictor and/or vasodilatator agents, as well as amine turnover, may increase, decrease or not change at all depending on the neurotransmission system studied, and on the experimental model and/or animal tested.

Acetylcholine↗
PubMed1994

Tyrosine phosphorylation and activation of NADPH oxidase in human neutrophils: a possible role for MAP kinases and for a 75 kDa protein.

Challenge of neutrophils with concanavalin A (ConA), formyl-methionyl-leucyl-phenylalanine (FMLP), and phorbol 12-myristate 13-acetate (PMA) induced the tyrosine phosphorylation of several proteins. Among these proteins we have identified two mitogen-activated protein kinase (MAPK) isoforms of 43 kDa (p43 MAPK) and 45 kDa (p45 MAPK) molecular mass. Moreover here we show that: (1) FMLP induced the tyrosine phosphorylation of the p43 MAPK, and ConA that of p45 MAPK, while PMA induced the tyrosine phosphorylation of both p43 and p45 MAPK; all these agonists induced the tyrosine phosphorylation of a 75 kDa protein (p75). (2) With FMLP or ConA as agonists, tyrosine phosphorylations of MAPK and p75 can be involved in the process of NADPH oxidase activation. On the contrary, PMA can activate the respiratory burst independently of these phosphorylations. (3) In Ca(2+)-depleted neutrophils, where phospholipid hydrolysis did not take place, ConA or FMLP did not activate the respiratory burst, but while ConA induced the tyrosine phosphorylation of p45 MAPK and p75, FMLP was not able to phosphorylate p43 MAPK and p75. (4) As previously observed in our laboratory, a double stimulation of Ca(2+)-depleted neutrophils with ConA plus FMLP induced a respiratory burst in the absence of activation of second messengers derived from phospholipase C, D and A2 activity. This respiratory burst was accompanied by tyrosine phosphorylation of both p43 and p45 MAPKs. These results indicate that when FMLP is the agonist, both the tyrosine phosphorylation of p43 MAPK and p75, and the activation of NADPH oxidase, are coupled to Ca(2+)-dependent mechanisms. On the contrary, ConA can induce the tyrosine phosphorylation of p45 MAPK and p75 independently of calcium, but an unknown Ca(2+)-dependent mechanism is necessary for the activation of NADPH oxidase by this agonist. This mechanism could be substituted by the induction of tyrosine phosphorylation of both p43 MAPK and p45 MAPK when Ca(2+)-depleted neutrophils are stimulated with ConA plus FMLP.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1994

Tyrosine phosphorylation of phospholipase C-gamma 2 is involved in the activation of phosphoinositide hydrolysis by Fc receptors in human neutrophils.

The stimulation of phosphoinositide hydrolysis by a number of agonists (phosphoinositide response) is a ubiquitous transmembrane signalling process for the regulation of several cell functions. Two mechanisms of activation have been identified that involve different phospholipases C: one regulated by G-proteins and another regulated by receptors having an intrinsic tyrosine kinase domain or that stimulate intracellular tyrosine kinase activity. This last mechanism is activated in several immunological cells, including lymphocytes, mastocytes, NK cells and monocytes, in response to agonists that bind antigen receptors, and receptors for IgE and IgG. In the present study, we have investigated the role of tyrosine phosphorylation in the stimulation of phosphoinositide hydrolysis mediated by Fc gamma Rs in human neutrophils. The results demonstrated that: 1) the activation of Fc gamma Rs with insoluble immune complexes (IIC) induced a tyrosine phosphorylation of several proteins that was dose-dependently inhibited by the tyrosine kinase inhibitor, genistein; 2) the activation of Fc gamma Rs caused a stimulation of phosphoinositide hydrolysis measured as [3H]inositol phosphates formation; 3) genistein depressed the activation of phosphoinositide hydrolysis; 4) among the several proteins that became tyrosine phosphorylated upon Fc gamma Rs activation by IIC, one 145 kDa protein was identified as PLC-gamma 2, using a specific antiserum. The phosphorylation of PLC-gamma 2 was completely inhibited by genistein. These results demonstrate that the phosphoinositide response to activation of Fc gamma Rs involves the tyrosine phosphorylation of PLC-gamma 2.

Genistein↗
PubMed1994

In human neutrophils the binding to immunocomplexes induces the tyrosine phosphorylation of Fc gamma RII but this phosphorylation is not an essential signal for Fc-mediated phagocytosis.

It has been recently suggested that protein tyrosine phosphorylation is involved in Fc gamma Rs-mediated signalling. In this paper we have investigated if in human neutrophils a tyrosine phosphorylation of Fc gamma RII takes places after the binding with immunocomplexes and if this phosphorylation plays a role in phagocytic signal. The immunoprecipitation with mAb anti-Fc gamma RII of lysates of neutrophils challenged in suspension with insoluble immunocomplexes (IIC) or sheep erythrocytes opsonized with IgG (E-IgG), followed by immunoblotting with anti-phosphotyrosine antibody, demonstrated that Fc gamma RII was tyrosine phosphorylated. When neutrophils were pretreated with different doses of tyrosine kinase inhibitors, genistein or erbstatin, the phosphorylation of Fc gamma RII induced by IIC or E-IgG was dose dependently inhibited. In these conditions both genistein and erbstatin failed to inhibit the phagocytosis of E-IgG. These results demonstrated that in human neutrophils in suspension the binding to Fc of IgG induces a tyrosine phosphorylation of Fc gamma RII but this phosphorylation is not an essential signal for phagocytosis of IgG-opsonized particles.

Antigen-Antibody Complex↗
PubMed1994

Exposure to kainic acid mimics the effects of axotomy in cerebellar Purkinje cells of the adult rat.

We have investigated the long-term structural changes which affect Purkinje cells exposed to a single dose of kainic acid. Following intraparenchymal injection of the excitotoxin in the cerebellar cortex (1 microliter of a 1 mg/ml solution), Purkinje cells which survived within the lesioned area or close to its edges showed remarkable axonal abnormalities, involving the formation of torpedoes, hypertrophy of recurrent collaterals and atrophy of the corticofugal portion of the axon. In addition, their dendritic trees were often affected by conspicuous regressive alterations. The climbing fibres contacting these Purkinje cells were characterized by thick perisomatic plexuses, whereas their peridendritic branches were atrophic. The dendrites innervated by such atrophic olivary arbours were studded with huge numbers of newly formed spines. These alterations were already present a few days after kainic acid administration and persisted for the total period of observation of 6 months after the lesion. The remarkable similarity between the abnormalities of Purkinje cells exposed to kainic acid and those observed after axotomy indicates that in these two conditions common mechanisms determine analogous long-lasting modifications in the affected neurons. It is proposed that kainic acid-induced intracellular calcium overload disrupts cytoskeletal components and impairs axonal transport, thus depriving the affected Purkinje cells of retrograde trophic influences from their target neurons. As a consequence the affected neurons undergo long-lasting regressive modifications and compensatory remodelling phenomena.

Animals↗
PubMed1994

Sulfatides trigger increase of cytosolic free calcium and enhanced expression of tumor necrosis factor-alpha and interleukin-8 mRNA in human neutrophils. Evidence for a role of L-selectin as a signaling molecule.

Sulfatides have been established recently as ligands for L-selectin, and we investigated whether they trigger transmembrane signals through ligation of L-selectin. We found that sulfatides trigger the increase of cytosolic free calcium in neutrophils and that this effect was strictly dependent on sulfation of the galactose ring, as non-sulfated galactocerebrosides were not stimulatory. Chymotrypsin and phorbol 12-myristate 13-acetate treatment of neutrophils caused shedding of L-selectin, but not of class I major histocompatibility complex antigens or beta 2 integrins, and blunted the capability of neutrophils to respond to sulfatides with an increase of cytosolic free calcium. Four different anti-L-selectin antibodies (DREG-200, LAM1/3, LAM1/6, and LAM1/10), but not four control antibodies directed against different surface molecules of neutrophils, also triggered an increase of cytosolic free calcium. The anti-L-selectin antibodies were stimulatory both if used in a soluble form, after cross-linking with anti-mouse F(ab')2 fragments, and immobilized to protein A of Staphylococcus aureus through the Fc fragment. With immobilized antibodies, an increase of cytosolic free calcium was found also by plating neutrophils on antibodies bound to protein A-coated coverslips and monitoring the increase of cytosolic free calcium by fluorescence microscopy. Both sulfatides and anti-L-selectin antibody effects were not inhibited by pertussis toxin, thus indicating that a pertussis toxin-sensitive GTP-binding protein was not involved in signal transduction. Sulfatides also triggered an increase of tumor necrosis factor-alpha and interleukin-8 mRNAs in neutrophils. Also to act as stimuli of cytokine mRNA expression, sulfatides required sulfation of the galactose ring, as non-sulfated galactocerebrosides were not stimulatory, and depended on expression of L-selectin, as shedding of this molecules induced by chymotrypsin blunted their effects. These findings suggest that L-selectin can transduce signals activating selective cell function.

Calcium↗
PubMed1994

Evidence that arcaine increases the N-methyl-D-aspartate-induced cardiovascular effects into the periaqueductal gray area of anesthetized rats.

In the present study the influence of arcaine (0.01-1 microgram/rat), an in vitro putative non-competitive antagonist of the NMDA receptors, on cardiovascular changes induced by intracerebral administration of N-methyl-D-aspartate (NMDA) (0.1 microgram/rat) has been evaluated. Both NMDA and arcaine were microinjected into the periaqueductal gray (PAG) area of anesthetized rats. Arcaine did not decrease NMDA-induced arterial hypertension and tachycardia, but, in a dose-related manner, increased the NMDA-induced cardiovascular effects. Moreover, treatment with arcaine was not able per se to modify arterial blood pressure and heart rate basal values. Although updated in vitro reports indicate arcaine as a blocker of the NMDA receptors by an open channel mechanism, our in vivo results, at the level of the PAG area, show this not to be true. Indeed the drug may facilitate NMDA receptor activation.

2-Amino-5-phosphonovalerate↗
PubMed1994

Embryonic Purkinje cells grafted on the surface of the adult uninjured rat cerebellum migrate in the host parenchyma and induce sprouting of intact climbing fibres.

By grafting solid pieces of cerebellar anlage onto the surface of the adult rat cerebellum, we have investigated the problem of the interactions between embryonic and adult neurons in an intact brain. A few days after grafting, embryonic astrocytic processes crossed the graft--host interface and radiated into the recipient molecular layer. Several grafted Purkinje cells also migrated into the host brain along such processes as well as adult Bergmann glia. Adult climbing fibres, labelled by means of Phaseolus vulgaris leucoagglutinin (PHA-L), sprouted new collateral branches which terminated on embryonic Purkinje cells at both extra- and intraparenchymal levels. No sign of activation of host astroglia or microglia was evident in the host cerebellum in relation to these processes. Embryonic Purkinje cells which migrated into the host cerebellum developed an adult-like morphology. Intraparenchymal grafts of neocortical embryonic tissue induced conspicuous growth of host olivary axons, characterized by a pattern which was different from that observed following cerebellar grafts. By contrast, when neocortical tissue was placed onto the surface of the recipient cerebellum, graft--host interactions were limited and climbing fibre sprouting was rarely seen. These results show that (i) supernumerary Purkinje cells can penetrate and settle in the adult intact cerebellar cortex, (ii) adult climbing fibres are able to innervate these new targets in the absence of any injury or activation of non-neuronal cells of the adult brain, and (iii) in the absence of damage to the adult brain, the plasticity of adult olivary axons is specifically elicited and controlled by embryonic Purkinje cells.

Animals↗
PubMed1994

Bioactive peptides: solid state, solution and molecular dynamics studies of a cyclolinopeptide A-related cystinyl cyclopentapeptide.

The conformational analysis of [sequence: see text] the disulphide cyclopeptide-related cyclolinopeptide A, has been carried out by solid state methods using x-ray diffraction techniques, in solution by nmr, CD, ir spectroscopies, and by molecular dynamics (MD) analysis. The structure of the monoclinic form, obtained from ethanol (a = 11.303(2) A, b = 14.467(8) A, c = 12.355(2) A, beta(degree) = 109.40(1), space group P2(1), Z = 2) presents two transannular H bonds with the formation of one type VIa beta-turn involving the C = O of the urethane moiety and the Phe3 NH, and an intramolecular H bond between the C = O of urethane group and the Phe4 NH. In the solid state all the peptide bonds are in the trans configuration with the exception of a cis peptide bond occurring between the Cys1 and Pro2 residues; the linkage S-S assumes right-handed chirality. The conformational study in solution by nmr spectroscopy indicates that the peptide is very flexible and that some conformer families are present at room temperature both in polar and apolar solvents. CD studies confirm that this cyclic system tends to give rise to a complex mixture of quasi-isoenergetic conformations, favored by the flexibility of the disulphide bridge and by the isomerism of the Xxx-Pro bond. MD studies carried out in vacuo and in solution shows that the structure determined by solid state represents a energy minimum. All hydrogen bonds found in the crystalline state are correctly reproduced in vacuo and in solution simulations.

Amino Acid Sequence↗
PubMed1994

Synthesis and pharmacological evaluation of oligoethylene ester derivatives as indomethacin oral prodrugs.

Five indomethacin oligoethylene ester derivatives (3-7) were synthesized and evaluated for their anti-inflammatory, analgesic, and ulcerogenic activity after oral administration. The molecular weight of the oligoethylene glycols used for synthesizing esters 3-7 ranged from 106 to 282. The chemical and enzymatic stabilities of esters 3-7 were evaluated in pH 7.4 and 2.0 buffers and in human plasma, respectively. All the prodrugs showed a good stability both in pH 7.4 phosphate buffer and in pH 2.0 buffer, and they were readily hydrolyzed by human plasma. Esters 3-7 showed an anti-inflammatory activity, determined as the percent inhibition of carrageenan-induced edema, similar to that of indomethacin, although at higher doses. From writhing test results, we observed that all the prodrugs exhibited better or similar analgesic activity compared to indomethacin. Esters 3-7 were significantly less irritating to the gastric mucosa than indomethacin, after oral administration, and esters 3-5 did not show any ulcerogenic activity, although they were administered at higher doses than indomethacin.

Animals↗