Biomedical subjects

M Riva

Publications and source records attributed to M Riva.

At least 19 recordsLinked to original sources

PubMed2003

Assessment of the risk of physical contamination of bread packaged in perforated oriented polypropylene films: measurements, procedures and results.

Perforated films used for wrapping factory-manufactured bread must permit a very rapid and intense moisture exchange because the packaging operation is carried out while the bread is still warm (about 80 degrees C) and releasing a high quantity of moisture. The open surface of the wrapping of those products sold in self-service retail outlets generates suspicion about possible contamination of bread not properly handled by the consumers and a better knowledge of the performance of these materials seems appropriate. Using two different approaches, the geometrical characteristics and perforation pattern of 13 different oriented polypropylene (OPP) films representative of the whole European market were assessed objectively. All the measured parameters (density of perforation, hole dimension, open surface, etc.) showed asymmetric distributions, i.e. with averages close to the lowest figures. Similar asymmetric distribution was shown from the 'risk of contamination' by artificial sweat and saliva: an empirical parameter which was measured by procedures developed to simulate the worst possible case of inappropriate manipulation of the packed bread. Good correlation was found between the 'risk of contamination' and both the 'hole surface' (mm(2)) and the 'open surface' (percentage holes surface/film surface), leading to the conclusion that the proposed procedures could represent useful methodologies for assessment of such a particular case of possible food contamination.

Bread↗

PubMed2002

JET quasistationary internal-transport-barrier operation with active control of the pressure profile.

Quasistationary operation has been achieved on the Joint European Torus tokamak in internal-transport-barrier (ITB) scenarios, with the discharge time limited only by plant constraints. Full current drive was obtained over all the high performance phase by using lower hybrid current drive. For the first time feedback control on the total pressure and on the electron temperature profile was implemented by using, respectively, the neutral beams and the ion-cyclotron waves. Although impurity accumulation could be a problem in steady state ITBs, these experiments bring some elements to answer to it.

Journal Article↗

PubMed2001

Differential roles of phosphorylation in the formation of transcriptional active RNA polymerase I.

Regulation of rDNA transcription depends on the formation and dissociation of a functional complex between RNA polymerase I (pol I) and transcription initiation factor Rrn3p. We analyzed whether phosphorylation is involved in this molecular switch. Rrn3p is a phosphoprotein that is predominantly phosphorylated in vivo when it is not bound to pol I. In vitro, Rrn3p is able both to associate with pol I and to enter the transcription cycle in its nonphosphorylated form. By contrast, phosphorylation of pol I is required to form a stable pol I-Rrn3p complex for efficient transcription initiation. Furthermore, association of pol I with Rrn3p correlates with a change in the phosphorylation state of pol I in vivo. We suggest that phosphorylation at specific sites of pol I is a prerequisite for proper transcription initiation and that phosphorylation/dephosphorylation of pol I is one possibility to modulate cellular rDNA transcription activity.

Escherichia coli↗

PubMed2001

Stimulatory role of dopamine on fibroblast growth factor-2 expression in rat striatum.

We have previously shown that systemic injection of (-)nicotine produces a selective up-regulation of fibroblast growth factor (FGF)-2 mRNA levels in rat striatum. Because (-)nicotine can increase striatal release of dopamine and glutamate, in the present study we have investigated the contribution of these neurotransmitters in the modulation of FGF-2 expression. We found that coinjection of dopaminergic D1 (SCH23390) or D2 (haloperidol) receptor antagonists prevents nicotine-induced elevation of FGF-2 expression. However, injection of the NMDA receptor antagonist MK-801 produced a significant increment of FGF-2 mRNA and protein levels in rat striatum similar to the effect produced by (-)nicotine alone. Interestingly this effect of MK-801 could also be prevented by D1 or D2 receptor antagonists, suggesting that an elevation of dopamine levels may be required for the regulation of the trophic molecule. Accordingly we found that the non-selective dopaminergic agonist apomorphine can similarly increase striatal FGF-2 mRNA levels. Despite the observation that both D1 and D2 receptors appear to contribute to the modulation of FGF-2 expression, only a direct activation of D2 receptors, through quinpirole administration, was able to mimic the effect of apomorphine. On the basis of FGF-2 neurotrophic activity, these results suggest that direct or indirect activation of dopaminergic system can be neuroprotective and might reduce cell vulnerability in degenerative disorders.

Animals↗

PubMed2001

Microbiological quality and shelf life modeling of ready-to-eat cicorino.

Growth of the microbial population resident in ready-to-use fresh cut cicorino, a variety of Chichorium intybus, was determined in the various preparation steps with the aim of defining the hazard critical control points. The investigation concerned cut cicorino from two producers. During the process a 1- to 1.5-fold increase of microbial counts was observed, and the retail product showed values of 10(5) to 10(6) CFU/g. The shelf life of the product was kinetically modeled in order to check the effects of storage temperature and assess the microbial indexes most relevant for hygiene and quality of the distributed product. A modified Gompertz function described the kinetics of microbial growth and allowed definition of a stability time and its dependence on temperature. Stability times were of 0.3, 3.7, and 4.7 days at storage temperatures of 20, 10, and 5 degrees C, respectively. Q10 (the fold decrease of stability time for an increase of 10 degrees C) was 3.85. The results from this study may be used to predict the effects of temperatures experienced in the distribution chain on bacterial levels in cicorino.

Bacteria↗

PubMed2000

The recruitment of RNA polymerase I on rDNA is mediated by the interaction of the A43 subunit with Rrn3.

RNA polymerase I (Pol I) is dedicated to transcription of the large ribosomal DNA (rDNA). The mechanism of Pol I recruitment onto rDNA promoters is poorly understood. Here we present evidence that subunit A43 of Pol I interacts with transcription factor Rrn3: conditional mutations in A43 were found to disrupt the transcriptionally competent Pol I-Rrn3 complex, the two proteins formed a stable complex when co-expressed in Escherichia coli, overexpression of Rrn3 suppressed the mutant phenotype, and A43 and Rrn3 mutants showed synthetic lethality. Consistently, immunoelectron microscopy data showed that A43 and Rrn3 co-localize within the Pol I-Rrn3 complex. Rrn3 has several protein partners: a two-hybrid screen identified the C-terminus of subunit Rrn6 of the core factor as a Rrn3 contact, an interaction supported in vitro by affinity chromatography. Our results suggest that Rrn3 plays a central role in Pol I recruitment to rDNA promoters by bridging the enzyme to the core factor. The existence of mammalian orthologues of A43 and Rrn3 suggests evolutionary conservation of the molecular mechanisms underlying rDNA transcription in eukaryotes.

Amino Acid Sequence↗

PubMed2000

The effect of anticonvulsant drugs on blood levels of methotrexate.

The reduced bioavailability of chemotherapeutic agents is one of the reasons that explains the limited efficacy of adjuvant chemotherapy in high grade glioma patients. We report how even the results of high dose sequential chemotherapy can be influenced by antiepileptic drugs.

Adult↗

PubMed2000

Comparison of plateletpheresis concentrates produced with Spectra LRS version 5.1 and LRS Turbo version 7.0 cell separators.

BACKGROUND: The importance of transfusing WBC-reduced blood components is widely recognized, as it reduces the risk of alloimmunization and transfusion-transmitted CMV infections. The latest generation of cell separators allows the collection of WBC-reduced apheresis platelet concentrates (APCs). MATERIALS AND METHODS: Consecutive APCs (n = 232) were retrospectively evaluated: 163 collected with the Spectra LRS [leukocyte-reduction system] Version 5.1 (Group A) and 69 with the LRS Turbo Version 7.0 (Group B) (both: COBE BCT). Donor peripheral blood count, procedure data, platelet yield, collection efficiency (CE), and residual WBC count in APCs were recorded. RESULTS: The platelet yield was higher in Group B than in Group A: 5.5 +/- 1.4 versus 4.4 +/- 1.1, p<0.0001; residual WBCs were <5 x 10(6) in 99.4 percent of Group A APCs and in 97.1 percent of Group B APCs. CE was higher in Group B than in Group A: 51.4 +/- 8.7 versus 43.6 +/- 6.3, p<0.0001. Moreover, a correlation between predonation platelet count and platelet yield was observed in both groups. A double product (platelet yield >6.0 x 10(11)) was obtained in 28.9 percent of Group B APCs and in 9.2 percent of Group A APCs. CONCLUSIONS: The Spectra LRS Turbo version 7.0 release showed a better CE and resulted in a higher platelet harvest than did the LRS version 5.1. High predonation platelet counts allow a higher platelet yield.

Blood Cell Count↗

PubMed1999

Sequence divergence of the RNA polymerase shared subunit ABC14.5 (Rpb8) selectively affects RNA polymerase III assembly in Saccharomyces cerevisiae.

ABC14.5 (Rpb8) is a eukaryotic subunit common to all three nuclear RNA polymerases. In Saccharomyces cerevisiae, ABC14.5 (Rpb8) is essential for cell viability, however its function remains unknown. We have cloned and characterised the Schizosaccharomyces pombe rpb8(+) cDNA. We found that S.pombe rpb8, unlike the similarly diverged human orthologue, cannot substitute for S.cerevisiae ABC14. 5 in vivo. To obtain information on the function of this RNA polymerase shared subunit we have used S.pombe rpb8 as a naturally altered molecule in heterologous expression assays in S.cerevisiae. Amino acid residue differences within the 67 N-terminal residues contribute to the functional distinction of the two yeast orthologues in S.cerevisiae. Overexpression of the S.cerevisiae largest subunit of RNA polymerase III C160 (Rpc1) allows S.pombe rpb8 to functionally replace ABC14.5 in S.cerevisiae, suggesting a specific genetic interaction between the S.cerevisiae ABC14.5 (Rpb8) and C160 subunits. We provide further molecular and biochemical evidence showing that the heterologously expressed S.pombe rpb8 molecule selectively affects RNApolymerase III but not RNA polymerase I complex assembly. We also report the identification of a S.cerevisiae ABC14.5-G120D mutant which affects RNA polymerase III.

Amino Acid Sequence↗

PubMed1999

Use of the laparoscopic knot introducer in urethrovesical anastomosis following radical prostatectomy.

One of the most delicate stages of retropubic radical prostatectomy intervention is urethrovesical anastomosis, especially if it is performed in a deep bony pelvis with a short urethral stump. Correct knot tying is essential to avoid the risk of postoperative anastomotic leakage. In such conditions, the urethrovesical anastomosis is performed with six 4-0 Monocril sutures and the knots are tied under vision using the laparoscopic knot introducer. In a 2-year period we performed 106 retropubic radical prostatectomies in our urology department. In four cases (3.8%) we performed urethrovesical anastomosis with the aid of the described technique. Two weeks after catheter placement, the radiologic control showed no leakage or contracture of the anastomosis. Mean follow-up is 14.8 months (range 8 to 20); all of the patients are continent. A second radiologic study 6 months after the intervention documented in all cases a correct new anatomical repair without stenoses or contracture. This technique is a minor modification of the direct urethrovesical anastomosis that facilitates the anastomosis between the urethral stump and the bladder neck and reduces the risk of anastomotic leakage due to incorrect suture knot positioning and tying.

Anastomosis, Surgical↗

PubMed1999

[Hyponatremia in neurosurgical patients].

Hyponatremia played an essential role in this case, determining the rapid transition from consciousness to a state of coma in female patient who had just come through the critical phase of intensive care. This circumstance underlines the importance of a correct water balance in patients undergoing neurosurgery, as well as a knowledge of the inappropriate antidiuretic hormone secretion (SIADH) syndrome responsible, either alone or in association, for the genesis of severe hyponatremia. In the differential diagnosis of hyponatremia, it is important to recall the role of an often mistaken syndrome (cerebral salt wasting syndrome) characterized by the secretion of a natriuretic factor that has still not been clearly identified.

Brain Injuries↗

PubMed1999

[Giromitra syndrome caused by false morel].

Three cases of mushrooms poisoning (by false morel) with associated gyromitra syndrome, due to a thermolabil toxin are reported. They showed a syndrome like to Amanita phalloides poisoning (gastroenteric symptomatology, diarrhoea) some hours after eating and then neurologic signs; they were hospitalized (without haemolytic signs) and were discharged from hospital a few days later in a good health.

Adult↗

PubMed1998

The RNA cleavage activity of RNA polymerase III is mediated by an essential TFIIS-like subunit and is important for transcription termination.

Budding yeast RNA polymerase III (Pol III) contains a small, essential subunit, named C11, that is conserved in humans and shows a strong homology to TFIIS. A mutant Pol III, heterocomplemented with Schizosaccharomyces pombe C11, was affected in transcription termination in vivo. A purified form of the enzyme (Pol III Delta), deprived of C11 subunit, initiated properly but ignored pause sites and was defective in termination. Remarkably, Pol III Delta lacked the intrinsic RNA cleavage activity of complete Pol III. In vitro reconstitution experiments demonstrated that Pol III RNA cleavage activity is mediated by C11. Mutagenesis in C11 of two conserved residues, which are critical for the TFIIS-dependent cleavage activity of Pol II, is lethal. Immunoelectron microscopy data suggested that C11 is localized on the mobile thumb-like stalk of the polymerase. We propose that C11 allows the enzyme to switch between an RNA elongation and RNA cleavage mode and that the essential role of the Pol III RNA cleavage activity is to remove the kinetic barriers to the termination process. The integration of TFIIS function into a specific Pol III subunit may stem from the opposite requirements of Pol III and Pol II in terms of transcript length and termination efficiency.

Amino Acid Sequence↗

PubMed1998

Intracranial hypotension syndrome: neuroimaging in five spontaneous cases and etiopathogenetic correlations.

Intracranial hypotension (IH) is essential or, more frequently, secondary. This syndrome is characterized by severe postural headache and low opening cerebrospinal fluid (CSF) pressure; although other symptoms may exist. In this study five patients are investigated. Neuroimaging showed: on computerized tomography scan (CT), poor visualization of the cerebral sulci with small ventricles; on magnetic resonance imaging (MRI), subdural fluid collections with enhancement on the convexity, along the tentorium and in the upper cervix after administration of contrast medium and downward displacement of the brain. Radionuclide cisternography was normal in the two patients who underwent this treatment as well as the meningeal biopsy in another patient. In all patients the opening CSF pressure was low or unmeasurable. The clinical syndrome spontaneously recovered contextually to normalization of neuroradiological findings. The possible pathogenesis (dural border cell layer tear) was discussed and the importance of diagnostic confirmation with MRI and measurement of CSF pressure when IH is thought to be present was underlined.

Adult↗

PubMed1998

Different patterns of induction of FGF-2, FGF-1 and BDNF mRNAs during kindling epileptogenesis in the rat.

Neurotrophic factors (NTF) play important roles in the developing and in the adult brain. NTF involvement in neuronal plasticity is suggested by the modulation of NTF expression patterns in different physiological and pathological situations and by the effects they produce in the adult brain (e.g. axonal sprouting induction and neuroprotection). We used the RNAase protection assay to investigate the expression patterns of some NTFs during amygdala kindling, an animal model of epilepsy in which 'pathological' neuronal plasticity appears to occur. After a single kindling stimulation, fibroblast growth factor-2 (FGF-2) mRNA levels were increased in the hippocampus, the cortex and the hypothalamus, whereas they were not significantly altered in the thalamus and the striatum. A single stimulation did not alter fibroblast growth factor-1 (FGF-1) and brain-derived neurotrophic factor (BDNF) gene expression. Fully kindled animals, left unstimulated for a week, did not exhibit any alteration in the mRNA levels for any of the NTFs examined. However, in contrast with the effect of a single stimulation, amygdala stimulation of kindled animals (evoking a generalized tonic-clonic seizure) produced a great increase in hippocampal and cortical BDNF mRNA levels, but FGF-1 mRNA levels were not altered, and FGF-2 mRNA levels were significantly increased only in the cortex. These results suggest that different NTFs can be recruited at different stages of kindling epileptogenesis and, accordingly, may play different parts in the adaptive changes taking place in this experimental paradigm.

Amygdala↗

PubMed1998

Nicotine prevents experimental parkinsonism in rodents and induces striatal increase of neurotrophic factors.

The repeated finding of an apparent protective effect of cigarette smoking on the risk of Parkinson's disease is one of the few consistent results in the epidemiology of this disorder. Among the numerous substances that originate from tobacco smoke, nicotine is by far the most widely studied. Nicotine is a natural alkaloid that has considerable stimulatory effects on the CNS. Its effects on the CNS are mediated by the activation of neuronal heteromeric acetylcholine-gated ion channel receptors (nAChRs, also termed nicotinic acetylcholine receptors). In the present study, we describe the neuroprotective effects of (-)-nicotine in two animal models of parkinsonism: diethyldithiocarbamate-induced enhancement of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine toxicity in mice and methamphetamine-induced neurotoxicity in rats and mice. The neuroprotective effect of (-)-nicotine was very similar to that of the noncompetitive NMDA receptor antagonist (+)-MK-801. In parallel experiments, we found that (-)-nicotine induces the basic fibroblast growth factor-2 (FGF-2) and the brain-derived neurotrophic factor in rat striatum. The effect of (-)-nicotine on the induction of FGF-2 was prevented by the nAChR antagonist mecamylamine. We also found that (+)-MK-801 was able to induce FGF-2 in the striatum. As trophic factors have been reported to be neuroprotective for dopaminergic cells, our data suggest that the increase in neurotrophic factors is a possible mechanism by which (-)-nicotine protects from experimental parkinsonisms.

Animals↗

PubMed1998

A chimeric subunit of yeast transcription factor IIIC forms a subcomplex with tau95.

The multisubunit yeast transcription factor IIIC (TFIIIC) is a multifunctional protein required for promoter recognition, transcription factor IIIB recruitment, and chromatin antirepression. We report the isolation and characterization of TFC7, an essential gene encoding the 55-kDa polypeptide, tau55, present in affinity-purified TFIIIC. tau55 is a chimeric protein generated by an ancient chromosomal rearrangement. Its C-terminal half is essential for cell viability and sufficient to ensure TFIIIC function in DNA binding and transcription assays. The N-terminal half is nonessential and highly similar to a putative yeast protein encoded on another chromosome and to a cyanobacterial protein of unknown function. Partial deletions of the N-terminal domain impaired tau55 function at a high temperature or in media containing glycerol or ethanol, suggesting a link between PolIII transcription and metabolic pathways. Interestingly, tau55 was found, together with TFIIIC subunit tau95, in a protein complex which was distinct from TFIIIC and which may play a role in the regulation of PolIII transcription, possibly in relation to cell metabolism.

Amino Acid Sequence↗

PubMed1998

Transient oculomotor cranial nerves palsy in spontaneous intracranial hypotension.

Transient sixth cranial nerves palsy may occur in rare cases after lumbar puncture, spinal anesthesia and myelography as well as in more rare cases of spontaneous intracranial hypotension. We report three cases of spontaneous intracranial hypotension with sixth cranial nerves palsy. One of these patients presented also third cranial nerve palsy, never reported in spontaneous intracranial hypotension.

Abducens Nerve↗