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S Rossi

Publications and source records attributed to S Rossi.

At least 19 recordsLinked to original sources
PubMed2001

Isothermal and non-isothermal characterization of catalytic nylon membranes chemically grafted: dependence on the grafting percentage.

The behaviour of five different hydrophobic beta-galactosidase derivatives, obtained by grafting different amount of butylmethacrylate (BMA) on planar nylon membranes, has been studied under isothermal and non-isothermal conditions.Under isothermal conditions the effect of the grafting percentage on the enzyme activity has been studied as a function of pH, temperature and substrate concentration. Independently from the parameters under observation, the yield of the catalytic process reaches the maximum value at a grafting percentage value equal to 21%. The apparent K(m) values result linearly increasing with the increase of the grafting percentage, while the apparent V(max) exhibits a maximum value.Under non-isothermal conditions, a decrease of the apparent K(m) values and increase of the apparent V(max) has been found in respect to the same values obtained under isothermal conditions.The percentage activity increases induced by the presence of a temperature gradient have been found to decrease with the increase of the percentage of graft BMA.A parameter correlating the percentage increase of enzyme activity under non-isothermal conditions with the hydrophobicity of the catalytic membrane has also been identified. This parameter is the ratio between thermoosmotic and hydraulic permeability.Results have been discussed in terms of reduction of diffusion limitations for substrate and products movement towards or away from the catalytic site by the process of thermodialysis.The usefulness of using non-isothermal bioreactors in industrial biotechnological processes has been confirmed.

Journal Article↗
PubMed2001

Multiresidual method for the gas chromatographic analysis of pesticides in honeybees cleaned by gel permeation chromatography.

The analysis of several organophosphorus and carbamate pesticide residues in the bodies of honeybees using gas chromatography (GC) and gel permeation chromatography (GPC) clean-up is described. Freeze-dried or lyophilized insect samples were blended with diatomaceous earth (Extrelut) then underwent elution with methylene chloride. This extraction method has shown good recovery on various spike standard levels. Samples are cleaned up by GPC with a Bio Beads SX 3 column and a cyclohexane-ethylacetate (1:1) eluant. Organophosphorus and carbamate compounds are quantified using capillary gas chromatography. Good linearity ranges were observed for all compounds. The extraction process was rapid and results were good, despite the complexity of the matrix on which it was applied. It allowed a reduction both in cost and the consumption of solvents, thereby safeguarding the health of the analyst and the environment. Environmental monitoring using bees was confirmed to be a valid procedure.

Animals↗
PubMed2001

Avidity analysis of the human immune response to a chitin binding protein of Toxoplasma gondii.

A 30-33 kDa electroeluted fraction of T. gondii tachyzoites improved discrimination between acute and chronic phase sera when used instead of the whole tachyzoite extract in an avidity-ELISA. In order to identify the components of these fractions, crude tachyzoite antigen was fractionated by anionic exchange chromatography. The 30-33 kDa antigen cluster eluted in the not-bound fraction could account for a large proportion of the antibody response against the 30-33 kDa electroeluted fraction. According to the N-terminal sequence data, this antigen fraction is composed mainly of SAG1 and another protein with high homology to chitin binding proteins from plants.

Animals↗
PubMed2001

Transurethral radiofrequency thermal ablation of prostatic tissue: a feasibility study in humans.

OBJECTIVES: To evaluate the feasibility and efficacy of ablating prostatic tissue by inducing thermal lesions using radiofrequency (RF) energy delivered transurethrally through electrodes mounted on a Foley-like catheter. METHODS: Twenty male patients, candidates for radical cystoprostatectomy to treat bladder carcinoma, underwent RF prostate ablation 1 to 8 days before surgery (mean 2.8). Stainless steel, internally cooled, 2-cm-long electrodes mounted on a Foley-like catheter were used to deliver RF energy to the prostatic tissue. Semicircular electrodes were used in 10 patients (group A) and circular electrodes were used in the remaining 10 patients (group B). The urethral, rectal, and prostatic tissue temperatures were recorded. Histologic step sections were performed on whole mounts of the prostates to define the volume of the thermal lesions. RESULTS: The mean RF energy delivered was 36.5 kJ (range 26.4 to 53.1) in group A and 82.3 kJ (range 38 to 149) in group B. The intraprostatic temperatures were between 44 degrees C and 80 degrees C in group A and between 60 degrees C and 119 degrees C in group B. The urethral and rectal temperatures never exceeded 42 degrees C. No major complications occurred. After the RF procedure, 5 patients who received more than 75 kJ of energy could not void and required catheterization. The mean prostate volume was 11.54 cm(3) for group A and 24.02 cm(3) for group B. The mean volumes of the thermal lesions and their relative percentages in relation to the whole prostate in groups A and B were, respectively, 1.69 cm(3) and 15% and 6.91 cm(3) and 29% (P = 0.049). Analysis of variance showed a significant correlation between the thermal lesion volume and the energy delivered, regardless of the electrode shape (P = 0.001). CONCLUSIONS: Satisfactory thermal ablation of prostatic tissue can be achieved using RF electrodes mounted on a Foley-like catheter. The procedure is effective, simple, and safe and, therefore, can be used in pilot clinical studies on patients with benign prostatic hyperplasia.

Aged↗
PubMed2001

Characterization of chitosan hydrochloride--mucin rheological interaction: influence of polymer concentration and polymer:mucin weight ratio.

The aim of the present work was to investigate the influence of polymer concentration and polymer:mucin weight ratio on chitosan--mucin interaction, assessed by means of viscosimetric measurements. Two hydration media, distilled water and 0.1 M HCl, were used. Chitosan solutions were prepared at concentrations greater than the characteristic entanglement concentration and mixed with increasing amounts of porcine gastric mucin. Viscosity measurements were performed on the polymer--mucin mixtures and on polymer and mucin solutions having the same concentrations as in the mixtures. The flow curves were fitted according to a modified form of Cheng--Evans equation in order to obtain the relevant model parameters: low shear viscosity eta(0) and high shear viscosity eta(infinity), indexes of the sample structure at rest and upon high shear, respectively. The formation of chitosan--mucin interaction products was determined on the basis of the changes in eta(0) and eta(infinity) of the mixtures as a function of polymer:mucin weight ratio. Rheological synergism parameter was also calculated. The results obtained suggest that two different types of rheological interaction occur between chitosan and mucin in both media, depending on polymer concentration and polymer:mucin weight ratio: one is characterized by a minimum in viscosity and occurs at higher polymer:mucin weight ratio, the other one produces a positive rheological synergism and is observed in presence of an excess of mucin. Only the last one causes a 'strengthening' of the mucoadhesive interface and it is responsible for the mucoadhesive joint. This hypothesis is confirmed by tensile stress measurements performed on HCS solutions in presence of mucin dispersions at different concentrations.

Animals↗
PubMed2001

Successful treatment of TIPS-induced hepatic failure with an hourglass stent-graft: a simple new technique for reducing shunt flow.

A simple new technique for creating an hourglass reducing stent-graft by means of targeted balloon expansion of each end of a commercially available device is presented. A 67-year-old man with progressive hepatic failure after TIPS creation was treated. A 48-mm-long Jostent stent-graft was placed inside the TIPS through a 10-F introducer and fully expanded only at the proximal and distal ends, resulting in an hourglass shape. Immediate increase of portal pressure was achieved, followed by complete clinical recovery. Advantages of covered versus bare reducing stents are discussed.

Aged↗
PubMed2001

Brain-stem compression in vertebrobasilar dolichoectasia. A multimodal electrophysiological study.

OBJECTIVE: To evaluate the effects of mechanical compression of the brain-stem in patients with vertebrobasilar dolichoectasia (VBD). METHODS: In the framework of a prospective, observational study that collected clinical and laboratory data in patients with VBD, we studied 20 patients with compression of the brain-stem due to ectatic, tortuous basilar or vertebral arteries. Patients with cerebral lesions other than small lacunae in the white matter of the cerebral hemispheres were excluded from the study. Patients underwent vestibular and auditory function testing, including brain-stem auditory evoked potentials (BAEPs), blink reflex (BR), somatosensory evoked potentials (SEPs), and motor evoked potentials (MEPs). RESULTS: Almost all of the patients complained of auditory or vestibular symptoms and none had symptoms or signs of impairment of long tracts or the facial and trigeminal nerves. The most consistent findings were BR abnormalities with prolongation of ipsilateral R1 latency in cases of compression of the pons (10/16) and prolongation of the R2 and R2c latencies with compression of the medulla oblongata (5/15). Subclinical impairment of corticospinal pathways was found in 13 out of 25 instances of compression, and this was more frequent with compression of the pons. Abnormal BAEPs or SEPs were less frequently encountered, and only in cases with compression of the pons. CONCLUSIONS: Neurovascular compression of the brain-stem, even with severe distortion, is seldom associated with overt clinical signs, whereas subclinical dysfunctions are relatively frequent. The central pathways of the BR and the corticospinal pathways are more susceptible to compression than acoustic and sensory pathways. BR, MEP and BAEP data provide a functional evaluation of the brain-stem and some cranial nerves, which is lacking in imaging studies. Functional investigations may be useful in the long-term management of these patients, since VBD may be progressive and surgical correction may be required at some stage.

Adult↗
PubMed2001

Pilot dose-finding trial on interferon alpha in combination with ribavirin for the treatment of chronic hepatitis C in patients not responding to interferon alone.

BACKGROUND: Effectiveness of combination therapy with standard interferon alpha doses and ribavirin is far from being demonstrated in patients with hepatitis C non responders to interferon alpha monotherapy. Recent kinetic studies revealed that these doses may be suboptimal. AIMS: To find the criteria for optimisation of the interferon dose, to be used in combination with ribavirin in patients with hepatitis C non responders to interferon alpha monotherapy. PATIENTS: Sixty-three patients enrolled in a pilot controlled trial were treated for 6 months with ribavirin ([1000-1200 mg daily) and were randomised to concurrently receive interferon alpha 2b for 6 months at: 3 Million Units thrice weekly [group A (21 patients)], 5 MU thrice weekly [group B (21 patients)] and 5 million units daily [group C (21 patients)]. RESULTS: A sustained virological response was observed in: 1 patient from group A (5%), 2 patients from group B (9%) and 8 patients from group C (38%; p=0.02 vs group A; p=0.03 vs group B). Side-effects were not significantly different between the 3 groups. Multivariate analysis showed that infection by hepatitis C virus genotypes 2 or 3 and interferon alpha dosage of 5 million units daily were independent predictors of sustained response. CONCLUSIONS: These results suggest that higher interferon doses administered daily in combination with ribavirin could be more effective in those patients with hepatitis C who had not responded to interferon alone.

Adolescent↗
PubMed2001

Hypothesis testing in a rule discovery problem: when a focused procedure is effective.

We investigated individuals' ability to use negative evidence in hypothesis testing. We compared performance in two versions of Wason's (1960) rule discovery problem. In the original version, a triple of numbers--(2, 4, 6)--was presented as an example of a rule that the experimenter had in mind (i.e., "increasing numbers"). Participants had to discover the rule by proposing new triples. In the other version, the same triple was presented as a counter-example to the experimenter's rule (i.e., "decreasing numbers"). We predicted that, in both conditions, participants would form hypotheses based on the features of the triple, and test only instances of the hypothesized rule. However, in the counter-example condition, such focused testing would invariably produce negative evidence. As a consequence, participants would be forced to revise their hypotheses. The reported results corroborated our predictions: Participants solved the counter-example version significantly better than the original problem.

Adult↗
PubMed2001

Brain oxygen tension, oxygen supply, and oxygen consumption during arterial hyperoxia in a model of progressive cerebral ischemia.

We investigated the changes in brain oxygen tension (ptiO2) after ventilation with pure O2 in order to (1) clarify the pathophysiology of O2 exchange in the cerebral microcirculation; and (2) investigate the relationship between brain O2 tension, O2 delivery, and consumption in steady-state conditions during stepwise cerebral blood flow (CBF) reductions. A swine model was developed to reduce CBF in three stable steps: (1) baseline (CBF 100%), (2) CBF of 50-60% of baseline, and (3) CBF of <30% of baseline. CBF was reduced by infusing saline into the left lateral ventricle through a catheter connected with an infusion pump. At each step, hyperoxia was tested by increasing the inspired oxygen fraction up to 100%, PtiO2 reflected the CBF reductions, since it was respectively 27.95 (+/-10.15), 14.77 (+/-3.58), and 3.45 (+/-2.89) mm Hg during the three CBF steps. Hyperoxia was followed by an increase in ptiO2, although the increase was significantly lower when hyperoxia was applied during progressive ischemia. O2 supply to the brain did not change during hyperoxia. Arteriovenous oxygen difference (AVDO2) decreased during the phases of intact CBF and moderate impairment, but not during the phase of severe CBF reduction. In conclusion, ptiO2 reductions closely reflect the imbalance between oxygen delivery and demand; this implies a link between low ptiO2 and defective O2 supply due to impaired CBF. However, this relation is not necessarily reciprocal, since manipulating brain oxygen tension does not always influence brain oxygen delivery, as in the case of ventilation with pure oxygen.

Animals↗
PubMed2001

Molecular typing and long-term comparison of clostridium difficile strains by pulsed-field gel electrophoresis and PCR-ribotyping.

Thirty-two related and 68 unrelated isolates of Clostridium difficile, isolated in different Italian hospitals since 1987, were analysed by PFGE and PCR-ribotyping to investigate their genetic relatedness. The isolates were classified into 28 groups by PFGE and 20 ribotypes by PCR-ribotyping. A single clone of C. difficile was recognised as the cause of three geographically and chronologically distant outbreaks. The correlation between PFGE and PCR-ribotyping results was good, with agreement for 77 (84%) of the 92 isolates typed by both methods. However, among sporadic isolates the discriminatory power of PFGE was more evident. Eight isolates that were untypable by PFGE could be analysed by PCR-ribotyping. The dendrograms generated showed that the genetic relatedness of the C. difficile isolates obtained by both techniques was comparable. The majority of the isolates in recent years appeared to be genetically unrelated to isolates from past infections. However, two clonal groups identified in all time periods had a common origin and this seems to indicate that they share some advantageous biological characteristics. The constant monitoring of C. difficile epidemiology will allow acquisition of further important data on this nosocomial pathogen.

Clostridioides difficile↗
PubMed2001

The action of acetyl-L-carnitine on the neurotoxicity evoked by amyloid fragments and peroxide on primary rat cortical neurones.

The amyloid beta-peptides have been implicated in the excitotoxic mechanism of neuronal injury in the pathogenesis of Alzheimer's disease. In this paper we examine the effect of different amyloid fragments (beta A1-40, A1-28, and A25-35), as well as potential neuroprotective compounds on rat cortical neuron viability. Exposure of neurones to beta A25-35 or A1-40 at concentrations as low as 1 microgram/ml inhibited, significantly, the MTT response and this level of inhibition was similar after 24-h or three-day exposure. Furthermore, the level of inhibition was not affected by the presence or absence of 5% horse serum in the medium. Preexposure (10 min) of neurones to ALC at concentrations of 0.1, 1, 5, and 10 mM attenuated the inhibition of the MTT response caused by beta A25-35 (50 micrograms/ml) in serum free medium for 24 h. The treatment of cells with vitamin E (100 microM), catalase (4 mg/ml), NGF (0.1 and 10 ng/ml), or cycloheximide (0.1 microgram/ml) significantly restored the MTT response that was inhibited by beta A25-35. The mechanism for the protective actions of these compounds against beta A25-35 toxicity is not clear but may involve free radical scavenger action and preservation of energy production, although other mechanisms, especially for ALC, such as a direct effect on A-beta interaction with charged anionic phospholipids and/or stabilizing action on membranes, are also possible.

Acetylcarnitine↗
PubMed2001

[Magnetic resonance imaging in the evaluation of parametrial invasion of carcinoma of the cervix uteri: optimization of the study protocol].

PURPOSE: To determine the efficacy of three different MR sequences in the evaluation of parametrial invasion by early-stage cervical cancer. MATERIAL AND METHODS: Eighteen consecutive patients with cervical cancer clinically assessed as stage IB1 underwent MR imaging examination with the use of the following sequences: FSE T2-weighted, FSE fat-suppressed T2w, and SE fat-suppressed Gadolinium-enhanced T1w. In all cases, the presence or absence of parametrial invasion on both sides per each sequence used was evaluated. Subsequently all the sequences have been considered together for the evaluation of tumor invasion. Gold standard of the study was the histopathologic analysis of the surgical specimens. RESULTS: At histological examination, parametrial invasion by tumor was found in 6 out of 36 parametria evaluated. The accuracy achieved with each of the sequences used was as follows: 94% with FSE T2w; 86% with FSE fat-suppressed T2w; and 67% with SE fat-suppressed Gadolinium-enhanced T1w. The simultaneous evaluation of all 3 sequences obtained an accuracy level similar to that achieved with FSE T2w. The difference between the accuracy of T2w sequences and that of fat-suppressed contrast-enhanced T1w sequences was statistically significant (p<0.01). DISCUSSION AND CONCLUSIONS: Our data suggest that the MR imaging protocol for the evaluation of parametrial tumor invasion could be restricted to FSE T2w sequences. These proved to have the highest negative predictive value (97%) which allows a reliable selection of patients who can be surgically treated.

Adenocarcinoma↗
PubMed2000

Structural and functional analysis of the cAMP binding domain from the regulatory subunit of Mucor rouxii protein kinase A.

The cAMP binding domain of the regulatory subunit (R) of Mucor rouxii protein kinase A was cloned. The deduced amino acid sequence was highly homologous in sequence and in size to the corresponding region in fungal and higher eukaryotic regulatory subunits (47-54%), but particularly homologous (62%) to Blastocladiella emersonii, a fungus classified in a different phylum. Amino acids reported to be important for interaction with cAMP, for cooperativity between the two cAMP binding domains, in the general folding of the domain, and for interaction with the catalytic subunit were conserved in all the fungal sequences. Based on either sequence or functional behavior, the M. rouxii R subunit cannot be classified as being more similar to RI or RII of mammalian systems. The M. rouxii protein sequence was modeled using as template the coordinates of the crystallized bovine regulatory subunit type Ialpha. The quality of the model is good. The two backbones could be perfectly overlapped, except for two loop regions of high divergence. The alpha helix C of domain A, proposed to have a strong interaction with the catalytic subunit, contains a leucine replacing a basic residue (arginine or lysine) commonly found in RI or RII. The domains A and B of the M. rouxii regulatory subunit were overexpressed as fusion proteins with GST. GST domain B protein was inactive. GST domain A was active; the kinetic parameters of affinity toward cAMP analogs, site selectivity, and dissociation kinetics of bound cAMP were analogous to the properties of the domain in the whole regulatory subunit.

Amino Acid Sequence↗
PubMed2000

Thymic atrophy in murine acute graft-versus-host disease is effected by impaired cell cycle progression of host pro-T and pre-T cells.

Reconstitution of the peripheral T-cell compartment is a critical aspect for the success of bone marrow transplantation and is also dependent on the reestablishment of normal thymic structure and function. Graft-versus-host disease (GVHD), however, exacerbates posttransplant immunodeficiency through a deleterious effect on thymic function. To investigate the mechanisms of GVHD-mediated thymic disease, 2 murine parent-->F(1 )transplantation models of acute and chronic GVHD, respectively, were studied. Acute GVHD was associated with changes in thymic architecture and a reduction in cellularity mainly because of the decrease in CD4(+)CD8(+), or double-positive (DP) thymocytes, to less than 15% of values found in mice without GVHD. Simultaneously, mature donor-derived T cells expanded in the confines of the allogeneic thymic microenvironment, leading to local inflammation. Through analysis of in vivo cell proliferation, we demonstrated that the ensuing depletion of DP thymocytes was secondary to a decreased commitment of resident pro-T and pre-T cells to enter the cell cycle. Moreover, DP cells themselves showed altered proliferative capacities in the presence of acute GVHD. These findings suggested that thymic atrophy in acute GVHD is effected by impaired cellular proliferation of immature host thymocytes and that the failure of these cells to enter the cell cycle is dependent on an interferon (IFN)-gamma-driven immune response. In contrast, interleukin-4-driven chronic GVHD was not accompanied by a sustained thymic infiltration of donor T cells. Consequently, there was a lack of apparent structural changes, a restricted in situ transcription of inflammatory cytokines, and a virtually unchanged cell cycle progression in vivo.

Animals↗