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Biomedical subjects

M Barbi

Publications and source records attributed to M Barbi.

At least 37 records · Page 2Linked to original sources
PubMed1996

Cytomegalovirus in peripheral blood leukocytes of infants with congenital or postnatal infection.

BACKGROUND: Cytomegalovirus (CMV) is the most frequent agent of viral infection in the fetus; it causes varying damage, particularly neurologic, which becomes evident at birth or in infancy in about 20% of infected individuals. Postnatal acquisition is usually asymptomatic and without sequelae. Laboratory diagnosis of congenital and postnatal infection is based on the demonstration of virus in urine. OBJECTIVES: To investigate the systemic spread of CMV in neonates with congenital or postnatal infection and to evaluate its significance in diagnosis and in monitoring anti-CMV treatments. DESIGN: Quantitative determinations of infective CMV (viremia) and viral antigen pp65 (antigenemia) were performed on peripheral blood leukocytes (PBL) from the buffy coat of heparinized blood from children with a diagnosis of congenital (n = 19) or postnatal (n = 19) infection based on viral isolation from urine. RESULTS: Antigen pp65 in PBL was detected particularly in children with symptomatic infection, both congenital (100%) and postnatal (79%; P > 0.05), and significantly less frequently (50%; P < 0.001) in those with asymptomatic infection. Viremia was observed less often but always in association with antigenemia. Both tests became negative within 6 months. Neither viral titer nor persistent positivity was related to clinical manifestations. In the nine infants given anti-CMV therapy (ganciclovir and/or hyperimmune gamma-globulins) an early suspension of treatment resulted in the appearance of antigenemia and/or viremia. CONCLUSIONS: Cytomegalovirus was detected in PBL mainly in the most severely affected children. Monitoring antigenemia and viremia in CMV-infected infants is recommended to demonstrate persistent systemic infection and to evaluate virologic results of treatment.

Antigens, Viral↗
PubMed1995

Double resistance to ganciclovir and foscarnet of four human cytomegalovirus strains recovered from AIDS patients.

Four human cytomegalovirus (HCMV) isolates from four different AIDS patients treated with both ganciclovir and foscarnet and not responding clinically to antiviral treatment, were studied in order to verify the occurrence of double resistance to both drugs, and to define whether single or multiple HCMV strains could be responsible for the double resistance. Peripheral blood leukocytes (PBL), the relevant conventional viral isolates, and plaque-purified strains from all four patients were examined by antiviral drug susceptibility testing by an immediate-early antigen plaque reduction assay and by restriction fragment length polymorphism (RFLP) analysis using polymerase chain reaction (PCR)-amplified multiple genome regions and endonucleases. All four HCMV strains had a high level of resistance to both ganciclovir and foscarnet. A single HCMV strain was shown to be responsible for the dual resistance in each patient. HCMV strain identity and uniqueness were shown for each of the four patients in blood samples, viral isolates, and plaque-purified strains. In addition, in two patients the same single HCMV strain shifted progressively from drug sensitivity to ganciclovir and then to ganciclovir-foscarnet resistance. These findings document that resistance to both ganciclovir and foscarnet of HCMV strains recovered from blood of AIDS patients represents an emerging problem. Although it is known that multiple HCMV strains may cocirculate in the blood of AIDS patients, single strains appear to be responsible for the dual resistance. Molecular mechanisms responsible for the double resistance of the four reported strains are under study.

AIDS-Related Opportunistic Infections↗
PubMed1995

Four dually resistant human cytomegalovirus strains from AIDS patients: single mutations in UL97 and UL54 open reading frames are responsible for ganciclovir- and foscarnet-specific resistance, respectively.

Four human cytomegalovirus strains with double resistance to both ganciclovir and foscarnet were recovered from acquired immunodeficiency syndrome (AIDS) patients. The four isolates were genetically unrelated and each of them consisted of a single viral population. In addition, for each isolate, UL97 and UL54 open reading frames sequencing showed a single aminoacid change in a conserved domain of each of the two genes.

AIDS-Related Opportunistic Infections↗
PubMed1994

Periodic forcing of a K+ channel at various temperatures.

The random sequence of openings and closings of single ion channels and the channel conductances have been the object of intense study over the past two decades with a view toward illuminating the underlying kinetics of the channel protein molecules. Channels that are sensitive to voltage, such as many K(+)-selective channels, have been particularly useful, because the kinetic rates can be manipulated by changing the membrane voltage. Most such studies have been performed under stationary conditions and usually at a single temperature. Here we report the results of experiments with sinusoidal modulation of the membrane potential performed at several temperatures. Dwell time and cycle histograms, objects not normally associated with ion channel experiments, are herein reported. From the last, the transition probability densities for channel opening and closing events are obtained. A new and unusual phase anticipation is observed in the cycle histograms, and its temperature dependence is measured.

Animals↗
PubMed1992

Antibody response to inactivated polio vaccine (E-IPV) in children born to HIV positive mothers.

In order to evaluate the response to immunization of HIV-infected children we studied the humoral response to an enhanced potency inactivated poliovaccine (E-IPV) of 43 children born of HIV seropositive mothers. All these subjects have been followed for 32 (15-48) months in order to ascertain their infection status. After a course of 2 doses of E-IPV, 88% of children had neutralizing antibody (n.a.) titers greater than 1:4 to the 3 poliovirus serotypes and 100% to at least 2 polio strains. No statistically significant differences both as rates of n.a. positive subjects and as antibody levels were found between HIV infected children and those who lost HIV antibodies. The poorest response was observed in subjects with full-blown immunodeficiency (CD4 less than 1000/mm3, reduced response to PWM). Sixteen children also received a booster dose of vaccine one year after the completion of the primary cycle. Infected and non-infected subjects responded to the same extent with high levels of n.a. to this immunization. Interestingly, the recall dose was also able to induce high n.a. titers in those HIV infected children who showed significant decreases of n.a. titers in the months following the end of the primary cycle.

Antibodies, Viral↗
PubMed1992

Immunization in children with HIV seropositivity at birth: antibody response to polio vaccine and tetanus toxoid.

OBJECTIVE: To evaluate the humoral response to routine childhood immunization of HIV-infected children. DESIGN: Response rate, antibody titres and persistence after polio and tetanus vaccination were compared in 72 children with HIV seropositivity at birth and divided according to HIV infection status as determined by clinical and laboratory tests. METHODS: Polio antibodies were titred in a microneutralization test (positive titres, > or = 1:4), and antibody to tetanus toxoid with a passive haemagglutination method (protective titres, > or = 1:1024). RESULTS: The response rates to polio and tetanus vaccination (> 80 and > 75%) were similar in the HIV-infected and non-infected children, as were antibody levels. In the subgroup with sera obtained some months after the last dose of vaccine, polio antibody levels decreased in all four HIV-infected and in three of the seven non-infected children; protective tetanus antitoxin levels were detected in three of the six infected and in all three non-infected children. CONCLUSIONS: This study demonstrates the ability of children with HIV infection to respond adequately to the two vaccines considered, although tetanus antitoxin levels were inferior, compared with those in the seroreverted children. The unsatisfactory antibody levels observed in the admittedly few HIV-positive children studied some months after the last vaccination could be the result of a lower initial protective level and not necessarily an expression of severely impaired immunocompetence. The administration of booster doses in addition to the traditional immunization schedule could be useful in children with HIV infection.

Antibodies, Bacterial↗
PubMed1991

Use of conditioned distributions in the analysis of ion channel recordings.

A method to test the Markov nature of ion channel gating is proposed. It makes use of singly and doubly conditional distributions. The application of this method to recordings from single BK channels provides evidence that at least two states of the underlying kinetic scheme are left at a constant rate. Moreover, the probabilities, when leaving a state, of reaching another given state are shown to be constant for all the states of the system.

Animals↗
PubMed1987

The Italian Cooperative Multiple Sclerosis case-control study: preliminary results on viral antibodies.

Viral antibodies to measles, HSV-1, HSV-2, EBV and HTLB-III have been tested in 120 sera and 90 CFS of 78 MS patients, 21 other neurological diseases and 21 non neurological disease controls included in the Italian Multicenter MS case-control study. A significantly higher frequency of HSV-2 antibodies was found in the MS cases than in the two control groups. Moreover the HSV-2 and the RBV-VCA cantibody levels were higher in the MS patients than in those with non neurological diseases. A clear or weak antibody response to the HTLV-III proteins was shown, using the Western Immunoblotting method, in 10.3% of the MS sera or CSF:8.6% of the sera and 1.8% of the CSF were positive. The significance of these findings in relation to the design of the multicenter case-control study is discussed.

Antibodies, Viral↗
PubMed1987

[Antiviral activity of a chemical contraceptive (nonoxynol-9)].

The aim of this study was to evaluate, in vitro, the antiviral activity of a chemical contraceptive (Nonoxynol-9). The results have demonstrated that such a compound is able to inhibit the infectivity of enveloped viruses. It seems that the activity of this contraceptive is due to the lesion of the envelope.

Cell Line↗
PubMed1985

[Congenital cytomegalovirus infections in a neonatal pathology unit].

In order to evaluate the incidence of congenital CMV infections we checked 200 babies in the special care baby unit of an obstetric clinic in Milan. In the same period 3779 babies were born in that clinic. Congenital CMV infection was diagnosed by virus isolation from urine specimens collected in the first week of life in two babies. One of them was asymptomatic, the other had the classical CID. Virological confirmation of a further CID observed in an infant hospitalized at that time in the unit was obtained. Different serological methods of congenital infections diagnosis, specific IgM, total IgM and IgA, rheumatoid factor determinations, were employed. Only the CMV-IgM ELA method didn't give false positive reactions and picked up 2 congenitally infected babies out of 3. From our data, we infer that the incidence of congenital CMV infection in the general milanese population might lie between 0.5-1% of live births. The level of seropositivity for CMV antibodies in the same population, as judged from the complement fixing antibodies determinations in the group of the mothers, was 87%.

Cytomegalovirus Infections↗
PubMed1980

[Seroepidemiologic survey of the spread of rotavirus infection in a Milan population].

The increasing evidence of involvement of Rotaviruses in the etiology of viral gastroenteritis prompted us to carry on a seroepidemiological survey on the population of Milan. The aim was to get informations on the extension of the circulation of these agents in our population. Utilising a commercial antigen prepared with the "Oslo" bovine strain, c.f.a. were titrated in sera from 575 healthy subjects (age 0 to > 60 years). Of them 232 were children under 4 years of age homogeneously distributed into 6 age classes: at birth, 1 day to 3 months, 4-6 months, 7-12 months, 13-24 months, 2-4 years. Rotavirus infection appears very common. About 80% of the subjects over 10 years have c.f.a. As it is shown by the sharp increase of antibody acquisition after an initial drop in the first 6 months (82% positive at birth and 41% between 4-6 months), the infection seems to occur very early in life, as much as the plateau is reached under 10 years of age. Moreover consistent antibody titers (greater than or equal to 1:32), which could indicate recent infection, first appear in babies 4 to 12 months of age. Such titres are absent in the adults and could be found again in people over 50. Positivity was significantly higher in females than in males (0.01 < P < 0.025). Transplacental c.f.a. passage was studied in paired sera of 37 women at delivery and in cord blood sera of their babies; 28 matched pairs of sera had coincidental titres, but there were additional three cord blood specimens with c.f.a. from newborns whose mothers were negative.

Adolescent↗
PubMed1980

Relevance of the single ommatidium performance in determining the oscillatory response of the Limulus retina.

The response of a healthy lateral eye of Limulus to constant, uniform and sufficiently intense light stimulation, consists of a sustained oscillatory discharge, all ommatidia firing synchronously in bursts, at intervals of about 0.2s (Barlow and Fraioli, 1978). This response has been analysed by a computer simulation, where the performance of the single unit is described by encoder models of the integrate-and-fire type, already extensively investigated. The results obtained show that the occurrence and the time features of the oscillatory response depend on the neural models adopted.

Animals↗
PubMed1980

Resonant response of a neural model and of Limulus ommatidia to double frequency stimulation.

Signals which are the sum of two sinusoids of frequencies v1 and v2 are used to stimulate: i) an electronic analog of the leaky integrator neural model, ii) the visual neurons of the Limulus lateral eye. This makes it possible to investigate the resonant amplification of the impulse density modulation for v1 + v2 which approaches the free-run discharge rate; this resonance is predicted by the Volterra series representation of the leaky integrator (Poggio and Torre, 1977). The resonant responses obtained look very similar for the simulated discharge and for the experimental one.

Animals↗