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Biomedical subjects

V Lombardi

Publications and source records attributed to V Lombardi.

At least 55 records · Page 3Linked to original sources
PubMed1993

Early detection of IgA specific antibodies in HIV-1 infected children by peptide-ELISA and peptide time-resolved fluoro-immunoassay.

The presence of specific IgA antibodies in sera from 25 infants born to HIV-1 seropositive mothers was investigated by peptide-ELISA and peptide time-resolved fluoro-immunoassay (TR-FIA). The infants had been monitored at different times after birth for clinical signs and/or symptoms of HIV-1 infection and for detection of HIV-1 in lymphocyte cultures. Serum samples had also been tested for HIV-1 IgG antibodies by commercial ELISA and Western blot and for p24 antigen. Eleven of 25 children were then identified as infected. IgA detection was performed after rProtein G treatment to remove interfering IgG. In the infected group, IgA specific antibodies to a synthetic peptide representing a highly conserved region of the transmembrane glycoprotein gp41 (env: 594-613) were detected in 27 (73%) out of 37 serum samples (9 of 11 children) by the peptide-ELISA test. IgA specific antibodies to the same peptide were found in 30 (81%) sera (9 of 11 children) by the peptide-TR-FIA. Specific HIV-1 IgA antibodies were detected as early as 2 months of age in serum samples from five out of seven children (71% sensitivity) using peptide-ELISA and from six out of seven (86% sensitivity) by peptide-TR-FIA. Conversely, IgA specific antibodies to HIV-1 were absent in two infected children as well as in the sera of all uninfected children tested during the follow up period. Since maternal IgA does not cross the placenta, IgA detection in the serum of the infant is indicative of HIV-1 infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Enzyme-Linked Immunosorbent Assay↗
PubMed1993

Epitope specificity, antibody-dependent cellular cytotoxicity, and neutralizing activity of antibodies to human immunodeficiency virus type 1 in autoimmune MRL/lpr mice.

The specificity and functional activity of antibodies to human immunodeficiency virus (HIV) in the sera of MRL/lpr mice were analyzed by peptide-ELISA, antibody-dependent cellular cytotoxicity, and virus neutralization. The specificity of the antibodies in the sera of autoimmune MRL/lpr mice was similar to that of HIV-infected persons; the mouse sera specifically recognized the V3 loop of gp120 and immunodominant regions of gp41 and p24. Moreover, such binding was inhibited both by human HIV-positive sera and by soluble peptides in competition experiments. MRL/lpr sera displayed anti-HIV antibody-dependent cellular cytotoxicity using human peripheral blood lymphocytes as effector cells and HIV-infected H9 cells. Furthermore, the fact that MRL/lpr sera neutralized in vitro infectious HIV (both strains IIIB and MN) suggests these antibodies recognize viral epitopes on the membrane of infected T cells.

Amino Acid Sequence↗
PubMed1992

Myosin head movements are synchronous with the elementary force-generating process in muscle.

Motor proteins such as myosin, dynein and kinesin use the free energy of ATP hydrolysis to produce force or motion, but despite recent progress their molecular mechanism is unknown. The best characterized system is the myosin motor which moves actin filaments in muscle. When an active muscle fibre is rapidly shortened the force first decreases, then partially recovers over the next few milliseconds. This elementary force-generating process is thought to be due to a structural 'working stroke' in the myosin head domain, although structural studies have not provided definitive support for this. X-ray diffraction has shown that shortening steps produce a large decrease in the intensity of the 14.5 nm reflection arising from the axial repeat of the myosin heads along the filaments. This was interpreted as a structural change at the end of the working stroke, but the techniques then available did not allow temporal resolution of the elementary force-generating process itself. Using improved measurement techniques, we show here that myosin heads move by about 10 nm with the same time course as the elementary force-generating process.

Actins↗
PubMed1992

Rapid regeneration of the actin-myosin power stroke in contracting muscle.

At the molecular level, muscle contraction is the result of cyclic interaction between myosin crossbridges, which extend from the thick filament, and the thin filament, which consists mainly of actin. The energy for work done by a single crossbridge during a cycle of attachment, generation of force, shortening and detachment is believed to be coupled to the hydrolysis of one molecule of ATP. The distance the actin filament slides relative to the myosin filament in one crossbridge cycle has been estimated as 12 nm by step-length perturbation studies on single fibres from frog muscle. The 'mechanical' power stroke of the attached crossbridge can therefore be defined as 12-nm shortening with a force profile like that shown by the quick recovery of force following a length perturbation. According to this definition, power strokes cannot be repeated faster than the overall ATPase rate. Here, however, we show that the power stroke can be regenerated much faster than expected from the ATPase rate. This contradiction can be resolved if, in the shortening muscle, the free energy of ATP hydrolysis is used in several actin-myosin interactions consisting of elementary power strokes each of 5-10 nm.

Actins↗
PubMed1992

Patterns of immunoglobulin G subclass reactivity to HIV-1 envelope peptides in children born to HIV-1-infected mothers.

OBJECTIVE: To analyse the pattern of immunoglobulin (Ig) G subclasses specific for HIV-1 envelope peptides in sera from HIV-1-infected mothers and their newborns. We sought to determine whether there was a selective transfer of antibodies from mother to child, and to establish diagnostic or prognostic properties by analysing HIV-1 peptide-specific IgG isotypes. DESIGN AND METHODS: Parallel sera from 12 HIV-1-infected mothers and their newborn children were analysed for IgG subclass responses to six HIV-1 envelope peptides by enzyme-linked immunosorbent assay. Levels of IgG were compared with levels of IgG1 and IgG3 to an immunodominant gp41 peptide in children's sera obtained during the first months of life. In a longitudinal study of 16 children born to HIV-1-seropositive mothers, of whom 11 were infected, the IgG1 and IgG3 responses to peptides representing an immunodominant epitope of gp41 and the principal neutralizing determinant of the gp120 V3 region were analysed. RESULTS: IgG1 and IgG3 were found to constitute the predominant peptide-specific antibody responses. A parallel distribution of IgG subclass reactivity was seen in maternal and paediatric sera. There was no evidence of selective antibody transfer. Comparable levels of IgG and IgG1 to the immunodominant peptide were seen in infected and uninfected children, while the IgG3 had disappeared in the majority of uninfected children. A decrease in peptide-specific IgG1 and IgG3 levels was observed in sequential sera from uninfected children, although the kinetic profile varied. Sera from infected children showed de novo synthesis of IgG1 and/or IgG3 binding to the selected HIV-1 peptides. Most children with rapid disease progression failed to produce IgG1 and/or IgG3 to the V3 peptide. CONCLUSION: Analysis of IgG subclass kinetics to selected HIV-1 peptides might be a useful additional diagnostic and prognostic tool in evaluating HIV-1 infection in children born to seropositive mothers.

Adult↗
PubMed1992

Tension transients during steady lengthening of tetanized muscle fibres of the frog.

1. Steady lengthenings at different velocities (0.02-1.6 microns/s per half-sarcomere, temperature 2.5-5.5 degrees C) were imposed on isolated frog muscle fibres at the plateau of the isometric tetanus (tension T0). When tension during lengthening had attained a steady value (Ti), which varied from about 1.5 to about 2 times T0 depending on lengthening velocity, tension transients were elicited by applying step length changes of different amplitudes. The change in length of a selected segment, close to the end of the fibre connected to the force transducer, was controlled by means of a striation follower. 2. The instantaneous plots of tension versus the length change during the step itself showed that at the high forces developed during steady lengthening, as at the plateau of isometric tetanus, the elasticity of the fibre was almost undamped in the whole range of lengthening velocities used. 3. The tension transient elicited by step length changes imposed in isometric conditions exhibited the characteristic four phases described previously: following the tension change simultaneous with the step (phase 1), there was a quick partial recovery (phase 2, the speed of which increased going from the largest step stretch to the largest step release), a subsequent pause or inversion in recovery (phase 3) and finally a slower approach to the tension before the step (phase 4). 4. In the region of small steps the plot of the extreme tension attained during the step (T1) versus step amplitude appeared more linear during steady lengthening than in isometric conditions and deviated progressively from linearity with increase in the size of step releases. The amount of instantaneous shortening necessary to drop tension to zero (Y0), measured by the abscissa intercept of the straight line drawn through T1 points for small steps, was about 4.1 nm per half-sarcomere in isometric conditions and 5.4 nm per half-sarcomere during lengthening at low speed (0.09 microns/s per half-sarcomere, Ti about 1.6 T0). Taken altogether this indicates, in agreement with previous work, that force enhancement during steady lengthening is due to increase in both number and extension of attached cross-bridges. During lengthening at high speed (0.8 microns/s per half-sarcomere), further enhancement in steady force (Ti about 1.9 T0) was accompanied by increase of Y0 to 6.3 nm per half-sarcomere, indicating that increase in lengthening velocity exclusively produces increase in cross-bridge extension.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Amplifications of multiple regions of the HTLV-I genome from DNA of an Italian spastic paraparesis patient but not from DNA of multiple sclerosis patients.

We searched for evidence of infection by the human T-cell lymphoma/leukemia virus type I (HTLV-I) in patients with multiple sclerosis (40 cases); brainstem encephalitis (1 case); Friedreich's ataxia (1 case); spastic paraparesis of unknown etiology (1 case). All patients were from the region of Abruzzo, Italy. Sera were all negative for anti-HTLV-I reactivity by the Western blotting (WB) analysis. DNAs from peripheral blood mononuclear cells were amplified using the polymerase chain reaction (PCR) technique with primers specific for the HTLV-I gag, pol, and env proviral regions. HTLV-I sequences were amplified only in the patient with spastic paraparesis of unknown etiology. In this case, HTLV-I infection might have been related to blood transfusions received 2 years prior to the onset of the neurologic symptoms. Members of the patient's family were negative for HTLV-I by PCR and WB. These data indicate that HTLV-I associated myelopathy is present also in Italy, but fail to substantiate an association of HTLV-I with multiple sclerosis.

Adolescent↗
PubMed1991

Overt and latent HIV 1 and HTLV-I infection in cohorts of at high risk individuals in Argentina.

We conducted a survey using serology and polymerase chain reaction assays to detect HIV 1 and/or HTLV-I antibodies and viral DNA, respectively, in 113 intravenous drug abusers and in 62 sexually active high risk individuals attending two Drug Addict Centres and a Centre for Venereal Diseases in Buenos Aires, Argentina. At the time of the survey 137 of these subjects were known to be HIV 1 seropositive but none of them was symptomatic. Serological tests for HTLV-I were found to be positive in 38 (21.7%) of the HIV 1 positive individuals, whereas all of the 38 HIV 1 seronegative subjects were also seronegative for HTLV-I antibodies. Gene amplification assays carried out in blood sample DNA from the 38 HIV 1/HTLV-I seronegative individuals, revealed HIV 1 DNA in six out of 28 intravenous drug abusers (21.5%). One subject (2.6%) was positive for both HIV 1 and HTLV-I DNA sequences, whereas four (10.5%) showed HTLV-I DNA only. To determine whether these individuals were infected with HTLV-I and/or HTLV-II, DNA samples were also amplified with HTLV-II specific primers and no evidence of HTLV-II infection was observed. None of the subjects seroconverted according to conventional serological tests during the 2 year follow-up period. The 10 seronegative subjects belonging to the sexual risk group were negative for both HIV 1 and HTLV-I in polymerase chain reaction assays. We conclude that not only HIV 1, but also HTLV-I is a widely spread infection in intravenous drug abusers and sexually active high risk individuals in Argentina.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Polymerase chain reaction, virus isolation and antigen assay in HIV-1-antibody-positive mothers and their children.

Diagnosis of perinatal HIV-1 infection is complicated by the persistence of maternal antibodies and the conflicting reports on polymerase chain reaction (PCR) reactivity in children born to HIV-1-seropositive mothers. We have compared PCR with other diagnostic methods for perinatal HIV-1 infection and have attempted also to identify maternal markers which correlate with risk of transmission. PCR was the most sensitive method for early diagnosis of perinatal transmission of HIV-1, but the PCR-positive children (n = 11) developed at least one additional sign of infection. The PCR-negative children (n = 76) were clinically healthy, virus isolation negative, and their serum was HIV-1-antigen-negative. All children who had become seronegative (n = 36) were both PCR- and isolation-negative. Antigenaemia in the mothers correlated significantly with higher risk of perinatal transmission of HIV-1, while no other parameters (clinical stage, lymphocyte subsets, PCR and isolation) showed such a correlation. This indicates that the level of virus expression may be of key importance for the risk of vertical transmission of HIV-1 infection.

CD4 Antigens↗
PubMed1990

The contractile response during steady lengthening of stimulated frog muscle fibres.

1. Steady lengthenings at different velocities (0.025-1.2 microns/s per half-sarcomere; temperature 2-5.5 degrees C) were imposed on isolated frog muscle fibres at the isometric tetanus plateau by means of a loudspeaker motor. The lengthening at the sarcomere level was measured by means of a striation follower either in fixed-end or in length-clamp mode. The force response was measured by a capacitance gauge transducer (resonance frequency 50 kHz). Preparations showing gross non-homogeneity during lengthening were excluded. 2. A steady tension was in all cases reached after about 20 nm per half-sarcomere of lengthening. Tension during this steady phase rose with speed of elongation up to 0.25-0.4 micron/s per half-sarcomere, when tension was 1.9-2 times isometric tetanic force (T0). Further increase in speed produced only very little increase in the steady tension. 3. During the transitory phase, before steady tension was reached, the tension rose monotonically if speed of lengthening was less than 0.25-0.3 micron/s per half-sarcomere; at higher speed the tension rose above the steady level, reaching a peak when extension was 10-14 nm per half-sarcomere, and then fell to the steady level. Tension at the peak continued to rise with speed of lengthening above 0.3 micron/s per half-sarcomere. 4. During the tension rise within the transitory phase of force response the segment elongated at a speed 15-20% lower than that imposed on the whole fibre, as a consequence of tendon compliance. 5. During the steady phase, non-homogeneity of lengthening speed began above a speed of lengthening which varied from fibre to fibre. At speeds below this value, segments elongated at the same speed as that imposed on the fibre. 6. Tension responses to large step stretches (up to 12 nm per half-sarcomere), applied at the plateau of isometric tetanus, showed that the instantaneous elasticity of contractile machinery is not responsible for the limit in force attained with high-speed lengthening. 7. Instantaneous stiffness was determined during the steady state of force response by superposing small steps (less than 1.5 nm per half-sarcomere) on steady lengthening at different velocities. Stiffness was 10-20% larger during lengthening than at the plateau of isometric tetanus and remained practically constant, independent of lengthening velocity, in the range of velocities used. 8. The results indicate that steady lengthening of a tetanized fibre induces a cross-bridge cycle characterized by fast detachment of the cross-bridge extended beyond a critical level.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

[The role of carrier ATPases and neuromediators in neurological disorders].

Physiological and biochemical processes which take place in the nervous system at stroke and neurotrauma are reviewed, and the experience of using low doses of steroid derivatives with piridamole in the treatment of central nervous system (CNS) disorders is summarized. ATPases (including Na,K-ATPase) are reported to play an important role in CNS functioning, the correlation between Na,K-ATPase activity and the extent of CNS injury is revealed. The use of NMR-spectroscopy method for investigation of brain and spinal cord condition in vivo is suggested.

Adenosine Triphosphatases↗
PubMed1989

HIV viral sequences in seronegative people at risk detected by in situ hybridisation and polymerase chain reaction.

A study was conducted to assess the occurrence of latent infection with the human immunodeficiency virus (HIV) among seronegative people at high risk of infection. The presence of HIV genomes was analysed by molecular techniques in two seronegative children born to mothers infected with HIV and in three regular sexual partners of seropositive drug addicts. The adults were selected from a seronegative cohort at high risk of infection because of their sexual contacts and the children selected because of impaired growth. HIV retroviral sequences were detected in four of the five subjects directly at the cellular level by in situ hybridisation in peripheral blood mononuclear cells. HIV genomic sequences were confirmed by in vitro amplification of viral DNA with the polymerase chain reaction technique. The existence of a latent viral infection state in these seronegative subjects indicates the unreliability of standard serological analysis in people who have been in regular contact with infected patients.

Acquired Immunodeficiency Syndrome↗