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J García

Publications and source records attributed to J García.

At least 271 records · Page 15Linked to original sources
PubMed1991

Fine mapping of canine parvovirus B cell epitopes.

In this report we describe the topological mapping of neutralizing domains of canine parvovirus (CPV). We obtained 11 CPV-specific monoclonal antibodies (MAbs), six of which are neutralizing. The reactivities were as determined by ELISA and Western blot (immunoblot) analysis. VP2, the most abundant protein of the CPV capsid, seemed to contain all the neutralization sites. Also, an almost full-length genomic clone of CPV was constructed in the bacterial plasmid pUC18 to enable expression of CPV proteins. All the neutralizing MAbs recognized recombinant VP2 when it was expressed as a free protein in Escherichia coli but not when expressed as a fusion protein with glutathione-S-transferase. When two large fragments containing about 85% and 67% of the C terminus of VP2 were expressed, no neutralization sites were detected. When fusion proteins containing the N terminus were expressed, two linear determinants were mapped, one between residues 1 to 10 of VP2, and the other between amino acids 11 and 23. The peptide 11 GQPAVRNERATGS 23, recognized by MAb 3C9, was synthesized chemically and checked for immunogenicity, not being able to induce neutralizing activity. Although the antibody response in rabbits to all the fusion proteins was uniformly high, the anti-CPV response was very variable. Protein from pCPVEx11, which contains a T cell epitope (peptide PKIFINLAKKKKAG) present in the VP1-specific region as well as the B cell epitopes, seemed to be the most effective in inducing virus neutralization.

Amino Acid Sequence↗
PubMed1991

Differential effects of ryanodine and tetracaine on charge movement and calcium transients in frog skeletal muscle.

1. Charge movement and myoplasmic calcium transients were simultaneously recorded from frog skeletal muscle fibres by using the double-seal Vaseline-gap technique. Calcium transients were monitored with the fluorescent indicator Rhod-2. 2. Ryanodine modified the kinetics and the total amount of charge moved during depolarizing pulses (Q(on)), while it did not significantly modify the charge after repolarization (Q(off)). The extracellular application of 100 microM-ryanodine elicited a temporary initial increase of the delayed component of charge movement (Q gamma) and the calcium transient. Both phenomena were later blocked with the same temporal course and to the same extent. 3. The blockade of Q gamma and the calcium transient was also observed with ryanodine concentrations of 1-10 microM. For membrane potentials positive to -10mV, the Qon measured was larger in the presence of ryanodine; Qoff was not modified. 4. Tetracaine (400-500 microM) blocked a similar delayed component of Qon, identified as Q gamma, as well as the calcium transient monitored simultaneously. This effect was observed in the first minutes after the addition of tetracaine to the extracellular solution. 5. Tetracaine blocked a faster initial component of Qon for voltages positive to -10 mV, corresponding to the voltage range of activation of the calcium current. At these same membrane potentials, Qoff was also reduced to a similar extent to Qon. 6. Ryanodine and tetracaine showed different effects on calcium current. Whereas the slow calcium current was not modified upon the addition of ryanodine, it was completely blocked in the presence of tetracaine. The blockade of the slow calcium current made evident the fast calcium current. The effects of tetracaine on the charge movement, the calcium transient and the slow calcium current were reversible. 7. These results suggest that ryanodine and tetracaine may act at different sites. Ryanodine exerts its effect on the sarcoplasmic reticulum ryanodine receptor, blocking calcium release and Q gamma, while tetracaine at these concentrations may affect the release channel and the dihydropyridine receptor, causing a blockade of the charge movement, calcium transient and calcium current.

Animals↗
PubMed1991

Calcium current and charge movement of mammalian muscle: action of amyotrophic lateral sclerosis immunoglobulins.

1. The Vaseline-gap voltage clamp technique was used to record dihydropyridine (DHP)-sensitive Ca2+ currents (ICa) and charge movement in single cut fibres from the rat extensor digitorum longus (EDL) muscle. Amyotrophic lateral sclerosis (ALS) immunoglobulin G (IgG) action on ICa and charge movement has been characterized. 2. ALS IgG reduced ICa amplitude. The peak ICa of EDL fibres (mean +/- S.E.M.) at 0 mV, expressed as amperes per membrane capacitance, was -4.79 +/- 0.029 A F-1, while after 30 min incubation in ALS IgG it was -2.52 +/- 0.04 A F-1. IgG from healthy patients, and from patients with other diseases (familial ALS, myasthenia gravis, chronic relapsing inflammatory polyneuritis, multiple sclerosis and one sample from Lambert-Eaton syndrome, LES) did not affect ICa, while IgG from patients with Guillain-Barré syndrome and one other sample from a patient with LES affected the ICa in a similar way as ALS IgG. 3. The time constant of ICa activation (alpha m) at 0 mV was 44.8 +/- 1.4 ms in control, and 36.6 +/- 1.5 ms after an incubation of 30 min in ALS IgG. The steady-state activation curve (m infinity) was shifted to more positive potentials by ALS IgG. 4. The rate constants of activation (range -20 to 30 mV) were altered by ALS IgG: alpha m decreased while beta m increased. These data suggest that ALS IgG favours the permanence of the Ca2+ channels in the closed state. 5. The time constant of Ca2+ channels deactivation at -90 mV with a pre-pulse to 0 mV was 4.4 +/- 0.5 ms in control and 4.1 +/- 0.6 ms in ALS IgG. The relationship between the deactivation time constant and membrane potential was not significantly modified by ALS IgG. 6. ICa inactivation was not affected by ALS IgG. The potentials of half-inactivation were -32.1 and -36.6 mV in control and ALS IgG, respectively. Similarly, the rate constants of inactivation (alpha h and beta h) remained unaltered by ALS IgG. 7. We successfully blocked ICa with 100 microM-TMB-8 (3,4,5-trimethoxybenzoic acid 8-(diethylamino)octyl ester hydrochloride), without major effects on charge movement. We adopted this procedure to study charge movement. ALS IgG reduced charge movement without significant effects on the effective valence and voltage dependence. Qon and Qoff, the charges during and after the pulse, were similarly affected by ALS IgG. 8. The actions of ALS IgG on DHP-sensitive Ca2+ current and charge movement suggest an interaction between ALS IgG and some component of the DHP-receptor complex.

Adult↗
PubMed1991

IgG from amyotrophic lateral sclerosis affects tubular calcium channels of skeletal muscle.

Amyotrophic lateral sclerosis (ALS) is a devastating human disease of upper and lower motoneurons. We studied the action of the immunoglobulin G (IgG) from ALS and disease control patients on dihydropyridine (DHP)-sensitive Ca2+ channels in single mammalian skeletal muscle fibers with the double Vaseline gap technique. The peak of the Ca2+ current (ICa) and the charge movement were reduced when the fibers were incubated in ALS IgG. These effects were lost when the IgG was boiled or adsorbed with skeletal tubular membranes. ALS IgG reduced skeletal muscle ICa in a similar fashion as nifedipine; the ICa blockade was voltage dependent, and the associated charge movement was reduced. These observations suggest that IgG from ALS patients reacts with the skeletal muscle DHP-sensitive Ca2+ channels or some associated regulatory moiety.

Adult↗
PubMed1991

[The spontaneous regression of a rhabdomyoma of the right ventricle].

Rhabdomyoma is the most common intracardiac tumor in the newborn. The diagnosis is made by the clinical history and the physical examination, the electrocardiogram, chest X-ray, and the echocardiographic data. It has a poor prognosis, 80% dying in the first year of life because congestive heart failure or sudden death. Rarely, spontaneous regression has been described. We present the case of a newborn diagnosed of tuberous sclerosis, with an echocardiographic image of a rhabdomyoma in the right ventricle with a spontaneous total regression of the tumor 2 years later.

Echocardiography↗
PubMed1990

[Treatment of resistant or relapsing Hodgkin's disease with high doses of chemotherapy followed by autologous bone marrow transplant].

Eleven patients with Hodgkin's disease were treated with high-dose chemotherapy followed by autologous bone marrow transplantation (ABMT). Four patients were resistant to initial therapy and 7 patients had relapsed but were progressing under second or third line therapy. The median time from initial diagnosis to transplantation was 44 months (range, 16 to 82). In 9 patients pre-ABMT consisted on high-dose CVB cyclophosphamide, etoposide and carmustine) chemotherapy, one patient was treated with BACT protocol (carmustine, cytosine arabinoside, cyclophosphamide and thioguanine) and other patient was treated with high-dose of busulfan and melphalan. In 8 patients complete remission (CR) was achieved, in one the remission was partial, one failed to respond and one case was not evaluable due to early death. Among CR patients, 2 died from late toxicity, and the other 6 remain in CR off therapy, one of them more than 33 months after ABMT. High-dose therapy produce severe myelosuppression in all patients. There were 3 treatment related death: one early death due to hemorrhagic myocarditis, one veno-occlusive disease of the liver and one due to cytomegalovirus sepsis. The high complete response rate in these heavily pretreated patients suggests that there may be an indication for high-dose therapy and ABMT in earlier resistant Hodgkin's disease. Moreover under such conditions, treatment related morbidity would be expected to be lower.

Adolescent↗
PubMed1990

Increased MEPP frequency as an early sign of experimental immune-mediated motoneuron disease.

Intracellular recordings of miniature end-plate potentials were performed in extensor digitorum longus muscles from guinea pigs with experimental immune-mediated motoneuron destruction. In the early stages of the disease, the miniature end-plate potential frequency was elevated compared to that in control and normal animals. The amplitude and time course of the miniature end-plate potentials as well as the resting potential of the muscle fibers were not altered, which implies integrity of the postjunctional membrane. The increase in frequency of miniature end-plate potential reflects an increase of basal acetylcholine release and documents dysfunction of the presynaptic terminal of the neuromuscular junction. The increased frequency was associated with high levels of antimotoneuronal IgG in the blood and the presence of IgG at motor end-plates. These data suggest that the presynaptic terminal of the neuromuscular junction may be involved in the immune attack in animal models of motoneuron degeneration.

Animals↗
PubMed1990

Charge movement and calcium currents in skeletal muscle fibers are enhanced by GTP gamma S.

G-proteins play several regulatory roles in the cell. They can modulate ionic channels directly or in association with second messengers. In skeletal muscle, G-proteins modulate the activity of calcium channels either by acting directly on the channel and/or through a cAMP-dependent phosphorylating mechanism. The activation of G-proteins by GTP gamma S can also induce force generation in skinned fibers. In this paper we studied the effect of GTP gamma S on charge movement and calcium currents (ICa) in rat and frog skeletal muscle, using the Vaseline gap technique. We observed an increase in both charge movement and ICa after the intracellular addition of 10-100 microM GTP gamma S. GDP beta S did not have any effect. Addition of protein kinase A catalytic subunit increased the ICa, probably through a phosphorylation process, but did not modify the charge movement. This suggests that protein kinase A and GTP gamma S are acting on different sites of the channel. It can be speculated that G-proteins may have a regulatory role in the excitation-contraction coupling mechanism by a direct effect on charge movement.

Animals↗
PubMed1990

Analysis of genetic variability in human respiratory syncytial virus by the RNase A mismatch cleavage method: subtype divergence and heterogeneity.

We have applied the RNase A mismatch cleavage method to the analysis of genetic variability among human Respiratory Syncytial (RS) viruses. Antisense RNA probes of the Long strain were hybridized to total RNA extracted from cells infected with other strains. The RNA:RNA heteroduplexes were digested with RNase A and the resistant products analyzed by gel electrophoresis. Each virus generated characteristic band patterns with the different probes. Comparative analyses of the cleavage patterns indicate that antigenic subtypes correlate with genetically distinct viral groups. Viruses within each subtype, however, show substantial genetic heterogeneity and progressive accumulation of genetic changes with time. This heterogeneity is also observed among viruses of the same epidemic outbreak which cannot be distinguished with a panel of monoclonal antibodies. Different genes and gene regions also differ in their rates of change. These results are discussed in terms of RS virus evolution.

Cell Line↗
PubMed1990

Rapid fluorescence method for screening Salmonella spp. from enteric differential agars.

Four hundred thirty-two lactose-negative colonies isolated from human feces on stool differential agar media were flooded with one drop of MUCAP Test reagent (Biolife Italiana S.r.I., Milan, Italy) and observed under a Wood lamp for the development of a blue fluorescence over or around the colony. On the basis of manual and automated conventional tests for the screening of Salmonella spp., the MUCAP Test yielded the following results: 79 true-positives, 314 true-negatives, 35 false-positives, and 4 false-negatives (sensitivity, 95%; specificity, 90%; positive predictive value, 69%; negative predictive value, 99%). The specificity of the test performed on colonies isolated on MacConkey agar (95%) was higher than that performed on colonies isolated on SS agar (88%; P less than 0.03). The MUCAP Test is an easy, rapid, and sensitive method for the screening of colonies suspected of being Salmonella spp., reducing the number of biochemical tests needed.

Agar↗
PubMed1990

Functional studies of Ca2+ channels from plasmalemma and sarcoplasmic reticulum membranes in muscle cells.

Physiological and biochemical studies (channel characteristics, intracellular Ca2+ determinations and, channel purification, cloning and expression) of the different components involved in the regulation of intercellular Ca2+ have provided new information about their specific role. Recent information favors a major role for plasmalemma Ca2+ channels in E-C coupling of cardiac muscle, while a major role for sarcoplasmic reticulum Ca2+ release channels (ryanodine receptors) is proposed for E-C coupling of skeletal muscle. In smooth muscle, both plasmalemma and sarcoplasmic reticulum (IP3 receptors) Ca2+ channels are involved in E-C coupling. These studies will be comparatively discussed for skeletal, cardiac and smooth muscle cells.

Animals↗
PubMed1990

[Prevalence of depression syndrome and its relationship with socioeconomic factors in a population of Valencia City, Carabobo state, Venezuela].

During the months of April and May of 1985, 3218 individuals were studied, in the city of Valencia, Carabobo State, Venezuela, there were chosen at random out of the population whose ages ranged between 15 years and over. A two parts questionnaire was made consisting on the Self-rating Depression Scale by Zung, and the study of socioeconomic factors of the individuals. Frank depression was found in 36.8% of individuals and 55% tendency towards depression, with a mean depression index of 0.48 and a standard deviation of 0.12. The groups that showed the largest prevalence of frank depression were: females 40.4%, ages ranging between 65 years and over 46.2%, widowhood 70.7%, illiterates 65.8%, crippled 50%, and those with low grade of satisfaction with their actual occupation 55.2%. These data suggest the high frequency of Depressive Syndrome in the studied population, and also the strong relationship existing between this syndrome and socioeconomic factors implicated.

Adolescent↗