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Biomedical subjects

R Blasco

Publications and source records attributed to R Blasco.

At least 91 records · Page 5Linked to original sources
PubMed1990

In vitro modifications of rat NTE and other esterases by chemicals which induce delayed neurotoxicity in vivo.

A rat in vitro model has been developed which permits direct study of the biochemical mechanisms involved in delayed neurotoxicity induced by any chemical compound, not only organophosphates. Using rat brain homogenate, a parallel study on the activity of neurotoxic esterase (NTE) and total esterases (TE) compared the action of metamidophos, which is known to induce delayed neurotoxicity, and the synthetic fatty acid anilides, oleylanilide and linoleylanilide. Inhibition in the activity of NTE and TE, unrelated to the concentration and the incubation time assayed, was caused by metamidophos, while the anilides showed a 2-phase concentration-time dependent behaviour. This confirmed the results we previously obtained in vivo. In both cases the appearance of delayed neuropathy was related to modification of NTE activity. We concluded that phosphorylation of the enzyme may not be the only biochemical requirement for the development of delayed neurotoxicity syndromes in which modification of NTE is produced.

Anilides↗
PubMed1989

Genetic variation of African swine fever virus: variable regions near the ends of the viral DNA.

Restriction endonuclease maps of the variable DNA regions of African swine fever virus field isolates from the Iberian peninsula showed that the changes in length are located in the terminal-inverted repetitions and in unique sequences close to the DNA ends. Analysis of nine clones derived from the spleen of an infected pig revealed the existence of frequent length changes within the inverted terminal repetitions. In each clone, changes occurred symmetrically at both terminal-inverted repetitions, suggesting the existence of a terminal-inverted repetition transposition or correction mechanism. Large deletions in unique sequences were detected more frequently in the region located from 8 to 20 kb from the left DNA end. The analysis of this DNA segment from a virulent African swine fever virus isolated in Lisbon (LIS57) showed that this virus strain contains about 8 kb more DNA sequence than the prototype avirulent virus strain (BA71). Hybridization of the additional sequences from LIS57 virus with DNA from different virus field isolates revealed that this DNA region is highly variable in vivo and that it contains several repeated sequences. DNA sequences present around the deletion end points in the variable regions indicate that the deletion process may take place by both homologous and nonhomologous recombination.

African Swine Fever Virus↗
PubMed1989

Variable and constant regions in African swine fever virus DNA.

An analysis of the SalI restriction pattern of African swine fever virus DNA showed that the SalI recognition sites did not change after more than 100 virus passages in porcine macrophages. The virus strain BA71V, obtained from the virus isolate BA71 by adaptation to grow in VERO cells, differed from the nonadapted virus in two deletions with a length of 2.5 and 7 kb located close to the DNA ends. A restriction analysis of several virus clones obtained from a naturally infected pig revealed length heterogeneity in both variable regions. A comparison of SalI restriction maps from 23 African swine fever virus field isolates (8 African, 11 European, and 4 American) has shown that the virus genome consists of a central region with a constant length of about 125 kb and two variable regions located close to the DNA ends with a length of 38-47 kb for the left DNA end, and 13-16 kb for the right DNA end. The total length of ASF virus DNA varied between 178 (BA71) and 189 (MOZ64) kb. The 23 African swine fever virus isolates were classified into five groups, according to the arrangement of the SalI sites in the central region. Four groups contained only African isolates, whereas all the European and American isolates belonged to the same group. This distribution of isolates suggests that all non-African virus field isolates have a common origin.

Africa↗
PubMed1986

Interaction of vasoactive intestinal peptide (VIP) with human peripheral blood lymphocytes: specific binding and cyclic AMP production.

VIP binding sites and cyclic AMP production by the peptide have been studied in human blood mononuclear cells before and after selective depletion of or enrichment for T-lymphocytes, B-lymphocytes-K-NK cells and monocytes. The specifically bound 125I-labelled VIP correlated significantly with the presence of B-lymphocytes and/or cells of K-NK system. The stoichiometric data were compatible with the existence of two classes of binding sites. T-lymphocytes and monocytes did not show binding of the tracer. The cyclic AMP production stimulated by VIP correlated significantly with the presence of B-lymphocytes and/or K-NK cells.

Adult↗
PubMed1984

Restriction site map of African swine fever virus DNA.

Treatment of African swine fever virus DNA (about 170 kbp) with the restriction endonucleases SalI, EcoRI, KpnI, PvuI, and SmaI yielded 14, 31, 17, 13, and 11 fragments, respectively. The order of the restriction fragments produced by each nuclease was established by identifying the crosslinked EcoRI and SalI terminal fragments and then finding overlapping fragments. The five restriction fragment maps were integrated into a single map by locating SalI, KpnI, PvuI, and SmaI sites in cloned EcoRI fragments, and orienting each fragment in the overall map.

African Swine Fever Virus↗
PubMed1984

Immunological abnormalities in the tonsils of patients with IgA nephropathy: inversion in the ratio of IgA: IgG bearing lymphocytes and increased polymeric IgA synthesis.

In the last few years the mucosal origin of the IgA deposited in the kidneys of patients with IgA nephropathy has been examined by several investigators. We have previously presented evidence that polymeric IgA may have a predominant role in the pathogenesis of IgA nephropathy. Taking into account that these patients often present with macroscopic haematuria following respiratory tract infections we have studied the possible existence of immunological abnormalities in the tonsils of patients with IgA nephropathy. Six patients and 13 controls suffering from chronic tonsillitis were submitted to tonsillectomy. Patients with IgA nephropathy showed a significant increase (P less than 0.00025) in IgA bearing lymphocytes (14.4 +/- 2.3) and a significant decrease (P less than 0.025) in IgG bearing lymphocytes (20.5 +/- 4.6) compared to the control group (2.9 +/- 1.4 and 31.6 +/- 3.6, respectively). After 7 days of culture with pokeweed mitogen the percentage of tonsillar cells producing polymeric IgA was significantly higher in the patients than in the controls (66.5 +/- 12.6 vs 33.4 +/- 10.3; P less than 0.005). These results also suggest a mucosal origin for the IgA deposited in the kidneys of these patients. Our data are consistent with the existence of an immunoregulatory dysfunction in the secretory immune system of patients with IgA nephropathy.

Adolescent↗
PubMed1983

T-cell dysfunctions in IgA nephropathy: specific abnormalities in the regulation of IgA synthesis.

This work was undertaken to determine the cellular abnormalities that could explain the high levels of serum IgA frequently found in patients with IgA nephropathy. Seventeen control subjects and twenty-seven patients who had received no therapy were studied. After in vitro pokeweed mitogen (PWM) stimulation, significantly higher amounts of IgA were produced by peripheral blood mononuclear cells (PBM) of patients when compared with those of the control group (560 +/- 97 vs 231 +/- 57 ng/ml, P less than 0.0025). No differences were observed in the synthesis of IgG and IgM. Twenty out of twenty-seven patients presented an increase in the percentages of OKT4+ cells (mean + 2 SD), in relation to the control group, with normal or elevated percentages of OKT8+ cells. The OKT4+/OKT8+ cell ratio was elevated in 12 out of 27 patients. All patients presented some abnormality in the generation of IgA-specific suppressor cells at variable doses of concanavalin A (Con A) on in vitro PWM-stimulated culture of PBM. In both assays low doses of Con A (2.5 micrograms/ml) induced a certain suppression of IgA synthesis in patients that was not observed in the majority of the control group. At these doses some patients also showed an enhancement in the synthesis of IgG and IgM. On the contrary, higher doses of Con A (50 micrograms/ml) produced significantly less IgA suppression than the controls. Normal IgA-suppression values were found at 10 micrograms/ml of Con A. T cells obtained from patients were significantly more efficient than T cells from controls in providing IgA-helper activity for normal allogeneic enriched B cells (P less than 0.025) in PWM-stimulated cocultures. These results show that patients with IgA nephropathy present, after mitogen stimulation in vitro, a specifically increased production of IgA as well as an augmentation in the activity of IgA-helper T cell and a deregulation on IgA-suppressor T-cell function. According to these data, it is suggested that the alteration observed in helper T cells might precede that of suppressor T cells. These immunoregulatory abnormalities might contribute to the pathogenesis of the disease.

Adolescent↗
PubMed1983

Abnormalities of immune regulation in patients with IgA mesangial glomerulonephritis (Berger's disease).

Regulation of the immune response was studied in 22 patients with IgA nephropathy. A significant increase in the IgA production by Pokeweed-stimulated peripheral mononuclear cells maintained in culture for seven days was observed. These patients had significantly less IgA suppressor cell activity, as assessed by the Concanavalin A-generated suppressor cell assay, than the normal controls. The fact that most of the patients studied had increased activity of helper T cells on IgA synthesis, together with an augmentation in the percentage of OKT4+ cells, suggest that the abnormalities in helper T cell function might be the primary defect in this nephropathy. The existence of similar alterations in some of the healthy relatives of the patients further supports a genetic basis for susceptibility to this disease.

Concanavalin A↗
PubMed1983

Immunological studies in a familial IgA nephropathy.

The hypothesis that abnormalities of immune function might occur in healthy first degree relatives of two patients with a familial IgA nephropathy was tested. After 7 days of culture, pokeweed mitogen stimulated peripheral blood mononuclear cells from the two affected members with IgA nephropathy (father and older son), as well as two other healthy sons, produced significantly more polymeric IgA than the controls. The fact that only the two patients with IgA nephropathy presented high serum levels of polymeric IgA favours the idea that a defect in the clearance of this immunoglobulin might be an important step in the appearance of this nephropathy. All the healthy members of the family had a normal OKT4+/OKT8+ cell ratio and a normal concanavalin A generated IgA suppressor cell function in contrast with the abnormalities observed in the two affected members and the previous results in a large number of patients with IgA nephropathy. These data suggest that the primary cellular abnormality might reside in B cells, being the T cell alterations observed in patients a secondary or subsequent phenomenon. These results further support the existence of genetic bases for the susceptibility to this disease.

Antibodies, Monoclonal↗
PubMed1982

Detection of monomeric and polymeric IgA containing immune complexes in serum and kidney from patients with alcoholic liver disease.

The purpose of this study was to characterize circulating IgA and the IgA deposited in the glomeruli of patients with alcoholic liver disease. In the 6 patients studied there was an increased proportion in monomeric IgA (3.5 fold) and IgA between 9-13S (8.94 fold), 13-17S (4.49 fold) and 17-21S (1.63 fold) fractions on 5-40% sucrose density gradient ultracentrifugation at physiological pH. All fraction between 9.12S decreased at acid pH, however a 3.28 fold increase in fractions where polymeric IgA is expected to appear. IgG eluted at acid pH from autopsy kidney was studied by the same procedures. At pH 7.4 about 55% of that IgA have a molecular weight comprised between 9-12S, decreasing to around 25% at acid pH. The existence of true polymeric IgA in serum and kidney was based on the capacity of high molecular weight IgA to bind human secretory component. The amount of immune complexes with monomeric IgA were higher than those with polymeric IgA in serum as well as in kidney. However, the percentage of heavy IgA (probably polymeric IgA) in kidney were, in each patient, higher than those observed in serum. Our results show the presence of high amounts of monomeric and polymeric IgA, both partially as immune complexes, in serum and kidneys of patients with alcoholic liver disease and IgA glomerulonephritis. Furthermore, our data suggest a role for human liver in the clearance of serum IgA such as has been demonstrated in the some animal species, especially in rats.

Antigen-Antibody Complex↗
PubMed1982

Increased rates of polymeric IgA synthesis by circulating lymphoid cells in IgA mesangial glomerulonephritis.

Recently we have described the existence of high levels of polymeric IgA, partially as immune complexes, in the serum and kidney from patients with IgA mesangial glomerulonephritis. As these patients often have macroscopic haematuria, following upper respiratory tract infections, our working hypothesis in this paper was that circulating lymphocytes from secretory tissues after viral stimulus could produce in these patients a large amount of polymeric IgA. To test it, peripheral blood lymphocytes (PBL) from patients and controls were cultured for seven days in the presence or absence of pokeweed mitogen (PWM). In cell culture supernatants immunoglobulin synthesis was measured by RIA and the proportion of polymeric and monomeric IgA was determined on Ultrogel Ac A22 column. There was no difference in spontaneous production of immunoglobulins between patients and controls. On the contrary, the IgA synthetized by PWM-stimulated PBL was significantly higher in patients than in controls. The percentages of IgA with molecular weight between 600,000 and 250,000 after supernate fractionation were significantly higher in patients than in controls. The true nature of polymeric IgA was confirmed by their ability to bind secretory component, the existence of covalent structures, and the decrease of the larger forms of IgA after reduction and alkylation. The percentage of IgA producing cells binding secretory component was significantly higher in patients than in controls (69 +/- 21 versus 44 +/- 27) after seven days of culture. IgM and IgG produced in patient culture were similar to controls. These results show that mitogen stimulated PBL from patients with Berger's disease synthetized a large amount of true polymeric IgA. It is suggested that a similar situation could occur in vivo after viral of other stimuli.

Cells, Cultured↗