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Biomedical subjects

A Nieto

Publications and source records attributed to A Nieto.

At least 253 records · Page 14Linked to original sources
PubMed1986

New experimental criteria for optimization of solid-phase antigen concentration and stability in ELISA.

A peroxidase saturation technique for the determination of coating antigen concentration necessary to saturate polystyrene plates with a wide range of different antigens is described. The same technique has also been used to compare the stability of antigen-polystyrene bonds for native and denaturated antigens. Furthermore, the inappropriate selection of solid-phase antigen concentration and its influence on ELISA results is analyzed and an experimental criterion to select the optimum antigen concentration is proposed. Two different antigens, BSA-Ar and hydatid antigen, were used for ELISA determination of specific antibodies as a model system. Optimum solid-phase antigen concentration was determined by two different methods: peroxidase saturation, in which binding of peroxidase to non-antigen-occupied polystyrene surface sites was used to evaluate the degree of coating by antigen; chequer-board titration, using several immune sera of different affinity. Optimum antigen concentration selected by chequer-board titration using low affinity sera was similar to that selected with peroxidase saturation. On the other hand, lower antigen concentration would be selected by chequer-board titration using high affinity sera. For this reason, the concentrations of low affinity antibodies would be underestimated using the chequer-board titration. These results indicate that peroxidase saturation should be used to avoid avidity-dependent artifacts in ELISA.

Animals↗
PubMed1986

Nucleotide and derived amino acid sequences of a cDNA coding for pre-uteroglobin from the lung of the hare (Lepus capensis).

An almost full-length cDNA coding for pre-uteroglobin from hare lung was cloned and sequenced. The derived amino acid sequence indicated that hare pre-uteroglobin contained 91 amino acids, including a signal peptide of 21 residues. Comparison of the nucleotide sequence of hare pre-uteroglobin cDNA with that previously reported for the rabbit gene indicated five silent point substitutions and six others leading to amino acid changes in the coding region. The untranslated regions of both pre-uteroglobin mRNAs were very similar. The amino acid changes observed are discussed in relation to the different progesterone-binding abilities of both homologous proteins.

Amino Acid Sequence↗
PubMed1986

Neurochemical significance of the red nucleus.

This study reviews some of the more prominent reports related to neuromelanin and the physiological significance of the substantia nigra and the red nucleus. The phylogenetic and ontogenetic parallelism between these two structures is considered. The presence of dopachrome in the red nucleus and of neuromelanin in the substantia nigra is discussed. An experimental study in four human brains in which the red nucleus was injected with zinc sulfate showed the presence of neuromelanin in the red nucleus. This is the first reported demonstration that dopachrome present in the red nucleus is the precursor of neuromelanin.

Adult↗
PubMed1986

Affinity maturation in the arsonate system: lack of dominance of high-affinity antibody subpopulations.

Affinity maturation was studied by the analysis of the kinetics of the appearance of antibody subpopulations with different affinities during the immune response, using an hapten-inhibition ELISA. The immune response in KLH-Ar-immunized A/J mice was used as a model system. Five antibody subpopulations of different affinity (10(3)-10(7) M-1) could be detected, the relative concentrations of which changed during affinity maturation. The high-affinity antibody subpopulations did not represent the major fraction at any stage during affinity maturation. The appearance of the highest affinity subpopulation (10(7) M-1), despite exhibiting relative concentrations no higher than 12%, produced an important increase in average affinity. On the other hand, its disappearance at the end of the maturation process could explain the average affinity decrease observed at this stage. Our results indicate that affinity maturation cannot be explained by the dominance of high-affinity clones, as proposed by Siskind & Benacerraf (1969). The increase in affinity could rather be due to the progressive appearance of low percentages of high-affinity clones, which are not present in the primary response and never become dominant.

Animals↗
PubMed1985

[Pharmacokinetics of a new slow-release theophylline preparation in asthmatic children].

This study compares the pharmacokinetics of two preparations of slow-release theophylline, one of them already known, and the other one a new product (micronized), very well accepted by pediatric patients. Two similar groups of fifteen patients each all of then asthmatic children under ten years of age, were selected and given a single oral dose of 10 mg/kg of one of the preparations. The pharmacokinetic parameters (T 1/2, Kel, VD, Cl and AUC) did not differ between both groups. The new product could further be used more safely, due to its lower incidence of "erratic" behaviour.

Asthma↗
PubMed1985

Glucocorticoids induce the expression of the uteroglobin gene in rabbit foetal lung explants cultured in vitro.

In 27-day-old rabbit foetal lung explants cultured in vitro, the synthesis of the protein uteroglobin decreased progressively during several days of culture. Addition of glucocorticoids to the medium progressively induced the synthesis of uteroglobin in a dose-dependent manner without affecting the synthesis of total proteins. The glucocorticoid-mediated induction of uteroglobin appears mainly due to increased amounts of uteroglobin mRNA and seems to be independent of simultaneous cell proliferation, suggesting a glucocorticoid-triggered differentiation of pre-existing cells. The results suggest a major role of glucocorticoids in the developmental regulation of the uteroglobin gene in the lung.

Animals↗
PubMed1985

Cell-free synthesis of preuteroglobin and processing to uteroglobin by polysomes from rabbit endometrium.

Polysomes from rabbit endometrium, incubated in a cell-free system in the presence of [35S]methionine, completed polypeptide chains pre-initiated in vivo. Polypeptide chains were analyzed by SDS-gel electrophoresis after immunoprecipitation with anti-uteroglobin. Endometrial polysomes, freed of membranes by detergent treatment, synthesized both mature uteroglobin and preuteroglobin not yet cleaved in vivo. Membrane-bound polysomes synthesized exclusively mature uteroglobin, indicating the processing of preuteroglobin by the membranes bound to the ribosomes.

Animals↗
PubMed1985

Antibodies to vimentin intermediate filaments in sera from patients with SLE and RA: quantitation by solid phase radioimmunoassay.

A solid phase radioimmunoassay was used to quantify levels of antibodies to vimentin intermediate filaments (VIF) of the cytoskeleton in sera from patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Significantly higher levels of these antibodies were found in 52% of the SLE sera studied, compared to 6% in RA sera and 10% of sera from healthy controls. These antibodies include IgG and IgM classes of immunoglobulins. Our results show that high levels of anti-VIF antibodies are more prevalent in SLE sera, whereas no significant differences are found between sera from patients with RA and healthy controls.

Adult↗
PubMed1985

Application of ELISA-inhibition to Aspergillus antigen standardization for immunodiagnosis.

An inhibition ELISA method was used to test culture filtrate antigens of Aspergillus fumigatus for the avidity of antibodies to them. Four different culture media were used to check the ability of this assay to distinguish between similar antigenic preparations. Differences between antigens exhibiting similar crossed immunoelectrophoresis patterns were observed by inhibition ELISA.

Antibodies, Fungal↗
PubMed1984

Glucocorticoid-dependent uteroglobin synthesis and uteroglobulin mRNA levels in rabbit lung explants cultured in vitro.

In rabbit lung explants cultured in vitro in a synthetic medium, the synthesis of the protein uteroglobin decayed progressively becoming virtually undetectable between 24-48 h of culture. Addition of glucocorticoids to the medium maintained the synthesis of uteroglobin. This glucocorticoid effect was dose-dependent with optima at about 0.1 microM and 1 microM for dexamethasone and cortisol respectively. Estradiol, progesterone, triiodothyronine, insulin or 10% calf serum added to the medium were ineffective in maintaining uteroglobin synthesis. Actinomycin D (10 micrograms/ml) added to the medium inhibited the effect of cortisol on uteroglobin synthesis. After 24 h of culture, both the relative levels of uteroglobin mRNA, measured by molecular hybridization, and uteroglobin synthesis were correlatively higher (up to 10-fold) in glucocorticoid-treated than in control explants.

Animals↗
PubMed1984

Nucleotide sequence of two rasH related-genes isolated from the yeast Saccharomyces cerevisiae.

A complete nucleotide sequence of two ras-related yeast genes (c- rassc -1 and c- rassc -2) isolated from the yeast strain Saccharomyces cerevisiae is reported. They encode predicted polypeptides of 40,000 and 41,000 daltons, respectively. The N-terminal 170 amino acids from both genes show extensive amino acid homology to other ras genes from vertebrates, whereas their C-termini have diverged. These genes should be useful in the elucidation of a normal biological function of ras-related genes in a simple system like yeast.

Amino Acid Sequence↗
PubMed1984

Antibodies to vimentin intermediate filaments in sera from patients with systemic lupus erythematosus.

Sera from patients with systemic lupus erythematosus and from healthy subjects were tested, using immunofluorescence and blotting techniques, for the presence of antibodies to intermediate filaments of the cytoskeleton of human skin fibroblasts. Both techniques showed that antibodies to intermediate filaments were found in a higher proportion of sera from patients (53%) than healthy subjects (9%). The antigen target was found to be the protein band that corresponded to vimentin (Mr 57,000).

Adolescent↗
PubMed1984

Direct measurement of antibody affinity distribution by hapten-inhibition enzyme immunoassay.

A rapid, simple and reliable technique for determining the affinities of antibody subpopulations in a complex mixture is described. The principle of this method is that antigen conc can be represented as the amount of antigen immobilized on the polystyrene surface of a microwell containing a fixed vol of diluted antibody. Thus, by measuring the proportion of antibody bound to different wells coated with varying amounts of antigen, it is a straightforward matter to calculate an affinity distribution. We have verified that: (1) the amount of antigen bound to a polystyrene plate is proportional to the concn of antigen used for sensitization and follows a typical saturation curve; (2) the antibodies bound to plates sensitized with low concns of antigen are of higher affinity than those bound to plates sensitized with high concns of antigen; (3) an apparent affinity constant (aK) is defined as the reciprocal concn of free hapten required for 50% inhibition of antibody binding to immobilized antigen; (4) the aK determined by this method is in close agreement with the intrinsic affinity constant (K) measured by fluorescence quenching or the Farr assay; and (5) that during the course of immunization in vivo there is a clear shift to higher-affinity antibody subpopulations.

Animals↗
PubMed1984

Uteroglobin mRNA from the lung of the hare (Lepus capensis): cell-free translation and properties.

Poly(A)-containing RNA was obtained from the lung of hares (Lepus capensis) and uteroglobin mRNA was characterized by cell-free translation and molecular hybridization to a rabbit uteroglobin cDNA probe. In the cell-free system, hare uteroglobin mRNA was preferentially translated as compared to the whole lung mRNA and it directed the synthesis of a precursor, preuteroglobin, containing about twenty additional amino acids. Hare uteroglobin mRNA was about 40 nucleotides larger than the homologous rabbit one, as analyzed by electrophoresis on agarose gel. Thermal stability of the hybrids formed between rabbit or hare uteroglobin mRNAs and the rabbit cDNA probe indicated differences in the nucleotide sequence of both mRNAs. The levels of uteroglobin mRNA and uteroglobin synthesis in lung are about two-fold higher in hare than in rabbit lung.

Animals↗
PubMed1983

Isolation and characterization of uteroglobin from the lung of the hare (Lepus capensis).

Uteroglobin has been purified from hare lung by gel filtration and chromatography on carboxymethyl-cellulose. Hare uteroglobin appears homogeneous by electrophoresis under both denaturing and nondenaturing conditions. Its chemical and immunological properties as well as its ability to bind progesterone are compared to those of rabbit uteroglobin. The two proteins have the same N-terminal residue (glycine) and both lack tryptophan but differ in amino acid composition. Sodium dodecyl sulfate-gel electrophoresis shows that hare uteroglobin is composed of two subunits of identical Mr (about 7000) held together by disulfide bridges. The amino acid composition indicates a subunit composed of 65-67 residues, which is compatible with the apparent Mr observed. Thus, hare uteroglobin appears to be slightly smaller than the rabbit protein. Hare uteroglobin partially reacts with anti-rabbit uteroglobin in a radioimmunoassay and also binds progesterone, although this binding is relatively unaffected by dithiothreitol. The synthesis of hare uteroglobin in the uterus appears to be rather insensitive to ovarian steroid hormones.

Amino Acids↗
PubMed1983

Projections of the caudate nucleus in cats and kittens.

Small electrolytic lesions were placed on the head of the caudate nucleus of kittens between 8 and 21 days postnatally and in adult cats. Coronal sections of the whole brain were studied under the light microscope with the Fink and Heimer staining method. Degenerating axon terminals could be recognized after a survival period of 30 h for kittens and 8 days for adults, as dark spots and broken fibers. The results indicate extensive degenerative lesions at both diencephalic and brain stem levels. In general the degenerative lesions were denser in kittens when compared with adult animals. The results of this study suggest that the caudate nucleus of immature animals could be more sensitive to the lesions occurring during the time of early synaptogenesis. Moreover, the caudate nucleus could be an important point of convergence of descending pathways exerting a diffuse modulatory action upon several brain structures related to movement.

Animals↗
PubMed1983

Hormonal activation of phospholipid methyltransferase in the Leydig cell.

Hormonal stimulation of purified rat Leydig cells with hCG caused a 2-fold increase in phospholipid methyltransferase activity within 10 min. This effect of gonadotropin was concentration dependent, with maximal activation of methyltransferase at 10(-12) M hCG, and was reproduced by 8-bromo-cAMP. Hormonal activation of phospholipid methyltransferase caused an increase in the maximum velocity of the enzyme, without changing the Km for S-adenosylmethionine. Analysis of the pattern of radiolabeled phospholipids from Leydig cells showed that the incorporation of methyl groups and the increase in phospholipid methylation stimulated by 8-bromo-cAMP occurred mainly in phosphatidyl-N-monomethylethanolamine. The rapid and highly sensitive increase in phospholipid methylation in hCG-stimulated Leydig cells is consistent with a role of methyltransferase in the hormonal activation mechanism probably at a step subsequent to cAMP production.

1-Methyl-3-isobutylxanthine↗