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Biomedical subjects

J Esparza

Publications and source records attributed to J Esparza.

At least 19 recordsLinked to original sources
PubMed1992

Use of synthetic peptides corresponding to sequences of Mycobacterium leprae proteins to study delayed-type hypersensitivity response in sensitized guinea pigs.

In this work we report the synthesis of 10 peptides (P1-P10) corresponding to one or several segments of the amino acid sequence of proteins from Mycobacterium leprae: 65 kDa, 28 kDa, 18 kDa, and 28 kDa superoxide dismutase, recently renamed antigens 2L, 9L, 12L, and 14L, respectively. They were assayed in the guinea pig model for the induction of a delayed-type hypersensitivity response in M. leprae and BCG-sensitized animals. To sensitize the animals two schemes were used: either a single dose of 5 x 10(9) irradiated or autoclaved whole bacilli, or four weekly intramuscular injections each containing 500 micrograms of soluble extract of M. leprae (MLSE) in incomplete Freund's adjuvant. Because the second scheme used far too much antigen, we decided to use the first scheme for the experiments we report here. DTH reactions of sensitized animals were induced after 30 days with intradermal injections of 5 micrograms of MLSE and with each of the 10 peptides at three different concentrations: 250 micrograms, 100 micrograms, and 0.05 micrograms. All M. leprae-sensitized guinea pigs gave indurations of 10 mm or more with MLSE, which indicates that the animals were sensitized. None of them gave DTH indurations with 250 micrograms or 100 micrograms, but some of them had positive DTH reactions with the 0.05 micrograms doses of the synthetic peptides. This is most likely due to the fact that we have used an outbred strain of guinea pigs. The peptides were also tested at 0.05 micrograms in animals sensitized with BCG. P7 and P10 seem to be nonspecific peptides; the remaining peptides only induced DTH in the M. leprae-sensitized guinea pigs. P3 (segments 65-85 of the 65-kDa protein) induced a positive DTH in 58% of the tested animals. In other experiments, guinea pigs were sensitized with a single injection (500 micrograms) of each of the synthetic peptides. All animals, except those sensitized with P4 and P8, had positive DTH responses when the homologous peptide was used. Those sensitized with P2, P4, P5, P7, and P8 were able to produce indurations when MLSE was used for the induction of the DTH reaction.

Amino Acid Sequence↗
PubMed1990

World Health Organization quality assessment programme on HIV testing.

A serum panel comprising 19 samples of known (five positives and 14 negatives) but undisclosed HIV-1-antibody content was distributed to 30 national reference laboratories for HIV serology. In order to simulate normal circumstances of referral, participants were asked to test the panel for HIV-1-antibody status using their normal procedures. Results of testing were returned by 28 participants. There were great variations in the number and combinations of tests used. The number used ranged from one to five assays per laboratory and none of the 24 laboratories using two or more tests employed the same combination. A high average success rate of 99% was seen with the positive samples. More errors occurred with the negative samples, with an average of 87% correct negative reports. Only four of the 14 negative specimens were reported as negative by all participants.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Hydatid disease of the spleen: imaging findings in nine patients.

Splenic involvement is uncommon in patients with hydatid disease. The radiologic and clinical findings in nine patients with splenic hydatidosis are described. The three men and six women were 41-76 years old (mean, 58 years). Their histories and physical findings, the results of serologic tests for hydatidosis, and imaging procedures were evaluated. Plain abdominal radiographs were obtained in all nine patients, sonograms in six, and CT scans in seven. Plain films showed calcification of the cyst wall in four of the nine patients. On sonograms, five lesions were anechoic and one was echogenic. On CT scans, all lesions except one were of lower attenuation than the surrounding spleen. None of the lesions enhanced after administration of IV contrast material. Although rare, splenic hydatidosis should be included in the differential diagnosis when a cystic splenic lesion is identified with sonography or CT.

Adult↗
PubMed1987

Arteriovenous malformation of the spinal cord in the neonate.

A newborn baby boy with a high-flow arteriovenous malformation (AVM) of the dorsal spinal cord is reported. The baby was born paraplegic. The myelogram suggested an increased vasculature, showing irregular worm-like radiolucent lesions of the dorsal spinal cord. Spinal angiography showed a huge arteriovenous angioma of the dorsal spinal cord with an intra-spinal aneurysmal sac. The vascular supply was decreased after two embolizations. This was followed by complete surgical resection of the aneurysmal sac.

Arteriovenous Malformations↗
PubMed1987

Characterization of rotaviruses isolated from pigs with diarrhoea in Venezuela.

The prevalence of porcine rotavirus infection was studied in 15 different herds located in the north-western region of Venezuela. The presence of rotavirus was studied by direct electron microscopy (EM) and by an enzyme-linked immunosorbent assay (ELISA). From 136 samples analyzed during the six months of the study (September 1983-February 1984), 38 (27.9%) were found to be positive for rotaviruses, with infection more common in animals that were 4-6 weeks old. Atypical rotaviruses were not detected in any of the samples examined. Most rotavirus positive specimens were subgrouped using specific monoclonal antibodies in an ELISA test. The majority of the samples (26 out of 38) were found to exhibit Subgroup I antigenicity. Only two specimens, collected from the same herd in two consecutive months, were found to belong to Subgroup II. To characterize further the circulating rotaviruses, electrophoretic analysis of the RNA genome was performed on samples selected from nine different herds. Great variability in the RNA electropherotypes was observed. No correlation was found between subgroup specificity and the migration of the two smaller segments (Genes 10 and 11), as has been described for human rotaviruses.

Animals↗
PubMed1987

Preliminary characterization of Escherichia coli isolated from pigs with diarrhoea in Venezuela.

The aetiology of neonatal porcine diarrhoea was studied in 15 different herds located in the north-western region of Venezuela. Of 56 strains of Escherichia coli analyzed, 16 (28.6%) were shown to produce heat-stable (STa) enterotoxin, as detected by infant mouse assay. Only four of these STa+ isolates also possessed the K88 pilus antigen, two were 987P+ and none possessed the K99 antigen, leaving 10 STa+ samples in which no pilus antigen was identified. Among the 40 STa negative samples were six K88+ specimens, one K99+, four 987P+, one which reacted as K88+ + K99+ and one K88+ + 987P+. Considering as pathogenic any strain showing at least one of the characters studied, pathogenic E. coli were detected with an overall frequency of 42.9%, being more prevalent during the second week of life. An electrophoretic analysis of the plasmid content of the field isolates of E. coli, revealed the presence of numerous species of extrachromosomal DNA, although no direction association could be made between a particular plasmid and any of the pathogenic characteristics identified. Results of Southern blot analysis indicate that the STa enterotoxin was preferentially encoded within an endemic plasmid of 4.9 Md. Other plasmids present in the E. coli isolates could be related to antibiotic resistance. With the exception of one strain, all E. coli isolates were resistant to more than one of the nine drugs tested; multiresistant E. coli were frequently isolated, including four strains which were resistant to seven antibiotics.

Animals↗
PubMed1987

Penetration and uncoating of rotaviruses in cultured cells.

Early steps of replication (penetration and uncoating) of the OSU strain of porcine rotavirus were studied in MA-104 cells. After adsorption of trypsin-treated viruses at 4 degrees, followed by a shifting of the temperature to 37 degrees, particles were seen within coated pits, coated vesicles, and secondary lysosomes, indicating that virus entry occurred by receptor-mediated endocytosis, and that uncoating (removal of the outer capsid) could occur by the effect of lysosomal enzymes. This latter aspect was studied using lysosomotropic drugs (chloroquine and ammonium chloride), which were found not to inhibit rotavirus replication, indicating that the low intralysosomal pH is not responsible for virus uncoating. The effect of Ca2+ concentration on intracellular rotavirus uncoating was investigated by treating cells with the calcium ionophore A23187, to increase the intracellular Ca2+ concentration during the early stages of virus replication. Under these conditions rotavirus uncoating did not occur, suggesting that the low Ca2+ concentration in the intracellular microenvironment may be responsible for rotavirus uncoating.

Ammonium Chloride↗
PubMed1986

VP7 serotype-specific glycoprotein of OSU porcine rotavirus: coding assignment and gene sequence.

With a reassortant from a cross of human rotavirus DS-1 (serotype 2) and OSU (serotype 5) it was determined that the OSU major neutralization glycoprotein antigen (VP7) was encoded by gene segment 9. A full-sized cloned cDNA copy of the OSU gene 9 was produced and sequenced. Hybridization of such labelled cDNA with the corresponding segment of a reassortant DS-1 X OSU virus confirmed the coding assignment. Comparison of the deduced amino acid sequence of the VP7 of OSU with those previously determined for five other rotavirus strains, representing four distinct serotypes, revealed some hydrophilic regions that exhibited significant homology and other hydrophilic domains with greater amino acid divergence. In one of the latter hydrophilic domains each of the five serotypes had a distinct amino acid substitution at residue 146, suggesting that it may be involved in serotype specificity.

Amino Acid Sequence↗
PubMed1986

The structure of the rotavirus inner capsid studied by electron microscopy of chemically disrupted particles.

The inner capsid structure of the OSU strain of porcine rotavirus was studied by electron microscopy of freeze-dried preparations and of negatively stained chemically disrupted virus particles. The analysis of the particles by the freeze-drying technique revealed a T:13 l (laevo) symmetry for the organization of the inner capsid. Treatment of single-capsid rotavirus particles with 30% formamide or 5 M-urea resulted in their degradation, giving rise to very similar products, corresponding to isolated vertices, edges and faces of the virus icosahedron. An analysis of such structures confirmed the triangulation number and handedness of the rotavirus inner capsid, and provided evidence for the open-mesh model, in which the five- and six-coordinated axes are represented by 'holes' formed by smaller trimeric morphological subunits.

Animals↗
PubMed1986

Symptomatic subependymoma: report of four new cases studied with computed tomography and review of the literature.

The authors describe four cases of subependymoma studied with computed tomography (CT) and review 18 previously reported cases in an attempt to define the most characteristic CT presentation of this rare, benign tumor. Subependymoma usually appears as an isodense, or even hypodense, intraventricular tumor on plain CT scan and shows minimal or no enhancement in postcontrast studies. Differential diagnosis between subependymoma and the more malignant true ependymoma is difficult, particularly when the tumor occurs in the posterior fossa. Recognition of subependymoma should prompt the surgeon to attempt radical tumor removal because it can be achieved without sacrificing contiguous tissue and carries a good prognosis.

Adolescent↗
PubMed1986

A model of semiautomatic type-specific diagnosis of brain tumours by computed tomography: mathematical fundaments and practical application.

Applying Escudero's formula to Bayes' theorem of conditional probabilities, we have developed a mathematical model to diagnose type-specific brain tumours with great accuracy. We have transformed a multidimensional system of n characteristics on computed tomography into a linear system, making this model very easy to use and, thus, accessible to the clinician and radiologist. We tested this model in 177 brain tumours. In 86% of the cases we obtained a type-specific correct diagnosis, achieving better results than those previously reported. Suggestions are given as to how to improve this method further.

Brain Neoplasms↗
PubMed1985

Outcome in children with severe head injuries.

We present a series of 56 children who suffered severe head injuries, with a Glasgow Coma Score (GCS) of less than 8. The cases were classified according to the type of morphologic lesion on computed tomography (CT) scan. Intracranial pressure (ICP) was monitored in all children in this series. A protocol that included artificial ventilation and other measures of treatment for intracranial hypertension was applied. Results were analyzed according to age, type of lesion, and ICP. The usefulness of the ICP recording and of obtaining a correct classification of lesions using the CT scan is emphasized.

Adolescent↗