Search PubMed⌕ Search

Biomedical subjects

J Esparza

Publications and source records attributed to J Esparza.

At least 91 records · Page 5Linked to original sources
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↗
PubMed1985

Biochemical evidence for the oligomeric (possibly trimeric) structure of the major inner capsid polypeptide (45K) of rotaviruses.

The major structural polypeptide of rotaviruses is p45K (VP6), which forms the morphological subunit of the inner capsid. Such subunits show a trimeric structure when examined with the electron microscope. Treatment of single-capsid rotavirus particles with 1.5 M-CaCl2 removes p45K, resulting in the generation of smooth cores. Sucrose density gradient centrifugation analysis of the removed p45K revealed that it has a sedimentation coefficient close to 7.3S, compatible with an oligomeric (possibly trimeric) structure. Polyacrylamide gel electrophoresis under reducing or non-reducing conditions indicated that p45K has intramolecular but not intermolecular disulphide bonds, suggesting that interactions between p45K monomers may be due to some other type of association, such as hydrophobic or charge interactions. Velocity sedimentation of infected cell extracts revealed that native p45K also behaves as an oligomeric protein. Such results were confirmed using p45K partially purified by DEAE-cellulose chromatography. The evidence obtained indicated that all p45K present in the virion is in the oligomeric form, not associated by disulphide bonding, and that most native p45K present in the infected cells is also in the oligomeric form, probably as a consequence of early protein-protein interaction in rotavirus morphogenesis.

Animals↗
PubMed1984

Molecular cloning of the complete genome of reovirus serotype 3.

All 10 genes of the Dearing strain of reovirus serotype 3 have been cloned in their entirety into pBR322. This has been proved by sequencing the terminal regions (50-100 residues long) of all 10 cloned genes; all such regions were found to be identical to the corresponding terminal regions of the double-stranded RNA genes that are present in reovirus particles. The lengths of the cloned reovirus genes were estimated by comparing their electrophoretic mobilities (and those of their PstI cleavage fragments) with those of accurately known marker DNA molecules. The genes range in size from about 3825 bp for the L genes to about 1200 bp for the S4 gene.

Base Sequence↗
PubMed1984

Epidemiological aspects of porcine rotavirus infection in Venezuela.

The prevalence of porcine rotavirus infection in Venezuela was studied from November 1980 to November 1981. Rotaviruses were identified in 21.3 per cent of 286 diarrhoeic samples analysed by electron microscopy and in none of the 48 controls. Rotaviruses were readily detected throughout the year, which may correspond to the absence of seasonal climatic variations in a tropical country such as Venezuela. Rotavirus infection was frequently observed in pigs that were two to six weeks old and was rare in younger animals. The age distribution of rotavirus infection correlated well with the presence of circulating antibodies, as measured by the complement fixation test. Sucking pigs less than two weeks old appeared to be protected from the infection by passive immunity; no antibodies were detected in the two- to three-week-old group, coinciding with an increased susceptibility to rotavirus infection. The antigenic specificity of the rotavirus isolates was confirmed by enzyme-linked immunosorbent assay test, using antibodies directed against the group-specific antigen of human rotavirus. Polyacrylamide gel electrophoresis of viral double-stranded RNA revealed an heterogeneity on the electropherotype of selected samples obtained at different times during the study period.

Age Factors↗
PubMed1983

Molecular cloning of a human rotavirus genome.

The genes of a field isolate of human rotavirus were cloned into pBR322. The strategy used involved polyadenylation of denatured double-stranded (ds) genomic RNA, followed by cDNA synthesis using reverse transcriptase. Oligo(dC) tails were added to the 3' end of the single-stranded cDNA and then separated by alkaline agarose electrophoresis. Sized cDNA of both polarities were allowed to hybridize and inserted into the PstI site of pBR322. Transformations done with sized cDNA always resulted in the selection of hybrid plasmids carrying inserts with a size representative of the original cDNA. Four individual clones were selected for preliminary characterization. One clone has an insert of 1360 base pairs (bp) and corresponds to gene 6. The second clone has an insert of 1140 bp and corresponds to one of the genes in the triplet 7-8-9. The other two genes, with inserts of 780 and 660 bp, were identified as corresponding to dsRNA segments 10 and 11.

Base Sequence↗
PubMed1982

Extradural hemorrhage in the posterior fossa in neonates.

The case of a neonate with an extradural hemorrhage in the left posterior fossa, the result of trauma at birth, is reported. The routine axial transverse CT scan did not detect the exact preoperative location of the clots in the extradural space of the posterior fossa. Good recovery was achieved following the operation.

Birth Injuries↗
PubMed1982

Cloning the double-stranded RNA genes of reovirus: sequence of the cloned S2 gene.

The genes of the Dearing strain of reovirus serotype 3, which consist of double-stranded RNA, have been cloned into pBR322 by tailing both strands of each gene with poly(A), transcribing them with reverse transcriptase, self-hybridizing the cognate plus and minus cDNA strands, incubating them with Escherichia coli DNA polymerase I to ensure that they are complete, and cloning the double-stranded cDNA molecules by standard procedures. The sequence of the cloned S2 gene has been determined. The sequence at the termini are exactly the same as those at the ends of the native double-stranded RNA gene. The gene is 1,329 nucleotides long and possesses a single long open reading frame that starts at the first initiation codon (residue 19) and extends for 331 codons, sufficient to encode a protein of the same size as the known S2 gene product, protein sigma 2, a major reovirus core component (Mr, 38,000). A second open reading frame of 85 codons, in a different phase, starts close to where the first ends. The protein translated from this reading frame is unknown.

Amino Acid Sequence↗
PubMed1981

Giant cerebral arteriovenous malformation producing a noncommunicating hydrocephalus.

The case of a woman with a large, mixed, cerebral arteriovenous malformation mainly involving the posterior fossa and producing a noncommunicating hypertensive hydrocephalus is reported. Relief of ventricular enlargement by means of a cerebrospinal fluid shunt unexpectedly resulted in stupor and Parinauds' syndrome. These complications were completely relieved by ligating the shunt. The vascular and mechanical factors involved in the production of hydrocephalus in this patient are discussed.

Adult↗
PubMed1981

Poly(A) polymerase activity in human rotavirus.

A poly(A) polymerase enzymic activity was found in partially purified preparations of a human rotavirus. The activity was demonstrated using conditions similar to those utilized for the detection of the poly(A) polymerase previously described in reovirus (incubation at 43 degrees C in 70 mM-tris buffer pH 7.5 containing 12 mM-Mn2+). The enzymic activity was associated only with complete, double-shelled particles. Characterization of the poly(A)-containing product of the in vitro reaction by gel filtration on Sephadex G-100, followed by chromatography on DEAE-cellulose in the presence of 7 M-urea, showed that it is composed of oligonucleotides of a chain length similar to, or slightly larger than, those observed in reovirus.

Adenosine Triphosphate↗
PubMed1981

Protein synthesis in cells infected with bovine rotavirus.

Bovine rotavirus was found to multiply efficiently in LLC-MK2 cells, a continuous line of rhesus monkey kidney, with a growth cycle which was essentially completed within 9 h after infection. The presence of low concentrations of trypsin (10 microgram/ml) in the virus inoculum was essential for infectivity. Polyacrylamide gel electrophoresis of infected cell extracts demonstrated the synthesis of at least eight virus-specific polypeptides 6 h post-infection with mol. wt. ranging from 102 X 10(3) to 29 X 10(3). Six polypeptides (about p102K, p91K, p84K, p37K and p34K) were identified as structural components of the virion. Two other polypeptides (54K and p29K) were identified as non-structural components. The synthesis of non-structural polypeptides appeared to precede that of the structural proteins. Pulse-chase experiments showed only one minor post-translation modification of the virus-specified proteins, namely an increase in the mobility of the 29K polypeptide.

Animals↗
PubMed1981

Composition and topography of structural polypeptides of bovine rotavirus.

The composition and topography of the structural polypeptides of bovine rotavirus was studied by polyacrylamide gel electrophoresis of radioactively labelled virus grown in LLC-MK2 cells and by lactoperoxidase-catalysed iodination of single- and double- capsid particles. Bovine rotavirus was found to possess at least six structural polypeptides, three of them associated with the inner capsid (p102K, p91K and p45K) and the others with the outer capsid (p84K, p37K and p34K). The most abundant polypeptide of the inner capsid was p45K, which accounted for approx, 80% of the protein mass, followed by p91K (approx, 20% of the protein mass) and p102K (approx. 1% of the protein mass). Polypeptide 45K is not readily available for iodination, indicating that it is partially covered by p91K, which is the most exposed polypeptide of the inner capsid. The number of polypeptide molecules per single capsid particle (calculated on the basis of an RNA content of 16%) was estimated to be approx. 6 molecules of p102K, 140 of p91K and 989 of p45K. The stoichiometry and degree of exposure of outer capsid polypeptides was more difficult to establish, even when it appears that p84K and p34K are the most exposed components.

Capsid↗
PubMed1981

Placental and fetal alterations due to Venezuelan equine encephalitis virus in rats.

Histopathological changes in the placentas, embryos, and fetuses of rats inoculated intraperitoneally with the virulent Guajira strain of Venezuelan equine encephalitis virus were studied by light microscopy and immunoperoxidase methods. Rats inoculated before day 15 of pregnancy showed necrosis and hemorrhages in the embryonic disks. Swelling of cytoplasm and nuclear pyknosis of cyto- and syncytotrophoblastic cells were noted as early as 2 days after inoculation. During weeks 1 and 2 of pregnancy, death of the embryos was always observed 3 to 4 days after Venezuelan equine encephalitis virus inoculation. Placental and fetal damage varied among the specimens. In rats 18 days pregnant and sacrificed 2 days after inoculation, there were some viable fetuses; the placentas showed inflammatory reactions in the mesometrial and decidual vessels. Other rats sacrificed at 3 to 4 days after inoculation showed large placental infarcts with fetal death. Viremia peaked during day 2 after inoculation. Immunoperoxidase stains demonstrated viral antigens present in the decidua, myometrium, and cyto- and syncytotrophoblastic cells. These experiments provide additional data regarding the pathogenesis and structural damage in the placental and fetal tissues caused by Venezuelan equine encephalitis virus.

Animals↗
PubMed1981

Hydrocephalus in cerebral cysticercosis. Pathogenic and therapeutic considerations.

The cases of 11 patients with hydrocephalus secondary to cerebral cysticercosis are analyzed. Most of the patients had suffered from epilepsy before they developed hydrocephalic symptoms, and computerized tomography showed that infestation of the parenchyma coexisted with ventricular or cisternal colonization. In four cases, the parasitic vesicles compromised cerebrospinal fluid (CSF) flow in the ventricular system, resulting in internal hydrocephalus. Communicating hydrocephalus, caused by the presence of Cysticercus larvae in the basal cisterns (Cysticercus racemosus), or by the occurrence of a chronic basal meningitis, or both, developed in seven more patients. Changes in CSF pressure were related to the number and location of the cysts and to the leptomeningeal inflammatory reactions evoked by them. The majority of patients presented with a chronic and relatively normotensive hydrocephalus. All patients except one had identifiable ventricular or cisternal Cysticercus larvae; these patients were treated with open removal of the cysts, and did well. However, most of them had impairment of CSF flow through the basal cisterns and required permanent CSF shunting. Communicating hydrocephalus due to leptomeningeal scarring was also successfully managed with extracranial shunting. Epilepsy was controlled with anticonvulsant therapy. Although good lasting results may be obtained with aggressive treatment of neurocysticercosis, patients are liable to relapse because surgery is only palliative in most instances.

Adult↗
PubMed1980

Multiplication of human rotavirus in cultured cells: an electron microscopic study.

Human rotaviruses were capable of efficient multiplication in LLC-MK2 cells when the inoculum was pre-treated with trypsin, centrifuged on to the cell monolayer and the infected cells maintained in a medium containing trypsin. However, not all of the human rotavirus isolates used to infect cells resulted in efficient virus production. The ability of human isolates to multiply in cultured cells was studied by direct observation of virus in the electron microscope, by radioactive labelling with 3H-uridine of the newly synthesized virus and by electron microscopic examination of thin sectioned infected cells. With one of the specimens used (F-617) only 5 to 10% of the cells showed evidence of virus multiplication, with the great majority of the infected cells showing numerous complete (double-capsid) virus particles scattered in the cytoplasm. When cells were inoculated with another human specimen (SIB-I), infected cells were more abundant, reaching a maximum of 60%; however, a variety of particle types, probably representing different subviral structures or different steps of rotavirus morphogenesis, were commonly observed. The presence of these aberrant or incomplete virus structures may represent a manifestation of the defectiveness of this virus and may explain the difficulties encountered in its serial passage.

Animals↗