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Biomedical subjects

M Sanchez

Publications and source records attributed to M Sanchez.

At least 19 recordsLinked to original sources
PubMed1992

Functional reconstitution of an immunoglobulin antigen receptor in T cells.

Humoral immune responses are initiated by binding of antigen to the immunoglobulins (Igs) on the plasma membrane of B lymphocytes. On the cell surface, Ig forms a complex with several other proteins, two of which, MB-1 and B29, have been implicated in receptor assembly. We have reconstituted Ig receptor function in T lymphocytes by transfection of cloned receptor components. We found that efficient transport of IgM to the surface of T cells required coexpression of B29. Furthermore, IgM and B29 alone were sufficient to reconstitute antigen-specific signal transduction by Ig in the transfected T cells. Crosslinking of IgM with either antireceptor antibodies or antigen induced a calcium flux, phosphoinositol turnover, and interleukin secretion in T cells. These experiments establish a requirement for B29 in Ig receptor function, and suggest that the signaling apparatus of T and B cells is structurally homologous.

Antibodies, Monoclonal↗
PubMed1992

Clinical pharmacokinetics of albendazole in patients with brain cysticercosis.

Albendazole pharmacokinetics were studied in eight patients who were receiving albendazole in doses of 15 mg/kg per day for 8 days as treatment of brain cysticercosis. Albendazole was not detected in plasma, but its main metabolite albendazole sulphoxide could be measured. Maximum plasma levels for albendazole sulphoxide ranged from 0.45 to 2.96 micrograms/mL. The half-life of albendazole sulphoxide was between 10 and 15 hours. A double peak was found in three patients. Mean residence time values were from 14 to 20 hours. Plasma levels of albendazole sulphoxide at the steady state showed great intraindividual variability. The results suggest that albendazole can be administered twice daily rather than three times as is currently done.

Administration, Oral↗
PubMed1992

Morphological changes in long bone development in fetal akinesia deformation sequence: an experimental study in curarized rat fetuses.

In order to investigate the transverse growth of the long bones during intrauterine development in the fetal akinesia deformation sequence (FADS), we studied curarized rat fetuses. Curarization was performed by daily subcutaneous administration of D-Tubocurarine from day 17 of gestation until term. Experimental fetuses were compared with a sham-operated control group. The total area and perimeter, the absolute and relative amount of periosteum and bone trabeculae, the major and minor axes, and the elongation factor were measured from histological cross-sections of the femoral metaphysis and diaphysis using an IBAS 1 image analysis system. Curarized rat fetuses showed growth retardation, a short umbilical cord, and multiple articular contractures, a phenotype consistent with FADS. Alterations in femoral shape and transverse growth that affected the diaphysis were noted in these fetuses. These included a decrease of total cross-section area and reduction of the absolute and relative amounts of bone trabeculae with marked thinning of the periosteum. Femoral cross-sections was rounder than controls. These results evidenced an impairment of the membraneous (periosteal) ossification of long bones produced by immobilization and/or decrease of muscular strength, and support our previous clinical findings of bone hypoplasia and osteopenia in FADS.

Animals↗
PubMed1992

Long bone development in extrinsic fetal akinesia: an experimental study in rat fetuses subjected to oligohydramnios.

The transverse growth of long bones during intrauterine development was studied in rat fetuses subjected to experimental oligohydramnios in order to determine whether the skeletal changes, if any, in extrinsic fetal akinesia were similar to those observed in curarized rat fetuses with the fetal akinesia deformation sequence. Oligohydramnios was induced by daily extraction of amniotic fluid from day 17 of gestation until term. Experimental fetuses were compared with a sham-operated control group. The total area and perimeter, the absolute and relative amount of periosteum and bone trabeculae, the major and minor axes, and the elongation factor were measured in histological cross sections of the femoral metaphysis and diaphysis with an IBAS 1 image analysis system. Rat fetuses in the experimental group showed multiple articular contractures, redundant skin, and lung hypoplasia, a phenotype consistent with the oligohydramnios sequence. No alterations in femoral shape and transverse growth of the metaphysis and diaphysis were noted in these fetuses. These results suggest that the main mechanical factor related to fetal bone modeling is muscular strength, while motion would be mainly involved in fetal joint development.

Animals↗
PubMed1992

Flow cytometric analysis of Saccharomyces cerevisiae autolytic mutants and protoplasts.

Simple methods, based on the technique of flow cytometry, have been developed for the phenotypic characterization of yeast autolytic mutants and for the analysis of the formation and regeneration of the yeast protoplasts. The expression of lytic mutations determined uptake of the fluorescent dye propidium iodide, which could be carefully monitored by flow cytometry. Mixed populations of lysed and viable cells were precisely quantified and sorted, and the technique was also applied to demonstrate protection from lysis of mutant cells with cell wall defects, in the presence of osmotic stabilizers. Protoplast formation and regeneration was monitored by analysing relative cell size; this was facilitated by the preparation of homogeneous protoplast preparations. The technique of flow cytometry proved superior to other conventional methods for these types of study.

Autolysis↗
PubMed1992

Hemolytic-uremic syndrome associated with pancreatitis in an HIV-positive patient.

Hemolytic-uremic syndrome (HUS) is a newly recognized hematologic manifestation of HIV infection that may be triggered by local or systemic infections as well as by immunological disorders. We report the case of a 36-year-old HIV-positive man, an intravenous drug abuser who developed HUS during an episode of acute pancreatitis. Hematologic and clinical improvement occurred following 2 weeks of nonaggressive therapy including vitamin E and fresh-frozen plasma.

Acute Disease↗
PubMed1992

Barium enemas in the frail elderly.

PURPOSE: The objective of this investigation was to determine the frequency of and predictors for inadequate barium enemas in the frail elderly. PATIENTS AND METHODS: The medical and radiologic records of 171 elderly institutionalized patients (mean age = 85.3 years), who underwent barium enema examinations, were retrospectively reviewed. The study outcome of primary interest was the radiologist's report of the adequacy of examination as indicated in the written summary of the results of the barium enema procedure. RESULTS: Eighty-eight (51.5%) of the 171 studies were deemed inadequate, with poor bowel preparation a primary or contributing factor in 89.7% of the inadequate studies. Among a variety of demographic and clinical factors, only long-term laxative and/or cathartic use was associated with an inadequate study (odds ratio = 7.0; 95% confidence interval 2.7 to 18.0). CONCLUSION: These results demonstrate a very high frequency of inadequate barium enema examinations in the very old and suggest a need for improved methods of bowel preparation in this patient population, especially in those who are long-term users of laxatives and cathartics.

Age Factors↗
PubMed1992

Changes in immunological response in tonsillectomized children. II. Decreased cellular response.

The immunological cellular response was studied in 22 children aged between 5 and 10 years. One week before and one month after tonsillectomy, the mitogenic response to phytohaemagglutinin (PHA), concanavalin (ConA) and pokeweed mitogen (PWM) was tested. Our results showed statistically significant decreases in stimulation index (SI) to PHA, ConA and PWM after tonsillectomy. This suggests that the tonsils may influence the cellular immune status in children. The higher level of preoperative activity in children with recurrent tonsillitis could be understood as the result of stimulation of lymphocytes by bacteria.

Child↗
PubMed1992

Regulation of thyrotropin receptor gene expression in rat FRTL-5 thyroid cells.

TSH receptor mRNA levels in FRTL-5 thyroid cells are autoregulated at a transcriptional level by the same hormones required for the growth and function of the cells: TSH, insulin, and insulin-like growth factor-I (IGF-I). Thus, the ability of TSH, via its cAMP signal, to down-regulate steady state receptor mRNA levels is preceded by the action of TSH to decrease pre-mRNA levels in nuclear run-on assays to the same quantitative level as evident in Northern analyses. In contrast, the receptor mRNA half-life is shown not to change when down-regulation is reversed by withdrawing TSH in the presence or absence of actinomycin-D. Evidence is additionally provided that TSH receptor mRNA levels are increased by insulin, IGF-I, or calf serum in both Northern and run-on assays. This action cannot be duplicated by hydrocortisone and is evident at more than 20-fold lower concentrations of IGF-I than insulin. Moreover, insulin, IGF-I, and/or calf serum are required for the autoregulatory negative transcriptional regulation of the TSH receptor by TSH/cAMP, as is the case for thyroglobulin. This occurs despite the opposite actions of TSH/cAMP on the two genes, positive in the case of thyroglobulin and negative with TSH receptor. The positive and negative regulatory actions, respectively, of insulin/IGF-I and TSH on receptor gene expression are associated with coincident increases or decreases in cell surface receptors measured by [125I]TSH binding. The autoregulation additionally involves the interplay of a second cAMP-modulated regulatory factor, one which up-regulates TSH receptor mRNA levels rather than causing down-regulation. Thus, cycloheximide inhibits the transcriptional action of both TSH/cAMP and insulin/IGF-I/serum within 4 h, i.e. a rapidly synthesized protein is an intermediate in both cases. The presence of cycloheximide for as little as 1 h, however, uncovers the ability of TSH/cAMP to increase TSH receptor mRNA levels. This activity is the result of the action of a stable cAMP-induced activator which can be detected physiologically, i.e. in the absence of cycloheximide. For example, low levels of a cAMP analog (0.2 mM), as opposed to high levels (greater than 1 mM), can increase TSH receptor RNA levels. Low levels also accelerate the insulin/IGF-I-dependent return of receptor mRNA to normal levels after TSH withdrawal.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Cochinmicins, novel and potent cyclodepsipeptide endothelin antagonists from a Microbispora sp. I. Production, isolation, and characterization.

Cochinmicins I, II, III are novel peptolides produced in submerged-fermentation cultures of Microbispora sp. ATCC 55140. These closely related compounds are separated by HPLC and are novel competitive endothelin antagonists. Cochinmicins II and III are stereoisomeric to each other. Cochinmicin I is the deschloro analog of cochinmicin III.

Animals↗
PubMed1992

HIV-associated papulosquamous diseases.

Persons infected with the human immunodeficiency virus (HIV) can develop a variety of dermatoses in which the primary lesions are scaly papules or plaques. These dermatoses can be the presenting clinical manifestations of HIV infection. Depending on the degree of immune dysfunction, the clinical and histopathologic appearance may be typical or quite unusual.

HIV Infections↗
PubMed1992

Localized vulvar pemphigoid in a child misdiagnosed as sexual abuse.

BACKGROUND: Various primary dermatoses can affect the vulva of children and be misdiagnosed as child abuse, with devastating social consequences. OBSERVATION: A 3-year-old girl with vulvar erosions was removed from her parent's care after a pediatrician and gynecologist diagnosed child abuse. Histopathologic and immunofluorescence studies were consistent with vulvar pemphigoid. CONCLUSION: Localized pemphigoid should be added to the differential diagnosis of vulvar lesions. Dermatologists, pediatricians, and gynecologists should be familiar with nonvenereal diseases that can exclusively affect this area. The dermatologist's expertise is particularly valuable in differentiating between primary diseases and sexual abuse.

Child Abuse, Sexual↗
PubMed1991

Trans-splicing as a possible molecular mechanism for the multiple isotype expression of the immunoglobulin gene.

We analyzed the molecular mechanism for the immunoglobulin (Ig) multiple isotype expression using a transgenic mouse (TG.SA) model system. Though most of the endogenous mu chain expression was excluded by the expression of the human rearranged mu transgene in the TG.SA mouse, a significant portion of splenic B lymphocytes could express the transgenic human IgM and endogenous mouse IgG simultaneously after stimulation with lipopolysaccharide and interleukin 4. The fluorescence-activated cell sorter-purified population of the human IgM+/mouse IgG+ cells expressed mRNA that consisted of properly spliced sequences of the transgenic VHDJH and the endogenous mouse C gamma genes (trans-mRNA), together with the transgenic human mu mRNA and germline transcripts of the mouse C gamma gene, without apparent rearrangement of the transgene. We also found that a lymphoma tumor, derived from the cross between the TG.SA mouse and another transgenic mouse carrying Ig H chain enhancer-driven c-myc oncogene, expressed about equal levels of the trans-mRNA and the transgenic mu mRNA without DNA rearrangement in either the transgene or the endogenous mouse switch region. These findings strongly support our previous proposal that the trans-splicing can account for the multiple isotype expression in this transgenic model and also suggest that novel molecular mechanism(s) might be involved in this reaction.

Animals↗
PubMed1991

Expression of type X collagen is transiently stimulated in redifferentiating chondrocytes pretreated with retinoic acid.

Growth of quail chondrocytes in the presence of retinoic acid (RA) results in the suppression of the differentiated phenotype. RA-treated chondrocytes recover their differentiated phenotype if they are cultured for an additional 15 days in the absence of RA. A few days after removal from RA, treated chondrocytes acquire the polygonal morphology characteristic of chondrocytes growing as attached cells; they also gradually resume collagen II expression and synthesize cultures. The levels of collagen X mRNA decrease during the second week of culture in the absence of RA. Finally, at the end of 15 days, the absolute levels of collagen II and collagen X mRNAs are very similar in control and recovering chondrocytes.

Animals↗
PubMed1991

Incidence of an estrogen receptor polymorphism in breast cancer patients.

We previously identified a polymorphism in the human estrogen receptor (ER) gene, within the coding region for the protein's amino terminal B-domain. In estrogen receptor-positive (ER+) breast tumors, the variant allele was preferentially associated with lower levels of ER, and was clinically correlated with frequent spontaneous abortions. DNA sequencing revealed a point mutation that changes codon 86 from Ala to Val and a silent mutation in codon 87. Because we initially detected the variant allele by analyzing RNA, only those tissues in which the ER gene is actively expressed were suitable for genotype analysis. We now describe an assay that uses genomic DNA as the substrate for determining the ER B genotype, DNA containing the polymorphic region of the ER gene is amplified by the polymerase chain reaction, then the amplified DNA is hybridized with radiolabeled oligonucleotide probes complementary to the wild type and variant ER alleles. This method allowed us to determine the ER B genotype of women with ER+ and ER- tumors, starting with minute amounts of DNA from frozen or paraffin embedded tissues. ER B genotyping was also performed on women without breast cancer using DNA extracted from blood cells. The combined results from analyses of RNA and DNA from 300 breast cancer patients showed that 12% were heterozygotes. In the ER+ group (n = 183), 11.5% carried the variant gene compared to 12.8% in the ER-negative group (n = 117) (chi 2 = 0.11; df = 1; p greater than 0.25).(ABSTRACT TRUNCATED AT 250 WORDS)

Breast Neoplasms↗