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Biomedical subjects

E Sanchez

Publications and source records attributed to E Sanchez.

At least 55 records · Page 3Linked to original sources
PubMed1995

Ocular dysfunction associated with mental handicap.

The aim of this article is to show the main general and ocular characteristics of a group of 46 mentally handicapped people of different IQ and age who were provided with visual care. Many different syndromes and neurological alterations have been described in the literature. The case types and number of people studied for each condition attending our clinics were: syndromes: Down's (25), Soto (2), West (2), Rubinstein-Taybi (1), triple X (1); neurological conditions: cerebral palsy (8), microcephaly (5), hydrocephaly (2). In our study the ocular findings were high incidence of ametropies: 58.7% hyperopia, 21.7% myopia, 19.5% astigmatism and 28% strabismus.

Adolescent↗
PubMed1993

Taxol shares the ability of bacterial lipopolysaccharide to induce tyrosine phosphorylation of microtubule-associated protein kinase.

Microtubule-associated proteins may mediate the activation of macrophages by bacterial LPS. Three lines of evidence support this hypothesis: a) Taxol, a microtubule-binding diterpene, mimics the ability of LPS to induce cytokines and down-regulate receptors for TNF-alpha. In recombinant inbred mouse strains differing at the Lps gene, responsiveness to these effects of Taxol co-segregates with responsiveness to LPS. b) In vitro, LPS binds specifically to MT and preferentially to beta-tubulin. c) LPS activates microtubule-associated protein-2 kinase (MAPK). The present studies bring together and extend these lines of evidence. a) Taxol, like LPS, rapidly induces tyrosine phosphorylation of MAPK in mouse macrophages, and triggers MAPK to phosphorylate an exogenous substrate. b) Tyrosine phosphorylation of MAPK is an extremely rapid cellular response both to taxol and LPS. c) Macrophages from C3H/HeJ mice, which carry a defective Lps gene, fail to activate MAPK in response to taxol or LPS, although they activate MAPK in response to insulin or IFN-gamma. These results suggest that tyrosine phosphorylation of MAPK is among the earliest known response of macrophages to LPS. Taxol mimics LPS with respect to immediate MAPK activation, later transcriptional events, and the genetic control of both sets of responses. LPS and taxol thus appear to share an early step in a functionally important signal transduction pathway that may involve MT.

Animals↗
PubMed1993

Identification by site-directed mutagenesis of amino acids in the B2 subsite of bovine pancreatic ribonuclease A.

In addition to hydrolysing RNA, bovine pancreatic ribonuclease splits esters of pyrimidine nucleoside 3'-phosphates, including dinucleotides. For a series of 3':5'-linked dinucleotides of general structure CpN, where N is a 5' linked nucleoside, kcat for the release of N varies enormously with the precise structure of N. Structural studies have been interpreted to indicate that the group N interacts with a subsite, B2, on the enzyme that comprises Gln69, Asn71 and Glu111. We report studies by site-directed mutagenesis that indicate that Gln69 is not involved in productive interactions with any of the dinucleotide substrates and that Asn71 is an important component of subsite B2 for all dinucleotide substrates tested. Glu111 appears to be functionally involved in catalysis for dinucleotide substrates solely when N is guanosine.

Amino Acids↗
PubMed1993

[Segmental ischemic colitis in lymphocytic thrombotic venulitis].

This case illustrates the difficulty of diagnosing a colonic stenosis of ischemic origin. A 70-year-old lady presents with abdominal pain, fever and melaena. Lc are 15.2, ESR 39 mm, CEA 2.7 ng/ml. A barium enema shows a stenosis of the transverse colon that is suspicious of neoplasia. At time of operation, an induration of the transverse colon is found with edema of the corresponding mesocolon but no tumour is palpated. A resection of this area is performed and an end to end anastomosis performed. Pathology shows an ischemic colitis secondary to a lymphocytic thrombotic venulitis. The patient is discharged home one month postoperatively. 4 weeks later she is readmitted with the same symptoms. A gastrograffin enema shows a similar stenosis in the transverse colon including the anastomosis. The diagnosis is made of a recurrent ischemic stenosis. The patient improves over a 10-day period of conservative treatment (anticoagulation, TPN, steroids). A control barium enema shows a near resolution of the stenosis. The majority of ischemic colitis are of arterial origin nevertheless ischemic colitis of venous origin exists. The factor causing venous ischemia are not known. It is though thought to be associated with hypersensitivity vasculitis of drug origin. Its initial diagnosis versus neoplasia is difficult but once made there is a good response to a conservative treatment.

Aged↗
PubMed1992

Interactions of bacterial lipopolysaccharide with microtubule proteins.

Bacterial LPS is a potent stimulator of immune cells, but its mechanisms are unknown. A possible role for microtubules in LPS actions has been indicated by previous findings that the microtubule-active agent, taxol, can mimic some effects of LPS in macrophages from normal strains of mice, but not from genetically LPS-hyporesponsive strains. In this report we demonstrate that isolated microtubules from mouse brain can bind LPS in vitro. LPS and tubulin coeluted through a gel filtration column, and LPS was cross-linked to microtubule proteins with an iodinatable, photoreactive agent, sulfosuccinimidyl 2-(p-azidosalicylamido) ethyl-1,3'-dithiopropionate. beta-Tubulin and microtubule-associated protein-2 (MAP), a predominant MAP in the brain, bound LPS specifically. Cross-linking was inhibited by an excess of unlabeled LPS or partially by unlabeled lipid A, but not by 2 M NaCl. Under the same conditions, neither myosin nor soybean trypsin inhibitor was labeled by the photoaffinity LPS probe, nor did these proteins compete for binding of LPS to beta-tubulin. These findings support the hypothesis that the microtubule network could be an intracellular target for LPS, and suggest further that a beta-tubulin-associated MAP could have an important role in LPS actions.

Affinity Labels↗
PubMed1991

Effects of dipyridamole on the short-term evolution of glomerulonephritis.

The aim of the present study is to evaluate the effect of dipyridamole (300 mg/day) versus placebo in a double-blind randomized trial on membranous glomerulonephritis (M-GMN), mesangial IgA glomerulonephritis (IgA-GMN), and segmentary and focal hyalinosis glomerulonephritis (SFH-GMN) during the first 3 months of treatment. In the case of M-GMN, proteinuria dropped by 60% of the basal value in patients treated with dipyridamole; in the case of IgA-GMN it dropped by 65-70%; and in the case of SFH-GMN it dropped by 40% of the basal value. Inhibition of proteinuria in M-GMN was correlated to platelet response, and above all, to the ADP-induced platelet aggregation in whole blood.

Dipyridamole↗
PubMed1991

Adrenal cyst: a case report.

The authors describe the case of a patient with a large adrenal cyst. They review the existing literature and discuss the problem of diagnosis an treatment.

Adolescent↗
PubMed1990

Widespread intradermal accumulation of mononuclear leukocytes in lepromatous leprosy patients treated systemically with recombinant interferon gamma.

Intradermal administration of recombinant interferon gamma (rIFN-gamma) to lepromatous leprosy patients has converted the local histology toward a tuberculoid pattern. However, such changes have been confined to the site of injection. In contrast, in the present study, marked, intradermal accumulation of CD3+, CD4+, CD8+, and CD1a+ T cells and Leu-M5+ mononuclear phagocytes was induced at a distance from the sites of administration, in a dose-dependent manner, by 10 daily intramuscular injections of 10-30 micrograms rIFN-gamma/m2. Mononuclear cell infiltration began within 3 d of onset of rIFN-gamma therapy and persisted at least 8 wk. Intramuscular administration of rIFN-gamma to lepromatous patients receiving concurrent chemotherapy can safely induce widespread histologic features of an upgrading reaction.

Adult↗
PubMed1990

Shared actions of endotoxin and taxol on TNF receptors and TNF release.

Bacterial lipopolysaccharide (LPS) exerts profound effects on mammalian hosts in part by inducing macrophages to release tumor necrosis factor-alpha (TNF-alpha); the mechanisms involved are unresolved. The microtubule stabilizer taxol shared two actions of LPS on macrophages: it rapidly decreased TNF-alpha receptors and triggered TNF-alpha release. Both actions of taxol were absent in LPS-hyporesponsive C3H/HeJ mice. In recombinant inbred mice, the genes controlling responses to LPS and to taxol were closely linked. Dexamethasone blocked release of TNF-alpha by both stimuli but did not block the decrease in TNF-alpha receptors. Thus, a protein associated with microtubules may be a cellular target of LPS.

Alkaloids↗
PubMed1990

Downregulation of tumor necrosis factor receptors on macrophages and endothelial cells by microtubule depolymerizing agents.

Exposure of murine and human macrophages and human umbilical vein endothelial cells to micromolar concentrations of five microtubule (MT)-depolymerizing agents (colchicine, nocodazole, podophyllotoxin, vincristine, and vinblastine) resulted in a loss of binding sites for iodinated TNF-alpha. The reduction amounted to 40-60% by 1 h and approximately 75% by 2-4 h. In 1 h, specific binding was reduced 50% by 0.1-5 microM of these drugs at 37 degrees C, but not at 4 degrees C. Inactive isomers of colchicine were ineffective, as were microfilament-destabilizing cytochalasins. The active agents did not compete with TNF-alpha R for binding. Antiserum against TNF-alpha did not neutralize the effect of colchicine and nocodazole. PGE1 and dibutyryl-cAMP could not mimic, and cyclooxygenase inhibitors could not prevent the drug effects. All the binding sites were regenerated within 3 h after removal of nocodazole, which binds tubulin reversibly, whereas little recovery was found even 18 h after the removal of colchicine, which binds tubulin irreversibly. These findings suggested that MT disassembly was responsible for the observed downregulation of TNF-alpha R. The protein synthesis inhibitor cycloheximide inhibited binding of TNF-alpha to a similar extent and with a similar time course as colchicine in the absence of added ligand. Neither drug affected binding of IFN-gamma to macrophages, nor binding of TNF-alpha to human polymorphonuclear leukocytes. Thus, an intact MT network appears to be important in maintenance of the steady state of TNF-alpha R on those cells in which TNF-alpha R turns over rapidly in the absence of ligand. The antiinflammatory actions of MT-depolymerizing agents may result in part from their interference with the ability of such cells to respond to TNF-alpha.

Animals↗
PubMed1990

Drug metabolism in Octodon degus: low inductive effect of phenobarbital.

1. Differential effects of phenobarbital pre-treatment on liver microsomal drug metabolizing enzymes were registered in Octodon degus. 2. Glucuronidation reaction for morphine was decreased but that for p-nitrophenol was significantly increased. 3. Oxidative reactions such as naphthalene hydroxylation, morphine and aminopyrine N-demethylation were modestly increased. 4. In phenobarbital treated Octodon degus, testosterone metabolic pathways were decreased, not inducible or absent. 5. Spectral studies revealed two binding sites with different affinities for aniline in Octodon degus liver microsomes. 6. The poor phenobarbital induction on drug metabolism in Octodon degus may be a result of deficiency of androgen metabolic pathways associated to drug metabolizing enzymes.

Aminopyrine N-Demethylase↗
PubMed1990

Malaria in the Amazon. Prevalence of Plasmodium falciparum antibodies in Amerindians inhabiting the Venezuelan Amazon.

The acquisition of antibodies to Plasmodium falciparum in various age groups was studied in 511 Amerindians inhabiting the north of the Venezuelan Amazon. The overall prevalence by ELISA was 91.2% and antibodies were acquired early in life. Seropositivity was 69.6% in the group aged two to five years and reached 86% at 10 years of age; 96.9% of the adults aged 31-40 years exhibited high ELISA values to P. falciparum. The high prevalence of malaria antibodies among Amazonians, from early on in life, reflects the high level of malaria transmission in that part of the world.

Adult↗
PubMed1990

Tumor necrosis factor and CD11/CD18 (beta 2) integrins act synergistically to lower cAMP in human neutrophils.

The ability of neutrophils (PMN) to undergo a prolonged respiratory burst in response to cytokines such as tumor necrosis factor-alpha (TNF) depends on expression of CD11/CD18 (beta 2) integrins and interaction with matrix protein-coated surfaces (Nathan, C., S. Srimal, C. Farber, E. Sanchez, L. Kabbash, A. Asch, J. Gailit, and S. D. Wright. 1989. J. Cell Biol. 109:1341-1349). We tested the hypothesis that changes in cAMP mediate the joint action of cytokines and integrins. When plated on FBS- or fibrinogen-coated surfaces, PMN responded to TNF with a sustained fall in intracellular cAMP. This did not occur without TNF; in suspended PMN; in PMN treated with anti-CD18 mAb; or in PMN genetically deficient in beta 2 integrins. A preceding fall in cAMP appeared essential for TNF to induce a respiratory burst, because drugs that elevate cAMP blocked the burst if added any time before, but not after, its onset. Adenosine analogues and cytochalasins also block the TNF-induced respiratory burst if added before, but not after, its onset. Both also blocked the TNF-induced fall in cAMP. The effect of cytochalasins led us to examine the relationship between cAMP and actin reorganization. The same conditions that led to a sustained fall in cAMP led at the same time to cell spreading and the assembly of actin filaments. As with the respiratory burst, cAMP-elevating agents inhibited TNF-induced cell spreading and actin filament assembly if added before, but not after, spreading began. Thus, occupation of TNF receptors and engagement of CD18 integrins interact synergistically in PMN to promote a fall in cAMP. The fall in cAMP is closely related to cell spreading and actin reorganization. These changes are necessary for TNF to induce a prolonged respiratory burst. We conclude that integrins can act jointly with cytokines to affect cell shape and function through alterations in the level of a second messenger, cAMP.

1-Methyl-3-isobutylxanthine↗
PubMed1989

Macrophages rapidly internalize their tumor necrosis factor receptors in response to bacterial lipopolysaccharide.

The effect of bacterial lipopolysaccharide (LPS) on macrophage receptors for tumor necrosis factor/cachectin (TNF-R) was studied. At equilibrium, iodinated recombinant human TNF alpha (rTNF alpha) bound to 1100 +/- 200 sites/cell on macrophage-like RAW 264.7 cells with a Kd of 1.3 +/- 0.1 x 10(-9) M. Preexposure of RAW 264.7 cells to 10 ng/ml LPS for 1 h at 37 degrees C resulted in complete loss of cell surface TNF alpha binding sites. 50% loss ensued after 1 h with 0.6 ng/ml LPS, or after 15 min with 10 ng/ml LPS. Complete loss of TNF alpha binding sites occurred without change in numbers of complement receptor type 3. No decrease in TNF-R followed preexposure to LPS at 4 degrees C, nor could LPS displace 125I-rTNF alpha from its binding sites. Although TNF-R disappeared from the surface of intact macrophages following exposure to LPS, specific TNF alpha binding sites were unchanged in permeabilized macrophages, indicating that TNF-R were rapidly internalized. Conditioned media from LPS-treated RAW 264.7 cells induced 30% down-regulation of TNF-R on macrophages from LPS-hyporesponsive mice (C3H/HeJ), suggesting that a soluble macrophage product may be responsible for a minor portion of the LPS effect. Additional evidence against endogenous TNF alpha being the major cause of TNF-R internalization was the rapid onset of the effect of LPS on TNF-R compared to the reported onset of TNF alpha production, the relatively high concentrations of exogenous rTNF alpha required to mimic the effect of LPS, and the inability of TNF alpha-neutralizing antibody to block the effect of LPS. LPS-induced down-regulation of TNF-R was complete or nearly complete not only in RAW 264.7 cells, but also in primary macrophages of both human and murine origin, was less marked in human endothelial cells, and was absent in human granulocytes and melanoma cells and mouse L929 cells. Thus, in situ, macrophages and some other host cells may be resistant to the actions of TNF alpha produced during endotoxinemia, because such cells may internalize their TNF-R in response to LPS before TNF alpha is produced.

Animals↗