Biomedical subjects

A Sanchez

Publications and source records attributed to A Sanchez.

At least 127 records · Page 7Linked to original sources

PubMed1997

p53 exon 5 mutations as a prognostic indicator of shortened survival in non-small-cell lung cancer.

Inactivation of the tumour-suppressor gene p53 has been described as one of the most common molecular changes found in lung tumours. Our purpose was to study the prognostic value of p53 alterations and to determine whether some specific mutation type in the p53 gene could be associated with poor clinical evolution in non-small-cell lung cancer (NSCLC) patients. To this end, we studied 81 resected primary NSCLCs in order to detect p53 alterations. p53 protein accumulation was analysed using immunohistochemistry methods; p53 gene mutations in exons 5-9 were studied using polymerase chain reaction-single-strand conformation polymorphism and sequencing techniques. p53 protein was immunodetected in 46.9% of lung carcinomas and 44.7% of p53-immunopositive tumours showed p53 mutations. Survival analysis was performed on 62 patients. No survival differences were found for patients with or without p53 immunopositivity. A shorter survival was found in patients with underlying p53 gene mutations, mainly in patients with squamous cell lung tumours; the worst prognosis was found when mutations were located in exon 5 (P = 0.007). In conclusion, the location of p53 mutations might be considered as a prognostic indicator for the evaluation of poor clinical evolution in NSCLC patients.

Carcinoma, Non-Small-Cell Lung↗

PubMed1997

The Lassa fever virus L gene: nucleotide sequence, comparison, and precipitation of a predicted 250 kDa protein with monospecific antiserum.

The large (L) RNA segment of Lassa fever virus (LAS) encodes a putative RNA-dependent RNA polymerase (RdRp or L protein). Similar to other arenaviruses, the LAS L protein is encoded on the genome-complementary strand and is predicted to be 2218 amino acids in length (253 kDa). It has an unusually large non-coding region adjacent to its translation start site. The LAS L protein contains six motifs of conserved amino acids that have been found among arenavirus L proteins and core RdRp of other segmented negative-stranded (SNS) viruses (Arena-, Bunya- and Orthomyxoviridae). Phylogenetic analyses of the RdRp of 20 SNS viruses reveals that arenavirus L proteins represent a distinct cluster divided into LAS-lymphocytic choriomeningitis and Tacaribe-Pichinde virus lineages. Monospecific serum against a synthetic peptide corresponding to the most conserved central domain precipitates a 250 kDa product from LAS and lymphocytic choriomeningitis virus-infected cells.

Amino Acid Sequence↗

PubMed1997

Molecular characterization of attenuated Junin virus strains.

The Junin virus strain Candid #1 was developed as a live attenuated vaccine for Argentine haemorrhagic fever. In this paper we report the nucleotide sequences of S RNA of Candid #1 and its more virulent ancestors XJ#44 and XJ (prototype). Their relationship to Junin virus wild-type MC2 strain and other closely and distantly related arenaviruses was also examined. Comparisons of the nucleotide and amino acid sequences of N and GPC genes from Candid #1 and its progenitor strains revealed some changes that are unique to the vaccine strain. These changes could be provisionally associated with the attenuated phenotype.

Amino Acid Sequence↗

PubMed1997

In vivo anti-influenza virus activity of a zinc finger peptide.

Matrix protein (M1) is a major structural protein of influenza virus, and it inhibits its own polymerase. A 19-amino-acid peptide, corresponding to a zinc finger region of the M1 sequence of influenza virus strain A/PR/8/34 (H1N1), centered around amino acids 148 to 166, was synthesized. This peptide, designated peptide 6, represents a zinc finger which includes a 7-amino-acid loop or finger and a 4-amino-acid tail at the carboxyl terminus, in addition to the 8 amino acids involved in the coordination of Zn. Three experiments were run to evaluate the activity of peptide 6 on infections induced in mice by influenza A/PR/8/34 and A/Victoria/3/75 (H3N2) viruses. Intranasal (i.n.) treatment of the H1N1 virus infection with 30 or 60 mg/kg of body weight/day, three times daily for 5 days, beginning 4 h pre-or 8 h post-virus exposure, was effective in preventing death, reducing the arterial oxygen decline, and inhibiting lung consolidation. Virus titers in the lungs determined on day 5 were reduced by up to 1.5 log10 in treated groups, but considerable variation in the titers of the recovered virus was seen. The H3N2 virus infection was treated i.n. with 30, 60, or 120 mg of peptide 6/kg/day by using the above-mentioned delayed initiation treatment schedule, and similar protection was seen, although lung virus titers were not reduced in the day-5 assay. Peptide 6 was well tolerated at doses up to 60 mg/kg/day. This zinc finger peptide may provide a new class of antivirals effective against influenza virus.

Administration, Intranasal↗

PubMed1997

Fatal myofascial necrosis due to imipenem-resistant Aeromonas hydrophila.

We report the case of a fatal myofascial necrosis caused by an imipenem-resistant Aeromonas hydrophila in a patient with a history of aplastic anemia. He presented with fever and left thigh tenderness. The CT scan was consistent with cellulitis and, after cultures were obtained, empirical treatment with imipenem and amikacin was started. Two days later, necrotic bullae appeared on his thigh, and cultures showed Aeromonas hydrophila which was imipenem-resistant. Although surgical debridement was performed and ciprofloxacin was initiated, the patient died.

Adult↗

PubMed1997

Persistence of subclinical intramammary pathogens in goats throughout lactation.

The goal of this study was to determine the persistence of caprine intramammary pathogens throughout lactation and to detect the bias in diagnoses when a single milk sample was used. We studied 131 goats throughout 7 mo of lactation. Goats were sampled monthly, and 1834 milk samples were bacteriologically analyzed. One hundred sixty-eight pathogens were isolated: 82.5% were micrococci, 9.5% were Gram-negative bacilli, and 8% were corynebacteria. An intramammary infection (IMI) was considered a true, persistent IMI when the same pathogen was isolated two or more times consecutively from the same half of the udder. One hundred one samples were considered to be truly positive, which produced persistent IMI caused by nine different species (eight Staphylococcus spp. and one Pseudomonas sp.). Statistical relationships were found between staphylococci and true-positive diagnosis and between corynebacteria and false-positive diagnosis. No relationship involving Gram-negative bacilli was detected. A single milk sample had a positive predictive value (60%), high sensitivity (96.2%), high specificity (96.1%), and highly negative predictive value (99.8%).

Animals↗

PubMed1996

Point mutations in a transcription terminator, lambda tI, that affect both transcription termination and RNA stability.

The terminator tI is located approx. 280 nucleotides beyond the int gene of bacteriophage lambda. Besides its role as a transcription terminator, tI may confer stability to the int message by protecting it from 3' exonucleolytic degradation. In order to study the role of the tI sequence in transcription termination and RNA stability, three different point mutations tI1, tI2, and tI3 were isolated and characterized. All the tI mutations map in the G + C-rich region of dyad symmetry in the terminator and decrease the transcriptional termination of tI in vivo from 99% for the wild type terminator to 81-93% as determined by galactokinase activity and in vitro from 80% for the wild type terminator to 8-12% using the E. coli RNA polymerase. Additionally, the tI mutations cause upstream transcript instability in vivo. This instability defect caused by tI mutations is compensated by the host mutant deficient in polynucleotide phosphorylase resulting in increased steady state levels of these mutant transcripts. The results show that the intact hairpin of tI is essential for efficient transcription termination and for maintaining mRNA stability by blocking the 3' to 5' exonucleolytic activity of polynucleotide phosphorylase.

Bacteriophage lambda↗

PubMed1996

The virion glycoproteins of Ebola viruses are encoded in two reading frames and are expressed through transcriptional editing.

In late 1994 and early 1995, Ebola (EBO) virus dramatically reemerged in Africa, causing human disease in the Ivory Coast and Zaire. Analysis of the entire glycoprotein genes of these viruses and those of other EBO virus subtypes has shown that the virion glycoprotein (130 kDa) is encoded in two reading frames, which are linked by transcriptional editing. This editing results in the addition of an extra nontemplated adenosine within a run of seven adenosines near the middle of the coding region. The primary gene product is a smaller (50-70 kDa), nonstructural, secreted glycoprotein, which is produced in large amounts and has an unknown function. Phylogenetic analysis indicates that EBO virus subtypes are genetically diverse and that the recent Ivory Coast isolate represents a new (fourth) subtype of EBO virus. In contrast, the EBO virus isolate from the 1995 outbreak in Kikwit, Zaire, is virtually identical to the virus that caused a similar epidemic in Yambuku, Zaire, almost 20 years earlier. This genetic stability may indicate that EBO viruses have coevolved with their natural reservoirs and do not change appreciably in the wild.

Animals↗

PubMed1996

Giant cavernous hemangioma of the liver: atypical CT and MR findings.

The CT and MR appearance of giant cavernous hemangiomas can be confusing, and some atypical radiographic findings have been described. We report the CT and MR features of a giant cavernous hemangioma of the liver with atypical presentation. CT showed a large hypodense geographical lesion involving the majority of the liver and multiple scattered peripheral lesions. The T2-weighted MR images revealed a huge hyperintense lesion with multiple satellite nodules.

Biopsy, Needle↗

PubMed1996

Pulsed controlled-released system for potential use in vaccine delivery.

Biodegradable polymeric devices intended to provide a viable route for single-dose vaccination were developed using controlled-release technology. One of the main challenges in the development of these devices was to overcome several water-mediated inactivation processes that occur in conventional polymeric systems. Our strategy was focused on the prevention of antigen exposure to environmental conditions. For this purpose a microencapsulation process was designed and optimized to provide an inert and insulated environment for the bioactive material inside controlled-release systems. Tetanus toxoid (TT) was used as a model antigen. The systems consist of core-wall microcapsule structures in which the antigenic protein is entrapped into oil-based cores of TT surrounded by outer polymer shells made of poly(D,L-lactide-co-glycolide), thus potentially protecting the bioactive material against deleterious conditions. Furthermore, using these microcapsules, pulses of immunochemically detected TT were programmed to release at two different times (3 and 7 weeks), as corroborated by in vitro release studies. The engineering of these specific antigen release properties was possible by careful selection of the copolymer composition and molecular weight. The final formulations were characterized with respect to morphology, structure, size distribution, and amount of immunochemically detected TT encapsulated. The new systems offer the potential to control the manner and timing of delivery. Over 92% of the TT released over a 63 day period from these microcapsules was immunochemically detected.

Capsules↗

PubMed1996

Polyester nanocapsules as new topical ocular delivery systems for cyclosporin A.

PURPOSE: Nanocapsules composed of an oily core (Migliol 840) (MG) surrounded by a poly-epsilon-caprolactone (PECL) coat were evaluated as potential vehicles for the topical ocular administration of cyclosporin A (CyA). METHODS: A 2(3) experimental factorial design was applied to optimize the coating of the oily nanodroplets by a solvent displacement technique and to encapsulate a high dose of CyA. The variables investigated were: volume of oil (MG), amount of polymer (PECL), and volume of the organic solvent (acetone) used to dissolve the polymer. RESULTS: Nanocapsules had a mean size in the range of 210-270 nm, a negative zeta potential (between -55 and -60 mV) and a maximum loading capacity of 50% (CyA/PECL ratio). These highly loaded nanocapsules displayed a thick spongeous polymer coating around the oily nanodroplets. The corneal levels of CyA were up to 5 times higher for the encapsulated CyA than for the oily solution of CyA. In addition, these levels remained significantly higher than those of the control group (oily solution) for up to 3 days. Furthermore, the area-under-the-curve (AUC) values were significantly increased for the encapsulated CyA (319.98) with respect to the oily control (74.34). CONCLUSIONS: The CyA-loaded nanocapsules are shown to be interesting vehicles for the improvement of the ocular penetration of CyA.

Administration, Topical↗

PubMed1996

Mechanisms for synchronous calcium oscillations in cultured rat cerebellar neurons.

Removal of Mg2+ caused oscillations of the cytosolic Ca2+ concentration ([Ca2+]i) and the membrane potential in cultured cerebellar granule neurons. Oscillations of [Ca2+]i were synchronous in all the cells, and were restricted to the neurons (immunocytochemically identified) that responded to exogenous N-methyl-D-aspartate (NMDA). Oscillations were blocked by Ca2+ removal, nickel, NMDA receptor antagonists, omega-agatoxin IVA, tetrodotoxin, sodium removal and gamma-aminobutyric acid, but not by dihydropyridines, omega-conotoxin M VIIA or by emptying the intracellular Ca2+ stores with thapsigargin or ionomycin. The upstroke of the [Ca2+]i oscillations coincided in time with an increase in manganese permeability of the plasma membrane. Propagation of the [Ca2+]i wave followed more than one pathway and the spatiotemporal pattern changed with time. Membrane potential oscillations consisted of transient slow depolarizations of approximately 20 mV with faster phasic activity superimposed. We propose that the synchronous [Ca2+]i oscillations are the expression of irradiation of random excitation through a neuronal network requiring generation of action potentials and functional glutamatergic synapses. Oscillations of -Ca2+-i are due to cyclic Ca2+ entry through NMDA receptor channels activated by synaptic release of glutamate, which requires Ca2+ entry through P-type Ca2+ channels activated by action potentials at the presynaptic terminal.

Animals↗

PubMed1996

Antiviral activity of influenza virus M1 zinc finger peptides.

Matrix protein (M1) of influenza virus inhibits its own polymerase; this suggested that a peptide segment of M1 with inhibitory properties could serve as an antiviral agent. A peptide synthesized to the Zn2+ finger region of the M1 sequence of influenza virus strain A/PR/8/34 centered around amino acids residues 148 to 166 was shown earlier to be 1,000-fold more effective as a polymerase inhibitor than M1. This peptide, designated peptide 6, represents a Zn2+ finger which includes a 7-residue "loop" and a 4-residue "tail" in addition to the 4 residues on either side of the loop involved in coordination of Zn2+. We have now demonstrated antiviral activity for this peptide in microassays measuring inhibition of the viral cytopathic effect. When the peptide was introduced into tissue culture 5 min after viral challenge with A/PR/8/34, antiviral activity was seen at levels as low as 0.1 nM; on a molar basis, the peptide was shown to be 1,000- to 2,500-fold more effective than ribavirin or amantadine. Antiviral activity was seen with addition of the peptide up to 1 h after viral infection; however, little or no activity was seen at later times, suggesting that viral replication is inhibited at an early stage, possibly at the level of transcription. Reduction in the finger loop or tail length reduced antiviral activity; reduction in the number of residues involved in coordination of Zn2+ abolished antiviral activity. In addition to A/PR/8/34, peptide 6 was shown to have antiviral activity against other type A influenza viruses, including those representing H1N1, H2N2, and H3N2 subtypes. Antiviral activity against type B influenza viruses was also seen. A low level of activity against vesicular stomatitis virus was observed. Zn2+ finger peptides or analogs of Zn2+ finger peptides may provide a new class of antiviral agents effective against influenza virus and possibly other viruses.

Amino Acid Sequence↗

PubMed1995

Modulation of neuropathic pain in rats by intrathecally injected serotonergic agonists.

The involvement of spinal cord serotonergic influences in the development of autotomy, a proposed behavioural model of denervation pain, was studied in rats subjected to sciatic and saphenous nerve transection 5 min after intrathecal injection of 100 or 200 mu g of several serotonergic receptor subtype agonists. Injection of 8-OH-DPAT, m-CPP, 2-m-5-HT and a low dose of 5-HT, significantly shifted one or more of the parameters describing autotomy to less intense behaviour. In contrast, the injection of CGS-12066B and DOI intensified autotomy. These results suggest both a modulatory role for spinal cord serotonin in the events occurring shortly after neurectomy and new therapeutic approaches for the prevention of certain pain syndromes, such as phantom limb pain.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed1995

High susceptibility to ultraviolet-induced carcinogenesis in mice lacking XPC.

Compromise of genetic information by mutation may result in the dysregulation of cellular growth control and subsequent tumour formation. Xeroderma pigmentosum (XP) is a rare autosomal disease characterized by hypersensitivity of the skin to sunlight and > 1,000-fold increased risk of skin cancers in sun-exposed parts of the body. Cell fusion studies have revealed eight complementation groups in XP (A-G, and an XP-variant form); group C is one of the most common forms of the disease. We have isolated a mouse homologue of the human gene for XP group C and generated XPC-deficient mice by using embryonic stem cell technology. Mice homozygous for the XPC mutant allele (xpcm1/xpcm1) are viable and do not exhibit an increased susceptibility to spontaneous tumour generation at one year of age. However, xpcm1/xpcm1 mice were found to be highly susceptible to ultraviolet-induced carcinogenesis compared with mice heterozygous for the mutant allele (xpcm1/+) and wild-type controls. Homozygous xpcm1 mutant mice also display a spectrum of ultraviolet-exposure-related pathological skin and eye changes consistent with the human disease xeroderma pigmentosum group C.

Amino Acid Sequence↗

PubMed1995

p53 deficiency does not affect the accumulation of point mutations in a transgene target.

DNA repair is required by organisms to prevent the accumulation of mutations and to maintain the integrity of genetic information. Mammalian cells that have been treated with agents that damage DNA have an increase in p53 levels, a p53-dependent arrest at G1 in the cell cycle, and a p53-dependent apoptotic response. It has been hypothesized that this block in cell cycle progression is necessary to allow time for DNA repair or to direct the damaged cell to an apoptotic pathway. This hypothesis predicts that p53-deficient cells would have an abnormal apoptotic response and exhibit a "mutator" phenotype. Using a sensitive assay for the accumulation of point mutations, small deletions, and insertions, we have directly tested whether p53-deficient cells exhibit an increased frequency of mutation before and after exposure to DNA-damaging agents. We report that wild-type and p53-deficient fibroblasts, thymocytes, and tumor tissue have indistinguishable rates of point mutation accumulation in a transgenic lacI target gene. These results suggest that the role of p53 in G1 checkpoint control and tumor suppression does not affect the accumulation of point mutations.

Animals↗

PubMed1995

Developmental regulation of the alpha-subunit of Gq/G11 as determined by quantitative immunoblot analysis.

We have used immunoblot analysis with glutathione and S-transferase fusion proteins as protein standards to examine expression of G alpha q/11 in membrane preparations from different organs and to assess changes during normal development. Adult rat tissues expressed 4-25 pmol/mg membrane protein G alpha q/11, with neonates expressing two to three times higher levels in several tissues (brain, heart, liver, and kidney). By contrast, levels of Gaq/11 in lung were similar in adults and neonates. A Gaq-specific antiserum confirmed the high expression in neonatal brain, heart, liver and kidney. Our results show that Gaq is developmentally regulated in many rat tissues.

Amino Acid Sequence↗

PubMed1995

Rapid and specific high-performance liquid chromatographic method for the determination of iodide in urine.

A rapid and specific method for the determination of iodide in urine by high-performance liquid chromatography on an anion-exchange column with electrochemical detection is described. The assay is reproducible as judged by the coefficient of variation of less than 4% at all concentrations used. The limit of detection was 0.1 mumol, and the calibration graph was linear for concentrations between 0.1 and 200 mumol. Using this method, healthy volunteers were found to excrete 69 +/- 39 mumol of iodide per mole of creatinine.

Adult↗