Biomedical subjects

V Sanchez

Publications and source records attributed to V Sanchez.

At least 37 records · Page 2Linked to original sources

PubMed1997

Temporal pattern of plasminogen activator activity in the developing chick cerebellum.

Plasminogen activators are considered to be involved in several developmental events. The present work aims at characterizing the developmental pattern of expression of plasminogen activators in the chick cerebellum. Soluble fractions derived by ultracentrifugation from Triton X-100 treated membrane fractions were used for determination of the enzyme activity with a radial fibrinolytic assay. By using specific inhibitors and different anti-plasminogen activators antibodies it is shown that only one type of the enzyme, the urokinase-type plasminogen activator, is expressed during the cerebellum ontogeny. Our results show the existence of a bimodal pattern of enzyme activity with two peaks that temporally coincide with the processes of massive neuronal migration, neurite outgrowth and synapse formation and plasticity. It is proposed that plasminogen activator could play a role in these developmental events and that its pattern of variability is developmentally regulated.

Animals↗

PubMed1997

The effect of neomycin on the kidney function of the horse.

The toxic effect of neomycin on the horse kidney was studied. Twelve horses were used, and were divided at random into three groups of four. The first group was treated twice a day with 10 mg/kg I.M. for 15 days and then euthanised; kidney and liver samples were studied and no histopathological changes were observed. Group 2 was treated with neomycin sulphate as in group 1, and group 3 was used as control. Blood samples were taken at 8.00 h and 20.00 h daily from both neomycin treated and control horses. Serum creatinine, potassium, sodium and urinary creatinine remained without change. On day 6 of treatment plasma urea (Urea)p decreased to 5.6 +/- 2.0 mmol/L (P < 0.001) as compared with controls (8.0 +/- 2 mmol/L). Urinary excretion of GGT increased on the third day of treatment to 118.6 +/- 1 IU/L for treated and 89 +/- 8 IU/L for controls (P < 0.001). Thereafter, GGT continued to be elevated significantly for the duration of the experiment, as compared with controls. The (GGT)/(Cr)u ratio increased significantly on the 9th day of treatment, and continued to be elevated for 6 days after treatment. Neomycin kinetics were similar during treatment. It was concluded that neomycin, in the dose used, was not harmful to kidney function in the horse.

Animals↗

PubMed1996

Purification of biological molecules by continuous flow electrophoresis in the Second International Microgravity Laboratory.

The RAMSES instrument is a continuous-flow electrophoresis device that performs separation and purification of biological materials on a preparative scale. It was flown on board the shuttle Columbia during the Second International Microgravity Laboratory mission that took place from 8 to 23 July 1994. This project had a technological aim to qualify the design and the technologies used, and a more scientific one to improve understanding of the phenomena involved in this process. To reach these goals, experiments were performed in which different samples and a variety of operating conditions were used, some of which cannot be applied on earth. Useful purifications were obtained, allowing samples to be collected for further analysis on the ground. These results confirm the predictions of a numerical model that could be used for future process optimization and the samples were found to have retained their biological activity.

Albumins↗

PubMed1996

Protein separation by continuous-flow electrophoresis in microgravity.

During the IML-2 space shuttle mission, the RAMSES instrument was operated in the Spacelab module. This continuous-flow electrophoresis device performs separation and purification of protein solutions on a preparative scale. Samples containing artificial mixtures of pure proteins were used to test the capabilities of the device, and useful separations were obtained for proteins having a mobility difference of only 3 x 10(-9) m2 V-1 s-1. Operating conditions that cannot be applied on earth were explored for two different sample concentrations, one of which is too high to allow treatment on earth. It agrees well with a previously published numerical model in that the main cause of loss in resolution in this process is the electrohydrodynamic spreading of the protein filaments.

Chromatography, Gel↗

PubMed1996

Antioxidants, Helicobacter pylori and stomach cancer in Venezuela.

A randomized chemoprevention trial on precancerous lesions of the stomach is being conducted in Tachira State, Venezuela. The aims of the study are to evaluate the efficacy of vitamin supplementation in preventing the progression rate of precancerous lesions. Here we report on the pilot phase of the study in which two antioxidant preparations were evaluated on their ability to raise antioxidant levels in plasma and in gastric juice. The study aimed also to determine the antibiotic sensitivity profiles of Helicobacter pylori isolates prevalent in the area. Forty-three subjects with precancerous lesions (chronic gastritis, chronic atrophic gastritis, intestinal metaplasia and dysplasia) of the stomach were randomized to one of two antioxidant treatments. Treatment 1 (250 mg of standard vitamin C, 200 mg of vitamin E and 6 mg of beta-carotene three times a day) or treatment 2 (150 mg of standard vitamin C, 500 mg of slow release vitamin C, 75 mg of vitamin E and 15 mg of beta-carotene once a day) for 7 days. Blood levels of total vitamin C, beta-carotene and alpha-tocopherol and gastric juice levels of ascorbic acid and total vitamin C were measured before and after treatment on day 8. Both treatments increased the plasma levels of total vitamin C, beta-carotene and alpha-tocopherol/cholesterol but not those of ascorbic acid or total vitamin C in gastric juice. Treatment 1 was the best choice and resulted in a greater increase in the plasma levels of beta-carotene and alpha-tocopherol. H. pylori was cultured from 90% of the gastric biopsies; 35 isolates were identified which were highly resistant to metronidazole, a front-line antibiotic recommended against H. pylori in other settings.

Adult↗

PubMed1996

Prevalence of precancerous lesions of the stomach in Venezuela.

Gastric biopsies from 1477 participants in a chemoprevention trial for precancerous lesions of the stomach in Venezuela were evaluated for the prevalence of precancerous lesions and Helicobacter pylori infection. These study subjects were selected from participants in an early detection program for gastric cancer using double-contrast X-ray. Overall, 94% had some type of chronic gastritis (CG) and were positive for H. pylori using Giemsa stain, 49% had atrophic gastritis, 34% had intestinal metaplasia (IM), and 6.5% had dysplasia. There were only three subjects (0.2%) with normal gastric mucosa, and 4% had only superficial gastritis. The prevalence of all of these precancerous lesions increased with age, but there was no clear difference by gender. The prevalence of the various lesions was higher in the antral mucosa than in the fundic mucosa. H. pylori infection was strikingly frequent in our study population, with prevalence rates ranging from 73% in subjects with superficial gastritis to 95% in those with atrophic gastritis and IM and 98% in those with CG. The prevalence of H. pylori was equally high in males and females, and it was significantly positively associated with the degree of infiltration of poly- and mononuclear cells and with that of active regeneration; it was inversely correlated with the degree of atrophy, IM, and dysplasia. Our findings support the precancerous nature of the various gastric lesions and the etiological role of H. pylori infection in CG.

Adult↗

PubMed1995

Determinants of plasma pepsinogen levels in a population at high risk for stomach cancer in Venezuela.

Determinants of plasma pepsinogens (PG) levels were studied in 1365 participants in a chemoprevention trial for gastric pre-cancerous lesions being conducted in Venezuela. Gastric biopsies, plasma samples and information on smoking and dietary habits were obtained at baseline examination. Both PG-I and PG-II levels increased progressively with the level of Helicobacter pylori infection in gastric biopsies, resulting in no clear trend in the I/II ratio. Instead, there was a progressive decrease in the I/II ratio with increasing degrees of infiltration of polynuclear cells and monocytes, atrophy, intestinal metaplasia and the stage of pre-cancerous lesions. The mean I/II ratios for atrophic gastritis or more advanced lesions were less than 4.0. When subjects with the I/II ratio 4 or higher were used as controls, severe reduction in the I/II ratio (< 2.0) was inversely associated with tobacco consumption. This may be due to a pharmacological effect of nicotine. The severe reduction of I/II ratio was also inversely associated with fresh fruit consumption. In addition, a decreased I/II ratio was positively associated with rice/pasta and arepas (tortilla made from corn) consumption and inversely associated with plantain consumption. Possible effects of vitamins and starchy food on the development of atrophic gastritis need to be studied further.

Adult↗

PubMed1995

The effects of cisapride on plasma L-dopa levels and clinical response in Parkinson's disease.

Cisapride (CIS) is a prokinetic agent that increases gastrointestinal motility in normal individuals and improves constipation in Parkinson's disease (PD). We studied the effects of CIS on the clinical response and the peripheral pharmacokinetics of orally administered L-dopa given to patients with PD. Twenty patients with idiopathic PD and chronic constipation, whose response to L-dopa was suboptimal or characterized by fluctuations, agreed to participate in an open study that lasted for 2 weeks. Fourteen patients completed the study (mean age 65 +/- 9.3 years, mean duration of treatment 5.7 +/- 4.2 years, mean L-dopa daily doses 658.9 +/- 269.9 mg); six patients were excluded due to lack of compliance or changes in medication during the study. The end points of the study included the mean levels of L-dopa, the height of the peak of L-dopa in plasma, mean plasma levels of 3-OM-dopa, and the speed and quality of gait and visuomanual coordination before and during treatment with CIS. CIS increased peak plasma levels of L-dopa by 37% and the mean plasma levels of L-dopa by 13% with respect to those obtained with the same dose of L-dopa before the addition of CIS. Therefore, CIS appears to increase early absorption of L-dopa through acceleration of gastric emptying. CIS also increased plasma 3-OM-dopa levels, improved visuomanual coordination, and reduced gait disability. CIS improves gastrointestinal function and response to L-dopa in patients with PD and could be a helpful add-on medication in these patients.

Aged↗

PubMed1995

Hepatitis C virus genotypes in serum and liver of children with chronic hepatitis C.

Hepatitis C virus (HCV) 1a, 1b, 2a, and 2b subtypes have been studied in 30 serum samples and in 20 paired liver biopsies from children with chronic hepatitis C. One serum sample was negative to the four HCV subtypes studied. HCV 1b was detected alone in 53.3% (16/30) of the serum samples; HCV 1a alone in 23.3% (7/30) and a mixed infection in 20% (6/30). In liver samples, HCV mixed infection was detected in a significantly higher proportion (50%: p < 0.05) than in serum, whereas HCV 1b was detected alone in 35% (7/20) and HCV 1a alone in the remaining 15% (3/20) of liver samples. These results suggest that serum HCV genotyping may not reflect the viral population infecting the liver of a given patient. Additional studies should be performed concerning the pathobiology of hepatitis C virus with relation to the subtypes detected in liver.

Adolescent↗

PubMed1994

Difficulty in eradicating Helicobacter pylori in a population at high risk for stomach cancer in Venezuela.

The bacterium Helicobacter pylori (HP) has been implicated in the etiology of precancerous lesions of the stomach and there is evidence suggesting that it may influence the efficacy of chemoprevention of gastric cancer with vitamin C. Eradication seldom has been attempted in populations from developing countries, with a high prevalence of HP frequently resistant to metronidazole. A randomized, double-blind, controlled trial to evaluate the efficacy of colloidal bismuth subcitrate (120 mg q.i.d.) and amoxycillin (500 mg q.i.d.) in eradicating HP was conducted in 220 subjects drawn from a population with a high prevalence of metronidazole-resistant HP in Tachira state, Venezuela. One month after completion of two weeks' treatment, eradication rates of 6.5 percent in the treatment group and two percent in the placebo group were estimated on the basis of HP diagnosis in biopsies, and of 13.9 percent compared with 3.9 percent on the basis of a 14C-urea breath test, although the negative predictive value of the breath test was very low compared with HP diagnosis in biopsies. In the treatment group, particularly among males, a significant decrease in bacterial load was detected. Reasons for failure of treatment in high HP-prevalence areas are discussed, and it is suggested that primary prevention of HP infection may be the optimal approach to reducing levels of stomach cancer in these high-risk groups.

Adult↗

PubMed1994

Novel injectable fluorinated contrast agents with enhanced radiopacity.

Novel emulsions containing iodinated fluorinated radiopaque (IFR) molecules were prepared and evaluated as injectable contrast agents with prolonged intravascular persistence. Various stable IFR/egg yolk phospholipid emulsions were produced, heat-sterilized, and tested as to their radiopacity, shelf-stability and in vivo tolerance. No significant change in mean particle sizes was observed over a 3-month storage period at 40 degrees C. Intravenous injection of an emulsion of a 0.39 g/kg bw dose of a typical IFR, C6F13CH = CIC6H13 (F6H6IE) in rabbits led to high contrast in the liver and spleen. The same radiopacity of the liver was achieved with 7 times less IFR than perfluorooctyl bromide. Histological examination after 24 h, and blood analysis after 24, 48 h and 7 days, demonstrated normal functioning of the liver, even when high concentrations of IFR were present. The neat IFR was tolerated i.p. in mice at a 45 g/kg bw dose. Emulsified IFR was tolerated in rats and mice i.v. at a 8 g/kg bw dose. The iodinated fluorinated molecule tested appears promising for the formulation of new contrast agents for diagnosis.

Animals↗

PubMed1993

Nosocomial acquisition of Candida parapsilosis: an epidemiologic study.

OBJECTIVE: The purpose of this study was to determine aspects of the epidemiology of nosocomial infection due to Candida parapsilosis. Candida species are important nosocomial pathogens; however, little epidemiologic information is available. PATIENTS AND METHODS: We prospectively cultured specimens from 98 patients admitted to the bone marrow transplant unit and a medicine intensive care unit (ICU) of a tertiary care hospital. Specimens from hands of personnel and environmental surfaces were also cultured. Environmental cultures were done before patients were admitted to a studied unit. Restriction enzyme analysis (REA) of chromosomal DNA was used as a typing system to determine the relatedness of strains. RESULTS: C. parapsilosis was identified from five patients, six hand cultures from four hospital staff, and two environmental surfaces. All five patients had negative initial cultures and acquired C. parapsilosis after admission to the study unit. There were no significant differences between patients and control subjects in age, underlying disease, immunosuppressive therapy, and instrumentation. The duration of antibiotic therapy (median: 32.8 versus 11.8 days, p = 0.05) and the duration in the unit (means: 30.1 versus 16.1 days, p = 0.048) was longer in patients than in controls. No common source was identified. REA revealed three strain types; however, one strain type was identical in four patients, three staff members, and two environmental surfaces. CONCLUSION: These results suggest exogenous acquisition of C. parapsilosis. Based upon isolation of identical patient strains of C. parapsilosis from inanimate surfaces before patients were admitted to a study unit, there is evidence that the organism may have been acquired from the hospital environment. The principal mechanism of transmission was probably indirect contact via the hands of hospital personnel.

Adolescent↗

PubMed1993

Detection of two early gene products of Epstein-Barr virus by fluorescence flow cytometry.

The intracellular expression of two early gene products of Epstein-Barr virus (EBV) was evaluated by fluorescence flow cytometry. Two Burkitt's lymphoma cell lines were superinfected by EBV from the P3HR-1 cell line. Twelve to 96 hr after superinfection the cells were fixed with paraformaldehyde and made permeable by saponin treatment. Monoclonal antibodies to the diffuse (D) and restricted (R) components of the early antigen (EA) complex were applied to the cells followed by fluorochrome-conjugated goat antibodies specific for the heavy chain isotypes of the monoclonal antibodies. Fluorescence flow cytometry revealed a clear separation in fluorescence intensity between cells containing EA-R or EA-D and negative cells. A major proportion of EA-positive cells displayed both antigens. In addition, a significant fraction expressed either EA-R or EA-D but not both. Expression of EA occurred more rapidly and peaked earlier in Daudi cells than in Raji cells. This apparent difference in EA expression between the two cell lines, however, was much less pronounced when one considered the proportion of cells expressing EA-R only, EA-D only, or both EA-R and EA-D, as a percentage of the total EA expression. Parallel fluorescence microscopy experiments revealed that the variation of the ratio of EA-R to EA-D expression with time correlated well between the two methods.

Antibodies, Monoclonal↗

PubMed1993

Nosocomial acquisition of Candida albicans: an epidemiologic study.

To evaluate the mechanism and risk factors associated with the nosocomial acquisition of Candida albicans, a 10-month prospective study was conducted in a 24-bed bone marrow transplant unit and an 8-bed medical intensive care unit of a university hospital. A total of 98 patients had samples taken on admission and during hospitalization for culture. Samples from hands of hospital personnel and environmental surfaces were also cultured. C. albicans was isolated from 52 patients, and each patient was matched with a control. Fourteen patients acquired C. albicans after admission to the study. Prior antibiotics and length of time spent in the unit were more common in patients with new acquisition of C. albicans than in controls (92% vs. 64% and 32.5 vs. 13.0 days, respectively). Restriction enzyme analysis revealed 32 strain types; 4 were common to 30 patients and 10 environmental surfaces. Identical strains of C. albicans from patients who were geographically and temporally associated suggests the exogenous nosocomial acquisition of C. albicans through indirect patient contact.

Adolescent↗

PubMed1992

Phorbol ester-induced amino-terminal phosphorylation of human JUN but not JUNB regulates transcriptional activation.

Phorbol ester tumor promoters activate gene transcription by regulating both the synthesis and posttranslational modification of the activator protein 1 (AP-1) transcription factor, c-Jun and JunB are components of the mammalian AP-1 complex. Here we demonstrate that in U-937 human leukemic cells, phorbol esters stimulate the phosphorylation of the amino terminus of human c-Jun (JUN) but not human JunB (JUNB). Mutational analysis indicates that serine-63 and -73, which reside within the putative regulatory domain of JUN, are required for both constitutive and phorbol 12-myristate 13-acetate-inducible N-terminal JUN phosphorylation. To determine the functional role of this N-terminal phosphorylation, we prepared several chimeric proteins containing the N-terminal 84 amino acids (positions 5-89) of human JUN or murine JUNB fused to the yeast GAL4 DNA-binding domain. This region was found to be sufficient for the phorbol ester-inducible transcriptional activity of JUN, but not JUNB. This induction was abolished by the mutation of serine-63 and -73 to leucine residues. Thus, we propose that phorbol esters enhance the trans-activation potential of JUN, but not JUNB, by the phosphorylation of the N-terminal regulatory domain of JUN.

Amino Acid Sequence↗

PubMed1992

P-type voltage-dependent calcium channel mediates presynaptic calcium influx and transmitter release in mammalian synapses.

We have studied the effect of the purified toxin from the funnel-web spider venom (FTX) and its synthetic analog (sFTX) on transmitter release and presynaptic currents at the mouse neuromuscular junction. FTX specifically blocks the omega-conotoxin- and dihydropyridine-insensitive P-type voltage-dependent Ca2+ channel (VDCC) in cerebellar Purkinje cells. Mammalian neuromuscular transmission, which is insensitive to N- or L-type Ca2+ channel blockers, was effectively abolished by FTX and sFTX. These substances blocked the muscle contraction and the neurotransmitter release evoked by nerve stimulation. Moreover, presynaptic Ca2+ currents recorded extracellularly from the interior of the perineural sheaths of nerves innervating the mouse levator auris muscle were specifically blocked by both natural toxin and synthetic analogue. In a parallel set of experiments, K(+)-induced Ca45 uptake by brain synaptosomes was also shown to be blocked or greatly diminished by FTX and sFTX. These results indicate that the predominant VDCC in the motor nerve terminals, and possibly in a significant percentage of brain synapses, is the P-type channel.

Action Potentials↗

PubMed1992

The relative importance of transport phenomena in recycling isoelectric focusing.

The various transport phenomena involved in recycling isoelectric focusing are analyzed for their contributions to band spreading so as to find ways of improving the resolution of this liquid-phase protein purification method. A numerical model is proposed that takes into account diffusion, electroosmosis and electrophoretic migration as a function of pH. The electrohydrodynamic effects have so far been neglected in these calculations. The results of these calculations are compared with experimental measurements performed in different chamber geometries, with a variety of proteins and under different operating conditions, always chosen to avoid flow instabilities. This comparison shows that the resolution of this process is greatly impaired if the electroosmotic slip velocity at the wall is not suppressed.

Electrochemistry↗

PubMed1992

Decreased protein kinase C activity is associated with programmed cell death (apoptosis) in freshly isolated rat hepatocytes.

Apoptosis of freshly isolated rat hepatocytes was induced by either the omission of fetal bovine serum in the culture medium or addition of the protein kinase C inhibitors polymyxin B or staurosporine. The time-course of DNA breakdown into oligonucleosome-sized fragments and the activity of protein kinase C was determined. Hepatocytes were found to be sensitive to bleomycin which induced a high degree of DNA breakdown even within 30 min incubation. Both staurosporine and polymyxin B induced DNA degradation in hepatocytes after three hours incubation, an effect that was partially prevented by phorbol myristate acetate (PMA). After eight hours incubation, PMA failed to counteract this action and itself produced the apoptosis of rat hepatocytes. The results suggest the involvement of protein kinase C in hepatocyte survival.

Alkaloids↗