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Biomedical subjects

G Contreras

Publications and source records attributed to G Contreras.

At least 19 recordsLinked to original sources
PubMed1998

[Expression of different HIV-1 phenotypic subpopulations through the natural history of the infection].

BACKGROUND: Multiple viral subpopulations coexist in an HIV infected patient with dynamics of selection established between them. In order to get insight on the phenotype of these subpoblations, and its relation with disease progression, we have studied the biological variability of HIV-1 in 113 patients. Variability was related with CD4+ T lymphocyte counts, clinical status, way of viral transmission and antiretroviral treatment. PATIENTS AND METHODS: 113 patients (80 adults and 33 children) were studied for HIV-1 isolation in cocultures of infected and non infected lymphocytes. Viral replication was evaluated as rapid (R)/slow (S) or high (H)/low (L). Syncytia formation was estimated in MT2 cell line (SI/NSI). The tropism toward lymphocytes and monocytes (LM) was studied on H9 and U937 cell lines. RESULTS: Up to 86.7% of viral isolates were R, 56.6% were H and 49.6% were SI. These percentages increased with disease progression. Eight viral strains were R/H/NSI cocultivated in MT2 cells and SI in cocultured lymphocytes (NSI/SI), which may be considered as a new phenotype. All the SI isolates and all the R/H (SI and NSI) isolates were LM. Three categories were established: R/H/SI/LM, R/H/NSI/LM and S/L/NSI/NLM. The first two categories corresponded to patients with CD4+ T lymphocytes <200 x 10(6)/I (56%, 50%). The third category corresponded to patients with > 500 x 10(6)/I (53.3%). CONCLUSIONS: Viral replication and SI phenotype, independently, are useful markers for severity of HIV infection. The biological differences among NSI of the 3 viral phenotype categories, including the new subgroup NSI/SI, may indicate the existence of more pathogenic NSI subpopulations.

Adolescent↗
PubMed1997

Effects of hemodialysis on left ventricular diastolic filling.

Diastolic Doppler filling parameters were measured before and after hemodialyses, performed once with and once without fluid removal. Changes occurred only with fluid removal and correlated with weight loss, indicating that they are the result of reduction in preload.

Aged↗
PubMed1997

Laboratory and clinical evaluation of a portable computerized peak flow meter.

A mini-Wright based peak flow meter (VMX Mini-Log), which stores the readings together with the time and date of each measurement, has recently been marketed but has not yet been evaluated. The accuracy, reproducibility, and interdevice variability of this instrument were investigated using a pneumotachograph connected in series as a standard. Flows from 100 to 700 L/min were generated by an explosive decompression chamber. The performance of this instrument was also tested in 20 normal subjects and in 20 patients with airflow obstruction. The accuracy of the instrument was expressed as the percentage of error, and reproducibility and interdevice variability were assessed using the coefficient of variation. In the laboratory evaluation, all devices recorded flow rates that were within +/-10% of the pneumotachograph readings at flows between 200 and 600 L/min. At the extreme flow rates of 100 and 700 L/min, the mean error was higher than 10%. The reproducibility of the VMX was within +/-5% at all the flows tested. The interdevice variability was less than 5% at flow rates between 200 and 700 L/min. When tested on normal subjects with PEF between 400 and 700 L/min, the VMX performed well. In patients with airflow obstruction, four devices had greater than 10% error. The largest error was observed in those patients with PEF below 200 L/min. The VMX Mini-Log peak flow meter is accurate and precise in the flow range between 200 and 600 L/min. Its performance, however, may be affected in subjects with airflow obstruction and PEF below 200 L/min.

Adolescent↗
PubMed1997

Cytoplasmic DNA in Entamoeba histolytica: its biological significance.

We report a study on the DNA organization in Entamoeba histolytica using a ribosomal DNA probe. The rDNA genes were found forming mers which were separated in a typical ladder pattern by pulse field electrophoresis. DNA rosette structures were visualized through electron microscopy in DNA eluted from bands recognized by the ribosomal probe. The in situ hybridization experiments using a DNA probe suggested that the rDNA genes are portioned between the nucleus and a cytoplasmic structure. These findings provide new data on DNA organization in E. histolytica and open the question concerning the presence of a novel organelle in this eukaryotic parasite.

Animals↗
PubMed1995

Diazepam induces tolerance in the isolated skin of Pleurodema thaul.

The effects of the long-term administration of diazepam on the potential difference and short-circuit current of the isolated skin of the toad Pleurodema thaul (P. thaul) were investigated. Diazepam applied in a concentration range of 4.6 x 10(-6) to 5.2 x 10(-5) M decreased both electrical parameters. This response was unaffected by flumazenil indicating that the action of diazepam is not induced through benzodiazepine receptors. Induction of tolerance to diazepam on its observed effects on potential difference and short-circuit current was obtained by the administration of a single dose of the drug in a slow release preparation. Skins tolerant to diazepam were also tolerant to the acute effects of verapamil on both electric parameters. Tolerance to diazepam effects was partly reversed by increasing Ca2+ concentration in the inner bathing solution. The results are consistent with a Ca2+ channel blocking effect of diazepam in the P. thaul skin.

Animals↗
PubMed1995

Diazepam decreases the response to the electrical stimulation of the nerve-skin preparation of the toad Caudiverbera caudiverbera.

1. The effect of diazepam was examined in the nerve skin preparation of the toad Caudiverbera caudiverbera. 2. Nerve stimulation was followed immediately by a transient increase in short-circuit current (SCC) and in the potential difference (PD), which consisted of a rapid and then a slow component. 3. Diazepam concentrations from 5.0 x 10(-5)M to 5.1 x 10(-4)M caused a dose-dependent block of both components to a 30% of their control values and also reduced the stimulatory responses to noradrenaline in this preparation. 4. Diazepam antagonized the potassium blocking effect of barium. 5. These results, based on electrophysiological and pharmacological evidence, are consistent with a calcium and sodium blocking effect of diazepam on the nerve skin junction of C. caudiverbera.

Adrenergic alpha-Agonists↗
PubMed1995

Peak expiratory flow monitoring is not a reliable method for establishing the diagnosis of occupational asthma.

This is a study of the reliability of peak expiratory flow (PEF) monitoring using a portable computerized peak flow meter, the VMX Mini-log, in 17 subjects referred for suspected occupational asthma. Subjects were requested to monitor their PEF six times daily using the VMX Mini-Log for 2 wk at work and at least 10 d away from work. They were unaware that their readings were stored by the flow meter in addition to the digital readout. Four subjects (22%) were unable to complete the monitoring. The results recorded by the subjects were compared with the results recorded by the VMX. Of those who completed the monitoring, only 55.3% of the records were completely accurate in terms of the value and the timing of the measurements, 23.3% were inaccurate either in terms of the recorded value or of the timing of the measurement, and the remainder were fabricated results (not recorded by the Mini-Log). Our results suggest that PEF monitoring using ordinary peak flow meters for assessment of work-relatedness of asthma has limitations and is not reliable.

Adult↗
PubMed1995

Nephrotic syndrome in autosomal dominant polycystic kidney disease.

Urinary protein excretion is generally less than 1 g/24 h in autosomal dominant polycystic kidney disease (ADPKD), and the association of the nephrotic syndrome with this condition is considered rare. A patient with ADPKD associated with nephrotic-range proteinuria is described. She exhibited a relatively rapid impairment of her renal function. An open renal biopsy revealed focal segmental glomerulosclerosis (FGS) with features consistent with secondary FGS. Twenty-one patients with ADPKD and nephrotic syndrome were retrieved from the literature. Fourteen of them (including this case) had a histopathologic evaluation, and FGS was the dominant diagnoses (five patients). Next in frequency were minimal-change disease and membranous nephropathy, with two patients each. Five other patients had a variety of diagnoses. Thus, it is difficult to ascertain if these associations are coincidental or represent a specific pathogenetic relationship. The evaluation of the data also suggests that the presence of proteinuria and nephrotic syndrome accelerates the course of ADPKD toward ESRD.

Aged↗
PubMed1994

[Complicated placental chorioangioma: infrequent cause of premature labor].

We report a case of a 32 week pregnant patient who was admitted to our ward in preterm labor. After delivery, the examination of the placental tissue showed a large pedunculated tumor, complicated with torsion. Histology of the tumor revealed a placental chorioangioma. We propose that the complication of the tumor is the etiologic factor that brought about preterm labor in this patient.

Adult↗
PubMed1994

[Association of cholesterolosis and cholelithiasis: pathogenic implications and effects of the natural history of cholelithiasis].

We studied 793 patients subjected to cholecystectomy to determine a) the relative frequency of cholesterolosis and cholelithiasis, b) the effects of their association on the natural history of biliary disease, c) the characteristics of gallstones associated to cholesterolosis and d) factors potentially associated to their pathogenesis. The gallbladders of all patients were examined and in 289 subjects a preoperative clinical history was taken. We observed that cholesterolosis is associated to earlier clinical manifestations of biliary disease and cholecystectomy, to a greater frequency of single calculus and to a higher weight/height index. It is concluded that there are relationships between the pathogenesis of cholesterolosis and cholelithiasis and that their association favors the development of clinical manifestations.

Adult↗
PubMed1994

[Adult T-cell lymphoma and Reed-Sternberg cells. A clinical case].

Adult T-cell lymphoma (ATL) is a neoplastic disease associated in 80% of cases with HTLV-I (Human T Lymphotropic virus type I) infection. 1-2% of HTLV-I carriers may develop the disease during their lives. In our country, the prevalence of HTLV-I infection is about 1%. We report a 72 y.o. woman HTLV-I positive, confirmed by Western-Blot. presenting with massive adenopathies, cutaneous tumor involvement, acute course and showing Reed-Sternberg cells (RSCs) in lymph node biopsy. The response to chemotherapy was poor, with the patient dying seven months after diagnosis. ATL and Hodgkin's disease (HD) are discussed highlighting that RSCs are not pathognomonic of HD though in their absence such diagnosis can not be made. RSCs are found in other benign and malignant disorders and it is especially important to differentiate HD from the other processes in order to dispense the appropriate treatment. This is the first case of ATL with RSCs reported in Chile. Hence, in our country we suggest systematic determination of the presence of HTLV infection when histopathology is compatible with HD and Non Hodgkin Lymphoma.

Aged↗
PubMed1993

Calcium channel blockers apparently decrease noradrenaline release from nerve-skin terminals in Caudiverbera caudiverbera.

1. The effects of three calcium channel blockers, verapamil, diltiazem and nifedipine were examined on the response of the skin neuroepithelial synapse of the toad Caudiverbera caudiverbera to electrical stimulation. 2. The stimulus induced a significant rise in potential difference (PD) and short-circuit current (SCC). The three calcium antagonists reduced the responses in a dose-dependent manner. The greatest reduction was induced by verapamil followed by diltiazem and nifedipine. 3. Amiloride treatment did not affect the responses to electrical stimulation, indicating that the response to nerve stimulation is not due to current flowing through sodium channels. 4. When the preparation was blocked by either of the three antagonists, the skin response to noradrenaline was not affected. 5. It may be concluded that verapamil, diltiazem or nifedipine reduce the release of noradrenaline at the neuroepithelial synapse of C. caudiverbera.

Amiloride↗
PubMed1993

Some aspects of the monkey neurovirulence test used for the assessment of oral poliovirus vaccines.

Twelve years of experience in three control laboratories with 8,000 macaca monkeys for the testing of 204 monovalent lots of the three types of oral poliovirus vaccine (OPV), have shown that the new monkey neurovirulence test (MNVT) adopted by the World Health Organization (WHO) is a reproducible and sensitive assay likely to ensure the safety of this vaccine in humans. When the test vaccine and the appropriate homotypic reference vaccine were tested in a single group of monkeys, the concurrent use of the reference vaccine considerably increased the reproducibility of the test. The usefulness of the WHO MNVT was further demonstrated in our laboratory when the test was applied to types 1 and 3 vaccine strains that were passaged serially in the intestinal tract of infants. The test was suitable for detecting increased monkey neurovirulence in these human passage strains that did not reach the level of neurovirulence of the "wild" types 1 and 3 strains tested concurrently (except human passage no. 7 of the type 3 vaccine that multiplied for a cumulative 109 days in seven infants). The statistical analysis of the data showed that the old intrathalamic (IT) assay used for many years in our laboratory was considerably less sensitive than the intraspinal WHO MNVT; a test vaccine with a two-fold increase in monkey neurovirulence showed a 41% chance of failing in the IT test (using 30 monkeys per vaccine), while this chance increased to 99% in the WHO assay (using 12 monkeys for types 1 and 2 vaccines and 20 monkeys for type 3 vaccine). Indeed, three of seven type 3 lots tested in our laboratory with both assays failed in the WHO assay but all lots passed in the IT test. Since the introduction of the WHO MNVT in Canada and the United Kingdom, the number of vaccine-associated paralytic poliomyelitis cases in the population continued to remain at a low level.

Animals↗
PubMed1992

[Prevalence of HIV-1 and other sexually transmitted diseases among Spanish prostitutes].

BACKGROUND: Many studies in Western countries point to the high prevalence of HIV infection in groups of prostitutes especially among those using intravenous drugs (IVDA). Furthermore, there appears to be a low but increasing number of heterosexually infected prostitutes. METHODS: A cross-sectional study was carried out in a sample of 374 prostitutes selected by collaborating groups in 11 provinces with the aim of studying the prevalence of HIV and its associated risk factors in Spanish prostitutes. Furthermore, the prevalence of other sexually transmitted diseases (HIV-2, HTLV-I/II, hepatitis B and syphilis), the frequency of different sexual activities and the use of condoms were investigated in this group. The data were collected by interview using a previously tested questionnaire. RESULTS: Serological analysis demonstrated that 54 persons were positive for HIV-1 (16%), none for HIV-2, 1 for HTLV-I/II, 113 for hepatitis B (46%) and 84 for syphilis (25%). The main risk factor for HIV infection was IVDA; 60% of this group was positive vs 3% of the non IVDA (OR = 47.6; confidence interval 18.4-128.0). Consistent condom use in this population is low, although it varies according to the type of relation and sexual partner. Forty-nine percent of the women having vaginal relations with their customers reported using condoms at all times or almost all times vs 36% for anal relations and 22% for oral relations. These percentages were reduced to 10%, 6% and 3%, respectively with private sexual partners. CONCLUSIONS: Studies concerning HIV prevalence and its associated risk factors in Spanish prostitutes should be continued in order to monitor trends in HIV infection and the use of protective measures.

Adolescent↗
PubMed1992

Impairment by cyclosporin A of reperfusion-induced arrhythmias.

This study introduces the immunosuppressor, cyclosporin A, as a cardioprotective drug. This effect was analyzed during development of reperfusion/induced arrhythmias after 5-min period of coronary ligation in hearts of rats under anesthesia. The results indicate that cyclosporin, when given before coronary occlusion, at a dose of 20 mg/kg, effectively protects against the high incidence of arrhythmias and the fall in blood pressure induced by reperfusion. In addition, in inhibits the delivery of lactic dehydrogenase and creatine kinase enzymes to the plasma. We propose that the protective effect could be related with its well documented action to restrain Ca(2+)-induced damage of mitochondrial functions.

Animals↗
PubMed1992

Genetic characterization of Sabin types 1 and 3 poliovaccine virus following serial passage in the human intestinal tract.

Poliovirus isolates types 1 and 3 were obtained from five and seven successive passages respectively, in infants who had been fed monovalent OPV in two separate clinical trials conducted in 1960. The purpose of these trials was to answer the question how much the vaccine virus would revert to its original neurovirulent phenotype following multiplication in the intestinal tract. Human passages were performed either by contact exposure or by feeding the excreted virus while the infants were maintained in isolation. Several virus isolates were obtained at each passage level. Infants participating in both studies showed no symptoms of disease. Antigenic studies (McBride, van Wezel) and protein analysis (PAGE) of the isolates, reported earlier from this laboratory, had shown that the isolates remained vaccine-like, although isolates from the later passages revealed some differences. Monkey neurovirulence test results showed that for both types 1 and 3 viruses the loss of attenuation of the vaccine strain upon passage was gradual, although the loss was faster for type 3. Examination of the oligonucleotide maps demonstrated that the oligonucleotide configuration of the isolates remained the same as for the vaccine strain but there was an increase of individual spot differences with increasing passage. The nucleotide sequence analysis of selected regions of the virus genomes revealed that there was no change from a G to A in nucleotide 480 of type 1 isolates; however, nucleotide 476 changed from a U to an A in type 1 passages 3, 4 and 5. Conversely, for type 3 the change of nucleotide 472 from a U to a C changed at the early first passage (4 days following administration of OPV), and remained a C in the six following passages; type 3 nucleotide 2034 did not change in the first passage from a U to a C, but it became a C in all further passages tested. The nucleotide changes mentioned for both virus types remained stable in successive passages. However, there was another nucleotide change for type 3 from a U to a C at position 1973 only for passages 5 and 6 which reverted to a U for passages 7L and 7LL. Study of selected human passage virus strains could further contribute to the identification of the critical nucleotides that are responsible for the attenuation of these two polio types of vaccine viruses.

Base Sequence↗
PubMed1992

Possible influence of measles virus infection of cynomolgus monkeys on the outcome of the neurovirulence test for oral poliovirus vaccine.

Macaque monkeys are susceptible to measles infection which triggers temporary immuno-depression similar to the well known phenomenon in humans. It is known that feral monkeys become infected with measles virus when they are exposed to humans. Since Macaca mulatta and M. fascicularis are species used to assay the neurovirulence of oral poliovirus vaccine, the immunodepression caused by measles infection of the test monkeys could significantly alter the results of the neurovirulence test. The serum titers of measles-neutralizing antibodies were studied in over 1500 monkeys used for neurovirulence tests. A high proportion of the feral monkeys had measles antibodies (51-100%); in contrast, none of 493 M. fascicularis monkeys which had been bred in a primate colony under strict isolation measures was found positive for measles antibodies. An increase in the prevalence of measles in the population of Ontario and Quebec provinces was accompanied with an increase in the proportion of measles-positive monkey and their serum antibody titers were found higher. It was observed that monkeys used in tests that had been performed during high measles prevalence presented with a poliomyelitis of more pronounced severity clinically and histologically. The analysis of 29 tests conducted on type 1 vaccines over several years showed a positive correlation (correlation coefficient = 0.5141, P less than 0.0022) between severity of poliomyelitis and the presence of measles serum antibodies in test monkeys (some animals seroconverted during the test). A similar observation, when type 3 Sabin vaccines were tested in M. fascicularis, was recently reported from another laboratory in Ontario.

Animal Husbandry↗