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Biomedical subjects

N Alvarez

Publications and source records attributed to N Alvarez.

At least 37 records · Page 2Linked to original sources
PubMed1997

Actinomyces graevenitzii sp. nov., isolated from human clinical specimens.

Four strains of a previously unknown, catalase-negative, facultatively anaerobic, gram-positive, rod-shaped organism originating from humans were characterized by biochemical, chemical, and molecular taxonomic methods. The four strains phenotypically closely resembled one another, and although they possessed characteristics consistent with membership in the genus Actinomyces, they differed from all previously recognized species of this genus. The results of comparative 16S rRNA gene sequencing studies demonstrated that the unknown human bacterium was phylogenetically a member of the genus Actinomyces. Within the genus Actinomyces, the unidentified bacterium formed a loose, but statistically significant, association with a subgroup which included Actinomyces bovis, the type species of the genus. 16S rRNA sequence divergence values of > 6%, however, unequivocally demonstrated that the unidentified bacterium represents a new subline of the genus Actinomyces. A new species, Actinomyces graevenitzii, is proposed for the four new isolates. The type strain of A. graevenitzii is CCUG 27294.

Actinomyces↗
PubMed1997

Streptococcus hyovaginalis sp. nov. and Streptococcus thoraltensis sp. nov., from the genital tract of sows.

Two groups of strains isolated from sows were shown to belong to new sublines in the genus Streptococcus. Based on phenotypic and phylogenetic analyses, we propose that these bacteria should be classified as two new species, Streptococcus hyovaginalis sp. nov. and Streptococcus thoraltensis sp. nov. These two species are found in the genital tract, but the capnophilic species S. thoraltensis may also occur in the intestinal tract of pigs. The type strain of S. hyovaginalis is SHV515 (= LMG 14710), and S69 (= LMG 13593) is the type strain of S. thoraltensis.

Animals↗
PubMed1994

Case-control study of gastric cancer screening in Venezuela.

A screening programme for early gastric cancer was introduced in the state of Tachira, Venezuela, in 1980. Screening was performed by photofluorography, using two mobile units. The efficacy of this programme in reducing mortality from stomach cancer was evaluated by means of a case-control study. Cases were 241 individuals who died from stomach cancer in the period 1985-89. Ten live controls per case were drawn from the electoral rolls, matched by sex, age and residence. Exposure to the screening examination of cases and controls was assessed through individual linkage with the programme's centralised database. After the exclusion of examinations occurring within the 6 months preceding the case's diagnosis, the odds ratio (OR) of dying from stomach cancer for those screened was 1.26 (CI 0.83-1.91) and the OR in females was lower than in males: 0.77 (CI 0.33-1.78) and 1.52 (CI 0.94-2.47) respectively. Odds ratios associated with years since last test and number of tests did not differ significantly from 1. These results show the inefficacy of the programme in reducing mortality from gastric cancer in the area. In an attempt to determine whether this result was due to selection bias, an analysis restricted to subjects who had been screened at least once was performed. When examinations occurring after an index date at various intervals before the case's diagnosis were excluded, the screening test appeared to protect from death, although confidence intervals of the odds ratios are large, for example OR = 0.47 (CI 0.24-0.98) when excluding tests within 1 month.

Age Factors↗
PubMed1994

Changes in left ventricular mass and filling after renal transplantation are related to changes in blood pressure: an echocardiographic and pulsed Doppler study.

To examine changes in left ventricular (LV) mass and function (diastolic and systolic) after successful renal allograft transplantation (RT), we prospectively studied 30 patients (19 men, 11 women, aged 37 +/- 13 years) by M-mode, two-dimensional and pulsed Doppler echocardiography at the time of surgery and 10 +/- 1.8 months later. At the time of transplantation all patients had been undergoing dialysis (4 peritoneal dialysis, 26 hemodialysis) for 2.5 +/- 3.2 years. A hematocrit of < or = 30% was present in 26 patients. After RT the mean hematocrit increased from 26 +/- 4 to 40 +/- 7 (p < 0.01), whereas systolic, diastolic and mean blood pressure (BP) remained unchanged. The LV mass index (LVMI) decreased from 201 +/- 56 to 171 +/- 41 g/m2, (p < 0.01); LV diastolic diameter corrected by body surface area (LVDDI) decreased from 298 +/- 38 to 279 +/- 35 (p < 0.01) and the LV end-diastolic volume index (LVEDVI) from 72 +/- 18 to 63 +/- 15 (p < 0.01). There were no changes in LV fractional shortening or LV end systolic wall stress. Peak late transmitral velocity (A wave) decreased from 77 +/- 16 to 68 +/- 12 cm/s (p < 0.01) with no changes in other Doppler-derived indexes of diastolic function. No fistula patency influence on changes in LV mass and function was found. After RT, BP decreased in 21 patients from 150 +/- 20 to 132 +/- 15 (p < 0.001; group I) and increased in 9 patients from 130 +/- 14 to 153 +/- 16 (p < 0.05, group II). Patients in group I suffered a reduction in LVMI (p < 0.001), LV end-diastolic diameter (p < 0.05), LVDDI (p < 0.001); LV end-diastolic volume (p < 0.05); LVEDVI (p < 0.01); cardiac index (p < 0.05), and peak late transmitral velocity (p < 0.01), but no changes in group-II patients were observed. We concluded that BP is a major determining factor with regard to changes in LV hypertrophy and function following RT. LV mass and volumes can be expected to decrease after RT in patients with BP reduction.

Adult↗
PubMed1993

Effect of anthelmintic treatment on the allergic reactivity of children in a tropical slum.

It is well known that helminthic infection can cause a polyclonal stimulation of the synthesis of IgE, which is dependent on interleukin-4 (IL-4) production, and it has been suggested that this can modulate the expression of allergic reactivity in tropical populations. We evaluated the effect of regular anthelmintic treatment, for a period of 22 months, on certain aspects of the allergic reactivity of children in a slum area of Caracas, Venezuela, where helminths are endemic. The treatment (Oxantel-Pyrantel; Quantrel) effectively eliminated intestinal helminthic infection and resulted in a significant decrease in the initially elevated total serum IgE levels. IL-4 was detectable in the serum, and a significant reduction in IL-4 was also observed after treatment. In contrast, both the immediate-hypersensitivity skin-test reactivity and serum levels of specific IgE antibody against environmental allergens were markedly increased in the treated children. In a group of children who were also evaluated in the same slum, but who declined treatment, a substantial increase in helminthic infection occurred, which was related to an acute deterioration of the socioeconomic conditions of Venezuela over the course of our study period. This was paralleled by a considerable increase in total IgE levels in these children and a decrease in the skin-test reactivities and specific IgE levels. The application of Prausnitz-Küstner passive transfer tests and analysis of specific IgE antibody levels indicated that the polyclonal stimulation of IgE synthesis by helminthic parasites results in mast cell Fc epsilon receptor saturation and suppression of specific IgE antibody synthesis. This inhibition of allergic reactivity is reversible by anthelmintic treatment.

Adolescent↗
PubMed1993

Ascaris reinfection of slum children: relation with the IgE response.

Total and Ascaris-specific serum IgE levels were measured in a group of 98 Ascaris-infected children from a slum area of Caracas, Venezuela, in whom the infections were eliminated by regular treatment for 22 months with the anthelmint Oxantel/Pyrantel ('Quantrel'). The children were re-evaluated at the end of the treatment programme, and then 8 months later, at which time reinfection was assessed. Total IgE levels at the beginning of the study were significantly higher in the children who became reinfected after treatment, compared with those who did not. The anthelmint treatment caused a significant decrease in the total IgE levels in most of the children, and after a period of 8 months without treatment these continued to decrease in the non-reinfected group, but increased again in the reinfected children. The reverse pattern was found for Ascaris-specific IgE antibody levels, and in fact an inverse correlation was found between total and anti-Ascaris IgE levels. Striking associations were found between reinfection and high pretreatment values of total IgE, but low levels of specific IgE antibody. These data support the concept that specific IgE antibody may participate in the protection against helminthic infection, and suggest that the polyclonal stimulation of IgE synthesis caused by these parasites may reduce the effectiveness of such responses. The results also indicate that different individuals have varying propensities to respond polyclonally to the helminths, and this influences their resistance to infection.

Animals↗
PubMed1993

Possible relationship between allergic disease and infection by Giardia lamblia.

In order to better understand the possible relationship between allergic reactivity and infection with G. lamblia, specific IgE responses and skin test reactivity were evaluated in allergic or nonallergic Venezuelan children, with or without G. lamblia infection. Two groups of children were studied: one from our Allergy Clinic and the other from a slum area of Caracas. The total serum IgE levels in children from the slum area were significantly higher in those with intestinal helminthic parasites and giardiasis, compared with those with helminthiasis only (P < .001). In atopic children with giardiasis we also found an enhanced IgE antibody response to common environmental allergens (P < .05). As G. lamblia produces intestinal mucosal damage, we also studied the reactivity to cow milk and found that 22% of the children belonging to the low socioeconomic level demonstrated the presence of significant levels of specific IgE against this antigen. Of these milk-positive subjects, 40% were infected by G. lamblia in contrast to only 21% of the milk-negative children (P < .05). These results suggest that children with giardiasis may be exposed to greater amounts of intestinally absorbed antigens. We also studied the specific allergic response to G. lamblia, and found that in an unselected group of children of low socioeconomic level, 25% had positive skin tests, as did 50% of persons with symptomatic giardiasis. The presence of serum anti-Giardia IgE was also demonstrated in 22% of patients with giardiasis.

Animals↗
PubMed1992

High-performance liquid chromatographic determination of N-[2(S)-(mercaptomethyl)-3-(2-methylphenyl)-1-oxopropyl]-L-methionine, the active plasma metabolite of a prodrug atriopeptidase inhibitor (SCH 42495), using a thiol selective (Au/Hg) amperometric detector.

A high-performance liquid chromatographic assay for the determination of N-[2(S)-(mercaptomethyl)-3-(2-methylphenyl)-1-oxopropyl]-L-methionine (SCH 42354; II), the active metabolite of the atriopeptidase inhibitor prodrug, N-[2(S)-(acetylthiomethyl)-3-(2-methylphenyl)-1-oxopropyl]-L-methi onine ethyl ester (SCH 42495; I), in human plasma was validated for use in clinical pharmacokinetic studies. Plasma (200 microliters) was processed by protein precipitation with acetone containing the internal standard, N-[2(S)-(mercaptomethyl)-3-(2-methylphenyl)-1-oxopropyl]-L- ethionine (III). Compound II was recovered (ca. 90%) in the supernatant after centrifugation and prepared for injection by the addition of 0.15 M monochloroacetic acid containing 0.2 mM EDTA. Separation of II and III was accomplished on commercially available reversed-phase C8 columns designed for the separation of basic compounds. Both compounds were detected using amperometric detection (+0.125 V versus Ag/AgCl) on a thin-layer Au/Hg amalgam electrode. The lower limit of quantitation was 10 ng/ml, where the inter-assay precision (coefficient of variation) was +/- 11.4% and the inter-assay accuracy (bias) was +1.0%. No endogenous interferences were observed in the extracts obtained from drug-free plasma. The detector response (using either peak area or height ratios of II to III) was linear from 0.01 to 1.0 micrograms/ml. Compound II was stable in plasma supplemented with EDTA and sodium hydrogensulfite for at least 3 months when stored frozen at -78 degrees C; no significant decomposition of II was observed following three freeze-thaw cycles. The feasibility of this liquid chromatographic assay with electrochemical detection was demonstrated with plasma samples from hypertensive subjects administered 100 mg of compound I.

Chromatography, High Pressure Liquid↗
PubMed1992

Bronchoconstriction in helminthic infection.

In order to determine whether infection by helminthic parasites can be associated with a state of bronchoconstriction, we evaluated the response to the inhalation of a bronchodilator before and after long-term anthelmintic treatment of children in a urban slum of Caracas, Venezuela. In untreated children, a direct association was found between the degree of helminthic infection and the increase in peak expiratory flow rates caused by the bronchodilator. The elimination of the infections was accompanied by a significant decrease in response to the bronchodilator. These results indicate that helminthic infection could contribute to the development of asthmatic conditions in areas where these parasites are endemic.

Albuterol↗
PubMed1990

The relationship between enlargement of the temporal horns of the lateral ventricles and dementia in aging patients with Down syndrome.

Head CT studies of patients with Alzheimer's disease (AD) show global atrophic changes. Tissue loss is especially prominent in the temporal lobes, with widening of the temporal horns of the lateral ventricles and, usually, widening of the temporal sulci. Some recent studies have found a familial form of AD to be mapped to chromosome 21. Down syndrome (DS) results from the inheritance of three chromosomes 21, and it has been shown that after the age of 35 the brains of patients with DS commonly show neuropathological changes similar to those in patients with AD. CT studies of 25 patients with DS (ages 29-64 years) were examined for tissue loss in the temporal regions, and this was compared to the findings commonly seen in patients with AD. The widths of CSF spaces varied considerably in patients with DS, but after the age of 50 most of them showed significant widening of the temporal horns. In some patients the horns were large enough to suggest obstructive hydrocephalus. Because of a new trend toward deinstitutionalization of patients with DS, radiologists will be seeing more studies on these patients and should familiarize themselves with the unique ways in which they manifest the aging process.

Activities of Daily Living↗
PubMed1989

The effects of the everyday environment on epileptic activity in three mentally retarded individuals.

Three mentally retarded epileptic subjects with frequent epileptiform EEG paroxysms were monitored with simultaneous radio-telemetered EEG and video recording while they were exposed to their everyday environmental conditions. These conditions included prompts and reinforcement for performing vocational training tasks, speech therapy, eating and drinking, and cues for resting, waiting, playing, exercising, and relaxing. Epileptiform EEG activity and the occurrence of clinical seizures varied as a function of the particular environmental conditions. Epileptiform EEG discharges were longer in duration, and clinical seizures were more frequent in all 3 subjects during conditions which produced inactive behavior than during conditions which produced active behavior. The modulation of epileptiform activity by everyday environmental conditions carries implications for (1) the optimum structuring of the environment for mentally retarded patients with frequent, subtle seizures, and (2) the analysis of the effects of epileptiform discharges on behavior.

Activities of Daily Living↗
PubMed1989

Discontinuance of antiepileptic medications in patients with developmental disability and diagnosis of epilepsy.

Fifty patients with developmental disabilities and past history of epilepsy but without reported seizures fo several years underwent trial reductions of an antiepileptic drug. After an 8-year follow-up there was recurrence of seizures in 26 patients. Predictors for a seizure free state off medication were: few documented seizures in lifetime, no gross neurological abnormalities, medication below therapeutic levels at time of discontinuance, and persistently normal EEGs before and after discontinuance. Successful withdrawal of medication may have resulted from early control of seizures or early treatment; lack of actual epileptic seizures but presence of "pseudoseizures"; isolated event seizures; or seizures that could have resulted from nonepileptic, self-limiting factors.

Adolescent↗
PubMed1986

Atlantoaxial instability in adults with Down syndrome: a clinical and radiological survey.

A survey of 129 adults with Down syndrome was undertaken to determine the prevalence of atlantoaxial instability (AAI) and to establish a base line for long term prospective study. Clinical and radiological evaluations were performed to determine optimal screening methods for this condition. The findings indicate that radiological evidence of AAI was found in 40% with anterior atlanto-odontoid distance (AAOD) of 3 mm or more and in 10% with 5 mm or more. These findings are similar to those reported in the pediatric age group. A preponderance of females with symptomatic AAI is noted. Clinical evaluation suggested the presence of spinal cord compression, which was confirmed by CT scan of the atlantoaxial region. There were no false negative clinical results. Among the false positive clinical findings other explanations were present in some cases. A comparison with the literature is offered along with guidelines on screening and management.

Adult↗
PubMed1986

Differential diagnosis of epileptic versus pseudoepileptic seizures in developmentally disabled persons.

One-hundred and twenty-four mentally retarded persons with behaviors suggestive of epilepsy were monitored with an 8-channel radiotelemetered electroencephalograph-video recording system (TEEG-VR). Target behaviors were identified by the clinical description of the primary care providers before the TEEG-VR sessions. Whenever possible, the known antecedents of those behaviors were replicated. The target behaviors were considered epileptic when they were observed simultaneously with epileptiform EEG patterns, and pseudoepileptic when nonepileptiform patterns were observed. Twenty persons were classified as epileptic, 50 as pseudoepileptic, 11 as both epileptic and pseudoepileptic, and 43 as inconclusive. Among the pseudoepileptics there were 15 with abnormal EEGs and 4 with epileptiform EEGs. The most frequent topographies of behavior were not significantly related to diagnosis. These included myoclonus, eye blink, head drop, cessation of ongoing activity, and hand and arm automatisms. The diagnosis of epilepsy in mentally retarded persons, on the basis of clinical description, interictal EEG, and medical history, may be inaccurate. TEEG-VR is extremely useful for obtaining a definitive diagnosis of each target behavior.

Adolescent↗