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Biomedical subjects

G Alvarez

Publications and source records attributed to G Alvarez.

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

Distinct genetic subdivision in sympatric and sibling species of the genus Littorina (Gastropoda: Littorinidae).

The genetic structure of two sibling and sympatric species of the genus Littorina was compared using allozymic loci. The two species are biologically and ecologically well-known and mostly show similar life history characteristics. Three populations of L. mariae Sacchi & Rastelli and L. obstusata (L.) were studied in the Muros-Noya Ria (Galicia, NW Spain). In addition, four microgeographical subsamples taken from one of the populations were analysed for each species. Age, sex and genotypes for nine polymorphic loci were studied in 1250 snails of both species. L. mariae showed larger genetic population subdivision and lower heterozygosity levels for the loci studied than did L. obtusata. Heterozygote deficiencies were found in only a few cases in natural populations of both species, usually affecting the Lap-1 locus. No significant genetic differences among age or sex classes were found. These results may be explained by the lower effective population size in L. mariae than in L. obtusata. Known differences between these species in generation interval and population density during the winter can cause the different effective population sizes suggested. These life history characteristics appear to provide the most likely explanations for the differences in genetic differentiation and heterozygosity between the two species. A previously unknown L. mariae morph from exposed shores is tentatively suggested to be conspecific.

Animals↗
PubMed1995

[Validation of a screening instrument for studying the prevalence of cerebrovascular diseases in the Chilean population].

We assessed a screening instrument, adapted from a model suggested by WHO, aimed to perform population studies on the prevalence of cerebrovascular disease in Chile. Sixty-two subjects, 31 with cerebrovascular diseases and 31 without, were asked about symptoms and requested to do simple movements by trained interviewers. The results of the instrument were compared with a neurological examination performed by two specialists. Global sensitivity and specificity of the instrument, using WHO evaluation criteria, were 100 and 38.7% respectively. When three or more symptoms and one positive sign were considered as cutoff points, global specificity increased to 61% and sensitivity decreased to 93%. It is concluded that the present instrument is highly sensitive but lacks specificity.

Aged↗
PubMed1994

Recognition of facial expression in diverging socioeconomic levels.

Cerebral organization has been seen to vary in different social or ethnic groups; also, sociocultural retardation is a serious obstacle to development in poorer countries. The ability of the right hemisphere to recognize facial emotions in a tachistoscopic task was tested in university and low-socioeconomic-level subjects. All were male and right-handed. The university students recognized facial emotions projected to their left field-right hemisphere significantly better than with their right field-left hemisphere; the low-socioeconomic-level subjects showed no differences in hemispheric performance. The explanation of laterality as a function of social class may be of importance in dealing with sociocultural retardation.

Adult↗
PubMed1993

On the detection of nonrandom associations between DNA polymorphisms in natural populations of Drosophila.

The capacity to detect nonrandom associations between restriction-map variants was examined in eight gene regions of Drosophila melanogaster (yellow-achaetescute, white, Zw, Adh, Est6, and rosy) and D. pseudoobscura (Adh and Xdh), on the basis of published population data. The statistical power from individual pairwise tests was both heterogeneous and generally low across gene regions. Sample sizes larger than those currently being used are needed to ensure any power to detect disequilibrium by individual tests. It is found that the heterogeneity in power is mostly explained by large differences in the intensity of sample disequilibrium among regions. The yellow-achaete-scute, Zw, and Adh loci of D. melanogaster displayed both the highest mean power (approximately 0.4) and a very great disequilibrium (mean absolute values of D' were 0.8-1). By contrast, all the other gene regions exhibited lower mean power (approximately 0.2) and moderate levels of disequilibrium (0.4-0.6). Although the proportion of significant pairwise associations, especially for white, Est6, and rosy in D. melanogaster and for Adh and Xdh in D. pseudoobscura, is more or less close to the type I error, simultaneous-inference significance tests show that gametic disequilibrium is occurring at the eight DNA regions examined.

Alcohol Dehydrogenase↗
PubMed1993

[Left-handedness and diabetes mellitus of autoimmune origin].

A controversial theory postulates that there is an association between left handedness and immune and speech disorders. There are reports of increased frequency of left handedness in type I diabetic patients. The aim of this study was to compare 65 type I diabetics, 65 type II diabetics and 130 normal controls using a 7 item questionnaire for handedness. No differences were found for strong left handedness. However the frequency of strong right handedness decreased significantly from controls to type II diabetics and type I diabetics. Since less intense right handedness is not the same as left handedness, it is concluded that the theory is not supported by the present findings.

Adult↗
PubMed1992

Distribution of insertion sequence IS1 in multiple-antibiotic resistant clinical Enterobacteriaceae strains.

The presence of insertion sequence IS1 in 70 multiple-antibiotic resistant clinical strains was determined. This 70-strain collection comprised 46 Escherichia coli, 18 Salmonella and 6 Shigella strains. The presence of IS1 was detected in the chromosome and plasmids of 73% and 63% of the strains, respectively, and 51% of the strains carried IS1 in both. The frequency of IS1 was higher in Salmonella than in E. coli and Shigella strains. A total of 31 strains carried large plasmids with IS1; 10 of these strains (32.3%) were able to transfer all or some of the antibiotic resistance markers to E. coli K12 or S. typhimurium recipient strains. Resistance markers of all clinical strains were maintained stably after several generations of growth. The presence of IS1 in a relatively high percentage of plasmids of multiple-antibiotic resistant clinical isolates, suggests a role for this sequence in the dissemination of genes which code for antibiotic resistance.

DNA Transposable Elements↗
PubMed1992

Multiple sclerosis in Chile.

So far as we know this series of 68 cases is one of the first clinical accounts of multiple sclerosis in South America. Average age of onset was 30.7 years and female:male ratio was 2:1. The most frequent initial symptom was motor impairment and less frequent was visual loss. Most affected site of involvement in established cases was the optic nerve. There were no familial cases. The severity of the disease in Chile proved to be the same as elsewhere. No characteristic clinical pattern peculiar to the region emerged.

Chile↗
PubMed1992

[Sclerosing cholangitis and AIDS].

Bile tract pathology in AIDS has been described as an incomplete biliary obstructive syndrome and acalculous cholecystitis. Most reported cases have been associated to bile ducts infection by Cytomegalovirus (CMV) and/or Cryptosporidium. We present a case of sclerosing cholangitis and acalculous cholecystitis in an AIDS patient in whom Cryptosporidium was identified in the cholecystectomy sample and this same agent together with Candida Albicans in bile. We highlight the need to suspect this pathology in HIV infected patients who present a bile obstruction picture and/or cholecystitis, the possible etiological role of Candida Albicans, which has not been previously described, as well as the increasing association of bile pathology and AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Differences in postural hypotension and ankle jerks in the elderly from two contrasting socio-economic levels.

Subjects in low socio-economic strata in underdeveloped countries are subjected to considerable adverse influences which may enhance age-related changes in the nervous system. We therefore assessed the presence of ankle jerks and the degree of postural hypotension in two groups, one from the upper socio-economic level (58 subjects) and the other from the lower socio-economic level (56 subjects). All subjects were over 65 years of age. Only 6% had bilateral loss of ankle jerks, with no difference between the groups. Postural hypotension of 30 mmHg or greater was more frequent in the upper socio-economic group, nine out of 58 versus two out of 56 in the lower group. We conclude that there is no relationship in the elderly between social deprivation and certain markers of neurological dysfunction, such as the absence of ankle jerks and postural hypotension. The reasons for a greater frequency of postural hypotension in the higher socio-economic group are unclear.

Aged↗
PubMed1991

[Brucellosis with nervous system involvement].

Cases of brucellosis with involvement of the nervous system which was diagnosed in the Miguel Servet Hospital during the period 1985-1987 are retrospectively studied. The total quantity of affected patients of brucellosis was 132. Of this quantity, 9 patients (6.8%) had neurological complications under the following clinical forms: epidural abscess (2), meningoencephalitis (1), meningitis (2), encephalitis (1), myelitis (1) and polyradiculitis (2). The most important epidemiological and clinical characteristics are analysed, pointing out the diagnostic difficulties we found when the neurological manifestations are predominant in the brucella infection.

Adolescent↗
PubMed1991

[Transient ischaemic attacks: what is the matter with them? Have they occurred in Chile or not?].

Transient ischaemic attacks are defined, with emphasis on abrupt onset, focal clinical manifestations, and transient nature of the episode which leaves no sequels. Management is discussed with a brief review of the use of aspirin and the controversy surrounding carotid endarterectomy. The personal position of the author is put forth that these attacks are rare in Chile, where the pattern of cerebrovascular disease resembles that seen in Negroes and Orientals rather than in Europeans.

Chile↗