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Biomedical subjects

G Alvarez

Publications and source records attributed to G Alvarez.

At least 19 recordsLinked to original sources
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↗
PubMed1990

Restriction site variation, length polymorphism and changes in gene order in the mitochondrial DNA of the yeast Kluyveromyces lactics.

The purpose of this work was to compare mitochondrial DNA restriction endonuclease patterns in strains of the yeast Kluyveromyces lactis, from different sources, to see how conserved is the organization of this organellar genome. The mitochondrial DNA of five independently-isolated strains and one of unknown origin were compared. Strains NRRL Y-1205, NRRL Y-8279 and NRRL Y-1140 gave identical patterns. Strain NRRL Y-1564 showed an insertion, with respect to the other three, of approximately 1250 bp. Strain W600B had also an insertion with extra restriction sites for EcoRI, HpaI, HaeIII, HincII and XbaI. On the other hand, strain Y-123 showed a restriction pattern quite different from the others. Sequences putatively encoding apocytochrome b, ATPase subunit 9 and ribosomal RNA large subunit, were localized on the physical maps of three strains. Results demonstrated that the order of these three genes shows a common feature in strains W600B and WM37 (auxotroph of Y-1140) but a different distribution in WM27 (auxotroph derived from Y-123). All these facts explain the extensive intraspecific polymorphism observed in the mtDNA of this yeast.

Adenosine Triphosphatases↗
PubMed1990

Genetic variation in a modifier system affecting the expression of bare mutant of Drosophila subobscura.

Genetic variation affecting the expression of Bare (Ba), a morphological mutant of Drosophila subobscura that reduces the number of bristles and is located on the O chromosome of this species, is reported. Our results show that O chromosomes extracted from a natural population (El Pedroso, Santiago de Compostela, Spain) show considerable genetic variation in modifier effect upon Ba expression. The amount of modifier variability is dependent on the chromosomal arrangement (OST and O3 + 4 + 7), since modifier variation is higher in OST than in O3 + 4 + 7 chromosomes. Investigations of the genetic architecture of this modifier system on the O chromosome carried out using biometrical methods indicate that a relatively small number of genetic "factors" can explain the differences in modifier effect between a wild O chromosome of high modifier effect and a marker chromosome of low score. In addition, the modifier effects show a non-uniform distribution along the O chromosome and some indication of clustering of modifier "factors" around the major locus (Ba) is also observed.

Analysis of Variance↗
PubMed1990

[Cerebral vasodilators].

Cerebral vasodilators (CVD) account for 1.6% of the annual expenditure on drugs in Chile. Two kinds are typified: what we have called orthodox CVD and calcium-channel blockers. They have two main uses in neurology: firstly, in acute ischaemic stroke where orthodox CVD (buflomedil, codergocrine mesylate, and nicergoline) are of no use and may even be harmful whereas calcium-channel blockers seem beneficial in neutralizing free radicals. Secondly they are used in ageing and dementia. These terms are defined and it is seen that they often end up converging. The methodology most often used in evaluating the cognitive benefits of CVD is analyzed; it is clearly plagued with subjectivity. Available literature on CVD is reviewed and no serious evidence to justify their use is found, especially in view of their cost and modest benefit accrued. A sample of the advertisements which appear in various scientific journals is scanned for VDC. It is seen that large transnationals spend 1 page in 10 of all advertising on orthodox CVD in neurological and psychiatric journals in Latin America: in similar journals of European and North American origin not one page was found.

Aging↗
PubMed1989

Multiple sclerosis following optic neuritis in Chile.

Twenty three unselected cases of optic neuritis were re-examined between 2 and 18 years after the onset of the disease, with a mean of 9.7 years. Only 8/23 (35%) had unilateral non-recurrent disease. One patient only (4.3%) went on to develop multiple sclerosis. These findings support the impression that demyelinating disease varies considerably in Latin America compared with northern industrialised countries.

Adolescent↗
PubMed1989

[Multiple sclerosis in health care in our country: electrophysiological, immunological and clinical analysis].

Among 70 patients referred for suspected multiple sclerosis (MS) a total of 40 met criteria for definite (17), likely (12) or possible (11) diagnosis of the disease. Visual evoked potentials provided evidence of CNS lesion in 13 cases. Abnormalities of somatosensory evoked potentials, particularly on stimulation of the posterior tibial nerve, were present in 90% of patients. Brainstem auditory evoked potentials were of little use, contributing to diagnosis of one subclinical lesion; they were normal in 14 cases with suspected brainstem involvement. A definite diagnosis of MS was made in 4 cases by study of oligoclonal bands. The most frequently involved sites were the optic nerve and the brainstem, followed by the spinal cord. Hemispheral location was demonstrated in only 3 cases. These findings of the first study on MS in our country suggest a different pattern for demyelinating diseases in Chile.

Adult↗
PubMed1989

Flow changes in hepatic veins in congestive cardiac insufficiency. A study using pulsed Doppler US.

Ten patients with right heart failure and tricuspid regurgitation were studied with both B Scan and pulsed Doppler ultrasound. Variations in the Doppler waveforms were seen in portal vein recordings which indicated flow characteristics similar to those of hepatic veins due to transmission of retrograde pressure waves through the hepatic capillary bed. It was concluded that the pulsed Doppler will permit non-invasive determination of physiological events that may have great practical importance in the diagnosis and treatment of patients with right heart failure.

Aged↗
PubMed1988

Effect of DNA supercoiling and catabolite repression on the expression of the tetA genes in Escherichia coli.

The effect of novobiocin, a gyrase inhibitor, and of catabolite repression on the expression of different classes of tetA genes in Escherichia coli was studied. The results obtained showed that the complete induction of the tetA genes corresponding to classes A, B, and D depends on DNA supercoiling, and that the expression of the tetA genes corresponding to classes A and C is not under catabolite repression.

Bacterial Proteins↗