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Biomedical subjects

A Ramos

Publications and source records attributed to A Ramos.

At least 163 records · Page 9Linked to original sources
PubMed1998

Stress and emotionality: a multidimensional and genetic approach.

The use of behavioural tests aiming to assess the psychological components of stress in animals has led to divergent and sometimes arbitrary interpretations of animal behaviour. This paper presents a critical evaluation of behavioural methods currently used to investigate stress and emotionality. One of its main goals is to demonstrate, through experimental evidence, that emotionality may no longer be seen as a unidimensional construct. Accordingly, following a discussion about concepts, we propose a multiple-testing approach, paralleled by factor analyses, as a tool to dissociate and study the different dimensions of emotionality. Within this multidimensional context, genetic studies (illustrated here by different rat models) are shown to be particularly useful to investigate the neurobiology of stress/emotionality. A genetic approach can be used (i) to broaden and dissect the variability of responses within and between populations and (ii) to search for the molecular bases (i.e. genes and gene products) which underlie such a variability.

Animals↗
PubMed1998

A genetic and multifactorial analysis of anxiety-related behaviours in Lewis and SHR intercrosses.

Lewis (LEW) and spontaneously hypertensive rats (SHR) have been shown to differ in a series of fear-related behaviours measured in different anxiety/emotionality tests. In the present study, we have investigated some of the genetic mechanisms underlying these differences. To this end, male and female rats from the two inbred strains were crossed to produce two parental (LEW and SHR), two F1 (LEW or SHR mother), and two F2 (LEW or SHR grandmother) groups. All rats were tested in the elevated plus-maze and in the open field, besides being characterised for systolic blood pressure (BP). LEW rats approached the open arms of the plus-maze and the central area of the open field less than SHRs. The two strains also differed in their BP (SHR > LEW). LEW/SHR differences were found to be due to direct effects of the genes, rather than to indirect maternal and grand-maternal effects. Central locomotion in the open field was shown to be the most heritable of all the traits considered herein. A factor analysis on the segregating F2 population produced three independent factors. The first one was associated to measures of anxiety from the elevated plus-maze, and the second to measures of locomotion in novel environments. Factor scores revealed that the parental strains differ in relation to the first but not to the second factor. This study demonstrates the usefulness of coupling genetic and multifactorial methods to investigate behavioural traits and it confirms LEW and SHR strains as an interesting genetic tool for the study of anxiety.

Analysis of Variance↗
PubMed1998

Genotoxicity of an extract of Calendula officinalis L.

A fluid extract of Calendula officinalis L. displayed genotoxic properties when assayed for mitotic segregation in the heterozygous diploid D-30 of Aspergillus nidulans. The extract of Calendula exhibited dose-dependent toxicity and genotoxicity (both mitotic crossing-over and chromosome malsegregation being observed) to Aspergillus in the range of five plate concentrations from 0.1 to 1.0 mg of solids/ml assayed. Mutagenicity testing with the Salmonella/microsome assay in strains TA 1535, TA 1537, TA 98 and TA 100 was negative in a plate incorporation protocol, with concentrations ranging from 50 to 5000 microg/plate (+/- S9). The mouse bone marrow micronucleus test, where the extract was dosed orally up to 1 g/kg for 2 days, was also negative.

Animals↗
PubMed1998

Prevention of peritonitis with disconnect systems in CAPD: a randomized controlled trial. The Mexican Nephrology Collaborative Study Group.

BACKGROUND: Recently, disconnect systems for CAPD that are associated with a reduced frequency of peritonitis have been introduced. Our objective was to compare the incidence of peritonitis using three current CAPD systems in a high-risk population with low educational and socioeconomic levels, and high prevalence of malnutrition. METHODS: In a prospective controlled trial, 147 patients commencing CAPD were randomly assigned to one of three groups: 29 to the conventional, 57 to the Y-set, and 61 to the twin bag systems. The number of peritonitis episodes was registered, and patients were followed up for an average of 11.3 months. RESULTS: The average peritonitis-free interval for the conventional group was 6.1 months, for the Y system was 12.0 months, and for the twin bag was 24.8 months (P < 0.001). By multivariate analysis, the only factor associated with peritonitis was the CAPD system. Peritonitis-related hospitalization was 5.3 +/- 2.0, 2.7 +/- 1.0, and 1.5 +/- 0.9 days/patient/year in the conventional, Y system, and twin bag groups, respectively. The cost per bag was similar for the conventional and Y system, but higher for the twin bag. However, the total costs of treatment (pesos/patient/year) were lower for twin bag (62,159 for the conventional, 70,275 for the Y system, and 54,387 for the twin bag), due to the lower peritonitis incidence and associated hospitalizations. CONCLUSIONS: Y system and twin bag use was associated with a reduction of 50 and 75% peritonitis incidence, respectively, in patients on CAPD. The cost of the twin bag was actually lower, because of savings from a decreased usage of antibiotics and fewer hospitalizations.

Adult↗
PubMed1998

Spanish study group on cochlear implants for persons with marginal benefit from acoustic amplification.

Recently the U.S. Food and Drug Administration approved the use of cochlear implants (CI) in patients with severe-to-profound sensorineural hearing loss with marginal benefit (< 30% speech discrimination) from hearing aids (HA). A multicentre trial was developed to determine whether this approval could be applied to the Spanish population. Nine postlingual adults from 3 centres were selected for the study. The mean preoperative unaided PTA threshold (0.25 to 4 KHz) was 108.6 dB HL for the poorer ear and 99.8 dB HL for the better. In all subjects the poorer ear was implanted with a Mini Nucleus 22 device. A single subject design study was used to compare performance with HA preoperatively and with CI postoperatively, or CI with contralateral HA. PTA measures and Spanish open set speech recognition tests were used. Comparing pre-implant levels with results after 6 months of CI use, all subjects improved significantly on all test measures: i) Mean aided soundfield threshold: 73.6 dB vs 39.8 dB ii) Mean bisyllabic recognition: 20% vs 57% iii) Mean consonant discrimination: 20% vs 49% iv) Mean CID sentences: 22% vs 73%. Five subjects discontinued use of the contralateral HA after implantation, three continued occasionally to use the HA, and one continued to use both on a full-time basis. Patients performed significantly better post-implant on speech recognition compared with their best pre-implant HA scores. Therefore the CI appears an appropriate treatment for Spanish speakers with a severe-to-profound hearing loss and marginal benefits with HA.

Adolescent↗
PubMed1998

Horizontal and vertical transmission of human immunodeficiency virus type 1 dual infections caused by viruses of subtypes B and C.

This article describes a case of horizontal (heterosexual) and subsequent vertical (mother to infant) transmission of 2 human immunodeficiency viruses type 1 (HIV-1) subtypes. Dual infection in a husband, his wife, and their child was initially detected by use of a restriction fragment length polymorphism assay of the proviral protease in peripheral blood mononuclear cells. The simultaneous presence of highly similar sets of HIV-1 subtypes B and C infecting the 3 family members was confirmed by DNA sequence analysis of pol, gag, and env genes. These data, together with available epidemiologic information, may indicate that the husband's high-risk sexual behavior was the source of dual infections. Because his wife did not report such activities, it was likely that he passed HIV-1 strains to his spouse, who subsequently transmitted them to their child.

Adult↗
PubMed1998

Cardiac valve calcification in haemodialysis patients: role of calcium-phosphate metabolism.

BACKGROUND: Cardiac valve calcification (VC) has been detected with increased frequency in haemodialysis (HD) patients, making it necessary to determine the potential pathogenic factors in uraemic patients. METHODS: A total of 92 chronic HD patients (39 female, 53 male) and 92 age and gender-matched nondialysis control subjects were evaluated by echocardiography and a severity score for VC was determined. Calcium phosphate metabolism was evaluated at the beginning of haemodialysis. RESULTS: We found a greater prevalence of VC in dialysis patients than in normal patients (mitral annulus 44.5% vs 10%, P = 0.02; aortic annulus 52% vs 4.3%, P = 0.01). HD patients with mitral calcification were found to be older than patients without calcification, were on long-term renal replacement therapy, had longer duration of predialysis arterial hypertension, had greater values of the highest value of mean calcium phosphate product in 6 successive months (CaxP) and the highest absolute value of calcium-phosphate product (CaxPmax). We also found a positive correlation between calcification score, age, and CaxP. No correlation was found between actual VC and arterial hypertension or parathyroid hormone. Multiple stepwise regression analysis selected age and CaxP as the most predictive parameters for mitral calcification (r = 0.47). Mitral calcification was associated more frequently with rhythm and cardiac conduction defects, valvular insufficiency and with peripheral vascular calcification. Aortic calcification was correlated with age (r = 0.42) and longer duration of predialysis arterial hypertension. CONCLUSION: Our study confirmed an increased prevalence of VC in HD patients and selected age and calcium phosphate product as the most predictive parameters. These findings support careful monitoring of calcium metabolism beginning at the early stages of end-stage renal failure to reduce the risk of heart disease.

Aged↗
PubMed1998

Host H-2 haplotype modulates the induction of host-versus-graft disease after the induction of neonatal tolerance to H-2 alloantigens.

Mice injected at birth with semiallogeneic spleen cells develop a host-versus-graft disease (HVGD) characterized by the polyclonal activation of donor B cells by alloreactive host CD4+ T cells, the production of autoantibodies (autoAb) and the development of an inmmunocomplex-mediated glomerulonephritis. It has been demonstrated that the recognition of MHC class II, but not class I or non MHC, alloantigens triggers the development of the autoimmune syndrome (AIS). The finding of different expression patterns of Ia molecules in different mouse strains, and a closed restriction of some immune responses to particular H-2 haplotypes, prompted us to analyze whether variations in the expressed MHC class II molecules modify the HVGD. First, newborn BALB/c mice received spleen cells from F1 hybrid mice obtained by mating BALB/c mice with several mouse strains differing in the H-2 haplotype. Second, spleen cells from different F1 mice were neonatally injected in mice of both parental strains. All groups of BALB/c mice injected with different combinations of F1 mice showed an HVGD with a very similar serological course. However, in some instances, duration was different when comparing both parental strains injected with spleen cells from the mutual F1 hybrids. These results suggest that host MHC, but not donor MHC haplotype may modulate the AIS associated with the induction of neonatal tolerance.

Animals↗
PubMed1998

[Outbreak of nosocomial diarrhea by Clostridium difficile in a department of internal medicine].

BACKGROUND: Clostridium difficile (DCD) is the main etiologic agent of nosocomial diarrhea of infectious origin. Most of the cases of DCD have been detected in a hospital environment. PATIENTS, MATERIAL AND METHODS: From October to November 1996 five cases of nosocomial diarrhea were detected with the presence of the toxin A of Clostridium difficile being observed in the stools. These patients were compared with a group of 19 patients without diarrhea (controls) who were admitted to the same ward during the same period as the patients with DCD. RESULTS: The hospital stay of the cases was greater (25 +/- 8 days) than that of the controls (14 +/- 10 days; p < 0.05). One hundred percent of the cases received antibiotics during admission (2 +/- 1.2 antibiotics per patient), versus 68% of the controls (1.1 +/- 0.9 antibiotics per patient, p > 0.05). The length of antibiotic treatment prior to the onset of the symptoms was 8 +/- 3 days (range 7-11 days). The type of antibiotic administered was similar in both groups. More of the cases with DCD (60%) had vesicle catheterization than the controls (11%, p < 0.05). All the patients with DCD presented abdominal pain and several liquid stools per day without blood or pus (3.2 +/- 0.45 stools per patient) and 2 (40%) fever. The mean length of diarrhea was 5.6 +/- 3.6 days. The serum albumin concentration on the first day of admission was significantly lower in the cases of DCD (2.9 +/- 0.4 mg/dl) than in the controls (3.3 +/- 3.4 mg/dl, p < 0.05). All the cases received antibiotic treatment for Clostridium difficile (oral metronidazol or vancomycin) with good clinical evolution. CONCLUSIONS: The patients with DCD had more often had vesicle catherization and presented a lower serum albumin concentration than the controls.

Adult↗
PubMed1998

[Visceral leishmaniasis in immunocompromised patients].

OBJECTIVE: Most patients who developed visceral leishmaniasis (VL) in our country are ímmunocompromised (IC) host, frequently HIV-infected patients. One objective was to know if there were differences about the clinical manifestations, diagnostic tests or prognosis in IC patients who were infected or not with HIV (HIV+ and HIV-, respectively). Also we wonder if some features were associated with death during the initial episodes of VL. METHOD: We studied 16 IC patients with VL, 9 were VIH+ and 7 were VIH-. Most frequently observed findings were fever (94%), splenomegaly (81%), hepatomegaly (69%), and constitutional syndrome (50%). HIV+ patients had symptoms during a lapse of time (70 +/- 78 days) larger than the VIH- cases had (17 +/- 12 days, p < 0.05). RESULTS: We performed a serology to Leishmania sp in 15 cases (94%) and were positive in 13 patients (77% in HIV+ and 100% in VIH patients). Seven patients (44%, 4 VIH- and 3 VIH+) died during the initial episode of VL. Nine patients (66%) who survived to it were followed-up during 68 +/- 49 months. Seven patients (4 VIH+ and 3 VIH-) showed several relapses (2.5 +/- 1.6 relapses/patient) through the follow-up. The patients who died during the initial episode had more frequently (p < 0.05) concentrations of albumin below 3 g/dl or of globulins below 4 g/dl, than the survivors had. The CD4+ lymphocyte counts in HIV+ patients were lower in patients who died during the initial episode of VL (19 +/- 15/mm) than in survivors (108 +/- 67/mm3, p = 0.07).

AIDS-Related Opportunistic Infections↗
PubMed1998

[Intestinal pneumatosis].

Intestinal pneumatosis is an infrequent disease of difficult clinical and radiologic diagnosis. It may be accompanied by pneumoperitoneum in up to 30% of the cases leading to differential diagnosis with pictures of visceral perforation. We herein present 4 cases of intestinal pneumatosis in whom pneumoperitoneum was associated in 3 patients. Diagnosis was intraoperative in 2 patients submitted to emergency surgery because of an associated acute gastrointestinal event (intestinal volvulus and acute cholecystitis). The other 2 cases were diagnosed by computerized tomography and colonoscopy, respectively, and given their satisfactory clinical evolution they received conservative treatment. The course of the disease was favorable in all the patients with the radiologic signs of pneumatosis disappearing.

Aged↗
PubMed1998

[Central pontine myelinolysis associated with cyclosporin in liver transplantation].

Liver transplant is the only effective treatment in the terminal liver disease. However, the complexity of the surgical technique and immunosuppression cause many neurologic complications. Three liver transplant recipients treated with cyclosporine developed a reversible neurologic syndrome characterized by early dysarthria, which evolved to anarthria, and tetraparesis. Brain MRI disclosed hyperintense lesions, on T2, and proton density-weighted images, in basis pontis. The substitution of the cyclosporine for FK 506, or its reduction, led to the clinical improvement of the patients. Therefore, cyclosporine may cause central pontine myelinolysis, being dysarthria the first manifestation of neurotoxicity. The early recognition of speech disorders in liver transplant recipients that receive cyclosporine should prompt withdrawal of the drug to avoid possible neurological sequelae. Furthermore, the strict control of natremias before and after the transplant may help to reduce the incidence of this type of complications, since a synergyc osmotic mechanism cannot be ruled out.

Adult↗
PubMed1998

[Extracorporeal membrane oxygenation in myocardial failure after pediatric heart surgery].

In spite of progressive improvement not only in myocardial protection but also in anesthetic and surgical techniques, the repair of complex congenital heart defects can still lead to cardiopulmonary compromise refractory to conventional treatment. We describe two patients in whom successful surgical repair of congenital heart defects was followed by severe heart failure refractory to medical treatment. Both patients were managed by extracorporeal membrane oxygenation (ECMO). We discuss the indications, contraindications and use of ECMO in the postoperative intensive care unit.

Bioprosthesis↗
PubMed1997

Cloning, sequencing and expression of the gene encoding elongation factor P in the amino-acid producer Brevibacterium lactofermentum (Corynebacterium glutamicum ATCC 13869).

The Brevibacterium lactofermentum EF-P gene, encoding the elongation factor protein P, was cloned and sequenced. According to DNA sequence analysis of this gene, the B. lactofermentum EF-P protein consists of 187 amino acids with a calculated molecular weight of 20,584. Southern hybridization of an internal fragment of the EF-P gene from B. lactofermentum with chromosomal DNAs from different microorganisms reveals that it is a unique gene product in B. lactofermentum and Corynebacterium glutamicum. The EF-P gene was expressed in E. coli using the T7 expression system and the calculated molecular weight of the expressed protein was 23,000. Disruption experiments using an internal fragment of the EF-P gene or a disrupted EF-P gene in suicide plasmids always failed, suggesting that the gene is needed for cell viability.

Amino Acid Sequence↗
PubMed1997

Structure of the acceptor stem of Escherichia coli tRNA Ala: role of the G3.U70 base pair in synthetase recognition.

The fidelity of translation of the genetic code depends on accurate tRNA aminoacylation by cognate aminoacyl-tRNA synthetases. Thus, each tRNA has specificity not only for codon recognition, but also for amino acid identity; this aminoacylation specificity is referred to as tRNA identity. The primary determinant of the acceptor identity of Escherichia coli tRNAAlais a wobble G3.U70 pair within the acceptor stem. Despite extensive biochemical and genetic data, the mechanism by which the G3.U70 pair marks the acceptor end of tRNAAla for aminoacylation with alanine has not been clarified at the molecular level. The solution structure of a microhelix derived from the tRNAAla acceptor end has been determined at high precision using a very extensive set of experimental constraints (approximately 32 per nt) obtained by heteronuclear multidimensional NMR methods. The tRNAAla acceptor end is overall similar to A-form RNA, but important differences are observed. The G3.U70 wobble pair distorts the conformation of the phosphodiester backbone and presents the functional groups of U70 in an unusual spatial location. The discriminator base A73 has extensive stacking overlap with G1 within the G1.C72 base pair at the end of the double helical stem and the -CCA end is significantly less ordered than the rest of the molecule.

Alanine-tRNA Ligase↗
PubMed1997

Activity of a nitroalkene derivative, 1-(5-bromofur-2-il)-2-bromo-2-nitroethene, in the Salmonella/microsome assay and the mouse bone marrow micronucleus test.

Mutagenicity of a substituted nitroalkene, 1-(5-bromofur-2-il)-2-bromo-2-nitroethene (BNF) was tested in the Salmonella/microsome assay using the strains TA 98, TA 100 and TA 100NR (nitroreductase deficient). BNF was a direct mutagen in TA 98 and TA 100; the response was lowered when exogenous metabolic activation (S9) was used. A further decrease in mutagenicity was observed in strain TA 100NR, as compared to the parental TA 100, which showed the involvement of nitroreduction in the overall response elicited by BNF. The micronucleus assay was carried out in Swiss male mice which were given a single i.p. dose of 10-20 mg/kg of BNF dissolved in peanut oil, bone marrow being sampled 24 and 48 h later. The micronucleated polychromatic erythrocyte counts (MNPCE) showed a weak response in the dose range of 10-17.5 mg/kg at the second sampling (48 h) and a significant rise for 20 mg/kg at 24 and 48 h.

Animals↗