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Biomedical subjects

O Ramos

Publications and source records attributed to O Ramos.

At least 19 recordsLinked to original sources
PubMed2001

Avalanches in one-dimensional piles with different types of bases.

We perform a systematic experimental study of the influence of the type of base on the avalanche dynamics of slowly driven 1D ball piles. The control of base details allows us to explore a wide spectrum of pile structures and dynamics. The scaling properties of the observed avalanche distributions suggest that self-organized critical behavior is approached as the "base-induced" disorder at the pile profile increases.

Journal Article↗
PubMed1999

Interrater reliability of plaque morphology classification in patients with severe carotid artery stenosis.

OBJECTIVE: Ultrasonographic assessment of carotid artery plaque morphology is widely used to identify patients at high risk for stroke. However, the reliability of plaque analysis in high-grade stenosis is uncertain. We determined the interrater reliability of sonographic plaque morphology analysis in patients with severe carotid artery stenosis. MATERIALS AND METHODS: Duplex Doppler was performed on 114 patients with 80-99% stenosis of the internal carotid artery using a Siemens Quantum 2000 D with a handheld 7.5 MHz transducer. B-mode pictures with and without color coding were printed on a Sony color video printer UP-5000 W. Three raters independently evaluated plaque echolucency, heterogeneity, calcification, and surface structure. Interrater agreement was calculated by a jackknife procedure generating kappa values and two-sided 95% confidence intervals. RESULTS: Kappa values and 95% confidence intervals were 0.05 (-0.07 to 0.16) for plaque surface structure, 0.15 (0.02 to 0.28) for plaque heterogeneity, 0.18 (0.09 to 0.29) for plaque echogenicity, and 0.29 (0.19 to 0.39) for plaque calcification. The upper bounds of all of the confidence intervals were below the 0.40 level suggested for minimal reliability. CONCLUSION: The low interrater agreement indicated that unaided visual assessment of static B-mode pictures to assess plaque morphology in patients with severe carotid artery stenosis is not reliable. Other evaluation procedures and standardized criteria, as yet undeveloped, are needed to improve reliability.

Arteriosclerosis↗
PubMed1995

Arsenic increased lipid peroxidation in rat tissues by a mechanism independent of glutathione levels.

The role of lipid peroxidation in the mechanism of arsenic toxicity was investigated in female rats pretreated with N-acetylcysteine (NAC, a glutathione [GSH] inducer) or with buthionine sulfoximine (BSO, a GSH depletor). Rats were challenged with sodium arsenite, and sacrificed 1 hr after this treatment. Results showed that arsenic decreased GSH levels and increased lipid peroxidation in liver, kidney, and heart, with a larger effect at 18.2 mg/kg than at 14.8 mg/kg for lipid peroxidation induction. In the liver of rats treated with arsenic, pretreatment with NAC increased the levels of GSH and decreased lipid peroxidation. In kidney and heart, NAC pretreatment protected the tissues against arsenic-induced depletion of GSH levels, but the same degree of protection was not found for lipid peroxidation induction. In its turn, BSO had an additive effect with arsenic in lowering the levels of GSH in the liver and kidney, but an inverse correlation between GSH levels and lipid peroxidation was found only in liver. Arsenic content in tissues of rats pretreated with NAC was lower than in rats treated only with arsenic. In rats with depleted levels of GSH (BSO-pretreated rats), a shift in arsenic tissue distribution was found, with higher levels in skin and lower levels in kidney. A clear tendency for a positive correlation between arsenic concentration and lipid peroxidation levels was found in liver, kidney, and heart.

Acetylcysteine↗
PubMed1994

Major histocompatibility complex class II alleles and haplotypes and blood groups of four Amerindian tribes of northern Colombia.

MHC class II alleles and haplotypes were determined from unrelated individuals and families of the Arhuaco (n = 107), Kogi (n = 42), Arsario (n = 18), and Wayú (n = 88) tribes located in the northern part of Colombia. Class II DRB, DQA1, and DQB1 alleles were determined by PCR-SSO and PCR-RFLP based methods. Four haplotypes, [DRB1*0407, DRB4*0101, DQA1*03, DQB1*0302]; [DRB1*0403, DRB4*0101, DQA1*03, DQB1*0302]; [DRB1*1402/1406, DRB3*0101, DQA1*0501, DQB1*0301]; and [DRB1*0802, DQA1*0401, DQB1*0402], were observed among these four tribes. In addition to these haplotypes, the Wayú Indians showed a frequency of 21.3% for the [DRB1*1602, DRB5*02, DQA1*0501, DQB1*0301] haplotype, 13.1% for the [DRB1*0411, DRB4*0101, DQA1*03, DQB1*0302] haplotype, and 8.1% for the [DRB1*0411, DRB4*0101, DQA1*03, DQB1*0402] haplotype. Red cell antigen typing was used to calculate genetic admixture. The Kogi and Arsario showed no genetic admixture while the Arhuaco tribe showed admixture with genes of African origin and the Wayú showed admixture with Caucasians as well as genes of African origin. These findings were confirmed by the MHC class II allele and haplotype data obtained, as alleles and haplotypes of Caucasian and African origin were detected in the Wayú and Arhuaco and not in the Kogi or Arsario. These studies will be important in disease association and transplantation studies for Amerindian and colombian populations and for correlating genetic traits with the anthropologic and linguistic data available in order to better understand the Amerindian populations.

Alleles↗
PubMed1992

[HIV infection and AIDS: neuropsychiatric and neuropsychological aspects].

The progressive confirmation of the neurotropic character of HIV, in juxtaposition to the recognition of AIDS dementia complex as an important central nervous system clinical manifestation, have engendered a greater interest in this phenomena. Consequently, a more precise description of the behavioral and mental aspects of this infection have evolved. This article has two purposes, to discuss the AIDS dementia complex concept and secondly, to review the neuropsychiatric and neuropsychological aspects of infection by HIV and AIDS, as it pertains to adult patients.

AIDS Dementia Complex↗
PubMed1991

[Insulin/glucagon relationship in spontaneous diabetic remission].

We define diabetic remission as the disappearance of clinical symptoms with normalization of blood glucose for a period over 15 days after withdrawal of insulin therapy. We studied 21 insulin-dependent diabetic children in remission (10 boys and 11 girls) and 29 normal children matched in age and sex as controls. Two tests were performed, intravenous glucose (IVGT) and glucose post-tolbutamide (PTGT). Two remission groups were studied with IVGT. Glucose, insulin, somatotropin and glucagon were determined in one and glucose and C-peptide in the other. Insulin secretion after IVGT was very low in the remission group, not surpassing basal value when stimulated. Only two girls showed normal or high insulin values during the study, and one of them showed the common hypoinsulinism of the remission group in a second study. The kinetics of glucagon and somatotropin secretion in the remission group were normal with low values of glucagon. When the integrated area (0-120 min) of hormone secretion (insulin, somatotropin and glucagon) was determined, the remission group had lower insulin and glucagon values (p less than 0.05) and identical growth hormone as the normal group. The insulin/glucagon ratio in normals and in remission were similar. During IVGT the remission group studied for C-peptide showed lower C-peptide values than normal group, resembling insulin behavior. In both groups, the glucose disappearance rate ("K" value) was higher in normals than in remissions (p less than 0.001). During the PTGT the normal group showed a peak of insulin secretion after tolbutamide and glucose stimulation. In the remission group, glucose was higher and insulin secretion lower than in the normal group, without a peak of insulin, and growth hormone and glucagon secretion were also lower.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Cost-effectiveness analysis of the treatment of end-stage renal disease in Brazil.

Cost-effectiveness analysis compared four treatments of end-stage renal disease in Brazil: continuous ambulatory peritoneal dialysis (CAPD), in-center hemodialysis (HD), cadaver donor transplantation (CD-Tx), and living related donor transplantation (LR-Tx). After 2 years, the costs per year of survival were CAPD, $12,134; HD, $10,065; CD-Tx, $6,978; and LR-Tx, $3,022. The HD cost was lower than CAPD partially because of the reuse of hemodialyzers in Brazil. Although less cost-effective, both dialysis treatments yielded more years of survival after 2 years. This analysis reveals a trade-off between cost per year of survival and years of survival.

Adolescent↗
PubMed1989

Staphylococcus aureus skin carriage and development of peritonitis in patients on continuous ambulatory peritoneal dialysis.

We conducted a 15-month prospective study to investigate the skin carriage of Staphylococcus aureus and the development of peritonitis in 43 patients undergoing continuous ambulatory peritoneal dialysis (CAPD). Sixteen of 43 patients (37%) were chronic carriers of S. aureus in the anterior nares and/or in the exit-site of the catheter; 12 patients (28%) were intermittent carriers, and 15 (35%) were noncarriers. Fifty episodes of peritonitis occurred during a total of 422 patient-months of observation. S. aureus was responsible for 16 episodes of peritonitis diagnosed in 15 patients. All episodes of S. aureus peritonitis occurred in chronic and intermittent carriers. Phage typing was performed on isolates from 8 patients with S. aureus peritonitis, and they were found to have the same phage type as that previously carried in the skin. We conclude that CAPD patients who are chronic or intermittent carriers of S. aureus are at higher risk of development of peritonitis than noncarriers.

Adolescent↗
PubMed1988

Elevated NK sensitivity of Raji cells carrying acceptor-bound C3 fragments.

The majority of cell lines derived from Burkitt lymphomas carry CR2 on their plasma membrane cell lines of haematopoietic origin can activate C3 present in human serum through the alternative pathway. However, only the lines that carry CR2 were shown to bind C3 fragments. This bond can be either fixation to acceptor sites or attachment to the CR. Our studies with Raji cells showed that when the possibility for the covalent acceptor bond was eliminated by using methylamine (MA)- or zymosan-treated serum, considerably lower amounts of C3 were bound. In the zymosan-treated serum C3 fragments are present that can bind to receptors but their capacity for acceptor bond is absent. These results indicate that when Raji cell are incubated in human serum some of the generated C3 fragments are bound to acceptors and a lower proportion through the specific interaction with complement receptors. Pretreatment of the CR2 carrying cell lines with human serum elevated their sensitivity to the lytic effect of human blood lymphocytes. We showed in this work that MA-treated serum did not induce this elevation. Zymosan-treated serum under conditions that excluded activation of the residual native C3 molecules, i.e., in the presence of EDTA, did not have the enhancing effect either. These results suggest that the increased lytic efficiency imposed by human serum was due to cleavage of C3 molecules by Raji and fixation of the C3 fragments by acceptor sites. Natural killer cells carry CR3; therefore it is likely that the attached C3 fragments bind also to the effector cells. The C3 molecules could elevate thereby the avidity between the target and the lytic lymphocytes. The observation that C3 fragments are not bound to the surface of CR2 negative lines in spite of their capacity to activate C3 suggests that the receptor molecule is either involved in the activation and/or serves also as an acceptor.

Complement C3↗
PubMed1987

Yellow-brown (Hamazaki-Wesenberg) bodies mimicking fungal yeasts.

We describe herein two cases in which yellow-brown (Y-B) bodies, also known as Hamazaki-Wesenberg bodies, were encountered in lymph nodes and initially misinterpreted as fungal organisms. Because of occasional "budding" forms and positive staining with "screening" fungal stains (Grocott methenamine silver and periodic acid-Schiff), Y-B bodies may closely resemble budding yeast fungi. We describe the characteristic light microscopic and ultrastructural morphologic features of Y-B bodies, and their histochemical staining reactions, and emphasize the value of the Fontana-Masson silver stain for recognition and identification of these bodies.

Adult↗
PubMed1986

[Chemical evaluation and determination of the nutritive value of a variety of Opaque-2 corn in the initial diet of broilers].

Chemical and amino acidic composition of Opaque-2 corn, cultivar CIMMYT-TL 81-A (Hungarian compound) locally produced were determined. In addition, the productive performance of broiler chicks fed Opaque-2 corn or normal corn (Pioneer) for the first 28 days of age was evaluated. The chemical and amino acid content results obtained for the Opaque-2 corn studied, compared well ranges previously reported. The productive performance at the end of the experiment was similar between the two treatments assayed.

Amino Acids↗
PubMed1984

[Monozygotic twins with a minimal cerebral dysfunction syndrome].

Two monozygotic boys, 5 years and 5 months old, with a normal IQ, whose father had suffered from stuttering, language retardation and dyslexia showed a minimal brain dysfunction syndrome. A genetic etiology is likely in these patients. Other etiological factors remain obviously possible in other patients.

Attention Deficit Disorder with Hyperactivity↗