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S Vargas

Publications and source records attributed to S Vargas.

At least 19 recordsLinked to original sources
PubMed2003

Cell adhesion and cytotoxicity studies over polyanionic collagen surfaces with variable negative charge and wettability.

This work describes the cytotoxicity, and the cell adhesion behavior of K562 cell line from human erythroleukemia transfected with the DNA for the alpha(2)beta(1) integrin over type-I collagen matrices with variable degree of carboxyl group and wettability. The results showed that type-I collagen materials with variable degree of carboxyl group prepared by selective hydrolysis of carboxyamide side chains of Asn and Gln residues present in the protein, independently from the extent of side chain hydrolysis, was characterized by preserved triple helix structure for materials with a carboxyl group content up to 87 +/- 17. Imbibition and wettability increased linearly with increasing carboxyl group content from 46 +/- 12 to 87 +/- 17, and no signs of cytotoxicity were detected. Nevertheless, in comparison to native collagen, K562 cell adhesion to PACMs was significantly improved by factors ranging from 1.60 to 1.47x, with the reduction in cell adhesion observed with increasing carboxyl content attributed to a balance between the inhibition of increasing negative charge and the stimulation by increased wettability. On the other hand, the overall improvement of K562 cell adhesion to polyanionic collagen was attributed to the introduction of new distinct motifs described as the minimal active recognition sequence for alpha(2)beta(1) integrins binding with type-I collagen produced as a result of Asn-Gly Glu-Ala alpha2(I)294-297, and Gly Gln-Arg-Gly Val-Val carboxyamide side chains hydrolysis.

Animals↗
PubMed2002

C455R notch3 mutation in a Colombian CADASIL kindred with early onset of stroke.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is caused by mutations in the notch3 epidermal growth factor-like repeats. A Colombian kindred carries a novel C455R mutation located in the predicted ligand-binding domain. Stroke occurred in the patients at an unusually early age (median age: 31 years) in comparison to the more frequent onset in the fourth decade of life in other CADASIL populations, including a second Colombian kindred with an R1031C mutation.

Adult↗
PubMed2000

Transmission of Pneumocystis carinii disease from immunocompetent contacts of infected hosts to susceptible hosts.

Pneumocystis carinii organisms constitute a large group of heterogeneous atypical microscopic fungi that are able to infect immunocompromised mammals by an airborne route and to proliferate in their lungs, inducing Pneumocystis carinii pneumonia. This pneumonia remains a crucial epidemiological challenge, since neither the source of Pneumocystis carinii infection in humans nor the process by which humans become infected has been clearly established. Polymerase chain reaction (PCR) assays have shown that profoundly immunosuppressed patients without pneumocystosis can be subclinically infected with Pneumocystis. Other PCR-based studies have suggested that healthy immunocompetent hosts are not latent carriers of the parasite. However, recent reports have indicated that Pneumocystis carinii can persist for limited periods in the lungs of convalescent rats after recovery from corticosteroid-induced pneumocystosis, and also that immunocompetent mammals can be transiently parasitized by Pneumocystis carinii after close contact with hosts with Pneumocystis carinii pneumonia. Can transiently parasitized hosts be a source of infection for immunosuppressed hosts? In order to investigate this important clinical question, the ability of immunocompetent BALB/c mice, which were carrying subclinical levels of Pneumocystis carinii, to transmit the infection by the airborne route to highly susceptible, uninfected mice with severe combined immunodeficiency was studied. The results indicated that the immunocompetent mice, transiently parasitized by Pneumocystis carinii organisms after close contact with Pneumocystis carinii-infected mice, were able to transmit the infection to Pneumocystis carinii-free mice with severe combined immunodeficiency.

Animals↗
PubMed2000

Clinical and cerebral blood flow changes in catatonic patients treated with ECT.

OBJECTIVE: To determine changes in clinical manifestations and cerebral blood flow (CBF) before and after administration of ECT to patients with catatonia due to schizophrenia or mood disorders. METHODS: A sample of nine patients who met DSM-IV criteria for catatonia was studied. Patients received between 5 and 15 sessions (thrice per week) of ECT. Severity of catatonia was measured with the Modified Rogers Scale (MRS). Changes in CBF were measured with a brain single positron emission computer tomography (SPECT) that was performed 1 week before the first ECT and 1 week after the last ECT. RESULTS: Catatonia was due to schizophrenia in five patients and mood disorders in four patients. There were no significant clinical and brain SPECT differences between these two groups before treatment. Pre- vs. post-ECT comparisons showed significant reduction of catatonic symptoms in both groups. However, patients with mood disorders needed less ECT sessions and showed greater clinical improvement. Brain SPECT showed significant increase in CBF in parietal, temporal, and occipital regions in patients with mood disorder and no significant changes in patients with schizophrenia. CONCLUSIONS: These results support the efficacy of ECT for treatment of catatonic patients, especially secondary to mood disorders, which seem to be correlated with improvements in CBF.

Adolescent↗
PubMed1999

Early switch from intravenous to oral antibiotics and early hospital discharge: a prospective observational study of 200 consecutive patients with community-acquired pneumonia.

UNLABELLED: To determine the proportion of patients who can be treated with early switch to oral antibiotics and early discharge, to evaluate clinical outcome and patient satisfaction for patients treated with early switch and early discharge, and to define the factors that interfere with early discharge for some of the patients who underwent early switch to oral antibiotic therapy. DESIGN: Prospective study. PARTICIPANTS: Two hundred consecutive hospitalized patients with community-acquired pneumonia. MAIN OUTCOME MEASURES: Number of days needed to switch to oral therapy and length of hospital stay. Clinical outcome and satisfaction with care were evaluated for those patients treated with early switch and early discharge. RESULTS: Early switch to oral antibiotics (within the first 3 days of hospitalization) was performed in 133 patients (67%). Clinical failure was documented in 1 patient. Early switch and early discharge was performed in 88 patients (44%). The mean length of hospital stay for this group was 3.4 days. The most common reason for prolonged hospitalization after the switch to oral antibiotics was the need for diagnostic workup. More than 95% of patients were satisfied with the care they had received. CONCLUSIONS: Using simple clinical and laboratory criteria, a significant proportion of hospitalized patients with community-acquired pneumonia (44%) can be treated with early switch and early discharge. This model did not affect patient outcome, decreased the length of hospitalization, and was associated with a high level of patient satisfaction.

Administration, Oral↗
PubMed1998

Reverse Micelle Systems Composed of Water, Triton X-100, and Phospholipids in Organic Solvents

Enzymes entrapped in systems formed with water, phospholipids, toluene, and Triton X-100 show a catalytic activity that is much lower and a thermostability that is much higher than that observed in totally aqueous systems or in other types of reverse micelles. By phase boundary titrations and dynamic light scattering, this work characterizes reverse micelle systems formed in either toluene or propylbenzene with Triton X-100 and water. Four regions with distinct structural features were encountered. Up to one molecule of water per one Triton X-100 molecule, the system was transparent; light scattering measurements of this region indicated that water hydrated Triton X-100 monomers. A turbid region was formed as water content was increased to water:Triton X-100 ratios of 7.6 in toluene and 4.2 in propylbenzene. This thermodynamically unstable region was formed by large polydisperse structures. Transparent systems containing small size (27-150 A) thermodynamically stable reverse micelles were formed when the ratio of water to Triton X-100 molecules in the reverse micelle was in the range of 7.6 to 26.8 in toluene and 4.2 to 15.1 in propylbenzene. In this region, micellar size increased with water content. Water concentrations higher than the latter values resulted in phase separation. A similar titration of the aforementioned systems in the presence of phospholipids revealed that in the first region of transparency up to 10 molecules of water hydrated a phospholipid molecule. The inclusion of phospholipids to the Triton X-100 systems caused a displacement of the boundaries of the second region of transparency toward higher water contents. Copyright 1998 Academic Press. Copyright 1998Academic Press

Journal Article↗
PubMed1998

Reverse Micelle Systems Composed of Water, Triton X-100, and Phospholipids in Organic Solvents

Catalysis, stability, and thermostability of yeast hexokinase were determined in the microenvironments of two organic solvent/Triton X-100/phospholipids systems. In the abscence of enzyme, phase diagrams showed two transparent/turbid transitions, and reverse micelles were only observed in the second region of transparency (T2), where particle size as a function of water content shows a minima (see previous paper in this issue). In the present work, enzyme activity was detected throughout the four regions of the phase diagrams of these systems. Catalysis increased with water content; nevertheless, the maximum activities that were reached in the toluene and propylbenzene systems were 30 and 1.6%, respectively, of the activity in all aqueous media. Because in the T2 region in the propylbenzene system, micelles are much smaller than in toluene (see preceding paper), it would appear that expression of catalysis depends on the size of the micelles. However, a comparison of the dimensions of hexokinase and those of reverse micelles in the T2 region, suggests that in this region, hexokinase entrapment increases the inner volume of the micelle. High enzyme thermostability was only observed in the first transparent region (T1) of the system that contained phospholipids. In this region, hexokinase induced the formation of reverse micelles from dispersed surfactant monomers. There is a striking similarity in the dimensions of hexokinase entrapped in reverse micelles as determined by dynamic light scattering measurements in the T1 region with those of hexokinase as obtained from X ray diffraction studies of the enzyme in a crystalline environment. This suggest that high thermostability, and low catalytic rates result from restrictions in mobility imposed by a low water environment. Copyright 1998 Academic Press. Copyright 1998Academic Press

Journal Article↗
PubMed1997

[Iodine nutrition in school children of four census areas of Chile].

BACKGROUND: Although endemic goiter is an easily controlled chronic disease, it continues to be a serious global public health problem. AIM: To study iodine nutrition in school age children from different areas of Chile. SUBJECTS AND METHODS: Thyroid gland was palpated in 4181 school age children from Calama, Santiago, Temuco and Punta Arenas. Urinary iodine excretion was measured to 9% of these children and iodine concentration in salt for human consumption obtained in each of these areas was determined. RESULTS: A 9% goiter prevalence in boys and 11% prevalence in girls was detected. The prevalence of goiter Ia was 6.5% and the figure in different geographic areas was similar. Iodine concentration in salt for human consumption was adequate according to Chilean legislation (82.6, 95.7, 96.8 and 93.2 micrograms ugI/g salt in Calama, Santiago, Temuco and Punta Arenas respectively). Urinary iodine excretion in boys and girls was 1695 and 1802 micrograms l/g creatinine in Calama, 680 and 732 in Santiago, 574 and 690 in Temuco, 570 and 528 in Punta Arenas. These values are well above recommendations. CONCLUSIONS: Endemic goiter is no longer a problem in Chile. The importance of a continuous surveillance of iodine nutrition in Chile and the reduction of salt iodine concentration required by Chilean legislation is underscored.

Censuses↗
PubMed1995

Application of new sepsis definitions to evaluate outcome of pediatric patients with severe systemic infections.

No published reports have stratified pediatric patients with systemic infections according to the new sepsis terminology guidelines. In addition little is known about the outcome of sepsis in developing countries. This large 12-year retrospective study evaluated the outcome of 815 infants and children with sepsis managed in a Latin American pediatric intensive care unit. Of these children 171 (21%) had sepsis, 497 (61%) had severe sepsis and 147 (18%) had septic shock. Multiorgan dysfunction was present in 120 (24%) and 77 (52%) patients with severe sepsis and septic shock, respectively. Infection was bacteriologically proved in 212 (26%) cases, with Staphylococcus aureus and Neisseria meningitidis being the most frequent responsible organisms. Three hundred nineteen (39%) patients died. Case-fatality rates were higher in patients with septic shock, multiorgan dysfunction, sepsis caused by Pseudomonas aeruginosa and meningococcemia than in those without these conditions. Although no difference in mortality was detected between culture-proved and culture-negative sepsis, more patients receiving an inappropriate antimicrobial agent died than those treated with an appropriate drug (53% vs. 34%, P = 0.012). We believe that with the use of the new terminology system a more reliable comparison of data from pediatric sepsis studies and of emerging immunomodulating therapeutic modalities can be achieved.

Adolescent↗
PubMed1994

Neonatal sepsis and meningitis in a developing Latin American country.

In a retrospective study at Hospital del Niño in Panama City, Panama, 577 neonates with culture-proved sepsis and/or meningitis were identified during an 18-year period (1975 to 1992). Overall there was an incidence of 3.5 cases/1000 live births. Three hundred thirty-three patients (58%) were of low birth weight (< 2500 g) and 260 (45%) were premature. Gram-negative bacilli, particularly species of Klebsiella and Escherichia coli, were responsible for 61% of infections, whereas Gram-positive isolates (especially staphylococci) and Candida strains accounted for 37 and 2%, respectively. The patterns of predominance among bacterial pathogens, however, changed during the period of study. In the later years of this study the frequency of Gram-negative bacteria declined whereas those of staphylococci and Candida increased. Likewise systemic infections caused by Group B Streptococcus organisms appeared recently. The case-fatality rate was 32%. Mortality was greater in infants with early onset sepsis than in those with late infections (44% vs. 22%, P < 0.0001; odds ratio, 2.8; 95% confidence interval, 1.9 to 4.1) and lesser in neonates infected by coagulase-negative staphylococci than in those infected by any other pathogen (12 vs. 39%, P < 0.001; odds ratio, 0.2; 95% confidence interval, 0.1 to 0.4). These findings provide guidelines for the selection of empiric antimicrobial agents in our country and possibly in other Latin American countries and suggest that a continued thorough epidemiologic evaluation is needed to anticipate bacteriologic changes over time.

Candidiasis↗
PubMed1990

Effects of vitamin D-binding protein on bone resorption stimulated by 1,25 dihydroxyvitamin D3.

Vitamin D and its metabolites are tightly bound to the serum vitamin D-binding protein (DBP) and only the free hormone is considered to be physiologically active. On the other hand, DBP could interact with cell membranes and even favor its intracellular entry. The present study was undertaken to examine the effects of DBP on bone resorption stimulated by 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]. Forelimb bones from 19-day-old fetal rats were cultured for 5 days in the presence of purified human or rat serum albumin (hSAP or rSAP) and 1,25(OH)2D3, with or without human or rat DBP (hDBP or rDBP). Bone resorption was assessed by measuring the release of previously incorporated 45Ca. We found that the resorptive response to 1,25(OH)2D3 was minimally altered by hDBP (5 microM). The minimal effects of hDBP on 1,25(OH)2D3 activity on rat bones might be explained by a 6-fold lower affinity of hDBP (1.1 x 10(7) M-1) than rDBP (5.9 x 10(7) M-1) for 1,25(OH)2D3 or by species differences in cellular recognition of DBP. In a homologous rat system, however, rDBP at low (0.5 microM) or physiological (5 microM) concentration significantly decreased 1,25(OH)2D3-induced bone resorption. These data therefore support the hypothesis that free rather than DBP-bound 1,25(OH)2D3 is physiologically important.

Animals↗
PubMed1989

[Prevalence of alcoholism during 3 decades in Chile (1952-1982)].

The level of alcoholism in Chile and its variations between 1952 and 1982 are studied by means of the Jellinek Method. The limitations and bias of the methodology employed are indicated and the results are compared with those of other children studies. The conclusion is that there was an increase in the number of alcoholics and in the alcoholism rate during the period analyzed, with a rate for 1982 70% higher than that for 1952. The efficacy of the policy for the prevention of alcoholism adopted in the period under study is called in question by the results presented.

Alcoholic Beverages↗
PubMed1989

[Effect of weekly mouthrinses with 0.2% neutral NaF solution on caries incidence in first permanent molars].

A 32-month study was undertaken to determine the caries inhibitory effect of a weekly rinse for one minute with a solution of 0.2% NaF on the first permanent molars. Subjects who participated in the study were 295 school children aged from 5 to 13 years who were divided by random selection in two groups, test and control who rinsed with either 0.2% NaF solution or a placebo under double-blind conditions. Reductions in caries increments on first permanent molars (20.7% DMFT and 31.9% DMFS) were seen in the test group as compared with the control group. A preventive effect was also seen in all first permanent molars surfaces, being the major protective effect in approximal surfaces (52% reduction) followed by occlusal (36%) and bucolingual surfaces (16%).

Adolescent↗