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J Rangel

Publications and source records attributed to J Rangel.

9 recordsLinked to original sources
PubMed2006

Characterization and epidemiologic subtyping of Shiga toxin-producing Escherichia coli strains isolated from hemolytic uremic syndrome and diarrhea cases in Argentina.

Argentina has a high incidence of hemolytic uremic syndrome (HUS); 12.2 cases per 100,000 children younger than 5 years old were reported in 2002. Shiga toxin (Stx)-producing Escherichia coli (STEC) is the primary etiologic agent of HUS, and STEC O157 is the predominant serogroup isolated. The main objective of the present work was to establish the phenotypic and genotypic characteristics of the STEC strains in general isolated from Argentine children during a prospective study and the clonal relatedness of STEC O157:H7 strains using subtyping techniques. One hundred and three STEC strains isolated from 99 children were included. The phenotypic and genotypic features were established, and a polymerase chain reaction-restriction fragment length polymorphism (PCRRFLP) was performed to determine stx2 variants. The clonal relatedness of E. coli O157 isolates was established by phage typing and pulsed-field gel electrophoresis (PFGE). The 103 STEC strains belonged to 18 different serotypes, and 59% were of serotype O157:H7. Stx2 was identified in 90.3%, and stx1 in 9.7%. Among the 61 STEC O157 strains, 93.4% harbored the stx2/stx2vh-a genes; PT4 (39.3%) and PT2 (29.5%) were the predominant phage types. Using PFGE with the enzyme XbaI, a total of 41 patterns with at least 80% similarity were identified, and seven clusters with identical profiles were established. Some of the clusters were further split by PFGE using BlnI as the second enzyme. Isolates with indistinguishable PFGE patterns were with one exception also indistinguishable by phage typing and stx genotyping. These findings confirmed that some isolates were genetically related. However, no epidemiological linkages were identified. STEC strains with different genotypes and belonging to diverse serotypes were isolated in Argentina. Some STEC O157 strains could not be distinguished by applying subtyping techniques such as PFGE and phage typing.

Argentina↗
PubMed2002

Anomalous diffusion in the nonasymptotic regime.

We analyze some properties of the one-dimensional Lévy flights, assuming that the one-step transition rates depend on the flight length x as p(alpha)(x) equivalent to x(-(alpha+2)). For flights on a finite, (2M+1)-site lattice, we can define an effective, size-dependent, diffusion coefficient D(alpha)(M) equivalent to [M(1-alpha) - 1]/(1 - alpha) if alpha < 1, with D1(M) equivalent to ln(M). Using the generalization of statistical mechanics given by Tsallis, we show that for flights on infinite systems, the generalized displacement moments are well defined provided that alpha > R - 3. These moments exhibit a power-law singularity if alpha --> 1(-) and R>2/3. The short- and intermediate-time properties of the generalized mean-square displacement are then studied numerically. This work suggests the conditions under which the asymptotic analytical formulas (obtained in the literature by the use of the generalized central limit theorem) could be applied to finite-time experiments. These formulas should work much better if alpha is close to zero than in the alpha -->1(-) neighborhood.

Journal Article↗
PubMed2002

Neutron angular distribution in a plasma focus obtained using nuclear track detectors.

The dense plasma focus (DPF) is a coaxial plasma gun in which a high-density, high-temperature plasma is obtained in a focused column for a few nanoseconds. When the filling gas is deuterium, neutrons can be obtained from fusion reactions. These are partially due to a beam of deuterons which are accelerated against the background hot plasma by large electric fields originating from plasma instabilities. Due to a beam-target effect, the angular distribution of the neutron emission is anisotropic, peaked in the forward direction along the axis of the gun. The purpose of this work is to illustrate the use of CR-39 nuclear track detectors as a diagnostic tool in the determination of the time-integrated neutron angular distribution. For the case studied in this work, neutron emission is found to have a 70% contribution from isotropic radiation and a 30% contribution from anisotropic radiation.

Copper↗
PubMed2000

Interactions between hormone-mediated and vaccine-mediated immunotherapy for pulmonary tuberculosis in BALB/c mice.

Problems of logistics, compliance and drug resistance point to an urgent need for immunotherapeutic strategies capable of shortening the current 6-month chemotherapy regimens used to treat tuberculosis, or of supplementing ineffective therapy. In this study we sought to define the mechanism of action of two immunotherapies, both of which have previously been shown to prolong survival. Secondly, we wished to identify any clinically useful synergy between these therapies. In BALB/c mice infected via the trachea with Mycobacterium tuberculosis H37Rv there is an initial phase of partial resistance dominated by type 1 cytokines plus tumour necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL-1), followed by a phase of progressive disease. This progressive phase is accompanied by increasing expression of IL-4, and diminished expression of IL-1 and TNF-alpha. Animals in this late progressive phase of the disease (day 60) were treated with two injections (day 60 and day 90) of 0.1 or 1.0 mg of heat-killed Mycobacterium vaccae, or with 3beta, 17beta-androstenediol (AED; 25 microg subcutaneously three times/week), or with both therapies. We show here using four techniques in parallel (morphometry, immunohistochemistry with automated cell counting, semiquantitative reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assays of cytokines in lung extracts) that treatment with M. vaccae causes a switch back towards a type 1 cytokine profile, restoration of expression of IL-1alpha and TNF-alpha, and a switch from pneumonia to granuloma. This is very similar to the changes previously seen after treatment with AED. However, there was no evidence for synergy between M. vaccae and AED.

Androstenediol↗
PubMed1999

Immunogenic and protective ability of the two developmental forms of Chlamydiae in a mouse model of infertility.

To compare the ability of elementary bodies (EB) and reticulate bodies (RB) of the Chlamydia trachomatis mouse pneumonitis (MoPn) biovar to induce a protective immune response, two groups of BALB/c mice were inoculated and boosted twice, with UV-inactivated EB or RB in Freund's adjuvant. Two weeks after the last immunization mice were challenged with C. trachomatis in the ovarian bursa. Vaginal cultures collected for 6 weeks after the intrabursal challenge showed that mice inoculated with EB were significantly protected, while mice inoculated with RB were not. Six weeks after the genital challenge mice were mated. Mice immunized with EB showed significant protection as demonstrated by the number of animals which were fertile and the number of embryos present in the uterine horns. In contrast, no significant protection against infertility was observed in the mice immunized with RB.

Animals↗
PubMedDate not supplied

[Arterial damage and the renin-angiotensin system in essential hypertension. Study of 63 cases].

Brunner, Laragh et al. have suggested that essential hypertensives with low plasma renin activity (PRA) are at lower risk of myocardial infarction or cerebrovascular accidents than those with high or normal PRA levels. In this paper we report on 63 patients with essential hypertension in whom the relation between PRA and the ocurrence of cardiovascular events was studied. The patients were categorized in high (11%), normal (70%) or low (19%) PRA subgroups, according to their 24-hour sodium excretion. Coronary angiogram was performed in 24 subjects. The three subgroups showed no significant differences in diastolic blood pressure, serum cholesterol levels, smoking habits or obesity. The incidence of cardiovascular complications was similar in patients with high or low PRA levels (28.5% and 33.3% respectively). In those hypertensives in whom coronary angiogram was done, coronary lesions were observed in 80% of the low renin subjects and in 37.5% of those patients with normal PRA. Therefore, no relation between PRA levels and vascular complications was observed in this series of patients. It is conclude that patients with essential hypertension must be treated as soon and effectively as possible regardless of their PRA value.

Adult↗
PubMedDate not supplied

[Renin-angiotensin-aldosterone system in the treatment of essential hypertension with a beta-adrenergic blocker: sotalol].

The administration of beta blockers has been useful in the treatment of essential hypertension. The anti-hypertensive effect of the beta-blocker sotalol was evaluated in 28 patients with essential hypertension. In all of the patients a determination of urinary aldosterone and plasma renin activity, before and after, three months of treatment with sotalol was done. In the pre-treatment tests, five patients (18%) had elevated renin values, in 13 (6%) renin was normal, and in 10 (36%) the renin activity in plasma was low. Treatment with sotalol caused normalization or significant lowering of diastolic pressure in the majority of cases with high or normal plasma renin. Patients with low plasma renin activity had less satisfactory results with the drug. Since there was no correlation between the lowering of arterial pressure and the degree of depletion of renin, we can conclude that anti-hypertensive mechanism of sotalol does not come from the decrease in secretion of renin. However our results suggest that patients with high renin respond better to treatment with sotalol, than cases with low renin levels.

Aldosterone↗
PubMedDate not supplied

[The renin-angiotensin-aldosterone system in the diagnosis of renovascular arterial hypertension].

Twenty one subjects with sistemic arterial hypertension and arteriographic signs of obstructive lesion of the renal artery were studied and classified in 3 groups: group A, 13 cases with bilateral renovascular lesions; group B, 4 patients with unilateral renovascular stenosis and group C, formed by 4 subjects with a segmental branch stenosis of a renal artery. In all cases an special protocol was followed to measure plasma renin activity (PRA) in blood taken from a peripheral vein, inferior vena cava and both renal veins and also to determine 24 hrs. urinary excretion of aldosterone (UEA). PRA and UEA were clasified as high, normal and low by comparing the results with those of normal subjects in a nomogram estimated in the same laboratory in which PRA and UEA values were correlated with 24 hrs. urinari sodium excretion. Besides, R greater than /R less than index (highest PRA of renal vein blood/PRA of contralateral renal vein) and V-A A index (V = PRA of renal vein blood; A = PRA of inferior vena cava) were calculated. Forty eight and thirty eight percentage of the cases had either high renin in peripheral venous blood or high UEA. Similar data in patients with essential hypertension previously studied in the same laboratory were 12 and 10% respectively. V-A A index was incongruent with the arteriographic image in 3 cases of group B; 4 cases of group A and 2 of group B had a pattern of bilateral stenosis, and one case in each group A and C had a unilateral stenosis pattern. In the other patients the samples were "non representative" due to a high level of PRA in the inferior vena cava blood comparable to PRA of the renal veins. Six cases of group A had a R greater than /R less than index superior to 1.5, which suggested a predominant vascular lesion in one side not always congruent with the arteriographic findings. In 3 cases of group B this index was higher than 1.5 in favor of the ipsilateral lesion. Three cases of group C had a normal R greater than /R less than index and one with a total oclussion of a segmental artery presented an index superior to 1.5, ipsilateral to the lesion. The latter index was of value in the diagnosis of renovascular arterial hypertension.

Aldosterone↗