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Biomedical subjects

E Parra

Publications and source records attributed to E Parra.

At least 19 recordsLinked to original sources
PubMed2007

Cell proliferation and tumor formation induced by eserine, an acetylcholinesterase inhibitor, in rat mammary gland.

Environmental chemicals may be involved in the etiology of breast cancer. There is substantial evidence that breast cancer risk is associated with prolonged exposure to female hormones. Among these hormonal influences a leading role is attributed to the ovarian hormone estradiol, since breast cancer does not develop in the absence of ovaries. The rat mammary gland has special characteristics that make it an ideal organ for studying development, cell proliferation and transformation. In vivo and in vitro model systems for cell proliferation and mammary carcinogenesis have allowed morphological and biochemical analysis under different experimental conditions. The aim of this study was to examine the effect of eserine, an acetylcholinesterase inhibitor, as are the organophosphorous compounds malathion and parathion, and 17beta estradiol on cell proliferation and tumor formation that takes place in the rat mammary gland after in vivo and in vitro treatment. These studies showed that eserine and 17beta estradiol were capable of inducing carcinogenesis in the epithelium of rat mammary glands. It was found that there was a significant increase in the number of cells per duct of the 44-day-old rat mammary gland after the 10-day eserine treatment, compared to the control. A higher increase was observed in the animals treated for 10 days with eserine followed by 30-daily injections of estrogen in comparison to control animals. In 12 animals, two mammary tumors were directly developed in response to 17beta estradiol injected at 39 days of age with a latency period of 180 and 245 days, respectively. Such tumors were metastatic to the lung. These results suggest that terminal end buds are major targets related to rat mammary carcinogenesis and 17beta estradiol can be an initiator and promoter in this process.

Animals↗
PubMed2006

[Hemodialysis prospective multicentric quality study].

In medicine a considerable amount of resources are used in research, but very little attention is paid to ensuring that the findings of research are implemented in routine clinical practice. This prospective study has the aim to evaluate the efficiency of some clinical management strategies (feedback, benchmarking and improving plans) on haemodialysis treatment results in 4 different dialysis centres. We collected consensus data related to haemodialysis results every 6-8 months and informed each centre about its own results (feedback) and how these related to the others(benchmarking). We designed improving plans for any bad result detected. By the end of two years of follow up, 294 patients had been included in the study. The results obtained at the end of the study had improved in comparison with those obtained at the beginning (statistically significant) for the following indicators: % of patients with Hb< 11 g/dl, % patients with Kt/v < 1.2, mean Kt/v, mean albumin, % patients with albumin< 3.5 g/dl y % patients with C reactive protein (CRP) > 5 mg/dl. No statistical changes were found in: mean erythropoietin (EPO) doses, blood pressure (BP), phosphorus plasmatic,calcium-phosphorus product, parathormone (PTHi) and vascular access distribution. We explained the absence of any improvement because of adequate start indicators in some areas (BP and vascular access), therapy with limited efficiency (calcitriol, calcium carbonate and others), lack of support resources (dietetic unit) or inadequate design/implementation of improving plans.In conclusion, our intervention illustrates that combined clinical management strategies(feedback, benchmarking and improving plans) are efficiency in improving some areas of haemodialysis treatment (anaemia, dialysis dose, nutrition and inflammation), although it does not improve calcium phosphate metabolism related indicators.

Aged↗
PubMed2005

[Macrocephaly the first manifestation of glutaric aciduria type I: the importance of early diagnosis].

INTRODUCTION: The clinical manifestations of glutaric aciduria type I (GA-I) usually develop during the first two years of life as acute encephalopathic crisis leading to irreversible dystonic. Progressive macrocephaly can be an early clinical sign. We report a 9 month old patient with macrocephaly diagnosed of GA-I in the presyntomatic stage. This early diagnosis and treatment avoided the irreversible neurologic damage associated to this disease. CASE REPORT: A 9 month old male referred to the pediatrics neurology clinic because of macrocephaly with a head circumference of 51 cm (> 97th percentle). At birth this head circumference was 37.5 cm (97th percentile) and showed rapid growth during the first 4 months of life. In the physical exam there was mild hypotonia and no other neurologic alterations with normal psychomotor development. In the work up for macrocephaly urinary organic acids were determined showing a glutaric acid: 78,000 mmol/mol creatinine (normal values: 2-10); 3-hydroxyglutaric acid: 250 mmol/mol creatinine (normal values: 1-12). Cerebral magnetic resonance (MR) performed at 12 months of age showed frontotemporal atrophy with enlargement of subarachnoid spaces, a high signal in T2 in the pallidus nucleus and subdural hematomas. Genetic analysis showed a mutation S 305 L/Q 352 X in GCDH gene. L-carnitine and riboflavin supplementation and a diet with restriction of lysine and tryptophan was started. Intercurrent illnesses were treated with intravenous fluid, glucose and L-carnitine. At 3 years and 6 month of age, he had not shown any encephalopathic crisis, he had a normal psychomotor development and no dystonia. MR shows mild temporal lobe atrophy without basal ganglia alterations. CONCLUSIONS: In GA-I, macrocephaly is an early sign before other neurologic alterations. In patients with little or no neurological symptoms, early treatment may prevent the acute encephalopathic crisis and neurological deterioration, improving the prognosis and may also normalize the basal ganglia neuroradiological alterations. Urinary organic acid analysis should be performed in the work up of macrocephaly of unknown aetiology.

Brain↗
PubMed2004

Maternal adaptation to high-altitude pregnancy: an experiment of nature--a review.

A long and productive history of studies at high altitude has demonstrated that chronic hypoxia plays a key role in the aetiology of intrauterine growth restriction (IUGR) and pre-eclampsia. Susceptibility to altitude-associated IUGR varies among high-altitude populations in relation to their duration of altitude exposure, with multigenerational residents demonstrating one-third the birth weight fall present in shorter-resident groups. Higher uteroplacental blood flow during pregnancy in multigenerational high-altitude residents suggests that such population differences are due, at least in part, to differences in maternal vascular responses to pregnancy. We hypothesize that natural selection acting on hypoxia-inducible factor (HIF)-targeted or -regulatory genes has enabled maternal vascular adaptation to pregnancy in long-resident high-altitude groups. Preliminary evidence in support of this hypothesis demonstrates that the potent HIF-targeted vasoconstrictor, endothelin-1 (ET-1), is differentially regulated by pregnancy and chronic hypoxia in Andean vs European residents of high altitude. Andeans show the normal, pregnancy-associated fall in ET-1 levels previously reported at low altitude, whereas Europeans have higher ET-1 levels and little pregnancy-associated change, like pre-eclamptic women. Single nucleotide polymorphisms (SNPs) in the ET-1 gene also differ in Andeans compared with low-altitude populations. We conclude that high altitude serves as an experiment of nature for elucidating genetic factors underlying susceptibility to complications of pregnancy and fetal life. Such studies may be important for identifying persons at risk for these complications at any altitude.

Acclimatization↗
PubMed2003

Relation of risk of systemic lupus erythematosus to west African admixture in a Caribbean population.

Risk of systemic lupus erythematosus (SLE) is higher in people of west African descent than in Europeans. The objective of this study was to distinguish between genetic and environmental explanations for this ethnic difference by examining the relationship of disease risk to individual admixture (defined as the proportion of the genome that is of west African ancestry); 124 cases of SLE and 219 matched controls resident in Trinidad were studied. Analysis of admixture was restricted to 52 cases and 107 controls who reported no Indian or Chinese ancestry. These individuals were typed with a panel of 26 single-nucleotide polymorphisms and five insertion/deletion polymorphisms chosen to have large allele frequency differentials between west African, European and Native American populations. A Bayesian model for population admixture, individual admixture and locus ancestry was fitted by Markov chain simulation. Mean west African admixture (M) was 0.81 in cases and 0.74 in controls (P=0.01). The risk ratio for SLE associated with unit change in M was estimated as 32.5 with a 95% confidence interval (CI) of 2.0-518. Adjustment for measures of socioeconomic status (household amenities in childhood and years of education) altered this risk ratio only slightly (adjusted risk ratio: 28.4, 95% CI 1.7-485). These results support an additive genetic model for the ethnic difference in risk of SLE between west Africans and Europeans, rather than an environmental explanation or an "overdominant" model in which risk is higher in heterozygous than in homozygous individuals. This conclusion lays a basis for localizing the genes underlying this ethnic difference in risk of SLE by admixture mapping.

Adult↗
PubMed2003

Time-resolved explosion of intense-laser-heated clusters.

We investigate the femtosecond explosive dynamics of intense laser-heated argon clusters by measuring the cluster complex transient polarizability. The time evolution of the polarizability is characteristic of competition in the optical response between supercritical and subcritical density regions of the expanding cluster. The results are consistent with time-resolved Rayleigh scattering measurements, and bear out the predictions of a recent laser-cluster interaction model [H. M. Milchberg, S. J. McNaught, and E. Parra, Phys. Rev. E 64, 056402 (2001)]].

Journal Article↗
PubMed2002

Resonant self-trapping of high intensity Bessel beams in underdense plasmas.

We present a comprehensive report based on recent work [Phys. Rev. Lett. 84, 3085 (2000)] on resonant self-trapping and enhanced absorption of high power Bessel beams in underdense plasmas. The trapping resonance is strongly dependent on initial gas pressure, Bessel-beam geometry, and laser wavelength. Analytic estimates, and simulations using a one-dimensional Bessel-beam-plasma interaction code consistently explain the experimental observations. These results are for longer, moderate intensity pulses where the self-trapping channel is induced by laser-heated plasma thermal pressure. To explore the extension of this effect to ultrashort, intense pulsed Bessel beams, we perform propagation simulations using the code WAKE [Phys. Rev. E 53, R2068 (1996)]. We find that self-trapping can occur as a result of a plasma refractive index channel induced by the combined effects of relativistic motion of electrons and their ponderomotive expulsion.

Journal Article↗
PubMed2002

Laparoscopic repair of postoperative perineal hernia.

Perineal hernia is an uncommon complication of abdominoperineal resection and pelvic exenteration. We present an alternative not previously described for the surgical repair of this type of hernia: laparoscopic repair of postoperative perineal hernia.

Herniorrhaphy↗
PubMed2001

Plasma hydrodynamics of the intense laser-cluster interaction.

We present a one-dimensional hydrodynamic model of the intense laser-cluster interaction in which the laser field is treated self-consistently. We find that for clusters initially as small as approximately 25 A in radius nonuniform expansion of the heated material results in long-time resonance of the laser field at the critical density plasma layer. A significant result of this is that the ponderomotive force, which is enhanced at the critical density surface, can be large enough to strongly modify the plasma hydrodynamics, even at laser intensities as low as 10(15) W/cm(2) for 800 nm laser pulses. Simulations of our recent experiments in extreme ultraviolet and x-ray generation from clusters explain the dependence of generation efficiency on laser pulse width.

Journal Article↗
PubMed2001

Identification of a CD28 response element in the CD40 ligand promoter.

Ligation of the T cell coreceptor CD28 or CD2 by its cognate ligands B7-1 or LFA-3, respectively, greatly aids the Ag-induced up-regulation of several genes, including IL-2 and CD40 ligand (CD40L). Using luciferase reporter constructs under the control of the 1.2 kb of 5' noncoding region of the human CD40L gene, we have found that stimulation through CD28 was required for a strong transcriptional activity of the CD40L promoter in response to TCR ligation, while the activity induced by CD2 was slightly lower than CD28. Deletion analysis demonstrated that the transcriptional elements mediating this effect were located within a 300-bp region upstream of the start site. Further dissection of this region and gel shift analyses demonstrated the presence of a CD28 response element in a region located between nucleotides -170 to -164 relative to the start site. Transcriptional studies with a CD40L enhancer-promoter carrying a mutation in this putative CD28 response element revealed that the activity was reduced by 80 and 70% after B7-1 and LFA-3 costimulation, respectively. The transcription factor complex bound to this site contained at least JunD, c-Fos, p50, p65, and c-REL:, but not c-Jun. Mutations introduced into the CD28RE also blocked the binding of this complex. These observations identify an important role for the CD28 signaling pathway in the regulation of CD40L promoter transcriptional activity.

Animals↗
PubMed2001

Skin reflectance in the Han Chinese and Tibetan populations.

Genetic and environmental factors are involved in the determination of skin pigmentation in humans. With the recent development of statistical and genetic tools in mapping complex traits in humans, it is becoming feasible to utilize such methods in identifying genes involved in skin pigmentation. Furthermore, the use of new portable reflectance spectroscopy instruments such as the Photovolt ColorWalk colorimeter allows researchers to measure skin reflectance of a large number of subjects with ease and accuracy. We used a new portable instrument (Photovolt ColorWalk) to study the skin reflectance of 372 Han Chinese and 274 Tibetan individuals to establish background reflectance measurements of unexposed skin of the inner upper arm in these two populations. In addition, we explored the effect of various factors such as age and gender on skin reflectance.

Adolescent↗
PubMed2001

Melting curve analysis of SNPs (McSNP): a gel-free and inexpensive approach for SNP genotyping.

High-throughput methods for assaying DNA variation require two important steps: (i) discriminating the variation and (ii) detecting the signal. In this report, we describe a novel SNP genotyping method that we refer to as melting curve analysis of SNPs (McSNP). McSNP combines a classic approach for discriminating alleles, restriction enzyme digestion, with a more recent method for detecting DNA fragments, melting curve analysis. Melting curve analysis is performed by slowly heating DNA fragments in the presence of the dsDNA-specific fluorescent dye SYBR Green I. As the sample is heated, fluorescence rapidly decreases when the melting temperature of a particular fragment is reached. We show that it is possible to determine the composition of simple mixtures of DNA fragments, such as those that result from restriction enzyme digestions of short PCR products. McSNP is well suited for high-throughput genotyping because 96 samples can be analyzed and automatically scored in 20 min. Our results clearly demonstrate that McSNP is a simple, inexpensive, and accurate means of genotyping SNP variation.

Genotype↗
PubMed2000

Resonant self-trapping and absorption of intense bessel beams

We report the observation of resonant self-trapping and enhanced laser-plasma heating resulting from propagation of high intensity Bessel beams in neutral gas. The enhancement in absorption and plasma heating is directly correlated to the spatial trapping of laser radiation.

Journal Article↗
PubMed2000

X-ray and extreme ultraviolet emission induced by variable pulse-width irradiation of Ar and Kr clusters and droplets

Measurements are presented of x-ray (>1.5 keV) and extreme ultraviolet (EUV, lambda=2-44 nm) emission from argon and krypton supersonic gas jets at room (T=300 K) and cryogenic (T=173 K) temperatures irradiated with constant energy (50 mJ), variable width laser pulses ranging from 100 fs to 10 ns. Two regimes of jet operation are explored: cluster formation (radius<100 nm) and droplet formation (radius>1 &mgr;m). The results for both clusters and droplets can be understood in terms of two time scales: a short time scale for optimal resonant absorption at the critical density layer in the expanding plasma, and a longer time scale for the plasma to drop below critical density.

Journal Article↗
PubMed2000

Tubular plasma generation with a high-power hollow bessel beam

A high power, hollow Bessel beam (J5) is generated using an axicon and a phase plate in combination. The optical breakdown of a gas target and generation of a tubular plasma fiber with such a beam is realized. Hydrodynamic simulations of the hollow beam-plasma breakdown and heating are in reasonable agreement with interferometric measurements of the plasma time evolution.

Journal Article↗
PubMed1999

Analysis of five Y-specific microsatellite loci in Asian and Pacific populations.

We have analyzed five Y-specific microsatellite loci (DYS388, DYS390, DYS391, DYS394, DYS395) in 17 Asian and Pacific populations representing a broad geographical area and different linguistic families, with an emphasis on populations from mainland and insular Southeast Asia. Analysis of gene diversity indicates that several of the studied populations have experienced substantial genetic isolation, and a reduction in male effective sizes (viz. the Northeast Indian populations Nishi, Adi and the Taiwanese aboriginals). The average values of the F(ST) and ((ST) statistics indicate a high degree of genetic differentiation among these populations at the five Y-specific markers (F(ST) =0.21 and ((ST) = 0.33, based on individual loci; F(ST) = 0.09 and ((ST) = 0.36, based on haplotypes), which conform to the expectation of a fourfold smaller effective size of the Y-linked loci compared with the autosomal loci. Dendrogram and principal coordinates analysis, with few exceptions, show a major separation between mainland and insular populations. Among the mainland populations, the Tibeto-Burman speakers from Northeast India cluster in a well-defined group, supported by high bootstrap values. The Southern Chinese, Northern Thai, So, and Cambodian also are integral to this cluster. The other major cluster is rather heterogeneous and includes, among others, the Austronesian-speaking populations. The Samoans of the Pacific, with a distinctive pattern of allelic distributions, stand as an outlier in the tree and PC representations. Although trends of genetic affinities among ethnically and geographically related populations are evident from the Y-specific microsatellite data, microsatellites are not optimal for deciphering complex migratory patterns of human populations, which could possibly be clarified by using additional and more stable genetic markers.

Asia, Southeastern↗
PubMed1999

Genetic variation at 9 autosomal microsatellite loci in Asian and Pacific populations.

Genetic variation at 9 autosomal microsatellite loci (CFS1R, TH01, PLA2A, F13A1, CYP19, LPL, D20S481, D20S473, and D20S604) has been characterized in 16 Asian and Oceanic populations, mostly from mainland and insular Southeast Asia. The neighbor-joining tree and the principal coordinates analysis of the genetic relationships of these populations show a clear separation of Papua New Guinea Highlanders and, to a lesser extent, Malayan aborigines (Orang Asli or Semai) from the rest of the populations. Although the number of markers used in this study appears to be inadequate for clarifying the patterns of genetic relationships among the studied populations, in the principal coordinates analysis a geographic trend is observed in the mainland and insular Southeast Asian populations. Furthermore, in an attempt to contrast the extent of variation between autosomal and Y-chromosome-specific microsatellite loci and to reveal potential differences in the patterns of male and female migrations, we have also compared genetic variation at these 9 autosomal loci with variation observed at 5 Y-chromosome-specific microsatellites in a common set of 14 Asian populations.

Asia↗