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Biomedical subjects

J Marti

Publications and source records attributed to J Marti.

At least 19 recordsLinked to original sources
PubMed2001

Cigarette smoking behavior among US Latino men and women from different countries of origin.

OBJECTIVES: This study sought to compare smoking behavior among Latino men and women from different countries of origin. METHODS: A telephone-administered survey was conducted in 8 cities with Latino men and women of different national origin living in census tracts with at least 70% Latino individuals. RESULTS: A total of 8882 participants completed the survey; 53% were women. The average age of respondents was 44 years; 63% were foreign-born, and 59% preferred Spanish for the interview. Current smoking was more prevalent among men (25.0%, 95% confidence interval [CI] = 23.7, 26.3) than among women (12.1%, 95% CI = 11.1, 13.0). Smoking rates were not significantly different by national origin among men, but Puerto Rican women had higher rates of smoking than other women. Central American men and women had the lowest smoking rates. Foreign-born respondents were less likely to be smokers (odds ratio [OR] = 0.77, 95% CI = 0.66, 0.90) than US-born respondents, and respondents with 12 years or less of education had an increased odds of smoking (OR = 1.17, 95% CI = 1.01, 1.35). High ac culturation was associated with more smoking in women (OR = 1.12, 95% CI = 1.00-1.25) and less smoking in men (OR = 0.86, 95% CI = 0.78-0.95). Puerto Rican and Cuban respondents were more likely to be current smokers and to smoke more than 20 cigarettes per day. CONCLUSIONS: Older, US-born, and more-educated respondents were less likely to be current smokers. Respondents of Puerto Rican and Cuban origin were more likely to smoke. Acculturation has divergent effects on smoking behavior by sex.

Acculturation↗
PubMed2000

Discovery of a high-energy gamma-ray-emitting persistent microquasar

Microquasars are stellar x-ray binaries that behave as a scaled-down version of extragalactic quasars. The star LS 5039 is a new microquasar system with apparent persistent ejection of relativistic plasma at a 3-kiloparsec distance from the sun. It may also be associated with a gamma-ray source discovered by the Energetic Gamma Ray Experiment Telescope (EGRET) on board the COMPTON-Gamma Ray Observatory satellite. Before the discovery of LS 5039, merely a handful of microquasars had been identified in the Galaxy, and none of them was detected in high-energy gamma-rays.

Journal Article↗
PubMed2000

Social networks and cancer screening in four U.S. Hispanic groups.

BACKGROUND: Evidence shows that social relationships play an important role in health and health behavior. We examined the relationship between social networks and cancer screening among four U.S. Hispanic groups. METHODS: We used telephone surveys to collect data in eight U.S. regions that have concentrations of diverse Hispanic-origin populations. We interviewed 8903 Hispanic adults, for a response rate of 83%; analysis was restricted to the 2383 women aged > or =40. As a measure of social integration, we formed a social network index from items on the number of close relatives and friends, frequency of contact, and church membership. We used logistic regression to estimate the effects of social integration on screening, adjusting for sociodemographic factors. RESULTS: Among Mexican, Cuban, and Central-American women, the effect of social integration on mammography screening was slight. The odds ratios (OR) per unit change in social integration category ranged from 1.16 to 1.22 with confidence intervals (CI) that overlapped with the null. For Pap smear screening, the effect was strongest among Mexican-American women (OR=1.44, 95% CI=1.21 to 1.72), but also evident among Central-American women (OR=1.22, 95% CI=0.72 to 2.06) and Cuban women (OR = 1.25, 95% CI = 0.81 to 1.93). Among Puerto Rican women, social integration had no effect on either mammography (OR=1.03) or Pap smear screening (OR=1.08). CONCLUSIONS: Independent of socioeconomic factors, social integration appears to influence cancer screening participation of Hispanic women. The modest effect is not universal across Hispanic groups and was stronger for Pap smear than for mammography screening behavior. Researchers should recognize Hispanic group differences in social network characteristics and the potential of social networks to change screening behavior.

Adult↗
PubMed2000

Breast cancer screening in regional Hispanic populations.

Although Hispanics' use of breast cancer screening services has been investigated, to date there have been no published studies of distinct Hispanic populations in different areas of the country. Using the diverse populations and sites involved in the National Hispanic Leadership Initiative on Cancer 'En Acción', this study examines ethno-regional differences in breast cancer screening rates among these groups and explores the correlates of screening participation. Data collected through telephone surveys were analyzed for women 40 years of age and older (n = 2082). After controlling for demographic variables traditionally related to breast cancer screening rates, it was found that ethno-regional differences in breast cancer screening practices clearly persisted. In addition to traditional demographic factors, other variables evidently underlie differences in Hispanics' utilization of breast cancer screening services. These variables may be cultural and should be investigated in future research. Meanwhile, researchers should not refer to the 'Hispanic' population at large without identifying, addressing and clarifying the ethno-regional characteristics of their samples.

Adult↗
PubMed2000

Dynamic properties of hydrogen-bonded networks in supercritical water

Dynamic properties of supercritical water at temperatures between 573 and 773 K and densities between 0.49 and 0.83 g/cm(3) have been investigated by molecular dynamics simulation and compared to states located on the vapor-liquid coexistence curve. A flexible simple point charge potential has been assumed for interactions in the subcritical states, whereas a reparameterization of that model has been performed to model the supercritical states. The hydrogen bonding structure and the diffusion coefficients in an ensemble of simulated states were previously analyzed and a good agreement with available experimental data was found. Dynamic properties of hydrogen bonding like the bond lifetimes and the influence of hydrogen bonds in the vibrational spectra are discussed along a range of simulation conditions. A nonlinear behavior of the hydrogen-bond lifetime as a function of temperature is observed in subcritical water whereas a linear dependence is found in supercritical water. Special attention is paid to the intermolecular vibrational spectrum (10-400 cm(-1)). It has been observed that the mode centered at 200 cm(-1), attributed to the intermolecular O-O stretching vibration in the ambient state remains active in the supercritical states.

Journal Article↗
PubMed1999

Differential expression of the RTP/Drg1/Ndr1 gene product in proliferating and growth arrested cells.

Using a differential display method to identify differentiation-related genes in human myelomonocytic U937 cells, we cloned the cDNA of a gene identical to Drg1 and homologous to other recently discovered genes, respectively human RTP and Cap43 and mouse Ndr1 and TDD5 genes. Their open reading frames encode proteins highly conserved between mouse and man but which do not share homology with other know proteins. Conditions in which mRNAs are up-regulated suggest a role for the protein in cell growth arrest and terminal differentiation. We raised antibodies against a synthetic peptide reproducing a characteristic sequence of the putative polypeptide chain. These antibodies revealed a protein with the expected 43 kDa molecular mass, up-regulated by phorbol ester, retinoids and 1,25-(OH)2 vitamin D3 in U937 cells. It was increased in mammary carcinoma MCF-7 cells treated by retinoids and by the anti-estrogen ICI 182,780 but not by 4-hydroxytamoxifen. The mouse Drg1 homologous protein was up-regulated by retinoic acid in C2 myogenic cells. The diversity of situations in which expression of RTP/Drg1/Ndr1 has now been observed shows that it is widely distributed and up-regulated by various agents. Here we show that ligands of nuclear transcription factors involved in cell differentiation are among the inducers of this novel protein.

Amino Acid Sequence↗
PubMed1999

Transforming growth factor-beta1 is an autocrine mediator of U937 cell growth arrest and differentiation induced by vitamin D3 and retinoids.

Vitamin D and retinoids cooperate to inhibit the proliferation and induce the differentiation of human myelomonocytic U937 leukemia cells. In the present work, we investigated the role of TGF-beta as an endogenous mediator of this process. We found that the TGF-beta1 precursor began to accumulate in cell culture supernatants soon after the addition of 1alpha,25 dihydroxyvitamin D3 (VD) and retinoids. We used neutralizing antibodies (AbTGF-beta) and antisense oligonucleotide (AS Oligo) to inhibit its possible effects. Our data demonstrated that AbTGF-beta partially inhibit the expression of the differentiated phenotype, as assessed by measurement of phagocytic activity, response to the chemotactic peptide fMLP, and lysozyme secretion. AS Oligo was also inhibitory, and the effects of AS Oligo and AbTGF-beta were cumulative. Cell growth inhibition induced by VD and retinoids was completely reversed, and differentiation was reduced by about 75% when both inhibitors were associated. Time course experiments based on the delayed addition of AbTGF-beta and AS Oligo showed that TGF-beta1 was required for cell differentiation 24 h after the addition of inducers. Studies on TGF-beta receptors revealed that, while the expression of type II receptor was stable, the level of type I TGF-beta receptor mRNA and the expression of the protein began to decline early during the differentiation process. As a whole, these results support the notion that an autocrine TGF-beta pathway, activated by VD and retinoids in U937 cells, is involved in the early steps of the process leading to cell growth arrest and differentiation.

Antibodies↗
PubMed1999

Hypospadias in a polar bear (Ursus maritimus).

Corrective surgery on a 1.5-yr-old male polar bear (Ursus maritimus) with hypospadias included amputation of the vestigial penis, bilateral orchiectomy with scrotal ablation, and distal perineal urethrostomy. Hypospadias in other species is a congenital deformity that may be caused by extra- and intrauterine factors resulting in a disruption of the testosterone balance during urethral development, but the causative mechanism in this bear is unknown. The urethrostomy site was functional without complications 8 mo after surgery.

Animals↗
PubMed1998

Carbon structures with three-dimensional periodicity at optical wavelengths

Porous carbons that are three-dimensionally periodic on the scale of optical wavelengths were made by a synthesis route resembling the geological formation of natural opal. Porous silica opal crystals were sintered to form an intersphere interface through which the silica was removed after infiltration with carbon or a carbon precursor. The resulting porous carbons had different structures depending on synthesis conditions. Both diamond and glassy carbon inverse opals resulted from volume filling. Graphite inverse opals, comprising 40-angstrom-thick layers of graphite sheets tiled on spherical surfaces, were produced by surface templating. The carbon inverse opals provide examples of both dielectric and metallic optical photonic crystals. They strongly diffract light and may provide a route toward photonic band-gap materials.

Journal Article↗
PubMed1997

Biological monitoring of styrene exposure and possible interference of acetone co-exposure.

The object of this study is the evaluation of some of the toxicokinetic effects of exposure to low concentrations of styrene, and the possible influence of simultaneous exposure to acetone. To this end we studied 19 workmen simultaneously exposed to both solvents. During a week of 4-h work shifts, the workmen underwent daily personal environmental monitoring and the collection of urine samples, at both the beginning and the end of the work period, for the determination of mandelic acid (MA) and phenylglyoxylic acid (PGA). The presence of the solvents in the atmosphere was evaluated using passive personal monitoring and gas chromatography. Average exposure to styrene and acetone were respectively 72.2 mg/m3 and 225.7 mg/m3. MA and PGA were quantified by high-performance liquid chromatography (HPLC). The daily urinary concentration averages, both at commencement and at the end of work shifts, of both the metabolites studied and of the sum of the two were in statistically significant linear correlation with the average daily styrene exposure. Concentrations of MA and PGA in urine samples collected at the start of the work shift averaged 61.5 mg/g creatinine and 45.2 mg/g creatinine respectively, representing 41% and 72% of those at the endo of the work shift which were 148.3 and 62.6 mg/g creatinine, respectively. With equal exposure to styrene, the average urinary concentrations of MA and PGA at both the beginning and end of the work shift increased significantly (P < 0.001) during the working week. Moreover, we found that with equal exposure to styrene, urinary excretion of MA, PGA and MA + PGA at the end of the shift was inversely correlated with the intensity of acetone exposure (r = 0.4659, 0.3410 and 0.542 respectively, P < 0.001). In conclusion, these results express slower urinary kinetics of styrene metabolites than is usually described in the literature, and favor a tendency to accumulate MA and PGA in the organism as a consequence of the retardation of urinary excretion kinetics. Acetone apparently represents one of the determining factors in this interference.

Acetone↗
PubMed1997

Potentiation of VD-induced monocytic leukemia cell differentiation by retinoids involves both RAR and RXR signaling pathways.

Retinoids and vitamin D (VD) cooperate to induce the differentiation and inhibit the proliferation of human myelomonocytic leukemia cells. Two classes of retinoids receptors, the RARs and RXRs, respectively, can mediate these effects. RXR forms heterodimers with a variety of nuclear receptors, including RAR and the VD receptor. We have previously found that VD treatment increases RXR alpha levels in myelomonocytic leukemia cells. By immunoanalysis, we observed in the present work that the RAR alpha protein is expressed in proliferating U937, HL-60 and THP-1 human leukemia cells and that VD treatment induces alterations of its electrophoretic pattern, although with large differences between cell lines. In the three cell lines, 9-cis RA, an agonist of both RARs and RXRs, cooperated with VD more efficiently than all-trans RA and RAR-specific synthetic ligands, thus suggesting an involvement of both RAR and RXR pathways in cell differentiation. Using U937 cells as a model, we delineated the relative contributions of RAR and RXR by assessing the effects of receptor-selective synthetic retinoids. The synergy between VD and all-trans RA or RAR-specific agonists (TTNPB and Ro 40-6055) was abrogated by a RAR alpha-specific antagonist (Ro 41-5253), confirming an involvement of RAR alpha. However, the cooperation between VD and 9-cis RA, although reduced, was not suppressed by the antagonist, suggesting also an involvement of the RXR pathway. The role of RXR as a ligand-activated receptor was confirmed using RXR-specific agonists (CD2608 and LGD1069), which also proved able to cooperate with VD. Finally, while each synthetic agonist alone was significantly less potent than 9-cis RA, combinations of the RAR and RXR selective agonists TTNPB and LGD1069 appeared to be as effective as the pan agonist 9-cis-RA. These results confirm that various retinoids can cooperate with VD and demonstrate that, at a whole cell level, optimal effects require the activation of both RAR and RXR receptors.

Alitretinoin↗
PubMed1997

Synthesis and biological activities of higher homologues of retinoic acid.

Homoretinoic and bishomoretinoic acid have been synthesized. Fast reaction under ultrasonic activation (Wolff rearrangement, saponification) produced compounds in high yields. Only the bishomo analogue exhibits a significative activity alone and a synergistic effect with vitamin D3 on the differentiation of U937 leukemic cell line.

Antineoplastic Agents↗
PubMed1996

Expression of Retinoid X Receptor alpha is increased upon monocytic cell differentiation.

1 alpha, 25-Dihydroxyvitamin D3 (VD) is a potent inducer of monocytic differentiation of both normal and leukemic cells. Its effects are mediated by its nuclear receptor (VDR). Efficient gene activation requires the heterodimerization of VDR with Retinoid X Receptors (RXR). In the present study using specific antibodies, we analyzed the expression of the RXR alpha protein in blood mononuclear cells from acute myeloid patients (AML) (10 cases) and from myelomonocytic cell lines arrested at different stages of differentiation. We observed that the RXR alpha expression increased during myelomonocytic differentiation, since the highest levels were found in AML samples and in myelomonocytic cell lines having the highest amounts of monocytic precursors. We also demonstrated that fresh leukemic cells, whatever their stage of differentiation, as well as myelomonocytic cell lines, respond to VD by an increase in RXR alpha levels. Combinations of all-trans retinoic acid (RA) and VD, in some cases, increased this effect. This response suggests the involvement of RXR alpha in monocytic differentiation upon VD treatment.

Calcitriol↗
PubMed1996

Forced swimming behavior is not related to the corticosterone levels achieved in the test: a study with four inbred rat strains.

The behavior of four inbred strains of rats in the holeboard and the forced swimming tests, and its relationship with a physiological index of stress (serum corticosterone) were studied in adult male rats. The strains were: Fisher 344 (FIS), Lewis (LEW), Spontaneously hypertensive (SHR), and Wistar-Kyoto (WKY). In the holeboard, SHR rats were the most active and WKY the less active, the other strains showing intermediate levels of activity. During the first exposure to forced swimming WKY were far more passive than the other three strains and the same was observed during the second exposure. When corticosterone levels after this second exposure to water was determined, LEW rats showed lower values than the other three strains. Therefore, no apparent relationship between behavior and stress-induced corticosterone secretion exists. Although a single point measurement of only on physiological index of stress has important limitations, the present data do not give support to a strong relationship between the behavior of the animals in the forced swimming test and emotional reactivity to stress. It is therefore possible that forced swimming behavior might not be mainly a panic-like reaction, but the result of the tendency of the animals to adopt passive strategies in inescapable situations. Although more studies are needed to firmly establish this assumption, WKY rats might be, at least potentially, a useful model of depressive-like behavior.

Animals↗