Methylene blue-mediated Photodynamic Therapy in human retinoblastoma cell lines.

Retinoblastoma is a malignant tumor of the retinal precursor cells and one of the rarest types of pediatric tumor, often occurring in the earliest years of life. Symptoms are conditioned by tumor size and location; one of the most recurrent symptoms is a white reflex in the pupillary area, called leukocoria or cat's eye reflex. In the present work, we studied the in vitro effectiveness of Photodynamic treatment (Pdt) in two types of human retinoblastoma, Y79 and WERI-Rb cell lines, using methylene blue (MB), a photosensitizer (PS) from the phenothiazine group. The two cell lines were incubated with varying concentrations of MB (3, 7, 10, 15, 20, 25, 30, 40, and 50 µM), in the absence of light (dark cytotoxicity) and, in the presence of 664 nm laser light (phototoxicity) with fluences of 1, 1.5, 3, 5, 7, 10, and 15 J/cm2. The Y79 cell line showed higher cellular uptake values for MB than the WERI-Rb cell line. After three hours of incubation, the Y79 and WERI-Rb took up 48% and 34% of the total photosensitizer present in the medium, respectively. Using MTT assay, the results showed that the Y79 cell line was more affected by the photo treatment as demonstrated by the combination of MB concentration and light doses compared with WERI-Rb cell line. The results were correlated with the more pronounced singlet oxygen emission observed in Y79 cells. While MB does show efficacy for eradication of retinoblastoma in vitro, only studies in appropriate animal models will reveal whether the selectivity of photokilling at tolerable drug and light doses is sufficient to suggest clinical trials.

Association of lifestyle and demographic factors with estrogenic and glucocorticogenic activity in Mexican American women.

Breast cancer risk is higher in US-born than in foreign-born Hispanics/Latinas and also increases with greater length of US residency. It is only partially known what factors contribute to these patterns of risk. To gain new insights, we tested the association between lifestyle and demographic variables and breast cancer status, with measures of estrogenic (E) and glucocorticogenic (G) activity in Mexican American women. We used Chemical-Activated LUciferase gene eXpression assays to measure E and G activity in total plasma from 90 Mexican American women, without a history of breast cancer at the time of recruitment, from the San Francisco Bay Area Breast Cancer Study. We tested associations of nativity, lifestyle and sociodemographic factors with E and G activity using linear regression models. We did not find a statistically significant difference in E or G activity by nativity. However, in multivariable models, E activity was associated with Indigenous American ancestry (19% decrease in E activity per 10% increase in ancestry, P = 0.014) and with length of US residency (28% increase in E activity for every 10 years, P = 0.035). G activity was associated with breast cancer status (women who have developed breast cancer since recruitment into the study had 21% lower G activity than those who have not, P = 0.054) and alcohol intake (drinkers had 25% higher G activity than non-drinkers, P = 0.015). These associations suggest that previously reported breast cancer risk factors such as genetic ancestry and alcohol intake might in part be associated with breast cancer risk through mechanisms linked to the endocrine system.

Birthplace and esophageal cancer incidence patterns among Asian-Americans.

The incidence of esophageal adenocarcinoma in the United States has risen rapidly over the last 30 years, whereas the incidence of esophageal squamous cell carcinoma has fallen dramatically. In contrast, parts of Asia have extremely high rates of squamous cell carcinoma, but virtually no adenocarcinoma. Within the United States, Asian-Americans as a whole, have low rates of esophageal adenocarcinoma and higher rates of squamous cell carcinoma. It is unclear what the patterns are for those Asians born in the United States. The relative influence of ethnicity and environment on the incidence of esophageal cancer in this population is unknown. We identified all cases of esophageal adenocarcinoma and squamous cell carcinoma from the California Cancer Registry 1988-2004, including 955 cases among 6 different Asian ethnicities. Time trends were examined using Joinpoint software to calculate the annual percentage changes in regression models. Rates of esophageal squamous cell carcinoma varied substantially among different Asian ethnic groups, but squamous cell carcinoma was much more common than adenocarcinoma in both foreign-born and US-born Asian-Americans. Rates of squamous cell carcinoma were slightly higher among US-born Asian men (4.0 per 100,000) compared with foreign-born Asian men (3.2 per 100,000) and White men (2.2 per 100,000), P = 0.03. Rates of adenocarcinoma were also slighter higher among US-born Asian men (1.2 per 100,000) compared with foreign-born Asian men (0.7 per 100,000), P = 0.01. Rates of squamous cell carcinoma decreased for both US-born and foreign-born Asians during this period, whereas adenocarcinoma remained low and stable. These results provide better insight into the genetic and environmental factors affecting the changing incidence of esophageal cancer histologies in the United States and Asia.

Hodgkin lymphoma incidence in California Hispanics: influence of nativity and tumor Epstein-Barr virus.

PURPOSE: For classical Hodgkin lymphoma (HL), migrant studies could elucidate contributions of environmental factors (including Epstein-Barr virus (EBV)) to the lower rates in non-whites. Given the well-described etiologic complexity of HL, this research requires a large, immigrant population, such as California Hispanics. METHODS: With 1988-2004 California Cancer Registry data (2,595 Hispanic, 8,637 white HL cases) and tumor cell EBV status on a subset (218 Hispanics, 656 whites), we calculated ethnicity- and nativity-specific HL incidence rates simultaneously by age, sex, and histologic subtype, and tumor cell EBV prevalence. RESULTS: Compared with white rates, Hispanic HL rates were lower overall (70 %) and for nodular sclerosis HL, particularly among young adults (60-65 % for females). However, they were higher among children (200 %) and older adults, and for mixed cellularity HL. Compared with rates in foreign-born Hispanics, rates in US-born Hispanics were higher among young adults (>threefold in females), lower for children and adults over age 70, and consistently intermediate compared with rates in whites. EBV tumor prevalence was 67, 32, and 23 % among foreign-born Hispanics, US-born Hispanics, and whites, respectively, although with variation by age, sex, and histology. CONCLUSIONS: Findings strongly implicate environmental influences, such as nativity-related sociodemographic differences, on HL occurrence. In addition, lower young adult rates and higher EBV prevalence in US-born Hispanics than in whites raise questions about the duration/extent of environmental change for affecting HL rates and also point to ethnic differences in genetic susceptibility. Lesser variation in mixed cellularity HL rates and greater variation in rates for females across groups suggest less modifiable factors interacting with environmental influences.

The phase-resolved photoacoustic method to indicate chemical assignments of paracetamol.

In this work, the phase-resolved photoacoustic method was applied to provide specific information on the chemical assignments of paracetamol in the near-infrared region. Two broad bands, centered at 1370 and 1130 nm, were well-resolved using this method, making it possible to assign the peaks centered at 1398, 1355 and 1295 nm to a C-H combination from a CH3 structure and the peak at 1305 nm to a C-H combination from the aromatic ring. This information represents a new finding in chemical studies regarding this medicament.

Tricritical-like behavior of the nonlinear optical refraction at the nematic-isotropic transition in the E7 thermotropic liquid crystal.

We use Z-scan technique to investigate the nonlinear optical response of the thermotropic liquid crystal E7 in the neighborhood of the nematic-isotropic phase transition. The analysis of the data for the nonlinear optical birefringence is compatible with an effective critical exponent of the order parameter, ß = 0.28 ± 0.03, which is close to the classical value, ß = 0.25 , for a tricritical point. The nonlinear optical absorption in the nematic range depends on the geometrical configuration of the nematic director with respect to the polarization beam, and vanishes in the isotropic phase.

Cu and Fe metallic ions-mediated oxidation of low-density lipoproteins studied by NMR, TEM and Z-scan technique.

In this work we report on a study of the morphological changes of LDL induced in vitro by metallic ions (Cu(2+) and Fe(3+)). These modifications were characterized by transmission electron microscopy, nuclear magnetic resonance and the Z-scan technique. The degree of oxidative modification of LDL was determined by the TBARS and lipid hydroperoxides assays. It is shown that distinct pathways for modifying lipoproteins lead to different morphological transformations of the particles characterized by changes in size and/or shape of the resulting particles, and by the tendency to induce aggregation of the particles. There were no evidence of melting of particles promoted by oxidative processes with Cu and Fe.

Cu and Fe metallic ions-mediated oxidation of low-density lipoproteins studied by NMR, TEM and Z-scan technique

In this work we report on a study of the morphological changes of LDL induced in vitro by metallic ions (Cu2+ and Fe3+). These modifications were characterized by transmission electron microscopy, nuclear magnetic resonance and the Z-scan technique. The degree of oxidative modification of LDL was determined by the TBARS and lipid hydroperoxides assays. It is shown that distinct pathways for modifying lipoproteins lead to different morphological transformations of the particles characterized by changes in size and/or shape of the resulting particles, and by the tendency to induce aggregation of the particles. There were no evidence of melting of particles promoted by oxidative processes with Cu and Fe.

Thermal diffusivity and the conformal transformation on nematic liquid crystals.

In this paper, we will study theoretically and experimentally the anisotropy of the thermal diffusivity in nematic liquid crystals. We will show that the Baalss-Hess conformal transformation [D. Baalss and S. Hess, Phys. Rev. Lett. 57, 86 (1986)], can be used to obtain a free of adjustable parameters equation that describes the anisotropy of the heat diffusion in these materials. The results of this theory will be compared with experimental data. This study will partially confirm the widely known experimental evidences that indicate that the thermal diffusivity is larger in the director direction than in the one perpendicular to it. For calamitic nematic phases this is true; for discotic nematic ones the reverse situation would be found; the diffusivity would become larger in the direction perpendicular to the director. We will also present experimental data supporting this theoretical prediction. The data comprehend the calamitic and discotic nematic lyotropic phases and a nematic thermotropic phase.

Thermodiffusion in a multicomponent lyotropic mixture in the vicinity of the critical micellar concentration by using the Z -scan technique.

Thermodiffusion in a lyotropic mixture of water and potassium laurate is investigated by means of an optical technique (Z scan) distinguishing the index variations due to the temperature gradient and the mass gradients. A phenomenological framework allowing for coupled diffusion is developed in order to analyze thermodiffusion in multicomponent systems. An observable parameter relating to the mass gradients is found to exhibit a sharp change around the critical micellar concentration, and thus may be used to detect it. The change in the slope is due to the markedly different values of the Soret coefficients of the surfactant and the micelles. The difference in the Soret coefficients is due to the fact that the micellization process reduces the energy of interaction of the ball of amphiphilic molecules with the solvent.

Nonlinear refractive index measurements of discotic and calamitic nematic lyotropic phases.

In this work, through the Z-scan technique, we report on measurements of the nonlinear refractive index (n{2}) in discotic and calamitic nematic phases at room temperature in lyotropic mixtures of potassium laurate, decanol and D(2)O . This technique presents high sensitivity when compared to conventional interferometry. The nonlinear optical birefringence (Deltan{2}) of these nematic phases was also determined. The sign and absolute value of this relevant nonlinear parameter are discussed in terms of structural changes in the micellar configuration which takes place in each nematic lyotropic phase.

Characterization of native and oxidized human low-density lipoproteins by the Z-scan technique.

The nonlinear optical response of human normal and oxidized by Cu2+ low-density lipoproteins particles (LDL), were investigated by the Z-scan technique as a function of temperature and concentration of LDL particles. The Z-scan signals increase linearly with concentration of normal LDL particles, following the usual Beer-Lambert law in a broad range of concentrations. The oxidized LDL particles do not show nonlinear optical response. On the other hand, normal LDL increases its nonlinear optical response as a function of temperature. These behaviors can be attributed to an absorbing element that is modified by the oxidative process. Contrarily, changes in the physical state of the cores and conformation of the ApoB100 protein due to an increase in temperature seems to enhance their nonlinear optical properties. This tendency is not due to aggregation of particles. The main contribution to the nonlinear optical response of normal LDL particles comes from the phospholipid fraction of the particles.

Surface-induced orientational phase transition in a lyotropic liquid crystal observed by nonlinear optical techniques.

We have observed a phase transition from a uniaxial to a biaxial nematic phase in a lyotropic liquid crystal as a function of decreasing film thickness. The results, obtained by optical second-harmonic generation experiments in a wedged cell geometry, are supported by additional Z -scan measurements and can be interpreted by wall-induced ordering effects.

Effect of the concentration of magnetic grains on the linear-optical-absorption coefficient of ferrofluid-doped lyotropic mesophases: deviation from the Beer-Lambert law.

In this paper is reported a systematic experimental study of the linear-optical-absorption coefficient of ferrofluid-doped isotropic lyotropic mixtures as a function of the magnetic-grains concentration. The linear optical absorption of ferrolyomesophases increases in a nonlinear manner with the concentration of magnetic grains, deviating from the usual Beer-Lambert law. This behavior is associated to the presence of correlated micelles in the mixture which favors the formation of small-scale aggregates of magnetic grains (dimers), which have a higher absorption coefficient with respect to that of isolated grains. We propose that the indirect heating of the micelles via the ferrofluid grains (hyperthermia) could account for this nonlinear increase of the linear-optical-absorption coefficient as a function of the grains concentration.

Behavior of the nonlinear refractive indices and birefringence in the neighborhood of first- and second-order phase transitions in lyotropic liquid crystals.

We investigated the behavior of the nonlinear refractive indices (n(2)) and birefringence (Delta n(2)) in the vicinity of the nematic-to-isotropic (N-I) and nematic uniaxial-to-nematic biaxial (N-N) phase transitions in a lyotropic liquid crystal. The single-beam Z-scan technique is used to measure n(2) in different relative configurations of the electric field of the laser beam and the symmetry axes of the phases. In the N-I transition, the nonlinear optical birefringence shows a discontinuity at the transition temperature (T(c)), as observed in the linear birefringence. On the other hand, in the N-N transition, Delta n(2) was shown to be proportional to /T-T(c)/(-beta), with beta approximately 0.5, in both uniaxial and biaxial nematic domains. No discontinuity was observed on Delta n(2) in the N-N transition. The symmetric invariants of the order parameter were shown to be linear functions of the temperature in the uniaxial nematic domain, in good agreement with the mean-field prediction.