Demonstration of a low V pi L modulator with GHz bandwidth based on electro-optic polymer-clad silicon slot waveguides

We demonstrate a near-infrared electro-optic modulator with a bandwidth of 3 GHz and a V(pi)L figure of merit of 0.8 V-cm using a push-pull configuration. This is the highest operating speed achieved in a silicon-polymer hybrid system to date by several orders of magnitude. The modulator was fabricated from a silicon strip-loaded slot waveguide and clad in a nonlinear polymer. In this geometry, the electrodes form parts of the waveguide, and the modulator driving voltage drops across a 200 nm slot.

Comparative sensitivity of harbour and grey seals to several environmental contaminants using in vitro exposure

In this study, we investigated the effects of cadmium chloride (CdCl(2)), mercury chloride (HgCl(2)), methylmercury chloride (CH(3)HgCl), and PCBs on lymphocyte proliferation in phocids. PBMCs isolated from harbour and grey seals were exposed in vitro to varying concentrations of contaminants. A reduction of viability occurred when cells were exposed to 10(-4)M HgCl(2) or CH(3)HgCl or to 50ppm of Aroclor 1254. In both grey and harbour seals, T-lymphocyte proliferation was suppressed when their cells were incubated with 5 x 10(-5)M CdCl(2) or 10(-4)M HgCl(2). An inhibition of proliferation occurred with CH(3)HgCl from 10(-6)M in grey seals and from 10(-5)M in harbour seals. In grey seals, Aroclor 1254 reduced lymphocyte proliferation at 15ppm. In both harbour and grey seals, CH(3)HgCl was ten times more immunotoxic that HgCl(2). From IC(50), chemicals were ranked in terms of toxicity as followed: CH(3)HgCl>CdCl(2)>HgCl(2)>Aroclor 1254.

Impacts of pollution in feral Mya arenaria populations: the effects of clam bed distance from the shore

This study examined the relationships between population characteristics and the expression of physiological biomarkers of stress in an intertidal clam population under pollution at sites differing in thermal history and coastline distance. The clam population metrics were age distribution, growth, condition factor, distance of the clam beds from the shore, and gonad development. Physiological biomarkers comprised biomarkers of defence such as superoxide dismutase, labile IIb metals in tissues, redox status of metallothioneins and glutathione S-transferase, of tissue damage such as lipid peroxidation and DNA strand breaks, of reproduction as determined by vitellogenin-like proteins and gonadosomatic index and immunocompetence such as phagocytosis and hemocyte viability. Age-related pigments were also examined to compare the physiological age of the clams with their chronological age. The results showed that all the above biomarkers were significantly affected at one of the two polluted sites at least. Distance from the shore was significantly correlated with most (81%) of the biomarkers examined. Clams collected at one polluted site were physiologically older than clams from the corresponding reference site. Canonical and adaptive regression (artificial neural networks) analyses found that the biomarkers measured in this study were able to predict the ecologically relevant endpoints. Biomarkers implicated in defense mechanisms, tissue damage and age-related pigments were most closely related to the clam population characteristics. Sensitivity analysis of the learning algorithm found that the following physiological and biochemical markers were the most predictive, in decreasing order, of clam population characteristics: glutathione S-transferase, phagocytosis, age pigments, lipid peroxidation in the gills, labile IIb metals and total MT levels. These biomarkers were affected by the distance of the clam beds from the shore, site quality (pollution) and reproduction activity.

Immunotoxicological effects of an activated-sludge-treated effluent on rainbow trout (Oncorhynchus mykiss)

Municipal effluents are often treated by biological processes designed to enhance natural biodegradation that introduce important changes to the local bacterial community and contaminant status. The purpose of this study was to examine the immunotoxicological effects of an activated sludge treated urban effluent on rainbow trout (Oncorhynchus mykiss). Trout specimens were exposed to increasing concentrations of the effluent at 0.1%, 1% and 10% v/v dilutions for 30 days at 15 degrees C. After the exposure period, the leukocytes were isolated from the anterior kidney and the following parameters were determined: phagocytic activity, lymphoblastic transformation and natural cytotoxic activity. The results revealed that phagocytic activity was not significantly affected by the biologically treated effluent. Natural cytotoxic activity was significantly increased at an effluent threshold concentration of 3% v/v at an effector/target cell ratio of 20:1 and 40:1. Stimulated lymphocyte T and B proliferation was significantly decreased at a threshold concentration of 0.3%. However, neither the unstimulated lymphocyte T nor lymphocyte B proliferation was significantly affected by effluent exposure. The results suggest that the activated-sludge-treated effluent increased cell-mediated cytotoxic activity with a concomitant decrease in cells responsible for antibody and cytokine production, indicating that the immune system of rainbow trout was directed towards the elimination of transformed cells, virus-infected cells and protozoan parasites at the expense of cytokine and antibody production.

An in-situ study of the impacts of urban wastewater on the immune and reproductive systems of the freshwater mussel Elliptio complanata

The goal of this study was to examine the disruptive effects of municipal effluents on the immune and reproductive systems of freshwater mussels. For 30 days, caged mussels were immersed in the Rivière des Mille Iles (Quebec, Canada), 150 m both upstream and downstream from two urban wastewater treatment plants: station F (Fabreville) and station A (Auteuil), which serve the city of Laval. Station F is 12 km upstream from station A. The immune and reproductive statuses of the mussels were thereafter determined. Though the weight/shell length ratio was not affected, the effluent induced mortality up to 60% at downstream sites. Total hemocyte counts increased, and phagocytosis and lysozyme activities were induced at station F, whereas these responses were suppressed at station A. Heterotrophic bacteria levels in mussels were negatively correlated with phagocytosis, showing the importance of this process in defending against infection. Inflammation biomarkers such as nitric oxide and cyclooxygenase activity were the same for all sites but were positively correlated with phagocytosis activity. The production of vitellogenin (Vtg)-like proteins was significantly induced at the site downstream from station A and was strongly associated with phagocytosis. This was further supported through analysis of covariance, of Vtg responses against phagocytosis, revealing that Vtg was no longer induced at the sites upstream and downstream from station A. The data support the contention that Vtg was involved, in part at least, in the immune system in mussels. Both Vtg and immune status are impacted by urban effluents and should be considered when using the Vtg biomarker to search for the presence of (xeno)estrogens in contaminated environments.

Immunohistochemical study of HLA-G expression in lung transplant recipients

Human leukocyte antigen-G (HLA-G), a nonclassical HLA class I protein, promotes immune tolerance of solid-organ allografts, yet its role in lung transplantation (LTx) is unknown. We examined the expression of HLA-G in lung allografts through immunohistochemistry by a cross-sectional study of 64 LTx recipients, classified into four groups (stable patients, acute rejection [AR], bronchiolitis obliterans syndrome [BOS] and symptomatic viral shedders). A marked expression of HLA-G in bronchial epithelial cells (BEC) was frequently observed in stable recipients (n = 18/35 [51%]), but not in patients with AR (n = 14) or with BOS (n = 8). HLA-G was also expressed by 4 of 7 symptomatic viral shedders. In addition, HLA-G-positive patients from the stable group (n = 35) experienced lower incidence of resistant AR and/or BOS during long-term follow-up, as compared with their HLA-G-negative counterparts. Finally, in vitro data showed that interferon-gamma, a cytokine present in lung allograft microenvironment, upregulated HLA-G mRNA and protein expression in primary cultured human BEC. We conclude that HLA-G expression in the bronchial epithelium of lung allograft is elevated in some LTx recipients in association with their functional stability, suggesting a potential role of HLA-G as a tolerance marker.

Pathomechanisms of cyst formation in pulmonary light chain deposition disease

Cystic lung light chain deposition disease (CL-LCDD) is a recently described rare disorder characterised by numerous cysts and diffuse monoclonal nonamyloid light chain deposits surrounded by macrophagic giant cells. The mechanisms responsible for cyst development remain unknown. The objectives of the present study were to analyse the major components of the pulmonary extracellular matrix in CL-LCDD and to determine the influence of metalloproteinases (MMPs) by comparison with other cystic lung disorders. A virtually complete degradation of the elastic network was found in CL-LCDD. To a lesser degree, loss of fibrillar and basement membrane collagens was also observed. Macrophagic giant cells expressed MMP-1, MMP-2, MMP-9, MMP-12 and MMP-14 and in situ zymography highlighted a strong gelatinolytic activity. As in CL-LCDD, cystic lesions in Langerhans' cell histiocytosis (LCH) and lymphangioleiomyomatosis (LAM) were characterised by the lack of elastic fibres. Similarly, MMP were expressed in CL-LCDD and LCH but the labelled cells were different. In contrast, few MMPs were detected in LAM. In conclusion, elastolysis is common to cystic lung light chain deposition disease and other cystic lung disorders, suggesting its implication in cyst formation. Moreover, in cystic lung light chain deposition disease, a role of metalloproteinases in elastolysis is strongly indicated by the metalloproteinase expression and activity pattern.

Investigation of transport processes inside karst aquifer by means of STATIS

Environmental data sets are often multidimensional and consequently display complex structure. This article shows the limitations of principal component analysis (PCA) for the study of such three-dimensional (3D) data sets. These limitations can be resolved by the use of the statistical tool STATIS. The inlet (a swallow hole) and the outlet (a spring) of a karst system of the Western Paris basin were sampled during three rain events of various intensities. These 3D geochemical data sets (variables x sites x dates) for a karst system were analyzed by STATIS method to identify hydrological processes. STATIS proceeds in three steps (interstructure, compromise, and intrastructure), which allows us to focus the analysis of hydrologic systems at different temporal and spatial scales. Compromise plane shows that suspended matter and flood are not simultaneous and highlights a rapid flow, characterized by turbidity and phosphate, which represents a point source contamination, and a ground water flow contaminated by nitrate. Intrastructure plane allows us to compare hydrochemical variations between the swallow hole and the spring lead. By this way, hydrological processes such as direct transfer and resuspension of intrakarstic sediments before and after the flood were identified what cannot be realized by comparison of inlet and outlet breakthrough curves. Finally, results obtained from the same data set by STATIS and a coupled study using PCA and normalized hysteresis curves were compared. This comparison shows the efficiency of STATIS at the identification of transport processes and vulnerability of karst system and its potential for hydrological applications.

Variation of daily warm season mortality as a function of micro-urban heat islands

Background:

Little attention has been paid to how heat-related health effects vary with the micro-urban variation of outdoor temperatures. This study explored whether people located in micro-urban heat islands are at higher risk of mortality during hot summer days.

Methods:

Data used included (1) daily mortality for Montreal (Canada) for June–August 1990–2003, (2) daily mean ambient outdoor temperatures at the local international airport and (3) two thermal surface images (Landsat satellites, infrared wavelengths). A city-wide temperature versus daily mortality function was established on the basis of a case-crossover design; this function was stratified according to the surface temperature at decedents’ place of death.

Results:

The risk of death on warm summer days in areas with higher surface temperatures was greater than in areas with lower surface temperatures.

Conclusions:

This study suggests that measures aimed at reducing the temperature in micro-urban heat islands (eg, urban greening activities) may reduce the health impact of hot temperatures. Further studies are needed to document the variation of heat-related risks within cities and to evaluate the health benefits of measures aimed at reducing the temperature in micro-urban heat islands.

HIV-1 integrase trafficking in S. cerevisiae: a useful model to dissect the microtubule network involvement of viral protein nuclear import

Intracellular transport of karyophilic cargos comprises translocation to the nuclear envelope and subsequent nuclear import. Small cargos such as isolated proteins can reach the nuclear envelope by diffusion but movement of larger structures depends on active translocation, typically using microtubules. Centripetal transport ends at the perinuclear microtubule organizing centre called the spindle pole body (SPB) in yeast. Previously, we found by two hybrids that the karyophilic lentiviral-encoded integrase (IN) interacts with two yeast microtubule-associated proteins, Dyn2p (dynein light chain protein) and Stu2p, a centrosomal protein (de Soultrait et al., 2002). Thus, to investigate the hinge between cytoplasmic retrograde transport and nuclear import, we decided to analyse HIV-1 IN trafficking in yeast as the model, since each of these biological mechanisms is evolutionarily conserved in eukaryotic cells. Here, we found an accumulation of IN at the SPB in yeast via Stu2p colocalization. Disruption of the microtubule network by nocodazole or IN expression in a dynein 2-deficient yeast strain prevented IN accumulation in the nuclear periphery and additionally inhibited IN transport into the nucleus. By mutagenesis, we showed that trafficking of IN towards the SPB requires the C-terminus of the molecule. Taking our findings together, we proposed a model in which IN nuclear import seems to depend on an essential intermediate step in the SPB. We found that Dyn2p and Stu2p play an important role in driving IN toward MTOC and could optimize nuclear entry of the retroviral enzyme. Our results suggest a new hypothesis in keeping with the current HIV-1 intracellular trafficking model.

Functional diversity in gravitropic reaction among tropical seedlings in relation to ecological and developmental traits

Gravitropism is necessary for plants to control the orientation of their axes while they grow in height. In woody plants, stem re-orientations are costly because they are achieved through diameter growth. The functional diversity of gravitropism was studied to check if the mechanisms involved and their efficiency may contribute to the differentiation of height growth strategies between forest tree species at the seedling stage. Seedlings of eight tropical species were grown tilted in a greenhouse, and their up-righting movement and diameter growth were measured over three months. Morphological, anatomical, and biomechanical traits were measured at the end of the survey. Curvature analysis was used to analyse the up-righting response along the stems. Variations in stem curvature depend on diameter growth, size effects, the increase in self-weight, and the efficiency of the gravitropic reaction. A biomechanical model was used to separate these contributions. Results showed that (i) gravitropic movements were based on a common mechanism associated to similar dynamic patterns, (ii) clear differences in efficiency (defined as the change in curvature achieved during an elementary diameter increment for a given stem diameter) existed between species, (iii) the equilibrium angle of the stem and the anatomical characters associated with the efficiency of the reaction also differed between species, and (iv) the differences in gravitropic reaction were related to the light requirements: heliophilic species, compared to more shade-tolerant species, had a larger efficiency and an equilibrium angle closer to vertical. This suggests that traits determining the gravitropic reaction are related to the strategy of light interception and may contribute to the differentiation of ecological strategies promoting the maintenance of biodiversity in tropical rainforests.

Protein kinase C-delta mediates von Willebrand factor secretion from endothelial cells in response to vascular endothelial growth factor (VEGF) but not histamine

BACKGROUND

Vascular endothelial growth factor (VEGF) and histamine induce von Willebrand factor (VWF) release from vascular endothelial cells. Protein kinase C (PKC) is involved in the control of exocytosis in many secretory cell types.

OBJECTIVES

We investigated the role of PKC and the interactions between PKC and Ca2+ signaling in both VEGF-induced and histamine-induced VWF secretion from human umbilical vein endothelial cells (HUVECs).

RESULTS

Several PKC inhibitors (staurosporine, Ro31-8220, myristoylated PKC peptide inhibitor and Go6983) block VEGF-induced but not histamine-induced VWF secretion. PKC-alpha and novel PKCs (PKC-delta, PKC-epsilon, and PKC-eta), but not PKC-beta, are expressed in HUVECs. Both VEGF and histamine activate PKC-delta. However, gene inactivation experiments using small interfering RNA indicate that PKC-delta (but not PKC-alpha) is involved in the regulation of VEGF-induced but not histamine-induced secretion. Both VEGF and histamine induce a rise in cytosolic free Ca2+ ([Ca2+]c), but the response to VEGF is weaker and even absent in a significant subset of cells. Furthermore, VEGF-induced secretion is largely preserved when the rise in [Ca2+]c is prevented by BAPTA-AM.

CONCLUSIONS

Our study identifies striking agonist specificities in signal-secretion coupling. Histamine-induced secretion is dependent on [Ca2+]c but not PKC, whereas VEGF-induced secretion is largely dependent on PKC-delta and significantly less on [Ca2+]c. Our data firmly establish the key role of PKC-delta in VEGF-induced VWF release, but suggest that a third, VEGF-specific, signaling intermediate is required as a PKC-delta coactivator.

The effects of a primary-treated municipal effluent on the immune system of rainbow trout (Oncorhynchus mykiss): exposure duration and contribution of suspended particles

Municipal sewage effluents are complex mixtures of contaminants known to disrupt both immune and endocrine functions in aquatic organisms. The present study sought to determine the impacts of municipal effluent on the immune systems of juvenile rainbow trout (Oncorhynchus mykiss), by exposing specimens to low concentrations (0.01%, 0.1%, 1% or 10%) of sewage effluent for periods of 28 or 90 days. The soluble and insoluble fractions of the effluent were also studied to assess the contribution of fractions rich in microorganisms and particles on fish immune systems. To this end, the trout were also exposed to soluble and insoluble fractions of the effluent for a period of 28 days. Immunocompetence was assessed by the following three parameters: phagocytosis, natural cytotoxic cells (NCC) and blastogenesis of lymphocytes under mitogen stimulation. Fish exposed to the 1% sewage effluent concentration for 28 days had enhanced phagocytic activity; at 90 days, phagocytic activity was reduced. T and B lymphocyte proliferation in fish from both groups was similarly stimulated. Phagocytosis and NCC activities were influenced more by the insoluble fraction than the soluble fraction of the effluent. Conversely, mitogen-stimulated T lymphocyte proliferation was enhanced in cells of fish exposed to the soluble fraction of the effluents, with a dampening effect on the insoluble (particulate) fraction of the effluent. In conclusion, the effects of the effluent and its fractions were higher at the cellular-mediated immunity level than at the acquired immunity level. Immunotoxicity data on the soluble fraction of the effluent were more closely associated to data on the unfractionated effluent, but the contribution of the particulate fraction could not be completely ignored for phagocytosis and B lymphocyte proliferation.

Effects of ozone, ultraviolet and peracetic acid disinfection of a primary-treated municipal effluent on the immune system of rainbow trout (Oncorhynchus mykiss)

Municipal sewage effluents are complex mixtures that are known to compromise the health condition of aquatic organisms. The aim of this study was to evaluate the impacts of various wastewater disinfection processes on the immune system of juvenile rainbow trout (Oncorhynchus mykiss). The trout were exposed to a primary-treated effluent for 28 days before and after one of each of the following treatments: ultraviolet (UV) radiation, ozonation and peracetic acid. Immune function was characterized in leucocytes from the anterior head kidney by the following three parameters: phagocytosis activity, natural cytotoxic cells (NCC) function and lymphocyte (B and T) proliferation assays. The results show that the fish mass to length ratio was significantly decreased for the primary-treated and all three disinfection processes. Exposure to the primary-treated effluent led to a significant increase in macrophage-related phagocytosis; the addition of a disinfection step was effective in removing this effect. Both unstimulated and mitogen-stimulated T lymphocyte proliferation in fish decreased dramatically in fish exposed to the ozonated effluent compared to fish exposed to either the primary-treated effluent or to aquarium water. Stimulation of T lymphocytes proliferation was observed with the peracetic acid treatment group. In conclusion, the disinfection strategy used can modify the immune system in fish at the level of T lymphocyte proliferation but was effective to remove the effects on phagocytosis activity.

Dysregulation of elastin expression by fibroblasts in pulmonary emphysema: role of cellular retinoic acid binding protein 2

BACKGROUND

All-trans retinoic acid (ATRA) stimulates elastin synthesis by lung fibroblasts and induces alveolar regeneration in animal models of pulmonary emphysema. However, ATRA treatment has had disappointing results in human emphysema. It was hypothesised that a defect in the ATRA signalling pathway contributes to the defect of alveolar repair in the human emphysematous lung.

METHODS

Fibroblasts were cultured from the lung of 10 control subjects and eight patients with emphysema. Elastin and retinoic acid receptor (RAR)-beta mRNAs were measured in those cells in the presence of incremental concentrations of ATRA. RARs, retinoic X receptors (RXRs) and cellular retinoic acid binding protein (CRABP) 1 and 2 mRNAs were measured as well as CRABP2 protein content. The effect of CRABP2 silencing on elastin and RAR-beta expression in response to ATRA was measured in MRC5 lung fibroblasts.

RESULTS

ATRA at 10(-9) M and 10(-8) M increased median elastin mRNA expression by 182% and 126% in control but not in emphysema fibroblasts. RAR-beta mRNA expression was induced by ATRA in control as well as emphysema fibroblasts. RARs, RXRs and CRABP1 mRNAs were similarly expressed in control and emphysema fibroblasts while CRABP2 mRNA and protein were lower in emphysema fibroblasts. CRABP2 silencing abrogated the induction of elastin but not RAR-beta expression by ATRA in MRC5 fibroblasts.

CONCLUSION

Pulmonary emphysema fibroblasts fail to express elastin under ATRA stimulation. CRABP2, which is necessary for elastin induction by ATRA in MRC-5 cells, is expressed at low levels in emphysema fibroblasts. This alteration in the retinoic acid signalling pathway in lung fibroblasts may contribute to the defect of alveolar repair in human pulmonary emphysema. These results are the first demonstration of the involvement of CRABP2 in elastin expression.