Enzymatic degradation of polar lipids in Vigna unguiculata leaves and influence of drought stress

¹⁴C-labelled polar lipids (monogalactosyl-diacylglycerol [MGDG], digalactosyl-diacylglycerol [DGDG], phosphatidylcholine [PC] and phosphatidylglycerol [PG]), purified from Vigna unguiculata leaves, were used as substrates to study the lipolytic activities of Vigna unguiculata leaf extracts. Analysis of the radioactive degradation products revealed the presence of at least three enzyme activities contributing to the hydrolysis of the four main leaf membrane lipids: Lipolytic acyl hydrolase (LAH) activities responsible for the deacylation of galactolipids and phospholipids, phospholipase D (PLD, EC 3.1.4.4) activity which gives rise to phosphatidic acid, and as suggested by the presence of diacylglycerols in minor quantities after phospholipid hydrolysis, phosphatidate phosphohydrolase (PAP, EC 3.1.3.4) and/or phospholipase C (PLC, EC 3.1.4.3.) activity. Under the conditions described in the present paper, the presence of phospholipase A (PLA₁, EC 3.1.1.3 and PLA₂, EC 3.1.1.4) activities remains hypothetical, due to the absence of lysophospholipids. LAH and PLD were partially soluble and partially associated with the membranes. When Vigna unguiculata plants were submitted to drought, the enzymatic degradation of galactolipids and phospholipids increased. The stimulation of lipolytic activities was greater in the drought-sensitive cultivar of Vigna unguiculata (cv. 1183) than in the drought-tolerant (cv. EPACE-1) one. In cv. 1183, MGDG- and DGDG-LAH activities in the membrane fractions were dramatically stimulated at a rather moderate water deficit (?0.75 MPa). A sharp increase in membrane phospholipolytic activities was also observed at mild drought stress (?1.2 MPa). In contrast, in cv. EPACE-1, the stimulation of lipolytic activities was less drastic and occurred at lower leaf water potentials (below ?1.2 MPa for galactolipases, and below ?1.4 MPa for phospholipases). Our results confirm the presence in leaves of higher plants of a very active LAH acting on galactolipids, whereas PLD is the main enzyme responsible for the degradation of phospholipids, particularly when plants are submitted to drought stress. The differences in stimulation of lipolytic activities between the two Vigna cultivars was in accordance with the different levels of membrane lipid degradation shown previously and could explain their different capacity to sustain drought.     

Transnational family ties of immigrants in the Netherlands

Inspired by recent efforts in the United States to quantify the degree of transnational ties that immigrants possess, this article explores and analyses the prevalence and determinants of transnational family ties of immigrants in the Netherlands. Using data from a representative survey of four immigrant groups in the Netherlands, this paper also aims to fill the gap in knowledge regarding the effects of incorporation into an immigrant's host society on transnational family ties. Findings show that, while the vast majority of immigrants with relatives in the country of origin have frequent contact with these relatives, only a third of respondents contribute to the livelihood of family members in the homeland. Incorporation characteristics show distinct patterns over different types of involvement. While incorporation variables have a negative effect on the frequency of contact, they show little effect on remittances.     

Chemical sensing of DNT by engineered olfactory yeast strain

With the increasing threat of environmental toxicants including biological and chemical warfare agents, fabricating innovative biomimetic systems to detect these harmful agents is critically important. With the broad objective of developing such a biosensor, here we report the construction of a Saccharomyces cerevisiae strain containing the primary components of the mammalian olfactory signaling pathway. In this engineered yeast strain, WIF-1alpha, olfactory receptor signaling is coupled to green fluorescent protein expression. Using this 'olfactory yeast', we screened for olfactory receptors that could report the presence of the odorant 2,4-dinitrotoluene, an explosive residue mimic. With this approach, we have identified the novel rat olfactory receptor Olfr226, which is closely related to the mouse olfactory receptors Olfr2 and MOR226-1, as a 2,4-dinitrotoluene-responsive receptor.     

Characterization of cytoskeleton mechanical properties and 3D-actin structure in twisted adherent epithelial cells

Evaluation of the cytoskeleton mechanical properties requires specific micromanipulation techniques such as the magnetic twisting cytometry technique, in which microbeads are specifically linked to the cytoskeleton via transmembrane receptors. The aim of the study was to assess the structural relationship between the bead and the cytoskeleton structure. The spatial arrangement of the CSK network was therefore studied in fixed cells probed by beads and stained for F-actin by rhodamined phallo?dine. The spatial character of the actin CSK network, both in the bead neighborhood and at the cell scale, could then be studied for various degrees of fluorescent intensity from 3D-images of the actin structure, reconstructed from z-stack views obtained by confocal microscopy. Results show the feasibility of the staining/reconstruction technique which allows to reveal the three-dimensional organization of the cytoskeleton structure including an internal cytosolic structure with a high fluorescent F-actin intensity, and a sub-membranous cortical structure with a low fluorescent F-actin intensity.     

Tensegrity behaviour of cortical and cytosolic cytoskeletal components in twisted living adherent cells

The present study is an attempt to relate the multicomponent response of the cytoskeleton (CSK), evaluated in twisted living adherent cells, to the heterogeneity of the cytoskeletal structure - evaluated both experimentally by means of 3D reconstructions, and theoretically considering the predictions given by two tensegrity models composed of (four and six) compressive elements and (respectively 12 and 24) tensile elements. Using magnetic twisting cytometry in which beads are attached to integrin receptors linked to the actin CSK of living adherent epithelial cells, we specifically measured the elastic CSK response at quasi equilibrium state and partitioned this response in terms of cortical and cytosolic contributions with a two-component model (i.e., a series of two Voigt bodies). These two CSK components were found to be prestressed and exhibited a stress-hardening response which both characterize tensegrity behaviour with however significant differences: compared to the cytosolic component, the cortical cytoskeleton appears to be a faster responding component, being a less prestressed and easily deformable structure. The discrepancies in elastic behaviour between the cortical and cytosolic CSK components may be understood on the basis of prestress tensegrity model predictions, given that the length and number of constitutive actin elements are taken into account.     

An accurate definition of the status of inactive hepatitis B virus carrier by a combination of biomarkers (FibroTest-ActiTest) and viral load

Background

The combination of transaminases (ALT), biopsy, HBeAg and viral load have classically defined the inactive status of carriers of chronic hepatitis B. The use of FibroTest (FT) and ActiTest (AT), biomarkers of fibrosis and necroinflammatory activity, has been previously validated as alternatives to biopsy. We compared the 4-year prognostic value of combining FT-AT and viral load for a better definition of the inactive carrier status.

Methods and Findings

1,300 consecutive CHB patients who had been prospectively followed since 2001 were pre-included. The main endpoint was the absence of liver-related complications, transplantation or death. We used the manufacturers'' definitions of normal FT (< = 0.27), normal AT (< = 0.29) and 3 standard classes for viral load. The adjustment factors were age, sex, HBeAg, ethnic origin, alcohol consumption, HIV-Delta-HCV co-infections and treatment.

Results

1,074 patients with baseline FT-AT and viral load were included: 41 years old, 47% African, 27% Asian, 26% Caucasian. At 4 years follow-up, 50 complications occurred (survival without complications 93.4%), 36 deaths occurred (survival 95.0%), including 27 related to HBV (survival 96.1%). The prognostic value of FT was higher than those of viral load or ALT when compared using area under the ROC curves [0.89 (95%CI 0.84–0.93) vs 0.64 (0.55–0.71) vs 0.53 (0.46–0.60) all P<0.001], survival curves and multivariate Cox model [regression coefficient 5.2 (3.5–6.9; P<0.001) vs 0.53 (0.15–0.92; P = 0.007) vs −0.001 (−0.003−0.000;P = 0.052)] respectively. A new definition of inactive carriers was proposed with an algorithm combining “zero” scores for FT-AT (F0 and A0) and viral load classes. This new algorithm provides a 100% negative predictive value for the prediction of liver related complications or death. Among the 275 patients with the classic definition of inactive carrier, 62 (23%) had fibrosis presumed with FT, and 3 died or had complications at 4 year.

Conclusion

In patients with chronic hepatitis B, a combination of FibroTest-ActiTest and viral load testing accurately defined the prognosis and the inactive carrier status.     

Concordance in a World without a Gold Standard: A New Non-Invasive Methodology for Improving Accuracy of Fibrosis Markers

Background

Assessing liver fibrosis is traditionally performed by biopsy, an imperfect gold standard. Non-invasive techniques, liver stiffness measurements (LSM) and biomarkers [FibroTest® (FT)], are widely used in countries where they are available. The aim was to identify factors associated with LSM accuracy using FT as a non-invasive endpoint and vice versa.

Methods

The proof of concept was taken using the manufacturers recommendations for excluding patients at high risk of false negative/positive. The hypothesis was that the concordance between LSM and FT, would be improved by excluding high-risk patients. Thereafter, the impact of potential variability factors was assessed by the same methods. Liver biopsy and independent endpoints were used to validate the results.

Results

Applying manufacturers'' recommendations in 2,004 patients increased the strength of concordance between LSM and FT (P<0.00001). Among the 1,338 patients satisfying recommendations, the methodology identified a significant LSM operator effect (P = 0.001) and the following variability factors (all P<0.01), related to LSM: male gender, older age, and NAFLD as a cause of liver disease. Biopsy confirmed in 391 patients these results.

Conclusion

This study has validated the concept of using the strength of concordance between non-invasive estimates of liver fibrosis for the identification of factors associated with variability and precautions of use.     

Dual assessment of airway area profile and respiratory input impedance from a single transient wave.

This report concerns the inference of geometric and mechanical airway characteristics based on information derived from a single transient planar wave recorded at the airway opening. We describe a new method to simultaneously measure upper airway area and respiratory input impedance by performing dual analysis of a single pressure wave. The algorithms required to reconstruct airway dimensions and mechanical characteristics were developed, implemented, and tested with reference to known physical models. Our method appears suitable to estimate, even under severe intensive care unit conditions, the respiratory system frequency response (above 10 Hz) in intubated patients and the patency of the endotracheal tube used to connect the patients to the ventilator.     

Segmental analysis of nasal cavity compliance by acoustic rhinometry.

To explore the determinants of possible collapse of the nasal valve region, a common cause of nasal obstruction, we evaluated the mechanical properties of the nasal wall. In this study, we determined the nasal cross-sectional area-to-negative pressure ratio (nasal wall compliance) in the anterior part of the nose in six healthy subjects by measuring nasal area by acoustic rhinometry at pressures ranging from atmospheric pressure to a negative pressure of -10 cmH(2)O. Measurements were performed at baseline and after nasal mucosal decongestion (oxymetazoline). At baseline, nasal wall compliance increased progressively from the nasal valve (0.031 +/- 0.016 cm2/cmH(2)O, mean +/- SD) to the anterior and medial part of the inferior turbinate (0.045 +/- 0.024 cm2/cmH(2)O) and to the middle meatus region (0.056 +/- 0.029 cm2/cmH(2)O). After decongestant, compliances decreased and became similar in the three regions. On the basis of these results, we hypothesize that compliance of the nasal wall is partly related to mucosal blood volume and quantity of vascular tissue, which differ in the three regions, increasing from the nasal valve to the middle meatus.