Arabidopsis leaf hydraulic conductance is regulated by xylem sap pH,controlled, in turn,by a P-type H+-ATPase of vascular bundle sheath cells

The leaf vascular bundle sheath cells (BSCs) that tightly envelop the leaf veins, are a selective and dynamic barrier to xylem sap water and solutes radially entering the mesophyll cells. Under normal conditions, xylem sap pH below 6 is presumably important for driving and regulating the transmembranal solute transport. Having discovered recently a differentially high expression of a BSC proton pump, AHA2, we now test the hypothesis that it regulates the xylem sap pH and leaf radial water fluxes. We monitored the xylem sap pH in the veins of detached leaves of wild-type Arabidopsis, AHA mutants and aha2 mutants complemented with AHA2 gene solely in BSCs. We tested an AHA inhibitor (vanadate) and stimulator (fusicoccin), and different pH buffers. We monitored their impact on the xylem sap pH and the leaf hydraulic conductance (K_leaf), and the effect of pH on the water osmotic permeability (P_f) of isolated BSCs protoplasts. We found that AHA2 is necessary for xylem sap acidification, and in turn, for elevating K_leaf. Conversely, AHA2 knockdown, which alkalinized the xylem sap, or, buffering its pH to 7.5, reduced K_leaf, and elevating external pH to 7.5 decreased the BSCs P_f. All these showed a causative link between AHA2 activity in BSCs and leaf radial hydraulic water conductance.     

Histochemical evidence of β‐chitin in parapodial glandular organs and tubes of Spiophanes (Annelida,Sedentaria: Spionidae), and first studies on selected Annelida

A generic character of the genus Spiophanes (Annelida, Sedentaria: Spionidae) is the presence of parapodial glandular organs. Parapodial glandular organs in Spiophanes species include secretory cells with cup‐shaped microvilli, similar to those present in deep‐sea inhabiting vestimentiferans and frenulate Siboglinidae. These cells are supposed to secrete β‐chitin for tube‐building. In this study, transverse histological and/or ultrathin sections of parapodial glandular organs and tubes of Spiophanes spp. as well as of Glandulospio orestes (Spionidae) and Owenia fusiformis (Oweniidae) were examined. Fluorescent markers together with confocal laser scanning microscopy, and Raman spectroscopy were used to detect chitin in the parapodial glandular organs of Spiophanes and/or in the glands of Owenia and Glandulospio. Tubes of these taxa were tested for chitin to elucidate the use of it for tube‐building. The examinations revealed a distinct labelling of the gland contents. Raman spectroscopy documented the presence of β‐chitin in both gland types of Spiophanes. The tubes of Spiophanes were found to have a grid‐like structure that seems to be built with this β‐chitin. Tests of tubes of Dipolydora quadrilobata (Spionidae) for chitin were negative. However, the results of our study provide strong evidence that Spiophanes species, O. fusiformis and probably also G. orestes produce chitin and supposedly use it for tube‐building. This implies that the production of chitin and its use as a constituent part of tube‐building is more widespread among polychaetes as yet known. The histochemical data presented in this study support previous assumptions inferring homology of parapodial glandular organs of Spionidae and Siboglinidae based on ultrastructure. Furthermore, transmission electron microscopy‐based evidence of secretory cells with nail‐headed microvilli in O. fusiformis suggests homology of parapodial grandular organs across annelids including Sipuncula. J. Morphol. 276:1433–1447, 2015. © 2015 Wiley Periodicals, Inc.     

DNA Isolation and AFLP Fingerprinting of Nectarine and Peach Varieties (Prunus persica)

Traditional identification of peach and nectarine varieties relies on the assessment of agronomic traits of the adult plant. This leads to a significant delay of time, constraints to breeders in the surveillance of germplasm and a risk for fruit growers and exporters. We describe a method for rapid assessment of peach and nectarine varieties based on AFLP fingerprinting and extraction of high quality DNA. The best primer pairs were selected from 64 primer combinations that reliably distinguished 8 peach and 6 nectarine varieties. A graphical representation of the detected polymorphisms was shown to simplify the analysis.     

Parents like me: biosociality and lay expertise in self-help groups of parents of screen-positive newborns

This study focuses on patterns of communication and interaction for peer support, which develop among parents of screen-positive children in the socio-medical space created by the diagnostic uncertainty of newborn screening, the limitations of established patient support groups and the daily challenges of screen-positive care management. Based on semi-structured interviews conducted in 2015–2017 with 34 Israeli parents whose child is screen positive, we describe and analyze the spontaneous grouping of parents using the WhatsApp instant messaging service for smartphones. These self-help groups did not reflect an attempt to forge an alternative movement of de-medicalization but rather to provide satisfactory answers to shared problems of care management under diagnostic uncertainty. These self-help groups are further discussed as a form of biosociality and lay expertise where elements of communication such as simplicity, reciprocity, and deliberative democracy serve as a complementary mirror-image of the asymmetrical patient–doctor communication.     

Optical‐mechanical signatures of cancer cells based on fluctuation profiles measured by interferometry

We propose to establish a cancer biomarker based on the unique optical‐mechanical signatures of cancer cells measured in a noncontact, label‐free manner by optical interferometry. Using wide‐field interferometric phase microscopy (IPM), implemented by a portable, off‐axis, common‐path and low‐coherence interferometric module, we quantitatively measured the time‐dependent, nanometer‐scale optical thickness fluctuation maps of live cells in vitro. We found that cancer cells fluctuate significantly more than healthy cells, and that metastatic cancer cells fluctuate significantly more than primary cancer cells. Atomic force microscopy (AFM) measurements validated the results. Our study shows the potential of IPM as a simple clinical tool for aiding in diagnosis and monitoring of cancer. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

In vitro enzyme evolution: the screening challenge of isolating the one in a million

The generation of large mutant libraries for in vitro enzyme evolution presents the challenge of effectively screening libraries of 10⁴–10⁷ mutants on the basis of simultaneously assaying their biocatalytic activity. In this review, we highlight the main steps involved in this process, describe the alternative approaches to address this challenge, survey the state-of-the-art technology and assess achievements already made. It is anticipated that, as a result of the expected accomplishment of further improvements in high-throughput screening that will allow routine screening of whole libraries, the number of useful new and improved enzymes derived through in vitro enzyme evolution will expand rapidly in the near future.