Expression of galanin and a galanin receptor in several sensory systems and bone anlage of rat embryos

Using in situ hybridization and immunohistochemistry the expression of, respectively, prepro-galanin (prepro-GAL) mRNA and GAL receptor-1 mRNA, as well as GAL-like and GAL message-associated peptide-like immunoreactivities, were studied in rats from embryonic day 14 (E14) to postnatal day 1. GAL expression was observed already at E14 in trigeminal and dorsal root ganglion neurons and at E15 in the sensory epithelia in developing ear, eye, and nose, as well as at E19 during bone formation. Also, GAL receptor-1 mRNA was expressed in the sensory ganglia of embryos but appeared later than the ligand. These findings suggest that GAL and/or GAL message-associated peptide may have a developmental role in several sensory systems and during bone formation.

Novel phenomena in dilute electron systems in two dimensions

For the past two decades, all two-dimensional systems of electrons were believed to be insulating in the limit of zero temperature. Recent experiments provide evidence for an unexpected transition to a conducting phase at very low electron densities. The nature of this phase is not understood and is currently the focus of intense theoretical and experimental attention.

Increase in the Quantum Yield of Photoinhibition Contributes to Copper Toxicity in Vivo1

The effect of copper on photoinhibition of photosystem II in vivo was studied in bean (Phaseolus vulgaris L. cv Dufrix). The plants were grown hydroponically in the presence of various concentrations of Cu2+ ranging from the optimum 0.3 μm (control) to 15 μm. The copper concentration of leaves varied according to the nutrient medium from a control value of 13 mg kg−1 dry weight to 76 mg kg−1 dry weight. Leaf samples were illuminated in the presence and absence of lincomycin at different light intensities (500–1500 μmol photons m−2 s−1). Lincomycin prevents the concurrent repair of photoinhibitory damage by blocking chloroplast protein synthesis. The photoinhibitory decrease in the light-saturated rate of O2 evolution measured from thylakoids isolated from treated leaves correlated well with the decrease in the ratio of variable to maximum fluorescence measured from the leaf discs; therefore, the fluorescence ratio was used as a routine measurement of photoinhibition in vivo. Excess copper was found to affect the equilibrium between photoinhibition and repair, resulting in a decrease in the steady-state concentration of active photosystem II centers of illuminated leaves. This shift in equilibrium apparently resulted from an increase in the quantum yield of photoinhibition (ΦPI) induced by excess copper. The kinetic pattern of photoinhibition and the independence of ΦPI on photon flux density were not affected by excess copper. An increase in ΦPI may contribute substantially to Cu2+ toxicity in certain plant species.