Magnetization Process of Atacamite: A Case of Weakly Coupled S=1/2 Sawtooth Chains.

We present a combined experimental and theoretical study of the mineral atacamite Cu_{2}Cl(OH)_{3}. Density-functional theory yields a Hamiltonian describing anisotropic sawtooth chains with weak 3D connections. Experimentally, we fully characterize the antiferromagnetically ordered state. Magnetic order shows a complex evolution with the magnetic field, while, starting at 31.5 T, we observe a plateaulike magnetization at about M_{sat}/2. Based on complementary theoretical approaches, we show that the latter is unrelated to the known magnetization plateau of a sawtooth chain. Instead, we provide evidence that the magnetization process in atacamite is a field-driven canting of a 3D network of weakly coupled sawtooth chains that form giant moments.

Glycinergic input of small-field amacrine cells in the retinas of wildtype and glycine receptor deficient mice.

Amacrine cells are known to express strychnine-sensitive glycine receptors (GlyRs), however, it is not known which of the four GlyRalpha subunits (alpha1-4) are expressed in this diverse group of cells. Herein, we studied the presence of glycine activated currents and spontaneous inhibitory postsynaptic currents (sIPSCs) of amacrine cells in the mouse retina. By recording glycinergic currents in retinal slices of wildtype mice and of mice deficient in GlyRalpha subunits (Glra1spd-ot, Glra2-/-, Glra3-/-), we could classify AII and narrow-field amacrine cells (NF, Types 5, 6, 7) on the basis of their alpha-subunit composition. Glycinergic sIPSCs of AII cells displayed medium fast kinetics (mean decay time constant tau=11+/-2 ms), which were completely absent in the Glra3-/- mouse, indicating that synaptic GlyRs of AII cells mainly contain the alpha3 subunit. Glycinergic sIPSCs of NF cells had slow kinetics (tau=27+/-6.8 ms) that were significantly prolonged in Glra2-/- mice (tau=69+/-16 ms). These data show that morphologically distinct amacrine cells express different sets of GlyRs.

Oestrogen receptor-beta and neurohypophysial hormones: functional interaction and neuroanatomical localisation.

Oestrogens affect fluid balance, influencing both ingestive behaviour and renal excretion. The renal effects are partly due to altered release of vasopressin and oxytocin. This study was designed to explore the role of oestrogen receptor-beta (ERbeta) in neurohypophysial hormonal function. Following dietary administration, soya isoflavones reach the brain in sufficient concentration to activate ERbeta, but not oestrogen receptor-alpha (ERalpha). ERbeta function was therefore manipulated by feeding rat diets differing in soya isoflavone content. Fluid balance and neurohypophysial hormone release were measured in male rats maintained for 14 days on a soya isoflavone-free diet or one containing 150 microg/g genistein+daidzein. Food and water intake, body weight, urine flow, osmolality and sodium concentrations were determined daily. After 14 days, plasma and urine osmolality and sodium, vasopressin and oxytocin concentrations were determined. There was no significant difference in weight gain between the two groups or in their excretion of sodium and water or plasma sodium and plasma oxytocin. However, plasma vasopressin was significantly lower in the iso-free group. Double-label immunocytochemistry was used to assess colocalisation of ERbeta with the neurohypophysial hormones in male rats. Cell nuclei showing ERbeta immunoreactivity were abundant in the posterior magnocellular paraventricular nucleus (PVNpm) and in the supraoptic nucleus (SON). Vasopressin-immunoreactive neurones were similarly distributed, forming the core of the PVNpm and the ventral portion of the SON; majority were positive for ERbeta. Cells with oxytocin immunoreactivity were located mainly at the periphery of the PVNpm and in the dorsal SON; only approximately a quarter of these cells showed ERbeta immunoreactivity. Thus, the difference in the effects of the soya diet on vasopressin and oxytocin release may be related to the ERbeta-activating properties of this diet and to the preponderance of this receptor in vasopressin as opposed to oxytocin cells.