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Using probes for rat neural nitric oxide synthase (NOS) mRNA and GnRH mRNA, we performed in situ hybridization to survey NOS mRNA distribution within the hypothalamus of the male and female rat and sought evidence for its expression in GnRH neurons. The NOS cRNA probe was radiolabelled with 35S, and a digoxigenin-labeled rat GnRH cRNA probe was used for double-label studies. NOS mRNA was localized in discrete hypothalamic areas, in grain clusters suggestive of individual neurons. NOS mRNA-positive cells were located mainly in the supraoptic and paraventricular nucleus, particularly overlying the magnocellular division. Rostrally, cells expressing NOS mRNA were especially prominent in the diagonal band of Broca, in a distribution very similar to GnRH neurons. Nevertheless, only one of 370 cells labeled for GnRH mRNA appeared to be positive for NOS mRNA. We conclude that NOS mRNA is located prominently in regions where CRH, AVP and oxytocin cells are located. NOS mRNA-positive cells are located in close proximity to GnRH neurons, but rarely do such neurons express NOS mRNA.

High temperature X-ray investigations of CeO2 films gave a linear thermal expansion coefficient of 11.6 × 10−6 K−1, corresponding to a temperature dependence of the lattice parameter of a 0 = (5.4067 + T × 6.37 × 10 −5 ) A . At oxygen partial pressures pO2 of 0.2–10−22 bar and at temperatures between 800 and 1100°C, the lattice parameter of α'-CeO2 changes linearly with the oxygen partial pressure. The conductivity of substoichiometric CeO2 in the field of the α' phase also changes linearly with the oxygen partial pressure. A plot of pO2vs. the conductivity σ gives a straight line with a slope σ ≈ p O 2 − 1 6 . This slope is constant over the total range of temperatures and oxygen partial pressures. So CeO2 thin films can be used for high temperature oxygen sensors.

The lattice parameters of annealed CeO 2 thin films are between 0.01 and 0.02 A smaller than the literature value for powders and single crystals. The adhesion of the thin films to silicon substrates is insufficient. Thin films on Al 2 O 3 substrates with a film thickness of less than 3 μm show good adhesion in the temperature range from room temperature to 1100°C. The mean value of the lattice parameter a 0 of CeO 2 for samples on Al 2 O 3 substrates is 5.395 A.

The neuroendocrine regulation of pulsatile growth hormone (GH) secretion involves the reciprocal interactions between growth hormone-releasing hormone (GHRH)- and somatostatin-containing neurones, residing primarily in the hypothalamic arcuate nucleus (ARC) and the periventricular nucleus (PeN), respectively. Considerable evidence supports the concept that GH itself participates in the regulation of its own rhythmic secretion through a reciprocal feedback on GHRH and somatostatin neurones. The direct actions of GH are mediated through GH receptors, and in the PeN, the majority of somatostatin neurones express this receptor. GH induces the expression of the immediate early gene c-fos in the ARC; however, few GHRH residing in the ARC express the GH receptor, suggesting that the action of GH on GHRH cells must be indirect through another population of unidentified cells. NPY neurones express c-fos in response to GH, and preliminary results suggest that NPY neurones in the ARC express the GH receptor. These observations suggest that NPY neurones play a physiological role in the feedback of regulation of GH secretion.

The performance of calcium ion-selective microelectrodes based on a neutral carrier for extra- and intra-cellular measurements of free Ca 2+ ions as reported in the recent literature is assessed. A novel membrane consisting of readily available components is presented which overcomes the technical problems associated with very fine electrode tips. Measured selectivity factors, log K pot CaM , for M 2+ = Na + , K + , and Mg 2+ are -5.5, -5.4, and

Certain natural (Stefanac and Simon, 1967) and synthetic (Morf et al., 1979) lipophilic ligands for cations(ion carriers, ionophores) made a wide range of microelectrodes with different selectivities available. Especially the development of electrically neutral ionophores led to clear improvements in selectivities and detection limits. Here we report on the present possibilities in the use of ion-selective liquid membrane microelectrodes.