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173. Impact-collision ion-scattering spectrometry studies of the VC0.8(111)-(8 × 1) surface

Author

Hammar, Mattias, Steele, B. E., Tsong, I. S. T., Hammar, Mattias, Steele, B. E., and Tsong, I. S. T.

Abstract

We use impact-collision ion-scattering spectrometry (ICISS) to verify that the (8 × 1) reconstructed surface of VC0.8(111) arises from the superposition of a rectangular surface vanadium layer on top of the hexagonal bulk, in agreement with a surface structure proposed earlier in a scanning tunneling microscopy (STM) study. However, a major discrepancy with the STM results is the absence of any pronounced buckling within the surface unit cell. The ICISS results suggest that the vanadium layer on the surface is perfectly planar. © 1994., Correspondence Address: Hammar, M.; Department of Physics and Astronomy, Arizona State University, Tempe, AZ 85287, United States NR 20140805

Published
1994
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197. Interaction of Kisspeptin and the Somatotropic Axis.

Author

Whitlock, B. K., Daniel, J. A., Wilborn, R. R., Maxwell, H. S., Steele, B. P., and Sartin, J. L.

Subjects
KISSPEPTIN neurons, LUTEINIZING hormone releasing hormone, HORMONES, METABOLISM, SOMATOTROPIN, GROWTH hormone releasing factor
Abstract

Kisspeptin, a regulator of gonadotropin-releasing hormone, has been hypothesized as an integrator of nutrition and hormones critical to metabolism and the regulation of reproduction. Growth hormone (GH) is necessary for optimal reproduction and recent evidence suggests that its secretion may be influenced by kisspeptin. The objectives of this study were to determine whether the effect of kisspeptin to stimulate GH release is due to an interaction with growth hormone-releasing hormone (GHRH) or somatostatin (SS), or an effect at the hypothalamus. Intravenous injection and infusion of kisspeptin [500 pmol/kg BW (650 ng/kg)/h × 5 h] to cows (n = 5) increased serum concentrations of luteinizing hormone (LH) but not GH. Pretreatment with kisspeptin injection and infusion in cows (n = 5) reduced the stimulatory effect of GHRH (0.05 μg/kg BW) on GH secretion. However, the magnitude of the GH response to GHRH (assessed by incremental AUC) was not affected by kisspeptin. In these same cows, administration of kisspeptin prevented the increase in GH induced by SS infusion (0.5 μg/kg BW/ h × 1.5 h) withdrawal. Peripheral administration of kisspeptin [200 and 1,000 pmol/kg BW (260 and 1,300 ng/kg)] increased serum concentrations of LH but not GH in ewes (n = 8). However, concentrations of GH were stimulated by central kisspeptin treatment [100 and 200 pmol/kg BW (130 and 260 ng/kg)] in ewes. In addition to activating the gonadotropic axis, kisspeptin can activate the somatotropic axis in ruminants. Present data support the concept of a central site of action for this effect. Copyright © 2010 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Published
2010
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