The decrease in growth hormone (GH) response after repeated stimulation with GH-Releasing hormone is partly caused by an elevation of somatostatin tonus.

Repeated injection of GHRH leads to a decrease in the GH response in normal subjects. Arginine (Arg) stimulates GH secretion by suppression of hypothalamic somatostatin. To confirm these findings, eight normal men were examined in a series of five settings: test 1 (GHRH/GHRH-TRH), 100 micrograms GHRH injected iv, followed by 100 micrograms GHRH, iv, after 120 min and 200 micrograms TRH, iv, after 150 min; test 2 (GHRH/Arg-TRH), like test 1, but instead of the second GHRH injection, a 30 g Arg infusion over 30 min; test 3 (GHRH/GHRH-Arg-TRH), like test 1, but additionally a 30 g Arg infusion after 120 min; test 4 (GHRH-Arg-TRH), iv GHRH and Arg infusion initially, followed by iv TRH after 30 min; and test 5 (TRH), 200 micrograms TRH, iv, at 0 min. For statistical evaluation, the area under the GH curve (AUC) from 0-120 min was compared with the AUC from 120-240 min. The GH response to the second administration of GHRH was significantly lower (P < 0.02) than the first increase [AUC, 0.5 +/- 0.01 min.mg/L (mean +/- SE) vs. 1.2 +/- 0.3]. No significant differences were found between the GH responses to either GHRH or Arg alone (AUC, 0.9 +/- 0.2 min.mg/L vs. 0.9 +/- 0.2). A larger GH increase (P < 0.02) was seen after GHRH-Arg compared to GHRH alone (AUC, 1.9 +/- 0.4 min.mg/L vs. 1.2 +/- 0.3). The GH response (P < 0.02) to GHRH-Arg stimulation was lower after previous GHRH injection than after GHRH-Arg stimulation alone (AUC, 1.9 +/- 0.4 min.mg/L vs. 3.5 +/- 0.9). There was a statistically significant difference between the TRH-stimulated TSH response in test 4 compared to that in test 5. We could show that decreasing GH responses to repeated GHRH can be avoided by a combined stimulation with GHRH/Arg. These findings suggest that the decreased GH response to a second GHRH bolus may be partly due to an elevated hypothalamic somatostatin secretion, which can be suppressed by Arg. The lower GH response to GHRH-Arg stimulation after a previous GHRH bolus suggests, furthermore, that the readily available GH pool in the human pituitary may be limited

Subtropical sea-surface warming and increased salinity during Eocene Thermal Maximum 2

Eocene Thermal Maximum 2 (ETM-2; ca. 54.2 Ma) represents the second largest of the major Eocene hyperthermals, yet comparatively little is known about the scale and rate of climatic change for key regions. Here we provide the first detailed records of subtropical sea-surface warming and salinization for ETM-2 at two subtropical locations, Ocean Drilling Program Sites 1209 (North Pacific) and 1265 (South Atlantic). Coupled planktic foraminiferal Mg/Ca and δ18O indicate 2-4 °C of rapid warming and local salinization of ~1-2 ppt at both sites. The increase in sea-surface temperature is equivalent to anomalies reported from higher latitude sites, and is consistent with theory on the expected pattern of spatial temperature response to greenhouse gas forcing in an ice-free world (i.e., no ice-albedo feedback). Similarly, the observed salinization is consistent with the hypothesis of enhanced meridional vapor transport and increased subtropical aridity in a warmer world

Subtropical sea-surface warming and increased salinity during Eocene Thermal Maximum 2

Eocene Thermal Maximum 2 (ETM-2; ca. 54.2 Ma) represents the second largest of the major Eocene hyperthermals, yet comparatively little is known about the scale and rate of climatic change for key regions. Here we provide the first detailed records of subtropical sea-surface warming and salinization for ETM-2 at two subtropical locations, Ocean Drilling Program Sites 1209 (North Pacific) and 1265 (South Atlantic). Coupled planktic foraminiferal Mg/Ca and δ18O indicate 2-4 °C of rapid warming and local salinization of ~1-2 ppt at both sites. The increase in sea-surface temperature is equivalent to anomalies reported from higher latitude sites, and is consistent with theory on the expected pattern of spatial temperature response to greenhouse gas forcing in an ice-free world (i.e., no ice-albedo feedback). Similarly, the observed salinization is consistent with the hypothesis of enhanced meridional vapor transport and increased subtropical aridity in a warmer world

Isotopic composition of benthic and planktic foraminifera and bulk sediment from ODP Holes198-1209A and 208-1265A

Eocene Thermal Maximum 2 (ETM-2; ca. 54.2 Ma) represents the second largest of the major Eocene hyperthermals, yet comparatively little is known about the scale and rate of climatic change for key regions. Here we provide the first detailed records of subtropical sea-surface warming and salinization for ETM-2 at two subtropical locations, Ocean Drilling Program Sites 1209 (North Pacific) and 1265 (South Atlantic). Coupled planktic foraminiferal Mg/Ca and δ18O indicate 2-4 °C of rapid warming and local salinization of ~1-2 ppt at both sites. The increase in sea-surface temperature is equivalent to anomalies reported from higher latitude sites, and is consistent with theory on the expected pattern of spatial temperature response to greenhouse gas forcing in an ice-free world (i.e., no ice-albedo feedback). Similarly, the observed salinization is consistent with the hypothesis of enhanced meridional vapor transport and increased subtropical aridity in a warmer world

Opinion of the Scientific Panel on Plant Health on the pest risk assessment made by Lithuania on Ambrosia spp. : (Question No EFSA-Q_2006-055A)

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