Role of growth hormone in regulating lipolysis, proteolysis, and hepatic glucose production during fasting

CONTEXT: Fasting is associated with suppressed insulin and augmented GH secretion. The involvement of each mechanism in the regulation of fuel mobilization during fasting is unknown. OBJECTIVE: To ascertain the role of GH in the regulation of the rates of lipolysis, proteolysis, and hepatic glucose production (HGP) during the physiological daily feed/fast cycle and after 2 d of complete fasting, we used a model of selective GH suppression by the administration of GHRH receptor antagonist (GHRH-A). DESIGN AND SETTING: We conducted an open label in-patient study in the General Clinical Research Center at the University of Michigan. PARTICIPANTS: Six healthy, nonobese volunteers participated. MAIN OUTCOME MEASURES: We assessed 24-h plasma GH concentration and rates of lipolysis, proteolysis, and HGP using stable isotope techniques after an overnight fast and after 2 d of fasting. RESULTS: GHRH-A suppressed plasma GH by about 65% during the fed state (P = 0.015) but did not alter the rates of lipolysis, proteolysis, or HGP. Fasting for 2 d suppressed plasma insulin concentration by about 80% and elevated plasma GH about 4-fold (both P < 0.01). This was accompanied by a doubling in the rate of lipolysis, an approximately 40% increase in proteolysis, and an approximately 30% decline in HGP (all P < 0.05). Preventing the fasting-induced increase in GH with GHRH-A largely abolished the increase in the rate of lipolysis. GHRH-A also augmented the fasting-induced reduction in HGP but did not alter proteolysis. CONCLUSIONS: Endogenous GH plays a very limited metabolic role during the daily feed/fast cycle but is essential for the increased lipolytic rate found with more prolonged fasting.     

Elastic Moduli of Non-Chiral Singe-Walled Silicon Carbide Nanotubes: Numerical Simulation Study

Silicon carbide nanotubes (SiCNTs) have generated significant research interest due to their potential use in the fabrication of electronic and optoelectronic nanodevices and biosensors. The exceptional chemical, electrical and thermal properties of SiCNTs are beneficial for their application in high-temperature and harsh-environments. In view of the limited thermal stability of carbon nanotubes, they can be replaced by silicon carbide nanotubes in reinforced composites, developed for operations at high temperatures. However, fundamentally theoretical studies of the mechanical properties of the silicon carbide nanotubes are at an early stage and their results are still insufficient for designing and exploiting appropriate nanodevices based on SiCNTs and reinforced composites. In this context, the present study deals with the determination of Young’s and shear moduli of non-chiral single-walled silicon carbide nanotubes, using a three-dimensional finite element model.     

Permanent inflation of detachable balloons with a low-viscosity, hydrophilic polymerizing system

A polymer system was developed for use in permanent inflation of detachable balloons, to avoid long-term reliance on the integrity of balloon shells or valve mechanisms. This system is based on 2-hydroxy-ethyl methacrylate (HEMA) as the monomer, in combination with a cross-linking agent and a water-soluble curing system. The low-viscosity, hydrophilic mixture can be exchanged through a small-bore catheter into a detachable balloon and polymerizes in 40-60 minutes at body temperature. Partially polymerized HEMA can cause vascular occlusion; hence, careful timing of balloon detachment is required. The evolution of the radiographic appearance of HEMA-filled balloons is predictable. The balloons remain radiopaque on plain radiographs as long as the balloon shell and valve mechanisms are competent. After rupture of the shell or failure of the valve mechanism, the balloons become invisible on plain radiographs but remain hyperattenuating on computed tomography scans.     

Problems of Psychological Monitoring in Astronaut Training

在进行职业训练时，对受训者的心理变化趋势进行监视是必要的。航天员心理因素的发展水平可通过心理测试来检测，以便能对其重要的心理指标进行评价，并给出综合评价。文中列出应进行测试的心理指标，并根据大量的样本统计给出了经验加权因子。测试结果的积累可以预测航天员将来飞行任务中处理复杂问题的能力，并能帮助改进训练过程及暴露缺点。     

Regional differences in the noradrenergic and cholinergic innervation of the pial arteries of the brain

Considerable regional differences in the noradrenergic innervation of the pial arteries of rats were found histochemically (by the condensation reaction with glyoxal). The distal portions of the arteries (arterial bordering zones) were not innervated or were much less richly innervated then the proximal portions (the zones of supply of the individual vessles_. Fibers detected by the reaction for acetylcholinesterase were more uniformly distributed. It is suggested that insufficiency of the noradrenergic innervation may be one factor responsible for the lower resistance of vessels of the arterial bordering zones to an acute rise of arterial pressure.Laboratory of Experimental Pathology of the Nervous System, Research Institute of Neurology, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR E. V. Shmidt.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 89, No. 2, pp. 141–143, February, 1980.