Hormonal regulation of metabolism in hepatocytes of the ureogenic teleostopsanus beta

Short-term exposure of isolated toadfish hepatocytes to high concentrations (100 nM) of glucagon, glucagon-like peptide (GLP) or epinephrine significantly increases the rate of lactate gluconeogenesis (1.3-fold) and glycogenolysis (5- to 7-fold). Half-maximal responsiveness to GLP is reached at about 2 nM for gluconeogenesis and 6 nM for glycogenolysis, while the value for glycogenolysis activated by catfish glucagon is 28 nM. Cells do not to respond to 5 nM epinephrine. Norepinephrine, urotensin II and leucine-enkephalin, each applied at 100 nM, increase the rate of glycogenolysis by 1.3 to 1.5-fold. All other hormones tested (vasotocin, isotocin, VIP, methionine-enkephalin, ovine prolactin, -endorphin, APY, salmon insulin) failed to affect metabolic flux through glycogenolysis or gluconeogenesis. None of the hormones altered the rate of urea synthesis or the rate of lactate oxidation by hepatocytes. Although toadfish hepatocytes are responsive to hormonal stimuli, they do not appear to be a useful model to study evolutionary trends in short-term hormonal regulation of urea synthesis. However, the obvious differences in mechanisms of control of urea synthesis in this species compared with ureogenic amphibians and mammals open an intriguing avenue for research.     

Pollen feeding in an orb-weaving spider

Juvenile orb-weaving spiders appear in spring, when insect prey are scarce but when aerial plankton, such as pollen and fungus spores, is abundant. Microscopic organic matter may be the main food of orb-weaving spiderlings, with insects providing only a dietary supplement. Pollen, which is caught on the sticky spirals of Araneus diadematus orb webs, doubles the life expectancy of spiderlings and alters their web-spinning behavior, so that they spin more frequently than do fasting controls. Fungus spores do not have the same nutritional value as pollen and may be deleterious to the spiderlings.     

Local Control of Microdomain Orientation in Diblock Copolymer Thin Films with Electric Fields

Local control of the domain orientation in diblock copolymer thin films can be obtained by the application of electric fields on micrometer-length scales. Thin films of an asymmetric polystyrene-polymethylmethacrylate diblock copolymer, with cylindrical polymethylmethacrylate microdomains, were spin-coated onto substrates previously patterned with planar electrodes. The substrates, 100-nanometer-thick silicon nitride membranes, allow direct observation of the electrodes and the copolymer domain structure by transmission electron microscopy. The cylinders aligned parallel to the electric field lines for fields exceeding 30 kilovolts per centimeter, after annealing at 250°C in an inert atmosphere for 24 hours. This technique could find application in nanostructure fabrication.     

Metabolic actions of glucagon-family hormones in liver

This review addresses direct and indirect metabolic actions of hormones co-encoded in the preproglucagon gene of fishes. Emphasis is placed on a critical analysis of the effects of glucagon and glucagon-like peptide (GLP) and the current knowledge of the respective modes of action is reviewed. In mammals GLPs exert no direct metabolic actions. In fish liver, GLP and glucagon act on similar targets of intermediary metabolism by enhancing flux through glycogenolysis, lipolysis and gluconeogenesis. Increases in substrate oxidation are not uniform. Hormonal activation of glycogen phosphorylase and triglyceride lipase and inhibition of pyruvate kinase are implicated in these actions. Hormone-dependent hyperglycemia, depletion of hepatic glycogen and increases in free fatty acids are noticeablein vivo. Glucagon also activates hepatic amino acid uptake and ammonia excretion. Glucagon actions are accompanied by large increases in hepatic cAMP and increased phosphorylation of pyruvate kinase. Metabolic effects measured after GLP administration are associated with minor, if any, increases in cAMP and effects on pyruvate kinase are variable. We hypothesize that different hepatic receptors with differing modes of intracellular message transduction are involved in glucagon and GLP actions while targetting identical metabolic routes. Responses of different species of fish cover a wide spectrum, and variation of response with the circannual cycle of experimental animals makes comparisons of results, even within one species, difficult.     

Hydrogen radicals, nitrogen radicals, and the production of O3 in the upper troposphere

The concentrations of the hydrogen radicals OH and HO2 in the middle and upper troposphere were measured simultaneously with those of NO, O3, CO, H2O, CH4, non-methane hydrocarbons, and with the ultraviolet and visible radiation field. The data allow a direct examination of the processes that produce O3 in this region of the atmosphere. Comparison of the measured concentrations of OH and HO2 with calculations based on their production from water vapor, ozone, and methane demonstrate that these sources are insufficient to explain the observed radical concentrations in the upper troposphere. The photolysis of carbonyl and peroxide compounds transported to this region from the lower troposphere may provide the source of HOx required to sustain the measured abundances of these radical species. The mechanism by which NO affects the production of O3 is also illustrated by the measurements. In the upper tropospheric air masses sampled, the production rate for ozone (determined from the measured concentrations of HO2 and NO) is calculated to be about 1 part per billion by volume each day. This production rate is faster than previously thought and implies that anthropogenic activities that add NO to the upper troposphere, such as biomass burning and aviation, will lead to production of more O3 than expected.     

食品安全控制中条码质量追溯标签的设计与应用

为实现对农产品“从农田到餐桌”的全方位的监控,从如何确定农产品“身份”出发,结合全球统一性的EAN·UCC编码体系,制定了农产品编码标准,设计了农产品追溯条码方案,并基于.net平台实现了农产品追溯标签的自动生成与打印。     

Measurement of channel catfish (Ictalurus punctatus) plasma insulin in species-specific radioimmunoassay

A single antibody, equilibrium, species specific radioimmunoassay (RIA) for catfish insulin was developed and validated for measurements of plasma levels of insulin in juvenile and adult channel catfish. The RIA appeared to be sensitive (20 pg/tube) and stable with intra-assay coefficient of variation between 5.7% and 3.1% and inter-assay coefficient of variation of 6.5%. The blood was collected from two strains of catfish, USDA 103 and Norris, which differ in food consumption and growth rates, the former strain consuming more food and growing faster (Silverstein et al. 1999). The experiments conducted from December to May included fasting and feeding periods from 5 to 14 days as well as either intravenous or intraperitoneal administration of glucagon-like peptide known for its anorexic effect in both mammals and fish (Silverstein et al. 2001). As in other piscine species studied before, fed fish had higher plasma insulin content than food-deprived fish. Feeding status prevailed over other treatments as the primary physiological factor determining circulating plasma insulin levels. This revised version was published online in August 2006 with corrections to the Cover Date.     

食品安全控制中条码质量追溯标签的设计与应用

（1中国科学院生态环境研究中心,北京 100085;2国家农业信息化工程技术研究中心,北京 100089）