Metabolic changes associated with active water vapour absorption in the mealworm Tenebrio molitor L. (Coleoptera, Tenebrionidae): a microcalorimetric study

Water vapour absorption (WVA) is an important mechanism for water gain in several xeric insects. Theoretical calculations indicate that the energetic cost of WVA should be small (5-10% of standard metabolic rate) assuming realistic efficiencies. In this study we explored the relationship between WVA, metabolic heat flux (HFmet.) and CO2 release in larvae of Tenebrio molitor using microcalorimetry. By comparing metabolic heat flux with the catabolic rate estimated from VCO2 , we were able to differentiate anabolic and catabolic rates prior to and during WVA, while simultaneously monitoring water exchange. Three to four hours before the onset of WVA, larvae showed clear increases in HFmet. and catabolic flux, and a simultaneous decrease in anabolic flux. Following the onset of WVA, HFmet. decreased again until indistinguishable from control (non-absorbing) values. Possible factors contributing to the "preparatory phase" are discussed, including mobilization of Malpighian tubule transporters and muscular activity in the rectum. Absorbing larvae reduced the water activity of the calorimetric cell to 0.906, agreeing with gravimetric estimates of the critical equilibrium activity. Periods of movement during WVA coincided with decreased uptake fluxes, consistent with the animal's hydrostatic skeleton and the need to close the anus to generate pressure increases in the haemocoel.     

Molecular Semiotics toward the Emergence of Life

Molecular imprints of organisms serving as both the agents and the products of the underlying sign activities are quantum mechanical in their origins. In particular, molecules in any reaction networks constituting a biological organism are semiotic or context-dependent in the sense that their activities reside within the proper coordination of the entire networks. The origin of life could have been related to a specific aspect of molecular semiotics, especially in the transition from molecules as the physical symbols of material units to molecules as the semiotic signs having the capacity of pointing to something else other than the molecules themselves. Quantum mechanical underpinning of the molecular imprints leading to the emergence of life is in the appraisal of the material capacities of both coherent assimilation and decoherent dissociation already latent in the imprints. One empirical evidence suggesting the likelihood of both coherent assimilation and decoherent dissociation in prebiotic settings could have been found in synthetic chemical reactions running in hydrothermal circulation of seawater through hot vents in the Haedean ocean on the primitive Earth.     

Adamantyl glycosphingolipids provide a new approach to the selective regulation of cellular glycosphingolipid metabolism

Mammalian glycosphingolipid (GSL) precursor monohexosylceramides are either glucosyl- or galactosylceramide (GlcCer or GalCer). Most GSLs derive from GlcCer. Substitution of the GSL fatty acid with adamantane generates amphipathic mimics of increased water solubility, retaining receptor function. We have synthesized adamantyl GlcCer (adaGlcCer) and adamantyl GalCer (adaGalCer). AdaGlcCer and adaGalCer partition into cells to alter GSL metabolism. At low dose, adaGlcCer increased cellular GSLs by inhibition of glucocerebrosidase (GCC). Recombinant GCC was inhibited at pH 7 but not pH 5. In contrast, adaGalCer stimulated GCC at pH 5 but not pH 7 and, like adaGlcCer, corrected N370S mutant GCC traffic from the endoplasmic reticulum to lysosomes. AdaGalCer reduced GlcCer levels in normal and lysosomal storage disease (LSD) cells. At 40 μM adaGlcCer, lactosylceramide (LacCer) synthase inhibition depleted LacCer (and more complex GSLs), such that only GlcCer remained. In Vero cell microsomes, 40 μM adaGlcCer was converted to adaLacCer, and LacCer synthesis was inhibited. AdaGlcCer is the first cell LacCer synthase inhibitor. At 40 μM adaGalCer, cell synthesis of only Gb(3) and Gb(4) was significantly reduced, and a novel product, adamantyl digalactosylceramide (adaGb(2)), was generated, indicating substrate competition for Gb(3) synthase. AdaGalCer also inhibited cell sulfatide synthesis. Microsomal Gb(3) synthesis was inhibited by adaGalCer. Metabolic labeling of Gb(3) in Fabry LSD cells was selectively reduced by adaGalCer, and adaGb(2) was produced. AdaGb(2) in cells was 10-fold more effectively shed into the medium than the more polar Gb(3), providing an easily eliminated "safety valve" alternative to Gb(3) accumulation. Adamantyl monohexosyl ceramides thus provide new tools to selectively manipulate normal cellular GSL metabolism and reduce GSL accumulation in cells from LSD patients.     

林生山黧豆中2,4—二氨基丁酸合成代谢的体外酶学研究

用~3H-天门冬氨酸为底物,林生山黧豆(Lathyrus sylvestris L.)叶片匀浆上清液为粗酶液,进行体外反应。结果表明,天门冬氨酸的放射性掺入到2,4-二氨基丁酸,加入谷氨酸则能抑制这种掺入。将上述粗酶液透析,加入可能的辅助因子,天门冬氨酸的放射性也掺入到2,4-二氨基丁酸。研究证实在体外天门冬氨酸可以作为2,4-二基丁酸合成的底物,在林生山黧豆体内存在催化天门冬氨酸转变为2,4-二氨基丁酸的合成酶(系)。以2,4-二氨基丁酸和γ-氨基丁酸为底物,用氨基酸自动分析仪测定产物含量,结果表明,2,4-二氨基丁酸和γ-氨基丁酸不互相转变。     

Therapeutic applications of ghrelin to cachexia utilizing its appetite-stimulating effect

Ghrelin, which is a natural ligand for the growth hormone (GH)-secretagogue receptor (GHS-R), stimulates food intake in both animals and humans. Ghrelin is the only circulating hormone known to stimulate appetite in humans. Ghrelin also stimulates GH secretion and inhibits the production of anorectic proinflammatory cytokines. As GH is an anabolic hormone, protein stores are spared at the expense of fat during conditions of caloric restriction. Thus, ghrelin exhibits anti-cachectic actions via both GH-dependent and -independent mechanisms. Several studies are evaluating the efficacy of ghrelin in the treatment of cachexia caused by a variety of diseases, including congestive heart failure, chronic obstructive pulmonary disease, cancer, and end-stage renal disease. These studies will hopefully lead to the development of novel therapeutic applications for ghrelin in the future. This review summarizes the recent advances in this area of research.     

Separation of fast from slow anabolism by site-specific PEGylation of insulin-like growth factor I (IGF-I)

Insulin-like growth factor I (IGF-I) has important anabolic and homeostatic functions in tissues like skeletal muscle, and a decline in circulating levels is linked with catabolic conditions. Whereas IGF-I therapies for musculoskeletal disorders have been postulated, dosing issues and disruptions of the homeostasis have so far precluded clinical application. We have developed a novel IGF-I variant by site-specific addition of polyethylene glycol (PEG) to lysine 68 (PEG-IGF-I). In vitro, this modification decreased the affinity for the IGF-I and insulin receptors, presumably through decreased association rates, and slowed down the association to IGF-I-binding proteins, selectively limiting fast but maintaining sustained anabolic activity. Desirable in vivo effects of PEG-IGF-I included increased half-life and recruitment of IGF-binding proteins, thereby reducing risk of hypoglycemia. PEG-IGF-I was equipotent to IGF-I in ameliorating contraction-induced muscle injury in vivo without affecting muscle metabolism as IGF-I did. The data provide an important step in understanding the differences of IGF-I and insulin receptor contribution to the in vivo activity of IGF-I. In addition, PEG-IGF-I presents an innovative concept for IGF-I therapy in diseases with indicated muscle dysfunction.     

A complete citric acid cycle in assimilatory metabolism of Pelobacter acidigallici,a strictly anaerobic,fermenting bacterium

Pelobacter acidigallici is a strictly anaerobic bacterium that ferments trihydroxybenzenes to 3 mol acetate/mol substrate. The key intermediate linking the catabolic sequences to the formation of cell matter is acetyl-CoA. Since P. acidigallici is independent of further external electron donors, it must oxidize part of the acetyl-CoA to provide reducing equivalents for anabolism. In this study we demonstrate the presence of all enzymes necessary to operate a modified citric acid cycle, with activities sufficient to support growth. Unusual enzymes in the cycle are 2-oxoglutarate synthase and succinyl-CoA: acetoacetate CoA transferase. Anaplerotic reactions are catalyzed by pyruvate synthase, PEP synthetase and PEP carboxylase. No CO dehydrogenase, hydrogenase, or formate dehydrogenase activity could be detected. The phylogenetic implications of these findings with respect to the relatedness of P. acidigallici to gramnegative, sulfur-reducing bacteria by 16 S rRNA cataloguing are discussed.Abbreviations CoA coenzyme A - DCPIP 2,4-dichlorophenolindophenol - DTNB 5,5-dithiobis(2-nitrobenzoic acid) Ellman's reagent - DTT 1,4-dithiothreitol - methyl viologen 1,1-dimethyl-4,4-bipyridinium dichloride - PEP phosphoenolpyruvate - PMS phenazin methosulfate - Tricine N-[tris(hydroxymethyl)-methyl]-glycine - Tris tris(hydroxymethyl)aminomethane     

Interleukin-15 increases myosin accretion in human skeletal myogenic cultures

Interleukin-15 (IL-15) has been shown to have anabolic effects on skeletal muscle in rodent studies conducted in vitro and in vivo. The mechanism of IL-15 action on muscle appears to be distinct from that of the well-characterized muscle anabolic factor insulin-like growth factor-I (IGF-I). IL-15 action has not been investigated in a human culture system nor in detail in primary skeletal myogenic cells. The purpose of this study was to compare the effects of IL-15 and IGF-I in primary human skeletal myogenic cells. Accretion of a major myofibrillar protein, myosin heavy chain (MHC), was used as a measure of muscle anabolism. We found that both growth factors induced increases in MHC accretion in primary human skeletal myogenic cultures; however, IL-15 and IGF-I actions were temporally distinct. IL-15 was more effective at stimulating MHC accretion when added to cultures after differentiation of myoblasts had occurred. In contrast, IGF-I was more effective at stimulating MHC accretion when added to cultures prior to differentiation of myoblasts. These results using a human system support recent findings from rodent models which indicate that the primary mode of IGF-I action on skeletal muscle anabolism is through stimulation of myogenic precursor cells, whereas the primary target of IL-15 action is the differentiated muscle fiber. Further, since clinical and experimental studies have shown IGF-I is not effective in preventing skeletal muscle wasting, the distinct mode of action of IL-15 suggests it may be of potential usefulness in the treatment of muscle wasting disorders.     

大黄鱼CCT基因的克隆及其表达量随稚鱼生长发育的变化

研究旨在克隆大黄鱼磷脂酰胆碱合成关键基因磷脂酰胆碱胞苷转移酶 (CCT)基因全长, 并检测其表达量随稚鱼生长发育的变化。利用同源克隆技术和RACE技术从大黄鱼肝脏中成功扩增出CCT的全长。同时应用real-time PCR法检测不同日龄大黄鱼稚鱼CCT的表达变化。序列分析表明, CCT全长2419 bp(Genbank登录号: KF006239.1), 包括273 bp 的5'端非编码区, 1107 bp的开放阅读框, 1010 bp的3'端非编码区,共编码369个氨基酸。系统进化树分析表明, 相比其他物种, 大黄鱼CCT基因与红鳍东方鲀的亲缘关系较近。定量结果表明, 孵化后, 大黄鱼仔稚鱼CCT的表达量随日龄的变化先显著升高, 在15日龄时达到最大值,随后显著下降并趋于平稳, CCT基因表达量的变化趋势与大黄鱼稚鱼消化系统的发育密切相关。