Glucose regulates lipid metabolism in fasting king penguins

This study aims to determine whether glucose intervenes in the regulation of lipid metabolism in long-term fasting birds, using the king penguin as an animal model. Changes in the plasma concentration of various metabolites and hormones, and in lipolytic fluxes as determined by continuous infusion of [2-3H]glycerol and [1-14C]palmitate, were examined in vivo before, during, and after a 2-h glucose infusion under field conditions. All the birds were in the phase II fasting status (large fat stores, protein sparing) but differed by their metabolic and hormonal statuses, being either nonstressed (NSB; n = 5) or stressed (SB; n = 5). In both groups, glucose infusion at 5 mg.kg-1.min-1 induced a twofold increase in glycemia. In NSB, glucose had no effect on lipolysis (maintenance of plasma concentrations and rates of appearance of glycerol and nonesterified fatty acids) and no effect on the plasma concentrations of triacylglycerols (TAG), glucagon, insulin, or corticosterone. However, it limited fatty acid (FA) oxidation, as indicated by a 25% decrease in the plasma level of beta-hydroxybutyrate (beta-OHB). In SB, glucose infusion induced an approximately 2.5-fold decrease in lipolytic fluxes and a large decrease in FA oxidation, as reflected by a 64% decrease in the plasma concentration of beta-OHB. There were also a 35% decrease in plasma TAG, a 6.5- and 2.8-fold decrease in plasma glucagon and corticosterone, respectively, and a threefold increase in insulinemia. These data show that in fasting king penguins, glucose regulates lipid metabolism (inhibition of lipolysis and/or of FA oxidation) and affects hormonal status differently in stressed vs. nonstressed individuals. The results also suggest that in birds, as in humans, the availability of glucose, not of FA, is an important determinant of the substrate mix (glucose vs. FA) that is oxidized for energy production.     

4-(3,4-dihydro-1H-isoquinolin-2yl)-pyridines and 4-(3,4-dihydro-1H-isoquinolin-2-yl)-quinolines as potent NR1/2B subtype selective NMDA receptor antagonists

A series of 4-(3,4-dihydro-1H-isoquinolin-2yl)-pyridines and analogous quinolines was prepared and evaluated as NR1/2B subtype selective NMDA receptor antagonists. 2-Hydroxyalkylamino substitution combines high affinity with selectivity (vs alpha1 and M1 receptors) and activity in vivo.     

Motions and structural variability within toxins: implication for their use as scaffolds for protein engineering

Animal toxins are small proteins built on the basis of a few disulfide bonded frameworks. Because of their high variability in sequence and biologic function, these proteins are now used as templates for protein engineering. Here we report the extensive characterization of the structure and dynamics of two toxin folds, the "three-finger" fold and the short alpha/beta scorpion fold found in snake and scorpion venoms, respectively. These two folds have a very different architecture; the short alpha/beta scorpion fold is highly compact, whereas the "three-finger" fold is a beta structure presenting large flexible loops. First, the crystal structure of the snake toxin alpha was solved at 1.8-A resolution. Then, long molecular dynamics simulations (10 ns) in water boxes of the snake toxin alpha and the scorpion charybdotoxin were performed, starting either from the crystal or the solution structure. For both proteins, the crystal structure is stabilized by more hydrogen bonds than the solution structure, and the trajectory starting from the X-ray structure is more stable than the trajectory started from the NMR structure. The trajectories started from the X-ray structure are in agreement with the experimental NMR and X-ray data about the protein dynamics. Both proteins exhibit fast motions with an amplitude correlated to their secondary structure. In contrast, slower motions are essentially only observed in toxin alpha. The regions submitted to rare motions during the simulations are those that exhibit millisecond time-scale motions. Lastly, the structural variations within each fold family are described. The localization and the amplitude of these variations suggest that the regions presenting large-scale motions should be those tolerant to large insertions or deletions.     

Mg-nucleotides induced dissociation of liposome-bound creatine kinase: reversible changes in its secondary structure and in the fluidity of the bilayer

MgADP binding to mitochondrial creatine kinase (mtCK) adsorbed on liposomes was induced by the photorelease of caged ADP. The nucleotide binding produced two types of structural changes. One was related to the well-established release of mtCK from the liposomes. The other corresponded to reversible structural changes induced by nucleotide binding to mtCK as demonstrated here. Infrared spectroscopy data show that the MgADP-induced desorption of mtCK from vesicles led to a slight increase in alpha-helix structures in mtCK at the expense of a small decrease in beta-sheet structures and a concomitant increase in the fluidity of the membranes. The desorption of mtCK induced by MgADP and MgATP was almost complete, as shown by centrifugation and enzymatic activity measurements. The photorelease of MgADP in a reactive medium containing phosphocreatine and mtCK associated with liposomes led to nucleotide binding and to the formation of MgATP and creatine. Addition of phosphocreatine also desorbed mtCK from liposomes, while addition of creatine did not. Interpretation of these results would suggest that ADP, ATP or phosphocreatine induce the release of mtCK from membranes, increase the phospholipid bilayer fluidity, and may also decrease the number of contact sites between inner and outer mitochondrial membranes, thus affecting the activity of other mitochondrial enzymes. It is tempting to propose that membrane mtCK binding regulation by nucleotide and PCr concentrations may serve as a physiological adaptation for energy supply.     

喜树细胞悬浮培养中生理生化指标的测定

以喜树(Camptotheca acuminata Decsne.)幼嫩叶片为材料,诱导和筛选愈伤组织,进行细胞悬浮培养。初步研究了液体培养条件下光照对喜树细胞生长和生理生化特性的影响。结果显示：在光照条件下培养细胞生长周期30d,在黑暗条件下培养细胞生长周期为27d,细胞的增殖曲线呈“S”形;在两种不同光照条件下,其培养液pH值先下降后回升;培养细胞中可溶性蛋白质含量及过氧化物酶活性均出现两个峰值,但出现的时间不同。     

Study of cell killing and morphology on S180 by ultrasound activating hematoporphyrin derivatives

The inhibition of ascitic S180 and induced sarcoma 180 in vivo was studied with the combination of hematoporphyrin derivatives (HpD) and ultrasound (US) at the frequency of 1.1 MHz and different intensities by light microscopy observation, electronic microscopy observation, cytochemical analysis and fluorescence labeling. The present study indicated that the injury of ascitic S180 increased as time passed and the inhibitory effect was stronger in US plus HpD group than that in other groups. Our results also indicated that the changes in cell structure, cytochrome C oxidase activity, the degradation and missing of DNA were the important factors that inhibited the tumor cell growth and even induced celldeath. The phenomenon of apoptosis of tumor cells indicated that cell death andinduced apoptosis exist in the treatment of sonodynamic therapy (SDT). Our study investigated the mechanism underlying the killing effect of S180 induced by USactivating HpD by the observation of cell morphology and dynamic changes from seminal injury to succeeded injury even to death. It would provide rich referencefor the study of SDT.     

高产磷酯酶C菌株筛选及其抗血小板功能的研究

在湖北省、湖南省、江苏省、山东省、广东省156个点采土样1268份,利用卵黄琼脂的LB培养基初筛获得产生乳白色晕圈的菌株648株;再用卵黄琼脂滤纸圆片检测获得产生乳白色晕圈和透明圈菌株266株;这些菌株用卵黄琼脂杯蝶法筛选出产生大于13．0mm乳白色晕圈及少量透明圈共73株,经过菌生物量、卵黄杯碟法和抗兔血小板聚集率的测定,从73株菌中筛选出15株,菌号为：183,198,247,424,587,596,692,744,754—1,791—2,779,970,998,1107,1182;将此15菌株经菌生物量、卵黄琼脂杯碟法、NPPC法和抗人血小板聚集率的测定,从中选出754—1,779,970,1107四株菌进行分类鉴定和已知菌CW—W—90—3菌对照比较的研究。     

Lipid raft distribution of CD4 depends on its palmitoylation and association with Lck,and evidence for CD4-induced lipid raft aggregation as an additional mechanism to enhance CD3 signaling

By mutagenesis, we demonstrated that the palmitoylation of the membrane-proximal Cys(396) and Cys(399)of CD4, and the association of CD4 with Lck contribute to the enrichment of CD4 in lipid rafts. Ab cross-linking of CD4 induces an extensive membrane patching on the T cell surface, which is related to lipid raft aggregation. The lipid raft localization of CD4 is critical for CD4 to induce the aggregation of lipid rafts. The localization of CD4 in lipid rafts also correlates to the ability of CD4 to enhance receptor tyrosine phosphorylation. Thus, our data suggest that CD4-induced aggregation of lipid rafts may play an additional role in CD4 signaling besides its adhesion to MHC molecules and association with Lck.