Chiral resolution of alpha,alpha'-bis[3-(N,N-diethylcarbamoyl)piperidino]-p-xylene, a novel antiplatelet compound.

alpha,alpha'-Bis[3-(N,N-diethylcarbamoyl)piperidino]-p-xylene dihydrobromide, a novel antiplatelet agent, was resolved into three isomers A, B, and C, on a chiral alpha 1-acid glycoprotein analytical column using a mobile phase of 0.025 M phosphate buffer containing 0.025 M tetrabutylammonium hydrogen sulfate, at a pH of 6.5. The effect of molarity, temperature, pH, flow rate, and organic modifiers on the enantioselectivity was examined. Based on circular dichroic spectra at 220 nm, A and C appear to be the (-)- and (+)-enantiomers, respectively, and B the meso diastereomer. Attempts at resolution using Pirkle type columns gave unsatisfactory results. It appears that both hydrophobic and polar interactions between the compound and the stationary phase are important determinants of resolution.     

Spatial patterns and sampling plans for cereal aphids [Hom.: Aphididae] killed by entomophthoralean fungi and hymenopterous parasitoids in spring wheat

Cereal aphids infesting spring wheat in southwestern Idaho were surveyed during 1988 and 1989 for the presence of entomophthoralean fungi and hymenopterous parasitoids. Cereal aphids killed by the fungi (cadavers) and parasitoids (mummies) includedDiuraphis noxia (Mordvilko),Metopolophium dirhodum (Walker),Sitobion avenae (F.), andSchizaphis graminum (Rondani). Taylor's power law was used to describe the relationships between mean densities of cadavers or mummies (number per tiller) and associated variances. Except forS. graminum mummies, which were at low levels throughout the growing seasons and tended to be randomly distributed, Taylor's slopes exceeded 1.0 for all the aphid cadavers and mummies, indicating varying degrees of clumping in spatial pattern. The spatial patterns ofD. noxia andM. dirhodum cadavers were similar, simply reflecting those of their own populations, but more aggregated than were their respective mummies resulting from parasitoid attack. The intercepts and slopes from the power law analysis were used to generate functional relationships between the proportion of wheat tillers bearing cadavers or mummies of each aphid species and the mean density, and develop optimal numerical (direct counting) and binomial (presence or absence) sample size curves for both cadavers and mummies of each aphid species.      

上海地区胃癌病人运铁蛋白(Tf)、组特异性成分(Gc)、α_1-抗胰蛋白酶(α_1-AT)亚型分布的研究

用薄层聚丙烯酰胺凝胶等电聚焦电泳分析了上海地区202例汉族胃癌病人及202例正常对照组的运铁聋白(Tf)和α_1-抗胰蛋白酶(α_1-AT)亚型的分布,发现胃癌组Tfc_1c_1纯合子频率(0.3713)和Tfc_1基因频率(0.5718)显著低于对照组(分别为0.5149和0.6782),均为p<0.01,胃癌组Tfc_2c_2纯合子频率(0.2228)和Tfc_2基因频率(0.4019)显著高于对照组(分别为0.1436,p<0.05和0.2970,p<0.01),胃癌组和对照组的α_1-抗胰蛋白酶亚型分布无显著差异。用薄层聚丙烯酰胺等电聚焦结合免疫固定分析了上海地区200例汉族胃癌病人和200例正常对照组的组特异性成分(Gc)亚型分布,发现胃癌组Go1F表型频率(0.22)和Gc1F基因频率(0.4375)均显著高于正常对照组(分别为0.14和0.3600,均为p<0.05)。     

Detection of covalent enzyme-substrate complexes of nitrilase by ion-spray mass spectroscopy

Nitrilase from Rhodococcus ATCC 39484 was found to consist of two species of Mr 40,258 +/- 2 and 40,388 +/- 2 Da. When the enzyme was incubated with nitrile substrates and the reaction quenched with acid, higher Mr species were observed. The mass differences were consistent with addition of a substrate molecule to each species. These results represent the first reported demonstration that this, or any other nitrilase forms a covalent intermediate with its substrates. The observation that the intermediate, suggested to be either a thioimidate or an acylenzyme, can be trapped by acidification indicates that the rate of breakdown of the intermediate is rate-limiting.     

Vibrational fluctuations of hydrogen bonds in a DNA double helix with nonuniform base pairs.

The Green's function technique is applied to a study of breathing modes in a DNA double helix which contains a region of different base pairs from the rest of the double helix. The calculation is performed on a G-C helix in the B conformation with four consecutive base pairs replaced by A-T. The average stretch in hydrogen bonds is found amplified around the A-T base pair region compared with that of poly(dG)-poly(dC). This is likely related to the A-T regions lower stability against hydrogen bond melting. The A-T region may be considered to be the initiation site for melting in such a helix.     

A method for separating bound versus unbound label during radioiodination

An inexpensive, highly effective, and safe method for the removal of bound versus unbound label during radiolabeling of proteins is described. The technique employs the use of membrane ultrafiltration technology and returns in one step a highly reproducible product of quality superior to that attained by gel chromatography. Advantages of this technique are a reduction in the quantity of liquid and solid radioactive waste and a significant limitation of potentially harmful manipulation and exposure times.     

Pyrophosphate contamination in crystalline phosphocreatine: a source of error in kinetic studies using coupled enzymes.

Commercial crystalline phosphocreatine generally contains a contaminant, probably pyrophosphate, that can inhibit nucleoside triphosphatases and may therefore cause errors in steady-state kinetic studies of creatine kinase-coupled r reactions. Ion-exchange chromatography reveals the presence of pyrophosphate in some batches of phosphocreatine sufficient to account for the observed inhibition. Chromatographically purified phosphocreatine shows no inhibitory effect.     

Sound localization behavior of the green treefrog (Hyla cinerea) and the barking treefrog (H. gratiosa)

Summary Female treefrogs (Hyla cinerea andH. gratiosa) can accurately localize a sound source (playback of male mating calls) if both ears are intact. When the sensitivity of one eardrum is attenuated, by coating it with a thin layer of silicone grease, females no longer can locate the sound source. This study demonstrates that female anurans rely on interaural cues for localization of a calling male. The neural basis for an anuran's sound localization ability presumably involves binaural convergence on single cells in the central auditory nervous system.This work was supported by research grants from the National Science Foundation and the U.S. Public Health Service. The assistance of Anne J.M. Moffat in measuring the directional characteristics of the loudspeaker is gratefully appreciated.     

Intercellular communication in the rat anterior pituitary gland: an in vivo and in vitro study

The concept of "stimulus-secretion coupling" suggested by Douglas and co-workers to explain the events related to monamine discharge by the adrenal medulla (5, 7) may be applied to other endocrine tissues, such as adrenal cortex (36), pancreatic islets (4), and magnocellular hypothalamic neurons (6), which exhibit a similar ion-dependent process of hormone elaboration. In addition, they share another feature, that of joining neighbor cells via membrane junctions (12, 26, and Fletcher, unpublished observation). Given this, and the reports that hormone secretion by the pars distalis also involves a secretagogue-induced decrease in membrane bioelectric potential accompanied by a rise in cellular [Ca++] (27, 34, 41), it was appropriate to test the possibility that cells of the anterior pituitary gland are united by junctions.     

Growth Type and Functional Trajectories: An Empirical Study of Urban Expansion in Nanjing,China

Drawing upon the Landsat satellite images of Nanjing from 1985, 1995, 2001, 2007, and 2013, this paper integrates the convex hull analysis and common edge analysis at double scales, and develops a comprehensive matrix analysis to distinguish the different types of urban land expansion. The results show that Nanjing experienced rapid urban expansion, dominated by a mix of residential and manufacturing land from 1985 to 2013, which in turn has promoted Nanjing’s shift from a compact mononuclear city to a polycentric one. Spatial patterns of three specific types of growth, namely infilling, extension, and enclave were quite different in four consecutive periods. These patterns result primarily from the existing topographic constraints, as well as government-oriented urban planning and policies. By intersecting the function maps, we also reveal the functional evolution of newly-developed urban land. Moreover, both self-enhancing and mutual promotion of the newly developed functions are surveyed over the last decade. Our study confirms that the integration of a multi-scale method and multi-perspective analysis, such as the spatiotemporal patterns and functional evolution, helps us to better understand the rapid urban growth in China.