Comparison of membrane organization in mitochondria from yeast and rat liver by nuclear magnetic resonance spectroscopy

Summary Proton magnetic resonance (PMR) and carbon-13 magnetic resonance (CMR) spectra of intact, unsonicated yeast and rat liver motochondria show differences which may be correlated with the composition of the membranes. High resolution PMR and CMR signals in intact yeast mitochondria have been assigned to regions of fluid lipid-lipid interaction on the basis of spectra of extracted lipid and protein, and the temperature dependence of NMR signals from the intact membrane. PMR spectra suggest that about 20% of total yeast phospholipid is in regions where both intramolecular fatty acid chain mobility and lateral diffusion of entire phospholipid molecules are possible. No such regions appear to exist in rat liver mitochondria. For both yeast and rat liver mitochondria, comparison of PMR and CMR spectra suggests that about 50% of phospholipid appears to be in regions where intramolecular fatty acid chain motion is considerable, but lateral diffusion is restricted. The remaining phospholipid appears to have little inter- or intramolecular mobility. Since NMR observation of lipid extracts from membranes indicates that phospholipid-sterol interactions do not account for the spectra of intact mitochondria, these effects are interpreted in terms of extensive lipid-protein interactions.     

A mechanistic study of aromatic hydroxylamine rearrangement in the rat

A modified crossover experiment was conducted to determine the mechanism of arylhydroxylamine rearrangement in the rat. When 1-hydroxy-1-phenyl-3-methylurea was incubated with fractionated liver homogenates or injected intraperitoneally in rats, 1-methylbenzimidazol-2-one was isolated as the major metabolite. Small amounts of the anticipated aminophenol, 1-(o-hydroxylphenyl)-3-methylurea were also isolated. Evidence is presented suggesting that hepatic isomerase-catalyzed rearrangements of hydroxylamines proceed via pathways analogous to those described for chemical model systems. Isomerization appears to be intermolecular involving the generation of a resonance-stabilized nitrenium ion capable of binding to amino acids and nucleotide bases.     

ENVIRONMENTAL AND HORMONAL CONTROL OF TURION GERMINATION IN MYRIOPHYLLUM VERTICILLATUM

Germination, or outgrowth, of Myriophyllum verticillatum turions involves a series of visible changes starting with reflexing of leaves followed by extension and curving of the axis, and then by root formation. Before abscission, turions grow out in response to long days (16 hr) but not short days (8 hr). After abscission, turions show maximal dormancy which can be fully broken by a cold treatment (4 C). Turions are heterogeneous in degree of dormancy and ability to respond to less complete dormancy-breaking treatments, e.g., long days at 20 C. Cytokinins (10^-6 m) break dormancy of non-cold-treated turions, whereas gibberellic acid (GA₃) is ineffective except at high concentrations (10^-3 m). Continuous treatment with cytokinins causes abnormal development after germination. GA₃, on the other hand, induces apparently normal development even at high concentration. Indoleacetic acid (IAA) induces outgrowth only at high concentrations (10^-3 - 10^-4 m), but these concentrations also produce abnormal development. Abscisic acid (ABA, 10^-5 m) retards outgrowth of cold-treated turions and can completely suppress it in non-cold-treated turions. The activity of ABA-like substances in turions remains about the same before and during germination, whereas other (unidentified) acidic inhibitors decrease markedly. The cytokinin activity changes in a complex pattern.     

基于文化与政治生态学的社会生态系统演进机制研究 ——以杭州与西湖为例

科学认识社会生态系统演进机制是对其进行有效管理的重要基础。以文化与政治生态学为理论基础,提出适合杭州—西湖社会生态系统的综合研究框架,识别了杭州—西湖社会生态系统的5个演进阶段,并分析出系统演进中的3种潜在状态。自然、政治、经济以及社会驱动力是影响杭州—西湖社会生态系统的主导因素,人类行为影响整个生态系统中扰动的频率、大小和形式并改变西湖生态系统的结构与功能,进而影响西湖为城市提供生态系统服务的潜能。在不同历史时期,基于自然、社会、经济、文化等多层面的需求,西湖在不同系统状态下为城市供给不同类别和质量的生态系统服务,总体而言供给与调节服务比例逐渐下降,文化服务逐渐上升,并且后者逐步成为最主要的生态系统服务类别。杭州与西湖在长期的互馈共生中建立了社会生态系统的自适应性调节机制,其背后的生态智慧可为现代风景园林规划提供重要启示。     

AVPR1A variation is linked to gray matter covariation in the social brain network of chimpanzees

The vasopressin system has been implicated in the regulation of social behavior and cognition in humans, nonhuman primates and other social mammals. In chimpanzees, polymorphisms in the vasopressin V1a receptor gene (AVPR1A) have been associated with social dimensions of personality, as well as to responses to sociocommunicative cues and mirror self‐recognition. Despite evidence of this association with social cognition and behavior, there is little research on the neuroanatomical correlates of AVPR1A variation. In the current study, we tested the association between AVPR1A polymorphisms in the RS3 promotor region and gray matter covariation in chimpanzees using magnetic resonance imaging and source‐based morphometry. The analysis identified 13 independent brain components, three of which differed significantly in covariation between the two AVPR1A genotypes (DupB?/? and DupB+/?; P < .05). DupB+/? chimpanzees showed greater covariation in gray matter in the premotor and prefrontal cortex, basal forebrain, lunate and cingulate cortex, and lesser gray matter covariation in the superior temporal sulcus and postcentral sulcus. Some of these regions were previously found to differ in vasopressin and oxytocin neural fibers between nonhuman primates, and in AVPR1A gene expression in humans with different RS3 alleles. This is the first report of an association between AVPR1A and gray matter covariation in nonhuman primates, and specifically links an AVPR1A polymorphism to structural variation in the social brain network. These results further affirm the value of chimpanzees as a model species for investigating the relationship between genetic variation, brain structure and social cognition with relevance to psychiatric disorders, including autism.     

On Weighted Log-Rank Combination Tests and Companion Cox Model Estimators

In randomized clinical trials, the log-rank test and Cox proportional hazards model are the gold standard in survival data analyses. While the log-rank tes     

Chiral separation of underivatized amino acids in supercritical fluid chromatography with chiral crown ether derived column

The supercritical fluid chromatographic separation of underivatized amino acids was explored using immobilized chiral crown ether column CROWNPAK CR-I (+) and mass spectrometric detection. The type of modifier, acidic additives, and the role of water were investigated. Enantioseparation was achieved for all 18 amino acids investigated with short retention times (less than 3 minutes) and average resolution of greater than 5.0. Analysis of enantiomerically pure standards demonstrated the D enantiomer eluted first for all amino acids using a CROWNPAK CR-I (+) column.