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排序方式: 共有377条查询结果,搜索用时 15 毫秒
1.
Aurel Popa Wagner Eugenia Psarrou Lieselotte Popa Wagner 《Analytical biochemistry》1983,129(2):326-328
A simple and sensitive high-performance liquid chromatography method with electrochemical detector is described for the determination of free 3-methoxy-4-hydroxyphenylacetic acid (HVA) in human plasma. The method does not involve any extraction, is specific and reproducible, and has the potential to measure serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) simultaneously. The plasma concentration of free HVA in eight normal, healthy adult volunteers was 10.9 ± 4.6 (mean ± SD). In a preliminary study, in one schizophrenic patient the plasma HVA increased twofold after neuroleptic treatment. 相似文献
2.
Electric field-induced lateral mobility of photosystem I in the photosynthetic membrane: A study by electrophotoluminescence 总被引:2,自引:2,他引:0 下载免费PDF全文
Electrophoretic movement of photosystem I (PS I) along the photosynthetic membrane of hypotonically swollen thylakoid vesicles was studied by analyzing the electric field-stimulated delayed luminescence (electrophotoluminescence) emitted from PS I. The electrophoretic mobility was inferred from the differences in electrophotoluminescence (EPL) of the photosynthetic vesicles in presence and absence of trains of low amplitude (<80 V/cm) prepulses of 1 ms duration at 4 ms spacing. The average apparent electric mobility, determined from the time course of EPL increase on one hemisphere or its decrease on the other one, as function of prepulse length and intensity was of the order of 3 · 10-5 cm2V-1s-1. The assymetric distribution of the PS I reached a steady state when the diffusional, electrostatic, and elastic forces balanced the electrophoretic driving force. A lateral diffusion coefficient of ~5 · 10-9 cm2s-1 was found for the PS I complex from the diffusional relaxation after cessation of the electric field pulse train. Experimental conditions such as concentration, temperature, and viscosity of the aqueous solution were not critical for the effect. Between 23 and 150 electron charges per moving particle were estimated from the measured electrophoretic mobility. 相似文献
3.
Chest pain among children is a common complaint in primary care practice. However, the demographic features and treatment of such patients are controversial. We distributed a questionnaire to 336 consecutive patients with a complaint of chest pain seen during 1 year at an urban pediatric emergency department. Such visits represented 0.6% of all emergency encounters; the male:female ratio was 1.0. Physical examination was done in 325 patients. Chest-wall pain was the most common diagnosis (in 28% of cases). Other causes included pulmonary (in 19%), minor traumatic (in 15%), idiopathic (in 12%) and psychogenic (in 5%); miscellaneous causes (in 21%) most often indicated pain referred from the upper respiratory tract and the abdomen. The most common physical finding was chest tenderness (in 41% of cases). Investigations included chest radiography (in 50% of cases), electrocardiography (in 18%) and determination of the hemoglobin concentration and of the leukocyte count (in 13%); the results were rarely positive. Only eight patients (2%) required admission to hospital, and there were no cases of myocardial ischemia. The findings suggest that health care costs may be reduced by more judicious use of investigations. We conclude that chest pain is an uncommon and usually benign complaint in the pediatric emergency department. Most causes are evident on careful physical examination. 相似文献
4.
Mariana Vlad E. Bordas Rodica Tomus Doina Sava Ecaterina Farkas G. Uza 《Biological trace element research》1993,38(1):47-54
Serum copper concentration increases significantly (p<0.01) in rats with experimental atherosclerosis compared to a control group. The serum zinc, the zinc, and copper concentration
in abdominal aorta and in liver decreases significantly (p<0.05) compared to the control group. Administration of copper sulfate for 100 d in these animals induces a significant increase
of serum copper (p<0.01), decrease of serum cholesterol (p<0.05) and increase of liver copper concentration as compared with the group fed only a high cholesterol diet. In the aorta
of these animals the copper concentration increases and edema and lipid infiltration are considerably less than in the group
of animals fed only a high lipid diet. 相似文献
5.
6.
Alexandru Vasincu Christiana M. Neophytou Simon Vlad Luca Krystyna Skalicka‐Wo
niak Anca Miron Andreas I. Constantinou 《Journal of biochemical and molecular toxicology》2020,34(3)
The aim of this study was to evaluate the impact that 6‐O‐(3″, 4″‐di‐O‐trans‐cinnamoyl)‐α‐ l ‐rhamnopyranosylcatalpol (Dicinn) and verbascoside (Verb), two compounds simultaneously reported in Verbascum ovalifolium, have on tumor cell viability, apoptosis, cell cycle kinetics, and intracellular reactive oxygen species (ROS) level. At 100 µg/mL and 48 hours incubation time, Dicinn and Verb produced good cytotoxic effects in A549, HT‐29, and MCF‐7 cells. Dicinn induced cell‐cycle arrest at the G0/G1 phase and apoptosis, whereas Verb increased the population of subG1 cells and cell apoptosis rates. Furthermore, the two compounds exhibited time‐dependent ROS generating effects in tumor cells (1‐24 hours). Importantly, no cytotoxic effects were induced in nontumor MCF‐10A cells by the two compounds up to 100 µg/mL. Overall, the effects exhibited by Verb in tumor cells were more potent, which can be correlated with its structural features, such as the presence of phenolic hydroxyl groups. 相似文献
7.
Gili R.S. Naveh Vlad Brumfeld Ron Shahar Steve Weiner 《Journal of structural biology》2013,181(2):108-115
The periodontal ligament (PDL), a soft tissue connecting the tooth and the bone, is essential for tooth movement, bone remodeling and force dissipation. A collagenous network that connects the tooth root surface to the alveolar jaw bone is one of the major components of the PDL. The organization of the collagenous component and how it changes under load is still poorly understood. Here using a state-of-the-art custom-made loading apparatus and a humidified environment inside a microCT, we visualize the PDL collagenous network of a fresh rat molar in 3D at 1 μm voxel size without any fixation or contrasting agents. We demonstrate that the PDL collagen network is organized in sheets. The spaces between sheets vary thus creating dense and sparse networks. Upon vertical loading, the sheets in both networks are stretched into well aligned arrays. The sparse network is located mainly in areas which undergo compressive loading as the tooth moves towards the bone, whereas the dense network functions mostly in tension as the tooth moves further from the bone. This new visualization method can be used to study other non-mineralized or partially mineralized tissues, and in particular those that are subjected to mechanical loads. The method will also be valuable for characterizing diseased tissues, as well as better understanding the phenotypic expressions of genetic mutants. 相似文献
8.
Jofre Carnicer Constantí Stefanescu Roger Vila Vlad Dincă Xavier Font Josep Peñuelas 《Global Ecology and Biogeography》2013,22(1):6-18
Aim Adaptive trait continua are axes of covariation observed in multivariate trait data for a given taxonomic group. These continua quantify and summarize life‐history variation at the inter‐specific level in multi‐specific assemblages. Here we examine whether trait continua can provide a useful framework to link life‐history variation with demographic and evolutionary processes in species richness gradients. Taking an altitudinal species richness gradient for Mediterranean butterflies as a study case, we examined a suite of traits (larval diet breadth, adult phenology, dispersal capacity and wing length) and species‐specific habitat measures (temperature and aridity breadth). We tested whether traits and species‐specific habitat measures tend to co‐vary, whether they are phylogenetically conserved, and whether they are able to explain species distributions and spatial genetic variation in a large number of butterfly assemblages. Location Catalonia, Spain. Methods We formulated predictions associated with species richness gradients and adaptive trait continua. We applied principal components analyses (PCAs), structural equation modelling and phylogenetic generalized least squares models. Results We found that traits and species‐specific habitat measures covaried along a main PCA axis, ranging from multivoltine trophic generalists with high dispersal capacity to univoltine (i.e. one generation per year), trophic specialist species with low dispersal capacity. This trait continuum was closely associated with the observed distributions along the altitudinal gradient and predicted inter‐specific differences in patterns of spatial genetic variability (FST and genetic distances), population responses to the impacts of global change and local turnover dynamics. Main conclusions The adaptive trait continuum of Mediterranean butterflies provides an integrative and mechanistic framework to: (1) analyse geographical gradients in species richness, (2) explain inter‐specific differences in population abundances, spatial distributions and demographic trends, (3) explain inter‐specific differences in patterns of genetic variation (FST and genetic distances), and (4) study specialist–generalist life‐history transitions frequently involved in butterfly diversification processes. 相似文献
9.
Ludmila Aricov Daniel George Angelescu Adriana Băran Vlad Tudor Popa Aurica Precupaş 《Journal of biomolecular structure & dynamics》2020,38(9):2659-2671
AbstractThe binding of drugs to serum proteins is governed by weak non-covalent forces. In this study, the nature and magnitude of the interactions between piroxicam (PRX) and bovine serum albumin (BSA) was assessed using spectroscopic, calorimetric and computational molecular methods. The fluorescence data revealed an atypical behavior during PRX and BSA interaction. The quenching process of tryptophan (Trp) by PRX is a dual one (approximately equal static and dynamic quenched components). The FRET results indicate that a non-radiative transfer of energy occurred. The association constant and the number of binding sites indicate moderate PRX and BSA binding. The competitive binding study indicates that PRX is bound to site I from the hydrophobic pocket of subdomain IIA of BSA. The synchronous spectra showed that the microenvironment around the BSA fluorophores and protein conformation do not change considerably. The Trp lifetimes revealed that PRX mainly quenches the fluorescence of Trp-213 situated in the hydrophobic domain. The CD and DSC investigation show that addition of PRX stabilizes the protein structure. ITC results revealed that BSA-PRX binding involves a combination of electrostatic, hydrophobic and hydrogen interactions. The analysis of the computational data is consistent with the experimental results. This thorough investigation of the PRX-BSA binding may provide support for other studies concerning moderate affinity drugs with serum protein.Communicated by Ramaswamy H. Sarma 相似文献
10.
The European endemic Erebia oeme (Hübner [1804]) (Lepidoptera: Nymphalidae: Satyrinae) is discovered in the Carpathian Chain, from where it was considered to be absent. The single population found is situated in the southern part of the Romanian Carpathians (Retezat Mountains), where it flies sympatrically and synchronically with Erebia medusa ([Denis & Schiffermüller] 1775). The similar external morphology of these two species probably caused E. oeme to be overlooked in the Carpathians, leading to an unexpected information gap in the otherwise thoroughly studied European continent. The morphology of the Romanian specimens is compared to populations from the rest of the species’ range and to E. medusa. In addition, we tested DNA barcoding as a method to discriminate between these species and confirmed that it represents an effective identification tool for the taxa involved. The habitat of E. oeme, adults of both sexes and their genitalia are illustrated in comparison with E. medusa. Based on the study of several collections, we show that E. oeme is likely to be extremely local in the Carpathians and provide arguments to consider the species as vulnerable in Romania. 相似文献