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991.
Siváková D Lajdová A Basistová Z Cvícelová M Karabová P Blazícek P 《Anthropologischer Anzeiger; Bericht über die biologisch-anthropologische Literatur》2008,66(2):199-209
Epidemiological studies have demonstrated that several specific environmental factors and candidate genes influence the human variation in blood pressure. The aim of this study was to investigate variables associated with blood pressure; with a particular emphasis on the differences in insertion/deletion (I/D) polymorphism of the human angiotensin-converting enzyme (ACE), the body composition and the recognized risk factors for atherosclerosis among elderly males and females. A total of 374 participants (174 males and 200 females) aged from 60 to 90 years were recruited from different parts of Slovakia. The elderly were not bed-ridden, nor mentally impaired, they were able to manage their daily activities by themselves. The ACE I/D polymorphism was determined by PCR amplification of the ACE gene sequence. Body composition variables were obtained by bioelectrical impedance analysis, using the BIA 101 soft tissue-body impedance analyzer (Akern, S.r.l.). The subjects were determined to be hypertensive (blood pressure > or = 140/90 mm Hg) or normotensive (blood pressure < or = 140/90 mm Hg ). These two subgroups of males and females did not differ significantly in their mean ages. As expected, the hypertensive subjects of both sexes showed significantly higher mean values in systolic (SBP) and diastolic blood pressure (DBP), in body mass index (BMI), and in the mean values of their plasma glucose and extracellular water (ECW). The genotype distribution and allele frequencies in the whole sample (D = 0.5474, I = 0.4526) fell within the Hardy-Weinberg equilibrium. The frequency of the deleterious D allele in the normotensive (0.5532) and hypertensive (0.5516) subjects was not significantly different. The ACE I/D genotypes did not associate either with the systolic (p = 0.836) or diastolic BP (p = 0.629). From the other variables that may induce differences in blood pressure, a statistical effect was detected for glucose, Na/K, and Apo A1/ApoB ratios and physical activity on SBP, and for ApoA1, physical activity, BMI and total cholesterol on DBP. 相似文献
992.
Numerous studies show that miss ratios at forward proxies are typically at least 40–50%. This paper proposes and evaluates a new approach for improving the throughput of Web proxy systems by reducing the overhead of handling cache misses. Namely, we propose to front-end a Web proxy with a high performance node that filters the requests, processing the misses and forwarding the hits and the new cacheable content to the proxy. Requests are filtered based on hints of the proxy cache content. This system, called Proxy Accelerator, achieves significantly better communications performance than a traditional proxy system. For instance, an accelerator can be built as an embedded system optimized for communication and HTTP processing, or as a kernel-mode HTTP server. Scalability with the Web proxy cluster size is achieved by using several accelerators. We use analytical models, trace-based simulations, and a real implementation to study the benefits and the implementation tradeoffs of this new approach. Our results show that a single proxy accelerator node in front of a 4-node Web proxy can improve the cost-performance ratio by about 40%. Hint-based request filter implementation choices that do not affect the overall hit ratio are available. An implementation of the hint management module integrated in Web proxy software is presented. Experimental evaluation of the implementation demonstrates that the associated overheads are very small. 相似文献
993.
Nadja E. Schoemaker Enrico Frigerio Daniela Fraier Jan H. M. Schellens Hilde Rosing Sindy Jansen Jos H. Beijnen 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2001,763(1-2)
A selective HPLC assay is described for the determination of free and total (free plus polymer-bound) camptothecin (CPT) in human plasma after administration of the anti-tumor drug MAG-CPT (polymer bound camptothecin). Total CPT levels were determined after hydrolysis and free CPT was extracted from acidified plasma using Oasis solid-phase extraction material. Extracts were analyzed on a Zorbax SB-C8 analytical column, using a mixture of acetonitrile–25 mM phosphate buffer (pH 4.0) as the eluent. Detection was performed fluorimetrically. Concentrations of polymer-bound CPT were calculated by subtraction of free from total CPT. The lower limits of quantitation of the methods were 100 ng/ml for total and 1.0 ng/ml for free CPT using 50 μl and 250 μl plasma, respectively. Special attention was paid to the stability of the analytes. The presented method was successfully applied in a clinical pharmacokinetic study in our institute. 相似文献
994.
Lorenzo Lusini Ranieri Rossi Daniela Giustarini Paolo Di Simplicio 《Chemico-biological interactions》2002,139(1):97-114
Menadione is selectively toxic to erythrocytes. Although GSH is considered a primary target of menadione, intraerythrocyte thiolic alterations consequent to menadione exposure are only partially known. In this study alterations of GSH and protein thiols (PSH) and their relationship with methemoglobin formation were investigated in human and rat red blood cells (RBC) exposed to menadione. In both erythrocyte types, menadione caused a marked increase in methemoglobin associated with GSH depletion and increased oxygen consumption. However, in human RBC, GSH formed a conjugate with menadione, whereas, in rat RBC it was converted to GSSG, concomitantly with a loss of protein thiols (corresponding to menadione arylation), and an increase in glutathione-protein mixed disulfides (GS-SP). Such differences were related to the presence of highly reactive cysteines, which characterize rat hemoglobin (cys beta125). In spite of the greater thiol oxidation in rat than in human RBC, methemoglobin formation and the rate of oxygen consumption elicited by menadione in both species were rather similar. Moreover, in repeated experiments under N2 or CO-blocked heme, it was found that menadione conjugation (arylation) in both species was not dependent on the presence of oxygen or the status of heme. Therefore, we assumed that GSH (human RBC) and protein (rat RBC) arylation was equally responsible for increased oxygen consumption and Hb oxidation. Moreover, thiol oxidation of rat RBC was strictly related to methemoglobin formation. 相似文献
995.
996.
Farmers’ genetic perceptions regarding their crop populations: An example with maize in the central valleys of Oaxaca, Mexico 总被引:1,自引:0,他引:1
Collaborative plant breeding is an approach to crop improvement that includes close attention to specific adaptation and interaction between farmers and formal plant breeders to better meet the needs of those farmers. Collegial interaction capable of making best use of the knowledge and skills of farmers and breeders will depend upon an understanding of those in terms that are relevant to each. To facilitate this interaction with the goal of making farmer selection practices more effective, the work described here sought to improve outside researchers’ understanding of farmers’ fundamental perceptions about their populations, growing environments, and expectations for response to selection. Various methods were used to accomplish this with a small sample of maize farmers in two communities in the Central Valleys of Oaxaca, Mexico. Farmers’ decisions about maize varietal type repertoires imply assessments based on genetic and environmental variation in the local context. A clear distinction was made between traits of high and low heritability and expected response to selection, however, some traits of interest to farmers such as large seed size may involve considerations other than their potential for expression in the progeny generation. 相似文献
997.
Daniela S. Nitiu 《Aerobiologia》2003,19(2):71-78
The behaviour of Celtis airborne pollenwas studied for a period of three years(1998–2000) in the city of La Plata. The pollengrains were captured with a Lanzoni trap andthe maximum pollination period was observed tooccur during the end of winter and spring inthe three years. The annual values of pollenconcentration varied, and a significantdecrease was observed during 2000. The greatestairborne pollen record was in October with anaverage of 82.3% in relation to its totalconcentration during 1998–2000. Based on theintradiurnal behaviour analysis, it wasobserved that the maximum pollination peakoccurs at 2H when the temperaturereaches its maximum values. Considering thethree sampling years, the meteorologicalvariables that most influenced the processes of pollen emission,dispersion and transportation in the atmospherewere: maximum and minimum temperature andrainfall. 相似文献
998.
Elena Loreti Daniela Bellincampi Christel Millet Amedeo Alpi Pierdomenico Perata 《Journal of plant physiology》2002,159(12):1383-1386
Elicitors of defence response can modulate pathways other than those related to pathogen attacks. In this paper, we demonstrate that, as with sugars, chitosan and oligogalacturonides (OGs) can repress the gibberellin signalling pathway leading to the induction of -amylase in barley embryos. These results are suggestive of a complex cross-talk between the defence, hormonal and metabolic signalling pathways. 相似文献
999.
F. Bonasoro Iain C. Wilkie Giorgio Bavestrello Carlo Cerrano M. Daniela Candia Carnevali 《Zoomorphology》2001,121(2):109-121
The common demosponge Chondrosia reniformis possesses the capacity to undergo an unusual creep process which results in the formation of long outgrowths from the parent
body. These shape changes, which have been interpreted as adaptive strategies related to environmental factors, asexual reproduction
or localised locomotor phenomena, are due mainly to the structural and mechanical adaptability of the collagenous mesohyl.
This contribution describes the morphological correlates of mesohyl plasticisation in C. reniformis. The microscopic anatomy of the mesohyl was examined when it was in different physiological conditions: (1) standard ”resting”
condition, (2) ”stiffened” condition and (3) dynamic ”creep” condition. In this last case four representative regions of the
sponge body were analysed: the parent region, the elongation region, the transition region and the propagule region. The results
show that the histological modification of the sponge mesohyl during plasticisation is limited and localised. The most significant
structural changes involve mainly cytological features of specific cellular components characterised by granule inclusions
(i.e. the spherulous cells) and the arrangement and density of the collagenous extracellular framework, though the integrity
of the collagen fibrils themselves is not affected. Morphological and functional aspects of mesohyl plasticisation invite
comparison with the mutable collagenous tissue of echinoderms. Possible functional analogies between these two tissues are
hypothesised.
Accepted: 29 June 2001 相似文献
1000.
Leptin is produced by adipose tissue and identified as a “satiety signal,” informing the brain when the body has consumed enough food. Specific areas of the hypothalamus express leptin receptors (LEPRs) and are the primary site of leptin action for body weight regulation. In response to leptin, appetite is suppressed and energy expenditure allowed. Beside this hypothalamic action, leptin targets other brain areas in addition to neuroendocrine cells. LEPRs are expressed also in the hippocampus, neocortex, cerebellum, substantia nigra, pancreatic β-cells, and chromaffin cells of the adrenal gland. It is intriguing how leptin is able to activate different ionic conductances, thus affecting excitability, synaptic plasticity and neurotransmitter release, depending on the target cell. Most of the intracellular pathways activated by leptin and directed to ion channels involve PI3K, which in turn phosphorylates different downstream substrates, although parallel pathways involve AMPK and MAPK. In this review we will describe the effects of leptin on BK, KATP, KV, CaV, TRPC, NMDAR and AMPAR channels and clarify the landscape of pathways involved. Given the ability of leptin to influence neuronal excitability and synaptic plasticity by modulating ion channels activity, we also provide a short overview of the growing potentiality of leptin as therapeutic agent for treating neurological disorders. 相似文献