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Selected AbstractsManganese cell labeling of murine hepatocytes using manganese(III)-transferrin,CONTRAST MEDIA & MOLECULAR IMAGING, Issue 3 2008Christopher H. Sotak Abstract Manganese(III)-transferrin [Mn(III),Tf] was investigated as a way to accomplish manganese-labeling of murine hepatocytes for MRI contrast. It is postulated that Mn(III),Tf can exploit the same transferrin-receptor-dependent and -independent metabolic pathways used by hepatocytes to transport the iron analog Fe(III),Tf. More specifically, it was investigated whether manganese delivered by transferrin could give MRI contrast in hepatocytes. Comparison of the T1 and T2 relaxation times of Mn(III),Tf and Fe(III),Tf over the same concentration range showed that the r1 relaxivities of the two metalloproteins are the same in vitro, with little contribution from paramagnetic enhancement. The degree of manganese cell labeling following incubation for 2,7,h in 31.5,µm Mn(III),Tf was comparable to that of hepatocytes incubated in 500,µm Mn2+ for 1,h. The intrinsic manganese tissue relaxivity between Mn(III),Tf-labeled and Mn2+ -labeled cells was found to be the same, consistent with Mn(III) being released from transferrin and reduced to Mn2+. For both treatment regimens, manganese uptake by hepatocytes appeared to saturate in the first 1,2,h of the incubation period and may explain why the efficiency of hepatocyte cell labeling by the two methods appeared to be comparable in spite of the ,16-fold difference in effective manganese concentration. Hepatocytes continuously released manganese, as detected by MRI, and this was the same for both Mn2+ - and Mn(III),Tf-labeled cells. Manganese release may be the result of normal hepatocyte function, much in the same way that hepatocytes excrete manganese into the bile in vivo. This approach exploits a biological process,namely receptor binding, endocytosis and endosomal acidification,to initiate the release of an MRI contrast agent, potentially conferring more specificity to the labeling process. The ubiquitous expression of transferrin receptors by eukaryotic cells should make Mn(III),Tf particularly useful for manganese labeling of a wide variety of cells both in culture and in vivo. Published in 2008 by John Wiley & Sons, Ltd. [source] Rain-gauge network evaluation and augmentation using geostatisticsHYDROLOGICAL PROCESSES, Issue 14 2008Ke-Sheng Cheng Abstract Rain-gauge networks are often used to provide estimates of area average rainfall or point rainfalls at ungauged locations. The level of accuracy a network can achieve depends on the total number and locations of gauges in the network. A geostatistical approach for evaluation and augmentation of an existing rain-gauge network is proposed in this study. Through variogram analysis, hourly rainfalls are shown to have higher spatial variability than annual rainfalls, with hourly Mei-Yu rainfalls having the highest spatial variability. A criterion using ordinary kriging variance is proposed to assess the accuracy of rainfall estimation using the acceptance probability defined as the probability that estimation error falls within a desired range. Based on the criterion, the percentage of the total area with acceptable accuracy Ap under certain network configuration can be calculated. A sequential algorithm is also proposed to prioritize rain-gauges of the existing network, identify the base network, and relocate non-base gauges. Percentage of the total area with acceptable accuracy is mostly contributed by the base network. In contrast, non-base gauges provide little contribution to Ap and are subject to removal or relocation. Using a case study in northern Taiwan, the proposed approach demonstrates that the identified base network which comprises of approximately two-thirds of the total rain-gauges can achieve almost the same level of performance (expressed in terms of percentage of the total area with acceptable accuracy) as the complete network for hourly Mei-Yu rainfall estimation. The percentage of area with acceptable accuracy can be raised from 56% to 88% using an augmented network. A threshold value for the percentage of area with acceptable accuracy is also recommended to help determine the number of non-base gauges which need to be relocated. Copyright © 2007 John Wiley & Sons, Ltd. [source] Influence of land use on plant community composition and diversity in Highland Sourveld grassland in the southern Drakensberg, South AfricaJOURNAL OF APPLIED ECOLOGY, Issue 5 2005T. G. O'CONNOR Summary 1Biodiversity conservation of grasslands in the face of transformation and global climate change will depend mainly on rangelands because of insufficient conservation areas in regions suited to agriculture. Transformed vegetation (pastures, crops and plantations) is not expected to conserve much biodiversity. This study examined the impact of land use on the plant diversity and community composition of the southern Drakensberg grasslands in South Africa, which are threatened with complete transformation to pastures, crops and plantations. 2The main land uses in this high rainfall region are: ranching or dairy production under private tenure using indigenous grassland, pastures (Eragrostis curvula, kikuyu and ryegrass) and maize; plantation forestry; communal tenure (maize and rangelands); and conservation. 3Plant diversity and composition were assessed using Whittaker plots. Transformed cover types were depauperate in species and ranged from kikuyu (1·4 species m,2) and ryegrass (2·9), to pine plantation (3·1), E. curvula pasture (3·1), commercial maize (3·2) and communal maize (7·8). With the exception of pine plantations, these communities supported mostly exotic (50 of 70 species) or ruderal indigenous species and made little contribution to plant species conservation. Abandoned communal cropland reverted to an indigenous grassland almost devoid of exotic species within c. 20 years. 4It was predicted that frequently cultivated sites (maize and ryegrass) would support less diversity than long-lived pastures (kikuyu and E. curvula). This was contradicted by the relatively high species diversity of communal maize fields, which was attributed to a lack of herbicides, and the depauperate communities of kikuyu and of E. curvula pasture, which were attributed, respectively, to a dense growth form and a severe mowing regime. 5Pine plantations harboured fourfold more indigenous species per plot (27) than other transformed types. Species were mostly shade-tolerant grassland relics that had persisted for 12 years since planting, and some forest colonizers. Indigenous species were unlikely to be maintained because of aggressive invasion by the exotic Rubus cuneifolius and severe disturbance associated with tree harvest and replanting. 6The richness of indigenous grasslands was expected to differ in response to grazing pressure but they differed only in composition. Grasslands were dominated by grasses, despite the richness of herbaceous species. The dominance of Themeda triandra was reduced under livestock grazing in favour of more grazing-tolerant species. Exotic species were inconspicuous except for the dicotyledon Richardia brasiliensis, a subdominant under communal grazing. 7Southern Drakensberg grasslands are probably now stocked with livestock six- to 35-fold higher than during pre-settlement times. A grassland protected for c. 50 years supported twofold greater richness (101 species plot,1) than grazed grasslands, suggesting that a 150-year history of increased mammalian grazing had already reduced plant diversity. 8Synthesis and applications. Land acquisition is costly, thus conservation of plant diversity in the southern Drakensberg requires a policy that inhibits transformation of rangelands. This can be achieved by enhancing their economic viability without changing the vegetation composition. Their inherent value must be recognized, such as for water production. The viability of commercial ranches can be improved by increasing their size. Conservation efforts need to be focused on plant taxa that only occur on unprotected rangelands. [source] Dispersal and genetic structure in the American marten, Martes americanaMOLECULAR ECOLOGY, Issue 6 2006T. BROQUET Abstract Natal dispersal in a vagile carnivore, the American marten (Martes americana), was studied by comparing radio-tracking data and microsatellite genetic structure in two populations occupying contrasting habitats. The genetic differentiation determined among groups of individuals using FST indices appeared to be weak in both landscapes, and showed no increase with geographical distance. Genetic structure investigated using pairwise genetic distances between individuals conversely showed a pattern of isolation by distance (IBD), but only in the population occurring in a homogeneous high-quality habitat, therefore showing the advantage of individual-based analyses in detecting within-population processes and local landscape effects. The telemetry study of juveniles revealed a leptokurtic distribution of dispersal distances in both populations, and estimates of the mean squared parent,offspring axial distance (,2) inferred both from the genetic pattern of IBD and from the radio-tracking survey showed that most juveniles make little contribution to gene flow. [source] Age-related lens yellowing per se contributes little to the increase in Farnsworth-Munsell 100 hue error scores with ageOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 1 2008Raymond O. Beirne Purpose:, To investigate the effects of real and simulated age-related changes in crystalline lens yellowing on Farnsworth,Munsell (FM) 100 hue total and partial error scores. Methods:, FM 100 hue total and partial error scores were measured in a group of younger (n = 10, mean age 22.2 ± 2.65 years) and a group of older (n = 10, mean age = 54.5 ± 2.64 years) normal observers along with psychophysical estimates of crystalline lens optical density and pupil size measurements. Three younger observers underwent repeated FM 100 hue testing using a variety of simulated age-related lens yellowing conditions, using filters with well-defined absorption properties which mimicked the real age-related lens yellowing changes of the older group. FM 100 hue scores were also measured under different levels of background illumination and pupil size in the 3 younger observers. Results:, FM 100 hue total and partial error scores were significantly higher in the older age group compared to the younger group (p <0.01). Lens density measures were significantly higher in the older age group compared to the young group (p<0.01), but showed less scatter with age than FM 100 hue error scores. Pupil size was significantly larger in the younger group compared to the older group (p<0.01). Simulated lens yellowing in the three younger observers, equivalent to the level of that of the older observers, did not affect any of their FM 100 hue total or partial error scores. Reductions in pupil size and illumination significantly affected the younger observers' performance, with increases in error score equivalent to the observed age-related decline between the younger and older group. Conclusions:, Lens yellowing per se makes little contribution to the increase in Farnsworth,Munsell 100 hue error score with increasing age. Retinal illumination levels and pupil size can significantly affect the error score and should be considered when interpreting FM 100 hue error scores in older subjects. Clinicians should also consider iris colour and macular pigment density when interpreting FM 100 hue error scores. [source] Respiratory impedance response to a deep inhalation in children with history of cough or asthmaPEDIATRIC PULMONOLOGY, Issue 6 2002François Marchal MD Abstract The aim of this study was to describe the change in respiratory impedance induced by a deep inhalation (DI) in children who developed a positive response to inhalation of methacholine (Mch). Eighteen children aged 4.5,12.5 years, presenting with chronic cough or doctor-diagnosed asthma, were studied at baseline after inhalation of Mch and after inhalation of a bronchodilator. Respiratory resistance (Rrs) and reactance (Xrs) were measured by the forced oscillation technique, varying transrespiratory pressure at 12 Hz around the head. The tidal flow (V,) and volume (V) dependence of Rrs before and after the DI was characterized according to the equation Rrs,=,K1,+,K2,·,|V,|,+,K3,·,V. DI induced no significant change at baseline or after inhalation of a bonchodilator. During Mch challenge, Rrs and K1 were significantly lower, and K3 and Xrs significantly less negative after DI than before, during both inspiration and expiration; there was no change in K2. We conclude that DI results in a decrease in Rrs in children with induced bronchoconstriction. The associated changes in Xrs, K1, and K3, and lack of decrease in K2, suggest that dilatation of airways occurs at the bronchial level, with little contribution of the upper airways or of a change in breathing patterns. Pediatr Pulmonol. 2002; 33:411,418. © 2002 Wiley-Liss, Inc. [source] China's Construction Land Expansion and Economic Growth: A Capital-output Ratio Based AnalysisCHINA AND WORLD ECONOMY, Issue 6 2008Huizhong Li O16; Q15; R52 Abstract Since 2003, the Chinese Government has been using land policy as an important macroeconomic policy. The present paper analyzes the impact of the expansion of construction land on economic growth in terms of the capital-output ratio. Using provincial panel data for China from 1999 to 2005, we conclude that the excess expansion of China's construction land led to an increase in the capital-output ratio. Therefore, expanding construction land has made little contribution to economic growth. This paper argues that contractionary land policy does not deter high economic growth, and is a necessary condition for a sustainable economic growth. [source] | |||||||||||||