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31.
We report a case of fetus in fetu presented as a complex intra-abdominal heterogeneous cystic lesion during ultrasound examination of the fetus at 25 weeks of gestation. Progressive growth of this mass was noted in the prenatal period. Fetal magnetic resonance imaging provided additional information to aid in the prenatal diagnosis. This allows proper counselling for the parents and helps to plan the postnatal management. Surgical excision was carried out in the early neonatal period and the diagnosis of fetus in fetu was confirmed. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
32.
Local adaptation of immunity against a trematode parasite in marine amphipod populations 总被引:1,自引:0,他引:1
Resources allocated to defence against parasites are not available for investment in other functions such as growth or reproduction,
resulting in trade-offs between different components of an organism’s fitness. In balancing the cost of infection and the
cost of immunity, selection should only favour individuals that allocate more energy to resistance and immune responses in
populations regularly exposed to debilitating parasites. Here, we compare the ability of amphipods, Paracalliope novizealandiae, to (1) avoid becoming infected and (2) to respond to infection by encapsulating and melanizing parasites, between two natural
populations exposed to different risk of parasitism. One population faces high levels of infection by the debilitating trematode
parasite Maritrema novaezealandensis, whereas the other population is not parasitised by this trematode nor by any other parasite. Under controlled experimental
conditions, with exposure to a standardized dose of parasites, amphipods from the parasite-free population acquired significantly
more parasites than those from the population regularly experiencing infection. Furthermore, a lower frequency of amphipods
from the parasite-free population succeeded at melanizing (and thus killing) parasites, and they melanized a lower percentage
of parasites on average, than amphipods from the parasitised population. These differences persist when individual factors,
such as amphipod sex or body length, are taken into account as potential confounding variables. These results support the
existence of local adaptation against parasites: an amphipod population that never experiences trematode infections is less
capable of resisting infection, both in terms of its first line of defence (avoiding infection) and a later line of defence
(fighting parasites following infection), than a population regularly exposed to infection. 相似文献
33.
Blood flow across the atrioventricular valves and outflow tracts was measured in 55 normal fetuses and 32 fetuses with haemoglobin (Hb) Bart's disease between 18 and 26 weeks of gestation. The mean velocities remained unchanged in both normal and affected fetuses over the gestations studied. The volume flow across both atrioventricular valves and outflow tracts increased as the gestation advanced in both normal and affected fetuses, but was significantly higher in affected than in normal fetuses. The same magnitude of increased flow was found in both hydropic and non-hydropic fetuses with Hb Bart's disease. These findings suggest that fetuses with severe and long-standing anaemia have a remarkable cardiac compensatory mechanism for the maintenance of tissue oxygenation. In response to anaemia and circulatory loading, the cardiac chambers and outflow tracts enlarge proportionately up to twice the normal values. Because of this response and the operation of the Frank-Starling mechanism, the heart is able to maintain a normal mean velocity of propulsion and the net output is increased to two to three times that in normal fetuses. Hydropic changes in these anaemic fetuses appear unrelated to cardiac failure as cardiac failure is not observed at the time that hydropic changes develop. 相似文献
34.
Gilbert C. S. Lui W. K. Li Anders Bjørgesæter Kenneth M. Y. Leung 《Environmental science and pollution research international》2014,21(1):177-192
This paper describes a novel statistical approach to derive ecologically relevant sediment quality guidelines (SQGs) from field data using a nonparametric empirical Bayesian method (NEBM). We made use of the Norwegian Oil Industrial Association database and extracted concurrently obtained data on species density and contaminant levels in sediment samples collected between 1996 and 2001. In brief, effect concentrations (ECs) of each installation (i.e., oil platform) at a given reduction in species density were firstly derived by fitting a logistic-type regression function to the relationship between the species density and the corresponding concentration of a chemical of concern. The estimated ECs were further improved by the NEBM which incorporated information from other installations. The distribution of these improved ECs from all installations was determined nonparametrically by the kernel method, and then used to determine the hazardous concentration (HC) which can be directly linked to the species loss (or the species being protected) in the sediment. This method also enables an accurate estimation of the lower confidence limit of the HC, even when the number of observations was small. To illustrate the effectiveness of this novel technique, barium, cadmium, chromium, copper, mercury, lead, tetrahydrocannabinol, and zinc were chosen as example contaminants. This novel approach can generate ecologically sound SQGs for environmental risk assessment and cost-effectiveness analysis in sediment remediation or mud disposal projects, since sediment quality is closely linked to species density. 相似文献
35.
Xian-Xiang Li Chun-Ho Liu Dennis Y.C. Leung 《Atmospheric environment (Oxford, England : 1994)》2009,43(15):2410-2418
A validated LES model was employed to simulate the street canyons of aspect ratio (AR) 3, 5, and 10. Three, five, and eight vertically aligned primary recirculations were found for the three cases, respectively, which showed decreasing strength with decreasing height. The ground-level wind speeds were found to be very small, making it extremely difficult for the ground-level pollutants to disperse. Local maxima of turbulence intensities were found at the interfaces between the primary recirculations and the shear layer. The pollutant trajectory followed the primary recirculations. High pollutant concentration and variance were found near the buildings where wind flowed upward. Large gradients of pollutant concentration and variance were also observed at the interfaces between the primary recirculations and the shear layer. Detailed analyses of concentration budget showed that the advection terms were responsible for pollutant redistribution within primary recirculations, while the turbulent transport terms were responsible for pollutant penetration between primary recirculations as well as pollutant removal from the street canyon. 相似文献
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40.
D.Q. Zheng J.K.C. Leung B.Y. Lee 《Atmospheric environment (Oxford, England : 1994)》2010,44(13):1699-1705
In the previous work (Zheng et al., 2007, Zheng et al., 2009), a data assimilation method, based on ensemble Kalman filter, has been applied to a Monte Carlo Dispersion Model (MCDM). The results were encouraging when the method was tested by the twin experiment and a short-range field experiment. In this technical note, the measured data collected in a wind tunnel experiment have been assimilated into the Monte Carlo dispersion model. The uncertain parameters in the dispersion model, including source term, release height, turbulence intensity and wind direction have been considered. The 3D parameters, i.e. the turbulence intensity and wind direction, have been perturbed by 3D random fields. In order to find the factors which may influence the assimilation results, eight tests with different specifications were carried out. Two strategies of constructing the 3D perturbation field of wind direction were proposed, and the result shows that the two level strategy performs better than the one level strategy. It is also found that proper standard deviation and the correlation radius of the perturbation field play an important role for the data assimilation results. 相似文献