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121.
W. F. Carey A. Poulos P. Sharp P. V. Nelson E. F. Robertson J. L. Hughes A. Gill 《黑龙江环境通报》1994,14(9):813-819
Variability in the level of expression of very long chain fatty acids (VLCFAs) is documented in cultured chorionic villus (CV) cells derived from two fetuses, one at risk for an unusual peroxisomal fatty acid β-oxidation defect, and the other at risk for the X-linked form of adrenoleucodystrophy (ALD). Cells from early subcultures of chorionic cells from both cases gave normal values for VLCFA ratios. The results for the fetus at risk for the β-oxidation defect were interpreted to indicate that the fetus was not affected; however, at birth, the infant was clinically and biochemically affected. In the case of the fetus at risk for X-linked ALD, although VLCFAs were normal in subculture 1, the levels of these fatty acids increased dramatically in subculture 3, suggesting an abnormal fetus. Termination of the pregnancy and subsequent biochemical and morphological follow-up confirmed that the fetus was indeed affected by ALD. 相似文献
122.
Mr. M. T. Rebello G. Hackett J. Smith F. E. Loeffler S. Robson N. Maclachlan R. W. Beard C. H. Rodeck R. Williamson D. V. Coleman C. Williams 《黑龙江环境通报》1991,11(1):41-46
Ten-ml samples of amniotic fluid were taken from pregnancies being terminated at 8–14 weeks' gestation. DNA was extracted from the amniotic cells by sequential centrifugation and analysed using the polymerase chain reaction (PCR). Fifteen samples were analysed for evidence of maternal contamination using Mfd5 oligo-nucleotide primers for repeat polymorphisms. Ten amniotic fluid samples were tested for the Delta-F508 deletion characteristic of cystic fibrosis to demonstrate a diagnostic application for the technique. In each case, DNA extracted from fetal tissue from the same pregnancy was included in the controls. In 14 of the 15 cases tested with the Mfd5 primers, both the amniotic fluid DNA and the fetal DNA showed no evidence of contaminating DNA. In one case, neither the amniotic fluid cells nor the fetal cells yielded results. In nine of the ten cases tested with the Delta-F508 primers, the amniotic fluid cell DNA provided accurate information about the genetic status of the fetus; in the tenth, the fetal DNA failed to amplify. The results indicate that adequate DNA can be extracted from amniotic fluid from 8 weeks' gestation onward and these samples are suitable for prenatal diagnosis using PCR. 相似文献
123.
The influence of source and timing of nitrogen fertilizers on yield and nitrogen use efficiency of four sweet potato cultivars 总被引:2,自引:0,他引:2
R. O. Ankumah V. Khan K. Mwamba K. Kpomblekou-A 《Agriculture, ecosystems & environment》2003,100(2-3):201
Nitrogen (N) availability is a very important determinant of crop yield. It is also one of the most expensive inputs in crop production. Thus, the efficient management of N by farmers with limited resource is a very important part of successful soil and crop management system. A field study was conducted on a Norfolk sandy loam soil at the George Washington Carver Agricultural Experiment Station, Tuskegee, AL, to evaluate the influence of fertilizer source and timing on the yield of four sweet potato [Ipomoea batatas (L.)] cultivars. Two N sources (urea, CO(NH2)2 and ammonium nitrate, NH4NO3), four sweet potato cultivars (‘Georgia Jet’, GA-Jet; ‘TU-82-155’, TU-155; ‘TU-1892’; and ‘Rojo Blanco’, Rojo-Bl) and three times (zero, single, and split applications) were used in a factorial designed experiment. Plants were harvested after 80 and 120 days and total and marketable yields determined. Nitrogen recovery efficiency, yield efficiency and physiological efficiency were also determined. Total and marketable yields of early maturing cultivars were significantly higher than of late maturing cultivars (P<0.05). The single application of N resulted in significantly higher yield in storage roots than split application (P<0.05). Physiological efficiency values were highly correlated with total marketable yields. Recovery rates increased with time. Late maturing cultivars tended to have higher N recovery and physiological efficiency than early maturing cultivars. These results suggest that cultivar maturity group should play an important part in N fertilization recommendations for sweet potato. 相似文献
124.
Sustaining the productive capacity of the land resource under the existing land-use system and increasing population pressure requires the use of appropriate technologies that will enhance farm productivity and income levels.This paper examines the effect on farm profitability of smallholder maize farmers’ use of intensification technologies in tropical agriculture. The survey was conducted in southwest Nigeria. A multi-stage sampling technique was used to select 300 respondents from two major agroclimatic zones in Osun State. Primary data were collected using a structured questionnaire and complemented with focus group discussions (FGDs), while the State’s Ministry of Agriculture provided secondary data.Pressure on land was found high because farmland was continuously cropped for an average of 10 years with a mean fallow period of 2 years only. Technologies used to intensify agriculture included inorganic fertilizer, organic manure, alley cropping, and tree planting.Results from costs and returns analysis showed that average net returns to inorganic fertilizer use ranked highest in the two zones, while tree planting ranked lowest. There was a significant ecoregional difference on the average net returns/year earned by users of mineral fertilizer. While organic manure use earned higher net returns than alley cropping practice in the rain forest, the reverse was the case for the derived savanna. FGDs revealed that respondents’ preferred to use inorganic fertilizer despite its inadequate supply because, apart from enhancing higher returns and net gains, it also improved output level and provided an opportunity for the continuous use of the scarce land.These results imply that economic returns play a critical role in farmers’ use of intensification technologies and consequently affect their resource management decisions. Policy measures aimed at promoting research on appropriate technologies that are profitable on farmers’ fields will be more effective in enhancing farmers’ use of intensification technologies. 相似文献
125.
The groundwater regime in Upper Palar basin, Tamilnadu has been highly contaminated in several locations due to discharge of effluents from a large number of tanneries. At some places total dissolved solids (TDS) concentration in groundwater was found as high as 8000 mg/l. Transmissivity and storativity of the regional aquifer were estimated at a few locations. The porosity and dispersivity values were not determined in the field. These parameters were assumed based on data available for similar geological formations elsewhere. The aquifer conceptualization thus arrived at formed the basis of a numerical groundwater flow model which was constructed using the finite difference method. The flow model was calibrated for steady state and then for transient condition for the period of 1984-92. The computed heads and calibrated parameters of the flow model were used to compute groundwater velocities. The migration of contaminants for a 20 year period was computed using the hydraulic heads and effective porosity value in a pathline model using FLOWPATH software. Mass transport model was constructed using Method of Characteristics (MOC) computer code in a separate model. The seepage rate of effluent is assumed at a rate of 30% of that discharged on the surface. The mass concentration of solute in the effluent reaching the water table was assumed as 40%, the same as in the surface effluent. The mass transport model was calibrated for a 20 year period. Prediction of contaminant migration from different clusters in the basin was analyzed. The prediction results indicated elevated TDS concentration of more than 4000 mg/l from most clusters. Also the area of the contaminated zone is likely to double in 20 years from contaminated zone of 1992. 相似文献
126.
127.
A population of 1639 patients were seen for chorionic villus sampling (CVS). Embryonic death was identified at ultrasound in 5.3 per cent of patients. The number of patients undergoing CVS was 1551, with 1416 transcervical procedures and 135 transabdominal procedures. The most common indication for CVS was advanced maternal age. Spontaneous pregnancy losses identified by increased risk of pregnancy loss with increasing aspiration attempts. The total fetal loss for this population was 5.4 per cent with the pregnancy loss estimated due to procedure being 1.2 per cent. Analysis of placentae from patients having CVS and amniocen-tesis showed no differences. Microbiological assessment prior to CVS was similar to previous publications. 相似文献
128.
Dr. Mertin haben wir für seine Hilfe bei der Interpretation der elektronenmikroskopischen Aufnahmen, der Deutschen Forschungsgemeinschaft und dem Fonds der Chemischen Industrie für ihre finanzielle Unterstützung zu danken. 相似文献
129.
130.