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91.
92.
F C Battaglia 《Journal of animal science》1992,70(10):3258-3263
Fetal amino acid nutrition and metabolism have been studied primarily in pregnant sheep. The umbilical uptake of amino acids changes during gestation, but at both mid- and late gestation the total supply exceeds that required for growth. Weight-specific protein synthetic rate decreases with increasing gestational age, and these changes are proportional to the changes in metabolic rate. The use of multiple tracer methodology coupled with measurement of net tracer fluxes into and out of fetal and placental tissues can be used to delineate amino acid metabolism in considerable detail. Such studies demonstrate that even essential amino acids can be oxidized extensively by the fetus. The oxidation rate of leucine exceeds its rate of accretion in tissue proteins. Glycine metabolism is unique in several ways; there is a large umbilical uptake of glycine without a measurable uterine uptake. In late gestation there is no significant umbilical uptake of serine, although there is a significant uterine uptake, suggesting net uteroplacental utilization. Glycine is oxidized within the fetal liver and used for serum production. The interorgan exchange of amino acids between the fetal liver and placenta is clearly of major importance for serine and glycine metabolism and is likely to be of major importance for most nonessential amino acids. 相似文献
93.
E Bezirtzoglou M B Romond C Romond 《Comparative immunology, microbiology and infectious diseases》1992,15(1):71-74
Studies were undertaken to determine the regulation of the bacterial intestinal implantation in 19 newborns delivered by caesarean section. Correlation was made with the infant feeding mode. The effect of human milk seemed to be the result of B. bifidum proliferation, in contrast to artificial alimentation that seemed to favour C. perfringens implantation. The question was raised by us as to whether this opposition was only related to alimentation. In fact, B. bifidum itself also had an effect as demonstrated by the lower mean counts of C. perfringens in bottle-fed infants carrying the bifido-bacterial flora (P = 0.05). None of the other faecal bacteria investigated in this study led to the same decrease. 相似文献
94.
分散松香施胶剂性能影响因素的探讨 总被引:7,自引:0,他引:7
对逆转法制备分散松香施胶剂过程中的主要因素如乳化剂的种类及用量、马来松香加合物含量、搅拌转速、加料速度和乳化温度等系统地进行了探讨,提出了合理的工艺条件,并对实际生产中可能出现的问题及解决办法进行了阐述。 相似文献
95.
Soil pH declined from 5.9 to 5.0 in 8 years beneath plantations of Eucalyptus saligna (Sm.) in Hawaii. In stands of Albizia falcataria, (L.) Fosberg, the soil pH change was more dramatic, declining from 5.9 to 4.6. We measured several components of soil acidity beneath four mixtures of the two tree species to gain insight on the processes responsible for the decline in soil pH. These components were studied using an empirical method of comparing acid quantity, degree of neutralization (depletion of base cations), and acid strength. The decline in soil pH differed between species as a result of differences in the degree of neutralization of the soil exchange complex; the larger decrease in soil pH under Albizia was produced by greater acidification of the exchange complex. Empirical titration curves suggested that differences in acid strength moderated the divergence in soil pH beneath the species. Had the acids accumulating in the soil under Albizia been as strong as those in the Eucalyptus soil, the difference in soil pH would have been greater. Though the two species had contrasting effects on soil pH, the differences in degree of neutralization, responsible for the pH decline, were small compared with differences in the amount of cations stored in tree biomass. Continued supply of nutrient cations (from weathering or fertilization) will ultimately control both the extent of soil pH decline and the level of productivity sustained by the forest. 相似文献
96.
A technique is described for biopsy of the bovine udder, employing sedation and local anaesthesia. Tissue samples of approximately 5 g were obtained by electrocautery from two quarters of the udder of a cow laterally recumbent. Care was taken to ensure complete haemostasis which was achieved by electrocoagulation and ligation. Postoperative recovery was rapid, and loss of yield was no greater in biopsied glands than in control glands of the same cow. Yield from all quarters returned to preoperative levels within 48 h. 相似文献
97.
98.
对50例冠心病和50例随机做平板运动试验(TET)者作频域心电图(FCG)对比分析探讨FCG对冠心病的诊断价值。结果表明:单纯根据FCG异常诊断冠心病有较高假阳性(65.22%)。如将FCG的阳性指标作综合判断,虽然敏感性降低(88.00%降至70.00%)。假阳性都明显降低(65.22%降至26.00%)。认为TET的特异性较FCG高。若两者均为阴性,则冠心病可能性很小。 相似文献
99.
100.
J W Tyler J S Cullor M C Thurmond D W Hird K M Parker 《American journal of veterinary research》1989,50(1):126-130
Serologic recognition of common lipopolysaccharide core antigens has been related to enhanced resistance to gram-negative bacterial disease in several species. Class-specific titers (IgG, IgM) were determined by direct ELISA, using intact Escherichia coli (J5) as a plate antigen. Serum samples were obtained from 224 neonatal swine between the ages of 36 and 60 hours. The mean (+/- SEM) log10 IgG titer against gram-negative core antigens was 1:1,713 +/- 0.4718 and the mean log10 IgM titer was 1:202 +/- 0.5644. The IgG titer was directly related with litter size, birth weight, and serum total IgG concentration; IgM titer was directly related with dam parity and serum total IgG concentration. 相似文献