菌根生物技术应用现状与研究进展

论述了菌根的类型、功能及其在林业上的应用现状，并指出菌根生物技术研究进展与方向，为林业生产提供参考。     

一种二元单亲演化差基因变异算法

设计了一种新的单亲遗传算法,该算法对个体和基因分别计算其适应值,并将适应值最差的基因 进行变异,从而大大提高了遗传算法的全局收敛速度。以n皇后问题为例,采用这种算法求解3000个皇 后问题所用时间平均约为55min,而求解100个皇后问题所用时间平均只有约124ms。实验表明,该算法 不仅能在短时内找到全局最优解(精确解),而且具有良好的稳定性。     

日粮锌、硒水平对肉鸡肠道黏膜屏障结构的影响

为了探讨微量元素锌和硒相互作用对肉鸡肠道黏膜屏障结构的影响，将24只1日龄AA肉鸡随机分3组，分别饲喂添加有高锌高硒(锌1000mg／kg、硒5mg／kg)、低锌低硒(锌34mg／kg、硒0．08mg／kg)或常锌常硒(锌50mg／kg、硒0．15mg／kg)的日粮45d后，观察肠黏膜上皮细胞、上皮内淋巴细胞和盲肠扁桃体的形态结构变化。结果表明：高锌高硒或低锌低硒组肉鸡的肠黏膜结构有明显的损伤，表现为肠黏膜上皮细胞萎缩，绒毛长度下降，上皮内淋巴细胞数量减少；盲肠扁桃体的弥散淋巴组织和淋巴小结中，淋巴细胞数量减少，细胞出现肿胀，有的核消失，结缔组织增生，淋巴小结萎缩。尤其是高锌高硒组的损伤最为严重。而常锌常硒组肉鸡肠黏膜和盲肠扁桃体的形态结构正常。结论：日粮中按锌50mg／kg、硒0．15mg／kg的比例添加，对于维持肠道黏膜的正常屏障结构是合适的。过高或过低的锌和硒对小肠黏膜有毒性作用，破坏其屏障功能；而且高锌和高硒可相互促进以增强其毒性作用。     

家兔选育性状典型相关分析

选择日本大耳白和新西兰两个品种家兔的生长、繁殖、以及体尺3组共17个性状，应用多元统计方法进行了典型相关分析，结果表明；日本大耳白兔的初生重、初生窝重、21日龄重、泌乳力、胸围等5个性状，新西兰兔的产活仔数、初生重、21日龄重、泌乳力、断奶窝重、母兔体重等6个性状为主要性状。     

蜂胶高生物活性黄酮组分的研究

本文探讨了蜂胶总黄酮中最具活性的黄酮类物质的提取分离、官能结构特征与功能关系、可能的功效,进而提出了如何看待蜂胶总黄酮含量高低的问题.     

The intravenous bile Acid loading test in the goat: determination of a procedural protocol and reference values

An intravenous bile acid loading test was performed on 16 goats using various dosages and sampling protocols. A recently developed enzymatic bile acid assay provided an economical and technologically simple method for bile acid analysis. Intravenous injection of bile salts into goats was well tolerated. Clearance times were rapid. A protocol for performance of the test was suggested and a practical reference range for T 1/2 clearance of 4+/-1 minute was determined. Further investigations of this test in the assessment of liver function in the ruminant appear warranted.     

Diurnal and individual variations in bile acids in the plasma of normal dairy cows

Blood samples were collected every 2 h during a 24 h period from 6 cows of one herd and 10 cows of another herd. In a third herd 9 cows were sampled every 2 h from 6 a.m. to 8 p.m. Concentrations of total bile acids, acetoacetate, glucose and free fatty acids were determined in blood plasma. A marked difference in individual bile acid concentrations and patterns of diurnal variation was found. For most cows the highest bile acid values were observed between 2 and 6 a.m. (overall mean (+/- SD) at 6 a.m.: 104 +/- 84 mumol/l, range: 20-307 mumol/l). Fourteen cows with a bile acid value greater than 90 mumol/l at 6 a.m. ("high BA") were characterized as a group by showing a pronounced decrease in the mean bile acid concentration after morning feeding. In the group of 11 cows with a 6 a.m. bile acid value less than 90 mumol/l ("low BA") the time of day did not contribute significantly to the bile acid variation. For the "high BA" group a nearly synchronous variation between the mean values of the 3 feeding dependent parameters (acetoacetate, glucose and free fatty acids) and the mean values of bile acids was found. The within animal coefficients of correlation between bile acids and the feeding dependent parameters were significantly higher in the "high BA" group than in the "low BA" group. No direct connection was found between bile acid levels and the quantity of concentrates fed or the individual milk yield.     

Genetic mapping and utilization of quantitative trichome-mediated insect resistance in potato

Introgression of trichome-mediated insect resistance from the wild speciesSolanum berthaultii has become a major focus of the potato improvement program at Cornell University during the past twelve years. Several quantitative characters are involved in this resistance which is effective against a wide range of pest types. Correlative biochemical assays have been developed to assay specific components of the resistance, and the effects of the resistance on the target pests have been studied. Quantitative laboratory assays and specific measurements of insect behavior and biology have increased the precision of selection and enable the investigation of the genetic control of the resistance.We are currently using restriction fragment length polymorphisms (RFLPs) for genetic mapping of factors controlling the trichome traits fromS. berthaultii. Backcrosses to both the wild and the cultivated species parents have been evaluated for phenotypes contributing to the resistance mechanism, including trichome density, sucrose ester and polyphenol oxidase production by the trichomes, and the enzymatic browning reaction responsible for insect entrapment. Genetic maps are being developed for these progenies, using RFLP markers previously mapped in potato. Field and greenhouse trials under insect infestations are also being conducted with the mapping progeny. Our goal is to locate genes responsible for quantitative insect resistance by correlating RFLP variation at mapped loci with the trichome phenotypes and insect resistance. Genetic markers for these traits will be useful in transfer of the effective wild chromosomal segments into and among tetraploid potatoes, and for a better understanding of the resistance mechanism.     

肉用禽育种中应使用的主要屠宰性状指标的探讨

通过对不同周龄、品种的肉鸡、肉鸭屠宰数据进行分析,发现体重、屠宰重、全净膛重、半净膛重、胴体重这几个指标之间呈高度相关(R＞0.94,P＜0.0001),说明可以把这几个指标合并为一个指标,考虑到育种公司测定的实际需求,建议用屠宰重代替全净膛重、半净膛重.由于腿肌重与腿重呈显著相关,用腿重来代替腿肌重,可以大幅度简化育种工作,提高育种效率.本研究认为可以用宰前体重、腿重、胸肌重、腹脂重作为肉用禽屠宰测定的主要指标,为了计算相关的率,可以考虑测量屠宰重指标.     

日粮纤维及其对幼龄单胃动物消化功能的影响

日粮纤维能提供大量的能量,而且有利于维持动物机体的正常消化功能。本文综述了日粮纤维的代谢及对幼龄单胃动物消化功能的影响。