用人工神经网络方法估计Ligistic方程参数

本文提出Logistic方程参数优化估计的人工神经网络方法,并选取一组标样进行具体尝试。结果表明,用这种方法估计Logistic方程参数效果极好。     

一类Holling功能性反应模型极限环的唯一性

考虑功能性反应的捕食-食饵模型这里y表示捕食者种群的密度,当a-（22）≠0时它具有线性密度制约,x表示食饵种群密度,当φ（x）≡ax/（1＋ωx）时称（1）为第二类功能性反应模型．文〔1〕研究了捕食者没有密度制约（对应于a_（22）=0）、食饵具有线性密度制约(对应于g（x）=b_1-a_(11)x）的Ⅱ类功能性反应模型（1）,得到了极限环存在性及唯一性的完整结论．最近文〔2〕在a_(22)≠O的条件下讨论了系统(1),得到了极限环的存在性与不存在性等福建省自然科学基金和国家自然科学基金资助项目（19371069号）．本文第一作者现为浙江大学访问学…     

草鱼出血病病毒多肽的荧光染色

将草鱼出血病病毒（ＧｒａｓｓＣａｒｐＨｅｍｏｒｒｈａｇｅＶｉｒｕｓ,ＧＣＨＶ）置于还原性的溶液中,然后加入等体积的ＮａＨＣＯ３配制的异硫氰酸荧光索溶液进行多肽的标记,再经ＳＤＳ－ＰＡＧＥ分析,在紫外灯下即可检测到ＧＣＨＶ全部的１１个结构多肽的荧光带。该方法最小检测量为５００ｎｇ,由该方法回收的多肽具有抗原活性,可作为抗原进行免疫学实验。     

穴位激光照射对兔子宫类固醇激素受体的影响

对兔用Ｈｅ－Ｎｅ激光照射穴位,照射外生殖器,用类固醇激素受体测定法测定子宫雌二醇受体（ＥＲ）和孕酮受体（ＰＲ）含量。照射穴位后部分实验组的ＥＲ和ＰＲ浓度上升,与正常对照组相比较有显著或极显著差别（Ｐ＜０．０５,Ｐ＜０．０１）,ＥＲ提高１．７－３．２倍,ＰＲ提高２．７－３．７倍。实验结果提示激光可通过类固醇激素受体浓度的提高,在受体水平上影响机体代谢。     

缢蛏碱性磷酸酶胍溶液中分子折叠与活力变化研究

报道了缢蛏碱性磷酸酶（简称ＡＬＰ）经不同浓度盐酸胍处理时酶的分子构象所发生的变化以及酶变化和失活的动力学过程。在胍中酶荧光发射峰强度下降,紫外差光谱在２４６ｎｍ和２８５ｎｍ处出现２个负峰,ＣＤ谱中酶的α螺旋度下降,且随浓度增大,变化程度也加大。动力学研究表明,酶在０．５ｍｏｌ／Ｌ、１．０ｍｏｌ／Ｌ、２．０ｍｏｌ／Ｌ３．０ｍｏｌ／Ｌ、４．０ｍｏｌ／Ｌ盐酸胍中的变性速度常数分别为３．２１×１０~（－４）ｓ~（－１）、６．３８×１０~（－４）ｓ~（－１）、２．１７×１０~（－３）ｓ~（－１）、２．３３×１０~（－３）ｓ~９－１）、５．１７×１０~（－３）ｓ~（－１）;而酶在相应盐酸胍中的失活速度常数分别为２．３３×１０~（－４）ｓ~（－１）、３．５７×１０~（－４）ｓ~（－１）、５．８６×１０~（－４）ｓ~（－１）、１．１４×１０~（－３）ｓ~（－１）、３．４５×１０~（－３）ｓ~（－１）;表现为失活与构象伸展变化基本平行。     

Increase in cytoskeletal actin induced by inositol 1,4-bisphosphate in saponin-permeated pig platelets

Inositol 1,4-bisphosphate (IP₂), which rapidly accumulates during cell activation, strongly stimulates an increase in cytoskeletal actin in saponin-permeated platelets, and the effect is insensitive to 5′-Chloro-5′-deoxyadenosine. Within 10 s, the amount of cytoskeletal actin in platelets rapidly increases by 41%, and then slowly increases further. IP₂ induces the increase in cytoskeletal actin in a dose-dependent manner. The half-maximal effect requires approximately 2 μM of IP₂ Inositol 1,4,5- triphosphate, the messenger for Ca²⁺ release, causes the increase in cytoskeletal actin, but is less effective than IP₂. Inositol 1-monophosphate and inositol 2-monophosphate have no effect on cytoskeletal actin. Phorbol 12-myristate 13-acetate, which has been shown to activate IP₃ 5′-phosphatase through protein kinase C, stimulates the increase in cytoskeletal actin. Spermine, an inhibitor of IP₃ 5′-phosphatase, inhibits the thrombin stimulated increase in cytoskeletal actin. These results suggest that IP₂ may be a messenger that controls the organization of actin filaments during cell activation. This study presents the first evidence for IP₂ as a messenger during cell activation.     

Localization of neuropeptide Y and atrial natriuretic peptide in the endothelial cells of human umibilical blood vessels

The localization of neuropeptide Y (NPY) and atrial natriuretic peptide (ANP) in the endothelial cells of human umbilical blood vessels was studied using the pre-embedding peroxidase-antiperoxidase (PAP) technique for electron microscopy and avidin-biotin-complex (ABC) immunostaining for endothelial cells cultured from umbilical vein. Subpopulations of NPY- and ANP-immunoreactive endothelial cells were present in term umbilical vein and artery. The umbilical vein contained more positive cells than the artery. The percentage of NPY- and ANP-immunoreactive umbilical vein cells in culture was 32% and 44%, respectively, out of a total of 3013 cells examined. The possibility that these potent vasoactive substances located in the endothelial cells of the non-innervated umbilical vessels are involved in the local regulation of blood flow is discussed.     

恒河猴、懒猴和树鼩的短时空间记忆功能与前额叶背侧部进化水平的相关性(英文)

本文研究探讨了进化地位不同的三种动物的短时空间记忆功能及其与前额叶背侧部进化水平的相关性。结果表明,在延缓反应作业中,经1000次训练后,7只恒河猴对空间位置的记忆时间平均为7.7±3.2min,懒猴为3.8±0.44min,而树鼩即使在延缓时间几乎为零秒的延缓反应中,其正确反应率也未达到90％标准。一种延缓时间仅测试一个单元,即不经训练的实验表明,恒河猴在延缓期为“0”—5min的各测试单元中,正确反应率稳定在80％以上;懒猴在延缓时间为“0”—4min的各测试单元中,平均正确反应率与恒河猴无明显差异,而当延缓时间增加到5min时,在延缓反应作业中取得的成绩显著下降;树鼩在延缓时间为1—5min的作业中取得的正确反应率在70％以下。3种动物在视觉辨别学习作业中却无明显差异。形态学研究表明,灵长类大脑前额叶的面积和结构的复杂性在进化过程中逐渐增大,如恒河猴大脑前额叶的表面积占大脑半球表面积的11.5％(Brodmann,1929),其内颗粒层发达,背侧部明显凸起,主沟区发达;懒猴的前额叶表面积占其大脑半球表面积的8.3％,背侧部凸起不显著,主沟未形成,额极内颗粒层分化明显,背侧部的内颗粒层较内侧部的发达程度差(Sanides,1967);树鼩的前额叶表面积占7.5％,额极的内颗粒层分化不明显,为非颗粒化区,此区之后为颗粒区     

Hydrolysis of phosphatidylcholine couples Ras to activation of Raf protein kinase during mitogenic signal transduction.

We have investigated the relationship between hydrolysis of phosphatidylcholine (PC) and activation of the Raf-1 protein kinase in Ras-mediated transduction of mitogenic signals. As previously reported, cotransfection of a PC-specific phospholipase C (PC-PLC) expression plasmid bypassed the block to cell proliferation resulting from expression of the dominant inhibitory mutant Ras N-17. In contrast, PC-PLC failed to bypass the inhibitory effect of dominant negative Raf mutants, suggesting that PC-PLC functions downstream of Ras but upstream of Raf. Consistent with this hypothesis, treatment of quiescent cells with exogenous PC-PLC induced Raf activation, even when normal Ras function was blocked by Ras N-17 expression. Further, activation of Raf in response to mitogenic growth factors was blocked by inhibition of endogenous PC-PLC. Taken together, these results indicate that hydrolysis of PC mediates Raf activation in response to mitogenic growth factors.