Ovine fetal electrocortical activity and regional cerebral blood flow

Fetuses of 12 near-term sheep were prepared for microsphere determination of cerebral blood flow. Experiments were performed 5 days postsurgery. The regional blood flows were measured in successive high (HV), low (LV) and high voltage electrocorticographic states. Comparisons were made between the observations made in the LV and averaged flanking HV cycles. Total cerebral blood flow was 95 +/- 8, 119 +/- 11 and 100 +/- 9 ml/min/100 g in HV, LV and HV, respectively. Low voltage electrocortical activity increased average cerebral blood flow by 22% (P less than 0.01). Significant changes were seen in all regions except the occipital cortex. The maximum change was observed in the thalamus in which the flows were 152 +/- 23, 243 +/- 35 and 138 +/- 20 ml/min/per 100 g tissue, respectively. The increase was 68% (P less than 0.001). The percent changes seen in the cerebrum are as follows: Frontal grey + 18%, frontal white + 22%, parietal white + 22%, temporal + 18%. A + 17% change was seen in the cord (P less than 0.03). It is concluded that in low voltage electrocortical activity all of the brain, except the occipital region, shows an increase in cerebral blood flow. This is probably secondary to a variance in cerebral activity. This preparation may be useful in localizing function in the fetal brain.     

Interaction and combination of separate A and B chains of insulin effects of D-and L-tryptophan in position A1

The S-thiomethyl derivatives of insulin A chain with A1-Gly replaced by D- or L-Trp have been prepared and their respective interaction and combination with the S-thiomethyl B chain studied. The UV difference spectra of the mixed against the separated [Trp1]A chains with the B chain at pH 10.8 are similar to those obtained for the unmodified chains except that the 295-nm-negative peak for ionized Tyr residue appears to be less marked. Fluorescence studies show very little environmental changes at the A1-Trp residues when mixed with the B chain. The intact hormone with A1-Gly replaced by D-Trp is known to be considerably more active than the analog with L-Trp replacement. However, for both derivatives the resynthesis of the whole molecules correctly joined by disulfide bridges starting from the separated reduced chains, gives similar low yields as shown by HPLC analysis and by receptor-binding assay. The replacement of A1-Gly by D-Trp appears to affect the separated A chain more than the intact hormone and replacements at A1 by both D- and L-Trp probably lead to significant conformational changes of the A chain so as to prevent its correct pairing with the B chain.     

Chromosome aberration and ploidy equilibrium of Vicia faba in tissue culture

Summary Different phytohormone concentrations induced different fequencies of various chromosome aberrations in calli of Vicia faba. NAA 10 ppm plus KT 2.5 ppm produced more haploids and NAA 30 ppm plus NAA 7.5 ppm produced more tetraploids and breakage. The relationship among the aberrations was analyzed. The hypothesis of ploidy equilibrium was established. The chromosome doubling rate and reduction rate of each treated group were calculated in relation to the observed data and the hypothesis. The frequency of tetraploids and breakage are correlated with each other. The frequency of total aberrations is linearly correlated with that of micronucleus formation. The regression equation is x=31.92+ 10.67 y.     

冬小麦春化过程中可溶性蛋白质组成的变化与形态发生的关系

冬小麦“农大139”经40天左右的春化处理才能迅速而整齐地抽穗,但经14—21天低温处理,已经具有在夏季抽穗的可能性,虽然抽穗推迟且极不整齐;再将春化时间延长,则抽穗百分比增加,且从播种到抽穗的时间缩短。这表明,春化过程中低温对发育的作用有两种效应:前期低温是诱发生理状态的转变,后期低温则只具有加速发育的作用,两个时期的转变是在春化的中期。蛋白质合成抑制剂乙基硫氨酸和对-氟苯丙氨酸能抑制冬小麦的春化,抑制时期也是在春化过程的中期。不同时间低温处理后冬小麦幼芽中可溶性蛋白质含量及组成发生了变化,春化过程中期(低温处理14天之后)不仅含量比对照增加了一倍,而且有新的蛋白质谱带出现。春麦中无类似现象,未经低温处理的春麦已含有冬麦中新出现的谱带。说明冬小麦春化过程的第14—21天左右是与春化过程有关的蛋白质合成的关键时期,该时期新合成的蛋白质与植株的发育状态之间存在着密切的相关关系。     

The FER gene is evolutionarily conserved and encodes a widely expressed member of the FPS/FES protein-tyrosine kinase family.

We have recently isolated human and rat cDNAs (designated FER and flk, respectively) which encode nonreceptor protein-tyrosine kinases which are very similar to one another and related in sequence and domain structure to the c-fps/fes gene product. We show that FER and flk are human and rat counterparts of an evolutionarily conserved gene, hereafter termed FER regardless of species. The human and rat FER genes encode a widely expressed 94-kilodalton protein-tyrosine kinase which is antigenically related to the fps/fes protein-tyrosine kinase. The structural and antigenic similarities between the FER and fps/fes proteins suggest that they are members of a new family of nonreceptor protein-tyrosine kinases.     

Resonance electroconformational coupling: A proposed mechanism for energy and signal transductions by membrane proteins

Recent experiments show that membrane ATPases are capable of absorbing free energy from an applied oscillating electric field and converting it to chemical bond energy of ATP or chemical potential energy of concentration gradients. Presumably these enzymes would also respond to endogenous transmembrane electric fields of similar intensity and waveform. A mechanism is proposed in which energy coupling is achieved via Coulombic interaction of an electric field and the conformational equilibria of an ATPase. Analysis indicates that only an oscillating or fluctuating electric field can be used by an enzyme to drive a chemical reaction away from equilibrium.In vivo, the stationary transmembrane potential of a cell must be modulated to become locally oscillatory if it is to derive energy and signal transduction processes.     

Modeling DNA supercoils and knots with B-spline functions

A method is offered to model the complex trajectories of closed circular DNA supercoils and knots. The trajectories are approximated by polygons and analytical expressions of the curves are generated from the polygons with B-spline functions. The resulting curves are used to evaluate the writhe and elastic energy of a series of interrelated supercoils, and to generate detailed atomic models of the deformed double helix.     

Temperature-dependent insertion of prolipoprotein into Escherichia coli membrane vesicles and requirements for ATP, soluble factors, and functional SecY protein for the overall translocation process.

The requirements for the translocation of prolipoprotein into membrane vesicles were examined in an in vitro system. As measured by the eventual modification and processing of the prolipoprotein to form mature lipoprotein, the overall translocation process was found to require ATP hydrolysis, the presence of some heat-labile soluble cytoplasmic translocation factors, and the function of a cytoplasmic membrane protein, SecY/PrlA. However, the initial step of complete insertion of prolipoprotein into the membrane vesicles occurred without apparent requirements of a nucleotide, cytoplasmic translocation factors, or a functional SecY/PrlA membrane protein. Immunopurified prolipoprotein spontaneously inserted into membrane vesicles at elevated temperatures and required ATP and cytoplasmic translocation factors to form mature lipoprotein. The prolipoprotein inserted most efficiently into liposomes made of negatively charged phospholipids, indicating the importance of phospholipids in protein translocation. These results suggest that ATP hydrolysis and the actions of both cytoplasmic translocation factors and a functional SecY/PrlA membrane protein occur at a step(s) after the insertion of the precursors into membrane vesicles. The initial step of spontaneous insertion of prolipoprotein into membranes is in good agreement with membrane trigger hypothesis proposed by W. Wickner (Annu. Rev. Biochem. 48:23-45, 1979) and the helical hairpin hypothesis proposed by D. M. Engleman and T. A. Steitz (Cell 23:411-422, 1981).     

椭圆斜羽叶的解剖研究及斜羽叶的系统分类位置

本文根据对椭圆斜羽叶(Plagiozamites oblongifolius)钙质石化化石的研究,认为其主要特征如下:羽状复叶,叶肉无海绵组织和栅栏组织分化。羽片叶脉维管束外韧式,木质部外始式,与现代苏铁属叶脉特征相近。羽轴维管束为“U”形,外始式木质部、梯状纹孔管胞,与现代苏铁属的羽轴维管束相似。根据上述特征,目前可将斜羽叶属归入原始苏铁类植物。但是,如果斜羽叶的生殖器官同 Noeggerathia 一样,为异孢型孢子囊穗,则斜羽叶可能为一种与苏铁类起源有关的原裸子植物。