Boundary conditions at the cartilage-synovial fluid interface for joint lubrication and theoretical verifications

The objective of this study is to establish and verify the set of boundary conditions at the interface between a biphasic mixture (articular cartilage) and a Newtonian or non-Newtonian fluid (synovial fluid) such that a set of well-posed mathematical problems may be formulated to investigate joint lubrication problems. A "pseudo-no-slip" kinematic boundary condition is proposed based upon the principle that the conditions at the interface between mixtures or mixtures and fluids must reduce to those boundary conditions in single phase continuum mechanics. From this proposed kinematic boundary condition, and balances of mass, momentum and energy, the boundary conditions at the interface between a biphasic mixture and a Newtonian or non-Newtonian fluid are mathematically derived. Based upon these general results, the appropriate boundary conditions needed in modeling the cartilage-synovial fluid-cartilage lubrication problem are deduced. For two simple cases where a Newtonian viscous fluid is forced to flow (with imposed Couette or Poiseuille flow conditions) over a porous-permeable biphasic material of relatively low permeability, the well known empirical Taylor slip condition may be derived using matched asymptotic analysis of the boundary layer at the interface.     

白洋淀和太湖地区鸟类绦虫区系的比较研究

本文对白洋淀和太湖地区鸟类绦虫区系进行了比较研究,并对太湖鸟类绦虫区系作了初步分析。结果表明,鸟类绦虫区系分布与宿主区系分布密切相关,亲缘关系相近的宿主有许多相同的或亲缘相近的绦虫,这种现象为研究宿主与寄生虫的演化提供了可靠途径;发现鸟的越冬地绦虫种类比迁徙地种类丰富,分析其原因,除温、湿度、中间宿主等生态条件之外,与鸟的迁徙有一定关系。太湖地区的绦虫具有北方型和随遇型,亦有世界性种类和东半球广布种,提出了两地区家禽和野生鸟类所寄生的共同种类的绦虫。     

Modeling with in vitro kinetic parameters for the elaboration of transfer RNA identity in vivo

A tRNA with "double identity" was created, and this tRNA was demonstrated in vitro to aminoacylate quantitatively with either of two amino acids. In contrast, acceptance of only one of these amino acids was observed in vivo, and a simple manipulation determined which one was accepted. Kinetic parameters were obtained for aminoacylation with each amino acid of the tRNA with double identity and of related tRNAs. Modeling with these parameters largely explains which amino acid specificity is observed in vivo. The results delineate some of the kinetic boundaries for the design and accommodation of tRNA sequence variations in the elaboration of identity in vivo.     

Endotoxin removal by anion-exchange polymeric matrix.

The effects of anion-exchange polymeric matrices on endotoxin removal from albumin and gamma-globulin solutions are evaluated. The positively charged cellulose acrylic media carrying DEAE or QAE functional groups remove significant amounts of endotoxin from tap water, but are less effective in protein solutions. With properly controlled pH levels and salt concentrations, the endotoxin level in a protein solution can be reduced; however, low endotoxin concentrations, less than 100 pg/ml, are more difficult to remove. The endotoxin removal capacity depends on the number of functional groups existing in the matrix, expressed as the number of milliequivalents (meq), and on the pH operable range, which is directly related to the pK alpha value of the matrix. The effects of pH and salt on endotoxin removal from albumin and gamma-globulin solutions by an anion-exchange polymeric matrix were evaluated statically in test tubes. In addition, a dynamic flow was performed under statically defined conditions on a 250-ml DEAE cartridge for the removal of endotoxin from albumin at a flow rate of 40 ml/min. A greater than 75% reduction in the endotoxin can be achieved, with protein loss occurring only in the early stage of removal. Such processes are useful for the reduction of endotoxin from biological solutions produced by natural sources or recombinant DNA technology.     

Effects of traces of rare earth elements on the protozoanBlepherisma and on mice

The growth of the protozoanBlepherisma is stimulated by Lanthanum (La) at concentrations as low as 0.32 ppm. In mice Yttrium (Y) and Ytterbium (Yb) are absorbed, accumulated, and metabolized. Both rare earth elements (RE) exhibit a high affinity for teeth and bones, accumulation occurs and metabolism is slow. In the livers of RE-exposed mice, concentrations are variable. The liver is apparently capable of absorbing and discharging RE in a manner depending on metabolic activity. The main route of discharge for ingested REs is the alimentary canal. Exposure of pregnant mice to RE leads to rapid placental transfer of RE; 14.1% of the total amount of RE administered was detected in newborn mice. Young, developing organisms appear to be especially susceptible to RE accumulation.     

九连小蘖悬浮培养细胞生理生化研究 Ⅰ.细胞生长与培养液的电导率和过氧化物酶活性的变化

本文报道了九连小蘖细胞悬浮培养过程中,细胞生长与培养液的电导率、pH值、可溶性糖含量及过氨化物酶活性的变化。实验表明细胞生长曲线与培养液的电导率、可溶性糖含量变化的曲线恰成镜像关系。而细胞生长曲线与培养液的过氨化物酶活性变化的曲线相互平行。从而,可以通过监测培养液的电导率和过氧化物酶活性的变化来了解细胞生长状况,并可作为植物细胞培养过程中生物量增长的参考指标。     

转铁蛋白结构与功能的研究——骆驼血清转铁蛋自的分离纯化及其含单一铁结合部位的结构域的制备和鉴定

分离纯化获得的骆驼血清转铁蛋白由分子量为73,000和63,000两个组分组成。两者至少N-端五肽顺序相同(Met-Pro-Asp-Lys-Thr)。骆驼血清转铁蛋白在生理pH下不能与人胎盘转铁蛋白受体结合。用胰蛋白酶酶解骆驼转铁蛋白可以同时得到两个合单一铁结合部位的结构域,分别来自转铁蛋白分子的N-端称N-端结构域(分子量34,700和40,700)和C-端称C-端结构域(分子量35,100)。在上述结果的基础上指出并讨论了反刍动物转铁蛋白在结构和功能上存在更多的共同性,而与其它哺乳动物的转铁蛋白有着明显的区别。     

Catalytic properties of X-prolyl dipeptidyl aminopeptidase from Lactococcus lactis subsp. cremoris nTR.

An X-prolyl dipeptidyl aminopeptidase (X-PDAP; EC 3.4.14.5) was identified to be loosely bound on the inner cell membrane fraction of Lactococcus lactis subsp. cremoris nTR. The biosynthesis of X-PDAP was continuously increased before the late-log growth phase of the bacteria. Both Gly-Pro-pNA and Ala-Ala-pNA were hydrolyzed by X-PDAP; the kcat/Km value of the former was about 10-fold that of the latter. The Ki of X-Pro and Pro-X were more specific to X-PDAP than those of X-Ala. The enzyme splitting a dipeptide sequentially from beta-casomorphin as a model catalytic pattern was identified and some properties of the enzyme were further characterized.     

Differences in thermotolerance induced by heat or sodium arsenite: correlation between redistribution of a 26-kDa protein and development of protein synthesis-independent thermotolerance in CHO cells

In previous studies, we have demonstrated the differences in thermotolerance induced by heat and sodium arsenite (Lee et al., Radiat. Res. 121, 295-303, 1990). In this study, we investigated whether a 26-kDa protein might play an important role in evincing these differences. Chinese hamster ovary (CHO) cells treated for either 1 h with 100 microM sodium arsenite (ARS) or 10 min at 45.5 degrees C became thermotolerant to a test heat treatment at 43 degrees C administered 6 or 12 h later, respectively. After the test heating at 43 degrees C for 1.5 h, the level of 26-kDa protein in the nucleus was decreased by 92% in nonthermotolerant cells, 78% in ARS-induced thermotolerant cells, and 3% in heat-induced thermotolerant cells. Inhibiting protein synthesis with cycloheximide (CHM, 10 micrograms/ml) after ARS treatment eliminated thermotolerance to 43 degrees C and delayed restoration of the 26-kDa protein in the nucleus. In contrast, CHM neither prevented the development of thermotolerance nor inhibited the restoration of the 26-kDa protein in heat-induced thermotolerant cells. However, when cells were exposed to cold (4 degrees C), immediately after initial heating, restoration of the 26-kDa protein and development of thermotolerance did not occur. These results demonstrate a good correlation between the restoration and/or the presence of this 26-kDa protein and the development of protein synthesis-independent thermotolerance.     

Construction and expression of nonsense suppressor tRNAs which function in plant cells

An Arabidopsis thaliana L. DNA containing the tRNA(TrpUGG) gene was isolated and altered to encode the amber suppressor tRNA(TrpUAG) or the ochre suppressor tRNA(TrpUAA). These DNAs were electroporated into carrot protoplasts and tRNA expression was demonstrated by the translational suppression of amber and ochre nonsense mutations in the chloramphenicol acetyltransferase (CAT) reporter gene. DNAs encoding tRNA(TrpUAG) and tRNA(TrpUAA) nonsense suppressor tRNAs caused suppression of their cognate nonsense codons in CAT mRNAs, with the tRNA(TrpUAG) gene exhibiting the greater suppression under optimal conditions for expression of CAT. The development of these translational suppressors which function in plant cells facilitates the study of plant tRNA gene expression and will make possible the manipulation of plant protein structure and function.