Fibronectin peptide DRVPHSRNSIT and fibronectin receptor peptide DLYYLMDL arrest gastrulation ofRana pipiens

Gastrulation is characterized by dramatic cell migration which is thought to require the interaction of cell adhesion molecules with extracellular molecules. We have tested two novel peptides, a fibronectin peptide and a fibronectin receptor peptide, for their effects on gastrulation of the leopard frogRana pipiens. The fibronectin peptide DRVPHSRNSIT corresponds to residues 1373–1383 of the cell-binding domain of fibronectin; the receptor peptide DLYYLMDL corresponds to residues 124–131 of 1 subunit of a variety of integrins including 51. Either of these peptides significantly inhibited gastrulation after being microinjected into mid-blastulae. These results indicate that these sequences may correspond to the ligand/receptor interaction sites of fibronectin and its receptor(s).     

High-affinity NGF binding requires coexpression of the trk proto-oncogene and the low-affinity NGF receptor.

Nerve growth factor (NGF) interacts with two different low-affinity receptors that can be distinguished by affinity crosslinking. Reconstitution experiments by membrane fusion and transient transfection into heterologous cells indicate that high-affinity NGF binding requires coexpression and binding to both the low-affinity NGF receptor and the tyrosine kinase trk gene product. These studies reveal a new growth factor receptor-mediated mechanism of cellular differentiation involving trk and the low-affinity NGF receptor.     

Retrograde transport of endocytosed Shiga toxin to the endoplasmic reticulum.

Shiga toxin and some other protein toxins that act on targets in the cytosol have previously been shown to enter the trans-Golgi network. Transport by this route may be necessary for translocation of the toxin to the cytosol and for intoxication, but it is not known whether the enzymatically active part of the toxins actually enters the cytosol from the trans-Golgi network. It has been suggested that such toxins are transported in a retrograde manner to the endoplasmic reticulum and that translocation occurs in this organelle, but retrograde transport of endocytosed material beyond the trans-Golgi network has never been demonstrated. Here we show that in butyric acid-treated A431 cells endocytosed Shiga toxin is not only transported to the trans-Golgi network, but also to all Golgi stacks, to the endoplasmic reticulum and to the nuclear envelope. Furthermore, butyric acid sensitizes the cells to Shiga toxin, which is consistent with the possibility that retrograde transport is required for translocation of the toxin to the cytosol.     

如何制造人体器官

很久以来,器官的排异性和捐赠器官的缺乏一直困扰着器官移植病人。最近,美国威斯康星大学的研究人员宣布,用干细胞可生长出人体器官,这种干细胞是迄今发现的发育最不成熟的人类细胞。科学家们当其在胚胎中尚未明确发育方向时将其取出,在一定方向对其施以一定的刺激,它们便可发育成肝脏、心脏、大脑或各种骨骼。对于全世界的医生来说,这一发现无疑预示着一个医学新纪元即将来临。虽然美国国会有人反对从丢弃的胚胎和人工流产的胎儿身上获取干细胞进行研究,甚至有70名立法人员在一封措辞坚定的信中要求联邦政府禁止一切此类研究,然而…     

On the occurrence of homovanillic acid and 3-methoxy-4-hydroxymandelic acid in human cerebrospinal fluid

Zusammenfassung Es wird papierchromatographisch gezeigt, dass Cerebrospinalflüssigkeit gesunder Menschen sowohl Homovanillinsäure als auch 3-Methoxy-4-hydroxymandelsäure enthält. Die Konzentration der ersteren ist etwa 75 ng/ml und die der letzteren etwa 25 ng/ml.

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Acknowledgment. This work has been supported by grants from Leo Ltd., Hälsingborg, and from the Medical Faculty, University of Göteborg (Sweden). For technical assistance we are indebted to Mrs.I. Olofson.     

Concordance between two linear orders: The Spearman and Kendall coefficients revisited

This paper discusses the two classic measures of concordance between two linear orders L and L′, the Kendall tau and the Spearman rho, equivalently, the Kendall and Spearman distances between such orders. We give an expression for ρ(L,L′)?τ(L,L′) as a function of the parameters of the partial order L∪L′, which allows the determination of extremal values for this difference and an investigation of when tau and rho are equal. This expression for ρ(L,L′)?τ(L,L′) is derived from a relation between the Kendall and Spearman distances between linear orders that is equivalent to both the Guilbaud (1980) formula linking rho, tau, and a third coefficient sigma, and Daniels’s (1950) inequality. We also prove an apparently new monotonicity property of rho. In the conclusion we point out possible extensions and add general historical comments.     

Synthesis of N-(2-hydroxy-1-phenoxyacetyl) prolyproline

Ionophores consist of molecules which surround and carry positive metal ions and other ions through biological membranes. One classe of ionophores which we have been developing contains dipeptides which are encouraged to become part of a ring because of possible hydrogen bond formation between the 2-hydroxy on the phenyl group and carboxyl group (COOH) of the final amide proline. Formation of a ring should increase the complexation ability of the ionophore. We report that the synthesis of N-(2-hydroxyl-1-phenoxyacetyl) prolyproline(1), a novel ionophore is prepared from activated 2-acetoxy phenoxyacetic acid (3a) and the appropriate dipeptide ester using coupling methods such as dicyclohexyl carbodiimide with hydroxyben-ztriazole or carbonyl diimidazole. Yang Dingqiao: born in 1958, Associate professor