The formation of variants with a reversion of properties of transformed cells. VIII.in vitro limited life span of variants isolated from tumors

1972 ◽  
Vol 10 (3) ◽  
pp. 607-612 ◽  
Author(s):  
Zelig Rabinowitz ◽  
Leo Sachs
1999 ◽  
Vol 19 (6) ◽  
pp. 4093-4100 ◽  
Author(s):  
Odile Begel ◽  
Jocelyne Boulay ◽  
Beatrice Albert ◽  
Eric Dufour ◽  
Annie Sainsard-Chanet

ABSTRACT Podospora anserina is a filamentous fungus with a limited life span. It expresses a degenerative syndrome called senescence, which is always associated with the accumulation of circular molecules (senDNAs) containing specific regions of the mitochondrial chromosome. A mobile group II intron (α) has been thought to play a prominent role in this syndrome. Intron α is the first intron of the cytochrome c oxidase subunit I gene (COX1). Mitochondrial mutants that escape the senescence process are missing this intron, as well as the first exon of theCOX1 gene. We describe here the first mutant of P. anserina that has the α sequence precisely deleted and whose cytochrome c oxidase activity is identical to that of wild-type cells. The integration site of the intron is slightly modified, and this change prevents efficient homing of intron α. We show here that this mutant displays a senescence syndrome similar to that of the wild type and that its life span is increased about twofold. The introduction of a related group II intron into the mitochondrial genome of the mutant does not restore the wild-type life span. These data clearly demonstrate that intron α is not the specific senescence factor but rather an accelerator or amplifier of the senescence process. They emphasize the role that intron α plays in the instability of the mitochondrial chromosome and the link between this instability and longevity. Our results strongly support the idea that in Podospora, “immortality” can be acquired not by the absence of intron α but rather by the lack of active cytochromec oxidase.


Psychiatry ◽  
1961 ◽  
Vol 24 (4) ◽  
pp. 318-323 ◽  
Author(s):  
Lawrence LeShan ◽  
Eda LeShan
Keyword(s):  

Author(s):  
Anthony Parton

An abstract and non-objective style of painting, Rayism ("Luchizm") was pioneered by the Russian artist Mikhail Larionov in early 1912. The style represented the first theoretically coherent and practically consistent response on the part of the Russian avant-garde to the challenges of French Cubism and Italian Futurism. In divorcing art from figuration and in its emphasis on the purely formal qualities of painting, Rayism prepared the way for the development of both Suprematism and Constructivism. Larionov’s innovative style was practiced chiefly by those artists in his immediate orbit: painters such as Natalia Goncharova, Alexander Shevchenko, and Mikhail Le-Dantiyu, who belonged to the Donkey’s Tail and Target group. While Rayism had a limited life-span in Russia, being overtaken by Suprematism in 1915, Larionov and Goncharova continued to practice the style throughout their careers, executing Rayist paintings right up to the 1950s. In its earliest phase, known as "Realistic Rayism" ("Realistichesky luchizm"), the style proceeded from Larionov’s interest in optics and Impressionist color theory and specifically from the idea that the color, contour, and form of our world is defined by rays of light reflected from all material objects. According to Larionov’s booklet Rayism (Luchizm) of 1912, his initial aim was to explore the nature of visual perception as it exists before the brain converts what we see into a comprehensible form.


2021 ◽  
Vol 2 (5) ◽  
pp. 60-70
Author(s):  
James A. Hartley ◽  

How does our limited life span determine our choices and our view on the preciousness of life? How would these views change if we lived forever? In this work of philosophical short story fiction, a traveling salesman sits at the bar after a long day drinking bourbon. He is approached and cleverly pitched a new product he has discovered on a distant rim planet, Life. The product stops the aging process. The first batch is free, and the salesman returns eight years later to get into the distribution business.


Res Publica ◽  
1994 ◽  
Vol 36 (1) ◽  
pp. 44-55
Author(s):  
Kris Deschouwer

Coalitions have a limited life-span. There has been quite some research on the duration of coalitions and on the factors explaining variations in duration. But there is so far no solid theory on the mechanics of the termination of coalitions.This article gives an overview of the mechanics of termination in Belgian politics. By using the contextual approach (Pridham), that has originally been produced to analyse coalition formation, this overview might be a first step in the construction of a comparative explanatory model. The historical context, the institutional setting, the international context and the economical situation are described as elements that affect the termination of coalitions. The Belgian ethno-linguistic cleavage proves to be a very effective coalition-killer.


2016 ◽  
Author(s):  
Monica Nordberg ◽  
Douglas M. Templeton ◽  
Ole Andersen ◽  
John H. Duffus
Keyword(s):  

1999 ◽  
Vol 77 (5) ◽  
pp. 664-672 ◽  
Author(s):  
Christian Bégin ◽  
Louise Filion

Genetically determined rules underlying black spruce (Picea mariana (Mill.) BSP) morphological development were revealed by using tree architecture analysis. Black spruce develops according to Rauh's model. Its relatively simple and well-hierarchized architecture comprises four categories of axes (A1-A4) and three distinct branching levels. First- and second-order axes (the trunk and branches) are monopodial, orthotropic structures with rhythmic growth and branching, and an unlimited life-span (or only limited by tree longevity). They are mainly devoted to spatial exploration and occupation. Axes A3 and A4 are monopodial, plagiotropic structures with a limited life-span, which are devoted to assimilation and reproduction. Female cones develop in terminal position on A3, whereas male reproductive structures develop in terminal or lateral position on A4. Reiteration (or duplication of axes) capacity is an important feature of the architecture of black spruce. Adaptive reiteration processes allow trees to renew their foliage and to reproduce vegetatively through layering. Traumatic reiteration processes tend to restore the tree's original architecture by replacing injured axes or parts of axes. In both cases, replicas originate from dormant buds located at the bottom of growth units (deferred or proleptic reiteration) or from growing axes (immediate or sylleptic reiteration).Key words: black spruce, growth form, tree architecture, architectural model, reiteration processes.


2010 ◽  
Vol 205 (2750) ◽  
pp. 18-19
Author(s):  
Colin Barras
Keyword(s):  

Sign in / Sign up

Export Citation Format

Share Document