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Rapid Growth Of Nerve: His discovery of the technique of Tissue culture in 1907, made with nerve cells from which he had observed the rapid growth of nerve of nerve fibers, provided his direct experimental evidence. Characteristi¬cally, he left the development of Tissue cul¬ture technique to others and devoted his efforts to pure research. He made fundamental trans¬plant studies of polarity and asymmetry in em¬bryonic organs and of the control of organ rapid growth of nerve.
It has been demonstrated experimentally (in another kind of nerve) by Keith Lucas in 1910, and by others, that the magnitude of impulses in a sensory nerve and the speed of conduction of these impulses along the nerve depend on the particular fiber and on its condition, and not on the magnitude of the stimulus—provided that the nerve responds at all. This principle—the all-or-nonc law—puts a severe limitation on the means that sensory nerves can use to transmit information from sense organs. It means that a nerve fiber cannot show the strength of a stimulus by the strength of its response.See Also The Growth Of Polycul-turalism:A number of challenging questions arise in this highly complex area which transcend the purely linguistic issues: the growth of polycul-turalism, the interface between linguistic inheritance and affiliation, and the dilemma of whether to change the experience or the expec¬tations for bilingual children. I recall the words of a bilingual child in an inner London school discussing her family profile: 'Just because I can speak two languages, Miss, it doesn't mean I'm two children ... I'm just me.'
Lateral growth in trees frequently begins later than growth in height, but the period of lateral growth is longer. Rates of lateral growth like¬wise are low at the outset, increasing after a few weeks and then diminishing. In view of the long annual period of lateral growth in trees, deleterious environmental conditions may exercise a pronounced effect on growth. In the wood of trees of temperate regions, narrow and wide growth rings may be observed, marking years characterized by unfavorable and favorable con¬ditions for growth.
On The Other Hand See Regulation Of Growth And Differentiation:This work suggests that drugs, hormones, and other powerful bio¬logically active compounds control the activity of specific genes in man by altering the attach¬ment of regulatory proteins to the DNA, either permitting or inhibiting the expression of the genetic potential of a given cell. All in all, the basic hypotheses of gene regulation and their chemical confirmation provide extremely power¬ful models with which to explain many aspects of the regulation of growth and differentiation in higher organisms as well as in simple bac¬teria.
The synthesis of dormin (abscisin II), known to play a major role in controlling the dor¬mancy of buds, tubers, and seeds, provided a significant advance in 1967 in the study of plant growth regulation. In an analysis of the inhibit¬ing mechanism in Lemna minor (duckweed), concentrations of one part per million of this synthetic compound inhibited growth by about 95%. DNA synthesis appeared to be suppressed, and the breaking of the dormancy was thought to be caused by reactivation of the enzyme DNA-polymerase by a growth hormone. |
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