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101.
Letter: crystallographic data fro lysoxyme from bacteriophage T4 总被引:3,自引:0,他引:3
The lysozyme of bacteriophage T4 has been crystallized in a form suitable for X-ray diffraction analysis. The space group is P3121 or enantiomorph, and the cell dimensions are , . 相似文献
102.
Models of a dual inheritance system 总被引:1,自引:0,他引:1
J Maynard Smith 《Journal of theoretical biology》1990,143(1):41-53
In higher plants, animals and fungi, there are two inheritance systems: the familiar system, depending on DNA sequence, used in transmitting information between sexual generations, and an epigenetic inheritance system, depending on gene activation, responsible for the transmission of states of differentiation during development. Occasionally, epigenetic changes are transmitted in sexual reproduction. A formal model of such a dual inheritance system is presented, and it is shown how the separation between the two systems can sometimes break down. The evolutionary significance of such breakdowns is discussed. 相似文献
103.
Charles A. Maynard 《In vitro cellular & developmental biology. Plant》1994,30(1):64-69
Summary A field test was established in 1987 to evaluate the growth of micropropagated black cherry plantlets and control seedlings.
The study also evaluated effects of two container types on initial survival and growth and of pruning on stem form and growth.
At the time of field establishment, plantlets had more extensive root systems than the control seedlings. Survival and height
growth were not influenced by container size. Through the first three growing seasons, seedlings were larger than micropropagated
plants, but growth differences diminished in the fourth through sixth seasons. Pruning increased the length of clear stem
by nearly five-fold but adversely affected diameter growth.
Although all clones were from ortet trees more than 50 yr old, none showed plagiotropic growth. Six-year results showed that
in a well-prepared and maintained plantation, black cherry trees derived from tissue culture can have at least 80% survival,
and growth rates in excess of 1 m per year. 相似文献
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The C(19)-steroid 5alpha-reductase activity in the microsomal fraction of rat adrenal tissue under various hormonal treatments was examined. In intact control rats the activity is similar in both males and females, and after gonadectomy it is markedly increased. Treatment with oestradiol (150mug/day per animal for 7 days) or testosterone propionate (2mg/day per animal for 7 days) lowered the activity of 5alpha-reductase in castrated animals to approximately the values for intact animals in both sexes, and in intact animals the activity was also decreased by these treatments. The enzyme activity was also decreased by adrenocorticotrophin treatment but to a lesser extent than by the steroid hormones. The activity of the 5alpha-reductase enzyme in the Snell adrenocortical tumour 494 is very low when incubated as a whole homogenate, but the activity in microsomal material of the tumour was measured and unexpectedly found to be similar to that in intact controls. 相似文献
107.
Seeds of Kochia indica Wight germinate rapidly in shallow water,but their germination is retarded on moist filter-paper. Theretardation is traced to a surface-active, saponin-like inhibitor,which is readily leached away in water and is adsorbed by charcoalor soil. Excised embryos may also remain dormant on filter-paper,but if rinsed in water quickly become active. Inhibition isfavoured by higher temperature (30°C. as against 20°or less), especially in an atmosphere of oxygen, although onceactive the embryos grow rapidly in such conditions. When theoxygen concentration is reduced to 5 per cent., germinationand growth are markedly retarded, but 5 per cent. CO2 has littleor no retarding effect. 相似文献
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