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31.
Sage C Huang M Karimi K Gutierrez G Vollrath MA Zhang DS García-Añoveros J Hinds PW Corwin JT Corey DP Chen ZY 《Science (New York, N.Y.)》2005,307(5712):1114-1118
In mammals, hair cell loss causes irreversible hearing and balance impairment because hair cells are terminally differentiated and do not regenerate spontaneously. By profiling gene expression in developing mouse vestibular organs, we identified the retinoblastoma protein (pRb) as a candidate regulator of cell cycle exit in hair cells. Differentiated and functional mouse hair cells with a targeted deletion of Rb1 undergo mitosis, divide, and cycle, yet continue to become highly differentiated and functional. Moreover, acute loss of Rb1 in postnatal hair cells caused cell cycle reentry. Manipulation of the pRb pathway may ultimately lead to mammalian hair cell regeneration. 相似文献
32.
We compared common ground flora species and vegetation structure in open-topped pheasant release pens with control areas in 43 ancient semi-natural woodlands (ASNW) in England in Spring 1988. Relationships between vegetation parameters and factors such as the density of birds in the pen and pen size were identified. The release pens ranged from 1 to 20 years old, mean pen size was 0.5 ha and the mean stocking density was 2250 pheasants per hectare of pen. Overall, the release pens had more bare ground and reduced vegetation below 50 cm structure compared to the control areas. The release pens also had lower average species diversity and percentage cover of shade tolerant perennials, in particular winter-green perennials. Annual species and perennials preferring fertile or disturbed soil all increased in percentage cover as stocking density increased above recommended levels. Bare ground increased inversely with pen size. Perennials characteristic of shady habitats decreased as stocking densities went up. The reduction of winter-green perennials was greatest in smaller, older pens. In a sub-sample of five sites, average phosphate and potassium levels were significantly higher in the pens than in the controls while pH and magnesium were not different. We estimate that 1 in 12 of all woodlands in England contains a pheasant release pen. We make recommendations for reducing impacts of these pens in ASNW. 相似文献
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Sage Chaiyapechara Kenneth K. M. Liu Frederic T. Barrows Ronald W. Hardy Faye M. Dong 《Journal of the World Aquaculture Society》2003,34(3):266-277
This study was conducted to determine the effects of increasing dietary lipid concentrations on fillet characteristics of post-juvenile rainbow trout. A feeding trial was conducted with fish meal based diets containing 10, 15, 20, 25, or 30% lipid for 24 wk. Menhaden oil was the lipid ingredient. Weight gain was significantly greater in fish fed the 30% lipid diet than in fish fed either 10%, 15% or 20% lipid diets. There were no significant differences in visceral somatic index. Fillet lipid concentration of fish fed the 30% lipid diet (9.2-g lipid/ 100-g fillet) was significantly higher (P < 0.05) than fish fed either the 10% or 15% lipid diets (5.8- and 6.9-g lipid/100-g fillet, respectively). In samples stored for 3 d at 5 C or S wk at -20 C, sensory panelists reported that the cooked fillets from fish fed the 30% lipid diet were "more fishy" than fish fed the 15% lipid diet, and preferred the cooked fillets from the 15% lipid treatment over the 30% lipid treatment. Triangle tests and fillet colorimetry showed no significant differences between fillets from fish fed the 15% and 30% lipid diets at any sampling time point. No significant differences in fillet concentrations of thiobarbituric reactive substances were observed among dietary treatments stored at either 5 C or -20 C. These results suggest that two main effects of feeding a 30% lipid diet (with fish oil as the lipid source) are a higher lipid concentration in the fillet and a "fishier" aroma compared to fillets from fish fed a 15% lipid diet. 相似文献
37.
Summary Independent but simultaneous selection by two breeding teams of the same segregating two-row winter barley material at Cambridge, England and Fiorenzuola, Italy was carried out over the years 1978–1982 with the objective of comparing the individual selection of the two breeding teams and assessing the adaptation of the surviving selections. Visual selection in the generations F3 to F5 did not result in any clear cut compartmentalisation of the material and both teams were as likely to select from families previously selected only by the other team as from families they had themselves previously selected. Lines with specific adaptation to each site as well as lines well adapted to both sites were identified from yield trials carried out in F5 and F6. The former showed only a very small yield advantage over lines with general adaptation to both sites. 相似文献
38.
Summary Nine hybrid wheats and their six parental lines were grown in a field trial at two seed densities. The ADP:0 ratios for mitochondria extracted from the six parental lines and for the appropriate 1:1 mixtures of mitochondria from these parental lines were measured. The percentage additional mitochondrial efficiency of the mixtures over their more efficient parental line was found to be significantly correlated with the percentage yield heterosis of fully restored relatively disease-free hybrids grown at the lower seed density. These results indicate that measurements of mitochondrial complementation may have some value as a first screening of potential parental lines and may thus facilitate the rational choice of suitable material for producing hybrid wheat. 相似文献
39.
We tested the effects of exponential nutrient loading and springtime carbon loading during nursery culture on the field performance
of black spruce (Picea mariana (Mill.) B.S.P.). Seedlings were grown from seed with a conventional, fixed dose fertilizer (10 mg N seedling−1) or an exponential nutrient loading regime (75 mg N seedling−1). The following spring, seedlings were exposed for two weeks to either ambient (370 ppm) or elevated levels of CO2 (800 ppm) and then planted in the field; seedling growth was followed for the next six years. Exponential nutrient loading
increased seedling height, stem diameter and leader growth, with the largest increases in height and leader length occurring
in the first three years after outplanting. Carbon loading increased seedling height and leader length, but only in seedlings
that had been exponentially nutrient loaded. A combination of carbon and nutrient loading increased shoot height 26%, stem
diameter 37% and leader length 40% over trees that received neither treatment. These results demonstrate that the growth enhancement
seen under exponential nutrient loading is maintained under field conditions for at least six years. Carbon loading just before
outplanting was a useful supplement to nutrient loading, but was ineffective in the absence of nutrient loading. 相似文献
40.
A 2 yr study was conducted in 1987 and 1988 to determine the effects of road salt run-off from New York State highway 28N on chloride levels in four tributary streams to Rich Lake, located in the central Adirondack Mountains of New York. All four study streams exhibited significant increases in chloride concentrations at sampling stations located 50 and 100 m downstream from the highway. Chloride concentrations in downstream samples were as much as 31 times higher than comparative upstream samples. Elevated chloride levels continued throughout the 6 mo period following the termination of winter salt applications. A water chemistry profile developed for Rich Lake revealed a slight increase in chloride content at lower depths. 相似文献