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111.
The hepatic alpha 1-adrenergic receptor mediates a variety of hepatic functions including respiration, glycogenolysis, gluconeogenesis, and growth. We have utilized a rat primary hepatocyte culture system to show that the alpha 1-adrenergic receptor can be activated in a stereoselective manner by a series of phenethylamines and catecholimidazolines resulting in the stimulation of DNA synthesis as determined by [3H]thymidine incorporation. The phenethylamines adhered to the Easson-Stedman hypothesis with a rank order of potency of (-)-(R)-norepinephrine (NE) greater than (+)-(S)-NE greater than the desoxy analog dopamine (DA) for the stimulation of DNA synthesis. However, the 2-substituted catecholimidazolines did not follow this trend and demonstrated an order of potency of the desoxy analog 3,4-dihydroxybenzyl imidazoline (DHT) greater than or equal to (-)-(R)-2-(3,4,alpha-trihydroxybenzyl)imidazoline (TBI) greater than (+)-(S)-TBI. 4-Substituted catecholimidazolines were less potent as inducers of DNA synthesis than the corresponding 2-substituted analogs with an order of potency of (+)-(R)-4-(3,4-dihydroxybenzyl)imidazoline (DBI) greater than (+,-)-(R,S)-DBI greater than (-)-(S)-DBI. When the beta-hydroxyl moiety of NE is replaced with an amino group as in 3,4-dihydroxyphenylethylenediamine, the isomers are less active than the beta-hydroxylated analogs and also demonstrate no stereoselectivity for the stimulation of DNA synthesis. These results demonstrate that the hepatic alpha 1-adrenergic receptor can recognize various isomeric forms of these compounds and that hepatocellular growth can be modulated in a stereoselective manner by phenethylamines and imidazolines. 相似文献
112.
The gap theory in forest dynamics 总被引:4,自引:0,他引:4
Shin-Ichi Yamamoto 《Journal of plant research》1992,105(2):375-383
Since the late 1970s, ecologists interested in forest dynamics have focused their attention to the responses of individuals,
populations and communities to “gaps” which are openings created in the forest canopy. This review intended to introduce some
collective knowledge on major subjects of the gap theory in forest dynamics, in relation to gap-disturbance regimes, tree
regeneration behaviour and community structure. 相似文献
113.
On the interpretation of some planktonology equations 总被引:1,自引:0,他引:1
D. A. Voronov 《Oecologia》1991,88(2):303-304
Summary The concept of the mean value of a function is used to interpret some population-dynamics equations. The well-known formula for the per capita growth rate r gives a precise mean value for any (not only exponentially growing) populations. This result is used to derive the birth and death rate equations of Paloheimo (1974) with minimal initial limitations.Abbreviations
t
time
-
N
number of animals
-
E
number of eggs
-
r
specific (i.e. per capita) population growth rate
-
b
specific birth rate
-
d
specific death rate
-
D
duration of embryonic development 相似文献
114.
Growth and photosynthetic response of nine tropical species with long-term exposure to elevated carbon dioxide 总被引:17,自引:0,他引:17
Summary Seedlings of nine tropical species varying in growth and carbon metabolism were exposed to twice the current atmospheric level of CO2 for a 3 month period on Barro Colorado Island, Panama. A doubling of the CO2 concentration resulted in increases in photosynthesis and greater water use efficiency (WUE) for all species possessing C3 metabolism, when compared to the ambient condition. No desensitization of photosynthesis to increased CO2 was observed during the 3 month period. Significant increases in total plant dry weight were also noted for 4 out of the 5 C3 species tested and in one CAM species, Aechmea magdalenae at high CO2. In contrast, no significant increases in either photosynthesis or total plant dry weight were noted for the C4 grass, Paspallum conjugatum. Increases in the apparent quantum efficiency (AQE) for all C3 species suggest that elevated CO2 may increase photosynthetic rate relative to ambient CO2 over a wide range of light conditions. The response of CO2 assimilation to internal Ci suggested a reduction in either the RuBP and/or Pi regeneration limitation with long term exposure to elevated CO2. This experiment suggests that: (1) a global rise in CO2 may have significant effects on photosynthesis and productivity in a wide variety of tropical species, and (2) increases in productivity and photosynthesis may be related to physiological adaptation(s) to increased CO2. 相似文献
115.
An inflatable minirhizotron system for root observations with improved soil/tube contact 总被引:3,自引:1,他引:2
Commonly used minirhizotrons consisting of a transparent tube inserted into the soil seldom attain good contact between the tube and the soil, which leads to root growth occurring in a gap rather than in the soil. A new system is described involving an inflatable flexible rubber wall, made from a modified motorcycle tube. Pressure ensures a proper tube/soil contact so that the environmental circumstances for root growth along the tube more closely correspond to those in the undisturbed soil. Before the endoscope slide is introduced into the minirhizotron for taking pictures, the inflatable tube is removed, so that there is no-often opaque-wall between the endoscope and the roots. This improves the picture quality and facilitates the analysis of root images. 相似文献
116.
Shoot apical meristems were used to establish regenerative axillary bud cultures of 9 muscadine grape cultivars. Meristems taken from 10 cm long shoots had less contamination (3%) and a higher survival rate (94%) than those from shorter or longer shoots. Of media tested, MS, 1/2 MS, and C2D resulted in equivalent shoot proliferation rates, whereas, WPM produced stunted shoots. When pooling results for 3 cultivars, 5, 10 and 20 M BA and 5 M TDZ produced the highest average number of shoots per cultured apex (3.4–3.8). However, shoots produced with TDZ were stunted and did not root well. For rooting of shoots directly in potting mix, a rooting powder pretreatment significantly increased the number of roots per shoot but did not affect percent rooting or root length. For rooting in vitro, 1 M NAA significantly increased all parameters measured. Although more shoots rooted in vitro than in vivo (77% vs. 46%), the latter was judged preferable since acclimatized plants were produced in less time and a major culture step was eliminated. Significant differences among cultivars were noted for measured responses in all experiments.Abbreviations BA
benzyladenine
- Kin
kinetin
- MS
Murashige & Skoog (medium)
- NAA
naphthaleneacetic acid
- TDZ
thidiazuron
- WPM
woody plant medium 相似文献
117.
Nicola J. Atkinson H. John Newbury Brian V. Ford-Lloyd 《Plant Cell, Tissue and Organ Culture》1991,27(1):77-79
A broadly applicable method for the successful induction of root systems in a number of cultivars of A. majus has been determined. This involves a double filter-paper bridge with a liquid medium for root induction and allows the transfer of culture-grown plantlets to a glasshouse environment with minimal disturbance to the plant as a whole. 100% survival of transferred plantlets has been achieved with the inclusion of a few simple precautions upon shoot transfer and during the initial stages of plant establishment in vivo. 相似文献
118.
A protoplast to plant system in roses 总被引:7,自引:0,他引:7
Derek Matthews John Mottley Imelda Horan Andrew V. Roberts 《Plant Cell, Tissue and Organ Culture》1991,24(3):173-180
High yields of protoplasts were isolated from embryogenic suspension cultures of Rosa persica x xanthina and Rosa wichuraiana using an enzyme mixture comprising 20 g l-1 cellulase Onozuka R10, 1 g l-1 Pectolyase Y-23 and 10 g l-1 hemicellulase. Agarose-immobilized protoplasts gave the most consistent growth at a plating density of 5×104 protoplasts ml-1 on the basic medium of Kao & Michayluk (KM8p) containing 2 mg l-1 naphthaleneacetic acid and 1 mg l-1 benzylaminopurine. At 25°C in the dark, 0.004% of R. persica x xanthina protoplasts developed into colonies. Using similar culture conditions, but with a plating density of 9×104 protoplasts ml-1, 0.017% of R. wichuraiana protoplasts developed into colonies. On transfer of R. persica x xanthina colonies to Schenk & Hildebrandt's medium containing 3 mg l-1 2,4-dichlorophenoxyacetic acid, globular and later stage embryos were formed. Approximately 30% of these embryos developed into plantlets on transfer to basal Schenk & Hildebrandt's medium. Further development of the plantlets took place on cellulose plugs (Sorbarods) soaked in Murashige & Skoog's medium containing 0.05 mg l-1 naphthaleneacetic acid, 0.05 mg l-1 indole-3-butyric acid and 0.1 mg l-1 benzylaminopurine. Rose breeding is now open to the full range of in vitro genetic manipulation techniques involving protoplast technology. 相似文献
119.
M. Dijak A. Sproule W. Keller R. Pandeya S. Gleddie 《Plant Cell, Tissue and Organ Culture》1991,25(3):189-197
Agrobacterium tumefaciens strains harbouring plasmid vectors pBCAT1, pVU1011 or pMON806 were used to transform leaf explants of Nicotiana tabacum cultivars Delgold and Candel, N. debneyi, and N. rustica var. NRT. Transgenic plants resistant to the selective agents kanamycin, hygromycin or methotrexate were regenerated and used as sources of leaf mesophyll protoplasts. Protoplasts divided and regenerated plants in the presence of selective agents at levels inhibitory to protoplasts of non-transformed plants. Cross-resistance of protoplasts to more than one selective agent was not observed in this study which suggests that this approach may lead to an efficient interspecific somatic hybrid selection system. 相似文献
120.
S. J. Ochatt 《Plant Cell, Tissue and Organ Culture》1991,25(2):161-167
Leaf protoplasts of axenic shoot cultures of Lonicera nitida cv Maigrun underwent sustained division to give multicellular colonies (microcalli) on a modified, ammonium-free MS (Murashige & Skoog) medium containing 0.5 mg l-1 NAA (1-naphthaleneacetic acid), 1.0 mg l-1 BAP (6-benzylaminopurine) and 150 mg l-1 casein enzymatic hydrolysate. Callus was produced upon transfer of cell colonies to MS medium with 2.0 mg l-1 NAA and 0.2 mg l-1 BAP. About 110 days from isolation protoplast-derived shoots were regenerated on a half-strength MS medium with 0.01 mg l-1 NAA, 5.0 mg l-1 BAP, 0.5 mg l-1 zeatin and a complex mixture of group B vitamins. The replacement of such mixture by 250 mg l-1 casein enzymatic hydrolysate promoted rhizogenesis in calli, with shoot buds being subsequently regenerated from the protoplast-derived roots. Micropropagation of protoplast-derived shoots (of either origin) was difficult, due to a strong apical dominance, but could be accomplished by transferring single-node explants to half-strength MS medium with 1.5 mg l-1 BAP. Such shoots were, in turn, successfully rooted and transferred to the glasshouse where they completed acclimatization.Abbreviations BAP
6-benzylaminopurine
- CPW
Power et al. (1989) medium
- 2,4-D
2,4-dichlorophenoxyacetic acid
- FDA
fluorescein diacetate
- F.P.E.
final plating efficiency
- f.wt.
fresh weight
- IAA
4-indole-3yl-acetic acid
- IBA
4-indole-3yl-butyric acid
- I.P.E.
initial plating efficiency
- MES
2-N-morpholinoethane sulfonic acid
- M.P.E.
intermediate plating efficiency
- MS
Murashige & Skoog (1962) medium
- NAA
1-naphthaleneacetic acid
- PVP-10
polyvinylpirrolidone
- Av MW 10,000, TIBA
2,3,5-tri-iodobenzoic acid
- Z
zeatin 相似文献