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101.
George W. Haughn Julie Smith Barbara Mazur Chris Somerville 《Molecular & general genetics : MGG》1988,211(2):266-271
Summary A gene encoding acetolactate synthase was cloned from a chlorsulfuron-resistant mutant of Arabidopsis. The DNA sequence of the mutant gene differed from that of the wild type by a single base pair substitution. When introduced into tobacco by Ti plasmid-mediated transformation the gene conferred a high level of herbicide resistance. These results suggest that the cloned gene may confer agronomically useful levels of herbicide resistnace in other crop species, and that it may be useful as a selectable marker for plant transformation experiments. 相似文献
102.
Summary Fruit of the blackberry, Rubus pennsylvanicus Poir. (Rosaceae), were examined to determine variation in maturation characteristics. Maturation timing and rate varied greatly among individual fruits, resulting in a bi-colored fruiting display comprised largely of two maturation stages, pre-ripe (salmon and scarlet) and ripe (dark brown and black). While ripe fruit were generally larger and heavier than pre-ripe fruit, exhibiting greater fresh and dry fruit weight, diameter, water content, and total seed weight, no significant differences were found in energy content, i.e. numbers of calories per gram pulp, or in pulp:seed ratio. The differences between ripe and pre-ripe fruit appear to be due largely to an increase in water content and seed weight with maturity. The fact that little energetic benefit accrues to the preferential selection of ripe fruit suggests that bi-colored Rubus displays may be considered to be unicolored. 相似文献
103.
104.
Mary K. Vaughan Damon C. Herbert George M. Vaughan Frank J. Weaker Anna I. Esquifino Russel J. Reiter 《Chronobiology international》1988,5(2):107-114
In young adult male rats bearing a donor anterior pituitary gland grafted for 3 weeks under a kidney capsule, serum prolactin (PRL) concentrations were elevated and exhibited a rhythm with the highest values in the light phase. Serum PRL in control animals did not exhibit a significant rhythm. Eutopic pituitary PRL content, manifesting a biphasic (12-hr) rhythm with crests during the day and night in controls, exhibited a similar pattern in grafted rats though an overall reduction in pituitary PRL content was seen in the grafted animals. Neither the normal biphasic serum testosterone rhythm nor the normal 24-hr rhythm (nocturnal surge) of pineal N-acetyltransferase activity and melatonin content were altered in the hyperprolactinemic rats. Serum thyroxine (T4) and triiodothyronine (T3) and their free indices (FT4 I, FT3 I) and serum thyrotropin (TSH) were highest during the day in controls and grafted rats and a 12-hr rhythmic component was detected in data for these variables. In the grafted animals, the 12-hr component was reflected in an additional peak at night detectable by testing of means. The overall serum T4 FT4 I, and TSH levels were lower in grafted rats though overall T3 and FT3I levels did not differ between grafted and controls. T3 uptake (T3 U) values were similar between controls and grafted rats, in both cases exhibiting a fall during the night. Changes in serum thyronines could not be explained by changes in serum binding as assessed by the T3U3 and thus may represent changes in thyroidal secretion of T4. The rhythm in serum PRL of grafted rats suggests the presence of rhythmic circulating factor(s) capable of influencing ectopic lactotrophs. The reduced eutopic pituitary PRL content suggests a role for PRL in influencing eutopic lactotrophs in the pituitary-grafted hyperprolactinemic male rat model. Though circulating testosterone and pineal melatonin synthesis were not altered in this model, thyroid function appeared to be so. 相似文献
105.
Axonal shortening and the mechanisms of axonal motility 总被引:1,自引:0,他引:1
Axons in tissue culture retract and shorten if their tips are detached from the substrate. The shortening reaction of the axon involves contractile forces that also arise during normal axonal motility, elongation, and retraction. We studied shortening in axonal segments isolated from their parent axons by transecting the axon between the growth cone and the most distal point of adhesion to the substrate. Within 15-20 minutes after transection, an isolated axonal segment shortened and pulled its tail end toward the growth cone. During the shortening process, long sinusoidal bends arose along the axon. The identical shortening reaction occurs without transection, when the axon tip is detached from the substrate. Pharmacological studies with inhibitors of glycolysis indicate that the shortening mechanisms utilize metabolic energy, presumably ATP. The rate of sinusoidal shortening is similar to both the rate of polymer translocation in the axon by slow axonal transport and the rate of normal axonal elongation. Taxol inhibits the shortening reaction with a similar dose dependence to its inhibition of axonal growth. Together, all these observations suggest that the same basic intracellular motility mechanisms are involved in normal axonal growth, in slow axonal transport, and in the shortening reaction: the intracellular dynamic system that utilizes ATP to generate longitudinal movements of polymers within the axon may be the same mechanism underlying both the retraction and the elongation of the axon. 相似文献
106.
Michael L. Mavrovouniotis Patrick Bayol Tu-Kien Michael Lam George Stephanopoulos Gregory Stephanopoulos 《Biotechnology Techniques》1988,2(1):23-28
Using Gibbs Energies of compounds, as well as Gibbs Energy changes and equilibrium constants of biochemical reactions, the contributions of functional groups to the Gibbs Energy (in aqueous solution, temperature 25°C, and pH=7) have been estimated. These contributions allow the estimation of the Gibbs Free Energy and the equilibrium constant of a biochemical reaction, given the structure of the reactants and products. 相似文献
107.
Variations in the gross morphology and surface architecture of the gill filaments and secondary lamellae of a freshwater catfish (Rita rita) have been investigated using scanning electron microscopy. Heterogeneity of the gill has been correlated with the distribution of lamellar water-flow at different regions of a gill filament. Higher lamellar water flow (cc/pore/cmH2O/sec) was estimated for the middle region of the filaments. The filaments are covered with epithelial cells whose surface is provided with well-developed microridges. The lamellae are generally covered with microvillous epithelial cells. The variations in surface architecture of the gill filaments and secondary lamellae have been correlated with their probable functions. 相似文献
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