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31.
Stuart K 《Parasitology today (Personal ed.)》1989,5(1):5-8
32.
Anna L. Ballard Alastair G. McEwan David J. Richardson J. Baz Jackson Stuart J. Ferguson 《Archives of microbiology》1990,154(3):301-303
Rhodobacter capsulatus strain BK5 possesses a membrane bound respiratory nitrate reductase rather than the periplasmic enzyme found in other strains. The enzyme in strain BK5 is shown to be both functionally and structurally related to the nitrate reductase of Paracoccus denitrificans and Escherichia coli.Abbreviation TMAO
trimethylamine-N-oxide 相似文献
33.
Summary Phosphinothricin is a non-selective herbicide which inhibits glutamine synthetase (EC 6.3.1.2) activity causing an overaccumulation of ammonia in higher plants. Alfalfa (Medicago sativa L) shoot tissue and petiole-derived callus exposed to phosphinothricin show 50 and 70% reductions, respectively, in glutamine synthetase activity with a concomitant rise of 10 and 20 fold, respectively, in endogenous ammonia. The diffusibility of ammonia may limit the use of a detoxifying gene, phosphinothricin acetyltransferase, as a selectable marker for alfalfa transformation. However, the addition of up to 40 times the standard levels of ammonium nitrate to the culture media used in this study had no effect on callus growth, although glutamine synthetase activity was inhibited by 50% and endogenous ammonia increased 27 fold. Therefore, ammonia accumulation may not be the primary cause of cell death in alfalfa after exposure to phosphinothricin. It follows that diffusion of ammonia from cell to cell would not restrict the selection for phosphinothricin acetyltransferase transformed cells, thereby indicating that this enzyme could be used as a selectable marker in transformation experiments.Abbreviations PPT
Phosphinothricin
- PAT
Phosphinothricin acetyltransferase 相似文献
34.
35.
Homozygous osteogenesis imperfecta unlinked to collagen I genes 总被引:4,自引:1,他引:3
Katherine Aitchison Donald Ogilvie Mary Honeyman Elizabeth Thompson Bryan Sykes 《Human genetics》1988,78(3):233-236
Summary In a consanguineous pedigree in which a severe type of osteogenesis imperfecta was segregating as an autosomal recessive trait, analysis of genetic markers for both collagen I structural loci COL1A1 and COL1A2 showed that the phenotype was unlinked to either locus. 相似文献
36.
The growth rate of a population of Euphausia lucens from thewest coast of South Africa was estimated from laboratory studiesand from monthly size-frequency distributions of samples collectedover a 1-year period. Laboratory studies indicated that growthrates ranged from 0.131 (larvae) to 0.047 mm day1 (juveniles),while size-frequency distributions suggested a growth rate of{small tilde}0.026 mm day1 for the adults. The mean annualbiomass from the inshore, intermediate and offshore regionsranged from 9.75 to 47.29 mg dry wt m3 with the highestbiomass being found in the inshore region. Calyptopis larvaewere present for most months of the year, indicating continuousrecrwtment. The relative contribution of flesh, moults and eggsto the total annual production was estimated separately forall three regions. Production due to growth (Pg) was estimatedto be 92.71185.60 mg dry wt m3 year1, whileexuviai production (Pe) varied between 60.01 and 281.38 mg drywt m year Production of eggs (Pr) was estimated to range from5.07 to 12.39 mg dry wt m year the lowest value being obtainedin the inshore region. Moult production represented {small tilde}6times the mean biomass in each region, while the P/B ratio forflesh production varied from 3.92 to 8.91, the highest ratiobeing obtained in the offshore region. Total P/B ratios rangedfrom 10.14 to 16.01. 相似文献
37.
Effect of nitrogen stress and abscisic acid on nitrate absorption and transport in barley and tomato
F. Stuart Chapin III David T. Clarkson John R. Lenton Colin H. S. Walter 《Planta》1988,173(3):340-351
The potential of barley (Hordeum vulgare L.) and tomato (Lycopersicon esculentum Mill.) roots for net NO
3
-
absorption increased two-to five fold within 2 d of being deprived of NO
3
-
supply. Nitrogen-starved barley roots continued to maintain a high potential for NO
3
-
absorption, whereas NO
3
-
absorption by tomato roots declined below control levels after 10 d of N starvation. When placed in a 0.2 mM NO
3
-
solution, roots of both species transported more NO
3
-
and total solutes to the xylem after 2 d of N starvation than did N-sufficient controls. However, replenishment of root NO
3
-
stores took precedence over NO
3
-
transport to the xylem. Consequently, as N stress became more severe, transport of NO
3
-
and total solutes to the xylem declined, relative to controls. Nitrogen stress caused an increase in hydraulic conductance (L
p) and exudate volume (J
v) in barley but decrased these parameters in tomato. Nitrogen stress had no significant effect upon abscisic acid (ABA) levels in roots of barley or flacca (a low-ABA mutant) tomato, but prevented an agerelated decline in ABA in wild-type tomato roots. Applied ABA had the same effect upon barley and upon the wild type and flacca tomatoes: L
p and J
v were increased, but NO
3
-
absorption and NO
3
-
flux to the xylem were either unaffected or sometimes inhibited. We conclude that ABA is not directly involved in the normal changes in NO
3
-
absorption and transport that occur with N stress in barley and tomato, because (1) the root ABA level was either unaffected by N stress (barley and flacca tomato) or changed, after the greatest changes in NO
3
-
absorption and transport and L
p had been observed (wild-type tomato); (2) changes in NO
3
-
absorption/transport characteristics either did not respond to applied ABA, or, if they did, they changed in the direction opposite to that predicted from changes in root ABA with N stress; and (3) the flacca tomato (which produces very little ABA in response to N stress) responded to N stress with very similar changes in NO
3
-
transport to those observed in the wild type.Abbreviation and symbols ABA
abscisic acid
- Jv
exudate volume
- Lp
root hydraulic conductance 相似文献
38.
J Bryan 《The Journal of cell biology》1988,106(5):1553-1562
Gelsolin, a Ca2+-modulated actin filament-capping and -severing protein, complexes with two actin monomers. Studies designed to localize binding sites on proteolytic fragments identify three distinct actin-binding peptides. 14NT, a 14-kD fragment that contains the NH2 terminal, will depolymerize F-actin. This peptide forms a 1:1 complex with G-actin which blocks the exchange of etheno-ATP from bound actin. The estimated association and dissociation rates for this complex are 0.3 microM-1 s-1 and 1.35 x 10(-6) s-1 which gives a maximum calculated Kd = 4.5 x 10(-12) M. 26NT, the adjacent peptide on the NH2-terminal half of gelsolin, binds to both G- and F-actin. This fragment has little or no intrinsic severing activity and will bind to F-actin to nearly stoichiometric ratios. The interactions of 14NT and 26NT with actin are largely Ca2+ independent and one of these sites, probably 14NT, is the EGTA-stable site identified in the intact protein. 41CT, the COOH-terminal half of gelsolin, forms a rapidly reversible 1:1 complex with actin, Kd = 25 nM, that slows but does not block etheno-ATP exchange. This interaction is Ca2+ dependent and is the exchangeable site in the intact protein. One of these sites is hidden in the intact protein, but cleavage into half fragments exposes all three and removes the Ca2+ dependence of severing. 相似文献
39.
Rankin L. L.; Enoka R. M.; Volz K. A.; Stuart D. G. 《Journal of applied physiology》1988,65(6):2687-2695
An experimental protocol designed to assess fatigability in motor units has been applied to two hindlimb muscles of anesthetized adult rats to study the effects of whole-muscle fatigue on the isometric twitch. Both soleus and extensor digitorum longus exhibited a linear relationship between fatigability (i.e., force decline after a 360-s fatigue test) and the magnitude of the twitch force following the fatigue test. Twitch force after the fatigue test was potentiated (i.e., greater than the value before the fatigue test) in many muscles, despite the development of considerable fatigue. This coexistence of fatigue and twitch potentiation was observed in 7% (5/70) of soleus and 48% (31/64) of extensor digitorum longus muscles. The coexistence was exhibited only by the least fatigable muscles of the fast-contracting extensor digitorum longus. The extensor digitorum longus muscles that did not exhibit twitch potentiation probably experienced a higher proportion of muscle-fiber inactivation, such as due to failure of neuromuscular propagation, that was induced by the fatigue regimen. 相似文献
40.
Comparison of diaphragmatic fatigue in newborn and older rabbits 总被引:1,自引:0,他引:1
Le Souef P. N.; England S. J.; Stogryn H. A.; Bryan A. C. 《Journal of applied physiology》1988,65(3):1040-1044
The ability to maintain occlusion pressure (i.e., fatigability) during activation of the diaphragm via phrenic nerve stimulation was compared in newborn (less than 14 days old) and older (greater than 30 days old) rabbits. The younger animals had lower maximum inspiratory pressures (MIP) and markedly greater falls in pressure during sustained diaphragmatic contractions at greater than 40% MIP than did the older animals. Histological analysis showed a paucity of high-oxidative type I fibers in the diaphragms of the young animals. We therefore conclude that the newborn rabbit diaphragm is extremely susceptible to fatigue and that this susceptibility correlates with the distribution of muscle fiber types. 相似文献