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In the Pedregal de San Angel reserve, in Mexico City, males of the butterfly Xamia xamiperch in and defend areas with well-defined topographic limits. These areas lack concentrations of receptive females and of larvae and adult resources. One individual defends the same territory an average of 5 h/day, up to a maximum of 23 days. The same areas are used as territories by different males during the year. These areas share some characteristic features which are described. Evidence is presented in support of the hypothesis that the territories function as mating stations. A possible scenario for the evolution of this territorial mating system is advanced. 相似文献
35.
Romero Jorge Liras Paloma Martín Juan F. 《Applied microbiology and biotechnology》1988,27(5-6):510-516
Summary Seven mutants of Streptomyces clavuligerus blocked in the biosynthesis of clavulanic acid, cephamycin C, or both antibiotics, have been isolated and characterized. Mutants nca1 and nca2 were unable to synthesize clavulanic acid but produced cephamycin C. Mutants nce1 and nce2 were completely blocked in cephamycin C production but formed clavulanic acid. A third group (mutants ncc1, ncc4 and ncc5) failed to produce both antibiotics. Arginase activity (forming ornithine) was very low in mutants ncc1 and ncc5. All the mutants blocked in clavulanic acid biosynthesis showed a normal ornithine--aminotransferase activity. Mutant ncc1, blocked in cephamycin biosynthesis, lacked completely lysine--aminotransferase (forming -aminoadipic acid) and isopenicillin N synthase. Two other mutants (nce2 and nce5) lacked isopenicillin N synthase. There was a good correlation between the isopenicillin N synthase and the lysine--aminotransferase activities of the nca mutants and the ability of those strains to produce cephamycin C. The condensing enzyme involved in the formation of the clavulanic acid nucleus appears to be different from the isopenicillin N synthase.Dedicated to Professor H.-J. Rehm on the occasion of his 60th birthday 相似文献
36.
Under continuous white light (WL), extension growth of the first internode in Sinapis alba L. was promoted by low red (R): far-red (FR) ratios reaching the stem and-or the leaves. Conversely, the growth promotion by end-of-day light treatments was only triggered by FR perceived by the leaves and cotyledons, while FR given to the growning internode alone was tatally ineffective. Continuous WL+FR given to the internode was also in-effective if the rest of the shoot remained in darkness. Both the background stem growth, and the growth promotion caused by either an end-of-day FR pulse or continuous WL+FR given to the internode, increased with increasing fluence rates of WL given to the rest of the shoot. The increase by WL of the growth-stimulatory effect of low phytochrome photoequilibria in the internode appears to be mediated by a specific blue-light-absorbing photoreceptor, as blue-deficient light from sodium-discharge lamps, or from filtered fluorescent tubes, promoted background stem growth similarly to WL but did not amplify the response to the R:FR ratio in the internode. Supplementing the blue-deficient light (94 mol·m-2·s-1) with low fluence rates of blue (<9 mol·m-2·s-1) restored the promotive effect of low R:FR reaching the internode.Abbreviations BL
blue light
- FR
far-red light
- PAR
photosynthetically active radiation
- Pfr/P
ratio between the FR-absorbing form and total phytochrome
- R
red light
- SOX
low-pressure sodium lamp
- WL
white light
Supported by the Consejo Nacional de Investigaciones Cientificas y Técnicas (República Argentina) and the ORS scheme (UK) 相似文献
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Cecilia Zazueta José A. Holguín Jorge Ramírez 《Journal of bioenergetics and biomembranes》1991,23(6):889-902
We describe a calcium transport that is sensitive to ruthenium red in liposomes reconstituted with mitochondrial extracts. This system is able to build an internally negative membrane potential, which allows the electrogenic influx of Ca2+ and Sr2+. Proteins with molecular weights higher than 35 kDa were incorporated to the vesicles, and enhanced the accumulation of the cation in an energy-dependent fashion. 相似文献
39.
Margarita Cacho Margarita Morán María Teresa Herrera Jorge Fernández-Tárrago 《Plant Cell, Tissue and Organ Culture》1991,25(2):117-123
The effects of the auxins 2,4-D, NAA and IAA either alone or in combination with kinetin or BA were investigated to assess the morphogenetic potential of leaf, root and hypocotyl explants of Digitalis thapsi. Calluses were obtained from the three explants in basal medium without the addition of growth regulators and in leaves, the calluses formed roots. Application of 2,4-D, NAA or BA increased callus formation. The presence of NAA induced root formation and that of BA induced shoot formation via callus interphase. Indole-3-acetic acid alone only induced the generation of roots in the hypocotyl callus. Kinetin was ineffective in all the explants tested. Combinations of NAA with kinetin or BA were more effective in inducing organogenesis in leaf explants. Optimum responses were obtained in hypocotyl and root explants by using IAA in combination with BA, the highest rate of shoot regeneration being observed in hypocotyl explants.Rooting of the differentiated shoots was readily achieved in media without growth regulators. Regenerated plantlets were transferred to soil and grew with a survival rate of 70%.Abbreviations BA
benzyladenine
- 2,4-D
2,4-dichlorophenoxyacetic acid
- IAA
indoleacetic acid, Kin-kinetin
- NAA
naphthaleneacetic acid 相似文献
40.
Jorge E. Moreira Arthur R. Hand L. A. Håkan Borg Stellan Sandler Michael Welsh Nils Welsh Décio L. Eizirik 《Virchows Archiv. B, Cell pathology including molecular pathology》1991,60(1):337-344
We have previously described a preferential reduction in the secretory response to nutrient secretagogues in pancreatic mouse
islets maintained in culture after in vitro exposure to streptozotocin (SZ). This reduction was associated with an impaired
substrate metabolism at the mitochondrial level. To further clarify this issue, mouse pancreatic islets were exposed in vitro
to 2.2 mM SZ for 30 min. At 4 h after SZ treatment ultrastructural changes were apparent in the endoplasmic reticulum and
Golgi areas of the B-cells. However, 2 and 6 days following SZ exposure the B-cells appeared well preserved, except for a
marked decrease in the number of insulin-containing secretory granules. A morphometric analysis of the B-cells 6 days after
SZ exposure showed a normal B-cell size and a normal volume fraction of B-cell mitochondria. However, there was a decrease
in total islet size and a 13% decrease in the volume fraction of B-cells in the islets. These mouse islets exhibited a decreased
content of the mitochondrial DNA-encoded cytochrome b mRNA, as evaluated by dot-blot analysis. As a whole, the data obtained
indicate that SZ treatment does not induce a decrease in the number of mitochondria or long-lasting ultrastructural damage
to this organelle. However, there is a clear decrease in the cytochrome b mRNA, suggesting that SZ can induce damage to the
mitochondrial DNA. 相似文献