共查询到20条相似文献,搜索用时 15 毫秒
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2′,3′-Dihydroxydihydrosuberosin its acetonide derivative and 7-hydroxycoumarin has been isolated from the extracts of Eremocitrus glauca. The s 相似文献
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Aneesh Kumar Nair Naik Dhiraj Dilip Pandit Sagar Subhash 《Journal of Plant Biology》2007,50(3):374-377
High-frequencyin vitro flowering is reported here fromin vitro regenerated shoots ofin vitro-raised seedlings of rare and endemicCeropegia lawii, Ceropegia maccannii, Ceropegia oculata, andCeropegia sahyadrica, as well as the widely distributedCeropegia bulbosa var.bulbosa andCeropegia hirsuta. In our first set of experiments, the MS medium contained 87 mM sucrose and was supplemented with varying concentrations of
BAP (4.4 to 26.6 μM). For the second set of trials, varying concentrations of sucrose (87 to 233 mM) were tested in MS media
containing a constant 4.4 p.M BAP. Sub-cultured apical as well as axillary buds flowered with similar frequencies after 30
d of incubation. For all six species, the highest percentage of flowering shoots was obtained with either 26.6 μM BAP or 175
mM sucrose. Although smaller in size, theirin vitro flowers were morphologically comparable within wVo-derived flowers. Variations among species were noted for the number of flower buds per shoot and the percentage of flower
formation. Because all six species showed similar responses in both experiments, we can suggest that this protocol is applicable
across the wide range ofCeropegia species. 相似文献
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Takayoshi Yamamoto Yuta Kambayashi Kohei Tsukano Tatsuo Michiue 《Development, growth & differentiation》2023,65(3):153-160
Neural tissue is derived from three precursor regions: neural plate, neural crest, and preplacodal ectoderm. These regions are determined by morphogen-mediated signaling. Morphogen distribution is generally regulated by binding to an extracellular matrix component, heparan sulfate (HS) proteoglycan. HS is modified by many enzymes, such as N-deacetyl sulfotransferase 1 (Ndst1), which is highly expressed in early development. However, functions of HS modifications in ectodermal patterning are largely unknown. In this study, we analyzed the role of Ndst1 using Xenopus embryos. We found that ndst1 was expressed in anterior neural plate and the trigeminal region at the neurula stage. ndst1 overexpression expanded the neural crest (NC) region, whereas translational inhibition reduced not only the trigeminal region, but also the adjacent NC region, especially the anterior part. At a later stage, ndst1 knocked-down embryos showed defects in cranial ganglion formation. We also found that Ndst1 activates Wnt signaling pathway at the neurula stage. Taken together, our results suggest that N-sulfonated HS accumulates Wnt ligand and activates Wnt signaling in ndst1-expressing cells, but that it inhibits signaling in non-ndst1-expressing cells, leading to proper neuroectodermal patterning. 相似文献
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An experiment was taken up to find out possibilities of manipulating the in vitro flowering in moth bean. Abscisic acid (ABA) and proline both alone and in combination influenced days to flower induction,
number of flowers per plant, number of pods per plant and seeds per pod. Frequency of flowering plants approached 100 % at
1 and 3 μM ABA and 800 μM proline. The range of flowering period (3 to 23.6 d) has also been influenced by various treatments. 相似文献
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Genoveva Trejo-Macías Alejandro Estrada Miguel Ángel Mosqueda Cabrera 《International journal of primatology》2007,28(4):931-945
The 2 howler species that occur in southern Mexico, Alouatta palliata mexicana and Alouatta pigra are endangered, mainly as a result of habitat loss and fragmentation from human activity. Little is known about the gastrointestinal
parasite communities affecting their populations, and lack of baseline information for populations of howler species in continuous
forest habitats, makes evaluations of gastrointestinal parasite prevalence in populations in fragmented landscapes difficult.
We report the results of a one-time broad survey of gastrointestinal parasites in fecal samples of individuals from several
demographically stable populations of Alouatta palliata mexicana and A. pigra existing in continuous and/or protected forests. We further report similar data for populations of both species in human-fragmented
landscapes. We detected 6 parasites for each howler monkey species, but only 3 of them (Trematode I, Controrchis biliophilus, Trypanoxyuris sp.) were common to both species. While parasitic prevalence in populations of both howler species was, in general, higher
in the fragmented habitat than in continuous and/or protected forests. The difference is only marginally significant in Alouatta pigra. Some parasites (Coccidia and Strongylid) only appeared in populations in fragmented landscapes. Preliminary data suggest
that adult males tended to have higher parasite prevalence values than those of adult females in both howler species. Parasite
prevalence is associated to average group size, but not to population density in Alouatta pigra. 相似文献
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We studied the oviposition performance of Fopius arisanus (Sonan) (Hymenoptera: Braconidae) attacking eggs of four fruit flies of the genus Anastrepha Schiner (Diptera: Tephritidae) under laboratory conditions. The complete process of oviposition on an individual egg of Anastrepha ludens (Loew) lasts in average 85.4 ± 2.9 s, including a tremor (25.8 ± 1.03 s) observed in the middle of this process related to
the egg’s descent. The average parasitism of A. ludens egg was 60.9 ± 7.5%, with only 1.2% of superparasitized eggs. During individual acts of oviposition, we noted that F. arisanus possesses a highly flexible ovipositor that curves easily as it searches for additional suitable eggs, which may be of particular
benefit when a female finds large clutches of eggs. The individual oviposition of F. arisanus in host fruits attacked by Anastrepha spp. varies with the egg clutch size of each fruit fly species: A. serpentina laid the biggest egg clutches (21.3 ± 1.4), followed by A. ludens (14.2 ± 0.9), and A. striata (1.0 ± 0.0) (=A. obliqua). The time spent by F. arisanus in individual ovipositions was parallel to these findings, reinforcing the idea that F. arisanus attacks several eggs in each individual insertion of its ovipositor. Neither formal oviposition acts, nor adult emergences
of F. arisanus were registered in A. obliqua. We discuss the potential of F. arisanus as natural enemy of fruit flies of the genus Anastrepha, and explore the eventual developing of its mass rearing.
Handling Editor: Torsten Meiners. 相似文献
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Recent studies suggest that evergreen plants may maintain their photosynthetic capacity through the winter. Since mild winters
are predicted to be more frequent in the future, the metabolic activity of plants is also likely to increase. The aim of the
present study was to assess how various environmental factors, such as temperature, photoperiod and preceding frost, affect
the recovery of photosynthesis during a mild spell in winter. The recovery of photosynthesis was studied in a series of growth
chamber experiments where the overwintering of lingonberry (Vaccinium vitis-idaea) was interrupted by an intermittent warm spell of 1 week during different phases of winter. Rapid activation was observed
in all the experiments during the first 3–4 days. No obvious effects of the phase of winter or photoperiod on the recovery
of photosynthesis were observed, but a severe freezing treatment prior to the warm spell retarded the recovery significantly.
Once recovered, however, lingonberry was able to maintain high rates of photosynthesis even at near-freezing temperatures,
which prevail in their natural sub-nivean environment. The apparent quantum yield of photosynthesis remained high through
the winter for lingonberry. This may prove advantageous for evergreen dwarf shrubs which overwinter in dim environments under
snow. 相似文献
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Lux-Lantos VA Bianchi MS Catalano PN Libertun C 《Cellular and molecular neurobiology》2008,28(6):803-817
Gamma-amino butyric acid (GABA), in addition to being a metabolic intermediate and the main inhibitory neurotransmitter in
the synaptic cleft, is postulated as a neurohormone, a paracrine signaling molecule, and a trophic factor. It acts through
pre- and post-synaptic receptors, named GABAA and GABAC (ionotropic receptors) and GABAB (metabotropic receptor). Here we reviewed the participation of GABAB receptors in the regulation of the hypothalamic-pituitary-gonadal axis, using physiological, biochemical, and pharmacological
approaches in rats, as well as in GABAB1 knock-out mice, that lack functional GABAB receptors. Our general conclusion indicates that GABAB receptors participate in the regulation of pituitary hormone secretion acting both in the central nervous system and directly
on the gland. PRL and gonadotropin axes are affected by GABAB receptor activation, as demonstrated in the rat and also in the GABAB1 knock-out mouse. In addition, hypothalamic and pituitary GABAB receptor expression is modulated by steroid hormones. GABA participation in the brain control of pituitary secretion through
GABAB receptors depends on physiological conditions, being age and sex critical factors.
These results indicate that patients receiving GABAB agonists/antagonists should be monitored for possible endocrine side effects. 相似文献
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We summarize our current view of the reaction mechanism in F1-ATPase as it has emerged from experiment, theory, and computational studies over the last several years. ATP catalysis in
the catalytic binding pockets of F1 takes place without the release of any significant free energy and is efficiently driven by the combined action of two water
molecules utilizing a so-called protein-relay mechanism. The chemical reaction itself is controlled by the spatial position
of a key arginine residue. 相似文献
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Codon-Anticodon Binding in tRNA<Superscript>phe</Superscript> 总被引:5,自引:0,他引:5
THE anticodon loop of tRNAphe of baker's yeast has the sequence (5′ to 3′) AY A A MeG U MeC. The unusual base Y, adjacent to the anticodon (AA MeG), is the only nucleotide in this tRNA which fluoresces at room temperature and because it absorbs to the red of all other bases, the excitation energy is localized on it exclusively. (7-Methyl guanine is another base in tRNAphe which fluoresces in these conditions but its emission is so weak that it can only be observed in tRNAphe from which Y has been excised.) The fluorescence spectrum undergoes a small blue shift in the presence of the complementary codon1 and we report now the use of this shift to determine the association constants for this binding at several temperatures. The results suggest a simple thermodynamic model for the codon recognition step during protein synthesis. 相似文献
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We study apical dominance in Alstroemeria, a plant with an architecture very different from the model species used in research on apical dominance. The standard explant
was a rhizome with a tip and two vertically growing shoots from which the larger part had been excised leaving ca. 1 cm stem. The axillary buds that resumed growth were located at this 1-cm stem just above the rhizome. They were released
by removal of the rhizome tip and the shoot tips. Replacement of excised tips by lanolin with indole-3-butyric acid (IBA)
restored apical dominance. The auxin transport inhibitors 2,3,5-triiodobenzoic acid (TIBA) and N-1-napthylphthalamic acid (NPA) reduced apical dominance. 6-Benzylaminopurine (BAP) enhanced axillary bud outgrowth but the
highest concentrations (> 9 μM) caused fasciation. Thidiazuron (TDZ) did not show improvement relative to BAP. Even though
the architecture of Alstroemeria and the model species are very different, their hormonal mechanisms in apical dominance are for the greater part very similar. 相似文献
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Previous studies have demonstrated that the obligate myrmecophytism between Macaranga ant-plants and Crematogaster plant-ants is highly species specific, although multiple Macaranga species can coexist in a microhabitat. However, the species specificity has been described based on the study of trees with
established plant-ant colonies. We studied how the process of settling into the partner Macaranga seedlings by single foundress Crematogaster queens contributes to species specificity. By sampling seedlings of three sympatric Macaranga myrmecophytes species in the field, we tested two hypotheses. The first is that foundresses correctly select their specific
partner plant species when they settle into seedlings. The second hypothesis is that the seasons in which seedlings available
for settling by foundresses appear are segregated among the Macaranga species, and the seasons in which foundress queens settle are synchronized to the appearance of seedlings of specific partner
species; thus species specificity is consequently generated. Our results support the former hypothesis but not the latter:
we always observed foundresses settling species-specific host plants, and seedlings suitable for settling were always available
in each Macaranga species.
Electronic Publication 相似文献
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The question of whether discontinuous DNA replication operates only for the lagging strand or for both strands in E. coli remains unresolved. In this study, the participation of priA, B, C and rep genes in discontinuous DNA replication was examined by analyzing the size distribution of nascent DNA synthesized in wild-type,
lig-7 and polA4113 genetic backgrounds. Inactivation of priA, but not priB, priC or rep, resulted in a significant increase of high molecular weight (HMW) DNA in the short pulse-labeled DNA in the wild-type lig
+
polA
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strains. Inactivation of priA also produced a significant increase of HMW DNA in the nascent DNA synthesized in lig-7 and polA4113 strains. These results indicate that PriA is involved in the discontinuous synthesis of nascent DNA. 相似文献
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Transglutaminase-like activity participates in cell wall biogenesis in <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> 总被引:1,自引:0,他引:1
Transglutaminases (TGases) catalyze the cross-linking between protein molecules by formation of an amide bond between γ-carboxyamide
group of glutamine and the ε-amine group of lysine under deamination of glutamine. We have demonstrated the participation
of transglutaminase-like activity in the isolated cell walls and in the process of cell wall regeneration in protoplasts of
the yeast Saccharomyces cerevisiae. A radioactive TGase substrate [3H]putrescine was incorporated into the isolated cell walls and into the TCA-insoluble fraction in regenerating protoplasts.
The incorporation was increased by adding exogenous artificial substrate of TGase N,N’-dimethylcasein and was inhibited by
TGase inhibitor cystamine and/or EDTA. These results suggest the existence of a TGase-type reaction involved in the formation
of covalent cross-links between glycoprotein molecules during cell wall construction in S. cerevisiae. 相似文献