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941.
John H. Miranda Richard W. Williams Graham Kerven 《In vitro cellular & developmental biology. Plant》2007,43(6):639-643
The oligogalacturonides derived from trifluoroacetic acid hydrolysis and their monomer galacturonic acid were tested for their
effect on development of strawberry explants (Fragaria × ananassa) in vitro. The addition of oligogalacturonides or galacturonic acid in the plant tissue culture medium at concentrations of 0.1 or
1.0 mM increased shoot and leaf number in the presence of added benzyl adenine. The response to oligogalacturonides or galacturonic
acid was maintained in the absence of benzyl adenine but was lessened. Conversely, root elongation was increased in the absence
of benzyl adenine. A combined analysis of these experiments also indicated the increase in shoot or leaf number. High-performance
anion exchange chromatography of the bioassayed oligogalacturonide samples using a pulsed amperometric detector revealed that
the sample consisted of galactouronides with a degree of polymerization from 1 to 5 and the proportion of the monomer was
very high (94%). 相似文献
942.
Antigenic variation in pneumocystis 总被引:1,自引:0,他引:1
Stringer JR 《The Journal of eukaryotic microbiology》2007,54(1):8-13
943.
944.
Abstract. Waitkera waitakerensis occupies lowland forests of New Zealand's North Island, where temperatures decrease in a southwestward direction. The mean annual temperatures of 18 collecting sites, as extracted from GIS data, are directly related to the first femur length of adult females. Neither site elevation nor phylogeny affected spider size or other variables examined. The direct relationship between spider body size and environmental temperature followed a pattern observed in other terrestrial arthropods with a univoltine life cycle and can probably be explained by the longer growing season of warmer regions. Egg diameter was uniform across the species. Site temperature and female first femur length were each directly related to the number of eggs deposited in egg sacs. The date of egg sac collection was inversely related to egg number, suggesting that clutch size declines during the reproductive season. Females deposit eggs beneath a triangular platform and then cover them with a lower silk sheet. The area of this upper platform and the volume of the egg sac were each directly related to egg number, but not to female first femur length. The depth of the lower covering was not related to egg number or to spider first femur length. This suggests that spiders use information about the volume of eggs in their abdomens to construct an egg sac whose volume will accommodate the volume of eggs to be laid and that females do so principally by adjusting the size of the sac's upper triangular platform. 相似文献
945.
Genetic quality of individuals impacts population dynamics 总被引:5,自引:4,他引:1
Ample evidence exists that an increase in the inbreeding level of a population reduces the value of fitness components such as fecundity and survival. It does not follow, however, that these decreases in the components of fitness impact population dynamics in a way that increases extinction risk, because virtually all species produce far more offspring than can actually survive. We analyzed the effects of the genetic quality (mean fitness) of individuals on the population growth rate of seven natural populations in each of two species of wolf spider in the genus Rabidosa , statistically controlling for environmental factors. We show that populations of different sizes, and different inbreeding levels, differ in population dynamics for both species. Differences in population growth rates are especially pronounced during stressful environmental conditions (low food availability) and the stressful environment affects smaller populations (<500 individuals) disproportionately. Thus, even in an invertebrate with an extremely high potential growth rate and strong density-dependent mortality rates, genetic factors contribute directly to population dynamics and, therefore, to extinction risk. This is only the second study to demonstrate an impact of the genetic quality of individual genotypes on population dynamics in a wild population and the first to document strong inbreeding–environment interactions for fitness among populations. Endangered species typically exist at sizes of a few hundred individuals and human activities degrade habitats making them innately more stressful (e.g. global climate change). Therefore, the interaction between genetic factors and environmental stress has important implications for efforts aimed at conserving the Earth's biodiversity. 相似文献
946.
唇形科独一味属和五种糙苏属植物的核形态研究 总被引:1,自引:0,他引:1
首次报道了唇形科Lamiaceae独一味属Lamiophlomis和五种糙苏属Phlomis植物的染色体数目和核型。它们的间期核均属球状前染色体型,有丝分裂前期染色体均为中间型。中期染色体核型公式如下:独一味L.rotata,2n=2x=22=18m 4sm;糙苏P.umbrosa,2n=2x=22=22m;裂萼糙苏P.ruptilis,2n=2x=22=22m;假秦艽P.betonicoides,2n=2x=22=22m;黑花糙苏P.melanantha,2n=2x=22=22m(2sat);糙毛糙苏P.strigosa,2n=6x=66=60m 6sm;染色体基数均为x=11。这表明独一味与糙苏属的糙苏组sect.Phlomoides植物具有相同的染色体基数,反映出两者较为密切的系统演化关系,推断独一味很可能是糙苏属的一个种。 相似文献
947.
In order to genotype hybrid genomes of distant asymmetric somatic hybrids, we synthesized hybrid calli and plants via PEG-mediated
protoplast fusion between recipient tall fescue (Festuca. arundinacea Schreb.) and donor wheat (Triticum aestivum L.). Seventeen and 25 putative hybrid clones were produced from the fusion combinations I and II, each with the donor wheat
protoplast treated by UV light for 30 s and 1 min, respectively. Isozyme and RAPD profiles confirmed that ten hybrid clones
were obtained from combination I and 19 from combination II. Out of the 29 hybrids, 12 regenerated hybrid plants with tall
fescue phenotype. Composition and methylation-variation of the nuclear and cytoplasmic genomes of some hybrids, either with
or without regenerative ability, were compared by genomic in situ hybridization, restriction fragment length polymorphism,
and DNA methylation-sensitive amplification polymorphism. Our results indicated that these selected hybrids all contained
introgressed nuclear and cytoplasmic DNA as well as obvious methylation variations compared to both parents. However, there
were no differences either in nuclear/cytoplasmic DNA or methylation degree between the regenerable and non-regenerable hybrid
clones. We conclude that both regeneration complementation and genetic material balance are crucial for hybrid plant regeneration. 相似文献
948.
Jesper Madsen Mikkel Tamstorf Marcel Klaassen Nina Eide Christian Glahder Frank Rigét Helene Nyegaard Fred Cottaar 《Polar Biology》2007,30(11):1363-1372
During four breeding seasons, 2003–2006, we studied the relationship between snow cover and nesting performance in pink-footed
geese (Anser brachyrhynchus) in a key breeding site on Svalbard. Snow cover in late May, i.e., at the time of egg laying of geese, was derived from MODIS
satellite images. Snow cover had a profound cascading effect on reproductive output via the number of nesting pairs and timing
of nesting, which affected nest success, while there was only a tendency for a negative effect on clutch size. Hence, we estimated
a five-fold difference in the number of young produced (to post-hatching) between years with little snow and years with high
snow cover. The results from the study area correlated with whole-population productivity estimates recorded in autumn. Thus,
snow cover derived from MODIS satellite images appears to provide a useful indicator of the breeding conditions in the Arctic. 相似文献
949.
Osler disease is an autosomal dominant disorder of the fibrovascular tissue characterized by arteriovenous malformations with multi-systemic haemorrhages. Recurrent epistaxis is the predominant symptom in more than 90% of patients. Recent studies showed circadian and seasonal patterns in the onset of nosebleeds, similar to acute cardiovascular events, such as myocardial infarction and stroke. The aim of this study was to determine whether such patterns would also apply to the onset of epistaxis in patients with Osler disease. In all, 110 patients with Osler disease who were under treatment for recurrent epistaxis at the University Hospital of Mannheim were requested to complete a questionnaire addressing the intensity and frequency of epistaxis according to the classification of Bergler et al., as well as circadian and circannual rhythmicity in the occurrence of epistaxis according to visual analogue scales (VAS). More than half of the patients claimed to experience daily to weekly episodes of recurrent epistaxis. The occurrence of epistaxis showed a biphasic 24 h pattern, with a primary peak in the morning (05:00-8:00 h) and smaller secondary peaks in the evening (17:00-20:00 h and 21:00-00:00 h). No significant seasonal variation was found in the onset of epistaxis. However, a slight tendency, with a peak in winter months, was observed. Similar to other chronobiological studies on nosebleeds, this study showed that the 24 h pattern and seasonal tendency in the onset of epistaxis even applied to patients with Osler disease. Further investigations are necessary to determine the pathological mechanism underlying this phenomenon. 相似文献
950.
Uluoglu C Durakoglugil DB Karasu C Ozbey G Gunes A Zengil H 《Chronobiology international》2007,24(6):1081-1094
The aim of this study was to investigate whether time-dependent variations in the relaxant effect of acetylcholine, an endothelium-dependent vasorelaxant via muscarinic receptors, and isoprenaline, a nonselective β-adrenoceptor agonist in rat aorta, are influenced by streptozotocin (STZ)-induced experimental diabetes. Adult male rats were divided randomly into two groups: control and STZ-induced (STZ, 55 mg/kg, intraperitoneal) diabetes. The animals were synchronized to a 12:12 h light-dark cycle (lights on 08:00 h) and sacrificed at six different times of day (1, 5, 9, 13, 17, and 21 hours after lights on; HALO) eight weeks after STZ injection. The in vitro responsiveness of thoracic aorta rings obtained from control and diabetic rats to acetylcholine (10-9-10-5 M) and isoprenaline (10-10-10-3 M) was determined in six different times. EC50 (the concentration inducing half of the maximum response) values and maximum responses were calculated from cumulative concentration-response curves of the agonists and were analyzed with respect to time and STZ treatment. Treatment, time, and interactions between treatment and time were tested by two-way analysis of variance (ANOVA). To analyze differences due to biological time, one-way ANOVA was used. STZ treatment did not significantly change EC50 values or maximum responses for both agonists. There were statistically significant time-dependent variations in the EC50 values for isoprenaline and maximum responses for both acetylcholine and isoprenaline in control groups by one-way ANOVA, but significant time-dependent variations disappeared in the aortas isolated from STZ-induced diabetic rats. The vasodilator responses to acetylcholine and isoprenaline failed to show any significant interaction (treatment×time of study) between STZ treatment and time of sacrifice in both EC50 values and maximum responses by two-way ANOVA. These results indicate there is a basic temporal pattern in the responses to acetylcholine and isoprenaline in rat aorta which continues in diabetes. It is shown for the first time that experimental diabetes does not change the 24 h pattern of responses to acetylcholine and isoprenaline, and that time-dependent variations in the responses to these agonists disappear in diabetic animals. Although further studies are required to define the underlying mechanism(s) of these findings, results suggest that experimental diabetes can modify the time-dependent vasorelaxant responses of rat aorta. This may help to understand the circadian rhythms in cardiovascular physiology and pathology or in drug effects in diabetes. 相似文献