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81.
For the first time in Acanthaceae a comparative study of orbicules forming stable, coherent orbicular walls and the respective pollen ornamentation was undertaken. A peculiar acetolysis resistant, often species specific orbicular wall is typical for many genera. In some cases the orbicular wall ornamentation resembles closely the pollen ornamentation, in others it differs to a variable degree. The presumed function of orbicular walls is discussed. 相似文献
82.
Ulrich Koenig Manfred Fobker Barbara Lengauer Marlene Brandstetter Guenter P Resch Marion Gr?ger Gabriele Plenz Johannes Pammer Caterina Barresi Christine Hartmann Heidemarie Rossiter 《Autophagy》2015,11(2):298-313
The epithelial derived Harderian gland consists of 2 types of secretory cells. The more numerous type A cells are responsible for the secretion of lipid droplets, while type B cells produce dark granules of multilamellar bodies. The process of autophagy is constitutively active in the Harderian gland, as confirmed by our analysis of LC3 processing in GFP-LC3 transgenic mice. This process is compromised by epithelial deletion of Atg7. Morphologically, the Atg7 mutant glands are hypotrophic and degenerated, with highly vacuolated cells and pyknotic nuclei. The mutant glands accumulate lipid droplets coated with PLIN2 (perilipin 2) and contain deposits of cholesterol, ubiquitinated proteins, SQSTM1/p62 (sequestosome 1) positive aggregates and other metabolic products such as porphyrin. Immunofluorescence stainings show that distinct cells strongly aggregate both proteins and lipids. Electron microscopy of the Harderian glands reveals that its organized structure is compromised, and the presence of large intracellular lipid droplets and heterologous aggregates. We attribute the occurrence of large vacuoles to a malfunction in the formation of multilamellar bodies found in the less abundant type B Harderian gland cells. This defect causes the formation of large tertiary lysosomes of heterologous content and is accompanied by the generation of tight lamellar stacks of endoplasmic reticulum in a pseudo-crystalline form. To test the hypothesis that lipid and protein accumulation is the cause for the degeneration in autophagy-deficient Harderian glands, epithelial cells were treated with a combination of the proteasome inhibitor and free fatty acids, to induce aggregation of misfolded proteins and lipid accumulation, respectively. The results show that lipid accumulation indeed enhanced the toxicity of misfolded proteins and that this was even more pronounced in autophagy-deficient cells. Thus, we conclude autophagy controls protein and lipid catabolism and anabolism to facilitate bulk production of secretory vesicles of the Harderian gland. 相似文献
83.
Species effects on resource supply rates: do they influence competitive interactions? 总被引:4,自引:0,他引:4
Suding Katharine Nash Larson Julia R. Thorsos Eileen Steltzer Heidemarie Bowman William D. 《Plant Ecology》2004,175(1):47-58
We examined two ways in which species effects on nitrogen supply rates could influence species competitive interactions and
lead to coexistence between species with very different patterns of resource use. First, through differential effects on the
rates of resource cycling, species may modify resources in divergent directions to better tolerate neighbors under self-modified
conditions (tolerance modification). Second, plant-induced shifts in resource supply could enhance the degree to which species
can suppress individuals (suppression modification). We addressed these hypothesized mechanisms in the non-successional moist
meadow alpine tundra, which is codominated by Acomastylis rossii, a slow-growing roseaceous forb with high nutrient retention that is associated with slow rates of nitrogen supply, and Deschampsia caespitosa, a graminoid with rapid growth potential that is associated with fast rates of nitrogen (N) supply. Neighbors inhibited Acomastylis transplants (the species with high N retention) less than Deschampsia transplants (the species with rapid potential growth) in both neighborhood types, and hence neighborhood type did not influence
species tolerance to neighbors. Likewise, Acomastylis neighborhoods inhibited transplant growth more than Deschampsia neighborhoods regardless of transplant species identity. When N supply rates were enhanced through repeated N additions in
the two neighborhood types or in the presence of each species’ litter, the inhibitory effects associated with Acomastylis were offset to a greater degree than those associated with Deschampsia, as predicted by the suppression modification. These effects appeared to be density or size-dependent, with few effects observed
at low density. Our results suggest that species effects on supply rates may influence competitive interactions, particularly
if these effects are complemented by other sources of temporal or spatial variation such as pulses in resource availability.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
84.
Willeke P Schlüter B Becker H Schotte H Domschke W Gaubitz M 《Arthritis research & therapy》2007,9(6):R115
The aim of this study was to evaluate the efficacy and safety of mycophenolate sodium (MPS) in patients with primary Sjögren syndrome (pSS) refractory to other immunosuppressive agents. Eleven patients with pSS were treated with MPS up to 1,440 mg daily for an observation period of 6 months in this single-center, open-label pilot trial. At baseline, after 3 months, and after 6 months, we examined the clinical status, including glandular function tests, as well as different laboratory parameters associated with pSS. In addition, subjective parameters were determined on the basis of different questionnaires. Treatment with MPS was well tolerated in 8 of 11 patients. Due to vertigo or gastrointestinal discomfort, two patients did not complete the trial. One patient developed pneumonia 2 weeks after treatment and was withdrawn. In the remaining patients, MPS treatment resulted in subjective improvement of ocular dryness on a visual analogue scale and a reduced demand for artificial tear supplementations. However, no significant alterations of objective parameters for dryness of eyes and mouth were observed, although a substantial improvement of glandular functions occurred in two patients with short disease duration. In addition, treatment with MPS resulted in significant reduction of hypergammaglobulinemia and rheumatoid factors as well as an increase of complement levels and white blood cells. MPS promises to be an additional therapeutic option for patients with pSS, at least in those with shorter disease duration. Further investigations about the efficacy and safety of MPS in pSS have to be performed in larger numbers of patients. 相似文献
85.
Anthony Darrouzet‐Nardi Heidi Steltzer Patrick F. Sullivan Aliza Segal Amanda M. Koltz Carolyn Livensperger Joshua P. Schimel Michael N. Weintraub 《Ecology and evolution》2019,9(4):1820-1844
In addition to warming temperatures, Arctic ecosystems are responding to climate change with earlier snowmelt and soil thaw. Earlier snowmelt has been examined infrequently in field experiments, and we lack a comprehensive look at belowground responses of the soil biogeochemical system that includes plant roots, decomposers, and soil nutrients. We experimentally advanced the timing of snowmelt in factorial combination with an open‐top chamber warming treatment over a 3‐year period and evaluated the responses of decomposers and nutrient cycling processes. We tested two alternative hypotheses: (a) Early snowmelt and warming advance the timing of root growth and nutrient uptake, altering the timing of microbial and invertebrate activity and key nutrient cycling events; and (b) loss of insulating snow cover damages plants, leading to reductions in root growth and altered biological activity. During the 3 years of our study (2010–2012), we advanced snowmelt by 4, 15, and 10 days, respectively. Despite advancing aboveground plant phenology, particularly in the year with the warmest early‐season temperatures (2012), belowground effects were primarily seen only on the first sampling date of the season or restricted to particular years or soil type. Overall, consistent and substantial responses to early snowmelt were not observed, counter to both of our hypotheses. The data on soil physical conditions, as well interannual comparisons of our results, suggest that this limited response was because of the earlier date of snowmelt that did not coincide with substantially warmer air and soil temperatures as they might in response to a natural climate event. We conclude that the interaction of snowmelt timing with soil temperatures is important to how the ecosystem will respond, but that 1‐ to 2‐week changes in timing of snowmelt alone are not enough to drive season‐long changes in soil microbial and nutrient cycling processes. 相似文献
86.
87.
Marc Trimborn Mahdi Ghani Diego J. Walther Monika Dopatka Véronique Dutrannoy Andreas Busche Franziska Meyer Stefanie Nowak Jean Nowak Claus Zabel Joachim Klose Veronica Esquitino Masoud Garshasbi Andreas W. Kuss Hans-Hilger Ropers Susanne Mueller Charlotte Poehlmann Ioannis Gavvovidis Detlev Schindler Karl Sperling Heidemarie Neitzel 《PloS one》2010,5(2)
Mutations in the human gene MCPH1 cause primary microcephaly associated with a unique cellular phenotype with premature chromosome condensation (PCC) in early G2 phase and delayed decondensation post-mitosis (PCC syndrome). The gene encodes the BRCT-domain containing protein microcephalin/BRIT1. Apart from its role in the regulation of chromosome condensation, the protein is involved in the cellular response to DNA damage. We report here on the first mouse model of impaired Mcph1-function. The model was established based on an embryonic stem cell line from BayGenomics (RR0608) containing a gene trap in intron 12 of the Mcph1 gene deleting the C-terminal BRCT-domain of the protein. Although residual wild type allele can be detected by quantitative real-time PCR cell cultures generated from mouse tissues bearing the homozygous gene trap mutation display the cellular phenotype of misregulated chromosome condensation that is characteristic for the human disorder, confirming defective Mcph1 function due to the gene trap mutation. While surprisingly the DNA damage response (formation of repair foci, chromosomal breakage, and G2/M checkpoint function after irradiation) appears to be largely normal in cell cultures derived from Mcph1gt/gt mice, the overall survival rates of the Mcph1gt/gt animals are significantly reduced compared to wild type and heterozygous mice. However, we could not detect clear signs of premature malignant disease development due to the perturbed Mcph1 function. Moreover, the animals show no obvious physical phenotype and no reduced fertility. Body and brain size are within the range of wild type controls. Gene expression on RNA and protein level did not reveal any specific pattern of differentially regulated genes. To the best of our knowledge this represents the first mammalian transgenic model displaying a defect in mitotic chromosome condensation and is also the first mouse model for impaired Mcph1-function. 相似文献
88.
In recent work we have isolated and characterized a highly repetitive DNA (MMV satellite IA) from Muntiacus muntjak vaginalis, the species with the most reduced karyotype in the Cervidae family. We have now analysed the genomes of nine related species for the presence of MMV satellite IA components, and have determined their organization and chromosomal distribution. Repetitive satellite IA type DNA is present in all species of the Cervidae, and also in the bovine, but not in a species of the Tragulidae suggesting that these sequences were generated after the phylogenetic separation of Bovidae and Tragulidae. Studies on the organization of the satellite IA DNA in the various species revealed three main repeat lengths: 1400, 1000 and 807 bp. The relative proportion of satellite IA sequences present in any one of the three registers is strikingly different within the various species and can be correlated with the phylogeny of the Cervidae. The chromosomal locations of the satellite IA sequences were determined in seven species by in situ hybridization. It turned out that the chromosomal rearrangements leading to the reduction in the number of chromosomes during karyotype evolution have led to the elimination of satellite I DNA at most locations. In all tandem fusions, the satellite IA sequences located at the centromeres of the ancestral acrocentric chromosomes are lost. In contrast, during the centric fusion that generates the M. m. vaginalis X chromosome satellite IA sequences are amplified. Sequence motifs, which are known to be involved in recombinational events are present in the satellite IA and might have contributed to the unique karyotype variation in the Cervidae. 相似文献
89.
Abstract: Bovine chromaffin secretory vesicle ghosts loaded with Na+ were found to take up Ca2+ when incubated in K+ media or in sucrose media containing micromolar concentrations of free Ca2+. Li+- or choline+loaded ghosts did not take up Ca2+. The Ca2+ accumulated by Na+-loaded ghosts could be released by the Ca2+ ionophore A23187, but not by EGTA. Ca2+ uptake was inhibited by external Sr2+, Na +, Li +, or choline +. All the 45Ca2+ accumulated by Na+-dependent Ca2+ uptake could be released by external Na +, indicating that both Ca2+ influx and efflux occur in a Na+-dependent manner. Na + -dependent Ca2+ uptake and release were only slightly inhibited by Mg2+. In the presence of the Na+ ionophore Monensin the Ca2+ uptake by Na +-loaded ghosts was reduced. Ca2+ sequestered by the Na+-dependent mechanism could also be released by external Ca2+ or Sr2+ but not by Mg2+, indicating the presence of a Ca2+/Ca2+ exchange activity in secretory membrane vesicles. This Ca2+/Ca2+ exchange system is inhibited by Mg2+, but not by Sr2+. The Na + -dependent Ca2+ uptake system in the presence of Mg2+ is a saturable process with an apparent Km of 0.28 μM and a Vmax= 14.5 nmol min?1 mg protein?1. Ruthenium red inhibited neither the Na+/Ca2+ nor the Ca2+/Ca2+ exchange, even at high concentrations. 相似文献
90.
Aktivitätsänderungen der Isocitritase (E C 4. 1. 3. 1.) Während der Photomorphogenese beim Senfkeimling (Sinapis alba L.) 总被引:1,自引:1,他引:0
Zusammenfassung In einer vorangegangenen Arbeit (Hock, Kühnert und Mohr, 1965) haben wir festgestellt, daß der Fettabbau im Senfkeimling über das aktive Phytochrom (= P730) in einem bestimmten Ausmaß reguliert werden kann. Die Annahme lag nahe, daß die Regulation über die Isocitritase erfolge.In der vorliegenden Arbeit haben wir festgestellt, daß P730 keinen Einfluß auf die Isocitritase-Aktivität des Senfkeimlings ausübt, obgleich sich die Isocitritase-Aktivität in dem von uns untersuchten Zeitraum (24–96 Std nach der Aussaat) stark verändert. Um diesen Nachweis zu führen, war es notwendig, störende phenolische Substanzen im Rohextrakt an Divergan zu adsorbieren und die Enzymaktivität auf die biologische Einheit Keimling zu beziehen.Puromycin hemmt die Isocitritase-Synthese stark; Actinomycin D hingegen hat kaum einen Einfluß. — Vielleicht liegt eine langlebige mRNS vor, und die Regulation erfolgt auf der Ebene der Translation. Auch andere Interpretationen sind jedoch möglich.
Changes of activity of isocitritase (E C 4. 1. 3. 1.) during photomorphogenesis in mustard seedlings (Sinapis alba L.)
Summary In a previous paper (Hock, Kühnert and Mohr, 1965) we have shown that fat degradation in the cotyledons of the mustard seedling (Sinapis alba L). is under the control of active phytochrome (=P730), at least to a certain extent. One could imagine that P730 might exert this control over fat consumption through isocitritase (E C 4. 1. 3. 1). In the present paper we demonstrate that P730 does not have any influence on the activity of isocitritase in the mustard seedling, although the enzyme activity does show a strong increase and a following decline during the time of our experimentation (Fig. 8, 9). — Isocitritase could be assayed in a satisfactory manner in the raw extract only after the adsorption of phenolic compounds on Divergan (Fig. 1, 3). Furthermore the biological unit of the seedling turned out to be the only reliable system of reference for the enzyme activity determined in the extract. Puromycin strongly inhibits isocitritase synthesis whereas Actinomycin D is hardly effective (Fig. 10). It has been concluded that there might exist a relatively stable m-RNA which has been formed during the early stage of germination. Regulation of enzyme synthesis might occur on the level of translation. The evidence for this conclusion is not convincing, however; other interpretations are not excluded.相似文献