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排序方式: 共有231条查询结果,搜索用时 15 毫秒
21.
22.
Threshold-dependent BMP-mediated repression: a model for a conserved mechanism that patterns the neuroectoderm 总被引:1,自引:0,他引:1
Subdivision of the neuroectoderm into three rows of cells along the dorsal-ventral axis by neural identity genes is a highly conserved developmental process. While neural identity genes are expressed in remarkably similar patterns in vertebrates and invertebrates, previous work suggests that these patterns may be regulated by distinct upstream genetic pathways. Here we ask whether a potential conserved source of positional information provided by the BMP signaling contributes to patterning the neuroectoderm. We have addressed this question in two ways: First, we asked whether BMPs can act as bona fide morphogens to pattern the Drosophila neuroectoderm in a dose-dependent fashion, and second, we examined whether BMPs might act in a similar fashion in patterning the vertebrate neuroectoderm. In this study, we show that graded BMP signaling participates in organizing the neural axis in Drosophila by repressing expression of neural identity genes in a threshold-dependent fashion. We also provide evidence for a similar organizing activity of BMP signaling in chick neural plate explants, which may operate by the same double negative mechanism that acts earlier during neural induction. We propose that BMPs played an ancestral role in patterning the metazoan neuroectoderm by threshold-dependent repression of neural identity genes. 相似文献
23.
In Drosophila, the 255kDa catalytic subunit (dpolεp255) and the 58kDa subunit of DNA polymerase ε (dpolεp58) have been identified. The N-terminus of dpolεp255 carries well-conserved six DNA polymerase subdomains and five 3'→5' exonuclease motifs as observed with Polε in other species. We here examined roles of dpolεp255 during Drosophila development using transgenic fly lines expressing double stranded RNA (dsRNA). Expression of dpolεp255 dsRNA in eye discs induced a small eye phenotype and inhibited DNA synthesis, indicating a role in the G1-S transition and/or S-phase progression of the mitotic cycle. Similarly, expression of dpolεp255 dsRNA in the salivary glands resulted in small size and endoreplication defects, demonstrating a critical role in endocycle progression. In the eye disc, defects induced by knockdown of dpolεp255 were rescued by overexpression of the C-terminal region of dpolεp255, indicating that the function of this non-catalytic domain is conserved between yeast and Drosophila. However, this was not the case for the salivary gland, suggesting that the catalytic N-terminal region is crucial for endoreplication and its defect cannot be complemented by other DNA polymerases. In addition, several genetic interactants with dpolεp255 including genes related to DNA replication such as RFC, DNA primase, DNA polη, Mcm10 and Psf2 and chromatin remodeling such as Iswi were also identified. 相似文献
24.
Yamauchi S Higashitani N Otani M Higashitani A Ogura T Yamanaka K 《Developmental biology》2008,318(2):348-359
Caenorhabditis elegans possesses two p97/VCP/Cdc48p homologues, named CDC-48.1 (C06A1.1) and CDC-48.2 (C41C4.8), and their expression patterns and levels are differently regulated. To clarify the regulatory mechanisms of differential expression of two p97 proteins of C. elegans, we performed detailed deletion analysis of their promoter regions. We found that the promoter of cdc-48.1 contains two regions necessary for embryonic and for post-embryonic expression, while the promoter of cdc-48.2 contains the single region necessary for embryonic expression. In particular, two elements (Element A and Element B) and three conserved boxes (Box a, Box b and Box c) were essential for cdc-48.1 expression in embryos and at post-embryonic stages, respectively. By using South-Western blotting and MALDI-TOF MS analysis, we identified HMG-12 and CAR-1 as proteins that bind to Element A and Element B, respectively, from the embryonic nuclear extract. Importantly, we found the decreased expression of p97 in embryos prepared from hmg-12(RNAi) or car-1(RNAi) worms. These results indicate that both HMG-12 and CAR-1 play important roles in embryonic expression of cdc-48.1. 相似文献
25.
Manabu Shibasaki Mieko Sakai Mayumi Oda Craig G Crandall 《Journal of applied physiology》2004,96(6):2115-2119
The objective of this study was to identify whether muscle mechanoreceptor stimulation is capable of modulating sweat rate. Seven healthy subjects performed two 20-min bouts of supine exercise on a tandem cycle ergometer (60 rpm at 65% of maximal heart rate). After one bout, the subject stopped exercising (i.e., no pedaling), whereas, after the other bout, the subject's legs were passively cycled (at 60 rpm) via a second person cycling the tandem ergometer. This allows for mechanical stimulation of muscle with minimal activation of central command. Esophageal temperature (T(es)), mean skin temperature (T(sk)), heart rate, mean arterial blood pressure, oxygen consumption, cutaneous vascular conductance (CVC), and sweat rate were not different during the two exercise bouts. Regardless of the mode of exercise recovery, there were no differences in T(es), T(sk), or CVC. In contrast, early in the recovery period, chest and forearm sweat rate were significantly greater in the passive cycling recovery mode relative to the no-pedaling condition (chest: 0.57 +/- 0.13 vs. 0.39 +/- 0.14, forearm: 0.30 +/- 0.05 vs. 0.12 +/- 0.02 mg.cm(-2).min(-1); both P < 0.05). These results suggested that muscle mechanoreceptor stimulation to the previously activated muscle is capable of modulating sweat rate. 相似文献
26.
Priscilla Ambrosi Juan Sebastian Chahda Hannah R. Koslen Hillel J. Chiel Claudia Mieko Mizutani 《PLoS computational biology》2014,10(8)
Morphogenetic gradients are essential to allocate cell fates in embryos of varying sizes within and across closely related species. We previously showed that the maternal NF-κB/Dorsal (Dl) gradient has acquired different shapes in Drosophila species, which result in unequally scaled germ layers along the dorso-ventral axis and the repositioning of the neuroectodermal borders. Here we combined experimentation and mathematical modeling to investigate which factors might have contributed to the fast evolutionary changes of this gradient. To this end, we modified a previously developed model that employs differential equations of the main biochemical interactions of the Toll (Tl) signaling pathway, which regulates Dl nuclear transport. The original model simulations fit well the D. melanogaster wild type, but not mutant conditions. To broaden the applicability of this model and probe evolutionary changes in gradient distributions, we adjusted a set of 19 independent parameters to reproduce three quantified experimental conditions (i.e. Dl levels lowered, nuclear size and density increased or decreased). We next searched for the most relevant parameters that reproduce the species-specific Dl gradients. We show that adjusting parameters relative to morphological traits (i.e. embryo diameter, nuclear size and density) alone is not sufficient to reproduce the species Dl gradients. Since components of the Tl pathway simulated by the model are fast-evolving, we next asked which parameters related to Tl would most effectively reproduce these gradients and identified a particular subset. A sensitivity analysis reveals the existence of nonlinear interactions between the two fast-evolving traits tested above, namely the embryonic morphological changes and Tl pathway components. Our modeling further suggests that distinct Dl gradient shapes observed in closely related melanogaster sub-group lineages may be caused by similar sequence modifications in Tl pathway components, which are in agreement with their phylogenetic relationships. 相似文献
27.
Hanamura S Kiyono M Lukasik-Braum M Mlengeya T Fujimoto M Nakamura M Nishida T 《Primates; journal of primatology》2008,49(1):77-80
A flu-like disease spread among chimpanzees (Pan troglodytes schweinfurthii) of the M group at Mahale Mountains National Park, Tanzania, from June to July 2006. This epizootic or epidemic killed up
to 12 chimpanzees. The obvious evidence of their deaths came from finding the bodies of three infants who had previously shown
some symptoms of the disease. At least one of these infants died of pneumonia. In addition, nine chimpanzees were missing
after the outbreak. These individuals were assumed to have been killed by this epizootic because most of them had contact
with the infected individuals on the last days they were observed. We also found two dead bodies during this period, which
were thought to be those of two missing individuals. We confirmed 23 (35.4%) of 65 individuals of the M group showed some
symptoms of the disease, although most of them (20/23) did not die. More than half of them (14/23) had kin showing symptoms.
Since this epizootic may have been caused by contact with humans, it will be necessary to establish and follow appropriate
protocols for researchers, tourists, and park staff to observe chimpanzees, and to explore the mechanism of disease transmission
from humans to chimpanzees and among chimpanzees. 相似文献
28.
Hanya G Matsubara M Hayaishi S Zamma K Yoshihiro S Kanaoka MM Sugaya S Kiyono M Nagai M Tsuriya Y Hayakawa S Suzuki M Yokota T Kondo D Takahata Y 《Primates; journal of primatology》2008,49(2):116-125
Feeding conditions, competitive regime, and female social relationships of Japanese macaques (Macaca fuscata) on Yakushima were compared between the two habitats at two different altitudes (coniferous forest, 1,000–1,200 m and coastal
forest, 0–200 m). Fruit availability was higher in the coastal forest. There was no consistent difference in the frequency
of agonistic interactions within a group during feeding between the two habitats. The coastal forest evoked stronger inter-group
contest competition compared to the coniferous forest as evidenced by a higher inter-group encounter rate and a higher proportion
of aggressive encounters to non-aggressive ones. Birth rate was higher in larger groups compared to smaller ones in the coastal
forest, but did not differ in the coniferous forest. In spite of these differences in competitive regime, no variation in
female social relationships was observed, such as direction and concentration on particular individuals in grooming, linearity
in dominance rank, counter-attack, and support of juvenile kin during agonistic interactions. The present results indicate
that the female social relationships of Japanese macaques are robust and do not change according to changes in the current
environment. 相似文献
29.
Kondou Y Higuchi M Takahashi S Sakurai T Ichikawa T Kuroda H Yoshizumi T Tsumoto Y Horii Y Kawashima M Hasegawa Y Kuriyama T Matsui K Kusano M Albinsky D Takahashi H Nakamura Y Suzuki M Sakakibara H Kojima M Akiyama K Kurotani A Seki M Fujita M Enju A Yokotani N Saitou T Ashidate K Fujimoto N Ishikawa Y Mori Y Nanba R Takata K Uno K Sugano S Natsuki J Dubouzet JG Maeda S Ohtake M Mori M Oda K Takatsuji H Hirochika H Matsui M 《The Plant journal : for cell and molecular biology》2009,57(5):883-894
Ectopic gene expression, or the gain-of-function approach, has the advantage that once the function of a gene is known the gene can be transferred to many different plants by transformation. We previously reported a method, called FOX hunting, that involves ectopic expression of Arabidopsis full-length cDNAs in Arabidopsis to systematically generate gain-of-function mutants. This technology is most beneficial for generating a heterologous gene resource for analysis of useful plant gene functions. As an initial model we generated more than 23 000 independent Arabidopsis transgenic lines that expressed rice fl-cDNAs (Rice FOX Arabidopsis lines). The short generation time and rapid and efficient transformation frequency of Arabidopsis enabled the functions of the rice genes to be analyzed rapidly. We screened rice FOX Arabidopsis lines for alterations in morphology, photosynthesis, element accumulation, pigment accumulation, hormone profiles, secondary metabolites, pathogen resistance, salt tolerance, UV signaling, high light tolerance, and heat stress tolerance. Some of the mutant phenotypes displayed by rice FOX Arabidopsis lines resulted from the expression of rice genes that had no homologs in Arabidopsis . This result demonstrated that rice fl-cDNAs could be used to introduce new gene functions in Arabidopsis. Furthermore, these findings showed that rice gene function could be analyzed by employing Arabidopsis as a heterologous host. This technology provides a framework for the analysis of plant gene function in a heterologous host and of plant improvement by using heterologous gene resources. 相似文献
30.
Hanya G Ménard N Qarro M Ibn Tattou M Fuse M Vallet D Yamada A Go M Takafumi H Tsujino R Agetsuma N Wada K 《Primates; journal of primatology》2011,52(2):187-198
Habitat, diet and leaf chemistry are compared between Japanese and Barbary macaques to reveal the similarities and differences in dietary adaptations of temperate primates living at the eastern and western extremes of the genus Macaca. Tree species diversity and proportion of fleshy-fruited species are much higher in Japan than in North Africa. Both species spend considerable annual feeding time on leaves. Japanese macaques prefer fruits and seeds over leaves, and Barbary macaques prefer seeds. These characteristics are adaptive in temperate regions where fruit availability varies considerably with season, since animals can survive during the lean period by relying on leaf and other vegetative foods. The two species are different with respect to the higher consumption of herbs by Barbary macaques, and the leaves consumed contain high condensed and hydrolysable tannin for Barbary but not for Japanese macaques. Barbary macaques supplement less diverse tree foods with herbs. Because of the low species diversity and high tannin content of the dominant tree species, Barbary macaques may have developed the capacity to cope with tannin. This supports the idea that digestion of leaves is indispensable to survive in temperate regions where fruit and seed foods are not available for a prolonged period during each year. 相似文献