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1.
A putative GDP–GTP exchange factor is required for development of the excretory cell in Caenorhabditis elegans 下载免费PDF全文
Norio Suzuki Matthew Buechner Kiyoji Nishiwaki David H. Hall Hiroyuki Nakanishi Yoshimi Takai Naoki Hisamoto Kunihiro Matsumoto 《EMBO reports》2001,2(6):530-535
The Caenorhabditis elegans excretory cell extends tubular processes, called canals, along the basolateral surface of the epidermis. Mutations in the exc-5 gene cause tubulocystic defects in this canal. Ultrastructural analysis suggests that exc-5 is required for the proper placement of cytoskeletal elements at the apical epithelial surface. exc-5 encodes a protein homologous to guanine nucleotide exchange factors and contains motif architecture similar to that of FGD1, which is responsible for faciogenital dysplasia. exc-5 interacts genetically with mig-2, which encodes Rho GTPase. These results suggest that EXC-5 controls the structural organization of the excretory canal by regulating Rho family GTPase activities. 相似文献
2.
Shigeo Koyasu Makoto Asada Akio Fukuda Yoshimi Okada 《Journal of molecular biology》1981,153(2):471-475
The mode of polymerization of two species of flagellins, flagellin A and flagellin B, in polar flagella of Caulobacter crescentus was examined. By immunological staining we found that 1 to 1.2 μm of the portion of the flagellar filament proximal to the cell was composed of flagellin B, whereas about 5 μm of the distal portion was composed of flagellin A. This result, together with the previous observation that a flagellin B-less mutant cannot form normal flagella but instead forms stubs in spite of their high level of flagellin A synthesis, indicates that flagellin B is very important for the formation of complete flagella and/or for the initiation of filament formation from the hook. 相似文献
3.
Hiroyuki Kozu Isao Kobayashi Mitsutoshi Nakajima Kunihiko Uemura Seigo Sato Sosaku Ichikawa 《Food biophysics》2010,5(4):330-336
This paper uses computational fluid dynamics to simulate and analyze intragastric fluid motions induced by human peristalsis.
We created a two-dimensional computational domain of the distal stomach where peristalsis occurs. The motion of the gastric
walls induced by an antral contraction wave (ACW) on the wall of the computational domain was well simulated using a function
defined in this study. Retropulsive flow caused by ACW was observed near the occluded region, reaching its highest velocity
of approximately 12 mm/s in the narrowest region. The viscosity of the model gastric contents applied in this study hardly
affected the highest velocity, but greatly affected the velocity profile in the computational domain. The shear rate due to
gastric fluid motion was calculated using the numerical output data. The shear rate reached relatively high values of approximately
20 s−1 in the most occluded region. The shear rate profile was almost independent of the fluid viscosity. We also simulated mass
transfer of a gastric digestive enzyme (pepsin) in model gastric content when peristalsis occurs on the gastric walls. The
visualized simulation results suggest that gastric peristalsis is capable of efficiently mixing pepsin secreted from the gastric
walls with an intragastric fluid. 相似文献
4.
Some RNAs, including both single- and double-stranded RNAs, when incubated with chick embryo cell culture induce cellular resistance against viruses. Evidence was now obtained indicating that the induction of cellular resistance by RNA depends on the cellular metabolic activity, especially on the synthesis of cellular RNA and protein. Thus, inhibitors of RNA and protein synthesis, actinomycin D and cycloheximide, were found to inhibit the development of an antiviral state when added before, or during the relatively early period of, incubation of the cells with RNA. In the course of induction of cellular resistance, three stages may be distinguished, the priming stage, the developing stage, and the established resistant stage. 相似文献
5.
Summary Two laboratory experiments were conducted to examine the ovipositional preferences of the egg parasitoidOoencyrtus nezarae Ishii (Hymenoptera: Encyrtidae) for parasitized and unparasitizedMegacopta punctatissimum Montandon (Hemiptera: Plataspidae). Females that had never oviposited or that had not oviposite for 3 days preferred recently parasitized hosts more than unparasitized hosts. The preference for recently parasitized hosts appeared to be mediated by the punctures in already parasitized hosts made by the ovipositor of the first female. Survival of the parasitoid progeny was lower in recently parasitized hosts than in unparasitized hosts. However, handling time of parasitized hosts was extremely short relative to that of unparasitized hosts, because the superparasitizing female could use the punctures made by the previous females. It is concluded that the females preferred the parasitized hosts over unparasitized hosts because the benefit of saving time and energy for drilling was more than the cost of progeny survival. 相似文献
6.
H Yamazaki Y Mori K Toyoshi H Mori S Sugie N Yoshimi Y Konishi 《Mutation research》1985,144(3):197-202
The genotoxicity of N-nitrosodipropylamine, 8 of its oxidized derivatives and N-nitroso-2,6-dimethylmorpholine was examined in the hepatocyte primary culture (HPC)/DNA repair test. Nine N-nitrosamines which are known to be carcinogenic and mutagenic were clearly positive in the HPC/DNA-repair test. N-Nitroso(2,3-dihydroxypropyl) (2-hydroxypropyl)amine did not elicit DNA repair, but showed a borderline mutagenic response in the Salmonella/microsome test. Thus, the HPC/DNA-repair test displays a comparable capacity to the bacterial mutagenesis test for detecting the genotoxic effects of this class of carcinogens. 相似文献
7.
T Shinoda H Iwata A Nakamura T Ohkubo N Yoshimi S Sugie T Tanaka K Kato 《Acta cytologica》1992,36(2):132-136
The cytologic appearance of a carcinosarcoma (malignant ameloblastoma and fibrosarcoma) of the maxilla in a 63-year-old man is described. On his first admission the diagnosis of malignant ameloblastoma was made on biopsy. After five surgical excisions, radiotherapy and chemotherapy, the diagnosis was changed to carcinosarcoma because the stromal cells of the tumor had become malignant. Aspiration biopsy cytology of the tumor, with a cystic lesion found at the left suborbital area, revealed malignant epithelial cells, indicating malignant ameloblastoma. Imprint smears of both surgically resected and autopsy material showed two types of malignant neoplastic cells, of epithelial and mesenchymal origin. 相似文献
8.
9.
Summary The location of leucine -naphthylamidase on the outer surface of the microvillous membrane of rabbit small intestine was examined by analyzing the interaction of antibodies against leucine -naphthylamidase or another microvillous enzyme, sucrase-isomaltase complex, with microvillous vesicles having different relative amounts of these enzymes, in respect to vesicle agglutination, inhibition of enzyme activity, and electron-microscopic morphology. The results obtained indicate that leucine -naphthylamidase, or at least its antigenic sites, protrude about 10 nm from the outer surface of the microvillous membrane. 相似文献
10.
The mode of chromosome segregation in an asymmetrically dividing bacterium, Caulobacter crescentus, was studied by examining the fate of labeled DNA strands. Swarmer cells (one type of Caulobacter daughter cell), in which single strands of DNA had been labeled with [3H]thymidine during the previous round of chromosome replication, were grown synchronously in a non-radioactive medium for two generations. The distribution of radioactivity among the cells was visualized by autoradiography under a phase-contrast microscope. The labeled DNA strands in each cell were found to consist of two conserved units. From this, we propose a model in which the swarmer cell has two identical chromosomes, which are segregated into the progeny swarmer cell and the progeny stalked cell after chromosome replication. 相似文献