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31.
Cleavage of dT8 and dT8 phosphorothioyl analogues by Escherichia coli DNA topoisomerase I: product and rate analysis 总被引:1,自引:0,他引:1
Escherichia coli DNA topoisomerase I catalyzes the cleavage of short, single-stranded oligodeoxynucleotides with dT8 as the shortest cleavable oligo(thymidylic acid). The 5'-32P-labeled products formed from the cleavage of [5'-32P]dT8 are dT5, dT4, and dT3 with over 70% of the substrate cleaved to dT4. Mg(II) ions affect this product distribution by increasing the percentage of dT4 formed. The substitution of a sulfur atom for a nonbridging oxygen atom in a phosphodiester linkage yields oligodeoxynucleotide phosphorothioyl (PS) analogues. The epimers of the analogues were separated, and the position and stereochemistry of the phosphorothiodiester bond were determined. Topoisomerase I is stereospecific in its reactivity toward these analogues. With the oligodeoxynucleotide PS analogue substrates, the rate of cleavage, the stereospecificity, and the product distribution depend upon the position and the stereochemistry of the phosphorothiodiester linkage. 相似文献
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Spongelike alginate nanoparticles as a new potential system for the delivery of antisense oligonucleotides. 总被引:3,自引:0,他引:3
I Aynié C Vauthier H Chacun E Fattal P Couvreur 《Antisense & nucleic acid drug development》1999,9(3):301-312
The aim of this study was to design a new antisense oligonucleotide (ON) carrier system based on alginate nanoparticles and to investigate its ability to protect ON from degradation in the presence of serum. Pharmacokinetics and tissue distribution of ON-loaded nanoparticles have been determined after intravenous administration. An original and dynamic process for ON loading into polymeric nanoparticles has been applied. It is based on the diffusion of ON or ON/polylysine complex into the nanoparticle or the alginate gel, respectively. Indeed, the single coincubation of ON with nanoparticles led, within a few days, to an extremely efficient association. The diffusion kinetic of ON was shown to be dependent on several parameters, incubation temperature, ON concentration, presence or absence of polylysine, polylysine molecular weight, and nanoparticle preparation procedure. This new alginate-based system was found to be able to protect [33P]-radiolabeled ON from degradation in bovine serum medium and to modify their biodistribution, as an important accumulation of radioactivity was observed in the lungs, in the liver, and in the spleen after intravenous administration into mice. ON may be associated efficiently with calcium alginate in a colloidal state. Such nanosponges are promising carriers for specific delivery of ON to lungs, liver, and spleen. 相似文献
35.
The ultrastructure of the interstitial cells of Cajal (ICC) in the oesophagus of the monkey resembled that described in the oesophagus of other mammalian species but differed in their paucity and almost lack of smooth endoplasmic reticulum, caveolae and filaments. The plasmalemma of the ICC was in close contact (20- to 30-nm gaps) with that of smooth muscle cells. This may occasionally take the form of a desmosome, but gap junctions have not been observed. Vesiculated axon profiles, containing large granular or agranular vesicles were in close contact (20- to 30-nm gaps) with the plasmalemma of ICC. In a few vesiculated profiles a presynaptic density could be recognized. The intercalation of the ICC between the vesiculated axon profiles and the smooth muscle cells suggest a role in oesophageal motility. Between 3 and 21 days following bilateral vagotomy some ICC showed regressive changes such as increased electron density and shrinkage of the cytoplasm, crowding of the organelles and dissolution of the nuclear chromatin material. Axon profiles in the vicinity of the affected ICC contained glycogen granules suggesting injury. In late stages, the number of ICC and smooth muscle contacts was reduced. The results suggest that the vagus nerves exert a trophic influence on the ICC and that the intercellular relationships between ICC and smooth muscle cells possess a degree of plasticity. It is tentatively suggested that these vagal effects may be mediated via the oesophageal myenteric ganglia. 相似文献
36.
Ultrastructure of the epithelial cells of the ventral prostate from the hopping mouse Notomys alexis
The large ventral prostate of the hopping mouse has abundant secretory units whose epithelial cells vary in height and which often have nuclei in the apical region of the cell. TEM observations indicated two epithelial cell types in which some unusual features occurred. Type A cells had granular endoplasmetic reticulum (GER) whose membranes often formed intracytoplasmic confronting cisternae. Type B cells had more fragmented and vesiculated GER with sparse ribosomes and less frequently also intracytoplasmic confronting confronting cisternae. In the latter cells, two types of granules were found, one of which was derived from the Golgi and the other possibly directly from the GER. Type A cells only had one type of granule present. A highly convoluted membrane was also found at the basal region in many of the cells. The significance of these unusual ultrastructural features has yet to be ascertained. 相似文献
37.
N. Wada Y. Kanda M. Tokuriki K. Kanda 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2000,186(7-8):771-779
We studied neuronal pathways from low-threshold muscle (group I, II) and cutaneous afferents (group A(alpha)beta) innervating the tail to motoneurons innervating trunk muscles (m. iliocostalis lumborum and m. obliquus externus abdominus) in 18 spinalized cats. Stimulation of group I muscle afferents produced excitatory postsynaptic potentials or excitatory postsynaptic potentials followed by inhibitory postsynaptic potentials in all motoneurons innervating the m. iliocostalis lumborum which showed effects (32%), and predominantly inhibitory postsynaptic potentials in motoneurons innervating the m. obliquus externus abdominus (47%). Stimulation of group I+II afferents produced significant increases of the incidence of motoneurons showing postsynaptic potentials (the notoneurons innervating the m. iliocostalis lumborum, 87%; the motoneurons innervating the m. obliquus externus abdominus, 82%). The effects of low threshold cutaneous afferents were bilateral, predominantly producing inhibitory postsynaptic potentials in motoneurons innervating both muscles. These results suggest that neuronal pathways from muscle afferents to back muscle motoneurons mainly increase the stiffness of the trunk to maintain its stability, while those to abdominal muscles help to extend the dorsal column by decreasing their activities. The results also indicate that neuronal pathways from cutaneous afferents to trunk motoneurons functionallY disconnect the tail from the trunk. 相似文献
38.
Silk fibroin with the alanyl carboxyl carbon enriched with 13C was obtained by giving a diet containing 13C-enriched alanine to the larvae of Bombyx mori and Antheraea pernyi at the fifth instar. Sericin-free fibroin fibers were prepared from cocoons, and gut was made from the liquid silk in the gland. The final 13C content was about 13%. Cross polarization/magic angle sample spinning spectra at 25 MHz and 75 MHz were measured for each sample at different orientations. Spectra were simulated using the principal values and orientations of the shielding tensor in the alanine crystal. The results indicate that the beta-structure of the fibroin may be a little more flattened than the typical pleated sheet beta-structure. 相似文献
39.
Y Aoyagi I Tasaki J Okumura T Muramatsu 《Comparative biochemistry and physiology. A, Comparative physiology》1988,89(3):433-436
1. Effect of low ambient temperature on protein turnover in the liver and whole body was investigated in chicks together with the contribution of protein synthesis to the total heat production. 2. Both protein synthesis and degradation in the whole body were increased, the latter to a larger extent, at low ambient temperature (LT, 22 degrees C) compared with adequate temperature (AT, 30 degrees C). Liver protein synthesis was not significantly altered by the temperature treatment. 3. The total heat production of LT group was as high as 160% of the AT group. 4. The increased heat production due to enhanced whole-body protein synthesis accounted for only 1.4% of the heat increment in thermogenesis at low ambient temperature, suggesting that protein synthesis would contribute little, if any, to cold-induced thermogenesis in chicks. 相似文献
40.
W Y Mok R C Luiz?o M do S Barreto da Silva 《Applied and environmental microbiology》1982,44(3):570-575
A total of 2,886 bats captured in the Amazon Basin of Brazil were processed for the isolation of fungi. From the livers, spleens, and lungs of 155 bats (5.4%), 186 fungal isolates of the genera Candida (123 isolates), Trichosporon (26 isolates), Torulopsis (25 isolates), Kluyveromyces (11 isolates), and Geotrichum (1 isolate) were recovered. Seven known pathogenic species were present: Candida parapsilosis, C. guilliermondii, C. albicans, C. stellatoidea, C. pseudotropicalis, Trichosporon beigelii, and Torulopsis glabrata. Twenty-three culture-positive bats showed identical fungal colonization in multiple organs or mixed colonization in a single organ. The fungal isolation rates for individual bat species varied from 1 fungus per 87 bats to 3 fungi per 13 bats, and the mycoflora diversity for members of an individual fungus-bearing bat species varied from 16 fungi per 40 bats to 7 fungi per 6 bats. Of the 38 fungal species isolated, 36 had not been previously described as in vivo bat isolates. Of the 27 culture-positive bat species, 21 had not been previously described as mammalian hosts for medically or nonmedically important fungi. 相似文献