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排序方式: 共有387条查询结果,搜索用时 578 毫秒
1.
Levans produced by four Zymomonas mobilis strains showed antitumour activity against sarcoma 180 and Ehrlich carcinoma in Swiss albino mice. Levans from two strains (ZAP and CP4) had the highest effects. NMR analysis showed that the polymers were composed only of fructose units. The results suggested that the antineoplasic effect is associated to the polysaccharide molecular weight and that a particular molecular weight range may be responsible for this effect. 相似文献
2.
Chondroid bone arises from mesenchymal stem cells in organ culture of mandibular condyles 总被引:1,自引:0,他引:1
M Silbermann A H Reddi A R Hand R Leapman K von der Mark A Franzen 《Journal of craniofacial genetics and developmental biology》1987,7(1):59-79
Mandibular condyles of fetal mice 19 to 20 days in utero comprising clean cartilage and its perichondrium were cultured for up to 14 days, and their capacity to develop osteoid and to mineralize in vitro was examined. After 3 days in culture the cartilage of the mandibular condyle appeared to have lost its inherent structural characteristics, including its various cell layers: chondroprogenitor, chondroblastic, and hypertrophic cells. At that time interval no chondroblasts could be seen; instead, most of the cartilage consisted of hypertrophic chondrocytes. By that time, the surrounding perichondrium, which contains pluripotential mesenchymal stem cells, revealed the first signs of extracellular matrix enclosing type I collagen, bone alkaline phosphatase, osteonection, fibronectin, and bone sialoprotein as demonstrated by immunofluorescent techniques. Electron microscopic examinations of the newly formed matrix revealed foci of mineralization within and along collagen fibers as is normally observed during bone development. The composition of the latter mineral deposits resembled calcium pyrophosphate crystals. Following 14 days in culture larger portions of the condyle revealed signs of osseous matrix, yet the tissue reacted positively for type II collagen. Hence, the condylar cartilage, a genuine representative of secondary-type cartilage, elaborated in vitro a unique type of bone that would be most appropriately defined as chondroid bone. Biochemical assays indicated that the de novo formation of chondroid bone was correlated with changes in alkaline phosphatase activity and 45Ca incorporation. The findings of the present study imply that mesenchymal stem cells that ordinarily differentiate into cartilage possess the capacity to differentiate into osteogenic cells and form chondroid bone. 相似文献
3.
Jorge E. Moreira Arthur R. Hand L. A. Håkan Borg Stellan Sandler Michael Welsh Nils Welsh Décio L. Eizirik 《Virchows Archiv. B, Cell pathology including molecular pathology》1991,60(1):337-344
We have previously described a preferential reduction in the secretory response to nutrient secretagogues in pancreatic mouse
islets maintained in culture after in vitro exposure to streptozotocin (SZ). This reduction was associated with an impaired
substrate metabolism at the mitochondrial level. To further clarify this issue, mouse pancreatic islets were exposed in vitro
to 2.2 mM SZ for 30 min. At 4 h after SZ treatment ultrastructural changes were apparent in the endoplasmic reticulum and
Golgi areas of the B-cells. However, 2 and 6 days following SZ exposure the B-cells appeared well preserved, except for a
marked decrease in the number of insulin-containing secretory granules. A morphometric analysis of the B-cells 6 days after
SZ exposure showed a normal B-cell size and a normal volume fraction of B-cell mitochondria. However, there was a decrease
in total islet size and a 13% decrease in the volume fraction of B-cells in the islets. These mouse islets exhibited a decreased
content of the mitochondrial DNA-encoded cytochrome b mRNA, as evaluated by dot-blot analysis. As a whole, the data obtained
indicate that SZ treatment does not induce a decrease in the number of mitochondria or long-lasting ultrastructural damage
to this organelle. However, there is a clear decrease in the cytochrome b mRNA, suggesting that SZ can induce damage to the
mitochondrial DNA. 相似文献
4.
5.
J M Hand S F Schwalm M A Auen A F Kreft J H Musser J Chang 《Prostaglandins, leukotrienes, and essential fatty acids》1989,37(2):97-106
The following communicates the pharmacology of Wy-48,252 (1,1,1-trifluoro-N-[3-(2-quinolinylmethoxy)phenyl]methanesulfonamide) a chemically novel and orally potent leukotriene (LT) D4 receptor antagonist. In the isolated guinea-pig trachea pretreated with indomethacin (5 microM) and L-cysteine (10 mM), Wy-48,252 antagonized TD4-induced contraction with a pKB = 7.6. Against LTC4 on tissues pretreated with IND and glutathione (10 mM), Wy-48,252 had a pKB greater than 5. Wy-48,252 (10 microM) did not antagonize pilocarpine-, histamine- or PGF2 alpha-induced tracheal contraction. Further, in the presence of indomethacin and chlorpheniramine (1 microM), Wy-48,252 dose-dependently inhibited the antigen-induced contraction of guinea-pig trachea in a manner consistent with antagonism at the LTD4 receptor and inhibition of LT synthesis. In the Konzett-Rossler model of i.v. LTD4-induced bronchoconstriction in indomethacin treated guinea pigs, intragastric Wy-48,252 (2 hr) had an ID50 of 100 micrograms/kg and a functional half-life of 5 hr. Against i.v. antigen-induced bronchoconstriction in guinea pigs treated with indomethacin and chlorpheniramine, intragastric Wy-48,252 (2 hr) had an ID50 of 0.6 mg/kg and a 5 hr half life. Intragastric Wy-48,252 also selectively blocked the cutaneous wheal reaction to intradermal LTD4 but not histamine. We conclude that Wy-48,252 is distinguished from other selective LTD4 receptor antagonists by its oral potency and should be useful in ascertaining the role of LTD4 mediated processes in asthma, allergy and animal models. 相似文献
6.
Localization of cellular regulatory proteins using postembedding immunogold labeling 总被引:1,自引:0,他引:1
Cyclic AMP-dependent protein kinase (cAPK) mediates the effects of catecholamines and hormones that cause elevation of intracellular cyclic AMP levels. The holoenzyme is a tetramer consisting of catalytic (C) and cyclic AMP-binding regulatory (R) subunits. The type I and type II cAPK isoenzymes are defined by R subunits (RI and RII) of differing molecular weight, primary structure, and cyclic AMP-binding properties. Postembedding immunogold labeling procedures and specific polyclonal and monoclonal antibodies to RI, RII, and C were used to study the subcellular distribution of cAPK subunits in several tissues. In the rat parotid gland, both RI and RII were present in the cytoplasm, nuclei, and secretory granules of the acinar cells, whereas secretory granules of intercalated and striated duct cells were poorly labeled. These results confirmed that the acinar secretory granules are the source of R subunits previously identified in saliva by specific photoaffinity labeling techniques. Zymogen granules of pancreatic acinar cells and secretory granules of seminal vesicle cells were labeled with antibody to RII. Pancreatic and seminal fluids were shown to contain cyclic AMP-binding proteins. The granules of several endocrine cells (pituitary, pancreatic islet, intestinal) also labeled with RII antibody. Double labeling of ovarian granulosa cells showed that both RI and C were present in the nuclei and cytoplasm. The localization of cAPK subunits revealed by postembedding immunogold labeling is consistent with the postulated regulatory functions of these proteins in gene expression, cell proliferation, exocytosis, and various metabolic events The widespread occurrence of cAPK subunits in secretory granules and their release to the extracellular environment suggests that they play an important role in secretory cell function. 相似文献
7.
8.
Variation in the ribosomal internal transcribed spacers (ITS1 and ITS2) among eight taxa of the Mimulus guttatus species complex 总被引:1,自引:0,他引:1
The internal transcribed spacer region (ITS1 and ITS2) of the 18S-25S
nuclear ribosomal DNA sequence and the intervening 5.8S region were
sequenced from three individuals in each of eight taxa of the Mimulus
guttatus species complex. Three discrete variants, or "types," of ITS
sequences were found, among which 30%-40% of sites differed, compared with
1%-2% within types. Dot plots indicate that these types were not related by
conspicuous rearrangements or inversions. More than one ITS type was often
found in the same taxon, and two of three ITS types span species
boundaries, indicating their presence prior to speciation. These ITS
sequences showed essentially no positional homology with the nearest
sequenced relative, tomato. In contrast, the 5.8S region was relatively
unvaried, with 8 of 162 sites varied in the sample among all eight taxa.
The phylogeny inferred by the most common ITS sequence type, rooted by the
two other ITS types, agreed with isozymes in showing the distinctness of M.
nudatus, M. laciniatus, and M. tilingii from the other five taxa.
相似文献
9.
M I Mednieks R A Jungmann C Fischler A R Hand 《The journal of histochemistry and cytochemistry》1989,37(3):339-346
A mouse monoclonal antibody of the IgM class, MAb BB1, specific for the type II regulatory subunit (RII) of cyclic AMP-dependent protein kinase (cAPK), was produced using a purified subcellular protein fraction from rat parotid gland as the original antigen. The antibody immunoprecipitated radioactivity labeled RII from bovine heart cAPK, and from rat and human parotid saliva. Western blot analysis revealed specific binding of the antibody to proteins of 52 and 54 KD in extracts of rat parotid tissue, parotid saliva, and bovine heart cAPK. Immunogold labeling of thin sections of rat parotid gland revealed specific labeling of acinar cell nuclei (especially the heterochromatin), cytoplasm (particularly in areas containing granular endoplasmic reticulum), and the content of secretory granules. Labeling was greatly reduced (approximately 84%) when the antibody was pre-absorbed with an excess of bovine heart cAPK. In duct cells the cytoplasm and nuclei were also labeled, but few gold particles were present over secretory granules. These results provide additional evidence for the presence of nuclear cAPK in rat parotid cells, and confirm previous observations on the presence of cAPK regulatory subunits in acinar secretory granules and saliva. The hybridoma reagent will be used for studies of stimulus responses in the parotid and for immunocytochemical analyses of RII distribution in other secretory tissues. 相似文献
10.