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排序方式: 共有429条查询结果,搜索用时 234 毫秒
1.
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
2.
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
3.
The phylogeny of the hominoid primates: a statistical analysis of the DNA-DNA hybridization data 总被引:1,自引:0,他引:1
Sibley and Ahlquist compared the single-copy nuclear DNA sequences of the
hominoid primates using DNA-DNA hybridization. From this data set they
estimated a phylogeny that clusters man and chimpanzees using a distance
Wagner procedure. However, no assessment of statistical confidence in this
estimated phylogeny was made, despite the fact that their data set contains
internal inconsistencies concerning the correct branching order. This paper
presents a modification of Pielou's Q- statistic that allows one to make
nonparametric tests of phylogenetic relationship from distance data. The
results of this analysis indicate that the estimated phylogeny of Sibley
and Ahlquist is without statistical significance owing to the internal
inconsistencies of the data set. A survey and additional analyses of other
types of molecular data indicate that the phylogeny that clusters
chimpanzees and gorillas and has the human lineage splitting off earlier is
statistically consistent with all the molecular data (including the DNA-DNA
hybridization data), whereas the phylogeny estimated by Sibley and Ahlquist
can be rejected at the 5% level using the data on restriction- endonuclease
sites in the mitochondrial genome.
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.
Dr AR Holmes RD Cannon HF Jenkinson 《Journal of industrial microbiology & biotechnology》1995,15(3):208-213
The yeastCandida albicans coaggregates with a variety of streptococcal species, an interaction that may promote oral colonization by yeast cells.C. albicans andCandida tropicalis are the yeasts most frequently isolated from the human oral cavity and our data demonstrate that both these species bind toStreptococcus gordonii NCTC 7869 while two otherCandida species (Candida krusei andCandida kefyr) do not. Adherence ofC. albicans was greatest when the yeast had been grown at 30° C to mid-exponential growth phase. For 21 strains ofC. albicans there was a positive correlation between the ability to adhere toS. gordonii and adherence to experimental salivary pellicle. Whole saliva either stimulated or slightly inhibited adherence ofC. albicans toS. gordonii depending on the streptococcal growth conditions. The results suggest that the major salivary adhesins and coaggregation adhesins ofC. albicans are co-expressed. 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.