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排序方式: 共有377条查询结果,搜索用时 15 毫秒
1.
Embryonic salivary gland epithelial branching activity is experimentally independent of epithelial expansion activity 总被引:4,自引:1,他引:3
Embryonic mouse submandibular salivary gland rudiments undergo morphogenesis in organ culture, characterized by extensive epithelial growth and expansion and repetitive branching activity. Tunicamycin, at a concentration of 25 ng/ml culture medium, decreases the degree of net protein accumulation by 83% and the degree of epithelial expansion by 70% compared to controls, over a 48-hr culture tenure. These decreases correlate with reduced incorporation of [3H]thymidine into DNA. Nevertheless, epithelial branching activity is uncompromised, undergoing an approximately 10-fold increase in lobe numbers, in both controls and tunicamycin-treated rudiments, during the same 48-hr period. The effect is most striking during the 24- to 48-hr culture interval, when controls and tunicamycin-treated rudiments each triple their lobe numbers and controls approximately double epithelial area, while tunicamycin virtually stops all epithelial expansion. 相似文献
2.
Brian Rodrigues Michael R. Spooner David L. Severson 《Molecular and cellular biochemistry》1992,116(1-2):33-37
An exogenous [3H]triolein emulsion was hydrolyzed by intact cardiac myocytes with functional LPL located on the cell surface. This surface-bound LPL could be released into the medium when cardiac myocytes were incubated with heparin. Incubation of cardiac myocytes with VLDL, or the products of TG breakdown, oleic acid or 2-monoolein, did not increase LPL activity in the medium. However, incubation of cardiac myocytes with either VLDL or oleic acid for > 60 min did reduce heparin-releasable LPL activity. In the heart, this inhibitory effect of FFA could regulate the translocation of LPL from its site of synthesis in the cardiac myocyte to its functional site at the capillary endothelium.Abbreviations LPL
lipoprotein lipase
- TG
triacylglycerol
- FFA
free fatty acids
- VLDL
very-low density lipoprotein 相似文献
3.
P J Spooner S B Clark D L Gantz J A Hamilton D M Small 《The Journal of biological chemistry》1988,263(3):1444-1453
A reproducible, fairly narrow-sized population of rat lymph chylomicrons, approximately 100 nm, was isolated by centrifugation and combined with low levels of [1-13C]oleic acid for NMR studies. The carboxyl chemical shift was monitored as a function of aqueous pH to characterize the ionization behavior of the fatty acid in these particles. The titration curves were very similar to those for oleic acid in equivalent-sized emulsion particles composed of egg phosphatidylcholine and triolein. A simple partition-ionization model was fitted to the data to derive values for apparent ionization constant, expressed as pKapp, of 7.4-7.5 and the "true" surface to core partition coefficient of approximately 7 for oleic acid in chylomicrons. The fatty acid in chylomicrons thus appeared to be largely associated with the surface regions of these particles. Addition of bovine serum albumin to the samples showed that near physiologic pH much of the fatty acid was bound to the albumin at fatty acid to albumin-binding stoichiometries as high as 5.1 and with mass ratios of greater than 2 in favor of the lipid or lipoprotein particles. Lowering the pH of the medium shifted the distribution of fatty acid away from albumin so that at pH 5 with the emulsion, virtually all the fatty acid was associated with the lipid. The behavior observed under physiologic conditions is consistent with the rapid clearance and redistribution of fatty acid generated in these particles by lipolytic processes. However, under conditions of severe acidosis, hyperlipidemia, and hypoalbuminemia a significant portion of fatty acids might be retained in triglyceride-rich lipoproteins and their remnants and affect subsequent metabolism. 相似文献
4.
Thorotrast uptake and transit in embryonic glia, heart fibroblasts and neurons in vitro 总被引:6,自引:0,他引:6
Norman K. Wessells Marilyn A. Luduea Paul C. Letourneau Joan T. Wrenn Brian S. Spooner 《Tissue & cell》1974,6(4):757-776
Thorotrast (colloidal ThO2) is incorporated into coated vesicles, various agranular vesicles and sacs, and a surface-associated system of membranous channels in times as short as 1 min by single cultured glial and heart cells. Thorotrast appears in ‘C’-shaped bodies and in small, dense bodies of the lysosomal series within ca. 25 min. With longer chase periods, thorotrast ‘clears’ from all cytoplasmic organelles except the lysosomal series. The technique of applying thorotrast and using varying chase periods fails to distinguish a class of membranous organelles, located close to the cell periphery, that might serve as a source of new cell surface during locomotory activity. Similarly, thorotrast (colloidal ThO2) is incorporated into almost all classes of membrane-bounded organelles of growth cones and axons of single nerve cells in vitro in times as short as 1 min. This includes elements of the smooth endoplasmic reticulum. No thorotrast enters the lysosomal granules in this short time. During various chase periods, the tracer disappears from the initial sites of incorporation and accumulates in dense bodies of the lysosome series within growth cones and axons. ‘C’-shaped bodies may be an intermediate in that process. No unique sites of endocytotic activity or of a complete absence of endocytosis were observed that could be correlated with growth cone function and axonal elongation, though the presence of the tracer in agranular sacs of the smooth endoplasmic reticulum in growth cones could reflect hypothesized cycling of cell surface (Bray, 1973). 相似文献
5.
6.
S. C. Darby C. R. Rizza R. Doll R. J. Spooner I. M. Stratton B. Thakrar 《BMJ (Clinical research ed.)》1989,298(6680):1064
OBJECTIVE--To estimate the cumulative incidence of AIDS by time since seroconversion in haemophiliacs positive for HIV and to examine the evidence for excess mortality associated with HIV in those who had not yet been diagnosed as having AIDS. DESIGN--Analysis of data from ongoing national surveys. SETTING--Haemophilia centres in the United Kingdom. PATIENTS--A total of 1201 men with haemophilia who had lived in the United Kingdom during 1980-7 and were positive for HIV. INTERVENTION--None. END POINTS--Diagnosis of AIDS; death in those not diagnosed as having AIDS. MEASUREMENTS AND MAIN RESULTS--Estimation of cumulative incidence of AIDS and number of excess deaths in seropositive patients not diagnosed with AIDS. Median follow up after seroconversion was 5 years 2 months. Eight five patients developed AIDS. Cumulative incidence of AIDS five years after seroconversion was 4% among patients aged less than 25 at first test positive for HIV, 6% among those aged 25-44, and 19% among those aged greater than or equal to 45. There was little evidence that type or severity of haemophilia or type of factor VIII or IX that had caused HIV infection affected the rate of progression to AIDS. Mortality was increased among those who had not been diagnosed as having AIDS, especially among those with "AIDS related complex." Thirteen deaths were observed among 36 patients diagnosed as having AIDS related complex against 0.65 expected, and 34 deaths in 1080 other patients against 22.77 expected; both calculations were based on mortality rates observed in haemophiliacs in the United Kingdom in the late 1970s. CONCLUSIONS--Rate of progression to AIDS depended strongly on age. There is a substantial burden of fatal disease among patients positive for HIV who have not been formally diagnosed as having AIDS. 相似文献
7.
8.
Comparison of four molecular markers in measuring relationships among the wild potato relatives Solanum section Etuberosum (subgenus Potatoe) 总被引:2,自引:0,他引:2
D. M. Spooner J. Tivang J. Nienhuis J. T. Miller D. S. Douches A. Contreras-M. 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1996,92(5):532-540
We evaluated chloroplast DNA (cpDNA), isozymes, single to low-copy nuclear DNA (RFLPs), and random amplified polymorphic DNAs (RAPDs) in terms of concordance for genetic distance of 15 accessions each of Solanum etuberosum and S. palustre, and 4 accessions of S. fernandezianum. These self-compatible, diploid (2n=24), and morphologically very similar taxa constitute all species in Solanum sect. Etuberosum, a group of non-tuber-bearing species closely related to Solanum sect. Petota (the potato and its wild relatives). Genetic distance and multidimentional scaling results show general concordance of isozymes, RFLPs and RAPDs between all three taxa; cpDNA shows S. etuberosum and S. palustre to be more similar to each other than to S. fernandezianum. Interspecific sampling variance shows a gradation of resolution from allozyme (low) to RAPD to RFLP (high); while intraspecific comparisons graded from RFLPs (low) to RAPDs (high; lack of sufficient allozyme variability within species precluded comparisons for allozymes). Experimental error was low in RFLPs and RAPDs.Names are necessary to report factually and available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable 相似文献
9.
H. L. Neibergs A. M. Ryan J. E. Womack R. L. Spooner J. L. Williams 《Animal genetics》1994,25(5):313-317
Polymerase chain reaction (PCR) primers designed to amplify the octapeptide repeat region of the bovine prion gene were used to test the association of genotypes with bovine spongiform encephalitis (BSE) in 56 BSE-affected and 177 unaffected animals. Three alleles (A, B, C) were detected as single-strand conformation polymorphisms (SSCPs) and two alleles (1,2 representing six or five copies of the octapeptide repeat respectively) were detected as amplified double-strand fragment length polymorphisms (AMFLPs). Observed genotypes of SSCPs and AMFLPs were analysed by x-square. The SSCP genotypes of nuclear family members of animals with BSE and BSE-affected animals were different (P < 0.001, P < 0.01) from unrelated animals of the same breed without BSE. No genotypic differences were found between the BSE-affected animals and their relatives (P > 0.469). No AMFLP genotypic differences were detected between BSE-affected animals, their relatives, unrelated animals of the same breed or animals of different breeds (P > 0.05). These data suggest that BSE-affected animals and their relatives are more likely to have the AA SSCP genotype than unrelated animals of the same breed or animals of different breeds. 相似文献
10.
Variation in heat-shock proteins among species of desert fishes (Poeciliidae, Poeciliopsis) 总被引:4,自引:0,他引:4
Analysis of the heat-shock proteins (hsps) of six closely related species
of Poeciliopsis demonstrated the existence of biochemical diversity in the
hsp100, hsp70, hsp60, and hsp30 protein families among species. Each
species expressed five to seven hsp70-related isoforms. Constitutive 70-kD
isoforms were identical among species, but four different patterns of
heat-inducible isoforms were seen in these six species. Members of the
hsp70 family of molecular chaperones are included among the most highly
conserved proteins known, and the possibility of variation in hsp70 among
closely related species has rarely been addressed. The hsp30 family is
known to be less conserved than the hsp70 family, and, as expected, the
Poeciliopsis hsp30 patterns showed more variation. Most of the hsp30
isoforms characteristic of a particular species were unique to that
species. Hsp100 and hsp60 were identical in five of the species, but
alternate isoforms were found in P. monacha. The small size and limited
geographical distribution of the P. monacha population have probably
contributed to the uniqueness of the monacha pattern. Two of the species
were shown to acquire thermotolerance, the ability to withstand normally
lethal temperatures when subjected to a gradual temperature increase.
Rapid-heating protocols commonly used to establish critical thermal maxima
of organisms do not include this inducible component of thermoresistance
and therefore do not adequately assess an organism's capacity to withstand
thermal stress.
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