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981.
Michael James Dixon David Foreman Seth Schor Mark William James Ferguson 《Development genes and evolution》1993,203(3):140-150
Mouse embryonic palatal mesenchymal (MEPM) cells were cultured either on plastic tissue culture dishes or on the surface of three-dimensional collagen gels or within collagen gel matrices in DMEM/F12 medium containing 2.5% donor calf serum. MEPM cells proliferated exponentially when cultured on collagen or on plastic. Cells cultured within collagen gels did not proliferate but remained viable. Addition of 10 ng/ml epidermal growth factor (EGF) or transforming growth factor alpha (TGF) stimulated the proliferation of those cells cultured on plastic or on collagen but not those cultured within collagen gels. Immunocytochemical analysis revealed that MEPM cells synthesise collagen types I, III, IV, V, VI and IX; fibronectin, heparan sulphate proteoglycan, laminin and tenascin in vitro. These molecules are all present in the developing palate in vivo. EGF and TGF produced a generalised stimulation of extracellular matrix (ECM) synthesis by MEPM cells in vitro. Biochemical analysis indicated that cells cultured within collagen gels had the highest intrinsic rate of protein synthesis. On all substrata neither EGF nor TGF markedly altered the types of ECM molecules synthesised but rather caused a general increase in the total amount produced. This stimulation was most marked where the cells were cultured within collagen gels. The lack of stimulation of proliferation of MEPM cells cultured within collagen gels (i.e. in a physiologically-relevant environment) by EGF or TGF together with the marked stimulation of ECM synthesis suggests that these factors may act as differentiation signals via their effects on ECM production.
Correspondence to: M.J. Dixon 相似文献
982.
983.
Azole substituted oligonucleotides promote antiparallel triplex formation at non-homopurine duplex targets. 总被引:5,自引:3,他引:2
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R H Durland T S Rao V Bodepudi D M Seth K Jayaraman G R Revankar 《Nucleic acids research》1995,23(4):647-653
The ability of certain azole substituted oligodeoxy-ribonucleotides to promote antiparallel triple helix formation with duplex targets having CG or TA interruptions in the otherwise homopurine sequence was examined. 2'-Deoxyribonucleosides of the azoles, which include pyrazole, imidazole, 1,2,4-triazole and 1,2,3,4-tetrazole were synthesized using the stereo-specific sodium salt glycosylation procedure. These nucleosides were successfully incorporated using solid-support, phosphoramidite chemistry, into oligonucleotides designed to interact with the non-homopurine duplex targets. The interaction of these modified oligonucleotides with all four possible base pairs was evaluated and compared to similar data for a series of natural oligonucleotides. The oligonucleotides containing simple azoles enhanced the triplex forming ability considerably at non-homopurine targets. Binding of these modified oligonucleotides to duplex targets containing TA inversion sites was particularly noteworthy, and compare favorably to unmodified oligonucleotides for binding to duplex targets containing CG as well as TA base pairs. The selectivity exhibited by certain azoles is suggestive of base pair specific interactions. Thus, the azoles evaluated during this study show considerable promise for efforts to develop generalized triplex formation at non-homopurine duplex sequences. 相似文献
984.
Fetal wound healing differs from its adult counterpart in that it is regenerative and occurs without scarring. The matrix macromolecule hyaluronan (HA) and various cytokines, including members of the TGF-β family, have been implicated in the control of scarring. We have previously reported that adult and fetal fibroblasts differ with respect to the effect of cell density on HA synthesis when cultured on plastic tissue culture dishes. Data regarding the effects of substratum and TGF-β1 on HA synthesis by these cells are presented in this communication. Our results indicate that HA synthesis by both fetal and adult fibroblasts is (a) up-regulated by culture on a collagen substratum and (b) differentially regulated by TGF-β1 in a manner which is dependent upon both substratum and cell density. TGF-β1 stimulated HA synthesis by confluent fetal fibroblasts growing on a plastic substratum, but inhibited HA synthesis on a collagen substratum; these data underscore the important role of the substratum in determining the precise effect of TGF-β1 on cell behavior. Related studies indicated that the migration of fetal and adult fibroblasts into the collagen substrata was modulated by TGF-β1 in a manner identical to its effect on HA synthesis. These observations are discussed in terms of the contribution of distinct fibroblast subpopulations to wound healing and the manner in which this is regulated by matrix and cytokines. 相似文献
985.
986.
P. K. Asha M. S. Shaila C. S. Vaidyanathan T. Ramakrishnan 《Journal of biosciences》1983,5(4):347-353
Isolated nuclei from differentiating cultures ofNicotiana sanderae showed increased levels of RNA polymerase activity as compared to the nuclei from callus cultures. The RNA synthetic activity
was dependent on nucleotide triphosphates and Mg2+ and was destroyed by RNase. Maximum activity was obtained in the presence of 50 mM (NH4)2 SO4 and α-amanitin inhibited 40% and 55% of the activity in the nuclei from callus and differentiating tissue respectively. The
nuclei from differentiating tissue elicited a 3-fold increase in RNA polymerase I and a 4-fold augmentation in RNA polymerase
II activities. 相似文献
987.
Captopril when administered intracerebroventricularly (icv) in doses of 100, 300, 500 and 1000 micrograms induced a dose dependent antinociceptive effect in rats. Naloxone pretreatment (10 mg/kg, ip) completely antagonised antinociceptive effect of captopril, suggesting thereby the involvement of brain enkephalinergic system. Captopril 300 micrograms, icv potentiated the antinociceptive effect of morphine in intact animals. The bilateral adrenalectomy did not have any effect on this potentiation as against the reported blockade of potentiation in adrenalectomized animals when captopril was administered by systemic route. Thus potentiation of morphine induced antinociception by icv captopril is unlikely to be exerted through an effect on adrenal function and is most likely due to increased brain enkephalin levels. 相似文献
988.
989.
Horace L. Barnett Fredrick L. Bergmann Catherine Short Bigelow Julia Joyce Harper Brashear Ricardo Callejas Jane Colten Fay Kenoyer Daily William A. Daily Ray Fields Dawson Thelma F. Engle Robert H. Farber Robert I. Fletcher F. Raymond Fosberg Jeanne Smith Gillum William D. Gray Mary Swan Hagen Charles B. Heiser Jerome C. Hixson James M. Koepper Marjorie H. Ladley H. Harvey Lafuze Bassett Maguire Lois Carter McClure Shirley A. Moses John W. Oswald Sally Pope Overman Value M. Poor Seth Pope Marion McBurney Rice Velva E. Rudd Richard D. Schein Kathryn Jung Schmidt Emory G. Simmons Albert C. Smith Charlotte Epple Smith Julian A. Steyermark Margaret Emily McGaughey Stoner James H. Tate Oswald Tippo Ruth E. Van Seventer Ken Wagner Winona H. Welch Howard Youse 《Brittonia》1989,41(3):236-284
Editor’s note: This tribute was prepared by Barbara Yuncker from a recorded interview she had with Dr. Callejas during his
six-week visit to the Garden’s Herbarium in September 1988 to study the Piperaceae specimens received from DePauw University. 相似文献
990.
Temporal fluctuations in HIV quasispecies in vivo are not reflected by sequential HIV isolations 总被引:135,自引:0,他引:135
A Meyerhans R Cheynier J Albert M Seth S Kwok J Sninsky L Morfeldt-M?nson B Asj? S Wain-Hobson 《Cell》1989,58(5):901-910
A genetic study has been made of the HIV tat gene from sequential HIV-1 isolates and the corresponding infected peripheral blood mononuclear cells. DNA was amplified by polymerase chain reaction (PCR) and cloned into a eukaryotic expression vector. Twenty clones were sequenced from each sample. Comparing the sequential HIV isolates, abrupt differences were seen between the major forms of each isolate. These progressive changes were not reflected at all among the in vitro samples. The fluctuation in the quasispecies in vivo may suggest a much more dynamic role for latently infected mononuclear cells. High frequencies of functionally defective tat genes were identified. Given such complexity and the evident differences between quasispecies in vivo and in vitro, the task of defining HIV infection in molecular terms will be difficult. 相似文献