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The effect of prostaglandin E2 (PGE2) on fibroblast proliferation was examined. The presence of PGE2 for 24 h inhibited the growth of quiescent cells stimulated with serum, platelet-derived growth factor and macrophage-derived factors. Maximal inhibition of nuclear labeling with [3H]thymidine occurred at concentrations greater than 10−7 M. The inhibitory effect of PGE2 was less potent in exponentially growing cells and was not the result of conversion of PGE2 to PGA2 during incubation in growth medium. The G1 phase was determined to be 12–14 h in untreated cultures. The extent of growth inhibition by PGE2 was similar with addition of PGE2 at 0, 3, 6, or 9 h following restimulation of quiescent cell cultures. Approximately 25% of the cells that enter S phase are refractory to PGE2-induced growth inhibition. Short-term exposure to PGE2 (5 min and 30 min) caused substantial growth inhibition. The serum-induced proliferation was also inhibited by the cAMP analogue, dibutyrl cAMP. Our results suggest that PGE2 affects a distinct subpopulation of cells. Restimulation of quiescent cells treated with PGE2 for 24 h, indicated that release from PGE2 exposure is associated with prolongation of the G1 phase of the cell cycle. 相似文献
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Mogi M Yang J Lambert JF Colvin GA Shiojima I Skurk C Summer R Fine A Quesenberry PJ Walsh K 《The Journal of biological chemistry》2003,278(40):39068-39075
Akt is an important regulator of cell survival, growth, and glucose metabolism in many cell types, but the role of this signaling molecule in hematopoietic stem cells is poorly defined. Side population (SP) cells are enriched for hematopoietic stem cell activity and are defined by their ability to efficiently efflux Hoechst 33342. Bone marrow from Akt1-null mice exhibited a reduced SP fraction. However, bone marrow cellularity, growth factor-responsive progenitor cultures, and engraftable stem cells were normal in these mice. Treatment of bone marrow with LY294002, an inhibitor of the Akt effector protein phosphatidylinositol 3-kinase, led to a reversible loss of the SP fraction. Bcrp1, which encodes the Hoechst dye transporter, was translocated from the membrane to the intracellular compartment under conditions that promote the SP-depleted state. Lentivirus-mediated overexpression of Akt1 in bone marrow markedly increased the SP fraction, whereas there was no effect on bone marrow from Bcrp(-/-) mice. These data suggest that Akt signaling modulates the SP cell phenotype by regulating the expression of Bcrp1. 相似文献
115.
Parmentier E Fontenelle N Fine ML Vandewalle P Henrist C 《Journal of morphology》2006,267(12):1461-1468
Most soniferous fishes producing sounds with their swimbladder utilize relatively simple mechanisms: contraction and relaxation of a unique pair of sonic muscles cause rapid movements of the swimbladder resulting in sound production. Here we describe the sonic mechanism for Ophidion barbatum, which includes three pairs of sonic muscles, highly transformed vertebral centra and ribs, a neural arch that pivots and a swimbladder whose anterior end is modified into a bony structure, the rocker bone. The ventral and intermediate muscles cause the rocker bone to swivel inward, compressing the swimbladder, and this action is antagonized by the dorsal muscle. Unlike other sonic systems in which the muscle contraction rate determines sound fundamental frequency, we hypothesize that slow contraction of these antagonistic muscles produces a series of cycles of swimbladder vibration. 相似文献
116.
Interactions between Mycobacterium tuberculosis bacilli and alveolar macrophages have been extensively characterized, while similar analyses in epithelial cells have not been performed. In this study, we microscopically examined endosomal trafficking of M. tuberculosis strain Erdman in A549 cells, a human type II pneumocyte cell line. Immuno‐electron microscopic (IEM) analyses indicate that M. tuberculosis bacilli are internalized to a compartment labelled first with Rab5 and then with Rab7 small GTPase proteins. This suggests that, unlike macrophages, M. tuberculosis bacilli traffic to late endosomes in epithelial cells. However, fusion of lysosomes with the bacteria‐containing compartment appears to be inhibited, as illustrated by IEM studies employing LAMP‐2 and cathepsin‐L antibodies. Examination by transmission electron microscopy and IEM revealed M. tuberculosis‐containing compartments surrounded by double membranes and labelled with antibodies against the autophagy marker Lc3, providing evidence for involvement and intersection of the autophagy and endosomal pathways. Interestingly, inhibition of the autophagy pathway using 3‐methyladenine improved host cell viability and decreased numbers of viable intracellular bacteria recovered after 72 h post infection. Collectively, these datasuggest that trafficking patterns for M. tuberculosis bacilli in alveolar epithelial cells differ from macrophages, and that autophagy is involved this process. 相似文献
117.
G. Roff E. C. E. Kvennefors K. E. Ulstrup M. Fine O. Hoegh-Guldberg 《Coral reefs (Online)》2008,27(2):373-377
Acroporid white syndrome, a disease-like syndrome from the Great Barrier Reef, results from degenerative host tissue at lesion
borders. Tissue preceding lesion borders appears visually healthy, but it is currently unclear whether the endosymbiotic zooxanthellae
(Symbiodinium) are physiologically impacted. Compared to healthy colonies, this study found no significant differences in symbiont density,
mitotic index or chlorophyll a content in tissue bordering (0 cm), and 8 cm away from white syndrome lesions. Using chlorophyll a fluorescence techniques, the border tissue did not appear to be photosynthetically compromised, and Symbiodinium extracted from this area were photosynthetically competent. Transmission electron microscopy revealed extensive degeneration
of host tissues surrounding symbionts in affected areas, however, Symbiodinium cells were structurally intact with no sign of in situ degradation. Collectively, these results suggest that Symbiodinium at white syndrome lesion borders exist in a dynamic intra-cellular state during active host tissue loss, yet remain physiologically
uncompromised. 相似文献
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Bishop T. Bosher Scott H. Newton† & Michael L. Fine 《Ethology : formerly Zeitschrift fur Tierpsychologie》2006,112(2):188-195
Although experimental evidence is lacking, the stout pectoral spine of catfishes has been interpreted as a defensive adaptation. The spine can be rigidly locked and abducted to produce stridulation sounds, which have been hypothesized to serve a warning function. We studied spine function in channel catfish (Ictalurus punctatus) as a deterrent to predation by largemouth bass (Micropterus salmoides) by presenting individuals with pairs of catfish, one with its pectoral spines clipped and the other intact. The number of initial attacks on clipped and intact fish was similar, suggesting that bass do not recognize the spine visually. Bass showed evidence of learning across trials, striking clipped fish fewer times and consuming them. Conversely, intact fish were attacked more than clipped ones because intact fish were repeatedly disgorged and attacked again, suggesting that bass become sensitized to the spine. Ingestion times were longer for intact than clipped fish, and fewer intact fish were eaten. Eighty‐eight percent of intact fish survived in the mouth of a bass one or more times. Catfish did not stridulate or use their spines to deter initial attacks, refuting the warning hypothesis. Locking and stridulation motions, only observed when catfish were held inside the mouth of a bass, did not deter subsequent attacks indicating that neither the spine nor stridulation carry a warning function. It is possible, therefore, that stridulation sounds function as a distress call. The spine functions against a gape‐limited predator by increasing the difficulty of ingestion but not capture. 相似文献