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  • Cell & Developmental Biology  (114)
  • 1995-1999  (114)
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  • 1
    ISSN: 0886-1544
    Keywords: actin ; microfilaments ; heparan sulfate proteoglycans ; heparin-binding proteins ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cell surface proteoglycans participate in molecular events that regulate cell adhesion, migration, and proliferation. To investigate the organization of these molecules at the cell surface, the distribution of two well-known proteoglycan ligands has been studied. These ligands, lipoprotein lipase and basic fibroblast growth factor, showed a characteristic binding pattern consisting of highly organized parallel arrays that crossed the upper surface of human skin fibroblasts. The proteoglycan nature of the binding sites was evident from their susceptibility to heparinases, and from ligand displacement by heparin. Parallel localization of the ligands and actin, and treatment of the cells with cytochalasin, showed that the binding proteoglycans are organized by the actin cytoskeleton. The ligands induced a different behaviour of the binding sites on incubation of the cells at 37°C. Lipoprotein lipase produced a movement of the binding proteoglycans along the actin filaments towards the cell center. In contrast, after binding of basic fibroblast growth factor the binding proteoglycans remained spread over the cell surface and actin depolymerization was induced. Since an increasing number of ligands appear to depend on proteoglycans for their interactions with their high affinity receptors, distribution and movement of proteoglycans at the cell surface that is organized by the actin cytoskeleton could direct and enhance the encounters between the ligands and their specific receptors. © 1995 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
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  • 2
    ISSN: 0730-2312
    Keywords: osteoporosis ; dexamethasone ; glucocorticoids ; prostaglandins ; phospholipase ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Eicosanoids are multifunctional autocrine/paracrine regulators of bone that are enzymatically derived from arachidonic acid (AA). The rate-limiting step in the eicosanoid biosynthetic pathways may be the release of AA from membrane glycerophospholipids by activated phospholipases. Free AA can serve as the substrate for cyclooxygenase(s) or lipoxygenases that catalyze the commitive steps in eicosanoid synthesis; alternatively, free AA may be used in reacylation processes, resulting in its reincorporation into cellular lipids. The hormones 17β-estradiol (17β-E2), dexamethasone (a synthetic glucocorticoid), and 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) have been identified as regulators of AA metabolism, at various levels, in several tissues including bone. The possibility that these osteotropic steroids modulate the availability of free AA in bone cells was studied in the human osteoblast-like (hOB) cell model system. Following a 48-h steroid pretreatment, bradykinin or the calcium ionophore A23187 were used as agonists to stimulate hOB cell release of AA. The principal findings from these investigations were that (1) 17β-E2 pretreatment potentiated the appearance of free AA following bradykinin stimulation of the cells but, did not alter their response to A23187 stimulation; (2) dexamethasone pretreatment limited bradykinin-induced increases in free AA levels but did not alter cell response to A23187 stimulation; (3) hOB cells derived from different trabecular bone compartments (manubrium of the sternum, femoral head) differed quantitatively in their responses to bradykinin stimulation of AA release; and (4) 1,25(OH)2D3 did not effect AA release stimulated by either agonist. The ability of the steroids to modulate AA release by hOB cells suggests that these hormones may indirectly mediate bone cell responses to other osteotropic hormones that act through eicosanoid-dependent processes. © 1996 Wiley-Liss, Inc.
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  • 3
    ISSN: 0730-2312
    Keywords: cyclooxygenase ; transforming growth factor-β1 ; tumor necrosis factor-α ; interleukin-1β ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Prostaglandin (PG) biosynthesis by cytokine stimulated normal adult human osteoblast-like (hOB) cells was evaluated by thin layer chromatography, high performance liquid chromatography, and specific immunoassays. PGE2 was the predominant PG formed under all incubation conditions tested. Control samples produced measurable amounts of PGE2, and the measured level of this metabolite increased by 22-fold (from 7 to 152 ng/ml) following a 20 h treatment with the combination of TGFβ and tumor necrosis factor-α(TNF). The production of 6-keto-PGF1α (the stable metabolite of prostacyclin) and of PGF2α were each increased by about five-fold (from about 0.5 to 2.5 ng/ml) in samples treated with the cytokines. Thus, TGFβ and TNF exerted a regulation of hOB cell PG biosynthesis that was principally directed towards an increased PGE2 biosynthesis, with lesser effects on the production of other PG metabolites. COX-2 mRNA levels were increased within 2 h of cytokine stimulation, reached a maximum at 6-12 h, and levels had appreciably diminished by 24 h after treatment. Both TGFβ and TNF could independently increase COX-2 mRNA levels and PG biosynthesis. However, the increased production of PGE2 resulting from TNF stimulation was blocked by the addition of an interleukin-1β (IL-1β) neutralizing antibody, suggesting that TNF regulation of hOB cell PG synthesis was secondary to its capacity to increase hOB cell IL-1β production. TGFβ regulation of PG production was not affected by the addition of the neutralizing antibody. These studies support the proposition that PGs can be important autocrine/paracrine mediators of bone biology, whose production by hOB cells is responsively regulated by osteotropic cytokines. J. Cell. Biochem. 64:618-631. © 1997 Wiley-Liss, Inc.
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  • 4
    ISSN: 0730-2312
    Keywords: prostaglandin ; phospholipase A2 ; age ; tumor necrosis factor-α ; transforming growth factor-β1 ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The eicosanoids, including prostaglandin E2 (PGE2) and other bioactive arachidonic acid metabolites, are important local mediators of bone remodeling. Presumably, the limited or excessive synthesis of the eicosanoids could compromise bone homeostasis. We have noted that the stimulated release of arachidonic acid by adult male donor derived human osteoblast-like (hOB) cells exceeded the stimulated release measured for female-derived hOB cells by 1.5-fold. Assays of PGE2 biosynthesis by cytokine-stimulated hOB cells also demonstrated a sex-linked difference, such that male hOB cell PGE2 production exceeded female cell production by 1.6-2.2-fold. The calcium-dependent cytoplasmic phospholipase A2 activity in subcellular fractions prepared from hOB cell homogenates was higher in both the cytosolic (1.6-fold) and particulate (1.5-fold) fractions from the male cells than in those prepared from female hOB cells, suggesting a molecular basis for the observed sexually dimorphic characteristics related to arachidonic acid metabolism by hOB cells. The relatively limited capacity of the female cells may limit needed intracellular and intercellular signaling during bone remodeling, thereby contributing to the development of bone pathology. J. Cell. Biochem. 71:74-81, 1998. © 1998 Wiley-Liss, Inc.
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  • 5
    ISSN: 0730-2312
    Keywords: 17β-estradiol ; phosphatidylinositol ; gas chromatography ; fatty acid metabolism ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The effects of treatment with the osteotropic steroids 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), 17β-estradiol, or dexamethasone on [1-14C]arachidonic acid (AA) uptake and distribution into glycerophospholipid classes by normal adult human osteoblast-like (hOB) cells were investigated. Total uptake of [1-14C]AA was decreased in cells treated with dexamethasone when assayed after a 24-, 48-, or 96-h exposure to the hormone. Specific radiolabel incorporation into phosphatidylcholine was reduced by a 48-h treatment with dexamethasone with a concurrent increase in the radiolabeling of phosphatidylethanolamine. However, these changes were transient, and by 96 h of dexamethasone treatment the distribution of the radiolabeled fatty acid had reequilibrated to resemble the pattern found for vehicle treated samples. Total uptake of [1-14C]AA was diminished by 96-h treatment with 1,25(OH)2D3 (79 ± 3% of control, P 〈 0.01); at that time point, a significant decrease in the proportional radiolabeling of the phosphatidylinositol pool was identified (92 ± 2% of control, P 〈 0.05). The 1,25(OH)2D3-dependent decrease in total uptake and in phosphatidylinositol incorporation of [1-14C]AA were found to be hormone dose dependent. Treatment with 24,25(OH)2D3 was without effect on either total [1-14C]AA uptake or the specific [1-14C]AA radiolabeling of the phosphatidylinositol pool. 1,25(OH)2D3 treatment decreased hOB cell uptake of [1-14C]oleic acid and decreased its proportional incorporation into the phosphatidylinositol pool. Gas chromatographic analyses revealed no 1,25(OH)2D3-dependent effects on total phosphatidylinositol lipid mass or on the mole percent of arachidonic acid within the phosphatidylinositol pool, leaving the mechanism of the effects of the secosteroid on hOB cell AA metabolism unexplained. 17β-Estradiol had no effects on the parameters of AA metabolism measured. As a consequence of their modulation of arachidonic acid uptake and its distribution into hOB cellular phospholipids, steroids might alter the biological effects of other hormones whose actions include the stimulated production of bioactive AA metabolites, such as prostaglandins or the various lipoxygenase products.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 162 (1995), S. 154-161 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In Xenopus laevis oocytes, the insulin mimics, vanadate and peroxovandates (PV), stimulated the uptake of 3H-2-deoxyglucose and incorporation of 35S-methionine into protein. For both hexose transport and protein synthesis, peroxovandates (produced by reacting vandate and H2O2) were at least as potent as vandate. Microinjection of peroxovandates into the oocytes stimulated 2-deoxyglucose uptake. However, methionine incorporation was not stimulated by microinjection of peroxovanadate or vanadate solutions. Consistent with these results and with the possibility that vandate and peroxovandates enter the cell on a phosphate transporter, raising the medium phosphate concentration from 1 mM to 10 mM blocked vanadate-stimulated hexose transport and partially reduced peroxovanadates stimulation of hexose transport. Increased medium phosphate did not reduce stimulation of protein synthesis by either effector. Taken together, these data indicate that vanadate/peroxovanadates act at both intracellular and extracellular sites. Action at the former stimulates hexose uptake and action at the latter, protein synthesis. © 1995 Wiley-Liss, Inc.This artilce is a US Government work and, as such, is in the public domain in the United States of America.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 164 (1995), S. 304-314 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The insulin mimic, peroxide of vanadate (pervanadate), stimulated 35S-methionine incorporation into Xenopus oocyte protein in a Mg2+-dependent manner. Reducing the extracellular Mg2+ concentration from 1.0 to 0.1 mM decreased the pervanadate-stimulated component of incorporation by 35%; with 0.01 mM Mg2+ or lower, the pervanadate-stimulated component was abolished. In addition, reducing extracellular Mg2+ to 0.01 mM inhibited about 50% of the insulinstimulated component of methionine incorporation. Mg2+ depletion had no effects on incorporation in controls or when protein synthesis was stimulated by Zn2+ or bovine growth hormone. Thus, not all substances that stimulated protein synthesis showed a dependence on extracellular Mg2+. Reducing extracellular Ca2+ had no effects on methionine incorporation in control cells or in cells stimulated by pervanadate or insulin. When oocytes maintained in a paraffin oil medium were brought into contact with a 0.5 m̈I droplet of buffer containing the Mg2+ indicator dye, mag-fura-2, and pervanadate, apparent droplet Mg2+ decreased rapidly, indicating net uptake by the cells. Insulin also caused a net uptake of Mg2+. In contrast, apparent extracellular Mg2+ was constant when cells were in contact with droplets containing no effectors. Together, these data indicate that extracellular Mg2+, but not Ca2+, is involved in the stimulation of protein synthesis by pervanadate, and to a lesser extent by insulin. Pervanadate appears to induce a net uptake of Mg2+, and this change in membrane transport may be an early event in signalling the increase in translation. © 1995 Wiley-Liss, Inc.
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  • 8
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Females of the marbled salamander, Ambystoma opacum, store sperm in exocrine glands called spermathecae in the roof of the cloaca. Eggs are fertilized by sperm released from the spermathecae during oviposition. Some sperm remain in the spermathecae following oviposition, but these sperm degenerate within a month and none persists more than 6 mo after oviposition. Thus, sperm storage between successive breeding seasons does not occur. Apical secretory vaculoes are abundant during the fall mating season and contain a substance that is alcian blue+ at pH 2.5. Production of secretory vacuoles decreases markedly after oviposition, and the glands are inactive by the summer months. Ambystoma opacum is a terrestrial breeder, and some mating occurs prior to arrival at pond basins where oviposition occurs. Mating prior to arrival at the ovipository site may prolong the breeding season, leading to fitness implications for both males and females. Females have opportunities for more matings, and the possibilities for sperm competition in the spermathecae are enhanced. © 1995 Wiley-Liss, Inc.
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  • 9
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Temperature-dependent sex determination (TSD), in which the temperature at which an egg incubates determines the sex of the individual, occurs in egg-laying reptiles of three separate orders. Previous studies have shown that the embryonic environment can have effects lasting beyond the period of sex determination. We investigated the relative roles of incubation temperature, exogenous estradiol, and gonadal sex (testis vs. ovary) in the differentiation of adult morphological and physiological traits of the leopard gecko, Eublepharis macularius. The results indicate that incubation temperature, steroid hormones, and gonads interact in the development of morphological and physiological characters with incubation temperature resulting in the greatest differences in adult phenotype. Incubation temperature did not affect reproductive success directly, but may influence offspring survival in natural situations through effects on adult female body size. Postnatal hormones seem to be more influential in the formation of adult phenotypes than prenatal hormones. These results demonstrate that TSD species can be used to investigate the effects of the physical environment on development in individuals without a predetermined genetic sex and thus provide further insight into the roles of gonadal sex and the embryonic environment in sexual differentiation. © 1995 Wiley-Liss, Inc.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 225 (1995), S. 31-50 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Radiographic and cinegraphic behavioral data, combined with anatomical evidence, indicate that the snout in Nerodia and Thamnophis consists of four movable elements (1, premaxilla; 2, paired nasals; 3, right septomaxilla and vomer; and 4, left septomaxilla and vomer), a condition we refer to as rhinokinetic. In thamnophiine snakes, movements of the snout bones allow the teeth of the right and left sides to separate further and increase the effective stroke distance of each palatomaxillary cycle during swallowing.Histological and microdissectional analyses suggest that snout movement is keyed to the placement of the cartilaginous nasal septum and associated nasal capsules relative to the surrounding bones. The nasal septum separates the paired septomaxillae and is surrounded by loose connective tissues that extend ventrally between the vomers. The nasal capsules separate the nasal bones from the underlying septomaxillae, and also surround the anterior ends of the septomaxillae, providing a cartilaginous cushion between these bones and the premaxilla. The extraordinary rotations of the snout tip seen during swallowing in thamnophiine snakes are thus due to motion at the prokinetic joint between snout and braincase, and at all rhinokinetic joints connecting the four functional elements of the snout. © 1995 Wiley-Liss, Inc.
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