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  • Cell & Developmental Biology  (23)
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  • 1
    ISSN: 0886-1544
    Keywords: calcium ; protein phosphorylation ; TFP ; Triton-extracted model ; ciliary orientation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: To explore possible roles of calmodulin in Ca2+-induced ciliary reversal, we tested the effects of calmodulin antagonists on Triton-extracted models of Paramecium. In the extracted models prepared by the method of Naitoh and Kaneko [Science 176:523-524, 1972], the Ca2+ -induced ciliary reversal was not inhibited by calmodulin antagonists, trifluoperazine (TFP), or 5-chloro-l-naphthalenesulphone amide (W-7). However, in the presence of adenosine 3′,5′-cyclic mono-phosphate (cAMP), whose concentration is below the one that alters the ciliary direction, TFP inhibited ciliary reversal and the models swam forward at 10-5 M Ca2+. When the washing medium in the preparation of the extracted models was replaced with one containing MgCl2, the extracted model showed sensitivity to calmodulin antagonists without addition of cAMP; at 10-5 M Ca2+, 40 μM TFP or 100 μM W-7 inhibited the ciliary reversal and the models swam forward. Such effect of antagonists was abolished by an inhibitor of cAMP-dependent protein kinase. On the other hand, addition of cAMP enhanced the inhibitory effect of antagonists. These results suggest that calmodulin antagonists act to increase the extent of cAMP-dependent protein phosphorylation that inhibits the Ca2+ -induced ciliary reversal.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 154 (1993), S. 222-228 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The intracellular pathway following receptor-mediated endocytosis of cholera toxin was studied using brefeldin A (BFA), which inhibited protein secretion and induced dramatic morphological changes in the Golgi region. In both mouse Y1 adrenal cells and CHO cells, BFA at 1 μg/ml caused a 80-90% inhibition of the cholera toxin (CT)-elevation of intracellular cAMP. The inhibition of the cytotoxicity of CT by BFA was also observed in a rounding assay of Y1 adrenal cells. The inhibition of CT cytotoxicity by BFA was dose dependent, with the ID50 value similar to the LD50 of BFA in Y1 adrenal cells. Binding and internalization of [125I]-cholera toxin in Y1 adrenal cells was not affected by BFA. Unlike the BFA-sensitive cell lines such as Y1 adrenal and CHO cells, BFA at 1 μg/ml did not inhibit the cytotoxicity of CT in PtK1 cells, of which the Golgi structure was BFA-resistant. These results strongly suggest that a BFA-sensitive Golgi is required for the protection of CT cytotoxicity by BFA. In contrast, elevation of the intracellular cAMP by forskolin, which acts directly on the plasma membrane adenylate cyclase, was not affected by BFA. These observations indicate that the intoxication of target cells by CT requires an intact Golgi region for its intracellular trafficking and/or processing. In this respect, CT shares a common intracellular pathway with ricin, Pseudomonas toxin, and modeccin, even though their structures and modes of action are very different. © 1993 Wiley-Liss, Inc.
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  • 3
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The transformation of certain cells reduces the requirement of extracellular Ca2+ for growth. The SV-40 transformed human lung fibroblasts, WI-38 VA13, require less Ca2+ than normal WI-38 cells. Spreading area of normal cells decreases when cultured in 10 μM Ca2+ medium. Intracellular calcium concentration ([Ca2+]i), of the normal and transformed cells cultured in 10μM and 2 mM Ca2+ media was measured by the fluorescence microscope technique using fura-2 as a probe. The [Ca2+], is measured in the resting state and during mobilization by serum or bradykinin stimulation. The lowering of extracellular calcium concentration results in a decrease in the resting state [Ca2+],i of both normal and transformed cells. Although the total decrease in [Ca2+]i is the same for both cell, the rate of decrease is much faster in normal cells than in transformed cells. Low extracellular Ca2+ reduces the number of cells responsive to the serum or bradykinin stimulation and decreases the peak [Ca2+]i value in both cells. In addition, we investigated, using BCECF as a fluorecent probe, the intracellular pH (pHi) of normal and transformed cells maintained at low and normal Ca2+. The low Ca2+ condition makes pHi acidic in normal cells but not in transformed cells. The acidification of the normal cell is accompanied by a decrease in the spreading area of the cells. The decrease of the cell attacment, followed by the reduced spreading area, induced the acidic pHi. These results suggest that the reduced Ca2+ requirement of transformed cells for growth is related to the mechanism of pHi regulation rather than Ca2+ homeostasis and, possibly, to the anchorage-independent growth, which is a unique feature of transformed cells. © 1993 Wiley-Liss, Inc.
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  • 4
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We examined expression of the c-myc oncogene in isolated perfused livers to elucidate the mechanisms involved in triggering the proliferation of hepatocytes after partial hepatectomy (PH). During perfusion with a 1:1 mixture of Dulbecco's modified Eagle's medium and the oxygen transport fluid FC-43, rat livers were two-thirds resected (PH), and further perfused for 1 1/2 hours at the physiological portal flow throughout the perfusion. Expression of c-myc in the perfused livers with PH(+) was ten times higher than in those with PH(-). Furthermore, expression of c-myc in the PH(-) livers perfused with a threefold volume of the physiological portal flow was 5-10 times higher than that in the livers perfused with the physiological portal flow. The perfusates that passed through the livers did not induce DNA synthesis of primary cultured hepatocytes. These results suggest that an increase in the portal flow volume may act as a trigger for hepatocyte proliferation after PH. © 1993 Wiley-Liss, Inc.
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  • 5
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The present study was performed to clarify second messenger signaling in parathyroid hormone (PTH)-induced c-fos gene expression, to characterize the participation of the c-fos gene in the regulation of osteoblast proliferation and function as well as osteoclast-like cell formation by PTH and to compare these effects of PTH with those of PTH-related peptide (PTHrP). Both human (h) PTH-(1-34) and hPTHrP-(1-34) at 10-8 M induced a transient c-fos gene expression to a similar degree in osteoblastic osteosarcoma cells, UMR-106. N6, O2' -dibutyryl adenosine 3′, 5′-cyclic monophosphate (dbcAMP) as well as Sp-diastereoisomer of adenosine cyclic 3′,5′-phosphorothioate (Sp-cAMPS), an activator of cAMP-dependent protein kinase (PKA), induced a weak c-fos gene expression. Although Rp-diastereoisomer of adenosine cyclic 3′,5′-phosphorothioate (Rp-cAMPS), an inhibitor of PKA, almost completely antagonized dbcAMP-and Sp-cAMPS-induced expression of c-fos gene, it did not cause an obvious inhibition of PTH-or PTHrP-induced expression. Phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C (PKC), induced an intense expression of the c-fos gene, while 4α-phorbol 12, 13-didecanoate (4αPDD), incapable of activating PKC, and calcium ionophores (A23187 and ionomycin) did not. Protein kinase C inhibitor (H-7, 50 μM) completely blocked the expression of the c-fos gene by PTH as well as by PTHrP. Antisense oligodeoxynucleotides (as-ODN) complementary to c-fos mRNA, which have been shown to inhibit its mRNA translation, at 1 μM significantly antagonized PTH-and PTHrP-induced inhibition of [3H] thymidine incorporation and stimulation of osteoclast-like cell formation in the presence of osteoblasts, but not an increase in alkaline phosphatase activity, compared to control oligodeoxynucleotides with same nucleotides as as-ODN but with a random sequence. The present study indicates the involvement of PKC system in c-fos gene expression by PTH as well as PTHrP and also indicates the involvement of the c-fos gene in the regulation of bone cell physiology by PTH and PTHrP. © 1994 Wiley-Liss, Inc.
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  • 6
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Interaction between c-fos and 1,25(OH)2 vitamin D3 (VD) on the type I collagen synthesis was studied. VD inhibited collagen synthesis and type I collagen mRNA expression in MC3T3-E1 osteoblastic cells. In contrast, VD reversed the inhibition of collagen synthesis and mRNA expression of the c-fos transfectants that overexpressed c-fos gene to a comparable level as those of the control transfectants. The gel shift assay showed that vitamin D receptor (VDR) complex binding to vitamin D responsive element (VDRE) was inhibited under constitutively expressed c-fos gene, suggesting that c-fos gene product, c-Fos, may inhibit the binding of VDR complex to VDRE by making a c-Fos-VDR complex. The result suggests the existence of a fine tuning between c-fos and VD in the bone metabolism which may be relevant to the pathogenesis of rheumatoid bone lesion. © 1995 Wiley-Liss, Inc.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    BioEssays 10 (1989), S. 62-69 
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Substance P and related tachykinin peptides probably act as neurotransmitters or modulators of neurotransmission, and regulate biological processes as diverse as salivary secretion and transmission of pain signals. Substance P peptide sequences are expressed in three distinct mRNAs that are generated from one gene by differential RNA splicing. In addition to substance P, as many as three other tachykinin peptides can be generated from the polyprotein precursors by differential posttranslational processing. Three tachykinin receptor subtypes have been extensively characterized which differentially interact with the naturally occurring tachykinin peptides. Therefore, the generation of diversity of tachykinin peptides results from differential precursor RNA splicing and differential posttranslational processing. The specificity of peptide responses is the result of selective receptor subtype expression.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    BioEssays 11 (1989), S. 163-167 
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Early morphogenesis of mouse submandibular gland provides an excellent model for the formation of epithelial lobules as a consequence of epithelial-mesenchymal interactions. Both proteoglycans and a glycosaminoglycan, high molecular weight components which contain amino-sugars and hexuronic acids, seem to be important in maintaining the lobular structure through the formation of epithelial basal lamina. Collagen also appears to play a crucial role in this morphogenesis. By visualizing the distribution of collagen fibrils and by changing the concentration of collagen in the gland, we have developed a new hypothesis which emphasizes the mechanical role of mesenchyme in epithelial cleft formation. Precise mechanisms for the involvement of these molecules have not been elucidated, yet it is now clear that knowledge of the function of the extracellular matrix components is a prerequisite for understanding the epithelial-mesenchymal interactions.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 34 (1993), S. 58-64 
    ISSN: 1040-452X
    Keywords: In vitro maturation ; Block of meiosis ; Domestic animals ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Membrana granulosa was isolated from healthy large antral follicles of prepubertal or cyclic gilts stimulated with PMSG or PMSG and hCG. Ultrastructural observations revealed that pieces of pig membrana granulosa were associated with the basement membrane. The cattle cumulus-enclosed oocytes (COC) were placed in the rolled pieces of the pig membrana granulosa (PMG). After 8 and 24 hr of coculture with PMG from prepubertal gilts, only 16% and 21% of oocytes underwent GVBD, respectively. PMG from PMSG-stimulated cyclic gilts blocked the resumption of meiosis in all COC. The inhibitory effect of heterologous granulosa cells was fully reversible. When COC were initially incubated for 2 and 4 hr, subsequent culture in PMG prevented GVBD in 100% and 36% of oocytes, respectively. This suggests that functional contact between COC and PMG was established during the first 2 hr of coculture. To follow metabolic cooperation between PMG and COC, PMG was prelabeled with 3H-uridine and cocultured with COC. Autoradiography on semithin sections revealed the intensive passage of 3H-uridine from PMG into the cumulus layer and an oocyte. COC placed in PMG after GVBD (8 and 12 hr of an initial incubation) did not extrude the first polar body. PMG isolated from cyclic gilts after PMSG and hCG stimulation also inhibited GVBD of COC. Since nearly all COC placed in PMG isolated 10 and 12 hr after hCG remained in the GV stage after 24 hr of coculture, the hCG stimulation did not substantially diminish the meiosis inhibiting activity of PMG. During coculture, cattle cumulus cells were closely associated with the basement membrane, but no gap junctions were formed among heterologous granulosa cells. These results suggest that an inhibitory factor secreted by pig granulosa cells is not species specific and it can act in vitro without the mediation of gap junctions. © 1993 Wiley-Liss, Inc.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 25 (1993), S. 189-200 
    ISSN: 1059-910X
    Keywords: Trophoblast ; Immunodeficient mice ; Extracellular matrix ; Cytokines ; Lymphokine-activated killer cells ; Abortion ; Murine pregnancy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The metrial gland develops in the uterus of many rodent species during normal pregnancy. It is a maternally-derived tissue that contains stromal and vascular elements plus a population of large cells, striking in their light microscopic appearance due to the presence of numerous cytoplasmic granules. These cells, which have become known in mice and rats as granulated metrial gland (GMG) cells, are derived from bone marrow precursors and recent work suggests they are a subset of lymphocytes belonging to the natural killer (NK) cell lineage. The functions of GMG cells during normal gestation have not been clearly defined. In vitro, GMG cells have been shown to produce cytokines and their cytokine profile is altered upon addition of medium containing the T cell growth factor interleukin-2 (IL-2). GMG cell granules contain the cytolytic protein perforin but GMG cells have a very limited capacity to kill in vitro unless they have been stimulated by IL-2 or interferon-gamma. Histological study of GMG cells has suggested they preferentially associate with fetal trophoblast. Since trophoblast appears resistant to immune lysis, except by IL-2-activated effector lymphocytes, and because resorbing murine embryos become infiltrated by lytic cells of the NK cell lineage, it is important to establish whether GMG cells are activated by pregnancy-associated events to play a major lytic role in vivo. © 1993 Wiley-Liss, Inc.
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