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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 183 (1985), S. 165-176 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cytodifferentiation and hard tissue formation were studied in Anolis to collect information regarding the phylogenetic history of enamel and the functional significance of the events seen in the mammalian tooth during differentiation. The differentiation of the ameloblasts of Anolis, like that of mammals, shows two phases: In the early phase, the cells are short and rich in free ribosomes, in the late phase the cells elongate, develop an extensive rough endoplasmic reticulum, and the Golgi apparatus moves into that part of the cell next to the basal lamina (the cell apex). The early epithelial-mesenchymal interface resembles that of mammals, suggesting that early mechanisms of induction and epithelial-mesenchymal interaction are similar in Anolis and in mammals.Preameloblast processes and preameloblast-preodontoblast contacts in Anolis are rudimentary compared to those of mammals. While in mammals the preameloblast processes shape the future DEJ (dentin-enamel junction), their involvement in establishing the shape of the DEJ of Anolis is questionable. We suggest that the great development of preameloblast-preodontoblast contacts in mammals may simply increase the efficiency of inductive interactions between these cell types.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 77 (1945), S. 351-377 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 4 Tab.
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  • 3
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The rejection of skin homografts in the snake, Thamnophis sirtalis is preceded by an infiltration of mononuclear cells into the graft bed. The initial arrangement of infiltrating cells in perivascular halos suggests that these cells emigrate from the blood stream of the host. A cytological study showed that the vast majority of the cells can be classified as small and mediumsized lymphocytes, monocytes and macrophages. Early stages of infiltration were associated with large proportions of lymphocytes while later stages were characterized by a predominance of macrophages. It was concluded that the mononuclear cells associated with graft rejection include large proportions of lymphocytes and macrophages and not just one kind of lymphoid cell.
    Additional Material: 4 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 198 (1988), S. 205-217 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Natural maturation of the oocytes of Oxycomanthus japonicus can be predicte in advance, and the multiple ovaries permit unintrusive serial biopsies. Ovaries were fixed for transmission electron micrscopy at 15-min intervals before, during, and after oocyte maturation. The start of maturation of each oocyte is signaled by the breakdown of the germinal vesicle and the disruption of a macula adhaerens associating the oocyte with nongerminal cells of the ovary. This disruption is followed by an ovulation of the oocyte into the ovarian lumen. Ovulation takes about 1 hr, and a continuous vitelline coat is produced around the oocyte during this interval. Within the oocyte cytoplasm, patches of nuage and the annulate lamellae disappear at 30 and 45 min after the start of oocyte maturation, respectively. Micropapillae become transiently abundant at the oocyte surface both at the time of germinal vesicle breakdown and around the time when the first and second polar bodies are produced. Oocyte maturation takes about 2 hr from start to finish, and the emission of the second polar body marks the beginning of the stage of the ovum. Within the cytoplasm of the ovum, the haploid chromosomes develop into chromosome-containing vesicles, which later fuse into a single female pronucleus. Pronuclear ova are retained in the ovarian lumen for about 1 hr and are then spawned into the surrounding seawater, where fertilization takes place.
    Additional Material: 24 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 23 (1992), S. 222-230 
    ISSN: 0886-1544
    Keywords: native electrophoresis ; tubulin isotypes ; dimerization ; complexes ; GTP binding ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The functional subunit of microtubules is a heterodimer consisting of α- and β-tubulin. An understanding of tubulin dimerization has been hampered because it has not proved possible to purify native tubulin monomers. To study the process whereby tubulin dimers are formed, we made use of tubulins synthesized by in vitro transcription and translation. We present evidence that the in vitro synthesis of different mouse α-tubulin isotypes involves a multimolecular complex. The synthesis of mouse β-tubulin isotypes also involves the formation of multimolecular complexes, though different isotypes behave somewhat differently from one another. The properties of in vitro synthesized α- and β-tubulin multimolecular complexes strongly suggest that they are intermediates in the biosynthesis of tubulin monomers. Upon release, these monomers can exchange with pre-existing tubulin heterodimers. © 1992 Wiley-Liss, Inc.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 141 (1989), S. 40-45 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: 2-Mercaptoethanol (2-ME) exerts several effects on murine lymphocytes in culture that might explain its ability to enhance survival and growth of these cells. The uptake of the essential amino acid cystine and consequently the maintenance of intracellular glutathione levels are enhanced by 2-ME. Furthermore, 2-ME (even in the disulfide form) causes lymphocytes to release thiols into the culture medium. These effects might protect the cells from oxidative damage. The additional cystine provided by treatment of lymphocyte cultures with 2-ME might also allow adequate protein synthesis to support survival and/or growth. This study was conducted to assess the relative importance of the antioxidant and protein synthesis effects of 2-ME. As expected, 2-ME increased cystine uptake at all concentrations that enhanced growth and survival, but four nonthiol antioxidants that enhanced growth and/or survival either did not substantially affect cystine uptake or decreased it and did not affect the release of cystine or its products. The results presented here demonstrate that antioxidant protection is necessary and sufficient for lymphocyte survival and that cystine uptake in untreated lymphocytes is sufficient to support the protein synthesis needed for survival and limited growth. However, we also noted that concentrations of 2-ME that stimulated maximal growth more than doubled protein synthesis as measured at 8 hr. Thus the portion of the effects of 2-ME not accounted for by antioxidant action could be accounted for by enhanced protein synthesis.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 139 (1989), S. 624-631 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Polyamine transport is an important mechanism by which cells regulate their intracellular polyamine content. It is well established that the lung has a high capacity for polyamine transport, and recently the polyamine putrescine has been shown to be selectively accumulated into the type II pneumocyte of rabbit lung slices (Saunders et al.:Lab. Invest., 95:380-386, 1988). In addition, it has been suggested that there may be more than one polyamine transport system in lung tissue (Byers et al.:Am. J. Physiol., 252:C663-C669, 1987). In the present study, we have examined whether there are differences in the distribution of putrescine and spermidine uptake activities in isolated rabbit lung cells. We report that pulmonary alveolar macrophages have a greater rate of uptake of both putrescine and spermidine than the total lung cell population. Kinetic analysis of the polyamine uptake system present in macrophages showed putrescine uptake consisted of a saturable (Km = 2.1 μM) and nonsaturable component whilst spermidine uptake consisted of both a high- and a low-capacity saturable component (Km = 0.16 μM and 1.97 μM, respectively). The rate of polyamine transport was similar to those reported for many proliferative or tumor cell-lines and appeans to be greater than any other major lung cell type. Inhibition studies of the transport of polyamines into pulmonary alveolar macrophages suggested that the uptake of both putrescine and spermidine was mediated by the same system, which could not be described by simple Michaelis-Menten kinetics. The transport appears to be reversible due to significant efflux. This is the first study to describe the presence of multiple polyamine transport systems in pulmonary alveolar macrophages.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 46 (1991), S. 21-26 
    ISSN: 0730-2312
    Keywords: hemopoiesis ; ES cells ; myoblasts ; osteoblasts ; hepatocytes ; neurones ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The notion that a single hormone may exert a broad range of effects has become well established. As such, leukemia inhibitory factor (LIF) is a prime example. LIF was initially described, purified, and genetically cloned on the basis of its ability to induce the differentiation and suppress the clonogenicity of the monocytic leukemia cell line, M1. Subsequently, it has become apparent that in vitro LIF inhibits the differentiation of pluripotential ES cells, stimulates the synthesis of hepatic acute-phase proteins, induces a switch in neurotransmitter phenotype from adrenergic to cholinergic, suppresses adipocyte lipoprotein lipase activity, and results in an increase in bone resorption. Moreover, elevation of LIF levels in vivo has a number of patho-physiological consequences, many of which parallel those effects observed in vitro. The challenge that lies ahead is to determine whether other sites of LIF action exist and to define more clearly the physiological role LIF plays in vivo.A major mechanism of cell-cell communication is by the production and secretion of polypeptide hormones by one cell type, which act either systemically or locally, via interaction with specific receptors on the surface of responsive cells. Recently, it has become apparent that hormones initially described and named, on the basis of a specific action, in many cases exert a spectrum of effects on a broad range of cell types. Moreover, the effects exerted are often mimicked closely by other hormones. Hormones that act in a pleiotropic manner are, for example, transforming growth factor-β (TGF-β), the various fibroblast growth factors (FGFs), interleukin-6 (IL-6), and leukemia inhibitory factor (LIF). This review will focus on the various biological effects ascribed to LIF.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 46 (1991), S. 69-77 
    ISSN: 0730-2312
    Keywords: cytokines ; cell proliferation ; polyamines ; cytotoxicity ; growth factors ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The activity of the polyamine biosynthetic enzyme, ornithine decarboxylase (ODC), has been shown to be rapidly modulated by a variety of growth regulatory molecules. In this report the effect of the growth modulatory peptide, tumor necrosis factor, on ODC activity was examined on two cell lines which express equivalent TNF binding properties, but differ in their growth response when exposed to this factor. TNF treatment of WI-38 fibroblasts stimulated both their growth and induced ODC activity 5-10-fold when measured 6-24 h after TNF incubation. TNF induced cytotoxicity in ME-180 cervical carcinoma cells and, interestingly, stimulated both ODC activity (3-6-fold) and putrescine accumulation when measured prior to the onset of cytotoxicity. Induction of ODC was TNF concentration-dependent and paralleled the concentration-dependency for cytotoxicity. Based upon studies with cycloheximide, de novo protein biosynthesis was required for TNF-mediated ODC induction in ME-180 cells.The effects of other growth inhibitory peptides and growth factors were analyzed for their combined effect on ODC activity in TNF-treated or untreated ME-180 cells. Interferon gamma treatment had no significant effect on basal ODC activity but inhibited TNF-mediated ODC induction by ∼50%. EGF treatment resulted in a potent stimulation of ODC activity which was not effected by TNF pre-treatment or coadministration on ME-180 cells. These results suggest that TNF has properties which are similar to those of a growth factor and distinct from those of other growth inhibitory peptides. The early growth factor-like actions of TNF occur on both normal fibroblasts and some tumor cells and evidence suggests that these effects are antagonistic to the antiproliferative effects of TNF.
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  • 10
    ISSN: 0730-2312
    Keywords: epidermal growth factor receptor ; tyrosine kinase activity ; phosphorylation ; c-myc ; control of cell growth ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The process of TNF-induced cytotoxicity is complex but appears to be mediated through a TNF-specific cell surface receptor. Recent evidence suggests that TNF action on tumor cells may be antagonized by epidermal growth factor (EGF) and other EGF-receptor modulatory peptides implicating a role for EGF-R in the process of TNF-induced cytotoxicity. In the present report, we investigated the biochemical actions of TNF of several biochemical events known to occur in the process of EGF signal transduction in intact cells. The actions of TNF were compared directly to those of EGF in both TNF-sensitive and -resistant tumor cell lines.In TNF-sensitive ME-180 cervical carcinoma cells, TNF (20 ng/ml) stimulated the tyrosine protein kinase activity of the EGF-receptor (EGF-R) fivefold when measured by receptor autophosphorylation in an immune complex kinase assay. TNF activation of EGF-R kinase activity in ME-180 was measurable 10 min after TNF incubation and enzymatic activity remained elevated 20 min after TNF addition. Activition of the receptor by TNF correlated with increased 32P incorporation into EGF-R protien when receptor was immunoprecipitated from 32P-equilibrated cells following a 20 min incubation with TNF. Acid hydrolysis of EGF-R protein isolated from TNF-treated ME-180 cells demonstrates an increase in the phosphotyrosine content of EGF-R when compared to receptor isolated from untreated cells. The results suggest that TNF increased EGF-R tyrosine protein kinase activity and the state of EGF-receptor tryosine phosphorylation in a manner similar to that reported for EGF. However, TNF does not appear to be structurally related to EGF since TNF was unable to directly activate EGF-R when incubated with extensively washed immunoprecipitates of EGF-R.In TNF-resistant T24 bladder carcinoma cells, TNF failed to alter EGF-R tyrosine protein kinase activity although both EGF and phorbol ester were shown to modulate the enzymatic activity of the receptor in these cells. These results indicate that the ability of TNF to modulate EGF-R kinase in target cells may correlate with its cytotoxic actions on TNF-sensitive tumor cells.Other biochemical activities associated with the induction or regluation of cellular growth were examined in TNF- or EGF-treated tumor cells. EGF stimulated a rapid 8-16-fold increase in the expression of the proto-oncogene c-myc when analyzed by dot-blot analysis of total cellular RNA or Northern blot hybridization of polyadenylated RNA. TNF treatment failed to alter c-myc expression in ME-180 cells when analyzed by either technique. The two structurally distinct peptides, TNF and EGF, induced similar patterns of ornithine decarboxylase activity (the rate-limiting enzyme in polyamine biosynthesis) in ME-180 cells but differed in their relative magnitude of maximal induction. Similar results were obtained in TNF- or EFG-treated T24 cells, suggesting the effects of TNF on polyamine biosynthesis are not related to its cytotoxic mechanism of action. These results indicate that TNF shares some of the early biochemical actions of EGF in tumor cells and some of these effects may be related to the mechanism of TNF-induced cytotoxicity.
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