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  • Life and Medical Sciences  (30,791)
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  • 1
    Electronic Resource
    Electronic Resource
    γ-Tubulin: The hub of cellular microtubule assemblies (1993)
    New York, NY : Wiley-Blackwell
    BioEssays 15 (1993), S. 637-643 
    Details
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In eukaryotic cells a specialized organelle called the microtubule organizing center (MTOC) is responsible for disposition of microtubules in a radial, polarized array in interphase cells and in the spindle in mitotic cells. Eukaryotic cells across different species, and different cell types within single species, have morphologically diverse MTOCs, but these share a common function of organizing microtubule arrays. MTOCs effect microtubule organization by initiating microtubule assembly and anchoring microtubules by their slowly growing minus ends, thus ensuring that the rapidly growing plus ends extend distally in each microtubule array. The goal is to define molecular components of the MTOC responsible for regulating microtubule assembly. One approach to defining the molecules responsible for MTOC function is to look for molecules common to all MTOCs. A newly discovered centrosomal protein, γ-tubulin, is found in MTOCs in cells from many different organisms, and has several properties which make it a candidate for both initiation of microtubule assembly and anchorage. The hypothesis that γ-tubulin plays a role in MTOCs in microtubule initiation and anchorage is currently being tested by a variety of experimental approaches.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bies.950151002
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  • 2
    Electronic Resource
    Electronic Resource
    γ-glutamyl transpeptidase (γ-GT) and maintenance of thiol pools in tumor cells resistant to alkylating agents (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 131 (1987), S. 240-246 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Previous studies from this laboratory have established that acquired resistance of murine L1210 leukemia cells to L-phenylalanine mustard (L-PAM) and other alkylating agents is accompanied by a two-to threefold elevation in their glutathione (GSH) concentration (Biochem. Pharm. 31:121). In an attempt to gain insight into the mechanism by which resistant tumor cells maintain their increased GSH content, we have assessed the possible role of γ-glutamyl transpeptidase (γ-GT), a membrane bound enzyme involved in GSH metabolism. These results indicate that the enzyme is present in both sensitive and resistant murine L1210 leukemia cells but that the cellular content of γ-GT is elevated two-to threefold in L-PAM resistant cells as compared to their sensitive counterparts. This elevation in enzymatic activity correlates well with the increased cellular GSH content in resistant cells. The results of a detailed kinetic analysis of γ-GT activity indicate that there is no difference, between cell types, in the apparent Km of the enzyme for the γ-glutamyl donor (L-γ-glutamyl-p-nitroanilide) or the acceptor (glycylglycine). However, the apparent Vmax is increased two-to threefold in L-PAM resistant tumor cells. Investigation into the role of γ-GT in the extracellular metabolism of GSH indicates that resistant tumor cells metabolize two-fold more GSH than do sensitive cells and that such metabolism results in a similar difference in the intracellular concentration of cysteine. Results of studies with cellular lysates also indicate a role for the enzyme in the supply of cysteine to the glutathione precursor pool of the tumor cell and in the maintenance of elevated GSH concentrations in cells resistant to alkylating agents.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041310214
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  • 3
    Electronic Resource
    Electronic Resource
    βVLDL uptake by pigeon monocyte-derived macrophages: Correlation of binding dynamics with three-dimensional ultrastructure (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 19 (1991), S. 139-151 
    Details
    ISSN: 0886-1544
    Keywords: lipoprotein ; receptor-mediated endocytosis ; nonspecific endocytosis ; microvilli ; membrane ruffles ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Endocytosis of pigeon beta migrating very-low-density lipoprotein (βVLDL) by monocyte-derived macrophages (monocyte/macrophages), cultured from Random Bred White Carneu (RBWC) pigeons, occurs by both coated and non-coated regions of the plasma membrane (Henson et al.: Exp. Mol. Pathol. 51:243-263, 1989). Secondary to binding, the βVLDL is translocated to lysosomes for degradation. Ultimately these events lead to foam cell formation in vitro. Utilizing video-enhanced contrast light microscopy in conjunction with whole mount intermediate-voltage transmission electron microscopy (IVEM) and high-resolution scanning EM, the dynamics of βVLDL binding have been correlated with ultrastructure. Beta VLDL conjugated to gold colloids was visualized at the surface of living cells by using Allen video-enhanced contrast-differential interference contrast microscopy (AVEC-DIC). Subsequent to AVEC-DIC, direct observation of the identical cells by IVEM and SEM was facilitated through the use of gold finder grids, and these EM observations confirmed identification of the videoobserved βVLDL particles.Upon addition of βVLDL, pigeon monocyte/macrophages underwent gross morphological changes. These changes were recorded by video as movements at the cytoplasmic periphery, and the movements involved extension of microvilli, expression of retraction fibers, and elaboration of membrane ruffles. When secondarily observed by stereo (3-D) IVEM and SEM, the identification of microvilli, retraction fibers, and membrane ruffles was confirmed and the lipoprotein-gold conjugates were associated with these ligand-induced membrane structures. Beta VLDL-gold conjugates were also associated with pit-like regions at the base of microvilli, while at the base of ruffles, βVLDL-gold conjugates were located in membrane invaginations and cytoplasmic vesicles.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970190302
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  • 4
    Electronic Resource
    Electronic Resource
    βIV is the major β-tubulin isotype in bovine cilia (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 25 (1993), S. 19-29 
    Details
    ISSN: 0886-1544
    Keywords: photoreceptor ; retina ; cilium ; trachea ; microtubules ; immunocytochemistry ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Four different isotypes of β-tubulin are known to be expressed in mammalian brain. Monoclonal antibodies against βII, βIII, and βIV were used to characterize the β-tubulin isotypes in two ciliated bovine tissues: non-motile sensory cilia of retinal rod cells and motile cilia of tracheal epithelium. Retinal rod outer segment (ROS) connecting cilia and cytoskeletons were purified by density gradient centrifugation. This preparation contained more than 20 major protein protein components, as shown by dodecyl sulfate polyacrylamide gel electrophoresis. Electroblots were used to quantitate the relative amounts of βII, βIII, and βIV. The connecting cilium and cytoskeleton of the rod outer segment has less type III β-tubulin than brain and more type IV. The ratio of βIV to βII in the ROS is nearly a factor of 8 larger than in brain. Electron microscopic immunocytochemistry showed extensive labeling of cilia by anti-type IV in thin sections of retinas and trachea, and also in purified ROS cilia and cyoskeletons. Labeling of cilia by anti-βII was also observed, although in the purified ROS cilia and cytoskeleton, the anti-βII labeling was primarily on amorphous non-ciliary material. The results suggest that both motile and non-motile cilia are enriched in the type IV β-tubulin subunit. © 1993 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970250104
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  • 5
    Electronic Resource
    Electronic Resource
    β3-Adrenergic activation of adenylyl cyclase in mouse white adipocytes: modulation by GTP and effect of obesity (1995)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 58 (1995), S. 464-473 
    Details
    ISSN: 0730-2312
    Keywords: fat cells ; adipose tissue ; β-adrenergic receptors ; guanine nucleotides ; β-adrenergic agonists ; β-adrenergic antagonists ; adrenoceptors ; ob/ob mouse ; guinea pig ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Lipolysis and adenylyl cyclase (AC) activation in response to β-adrenergic agents are abnormally low in white epididymal adipose tissue (WAT) of the ob/ob mouse. The abundance of G-proteins (Gsα and Giα) linked to AC is also abnormally low. By contrast, β-adrenergic receptor (β-AR) levels were previously found to be normal in WAT and elevated in liver. The relative importance of various forms of the β-AR in mouse WAT was reassessed in view of the discovery of the β3-AR. The results show that (1) the β3-AR is mainly responsible for AC activation in lean-mouse WAT; (2) the β3-AR is only partly responsible for AC activation in obese mouse WAT; and (3) GTP modulates β3 - -but not β1 - -or β2-AR activation of AC in a biphasic manner. Therefore, the β3-AR appears responsible for the well-known bimodal effect of GTP on β-adrenergic receptor-mediated AC activity in WAT.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240580409
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  • 6
    Electronic Resource
    Electronic Resource
    β1 integrins isolated from embryonic chicken fibroblasts bind to monomers and polymers of type I collagen (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 152 (1992), S. 558-567 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The avian integrin β1 subfamily consists of multiple α-β subunit heterodimers. We employed two different physical states of type I collagen, monomers and fibrils, in the isolation and characterization of avian collagen integrins. Affinity chromatography showed that three integrins, tentatively designated α155β1 (band 1), α5aβ1, and α3β1 (band 2), bind fibrillar and monomeric collagen under physiological ionic conditions and require divalent cations for binding activity. Sodium chloride gradients (0-0.5 M) were used to assess the functional ability of the integrins to remain bound to the two forms of type I collagen. The results show that integrins elute from the two forms of collagen with distinct fractionation profiles. One integrin, α155β1, binds fibrillar collagen with relatively higher affinity than the other β1 receptors. This same avian integrin, α155β1, is immunoreactive with an antiserum (Hynes et al., 1989) raised against a peptide that corresponds to the entire α5 cytoplasmic domain, and coincidently, part of the α6 cytoplasmic domain (de Curtis et al., 1991). Cell biological studies employing double immunofluorescence show that integrins recognized by this antiserum co-localize with extracellular deposits of type I collagen. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041520316
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  • 7
    Electronic Resource
    Electronic Resource
    β1 integrin cytoplasmic domain regulates the constitutive conformation detected by MAb 15/7, but not the ligand-induced conformation (1998)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 71 (1998), S. 63-73 
    Details
    ISSN: 0730-2312
    Keywords: integrin ; activation epitopes ; ligand binding ; focal adhesions ; cytoplasmic domains ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The anti-integrin β1 MAb 15/7 sometimes may be a reporter of integrin activation or ligand occupancy. However, certain β1 tail deletions eliminate ligand binding despite inducing maximal constitutive 15/7 expression [Puzon-Mclaughlin et al. (1996): J Biol Chem 271:16580-16585]. Here we describe β1 tail mutations (e.g., double point mutations [D759L/F763L, F766L/E769L], or replacement of the β1 tail by the β5 tail) that prevent rather than induce constitutive appearance of the 15/7 epitope. Despite variable losses of constitutive 15/7 epitope, these mutants all retained a similar inducible 15/7 epitope component as seen upon incubation with GRGDSP peptide ligand. In addition, constitutive 15/7 expression did not correlate with integrin localization into focal adhesions. In conclusion, we show for the first time for a fully functional integrin that specific mutations within the β1 tail can down-regulate the constitutive appearance of an extracellular conformation defined by MAb 15/7. Because this regulation occurs away from the ligand binding site and does not correlate with responsiveness to integrin ligand, cell adhesion, or localization into focal adhesions, a novel type of conformational regulation is suggested. J. Cell. Biochem. 71:63-73, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    β-Tubulin mutation suppresses microtubule dynamics in vitro and slows mitosis in vivo (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 30 (1995), S. 285-300 
    Details
    ISSN: 0886-1544
    Keywords: microtubule dynamics ; β-tubulin ; mitosis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Microtubule (MT) dynamics vary both spatially and temporally within cells and are thought to be important for proper MT cellular function. Because MT dynamics appear to be closely tied to the guanosine triphosphatase (GTPase) activity of β-tubulin subunits, we examined the importance of MT dynamics in the budding yeast S. cerevisiae by introducing a T107K point mutation into a region of the single β-tubulin gene, TUB2, known to affect the assembly-dependent GTPase activity of MTs in vitro. Analysis of MT dynamic behavior by video-enhanced differential interference contrast microscopy, revealed that T107K subunits slowed both the growth rates and catastrophic disassembly rates of individual MTs in vitro. In haploid cells tub2-T107K is lethal; but in tub2-T107K/tub2-590 heterozygotes the mutation is viable, dominant, and slows cell-cycle progression through mitosis, without causing wholesale disruption of cellular MTs. The correlation between the slower growing and shortening rates of MTs in vitro, and the slower mitosis in vivo suggests that MT dynamics are important in budding yeast and may regulate the rate of nuclear movement and segregation. The slower mitosis in mutant celis did not result in premature cytokinesis and cell death, further suggesting that cell-cycle control mechanisms “sense” the mitotic slowdown, possibly by monitoring MT dynamics directly. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970300406
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  • 9
    Electronic Resource
    Electronic Resource
    β-Glucuronidase activity is present in the microscopic epididymis of the Tfm/Y mouse (1987)
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 8 (1987), S. 11-15 
    Details
    ISSN: 0192-253X
    Keywords: testicular feminization ; androgen induction ; meiosis inducing substance ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The sex-linked recessive gene Tfm in the mouse produces a condition of testicular feminization (androgen insensitivity syndrome, AIS) in hemizygotes, comparable to the condition of the same name in humans. The murine mutant was originally believed to have no derivatives of the mesonephric duct system (MDS), and this absence was ascribed to dependence of these derivatives on androgens for survival. However, microscopical epi-didymides, retia testes, and vasa deferentia were identified in these animals in our laboratory. These micro-organs may play a role in meiosis induction in Tfm/Y animals. The present study was designed to determine whether survival of these organs is due to retention of an ability to respond to androgens, or whether they are unique amongst MDS derivatives in being independent of androgens.Previous studies in our laboratory demonstrated that the enzyme β-glucuronidase (βG) is androgen sensitive in the epididymis of the normal mouse. In the present investigation we used this enzyme as a marker to study androgen sensitivity in the microscopical epididymides of Tfm/Y hemizygotes and in the epididymides of control +/Y litter-mate brothers. Both mutant and control animals were studied with and without exogenous androgen stimulation.Tfm/Y hemizygotes demonstrated low levels of diffuse, cytoplasmic βG activity that appears to be unresponsive to exogenous androgen stimulation. In light of our previous studies, this distribution of βG reaction products suggests some degree of androgen sensitivity. The survival of these micro-organs and their partial androgen sensitivity may be related to the role of the MDS in inducing meiosis.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/dvg.1020080103
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  • 10
    Electronic Resource
    Electronic Resource
    β-Galactosidase - An indicator of the maturational stage of mouse and human mononuclear phagocytes (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 112 (1982), S. 385-390 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Resident, elicited, and activated mouse peritoneal macrophages exhibit a differential expression of the activity of the enzyme b̃-galactosidase; freshly harvested resident macrophages express a remarkably high activity whereas the latter two populations are almost void of enzymic activity. During in vitro cultivation there is an enhancement in the level of the enzyme in the three populations, and a significant proportion of both thioglycollate-elicited and Corynebacterium parvum-activated macrophages acquire b̃-galactosidase activity. Cells within in vitro differentiated bone marrow-derived mononuclear phagocyte colonies are heterogeneous with respect to expression of b̃-galactosidase activity. The percentage of cells expressing medium to intense enzymic activity is augmented with time in culture. Essentially the same pattern is observed in colonies differentiated from bone marrow of mice bearing acute or chronic inflammation. Freshly isolated human peripheral blood monocytes are essentially void of detectable b̃-galactosidase activity. Eighty to ninety percent of the monocytes acquire medium to intense activity during a 7-day cultivation period. The data support the suggestion that b̃-galactosidase expression in mononuclear phagocytes is a correlate of their maturational stage both in vivo and in vitro and does not reflect the state of elicitation or activation of these cells.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041120312
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