Library

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 1980-1984  (103)
  • 1980  (103)
  • Molecular Cell Biology  (102)
  • Nuclear reactions
  • 1
    ISSN: 1432-2048
    Keywords: Boron ; Foliar nutrition ; Nuclear reactions ; Transport (boron) ; Trifolium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The growth of white clover (Trifolium repens L.) is severely inhibited by boron starvation, but a foliar treatment with boric acid can transitorily alleviate the deficiency symptoms. The 10B(n ,α)7 Li nuclear reaction has been used to study boron transport in the plant after foliar application. More than 98% of the boron supplied remained at the point where it was applied to the leaves, and less than 2% was useful to the growth of the treated plant. This small “efficient” portion of boron was quite mobile. It was distributed to the different parts of the plant, then was transferred from the oldest parts to the newly formed leaves. Physiological and agronomical implications of these data are discussed.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 353-369 
    ISSN: 0091-7419
    Keywords: adrenocortical ; ACTH ; FGF ; cAMP ; fetal zone ; replication ; regulation ; steroidogenesis ; antioxidant ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Monolayer cultures of bovine and human adrenocortical cells have been used to study regulation of growth and function. Homogeneous bovine adrenocortical cells exhibit a finite life span of ∼60 generations in culture. Full maintenance of differentiated function (steroid hormone synthesis) requires an inducer such as ACTH and antioxidizing conditions. Full induction of differentiated function occurs only when cellular hypertrophy is stimulated by growth factors such as fibroblast growth factor and serum. ACTH and other agents that increase cellular cAMP inhibit replication but do not block growth factor-induced cellular hypertrophy. ACTH and growth factors together result in a hypertrophied, hyperfunctional cell. Replication ensues only when desensitization to the growth inhibitory effects of ACTH occurs.Cultures of the definitive and fetal zones of the human fetal adrenal cortex synthesize the steroids characteristic of the two zones in vivo. ACTH stimulates production of dehydroepiandrosterone (DHA), the major steroid product of the fetal zone, and of cortisol, the characteristic steroid product of the definitive zone. Prolonged ACTH treatment of fetal zone cultures results in a preferential increase in cortisol production so that the pattern of steroid synthesis becomes that of the definitive zone. The preferential increase in cortisol production by fetal zone cultures results from induction of 3β-hydroxysteroid dehydrogenase, Δ4,5 isomerase activity, which is limiting in fetal zone cells. ACTH thus causes a phenotypic change in fetal zone cells to that of definitive zone cells.In both bovine and human adrenocortical cells, the principal effect of ACTH is to induce full expression of differentiated function. This occurs only under conditions where growth substances and nutrients permit full amplication.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980) 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 405-422 
    ISSN: 0091-7419
    Keywords: glutamine synthetase ; electron microscopy ; computer averaging ; pattern recognition ; radiation damage ; low dose ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Averaged projections of individual glutamine synthetase molecules have been obtained by using electron microscopy and image processing. The methodology of correlation averaging under low dose conditions is described in detail. Because of their low signal-to-noise ratio, images made under low dose conditions cannot be directly interpreted in terms of high resolution features. Computer averaging of these images reveals a division of the subunit projection into two domains whose sizes agree with results of Lei et al [2] limited proteolysis experiments.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 441-459 
    ISSN: 0091-7419
    Keywords: EGF receptors ; biotinyl EGF ; covalent EGF-receptor complexes - and 3T3 cell growth regulation ; on human placental membranes ; on cultured cells ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A small portion of the 125I-EGF that binds specifically to intact cells or isolated membranes from a variety of sources becomes directly and irreversibly linked to EGF receptors. This provides a simple technique for affinity labeling the EGF receptor. Membranes isolated from the human epidermoid carcinoma cell line A431, which posesses extraordinarily high numbers of EGF receptors, gave rise to three major direct linkage complexes of MW = 160,000, 145,000, and 115,000. The time course for formation of each is similar, showing that 125I-EGF can form direct linkage complexes with several preexisting forms of the EGF receptor. The direct linkage of EGF to receptor is slow in comparison to 125I-EGF binding, but both processes have similar susceptibilities to competition by unlabeled EGF.EGF was modified chemically with the amino site-specific reagent, N-hydroxysuccinimidyl biotin. The biotinyl-EGF had a reduced capacity to engage in direct linkage complex formation with no concomitant reduction in its ability to bind to EGF receptors. Since native and biotinyl EGF have identical abilities to stimulate the uptake of 3H-thymidine into DNA when incubated with cultured murine 3T3 cells, the direct linkage of EGF to its receptor does not appear to play an important role in EGF-stimulated mitogenesis.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 423-439 
    ISSN: 0091-7419
    Keywords: granulopoiesis ; colony stimulating factor ; diffusion chamber granulopoiesis ; radioimmunoassay for colony stimulating factor ; long-term marrow cultures ; purification of colony stimulating factor ; binding of colony stimulating factor ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The proliferation and maturation of granulocytic-monocytic stem cells appears to be controlled by a series of closely related glycoproteins termed “colony-stimulating factors” (CSFs). Recently, we devised a 6-step scheme for the purification of murine fibroblast (L-cell)-derived CSF. Ten liter pools of conditioned media were concentrated by ultrafiltration, precipitated by ethanol, and separated on DEAE cellulose, Con-A Sepharose, and Sephadex G 150. The CSF was separated from trace contaminants, including endotoxin, by density gradient centrifugation. The purified material was radioiodinated and used to define the serum half-life and in vivo distribution. Following IV injection there was a biphasic serum clearance with a t½ of 24-40 min and 2-2½ hours in the first and second phases. Approximately 25% of the tracer was excreted in the urine at 6 h; however, urinary radioactivity was due to low molecular weight peptides. Simultaneous studies by radioimmunoassay showed a similar rapid serum clearance of unlabeled CSF but virtually no urinary CSF activity. Thus, assays for urinary CSF may not provide useful measures of in vivo CSF activity. Further in vitro studies have defined the interaction of CSF with responsive cells in the marrow. Varying doses of CSF were incubated with 107 marrow cells for intervals of 24-48 h. The major increment in cell-associated radioactivity occurred between 6 and 16 h. The reaction was saturable with 1-2 ng/ml CSF. Binding was prevented by cold CSF, but not by other proteins. Irradiation yielded only a minimal reduction in CSF binding. The interaction of CSF with marrow cells appeared to require new protein synthesis, as binding was completely inhibited by cycloheximide and puromycin. Irradiated mice injected with antibodies to CSF showed an inhibition of granulopoiesis by marrow cells in peritoneal diffusion chambers; however, granulopoiesis in the intact bone marrow was unaffected. Granulpoiesis in long-term marrow cultures was also unaffected by anti-CSF. These different responses may be due to accelerated clearance of injected CSF in nonirradiated mice or to extensive stromal interactions that modulate and perhaps control granulocytic differentiation in the intact bone marrow microenvironment.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 461-471 
    ISSN: 0091-7419
    Keywords: protein phosphorylation ; permeabilized cells ; EGF receptors - transmembrane distribution ; fragmentation by trypsin ; phosphate acceptor site ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A small quantity of the 125I-EGF (epidermal growth factor) bound specifically to EGF receptors on the human epidermoid carcinoma cell line A431 associates covalently. The direct linkage complex formed migrates during gel electro-phoresis as a single diffuse band of MW = 160,000-170,000. In contrast, direct linkages complexes of 160,000, 145,000, and 115,000 daltons are formed when EGF is incubated with membranes isolated from these cells; these arise from EGF receptor modification during membrane isolation. None of these modifications affected the affinity of the EGF binding site for 125I-EGF.The electrophoretic mobilities of the MW = 160,000 and 145,000 direct linkage complexes were similar to those of the major 32Pi-labeled products of the EGF-stimulated phosphorylation reaction described by Carpenter et al [Nature 276:409-410, 1978], indicating that proteolytic fragments of EGF receptors are the major phosphate acceptors in this reaction. EGF receptors on intact A431 cells accepted phosphate effectively from γ-32Pi-ATP only when the cells were permeabilized with lysolecithin. This shows that the EGF binding and phosphate acceptor sites lie on opposing faces of the membrane. When the 145,000 dalton form of receptor is labeled with EGF or 32Pi and the labeled peptides subjected to tryptic hydrolysis under identical conditions, all phosphates is lost from high molecular weight products under conditions where the EGF-receptor covalent complex is converted largely to a 115,000 dalton form. This suggests that the phosphate acceptor site lies on the cytoplasmic side of the membrane on a region of receptor extending 30,000 daltons from the 115,000 dalton fragment containing the EGF binding site.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 473-481 
    ISSN: 0091-7419
    Keywords: protein transport ; phosvitin ; receptor ; coated vesicles ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: By two independent methods, the solubilized receptor for phosvitin (PV) has a subunit MW of 116K. Affinity chromatography, showed that only 2 of the more than 25 proteins present in the total detergent solubilized oocyte membrane extract were retained on a PV-agarose column. These proteins of MW of 116K and 100K could be eluted from PV-agarose with free PV. By gel exclusion chromatography, the receptor-125I-PV complexes elute in the void volume of a Biogel A-1.5 column. When these void fractions were assayed by SDS-PAGE only a single protein of MW of 116K was observed in addition to 125I-PV.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 499-509 
    ISSN: 0091-7419
    Keywords: fibroblasts ; diabetic mice ; insulin ; deoxy D-glucose ; ornithine decarboxylase ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Fibroblastic cultures from the skin of nondiabetic and diabetic (db/db) mice have been used to investigate alterations in the biological responses of diabetic cells to insulin. Confluent cultures from the skin of both nondiabetic and diabetic animals possess specific receptors for insulin. Diabetic fibroblasts exhibit only 36% as much specific binding of insulin as nondiabetic fibroblasts, because of a decrease in the total number of binding sites, without a change in binding affinity. Insulin caused a time- and dose-dependent increase in the rate of 2-deoxy D-glucose (dGlc) uptake and in ornithine decarboxylase (ODC) activity of both nondiabetic and diabetic fibroblasts. In nondiabetic cells, half-maximal increase in dGlc uptake was obtained with 0.3 nM insulin, and a maximum increase of 120% was obtained with 4.1 nM insulin. In contrast, diabetic cultures required 0.8 nM insulin for a half-maximal increase in dGlc uptake, and maximum stimulation with 4.1 nM insulin was only 50% above control levels. With 4-fold higher insulin concentrations, ODC activity of diabetic cells was only 40% that of nondiabetic cells. In nondiabetic cells, down regulation of insulin receptors by insulin abolished the ability of insulin to stimulate dGlc uptake. These results demonstrate that cells cultured from diabetic animals, which possess a decreased number of insulin receptors, also exhibit decreased stimulation of deoxy D-glucose uptake and ornithin decarboxylase activity by insulin.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 483-498 
    ISSN: 0091-7419
    Keywords: myoblast differentiation ; muscle cell culture ; mitogens ; growth factors ; myoblast cell lines ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Regulation of the transition of mouse myoblasts from proliferation to terminal differentiation was studied with clonal density cultures of a permanent clonal myoblast cell line. In medium lacking mitogenic activity, mouse myoblasts withdraw from the cell cycle, elaborate muscle-specific gene products, and fuse to form multinucleated myotubes. Addition of a purified mitogen, fibroblast growth factor, to mitogen-depleted medium stimulates continued proliferation and prevents terminal differentiation. When mitogens are removed for increasing durations and then refed, mouse myoblasts irreversibly commit to terminal differentiation: after 2-4 h in the absence of mitogens, myoblasts withdraw from the cell cycle, elaborate muscle-specific gene products, and fuse in the presence of mitogens that have been fed back. Population kinetics of commitment determined with 3H-thymidine labeling and autoradiography suggest the following cell-cycle model for mouse myoblast commitment: (1) if mitogens are present in the extracellular environment of myoblasts in G1 of the cell cycle, the cells enter S and continue through another cell cycle; (2) if mitogens have been absent for 2 or more hours, cells in G1 do not enter S; the cells commit to differentiate, permanently withdraw from the cell cycle (will not enter S if mitogens are refed), and they subsequently elaborate acetylcholine receptors and fuse (even if mitogens are refed); (3) cells in other phases of the cell cycle continue to transit the cell cycle in the absence of mitogens until reaching the next G1. The commitment kinetics and experiments with mitotically synchronized cells suggest that the commitment “decision” is made during G1. Present results do not, however, exclude commitment of some cells in other phases of the cell cycle.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 11
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 45-109 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 12
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 111-217 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 13
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 219-295 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 14
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 297-381 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 15
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 211-217 
    ISSN: 0091-7419
    Keywords: pinocytosis ; cell density ; growth control ; growth factors ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In sub-confluent cultures of Balb/c-3T3 cells, pinocytosis rates were increased after exposure to specific growth factors (serum; platelet-derived growth factor, PDGF; epidermal growth factor, EGF). Conversely, as cells became growth-inhibited with increasing culture density, there was a corresponding decline in pinocytosis rate per cell. In order to test whether density-inhibition of pinocytosis was influenced either by the growth cycle or by cell contact independently of growth, cells were induced into a quiescent state at a range of subconfluent and confluent densities. Under such conditions, cell density did not significantly inhibit pinocytosis rate. When confluent quiescent cultures in 2.5% serum were exposed to 10% serum, the resulting round of DNA synthesis was accompanied by enhanced pinocytosis per cell, even though the cells were incontact with one another. Furthermore, in a SV40-viral transformed 3T3 cell line, both the growth fraction and the pinocytosis rate per cell remained unchanged over a wide range of culture densities. These studies indicate that density-dependent inhibition of pinocytosis in 3T3 cells appears to be secondary to growth-inhibition rather than to any direct physical effects of cell-cell contact.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 16
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 219-227 
    ISSN: 0091-7419
    Keywords: lectins ; lectin binding sites ; cell surfaces ; extracellular materials ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A lactose-binding lectin previously purified from embryonic chicken muscle and adult chicken liver, and here referred to as chicken-lactose-lectin-I (CLL-I), was added to sections of various adult chicken tissues to detect available binding sites. Both the sites of binding of added CLL-I as well as the tissue distribution of endogenous CLL-I were determined by indirect immunofluorescence using a rabbit antibody to CLL-I followed by fluorescent goat anti-rabbit IgG. Some tissues such as intestine and kidney showed abundant extracellular binding sites for the lectin, primarily between cells, in basement membrane, and in material on the luminal surface. In contrast, adult heart showed no significant binding sites for CLL-I. Adult pancreas showed considerable endogenous CLL-I in an extracellular site surrounding exocrine lobules, but added CLL-I did not bind substantially. The distribution of CLL-I binding sites in intestine were mimicked by those of purpurin, another lactose-binding lectin. CLL-I binding sites were also detected on the surface of cultured chick embryo skin fibroblasts. The factors controlling the specific distribution of occupied and unoccupied CLL-I binding sites are not known.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 17
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 447-456 
    ISSN: 0091-7419
    Keywords: hybridoma cells ; insulin action ; insulinomimetic antibodies ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: SJL mice were injected intraperitoneally with adipocyte plasma membranes or with intrinsic membrane proteins obtained by extraction of plasma membranes with dimethylmaleic anhydride. Three days after the boost injection, the spleens were removed and fused with NS-1, a thioguanine-resistant myeloma cell line derived from P3X63 Ag8 (Balb/c). Following selection for hybrids with hypoxanthine, aminopterin, and thymidine, medium of the hybrid cells was tested for its ability to bind to the plasma membrane of the adipocyte and to stimulate the oxidation of D-(1-14C) glucose to 14CO2. Approximately 40% of the wells containing hybridomas derived from splenocytes of SJL mice immunized with plasma membranes produced immunoglobulin that bound to adipocyte plasma membranes. About 30% of these mimicked the ability of insulin to stimulate the oxidation of D-(1-14C) glucose to 14CO2 in adipocytes. Media from 51% of the wells containing hybridomas derived from splenocytes of SJL mice immunized with intrinsic membrane proteins produced immunoglobulin that bound to the plasma membrane and 48% of those stimulated glucose oxidation. The bioactivity of the hybrid cell media could be blocked by adsorption with intrinsic membrane proteins or by the removal of immunoglobulins using formalin-fixed Staphylococcus aureus. The hybrids generated in this study can be divided into three categories: (1) hybrids that secrete antibodies that can bind to plasma membranes and mimic insulin action of glucose transport; (2) hybrids that secrete antibodies that bind to plasma membranes but do not stimulate the oxidation of D-(1-14C) glucose to 14CO2; and (3) hybrids that produce no antimembrane antibodies. The data suggest that interaction of immunoglobulins with specific membrane proteins is essential in mimicking the action of insulin on glucose transport and oxidation in the rat adipocyte.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 18
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 467-478 
    ISSN: 0091-7419
    Keywords: thrombin ; initiation of cell division ; receptor visualization ; fluorescent labeling ; proteolysis of receptors ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The localization of thrombin receptors on mouse embryo (ME) cells has been examined by direct fluorescence microscopy using a fluorescein aminelabeled thrombin. Two fluorescein amines, 4-(N-6-aminoethyl thioureal)-fluorescein and 4-(N-6-aminohexyl thioureal)-fluorescein, were synthesized and attached to the carbohydrate moiety of highly purified human α-thrombin by periodate oxidation of the carbohydrate and selective reduction of the Schiff's base using sodium cyanoborohydride. Preparations of fluorescent thrombin with from 1 to 4 fluoresceins per molecule of thrombin retained their ability to proteolytically cleave fibrinogin to form fibrin clots, to bind to thrombin receptors on ME cells, and to initiate cell division. After incubating mitogenic concentrations of the fluorescein amine labeled thrombin with ME cells at 4°C, a diffuse fluorescent pattern was observed over the surface of the ME cells. This diffuse pattern was specific: it was not observed on cells from parallel cultures incubated with fluorescent thrombin plus a 20-fold excess of unlabeled thrombin. Thus, thrombin receptors appear to be distributed randomly over the surface of ME cells prior to interaction with thrombin. Increasing the temperature to 37°C following binding at 4° C resulted in a rapid dissociation of the fluorescent pattern from the cells leaving only the autofluorescent vesicles. This result may reflect the unique ability of thrombin to proteolytically cleave its own receptor.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 19
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 479-488 
    ISSN: 0091-7419
    Keywords: T cell factors ; polyclonal antibody formation ; Fc fragments ; interleukin 2 ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: T lymphocytes are stimulated to release T-cell-replacing factors in response to Fc fragments of human IgG. Lyt 1+23- T cells are directly triggered to factor production by Fc subfragments, derived from intact Fc fragments by macrophage-dependent enzymatic cleavage. These factor(s) replace T cell function in two Fc-mediated immune responses; induction of polyclonal antibody synthesis, and potentiation of anti-SRBC responses.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 20
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 501-511 
    ISSN: 0091-7419
    Keywords: bone marrow cultures ; hemopoiesis in vitro ; mouse genotype ; factor-dependent cell lines ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Long-term bone marrow cultures established from C57Ks/J mice have been shown to spontaneously release endogenous ecotropic RNA type-C virus (retrovirus). C57Ks/J marrow cultures produced granulocyte-macrophage progenitor cells (GM-CFUc) and immature and mature granulocytes for over 45 weeks. In contrast, NIH Swiss mouse marrow cultures failed to release detectable ecotropic virus and generated GM-CFUc and granulocytes for 25-35 weeks and established WEHI-3 conditioned medium (CM) dependent cell lines in vitro and did not establish permanent cell lines. To determine whether viral and/or cellular genes regulated the longevity of C57Ks/J marrow cultures, groups of cultures were established from the marrow of (NIH-Swiss × C57Ks/J) F1 hybrid, F2 hybrid, and (NIH Swiss × C57Ks/J) X NIH Swiss backcross generations. Release of endogenous ecotropic virus was measured weekly in each culture as was the duration of production of immature granulocytic cells and GM-CFUc over a 58-week period. The results demonstrated a complex pattern of inheritance of longevity of long-term in vitro hemopoiesis. Increased longevity did not absolutely correlate with detectable replication of the C57Ks/J N-tropic virus.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 21
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 489-499 
    ISSN: 0091-7419
    Keywords: PDGF ; somatomedin ; SV40 ; cell cycle ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The platelet-derived growth factor (PDGF), which is found in serum but not in plasma, has been purified to homogeneity; it stimulates replication at a concentration of 10-10M. Brief treatment with PDGF causes densityinhibited Balb/c-3T3 cells to become competent to synthesize DNA; pituitary fibroblast growth factor (FGF) or precipitates of calcium phosphate also induce competence. Continuous treatment with plasma allows competent, but not incompetent, cells to synthesize DNA. A critical component of plasma is somatomedin, a group of hormones with insulin-like activity; multiplication-stimulating activity (MSA) or insulin replace plasma somatomedin in promoting DNA synthesis.We have studied the molecular correlates of competence and the role of SV40 gene A products in regulating DNA synthesis. Treatment of quiescent cells with pure PDGF or FGF causes the preferential synthesis of five cytoplasmic proteins (approximate molecular weight 29,000, 35,000, 45,000, 60,000, and 72,000 detected by SDS-PAGE under reducing conditions). Two of these competence-associated proteins (29,000 and 35,000 daltons) are found within 40 min of PDGF addition; they are not induced by plasma, insulin, or epidermal growth factor (EGF), PDGF, FGF, or calcium phosphate induce an ultrastructure change within the centriole of 3T3 cells; this ultrastructural modification of the centriole is detectable by immunofluorescence within 2 h of PDGF treatment. Plasma, EGF, or MSA do not modify the centriole. SV40 induces replicative DNA synthesis in growth-arrested 3T3 cells but does not cause this alteration in centriole structure.Gene A variants of SV40, including a mutant with temperature-sensitive (ts) T-antigen (ts A209), a deletion in t-antigen (dl 884), and several ts A209 strains containing t-antigen deletions were used to induce DNA synthesis in Balb/c-3T3 cells. Like wild type SV40, all strains induced DNA synthesis equally well under permissive or nonpermissive conditions. Addition of PDGF or plasma had little effect on SV40-induced DNA synthesis. Thus, the viral function that induces replicative DNA synthesis in Balb/c-3T3 cells is not t and is not temperature sensitive. This SV40 gene function overrides the cellular requirement for hormonal growth factors. It does not induce transient centriole deciliation, a hormonally regulated event.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 22
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 33-46 
    ISSN: 0091-7419
    Keywords: smooth muscle cell proliferation ; fibroblast proliferation ; membrane proteases ; protease inhibitors ; heparin ; cartilage factors ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Proliferating rat smooth muscle cells and fibroblasts have membrane-associated protease activity. High concentrations of heparin inhibited membrane-associated protease activity and cell proliferation, while low concentration of heparin promoted smooth muscle cell proliferation. The inhibition of protease activity and proliferation was abolished when heparin was treated with protamine sulfate or when acid treated fetal calf serum was used. Heparin required the presence of an acid labile factor(s) in serum for the inhibition of protease activity and proliferation. Heparin and antithrombin III in the presence of acid-treated fetal calf serum did not inhibit cell proliferation or protease activity. Cartilage factors isolated from bovine nasal cartilage containing trypsin inhibitory activity, but not papain inhibitory activity, inhibited rat smooth muscle and fibroblast proliferation and surface associated protease activity. The cartilage factors did not require acid-labile components in the fetal calf serum for the inhibitory activity. The inhibitory activity due to heparin and cartilage factors was not permanent under our experimental condition. Protein synthesis was not inhibited by heparin or the cartilage factors. In rat smooth muscle cells and fibroblasts, the expression of surface-associated protease activity was related to the proliferative state of the cells. Surface protease activity was only present on proliferating cells. When surface protease activity was inhibited by high concentrations of heparin in the presence of an acid-labile serum component(s) or cartilage factors, cell proliferation was also inhibited.
    Additional Material: 8 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 23
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 255-266 
    ISSN: 0091-7419
    Keywords: cytodifferentiation ; dexamethasone ; methylisobutylxanthine ; fetal calf serum ; retinoic acid ; preadipocytes ; adipose conversion ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The role of retiinoic acid in modulating the differentiation of 3T3-L2 fibroblasts into adipocytes has been examined. Results indicate that the retinoid is capable of effectively inhibiting the degree of adipose conversion which is brought about by treatment of preadipocytes with 1-methyl-3-isobutylxanthine plus dexamethasone. Morphological and enzymatic (fatty acid synthetase activity) expression of the adipose phenotype are both inhibited more than 90% by 10-6 M retinoic acid. The inhibition is concentration dependent with retinoic acid levels as low as 10-11 M capable of reducing adipose conversion by 20%. Retinoic acid must be administered simultaneously with the triggering agents to be effective. Exposure of nongrowing preadipocytes to retinoic acid does not alter the ability of the cells to differentiate in response to a subsequent treatment with methylisobutylxanthine plus dexamethasone. Further, the inhibition is reversible. Cultures in which methylisobutylxanthine plus dexamethasone triggered differentiation has been blocked by addition of retinoic acid (10-6M) will readily undergo adipose conversion in response to a second treatment with methylisobutylxanthinthine plus dexamethasone in the absence of the retioid. Similar inhibition of differentiation was found when cultures were treated with drugs in medium supplemented with either newborn calf serum or fetal calf serum. However, the extent to which methylisobutylxanthine plus dexamethasone are able to promote differentiation in these cells is considerably greater in medium containing fetal calf serum.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 24
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 281-294 
    ISSN: 0091-7419
    Keywords: carbohydrates ; transport ; chemotaxis ; regulation ; phosphotransferase system ; bacteria ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The phosphotransferase system (PTS) in Escherichia coli is a multifunctional, multicomponent enzyme system. Its primary functions deal with carbon source acquisition, while its secondary functions are concerned with the regulation of bacterial physiology. The primary functions of the system include (1) extracellular detection, (2) unidirectional and exchange transmembrane transport, and (3) phosphoenolpyruvate-dependent and sugar phosphate-dependent phosphorylation of the sugar substrates of the system. The secondary functions include (1) regulation of the activities of adenylate cyclase and various non-PTS permeases and (2) regulation of the induced synthesis of several PTS enzymes. Both the primary and secondary functions appear to be elicited by the binding of a sugar substrate to an Enzyme II complex. One of these integral transmembrane enzymes, the mannitol Enzyme II (IImtl), has been solubilized with detergent, purified to homogeneity, and reconstituted in an artificial membrane system. The molecular weight of this protein, IImtl, is 60,000 daltons. It possesses an extracellular sugar binding site and distinct intracellular combining sites for sugar phosphate and phospho-HPr. An essential sulfhydryl group and an antibody combining site are localized to the cytoplasmic surface of the enzyme, while a dextran combining site is localized to the external surface. Preliminary experiments suggest that the different functions of the Enzyme IImtl can be dissected by genetic and biochemical techniques. These studies emphasize the functional complexity of the PTS and its integral membrane protein constituents.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 25
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 329-342 
    ISSN: 0091-7419
    Keywords: cell cycle ; transition probability ; limit cycle oscillator ; generation time ; phase response ; division delay ; cellular clock ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In synchronized V79 cells perturbed by serum, heat shock, or ionizing radiation at half-hour intervals through a modal 8.5-hour cell cycle, phase-response curves show a characteristic biphasic pattern of advances and delays in subsequent cell divisions. These observations, together with previous observations of quantizement of generation times in this and other cell lines have led us to consider a model incorporating, in the simplest case, a two-component oscillator with two threshold crossings required per cell cycle. By assuming that oscillator variables respond in a simple way to the experimental perturbations, for example, by first order destruction due to heat shock, a map of the qualitative features of the oscillator can be obtained by matching simulated with experimental phase response curves. Random fluctuations in oscillator variables about a fixed trajectory lead to subthreshold oscillations and result in a distribution of generation times which is roughly a negative exponential, but quantized within this exponential envelope. The extent of the random fluctuations can be determined from comparison with data on desynchronization of a cell population after mitotic selection. The same parameters which correctly simulate phase response and the desynchronization data also give good agreement with generation time distribution data.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 26
    ISSN: 0091-7419
    Keywords: receptor-mediated endocytosis ; acetylated LDL ; malondialdehyde ; polynucleotides ; familial hypercholesterolemia ; atherosclerosis ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Macrophages isolated from a variety of organs in several animal species exhibit high affinity binding sites that recognize chemically modified proteins. One of these binding sites recognizes human plasma low density lipoprotein (LDL) in which the positive charges on the epsilon-amino groups of lysine have been removed or neutralized by chemical modification, thus giving the protein an enhanced negative charge. Effective treatments include reaction of LDL with organic acid anhydrides (acetylation or maleylation) and reaction with aldehydes, such as treatment with malondialdehyde. After the negatively-charged LDL binds to the surface receptor sites, it is rapidly internalized by the macrophages by endocytosis and hydrolyzed in lysosomes. The liberated cholesterol is reesterified in the cytoplasm, producing massive cholesteryl ester deposition. The binding site for negatively-charged LDL has been demonstrated so far only on macrophages and other scavenger cells. It is not expressed in cultured fibroblasts, smooth muscle cells, lymphocytes, or adrenal cells. In addition to its affinity for acetylated LDL and malondialdehyde-treated LDL, the macrophage site binds a variety of polyanions. It exhibits a particularly high affinity for certain sulfated polysaccharides (dextran sulfate and fucoidin), certain polynucleotides (polyinosinic acid and polyguanylic acid), polyvinyl sulfate, and maleylated albumin. It is possible that the site that binds negatively-charged LDL may be responsible for the massive accumulation of cholesteryl esters that occurs in vivo in macrophages and other scavenger cells in patients with high levels of circulating plasma LDL.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 27
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 295-304 
    ISSN: 0091-7419
    Keywords: secretory granules ; ATP-induced lysis ; osmotic gradient ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Secretory vesicles isolated from a variety of mammalian tissues are known to lyse and thereby release their secretory products when exposed to ATP. This process, which will be termed ATP-induced lysis, has been studied most extensively using adrenal chromaffin-granule preparations. We report here that ATP causes the lysis of a highly purified preparation of rat parotid secretory granules. The rate of granule lysis was measured spectrophotometrically, and ATP-induced lysis was expressed as the increase in the rate of lysis (r = % lysis per min) when ATP was added. This lytic process was characterized with respect to pH, temperature, osmolarity, and the ionic composition of the media ATP-induced lysis of parotid granules was found to have the following properties in common with the extensively characterized chromaffin-granule process: 1It is a saturable function of ATP with half-maximal rates observed at 0.5 ± 0.1 mM ATP.2It is temperature dependent, eg, r = 6.1 ± 2.1%/min at 30°C vs 12.2 ± 2.5%/min at 37°C.3It is inhibited in hyperosmotic media, eg, r = 5.3 ± 0.3%/min at 0.3 OsM vs 0.8 ± 0.2%/min at 0.4 OsM.4It shows a nucleotide preference of ATP = GTP 〉 ADP 〉 AMP 〉 CTP = ITP.5It has an anion requirement.The above findings, combined with reports of ATP-induced lysis of cholinergeric, insulin, and posterior-pituitary vesicles, imply that ATP-induced lysis may reflect an ATP-dependent property of all secretory vesicles, and as such, this vesicle property could play a similar role in each exocytotic release process. Using a model system, Miller and Racker [22] made a surprising finding that the extent to which liposomes fuse with a black lipid membrane depends on the osmotic gradient across the vesicle membrane. In view of the osmotic dependence of ATP-induced lysis in this and other secretory-vesicle preparations, we postulate that ATP may prime secretory vesicles for fusion with the plasma membrane by inducing and/or maintaining an osmotic gradient across the vesicle membrane.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 28
    ISSN: 0091-7419
    Keywords: Salmonella typhimurium ; methylation ; chemotaxis ; flagellar synthesis ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A specific in vitro assay was developed for the protein carboxyl methyltransferase that is involved in the chemotactic behaviour of Salmonella typhimurium. This cytosolic enzyme catalyzes an S-adenosyl-L-methionine-dependent methyl esterification of glutamyl residues on a class of 60,000-dalton inner-membrane proteins. The activity was found to display a pH optimum of 6.5 and be sensitive to the concentration of salts in the assay medium. No detectable activity was found towards a variety of other proteins which serve as substrates for mammalian and other bacterial carboxyl methyltransferases. This assay was used to quantitate the methylation of the 60,000-dalton methyl-accepting proteins in response to chemoeffectors. Small but reproducible concentration-dependent changes in the initial rates of in vitro methylation were observed with chemotactic attractants and repellents. The specific methyltransferase activity was found to be absent in several mutants in flagellar synthesis (fla-), suggesting that the synthesis of this enzyme is coordinately regulated with that of flagellin and basal bodies. The hydrodynamic properties of the enzyme in crude extracts were determined by gel filtration and sucrose velocity gradient centrifugation, and a native molecular weight of 41,000 was calculated from these data.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 29
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 329-337 
    ISSN: 0091-7419
    Keywords: nerve growth factor ; peripheral neurons ; ion fluxes ; transport ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Nerve growth factor (NGF) is likely to exert its trophic action on dorsal root ganglion (DRG) and on sympathetic ganglion neurons by controlling a crucial function of these cells. This function would in turn regulate other cellular machineries and, ultimately, lead to the traditional NGF consequences, such as survival and neuritic growth. A corollary of this view is that the key to NGF action must lie in short-latency events, occurring within minutes of NGF administration. Chick embryo DRG dissociates have proved to be an effective experimental system to investigate short-latency responses to NGF, in that (1) measurable functional deficits develop over 6 h of NGF deprivation in vitro and (2) delayed presentation of NGF promptly and fully restores the defective function. The first deficit observed in this experimental system, a decline in RNA-labeling capability, led to the recognition that NGF controls the transport of selected exogenous substrates, all of which are Na+-coupled and depend on an Na+ gradient across the neuronal membrane. Subsequent work showed that NGF controlled such transport systems by actually regulating the neuronal ability to control intracellular Na+. Under NGF deprivation, the DRG cells accumulate Na+ to levels that reflect, and presumably equate, the extracellular Na+ concentrations. Conversely, on delayed NGF administration, the accumulated Na+ is actively extruded to an extent and at a speed that depends on the NGF concentration. The Na+ response is elicited by both Beta and 7S NGF, but not by other proteins tested. All ganglionic systems that display a requirement for exogenous NGF in culture have also displayed the Na+ response to NGF. The Na+ response is grossly paralleled by a K+ response. DRG dissociates, in which intracellular K+ has been pre-equilibrated with extracellular 86Rb+, lose their 86Rb+ over 6 h of NGF deprivation and restore it on delayed NGF administration. The regulation by NGF of mechanisms controlling intracellular Na+ and K+ levels in their target neurons is likely to occupy an early and fundamentl place in the sequence of events underlying the mode of action of this factor.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 30
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 339-372 
    ISSN: 0091-7419
    Keywords: extracellular matrix ; FGF ; vascular endothelial cells ; vascular smooth muscle cells ; aging ; differentiation ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In this short review we describe the observations which have led us to conclude that one of the most important components involved in modulating cell proliferation in vitro, and probably in vivo as well, may be the extrac-cellular matrix upon which cells rest.
    Additional Material: 22 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 31
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 373-383 
    ISSN: 0091-7419
    Keywords: hydroperoxide ; mitogenesis ; 15-HPAA ; arachidonic acid ; inhibition ; lymphocyte activation ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Incubation of murine spleen cells with the oxidation product of soybean lipoxidase-treated arachidonic acid results in profound inhibition of induction of proliferation and maturation of these cells. The active entity was shown to be the 15-hydroperoxide of arachidonic acid (15-HPAA). Inhibition of the enzymes of the cyclo-oxygenase pathway fails to disturb this effect, indicating that 15-HPAA is not a substrate for this series of enzymes. 15-HPAA produced in this manner interfered with RNA synthesis, DNA synthesis, and blastogenesis, while failing to exert cytotoxic effects on the cells themselves. A variety of lymphocyte subpopulations, distinguished by their responsiveness to a diverse group of mitogens, were all equally inhibited by the addition of 15-HPAA to culture. Addition of this agent even as late as 24 h after initiation of culture resulted in profound inhibition of the proliferative and differentiative responses of splenic B cells to bacterial lipopolysaccharide (LPS). Exposure of cells to 15-HPAA for 10-30 min was adequate to initiate inhibition, an event that exhibited marked temperature dependence. The effects of pre-incubation with 15-HPAA could not be reversed in its absence in recovery periods of up to 6 h prior to addition of LPS. The implications of these data with reference to cellular activation mechanisms are discussed.
    Additional Material: 9 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 32
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 395-400 
    ISSN: 0091-7419
    Keywords: MHC ; erythropoiesis ; differentiation marker ; B-G locus ; monoclonal antibody ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The spectrum of reactivity with various types of cells of a monoclonal antibody (CH-4) which detects a private MHC antigen of chickens was analysed. CH-4 agglutinates only RBCs that possess the B2 (MHC) haplotype. A new rosetteforming cell (RFC) assay was devised to detect individual cells (excluding RBCs) that possess the CH-4 specificity on their cell surfaces. RBCs that have CH-4 chemically coupled to their surfaces attach to, and form rosettes with, B2 antigen-bearing cells. Most non-RBC RFC were detected in active erythropoietic organs (adult bone marrow and embryonic spleen), and none were found in organs where erythropoiesis does not occur: adult thymus and bursa. Preincubation of bone marrow cells with CH-4 plus complement almost completely inhibits their capacity to form CFU-E without affecting their ability to form GM-CFU. In addition, CH-4 plus complement does not inhibit the capacity of B2/B2 lymphocytes to induce a graft-versus-host reaction under conditions where anti-B2 lymphocyte alloantisera are completely inhibitory. Our results strongly suggest that CH-4 monoclonal antibodies detect a private specificity on a gene product of the B-G locus whose expression is restricted to erythroid stem cells and erythrocytes.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 33
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 401-410 
    ISSN: 0091-7419
    Keywords: glucocorticoids ; glucocorticoid receptor ; lymphocytolysis ; T-lymphoma ; thymoma ; cell variants ; cell hybrids ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The glucocorticoid-induced lysis of lymphoid cell lines offers a genetic approach to steroid hormone action because unresponsive variants can easily be selected as resistant to this lytic effect. The present state of analysis of lymphocytolysis in two murine cell lines, the S49 T-lymphoma and the W7 thymoma, is reviewed. All glucocorticoid-resistant variants isolated so far result from various defects in the glucocorticoid receptor. The absence of variants blocked at another step of the lytic mechanism is discussed. The observed hemizygosity of the glucocorticoid receptor locus in the S49 line and the instability of cell hybrids illustrate some of the potential problems encountered in somatic cell genetics.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 34
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 421-446 
    ISSN: 0091-7419
    Keywords: evolution ; membrane transport ; proton pumps ; ATPase ; oxidative phosphorylation ; flavoproteins ; quinone ; cytochromes ; photosynthesis ; bacterial rhodopsin ; protonmotive force ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: One of the first problems encountered by primitive cells was that of volume regulation; the continuous entry of ions, (eg, NaCl) and water in response to the internal colloid osmotic pressure threatening to destroy the cell by lysis. We propose that to meet this environmental challenge cells evolved an ATP-driven proton extrusion system plus a membrane carrier that would exchange external protons with internal Na+. With the appearance of the ability to generate proton gradients, additional mechanisms to harness this source of energy emerged. These would include proton-nutrient cotransport, K+ accumulation, nucleic acid entry, and motility. A more efficient system for the uptake of certain carbohydrates by vectorial phosphorylation via the PEP-phosphotransferase system probably appeared rather early in the evolution of anaerobic bacteria.The reversal of the proton-ATPase reaction to give net ATP synthesis became possible with the development of other types of efficient proton transporting machinery. Either light-driven bacterial rhodopsin or a redox system coupled to proton translocation would have served this function. Oxidation of one substrate coupled to the reduction of another substrate by membrane-bound enzymes evolved in such a manner that protons were extruded from the cell during the reaction. The progressive elaboration of this type of redox proton pump permitted the use of exogenous electron acceptors, such as fumarate, sulfate, and nitrate. The stepwise growth of these electron transport chains required the accretion of several flavoproteins, iron-sulfur proteins, quinones, and cytochromes. With modifications of these four basic components a chlorophyll-dependent photosynthetic system was subsequently evolved. The oxygen that was generated by this photosynthetic system from water would eventually accumulate in the atmosphere of the earth. With molecular oxygen present, the emergence of cytochrome oxidase would complete the respiratory chain.The proton economy of membrane energetics has been retained by most present-day microorganisms, mitochondria, chloroplasts, and cells of higher plants. A secondary use of the energy stored as an electrochemical difference of Na+ for powering membrane events probably also evolved in microorganisms. The exclusive use of the Na+ economy is distinctive of the plasma membrane of animal cells; the Na+-K+ ATPase sets up an electrochemical Na+ gradient that provides the energy for osmoregulation, Na+-nutrient cotransport, and the action potential of excitable cells.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 35
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 513-524 
    ISSN: 0091-7419
    Keywords: long-term marrow cultures ; cell-cell interactions ; microenvironment ; stem cell ; proliferation modulators ; GM-CFC ; differentiation ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In long-term marrow cultures haemopoiesis can be maintained in vitro for up to 6 months. Critical analysis of the cell populations produced has shown that the stem cells and their committed progeny have characteristics in common with the corresponding cell types in vivo. The maintenance of haemopoiesis in vitro is associated with the development of an appropriate inductive environment provided by bone marrow derived adherent cells. Analysis of the interactions between environmental and haemopoietic cells has been facilitated by the development of in vitro systems reproducing the naturally occurring genetic environmental defects and other systems where the development of a competent inductive environment shows a dependency upon corticosteroid hormones. Investigations have shown that stem cell proliferation may be controlled by production of opposing activities, one stimulatory for DNA synthesis, the other inhibitory. A model is proposed whereby modulation in the production of these factors is determined by the physical presence of stem cells in a proposed cellular milieu, within the adherent layer. The adherent layer, apart from acting at the level of stem cell proliferation, can also modify the response of differentiating cells (eg, GM-CFC) to exogenous stimulatory activities. Addition of GM-CSF or of CSF-antiserum has no effect on haemopoiesis in long-term cultures.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 36
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 525-532 
    ISSN: 0091-7419
    Keywords: T lymphocytes ; HLA-D ; cloning ; TCGF ; PLT lymphocyte typing ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The long-term maintenance of T cells “cloned” by limiting dilution in TCGF was enhanced by the use of irradiated autologous lymphoblastoid cell line (LCL) cells as well as irradiated LCL cells of the individual to which the T cells were originally primed. It was possible to obtain more than 1 × 1012 cells from a “clone” seeded at one cell per well. Some of the clones tested express primed LD-typing activity.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 37
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980) 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 38
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 47-63 
    ISSN: 0091-7419
    Keywords: serum spreading factor ; cell proliferation ; cell morphology ; cell substratum ; serum-free medium ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A heat-sensitive, trypsin-sensitive factor that promoted growth and spreading of cells in serum-free, hormone-supplemented medium was partially purified from human serum. The major portion of the proteins in these preparations migrated upon SDS-polyacrylamide gel electrophoresis with a mobility consistent with molecular weights between 60,000 and 90,000. The spreading activity, which we have termed serum spreading factor, stimulated growth and spreading of a wide variety of cell types. The serum spreading factor was similar to fibronectin in that it showed an affinity for the plastic cell culture substrate but was shown to be distinct from fibronectin by several criteria. This factor may prove useful in studies of cell attachment and spreading and in studies of the relationship of cell shape and cell proliferation.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 39
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 121-127 
    ISSN: 0091-7419
    Keywords: H-2K alloantigens ; mixed lymphocyte culture ; H-2 I alloantigens ; cytotoxic memory ; alloimmune responses ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: AQR mice were immunized with H-2K and H-2 I encoded alloantigens presented by (Ax6R)F1 splenocytes. Spleen cells from these alloimmune mice were subsequently restimulated in vitro with B10.A lymphocytes and/or B10.T(6R) lymphocytes, thus presenting them with the immunizing H-2K and H-2 I alloantigens independently. When stimulated with B10.A lymphocytes, alloimmune lymphocytes develop significant cytotoxicity against the immunizing H-2K target antigens. When stimulated with a similar number of B10.T(6R) spleen cells, alloimmune lymphocytes undergo a prominant proliferative response, but develop little, if any, cytotoxicity against the immunizing H-2 K target antigens. The most efficient restimulation of cytotoxicity occurs when the alloimmune spleen cells are simultaneously restimulated by B10.A and B10.T(6R) lymphocytes. Stimulation with the immunizing H-2 I alloantigens alone is not sufficient for regeneration of detectable cytotoxic responses from alloimmune spleen populations. Stimulation with the immunizing H-2K alloantigens alone appears to be both necessary and sufficient to stimulate alloimmune cytotoxic responses. Although the immunizing H-2 I alloantigens are apparently not required to generate alloimmune cytotoxic responses, they markedly potentiate the cytotoxic responses induced by the immunizing H-2K alloantigens.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 40
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 163-174 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 41
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 139-148 
    ISSN: 0091-7419
    Keywords: mitochondria ; protein synthesis ; cytochrome b-c1 ; biogenesis ; repiratory chain ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Complex III isolated from yeast mitochondria catalyzed an antimycin A and Diuron-sensitive coenzyme QH2-cytochrome c reductase activity with a turnover number of 15.7 sec-1 and contained 10 nmoles of cytochrome b and 4.6 nmoles of cytochrome c1 per mg of protein. Electrophoresis in sodium dodecyl sulfate acrylamide gels resolved Complex III into 10 bands with apparent molecular weights of 50,000, 40,000, 30,000, 29,000, 24,000, 17,000, 16,000, 12,000, 8,400, and 5,800. Yeast cells were labeled under nongrowing conditions with (35S)-methionine in the absence or presence of inhibitors of cytoplasmiċ or mitochondrial protein synthesis. Labeled Complex III was isolated by immunoprecipitation from detergent-solubilized mitochondria using antiserum raised against the purified complex. Analysis of the immunoprecipitates by polyacrylamide gel electrophoresis revealed that a 30,000-dalton protein, cytochrome b, as well as 16,000-dalton protein were labeled in the presence of cycloheximide, indicating that they are products of mitochondrial protein synthesis. Immunoprecipitates from mitochondria obtained from cells labeled in the presence of chloramphenicol contained a new radioactive peak with a molecular weight of 100,000. In addition, significant decreases in the labeling of the proteins with molecular weights of 50,000, 40,000, 30,000, and 16,000 were observed. When Complex III was isolated by immunoprecipitation from intact spheroplasts after a 5-minute pulse with (35S)-methionine, the 100,000-dalton protein was labeled in the immunoprecipitate whether or not chloramphenicol was present; however, after a 1-hour chase with unlabeled methionine, decreased labeling of the 100,000-dalton protein was observed concomitant with an increased labeling of the 50,000- and 40,000-dalton proteins. These results suggest that a protein with a molecular weight of 100,000 may either be a precursor or a partially assembled form of other proteins of Complex III, most probably the two largest polypeptides.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 42
    ISSN: 0091-7419
    Keywords: cell surface receptors ; type C viral glycoproteins ; growth factors ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We have described previously the detection and tissue distribution of free cell surface receptors for ecotropic R-MuLV envelope glycoprotein and the growth factor EGF in vivo [1]. More recently, we have reported the chromosomal map position of the ecotropic viral receptor and its conservation between subspecies of the genus Mus [2]. This work has shown, for the first time, the presence of multiple, independently segregating cell surface receptor genes specific for different classes of ecotropic type C viral envelope glycoprotein. In this report we extend these findings and identify chromosome 2 as coding for the receptor used by M813, an ecotropic MuLV from a feral Asian mouse. This new receptor is probably also used by oncogenic, recombinant (MCF class) MuLV of C3H origin.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 43
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 397-403 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 44
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 383-395 
    ISSN: 0091-7419
    Keywords: bone marrow ; stem cell differentiation ; allogeneic effect factor ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: This study was designed to investigate the effects of allogeneic effect factor (AEF), a soluble mediator derived from short-term mixed lymphocyte cultures (MLC) of in vitro alloantigen-primed T cells, on cultures of murine bone marrow cells. Cultures established under suboptimal conditions namely, in the absence of a pre-established adherent cell layer as required in conventional Dextertype cultures-declined and lost their stem cell activity rapidly. In contrast, supplementation of these cultures, at initiation and thereafter, with AEF, but not with T cell growth factor (TCGF), induced cell growth and proliferation for several weeks. Such AEF-supplemented cultures exhibited cellular heterogeneity and stem cell activity for significantly longer periods than the control cultures. Even in conventional Dexter cultures, established under optimal conditions, AEF had a beneficial effect on cellular growth and proliferation and myeloid progenitor cell (CFU-C) activity. Furthermore, cells capable of synergizing with suboptimal numbers of mature T cells in con A-induced mitogenic responses, shown by others to be pre-T cells, were detected in the AEF-supplemented cultures for several weeks.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 45
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 371-382 
    ISSN: 0091-7419
    Keywords: thymocyte subpopulations ; differentiation antigens ; PNA fractionation ; density gradient ; biosynthetic labeling ; short-term culture ; non-coordinate regulation ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Mouse thymocyte populations enriched in functionally incompetent, “immature” cells on the one hand, or in competent “mature” cells on the other hand, express different steady-state levels of certain surface antigens and marker enzymes. In the cases of the glycoproteins H-2 (K and D), Qa, and TL, and the DNA polymerase terminal deoxynucleotidyl transferase (TdT), these levels reflect different rates of de novo synthesis in the two populations. Thus each population appears to manifest a characteristic pattern of synthetic rates for the various products relative to total protein synthesis. To investigate the maintenance of these patterns, enriched pools of “immature” and “mature” thymocytes were incubated in vitro for 24 h, and the rates of product synthesis before and after culture were compared. H-2 synthesis, initially most rapid in the mature cells, continued to be made at the highest rate in this population. TdT synthesis, a characteristic activity of the immature cells, was not induced in the mature cells, but proceeded at an increased relative rate in the immature population. Therefore, the differences between the rates of H-2 and TdT synthesis were stable properties of the two thymocyte populations. Another marker of immature cells, TL, did not continue to be produced in parallel with TdT. Rather, its synthesis was selectively curtailed in relation to the continuing protein synthesis in the immature cultures. This non-coordinate regulation of TL and TdT production in immature thymocytes may be due to several mechanisms. These are discussed with regard to their implications for pathways of thymocyte maturation.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 46
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 511-525 
    ISSN: 0091-7419
    Keywords: EGF receptors - solubilization ; aggregates in nonionic detergent ; gel filtration chromatography ; zonal sedimentation ; on A431 membranes ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Between 60% and 100% of epidermal growth factor (EGF) binding activity was recovered from membranes of the A431 human epidermoid carcinoma cell line treated with solutions containing the nonionic detergent Triton X-100. Approximately half of the recovered binding activity was sedimented at low centrifugal forece and hence was operationally insoluble in nonionic detergent solution. Receptors in both the detergent-soluble and -insoluble fractions displayed similar affinities for 125I-EGF, and the values were in good agreement with those obtained for receptors in untreated membranes. The receptors in both fractions also formed identical direct linkage complexes with 125I-EGF in similar yield, providing no evidence for partitioning of different molecular species of EGF receptors in the detergent-soluble and -insoluble fractions.Gel chromatography of the detergent-soluble membrane fraction on Sepharose 6-B revealed heterogeneity of 125I-EGF binding activity; the smallest and most monodisperse peak of activity resolved by this technique was eluted at a Stokes radius of 95 Å. Operationally soluble 125I-EGF binding activity also behaved heterogeneously during velocity sedimentation; more than half the activity sedimented more rapidly than the apparently monidisperse, 7S form. An average of less than half the nonionic detergent-solubilized activity recovered from 10 independent membrane preparations behaved as an apparently monodisperse entity. Since a maximum of 60% of 125I-EGF binding activity was operationally soluble, less than 25% of the total EGF binding activity was recovered in an apparently monodisperse form. The remaining 75% of the EGF receptors displayed a marked tendency to exist as aggregates in nonionic detergent solutions.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 47
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980) 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 48
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 527-537 
    ISSN: 0091-7419
    Keywords: leucine transport genes ; cloning ; regulation ; rho factor ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Leucine is transported into E coli by two osmotic shock-sensitive, high-affinity systems (LIV-I and leucine-specific systems) and one membrane bound, low-affinity system (LIV-II). Expression of the high-affinity transport systems is altered by mutations in liv R and 1st R, genes for negatively acting regulatory elements, and by mutations in rho, the gene for transcription termination. All four genes for high-affinity leucine transport (livJ, livK, livH, and livG) are closely linked and have been cloned on a plasmid vector, pOX1. Several subcloned fragments of this plasmid have been prepared and used in complementation and regulation studies. The results of these studies suggest that livJ and livK are separated by approximately one kilobase and give a gene order of livJ-livK-livH. livJ and livK appear to be regulated in an interdependent fashion; livK is expressed maximally when the livJ gene is inactivated by mutation or deletion. The results support the existence of separate promoters for the livJ and livK genes. The effects of mutations in the rho and livR genes are additive on one another and therefore appear to be involved in independent regulatory mechanisms. Mutations in the rho gene affect both the LIV-I and leucinespecific transport systems by increasing the expression of livJ and livK, genes for the LIV-specific and leucine-specific binding proteins, respectively.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 49
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 1-43 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 50
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980) 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 51
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 101-116 
    ISSN: 0091-7419
    Keywords: λ receptor ; maltose-binding protein ; outer membrane permeability ; maltodextrin transport ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The λ receptor is a peptidoglycan-associated integral protein that spans the outer membrane. Beside its function in phage λ adsorption it participates in transport. The latter function can be summarized as follows: (1) Receptor allows the nonspecific permeation of small molecules other than maltose and maltodextrins (in close analogy to a molecular sieve). Here the only criterion for selectivity is size and it has the properties of an unspecific pore. In this respect, it is similar to the outer membrane proteins Ia, Ib, and Ic, the porins. (2) It is a binding protein for maltodextrins. Binding affinity is low but increases by a factor of 500 as the chain length of the maltodextrins increases. In contrast, the affinity of the periplasmic maltose-binding protein for maltose and maltodextrins is similarly high (in the μM range). (3) In the in vitro system of liposomes, the λ receptor facilitates specifically the diffusion of maltodextrins that exceed the size limit given by its porin function. This clearly demonstrates that the λ receptor alone is able to specifically overcome the permeability barrier of the outer membrane for maltodextrins. (4) From the genetic and kinetic analysis of maltose and maltodextrin transport, it can be concluded that the λ receptor interacts with the periplasmic maltose-binding protein. (5) Electron microscopic studies indicate a location for the maltose-binding protein in the outer cell envelope. This location is dependent on the presence of the λ receptor.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 52
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 117-130 
    ISSN: 0091-7419
    Keywords: S typhimurium histidine transport operon ; cloning ; E coli histidine transport ; genetics ; gene duplications ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The genes for the well-characterized high-affinity histidine transport system of S typhimurium have been cloned in λgt4. Genetic and physiological analyses of the analogous transport system of E coli were undertaken in order that available λ vectors, recombinant DNA techniques, and a genetic selection for transport function might be used to isolate the Salmonella genes. The presence of the transport genes on a 12.4 Kb cloned DNA fragment has been confirmed (1) genetically, by complementation studies; (2) physiologically, by the rates of histidine uptake by bacteria containing this DNA; and (3) by demonstrating that the cloned DNA codes for the previously identified transport proteins J and P. The isolated fragment carries the entire transport operon, the argT gene and the ubiX locus, but neither the purF gene nor the ack/pta loci.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 53
    ISSN: 0091-7419
    Keywords: 1H NMR ; periplasmic binding protein ; histidine-binding protein J ; membrane transport ; pore model ; transport of L-histidine ; Salmonella typhimurium ; substrate-induced conformational changes ; deuterated amino acids ; partially deuterated protein ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Genetic evidence suggests that the high-affinity L-histidine transport in Salmonella typhimurium requires the participation of a periplasmic binding protein (histidine-binding protein J) and two other proteins (P and Q proteins). The histidine-binding protein J binds L-histidine as the first step in the high-affinity active transport of this amino acid across the cytoplasmic membrane. High-resolution proton nuclear magnetic resonance spectroscopy at 600 MHz is used to investigate the conformations of this protein in the absence and presence of substrate. Previous nuclear magnetic resonance results reported by this laboratory have shown that there are extensive spectral changes in this protein upon the addition of L-histidine. When resonances from individual amino acid residues of a protein can be resolved in the proton nuclear magnetic resonance spectrum, a great deal of detailed information about substrate-induced structural changes can be obtained. In order to gain a deeper insight into the nature of these structural changes, deuterated phenylalanine or tyrosine has been incorporated into the bacteria. Proton nuclear magnetic resonance spectra of selectively deuterated histidine-binding protein J were obtained and compared to the normal protein. Several of the proton resonances have been assigned to the various aromatic amino acid residues of this protein. A model for the high-affinity transport of L-histidine across the cytoplasmic membrane of S typhimurium is proposed. This model, which is a version of the pore model, assumes that both P and Q proteins are membrane-bound and that the interface between these two proteins forms the channel for the passage of substrate. The histidine-binding protein J serves as the “key” for the opening of the channel for the passage of L-histidine. In the absence of substrate, this channel or gate is closed owing to a lack of appropriate interactions among these three proteins. The channel can be opened upon receiving a specific signal from the “key”; namely, the substrate-induced conformational changes in the histidine-binding protein J molecule. This model is consistent with available experimental evidence for the high-affinity transport of L-histidine across the cytoplasmic membrane of S typhimurium.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 54
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 147-163 
    ISSN: 0091-7419
    Keywords: gene fusions ; λ receptor ; major outer membrane proteins ; signal sequence mutations ; ribosome ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In the last few years, several laboratories have demonstrated that many proteins (both from eukaryotic and prokaryotic organisms) that are destined to be localized in noncytoplasmic locations initially are synthesized as a precursor with a 15-30 amino acid extension at the NH2-terminal end of the molecule. This extra peptide has been termed the signal sequence, and it has been proposed that this signal plays a role in the localization of the extracytoplasmic protein. We are studying the process by which proteins are exported to the envelope region of Escherichia coli. Our work deals primarily with the outer membrane proteins, λ receptor, the product of the lamB gene, and the major outer membrane (porin) proteins 1a and 1b, products of the ompF and ompC genes.Using techniques of gene fusion, we have demonstrated that information specifying the cellular location of the λ receptor is contained within the lamB gene. Furthermore, we have shown that this information is capable of directing even a normally cytoplasmic protein, β-galactosidase, to the outer membrane. Some of this information is contained within the signal sequence. Mutations that alter this sequence prevent export of the λ receptor protein. Again using techniques of gene fusion, we have shown that the signal sequence alone is not sufficient to cause export of β-galactosidase from the cytoplasm. Other information within the lamB gene is required.Selection procedures have been developed to isolate mutations that exhibit a general alteration in the export process. Genetic analysis of these mutations has provided evidence for the involvement of the ribosome in the process of protein localization.The structural genes for the porin proteins, 1a and 1b, are regulated at the transcriptional level by the ompB locus. This has permitted us to extend our studies on outer membrane protein localization to protein 1. With this genetic system, it should be possible to determine if E coli employs more than a single mechanism for the export of proteins to the outer membrane.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 55
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 165-174 
    ISSN: 0091-7419
    Keywords: 5′-p-fluorosulfonylbenzoyladenosine ; ATP binding site ; affinity probe ; Na+ ; K+-ATPase ; substrate analog ; dog kidney ; canine kidney ; catalytic subunit ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We have investigated the suitability of 5′-p-fluorosulfonylbenzoyladenosine (FSBA) as an ATP site affinity probe for the canine kidney Na+,K+-ATPase. The purified enzyme is slowly inactivated by this compound in suitable buffers, losing about half of its activity over a two-hour period. The rate of inactivation is more rapid in 0.1 M KCl than in 0.1 M NaCl. Low concentrations of ATP protect the enzyme against inactivation, with half-maximal effects at 4 μM ATP in 0.1 M NaCl and 350 μM ATP in 0.1 M KCl. ADP also protects against FSBA inhibition, but AMP is ineffective when present at 100 μM levels. This pattern is consistent with the previously described nucleotide specificity of the Na+,K+-ATPase. Addition of protective amounts of ATP after inactivation has occurred does not restore enzyme activity, indicating that inhibition is irreversible.Measurement of the concentration-dependence of FSBA inactivation suggests an apparent Kd for binding of this compound well above 1 mM, the solubility limit of the analog. This finding is reinforced by the failure of 1 mM FSBA to compete effectively with ATP for the high-affinity ATP site of the enzyme. Nevertheless, attachment of the analog to this site is indicated by its ability to prevent [3H]-ADP binding in proportion to the number of sites it has inactivated. Studies with [3H]-FSBA show that about 1 mole of the analog attaches specifically to the α subunit per mole of enzyme inactivated. A similar amount of nonspecific labeling also occurs with negligible effect on enzyme activity. These findings suggest that FSBA may be useful in probing the topography of the high-affinity ATP binding site of the Na+,K+-ATPase and related enzymes.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 56
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 175-182 
    ISSN: 0091-7419
    Keywords: adenosine release ; cyclic AMP ; neuroblastoma ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Previous work in our laboratory led us to postulate that N2a cells release adenosine into growth medium, where it acts at the extracellular adenosine receptors to modulate the sensitivity of the cells to the cyclic AMP-elevating effect of adenosine [Green, RD, J Pharmacol Exp Ther 201:610, 1977]. We have now devised a high-performance liquid chromatographic (HPLC) procedure capable of quantitating the concentrations of adenosine in cells and tissue culture media. Growth media of N2a cells and a variant of N2a cells deficient in hypoxanthine-guanine phosphoribosyltransferase (HGPRT-) contain 10-20 nM adenosine, while that of a variant deficient in adenosine kinase (AK-) is elevated severalfold. It appears that the concentration of adenosine in growth media is determined by both the rate at which it is released by cells into the medium and the rate at which it is metabolized by adenosine deaminase present in the serum in the growth medium. Both N2a and AK- cells release considerable amounts of adenosine into serum-free medium (SFM) over a short period. Adenosine release is greater from AK- cells and is accelerated by erythro-9-(2-hydroxy-3-nonyl)-adenine (EHNA), a potent adenosine deaminase inhibitor. This accelerated release is retarded by dipyridamole and homocysteine. Surprisingly, dipyridamole and 4-(3-butoxy-4-methoxybenzyl)-2-imidazolidinone (Ro 20 1724), a potent phosphodiesterase inhibitor, stimulate basal adenosine release from N2a but not from AK- cells. It remains to be determined if this is due to an effect of these compounds on adenosine kinase. These results give further support for the hypothesis that adenosine in growth medium modulates the sensitivity of the cells to the cyclic AMP-elevating affect of adenosine, and furthermore they suggest that adenosine in growth media may tonically stimulate adenylate cyclase and affect processes controlled by the cyclic AMP:cyclic AMP-dependent protein kinase system.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 57
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980) 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 58
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 411-419 
    ISSN: 0091-7419
    Keywords: turkey erythrocyte ; β-adrenergic receptor ; GTPase ; adenylate cyclase ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We have recently described the affinity chromatography purification of the turkey erythrocyte β-adrenergic receptor. The minute amounts obtained initially precluded extensive biochemical characterization. To improve the yield of the receptor, the erythrocyte membranes have been prepared by a new method. This procedure resulted in a 10-fold higher receptor density in comparison with the membrane preparation used previously. The new membranes also contained a catecholamine-sensitive guanine triphosphatase and an adenylate cyclase sensitive to Gpp(NH)p and l-epinephrine. Solubilization by a double digitonin extraction resulted in a preparation containing 4-6 pmoles of 3H-dihydroalprenolol binding sites per mg of membrane protein.A single step of affinity chromatography on alprenolol-sepharose of the soluble digitonin extract resulted in an additional 1,000-fold purification of the receptor. The overall purification factor was 20,000 relative to the binding activity of the crude membrane preparations.Electrophoresis in SDS-polacrylamide of iodinated purified β-receptors revealed, after autoradiography, the presence of four major components. Three of these, corresponding to molecular weights of 170,000, 33,000, and 30,000, respectively, were not affected by reduction with β-mercaptoethanol and were not observed when the digitonin extracts were loaded on the affinity gel in the presence of an excess of l-propranolol. A fourth 52,000-dalton component (60,000 daltons after reduction with β-mercaptoethanol) remained apparent even when affinity purification was prevented by addition of l-propranolol.Our results suggest that the β-adrenergic receptor is composed of at least three subunits that interact by noncovalent bonds.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 59
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 457-466 
    ISSN: 0091-7419
    Keywords: lymphocyte activating factor (LAF) ; Interleukin I ; purification of human IL-1 ; hollow fiber diafiltration ; isoelectric focusing ; polyacrylamide gel ; electrophoresis ; human monocytes ; endotoxin stimulation ; IL-1 release ; thymocyte mitogenic activity ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Interleukin I (IL-1) is a lymphocyte stimulant released by human monocytes cultured for 18-24 hours in tissue culture medium containing 5% serum and the non-specific immunostimulant lipopolysaccharide (LPS). Human IL-1 is found in the conditioned medium in a low molecular weight (∼ 13,000) and a high molecular weight (∼ 85,000) form. The high MW activity may result from the formation of a complex between IL-1 and serum constituents. During the course of purification, the low MW IL-1 activity is often recovered in a high MW form. Hollow fiber diafiltration and membrane ultrafiltration has been found to rapidly separate low MW IL-1 from all measurable protein with a yield of 4% of the original activity. The IL-1 which converts to the high MW form during the purification is recoverable, 21% of the original activity, but contains small amounts of serum proteins. Isoelectric focusing (IEF) of the low MW IL-1 resulted in a very highly purified sample which was analyzed by polyacrylamide gel electrophoresis (PAGE). Utilizing a new staining procedure which detects less than 1 ng of protein per band, the IEF-purified IL-1 revealed trace quantities ( 〈 1 ng) of a slowly migrating protein similar to immunoglobulin and no other bands. There were no bands which corresponded with the known electrophoretic mobility of IL-1. Since the samples applied to the gel contained significant biological activity, this result implies that human IL-1 is biologically active in picogram quantities.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 60
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 533-539 
    ISSN: 0091-7419
    Keywords: T lymphocytes ; TCGF ; continuous marrow cultures ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In the present study we investigated the presence of T-lymphocyte progenitors in the long-term murine bone marrow culture system described by Dexter: mature Thy-1 antigen-bearing T lymphocytes are lost in these cultures after a few days. By culturing nonadherent cells from such cultures in the presence of a supernatant of concanavalin A-stimulated spleen cells, a source of T-cell growth factor, we found that Thy-1 positive blast cells proliferated together with a second population of Thy-1 negative cells. These two populations of cells have been maintained in long-term in vitro cultures by passaging the cells in fresh conditioned medium at regular intervals. Moreover, we have been able to establish pure cultures of the Thy-1-bearing blast cells after separating them from the non-T cells using their adherence property to plastic surfaces. Long-term cultures of T lymphocytes can thus be established from long-term marrow cultures as well as from the spleen, thymus or fresh bone marrow.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 61
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 1-11 
    ISSN: 0091-7419
    Keywords: red cell membranes ; ATPase ; Ca2+ ; Mg2+ ; diamide ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: An Mg2+-dependent low ATPase activity can be detected in erythrocyte “white membranes,” in addition to that of the well known (Ca2+ + Mg2+)-ATPase. The thiol oxidizing agent diamide affects both activities. The oxidation of neighboring thiols seems to leave the mechanism of the (Ca2+ + Mg2+)-ATPase amplification system evoked by Ca2+ largely unaffected. The perturbation caused by diamide in the membranes seems to affect primarily a step of the ATP hydrolysis mechanism that is common to both ATPase activities. The effectiveness of diamide seems to be the same when either Ca2+ and Mg2+, or Mg2+ alone are present during the reagent action. Reduction of disulfide bonds by DTE after diamide treatment restores the (Ca2+ + Mg2+)-ATPase activity but is unable to take the Mg2+-ATPase activity back to the original level.The hypothesis is discussed that the redox state of one (or more than one) couple of —SH close to each other and possibly connected to the active site, may be an important factor in optimizing the efficiency of Ca action on the (Ca2+ + Mg2+)-ATPase.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 62
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 13-19 
    ISSN: 0091-7419
    Keywords: properties of acetylcholine receptor ; reconstitution of acetylcholine receptor ; subunit composition of acetylcholine receptor ; proteolysis of acetylcholine receptor ; Ca2+ activated protease ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Purified acetylcholine receptor reconstituted into liposomes catalyzes carbamylcholine-dependent ion flux [10]. An endogenous protease activated by Ca2+ gives rise to an acrylamide gel pattern of the receptor with the 40,000-dalton subunit apparently as the major component. Exogenous proteases nick the proteins so extensively that the acrylamide gel pattern reveals polypeptides of 20,000 daltons or less. In either case the receptor sediments at 9S, indicating that the polypeptide chains associated. Moreover, the nicked receptors bind α-bungarotoxin and catalyze carbamylcholine-dependent ion flux after reconstitution.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 63
    ISSN: 0091-7419
    Keywords: glucagon ; adenylate cyclase ; anaesthetics ; membrane bilayer fluidity ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The cationic local anaesthetics carbocaine and unpercaine were found to increase the fluoride-stimulated adenylate cyclase up to a maximum level; above this maximum level further increases in drug concentration inhibited the enzyme. At concentrations where this activity was stimulated, a fatty acid spin label detected an increase in bilayer fluidity, which, it is suggested, is responsible for the activation of the enzyme. A solubilized enzyme was unaffected by the drugs, a finding consistent with this proposal.These cationic drugs began to inhibit the glucagon-stimulated activity at concentrations where they activated the fluoride-stimulated activity. It is suggested that this is due to their effect on the coupling interaction between the receptor and catalytic unit.The anionic drugs, phenobarbital, pentobarbital, and salicylic acid, all inhibited the fluoride-stimulated enzyme. This may be due in part to a direct effect on the protein and in part to the interaction of the drugs with the bilayer. The drugs had small inhibitory effects on the lubrol-solubilized enzyme.The glucagon-stimulated enzyme was initially inhibited by the anionic drugs at low concentrations, then activated, and finally inhibited with increasing drug concentration. The reasons for such changes are complex, but there was no evidence from electron spin resonance studies to suggest that the elevations in activity were due to increases in bilayer fluidity.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 64
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980) 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 65
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 149-162 
    ISSN: 0091-7419
    Keywords: muscarinic receptor ; [3H] cis methyldioxolane ; regulation ; guanine nucleotides ; N-ethylmaleimide ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The regulation of muscarinic receptor binding by guanine nucleotides and N-ethylmaleimide (NEM) was investigated using the agonist ligand, [3H] cis methyldioxolane ([3H] CD). Characterization studies on rat forebrain homogenates showed that [3H] CD binding was linear with tissue concentration and was unaffected by a change in pH from 5.5 to 8.0. The regional variation in [3H] CD binding in the rat brain correlated generally with [3H] (-)3-quinuclidinyl benzilate ([3H] (-)QNB) binding, although the absolute variation in binding was somewhat less. At a concentration of 100 μM, the GTP analogue, guanyl-5′-yl imidodiphosphate [Gpp(NH)p], caused a 43-77% inhibition of [3H] CD binding in the corpus striatum, ileum, and heart. The results of binding studies using several Gpp(NH)p concentrations demonstrated that the potency of this guanine nucleotide for inhibition of [3H] CD binding was greater in the heart than in the ileum. In contrast to its effects on [3H] CD binding, Gpp(NH)p caused an increase in [3H] (-)QNB binding in the heart heart and ileum and no change in [3H] (-)QNB binding in the corpus striatum. When measured by competitive inhibition of [3H] (-)QNB binding to the longitudinal muscle of the ileum, Gpp(NH)p (100 μM) caused an increase in the IC50 values of a series of agonists in a manner that was correlated with the efficacy of these compounds. The results of binding studies on NEM treated forebrain homogenates revealed an enhancement of [3H] CD binding by NEM.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 66
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 201-208 
    ISSN: 0091-7419
    Keywords: Fc fragments ; immune complexes ; macrophages ; polyclonal antibody response ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Murine splenic B lymphocytes are induced to proliferate and undergo polyclonal activation in the presence of Fc fragments, AHGG, antigen-antibody complexes, and CH3 fragments derived from plasmin digestion of human Ig. The unifying feature of the polyclonal antibody response induced by these agents is that in all cases a portion of the constant region of the Ig molecule (ie, Fc region) is present. Fragments of Ig lacking the Fc piece, such as Fab and F(ab′)2 were found not to be stimulatory. In addition, a model is proposed to account for the regulatory effects of antigen-antibody complexes on an ongoing humoral immune response.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 67
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 175-182 
    ISSN: 0091-7419
    Keywords: T cell ; constant region ; receptor ; suppressor ; lymphocyte surface antigen ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: An anti-T cell serum raised in allotype congenic mice recognizes the product of a new locus coding for a heavy chain-linked polypeptide found on a subpopulation of T cells. Anti-Tsd raised in BALB/cAnN mice against selected C.AL-20 T cells reacts with a cell surface antigen in virgin animals that is found on 25% of mature thymocytes and Lyt-bearing T cells, but not on prothymocytes, Lyt1 T cells or B cells. The antigen is restricted to strains bearing the Ig-1d and Ig-1e heavy chain allotype haplotypes, and is expressed in the F1 animal. The antigen is unlinked in expression to the Lyt2, H-2, or kappa light chain loci. The antigen is not detected in the hematopoietic cells in the bone marrow and appears to mark only the mature peripheral pool of T cells. As previously reported, the antiserum blocks the binding of suppressor T cells to the cross-reactive idiotype for arsonate, while reagents specific for Fab, Fc and Ig were ineffective. It seems probable that the marker may represent a T cell constant region marker analogous to the Igh products on immunoglobulin. Antiserum against this marker induces in vivo triggering of Ts cells for a wide variety of T-dependent antigens. All subclasses of anti-hapten antibodies are suppressed; no affinity restrictions or clonotype specificity is observed in suppressed adult mice. Results suggest that precursor T cells regulating major serum idiotypes regulate individual idiotypes.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 68
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 183-199 
    ISSN: 0091-7419
    Keywords: primary and secondary hormones ; mitogenicity ; insulin ; insulin-like growth factor ; nerve growth factor ; relaxin ; epidermal growth factor ; receptor-mediated endocytosis ; lysomes ; hormone mechanisms ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Polypeptide growth factors are substances that stimulate an increase in cell size and/or cell number during embryonic development. In some cases, they have a similar effect on tissues in the mature organism where they function as “maintenance” factors to sustain cell viability. While their profound impact on cell behavior is well recognized, their relationship to other regulators of cell function has remained generally ill-defined. However, the developing appreciation of their hormone-like behavior suggests that they may be conveniently grouped with many other endocrine agents to form a broader group of secondary hormones. The utility of the classification is illustrated by the insulin-related family of molecules. It also serves to emphasize the similarities in function shared by many of these substances including trophic stimulation and modulation of gene expression. Internalization, though, appears to be another common feature. However, whether the uptake of the growth factor mediates an intracellular action or is designed solely to regulate responsiveness at the cell surface and/or degradation remains an important unanswered question. A brief review of two growth factors (nerve growth factor and epidermal growth factor) serves to outline the possible functions that may be served by this endocytotic process.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 69
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 209-214 
    ISSN: 0091-7419
    Keywords: growth regulation ; epidermal growth factor ; density inhibition of growth ; extracellular matrix ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The role of the binding of succinylated concanavalin A to tissue culture cells in influencing epidermal growth factor (EGF)-mediated cell proliferation has been studied. Succinylated concanavalin A dramatically reduces the stimulation of 3T6 cells by EGF in Dulbecco's modified Eagle's medium (DME) containing insulin and vitamin B12 as additional growth factors, but no serum. Furthermore, binding studies using 125I-labeled EGF have shown that the binding of EGF to the cell surface is reduced upon addition of succinylated concanavalin A.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 70
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 215-222 
    ISSN: 0091-7419
    Keywords: T lymphocyte progenitors ; colonies ; CFU-preT ; bone marrow ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Thy-1.2 negative progenitors give rise to Thy-1.2 positive colony cells when mouse bone marrow is cultured in vitro. The bone marrow cells are immobilized in a viscous medium containing methyl cellulose; discrete colonies are identifiable at 2 days and contain 30-60 cells by day 3 of culture. Colonies are tightly packed spheres (raspberries) and grow suspended in the gel. Growth of the raspberry colonies is absolutely dependent upon the presence of the appropriate serum (horse or human; not fetal calf) and conditioned medium from pokeweed mitogen-stimulated mouse spleen cells. As little as 0.1% of the conditioned medium is sufficient to promote raspberry colony growth. Under these conditions, nude mouse bone marrow yields as many colonies (1 per 1,000 nucleated cells plated) as normal marrow. Thymus, lymph node; and spleen (normal or nude) do not form colonies. Colony precursors are predominantly in S phase of the cell cycle, as determined by tritiated thymidine suicide of fresh bone marrow. Their numbers fall with age. Because the cells in colonies are Thy-1 positive, peanut agglutinin-positive, and active in a pre-T cell synergy assay, we conclude that their precursors are early committed T cell progenitors, and propose that they be called CFU-preT.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 71
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 233-240 
    ISSN: 0091-7419
    Keywords: smooth surface tumorigenesis ; cell differentiation ; BALB/3T3 ; mesenchymal precursor cells ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The BALB/3T3 clone A31 mouse embryo cell line has been used by many investigators as a model “normal” “fibroblast” line for a variety of in vitro studies. It has been shown, however, that these cells are not “normal” because they will produce tumors within 2-4 months if 3 × 104 cells are implanted subcutaneously in BALB/c mice attached to 0.2 × 5 × 10-mm plastic plates. Previous studies also suggested that these cells were not fibroblasts because they gave rise to tumors with the characteristics of vascular endothelium not fibroblasts. We now report that BALB/3T3 (clone A31), BALB/3T3-T, a proadipocyte subclone of clone A31 cells, and six recent subclones of BALB/3T3-T cells show additional differentiation patterns when tumors derived by implantation of these cells attached to plastic plates are examined. Differentiation into pericytes, chondrocytes, and fibroblasts was observed. We conclude that the BALB/3T3 clone A31 cell line and related lines are multipotent mesenchymal cells which are capable of differentiation into a variety of cell types.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 72
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 241-254 
    ISSN: 0091-7419
    Keywords: cytoskeletons ; cell growth ; protein kinase ; morphology ; cyclic AMP ; phosphorylation ; transformation ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Treatment of transformed Chinese hamster ovary cells with dibutyryl cAMP or other agents that elevate cAMP results in the acquisition of growth and morphology characteristic of normal fibroblasts. The role of specific protein phosphorylation in this process of morphological reversion has been examined using metabolic labelling of Chinese hamster ovary (CHO) cells with 32P-orthophosphate in the presence or absence of N6O2′-dibutyryladenosine 3′:5′-cyclic monophosphoric acid (Bt2cAMP). Analysis of labelled cultures by SDS gel electrophoresis and radioautography demonstrate dramatic changes in the phosphorylation of only 2 cellular proteins during reverse transformation. A 55,000 dalton protein (pp55) was phosphorylated and a 20,000 dalton protein (pp20) was dephosphorylated. The time course of these events was consistent with the kinetics of morphological reversion. The lower molecular weight species, pp20, was dephosphorylated within 15-30 minutes, prior to all morphological changes except membrane tranquilization. The higher molecular weight protein, pp55, was maximally phosphorylated over 1-2 hours following addition of Bt2cAMP, paralleling early stages in the establishment of fibroblastic form. The phosphorylated forms of pp20 and pp55 were both extracted from cellular cytoskeletons by 0.5% Triton X-100, but analysis of 35S-methioninelabelled cultures suggested that unphosphorylated pp 20 may be bound to the cytoskeleton. Since pp20 was found to comigrate with the 20,000 dalton myosin light chain, it is possible that dephosphorylation of CHO cell myosin induced by cAMP may alter its interaction with actin microfilaments and modulate the assembly of stress fibers during morphological reversion.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 73
    ISSN: 0091-7419
    Keywords: retroviruses ; embryonal carcinoma ; viral DNA forms ; transfection ; diazobenzyloxymethylpaper transfer ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Replication of Gross strain N-tropic type C retrovirus was markedly restricted in a pluripotential undifferentiated embryonal cell line (PCC4) of murine teratocarcinoma, whereas the same virus could cause productive infection in a myoblast-derived differentiated line (PCD1) of the same tumor origin. To investigate the restriction mechanism, we compared the initial viral DNA formation in these two cell lines. Analyses by means of a modified Hirt extraction procedure and a modified Southern gel transfer method indicated that PCC4 and PCD1 cells supported the synthesis of viral DNA intermediates after inoculation of the Gross virus. In both cells, a linear DNA duplex (form III viral DNA) appeared at 4 hr, reached a maximal level at 8-9 hr, and declined rapidly thereafter, while two closed-circular supercoiled DNA duplexes (form I viral DNA) showed their appearance, increase and decline in the 8-24 hr period. During the period from 34 to 78 hr after virus inoculation, another burst of viral DNA synthesis occurred in PCD1 cells, presumably due to secondary virus infection, while at this period both form III and form I viral DNAs became undetectable in PCC4 cells. The Hirt supernatant DNAs prepared from PCD1 and PCC4 cells 10 hr after virus inoculation were equally infectious for NIH3T3 cells in a DNA transfection assay. Both PCD1 and PCC4 cells were very poor recipients for DNA transfection, although one positive result with PCD1 cells might suggest a difference between the two cell types in this aspect. These results indicate that restriction of type C retrovirus in undifferentated embryonl carcinoma cells occurs at a step subsequent to formation and maturation of viral DNA intermediates.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 74
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980) 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 75
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 267-279 
    ISSN: 0091-7419
    Keywords: acetylcholine receptor ; experimental autoimmune myasthenia gravis ; antigen-binding fragments ; subunit antisera ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Conditions are described for an assay that allows the percent inhibition of α-bungarotoxin binding to acetylcholine receptors by antisera and monovalent antigen-binding fragments of antibody molecules (Fab) to be determined. Anti-Torpedo californica acetylcholine-receptor antisera, prepared in New Zealand White rabbits and Lewis rats, were tested for the ability to inhibit [125I]-α-bungarotoxin binding to membrane-associated and detergent-solubilized T californica acetylcholine receptors. Similar inhibition studies were performed using rabbit antisera and antigen-binding fragments prepared against each of the four acetylcholine receptor subunits. Antisera and antigen-binding fragments prepared against intact receptor could inhibit a maximum of 50% of the α-bungarotoxin binding to solubilized receptor. The results using monovalent antigen-binding fragments indicated that the inhibition was not due to antibody-mediated aggregation of receptor molecules. Rabbits and rats immunized with receptor denatured by sodium dodecyl sulfate all produced antisera that could bind to nondenatured receptor, but none of these animals developed experimental autoimmune myasthenia gravis. These results suggest that the antigenic determinants present on acetylcholine receptors responsible for induction of experimental auto-immune myasthenia gravis are lost with sodium dodecyl sulfate denaturation. A strong correlation was also observed between the presence of experimental autoimmune myasthenia gravis in rats and rabbits and the ability of the antisera from these animals to inhibit 50% of α-bungarotoxin binding to solubilized acetylcholine receptors.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 76
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 295-303 
    ISSN: 0091-7419
    Keywords: sodium channels ; neurotoxins ; ion transport ; photoaffinity labelling ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Anthopleurin A, a polypeptide toxin from the Pacific sea anemone Anthopleura xanthogrammica, enhances persistent activation of voltage-senstive sodium channels by the alkaloid toxins veratridine and batrachotoxin with K0.5 = 20 nM. This effect is inhibited by depolarization. There is a close correlation between enhancement of sodium channel activation and block of [125I] scorpion toxin binding by unlabeled scorpion toxin, sea anemone toxin II from Anemonia sulcata, and Anthopleurin A, indicating that these three polypetide toxins interact with a common receptor site in modifying sodium channel function. Photoactivable derivatives of scorpion toxin label a single Mr ∼ 250,000 polypeptide chain at the polypeptide toxin receptor site. Labeling is blocked by unlabeled scorpion toxin or depolarization and is not observed in variant neuroblastoma clones, which lack sodium channels. These results identify a protein component of the polypeptide toxin receptor site of voltage-sensitive sodium channels.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 77
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 305-311 
    ISSN: 0091-7419
    Keywords: in vitro synthesis ; branched-chain amino acid binding proteins ; precursors ; processing ; periplasmic proteins ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The synthesis of the leucine-specific and LIV-binding proteins was examined in vitro in a coupled transcription/translation system using the hybrid plasmids pOX7 and pOX13 as templates. Plasmid pOX7 contains the livK gene coding for the leucine-specific binding protein, and pOX13 contains the liv J gene coding for the LIV-binding protein. Both binding proteins were synthesized in vitro as precursor forms with molecular weights approximately 2,500 greater than their respective mature forms. Conversion of the precursor forms to their mature forms occurred during post-translational incubation following synthesis in the presence of membrane. The precursor of the LIV-binding protein was processed more rapidly than the leucine-specific binding protein precursor. Processing activity could be removed from the in vitro synthesis system by centrifugation, suggesting that the processing activity was membrane associated. Restoration of post-translational processing activity was achieved by adding inside-out membrane vesicles to membrane-depleted reaction mixtures.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 78
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 313-328 
    ISSN: 0091-7419
    Keywords: skeletal muscle ; myogenesis ; chick embryo ; hyaluronic acid ; glycosaminoglycan ; extracellular matrix ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: During chick embryogenesis, massive alterations occur in the migrating cell's substratum, or extracellular matrix. The possibility that some of the components of this milieu play a regulatory role in cell differentiation was explored in a cell-culture system derived from embryonic chick skeletal muscle tissue. In particular, the effects of collagen and the glycosaminoglycans were studied. Collagen is required for muscle cell attachment and spreading onto plastic and glass tissue-culture dishes. A major constituent of the early embryonic extracellular space, hyaluronate (HA), while having no significant effect on collagen-stimulated cell attachment and spreading, was found to inhibit myogenesis. The muscle-specific M subunit of creatine kinase was preferentially inhibited. Control experiments indicated that the inhibition was specifically caused by HA and not by other glycosaminoglycans. A general metabolic inhibition of the cultures was not observed. Muscle cells could bind to HA-coated beads at all stages of differentiation but were inhibited only when HA was added within the first 24 h of culture. Endogenous GAG in the culture is normally degraded during the first 24 h after plating as well; this may parallel the massive degradation of HA that occurs in the early embryo in vivo. These findings suggest a regulatory role for HA in modulating skeletal muscle differentiation, with degradation of an inhibitory component of the cell substratum a requirement for myogenesis.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 79
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980) 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 80
    ISSN: 0091-7419
    Keywords: human fibroblast ; ascorbate ; procollagen ; fibronectin ; axial periodicity ; native collagen fibrils ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Fibronectin and collagens are major constituents of the cell matrix of fibroblasts. Fibronectin is a 220,000 dalton glycoprotein that mediates a variety of adhesive functions of cells examined in vitro. Fibronectin is secreted in a soluble form and interacts with collagen to form extracellular filaments. Fibronectin and procollage type I were localized using the peroxidase anti-peroxidase method. Under standard culture conditions, fibronectin and procollagen were localized to non-periodic 10 nm extracellular fibrils, the cell membrane and plasma membrane vesicles. Ascorbate treatment of cells leads to a new larger fibril with a diameter of approximately 40 nm. Antibodies to fibronectin and procollagen I react to these native collagen fibrils with an axial periodicity of approximately 70 nm. Fibronectin is clearly associated with native collagen fibrils produced by ascorbate treated cells and there is an asymetric distribution or segregation of fibronectin on these collagen fibrils with a 70 nm axial repeat.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 81
    ISSN: 0091-7419
    Keywords: lipoprotein ; trypsin ; dielectric measurements ; counterions ; α-dispersion ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The relative permittivity of aqueous solutions of human serum low density lipoprotein (LDL) and partially trypsin digested lipoprotein (T-LDL) has been determined for various concentrations at 20°C over the frequency range 0.15-100 MHz. Comparison of the dielectric dispersion curves for the digested lipoprotein with those for the native preparation revealed a larger low-frequency dielectric increment, which may be attributed to an increase in the number of counterions moving over the surface of the molecule. An explanation of this observation is an elevation of 70% in the net negative charge on the surface of the trypsin-treated particle as compared to its native counterpart.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 82
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 35-46 
    ISSN: 0091-7419
    Keywords: estrogen receptor ; glucocorticoid receptor ; estradiol ; diethylstilbestrol ; dexamethasone ; B-16 mouse melanoma ; Syrian hamster melanoma ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The Transplantable B-16 melanotic melanoma carried in syngeneic C57B1/6J female mice and the Syrian hamster melanoma cell line, RPMI 3460, were utilized to determine whether steroid-hormone receptors are present in animal melanomas. In the B-16 melanoma, a cytoplasmic-estrogen receptor is detectable, but there is no evidence for androgen or progestin receptors. Some tumors contain a glucocorticoid-binding macromolecule. Sucrosedensity gradient centrifugation of cytosol after incubation with [3H]-estradiol revealed an 8S peak that was suppressed by excess radioinert diethylstilbesterol. Binding varied from 5-35 fmoles per mg cytosol protein. Scatchard analysis of [3H]-estradiol binding in cytosol yielded a single class of high-affinity binding sites; the dissociation constant is 6 × 10-10 M. The receptor molecule is shown to be estrogen-specific by ligand competition assays. In contrast to B-16 melanoma, no estrogen, androgen, or progestin receptor can be found in the Syrian hamster melanoma cell line. However, a substantial level of specific binding is observed using [3H]-dexamethasone. Sucrose-gradient centrifugation of cytosol from this cell line after incubation with [3H]-dexamethasone revealed a 7S peak that was suppressed by excess radioinert dexamethasone. Scatchard analysis indicated a single class of high affinity sites with a dissociation constant of 2 × 10-9 M. Binding levels from 70-610 fmoles per mg cytosol protein were observed. The Syrian hamster melanoma cells also exhibit a biological response to glucocorticoids: Dexamethasone causes both an inhibition of growth and a decrease in final-cell density in these cells.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 83
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 1-13 
    ISSN: 0091-7419
    Keywords: human erythrocyte membranes ; membrane microvesicles ; sialoglycopeptides ; protein content of membranes ; enzymic content of membranes ; acetylcholinesterase ; Mg++-ATPase ; Na+ ; K+-ATPase ; NADH oxidoreductase ; GAPD of membranes ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Shearing of ghosts in a French pressure cell produces three classes of microvesicles that differ from endocytic vacuoles, exocytic vacuoles, and inside-out vesicles. It was thought that an analysis of these vesicles might provide some clues about the assembly of proteins within the human erythrocyte membrane. The microvesicles were separated into three visible bands, labeled top, middle, and bottom, and assayed for activity of Mg++-ATPase, Na+, K+-ATPase, acetylcholinesterase, glyceraldehyde-phosphate dehydrogense, and NADH oxidoreductase. Their proteins were also characterized by polyacrylamide gel electrophoresis with both Coomassie blue staining, to assess total protein content and distribution, and PAS-staining, to characterize sialoglycopeptides. In order to minimize problems inherent in ghost preparation, Dodge or hypotonic ghosts and glycol or isotonic ghosts were used in all studies. Middle membrane vesicles most resembled intact ghosts. Top vesicles had reduced levels of NADH oxidoreductase and more PAS-2 at the expense of PAS-1. The bottom vesicle class was very much enriched with PAS-1 at the expense of PAS-2, and PAS-3 was completely absent. In addition bottom vesicles had highest NADH oxidoreductase activity but lowest activity of all the other enzymes measured. These vesicle classes could not have been produced by tangential shearing through the membrane, nor could radial shearing through a membrane in which all proteins were free to move laterally have accounted for the three discrete vesicle classes or for their different patterns of enzymes and proteins. The analysis of the microvesicles produced by shearing is most consistent with radial shearing through membranes where there may be fixed domains superimposed on the basic fluid-mosaic structure.
    Additional Material: 9 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 84
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 53-65 
    ISSN: 0091-7419
    Keywords: α-actinin ; plasma membranes ; actin attachment ; immunoautoradiography on gels ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The role of α-actinin in the attachment of actin to plasma membranes has been investigated. Specific antibody staining of SDS gels has indicated that α-actinin is a major component in isolated plasma membranes prepared from three different cell types by two different procedures. Using specific extraction conditions, most of the α-actinin can be selectively extracted from the membranes with relatively little parallel release of actin. This selective dissociation of α-actinin from the plasma membrane leads us to conclude that α-actinin is present in these membrane preparations, because it is bound to actin, and that α-actinin does not form a direct link between actin and the membrane.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 85
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 93-100 
    ISSN: 0091-7419
    Keywords: riboflavin ; vitamin ; Bacillus subtilis ; binding activity ; membrane vesicle ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Riboflavin uptake and membrane-associated riboflavin-binding activity have been investigated in Bacillus subtilis. The uptake and binding activity of the vitamin were found to be repressed coordinately by riboflavin present in the growth medium. The uptake of riboflavin has been shown to have properties of a carrier-mediated process, and membrane vesicles have been shown to demonstrate riboflavin counterflow and exchange. The membrane-associated binding activity for riboflavin has been solubilized with detergents, and a procedure for the partial purification of this component is described. The partially purified riboflavin-binding component has properties expected for a carrier involved in riboflavin uptake, as it shows saturation kinetics and is inhibited by riboflavin analogues. Evidence is also presented showing that reduced riboflavin binds to a greater extent than oxidized riboflavin, and the possible role of the reduced riboflavin in riboflavin uptake is discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 86
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 83-92 
    ISSN: 0091-7419
    Keywords: H halobium ; sodium transport ; retinal protein ; light-energy transduction ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Light-induced sodium extrusion from H halobium cell envelope vesicles proceeds largely through an uncoupler-sensitive pathway involving bacteriorhodopsin and a proton/sodium antiporter. Vesicles from bacteriorhodopsin-negative strains also extrude sodium ions during illumination, but this transport is not sensitive to uncouplers and has been proposed to involve a light-energized primary sodium pump. Proton uptake in such vesicles is passive, and under steady-state illumination the large electrical potential (negative inside) is just balanced by a pH difference (acid inside), so that the protonmotive force is near zero. Action spectra indicated that this effect of illumination is attributable to a pigment absorbing near 585 nm (of 568 for bacteriorhodopsin). Bleaching of the vesicles by prolonged illumination with hydroxylamine results in inactivation of the transport; retinal addition causes partial return of the activity. Retinal addition also causes the appearance of an absorption peak at 588 nm, while the absorption of free retinal decreases. The 588 nm pigment is present in very small quantities (0.13 nmole/mg protein), and behaves differently from bacteriorhodopsin in a number of respects. Vesicles can be prepared from bacteriorhodopsin-containing H halobium strains in which primary transport for both protons and sodium can be observed. Both pumps appear to cause the outward transport of the cations. The observations indicate the existence of a second retinal protein, in addition to bacteriorhodopsin, in H halobium, which is associated with primary sodium translocation. The initial proton uptake normally observed during illumination of whole H halobium cells may therefore be a passive flux in response to the primary sodium extrusion.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 87
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 191-197 
    ISSN: 0091-7419
    Keywords: growth factors ; growth inhibitors ; models of growth control ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Present understanding of the control of animal cell proliferation is summarized briefly. Major gaps in present knowledge are listed. Models of growth control are discussed.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 88
    ISSN: 0091-7419
    Keywords: reconstitution ; ribose ; transport ; Escherichia coli ; Salmonella typhimurium ; ribose-binding protein ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Highly purified ribose-binding protein from Escherichia coli has been used to reconstitute a binding-protein-dependent ribose transport in spheroplasts derived from a binding-protein-deficient mutant of E coli K 12, and in spheroplasts derived from Salmonella typhimurium. The cross-species reconstitution was nearly as efficient as the reconstitution of the E coli strain from which the binding protein was derived. Antibody raised against the ribose binding protein completely prevented reconstitution, whereas it had no effect on whole cells. The reconstitution procedure has been improved by generating spheroplasts from cells grown in a rich medium and by reducing the background uptake in spheroplasts through a special washing procedure. Rapid purification of ribose binding protein by high pressure liquid chromatography is also described.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 89
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 199-209 
    ISSN: 0091-7419
    Keywords: erythropoiesis ; granulopoiesis ; colony stimulating factors ; hematopoiesis ; erythroid cell-growth ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Medium conditioned by the monocyte-like cell line GCT contains colony-stimulating activity (CSA), a mediator of in vitro granulopoiesis. Also, the conditioned medium (CM) contains erythroid-enhancing activity (EEA), which can be demonstrated in a system utilizing either nonadherent marrow or blood mononuclear cells, erythropoietin (1-2 units/ml), and 20 ml/dl fetal calf serum. Under these conditions, GCT CM enhances the growth of CFU-E and BFU-E. Attempts were made to characterize the molecular features of EEA. Serum-free GCT cell CM was fractionated on Sephacryl S200 and Ultrogel AcA54. EEA and CSA cochromatographed with apparent molecular weights of ∼ 40,000 daltons on Sephacryl and ∼ 30,000 daltons on Ultrogel. Fractionation on DEAE Sephacel led to an apparent separation of CSA from EEA; however, when diluted, the fractions containing CSA had EEA. Undiluted fractions containing potent CSA inhibited erythropoiesis; however, dilution of these fractions resulted in marked EEA. Diluted crude GCT CM and DEAE Sephacel fractions enriched in EEA were also capable of sustaining BFU-E in liquid culture and mediating erythropoietin-independent colony growth. CSA could not be unequivocally separated from EEA on concanavalin A-Sepharose, since the diluted void volume containing CSA also had EEA. EEA was present in CM boiled for 60 minutes, whereas CSA was markedly reduced but not abolished. The inverse relationship between CSA concentration and EEA mandates dilution of fractions when bioassayed for these two activities. Although CSA and EEA are similar in molecular weight, they appear to be partially separable by ion-exchange chromatography and heat stability.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 90
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 229-241 
    ISSN: 0091-7419
    Keywords: T-cell growth factor ; T-cell proliferation ; cellular regulation ; B-lymphoblastoid cell lines ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Using conditioned media (CM) from phytohemagglutinin (PHA)-stimulated peripheral blood lymphocytes (PBL) we observed long-term selective growth of T-cells from normal human donors. This T-cell growth was continuously dependent on addition of a factor called T-cell growth factor (TCGF). The optimal method for preparing highly active CM from single donor PBL involves the addition of mitomycin C-treated B-lymphoblastoid cell lines to the mixture of PBL and PHA. A number of different cell lines greatly augmented the production of TCGF in 18/18 cases. Preparation of plasma membranes from the Daudi cell line could replace the intact cells in the production of TCGF but those from the cell line, Molt-4, could not. Since the cell surface of Daudi possesses HLA-D antigens but not HLA-A, B, and C, and Molt-4 has HLA-A and B and not HLA-D, it is possible that the Ia antigens (HLA-DRW in man) are important in the release of TCGF. Using this method for growth factor production, an analysis was made concerning the events necessary for lymphocyte activation and the requirements for production and release of TCGF. Removal of PHA 12 hr after incubation had no effect on lymphocyte transformation but decreased TCGF release by 90%. In addition, colchicine and cytosine arabinoside inhibited DNA synthesis but had no effect on TCGF release. Little or no TCGF activity was present after cellular protein synthesis was inhibited by puromycin and cycloheximide. These results suggest that TCGF production: (a) requires protein synthesis; (b) requires binding of the stimulating agent; (c) can occur in a non-dividing cell, probably a terminally differentiated T-cell, without the need for cellular proliferation; and (d) needs the assistance of an adherent cell which probably is a monocyte-macrophage. The ability to produce TCGF from single human donors will allow better understanding of the nature and action of TCGF.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 91
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 243-253 
    ISSN: 0091-7419
    Keywords: embryonal carcinoma cells ; laminin ; extracellular matrices ; basement membranes ; retinoic acid ; embryogenesis ; parietal endoderm ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In this paper we have examined the growth and differentiation of the embryonal carcinoma cell line, F9, in the defined medium EM-3 at low density. We show that the growth of F9 and their differentiated cells (F9-diff) in EM-3 is strongly density dependent. At low cell densities the growth of both cell types is severely limited and most of the cells do not survive. Although this poses a problem for working with F9 and F9-diff in EM-3, it provides a convenient assay for identifying molecules that support their growth at low density. Using this assay, we have determined that laminin, a newly isolated glycoprotein of basement membranes, significantly improves the growth and short-term survival of both F9 and F9-diff. However, addition of laminin to EM-3 is insufficient to promote the clonal growth of these cell types. Our findings also indicate that laminin promotes the attachment of F9 and F9-diff in defined media. On the basis of our results, we propose an attachment function for laminin during the early stages of mammalian development.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 92
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 255-269 
    ISSN: 0091-7419
    Keywords: erythroid precursors ; glycophorin A ; spectrin ; bone marrow ; anemic mouse spleen ; plasma membrane ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Specific antibodies to human glycophorin A and spectrin were used to study the expression of these membrane proteins in normal and pathologic human bone marrow. In immunofluorescence experiments spectrin and glycophorin A are found in 50-60% of the nucleated cells in normal bone marrow. These two proteins are expressed at all stages of red cell differentiation and can be traced at least to the earliest morphologically recognizable nucleated red cell precursor, the proerythroblast; the two proteins are specific for cells of the red cell series and are not found to be expressed in lymphocytic, granulocytic cells or platelets. These conclusions were drawn from studies on bone marrow in patients with a temporary block in erythropoiesis at the level of stem cells or of the pronormoblast. Bone marrow from these individuals either lacked all nucleated cells stainable for glycophorin A and spectrin or contained only pronormoblasts. Similar findings were obtained on spleen cells from mice which were made severely anemic by multiple injections with N-acetyl-phenylhydrazine. Antibodies to a sialoglycoprotein isolated from mouse red cell membranes stain 70-80% of all cells in the spleen of anemic animals, while only 1-2% of such cells are seen in the spleen of normal animals. Spectrin and glycophorin A could be labeled metabolically and isolated using specific antibodies. The human tumor cell line K562 expresses both membrane proteins, but induction experiments with various agents thus far have failed to change their expression.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 93
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980) 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 94
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 271-280 
    ISSN: 0091-7419
    Keywords: Interleukin 2 ; cytotoxic lymphocytes ; UV irradiation ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The lymphokine Interleukin 2 (IL2) restores T cell responses in a number of in vitro systems where immunogenicity has been compromised. UV irradiation of the stimulating allogeneic cells in a mixed leukocyte culture eliminates the production of cytotoxic T lymphocytes and greatly reduces the DNA synthesis response. IL2 restores both parameters. UV-irradiated stimulators are also unable to induce the normal production of IL2 which is observed in a mixed leukocyte culture. The cytotoxic activity of allogeneically stimulated thymocytes is almost completely lost within 24 hours after removal of IL2 at 5 days, indicating that the lymphokine is continuously required to maintain CTL. Thymocytes in 4-day cultures do not adsorb IL2 unless they are simultaneously activated with a mitogen. Finally, IL2 does not adequately restore a secondary response to the purified protein derivative of tuberculin (PPD) in adherent-cell-depleted cultures, indicating that macrophages, in addition to being required for IL2 production, have other functions. These probably include the presentation of soluble antigens to responding cells.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 95
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 305-313 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 96
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 281-294 
    ISSN: 0091-7419
    Keywords: glycosaminoglycans ; cell cycle ; biosynthesis ; fibroblasts ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Cultures of embryonic fibroblasts from Balb/c or CBA/J mice were given 12-h pulses of 14C-galactose, or were double-labelled with 3H-galactose and 35H-sulfate. The time course of the rates of labelling of glycosaminoglycans - galactose label was found in the uronic acid moiety - was studied in synchronously and asynchronously growing cultures. Partial synchrony was achieved by trypsinising quiescent, confluent cells and subsequent transfer of cells to new cultures with fresh medium. Synchrony was monitored by measurement of thymidine uptake in parallel cultures. The distribution of label in the hyaluronic acid, chondroitin sulfate, and heparan sulfate fractions from cells and culture media was determined at each time point.Peaks of DNA synthesis were accompanied by or followed 12 h later by a maximal rate of labelling with galactose of secreted glycosaminoglycans, and - with the exception of hyaluronic acid - also of cellular glycosaminoglycans. The rate of labelling with galactose of glycosphingolipids in parallel cultures followed a different time course. In double-label experiments the rates of labelling of glycosaminoglycan sulfates with 3H-galactose and 35S-sulfate did not go parallel. In older, quiescent cultures the labelling rate with galactose decreased while the sulfation rate increased.It is discussed that the labelling rate with galactose is indicative of the biosynthetic rate of the glycosaminoglycans. The conclusion is reached that glycosaminoglycans are preferentially synthesized and secreted after the S phase of the cell cycle.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 97
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 13 (1980), S. 385-394 
    ISSN: 0091-7419
    Keywords: insulin-like ; somatomedin ; chick chondrocytes ; peptides ; HPLC ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Plasma contains a number of insulin-like activities (ILA) of molecular weights 7,000 to 90,000 (somatomedins and insulin-like proteins) which stimulate cellular metabolism and may function as growth factors. We have found evidence for the presence of an 800 Dalton peptide in human plasma which markedly stimulates the metabolism of chick chondrocytes.This peptide was extracted from human Cohn fraction IV-1 by procedures similar to those used for somatomedin isolations. At the Sephadex G-50 column separation step, the fraction with molecular weights of 300-1,000 was found to markedly stimulate chick chondrocyte metabolism. Rechromatography on Sephadex G-25 concentrated activity in peptides of molecular weight of about 800. An HPLC separation on a silica C-18 reverse phase column gave elution of the active peptide at 18% acetonitrile in water. This bioactivity appears to be a peptide which is free of lipids, carbohydrates, nucleic acids, metal ions, and immunoreactive insulin. This factor markedly increased the metabolism of cultured chick chondrocytes, but had only marginal activity on rat chondrocytes. When added at 1 μg/ml to chick chondrocytes cultured in F-12 medium plus 1.5% fetal calf serum, the HPLC-purified activity increased DNA synthesis 7.3-fold, lipid synthesis 10.2-fold, and lactate production 2.9-fold after 48 h incubation.However, unlike somatomedins A and C, this factor did not displace insulin from placental membranes. These results suggest that low-molecular-weight peptides, which are smaller than the somatomedins, may contribute to the total ILA of human plasma.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 98
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 65-75 
    ISSN: 0091-7419
    Keywords: lymphocyte ; calcium ; phytohemagglutinin ; A23187 ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Calcium has been suggested as an internal second messenger when lymphocytes are stimulated by mitogens to enter the cell cycle. We have assessed the effect of 2 lymphocyte stimulants, the plant lectin phytohemagglutinin (PHA) and the calcium ionophore A23187, on human lymphocyte nucleic acid synthesis, total cell calcium content, and 4 5Ca labeling. We have used an ultrasensitive method for the measurement of total cell calcium in the same samples used for radiolabeling. Mitogenic concentrations of A23187 (∼ .25 μ mole/liter) caused an increase in both total cell calcium and 4 5Ca labeling. These increases were almost completely blocked by inhibitors of mitochondrial respiration, suggesting that the calcium increment after ionophore treatment was located in the mitochondria. In contrast, total cell calcium was not altered at optimal mitogenic PHA concentrations (0.1 μg/ml and above). However, at the minimum PHA concentrations that caused stimulation (0.025 to 0.1 μg/ml), the dose response of 4 5Ca uptake was very similar to that of DNA sysnthesis. Importantly, we could not stimulate DNA synthesis with PHA without increasing lymphocyte 4 5Ca labeling. Thus, an increase in total cell calcium is not essential for mitogenesis; however, an increase in 4 5Ca exchange is closely associated with the mitogenic effects of A23187 and PHA.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 99
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 77-83 
    ISSN: 0091-7419
    Keywords: pluripotent stem cells ; restricted stem cells ; CFU-S ; T lymphocytes ; B lymphocytes ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Mature, functional lymphocytes rapidly disappear from long-term cultures of mouse bone marrow cells and never reappear. One reason for the loss of B lymphocytes is that the optimal culture conditions for maintenance of myeloid stem cells are suboptimal for lymphocyte survival. However, despite the absence of functional lymphocytes, stem cells from such cultures retain the ability to reconstitute irradiated mice with mitogen-responsive B and T lymphocytes. In fact, in vitro grown stem cells repopulate the lymphoid system better than the myeloid system; the defective myeloid potential does not result from the absence in the cultures of Thy-1 bearing regulatory cells (TSRC). Although the cultures lack mature lymphocytes, they contain putative T cell precursors detectable with an in vitro colony-forming assay (CFU-T). In vitro maintenance of CFU-T requires an appropriate adherent monolayer. Monolyaters from congenitally anemic mice of genotype S1/S1d fail to support either myeloid precursors or CFU-T.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 100
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 85-96 
    ISSN: 0091-7419
    Keywords: embryonal carcinoma ; nucleosome repeat length ; extra-embryonic endoderm ; parietal endoderm ; H1 histones ; murine teratocarcinoma ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The histone compositions and average distance between nucleosomes have been determined for F9.22 and PSA1 murine embryonal carcinoma cell lines, for primary extra-embryonic endoderm derived from the in vitro differentiation of PSA1 embryonal carcinoma cells, and for two long-term extra-embryonic endodermal cell lines. A change in the relative proportions of two forms of the H1 histones (H1A and H1B) was found to correlate with the extra-embryonic endodermal differentiated phenotype. The embryonal carcinoma cells had a ratio of H1A/H1B of 1.49 or greater. In contrast, extra-embryonic endoderm from either cell lines or freshly isolated from differentiating embryonal carcinoma cell cultures had a ratio of H1A/H1B of less than 0.9. Partial peptide mapping of gel purified H1A and H1B suggest the two proteins differ in primary structure. The nucleosome repeat length of the embryonal carcinoma cell lines was 196 bp of DNA. Primary extra-embryonic endoderm was found to have a value of 205 bp, but the long-term extra-embryonic endodermal cell lines had an average nucleosome repeat length of 187 bp. Since both freshly isolated primary endoderm and the long-term endodermal cell lines express differentiated functions (basement membrane glycoproteins and plasminogen activator activity), there appears to be no simple correlation between the nucleosome repeat length and the expression of these differentiated functions.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...