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  • Life Sciences  (617)
  • Wiley-Blackwell  (617)
  • American Association for the Advancement of Science
  • Springer
  • 1980-1984  (102)
  • 1975-1979  (515)
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  • Wiley-Blackwell  (617)
  • American Association for the Advancement of Science
  • Springer
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  • 101
    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.
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  • 102
    ISSN: 0091-7419
    Keywords: vertebrate photoreceptor ; cyclic GMP ; cyclic nucleotide regulation ; phosphodiesterase ; light activated GTPase ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We report experiments which involve a light sensitive GTPase in the light dependent activation of retinal rod 3′5′-cyclic guanosine monophosphate (cGMP) phosphodiesterase (PDE). The data suggest that the light activated GTPase is intermediate between rhodopsin and PDE in the light-dependent activation sequence. We list the many striking similarities between hormone sensitive adenylate cyclase and light activated PDE in order to emphasize that the findings presented herein may have predictive value for ongoing studies of the hormone sensitive adenylate cyclase specifically regarding the role of the hormone activated GTPase in the activation sequence.
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  • 103
    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.
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  • 104
    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.
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  • 105
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    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.
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  • 106
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    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 14 (1980), S. 107-120 
    ISSN: 0091-7419
    Keywords: hematopoietic stroma ; cloning ; in vitro culture ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The role of hematopoietic microenvironments in the regulation of maturation and differentiation of hematopoietic cells, although heavily debated, remains uncertain. Several investigators have suggested that the adherent “stromal” cell populations, which grow as colonies in cultures of lymphomyeloid tissues, include the cells involved in such regulatory processes. Grossly, the colonies described by several investigators appear similar morphologically, and the cells giving rise to them have been variously termed (1) fibroblast colony forming cells (FCFC), (2) plaque forming units-culture (PFU-C), (3) macrophage colonies, and (4) marrow stromal cells. FCFC have been reported to re-establish their parent microenvironment when transplanted in an allogeneic system. In this study, cloned and enriched cell populations obtained from such colonies in cultures of murine lymphomyeloid tissues have been characterized by their growth in culture and using morphological, histochemical, and electron microscopic techniques. The results demonstrated that, although the initial stromal colonies appeared to be identical, the constituent cell types varied considerably. Some colonies were comprised primarily of macrophages, while others appeared to contain predominantly fibroblasts; two additional cell types that established colonies have not yet been satisfactorily identified. These results demonstrate the heterogeneity of lymphomyeloid stromal colonies. There is a need for caution in the analysis of experiments in which uncharacterized stromal cell colonies are transplanted or employed as supporting monolayers in culture systems in experiments designed to evaluate the origins and functions of lymphohematopoietic stroma.
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  • 107
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    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
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  • 108
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    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.
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  • 109
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    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.
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  • 110
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    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.
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  • 111
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    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.
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  • 112
    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.
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  • 113
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    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.
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  • 114
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    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.
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  • 115
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    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.
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  • 116
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    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
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  • 117
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    Journal of Supramolecular Structure 10 (1979), S. 359-364 
    ISSN: 0091-7419
    Keywords: ribosomes ; crystallization ; hypothermia ; chick embryos ; degeneration ; cell suffering ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The relationship between ribosome crystallization and cell degeneration has been studied in chick embryos at various temperatures, and new methods of inducing ribosome microcrystals are described. A model is discussed that reinterprets the role of low temperatures in these phenomena and provides a unitary explanation of the various cases in which the occurrence of ribosome crystallization in chick embryos has been reported.
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  • 118
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    Journal of Supramolecular Structure 10 (1979), S. 397-404 
    ISSN: 0091-7419
    Keywords: electron microscopy ; hybrid ribosome ; ribosome structure ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Small 40S Artemia salina and large 50S Escherichia coli ribosomal subunits can be assembled into 73S hybrid monosomes active in model assays for protein synthesis. The reciprocal combination-small 30S E coli and large 60S A salina-fails to form hybrids. The 73S hybrid particles strongly resemble homologous 70S E coli and 80S A salina monosomes. The morphologic differences between the corresponding eukaryotic and prokaryotic ribosomal particles, established by electron microscopy, do not significantly affect the assembly and mutual orientation of 40S A salina and 50S E coli subunits in the heterologous monosome. The fact that the structure of the interface, the supposed site of protein synthesis, is preserved in the active hybrid implies that retention or loss of biologic activity of hybrid ribosomes is determined by the extent of conformational changes in the interface.
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  • 119
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    Journal of Supramolecular Structure 10 (1979), S. 433-441 
    ISSN: 0091-7419
    Keywords: macrophage (alveolar) ; plasma membrane ; Ca2+-ATPase reaction ; membrane phosphorylation ; Ca2+ buffering ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: ATPase activity and phosphorylation by [γ-32P] ATP of isolated plasma membrane of alveolar macorphages are stimulated in a parallel fashion by physiologic concentrations of Ca2+, with half-maximal activating effect of this ion at (3-7) × 10-7 M. For various membrane preparations, a direct proportionality exists between Ca2+-dependent ATPase activity and amount of 32P incorporated. Labeling of membrane attains the steady-state level by 10 sec at 0°C, and is rapidly reversed by adenosine diphosphate (ADP). K+ decreases the amount of membrane-bound 32P, mainly by enhancing the rate of dephosphorylation of the 32P-intermediate. Hydroxylamine causes a release of about 90% of 32P bound to the membrane, thus indicating that the 32P-intermediate contains an acyl-phosphate bond. When the labeled plasma membrane is solubilized and electrophoresed on acrylamide gels in the presence of sodium dodecyl sulphate, the radioactivity appears to be largely associated with a single protein fraction of 132,500 ± 2,000 apparent molecular weight. These features of the macrophage Ca2+-ATPase suggest that the enzyme activity might be part of a surface-localized Ca2+-extrusion system, participating in the regulation of Ca2+-dependent activities of the macrophage.
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  • 120
    ISSN: 0091-7419
    Keywords: cell adhesion ; adhesion proteins ; fibronectin ; chondronectin ; collagen substrates ; gangliosides ; cell surface ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Fibronectin mediates the adhesion of fibroblasts to collagen substrates, binding first to the collagen and then to the cells. We report here that the interaction of the cells with the fibronectin-collagen complex is blocked by specific gangliosides, GD1 a and GT1, and that the sugar moieties of these gangliosides contain the inhibitory activity. The gangliosides act by binding to fibronectin, suggesting that they may be the cell surface receptor for fibronectin. Evidence is presented that other adhesion proteins or mechanisms of attachment exist for chondrocytes, epidermal cells, and transformed tumorigenic cells, since adhesion of these cells is not stimulated by fibronectin. Chondrocytes adhere via a serum factor that is more temperature-sensitive and less basic than fibronectin. Unlike that of fibroblasts chondrocyte adhesion is stimulated by low levels of gangliosides. Epidermal cells adhere preferentially to type IV (basement membrane) collagen but at a much slower rate than fibroblasts or chondrocytes. This suggests that these epidermal cells synthesize their own specific adhesion factor. Metastatic cells cultured from the T241 fibrosarcoma adhere rapidly to type IV collagen in the absence of fibronectin and do not synthesize significant amounts of collagen or fibronectin. Their growth, in contrast to that of normal fibroblasts, is unaffected by a specific inhibitor of collagen synthesis. These data indicate the importance of specific collagens and adhesion proteins in the adhesion of certain cells and suggest that a reduction in the synthesis of collagen and of fibronectin is related to some of the abnormalities observed in transformed cells.
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  • 121
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    Journal of Supramolecular Structure 11 (1979), S. 117-122 
    ISSN: 0091-7419
    Keywords: dynein ATPase ; latency ; high-affinity binding site ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The enhancing effect of low concentrations (eg, 8 μM) of bis(4-fluoro-3-nitrophenyl)sulfone (FNS) on 30S dynein ATPase activity is increased when 1 mM dithiothreitol (DTT) is present. The effect of FNS + DTT is optimal at pH 7.5. Activation of the latent ATPase activity of 30S dynein by FNS + DTT is partially prevented by 1-3 μM ATP. Adenylylimidodiphosphate (AMP-PNP) is less effective than ATP, while β,γ-methylene-adenosine triphosphate (AMP-PCP), though a much stronger inhibitor of ATPase activity than AMP-PNP, does not protect against enhancement. These results demonstrate the presence of a high-affinity ATP-binding site on 30S dynein.
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  • 122
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    Journal of Supramolecular Structure 11 (1979) 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
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  • 123
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    Journal of Supramolecular Structure 11 (1979), S. 467-476 
    ISSN: 0091-7419
    Keywords: metastatic potential ; growth rates ; chromosome number and range ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We investigated whether the metastatic potential of various tumor cell lines was related to chromosome counts or to rate of growth in vitro or in vivo. Clones of known metastatic potential derived from a C3H- fibrosarcoma induced by UV radiation (UV-2237) and from C57BL/6 B16 melanoma were tested for these characteristics. No correlation was found between the growth rate of these clones in monolayer culture or at a subcutaneous site and their ability to produce metastases. The cells from clones of UV-2237 were mainly in the diploid range with only one exception, and the B16 clones were all hyperploid. Thus, there was also no correlation between malignant behavior of the clones and gross changes in chromosome number.
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  • 124
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    Journal of Supramolecular Structure 11 (1979), S. 493-502 
    ISSN: 0091-7419
    Keywords: cell surface ; plasma membrane ; glycoproteins ; affinity chromatography ; lectins ; Novikoff hepatocellular carcinoma ; neuraminidase ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Novikoff hepatocellular carcinoma cells were radioiodinated by a cell surface-specific method using lactoperoxid ase/125I. The iodinated proteins were solubilized in 0.5% Nonidet P-40 and subjected to affinity chromatography on Sepharose-conjugated lectins (Ricinus communis agglutinins I or II, soybean agglutinin, concanavalin A, or wheat germ agglutinin) and analyzed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Almost all the iodinated proteins bound to one or more of the Sepharose-conjugated lectins, presumptive evidence that these peptides are glycosylated. Lectin affinity chromatography resolved defined subsets of iodinated glycoproteins and suggested that certain glycoproteins could be fractionated on the basis of heterogeneity of their heterosaccharide moieties. Incubation of the iodinated cells with neuraminidase resulted in increased binding of iodinated proteins to Sepharose-conjugated Ricinus communis agglutinins I and II and soybean agglutinin and decreased binding to Sepharose-conjugated wheat germ agglutinin. Binding of iodinated proteins to concanavalin A was unaffected by neuraminidase treatment of the cells. These studies demonstrate the utility of lectins for the multicomponent analysis of plasma membrane proteins.
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  • 125
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    Journal of Supramolecular Structure 11 (1979), S. 539-546 
    ISSN: 0091-7419
    Keywords: SV40 transformation ; tumorigenicity ; anchorage independence ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A syndrome of in vitro properties correlates with the tumorigenicity of SV40-transformed rodent cells. These properties are plasminogen activator production, loss of large actin cables, and anchorage-independent growth. An established rat fibroblast line, its SV40 transformant, several T-antigen negative revertants, and a spontaneous retransformant isolated form one of the revertants were analyzed in vivo for their tumorigenicity and in vitro for the syndrome. The two transformed lines were highly tumorigenic, and had clearly abnormal in vitro properties. The parental rat line was weakly tumorigenic in nude mice and demonstrated a slightly transformed response in the in vitro assays. The revertants were completely nontumorigenic. Expression of the in vitro syndrome was not uniform for all revertants; however, most cell lines maintained the correlation of the syndrome and tumorigenicity.
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  • 126
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    Journal of Supramolecular Structure 11 (1979), S. 563-577 
    ISSN: 0091-7419
    Keywords: plasma membrane ; lectin receptors ; affinity chromatography ; membrane proteins ; hybridoma ; monoclonal antibody ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Concanavalin A-binding (Con A)-binding cell surface glycoproteins were isolated, via Con A-affinity chromatography, from Triton X-100-solubilized Chinese hamster ovary (CHO) cell plasma membranes. The Con A binding glycoproteins isolated in this manner displayed a significantly different profile on sodium dodecyl sulfate-polyacrylamide gels than did the Tritonsoluble surface components, which were not retarded by the Con A-Sepharose column. [125I]-Con A overlays of the pooled column fractions displayed on sodium dodecyl sulfate-polyacrylamide gel electro-phoresis (SDS-PAGE) demonstrated that there were virtually no Con A receptors associated with the unretarded peak released by the Con A-Sepharose column, whereas the material which was bound and specifically eluted from the Con A-Sepharose column with the sugar hapten α-methyl-D-mannopyranoside contained at least 15 prominent bands which bound [125I]-Con A.In order to produce monoclonal antibodies against various cell surface Con A receptors, Balb/c mice were immunized with the pooled Con A receptor fraction. Following immunization spleens were excised from the animals and single spleen cell suspensions were fused with mouse myeloma P3/X63-Ag8 cells. Numerous hybridoma clones were subsequently picked on the basis of their ability to secrete antibody which could bind to both live and glutaraldehyde-fixed CHO cells as well as to the Triton-soluble fraction isolated from the CHO plasma membrane fraction. Antibody from two of these clones was able to precipitate a single [125I]-labeled CHO surface component of ∼265,000 daltons.
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  • 127
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    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.
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  • 128
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    Journal of Supramolecular Structure 11 (1979), S. 9-24 
    ISSN: 0091-7419
    Keywords: nascent chains ; co-translational modification ; glycosylation ; polypeptide folding ; covalent assembly ; heavy and light chains ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We have investigated the in vivo co-translational covalent modification of nascent immunoglobulin heavy and light chains. Nascent polypeptides were separated from completed polypeptides by ion-exchange chromatography of solubilized ribosomes on QAE-Sephadex. First, we have demonstrated that MPC 11 nascent heavy chains are quantitatively glycosylated very soon after the asparaginyl acceptor site passes through the membrane into the cisterna of the rough endoplasmic reticulum. Nonglycosylated completed heavy chains of various classes cannot be glycosylated after release from the ribosome, due either to rapid intramolecular folding and/or intermolecular assembly, which cause the acceptor site to become unavailable for the glycosylation enzyme. Second, we have shown that the formation of the correct intrachain disulfide loop within the first light chain domain occurs rapidly and quantitatively as soon as the appropriate cysteine residues of the nascent light chain pass through the membrane into the cisterna of the endoplasmic reticulum. The intrachain disulfide loop in the second or constant region domain of the light chain is not formed on nascent chains, because one of the cysteine residues involved in this disulfide bond does not pass through the endoplasmic reticulum membrane prior to chain completion and release from the ribosome. Third, we have demonstrated that some of the initial covalent assembly (formation of interchain disulfide bonds) occurs on nascent heavy chains prior to their release from the ribosome. The results are consistent with the pathway of covalent assembly of the cell line, in that completed light chains are assembled onto nascent heavy chains in MPC 11 cells (IgG2b), where a heavy-light half molecule is the major initial covalent intermediate; and completed heavy chains are assembled onto nascent heavy chains in MOPC 21 cells (IgG1), where a heavy chain dimer is the major initial disulfide linked intermediate.
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  • 129
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    Journal of Supramolecular Structure 11 (1979), S. 33-49 
    ISSN: 0091-7419
    Keywords: cell enucleation ; cell reconstruction ; nuclear control of tumorigenicity ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The techniques of somatic cell hybridization have provided a valuable means of studying mechanisms of regulation of mammalian cell differentiation and transformation. Most previous studies have indicated that fusions between tumorigenic and nontumorigenic cells result in hybrid cells that are usually tumorigenic. In recent years it has been demonstrated that the phenotypic expression of tumorigenicity is at least partially due to the extensive chromosome loss that occurs in most interspecific and some intraspecific hybrid cells. In the present study we have utilized enucleation techniques that permit cells to be divided into nuclear (karyoplast) and cytoplasmic (cytoplast) cell fragments. Even though these nuclear and cytoplasmic fragments are metabolically stable for short periods of time, in our hands they ultimately degenerate. Viable cells can be reconstructed by PEG-induced fusion of karyoplasts to cytoplasts. Since reconstructed cells apparently do not segregate chromosomes, they may provide a clearer understanding of the interactions between the nucleus and the cytoplasm in the control of the expression of tumorigenicity. We have reconstructed cells using karyoplasts from the tumorigenic Y-1 cell line and cytoplasts from a nontumorigenic cell line, A-MT-BU-A1. In addition we have reconstructed cells containing Y-1 cytoplasts and A-MT-BU-A1 karyoplasts. The reconstructed cells porduced were assayed for tumorigenicity by their ability to grow in soft agar and in nude mice. The results of these experiments indicate that the reconstructed cells containing a tumorigenic nucleus and a nontumorigenic cytoplasm ultimately are tumorigenic and conversely the reconstructed cells containing a nontumorigenic nucleus and a tumorigenic cytoplasm are nontumorigenic. These experiments support the concept that with these cell lines the nucleus (karyoplast) is sufficient to control the phenotypic expression of tumorigenicity.
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  • 130
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    Journal of Supramolecular Structure 11 (1979) 
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    Keywords: Life Sciences ; Molecular Cell Biology
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  • 131
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    Journal of Supramolecular Structure 11 (1979), S. 123-138 
    ISSN: 0091-7419
    Keywords: pea stem membranes ; L-cell membranes ; polyisoprenyl oligosaccharides ; glycoprotein synthesis ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Membrane preparations from growing regions of pea stems and activelydividing mouse L-cells form lipid-linked saccharides from GDP-mannose and UDP-N-acetylglucosamine. These lipids have properties which are consistent with those of mono-and di-phosphoryl polyisoprenyl derivatives.In experiments using plant membranes, the monophosphoryl derivative labeled with GDP-(14C) mannose contains mannose only, while the diphosphoryl derivative labeled with the same nucleotide sugar is heterogeneous, containing oligosaccharides corresponding to mannosaccharides of 5, 7, and 9-12 residues. Only the diphosphoryl polyisoprenyl derivatives are labeled with UDP-(14C)glucosamine and these contain predominantly chitobiose and N-acetylglucosamine itself. Unlabeled GDP-mannose added after UDP-N-acetyl (14C)glucosamine results in the formation of higher lipid-linked oligosaccharides which are apparently the same as those which are labeled with GDP-(14C)mannose alone. Incubation of the membranes with GDP-(14C)mannose in the presence of Mn2+, unlabeled UDP-glucose or unlabeled UDP-N-acetylglucosamine results in marked changes in the accumulation of both the polyisoprenyl monophosphoryl mannose and polyisoprenyl diphosphoryl oligosaccharides.Animal cell membranes synthesise lipid-linked oligosaccharides when incubated with UDP-N-acetylglucosamine and GDP-mannose. These oligosaccharides are similar in size to those synthesised by the plant membranes but their formation is more efficient. The potential roles of these compounds in glycoprotein biosynthesis in both plant and animal tissues is discussed.
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  • 132
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    Keywords: cellular adhesion ; platelets ; fibronectin ; hemostasis ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Platelets are cells which develop adhesive properties following stimulation. Since fibronectin (fn) mediates adhesive properties of several cells, we sought evidence for platelet associated fn. Lysates of suspensions of washed human platelets containing ≤50 ng soluble fn/109 cells contained 2.85 μg fn antigen per 109 cells. The platelet fn antigen competition curve showed a similar slope to the curve for purified plasma fn suggesting antigenic identity. Immunofluorescent staining for fn was minimal in intact cells suggesting that the majority of fn antigen is intracellular. In permeable platelets, fluorescent staining for fn was seen in a punctate distribution suggesting a granule localization. Stimulation of platelet secretion by thrombin released platelet fn antigen. Suramin, a drug which inhibits platelet secretion, inhibited fn release. The apparent secretion of platelet fn, taken with the immunofluorescent data, support the localization of a portion of platelet fn antigen in a storage granule.
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  • 133
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    Journal of Supramolecular Structure 11 (1979), S. 175-187 
    ISSN: 0091-7419
    Keywords: growth control ; 3T3 cells ; Schwann cells ; neurites ; plasma membranes ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Control of cell growth by cell to cell contact is reviewed with particular emphasis on two systems - contact inhibition of growth observed with Swiss 3T3 cells and the mitogenic stimulation of Schwann cells by dorsal root ganglia neurites. In both cases the biological effect can be reproduced by the addition of surface membranes to the corresponding cells. In the case of contact inhibition of 3T3 cells, biological activity appears to correlate with membrane binding to the cells. An octylglucoside extract of 3T3 plasma membranes retains the biological activity (growth inhibition) of the original membranes.
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  • 134
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    Journal of Supramolecular Structure 11 (1979), S. 207-216 
    ISSN: 0091-7419
    Keywords: renal epithelium ; primary cultures ; prostaglandins ; mammalian cell growth ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Madin Darby canine kidney cells can grow in synthetic medium supplemented with 5 factors - insulin, transferrin, prostaglandin E1, hydrocortisone and triiodothyronine - as a serum substitute. These 5 factors permit growth for one month in the absence of serum, and a growth rate equivalent to that observed in serum-supplemented medium. Dibutyryl cAMP substitutes for prostaglandin E1 in the medium, suggesting that increased growth of Maden Darby canine kidney cells results from increased intracellular cAMP. Potential applications of the serum-free medium are discussed. The medium permits the selective growth of primary epithelial cell cultures in the absence of fibroblast over-growth, and a defined analysis of the mechanisms by which hormones regulate hemicyst formation.
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  • 135
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    Journal of Supramolecular Structure 11 (1979), S. 217-225 
    ISSN: 0091-7419
    Keywords: fibrosarcoma culture media ; gel permeation chromatography ; fibronectin-radioimmunoassay ; fibronectin-releasing peptides ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A sensitive radioimmunoassay, specific for human fibronectin, was used to measure the ability of certain biologically active polypeptides to release fibronectin from cultured human lung fibroblasts into their culture media. Concentrated, serum-free culture supernatant from a human fibrosarcoma cell line was fractionated by gel filtration chromatography in the presence of acetic acid. Various polypeptides with molecular weights between 46,000 and 6,000 were tested for their ability to release fibronectin from cells. The column fraction, containing polypeptides with an apparent molecular weight of 10,000, exhibited the ability to rapidly release fibronectin from target cells. The activity could be inhibited by phenylmethyl sulphonylfluoride. Several other hormonal factors, tested in parallel with the column fractions, failed to show this effect. The 10,000 dalton molecular weight polypeptides may represent a family of cellular gene products responsible for maintenance of low levels of surface associated fibronectin in fibrosarcoma cells and thus be related to their infiltrating properties by preventing the formation of the extracellular matrix.
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  • 136
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    Journal of Supramolecular Structure 11 (1979), S. 227-235 
    ISSN: 0091-7419
    Keywords: fibronectin ; factor XIII ; transglutaminase ; collagen ; polyamine ; ∊(γ-glutamyl)-lysin ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Soluble fibronectin is found in body fluids and media of cultured adherent cells. Insoluble fibronectin is found in tissue stroma and in extracellular matrices of cultured cells. Fibronectin is a substrate for factor XIIIa (plasma transglutaminase) and can be cross-linked to collagen and to the α chain of fibrin. We have used sodium dodecyl sulfate-polyacrylamide gel electrophoresis to investigate the possibility that factor XIIIa -mediated cross-linking is influenced by polyamines. Spermidine inhibited cross-linking between fibronectin and type I collagen, isolated α1 (I) collagen chains, or iodinated cyanogen bromide fragment 7 of α1 (I) chains (125I-α1 (I)-CB7). Half-maximal inhibition of crosslinking between 125I-α1 (I)-CB7 and fibronectin was observed when 0.1 mM spermine or spermidine was present. Spermidine, 0.7 mM, partially inhibited cross-linking between fibronectin and the α chain of fibrin but failed to inhibit cross-linking between the fibrin monomers of a fibrin clot. Spermidine also failed to inhibit cross-linking between fibronectin molecules when aggregation of fibronectin was induced with dithiothreitol. In contrast, 0.7 mM monodansylcadaverine inhibited fibronectin-collagen, fibronectin-fibrin, fibronectin-fibronectin, and fibrin-fibrin cross-linking. Spermidine or spermine, 0.7 mM, enhanced the cross-linking between molecules of partially amidinated fibronectin, suggesting that N1,8-(di-γ-glutamyl)-polyamine cross-linkages were formed. Spermidine and spermine failed to enhance cross-linking between monomers of amidinated fibrin. These results indicate that physiologic concentrations of polyamines specifically disturb transglutaminase-catalyzed cross-linking between fibronectin and collagen.
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  • 137
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    Journal of Supramolecular Structure 11 (1979), S. 237-250 
    ISSN: 0091-7419
    Keywords: coated vesicles ; coat dissembly ; coat reassembly ; coat dissociation ; clathrin ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Disruption of the coat of coated vesicles is accompanied by the release of clathrin and other proteins in soluble form. The ability of solubilized coated vesicle proteins to reassemble into empty coats is influenced by Mg2+, Tris ion concentration, pH, and ionic strength. The proteins solubilized by 2 M urea spontaneously reassemble into empty coats following dialysis into isolation buffer (0.1 M MES-1 mM EGTA-1 mM MgCl2-0.02% NaN3, pH 6.8). Such reassembled coats have sedimentation properties similar to untreated coated vesicles. Clathrin is the predominant protein of reassembled coats; most of the other proteins present in native coated vesicles are absent. We have found that Mg2+ is important in the coat assembly reaction. At pH 8 in 0.01 M or 0.1 M Tris, coats dissociate; however, 10 mM MgCl2 prevents dissociation. If the coats are first dissociated at pH 8 and then the MgCl2 raised to 10 mM, reassembly occurs. These results suggest that Mg2+ stabilizes the coat lattice and promotes reassembly. This hypothesis is supported by our observations that increasing Mg2+ (10 μM-10 mM) increases reassembly whereas chelation of Mg2+ by (EGTA) inhibits reassembly. Coats reassembled in low-Tris (0.01 M, pH 8) supernatants containing 10 mM MgCl2 do not sediment, but upon dialysis into isolation buffer (pH 6.8), these coats become sedimentable. Nonsedimentable coats are noted also either when partially purified clathrin (peak I from Sepharose CL4B columns) is dialyzed into low-ionic-strength buffer or when peaks I and II are dialyzed into isolation buffer. Such nonsedimentable coats may represent intermediates in the assembly reaction which have normal morphology but lack some of the physical properties of native coats. We present a model suggesting that tightly intertwined antiparallel clathrin dimers form the edges of the coat lattice.
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  • 138
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    Journal of Supramolecular Structure 11 (1979), S. 259-267 
    ISSN: 0091-7419
    Keywords: cell surface receptors ; proteolysis of receptors ; positive or negative regulation ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Addition of highly purified thrombin t o cultures of several kinds of nondividing fibroblasts brings about cell division. This stimulation occurs in serum-free medium, permitting studies on its mechanism under chemically defined conditions. Previous studies have shown that action of thrombin a t the cell surface is sufficient to cause cell division and that the proteolytic activity of thrombin is required for its mitogenic effect. These results prompted experiments which showed that there is a cell surface receptor for thrombin and that thrombin must hind to its receptor and cleave it to stimulate cell division. Some of the thrombin that hinds to its receptors becomes attached to them by a linkage that appears to be covalent. However, it is presently unknown whether this direct thrombin receptor complex plays a role in the stimulation.These results raise a number of question that should be explored in future studies. They also provide a foundation on which to build hypotheses about tentative molecular mechanisms that might be involved in the stimulation. Knowledge that thrombin must cleave its receptor to bring about cell division suggests two alternative mechanisms for stimulation by proteolysis. In one the receptor is a negative effector which prevents cell division when it is intact, but not after it has been cleaved. Alternatively, a fragment of the receptor could be a positive effector. In this mechanism, proteolysis by thrombin would produce a specific receptor fragment which brings about cell proliferation. If every protease which cleaves the receptor also stimulates cell division, the receptor is probably a negative effector. In contrast, if certain proteases cleave the receptor but do not stimulate the cells, a fragment of the receptor is likely a positive effector. With negative regulation by the receptor, the controlling events would occur before proteolysis of it, and it might be possible to find putative regulatory molecules by identification of nearest neighbors of the receptor. This should be possible by using bifunctional crosslinking reagents. If a fragment of the thrombin receptor turns out to be a positive effector, it should be possible to identify and study fragments by analyzing the metabolic fate of the receptor. Techniques are now available for this kind of analysis and it should also be possible to determine whether receptor fragments remain in the membrane or whether they are translocated to specific sites within the cell. A critical question to be asked is which of these events and interactions involving the thrombin receptor are necessary for stimulation of cell division. It now appears that the best way to answer this question is to examine these events in a large number of cloned cell populations that are responsive or unresponsive to the mitogenic action of thrombin. If a thrombin-mediated event occurs in all responsive clones but is altered or absent in sonie unresponsive clones, it is probably necessary for stimulation of cell division.
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  • 139
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    Journal of Supramolecular Structure 11 (1979), S. 295-309 
    ISSN: 0091-7419
    Keywords: threshold effects ; liposomes ; aggregation ; ricin ; concanavalin A ; synthetic glycolipids ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Cholesterol analogs containing sugar residues linked by spacer groups to the cholesterol O can be incorporated into egg yolk lecithin small unilamellar liposomes. The synthetic glycolipid analogs distribute evenly on both sides of the bilayer. These liposomes are aggregated by the appropriate lectin. For example, when the sugar residue is a β-galactoside the liposomes are aggregated by ricin and when it is an α-mannoside they are aggregated by Con A. The lectin-mediated aggregation of these liposomes is reversed by the addition of the appropriate sugar. The rates but not the extents of aggregation of these liposomes are highly sensitive to the amount of glycolipid incorporated. Below approximately 5% glycolipid incorporation the rate of the lectin-mediated aggregation of these liposomes is exceedingly slow, whereas above this level rapid aggregation proceeds. At all concentrations studied the synthetic glycolipids are incorporated in a unimodal fashion so that the observed threshold effects cannot be based on possible differences in the manner in which the glycolipids are incorporated at different concentrations. This conclusion is based on (1) studies with galactose oxidase that show that the percentage of galactose oxidation in a liposome prepared from a galactosyl-containing glycolipid is independent of glycolipid concentration, and (2) studies on the aggregation of liposomes containing mixed glycolipids in which the glycolipids are shown to behave independently. The importance of a critical density of membrane-bound receptors in order for aggregation to occur is discussed.
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  • 140
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    Journal of Supramolecular Structure 11 (1979), S. 311-317 
    ISSN: 0091-7419
    Keywords: dynein ; flagella ; ATPase ; sperm motility ; sea urchin ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A high-resolution sodium dodecyl sulfate polyacrylamide gel electrophoresis system has been used to show the presence, in both whole sperm and isolated flagellar axonemes, of eight polypeptides migrating in the 300,000-350,000 molecular weight range characteristic of the heavy chains of dynein ATPase. Previously, only five such chains have been discernible. Extraction of isolated axonemes for 10 min at 4°C with a solution containing 0.6 M NaCl, pH 7, releases a mixture of particles that separate, in sucrose density gradient centrifugation, into a major peak, dynein 1 ATPase, sedimenting at 21 S and a minor peak at 12-14S. The polypeptide compositions of these two peaks are different. The dynein 1 peak, which contains most of the protein on the gradient, contains approximately equal quantities of two closely migrating heavy chains, with a small amount of a third, more slowly migrating chain; no other heavy chains appear in this peak. Two groups of smaller polypeptides (three intermediate chains, within the apparent molecular weight range 76,000-122,000 and four newly discovered light chains, within the apparent molecular weight range 14,000-24,000) cosediment with the 21 S peak. The heavy chain composition of the 12-14S peak is more complex, all eight heavy chains occurring in approximately the same ratios as occur in intact axonemes.
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  • 141
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    Journal of Supramolecular Structure 11 (1979), S. 339-347 
    ISSN: 0091-7419
    Keywords: switch hypothesis ; cilia ; motility ; vanadate ; calcium ; dynein ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Lateral (L) cilia of freshwater mussel (Margaritana margaritifera and Elliptio complanatus) gills can be arrested in one of two unique positions. When treated with 12.5 mM CaCl2 and 10-5 M A23187 they arrest in a “hands up” position, ie, pointing frontally. When treated with approximately 10 mM vanadate (V) they arrest in a “hands down” position, ie, pointing abfrontally. L-cilia treated with 12.5 mM CaCl2 and 1 mM NaN3 also arrest in a “hands down” position; substitution of 20 mM KC1 and 1 mM NaN3 causes cilia to move rapidly and simultaneously to a “hands up” position.The observations suggest that there are two switching mechanisms for activation of active sliding in ciliary beat one at the end of the recovery stroke and the other at the end of the effective stroke; the first is inhibited by calcium and the second by vanadate or azide. This is consistent with a model of ciliary beating where microtubule doublet numbers 1, 2, 3, and 4 are active during the effective stroke while microtubule doublets numbers 6, 7, 8, and 9 are passive, and the converse occurs during the recovery stroke.
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  • 142
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    Journal of Supramolecular Structure 11 (1979), S. 429-444 
    ISSN: 0091-7419
    Keywords: (H++K+)-ATPase ; transport ATPase ; proton transport ; phospholipids ; phospholipase A2 ; CD spectrum ; gastric ATPase ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The phospholipid and fatty acid composition and role of phospholipids in enzyme and transport function of gastric (H++K+)-ATPase vesicles was studied using phospholipase A2 (bee venom). The composition (%) was phosphatidylcholine (PC) 33%; sphingomyelin (sph) 25%; phosphatidylethanolamine (PE) 22%; phosphatidylserine (PS) 11%; and phosphatidylinositol (PI) 8%. The fatty acid composition showed a high degree of unsaturation. In both fresh and lyophilized preparations, even with prolonged incubation, only 50% of phospholipids were hydrolyzed, but the amount of PE and PS disappearing was increased following lyophilization. There was a marked decrease in K+-ATPase activity (75%) but essentially no loss of the associated K+ p-nitrophenyl phosphatase was found. ATPase activity could be largely restored by various phospholipids (PE 〉 PC 〉 PS). There was also an increase in Mg2+-ATPase activity, partially reversed in fresh preparations by the addition of phospholipids (PE 〉 PS 〉 PC). Proton transport activity of the preparation was rapidly inhibited, initially due to a large increase in the HC1 permeability of the preparation. Associated with these enzymatic and functional changes, the ATP-induced conformational changes, as indicated by circular dichroism spectra were inhibited.
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  • 143
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    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.
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  • 144
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    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.
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  • 145
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    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.
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  • 146
    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.
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  • 147
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    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.
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  • 148
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    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.
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  • 149
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    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.
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  • 150
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    Journal of Supramolecular Structure 14 (1980), S. 397-403 
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    Keywords: Life Sciences ; Molecular Cell Biology
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  • 151
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    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.
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  • 152
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    Journal of Supramolecular Structure 13 (1980) 
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    Keywords: Life Sciences ; Molecular Cell Biology
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  • 153
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    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.
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  • 154
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    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.
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  • 155
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    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.
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  • 156
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    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
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  • 157
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    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.
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  • 158
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    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.
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  • 159
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    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.
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  • 160
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    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.
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  • 161
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    Journal of Supramolecular Structure 3 (1975), S. 80-89 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Fluorescent polymers were obtained by oxidizing partly emulsified linolenic acid with different oxidants. The speed of formation of polymers differed for the various oxidants, and the difference was not a simple function of the oxidation potential. The speed of polymerization also depended on the nature of the emulsion.The presence of egg albumen in the emulsion enhanced polymer formation with all oxidants. When the oxidants used are arranged in the order of decreasing speed of polymer formation, the order is different in the presence of albumen from what it is in the absence of albumen.With different oxidation catalysts most antioxidants and amino acids tested enhanced polymerization. In oxidation with ferric ions, with K-dichromate, and without added oxidants the only antioxidants which delayed polymerization were “inhibitors”. “Retarders” enhanced polymerization. With KMnO4 slight delay was caused by some retarders.The findings indicate that not only oxidation catalysts, but also proteins, amino acids, and antioxidants enhance polymerization. The possibility is suggested that in animal cells lipid pigment formation might represent a mechanism for neutralizing free radicals.
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  • 162
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    Journal of Supramolecular Structure 4 (1976), S. 141-159 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The specificity of lactoperoxidase-catalyzed iodination for the proteins of the hepatoma tissue culture cell plasma membrane was examined by histochemical, biochemical, and cell fractionation techniques. Light microscope autoradiography of sectioned cells shows the incorporated label to be localized primarily at the periphery of the cell. Most of this label can be released from the cell by trypsin but not by collagenase or hyaluronidase. The label is recovered from the cells as either monoiodotyrosine or diiodotyrosine after hydrolysis of cell extracts with a mixture of proteolytic enzymes. The label co-purifies during cell fractionation with an authentic liver cell plasma membrane marker enzyme, 5′-nucleotidase. Thus, the incorporated iodide is itself a valid marker for those membrane polypeptides having tyrosine residues accessible to the lactoperoxidase. The polypeptide complexity of the purified plasma membrane was examined by high resolution dodecyl sulfate-polyacrylamide gel electrophoresis. At least 50 polypeptides in the membrane are accessible to iodination. These polypeptides probably represent the bulk of the protein mass of the membrane and iodinating them does not affect cell viability, growth rate, or cell function. Labeling experiments with fucose and glucosamine show that at least nine of the iodinated peptides may be glycoproteins.
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  • 163
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    Journal of Supramolecular Structure 4 (1976), S. 181-184 
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    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: ATP stimulates chromaffin granules from the bovine adrenal medulla to release epinephrine and specific soluble proteins. ATP analogs substituted in the β-γ-position with either nitrogen or carbon were also found to be effective at inducing release from isolated chromaffin granules. However, an ATP analog substituted at the α-β position with carbon was strongly inhibitory. Cyclic AMP was also found to be synthesized by isolated chromaffin granules under release conditions. ATP analogs were effective as substrates for adenylate cyclase in the same order as their efficiency for inducing release from vesicles. Hydrolysis at the β-γ linkage of ATP therefore is probably not necessary for release; however, hydrolysis at the α-β position may be important in the release process. Cyclic AMP may be produced and play a regulatory role in this event.
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    Journal of Supramolecular Structure 4 (1976), S. 185-197 
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    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The present study was undertaken to localize adenylate cyclase activity in salivary glands by cytochemical means. For the study, serous parotid glands and mixed sublingual glands of the rat were used. Pieces of the fixed glands were incubated with adenosine triphosphate (ATP) or adenylyl-imidodi-phosphate (AMP-PNP) as substrate: inorganic pyrophosphate or PNP liberated upon the action of adenylate cyclase on the substrates is precipitated by lead ions at their sites of production.In both glands, the reaction product was detected along the myoepithelial cell membranes in contact with secretory cells, indicating that a high level of adenylate cyclase activity occurs in association with these cell membranes. The association with a high level of the enzyme activity might be related to the contractile nature of myoepithelial cells which are supposed to aid secretory cells in discharging secretion products.A high level of adenylate cyclase activity was also detected associated with serous secretory cells (acinar cells of the parotid gland and demilune cells of the sublingual gland), but not with mucous secretory cells. In serous cells, deposits of reaction product were localized along the extracellular space of the apical cell membrane bordering the lumen. This is the portion of the cell membrane which fuses with the granule membranes during secretion. Since the granule membranes are not associated with a detectable level of adenylate cyclase activity, it appears that the enzyme activity becomes activated or associated with the granule membranes as they become part of the cell membrane by fusion. The association with a high level of adenylate cyclase activity appears to be related to the ability of the membrane to fuse with other membranes. It is likely, since the luminal membrane of mucous cells which does not fuse with mucous granule membranes during secretion is not associated with a detectable enzyme activity.
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  • 165
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    Journal of Supramolecular Structure 4 (1976), S. 221-231 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The HLB dependency for the solubilization of membrane proteins and adenylate cyclase activity from a plasma membrane-enriched fraction from rat liver has been determined. The HLB (hydrophilic/lipophilic/balance) number of a detergent is an empirical measure of its relative hydrophobicity. Detergent HLB numbers vary systematically with the length of the ethylene oxide chain for a homologous series of detergents such as the Triton X series. These detergents have a constant hydrophobic moiety, octylphenyl, and a variable polar portion, polyethoxyethanol. Basal-NaF-epine-phrine-, and glucagon-stimulated adenylate cyclase activities were solubilized in the HLB range of 16.8-17.4. Solubilization was most effective in 0.01 M Tris buffers at pH 7.5 containing 1-5 mM mercaptoethanol, 1 mM MgCl2, and 0.1% Triton X-305. The detergent to membrane protein ratio used in these studies was 3:1.Criteria for solubilization included lack of sedimentation at 100,000 × g, the absence of particulate material in the supernatant when examined by electron microscopy, and inclusion of hormonally sensitive adenylate cylcase activity in Sephadex G-200 gels. The apparent molecular weight of the solubilized enzyme was approximately 200,000 in the presence of Triton X-305. The solubilized enzyme was stimulated 5-fold by NaF, 7-fold by glucagon, and 20-fold by epinephrine compared to the particulate enzyme used in this study which was stimulated 10-fold, 3,4-fold, and 4-fold by NaF, epinephrine, and glucagon, respectively. The solubilized enzyme is stable for several weeks when stored at -60° C.
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  • 166
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    Journal of Supramolecular Structure 4 (1976), S. 241-258 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The binding of many polypeptide hormones to cell surface receptors does not appear to follow the law of mass action. While steady-state binding data are consistent in many cases with either heterogeneous populations of binding sites or interactions of the type known as negative cooperativity, study of the kinetics of dissociation of the hormone receptor complex allows an unambiguous demonstration of cooperative interactions. Negative cooperativity, which seems to be wide-spread among hormone receptors, provides exquisite sensitivity of the cell at low hormone concentrations while buffering against acutely elevated hormone levels. The molecular mechanisms underlying the cooperativity are still largely unknown. Cooperativity may stem from a conformational transition in individual receptors or involve receptor aggregation in the fluid membrane (clustering) or more extensive membrane phenomena. Thus, new models of hormone action must be considered which integrate the progress in our knowledge of both the complex mechanisms regulating hormone binding to their surface receptors, and the dynamic properties of the cell membrane.
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  • 167
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    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Simian virus 40 (SV40) induces cell division in microcultures of sparsely plated nongrowing mouse BALB/3T3 cells during acute infection at moderate multiplicities of infection (MOI = 10-100). The infected cells are killed when a MOI of 1,000 is used. SV40 tumor (T) antigen is synthesized in the infected cells, but viral DNA, virion antigen, and progeny virions are not synthesized (abortive infection). The addition of exogenous dibutyryl adenosine 3′-5′-monophosphate (dbcAMP) at the time of infection stimulates the SV40-induced cell division at all MOI and inhibits SV40-induced cell death at high MOI. The percentage of T antigen-positive cells, as monitored by immunofluorescence, is also increased by the addition of dbcAMP at the time of infection. This regulation of SV40-induced cell division and T antigen formation by exogenous dbcAMP occurs within the first 6 hr after infection at 37° C and is dependent upon both the MOI and the concentration of added dbcAMP. The addition of dbcAMP to productively infected TC7 monkey cells has little effect on the SV40-induced cell death or T antigen formation.
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  • 168
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    Journal of Supramolecular Structure 4 (1976), S. 289-303 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Vasopressin-sensitive pig kidney adenylate cyclase is sensitive to several effectors, such as Mg2+, other divalent cations, and guanyl nucleotides. The purpose of the present study was to compare the main characteristics of adenylate cyclase activation by vasopressin, Mg2+, and GMPPNP, respectively. Mg2+·ions were shown to exert at least three different effects on adenylate cyclase. The substrate of the adenylate cyclase reaction is the Mg-ATP complex. Mg2+ interacts with an enzyme regulatory site. Finally, Mg2+ can modulate the hormonal response, with Mg2+ions affecting the coupling function-that is, the quantitative relationship between receptor occupancy and adenylate cyclase activation. At all the magnesium concentrations tested, from 0.25 mM to 16 mM, adenylate cyclase activation was not a direct function of receptor occupancy. At low Mg2+ concentrations, adenylate cyclase activation dose-response curve to the hormone tended to be superimposable to the hormone dose-binding curve. These results suggest a role of magnesium at the coupling step between the hormone-receptor complex and adenylate cyclase response. Cobalt, but not calcium, ions could exert the same effects as Mg2+ ions on this coupling step.GMPPNP induced considerable adenylate cyclase activation (15 to 35 times the basal value). Activation by GMPPNP was highly time and temperature dependent. At 30° C, a 20 to 60 min preincubation period in the presence of GMPPNP was needed to obtain maximal activation. The higher the dose of GMPPNP in the medium, the longer it took to reach equilibrium. At 15° C, activation was still increasing with time after 3 hr preincubation in the presence of the nucleotide. GMPPNP was active in a 10-8 M to 10-5 M concentration range. Unlike the results obtained with lysine vasopressin, the kinetic characteristics of dose-dependent adenylate cyclase activation curves by GMPPNP were unaffected by varying Mg2+ concentrations except for the increase in velocity when raising Mg2+ concentration. It was not clear whether or not the activation processes by the hormone and by GMPPNP had common mechanisms.
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  • 169
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    Journal of Supramolecular Structure 5 (1976), S. 317-334 
    ISSN: 0091-7419
    Keywords: actin ; cytoskeleton ; filament ; gel ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: This is a review of the evidence that the cytoplasmic contractile proteins function as a cytoskeletal system inthe cytoplasmic matrix. Biochemical experiments show that cycoplasmic actin filaments can form a solid gel under conditions likely to exist in living cells. The actin filaments are associated with other proteins which may stabilize the gel and which are involved with motile force generation like myosin. Ultrastructural studies show that actin filaments are difficult to preserve, but that under stabilizing conditions networks of actin filaments are found throughout the cytoplasmic matrix.
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  • 170
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    Journal of Supramolecular Structure 5 (1976), S. 457-473 
    ISSN: 0091-7419
    Keywords: sporulation ; membranes ; Bacillus subtilis ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Membrane protein alterations during the early stages of sporuloation were examined by polyacrylamide gel electrophoresis. Solubilized samples of the vegetative cell membrane (VCM), sporulation membrane fraction (SMF), and inner forespore membranes (IFM) were compared with respect to their protein compositions. The VCM contained 39 protein components, distinguishable as separate bands on gel electrophoresis, and these ranged in molecular weight from 16,000 to greater than 100,000. During the first 5 hr of sporulation, 6 of these 39 protein bands disappeared, 8 increased and 12 decreased in concentration, and 13 showed no discernible change. In addition, 15 new protein components were identified in the SMF during the fireist 5 hr. The new components consisted of 7 protein bands that were transiently associated with the SMF, and 8 proteins that persisted in the SMF from their time of appearance until at least T5 of sporulation. Comparison of the protein composition of the IFM with those of the VCM and SMF revealed that membrane protein alterations occur during sporulation.The turnover of H3-tryptophan-labeleld membrane protein was followed during growth and sporulation. During the 30 min of growth following a simple chase with excess unlabeled tryptophan, membrane protein appeared stable, whereas 5-10% of the nonmembrane protein turned over to acid-soluble material. However, manipulation of the cells by dilution ito fresh medium, or centrifugation, as part of the chase procedure, resulted in elution of membrane protein to the cytoplasm. In contrast, proteins labeled during vegetative growth were always eluted to the cytoplasm during the first 2 hr of sporulation, and this was followed by a period of reassociation with the membrane fraction. The results are discussed with respect to membrane differentiation as it relates to spore development.
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  • 171
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    Journal of Supramolecular Structure 5 (1976), S. 515-520 
    ISSN: 0091-7419
    Keywords: mutant RCAII ; ricin ; toxin ; protein synthesis ; variant cell line ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Ricinus communis agglutinin II (RCAII, ricin, toxin) at low concentrations inhibits protein synthesis in cell-free extracts, but not in intact cells, of an RCAII-resistant mouse lymphoma variant cell line. The concentration dependence of the inhibition by RCAII was the same in cell-free extracts of both RCAII-resistant variant and RCAII-sensitive parental cells, while intact parental cells are 250 times more sensitive to RCAII toxicity. The onset of RCAII inhibition of cell-free protein synthesis was extremely rapid in both cases, being complete in a few minutes. Under these condidtions RCAII inhibits protein synthesis in intact RCAII-sensitive parental cells, but maximal inhibition requires several hours to occur. These results support our previous electron microscopic observations that the variant cells are defective in the uptake of RCAII by endocytosis at low toxin concentrations.
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  • 172
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    Journal of Supramolecular Structure 7 (1977), S. 223-234 
    ISSN: 0091-7419
    Keywords: cell surfaces ; carbohydrates ; implantation ; lectin binding ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Preimplantation embryos were obtained from the uteri and oviducts of 2 strains of mice, Swiss CD-1 and B6 CBA. After removal of the zona pellucida by treatment with pronase, FITC-lectins were bound to the embryonic cell surfaces at either 4°C or 37°C. Both morula and blastocyst stage embryos bound the following lectins, FITC-ConA, FITC-WGA, FITC-RCAII and FITC-RCAI. No difference in binding was observed between the morula stage and the blastocyst stage within each mouse strain for each specific lectin. However B6 CBA embryos bound less FITC-ConA and FITC-WGA than the corresponding Swiss CD-1 embryos. The topographical arrangement of the lectin receptors was observed to differ between 4°C and 37°C for FITC-Con A, FITC-RCAII, and FITC-RCAI. While lectins bound at 4°C showed a pattern of continuous labeling, the same lectin at 37°C showed aggregation of lectin receptors into patches indicating lateral mobility of these receptors within the embryonic cell membranes. In contrast FITC-WGA bound at 4°C and 37°C demonstrated continuous labeling of embryos at both temperatures. FITC-fucose binding protein did not bind to Swiss CD-1 embryos.The invasiveness of trophoblastic cells of mouse blastocysts was studied by culturing isolated embryos without prior enzyme treatment on reconstituted collagen gels. After 4 days in BME containing only glutamine and bovine serum albumin as supplements, the embryos shed their zona pellucida and implanted into the collagen gel as indicated by zones of lysis in proximity to the embryonic cells when analyzed by scanning electron microscopy.
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  • 173
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    Journal of Supramolecular Structure 7 (1977), S. 1-97 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
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  • 174
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    Journal of Supramolecular Structure 7 (1977), S. 301-306 
    ISSN: 0091-7419
    Keywords: cytoplasmic activator ; red blood cells ; membrane ATPase ; Ca2+ transport ; (Ca2+-Mg2+)ATPase ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Human red blood cells (RBC) contain a cytoplasmic, nonhemoglobin protein which activates the (Ca2+-Mg2+) ATPase of isolated RBC membranes. Results presented in this paper confirm that activation of (Ca2+-Mg2+)ATPase is associated with binding of the cytoplasmic activator to the membrane. Binding of the cytoplasmic activator is reversible and dependent on ionic strength and Ca2+. Cytoplasmic activator is sensitive to trypsin but is not degraded when intact RBC are exposed to trypsin. Cytoplasmic activator does not modify the (Ca2+-Mg2+)-ATPase of membranes from RBC exposed to activator prior to hemolysis. Thus, the activator is located in the cell and appears to act by binding to the inner membrane surface.
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  • 175
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    Journal of Supramolecular Structure 7 (1977), S. 371-379 
    ISSN: 0091-7419
    Keywords: Sindbis ; glycoproteins ; cell surface ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The carbohydrate portions of the Sindbis virus glycoproteins were compared with the carbohydrate portions of cell surface glycoproteins from uninfected host cells. Comparisons of the size of glycopeptides were made using gel filtrations. Comparisons of sugar linkages were made by methylation analysis. The conclusion was that the Sindbis carbohydrate is similar to a portion of the host carbohydrate. Thus, the Sindbis carbohydrate structures appear to be structures normally made in the uninfected host cell, but which are added to the Sindbis glycoproteins in virus-infected cells.
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  • 176
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    Journal of Supramolecular Structure 7 (1977), S. 381-395 
    ISSN: 0091-7419
    Keywords: dolichyl phosphomannose ; glycoproteins ; mannosyltransferases ; polyprenyl phosphosugars ; retina ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Large-scale incubations were carried out with homogenates of the retinas of the 15-16-day-old chick embryo in the presence of GDP[U-14C] mannose, from which there were isolated a mannolipid (Lipid I), oligosaccharide-lipids (Lipid II), and glycoprotein (residue). These incubations were performed in the presence of endogenous acceptors as well as dolichyl phosphate. [14C] Mannolipid I was subjected to chromatography on DEAE cellulose and silicic acid. The response to these, as well as TLC, enzymatic, and chemical treatments, were consistent with the product being dolichyl phosphomannose. [14C] Lipid II was purified by DEAE cellulose chromatography and gel filtration on LH-20. Responses to these treatments, as well as TLC and paper chromatography, were consistent with this product being of the class of the oligosaccharide-pyrophosphate-lipids. The residue remaining after removal of the lipids was shown to contain glycoproteins by conversion of high-molecular-weight radioactive material to low-molecular-weight [14C] mannose-containing glycopeptides by the action of pronase. These reactions and their products are consistent with there being in the retina, the pathway for glycoprotein synthesis involving the participation of the lipid-activated carbohydrates.When the incubations were performed in the presence of ATP or ADP there was a decrease in the labeling of Lipid I, accompanied by an increase in the labeling of Lipid II and glycoprotein. When incubated in the presence of dolichyl phosphate and deergent, however, the stimulatory effect of ATP did not occur. The effect on these activities of a variety of other nucleotide phosphates was also examined.
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  • 177
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    Journal of Supramolecular Structure 7 (1977), S. 435-442 
    ISSN: 0091-7419
    Keywords: lipoprotein structure ; x-ray scattering ; thermal trasnsitions ; interaction arterial proteoglycans ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The structure and thermal behavior of human serum low-density lipoproteins showing either a high or a low reactivity against a proteoglycan isolated from human arteries have been found to be different from each other. It is suggested that modifcations in the lipoprotein surface structure induced by the physical state of the neutral lipids could modulate the affinity of the macromolecule for the arterial component.
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  • 178
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    Journal of Supramolecular Structure 7 (1977), S. 515-530 
    ISSN: 0091-7419
    Keywords: breast ; prostate ; carcinoma ; glycoproteins ; organ culture ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We demonstrate that a technique is available to investigate glycoprotein synthesis in organ cultures of human breast and prostate surgical specimens where the 3-dimensional epithelial cell arrangement remains intact. Malignant breast and prostate epithelium maintained their capacity to synthesize glycoproteins for at least 3 days as followed by the incorporation of [3H] glucosamine into macromolecules. Over 70% of incorporation was by malignant cells as judged by autoradiography. Labeled glycoproteins were released into glandular lumina and consequently into the culture fluid. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed predominantly one group of macromolecules released with an apparent molecular weight of 48,000 ± 6,000 daltons. This glycoprotein was found in all of the breast specimens studied, which included 1 medullary, 1 infiltrating lobular, and 8 infiltrating duct carcinomas. The pattern was independent of the availability of estrogen receptors. A similar glycoprotein was also observed in the culture media from a Grade I and a Grade II well-differentiated infiltrating prostate carcinoma. Incorporation was below the level of detection in 4 of 6 cases of benign prostatic hyperplasia. A more complex pattern of labeled glycoproteins was found in the media of a Grade II and a Grade III poorly-differentiated prostate carcinoma. The established human mammary carcinoma cell line MCF-7 synthesized and released a similar 48,000 molecular weight glycoprotein but additional components with larger molecular weights were also released. An intriguing interpretation that 3-dimensional tissue integrity restricts some glycorprotein synthesis is discussed. Cells grown in 2-dimensional monolayers could escape from such a topographic restriction and express additional families of glycoproteins.
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  • 179
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    Journal of Supramolecular Structure 8 (1978), S. 39-49 
    ISSN: 0091-7419
    Keywords: affinity chromatography ; plasma membrane ; neoplastic transformation ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The probe 2,4,6-trinitrobenzene sodium sulfonate may be used under appropriate conditions for selective labelling of plasma membrane proteins exposed at the outer cell surface. Labeled proteins, solubilized by detergents, can be purified by reverse immunoadsorption using antiprobe antibodies covalently linked to Sepharose 4B. This method has been applied to an investigation of the outer cell surface structure of chicken embryo and hamster fibroblasts. Coelectrophoresis in sodium dodecyl sulfate-polyacrylamide gels of probe-labeled membrane proteins purified from baby hamster kidney fibroblasts have shown that 7 major protein groups of different molecular weight are exposed on both control and Rous sarcoma or polyoma virus-transformed cells. Moreover, the transformed cells display a nonvirion component of 80-100 k daltons that is not labeled by the probe in normal cells. In fibroblasts transformed by a temperature sensitive Rous sarcoma virus mutant, that transforms at 37°C but not at 41°C, the expression of this component is related to the expression of the transformed phenotype.
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  • 180
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    Journal of Supramolecular Structure 8 (1978), S. 129-138 
    ISSN: 0091-7419
    Keywords: freeze-fracturing ; membranes ; lipid phase separations ; B stearothermophilus ; temperature adaptation ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Bacillus stearothermophilus cells vary the lipid fatty acid composition of cytoplasmic membranes with growth temperature. Spin label studies of such membranes have been interpreted to indicate lateral lipid phase separations at the growth temperature. We have now used freeze-fracture electron microscopy to confirm the spin label studies. Freeze-fracture faces of protoplasts indicate slight but distinct protein aggregation at the growth temperature. Aggregation increases rapidly with decreasing quench temperature in wild-type cells. In contrast we were unable to demonstrate extended protein segregation in membranes of a temperature-sensitive mutant that contains more than 58% branched fatty acids.Storage of protoplasts for prolonged times below the lipid phase transition results in the appearance of corrugated fracture faces with 300- to 500-Å repeat patterns, although this organism does not synthesize lecithins.
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  • 181
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    Journal of Supramolecular Structure 8 (1978), S. 177-190 
    ISSN: 0091-7419
    Keywords: fish melanophores ; electron microscopy ; microtubules ; tubulin ; quantitative analysis ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Isolated melanophores of the angelfish, Pterophyllum scalare, have been used in a morphometric analysis and a quantitative study of their microtubule system. Using transverse sections spaced at regular intervals, the changes associated with the process of pigment aggregation have been determined. Upon the concentration of pigment granules in the central cell region, almost half of the cytoplasmic portion is also withdrawn from the peripheral cell regions. Counts of microtubules within a cell sector in cells with pigment aggregated and dispersed, respectively, reveal (a) a constancy of the number of microtubules in this sector regardless of the distance from the cell center, and (b) a reduction of microtubule number in cells with pigment aggregated by about 58%. On the basis of these counts, the total number of microtubules has been calculated. In the dispersed state, about 2,400 microtubules extend between the center and the periphery of the cell, while their number is about 1,000 in the aggregated state.Using a 13-protofilament model of a microtubule and relevant data on size and molecular weight of microtubule subunits, the amount of tubulin present as microtubules is calculated. In the average, the cells contain 1.95·108 monomers corresponding to 1.78·10-8 mg tubulin. A tentative estimation of the concentration of tubulin inside a melanophore yields values of 6.1 mg/ml for the whole cell and 16.5 mg/ml for the cytoplasm alone (excluding membrane-bound organelles). Based on this estimation, a comparison, with microtubule assembly in vitro is made.
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  • 182
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    Journal of Supramolecular Structure 8 (1978), S. 191-213 
    ISSN: 0091-7419
    Keywords: amino-phospholipids ; chemical probes ; red cell membrane ; valinomycin ; ion transport ; membrane topology ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The red cell membrane has an asymmetric arrangement of phospholipids. The amino-phospholipids are localized primarily on the inner surface of the membrane and the choline phospholipids are localized to a large extent on the outer surface of the membrane. Evidence is presented based on the use of covalent chemical probes in sequence that the red cell membrane contains heterogeneous domains of PE and PS and that the transport systems for Pi and K+ are asymmetrically arranged. Certain amino groups of PE, PS, and/or protein localized on the outer membrane surface are involved in Pi transport and certain amino groups of PE, PS, and/or protein localized on the inner surface of the membrane are involved in K+ transport.Cross-linking studies with DFDNB show that the cross-linked PE-PE molecules are rich in plasmalogens. This suggests that clusters of plasmalogen forms of PE occur in the membrane. Both PE and PS are cross-linked to membrane protein. These PE and PS molecules contain 24-28% 16:0 and 18:0 fatty acids and 12% fatty aldehydes. PE and PS molecules are cross-linked to a spectrin-rich fraction. It is proposed that the binding of spectrin to membrane PE and PS may help anchor spectrin to the inner surface of the membrane and regulate shape changes in the cell.K+-valinomycin forms a complex with TNBS and converts it from a non-penetrating proble to a penetrating probe. Valinomycin enhances K+ leak and Pi leak in the red cells. SITS inhibits completely the valinomycin-induced Pi leak and inhibits partially the valinomycin induced K+ leak. Valinomycin and IAA have additive effects on Pi leak. Ouabin has no effect on basal or valino-mycin-induced Pi leak. These data suggest that Pi leak and K+ leak occur by separate transport systems.In summary, the amino-phospholipids in the red cell membrane are asymmetrically arranged; some occur in clusters and some are closely associated with membrane proteins. Amino-phospholipids also are believed to bind spectrin to the inner surface of the membrane and also may play a role in cation and anion leak.
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  • 183
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    Journal of Supramolecular Structure 8 (1978), S. 215-221 
    ISSN: 0091-7419
    Keywords: spectrin ; erythrocyte membrane ; membrane attachment site ; membrane protein mobility ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Interactions between spectrin and the inner surface of the human erythrocyte membrane have been implicated in the control of lateral mobility of the integral membrane proteins. We report here that incubation of “leaky” erythrocytes with a water-soluble proteolytic fragment containing the membrane attachment site for spectrin achieves a selective and controlled dissociation of spectrin from the membrane, and increases the rate of lateral mobility of fluorescein isothiocyanate-labeled integral membrane proteins (〉 70% of label in band 3 and PAS-1). Mobility of membrane proteins is measured as an increase in the percentage of uniformly fluorescent cells with time after fusion of fluorescent with nonfluorescent erythrocytes by Sendai virus. The cells are permeable to macromolecules since virus-fused erythrocytes lose most of their hemoglobin. The membrane attachment site for spectrin has been solubilized by limited proteolysis of inside-out erythrocyte vesicles and has been purified (V). Bennett, J Biol Chem 253:2292 (1978). This 72,000-dalton fragment binds to spectrin in solution, competitively inhibits association of 32P-spectrin with inside-out vesicles with a Ki of 10-7M, and causes rapid dissociation of 32P-spectrin from vesicles. Both acid-treated 72,000-dalton fragment and the 45,000 dalton-cytoplasmic portion of band 3, which also was isolated from the proteolytic digest, have no effect on spectrin binding, release, or membrane protein mobility. The enhancement of membrane protein lateral mobility by the same polypeptide that inhibits binding of spectrin to inverted vesicles and displaces spectrin from these vesicles provides direct evidence that the interaction of spectrin with protein components in the membrane restricts the lateral mobility of integral membrane proteins in the erythrocyte.
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  • 184
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    Journal of Supramolecular Structure 6 (1977), S. 125-133 
    ISSN: 0091-7419
    Keywords: amino acid transport ; gradient hypothesis ; electrogenic cation pump ; electrolyte movements ; ouabain ; furosemide ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The existence of an electrogenic Na+ pump in Ehrlich cells which substantially contributes to the membrane potential, previously derived from the distribution of the lipid soluble cation tetraphenylphosphonium (TPP+), could be confirmed by an independent method based on the quenching of fluorescence of a cyanine dye derivative, after the mitochondrial respiration had been suppressed by appropriate inhibitors. The mitochondrial membrane potential, by adding to the overall potential as measured in this way is likely to cause an overestimation of the membrane potential difference (p.d.). But since this error tends to diminish with increasing pump activity, the true p.d. of the plasma membrane should easily account for the driving force to drive the active accumulation of amino acids in the absence of an adequate Na+ concentration gradient. Accordingly, the F2-aminoisobutyric acid (AIB) uptake rises linearly with the distribution of TPP+ at constant Na+ concentrations, suggesting that each responds directly to membrane potential. There is evidence that the electrogenic (free) movement of Cl- is slow, at least at normal p.d., whereas a major part of the Cl- movement across the cellular membrane appears to occur by an electrically silent Cl--base exchange mechanism. By such a mode Cl-, together with an almost stoichiometric amount of K+, may under certain conditions move into the cell against a high adverse electrical potential difference. This “paradoxical” movement of K+Cl- contributing to the deviation of the Cl- distribution from the electrochemical equilibrium distribution, is not completely understood. It is insensitive towards ouabain but can almost specifically be inhibited by furosemide. As a likely explanation a H+-K+ exchange pump was previously offered, even though unequivocal evidence of such a pump is so far lacking. According to available evidence the electrogenic movement of free Cl- is too small, at least at normal orientation of the p.d., to significantly shunt the electrogenic pump potential so that the establishment of such a potential is plausible. The evidence presented is considered strong in favor of the gradient hypothesis since even in the absence of an adequate Na+ concentration gradient, the electrogenic Na+ pump will contribute sufficient extra driving force to actively transport amino acid into the cells.
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  • 185
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    Journal of Supramolecular Structure 6 (1977), S. 135-153 
    ISSN: 0091-7419
    Keywords: periplasmic proteins ; transport ; precursor ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The cold osmotic shock procedure releases a protein (GLPT) from the cell envelope of Escherichia coli that is related to the transport of sn-glycerol-3-phosphate in this organism. The evidence for this correlation is as follows: (1) GLPT is under the regulatory control of the glpR gene. (2) Some glpT mutants that were isolated as phosphonomycin resistant clones do not synthesize GLPT. Revertants of these mutants (growth on sn-glycerol 3-phosphate) again synthesize GLPT. (3) Some amber mutations in glpT reduce the amount of GLPT while suppressed strains produce normal amounts. (4) Transfer of a plasmid carrying the glpT genes into a strain lacking GLPT and sn-glycerol-3-phosphate transport restores both functions in the recipient. Transport and GLPT synthesis in the plasmid carrying strain are increased 2- to 3-fold over a fully induced wild-type strain, but appear to be constitutive. GLPT is a soluble protein of molecular weight 160,000 composed of 4 identical subunits. The 160,000 molecular weight complex is stable in 1% sodium dodecylsulfate at room temperature. Upon boiling in 1% sodium dodecylsulfate GLPT dissociates into its subunits. Likewise, 8 M urea at room temperature dissociates GLPT into its subunits. Dialysis of dissociated GLPT against phosphate or Tris-HCl buffer, pH 7.0, allows renaturation to the tetrameric form. The protein is acidic in nature (isoelectric point 4.4).In contrast to the typical transport-related periplasmic-binding proteins, no conditions could be found where pure GLPT exhibited binding activity toward its supposed substrate, sn-glycerol-3-phosphate.In vivo new appearance of transport activity for sn-glycerol-3-phosphate transport occurs only shortly before cell division. However, GLPT synthesis does not fluctuate during the cell cycle. The available evidence indicates a cell-division-dependent processing of GLPT in the cell envelope as a reason for the alteration in transport activity.Transport in whole cells is sensitive to the cold osmotic shock procedure, demonstrating the participation of an essential periplasmic component. However, isolated membrane vesicles that are devoid of periplasmic components, including GLPT, are fully active in sn-glycerol-3-phosphate transport. Therefore, we conclude that GLPT is essential in overcoming a diffusion barrier for sn-glycerol-3-phosphate established by the outer membrane. Attempts to isolate mutants that are transport negative in whole cells due to a defect in GLPT but are active in isolated membrane vesicles have failed so far. All GLPT mutants tested, whether or not they synthesize GLPT, are not active in isolated membrane vesicles.Iodination of whole cells with [125I] followed by osmotic shock reveals that several shock-releasable proteins including GLPT become radioactively labeled. This indicates that some portions of GLPT are accessible to the external medium.
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  • 186
    ISSN: 0091-7419
    Keywords: cilia ; dynein ; conformation change ; sulfhydryl groups ; ATPase activity ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Incubation of glycerol-extracted, Triton X-100 demembranated Tetrahymena cilia with 2-10 vol % acetone caused an enhancement of ATPase activity by 2- to 3- fold, depending on concentration and time of incubation. Axonemal ATPase activity was also increased upon incubation with bis (4-fluoro-3-nitrophenyl) sulfone (FNS). Acetone and FNS enhanced the activity of solubilized 30S dynein, but slightly inhibited that of 14S dynein. Heating at 38°C, incubation with FNS, and incubation with acetone activated axonemal ATPase to the same extent. Subsequent studies of (1) the effect of time of preincubation with a spin-labeled maleimide (SLM) at 25°C as a function of pH on the ATPase activity, (2) the concentration dependence of the inhibition of ATPase activity by N-ethylmaleimide or SLM, (3) the ratio of ATPase activity assayed at 25°C to that assayed at 0°C, and (4) the ratio of ATPase activity at pH 8.6 to that at pH 6.9 did not reveal any difference in the properties of the axonemal ATPase after near maximal enhancement by the heat, acetone, or FNS treatments. It was concluded that enhancement of ATPase activity by gentle heat treatment, by incubation with acetone (or other organic solvents), or by FNS results from a conformation change of 30S dynein.The effect of acetone and of FNS on the pellet height response (a measure of the increase in height of the pellet of cilia precipitated by brief centrifugation in the presence of ATP as compared to the absence of ATP) was also determined. Enhancement of ATPase by these reagents did not lead to a decrease in pellet height response. This observation, in conjunction with other data, indicates that there are at least 3 states of the cross-bridge cycle of dynein arms in cilia.
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  • 187
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    Journal of Supramolecular Structure 6 (1977), S. 169-177 
    ISSN: 0091-7419
    Keywords: Halobacterium halobium ; amino acid transport ; sodium-proton exchange ; asymmetry of transport system ; reconstitution of glutamate transport ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Cell envelope vesicles prepared from H. halobium contain bacteriorhodopsin and upon illumination protons are ejected. Coupled to the proton motive force is the efflux of Na+. Measurements of 22Na flux, exterior pH change, and membrane potential, ΔΨ (with the dye 3,3′-dipentyloxadicarbocyanine) indicate that the means of Na+ transport is sodium/proton exchange. The kinetics of the pH changes and other evidence suggests that the antiport is electrogenic (H+/Na+ 〉 1). The resulting large chemical gradient for Na+ (outside 〉 inside), as well as the membrane potential, will drive the transport of 18 amino acids. The 19th, glutamate, is unique in that its accumulation is indifferent to ΔΨ: this amino acid is transported only when a chemical gradient for Na+ is present. Thus, when more and more NaCl is included in the vesicles glutamate transport proceeds with longer and longer lags. After illumination the gradient of H+ collapses within 1 min, while the large Na+ gradient and glutamate transporting activity persists for 10-15 min, indicating that proton motive force is not necessary for transport. A chemical gradient of Na+, arranged by suspending vesicles loaded with KCl in NaCl, drives glutamate transport in the dark without other sources of energy, with Vmax and Km comparable to light-induced transport. These and other lines of evidence suggest that the transport of glutamate is facilitated by symport with Na+, in an electrically neutral fashion, so that only the chemical component of the Na+ gradient is a driving force.The transport of all amino acids but glutamate is bidirectional. Actively driven efflux can be obtained with reversed Na+ gradients (inside 〉 outside), and passive efflux is considerably enhanced by intravesicle Na+. These results suggest that the transport carriers are functionally symmetrical. On the other hand, noncompetitive inhibition of transport by cysteine (a specific inhibitor of several of the carriers) is only obtained from the vesicle exterior and only for influx: these results suggest that in some respects the carriers are asymmetrical.A protein fraction which binds glutamate has been found in cholate-solubilized H. halobium membranes, with an apparent molecular weight of 50,000. When this fraction (but not the others eluted from an Agarose column) is reconstituted with soybean lipids to yield lipoprotein vesicles, facilitated transport activity is regained. Neither binding nor reconstituted transport depend on the presence of Na+. The kinetics of the transport and of the competitive inhibition by glutamate analogs suggest that the protein fraction responsible is derived from the intact transport system.
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  • 188
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    Journal of Supramolecular Structure 8 (1978), S. 455-463 
    ISSN: 0091-7419
    Keywords: protein mobility ; spectrin shape ; spectrin binding ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Transmembrane proteins of the human erythrocyte show restricted in-plane mobility. Many of the restrictions on mobility are attributable to the molecules of spectrin which are located on the protoplasmic surface of the erythrocyte membrane. These molecules are elongate, form end-to-end heterodimer associations, and bind selectively to protein (or proteins) accessible on inside-out, but not right-side out, membrane vesicles.
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  • 189
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    Journal of Supramolecular Structure 8 (1978), S. 447-453 
    ISSN: 0091-7419
    Keywords: membrane proteins ; transport proteins ; glucose transport ; reconstitution of glucose transport ; purification of glucose transporter ; cytochalasin B ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The D-glucose transporter from human erythrocytes has been purified and reconstituted by Kasahara and Hinkle (J Biol Chem 252:7394-7390). Using a similar purification scheme, we have isolated the protein with 65% of the extracted phospholipid at a lipid-protein ratio of 14:1 by weight. The KD (0.14 μM) and extent (11 nmoles/mg protein) for binding of 3H-cytochalasin B was determined by equilibrium dialysis. Glucose was a linear competitive inhibitor of binding of cytochalasin B, with an inhibition constant of 30 mM. To further characterize the protein, samples were filtered in the presence of sodium dodecyl sulfate (SDS) through Sepharose 6B to remove 95% of the lipid followed by filtration of Sephadex G150 to remove the remaining lipid and a contaminating amount of a minor, lower-molecular-weight protein. This preparation contains only 24% acidic and basic amino acids. The protein also contains 5% neutral sugars (of which 3% is galactose), 7% glucosamine, and 5% sialic acid.
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  • 190
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    Journal of Supramolecular Structure 8 (1978), S. 465-471 
    ISSN: 0091-7419
    Keywords: spectrin ; fractionation ; trypsin digestion ; peptide mapping ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The two major polypeptides of erythrocyte membrane spectrin have been isolated by preparative polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The tryptic peptide maps of the two polypeptides have been prepared by thin-layer chromatography and electrophoresis. Radioactive peptides have been prepared by 14C-carboxymethylation and chloramine T-catalysed 125I iodination. Maps of both sets of peptides demonstrate a marked similarity between the two parent polypeptides.
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  • 191
    ISSN: 0091-7419
    Keywords: down regulation ; epidermal growth factor ; epidermal growth factor receptor ; mitogenesis ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Swiss 3T3 and C3H-M2 cells have a greater mitogenic response to epidermal growth factor (EGF) than do C3H-10T1/2 cells. The latter cell line, however, has a number of EGF receptors per cell intermediate between the two cell lines that have a more vigorous response to EGF. Scatchard analysis of binding data indicate that all three cell lines have one class of EGF receptor, with indistinguishable affinity for the ligand. When exposed to 10-nM EGF all three cell lines “down-regulate” their EGF receptors with the same time course, and to the same precentage of initial receptors.
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  • 192
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    Journal of Supramolecular Structure 6 (1977), S. 259-274 
    ISSN: 0091-7419
    Keywords: conformational analysis ; polysaccharides ; cooperative interactions ; synergistic interactions ; cooperative cation binding ; spectroscopic techniques ; circular dichroism ; nuclear magnetic resonance ; optical rotation ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: For consideration of their conformations and interactions, carbohydrate chains can conveniently be divided into 3 classes on the basis of their covalent structure; namely periodic (a), interrupted periodic (b), and aperiodic (c) types. In aqueous solution carbohydrate chains often exist as highly disordered random coils. Under appropriate conditions, however, polysaccharides of types (a) and (b) can adopt a variety of ordered conformations. Physical methods, and in particular optical rotation, circular dichroism, and nuclear magnetic resonance, provide sensitive probes for the study of the mechanism and specificity of these disorder-order transitions in aqueous solution.Intermolecular interactions between such polysaccharide chains arise from co-operative associations of long structurally regular regions which adopt the ordered conformations. For acidic polysaccharides these cooperative associations may involve alignment of extended ribbons with cations sandwhiched between them. In other systems the interactions involve double belices which may then aggregate further, and geometric “matching” of different polysaccharide chains can also occur. These ordered, associated regions are generally terminated by deviations from structural regularity or by “kinks” which prevent complete aggregation of the molecules.The complex carbohydrate chains which occur at the periphery of animal cells have very different, aperiodic structures and although their conformations are as yet poorly understood, preliminary indications are considered.
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  • 193
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    Journal of Supramolecular Structure 3 (1975), S. 304-313 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: EPR and water proton relaxation rate (1/T1) studies of partially (40%) and “fully” (90%) purified preparations of membrane-bound (Na++K+) activated ATPase from sheep kidney indicate one tight binding site for Mn2+ per enzyme dimer, with a dissociation constant (KD = 0.88 μM) in agreement with the kinetically determined activator constant, identifying this Mn2+-binding site as the active site of the ATPase. Competition studies indicate that Mg2+ binds at this site with a dissociation constant of 1 mM in agreement with its activator constant.Inorganic phosphate and methylphosphonate bind to the enzyme-Mn2+ complex with similar high affinities and decrease l/T1 of water protons due t o a decrease from four to three in the number of rapidly exchanging water protons in the coordination sphere of enzyme-bound Mn2+. The relative effectiveness of Na+ and K+ in facilitating ternary complex formation with HPO2-4 and CH3PO2-3 as a function of pH indicates that Na+ induces the phosphate monoanion t o interact with enzyme-bound Mn2+, while K+ causes the phosphate dianion to interact with the enzyme-bound Mn2+. Thus protonation of an enzyme-bound phosphoryl group would convert a K+-binding site to a Na+-binding site. Dissociation constants for K+ and Na+, estimated from NMR titrations, agreed with kinetically determined activator constants of these ions consistent with binding t o the active site.Parallel 32Pi-binding studies show negligible formation (〈 7%) of a covalent E-P complex under these conditions, indicating that the NMR method has detected an additional noncovalent intermediate in ion transport. Ouabain, which increases the extent of phosphorylation of the enzyme to 24% at pH 7.5 and t o 106% at pH 6.1, produced further decreases in l/T 1 of water protons. Preliminary 31P-relaxation studies of CH3PO2-3 in the presence of ATPase and Mn2+ yield an Mn to P distance (6.9 ± 0.5 Å) suggesting a second sphere enzyme-Mn-ligand-CH3PO2-3 complex.Previous kinetic studies have shown that T1+ substitutes for K+ in the activation of the enzyme but competes with Na+ at higher levels. From the paramagnetic effect of Mn2+ at the active site on the enzyme on I/T1 of 205T1 bound at the Na+ site, a Mn2+ to T1+ distance of 4.0 ± 0.1 Å is calculated, suggesting the sharing of a common ligand atom by Mn2+ and T1+ on the ATPase. Addition of P. increases this distance to 5.4 Å consistent with the insertion of P between Mn2+ and T1+. These results are consistent with a mechanism for the \documentclass{article}\pagestyle{empty}\begin{document}$ (\mathop {\rm N}\limits^{\rm i} {\rm a}^{\rm + } {\rm + K}^ +) $\end{document}-ATPase and for ion transport in which the ionization state of Pi at a single enzyme active site controls the binding and transport of Na+ and K+, and indicate that the transport site for monovalent cations is very near the catalytic site of the ATTase. Our mechanism also accounts for the order of magnitude weaker binding of Na+ compared to K+.
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  • 194
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    Journal of Supramolecular Structure 3 (1975), S. 103-103 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 195
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    Journal of Supramolecular Structure 6 (1977), S. 301-311 
    ISSN: 0091-7419
    Keywords: red cell ; erythrocyte ; membrane ; scanning electron microscope ; spectrin ; actin ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A web-like reticulum underlying the human erythrocyte membrane was studied at a resolution of 5-10 nm by means of a scanning electron microscope. The network was visualized in isolated membranes (ghosts) torn open to reveal their interior space and in residues derived from ghosts extracted with Triton X-100. It formed a continuous (rather than patchy) cover over the entire cytoplasmic surface, except where lifted off or torn away. Filaments (5-40 nm in diameter), annular figures (40-60 nm in diameter), and nodes (30-100 nm in diameter) were prominent in different networks. The dimensions of the filaments and the interstices in the reticulum varied with conditions, suggesting that the network has elastic properties. This reticulum is probably related to the erythrocyte membrane proteins spectrin and actin.
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  • 196
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    Journal of Supramolecular Structure 6 (1977), S. 313-323 
    ISSN: 0091-7419
    Keywords: peripheral and integral proteins ; membrane biosynthesis ; hydrophobic and hydrophilic interactions ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Membranes are structures whose lipid and protein components are at, or close to, equilibrium in the plane of the membrane, but are not at equilibrium across the membrane. The thermodynamic tendency of ionic and highly polar molecules to be in contact with water rather than with nonpolar media (hydrophilic interactions) is important in determining these equilibrium and nonequilibrium states. In this paper, we speculate about the structures and orientations of integral proteins in a membrane, and about how the equilibrium and nonequilibrium features of such structures and orientations might be influenced by the special mechanisms of biosynthesis, processing, and membrane insertion of these proteins. The relevance of these speculations to the mechanisms of the translocation event in membrane transport is discussed, and specific protein models of transport that have been proposed are analyzed.
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  • 197
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    Journal of Supramolecular Structure 6 (1977), S. 355-362 
    ISSN: 0091-7419
    Keywords: amino acid transport ; mammary gland ; cell proliferation ; feedback regulation ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The regulation of the uptake of the amino acid analog α-aminoisobutyric acid was studied in diced mammary glands from pregnant mice. Stimulation of uptake by insulin was not prevented by inhibitors of protein synthesis; protein synthesis inhibitors decreased uptake by 20%; this response occurred more promptly in insulintreated tissues. Elimination of extracellular amino acids led to a substantial increase in transport which was not abolished by inhibitors of protein synthesis. These results indicate that insulin does not increase amino acid transport in this system by altering synthesis and degradation of transport protein. They are consistent with a model in which the activity of the existing amino acid transport protein is subject to negative feedback regulation from the intracellular amino acid pool.
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  • 198
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    Journal of Supramolecular Structure 9 (1978), S. 391-398 
    ISSN: 0091-7419
    Keywords: parathyroid hormone ; adenylate cyclase ; calcium ; guanylylimidodiphosphate ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The effects of calcium ion on the adenylate cyclase system was studied in isolated, renal basal-lateral plasma membranes of the rat. Bovine parathyroid hormone (bPTH) and a guanyl triphosphate analogue, Gpp(NH)p were used to stimulate cyclase activity.Under conditions of maximal stimulation, calcium ions inhibited cyclic adenosine monophosphate (cAMP) formation, the formation rate falling exponentially with the calcium concentration. Fifty percent inhibition of either bPTH- or Gpp(NH)p-stimulated activity was given by approximately 50 μM Ca++. Also the Hill coefficient for the inhibition was close to unity in both cases. The concentration of bPTH giving half-maximal stimulation of cAMP formation (1.8 × 10-8 M) was unchanged by the presence of calcium.These data suggest that calcium acts at some point other than the initial hormone-receptor interaction, presumably decreasing the catalytic efficiency of the enzymic moiety of the membrane complex.
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  • 199
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    Journal of Supramolecular Structure 9 (1978), S. 363-371 
    ISSN: 0091-7419
    Keywords: cytochalasin B ; insulin action ; adipocytes ; plasma membranes ; D-glucose transport ; protein reagents ; membrane reconstitution ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Sensitivity of the adipocyte D-glucose transport system in intact plasma membranes or following solubilization and reconstitution into phospholipid vesicles to several protein-modifying reagents was investigated. When intact plasma membranes were incubated with N-ethylmaleimide (20 mM) or fluorodinitrobenzene (4 mM), D-glucose transport activity was virtually abolished. However, washing the membranes free of unreacted reagents restored transport activity, indicating that covalent interaction with the membranes did not mediate the transport inhibition. Reaction of [3H] N-ethylmaleimide with plasma membranes under similar conditions resulted in extensive labeling of all protein fractions resolved on dodecyl sulfate gels. Similarly, addition of N-ethyl-maleimide to cholate-solubilized membrane protein had no effect on transport activity in artifical phospholipid vesicles reconstituted under conditions where the membrane protein was free of unreacted N-ethylmaleimide. Transport activity in plasma membranes was also inhibited by both reduced and oxidized dithiothreitol or glutathione (15 mM) in a readily reversible manner, consistent with a noncovalent mode of inhibition. Thus, the insulin-responsive adipocyte D-glucose transport system differs from the red cell hexose transport system in its remarkable insensitivity to modulation by covalent blockade of sulfhydryal or amino groups by the reagents studied.
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  • 200
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    Journal of Supramolecular Structure 3 (1975), S. 521-521 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
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