bluuebunny/crossref_metadata_2025 huggingface dataset:
Recombination of human erythrocyte apoprotein and lipid. I. Interaction of apoprotein and lipid at the air‐water interface
Authors: Morse Philip D.
Published: May 2005

The formation and stabilization of a complex between total erythrocyte apoprotein and monolayers of total erythrocyte lipid as measured by changes of surface pressure (Δπ) and rate of change of surface pressure (dπ/dt) was studied as a function of pH, ionic strength, and lipid surface pressure. Penetration of apoprotein into lipid monolayers was favored by conditions in which lipid and apoprotein were oppositely charged. Once the interaction was completed, the resultant surface complex was resistant to large changes in subphase pH and ionic strength as shown by the insensitivity of Δπ to these parameters. The dπ/dt, however, showed strong dependence on pH and ionic strength, but not on lipid surface pressure. A sharp decrease in dπ/dt around pH 3.5–4.5 is associated with the change in apoprotein charge from (+) to (−). Comparison of complex formation between apoprotein and bovine serum albumin, cytochrome c, and human hemoglobin suggests that erythrocyte apoprotein was specialized in its interaction with erythrocyte lipids. The data show that formation of an apoprotein‐lipid complex at the air‐water interface has both electrostatic and hydrophobic components. This contradicts results from other laboratories studying erythrocyte membrane recombination by bulk methods.
Recombination of human erythrocyte apoprotein and lipid. II. Visualization of apoprotein‐lipid bilayer complex by freeze‐etching
Authors: Wehrli Ernst , Morse Philip D.
Published: May 2005

Bilayers of human erythrocyte apoprotein‐lipid complexes were made by dipping a mica plate through monolayers of the complex formed at the air‐water interface. Stearic acid and erythrocyte lipid alone served as controls. Freeze‐fracture images of the complex at high lipid surface pressures (30 dynes/cm) showed particles (average diameter, 109 Å ± 18 Å) similar to those of erythrocyte ghosts (average diameter, 102 Å ± 19 Å). Control surfaces were smooth. We conclude that part or all of the protein molecule penetrated into the lipid bilayer and that erythrocyte apoprotein‐lipid complexes yield fracture faces similar to the native erythrocyte membrane.
The sub‐membrane reticulum of the human erythrocyte: A scanning electron microscope study
Authors: Hainfeld James F. , Steck Theodore L.
Published: May 2005

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.
Defective transport of thymidine by cultured cells resistant to 5‐bromodeoxyuridine
Authors: Lynch Thomas P. , Cass Carol E. , Paterson Alan R. P.
Published: May 2005

A line of HeLa cells resistant to 5‐bromo‐2′‐deoxyuridine (BUdR) was established by continuous culture in growth medium containing BUdR; during the selection period, BUdR concentrations, initially 15 μM, were gradually increased to 100 μM. Cells of a clone (HeLa/B5) established from this line were also resistant to 5‐fluoro‐2′‐deoxyuridine (FUdR), but not to the free base, 5‐fluorouracil. Although extracts of HeLa/B5 cells exhibited levels of thymidine kinase activity comparable to those of parental cells, rates of uptake of BUdR, FUdR, and thymidine into intact cells were much reduced. The kinetics of uptake of uridine and adenosine, nucleosides which appear to be transported independently of thymidine in HeLa cells, were similar for HeLa/B5 and the parental line (HeLa/0). Relative to thymidine uptake by HeLa/0 cells, that by HeLa/B5 cells was distinctly less sensitive to nitrobenzlthionosine (NBMPR), a specific inhibitor of nucleoside transport in various types of animal cells. Despite this difference in NBMPR sensitivity, both cell lines possessed the same number of high affinity NBMPR binding sites per mg cell protein. The altered kinetics of thymidine uptake and the NBMPR insensitivity of that function in HeLa/B5 cells suggest that resistance to BUdR is due to an altered thymidine transport mechanism.
Association of (Ca+Mg)‐ATPase activity with ATP‐dependent Ca uptake in vesicles prepared from human erythrocytes
Authors: Quist Eugene E. , Roufogalis Basil D.
Published: May 2005

Ghost membranes prepared from human erythrocytes exhibit 2 distinct (Ca+Mg)‐ATPase1 activities (Quist and Roufogalis, Arch Biochem Biophys 168:240, 1975). (Ca+Mg)‐ATPase activity dependent on a water soluble protein fraction is selectively lost from ghost membranes during preparation of vesicles under low ionic strength, slightly alkaline conditions. In this study, the Ca2+ dependence of the remaining membrane bound (Ca+Mg)‐ATPase activity and ATP‐dependent Ca uptake in vesicles were compared. The C2+ activation curves for (Ca+Mg)‐ATPase activity and Ca uptake into vesicles were parallel over a Ca2+ range of 0.3–330 μM, and both curves have 2 apparent KA values for Ca2+ of 0.45 and 100 μM. Addition of a concentrated soluble protein fraction containing predomintly spectrin to the vesicles increased (Ca+Mg)‐ATPase activity over twofold but did not affect the rate of Ca uptake. These findings suggest that the (Ca+Mg)‐ATPase activity remaining in vesicles after extraction of the water soluble proteins is associated with the Ca pump whereas (Ca+Mg)‐ATPase activity dependent on the soluble protein fraction is associated with some other function.
Methods for rapidly altering the permeability of mammalian cells
Authors: Heppel Leon A. , Makan Nizar
Published: May 2005

Various agents alter mammalian cells so that they rapidly become nonspecifically permeable to substances that ordinarily do not penetrate intact cells. Thus, toluene renders liver cells permeable to nucleotides and macromolecules. Tween 80 and Tween 60 act in similar fashion, and the effect is reversible. Dextran sulfate reversibly alters the permeability of Ehrlich ascites tumor cells, which offers a tool for studying the control of macromolecular syntheses and other processes. Brief exposure to external ATP alters the permeability of certain transformed mouse cells but not of untransformed cells. The effect of ATP is rapidly reversible.
L‐arabinose transport and the L‐arabinose binding protein of escherichia coli
Authors: Hogg Robert W.
Published: May 2005

The active accumulation of L‐arabinose by arabinose induced cultures of Escherichia coli is mediated by 2 independent transport mechanisms. One, specified by the gene locus araE, is membrane bound and possesses a relatively “low affinity.” The other, specified in part by the genetic locus araF, contains as a functional component the L‐arabinose binding protein and functions with a “high affinity” for the substrate. The L‐arabinose binding protein has been purified, partially characterized, crystallized, and sequenced.
Microbial carbohydrate specific antibodies distinguish between different stages of differentiating mouse cerebellum
Authors: Trenkner Ekkhart , Sarkar Siddhartha
Published: May 2005

High titered anticarbohydrate antibodies were used to identify cell surface carbohydrates during different stages in histogenesis of mouse cerebellum in a micro tissueculture system which mimics selected features of in vivo cerebellum development. Blockage of fiber formation within the first few days in vitro and inhibition of cell migrations by carbohydrate‐specific antibodies served as an assay system for possible contributions of surface carbohydrates to the behavior of developing cerebellar cells. Microbial strains were selected on the basis of carbohydrate structures of their cell wall antigens, and anticarbohydrate antibodies were raised against treated whole bacteria and yeast in rabbits. We found that antibodies to mannan were active at all stages of development tested (embryonic day 13, E13; the day of birth, P0; and postnatal day 7, P7). Antibodies to sialic acids prepared against strains B and C of Neisseria meningitidis distinguish different subterminal structures: anti‐B reacted with E 13 and P0 cerebellar cells, and anti‐C mostly with cells older than P7. Antifetuin antibody recognized E 13 and P0 but not P7 cell populations. Pneumococcus C strain R36A‐specific antibodies were effective only after coating cells to C type carbohydrate before application of the antibody. The results demonstrate that antimicrobial carbohydrate antibodies cross‐react with mammalian cell surface carbohydrate structures and therefore can be used as a powerful tool in tissue culture to analyze those structures which might control cell behaviors pertinent to cerebellar development.
Subcellular fractionation of brown adipose tissue
Authors: Giacobino J.‐P.
Published: May 2005

The present study proposes a technique, using Metrizamide, which permits the preparation of brown adipose tissue plasma membranes from the crude mitochondria as well as from the crude microsome fraction. These plasma membranes have high relative specific activities of their marker enzyme, 5′‐nucleotidase (15 ± 3 and 14 ± 2 respectively) and, particularly those originating in the crude microsomes, are relatively free of mitochondria contamination. This study also shows the influence of the mode of cell disruption on microsome integrity. When cell disruption was achieved by grinding in liquid nitrogen the purified microsome NADPH cytochrome c reductase specific activity was found to be 3.5 times greater than that of microsomes obtained after homogenization of the tissue.
Alkaline phosphatase of basal lateral and brush border plasma membranes from intestinal epithelium
Authors: Hanna S. D. , Mircheff A. K. , Wright E. M.
Published: May 2005

The alkaline phosphatases present on isolated brush border and basal lateral membranes of rat duodenal epitheilum were examined by means of a variety of biochemical assays and physical methods. The two alkaline phosphatases have similar pH optima of 9.6–9.8, similar substrate km's for p‐nitrophenyl phosphate (PNPP) of 71 micromolar, similar responses to the inhibitors 2‐mercaptoethanol, theophylline, phenylalanine, and ethylenediaminetetraacetic acid (EDTA), similar sensitivities to calcium, magnesium, zinc, sodium, and potassium, and similar insensitivities to digestion with trypsin or papain. The two enzymes also exhibit similar molecular weights on SDS‐polyacrylamide gels in the range 124,000–150,000, and both enzymes show an Rf value of 0.092 on Triton X‐100 polyacrylamide gels, indicating similar intrinsic charges. The Vmax of the brush border enzyme is ten times greater than that of the basal lateral enzyme, 140 μmoles/mg‐h as opposed to 14 μmoles/mg‐h. The differences in Vmax are a reflection of the known distribution of alkaline phosphatase in rat duodenum, there being more alkaline phosphatase activity present on the brush border than on the basal lateral surface. One other major difference was observed between the two enzymes, the stimulation of the basal lateral and not the brush border alkaline phosphatase by SDS, Triton X‐100, or cholate. We conclude that the enzymes are very similar to one another and probably perform similar membrane functions.
Growth rate and chromosome number of tumor cell lines with different metastatic potential
Authors: Cifone Maria A. , Kripke Margaret L. , Fidler Isaiah J.
Published: May 2005

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.
Ganglioside patterns of metastatic and non‐metastatic transplantable hepatocellular carcinomas of the rat
Authors: Kloppel Thomas M. , Morré D. James , Jacobsen Linda B.
Published: May 2005

In previous investigations, we correlated levels of sialic acid, gangliosides, and ganglioside glycosyltransferases with tumorigenesis over a 24‐week continuum of growth of hepatocellular neoplasms of the rat induced by the carcinogen N‐2‐fluorenylacetamide. However, metastatic tumors developed only rarely and were not analyzed. To investigate surface changes associated with metastasis, well‐differentiated and poorly differentiated hepatocellular carcinomas were transplanted to syngeneic recipient rats. From those, several metastatic and nonmetastatic isolates were obtained and compared. Both total and ganglioside sialic acid amounts in transplantable hepatomas were elevated above control liver values but were significantly lower for metastatic lines than for nonmetastatic lines. The nonmetastatic lines were characterized by ganglioside patterns depleted in the precursor ganglioside GM3 (sialic acid‐galactose‐glucose‐ceramide) and elevated in the products of the monosialoganglioside pathway. In contrast, metastatic isolates exhibited a restoration of GM3 and nearer normal amounts of other gangliosides. The findings point to differences in sialic acid‐containing glycolipids, comparing metastatic and nonmetastatic hepatocellular carcinomas, and further extend the concept that ganglioside alterations do not cause tumorigenesis but are the end result of a cascade of events which apparently continue beyond the onset of metastasis.
Selection of malignant melanoma variant cell lines for ovary colonization
Authors: Brunson Kenneth W. , Nicolson Garth L.
Published: May 2005

Murine melanoma line B16‐F1, which shows some specificity for metastatic organ colonization of lung but rarely metastasizes to ovary, was used to select variant cell lines with increased preference for experimental ovary metastasis. Ovary‐colonizing melanoma cell lines were sequentially selected in syngeneic C57BL/6 mice by repeated intravenous administration and surgical recovery of ovarian melanoma tumors for tissue culture. After ten selections for experimental ovary metastasis, line B16‐010 was established which formed experimental metastatic ovary tumors in almost every test animal. In tissue culture B16–010 cells grew in circular in circular colonies with rounded, smooth cell peripheries compared to B16‐F1 cells which were flatter, grew in irregular patterns, and exhibited long cellular projections. Ovary‐selected B16 lines contained less melainin pigment (B16‐010 < B16‐05 < B16‐01 ≅ B16‐F1) compared to the parental melanoma line. Together with previous cloning and selection data, these results are consistent with the preexistence of highly malignant cells in the parental tumor population that possess the ability to metastasize to specific organs.
Alteration of insulin binding and cytoskeletal organization in cultured fibroblasts by tertiary amine local anesthetics
Authors: Raizada Mohan K. , Fellows Robert E.
Published: May 2005

Tertiary amine local anesthetics cause a time‐ and dose‐dependent, reversible increase in insulin binding sites in cultured chick embryo fibroblasts. Incubation of fibroblasts with 0.2 mM dibucaine for 3 h at 37°C results in a twofold to threefold increase in insulin binding, with an increase in average number of binding sites (Ka = 3.0 × 107M−1) from 9 × 103 to 29 × 103 per cell. Trypsin or ethylenegly coltetraacetic acid (EGTA) alone increases insulin binding twofold to threefold, but fails to further increase 125I‐insulin binding in cells pretreated with dibucaine. Transformation of chick embryo fibroblasts with Rous sarcoma virus causes a threefold to fivefold increase in insulin binding, which is not further increased by incubation with dibucaine. As demonstrated by transmission electron microscopy, dibucaine and trypsin also induce changes in the cytoskeleton of chick embryo fibroblasts, characterized by disorganization and disappearance of microfilament and microtubule bundles. These alterations are accompanied by gross morphologic changes, including rounding of cells and appearance of numerous ruffles and blebs on the cell surface. These observations are consistent with the hypothesis that expression of surface receptors in cultured chick embryo fibroblasts is related to the organization and disorganization of cytoskeletal structures.
Production of monoclonal antibodies against a cell surface concanavalin a binding glycoprotein
Authors: Starling James J. , Simrell Charles R. , Klein Paul A. , Noonan Kenneth D.
Published: May 2005

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.
Modulation of cell surface iron transferrin receptors by cellular density and state of activation
Authors: Larrick James W. , Cresswell Peter
Published: May 2005

This report describes investigations of plasma membrane transferrin receptors on a variety of lymphoid cell lines and normal peripheral blood lymphocytes during activation and cell growth cycles. Transformed lymphoid cell lines have as many as 1,000 times the number of receptors found on normal resting lymphocytes. The number of iron transferrin receptors on continuous cell lines as well as normal human fibroblasts is down‐regulated during the transition from log‐phase growth to stationary plateau growth. When normal lymphocytes are transformed by mixed lymphocyte culture or mitogens, they rapidly express a 50‐fold increase in the number of transferrin binding sites. This appearance of iron transferrin receptors anticipates nuclear changes during cell activation and subsequent mitosis of normal cells.
The role of colony‐stimulating factor in granulopoiesis
Authors: Shadduck Richard K. , Pigoli Giuseppe , Waheed Abdul , Boegel Florence
Published: May 2005

The proliferation and maturation of granulocytic‐monocytic stem cells appears to be controlled by a series of closely related glycoproteins termed “colony‐stimulating factors” (CSFs). Recently, we devised a 6‐step scheme for the purification of murine fibroblast (L‐cell)‐derived CSF. Ten liter pools of conditioned media were concentrated by ultrafiltration, precipitated by ethanol, and separated on DEAE cellulose, Con‐A Sepharose, and Sephadex G 150. The CSF was separated from trace contaminants, including endotoxin, by density gradient centrifugation. The purified material was radioiodinated and used to define the serum half‐life and in vivo distribution. Following IV injection there was a biphasic serum clearance with a t½ of 24–40 min and 2–2½ hours in the first and second phases. Approximately 25% of the tracer was excreted in the urine at 6 h; however, urinary radioactivity was due to low molecular weight peptides. Simultaneous studies by radioimmunoassay showed a similar rapid serum clearance of unlabeled CSF but virtually no urinary CSF activity. Thus, assays for urinary CSF may not provide useful measures of in vivo CSF activity. Further in vitro studies have defined the interaction of CSF with responsive cells in the marrow. Varying doses of CSF were incubated with 107 marrow cells for intervals of 24–48 h. The major increment in cell‐associated radioactivity occurred between 6 and 16 h. The reaction was saturable with 1–2 ng/ml CSF. Binding was prevented by cold CSF, but not by other proteins. Irradiation yielded only a minimal reduction in CSF binding. The interaction of CSF with marrow cells appeared to require new protein synthesis, as binding was completely inhibited by cycloheximide and puromycin. Irradiated mice injected with antibodies to CSF showed an inhibition of granulopoiesis by marrow cells in peritoneal diffusion chambers; however, granulopoiesis in the intact bone marrow was unaffected. Granulpoiesis in long‐term marrow cultures was also unaffected by anti‐CSF. These different responses may be due to accelerated clearance of injected CSF in nonirradiated mice or to extensive stromal interactions that modulate and perhaps control granulocytic differentiation in the intact bone marrow microenvironment.
Direct linkage of EGF to its receptor: Characterization and biological relevance
Authors: Linsley Peter S. , Fox C. Fred
Published: May 2005

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.
Controlled proteolysis of EGF receptors: Evidence for transmembrane distribution of the EGF binding and phosphate acceptor sites
Authors: Linsley Peter S. , Fox C. Fred
Published: May 2005

A small quantity of the 125I‐EGF (epidermal growth factor) bound specifically to EGF receptors on the human epidermoid carcinoma cell line A431 associates covalently. The direct linkage complex formed migrates during gel electro‐phoresis as a single diffuse band of MW = 160,000–170,000. In contrast, direct linkages complexes of 160,000, 145,000, and 115,000 daltons are formed when EGF is incubated with membranes isolated from these cells; these arise from EGF receptor modification during membrane isolation. None of these modifications affected the affinity of the EGF binding site for 125I‐EGF.

The electrophoretic mobilities of the MW = 160,000 and 145,000 direct linkage complexes were similar to those of the major 32Pi‐labeled products of the EGF‐stimulated phosphorylation reaction described by Carpenter et al [Nature 276:409–410, 1978], indicating that proteolytic fragments of EGF receptors are the major phosphate acceptors in this reaction. EGF receptors on intact A431 cells accepted phosphate effectively from γ‐32Pi‐ATP only when the cells were permeabilized with lysolecithin. This shows that the EGF binding and phosphate acceptor sites lie on opposing faces of the membrane. When the 145,000 dalton form of receptor is labeled with EGF or 32Pi and the labeled peptides subjected to tryptic hydrolysis under identical conditions, all phosphates is lost from high molecular weight products under conditions where the EGF‐receptor covalent complex is converted largely to a 115,000 dalton form. This suggests that the phosphate acceptor site lies on the cytoplasmic side of the membrane on a region of receptor extending 30,000 daltons from the 115,000 dalton fragment containing the EGF binding site.
Control of mouse myoblast commitment to terminal differentiation by mitogens
Authors: Linkhart Thomas A. , Clegg Christopher H. , Hauschka Stephen D.
Published: May 2005

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.
Regulation of high‐affinity leucine transport in escherichia coli
Authors: Landick Robert , Anderson James J. , Mayo Mary M. , Gunsalus Robert P. , Mavromara Penelope , Daniels Charles J. , Oxender Dale L.
Published: May 2005

Leucine is transported into E coli by two osmotic shock‐sensitive, high‐affinity systems (LIV‐I and leucine‐specific systems) and one membrane bound, low‐affinity system (LIV‐II). Expression of the high‐affinity transport systems is altered by mutations in liv R and 1st R, genes for negatively acting regulatory elements, and by mutations in rho, the gene for transcription termination. All four genes for high‐affinity leucine transport (livJ, livK, livH, and livG) are closely linked and have been cloned on a plasmid vector, pOX1. Several subcloned fragments of this plasmid have been prepared and used in complementation and regulation studies. The results of these studies suggest that livJ and livK are separated by approximately one kilobase and give a gene order of livJ–livK–livH. livJ and livK appear to be regulated in an interdependent fashion; livK is expressed maximally when the livJ gene is inactivated by mutation or deletion. The results support the existence of separate promoters for the livJ and livK genes. The effects of mutations in the rho and livR genes are additive on one another and therefore appear to be involved in independent regulatory mechanisms. Mutations in the rho gene affect both the LIV‐I and leucinespecific transport systems by increasing the expression of livJ and livK, genes for the LIV‐specific and leucine‐specific binding proteins, respectively.
The resolution of two populations of lysosomal organelles containing endocytosed wistaria floribunda agglutinin from murine fibroblasts
Authors: Merion Michael , Poretz R. D.
Published: May 2005

Subcellular fractionation of Balb/c 3T3 fibroblasts exposed to Wistaria floribunda agglutinin was performed to localize fractions containing internalized lectin. Employing two sequential self‐generating silica sol density gradients, the postnuclear supernatant of cell homogenates was resolved into five distinct cellular components. Lysosome enzyme activities were displayed by two populations of vesicles, each separated from plasma membrane, golgi, and mitochondria markers. The more dense of these fractions exhibited morphological and biochemical properties ascribed to secondary lysosomes: The more buoyant population was similar to that reported by Rome et al [11] who noted that it may be a product of vesiculated golgi endoplasmic reticulum lysosome (GERL). Treatment with W floribunda agglutinin of cells, surface radioiodinated demonstrated that plasma membrane proteins were localized within both the buoyant and dense lysosome populations in as little as 10 min after exposure to lectin. Prolonged incubation of the cells with W floribunda agglutinin resulted in maintenance of this distribution. However, when nonradiactive cells were exposed to 125I‐labeled W floribunda agglutinin for 10 min, radioactivity was detected only in the buoyant population of lysosomes as well as the plasma membrane/golgi fraction. Treatment of cells with W floribunda agglutinin for 30 min resulted in appearance of lectin associated radioactivity in the dense lysosome fraction in addition to those populations containing radioactivity seen after a 10‐min incubation. These data indicate that the endocytosis of W floribunda agglutinin differed substantially from the internalization of a portion of the plasma membrane proteins. Furthermore, we found radioactivity associated with both plasma membrane proteins W floribunda agglutinin in regions of the density gradient fractionation that virtually lacked golgi and lysosome markers. These fractions may have represented populations of nonlysosome vesicles formed during the process of endocytosis.
Spannungsrißkorrosion austenitischer Stähle in Meerwasser
Authors: Kohl H.
Published: May 2005

Stabil austenitische MnCr‐ und CrNi‐Stähle wurden in kaltem künstlichem Meerwasser auf Spannungsrißkorrosion geprüft. Folgende Stahlgruppen wurden untersucht: (%).
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Stable A ist im abgeschreckten Zustand beständig, weist aber nach Reizglühung zwischen 500 und 800°C starke Anfälligkeit für Spannungsrißkorrosion auf. Die Risse verlaufen interkristallin. Spannungsrißkorrosion wird bei diesem Stahl nicht nur durch Meerwasser, sondern auch durch Leitungswasser und destilliertes Wasser hervorgerufen. Die Standzeit der Proben ist abhängig von der Höhe der Zugspannung: höhere Spannung gibt kürzere standzeit. Spannungsfreie Proben zeigen keinen interkristallinen Angriff.

Stahlgruppe B zeigt ebenfalls im reizgeglühten Zustand starke, interkristallin verlaufende Spannungsrißkorrosion in kaltem Meerwasser. Der Bereich der Anfälligkeit wird mit fallendem Kohlenstoffgehalt kleiner. Die Standzeit anfälliger Zugproben ist wie bei Stahl A stark abhängig von der Höhe der Zugspannung. Spannungsfreie Proben zeigen interkristallinen Lochfraß.

Bei Stahlgruppe C tritt in Abhängigkeit von Kohlenstoffgehalt und Reizglühung interkristalliner Lochfraß auf. Der Einfluß der Zugspannung und die genauen Bereiche der Anfälligkeit müssen für diesen Korrosionsangriff noch geklärt werden. Spannungsrißkorrosion konnte bei dieser Stahlgruppe bei Prüfung in kaltem künstlichem Meerwasser nicht beobachtet werden.
Untersuchungen mit Korrosionsinhibitoren in der Gasphase
Authors: Garz I. , Schwabe K.
Published: May 2005

Aus Untersuchungen über die Korrosionshemmung durch Dichamin und seine Salze in der Gasphase wird geschlossen, daß die im Gegensatz zur wäßrigen Lösung ausgezeichnete Inhibitorwirkung des Dichamins eine Folge seines hohen Dampfdruckes und der Bildung eines hydrophoben Adosrptionsfilmes an der Metalloberfläche ist. Daß die Inhibitorwirkung des Dichamins durch Salzbildung mit Säuren herabgesetzt oder sogar in Stimulation verkehrt wird, liegt an der geringeren Flüchtigkeit der Salze, aus denen das Amin erst durch eine hydrolytische Spaltung in Freiheit gesetzt werden kann. Flüchtige Säurekomponenten treten an der Metalloberfläche als aggressive Substanzen hinsichtlich der Adsorption in kinetische Konkurrenz mit Dichamin, deren Ergebnis für die Korrosion entscheidend ist. Es entstehen mehr order weniger hydrophile Salzschichten, die eine Inhibition durch das Amin erschweren. Die salpetrige Säure stellt auf Grund ihrer oxydativen Eigenschaften einen Sonderfall dar. Sie wird aus ihren Salzen durch hydrolytische Spaltung in Freiheit gesetzt und ist so leicht flüchtig, daß sie zum Antransport an die Metalloberfläche nicht die Verbindung mit dem Dichamin zu Dichan benötigt. Eine synergetische Verstärkung der Inhibitorwirkung bei Kombination von Dichamin und salpetriger Säure tritt nicht ein, da die Wirkung des Dichamins von keinem seiner Salze erreicht, geschweige denn übertroffen wird.
Carbonatbildung in inhibierten Chloridsolen
Authors: Piatti Luigi , Fot E. , Weber JoS.
Published: May 2005

Gelangt Luft in Chlorid‐Kühlsolen, bilden sich mit absorbiertem Kohlendioxid Carbonate. In Calciumchlorid‐Lösungen entsteht dabei Calciumcarbonat. Fällt dieses aus, wird Salzsäure frei, der pH‐Wert sinkt stark ab und der Kälteträger wird erheblich korrosiver. In Kochsalz‐Solen bleibt das sich bildende Natriumcarbonat bzw. ‐bydrogencarbonat in Lösung und der pH‐Wert ändert sich nur geringfügig.

Anders ist es dagegen in Kochsalz‐Solen mit Natriumnitrit als Inhibitor in Gegenwart von Eisen. Bei reichlichem Zutritt von Luft entstehen neben Eisen(III)‐hydroxid soviel Carbonate, daß der pH‐Wert in ein schädliches Gebiet ansteigt.

In Kälteanlagen, die Eisenwerkstoffe enthalten und mit einer durch Natriumnitrit inhibierten Natriumchlorid‐Sole arbeiten, ist deshalb auf weitestgehenden Ausschluß von Luft zu achten.
Zum Verhalten von Natriumsilikat als Korrosionsinhibitor für Aluminium in alkalischen Lösungen
Authors: Wildbrett Gerbar , von Grundberr Klaus. , Kiermeier Freidrich
Published: May 2005

Natriumsilikat (Na2O : SiO2= 1 : 2,5) vermag selbst bei 80°C und gleichzeitig intensiver, mechanischer Beanspruchung des Metalls durch einen scharfen Sprühstrahl (30 atü Spritzdruck vor der Düse) Korrosion von Reinaluminium (99,5%) durch alkalische Lösungen (ph 11) zu unterbinden. Hierfür genügen schon sehr geringe Mengen adsorbierten Silikates je Flächeneinheit. Allerdings darf die SiO2‐Konzentration in der Lösung einen bestimmten, von den äußeren Bedingungen abhängigen Mindestwert nicht unterschreiten, damit ausreichend Silikat adsorbiert werden kann. Mit steigenden Temperaturen und Spritzdrücken erfordert ein wirksamer Korrosionsschutz zunehmend höhere Silikatkonzentrationen. Der korrosionsverhütende Film auf der Metalloberfläche baut sich wenigstens primär aus nicht aggregiertem Silikat auf. Verschiedene Metalle entziehen silikathaltigen Lösungen unterschiedliche Mengen des Korrosionsinhibitors. Hierfür dürfte nicht allein das spezifische Adsorptionsvermögen für Silikationen ausschlaggebend sein, sondern auch die Korrosionsbeständigkeit des einzelnen Metalls in der Lösung.
Eigenschaften von Chemieapparateemail
Authors: Scharbach Heinz
Published: May 2005

Es wird versucht, einen möglichst umfassenden Überblick der chemischen und physikalischen Eigenschaften von Apparate‐ und Behälteremail zu geben. Beschrieben ist die Beständigkeit gegen Säuren, Laugen, organische Substanzen und Wasser sowie die Oberflächeneigenschaften. Aus den Werkstoffdaten der Partner wird die Beständigkeit gegen Druck, Schlag, Verschleiß und Temperaturschock im Verbund obgeleitet.

Iso‐Korrosionskurven (0,1 mm/jhr.)) im Temperatur‐Konzentrationsfeld zeigen die thermischen Einsatzgrenzen gegen HCl (140 bis 200° C), H2SO4 (140 bis 350° C), HNO3 (140 bis 220° C), CH3COOH (140 bis 300° C), H3PO4 (140 bis 110° C), und NaOH (140 bis 55° C) auf.

Die nachfolgenden Diagramme wurden ermittelt:
Temperaturschockbeständigkeit in Abbängigkeit der Behältertemperatur (δ tRT ≈ 150° C) Schlagbeständigkeit in Abhängigkeit von Auftreffradius und Emaildicke (0,03 bis 2,5 mkp) Elektrische Durchschlagsspannung in Abbängigkeit von Emaildicke und Temperatur (D20 kV|RT = 0,7 mm) Einbezogen wurde eine Diagramm über die Abhängigkeit der Wärmeleitzahlen von der Stahlwanddicke

.
On the mechanism of high‐temperature sulphur corrosion of binary alloys
Authors: Brückman A. , Mrowec St.
Published: May 2005

Taking into account the phase composition and morphology of the scales three groups of alloys may be distinguished. The first of them contains alloys forming monophase scales which constitute solid solutions of sulphides of both alloy components (AgCu type). The mte of corrosion of these alloys is a monotonous function of their composition, and the mechanism of scale formation depends on the geometrical configuration of the reaction system. The second group includes alloys the components of which form sulphides of limited mutual solubility or sulphides having spinel structures (FeCr type); the scale may then be a mono‐ or double phase one and the exact structure is a function of the concentration of the alloying element. The metals belonging to the third group form mutually immiscible sulphides (CuZn type). The scales form double layers, the external layer being made up by sulphides of the base metal, while the internal layer is a heterophase mixture of the sulphides of both alloy components. The kinetics and the mechanism of the corrosion of these alloys is largely independent from the atmosphere (elemental sulphur or H2H2S mixture).
Corrosion of Ni in Molten Alkali Sulphates
Authors: Balajka J. , Danêk V.
Published: May 2005

The corrosion of Ni base alloys under molten ash deposits containing considerable quantities of alkali sulphates can take place as a sulphidation or oxidation. The former is very dangerous with respect to gas turbine operation since it gives rise to a decrease in strength of the materials; this type of corrosion is also predominant under thick layers of molten deposits at higher oxygen pressures, the effect being then increased by the poorer transport properties of the melt respect to oxygen diffusion. When cobalt sulphate is found in the ash the accelerated oxidation of Ni base alloys is due to the stable redox system Co+2/Co+2 in the melt Increasing the acidity of the flue gases (increasing SO3 content) enhances the corrosion rate and the solubility of corrosion products in the melt.
Kavitations‐Korrosion, Schadensbilder und Mechanismen – Vergleich zwischen Strömungskavitation, Kavitation durch rotierende gelochte Scheibe und Schwingungskavitation
Authors: Höss S. , Hirth F. W. , Louis H. , Bauer G. H.
Published: May 2005

Im Rahmen eines Ringversuches wurde in verschiedenen Kavitationsversuchseinrichtungen (Schwinger, rotierende Scheibe, Strömungskanal) die Auswirkung der implodierenden Blasen auf das Material Aluminium untersucht.

Das Materialverhalten wurde makroskopisch (Masseverlust – Laufdauer – sowie daraus abgeleitete Kurven) und mikroskopisch (rasterelektronenmikroskopische Aufnahmen) erfaßt.

Zahlreiche Gemeinsamkeiten im Schädigungsablauf und Schädigungsbild konnten festgestellt werden.
Polarisationsmessungen an Kurzschlußelementen und Schweißverbindungen aus Aluminiumlegierungen
Authors: Grauer R. , Wiedmer E.
Published: May 2005

Zur Untersuchung des Korrosionsverhaltens von geschweißten AlZnMg‐Legierungen wurden Potential/Weg‐Profile unter anodischer Polarisation in Natriumchloridlösungen registriert. Es wird mit theoretischen überlegungen gezeigt, daß diese Methode für Al‐Legierungen besonders geeignet ist, weil in solchen Lösungen Stromdurchbrüche auftreten. Die Leistungsfähigkeit der Methode wurde mit Modellelementen aus zwei Legierungen mit unterschiedlichem Durchbruchspotential überprüft.
Korrosionsuntersuchungen zur Entwicklung von Dekontaminationslösungen für Nuklearanlagen. Teil I: Das Korrosionsverhalten verschiedener Werkstoffe der Kerntechnik in sauren und alkalischen Redoxlösungen
Authors: Wiedemann Karl‐Heinz
Published: May 2005

Das Korrosionsverhalten einiger Werkstoffe der Kerntechnik wurde in zwei Typen von Dekontaminationslösungen, einem sauren und einem alkalischen Redoxsystem, untersucht.

In salpetersauren Cer(IV)‐Lösungen wird die Metallauflösung an dem niedriglegierten Stahl 21 CrMo V 5 11 praktisch nur von der Salpetersäurekonzentration, an der Molybdänlegierung TZM sowie an X10CrNiTi 18 9 und der Nickelchromlegierung Nimonic 80 A sowohl von der Salpetersäure wie auch von der Ce(IV)‐Konzentration der Lösung bestimmt. Die flächenbezogenen Massenverluste sind an 21CrMo V 5 11 um zwei bis vier Größenordnungen, an TZM bis zu zwei bis drei Größenordnungen größer als an X10CrNiTi 18 9 oder Nimonic 80 A. An Metallkombinationen besteht keine Kontaktkorrosionsgefahr.

In alkalischen Permanganatlösungen sind die Massenverluste an den untersuchten Werkstoffen von der Natriumhydroxidkonzentration unabhängig, an 21CrMo V 5 11, an X10CrNiTi 18 9 und an Nimonic 80 A bei Permanganatgehalten ab 3 g/L auch von diesen nahezu unabhängig. Diese Werkstoffe unterscheiden sich in ihrem Korrosionsverhalten nicht und werden nur relativ schwach korrodiert. An der Molybdänlegierung TZM nimmt der Massenverlust mit der Permanganatkonzentration in der Lösung zu und ist um bis zu zwei Größenordnungen größer als an den Stählen und an Nimonic 80 A.

An TZM ist bei Kontakt mit den anderen edleren Werkstoffen der Massenverlust drei‐ bis viermal größer als bei freier Korrosion.

In beiden Lösungstypen ist der Metallabtrag an den Stählen und an Nimonic 80 A gleichmäßig flächenhaft, an TZM ungleichmäßig.
Einfluß einer Eisenaufmischung auf das Korrosionsverhalten von NiCu30 Fe‐Stahlplattierungen
Authors: Altpeter Edelgard , Rockel Manfred B.
Published: May 2005

Durch elektrochemische Versuche in belüftetem künstlichem Meerwasser (ASTM‐Norm D 1141‐75) bei 25,50 und 80°C und durch Auslagerung in einem Meerwasserprüfstand auf Helgoland wurden die Korrosionseigenschaften von Auftrags‐ und Verbindungsschweißungen der Verbundwerkstoffe NiCu30Fe/Stahl im Hinblick auf den Einfluß einer Fe‐Aufmischung untersucht. Zum Vergleich dienten NiCu30Fe‐Bleche mit definierten Fe‐Gehalten zwischen 0 und 14%

Alle Angaben in Masse‐%.

. Bei homogener Fe‐Verteilung wird in belüftetem KMW von 25°C bis zu einem Fe‐Gehalt von 10% kein negativer Einfluß des Eisens auf die Lochfraßbeständigkeit gefunden. Mit steigender Temperatur (50 und 80°C) verschlechtert sich die Lochfraßbeständigkeit, und der Fe‐Einfluß nimmt geringfügig zu. Bei der Beanspruchung in Meerwasser, Helgoland, wird in der Dauertauchzone die Korrosion in erster Linie durch den maritimen Bewuchs bestimmt, der zu muldenförmigem Korrosionsangriff führt. In der Wechseltauchzone verursachen bei sehr niedrigen integralen Abtragungsraten Fe‐Gehalte deutlich oberhalb 6,7% die Bildung von feinen rosthaltigen Lokalkorrosionsstellen. Die Verbindungsschweißungen lassen leichte Lochfraßerscheinungen im Schweißgutbereich erkennen, die wahrscheinlich weniger auf eine Fe‐Aufmischung als auf das gegenüber dem Grundwerkstoff leicht abgesenkte freie Korrosionspotential des Schweißgutes zurückzuführen sind. Mit integralen Fe‐Gehalten in der Decklage zwischen 0,5 und 3% haben die Auftragschweißungen eine gleich gute Korrosionsbeständigkeit wie handelsübliches NiCu30Fe‐Blech.

In der Wechseltauchzone, dem vorwiegenden Anwendungsbereich, zeigt der nach unterschiedlichen Schweißverfahren geschweißte Werkstoff mit Abtragungsraten < 0,01 mm/a eine gute Beständigkeit. Dabei haben Fe‐Gehalte bis etwa 8% Fe, die mit zweilagigen Schweißungen nach allen bekannten Schweißverfahren eingehalten werden können, keinen negativen Einfluß auf die Korrosionsbeständigkeit.
Behaviour of CuNi10Fe1Mn‐clad ship plates in seawater
Authors: Drodten P. , Pircher H.
Published: May 2005

CuNi10Fe1Mn‐clad shipbuilding plates were subjected to long‐term exposure tests in natural seawater. This involved mounting the test pieces in the immersion zone of the test rig on Helgoland and on the outer wall of the hull of a sea‐going tug. A part of the test pieces were given defects of differing shape and size extending through the cladding to the base material. The corrosion of the shipbuilding steel, which is more intensive at these defects, is dependent upon the cathode and anode area ratio SC/SA and attains a limit value at SC/SA > 140. This limit value is governed by the oxygen content of the seawater and is much lower in the summer than it is in the winter. The highest corrosion rate, at 1 mm/month, was measured only on very small defects during the winter months. The resistance of the CuNi10 material to marine fouling maintained itself over the entire period, and the loss of cladding material as a result of corrosion or abrasion was negligible, even on those test pieces exposed to high mechanical stress on the tug.
Korrosionsverhalten des Werkstoffs 1.4539 und von Nickelbasis‐Legierungen in Gaswässern
Authors: Rolle D. , Kalfa H. , Bühler H.‐E.
Published: May 2005

In Laboruntersuchungen mit synthetischen Gaswässern, welche die Gase Ammoniak, Kohlendioxid, Schwefelwasserstoff und Cyanwasserstoff enthielten, wurde der Einfluß der Medienkomponenten auf die Korrosion des Werkstoffs 1.4539, sowie der Nickelbasis‐Werkstoffe Hastelloy C‐4, C‐22 und C‐276 untersucht. Schwefelwasserstoff wurde als die korrosionsbestimmende Verbindung identifiziert. Für den Chromnickelstahl wurden in einem kritischen pH‐Bereich bei Sulfid‐Konzentrationen > 2% bereits bei 50°C Abtragsgeschwindigkeiten um 2 mm ° a−1ermittelt. Da Cyanid die Korrosion durch Auflösung sulfidischer Deckschichten durch Komplexierung der Eisenionen stimuliert, wird im kritischen Bereich eine Erhöhung der Massenverlustrate bei zunehmender Cyanid‐Konzentration gefunden.

Die wesentlich beständigeren Nickelbasis‐Legierungen wiesen erst bei Erhöhung der Temperatur auf 100°C merkliche Massenverluste nach Auslagerung im Autoklav auf. Die Abstufung in den Verlustraten C‐22 >P C‐4 > C‐276 konnte durch die unterschiedlichen Gehalte an höherwertigen Legierungselementen erklärt werden. Die Überprüfung der Nickelbasis‐Legierungen des Typs Hastelloy und der Werkstoffe 1.4539 sowie 1.4571 mit Hilfe des dynamischen Zugversuchs (CERT‐Methode) hat in den untersuchten Medien keine Gefahr bezüglich Spannungsrißkorrosion aufgezeigt. Die mechanischen Kennwerte, wie Bruchenergie, Bruchdehnung und Brucheinschnürung ergaben im Vergleich zu den in neutralem Medium (Glycerin) geprüften Proben keine Veränderung.

Die metallographische Analyse zeigt in Abhängigkeit von der Aggressivität der flüssigen Phase lokale Korrosionserscheinungen im stark verformten Einschnürbereich, der über Grübchenbildung bis zu begrenzten Oberflächenrissen führen. Diese Erscheinungen treten bei allen Werkstoffen etwa gleich ausgeprägt auf.