bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanisms of lymphocyte‐mediated lysis
Authors: Joag Sanjay , Zychlinsky Arturo , Young John Ding‐E
Published: December 2004

Cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells use multiple mechanisms to destroy their target cells. Pore formation resulting in osmotic lysis of the target is one mechanism; the pore‐forming protein (perforin) responsible for this activity has been purified. Antigenically and functionally it resembles proteins of the membrane attack complex of complement. The other known mediators of cytotoxicity appear to be closely interrelated. Tumor necrosis factor (TNF), lymphotoxin (LT), and leukalexin are the three members of this group that have been purified, although their mechanisms of action are still unknown. CTLs fragment the DNA of target cells, as do TNF, LT, and leukalexin; this may be one of the mechanisms of action of these mediators. CTLs and NK cells do not self lyse. The basis of this phenomenon is unclear, although recent advances have shed some light on the problem.
Novel gene exon homologous to pancreatic phospholipase A2: Sequence and chromosomal mapping of both human genes
Authors: Seilhamer J. J. , Randall T. L. , Johnson L. K. , Heinzmann C. , Klisak I. , Sparkes R. S. , Lusis A. J.
Published: December 2004

We described previously the cloning and DNA sequence of the human gene encoding pancreatic phospholipase A2 [DNA 5, 519]. When pancreatic phospholipase A2 (PLA2) cDNA was used to screen a human genomic library, two classes of clones were obtained. One class encoded the pancreatic enzyme, and a second class encoded one exon of an apparently related PLA2. No additional PLA2 gene exons displayed sufficient homology to be detected by the probe. A homologous sequence in both rat and porcine genomic DNA was detected by DNA blot hybridization, and the corresponding gene fragments were cloned and sequenced. Within the deduced amino acid sequences, the presence of known functional residues along with the high degree of interspecies conservation suggests the genes encode a functional PLA2 enzyme form. The encoded sequence lacks Cys11, as do the “type II” viperid venom and other nonpancreatic mammalian PLA2 enzymes. The sequence is distinct from porcine intestinal PLA2 and appears not to be a direct homolog of the recently published rabbit ascites and rat platelet enzymes. Hybridization of DNA probes containing sequences from these genes to genomic DNA blots of mouse/human somatic cell hybrids permitted chromosomal assignment for both. The pancreatic gene mapped to human chromosome 12, and the homologous gene mapped to chromosome 1.
Developmentally regulated 75‐kilodalton protein expressed in LLC‐PK1 cultures is a component of the renal Na+/glucose cotransport system
Authors: Wu Jin‐Shyun Ruth , Lever Julia E.
Published: December 2004

Na+/D‐glucose symport is a secondary active glucose transport mechanism expressed only in kidney proximal tubule and in small intestine. A monoclonal antibody that recognized the Na+/glucose symporter of pig renal brush border membranes also recognized a 75‐kD protein in apical membranes isolated from highly differentiated LLC‐PK1 cultures, an epithelial cell line of pig renal proximal tubule origin. The 75‐kD antigen was enriched from solubilized LLC‐PK1 apical membranes by means of high‐pressure liquid chromatography. The symporter antigen became apparent on the apical membrane surface after the development of a confluent monolayer in correlation with the expression of transport activity. Long‐term treatment of cultures with the differentiation inducer hexamethylene bisacetamide was accompanied by a dramatically increased expression of the symporter antigen as detected quantitatively by Western blot analysis and qualitatively by immunofluorescence staining. The number of symporter‐positive cells was dramatically increased after inducer treatment as predicted for differentiation‐regulated expression. These results identify a 75‐kD protein as a component of a developmentally regulated renal Na+/glucose symporter expressed in cell culture.
Characteristics of the binding of human C‐reactive protein (CRP) to laminin
Authors: Swanson Steven J. , McPeek Mary M. , Mortensen Richard F.
Published: December 2004

Human CRP binds to the basement membrane protein laminin in vitro in a Ca2+‐dependent manner via the phosphorylcholine (PC) binding site of C‐reactive protein (CRP). The binding was saturable at a molar ratio of 4 (CRP/laminin). The specificity of the binding was shown by inhibition of binding of labeled CRP to laminin by unlabeled CRP, but not by human IgG. Specific binding was optimal in the presence of 5 mM Ca2+, but did not occur in the absence of Ca2+ or in the presence of EDTA. The binding of Ca2+ to CRP causes a conformational change in the molecule, which is required for binding to PC and to laminin. The PC binding site of CRP was implicated in the binding to laminin on the basis of inhibition by both soluble PC and anti‐idiotypic mAbs directed to the TEPC‐15 PC‐binding idiotype found on mouse antibodies to PC. In addition, mouse mAbs specific for the CRP PC binding site displayed decreased reactivity with CRP already bound to laminin. The binding of CRP to laminin provides a possible explanation for selective deposition of CRP at inflamed sites. The CRP‐laminin interaction may serve as a means of concentrating CRP at sites of tissue damage so that the CRP might function as a ligand for leukocytes, an event that will result in removal of necrotic tissue and cell debris.
The role of the idiotypic network in the induction of experimental systemic lupus erythematosus
Authors: Mozes Edna , Brocke Stefan , Shoenfeld Yehuda , Mendlovic Shlomo
Published: December 2004

Systemic lupus erythematosus (SLE) has been induced in C3H.SW mice by their immunization with a human monoclonal anti‐DNA antibody that bears a common idiotype‐16/6 Id. Following immunization, high levels of murine anti‐16/6 and anti‐anti‐16/6 antibodies were detected in the sera of the immunized mice. Elevated titers of autoantibodies reacting with ssDNA, dsDNA, poly(I), poly(G), RNP, Ro, and La were also observed. The serological findings were associated with significant proteinuria, leukopenia, and elevated erythrocyte sedimentation rate. Immune complex deposition in the glomerular mesangium and sclerosis of the glomeruli were demonstrated. To study whether or not anti‐idiotypic antibodies are involved in the induction of the disease, a murine monoclonal antibody against the 16/6 Id was prepared and injected into C3H.SW mice. The anti‐16/6 Id antibody induced experimental SLE similarly to the 16/6 Id with an accelerated kidney pathology. A study performed on different mouse strains indicated that the susceptibility to the induction of SLE by the 16/6 Id is strain dependent and directly correlates to their ability to produce anti‐16/6 Id specific antibodies.
The interaction of plasminogen activator with a reconstituted basement membrane matrix and extracellular macromolecules produced by cultured epithelial cells
Authors: McGuire Paul G. , Seeds Nicholas W.
Published: December 2004

Laminin and fibronectin are glycoproteins that influence cell behavior and mediate cell/substratum adhesion. We have examined the interaction of these macromolecules with the serine protease plasminogen activator (PA) in two types of extracellular matrices; one produced by the murine Engelbreth‐Holm‐Swarm (EHS) tumor (Matrigel™), and another by normal kidney epithelial cells in culture. Matrigel™ was found to contain significant quantities of tissue‐type PA (tPA). Two of the major components of Matrigel™, laminin and type IV collagen, were also examined. Tissue‐type PA was associated with purified preparations of laminin; however, it was not found associated with type IV collagen. Normal kidney epithelial cells in culture secrete large amounts of urokinase (UK) and deposit a subepithelial matrix containing both laminin and fibronectin. These matrix macromolecules were isolated from the deposited matrix by immunoprecipitation, examined by zymography, and found to contain UK. The potential role of this interaction in the mechanisms of cell migration and matrix remodeling is discussed.
Evidence of an auxin‐mediated phosphoinositide turnover and an inositol (1,4,5)trisphosphate effect on isolated membranes of Daucus carota L.
Authors: Zbell Bernd A. , Walter‐Back Cornelia , Bucher Hubert
Published: December 2004

Microsomal membranes from carrot suspension cells were phosphorylated in vitro with [γ‐32P]ATP. In the presence of submicromolar concentrations of the natural auxin indoleacetic acid (IAA), a rapid, but transient decrease of the [32P] label could be detected in the phospholipid extracts of the membranes. The phytohormone effect was not the result of an inhibition of the lipid phosphorylation reactions, but was caused by a simultaneous release of water‐soluble compounds, which, according to their chromatographic properties, were assumed to contain inositol polyphosphates. Although the [32P]‐labeled lipids, as well as the inositol polyphosphates, were not identified unequivocally by chemical analysis, these findings point to an auxin‐mediated control of a phosphoinositidase C‐like reaction similar to the hormone‐stimulated phosphoinositide response in animals. Exogenously applied inositol (1,4,5)trisphosphate [(1,4,5)IP3] was found to release 45Ca2+ from preloaded membrane vesicles of carrot cells. Both the detection of the auxin‐stimulated phosphoinositide response and the (1,4,5)IP3‐mediated Ca2+ release on isolated cell membranes offer new experimental approaches for the identification of the putative auxin receptor and its signal transduction pathway.
Purification and partial characterization of a hepatocyte antiproliferative glycopeptide
Authors: Auger Geneviève , Blanot Didier , Van Heijenoort Jean , Nadal Claude , Gournay Marie‐Françoise , Winchenne Jean‐Jacques , Boffa Georges A. , Lambin Patrick , Maes Pierrette , Tartar André
Published: December 2004

A low molecular weight compound, which inhibits the G1‐S transition in rat hepatocytes, was obtained by tryptic hydrolysis of human α2‐macroglobulin followed by ultrafiltration at pH 10. It was purified by high‐performance liquid chromatography on μBondapak C18 and μBondapak NH2 with a practically quantitative yield; from 5.1 g of α2‐macroglobulin, 2.8 μg of purified compound were recovered. Inactivation by specific enzymes and chemical analyses showed that the inhibitor is a sialylated glycopeptide whose peptide moiety contains a pyroglutamyl residue. Its molecular mass, estimated by gel permeation chromatography, would be in the interval 3,500–4,600. However, amino acid analyses indicated that it is not yet pure. All these data suggest that α2‐macroglobulin could be the carrier of the precursor form of the glycopeptide.
Thermal properties of young red blood cells are indicative of an age‐dependent regulation of membrane‐skeleton interaction
Authors: Grimaldi Paola , Minetti Maurizio , Pugliese Pellegrina , Isacchi Giancarlo
Published: December 2004

The effects of red blood cell (RBC) age on membrane thermal properties have been investigated by using a 16‐nitroxide stearic acid spin probe. We detected in unfractionated and most dense cells (2% fraction of circulating cells) a thermal transition at 40°C that in young cells (1% fraction) was lowered at 33–35°C. Spectrin seems to be directly involved in the transition detected in both young and unfractionated cells, as showed by the disappearance of the breaks after low salt extraction of spectrin. A further indication for a role of spectrin in this transition comes from its characteristic thermal unfolding above 40°C.

However, young cells did not show changes either in the thermal unfolding of spectrin or in the distribution of spectrin dimer, tetramer, and high oligometric forms. These data rule out that spectrin of young RBC is modified in its thermal properties and indicate that young cells may have a different spectrin‐membrane interaction.

Treatment of unfractionated ghosts with an antibody specific for a fragment of the 10K domain of protein 4.1, which is fully competent for the spectrin‐actin binding, produced an evident lowering of the transition temperature. The same antibody did not affect the thermal transition of young ghosts. Our results suggest that spectrin‐membrane interactions may be regulated during RBC lifespan.
Can glutathione‐S‐transferases function as intracellular heme carriers?
Authors: Kirschner‐Zilber Ilana , Laufer Hava , Shaklai Nurith
Published: December 2004

The possibility that glutathione‐S‐transferases can serve as heme carriers in cells was studied via the following two characteristics: the ability to bind hemin reversibly and the coordination between heme and glutahione‐S‐transferases level in the cell. Two erythroleukemic cell lines that can be induced to synthesize hemoglobin were studied, K‐562 and Friend murine erythroleukemia cells. It was found that hemin‐associated glutathione‐S‐transferase tends to lose its native structure as expressed by partial irreversible inhibition of glutathione conjugation activity. In K‐562 cells, a small increase in heme synthesis was induced, but under no condition could glutathione‐S‐transferase be elevated. In addition, introduction of high hemin from without caused large hemoglobin production but did not inducechanges in the glutathione‐S‐transferase content. Dimethyl sulfoxide‐induced Friend murine eryth‐roleukemia cells synthesized a large amount of endogenous hemin that had to be transported from the mitochondria for hemoglobin synthesis. Although a concomitant increase in glutathione‐S‐transferase level (20–40%) was observed, it was only short‐lived, unlike hemin, which continued to increase. These data indicate a lack of correlation between glutathione‐S‐transferase and hemin or hemoglobin levels. Finally, dimethyl sulfoxide‐induced cells were treated with succinyl acetone to inhibit heme synthesis. These cells showed the same increased levels and time‐dependent pattern of gluathione‐S‐transferase as untreated cells. A similar phenomenon was observed when different substrates were used to measure the activities of glutathione‐S‐transferases. These results raise doubts about the possibility of glutathione‐S‐transferases functioning as heme carriers in cells.
Developmental changes in expression of a tumor‐associated protein in the rat fetus
Authors: Runge Steven W. , Larroya Saroj , Schumm Dorothy E. , Webb Thomas E.
Published: December 2004

Monoclonal antibodies specific for a rat tumor‐associated protein cross‐react with a similar protein present in the cytosol of the rat fetus. The oncofetal protein exists as two species of approximate molecular weight 50 and 55 kDa which promote the transport of RNA from isolated nuclei. During rat fetal development, the protein first increases in concentration from approximately 12 to 16 days gestation and then drops to non‐detectable levels perinatally.
Modulation of transforming growth factor alpha‐dependent expression of epidermal growth factor receptor gene by transforming growth factor beta, triiodothyronine, and retinoic acid
Authors: Fernandez‐Pol J. A. , Klos D. J. , Hamilton P. D.
Published: December 2004

We have investigated the actions of transforming growth factor (TGF) type α on epidermal growth factor (EGF) receptor mRNA expression in MDA‐468 human mammary carcinoma cells in serum‐free media. We found that exposure of MDA‐468 cells to TGFα results in elevated levels of EGF receptor mRNA. This increase in mRNA accumulation showed time and dose dependence. Addition of TGFβ1 enhanced the accumulation of EGF receptor mRNA induced by TGFα in a time and dose‐dependent manner. We also found that triiodothyronine at physiological concentrations exerts synergistic control on the action of TGFα alone, or in association with TGFβ1, on EGF receptor mRNA expression. Similarly, retinoic acid treatment also enhanced in a time‐ and dose‐dependent manner the TGFα‐dependent response of EGF receptor mRNA and acted synergistically with TGFβ1. The results described here suggest that optimum regulation of EGF receptor gene expression by TGFα is a complex process involving synergistic interactions with heterologous growth factors and hormones.
ras‐Transformation of MDCK cells alters responses to phorbol ester without altering responses to bradykinin
Authors: R. Slivka Sandra , Godson Catherine , A. Insel Paul
Published: December 2004

The results of studies to evaluate the hypothesis that the 21 kDa GTP‐binding protein derived from the ras oncogene is involved in regulation and coupling of hormone receptors to phospholipase activity have thus far been inconsistent. We therefore examined the effect of H‐ras transformation on basal, tumor‐promoting phorbol ester (TPA)‐stimulated, and bradykinin‐mediated phospholipid hydrolysis in Madin Darby canine kidney cells (MDCK) by comparing H‐ras‐transformed MDCK cells (MDCK‐RAS) to two non‐transformed strains of MDCK cells (MDCK‐DI and MDCK‐ATCC). In unstimulated MDCK‐RAS, diacylglycerol (DAG), inositol phosphate accumulation, and choline phosphate release were increased while arachidonic acid and arachidonic acid metabolite (AA) release was not increased, suggesting that ras transformation increased phospholipase C activity. Protein kinase C (PK‐C) activity was decreased, and specific binding of (3H) phorbol ester was reduced in MDCK‐RAS relative to the non‐transformed MDCK cells suggesting that elevated DAG may activate and thereby down‐regulate PK‐C. Consistent with this finding in MDCK‐RAS, TPA‐stimulated AA release and subsequent prostaglandin E2 production were decreased, while TPA‐stimulated choline phosphate release was increased. Bradykinin receptor‐stimulated phospho‐lipid hydrolysis in MDCK‐RAS was similar to that of non‐transformed cells, suggesting that the ras‐derived protein does not directly couple bradykinin receptors to phospholipases in MDCK cells. However, the ability of TPA‐treatment to inhibit bradykinin‐stimulated phosphoinositide hydrolysis and enhance bradykinin‐stimulated AA release was attenuated in MDCK‐RAS. Additionally, in MDCK‐RAS the conversion of arachidonic acid to prostaglandin E, was substantially reduced. We conclude that rus transformation of MDCK cells increases DAG levels, thereby activating and, in turn, down‐regulating PK‐C and certain responses to TPA. Since activation of PK‐C may result in a variety of effects on signal transduction pathways, we propose that increased DAG and altered PK‐C levels associated with rus transformation may account for the inconsistent effects previously observed in studies evaluating the effect of rus transformation on phospholipases and other signal transduction systems.
Modulation of HPV18 and BPV1 transcription in human keratinocytes by simian virus 40 large T antigen and adenovirus type 5 E1A antigen
Authors: Bernard Bruno A. , Bailly Catherine , Lenoir Marie‐Cecile , Darmon Michel Y.
Published: December 2004

Transcription of early open reading frames initiated from the long control region (LCR) of HPV18 and BPV1 is known to be modulated by homologous and heterologous papillomavirus E2 gene products. Using CAT constructs transfected into normal human keratinocytes, we show that SV40 large T antigen activates transcription from the LCR of both viruses, whereas Ad5‐Ela antigen represses transcription from the HPV18‐LCR but activates transcription from BPVI‐LCR. Experiments using constructs containing subfragments of the HPV18‐LCR cloned in enhancer configuration ahead of the SV40 early promoter or the HSVI‐Tk promoter suggest that the effect of Ad5‐Ela antigen on HPV18 transcription is probably due to a repression of the enhancer function of the LCR. The mechanism of transcription stimulation by SV40 large T antigen is less clear. The 230 bp Rsal‐Rsal central domain of the HPV18‐LCR seems involved both in transcriptional stimulation by SV40 large T antigen and transcriptional inhibition by adenovirus Ela antigen.
Co‐transformation of Lec1 CHO cells with N‐acetylgucosaminyltransferase 1 activity and a selectable marker
Authors: Ripka James , Pierce Michael , Fregien Nevis
Published: December 2004

In animal cells, the enzyme α( 1,3)‐mannoside‐β( 1,2)‐N‐acetylglucosaminyltransferase I (GlcNAc‐TI, EC.2.4.1.101) catalyzes the addition of N‐acetylglucosamine to the ASN‐linked Man GlcNAc oligosaccharide. The Chinese hamster ovary (CHO) mutant cell line Lecl is deficient in this enzyme activity and, therefore, accumulates mannose‐terminating cell surface ASN‐linked oligosaccharides. Consequently, Lecl cells are sensitive to the cytotoxic effects of the mannose‐binding lectin Concanavalin A (Con A). Lecl cells were co‐transformed with human DNA from A431 cells and eukaryotic expression plasmids containing the bacterial neo gene by calcium phosphate/DNA‐mediated transformation. Co‐transformants were selected for resistance to Con A and G‐418. DNA from a primary co‐transformant was purified and used to transform Lecl cells, resulting in secondary co‐transformants. Both primary and secondary co‐transformants exhibited in vitro GlcNAc‐TI‐specific enzyme activity, DNA gel blot analysis indicated that secondary co‐transformants contained both human and neo sequences.
Role of glycosylation in the transport of recombinant glycoproteins through the secretory pathway of lepidopteran insect cells
Authors: Jarvis Donald L. , Oker‐Blom Christian , Summers Max D.
Published: December 2004

Cell lines established from the Lepidopteran insect Spodoptera frugiperda (e.g., Sf9) are used routinely as hosts for the expression of foreign proteins by baculovirus vectors. Previously, we showed that human tissue plasminogen activator (t‐PA) was expressed, N‐glycosylated, and secreted by Sf9 cells infected with a recombinant baculovirus (Jarvis DL, Summers MD: Mol Cell Biol 9:214–223, 1989). We also showed that t‐PA secretion was blocked by tunicamycin.(TM), an inhibitor of N‐glycosylation, but not by castanospermine (CS) or N‐methyldeoxynojirimycin, inhibitors of the initial steps in N‐linked oligosaccharide processing. This suggestedthat the addition, but not the processing, of N‐linked oligosaccharides is required for the secretion of recombinant t‐PA from baculovirus‐infected Sf9 cells. In this study, we present a more generalized evaluation of the role of N‐glycosylation in the transport of recombinant glycoproteins through the Sf9 cell secretory pathway. Several different secretory or membrane‐bound glycoproteins were expressed in control, TM‐treated, or CS‐treated Sf9 cells, and their appearance in the medium or on the cell surface was measured. The results showed that TM blocked the transport of some, but not all, of these proteins, whereas CS did not block the transport of any. This suggests that N‐glycosylation is sometimes required for the transport of recombinant glycoproteins through the Sf9 secretory pathway, while processing of the oligosaccharides is not. At least two other proteins, p80 and p31, consistently coimmunoprecipitated with the nonglycosylated precursors of recombinant glycoproteins expressed in TM‐treated Sf9 cells. Neither was antigenically related to any of the recombinant proteins. Relatively larger amounts of p80 and p31 were coprecipitated when transport was completely blocked by TM compared to when transport was only reduced or was unaffected. These results suggest that p80 and p31 block the transport of some nonglycosylated glycoprotein precursors in TM‐treated Sf9 cells by binding to them and producing transport‐incompetent heterooligomeric com‐plexes. If this speculation is correct, then p80 and p31 are functionally analogous to the mammalian immunoglobulin heavy chain binding/glucose‐regulated 78 kilodalton protein (BiP/GRP78).
Expression of low levels of peripheral lymph node‐associated vascular addressin in mucosal lymphoid tissues: Possible relevance to the dissemination of passaged AKR lymphomas
Authors: Bargatze Robert P. , Streeter Philip R. , Butcher Eugene C.
Published: December 2004

Lymphoid tumors display a wide variety of growth patterns in vivo, from that of a solitary extralymphoid tumor, to a general involvement of all lymphoid organs. Normal lymphocytes are uniquely mobile cells continuously recirculating between blood and lymph throughout much of their life cycle. Therefore, it is reasonable to propose that disseminating malignant lymphocytes may express recirculation characteristics or homing properties consistent with that of their normal lymphoid counterparts. Trafficking of lymphocytes involves the expression and recognition of both lymphocyte homing receptors and their opposing receptors on endothelium, the vascular addressins. These cell surface elements direct the tissue‐selective localization of lymphocyte subsets in vivo into organized lymphoid organs and sites of chronic inflammation where specific binding events occur between lymphocytes and the endothelium of specialized high endothelial venules (HEV). Ina recent murine study of 13 lymphoma lines, we found that lymphomas that bind well to high endothelial venules, in the Stamper‐Woodruff in vitro assay (an assay of lymphocyte binding to venules in frozen sections of peripheral lymph nodes or Peyer's patches), spread hematogenously to all high endothelial venule bearing lymphoid organs, whereas non‐binding lymphomas did not. In some cases lymphomas that bound with a high degree of selectivity to peripheral lymph node (PLN) high endothelial venules exhibited only limited organ preference of metastasis, involving the mucosal lymphoid organs Peyer's patches (PP) in addition to the peripheral lymph nodes of adoptive recipients. Here we demonstrate that Peyer's patch high endothelial venules express a low but functional level of peripheral lymph node addressin (MECA‐79) that can be recognized by lymphomas expressing the peripheral lymph node homing receptor (MEL‐14 antigen). Utilization of the peripheral lymph node associated endothelial cell recognition system could explain the ability of lymphoid neoplasms, selectively expressing lymph node homing receptors, to disseminate to both periph‐eral lymph nodes and to organized mucosal lymphoid tissues in vivo.
Adenylyl cyclase in yeast: Antibodies and mutations identify a regulatory domain
Authors: Heideman Warren , Casperson Gerald F. , Bourne Henry R.
Published: December 2004

The adenylyl cyclase system of the yeast Saccharomyces cerevisiae contains the CYR1 polypeptide, responsible for catalyzing formation of cAMP from ATP, and two RAS polypeptides, responsible for stimulation of cAMP synthesis by guanine nucleotides. We have obtained rabbit antibodies that recognize the CYR1 protein. Antibodies were raised against synthetic oligopeptides and against a recombinant β‐galactosidase CYR1 fusion protein. These antibodies have allowed the identification of the CYR1 gene product as a 205 kDa protein. Treatment with trypsin (2 μg/ml) reduced the size of the CYR1 protein from 205 to 155 kDa and produced an activated enzyme which no longer responded to guanine nucleotides. This result is consistent with a model in which adenylyl cyclase activity is regulated by an inhibitory domain near the amino‐terminus of the CYR1 protein. This model is further supported by the finding that adenylyl cyclase activity is also markedly elevated and unresponsive to guanine nucleotides in mutant yeast strains that express only the carboxy‐terminal half of the CYR1 protein. Treatment with high trypsin concentrations (>10 μg/ml) caused release of adenylyl cyclase activity from the membrane. Comparison of immunoreactive CYR1 fragments released by trypsin and membrane bound genetically altered proteins suggests that the CYRI protein is attached to the membrane via a separate trypsin sensitive anchoring protein rather than via a membrane anchoring domain.
Spore coat is altered in modB glycosylation mutants of Dictyostelium discoideum
Authors: Aparicio Jennifer G. , Erdos Gregory W. , West Christopher M.
Published: December 2004

The modB mutation eliminates specific carbohydrate epitopes from glycoproteins which are expressed primarily in prespore and spore cells of differentiating Dictyostelium discoideum. Spores formed by the mutant show several phenotypes. Whereas mutant spores germinate efficiently after heat activation, they germinate poorly after urea activation. Following germination, at least one glycosylation‐defective glycopro‐tein is cleaved, and the larger fragment is released in soluble form from the spore coat. However, an earlier difference in the spore coat can be traced back to the nongerminated spore coat, as detected by the elutability of protein from intact spores by chemical extraction. An altered character of the pregermination spore coat is also suggested by increased labeling by a fluorescent lectin which binds to its interior. The findings are consistent with a change in the character of certain molecular contacts leading to altered characteristics of the mutant spore coat, which are specific because they are distinctive from changes observed in another glycosylation mutant which affects a different epitope.
Structure of O‐glycosidically linked oligosaccharides synthesized by the insect cell line Sf9
Authors: Thomsen Darrell R. , Post Leonard E. , Elhammer Åke P.
Published: December 2004

The O‐glycosidically linked Oligosaccharides on the pseudorabies virus (PRV) glycoprotein gp50 synthesized by three different cell lines were studied. The intact membrane protein (gp50) was expressed in Vero cells and in the insect cell line Sf9. In addition, a truncated, secreted form lacking the transmembrane and cytoplasmic domains (gp50T), was expressed in CHO and Sf9 cells. The protein, both in intact and truncated form, synthesized by the two mammalian cells contained only the disaccharide Galβ1‐3GalNAc, either unsubstituted or substituted with one or tow sialic acid residues. By contrast, the major O‐linked structure on gp50 and gp50T synthesized by Sf9 cells was the monosaccharide GalNAc. The Sf9 cells also linked lower amounts of Galβ1‐3GalNAc to gp50 (12%) and gp50T (26%). None of the structures synthesized by Sf9 cells contained sialic acid. Measurements of the two relevant glycosyltransferases revealed that while all three cell lines contain comparable levels of the UDP‐GalNAc:polypeptide, N‐acetylgalactosaminyltransferase activity, there is a greater variation in the levels of UDP‐Gal: N‐acetylgalactosamine, β1‐3 galactosyltransferase, with the Sf9 cells containing the lowest level.
Aufbau und Konstruktion moderner Antriebe für die chemische Industrie
Authors: Büttner P.
Published: December 2004

Aufgabe und Bedeutung der Zahnradgetriebe im chemischen Apparatebau — Ausführungsformen, deren Vorteile und Anwendungsbereich (Schneckengetriebe, Stirnradgetriebe, Kegelgetriebe und stufenlose Flüssigkeitsgetriebe).
Hastelloy‐Legierungen
Authors: Franke E.
Published: December 2004

Entwicklung, Zusammensetzung, Verarbeitung, allgemeines physikalisches, mechanisches und technologisches Verhalten — Korrosionschemisches Verhalten in anorganischen und organischen Säuren, Salzen, Nichtmetallen und Gasen — Überblick über die Verwendungsgebiete — Zusammenfassung.
Beitrag zum „kathodischen Korrosionsschutz”︁
Authors: Thury Wolfgang
Published: December 2004

Nach einer kurzen Definition des Begriffes „kathodischer Korrosionsschutz”︁ wird auf die Möglichkeiten und Grenzen der Anwendung des kathodischen Schutzes mit einer äußeren Stromquelle und einer unlöslichen Hilfsanode hingewiesen. Die Erscheinung der „kathodischen Korrosion”︁, die die Möglichkeiten der Anwendung des kathodischen Schutzes begrenzt, wird eingehend besprochen.

Versuche mit Eisen und Aluminum in einigen typischen Korrosionsmitteln werden mitgeteilt, wobei der Bedarf an elektrischer Energie je m2 und Jahr einen Anhaltspunkt für die Kosten des kathodischen Schutzes gibt.
Vorbehandlung und Passivierung der Leichtmetalle für den Anstrich
Authors: Scheifele Bernhard F. H.
Published: December 2004

Aluminium‐ und Magnesium‐Legierungen bilden an der Luft natürliche Oxydhäute, deren Verstärkung durch die verschiedenen Verfahren der chemischen und elektrolytischen Oxydation der Leichtmetalle angestrebt wird. Außer durch die unlöslichen Oxydschichten werden Leichtmetalle ebenso wie Eisenmetalle auh durch unlösliche Metallsalzschichten (Phosphatfilme etc.) geschützt. Auch die durch die sog. Reaktionsprimer oder Metallwandler erzeugten metallorganischen Deckschichten werden als antikorrosive Überzüge und Haftgründe für die nachfolgende Lackierung angewendet.
Über die Korrosion von Metallen und Metallüberzügen im tropischen und subtropischen Klima
Authors: Machu Willi
Published: December 2004

Im tropischen Klima können oft extrem hohe Temperaturen und Feuchtigkeitsgehalte auftreten, die naturgemäß zu besonders starken Korrosionen führen können. Besonders gefährlich sind die starken Temperaturschwankungen zwischen der Tageshöchsttemperatur und den niedrigsten Temperaturen bei Nacht, die durch Kondensation von Wasserdampf zu starken Schwitzkorrosionen selbst unter sonst nicht besonders stark aggressiven Bedingungen führen, Schwitzkorrosionen können bereits beim Transport innerhalb der Verpackung und bei Lagerung auftreten. Sie werden durch geringe Chloridmengen, meist aus zerstäubtem Seewasser stammend, stark beschleunigt. An einem näher untersuchten Beispiel wird gezeigt, daß der Angriff auch in den Wüstengegenden, weitab vom Meere, durch vom Winde aufgewirbelten salzhaltigen Sand erheblich beschleunigt werden kann. Abschließend wird eine Übersicht über das Verhalten verschiedener Metalle und Metallüberzüge im tropischen und subtropischen Klima gegeben.
Filter aus Sintermetallen Aufbau, Werkstoffeigenschaften und Einsatzmöglichkeiten
Authors: Frehn F. , Hotop W. , Stempel G.
Published: December 2004

Die schon seit längerer Zeit in den USA und neuerdings auch in Europa verwendeten Filter aus porösen Sintermetallen gewinnen steigende Bedeutung für das chemische Apparatewesen. Um die Möglichkeiten ihres Einsatzes zu veranschaulichen, wird der Aufbau poröser Sintermetalle und der Einfluß der kornform der verwendeten Pulver auf die Anordnung der erwünschten Filterkanäle erläutert. Die bis jetzt zur Verfügung stehenden Werkstoffe und ihre Eigenschaften werden hinsichtlich ihres Druckverlustes, der chemischen Beständigkeit, sowie der mechanischen und physikalischen Eigenschaften besprochen.

Beispiele aus der Praxis Zeigen die Einsatzmöglichkeiten. Außer für Filter erstreckt sich der Einsatz poröser Sintermetalle auf die Gebiete „gleichmäßige Verteilung von Gasen und Flüssigkeiten”︁, „Separatoren”︁, „Mengenbegrenzer”︁ und „Flammensperren”︁.

Die angeführten Beispiele sollen dazu anregen, die spezifischen Eigenschaften poröser Sintermetalle sinnvoll auszunutzen, z. B. vorhandene Konstruktionen durch Einsatz von porösen Sintermetallen zu verbessern, die Wirtschaftlichkeit von Arbeitsprozessen zu steigern, ihre Betriebssicherheit zu erhöhen oder sogar neue Wege in der Verfahrenstechnik zu erschließen.
Trinkwasserleitungsrohre aus Kunststoffen
Authors: Reinholdt W.
Published: December 2004

Der Aufsatz vergleicht erdverlegte Kaltwasser‐Rohrleitungen verschiedener Baustoffe hinsichtlich ihres Verhaltens gegenüber der Boden‐ und Grundwasseraggressivität miteinander. Besonders herausgestellt sind Erfahrungen mit Kunststoffrohren (Polyvinylchlorid) im alluvialen Küstenboden.
A modification of the rule of mixture in estimating strengths of a Composite
Authors: Sarkar B. K. , Mukherjee M. K. , Natarajan A.
Published: December 2004

Strengths of a composite when determined by actual tests shows a lower value than those obtained through theoretical estimation by applying the simple rule of mixtures. This discrepancy has been attributed largely to the presence of defects in the composite like debonding, porosities, cracks etc. To establish a design criteria to a more practically closer strength values an empirical formulae is presented. The formulae accounts for defect level upto 30%. The results were obtained through computational facilities using IBM (360/44) Computer. The drop in strength with increasing defect level is shown to occur and the effect is more predominant when defects are more in fibres than in matrix.
Kontinuierliche Verfolgung der Korrosion des Stahls X 2 CrNiSi 18 15 in 98%iger Salpetersäure
Authors: Vehlow J.
Published: December 2004

Mit einem radionuklidtechnischen Verfahren wurde die Korrosion von Eisen, Chrom und Nickel des siliziumhaltigen Stahls X2 CrNiSi 18 15 in 98%iger Salpetersäure im Temperaturbereich 30 bis 50°C verfolgt. Die Korrosionsreaktion ist durchtrittsbestimmt, der Aufbau der oxidischen Deckschicht ist abhängig vom Fortschritt der Korrosion. Aus den Verhältnissen von Chrom zu Eisen im Korrosionsmedium läßt sich der Chromüberschuß in der Oxidschicht abschätzen.
Aktivierungsenthalpien und Mechanismen der unterkritischen Rißausbreitung in Aluminiumoxidkeramiken
Authors: Devezas Tessaleno C. , Kleinlein F. W. , Ilschner Bernhard
Published: December 2004

An zwei Qualitäten kommerzieller Al2O3‐Keramik unterschiedlichen SiO2‐Gehalts wurde an Doppeltorsionsproben die langsame Rißausbreitung im Temperatubereich von 25 bis 1000°C untersucht. Es wurden drei Bereiche gefunden, die eine unterschiedliche Abhängigkeit der effektiven Aktivierungsenthalpien vom Spannungsintensitätsfaktor aufweisen. Bei niedrigen Temperaturen steuert im wesentlichen die Reaktion des Wasserdampfes der umgebenden Luft mit der Korngrenzenphase die Rißausbreitung, bei hohen Temperaturen spielt die Erweichung dieser Korngrenzenphase die entscheidende Rolle.
Ermittlung mechanischer Kenndaten von Kohlenstoffaserverstärktem Kohlenstoff (CFC) mit dem Biege‐ und Zugversuch
Authors: Popp G. , Böder H. , Gruber U.
Published: December 2004

CFC ist ein Hochtemperaturmaterial, welches bei hoher mechanischer Belastung bis zu 2200°C unter Inertatmosphäre eingesetzt werden kann. Da in Deutschland für CFC keine Materialprüfnormen existieren, hat die SIGRI GmbH materialspezifische Prüfgeometrien entwickelt. Gemessen wurde die Biegefestigkeit, die Zugfestigkeit und die interlaminare Scherfestigkeit. Weiter wurden hierzu die entsprechenden Prüfkörpergeometrien entwickelt. Es wird außerdem gezeigt, daß bei einem (0°/90°)‐CFC‐Verbund die Zugfestigkeit in 0°‐Richtung geprüft, deutlich höher ist als die Biegefestigkeit; bei einem (0°/±45°/90°)‐Laminat ist es gerade umgekehrt. Bei bekanntem Laminataufbau läßt sich der Bruchmodus voraussagen.
Investigations into the fatigue crack initiation and propagation behaviour in austenitic stainless steel X5 CrNi 18 9 (1.4301)
Authors: Krompholz K. , Ullrich G.
Published: December 2004

Controlled load fatigue‐crack growth rate tests were conducted using three point bend type specimens. The austenitic stainless steel X5 CrNi 18 9 (material number 1.4301, similar to AISI 304) was tested. For this high toughness material, the crack initiation and crack propagation is discussed in terms of linear‐elastic analysis even for the highest plasticity regime. The curve for the onset of stable crack growth during fatigue starting from a notch is discussed as well as the stable crack growth up to large plasticity. From the standpoint of load controlled fatigue it is indicated that the time between crack initiation and crack length at the „end of life”︁ is large.
Umformbare Al‐Werkstoffe – für jede Anwendung
Authors: Furrer P. , Rodrigues P. M. B.
Published: December 2004

Der Einsatz von Al‐Werkstoffen in Anwendungsbereichen, wo eine gute Umformbarkeit und eine hohe Festigkeit gefordert werden, wird durch eine entsprechende Steuerung der Gefügeausbildung durch Wahl von Legierungszusammensetzung und Verarbeitungsprozedere möglich. Eine wichtige Rolle spielt auch die kritische Analyse des Umformungsprozesses im Hinblick auf die Vermeidung kritischer Materialbeanspruchungen. Die weitere Werkstoffentwicklung kann den Al‐Legierungen noch zahlreiche Anwendungsbereiche erschließen. Von größter Bedeutung ist allerdings die Wahl eines angepaßten Umformverhaltens, wenn die vorteilhaften Materialeigenschaften vollständig ausgeschöpft werden sollen.
Dauerschwingfestigkeit und zyklisches Werkstoffverhalten
Authors: Liu J. , Zenner H.
Published: December 2004

Die experimentelle Ermittlung der Dauerfestigkeit ist aufwendig, so daß man versucht, sie mit Hilfe von Kurzverfahren und sog. Korrelationsformeln abzuschätzen. In der vorliegenden Arbeit wird für unlegierte und niedriglegierte Stähle gezeigt, daß zwischen der Werkstoff‐Dauerfestigkeit σW (glatte Probe, axiale Beanspruchung, Mittelspannung null) und der zyklischen Streckgrenze R′p0,2 eine engere Korrelation besteht als zu den statischen Kennwerten Rm und Rp0,2. Eine weitere Verbesserung ergibt sich, wenn die Dauerfestigkeit gleich der zyklischen Spannung bei einer plastischen Dehnungsamplitude εa, p = 0,026% gesetzt wird, σW = σ0,026.
Beschreibung des Kriechverhaltens einiger warmfester stähle
Authors: Kloos K. H. , Granacher J. , Oehl M.
Published: December 2004

Das Zeitdehnverhalten wichtiger warmfester Stähle wird mit dem Ziel der Aufstellung von Kriechgleichungen untersucht Für zwei schon durch umfangreiche Ergebnisse belegte Versuchswerkstoffe werden Gleichungen entwickelt, die für den gesamten anwendungsrelevanten Temperatur‐, Spannungs‐ und Zeitbereich gültig sind.
Thermisches Entgraten von Flugzeugbremsgehäusen
Authors: Richter H. , Regenscheit W.
Published: December 2004

An einem thermisch entgrateten Bremsgehäuse aus einer warmausgelagerten Aluminiumlegierung wurden metallografische Untersuchungen und röntgenografische Eigenspannungsmessungen vorgenommen. Bei ordnungsgemäßem Entgratungsprozeß sind in Bereichen mit ausreichendem Materialquerschnitt und nicht zu scharfen Kanten keine nachteiligen Gefügeveränderungen un/oder Eigenspannungszustände in der Randschicht zu envarten. Bei thermischer Überbeanspruchung werden jedoch in der Randschicht sehr hohe Zugeigenspannungen in der Größenordnung der Dehngrenze erzeugt.
Theoretische und experimentelle Untersuchungen zur Faserausrichtung beim Strangpressen von Kurzfaser‐Verbundwerkstoffen
Authors: Langhans K. , Roeder E.
Published: December 2004

Kurzfaserverstärkte Werkstoffe erzielen ihre höchste Verstärkungswirkung, wenn die eingelagerten diskontinuierlichen Fasern parallel zur Belastungsrichtung orientiert sind. Ein Herstellverfahren für derartige Materialien, bei dem dies in hohem Maße erreicht werden kann, ist das Strangpressen, das aufgrund seines vergleichsweise einfachen Funktionsprinzips auch gute Voraussetzungen zur theoretischen Betrachtung der Kurzfaser‐Ausrichtung bietet.

Im vorliegenden Aufsatz wird zunächst eine Modellbetrachtung dargelegt, die die Orientierungsänderung der Kurzfasern beim Strangpressen mittels einfacher mathematischer Abbildungen beschreibt. Im Anschluß daran erfolgt die Erläuterung einer Finite‐Elemente‐Berechnung, mit der die Faserausrichtung auf‐ grund einer Simulation des Strömungsverhaltens des Matrixmate‐rials theoretisch untersucht werden kann. Obwohl diese Berechnung im Gegensatz zum erstgenannten Modell auf zwei Dimensionen beschränkt bleibt, vermag sie wegen der Berücksichtigung zusätzlicher Einflußgrößen detailliertere Ergebnisse zu liefern. Abschließend beschriebene strukturelle Untersuchungen stranggepreßter kurzfaserverstärkter Glas‐Verbundwerkstoffe ergaben gute Übereinstimmungen der experimentell ermittelten Faser‐orientierung mit den Resultaten der theoretischen Betrachtungen und belegten somit die prinzipielle Eignung der Modelle zur Beschreibung des Ausrichtungsverhaltens von Kurzfasrern beim Strangpressen.
Untersuchung des Wärmeausdehnungsverhaltens elektronenstrahlgeschweißter sowie hochtemperaturgelöteter NiCr20TiAl‐Verbindungen
Authors: Wielage B. , Lebküchner‐Neugebauer J. , Dammer R.
Published: December 2004

Das Wärmeausdehnungsverhalten gefügter NiCr20TiAl‐Verbindungen wird wesentlich durch die Temperaturbelastung beim Fügeprozeß sowie durch die anschließende Wärmebehandlung beeinflußt. Die Wärmeausdehnungskoeffizienten (in 10−6 · K−1) während der Aufheizphase betragen für NiCr20TiAl im lösungsgeglühten Zustand 16,74, für den elektronenstrahlgeschweißten Verbund 17,33, für den mit L‐Ni5 gelöteten Verbund nach dem Auslagern 15,63. In der Abkühlphase treten niedrigere Wärmeausdehnungskoeffizienten auf, was vermutlich auf die γ′‐Aushärtung zurückzuführen ist.
Corrosion Behaviour of brass in nitric acid solutions
Authors: Al‐Suhybani A. A. , Hazza A. A. , Al‐Mishary M.
Published: December 2004

The corrosion of Brass in nitric acid solutions is studied using thermometric, mass loss and polarization methods. The three methods gave almost similar results. The rate of corrosion was found to increase steadily with nitric acid concentration till about 9M where it starts to slow down. Different inorganic anions at different concentration were used as additives at 5 and 9 M acid and they behave as mixed inhibitors. The open circuit potentials (OCP) were found to depend on acid as well as inhibitor concentrations.

The effect of CrO and CI− were studied in more detail than other anions. The effect of nitrate ion is to accelerate corrosion at low acid concentration and slightly inhibits the corrosion at 9 M acid. This behaviour was attributed to the adsorption of the ion on the Zn part of the alloy where it enhances corrosion while the ion adsorped on the Cu part of the alloy leads to the retardation of corrosion and the net effect will be the result of these opposing processes.
The influence of Specimen Geometry on the J‐integral R‐curves for a ferritic steel
Authors: Krompholz K. , Ullrich G.
Published: December 2004

For a ferritic construction steel similar to St37‐2 the cross section of three‐point bend type specimens was selected to be B : w = 1 : 2 and 1 : 1 (B: thickness, w: specimen width, and w = 25 mm was kept constant). For these two geometries the onset of stable crack growth J0 was found to be identical, the slope of the J‐integral R‐curves revealed only small differences. A small size defect in the microstructure of one specimen delivered a pronounced change in the tearing modulus. The reserve in stable crack growth is small. The results of this material is compared with the results obtained earlier for the nuclear grade material A 533 B1 in connection with different crack length to specimen width ratios.
Über den Einfluß von Eigenspannungen, Nahtgeometrie und mehrachsigen Spannungszuständen auf die Betriebsfestigkeit geschweißter Konstruktionen aus Baustählen
Authors: Sonsino C. M.
Published: December 2004

Für eine betriebsfeste Bemessung von geschweißten Konstruktionen sind u.a. Einflüsse aus Eigenspannungen, Nahtgeometrien und mehrachsigen Spannungszuständen auf die Lebensdauer zu berücksichtigen. Erkenntnisse zum Einfluß von Eigenspannungen im Bereich der Dauerfestigkeit lassen sich, je nach von der Nahtgeometrie abhängigen Spannungskonzentration und Spannungsabbau, nicht unbedingt auf den Bereich der Zeitfestigkeit oder auf zeitlich veränderliche Belastungen mit die Dauerfestigkeit zum Teil überschreitenden Anteilen übertragen. Eine Verbesserung rung der Nahtgeometrie, z. B durch die WIG‐Behandlung, führt grundsätzlich zu einem besseren Schwingfestigkeitsverhalten, wenn Nahtübergangsradien ausreichend groß sind. Im Hinblick auf eine Übertragbarkeit von mit Proben gewonnenen Ergebnissen auf große Bauteile müssen Kriterien wie Strukturspannung oder örtliche Vergleichsspannung, Anriß und der Größeneinfluß beachtet werden. Für eine Schadensakkumulationsberechnung wird als Schadenssumme D = 0,5 empfohlen. Bezüglich einer Bewertung von mehrachsigen Spannungszuständen kann beim Vorliegen von konstanten Hauptspannungsrichtungen die Gestaltänderungsenergiehypothese sowohl auf der Basis von Struktur‐ als auch örtlichen Spannungen befriedigend angewendet werden. Falls jedoch Veränderungen von Hauptspannungsrichtungen, z. B. infolge einer Phasenverschiebung zwischen Normal‐ und Schubspannungen auftreten, versagen alle bekannten Hypothesen durch eine hohe Überschätzung der Lebensdauer. Für solche Fälle ist gegenwärtig ein experimenteller Betriebsfestigkeitsnachweis zu empfehlen.
Rechnerische Beschreibung des Kriechverhaltens ausgewählter hochwarmfester Legierungen. Teil 1: Kriechgleichungen Für einzelne Versuchswerkstoffe
Authors: Kloss K. H. , Granacher J. , Pfenning A.
Published: December 2004

Für hochwarmfeste Werkstoffe werden Gleichungen vorgestellt, die auf den Ergebnissen von Warmzug‐, Zeitstand‐ und Glühversuchen an einzelnen Versuchswerkstoffen beruhen und die elastoplastische Verformung, das Kriechen und die Kontraktion dieser Werkstoffe im gesamten, anwendungsrelevanten Temperatur‐, Spannungs‐ und Zeitbereich beschreiben.