bluuebunny/crossref_metadata_2025 huggingface dataset:
Hybrid Ia antigens: Genetic, serologic, and biochemical analyses
Authors: Lafuse William P. , Yokota Shumpei , David Chella S.
Published: May 2005

Ia specificities 22 and 23 were found to be determinants on hybrid Ia molecules, formed by the noncovalent binding of a 26,000–28,000 dalton beta polypeptide chain (Ae) coded by the I‐A subregion and a 32,000–35,000 dalton alpha chain (Eα) coded by the I‐E subregion. For expression of Ia. 23 the Ae chain, coded by the I‐A subregion, must be derived from the H‐2d haplotype, while Ab, As, or Ak can provide the complementing beta chain for the expression of Ia. 22. For expression of Ia. 22 and Ia. 23, most Ia. 7 positive strains can provide the complementing alpha chain (Eα), with the one exception of B 10. PL (Eu), which is Ia. 7 positive but will not complement with Ad to express Ia. 23. Antisera were also produced against hybrid Ia antigens by immunizing with F1 cells expressing Ia. 22 or Ia. 23 generated by transcomplementation. These antisera detect the same specificities as conventional anti‐Ia. 22 and anti‐Ia. 23 sera produced against cis‐complementing Ia antigens. It is postulated that hybrid Ia determinants are involved in recognition and generation of immune response to antigens under dual Ir gene control. It is also suggested that there are 2 types of Ia specificities: (1) allotypic Ia specificities expressed on the alpha or beta chains (for example, Ia. 7 on the Eα chain) and (2) hybrid Ia specificities, which are unique interaction determinants formed by the association of alpha and beta chains (for example, Ia. 22 and Ia. 23). These interaction gene products may be involved in antigen recognition and presentation.
Polyclonal activation of Ts cells with antiserum directed against an IGH‐1 linked candidate for a T‐cell receptor constant region marker
Authors: Owen Frances L.
Published: May 2005

An anti‐T cell serum raised in allotype congenic mice recognizes the product of a new locus coding for a heavy chain‐linked polypeptide found on a subpopulation of T cells. Anti‐Tsd raised in BALB/cAnN mice against selected C.AL‐20 T cells reacts with a cell surface antigen in virgin animals that is found on 25% of mature thymocytes and Lyt‐bearing T cells, but not on prothymocytes, Lyt1 T cells or B cells. The antigen is restricted to strains bearing the Ig‐1d and Ig‐1e heavy chain allotype haplotypes, and is expressed in the F1 animal. The antigen is unlinked in expression to the Lyt2, H‐2, or kappa light chain loci. The antigen is not detected in the hematopoietic cells in the bone marrow and appears to mark only the mature peripheral pool of T cells. As previously reported, the antiserum blocks the binding of suppressor T cells to the cross‐reactive idiotype for arsonate, while reagents specific for Fab, Fc and Ig were ineffective. It seems probable that the marker may represent a T cell constant region marker analogous to the Igh products on immunoglobulin. Antiserum against this marker induces in vivo triggering of Ts cells for a wide variety of T‐dependent antigens. All subclasses of anti‐hapten antibodies are suppressed; no affinity restrictions or clonotype specificity is observed in suppressed adult mice. Results suggest that precursor T cells regulating major serum idiotypes regulate individual idiotypes.
Regulation of B lymphocyte activation by the Fc portion of immunoglobulin
Authors: Morgan Edward L. , Weigle William O.
Published: May 2005

Murine splenic B lymphocytes are induced to proliferate and undergo polyclonal activation in the presence of Fc fragments, AHGG, antigen‐antibody complexes, and CH3 fragments derived from plasmin digestion of human Ig. The unifying feature of the polyclonal antibody response induced by these agents is that in all cases a portion of the constant region of the Ig molecule (ie, Fc region) is present. Fragments of Ig lacking the Fc piece, such as Fab and F(ab′)2 were found not to be stimulatory. In addition, a model is proposed to account for the regulatory effects of antigen‐antibody complexes on an ongoing humoral immune response.
Specific protein phosphorylation during cyclic AMP‐mediated morphological reversion of transformed cells
Authors: Bloom George S. , Lockwood Arthur H.
Published: May 2005

Treatment of transformed Chinese hamster ovary cells with dibutyryl cAMP or other agents that elevate cAMP results in the acquisition of growth and morphology characteristic of normal fibroblasts. The role of specific protein phosphorylation in this process of morphological reversion has been examined using metabolic labelling of Chinese hamster ovary (CHO) cells with 32P‐orthophosphate in the presence or absence of N6O2′‐dibutyryladenosine 3′:5′‐cyclic monophosphoric acid (Bt2cAMP). Analysis of labelled cultures by SDS gel electrophoresis and radioautography demonstrate dramatic changes in the phosphorylation of only 2 cellular proteins during reverse transformation. A 55,000 dalton protein (pp55) was phosphorylated and a 20,000 dalton protein (pp20) was dephosphorylated. The time course of these events was consistent with the kinetics of morphological reversion. The lower molecular weight species, pp20, was dephosphorylated within 15–30 minutes, prior to all morphological changes except membrane tranquilization. The higher molecular weight protein, pp55, was maximally phosphorylated over 1–2 hours following addition of Bt2cAMP, paralleling early stages in the establishment of fibroblastic form. The phosphorylated forms of pp20 and pp55 were both extracted from cellular cytoskeletons by 0.5% Triton X‐100, but analysis of 35S‐methioninelabelled cultures suggested that unphosphorylated pp 20 may be bound to the cytoskeleton. Since pp20 was found to comigrate with the 20,000 dalton myosin light chain, it is possible that dephosphorylation of CHO cell myosin induced by cAMP may alter its interaction with actin microfilaments and modulate the assembly of stress fibers during morphological reversion.
The in vitro synthesis and processing of the branched‐chain amino acid binding proteins
Authors: Daniels Charles J. , Anderson James J. , Landick Robert , Oxender Dale L.
Published: May 2005

The synthesis of the leucine‐specific and LIV‐binding proteins was examined in vitro in a coupled transcription/translation system using the hybrid plasmids pOX7 and pOX13 as templates. Plasmid pOX7 contains the livK gene coding for the leucine‐specific binding protein, and pOX13 contains the liv J gene coding for the LIV‐binding protein. Both binding proteins were synthesized in vitro as precursor forms with molecular weights approximately 2,500 greater than their respective mature forms. Conversion of the precursor forms to their mature forms occurred during post‐translational incubation following synthesis in the presence of membrane. The precursor of the LIV‐binding protein was processed more rapidly than the leucine‐specific binding protein precursor. Processing activity could be removed from the in vitro synthesis system by centrifugation, suggesting that the processing activity was membrane associated. Restoration of post‐translational processing activity was achieved by adding inside‐out membrane vesicles to membrane‐depleted reaction mixtures.
Mapping the mitotic clock by phase perturbation
Authors: Klevecz R. R. , King G. A. , Shymko R. M.
Published: May 2005

In synchronized V79 cells perturbed by serum, heat shock, or ionizing radiation at half‐hour intervals through a modal 8.5‐hour cell cycle, phase‐response curves show a characteristic biphasic pattern of advances and delays in subsequent cell divisions. These observations, together with previous observations of quantizement of generation times in this and other cell lines have led us to consider a model incorporating, in the simplest case, a two‐component oscillator with two threshold crossings required per cell cycle. By assuming that oscillator variables respond in a simple way to the experimental perturbations, for example, by first order destruction due to heat shock, a map of the qualitative features of the oscillator can be obtained by matching simulated with experimental phase response curves. Random fluctuations in oscillator variables about a fixed trajectory lead to subthreshold oscillations and result in a distribution of generation times which is roughly a negative exponential, but quantized within this exponential envelope. The extent of the random fluctuations can be determined from comparison with data on desynchronization of a cell population after mitotic selection. The same parameters which correctly simulate phase response and the desynchronization data also give good agreement with generation time distribution data.
Cell surface receptors for endogenous mouse type C viral glycoproteins and epidermal growth factor: Tissue distribution in vivo and possible participation in specific cell‐cell interaction
Authors: Rapp U. R. , Marshall Thomas H.
Published: May 2005

We have described previously the detection and tissue distribution of free cell surface receptors for ecotropic R‐MuLV envelope glycoprotein and the growth factor EGF in vivo [1]. More recently, we have reported the chromosomal map position of the ecotropic viral receptor and its conservation between subspecies of the genus Mus [2]. This work has shown, for the first time, the presence of multiple, independently segregating cell surface receptor genes specific for different classes of ecotropic type C viral envelope glycoprotein. In this report we extend these findings and identify chromosome 2 as coding for the receptor used by M813, an ecotropic MuLV from a feral Asian mouse. This new receptor is probably also used by oncogenic, recombinant (MCF class) MuLV of C3H origin.
Promotion of hematopoietic stem cell differentiation in vitro by a soluble mediator, allogeneic effect factor
Authors: Altman Amnon , Gilmartin Thomas D. , Katz David H.
Published: May 2005

This study was designed to investigate the effects of allogeneic effect factor (AEF), a soluble mediator derived from short‐term mixed lymphocyte cultures (MLC) of in vitro alloantigen‐primed T cells, on cultures of murine bone marrow cells. Cultures established under suboptimal conditions namely, in the absence of a pre‐established adherent cell layer as required in conventional Dextertype cultures–declined and lost their stem cell activity rapidly. In contrast, supplementation of these cultures, at initiation and thereafter, with AEF, but not with T cell growth factor (TCGF), induced cell growth and proliferation for several weeks. Such AEF‐supplemented cultures exhibited cellular heterogeneity and stem cell activity for significantly longer periods than the control cultures. Even in conventional Dexter cultures, established under optimal conditions, AEF had a beneficial effect on cellular growth and proliferation and myeloid progenitor cell (CFU‐C) activity. Furthermore, cells capable of synergizing with suboptimal numbers of mature T cells in con A‐induced mitogenic responses, shown by others to be pre‐T cells, were detected in the AEF‐supplemented cultures for several weeks.
Proteolytic domains of the epidermal growth factor receptor of human placenta
Authors: O'Keefe Edward J. , Battin Teresa K. , Bennett Vann
Published: May 2005

Microsomal membranes from human placenta, which bind 5–20 pmol of 125I‐epidermal growth factor (EGF) per mg protein, have been affinity‐labeled with 125I‐EGF either spontaneously or with dimethylsuberimidate. Coomassie blue staining patterns on SDS polyacrylamide gels are minimally altered, and the EGF‐receptor complex appears as a specifically labeled band of 180,000 daltons which is not removed by urea, neutral buffers, or chaotropic salts but is partially extracted by mild detergents. Limited proteolysis by alpha chymotrypsin and several other serine proteases yields labeled fragments of 170,000, 130,000, 85,000, and 48,000 daltons. More facile cleavage by papain or bromelain rapidly degrades the hormone‐receptor complex to smaller labeled fragments of about 35,000 and 25,000 daltons. These fragments retain the binding site for EGF, are capable of binding EGF, and remain associated with the membrane. Alpha chymotryptic digestion of receptor solubilized by detergents yields the same fragments obtained with intact vesicles, suggesting that the fragments may represent intrinsic proteolytic domains of the receptor.
Alterations in growth requirements of kidney epithelial cells in defined medium associated with malignant transformation
Authors: Taub Mary , Ü Ben , Chuman Lorraine , Rindler Michael J. , Saier Milton H. , Sato Gordon
Published: May 2005

The possibility has been investigated that (1) the supplements required for the growth of the Madin Darby Canine Kidney (MDCK) cell line in serum‐free Medium K‐l are indeed requirements for the growth of normal kidney cells in vitro, and (2) that alterations in these growth requirements are associated with malignant transformation. Consistent with the hypothesis that MDCK cells resemble normal kidney cells in culture, primary cultures of baby mouse kidney epithelial cells grow in Medium K‐l and respond to the 5 components in the‐medium. The growth properties of Moloney sarcoma virus (MSV)‐transformed MDCK cells in defined media have been examined. Unlike MDCK cells, MSV‐transformed MDCK cells form tumors in adult nude mice. Although they still respond to the 5 factors in Medium K‐l, the optimal dosage for insulin is lower for the MSV transformants than for MDCK cells. The MSV transformants also have an additional requirement for growth in Medium K‐l – fibronectin. Variants of MDCK cells have been isolated that have lost the PGE1 requirement for growth in defined medium. These variant cells have acquired (1) the ability to form tumors in adult nude mice and (2) an alteration affecting cAMP metabolism, in addition to PGE1 independence.
Effect of heme on globin messenger RNA synthesis in spleen erythroid cells
Authors: Fuchs O. , Ponka P. , Borova J. , Neuwirt J. , Travnicek M.
Published: May 2005

Synthesis of globin mRNA in erythroid spleen cells from anemic mice was measured after in vitro incubation under conditions in which the level of intracellular heme was manipulated. This newly synthesized globin mRNA was isolated by hybridization with globin cDNA covalently bound to cellulose. Isonicotinic acid hydrazide (INH) and penicillamine were used as specific inhibitors of heme synthesis. It has been found that a 120‐min incubation of spleen erythroid cells with 5 mM INH or 5mM penicillamine reduced [3H] uridine incorporation into globin mRNA by 24% or 36%, respectively. The addition of heme to INH‐ or penicillamine‐treated cells almost completely restored [3H] uridine incorporation into globin mRNA. These results indicate that heme stimulates transcription or processing of globin mRNA.
Spectrin‐4.1‐actin complex of the human erythrocyte: Molecular basis of its ability to bind cytochalasins with high‐affinity and to accelerate actin polymerization in vitro
Authors: Lin Diane Chang
Published: May 2005

The spectrin‐4.1‐actin complex isolated from the cytoskeleton of human erythrocyte [3] was found to be similar to muscle F‐actin in several aspects: Both the complex and F‐actin nucleate cytochalasin‐sensitive actin polymerization; both bind dihydrocytochalasin B with similar binding constants; both can be depolymerized by DNase I with loss of cytochalasin binding activity. From these results, we conclude that the actin in the complex is in an oligomeric form. However, the presence of spectrin and band 4.1 in the complex not only stabilized the actin in the complex as evidenced by its resistance to depolymerization in low‐ionic‐strength conditions and to DNase I as compared with F‐actin, but also altered the characteristics of the binding site(s) for cytochalasins believed to be located at the “barbed” (polymerizing) end of the oligomeric actin.
Effects of guanine nucleotides on cns neuropeptide receptors
Authors: Moody Terry W. , Taylor Duncan P. , Pert Candace B.
Published: May 2005

The effect of nucleotides on central nervous system neuropeptide receptor binding was investigated. The guanine nucleotides, guanosine‐5′‐triphosphate and guanylyl‐5′‐imidodiphosphate, significantly inhibited the binding of radiolabeled vasoactive intestinal polypeptide but not that of [Tyr4]bombesin to rat brain membranes. Vasoactive intestinal polypeptide binding was inhibited by guanine nucleotides in a dose‐dependent manner. Using a 20 μM dose, 60% of the specific vasoactive intestinal polypeptide binding was inhibited by guanylyl‐5′‐imidodiphosphate, which was more potent than guanosine‐5′‐triphosphate, whereas other nucleotides were not effective. This reduction in binding was a consequence of lower affinity of the receptor for vasoactive intestinal polypeptide, which in turn resulted from an increased rate of dissociation.
Subcellular structures involved in internalization and degradation of epidermal growth factor
Authors: Fine Richard E. , Goldenberg Richard , Sorrentino Joseph , Herschman Harvey R.
Published: May 2005

Epidermal Growth Factor (EGF), a small polypeptide which acts as a mitogen for many cell types, has previously been shown to bind to a specific plasma membrane receptor on 3T3 cells. If 125I‐EGF is bound to 3T3 cells for one hour at 4°C, it remains predominantly associated with the plasma membrane‐containing fractions obtained by subjecting cell supernatants to equilibrium sedimentation on sucrose gradients. When binding is followed by a 10‐minute incubation at 37°C, over 50% of the 125I‐EGF is associated with two internal membrane‐containing peaks having higher densities than the plasma membrane. After one hour at 37°C, over 80% of the 125I‐EGF is degraded and removed from the cells.

The most rapidly labeled internal peak corresponds in density to brain‐coated vesicles (CVs). Antiserum prepared against coated vehicles from brain precipitates the 125I‐EGF in this peak. In addition, CVs containing 125I‐EGF can be co‐purified from 3T3 cells exposed to 125I‐EGF, using brain as a carrier. Several lines of evidence suggest that the other 125I‐EGF‐labeled intracellular peak is 125I‐EGF in lysosomes.

These results provide kinetic and biochemical evidence for a unidirectional pathway for EGF catabolism by 3T3 cells. EGF first binds to the plasma membrane bound receptors, is then moved to the cytoplasm in CVs, and finally appears in lysosomes, where it is degraded and released from the cells. Ten‐millimolar NH4Cl blocks lysosomal hydrolysis of EGF almost completely. Subsequently, EGF internalization is inhibited. This finding suggests that the pathway for EGF internalization and degradation is tightly coupled.
Sulfated glycoproteins and extracellular matrix of cultured human pulmonary endothelial cells
Authors: Heifetz Aaron , Johnson Alice R.
Published: May 2005

Endothelial cells derived from human pulmonary arteries incorporate (3H)‐glucosamine and 35SO4 into glycosaminoglycans and into the carbohydrate side chains of glycoproteins. These 3H/35S‐carbohydrate chains were isolated from cells and culture medium after Pronase digestion. The 3H/35S‐glycosaminoglycans were separated from the 3H/35S glycopeptides by chromatography on Sephadex G‐50. The distribution of cellular glycosaminoglycans and glycopeptides indicated that 30–60% of the cellular 35S‐glycopeptides may be associated with the matrix components that are synthesized by the cell and attached to a plastic substratum. Human pulmonary arterial endothelial cells were grown on collagen or on a matrix derived from vascular smooth muscle cells in order to investigate how smooth muscle cell extracellular matrix components may regulate the synthesis of endothelial cell glycoconjugates. Endothelial cells grown on plastic release various proportions of the glycoconjugates they synthesize into the culture medium. However, these same cells, when grown on substratum composed of extracellular matrix materials, synthesized altered proportions of cell‐associated glycosaminoglycans and reduced the levels of total glycosaminoglycans they released into the culture medium. Thus the growth of endothelial cells on a matrix of smooth muscle cell components indicates that the glycosaminoglycan materials released into the culture medium by cells grown on a plastic substratum may not be an accurate reflection of the levels or composition of extracellular matrix materials made by endothelial cells in vivo.
Heparin‐inhibitable lectins: Marked similarities in chicken and rat
Authors: Roberson Marie M. , Ceri Howard , Shadle Paula J. , Barondes Samuel H.
Published: May 2005

Extracts of young rat lung contain a heparin‐inhibitable lectin that closely resembles one recently purified from chicken liver. Both lectins interact with heparin and N‐acetyl‐D‐galactosamine, and were purified by gel filtration on Sepharose CL‐2B followed by affinity chromatography on heparin‐Sepharose. They both behave as high molecular weight aggregates that can be dissociated into two peptides with apparent molecular weights of 13,000 and 16,000 by gel electrophoresis in SDS. Samples of purified lectin contained up to 20% DNA by weight, and the degree of lectin aggregation and hemagglutination activity was greatly reduced by treatment with micrococcal nuclease without inhibiting heparin‐binding activity. Association of lectin with DNA is an artifact of homogenization in high salt, since only 2% of the lectin is found associated with a purified nuclear fraction.
Stimulation of DNA polymerase α by a nuclear DNA/protein complex
Authors: Balabanova Henny , Fridlender Berthold R. , Anderer F. Alfred
Published: May 2005

A nuclear DNA complex containing DNA polymerase and SV40 T‐antigen was isolated from nuclei of SV40‐transformed mouse fibroblasts. DNA polymerase could be separated from the complex. The remaining DNA/T‐antigen‐containing complex stimulated DNA polymerase a activity about 10‐fold. The complex contained 4 major proteins with molecular weights of 46, 54, 76, and 94 kilodalton (KD). The stimulation activity was retained by protein A–Sepharose loaded with specific IgG from SV40‐tumor bearer serum, or from antisera against the 94 KD and 76 KD components and was partially inhibited in the presence of these antisera. The stimulation activity was completely abolished by treatment of the complex with trypsin or DNase I.
Two chick embryonic adhesion systems: Molecular vs tissue specificity
Authors: Thomas William A. , Edelman Bruce A. , Lobel Susan M. , Breitbart Arnold S. , Steinberg Malcom S.
Published: May 2005

We have investigated the adhesive properties of cells from several neural and nonneural chick embryonic tissues dissociated using modifications of the standard dissociation procedures employed routinely in this laboratory to obtain retinal cells. Each of these tissues (7‐day optic tectum, retina, and heart, and 3.75‐day hmb bud) displayed both Ca++‐dependent (CD) and Ca++‐independent (CI) aggregation, the relative rates of which differed from tissue to tissue In every case, cells prepared so as to display one mode of aggregation or the other cross‐adhered readily to cells—regardless of tissue origin—displaying the same mode of aggregation. Cross adhesion was negligible between cells—even from the same tissue—prepared so as to display different modes of aggregation. Anti‐retinal Fab molecules which inhibit selectively either the CI or CD aggregation of retina cells strongly inhibited the corresponding aggregation of optic tectum cells, but had no effect upon the aggregation (CI or CD) of heart cells. These results demonstrate the exis‐tence in the tissues examined of dual adhesion mechanisms similar in Ca++ dependence and recognition properties to those of the retina, but showing certain immunological distinctions from the latter. The imrmunological relationship among the adhesion mechanisms from the various tissues is under continuing investigation.
Bacterial attachment as related to cellular recognition in the rhizobium‐legume symbiosis
Authors: Dazzo Frank B.
Published: May 2005

Bacterial attachment is viewed as a cellular recognition event during the infection of legumes by the nitrogen‐fixing symbiont, Rhizobium. Studies on the biochemical basis of selective attachment are reviewed, and suggest that this recognition process is accomplished by specific glycoprotein lectin–polysaccharide interactions on the surfaces of the symbionts. An understanding of host specificity may lead to ways to broaden the host range of nitrogen‐fixing symbioses.
Specific reversal of cytolytic T lymphocyte – target cell interaction
Authors: Balk Steven P. , Mescher Matthew F.
Published: May 2005

A functional assay is described that measures the reversal of specific cytolytic T cell (CTL)‐target cell binding. Binding of 51Cr‐labeled P815 cells was stable in suspension but could be readily reversed by the addition of unlabeled P815 cells. The reversal of CTL‐tumor cell and CTL‐spleen cell binding was H‐2 specific; only cells of the same H‐2 type as the bound target cell could induce reversal. In all cases, tumor cells were substantially more efficient than spleen cells in inducing specific reversal.
Expression of glial antigens C1 and M1 in developing and adult neurologically mutant mice
Authors: Sommer I. , Schachner M.
Published: May 2005

The distribution of two glial antigens (C1 and M1) has been studied by indi‐rect immunofluorescence during postnatal development of the cerebella of normal and neurologically mutant mice (weaver, staggerer, reeler, Purkinje cell degeneration, and wobbler). During the first postnatal week of normal development, C1 antigen is expressed in ependyma, Bergmann glial fibers (BG), and astrocytes of the internal granular layer and white matter. After day 10, C1 antigen is restricted to BG and ependymal cells. During the sec‐ond and third week, BG undergo a transient loss of C1 antigen that starts in medioventral areas and spreads in a gradient dorsally and laterally.

In reeler, weaver, and staggerer, C1 antigen expression is normal during the first postnatal week, and subsides in BG in a similar spatial gra‐ dient as described for the normal littermates. However, the loss of C1 anti‐gen in BG occurs earlier (first in reeler, then in weaver, and last in staggerer) and is not reversible as it is in normal mice. In Purkinje cell de‐generation, C1 antigen expression is diminished in BG after the onset of be‐havioral abnormalities. Wobbler is normal with respect to C1 antigen ex‐pression at adult ages.

M1 antigen is detectable in white matter astrocytes from postnatal day 7 on, and persists in these cells into adulthood. Astrocytes of the internal granular layer and BG express M1 antigen only transiently in normal mice during the second and third weeks. The appearance of M1 antigen in BG occurs in a spatiotemporal gradient, matching the one in which C1 antigen disappears. M1 antigen expression is abnormally maintained in BG of reeler, staggerer, and weaver. In Purkinje cell degeneration, M1 antigen is ex‐pressed abnormally at the onset of behavioral abnormalities first in.astro‐cytes of the internal granular layer and, with growing age, increasingly also in BG. In wobbler, BG do not express M1 antigen. However, astrocytes of the granular layer are abnormally M1 antigen‐positive.
Suppression of tumorigenicity in cybrids
Authors: Shay Jerry W. , Lorkowski Gay , Clark Mike A.
Published: May 2005

We investigated cytoplasmic control of tumorigenicity in cybrids. Cytoplasts derived from nontumorigenic cells were fused to the highly tumorigenic 984 Cl 10–15 cell line derived from a murine teratoma. The resultant cybrids did not retain the tumorigenicity of the original cell line. In addition, the majority demonstrated the ability to differentiate into skeletal muscle. The results of these experiments indicate a heritable suppression of the tumorigenic phenotype by nontumorigenic cytoplasm. These findings are in contrast to our previous experiments in which we used a different experimental system and demonstrated a nuclear control of tumorigenicity in cybrids.
The in vivo formation and repair of DNA adducts from 1′‐hydroxysafrole
Authors: Phillips David H. , Hanawalt Philip C. , Miller James A. , Miller Elizabeth C.
Published: May 2005

1′‐Hydroxysafrole is a proximate carcinogenic metabolite of the naturally occurring hepatocarcinogen safrole. Comparison by high‐performance liquid chromatography of the nucleoside adducts obtained from hepatic DNA of adult female mice treated with [2′,3′‐3H]1′‐hydroxysafrolc with those formed by reaction of deoxyribonucleo‐sides with electrophilic derivatives of 1′‐hydroxysafrole indicated that the four in vivo adducts studied were derived from an ester of 1′‐hydroxysafrole. Three of the four adducts comigrated with products of the reaction of 1′‐acetoxysafrole with deoxyguanosine, whereas the fourth adduct comigrated with the major reaction product of the ester with deoxyadenosine. Analysis of the three deoxyguanosine ad‐ducts indicated that all three involve substitution on the 2‐amino group of guanine. A sample of the major adduct prepared from deoxyguanylic acid has been charac‐terized from its NMR spectrum as N2‐(trans‐isosafrol‐3′‐Y1)‐deoxyguanosine, and the deoxyadenosine adduct has been similarly characterized as N6‐(trans‐isosafrol‐3′‐yl)‐deoxyadenosine.

Repair replication was measured in cultured human T98G cells exposed to 1′‐acetoxysafrole using the combined 5‐bromodcoxyuridine density label and radioiso‐topic label metnod. At a concentration of 1 mM 1′‐acetoxysafrole, the amount of repair synthesis approached maximum values only about 15% of those obtained af‐ter saturating doses of ultraviolet light. Repair patch size distribution was found to be similar in cells treated with ultraviolet light or 1′‐acetoxysafrole as determined by the density of repair‐labeled DNA relative to that of parental DNA.
Lymphocyte recognition of H‐2 antigen in liposomes
Authors: Herrmann Steven H. , Mescher Matthew F.
Published: May 2005

Liposomes containing purified H‐2Kk will specifically stimulate generation of a secondary allogeneic cytolytic T lymphocyte response. Effective recognition was found to depend on the structure of the liposomes. Including detergent‐insoluble plasma membrane matrix during formation resulted in liposomes having two‐ to fourfold more activity than those prepared using just lipid and H‐2.
Endogenous lectins in chickens and slime molds: Transfer from intracellular to extracellular sites
Authors: Barondes Samuel H. , Beyer Eric C. , Springer Wayne R. , Cooper Douglas N.
Published: May 2005

Endogenous lectins in both cellular slime molds and chicken tissues have been localized primarily intracellularly, in contrast with the predominantly extracellular localization of the glycoproteins, glycolipids, and glycosaminoglycans with which they might interact. Here we present evidence that lectins in both of these organisms may be externalized and become associated with the cell surface and/or extracellular materials. In chicken intestine, chicken‐lactose‐lectin‐II is shown to be localized in the secretory granules of the goblet cells, along with mucin, and to be secreted onto the intestinal surface. In embryonic muscle, chicken‐lactose‐lectin‐I is shown to be externalized with differentiation, ultimately becoming localized on the surface of myotubes and in the extracellular spaces. In a cellular slime mold, Dictyostelium purpureum, externalization of lectin is elicited by either polyvalent glycoproteins that bind the small amount of endogenous cell surface lectin, or by slime mold or plant lectins that bind unoccupied complementary cell surface oligosaccharides. These results suggest that externalization of endogenous lectin may be a response to specific external signals. We conclude that lectins are frequently held in intracellular reserves awaiting release for specific external functions.
Effects of nicotinamide on NAD and poly (ADP‐ribose) metabolism in DNA‐damaged human lymphocytes
Authors: Sims James L. , Berger Sosamma J. , Berger Nathan A.
Published: May 2005

The effect of nicotinamide on unscheduled DNA synthesis was studied in resting human lymphocytes. In cells treated with UV irradiation or with MNNG, nicotinamide caused a two‐fold stimulation of unscheduled DNA synthesis and retarded the rate of NAD+ lowering caused by these treatments. Nicotinamide also reduced the burst of poly(ADP‐ribose) synthesis caused by MNNG treat‐ment. Thus under conditions that it enhances unscheduled DNA synthesis, nicotinamide causes marked effects on the metabolism of NAD+ and poly(ADP‐ribose). The effect of nicotinamide on unscheduled DNA synthesis was shown to be independent of protein or polyamine synthesis.
Cellular transformation by radiation: Induction, promotion, and inhibition
Authors: Borek Carmia
Published: May 2005

Mammalian cell cultures offer powerful tools for evaluating qualitatively and quantitatively the oncogenic potential of radiation over a wide range of doses with particular importance at the low dose range that is relevant to human exposure and risk. Our studies have shown that early events in the process of radiation induced transformation in both rodent and human cells requires initial replication for fixation of transformation as a hereditary property of the cells and further clonal expansion for full expression. Early events (fixation) are inhibited by cell–cell contact and high cell density but can be modified at low temperature where repair processes are slowed. Cell–cell contact and communication in tissue organization may be in part responsible for our findings that radiation oncogenesis induced in utero in hamsters is expressed at a lower frequency than that induced in vitro.

Quantitative studies carried out on hamster embryo cells indicate that neutrons are more effective in their carcinogenic potential than x‐rays but also more toxic, that splitting the dose of x‐rays at low doses leads to enhanced transformation, but that at high doses protracted radiation has a sparing effect. At all dose ranges survival was increased by protracting the radiation dose, thus suggesting that different repair processes must be involved for survival and transformation. Similar observations were seen when the protease inhibitor Antipain was found to enhance transformation in rodent and human cells when present at the time of radiation, but was protective when added after radiation. Survival was not modified under any of those conditions, and Antipain did not affect DNA replication and repair. In our qualitative studies, once cells are transformed by radiation, they exhibit a wide range of structural and functional phenotypic changes, some of which are membrane‐associated and are expressed within days after induction.

Our current studies on nutritional and hormonal influences on radiation transformation indicate the following: Pyrolysate products from broiled protein foods act in synergism with radiation to produce transformation, whereas vitamin A analogs are powerful, preventive agents. Retinoids inhibit both x‐ray‐induced transformation and its promotion by TPA: these modifications (enhancement by TPA, inhibition by retinoids) are not reflected in sister chromatid exchanges, but are reflected in the level of membrane associated enzymes Na/K ATPase. Whereas retinoids modify late events (expression, promotion), we find that thyroid hormone plays a crucial role in the early phases of radiation and chemically induced transformation. Under hypothyroid conditions no transformation is observed. The addition of triiodothyronine at physiological levels results in a transformation rate that is dose‐related.

Our recent success in transforming human skin fibroblasts will enable quantitative and qualitative studies of radiation carcinogenesis in a system relevant to man.
Flagellar adhesion and deadhesion in chlamydomonas gametes: Effects of tunicamycin and observations on flagellar tip morphology
Authors: Snell William J.
Published: May 2005

The aggregation‐dependent loss of flagellar adhesiveness in Chlamydomonas reinhardi has been correlated with changes in flagellar tip morphology during adhesion and deadhesion. As aggregating mt− and impotent (able to adhere, but not fuse) mt+ gametes begin to disaggregate in the presence of the protein synthesis inhibitor cycloheximide, there is a concomitant change in flagellar tip morphology from the activated bulbous form to the nonactivated tapered shape. The requirement of protein‐synthetic activity for the maintenance of flagellar adhesiveness during aggregation may be due in part to turnover of proteins involved in formation or stabilization of activated flagellar tips.

Incubation of aggregating gametes with tunicamycin indicates that, like protein synthesis inhibitors, this inhibitor of glycosylation also causes adhering gametes to deadhere. The results suggest that protein glycosylation may be essential for maintenance of adhesiveness during aggregation.
Effect of serum, fibronectin, and laminin on adhesion of rabbit intestinal epithelial cells in culture
Authors: Burrill Peter H. , Bernardini Isa , Kleinman Hynda K. , Kretchmer Norman
Published: May 2005

Rabbit intestinal epithelial cells, obtained after a limited hyaluronidase digestion, were incubated in medium with or without calf serum, on bacteriological plastic dishes. The dishes, either plain or coated with an air‐dried type I collagen film, were pretreated with medium alone or with medium containing purified laminin or purified fibronectin. Cells did not attach in significant numbers to untreated bacteriological plastic, even in the presence of serum. Cells did attach to collagen‐coated dishes, and were judged viable on the basis of their incorporation of radiolabeled leucine into cell protein. Cell adhesion to the collagen substrate increased in proportion to the concentration of serum in the medium, with maximal attachment at 5% serum or greater. Pretreatment of plain or collagen‐coated dishes with increasing amounts of fibronectin enhanced cell adhesion in a concentration‐dependent manner. Either serum, or fibronectin‐free serum in the medium enhanced cell attachment to substrates pretreated with cither fibronectin or laminin. Thus, intestinal epithelial cells appear to possess surface receptors for both laminin and fibronectin. The evidence further suggests that calf serum may contain factors, other than fibronectin, capable of enhancing intestinal epithelial cell attachment to collagen substrates.
Antigen‐specific mouse lymphocyte stimulation by DNP‐conjugated T‐independent antigens studied by photobleaching recovery
Authors: Peacock James S. , Barisas B. George
Published: May 2005

Fluorescence photobleaching recovery techniques have allowed us to measure the lateral mobility of T‐independent antigens bound to antigen‐specific mouse B cells. The in vitro immunogenicity or tolerogenicity of antigens we have examined, DNP‐polymerized flagellin (DNP‐POL), and DNP‐linear dextran (DNP‐DEX), depend upon the antigen dose and epitope density. These factors also determine the mobility of antigen bound to B cell surfaces. For DNP‐POL bound to DNP‐specific cells, the observed diffusion constants D decrease monotonically with increasing antigen dose and epitope density. Values of D range from 10.4 × 10−11 cm2 sec−1 for DNP0.4‐POL at 0.15 μg/ml to 0.8 × 10−11cm2 sec−1for DNP3.5‐POL at 30 μg/ml. For receptor‐bound DNP‐DEX, D depends strongly on antigen epitope density but not observably on antigen concentration. For epitope densities of 1.2 or less, D is close to the value of 21 × 10−11cm2sec−1 observed for single slg receptors. By an epitope density of 4.8, D has fallen to 2.1 × 10−11cm2sec−1. Peak immunogenicities for DNP‐POL and DNP‐DEX arc observed when antigen‐ receptor aggregates have mobilities 14‐fold and 3‐fold lower, respectively, than a single slg molecule.
Glycoprotein differences among cells of the 14‐day embryonic chick neural retina
Authors: Sheffield Joel B.
Published: May 2005

In order to test the hypothesis that the progressive layering and differentiation of cell types during the development of the neural retina are associated with cell surface alterations we have separated distinct cell populations from the 14‐day embryonic chick retina. Cells of these populations have been shown to differ in associative behavior and intramembrane particle content. We now report that these cells differ in cell surface glycoproteins. Proteins were labeled with two different extrinsic labels and one metabolic label. We used enzymatic transfer of galactose from UDP‐gal to cellular acceptors, and borotritide reduction after galactose oxidation as extrinsic labels. Glucosamine incorporation was used as the metabolic label. In all these cases, we were able to identify bands on electrophoretic gels which were unique to individual populations.
Association dynamics and lateral transport in biological membranes
Authors: Koppel Dennis E.
Published: May 2005

A theoretical analysis is presented for the interrelated effects of lateral diffusion and a simple form of molecular association (A + B ⇌ C) in biological membranes. Expressions are derived for the characteristic functions measured in fluorescence redistribution after photobleaching experiments, corresponding to both the Fourier transform analysis of concentration in a plane and the normal mode analysis for a spherical surface. The results are related to the reputed binding of integral membrane proteins to submembranous cytoskeletal elements.
The synthesis of a proteinase inhibitor, α‐1‐antichymotrypsin, by human breast epithelial cells
Authors: Tokes Zoltan A. , Gendler Sandra J. , Dermer Gerald B.
Published: May 2005

The synthesis and release of glycoproteins were studied in organ cultures of human breast surgical specimens and in established breast epithelial cell lines, MCF‐7 and MDA‐MB‐231. Biosynthesis was monitored by the incorporation of 14C‐glucosamine. Labeled macromolecules in the culture supernatants were analyzed by biochemical and immunological techniques. One to 8% of the labeled glycoproteins from benign breast and infiltrating ductal carcinoma specimens was precipitated by antibodies produced against human serum 7α‐1‐antichymotrypsin. Twelve percent of the total glycoproteins from the culture supernatants of the MCF‐7 cell line was identified as α‐1‐antichymo‐trypsin. Both the normal serum and the human breast epithelia‐derived proteinase inhibitor can be resolved into similar subclasses by two‐dimensional gel electrophoresis. MDA‐MB‐231 and MCF‐7 cells which were extensively washed with EDTA, serum‐free medium, and phosphate‐buffered saline retain this proteinase inhibitor on their cell surfaces. Three to 4% of the total cell‐surface iodinated components was immunoprecipitated by these specific antibodies. Since α‐1‐antichymotrypsin is a potent inhibitor of neutral proteinases such as cathepsin G, the demonstration of its synthesis by benign and malignant breast epithelial cells is of considerable interest. This glycoprotein may represent the epithelia's own protective shield of cell surface components and the cell's attempt to moderate the effects of invading leukocytes. In addition, it may play a regulatory role in the maintenance of three‐dimensional glandular structures.
Simian virus 40 as a probe for studying inducible repair functions in mammalian cells
Authors: Mezzina M. , Gentil A. , Sarasin A.
Published: May 2005

We describe the use of Simian Virus 40 (SV40) as a molecular probe for studying the cellular functions induced in cultured monkey kidney cells in response to DNA damaging agents.

Ultraviolet (UV) irradiation of SV40‐infected cells inhibits viral DNA replication. Replication forks are blocked by the first pyrimidine dimer encountered. In some cases, a single‐strand break seems to occur at the level of the dimer inhibiting the fork of replication. This break, which can be visualized by electron microscopy studies, might be the first step in an excision repair pathway.

Treatment of monkey kidney cells with acetoxy‐acetyl‐aminofluorene or UV light before infection with UV‐irradiated SV40 induces a mutagenic replication mode, as shown by an increase of the mutation frequency of thermosensitive SV40 mutants.

A possible recombination assay using various SV40 mutants infecting the same cell is proposed and discussed.
Effects of multiple membranes on measurements of cell surface dynamics by fluorescence photobleaching
Authors: Petersen N. O. , McConnaughey W. B.
Published: May 2005

Fluorescence photobleaching recovery curves on a pair of membranes at various separations were calculated from a detailed knowledge of the variation in relative illumination areas and intensities as well as in relative contributions to the collected intensity with membrane separation. The observed diffusion coefficients were found to be relatively insensitive to membrane separation in all cases. Only for membranes with very different mobilities are there significant differences in fractional recoveries. Systematic variations in fractional recoveries with cell thickness may be indicative of differential mobility in the apical and basal membranes.
Eigenschaften von Polypropylen unter besonderer Berücksichtigung des chemischen Apparatebaus
Authors: Müller W.
Published: May 2005

Neben dem Polyäthylen gewinnt das isotaktische Polypropylen mehr und mehr an Bedeutung. Die speziellen Eigenschaften dieses Materials haben sich sehr schnell als für den technischen Sektor besonders günstig erwiesen. Aus der Struktur des Polymeren erklärt sich eine ganze Reihe von Eigenschaften, z. B. Dichte, Erweichungspunkt, Permeabilität von Gasen, Härte, Steifigkeit und die ausgezeichnete Chemikalienbeständigkeit. Eine weitere wertvolle Eigenschaft stellt die gute Verschweißbarkeit dar. Erfahrungen auf diesem Gebiet konnten schon in großem Umfang bei der Verarbeitung von Halbzeug aus Niederdruckpolyäthylen gewonnen werden. Neben der Drahtschweißung wird auch sehr oft die Heizelementschweißung (ohne Zusatzdraht) angewandt.

Wichtig für den chemischen Apparatebau ist die sogenannte Zeitstandfestigkeit bzw. das Zeitstandverhalten. In verschiedenen Diagramme wird dies in Kontakt mit Wasser, Luft und Chemikalien, z. B. Schwefelsäure verschiedener Konzentration, dargestellt.
Vorgänge bei der Schutzschichtbildung in verzinkten Stahlrohren
Authors: Friehe W. , Schwenk W.
Published: May 2005

Die vorliegenden Untersuchungen über den Einfluß der Zeit und der Fließgeschwindigkeit auf den Zinkabtrag gestatten folgende Aussagen:

Die Zinkabtragsrate ist zeitlich konstant und abhängig vom pH‐Wert des Wassers und von der Fließbedingung. Die ist näherungsweise umgekehrt proportional der Diffusionsgrenzschichtdicke.

Elektrochemische Meßgrößen zeigen, daß anodische und kathodische Teilvorgänge stark gehemmt sind und daß zeitlich die Hemmwirkung stetig zunimmt. Das führt dazu, daß die Stern‐Geary‐Beziehung nicht anwendbar ist und somit eine schnelle Bestimmung der Abtragsrate elektrochemisch nicht erfolgen kann. Die Interpretation von i(U)‐Kurven und Polarisationswiderständen ist z. Z. mit den vorliegenden Untersuchungsergebnissen nicht möglich.
Hydrogen penetration rates of iron. Effect of halide ions, hydrogen sulfide and hexynol
Authors: Nobe Ken , Pearson I. M. , Saito Y.
Published: May 2005

The effect of the halides (Cl−, Br− and I−) on the rates of the hydrogen evolution reaction (h. E. R.) and hydrogen penetration (h. P.) of iron in H2SO4 is determined. The H. E. R. and H. P. of Fe in these same electrolytes with the addition of H2S are also studied. The inhibition of corrosion and h. p. in the H2S environment by hexynol are compared. With halide addition her., icorr and h. p. decreased in the following order, Cl−> Br−> I−. H2S catalyzed both the h. e. r. and h. p. The catalytic activity does not appear dependent on the H2S concentration for the H. E. R. but does for H. P. The fraction of hydrogen generated which is absorbed by Fe is greater during corrosion when a new surface is formed continuously than during cathodic polarization. The addition of the acetylenic alcohol, hexynol, in H2SO4 containing H2S and halides inhibited the h. e. r. corrosion and h. p.