bluuebunny/crossref_metadata_2025_split huggingface dataset:
Altered aminoacyl‐tRNA synthetase complexes in CHO cell mutants
Authors: Pahuski Eddie , Klekamp Mark , Condon Tom , Hampel A. E. 
Published: February 2005

AbstractThe Chinese hamster ovary (CHO) aminoacyl‐tRNA synthetase mutants Gln‐2, His‐1, and Lys‐101 were analyzed for alterations in respective particulate enzyme forms. The mutant Gln‐2 showed a preferential loss of the lower molecular weight enzyme form for glutamine. His‐1 showed alterations of the enzyme complexes for several other aminoacyl‐tRNA activities but only decreased activity for itself. The mutant Lys‐101 only showed an altered Lysyl‐tRNA synthetase. These results provide evidence for a model of the intracellular role of the aminoacyl‐tRNA synthetase complexes wherein the high molecular weight forms utilize amino acids directly from the extracellular pool while the low molecular weight forms utilize intracellular pools.
Influence of physical exercise after long‐lasting hypodynamia on the morphological parameters of muscle fibers
Authors: Marciniak Marianna , Barańska Wanda , Rózycka Monika 
Published: February 2005

AbstractThe purpose of this research was morphometric ultrastructure evaluation of the fibers in muscles taking part in the flight of pigeons forced to exercise after a long period of hypodynamia. It was found that following physical exercise, after 12 and 18 months of mobility limitation, there appeared marked qualitative and quantitative changes: a diminution of the volume fraction and number of mitochondria, increase of smooth sarcoplasmic reticulum and sarcoplasm, and a significant decrease of the number of glycogen granules as compared with those after 18 months hypodynamia. The above described changes were more pronounced in the supracoracoideus than in the pectoralis muscle.
Complementation for the growth response to insulin and MSA occurs at a step distal to hormone‐receptor interaction in mouse embryo fibroblast × melanoma cell hybrids
Authors: Coppock Donald L. , Straus Daniel S. 
Published: February 2005

AbstractThe PG19 mouse melanoma cell line does not respond to the mitogenic effects of insulin either in serum‐deprived quiescent cultures or when growing in hormone‐supplemented serum‐free medium, while melanoma × mouse embryo fibroblast hybrids respond under both conditions. It has been proposed that some growth effects of insulin are mediated by its binding to receptors for insulin‐like growth factors. To determine whether the PG19 cells do not respond to insulin because they lack receptors for MSA (multiplication‐stimulating activity, an insulin‐like growth factor produced by BRL‐3A cultured rat liver cells), we have examined growth effects and receptor binding of MSA in the melanoma and hybrid cells. MSA stimulates [3H]thymidine incorporation in three melanoma × mouse embryo fibroblast hybrid clones but not in the parental melanoma cells. Thus the pattern of response of the melanoma cells and hybrids to MSA directly parallels their response to insulin. The melanoma cells and hybrids all have high‐affinity specific MSA binding sites (KD = 10–27 nM), indicating that the inability of the melanoma cells to respond to MSA is not attributable to a lack of MSA receptors. Insulin competes very poorly for binding of MSA to hybrid clone 7 but is nevertheless able to stimulate [3H]thymidine incorporation in this clone. This strongly suggests that the effects of insulin on [3H]thymidine incorporation in this clone are not mediated by its binding to MSA receptors. Insulin and MSA stimulate protein synthesis and inhibit protein degradation in the hybrids but not in the parental melanoma cells. These results suggest that both insulin and MSA action are blocked in the melanoma cells at a step distal to the binding of either hormone to its cellular receptors but prior to stimulation of protein synthesis.
Intracellular pH and the cell cycle of mitogen‐stimulated murine lymphocytes
Authors: Gerson Donald F. , Kiefer Hansruedi 
Published: February 2005

AbstractRapidly proliferating, polyclonally stimulated mouse spleen lymphocytes were separated by density‐gradient unit‐gravity sedimentation. The following measurements were made on each fraction: the average intracellular water volume, the distribution of DNA content by flow microfluorometry, the rate of 3H‐thymidine incorporation, and the intracellular pH. Fractions of cells with a small average intracellular volume were predominately in G0 or G1 phase of the cell cycle, while fractions of larger cells had higher proportions of cells in S or G2. Multiple regression analysis of the data for both T and B lymphocytes indicated that the intracellular pH of cells in G0, G1, or G2 is around pH 7.2, and that the intracellular pH of cells in S phase of the cell cycle is around pH 7.4.
The biochemical and ultrastructural effects of tunicamycin and D‐glucosamine in L1210 leukemic cells
Authors: Morin Michael J. , Porter Carl W. , McKernan Patricia , Bernacki Ralph J. 
Published: February 2005

AbstractTunicamycin was found to specifically inhibit the incorporation of a number of sugars into L1210 leukemia cell glycoproteins. This inhibition of glyco‐protein biosynthesis led to a cessation of cell growth which was reversible in a dose‐dependent and time‐dependent manner. After removal of the antibiotic from L1210 cell cultures resumption of sugar incorporation preceded that of thymidine incorporation and the recovery of cell growth. The treatment of cells with tunicamycin resulted in a significant increase in the intracellular pool of UDP‐N‐acetylglucosamine which occurred concurrently with alterations in cell ultrastructure including distentions of the endoplasmic reticulum and nuclear membranes. Similar ultrastructural changes and increases in the intracellular pools of UDP‐sugars were observed in L1210 cells exposed to 5 mM D‐glucosamine, which suggested that the antiproliferative effects of tunicamycin may be related to the accumulation in the endoplasmic reticulum of one or more nucleotide sugar precursors of asparagine‐linked glycoprotein biosynthesis. However, the biological effects of tunicamycin could be distinguished from those caused by D‐glucosamine. Exposure of L1210 cells to tunicamycin resulted in specific alterations in the biochemical composition of the plasma membrane and in the inhibition of cellular agglutination by wheat germ agglutinin which were not apparent following exposure to equitoxic concentrations of the aminosugar. These studies, together with those which demonstrated that recovery of the cellular capacity to synthesize glycoproteins was obligatory for the recovery of cellular proliferation in tunicamycin‐treated cells, suggested that inhibition of the synthesis of glycoproteins was the major factor limiting L1210 leukemic cell proliferation.
Growth‐dependent AIB and meAIB uptake in LLC‐PK1 cells: Effects of differentiation inducers and of TPA
Authors: Amsler Kurt , Shaffer Carolyn , Cook John S. 
Published: February 2005

AbstractCultured pig kidney cells designated LLC‐PK1, previously shown to acquire Na + ‐dependent concentrative transport of hexoses as the cells become growth arrested, also show Na + ‐dependent concentrative uptake of the amino acid analogs α‐aminoisobutyric acid (AIB) and (methyl) meAIB. This A system‐like transport is most active in sparse, growing cultures and becomes stepped down at confluence. The cell/medium equilibrium distribution ratio of the lipophilic cation tetraphenylphosphonium ion (TPP+) decreases in parallel fashion, suggesting that a decrease in membrane potential may be a major factor in the stepdown. Differentiation inducers (hexamethylene bisacetamide) and phosphodiesterase inhibitors (theophylline, methylisobutyl xanthine) accelerate the stepdown, but even in the presence of these compounds addition of the tumor promoter 12‐0‐tetradecanoylphorbol‐13‐acetate (TPA) results in the maintenance of a high level of AIB and meAIB uptake. In all these respects the changes in A system‐like amino acid transport are the reciprocal of those seen for concentrative hexose transport, although the driving force appears to be the same for both systems. The TPA analogs phorbol and 4‐0‐methyl TPA which are inactive in tumor promotion are inactive in this system as well. In confluent, already stepped‐down cultures, addition of TPA leads to a rapid (2–6 hour) stimulation of AIB and meAIB uptake. The enhancement is sensitive to cycloheximide and actinomycin D. The ouabain‐sensitive fraction of meAIB uptake is not markedly changed in the TPA‐enhanced uptake, nor is the TPP+ distribution ratio elevated in TPA‐treated cells, making it unlikely that the TPA effect is through an alteration in the membrane potential.
Receptor‐mediated endocytosis and exocytosis of transferrin in concanavalin A‐stimulated rat lymphoblasts
Authors: Hamilton Thomas A. 
Published: February 2005

AbstractIron‐loaded transferrin has been shown to be necessary for the support of cell proliferation in culture. This function depends upon interaction of transferrin with a specific high‐affinity cell surface receptor. The present report is directed toward determining the consequences of the interaction of transferrin with this receptor on Concanavalin A‐stimulated rat lymphocytes. Three specific questions have been posed: (a) Is transferrin endocytosed following binding to its specific receptor in a temperature‐dependent fashion? (b) Following endocytosis, is the carrier protein released from the cell in a structurally and functionally intact form? and (c) Is the cell surface transferrin receptor also endocytosed following ligand binding? The results provide affirmative answers to all questions. Using two independent probes of the cell surface versus intracellular location of transferrin we observed that cell‐bound transferrin moved from the cell surface to the inside of the cell and subsequently back to the medium. This process occurred in a temperature‐dependent fashion. When cells containing only intracellular transferrin were further incubated at 37°C approximately 80% of cell‐bound transferrin was released to the medium. Nearly all of this material retained reactivity with antibody to transferrin. In addition, exocytosed transferrin exhibited qualitatively and quantitatively equivalent binding reactivity with the transferrin receptor and showed identical electophoretic mobility on SDS gel electrophoresis. Finally, using similar methodology to that employed with transferrin itself, we provide evidence that the specific receptor is also endocytosed.
Folate utilization in friend erythroleukemia cells
Authors: Steinberg Stephen E. , Fonda Susan , Campbell Caryl L. , Hillman Robert S. 
Published: February 2005

AbstractIn order to study the generation, factors controlling endogenous folate pools, and their functional importance, Friend erythroleukemia cells were grown in media containing 100; 1,000; and 10,000 ng/ml of tritiated pteroylglutamic acid (3H)PteGIu1 and then studied in unlabeled media with varying amounts of PteGlu1. The intracellular folate pool was directly proportional to the PteGlu1 in which the cells were incubated. At equilibrium, greater than 95% of the labeled intracellular folate pool chromatographed as polyglutamyl folate, regardless of the exogenous folate concentration. The functional importance of the intracellular folate pool was studied by varying the endogenous pool and the exogenous (media) supply. The ability of the cells to replicate in the absence of exogenous folate was directly proportional to the intracellular polyglutamyl folate pool. The maximal rate of replication, however, required exogenous PteGlu1 in addition. The cell doubling time was the most important determinant of intracellular folate turnover; changes in the intracellular pool size and the extracellular folate concentration had no effect on the turnover time. In a rapidly proliferating tissue, the onset of functional folate deficiency will be determined by dilution of intracellular polyglutamates among progeny until a critical level is reached.
Neovascular responses induced by cultured aortic endothelial cells
Authors: Harris‐Hooker Sandra A. , Gajdusek Corinne M. , Wight Thomas N. , Schwartz Stephen M. 
Published: February 2005

AbstractNeovascularization was studied in the chorioallantoic memebrane of the chick embryo after implantation of bovine aortic endothelial and smooth muscule cells, Swiss and BALB/c 3T3 cells and human diploid fibroblasts cultured separately on microcarrier beads. Quantitative analysis of neovascularization indicated a 3 1/2‐fold increase in the number of blood vessels responding to endothelial cells while smooth muscle cells induced a twofold increase when compared to the response of beads without cells. Skin fibroblasts and Swiss 3T3 cells did not elicit a comparable response. The marked angiogenic response induced by endothelial cells was characterized by a 137% increase in total vessel length and a 35% increase in average vessel area when compared to controls. Two of the properties required for an angiogenesis factor—stimulation of cellular migration and proliferation—can also be demonstrated using endothelial cell‐conditioned medium in cell culture systems. Medium from cultured bovine aortic endothelium stimulates DNA synthesis, proliferation, and migration of smooth muscle cells. In adition, conditioned media from both endothelial cells and smooth muscle cells produced an angiogenic response in the chorioallantoic membrane assay, which was comparable to that produced by intact cells growing on microcarrier beads. Similar responses were not evident with medium conditioned by other cell types. These results indicate the potential importance of endothelial cells and endothelial cell products in regulating blood vessel growth.
Bovine endothelial cells transformed in vitro by benzo(a)pyrene
Authors: Grinspan Judith B. , Mueller Stephen N. , Levine Elliot M. 
Published: February 2005

AbstractA cloned strain of bovine vascular endothelial cells with a finite in vitro lifespan was treated with benzo(a)pyrene (BP) after approximately 75% of its lifespan was completed. Untreated cultures of this strain senesced upon serial subcultivation and contained large, nondividing cells. In three out of seven trials, BP treatment produced transformed cells appeared in the cultures concomitant with the senescence of the parent cells. All transformed cell lines examined exhibited indefinite lifespans and altered karyotypes. Two of the lines retained most of the characteristics of normal endothelial cells, except that one became aneuploid and the other polyploid, Neither of these lines formed tumors when inoculated into nude mice. The remaining two lines retained mostly diploid kayotypes, but a high percentage of cells contained Robertsonian translocations. In one line cell volume was markedly reduced. In addition, these lines grew in multilayers, were anchorage independent, and proliferated in medium containing 0.5% serum. When 107 cells of these lines were injected into nude mice, tumors appeared within 1 week and were identified as malignant hemangioendotheliomas of bovine origin.
Lateral transmission of tension in frog myofibers: A myofibrillar network and transverse cytoskeletal connections are possible transmitters
Authors: Street Sibyl F. 
Published: February 2005

AbstractThe extensibility of the sarcolemma of single myofibers can be reduced locally by leaving a segment covered by a sleeve of surrounding tissue composed of cut myofibers, blood vessels, and connective tissue, hereafter referred to as “the splint.” Splinted fibers from frog semitendinosus muscle were used to study mechanical connections (transverse coupling) between myofibrillar components and sarcolemma. The transverse coupling is strong enough to insure a tight correlation between myofibril length and overlying sarcolemma length in both resting and activated fibers and to transmit nearly maximum isometric tension to the splint. Lateral transmission of active tension was demonstrated with a preparation which had the distal two‐thirds of an intact fiber covered by a splint and the proximal third dissected clean. When the outer end of the splint was pinned down and only the distal tendon was held, tension generated in the splinted fiber was transmitted to, and recorded from, the splint. Parameters of isometric tension transmitted laterally were not significantly different from those of tension transmitted longitudinally. Myofibrils branch profusely and form a network that may act as a unitary force generator and transmitter. In splinted fibers its output is possibly picked up circumferentially and transmitted across the sarcolemma by a microfilament network. A cap of relatively inextensible sarcolemma “splints” myofiber ends. Resting tension is transmitted to and from the myofibrils by transverse coupling beyond the cap and the region of short sarcomere spacing it covers. Transverse cytoskeletal connections at Z and M regions are described. Immobilization of the sarcolemma allows study of myofibril‐sarcolemma linkage in intact libers. Both active and resting tension were transmitted laterally.
Inhibition of carbohydrate incorporation in transformed cells by a cancer‐associated galactosyltransferase acceptor (CAGA)
Authors: Podolsky Daniel K. , Fournier Deborah , Isselbacher Kurt J. 
Published: February 2005

AbstractThe effect of cancer‐associated galactosyltransferase acceptor (CAGA) on incorporation of a variety of macromolecular precursors has been studied in transformed and nontransformed cells. Incorporation of [3H]‐mannose, [3H]‐galactose, and [3H]‐glucosamine into acid precipitable material after one‐hour pulse was inhibited more than 70% within four hours after exposure to CAGA in polyoma‐transformed BHK cells and within eight hours after exposure in chick embryo fibroblasts infected with a temperaturesensitive RSV mutant (Ts68) grown at the permissive temperature (CEF‐RSV 37°C). Initial short‐term rate of uptake (< one minute) and total long‐term uptake (one hour) of the labelled carbohydrates (acid‐soluble and acidinsoluble material) was inhibited less than 15% over this period. Incorporation of 14C‐leucine, 3H‐serine,3H‐uridine, and 3H‐thymidine into acid‐precipitable material was also inhibited > 85% in transformed cells, but more than 12‐hour exposure to CAGA was required before maximal inhibition was detected. Uptake of these labelled precursors was inhibition was detected. Uptake of these labelled precursors was inhibited less than 20% up to eight hours after exposure to CAGA. In nontransformed cells (BHK and CEF) incorporation of labelled monosaccharides as well as protein and nucleic acid precursors into acid‐precipitable material was reduced less than 25% up to 12 hours following exposure to CAGA. Infected CEF grown at the nonpermissive temperature (CEF‐RSV 14°C) were affected to an extent similar to other nontransformed cells. These data suggest that the specific action of CAGA on transformed cells may be due to inhibition of glycoconjugate synthesis.
Selective induction of enhanced complement receptor 3 activity on murine macrophages
Authors: Yen Shing‐Erh , Walker William S. 
Published: February 2005

AbstractA high proportion of murine resident peritoneal macrophages bear complement receptors 1 and 3 (CR1, CR3) which bind C3b and iC3b components of complement, respectively. By contrast, macrophages derived from bone marrow, blood, and the elicited peritoneal exudate are predominantly CR1+3−. To determine if the microenvironment of the normal peritoneal cavity influences CR3 phenotype, we studied the effects of lavage from the cavity on cultures of primary peritoneal exudate macrophages, and on macrophages derived from progenitors in the bone marrow, blood, and peritoneal exudate. The cell‐free peritoneal lavage (CFPL), after 24 hr or culture, induced CR3 on primary and culture‐derived populations of peritoneal exudate macrophages but had no effect on the CR3‐ phenotype of macrophages derived from bone marrow or blood. The CR3‐inducing activity in CFPL was abolished by heating at 70°C for 30 min and by trypsin, and was not affected by adsorption with EA(IgM)iC3b indicator cells, demonstrating that it is not soluble CR3. Finally, exudate macrophages exposed to CFPL required at least 24 hr before they expressed CR3; such macrophages regenerated CR3 after the receptors were removed by trypsin. The selective effect of the activity in CFPL for peritoneal exudate macrophages indicates that the local microenvironment of the peritoneal cavity can influence the expression of CR3.
Cell repair after liver injury: An analysis of some metabolic conditions required for the stimulation of RNA synthesis in postischemic liver nuclei
Authors: Piccoletti Roberta , Bernelli‐Zazzera Aldo 
Published: February 2005

AbstractNuclei isolated from liver cells recovering from reversible (non‐necrogenic) ischemia show an increased RNA synthesis. The postischemic effect is not abolished by previous adrenalectomy and occurs in fasted as well as in fed animals. Treatment with cycloheximide, at a dose that severely inhibits protein synthesis without primary effects on RNA synthesis, suppresses the postischemic stimulation of RNA synthesis even if cycloheximide is administered when stimulation is already well developed. Postischemic liver nuclei respond only weakly to the additional stimulation of RNA synthesis caused by the presence of cytosol and albumin in the incubation medium.
Regulation of intracellular protein degradation in IMR‐90 human diploid fibroblasts
Authors: Auteri Joseph S. , Okada Annabelle , Bochaki Victor , Fred Dice J. 
Published: February 2005

AbstractHuman diploid fibroblasts (IMR‐90) regulate their overall rates of proteolysis in response to the composition of the culture medium and the ambient temperature. The magnitude and, in some cases, the direction of the response depend on the half‐lives of the cellular proteins that are radioactively labeled and the time chosen for measurements of protein degradation. Fetal calf serum, insulin, fibroblast growth factor, epidermal growth factor, and amino acids selectively regulate catabolism of long‐lived proteins without affecting degradation of short‐lived proteins. Fetal calf serum reduces degradative rates of long‐lived proteins and is maximally effective at a concentration of 20%, but the effect of serum on proteolysis is evident only for the first 24 hr. Insulin inhibits degradation of long‐lived proteins in the presence or absence of glucose and amino acids in the medium, but is maximally effective only at high concentrations (10−5 M). Amino acid deprivation increases degradative rates of long‐lived proteins for the first 6 hr, but then decreases their catabolism for the subsequent 20 hr. Lowered temperature is the only condition tested that significantly alters degradative rates of short‐lived proteins. Although cells incubated at 27°C have reduced rates of degradation for both short‐lived and long‐lived proteins compared to cells at 37°C, lowered temperature reduces catabolism of long‐lived proteins to a greater extent.
Factors influencing survival and growth of mammalian cells exposed to hypothermia. I. Effects of temperature and membrane lipid perturbers
Authors: Kruuv J. , Glofcheski D. , Cheng K.‐H. , Campbell S. D. , Al‐Qysi H. M. A. , Nolan W. T. , Lepock J. R. 
Published: February 2005

AbstractThe Arrhenius plot of the rate of V79 Chinese hamster cell inactivation due to hypothermia has a “break” around 7–10°C with optimum storage temperature for unprotected cells being about 10°C. Addition of the membrane lipid perturber, butylated hydroxytoluene, improves survival of cells when compared to controls at temperatures below this break but not above. Arrhenius plots of growth rates of the cells show breaks at 30 and 40°C. Measurements of membrane fluidity by electron spin resonance or membrane polarization anisotropy by fluorescence spectrophotometry techniques as a function of temperature in these cells also reveal “breaks” centered around 8 and 30°C. Hence, the changes in the rate of cell inactivation and growth as a function of temperature may be related to membrane lipid phase changes.