bluuebunny/crossref_metadata_2025_split huggingface dataset:
Butyrate enhances the synthesis of interphotoreceptor retinoid‐binding protein (IRBP) by Y‐79 human retinoblastoma cells
Authors: Kyritsis Athanassios P. , Wiggert Barbara , Lee Ling , Chader Gerald J. 
Published: February 2005

AbstractThe synthesis and secretion of interphotoreceptor retinoid‐binding protein (IRBP) from Y‐79 human retinoblastoma cells was investigated using immunocytochemistry and SDS‐polyacrylamide gel electrophoresis. Indirect immunofluorescence of cells growing in monolayer culture for 11 and 13 days showed no significant IRBP staining although by SDS‐polyacrylamide gel electrophoresis, a small amount of IRBP was detected in the culture medium, suggesting synthesis and extracellular secretion. Butyrate (2mM) treatment of cells starting on the eighth day of culture resulted in a dramatic increase of IRBP fluorescence 3–5 days after treatment. Treatment of cells in all conditions with 1 μM monensin for 3 h showed concentration of IRBP in the Golgi apparatus of about 10–20% of cells as proved by a double immunofluorescent technique, employing anti‐IRBP antibody and wheat‐germ agglutinin. Incubation of cells with either radiolabeled amino acids or glucosamine followed by analysis of cell cytosol and culture medium by SDS‐polyacrylamide gel electrophoresis also confirmed that (1) IRBP is synthesized by the Y‐79 cells and secreted into the medium and (2) its production is markedly increased by butyrate treatment. The enhancement of IRBP synthesis by butyrate suggests biochemical differentiation of Y‐79 cells possibly into photoreceptor‐like cells and offers a new system for studying the properties of this unique retinoid‐binding protein and of factors that control its synthesis and secretion.
Binding and phagocytosis of fibronectin‐coated beads by BHK cells: Receptor specificity and dynamics
Authors: McAbee Douglas D. , Grinnell Frederick 
Published: February 2005

AbstractStudies on the receptor specificity and dynamics involved in fibroblast phagocytosis of latex beads revealed the following: (1) Ligands other than fibronectin such as concanavalin A (ConA) and serum spreading factor, when coated on latex beads, were found to promote phagocytosis of the beads. This indicates that fibroblast phagocytosis, like spreading, is a ligand‐receptor mediated phenomenon not specifically requiring fibronectin (pFN); (2) Anti‐pFN antibodies were found to inhibit the ability of cells to ingest pFN‐coated beads that previously were bound on the cell surfaces. Consequently, binding of beads to the cell surfaces per se is not a sufficient signal to promote ingestion of the beads; (3) Finally, divalent cations protected receptor function necessary for phagocytosis of pFN‐coated beads from proteolysis by trypsin, as previously was found for receptors involved in cell attachment and spreading on pFN‐coated culture dishes. Recovery experiments carried out with cells whose surface receptors had been destroyed indicated that there was an internal (or cryptic cell surface) pool of receptors that amounted to at least 50% of the receptors normally found on the cell surface. After complete destruction of the cell surface and cryptic pools of receptors, reappearance of receptors required for bead binding and phagocytosis required several hours and did not occur in the absence of new protein synthesis.
Receptor‐mediated endocytosis of human transferrin and its cell surface receptor
Authors: Larrick J. W. , Enns C. , Raubitschek A. , Weintraub H. 
Published: February 2005

AbstractWe have studied the process of transferrin endocytosis in human erythromyeloid cell line K562 using fluorescein (FL) and rhodamine (RD) labeled iron‐saturated transferrin (FeTF), and a fluorescein labeled monoclonal antibody to the transferrin receptor (FL‐mAB). Because the antireceptor antibody and FeTF bind to different sites on the TF receptor molecule, it is possible to simultaneously and independently follow receptor and ligand. We have measured the relative amounts of transferrin or antireceptor antibody bound in the presence or absence of proteolytic enzymes using a cell sorter. At 4°C almost all of the FL‐TF and the FL‐mAB is surface bound in a diffuse pattern. Within minutes of elevating the temperature to 37°C surface aggregates form and the FL‐TF is internalized. At this time about one sixth of the transferrin is still surface bound and accessible to papain digestion. The remainder localizes in a perinuclear cluster of vesicles. Monoclonal antibody binds to the cell surface transferrin receptor but is not internalized at 4°C or 37°C. When unlabeled diferric transferrin is added, it promotes the uptake of the FI‐mAB. The addition of goat anti‐mouse immunoglobulin also promotes FL‐mAB uptake. These studies support the concept that a specific trigger is required for transferrin receptor endocytosis.
Respiratory metabolism of L‐929 cells at different water contents and volumes
Authors: Clegg James S. , Gordon Elaine P. 
Published: February 2005

AbstractOxygen consumption was measured in mouse L‐929 cells whose volumes and water contents were reduced by adding sorbitol to the medium. The volume of water lost due to a given sorbitol supplement exceeded the loss in apparent cell volume. An explanation is given for this discrepancy. The rate of oxygen uptake in the absence of exogenous respiratory substrate was essentially the same in cells whose total volume was reduced by 45%, amounting to a loss of about 70% of the total cell water, compared to controls at ‘physiological’ volume and water content. Cells under these same conditions responded to added substrates (pyruvate, glucose, and glutamine) and inhibitors (iodoacetate and 2‐deoxyglucose) in nearly the same way as control cells. These observations are in accord with and add to previous work showing that very large fluctuations in cell volume and water content have only modest effects on the rates and directions of a variety of metabolic processes. The results are interpreted in terms of current views on the composition and organization of the aqueous compartments of eucaryotic cells.
Role of phorbol ester receptors in the 12‐0‐tetradecanoyl‐phorbol‐13‐acetate (TPA)‐induced down‐regulation of colony‐stimulating factor (CSF‐1) binding to murine peritoneal exudate macrophages
Authors: Chen Ben D.‐M. , Wilkins Kimberly L. 
Published: February 2005

AbstractTreatment of murine peritoneal exudate macrophages (PEM) by tumor‐promoting phorbol esters (TPA) results in a rapid loss of binding activity to radioactive‐labeled colony‐stimulating factor ([125I]‐CSF‐1) on the cell surface. The inhibitory effect of TPA on PEM is transient; treated cells recover full [125I]‐CSF‐1 binding activity in less than 6 hr at 37°C either in the presence or after the removal of added TPA. The role of phorbol ester receptors in the induction of [125I]‐CSF‐1 binding inhibition was studied. The biologically active ligand [3H]‐phorbol 12,13‐dibutyrate ([3H]‐PDBu) bound specifically to cultured murine PEM. At 0°C, stable and equilibrium binding occurred after 2–3 hr. Scatchard analysis revealed linear plots with a dissociation constant and receptor number per cell of 20.9 nM and 3.9 × 105/cell, respectively. Treatment of PEM with biologically active phorbol esters at 37°C rapidly inhibited the binding activity of [3‐H]‐PDBu on cell surface (down‐regulation) and rendered these cells refractory to the TPA‐induced [125I]‐CSF‐1 binding inhibition by the subsequent TPA treatment. The inhibition of phorbol ester binding activity on TPA‐treated PEM is caused by a reduction in the total number of available phorbol ester receptors rather than by a decrease in receptor affinity as judged by Scatchard analysis. The disappearance of [3H]‐PDBu binding activity is reversible and transient. However, unlike CSF‐1 receptors the restoration of phorbol ester receptors on TPA‐treated PEM is a very slow process; a prolonged incubation of up to 72 hr after the removal of TPA was required for PEM to regain fully its [3H]‐PDBu binding activity. Furthermore, the degree of TPA‐induced CSF‐1‐receptor down‐regulation is closely associated with the number of available phorbol ester receptors present on PEM at the time of treatment. Thus, the refractoriness to TPA diminished as the phorbol ester receptors on PEM recovered. A 72‐hr incubation time at 37°C was needed for PEM to lose their refractoriness and again become fully sensitive to TPA‐induced CSF‐1‐receptor down‐regulation. This study provides evidence that the loss of CSF‐1‐receptors induced by TPA treatment requires the presence of phorbol ester receptors and proceeds presumbaly via a co‐internalization of both CSF‐1 and phorbol ester receptors; the refractoriness to TPA is thereby induced by a transient loss of available phorbol ester receptors.
Modulation of intracellular potassium and ATP: Effects on coated pit function in fibroblasts and hepatocytes
Authors: Larkin Janet M. , Donzell William C. , Anderson Richard G. W. 
Published: February 2005

AbstractPreviously we reported that cultured human fibroblasts depleted of intracellular potassium (K+) had a reduced number of surface coated pits and were unable to internalize receptor‐bound molecules such as low density lipoprotein (LDL). We have extended these studies in two important ways. First, we have developed a method for modulating the number of coated pits in situ. Human fibroblasts incubated in K+‐free buffer that contains 4μm nigericin rapidly become depleted of K+ and lose the ability to internalize 125I‐LDL. When rat livers are perfused with the same buffer, there is a 75% decrease in the number of surface coated pits in hepatocytes. Secondly, we have explored the possibility that K+‐depletion effects coated pit function by lowering intracellular ATP. We found that although this protocol lowers intracellular ATP by 40–70%, when ATP concentrations are lowered > 95% by metabolic inhibitors, receptor‐mediated endocytosis is unaffected.
Activation and de novo synthesis of transglutaminase in cultured glioma cells
Authors: Korner G. , Bachrach U. 
Published: February 2005

AbstractThe activity of transglutaminase (TGase) was measured in cultured C6 glioma cells after their stimulation by either isoproterenol and isobutyl‐methylxanthine or by a serum‐containing medium. The activity fluctuated in a biphasic manner, with the peaks at 2–3 hr and 7–8 hr poststimulation. The first peak of TGase activity was affected neither by cycloheximide nor by actinomycin D, which inhibited protein synthesis. The second peak, on the other hand, was completely eliminated by cycloheximide and was reduced by actinomycin D. Immunological procedures were employed to find out whether or not the activity of TGase corresponded with the presence of the TGase antigen in the cultured cells. Indirect immunofluorescent staining and radioimmunoblot techniques suggested that unstimulated cells contained an inactive enzyme. This inactive, or cryptic, enzyme had the same molecular weight as its active counterpart. Activation of the enzyme was mediated by cell stimulation, probably by its release from the membrane. This step did not require protein synthesis, unlike the second step, which was dependent on de novo protein synthesis.
Ecto‐nucleotide triphosphatase activity of human lymphocytes: Studies of normal and CLL lymphocytes
Authors: Segel George B. , Ryan Daniel H. , Lichtman Marshall A. 
Published: February 2005

AbstractWe have studied the apparent kinetic parameters of the ecto‐nucleotide triphosphatase from CLL B lymphocytes and compared them to blood and tonsillar B and T cells. The Vmax of the ecto‐ATPase activity in CLL B lymphocytes, was 65 ± 10 fmol Pi/cell per 30 min compared to 37 ± 2.1 in blood B lymphocytes, and 8.5 ± 1.7 in blood T lymphocytes. The ATPase of membranes prepared from CLL, tonsillar B and T, and blood T lymphocytes had a relationship among the cell types similar to that seen in intact cells. However, no difference in the km for ATP, .17 mM, or the km for magnesium, .15 mM was found in the ecto‐ATPase of CLL lymphocytes as compared to blood or tonsillar B cells. The ectoenzyme of CLL cells hydrolyzed GTP, ITP, CTP, and UTP as well as ATP. Further, ATP added to an enzyme assay containing an alternative nucleotide did not result in increased phosphate release. Nucleotide acceptance of blood B and T lymphocytes was very similar to that of CLL B cells. ATP inhibited phosphate release when present in excess of magnesium in both CLL and blood B lymphocytes. These data indicate that there is greater ectonucleotide triphosphatase activity in tonsillar and blood B lymphocytes, including CLL, as compared either to blood or tonsillar T lymphocytes. However, CLL cells showed no qualitative difference from blood or tonsillar B cells in ectonucleotidase activity. Thus, the higher activity in CLL cells is “B cell‐like” and might reflect, also, their maturation stage or monoclonal origin.
Late G1 amino acid restriction point in human dermal fibroblasts
Authors: Cooper Janet L. , Wharton Walker 
Published: February 2005

AbstractHuman dermal fibroblasts arrested in G0 by maintenance in medium supplemented with 0.1% serum were not restimulated to divide when fresh medium containing 10% dialyzed serum but lacking group B amino acids (cystine, isoleucine, lysine, phenylalanine and tyrosine) was added. Unlike rodent cells, the addition of fresh serum‐supplemented medium lacking only isoleucine did not cause a growth arrest. The amino acid sensitive growth arrest in human fibroblasts was dependent both on presynchronization in G0 as well as a prestarvation for amino acids prior to stimulation with high serum.When cells were restimulated in the absnece of amino acids, they arrested predominantly in G1, although a small percentage of cells entered early S phase. When medium containing a complete complement of amino acids was then added, cells initiated DNA synthesis following a minimum lag of 2–3 hr. Growth arrested cells initiated DNA synthesis even when complete unsupplemented medium was added, although the addition of high concentrations of insulin or 10% serum increased the rate of entry.
Identification of novel, stage‐specific polypeptides associated with the differentiation of mammary epithelial stem cells to alveolar‐like cells in culture
Authors: Paterson Frieda C. , Rudland Philip S. 
Published: February 2005

AbstractA linear pathway of morphologically intermediate cells has been identified between the cuboidal epithelial stem cells and the doming alveolar‐like cultures of the cell line Rat Mammary (Rama) 25 in the order: cuboidal → grey → dark → dark droplet cell → doming cultures. The overall process can be accelerated by dimethyl sulfoxide (DMSO) or retinoic acid (RA) in the presence of mammotrophic hormones. From 400–450 [35S]methionine‐labeled polypeptides that are routinely separated by two‐dimensional gel electrophoresis approximately only 3% change during this process. As the Rama 25 cultures become confluent, three polypeptides of molecular weights (MW) 35 kD (pl = 7.7), 45 kD (pl = 7.5) and 33 kD (pl = 7.7) increase dramatically in radioactive abundance. These increases correspond to increases in numbers of grey cells for the 35 kD polypeptide, to increases in numbers of dark cells together with increases in peanut lectin‐binding‐ability for the 45 kD polypeptide, and to increases in the numbers of dark cells and in the numbers of droplet cells for the 33 kD polypeptide. After treatment with DMSO, RA or in spontaneously doming cultures, a second set of four polypeptides of MW 26 kD (pl = 5.9), 27 kD (pl = 6.2), 30 kD (pl = 7.2), and the same 33 kD polypeptide as above increase with the increase in numbers of droplet cells, domes, and increase in casein secretion. A variant of Rama 25, Rama 259, which fails to produce droplet cells, domes, or to secrete casein with DMSO and hormones also shows the same changes in the first set but not in the second set of polypeptides. The elongated, myoepithelial‐like cell line derived from Rama 25, Rama 29, which cannot undergo any of the above intercellular conversions, fails to show changes in any of these polypeptides. Major changes in radioactive polypeptides have been confirmed for nonradioactive polypeptides and for polypeptides labeled for 4 hr with [35S]methionine. The synthesis of these novel polypeptides thus marks specific morphological stages of the differentiation of mammary epithelial stem to alveolar‐like cells in culture, and as such may mark similar differentiation stages in vivo.
The activation of specific gene transcription in the adipose conversion of 3T3 cells
Authors: Djian Philippe , Phillips Marjorie , Green Howard 
Published: February 2005

AbstractDuring the adipose conversion of 3T3 cells, there occur sequential changes in cellular protein and mRNA composition. To determine if there are also changes in transcription, we have studied the transcripts of specific genes in isolated nuclei prepared before and after adipose conversion. Transcription of three genes encoding adipocyte‐specific proteins was detectable only in adipocytes, whereas transcription of actin and collagen type I genes occurred in both adipocytes and preadipocytes. The activation of transcription of adipocyte‐specific genes was not synchronous. Thus temporal differences in the appearance of different adipocyte mRNAs probably result from differences in the times of activation of transcription.
Fibrin‐enhanced endothelial cell organization
Authors: Olander J. V. , Bremer M. E. , Marasa J. C. , Feder J. 
Published: February 2005

AbstractThe formation of cloned bovine endothelial cells into capillary‐like tubes is accelerated from 3–7 days to 2–18 h in the presence of fibrin. Indirect immu‐nofluorescence showed the presence of both fibrin and fibronectin in the strands along which the cells organized. Electronmicroscopy revealed the same type of cell structures as form in the absence of fibrin; it also revealed a gradual decrease with time of the fibrin within the putative lumen. Fibrin and fibronectin are commonly present during angiogenesis in vivo, thus these in vitro observations may well have relevance to the in vivo process.
Cell growth and differentiation in vitro in mouse macrophages transformed by a tsA mutant of simian virus 40. III. Large T antigen level and cell proliferation and survival in an SV40 tsA640‐transformed macrophage line
Authors: Tanigawa Takahiko , Shimura Hideo , Yamada Koji , Okuda Atsuyuki , Takayama Hisao , Takagi Atsushi , Tanaka Yoshinori , Kimura Genki 
Published: February 2005

AbstractThe levels of simian virus 40 (SV40) large T antigen in a tsA‐transformed mouse macrophage line at the permissive (33°C) and the nonpermissive (30°C) temperature were examined by immunofluorescence, sodium dodecylsulfate‐polyacrylamide gel electrophoresis, complement fixation, and enzyme‐linked immunosorbent assay. When the cells were confluent and rested at 33°C, and then were shifted to 39°C, the amount of large T antigen per cell decreased, and most cells survived and remained phagocytic. When the cells were proliferating at 33°C, and then were shifted to 39°C, the cells died with only a small reduction in the amount of large T antigen. Therefore, the physiological state of the cells may determine the survival of cells by affecting the level of large T antigen after exposure to 39°C. The confluent cells may be rested with a concomitant decrease of large T antigen. The proliferating cells may not survive in the presence of a relatively high level of functionally defective large T antigen at 39°C.
Calcium‐mediated regulation of the low density lipoprotein receptor and intracellular cholesterol synthesis in human epidermal keratinocytes
Authors: Ponec Maria , Havekes Louis , Kempenaar Johanna , Lavrijsen Sjan , Wijsman Marian , Boonstra Johannes , Vermeer Bert Jan 
Published: February 2005

AbstractUnlike cells cultured under physiological Ca2+ concentrations (1–2 mM), keratinocytes cultured in media containing Ca2+ in low concentrations (less than 0.1 mM) do not stratify. The latter cells also differ with respect to several features of the regulation of cholesterol synthesis. In keratinocytes cultured in medium containing high Ca2+ concentrations (1.6 mM) and fetal calf serum, the rate of cholesterol synthesis was 20–30 times higher than in keratinocytes exposed to a low Ca2+ concentration. The rate of cholesterol synthesis did not change when high‐calcium cells were deprived of extracellular sources of cholesterol but increased (8–10 fold) in deprived low‐calcium cells. Furthermore, the addition of low density lipoprotein (LDL) reduced cholesterol synthesis markedly in low‐calcium cells but had no effect on high‐calcium cells. Finally, in keratinocytes cultured at low calcium concentrations the association and degradation of 125I‐LDL was 20–30 times higher than in keratinocytes cultured under high‐calcium conditions. Switching of the cells from the low‐calcium to the high‐calcium medium resulted in the induction of terminal differentiation within 15 hours and was accompanied by increased cholesterol and protein synthesis, increased competence of cells to form cornified envelopes, and reduced association of 125I‐LDL. A gradual increase of the extracellular Ca2+ concentration was accompanied by a corresponding increase of cholesterol and protein synthesis and a decrease of the response of intracellular cholesterol synthesis to changes in the extracellular concentrations of lipoprotein. Various morphological techniques showed virtually no binding and internalization of LDL by keratinocytes cultured at the high‐calcium level, whereas both were observed at the low‐calcium level. Once internalized, the LDL was delivered to dense bodies representing lysosomes. It is concluded that in human epidermal keratinocytes, the expression of the LDL receptor and the endogenous synthesis of cholesterol are regulated by the conditions determined by the differentiation stage of the cells.
Effects of bicarbonate on resting potentials in mammalian skeletal muscle
Authors: Grossie J. 
Published: February 2005

AbstractIn the absence of external HCO3, resting membrane potentials (Vm) in extensor digitorum longus muscle were depolarized as compared to the normal Vm in the presence of HCO3. Removal of Na or Cl from the HCO3‐free media induced repolarization. In muscle in HCO3 buffer at 20°C, internal K, Na, and Cl activities were analyzed with liquid ion selective microelectrodes. The averages were respectively, 119.7 ± 2.1, 6.69 ± 0.3, and 3.41 ± 0.06 mM. In a high proportion of cells analyzed, the equilibrium potential for Cl was negative to Vm. Removing external HCO3, decreased internal K while internal Na and Cl increased. An increase in temperature and the application of HCO3 significantly lowered internal activities of both Na and Cl. Removal of HCO3 with temperature held constant caused a rapid depolarization, an increase in internal Na and Cl, and a decrease in internal K. Furosemide (10 μM) induced a repolarization of cells that were previously depolarized in the HCO3‐free state, but the drug does not decrease internal Na.
Reinitiation of cellular DNA synthesis in BrdU‐selected nondividing senescent WI‐38 cells by simian virus 40 infection
Authors: Gorman Scott D. , Cristofalo Vincent J. 
Published: February 2005

AbstractBromodeoxyuridine‐selected nondividing senescent WI‐38 cells were stimulated to synthesize DNA, as evidenced by incorporation of [3H]thymidine into nuclei of senescent cells, after infection with simian virus 40 (SV40). Cellular DNA synthesis was confirmed by DNA‐DNA hybridization experiments and the use of temperature‐sensitive A gene mutants. The DNA synthesis was, at least in part, semiconservative, as microdensitometry of Feulgen‐stained nuclei revealed increased DNA content in a large fraction of the cells in the infected population. Thus, senescent cells retain the capacity to replicate their DNA, despite their intrinsic inability to initiate DNA synthesis.