bluuebunny/crossref_metadata_2025_split huggingface dataset:
Increased phagocytosis of outer segments in the presence of serum by cultured normal, but not dystrophic, rat retinal pigment epithelium
Authors: Edwards Ross B. , Flaherty Paula M. 
Published: February 2005

AbstractCultured normal rat retinal pigment epithelium (PE) ingested six times more rod outer segments in the presence of 20% fetal bovine serum than in serumfree medium. PE cultured from Royal College of Surgeons (RCS) rats with hereditary retinal dystrophy, known to have a defect in vivo in the phagocytosis of shed outer segment tips, ingested amounts of outer segments comparable to normal PE in serum‐free medium but did not show an increase in the presence of serum. In both strains of rat PE phagocytosis of latex spheres was similar in the absence of serum and was six‐fold higher in the presence of serum, showing that the RCS phagocytic deficiency for outer segments in vitro is not due to a general defect in the phagocytic capacity of the cell. Increased phagocytosis of outer segments by normal PE was observed in the presence of the high molecular weight fraction of ultrafiltered serum but was not seen with serum that was heated at 93°C or precipitated with 5% trichloroacetic acid. Bovine serum albumin had no effect on phagocytosis. These results are consistent with the idea that the phagocytosis of outer segments by cultured normal rat PE, but not by cultured RCS rat PE, is increased in the presence of a specific protein or other macromolecular component of fetal bovine serum.
1,2‐diacylglycerols mimic phorbol 12‐myristate 13‐acetate activation of the sea urchin egg
Authors: Shen Sheldon S. , Burgart Lawrence J. 
Published: February 2005

AbstractPhorbol diesters have been reported to stimulate the Na+/H+ antiport of a variety of cells including sea urchin eggs. Since stimulation of the Na+/H+ antiport is necessary for metabolic derepression during fertilization and protein kinase C is a target of phorbol diesters, enhanced Na+/H+ exchange during fertilization may be a result of protein kinase C activity. Protein kinase C is probably physiologically activated by diacylglycerols, which are derived from hydrolysis of phosphatidylinositol. Treatment of sea urchin eggs with 1,2‐diacylglycerols was found to stimulate the Na+/H+ antiport. The 1,3‐isomers were without effect. Further, the effects of 1,2‐diacylglycerol and phorbol diester are not additive with respect to Na+/H+ exchange. While a direct participation of protein kinase C activity during fertilization remains to be demonstrated, these data support the hypothesis that protein kinase C activity plays a role in fertilization. However, the cytotoxic effect of protein kinase C activators suggests effects associated with their pleiotropic nature.
Synthesis and stability of nuclear matrix proteins in resting and serum‐stimulated swiss 3T3 cells
Authors: Milavetz Barry I. , Edwards Dylan R. 
Published: February 2005

AbstractThe major [35S]methionine‐radiolabeled nuclear matrix proteins of mouse 3T3 cells were isolated, and most of these were found to be similar in molecular weight, charge, and protease fingerprint to the nuclear matrix proteins of African green monkey kidney cells, which are found tightly bound to simian virus 40 chromosomes. These nuclear matrix proteins were found to be synthesized in quiescent and serum‐stimulated cells and to be turned over slowly during pulse‐chase experiments. In contrast, a 70‐Kd (kilodalton) neutral protein identified as lamin a was found to be turned over rapidly, producing a 68‐Kd protein with a similar isoelectric point. In addition, we observed a decrease in the amounts of two chromatin‐bound matrix proteins and a relative increase in lamin a following labeling in the presence of 2 μg/ml actinomycin D. However, these effects do not appear to be a result of inhibition of transcription, since they were not observed with other inhibitors (α‐amanitin and 5,6‐dichloro‐1‐β‐D‐ribofuranosylbenzimidazole).
Effects of ornithine decarboxylase inhibition on c‐myc expression during murine erythroleukemia cell proliferation and differentiation
Authors: Watanabe Tetsu , Sherman Matthew , Shafman Timothy , Iwata Tadatoshi , Kufe Donald 
Published: February 2005

AbstractThe polyamines putrescine, spermidine, and spermine have been implicated in the regulation of cellular proliferation and differentiation. We have previously demonstrated that spermidine is required for proliferation of murine Friend erythroleukemia (MEL) cells. We have also shown that spermidine is required at a transcriptional level for induction of MEL globin synthesis. Since studies monitoring c‐myc expression have suggested that this gene also plays a role in both growth and differentiation, we have monitored the effects of inhibiting ornithine decarboxylase (ODCase) activity and polyamine synthesis on levels of c‐myc transcripts. The results demonstrate that the level of c‐myc RNA is independent of ODCase inhibition and depletion of intracellular spermidine. More importantly, arrest of MEL proliferation is not associated with detectable changes in c‐myc expression, while under these conditions there is a decline in ODCase transcripts. During induction of MEL differentiation with dimethyl sulfoxide (DMSO) and hexamethylene bisacetamide (HMBA), c‐myc and ODCase undergo similar changes in patterns of expression. However, although spermidine is required for appearance of the differentiated MEL phenotype, depletion of this polyamine by ODCase inhibition had no detectable effect on the biphasic changes in c‐myc RNA observed during MEL differentiation. Thus, these biphasic changes in c‐myc expression are not sufficient for induction of the mature phenotype. Finally, these results would indicate that the regulation of c‐myc expression during both proliferation and differentiation is independent of ODCase activity and inhibition of proliferation by spermidine depletion.
Demonstration of the specific binding of bovine transferrin to the human transferrin receptor in k562 cells: Evidence for interspecies transferrin internalization
Authors: Tsavaler Larisa , Stein Barry S. , Sussman Howard H. 
Published: February 2005

AbstractSpecific binding of ferric bovine transferrin to the human transferrin receptor was investigated using K562 cells propagated in serum‐free medium without transferrin supplemented with 10−5 elemental iron. Affinity chromatography of solubilized extracts of K562 cells surface‐labeled with 125I was performed using bovine transferrin‐ and human transferrin‐Sepharose 4B resins. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis of resin eluates reveal that bovine transferrin specifically binds a Mr = 188,000 protein which dissociates into a Mr = 94,000 protein under reducing conditions, a finding identical to what is seen with human transferrin. The Mr = 94,000 reduced protein isolated by bovine transferrin resin shows an identical one‐dimensional partial proteolytic digestion map with that of the human transferrin receptor.Unlabeled bovine transferrin was shown to specifically compete 125I‐labeled human transferrin from the human transferrin receptor on the surface of K562 cells at 4°C in a similar manner as unlabeled human transferrin; however, approximately a 2,000‐fold higher concentration of bovine ligand was required to achieve comparable competition (50% inhibition of binding).Indirect immunofluorescence cytolocalization of bovine transferrin in K562 cells grown in serum‐free medium supplemented with ferric bovine transferrin reveal patterns similar to those seen for human transferrin (both focal perinuclear and diffuse cytoplasmic fluorescence). Monensin treatment results in a dramatic accumulation of bovine ligand in perinuclear aggregates, suggesting that it is recycled through the Golgi, as is human transferrin. K562 cells grown in serum‐free medium supplemented with either 300 μg/ml of ferric human or ferric bovine transferrin were found to demonstrate super‐imposable growth curves.
Phosphate transport in Ehrlich ascites tumor cells: Inhibition by H+
Authors: Bowen Jesse W. , Levinson Charles 
Published: February 2005

AbstractThe effect of changes in extracellular pH (pHo) and intracellular pH (pHi) on Na + ‐dependent and Na+ ‐independent inorganic phosphate (Pi) transport in Ehrlich cells was investigated. In the presence of Na+, acutely reducing pHo from 7.30 to 5.50 results first in a transient (∼7 min) stimulation of Pi transport. The enhanced rate of transport is a saturable function of the extracellular [H+]; the Ks equals 2.3 × 10−6 M (pHo 6.68). However, Pi transport is progressively inhibited as pHi falls below 6.50. The effect of pHi on Pi transport measured at various intracellular [Na+] suggests that inhibition develops as a consequence of H+ interaction with an intracellular Na+ site(s) on the Na+‐dependent carrier. At pHo 7.4, about 15% of the steady state Pi flux persists in the absence of Na+. However, when pHo is reduced, transport is stimulated to the same extent and with the same time course and kinetic characteristics as in the presence of Na+. Thus, H+ stimulated Pi transport does not require Na+, raising the possibility that the Na+‐independent component is mediated by the anion (CI−) exchanger.
Calcitonin and vasopressin affect epithelial properties in a renal cell line
Authors: Wohlwend Annelise , Vassalli Jean‐Dominique , Bertrand Daniel , Orci Lelio 
Published: February 2005

AbstractWe have used a stable clonal variant (D + Sc), isolated from the LLC‐PK1 pig kidney‐derived cell line and selected for its extensive capacity to form domes, in order to study the hormonal modulation of epithelial permeability in culture. Calcitonin, vasopressin, and other agents that raise intracellular adenosine 3′,5′‐cyclic monophosphate levels caused a rapid and dramatic decrease in the size and number of domes. This effect was independent of RNA and protein synthesis, and thus appeared unrelated to the production of urokinase, a proteinase synthesized by the cells in response to these agents. Calcitonin caused a decrease in transepithelial electrical resistance, suggesting that the effect of the hormone on domes was due to an increase in the permeability of a paracellular pathway. Thus, in addition to the wellknown effects of vasopressin on collecting duct permeability, part of the in vivo effect(s) of calcitonin and vasopressin on the renal tubule might also involve alterations of epithelial permeability related to those described here.
Concanavalin a inhibits oral regeneration in Stentor coeruleus through a mechanism involving binding to the cell surface
Authors: Maloney Michael S. 
Published: February 2005

AbstractConcanavalin A (Con A) has been shown to induce delays in oral regeneration in the ciliate Stentor coeruleus. Associated with the delayed oral regeneration is a shedding of the cell's extracellular pellicle with the loss of some pigment granules. It is shown that the delays in oral regeneration are not the result of the pigment shedding. The delays are localized in the earliest stages of oral regeneration prior to stage 4. The delays caused by Con A are completely reversible by the addition of 2 mg/ml α‐D‐methyl mannoside either at the time of Con A exposure or 5 min later. Con A clearly binds to the cell surface as shown by the binding of FITC‐Con A and its reversal by α‐methyl mannoside. Crosslinking of Con A receptor molecules may be responsible for the effects of Con A since succinyl Con A, which does not crosslink these receptors, has no effect on oral regeneration even at double the Con A concentration. Calcium ions are also implicated in the action of Con A because an excess of extracellular calcium (10 mM) completely eliminates the Con A delays when added simultaneously with Con A. Examination of the minimum extracellular calcium concentration required for this effect showed that 2 mM calcium can reverse most of the delays but that 5 mM is ncessary to completely reverse the delays caused by Con A. If the addition of calcium is delayed for various times after Con A addition, the extracellular calcium is progressively less effective in reversing the Con A delays.
Increased level of cAMP‐dependent protein kinase in aging human lung fibroblasts
Authors: Liu Alice Y.‐C. , Chang Zee‐Fen , Chen Kuang Yu 
Published: February 2005

AbstractRegulation of the expression of cAMP‐dependent protein kinase in cellular aging was studied using the IMR‐90 diploid human lung fibroblasts. The level of cAMP‐dependent protein kinase present in cell extracts was monitored by (1) photoactivated incorporation of 8‐N3‐[32P]cAMP into the 47,000‐ and 54,000‐dalton regulatory subunits of the type I and type II cAMP‐dependent protein kinases, respectively; (2) cAMP‐dependent phosphorylation of histone II AS catalyzed by the catalytic subunit of the kinase; and (3) fractionation and analysis of the type I and type II cAMP‐dependent protein kinase by DEAE‐Sephacel column chromotography. Our results showed an approximately two‐ to threefold increase in the level of the type I cAMP‐dependent protein kinase and a somewhat smaller increase in the type II kinase in extracts of the “old” IMR‐90 cells (population doubling >48) as compared to that of the “young” cells (PDL 22–27). The timing of the increase in cAMP‐dependent protein kinase coincided with a significant decrease in the proliferative potential of the cells. This result together with previously demonstrated effects of cAMP in the control of cell growth and differentiation and the increased expression of cAMP‐dependent protein kinase during terminal differentiation of the murine preadipocytes (3T3‐L1) and myoblast (L‐5, L‐6, and C2C13) suggests that regulation of the levels of cAMP and cAMP‐dependent protein kinase plays a significant role in the control of cell growth and differentiation.
Binding of iodinated multipotential colony‐stimulating factor (interleukin‐3) to murine bone marrow cells
Authors: Nicola N. A. , Metcalf D. 
Published: February 2005

AbstractMultipotential colony‐stimulating factor (Multi‐CSF or interleukin‐3) was radioiodinated to high specific radioactivity (1–4 × 105 cpm/ng) with no detectable loss of biological activity and its binding to murine bone marrow cells and factor‐dependent cell lines studied. Both the native glycosylated molecule purified from a cloned T‐cell line (LB3) and the purified non‐glycosylated recombinant molecule produced by E. coli could be radioiodinated. Comparative binding studies with these derivatives demonstrated equal binding affinities and equal numbers of binding sites on various cell types indicating that carbohydrate moieties are not involved in the binding interactions. Binding of 125I‐Multi‐CSF to several factor‐dependent continuous hemopoietic cell lines showed the presence of specific receptors on all cell lines, the receptor number per cell varying from 700 to 13,000 and the apparent dissociation constant from 400 pM to 1 nM. Specific binding of 125I‐Multi‐CSF was also observed to normal murine hemopoietic cells and the binding to murine bone marrow cells was studied in detail. Bone marrow cells showed 117–130 receptors per cell on average and an apparent dissociation constant of 126–233 pM. However, quantitative autoradiographic analysis indicated that receptors for 125I‐Multi‐CSF were not distributed randomly on bone marrow cells–‐nucleated erythroid and lymphoid cells were not labeled while essentially all neutrophilic granulocyte, eosinophilic granulocyte and monocytic cells were labeled. Moreover, in each of the labeled cell lineages grain counts (reflecting receptor number) decreased with increasing maturation and a small subpopulation of marrow cells (0.4–1.5% and including blast cells, monocytes, promyelocytes, and myelocytes) exhibited very high grain counts. The existence of such a subset of marrow cells raises the possibility of functional heterogeneity among marrow cells in their response to Multi‐CSF.
Morphologic and biochemical variability of tissue and cultured cells from human pheochromocytoma
Authors: Jaques Sandford , Tobes Michael C. 
Published: February 2005

AbstractPrimary cell cultures from 18 human pheochromocytomas were maintained in culture for 10 to 12 days and characterized. The cell yields ranged from 1.0 to 60.1 × 106 cells/g wet weight of tissue. Cell size, as determined by histofluorescent microscopy, varied as much as seven‐fold among cells derived from a given tumor and ten‐fold between cells from all tumors. Cell catecholamine content, norepinephrine (NE) plus epinephrine, ranged from 0.4 to 89.5 nmol/106 cells at day 5 in culture and did not correlate with catecholamine content of the tissue from which the cells were obtained. Cell catecholamine content decreased with time in culture, but this decrease could not be related to a change in cell viability, the type of media used, an inability to convert dopamine to NE, or an alteration in the uptake of 3H‐NE. Cellular uptake of 1.0 μM 3H‐NE varied as much as 230‐fold between all cell dispersions. The basal and acetylcholine stimulated release of both preloaded 3H‐NE and the endogenous catecholamines was quite variable. There was no correlation between the release rate, either basal or stimulated, of preloaded 3H‐NE and the endogenous catecholamines. This study represents the largest existing data base on culturing cells from these tumors and describes many of the morphologic and biochemical characteristics of this cell system.
Induction of fibronectin expression, actin cable formation, and entry into S phase following reexpression of T antigen in mouse macrophages transformed by the tsA640 mutant of SV40
Authors: Takayama Hisao , Tanigawa Takahiko , Tanaka Yoshinori , Kimura Genki 
Published: February 2005

AbstractMouse macrophages transformed by a temperature‐sensitive mutant (tsA640) of simian virus 40 (SV40) were examined by immunofluorescence microscopy for fibronectin expression and actin distribution. Resting cultures of tsA640 transformants incubated at a temperature nonpermissive for SV40 large T antigen (39.0°C) exhibited phagocytic activity and did not exhibit cellular fibronectin and actin cables, like primary cultures of resident macrophages. When the resting cultures were sparsely seeded and shifted down to the permissive temperature of 33.0°C, expression of large T antigen in the nucleus, expression of fibronectin in the cytoplasm, and cellular entry into S phase occurred in that temporal order, followed by actin cable formation, cellular proliferation, and diminishment of phagocytic activity. The expression of T antigen and fibronectin was sensitive to actinomycin D and cycloheximide. The expression of fibronectin was insensitive to inhibitors of DNA synthesis, whereas the expression of actin cables was sensitive. These results suggest that SV40 T antigen leads macrophages to express fibronectin and actin cables, as well as resumption of cell proliferation, and that entry into S phase is not required for fibronectin expression but may be required for actin cable formation.
Bi‐functional action of transforming growth factor‐β on DNA synthesis in early passage human fetal fibroblasts
Authors: Hill D. J. , Strain A. J. , Elstow S. F. , Swenne I. , Milner R. D. G. 
Published: February 2005

AbstractWe investigated the influence of transforming growth factor‐β (TGF‐β) on DNA synthesis in human fetal fibroblasts, as measured by the incorporation of [3H] thymidine and cell replication. In serum‐free medium, without additional peptide growth factors, TGF‐β had no action on thymidine incorporation. However, in the presence of 0.1% v/v fetal calf serum, TGF‐β exhibited a bi‐functional action on the cells. A dose‐dependent stimulation of [3H] thymidine incorporation, and an increase in cell number, occurred with fibroblasts established from fetuses under 50 g body weight, with a maximum stimulation seen at 1.25 ng/ml. For fibroblasts from fetuses of 100 g or greater body weight, TGF‐β caused a dose‐related decrease in thymidine uptake with a maximal inhibition at 2.5 ng/ml, and a small decrease in cell number. When DNA synthesis was stimulated by the addition of somatomedin‐C/insulin‐like growth factor I, epidermal growth factor, or platelet‐derived growth factor, their actions were potentiated by the presence of TGF‐β on cells derived from fetuses under 50 g body weight, but inhibited on cells obtained from the larger fetuses wieghing more than 100 g. Similar results were found for changes in cell number in response to TGF‐β when stimulated by SM‐C/IGF I. The ability of TGF‐β to modulate [3H] thymidine incorporation did not involve a change in the time required for growth‐restricted cells to enter the S phase of the replication cycle. These data suggest that TGF‐β may exert either a growth‐promoting or growth‐inhibiting action on human fetal connective tissues in the presence of other peptide growth factors, which is dependent on fetal age and development.
Isolation and partial characterization of endothelial cell extracellular complexes
Authors: Hatcher Victor B. , Fadl‐Allah Nora , Levitt Mindy A. , Brown Andrea , Margossian Sarkis S. , Gordon Portia B. 
Published: February 2005

AbstractHuman endothelial cells release components into the growth medium that stimulate cell‐substratum adhesion. Several macromolecular components were isolated by ultracentrifugation of the endothelial cell conditioned medium. The components were heterogeneous, consisting of several sizes when examined by sedimentation velocity and gel filtration. When the extracellular components were evaluated by electron microscopy, structurally discrete particles were observed. The extracellular components and the complexes mediated cell‐substratum adhesion to both human umbilical and arterial endothelial cells. The majority of the extracellular components that promote endothelial cell adhesion were pelleted by ultracentrifugation. Although the complexes contained fibronectin, antibodies to fibronectin did not inhibit cell adhesion to the complexes. Significant inhibition of endothelial cell adhesion was observed in the presence of heparin and heparan sulfate. The supernatant fraction following ultracentrifugation of the growth medium contained a component that suppressed endothelial cell adhesion to culture dishes coated with fibronectin, type I collagen, and endothelial cell complexes. SDS‐polyacrylamide gel electrophoresis indicated that the complexes contained several components, and the majority of the large‐molecular‐weight components were pelleted by ultracentrifugation. The conditioned medium from human endothelial cells contains specific complexes that promote cell‐substratum adhesion and components that suppress cell‐substratum adhesion.