bluuebunny/crossref_metadata_2025_split huggingface dataset:
Purified HDL‐apolipoproteins, A‐I and C‐III, substitute for HDL in promoting the growth of SV40‐transformed REF52 cells in serum‐free medium
Authors: Chen Jan‐Kan , Labrake‐Farmer Sharon , McClure Don B. 
Published: February 2005

AbstractThe lipid‐free apolipoproteins of human high density lipoprotein (HDL) have been assayed for their ability to substitute for native HDL in promoting the growth of a SV40‐transformed REF52 cell line in serum‐free medium. Total HDL‐apolipoproteins (apoHDL) were found to mimic almost exactly the growth promoting effects of whole HDL. The apoHDL‐associated growth promoting activity eluted from a Sephacryl S‐200 column in two separate fractions coin‐ciding with the protein peaks of apolipoprotein A‐I and the C group of apolipoproteins. These two fractions, designated S‐II and S‐IV, respectively, acted additively in promoting WT1A cell growth when tested at saturating concentrations. The active component in the S‐II fraction maximally stimulated WT1A cell growth at 40–60 μg/ml and was identified as apolipoprotein A‐1 by NaDodSO4 polyacrylamide gel electrophoresis and affinity chromatography on anti‐(apoA‐I). The active component in the S‐IV fraction was maximally active at 1–2 μg/ml and was identified as apolipoprotein C‐III by DEAE ion exchange high pressure liquid chromatography and polyacrylamide gel electrophoresis (at pH 8.3) in 6 M urea. These results indicate that the growth promoting effect of HDL on WT1A cells is mediated via the HDL‐apolipoproteins, A‐I and C‐III, and that the mechanism responsible does not necessarily involve their participation in the uptake (or utilization) of HDL‐associated lipids.
Transport and metabolism of adenosine in human erthrocytes: Effect of transport inhibitors and regulation by phosphate
Authors: Plagemann Peter G. W. 
Published: February 2005

AbstractRapid kinetic techniques were applied to determine the effect of transport inhibitors on the transport and metabolism of adenosine in human red cells. Dipyridamole inhibited the equilibrium exchange of 500 μM adenosine by deoxcoformycin‐treated cells in a similar concentration dependent manner as the equilibrium exchange and zero‐trans influx of uridine with 50% inhibition being observed at about 20 nM. lntracellular phosphorylation of adenosine at an extracellular concentration of 5 μM pM was inhibited only by dipyridamole concentrations ≥ 100nM, which inhibited transport about 95%. Lower concentrations of dipyridamole actually stimulated adenosine phosphorylation, because the reduced influx of adenosine lessened substrate inhibition of adenosine kinase. When the cells were not treated with deoxycoformycin, > 95% of the adenosine entering the cells at a concentration of 100μM became deaminated. A 95–98% inhibition of adenosine transport by treatment with dipyridamole, dilazep, or nitrobenzylthioinosine inhibited its deamintion practically completely, whereas adenosine phosphorylation was inhibited only 50‐85%. Whether adenosine entering the cells is phosphorylated or deaminated is strictly based on the kinetic properties of the responsible enzymes, substrate inhibition of adenosine kinase, and the absolute intracellular steady state concentration of adenosine attained. The latter approaches the extracellular concentration of adenosine, since transport is not rate limiting, except when modulated by transport inhibitors.In spite of the extensive adenosine deamination in cells incubated with 100 7μM adenosine, little IMP accumulated intracellularly when the medium phosphate concentration was 1 mM, but IMP formation increased progressively with increase in phosphate Concentration to 80 mM. The intracellular phosphoribosylation of adenine and hypoxanthine were similarly dependent on phosphate concentration.The results indicate that adenosine is the main purine source for erythrocytes and is very efficiently taken up and converted to nucleotides under physiological conditions, whereas hypoxanthine and adenine are not significantly salvaged. Hypoxanthine resulting from nucleotide turnover in these cells is expected to be primiarily released from the cells. Adenosine was also phosphorolyzed in human red cells presumably by 5′‐methyltioadenosine phosphorylase, but this reaction seems without physiological significance as it occurs only at high adenosine and phosphate concentrations and if deamination is inhibited.
Prostaglandin E2 synthesis in the inner medullary collecting duct of the rat: Implications for vasopressin‐dependent cyclic AMP formation
Authors: Jackson Brian A. 
Published: February 2005

AbstractThe effects of osmolality on prostaglandin E2 (PGE2) biosynthetic capacity and the interaction between endogenous PGE2 synthesis and vasopressin (AVP)‐dependent cyclic AMP generation were examined in papillary collecting ducts (PCD) microdissected from collagenase‐digested rat kidneys. Increasing medium osmolality with NaCl:urea (1:2 molar ratio) progressively increased PGE2 synthesis in PCD up to 1,500 mOsm. Addition of NaCl:urea or NaCI alone were equally effective in stimulating PGE2 biosynthetic capacity in PCD. In contrast, addition of urea alone had a much smaller stimulatory effect on PGE2 synthesis. Inhibition of endogenous PGE2 synthesis with naproxen (10−5M) suppressed AVP‐dependent cAMP formation in PCD when incubated in 300 mOsm medium but had no effect when incubated in 1,500 mOsm medium. Addition of 2.5×10−5 M PGE2 also suppressed AVP‐dependent cAMP formation in PCD only when incubated in 300 mOsm medium. The present study suggests that the PCD is a site of active PGE2 synthesis that is modulated by osmolality. Our results do not support the concept that endogenous PGE2 antagonizes vasopressin action via inhibition of AVP‐dependent cAMP formation.
Growth inhibition of 3T3 fibroblasts by lysosomotropic amines: Correlation with effects on intravesicular pH but not vacuolation
Authors: Cain Cynthia Corley , Murphy Robert F. 
Published: February 2005

AbstractThe effects of five lysosomotropic amines on the growth of Swiss 3T3 fibroblasts were measured and compared with effects on intravesicular pH. Tributylamine and benzylamine, amines that affect intravesicular pH without causing vacuolation, were found to inhibit cell growth to a similar extent as vacuologenic amines previously tested. Excellent correlation between the half‐maximal concentrations for the growth and pH effects were found for tributylamine, benzylamine, chloroquine, and ammonium chloride. The results suggest that growth inhibition by these amines is a direct result of their effects on pH and not due to other effects (such as vacuolation). In contrast, a 100‐fold difference in the half‐maximal concentrations was found for methylamine, suggesting that methylamine inhibits growth by a mechanism unrelated to pH.
Tyrosine phosphorylation in cells treated with transforming growth factor‐β
Authors: Libby James , Martinez Ricardo , Weber Michael J. 
Published: February 2005

AbstractCells stimulated with epidermal growth factor (EGF) or any one of a diverse group of other mitogenic agents display an increased tyrosine phosphorylation of a pair of 42,000 Mr proteins. Transforming Growth Factor‐β (TGF‐β) is able to potentiate the mitogenic effects of Epidermal Growth Factor on some fibroblastic cells (such as the NRK‐49F cell line) and, in addition, permits the anchorage‐independent growth of these cells. In this study we asked whether these growth‐regulatory actions of Transforming Growth Factor‐β are associated with changes in tyrosine phosphorylation of cellular proteins, in particular the 42,000 Mr proteins. We found no effect of Transforming Growth Factor‐β on the extent or time‐course of tyrosine phosphorylation, either by itself or in combination with Epidermal Growth Factor. Since the tyrosine phosphorylation of the 42,000 Mr proteins is stimulated both by receptors with tyrosine kinase activity and by diacylglycerol analogs (but not by Transforming Growth Factor‐β), we suggest that the activity of the receptor for Transforming Growth Factor‐β is linked neither to tyrosine phosphorylation nor to phosphatidyl inositol turnover.
Murine basophil—mast differentiation: Toward optimal conditions for selective growth and maturation of basophil—mast or allied cells
Authors: Lanotte M. , Arock M. , Lacaze N. , Guy‐Grand D. 
Published: February 2005

AbstractRecent investigations revealed that basophil‐mast cells were related to the hemopoietic system. Strikingly, murine bone marrow showed a singular paucity in cells with basophil‐mast features; moreover in clonogenic assays (methylcellulose, agarose) bone marrow was found to be manifestly poor in basophil‐mast progenitor cells. Our work brought to light several new facts concerning the culture and differentiation of this cell type: 1° pure and mixed mast clones can be derived in large numbers from bone marrow, provided progenitors are cultured in collagen matrix. Up to 1,382 hemopoietic clones were analysed in situ after staining: 30% contained mast cells (34 per 105 cells), thus the basophil‐mast lineage was one of the most frequent. We concluded that other cloning media were noticeably nonoptimal for the growth and/or maturation of mast cells. We suggested that collagen and the molecular edifices derived from it, both found in variable amounts in the natural mast environments, should play essential roles in mast phenotype expression. 2° Cholera toxin (CT) selectively eradicated nonmast progenies: mast progenitors and mast progenies were resistant. In this way, pure and rapidly expanding mast cell clones were obtained at a frequency never reported before. CT possibly acts both directly, as a stimulator of mast cell proliferation, or indirectly on marrow subpopulations which repress basophil‐mast cell growth and maturation. In vitro culture conditions, specifically designed for basophil‐mast lineage, should prove of interest in the search for an unifying hypothesis concerning the multiple forms of mast cells found in various tissues.
Enhanced synthesis of the glucose/calcium‐regulated proteins in a hamster cell mutant deficient in transfer of oligosaccharide core to polypeptides
Authors: Lee Amy S. , Wells Steven , Kim Kyu Seong , Scheffler Immo E. 
Published: February 2005

AbstractThe properties of two Chinese hamster temperature‐sensitive mutants, K12 and H3.5, were examined. Both mutants originated from the same parental cell line, Wg1A, and were isolated as cell cycle mutants arrested in G1. Previously, we had been shown that the H3.5 ts mutation affected the transfer of the oligosaccharide from the lipid carrier to the nascent polypeptide and that the K12 ts mutation regulated the transcription of two glucose/calcium‐regulated genes. We report here that these two mutants exhibit almost identical phenotypes at the biochemical level. Furthermore, a genetic complementation test demonstrates that the two ts lesions must be closely related, or even identical. Our results suggest that a specific defect in glycosylation may result in the overproduction of the glucose/calcium‐regulated proteins and is capable of activating the promoter of the major glucose‐regulated gene.
Correlation between plasma membrane surface area and transferrin secretion rate in isolated hepatocytes
Authors: Pechinot D. , Foucrier J. , Feldmann G. 
Published: February 2005

AbstractIt is generally considered that in exocytosis the size of the secreting cells does not increase when the membranes of exocytosis vesicles fuse with the plasma membrane. As the factors involved in the regulation of this phenomenon are poorly understood, we thought it worthwhile to investigate the relationship between the plasma membrane surface area and secretory activity. Isolated rat hepatocytes were prepared by liver collagenase perfusion. Secretion of the plasma protein, transferrin (Tf) was detected at the single cell level with specific anti‐rat transferrin antibodies using the reverse hemolytic plaque test. Hepatocyte surface and hemolytic ring surface areas were calculated from diameters of hepatocyte and hemolytic plaque measured after 5h of incubation. A highly significant correlation was established between the plaque‐forming hepatocyte surface areas and the corresponding hemolytic surface areas. This result was confirmed using an automatic image analysis method. Two‐month‐old rats were compared to 4‐month‐old rats. We observed that the ratio of the quantity of transferrin secreted by hepatocytes to the hepatocyte surface area was constant for a given incubation time, whatever the size of the hepatocytes. These results suggest that the plasma membrane surface area of hepatocytes may constitute a limiting factor in Tf secretion.
Properties of colony‐stimulating factors produced by macrophage cell lines and hybrid cells
Authors: Ohki Kazunori , Nagayama Ariaki 
Published: February 2005

AbstractColony‐stimulating factors (CSFs) produced by two simian virus 40(SV40) transformed macrophage cell lines ( BAM1 and BAM3 ), and three hybrids (HM3‐11, HM3‐12, and HM3‐14) derived from fusion between BAM3 and a Chinese hamster cell line (hs222‐16) were examined. HM3‐11 and HM3‐14 produce two molecular species of CSF, which are not found in the conditionec media from cultures of BAM1 and BAM3 or lipopolysaccharide (LPS), phorbolmyristate‐acetate (PMA), and zymosan‐stimulated BAM3. HM3‐12, which is classified into another group in terms of CSF secretion, does not produce these two CSFs. On the basis of various criteria, one of these CSF species ( peak 1‐CSF ) was characterized as a macrophage‐colony‐stimulating factor (M‐CSF). The other CSF (peak 2‐CSF) induced a group of bone marrow cells in granulocytes and macrophages as well as growth of a mast cell line, IC2. This CSF has an apparent molecular weight of 18,000, estimated by SDS‐polyacrylamide gel electrophoresis. Unlike interleukin 3 (IL3) from WEHI‐3 cells, the growth factor activity of peak 2‐CSF binds to DEAE‐Sephacel. Thus, peak 2‐CSF is similar to a granuclocyte‐macrophage colony‐stimulating factor (GM‐CSF) rather than to IL3. The anti L cell CSF serum does not inhibit the CSF activity in Chinese hamster fibroblast conditioned medium, and the IC2 cells do not respond to Chinese hamster lung conditioned medium (CHLCM), suggesting that peak 1‐ and peak 2‐CSF are of mouse origin.
Altered type I protein kinase in adhesion defective CHO cell variants
Authors: Cheung E. , Brown P. J. , Juliano R. L. 
Published: February 2005

AbstractADv cells are Chinese hamster ovary (CHO) cell variants which cannot adhere to fibronectin coated substrata (Harper amp; Juliano: J. Cell Biol., 1980; Nature 1981a, b). We have shown that the defect in some clones of ADv cells is distal to the initial interaction between fibronectin and its cell surface receptors (Cheung and Juliano: Exp. Cell Res., 1984), and that it extends to fibronectin mediated aggregation and endocytosis. The adhesion defect in some ADv clones can be corrected by raising intracellular cAMP levels (Cheung & Juliano: J. Cell Physiol., 1985). Here we examine the protein kinase activities and phosphorylation patterns in an adhesion defective variant clone ADv F11CA11. Analysis of the cAMP dependent protein kinase activity (cAdPK) in crude extracts of F11CA11 cells shows an apparent increase in K (activation) as compared to wild type (WT) CHO cell extracts. Further, the DE‐52 cellulose chromatography profile of cAdPK in the F11CA11 variant is markedly different from WT in that the type I cAdPK peak elicited by 1 μM cAMP is essentially missing in F11CA11, while the type II cAdPK peak is similar to that in WT. Raising the cAMP level to 100 μM elicits a type I peak in F11CA11 with about 45% of the activity of the WT peak. Binding studies with 3H‐cAMP reveal that the type I peak in F11CA11 has a Kd of 1.7 times; 10−8 M as compared to 2.0 × 10−9 M for WT, whereas the type II peak Kd is approximately 1 × 10−9 M for both WT and F11CA11. Two‐dimensional polyacrylamide gel analysis of 32Pi labeled WT cells and F11CA11 cells with or without cAMP treatment reveals the presence of a protein(s) of 50 kilodaltons which is phosphorylated in WT cells and in cAMP treated F11CA11 cells but not in untreated F11CA11 cells. These findings, coupled with our previous observations, strongly indicate taht the adhesion defect in ADvF11CA11 cells is associated with an altered type I cAdPK having lower affinity for cAMP. At normal cellular cAMP levels this enzyme fails to phosphorylate one or more critical protein substrates; however, by raising internal cAMP levels, the defect can be overcome. Thus type I cAdPK seems to play an important role in the regulation of fibronectin mediated cell adhesion, cell aggregation, and endocytosis.
Carbonic anhydrase cytochemistry in mitochondria‐rich cells of salamander larvae gill epithelium as related to age and H+ and Na+ concentrations
Authors: Lewinson D. , Rosenberg M. , Goldenberg S. , Warburg M. R. 
Published: February 2005

AbstractCarbonic anhydrase (CAH) was localized in the mitochondria‐rich cells (MRC) of 1‐week‐old salamander larvae gill epithelium, in both MRC and pavement cells of 6‐week‐old larvae, and in regenerated stems of previously amputated gills. CAH activity of the MRC was measured quantitatively using a microscope densitometric technique. Changes in CAH activity per cell and changes in the numbers of CAH‐positive MRC were followed under different H+ and Na+ concentrations at the two age groups. CAH activity per cell increased with age, whereas the numbers of CAH‐positive MRC dropped. CAH activity per cell in the 1‐week‐old age group reached maximal values at pH 7.4 and stayed relatively high in the more alkaline media. Moderate increases of Na+ concentrations had small but significant effects on increasing CAH activity of gill MRC. When taking into consideration not only the changes in cellular activity but also the changes in the number of CAH‐positive cells under the different acclimation media, an activity index (ICAH) was calculated. Thus, the ICAH in the 1‐week‐old was found to be dependent on the decline of ambient H+ concentrations (expressed as increasing pH), reaching maximal effect at pH 8.0. On the other hand, raising the Na+ concentrations of the acclimation media to 110 and 220 mOsm/liter caused a maximal inhibition of tissue CAH activity as expressed by ICAH. In conclusion, it is suggested that salamander larvae gill MRC take part in the adaptation of the larvae to changing H+ concentrations of their milieu rather than in their adaptation to changes in its osmolality.
Conditional responsiveness of a chemically transformed cell line to growth factor stimulated DNA synthesis
Authors: Whipple A. P. , Furlanetto R. W. , Scher C. D. 
Published: February 2005

AbstractBP3T3, a clonal benzo(a)pyrene‐transformed BALB/c‐3T3 cell line, is conditionally responsive to growth factor stimulation. Density arrested cell populations deprived of growth factors by pretreatment with 0.5% platelet‐poor plasma synthesized DNA both in response to ng/ml concentrations of PDGF, EGF, and somatomedin C, and in response to insulin, plasma, and serum. The above agents acted singly to induce DNA synthesis, but synergism is suggested because a higher percentage of cells were stimulated to enter the S phase when the growth factors were added in combination. Desensitization to growth factors occurred when cultures were pretreated with the high concentration of growth factors present in 10% serum (or plasma). In desensitized cultures none of the above agents, added singly or in combination, stimulated DNA synthesis. This effect appears to be global because pretreatment with one growth factor (e.g., insulin) inhibited the action of another (e.g., PDGF). Cell density appears to play a critical role in regulating DNA synthesis. Unlike nontransformed BALB/c‐3T3 cells whose density is regulated by the serum concentration, the density of BP3T3 cells reached a plateau when cultures were grown in a serum (or plasma) concentration of 3% or greater. Such density arrested cultures were growth factor unresponsive; however, the cells rapidly responded to growth factors by synthesizing DNA and replicating when reseeded at a lower cell density. Thus the growth of BP3T3 cells is regulated by both growth factors and cell density.
Requirement of prostaglandin F2α in 17β‐estradiol stimulation of DNA synthesis in rabbit endometrial cultures
Authors: Orlicky D. J. , Lieberman R. , Williams C. , Gerschenson L. E. 
Published: February 2005

AbstractWe have hypothesized that two of the endogenously synthsized endometrial prostaglandins (PGs), prostaglandin F2α (PGF2α), and prostaglandin E1 (PGE1), play a regulatory role in growth control of the rabbit endometrium. PGF2α increases DNA synthesis and PGE1 inhibits that effect. Primary cultures of rabbit endometrial cells were used to examine the possible role of these PGs in the mechanism of action of 17β‐estradiol on DNA synthesis. Towards this end, binding, second messenger and DNA synthesis experiments were performed. 17β‐estradiol stimulation restulted in a time dependent (optimal: approximately 6 h) and 17β‐estradiol concentration dependent (optimal: approximately 10−7 M 17β‐estradiol in phenol red‐containing medium) increase in [3H]PGF2α binding. Scatchard type analysis of the binding data revealed an increase in receptor number while the receptor affinity for [3H]PGF2α remained the same as in the control treated cultures. This 17β‐estradiol stimulated increase in PGF2α receptor allowed a suboptimal concentration of PGF2α (10−9M) to increase intracellular levels of inositol polyphosphates, while by itself this concentration of PGF2α caused no significant change in intracellular inositol polyphosphate levels. 17β‐estradiol, alone among the several studied steroid hormones, could increase [3H]PGF2α binding. Proliferation studies revealed that, in these primary cultures of rabbit endometrium, 17β‐estradiol could increase DNA synthesis but not in the presence of indomethacin, unless PGF2α was addd to the medium at a concentration (10−9M) near or above what is normally accumulated in the medium by these cultures. In the absence of 17β‐estradiol stimulation, addition of these same low concentrations of PGF2α had no effect on DNA synthesis. Apparently, through its effect on the PGF2α receptor, 17β‐estradiol enhances the PGF2α stimulated DNA synthesis response approximately 100 fold. The DNA synthesis inducd by 17β‐estradiol can be inhibited by PGE1, as can PGF2α‐induced DNA synthesis. We propose that 17β‐estradiol may be mediating its mitogenic effect through an alteration of the prostglandin agonist:antagonist control of proliferation in rabbit endometrial cultures. In additon we suggest that, if 17β‐estradiol acts to increase PGF2α receptors as part of its mode of action, this may be of importance in other tissues possessing both prostaglandin and 17β‐estradiol receptos.