bluuebunny/crossref_metadata_2025_split huggingface dataset:
Altered hormonal responses: Markers for embryonal and embryonic carcinoma stem cells and their differentiated derivatives
Authors: Liapi Charis , Gerbaud Pascale , Anderson Wayne B. , Brion Daniele Evain 
Published: February 2005

AbstractTeratocarcinoma cells in culture offer an in vitro system for studying certain aspects of embryonic differentiation. To gain some insight into regulatory systems that might be operative during early development, we have characterized the alterations that occur in the hormonal responsiveness of the membrane adenylate cyclase of different embryonal carcinoma cell lines with differentiation. Each undifferentiated embryonal carcinoma stem cell studied (F9, PCC4, PC13, P19) has an adenylate cyclase system predominantly activated by calcitonin. Of great interest is the fact that cAMP production is also enhanced specifically by calcitonin in an embryo‐derived stem cell line. Differentiation of the embryonal carcinoma stem cell population toward parietal endoderm results in a decrease in calcitonin activation with a concomitant appearance of sensitivity to parathyroid hormone. Differentiation toward visceral endoderm is characterized by a lack of response of the adenylate cyclase system to both calcitonin and parathyroid hormone. These results indicate that the changes noted in adenylate cyclase hormonal responsiveness might serve as useful markers during early stages of differentiation.
Modulation of fibronectin, laminin, and cellular adhesion in the transformation and differentiation of murine AKR fibroblasts
Authors: Chakrabarty Subhas , Brattain Michael G. , Ochs Robert L. , Varani James 
Published: February 2005

AbstractThe functional relationship between membrane/cell surface expression of fibronectin and laminin and transformation/differentiation was examined in an AKR mouse fibroblastic cell model. This model consisted of the untransformed AKR‐2B cells, their chemically transformed counterpart (AKR‐MCA cells) and the chemically differentiated from of the AKR‐MCA cells. The transformed AKR‐MCA cells were found to express more surface laminin and less fibronectin than the untransformed AKR‐2B cells. The transformed AKR‐MCA cells were slower to attach and spread on both plastic and type IV collagen‐coated dishes in comparison of the AKR‐2B cells. However, a higher percentage of the AKR‐MCA cells ultimately attached and spread on the type IV collagen‐coated dishes. The induction of differentiation in the AKR‐MCA cells by N, N‐dimethylformamide (DMF) restored fibronection to the surface of the AKR‐MCA cells but reduced laminin expression only slightly. The DMF‐treated AKR‐MCA cells resembled the AKR‐2B cells in that they rapidly attached and spread on plastic dishes and dishes coated with type IV collagen. They also resembled the AKR‐ MCA cells in that a high proportion ultimately attached and spread on the collagen‐coated dishes.
Hormone‐sensitive adenylyl cyclase in preadipocytes cultured from adipose tissue: Comparison with 3T3‐L1 cells and adipocytes
Authors: Kirkland James L. , Piñeyro Marco A. , Lu Zhongding , Gregerman Robert I. 
Published: February 2005

AbstractThe adenylyl cyclase system of preadipocytes derived from the stromal vascular fraction of perirenal rat fat pads was characterized. Unlike mature adipocytes, preadipocyte adenylyl cyclase was only weakly stimulated by catecholamines and adrenocorticotrophic hormone, but was stimulated by guanine nucleotides. Parathyroid hormone and 2‐chloroadenosine also stimulated preadipocyte adenylyl cyclase. The adenylyl cyclase system of preadipocytes resembled that of undifferentiated 3T3‐L1 cells. However, agents which induced the differentiation of the 3T3‐L1 cell adenylyl cyclase system did not have asimilar effect on predipocytes. A medium (CDM6) which induced some differentiation of preadipocyte adenylyl cyclase was developed. The observations that the adenylyl cyclase system of preadipocytes and undifferentiated 3T3‐L1 cells are similar, that preadipocyte adenylyl cyclase can be induced to develop along lines similar to early differentiation of 3T3‐L1 cells, and that the adenylyl cyclase system of fully‐differentiated 3T3‐L1 cells has characteristics intermediate between predipocytes and adipocytes, suggest that the differentiation of predipocyte and 3T3‐L1 adenylyl cyclase in vitro mimics adipose adenylyl cyclase development in vivo. The increased catecholamine and ACTH stimulation, and reduced GTP and adenosine sensitivites of adipocytes compared to preadipocytes suggest that a number of genes affecting adenylyl cyclase‐associated regulatory and receptor proteins are coordinately repressed and derepressed during development.
Mitogenic stimulation of human breast cancer cells in a growth factor‐defined medium: Synergistic action of insulin and estrogen
Authors: van der Burg Bart , Rutteman Gerard R. , Blankenstein Marinus A. , de Laat Siegfried W. , van Zoelen Everardus J. J. 
Published: February 2005

AbstractThe cooperative action of 17β‐estradiol (E2) and polypeptide growth factors in stimulating proliferation of human breast cancer cells in vitro was investigated. To prevent background estrogenic stimulation, only phenol red‐free media were used. When cultured in media supplemented with steroid‐stripped serum in which all polypeptide growth factor activity had been chemically inactivated, MCF7 cells were unable to proliferate and became virtually quiescent. In the additional presence of insulin, epidermal growth factor (EGF), and E2, however, cells proliferated as rapidly as did cells cultured in media supplemented with fetal calf serum. Analysis by DNA flow cytometry showed that in the absence of external growth factors, MCF7 cells became arrested predominantly in the G1/G° phase of the cell cycle. Upon addition of insulin in combination with EGF and E2, however, cells reentered the cell cycle with a high degree of synchrony. When added alone, E2 induced only slight mitogenic effects under these growth factor‐defined conditions. In contrast, this steroid induced optimal proliferation in conventional steroid‐stripped serum, which in itself contained considerable mitogenic activity. Insulin (at 10 μg/ml) was the most potent stimulator of MCF7 cell proliferation under growth factor‐defined conditions, resulting in a more than sixfold increase in cell number after 96 hours. Other growth factors such as platelet‐derived growth factor (PDGF), transforming growth factor β (TGFβ), and EGF had little effect by themselves and only slightly influenced insulin‐induced proliferation. At suboptimal concentrations of insulin (10‐100 ng/ml), however, strong synergism was observed between E2 and insulin in inducing MCF7 proliferation. Using the CG5 cell line, a highly E2‐sensitive MCF7 variant, synergism with E2 was already observed at 1 ng/ml insulin. It is concluded that MCF7 cells require insulin (or insulin‐like growth factors) for proliferation. At suboptimal insulin concentrations, E2 acts synergistically with insulin, possibly by inducing autocrine production of polypeptide growth factors by these cells.
Biochemical and morphological characterization of growth and differentiation of normal human neonatal keratinocytes in a serum‐free medium
Authors: Pillai Sreekumar , Bikle Daniel D. , Hincenbergs Mara , Elias Peter M. 
Published: February 2005

AbstractGrowth and differentiation of keratinocytes in a serum‐free medium (keratinocyte growth medium of KGM) was studied and compared to that under conditions in which serum and feeder cell layers were used. Cells were grown in KGM containing 0.1 mM calcium (KGM/low calcium), KGM containing 1.2 mM calcium (KGM/normal calcium), or Dulbecco's modified Eagles medium containing 5% fetal calf serum and 1.8 mM calcium in presence of mitomycin treated 3T3 M cells (DMEM/5% FCS). Plating efficiency and rate of growth were similar in the three media till confluence. In postconfluent cultures, protein and DNA content of cells attached to the plate in KGM/low‐calcium dishes decreased as an increased number of cells were shed into the medium. Cell shedding was much less evident in the presence of normal calcium. Cells grown in KGM/low calcium had a higher rate of cell proliferation (3H‐thymidine incorporation into cellular DNA) than cells grown in normal calcium. Transglutaminase activity, involucrin content, and cornified envelope formation were greatest in cells grown in KGM/normal calcium, intermediate in cells grown in DMEM/5% FCS, and least in cells grown in KGM/low calcium. Keratin profiles from cells grown in KGM/low calcium showed a lower percentage of high molecular weight bands compared to the keratin profiles from cells grown in the presence of normal calcium. Keratinocytes in KGM/low calcium grew as a monolayer of cuboidal cells with few features of differentiation, whereas cells grown in KGM/normal calcium stratified into multilayered islands (3–5 layers) surmounted by 2–4 layers of enucleated cells with thickened cornified envelopes. Cells grown in KGM/normal calcium also contained tonofilaments and lamellar bodies unlike cells grown in KGM/low calcium. Cells grown in DMEM/5% FCS also formed stratified layers comparable to cells grown in KGM/normal calcium but lacked cornified cells, keratohyalin granules, tonofilament bundles, and lamellar bodies. These studies indicate the usefulness of serum‐free conditions for the culture of human keratinocytes and confirm the importance of extracellular calcium in keratinocyte differentiation.
Interleukin‐1 regulation of hematopoietic growth factor production by human stromal fibroblasts
Authors: Yang Yu‐Chung , Tsai Shickwann , Wong Gordon G. , Clark Steven C. 
Published: February 2005

AbstractThe human stromal fibroblastoid cell strain designated ST‐1 represents a normal population of cells capable of supporting hematopoiesis in vitro. These cells constitutively elaborate hematopoietic growth factor activity into the medium and the level of production of this activity dramatically increases following stimulation of the cells with IL‐1. This enhanced production is due at least in part to increased expression of the genes for GM‐CSF, G‐CSF, and IL‐6, but not IL‐3. The IL‐1 treatment had little effect on the expression of M‐CSF, a factor made constitutively by the cells. These results are consistent with the model that hematopoiesis is regulated at least in part by constant short‐range interactions of humoral factors produced by stromal cells both with other types of stromal cells and with the hematopoietic progenitors.
Hyaluronate appears to be covalently linked to the cell surface
Authors: Green Shawn J. , Underhill Charles B. 
Published: February 2005

AbstractThe purpose of this study was to examine the nature of the linkage between cell‐surface hyaluronate and the plasma membrane. To accomplish this, rat fibrosarcoma cells were cultured in the presence of [3H]‐acetate to isotopically label the hyaluronate, and then fixed with glutaraldehyde, which cross‐links proteins but does not react directly with hyaluronate. The glutaraldehyde fixation stabilized the cells so that they could be manipulated in ways which would otherwise destroy cells. The fixed cells were then subjected to various treatments, and the amount of hyaluronate remaining on the cell surface was assayed via exhaustive digestion with Streptomyces hyaluronidase. Using this technique, we found that (1) cell‐surface hyaluronate was quite stable for extended periods of time even in the presence of a large excess of non‐labeled hyaluronate; (2) 4 M guanidine HCI and detergents did not extract a significant portion of cell‐surface hyaluronate; (3) solutions of varying ionic strength (0–1 M NaCI) had no effect on the retention of hyaluronate; (4) the cell coat was stable in the range of pH 4–11, but outside this range a significant amount of hyaluronate was released; and (5) treatment with proteases released cell‐surface hyaluronate. These results are consistent with the possibility that hyaluronate is covalently linked to a protein associated with the plasma membrane. Further support for this model came from experiments with the detergent Triton X‐114, which can be used to separate soluble proteins from hydrophobic proteins. When nonfixed rat fibrosarcoma cells were extracted with this detergent and then partitioned by centrifugation, approximately 30 times as much hyaluronate was present in the detergent fraction which contained the hydrophobic proteins, as compared to the extracts pretreated with trypsin prior to phase separation. Again, these results suggest that cell‐surface hyaluronate is directly linked to a hydrophobic core protein intercalated in the plasma membrane.
Activation and proliferation signals in murine macrophages: Stimulation of glucose uptake by hemopoietic growth factors and other agents
Authors: Hamilton John A. , Vairo Gino , Lingelbach Suzanne R. 
Published: February 2005

AbstractPurified colony‐stimulating factor (CSF‐1) (or macrophage colony stimulating factor [M‐CSF]) stimulated the glucose uptake of murine bone marrow‐derived macrophages (BMM) and resident peritoneal macrophages (RPM) as measured by 3H‐2‐deoxyglucose (2‐DOG) uptake. Similar concentrations of CSF‐1 stimulated the 2‐DOG uptake and DNA synthesis in BMM. Other purified hemopoietic growth factors, granulocyte‐macrophage CSF (GM‐CSF) and interleukin‐3 (IL‐3) (or multi‐CSF), and the tumor promoter, 12‐O‐tetrade‐canoyl‐phorbol‐13‐acetate (TPA), even though differing in their mitogenic capabilities on BMM, were also stimulators of 2‐DOG uptake in BMM and RPM. The nonmitogenic agents, lipopolysaccharide (LPS) and concanavalin A (Con A), were also active. The inhibition by cytochalasin B and by high concentrations of D‐glucose suggest that the basal and stimulated 2‐DOG uptake occurred via a carrier‐facilitated D‐glucose transport system. The responses of the two macrophage populations to the hemopoietic growth factors and to the other agents were quite similar, suggesting that events that are important for the induction of DNA synthesis are not tightly coupled to the earlier rise in glucose uptake. For the BMM, the ability of a particular agent to stimulate glucose uptake did not parallel its ability to promote cell survival. However, stimulation of glucose uptake could still be a necessary but insufficient early macrophage response for cell survival and subsequent DNA synthesis.
Modulation of cyclic AMP levels and differentiation by adenosine analogs in mouse erythroleukemia cells
Authors: Sherman Matthew L. , Shafman Timothy D. , Kufe Donald W. 
Published: February 2005

AbstractFriend virus‐transformed mouse erythroleukemia (MEL) cells can be induced to undergo erythroid differentiation by a variety of compounds, including dimethyl sulfoxide (DMSO) and the adenosine analog xylosyladenine. The present studies have monitored the effects of the stable adenosine receptor ligand N6‐phenylisopropyladenosine (PIA) on induction of MEL cell differentiation. PIA has been previously shown to stimulate adenylate cyclase activity in rat hepatic and mouse Leydig l‐10 cells as well as inhibit adenylate cyclase in adipocytes. In the present study, PIA was ineffective as an inducer of the differentiated MEL cell phenotype. However, the results demonstrate that PIA inhibits the induction of MEL cell differentiation by DMSO and xylosyladenine. The extent of this inhibition as determined by benzidine staining, induction of globin RNA, and loss of self‐renewal capacity was dependent on PIA concentration. The results also demonstrate that PIA induces a rapid and sustained increase in cyclic AMP (cAMP) levels. Furthermore, there was a highly significant correlation between cAMP levels and inhibition of xylosyl‐adenine‐induced differentiation (r = 0.962, P < 0.0005). This relationship is further supported by the demonstration that prostaglandins E1 and E2 increase MEL cell cAMP levels and inhibit induction of the differentiated MEL cell phenotype. Moreover, PIA inhibited induction of MEL cell differentiation by butyric acid, diazepam, hypoxanthine, and the aminonucleoside analog of puromycin. These results suggest that cAMP may act as a negative regulatory signal in the induction of MEL cell differentiation.
Normalization of epidermal growth factor receptor and transforming growth factor production in drug resistant variants derived from adenovirus transformed cells
Authors: Sircar S. , Weber J. M. 
Published: February 2005

AbstractVariants (G2, G5) resistant to the cancer chemotherapeutic drug methylglyoxal bis (guanylhydrazone) (MGBG) were isolated from adenovirus type 2 transformed rat brain cells (F4; Sircar et al., 1987). Although at least one of these variants continued to express the adenovirus Ela and Elb transforming proteins, they both exhibited a detransformed phenotype as witnessed by flat morphology, loss of anchorage independent growth, and tumor forming capacity. Reverse transformation suggested the possibility of changes in growth factor receptors and the production of transforming growth factors. To test this possibility, we investigated the status of epidermal growth factor receptors (EGF‐r) and transforming growth factor alpha (TGF‐α) production in F4, G2 and G5 cells. The level of 125I‐labeled EGF binding to intact drug resistant cells increased by 2‐ to 3‐fold compared to the transformed parental cell. Scatchard analysis suggests that increased binding was the result of increased receptor levels rather than altered affinity of receptor for ligand. The production of growth factors which compete with 125I‐labeled EGF binding declined in the detransformed G2 and G5 cells to a level intermediate between transformed (F4) and normal cells (FR3T3). EGF‐receptor increase and the complementary decrease in growth factor production in the drug resistant variants may be associated with detransformation.
Tumor necrosis factor stimulates proliferation of human osteosarcoma cells and accumulation of c‐myc messenger RNA
Authors: Kirstein Martina , Baglioni Corrado 
Published: February 2005

AbstractThe objective of this study was to establish whether human recombinant tumor necrosis factor (TNF) can significantly stimulate the proliferation of some tumor cells. Treatment with TNF had little or no effect on the growth of human tumor cells and murine NIH/3T3 cells cultured in medium with high serum concentration. Two tumor lines, SK‐MEL‐109 melanoma and HOS osteosarcoma cells, were adapted to grow in medium supplemented with 0.5% serum. The growth of these SK‐MEL‐109 cells was inhibited by TNF, but that of the HOS cells was greatly stimulated by TNF in a dose‐dependent way. Treatment with 10 ng/ml of TNF resulted in a two‐fold increase in the rate of cell division. This effect of TNF was also shown by measuring DNA and protein synthesis. The continuous presence of TNF was not required for its mitogenic activity on HOS cells cultured with 0.5% serum, since treatment for only one day with TNF resulted in prolonged growth stimulation. The failure of TNF to promote division of cells cultured in medium with 10% serum may possibly be explained by the presence of saturating amounts of growth factors in serum. Interferons abolished the mitogenic activity of TNF on HOS cells. Furthermore, TNF did not show synergism with insulin or epidermal growth factor in stimulating growth of these cells. The level of c‐myc mRNA was increased five‐fold after 30 minutes of treatment with TNF. This shows that TNF is a growth factor for HOS cells and that it induces accumulation of c‐myc mRNA.
Inhibition of imidazole‐induced tyrosinase activity by estradiol and estriol in cultured B 16/C3 melanoma cells
Authors: Kline Ellis L. , Smith Terry J. , Carland Karen A. , Blackmon Barbara 
Published: February 2005

AbstractThe effect of estrogens on tyrosinase (EC 1.14.18.1) activity was studied in B16/C3 melanoma cultures. Estradiol, estriol, and other related steroids failed to influence tyrosinase activity when added to the medium of proliferating cultures. Imidazole (10 mM), on the other hand, induced the activity of that enzyme 3‐fold, as reported previously. Estradiol and estriol blocked imidazole induction, however, unlike the other estrogenic compounds. The blockade occurred within 15 min of hormone addition and was reversible. Dose‐response studies revealed that the maximal estradiol effect occurred at 0.75 nM and the half‐maximal effect occurred at 0.5 nM. Estriol was more potent, with the maximal blockade occurring at ∼ 0.5 nM and half‐maximal effect at 0.25 nM. The induction of tyrosinase by imidazole and the blockade of this induction by estradiol and estriol could not be demonstrated in broken cell preparations, suggesting that direct enzyme activation‐inactivation was not involved. Studies utilizing inhibitors of protein and RNA synthesis suggest that this effect is mediated at a pre‐translational level and is independent of mRNA destabilization.
Effect of nicotine on transferrin binding and iron uptake by cultured rat placenta
Authors: McArdle Harry J. , Tysoe Jenny 
Published: February 2005

AbstractThe effect of nicotine on transferrin and iron transport in placental cells has been studied. Nicotine inhibits iron uptake but has little effect on the steady‐state levels of transferrin. The effect is temperature and concentration dependent and is not reversible. At a concentration of 15 mM nicotine inhibited transferrin endocytosis by 40%, while iron uptake was decreased by nearly 60%. Nicotine exerted a similar effect on reticulocytes, but other amines, either tertiary or quaternary, had little or no effect on either iron uptake or steady‐state intracellular transferrin levels. The results suggest that nicotine acts by blocking uptake, probably by acting as a weak base inhibiting iron release from transferrin, and inhibiting exocytosis with a resultant block of endocytosis. The concentrations required to exert an effect are too high to implicate inhibition of iron transport in the effects of smoking on pregnancy.
Enhanced transbilayer mobility of phospholipids in malaria‐infected monkey erythrocytes: A spin‐label study
Authors: Beaumelle Bruno D. , Vial Henri J. , Bienvenüe Alain 
Published: February 2005

AbstractUsing a recently described technique of electron spin resonance spectroscopy, we determined the rate of transbilayer mobility (flip) of the four major simian‐erythrocyte phospholipids in the erythrocyte membrane after infection by Plasmodium knowlesi. The development of the malarial parasite induces a very large increase in the flip rate of these phospholipids (mainly during the ring stage and at the beginning of trophozoite maturation). The half flip time fell from 2 and 3 hr in the case of choline phospholipids in healthy erythrocytes to less than 15 min in erythrocytes infected with the last stage of the parasite.