bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calpain activation in apoptosis
Authors: Squier Margaret K. T. , Miller Anita C. K. , Malkinson Alvin M. , Cohen J. John 
Published: February 2005

AbstractProgrammed cell death is an active process wherein the cell initiates a sequence of events culminating in the fragmentation of its DNA, nuclear collapse, and disintegration of the cell into small, membrane‐bound apoptotic bodies. Examination of the death program in various models has shown common themes, including a rise in cytoplasmic calcium, cytoskeletal changes, and redistribution of membrane lipids. The calcium‐dependent neutral protease calpain has putative roles in cytoskeletal and membrane changes in other cellular processes; this fact led us to test the role of calpain in a well‐known model of apoptotic cell death, that of thymocytes after treatment with dexamethasone. Assays for calcium‐dependent proteolysis in thymocyte extracts reveal a rise in activity with a peak at about 1 hr of incubation with dexamethasone, falling to background at approximately 2 hr. Western blots indicate autolytic cleavage of the proenzyme precursor to the calpain I isozyme, providing additional evidence for calpain activation. We have also found that apoptosis in thymocytes, whether induced by dexamethasone or by low‐level irradiation, is blocked by specific inhibitors of calpain. Apoptosis of metamyelocytes incubated with cycloheximide is also blocked by calpain inhibitors. These studies suggest a required role for calpain in both “induction” and “release” models of apoptotic cell death. © 1994 wiley‐Liss, Inc.
Progressive loss of sensitivity to endothelium‐derived growth inhibitors expressed by human melanoma cells during disease progression
Authors: Rak Janusz W. , Hegmann Erik J. , Lu Chao , Kerbel Robert S. 
Published: February 2005

AbstractTumor progression is frequently associated with changes in responsiveness of tumor cells to paracrine growth factors. A potential major source of such paracrine factors in solid tumors are endothelial cells since this type of cell can constitute a sizeable fraction of the cellular composition of solid tumors. As an initial step to examining the possible effects of endothelial cell‐associated growth factors on tumor cell growth, a panel of human melanoma cell lines representative of different stages of tumor progression was employed for studies utilizing endothelial cell‐derived growth modulators. Macrovascular or microvascular human endothelial cells from umbilical vein or from skin, respectively, inhibited melanoma cell growth in direct coculture experiments. The potency of this inhibitory effect diminished as a function of melanoma progression. Conditioned media from endothelial cell cultures mimicked the effect of the cell coculture experiments, suggesting the involvement of soluble growth factor(s). Approximately 50–75% of the conditioned media inhibitory effect was abrogated by addition of the neutralizing antibody to interleukin‐6 (IL‐6). Gel filtration chromatography revealed the presence of additional inhibitors in endothelial cell conditioned medium. Two peaks of activity were detected with apparent molecular weights of approximately 100–150 Kd and 20–30 Kd, the latter containing IL‐6 activity. Whereas early‐stage radial growth phase (RGP) primary tumor‐derived melanoma cells were sensitive to at least three different endothelial products of high or low molecular weight (including IL‐6), melanoma cells from more advanced metastatic lesions were resistant to the latter activities, and retained only partial sensitivity to the high molecular weight inhibitor. More advanced vertical growth phase (VGP) primary melanoma cell lines expressed intermediate inhibition‐sensitive phenotypes. Thus human melanoma development appears to be associated with progressive loss of sensitivity to the growth inhibitory effects of IL‐6 and other factors produced by endothelial cells. This is likely to be a result of a selection process when tumor cells are confronted with adjacent vasculature during the progress of tumor angiogenesis. © 1994 wiley‐Liss, Inc.
Temporal expression of myogenic regulatory genes during activation, proliferation, and differentiation of rat skeletal muscle satellite cells
Authors: Smith C. K. , Janney M. J. , Allen R. E. 
Published: February 2005

AbstractThe satellite cell is responsible for growth and repair of postnatal skeletal muscle. We investigated the expression of the myogenic regulatory gene (MRG) family in these cells in the stages from quiescence to fusion. Using polymerase chain reaction amplification of reverse‐transcribed RNA (RT‐PCR) isolated from adult rat satellite cells, we demonstrated a temporal sequence of gene activation, which is distinct from that previously observed in embryonic somitic cells. No MRG expression was detected in predominantly quiescent cells. MyoD is activated by 12 h in cell culture, prior to the first evidence of proliferation. MRF4 and myf‐5 appear by 48 h and may be associated with the first division cycle. Myogenin is not detectable until 72 h after satellite cell recovery from the muscle fiber, coincidental with the first evidence of differentiation. © 1994 wiley‐Liss, Inc.
Transforming growth factor‐β regulation of retinoblastoma gene product and E2F transcription factor during cell cycle progression in mouse fibroblasts
Authors: Kim Tae‐Aug , Ravitz Michael J. , Wenner Charles E. 
Published: February 2005

AbstractThe mechanism by which transforming growth factor beta (TGFβ) exerts growth stimulatory effects was examined in C3H/10T1/2 mouse fibroblasts by study of cell cycle regulation of the retinoblastoma gene product (p110Rb) and transcriptional regulation of the p110Rb‐associated transcription factor, E2F. Northern blotting analysis shows that TGFβ and/or epidermal growth factor (EGF) stimulate by three to sixfold the level of Rb mRNA which is also reflected by the increased levels of p110Rb. p110Rb becomes phosphorylated in mid‐G1 and further phosphorylated at the G1/S transition. Hyperphosphorylation of p110Rb by TGFβ can be observed when cells are in S phase. TGFβ stimulates by three to fourfold the activity of cdk2 kinase consistent with the observed phosphorylation of p110Rb and also with the possibilit that the kinase is involved in phosphorylating p110Rb close to the G1/S transition. Thus, TGFβ as a growth stimulator induces, as does EGF, the phosphorylation of p110Rb during cell cycle progression. Transient transfection of E2F promoter constructs was used to analyze the effect of TGFβ on the modulation of E2F‐mediated transcription. The data revealed that TGFβ can stimulate wild‐type adenoviral E2 promoter activity by 12‐fold. Taken together, TGFβ‐induced phosphorylation of p110Rb in mouse fibroblasts appears to exert a positive regulatory function upon genes that have a pivotal role in the G1/S transition of the cell cycle. © 1994 Wiley‐Liss, Inc.
Age and development‐related changes in osteopontin and nitric oxide synthase mRNA levels in human kidney proximal tubule epithelial cells: Contrasting responses to hypoxia and reoxygenation
Authors: Hwang Shiaw‐Min , Denhardt David T. , Wilson Patricia D. , Laskin Jeffrey D. 
Published: February 2005

AbstractOsteopontin (OPN) encodes a secreted glycosylated phosphoprotein containing a GRGDS motif that can mediate cell attachment through the αvβ3 integrin, and has recently been shown to down‐regulate nitric oxide synthase (NOS) expression. We report here that primary cultures of renal proximal tubule epithelial (PTE) cells prepared from human kidneys of different developmental stages and ages show a positive correlation between developmental age and the expression, at the mRNA level, of both OPN and constitutive NOS. However, OPN and NOS responded in different manners, as assessed by mRNA measurements, to hypoxia‐reoxygenation injury. The OPN mRNA level, assessed by Northern blotting, increased slightly during 60 min of hypoxia and more substantially during subsequent reoxygenation of primary PTE cells derived from the kidneys of young but not of aged donors. The abundance of NOS mRNA, measured using a cDNA probe to the constitutive form of the enzyme, was enhanced during hypoxia in kidneys derived from humans of all ages, and then decreased during reoxygenation—possibly as the result of increased OPN expression. PTE cells from aged kidneys are more susceptible to cell death under hypoxic conditions than PTE cells from young kidneys. An investigation of the effect of an oxidant on OPN and NOS mRNA levels revealed that within 30 min of exposure to H2O2, NOS mRNA levels decreased simultaneously with an increase in OPN mRNA levels. Nitric oxide (NO), the product of NOS, is at low levels an important signal transduction molecule participating in the regulation of vascular tone and renal reabsorption; at high levels it is cytotoxic. We suggest that the diminished ability of cells from old kidneys to down‐regulate NO production and to increase OPN expression after hypoxia‐reoxygenation may contribute to their increased susceptibility to oxidant injury. © 1994 Wiley‐Liss, Inc.
Correlation of transformation from epithelial to mesenchymal‐like morphology and endogenous bFGF levels in human nasopharyngeal carcinoma cells
Authors: Chen Jan‐Kan , Shen Ling‐Shang , Chao Hsiou‐Hsian 
Published: February 2005

AbstractCG‐1 human nasopharyngeal carcinoma cells in monolayer culture formed both cohesive, epithelial‐like colonies and scattered, fibroblastic‐like colonies in mixed proportions. In the presence of exogenously added bFGF (4 ng/ml), about 85% of the colonies formed were fibroblastic‐like. CG‐1 cells were capable of synthesizing and releasing bFGF, and, when compared by the immunological method, cells in fibroblastic‐like colonies were found to contain higher levels of endogenous bFGF than cells in the epithelial‐like colonies. Furthermore, cells in the peripheral region of the epithelial‐like colonies, which were fibroblastic‐like in morphology, also appeared to contain higher levels of endogenous bFGF. In addition, in the presence of suramin, neutralizing antibody to bFGF, or neutralizing antibodies to bFGF and EGF, the number of cohesive colonies formed was greatly increased. Moreover, addition of the 2 M NaCl‐eluted heparin‐Sepharose fraction of the CG‐1 cell‐coditioned medium promoted the formation of dispersed colony in a dose‐dependent manner. The results suggest that bFGF can regulate CG‐1 cell phenotype in an autocrine manner. © 1994 Wiley‐Liss, Inc.
Cleavage of the epidermal growth factor receptor by a membrane‐bound leupeptin‐sensitive protease active in nonionic detergent lysates of senescent but not young human diploid fibroblasts
Authors: Carlin Cathleen , Phillips Paul D. , Brooks‐Frederich Katherine , Knowles Barbara B. , Cristofalo Vincent J. 
Published: February 2005

AbstractNumerous studies suggest that epidermal growth factor (EGF) signaling is impaired in nonproliferating senescent human diploid fibroblasts downstream of receptor binding. One possible explanation for these results is that senescent cells possess unique enzymatic activities capable of regulating functional levels of the EGF receptor. To test that hypothesis, nonionic detergent lysates of young and senescent cells were compared for proteolytic activity directed towards the EGF receptor, and a protease that cleaves the 170 kDa EGF receptor was identified in lysates from senescent but not young cells. Although studies presented here were carried out with WI‐38 cells, our data indicate that other senescent fibroblasts possess a similar activity. The degradation product immunoprecipitated by a monoclonal antibody specific for an EGF receptor exocytosolic epitope had an approximate molecular weight of 100,000. This product was also detected following cell surface labeling with 125I, and by cross‐linking 125I‐EGF to intact cells with disuccinimidyl suberate. The proteolytic activity in senescent cell lysates was specifically inhibited by leupeptin and did not require divalent cations; it was also inactivated by aprotic solvents such as dimethylsulfoxide (DMSO) or ethylene carbonate. Interestingly, this protease was not active during ligand‐induced intracellular processing of the EGF receptor, suggesting that it does not normally function in endocytic or lysosomal compartments. The susceptibility of the protease to inactivation by cell surface trypsinization is consistent with a plasma membrane localization. Since EGF receptor cleavage is not observed unless senescent cells are solubilized with nonionic detergents, it seems likely that the protease is confined to specialized regions of the plasma membrane. Whether or not the EGF receptor is a physiologic target for this protease is unclear. Its expression at the cell surface is nevertheless significant, since it suggests there are mechanisms for regulating membrane‐bound proteins, or biologically active peptides in the extracellular space, in senescent cells that are either absent or inactive in young cells. © 1994 Wiley‐Liss, Inc.
Calmodulin‐like effect of oncomodulin on cell proliferation
Authors: Blum Janaki K. , Berchtold Martin W. 
Published: February 2005

AbstractOncomodulin (OM) is a Ca2+ binding protein (CABP) structurally closely related to parvalbumin. Expression of OM is restricted to early embryonic stages, the placental cytotrophoblasts, and neoplastic tissues. The function of OM as a calmodulin (CaM)‐like enzyme modulator is controversial. Two types of experiments demonstrate that OM may act in an analogous fashion to CaM in T14 and T10 cancerous cell lines, which both express OM. First, both OM transcript and protein levels increased at the G1/S boundary in a similar manner to CaM, though not to the same extent, in the chemically transformed rat fibroblast cell line T14 synchronized at mitosis by nocodazole. Second, antisense oligonucleotides specific to the OM ATG region inhibited growth of T14 in a similar dose‐dependent manner as observed with CaM‐specific antisense probes. © 1994 Wiley‐Liss, Inc.
cDNA from human ocular ciliary epithelium homologous to βig‐h3 is preferentially expressed as an extracellular protein in the corneal epithelium
Authors: Escribano Julio , Hernando Nati , Ghosh Sikha , Coca‐Prados Miguel , Crabb John 
Published: February 2005

AbstractThe non‐pigmented ciliary epithelium is largely responsible for the formation of aqueous humor in the mammalian eye. To provide a basis for studies at the molecular level, a directional expression cDNA library was constructed in Uni‐ZAP XR vector from poly A+ RNA of the human non‐pigmented ciliary epithelial derived ODM‐2 cell line. Fifty‐three cDNA clones were isolated from the library and characterized by partial sequence analysis. Approximately 49% of the clones exhibited homology with known genes in the GenBank/EMBL databases. The putative identification of these clones may reflect the transcriptional activity of the ODM‐2 cells in culture. One of the identified clones, ODM‐42‐I, was found to be specific and highly expressed in the corneal epithelium. This clone had an exact match with a recently discovered human gene, βig‐h3 (Skonier et al., 1992, DNA Cell Biol., 11: 511–522), which codes a surface recognition protein, inducible by transforming growth factor beta (TGF‐β), and containing a putative binding site (RDG) for integrins. The ODM‐42‐I cDNA clone displays a distinctive pattern of expression found in the human eye, expressed almost exclusively in the cornea. Further studies, using sera from a synthetic peptide to the carboxy‐terminal region of ODM‐42‐I, reveal that the protein is heterogeneous in charge and is preferenctially expressed on the extracellular surface of corneal epithelial cells, and might share immunologic properties with integrins β1. © 1994 Wiley‐Liss, Inc.
Prostaglandin‐stimulated second messenger signaling in bone‐derived endothelial cells is dependent on confluency in culture
Authors: Ida Rodney , Lee Austin , Huang Jason , Yamaguchi Dean T. , Brandi Maria Luisa 
Published: February 2005

AbstractNew bone formation is associated with an increase in blood flow by the invasion of capillaries. Endothelial cells that line the capillaries can produce paracrine factors that affect bone growth and development, and in turn, could be affected by products produced by bone cells, in particular the osteoblasts. Since osteoblasts produce prostaglandins E2 and F2α (PGE2, PGF2α), it was investigated if these PGs were agonists to bone‐derived endothelial cells (BBE) by assessing changes in cAMP and free cytosolic calcium concentration ([Ca2+]i) second messenger generation. We found that confluent cultures of BBE cells, a clonal endothelial cell line derived from bovine sternal bone, responded to 1 μM PGE2 by an increase in cAMP. PGF2α at the same concentration was less potent in stimulating an increase in cAMP production in confluent BBE cells. Subconfluent cells with a morphology similar to that of fibroblastic cells were not as sensitive to PGE2‐stimulated cAMP generation. PGF2α failed to elicit any cAMP production in subconfluent cultures. PGE2 and PGF2α both stimulated an increase in [Ca2+]i concentration in a dose‐dependent manner. The potency of PGE2 was similar to that of PGF2α in stimulating an increase in [Ca2+]i. The Ca2+ response was mostly independent of extracellular Ca+, was unchanged even with prior indomethacin treatment, was unaffected by caffeine pretreatment, but was abolished subsequent to thapsigargin pretreatment. The PG‐induced increase in [Ca2+]i was also dependent on the confluency of the cells. In a subconfluent state, the responses to PGE2 or PGF2α were either negligible, or only small increases in [Ca2+]i were noted with high concentrations of these two PGs. Consistent, dose‐dependent increases in [Ca2+]i were stimulated by these PGs only when the cells were confluent and had a cobblestoned appearance. Since it was previously demonstrated that BBE cells respond to parathyroid hormone (PTH) by the production of cAMP, we tested if bovine PTH(1‐34) amide bPTH(1—34) also increased [Ca2+]i in these cells. No change in [Ca2+]i was found in response to bPTH (1—34), although bPTH (1—34) stimulated a nine to tenfold increase in cAMP. We conclude that BBE cells respond to PGE2 and PGF2α but not to bPTH(1—34) by an increase in [Ca2+]i probably secondary to stimulation of phospholipase C and that the cAMP and [Ca2+]i second messenger responses in BBE cells are dependent on the state of confluency of the cells. © 1994 Wiley‐Liss, Inc.
Thyroid‐induced changes in the growth of the Liver, Kidney, and Diaphragm of Neonatal Rats
Authors: Canavan James P. , Holt Janet , Easton Juliet , Smith Kaye , Goldspink David. F. 
Published: February 2005

AbstractEu‐, hypo‐ and hyper‐thyroid rats were studied 12 days postpartum. Hypothyroidism was induced by administering propylthiouracil (PTU) via the mother's drinking water beteen late gestation and throughout lactation. This procedure effectively blocked the normal early postnatal surge of T3 and T4. In contrast, hyperthyroidism was induced in the young pups by daily injections of T4 from day 3 postpartum. The effects of these experimental manipulations of thyroid status on the rates of protein turnover and growth of the liver, kidney, and diaphragm were studied and compared with measurements made on appropriate euthyroid control tissues. Tissue rates of protein synthesis were decreased in response to hypothyroidism with consequent growth retardation of all three tissues and the whole animal. In contrast, the three body tissues responded very differently to the induction of hyperthyroidism. Hepatic rates of protein synthesis and growth were completely unaffected by thyroid excess. The response of the diaphragm was essentially the reverse of that seen with hypothyroidism, i.e., the enhanced rates of protein synthesis and protein degradation leading to muscle hypertrophy. The rates of protein turnover in the kidney were also increased, but unlike the diaphragm the net result was renal atrophy. Clearly, thyroid hormones influence the normal rapid growth of the neonate and its individual tissues. However, beyond a certain concentration the threshold of responsiveness to these hormones seems to vary between individual tissues. © 1994 Wiley‐Liss, Inc.
Growth and intestinal differentiation are independently regulated in HT29 colon cancer cells
Authors: Schroy Paul C. , Rustgi Anil K. , Ikonomu Ekaterini , Liu Xiu P. , Polito Joseph , Andry Chris , O'Keane J. Connor 
Published: February 2005

AbstractThe polar‐planar compound hexamethylene bisacetamide (HMBA) can inhibit HT29 colon carcinoma cell growth and induce a more benign phenotype, as defined by decreased anchorage‐independent clonogenicity, loss of a cell surface malignancy marker, and decreased in vivo tumorigenicity. The principle aim of this study was to determine whether HMBA's effects on HT29 cell growth and biologic behavior correlate with effects on intestinal differentiation. Parallel studies were performed with sodium butyrate (NaBT), a potent inducer of intestinal differentiation HT29 cell growth, proliferation, and markers of intestinal differentiation were assayed after short‐ and long‐term treatment with HMBA, NaBT, or the combination. Both 5 mM HMBA and 5 mM NaBT were potent inhibitors of monolayer growth; in combination their effects were nearly additive. Inhibition of DNA synthesis was detectable within 6 h of treatment and was preceded by down‐regulation of c‐myc expression. Soft agar clonogenicity was also decreased by 90%, > 99%, and > 99% by HMBA, NaBT, and the combination, respectively. Despite these parallel effects on growth and in vitro markers of a benign phenotype, effects on intestinal differentiation were discordant. NaBT induced significant increases in membrane‐associated alkaline phosphatase activity, cytosolic mucin content, PAS+/diastase‐resistant cells, and ultrastructural evidence of intestinal cell differentiation. HMBA not only failed to induce markers of intestinal differentiation, but attenuated NaBT's effects when used in combination. These data suggest that growth and intestinal differentiation may be independently regulated in HT29 cells. They also suggest that expression of intestinal markers of differentiation is not a prerequisite for the acquisition of a more benign phenotype. © 1994 Wiley‐Liss, Inc.
Modulation of potassium channels by protein tyrosine kinase inhibitors
Authors: Saad A. H. , Kuo S. S. , Koong A. C. , Hahn G. M. , Giaccia A. J. 
Published: February 2005

AbstractExposure of non‐excitatory cells to the tyrosine kinase (PTK) inhibitors, genistein, herbimycin A, and tyrphostin, induced at least two families of K+ currents. The first, a TEA‐insensitive slow‐inactivating K+ current, is induced within 3 min following treatment with 140 mM genistein or 100 nM herbimycin A. The second current, a TEA‐sensitive delayed rectifier, is induced within 30 min following treatment with 50 mM genistein or 10 nM herbimycin A. Currents with similar biophysical and pharmacological characteristics are induced in these cells following exposure to ionizing radiation. The radiation‐induced currents are inhibited by pretreatment with the free radical scavenger, N‐Acetyl L‐Cysteine, or by pretreatment with the protein kinase C inhibitor, staurosporine; those induced by PTK inhibitors are not. The latter, therefore, do not appear to be mediated through free radicals or require serine/threonine phosphorylation for activation. Once the channels are activated by the PTK inhibitors, phosphorylation of the channel at serine/threonine residues results in slower inactivation of the induced current. We propose that protein tyrosine phosphorylation of the K+ channel protein itself or of a factor that interacts with it maintains the K+ channels of non‐excitatory cells in a closed state. Following exposure to ionizing radiation, free radical‐induced activation of serine/threonine kinase(s) results in phosphorylation of the channel and/or inactivation of a tyrosine kinase that in turn leads to activation of the K+ channels. © 1994 Wiley‐Liss, Inc.