bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of amino acid‐induced changes in ion fluxes in the regulation of hepatic protein synthesis
Authors: Rivas Teresa , Urcelay Elena , González‐Manchón Consuelo , Parrilla Roberto , Ayuso Matilde S.
Published: February 2005

Alanine is a powerful stimulator of hepatic protein synthesis whose mechanism of action has not yet been ascertained. The present work aimed to elucidate whether rate changes in ion fluxes accompanying the transport of this amino acid could play a role in the stimulation of protein synthesis. In perfused livers, the utilization of alanine produced a net uptake of K+ of 1.5 μMol/min/liver, a progressively increasing efflux of Ca2+ to reach a maximum of 0.9 μMol/min/liver, and alkalization of the extracellular medium. Inhibition of Na+/K+ exchange by ouabain reversed only the uptake of K+, indicating that this is the main way for the efflux of Na+ cotransported with alanine. In isolated hepatocytes, the uptake of alanine increased the intracellular content of K+ and the cell volume. The following observations suggest that these changes, and not an increased intracellular concentration of Na+, are associated with the stimulation of protein synthesis: 1) Ouabain inhibited the alanine stimulation of L‐[3H]‐valine incorporation into protein without altering the basal rate of protein labeling; 2) ouabain had no effects on alanine uptake indicating that Na+ influx is not involved in the alanine stimulation of protein synthesis; 3) disruption of Na+ gradient across the plasma membrane by specific ionophores, monensin and gramicidin D, inhibited both basal and alanine‐stimulated protein synthesis, but substitution of extracellular Na+ by K+ did not prevent the stimulatory action of alanine. The observation that hypotonic buffer enhanced protein synthesis to the same degree than alanine in liver cells indicates that alanine‐induced cell swelling could be sufficient to stimulate protein synthesis. © 1995 Wiley‐Liss, Inc.
Calcium signal induced by mechanical perturbation of osteoclasts
Authors: Xia Shen‐Ling , Ferrier Jack
Published: February 2005

Multinucleated osteoclasts from rabbit long bone, 1–6 days in culture, respond to mechanical perturbation with a transient increase of intracellular calcium concentration ([Ca2+]i), as measured with the fluorescent indicator fluo‐3 on a confocal laser scanning microscope. In experiments with different extracellular calcium concentrations (from 11.8 mM to calcium‐free), the incidence, the magnitude, and the duration of [Ca2+]i responses decreases with decreasing bathing [Ca2+]. Following mechanical perturbation, a thapsigargin‐induced [Ca2+]i response has a lower magnitude than the thapsigargin‐induced response without mechanical perturbation. In thapsigargin‐pretreated osteoclasts the mechanical perturbation‐induced rise in [Ca2+]i is larger and longer than in control cells. Ni2+ inhibits the incidence and decreases both the magnitude and the duration of the responses, while nifedipine, verapamil, and Gd3+ have no effect. These measurements show that rabbit osteoclasts transduce a mechanical perturbation of the cell membrane into a [Ca2+]i signal via both a calcium influx and an internal calcium release. © 1995 Wiley‐Liss, Inc.
Tyrosine kinases are involved with the expression of inducible nitric oxide synthase in human articular chondrocytes
Authors: Geng Yu , Maier Rainer , Lotz Martin
Published: February 2005

The present study characterizes mechanisms involved with the induction of nitric oxide (NO) production, nitric oxide synthase (NOS) enzymatic activity and mRNA expression in human articular chondrocytes. Activation of chondrocytes with lipopolysaccharide (LPS) or IL‐1 resulted in time‐ and dose‐dependent increases in iNOS mRNA followed by increased NOS enzymatic activity and NO release. The protein tyrosine kinase (PTK) inhibitors herbimycin A or genistein reduced IL‐1 or LPS‐induced NO release and NOS enzymatic activity. This was associated with inhibition of iNOS mRNA expression as determined by reverse transcription‐polymerase chain reaction (RT‐PCR) and in situ hybridization. In contrast, inhibitors of protein kinase C (PKC) or protein kinase A (PKA) did not affect these responses. These results were confirmed in experiments with second messenger agonists where neither activation of PKC, nor increases in cyclic adenosine monophosphate (cAMP) or increased intracellular calcium levels were associated with the induction of iNOS mRNA or NO release. These results suggest that PKC, PKA and calcium‐dependent signals are not required or sufficient for the stimulation of NO production. However, NO production is dependent on tyrosine kinases due to their role in the expression of iNOS mRNA. © 1995 Wiley‐Liss, Inc.
Cell cycle reentry of mammalian fibroblasts is accompanied by the sustained activation of P44mapk and P42mapk isoforms in the G1 phase and their inactivation at the G1/s transition
Authors: Meloche Sylvain
Published: February 2005

Mitogen‐activated protein (MAP) kinases are serine/threonine kinases that are rapidly activated in response to mitogenic stimuli. Here we examined the enzymatic activity and phosphorylation state of the individual p44mapk and p42mapk isoforms during early G1 and late G1 phase of the mammalian cell cycle. Release of fibroblast cells from early G1 block was accompanied by a rapid rise in the myelin basic protein (MBP) kinase activity of p44mapk and p42mapk, which declined slowly over several hours to reach negligible values as cells enter S phase. When cells were released from late G1 block, the activity of p44mapk and p42mapk increased transiently, and then rapidly declined to baseline values during G1 to S phase transition. Cells released at the G1/S boundary in a medium lacking growth factors entered S phase in the complete absence of MAP kinase activity. Unlike MAP kinases, the histone H1 kinase activity of p33cdk2 was elevated in late G1‐arrested cells and continued to increase during S phase entry. The enzymatic activation of p44mapk and p42mapk in both early G1 and late G1 phase was accompanied by an increase in the phosphothreonine and phosphotyrosine content of the proteins. These findings suggest that the sustained activation of MAP kinases during G1 progression and their inactivation at the G1/S transition are two regulatory processes involved in the mitogenic response to growth factors. © 1995 Wiley‐Liss, Inc.
Correlation between the number of melanosomes, tyrosinase mrna levels, and tyrosinase activity in cultured murine melanoma cells in response to various melanogenesis regulatory agents
Authors: Ando Hideya , Itoh Akira , Mishima Yutaka , Ichihashi Masamitsu
Published: February 2005

Tyrosinase is the rate limiting enzyme critically associated with melanin synthesis. The melanosomes are specialized membrane‐bound organelles within melanocytic cells in which melanin polymers are ultimately deposited. To determine whether tyrosinase correlates with the number of melanosomes, we examined the relationship between tyrosinase activity, tyrosinase mRNA levels, and the number of melanosomes in B16 murine melanoma cells, using melanogenesis regulatory agents. 12‐O‐Tetradecanoylphorbol‐13‐acetate (TPA) or linoleic acid decreased tyrosinase activity, while dibutyryl cyclic adenosine monophosphate (dbcAMP) or palmitic acid increased it. The tyrosinase mRNA levels were not always correlated with tyrosinase activity, i.e., TPA down‐regulated, dbcAMP upregulated, while linoleic acid or palmitic acid did not alter the message levels, indicating that fatty acid regulation of melanogenesis was due to post‐transcriptional events. The number of melanosomes changed when agents which modulate the tyrosinase gene expression were added, since TPA decreased, dbcAMP increased, and linoleic acid or palmitic acid did not alter their number. These results suggest that the number of melanosomes changed in relation to tyrosinase mRNA level but not to tyrosinase activity in response to melanogenesis regulatory agents. © 1995 Wiley‐Liss, Inc.
Use of a new fluorescent probe, seminaphthofluorescein‐calcein, for determination of intracellular pH by simultaneous dual‐emission imaging laser scanning confocal microscopy
Authors: Zhou You , Marcus Elizabeth M. , Haugland Richard P. , Opas Michal
Published: February 2005

A new pH indicator, seminaphthofluorescein (SNAFL)‐calcein acetoxymethyl ester, was used for intracellular pH (pHi) measurement in living MDCK cells with a laser scanning confocal microscope (LSCM) equipped with an Argon/Krypton laser and dual‐excitation and dual‐emission (FITC/Texas Red) filter set. SNAFL‐calcein excitation maxima are ∼492/540 nm (acid/base) and emission maxima are ∼535/625 nm (acid/base) with a pKa value at ∼7.0. The absorption/emission spectra of SNAFL‐calcein indicate that the ratio of emission intensities of its basic/acidic forms is pH dependent. With an Argon/Krypton LSCM, we were able to monitor the acidic and basic forms of this dye simultaneously using dualexcitation (488/568 nm) and dual‐emission (525–614 nm/∼615 nm) wavelengths (λs). The simultaneous dual‐excitation/emission LSCM system allows for efficient recording of pHi dynamics (time resolution ≈︁ 1 sec) in living cells. We have analyzed emission stability of the dye at different temperatures (22°C and 37°C) and constant pH, and at the same temperature (22D°C) but various pHs (6.6, 7.0, and 7.4). Bleaching rate is slightly higher at 37°C than that at 22°C. The basic form of the dye (λEm ≈︁ 625 nm) has a slightly higher bleaching rate than the acidic form (λEm ≈︁ 535 nm) in standard culture medium (pH 7.3) at either 22°C or 37°C. The pHi in MDCK cells calculated from ratio images (535 nm/625 nm) was 7.19 ± 0.03 (mean ± SEM, n = 20). Calibration experiments show that the useful pH range of SNAFL‐calcein appears to be between 6.2 and 7.8, as the dye is difficult to calibrate outside this pH range. © 1995 Wiley‐Liss, Inc.
Regulation of AP‐3 enhancer activity during hematopoietic differentiation
Authors: Adler Victor , Kraft Andrew S.
Published: February 2005

Phorbol ester treatment of the human leukemic cell line U937 induces macrophage differentiation over 24–28 hr. This differentiation is mediated by the activation and/or repression of specific gene transcription by proteins, enhancer binding factors, that bind to the DNA upstream of the start site of transcription. We find that differentiation of U937 cells induced by phorbol eters and bryostatin 1, activators of protein kinase C, and the phosphatase inhibitor, okadaic acid, stimulates transcription from an enhancer sequence which contains multimerized AP‐3 binding sequences but not from one that contains multimerized AP‐2 binding motifs. Electrophoretic mobility shift assays (EMSA) demonstrate that AP‐3 DNA binding activity peaks at 24 hr, remains elevated for 24 hr, and then decreases thereafter. Southwestern blotting demonstrates that the AP‐3 enhancer sequence binds to a 48 kDa protein present in these leukemic cells. Because the AP‐3‐oligomer also contains an overlapping NF‐kB‐like site, the role of NF‐kB proteins in regulating transcription from this multimerized oligonucleotide was investigated. Transfection of U937 cells with NF‐kB family members demonstrated activation of AP‐3‐mediated transcription by rel A but little effect induced by NFKB1 and c‐rel. It is unlikely, however, that phorbol ester‐induced transcription from this AP‐3 sequence is solely mediated by this NF‐kB family member since treatment of U937 cells with antisense rel A oligodeoxynucleotides did not block phorbol ester‐mediated transcription from the AP‐3 site. These data demonstrate that AP‐3, but not AP‐2 sequences, functions to activate mRNA transcription during phorbol ester‐induced hematopoietic differentiation and suggests a complex interaction between NF‐kB and AP‐3 proteins in the regulation of this enhancer element. © 1995 Wiley‐Liss, Inc.
Effects of hypotonic and hypoionic media on drug pumping by P‐glycoprotein expressed in epithelial and nonepithelial cell lines
Authors: Ambasch Karina , Cabantchik Z. Ioav , Slotki Itzchak N.
Published: February 2005

The effects of anisotonic and anisoionic media on the drug‐pumping function of P‐glycoprotein (Pgp) were studied in epithelial and nonepithelial cells. We used HT‐29 colon cells (HT‐29/Pgp−) induced to express Pgp and MDR phenotype (HT‐29/Pgp+) and NIH3T3 (3T3/Pgp−) cells which were stably transfected with human MDR1 DNA (3T3/Pgp+). Intracellular concentrations of rhodamine 123 (R‐123) preloaded into cells were monitored as a function of time by fluorescence imaging microscopy, while cells were superfused with media of different tonicity and/or ionic strength. Efflux was analyzed by a single exponential decay function. In all media tested efflux was considerably higher in Pgp+ than Pgp− cells. In both HT‐29 and 3T3 cells loaded with dye in isotonic conditions, dye efflux was not significantly different whether it was measured in isoionic‐isotonic (130 mM NaCI, 300 mOsm), hypoionic‐isotonic (87 mM NaCI), or hypoionic‐hypotonic (200, 150, or 100 mOsm) media throughout the entire experiment or whether the media were changed during the experiment. Similar results were obtained when cells were preincubated and preloaded with dye under hypotonic conditions. Under extreme hypotonic and hypoionic challenge (changing from 130 mM NaCI‐300 mOsm to 43 mM NaCI‐100 mOsm medium), 3T3 cells, but not HT‐29 cells, underwent marked shape and size changes which reduced R‐123 cell‐associated fluorescence. The changes were most conspicuous in Pgp+ cells, possibly reflecting a Pgp effect on the osmotic or osmoregulatory properties of the cells. However, drug‐pumping activity remained essentially unimpaired even under the most extreme hypotonic/hypoionic conditions. © 1995 Wiley‐Liss, Inc.
Ca2+‐Atpase inhibitor, cyclopiazonic acid, releases Ca2+ from intracellular stores in rbl‐2h3 mast cells and activates a Ca2+ influx pathway that is permeable to sodium and manganese
Authors: Falcone Daniel , Fewtrell Clare
Published: February 2005

Cyclopiazonic acid has been reported to inhibit the Ca2+‐ATPase of intracellular calcium stores in some nonexcitable cell types, such as myeloid cells and lymphocytes. The present study examines the effects of cyclopizonic acid on rat basophilic leukemia (RBL) cells, a mucosal mast cell line. Addition of cyclopiazonic acid to fura‐2‐loaded RBL cells evoked a biphasic increase in free ionized intracellular calcium. Release of stored calcium accounted for the first phase of this response. The second phase was determined to be calcium entering through an influx pathway activated by cyclopiazonic acid. The influx pathway was selective for calcium, But was somewhat permeable to manganese. However, in a Ca2+‐free solution containing EGTA, sodium ions permeated freely. This influx pathway appears to be identical to that which is activated by antigen, the physiological stimulus to the cells. Cyclopiazonic acid also induced secretion when combined with the phorbol ester 12‐0‐tetradecanoyl phorbol 13‐acetate, which activates protein kinae C. © 1995 Wiley‐Liss, Inc.
Induction of intercellular adhesion molecule‐1 by monocyte adhesion to endothelial cells in human culture system
Authors: Combe Christian , Duplàa Cecile , Couffinhal Thierry , Moreau Catherine , Bonnet Jacques
Published: February 2005

Increased monocyte adhesion to the endothelial lining of blood vessels by cytokine‐inducible adhesion proteins is a crucial event in inflammatory processes. Moreover, adherence is known to induce cytokine gene expression, suggesting a possible positive feedback mechanism. Therefore, we determined whether monocyte adhesion to endothelial cells (ECs) amplifies their adhesion by inducing intercellular adhesion molecule 1 (ICAM‐1), and whether such positive feedback mechanism could be mediated by secretion of interleukin‐1 (IL‐1). Using monocyte‐EC couples obtained after monocyte adhesion to ECs, and methods of quantitative polymerase chain reaction and immunofluorescence flow cytometry, we showed a biphasic increase of ICAM‐1 mRNA content (2 and 16 hours) and a time‐dependent increase of cell surface expression of ICAM‐1, mainly on ECs, and couple adhesiveness, after monocyte adhesion to ECs. Anti‐ICAM‐1 monoclonal antibody inhibited 63% of the enhancement of adhesiveness induced on monocyte‐EC couples by previous monocyte adhesion, suggesting that monocyte adhesion to ECs induces an increase of couple adhesiveness which is partially dependent on the ICAM‐1 pathway. The early ICAM‐1 mRNA induction was associated with a fast induction of IL‐1b̃ mRNA and a 7.7‐fold increase in IL‐1b̃ protein in supernatant. However, 30% of this 2‐hour ICAM‐1 mRNA peak was abolished by recombinant soluble human IL‐1 receptor, suggesting that the early ICAM‐1 overexpression was partially mediated by IL‐1b̃, and could be induced directly by adherence. The second ICAM‐1 mRNA peak was accompanied by a marked increase in IL‐1b̃ mRNA and protein secretion (2.6 ng/ml). The binding to ICAM‐1 did not appear to directly stimulate IL‐1b̃ synthesis. These results indicate that monocyte adhesion to endothelial cells appears to stimulate their own recruitment via induction of ICAM‐1 thereby constituting a self‐perpetuating positive feedback system. © 1995 Wiley‐Liss, Inc.
Secretion of plasminogen activator and lysosomal enzymes from mouse skeletal muscle: Effect of denervation
Authors: Von Steyern Fredrik Vult , Josefsson Jan‐Owe
Published: February 2005

Levels of hydrolytic enzymes increase in skeletal muscle after denervation and their activities in the extracellular matrix appear to be important for interaction between muscle and nerve. Using enzymatic assays for b̃‐glucuronidase, b̃‐galactosidase, and plasminogen activator, we show that secretion of these enzymes from mouse skeletal muscle increases after denervation and that drugs interfering with the secretory pathway or the reuptake of enzymes modulate this release. Thus, brefeldin A inhibited secretion of plasminogen activator activity and mannan increased secreted amounts of b̃‐glucuronidase, but not of b̃‐galactosidase, in denervated muscle. In innervated muscle, brefeldin A decreased secreted activity of plasminogen activator, but mannan had no effect on secretion of either b̃‐glucuronidase or b̃‐galactosidase. Furthermore, secretion of plasminogen activator was temperature dependent. These observations, together with previous studies, suggest that secretion of hydrolytic enzymes from adult skeletal muscle may be of physiological significance in nerve‐muscle communication. © 1995 Wiley‐Liss, Inc.
Two nuclear proteins in tracheal epithelial cells are recognized by antibodies specific to a squamous differentiation marker, sprl
Authors: Tesfaigzi Johannes , An Gang , Wu Reen , Carlson Don M.
Published: February 2005

In cell‐free translations of RNA from primary cultures of pig trachea surface epithelial cells we observed that a mRNA encoding a 20kDa proline‐rich protein (sPRP) was dramatically induced during culturing (Tesfaigzi et al., 1990, Biochem. Biophys. Res. Commun., 172:M1304–1309). This mRNA was no detected in tracheal tissue or in epithelial cells prior to culturing. Antisera were raised to synthetic peptide sequences corresponding to 23 amino acids on the C‐terminus (C23‐antiserum) and 29 amino acids on the N‐terminus (N29 antiserum) of sPRP. On Western blot analysis, C23 antiserum reacted with a 20 kDa protein in cytosolic extracts from pig tracheal cells maintained in culture for 4 days. The reaction with the 20 kDa protein was inhibited by adding C23 peptide. Two nuclear proteins (66 and 70 kDa) obtained by micrococcal nuclease treatment of tracheal cell nuclei were detected on Western blots with C23 antiserum. These proteins were present in cells both before and after culturing. Sucrose gradient fractionation indicated that these nuclear proteins are associated with chromatin. Small amounts of the 66 and 70 kDa proteins were obtained from nuclear matrix fractions. These nuclear proteins also reacted with N29 antiserum. Since these proteins share similar epitopes with the N‐ and C‐termini of sPRP, it is likely that the 20 kDa protein (sPRP) is part of these proteins. However, purification of the nuclear proteins followed by an amino acid sequence analysis is necessary to clarify whether sPRP is part of these proteins. © 1995 Wiley‐Liss, Inc.
Synergistic interaction of interleukin‐1β and growth factors in primary cultures of rat aortic smooth muscle cells
Authors: Bourcier Todd , Dockter Michael , Hassid Aviv
Published: February 2005

Activated macrophages release cytokines and growth factors that may contribute to the growth of vascular smooth muscle cells in injured blood vessels. In the present study, we investigated the interactions between interleukin‐1b̃ (IL‐1b̃) and basic fibroblast growth factor (FGF‐2) in primary rat aortic smooth muscle cells, relative to their effects on DNA synthesis and cell proliferation. We report that femtomolar levels of IL‐1b̃, which alone were non‐mitogenic or weakly mitogenic, synergistically increased FGF‐2‐induced [3H]thymidine incorporation and cell proliferation. The potentiating effect of IL‐1b̃ extended to PDGF‐AB and EGF, but not to IGF‐1‐induced thymidine incorporation. An antagonist of the IL‐1 receptor, IL‐1ra, blocked the co‐mitogenic effect of IL‐1b̃. Stimulation of cells with FGF‐2 and IL‐1b̃ increased both DNA content and proliferation, an observation that was consistent with the thymidine incorporation experiments. An inhibitor of NO synthase, N5‐iminoethyl L‐ornithine (L‐NIO), did not block the co‐mitogenic effect of IL‐1b̃, despite effective inhibition of NO synthase activity, suggesting that the synergistic interaction between IL‐1b̃ and FGF‐2 was independent of the NO/cGMP pathway. The mechanism of co‐mitogenesis appeared to be independent of the intermediacy of PDGF‐AA, IL‐6, and prostanoids, and was not associated with increased levels of c‐fos mRNA, FGF receptor‐1 protein, or FGF‐2‐induced early and delayed tyrosine phosphorylation events. We conclude that IL‐1b̃ interacts with FGF‐2 to amplify the proliferation of primary rat aortic smooth muscle cells, an effect that may be important in vascular smooth muscle cell proliferation following vascular injury. © 1995 Wiley‐Liss, Inc.
Tenascin‐C induction by the diffusible factor epidermal growth factor in stromal‐epithelial interactions
Authors: Sakai Takao , Ohta Masatsugu , Furukawa Yusuke , Saga Yumiko , Aizawa Shinichi , Kawakatsu Hisaaki , Saito Masaki
Published: February 2005

Tenascin‐C, a six‐armed extracellular matrix glycoprotein, is expressed in a temporally and spatially restricted pattern during carcinogenesis and invasion or metastasis of carcinoma cells in association with stromal‐epithelial interactions. The human epidermoid carcinoma‐derived cell lines, A431 and HEp‐2, which do not express tenascin‐C by themselves in vitro, do express tenascin‐C after transplantation into nude mice, and transforming growth factor β1 (TGF‐β1) induces them to express tenascin‐C in vitro. Epidermal growth factor (EGF) induced tenascin‐C in these cells more effectively (about 3.5‐fold greater) than did TGF‐β1. Hepatocyte growth factor (HGF) and platelet‐derived growth factor (PDGF) had little effect on the induction of tenascin‐C. EGF also induced other extracellular matrix components, fibronectin and laminin. Tenascin‐C was also induced when the carcinoma cells were co‐cultured with embryonic fibroblasts from mice which were homozygous for a null mutation in the tenascin‐C gene, or when the conditioned medium from these cells was added. The induction of tenascin‐C in the co‐culture was reduced by treating the cells with antibodies against EGF or its receptor. The addition of EGF caused both cell types to disrupt their cytoskeleton and focal contacts as evidenced by the loss of stress fibers and vinculin plaques. EGF did neither induce tenascin‐C nor affect the morphology in tenascin‐C‐nonproducing A549 carcinoma cells, which did not produce tenascin‐C after transplantation. Thus, EGF induces tenascin‐C in tenascin‐C‐nonproducing human carcinoma cells through EGF receptors. Furthermore, in stromalepithelial interactions, the diffusible factor EGF participates in the induction of human tenascin‐C in these cells through EGF receptors. © 1995 Wiley‐Liss Inc.
Increased tumorigenicity in the human pancreatic cell line MIA PaCa‐2 Is associated with an aberrant regulation of an IGF‐1 autocrine loop and lack of expression of the TGF‐β type RII receptor
Authors: Freeman James W. , Mattingly Cynthia A. , Strodel William E.
Published: February 2005

The growth characteristics associated with tumorigenicity were determined in clones of MIA PaCa‐2 and PANC‐1 pancreatic carcinoma cells. MIA PaCa‐2 cells differed from PANC‐1 cells in that they rapidly formed tumors in nude mice, formed colonies more rapidly and formed larger colonies in soft agar, and were cloned more efficiently when seeded at low density. MIA PaCa‐2 cells but not PANC‐1 cells were stimulated to escape quiescence and undergo DNA synthesis with nutrient media lacking growth factors. Both cell lines were stimulated to proliferate with serum‐free media containing EGF, transferrin, and insulin. Antibody neutralization assays indicated that an IGF‐1 autocrine loop was required for the nutrient stimulation of growth in MIA PaCa‐2 cells and for the growth‐factor stimulation in both MIA PaCa‐2 and PANC‐1 cells. Both cell lines were stimulated to proliferate with exogenous IGF‐1 in basal media; this stimulation was specifically blocked by antibodies to IGF‐1 or its receptor. MIA PaCa‐2 and PANC‐1 cells expressed similar levels of IGF‐1 receptor mRNA and showed similar binding kinetics in receptor binding assays. In contrast to PANC‐1 cells, MIA PaCa‐2 cells were insensitive to TGF‐β1 and did not express TGF‐β receptor type II. The results suggest that the growth‐factor independence is representative of a more tumorigenic phenotype. We hypothesize that growth‐factor independence of MIA PaCa‐2 cells is mediated by an aberrant regulation of an IGF‐1 autocrine loop. A decreased regulation of this IGF‐1 loop may be potentiated by loss of response to TGF‐β. © 1995 Wiley‐Liss Inc.
Retinoic acid nuclear receptor β inhibits breast carcinoma anchorage independent growth
Authors: Li Xiao‐Su , Shao Zhi‐Ming , Sheikh M. Saeed , Eiseman Julie L. , Sentz Dorothy , Jetten Anton M. , Chen Jian‐Chyi , Dawson Marcia I. , Aisner Seena , Rishi Arun K. , Gutierrez Peter , Schnapper Lauren , Fontana Joseph A.
Published: February 2005

Retinoids modulate cellular proliferation and mediate gene function through a series of nuclear receptors. The retinoic acid nuclear receptor β (RARβ) plays an important role in the differentiation of a number of cell types. We now demonstrate that RARβ expresion is confined to normal mammary tissue and is not expressed in either immortalized normal or malignant cell lines. Treatment of RARβ‐transfected MDA‐MB‐231 cells with 1 μM all‐trans‐retinoic acid (RA) significantly inhibited monolayer growth of the cells which express recombinant RARβ. RARβ‐expressing MDA‐MB‐231 cells formed significantly smaller and fewer colonies soft agar than the mock‐transfected cells. Addition of 1 μM RA stimulated colony size and number in the RARβ‐transfected MDA‐MB‐231 cells. In contast to the RARβ‐expressing cells, colony formation by the RARβ‐expressing cells was similar to the mock‐transfected controls and the addition of 1 μM RA to the RARα‐transfected cells inhibited colony formation. While demonstrating decreased colony formation in agar, RARβ‐expressing MDA‐MB‐231 cells failed to exhibit decreased growth in SCID mice. Our results show that RARβ functions as a negative regulator of growth in breast epithelial cells. In addition, the growth of these cells is differentially regulated by RARα and RARβ which is most likely the result to the modulation of different genes. © 1995 Wiley‐Liss Inc.
Clonal heterogeneity of the sensitivity of human colon carcinoma cell lines to TGFβ isoforms
Authors: Zhou Guo‐Hao K. , Sechrist Gwendolyn L. , Brattain Michael G. , Mulder Kathleen M.
Published: February 2005

Spontaneously arising, TGFβ1‐resistant colonies were isolated directly from the soft agarose plates of MOSER human colon carcinoma cells grown in the presence of TGFβ1 but in the absence of serum. The colonies were cloned by limiting dilution and screened in a monolayer proliferation assay for sensitivity to TGFβ1 and TGFβ2 isoforms. Cell clones selectively sensitive or resistant to these isoforms in the growth inhibition assay displayed similar differential sensitivities to TGFβ isoforms for production of the extracellular matrix proteins laminin and fibronectin, as well as for the expression of the colon cell differentiation marker carcinoembryonic antigen. Differential receptor binding profiles for TGFβ1 and TGFβ2 were observed among the clones. The isolation of cell clones selectively resistant or sensitive to TGFβ isoforms as well as the identification of differential receptor binding profiles among the clones indicate the heterogeneity of TGFβ responsiveness that exists naturally in human colon tumor cells and stress the importance of defining mechanisms underlying differential responsiveness to TGFβ isoforms. © 1995 Wiley‐Liss Inc.
Ornithine decarboxylase activity is associated with proliferation but not with T3‐induced differentiation of Caco‐2 cells
Authors: Jumarie Catherine , Malo Christiane
Published: February 2005

Omithine decarboxylase (ODC) activity and polyamine (putrescine, spermidine, spermine) concentrations were measured in parallel in enterocyte‐like Caco‐2 cells maintained under various culture conditions. ODC activity was maximal at the begining of the exponential growth phase, decreasing dramatically thereafter to a negligible level at confluency (day 9). Kinetic studies performed on day 3 revealed the presence of a single enzyme with a Km around 200 μM and a Vmax of about 2 nmol CO2 released/h/mg protein. Similar values were obtained in both serum‐supplemented and transferrin/selenium (TS)‐defined culture media, indicating that ODC kinetic parameters are not affected by any factors present in serum. Polymine concentrations were maximal on day 5. By day 9, they returned to initial levels and remained at these fairly high values until day 21. Since we have previously shown (Jumarie and Malo, 1994, In Vitro Cell. Dev. Biol., 30A:753–760) that triiodothyronine (T3) stimulates differentiation but not proliferation of Caco‐2 cells maintained in TS‐defined medium, we investigated if it induces differentiation by a polyamine‐dependent mechanism. Short‐ and long‐term measurements revealed similar ODC activity and polyamine levels whether T3 was present or not in the culture medium. These results clearly demonstrate that polyamine synthesis is more likely to be associated with Caco‐2 cell proliferation, and that the T3 effect on Caco‐2 cell differentiation does not involve polyamine biosynthesis. Moreover, our data show that ODC activity is not solely regulated by intracellular polyamine concentration. © 1995 Wiley‐Liss Inc.
Electrical stability of erythrocytes in the presence of divalent cations
Authors: Tomov T. Ch. , Tsoneva I. Ch. , Doncheva J. Ch.
Published: February 2005

Erythrocytes suspended in a medium of low ionic strength lyse under the effect of an exponential electrical pulse. The percentage of haemolysed cells decreases several-fold in the presence of divalent cations. The protective action of the ions studied increases in the following order: Ca++, Mg++, Zn++. It is assumed that divalent ions bind to the negative charges of the lipid and protein molecules and reduce their electrostatic repulsion, which results in stabilization of the membranes.
Transport of L-cystine in human umbilical vein endothelial cells in culture
Authors: Ewadh M. J. A. , Tudball N. , Rose F. A.
Published: February 2005

The uptake of L-cystine into cultured human umbilical vein endothelial cells has been shown to occur by a Na+-independent system which is inhibited by L-glutamate and L-homocysteine, but not by other amino acids. It is likely that the system transporting L-cystine is shared by L-glutamate. Thiol groups associated with membrane bound components appear to be essential for L-cystine uptake but it is not yet evident whether these constitute an integral part of the transporter per se.
Synthetic DNA and Biology
Authors: Smith Michael
Published: February 2005

“Most of the significant work has been summarized in a number of reviews and articles. In these there was, of necessity, a good deal of simplification and omission of detail …. With the passage of time, even 1 find myself accepting such simplified accounts.”
Erosion and exhumation in accretionary orogens: Experimental and geological approaches
Authors: Konstantinovskaia Elena , Malavieille Jacques
Published: February 2005

This study examines the role of erosion on exhumation and deformation history of accretionary orogens through experimental and geological methods. Fault propagation, kinematics, and exhumation rates in an eroded thrust wedge are analyzed through scaled sandbox simulations by testing different parameters (friction, rheologic layering, and sediment input/output ratio). A model Coulomb wedge is submitted to erosion under flux steady state conditions; that is, the volume of eroded material remains equal to the volume of newly accreted material, maintaining a constant surface slope during shortening. Results show that the way of exhumation depends on the internal dynamics of thrust wedges and, conversely, on how this dynamics is modified by erosion. In the eroded thrust wedges the diversity of exhumation patterns is controlled by the mode of fault propagation, depending on the basal friction (high or low). The vertical component of exhumation is generally higher for the wedges with high basal friction than for low‐friction wedges. The uplift of material occurs along a cluster of subvertical thrusts in the middle part of the eroded thrust wedge with low basal friction. The material is exhumed along a series of inclined (20°–50°) thrusts in the rear of the high‐friction wedge. The zone of maximum exhumation is generally localized in the middle part of the thrust wedge and migrates toward the backstop with continued shortening. The vertical exhumation rate increases with time, and the material accreted later is rapidly transferred to the main exhumation zone compared to the material accreted during the early stages. The exhumation occurs at rates 2 times faster in the wedges with half the thickness than in full thickness wedges. The total quantity of eroded material at the end of convergence constitutes 36–50% of initial model area for the thrust wedges with low basal friction and 20–40% for the high basal friction wedges. The extent of basal underplating increases with total shortening. The area of basal underplated material constitutes up to 30 and 40% of the eroded thrust wedge area for the models with low and high basal friction, respectively. Presence of décollements in the accreted series allows underplating of thrust units developing an anticlinal stack, whose growth and location is favored by erosion. Our results are compared to different present‐day active and ancient convergent orogens (Himalaya, Taiwan, Southern Alps of New Zealand, and Cascadia orogen), allowing the different specific exhumation processes to be characterized.
Observed variability of the South Pacific westward sea level anomaly signal in the presence of bottom topography
Authors: Maharaj Angela M. , Cipollini Paolo , Holbrook Neil J.
Published: February 2005

This study investigates the behavior of westward propagating sea level anomalies across the South Pacific Ocean, with a focus on the long Rossby wave signal determined from filtered TOPEX/Poseidon and ERS satellite altimeter data. An evaluation of the energy variability of the signal using a two‐dimensional Radon Transform analysis suggests that Rossby waves interact with both ridges and seamounts at various locations across the basin. Anomalously slow Rossby wave phase speeds are found over steep, isolated bathymetric features in the tropical South Pacific and over the plateau around New Zealand. Interaction with ridges increases the energetic variability, range of dominant propagation speeds, and meridional deviations in the Rossby wave signal.
Microstructure of inhomogeneous polyatomic mixtures from a density functional formalism for atomic mixtures
Authors: Tripathi Sandeep , Chapman Walter G.
Published: February 2005

A free energy density functional theory (DFT) for inhomogeneous polymeric mixtures is developed by treating the polyatomic system as a strongly associating atomic fluid mixture. The theory, derived in terms of segment density, retains the simple form of the DFTs for atomic fluids. Invoking the complete bonding limit of a stoichiometric mixture in the association free energy functional yields a computationally simple and accurate functional for the polyatomic system. Comparisons of theory calculations with molecular simulations are presented for inhomogeneous solutions and blends of linear and branched chains, demonstrating the capability of the theory to accurately capture the entropic and enthalpic effects governing the microstructure.
Electronic decay following ionization of aqueous Li+ microsolvation clusters
Authors: Müller Imke B. , Cederbaum Lorenz S.
Published: February 2005

Ionization in the energetical range between 35eV and 75eV of aqueous Li+ microsolvation clusters may initialize several different electronic decay processes. Electronic decay following H2O 2s ionization in a cationic cluster is reported. Li ionization probes the efficiency of electron transfer mediated decay (ETMD) processes. We report estimated ETMD lifetimes in the range of 20–100fs for clusters with one to five water monomers. Furthermore, tertiary electron emission may occur via a combined cascade of electron transfer mediated decay and intermolecular Coulombic decay.
General calculation of 4f-5d transition rates for rare-earth ions using many-body perturbation theory
Authors: Duan Chang-Kui , Reid Michael F.
Published: February 2005

The 4f-5d transition rates for rare-earth ions in crystals can be calculated with an effective transition operator acting between model 4fN and 4fN−15d states calculated with effective Hamiltonian, such as semiempirical crystal Hamiltonian. The difference of the effective transition operator from the original transition operator is the corrections due to mixing in transition initial and final states of excited configurations from both the center ion and the ligand ions. These corrections are calculated using many-body perturbation theory. For free ions, there are important one-body and two-body corrections. The one-body correction is proportional to the original electric dipole operator with magnitude of ≈40% of the uncorrected electric dipole moment. Its effect is equivalent to scaling down the radial integral ⟨5d∣r∣4f⟩ to about 60% of the uncorrected HF value. The two-body correction has magnitude of ≈25% relative to the uncorrected electric dipole moment. For ions in crystals, there is an additional one-body correction due to ligand polarization, whose magnitude is shown to be about 10% of the uncorrected electric dipole moment.
Stationary phase evaluations of quantum rate constants
Authors: Yang Shilong , Cao Jianshu
Published: February 2005

We compute the quantum rate constant based on two extended stationary phase approximations to the imaginary-time formulation of the quantum rate theory. The optimized stationary phase approximation to the imaginary-time flux-flux correlation function employs the optimized quadratic reference system to overcome the inaccuracy of the quadratic expansion in the standard stationary phase approximation, and yields favorable agreements with instanton results for both adiabatic and nonadiabatic processes in dissipative and nondissipative systems. The integrated stationary phase approximation to the two-dimensional barrier free energy is particularly useful for adiabatic processes and demonstrates consistent results with the imaginary-time flux-flux correlation function approach. Our stationary phase methods do not require calculation of tunneling paths or stability matrices, and work equally well in the high-temperature and the low-temperature regimes. The numerical results suggest their general applicability for calibration of imaginary-time methods and for the calculation of quantum rate constants in systems with a large number of degrees of freedom.
A simple model of entropy relaxation for explaining effective activation energy behavior below the glass transition temperature
Authors: Bisquert Juan , Henn François , Giuntini Jean-Charles
Published: February 2005

Strong changes in relaxation rates observed at the glass transition region are frequently explained in terms of a physical singularity of the molecular motions. We show that the unexpected trends and values for activation energy and preexponential factor of the relaxation time τ, obtained at the glass transition from the analysis of the thermally stimulated current signal, result from the use of the Arrhenius law for treating the experimental data obtained in nonstationary experimental conditions. We then demonstrate that a simple model of structural relaxation based on a time dependent configurational entropy and Adam–Gibbs relaxation time is sufficient to explain the experimental behavior, without invoking a kinetic singularity at the glass transition region. The pronounced variation of the effective activation energy appears as a dynamic signature of entropy relaxation that governs the change of relaxation time in nonstationary conditions. A connection is demonstrated between the peak of apparent activation energy measured in nonequilibrium dielectric techniques, with the overshoot of the dynamic specific heat that is obtained in calorimetry techniques.
Demonstration of low power radiation pressure actuation for control of test masses
Authors: Feat M. , Zhao C. , Ju L. , Blair D. G.
Published: February 2005

We demonstrate a scheme for radiation pressure force actuation for noncontacting control of a suspended test mass. We present results of the frequency response and active damping of a 35 g low frequency resonator under radiation pressure using less than 1 W of diode laser power.
Incipient speciation ofCatostylus mosaicus(Scyphozoa, Rhizostomeae, Catostylidae), comparative phylogeography and biogeography in south‐east Australia
Authors: Dawson Michael N
Published: February 2005

Aim Phylogeography provides a framework to explain and integrate patterns of marine biodiversity at infra‐ and supra‐specific levels. As originally expounded, the phylogeographic hypotheses are generalities that have limited discriminatory power; the goal of this study is to generate and test specific instances of the hypotheses, thereby better elucidating both local patterns of evolution and the conditions under which the generalities do or do not apply.

Location Coastal south‐east Australia (New South Wales, Tasmania and Victoria), and south‐west North America (California and Baja California).

Methods Phylogeographic hypotheses specific to coastal south‐east Australia were generateda priori, principally from existing detailed distributional analyses of echinoderms and decapods. The hypotheses are tested using mitochondrial cytochrome c oxidase subunit I (COI) and nuclear internal transcribed spacer 1 (ITS1) DNA sequence data describing population variation in the jellyfishCatostylus mosaicus,integrated with comparable data from the literature.

Results Mitochondrial COI distinguished two reciprocally monophyletic clades ofC. mosaicus(mean ± SD: 3.61 ± 0.40% pairwise sequence divergence) that were also differentiated by ITS1 haplotype frequency differences; the boundary between the clades was geographically proximate to a provincial zoogeographic boundary in the vicinity of Bass Strait. There was also limited evidence of another genetic inhomogeneity, of considerably smaller magnitude, in close proximity to a second hypothesized zoogeographic discontinuity near Sydney. Other coastal marine species also show genetic divergences in the vicinity of Bass Strait, although they are not closely concordant with each other or with reported biogeographic discontinuities in the region, being up to several hundreds of kilometres apart. None of the species studied to date show a strong phylogeographic discontinuity across the biogeographic transition zone near Sydney.

Main conclusions Patterns of evolution in the Bass Strait and coastal New South Wales regions differ fundamentally because of long‐term differences in extrinsic factors. Since the late Pliocene, periods of cold climate and low sea‐level segregated warm temperate organisms east or west of an emergent Bassian Isthmus resulting in population divergence and speciation; during subsequent periods of warmer and higher seas, sister taxa expanded into the Bass Strait region leading to weakly correlated phylogeographic and biogeographic patterns. The Sydney region, by contrast, has been more consistently favourable to shifts in species’ ranges and long‐distance movement, resulting in a lack of intra‐specific and species‐level diversification. Comparisons between the Sydney and Bass Strait regions and prior studies in North America suggest that vicariance plays a key role in generating coastal biodiversity and that dispersal explains many of the deviations from the phylogeographic hypotheses.
Progression of programmed cell death in tobacco BY‐2 cells is delineated by specific changes in de novo and salvage synthesis of purine nucleotides
Authors: Stasolla Claudio , Loukanina Natalia , Yeung Edward C. , Thorpe Trevor A.
Published: February 2005

Alterations in the pattern of purine nucleotide synthesis and degradation were investigated during programmed cell death (PCD) of tobacco BY‐2 cells, induced by a simultaneous increase in the endogenous levels of nitric oxide (NO) and hydrogen peroxide. The de novo synthesis of purine nucleotides was estimated by following the metabolic fate of the [8‐14C]5‐aminoimidazole‐4‐carboxamide‐1‐β‐d‐ribofuranoside (AICAR), the salvage synthesis was investigated using [8‐14C]adenine and adenosine, and the degradation pathway was studied by following the incorporation of [8‐14C]inosine. The results indicated that specific changes in purine metabolism occurred during the death programme of tobacco cells. During the early phases of PCD, increases in the salvage activity of adenine and adenosine were observed, and these were related to the high activity of the two major salvage enzymes: adenine phosphoribosyltransferase (APRT) and adenosine kinase (ARK). During the following stages, a large fraction of purine nucleotide was also produced through the de novo pathway, suggesting a tight regulation between salvage and de novo synthesis. These changes were strictly associated with PCD, as they did not occur if NO or hydrogen peroxide was increased individually, or if actinomycin, which inhibits the death programme, was added to the medium in the presence of NO and hydrogen peroxide. These changes in purine nucleotide synthesis represent an early metabolic switch which may be needed to ensure the proper execution of all the high‐energy demand processes characteristic of the death programme.