The Journal of Cellular Physiology publishes reports of high biological significance in areas of eukaryotic cell biology and physiology, focusing on those articles that adopt a molecular mechanistic approach to investigate cell structure and function. There is appreciation for the application of cellular, biochemical, molecular and in vivo genetic approaches, as well as the power of genomics, proteomics, bioinformatics and systems biology. In particular, the Journal encourages submission of high-interest papers investigating the genetic and epigenetic regulation of proliferation and phenotype as well as cell fate and lineage commitment by growth factors, cytokines and their cognate receptors and signal transduction pathways that influence the expression, integration and activities of these physiological mediators. Similarly, the Journal encourages submission of manuscripts exploring the regulation of growth and differentiation by cell adhesion molecules in addition to the interplay between these processes and those induced by growth factors and cytokines. Studies on the genes and processes that regulate cell cycle progression and phase transition in eukaryotic cells, and the mechanisms that determine whether cells enter quiescence, proliferate or undergo apoptosis are also welcomed. Submission of papers that address contributions of the extracellular matrix to cellular phenotypes and physiological control as well as regulatory mechanisms governing fertilization, embryogenesis, gametogenesis, cell fate, lineage commitment, differentiation, development and dynamic parameters of cell motility are encouraged. Finally, the investigation of stem cells and changes that differentiate cancer cells from normal cells including studies on the properties and functions of oncogenes and tumor suppressor genes will remain as one of the major interests of the Journal.
AbstractGlycoproteins expressed on the luminal surfaces of microvascular endothelium derived from various murine organs were analyzed and compared with those expressed by cultured vascular endothelial cells. Cell‐surface vascular proteins were radiolabeled in situ via intracardiac perfusion with lactoperoxidase/Na125l. Autoradiography confirmed that the radiolabel was restricted to the vessel lumen in most tissues. Controls contained 125l‐labeled serum proteins to identify adsorbed serum components. Glycoproteins were analyzed by western enzymelinked lectin analysis using detergent extracts of 125l‐labeled microvessels isolated from different organs. The western transfers were probed with a panel of lectin‐peroxidase conjugates to determine differences in protein glycosylation. The same transfers were also screened for exposed 125l‐labeled cell‐surface proteins by autoradiography. This dual analysis detected glycoprotein patterns unique for each organ. At least seven major proteins (Mr ∼ 180 K, 130 K, 95 K, 80 K, 75 K, 60 K, 12 K) were common to microvessels derived from each organ; however, certain glycoproteins appeared to be expressed differentially in particular organs. For example, a Mr ∼ 135 K WGA‐binding glycoprotein was detected in brain microvessels, whereas another WGA‐binding glycoprotein of Mr ∼ 40 K was detected only in kidney. In lung microvessels, a Mr ∼ 140 K WGA binding glycoprotein and a Mr ∼ 55 K RCA‐l‐binding galactoprotein were expressed preferentially, and liver microvessels displayed Mr ∼ 220 K protein and a Mr ∼ 135 K PNA‐binding galactoprotein. The cell‐surface‐iodinated protein profiles from in situ labeled microvessels were similar to profiles derived from cultured bovine aortic endothelial cells and several short‐term endothelial cell cultures isolated from different organs. The results from this study suggest that organ‐associated endothelia express glycoprotein fingerprints unique to each organ.
Mineral trioxide aggregate (MTA), as a bioactive material, has a widespread application in clinical practice. To date, the effects of MTA on the proliferation and differentiation of human periodontal ligament stem cells (hPDLSCs) remain unclear. hPDLSCs were isolated from human periodontal ligament tissues and cultured with MTA conditioned media. Cell counting kit‐8 (CCK‐8) assay was performed to assess the proliferation capacity of MTA‐treated hPDLSCs. Immunofluorescence assay, alkaline phosphatase (ALP) activity, alizarin red staining, real‐time RT‐PCR, and western blot analyses were used to investigate the odonto/osteogenic capacity of hPDLSCs as well as the involvement of NF‐κB and MAPK pathways. ALP activity assay revealed that 2 mg/ml was the optimal concentration for the induction of hPDLSCs by MTA. The protein expression of DSP, RUNX2, OCN, OSX, OPN, DMP1, ALP, and COL‐I in MTA‐treated hPDLSCs was significantly higher than those in control group (p < 0.01). When hPDLSCs were treated with the inhibitors of NF‐κB and MAPK pathways (U0126, SP600125, SB203580, and BMS345541), the effects of MTA on the differentiation of hPDLSCs were suppressed. Mechanistically, P65 was detected to transfer from cytoplasm to nuclei, as indicated by western blot and immunofluorescence assay. Moreover, MAPK‐related proteins and its downstream transcription factors were also upregulated in MTA‐treated hPDLSCs. Together, mineral trioxide aggregate can promote the odonto/osteogenic capacity of hPDLSCs via activating the NF‐κB and MAPK pathways.
James Watt, Amelia H. Baker, Brett Meeks, Paola Divieti Pajevic, Elise F. Morgan, Louis C. Gerstenfeld, Jennifer J. Schlezinger
The retinoid X receptors (RXR), peroxisome proliferator activated receptor gamma (PPARγ), and liver X receptors (LXR) all have been shown to regulate bone homeostasis. Tributyltin (TBT) is an environmental contaminant that is a dual RXRα/β and PPARγ agonist. TBT induces RXR, PPARγ, and LXR‐mediated gene transcription and suppresses osteoblast differentiation in vitro. Bone marrow multipotent mesenchymal stromal cells derived from female C57BL/6J mice were more sensitive to suppression of osteogenesis by TBT than those derived from male mice. In vivo, oral gavage of 12 week old female, C57Bl/6J mice with 10 mg/kg TBT for 10 weeks resulted in femurs with a smaller cross‐sectional area and thinner cortex. Surprisingly, TBT induced significant increases in trabecular thickness, number, and bone volume fraction. TBT treatment did not change the Rankl:Opg RNA ratio in whole bone, and histological analyses showed that osteoclasts in the trabecular space were minimally reduced. In contrast, expression of cardiotrophin‐1, an osteoblastogenic cytokine secreted by osteoclasts, increased. In primary bone marrow macrophage cultures, TBT marginally inhibited the number of osteoclasts that differentiated, in spite of significantly suppressing expression of osteoclast markers Nfatc1, Acp5, and Ctsk and resorptive activity. TBT induced expression of RXR‐ and LXR‐dependent genes in whole bone and in vitro osteoclast cultures. However, only an RXR antagonist, but not an LXR antagonist, significantly inhibited TBTs ability to suppress osteoclast differentiation. These results suggest that TBT has distinct effects on cortical versus trabecular bone, likely resulting from independent effects on osteoblast and osteoclast differentiation that are mediated through RXR.
AbstractMDCK kidney epithelial cell cultures exposed to the differentiation inducer hexamethylene bisacetamid (HMBA) for 24 hours exhibited a 50% decrease in transport activity per (Na+, K+)‐ATPase molecule (turnover number) but an unchanged number of pump sites (Kennedy and Lever, 1984). Inhibition of protein synthesis by either 10 μM cycloheximide or 2 μM emetine blocked the inhibitory effects of HMBA on Na+/K+ pump efficiency assessed by measurements of [3H]‐ouabain binding to intact cells, (Na+, K+) ATPase activity of detergent‐activated cell extracts, and ouabain‐sensitive Rb+ uptake. In the absence of inducer treatment, inhibition of protein synthesis increased Na+/K+ pump turnover number by twofold while maintaining Na+/K+ pump activity per cell at a constant level. Intracellular Na+ levels were decreased after cycloheximide treatment; therefore, pump stimulation was not due to substrate effects. Furthermore, cycloheximide effects of Rb+ uptake could be dissociated from effects on tight junctions. These observations suggest that the transport activity of the (Na+, K+) ATPase is tightly regulated by factors dependent on protein synthesis.
A. Jungwirth, Markus Ritter, Markus Paulmichl, Florian Läng
AbstractTo elucidate mechanisms of mercury toxicity, the cell membrane potential has been determined continuously in cultured kidney (MDCK)‐cells during reversible application of mercury ions to extracellular perfusate. Exposure of the cells to 1μM mercury ions is followed by rapid, sustained, and slowly reversible hyperpolarization of the cell membrane, increase of cell membrane potassium selectivity, and decrease of cell membrane resistance. Thus, mercury ions enhance the potassium conductance of the cell membrane. Half maximal hyperpolarizing effect is elicited by ≈0.2 μM. Higher concentrations of mercury ions (> 10 μM) eventually depolarize the cell membrane. At extracellular calcium activity reduced to less than 0.1 μM, 1 μM mercury ions still leads to a sustained hyperpolarization and increase of potassium selectivity of the cell membrane. As evident from fluorescence measurements, 10 μM, but not 1 μM mercury ions leads to a rapid increase of intracellular calcium activity. Pretreatment of the cells with either pertussis toxin or cholera toxin does not blunt the hyperpolarizing effect of mercury ions. In conclusion, mercury ions activate the potassium conductance by a mechanism independent of increase of intracellular calcium activity and of cholera toxin‐or pertussis toxin‐sensitive G‐proteins. This activation of potassium conductance may account for early effects of mercury intoxication, such as kaliuresis.
Markus Paulmichl, Josef Pfeilschifter, Ewald Wöll, Florian Läng
AbstractPrevious studies have shown that ATP enhances intracellular calcium concentration and activates potassium channels in Madin Darby canine kidney (MDCK)‐cells, thus leading to hyperpolarization of the cell membrane. The present study has been performed to elucidate the intracellular mechanisms involved. To this end, the effects of ATP on the potential difference across the cell membrane (PD), on formation of inositol phosphates, and on intracellular calcium concentration (Cai) have been analyzed in cells without or with pretreatment with pertussis toxin or 12‐O‐tetradecanoyl phorbol 13‐acetate diester (TPA). In untreated cells, ATP leads to a sustained hyperpolarization and an increase of inositol 1,4,5‐tris‐phosphate (IP3), inositol 1,3,4,5‐tetrakisphosphate (IP4), and Cai. In the absence of extracellular calcium, the effect of ATP on PD and Cai is only transient. In cells pretreated with pertussis toxin, the effect of ATP on inositol trisphosphate is almost abolished, but ATP still leads to an increase of PD and Cai, which is sustained in the presence, and transient in the absence, of extracellular calcium. In cells pretreated with TPA, the effect of ATP on inositol trisphosphate is reduced and the effect on Cai blunted; but ATP still leads to a hyperpolarization of the cell membrane, which is sustained in the presence, and transient in the absence, of extracellular calcium. The observations indicate that ATP activates phospholipase C by a phorbol ester and pertussis toxin sensitive mechanism. In addition, ATP enhances Cai by pertussis toxin insensitive mechanisms allowing recruitment of calcium from both, extracellular fluid and intracellular stores. Calcium then activates the potassium channels and thus leads to the hyperpolarization of the cell membrane.
J. D. Valentich, Jason Adam Wasserman, Joseph Leighton
AbstractCertain epithelial cell lines have morphologic, physiologic, biochemical and pharmacologic characteristics of transporting epithelia from intact organs. In this paper we show that dibutyryl cyclic AMP, 5′ AMP, adenosine and cyclic AMP phosphodiesterase inhibitors stimulate hemicyst formation by the dog kidney cell line MDCK. It is suggested that this effect is explained by elevation of intracellular cyclic AMP levels by means of an exogenous non‐metabolizable source of cyclic AMP, phosphodiesterase inhibition or adenyl cyclase stimulation. Since hemicyst formation is in part due to transepithelial fluid transport, these findings raise the possibility that this fraction might be modulated by cAMP in an established cell line. We believe that cultured epithelial cells may provide an exploitable model system to investigate at the cellular and subcellular levels, the mechanism by which cyclic AMP modifies water and solute movements across epithelia.
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