The effects of γ-rays on poly-L-glutamic acid in aqueous solution

Summary Salt-free and 0.2 M NaCl oxygenated aqueous solutions of poly-L-glutamic acid were irradiated with⁶⁰Co--radiation at variouspH's to examine whether or not the changes caused by the exposure to ionizing radiation depend onpH, that is, the conformations of polypeptide.TheG-values (the number of main-chain scissions per 100 eV of energy absorbed) in both salt-free and 0.2 M NaCl solutions of poly-L-glutamic acid were found to change sharply withpH. and to have a maximum value at thepH of a mid-point of helix-coil transition. The change ofG-values withpH was discussed in terms of the conformational change of poly-L-glutamic acid.     

Different effects of α- and γ-glycine on the aberrant activity of pyramidal neurons of hippocampal slices

Experiments in vitro on hippocampal slices of mouse have shown that solutions prepared from polymorphic modifications α- and γ-glycine have different effect on the aberrant activity of neurons. In the presence of α-glycine the excitability of these neurons decreased more slowly, prolonging its modulating effect on NMDA type glutamate receptors. This effect agrees with higher biological activity of α-polymorphic modifications (as compared with that of the α-form) that previously observed with respect to behavior of mice from the line with genetic diathesis to catalepsy, which were used as a biological model for investigation of some pathological behavior forms.     

Effects of low-dose γ-rays on the embryonic development of mouse melanoblasts and melanocytes in the epidermis and hair bulbs

The effects of low-dose γ-rays on the embryonic development of animal cells are not well studied. The mouse melanocyte is a good model to study the effects of low-dose γ-rays on the development of animal cells, as it possesses visible pigment (melanin) as a differentiation marker. The aim of this study is to investigate in detail the effects of low-dose γ-rays on embryonic development of mouse melanoblasts and melanocytes in the epidermis and hair bulbs at cellular level. Pregnant females of C57BL/10J mice at nine days of gestation were whole-body irradiated with a single acute dose of γrays (0.1, 0.25, 0.5, and 0.75 Gy), and the effects of γ-rays were studied by scoring changes in the development of epidermal melanoblasts and melanocytes, hair follicles, and hair bulb melanocytes at 18 days in gestation. The number of epidermal melanoblasts and melanocytes, hair follicles, and hair bulb melanocytes in the dorsal and ventral skins was markedly decreased even at 0.1 Gy-treated embryos (P < 0.001), and gradually decreased as dose increased. The effects on the ventral skin were greater than those on the dorsal skin. The dramatic reduction in the number of melanocytes compared to melanoblasts was observed in the ventral skin, but not in the dorsal skin. These results suggest that low-dose γ-rays provoke the death of melanoblasts and melanocytes, or inhibit the proliferation and differentiation of melanoblasts and melanocytes, even at the low dose.     

Effects of γ-rays on Poly-L-glutamic acid and Poly-D,L-glutamic acid in the solid state

Summary Poly-L-glutamic acid and poly-D,L-glutamic acid, as models of proteins, were irradiated with⁶⁰Co--radiation in air and under vacuo to examine whether or not the changes caused by the exposure to ionizing radiation depend on the conformations of polypeptides.It was found that theG- values (yield of main-chain scissions per 100 eV of energy absorbed) of both polypeptides are approximately equal for the irradiation in air, while under vacuo theG- value of poly-D,L-glutamic acid is larger than that of poly-L-glutamic acid. This observation for irradiation under vacuo was ascribed to the stabilizing effect of intramolecular hydrogen bond bridges in poly-L-glutamic acid. It was also found that the-helical structure of poly-L-glutamic acid is destroyed by the exposure to ionizing radiation.     

Direct vs. indirect effects of trypan blue on the ectodermal cells of the 11.5-day rat embryo?

The effect of trypan blue on the 11.5-day rat conceptus after intravitelline vessel administration is described. For comparison, conceptuses injected with varying volumes of Hanks' BSS have also been studied. Trypan blue significantly retarded the growth and development of conceptuses after 6 hours incubation in vitro. The SEM revealed rounded ectodermal cells, some of which appeared disrupted. These cells seemed to cause some of the intersomitic grooves to disappear, making a number of the somites indistinct from the outside. Unlike cells of uninjected embryos, the surfaces of the affected ectodermal cells lacked microvilli and their perimeters were lined with microvilli-like structures which appeared matted together. It was concluded that trypan blue affected the embryo directly probably by disturbing its fluid and ionic balance.     

Inhibitory effects of γ-tocotrienol on invasion and metastasis of human gastric adenocarcinoma SGC-7901 cells

Natural vitamin E is a mixture of two classes of compounds, tocopherols and tocotrienols. Recent research has revealed that tocotrienols, especially γ-tocotrienol, exhibit not only the same antioxidant ability as tocopherols, but also remarkable anticancer capacity in cancer cell lines. In this study, the invasion and metastatic capacities of gastric adenocarcinoma SGC-7901 cells and the correlation with antimetastasis mechanisms induced by γ-tocotrienol were explored. The results showed the inhibitory effects of γ-tocotrienol at doses of 15, 30, 45 and 60 μmol/L for 48 h on cell migration and cell matrigel invasion; activities of matrix metalloproteinase (MMPs) increased in SGC-7901 cells when compared to the control group (P<.05 or P<.01). An increasing trend in the chemotactic responses to fibronectin (FN) in SGC-7901 cells was found in the γ-tocotrienol treatments. SGC-7901 cell attachment decreased in the γ-tocotrienol-treated groups in comparison with the control group (P<.01). The mRNA expressions of MMP-2 and MMP-9 showed that γ-tocotrienol significantly reduced the matrigel invasion capability through down-regulation of the mRNA expressions of MMP-2 and MMP-9 (P<.01), and up-regulation of tissue inhibitor of metalloproteinase-1 (TIMP-1) and TIMP-2 in SGC-7901 cells by treatment with γ-tocotrienol for 48 h (P<.05). γ-Tocotrienol also significantly increased the mRNA expression of nm23-H1 in SGC-7901 cells (P<.01). These findings suggest a potential mechanism of γ-tocotrienol-mediated antitumor metastasis activity and indicate the role of vitamin E as potential chemopreventative agents against gastric cancer.     

Direct and indirect effects of ant–trophobiont interactions on the reproduction of a hummingbird-pollinated mistletoe

Plant Ecology - Fluid-feeding herbivores directly affect host plants through sap consumption. Moreover, they establish mutualistic relationships with ants, which might generate additional...     

Divergent effects of compounds on the hydrolysis and transpeptidation reactions of γ-glutamyl transpeptidase

A novel class of inhibitors of the enzyme γ-glutamyl transpeptidase (GGT) were evaluated. The analog OU749 was shown previously to be an uncompetitive inhibitor of the GGT transpeptidation reaction. The data in this study show that it is an equally potent uncompetitive inhibitor of the hydrolysis reaction, the primary reaction catalyzed by GGT in vivo. A series of structural analogs of OU749 were evaluated. For many of the analogs, the potency of the inhibition differed between the hydrolysis and transpeptidation reactions, providing insight into the malleability of the active site of the enzyme. Analogs with electron withdrawing groups on the benzosulfonamide ring, accelerated the hydrolysis reaction, but inhibited the transpeptidation reaction by competing with a dipeptide acceptor. Several of the OU749 analogs inhibited the transpeptidation reaction by slow onset kinetics, similar to acivicin. Further development of inhibitors of the GGT hydrolysis reaction is necessary to provide new therapeutic compounds.     

Different effects on cell proliferation and migration abilities of endothelial cells by LPA₁ and LPA₃ in mammary tumor FM3A cells

Lysophosphatidic acid (LPA) receptors belong to G protein-coupled transmembrane receptors and mediate a variety of cellular responses through the binding of LPA. So far, six types of LPA receptors (LPA receptor-1 (LPA?) to LPA?) have been identified. Recently, it has been demonstrated that each LPA receptor has opposite effects on malignant property of cancer cells. In this study, to evaluate an involvement of LPA receptors on angiogenic process in mammary tumor cells, we generated Lpar1- and Lpar3-expressing (FM3A-a1 and FM3A-a3A9, respectively) cells from FM3A cells, and investigated the effects on cell proliferation and migration abilities of endothelial F-2 cells by those cells. In Vegf-A and Vegf-C genes, FM3A-a1 cells indicated high expression and FM3A-a3A9 cells showed low expression, compared with control cells. When F-2 cells were cultured with a supernatant from FM3A-a1 cells, the cell growth rate and migration ability of F-2 cells was significantly higher than control cells. By contrast, a supernatant from FM3A-a3A9 cells significantly inhibited those abilities of F-2 cells. These results suggest that LPA? and LPA? may play opposite roles on the regulation of endothelial cells in mouse mammary tumor FM3A cells.     

Inhibition of the UV induction of sister-chromatid exchanges in ICR-2A frog cells by pretreatment with γ-rays

Exposure of ICR-2A cells to UV induced the formation of sister-chromatid exchanges (SCEs). However, pretreatment of UV-irradiated cells with γ-rays resulted in a reduction in the level of SCEs. This effect was observed over a range of UV fluences (1–5 J/m²) and γ-ray doses (50–500 rad). In addition, the deprassion of UV-induced SCEs was greatest when the UV treatment was performed within 3 h after γ-irradiation. At later times the level of SCEs approached that of cells exposed only to UV.     

Modeling of the effects of IL-17 and TNF-α on endothelial cells and thrombus growth

Rheumatoid and psoriatic arthritis are chronic inflammatory diseases, with massive increase of cardiovascular events (CVE), and contribution of the cytokines TNF-α and IL-17. Chronic inflammation inside the joint membrane or synovium results from the activation of fibroblasts/synoviocytes, and leads to the release of cytokines from monocytes (Tumor Necrosis Factor or TNF) and from T lymphocytes (Interleukin-17 or IL-17). At the systemic level, the very same cytokines affect endothelial cells and vessel wall. We have previously shown [1], [2] that IL-17 and TNF-α, specifically when combined, increase procoagulation, decrease anticoagulation and increase platelet aggregation, leading to thrombosis. These results are the basis for the models of interactions between IL-17 and TNF, and genes expressed by activated endothelial cells. This work is devoted to mathematical modeling and numerical simulations of blood coagulation and clot growth under the influence of IL-17 and TNF-α. We show that they can provoke thrombosis, leading to the complete or partial occlusion of blood vessels. The regimes of blood coagulation and conditions of occlusion are investigated in numerical simulations and in approximate analytical models. The results of mathematical modeling allow us to predict thrombosis development for an individual patient.     

Different effects of thymidine and 5-fluorouracil 2′-deoxyriboside on biosynthetic events in cultured P815Y mast cells

1. Addition of 2mm-thymidine, although resulting in the cessation of cell division, allows the continuation of phospholipid and protein synthesis and results in an increase in mean cell volume for at least 15h. 2. 5-Fluorouracil 2'-deoxyriboside inhibits cell division but differs from thymidine by inhibiting the synthesis of phospholipid and protein in a more marked manner. 3. The relation between these results and the P815Y cell cycle is discussed.     

Characterization and in vitro cytotoxicity of doxorubicin-loaded γ-polyglutamic acid-chitosan composite nanoparticles

In this study, γ-polyglutamic acid (γ-PGA) and chitosan (CS) nanoparticles were characterized as a carrier for the anti-cancer drug doxorubicin (DOX). Using ionic complexation between the positively charged DOX and the negatively charged polyelectrolyte γ-PGA, DOX:γ-PGA complexes were produced with an efficiency of approximately 99%. SEM micrographs demonstrated that the complexation of γ-PGA and DOX alone does not lead to the formation of nanoparticles and that the addition of a third component, chitosan, is required. Drug-loaded DOX:γ-PGA:CS nanoparticles were produced with particle sizes ranging from ~150 to ~630 nm. The stability of the DOX:γ-PGA:CS nanoparticles was examined by suspending the nanoparticles in different kinds of aqueous media. For the first time, in vitro studies with DOX-loaded nanoparticles demonstrated the cytotoxicity of the nanoparticles against a human oral squamous cell carcinoma cell line (HN-5a). Non-drug-loaded γ-PGA:CS nanoparticles did not display cytotoxic effects. It was shown that the encapsulated or surface-bound DOX did not lose its bioactivity and the prepared drug-loaded particles exhibited a considerable anti-proliferative activity against the human cancer cell line.     

Different roles of TGF-β in the multi-lineage differentiation of stem cells

Stem cells are a population of cells that has infinite or long-term self-renewal ability and can produce various kinds of descendent cells.Transforming growth factor β(TGF-β) family is a superfamily of growth factors,including TGF-β1,TGF-β2 and TGF-β3,bone morphogenetic proteins,activin/inhibin,and some other cytokines such as nodal,which plays very important roles in regulating a wide variety of biological processes,such as cell growth,differentiation,cell death.TGF-β,a pleiotropic cytokine,has been proved to be differentially involved in the regulation of multi-lineage differentiation of stem cells,through the Smad pathway,non-Smad pathways including mitogen-activated protein kinase pathways,phosphatidylinositol-3-kinase/AKT pathways and Rholike GTPase signaling pathways,and their cross-talks.For instance,it is generally known that TGF-β promotes the differentiation of stem cells into smooth muscle cells,immature cardiomyocytes,chondrocytes,neurocytes,hepatic stellate cells,Th17 cells,and dendritic cells.However,TGF-β inhibits the differentiation of stem cells into myotubes,adipocytes,endothelial cells,and natural killer cells.Additionally,TGF-β can provide competence for early stages of osteoblastic differentiation,but at late stages TGF-β acts as an inhibitor.The three mammalian isoforms(TGF-β1,2 and 3) have distinct but overlapping effects on hematopoiesis.Understanding the mechanisms underlying the regulatory effect of TGF-β in the stem cell multi-lineage differentiation is of importance in stem cell biology,and will facilitate both basic research and clinical applications of stem cells.In this article,we discuss the current status and progress in our understanding of different mechanisms by which TGF-β controls multi-lineage differentiation of stem cells.     

Fluorescence and molecular dynamics studies of the acetylcholine receptor γM4 transmembrane peptide in reconstituted systems

A combination of fluorescence spectroscopy and molecular dynamics (MD) is applied to assess the conformational dynamics of a peptide making up the outermost ring of the nicotinic acetylcholine receptor (AChR) transmembrane region and the effect of membrane thickness and cholesterol on the hydrophobic matching of this peptide. The fluorescence studies exploit the intrinsic fluorescence of the only tryptophan residue in a synthetic peptide corresponding to the fourth transmembrane domain of the AChR γ subunit (γM4-Trp⁶) reconstituted in lipid bilayers of varying thickness, and combine this information with quenching studies using depth-sensitive phosphatidylcholine spin-labeled probes and acrylamide, polarization of fluorescence, and generalized polarization of Laurdan. A direct correlation was found between bilayer width and the depth of insertion of Trp⁶. We further extend our recent MD study of the conformational dynamics of the AChR channel to focus on the crosstalk between M4 and the lipid-belt region. The isolated γM4 peptide is shown to possess considerable orientational flexibility while maintaining a linear α-helical structure, and to vary its tilt depending on bilayer width and cholesterol (Chol) content. MD studies also show that γM4 also establishes contacts with the other TM peptides on its inner face, stabilizing a shorter TM length that is still highly sensitive to the lipid environment. In the native membrane the topology of the M4 ring is likely to exhibit a similar behavior, dynamically modifying its tilt to match the hydrophobic thickness of the bilayer.     

Role of calpain-9 and PKC-δ in the apoptotic mechanism of lumen formation in CEACAM1 transfected breast epithelial cells

CEACAM1-4S (carcinoembryonic antigen-related cell adhesion molecule 1) is a type I membrane protein with a short (12-amino acid) cytoplasmic tail. Wild type CEACAM1-4S-transfected MCF7 cells form glands with lumena when grown in 3D culture, while null mutations of two putative phosphorylation sites (T457A and S459A) in the cytoplasmic domain fail to undergo lumen formation. When gene chip analysis was performed on mRNA isolated from both wild type and T457A,S459A mutated CEACAM1-4S-transfected MCF7 cells grown in 3D culture, calpain-9 (CAPN9) was identified out of over 400 genes with a > 2 log 2 difference as a potential inducer of lumen formation. Inhibition of CAPN9 expression in MCF7/CEACAM1-4S cells by RNAi or by calpeptin or PD150606 inhibited lumen formation. Transfection of CAPN9 into wild type MCF7 cells restores lumen formation demonstrating that calpain-9 may play a critical role in lumen formation. Additionally, we demonstrate that the apoptosis related kinase, PKC-δ, is activated by proteolytic cleavage during lumen formation exclusively in wild type CEACAM1-4S-transfected MCF7 cells grown in 3D culture and that lumen formation is inhibited by either RNAi to PKC-δ or by the PKC-δ inhibitor rottlerin.