Insulin regulates GLUT1-mediated glucose transport in MG-63 human osteosarcoma cells

Osteosarcoma is the most common type of malignant bone cancer, accounting for 35% of primary bone malignancies. Because cancer cells utilize glucose as their primary energy substrate, the expression and regulation of glucose transporters (GLUT) may be important in tumor development and progression. GLUT expression has not been studied previously in human osteosarcoma cell lines. Furthermore, although insulin and insulin-like growth factor (IGF-I) play an important role in cell proliferation and tumor progression, the role of these hormones on GLUT expression and glucose uptake, and their possible relation to osteosarcoma, have also not been studied. We determined the effect of insulin and IGF-I on GLUT expression and glucose transport in three well-characterized human osteosarcoma cell lines (MG-63, SaOs-2, and U2-Os) using immunocytochemical, RT-PCR and functional kinetic analyses. Furthermore we also studied GLUT isoform expression in osteosarcoma primary tumors and metastases by in situ hybridization and immunohistochemical analyses. RT-PCR and immunostaining show that GLUT1 is the main isoform expressed in the cell lines and tissues studied, respectively. Immunocytochemical analysis shows that although insulin does not affect levels of GLUT1 expression it does induce a translocation of the transporter to the plasma membrane. This translocation is associated with increased transport of glucose into the cell. GLUT1 is the main glucose transporter expressed in osteosarcoma, furthermore, this transporter is regulated by insulin in human MG-63 cells. One possible mechanism through which insulin is involved in cancer progression is by increasing the amount of glucose available to the cancer cell.     

A study of the anti‐plasmodium activity of angiotensin II analogs

Controlling the dissemination of malaria requires the development of new drugs against its etiological agent, a protozoan of the Plasmodium genus. Angiotensin II and its analog peptides exhibit activity against the development of immature and mature sporozoites of Plasmodium gallinaceum. In this study, we report the synthesis and characterization of angiotensin II linear and cyclic analogs with anti‐plasmodium activity. The peptides were synthesized by a conventional solid‐phase method on Merrifield's resin using the t‐Boc strategy, purified by RP‐HPLC and characterized by liquid chromatography/ESI (+) MS (LC‐ESI(+)/MS), amino acid analysis, and capillary electrophoresis. Anti‐plasmodium activity was measured in vitro by fluorescence microscopy using propidium iodine uptake as an indicator of cellular damage. The activities of the linear and cyclic peptides are not significantly different (p < 0.05). Kinetics studies indicate that the effects of these peptides on plasmodium viability overtime exhibit a sigmoidal profile and that the system stabilizes after a period of 1 h for all peptides examined. The results were rationalized by partial least‐square analysis, assessing the position‐wise contribution of each amino acid. The highest contribution of polar amino acids and a Lys residue proximal to the C‐terminus, as well as that of hydrophobic amino acids in the N‐terminus, suggests that the mechanism underlying the anti‐malarial activity of these peptides is attributed to its amphiphilic character. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.     

A common haplotype of <Emphasis Type="Italic">DRD3</Emphasis> affected by recent positive selection is associated with protection from schizophrenia

The number and frequency of susceptibility alleles at loci associated to most psychiatric disorders is largely unknown, in spite of its relevance for the design of studies aiming to find these alleles. Both, common polymorphisms and rare mutations may contribute to the genetic susceptibility to complex psychiatric disorders, being the relative relevance of each type of variation currently under debate. Here, we confirmed the existence of a common protective haplotype against schizophrenia at the dopamine D₃ receptor (DRD3) gene, by replication and pooled analysis with previous data (Mantel–Haenszel χ² P value = 0.00227; OR = 0.79, 95% CI 0.68–0.92, based on 794 cases and 1,078 controls from three independent populations of European origin). This protective haplotype is at very low frequency in Sub-Saharan Africans (median 0.06) and at intermediate frequencies in other populations (median 0.25). We also revealed, by examining the patterns of linkage disequilibrium around this gene, that the protective haplotype has reached high frequency in non-African populations due to selection acting, most probably, on a linked functional polymorphism, the non-synonymous single nucleotide polymorphism Ser9Gly (rs6280), also at DRD3. Thus, this finding shows that the natural selection may play a role in the existence of common alleles conferring different susceptibility to schizophrenia. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

High yield of endoreduplication induced by ICRF-193: a topoisomerase II catalytic inhibitor

Previous studies have demonstrated that phenolic compounds, including genistein (4',5,7-trihydroxyisoflavone) and resveratrol (3,4',5-trihydroxystilbene), are able to protect against carcinogenesis in animal models. This study was undertaken to examine the ability of genistein and resveratrol to inhibit reactive oxygen species (ROS)-mediated strand breaks in phi X-174 plasmid DNA. H(2)O(2)/Cu(II) and hydroquinone/Cu(II) were used to cause oxidative DNA strand breaks in the plasmid DNA. We demonstrated that the presence of genistein at micromolar concentrations resulted in a marked inhibition of DNA strand breaks induced by either H(2)O(2)/Cu(II) or hydroquinone/Cu(II). Genistein neither affected the Cu(II)/Cu(I) redox cycle nor reacted with H(2)O(2) suggest that genistein may directly scavenge the ROS that participate in the induction of DNA strand breaks. In contrast to the inhibitory effects of genistein, the presence of resveratrol at similar concentrations led to increased DNA strand breaks induced by H(2)O(2)/Cu(II). Further studies showed that in the presence of Cu(II), resveratrol, but not genistein was able to cause DNA strand breaks. Moreover, both Cu(II)/Cu(I) redox cycle and H(2)O(2) were shown to be critically involved in resveratrol/copper-mediated DNA strand breaks. The above results indicate that despite their similar in vivo anticarcinogenic effects, genistein and resveratrol appear to exert different effects on oxidative DNA damage in vitro.     

Factors affecting malate dehydrogenase activity in freezing-thawing processes

Malate dehydrogenases from several sources show different behaviour when frozen-thawed in 100 mM sodium phosphate buffer, pH 7.4, containing chaotropic ions. The effects produced by the addition of various metabolites, protein concentration and buffer medium used on the loss of activity induced by the freezing-thawing process are reported. The major part of the loss of activity is caused by the formation of "wrong" aggregates of high mol. wt.     

Characterization of Epstein–Barr virus reactivation in a modeled spaceflight system

Epstein–Barr virus (EBV) is the causative agent of mononucleosis and is also associated with several malignancies, including Burkitt's lymphoma, Hodgkin's lymphoma, and nasopharyngeal carcinoma, among others. EBV reactivates during spaceflight, with EBV shedding in saliva increasing to levels ten times those observed pre‐and post‐flight. Although stress has been shown to increase reactivation of EBV, other factors such as radiation and microgravity have been hypothesized to contribute to reactivation in space. We used a modeled spaceflight environment to evaluate the influence of radiation and microgravity on EBV reactivation. BJAB (EBV‐negative) and Raji (EBV‐positive) cell lines were assessed for viability/apoptosis, viral antigen and reactive oxygen species expression, and DNA damage and repair. EBV‐infected cells did not experience decreased viability and increased apoptosis due to modeled spaceflight, whereas an EBV‐negative cell line did, suggesting that EBV infection provided protection against apoptosis and cell death. Radiation was the major contributor to EBV ZEBRA upregulation. Combining modeled microgravity and radiation increased DNA damage and reactive oxygen species while modeled microgravity alone decreased DNA repair in Raji cells. Additionally, EBV‐infected cells had increased DNA damage compared to EBV‐negative cells. Since EBV‐infected cells do not undergo apoptosis as readily as uninfected cells, it is possible that virus‐infected cells in EBV seropositive individuals may have an increased risk to accumulate DNA damage during spaceflight. More studies are warranted to investigate this possibility. J. Cell. Biochem. 114: 616–624, 2013. © 2012 Wiley Periodicals, Inc.     

Growth Rate of the Microalga Tetraselmis suecica Changes the Biochemical Composition of Artemia Species

The impact of different microalgal semicontinuous cultures on growth and biochemical composition in the next link of the food chain was tested using the filter feeder Artemia species as a model. The marine microalga Tetraselmis suecica was cultured semicontinuously with renewal rates between 10% and 50% and used to feed Artemia. Microalgal cultures maintained with a low renewal rate that had biochemical composition similar to that of the stationary-phase cultures commonly used in aquaculture produced poor growth and survival and low food-conversion efficiency compared to cultures maintained with a high renewal rate. Changes in the renewal rate in microalgal cultures also resulted in important changes in the gross biochemical composition of the filter feeder. The gross biochemical composition of the Artemia resembled that of the microalgae used as food except for total lipid content. The percentage of protein in the organic fraction of Artemia increased from 45% to 65% of the organic weight with increasing renewal rates in the microalgal cultures, while the carbohydrate percentage decreased under the same conditions. Higher renewal rates resulted in higher lipid percentages in the microalga, but in Artemia the percentage of lipids decreased from 19% of the organic weight with a renewal rate of 10%, to 13% with a renewal rate of 50%. The percentage of all polyunsaturated fatty acids in Artemia, including 20:5n-3, increased slightly with increasing renewal rates in the microalgal cultures. Results emphasize the importance of controlling microalgal nutritional value for the success of aquaculture food chains in which filter feeders are involved. Received October 15, 2000; accepted December 29, 2000.     

Comparative insight into the Zn(II)-, Cd(II)- and Cu(I)-binding features of the protozoan Tetrahymena pyriformis MT1 metallothionein

Tetrahymena pyriformis MT1 (TpyMT1) is a model among ciliate metallothioneins (MTs). Here, we report on the analytic (ICP-AES, GC-FPD), spectroscopic (CD, UV-Vis, Raman) and spectrometric (ESI-MS) characterization of its recombinant Cd(II)-, Zn(II)- and Cu(I)-complexes, and of those formed during in vitro Zn/Cd and Zn/Cu replacement. In the presence of Cd(II), TpyMT1 renders a major Cd 11-TpyMT1 species, which is also the final step reached in the in vitro Zn/Cd exchange process in Zn 11-TpyMT1. Spectroscopic data supports a different folding of the isostoichiometric Cd 11- and Zn 11-TpyMT1 complexes. Unexpectedly, TpyMT1 biosynthesis in Zn(II)-rich cultures was sensitive to the aeration degree, so that high oxygenation rendered undermetalated, partially-oxidized, complexes (Zn9-TpyMT1). Biosynthesis in Cu(I)-rich media rendered extremely heterogeneous mixtures of CuxZny-species (x+y=8-20), where the higher the aeration, the higher the Zn(II) content. The complexity of these samples was reproduced during the Zn/Cu replacement, as the number of generated species increased gradually with the addition of copper to Zn(11)-TpyMT1. According to our results, a clear preference of TpyMT1 for Cd(II) binding, rather than for Zn(II), and especially Cu(I) can be postulated. This character is totally consistent with the induction pattern of the TpyMT1 gene and the postulated role of TpyMT1 in Cd-detoxification.