Fourth-Order Perturbation Theory for the Half-Filled Hubbard Model in Infinite Dimensions

We calculate the zero-temperature self-energy to fourth-order perturbation theory in the Hubbard interaction $U$ for the half-filled Hubbard model in infinite dimensions. For the Bethe lattice with bare bandwidth $W$, we compare our perturbative results for the self-energy, the single-particle density of states, and the momentum distribution to those from approximate analytical and numerical studies of the model. Results for the density of states from perturbation theory at $U/W=0.4$ agree very well with those from the Dynamical Mean-Field Theory treated with the Fixed-Energy Exact Diagonalization and with the Dynamical Density-Matrix Renormalization Group. In contrast, our results reveal the limited resolution of the Numerical Renormalization Group approach in treating the Hubbard bands. The momentum distributions from all approximate studies of the model are very similar in the regime where perturbation theory is applicable, $U/W \le 0.6$. Iterated Perturbation Theory overestimates the quasiparticle weight above such moderate interaction strengths.Comment: 19 pages, 17 figures, submitted to EPJ

Atividade β-galactosidase associada com a senescência em fibroblastos do estroma ovariano in vitro

Introducción: Un campo de investigación creciente de la biología es la senescencia celular, mecanismo que ha sido asociado -bajo determinadas circunstancias- con la transformación maligna.Teniendo en cuenta la elevada incidencia de cáncer ovárico y su génesis preferencial a partir del epitelio superficial del ovario, así como la posibilidad de ocurrencia de una transición epiteliomesenquimática, se evaluó, tanto el crecimiento in vitro de los fibroblastos del estroma cortical, como la actividad a pH 6 de la β-galactosidasa, enzima cuya expresión ha sido clásicamente considerada como marcador de senescencia replicativa. Metodología: 48 muestras de fibroblastos de la corteza ovárica provenientes de donantes sin antecedentes de cáncer fueron cultivadas en forma seriada hasta el final de su vida replicativa. Mediante el método quimioluminiscente, en cada pase fue cuantificada la actividad β-galactosidasa a pH 6. Como control se utilizaron cultivos de células del epitelio superficial ovàrico de las mismas donantes. La actividad enzimática fue también evaluada en fibroblastos previamente inducidos a senescencia con peróxido de hidrógeno. Resultados: Las lecturas de actividad enzimática, analizadas en conjunto con la capacidad replicativa, indican que los cultivos de fibroblastos alcanzaron el estado senescente hacia los pases 4-5, lo que también ocurrió con las células epiteliales. Los fibroblastos inducidos a senescencia mostraron valores variables de actividad enzimática. Conclusiones: La semejanza entre los fibroblastos y las células epiteliales en cuanto al inicio de la senescencia podría estar relacionado con la transición epitelio-mesenquimática que ha sido descrita como factor de riesgo de cáncer derivado del epitelio superficial ovàrico. Valores bajos de actividad β-galactosidasa podrían sugerir que, en algunos casos, ocurrió inactivación de las vías de respuesta al estrés oxidativo.Introduction: A growing biological research field is the cellular senescence, a mechanism that has been associated, under certain circumstances, with malignant transformation. Given the high incidence of ovarian cancer and its main origin from the ovarian surface epithelium, as well as the possibility that an epithelial-mesenchymal transition occurs, we evaluated both the in vitro growth of stromal fibroblasts from the ovarian cortex and their β-galactosidase activity at pH 6, enzyme whose expression is considered as a marker of replicative senescence. Methods: 48 samples of ovarian cortical fibroblasts from donors without a history of cancer were serially cultured until the end of their replicative life. β-galactosidase activity at pH 6 was quantified in each passage by the chemiluminiscent method. As control, we used ovarian epithelial cell cultures from the same donors. The enzyme activity was also evaluated in fibroblasts previously induced to senescence by exposure to hydrogen peroxide. Results: The analysis of the enzyme activity and the replicative capacity taken together showed that the fibroblast cultures reached the senescent state at passages 4-5, as what happened with the control epithelial cells. Fibroblasts induced to senescence showed high variability in the values of enzymatic activity. Conclusions: The similarity between both types of cells in reaching the senescent state deserves to be taken into account in relation to the epithelialmesenchymal transition that has been proposed to explain their behavior in the genesis of cancer arising from ovarian surface epithelium. Low β-galactosidase activity values at pH 6 would suggest possible inactivation of the response pathways to oxidative stress.Introdução: um campo de pesquisa crescente da biologia é a senescência celular, mecanismo que tem sido associado, sob determinadas circunstancias, com a transformação maligna. Tendo em conta a elevada incidência de câncer ovariano e sua gênese preferencial a partir do epitélio superficial do ovário, assim como a possibilidade de ocorrência de uma transição epitélio-mesenquimática, se avaliou, tanto o crescimento in vitro dos fibroblastos do estroma cortical, como a atividade a pH 6 da β-galactosidase, enzima cuja expressão tem sido classicamente considerada como marcador de senescência replicativa. Metodologia: 48 amostras de fibroblastos do córtex ovariano provenientes de doadores sem antecedentes de câncer foram cultivadas em forma seriada até o final de sua vida replicativa. Mediante o método quimioluminescente, em cada passe foi quantificada a atividade β-galactosidase a pH 6. Como controle utilizou-se cultivos de células do epitélio superficial ovariano das mesmas doadoras. A atividade enzimática foi também avaliada em fibroblastos previamente induzidos a senescência com peróxido de hidrogeno. Resultados: as leituras da atividade enzimática, analisada em conjunto com a capacidade replicativa, indicam que os cultivos de fibroblastos alcançaram o estado senescente para os passes 4-5, o que também ocorreu com as células epiteliais. Os fibroblastos induzidos a senescência mostraram valores variáveis de atividade enzimática. Conclusões: as semelhanças entre os fibroblastos e as células epiteliais em quanto ao inicio da senescência poderia estar relacionado com a transição epitélio-mesenquimática que tem sido descrita como fator de risco de câncer derivado do epitélio superficial ovariano. Valores baixos de atividade β-galactosidase poderiam sugerir que, em alguns casos, ocorreu inativação das vias de resposta ao estresse oxidativo

The novel isoxazoline ectoparasiticide fluralaner: Selective inhibition of arthropod γ-aminobutyric acid- and l-glutamate-gated chloride channels and insecticidal/acaricidal activity

AbstractIsoxazolines are a novel class of parasiticides that are potent inhibitors of γ-aminobutyric acid (GABA)-gated chloride channels (GABACls) and l-glutamate-gated chloride channels (GluCls). In this study, the effects of the isoxazoline drug fluralaner on insect and acarid GABACl (RDL) and GluCl and its parasiticidal potency were investigated. We report the identification and cDNA cloning of Rhipicephalus (R.) microplus RDL and GluCl genes, and their functional expression in Xenopus laevis oocytes. The generation of six clonal HEK293 cell lines expressing Rhipicephalus microplus RDL and GluCl, Ctenocephalides felis RDL-A285 and RDL-S285, as well as Drosophila melanogaster RDLCl-A302 and RDL-S302, combined with the development of a membrane potential fluorescence dye assay allowed the comparison of ion channel inhibition by fluralaner with that of established insecticides addressing RDL and GluCl as targets. In these assays fluralaner was several orders of magnitude more potent than picrotoxinin and dieldrin, and performed 5-236 fold better than fipronil on the arthropod RDLs, while a rat GABACl remained unaffected. Comparative studies showed that R. microplus RDL is 52-fold more sensitive than R. microplus GluCl to fluralaner inhibition, confirming that the GABA-gated chloride channel is the primary target of this new parasiticide. In agreement with the superior RDL on-target activity, fluralaner outperformed dieldrin and fipronil in insecticidal screens on cat fleas (Ctenocephalides felis), yellow fever mosquito larvae (Aedes aegypti) and sheep blowfly larvae (Lucilia cuprina), as well as in acaricidal screens on cattle tick (R. microplus) adult females, brown dog tick (Rhipicephalus sanguineus) adult females and Ornithodoros moubata nymphs. These findings highlight the potential of fluralaner as a novel ectoparasiticide

Quantification of cell-free DNA for evaluating genotoxic damage from occupational exposure to car paints

cfDNA concentrations and type of comet in the exposed individuals - grouped by car paint shops - and BTX concentrations in the indoor air. Table S2. Socio-demographic data of the exposed cohort. Table S3. Socio-demographic data of the non-exposed cohort. Table S4. Exposed cohort. cfDNA and total count and types of comet. Table S5. Non-exposed cohort. cfDNA and total count and types of comet. Table S6. Air borne solvents concentrations in workshops. Table S7. Exposed cohort. Comet score data. Table S8. Non-exposed cohort. Comet score data. (DOCX 73 kb

Effects of fructooligosaccharides on cecum polyamine concentration and gut maturation in early-weaned piglets

Polyamines are molecules involved in cell growth and differentiation and are produced by bacterial metabolism. However, their production and effects by the microbiota selected by fructooligosaccharides consumption are controversial. In this study, we investigated the influence of supplementation of fructooligosaccharides on the cecal polyamine production by the microflora selected, and its effect on gut maturation in newborn piglets. Twenty piglets were fed a control formula (n = 10) or a formula supplemented with fructooligosaccharides (8 g/l) (n = 10) for 13 days. Colony-forming unit’s count of cecal content was done in different media. Several intestinal development parameters were measured as well as the polyamine concentration in the cecal mucosa and cecal content. A dose-dependent study on in vitro polyamine production by fructooligosaccharides addition to the isolated cecal content was performed. Bifidogenic activity of fructooligosaccharides increased polyamine concentration in the cecal content, mainly putrescine, with no beneficial effect on gut maturation. Bifidobacterium spp. were able to produce polyamines, but they were not the most significant bacterial producer of polyamines in the cecum of piglets fed fructooligosaccharides. Bifidogenic activity of fructooligosaccharides did not lead to an increase in gut maturation in piglets of 15 days of age although polyamines were increased in the cecal content

Drug-induced trafficking of p-glycoprotein in human brain capillary endothelial cells as demonstrated by exposure to mitomycin C.

P-glycoprotein (Pgp; ABCB1/MDR1) is a major efflux transporter at the blood-brain barrier (BBB), restricting the penetration of various compounds. In other tissues, trafficking of Pgp from subcellular stores to the cell surface has been demonstrated and may constitute a rapid way of the cell to respond to toxic compounds by functional membrane insertion of the transporter. It is not known whether drug-induced Pgp trafficking also occurs in brain capillary endothelial cells that form the BBB. In this study, trafficking of Pgp was investigated in human brain capillary endothelial cells (hCMEC/D3) that were stably transfected with a doxycycline-inducible MDR1-EGFP fusion plasmid. In the presence of doxycycline, these cells exhibited a 15-fold increase in Pgp-EGFP fusion protein expression, which was associated with an increased efflux of the Pgp substrate rhodamine 123 (Rho123). The chemotherapeutic agent mitomycin C (MMC) was used to study drug-induced trafficking of Pgp. Confocal fluorescence microscopy of single hCMEC/D3-MDR1-EGFP cells revealed that Pgp redistribution from intracellular pools to the cell surface occurred within 2 h of MMC exposure. Pgp-EGFP exhibited a punctuate pattern at the cell surface compatible with concentrated regions of the fusion protein in membrane microdomains, i.e., lipid rafts, which was confirmed by Western blot analysis of biotinylated cell surface proteins in Lubrol-resistant membranes. MMC exposure also increased the functionality of Pgp as assessed in three functional assays with Pgp substrates (Rho123, eFluxx-ID Gold, calcein-AM). However, this increase occurred with some delay after the increased Pgp expression and coincided with the release of Pgp from the Lubrol-resistant membrane complexes. Disrupting rafts by depleting the membrane of cholesterol increased the functionality of Pgp. Our data present the first direct evidence of drug-induced Pgp trafficking at the human BBB and indicate that Pgp has to be released from lipid rafts to gain its full functionality

Similarities and differences in the localization, trafficking, and function of P-glycoprotein in MDR1-EGFP-transduced rat versus human brain capillary endothelial cell lines

Background!#!In vitro models based on brain capillary endothelial cells (BCECs) are among the most versatile tools in blood-brain barrier research for testing drug penetration into the brain and how this is affected by efflux transporters such as P-glycoprotein (Pgp). However, compared to freshly isolated brain capillaries or primary BCECs, the expression of Pgp in immortalized BCEC lines is markedly lower, which prompted us previously to transduce the widely used human BCEC line hCMEC/D3 with a doxycycline-inducible MDR1-EGFP fusion plasmid. The EGFP-labeled Pgp in these cells allows studying the localization and trafficking of the transporter and how these processes are affected by drug exposure. Here we used this strategy for the rat BCEC line RBE4 and performed a face-to-face comparison of RBE4 and hCMEC/D3 wild-type (WT) and MDR1-EGFP transduced cells.!##!Methods!#!MDR1-EGFP-transduced variants were derived from WT cells by lentiviral transduction, using an MDR1-linker-EGFP vector. Localization, trafficking, and function of Pgp were compared in WT and MDR1-EGFP transduced cell lines. Primary cultures of rat BCECs and freshly isolated rat brain capillaries were used for comparison.!##!Results!#!All cells exhibited typical BCEC morphology. However, significant differences were observed in the localization of Pgp in that RBE4-MDR1-EGFP cells expressed Pgp primarily at the plasma membrane, whereas in hCMEC/D3 cells, the Pgp-EGFP fusion protein was visible both at the plasma membrane and in endolysosomal vesicles. Exposure to doxorubicin increased the number of Pgp-EGFP-positive endolysosomes, indicating a lysosomotropic effect. Furthermore, lysosomal trapping of doxorubicin was observed, likely contributing to the protection of the cell nucleus from damage. In cocultures of WT and MDR1-EGFP transduced cells, intercellular Pgp-EGFP trafficking was observed in RBE4 cells as previously reported for hCMEC/D3 cells. Compared to WT cells, the MDR1-EGFP transduced cells exhibited a significantly higher expression and function of Pgp. However, the junctional tightness of WT and MDR1-EGFP transduced RBE4 and hCMEC/D3 cells was markedly lower than that of primary BCECs, excluding the use of the cell lines for studying vectorial drug transport.!##!Conclusions!#!The present data indicate that MDR1-EGFP transduced RBE4 cells are an interesting tool to study the biogenesis of lysosomes and Pgp-mediated lysosomal drug trapping in response to chemotherapeutic agents and other compounds at the level of the blood-brain barrier

A face-to-face comparison of claudin-5 transduced human brain endothelial (hCMEC/D3) cells with porcine brain endothelial cells as blood–brain barrier models for drug transport studies

Background!#!Predictive in vitro models of the human blood-brain barrier (BBB) are essential in early drug discovery and development. Among available immortalized human brain capillary endothelial cell lines (BCECs), the hCMEC/D3 cell line has become the most widely used in vitro BBB model. However, monolayers of hCMEC/D3 cells form only moderately restrictive barriers, most likely because the major tight junction protein, claudin-5, is markedly downregulated. Thus, hCMEC/D3 monolayers cannot be used for vectorial drug transport experiments, which is a major disadvantage of this model.!##!Methods!#!Here we transduced hCMEC/D3 cells with a claudin-5 plasmid and compared the characteristics of these cells with those of hCMEC/D3 wildtype cells and primary cultured porcine BCECs.!##!Results!#!The claudin-5 transduced hCMEC/D3 exhibited expression levels (and junctional localization) of claudin-5 similar to those of primary cultured porcine BCECs. The transduced cells exhibited increased TEER values (211 Ω cm!##!Conclusions!#!The claudin-5 transduced hCMEC/D3 cells provide a tool to studying the contribution of claudin-5 to barrier tightness and how this can be further enhanced by additional transfections or other manipulations of this widely used in vitro model of the BBB

Pigment epithelium-derived factor: Clinical significance in estrogen-dependent tissues and its potential in cancer therapy

Pigment epithelium-derived factor (PEDF) is a glycoprotein that belongs to the family of noninhibitory serpins. The broad spectrum of PEDF biological activity is evident when considering its effects in promoting cell survival and proliferation, as well as its antiangiogenic, antitumor, and antimetastatic properties. Although the structural domains of the PEDF gene that mediate such diverse effects and their mechanisms of action have not been completely elucidated, there is a large body of evidence describing their diverse range of activities; this evidence combined with the regulation of PEDF expression by sex steroids and their receptors have led to the idea that PEDF is not only a diagnostic and prognostic marker for certain diseases such as cancer, but is also a potential therapeutic target. In this manner, this paper aims to generally review the regulation of PEDF expression and PEDF interactions, as well as the findings that relate PEDF to the role of estrogens and estrogen receptors. In addition, this manuscript will review major advances toward potential therapeutic applications of PEDF. © 2015, Mashhad University of Medical Sciences. All rights reserved