Network of phase-locking oscillators and a possible model for neural synchronization

In order to model the synchronization of brain signals, a three-node fully-connected network is presented. The nodes are considered to be voltage control oscillator neurons (VCON) allowing to conjecture about how the whole process depends on synaptic gains, free-running frequencies and delays. The VCON, represented by phase-locked loops (PLL), are fully-connected and, as a consequence, an asymptotically stable synchronous state appears. Here, an expression for the synchronous state frequency is derived and the parameter dependence of its stability is discussed. Numerical simulations are performed providing conditions for the use of the derived formulae. Model differential equations are hard to be analytically treated, but some simplifying assumptions combined with simulations provide an alternative formulation for the long-term behavior of the fully-connected VCON network. Regarding this kind of network as models for brain frequency signal processing, with each PLL representing a neuron (VCON), conditions for their synchronization are proposed, considering the different bands of brain activity signals and relating them to synaptic gains, delays and free-running frequencies. For the delta waves, the synchronous state depends strongly on the delays. However, for alpha, beta and theta waves, the free-running individual frequencies determine the synchronous state. (C) 2011 Elsevier B.V. All rights reserved.

Protein-Energy Malnutrition Modifies the Production of Interleukin-10 in Response to Lipopolysaccharide (LPS) in a Murine Model

Malnutrition modifies resistance to infection by impairing a number of physiological processes including hematopoesis and the immune response. In this study, we examined the production of Interleukin-4 (IL-4) and IL-10 in response to lipopolysaccharide (LPS) and also evaluated the cellularity of the blood, bone marrow, and spleen in a mouse model of protein-energy malnutrition. Two-month-old male Swiss mice were subjected to protein-energy malnutrition (PEM) with a low-protein diet (4%) as compared to the control diet (20%). When the experimental group lost approximately 20% of their original body weight, the animals from both groups received 1.25 mu g of LPS intravenously. The Cells ill the blood, bone marrow, and spleen were counted, and circulating levels of IL-4 and IL-10 were evaluated in animals stimulated with LPS. Cells from the spleen, bone marrow, and peritoneal cavity of non-inoculated animals were collected for Culture to evaluate the production of IL-4 and IL-10 after stimulating these cells with 1.25 mu g of LPS in vitro. Malnourished animals presented leucopenia and a severe reduction in bone marrow, spleen, and peritoneal cavity cellularity before and after Stimulus with LPS. The circulating levels of IL-10 were increased in malnourished animals inoculated with LPS when compared to control animals, although the levels of IL-4 did not differ. In cells cultured with LPS, we observed high levels of IL-10 in the bone marrow cells of malnourished animals. These findings suggest that malnourished mice present a deficient immune response to LPS. These alterations may be partly responsible for the immunodeficiency observed in these malnourished mice.

Rational Design and 3D-Pharmacophore Mapping of 5 `-Thiourea-Substituted alpha-Thymidine Analogues as Mycobacterial TMPK Inhibitors

Thymidine monophosphate kinase (TMPK) has emerged as an attractive target for developing inhibitors of Mycobacterium tuberculosis growth. In this study the receptor-independent (RI) 4D-QSAR formalism has been used to develop QSAR models and corresponding 3D-pharmacophores for a set of 5`-thiourea-substituted alpha-thymidine inhibitors. Models were developed for the entire training set and for a subset of the training set consisting of the most potent inhibitors. The optimized (RI) 4D-QSAR models are statistically significant (r(2) = 0.90, q(2) = 0.83 entire set, r(2) = 0.86, q(2) = 0.80 high potency subset) and also possess good predictivity based on test set predictions. The most and least potent inhibitors, in their respective postulated active conformations derived from the models, were docked in the active site of the TMPK crystallographic structure. There is a solid consistency between the 3D-pharmacophore sites defined by the QSAR models and interactions with binding site residues. This model identifies new regions of the inhibitors that contain pharmacophore sites, such as the sugar-pyrimidine ring structure and the region of the 5`-arylthiourea moiety. These new regions of the ligands can be further explored and possibly exploited to identify new, novel, and, perhaps, better antituberculosis inhibitors of TMPKmt. Furthermore, the 3D-pharmacophores defined by these models can be used as a starting point for future receptor-dependent antituberculosis drug design as well as to elucidate candidate sites for substituent addition to optimize ADMET properties of analog inhibitors.

Dexamethasone Effects in the Strongyloides venezuelensis Infection in A Murine Model

The aim of this study was to investigate the immunomodulatory effects of glucocorticoids on the immune response to Strongyloides venezuelensis in mice. Balb/c mice were infected with S. venezuelensis and treated with Dexamethasone (Dexa) or vehicle. Dexa treatment increased circulating blood neutrophil numbers and inhibited eosinophil and mononuclear cell accumulation in the blood, bronchoalveolar, and peritoneal fluid compared with control animals. Moreover, Dexa decreased tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), interleukin-3 (IL-3), IL-4, IL-5, IL-10, and IL-12 production in the lungs and circulating immunoglobulin G1. (IgG1), IgG2a, and IgE antibody levels while increasing the overall parasite burden in the feces and intestine. Dexa treatment enhanced the fertility of female nematodes relative to untreated and infected mice. In summary, the alterations in the immune response induced by Dexa resulted in a blunted, aberrant immune response associated with increased parasite burden. This phenomenon is similar to that observed in S. stercoralis-infected humans who are taking immunosuppressive or antiinflammatory drugs, including corticosteroids.

Sequence analysis, chromosomal distribution and long-range organization show that rapid turnover of new and old pBuM satellite DNA repeats leads to different patterns of variation in seven species of the Drosophila buzzatii cluster

We aimed to study patterns of variation and factors influencing the evolutionary dynamics of a satellite DNA, pBuM, in all seven Drosophila species from the buzzatii cluster (repleta group). We analyzed 117 alpha pBuM-1 (monomer length 190 bp) and 119 composite alpha/beta (370 bp) pBuM-2 repeats and determined the chromosome location and long-range organization on DNA fibers of major sequence variants. Such combined methodologies in the study of satDNAs have been used in very few organisms. In most species, concerted evolution is linked to high copy number of pBuM repeats. Species presenting low-abundance and scattered distributed pBuM repeats did not undergo concerted evolution and maintained part of the ancestral inter-repeat variability. The alpha and alpha/beta repeats colocalized in heterochromatic regions and were distributed on multiple chromosomes, with notable differences between species. High-resolution FISH revealed array sizes of a few kilobases to over 0.7 Mb and mutual arrangements of alpha and alpha/beta repeats along the same DNA fibers, but with considerable changes in the amount of each variant across species. From sequence, chromosomal and phylogenetic data, we could infer that homogenization and amplification events involved both new and ancestral pBuM variants. Altogether, the data on the structure and organization of the pBuM satDNA give insights into genome evolution including mechanisms that contribute to concerted evolution and diversification.

Cation Transport Coupled to ATP Hydrolysis By the (Na, K)-ATPase AN INTEGRATED, ANIMATED MODEL

An Adobe (R) animation is presented for use in undergraduate Biochemistry courses, illustrating the mechanism of Na(+) and K(+) translocation coupled to ATP hydrolysis by the (Na, K)-ATPase, a P(2c)-type ATPase, or ATP-powered ion pump that actively translocates cations across plasma membranes. The enzyme is also known as an E(1)/E(2)-ATPase as it undergoes conformational changes between the E(1) and E(2) forms during the pumping cycle, altering the affinity and accessibility of the transmembrane ion-binding sites. The animation is based on Horisberger`s scheme that incorporates the most recent significant findings to have improved our understanding of the (Na, K)-ATPase structure function relationship. The movements of the various domains within the (Na, K)-ATPase alpha-subunit illustrate the conformational changes that occur during Na(+) and K(+) translocation across the membrane and emphasize involvement of the actuator, nucleotide, and phosphorylation domains, that is, the ""core engine"" of the pump, with respect to ATP binding, cation transport, and ADP and P(i) release.

HUMAN CHOLESTERYL ESTER TRANSFER PROTEIN EXPRESSION ENHANCES THE MOUSE SURVIVAL RATE IN AN EXPERIMENTAL SYSTEMIC INFLAMMATION MODEL: A NOVEL ROLE FOR CETP

Mice expressing human cholesteryl ester transfer protein (huCETP) are more resistant to Escherichia coli bacterial wall LIPS because death rates 5 days after intraperitoneal inoculation of LIPS were higher in wild-type than in huCETP(+/-) mice, whereas all huCETP(+/+) mice remained alive. After LIPS inoculation, plasma concentrations of TNF-alpha and IL-6 increased less in huCETP(+/+) than in wild-type mice. LPS in vitro elicited lower TNF-alpha production by CETP expressing than by wild-type macrophages. In addition, TNF-alpha production by RAW 264.7 murine macrophages increased on incubation with LPS but decreased in a dose-dependent manner when human CETP was added to the medium. Human CETP in vitro enhanced the LIPS binding to plasma high-density lipoprotein/low-density lipoprotein. The liver uptake of intravenous infused C-14-LPS from Salmonella typhimurium was greater in huCETP(+/+) than in wild-type mice. Present data indicate for the first time that CETP is an endogenous component involved in the first line of defense against an exacerbated production of proinflammatory mediators.

Human breast tumor slices: A model for identification of vitamin D regulated genes in the tumor microenvironment

While many studies have addressed the direct effects of 1 alpha,25(OH)(2)D(3) on breast cancer (BC) cells, stromal-epithelial interactions, which are important for the tumor development, have been largely ignored. In addition, high concentrations of the hormone, which cannot be attained in vivo, have been used. Our aim was to establish a more physiological breast cancer model, represented by BC tissue slices, which maintain epithelial-mesenchymal interactions, cultured with a relatively low 1 alpha,25(OH)(2)D(3) concentration, in order to evaluate the vitamin D pathway. Freshly excised human BC samples were sliced and cultured in complete culture media containing vehicle, 0.5 nM or 100 nM 1 alpha,25(OH)(2)D(3) for 24 h. BC slices remained viable for at least 24 h, as evaluated by preserved tissue morphology in hematoxylin and eosin (HE) stained sections and bromodeoxyuridine (BrdU) incorporation by 10% of tumor cells. VDR mRNA expression was detected in all samples and CYP24A1 mRNA expression was induced by 1 alpha,25(OH)(2)D(3) in both concentrations (but mainly with 100 nM). Our results indicate that the vitamin D signaling pathway is functional in BC slices, a model which preserves stromal-epithelial interactions and mimics in vivo conditions. (C) 2010 Elsevier Ltd. All rights reserved.

ADAM23 Negatively Modulates alpha(v)beta(3) Integrin Activation during Metastasis

The ADAM23 gene is frequently silenced in different types of tumors, and, in breast tumors, silencing is correlated with tumor progression, suggesting that it might be associated with the acquisition of a metastatic phenotype. ADAM23 exerts its function mainly through the disintegrin domain, because its metalloprotease domain is inactive. Analysis of ADAM23 binding to integrins has revealed a specific interaction with alpha(v)beta(3) integrin mediated by the disintegrin domain. Altered expression of alpha(v)beta(3) integrin has been observed in different types of tumors, and expression of this integrin in the activated form has been shown to promote metastasis formation. Here, we investigated the possibility that interaction between ADAM23 and alpha(v)beta(3) integrin might negatively modulate alpha(v)beta(3) activation during metastatic progression. ADAM23 expression was knocked down using short hairpin RNA in the MDA-MB-435 cell line, which has been extensively used as a model for alpha(v)beta(3) integrin activation. Ablation of ADAM23 enhanced alpha(v)beta(3) integrin activation by at least 2- to 4-fold and ADAM23 knockdown cells showed enhanced migration and adhesion to classic alpha(v)beta(3) integrin ligands. Ablation of ADAM23 expression also enhanced pulmonary tumor cell arrest in immunodeficient mice. To complement our findings with clinical evidence, we showed that silencing of ADAM23 gene by DNA promoter hypermethylation in a collection of 94 primary breast tumors was significantly associated with lower distant metastases-free and disease-specific survivals and was an independent prognostic factor for poor disease outcome. Our results strongly support a functional role of ADAM23 during metastatic progression by negatively modulating alpha(v)beta(3) integrin activation. [Cancer Res 2009;69(13):5546-52]

Inducible nitric oxide synthase inhibition attenuates lung tissue responsiveness and remodeling in a model of chronic pulmonary inflammation in guinea pigs

We evaluated the influence of iNOS-derived NO on the mechanics, inflammatory, and remodeling process in peripheral lung parenchyma of guinea pigs with chronic pulmonary allergic inflammation. Animals treated or not with 1400W were submitted to seven exposures of ovalbumin in increasing doses. Seventy-two hours after the 7th inhalation, lung strips were suspended in a Krebs organ bath, and tissue resistance and elastance measured at baseline and after ovalbumin challenge. The strips were submitted to histopathological measurements. The ovalbumin-exposed animals showed increased maximal responses of resistance and elastance (p < 0.05), eosinophils counting (p < 0.001), iNOS-positive cells (p < 0.001), collagen and elastic fiber deposition (p < 0.05), actin density (p < 0.05) and 8-iso-PGF2 alpha expression (p < 0.001) in alveolar septa compared to saline-exposed ones. Ovalbumin-exposed animals treated with 1400 W had a significant reduction in lung functional and histopathological findings (p < 0.05). We showed that iNOS-specific inhibition attenuates lung parenchyma constriction, inflammation, and remodeling, suggesting NO-participation in the modulation of the oxidative stress pathway. (C) 2008 Elsevier B.V. All rights reserved.

Different strains of mice present distinct lung tissue mechanics and extracellular matrix composition in a model of chronic allergic asthma

The impact of genetic factors on asthma is well recognized but poorly understood. We tested the hypothesis that different mouse strains present different lung tissue strip mechanics in a model of chronic allergic asthma and that these mechanical differences may be potentially related to changes of extracellular matrix composition and/or contractile elements in lung parenchyma. Oscillatory mechanics were analysed before and after acetylcholine (ACh) in C57BL/10, BALB/c, and A/J mice, subjected or not to ovalbumin sensitization and challenge. In controls, tissue elastance (E) and resistance (R), collagen and elastic fibres` content, and alpha-actin were higher in A/J compared to BALB/c mice, which, in turn, were more elevated than in C57BL/10. A similar response pattern was observed in ovalbumin-challenged animals irrespective of mouse strain. E and R augmented more in ovalbumin-challenged A/J [E: 22%, R: 18%] than C57BL/10 mice [E: 9.4%, R: 11 %] after ACh In conclusion, lung parenchyma remodelled differently yielding distinct in vitro mechanics according to mouse strain. (C) 2008 Elsevier B.V. All rights reserved.

Protective effect of octreotide and infliximab in an experimental model of indomethacin-induced inflammatory bowel disease

Indomethacin administration in animals increases permeability of the small intestine, leading to inflammation that mimics Crohn`s disease. Nonsteroidal anti-inflammatory drugs increase the permeability of the intestinal epithelial barrier and should therefore be used with caution in patients with Crohn`s disease. We analyzed the protective effects of octreotide and the tumor necrosis factor-alpha inhibitor infliximab in a rat model of indomethacin-induced enterocolitis. Male Wistar rats received 20 mg of infliximab or 10 mu g of octreotide 24 h prior to injection with indomethacin. Intestinal permeability was analyzed using Cr-51-ethylenediaminetetraacetic acid clearance. No microscopic or macroscopic alterations were observed in the rats receiving infliximab or octreotide, both of which increased permeability (P < 0.001 versus controls). Our macroscopic and microscopic findings might be related to the low specificity of infliximab and suggest that cytokines affect the intestinal epithelial barrier, as evidenced by the protective effect that infliximab had on the permeability parameters evaluated.

Assisted ventilation modes reduce the expression of lung inflammatory and fibrogenic mediators in a model of mild acute lung injury

The goal of the study was to compare the effects of different assisted ventilation modes with pressure controlled ventilation (PCV) on lung histology, arterial blood gases, inflammatory and fibrogenic mediators in experimental acute lung injury (ALI). Paraquat-induced ALI rats were studied. At 24 h, animals were anaesthetised and further randomized as follows (n = 6/group): (1) pressure controlled ventilation mode (PCV) with tidal volume (V (T)) = 6 ml/kg and inspiratory to expiratory ratio (I:E) = 1:2; (2) three assisted ventilation modes: (a) assist-pressure controlled ventilation (APCV1:2) with I:E = 1:2, (b) APCV1:1 with I:E = 1:1; and (c) biphasic positive airway pressure and pressure support ventilation (BiVent + PSV), and (3) spontaneous breathing without PEEP in air. PCV, APCV1:1, and APCV1:2 were set with P (insp) = 10 cmH(2)O and PEEP = 5 cmH(2)O. BiVent + PSV was set with two levels of CPAP [inspiratory pressure (P (High) = 10 cmH(2)O) and positive end-expiratory pressure (P (Low) = 5 cmH(2)O)] and inspiratory/expiratory times: T (High) = 0.3 s and T (Low) = 0.3 s. PSV was set as follows: 2 cmH(2)O above P (High) and 7 cmH(2)O above P (Low). All rats were mechanically ventilated in air and PEEP = 5 cmH(2)O for 1 h. Assisted ventilation modes led to better functional improvement and less lung injury compared to PCV. APCV1:1 and BiVent + PSV presented similar oxygenation levels, which were higher than in APCV1:2. Bivent + PSV led to less alveolar epithelium injury and lower expression of tumour necrosis factor-alpha, interleukin-6, and type III procollagen. In this experimental ALI model, assisted ventilation modes presented greater beneficial effects on respiratory function and a reduction in lung injury compared to PCV. Among assisted ventilation modes, Bi-Vent + PSV demonstrated better functional results with less lung damage and expression of inflammatory mediators.

Histopathology, humoral and cellular immune response in the murine model of Leishmania (Viannia) shawi

Leishmania (Viannia) shawl was recently characterized and few studies concerning modifications in cellular and humoral immune responses in experimental leishmaniasis have been conducted. In this work, immunopathological changes induced by L. shawl in chronically infected BALB/c mice were investigated. Infected BALB/c mice developed increased lesion size associated with strong inflammatory infiltrate diffusely distributed in the dermis, with highly infected macrophages. The humoral immune response was predominantly directed toward the IgG1 isotype. The functional activity of CD4(+) and CD8(+) T cells showed significantly increased TNF-alpha mRNA levels associated with reduced IFN-gamma expression by CD4(+) T cells and the double negative (dn) CD4CD8 cell subset. High IL-4 levels expressed by CD8(+) T cells and dnCD4CD8 and TGF-beta by CD4(+) and CD8(+) T cells were detected, while IL-10 was highly expressed by all three cell subpopulations. Taken together, these results show an evident imbalance between TNF-alpha and IFN-gamma that is unfavorable to amastigote replication control. Furthermore, L. shawi seems to regulate different cell populations to express deactivating cytokines to avoid its own destruction. This study indicates BALB/c mice as a potentially good experimental model for further studies on American cutaneous leishmaniosis caused by L. shawi. (C) 2010 Elsevier Ireland Ltd. All rights reserved.

Chronic Acetonemia Alters Liver Oxidative Balance and Lipid Content in Rats. A Model of Nash?

Acetone is considered to be a substance that can disturb cellular oxidative status, being also associated with the production of glucose during its metabolization. The objective of the present study was to determine the effects of chronic treatment with acetone in oxidative stress and metabolic parameters in rats. Twenty male Wistar rats were divided into two groups: control (CG) and chronic acetone group (CAG). After 28 days of acetone ingestion in a 5% aqueous solution (CAG) or water (CG) the animals were euthanized and urine, plasma and liver were collected for the determination of acetone, glucose, lipemia, hepatic fat, malondialdehyde (MDA), reduced glutathione (GSH), and vitamin E. As expected, urinary and plasma acetone levels were higher in CAG. There was no difference in hepatic MDA values between groups, whereas hepatic GSH was lower in CAG than in CG and hepatic vitamin E was higher in CAG than in CG. There was also an increase in glycemia, cholesterolemia and hepatic fat in CAG compared to CG. Chronic treatment with a 5% acetone solution produced an increase in acetonemia that was able to promote changes in hepatic oxidative metabolism and in lipid content in rats similar to those observed in nonalcoholic steatohepatitis.