Evidence for Lymphatic Aβ Clearance in Alzheimer’s Transgenic Mice

Evidence has shown that lymphatic drainage contributes to removal of debris from the brain but its role in the accumulation of amyloid β peptides (Aβ) has not been demonstrated. We examined the levels of various forms of Aβ in the brain, plasma and lymph nodes in a transgenic model of Alzheimer’s disease (AD) at different ages. Herein, we report on the novel finding that Aβ is present in the cervical and axillary lymph nodes of AD transgenic mice and that Aβ levels in lymph nodes increase over time, mirroring the increase of Aβ levels observed in the brain. Aβ levels in lymph nodes were significantly higher than in plasma. At age 15.5 months, there was a significant increase of monomeric soluble Aβ40 (p=0.003) and Aβ42 (p=0.05) in the lymph nodes over the baseline values measured at 6 months of age. In contrast, plasma levels of Aβ40 showed no significant changes (p=0.68) and plasma levels Aβ42 significantly dropped (p=0.02) at the same age. Aβ concentration was low to undetectable in splenic lymphoid tissue and several other control tissues including heart, lung, liver, kidneys and intestine of the same animals, strongly suggesting that Aβ peptides in lymph nodes are derived from the brain

Beneficial insects associated with attractive weed plants in agroecosystems from the eastern slope of the Andes in the Colombian Orinoco basin

Se estudió la biodiversidad de insectos benéficos asociados a plantas arvenses en agroecosistemas de cacao, guanábana y arroz. Se realizaron muestreos en cinco especies de plantas arvenses asociadas a los agroecosistemas: Crotalaria striata, Indigofera hirsuta, Hyptis capitata, Melampodium divaricatum y Stachytarpheta cayennensis. Los insectos se colectaron mediante muestreos sistemáticos con red entomológica y observaciones directas a través de un transecto lineal. Se realiza por primera vez un inventario detallado de la diversidad de insectos benéficos asociada a agroecosistemas del departamento del Meta, compuesta por 66 especies/morfoespecies. Se reportan datos de interés de diez especies, entre ellos la ampliación del rango de distribución de ocho especies para la Orinoquia, así como el registro de dos nuevos géneros para Colombia: Myzinum (Hymenoptera: Tiphiidae) y Chaetogaedia (Diptera: Tachinidae). Se constata una amplia biodiversidad taxonómica y ecológica de insectos benéficos en estos ecosistemas transformados, diversidad entomológica asociada especialmente a la presencia de plantas arvenses que actúan como fuentes de alimentos suplementarios y sitios de refugio para estos insectos. Este estudio pretende aportar datos de interés para el manejo integrado de plagas, programas de restauración ecológica y conocimiento de la biología de las especies registradas.The biodiversity of beneficial insects associated with weed plants in agroecosystems of cocoa, soursop and rice was studied. Five species of weed plants associated with these agroecosystems were considered for the samplings: Crotalaria striata, Indigofera hirsuta, Hyptis capitata, Melampodium divaricatum and Stachytarpheta cayennensis. Beneficial insects were collected through systematic samplings using an entomological net, together with direct observations through a linear transect. A detailed inventory of the community of beneficial insects associated with agroecosystems in the departamento del Meta is provided for the first time, composed of 66 species/morphospecies. Eight species were recorded for the first time from the Orinoco basin, and two genera are new from Colombia: Myzinum (Hymenoptera: Tiphiidae) and Chaetogaedia (Diptera: Tachinidae). A high taxonomic and ecological biodiversity of beneficial insects was found to be associated with weed plants within these transformed agroecosystems, which provided supplementary trophic resources and refuge to the beneficial insects. This study provides interesting data for integrated pest management plans and ecological restoration programs, and contributes to the knowledge of the biology of the species reported

DCO2/PaCO2 correlation on high-frequency oscillatory ventilation combined with volume guarantee using increasing frequencies in an animal model

To examine the correlation DCO2/PaCO2 on high-frequency oscillatory ventilation (HFOV) combined with volume guarantee (VG) throughout increasing frequencies in two different respiratory conditions, physiological and low compliance. Neonatal animal model was used, before and after a bronchoalveolar lavage (BAL). HFOV combined with VG was used. The frequency was increased from 10 to 20 Hz, and high-frequency tidal volume (VThf) was gradually decreased maintaining a constant DCO2. Arterial partial pressure of carbon dioxide (PaCO2) was evaluated after each frequency and VThf change. Six 2-day-old piglets were studied. A linear decrease in PaCO2 was observed throughout increasing frequencies in both respiratory conditions while maintaining a constant DCO2, showing a significant difference between the initial PaCO2 (at 10 Hz) and the PaCO2 obtained at 18 and 20 Hz. A new DCO2 equation (corrected DCO2) was calculated in order to better define the correlation between DCO2 and the observed PaCO2.Conclusion: The correlation DCO2/PaCO2 throughout increasing frequencies is not linear, showing a greater CO2 elimination efficiency at higher frequencies, in spite of maintaining a constant DCO2. So, using frequencies close to the resonant frequency of the respiratory system on HFOV combined with VG, optimizes the efficiency of gas exchange.What is Known: • The efficacy of CO2removal during high-frequency oscillatory ventilation (HFOV), described as the diffusion coefficient of CO2(DCO2) is related to the square of the high-frequency tidal volume (VThf) and the frequency (f), expressed as DCO2= VThf2× f.What is New: • The correlation between DCO2and PaCO2throughout increasing frequencies is not linear, showing a greater CO2elimination efficiency at higher frequencies. So, using very high frequencies on HFOV combined with volume guarantee optimizes the efficiency of gas exchange allowing to minimize lung injury.ISCIIIDepto. de Salud Pública y Materno - InfantilFac. de MedicinaTRUEpu

Evidence of a novel mechanism for partial γ-secretase inhibition induced paradoxical increase in secreted amyloid β protein.

BACE1 (β-secretase) and α-secretase cleave the Alzheimer's amyloid β protein (Aβ) precursor (APP) to C-terminal fragments of 99 aa (CTFβ) and 83 aa (CTFα), respectively, which are further cleaved by γ-secretase to eventually secrete Aβ and Aα (a.k.a. P3) that terminate predominantly at residues 40 and 42. A number of γ-secretase inhibitors (GSIs), such as N-[N-(3,5-Difluorophenacetyl-L-alanyl)]-S-phenylglycine t-butyl ester (DAPT), have been developed with the goal of reducing Aβ to treat Alzheimer's disease (AD). Although most studies show that DAPT inhibits Aβ in a dose-dependent manner several studies have also detected a biphasic effect with an unexpected increase at low doses of DAPT in cell cultures, animal models and clinical trials. In this article, we confirm the increase in Aβ40 and Aβ42 in SH-SY5Y human neuroblastoma cells treated with low doses of DAPT and identify one of the mechanisms for this paradox. We studied the pathway by first demonstrating that stimulation of Aβ, a product of γ-secretase, was accompanied by a parallel increase of its substrate CTFβ, thereby demonstrating that the inhibitor was not anomalously stimulating enzyme activity at low levels. Secondly, we have demonstrated that inhibition of an Aβ degrading activity, endothelin converting enzyme (ECE), yielded more Aβ, but abolished the DAPT-induced stimulation. Finally, we have demonstrated that Aα, which is generated in the secretory pathway before endocytosis, is not subject to the DAPT-mediated stimulation. We therefore conclude that impairment of γ-secretase can paradoxically increase Aβ by transiently skirting Aβ degradation in the endosome. This study adds to the growing body of literature suggesting that preserving γ-secretase activity, rather than inhibiting it, is important for prevention of neurodegeneration

DAPT induced increase in Aβ does not alter APP processing.

<p>Western blots of cell lysates of SH-SY5Y cells from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0091531#pone-0091531-g002" target="_blank">Fig 2</a> were detected in triplicates using the O443 antibody (A) and 82E1 (B); and media were analyzed with the WO2 antibody against Aβ1-16 (C) as described in Materials and Methods. Full-length APP from A (D), CTFα from A (F) and CTFβ from B (G) were quantified using the AlphaEase software and total sAPP (E; measured by an ELISA assay from R&D systems) were plotted as bar graphs. Full-length and secreted APP in panels D and E are not different from vehicle-treated controls. Tukey-Kramer analysis shows that there is significant dose-dependent increase in CTFβ (p<0.0001) and CTFα (p<0.0001) with DAPT treatment. Note that CTFβ reaches saturation at 50 nM DAPT whereas O443 does not saturate even at 100 nM. Panel H: Schematic of the APP695 protein as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0091531#pone-0091531-g001" target="_blank">Fig 1</a>.</p

Low doses of DAPT unexpectedly increase Aβ40 and Aβ42 levels.

<p>SH-SY5Y-APP cells were cultured in six-well dishes and treated with either vehicle (DMSO) or DAPT at 12.5 to 1000 nM for 2 (orange), 4 (blue) and 8 h (red). Media were analyzed by sensitive and specific sandwich ELISA assays that use end-specific antibodies to specifically capture the Aβ40 (A) and Aβ42 (B) and were detected using the end-specific antibodies for the Aβ N-terminus (3D6, Innogenetics). After Tukey-Kramer adjustment the P values for left panel (A) showed highly significant stimulation of Aβ40 at 12.5 and 25 nM (p<0.0001) at 8 h and significant stimulation at 2 and 4 h. A similar stimulation was also observed for Aβ42 at 12.5 and 25 nM (p<0.0002). Inhibition at a dose of 1 μM was highly significant (p<0.0001) for Aβ40 and 42 as expected (Data not shown). For all graphs significance indicated by symbols # p<0.01 and * p<0.05.</p