Estudio informativo variante San Martín de Valderaduey. CL-612, de Villamartín de Campos (N-610) a Zamora (N-630)

El presente Estudio tiene como fin primordial, la construcción de una Variante de trazado de la carretera CL-612 a su paso por la localidad de San Martín de Valderaduey, evitando así la travesía actual que presenta la CL-612 entre dicho núcleo y el de Villárdiga. Esta nueva variante exige para su realización la disposición de una estructura de tipo puente sobre el cauce del río Valderaduey, por lo que se plantean alternativas que circunvalen de manera global ambas localidades.

Variante de la carretera CL-605 en Barroman(Avila)

La carretera CL-605 de Segovia a Zamora se engloba en la Red Básica de Carreteras de la Junta de Castilla y León, con una longitud de unos 170 kms que se desarrollan en las provincias de Segovia, Ávila, Salamanca y Zamora. Su paso por la provincia de Ávila se sitúa entre sus P.P.K.K. aproximados 54+350 y 97+130, atravesando los términos municipales de Arévalo, Aldeaseca, Villanueva del Aceral, Barromán y Madrigal de las Altas Torres. En los cinco casos, las correspondientes localidades se sitúan en las inmediaciones de la carretera, aunque esta atraviesa la zona urbana definiendo una travesía de población sólo en los casos de Arévalo, Aldeaseca y Barromán. Este proyecto tiene por objeto definir y valorar las obras necesarias para la construcción de la variante de la última de las poblaciones indicadas, Barromán, desarrollando la alternativa elegida de las planteadas en el “Estudio de Alternativas” redactado en el mes de enero de 2012. En dicho estudio se procedió a definir cuatro posibles trazados, estimando la valoración de las obras a realizar para su construcción y definiendo y evaluando los criterios que permitieron realizar una comparación del carácter más objetivo posible entre las cuatro alternativas.

D. Jacobi Parez [sic] de Vale[n]tia ... ordinis diui Augustini ... expositiones in. CL. psal. Dauidicos ... Cantica ferialia in biblijs contenta. Cantica eua[n]gelica B[e]n[e]dictus Magnificat nu[n]c dimit. Gl[or]ia in excel. Ca[n]ticu[m] Amb. et Aug. Te Deum. Cantica canticor[um] Premissis Questio[n]ib[us] et earu[m] subtilissimis resolutionibus co[n]tra Judeos nostre fidei adversa [Texto impreso] : Cum tabula in totu[m] opus collecta

Marca tip. en port. y colofón en h. [27]

Regulation of CFTR Cl− channel gating by ATP binding and hydrolysis

Opening and closing of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl− channel is regulated by the interaction of ATP with its two cytoplasmic nucleotide-binding domains (NBD). Although ATP hydrolysis by the NBDs is required for normal gating, the influence of ATP binding versus hydrolysis on specific steps in the gating cycle remains uncertain. Earlier work showed that the absence of Mg2+ prevents hydrolysis. We found that even in the absence of Mg2+, ATP could support channel activity, albeit at a reduced level compared with the presence of Mg2+. Application of ATP with a divalent cation, including the poorly hydrolyzed CaATP complex, increased the rate of opening. Moreover, in CFTR variants with mutations that disrupt hydrolysis, ATP alone opened the channel and Mg2+ further enhanced ATP-dependent opening. These data suggest that ATP alone can open the channel and that divalent cations increase ATP binding. Consistent with this conclusion, when we mutated an aspartate thought to bind Mg2+, divalent cations failed to increase activity compared with ATP alone. Two observations suggested that divalent cations also stabilize the open state. In wild-type CFTR, CaATP generated a long duration open state, whereas ATP alone did not. With a CFTR variant in which hydrolysis was disrupted, MgATP, but not ATP alone, produced long openings. These results suggest a gating cycle for CFTR in which ATP binding opens the channel and either hydrolysis or dissociation leads to channel closure. In addition, the data suggest that ATP binding and hydrolysis by either NBD can gate the channel.

Local osmotic gradients drive the water flux associated with Na+/glucose cotransport

It recently was proposed [Loo, D. D. F., Zeuthen, T., Chandy, G. & Wright, E. M. (1996) Proc. Natl. Acad. Sci. USA 93, 13367–13370] that SGLT1, the high affinity intestinal and renal sodium/glucose cotransporter carries water molecules along with the cosubstrates with a strict stoichiometry of two Na+, one glucose, and ≈220 water molecules per transport cycle. Using electrophysiology together with sensitive volumetric measurements, we investigated the nature of the driving force behind the cotransporter-mediated water flux. The osmotic water permeability of oocytes expressing human SGLT1 (Lp ± SE) averaged 3.8 ± 0.3 × 10−4 cm⋅s−1 (n = 15) and addition of 100 μM phlorizin (a specific SGLT1 inhibitor) reduced the permeability to 2.2 ± 0.2 × 10−4 cm⋅s−1 (n = 15), confirming the presence of a significant water permeability closely associated with the cotransporter. Addition of 5 mM α-methyl-glucose (αMG) induced an average inward current of 800 ± 10 nA at −50 mV and a water influx reaching 120 ± 20 pL cm−2 ⋅s−1 within 5–8 min. After rapidly inhibiting the Na+/glucose cotransport with phlorizin, the water flux remained significantly elevated, clearly indicating the presence of a local osmotic gradient (Δπ) estimated at 16 ± 2 mOsm. In short-term experiments, a rapid depolarization from −100 to 0 mV in the presence of αMG decreased the cotransport current by 94% but failed to produce a comparable reduction in the swelling rate. A mathematical model depicting the intracellular accumulation of transported osmolytes can accurately account for these observations. It is concluded that, in SGLT1-expressing oocytes, αMG-dependent water influx is induced by a local osmotic gradient by using both endogenous and SGLT1-dependent water permeability.

Control of Cl− Efflux in Chara corallina by Cytosolic pH, Free Ca2+, and Phosphorylation Indicates a Role of Plasma Membrane Anion Channels in Cytosolic pH Regulation1

Enhanced Cl− efflux during acidosis in plants is thought to play a role in cytosolic pH (pHc) homeostasis by short-circuiting the current produced by the electrogenic H+ pump, thereby facilitating enhanced H+ efflux from the cytosol. Using an intracellular perfusion technique, which enables experimental control of medium composition at the cytosolic surface of the plasma membrane of charophyte algae (Chara corallina), we show that lowered pHc activates Cl− efflux via two mechanisms. The first is a direct effect of pHc on Cl− efflux; the second mechanism comprises a pHc-induced increase in affinity for cytosolic free Ca2+ ([Ca2+]c), which also activates Cl− efflux. Cl− efflux was controlled by phosphorylation/dephosphorylation events, which override the responses to both pHc and [Ca2+]c. Whereas phosphorylation (perfusion with the catalytic subunit of protein kinase A in the presence of ATP) resulted in a complete inhibition of Cl− efflux, dephosphorylation (perfusion with alkaline phosphatase) arrested Cl− efflux at 60% of the maximal level in a manner that was both pHc and [Ca2+]c independent. These findings imply that plasma membrane anion channels play a central role in pHc regulation in plants, in addition to their established roles in turgor/volume regulation and signal transduction.