In order to elucidate the effects of chilling-stress at night on photosystem 2 (PS2) efficiency under dim irradiance (DI), mango leaves were chilled to varied extent (8-3 °C) and for varied duration (0-12 h) in growth cabinets in the dark, and then exposed to DI (20 μmol m-2 s-1 PPFD) at each chilling-temperature for 1 h. Chilling in the dark had little effect on Fv/Fm of mango leaves. But both the extent and duration of chilling pre-treatments significantly affected Fv'/Fm' when leaves were exposed to DI. This down-regulation of PS2 efficiency was closely related to xanthophyll de-epoxidation, assessed as photochemical reflectance index (PRI) and calculated from leaf spectral reflectance [(R531 - R570)/(R531 + R570)], and non-photochemical quenching (NPQ). The down-regulation of PS2 is a defence mechanism initiated at predawn in winter to alleviate the damage of PS2 by the sudden and strong irradiation at sunrise. Mango leaves, transferred suddenly from warm and dark room to DI and chilling showed a slight down-regulation of PS2 efficiency, in spite of an increased xanthophyll de-epoxidation. This might have been due to the unavailability of some cofactors required for NPQ. and J.-H. Weng ... [et al.].
Microseismic monitoring has become a standard technique to map the development of hydraulic fracturing. This study is a case study of a downhole monitoring of the hydraulic fracturing in a lateral well in Northern Poland. The downhole monitoring array detected a large number of microseismic events indicating successful development of a hydraulic fracture. We show evidence that some stages interacted with the pre-existing natural fault system also mapped from surface active seismic imaging. The mapped hydraulic fracture shows a slight asymme try of the developed hydraulic fractures. We show that the observed microseismicity is cons istent with microseismicity usually observed in the North American shale gas stimulations., Eryk Święch, Paweł Wandycz, Leo Eisner, Andrzej Pasternacki and Tomasz Maćkowski., and Obsahuje bibliografické odkazy
The endothelium contributes to the maintenance of vasodilator
tone by releasing endothelium-derived relaxing factors, including
nitric oxide (NO). In hypertension, endothelial nitric oxide
synthase (eNOS) produces less NO and could be one of the
contributing factors to the increased peripheral vascular
resistance. Agonist-induced Ca2+ entry is essential for the
activation of eNOS. The transient receptor potential vanilloid
type 4 (TRPV4) channel, a Ca2+-permeant cation channel, is
expressed in the endothelial cells and involved in the regulation
of vascular tone. The present study aimed to investigate the role
of TRPV4 channel in endothelium-dependent NO-mediated
relaxation of the resistance artery in hypertensive rats. Using
a wire myograph, relaxation response to the TRPV4 activator,
4α-phorbol-12,13-didecanoate (4αPDD) was assessed in
mesenteric arteries obtained from Wistar-Kyoto (WKY) and
spontaneously hypertensive rats (SHRs). Compared to WKY, SHR
demonstrated a significantly attenuated 4αPDD-induced
endothelium-dependent NO-mediated relaxation. Immunohistochemical analysis revealed positive staining for TRPV4 in the
endothelium of mesenteric artery sections in both WKY and SHR.
Furthermore, TRPV4 mRNA and protein expressions in SHR were
significantly lower than their expression levels in WKY rats.
We conclude that 4αPDD-induced endothelium-dependent
NO-mediated vasorelaxation is reduced in SHR and downergulation of TRPV4 could be one of the contributing mechanisms.
The hyperpolarization-activated cyclic-nucleotide-gated
non-selective cation (HCN) channels play a potential role in the
neurological basis underlying drug addiction. However, little is
known about the role of HCN channels in methamphetamine
(METH) abuse. In the present study, we examined the changes
in working memory functions of METH re-exposed mice through
Morris water maze test, and investigated the protein expression
of HCN1 channels and potential mechanisms underlying the
modulation of HCN channels by Western blotting analysis. Mice
were injected with METH (1 mg/kg, i.p.) once per day for
6 consecutive days. After 5 days without METH, mice were
re-exposed to METH at the same concentration. We found that
METH re-exposure caused an enhancement of working memory,
and a decrease in the HCN1 channels protein expression in both
hippocampus and prefrontal cortex. The phosphorylated
extracellular regulated protein kinase 1/2 (p-ERK1/2),
an important regulator of HCN channels, was also obviously
reduced in hippocampus and prefrontal cortex of mice with METH
re-exposure. Meanwhile, acute METH exposure did not affect the
working memory function and the protein expressions of HCN1
channels and p-ERK1/2. Overall, our data firstly showed the
aberrant protein expression of HCN1 channels in METH
re-exposed mice with enhanced working memory, which was
probably related to the down-regulation of p-ERK1/2 protein
expression.
This paper is a continuation of [6], where irreducibility in the sense of Duffus and Rival (DR-irreducibility) of monounary algebras was defined. The definition is analogous to that introduced by Duffus and Rival [1] for the case of posets. In [6] we found all connected monounary algebras A possessing a cycle and such that A is
DR-irreducible. The main result of the present paper is Thm. 4.1 which describes all connected monounary algebras A without a cycle and such that A is DR-irreducible.Other types of irreducibility of monounary algebras defined by means of the notion of a retract were studied in [2]–[5].