Home-range use patterns and movements of the Siberian flying squirrel in urban forests: Effects of habitat composition and connectivity

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Possible involvement of caveolin in attenuation of cardioprotective effect of ischemic preconditioning in diabetic rat heart

<p>Abstract</p> <p>Background</p> <p>Nitric oxide (NO) has been noted to produce ischemic preconditioning (IPC)-mediated cardioprotection. Caveolin is a negative regulator of NO, which inhibits endothelial nitric oxide synthase (eNOS) by making caveolin-eNOS complex. The expression of caveolin is increased during diabetes mellitus (DM). The present study was designed to investigate the involvement of caveolin in attenuation of the cardioprotective effect of IPC during DM in rat.</p> <p>Methods</p> <p>Experimental DM was induced by single dose of streptozotocin (50 mg/Kg, <it>i.p</it>,) and animals were used for experiments four weeks later. Isolated heart was mounted on Langendorff's apparatus, and was subjected to 30 min of global ischemia and 120 min of reperfusion. IPC was given by four cycles of 5 min of ischemia and 5 min of reperfusion with Kreb's-Henseleit solution (K-H). Extent of injury was measured in terms of infarct size by triphenyltetrazolium chloride (TTC) staining, and release of lactate dehydrogenase (LDH) and creatin kinase-MB (CK-MB) in coronary effluent. The cardiac release of NO was noted by measuring the level of nitrite in coronary effluent.</p> <p>Results</p> <p>IPC- induced cardioprotection and release of NO was significantly decreased in diabetic rat heart. Pre-treatment of diabetic rat with daidzein (DDZ) a caveolin inhibitor (0.2 mg/Kg/s.c), for one week, significantly increased the release of NO and restored the attenuated cardioprotective effect of IPC. Also perfusion of sodium nitrite (10 μM/L), a precursor of NO, significantly restored the lost effect of IPC, similar to daidzein in diabetic rat. Administration of 5-hydroxy deaconate (5-HD), a mito K_ATPchannel blocker, significantly abolished the observed IPC-induced cardioprotection in normal rat or daidzein and sodium nitrite perfused diabetic rat heart alone or in combination.</p> <p>Conclusions</p> <p>Thus, it is suggested that attenuation of the cardioprotection in diabetic heart may be due to decrease the IPC mediated release of NO in the diabetic myocardium, which may be due to up -regulation of caveolin and subsequently decreased activity of eNOS.</p

Crystallisation behaviour and in vitro characterisation of TiO2 doped spodumene glass ceramics

Crystallisation behaviour of Li2O-Al2O3-SiO2 system (LAS) glass ceramics containing TiO2 doping and non-doping is investigated by differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The introduction of TiO2 decreases the crystallising peak temperature T-p and the crystallising activation energy E and improves the crystallisation stage to obtain fine crystal with a size of similar to 100 nm. A controlled surface reaction of the ceramic is an important factor governing the bioinert and biodegradation nature of the implanted ceramic. The addition of TiO2 improves the chemical durability of the glass ceramic, by reducing the number of non-bridging oxygens, suppressing the tendency for amorphous phase separation and provides a more dense and stable structure. This results in a decrease in the release rate of Li+, Al3+ and Si4+ ions in a simulated body fluid

In vitro characterisation and microstructure of B2O3/P2O5 doped bioactive spodumene glass–ceramics

Glasses with compositions of (100-X-Y)Li2O.Al2 O3.4SiO2+XB2 O3+YP2O5 where X=0-2.5 and Y=0-10 (wt-%) were melted in a platinum crucible at 1500°C with air as the furnace atmosphere. The green compact pellets were prepared and fired at 500°C. The samples were sintered in air atmosphere at selected temperatures in the range of 750-900°C for up to 20 h. It has been found that the addition of B2O3 and P2O5 has a remarkable effect on the amount of β spodumene (β-S), relative to high quartz solid solution (h-QSS). The glass ceramics that contain appropriate amounts of B2O3 and P2O5 promise good sinterability at temperature as low as 850°C. There were two major types of phase transformation in the present investigation: crystallisation of the present glass to a metastable h-QSS and subsequent transformation from h-QSS to a stable β-S. In vitro test revealed that the spodumene glass ceramic is much more durable in human body fluid. It is further observed that the addition of B2O3 and P2O5 enhanced the chemical durability of glass ceramics