Analysis on damage causes of built-in corridor in core rock-fill dam on thick overburden:A case study

The stress state of the built-in corridor in core rock-fill dam on thick overburden is extremely complex,which may produce cracking and damage.The purpose of this paper was to investigate the effect of thick overburden on the stress and deformation of the built-in corridor in a rock-fill dam,and ascertain the damage causes of the corridor.The rationality of the analysis method for corridor with similar structure is another focus.The approach is based on finiteelement method and the calculation result accuracy is verified by the field monitoring data.The improved analysis method for corridors with similar structure is proposed by comparing various corridor load calculation methods and concrete constitutive models.Results demonstrate that the damage causes of the corridor are the deformability difference between the overburden and concrete and the special structural form.And the calculation model considering dam construction process,contact between concrete and surrounding soil,and concrete damage plasticity can reasonably reflect the mechanical behavior of the corridor.The research conclusions may have a reference significance for the analysis of tunnels similar to built-in corridors.

THE PROTECTIVE EFFECT OF Na^+ CHANNEL BLOCKERS AGAINST CELL DAMAGE CAUSED BY ISCHEMIA

In order to observe it blockers of sodium channel obsesses the neuroprotective effect on hippocampal CA 1 pyramidal cell under the condition of transient brain ischemia, the present experiment used 24 male Wistar rats aged 9 months and divided them into four groups. Lidocaine and/or furosemide were injected introcerebroventicularlly (I.C.V). Stained with H E and accounted the CA 1 pyramidal cell numbers by computer in each group suggested following findings: Although 5 μl of 2% lidocaine was injected I.C.V, the results indicated lidocaine didn't have any blockade to pyramidal cell injuries in hippocampal CA 1 area (P<0 05). In the group medicated with 2 5μl of both 2% lidocaine and 2% furosemide, the results showed that the combined approach had a blockade to injuries of pyramidal cells compared with control group (P<0 01). The present experiment indicates that the combined blockade of lidocaine and furosemide injected I.C.V. to Na + channel can prevent the injuries from hippocampal neurons owing to ischemia.

ACIDIC FIBROBLAST GROWTH FACTOR REDUCES RAT SKELETAL MUSCLE DAMAGE CAUSED BY ISCHEMIA AND REPERFUSION

Acute interruption of arterial blood flow to the extremities is often associated with significant morbidity and mortality. Broad spectrum mitogenic and non mitogenic activities of FGFs inspired us to study its protecting effects on tissue injuries in ischemia reperfusion condition. We found that systemic administration of aFGF after reperfusion onset prevented severe skeletal muscle injuries. In rats treated with aKGF, the tissue edema was reduced significantly, the tissue viability was increased, and the muscle fibers contained more succinate dehydrogenase (SDH) and adenosine triphosphatasc (ATPase). The pathological results supported the concept of improved prevention with aFGF treatment. The possible tissue protection by aFGF may come from its ability to regulate the concentration of evtra- and intracellular calcium ion. Besides, it may moderate other Ca2+ dependent enzyme conversion processes. Also, it may take part in the vascular tone regulation under ischemia and reperfusion conditions. These results suggest further study of tissue ischemia prevention with FGF and its possible mechanisms in the future.

PENTOXIFYLLINE AMELIORATES PULMONARY DAMAGE CAUSED BY STREPTOCOCCUS PNEUMONIAE INFECTION IN MOUSE

Streptococcus pneumoniae stimulated mouse peritoneal macrophagc to release tumor necrosis factor-α (TNFα) in vitro. When penicillin was added into the medium with bacteria, TNFα release was accelerated. Pentoxifylline (PTX), a phosphodiesterase inhibitor, significantly attenuated TNFα release caused either by Streptococcus pneumoniae or by its lysates. In this experiment, 150 Kunming mice were infected with Streptococcus peumoniae through inspiration. Dynamic changes of TNFα concentration in serum and bronchoalveolar lavage fluid were determined, and pulmonary pathological changes were also observed. It was found that PTX significantly attenuated TNFα activity in serum and bronchoalveolar lavage fluid, and inhibited white blood cell chemotaxis, emigration and infiltration. In conclusion, Streptococcus pneumoniae infection stimulates the release of TNFα which is probably the major mediater that causes tissue damage during Streptococcus pneumoniae infection. The mechanism is probably that Steptococcus pneumoniae and its lysates activate TNFα gene transcription. As penicillin accelerates TNFα release, treatment with penicillin alone may aggravate the tissue damage. Combined treatment with PTX may be more reasonable.

Effect of oxidative stress-associated damage to the lung tissue caused by different body mass index in the rat models

Objective To investigate the influence of different diets on serum protein expression levels of 4-hydroxynonenal(4-HNE),thioredoxin(Trx),thioredoxin reductase(TrxR)and the sctivities of Trx and TrxR,and to explore the effect of damage to the lung tissue and the underlying mechanisms of different body mass index caused by different diets in the rat models.Methods