Oxygen enrichment of room air is an effective way to resist hypoxia at high altitude, but it may introduce a potential fire hazard. In common, the burning rate of light and thin homogeneous solid in oxygen enriched atmosphere was used to assess the fire hazard. For the purpose of measuring the burning rate of light and thin homogeneous solid in oxygen enriched atmosphere, we used the methods of laser contact ignition and direct calculation of burning rate, and invented a device that includes mixing gas system, ignition equipment, system of measuring the burning rate and self-made specimen frame. By using the homemade device, we studied the burning rate of filter paper under low pressure and in oxygen-enriched atmosphere and in that of the oxygen concentration of reached stationary burning rate. The results showed that this device was simple, and could obtain the burning rate of light and thin homogeneous solid quantitatively.
Air Pressure ; Altitude ; Atmosphere Exposure Chambers ; Environment, Controlled ; Equipment Design ; Fires ; prevention & control ; Oxygen ; analysis

OBJECTIVETo study the changes in the mRNA expression of endothelial cellular adhesion molecules in the cerebral blood vessels in rats with prestroke condition caused by simulated cold wave.

METHODSTwo-kidney two-clip renovascular hypertension was induced in 48 male SD rats, which were subsequently randomly assigned into cold wave exposure and non-exposed group (n=24). Each group was further divided into 4 sub-groups according to their systolic blood pressure, namely the sham-operated group with blood pressure (BP)<140 mmHg, mild hypertensive group with BP of 160-199 mmHg, moderate hypertensive group with BP of 200-219 mmHg, and severe hypertensive group with BP no less than 220 mmHg. Cold wave exposure was simulated by housing the rats in an artificial climate chamber with 3 cycles of 12 h light at 22 degrees celsius; and 12 h dark at 4 degrees celsius;. The non-exposed group was kept at 22 degrees celsius; throughout the experiment. After the exposure, the rats were sacrificed and the tissues of the frontal lobe were slice into 2.0-mm-thick coronal sections for real-time RT-PCR detection of vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), and p-selectin mRNA expressions. The 5.0-microm-thick frozen sections from the bregma section underwent in situ hybridization of VCAM-1, ICAM-1, and p-selectin. The other sections were stained with HE to observe the infarct lesions, and the rats with cerebral infraction were excluded from the statistical analysis.

RESULTSIn rats with cold wave exposure-induced prestroke condition and BP <220 mmHg, VCAM-1, ICAM-1, and p-selectin mRNA expressions all increased compared with those in the non-exposed group. In rats with BP>or=220 mmHg and cold exposure, the expressions all decreased to some extent compared with those in the non-exposed treatment. In the non-exposed rats, a positive correlation of BP to VCAM-1, ICAM-1, and p-selectin mRNA expressions were noted, and this correlation was also found in cold-wave-exposed rats with BP <220 mmHg; VCAM-1, ICAM-1, and p-selectin mRNA expressions decreased dramatically in the exposed rats with BP >or=220 mmHg compared with those in rats with BP <220 mmHg.

CONCLUSIONPersistent and severe hypertension impairs the modulatory function of the cerebral vascular endothelia, which is a prerequisite for the stroke vulnerability. The modulatory function deteriorates as the BP further increases.

Animals ; Atmosphere Exposure Chambers ; Cerebral Arteries ; metabolism ; Cold Temperature ; Environment, Controlled ; Equipment Design ; Hypertension, Renovascular ; complications ; metabolism ; Intercellular Adhesion Molecule-1 ; genetics ; metabolism ; Male ; P-Selectin ; genetics ; metabolism ; RNA, Messenger ; genetics ; metabolism ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Stroke ; etiology ; metabolism ; Vascular Cell Adhesion Molecule-1 ; genetics ; metabolism