AIM:To develop a microbiological method for determining plasma doxycyclineMETHODS:Plasma concentration of doxycycline was detected with Staphylococcus aureus ATCC 26003 and Micrococcus luteus ATCC 28001 strains in a variety of culture media and pHsRESULTS:Linear scope of doxycycline(016～100mg/L,r=09 985) could be achieved with using a microbiological method,which consisted of staphylococcus aureus and bovine heart soup culture medium at pH 50CONCLU_SION:This method can be used in study of pharmacokinetics and bioavailability of doxycycline

Aim To assess the effect and mechanism of N acetylcysteine (NAC, antioxidant) on nuclear factor ?B (NF ?B) in lung tissue and bronhial alveolar lavage fluid(BALF) of rats undergoing acute and chronic smoking. Methods All Wistar rats were divided randomly into three groups: control group, smoking group and intervention group. The latter two groups were applied to observing NF ?B expression during different periods (1, 2, 7, 14, 60d). Western Blot assay was used to analyze the activation of NF ?B. Results The first and second day the expression of NF ?B in lung tissue ( 36.9 ? 8.1 and 36.9 ? 8.0 )and in BALF( 24.0 ? 6.1 and 21.2 ? 5.8 ) rose significantly comparing with that in the control groups ( 7.3 ? 2.8 and 5.7 ? 2.6 )respectively (P