Determination of free ceftriaxone concentration and its application in predicting lung tissue concentration

The purpose of this study was to establish a method for determining the free concentration of ceftriaxone based on hollow fiber centrifugal ultrafiltration(HFCF-UF)technology in combination with high-performance liquid chromatography(HPLC)for free pharmacokinetic studies and the prediction of ceftriaxone concentrations in lung tissue.This method only required centrifugation for a short time,and the filtrate could be injected directly for HPLC analysis without further treatment.The specificity,linearity,precision and stability of this method were validated for quantification of free ceftriaxone.Under the optimized conditions,the absolute recoveries were more than 92.5%.The intraday and interday precision RSDs were less than 3.6%.Additionally,nonspecific adsorption(NSB)between the analyte and the ultrafiltration membrane was considered.This method was successfully applied to the analysis of the free ceftriaxone concentration in rat plasma and lung tissue.The free ceftriaxone concentration of lung tissue could be predicted by using the linear formula Cfl=Cfp(0.342 x–0.0129)(x:time).This method also provides a reliable alternative for accurate monitoring of the free ceftriaxone concentration in therapeutic drug monitoring(TDM).

Differences Between the Concentrations in Rabbit Body Fluid of Berberine Hydrochloride, Chlorogenic Acid, Baicalin, and Their Minimal Inhibitory Concentrations

To explore the relationship between the heat-clearing and detoxicating functions and the bacteriostatic actions of berberine hydrochloride （Ber. H）, chlorogenic acid （Chlo. A）, and baicalin （Bai）, their concentrations in rabbit body fluid were compared with their minimal inhibitory concentrations （MICs）. Their concentrations in rabbit blood and tissue fluid were determined by reversed-phase high performance liquid chromatography, and their MICs to Escherichia coli were determined by tube dilution method. The results showed that the peak concentrations of Ber. H, Chlo. A, and Bai in rabbit blood were 3.2, 5.03, and 7.63 μg mL^-1, and in rabbit tissue fluid were 0.12, 0.11, and 0.12 μg mL^-1, respectively. Their MICs to E. coli were, respectively, 1.0×10^3, 3.75 × 10^3, and 6.75 ×10^3μg mL^-1, which were far higher than the concentrations in rabbit body fluids. This study indicates that Ber. H, Chlo. A, and Bai have weak bacteriostatic actions and do not reach their effective inhibitory concentrations in rabbit body fluids, and their heat-clearing and detoxicating functions are independent on the bacteriostatic actions.

Why are Nitrogen Concentrations in Plant Tissues Lower under Elevated CO_2? A Critical Examination of the Hypotheses

Plants grown under elevated atmospheric [CO2] typically have decreased tissue concentrations of N compared with plants grown under current ambient [CO2]. The physiological mechanisms responsible for this phenomenon have not been definitely established, although a considerable number of hypotheses have been advanced to account for it. In this review we discuss and critically evaluate these hypotheses. One contributing factor to the decreases in tissue N concentrations clearly is dilution of N by increased photosynthetic assimilation of C. In addition, studies on intact plants show strong evidence for a general decrease in the specific uptake rates （uptake per unit mass or length of root） of N by roots under elevated CO2. This decreased root uptake appears likely to be the result both of decreased N demand by shoots and of decreased ability of the soil-root system to supply N. The best-supported mechanism for decreased N supply is a decrease in transpiration-driven mass flow of N in soils due to decreased stomatal conductance at elevated CO2, although some evidence suggests that altered root system architecture may also play a role. There is also limited evidence suggesting that under elevated CO2, plants may exhibit increased rates of N loss through volatilization and/or root exudation, further contributing to lowering tissue N concentrations.

Long-distance ABA transport can mediate distal tissue responses by affecting local ABA concentrations

Environmental stresses that perturb plant Hwater relations influence abscisic acid(ABA) concentrations, but it is unclear whether long-distance ABA transport contributes to changes in local ABA levels. To determine the physiological relevance of ABA transport, we made reciprocal-and self-grafts of ABA-deficient flacca mutant and wild-type(WT) tomato plants, in which low phosphorus(P) conditions decreased ABA concentrations while salinity increased ABA concentrations. Whereas foliar ABA concentrations in the WT scions were rootstock independent under control conditions, salinity resulted in long-distance transport of ABA: flacca scions had approximately twice as much ABA when grafted on WT rootstocks compared to flacca rootstocks. Root ABA concentrations were scion dependent: both WT and flacca rootstocks had less ABA with the flacca mutant scion than with the WT scion under control conditions. In WT scions, whereas rootstock genotype had limited effects on stomatal conductance under control conditions, a flacca rootstock decreased leaf area of stressed plants, presumably due to attenuated root-to-shoot ABA transport. In flacca scions, a WT rootstock decreased stomatal conductance but increased leaf area of stressed plants, likely due to enhanced root-to-shoot ABA transport. Thus, long-distance ABA transport can affect responses in distal tissues by changing local ABA concentrations.

Signals Analysis and Clinical Validation of Blood and Oxygen Data in Human Brain

With a self-made near-infrared analytical instrument to blood and oxygen parameters in human brain, 80 cases in which 20 are healthy persons and 30 are anaesthetised cases and others are patients with heart function lack is taken to examine, and the data of blood and oxygen in brain tissue were collected and analyzed by the method of power spectrum and correlation function. The results indicate that: (1) The average brain oxygen saturation of healthy persons and anaesthetised cases is about 80%, in accord with normal parameter of physiology. Contrastively, the average brain oxygen saturation of patients with heart function lack is 72.8%, which is obviously less than that of healthy persons and anaesthetised cases. The probability of medical statistics is less than 0.01. (2) The shapes of wave of brain blood and oxygen for the healthy person and the anaesthetised case reveal small periodical fluctuations with stable shape and base line, and the trend of increase or decrease of blood and oxygen parameters in brain tissue is synchronous and a phase reversal, but for the patient with heart function lack in a brain oxygen lack state, the shapes of wave are irregular. This is a hint that near infrared light passing through tissue can reflect the intuitionistic change of brain blood and oxygen parameters.(3) The power spectra of brain blood and oxygen for the healthy person and the anaesthetised case has a clear main peak, narrow bandwidth and perfect superposition each other, but the power spectra for the patient with heart function lack in a brain oxygen lack state is on the contrary.(4) The average cross correlation coefficient of brain blood and oxygen for healthy persons and anaesthetised cases is -0.9825±0.1027 close to -1. But the average cross correlation coefficient for patients with heart function lack in a brain oxygen lack state is merely -0.8923±0.1035 which is obviously greater than -1 and the probability of medical statistics is less than 0.01. The clinic experiments have proved that the shapes of waves, the power spectrum and cross correlation coefficient of brain blood and oxygen are useful to analyze the physiological status and changes of blood and oxygen in human brain.