Isolation and characterization of the thermoresistant gluconokinase from Escherichia coli

It is known that two gluconokinases are inducibly expressed during the utilization of gluconate by E. coli. One is thermoresistant (activity stable for 3 h at 30 °C) and the other thermosensitive (losses 75% or more of its activity under the above conditions). The thermoresistant gluconokinase (EC 2.7.1.12) was isolated, purified and characterized for the first time from the E. coli mutant Ca26, a K12 derivative which lacks the thermosensitive activity. The enzyme was purified 43 fold with a recovery of 11%. The M_r of the enzyme was 100 kDa with three equal subunits of approximately 29.5 kDa. The enzyme exhibited Michaelis-Menten kinetics and the K_m values for gluconate and ATP were 0.02 mM and 0.045 mM respectively.     

Relationships between total and unbound propofol in plasma and CSF during continuous drug infusion

BACKGROUND: Propofol is one of the most frequently applied intravenous anesthetics. Although it has been used for a long period, its pharmacokinetics, especially central nervous system pharmacokinetics, are not fully recognized. OBJECTIVE: Investigation of the relationships between total propofol concentration in blood, total propofol concentration in cerebrospinal fluid (CSF), free propofol concentration in blood, and free anesthetic concentration in CSF in patients undergoing elective neurosurgery and anesthetized with propofol. METHODS: Eleven patients scheduled for elective intracranial procedures were studied. Propofol was applied in the form of target control infusion. During anesthesia, fractional doses of fentanyl and cisatracurium were administered as necessary. After tracheal intubation the lungs were ventilated to achieve normocapnia with an oxygen-air mixture (Fi O2 = 0.33). CSF and blood were taken at the moment of intraventricular drainage application. RESULTS: The unbound propofol concentration in plasma is 1.12% (SD 0.61%; SEM 0.18%) of the total concentration in plasma, and the free propofol concentration in plasma is 71.6% (SD 61.0%; SEM 18.4%) of the total CSF propofol concentration. The free anesthetic concentration in CSF is 30.9% (SD 15.7%; SEM 4.7%) of the total CSF propofol concentration, and 61.8% (SD 34.9%; SEM 10.5%) of the free propofol concentration in plasma. CONCLUSION: The relationship between unbound drug concentrations in plasma and in CSF determined in this study leads to the postulate that propofol is transported from blood to CSF by passive diffusion.     

Matrix solid-phase dispersion (MSPD) in chromatographic analysis of essential oils in herbs

Matrix solid-phase dispersion (MSPD) is a simple and cheap sample preparation procedure allowing for the reduction of organic solvent consumption, exclusion of sample component degradation, improvement of extraction efficiency and selectivity, elimination of additional sample clean-up and pre-concentration step before chromatographic analysis.     

Furanylfentanyl in whole blood measured by GC–MS/MS after QuEChERS extraction in a fatal case

Forensic Toxicology - The purpose of this work is the determination of the probable cause of a person’s death on the basis of analytical results obtained from the deceased’s blood...     

PLE in the analysis of plant compounds. Part I. The application of PLE for HPLC analysis of caffeine in green tea leaves

A broad spectrum of sample preparation methods is currently used for the isolation of pharmacologically active compounds from plant and herbal materials. The paper compares the effectiveness of infusion, microwave assisted solvent extraction (MASE), matrix solid-phase dispersion (MSPD) and pressurised liquid extraction (PLE) as sample preparation methods for the isolation of caffeine from green tea leaves. The effect of PLE variables, such as extraction temperature, pressure and time, on the yield of caffeine from the investigated matrix is discussed.

The obtained results revealed that PLE, in comparison with other sample preparation methods applied, has significantly lower efficacy for caffeine isolation from green tea leaves. The evaluation of PLE conditions leads to the conclusion that elevated pressure applied in the PLE process is the factor hindering the extraction.     

The Role of Human Lungs in the Biotransformation of Propofol

Background: The metabolism of propofol is very rapid, and its transformation takes place mainly in the liver. There are reports indicating extrahepatic metabolism of the drug, and the alimentary canal, kidneys, and lungs are mentioned as the most probable places where the process occurs. The aim of this study was to determine whether the human lungs really take part in the process of propofol biotransformation.

Methods: Blood samples were taken from 55 patients of American Society of Anesthesiologists grade 1-3 scheduled for elective intracranial procedures (n = 47) or for pulmonectomy (n = 8). All patients were premedicated with diazepam (10 mg) administered orally 2 h before anesthesia. Propofol total intravenous anesthesia was performed at the following infusion rates: 12 mg [middle dot] kg-1 [middle dot] h-1, 9 mg [middle dot] kg-1 [middle dot] h-1, and 6 mg [middle dot] kg-1 [middle dot] h-1. Fentanyl and pancuronium bromide were also administered intermittently. After tracheal intubation, the lungs were ventilated to normocapnia with an oxygen-air mixture (fraction of inspired oxygen = 0.33). Blood samples for propofol and 2,6-diisopropyl-1,4-quinol analysis were taken simultaneously from the right atrium and the radial artery, or the pulmonary artery and the radial artery. The concentration of both substances were measured with high-performance liquid chromatography and gas chromatography-mass spectroscopy.

Results: The concentration of propofol in the central venous system (right atrium or pulmonary artery) is greater than in the radial artery, whereas the opposite is observed for propofol's metabolite, 2,6-diisopropyl-1,4-quinol. Higher propofol concentrations are found in blood taken from the pulmonary artery than in the blood collected from the radial artery.     

The changes of propofol concentration in human cerebrospinal fluid after drug infusion

OBJECTIVE: Investigation of the propofol concentration changes in cerebrospinal fluid (CSF) after the termination of the drug infusion. METHODS: Nine patients (American Society of Anesthesiologists classes I-III) scheduled for elective intracranial procedures were studied. Propofol was applied in the form of target control infusion. During anesthesia, fractional doses of fentanyl and cisatracurium were administered as necessary. After tracheal intubation, the lungs were ventilated to achieve normocapnia with an oxygen-air mixture (fraction of inspired oxygen = 0.33). Arterial blood and CSF samples (from an intraventricular drain) were taken simultaneously at the end of propofol infusion and then at 15, 30, 45, 60, 90, and 120 minutes after the end of infusion. RESULTS: A pronounced decrease of the anesthetic concentration in plasma (P < 0.001) was observed during the first 15 minutes after infusion termination, followed by further yet slower decrease of the drug concentration. At the end of propofol infusion, the concentration of propofol in CSF was 65.59 ng/mL (SD, 26.91 ng/mL) and remained almost stable for approximately 30 minutes; afterward, a slow decrease of CSF propofol concentration was observed. CONCLUSION: The statement that CSF can be regarded as a significant route for drugs delivery to the brain is disputable for propofol. The obtained results show that, in contrast to the situation from induction of anesthesia, back transport of the drug from CSF to blood is markedly slower, supporting the thesis about propofol transport from blood to CSF by passive diffusion.