Rafal Kalitynski

Cellular envelope phospholipids from Legionella lytica

The composition of phospholipids from the cellular envelope of Legionella lytica grown on artificial medium was determined by two-dimensional thin-layer chromatography. Phosphatidylcholine, phosphatidylethanolamine, and phosphatidyl-N-monomethylethanolamine were the predominant phospholipids, while diphosphatidylglycerol, phosphatidylglycerol, and phosphatidyl-N,N-dimethylethanolamine were present at low concentrations. A trace amount of lipids carrying glycosyl residues was also observed. The fatty acids and their distribution in individual phospholipids were characterized using liquid chromatography/mass spectrometry (LC/MS), matrix-assisted laser desorption ionization-time of flight, and gas chromatography/MS methods. The characteristic feature of L. lytica phospholipids was the presence of an unbranched chain (which differentiates this bacterium from Legionella pneumophila) and branched iso and anteiso fatty acids as well as cis-9,10-methylenehexadecanoic acid. According to spectroscopic LC/MS data, the localization of saturated and unsaturated fatty acid residues on phosphorylglycerol was determined. Some aspects of the significance of phosphatidylcholine, one of the main phospholipids in L. lytica, are addressed and taxonomic implications of the data are discussed.

Changes of Propofol Concentration in Cerebrospinal Fluid During Continuous Infusion

We studied the changes in the propofol concentration in the cerebrospinal fluid (CSF) in 14 patients, undergoing elective intracranial procedures, who were anesthetized with propofol administered by target-controlled infusion. During anesthesia, fentanyl and cisatracurium were administered as required. After intubation of the trachea, the lungs of the patients were ventilated to normocapnia with an oxygen-air mixture (Fio2 = 0.33). Arterial blood and CSF samples (from an intraventricular drain) were collected between 90–180 min after the induction of anesthesia. Blood propofol concentrations were stable, between 5.0 ± 1.89 and 4.5 ± 1.7 &mgr;g/mL (mean ± sd). There was a significant decrease in the CSF propofol concentration, from 52.2 ± 35.01 ng/mL at 90 min to 28.6 ± 21.9 ng/mL at 150 min (P < 0.05). The CSF propofol concentration at 180 min (21.4 ± 14.0 ng/mL) was not significantly different from the concentration at 150 min. Some possible reasons for this decrease after commencing continuous intraventricular drainage are discussed.

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.

Legionella bozemanae synthesizes phosphatidylcholine from exogenous choline

The phospholipid class and fatty acid composition of Legionella bozemanae were determined using thin-layer chromatography, gas-liquid chromatography, and matrix-assisted laser desorption ionization-time of flight mass spectrometry. Phosphatidylcholine, phosphatidylethanolamine, and diphosphatidylglycerol were the predominant phospholipids, while phosphatidyl-N-monomethylethanolamine, phosphatidylglycerol, and phosphatidyl-N,N-dimethylethanolamine were present at low concentrations. With the use of the LC/MS technique, PC16:0/15:0, PC17:/15:0, and PE16:1/15:0 were shown to be the dominant phospholipid constituents, which may be taxonomically significant. Two independent phosphatidylcholine synthesis pathways (the three-step methylation and the one-step CDP-choline pathway) were present and functional in L. bozemanae. In the genome of L. bozemanae, genes encoding two potential phosphatidylcholine forming enzymes, phospholipid N-methyl transferase (PmtA) and phosphatidylcholine synthase (Pcs), homologous to L. longbeachae, L. drancourtii, and L. pneumophila pmtA and pcs genes were identified. Genes pmtA and pcs from L. bozemanae were sequenced and analyzed on nucleotide and amino acid levels. Bacteria grown on an artificial medium with labelled choline synthesized phosphatidylcholine predominantly via the phosphatidylcholine synthase pathway, which indicates that L. bozemanae phosphatidylcholine, similarly as in other bacteria associated with eukaryotes, is an important determinant of host-microbe interactions.

Influence of intralipid on free propofol fraction assayed in human serum albumin solutions and human plasma

AbstractAim:It is generally assumed that only unbound drugs can reach the site of action by diffusing across the membranes and exerting pharmacological effects by interacting with receptors. Recent research has shown that the percentage of free drugs may depend on the total drug concentration. The aim of the paper is to verify whether the mentioned dependence reported for propofol also takes place in plasma and human serum albumin samples in the presence of intralipid — the medium used as a vehicle for propofol infusions and a parenteral nutrition agent.Methods:Artificial plasma samples and human plasma were spiked with intralipid or ethanolic solutions of propofol. The samples were then assayed for free propofol concentration using ultrafiltration and high performance liquid chromatography with fluorimetric detection.Results:The decrease of the total drug concentration results in free propofol fraction increase, irrespectively of the used type of propofol solvent and sample type. The addition of intralipid causes the lowering of the overall free drug fraction with respect to the samples spiked with ethanolic solutions of the drug.Conclusion:The presence of intralipid does not influence the phenomenon of free propofol fraction rise at low total drug concentration. Such a rise cannot be ignored in clinical conditions when the drug is applied for sedative, antiemetic or other low-dosage purposes.

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.