Relationship between the matrix effect and the physicochemical properties of analytes in gas chromatography.

The phenomenon "matrix-induced chromatographic response enhancement" (matrix effect) causes quantitative errors in gas chromatography (GC) analyses. This effect varies according to the analyte nature, matrix type and concentration, and GC-system parameters. By focusing on the physicochemical properties of analytes, a predictive model was developed for the matrix effect using quantitative structure-property relationships. Experimental values of the matrix effect were determined for 58 compounds in a serum extract obtained from solid-phase extraction as the matrix. Eight molecular descriptors were selected, and the matrix-effect model was developed by multiple linear regression. The developed model predicted values for the matrix effect without any further experimental measurements. It also indicated that the molecular polarity (particularly H-bond donors) and volume of the analyte increase the matrix effect, while hydrophobicity and increasing number of nonpolar carbon atoms in the analyte decrease the matrix effect. The model was applied to the analysis of barbiturates. The predicted values indicated that N-methylation decreases the matrix effect, and the relative predicted values were effective for the selection of an internal standard. The obtained insight into the matrix effect and the prediction data will be helpful for developing quantitative analysis strategies.

Fatal human poisoning with Padan: a cartap-containing pesticide.

We report a patient who ingested about 13 g of Padan SG, a cartap-containing pesticide. After ingestion, the patient developed multiple seizures and dyspnea and lost consciousness. The patient did not recover and died on the fifth hospital day despite treatment at the early stage of poisoning. The cause of death was multisystem organ failure. Results of toxicological analysis were as follows: concentrations of nereistoxin (cartap metabolite) were 10.6 microg/mL in plasma, 18.2 microg/mL in urine, and 2.6 mg/mL in gastric fluid. Results of drug screening of urine by Triage DOA Panels and using an organophosphate detection kit were negative.

Time-of-flight mass spectrometry (TOF-MS) exact mass database for benzodiazepine screening.

Time-of-flight mass spectrometry coupled with liquid chromatography (TOF-MS) has been developed for screening and determination of benzodiazepines with an exact mass database. Benzodiazepines display similar chemical structures and molecular weights, and thus show similar mass spectra and protonated molecule ions. Discrimination of mass spectrometry at low resolving power using single liquid chromatography mass spectrometry (LC-MS) is commonly difficult. TOF-MS analysis was performed using a 1100 TOF (Agilent Technologies) equipped with a Zorbax C18 Extend column. Purine and fluorine compound solution was always introduced into the ion source, and real-time mass adjusting was performed. Specimens were prepared utilizing the liquid-liquid extraction procedure with 1-chlorobutane. Benzodiazepines are widely used in medical practice in Japan, and data acquired from TOF-MS measurements of 41 benzodiazepines, including active metabolites, were used to create an exact mass database. This database comprised molecular formulae, calculated exact masses and retention times. Calibrations were also included in a database. Precision for the 41 drugs was considered sufficient for quantitative analysis. In analysis of samples from patient who had taken > or =2 benzodiazepines, selectivity was improved using the TOF-MS exact mass database. TOF-MS is effective for forensic toxicology in discriminating between benzodiazepines with similar structure and metabolites.

Western blot analysis for 4-hydroxy-2-nonenal (HNE)-modified proteins in paraquat-treated mice.

Paraquat (PQ) is widely used in agriculture as a non-selective contact herbicide. Ingestion of PQ results in multiple organ failure within one week, although the primary damage induced by PQ occurs in the lungs. It is known that reactive oxygen species (ROS) play an important role in pathological changes in PQ poisoning, although the exact mechanism of PQ toxicity has not been completely elucidated. In this study, we investigated changes in 4-hydroxy-2-nonenal (HNE)-modified proteins as markers of lipid peroxidation in PQ-treated mice. C57BL/6J mice were given PQ (10 or 50 mg/kg) intraperitoneally. After 24 h, blood and tissues were collected under isofluorene anesthesia. For histochemical studies, frozen tissue sections were immunostained with an anti-HNE monoclonal antibody. Immunoreactivity using the anti-HNE antibody was strongly increased in the kidney after PQ treatment. The expression levels of HNE-modified proteins in tissue homogenates were analyzed by Western blotting. Tissue homogenates were separated by 12.5% SDS-PAGE and transferred onto a polyvinylidene difluoride membrane. The membrane was immunostained with an anti-HNE antibody. Reactive bands were visualized with diaminobenzidine (DAB). Then the membrane was immunostained again with an anti-actin antibody and visualized with New Fuchsin. An anti-actin antibody-positive band was used to correct the protein content in tissue homogenates. The intensity of the 41-kDa protein band in the kidney and that of the 51-kDa protein band in the lung were significantly increased. These findings suggest an important role of ROS in the development of paraquat toxicity in the kidney and lung. On the other hand, an increase in peroxidation was not observed in the liver protein. It has been reported that oxidative stress after paraquat administration involved nitration of proteins by the activation of nitric oxide synthase (NOS). Therefore, paraquat may exert its toxicological action on different organs by different mechanisms.

Enhanced lipid peroxidation in tourniquet-release mice.

BACKGROUND: The pathogenesis of ischemia-reperfusion involves generation of reactive oxygen and resulting lipid peroxidation. However, investigation that ischemia-reperfusion following tourniquet release enhances lipid peroxidation is insufficient. METHODS: Tourniquet was applied to a unilateral hind limb of mice for 3h followed by 5-, 15-, 30- and 60-min release. To examine superoxide production immunohistochemically in ischemia-reperfusion muscles, a primary antibody directed to 4-hydroxy-nonenal (HNE) was used. Furthermore, we analyzed 7alpha- and 7beta-hydroperoxycholest-5-en-3beta-ol, 7alpha- and 7beta-hydroxycholesterol, and 7-ketocholesterol by HPLC in the gastrocnemius muscles, kidneys, liver, heart and lungs of mice after 1-h reperfusion. RESULTS: Increased HNE immunoreactivitiy was observed in the tourniquet-applied side of gastrocnemius muscles of hind limb particularly after 5-min reperfusion. All the oxysterols were significantly higher in the gastrocnemius muscles of the tourniquet-applied side than of the contralateral muscles. Oxysterols were elevated in the kidneys and the liver. Together with the presence of high blood urea nitrogen, these data indicate that the kidney is vulnerable to ischemia-reperfusion. CONCLUSIONS: The enhanced oxidative stress due to ischemia-reperfusion appears to increase HNE in muscle and oxysterols by peroxidation not only in the gastrocnemius muscles but also in the kidneys and liver.

Diagnostic Performance of Triagetrade mark for Benzodiazepines: Urine Analysis of the Dose of Therapeutic Cases.

We evaluated the diagnostic performance of Triage for benzodiazepines in 74 urine specimens from outpatients given therapeutic doses of benzodiazepines and compared the results of EMIT assays. Results obtained in all urine samples were confirmed using liquid chromatography-mass spectrometry (LC-MS). Overall agreement between results of Triage and EMIT assays was 73%. All of the Triage-positive samples were also positive by EMIT assays. Results of Triage and EMIT assays were different for 20 samples obtained from patients given thienodiazepines (etizolam, brotizolam, and clotiazepam) and nitrobenzodiazepines (nitrazepam, flunitrazepam, and clonazepam). LC-MS confirmed parent drugs in urine specimens, consistent with the prescriptions of drugs. The low agreement between Triage and EMIT results in this study might be due to low sensitivity of Triage for thienodiazepines. Thienodiazines are frequently prescribed benzodiazepines, and Triage panel is the most frequently used screening kit in Japan. It should be noted that negative results obtained by a Triage test might not mean the absence of thienodiazepines.

Diagnostic performance of Triage for benzodiazepines: urine analysis of the dose of therapeutic cases.

We evaluated the diagnostic performance of Triage for benzodiazepines in 74 urine specimens from outpatients given therapeutic doses of benzodiazepines and compared the results of EMIT assays. Results obtained in all urine samples were confirmed using liquid chromatography-mass spectrometry (LC-MS). Overall agreement between results of Triage and EMIT assays was 73%. All of the Triage-positive samples were also positive by EMIT assays. Results of Triage and EMIT assays were different for 20 samples obtained from patients given thienodiazepines (etizolam, brotizolam, and clotiazepam) and nitrobenzodiazepines (nitrazepam, flunitrazepam, and clonazepam). LC-MS confirmed parent drugs in urine specimens, consistent with the prescriptions of drugs. The low agreement between Triage and EMIT results in this study might be due to low sensitivity of Triage for thienodiazepines. Thienodiazines are frequently prescribed benzodiazepines, and Triage panel is the most frequently used screening kit in Japan. It should be noted that negative results obtained by a Triage test might not mean the absence of thienodiazepines.

Nitric oxide synthase expressions in mice skeletal muscle subjected to ischemia/reperfusion injury.

Nitric oxide synthase (NOS) expressions in skeletal muscle subjected to ischemia/reperfusion (I/R) were studied using a hind limb tourniquet ischemia model in mice. A rubber band was applied to a hind limb for 3 h under isoflurane anesthesia followed by 1 or 4 h of reperfusion. Increased NADPH diaphorase activity and NOS immunoreactivity were histochemically detected in the cells of muscle that had been subjected to I/R. The results of RT-PCR of the muscle subjected to I/R showed that NOS mRNA expressions were not significantly increased until 4 h after the start of reperfusion. Since there was no significant difference between histochemical findings or between water contents of the hind limbs or organs in interleukin (IL)-6-deficient mice and the wild-type mice, IL-6 may not be involved in the early stage of I/R muscle injury such as that in this model. O(2)(-) production in the cells of muscle that had been subjected to I/R was observed using an in situ detection method with hydroethidine, and the O(2)(-) was inhibited by intravenous administration of L-NAME or L-NMMA, but not L-NIL, 30 min before tourniquet release. Further study is needed to evaluate the role of O(2)(-) produced by constitutive NOS in muscle subjected to I/R in the pathophysiology of tourniquet shock.