Determination of ketamine in rabbit plasma by gradient elution liquid chromatography/electrospray mass spectrometry

A sensitive and simple liquid chromatography/electrospray mass spectrometry (LC-ESI-MS) method for determination of ketamine in rabbit plasma using one-step protein precipitation was developed and validated. After addition of methadone as internal standard (IS), protein precipitation by acetonitrile was used as sample preparation. Chromatographically separation was achieved on an SB-C18 (2.1 mm × 50 mm, 3.5 μm) column with methanol-0.1 % formic acid as the mobile phase with gradient elution. Electrospray ionization (ESI) source was applied and operated in positive ion mode; multiple reaction monitoring (MRM) mode was used to quantification using target fragment ions m/z 237.7 → 219.7 for ketamine and m/z 309.9 → 264.8 for the IS. Calibration plots were linear over the range of 5-1000 ng/mL for ketamine in rabbit plasma. Lower limit of quantification (LLOQ) for ketamine was 5 ng/mL. Mean recovery of ketamine from plasma was in the range of 97.5-100.1 %. RSD of intra-day and inter-day precision were both less than 11 %. This method is simple and sensitive enough to be used in pharmacokinetic research for determination of ketamine in rabbit plasma.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Determination of ketamine in rabbit plasma by gradient elution liquid chromatography/electrospray mass spectrometry

A sensitive and simple liquid chromatography/electrospray mass spectrometry (LC-ESI-MS) method for determination of ketamine in rabbit plasma using one-step protein precipitation was developed and validated. After addition of methadone as internal standard (IS), protein precipitation by acetonitrile was used as sample preparation. Chromatographically separation was achieved on an SB-C18 (2.1 mm × 50 mm, 3.5 μm) column with methanol-0.1 % formic acid as the mobile phase with gradient elution. Electrospray ionization (ESI) source was applied and operated in positive ion mode; multiple reaction monitoring (MRM) mode was used to quantification using target fragment ions m/z 237.7 → 219.7 for ketamine and m/z 309.9 → 264.8 for the IS. Calibration plots were linear over the range of 5-1000 ng/mL for ketamine in rabbit plasma. Lower limit of quantification (LLOQ) for ketamine was 5 ng/mL. Mean recovery of ketamine from plasma was in the range of 97.5-100.1 %. RSD of intra-day and inter-day precision were both less than 11 %. This method is simple and sensitive enough to be used in pharmacokinetic research for determination of ketamine in rabbit plasma.Colegio de Farmacéuticos de la Provincia de Buenos Aire

The Operculum-Plug Area and Membranous Structure of the Eggs of Trichuris Trichiura

Eggs of Trichuris trichiura were prepared for scanning electron microscopy (SEM) by the dimethylsulfoxide freeze-cracking method. The egg-shell and oocyte were examined by SEM. The egg has a chitinous shell which consists of more than 10 layers of dense lamellae. The shell is bordered by a limiting membrane. An operculum and a collar made of chitinous shell together form the opercular area. The operculum is an empty cavity. The chitinous fibers of the egg-shell in this area are diffuse and loose, with numerous micropores or spaces. The egg-shell in this area therefore appears to form a fine tubular network. The oocyte is an undifferentiated cell with a biconcave drum-like shape. The perivitelline space is conspicuous at both ends of the cell

Determination of tetramethylpyrazine in rat plasma by liquid chromatography/electrospray mass spectrometry

A sensitive and selective liquid chromatography/electrospray mass spectrometry (LC-ESIMS) method for determination of tetramethylpyrazine in rat plasma was developed. After addition of phenacetin as internal standard, protein precipitation by acetonitrile was used as sample preparation. Chromatographic separation was achieved on a Zorbax SB-C18 (2.1 mm×150 mm, 5 µm) column with (40:60, v/v) acetonitrile-water containing 0.1 % formic acid as mobile phase. Electrospray ionization (ESI) source was applied and operated in positive ion mode; selected ion monitoring (SIM) mode was used to quantify tetramethylpyrazine using target fragment ions m/z 136.9 for tetramethylpyrazine and m/z 179.8 for the IS. Calibration plots were linear over the range of 20-4000 ng/mL for tetramethylpyrazine in plasma. Lower limit of quantitation (LLOQ) for tetramethylpyrazine was 20 ng/mL. Mean recovery of tetramethylpyrazine from plasma was in the range 95.4-97.2 %. RSD of intra-day and inter-day precision were less than 9 %, respectively. This method is simple, sensitive and fast enough to be used in pharmacokinetic research for determination of tetramethylpyrazine in rat plasma.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Determination of tetramethylpyrazine in rat plasma by liquid chromatography/electrospray mass spectrometry

A sensitive and selective liquid chromatography/electrospray mass spectrometry (LC-ESIMS) method for determination of tetramethylpyrazine in rat plasma was developed. After addition of phenacetin as internal standard, protein precipitation by acetonitrile was used as sample preparation. Chromatographic separation was achieved on a Zorbax SB-C18 (2.1 mm×150 mm, 5 µm) column with (40:60, v/v) acetonitrile-water containing 0.1 % formic acid as mobile phase. Electrospray ionization (ESI) source was applied and operated in positive ion mode; selected ion monitoring (SIM) mode was used to quantify tetramethylpyrazine using target fragment ions m/z 136.9 for tetramethylpyrazine and m/z 179.8 for the IS. Calibration plots were linear over the range of 20-4000 ng/mL for tetramethylpyrazine in plasma. Lower limit of quantitation (LLOQ) for tetramethylpyrazine was 20 ng/mL. Mean recovery of tetramethylpyrazine from plasma was in the range 95.4-97.2 %. RSD of intra-day and inter-day precision were less than 9 %, respectively. This method is simple, sensitive and fast enough to be used in pharmacokinetic research for determination of tetramethylpyrazine in rat plasma.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Determination of tetramethylpyrazine in rat plasma by liquid chromatography/electrospray mass spectrometry

A sensitive and selective liquid chromatography/electrospray mass spectrometry (LC-ESIMS) method for determination of tetramethylpyrazine in rat plasma was developed. After addition of phenacetin as internal standard, protein precipitation by acetonitrile was used as sample preparation. Chromatographic separation was achieved on a Zorbax SB-C18 (2.1 mm×150 mm, 5 µm) column with (40:60, v/v) acetonitrile-water containing 0.1 % formic acid as mobile phase. Electrospray ionization (ESI) source was applied and operated in positive ion mode; selected ion monitoring (SIM) mode was used to quantify tetramethylpyrazine using target fragment ions m/z 136.9 for tetramethylpyrazine and m/z 179.8 for the IS. Calibration plots were linear over the range of 20-4000 ng/mL for tetramethylpyrazine in plasma. Lower limit of quantitation (LLOQ) for tetramethylpyrazine was 20 ng/mL. Mean recovery of tetramethylpyrazine from plasma was in the range 95.4-97.2 %. RSD of intra-day and inter-day precision were less than 9 %, respectively. This method is simple, sensitive and fast enough to be used in pharmacokinetic research for determination of tetramethylpyrazine in rat plasma.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Genetic Identification and Molecular Modeling Characterization Reveal a Novel PROM1 Mutation in Stargardt4-like Macular Dystrophy

Stargardt disease-4 (STGD4) is an autosomal dominant complex, genetically heterogeneous macular degeneration/dystrophy (MD) disorder. In this paper, we used targeted next generation sequencing and multiple molecular dynamics analyses to identify and characterize a disease-causing genetic variant in four generations of a Chinese family with STGD4-like MD. We found a novel heterozygous missense mutation, c.734T\u3eC (p.L245P) in the PROM1 gene. Structurally, this mutation most likely impairs PROM1 protein stability, flexibility, and amino acid interaction network after changing the amino acid residue Leucine into Proline in the basic helix-loop-helix leucine zipper domain. Molecular dynamic simulation and principal component analysis provide compelling evidence that this PROM1 mutation contributes to disease causativeness or susceptibility variants in patients with STGD4-like MD. Thus, this finding defines new approaches in genetic characterization, accurate diagnosis, and prevention of STGD4-like MD

Determination of meropenem in rabbit plasma by LC-MS/MS

A sensitive and selective liquid chromatography tandem mass spectrometry (LC–MS/MS) method for determination of meropenem in rabbit plasma was developed. After addition of triazolam as internal standard (IS), protein precipitation by acetonitrile was used in sample preparation. Chromatographic separation was achieved on a Restek Allure (TM) PFP Propyl (2.1 mm × 100 mm, 5 μm) column with acetonitrile-0.1 % formic acid as mobile phase with gradient elution. Electrospray ionization (ESI) source was applied and operated in positive ion mode; multiple reaction monitoring (MRM) mode was used to quantification using target fragment ions m/z 384.1 → 339.9 for meropenem and m/z 342.7 → 307.8 for the IS. Calibration plots were linear over the range of 0.1-40 μg/mL for meropenem in plasma. Lower limit of quantification (LLOQ) for meropenem was 0.1 μg/mL. Mean recovery of meropenem from plasma was in the range 85.6 %-96.5 %. CV of intra-day and inter-day precision were both less than 15 %. This method is simple and sensitive enough to be used in pharmacokinetic research for determination of meropenem in rabbit plasma.Colegio de Farmacéuticos de la Provincia de Buenos Aire