DNA Methylation Analysis Reveals Potential Mechanism in Takifugu rubripes Against Cryptocaryon irritans Infection

Takifugu rubripes (T. rubripes) is a valuable commercial fish, and Cryptocaryon irritans (C. irritans) has a significant impact on its aquaculture productivity. DNA methylation is one of the earliest discovered ways of gene epigenetic modification and also an important form of modification, as well as an essential type of alteration that regulates gene expression, including immune response. To further explore the anti-infection mechanism of T. rubripes in inhibiting this disease, we determined genome-wide DNA methylation profiles in the gill of T. rubripes using whole-genome bisulfite sequencing (WGBS) and combined with RNA sequence (RNA-seq). A total of 4659 differentially methylated genes (DMGs) in the gene body and 1546 DMGs in the promoter between the infection and control group were identified. And we identified 2501 differentially expressed genes (DEGs), including 1100 upregulated and 1401 downregulated genes. After enrichment analysis, we identified DMGs and DEGs of immune-related pathways including MAPK, Wnt, ErbB, and VEGF signaling pathways, as well as node genes prkcb, myca, tp53, and map2k2a. Based on the RNA-Seq results, we plotted a network graph to demonstrate the relationship between immune pathways and functional related genes, in addition to gene methylation and expression levels. At the same time, we predicted the CpG island and transcription factor of four immune-related key genes prkcb and mapped the gene structure. These unique discoveries could be helpful in the understanding of C. irritans pathogenesis, and the candidate genes screened may serve as optimum methylation-based biomarkers that can be utilized for the correct diagnosis and therapy T. rubripes in the development of the ability to resist C. irritans infection.

Chemotherapy combined with bevacizumab for small cell lung cancer with brain metastases: A case report

BACKGROUND

Small cell lung cancer (SCLC) is a common and aggressive subtype of lung cancer. It is characterized by rapid growth and a high mortality rate. Approximately 10% of patients with SCLC present with brain metastases at the time of diagnosis, which is associated with a median survival of 5 mo. This study aimed to summarize the effect of bevacizumab on the progression-free survival (PFS) and overall survival of patients with brain metastasis of SCLC.

CASE SUMMARY

A 62-year-old man was referred to our hospital in February 2023 because of dizziness and numbness of the right lower extremity without headache or fever for more than four weeks. The patient was diagnosed with limited-stage SCLC. He received 8 cycles of chemotherapy combined with maintenance bevacizumab therapy and achieved a PFS of over 7 mo.

CONCLUSION

The combination of bevacizumab and irinotecan effectively alleviated brain metastasis in SCLC and prolonged PFS.

A non-toxic recombinant protein rSUMO-CPBm4 as a potential vaccine candidate against Clostridium perfringens type C beta enterotoxemia

Beta toxin (CPB) is a lethal toxin and plays a key role in enterotoxemia of ruminants caused by Clostridium perfringens type C strain. The existing vaccines based on crude CPB need time-consuming detoxification and difficult quality control steps. In this study, we synthesized the rCPBm4 of C. perfringens type C strain and small ubiquitin-like modifier (SUMO)-tag CPBm4 (rSUMO-CPBm4) by introducing four amino acid substitutions: R212E, Y266A, L268G, and W275A. Compared with rCPBm4, rSUMO-CPBm4 was expressed with higher solubility in Escherichia coli BL21 (DE3). Neither rCPBm4 nor rSUMO-CPBm4 was lethal to mice. Although rCPBm4 and rSUMO-CPBm4 were reactogenic with polyclonal antibodies against crude CPB, rabbits vaccinated with rSUMO-CPBm4 developed significant levels of toxin-neutralizing antibody (TNA) titers that conferred protection against crude toxin challenge. These data suggest that genetically detoxified rSUMO-CPBm4 is a promising subunit vaccine candidate for C. perfringens type C beta enterotoxemia.

[A study on knowledge, attitude, and vaccination behavior of herpes zoster vaccine among urban residents in selected areas of China]

Objective: To understand the knowledge, attitude, and current status of vaccination of herpes zoster vaccination among urban residents aged 25 years and above in China. Methods: In August to October 2022, a convenience sampling method was used to survey residents aged 25 years and above at 36 community centers in 9 cities across China. Questionnaires were used to collect basic information, knowledge, and attitude toward herpes zoster and its vaccination, as well as vaccination status and reasons for non-vaccination among residents. Results: A total of 2 864 urban residents were included in the study. The total score of residents' cognition of herpes zoster and its vaccine was 3.01±2.08, and the total score of their attitude was 18.25±2.76. Factors such as being male (β=-0.45, P<0.001), older than 40-59 years (β=-0.34, P=0.023) or ≥60 years (β=-0.68, P<0.001), married (β=-0.69, P=0.002) were negatively associated with knowledge score. The educational level of high school or secondary school (β=0.44, P=0.036), college (β=0.65, P=0.006), bachelor's degree and above (β=1.20, P<0.001), annual net household income ≥120 000 Yuan in 2021 (β=0.42, P=0.020), having urban employee medical insurance (β=0.62, P=0.030), having public or commercial medical insurance (β=0.65, P=0.033), and having a history of chickenpox (β=0.29, P=0.025) were positively associated with knowledge scores. Being male (β=-0.38, P=0.008) and not remembering a history of chickenpox (β=-0.49, P=0.012) were negatively associated with attitude scores. Annual net household income in 2021 was between 40 000-80 000 Yuan (β=0.44, P=0.032) or between 80 000-120 000 Yuan (β=0.62, P=0.002) or ≥120 000 Yuan (β=0.93, P<0.001), and a history of herpes zoster (β=0.59, P=0.004) were positively associated with attitude scores. Of the 2 864 residents surveyed, only 29 (1.01%) had received the herpes zoster vaccine, with a vaccination rate of 1.70% for those aged 50 years and above, with the main reason for non-vaccination being lack of knowledge about the herpes zoster vaccine, followed by the high price. 42.67% of the population said they would consider getting the herpes zoster vaccine in the future. Conclusion: Low knowledge of herpes zoster and its vaccine, positive attitudes towards the preventive effects of herpes zoster and its vaccine, and extremely low vaccination rates among the urban population in China call for multiple measures to strengthen health education and vaccination recommendations for residents, especially for the elderly, low-education and low-income populations.

Transcriptome analysis in Takifugu rubripes and Dicentrarchus labrax gills during Cryptocaryon irritans infection

Takifugu rubripes and Dicentrarchus labrax are important commercial fish in China that are under serious threat from Cryptocaryon irritans. C. irritans is a ciliated obligate parasite that causes marine white spot disease and leads to heavy economic losses. We analysed the transcriptome in the gills of T. rubripes and D. labrax to compare differentially expressed genes (DEGs) and pathways during infection with C. irritans. In total, we identified 6,901 and 35,736 DEGs from T. rubripes and D. labrax, respectively. All DEGs were annotated into GO terms; 6,901 DEGs from T. rubripes were assigned into 991 sub-categories, and 35,736 DEGs from D. labrax were assigned into 8,517 sub-categories. We mapped DEGs to the KEGG database and obtained 153 and 350 KEGG signalling pathways from T. rubripes and D. labrax, respectively. Immune-related categories included Toll-like receptors, MAPK, lysosome, C-type lectin receptor and NOD-like receptor signalling pathways were significantly enriched pathways. In immune-related signalling pathways, we found that AP-1, P38, IL-1β, HSP90 and PLA were significantly up-regulated DEGs in T. rubripes, but P38 and PLA were significantly down-regulated in D. labrax. In this study, transcriptome was used to analyse the difference between scaly and non-scaly fish infection by C. irritans, which not only provided a theoretical basis for the infection mechanism of C. irritans, but also laid a foundation for effectively inhibiting the occurrence of this disease. Our work provides further insight into the immune response of host resistance to C. irritans.

[Effect of electrothermal acupuncture on moderate to severe cancer pain with yin-cold stagnation: a randomized controlled trial]

OBJECTIVE

To observe the effectiveness and safety of electrothermal acupuncture therapy for patients of moderate to severe cancer pain with yin-cold stagnation.

METHODS

A total of 60 patients of moderate to severe cancer pain with yin-cold stagnation were randomized into an observation group and a control group, 30 cases in each one. In the control group, opioid painkillers (oxycodone hydrochloride prolonged-release tablet or morphine sulfate sustained-release tablet) were taken. On the basis of the control group, electrothermal acupuncture was applied at Guanyuan (CV 4), Qihai (CV 6), Zusanli (ST 36), Hegu (LI 4), Sanyinjiao (SP 6) in the observation group, 30 min each treatment, once a day for 5 days. Before and after treatment, the scores of pain numerical rating scale (NRS) and Karnofsky performance scale (KPS) were observed in the two groups. The pain remission rate, reduction of opioid painkillers and safety were compared.

RESULTS

The variation of NRS scores in the observation group were larger than the control group 3, 5 days into treatment (P<0.01, P<0.05). The variation of KPS score in the observation group was larger than the control group after treatment (P<0.05). The pain remission rate was 100.0% (30/30) in the observation group, higher than 86.7% (26/30) in the control group (P<0.05). The reduction of opioid painkillers in the observation group was larger than the control group (P<0.01). There was no adverse reaction during the treatment in the two groups.

CONCLUSION

On the basis of the conventional western medication for analgesia, electrothermal acupuncture could relieve pain, reduce the dose of opioid painkillers and improve the quality of life in patients of moderate to severe cancer pain with yin-cold stagnation, has a better safety.

Associations of maternal upper respiratory tract infection/influenza during early pregnancy with congenital heart disease in offspring: evidence from a case-control study and meta-analysis

Background

Evidences regarding the associations between maternal upper respiratory tract infection/influenza during pregnancy and the risk of congenital heart disease (CHD) is still controversial. This study was specifically designed to examine the associations by a case-control study and a meta-analysis of the published evidences and our finding.

Methods

A hospital-based case-control study involving 262 children with simple CHD and 262 children with complex CHD, along with 262 control children, was conducted through June, 2016 to December, 2017. All children were aged 0–2 years old. Furthermore, a meta-analysis based on both previously published studies and our case-control study was performed.

Results

In the case-control study, after adjusting for possible confounders, maternal upper respiratory tract infection/influenza during early pregnancy was found to be related to an increased risk of CHD (OR = 3.40 and 95% CI: 2.05–5.62 for simple CHD; OR = 2.39 and 95% CI: 1.47–3.88 for complex CHD). After a meta-analysis, the adverse impact was still kept significant (OR = 1.47 and 95% CI: 1.28–1.67 for simple CHD; OR = 1.44 and 95% CI: 1.14–1.75 for complex CHD). The very similar associations were also observed among single type of CHD, herein, ventricular septal defects (VSD) and tetralogy of fallot (TOF) in the case-control study. In the subsequent meta-analysis, however, the significant association only existed in VSD.

Conclusions

Although there is still conflicting in TOF, the results are overall consistent, which provide new enforced evidence that maternal upper respiratory tract infection/influenza during early pregnancy, in general, play an important role in the occurrence of CHD.

[Characteristics of epidemiology and antimicrobial resistance of gram-negative bacterial bloodstream infections in children]

Objective: To study the epidemiology and antimicrobial resistance of Gram-negative bacterial bloodstream infections in children, and to guide the choice of antimicrobials and the control of nosocomial infection. Method: Clinical data, bacteriology and antimicrobial susceptibility test results were collected retrospectively in hospitalized children who were diagnosed with gram-negative bacterial bloodstream infections in Yuying Children's Hospital of Wenzhou Medical University from January, 2010 to December, 2015. Result: A total of 399 cases (253 male and 146 female) were identified. The age ranged from 16 hours to 16 years (median age 10.1 months). The majority of cases were collected from division of neonatology (n=261, 65.4%), followed by 31 cases (7.8%) from pediatric intensive care unit and 29 cases (7.3%) from Gastroenterology Department; 275 cases (68.9%) had underlying diseases, mainly including preterm birth(n=172), neonatal respiratory distress syndrome(n=67) and newborn asphyxia(n=53). Eighty cases had received invasive procedures and 20 had surgical operation; 149 cases (37.3%) were community-acquired and 250 cases (62.7%) were hospital acquired. Fifty cases had complications, among those, 40 cases had septic shock, 32 cases had multiple organ dysfunction syndrome and 7 cases had disseminated intravascular coagulation; 288 cases were cured, 48 improved, 17 gave up treatment and discharged, and 46 died; totally 408 strains were isolated from 399 children, including Enterobacteriaceae (346, 84.8%), non-fermentative Gram-negative bacteria (49, 12.0%) and other gram-negative bacteria (13, 3.2%). The resistance rates of Escherichia coli (n=175) and Klebsiella pneumoniae (n=106) to carbapenems, β-lactams enzyme and its inhibitors, amikacin and cefoxitin were all lower than 10%. Totally 245 multi-drug resistant strains (60.1%) were isolated, including 225 strains of Enterobacteriaceae and 18 strains of non-fermentative Gram-negative bacteria (P<0.01) . Nine strains of Carbapenem-resistant Enterobacteriaceae were isolated, which were all sensitive to amikacin and the sensitive rates to fluoroquinolone reached 88.9%. Five strains which were detected sensitive to tigecycline were all sensitive. The proportion of Klebsiella sp in Gram-negative bacteria between 2013-2015 and 2010-2012 were 32.9% and 21.2%, respectively. The resistance rates of Escherichia coli and Klebsiella pneumoniae to β-lactams and its enzyme inhibitors and carbapenems had no significant change. Conclusion: Gram-negative bacterial bloodstream infections occur more frequently in newborns. Most children had combined underlying diseases. Escherichia coli and Klebsiella pneumoniae are the most common pathogens. β-Lactams and its enzyme inhibitors and carbapenems are the empirical choice of antimicrobial therapy for severe Enterobacteriaceae bloodstream bacterial infections.

Adsorptive separation of hemoglobin by molecularly imprinted chitosan beads

A simply hemoglobin (Hb) molecularly imprinted polymer (MIP) was prepared using Hb as the imprinted molecule, acrylamide as the functional monomer and cross-linked chitosan beads as the supporting matrix. The MIP was achieved by entrapment of the selective soft polyacrylamide gel in the pores of the cross-linked chitosan beads by letting acrylamide monomer and the protein diffuse into the pores of chitosan beads before starting the polymerization. The chitosan beads were freed from the surrounding polyacrylamide gel by washing. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms. Langmuir analysis showed that an equal class of adsorption was formed in the MIP and the adsorption equilibrium constant and the maximum adsorption capacity were evaluated. The MIP has much higher adsorption capacity for Hb than the non-imprinted polymer with the same chemical composition, and the MIP also has a higher selectivity for the imprinted molecule. The MIP can be reused in an easy way and the reproduction coefficient was approximately 100% at low concentration.

Glycosylasparaginase inhibition studies: competitive inhibitors, transition state mimics, noncompetitive inhibitors

Glycosylasparaginase catalyzes the hydrolysis of the N-glycosylic bond between asparagine and N-acetylglucosamine in the catabolism of N-linked glycoproteins. Previously only three competitive inhibitors, one noncompetitive inhibitor, and one irreversible inhibitor of glycosylasparaginase activity had been reported. Using human glycosylasparaginase from human amniotic fluid, L-aspartic acid and four of its analogues, where the alpha-amino group was substituted with a chloro, bromo, methyl or hydrogen, were competitive inhibitors having Ki values between 0.6-7.7 mM. These results provide supporting evidence for a proposed intramolecular autoproteolytic activation reaction. A proposed phosphono transition state mimic and a sulfo transition state mimic were competitive inhibitors with Ki values 0.9 mM and 1.4 mM, respectively. These results support a mechanism for the enzyme-catalyzed reaction involving formation of a tetrahedral high-energy intermediate. Three analogues of the natural substrate were noncompetitive inhibitors with Ki values between 0.56-0.75 mM, indicating the presence of a second binding site that may recognize (substituted)acetamido groups.

Glycosylasparaginase activity requires the alpha-carboxyl group, but not the alpha-amino group, on N(4)-(2-Acetamido-2-deoxy-beta-D-glucopyranosyl)-L-asparagine

Glycosylasparaginase catalyzes the hydrolysis of the N-glycosylic bond in N(4)-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-L-asparagine in the catabolism of N-linked oligosaccharides. A deficiency, or absence, of enzyme activity gives rise to aspartylglycosaminuria, the most common disorder of glycoprotein metabolism. The enzyme catalyzes the hydrolysis of a variety of asparagine and aspartyl compounds containing a free alpha-carboxyl group and a free alpha-amino group; computational studies suggest that the alpha-amino group actively participates in the catalytic mechanism. In order to study the importance of the alpha-carboxyl group and the alpha-amino group on the natural substrate to the reaction catalyzed by the enzyme, 14 analogues of the natural substrate were studied where the structure of the aspartyl group of the substrate was changed. The incremental binding energy (DeltaDeltaGb) for those analogues that were substrates was calculated. The results show that the alpha-amino group may be substituted with a group of comparable size, for the alpha-amino group contributes little, if any, to the transition state binding energy of the natural substrate. The alpha-amino group position acts as an "anchor" in the binding site for the substrate. On the other hand, the alpha-carboxyl group is necessary for enzyme activity; removal of the alpha-carboxyl group or changing it to an alpha-carboxamide group results in no hydrolysis reaction. Also, N-acetyl-D-glucosamine is not sufficient for binding to the active site for efficient hydrolysis by the enzyme. These results provide supporting evidence for a proposed intramolecular autoproteolytic activation reaction for the enzyme. However, the results raise a question as to an important role for the alpha-amino group in the catalytic mechanism as indicated in computational studies.

Parallel extraction columns and parallel analytical columns coupled with liquid chromatography/tandem mass spectrometry for on-line simultaneous quantification of a drug candidate and its six metabolites in dog plasma

A method with parallel extraction columns and parallel analytical columns (PEC-PAC) for on-line high-flow liquid chromatography/tandem mass spectrometry (LC/MS/MS) was developed and validated for simultaneous quantification of a drug candidate and its six metabolites in dog plasma. Two on-line extraction columns were used in parallel for sample extraction and two analytical columns were used in parallel for separation and analysis. The plasma samples, after addition of an internal standard solution, were directly injected onto the PEC-PAC system for purification and analysis. This method allowed the use of one of the extraction columns for analyte purification while the other was being equilibrated. Similarly, one of the analytical columns was employed to separate the analytes while the other was undergoing equilibration. Therefore, the time needed for re-conditioning both extraction and analytical columns was not added to the total analysis time, which resulted in a shorter run time and higher throughput. Moreover, the on-line column extraction LC/MS/MS method made it possible to extract and analyze all seven analytes simultaneously with good precision and accuracy despite their chemical class diversity that included primary, secondary and tertiary amines, an alcohol, an aldehyde and a carboxylic acid. The method was validated with the standard curve ranging from 5.00 to 5000 ng/mL. The intra- and inter-day precision was no more than 8% CV and the assay accuracy was between 95 and 107%.

Bioanalytical method validation design for the simultaneous quantitation of analytes that may undergo interconversion during analysis

In the analysis of post-dose biological samples for quantitative determination of two analytes that can potentially undergo interconversion, it is essential to minimize the interconversion during the multiple steps of the bioanalytical method. However, even after optimizing the conditions of each step, some interconversion may be unavoidable. Even then, a method can be developed for the accurate simultaneous determination of the two analytes in post-dose biological samples if the composition, in terms of the ratio of the concentrations of the two analytes, of the calibration standards and quality control (QC) samples are selected judiciously, in relation to the composition of the unknown samples to be analyzed. As an example of such interconverting analytes, a delta-hydroxy acid compound (analyte 1) and its delta-lactone (analyte 2) were selected as model compounds that can potentially undergo interconversion. The effects of changing the relative concentrations of the two analytes in QC samples vis-à-vis the calibration standards on the performance of the method under conditions were investigated where: (a) the interconversion between the two analytes was minimized; (b) the conversion of analyte 2 to analyte 1 was enhanced; (c) the interconversion between the two analytes was enhanced. The results showed that the method performance, as measured by the accuracy and precision of the QC samples, was not acceptable when the ratio of concentration of analyte 1 to that of analyte 2 in the QC samples was different from that in the calibration standards and the conditions used facilitated the conversion of one analyte to the other. However, when the relative concentration of the two analytes in the QC samples was identical to that of the calibration standards, the method performance was acceptable under all three conditions of interconversion. This was because the same degree of interconversion took place in the QC samples and calibration standards. The purpose of QC samples in bioanalytical methods is to gauge how the method will perform for the analysis of post-dose test samples and hence, ideally, the relative concentrations of the analytes in QC samples, should be selected to mimic the anticipated concentrations in the test samples. However, the relative concentrations of the analytes in test samples may not be known a-priori, or may change from sample to sample; therefore, it is not always possible to construct QC samples that exactly mimic the relative concentrations of analytes in the test samples. Thus, in order to cover the variety of test samples, the method should include, in addition to QC samples that contain the analytes at the same relative concentration as in the calibration standards, QC samples with relative concentrations that are different from those in the calibration standards, including those that contain only analyte 1 and only analyte 2. In addition, the conditions adopted for the method should favor the minimization of the conversion of the analyte that is expected to be the major component in the post-dose test samples.

Peripheral electric stimulation inhibits morphine-induced place preference in rats

Conditioned place preference (CPP) is a commonly used model to detect rewarding effect of drugs. To observe the effect of peripheral electric stimulation (PES) on morphine-induced CPP, we trained the rats with morphine in a CPP paradigm. Twelve hours before the testing phase, rats were given PES via stainless-steel needles with frequencies of 2, 100, or 2/100 Hz, respectively. PES of 2 and 2/100 Hz significantly decreased CPP in morphine-trained animals in a naloxone reversible manner, while PES of 100 Hz, foot shock, needle insertion, or plain restraining, showed no effect. Thus, PES with a low-frequency component (2 Hz) could specifically inhibit the expression of morphine-induced CPP, presumably via activation of opioid receptors.

Ternary-column system for high-throughput direct-injection bioanalysis by liquid chromatography/tandem mass spectrometry

As a continuation of our efforts to improve our high-flow on-line bioanalytical approach for high-throughput quantitation of drugs and metabolites in biological matrices by high-performance liquid chromatography (LC) and tandem mass spectrometry (MS/MS), we have developed a ternary-column on-line LC/MS/MS system with dual extraction columns used in parallel for purification and an analytical column for analysis. The advantage of the dual extraction column system is that sample analysis can take place in one of the extraction columns while the other column is being equilibrated. Thus, the equilibration time does not add to the run time, hence shortening the injection cycle time and increasing the sample throughput. Moreover, the use of two extraction columns in parallel increases the number of samples that can be injected before the system fails due to an overused extraction column. Such a system has successfully been used to develop and validate a positive ion electrospray LC/MS/MS bioanalytical method for the quantitative determination of a guanidine-containing drug candidate in rat plasma. The system used for this work utilized two Oasis HLB extraction columns (1 x 50 mm, 30 microm), one C18 analytical column (3.9 x 50 mm, 5 microm), a ten-port switching value and a tandem mass spectrometer. The on-line analysis was accomplished by the direct injection of 10 microL of the sample, obtained by mixing a rat plasma sample 1:1 with an aqueous internal standard solution. Selected reaction monitoring (SRM) was utilized for the detection of the analyte and internal standard. The standard curve range was 1.00-200 ng/mL. The intra- and inter-day precision and accuracy were within 6.6%. The on-line purification step lasted for only 0.3 min and total run time was only 1.6 min.

A simple liquid-liquid extraction with hexane for low-picogram determination of drugs and their metabolites in plasma by high-performance liquid chromatography with positive ion electrospray tandem mass spectrometry

Four sensitive, specific and accurate methods, based on high-performance liquid chromatography (HPLC) with positive ion electrospray tandem mass spectrometry (MS/MS) coupled with liquid-Liquid extraction (LLE), have been developed and validated for the low-picogram determination of two drug candidates and a metabolite (compounds I-III) in human, monkey and rat plasma. In the LLE procedure, hexane or a mixture of hexane and methyl t-butyl ether was used to isolate these compounds from plasma of the different species after basification of each biological sample with sodium carbonate. The reconstituted extracts were then injected into a positive ion electrospray LC/MS/MS system for the quantitative analysis. The lower limit of quantitation of the methods ranged from 20 to 200 pg/mL. The use of hexane for the LLE proved to be simple, rapid and reproducible, and provided very clean extracts with little interference. The inter- and intra-day precision for the four methods was within 9%, and the accuracy was in the range 94-107%. The effect of pH on the isomerization of I (E-isomer) to its Z-isomer (II) showed that the rate of isomerization increased with decrease in pH and that there was no isomerization at pH >/=6.

A versatile system of high-flow high performance liquid chromatography with tandem mass spectrometry for rapid direct-injection analysis of plasma samples for quantitation of a beta-lactam drug candidate and its open-ring biotransformation product

A bioanalytical method has been developed and validated for quantitation of a beta-lactam drug candidate and its open-ring biotransformation product utilizing high-flow high-performance liquid chromatography (HPLC) for on-line purification of plasma samples and electrospray tandem mass spectrometry for detection and quantitation. The HPLC system used two columns: an Oasis column (1 x 50 mm, 30 microm) as the on-line extraction column and a conventional C18 column (2 x 50 mm, 5 microm) as the analytical column. Each plasma standard or quality control (QC) sample (50 microL) was mixed with 50 microL of a working solution of the internal standard in aqueous 0.5 M ammonium acetate (pH 4.0). Portions (10 microL) of these samples were then injected into an Oasis column with a mobile phase consisting of 100% aqueous 1 mM formic acid at a high flow rate (4.0 mL/min), with the effluent from the Oasis column directed to waste and not to the mass spectrometer. After the purification step, the Oasis column effluent was directed to the analytical column and the mass spectrometer and the analytes were eluted with methanol/aqueous 1 mM formic acid (70:30) at a flow rate of 1.0 mL/min. The total analysis time was 1.6 min per sample. The standard curve range was 0.980 to 250 ng/mL. The accuracy, inter-day precision and intra-day precision were within 10% for both compounds.

The use of high-flow high performance liquid chromatography coupled with positive and negative ion electrospray tandem mass spectrometry for quantitative bioanalysis via direct injection of the plasma/serum samples

Two bioanalytical methods have been developed and validated utilizing high flow high performance liquid chromatography (HPLC) for on-line purification of plasma and serum samples and electrospray tandem mass spectrometry for detection and quantitation. Each plasma or serum sample, after mixing with an aqueous solution of the internal standard, was injected into a small diameter (1 x 50 mm) column packed with large particles of OASIS (30 microns), with a 100% aqueous mobile phase at a high flow rate (3-4 mL/min). The combination of the high linear speed (6-8 cm/s) of the aqueous mobile phase and the large particle size resulted in the rapid passage of the proteins and other large biomolecules through the column while the small-molecule analytes were retained on the column. During this purification period, the HPLC effluent was directed to waste. After the purification step, the HPLC mobile phase was rapidly changed from 100% aqueous to < or = 100% organic, the flow was reduced to 0.5-0.8 mL/min, and the column effluent was directed towards the mass spectrometer. The small molecule analytes were eluted during this period. In the method developed and validated for the quantitative determination of compound I in rat plasma (method A), the same OASIS column (1 x 50 mm, 30 microns) served as the purification and analytical (elution) column. In the method developed for the simultaneous determination of pravastatin and its positional isomer biotransformation product (SQ-31906) in human serum (method B), the purification column was connected to a conventional C18 analytical column (3.9 x 50 mm, 5 microns) to achieve the required chromatographic separation between the two isomers. For method A, where 50 microL of rat plasma mixed 1:1 with water containing the internal standard was injected, the standard curve range was 1 to 1,000 ng/mL. For method B, where 200 microL of a human serum sample mixed 4:1 with water containing the internal standard was injected, the standard curve range was 0.5 to 100 ng/mL. The total analysis time for each method was < or = 5 min per sample. The accuracy, inter-day precision and intra-day precision were within 10% for both methods.