Sensitivity volume as figure-of-merit for maximizing data importance in electrical impedance tomography.

Objective.Electrical impedance tomography (EIT) is a noninvasive imaging method whereby electrical measurements on the periphery of a heterogeneous conductor are inverted to map its internal conductivity. The EIT method proposed here aims to improve computational speed and noise tolerance by introducing sensitivity volume as a figure-of-merit for comparing EIT measurement protocols.Approach.Each measurement is shown to correspond to a sensitivity vector in model space, such that the set of measurements, in turn, corresponds to a set of vectors that subtend a sensitivity volume in model space. A maximal sensitivity volume identifies the measurement protocol with the greatest sensitivity and greatest mutual orthogonality. A distinguishability criterion is generalized to quantify the increased noise tolerance of high sensitivity measurements.Main result.The sensitivity volume method allows the model space dimension to be minimized to match that of the data space, and the data importance to be increased within an expanded space of measurements defined by an increased number of contacts.Significance.The reduction in model space dimension is shown to increasecomputational efficiency, accelerating tomographic inversion by several orders of magnitude, while the enhanced sensitivitytolerates higher noiselevels up to several orders of magnitude larger than standard methods.

Blood group-specific apheresis in combination with daratumumab as a rescue therapy of acute antibody-mediated rejection in a case of ABO- and human leukocyte antigen-incompatible kidney transplantation.

We report a case of antibody-mediated rejection treated with the human CD38 monoclonal antibody daratumumab in a 58-year-old female patient with end-stage kidney disease due to autosomal dominant polycystic kidney disease who received an ABO- and human leukocyte antigen antibody-incompatible living donor kidney transplant. The patient experienced an episode of severe antibody-mediated rejection within the first week of transplantation. Blood-group-antibody selective immunoadsorption in combination with administration of four doses of daratumumab (each 1800 mg s.c.) led to a persistent decrease of ABO- and more interestingly donor-specific human leukocyte antigen antibody reactivity and resulted in clinical and histopathological remission with full recovery of graft function, which has remained stable until post-transplant day 212. This case illustrates the potential of targeting CD38 in antibody-mediated rejection.

Retinal vessel caliber and tortuosity and prediction of 5-year incidence of hypertension.

PURPOSE: With arterial hypertension as a global risk factor for cerebrovascular and cardiovascular diseases, we examined whether retinal blood vessel caliber and tortuosity assessed by a vessel-constraint network model can predict the incidence of hypertension. METHODS: The community-based prospective study included 9230 individuals who were followed for 5 years. Ocular fundus photographs taken at baseline were analyzed by a vessel-constraint network model. RESULTS: Within the 5-year follow-up, 1279 (18.8%) and 474 (7.0%) participants out of 6813 individuals free of hypertension at baseline developed hypertension and severe hypertension, respectively. In multivariable analysis, a higher incidence of hypertension was related to a narrower retinal arteriolar diameter ( P  < 0.001), wider venular diameter ( P  = 0.005), and a smaller arteriole-to-venule diameter ratio ( P  < 0.001) at baseline. Individuals with the 5% narrowest arteriole or the 5% widest venule diameter had a 17.1-fold [95% confidence interval (CI):7.9, 37.2] or 2.3-fold (95% CI: 1.4, 3.7) increased risk for developing hypertension, as compared with those with the 5% widest arteriole or the 5% narrowest venule. The area under the receiver operator characteristic curve for predicting the 5-year incidence of hypertension and severe hypertension was 0.791 (95% CI: 0.778, 0.804) and 0.839 (95% CI: 0.821, 0.856), respectively. Although the venular tortuosity was positively associated with the presence of hypertension at baseline ( P  = 0.01), neither arteriolar tortuosity nor venular tortuosity was associated with incident hypertension (both P  ≥ 0.10). CONCLUSION AND RELEVANCE: Narrower retinal arterioles and wider venules indicate an increased risk for incident hypertension within 5 years, while tortuous retinal venules are associated with the presence rather than the incidence of hypertension. The automatic assessment of retinal vessel features performed well in identifying individuals at risk of developing hypertension.

[Clinical features and survival analysis in non-M(3) acute myeloid leukemia patients with ASXL1 gene mutation].

Objective: To examine the survival rates and clinical characteristics of people with newly discovered non-M(3) acute myeloid leukemia (AML) who carry the ASXL1 gene mutation. Methods: From January 2016 to April 2021, the clinical information of patients with newly diagnosed non-M(3) AML at Shandong University's Qilu Hospital was retrospectively examined, and their clinical characteristics and survival were compared and analyzed. Gene mutation was detected by next-generation sequencing. Results: ① The study included 256 AML patients who were initially diagnosed and had complete data, including 47 cases of ASXL1 gene mutation-positive (ASXL1(+)) patients and 209 cases of ASXL1 gene mutation-negative (ASXL1(-)) patients. All patients were divided into three groups: elderly (≥60 years old, n=92) , middle-aged (45-59 years old, n=92) , and young (≤44 years old, n=72) . ②WBC, and age were higher in patients with ASXL1 mutations compared to ASXL1(-) patients, while complete response after the first round of treatment (CR(1)) was lower (P<0.05) . In the elderly group, WBC and the proportion of aberrant cells in nuclear cells in ASXL1(+) patients were higher than those in ASXL1(-) patients (P<0.05) . In the young group, the WBC of ASXL1(+) patients was higher than that of ASXL1(-) patients (z=-2.314, P=0.021) . ③IDH2 mutation and ASXL1 mutation was related (P=0.018, r=0.34) . In ASXL1(+) patients, the proportion of peripheral blasts in the high VAF group (VAF>40% ) was higher than that in the low VAF group (VAF<20% ) , and the proportion of aberrant nuclear cells was higher in the duplication and replacement mutation patients than in the deletion mutation patients (P<0.05) . ④The overall survival (OS) and progression-free survival (PFS) of ASXL1(+) patients were shorter than those of ASXL1(-) patients (median, 10 months vs 20 months, 10 months vs 17 months; P<0.05) . The proportion number of aberrant cells in nuclear cells (≥20% ) , complex karyotypes, and TET2 mutation were all independent risk variables that had an impact on the prognosis of ASXL1(+) patients, according to multivariate analysis (P<0.05) . Conclusion: ASXL1-mutated non-M(3) AML patients have higher WBC in peripheral blood, a higher proportion of aberrant cells in nuclear cells, lower CR(1) rate, and shorter OS and PFS. Additionally, a poor prognosis is linked to higher VAF, duplication, and substitution mutations in the ASXL1 gene, as well as the high proportion of aberrant cells in nuclear cells, complex karyotype, and TET2 mutation.

The prognostic role of baseline 18F-FDG PET/CT SUVmax and SUVmax change in patients with node-positive breast cancer receiving neoadjuvant chemotherapy. / El papel pronóstico del SUVmáx basal y cambio del SUVmáx en la PET/TC con18F-FDG en pacientes con cáncer de mama con ganglios positivos que reciben quimioterapia neoadyuvante.

OBJECTIVE: This study aimed to determine the prognostic role of baseline maximum standardized uptake value (SUVmax) obtained by pretreatment PET/CT and the change in SUVmax (ΔSUVmax [%]) in patients with axillary lymph node-positive breast cancer receiving neoadjuvant chemotherapy (NAC). METHODS: One hundred and eighty patients with baseline SUVmax and 121 patients with SUVmax measurement after treatment were evaluated in the study. The baseline SUVmax value of the breast (SUVmaxBI) and axilla (SUVmaxAI) and the change in the SUVmax of the breast (ΔSUVmaxB) and axilla (ΔSUVmaxA) were measured. The optimal cut-off value of SUVmax and ΔSUVmax were determined by ROC curve analysis. Disease-free survival (DFS) and overall survival (OS) were calculated using Kaplan-Meier curves. RESULTS: ΔSUVmaxB, pCRB, pCRA, and pCR parameters were found to be associated with relapse (p < 0.001, p = 0.033, p = 0.016, and p = 0.013, respectively). ΔSUVmaxB and SUVmaxAI were associated with mortality (p = 0.001 and p = 0.006, respectively). Multiple Cox regression analyses revealed that ΔSUVmaxB value was an independent prognostic factor for relapse and mortality (p = 0.013 and p = 0.010, respectively). CONCLUSION: The results showed that ΔSUVmaxB was an independent prognostic factor for relapse and mortality in patients with axillary lymph node-positive breast cancer who received NAC.

Aeroallergen sensitisation patterns of children aged 5 years and younger with asthma and/or allergic rhinitis in Istanbul.

AIM OF THE STUDY: The purpose of the study was to determine the aeroallergen sensitisation patterns of children aged 5 years and younger with asthma (AS) and/or allergic rhinitis (AR) in Istanbul, Turkey. METHODS: This cross-sectional observational study was conducted between January and December 2018 in the outpatient clinic of a hospital department of pediatric allergy. Patients, who had regular outpatient controls, full clinical and laboratory records, positive skin prick test results, and were willing to participate in the study, were included. RESULTS: In total, 148 children aged 5 years or younger who had positive skin prick test results were included in the study. The male/female ratio and the mean age at onset of symptoms were 87/61 and 2.13±1.33 (0.4-4.5) years, respectively. Of the 148 patients, 63 (42.6%) had AS, 11 (7.4%) AR, and 74 (50.0%) had both AS and AR. The age of the patients, age at symptom onset, male/female ratio, number of allergen sensitivities, total IgE levels, total eosinophil levels, and skin prick test results for aeroallergens did not differ between the patients with AS, AR, and AS+AR. House dust mite (HDM) was the most common aeroallergen in patients, while the cockroach was the least common aeroallergen. The severity of asthma and control levels were not found to be associated with aeroallergen sensitisation in children. CONCLUSION: One out of every four atopic children aged 5 years or younger is sensitised to aeroallergens. The most common sensitisation is to house dust mites. Weed aeroallergen may be related to severity of asthma in children aged 5 years or younger in Istanbul. We speculate that HDM and weed allergens could be used in the diagnostic or treatment strategies for the management of asthmatic children aged 5 years or younger.

The Effect on Survival and Mortality of the Highest SUVmax Value on Metastatic Foci in Postoperative Kidney Tumors.

OBJECTIVE: One-third of patients newly diagnosed with a kidney tumor have metachoronous disease, 25-50% have synchronous metastasis, and approximately 30-40% of patients have metastasis at the time of diagnosis. Metastasis mostly occurs in the lungs, regional lymph nodes, bones, and liver. The present study was aimed to determine the effect on mortality the values of standard uptake value (SUV)max measured with positron emission tomography (PET) in metastases of kidney tumors. MATERIAL AND METHODS: A retrospective review was conducted of the files of 77 patients newly diagnosed with kidney tumor and disease staging determined with PET in the Nuclear medicine Department of Saglik Bilimleri University Diyarbakir Gazi Yasargil Training and Research Hospital between August 2007 and April 2012. The gender, age, histological types, metastases, SUVmax values, and dates of death of the patients were recorded in the SPSS software. RESULTS: It was observed that higher SUVmax values indicated a shorter survival time (r = .303) (P = 0.022). Patients with metastasis lived for a shorter period (P < 0.001), particularly those with liver metastasis (r = .515) (P = 0.049). Metastases were most frequently seen in lymph nodes (42.1%); the SUVmax values of lung metastases were higher (P = 0.025) and papillary carcinomas showed higher SUVmax uptake (P = 0.015). CONCLUSIONS: In the present study, it was concluded that the higher the SUVmax value the shorter the survival time. The survival time of patients with metastasis was shorter, and this could be estimated through the measured SUVmax values.

Investigation of the relationship between non-alcoholic fatty liver disease and coronary artery disease.

AIMS: The purpose of the study was to examine the association between visceral adiposity form of non-alcoholic fatty liver and coronary artery disease severity and also to investigate the relationship between the epicardial adipose tissue thickness and non-alcoholic fatty liver disease with clinical and anthropometric measurements. MATERIALS AND METHODS: This study included 105 patients (mean age of patients were 57 ± 11, 82 of them male) who were hospitalized for coronary angiography because of chest pain. Nonalcoholic fatty liver disease was investigated by using ultrasonography. Thickness of the epicardial adipose tissue was measured by transthorasic echocardiography to right ventricular free wall adjacent to the parasternal long and short axis images. Gensini score was used for the severity of coronary artery disease. RESULTS: In patients with non-alcoholic fatty liver disease, right ventricular free wall epicardial adipose tissue thickness average of parasternal long and short axis were thicker than those who do not have non alcholic fatty liver disease (0,90 ± 0,19 cm; 0.58 ± 0.18 cm, p<0.001). Also, in patients with severe coronary artery disease, right ventricular free wall parasternal long and short axis average thickness of epicardial fat tissue was thicker than those of patients without severe coronary stenosis (0.86 ± 0.21 cm; 0,66 ± 0.26 cm, p=0.001). For predictability of coronary artery disease, Receiver Operating Characteristic analysis of the area under the curve was found to be 0.60 (50.2 to 74.7, 95% Confidence Limits). CONCLUSIONS: Not only the fatty tissue which surrounds the heart effects the coronary arteries but also other visceral organs adiposity effects the coronary arteries atherosclerotic process.

High-throughput mass spectrometric cytochrome P450 inhibition screening.

We describe here a high-throughput assay to support rapid evaluation of drug discovery compounds for possible drug-drug interaction (DDI). Each compound is evaluated for its DDI potential by incubating over a range of eight concentrations and against a panel of six cytochrome P450 (CYP) enzymes: 1A2, 2C8, 2C9, 2C19, 2D6, and 3A4. The method utilizes automated liquid handling for sample preparation, and online solid-phase extraction/tandem mass spectrometry (SPE/MS/MS) for sample analyses. The system is capable of generating two 96-well assay plates in 30 min, and completes the data acquisition and analysis of both plates in about 30 min. Many laboratories that perform the CYP inhibition screening automate only part of the processes leaving a throughput bottleneck within the workflow. The protocols described in this chapter are aimed to streamline the entire process from assay to data acquisition and processing by incorporating automation and utilizing high-precision instrument to maximize throughput and minimize bottleneck.

Methyl palmitate attenuates lipopolysaccharide-induced acute lung injury in mice.

AIM: The study is aimed to determine the beneficial effects of methyl palmitate (MP) which has antioxidant and anti-inflammatory effects demonstrated on murine model of acute lung injury induced by lipopolysaccharide (LPS). MATERIALS AND METHODS: Forty male BALB/C mice were randomly allocated into four groups (n=10, each): control group, methyl palmitate group (300 mg/kg), LPS group, and methyl palmitate -treated groups. Methyl palmitate or vehicle was given with an intraperitoneal administration 1 h before an intratracheal instillation of LPS (5 mg/kg). The severity of pulmonary injury was evaluated 6 h after LPS challenge. All experimental procedures complied with the requirements of the Animal Care and Ethics Committee of the Adnan Menderes University. RESULTS: Methyl palmitate pretreatment significantly attenuated LPS-induced pulmonary histopathologic changes, alveolar hemorrhage, and neutrophil infiltration. Methyl palmitate pretreatment also reduced the concentrations of malondialdehyde in lung tissues. CONCLUSIONS: This study indicates that methyl palmitate may have a protective effect against LPS-induced acute lung injury, and the potential mechanism of this action may involve the inhibition of NF-κB. activation.

Pretreatment parameters obtained from peripheral blood sample predicts invasiveness of bladder carcinoma.

PURPOSE: To predict the invasiveness of urothelial bladder carcinoma using a logistic regression model on preoperative peripheral blood samples. PATIENTS AND METHODS: Hospital data of patients operated for urothelial carcinoma were reviewed retrospectively. Preoperative blood samples were collected before the first cystoscopic examination. Any kind of infection or inflammation was an exclusion criterion. Patients were grouped as having a non-muscle-invasive or muscle-invasive urothelial carcinoma. The mean age was 69 years and was determined as the cut-off value. According to receiver operating characteristic curves, threshold points were determined for lymphocytes, neutrophil count, neutrophil-to-lymphocyte ratio (NLR), thrombocytes and mean platelet volume. Demographic specialties, parameters obtained from blood samples, tumor size and multiplicity were evaluated and significant parameters were put into a logistic regression model. RESULTS: The study group consisted of 80 non-muscle-invasive and 102 muscle-invasive patients. Age (≤69 vs. >69), female gender, NLR (2.57), mean platelet volume (7.9/fl) and platelet count (400,000/µl) were significant parameters and put in a model. Using odds ratios, the probability of tumor invasiveness was calculated by a formula. CONCLUSION: Age, female gender, NLR and platelet count were found to be the predictors of invasiveness of urothelial carcinoma.

Exploring the relationship between the severity of oligozoospermia and the frequencies of sperm chromosome aneuploidies.

The study was aimed to investigate the association between the degree of oligozoospermia and sperm chromosome aneuploidy frequencies in male infertility and to determine whether chromosomal profiles of sperm nuclei would be used for a supportive test before additive reproduction technics. The meiotic segregation profiles of chromosomes X, Y, 13, 18 and 21 were compared by fluorescent in-situ hybridisation (FISH) on the spermatozoa of 30 normally karyotyped oligozoospermic (10 mild, 11 moderate, nine severe) cases without Y-microdeletions, and 10 normozoospermic cases. The results showed significantly higher frequencies of chromosomes 13, 18, 21 disomies (P < 0.001) in the group of patients with moderate and severe oligozoospermia compared with the disomy frequencies of normozoospermic group. The statistically significant differences were also determined in disomy frequencies of sex chromosomes (XY, XX and YY) in between oligozoospermic and normozoospermic groups (P < 0.001, P < 0.001, P < 0.040, respectively). Because oligozoospermic patients are the ones consulted the most for assisted reproductive techniques, identification of sperm aneuploidy rates in men could be considered as an appropriate supportive test before the reproductive implementations. Furthermore, the patients should be counselled with respect to genetic screening results for the potential risk of aneuploid embryo and pre-implantation genetic diagnosis or prenatal diagnosis.

Advances in label-free screening approaches for studying histone acetyltransferases.

Histone acetyltransferases (HATs) catalyze the transfer of an acetyl group from an acetyl-coenzyme A donor molecule to specific lysine residues within proteins. The acetylation state of proteins, particularly histones, is known to modulate their intermolecular binding properties and control various cellular processes, most notably transcriptional activation. In addition, deregulation of HAT activity has been linked to the development of a number of cancers; therefore, compounds that affect these enzymes have strong potential as therapeutic agents. The research presented here demonstrates three label-free HAT screening approaches, all based on the fast and direct measurement of one or more substrate-product pairs by high-throughput mass spectrometry techniques. The first approach involves monitoring all possible acetylation states of a peptide concurrently to measure HAT activity. The second approach measures acetylation reactions, on both peptides and whole protein substrates, via direct detection of the acetyl-coenzyme A cosubstrate and coenzyme A coproduct. Lastly, the authors demonstrate the ability to monitor directly the acetylation state of whole histone proteins in the same high-throughput manner using time-of-flight mass spectrometry. The generation of compound-mediated inhibition data using each of these techniques establishes mass spectrometry as a versatile, label-free, and biologically relevant screening approach to this challenging target class.

Advances in label-free screening approaches for studying sirtuin-mediated deacetylation.

The sirtuin enzymes, a class of NAD(+)-dependent histone deacetylases, are a focal point of epigenetic research because of their roles in regulating gene expression and cellular differentiation by deacetylating histones and a host of transcription factors, including p53. Here, the authors present two label-free screening methodologies to study sirtuin activity using high-throughput mass spectrometry. The first method involves the detection of native peptides and provides a platform for more detailed mechanistic studies by enabling the concurrent and direct measurement of multiple modification states. The second method obviates the need for substrate-specific assay development by measuring the O-acetyl-ADP-ribose co-product formed by sirtuin-dependent deacetylation. Both methodologies were applied to investigating the deacetylation of multiple-peptide substrates by multiple-sirtuin enzymes. Kinetic data, including binding constants, inhibition, and, in some cases, activation, are demonstrated to correlate well, both between the methodologies and with previous literature precedent. In addition, the ability to monitor sirtuin activity via O-acetyl-ADP-ribose production permits experimentation on whole-protein substrates. The deacetylation of whole-histone proteins by SIRT3, and inhibition thereof, is presented and demonstrates the feasibility of screening sirtuins using more biologically relevant molecules.

Critical appraisal of the PADUA classification and assessment of the R.E.N.A.L. nephrometry score in patients undergoing partial nephrectomy.

PURPOSE: We validated the PADUA classification and assessed the R.E.N.A.L. nephrometry score to predict perioperative complications of partial nephrectomy. In addition, we assessed their interobserver variability, and the ability to predict the use of ischemia and ischemia time. MATERIALS AND METHODS: Data from consecutive cases of partial nephrectomy with or without ischemia from 3 centers were retrospectively collected. Associations between preoperative variables and complications were evaluated in univariate and multivariate analyses. Reproducibility was assessed by determining Fleiss' generalized kappa and intraclass correlation coefficients in a subcohort scored by 3 physicians with different degrees of urological expertise. RESULTS: A total of 134 partial nephrectomies were included in the study and 31 cases (23%) presented with complications. On univariate analyses complications were associated with age (p = 0.02), tumor size on computerized tomography (p = 0.01), pT stage (p = 0.001), and PADUA (p = 0.001) and R.E.N.A.L. scores (p = 0.02). In 3 multivariate models PADUA score 10 or greater (OR 3.98, p = 0.01), R.E.N.A.L. score 9 or greater (OR 4.21, p = 0.02), tumor size in cm (OR 1.35, p = 0.02) and age (OR 1.04, p = 0.04) were independent predictors of complications. The R.E.N.A.L. nephrometry score predicted the use of ischemia (p = 0.03) and both scores predicted ischemia time (both p <0.001). Kappa was 0.37 to 0.80 for PADUA components and 0.23 to 0.73 for R.E.N.A.L. components. The intraclass correlation coefficient was 0.73 for PADUA and 0.70 for R.E.N.A.L. score. CONCLUSIONS: The highest categories of PADUA and R.E.N.A.L. scores as well as clinical tumor size predict the risk of perioperative complications of partial nephrectomy. Both scores can indicate ischemia time. Their reproducibility is substantial but the implementation of these systems in clinical practice needs further refinement.

Ultrafast mass spectrometry based bioanalytical method for digoxin supporting an in vitro P-glycoprotein (P-gp) inhibition screen.

The evaluation of interactions between drug candidates and transporters such as P-glycoprotein (P-gp) has gained considerable interest in drug discovery and development. Inhibition of P-gp can be assessed by performing bi-directional permeability studies with in vitro P-gp-expressing cellular model systems such as Caco-2 (human colon carcinoma) cells, using digoxin as a substrate probe. Existing methodologies include either assaying (3)H-digoxin with liquid scintillation counting (LSC) detection or assaying non-labeled digoxin with liquid chromatography-tandem mass spectrometric (LC-MS/MS) analysis at a speed of several minutes per sample. However, it is not feasible to achieve a throughput high enough using these approaches to sustain an early liability screen that generates more than a thousand samples on a daily basis. To address this challenge, we developed an ultrafast (9 s per sample) bioanalytical method for digoxin analysis using RapidFire™, an on-line solid-phase extraction (SPE) system, with MS/MS detection. A stable isotope labeled analog, d3-digoxin, was used as internal standard to minimize potential ionization matrix effect during the RF-MS/MS analysis. The RF-MS/MS method was more than 16 times faster than the LC-MS/MS method but demonstrated similar sensitivity, selectivity, reproducibility, linearity and robustness. P-gp inhibition results of multiple validation compounds obtained with this RF-MS/MS method were in agreement with those generated by both the LC-MS/MS method and the (3)H-radiolabel assay. This method has been successfully deployed to assess P-gp inhibition potential as an important early liability screen for drug-transporter interaction.

Posttransplantation therapeutic rapamycin concentration protects nitric oxide-related vascular endothelial function: comparative effects in rat thoracic aorta and coronary endothelial cell culture.

OBJECTIVE: To investigate the potential effects of therapeutic dosages of the immunosuppression agent rapamycin on endothelial function with regard to nitric oxide (NO) synthesis in rat thoracic aorta in vivo and rat coronary endothelial cells in vitro. MATERIALS AND METHODS: Male Wistar rats were injected with rapamycin, 1.5 mg/kg/d intraperitoneally for 14 days. After the rats were sacrificed, the thoracic aortas were suspended in organ chambers and evaluated for endothelium-dependent and endothelium-independent vascular responses. RESULTS: Rapamycin administration resulted in increased relaxant responses to L-arginine and to greater concentrations of the calcium ionophore (A23187) in the aortas. However, potassium chloride, acetylcholine, sodium nitroprusside, and N(G)-nitro-L-arginine methyl ester responses remained unchanged. In addition, phenylephrine-induced contractions were significantly decreased in the aortas regardless of the presence of functional endothelium. In a series of in vitro experiments, isolated rat coronary endothelial cells were incubated with therapeutic concentrations of rapamycin (10 nmol/L). Nitrite accumulation in the supernatants revealed that rapamycin decreased nitrite release induced by interleukin-1beta but did not affect basal or A23187-stimulated nitrite levels. Western blot analysis demonstrated that rapamycin decreased inducible NO synthase protein expression in coronary endothelial cells. CONCLUSION: Posttransplantation therapeutic concentrations of rapamycin not only preserve vascular endothelial function mediated by NO synthesis but possibly interact in vivo with adrenergic receptors in favor of vasodilatory mechanisms.

Development of a high-throughput online solid-phase extraction/tandem mass spectrometry method for cytochrome P450 inhibition screening.

A high-throughput online solid-phase extraction/tandem mass spectrometry (online SPE/MS/MS) system has been developed to support rapid evaluation of drug discovery compounds for possible drug-drug interaction (DDI). Each compound is evaluated for its DDI potential by incubating over a range of 8 test concentrations and against a panel of 6 cytochrome P450 (CYP) enzymes, 1A2, 2C8, 2C9, 2C19, 2D6, and 3A4. Previously, a postassay pooling and a 2-min gradient LC/MS/MS method had been reported to increase sample throughput, allowing for a 96-well plate of samples to be analyzed in under 4 h. The development of a new online SPE/MS/MS system has reduced the analysis time to less than 15 min per 96-well plate, translating to a 15-fold time savings compared to the 2-min LC/MS/MS method. Sampling precision without internal standard correction ranged from 3.1% to 5.6% relative standard deviation, and the carryover was determined to be between 1.0% and 4.1%. One hundred twenty in-house compounds were assayed and pooled for analyses using both the online SPE/MS/MS and LC/MS/MS, and the correlation coefficients ranged from 0.89 to 1.13, when comparing the IC(50) results obtained from the 2 approaches for each of the CYP enzymes.

Screening for antibacterial inhibitors of the UDP-3-O-(R-3-hydroxymyristoyl)-N-acetylglucosamine deacetylase (LpxC) using a high-throughput mass spectrometry assay.

A high-throughput mass spectrometry assay to measure the catalytic activity of UDP-3-O-(R-3-hydroxymyristoyl)-N-acetylglucosamine deacetylase, LpxC, is described. This reaction is essential in the biosynthesis of lipopolysaccharide (LPS) of gram-negative bacteria and is an attractive target for the development of new antibacterial agents. The assay uses the RapidFire mass spectrometry platform to measure the native LpxC substrate and the reaction product and thereby generates a ratiometric readout with minimal artifacts due to detection interference. The assay was robust in a high-throughput screen of a library of more than 700,000 compounds arrayed as orthogonal mixtures, with a median Z' factor of 0.74. Selected novel inhibitors from the screening campaign were confirmed as binding to LpxC by biophysical measurements using a thermal stability shift assay. Some inhibitors showed whole-cell antimicrobial activity against a sensitive strain of Escherichia coli with reduced LpxC activity (strain D22; minimum inhibitory concentrations ranging from 0.625-20 microg/mL). The results show that mass spectrometry-based screening is a valuable high-throughput screening tool for detecting inhibitors of enzymatic targets involving difficult to detect reactions.