Implementation of sonopartogram: multicenter feasibility study

OBJECTIVES

Well-established clinical practice to assess progress in labor involves routine abdominal palpation and vaginal examination (VE). However, VE is subjective, poorly reproducible and painful for women. In this study, our aim is to evaluate the feasibility of systematically integrating transabdominal and transperineal ultrasound assessment of fetal position, psAOP, HPD and SCD to monitor labor progress in women undergoing induction of labor (IOL). We also aim at determining if ultrasound can reduce women's pain during examinations.

METHODS

Women were recruited as they presented for IOL in three maternity units. Ultrasound assessments were performed in 100 women between 37+0 and 41+6 weeks' gestation. A baseline combined transabdominal and transperineal scan was performed, including the assessment of fetal biometry, umbilical artery and middle cerebral artery Dopplers, amniotic fluid index (AFI), fetal spine and occiput positions, psAOP, HPD, SCD, and cervical length. Intrapartum scans were performed instead of VEs according to protocol. Participants were asked to indicate their level of pain by verbally giving a pain score from 0 - 10 (with 0 representing no pain) during assessment. The repeated measures data were analyzed by mixed effect models to identify the significant factors that affected the relationship between psAOP, HPD, SCD and mode of delivery.

RESULTS

223 intrapartum ultrasound scans with a median of 2 scans per participant (interquartile range (IQR) = 1 - 3), and 151 VEs were performed with a median of 1 per participant (IQR = 0 - 2). There were no adverse fetal or maternal outcomes. After excluding those with epidural anesthesia during examination, median pain score for intrapartum scan was 0 (IQR = 0 - 1) and 3 for VE (IQR = 0 - 6). Cesarean delivery and epidural anesthesia were significantly associated with slower rate of change in psAOP, HPD and SCD. Maternal height, parity and neonatal birth weight did not affect ultrasound measurements of labor progress.

CONCLUSIONS

Comprehensive transabdominal and transperineal ultrasound assessment can be successfully used to assess progress in labor and can reduce the level of pain experienced during examination. Ultrasound assessment may be able to replace some transabdominal and VE examinations during labor. This article is protected by copyright. All rights reserved.

Prediction of spontaneous preterm birth and preterm prelabor rupture of membranes using maternal factors, obstetric history and biomarkers of placental function at 11-13 weeks

OBJECTIVES

To determine whether first-trimester biomarkers of placental function can be used to screen for spontaneous preterm birth (sPTB), and to develop prediction models using maternal factors, obstetric history and biomarkers of placental function at 11-13 weeks for the calculation of patient-specific risk for sPTB.

METHODS

This was a retrospective secondary analysis of data derived from a prospective cohort study on first-trimester screening for pre-eclampsia in singleton pregnancies attending for routine Down syndrome screening at 11 + 0 to 13 + 6 weeks' gestation at a tertiary obstetric unit between December 2016 and September 2019. A split-sample internal validation method was used to explore and develop prediction models for all sPTB at < 37 weeks and for PTB at < 37 weeks after preterm prelabor rupture of membranes (PPROM) using maternal risk factors, uterine artery Doppler indices, serum placental growth factor (PlGF), pregnancy-associated plasma protein-A (PAPP-A) and β-human chorionic gonadotropin (β-hCG). Screening performance was assessed using receiver-operating-characteristics (ROC)-curve analysis, with calculation of the areas under the ROC curves (AUCs).

RESULTS

A total of 9298 singleton pregnancies were included in this study. sPTB at < 37 weeks occurred in 362 (3.89%) cases, including 231 (2.48%) cases of PPROM. sPTB at < 34 weeks occurred in 87 (0.94%) cases, including 39 (0.42%) cases of PPROM. Identified maternal risk factors for sPTB at < 37 weeks included chronic hypertension, conception using in-vitro fertilization and history of PTB. Maternal risk factors for PPROM at < 37 weeks included conception using in-vitro fertilization and history of PTB. Median PlGF multiples of the median (MoM) and PAPP-A MoM were significantly reduced in women with sPTB at < 37 weeks, as well as in those who had PPROM, compared to those who delivered at term. Screening by a combination of maternal risk factors, PAPP-A and PlGF achieved better performance in predicting sPTB at < 37 weeks (AUC, 0.630 vs 0.555; detection rate (DR), 24.8% vs 16.6% at a false-positive rate (FPR) of 10%; P ≤ 0.0001) and PPROM at < 37 weeks (AUC, 0.643 vs 0.558; DR, 28.1% vs 17.0% at a FPR of 10%; P ≤ 0.0001) than using maternal risk factors alone. Both models were successfully applied to the internal validation dataset, with AUCs of 0.628 and 0.650, respectively.

CONCLUSIONS

We demonstrated that low levels of maternal serum PAPP-A and PlGF in the first trimester are associated with increased risks of sPTB and PPROM at < 37 weeks. However, further research is needed to identify additional biomarkers to improve the screening performance of the combined model that includes maternal risk factors, PAPP-A and PlGF before clinical application. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

A phase 1, multicenter, open-label, first-in-human study of DS-6157a in patients (pts) with advanced gastrointestinal stromal tumor (GIST)

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Background: GPR20 is selectively and abundantly expressed in GISTs, the most common sarcoma of digestive tract. DS-6157a is an anti-GPR20 antibody-drug conjugate with a novel tetrapeptide-based linker and DNA topoisomerase I inhibitor exatecan derivative (DXd). The target drug-to-antibody ratio is ̃8. The DXd payload, when released, inhibits topoisomerase I and induces cell apoptosis. Methods: This study conducted in the US and Japan was designed to include a dose-escalation (Part 1) and a dose-expansion (Part 2) in adult pts with advanced GIST (NCT04276415). Part 1 evaluated safety, tolerability, efficacy, and pharmacokinetics (PK) to determine the maximum-tolerated dose (MTD) and/or recommended dose for expansion. Key eligibility criteria included ECOG PS of 0 or 1, measurable disease per RECIST v1.1, and adequate bone marrow, hepatic, and renal function. DS-6157a was administered every 3 weeks as monotherapy. Pts had tumor assessments per RECIST 1.1 every 6 weeks (wks) for 36 wks, then every 9 wks thereafter. Results: At data cutoff, 34 pts were available for full analysis: median treatment duration was 9.9 wks (range, 3-56 wks) and 5 pts (14.7%) were ongoing; median age 60.5 years (y) (range, 29-81 y); 19 pts (56%) were male; 47% of pts were Asian and 47% were white. Baseline GPR20 expression was highly prevalent, and dose-dependent PK exposure was confirmed within the range of dose levels. The MTD was 6.4 mg/kg. One pt with SDH-deficient GIST with both SDH B and NF1 mutations, had a confirmed PR with shrinkage of -75%; 18 pts (53%) experienced stable disease and 10 pts (29%) experienced progressive disease as best response. Median progression-free survival across all dose levels was 3.6 months (95% CI, 1.6, 6.9). Treatment-emergent AEs (TEAEs) occurred in all pts and treatment-related TEAEs (TRAEs) in 32 pts (94%). The most common (≥25%) all-grade (Gr) TEAEs were nausea (82%), decreased appetite (59%), fatigue (47%), anemia (44%), constipation (38%), decreased platelets (35%), and vomiting (32%). Gr ≥3 TRAEs occurred in 14 pts (41%); the most common were decreased platelets (21%) and anemia (18%). Serious TEAEs (SAEs) occurred in 9 pts (27%) and related SAEs in 4 pts (12%). Related Gr 4 SAEs in 2 pts included abnormal hepatic function, neutropenia, thrombocytopenia and leukopenia. There was 1 treatment related death (hepatic failure). Further investigations are on-going to understand the modest clinical efficacy observed. The study did not proceed to Part 2, because the data from Part 1 did not meet efficacy targets. Conclusions: DS-6157a was generally well tolerated with early signs of moderate clinical activity. While there were no objective responses in pts with KIT-mutant GIST, tumor shrinkage was observed in all 4 pts with KIT wild-type GIST treated at different doses, including a confirmed PR at the MTD in a pt with SDH-deficient GIST with both SDH B and NF1 mutations. Clinical trial information: NCT04276415.

Multipactor experiments on an S-band coaxial test cell

Radio frequency vacuum electronics are prone to multipactor discharges. These electron discharges, driven by secondary electron emission, can disrupt and damage devices and are particularly important in satellite communication systems. We present results from a new S-band coaxial multipactor test cell which demonstrates scaling to much higher frequencies (3.05 GHz) than previous coaxial experiments (10-150 MHz). The multipactor breakdown threshold has been found to agree very well with our earlier simulated predictions. The significant effect from multipactor self-conditioning has also been demonstrated and characterized. Future experiments will use this test cell to investigate various multipactor mitigation strategies.

Phase 1/2 study of ceritinib in Chinese patients with advanced anaplastic lymphoma kinase-rearranged non-small cell lung cancer previously treated with crizotinib: Results from ASCEND-6

BACKGROUND

Patients with anaplastic lymphoma kinase-rearranged (ALK+) non-small cell lung cancer (NSCLC) treated with crizotinib inevitably relapse, with brain as common site of progression.

PATIENTS AND METHODS

ASCEND-6, a phase 1/2, single-arm study, included adult Chinese patients with stage IIIB or IV ALK+ NSCLC pretreated with crizotinib as the last therapy (irrespective of prior chemotherapies [≤2]). Primary endpoints were pharmacokinetics (PK), safety, and tolerability. Key secondary endpoint was overall response rate (ORR; investigator assessed).

RESULTS

Of the 103 enrolled patients, all received prior crizotinib, 70 % received ≥1 prior chemotherapy regimen, and 63.1 % had brain metastases at baseline. In the phase 1 component, 20 patients completed a 5-day PK run-in period. Median T_max (n = 16) was ∼6 h; geometric means of AUC_{0-24 h} (n = 16) and C_max (n = 16) at steady state were 22,000 ng*h/mL and 1080 ng/mL, respectively. In the final analysis, median follow-up time was 34 months (range: 27.8-40.6). The ORR was 41.7 % (95 % confidence interval [CI]: 32.1-51.9), and median progression-free survival was 7.2 months (95 % CI: 4.1-7.5). Median overall survival was 17.5 months (95 % CI: 10.8-24.3). Most frequent adverse events, regardless of study drug relationship (mostly grade 1/2), were diarrhea (74.8 %), vomiting (62.1 %), alanine transaminase increased (59.2 %), aspartate transaminase increased (58.3 %), and nausea (58.3 %).

CONCLUSIONS

Ceritinib PK in Chinese patients is consistent with those observed in the global ASCEND-1 study. Ceritinib was well tolerated and showed durable responses in Chinese patients with ALK+ NSCLC who progressed after crizotinib and ≤2 prior lines of chemotherapy.

Does escalation results from phase Ib/II Norse study of erdafitinib (ERDA) + PD-1 inhibitor JNJ-63723283 (Cetrelimab [CET]) in patients (pts) with metastatic or locally advanced urothelial carcinoma (mUC) and selected fibroblast growth factor receptor (FGFR) gene alterations

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Background: ERDA, an oral pan-FGFR inhibitor, is approved by the US FDA for pts with metastatic urothelial carcinoma (mUC) with susceptible FGFR3/2 gene alterations and progressed after ≥1 line of prior platinum-containing chemotherapy (PCC).1 CET, an IgG4, binds to anti-programmed cell death proteins (PD-1) and has shown activity in solid tumors.2 ERDA+CET may demonstrate complementary mechanisms as neoantigen release by ERDA may prime the tumor microenvironment for response. NORSE is a phase 1b/2 study to evaluate ERDA+CET in pts with mUC. Methods: Adult mUC pts with specific FGFR alterations who have progressed after ≥1 prior systemic therapy and no prior FGFR or PD-1/PD(L)-1 inhibitors enrolled in 3 dose levels (DL) of ERDA (DL1: 6 mg, DL2A: 8 mg, DL2: 8 mg with uptitration [UPT] to 9 mg) + CET (IV, 240 mg). Cohorts enrolled until dose limiting toxicity (DLT) or RP2D was identified. Primary endpoints: DLT and adverse events (AEs). Results: Of 15 pts (DL1: 4, DL2A: 3, DL2: 8), 11 continued on treatment at the time of the data cut. 14/15 pts experienced AEs; 3 experienced serious unrelated AEs (urinary tract infection, urosepsis, and large intestinal obstruction) all in DL1, 2 led to death; 10 experienced Grade >3 AEs and 2 experienced AEs of special interest, considered related to ERDA (Table). No DLTs were observed in any cohorts, 8 mg with UPT + CET was established as the RP2D. At data cut-off, investigator-assessed best overall response rate (CR+PR+uCR+uPR) in pts treated with the RP2D was 71% and disease control rate was 100% for RECIST 1.1 evaluable pts (n=7). Conclusions: 8 mg ERDA with UPT+240 mg CET was well tolerated and established as the RP2D. The combination of ERDA+CET is being further explored in the ongoing randomized phase 2 study in first-line cisplatin-ineligible mUC pts (NCT03473743). Clinical trial information: 2017-001980-19. [Table: see text]

Ceritinib plus Nivolumab in Patients with Advanced ALK-Rearranged Non-Small Cell Lung Cancer: Results of an Open-Label, Multicenter, Phase 1B Study

INTRODUCTION

Induction of programmed death ligand 1 (PD-L1) expression due to constitutive oncogenic signaling has been reported in NSCLC models harboring echinoderm microtubule associated protein like 4 gene (EML4)-ALK receptor tyrosine kinase gene (ALK) rearrangements. We assessed the safety and activity of ceritinib plus nivolumab in these patients.

METHODS

In this open-label, phase 1B, multicenter, dose escalation and expansion study, previously treated (with ALK receptor tyrosine kinase [ALK] inhibitor [ALKI]/chemotherapy) or treatment-naive patients with stage IIIB or IV ALK-rearranged NSCLC received nivolumab, 3 mg/kg intravenously every 2 weeks, plus ceritinib, 450 mg/300 mg daily, with a low-fat meal.

RESULTS

In total, 36 patients were treated (a 450-mg cohort [n=14] and a 300-mg cohort [n=22]). In the 450-mg cohort, four patients experienced dose-limiting toxicities. In the 300-mg cohort, two patients experienced dose-limiting toxicities. Among ALKI-naive patients, the overall response rate (ORR) was 83% (95% confidence interval [CI]: 35.9-99.6) in the 450-mg cohort and 60% (95% CI: 26.2-87.8) in the 300-mg cohort. Among ALKI-pretreated patients, the ORR was 50% (95% CI: 15.7-84.3) in the 450-mg cohort and 25% (95% CI: 5.5-57.2) in the 300-mg cohort. The ORR point estimate was observed to be greater in patients who were positive for PD-L1 than in those who were negative for PD-L1, with overlapping CIs (e.g., at a cutoff ≥1% PD-L1, 64% of patients [95% CI: 35.1-87.2] had confirmed responses as compared with those with negative PD-L1 staining (31% [95% CI: 11.0-58.7]). The most frequently reported grade 3 or 4 adverse events were increased alanine aminotransferase level (25%), increased gamma-glutamyl transferase level (22%), increased amylase level (14%), increased lipase level (11%), and maculopapular rash (11%). The incidence of all-grade rash (grouped term) was 64% in both cohorts; grade 3 rash was reported in 29% and 14% of patients in the 450-mg and 300-mg cohorts, respectively; no grade 4 rash was reported.

CONCLUSION

Ceritinib plus nivolumab has activity; ORR appears to correlate with PD-L1 at baseline. Toxicity, especially rash, is more common than with either single agent.

Application of time-dependent modeling for the exposure-efficacy analysis of ceritinib in untreated ALK-rearranged advanced NSCLC patients

PURPOSE

Ceritinib 750 mg/day was approved for the treatment of patients with untreated anaplastic lymphoma kinase (ALK)-rearranged non-small cell lung cancer (NSCLC) based on ASCEND-4 study. The objective of this article is to introduce the use of time-dependent modeling approach in the updated exposure-efficacy analysis of ceritinib for the first-line indication.

METHODS

Exposure-efficacy analyses, including data from 156 patients, were first conducted using time-independent logistic regression model for response of complete or partial response and Cox regression model for progression-free survival (PFS). The exposure measure used was average C_trough, which is defined as the geometric mean of all evaluable C_trough for each patient. To further investigate the impact of exposure measure on exposure-efficacy analyses, a time-dependent modeling approach was used, where exposure at different time intervals was associated with the corresponding response endpoints in a longitudinal manner.

RESULTS

With exposure measure being average C_trough, it was observed that higher exposure was associated with reduced efficacy in terms of response (odds ratio = 0.77) and PFS [hazard ratio (HR) = 1.12]. These time-independent models do not account for the impact of time-varying concentration due to dose modifications. Subsequently, a new time-dependent modeling approach was used, where exposure and efficacy were associated longitudinally in the analyses. The results showed that the odds ratio of response became 1.07, and the HR of PFS became 1.04, indicating no apparent reverse relationship between exposure and efficacy across the exposure range studied.

CONCLUSION

The drug effect on efficacy in clinical trials could be better characterized using time-dependent exposure-response models.

Assessment of drug-drug interaction potential between ceritinib and proton pump inhibitors in healthy subjects and in patients with ALK-positive non-small cell lung cancer

PURPOSE

The impact of proton pump inhibitors (PPIs) on the pharmacokinetics (PK) and efficacy of ceritinib was evaluated.

METHODS

A healthy subject drug-drug interaction (DDI) study was conducted to assess the effect of esomeprazole on the PK of a single 750 mg dose of ceritinib. To further investigate the impact of PPIs on the PK and efficacy of ceritinib in ALK-positive cancer patients, two subgroup analyses were performed. Analysis 1 evaluated ceritinib steady-state trough concentration (C_trough,ss) and overall response rate (ORR) by concomitant use of PPIs in patients from the ASCEND-1, -2, and -3 studies; analysis 2 evaluated ceritinib single-dose and steady-state AUC_0-24h and C _max by concomitant PPI use in patients from ASCEND-1 using a definition of PPI usage similar to that used in the healthy subject study.

RESULTS

In the healthy subject study, co-administration of a single 750 mg dose of ceritinib with esomeprazole 40 mg for 6 days decreased ceritinib AUC_0-∞ by 76% and C _max by 79%. However, based on subgroup analysis 1, patients had similar C _trough,ss and ORR regardless of concomitant PPI usage. Based on analysis 2, co-administration of a single 750 mg ceritinib dose with PPIs for 6 days in patients suggested less effect on ceritinib exposure than that observed in healthy subjects as AUC_0-24h decreased by 30% and C _max decreased by 25%. No clinically meaningful effect on steady-state exposure was observed after daily dosing.

CONCLUSIONS

Long-term administration of ceritinib with PPIs does not adversely affect the PK and efficacy of ceritinib in ALK-positive cancer patients.

[The clinical advantage of using three dimensional visualization technology in hepatic surgery]

The three-dimensional body visible system is a further development of the three-dimensional CT reconstruction system. It has a lot of merits over the latter system. Clinical application of the three-dimensional body visible system in liver surgery showed the system to have the following merits: (1) The system can support the Couinaud classification of liver anatomy into two hemilivers, four sectors and eight segments. As the system can rotate the liver to any angle and it has the ability to make part or whole of the liver transparent thus making the internal blood vessels and bile ducts visible. Learning liver anatomy and liver surgery becomes easier. (2)The system can clearly localize liver tumors within the liver segment(s). (3)It can help clinicians to decide and to plan different operations on an individual. (4)By carrying out simulation partial hepatectomy using this system, it can help clinicians to estimate the difficulty and the risks involved in different options of liver resection and finally.(5)The system helps clinicians to identify anomalies in hepatic artery, portal vein, hepatic vein and bile duct, thus making the operation safer. In conclusion, this system significantly improves on the conventional three-dimensional CT reconstruction system. It is especially useful for inexperienced liver surgeons.

Therapeutic inertia in the management of hyperlipidaemia in type 2 diabetic patients: a cross-sectional study in the primary care setting

OBJECTIVES

To study the prevalence of therapeutic inertia in lipid management among type 2 diabetic patients in the primary care setting and to explore associated factors.

METHODS

This was a cross-sectional study involving type 2 diabetic patients with suboptimal lipid control followed up in all general out-patient clinics of Kowloon Central Cluster in Hong Kong from 1 October 2011 to 30 September 2013. Main outcome measures included prevalence of therapeutic inertia in low-density lipoprotein management among type 2 diabetic patients and its association with patient and physician characteristics.

RESULTS

Based on an agreed standard, lipid control was suboptimal in 49.1% (n=9647) of type 2 diabetic patients who attended for a regular annual check-up (n=19 662). Among the sampled 369 type 2 diabetic patients with suboptimal lipid control, therapeutic inertia was found to be present in 244 cases, with a prevalence rate of 66.1%. When the attending doctors' profiles were compared, the mean duration of clinical practice was significantly longer in the therapeutic inertia group than the non-therapeutic inertia group. Doctors without prior training in family medicine were also found to have a higher rate of therapeutic inertia. Patients in the therapeutic inertia group had longer disease duration, a higher co-morbidity rate of cardiovascular disease, and a closer-to-normal low-density lipoprotein level. Logistic regression analysis revealed that lack of family medicine training among doctors was positively associated with the presence of therapeutic inertia whereas patient's low-density lipoprotein level was inversely associated.

CONCLUSIONS

Therapeutic inertia was common in the lipid management of patients with type 2 diabetes in a primary care setting. Lack of family medicine training among doctors and patient's low-density lipoprotein level were associated with the presence of therapeutic inertia. Further study of the barriers and strategies to overcome therapeutic inertia is needed to improve patient outcome in this aspect of chronic disease management.

Technique for fabrication of ultrathin foils in cylindrical geometry for liner-plasma implosion experiments with sub-megaampere currents

In this work, we describe a technique for fabricating ultrathin foils in cylindrical geometry for liner-plasma implosion experiments using sub-MA currents. Liners are formed by wrapping a 400 nm, rectangular strip of aluminum foil around a dumbbell-shaped support structure with a non-conducting center rod, so that the liner dimensions are 1 cm in height, 6.55 mm in diameter, and 400 nm in thickness. The liner-plasmas are imploded by discharging ∼600 kA with ∼200 ns rise time using a 1 MA linear transformer driver, and the resulting implosions are imaged four times per shot using laser-shadowgraphy at 532 nm. This technique enables the study of plasma implosion physics, including the magneto Rayleigh-Taylor, sausage, and kink instabilities on initially solid, imploding metallic liners with university-scale pulsed power machines.

Absolute Instability near the Band Edge of Traveling-Wave Amplifiers

Applying the Briggs-Bers "pole-pinch" criterion to the exact transcendental dispersion relation of a dielectric traveling wave tube (TWT), we find that there is no absolute instability regardless of the beam current. We extend this analysis to the circuit band edges of a linear beam TWT by approximating the circuit mode as a hyperbola in the frequency-wave-number (ω-k) plane and consider the weak coupling limit. For an operating mode whose group velocity is in the same direction as the beam mode, we find that the lower band edge is not subjected to absolute instability. At the upper band edge, we find a threshold beam current beyond which absolute instability is excited. The nonexistence of absolute instability in a linear beam TWT and the existence in a gyrotron TWT, both at the lower band edge, is contrasted. The general study given here is applicable to some contemporary TWTs such as metamaterial-based and advanced Smith-Purcell TWTs.

Ceritinib in ALK-rearranged non-small-cell lung cancer

BACKGROUND

Non-small-cell lung cancer (NSCLC) harboring the anaplastic lymphoma kinase gene (ALK) rearrangement is sensitive to the ALK inhibitor crizotinib, but resistance invariably develops. Ceritinib (LDK378) is a new ALK inhibitor that has shown greater antitumor potency than crizotinib in preclinical studies.

METHODS

In this phase 1 study, we administered oral ceritinib in doses of 50 to 750 mg once daily to patients with advanced cancers harboring genetic alterations in ALK. In an expansion phase of the study, patients received the maximum tolerated dose. Patients were assessed to determine the safety, pharmacokinetic properties, and antitumor activity of ceritinib. Tumor biopsies were performed before ceritinib treatment to identify resistance mutations in ALK in a group of patients with NSCLC who had had disease progression during treatment with crizotinib.

RESULTS

A total of 59 patients were enrolled in the dose-escalation phase. The maximum tolerated dose of ceritinib was 750 mg once daily; dose-limiting toxic events included diarrhea, vomiting, dehydration, elevated aminotransferase levels, and hypophosphatemia. This phase was followed by an expansion phase, in which an additional 71 patients were treated, for a total of 130 patients overall. Among 114 patients with NSCLC who received at least 400 mg of ceritinib per day, the overall response rate was 58% (95% confidence interval [CI], 48 to 67). Among 80 patients who had received crizotinib previously, the response rate was 56% (95% CI, 45 to 67). Responses were observed in patients with various resistance mutations in ALK and in patients without detectable mutations. Among patients with NSCLC who received at least 400 mg of ceritinib per day, the median progression-free survival was 7.0 months (95% CI, 5.6 to 9.5).

CONCLUSIONS

Ceritinib was highly active in patients with advanced, ALK-rearranged NSCLC, including those who had had disease progression during crizotinib treatment, regardless of the presence of resistance mutations in ALK. (Funded by Novartis Pharmaceuticals and others; ClinicalTrials.gov number, NCT01283516.).

Novel scaling laws for the Langmuir-Blodgett solutions in cylindrical and spherical diodes

It is found that the Langmuir-Blodgett solutions for the space charge limited current density, for both cylindrical and spherical diodes, may be approximated by Japp=(4/9)ε0sqrt[(2e/m)](Ec3/2/sqrt[D]) over a wide range of parameters, where Ec is the surface electric field on the cathode of the vacuum diode and D is the anode-cathode spacing. This dependence is valid whether Ra/Rc is greater than or less than unity, where Ra and Rc are, respectively, the anode and cathode radius. Minor empirical corrections to the above scaling yield fitting formulas that are accurate to within 5% for 3×10(-5)<Rc/Ra<500. An explanation of this scaling is given. An accurate transit time model yields the Langmuir-Blodgett solutions even in the Coulomb blockade regime for a nanogap, where the electron number may be in the single digits, and the transit time frequency is in the THz range.

Mechanistic modeling of antigen sink effect for mavrilimumab following intravenous administration in patients with rheumatoid arthritis

Mavrilimumab is a fully human monoclonal antibody that binds to granulocyte-macrophage colony stimulating factor receptor α (GM-CSFRα) with high affinity and specificity and has potential application in various inflammatory diseases. The objective of this investigation was to develop a mechanistic population model to characterize the pharmacokinetics of mavrilimumab, the GM-CSFRα-mediated clearance, and receptor occupancy following single intravenous dosing to patients with rheumatoid arthritis. The internalization rate of mavrilimumab-GM-CSFRα complex was fixed to a value determined from quantitative confocal fluorescent imaging. The estimated typical first-order clearance and the central and peripheral distribution volumes were 3.79 mL/kg/d, 39.6 mL/kg, and 50.3 mL/kg, respectively. The systemic GM-CSFRα expression level was estimated to be 0.0782 nM, and the equilibrium dissociation constant (0.103 nM) was in good agreement with the monovalent affinity determined by surface plasmon resonance. By fitting to the observed pharmacokinetic data, the mechanistic model predicted that systemically greater than 90% GM-CSFRα blockade by mavrilimumab was achieved and maintained up to 4, 7, and 11 weeks following single 1-, 3-, and 10-mg/kg administrations, respectively. Posterior visual predictive check and bootstrapping suggest that the mechanistic model is reasonably robust and can be used to predict mavrilimumab exposure under various scenarios for future clinical trial design.

Anisotropy and feedthrough in magneto-Rayleigh-Taylor instability

The magneto-Rayleigh-Taylor instability (MRT) of a finite slab is studied analytically using the ideal MHD model. The slab may be accelerated by an arbitrary combination of magnetic pressure and fluid pressure, thus allowing an arbitrary degree of anisotropy intrinsic to the acceleration mechanism. The effect of feedthrough in the finite slab is also analyzed. The classical feedthrough solution obtained by Taylor in the limit of zero magnetic field, the single interface MRT solution of Chandrasekhar in the limit of infinite slab thickness, and Harris' stability condition on purely magnetic driven MRT, are all readily recovered in the analytic theory as limiting cases. In general, we find that MRT retains robust growth if it exists. However, feedthrough may be substantially reduced if there are magnetic fields on both sides of the slab, and if the MRT mode invokes bending of the magnetic field lines.

Unstable spiral modes in disk-shaped galaxies: A general fluid dynamical theory with some preliminary results

A numerical scheme has been devised to calculate discrete spiral modes in a fluid-dynamical model of disk galaxies. The procedure is free from the usual restrictions imposed upon the asymptotic theory. A radiation condition has been formulated as one of the boundary conditions. For a test model galaxy with moderately low surface density, quantitative agreement is found between the asymptotic spiral modes and the corresponding ones obtained from the present scheme. The present scheme should find ready application to the study of open spiral modes.

Unstable spiral modes in disk-shaped galaxies: Enhancement of growth rate

An additional effect not considered in our earlier papers is found to enhance the rate of growth of spiral modes in disk-shaped galaxies. This enhanced growth appears to be attributable to the combined influence of differential rotation and tangential forces. For certain galaxy models, rapid temporal growths are possible (comparable to those found in numerical experiments), but in many real galaxies, these tendencies to extreme growth rates are probably reduced to lower levels by competing effects such as wave absorption at inner Lindblad resonance.

Unstable spiral modes in disk-shaped galaxies

The mechanisms for the maintenance and the excitation of trailing spiral modes of density waves in diskshaped galaxies, as proposed by Lin in 1969 and by Mark recently, are substantiated by an analysis of the gas-dynamical model of the galaxy. The self-excitation of the unstable mode in caused by waves propagating outwards from the corotation circle, which carry away angular momentum of a sign opposite to that contained in the wave system inside that circle. Specifically, a simple dispersion relationship is given as a definite integral, which allows the immediate determination of the pattern frequency and the amplification rate, once the basic galactic model is known.

Discrete spiral modes in disk galaxies: Some numerical examples based on density wave theory

Discrete growing spiral modes are calculated, on the basis of principles of stellar dynamics, according to the recently developed asymptotic theory of density waves for spiral structure in galaxies. From the growth rates obtained, it appears likely that several spiral modes coexist in a given disk galaxy. General properties of these modes are described for two galaxy models, and some of their important observational implications are discussed.

Acute glucose-lowering and insulin-sensitizing action of FGF21 in insulin-resistant mouse models--association with liver and adipose tissue effects

Recombinant fibroblast growth factor (FGF)21 has antihyperglycemic, antihyperlipidemic, and antiobesity effects in diabetic rodent and monkey models. Previous studies were confined to measuring steady-state effects of FGF21 following subchronic or chronic administration. The present study focuses on the kinetics of biological actions of FGF21 following a single injection and on the associated physiological and cellular mechanisms underlying FGF21 actions. We show that FGF21 resulted in rapid decline of blood glucose levels and immediate improvement of glucose tolerance and insulin sensitivity in two animal models of insulin resistance (ob/ob and DIO mice). In ob/ob mice, FGF21 led to a 40-60% decrease in blood glucose, insulin, and amylin levels within 1 h after injection, and the maximal effects were sustained for more than 6 h despite the 1- to 2-h half-life of FGF21. In DIO mice, FGF21 reduced fasting blood glucose and insulin levels and improved glucose tolerance and insulin sensitivity within 3 h of treatment. The acute improvement of glucose metabolism was associated with a 30% reduction of hepatic glucose production and an increase in peripheral glucose turnover. FGF21 appeared to have no direct effect on ex vivo pancreatic islet insulin or glucagon secretion. However, it rapidly induced typical FGF signaling in liver and adipose tissues and in several hepatoma-derived cell lines and differentiated adipocytes. FGF21 was able to inhibit glucose release from H4IIE hepatoma cells and stimulate glucose uptake in 3T3-L1 adipocytes. We conclude that the acute glucose-lowering and insulin-sensitizing effects of FGF21 are potentially associated with its metabolic actions in liver and adipose tissues.

Pharmacokinetic and pharmacodynamic modeling of a monoclonal antibody antagonist of glucagon receptor in male ob/ob mice

Elevated basal concentrations of glucagon and reduced postprandial glucagon suppression are partly responsible for the increased hepatic glucose production seen in type 2 diabetic patients. Recently, it was demonstrated that an antagonistic human monoclonal antibody (mAb) blocking glucagon receptor (GCGR) has profound glucose-lowering effects in various animal models. To further understand the effects on glucose homeostasis mediated by such an antibody, a pharmacokinetic-pharmacodynamic (PK-PD) study was conducted in a diabetic ob/ob mouse model. Four groups of ob/ob mice were randomized to receive single intraperitoneal administration of placebo, 0.6, 1, or 3 mg/kg of mAb GCGR, a fully human mAb against GCGR. The concentration-time data were used for noncompartmental and compartmental analysis. A semi-mechanistic PK-PD model incorporating the glucose-glucagon inter-regulation and the hypothesized inhibitory effect of mAb GCGR on GCGR signaling pathway via competitive inhibition was included to describe the disposition of glucose and glucagon over time. The pharmacokinetics of mAb GCGR was well characterized by a two-compartment model with parallel linear and nonlinear saturable eliminations. Single injection of mAb GCGR caused a rapid glucose-lowering effect with blood glucose concentrations returning to baseline by 4 to 18 days with increasing dose from 0.6 to 3 mg/kg. Elevation of glucagon concentrations was also observed in a dose-dependent manner. The results illustrated that the feedback relationship between glucose and glucagon in the presence of mAb GCGR could be quantitatively described by the developed model. The model may provide additional understanding in the underlying mechanism of GCGR antagonism by mAb.

Microwave window breakdown experiments and simulations on the UM/L-3 relativistic magnetron

Experiments have been performed on the UM/L-3 (6-vane, L-band) relativistic magnetron to test a new microwave window configuration designed to limit vacuum side breakdown. In the baseline case, acrylic microwave windows were mounted between three of the waveguide coupling cavities in the anode block vacuum housing and the output waveguides. Each of the six 3 cm deep coupling cavities is separated from its corresponding anode cavity by a 1.75 cm wide aperture. In the baseline case, vacuum side window breakdown was observed to initiate at single waveguide output powers close to 20 MW. In the new window configuration, three Air Force Research Laboratory-designed, vacuum-rated directional coupler waveguide segments were mounted between the coupling cavities and the microwave windows. The inclusion of the vacuum side power couplers moved the microwave windows an additional 30 cm away from the anode apertures. Additionally, the Lucite microwave windows were replaced with polycarbonate windows and the microwave window mounts were redesigned to better maintain waveguide continuity in the region around the microwave windows. No vacuum side window breakdown was observed in the new window configuration at single waveguide output powers of 120+MW (a factor of 3 increase in measured microwave pulse duration and factor of 3 increase in measured peak power over the baseline case). Simulations were performed to investigate likely causes for the window breakdown in the original configuration. Results from these simulations have shown that in the original configuration, at typical operating voltage and magnetic field ranges, electrons emitted from the anode block microwave apertures strike the windows with a mean kinetic energy of 33 keV with a standard deviation of 14 keV. Calculations performed using electron impact angle and energy data predict a first generation secondary electron yield of 65% of the primary electron population. The effects of the primary aperture electron impacts, combined with multiplication of the secondary populations, were determined to be the likely causes of the poor microwave window performance in the original configuration.

Fully human monoclonal antibodies antagonizing the glucagon receptor improve glucose homeostasis in mice and monkeys

Antagonizing the glucagon signaling pathway represents an attractive therapeutic approach for reducing excess hepatic glucose production in patients with type 2 diabetes. Despite extensive efforts, there is currently no human therapeutic that directly inhibits the glucagon/glucagon receptor pathway. We undertook a novel approach by generating high-affinity human monoclonal antibodies (mAbs) to the human glucagon receptor (GCGR) that display potent antagonistic activity in vitro and in vivo. A single injection of a lead antibody, mAb B, at 3 mg/kg, normalized blood glucose levels in ob/ob mice for 8 days. In addition, a single injection of mAb B dose-dependently lowered fasting blood glucose levels without inducing hypoglycemia and improved glucose tolerance in normal C57BL/6 mice. In normal cynomolgus monkeys, a single injection improved glucose tolerance while increasing glucagon and active glucagon-like peptide-1 levels. Thus, the anti-GCGR mAb could represent an effective new therapeutic for the treatment of type 2 diabetes.

Effect of soft metal gasket contacts on contact resistance, energy deposition, and plasma expansion profile in a wire array Z pinch

Soft metal gaskets (indium and silver) were used to reduce contact resistance between the wire and the electrode in an aluminum wire Z pinch by more than an order of magnitude over the best weighted contact case. Clamping a gasket over a Z-pinch wire compresses the wire to the electrode with a greater normal force than possible with wire weights. Average contact resistance was reduced from the range of 100-3000 Omega (depending on wire weight mass) to 1-10 Omega with soft metal gaskets. Single wire experiments (13 microm Al 5056) on a 16 kA, 100 kV Marx bank showed an increase in light emission (97%) and emission volume (100%) of the plasma for the reduced contact resistance cases. The measured increases in plasma volume and light emission indicate greater energy deposition in the ablated wire. Additionally, dual-wire experiments showed plasma edge effects were significantly decreased in the soft metal gasket contact case. The average height of the edge effects was reduced by 51% and the width of the edge effects was increased by 40%, thus the gasket contact case provided greater axial uniformity in the plasma expansion profile of an individual wire.

Metal-oxide-junction, triple point cathodes in a relativistic magnetron

Triple point, defined as the junction of metal, dielectric, and vacuum, is the location where electron emission is favored in the presence of a sufficiently strong electric field. To exploit triple point emission, metal-oxide-junction (MOJ) cathodes consisting of dielectric "islands" over stainless steel substrates have been fabricated. The two dielectrics used are hafnium oxide (HfO(x)) for its high dielectric constant and magnesium oxide (MgO) for its high secondary electron emission coefficient. The coatings are deposited by ablation-plasma-ion lithography using a KrF laser (0-600 mJ at 248 nm) and fluence ranging from 3 to 40 J/cm(2). Composition and morphology of deposited films are analyzed by scanning electron microscopy coupled with x-ray energy dispersive spectroscopy, as well as x-ray diffraction. Cathodes are tested on the Michigan Electron Long-Beam Accelerator with a relativistic magnetron, at parameters V=-300 kV, I=1-15 kA, and pulse lengths of 0.3-0.5 micros. Six variations of the MOJ cathode are tested, and are compared against five baseline cases. It is found that particulate formed during the ablation process improves the electron emission properties of the cathodes by forming additional triple points. Due to extensive electron back bombardment during magnetron operation, secondary electron emission also may play a significant role. Cathodes exhibit increases in current densities of up to 80 A/cm(2), and up to 15% improvement in current start up time, as compared to polished stainless steel cathodes.

Role of ions in a crossed-field diode

The effect of ions in a magnetically insulated crossed-field gap is studied using a single particle orbit model, shear flow model, and particle-in-cell simulation. It is found that, in general, the presence of ions in a crossed-field gap always increases the electrons' excursion toward the anode region, regardless of the location of the ions. Thus, the rate at which the electrons migrate toward the anode, which is a measure of the diode closure rate, is related to the rate at which ions are introduced into the crossed-field gap. This anode migration of electrons is unrelated to crossed-field ambipolar diffusion. The implications of these findings are explored, such as pulse shortening in relativistic magnetrons and bipolar flows in pulsed-power systems.

effect of OATP1B transporter inhibition on the pharmacokinetics of atorvastatin in healthy volunteers

The inhibition of hepatic uptake transporters, such as OATP1B1, on the pharmacokinetics of atorvastatin is unknown. Here, we investigate the effect of a model hepatic transporter inhibitor, rifampin, on the kinetics of atorvastatin and its metabolites in humans. The inhibitory effect of a single rifampin dose on atorvastatin kinetics was studied in 11 healthy volunteers in a randomized, crossover study. Each subject received two 40-mg doses of atorvastatin, one on study day 1 and one on study day 8, separated by 1 week. One intravenous 30-min infusion of 600 mg rifampin was administered to each subject on either study day 1 or study day 8. Plasma concentrations of atorvastatin and metabolites were above the limits of quantitation for up to 24 h after dosing. Rifampin significantly increased the total area under the plasma concentration-time curve (AUC) of atorvastatin acid by 6.8+/-2.4-fold and that of 2-hydroxy-atorvastatin acid and 4-hydroxy-atorvastatin acid by 6.8+/-2.5- and 3.9+/-2.4-fold, respectively. The AUC values of the lactone forms of atorvastatin, 2-hydroxy-atorvastatin and 4-hydroxy-atorvastatin, were also significantly increased, but to a lower extent. An intravenous dose of rifampin substantially increased the plasma concentrations of atorvastatin and its acid and lactone metabolites. The data confirm that OATP1B transporters represent the major hepatic uptake systems for atorvastatin and its active metabolites. Inhibition of hepatic uptake may have consequences for efficacy and toxicity of drugs like atorvastatin that are mainly eliminated by the hepatobiliary system.

Pharmacokinetics of atorvastatin and its hydroxy metabolites in rats and the effects of concomitant rifampicin single doses: relevance of first-pass effect from hepatic uptake transporters, and intestinal and hepatic metabolism

Pharmacokinetic coadministration experiments with atorvastatin (ATV) and rifampicin (RIF) in rats were performed to investigate the potential involvement of hepatic uptake transporters, Oatps (organic anion-transporting polypeptides), during hepatic drug elimination, as an in vivo extension of our recently published cellular and isolated perfused liver studies. ATV was administered orally (10 mg/kg) and intravenously (2 mg/kg) to rats in the absence and presence of a single intravenous dose of RIF (20 mg/kg), and pharmacokinetic parameters were compared between control and RIF-treatment groups. RIF markedly increased the plasma concentrations of ATV and its metabolites when ATV was administered orally. The area under the plasma concentration-time curve (AUC(0-infinity)) for ATV also increased significantly after intravenous dosing of ATV with RIF, but the extent was much less than that observed for oral ATV dosing. Significant increases in plasma levels were observed for both metabolites as well. The 7-fold higher AUC ratio of metabolites to parent drug following oral versus intravenous ATV dosing suggests that ATV undergoes extensive gut metabolism. Both hepatic and intestinal metabolism contribute to the low oral bioavailability of ATV in rats. In the presence of RIF, the liver metabolic extraction was significantly reduced, most likely because of RIF's inhibition on Oatp-mediated uptake, which leads to reduced hepatic amounts of parent drug for subsequent metabolism. Gut extraction was also significantly reduced, but we were unable to elucidate the mechanism of this effect because intravenous RIF caused gut changes in availability. These studies reinforce our hypothesis that hepatic uptake is a major contributor to the elimination of ATV and its metabolites in vivo.

Multiple transporters affect the disposition of atorvastatin and its two active hydroxy metabolites: application of in vitro and ex situ systems

Atorvastatin (ATV) is primarily metabolized by CYP3A in the liver to form two active hydroxy metabolites. Therefore, the sequential transport system governed by hepatic uptake and efflux transporters is important for the drug disposition and metabolism. Here, we assessed the interaction of ATV with hepatic uptake transporter organic anion transporting polypeptide (Oatp) and efflux transporter multidrug resistance associated protein 2 (MRP2/Mrp2) in vitro and ex situ using the isolated perfused rat liver (IPRL). Rifampicin (RIF) was chosen as an inhibitor for Oatp in both uptake and IPRL studies. Its inhibitory effects on MRP2 and metabolism were also tested using MRP2-overexpressing cells and rat microsomes, respectively. Our results indicate that RIF effectively inhibits the Oatp-mediated uptake of ATV and its metabolites. Inhibition on MRP2-mediated efflux of ATV was also observed at a high RIF concentration. Compared with ATV alone in the IPRL, the area under the curve(s) (AUC) of ATV was significantly increased by RIF, whereas the AUC of both metabolites were also increased in a concentration-dependent manner. However, the extent of metabolism was significantly reduced, as reflected by the reduced amounts of metabolites detected in RIF-treated livers. In conclusion, inhibition of Oatp-mediated uptake seems to be the major determinant for interaction between ATV and RIF. Metabolites of ATV were subject to Oatp-mediated uptake as well, suggesting that they undergo a similar disposition pathway as the parent drug. These data emphasize the relevance of uptake transporter as being one of the major players in hepatic drug elimination, even for substrates that undergo metabolism.

Thomson scattering and ponderomotive intermodulation within standing laser beat waves in plasma

Electrons in a standing electromagnetic wave--an optical lattice--tend to oscillate due to the quiver and ponderomotive potentials. For sufficiently intense laser fields (Ilamda2 approximately < or = 5 x 10(17) W cm(-2) microm2) and in plasmas with sufficiently low electron densities (n approximately < or = 10(18) cm(-3)), these oscillations can occur faster than the plasma can respond. This paper shows that these oscillations result in Thomson scattering of light at both the laser and ponderomotive bounce frequencies and their harmonics as well as at mixtures of these frequencies. We term this mixing ponderomotive intermodulation. Here, the case of counterpropagating laser beams creating a one-dimensional (1D) optical lattice is analyzed. The near-equilibrium electron orbits and subsequent Thomson scattering patterns are computed in the single-particle limit. Scaling laws are derived to quantify the range of validity of this approach. Finally, collective plasma and laser focusing effects are included by using particle-in-cell (PIC) techniques. This effect resulting in light-frequency conversion has applications both as an infrared light source and as a means to diagnose high laser intensities inside dense plasmas.

Ex Situ Inhibition of Hepatic Uptake and Efflux Significantly Changes Metabolism: Hepatic Enzyme-Transporter Interplay

The disposition of digoxin and the influence of the organic anion transporting polypeptide (Oatp)2 inhibitor rifampicin and the P-glycoprotein (P-gp) inhibitor quinidine on its hepatic disposition were examined in the isolated perfused rat liver. Livers from groups of rats were perfused in a recirculatory manner after a bolus dose of digoxin (10 microg), a dual substrate for Oatp2 and P-gp as well as CYP3A. Perfusions of digoxin were also examined in groups of rats in the presence of the inhibitors: rifampicin (100 microM) or quinidine (10 microM). In all experiments, perfusate samples were collected for 60 min. Digoxin and its primary metabolite were determined in perfusate and liver by liquid chromatography/mass spectrometry. The area under the curve (AUC) from 0 to 60 min was determined. The AUC +/- S.D. of digoxin was increased from control (3880 +/- 210 nM x min) by rifampicin (5200 +/- 240 nM x min; p < 0.01) and decreased by quinidine (3220 +/- 340 nM x min; P < 0.05). It is concluded that rifampicin limits the hepatic entrance of digoxin and reduced the hepatic exposure of digoxin to CYP3A by inhibiting the basolateral Oatp2 uptake transport, whereas quinidine increased the hepatic exposure of digoxin to CYP3A by inhibiting the canalicular P-gp transport. These data emphasize the importance of uptake and efflux transporters on hepatic drug metabolism.

New scaling of child-langmuir law in the quantum regime

This paper presents a consistent quantum mechanical model of Child-Langmuir (CL) law, including electron exchange-correlation interaction, electrode's surface curvature, and finite emitter area. The classical value of the CL law is increased by a larger factor due to the electron tunneling through the space-charge potential, and the electron exchange-correlation interaction becomes important when the applied gap voltage Vg and the gap spacing D are, respectively, on the order of Hartree energy level, and nanometer scale. It is found that the classical scaling of Vg(3/2) and D(-2) is no longer valid in the quantum regime, and a new scaling of Vg(1/2) and D(-4) is established. The smooth transition from the classical regime to the quantum regime is also demonstrated.

Suppression of third-order intermodulation in a klystron by third-order injection

The first observations and measurements are reported on suppression of the third-order intermodulation (IM3) product arising from nonlinear mixing of two drive frequencies in a klystron, by externally injecting a wave at the IM3 product frequency. Optimum amplitude and phase of the injected wave for maximum suppression are examined. Results indicate that suppression of the IM3 product by as much as 30 dB can be achieved. Experimental results compare favorably with predictions of a 1D simulation code that takes into account all kinematical and dynamical effects including charge overtaking and space charge forces.

Backscattering of an intense laser beam by an electron

We present a novel, simple asymptotic expansion for the spectrum of radiation that is backscattered from a laser by a counterpropagating (or copropagating) electron. The solutions are presented in such a way that they explicitly show the relative merit of using an intense laser and of an energetic electron beam in x-ray production in the single particle regime. Simple scaling laws are given.

Characterization of glucose microsensors for intracellular measurements

Ultrasmall glucose sensors have been constructed by using platinum-deposited carbon ring microelectrodes with glucose oxidase. Response times as low as 270 ms have been obtained with these sensors. Moreover, there is a linear relationship between sensor tip diameter and response times. The use of these sensors has been demonstrated in the detection of glucose in single-cell cytoplasm of the large dopamine cell of the pond snail Planorbis corneus. Current responses obtained at these sensors implanted into a cell increase following injection of 2 pL of glucose solution (3 M) into the cell. Results obtained from these experiments show that these sensors are suitable for glucose monitoring in ultrasmall environments. In addition, characterizations of these sensors have been investigated under different O2 concentrations. At atmospheric oxygen concentrations, glucose levels in the submillimolar range can be measured without oxygen interference; however, oxygen interference can be substantial at low oxygen concentrations.

Simple theory for the two-dimensional Child-Langmuir law

This paper presents, for the first time, a simple analytic theory for the two-dimensional (2D) Child-Langmuir law. For electron emission over a finite patch on a planar cathode, the limiting current density is derived approximately from first principles. The scaling laws are in excellent agreement with simulation results. They predict the onset of virtual cathode formation in a 2D geometry; they also indicate that electrons emitted from a cathode over only a restricted area may have a current density much exceeding the classical (1D) Child-Langmuir value.

Limiting current density in a crossed-field nanogap

Using a mean-field theory, we have studied the quantum extension on the limiting current density in a crossed-field nanogap. When the gap spacing is less than the electron wavelength, our results show that the limiting current density is increased by a large factor from the classical values due to the effects of electron tunneling. The effects of the external magnetic field diminish with a decrease of gap spacing. Smooth transition from the classical regime to the quantum regime is demonstrated.

Alcoholic carbowax prefixation and formal alcohol fixation. A new technique for urine cytology

OBJECTIVE

To compare the cellular yield and sensitivity of cancer detection by urine cytology using alcoholic carbowax as a prefixative and formal alcohol as a final fixative with the conventional centrifugation-and-smearing method.

STUDY DESIGN

Four hundred seventeen voided urine specimens were examined. Each specimen was divided into two equal portions. One portion was centrifuged and wet fixed (CS). The other was treated with alcoholic carbowax as a prefixative and then fixed in formal alcohol (CW). The smears were studied for cellular yield, morphology, cancer detection rate and typing.

RESULTS

The CW method yielded significantly more cells with excellent morphology. It detected 25 more abnormal cases out of a total of 86, including 5 more transitional cell carcinomas, as compared to the CS method. This finding was statistically significant (P < .0000003).

CONCLUSION

The CW method is simple and enhances cellular yield and the cancer detection rate as compared to the conventional centrifuge-and-smear technique.

Determination of pramipexole (U-98,528) in human plasma by high-performance liquid chromatography with atmospheric pressure chemical ionization tandem mass spectrometry

A highly sensitive and selective HPLC-MS-MS method was developed for the determination of pramipexole in human plasma. The analytes, pramipexole and BHT-920 (internal standard), were extracted from plasma at basic pH with methyl tert.-butyl ether (MTBE). MTBE was evaporated to dryness and reconstituted in 100 microliters of (95:5) methanol-water. Chromatographic separation was achieved on a Zorbax SB-CN column with a mobile phase of (15:5:80) water-0.1 M ammonium acetate-methanol. The analytes were detected utilizing HPLC in conjunction with atmospheric pressure chemical ionization (APCI) tandem mass spectrometry (MS-MS). The assay was linear in the concentration ranges of 50 to 5000 pg/ml. The analysis of pooled quality controls (150, 750, and 3000 pg/ml) demonstrated excellent precision with relative standard deviations (R.S.D.) (n = 18) of 7.2%, 5.3% and 5.2%, respectively. The method is accurate with all intra-day (n = 6) and overall (n = 18) mean values being less than 11.7% from theoretical.

Determination of pramipexole (U-98,528) in human plasma and urine by high-performance liquid chromatography with electrochemical and ultraviolet detection

A sensitive and selective high-performance liquid chromatographic (HPLC) method was developed for the determination of pramipexole in human plasma and urine. Plasma/urine is made alkaline before pramipexole and BHT-920 (internal standard) are extracted by ethyl ether and back-extracted with a solution that contains heptanesulfonic acid. Separation is achieved by ion-pair chromatography on a Zorbax Rx C8 column with electrochemical detection at 0.6 V for plasma and ultraviolet detection at 286 nm for urine. The retention times of pramipexole and internal standard are approximately 14.4 and 10.7 min, respectively. The assay is linear in concentration ranges of 50 to 15,000 pg/ml (plasma) and 10 to 10,000 ng/ml (urine). The correlation coefficients are greater than 0.9992 for all curves. For the plasma method, the analysis of pooled quality controls (300, 3000, and 10,000 pg/ml) demonstrates excellent precision with relative standard deviations (R.S.D.) (n = 18) of 1.1%, 2.3%, and 6.8%, respectively. For the urine method, quality control pools prepared at 30, 300, and 3000 ng/ml had R.S.D. values (n = 18) of 2.9%, 1.7%, and 3.0%, respectively. The plasma and urine controls were stable for more than nine and three months, respectively. The mean recoveries for pramipexole and internal standard from plasma were 97.7% and 98.2%, respectively. The mean recoveries for pramipexole and internal standard from urine were 89.8% and 95.1%, respectively. The method is accurate with all intra-day (n = 6) and overall (n = 18) mean values for the quality control samples being less than 6.4 and 5.8% from theoretical for plasma and urine, respectively.