Stereotactic Radiosurgery (SRS) for Large Brain Metastases: Dosimetric and Clinical Predictors of Local Progression and Radionecrosis

PURPOSE/OBJECTIVE(S)

Stereotactic radiosurgery (SRS) provides high rates of local control for small brain metastases with low rates of radionecrosis (RN). Larger targets are associated with increased risk of both local progression (LP) and RN. In this analysis, we hypothesized that dosimetric and clinical parameters predict for risk of LP and RN in SRS targets larger than two centimeters.

MATERIALS/METHODS

We retrospectively reviewed patients with one or more targets with either an intact versus post-operative cavity larger than 2.0 cm treated with LINAC-based SRS between 2017 and 2022 at one institution. We assessed for association between patient, treatment, and disease variables with LP and RN. Variables assessed included tumor resection status, PDL1 positivity, target volume, maximum and minimum target dose, EQD2 and BED (a/b = 2 for necrosis and a/b = 10 for tumor control), as well as receipt of steroids, bevacizumab, or systemic therapy before or after SRS. Radionecrosis was determined by characteristic radiographic changes. Analyses were performed for the entire cohort and within subsets including by resection status and dose fractionation.

RESULTS

A total of 178 lesions in 143 patients were included. Targets with volume diameters measuring at least 2 cm were used. Median follow-up was 2.3 years. Overall survival at 1 and 2 years was 56% and 32%, respectively. Most lesions (n = 119) were resected and treated with SRS post-operatively. The most common dose and fractionation schemes used were 30 Gy in 5 fractions (n = 89) and 27 Gy in 3 fractions (n = 63). For the entire cohort, the cumulative incidence of LP 1 and 2 years was 26% and 34%, respectively. The cumulative incidence of radiographic radionecrosis at 1 and 2 years was 12% and 17%, respectively. There was no difference in LP or RN between 27 Gy in 3 fractions versus 30 Gy in 5 fractions (p>0.5 for both). Median planning target volume (PTV) size was 18.5 cc for the 27 Gy in 3 fraction group compared to 21.9 cc in the 30 Gy in 5 fraction group. Minimum or maximum dose within the target was not associated with increased risk of LP or RN. Among patients receiving 27 Gy in 3 fractions, patients treated with resection followed by SRS had lower risk of LP compared to those treated with SRS alone (HR: 0.15, 95% CI: 0.03-0.64, p = 0.011). Among patients receiving 30 Gy in 5 fractions, patients who received corticosteroids prior to SRS had a lower risk of RN (HR: 0.14, 95% CI: 0.03-0.66, p = 0.013). For the entire cohort as well as within all subgroups, PD-L1≥1% was associated with increased risk of RN (p<0.001 for all).

CONCLUSION

Selecting the optimal SRS dose fractionation and planning parameters to minimize both LP and RN remains a challenge for large targets. In this analysis, 27 Gy in 3 fractions appeared to provide equivalent LP and RN compared to 30 Gy in 5 fractions, and may be more convenient for patients. Patients with PD-L1≥1% with large brain targets treated with SRS may be at increased risk of RN; corticosteroid prophylaxis may be considered in this population.

Local Control after Re-Irradiation of Spinal Metastases with Stereotactic Body Radiation Therapy

PURPOSE/OBJECTIVE(S)

Determine local control (LC) rate and risk of vertebral compression fractures (VCFs) and radiation myelitis (RM) for patients receiving re-irradiation of spinal metastases (SMs) using stereotactic body radiation therapy (SBRT) from large single-institutional experience with long follow-up.

MATERIALS/METHODS

Retrospectively identified patients receiving re-irradiation SBRT (rSBRT, 1, 3, or 5 fractions) to SMs previously treated with radiation therapy (RT) and having follow up imaging to assess local control. 1 fraction patients typically received 20-24 Gy and 16-18 Gy to the high- and low-risk planning target volumes (PTVs), respectively, and 27-39 Gy and 21-24 Gy for the 3 fraction patients, with a single level of 50 Gy for 5 fractions. Patient and treatment characteristics for previous RT (pRT) and rSBRT were collected, including histology and dose-volume histogram statistics (DVH). Kaplan-Meier estimates of overall survival (OS), and cumulative incidence (competing with death) of local failure with death as a competing risk was computed for the whole cohort and stratified by radioresistance of histology, and risk of VCF for RM (for treatments at L1 and above) and 95% confidence intervals. Equivalent dose in 2 Gy fractions (EQD2) for PTV and spinal cord (SC) DVH statistics was computed for each individual course and cumulatively, using a/b = 10 Gy for tumor and 2 Gy for SC.

RESULTS

Identified 107 lesions in 91 patients. 48 (45%) had radioresistant histologies. For all patients, at 1 and 2 years, respectively OS was 64% (55-74%) and 43% (34-55%), LC was 88% (81-94%) and 85% (78-91%) with median follow-up of 52 months (Table 1). OS and LC were not significantly different between radiosensitivity groups (p>0.05). Risk of VCF at 1 and 2 years was 7% (3-13%) and 9% (4-16%). RM was identified in 1 patient, who received 30 Gy in 5 fractions to T1, and had 1-fraction rSBRT 21 months later. SC Dmax was 31.5 Gy for pRT and 10.4 Gy, for rSBRT, resulting in total SC EQD2 of 73 Gy. RM was confirmed on MRI 8 months after rSBRT. Cumulative RM risk at 8 months after rSBRT was estimated at 1% (0-4%). Median EQD2 for the minimum dose to the high and low risk PTVs were 17.7 Gy (interquartile range, IQR, 13.0-27.6 Gy) and 13.7 Gy (IQR, 10.8-19.3 Gy) for rSBRT, and maximum EQD to SC for previous RT, rSBRT, and cumulatively was 38 Gy (IQR, 30-41 Gy), 27 Gy (IQR, 22-36 Gy), and 65 Gy (IQR, 54-73 Gy).Re-irradiation of spinal metastasis with SBRT can be delivered safely and provide high rates of local control, including for radioresistant tumors, as demonstrated with the longest reported follow-up in this setting.

CONCLUSION

Re-irradiation of SM with SBRT provides high rates of LC even for radioresistant tumors, and low risk of VCF and RM, based on the longest reported follow-up in this setting.

Frameless Fractionated Linear Accelerator-Based Stereotactic Radiotherapy for Brain Metastases: Results of a Single-Arm Phase II Multi-Institutional Clinical Trial

PURPOSE/OBJECTIVE(S)

Stereotactic radiotherapy (SRT) yields high rates of local control for brain metastases while minimizing neurocognitive side effects. While advanced SRT platforms are widely available in urban centers, rural/suburban patients face geographic and socioeconomic barriers to access SRS. For this reason, we conducted a multi-institutional Phase 2 clinical trial to test the safety and efficacy of 3-5 fraction frameless fractionated stereotactic radiotherapy (FFSRT) for brain metastases in an integrated academic satellite network MATERIALS/METHODS: This IRB-approved Phase 2 trial was conducted for patients ≥18-years-old with 1-4 brain metastases. Brain metastases involving the optic pathway or brainstem were excluded. Gross tumor volume (GTV) was delineated with a volumetric brain MRI and planning target volume (PTV) was GTV + 2 mm margin. Radiation dose was based on GTV size: < 3.0 cm, 27 Gy in 3 fractions, and 3.0-3.9 cm, 30 Gy in 5 fractions. Toxicity was evaluated using the Common Terminology Criteria for Adverse Events (CTCAE) version 4.

RESULTS

Of 76 evaluable patients, the median age was 67 years, 56.6% were female, 82.9% were white/Caucasian and 89.6% had an Eastern Cooperative Oncology Group performance status ≤ 2. Most brain metastases were from lung cancer (51.3%) and breast cancer (15.7%). With median follow-up of 10 months, local control was 93%, median survival was 1.8 years (95% confidence interval (CI): 1.5-2.4 years), 1-year OS was 73.8% (95% CI: 0.59-0.84), and 2-year OS was 31% (95% CI: 0.12-0.52). There were no CTCAE Grade ≥ 3 protocol-related adverse events.

CONCLUSION

Outcomes of this trial compare favorably with contemporary SRT trials for brain metastases. FFSRT may provide opportunities to expand SRS access for underserved populations across the MDACC enterprise and in future clinical trials for brain metastases.

Assessment of Minimum Dose as a Strong Predictor of Local Failure after Spine SBRT

PURPOSE/OBJECTIVE(S)

Stereotactic body radiation therapy (SBRT) has demonstrated robust clinical benefits in carefully selected patients, improving local control and even overall survival (OS). Even so, a wide range of dose-fractionation schemes are used in clinical practice. We seek to assess a large database to determine clinical and dosimetric predictors of local failure after spine SBRT.

MATERIALS/METHODS

From a large institutional database, spine SBRT treatments with subsequent imaging follow-up to assess local control were identified. Patients were treated with a simultaneous integrated boost technique using 1 or 3 fractions, generally delivering 20-24 Gy in 1 fraction to the high dose volume and 16 Gy to the low dose volume (or 30-36 Gy and 24 Gy for 3 fraction treatments). Exclusions included: lack of imaging follow-up, proton therapy, and benign primary histologies. Statistical analyses included Cox proportional hazards analyses and the robust log-rank statistic for cut-point analysis. The cumulative incidence of local failure with death as a competing risk was considered as the primary endpoint.

RESULTS

A total of 522 eligible spine SBRT treatments (68% single fraction) were identified in 377 unique patients. Patients had a median OS of 43.7 months (95% confidence interval: 34.3-54.4). The cumulative incidence of local failure was 19.3% (15.3-23.2) at 1 year and 25.6% (21.1-29.9) at 2 years. Univariate analysis identified that the minimum dose (normalized for the prescription dose) was a strong predictor of local failure (p = 0.0093). Among patients treated with a single fraction, statistical significance was maintained (p = 0.024). No other dosimetric factors were predictive of local failure. In a cut point analysis, the log-rank statistic was maximized at 15.8 Gy minimum dose for single-fraction treatment (HR = 0.51, 95% CI: 0.34 - 0.75, p = 0.0009). Cumulative incidence of local failure was 15.1% (9.8-20.2) vs. 24.7% (17.2-31.5) at 1 year using this cut-off. Comparable local control was demonstrated with a minimum dose of 14 Gy (HR = 0.57, 95%: 0.37 - 0.87, p = 0.009), with reduced local control with lower minimum doses. Among a range of clinical factors assessed, only epidural and soft tissue involvement were predictive of local failure (HR = 1.80 and 1.98, respectively). Multivariable analyses incorporating soft tissue involvement, epidural extension, and multilevel disease confirmed the 15.8 Gy cutoff for single fraction cases (HR = 0.58, 95% CI: 0.38-0.88, p = 0.011).

CONCLUSION

Spine SBRT offers favorable local control using a range of dose-fractionation schemes; however, minimum dose has a strong association with local control, unlike any other dosimetric factors tested. Furthermore, statistical significance was maintained even when considering epidural extension and potential limitations from dose to the spinal cord. Our data suggests that the minimum dose should be prioritized during treatment planning, ideally to at least 14 - 15.8 Gy for single fraction.

Sensitivity of the PROMIS-10 for Capturing Radiation-Related Quality of Life Changes

PURPOSE/OBJECTIVE(S)

Patient reported outcomes (PROs) are becoming more common when assessing the effects of radiotherapy (RT). The aim of this study was to assess the sensitivity of the Mental and Physical domains of the Patient-Reported Outcomes Measurement Information System 10 (PROMIS-10) to radiotherapy and determine what predictors were associated with change in quality of life.

MATERIALS/METHODS

Patients, regardless of cancer type, were enrolled on a multi-site prospective registry. Inclusion criteria included curative radiotherapy and completion of the PROMIS-10 prior to treatment (Baseline) and at End of Treatment (EOT). To assess the strongest predictors of change in the T score of mental and physical health, we included 14 demographic characteristics and treatment variables in a multivariable stepwise regression.

RESULTS

A total of 7,586 patients were eligible for the analysis. The median age was 65 (range 18-94), 54% were males, and 94% were white. A majority received photons (62.5%) and the others received protons (37.5%) with an average dose of 52.3 Gy (range 20-80 Gy) over an average of 22.6 fractions (range 1-66). Patient disease sites were sub-grouped into 12 categories: Breast (25.5%), GU (23.0%), H&N (11.1%), CNS (8.5%), Pancreas-Biliary (6.7%), Thoracic (5.7%), Soft Tissue/Bone (5.0%), Esophagus-Gastric (4.7%), Colorectal-Anus (4.4%), Heme/Lymph (2.6%), GYN (1.8%), and Skin/Melanoma (1.0%). For both outcomes, the model selected disease group as an important predictor and it explained the most variance in the outcome compared to the rest of the predictors. When probing the effect of disease group, H&N, Esophagus-Gastric, Skin/Melanoma, and Colorectal-Anus had the largest mean decrease in quality of life for both domains. For mental health, the model also selected radiation type. Patients treated with protons indicated a bigger decrease in mental health compared to patients treated with photons (b = 0.43, 95% CI: -0.01, 0.69). For physical health, the model selected total fractions, ethnicity, and T stage. As number of fractions increased, the physical health change scores became more negative, on average (b = -0.03, 95% CI: -0.05, -0.01). Hispanic/Latino patients indicated a smaller decrease in physical health compared to White (b = -1.50, 95% CI: -2.60, -0.40) and Unknown ethnicity patients (b = -1.82, 95% CI: -3.36, -0.27). Finally, patients with a T stage of 3 or greater indicated a smaller decrease in physical health than patients with a T stage less than 3 (b = 0.76, 95% CI: 0.35, 1.16).

CONCLUSION

The PROMIS-10 did not capture significant change for patients undergoing curative radiotherapy except for patients with Head & Neck, Esophagus-Gastric, Skin, and Colorectal-Anus cancer. Further analyses should explore which patients experience the greatest change in quality of life within disease group.

Epigenetic Modification as a Regulatory Mechanism for Spatiotemporal Dynamics of ANO1 Expression in Salivary Glands

Anoctamin1 (ANO1), a calcium activated chloride channel, is known to play a critical role in salivary secretion. In the salivary gland, ANO1 is expressed exclusively in the acinar cells, with no expression in the ductal cells. However, the mechanisms that determine this distinctive cell type-dependent expression pattern of ANO1 remain unknown. In this study, we discovered that the cell-dependent expression of ANO1 during salivary gland organogenesis is regulated by DNA methylation of ANO1 CpG islands. ANO1 CpG islands in e12 embryonic submandibular glands (eSMG) are highly methylated, but those in e14 eSMG or adult SMG are significantly unmethylated. The differential expression pattern of ANO1 in duct and acini is defined at e14. Artificial demethylation by treatment with the demethylating agent 5-aza-2'-deoxycytidine (5-Aza-CdR), induced the expression of ANO1 in both the ductal cell line Human Submandibular Gland (HSG) and in the duct cells of adult mouse SMG. During the trans-differentiation in Matrigel of duct-origin HSG cells into acinar-like phenotype, significant demethylation of ANO1 CpG islands is observed. This may be due to the reduced expression of DNA methyltransferase (DNMT) 3a and 3b. These results suggest that the differential expression of ANO1 in salivary glands during organogenesis and differentiation is mainly regulated by epigenetic demethylation of the ANO1 gene.

Tissue Distribution of Kir7.1 Inwardly Rectifying K+ Channel Probed in a Knock-in Mouse Expressing a Haemagglutinin-Tagged Protein

Kir7.1 encoded by the Kcnj13 gene in the mouse is an inwardly rectifying K⁺ channel present in epithelia where it shares membrane localization with the Na⁺/K⁺-pump. Further investigations of the localisation and function of Kir7.1 would benefit from the availability of a knockout mouse, but perinatal mortality attributed to cleft palate in the neonate has thwarted this research. To facilitate localisation studies we now use CRISPR/Cas9 technology to generate a knock-in mouse, the Kir7.1-HA that expresses the channel tagged with a haemagglutinin (HA) epitope. The availability of antibodies for the HA epitope allows for application of western blot and immunolocalisation methods using widely available anti-HA antibodies with WT tissues providing unambiguous negative control. We demonstrate that Kir7.1-HA cloned from the choroid plexus of the knock-in mouse has the electrophysiological properties of the native channel, including characteristically large Rb⁺ currents. These large Kir7.1-mediated currents are accompanied by abundant apical membrane Kir7.1-HA immunoreactivity. WT-controlled western blots demonstrate the presence of Kir7.1-HA in the eye and the choroid plexus, trachea and lung, and intestinal epithelium but exclusively in the ileum. In the kidney, and at variance with previous reports in the rat and guinea-pig, Kir7.1-HA is expressed in the inner medulla but not in the cortex or outer medulla. In isolated tubules immunoreactivity was associated with inner medulla collecting ducts but not thin limbs of the loop of Henle. Kir7.1-HA shows basolateral expression in the respiratory tract epithelium from trachea to bronchioli. The channel also appears basolateral in the epithelium of the nasal cavity and nasopharynx in newborn animals. We show that HA-tagged Kir7.1 channel introduced in the mouse by a knock-in procedure has functional properties similar to the native protein and the animal thus generated has clear advantages in localisation studies. It might therefore become a useful tool to unravel Kir7.1 function in the different organs where it is expressed.

Distribution of virulence determinants among antimicrobial-resistant and antimicrobial-susceptible Escherichia coli implicated in urinary tract infections

INTRODUCTION

Uropathogenic Escherichia coli (UPEC) rely on the correlation of virulence expression with antimicrobial resistance to persist and cause severe urinary tract infections (UTIs).

OBJECTIVES

We assessed the virulence pattern and prevalence among UPEC strains susceptible and resistant to multiple antimicrobial classes.

METHODS

A total of 174 non-duplicate UPEC strains from patients with clinically significant UTIs were analysed for susceptibility to aminoglycoside, antifolate, cephalosporin, nitrofuran and quinolone antibiotics for the production of extended-spectrum β-lactamases and for the presence of six virulence determinants encoding adhesins (afimbrial, Type 1 fimbriae, P and S-fimbriae) and toxins (cytotoxic necrotising factor and haemolysin).

RESULTS

Relatively high resistance rates to nalidixic acid, ciprofloxacin, cephalothin and trimethoprim-sulfamethoxazole (82%, 78%, 62% and 59%, respectively) were observed. Fourteen distinct patterns were identified for the virulence determinants such as afaBC, cnfI, fimH, hylA, papEF and sfaDE. The toxin gene, cnfI (75.3%), was the second most prevalent marker to the adhesin, fimH (97.1%). The significant association of sfaDE/hylA (P < 0.01) among antimicrobial resistant and susceptible strains was also observed notwithstanding an overall greater occurrence of virulence factors among the latter.

CONCLUSIONS

This study provides a snapshot of UPEC complexity in Jamaica and highlights the significant clonal heterogeneity among strains. Such outcomes emphasise the need for evidence-based strategies in the effective management and control of UTIs.

Growth of single-layer boron nitride dome-shaped nanostructures catalysed by iron clusters

We report on the growth and formation of single-layer boron nitride dome-shaped nanostructures mediated by small iron clusters located on flakes of hexagonal boron nitride. The nanostructures were synthesized in situ at high temperature inside a transmission electron microscope while the e-beam was blanked. The formation process, typically originating at defective step-edges on the boron nitride support, was investigated using a combination of transmission electron microscopy, electron energy loss spectroscopy and computational modelling. Computational modelling showed that the domes exhibit a nanotube-like structure with flat circular caps and that their stability was comparable to that of a single boron nitride layer.

Ag-catalysed cutting of multi-walled carbon nanotubes

In this work, the cutting of carbon nanotubes is investigated using silver nanoparticles deposited on arc discharge multi-walled carbon nanotubes. The composite is subsequently heated in air to fabricate shortened multi-walled nanotubes. Complementary transmission electron microscopy and spectroscopy techniques shed light on the cutting mechanism. The nanotube cutting is catalysed by the fundamental mechanism based on the coordination of the silver atoms to the π-bonds of carbon nanotubes. As a result of the metal coordination, the strength of the carbon-carbon bond is reduced, promoting the oxidation of carbon at lower temperature when heated in air, or lowering the activation energy required for the removal of carbon atoms by electron beam irradiation, assuring in both cases the cutting of the nanotubes.

Osseous Pseudoprogression in Vertebral Bodies Treated with Stereotactic Radiosurgery: A Secondary Analysis of Prospective Phase I/II Clinical Trials

BACKGROUND AND PURPOSE

Osseous pseudoprogression on MR imaging can mimic true progression in lesions treated with spine stereotactic radiosurgery. Our aim was to describe the prevalence and time course of osseous pseudoprogression to assist radiologists in the assessment of patients after spine stereotactic radiosurgery.

MATERIALS AND METHODS

A secondary analysis of 2 prospective trials was performed. MRIs before and after spine stereotactic radiosurgery were assessed for response. "Osseous pseudoprogression" was defined as transient growth in signal abnormality centered at the lesion with a sustained decline on follow-up MR imaging that was not attributable to chemotherapy.

RESULTS

From the initial set of 223 patients, 37 lesions in 36 patients met the inclusion criteria and were selected for secondary analysis. Five of the 37 lesions (14%) demonstrated osseous pseudoprogression, and 9 demonstrated progressive disease. There was a significant association between single-fraction therapy and the development of osseous pseudoprogression (P = .01), and there was a significant difference in osseous pseudoprogression-free survival between single- and multifraction regimens (P = .005). In lesions demonstrating osseous pseudoprogression, time-to-peak size occurred between 9.7 and 24.4 weeks after spine stereotactic radiosurgery (mean, 13.9 weeks; 95% CI, 8.6-19.1 weeks). The peak lesion size was between 4 and 10 mm larger than baseline. Most lesions returned to baseline size between 23 and 52.4 weeks following spine stereotactic radiosurgery.

CONCLUSIONS

Progression on MR imaging performed between 3 and 6 months following spine stereotactic radiosurgery should be treated with caution because osseous pseudoprogression may be seen in more than one-third of these lesions. Single-fraction spine stereotactic radiosurgery may be associated with osseous pseudoprogression. The possibility of osseous pseudoprogression should be incorporated into the prospective criteria for assessment of local control following spine stereotactic radiosurgery.

Abstract C188: A phase 1 study of RXDX-105, an oral RET, BRAF and EGFR tyrosine kinase inhibitor, in patients with advanced or metastatic cancers

Background: RXDX-105 is a potent RET, BRAF and EGFR tyrosine kinase inhibitor (TKI) that exhibits high target affinity at low nanomolar concentrations. The RET proto-oncogene encodes a receptor tyrosine kinase for members of the glial cell line-derived neurotrophic factor (GDNF) family of extracellular signaling molecules. RET gain of function alterations are associated with the development of various types of human cancer, including non-small cell lung cancer (NSCLC). BRAF plays a key role in regulating the MEK/ERK signaling pathway, which affects cell division and differentiation. Acquired BRAF mutations can result in constitutive activation of this pathway, thereby fueling cancer growth. RXDX-105 is being developed as an oral therapy for patients with solid tumors that harbor RET or BRAF mutations or gene rearrangements.

Methods: Adult pts with advanced solid tumors were enrolled in a Ph 1 single agent dose escalation study with a standard 3 + 3 design to determine the recommended Ph 2 dose. Oral RXDX-105 was given as a fixed dose on a continuous daily schedule. Tumor response was assessed at baseline and every 8 wks (RECIST v1.1). Treatment-emergent adverse events (AEs) were recorded according to NCI CTC v4.03. Pharmacokinetic (PK) assessment was also a study objective.

Results: To date, 35 pts (17 M and 18 F) received RXDX-105 across 7 dose levels (20 to 275 mg QD). Median age was 60.5 years (range 27-81). The most frequent tumors (pts) were metastatic CRC (13), ovarian cancer (3), NSCLC (3), cholangiocarcinoma (3), and pancreatic cancer (3). Median number of cycles was 2 (range 1 to 23).

34 pts experienced AEs; 6 pts experienced treatment-related G3 AEs, including anemia, hypophosphatemia, fatigue, diarrhea, abdominal pain, rash and muscle weakness. 22 SAEs were reported from 9 pts, with none considered treatment-related. No treatment-related deaths occurred. The most common AEs were: fatigue (17 pts), vomiting (13 pts), abdominal pain (12 pts), nausea (11 pts), decreased appetite (10 pts), and rash (10 pts). At the time of this report, 3 pts have had DLTs; 1 pt at 200 mg with G2 hand and foot syndrome, 1 pt at 275 mg with G3 fatigue, and 1 pt at 275 mg with G3 asymptomatic hypophosphatemia. The protocol was amended to exclude hypophosphatemia as a DLT since it has been observed with approved TKIs and can be managed by supplementation.

The PK data to date have demonstrated that RXDX-105 is absorbed with a median Tmax between 2 and 6 hrs at steady state. RXDX-105 plasma concentrations declined slowly after reaching Cmax with an average terminal half-life of 28 to 42 hrs across dose levels. There was a loss of dose proportionality at doses above 150 mg, possibly due to pH-dependent drug dissolution in the stomach. The impact of the fed state on exposure is being explored.

11 pts have been on treatment for ≥ 12 weeks. No objective responses have been observed; however, 1 pt with BRAF V600E-positive papillary thyroid cancer, previously treated with RAI, EBRT and multiple surgical resections, has been on study with stable disease for almost 2 years (23 cycles). Additionally, 2 heavily pre-treated pts with squamous NSCLC achieved clinical benefit with SD for &gt; 6 months; 1 patient continues.

Conclusions: To date, treatment with RXDX-105 demonstrates an acceptable safety profile. Improvements in bioavailability are being investigated. Dose escalation continues.

Citation Format: Ding Wang, Manish Patel, Marwan Fakih, A. Craig Lockhart, Anthony J. Olszanski, Rupal Patel, Peter D. Brown, Jennifer W. Oliver, Pratik S. Multani. A phase 1 study of RXDX-105, an oral RET, BRAF and EGFR tyrosine kinase inhibitor, in patients with advanced or metastatic cancers. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C188.

Healthcare worker influenza immunization vaccinate or mask policy: strategies for cost effective implementation and subsequent reductions in staff absenteeism due to illness

BACKGROUND

A new policy requiring staff in clinical areas to vaccinate or wear a mask was implemented in British Columbia (BC) in the 2012/13 winter. This review assessed the impact of the policy on absenteeism in health care workers.

METHODS

A retrospective cohort study of full-time HCW that worked prior to and during the 2012/13 influenza season in a health authority in BC. The rate of absenteeism due to all cause illness was compared between vaccinated and unvaccinated staff controlling for behaviors outside influenza season.

RESULTS

Of the 10079 HCW, 77% were vaccinated. By comparison to absenteeism rates in the pre-influenza season, unvaccinated staff in winter had twice the increase in absenteeism due to all-cause illness than vaccinated staff.

CONCLUSION

After controlling for baseline differences between those vaccinated and unvaccinated, influenza vaccination was associated with reduced absenteeism, saving the Health Authority substantial money. Having regular staff in attendance increases the quality of care.

Allelochemicals produced during glucosinolate degradation in soil

A variety of plant pests are suppressed by the incorporation of cruciferous plant material into soil. Although this effect is attributed to decomposition of glucosinolates into toxic products, little is known concerning glucosinolate degradation in the soil environment. Arenas (30 × 18 × 8 cm) that contained soil amended with 30 g defatted winter rapeseed meal (Brassica napus L.)/kg soil on one half and unamended soil on the other were constructed. Isothiocyanate concentrations in the soil were measured using infrared analysis of CC14 extracts, and ionic thiocyanate (SCN(-)) using ion chromatography on aqueous extracts. Quantities were monitored during a 100-hr time period in conjunction with a wireworm bioassay. Isothiocyanate production reached a maximum of 301 nmol/g soil at 2 hr, but decreased by 90% within 24 hr. Production of SCN(-) reached a maximum of 180 nmol/g soil at 8 hr but persisted longer than isothiocyanate. Separate late instar wire-worms (Limonius infuscatus Mots.) were repelled by the presence of rapeseed meal in less than 24 hr even though the meal was shown in separate experiments not to be toxic. We propose that rapidly produced isothiocyanates are responsible for this repellency, but other products such as SCN(-) may play a role.

Cerebrospinal Fluid Secretion by the Choroid Plexus

The choroid plexus epithelium is a cuboidal cell monolayer, which produces the majority of the cerebrospinal fluid. The concerted action of a variety of integral membrane proteins mediates the transepithelial movement of solutes and water across the epithelium. Secretion by the choroid plexus is characterized by an extremely high rate and by the unusual cellular polarization of well-known epithelial transport proteins. This review focuses on the specific ion and water transport by the choroid plexus cells, and then attempts to integrate the action of specific transport proteins to formulate a model of cerebrospinal fluid secretion. Significant emphasis is placed on the concept of isotonic fluid transport across epithelia, as there is still surprisingly little consensus on the basic biophysics of this phenomenon. The role of the choroid plexus in the regulation of fluid and electrolyte balance in the central nervous system is discussed, and choroid plexus dysfunctions are described in a very diverse set of clinical conditions such as aging, Alzheimer's disease, brain edema, neoplasms, and hydrocephalus. Although the choroid plexus may only have an indirect influence on the pathogenesis of these conditions, the ability to modify epithelial function may be an important component of future therapies.

Higher World Health Organization grades of follicular lymphoma correlate with better outcome in two Nordic Lymphoma Group trials of rituximab without chemotherapy

Abstract A common treatment for follicular lymphoma is rituximab monotherapy. To identify patients for whom this regimen is adequate as first-line therapy, we applied the World Health Organization (WHO) classification for grading follicular lymphoma in a prospective central pathology review of the biopsies of previously untreated patients in two randomized trials of rituximab without chemotherapy. In the first trial (n₁ = 53), higher WHO grades correlated with longer time to next treatment, independently of clinical prognostic factors (p = 0.030); the finding was replicated in the second trial (n₂ = 221; p = 0.019). Higher grades were associated with better treatment responses (p = 0.018). Furthermore, also grades externally confirmed by independent local pathologists correlated with time to next treatment (p = 0.048). Flow cytometry in a separate patient series showed that the intensity of CD20 increased with the malignant cell size (p < 0.00005). In conclusion, WHO grade 1 follicular lymphoma correlates with inferior outcome after rituximab monotherapy. WHO grading might provide a clinically useful tool for personalized therapy.

Identification of the stem rust resistance gene Pg9 and its association with crown rust resistance and endosperm proteins in 'Dumont' oat

The Canadian oat cultivar 'Dumont' is known to have genes Pc38 and Pc39 for crown rust resistance and genes Pg2 and Pg13 for stem rust resistance. When crossed to a susceptible oat line OT328, 'Dumont' was shown to have an additional dominant gene for crown rust resistance, designated PcX. Tests of segregating progeny indicated that the stem rust resistance gene Pg9 is present and is tightly linked in coupling to PcX. The presence of Pg9 in 'Dumont' was confirmed in crosses involving the cultivar 'Ukraine', which has Pg9 and a crown rust resistance gene tightly linked to it. The association of rust resistance with endosperm proteins in 'Dumont' was investigated. The linkage of gene Pg13 with a 56.6-kDa polypeptide locus (map distance of 10.47 +/- 2.70 cM) was demonstrated using sodium dodecylsulfate - polyacrylamide gel electrophoresis (SDS-PAGE). A 27.9-kDa polypeptide was shown to be associated with the linked PcX/Pg9 loci by SDS-PAGE but appeared to be more reliably separated as an avenin band, designated B4, using acid-PAGE. Another avenin band, designated B2, also was shown to be associated with the PcX/Pg9 loci using acid-PAGE. The loci conditioning the B2 and B4 bands appeared to be tightly linked or allelic and are separated from the linked PcX/Pg9 loci by a map distance of 1.03 +/- 0.36 cM. The association of Pg13 with a 56.6-kDa polypeptide and the tight linkage between PcX/Pg9 and the B2 (in coupling) and B4 (in repulsion) avenin loci offer a useful tool to breeders to detect the presence of these genes in oat breeding.

A novel surface electrocardiogram-based marker of ventricular arrhythmia risk in patients with ischemic cardiomyopathy

Background

Better sudden cardiac death risk markers are needed in ischemic cardiomyopathy (ICM). Increased heterogeneity of electrical restitution is an important mechanism underlying the risk of ventricular arrhythmia (VA). Our aim was to develop and test a novel quantitative surface electrocardiogram–based measure of VA risk in patients with ICM: the Regional Restitution Instability Index (R2I2).

Methods and Results

R2I2, the mean of the standard deviation of residuals from the mean gradient for each ECG lead at a range of diastolic intervals, was measured retrospectively from high-resolution 12-lead ECGs recorded during an electrophysiology study. Patient groups were as follows: Study group, 26 patients with ICM being assessed for implantable defibrillator; Control group, 29 patients with supraventricular tachycardia undergoing electrophysiology study; and Replication group, 40 further patients with ICM. R2I2 was significantly higher in the Study patients than in Controls (mean ± standard error of the mean: 1.09±0.06 versus 0.63±0.04, P<0.001). Over a median follow-up period of 23 months, 6 of 26 Study group patients had VA or death. R2I2 predicted VA or death independently of demographic factors, electrophysiology study result, left ventricular ejection fraction, or QRS duration (Cox model, P=0.029). R2I2 correlated with peri-infarct zone as assessed by cardiac magnetic resonance imaging (r=0.51, P=0.024). The findings were replicated in the Replication group: R2I2 was significantly higher in 11 of 40 Replication patients experiencing VA (1.18±0.10 versus 0.92±0.05, P=0.019). In combined analysis of ICM cohorts, R2I2 ≥1.03 identified subjects with significantly higher risk of VA or death (43%) compared with R2I2 <1.03 (11%) (P=0.004).

Conclusions

In this pilot study, we have developed a novel VA risk marker, R2I2, and have shown that it correlated with a structural measure of arrhythmic risk and predicted risk of VA or death in patients with ICM. R2I2 may improve risk stratification and merits further evaluation. (J Am Heart Assoc. 2012;1:e001552 doi: 10.1161/JAHA.112.001552.)

Pooled safety analysis of omacetaxine mepesuccinate in patients with chronic myeloid leukemia (CML) resistant to tyrosine-kinase inhibitors (TKIs)

6604

Background: Subcutaneous omacetaxine mepesuccinate (“omacetaxine”) is a reversible, transient inhibitor of protein elongation that does not depend on BCR-ABL signaling. It showed significant clinical activity in two phase 2, open-label, multicenter studies of patients with CML who were resistant/intolerant to prior TKI therapy. However, omacetaxine tolerability data across the 3 phases of CML are limited. Methods: Safety data were pooled from all patients in the 2 studies plus a small pilot study. Omacetaxine 1.25 mg/m2 was given subcutaneously twice daily: ≤14 successive days per 28-day cycle for induction, ≤7 days/cycle as maintenance. Days of dosing could be adjusted and recombinant growth factors given, as clinically indicated. Results: Of 207 pooled patients (median age, 57 years), 108 were in chronic (CP), 55 in accelerated (AP), and 44 in blast phase (BP). Median treatment was 4 cycles (range, 1–41). On study, 80% of patients had ≥1 hematologic adverse event (AE), 60% had a serious AE (SAE), 30% had a hematologic SAE, 34% had an SAE that resulted in hospitalization, and 15% discontinued treatment due to an SAE (most commonly disease progression). There were 49 (24%) deaths (15 CP, 11 AP, and 23 BP). Of the 8 that were treatment related (5 CP, 2 AP, 1 BP), the most common cause was sepsis (3 patients). The most common AEs were thrombocytopenia (60%), anemia (51%), diarrhea (40%), neutropenia (37%), and nausea (30%). Injection site reactions (eg, injection site pain, erythema) occurred in 32%, with the majority being low grade. Infections (eg, pneumonia, bronchitis) occurred in 51%. Treatment-related grade 3/4 hematologic AEs included thrombocytopenia (52%), neutropenia (31%), anemia (30%), leukopenia (12%), and febrile neutropenia (11%). The most common treatment-related grade 3/4 nonhematologic AE was fatigue (4.3%). Overall, there were 34 (16%) grade 3/4 infections (12 CP, 11 AP, 11 BP). Conclusions: In the largest safety analysis to date, subcutaneous omacetaxine 1.25 mg/m2 showed an acceptable safety profile in all phases of CML. AEs were primarily hematologic, and grade 3/4 nonhematologic AEs were not common. Support: Teva Pharmaceutical Industries Ltd.

Omacetaxine mepesuccinate in chronic-phase chronic myeloid leukemia (CML) in patients resistant, intolerant, or both to two or more tyrosine-kinase inhibitors (TKIs)

6596

Background: Omacetaxine mepesuccinate (“omacetaxine”) is a first-in-class, reversible, transient inhibitor of protein elongation that facilitates tumor cell death without depending on BCR-ABL signaling. Clinical activity was shown in two phase 2, open-label, multicenter studies of patients with treatment-resistant CML who had failed at least prior imatinib, many of whom were also resistant to or intolerant of dasatinib and/or nilotinib. Methods: A subset of data from the phase 2 studies included patients in chronic phase who were resistant/intolerant to ≥2 approved TKIs. Omacetaxine 1.25 mg/m2 was given subcutaneously twice daily: ≤14 consecutive days/28-day cycle for induction, ≤7 days/cycle as maintenance. Patients had never achieved or lost response to ≥2 TKIs (R group), were intolerant of ≥2 TKIs (I), or resistant to 1 and intolerant of another (R/I) were evaluated. Results: Of 81 patients (median age, 58 years), 69 were R, 7 I, and 5 R/I. Major cytogenetic response occurred in 13 (19%) in the R group (median duration not reached), 2 (29%) I (median duration 7.4 months), and 1 (20%) R/I (duration 17.7 months). For all patients, cycles of exposure and study duration were 7 cycles and 9.1 months (R); 4 cycles, 7.3 months (I); and 2 cycles, 2.3 months (R/I). Median overall survival in months were 33.9 (R), not reached (I), and 25.0 (R/I). Of 66 (81%) patients with treatment-related grade 3/4 adverse events (AEs), the most common were thrombocytopenia in 44 R, 6 I, and 4 R/I patients and neutropenia in 32 R, 4 I, and 1 R/I. Fifteen patients had an AE leading to discontinuation (10 R, 2 I, 3 R/I), primarily disease progression. There were 9 deaths (the most common were disease progression, sepsis), 8 I, 1 R/I; 2 were considered related to treatment (both sepsis). Conclusions: This subset analysis of patients with chronic-phase CML and prior therapy with ≥2 TKIs shows that omacetaxine provides efficacy and tolerability across TKI-R, I, and R/I groups. Interpretation of the I and the R/I group data was limited by small sample sizes. Support: Teva Pharmaceutical Industries Ltd.

Phase I dose-escalation study to evaluate the safety, pharmacokinetics, and pharmacodynamics of CEP-9722 (a PARP1-2 inhibitor) as single‑agent and in combination with temozolomide in patients with advanced solid tumors (NCT00920595)

3052

Background: Poly-ADP-ribose (PAR) polymerases (PARPs) are essential in cellular processing of DNA damage via the base excision repair pathway. CEP-9722, an orally available PARP1-2 inhibitor, demonstrated single-agent antitumor activity and synergy with temozolomide (TMZ) in xenograft models. This phase I study evaluated the pharmacokinetics, pharmacodynamics, and the maximum tolerated dose (MTD) of CEP-9722 in monotherapy and combination with TMZ. Methods: Adult patients with advanced solid tumors were enrolled in cohorts of 3-6 patients to receive a 14-day cycle of CEP-9722 (days 1-5), followed by 28-day cycles of CEP-9722 (days 1-5) plus TMZ (150 mg/m2 days 1-5). The dose of CEP-9722 was 150 mg/day in the first cohort and was escalated depending on the occurrence of dose-limiting toxicities (DLTs) during cycles 1 and 2. The safety, pharmacokinetics, and pharmacodynamics (PAR levels in peripheral blood mononuclear cells) of CEP-9722 were analyzed. Results: Overall, 26 patients (18F,8 M) 18 to 71 years of age were enrolled in 5 cohorts of 3-9 patients and treated with CEP-9722 at 150-1000 mg/day. The MTD of CEP-9722 in combination with TMZ (150 mg/m2) was reached at 1000 mg/day. The recommended dose was 750 mg/day. A total of 9 patients were treated at the recommended dose. DLTs were observed in 2 patients during cycle 1 (1 grade 3 myositis at 750 mg/day and 1 grade 3 asthenia at 1000 mg/day) and 2 patients during cycle 2 (1 grade 3 asthenia at 300 mg/day and 1 persistent grade 2 weight loss at 1000 mg/day). Overall during this study, 4 grade 3 treatment-related adverse events were observed. The pharmacokinetics showed high intra- and inter-patient variability at all doses. The pharmacodynamic analysis demonstrated PARP inhibition at all doses, but the high inter- and intra-patient variability prevented any conclusion regarding a dose / PARP inhibition relationship. Conclusions: TheMTD of CEP-9722 when administered with TMZ was 1000 mg days 1-5 and the combination CEP-9722/TMZ was well tolerated. In addition, a clear signal of PARP inhibition was demonstrated.

Subcutaneous omacetaxine mepesuccinate in patients with chronic phase (CP) or accelerated phase (AP) chronic myeloid leukemia (CML) resistant/intolerant to two or three approved tyrosine-kinase inhibitors (TKIs)

6513

Background: Omacetaxine mepesuccinate (“omacetaxine”) is a first-in-class, reversible, transient inhibitor of protein elongation that facilitates tumor cell death without depending on BCR-ABL signaling. Clinical activity was shown in two phase 2, open-label, multicenter studies in treatment-resistant CML. Methods: A subset from the phase 2 studies included patients in CP or AP who were resistant/intolerant to ≥2 approved TKIs. Omacetaxine 1.25 mg/m2 was given SC twice daily: ≤14 consecutive days/28-day cycle for induction, ≤7 days/cycle as maintenance. Secondary results were calculated for responses by number of prior TKIs. Results: Of 122 patients (median age, 60 years), 62 had received 2 TKIs (100% imatinib; 76% dasatinib; 24% nilotinib) and 60 had received all 3 approved TKIs. Prior non-TKI therapies (eg, 52% hydroxyurea, 34% interferon) were common. Of 45 CP patients in the 2 TKI group, 12 (27%) had major cytogenetic response (MCyR; median duration of 17.7 mo), and of 36 in the 3 TKI group, 4 (11%) had MCyR (median duration not reached). Of 17 AP patients in the 2 TKI group, 6 (35%) had major hematologic response (MaHR; median duration, 13.4 mo), and of 24 in the 3 TKI group, 5 (21%) had MaHR (median duration, 6.4 mo). Median months of survival in the 2 and 3 TKI groups were 30.1 and not reached for CP and 12.0 and 24.6 for AP. Treatment-related grade 3/4 adverse events (AEs) occurred in 52 (84%) patients in the 2 TKI group and 42 (70%) in the 3 TKI group (most common: thrombocytopenia [71%, 48%]). Fifteen (24%) and 16 (27%) had an AE leading to discontinuation, primarily disease progression. There were 20 deaths (primarily disease progression), 11 in the 2 TKI group and 9 in the 3 TKI group; 4 were considered related to treatment (sepsis in 2, pancytopenia, febrile neutropenia). Conclusions: In patients with heavily pretreated CML, response to omacetaxine therapy occurred whether they had received 2 or 3 prior TKIs. The drug was well tolerated. Tolerability was similar across the TKI groups in both CP and AP patients. Support: Teva Pharmaceutical Industries Ltd.

The glucokinase activator GKA50 causes an increase in cell volume and activation of volume-regulated anion channels in rat pancreatic β-cells

Glucokinase plays a key role in the metabolism of glucose by pancreatic β-cells. In this study the effects of the glucokinase activator GKA50 on cell volume and electrical activity in rat β-cells were examined. One micro molar GKA50 caused an increase in β-cell volume in the presence of 4mM glucose. GKA50 also caused a depolarisation of β-cell membrane potential and increased electrical activity. These changes were associated with the activation of inward whole-cell currents, and were attenuated by the anion channel inhibitor 5-nitro-2-(3-phenylpropylamino) benzoic acid. In single channel experiments, the open probability of volume-regulated anion channels (VRAC) was increased from 0.03±0.01 to 0.19±0.04 (n=3) by the GKA50. The data suggest that a GKA50-evoked increase in glucose metabolism causes an increase in β-cell volume. This in turn activates VRAC leading to a depolarisation of the cell membrane potential.

Functional characterization of bestrophin-1 missense mutations associated with autosomal recessive bestrophinopathy

PURPOSE

Autosomal recessive bestrophinopathy (ARB) is a retinal dystrophy affecting macular and retinal pigmented epithelium function resulting from homozygous or compound heterozygous mutations in BEST1. In this study we characterize the functional implications of missense bestrophin-1 mutations that cause ARB by investigating their effect on bestrophin-1's chloride conductance, cellular localization, and stability.

METHODS

The chloride conductance of wild-type bestropin-1 and a series of ARB mutants were determined by whole-cell patch-clamping of transiently transfected HEK cells. The effect of ARB mutations on the cellular localization of bestrophin-1 was determined by confocal immunofluorescence on transiently transfected MDCK II cells that had been polarized on Transwell filters. Protein stability of wild-type and ARB mutant forms of bestrophin-l was determined by the addition of proteasomal or lysosomal inhibitors to transiently transfected MDCK II cells. Lysates were then analyzed by Western blot analysis.

RESULTS

All ARB mutants investigated produced significantly smaller chloride currents compared to wild-type bestrophin-1. Additionally, co-transfection of compound heterozygous mutants abolished chloride conductance in contrast to co-transfections of a single mutant with wild-type bestrophin-l, reflecting the recessive nature of the condition. In control experiments, expression of two dominant vitelliform macular dystrophy mutants was shown to inhibit wild-type currents. Cellular localization of ARB mutants demonstrated that the majority did not traffic correctly to the plasma membrane and that five of these seven mutants were rapidly degraded by the proteasome. Two ARB-associated mutants (p.D312N and p.V317M) that were not trafficked correctly nor targeted to the proteasome had a distinctive appearance, possibly indicative of aggresome or aggresome-like inclusion bodies.

CONCLUSIONS

Differences in cellular processing mechanisms for different ARB associated mutants lead to the same disease phenotype. The existence of distinct pathogenic disease mechanisms has important ramifications for potential gene replacement therapies since we show that missense mutations associated with an autosomal recessive disease have a pathogenic influence beyond simple loss of function.

A dual action of saturated fatty acids on electrical activity in rat pancreatic β-cells. Role of volume-regulated anion channel and KATP channel currents

Free fatty acids (FFAs) exert complex actions on pancreatic β-cells. Typically, an initial potentiation of insulin release is followed by a gradual impairment of β-cell function, the latter effect being of possible relevance to hyperlipidaemia in type 2 diabetes mellitus. The molecular actions of FFAs are poorly understood. The present study investigated the acute effects of saturated FFAs on electrophysiological responses of rat pancreatic β-cells. Membrane potential and KATP channel activity were recorded using the perforated patch technique. Volume-regulated anion channel (VRAC) activity was assessed from conventional whole-cell recordings. Cell volume regulation was measured using a video-imaging technique. Addition of octanoate caused a transient potentiation of glucose-induced electrical activity, followed by a gradual hyper-polarisation and a prolonged inhibition of electrical activity. Octanoate caused an initial increase in VRAC activity followed by a secondary inhibition coinciding with increased KATP channel activity. Similar effects were observed with palmitate and 2-bromopalmitate whereas butyrate was virtually ineffective. Octanoate and palmitate also exerted a dual effect on electrical activity evoked by tolbutamide. Octanoate significantly attenuated cell volume regulation in hypotonic solutions, consistent with VRAC inhibition. It is concluded that medium and long chain FFAs have a dual action on glucose-induced electrical activity in rat pancreatic β-cells: an initial stimulatory effect followed by a secondary inhibition. These effects appear to be the result of reciprocal actions on VRAC and KATP channel currents, and could contribute towards the stimulatory and inhibitory actions of FFAs on pancreatic β-cell function.

Environmental risk factors associated with leptospirosis among butchers and their associates in Jamaica

BACKGROUND

Leptospirosis, a spirochetal zoonosis, is considered an occupational disease of persons engaged in agriculture, sewage works, forestry, and butchery.

OBJECTIVE

To determine the environmental sources and the knowledge, attitude and practices for leptospirosis among butchers and slaughterhouse workers, as well as the seroprevalence of leptospirosis among cattle and pigs presented for slaughter.

METHODS

Using an interviewer administered questionnaire, all 110 butchers and other slaughterhouse workers in the parishes of Kingston and St. Andrew, Jamaica were surveyed. In addition, 179 blood samples from animals presented for slaughter were tested for anti-Leptospira antibodies using the microscopic agglutination test (MAT).

RESULTS

Analyses indicated that people with the studied occupations are at risk for developing leptospirosis due to several environmental risk factors that exist in slaughterhouses. Among the risk factors, limited knowledge of the disease and its transmission, lower educational level attained, younger age and unhealthy behaviors (e.g., hand washing and improper or lack of use of personal protective gears), presence of stray dogs and rodents, and inadequate maintenance of physical plants, were found to be important. Of the total number of animal samples tested, 20 (11%) were positive. Canicola and Hardjo (among cattle) and Bratislava (among pigs) were the major seroreactors.

CONCLUSION

Butchers and slaughterhouse workers engaged in animal handling and slaughtering could be frequently exposed to leptospirosis, and hence control strategies targeting at these populations should be implemented.

Comparison of antibiotic resistance and virulence factors in pigmented and non-pigmented Pseudomonas aeruginosa

OBJECTIVE

Pseudomonas aeruginosa produces multiple virulence factors that have been implicated in pathogenesis and quorum sensing. The aim of this study was to determine differences in the virulence factors of pigmented and non-pigmented P aeruginosa isolates.

METHODS

Associations were assessed between pigment production (pyocyanin and pyoverdin) and production of DNase, elastase, lipase, protease, siderophore, twitching motility, antibiotic resistance patterns and virulence-associated genes in 57 non-duplicate P aeruginosa isolates from wounds, sputum, urine, high vaginal swab (HVS), ear, eye and respiratory tract swabs and aspirates of peritoneum and ulcers.

RESULTS

Most (82.5%) of the isolates produced either pigment. Pigmented isolates produced more frequently and significant more (p < 0.05) DNase, elastase, lipase protease, and siderophore. Imipenem was the only antibiotic to which all isolates were susceptible (p < 0.05), while 93% and 32% were resistant to tetracycline and norfloxacin, respectively. There was however no significant difference between pigmented and non-pigmented isolates when antibiotic resistance was compared. While isolates had multiple virulence-associated genes, exoS (51%), rhlA (37%) and rhlB (46%) were the predominant genes detected. Except for exoY, genes were present in pigmented isolates more frequently than in non-pigmented isolates.

CONCLUSION

The results of this study suggest that antibiotic resistance per se might not be associated with the pigment production in P aeruginosa. However pigment production appeared to be more significantly associated with multi-drug resistance, presence of virulence-associated genes, and expression of certain virulence factors, most notably elastase, protease, siderophore and DNase activity. Since pigment production is easy to determine, this might to be a good starting point to identify the virulence status of an isolate.

Epithelial pathways in choroid plexus electrolyte transport

A stable intraventricular milieu is crucial for maintaining normal neuronal function. The choroid plexus epithelium produces the cerebrospinal fluid and in doing so influences the chemical composition of the interstitial fluid of the brain. Here, we review the molecular pathways involved in transport of the electrolytes Na+, K+, Cl-, and HCO3(-)across the choroid plexus epithelium.

The emergence of qnr-mediated quinolone resistance among Enterobacteriaceae in Jamaica

OBJECTIVE

Quinolone resistance is usually caused by various chromosomal mutations, but has been more recently associated with plasmids which carry the qnr determinant. The aim of this study is to investigate the prevalence of qnr genes in clinical isolates of Enterobacteriaceae in Jamaica.

METHODS

A total of 255 non-duplicate fluoroquinolone-resistant Enterobacteriaceae clinical isolates, comprising 232 Escherichia coli, 20 Klebsiella species and three Enterobacter spp were collected between October 2007 and November 2008 from hospitalized patients in Jamaica. The presence of the qnr gene was screened by PCR using specific primers for qnrA, qnrB and qnrS in extracted plasmid DNA.

RESULTS

Eighty-three (32.5%) of these isolates were qnr-positive, of which 47.0% housed the qnrA gene only, 1.2% qnrB and 9.6% qnrS only. Another 36.1% possessed both qnrA and qnrS genes. Approximately 30% of the quinolone-resistant E coli isolates harboured the qnr gene while 50% Klebsiella spp and all Enterobacter spp were positive.

CONCLUSION

The emergence of qnr-mediated quinolone resistance among clinical Enterobacteriaceae isolates is described for the first time in Jamaica.

Electrical activity in pancreatic islet cells: The VRAC hypothesis

A major aspect of stimulation of β-cell function by glucose is the induction of electrical activity. The ionic events that underlie β-cell electrical activity are understood in some detail. At sub-stimulatory glucose concentrations, the β-cell is electrically 'silent'. Increasing the glucose concentration to stimulatory levels results in a gradual depolarisation of the membrane potential to a threshold potential where 'spikes' or action potentials are generated. These action potentials represent the gating of voltage-sensitive Ca²(+) channels, leading to Ca²(+) entry into the cell, thus triggering the release of insulin. The stimulatory actions of glucose on the β-cell depend on the metabolism of the hexose. A major question concerns the molecular mechanism(s) whereby β-cell plasma membrane potential is regulated by changes in glucose metabolism in the cell. This article provides a brief summary of the evidence suggesting that, in addition to metabolically-regulated K(ATP) channels, β-cells are equipped with a volume-regulated anion channel that is activated by glucose concentrations within the range effective in modulating electrical activity and insulin release.

Opposing effects of tenidap on the volume-regulated anion channel and K(ATP) channel activity in rat pancreatic beta-cells

Tenidap (5-chloro-2-hydroxy-3-(thiophene-2-carbonyl)indole-1-carboxamide) is a non-steroidal anti-inflammatory and anti-rheumatic drug with several cellular actions including inhibition of anion transport processes. Since other anion transport inhibitors have been shown to inhibit activity of the volume-regulated anion channel (VRAC), the present study investigated the effects of tenidap on activity of this channel in pancreatic beta-cells. Membrane potential, VRAC currents and input conductance were recorded from single rat beta-cells in primary culture using perforated patch, conventional whole-cell and cell-attached configurations of the patch-clamp technique. Relative cell volume was measured using a video-imaging method. Tenidap (0.1mM) was found to rapidly hyperpolarise the beta-cell membrane potential and terminate glucose-induced electrical activity. This effect was associated with a pronounced outward current shift at a holding potential of -65mV. Tenidap was found to inhibit activity of the volume-regulated anion channel with IC(50) values of 31 and 43microM for outward and inward currents respectively. Tenidap also markedly increased beta-cell input conductance, representing an activation of the K(ATP) conductance. beta-cell regulatory volume decrease following hypotonically-induced cell swelling was sensitive to inhibition by 50microM tenidap. Tenidap is a potent inhibitor of the volume-regulated anion channel and K(ATP) channel activator in rat pancreatic beta-cells. These actions could at least in part explain the recently reported inhibitory actions of the drug on electrical and secretory activity in the beta-cell, and could also underlie other pharmacological actions of the drug.

Missense mutations in a retinal pigment epithelium protein, bestrophin-1, cause retinitis pigmentosa

Bestrophin-1 is preferentially expressed at the basolateral membrane of the retinal pigmented epithelium (RPE) of the retina. Mutations in the BEST1 gene cause the retinal dystrophies vitelliform macular dystrophy, autosomal-dominant vitreochoroidopathy, and autosomal-recessive bestrophinopathy. Here, we describe four missense mutations in bestrophin-1, three that we believe are previously unreported, in patients diagnosed with autosomal-dominant and -recessive forms of retinitis pigmentosa (RP). The physiological function of bestrophin-1 remains poorly understood although its heterologous expression induces a Cl--specific current. We tested the effect of RP-causing variants on Cl- channel activity and cellular localization of bestrophin-1. Two (p.L140V and p.I205T) produced significantly decreased chloride-selective whole-cell currents in comparison to those of wild-type protein. In a model system of a polarized epithelium, two of three mutations (p.L140V and p.D228N) caused mislocalization of bestrophin-1 from the basolateral membrane to the cytoplasm. Mutations in bestrophin-1 are increasingly recognized as an important cause of inherited retinal dystrophy.

Studies of the mechanism of activation of the volume-regulated anion channel in rat pancreatic beta-cells

There is evidence that depolarization of the pancreatic beta cell by glucose involves cell swelling and activation of the volume-regulated anion channel (VRAC). However, it is unclear whether cell swelling per se or accompanying changes in intracellular osmolality and/or ionic strength are responsible for VRAC activation. VRAC activity was measured in rat beta cells by conventional or perforated patch whole-cell recording. Cell volume was measured by video imaging. In conventional whole-cell recordings, VRAC activation was achieved by exposure of the cells to a hyposmotic bath solution, by application of positive pressure to the pipette, or by use of a hyperosmotic pipette solution. Increased concentrations of intracellular CsCl also caused channel activation, but with delayed kinetics. In perforated patch recordings, VRAC activation was induced by isosmotic addition of the permeable osmolytes urea, 3-O-methyl glucose, arginine, and NH4Cl. These effects were all accompanied by beta-cell swelling. It is concluded that increased cell volume, whether accompanied by raised intracellular osmolality or ionic strength, is a major determinant of VRAC activation in the beta cell. However, increased intracellular ionic strength markedly reduced the rate of VRAC activation. These findings are consistent with the hypothesis that the accumulation of glucose metabolites in the beta cell, and the resultant increase in cell volume, provides a signal coupling glucose metabolism with VRAC activation.

Contrasting effects of glycerol and urea transport on rat pancreatic beta-cell function

BACKGROUND/AIMS

Pancreatic beta-cell function is influenced by changes in cell volume. Such volume changes depend on water permeability of the plasma membrane, conferred in part by aquaporins. Islet cells express aquaporin 7 (AQP7), which is permeable to urea and glycerol in addition to water. We therefore investigated the effects of glycerol and urea on rat pancreatic beta-cell function.

METHODS

Electrical activity and whole-cell current were studied using the perforated patch technique. Cell volume was measured by video-imaging and insulin release by radioimmunoassay. Aquaporin 7 expression was studied by RT-PCR, Western blot and double fluorescent immunolabelling.

RESULTS

The isosmotic addition of glycerol and urea resulted in depolarization of the plasma membrane and electrical activity, accompanied by beta-cell swelling, activation of the volume-regulated anion channel (VRAC) and insulin release. However, the effects of glycerol, in contrast to urea, persisted throughout exposure to the osmolyte. Glycerol also caused beta-cell activation when added hyperosmotically. A non-metabolizable glycerol analogue had comparable effects to urea on beta-cells. The expression of AQP7 was demonstrated in rat beta-cells.

CONCLUSION

Glycerol and urea can activate beta-cells via their rapid uptake across the beta-cell plasma membrane, possibly via AQP7. This results in cell swelling, VRAC activation, electrical activity and insulin release. Glycerol appears to exert an additional effect, possibly related to its intracellular metabolism.

An appraisal of ultramicrotomy, FIBSEM and cryogenic FIBSEM techniques for the sectioning of biological cells on titanium substrates for TEM investigation

Ultramicrotomy, focused ion beam scanning electron microscopy (FIBSEM) and cryogenic FIBSEM (cryo-FIBSEM) techniques, as developed for the controlled cross-sectioning of mesenchymal stem cells (MSCs) and human osteoblasts (HObs) on titanium (Ti) substrates for transmission electron microscopy (TEM) investigation, are compared. Conventional ultramicrotomy has been used to section cells on Ti-foil substrates embedded in resin, but significant problems with cell detachment using this technique restricted its general applicability. Conventional FIBSEM 'lift-out' procedures were found to be effective for the preparation of uniform sections of fixed and dehydrated cell/Ti specimens, but the control of cell staining remains an issue. Cryo-FIBSEM procedures used with an 'H-bar' sample geometry enabled the sectioning of fixed and hydrated cell/Ti specimens, but issues remain over ion beam-induced artefacts and control of frost on the sample foils.

HCO 3--dependent volume regulation in alpha-cells of the rat endocrine pancreas

Ion transport activity in pancreatic α-cells was assessed by studying cell volume regulation in response to anisotonic solutions. Cell volume was measured by a video imaging method, and cells were superfused with either 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid-buffered or HCO₃⁻-buffered solutions. α-Cells did not exhibit a regulatory volume increase (RVI) in response to cell shrinkage caused by hypertonic solutions. A RVI was observed, however, in cells that had first undergone a regulatory volume decrease (RVD), but only in HCO₃⁻-buffered solutions. RVI was also observed in response to a HCO₃⁻-buffered hypertonic solution in which the glucose concentration was increased from 4 to 20 mM. The post-RVD RVI and the glucose-induced RVI were both inhibited by 10 μM 5-(N-methyl-N-isobutyl) amiloride or 100 μM 2,2′-(1,2-ethenediyl) bis (5-isothio-cyanatobenzenesulfonic acid), but not by 10 μM benzamil nor 10 μM bumetanide. These data suggest that Na⁺–H⁺ exchangers and Cl⁻–HCO₃⁻ exchangers contribute to volume regulation in α-cells.

Domain walls in the (Ga,Mn)as diluted magnetic semiconductor

We report experimental and theoretical studies of magnetic domain walls in an in-plane magnetized (Ga,Mn)As dilute moment ferromagnetic semiconductor. Our high-resolution electron holography technique provides direct images of domain wall magnetization profiles. The experiments are interpreted based on microscopic calculations of the micromagnetic parameters and Landau-Lifshitz-Gilbert simulations. We find that the competition of uniaxial and biaxial magnetocrystalline anisotropies in the film is directly reflected in orientation dependent wall widths, ranging from approximately 40 to 120 nm. The domain walls are of the Néel type and evolve from near-90 degrees walls at low temperatures to large angle [11[over ]0]-oriented walls and small angle [110]-oriented walls at higher temperatures.

Biallelic mutation of BEST1 causes a distinct retinopathy in humans

We describe a distinct retinal disorder, autosomal-recessive bestrophinopathy (ARB), that is consequent upon biallelic mutation in BEST1 and is associated with central visual loss, a characteristic retinopathy, an absent electro-oculogram light rise, and a reduced electroretinogram. Heterozygous mutations in BEST1 have previously been found to cause the two dominantly inherited disorders, Best macular dystrophy and autosomal-dominant vitreoretinochoroidopathy. The transmembrane protein bestrophin-1, encoded by BEST1, is located at the basolateral membrane of the retinal pigment epithelium in which it probably functions as a Cl(-) channel. We sequenced BEST1 in five families, identifying DNA variants in each of ten alleles. These encoded six different missense variants and one nonsense variant. The alleles segregated appropriately for a recessive disorder in each family. No clinical or electrophysiological abnormalities were identified in any heterozygotes. We conducted whole-cell patch-clamping of HEK293 cells transfected with bestrophin-1 to measure the Cl(-) current. Two ARB missense isoforms severely reduced channel activity. However, unlike two other alleles previously associated with Best disease, cotransfection with wild-type bestrophin-1 did not impair the formation of active wild-type bestrophin-1 channels, consistent with the recessive nature of the condition. We propose that ARB is the null phenotype of bestrophin-1 in humans.

Ion channel diversity, channel expression and function in the choroid plexuses

Knowledge of the diversity of ion channel form and function has increased enormously over the last 25 years. The initial impetus in channel discovery came with the introduction of the patch clamp method in 1981. Functional data from patch clamp experiments have subsequently been augmented by molecular studies which have determined channel structures. Thus the introduction of patch clamp methods to study ion channel expression in the choroid plexus represents an important step forward in our knowledge understanding of the process of CSF secretion.

Two K⁺ conductances have been identified in the choroid plexus: Kv1 channel subunits mediate outward currents at depolarising potentials; Kir 7.1 carries an inward-rectifying conductance at hyperpolarising potentials. Both K⁺ channels are localised at the apical membrane where they may contribute to maintenance of the membrane potential while allowing the recycling of K⁺ pumped in by Na⁺-K⁺ ATPase. Two anion conductances have been identified in choroid plexus. Both have significant HCO₃^- permeability, and may play a role in CSF secretion. One conductance exhibits inward-rectification and is regulated by cyclic AMP. The other is carried by an outward-rectifying channel, which is activated by increases in cell volume. The molecular identity of the anion channels is not known, nor is it clear whether they are expressed in the apical or basolateral membrane. Recent molecular evidence indicates that choroid plexus also expresses the non-selective cation channels such as transient receptor potential channels (TRPV4 and TRPM3) and purinoceptor type 2 (P2X) receptor operated channels. In conclusion, good progress has been made in identifying the channels expressed in the choroid plexus, but determining the precise roles of these channels in CSF secretion remains a challenge for the future.

Curcumin induces electrical activity in rat pancreatic beta-cells by activating the volume-regulated anion channel

Curcumin, the principal active component of turmeric, is reported to exert a number of therapeutic actions, including a hypoglycaemic/antidiabetic action. The underlying mechanisms to this action are essentially unknown. We have investigated the hypothesis that a direct stimulatory action on the pancreatic beta-cell could contribute towards the hypoglycaemic activity of this compound. Electrical and ion channel activity were recorded in rat beta-cells using the patch-clamp technique. beta-Cell volume was measured using a video-imaging technique. Insulin release was measured from intact islets by radioimmunoassay. Curcumin (2-10 microM) activated the volume-regulated anion channel in beta-cells. Single channel studies indicated that activation was the result of increased channel open probability. This effect was accompanied by depolarisation of the cell membrane potential, the generation of electrical activity and enhanced insulin release. Curcumin also decreased beta-cell volume, presumably reflecting loss of Cl(-) (and hence water) as a result of anion channel activation. These findings are consistent with the suggestion that Cl(-) fluxes play an important role in regulating beta-cell function. The stimulation of beta-cell function by curcumin could contribute to the hypoglycaemic actions of this compound, and these findings identify a novel potential therapeutic target for the treatment of type 2 diabetes mellitus.

Glucose-induced swelling in rat pancreatic alpha-cells

Pancreatic beta-cells increase in volume when exposed to elevated concentrations of extracellular glucose. This study has examined the effects of glucose on the volumes of pancreatic alpha-cells, which like beta-cells are regulated by glucose, and intestinal epithelial Caco-2 cells which are unresponsive to glucose. Cell volume changes were monitored by a video-imaging method. Increasing the extracellular glucose concentration caused a concentration-dependent increase in alpha-cell volume over the range 1-20mM. Glucose-induced swelling was not, however, observed in Caco-2 cells. The glucose-induced swelling in both alpha- and beta-cells was abolished by 0.5mM phloretin, an inhibitor of the GLUT proteins, indicating that GLUT mediated glucose transport is a pre-requisite for swelling. Glucose metabolism also appears to be essential, as islet cell swelling was not observed with 16 mM 3-O-methyl glucose. These data suggest that glucose-induced swelling may be a property exclusive to glucose-regulated cells.