A high-speed scintillation-based electronic portal imaging device to quantitatively characterize IMRT delivery

We have developed an electronic portal imaging device (EPID) employing a fast scintillator and a high-speed camera. The device is designed to accurately and independently characterize the fluence delivered by a linear accelerator during intensity modulated radiation therapy (IMRT) with either step-and-shoot or dynamic multileaf collimator (MLC) delivery. Our aim is to accurately obtain the beam shape and fluence of all segments delivered during IMRT, in order to study the nature of discrepancies between the plan and the delivered doses. A commercial high-speed camera was combined with a terbium-doped gadolinium-oxy-sulfide (Gd2O2S:Tb) scintillator to form an EPID for the unaliased capture of two-dimensional fluence distributions of each beam in an IMRT delivery. The high speed EPID was synchronized to the accelerator pulse-forming network and gated to capture every possible pulse emitted from the accelerator, with an approximate frame rate of 360 frames-per-second (fps). A 62-segment beam from a head-and-neck IMRT treatment plan requiring 68 s to deliver was recorded with our high speed EPID producing approximately 6 Gbytes of imaging data. The EPID data were compared with the MLC instruction files and the MLC controller log files. The frames were binned to provide a frame rate of 72 fps with a signal-to-noise ratio that was sufficient to resolve leaf positions and segment fluence. The fractional fluence from the log files and EPID data agreed well. An ambiguity in the motion of the MLC during beam on was resolved. The log files reported leaf motions at the end of 33 of the 42 segments, while the EPID observed leaf motions in only 7 of the 42 segments. The static IMRT segment shapes observed by the high speed EPID were in good agreement with the shapes reported in the log files. The leaf motions observed during beam-on for step-and-shoot delivery were not temporally resolved by the log files.     

Cellular and molecular actions of dinitroaniline and phosphorothioamidate herbicides on Plasmodium falciparum: tubulin as a specific antimalarial target

Microtubules play important roles in cell division, motility and structural integrity of malarial parasites. Some microtubule inhibitors disrupt parasite development at very low concentrations, but most of them also kill mammalian cells. However, the dinitroaniline family of herbicides, which bind specifically to plant tubulin, have inhibitory activity on plant cells but are relatively non-toxic to human cells. Certain dinitroanilines are also inhibitory to various protozoal parasites including Plasmodium. Here we demonstrate that the dinitroanilines trifluralin and oryzalin inhibited progression of erythrocytic Plasmodium falciparum through schizogony, blocked mitotic division, and caused accumulation of abnormal microtubular structures. Moreover, radiolabelled trifluralin interacted with purified, recombinant parasite tubulins but to a much lesser extent with bovine tubulins. The phosphorothioamidate herbicide amiprophos-methyl, which has the same herbicidal mechanism as dinitroanilines, also had antimalarial activity and a similar action on schizogony. These data suggest that P. falciparum tubulin contains a dinitroaniline/phosphorothioamidate-binding site that is not conserved in humans and might be a target for new antimalarial drugs.     

Carotid chemoreceptor modulation of sympathetic vasoconstrictor outflow during exercise in healthy humans

Recently, we have shown that specific, transient carotid chemoreceptor (CC) inhibition in exercising dogs causes vasodilatation in limb muscle. The purpose of the present investigation was to determine if CC suppression reduces muscle sympathetic nerve activity (MSNA) in exercising humans. Healthy subjects ( N = 7) breathed hyperoxic gas ( F _IO2∼1.0) for 60 s at rest and during rhythmic handgrip exercise (50% maximal voluntary contraction, 20 r.p.m.). Microneurography was used to record MSNA in the peroneal nerve. End-tidal P _CO2 was maintained at resting eupnoeic levels throughout and breathing rate was voluntarily fixed. Exercise increased heart rate (67 versus 77 beats min⁻¹), mean blood pressure (81 versus 97 mmHg), MSNA burst frequency (28 versus 37 bursts min⁻¹) and MSNA total minute activity (5.7 versus 9.3 units), but did not change blood lactate (0.7 versus 0.7 m m ). Transient hyperoxia had no significant effect on MSNA at rest. In contrast, during exercise both MSNA burst frequency and total minute activity were significantly reduced with hyperoxia. MSNA burst frequency was reduced within 9–23 s of end-tidal P _O2 exceeding 250 mmHg. The average nadir in MSNA burst frequency and total minute activity was −28 ± 2% and −39 ± 7%, respectively, below steady state normoxic values. Blood pressure was unchanged with hyperoxia at rest or during exercise. CC stimulation with transient hypoxia increased MSNA with a similar time delay to that obtained with CC inhibition via hyperoxia. Consistent with previous animal work, these data indicate that the CC contributes to exercise-induced increases in sympathetic vasoconstrictor outflow.     

Analysis of ASPM in an ethnically diverse cohort of 400 patient samples: perspectives of the molecular diagnostic laboratory

Primary Autosomal Recessive Microcephaly (MCPH) is characterized by congenital microcephaly usually without additional clinical findings. The most common gene implicated in MCPH is ASPM and a large percentage of mutations described have been homozygous and in consanguineous families primarily of East Asian and Middle Eastern origin. ASPM sequencing was performed on 400 patients between the years 2009 and 2012. Seventy of the patient samples were also analyzed for copy number changes in the ASPM gene. Forty protein truncating mutations, including 29 novel mutations, were identified in 39 patients with MCPH. Approximately one third of patients were compound heterozygotes, indicative of non‐consanguinity in these patients. In addition, 46 non‐synonymous variants were identified and interpreted as variants of uncertain significance. No deletion/duplication in ASPM was identified in the patients analyzed. A wide ethnic distribution was observed, including the first reported patients with ASPM‐related MCPH of Hispanic descent. Clinical information was collected for 26 of the ASPM‐positive patients and 41 of the ASPM‐negative patients. As more individuals are identified with MCPH, we anticipate that we will continue to identify ASPM mutation‐positive patients from all ethnic origins supporting the occurrence of this genetic condition beyond that of consanguineous families of certain ethnic populations.     

Xenophagy in Helicobacter pylori‐ and Epstein–Barr virus‐induced gastric cancer

Helicobacter pylori and Epstein–Barr virus (EBV) account for roughly 80% and 10%, respectively, of gastric carcinomas worldwide. Autophagy is an evolutionarily conserved and intricately regulated cellular process that involves the sequestration of cytoplasmic proteins and organelles into double‐membrane autophagosomes that eventually fuse with lysosomes for degradation of the engulfed content. Emerging evidence indicates that xenophagy, a form of selective autophagy, plays a crucial role in the pathogenesis of H. pylori‐ and EBV‐induced gastric cancer. Xenophagy specifically recognizes intracellular H. pylori and EBV and physically targets these pathogens to the autophagosomal–lysosomal pathway for degradation. In this connection, H. pylori or EBV‐induced dysregulation of autophagy may be causally linked to gastric tumourigenesis and therefore can be exploited as therapeutic targets. This review will discuss how H. pylori and EBV infection activate autophagy and how these pathogens evade recognition and degradation by the autophagic pathway. Elucidating the molecular aspects of H. pylori‐ and EBV‐induced autophagy will help us better understand the pathogenesis of gastric cancer and promote the development of autophagy modulators as antimicrobial agents. Published by John Wiley & Sons, Ltd     

Helicobacter pylori: prevalence of antimicrobial resistance in clinical isolates

This study aims to determine the in vitro susceptibility of Helicobacter pylori to clarithromycin, metronidazole, amoxycillin and tetracycline, the four antibiotics commonly used in eradication therapies. These data are used to evaluate the efficacy of current empiric treatment of H. pylori infection in the Southern Region of Ireland. Culture is performed on gastric biopsy samples obtained from 147 consecutive patients undergoing gastroscopy for investigation of dyspepsia. Susceptibility testing to metronidazole, clarithromycin, amoxycillin and tetracycline is performed on the isolates by Etest. Isolates demonstrating clarithromycin resistance are subjected to polymerase chain reaction (PCR) amplification and nucleotide sequence analysis to identify the presence of point mutations in the peptidyltransferase region of the 23S rRNA gene previously associated with resistance to clarithromycin. Prevalence of H. pylori in the population studied was 31% (45 isolates). Antimicrobial resistance to metronidazole and clarithromycin was detected in nine (20%) and four (8.9%) of the isolates, respectively. A single isolate demonstrated co-resistance to metronidazole and clarithromycin (2.2%). No resistance was detected to either amoxycillin or tetracycline. The low level of resistance demonstrated among this group of isolates indicates that the empiric treatment currently in place in the Southern Region of Ireland is likely to be successful.     

Unusual manifestations of primary cytomegalovirus infection in patients without HIV infection and without organ transplants

Primary cytomegalovirus (CMV) infection with marked constitutional symptoms is rare in immunocompetent individuals and in those with iatrogenic immunosuppression, except transplant recipients. Four patients admitted to hospital with clinical illnesses associated with primary CMV infection were identified over a 12-month period. Their medical records were reviewed with regard to clinical and laboratory data, and outcome. Primary CMV infection was defined by the concomitant presence of CMV IgM and low avidity CMV IgG antibody. Of two patients with no known underlying illness, one presented with thrombocytopenic purpura and the other with vasculitis. Two patients receiving immunosuppressants for underlying ulcerative colitis presented with CMV-induced pancytopenia and CMV colitis. Atypical lymphocytosis was a feature on blood film examination in three of the four cases. One patient with disseminated CMV infection died of progressive multiorgan failure despite antiviral treatment. CMV disease following primary CMV infection should be considered in otherwise immunocompetent individuals with atypical lymphocytosis on blood film analysis, and particularly in patients on immunosuppressants such as those with ulcerative colitis, since early diagnosis and treatment with antiviral drugs may improve outcome.     

Evaluation of surface and build-up region dose for intensity-modulated radiation therapy in head and neck cancer

Despite much development, there remains dosimetric uncertainty in the surface and build-up regions in intensity-modulated radiation therapy treatment plans for head and neck cancers. Experiments were performed to determine the dosimetric discrepancies in the surface and build-up region between the treatment planning system (TPS) prediction and experimental measurement using radiochromic film. A head and neck compression film phantom was constructed from two semicylindrical solid water slabs. Treatment plans were generated using two commercial TPSs (PINNACLE3 and CORVUS) for two cases, one with a shallow (approximately 0.5 cm depth) target and another with a deep (approximately 6 cm depth) target. The plans were evaluated for a 54 Gy prescribed dose. For each case, two pieces of radiochromic film were used for dose measurement. A small piece of film strip was placed on the surface and another was inserted within the phantom. Overall, both TPSs showed good agreement with the measurement. For the shallow target case, the dose differences were within +/- 300 cGy (5.6% with respect to the prescribed dose) for PINNACLE3 and +/- 240 cGy (4.4%) for CORVUS in 90% of the region of interest. For the deep target case, the dose differences were +/- 350 (6.5%) for PINNACLE3 and +/- 260 cGy (4.8%) for CORVUS in 90% of the region of interest. However, it was found that there were significant discrepancies from the surface to about 0.2 cm in depth for both the shallow and deep target cases. It was concluded that both TPSs overestimated the surface dose for both shallow and deep target cases. The amount of overestimation ranges from 400 to 1000 cGy (approximately 7.4% to 18.5% with respect to the prescribed dose, 5400 cGy).