Measurement of neutron yield for a medical linear accelerator below 10 MV.

BACKGROUND: The recent trend toward 10 MV for volumetric radiotherapy treatment such as volumetric modulated arc therapy (VMAT), stereotactic radiosurgery (SRS), and stereotactic ablative body radiotherapy (SABR) introduces photoneutron production, with implications for non-therapeutic patient dose and additional shielding requirements for treatment room design. The sharply nonlinear drop-off in photoneutron production below 10 MV to negligible at 6 MV has scarcely been characterized quantitatively, yet can elucidate important practical insights. PURPOSE: To measure photoneutron yields in a medical linac at 8 MV, which may strike a reasonable balance between usefully increased beam penetration and dose rate as compared to 6 MV while reducing photoneutron production which is present at 10 MV. METHODS: A Varian iX linear accelerator undergoing decommissioning at our clinic was made to operate over a range of photon energies between 6 and 15 MV by calibrating the bending magnet and adjusting other beam generation parameters. Neutron dose within the treatment room was measured using an Anderson-Braun type detector over a continuum of intermediate energies. RESULTS: The photoneutron production for energies below 10 MV was measured, adding to data that is otherwise scarce in the literature. Our results are consistent with previously published results for neutron yield. We found that the photoneutron production at 8 MV was about 1/10 of the value at 10 MV, and about 10 times higher than detector background at 6 MV. CONCLUSIONS: Photoneutron production drops off below 10 MV, but is still present at 8 MV. An 8 MV beam is more penetrating than a 6 MV beam, and may offer a suitable tradeoff for modern radiotherapy techniques such as VMAT, SRS, and SABR. Further studies are needed to better understand the impact on treatment plan quality between 8 and 10 MV beams considering the benefits to facility requirements and non-therapeutic patient dose.

Green sweet potato leaves increase Nrf2-mediated antioxidant activity and facilitate benzo[a]pyrene metabolism in the liver by increasing phase II detoxifying enzyme activities in rats.

Sweet potato leaves (SPL) are a valuable source of phytonutrients with nutritional and various health-promoting benefits. This study evaluated the effects of green and purple SPL supplementation on hepatic xenobiotic-metabolizing enzymes (XME) and membrane transporters, and benzo[a]pyrene (B[a]P) metabolism and B[a]P accumulation in rats. The experiments were conducted in standard and B[a]P-treated rat models. The first experiment showed that rats fed a diet containing 5% (w/w) green or purple SPL for two weeks showed increased hepatic activity of cytochrome P-450 (CYP)1A1/1A2 and glutathione S-transferase. Green SPL supplementation also increased the CYP2C, CYP2D and CYP3A and multidrug resistance-associated protein 2 levels in the liver. Notably, green and purple SPL induced nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 protein expression and reduced oxidative stress in the liver. The second experiment was to evaluate the effects of green and purple SPL supplementation on B[a]P metabolism and B[a]P accumulation in rats. Rats were fed SPL diets (the same as experiment I) for two weeks. When rats were exposed to a single dose (25 mg per kg BW) of B[a]P, green SPL had no effect on B[a]P-induced elevation of CYP1A1 activity but induced GST activity in the intestinal mucosa and the liver. Green SPL also increased hepatic UDP-glucuronosyltransferase activity and reduced B[a]P levels in the plasma, liver, and intestinal mucosa. A lower plasma 8-hydroxy-2'-deoxyguanosine level was found after B[a]P treatment only in the green SPL group. This study suggests that, in the standard rat model, green and purple SPL may increase Nrf2-mediated antioxidant activity and facilitate the xenobiotic detoxification process by increasing hepatic XME and transporters. When exposed to B[a]P, however, only green SPL consumption may increase hepatic B[a]P metabolism and lower the B[a]P level in the liver by increasing phase II detoxifying enzyme activities.

Correction: Green sweet potato leaves increase Nrf2-mediated antioxidant activity and facilitate benzo[a]pyrene metabolism in the liver by increasing phase II detoxifying enzyme activities in rats.

Correction for 'Green sweet potato leaves increase Nrf2-mediated antioxidant activity and facilitate benzo[a]pyrene metabolism in the liver by increasing phase II detoxifying enzyme activities in rats' by Ray-Yu Yang et al., Food Funct., 2022, https://doi.org/10.1039/d2fo01049f.

Automated conversion of Millennium-120 VMAT plans to HDMLC geometry: Software development and treatment of first patients.

PURPOSE: To provide plan backup resiliency for patients treated on a solitary high definition multileaf collimator (HDMLC) linac by developing a fully integrated Eclipse script, which converts patient plans initially optimized on Millennium-120 (M120) MLC to dosimetrically equivalent leaf motions for delivery on HDMLC. In the event of HDMLC machine downtime, affected patients can be transferred to Millennium-120 units, and their backup plan delivered without delay. METHODS: Write-enabled Eclipse scripting is leveraged to generate HDMLC treatment fields with control points parameterized to mimic apertures of an existing Millennium-120 VMAT plan. Non-parity between intermediate control point gantry angles of script generated arcs relative to VMAT is reconciled through an interpolation subroutine to correct for the apertures and monitor units that would have existed at intermediate angles. Differences in dosimetric leaf gap are corrected by displacing the subset of leaves undergoing dynamic motion. A nominal change to plan normalization corrects for remaining discrepancies between beam models. RESULTS: Over 220 non-SABR VMAT patients were treated on a solitary HDMLC linac with plans converted using the developed script. All have undergone streamlined RO review and physics quality assurance (QA), where the converted plan replicates the original leaf patterns, representing a minor dosimetric perturbation. Analyzing a subset of converted plans delivered at four anatomical sites, on average 99.3% of points pass the 1%/1 mm gamma criterion. Dose-volume histograms between the original and converted plans are in excellent agreement. ArcCheck measurements comparing delivery of the converted HDMLC plan to the calculated M120 dose distribution averaged a gamma pass rate of 99.4% (95.2%) at a 3%/3 mm (2%/2 mm) criterion. The conversion process takes 30 s to run, avoids errors in exporting/re-importing, and generates leaf motions deliverable within machine limits. CONCLUSION: The methodology developed for automated plan conversion helped maximize the utilization of a solitary HDMLC linac, while preserving backup interoperability with minimal overhead.

Nutritional composition of mungbean and soybean sprouts compared to their adult growth stage.

This study determined the level of phytonutrients in mungbean and soybean sprouts compared to mature mungbean grain and vegetable soybean. The comparison included landraces and improved mungbean and soybean varieties to assess the effect of breeding on the phytonutrient content of both crops. Sprouting mungbean enhanced vitamin C content 2.7-fold compared to mature mungbean grain. Relatively old mungbean accessions were superior in protein, calcium (Ca), iron (Fe), zinc (Zn), carotenoid and vitamin C content compared to improved mungbean lines at the fully mature stage. With regard to nutritional value, the vegetable soybean stage was superior to soybean sprouts in terms of content of protein (14% increase), Zn (45%), Ca (72%), and Fe (151%). Isoflavones, reported to have beneficial effects on human health, are found at high concentrations in soybean sprouts and could easily provide the recommended anticarcinogenic dose range from 1.5 to 2.0mg/kg of body weight per day.

Pegylated glucose gold nanoparticles for improved in-vivo bio-distribution and enhanced radiotherapy on cervical cancer.

Pharmacokinetics and bio-distribution are crucial factors affecting the performance of an intravenous drug. In this study, we explore the combined use of glucose and polyethylene glycol (PEG) ligands to further improve gold nanoparticle (GNP) pharmacokinetics and bio-distribution, with the aim of using the drug for in-vivo radiotherapy. The inclusion of PEG was found to significantly prolong the half-life period, where PEG-Glu-GNPs achieved 6.17 +/- 3.71 h, compared to 1.23 +/- 0.14 h for Glu-GNPs and 1.07 +/- 0.22 h for uncoated GNPs. Our data indicates that nanoparticle size impacts cell uptake performance, with 20 nm being the optimal diameter for cancer treatment applications. Although PEG-Glu-GNPs mainly distributed in the spleen, liver, lung, and kidneys, the concentration of PEG-Glu-GNPs in tumour tissue was 20 times higher than healthy cells in the uterus and ovaries, reaching 9.22 +/- 2.41 microg/g cancer tissue at 48 h after injection. This difference in uptake holds promise for selective tumor targeting which can in turn lead to more effective radiotherapy through the interaction of X-rays and GNPs. Specifically tumor size after 47 days of treatment had reduced to (769 +/- 92) mm3 compared to (1432 +/- 269) mm3 using X-rays alone and (3514 +/- 1818) mm3 without any treatment. Moreover, the mice remained healthy without statistically significant weight loss. Results of our pharmacokinetic and bio-distribution study as well as therapeutic data for PEG-Glu-GNPs in our tumor bearing animal model demonstrate that PEG-Glu-GNPs provide excellent in-vivo stability, tumor targeting function, and radiotherapeutic enhancement effects, providing useful insights for further clinical studies.

Fruit quality and bioactive compounds with antioxidant activity of tomatoes grown on-farm: comparison of organic and conventional management systems.

Replicated field trials at three matched farm pairs in southern and central Taiwan were established in October 2004 and 2005 to compare fruit quality and nutritional parameters of tomatoes grown on-farm under organic versus conventional management systems in tropical and subtropical environments. Two processing tomato varieties were evaluated using a randomized complete block design at each of the farms. Aggregation of farms by type (organic vs conventional) across two years resulted in no significant differences between organic and conventional farming systems for all tomato fruit parameters measured, including quality (pH, soluble solids, acidity, and color), content of bioactive compounds with antioxidant activity (beta-carotene, lycopene, ascorbic acid, and total phenolics), and antioxidant activity. This study indicated no consistent effect of the farming system on tomato fruit parameters. Farm management skills combined with site-specific effects contributed to high lycopene levels, and the choice of variety significantly influenced the content of bioactive compounds, particularly ascorbic acid and total phenolics.

Overexpression of Arabidopsis thaliana tryptophan synthase beta 1 (AtTSB1) in Arabidopsis and tomato confers tolerance to cadmium stress.

Tryptophan (Trp) is an essential amino acid in humans, and in plants, it plays a major role in the regulation of plant development and defence responses. However, little is known about Trp-mediated cadmium (Cd) tolerance. Gene expression analysis showed that Arabidopsis thaliana tryptophan synthase beta 1 (AtTSB1) is up-regulated in plants treated with Cd; hence, we investigated whether this gene is involved in Cd tolerance. Exogenous application of Trp to wild-type Arabidopsis enhances Cd tolerance. Cd tolerance in the Trp-overproducing mutant trp5-1 was associated with high chlorophyll levels and low lipid peroxidation, as indicated by malondialdehyde 4-hydroxyalkenal level, whereas the wild-type developed symptoms of severe chlorosis. Moreover, the Trp-auxotroph mutant trp2-1 was sensitive to Cd. CaMV 35S promoter-driven AtTSB1 enhanced Trp accumulation and improved Cd tolerance in transgenic Arabidopsis and tomato plants without increasing the level of Cd. Moreover, reverse transcription-polymerase chain reaction confirmed that enhanced level of Trp in AtTSB1 transgenic Arabidopsis plants affected the expression of AtZIP4 and AtZIP9 metal transporters, which interfered with Cd ion trafficking, a mechanism of transcriptional regulation that does not exist in wild-type plants. Overexpression of AtTSB1 in transgenic tomato also produced higher Trp synthase-beta enzyme activity than that in wild-type plants. These results implicate that Trp could be involved in Cd defence.

Activation of Helicobacter pylori inorganic pyrophosphatase and the importance of Cys16 in thermostability, enzyme activation and quaternary structure.

The inorganic pyrophosphatase from the human pathogen Helicobacter pylori (HpPPase) is a family I PPase. It is a homohexamer consisting of identical 20-kDa subunits. Hydrolysis of inorganic pyrophosphate (PP(i)) by HpPPase relied on the presence of magnesium and followed Michaelis-Menten kinetics, with k (cat) being 344 s(-1) and K (m) being 83 microM at pH 8.0, which was the optimal pH for catalysis. HpPPase was activated by both thiol and non-thiol reductants, distinct from the previously suggested inactivation/reactivation process involving formation and breakage of disulfide bonds. Substitution of Cys16 of HpPPase, which was neither located at the active site nor evolutionarily conserved, resulted in a loss of 50% activity and a reduction in sensitivity to reductants and oxidized glutathione. In addition, the C16S replacement caused a considerable disruption in thermostability, which exceeded that resulted from active-site mutations such as Y140F HpPPase and those of Escherichia coli. Although Cys16 was not located at the subunit interface of the hexameric HpPPase, sedimentation analysis results suggested that the C16S substitution destabilized HpPPase through impairing trimer-trimer interactions. This study provided the first evidences that the single cysteine residue of HpPPase was involved in enzyme activation, thermostability, and stabilization of quaternary structure.