Fine genetic mapping of RXopJ4, a bacterial spot disease resistance locus from Solanum pennellii LA716.

The RXopJ4 resistance locus from the wild accession Solanum pennellii (Sp) LA716 confers resistance to bacterial spot disease of tomato (S. lycopersicum, Sl) caused by Xanthomonas perforans (Xp). RXopJ4 resistance depends on recognition of the pathogen type III effector protein XopJ4. We used a collection of Sp introgression lines (ILs) to narrow the RXopJ4 locus to a 4.2-Mb segment on the long arm of chromosome 6, encompassed by the ILs 6-2 and 6-2-2. We then adapted or developed a collection of 14 molecular markers to map on a segregating F(2) population from a cross between the susceptible parent Sl FL8000 and the resistant parent RXopJ4 8000 OC(7). In the F(2) population, a 190-kb segment between the markers J350 and J352 cosegregated with resistance. This fine mapping will enable both the identification of candidate genes and the detection of resistant plants using cosegregating markers. The RXopJ4 resistance gene(s), in combination with other recently characterized genes and a quantitative trait locus (QTL) for bacterial spot disease resistance, will likely be an effective tool for the development of durable resistance in cultivated tomato.

Ultrastable Plasmonic Bioink for Printable Point-Of-Care Biosensors.

Point-of-care biosensors are critically important for early disease diagnosis and timely clinical intervention in resource-limited settings. The real-world application of these biosensors requires the use of stable biological reagents and cost-effective fabrication approaches. To meet these stringent requirements, we introduce a generic encapsulation strategy to realize ultrastable plasmonic bioink by encapsulating antibodies with an organosiloxane polymer through in situ polymerization. Plasmonic nanostructures serve as sensitive nanotransducers, allowing for label-free biochemical detection. The plasmonic bioink with encapsulated antibodies exhibits excellent thermal, biological, and colloidal stabilities making it compatible with printing process. As a proof-of-concept, we demonstrate the printability of the ultrastable plasmonic bioinks on different types of substrates with direct writing techniques. The organosiloxane polymer preserves the biorecognition capabilities of the biosensors under harsh conditions, including elevated temperature, exposure to chemical/biological denaturants, and ultrasonic agitation. Plasmonic biochips fabricated with the ultrastable ink exhibit superior stability compared to the biochips with unencapsulated antibodies.

A robustness check procedure for hypofractionated Gamma Knife radiosurgery.

OBJECTIVEInterfractional residual patient shifts are often observed during the delivery of hypofractionated brain radiosurgery. In this study, the authors developed a robustness treatment planning check procedure to assess the dosimetric effects of residual target shifts on hypofractionated Gamma Knife radiosurgery (GKRS).METHODSThe residual patient shifts were determined during the simulation process immediately after patient immobilization. To mimic incorporation of residual target shifts during treatment delivery, a quality assurance procedure was developed to sample and shift individual shots according to the residual uncertainties in the prescribed treatment plan. This procedure was tested and demonstrated for 10 hypofractionated GKRS cases.RESULTSThe maximum residual target shifts were less than 1 mm for the studied cases. When incorporating such shifts, the target coverage varied by 1.9% ± 2.2% (range 0.0%-7.1%) and selectivity varied by 3.6% ± 2.5% (range 1.1%-9.3%). Furthermore, when incorporating extra random shifts on the order of 0.5 mm, the target coverage decreased by as much as 7%, and nonisocentric variation in the dose distributions was noted for the studied cases.CONCLUSIONSA pretreatment robustness check procedure was developed and demonstrated for hypofractionated GKRS. Further studies are underway to implement this procedure to assess maximum tolerance levels for individual patient cases.

Fair hearing outcomes of patients recommended discharge from methadone maintenance.

A system known as fair hearings is a due process opportunity for patients who are involuntarily discharged from methadone maintenance treatment to challenge the discharge recommendation. We know very little about the processes and outcomes of fair hearings. For this study, we used a mixed methods approach to retrospectively analyze 73 fair hearing reports that were documented from a California methadone maintenance treatment program between 2000 and 2014. The aims of the study were to identify the reasons for involuntary discharge recommendation from methadone maintenance, describe the factors involved when fair hearing outcomes decided in favor of the clinic, and describe the factors involved when fair hearing outcomes decided in favor of the patient. We found that patient attendance at the fair hearing meeting was significantly related to the outcome ruling in favor of the patient. We organized the reasons for discharge recommendations into five categories: 1) suspected diversion, 2) behavioral/interpersonal, 3) repeated, unexcused absences, 4) co-occurring substance use, and 5) multiple sources of opioids. For each category, we use excerpts from fair hearing reports to provide context to the circumstances involved in an outcome favoring the patient or the clinic.

Sharpening peripheral dose gradient via beam number enhancement from patient head tilt for stereotactic brain radiosurgery.

Sharp dose fall-off is the hallmark of brain radiosurgery for the purpose of delivering high dose radiation to the target while minimizing peripheral dose to regional normal brain tissue. In this study, a technique was developed to enhance the peripheral dose gradient by magnifying the total number of beams focused toward each isocenter through pre-programmed patient head tilting. This technique was tested in clinical settings on a dedicated brain radiosurgical system (GKPFX, Gamma Knife Perfexion, Elekta Oncology) by comparing dosimetry as well as delivery efficiency for 20 radiosurgical cases previously treated with the system. The 3-fold beam number enhancement (BNE) treatment plans were found to produce nearly identical target volume coverage (absolute value < 0.5%, P > 0.2) and dose conformity (BNE CI = 1.41 ± 0.22 versus 1.41 ± 0.11, P > 0.99) as the original treatment plans. The total beam-on time for the 3-fold BNE treatment plans were also found to be comparable (<0.5 min or 2%) with those of the original treatment plans for all the cases. However, BNE treatment plans significantly improved the mean gradient index (BNE GI = 2.94 ± 0.27 versus original GI = 2.98 ± 0.28 P < 0.0001) and low-level isodose volumes, e.g. 20-50% prescribed isodose volumes, by 1.7%-3.9% (P < 0.03). With further 4-5-fold increase in the total number of beams, the absolute gradient index can decrease by as much as -0.5 in absolute value or -20% for a treatment. In conclusion, BNE via patient head tilt has been demonstrated to be a clinically suitable and efficient technique for physically sharpening the peripheral dose gradient for brain radiosurgery.

Quality assurance of stereotactic alignment and patient positioning mechanical accuracy for robotized Gamma Knife radiosurgery.

The automatic patient positioning system and its alignment is critical and specified to be less than 0.35 mm for a radiosurgical treatment with the latest robotized Gamma Knife Perfexion (GKPFX). In this study, we developed a quantitative QA procedure to verify the accuracy and robustness of such a system. In particular, we applied the test to a unit that has performed >1000 procedures at our institution. For the test, a radiochromic film was first placed inside a spherical film phantom and then irradiated with a sequence of linearly placed shots of equal collimator size (e.g. 4 mm) via the Leksell Gamma Knife Perfexion system (PFX). The shots were positioned with either equal or unequal gaps of approximately 8 mm both at center and off-center positions of the patient positioning system. Two independent methods of localizing the irradiation shot center coordinates were employed to measure the gap spacing between adjacent shots. The measured distance was then compared with the initial preset values for the test. On average, the positioning uncertainty for the PFX delivery system was found to be 0.03 ± 0.2 mm (2σ). No significant difference in the positioning uncertainty was noted among measurements in the x-, y- and z-axis orientations. In conclusion, a simple, fast, and quantitative test was developed and demonstrated for routine QA of the submillimeter PFX patient positioning system. This test also enables independent verification of any patient-specific shot positioning for a critical treatment such as a tumor in the brainstem.