Characterization and Aggressiveness of Take-All Root Rot Pathogens Isolated from Symptomatic Bermudagrass Putting Greens.

Take-all root rot is a disease of ultradwarf bermudagrass putting greens caused by Gaeumannomyces graminis (Gg), Gaeumannomyces sp. (Gx), Gaeumannomyces graminicola (Ggram), Candidacolonium cynodontis (Cc), and Magnaporthiopsis cynodontis (Mc). Many etiological and epidemiological components of this disease remain unknown. Improving pathogen identification and our understanding of the aggressiveness of these pathogens along with growth at different temperatures will advance our knowledge of disease development to optimize management strategies. Take-all root rot pathogens were isolated from symptomatic bermudagrass root and stolon pieces from 16 different golf courses. Isolates of Gg, Gx, Ggram, Cc, and Mc were used to inoculate 'Champion' bermudagrass in an in planta aggressiveness assay. Each pathogen was also evaluated at 10, 15, 20, 25, 30, and 35°C to determine growth temperature optima. Infected plant tissue was used to develop a real-time PCR high-resolution melt assay for pathogen detection. This assay was able to differentiate each pathogen directly from infected plant tissue using a single primer pair. In general, Ggram, Gg, and Gx were the most aggressive while Cc and Mc exhibited moderate aggressiveness. Pathogens were more aggressive when incubated at 30°C compared with 20°C. While they grew optimally between 24.4 and 27.8°C, pathogens exhibited limited growth at 35°C and no growth at 10°C. These data provide important information on this disease and its causal agents that may improve take-all root rot management.

Determination of commissioning criteria for multileaf-collimator, stereotactic radiosurgery treatments on Varian TrueBeam and Edge machines using a novel anthropomorphic phantom.

An anthropomorphic phantom has been developed by Varian Medical Systems for commissioning multileaf-collimator (MLC), stereotactic radiosurgery (SRS) treatments on Varian TrueBeam and Edge linear accelerators. Northwest Medical Physics Center (NMPC) has collected end-to-end data on these machines, at six independent clinical sites, to establish baseline dosimetric and geometric commissioning criteria for SRS measurements with this phantom. The Varian phantom is designed to accommodate four interchangeable target cassettes, each designed for a specific quality assurance function. End-to-end measurements utilized the phantom to verify the coincidence of treatment isocenter with a hidden target in a Winston-Lutz cassette after localization using cone-beam computed tomography (CBCT). Dose delivery to single target (2 cm) and single-isocenter, multitarget (2 and 1 cm) geometries was verified using ionization chamber and EBT3 film cassettes. A nominal dose of 16 Gy was prescribed for each plan using a site's standard beam geometry for SRS cases. Measurements were performed with three Millennium and three high-definition MLC machines at beam energies of 6-MV and 10-MV flattening-filter-free energies. Each clinical site followed a standardized procedure for phantom simulation, treatment planning, quality assurance, and treatment delivery. All treatment planning and delivery was performed using ARIA oncology information system and Eclipse treatment planning software. The isocenter measurements and irradiated film were analyzed using DoseLab quality assurance software; gamma criteria of 3%/1 mm, 3%/0.5 mm, and 2%/1 mm were applied for film analysis. Based on the data acquired in this work, the recommended commissioning criteria for end-to-end SRS measurements with the Varian phantom are as follows: coincidence of treatment isocenter and CBCT-aligned hidden target < 1 mm, agreement of measured chamber dose with calculated dose ≤ 5%, and film gamma passing > 90% for gamma criteria of 3%/1 mm after DoseLab auto-registration shifts ≤ 1 mm in any direction.

Hand size affects branching of the deep ulnar nerve and deep palmar arch.

PURPOSE: Understanding the anatomy of the deep neurovascular structures of the hand is essential in surgical planning. There is a lack of literature regarding hand size and its influence in branching variation and the distances between branches of various neurovascular structures. Our study quantifies the variation in branching distances of the deep ulnar nerve and deep palmar arch branches. METHODS: Twenty-five fresh-frozen cadaveric hands were dissected. Each branch of the deep ulnar nerve and deep palmar arch was identified. The distance from the most distal portion of the pisiform to the proximal aspect of the branch was measured. The relationship between the length of the third metacarpal and the distance of each branch from the pisiform was examined. RESULTS: There was no relationship between branching differences in the deep ulnar nerve and the length of the third metacarpal. There was a significant association between the length of the third metacarpal and the second, third, and fourth branches of the deep palmar arch (p < 0.05). CONCLUSIONS: Our study found a significant association between the branching distances of the second, third, and fourth branches of the deep palmar arch and hand size as measured by the length of the third metacarpal.

Pythium spp. Associated with Root Rot and Stunting of Winter Crops in North Carolina.

Annual double-crop rotation systems that incorporate winter wheat, clary sage, or a cover crop are common in eastern North Carolina. Stunting and root rot of clary sage (Salvia sclarea L.) reduce yields of this crop, especially in wet soils. Stunting and reduced stand establishment also afflict winter cover crops, including rye, rapeseed, and winter pea. Pythium spp. are causal agents of root rot of winter wheat in this region, but their role in root rot and stunting of other winter crops is not understood. During the growing seasons of 2018 to 2019 and 2019 to 2020, samples of clary sage, rye, rapeseed, and winter pea displaying symptoms of stunting were collected across eastern North Carolina, resulting in the recovery of 420 isolates of Pythium from the roots of all hosts. Pythium irregulare, Pythium spinosum, and the complex Pythium sp. cluster B2A were the species most frequently isolated from clary sage. P. irregulare and P. spinosum were aggressive pathogens of clary sage at 18°C and caused moderate root rot at 28°C. Koch's postulates confirmed that isolates belonging to Pythium sp. cluster B2A, Pythium sylvaticum, Pythium pachycaule, Pythium aphanidermatum, Pythium myriotylum, and Pythium oopapillum are pathogens of clary sage. P. irregulare (37% of all isolates) and members of the species complex Pythium sp. cluster B2A (28% of all isolates) constituted the majority of isolates collected from all hosts and were the species most frequently isolated from rye, rapeseed, and winter pea. In pathogenicity assays, isolates representing P. irregulare and P. spinosum caused slight to moderate root necrosis on rye, rapeseed, and winter pea. Isolates representing Pythium sp. cluster B2A caused slight to moderate root necrosis on rapeseed and clary sage, but no symptoms on rye or winter pea.

Evaluating Fungicide Selections to Manage Pythium Root Rot on Poinsettia Cultivars with Varying Levels of Partial Resistance.

Pythium aphanidermatum is the predominant species causing Pythium root rot of commercially grown poinsettia (Euphorbia pulcherrima Willd. ex Kotzch) in North Carolina. Pythium root rot is managed primarily through a combination of sanitation practices and preventative fungicide applications of mefenoxam or etridiazole. Insensitivity to mefenoxam is common but growers continue to rely on it from lack of inexpensive and efficacious alternatives. This research was conducted to identify alternative fungicides for Pythium root rot control and to evaluate their efficacy on poinsettia cultivars with varying levels of partial resistance. Greenhouse studies were conducted to assess efficacy of fungicide treatments in seven poinsettia cultivars inoculated with a mefenoxam-sensitive isolate of P. aphanidermatum. One study examined control with a single fungicide drench made at transplant and a second study examined repeat fungicide applications made throughout the experiment. Treatments containing etridiazole, mefenoxam, fenamidone, and cyazofamid provided control of Pythium root rot across all cultivars in both experiments whereas Fosetyl-al, potassium phosphite, and Trichoderma spp. failed to offer satisfactory control. Azoxystrobin, pyraclostrobin, and propamocarb reduced disease on some cultivars but failed to control Pythium root rot on highly susceptible cultivars. Four isolates of P. aphanidermatum cultured from plants growing in commercial greenhouses were evaluated for in vitro sensitivity to fungicides labeled for Pythium root rot control at four rates. Etridiazole, fosetyl-al, and potassium phosphite completely inhibited mycelial growth, whereas isolates varied in response to mefenoxam, cyazofamid, propamocarb, fenamidone, azoxystrobin, and pyraclostrobin in vitro. Twenty-one additional isolates then were evaluated at label rates of these fungicides. Seven isolates were insensitive to label rates of all three quinone outside inhibitors and one isolate was insensitive to the quinone outside inhibitors and mefenoxam. These results provide guidelines for selecting fungicides to maximize control of Pythium root rot on poinsettia cultivars.

Pythium spp. Associated with Root Rot and Stunting of Winter Wheat in North Carolina.

In eastern North Carolina, mild to severe stunting and root rot have reduced yields of winter wheat, especially during years with abundant rainfall. Causal agents of root rot of wheat in this region were previously identified as Pythium irregulare, P. vanterpoolii, and P. spinosum. To investigate species prevalence, 114 isolates of Pythium were obtained from symptomatic wheat plants collected in eight counties. Twelve species were recovered, with P. irregulare (32%), P. vanterpoolii (17%), and P. spinosum (16%) the most common. Pathogenicity screens were performed with selected isolates of each species, and slight to severe necrosis of young roots was observed. The aggressiveness of five isolates each of P. irregulare, P. vanterpoolii, and P. spinosum was compared on a single cultivar of wheat at 14°C, and very aggressive isolates were found within all species. In vitro growth of these isolates was measured at 14 and 20°C, and all isolates grew faster at the warmer temperature. The effects of varying temperatures and rates of nitrogen on root rot caused by Pythium spp. alone or in combination were investigated. All inoculation treatments caused severe root rot under all conditions tested, and disease was more severe at 12 and 14°C compared with 18 and 20°C; however, there was no effect of nitrogen application.

Genome Resources for Seven Fungal Isolates That Cause Dollar Spot Disease in Turfgrass, Including Clarireedia jacksonii and C. monteithiana.

Fungi in the genus Clarireedia are widespread and destructive pathogens of grasses worldwide, and are best known as the causal agents of dollar spot disease in turfgrass. Here, we report genome assemblies of seven Clarireedia isolates, including ex-types of the two most widespread species, Clarireedia jacksonii and C. monteithiana. These datasets provide a valuable resource for ongoing studies of the dollar spot pathogens that include population diversity, host-pathogen interactions, marker development, and disease control.

Histological Assessment of Wallerian Degeneration of the Rat Tibial Nerve Following Crush and Transection Injuries.

BACKGROUND: Wallerian degeneration (WD) following peripheral nerve injury (PNI) is an area of growing focus for pharmacological developments. Clinically, WD presents challenges in achieving full functional recovery following PNI, as prolonged denervation of distal tissues for an extended period of time can irreversibly destabilize sensory and motor targets with secondary tissue atrophy. Our objective is to improve upon histological assessments of WD. METHODS: Conventional methods utilize a qualitative system simply describing the presence or absence of WD in nerve fibers. We propose a three-category assessment that allows more quantification: A fibers appear normal, B fibers have moderate WD (altered axoplasm), and C fibers have extensive WD (myelin figures). Analysis was by light microscopy (LM) on semithin sections stained with toluidine blue in three rat tibial nerve lesion models (crush, partial transection, and complete transection) at 5 days postop and 5 mm distal to the injury site. The LM criteria were verified at the ultrastructural level. This early outcome measure was compared with the loss of extensor postural thrust and the absence of muscle atrophy. RESULTS: The results showed good to excellent internal consistency among counters, demonstrating a significant difference between the crush and transection lesion models. A significant decrease in fiber density in the injured nerves due to inflammation/edema was observed. The growth cones of regenerating axons were evident in the crush lesion group. CONCLUSION: The ABC method of histological assessment is a consistent and reliable method that will be useful to quantify the effects of different interventions on the WD process.

Mutant SOD1 prevents normal functional recovery through enhanced glial activation and loss of motor neuron innervation after peripheral nerve injury.

BACKGROUND: Amyotrophic lateral sclerosis (ALS) is poorly understood with no effective therapeutics. One long entertained observation is that ALS may be precipitated focally by nerve injury. Many patients with ALS are athletes or veterans, and some have suffered nerve injuries at the site where ALS first presents. Here we explore how a genetic SOD1 mutation alters the inflammatory response and affects functional recovery after an environmental insult in a rat model. METHODS: Unilateral sciatic nerve crush injuries were performed in SOD1 G93A rats prior to disease symptom onset. Functional recovery was compared between injured wild-type littermates and uninjured SOD1 rats. Spinal cord tissues were analyzed quantitatively for SOD1 expression, glial reactivity, and motor neuron synaptic integrity. RESULTS: Injured SOD1 rats failed to recover and showed hastened functional decline with decreased survival. Injury induced extracellular SOD1 expression was associated with heightened, prolonged microglial and astrogial activation in the ventral horn. This inflammatory response spread to uninjured motor neuron pools and was associated with increased motor neuron synaptic loss. DISCUSSION: This study identified a relationship between genetic and environmental contributions to disease onset and progression in ALS. The findings suggest that injury induced SOD1 mutant protein induces a heightened and prolonged inflammatory response resulting in motor neuron degeneration through synaptic loss. Once initiated, this process spreads to adjacent motor neurons leading to contiguous spread of the disease. Treatments that suppress this heightened glial response could slow disease progression in ALS patients with focal sites of disease onset. SIGNIFICANCE STATEMENT: The contribution of environmental factors such as peripheral nerve insults in ALS is not well understood. Here we examined the effect of a single sciatic nerve injury in SOD1 (G93A) rats to explore the contribution of this environmental insult on disease onset and progression. After the injury, SOD1 animals failed to recover and had a more rapid functional decline. Histopathologically, SOD1 animals had heightened SOD1 expression, microglial and astroglial responses, and a reduction of motor neuron innervation. Taken together, these results provide a plausible mechanism of how the SOD1 mutated protein promotes an abnormal response to injury that leads to neurodegenerative changes in an ALS model that is amenable to therapeutic testing.

Identification and Pathogenicity of Bacteria Associated with Etiolation and Decline of Creeping Bentgrass Golf Course Putting Greens.

Bacterial etiolation and decline has developed into a widespread issue with creeping bentgrass (CBG) (Agrostis stolonifera) putting green turf. The condition is characterized by an abnormal elongation of turfgrass stems and leaves that in rare cases progresses into a rapid and widespread necrosis and decline. Recent reports have cited bacteria, Acidovorax avenae and Xanthomonas translucens, as causal agents; however, few cases exist where either bacterium were isolated in conjunction with turf exhibiting bacterial disease symptoms. From 2010 to 2014, turfgrass from 62 locations submitted to the NC State Turf Diagnostic Clinic exhibiting bacterial etiolation and/or decline symptoms were sampled for the presence of bacterial pathogens. Isolated bacteria were identified using rRNA sequencing of the 16S subunit and internal transcribed spacer region (16S-23S or ITS). Results showed diverse bacteria isolated from symptomatic turf and A. avenae and X. translucens were only isolated in 26% of samples. Frequently isolated bacterial species were examined for pathogenicity to 4-week-old 'G2' CBG seedlings and 8-week-old 'A-1' CBG turfgrass stands in the greenhouse. While results confirmed pathogenicity of A. avenae and X. translucens, Pantoea ananatis was also shown to infect CBG turf; although pathogenicity varied among isolated strains. These results illustrate that multiple bacteria are associated with bacterial disease and shed new light on culturable bacteria living in CBG turfgrass putting greens. Future research to evaluate additional microorganisms (i.e., bacteria and fungi) could provide new information on host-microbe interactions and possibly develop ideas for management tactics to reduce turfgrass pests.

Brachypodium: A Potential Model Host for Fungal Pathogens of Turfgrasses.

Brachypodium distachyon is a C3 grass that is an attractive model host system for studying pathogenicity of major turfgrass pathogens due to its genetic similarity to many cool-season turfgrasses. Infection assays with two or more isolates of the casual agents of dollar spot, brown patch, and Microdochium patch resulted in compatible interactions with B. distachyon inbred line Bd21-3. The symptoms produced by these pathogens on Bd21-3 closely resembled those observed on the natural turfgrass host (creeping bentgrass), demonstrating that B. distachyon is susceptible to the fungal pathogens that cause dollar spot, brown patch, and Microdochium patch on turfgrasses. The interaction between Sclerotinia homoeocarpa isolates and Brachypodium ecotypes was also investigated. Interestingly, differential responses of these ecotypes to S. homoeocarpa isolates was found, particularly when comparing B. distachyon to B. hybridum ecotypes. Taken together, these findings demonstrate that B. distachyon can be used as a model host system for these turfgrass diseases and leveraged for studies of molecular mechanisms contributing to host resistance.

Plant Growth Regulator Effects on Bacterial Etiolation of Creeping Bentgrass Putting Green Turf Caused by Acidovorax avenae.

Bacterial etiolation, caused by Acidovorax avenae, is a widespread problem in creeping bentgrass putting green turf. The symptoms normally appear as abnormally elongated turfgrass stems and leaves. Observations at multiple field sites suggest the involvement of plant growth regulators (i.e., GA-biosynthesis inhibitors) commonly applied to turf, alluding to a phytohormone imbalance caused by the bacterium. A 2-year field study examined the effects of trinexapac-ethyl, flurprimidol, and paclobutrazol on bacterial etiolation severity caused by A. avenae. Trinexapac-ethyl applied at 0.05 kg a.i. ha-1 every 7 days and 0.10 kg ha-1 every 14 days increased etiolation compared with all other treatments in both years. Flurprimidol and paclobutrazol were not different from the control but high-rate applications caused phytotoxicity that lowered turf quality early in 2014. When the etiolated turfgrass was removed with mowing, turfgrass treated with trinexapac-ethyl exhibited the highest turfgrass quality on most rating dates. Results from this work illustrate that using plant growth regulator materials with different modes of action is a solution to managing creeping bentgrass growth while limiting the potential for bacterial etiolation outbreaks.

Long-term effects of simulated childbirth injury on function and innervation of the urethra.

AIMS: Pudendal nerve and external urethral sphincter (EUS) injury during vaginal delivery are risk factors for stress urinary incontinence (SUI). Although most patients with short-term postpartum SUI regain continence within 1 year, they have a higher predisposition to develop recurrent SUI years later, suggesting a possible mechanistic relationship. In contrast, animal models generally recover spontaneously and have not been studied much in the long term. The aim of this study was to investigate the long-term effects of simulated childbirth injury in rats. METHODS: Thirty-four Sprague-Dawley female rats underwent sham injury or pudendal nerve crush and vaginal distension (PNC + VD), a simulated childbirth injury. Nine weeks later, leak point pressure (LPP) and EUS electromyography (EMG) were recorded simultaneously. The pudendal nerve was harvested for histological analysis. EUS neuromuscular junctions (NMJs) and their innervation were qualitatively assessed using immunofluorescence. A t-test was used to compare quantitative outcomes between groups, with P < 0.05 indicating a significant difference. RESULTS: There was no significant difference in LPP or EUS EMG amplitude or firing rate between the two groups. Nonetheless after PNC + VD, NMJs in the EUS were diffuse and were innervated by tortuous and multiple axons, demonstrating that reinnervation of the EUS was still in progress. CONCLUSIONS: Although continence function recovered 9 weeks after simulated childbirth injury, innervation of EUS was not complete at this time point, suggestive of persistent neurogenic deficiency which when compounded by the effects of aging may lead to a delayed recurrence of SUI in this animal model with increased age.

Molecular Characterization and Phylogenetic Relationships of Plant-Parasitic Nematodes Associated with Turfgrasses in North Carolina and South Carolina, United States.

The near-full-length 18S ribosomal DNA (rDNA) gene and internal transcribed spacer 1 region were amplified and sequenced from 52 nematode populations belonging to 28 representative species in 13 families recovered from turfgrasses in North Carolina (38 populations) and South Carolina (14 populations). This study also included 13 nematode populations from eight other plant hosts from North Carolina for comparison. Nematodes were molecularly characterized and the phylogenetic relationships were explored based on 18S rDNA sequences. Phylogenetic analysis using Bayesian inference was performed using five groups of the plant-parasitic nematode populations Tylenchids, Criconematids, Longidorids, Xiphinematids, and Trichodorids. The 65 nematode populations were clustered correspondingly within appropriate positions of 13 families, including Belonolaimidae, Caloosiidae, Criconematidae, Dolichodoridae, Hemicycliophoridae, Hoplolaimidae, Heteroderidae, Longidoridae, Meloidogynidae, Paratylenchidae, Pratylenchidae, Telotylenchidae, and Trichodoridae. This study confirms previous morphological-based identification of the plant-parasitic nematode species found in turfgrasses and provides a framework for future studies of plant-parasitic nematodes associated with turfgrasses based upon DNA sequences and phylogenetic relationships.

Block Scheduling for LARC in a Family Medicine Residency Program.

BACKGROUND AND OBJECTIVES: Only 20% of family physicians report providing long-acting reversible contraception (LARC). Clinician-related barriers include confidence and comfort with LARC counseling and insertion/removal, and limited availability and uptake. Training during residency may address barriers and increase access/availability of LARC to support reproductive autonomy. We sought to determine the impact of block scheduling LARC clinics on resident comfort and confidence with LARC counseling and insertion/removal. METHODS: LARC block schedules were established in a Midwest family medicine residency's primary clinic (FMC) and in a federally qualified health center rotation clinic. Baseline and end-of-study surveys, compared by Mann-Whitney U and Wilcoxon signed-rank tests, were used to assess comfort and confidence with counseling and inserting LARC. The number of LARC devices placed at the FMC were collected for the intervention year and the year prior. RESULTS: Twenty of 30 residents completed the baseline survey; 13 completed the end-of-study survey. At the group and individual levels, comfort increased for counseling on Levonorgestrel (LNG) intrauterine devices (IUDs) and for inserting implants and LNG IUDs. Individual comfort increased for copper IUDs. Resident willingness to recommend LARC increased, and more devices were placed during the intervention year than the year prior in the FMC (all: P<.05). CONCLUSIONS: Block scheduling of LARC clinics was associated with increased residents' comfort and confidence with counseling and placement of implants (LNG IUDs) and with an increase in LARCs placed at one clinic. Changes to scheduling may be an effective educational strategy that may increase access/availability to LARC.

Pudendal nerve stretch reduces external urethral sphincter activity in rats.

PURPOSE: Most animal models of stress urinary incontinence simulate maternal injuries of childbirth since delivery is a major risk factor but they do not reproduce the nerve stretch known to occur during human childbirth. We hypothesized that pudendal nerve stretch produces reversible dysfunction of the external urethral sphincter. MATERIALS AND METHODS: Female virgin Sprague-Dawley® rats were anesthetized with urethane. Bilateral pudendal nerve stretch or sham injury was performed for 5 minutes. External urethral sphincter electromyography and leak point pressure were recorded immediately before and after, and 10, 30, 60 and 120 minutes after pudendal nerve stretch. Post-pudendal nerve stretch results were compared to prestretch values and to values in sham injured animals. The pudendal nerves underwent qualitative histological assessment. The nucleus of Onuf was evaluated by immunohistochemistry and polymerase chain reaction for ß-APP and c-Fos expression as markers of neuronal activity and injury. RESULTS: A total of 14 rats underwent bilateral pudendal nerve stretch (9) or sham injury (5). Each nerve was stretched a mean ± SEM of 74% ± 18% on the left side and 63% ± 13% on the right side. Electromyography amplitude decreased significantly immediately after stretch compared to before stretch and after sham injury (p = 0.003) but it recovered by 30 minutes after stretch. There was no significant change in leak point pressure at any time. Two hours after injury histology showed occasional neuronal degeneration. ß-APP and c-Fos expression was similar in the 2 groups. CONCLUSIONS: Acute pudendal nerve stretch produces reversible electrophysiological dysfunction but without leak point pressure impairment. Pudendal nerve stretch shows promise in modeling injury. It should be tested as part of a multi-injury, chronic, physiological model of human childbirth injury.

Characteristics of optically stimulated luminescence dosimeters in the spread-out Bragg peak region of clinical proton beams.

PURPOSE: Optically stimulated luminescent detectors (OSLDs) have a number of advantages in radiation dosimetry making them excellent dosimeters for quality assurance and patient dose verification. Although the dosimeters have been investigated in several modalities, relatively little work has been done in examining the dosimeters for use in clinical proton beams. This study examined a number of characteristics of the response of the dosimeters in the spread-out Bragg peak (SOBP) region of clinical proton beams. METHODS: Optically stimulated luminescence (OSL) dosimeters from Landauer, Inc., specifically the nanoDot dosimeter, were investigated. These dosimeters were placed in a special phantom with a recess to fit the dosimeters without an air gap. Beams with nominal energies of 160, 200, and 250 MeV were used in the passively-scattered proton beam at the MD Anderson Cancer Center Proton Therapy Center. Dosimetric properties including linearity, field size dependence, energy dependence, residual signal as a function of cumulative dose, and postirradiation fading were investigated by taking measurements at the center of SOBPs. RESULTS: The dosimeters showed 1% supralinearity at 200 cGy and 5% supralinearity at 1000 cGy. No noticeable field size dependence of the detector was found for field sizes from 2 × 2 cm(2) to 18 × 18 cm(2). Residual signal as a function of cumulative dose showed a small increase for measurements up to 1000 cGy. Readout signal depletion of the dosimeters after consecutive readings showed a slightly larger depletion in protons for doses up to 500 cGy but not by a clinically significant amount. Within the center of various SOBP widths and proton energies the variation in response was less than 2%. An average beam quality factor of 1.089 with experimental standard deviation of 0.007 was determined and applied to the data such that the results were within 1.2% of ion chamber data. CONCLUSIONS: The nanoDot OSL dosimeter characteristics were studied in the SOBP region of clinical proton beams. To achieve accurate dosimetric readings, corrections to the dosimeter response were applied. Corrections tended to be minimal or broadly consistent. The nanoDot OSLD was found to be an acceptable dosimeter for measurement in the SOBP region for a range of clinical proton beams.

Safety of local anesthetics administered intrathecally in diabetic rats.

OBJECTIVES: Although retrospective studies show the risk of neurological complications after spinal anesthesia with local anesthetics is small in diabetic patients, there is still concern about the safety of different local anesthetics in diabetics undergoing neuroaxial anesthesia. We examined block duration and histology of spinal cord and roots with intrathecal local anesthetics in diabetic rats. METHODS: Rats were made diabetic with streptozotocin injection. Blood glucose levels confirmed diabetes, and diabetic neuropathy was verified by tactile hypersensitivity. Diabetic and nondiabetic rats received four intrathecal injections at 3-4-day intervals of 0.75% bupivacaine, with/without 100 µg/mL epinephrine; and 2% lidocaine, with/without 100 µg/mL epinephrine, and duration of sensory (pinprick) and motor (toe-spreading reflex) response inhibition recorded. Four days after the last drug injection, histology of spinal cord and roots was performed. RESULTS: All streptozotocin rats became diabetic and had pronounced tactile allodynia. Intrathecal injection of local anesthetics showed longer duration of sensory and motor block in diabetic rats vs nondiabetics. Histology of caudal spinal cord showed no difference in neuropathology between diabetic and nondiabetic rats. Necrotic neurons were not seen in either group, and white-matter pathology involved less than 0.1% of fibers. Histology of the spinal roots also showed no difference in pathology between groups, and pathology involved less than 0.1% of fibers. Neuron somas in the dorsal root ganglia were normal. CONCLUSIONS: Duration of local anesthetic spinal block is longer in diabetic animals than in nondiabetics. However, there was no increased pathology of spinal cord, roots, or dorsal root ganglia.

Compound Motor Action Potentials During a Modest Nerve Crush.

Nerve crush injury results in axonotmesis, characterized by disruption of axons and their myelin sheaths with relative sparing of the nerve's connective tissue. Despite the widespread use of crush injury models, no standardized method for producing these lesions has been established. We characterize a crush model in which a narrow forceps is used to induce a modest and controlled compressive injury. The instantaneous compound motor action potential (CMAP) is monitored in situ and in real-time, allowing the characterization of neuromuscular response during and after injury. The tibial nerves of 11 anesthetized rats were surgically isolated. After the placement of electrodes, CMAPs were elicited and registered using a modular-data-acquisition system. Dumont-#5 micro-forceps were instrumented with a force transducer allowing force measurement via a digital sensor. Baseline CMAPs were recorded prior to crush and continued for the duration of the experiment. Nerve crushing commenced by gradually increasing the force applied to the forceps. At a target decrease in CMAP amplitude of 70%-90%, crushing was halted. CMAPs were continually recorded for 5-20 min after the termination of the crushing event. Nerves were then fixed for histological assessment. The following post-crush mean values from 19 trials were reported: peak CMAP amplitude decreased by 81.6% from baseline, duration of crush was 17 sec, rate of applied force was 0.03 N/sec, and maximal applied force was 0.5 N. A variety of agonal phenomena were evident post-lesion. Following the initial decrease in CMAP, 8 of 19 trials demonstrated a partial and transient recovery, followed by a further decline. Thirteen trials exhibited a CMAP amplitude near zero at the end of the recording. Twelve trials demonstrated a superimposed EMG background response during and after the crush event, with disappearance occurring within 4-8 min. Qualitative histology assessment at the lesion site demonstrated a correspondence between CMAP response and partial sparing of nerve fibers. By using a targeted decline in CMAP amplitude as the endpoint, researchers may be able to produce controlled, brief, and reproducible crush injuries. This model can also be used to test interventions aimed at enhancing subsequent regeneration and behavioral recovery.

Angular dependence of the nanoDot OSL dosimeter.

PURPOSE: Optically stimulated luminescent detectors (OSLDs) are quickly gaining popularity as passive dosimeters, with applications in medicine for linac output calibration verification, brachytherapy source verification, treatment plan quality assurance, and clinical dose measurements. With such wide applications, these dosimeters must be characterized for numerous factors affecting their response. The most abundant commercial OSLD is the InLight/OSL system from Landauer, Inc. The purpose of this study was to examine the angular dependence of the nanoDot dosimeter, which is part of the InLight system. METHODS: Relative dosimeter response data were taken at several angles in 6 and 18 MV photon beams, as well as a clinical proton beam. These measurements were done within a phantom at a depth beyond the build-up region. To verify the observed angular dependence, additional measurements were conducted as well as Monte Carlo simulations in MCNPX. RESULTS: When irradiated with the incident photon beams parallel to the plane of the dosimeter, the nanoDot response was 4% lower at 6 MV and 3% lower at 18 MV than the response when irradiated with the incident beam normal to the plane of the dosimeter. Monte Carlo simulations at 6 MV showed similar results to the experimental values. Examination of the results in Monte Carlo suggests the cause as partial volume irradiation. In a clinical proton beam, no angular dependence was found. CONCLUSIONS: A nontrivial angular response of this OSLD was observed in photon beams. This factor may need to be accounted for when evaluating doses from photon beams incident from a variety of directions.