Dosimetric and biologic intercomparison between electron and proton FLASH beams.

BACKGROUND AND PURPOSE: The FLASH effect has been validated in different preclinical experiments with electrons (eFLASH) and protons (pFLASH) operating at an average dose rate above 40 Gy/s. However, no systematic intercomparison of the FLASH effect produced by eFLASHvs. pFLASH has yet been performed and constitutes the aim of the present study. MATERIALS AND METHODS: The electron eRT6/Oriatron/CHUV/5.5 MeV and proton Gantry1/PSI/170 MeV were used to deliver conventional (0.1 Gy/s eCONV and pCONV) and FLASH (≥110 Gy/s eFLASH and pFLASH) dose rates. Protons were delivered in transmission. Dosimetric and biologic intercomparisons were performed using previously validated dosimetric approaches and experimental murine models. RESULTS: The difference between the average absorbed dose measured at Gantry 1 with PSI reference dosimeters and with CHUV/IRA dosimeters was -1.9 % (0.1 Gy/s) and + 2.5 % (110 Gy/s). The neurocognitive capacity of eFLASH and pFLASH irradiated mice was indistinguishable from the control, while both eCONV and pCONV irradiated cohorts showed cognitive decrements. Complete tumor response was obtained after an ablative dose of 20 Gy delivered with the two beams at CONV and FLASH dose rates. Tumor rejection upon rechallenge indicates that anti-tumor immunity was activated independently of the beam-type and the dose-rate. CONCLUSION: Despite major differences in the temporal microstructure of proton and electron beams, this study shows that dosimetric standards can be established. Normal brain protection and tumor control were produced by the two beams. More specifically, normal brain protection was achieved when a single dose of 10 Gy was delivered in 90 ms or less, suggesting that the most important physical parameter driving the FLASH sparing effect might be the mean dose rate. In addition, a systemic anti-tumor immunological memory response was observed in mice exposed to high ablative dose of electron and proton delivered at CONV and FLASH dose rate.

Dosimetric and biologic intercomparison between electron and proton FLASH beams.

Background and purpose: The FLASH effect has been validated in different preclinical experiments with electrons (eFLASH) and protons (pFLASH) operating at a mean dose rate above 40 Gy/s. However, no systematic intercomparison of the FLASH effect produced by e vs. pFLASH has yet been performed and constitutes the aim of the present study. Materials and methods: The electron eRT6/Oriatron/CHUV/5.5 MeV and proton Gantry1/PSI/170 MeV were used to deliver conventional (0.1 Gy/s eCONV and pCONV) and FLASH (≥100 Gy/s eFLASH and pFLASH) irradiation. Protons were delivered in transmission. Dosimetric and biologic intercomparisons were performed with previously validated models. Results: Doses measured at Gantry1 were in agreement (± 2.5%) with reference dosimeters calibrated at CHUV/IRA. The neurocognitive capacity of e and pFLASH irradiated mice was indistinguishable from the control while both e and pCONV irradiated cohorts showed cognitive decrements. Complete tumor response was obtained with the two beams and was similar between e and pFLASH vs. e and pCONV. Tumor rejection was similar indicating that T-cell memory response is beam-type and dose-rate independent. Conclusion: Despite major differences in the temporal microstructure, this study shows that dosimetric standards can be established. The sparing of brain function and tumor control produced by the two beams were similar, suggesting that the most important physical parameter driving the FLASH effect is the overall time of exposure which should be in the range of hundreds of milliseconds for WBI in mice. In addition, we observed that immunological memory response is similar between electron and proton beams and is independent off the dose rate.

Adolescent and adult differences in major depression symptom profiles.

BACKGROUND: Depression is the leading global cause of disability and often begins in adolescence. The genetic architecture and treatment response profiles for adults and adolescents differ even though identical criteria are used to diagnose depression across different age groups. There is no clear consensus on how these groups differ in their symptom profiles. METHODS: Using data from a two-generation family study, we compared the presentation of DSM-IV depressive symptoms in adolescents and adults with MDD (Major Depressive Disorder). We also compared DSM-IV depressive symptom counts using latent class analysis. RESULTS: Vegetative symptoms (appetite and weight change, loss of energy and insomnia) were more common in adolescent MDD than adult MDD. Anhedonia/loss of interest and concentration problems were more common in adults with MDD. When using latent class analysis to look at depressive symptoms, a vegetative symptom profile was also seen in adolescent depression only. LIMITATIONS: Adults and adolescents were recruited in different ways. Adolescent cases were more likely to be first-onset while adult cases were recurrences. It was not possible to examine how recurrence affected adolescent depression symptom profiles. CONCLUSION: Differences in how depression presents in adolescents and adults may be consistent with different pathophysiological mechanisms. For adolescents, we found that vegetative/physical disturbances were common (loss of energy, changes in weight, appetite and sleep changes). For adults, anhedonia/loss of interest and concentration difficulties were more common.

MRI-guidance for motion management in external beam radiotherapy: current status and future challenges.

High precision conformal radiotherapy requires sophisticated imaging techniques to aid in target localisation for planning and treatment, particularly when organ motion due to respiration is involved. X-ray based imaging is a well-established standard for radiotherapy treatments. Over the last few years, the ability of magnetic resonance imaging (MRI) to provide radiation-free images with high-resolution and superb soft tissue contrast has highlighted the potential of this imaging modality for radiotherapy treatment planning and motion management. In addition, these advantageous properties motivated several recent developments towards combined MRI radiation therapy treatment units, enabling in-room MRI-guidance and treatment adaptation. The aim of this review is to provide an overview of the state-of-the-art in MRI-based image guidance for organ motion management in external beam radiotherapy. Methodological aspects of MRI for organ motion management are reviewed and their application in treatment planning, in-room guidance and adaptive radiotherapy described. Finally, a roadmap for an optimal use of MRI-guidance is highlighted and future challenges are discussed.

Late outcome of reoperative coronary revascularization on the beating heart.

BACKGROUND: Reoperative (redo) coronary artery bypass grafting (CABG) is associated with a higher morbidity and mortality than first-time CABG. An off-cardiopulmonary bypass (off-pump) approach to redo CABG, however, may potentially benefit redo patients. The aim of the present report is to describe the early and long-term clinical outcome of patients who underwent off-pump redo CABG between July 1985 and January 1999 in our institution. METHODS: Redo patients (n = 138) represented 13% of patients who had off-pump CABG during the period of study (n = 1072). Mean patient age was 63 +/- 12 years, and 67% were men. Surgical approaches included median sternotomy (n = 93, 67%), anterior (n = 20, 15%) and lateral (n = 25, 18%) minimally invasive direct coronary artery bypass (MIDCAB). RESULTS: Operative mortality was 2% (n = 3). Target lesion re-intervention was 6% (n = 9) Actuarial survival at a mean period of follow-up of 2.5 +/- 1 year (range: 1 month to 11 years) was 83%. Event-free survival (freedom from death, myocardial infarction, and repeat intervention) was 67%. Overall cardiac-related mortality was 10% (n = 14). CONCLUSION: Off-pump redo CABG can be safely performed with a relatively low mortality rate and a low rate of target lesion revascularization.

The diageotropica mutation alters auxin induction of a subset of the Aux/IAA gene family in tomato.

The diageotropica (dgt) mutation has been proposed to affect either auxin perception or responsiveness in tomato plants. It has previously been demonstrated that the expression of one member of the Aux/IAA family of auxin-regulated genes is reduced in dgt plants. Here, we report the cloning of ten new members of the tomato Aux/IAA family by PCR amplification based on conserved protein domains. All of the gene family members except one (LelAA7) are expressed in etiolated tomato seedlings, although they demonstrate tissue specificity (e.g. increased expression in hypocotyls vs. roots) within the seedling. The wild-type auxin-response characteristics of the expression of these tomato LelAA genes are similar to those previously described for Aux/IAA family members in Arabidopsis. In dgt seedlings, auxin stimulation of gene expression was reduced in only a subset of LelAA genes (LelAA5, 8, 10, and 11), with the greatest reduction associated with those genes with the strongest wild-type response to auxin. The remaining LelAA genes tested exhibited essentially the same induction levels in response to the hormone in both dgt and wild-type hypocotyls. These results confirm that dgt plants can perceive auxin and suggest that a specific step in early auxin signal transduction is disrupted by the dgt mutation.

The auxin-resistant diageotropica mutant of tomato responds to gravity via an auxin-mediated pathway.

Hypocotyls of the diageotropica (dgt) mutant of tomato (Lycopersicon esculentum Mill.) do not elongate in response to exogenous auxin, but can respond to gravity. This appears paradoxical in light of the Cholodny-Went hypothesis, which states that shoot gravicurvature results from asymmetric stimulation of elongation by auxin. While light-grown dgt seedlings can achieve correct gravitropic reorientation, the response is slow compared to wild-type seedlings. The sensitivity of dgt seedlings to inhibition of gravicurvature by immersion in auxin or auxin-transport inhibitors is similar to that of wild-type plants, indicating that both an auxin gradient and auxin transport are required for the gravitropic response and that auxin uptake, efflux, and at least one auxin receptor are functional in dgt. Furthermore, dgt gravicurvature is the result of asymmetrically increased elongation as would be expected for an auxin-mediated response. Our results suggest differences between elongation in response to exogenous auxin (absent in dgt) and elongation in response to gravistimulation (present but attenuated in dgt) and confirm the presence of two phases during the gravitropic response, both of which are dependent on functional auxin transport.

Sports injuries: An important cause of morbidity in urban youth. District of Columbia Child/Adolescent Injury Research Network.

INTRODUCTION: Sports injuries account for substantial morbidity and medical cost. To direct intervention, a population-based study of the causes and types of sports injuries was undertaken. METHOD: An injury surveillance system was established at all trauma center hospitals that treat residents 10 to 19 years old in the District of Columbia and the Chief Medical Examiner's Office. Medical record abstractions were completed for those seen in an emergency department, admitted to the hospital, or who died from injury June 1996 through June 1998. FINDINGS: Seventeen percent (n = 2563) of all injuries occurred while participating in 1 of 6 sports (baseball/softball, basketball, biking, football, skating, and soccer) resulting in an event-based injury rate of 25.0 per 1000 adolescents or 25.0/1000 population year. Rates were higher in males for all sports. The most common mechanisms were falls (E880-888) and being struck by or against objects (E916-918). Hospitalization was required in 2% of visits and there were no deaths. Of those requiring hospitalization, 51% involved other persons, 12% were equipment-related, and 8% involved poor field/surface conditions. Of all baseball injuries, 55% involved ball or bat impact often of the head. Basketball injuries included several injuries from striking against the basketball pole or rim or being struck by a falling pole or backboard. Biking injuries requiring admission included 2 straddle injuries onto the bike center bar and collision with motor vehicles. Of all football injuries, 48 (7%) involved being struck by an opponent's helmet and 63 (9%) involved inappropriate field conditions including falls on or against concrete, glass, or fixed objects. In soccer there were 4 goal post injuries and a large proportion of intracranial injuries. There were 51 probable or clear assaults during sports and an additional 30 to 41 injuries from baseball bat assaults. CONCLUSIONS: Many sports including noncontact sports involved injuries of the head suggesting the need for improved head protection. Injuries involving collisions with others and assaults point to the need for supervision and enforcement of safety rules. The 16% of sports injury visits and 20% of hospitalizations related to equipment and environmental factors suggest that at least this proportion of injury may be amenable to preventive strategies. Design change may be warranted for prevention of equipment-related injuries. The many injuries involving inappropriate sports settings suggest the need for and use of available and safe locations for sports.

Injury surveillance in a pediatric emergency department.

In this study we have tried to determine physician success in the collection of injury data during the emergency department visit. Prospective data were collected from all children between the ages of 0 to 18 treated for an injury. Data were collected at the time of the visit and by chart review the next day. At an urban, university-affiliated, children's hospital, data were collected on 2,156 injured children. Fifty-one percent of the data forms were completed by the treating physician. Physician completion rate was lower on the weekends (46%) than on weekdays (52%, P = .02). The most common mechanisms of injury were falls (34%), motor-vehicle crashes or pedestrians struck (13%), and nonintentional struck by blunt object (12%). The most common mechanism of injury in all age groups was falls. Our results demonstrate that emergency physicians are not successful data collectors. However, when physician data collection is combined with next-day review of patient records, virtually 100% of patients are captured. Active emergency department data collection is important because in contrast to studies which use hospital discharge and mortality data, we found that overall falls account for more injuries presenting to the ED than transportation-related causes. An active surveillance system in emergency departments that does not require extra work on the part of the treating physician would be ideal and may give a more comprehensive description of the scope of the injury problem.

High-resolution mapping and genetic characterization of the Lazy-2 gravitropic mutant of tomato.

Mutation of the Lazy-2 (Lz-2) gene in tomato (Lycopersicon esculentum mill.) produces a phytochrome-dependent reversal of shoot gravitropism, providing a unique genetic resource for investigating how signals from light modulate gravitropism. We mapped the Lz-2 gene using RFLPs and a PCR-based technique to assess the feasibility of positional cloning. Analysis of a 1338 plant backcross population between L. esculentum and L. pennellii placed Lz-2 within a 1.2 cM interval on chromosome 5, 0.4 cM from TG504-CT201A interval. The inabililty to resolve these markers indicates that Lz-2 resides in a centromeric region in which recombination is highly suppressed. Lazy-2 is tightly linked to but does not encode the gene for ACC4, an enzyme involved in ethylene biosynthesis. We also observed that Lz-2 is partially dominant under certain conditions and stages of development.

Ethylene plays multiple nonprimary roles in modulating the gravitropic response in tomato.

Ethylene is known to interact with auxin in regulating stem growth, and yet evidence for the role of ethylene in tropic responses is contradictory. Our analysis of four mutants of tomato (Lycopersicon esculentum) altered in their response to gravity, auxin, and/or ethylene revealed concentration-dependent modulation of shoot gravitropism by ethylene. Ethylene inhibitors reduce wild-type gravicurvature, and extremely low (0.0005-0.001 microliter L-1) ethylene concentrations can restore the reduced gravitropic response of the auxin-resistant dgt (diageotropica) mutant to wild-type levels. Slightly higher concentrations of ethylene inhibit the gravitropic response of all but the ethylene-insensitive nr (never-ripe) mutant. The gravitropic responses of nr and the constitutive-response mutant epi (epinastic) are slightly and significantly delayed, respectively, but otherwise normal. The reversal of shoot gravicurvature by red light in the lz-2 (lazy-2) mutant is not affected by ethylene. Taken together, these data indicate that, although ethylene does not play a primary role in the gravitropic response of tomato, low levels of ethylene are necessary for a full gravitropic response, and moderate levels of the hormone specifically inhibit gravicurvature in a manner different from ethylene inhibition of overall growth.

Cloning, expression and N-terminal myristoylation of CpCPK1, a calcium-dependent protein kinase from zucchini (Cucurbita pepo L.).

We have isolated a full-length cDNA clone (CpCDPK1) encoding a calcium-dependent protein kinase (CDPK) gene from zucchini (Cucurbita pepo L.). The predicted amino acid sequence of the cDNA shows a remarkably high degree of similarity to members of the CDPK gene family from Arabidopsis thaliana, especially AtCPK1 and AtCPK2. Northern analysis of steady-state mRNA levels for CpCPK1 in etiolated and light-grown zucchini seedlings shows that the transcript is most abundant in etiolated hypocotyls and overall expression is suppressed by light. As described for other members of the CDPK gene family from different species, the CpCPK1 clone has a putative N-terminal myristoylation sequence. In this study, site-directed mutagenesis and an in vitro coupled transcription/translation system were used to demonstrate that the protein encoded by this cDNA is specifically myristoylated by a plant N-myristoyl transferase. This is the first demonstration of myristoylation of a CDPK protein which may contribute to the mechanism by which this protein is localized to the plasma membrane.

Genetic analysis of the roles of phytochromes A and B1 in the reversed gravitropic response of the lz-2 tomato mutant.

The lz-2 mutation in tomato (Lycopersicon esculentum) causes conditional reversal of shoot gravitropism by light. This response is mediated by phytochrome. To further elicit the mechanism by which phytochrome regulates the lz-2 phenotype, phytochrome-deficient lz-2 plants were generated. Introduction of au alleles, which severely block chromophore biosynthesis, eliminated the reversal of hypocotyl gravitropism in continuous red and far-red light. The fri1 and tri1 alleles were introduced to specifically deplete phytochromes A and B1, respectively. In dark-grown seedlings, phytochrome A was necessary for response to high-irradiance far-red light, a complete response to low fluence red light, and also mediated the effects of blue light in a far-red reversible manner. Loss of phytochrome B1 alone did not significantly affect the behaviour of lz-2 plants under any light treatment tested. However, dark-grown lz-2 plants lacking both phytochrome A and B1 exhibited reduced responses to continuous red and were less responsive to low fluence red light and high fluence blue light than plants that were deficient for phytochrome A alone. In high light, full spectrum greenhouse conditions, lz-2 plants grew downward regardless of the phytochrome deficiency. These results indicate that phytochromes A and B1 play significant roles in mediating the lz-2 phenotype and that at least one additional phytochrome is involved in reversing shoot gravitropism in this mutant.

The diageotropica gene differentially affects auxin and cytokinin responses throughout development in tomato.

The interactions between the plant hormones auxin and cytokinin throughout plant development are complex, and genetic investigations of the interdependency of auxin and cytokinin signaling have been limited. We have characterized the cytokinin sensitivity of the auxin-resistant diageotropica (dgt) mutant of tomato (Lycopersicon esculentum Mill.) in a range of auxin- and cytokinin-regulated responses. Intact, etiolated dgt seedlings showed cross-resistance to cytokinin with respect to root elongation, but cytokinin effects on hypocotyl growth and ethylene synthesis in these seedlings were not impaired by the dgt mutation. Seven-week-old, green wild-type and dgt plants were also equally sensitive to cytokinin with respect to shoot growth and hypocotyl and internode elongation. The effects of cytokinin and the dgt mutation on these processes appeared additive. In tissue culture organ regeneration from dgt hypocotyl explants showed reduced sensitivity to auxin but normal sensitivity to cytokinin, and the effects of cytokinin and the mutation were again additive. However, although callus induction from dgt hypocotyl explants required auxin and cytokinin, dgt calli did not show the typical concentration-dependent stimulation of growth by either auxin or cytokinin observed in wild-type cells. Cross-resistance of the dgt mutant to cytokinin thus was found to be limited to a small subset of auxin- and cytokinin-regulated growth processes affected by the dgt mutation, indicating that auxin and cytokinin regulate plant growth through both shared and separate signaling pathways.

A technique for calculating range spectra of charged particle beams distal to thick inhomogeneities.

A method was developed for calculating range spectra of charged particles after passing through an inhomogeneous structure whose thickness was comparable to the range of the incident particles. It was shown that the spectra are strongly affected by the influence of multiple Coulomb scattering at interfaces parallel to the beam direction of two media with different relative stopping power. The calculations are in agreement with Monte Carlo simulations. The degraded Bragg peak was calculated on the basis of the computed range spectra behind the inhomogeneity interface. The method can be included into charged particle treatment planning systems where broad pencil beams are used to predict the deteriorated Bragg peak behind inhomogeneity interfaces more precisely.

Multiplex titration RT-PCR: rapid determination of gene expression patterns for a large number of genes.

We have developed an improved method for determination of gene expression levels with RT-PCR. The procedure is rapid and does not require extensive optimization or densitometric analysis. Since the detection of individual transcripts is PCR-based, small amounts of tissue samples are sufficient for the analysis of expression patterns in large gene families. Using this method, we were able to rapidly screen nine members of the Aux/IAA family of auxin-responsive genes and identify those genes which vary in message abundance in a tissue- and light-specific manner. While not offering the accuracy of conventional semi-quantitative or competitive RT-PCR, our method allows quick screening of large numbers of genes in a wide range of RNA samples with just a thermal cycler and standard gel analysis equipment.

Molecular genetic analysis of plant gravitropism.

The analysis of mutants is a powerful approach for elucidating the components of complex biological processes. A growing number of mutants have been isolated which affect plant gravitropism and the classes of mutants found thus far provide important information about the gravity response mechanism. The wide variety of mutants isolated, especially in Arabidopsis, indicates that gravitropism is a complex, multi-step process. The existence of mutants altered in either root gravitropism alone, shoot gravitropism alone, or both indicates that the root and shoot gravitropic mechanisms have both separate and common steps. Reduced starch mutants have confirmed the role of amyloplasts in sensing the gravity signal. The hormone auxin is thought to act as the transducing signal between the sites of gravity perception (the starch parenchyma cells surrounding the vascular tissue in shoots and the columella cells of root caps) and asymmetric growth (the epidermal cells of the elongation zone(s) of each organ). To date, all mutants that are resistant to high concentrations of auxin have also been found to exhibit a reduced gravitropic response, thus supporting the role of auxin. Not all gravitropic mutants are auxin-resistant, however, indicating that there are additional steps which do not involve auxin. Studies with mutants of tomato which exhibit either reduced or reversed gravitropic responses further support the role of auxin redistribution in gravitropism and suggest that both red light and cytokinin interact with gravitropism through controlling lateral auxin transport. Plant responses to gravity thus likely involve changes in both auxin transport and sensitivity.

Auxin-cytokinin interactions in higher plants: old problems and new tools.

The plant hormones auxin and cytokinin interact in a complex manner to control many aspects of growth and differentiation. Recent advances in understanding their metabolism and the cell cycle are now helping to clarify the mechanisms by which these hormones act together to control various physiological and developmental responses. Molecular and genetic tools are being used to reveal interactions between auxin and cytokinin at multiple levels, including mutual regulation of active hormone availability, input into multiple signal transduction pathways, alteration of gene expression, post-translational modifications and direct modulation of enzyme activity.