Evaluating phytochemical and microbial contributions to atrazine degradation.

The inclusion of warm-season grasses, such as switchgrass (Panicum virgatum) and eastern gamagrass (EG) (Tripsacum dactyloides), in vegetated buffer strips has been shown to mitigate herbicide contamination in runoff and increase herbicide degradation in soil. The mode of action by which buffer strip rhizospheres enhance herbicide degradation remains unclear, but microorganisms and phytochemicals are believed to facilitate degradation processes. The objectives of this study were to: 1) screen root extracts from seven switchgrass cultivars for the ability to degrade the herbicide atrazine (ATZ) in solution; 2) determine sorption coefficients (Kd) of the ATZ-degrading phytochemical 2-ß-D-glucopyranosyloxy-4-hydroxy-1,4-benzoxazin-3-one (DBG) to soil and Ca-montmorillonite, and investigate if DBG or ATZ sorption alters degradation processes; and 3) quantify ATZ degradation rates and soil microbial response to ATZ application in mesocosms containing soil and select warm-season grasses. Phytochemicals extracted from the roots of switchgrass cultivars degraded 44-85% of ATZ in 16-h laboratory assays, demonstrating that some switchgrass cultivars could rapidly degrade ATZ under laboratory conditions. However, attempts to isolate ATZ-degrading phytochemicals from plant roots were unsuccessful. Sorption studies revealed that DBG was strongly sorbed to soil (Kd = 87.2 L kg-1) and Ca-montmorillonite (Kd = 31.7 L kg-1), and DBG driven hydrolysis of ATZ was entirely inhibited when either ATZ or DBG were sorbed to Ca-montmorillonite. Atrazine degradation rates in mesocosm soils were rapid (t0.5 = 8.2-11.2 d), but not significantly different between soils collected from the two switchgrass cultivar mesocosms, the eastern gamagrass cultivar mesocosm, and the unvegetated mesocosm (control). Significant changes in three phospholipid fatty acid biomarkers were observed among the treatments. These changes indicated that different ATZ-degrading microbial consortia resulted in equivalent ATZ degradation rates between treatments. Results demonstrated that soil microbial response was the dominant mechanism controlling ATZ degradation in the soil studied, rather than root phytochemicals.

Paving the way for application of next generation risk assessment to safety decision-making for cosmetic ingredients.

Next generation risk assessment (NGRA) is an exposure-led, hypothesis-driven approach that has the potential to support animal-free safety decision-making. However, significant effort is needed to develop and test the in vitro and in silico (computational) approaches that underpin NGRA to enable confident application in a regulatory context. A workshop was held in Montreal in 2019 to discuss where effort needs to be focussed and to agree on the steps needed to ensure safety decisions made on cosmetic ingredients are robust and protective. Workshop participants explored whether NGRA for cosmetic ingredients can be protective of human health, and reviewed examples of NGRA for cosmetic ingredients. From the limited examples available, it is clear that NGRA is still in its infancy, and further case studies are needed to determine whether safety decisions are sufficiently protective and not overly conservative. Seven areas were identified to help progress application of NGRA, including further investments in case studies that elaborate on scenarios frequently encountered by industry and regulators, including those where a 'high risk' conclusion would be expected. These will provide confidence that the tools and approaches can reliably discern differing levels of risk. Furthermore, frameworks to guide performance and reporting should be developed.

Transient glacial incision in the Patagonian Andes from ~6 Ma to present.

We report a mountain-scale record of erosion rates in the central Patagonian Andes from >10 million years (Ma) ago to present, which covers the transition from a fluvial to alpine glaciated landscape. Apatite (U-Th)/He ages of 72 granitic cobbles from alpine glacial deposits show slow erosion before ~6 Ma ago, followed by a two- to threefold increase in the spatially averaged erosion rate of the source region after the onset of alpine glaciations and a 15-fold increase in the top 25% of the distribution. This transition is followed by a pronounced decrease in erosion rates over the past ~3 Ma. We ascribe the pulse of fast erosion to local deepening and widening of valleys, which are characteristic features of alpine glaciated landscapes. The subsequent decline in local erosion rates may represent a return toward a balance between rock uplift and erosion.

Chloro-triazine transport to streams-evaluating methods for partitioning deisopropylatrazine sources.

Streams in the Salt River Basin (SRB) of northeastern Missouri, USA, have been chronically contaminated by atrazine and metabolites, with peak annual transport occurring from spring to early summer. Since 2005, increased fall-applied simazine has introduced a second chloro-triazine herbicide that degrades to deisopropylatrazine (DIA), creating the need for a method to partition DIA between its two parent sources - i.e., DIA derived from atrazine (DIAATR) and that from simazine (DIASIM). Distinguishing DIA parent sources would extend current understanding of chloro-triazine transport, leading to more accurate risk assessments and improved watershed-scale load estimates. The objectives of this study were to evaluate proposed methods for DIA partitioning, and to apply the most effective method to estimate DIAATR and DIASIM concentrations and loads. Three DIA partition methods were developed and statistically evaluated: 1) edge-of-field (EOF) based on DIA and deethylatrazine (DEA) concentrations in runoff from atrazine treated fields; 2) DIA:DEA concentration ratios (D2R) in runoff from atrazine treated fields; and 3) concentration ratios of simazine:atrazine (SAR) in streams. Stream samples were collected year-round at 7 SRB stream sites from 2005 to 2010 and daily, quarterly, and annual concentrations and loads of atrazine, DEA, DIA, and simazine computed. The SAR method was superior to EOF and D2R in its ability to estimate concentrations and loads of DIASIM and DIAATR that were more accurate and highly correlated to observed transport of simazine, atrazine, and DIA. The SAR method results demonstrated the differences in DIASIM and DIAATR transport timing, with peak DIASIM transport occurring from mid-Nov to Apr and peak DIAATR transport from May to Jun. Dual season triazine applications within a watershed substantially increased the period of high chloro-triazine concentrations in streams from ~3 to ~8 months/yr, potentially increasing the risk of toxicity to aquatic ecosystems.

Benzoxazinone-Mediated Triazine Degradation: A Proposed Reaction Mechanism.

The role of benzoxazinones (Bx, 2-hydroxy-2H-1,4-benzoxazin-3(4H)-one) in triazine resistance in plants has been studied for over half a century. In this research, fundamental parameters of the reaction between DIBOA-Glc (2-ß-d-glucopyranosyloxy-4-hydroxy-1,4-benzoxazin-3-one) and atrazine (ATR, 6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine) were examined. Through a series of experiments employing a variety of chromatographic and spectroscopic techniques, the DIBOA-Glc/ATR reaction was characterized in terms of reactant and product kinetics, stoichiometry, identification of a reaction intermediate, and reaction products formed. Results of these experiments demonstrated that the reaction mechanism proceeds via nucleophilic attack of the hydroxamic acid moiety of DIBOA-Glc at the C-2 position of the triazine ring to form hydroxyatrazine (HA, 2-hydroxy-4-ethylamino-6-isopropylamino-s-triazine), with associated degradation of DIBOA-Glc. Degradation of reactants followed first-order kinetics with a noncatalytic role of DIBOA-Glc. A reaction intermediate was identified as a DIBOA-Glc-HA conjugate, indicating a 1:1 DIBOA-Glc:ATR stoichiometry. Reaction products included HA and Cl(-), but definitive identification of DIBOA-Glc reaction product(s) was not attained. With these reaction parameters elucidated, DIBOA-Glc can be evaluated in terms of its potential for a myriad of applications, including its use to address the problem of widespread ATR contamination of soil and water resources.

Building on a solid foundation: SAR and QSAR as a fundamental strategy to reduce animal testing.

The development of more efficient, ethical, and effective means of assessing the effects of chemicals on human health and the environment was a lifetime goal of Gilman Veith. His work has provided the foundation for the use of chemical structure for informing toxicological assessment by regulatory agencies the world over. Veith's scientific work influenced the early development of the SAR models in use today at the US Environmental Protection Agency. He was the driving force behind the Organisation for Economic Co-operation and Development QSAR Toolbox. Veith was one of a few early pioneers whose vision led to the linkage of chemical structure and biological activity as a means of predicting adverse apical outcomes (known as a mode of action, or an adverse outcome pathway approach), and he understood at an early stage the power that could be harnessed when combining computational and mechanistic biological approaches as a means of avoiding animal testing. Through the International QSAR Foundation he organized like-minded experts to develop non-animal methods and frameworks for the assessment of chemical hazard and risk for the benefit of public and environmental health. Avoiding animal testing was Gil's passion, and his work helped to initiate the paradigm shift in toxicology that is now rendering this feasible.

Toxicity and outcomes after chemoradiation for esophageal cancer in patients age 75 or older.

Randomized trials of chemoradiation for esophageal cancer have included very few patients age > or = 75. In this retrospective study, we describe the outcomes and toxicity of full-dose chemoradiation in elderly patients with esophageal cancer. Patients, age > or = 75, treated with full-dose chemoradiation for esophageal carcinoma from 2002 to 2008 were retrospectively reviewed. Thirty-four patients were identified with a median age of 79.5 (range 75-89). The median Eastern Cooperative Oncology Group performance status was 1 (range 0-3) and the median Adult Comorbidity Evaluation-27 score was 1 (range 0-3). Twenty-eight patients received definitive and six received neoadjuvant chemoradiation. The median radiation dose delivered was 50.4 Gray (range 3.6-68.4 Gray). Platinum-based chemotherapy was used in 79.4% of patients. Fifty percent of the patients completed all planned radiation therapy (RT) and chemotherapy; 85.3% completed RT. Acute toxicity > or = grade 4 occurred in 38.2% of patients, and 70.6% of the patients required hospitalization, emergency department visit, and/or RT break. Median follow-up was 14.5 months among 7 survivors, and median survival was 12.0 months (95% confidence interval [CI]: 9.7 to 24.1 months). The actuarial overall survival at 2 years was 29.7% (95% CI: 16.6 to 52.6%). There were four treatment-related deaths. The median time to any recurrence was 10.4 months. Nineteen patients had a local and/or distant recurrence. In conclusion, elderly patients experienced substantial morbidity from chemoradiation, and long-term survival was low. Future efforts to improve treatment tolerability in the elderly are needed.

Chemoradiotherapy in gastrointestinal malignancies.

Over the past 30 years, significant advances have been made in the integration of radiation therapy and chemotherapy in the treatment of patients with localised gastrointestinal malignancies. The therapeutic goal of chemoradiotherapy is to enhance local control resulting in improved survival and outcome of these patients. To define the optimal sequence, agents and efficacy of these modalities, an array of randomised studies have been conducted in malignancies of the oesophagus, stomach, pancreas, colon, rectum and anus. In oesophageal cancer, recent studies from Germany and France indicate that patients treated with 'definitive' chemoradiotherapy have similar survival to patients undergoing neoadjuvant chemoradiotherapy followed by surgery. For patients with locally advanced rectal cancer undergoing surgery, a phase III trial from Germany showed higher rates of local control with less acute and late morbidity for patients receiving neoadjuvant chemoradiotherapy vs adjuvant chemoradiotherapy. In contrast, the role of chemoradiotherapy in pancreatic cancer patients remains unclear and contentious. This overview highlights current results, controversies and potential future directions in the chemoradiotherapeutic treatment of selected gastrointestinal malignancies.

Viability effects and not meoitic drive cause dramatic departures from Mendelian inheritance for malic enzyme in hybrids of Tigriopus californicus populations.

The genetic basis of post-zygotic reproductive isolation is beginning to be untangled in closely related species, but less is known about the genetics of reproductive isolation between divergent populations. Here, two genes encoding malic enzyme (ME) are isolated from the copepod Tigriopus californicus and their influence upon lowered viability in F(2) hybrids of genetically divergent populations is determined. Each ME gene has diverged extensively between T. californicus populations and one gene shows evidence for a recent selective sweep. Segregation patterns of genotypes for both ME genes in adult F(2) hybrids reveal dramatic departures from Mendelian inheritance, deviations that are not seen in F(2) nauplii implying that selection is acting during development based upon the genotype at these ME genes. These results imply that selection against deleterious gene combinations and not aberrant segregation (i.e. meiotic drive) is likely to lead to dramatic departures from Mendelian inheritance observed in these crosses.

Outcomes in a series of 103 retroperitoneal sarcomas.

AIMS: To report the effect on outcome of selection in patients receiving intra-operative electron beam radiation (IOERT) and external beam radiation therapy (EBRT). METHODS: One hundred and three patients treated for primary RS were studied. Median follow-up was 27 months. Clinical presentation, tumor characteristics, and treatment methods were analyzed to determine impact on survival and recurrence and if selection was occurring. RESULTS: Mean age was 55+/-17 years. Mean tumor size was 15+/-6cm and 88 were high-grade. Complete gross tumor resection (CR) occurred in 62 patients and improved survival vs. both debulking (p=0.0005) and biopsy (p<0.0001). The 5- and 10-year survival rates were 62% and 52% for those with CR vs. 29% and 20% after incomplete resection. Among the 62 CR patients, there was selection to receive additional EBRT+/-IOERT in patients with high-grade tumors (p=0.005) and/or microscopically positive margins (p=0.011). In these high-risk patients there was a trend for IOERT to further augment survival vs. EBRT alone and to increase the time to both local and distant recurrences (p=0.036). CONCLUSIONS: Complete gross resection is the primary form of curative treatment for retroperitoneal sarcomas. Selection led to patients with high-risk tumors receiving additional radiation therapy. There appears to be a beneficial effect of IOERT plus EBRT in these high-risk patients after complete tumor resection.

Unusual structure of ribosomal DNA in the copepod Tigriopus californicus: intergenic spacer sequences lack internal subrepeats.

Eukaryotic nuclear ribosomal DNA (rDNA) is typically arranged as a series of tandem repeats coding for 18S, 5.8S, and 28S ribosomal RNAs. Transcription of rDNA repeats is initiated in the intergenic spacer (IGS) region upstream of the 18S gene. The IGS region itself typically consists of a set of subrepeats that function as transcriptional enhancers. Two important evolutionary forces have been proposed to act on the IGS region: first, selection may favor changes in the number of subrepeats that adaptively adjust rates of rDNA transcription, and second, coevolution of IGS sequence with RNA polymerase I transcription factors may lead to species specificity of the rDNA transcription machinery. To investigate the potential role of these forces on population differentiation and hybrid breakdown in the intertidal copepod Tigriopus californicus, we have characterized the rDNA of five T. californicus populations from the Pacific Coast of North America and one sample of T. brevicornicus from Scotland. Major findings are as follows: (1) the structural genes for 18S and 28S are highly conserved across T. californicus populations, in contrast to other nuclear and mitochondrial DNA (mtDNA) genes previously studied in these populations. (2) There is extensive differentiation among populations in the IGS region; in the extreme, no homology is observed across the IGS sequences (>2 kb) from the two Tigriopus species. (3) None of the Tigriopus IGS sequences have the subrepeat structure common to other eukaryotic IGS regions. (4) Segregation of rDNA in laboratory crosses indicates that rDNA is located on at least two separate chromosomes in T. californicus. These data suggest that although IGS length polymorphism does not appear to play the adaptive role hypothesized in some other eukaryotic systems, sequence divergence in the rDNA promoter region within the IGS could lead to population specificity of transcription in hybrids.

Familial schwannomatosis: exclusion of the NF2 locus as the germline event.

BACKGROUND: Schwannomatosis is a recently recognized disorder, defined as multiple pathologically proven schwannomas without vestibular tumors diagnostic of neurofibromatosis 2 (NF2). Some investigators have questioned whether schwannomatosis is merely an attenuated form of NF2. METHODS: The authors identified eight families in which a proband met their diagnostic criteria for schwannomatosis. Archived and prospectively acquired tumor specimens were studied by mutational analysis at the NF2 locus, loss of heterozygosity analysis along chromosome 22, and fluorescent in situ hybridization analysis of NF2 and the more centromeric probe BCR. Linkage analysis could be performed in six of eight families. RESULTS: Clinical characterization of these kindreds showed that no affected family member harbored a vestibular tumor. Molecular analysis of 28 tumor specimens from 17 affected individuals in these kindreds revealed a pattern of somatic NF2 inactivation incompatible with our current understanding of NF2 as an inherited tumor suppressor gene syndrome. Linkage analysis excluded the NF2 locus in two kindreds, and showed a maximum lod score of 6.60 near the more centromeric marker D22S1174. CONCLUSIONS: Schwannomatosis shows clinical and molecular differences from NF2 and should be considered a third major form of neurofibromatosis. Further work is needed to identify the inherited genetic element responsible for familial schwannomatosis.

Ikaros expression as a marker for lymphoid progenitors during zebrafish development.

The Ikaros gene encodes a transcription factor that, in mice, has been shown to be essential for the correct differentiation of B and T lymphocytes and is expressed in all cells of the lymphoid lineage, including pluripotent hematopoietic stem cells. During development in zebrafish, Ikaros expression begins in lateral mesoderm, and continues in the intermediate cell mass (ICM), which is derived from lateral mesoderm and has been shown to generate primitive hematopoietic precursors. Cells expressing Ikaros were then seen on the ventral side of the dorsal aorta, known to be a location of definitive hematopoietic precursors in birds and mammals. Ikaros-expressing cells were also found in the pharyngeal region, near the forming thymus. Later, such cells were seen in the pronephros, the site of hematopoiesis in adult fish. The timing of appearance of Ikaros-expressing cells suggests that, similar to other vertebrates, lymphocytes in the thymus arise from hematopoietic tissue located near the dorsal aorta or in the ICM.

Intraoperative radiation therapy.

The modern use of intraoperative radiation therapy (IORT) was initiated by the studies of Abe and colleagues at the University of Kyoto. This work stimulated significant laboratory and clinical investigation into the use of IORT throughout Japan, Europe, and the United States. Because of this experience, single high doses of irradiation can be safely delivered to a tumor volume in appropriate clinical situations. Most importantly, this high dose of additional radiation treatment yields improved local control of selected tumors. Treatment programs of external beam radiation therapy, surgical resection, and IORT for patients with locally advanced primary and recurrent rectal carcinoma and retroperitoneal sarcoma have yielded excellent local control and higher survival rates. The future of IORT will be in the successful integration of this therapy into multimodality treatment programs of chemotherapy, external beam irradiation, and surgery for locally advanced malignancies.

Viability of cytochrome c genotypes depends on cytoplasmic backgrounds in Tigriopus californicus.

Because of their extensive functional interaction, mitochondrial DNA (mtDNA) and nuclear genes may evolve to form coadapted complexes within reproductively isolated populations. As a consequence of coadaptation, the fitness of particular nuclear alleles may depend on mtDNA genotype. Among populations of the copepod Tigriopus californicus, there are high levels of amino acid substitutions in both the mtDNA genes encoding subunits of cytochrome c oxidase (COX) and the nuclear gene encoding cytochrome c (CYC), the substrate for COX. Because of the functional interaction between enzyme and substrate proteins, we hypothesized that the fitness of CYC genotypes would depend on mtDNA genotype. To test this hypothesis, segregation ratios for CYC and a second nuclear marker (histone H1) unrelated to mitochondrial function were scored in F2 progeny of several reciprocal interpopulation crosses. Genotypic ratios at the CYC locus (but not the H1 locus) differed between reciprocal crosses and differed from expected Mendelian ratios, suggesting that CYC genotypic fitnesses were strongly influenced by cytoplasmic (including mtDNA) background. However, in most cases the nature of the deviations from Mendelian ratios and differences between reciprocal crosses are not consistent with simple coevolution between CYC and mtDNA background. In a cross in which both newly hatched larvae and adults were sampled, only the adult sample showed deviations from Mendelian ratios, indicating that genotypic viabilities differed. In two of six crosses, large genotypic ratio differences for CYC were observed between the sexes. These results suggest that significant variation in nuclear-mtDNA coadaptation may exist between T. californicus populations and that the relative viability of specific cytonuclear allelic combinations is somehow affected by sex.

Radiation therapy in the management of rectal cancer.

Substantial advances have been made in the adjuvant management of patients with resectable rectal cancer. Increasing interest in patient quality of life has promoted the use of radiation therapy to enhance sphincter-preserving surgical approaches as an alternative to the standard abdominoperineal resection. Because of the suggestion of enhanced sphincter preservation with preoperative therapy and the potential advantage of decreased acute morbidity, randomized trials comparing preoperative and postoperative adjuvant combined modality therapy are ongoing. Recent progress in adjuvant postoperative treatment regimens relates to the integration of systemic therapy to radiation, and redefining the techniques for both modalities. The incorporation of improved radiation planning may reduce treatment-related bowel toxicity. The integration of novel chemotherapeutic agents in the adjuvant therapy of rectal cancer remains an active area of investigation.

Squamous cell carcinoma of the anal canal and anal margin.

Squamous cell carcinomas of the anal canal and margin are relatively uncommon neoplasms of the distal gastrointestinal tract and surrounding skin. The major risk factors for tumor development have been defined through various epidemiologic studies. Randomized, phase III trials have defined the standard of care for anal cancer tumors to be a combined modality approach of radiation therapy and chemotherapy. This nonsurgical, organ-sparing regimen results in good anal sphincter function in the majority of patients, and treatment efficacy is favorable when compared with historic surgical series. Anal margin tumors are staged and treated as skin cancers, with a more favorable prognosis.

Long-term results of intraoperative electron beam radiotherapy for primary and recurrent retroperitoneal soft tissue sarcoma.

PURPOSE: This study assesses the long-term outcome of patients with retroperitoneal sarcoma treated by preoperative external beam radiotherapy, resection, and intraoperative electron beam radiation (IOERT). METHODS AND MATERIALS: From 1980 to 1996, 37 patients were treated with curative intent for primary or recurrent retroperitoneal soft tissue sarcoma. All patients underwent external beam radiotherapy with a median dose of 45 Gy. This was followed by laparotomy, resection, and IOERT, if feasible. Twenty patients received 10-20 Gy of IOERT with 9-15 MeV electrons. These patients were compared to a group of 17 patients receiving preoperative irradiation without IOERT. RESULTS: The 5-yr actuarial overall survival (OS), disease-free survival, local control (LC), and freedom from distant disease of all 37 patients was 50%, 38%, 59%, and 54%, respectively. After preoperative irradiation, 29 patients (78%) underwent gross total resection. For 16 patients undergoing gross total resection and IOERT, OS and LC were 74% and 83%, respectively. In contrast, these results were less satisfactory for 13 patients undergoing gross total resection without IOERT. For these patients, OS and LC were 30% and 61%, respectively. Four patients experienced treatment-related morbidity. CONCLUSIONS: In selected patients, IOERT results in excellent local control and disease-free survival with acceptable morbidity.

Intraoperative radiation therapy for locally advanced recurrent rectal or rectosigmoid cancer.

BACKGROUND AND PURPOSE: To update and summarize the experience at the Massachusetts General Hospital of a treatment program of high-dose preoperative irradiation, surgical re-resection, and intraoperative radiation therapy (IORT) as a salvage treatment for patients with recurrent rectal or rectosigmoid carcinoma. PATIENTS AND METHODS: From June 1978 to February 1997, the records of 69 patients with locally recurrent rectal carcinomas or rectosigmoid carcinomas without metastases referred for consideration of IORT were reviewed. Forty-nine patients received IORT and local control and disease-free survival curves were calculated using the actuarial method of Kaplan-Meier. RESULTS: The 5-year overall survival, local control and disease-free survival rates of 49 patients receiving IORT were 27, 35, and 20%, respectively. Thirty-four patients who underwent a macroscopic complete resection had a significantly better 5-year overall survival than the remaining 15 patients with gross residual disease (33 vs. 13%, P=0.05, log rank). For those patients, local control and disease-free survival rates were 46 and 27%, respectively. Patients with a microscopic complete resection had a superior 5-year overall survival than partially resected patients (40 vs. 14%, P=0.0001, log rank). Chemotherapy had no significant influence on overall or disease-free survival. CONCLUSION: The current analysis shows the importance of a microscopic complete resection in a multi-modality approach with IORT for survival and local control. Salvage is rare for patients undergoing subtotal resection.