A discrete time relativistic Toda lattice

Four integrable symplectic maps approximating two Hamiltonian flows from the relativistic Toda hierarchy are introduced. They are demostrated to belong to the same hierarchy and to examplify the general scheme for symplectic maps on groups equiped with quadratic Poisson brackets. The initial value problem for the difference equations is solved in terms of a factorization problem in a group. Interpolating Hamiltonian flows are found for all the maps.Comment: 32 pages, LaTe

The chemical compound 'Heatin' stimulates hypocotyl elongation and interferes with the Arabidopsis NIT1-subfamily of nitrilases

Temperature passively affects biological processes involved in plant growth. Therefore, it is challenging to study the dedicated temperature signalling pathways that orchestrate thermomorphogenesis, a suite of elongation growth-based adaptations that enhance leaf-cooling capacity. We screened a chemical library for compounds that restored hypocotyl elongation in the pif4-2-deficient mutant background at warm temperature conditions in Arabidopsis thaliana to identify modulators of thermomorphogenesis. The small aromatic compound 'Heatin', containing 1-iminomethyl-2-naphthol as a pharmacophore, was selected as an enhancer of elongation growth. We show that ARABIDOPSIS ALDEHYDE OXIDASES redundantly contribute to Heatin-mediated hypocotyl elongation. Following a chemical proteomics approach, the members of the NITRILASE1-subfamily of auxin biosynthesis enzymes were identified among the molecular targets of Heatin. Our data reveal that nitrilases are involved in promotion of hypocotyl elongation in response to high temperature and Heatin-mediated hypocotyl elongation requires the NITRILASE1-subfamily members, NIT1 and NIT2. Heatin inhibits NIT1-subfamily enzymatic activity in vitro and the application of Heatin accordingly results in the accumulation of NIT1-subfamily substrate indole-3-acetonitrile in vivo. However, levels of the NIT1-subfamily product, bioactive auxin (indole-3-acetic acid), were also significantly increased. It is likely that the stimulation of hypocotyl elongation by Heatin might be independent of its observed interaction with NITRILASE1-subfamily members. However, nitrilases may contribute to the Heatin response by stimulating indole-3-acetic acid biosynthesis in an indirect way. Heatin and its functional analogues present novel chemical entities for studying auxin biology

Pancreatic cancer: Patterns in a low- to middle- income Ppopulation, Zambia

Introduction: In 2007, the Cancer Disease Hospital (CDH) was opened as the national referral center for patients diagnosed with cancer in Zambia. Since inception of the CDH, there has been no systematic analysis of the disease burden and implication on healthcare delivery with regards to pancreatic cancer. There are limited studies describing patterns of pancreatic cancer in a native African population. Data suggest African-Americans have a higher incidence and poorer prognosis of pancreatic cancer than non-African Americans.Objective: Our aim is to describe the demographic features (age, gender) of pancreatic cancer using the Cancer Disease Hospital (CDH) data base in a native African population and compare with the African-American cohort using the  Surveillance, Epidemiology End Results (SEER) Program database.Methods: This was a retrospective study of patients diagnosed with pancreatic  cancer at the CDH in Zambia, Southern Africa between 2007 and 2014. We entered the term “pancreatic cancer” into the CDH database, extracted patient medical records numbers, and manually located the records for review. From each chart we extracted: age, gender, geographic origin, ethnicity, clinical features at presentations, location of tumor, stage at diagnosis and treatment. Data collection tool and master code sheet created a priori were used. Data was analyzed using statistical analysis software (SAS). Descriptive statistics including means, medians as well as frequency distributions and crosstabulations were used. SEER database was used to compare subjects  between Zambia and USA. Groups were compared using Chi-square tests and Wilcoxon Signed Rank test. Ap-value less than 0.05 was used as the level of significance.Results: Thirty-eight charts were identified in the CDH dataset, of which 27 were included in final analysis and 11 excluded (5 non-pancreatic cancer diagnosis, 6 not manually located). The mean age of diagnosis was 55.7 years in the native African population, compared to 66.7 years for the African-Americans in the SEER  database, p < 0.0001. There were 63.0% males (CDH) compared to 48.1% (SEER), p=0.121. Further review of the CDH database revealed that the most common presenting symptom was abdominal pain (52.6%), mode of diagnosis surgical (83%, missing 3), histopathology adenocarcinoma (86%, missing 6), location head of pancreas (83%, missing 9) and stage 4 at diagnosis (100%, missing 3).Conclusion: Pancreatic cancer occurs at a younger age in Zambians when compared to the African American, USApopulation. There is no statistically significant difference in sex presentation between Zambian and USAblack population

Salicylic Acid Biosynthesis and Metabolism

Salicylic acid (SA) has been shown to regulate various aspects of growth and development; it also serves as a critical signal for activating disease resistance in Arabidopsis thaliana and other plant species. This review surveys the mechanisms involved in the biosynthesis and metabolism of this critical plant hormone. While a complete biosynthetic route has yet to be established, stressed Arabidopsis appear to synthesize SA primarily via an isochorismate-utilizing pathway in the chloroplast. A distinct pathway utilizing phenylalanine as the substrate also may contribute to SA accumulation, although to a much lesser extent. Once synthesized, free SA levels can be regulated by a variety of chemical modifications. Many of these modifications inactivate SA; however, some confer novel properties that may aid in long distance SA transport or the activation of stress responses complementary to those induced by free SA. In addition, a number of factors that directly or indirectly regulate the expression of SA biosynthetic genes or that influence the rate of SA catabolism have been identified. An integrated model, encompassing current knowledge of SA metabolism in Arabidopsis, as well as the influence other plant hormones exert on SA metabolism, is presented