The role of matrix metalloproteinases 2 and 9 during rat tongue carcinogenesis induced by 4-nitroquinoline 1-oxide

Matrix metalloproteinases (MMPs) are implicated in a wide range of physiological and pathological processes, including morphogenesis, wound healing, angiogenesis, inflammation, and cancer. The purpose of this study was to characterize the role of MMPs as depicted by the expression of MMP-2 and MMP-9 during 4-nitroquinoline 1-oxide-induced rat tongue carcinogenesis. Male Wistar rats were distributed into three groups of 10 animals each and treated with 4-nitroquinoline 1-oxide solution at 50 ppm through their drinking water for 4, 12, and 20 weeks. Ten animals were used as control group. No histopathological abnormalities were induced in the epithelium after 4 weeks of carcinogen exposure; however, immunoexpression of MMP-2 was noticed. The same picture occurred to MMP-9, in which positive expression was detected for this immunomarker. MMP-2 and MMP-9 showed positive expression either in pre-neoplastic lesions at 12 weeks following carcinogen exposure or in well-differentiated squamous cell carcinoma induced after 20 weeks of treatment with 4NQO. Taken together, our results support the belief that MMP-2 and MMP-9 play important role during malignant transformation and conversion of oral mucosa as assessed by immunohistochemistry.     

Relationship between N, P, and K and the quality and stem structural characteristics of Caesalpinia echinata Lam. plants

This study was carried out to evaluate the effect of N, P, and K on the growth of Caesalpinia echinata plants and on the anatomical and chemical characteristics of their stems. Eight-month-old plants were grown in polyethylene pots of 8 L containing soil. The pots were arranged in randomized blocks where they received N, P, and K in isolated form, and NPK combined in 10:10:10 and 04:14:08 ratios. The applications were repeated at intervals of 90 days for 450 days, between January 2008 and April 2009. The nitrogen fertilization (N) and in the form NPK 04:14:08 provided greater stem growth and leaf area, but with lower values of Dickson quality index, which suggests lower survival potential under field conditions. Fertilizations do not influence the insoluble lignin concentration and the components of cellulose and hemicelluloses of the secondary xylem of the stem. In the stem bark, however, the levels of xylose, glucose, and insoluble lignin were higher in P and K when compared to N and the NPK forms. Nevertheless, the levels of xylose and insoluble lignin in all the treatments were lower than those in the control group. Concerning anatomical characteristics, there was higher diameter of the vessel element and reduced length of its cells for the NPK combination. All the fertilizing formulas reduced fiber wall thickness of the secondary xylem compared to control. The results suggest phosphate fertilization as the most recommended for growing C. echinata plants with increased chances of survival under field conditions.     

Erythrina speciosa (Leguminosae-Papilionoideae) under soil water saturation: morphophysiological and growth responses

Background and Aims

Erythrina speciosa is a Neotropical tree that grows mainly in moist habitats. To characterize the physiological, morphological and growth responses to soil water saturation, young plants of E. speciosa were subjected experimentally to soil flooding.

Methods

Flooding was imposed from 2 to 4 cm above the soil surface in water-filled tanks for 60 d. Non-flooded (control) plants were well watered, but never flooded. The net CO₂ exchange (A_CO2), stomatal conductance (g_s) and intercellular CO₂ concentration (C_i) were assessed for 60 d. Soluble sugar and free amino acid concentrations and the proportion of free amino acids were determined at 0, 7, 10, 21, 28 and 45 d of treatments. After 28, 45 and 60 d, dry masses of leaves, stems and roots were determined. Stem and root cross-sections were viewed using light microscopy.

Key Results

The A_CO2 and g_s were severely reduced by flooding treatment, but only for the first 10 d. The soluble sugars and free amino acids increased until the tenth day but decreased subsequently. The content of asparagine in the roots showed a drastic decrease while those of alanine and γ-aminobutyric increased sharply throughout the first 10 d after flooding. From the 20th day on, the flooded plants reached A_CO2 and g_s values similar to those observed for non-flooded plants. These events were coupled with the development of lenticels, adventitious roots and aerenchyma tissue of honeycomb type. Flooding reduced the growth rate and altered carbon allocation. The biomass allocated to the stem was higher and the root mass ratio was lower for flooded plants when compared with non-flooded plants.

Conclusions

Erythrina speciosa showed 100 % survival until the 60th day of flooding and was able to recover its metabolism. The recovery during soil flooding seems to be associated with morphological alterations, such as development of hypertrophic lenticels, adventitious roots and aerenchyma tissue, and with the maintenance of neutral amino acids in roots under long-term exposure to root-zone O₂ deprivation.Key words: Erythrina speciosa, aerenchyma, amino acid content, biomass allocation, photosynthesis, flooding adaptations, stomatal conductance, O₂ deficiency, γ-aminobutyric acid (GABA)     

Climate change and the ecophysiology of Bertholletia excelsa seedlings

Plant Growth Regulation - The Bertholletia excelsa a species native to the Amazon region of great national and international interest, mainly for the nutritional benefits of its seeds. However,...