Controlo mecânico de infestantes

As infestantes são plantas indesejáveis que crescem juntamente com as plantas cultivadas e que interferem no seu desenvolvimento normal. As infestantes podem ser uma das principais causas da diminuição do rendimento das culturas, porque competem com elas para o espaço, para a água, luz solar, nutrientes e dióxido de carbono, podem segregar substâncias alelopáticas, ser o meio no qual temporariamente se instalam alguns organismos responsáveis por inúmeras pragas e doenças que atacam as culturas dificultando assim o combate às mesmas, dificultam a colheita quer esta seja manual ou mecanizada, podem contaminar o produto final, depreciando-o e, asseguram a reinfestação para as culturas seguintes. O controlo de infestantes ter-se-á iniciado quando o homem deixou a de ser nómada e de assegurar as suas necessidades através da colheita de frutos e da caça e passou após a “domesticação“ das espécies animais e vegetais a fazer agricultura, tornando-se sedentário. Portanto, desde o início da agricultura, que o homem tem feito grandes esforços para controlar as plantas infestantes, primeiro à mão, depois com o uso de alguns artefactos, ferramentas e equipamentos para melhorar a eficiência no seu controlo. Hoje existem equipamentos mecânicos sofisticados tal como, substâncias químicas ou biológicas que permitem o seu controlo prevenindo ou retardando a sua germinação ou crescimento. Interferência das plantas infestantes com a cultura pode gerar perdas significativas, na qualidade e quantidade de alimentos produzidos, desperdiçando enormes quantidades de energia, especialmente não renováveis. Os custos no controlo e os efeitos sobre os rendimentos são muito variáveis, dependendo do agricultor, das espécies de plantas infestantes e da estratégia ou estratégias adoptadas para garantir a eficácia no controlo. Nas últimas cinco décadas têm vindo a fazer-se significativos avanços científicos e tecnológicos na criação de estratégias para o aumento da eficácia no controlo de infestantes seja mecanicamente, seja através da utilização de substâncias químicas ou biológicas menos tóxicas para o homem, menos agressivas ao meio ambiente, com menores custos de produção e ao mesmo tempo, mais selectivas para as culturas onde são aplicadas. A alternativa ao controlo químico de infestantes através da aplicação de herbicidas é o controlo mecânico pela utilização de diversas alfaias agrícolas, tais como a charrua de aivecas, a charrua de discos, o escarificador de braços rígidos, o escarificador de braços flexíveis (vibrocultor) e a fresa. O controlo mecânico de infestantes poderá ser levado a cabo também por máquinas de corte, como por exemplo, as gadanheiras. Cortar as infestantes numa fase de desenvolvimento antes da produção de semente evita a sua propagação. Se o agricultor optar pela sementeira directa como técnica de instalação das culturas, a única alternativa que tem para o controlo de infestantes é a química, mas se optar pelo sistema de mobilização tradicional ou pela mobilização reduzida poderá controlar as infestantes, química e/ou mecanicamente. A eficácia das diferentes alfaias no controlo de infestantes depende da própria alfaia, da época do ano em que se realiza esse controlo, do estado do solo, das espécies de infestantes presentes e seu estádio de desenvolvimento. Iremos no presente trabalho, referir os aspectos mais importantes do controlo mecânico de infestantes

Systemic chemotherapy induces microsatellite instability in the peripheral blood mononuclear cells of breast cancer patients

INTRODUCTION: Systemic chemotherapy is an important part of treatment for breast cancer. We conducted the present study to evaluate whether systemic chemotherapy could produce microsatellite instability (MSI) in the peripheral blood mononuclear cell fraction of breast cancer patients. METHODS: We studied 119 sequential blood samples from 30 previously untreated breast cancer patients before, during and after chemotherapy. For comparison, we also evaluated 20 women who had no relevant medical history (control group). RESULTS: In 27 out of 30 patients we observed MSI in at least one sample, and six patients had loss of heterozygosity. We found a significant correlation between the number of MSI events per sample and chemotherapy with alkylating agents (P < 0.0001). We also observed an inverse correlation between the percentage of cells positive for hMSH2 and the number of MSI events per sample (P = 0.00019) and use of alkylating agents (P = 0.019). CONCLUSION: We conclude that systemic chemotherapy may induce MSI and loss of heterozygosity in peripheral blood mononuclear cells from breast cancer patients receiving alkylating agents, possibly mediated by a chemotherapy-induced decrease in the expression of hMSH2. These effects may be related to the generation of secondary leukaemia in some patients, and may also intensify the genetic instability of tumours and increase resistance to treatment

BIOSYNTHESIS OF GLYCOSAMINOGLYCANS IN THE ENDOMETRIUM DURING THE INITIAL-STAGES OF PREGNANCY OF THE MOUSE

Significant changes in the synthesis of glycosaminoglycans occur during the transformation of stromal cells of the endometrium into decidual cells which takes place during the initial stages of pregnancy in mice. Hyaluronic acid, which is practically absent in the endometrium of virgin mice, increases dramatically on the fifth day of pregnancy, reaching its maximal concentration on day 6 followed by a 50% decrease on day 7. Changes in hyaluronic acid concentration also occur in pseudopregnant mice indicating that they are not related to the presence of the embryo in the uterus. The absolute concentration of the sulfated glycosaminoglycans, e.g., heparan sulfate, dermatan sulfate and chondroitin sulfate in the decidua did not change significantly. There was, however, a striking decrease of their biosynthesis in pregnant and pseudopregnant mice when compared to virgin mice, as shown by the use of radioactive inorganic sulfate as a precursor for the study of in vivo synthesis. A radioautographical analysis confirmed that the highest incorporation of radioactive sulfate was observed in virgin endometria when compared to pregnant ones. These studies also have shown a characteristic pattern of labeling in different regions of the endometrium that repeats itself during the different days of pregnancy.ESCOLA PAULISTA MED,DEPT BIOCHEM,BR-04023 SAO PAULO,BRAZILESCOLA PAULISTA MED,DEPT BIOCHEM,BR-04023 SAO PAULO,BRAZILWeb of Scienc

(a) The clinical course of one of the studied patients who received three cycles of neoadjuvant paclitaxel (P) followed by four cycles of neoadjuvant doxorubicin with cyclophosphamide (AC) before surgery (Sx) and radiation therapy (Rxt)

<p><b>Copyright information:</b></p><p>Taken from "Systemic chemotherapy induces microsatellite instability in the peripheral blood mononuclear cells of breast cancer patients"</p><p>Breast Cancer Research 2004;7(1):R28-R32.</p><p>Published online 4 Nov 2004</p><p>PMCID:PMC1064099.</p><p>Copyright © 2004 Fonseca et al., licensee BioMed Central Ltd.</p> Each star below the straight line indicates a blood sample collection (time intervals between collections are not to scale). Single-strand conformation polymorphism (SSCP) gels for two MSI markers PCR15.1 and ALU from the patient represented in panel a, showing the occurrence of LOH and MSI (black arrows). Each lane corresponds to one of the blood samples collected from this patient. Note that MSI disappears whereas LOH persists

Invasion capacity and percentage of apoptosis in EC-derived cell lines.

<p>(A) Values of relative invasiveness of EJ-ras EC, Adh1⁻EC and Adh2⁻EC cells normalized with those of EC cells (100%). Invasion activity of EC-derived cell lines was analyzed by using a Transwell coated with ECL cell attachment matrix as described in Methods. (B) Percentage of apoptotic cells detected by Annexin V-FITIC/PI double staining method in EC, EJ-<i>ras</i> transfected cells (EJ-ras EC), and EC anoikis resistant (Adh1vEC and Adh2⁻EC) cells. All experiments were repeated three times. The bars represent the standard error. * P≤0.05.</p

[³⁵S] sulfated glycosaminoglycans synthesized by EC, EJ-ras EC, Adh1⁻EC and Adh2⁻EC cells.

<p>(A) Endothelial cells were exposed to [³⁵S]sulfate for 18 h. The radioactive glycosaminoglycan-free chains were prepared, from both cells and conditioned medium, by incubation with proteolytic enzyme. Aliquots were subjected to electrophoresis for 60 min in 0.6% agarose (0.05 M 1,3-diaminopropane-acetate buffer pH 9.0) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116001#pone.0116001-Liu1" target="_blank">[38]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116001#pone.0116001-Buonassisi1" target="_blank">[39]</a>. The radioactive compounds were located in the gels, as described in Methods. CS: chondroitin sulfate; DS: dermatan sulfate; HS: heparan sulfate; OR: origin. (B) Quantification of the experiment shown in A. For further details, see Methods. The experiments were performed in duplicates and repeated three times. EC: parental endothelial cells; EJ-ras EC: EJ-ras transfected endothelial cells; Adh1⁻EC and Adh2⁻EC: anoikis-resistant endothelial cells. The bars represent the standard error. * P≤0.05.</p

Adhesion rate of EC-derived cell lines.

<p>(A), (B) and (C) Assay adhesion of parental (EC), EJ-ras transfected endothelial cells (EJ-ras EC), and anoikis-resistant endothelial cells (Adh1⁻EC and Adh2⁻EC) on fibronectin, laminin, and collagen IV, respectively. ABS: absorbance. The experiments were performed in triplicates and repeated three times. The bars represent the standard error. * P≤0.05.</p