The trypanosomatid cytoskeleton is responsible for the parasite's shape and it is modulated throughout the different stages of the parasite's life cycle. When parasites are exposed to media with reduced osmolarity, they initially swell, but subsequently undergo compensatory shrinking referred to as regulatory volume decrease (RVD). We studied the effects of anti-microtubule (Mt) drugs on the proliferation of Leishmania mexicana promastigotes and their capacity to undergo RVD. All of the drugs tested exerted antiproliferative effects of varying magnitudes [ansamitocin P3 (AP3)> trifluoperazine > taxol > rhizoxin > chlorpromazine]. No direct relationship was found between antiproliferative drug treatment and RVD. Similarly, Mt stability was not affected by drug treatment. Ansamitocin P3, which is effective at nanomolar concentrations, blocked amastigote-promastigote differentiation and was the only drug that impeded RVD, as measured by light dispersion. AP3 induced 2 kinetoplasts (Kt) 1 nucleus cells that had numerous flagella-associated Kts throughout the cell. These results suggest that the dramatic morphological changes induced by AP3 alter the spatial organisation and directionality of the Mts that are necessary for the parasite's hypotonic stress-induced shape change, as well as its recovery.

Uno de los sistemas de propagación in vitro más utilizado en el cultivo de la caña de azúcar, Saccharum sp., es la embriogénesis somática. Durante este proceso ocurren cambios en la expresión de las proteínas que pueden ser determinados mediante el análisis de patrones isoenzimáticos, permitiendo estos la evaluación temprana de los cultivos embriogénicos antes de que los cambios morfogenéticos se hagan evidentes. En el trabajo se estudió la presencia de la actividad fosfatasa ácida (ACP) a partir de callos embriogénicos (E) y no embriogénicos (NE) de caña de azúcar. Con el fin de detectar esta actividad se realizaron electroforesis en geles de poliacrilamida al 10% en condiciones nativas, incubándose luego el gel en presencia de los sustratos a-naftil fosfato y b-naftil fosfato a pH ácido. Paralelamente, se determinó la misma actividad en ensayos enzimáticos a punto final, con ligeras modificaciones. Los perfiles electroforéticos mostraron una única banda en ambos extractos, no observándose diferencias significativas en la intensidad de las mismas. No obstante, el ensayo enzimático reveló una mayor actividad fosfatasa ácida (1,5 veces) en los extractos de callos E que en los NE. Estos resultados preliminares sugieren que esta actividad podría utilizarse como marcadora de los procesos de diferenciación que ocurren durante el cultivo in vitro.

Somatic embryogenesis is one of the in vitro propagation systems used more extensively for sugarcane Saccharum sp., culture. During this process changes in the protein expression patterns are observed and they can be determined using isoenzimatic analysis. This approach allows early evaluation of the embryogenic potential before the morphogenetic changes become evident. In this work, the acid phosphatase activity (PAC) from embryogenic (E) and non embryogenic (NE) calluses of sugarcane was studied. Gel electrophoresis was performed using polyacrylamide 10% gels under native conditions, followed by incubation with a-naftil phosphate and ß-naftil phosphate solutions at acid pH. The same activity was determined on enzymatic assays to end point according to Gottlieb and Dwyer (1981), with some modifications. Electrophoretic profiles showed just one band of the same intensity in each extract. Nevertheless, enzymatic assays revealed a higher acid phosphatase activity (1,5 times) in E callus extracts that in the NE. These preliminary results suggest that acid phosphatase activity could be used as a marker for differentiation processes during in vitro culture.