Evaluaciones del inicio floral de cuatro cultivares de mango sometidos a diferentes intensidades de poda y a la aplicación de paclobutrazol (PBZ) fueron realizadas durante cuatro ciclos de producción, y a través de los registros climáticos se establecieron relaciones con las condiciones durante la ocurrencia del proceso. Los cultivares fueron: Haden, Tommy Atkins, Springfels y Edward, sembrados a una distancia de seis metros entre sí (278 pl ha-1). Los tratamientos fueron: testigo (T) en libre crecimiento, T+ PBZ (aplicado al suelo 2,5 g i.a por planta), poda (P) a 2 m de altura del suelo, P + PBZ, P + corte lateral de las ramas a un radio de 2 m. del tronco (P+L) y P + entresaque de 1-2 ramas primarias desde su inserción en el tronco (P+E). Los resultados indicaron que el inicio de la floración está asociado al incremento del número de días con temperaturas nocturnas iguales e inferiores a 20ºC; así como sugieren, la existencia de requerimientos del número de días acumulados por debajo de 20ºC, distinto entre los cultivares. Independientemente del ciclo anual, la floración se inicio en el tratamiento T y T+PBZ del Edward , que ha excepción del ciclo 1998-1999, se anticipo en 2 a 3 semanas del resto de los cultivares y tratamientos. La aplicación de la poda (P) independientemente de su intensidad y del cultivar, retardó el inicio de la floración. La ocurrencia de una acentuada disminución de las lluvias precediendo el inicio de la floración, creó condiciones que favorecen al proceso propiciando una reducción y/o paralización del desarrollo vegetativo que permite la maduración de las hojas.

Evaluations of the floral behaviour of four mango cultivars submited to different pruning intensities and paclobutrazol aplications were made over four production cycles and through climatic registers relationships between previous and present climatic conditions during flowering were established. The cultivars Haden, Tommy Atkins, Springfels and Edward grafted on "Criollo" stalks were planted at 6x6 m (278 trees ha-1) to evaluate the pruning effect at a height of 2m, the Paclobutrazol (PBZ) effect when applied to the soil (2,5 g. ai per tree) and flowering promoter Potassium Nitrate (KNO3), at 6% on the vegetative growth, flowering and yield of mango cultivars. The treatments were: Checker (T), T + PBZ, Pruning (P) and P + PBZ. P + lateral branches pruning of radius at 2 m (P+L) and P + pruning of internal primary branches (P+E). The results indicated that innitiation of flowering is associated with the increment of the number of days with night temperatures under or equal to 20ºC; also they suggest the existence of different requirement of number of days under 20ºC among cultivars, independent of the annual-production cycle. With the exception of the 1998-1999 cycle, the flowering started first in the treatment T and T + PBZ in Edward with an anticipation of 2-3 weeks in relation to the other cultivars and treatments considered. The pruning aplication delayed (P) the beginning of flowering, regardles of its intensity and the cultivar. The ocurrence in all cycles of a marked disminishing of rain, which preceded the beginning of flowering, propiciated a lower vegetative development and leaf maduration, which created a conditions that favoured the leaf maturing process.

The interaction of plasminogen, tissue plasminogen activator (t-PA) and urokinase with a clinical strain of Helicobacter pylori was studied. Plasminogen bound to the surface of H. pylori cells in a concentration-dependent manner and could be activated to the enzymatic form, plasmin, by t-PA. Affinity chromatography assays revealed a plasminogen-binding protein of 58.9 kDa in water extracts of surface proteins. Surface-associated plasmin activity, detected with the chromogenic substrate CBS 00.65, was observed only when plasminogen and an exogenous activator were added to the cell suspension. The two physiologic plasminogen activators, t-PA and urokinase, were also shown to bind to and remain active on the surface of bacterial cells. epsilon-Aminocaproic acid caused partial inhibition of t-PA binding, suggesting that the kringle 2 structure of this activator is involved in the interaction with surface receptors. The activation of plasminogen by t-PA, but not urokinase, strongly depended on the presence of cells and a 25-fold enhancer effect on the initial velocity of activation by t-PA compared to urokinase was established. Furthermore, a relationship between cell concentration and the initial velocity of activation was demonstrated. These findings support the concept that plasminogen activation by t-PA on the bacterial surface is a surface-dependent reaction which offers catalytic advantages.

We cloned the streptokinase (STK) gene of Streptococcus equisimilis in an expression vector of Escherichia coli to overexpress the profibrinolytic protein under the control of a tac promoter. Almost all the recombinant STK was exported to the periplasmic space and recovered after gentle lysozyme digestion of induced cells. The periplasmic fraction was chromatographed on DEAE Sepharose followed by chromatography on phenyl-agarose. Active proteins eluted between 4.5 and 0% ammonium sulfate, when a linear gradient was applied. Three major STK derivatives of 47.5 kDa, 45 kDa and 32 kDa were detected by Western blot analysis with a polyclonal antibody. The 32-kDa protein formed a complex with human plasminogen but did not exhibit Glu-plasminogen activator activity, as revealed by a zymographic assay, whereas the 45-kDa protein showed a Km = 0.70 µM and kcat = 0.82 s-1, when assayed with a chromogen-coupled substrate. These results suggest that these proteins are putative fragments of STK, possibly derived from partial degradation during the export pathway or the purification steps. The 47.5-kDa band corresponded to the native STK, as revealed by peptide sequencing