NaStEP, an essential protein for self-incompatibility in Nicotiana, performs a dual activity as a proteinase inhibitor and as a voltage-dependent channel blocker.

The S-specific pollen rejection response in Nicotiana depends on the interaction between S-RNase and a suite of SLF proteins. However, the biochemical pathway requires other essential proteins. One of them is the stigmatic protein NaStEP, which belongs to the Kunitz-type protease inhibitor family. Within the pollen tubes, NaStEP is a positive regulator of HT-B stability, likely inhibiting its degradation and, additionally, interacts with NaSIPP, a mitochondrial phosphate carrier. To gain a deeper understanding of the biochemical role of NaStEP in pollen rejection, we evaluated whether the activity of NaStEP as protease inhibitor is specific to a particular type of protease and whether it has the function of a voltage-dependent channel (VDC) blocker. Our findings indicate that, in vitro, NaStEP inhibits a subtilisin-like protease in an irreversible manner, but not other proteases, such as thermolysin and papain. Furthermore, we found that subtilisin processes the native NaStEP (24 kDa) into two lower molecular weight peptides of 21 and 14 kDa. Moreover, when we incubated NaStEP along with Xenopus leavis oocytes expressing the voltage-dependent potassium channel Kv 1.3, the current was blocked, indicating that NaStEP acts as a VDC blocker. These data allow us to propose NaStEP acts as a key molecule with two functions, one protecting HT-B from degradation by inhibiting a subtilisin-like protease and the second one by forming a complex with a mitochondrial VDC that could destabilize the mitochondria to trigger cell death, which would reinforce S-specific pollen rejection in Nicotiana.

Novel TASK channels inhibitors derived from dihydropyrrolo[2,1-a]isoquinoline.

TASK channels belong to the family of K(+) channels with 4 transmembrane segments and 2 pore domains (4TM/2P) per subunit. These channels have been related to apoptosis in cerebellar granule neurons (CGN), as well as cancer in other tissues. TASK current is regulated by hormones, neurotransmitters, anesthetics and divalent cations, which are not selective. Recently, there has been found some organic compounds that inhibit TASK current selectively. In order to find other modulators, we report here a group of five dihydropyrrolo[2,1-a]isoquinolines (DPIs), four of them with putative anticancer activity, that were evaluated on TASK-1 and TASK-3 channels. The compounds 1, 2 and 3 showed IC50 < 320 µM on TASK-1 and TASK-3, intermediate activity on TASK-1/TASK-3 heterodimer, moderate effect over hslo and TREK-1 (500 µM), and practically not inhibition on Shaker-IR, herg and IRK2.1 potassium channels, when they were expressed heterologously in Xenopus laevis oocytes. In rat CGN, 500 µM of these three compounds induced a decrement by >39% of the TASK-carried leak current. Finally, only compound 1 showed significant protection (∼36%) against apoptotic death of CGN induced by K(+) deprivation. These results suggest that DPI compounds could be potential candidates for designing new selective inhibitors of TASK channels.

Electrochemical strategy to scout 1,4-naphthoquinones effect on voltage gated potassium channels.

Naphthoquinone (NQ) was tested on voltage-gated ion channels expressed in Xenopus laevis oocytes. The activity of potassium Shaker channel with Inactivation domain Removed (ShIR) was not affected; in contrast, NQ diminished Kv1.3 currents. A current decrease was barely observed with the oxidant H(2)O(2). These findings suggested that redox properties were involved in the naphthoquinone-Kv1.3 channel interaction. NQ and some derivatives (NQs) were characterized in DMSO and physiological (ND-96) media by cyclic voltammetry. A typical two-stage mono-electronic reduction mechanism was observed in DMSO, while a one-stage bi-electronic reduction process was found in ND-96 medium. NQs with the lowest and the highest redox potential values were tested on both channels. Voltage-clamp recordings showed that inhibition of Kv1.3 was dependent on NQs redox potential. Results demonstrated that structural features (aromaticity and substituents prone to hydrogen bonds formation) of NQs were also important. This effect could be explained by interactions of some channel residues with NQs that contribute to favor their reduction process in the protein surroundings. The electrochemical strategy presented to simulate the cellular environments (aqueous and non-aqueous) that NQs may face, is an important contribution to pre-select (in a fine and simple way) the best redox compounds for electrophysiological testing.

Slotoxin, alphaKTx1.11, a new scorpion peptide blocker of MaxiK channels that differentiates between alpha and alpha+beta (beta1 or beta4) complexes.

A novel peptide from Centruroides noxius Hoffmann scorpion venom was isolated and sequenced. The 37 amino acid peptide belongs to the charybdotoxin sub-family (alphaKTx1) and was numbered member 11. alphaKTx1.11 has 75% sequence identity with iberiotoxin and 54% with charybdotoxin. alphaKTx1.11 revealed specificity for mammalian MaxiK channels (hSlo), thus, was named slotoxin. Slotoxin blocks the MaxiK pore-forming alpha subunit reversibly (K(d)=1.5 nM). Slotoxin association with alpha+beta (beta1 or beta4) channels was approximately 10 times slower than iberiotoxin and charybdotoxin, leading to a lack of effect on alpha+beta4 when tested at 100 nM for 5 min. Thus, slotoxin is a better tool to distinguish MaxiK alpha+beta complexes.

Aislamiento de ácido algínico y sus sales a partir de algas pardas cubanas / The isolation of alginic acid and its salts from some Cuban brown algae

Se señala que en la literatura al respecto son numerosos los métodos descritos para el aislamiento y purificación del ácido algínico y sus sales, utilizando como materia prima algas pardas con un elevado contenido de algínico, tales como Macroscytis, Piriferia, Laminaria, etc. Se da a conocer el sistema de recolección de algas de "arribazones", las cuales fundamentalmente están constituidas por algas pardas (Sargassumnatans), así como el método utilizado para el aislamiento y purificación del ácido algínico y su sal sódica. Se presentan algunas consideraciones preliminares de carácter económico(AU)

Prostaglandina A(2). Estudio comparativo de métodos fisicoquímicos de caracterización / Prostaglandin A(2). A comparative study of physicochemical methods of characterization

En este trabajo se describen y comparan diferentes métodos fisicoquímicos de caracterización y análisis para la PGA(2) purificada o no. Se proponen los ensayos mínimos necesarios para el control de estos productos obtenidos al nivel semindustrial, y se muestran los parámetros fisicoquímicos típicos para la PGA(2) cruda y purificada obtenida en nuestro país(AU)

Resultados preliminares de la composición del extracto placentario EP-50 utilizado en Cuba en la terapéutica del vitíligo / Preliminary results of the study of the composition of the placental extract 50 (EP-50) used in the treatment of vitiligo in Cuba

Se indica que en 1976, Miyares y colaboradores describieron la acción repigmentante del extracto placentario humano EP-50 33A en la terapéutica experimental del vitíligo. Los resultados positivos obtenidos, estimularon el desarrollo de un estracto más concentrado, el EP-50, con el cual se obtiene igual respuesta en menor tiempo y sin reacciones secundarias. En este trabajo se describen los resultados preliminares obtenidos en el estudio de la composición de dicho extracto, y se exponen conjuntamente los métodos de fraccionamiento con solventes, purificaciones en columna e identificaciones preliminares empleadas. Sobre la base de los resultados obtenidos, se plantea un estudio más profundo del extracto para determinar su mecanismo de acción en la terapéutica del vitíligo(AU)

Un nuevo procedimiento para la obtención industrial de mandelato de metenamina / A new procedure for the industrial obtention of methenamine mandelate

Se indica que el mandelato de metenamina (mandelamina) es un antiséptico urinario de amplio empleo en la terapéutica humana. Nuestro trabajo describe un nuevo procedimiento industrial, mediante el cual se obtiene mandelato de metenamina con calidad farmacéutica. Por ello se hace reaccionar a temperatura de reflujo, ácido mandélico con metenamina en un disolvente orgánico, el producto se separa de la reacción por cristalización y filtración. Se analiza la influencia de la calidad de los agentes reaccionantes sobre el rendimiento y calidad del producto. Se incluyen los datos obtenidos en los ensayos al nivel de producción experimental. Sobre la base de los resultados obtenidos se concluye que el procedimiento, por su sencillez y economía, es adecuado para la obtención industrial del mandelato de metenamina calidad USP(AU)