4,4,14 alpha-trimethyl 9 beta,19-cyclo-5 alpha-26-homocholesta-24,26-dien-3 beta-ol: a potent mechanism-based inactivator of delta 24(25)- to delta 25(27)-sterol methyl transferase

The title compound (4A) was synthesized and tested as a mechanism-based inactivator of the sterol methyl transferase (SMT) enzyme from Prototheca wickerhamii. Using cycloartenol as substrate, 4A was found to exhibit time-dependent inactivation kinetics, generating a Ki value of 30 microM and Kinact value of 0.30 min-1.     

Cyclohexane transformation during water chlorination

Cyclohexane transformation was studied during water chlorination. Three mechanisms of cyclohexane transformation in the presence of chlorine were determined. Over 70 reaction products were identified. Five of them have mutagenic activity.     

The present state of the art in chemotherapy for soft tissue sarcomas in adults: the EORTC point of view

In the present study effects of light on the sleep duration of anesthetized hornets (Vespa orientalis) were investigated. Following initial anesthesia by diethyl ether the sleeping time of workers and drones at 22 degrees C in the dark was 59 +/- 15 min. After repeated anesthesia the sleeping time was 30 +/- 15 min in the dark. When exposed to polychromatic light from a halogen lamp of 230 mW/cm2, focused on a spot of the cuticle of the hornet, the sleeping time was markedly shortened so that following initial as well as repeated anesthesia the hornets woke up after 4.5 +/- 2.9 min. Any decrease in light intensity resulted in an increase in the sleeping time but irradiances of less than 14 mW/cm2 had no measurable influence on the wake-up time. After illumination with polychromatic light from a mercury lamp the sleeping times were much shorter than after illumination with a halogen lamp at the same conditions and intensity. This difference is attributed to the relatively higher portion of U.V. light in the total emission of the Hg lamp. Effects of the spectral composition of the incident light beam on the wake-up of the sleeping hornets were also investigated. Near U.V. light in the 300-400 nm region was found to be most efficient. Shorter wavelengths as well as wavelengths between 400-470 nm had less influence and wavelengths above 470 nm had very little effect on the wake up. The sleeping times of hibernating queens were relatively longer than those of workers and drones under the same conditions. These effects are ascribed to the extraretinal light perception. The possible reasons underlying this phenomenon are discussed.     

Leishmania mexicana: proteinase activities and megasomes in axenically cultivated amastigote-like forms

Proteinase activities and megasomes were examined in axenically cultivated amastigote-like forms, freshly isolated lesion amastigotes, and promastigotes. Megasomes were absent in promastigotes and present in both amastigote stages, but they seemed to be less numerous and more homogeneous in cultured amastigote-like forms. Contrasting with the poor detection of proteinase activities in promastigote lysates, both types of amastigotes shared multiple proteinases, which were classified in two groups: (a) 60 to > 100 kDa, o-phenanthroline-sensitive activities; and (b) 23- to 40-kDa cysteine proteinases, of which those resolving as 35- to 40-kDa bands in gelatin gels were more clearly visualized in lysates of cultured amastigote-like forms. Incubation of both kinds of amastigotes with 0.25 to 1.0 microM of either Z-Phe-AlaCHN2 or Z-Tyr-AlaCHN2 selectively inactivated cysteine proteinases, but not the 35- to 40-kDa activities, which, again, were detected with higher intensity in cultured amastigote-like forms. The expression of the 35- to 40-kDa proteinases progressively increased when promastigotes were allowed to transform into amastigote-like forms or when lesion amastigotes were incubated at 34 degrees C for different time periods prior to exposure to Z-Phe-AlaCHN2; activities comparable to those of amastigote-like forms were attained within 24 to 48 hr. The activities resistant to Z-Phe-AlaCHN2 in vivo were fully inhibited by E-64 or Z-Phe-AlaCHN2 during gelatin digestion, suggesting that the 35- to 40-kDa proteinases were mainly inactive before cell lysis. The presence of cycloheximide (at 10, 50, and 100 micrograms/ml) during the pulse with Z-Phe-AlaCHN2 abolished the 35- to 40-kDa activities of lesion amastigotes and significantly reduced gelatin digestion by the similar enzymes of cultured amastigote-like forms. In the latter, the 35- to 40-kDa proteinases were no more detected when cycloheximide was given 60 min prior to Z-Phe-AlaCHN2. The results indicate higher rates of synthesis of the 35- to 40-kDa enzymes, and the existence of a more representative pool of inactive enzyme precursors, in cultured amastigote-like forms.