Activation by phorbol esters of protein kinase C in MCF-7 human breast cancer cells

Exposure of MCF-7 human breast cancer cells to the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) leads to the inhibition of cell proliferation. We investigate here the short-term effects of TPA on subcellular distribution of protein kinase C, and on protein phosphorylation in cultured MCF-7 cells. We report a rapid and dramatic decrease in cytosolic protein kinase C activity after TPA treatment. Only 30% of the enzymatic activity lost in the cytosol was recovered in the particulate fraction. These data suggest that subcellular translocation of protein kinase C is accompanied by a rapid down-regulation of the enzyme (70%). Furthermore, TPA and other protein kinase C activators rapidly induce the phosphorylation of a 28 kDa protein in intact MCF-7 cells. Phorbol esters devoid of tumor-promoting activity are ineffective both for inducing these early biochemical events and for inhibiting cell proliferation.     

High-performance liquid chromatography of coenzyme A esters formed by transesterification of short-chain acylcarnitines: Diagnosis of acidemias by urinary analysis

A protocol for the identification and estimation of short-chain esters of carnitine is described; it is useful for the diagnosis of acidemias. By this method, carnitine esters in urine are converted to coenzyme A esters enzymatically with carnitine acetyltransferase (CAT): short-chain acylcarnitine + CoA cat in equilibrium short-chain acyl-CoA + carnitine. The coenzyme A esters are separated by high-performance liquid chromatography using a radial compression system with a C8 Radial-Pak cartridge and a mobile phase containing 0.025 M tetraethylammonium phosphate in a linear gradient of 1 to 50% methanol. Coenzyme A esters are quantitated by integrator determination of the area under the 254-nm absorption peaks. Enzymatic conversion approaches 100% for acetyl and propionyl esters except in the presence of high levels of free carnitine, which lowers the proportion of ester as acyl-CoA at equilibrium. However, since acidemia patients produce urine low in free carnitine, this problem is minimized. The method is rapid and simple and identifies propionic, methylmalonic, and isovaleric acidemias.     

Rapeseed oil methyl esters preparation using heterogeneous catalysts

The classical method of fatty acids methyl esters (FAME) production is based on triglyceride transesterification to methyl esters. Sodium hydroxide dissolved in methanol is used as a catalyst. The purpose of this work was to examine a heterogeneous catalyst, in particular calcium compounds, to produce methyl esters of rapeseed oil. This research showed that the transesterification of rapeseed oil by methyl alcohol can be catalysed effectively by basic alkaline-earth metal compounds: calcium oxide, calcium methoxide and barium hydroxide. Calcium catalysts, due to their weak solubility in the reaction medium, are less active than sodium hydroxide. However, calcium catalysts are cheaper and lead to decreases in the number of technological stages and the amount of unwanted waste products. It was found that the transesterification reaction rate can be enhanced by ultrasound as well as by introducing an appropriate reagent into a reactor to promote methanol solubility in the rapeseed oil. Tetrahydrofuran was used as additive to accelerate the transesterification process.     

Cell survival and multiplication

Abstract There are clear similarities in the control mechanisms for cell survival and multiplication in the two eukaryotes, the ciliate Tetrahymena thermophila and the yeast, Saccharomyces cerevisiae . Cell multiplication in both organisms is activated by the same compounds (phorbol esters, diacylglycerol, tetrapyrroles, etc.). These compounds also affect cell multiplication and other activities in mammalian cell systems. This homology in control mechanisms in two distinct groups of unicellular eukaryotes on the one hand, and in cells from multicellular animals on the other, leads us to propose that these cytoplasmic control mechanisms for cell survival and multiplication originated in the unicellular eukaryotes.     

The lipid composition of the wax particles from adult whiteflies, Bemisia tabaci and Trialeurodes vaporariorum

Adult whiteflies are characterized by the presence of copious amounts of wax particles covering all surfaces of the body except the eyes. The lipid composition was determined for wax particles removed from the surfaces of the sweetpotato whitefly, Bemisia tabaci (Gennadius), and the greenhouse whitefly, Trialeurodes vaporariorum (Westwood). The lipid components in the wax particles of both species were mostly mixtures of long-chain aldehydes and long-chain primary alcohols. The major wax particle components for B. tabaci were C₃₄ aldehyde and C₃₄ alcohol and small amounts of C₃₂ aldhyde and alcohol. For the wax particles from T. vaporariorum, C₃₂ aldehyde and C₃₂ alcohol were the major components with lesser amounts of the C₃₀ components. These findings were compared to the surface lipids of fully-waxed B. tabaci and T. vaporariorum adults that contained, in addition to the major amounts of long-chain aldehydes and alcohols, quantities of long-chain wax esters. Wax esters were not present in lipid extracts from the surface of B. tabaci whiteflies at the time of adult emergence (prior to deposition of wax particles). Thus, the appearance of wax esters on the cuticular surfaces occurred during the period of deposition of wax particles. The quantities of wax esters in the surface lipid extracts of wing tissues separated from the bodies of adult whiteflies indicated that the wing surfaces were a major site of wax ester deposition.     

Combining regio- and enantioselectivity of lipases for the preparation of (R)-4-chloro-2-butanol

Preparation of 98% ee (R)-4-chloro-2-butanol was carried out by the enzymatic hydrolysis of chlorohydrin esters, using fungal resting cells and commercial enzymes. Hydrolyzes were carried out using lipases from Candida antarctica (Novozym 435), C. rugosa, Rhizomucor miehei (Lipozyme IM), Burkolia cepacia, and resting cells of Rhizopus oryzae and Aspergillus flavus. The influence of the enzyme, the solvent, the temperature, and the alkyl chain length on the selectivity of hydrolyzes of isomeric mixtures of chlorohydrin esters is described. Regioselectivity was higher than 95% for some of the tested lipases. Novozym 435 allowed preparation of the (R)-4-chloro-2-butanol after 15 min of reaction at 30-40 degrees C.     

平菇转化叶黄素酯研究

目前针对有关天然产物的生物转化研究较少,首次报道了平菇转化叶黄素酯的研究。在对平菇在叶黄素酯培养基生长的观察中,发现对于固体培养基,菌丝体可利用叶黄素酯但不能增生,而孢子悬液不能生长,但在发酵液中两者生长良好,可见只有菌丝体可分泌水解酶,而且谊酶在溶液环境下效价高。同时利用高效液相色谱测定其降解效果发现,平菇首先将叶黄素酯转化为叶黄素,同时也可将叶黄素转化为其它物质,故控制发酵时间非常重要,这为今后的工业化提供了基础。     

Contact chemostimuli in the mating behaviour of the cattle tick,Boophilus microplus

Mating of the cattle tick Boophilus microplus is mediated by chemical stimuli on the cuticle of females. Males are arrested on the dorsum of females attached to the host, frequently sample the substrate, and then tip-over to the ventrally located gonopore. These behaviours are also observed in vitro when males are placed on a small glass bead treated with a female extract. Time spent and tip-over by male ticks on dummies is used in an assay to test the behavioural significance of fractions of the extract. TLC separation yields one apolar fraction that arrests males, though much less so than the whole extract, but lost tip-over behaviour. This apolar fraction contains a series of cholesteryl esters that, when tested individually, show no arrestment activity at levels present in the extract but, when combined, are as active as the fraction. When a small silica column is used for fractionation, all biological activity is reproduced after recombining the fractions. In addition to the early eluting apolar fraction containing cholesteryl esters, a set of highly active more polar fractions is isolated. Electrophysiological recordings from gustatory sensilla on the pedipalps of male B. microplus, which are regularly brought into contact with the cuticle of the female during mating, provide evidence for receptors in two of them responding to the whole extract and to the behaviourally active polar fractions. Mating behaviour involving arrestment and tip-over is clearly initiated by a mixture of chemical stimuli, and tip-over behaviour is associated with the more polar material. Arch. Insect Biochem. Physiol. 39:65–80, 1998. © 1998 Wiley-Liss, Inc.