Énuloses dérivés di-O-isopropylidènes du d-glucose,d-galactose et d-fructose

The production of modified amyloses often involves the p-toluenesulfonylation of the primary hydroxyl group of the d-glucopyranosyl residues, but it was not known whether this esterification is random when ～20% of the d-glucopyranosyl residues have been substituted. The reaction of p-toluenesulfonyl chloride with amylose in pyridine, in C-methylpyridines, in aqueous 2m KOH, and in dimethyl sulfoxide-pyridine yielded unsatisfactory products. However, p-toluenesulfonylation of 2,3-di-O-acetylamylose in pyridine yielded products that were converted into 2,3-di-O-acetyl-6-deoxy-6-iodoamylose, and thence into 6-deoxyamylose, a suitable substrate for the amylase to be used in the determination of random substitution. The hydrolysis products formed by the action of the crystalline, liquefying amylase of Bacillus subtilis were separated and analyzed. When a summation of the minimum number of separated, modified D-glucopyranosyl residues was compared to a computer-based calculation of the clustering expected, the results showed random esterification.     

Spat collection studies on pearl oysters Pinctada mazatlanica and Pteria sterna (Bivalvia,Pteriidae) in Bahia de La Paz,South Baja California,Mexico

The present work deals with the temporal and bathymetrical variations of the epifaunal community associated with two species of pearl oysters (Pinctada mazatlanica and Pteria sterna) during a seed collecting season from June to November 1989. A total of 63 items (species, genera and/or families) were recorded; their variations in presence and abundance were followed during three periods (June–July, August–September and October–November). The collectors were examined for different immersion times (2, 4, 6 and 8 weeks) for each period. Community structure was compared through the Brillouin Index, the Morisita Index and the Importance Value.We define the chronology of spatfall for both species of pearl oysters and their bathymetrical distribution. Relationships between these species and the epifaunal community present into the collectors were analysed, searching for possible noxious effects on the survival of juvenile pearl oysters, and identifying index species related with their spatfall. A strategy for starting massive seed collection of both species is established, particularly for P. mazatlanica.     

Role of membrane colchicine binding proteins in the transmission of prolactin message to casein genes in the rabbit mammary gland

Previous work demonstrated that tubulin binding drugs specifically inhibit the capacity of prolactin to initiate casein and DNA synthesis in the mammary cell. It was concluded that microtubules or other tubulin containing cellular structures were involved in the transmission of the prolactin message to genes. In the present work, it is shown that griseofulvin, an antimitotic drug which alters microtubule structure and function, does not prevent prolactin actions. Autoradiographic studies showed that [3H]colchicine binds preferentially to plasma and Golgi membranes in the mammary cell. Short term cultures of mammary explants with [3H]colchicine demonstrated that the labelled drug binds to membranous cellular structures which were isolated from explants at the end of the culture. Fractions containing plasma and Golgi membranes contained the highest amount of radioactivity. Solubilisation of the membranes by Triton X-100 dissociated the [3H]colchicine from the prolactin receptors as judged by a chromatography of the soluble fraction on a Sepharose 6 B column. On the column, the labelled colchicine remains associated with a molecular entity which may be free tubulin. In all cases, the binding of [3H]colchicine was greatly attenuated by an excess of unlabelled colchicine but was only slightly affected by the competition with lumicolchicine. These results suggest that mammary membranes contain tubulin and that binding of drugs to this molecule inhibits the generation of the prolactin second messengers eliciting the hormonal actions in the mammary cell. This also suggests that microtubules are probably not involved in the mechanism of prolactin action.