Concerning the intermediacy of organic radicals in vitamin B12-dependent enzymic reactions

The vitamin B12 coenzyme adenosylcobalamin assists the enzymic catalysis of molecular rearrangements of the type (formula; see text) in which the migrating group X can be OH, NH2 or a suitable substituted carbon atom such as C(=CH2)CO2H. This paper discusses evidence for the participation of organic radicals as intermediates in these reactions. Theoretical and model studies supporting the intermediacy of radicals in the reactions catalysed by the enzymes diol dehydratase and alpha-methyleneglutarate mutase are described. For the model studies, alkyl radicals, alkylcobaloximes (alkyl represents, for example, ethoxycarbonyl substituted, but-3-enyl and cyclopropylmethyl) and also dihydroxyalkylcobalamins have been investigated. The Co-C alpha-C beta angle of 125 degrees in adenosylcobalamin is shown to be an 'especial' angle by analysis of the crystal structures of R- and S-2,3-dihydroxypropylcobalamin.     

Immunohistochemical and electron microscopic identification of serotonin, melatonin and beta-endorphin in the granules of natural killers

The ability of serotonin, melatonin and beta-endorphin synthesis by secreting granules of natural killer cells (NK cells) was established by immunohistochemical method. It was shown that cytotoxic effect of NK cells can be to a certain extent related to the presence of secreting granules. A possible direct contribution of NK cell-synthesized hormones to the natural killer antitumour effect is discussed.     

A rapid method for the purification of supercoiled PM2 DNA by affinity chromatography on H1 histone covalently coupled to agarose.

A simple and rapid method is described for the purification of supercoiled PM2 DNA by affinity chromatography on columns of H1 histone covalently coupled to agarose. The method does not require the use of intercalating agents or ultracentrifugation procedures. Under the conditions most appropriate for purification, elution is carried out in a single step with buffered 0.7 M NaCl after the sample has been loaded onto the column in buffered 0.2 M NaCl. The DNA eluted at the higher salt concentration consists of supercoiled closed circular DNA at greater than 90% purity independently of the ratio of supercoiled to nicked circular DNA in the input mixture.     

Tubulin polymerisation in the presence of GMP-PCP

Microtubules induced by the binding of GTP or of a non-hydrolysable analog of GTP onto the exchangeable site of tubulin appear very similar according to electron microscopy and polymerisation kinetics criteria. However, we show here that the exchangeable sites or “E” sites of the tubulin subunits remain available for nucleotide exchange inside the GMP-PCP-microtubules contrary to the “E” sites inside the GDP-microtubules. Moreover, under specific conditions, GMP-PCP induces the polymerisation of tubulin into a bidimensional, pseudocrystallin structure. Such a “crystallisation” is inhibited by GTP and GDP.     

The portal vein and its main affluents. An anatomic and morphometric study

There are reported the results of certain measurements made on 158 human cadavers of both sexes. A series of main parameters are given, such as the distance between the superior mesenteric vein and on the one hand its confluence with other vessels and on the other hand the pancreas and the horizontal part of the duodenum: the distance between the superior mesenteric vein together with the portal vein, and the inferior caval vein; the diameters of the portal trunk and the confluence angle between the roots of the portal vein. The results reflect the possibility to perform a troncular portocaval anastomosis in at least 90 per cent of the cases. The authors' attention was, however, directed towards the anatomy of the superior mesenteric vein, as this vessel is preferred by some surgeons in the achievement of the portocaval anastomosis.