Increased leukocyte aggregation in patients with hypercholesterolaemia

Leukocyte aggregation induced by N-formylmethionyl-leucyl-phenylalanine (FMLP) has been measured in a group of patients with hypercholesterolaemia (n = 22) and in a group of control subjects (n = 26), age- and sex-matched. When hypercholesterolaemic patients were divided into two groups, with a discriminatory level of 7.7 mmol/l of plasma cholesterol, FMLP-induced leukocyte aggregation of patients with greater than 7.7 mmol/l of plasma cholesterol was significantly higher compared both with control subjects and patients with plasma cholesterol levels less than 7.7 mmol/l. A positive significant correlation was found between leukocyte aggregation and plasma cholesterol, whereas no correlation was observed between leukocyte aggregation and plasma triglycerides or APO-B levels. These findings provide further support for the hypothesis that elevated plasma cholesterol levels may induce a cellular membrane abnormality responsible for the increased leukocyte aggregation and, subsequently, endothelial damage.

The Crystal Structure of Cis-1,4 Polybutadiene

In previous works, we announced the identification and discussed the structure of three of the four possible pure stereoisomers of polybutadiene ; two with 1,2 enchainment (isotactic and syndiotactic respectively) and the third with trans-1,4 enchainment. In a letter to the Editor of Angewandte Chemie we have given preliminary data concerning the crystal structure of the polymer with cis-1,4 configuration, of which we succeeded in preparing sufficiently long and crystallizable macro-molecular chains formed by cis-1, 4 units. All the various stereoisomeric polymers we examined were prepared with different catalysts, all obtained by reaction of metalalkyls on suitable compounds of transition elements. For all these catalysts the mechanism of the polymerization reaction is of the co-ordinated anionic type. The different behavior can be ascribed to the mode of co-ordination of the olefin with the metallorganic complex of the transition metal.

General Considerations on the Structure of Crystalline Hydrocarbon Polymers

Owing to the discovery of stereospecific polymerization processes effected in our Institute, we were able to determine, in the last few years, the crystal structure of a great number of new polymers. In this work we will discuss the general principles leading to the determination of the shape and mode of packing of macromolecules in the crystals.

The Structure of Crystalline 1,2-Polybutadiene and of Other Syndyotactic Polymers

Systematic x-ray and electron diffraction studies of polymers of 1,3-butadiene prepared by different anionic catalysts have made it possible for us to identify two types of highly crystalline materials. One of us (G. N.) has already reported that our synthesis was carried out with the aid of different highly selective catalysts. The description of the preparation of these catalysts, which have made it possible for the first time to prepare these new polymers, will be separately published by one of us (G. N.) with L. Porri. Infrared analysis carried out by E. Mantica and D. Morero in our Institute has established that one type of these crystalline polymers obtained with heterogeneous catalysts represents a continuous l,4-trans arrangement of the monomer units. X-ray diffraction has shown that this material is dimorphous, having one crystalline modification that is stable at room temperature and another stable above 60° C. The x-ray melting point of a polymer having a molecular weight of the order of 100,000 is around 130° C. The low-temperature modification has an identity period of 4.9 A along the chain axis and a hexagonal packing with a period of a=4.54 A perpendicular thereto, but the symmetry of the crystals, as a whole, is lower. The high temperature modification seems to have the chains in helicoid form. The other crystalline polymer consists essentially of 1,2-monomer units; infrared studies have shown that more than 90 per cent of its double bonds are of the vinyl type and the residual 10 per cent represents a mixture of cis and trans. The higher the proportion of 1,2-units, the more crystalline is the material. Figure 1 shows the infrared absorption curves of two different typical samples of the product. In this article, we limit ourselves to describing the structure of the latter polymer, which, in our opinion, is the more interesting material and which we shall simply call 1,2-polybutadiene. We shall report on the structure of the two modifications of the l,4-trans-polybutadiene in another paper together with the study of the structure of other crystalline polydienes.