A stereochemical and statistical analysis of metallocene-promoted polymerization

The metallocene catalysts active in propylene polymerization can be divided into five classes, depending on whether the catalytic sites are chirotopic or not, and on the symmetry relationship between the catalytic sites bound to the same metal atom. Under the hypothesis of a purely alternating mechanism for propagation, class III and class IV catalysts, respectively, give rise to prevailingly isotactic and syndiotactic polymers. Four probabilistic schemes have been developed for interpreting the stereosequence distribution of polypropylene in terms of pentads. They take into account the two sources of steric control, chirotopicity of the catalyst site and configuration of the chain end, and the presence, besides the alternating mechanism, of successive addition steps at the same catalytic site.     

Solid-liquid diagram of polyethylene-perhydrotriphenylene mixtures. Congruent melting of an inclusion compound containing a macromolecular constituent

The melting diagram of polyethylene-perhydrotriphenylene mixturs shows the presence of an addition compound which melts congruently at 178,2°C. This adduct, whose structure was described as an inclusion compound, does not exist in the liquid phase and does not form mixed crystals with the pure constituents. An equation for the liquidus curve has been calculated on the basis of the Flory-Huggins theory and fits the experimental data by placing the interaction parameter χ=0.     

The expression of HSP60 and HSP10 in large bowel carcinomas with lymph node metastase

Background

Cancer serum protein profiling by mass spectrometry has uncovered mass profiles that are potentially diagnostic for several common types of cancer. However, direct mass spectrometric profiling has a limited dynamic range and difficulties in providing the identification of the distinctive proteins. We hypothesized that distinctive profiles may result from the differential expression of relatively abundant serum proteins associated with the host response.

Methods

Eighty-four antibodies, targeting a wide range of serum proteins, were spotted onto nitrocellulose-coated microscope slides. The abundances of the corresponding proteins were measured in 80 serum samples, from 24 newly diagnosed subjects with lung cancer, 24 healthy controls, and 32 subjects with chronic obstructive pulmonary disease (COPD). Two-color rolling-circle amplification was used to measure protein abundance.

Results

Seven of the 84 antibodies gave a significant difference (p < 0.01) for the lung cancer patients as compared to healthy controls, as well as compared to COPD patients. Proteins that exhibited higher abundances in the lung cancer samples relative to the control samples included C-reactive protein (CRP; a 13.3 fold increase), serum amyloid A (SAA; a 2.0 fold increase), mucin 1 and α-1-antitrypsin (1.4 fold increases). The increased expression levels of CRP and SAA were validated by Western blot analysis. Leave-one-out cross-validation was used to construct Diagonal Linear Discriminant Analysis (DLDA) classifiers. At a cutoff where all 56 of the non-tumor samples were correctly classified, 15/24 lung tumor patient sera were correctly classified.

Conclusion

Our results suggest that a distinctive serum protein profile involving abundant proteins may be observed in lung cancer patients relative to healthy subjects or patients with chronic disease and may have utility as part of strategies for detecting lung cancer.     

Improving the preservation of the urethral sphincter and neurovascular bundles during open radical retropubic prostatectomy

OBJECTIVES: To describe a technique for open nerve-sparing radical retropubic prostatectomy. METHODS: The technique basically implies incising the levator and prostatic fasciae high anteriorly (1 and 11 o'clock positions) over the prostate, developing the plane between the prostatic capsule and prostatic fascia, and displacing the neurovascular network localized between the two fasciae laterally. This allows for a minimal-touch dissection of the external urethral sphincter and a very efficient dissection of the neurovascular bundles at the level of membranous urethra and prostatic apex. RESULTS: Forty-two patients underwent a bilateral nerve-sparing operation and were followed- up for 6 months. Six patients (14.3%) had positive margins: 4 patients had pT2 disease (in all, the positive margin was monofocal) and 2 patients had pT3 disease (both had multifocal positive margins). Continence (defined as being dry or having one pad remain dry for 24 hours) was achieved in 44% of patients at catheter removal, and in 60%, 72%, and 90% of patients at the 1-, 3-, and 6-month follow-up visits. Potency (defined as an erectile function domain score > or =26) was obtained in 15%, 40%, and 52% of patients at the 1-, 3-, and 6-month follow-up visits. All patients used a PDE5-inhibitor during the investigation period. CONCLUSIONS: These preliminary results suggest that the high incision of the levator and prostatic fasciae may facilitate efficient preservation of the external urethral sphincter and the neurovascular bundles innervating the corpora cavernosa and the sphincter.