Hydroxyapatite-polyethylene composites: effect of grafting and surface treatment of hydroxyapatite

The mechanical properties of hydroxyapatite-polyethylene composites have been improved by increasing the interfacial bond between the hydroxyapatite reinforcing particles and the polyethylene. Two types of surface treatment have been investigated: both use silane coupling of the hydroxyapatite, either with or without grafting of the polyethylene. These treatments have lead to the presence of a silicon-containing interphase promoting chemical adhesion and penetration of the polymer into cavities in the ceramic particles. The resultant bond has improved the mechanical properties and fracture behaviour of the composites.This paper was accepted for publication after the 1995 Conference of the European Society of Biomaterials, Oporto, Portugal, 10–13 September.     

The role of perturbations,shunts, cusps and convexity reversals in elucidating enzyme kinetic mechanisms and hysteresis pathways

Irregular perturbations and convexity reversals in enzyme kinetic reactions are mathematically modeled by inhibition, catalytic, and rearrangement reactions. The convexity reversal model is especially interesting since it offers a simple alternative to the conformational argument of allosterism and the subunit coupling notion inherent to the Hill equation. Another unusual pattern, a cusp-like intersection on a fermentation hysteresis trajectory, is tentatively attributed to enzyme denaturation countering enzyme production. The role of convexity in reaction schemes where intermediate concentrations are not measured is also discussed. It is proposed that negative convexity in an early reaction rate transient is a clue to the presence of a shunting pathway in the chemical mechanism.     

Modeling ordinal scale disagreement.

Proposes an approach for modeling chance-adjusted disagreement between 2 raters. By examining a hierarchy of log-linear models, it is shown how ordinal scale disagreement can be modeled in a manner analogous to the analysis of association in a contingency table. A series of hypotheses based on the magnitude and direction of the discrepancies of the ratings is considered. An example based on data from the National Institute of Mental Health Clinical Research Branch Collaborative Program on the Psychobiology of Depression is presented to illustrate the approach. (37 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A trial of the synthetic malaria vaccine SPf66 in Tanzania: rationale and design

By using acetyl strophanthidin (AS) 0.2 mumol/L, the delayed after-depolarization (DAD) was induced in sheep cardiac Purkinje fibers and recorded with intra-cellular microelectrode. When beta-adrenoceptor was blocked by propranolol 1.0 mumol/L, phenylephrine 1.0 mumol/L increased the amplitude of DAD from 8.1 +/- 2.2 mV to 9.5 +/- 2.8 mV, prolonged the duration of DAD from 240 +/- 47 ms to 273 +/- 47 ms (n = 13, P < 0.01) and increased the up rising velocity of DAD from 0.039 +/- 0.023 V/s to 0.051 +/- 0.026 V/s (n = 13, P < 0.05). The DAD occurred earlier for 30 +/- 47 ms to preceding action potential (n = 13, P < 0.05). When triggered action potentials were induced by norepinephrine 1.0 mumol/L on the basis of DAD, propranolol 1.0 mumol/L could suppress the triggered beats while phentolamine 1.8 mumol/L showed little effect. The above results indicate that excitation of alpha-receptor had only slight augmentation effect on DAD. However, for the triggered activity induced by DAD, the inhibitory effect of beta-blockers are stronger than that of alpha-blockers.     

Gene transfer approaches to the regulation of vascular cell proliferation

The anatomopathology of 25 cases of bilharzial cancer is reported involving 20 men and 5 women. The macroscopic studies of the tumors revealed an unifocal, budding and infiltrating pattern. The significant type appeared to be the squamous carcinoma in 13 of the cases. All the 25 cases showed the presence of a bilharzial infestation with several patterns: tumoral clusters of squamous carcinoma and urothelial cells, clusters of scattered signet ring cells, elongated or undifferentiated atypical cells. The chronic inflammatory stroma contained bilharzia ova. The role played by metaplasia of the vesical urothelium is accepted by the majority of authors to explain the histogenesis of theses tumors.