Kinetic constraints and features imposed by the immobilization of enzymes onto solid matrices: a key to advanced biotransformation.

The kinetics of immobilized enzymes can not be analyzed by means of the simple Michaelis-Menten concept, which generally fails to describe the immobilized state due to both its probable barriers, and because the active concentration of the enzyme approaches, or even exceeds this of its substrate(s). In such cases, the various experimental data are usually treated by complex rate equations comprising too many parameters acquiring different natures and meanings, depending on both the properties of the immobilization state and the experimental conditions; thus, more likely, only apparent values of the Michaelis-Menten kinetic parameters can be estimated experimentally. Likewise, immobilization is often a key method in optimizing the operational performance of enzymes, in both laboratory and industrial scale, and affects considerably the kinetics in non-aqueous and non-conventional media due to several issues as the structural changes of the enzyme molecule, the heterogeneity of the system, and the partial or total absence of water. In this work a theoretical approach is described on the formulation of simplified rate equations, reflecting also the actual mass balances of the reactants, in the case where esterification synthetic reactions are catalyzed by immobilized lipases, in either a non-aqueous organic solvent or in a non-solvent system.

Infections in traumatic brain injury patients.

Traumatic brain injury (TBI) victims are considered to be at high risk for infection. The purpose of this cohort study was to delineate the rates, types and risk factors for infection in TBI patients. Retrospective surveillance of infections was conducted for all TBI patients, aged ≥18 years, cared for at the Department of Neurosurgery of the University Hospital of Heraklion, Greece, between 1999 and 2005. A total of 760 patients (75% men) with a median age of 41 years were included. Most (59%) were injured in a motor vehicle accident. One third of them underwent a surgical procedure. Two hundred and fourteen infections were observed. The majority were infections of the lower respiratory tract (47%), followed by surgical site infections (SSI) (17%). Multivariate analysis showed that SSI development was independently associated with the performance of ≥2 surgical procedures (OR 16.7), presence of concomitant infections, namely VAP (OR 5.7) and UTI (OR 8.8), insertion of lumbar (OR 34.5) and ventricular drains (OR 4.0), and cerebrospinal fluid (CSF) leak (OR 3.8). Development of meningitis was associated with prolonged hospitalization (OR 1.02), especially >7 days ICU stay (OR 25.5), and insertion of lumbar (OR 297) and ventricular drains (OR 9.1). There was a notable predominance of Acinetobacter spp. as a VAP pathogen; gram-positive organisms remained the most prevalent in SSI cases. Respiratory tract infections were the most common among TBI patients. Device-related communication of the CSF with the environment and prolonged hospitalization, especially in the ICU setting, were independent risk factors for SSIs and meningitis cases.

The management of glomus jugulare tumours.

The treatment details of 58 patients treated for glomus jugulare tumours in Newcastle upon Tyne are examined in the light of other studies reported in the literature. For the group of 55 patients treated by radiotherapy, the 20 year survival is 94% (determined actuarially). The 20 year disease-free survival (determined actuarially) is 77%. This is comparable with other series reported. As no glomus tympanicum tumour has recurred following surgery and there has been no morbidity due to these tumours they have not been included in the series. It is recommended that patients who are fit and have tumours confined to the tympanum should have primary surgical treatment. All other patients should be treated by accurately planned radiotherapy, using a dose of 50Gy in 5 weeks to the tumour volume. The morbidity of this treatment policy will be low.