S. Di Martino

Influence of the spacer length on the activity of enzymes immobilised on nylon/polyGMA membranes: Part 1. Isothermal conditions

β-Galactosidase has been immobilised through spacers of different length on nylon membranes grafted with glycidyl methacrylate. Hexamethylendiamine, ethylendiamine or hydrazine have been separately used as spacers. The behaviour of the catalytic membranes has been studied in a bioreactor operating under non-isothermal conditions as a function of the applied temperature difference ΔT. Comparison of the enzyme reaction rates under isothermal and non-isothermal conditions resulted in percentage activity increases (PAI) and reduction of the production time (τr) proportional to the size of the applied ΔT. Both these parameters increased with the increase of the spacer length. Results have been discussed in the frame of reference of the process of thermodialysis which reduces the limitations to the diffusion of substrate and reaction products across the catalytic membrane, limitations introduced by the grafting and immobilisation process. The advantages of employing non-isothermal bioreactors in biotechnological productive processes have been outlined.

Plasma melatonin and cortisol circadian patterns in patients with obsessive-compulsive disorder before and after fluoxetine treatment

The circadian rhythms of melatonin and cortisol were evaluated in seven outpatients with obsessive-compulsive disorder (OCD) before and after 8 weeks of fluoxetine treatment (20 mg/day in the first 2 weeks, and 40 mg/day afterwards), and in seven healthy subjects matched to patients on age, sex and season of testing. The results confirm our previous findings of a decreased 24-h production of melatonin (p < .05; two-way ANOVA with repeated measures) and of an increased circadian secretion of cortisol (p < .01) in OCD patients with respect to matched controls, and show, for the first time, that these hormonal alterations do not significantly change after 2 months of fluoxetine administration, in spite of a good clinical improvement. These data suggest that the normalization of the biochemical changes underlying the altered endocrine parameters in obsessive-compulsive patients is not necessary for effective therapy or clinical remission.

Urea removal from agricultural waste waters by means of urease immobilized on nylon membranes grafted with cyclohexyl-methacrylate

Abstract In view of the treatment of agricultural waste waters, urea polluted, a catalytic and hydrophobic membrane was constructed by immobilizing urease on a nylon sheet grafted with cyclohexyl methacrylate (CHMA). Hexamethylenediamine (HMDA) and glutaraldehyde (GA) were used as spacer and crosslinking agent, respectively. With reference to the soluble counterpart immobilized urease was found to exhibit (i) a shift of the optimum pH towards more acidic values; (ii) a shift of the optimum temperature towards higher temperatures; (iii) higher values of Km. The latter result indicated an apparent loss of affinity of immobilized urease towards urea. To recovery this affinity loss, the catalytic membranes were employed in a bioreactor operating under non-isothermal conditions. Under these conditions the catalytic membranes exhibited reaction rates higher and apparent Km smaller than those measured under comparable isothermal conditions. As a consequence, percentage increases of enzyme activity and reduction of the production times, proportional to the magnitude of the applied temperature difference were observed. Results have been discussed in the frame of reference of the process of thermodialysis. The technology of the non-isothermal bioreactors confirmed its usefulness also in the reduction of urea concentration in aqueous solutions.

Modulation of immobilized enzyme activity by altering the hydrophobicity of nylon-grafted membranes: Part 1. Isothermal conditions

Abstract Lactose hydrolysis by β-galactosidase immobilized on two nylon membranes, differently grafted, has been studied in a bioreactor operating under isothermal and non-isothermal conditions. One membrane (M 1 ) was obtained by chemical grafting of methylmethacrylate (MAA); the other one (M 2 ) by a double chemical grafting: styrene (Sty) and MAA. Hexamethylenediamine was used as a spacer between the grafted membranes and the enzyme. Both membranes have been physically characterized studying their permeabilities in presence of pressure or temperature gradients. Under non-isothermal conditions, the increase in activity of membrane M 2 was higher than that of membrane M 1 . The α and β coefficients, giving the percentage of activity increase when a temperature difference of 1°C is applied across the catalytic membranes, have been calculated. Results have been discussed with reference to the greater hydrophobicity of membrane M 2 with respect to membrane M 1 , the hydrophobicity being a prerequisite for the occurrence of the process of thermodialysis.

Extraocular muscle antibodies and the occurrence of ophthalmopathy in Graves' disease.

objective  The aim of this study was twofold: first to investigate the presence of extraocular muscle antibodies (EMAb) in sera of Graves’ patients with ophthalmopathy characterized by clinical extraocular muscle (EM) involvement; second to evaluate in Graves’ patients without ophthalmopathy whether longitudinal variations of EMAb have a predictive role for the development of eye disease.

A new approach to the study of Graves’ ophthalmopathy: standardized A-scan echography and octreotide scintigraphy as possible parameters for disease activity

Eight patients, two male and six female, aged between 24 and 48 years, with Graves’ disease and severe ophthalmopathy were included in the study. A standardized A-scan echography was performed to evaluate the reflectivity of the extraocular muscles (EOMs); a planar scintigraphy (PS) and/or a single photon emission computed tomography (SPECT) were also performed at various times after endovenous injection of 111 MBq In-111 OCT, a somatostatin analogue.