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Biomedical subjects

G Bardeletti

Publications and source records attributed to G Bardeletti.

8 recordsLinked to original sources
PubMed1992

Enzyme immobilization on a low-cost magnetic support: kinetic studies on immobilized and coimmobilized glucose oxidase and glucoamylase.

Glucose oxidase (GOx) and glucoamylase (GA) were immobilized and coimmobilized through their carbohydrate moieties onto polyethyleneimine-coated magnetite crosslinked with glutaraldehyde and derivatized with adipic dihydrazide. The carbohydrates were oxidized with sodium periodate, and at optimal concentration, their Vm increased up to 18% for GOx and up to 16% for GA. After immobilization, a remaining activity as high as 88% and 70% for GA with maltose and maltodextrin respectively as substrates was obtained, independently of the particle loading. On the contrary, the remaining activity of GOx strongly decreased at high particle loading. Nevertheless, half of its initial activity was recovered at low loading and was not significantly affected when GA was coimmobilized by saturating the reactive groups left on the particle. The Vm of both immobilized enzymes was improved by crosslinking their carbohydrates with adipic dihydrazide, a treatment which allows further coimmobilization of the other enzyme on a second layer.

Enzymes, Immobilized↗
PubMed1979

Rubella virus maturation and production in two host cell systems.

When inoculated at the same MOI, Vero cells released a larger amount of infectious rubella virus into the culture medium than did BHK21 cells, However, BHK21 cells (in monolayer or in suspension) produced more intracellular infectious virus than Vero cells when tested 24 h after infection. Maturation of the virus in BHK21 cells occurred at the plasma membrane and, in a larger quantity, in the cytoplasm (Golgi apparatus and vacuoles). Viral particles consisted of an electron-dense core (32 nm) surrounded by a capsid and enveloped by a single membrane (8-10 nm). Aberrant forms (elongated and twisted) in the vacuole and double virions in the plasma membrane were observed as early as 65 h after infection.

Animals↗
PubMed1977

Respiration and ATP level in BHK21/13S cells during the earlist stages of rubella virus replication.

This study is concerned with the effect of virus infection on the energy balance of the cell and the possible involvement of mitochondria in virus replication. The process of rubella virus adsorption and penetration is immediately associated with a stimulation of O2 uptake. Shortly afterwards, ATP levels decline, possible because of increased ATP utilization. Virus infection appears to protect mitochondria against the uncoupling effect of dinitrophenol.

Adenosine Triphosphate↗
PubMed1976

Phospholipid and cholesterol composition of rubella virus and its host cell BHK 21 grown in suspension cultures.

Analysis of total lipid, phospholipid and cholesterol distribution has been conducted in parallel on BHK 21/13S cells grown in suspension cultures, on purified Rubella virus and on cells infected by the virus. Extracellular virus was purified by use of a previously described procedure (3,4). A higher content of lipid and phospholipid was found in infected cells (versus control cells) which were characterized by the presence of an unidentified nonphosphorylated lipid fraction that was detected neither in the control cells nor in the purified virus. The level and the nature of phospholipids and cholesterol of BHK 21/13S cells (infected or not) were compared to those of various clones of BHK 21cells. The same phospholipids were detected in the virus and in the cells but phosphatidyl choline level was much higher than in the control cells and lower than in the infected cells, while phosphatidyl ethanolamine content was lower than in the cells (infected or not). The presence of cardiolipin (4.4 per cent), the amount of sphingomyelin (6.9 per cent) and the molar ratio of cholesterol to phospholipids (0.26) in varions seem to favor a rubella virus maturation site in the cells.

Cell Line↗
PubMed1975

Morphology, biochemical analysis and neuraminidase activity of rubella virus.

A simple and reproducible method for the production of purified rubella virus is described. Purified virus was subjected to morphological and chemical analysis. The virus particles were rather pleomorphic (60 nm diameter), sometimes with one or more peripheral protrusions. The viral surface, revealed by negative staining, was composed of spikes 6 nm long, featuring enlarged ends. In SDS-urea-polyacrylamide gel electrophoresis, 4 major and 4 minor polypeptide bands were revealed. Total lipids and phospholipids were analysed on the same preparation. The viral particles were composed of RNA: 0.030 mg, and lipids: 0.245 mg, of which 0.169 mg were phospholipids for each mg of viral protein. Biologically, the purified virus preparation showed high infectivity, a high hemagglutination titre and a weak neuraminidase activity under defined conditions.

Cell Line↗
PubMedDate not supplied

Glucoamylase immobilization on a magnetic microparticle for the continuous hydrolysis of maltodextrin in a fluidized bed reactor.

Glucoamylase (GA) has been successfully immobilized through its carbohydrates previously oxidized with periodate onto a low-cost magnetic microparticle made of polyethyleneimine-coated magnetite crosslinked with glutaraldehyde (M-GAD) and derivatized with adipic dihydrazide (ADH). A stabilization posttreatment consisting of crosslinking its carbohydrates with ADH, increased the remaining activity from 54 to 71%, calculated on the Vm values and measured at 50 degrees C and pH 4.5 with maltodextrin (DE 11-14) as substrate. This treatment also improved the enzyme stability and lowered the deactivation rate constant kd to a third of its value. A 30% maltodextrin solution has been continuously hydrolyzed at 50 degrees C and pH 4.5 in a recycled, fluidized bed reactor (FBR) containing GA immobilized on these magnetic microparticles. They easily settled in this highly viscous medium because of their high density (5 g/mL), and washout of ultrafines was prevented by surrounding the top of the bed with an electromagnet. The small particle size (20 microns) allowed a high enzyme loading in the reactor and also a high bed voidage, which is recommended to avoid extensive pressure drop and consequent channeling problems. The kinetic of hydrolysis fitted with the plug-flow model; this is explained by the insignificant backmixing effects observed. After 2 wk of hydrolysis under process conditions leading to a conversion of 70%, which corresponds to a high-conversion syrup, the immobilized GA only lost 4% of its initial activity.

Biosensing Techniques↗