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Biomedical subjects

L Stefanova

Publications and source records attributed to L Stefanova.

14 recordsLinked to original sources
PubMed2005

Role of antioxidant enzymes in survival of conidiospores of Aspergillus niger 26 under conditions of temperature stress.

AIMS: A better understanding of the role of antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT) in the protection of Aspergillus niger spores against thermal stress. METHODS AND RESULTS: Conidiospores from A. niger 26 were subjected to wide range of temperatures (30, 50, 60 and 80 degrees C). The stress response was investigated by the determination of spore germination and mycelial growth of survivors under submerged cultivation. Exposure to any temperature above the optimal value induced an increase in SOD and CAT activities. PAGE demonstrated enhanced level of Cu/ZnSOD under stress conditions. We compared the influence of heat shock and superoxide-generating agent paraquat on growth and antioxidant enzyme defence and found different response to the both type of stresses. CONCLUSIONS: Heat stress elicits the enhanced synthesis of enzymes whose functions are to scavenge reactive oxygen species. These results suggested an association between thermal and oxidative stress. SIGNIFICANCE AND IMPACT OF THE STUDY: Evidence is provided for the possibility that oxidative stress plays a major role in the effect of heat in low eucaryotes such as A. niger. This knowledge may be of importance in controlling both fermentation and pathogenicity.

Antioxidants↗
PubMed1995

Biosynthesis of extracellular low-molecular-mass papain and trypsin inhibitors by Streptomyces sp. 22: effect of cultural conditions.

The production of extracellular inhibitors of papain and trypsin by Streptomyces sp. 22 was studied under different cultural conditions including complex and defined media, temperatures ranging from 18 degrees C to 37 degrees C and a variety of sole carbon and nitrogen sources. In complex nutritionally rich medium, maximal specific growth rates were obtained at 37 degrees C, whereas the highest specific production rates for both papain and trypsin inhibitors were registered at 18 degrees C. Studies on the effect of different carbon and nitrogen sources in defined media underline the importance of the nitrogen source as a strong regulator of the biosynthesis of both inhibitors. Enhanced formation of the inhibitory compounds occurred in the presence of casein. The dynamics of the formation of both inhibitors in defined media showed close association with growth. However, a partial separation of production phases for papain and trypsin inhibitors was observed in complex medium. The results imply differences in the regulation of biosynthesis of the two inhibitors.

Culture Media↗
PubMed1980

[Laboratory trials of culturing BHK 21 C 13 cells in a roller using an enzymatic egg hydrolysate-based nutrient medium].

Experiments were carried out to find the optimal conditions for the replication of BHK 21 C 13 cells in one 1 roller glassware with the use of a nutrient medium containing products of the enzymatic breakdown of white of egg. Studied was the sensitivity of these cells to the type C strain 'Hungary' of the foot-and-mouth disease virus. Two series of F. M. D. vaccines were produced, which proved to be sterile and innocuous for guinea pigs. Immunogenicity trials with regard to these animals revealed that the VD50 (vaccinal dose) values ranged from 0.12 to 0.26 cm3.

Animals↗
PubMed1979

[Production and use of a nutrient medium with egg hydrolysate for monolayer reproduction of BHK 21/13 cells].

Experiments aiming to reproduce BHK 21/13 cells in Roux retorts by use of a semi-synthetic nutrient medium, based on protein hydrolyzate synthetized by the authors, were carried out. Results obtained show that the lower peptides and free amino acids found in ovarian hydrolizate meet the requirements of the cell line in respect to quality and quantity. The successfull cultivation of BHK 21/13 cells in hydrolyzate medium made possible a considerable reduction in the percentage involvement of serum, which is usually used in the classical nutrient media of the type Eagle BME intended for the propagation of diploid cell strains.

Animals↗