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Biomedical subjects

A Konrad

Publications and source records attributed to A Konrad.

9 recordsLinked to original sources
PubMed2000

Virus-specific adaptations for the production of a pseudorecombinant virus formed by two distinct bipartite geminiviruses from Central America.

Most whitefly-transmitted geminiviruses possess bipartite genomes comprising DNAs A and B. The production of viable pseudorecombinants by reassortment of infectious cloned components is generally limited to isolates/strains of a particular virus. Following exchange of cloned genomic components of Sida golden mosaic virus from Costa Rica (SiGMV/Co) and Sida golden mosaic virus from Honduras (SiGMV/Ho(yv)), the pseudorecombinant viruses were infectious in various plant species. Three DNA B components (B(1), B(2), B(3)), different in a few nucleotides, were isolated from Sida rhombifolia naturally infected with SiGMV/Ho(yv). Only SiGMV/Ho(yv) DNA B(2) was able to form a viable pseudorecombinant with SiGMV/Co DNA A. In protoplasts, as well as in inoculated leaves, SiGMV/Co DNA A trans-replicated the heterogenomic SiGMV/Ho(yv) DNA B(1) component, indicating that impaired movement is involved in the deficiency of SiGMV/Ho(yv) DNA B(1) to form a pseudorecombinant virus with SiGMV/Co DNA A. Even after extensive mutation analysis of SiGMV/Ho(yv) DNA B(1) and B(2), we were unable to pinpoint differences in SiGMV/Ho(yv) DNA B(2) that allowed the formation of a pseudorecombinant virus with SiGMV/Co DNA A. We observed a gradual increase of infectivity from noninfectious SiGMV/Co DNA A/SiGMV/Ho(yv) DNA B(1) and B(3) pseudorecombinant virus to pseudorecombinant viruses showing normal systemic spread of both genomic components associated with symptomatic plants.

Adaptation, Physiological↗
PubMed1992

Safety and economic aspects of continuous mammalian cell culture.

Mammalian cell cultures are the most appropriate host cells for recombinant DNA derived products if complex protein structures have to be synthesized in their native form. Due to their physiological behaviour they grow either adherent or in suspension. For the attachment of adherent cells, microcarriers or wire springs can be applied to increase the internal surface of the bioreactor. Both systems provide a simplified media exchange but, however, show some limitations in scale up. In contrast, suspension culture systems as homogeneous systems independent of any carrier have not shown any limitation in scale up. Because most cell lines which are of commercial interest grow in suspension, this technology is best advanced and used in batch and continuous mode. Although mammalian cell cultures are sensitive to hydrodynamic shear forces, technologies for deep tank production are developed which allow stirrer tip speed of up to 1.5 m s-1 sufficient for oxygen uptake, suspension of cells and homogeneous supply with nutrients. For long term bioprocesses without selection pressure it has to be considered that transformed cell lines might show genetic instability due to their variations of chromosomes. In addition, sterile technology becomes an important factor in long term bioprocesses. The decision as to which cell culture system should be chosen, whether batch or continuous processes should be applied essentially is based on the capital investment, the amount of material to be produced, genetic stability of the production cell line, reliability of sterile technology and the flexibility required in the production plant. Under the assumption that 20 kg of a protein have to be produced per year and the same product concentrations in the harvest fluid are reached in the batch process and for instance in the chemostat, it can be considered that the capital investment for one 10,000 l batch process and a 2 x 2,000 l continuous process, necessary to produce the amount of material, is comparable. Risk of microbial contamination or technical failure can be considered to be fairly low in the batch process. The economic risk for long term bioprocess in the chemostat can be expected to be medium and high in the perfusion system which is in the large scale not technically fully satisfactory. In addition, due to the longer down time period after contaminations and the start up of the continuous process, the annual yield of the batch process can be considered to be higher.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1983

Impaired bactericidal activity of cord sera against Salmonella strains.

Weaker bactericidal activity of cord sera against Salmonella bacilli was shown in comparison with maternal venous sera. No correlation was found between the bactericidal activity and the levels of complement, immunoglobulins and lysozyme in cord sera. Worthy of notice is detected in these researches specificity of bactericidal action of cord sera.

Blood Bactericidal Activity↗
PubMedDate not supplied

Electrocardiographic changes in cardiomyopathic Syrian hamsters (strain BIO 8262).

Under ether anesthesia electrocardiograms were derived from Syrian hamsters (strain BIO 8262) suffering from cardiomyopathy and muscular dystrophy. In addition, ventricular weights and body weight were determined. Young hamsters -- not yet showing morphological signs of the cardiomyopathy with the exception of possible left ventricular hypertrophy -- demonstrated only a longer ventricular activation time than normal hamsters. With the onset of cardiac necrotization left axis deviation in frontal plane projection and right bundle branch blocks are developing in the cardiomyopathic hamsters followed by first degree atrioventricular conduction defects. During the late stage of the cardiomyopathy left bundle branch blocks are additionally arising, while left ventricular hypertrophy is disappearing. Since no overt heart failure is occurring in this strain of cardiomyopathic hamsters, gradual development of high degree conduction defects is assumed to terminate their lives. The electrocardiographic pattern of the hamster cardiomyopathy fits partly into that of human primary as well as secondary cardiomyopathy. Nevertheless, it seems to form an entity of its own, as arrhythmias, higher degree atrioventricular conduction disturbances, typical signs of ventricular or septal hypertrophy, abnormal P and Q waves, ST segment and T wave changes are lacking.

Animals↗