Large scale production of recombinant mouse and rat growth hormone by fed-batch GS-NSO cell cultures

Investigations of biological effects of prolonged elevation of growth hormone in animals such as mice and rats require large amounts of mouse and rat growth hormone (GH) materials. As an alternative to scarce and expensive pituitary derived materials, both mouse and rat GH were expressed in NSO murine myeloma cells transfected with a vector containing the glutamine synthetase (GS) gene and two copies of mouse or rat GH cDNA. For optimal expression, the mouse GH vector also contained sequences for targeting integration by homologous recombination. Fed-batch culture processes for such clones were developed using a serum-free, glutamine-free medium and scaled up to 250 L production scale reactors. Concentrated solutions of proteins, amino acids and glucose were fed periodically to extend cell growth and culture lifetime, which led to an increase in the maximum viable cell concentration to 3.5×10⁹ cells/L and an up to 10 fold increase in final mouse and rat rGH titers in comparison with batch cultures. For successful scale up, similar culture environmental conditions were maintained at different scales, and specific issues in large scale reactors such as balancing oxygen supply and carbon dioxide removal, were addressed. Very similar cell growth and protein productivity were obtained in the fed-batch cultures at different scales and in different production runs. The final mouse and rat rGH titers were approximately 580 and 240 mg/L, respectively. During fed-batch cultures, the cell growth stage transition was accompanied by a change in cellular metabolism. The specific glucose consumption rate decreased significantly after the transition from the growth to stationary stage, while lactate was produced in the exponential growth stage and became consumed in the stationary stage. This was roughly coincident with the beginning of ammonia and glutamate accumulation at the entry of cells into the stationary stage as the result of a reduced glutamine consumption and periodic nutrient additions.     

Inhibition of the predatory activity ofBdellovibrio by various environmental pollutants

The predatory activity of bdellovibrios is affected by various environmental pollutants such as detergents, heavy metals, and pesticides. This was shown in a two-membered system ofBdellovibrio andPhotobacterium, in which the effect of the predator on the bioluminescence of the prey indicated the activity of the former. The high sensitivity of the bdellovibrios toward certain chemicals (e.g., CdCl₂) indicates the possibility of using the system for biological monitoring of those chemicals.     

Bacteriorhodopsin in a bloom of halobacteria in the Dead Sea

A dense bloom of red halobacteria developed in the Dead Sea in the summer 1980, bacterial densities of up to 1.9 x10⁷ cells ml^-1 were observed. The population consisted of two types: pleomorphic, cup-shaped cells and rod-shaped cells. A high content of bacteriorhodopsin was found in the bloom (up to 0.4 nmol per mg protein). The rod-shaped Halobacterium was isolated and was shown to contain bacteriorhodopsin.Abbreviations 20 specific gravity at 20°C - Tris Tris-(hydroxymethyl)-aminomethane     

Interallelic Complementation among Der/Flb Alleles: Implications for the Mechanism of Signal Transduction by Receptor-Tyrosine Kinases

The large number of available embryonic lethal alleles in the Drosophila EGF receptor homolog (DER)/faint little ball locus allowed us to test the possibility of positive or negative interactions among different DER alleles. These interactions were monitored by examining the embryonic cuticular phenotypes of different heteroallelic combinations. Several positive interactions were identified, while negative interactions were restricted to a single allele. This is the first example of positive interactions within the same cell type among alleles of a receptor tyrosine kinase gene. The basis for these interactions is likely to arise from the mechanism of signal transduction by receptor tyrosine kinases, which involves receptor aggregation. A combination of two different DER mutant proteins defective in temporally distinct stages of the signal transduction process, may thus form a functional heterodimer. The mutation sites in four alleles showing positive interactions were localized. They identify regions within the protein which are likely to be important for these temporally distinct signal transduction processes.     

Effect of pH and butyrate concentration on the production of acetone and butanol by Clostridium acetobutylicum grown in continuous culture

Summary When Clostridium acetobutylicum was grown in continuous culture under glucose limitation at neutral pH and varying dilution rates the only fermentation products formed were acetate, butyrate, carbon dioxide and molecular hydrogen. The Y _glucose ^max and (Y _ATP ^max ) _gluc ^exp values were 48.3 and 23.8 dry weight/mol, respectively. Acetone and butanol were produced when the pH was decreased below 5.0 (optimum at pH 4.3). The addition of butyric acid (20 to 80 mM) to the medium with a pH of 4.3 resulted in a shift of the fermentation from acid, to solvent formation.A preliminary report of part of this work was presented at a symposium Trends in the Biology of Fermentations for Fuels and Chemicals held December 7–11, 1980, at Brookhaven National Laboratory, Upton, New York; Gottschalk and Bahl 1981     

Properties of marine bdellovibrios

Marine bdellovibrio isolates from the Israeli littoral of the Mediterranean Sea were screened and characterized in terms of host range, temperature and salinity ranges, cation requirement, mutation frequency, and G + C% mole content. Ten types of isolates were distinguished on the basis of these parameters.     

Über die rationelle Milchpasteurisierung

Ohne ZusammenfassungDie Arbeit wurde dem R. Istituto Lombardo Scienze e Lettere am 5. Juni 1934 vorgelegt (Rend. 67, 671, 1934).