Biosynthesis of methionine in an ethionine-resistant strain ofCandida utilis

The strainCandida utilis T 20 adapted to a high concentration of ethionine, excretes considerable amounts of methionine in a synthetic medium, about 40 times as much as the original non-adapted strain. At the same time, the amount of methionine in yeast cells incrncreased, predominantly in the pool (9 times as much as in the control). This ability to produce greater amounts of methionine in the pool or to excrete it into the medium is not permanent, since after 5 passages on agar with ut ethionine the amount of methionine was practically not increased as compared with the original non-adapted strain. An increase in free methionine and of methionine excreted into the medium was found on cultivating the strain in a molasses-containing medium, too.     

Gel-entrapped penicillin G acylase optimized by an enzyme thermistor

Summary Direct activity determination by a flow-through microcalorimetry in the enzyme thermistor system was employed for a fast comparison of (poly)acrylamide gel-entrapped penicillin G acylase preparations. Composition of the pre-polymerization cocktail and both the storage and operational stabilities of optimal gel-entrapped enzyme preparations isolated from the Escherichia coli industrial strain were optimized by this method. The validity of the results was corroborated by spectrophotometric measurements.     

Cell division and sister chromatid exchanges in 45,X/46,X,i(Xq) mosaicism

Summary The kinetics of cell division and sister chromatid exchanges were studied in PHA-stimulated short-term cultivations of peripheral blood by means of the BUDR/FPG technique in controls and in five patients with 45,X/46,X,i(Xq) mosaicism. No significant differences in the length of the cell cycle were observed between 45,X/46,X,i(Xq) and control 46,XX cells. The number of SCE on late i(Xq) was only nonsignificantly elevated (0.6 per i(Xq)) against the value expected on the basis of its relative length.     

Effect of changed cultivation conditions on the morphology ofAspergillus niger and on citric acid biosynthesis in laboratory cultivation

Cultivation ofAspergillus niger 97A in baffled flasks on a shaker brings about metabolic changes demonstrated in increased citric acid biosynthesis, morphological changes and alterations in the mycelial cell wall.     

Staining pattern of acid non-specific esterase in lymphocytes, plasmocytes, monocytes, and leukemic cells

The pattern of staining for ANAE in lymphocytes, plasmocytes, monocytes and leukemic cells has been studied and the effect of NaF and E 600 on this staining reaction has been investigated. In lymphocytes the transition occasionally occurring between a dot-like (T type) and granular positivity may cause difficulties when using this reaction as a marker of resting T lymphocytes. In plasmocytes as well as in myeloma cells a number of coarse granules was present in most cells and in some cases even large blocks of the reaction product occurred. NaF and E 600 inhibits already in lower concentration (2 mM and 10 micronM respectively) the strong diffuse reaction in monocytes, the effect on other cells being negligible. Using higher concentrations the inhibitory effect of NaF (20 mM) was more pronounced in plasmocytes in comparison with T lymphocytes which on the other hand, were, in general more sensitive to E 600 (10 mM). Partially diffuse or dense granular pattern of ANAE was found in a number of hairy cells. "Lymphoblastic" leukemias in children most frequently displayed negative or fine granular reaction in a varying number of blasts and similar findings were noted in the majority of cytochemically undifferentiated leukemias in adults. In some of them, however, a similar pattern of ANAE as in myeloblastic leukemias with dispersed or partial diffuse positivity was observed. The significance of these findings is briefly discussed.     

The effect of ultrasound and its combination with radiation on the genetic material ofSaccharomyces cerevisiae

Ultrasonication at 20 kHz, intensity 35 W/cm² and amplitude 15–25 μm of a diploid strain ofSaccharomyces cerevisiae was found to act as a weak mutagen with maximum efficiency at the 20 % survival of the cells. Under these conditions, the frequency of reversion of the suppressible allele ilv1-92 increased ten times, the frequency of mitotic gene conversion four times. Doses leading to survivals lower than 20 % led to a slight increase in the frequency of cytoplasmic respiration-deficient mutants. Submutagenic doses applied immediately after γradiation or UV light did not substantially increase the effect of these physical agents on the genetic material of the yeast strain investigated. Application of ultrasound prior to UV radiation did not considerably influence the effect of the radiation either.     

Variability ofAspergillus niger after treatment withN-methyl-N′-nitro-N-nitrosoguanidine

N-Methyl-N'-nitro-N-nitrosoguanidine influences strongly the variability of Aspergillus niger MU 90, particularly on long-term treatment. The number of spores capable of growth decreases with the duration of treatment and the number of morphological and biochemical mutants considerably increases. The highest number of mutants with increased organic acid production was obtained after a mutagenic treatment when the number of surviving spores decreased below 1%.