Subcellular organization of Streptomyces aureofaciens and overproduction of chlortetracycline

Biosynthesis of chlortetracycline is localized differently under low- and high-production conditions (standard low-production strain and its high-production variant). The experimental evidence was based on the assay of anhydrotetracycline oxygenase in subcellular fractions, ultracytochemical localization and electron-probe X-ray microanalysis of the product in the mycelium. Overproduction of chlortetracycline is closely associated with compartmentation of biosynthetic enzymes and with an efficient export of the antibiotic out of the cell.     

Timing of laparoscopic aspiration of preovulatory oocytes in heifers

Twenty-one heifers were synchronized with PGF(2) alpha and 22 heifers were stimulated with FSH-P in decreasing doses and synchronized with PGF(2) alpha. The beginning of LH rise was observed to be 47.6+/-14.0 h and 35.9+/-1.3 h (P < 0.05) and the peak of LH rise was observed at 53.8 +/- 13.4 h and 40.14+/-1.4 h (P < 0.05) after the luteolyticum administration in the synchronized and superovulated group respectively. The beginning of LH rise was observed 6.9+/-6.7 h and 4.8+/-2.6 h (P < 0.05) and the LH peak was observed 11.8+/-7.7 h and 8.3+/-3.2 h (P < 0.05) after the frist symptoms of oestrus in the synchronized and superovulated group respectively. Ovulation was not observed in stimulated heifers in the period of 23-25 h after the preovulatory LH rise. Compact cumulus oophorus was seen at 30.5%, expanded at 67.0 and partial at 2.5% during this interval of 23-25h. Within this same interval 26.9%, 51.3% and 21.8% oocytes without perivitelline space, with perivitelline space and with extruded first polar body were aspirated respectively. It may be concluded from the reported results that to recover fully mature oocytes for in vitro fertilization, it will be necessary to monitor the preovulatory period of the donor cow in great detail.     

Gibberella fujikuroi mutants obtained with UV radiation and N-methyl-N'-nitro-N-nitrosoguanidine

N-methyl-N'-nitro-N-nitrosoguanidine (nitrosoguanidine) and to a lesser extent UV radiation are very mutagenic for Gibberella microconidia. The recommended nitrosoguanidine doses lead to much higher frequencies of mutants than are found in other microorganisms. The frequency of mutants among the survivors increases linearly with the nitrosoguanidine dose (molar concentration X time); the absolute number of viable mutants in a given population reaches a maximum for a dose of ca. 0.7 M X s. The microconidia are uninucleate. The onset of germination brings about increased lethality of nitrosoguanidine, but it does not modify the action of UV radiation. Mycelia are more resistant than spores to both agents. Visible illumination effectively prevents lethality when given immediately after UV radiation. Auxotrophs and color mutants are very easily obtained. Pink adenine auxotrophs and several classes of color mutants are affected in the biosynthesis of the carotenoid pigment, neurosporaxanthin.     

An improved method to isolate lichen algae by gel filtration

Photobiont cells of the lichen Evernia prunastri have completely been separated from their fungal partner by filtration through a bed of Sepharose 2B. Both mannitol and ribitol have been quantified by gas-liquid chromatography in the different steps of the isolation procedure. Absence of mannitol, which is exclusively produced by the mycobiont, has been used as the best probe to monitor isolation.     

Invertase immobilization via its carbohydrate moiety

After periodate oxidation of its glycosidic component, invertase was covalently bound onto three types of modified solid supports: glycidyl methacrylate, styrene-divinylbenzene copolymers, and bead cellulose. Direct reaction of the invertase aldehyde groups that were formed with amino groups of the support and use of the modified Ugi reaction have been employed as immobilization procedures. Apart from binding methods, the important effects of the buffer, support, conditions of periodate oxidation, and the length of the spacer on the activity of the enzyme conjugate have been investigated. Superior conjugate activity was obtained, via modified Ugi reaction, by the immobilization of a suitably oxidized invertase to a styrene-divinylbenzene copolymer having free amino groups.     

New C-nucleoside analogs by dehydration of 1-benzyl-4,5,6,7-tetrahydro-6,6-dimethyl-2-(d-galacto-pentitol-1-yl)-indol-4-one

The reaction between 2-(benzylamino)-2-deoxy-d-glycero-l-gluco-heptose and 5,5-dimethyl-1,3-cyclohexanedione yields 1-benzyl-4,5,6,7-tetrahydro-6,6-dimethyl-2-(d-galacto-pentitol-1-yl)-indol-4-one (2). Acid-catalyzed, intramolecular dehydration of 2 under kinetically controlled conditions gives 1-benzyl-4,5,6,7-tetrahydro-2-α-d-lyxofuranosyl-6,6-dimethylindol-4-one; the anomeric configuration of this compound is only suggested. When the dehydration reaction is conducted under thermodynamically controlled conditions, it produces a 1:1 mixture of the α- and β-d-lyxopyranosyl compounds. The structures of the new compounds were elucidated by chemical and physical methods.     

The biology of Butomus umbellatus in shallow waters with fluctuating water level

Butomus umbellatus L. is a plant species typical of littoral communities of river and stream shores. It can form continuous stands in shallow reservoirs with fluctuating water level. Their expansion is promoted by: (a) intensive vegetative reproduction of plants, (b) crowded sprouting from rhizome fragments on emerged pond bottom, (c) shallow water layer in the year following summer drainage. Expansion of B. umbellatus depends on ploidy level: two cytotypes were found in the Czech and Slovak Republics, differing in their reproductive ability. Seed production of triploids is strongly limited (they are self-incompatible within clones), while diploids can be fully fertile. Nevertheless, even in diploids, the efficiency of seed reproduction under natural conditions is low. Triploids spread by intensive vegetative reproduction, which is decisive for clonal growth of populations and their regeneration after scraping of bottom surface. During seasonal development, maximum of aboveground biomass is produced in early summer, while underground biomass increases till autumn. Growth of the plants is limited by cutting before maximum underground biomass is attained, or by duck grazing.