The influence of Zn2+ ions on the tryptophan biosynthesis in plants

Zn²⁺ ions slightly enhance at low concentrations (0.01 μg ml^-1) the activity of tryptophan synthase obtained from the shoots of 14-day-old pea seedlings (Pisum sativum L.). On the contrary, high concentrations of Zn²⁺ (10 μg ml^-l) exert an inhibitory effect. The direct Zn²⁺ activation of tryptophan synthase, establishedin vitro with a partially purified enzyme preparation, is relatively low and obviously is not decisive from the point of view of tryptophan biosynthesis of the enzyme and thus they are participating in thein vivo experiments.     

Enhanced accumulation of cadmium in Linum usitatissimum L. plants due to overproduction of metallothionein α-domain as a fusion to β-glucuronidase protein

As most cultivars of flax and linseed (Linum usitatissimum L.) are capable of accumulating cadmium (Cd), they are suitable candidates for phytoextraction of the metal from contaminated soils. In an attempt to enhance the phytoextraction capacity of L. usitatissimum through overproduction of an efficient heterologous Cd-binding peptide, we engineered linseed breeding line AGT 917 to constitutively express genetic fusion of α-domain of mammalian metallothionein 1a (αMT1a) and β-glucuronidase gus gene under the control of CaMV 35S promoter. An improved transformation protocol was developed, which involved co-cultivation of AGT 917 hypocotyl segments with partially removed epidermis with Agrobacterium suspension for 10 min in the presence of 200 mg l^?1 cellulase. The enzyme treatment increased the transformation efficiency (TE) 1.6-fold as compared to agroinfection without cellulase. Less pronounced impact on TE exerted 100 mg l^?1 acetosyringone, increasing TE 1.3-fold. When tested in soils amended with Cd at 20 and 360 mg kg^?1, the mature αMT1a::gus plants accumulated more Cd than parental AGT 917: the stem Cd concentrations in the best performing αMT1/2 line were 3.3- and 1.9-fold higher, respectively. Moreover, hypocotyl explants of αMT1/2 line showed 1.7-fold higher biomass than those of AGT 917 on media containing 15 mg Cd l^?1, indicating that αMT1a::gus did confer higher Cd tolerance to engineered plant. Overproduction of metal-binding peptides thus appears to be a viable strategy for the production of L. usitatissimum with improved phytoremediation capacity.     

The effect of acetyldexphenmetrazine and dexphenmetrazine on the susceptibility to audiogenic seizures in mice.

The antiepileptic effect of dexphenmetrazine (DP) and acetyldexphenmetrazine (ADP) was tested on audiogenic seizures in a 100% susceptible strain of mice. DP had no antiepileptic effect, however, it markedly suppressed the postparoxysmal motor inhibition. ADP had a distinct anticonvulsive effect--it suppressed the convulsive component of the seizure, leaving its running component unaffected. The results are compared with the effect of both drugs on electrographic epileptic phenomena in the turtle brain (Servít and Strejcková 1976).     

Environmental determinants of the distribution of planktonic diplonemids and kinetoplastids in the oceans

We analysed a widely used barcode, the V9 region of the 18S rRNA gene, to study the effect of environmental conditions on the distribution of two related heterotrophic protistan lineages in marine plankton, kinetoplastids and diplonemids. We relied on a major published dataset (Tara Oceans) where samples from the mesopelagic zone were available from just 32 of 123 locations, and both groups are most abundant in this zone. To close sampling gaps and obtain more information from the deeper ocean, we collected 57 new samples targeting especially the mesopelagic zone. We sampled in three geographic regions: the Arctic, two depth transects in the Adriatic Sea, and the anoxic Cariaco Basin. In agreement with previous studies, both protist groups are most abundant and diverse in the mesopelagic zone. In addition to that, we found that their abundance, richness, and community structure also depend on geography, oxygen concentration, salinity, temperature, and other environmental variables reflecting the abundance of algae and nutrients. Both groups studied here demonstrated similar patterns, although some differences were also observed. Kinetoplastids and diplonemids prefer tropical regions and nutrient-rich conditions and avoid high oxygen concentration, high salinity, and high density of algae.     

Influence of different occupations with possible mutagenic effects on reproduction and level of induced chromosomal aberrations in peripheral blood.

In a group of 200 dysfertile couples (400 persons), the possible role of different occupations in failures of reproduction was assessed. These couples were examined from different points of view, classical genetic examination (pedigree, kayrotype, etc.) included. The suspected genotoxic effects in the personal history were checked also by testing the level of induced chromosomal aberrations. A significantly increased level of induced chromosomal aberrations was detected in 37 persons, i.e., 9.3% of the whole group under study. The average level of induced aberration in these subjects was 6.8%, as opposed to the control group (fertile and dysfertile persons without any unusual exposure to mutagens) with a mean of 1.58% aberrant cells in peripheral blood. Most of the occupations with demonstrated genotoxic effects involve daily contact with chemicals of different types. In some persons also intensive therapy in the recent past had genotoxic effects.