Dimethyl sulfoxide: A solvent for cytokinins in theAmaranthus bioassay

Dimethyl sulfoxide present in the agar medium at concentration 0.2 % (v/v) and lower does not inhibit cytokinin-induced betacyanin synthesis in theAmaranthus caudatus seedlings. The activity of kinetin, N⁶-(Δ²-isopentenyl)adenine andtrans- zeatin is the same when these cytokinins are dissolved in either water or dimethyl sulfoxide and incorporated into the medium after autoclaving. A simple method is described which allows the cytokinin activity of slightly water-soluble and thermolabile compounds,e.g. aromatic urea and thiourea derivatives, to be determined in theAmaranthus bioassay.     

The role ofH-2 regions in overcoming tissue incompatibility

Neonatal transplantation tolerance to the products of theH-2 ^b complex was induced in B10.A (H-2 ^a ) mice. On the basis of the survival of skin allografts it was found that antigens determined by theD region of theH-2 ^b complex (of the B10.A(2R) strain) were most easily overcome and that tolerance to the products of theD end of theH-2 complex (of the B10.A(4R) strain) was also easy to induce. The antigens produced by theK end ofH-2 (of the B10.A(5R) and B10.A(3R) strains) represented a stronger incompatibility barrier and a difference in the entireH-2 ^b complex caused strongest resistance to tolerance induction. When tolerance to the products of the entireH-2 ^b complex was induced in newborn B10.A mice, and the neonatally treated animals were grafted simultaneously with five different grafts, those disparate at theK end ofH-2 and in the entireH-2 region were rejected in some animals, while the grafts disparate at theD end of H-2 remained intact in the same mice. No dependence on theI-J subregion was observed in this system. Furthermore, tolerance was more easily inducible in male than in female B10.A mice.     

Sensitivity of various yeasts to crude cellulolytic enzyme complexes fromTrichoderma reesei

Summary Twenty-six yeast strains, representative of different yeast genera, were tested for their sensitivity to crude extracellular cellulolytic enzyme complexes obtained from the fungusTrichoderma reesei QM 9414 and its mutants M 6 and MHC 22 (Microcrystalline cellulose was the sole carbon source.) Practically all the yeast strains tested were found to be sensitive, exhibiting signs of cellwall weakening and lysis during prolonged incubation with the emzymes fromTrichoderma. Under growth conditions, the effect of cellulolytic enzymes on yeast cells and their growth rates was much less pronounced. However, at increased cellulase concentrations (5 mg/ml) in the growth medium, lysis of stationary phase yeast cells was observed.     

Ontogeny of lymphatic structures in the pig omentum

Summary The development of lymphoid populations in the omentum majus during the prenatal and postnatal life of the pig was studied. T lymphocytes, monocytes and mast cells were first found on the 40th day of gestation. B lymphocytes appeared on the 72nd day of gestation when the first macrophage aggregates were formed. Macrophages appeared to be the prerequisite for the formation of dense lymphatic areas (DLA's). At later stages T cells were observed only in the omentum of germfree pigs. DLA's of conventional pig omentum are filled exclusively with B cells.     

The influence of carotenoids on the conformation of chlorophyll-protein complexes isolated from the cyanobacterium Plectonema boryanum. Absorption and circular dichroism study

Thylakoid membranes of the cyanobacterium Plectonema boryanum solubilized with Triton X-100 can be resolved into three fractions of pigment-protein complexes (Hladík, J. and Sofrová, D. (1981) Photosynthetica 15, 490–503). Fraction I contained relatively the highest amount of carotenoids as well as monomeric forms of chlorophyll a, Fractions II and III contained chlorophyll-protein complexes with a characteristic exciton-split circular dichroism in the red region. It has been shown that fraction III is an oligomeric form of the chlorophyll-protein complex of fraction II. Circular dichroism spectra indicate that, different from fraction II, fraction III contains specifically oriented and space-fixed molecules of carotenoids. Thermal dissociation of fracion III to fraction II is accompanied by disappearance of the positive circular dichroism effect of carotenoids in the 500–550 nm region, thus causing deorganization of the carotenoids, proceeding in parallel to the geometrical rearrangement of chlorophyll molecules. Extraction of the carotenoids of fraction III with heptane is acompanied by dissociation of fraction III. We assume that the observed effects are due to binding of the two pigments to the protein component of the complex and that carotenoids can mediate a part of the interactions which stabilize the structure of pigment-protein complexes. Thus, besides the light-harvesting and protective functions, carotenoids can also play a structural role.     

The importance of FeEDTA for reversibility of phosphate-induced chlorosis in maize (Zea mays L.)

Chlorosis induced with a supraoptimum dose of phosphorus in nutrient solution (69 mg P l^-1) was reverted by spraying of leaves of chlorotio maize plants (Zea mays L.) with FeEDTA. Biomass formation, chlorophyll and iron content were decreased in the above-ground parts of plants grown under chlorosis-inducing conditions. Spraying always decreased content of inorganic phosphorus (P_i/Fe ratio was significantly changed), increased chlorophyll content in old plants and stimulated dry mass formation at supraoptimum phosphorus doses. FeEDTA application improved phosphate utilization (portion of phosphate in organic bonds was increased). This may be the basis of chlorosis-reverting effect of FeEDTA.     

Responses of epidermal diffusive conductance to simultaneous changes in two factors: Determination of interactions

Responses of the epidermal diffusive conductance (gep) to irradiance (I) during ontogeny of primary bean leaves or during their wilting were followed. Effects ofI, leaf age and leaf water potential (Ψw) as well as interactive effects (I × leaf age andI × Ψw) ongep were statistically significant.     

Synthesis of Pyrrolo[2′,3′:4,5]Furo[3,2-c]Pyridine-2-Carboxylic Acids

1H-Pyrrolo[2′,3′:4,5]furo[3,2-c]pyridine-2-carboxylic acid (6a) and its 1-methyl (6b) and 1-benzyl (6c) derivatives were synthesized. 3-(5-Methoxycarbonyl-4H-furo[3,2-b]-pyrrole-2-yl)propenoic acid (1) was converted to the corresponding azide 2, which in turn was cyclized to give 3 by heating in diphenylether. The pyridone 3 obtained was aromatized with phosphorus oxychloride, then reduced with zinc in acetic acid to give methyl 1H-pyrrolo[2′,3′:4,5]furo[3,2-c]pyridine-2-carboxylate (5), which by hydrolysis gave the corresponding carboxylic acid 6a.     

Stabilization of a miniderivative of the broad-host-range IncW plasmid pSa by insertion of plasmid R1parB region

The plasmid vector pEM100 (13.5 kb) constructed from pGV1106, a miniderivative of the broad-host-range IncW pSa plasmid, and the pAM330 plasmid ofBrevibacterium lactofermentum is not stably maintained inEscherichia coli host cells under nonselective growth conditions. By insertion of a 0.9 kb DNA fragment containing theparB locus (responsible for the maintenance of plasmid R1 inE. coli cells) to plasmid pEM100, plasmid pEM110 was prepared which is maintained in a population ofE. coli cells growing without a selection pressure very stably. Translated by Č. Novotny