Simultaneous and independent effects of abscisic acid on stomata and the photosynthetic apparatus in whole leaves

(±)-Abscisic acid (ABA) at 10^-5 M was added to the transpiration stream of leaves of 16 species (C₃ and C₄, monocotyledons and dicotyledons). Stomatal responses followed one of three patterns: i) stomata that were wide and insensitive to CO₂ initially, closed partially and became sensitive to CO₂; ii) for stomata that were sensitive to CO₂ before the application of ABA, the range of highest sensitivity to CO₂ shifted from high to low intercellular partial pressures of CO₂, for instance in leaves of Zea mays from 170–350 to 70–140 bar; iii) when stomata responded strongly to ABA, their conductance was reduced to a small fraction of the initial conductance, and sensitivity to CO₂ was lost. The photosynthetic apparatus was affected by applications of ABA to various degrees, from no response at all (in agreement with several previous reports on the absence of effects of ABA on photosynthesis) through a temporary decrease of its activity to a lasting reduction. Saturation curves of photosynthesis with respect to the partial pressure of CO₂ in the intercellular spaces indicated that application of ABA could produce three phenomena: i) a reduction of the initial slope of the saturation curve (which indicates a diminished carboxylation efficiency); ii) a reduction of the level of the CO₂-saturated rate of assimilation (which indicates a reduction of the ribulose-1,5-bisphosphate regeneration capacity); and iii) an increase of the CO₂ compensation point. Photosynthesis of isolated mesophyll cells was not affected by ABA treatments. Responses of the stomatal and photosynthetic apparatus were usually synchronous and often proportional to each other, with the result that the partial pressure of CO₂ in the intercellular spaces frequently remained constant in spite of large changes in conductance and assimilation rate. Guard cells and the photosynthetic apparatus were able to recover from effects of ABA applications while the ABA supply continued. Recovery was usually partial, in the case of the photosynthetic apparatus occasionally complete. Abscisic acid did not cause stomatal closure or decreases in the rate of photosynthesis when it was applied during a phase of stomatal opening and induction of photosynthesis that followed a transition from darkness to light.Abbreviations and symbols A rate of CO₂ assimilation - ABA (±)-abscisic acid - c _a partial pressure of CO₂ in the ambient air or in the gas supplied to the leaf chambers - c _i partial pressure of CO₂ in the intercellular spaces of a leaf - e _a partial pressure of H₂O in the air - g conductance for water vapor - J quantum flux - T ₁ leaf temperature     

Chemotherapy and trace element levels in blood and tissue of rats implanted with prostate tumor cells

Male Copenhagen rats with transplanted prostatic adeno-carcinoma were treated with different polyamine synthesis inhibitors, such as methylglyoxal-bis-guanylhydrazone (MGBG), erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA) combined with 9-β-d-arabin-ofuranosyl-adenine (ARA-A), α-difluoromethyl-ornithine (DFMO), and some of their combinations. Levels of the essential trace elements—copper, zinc, magnesium, iron, selenium, and manganese —have been determined in blood, tumor, kidney, and liver of these animals and are discussed in terms of efficiency of the treatment. MGBG had the strongest effect on trace element levels in tissues of treated animals. MGBG combined with DFMO exhibited the highest antitumor activity of all treatment protocols. Selenium given as selenite with drinking water was used as an adjuvant with the most toxic combination, (ARA-A/EHNA, MGBG). Selenite reduced the toxicity of these therapeutic agents.     

The potential use of silicon compounds as oxygen carriers for free and immobilized cells containing l-amino acid oxidase

Summary The relatively low solubility of oxygen in water presents a problem in particular when immobilized cells are used or enzymes are applied for oxygen dependent reactions. The other main purpose is the requirement of oxygen for the increase of biomass. In this investigation the usefulness of silicon emulsions as oxygen carriers is demonstrated.In case of l-amino acid oxidase activity of immobilized cells, an increase by a factor of four was found in the presence of silicon emulsions. Likewise, growth medium enriched with silicon emulsions showed a significantly increased growth of cells inside alginate beads compared to normal growth medium.     

Effect of light intensity on ammonia assimilation in maize leaves

The effect of light on the metabolism of ammonia was studied by subjecting detached maize leaves to 150 or 1350 mol m^–2 s^–1 PAR during incubation with the leaf base in 2 mM ¹⁵NH₄Cl. After up to 60 min, leaves were extracted. Ammonia, glutamine, glycine, serine, alanine, and aspartate were separated by isothermal distillation and ion exchange chromatography. ¹⁵N enrichments were analyzed by emission spectroscopy. The uptake of ammonium chloride did not influence CO₂ assimilation (8.3 and 17.4 mol m^–1 s^–1 at 150 and 1350 mol m^–2 s^–1 PAR, respectively). Leaves kept at high light intensity contained more serine and less alanine than leaves from low light treatments. Within 1 h of incubation the enrichment of ammonia extracted from leaves rose to approximately 20% ¹⁵N. In the high light regime the amino acids contained up to 15% ¹⁵N, whereas in low light ¹⁵N enrichments were small (up to 6%). The kinetics of ¹⁵N incorporation indicated that NH₃ was firstly assimilated into glutamine and then into glutamate. After 15 min ¹⁵N was also found in glycine, serine and alanine. At high light intensity nearly half of the ¹⁵N was incorporated in glycine. On the other hand, at low light intensity alanine was the predominant ¹⁵N sink. It is concluded that light influences ammonia assimilation at the glutamine synthetase reaction.     

Molecular cloning of a pea mRNA encoding an early light induced,nuclear coded chloroplast protein

Summary cDNA clones were isolated for a chloroplast protein, the mRNA of which is induced to maximum levels within 2–4 h after onset of illumination in five day old, etiolated pea seedlings. The cDNA library was constructed from poly(A)⁺-mRNA which was isolated from 4 h illuminated seedlings. The extremely short induction period of the early light induced protein(ELIP)-mRNA established the basis of our screening procedure. Colony hybridization experiments were performed with³²P-labelled cDNA probes, synthesized from RNA of seedlings which had been exposed to different programs of illumination. Plasmid DNAs were isolated from colonies showing strong hybridization signals exclusively with cDNA corresponding to the 4 h-mRNA. Hybrid released translation of preselected plasmids p 17/C2 and p17/C4 revealed a peptide of M_r 24 000. After posttranslational importin vitro, the processed product of M_r 17 000 appears in the chloroplast. Using these clones, the expression of the ELIP-mRNA was investigated by DOT-hybridization. The ELIP-mRNA reaches maximum levels within 2–4 hours after onset of illumination. Our results correspond precisely to thein vivo characteristics and indicate positive identification of the sought clones.     

B lymphocyte receptors and polyphosphoinositide degradation

Resting B lymphocytes can be activated and induced to proliferate by antibodies against their antigen receptors (anti-lg). We demonstrate an early increase in the level of [3H]inositol trisphosphate in [3H]inositol-labeled murine B cells, which suggests breakdown of phosphatidylinositol bisphosphate by phospholipase C. In line with this, the level of [3H]1,2-diacylglycerol was also elevated after incubation of [3H]arachidonic-acid-labeled B cells with anti-Ig. Anti-lg also caused a rapid increase in the level of cytosolic Ca2+ in B cells. In contrast, two other polyclonal B cell activators, lipopolysaccharide and phorbol myristate acetate, failed to induce any of these effects. Our results suggest that anti-lg may induce B cell growth via phosphoinositide degradation and Ca2+ mobilization, and that phorbol myristate acetate, and possibly lipopolysaccharide, bypass these initial events.     

Covalent immobilization of the multienzyme enniatin synthetase

Summary The multienzyme enniatin synthetase was covalently immobilized to N-hydroxysuccinimide activated agarose. The stability of the immobilized enzyme at 25°C was enhanced compared to the soluble enzyme. Immobilization experiments also indicated that the enniatins are synthesized by a single molecule and thus do not require interactions of several enzyme molecules.     

Primary production data from the south-eastern Weddell Sea

Summary Phytoplankton production for three size classes (<20 m, 20–100 m, >100 m), total primary production and qualitative composition of phytoplankton populations were recorded from 18 stations in the south-eastern Weddell Sea in February/March 1983. Total primary production ranged between 80 and 1670 mg C m^-2 d^-1 with an average of 670 mg C m^-2 d^-1, nearly 70% of which was contributed by the <20 m size fraction (usually pennate and/or centric diatoms). Production of phytoplankton was in the higher range of values reported by other authors for the same region. Variations in primary production could not be attributed to composition of populations, ambient light levels or concentrations of macronutrients (N, P, Si). Phytoplankton populations had a higher diversity in the deeper parts of the Weddell Sea and coincided with different oceanographic situations. Three zones (along the shelf-ice edge from Atka Bay to Halley Bay, west of Halley Bay and off the Filchner/Rønne Ice Shelf) with different communities could be clearly distinguished.     

Observations on Echinococcus granulosus of cattle origin in Switzerland

Switzerland is one of the few countries where high fertility rates have been reported in cattle hydatid cysts and where the cattle/dog cycle is the most important for the maintenance of Echinococcus granulosus. The developmental and morphological characteristics of E. granulosus of Swiss cattle origin were studied and compared with that of E. granulosus of domestic animal origin from Great Britain and Australia, countries where bovine hydatid cysts are usually sterile and cattle play little role in the life-cycle of the parasite. Adult E. granulosus of Swiss cattle origin differed markedly in its developmental characteristics compared to other isolates, particularly in its rate of maturation in dogs, producing eggs as early as 35 days post-infection. The morphology of E. granulosus of Swiss cattle origin was characteristic and it could be easily distinguished from other isolates of the parasite. Further, E. granulosus of Swiss cattle origin was found to closely resemble that occurring in cattle in South Africa where high fertility rates have also been reported in bovine hydatid cysts. It is concluded that a strain of E. granulosus exists which is adapted to cattle and that further studies are required to determine whether this strain warrants formal taxonomic status as the species E. ortleppi which was originally described for the parasite of South African cattle origin.     

Calcium domains associated with individual channels can account for anomalous voltage relations of CA-dependent responses.

Computer-assisted modeling of calcium influx through voltage-activated membrane channels predicted that buffer-limited elevation of cytoplasmic free calcium ion concentration occurs within microscopic hemispherical "domains" centered upon the active Ca channels. With increasing depolarization, the number of activated channels, and hence the number of Ca domains, should increase; the single-channel current should, however, decrease, thereby decreasing Ca2+ accumulation in each domain relative to the macroscopic current. Such voltage dependence of the microscopic distribution of Ca2+ may influence relations between total Ca2+ entry and Ca-dependent processes. Ca-mediated inactivation of Ca channels in Aplysia neurons exhibits behavior consistent with the calcium domain hypothesis.