Transformed plants with elevated levels of chloroplastic SOD are not more resistant to superoxide toxicity

The petunia nuclear gene which encodes the chloroplast isozyme of superoxide dismutase, SOD-1, has been fused with an efficient rbcS promoter fragment and 3 flanking region and introduced into tobacco and tomato cells. Transformed plants carrying this chimeric gene have up to 50-fold the levels of SOD-1 which occur in wild-type plants. However, tobacco plants with 30-to 50-fold the normal SOD-1 activity do not exhibit resistance to the light-activated herbicide paraquat. Similarly, tomato plants with 2-to 4-fold increases in SOD-1 do not exhibit tolerance to photoinhibitory conditions known to increase superoxide levels (high light, low temperatures and low CO₂ concentrations). Our data indicate that increasing the chloroplastic SOD level in a plant cell is not sufficient to reduce the toxicity of superoxide.     

Multiple fruiting of the edible mushroomCoprinus cinereus from explants of the stipe

Summary Carpophores were developed on defined medium from explants of stipes produced in the dark using an expansionless mutant (no. 190) ofCoprinus cinereus. Explants taken from stipes within 24 h of formation developed multiple fruit within 3–12 days without formation of mycelia. Fruiting levels were affected by stipe age (24 h), medium composition, explant size, and polarity of the explant on fruiting medium. This method offers a new tool for developmental studies and may also be of use to commercial mushroom growers.     

Free amino acid levels and the regulation of nitrate uptake in maize cell suspension cultures

The ability of individual amino acids to regulate nitrate uptakeand induction was studied in a Zea mays embryo cell line grownin suspension culture. The maize cells exhibited a marked preferencefor absorbing amino acids over nitrate when both were presentin culture medium. The addition of an individual amino acid(2 mM glutamine, glycine, aspartic acid, or arginine) to theculture medium with 1 mM nitrate completely inhibited nitrateuptake and resulted in a cycle of low levels of nitrate influxfollowed by efflux to the growth medium. Glutamine was readilyabsorbed by the cells and was particularly effective in supportingoptimum cell growth in the absence of an inorganic nitrogensource as compared to the three other amino acids evaluated.However, neither glutamine nor any of the remaining 19 proteinaceousamino acids appeared to be solely responsible for regulationof nitrate uptake and induction. The ability of amino acidsto regulate nitrate uptake and assimilation appears to be morerelated to their overall levels in the cell rather than to anaccumulation of a specific amino acid. Key words: Amino acids, nitrate uptake, maize, regulation, cell suspension culture     

Characterisation of the anti-bladder-cancer monoclonal antibody BLCA-8: Identification of its antigen as a neutral glycolipid

A monoclonal antibody, BLCA-8, was raised against the human bladder cancer cell line, UCRU-BL-17CL. By flow cytometry and immunoperoxidase staining, this antibody was found to possess high specificity for bladder tumours, some reactivity with fetal tissues, and no reactivity with normal bladder, or any normal or malignant tissue. This high specificity and the stability of the antigen to the urinary environment suggest that BLCA-8 may have potential for use as an anti-bladder-cancer therapeutic agent. By thin-layer chromatography and autoradiography, BLCA-8 was found to bind four components within the neutral lipid fraction of a bladder cancer cell line, UCRU-BL-17/23. These components hadR _F values of 0.22, 0.16/0.15 (doublet), 0.12 and 0.08, and migrated below globoside, indicating the presence of more than four sugars. By enzyme-linked immunosorbant assay and thin-layer chromatography it was found that the binding of BLCA-8 to the lipid extract was increased by both mild alkaline hydrolysis and enzymatic treatments, indicating that adjacent phospholipids and glycolipids interfere with the accessibility of the antibody-binding site. Full biochemical characterisation of the BLCA-8 antigen is currently underway.     

Effect of abscisic acid, osmolarity and partial desiccation on the development of recalcitrant mango somatic embryos

Inhibition of mango somatic embryo growth was inducedin vitro by treatments for 4 or more weeks with abscisic acid (0–100 M ABA) with and without high osmolarity provided by mannitol (0–10%). High osmolarity and ABA significantly affected somatic embryo length, precocious germination and the production of good quality secondary somatic embryos. High osmolarity also affected root elongation. Abscisic acid was more effective in suppressing growth and development of 0.5 cm-length somatic embryos than smaller somatic embryos. Development beyond the heart stage was significantly inhibited by both ABA and mannitol treatments. The recovery of good quality somatic embryos was enhanced by high levels of ABA (100 M) with and without mannitol (0–5%). Somatic embryos that had been pulsed with ABA were partially desiccated at different relative humidities. Weight loss was affected only by relative humidity; and ABA did not enhance desiccation tolerance.Abbreviations ABA Abscisic acid - 2,4-D 2,4-Dichlorophenoxyacetic acid - MM1 Mango maturation medium - RH Relative humidity     

Higher level relationships of Apiales (Apiaceae and Araliaceae) based on phylogenetic analysis of rbcL sequences

The two families of the order Apiales (Apiaceae and Araliaceae) represent a classic example of the difficulty in understanding evolutionary relationships between tropical-temperate family pairs. In Apiales, this problem is further compounded by phylogenetic confusion at almost every taxonomic level, including ordinal, interfamilial, and infrafamilial, due largely to difficulties in understanding trends in morphological evolution. Phylogenetic analyses of rbcL sequences were employed to resolve relationships at the ordinal and familial levels. The results of the ordinal analysis confirm the placement of Apiales in an expanded subclass Asteridae as the sister group to Pittosporaceae, and refute the traditional alliance of Apiales with Cornales and Rosidae. This study has also resolved relationships of a number of enigmatic genera, suggesting, for example, that Melanophylla, Aralidium, Griselinia, and Toricellia are close relatives of Apiales. Clarification of phylogenetic relationships has concomitantly provided insights into trends of morphological evolution, and suggests that the ancestral apialean taxon was probably bicarpellate, simple-leaved, woody, and paleotropical. Phylogenetic analysis at the family level suggests that apiaceous subfamily Hydrocotyloideae, often envisioned as an intermediate group between Apiaceae and Araliaceae, is polyphyletic, with some hydrocotyloids closely allied with Araliaceae rather than Apiaceae. With the exception of some hydrocotyloids, Apiaceae appear to be monophyletic. The relationship between Apiaceae and Araliaceae remains problematic. Although the shortest rbcL trees suggest that Apiaceae are derived from within a paraphyletic Araliaceae, this result is only weakly supported.     

Effect of temperature and temperature acclimation on the ryanodine sensitivity of the trout myocardium

The influence of acute temperature change and temperature acclimation on the sensitivity of contracture development to ryanodine were examined in the rainbow trout myocardium using two preparations: in vitro isolated ventricular strips and in situ working perfused hearts. Ryanodine effects in vitro were dependent on test temperature (8 and 18 °C), pacing frequency (0.2–1.5 Hz) and acclimation temperature (8 and 18 °C). At a pacing frequency of 0.2 Hz and a test temperature of 18 °C, ryanodine depressed isometric tension development in ventricular strips both from trout acclimated to 8 and 18 °C but the decrease was significantly greater in strips from 8 °C-acclimated trout. No ryanodine effect was observed in either acclimation group at a test temperature of 8°C. The effect of ryanodine in vitro was reduced or lost at pacing frequencies greater than 0.2 Hz and at 0.6 Hz ryanodine depressed tension development at 18 °C only in strips from 8 °C-acclimated trout. Ryanodine did not affect tension development at stimulation rates above 0.6 Hz in any test group. Likewise, ryanodine did not significantly impair cardiac performance of in situ working perfused heart preparations which operated at intrinsic beat frequencies in excess of 0.6 Hz. These results suggest that the sarcoplamic reticulum calcium release channel of the trout myocardium is expressed but is not functionally involved in beat-to-beat regulation of contractility at either (1) low temperature (8 °C), or (2) at routine physiological heart rate (>0.6 Hz). However, under conditions in which involvement of the sarcoplasmic reticulum is observed (18 °C and a heart rate < 0.6 Hz), prior acclimation to low temperature results in either a greater capacity of the sarcoplasmic reticulum to store releasable calcium or an increase in the amount of calcium that is in releasable form.Abbreviations bm body mass - E-C coupling, excitation-contraction coupling - IVS isometric ventricular strip - SR sarcoplasmic reticulum - TES N-tris[hydroxy-methyl]methyl-2-aminoethane sulfonic acid - WPH in situ working perfused heart     

Slow oscillations of free intracellular calcium ion concentration in human fibroblasts responding to mechanical stretch

Calcium transients in single, human gingival fibroblasts were studied after mechanical stretching of flexible culture substrates. A model system was developed to reproducibly stretch and rapidly (< 1 sec) refocus cells in the same focal plane so that changes in the concentration of free intracellular calcium ions ([Ca²⁺]_i) were monitored without delay. Attached cells were grown on flexible bottom Petriperm dishes, loaded with fura-2/AM, and stretched by 1% or 2.8% of substrate area. The stretch caused no significant cell detachment or membrane lesions. A 1% stretch induced no calcium response, but a 2.8% stretch stimulated an initial calcium transient and the subsequent generation of [Ca²⁺]_i oscillations of up to 2,000 sec. At 1% stretch, there was no calcium response. Cell shape and plating time were important determinants in the calcium response to mechanical stimulation: the responder cells were small and round without long processes. Major calcium transients were inhibited completely by 5 mM EGTA or by 10 μM gadolinium ions, by 50 μM nifedipine, or 250 μM verapamil, suggesting an influx of calcium through stretch-activated (SA) channels and L-type calcium channels. Depolarization by high KCl (144 mM) in the extracellular medium enhanced the amplitude of calcium transients by 54%. Calcium oscillations were not inhibited by preincubation with thapsigargin, caffeine, cholera toxin, staurosporine or 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7), indicating that IP₃ sensitive pools, IP₃ insensitive pools, G₅α subunits, and protein kinase C, respectively, were not involved in the generation of calcium oscillations. Pretreatment with genistein, a specific tyrosine kinase inhibitor or cytochalasin D, an inhibitor of actin polymerization, or pertussis toxin, an inhibitor of G_iα and G_oα subunits, completely abolished calcium transients and oscillations. These results indicate that Ca²⁺ flux due to mechanical stretching is likely mediated through SA ion channe s and is dependent on tyrosine kinases, pertussis toxin-sensitive subunits of G-proteins, and actin filaments. © 1994 Wiley-Liss, Inc.