Differences in the metabolic responses of root tips of wheat and rye to aluminium stress

The effects of aluminium (Al) ions on the metabolism of root apical meristems were examined in 4-day-old seedlings of two cereals which differed in their tolerance to Al: wheat cv. Grana (Al-sensitive) and rye cv. Dakowskie Nowe (Al tolerant). During a 24 h incubation period in nutrient solutions containing 0.15 mM and 1.0 mM of Al for wheat and rye, respectively, the activity of first two enzymes in the pentose phosphate pathway (G-6-PDH and 6-PGDH) decreased in the sensitive cultivar. In the tolerant cultivar activities of these enzymes increased initially, then decreased slightly, and were at control levels after 24 h. In the Al-sensitive wheat cultivar a 50% reduction in the activity of 6-phosphogluconate dehydrogenase was observed in the presence of Al. Changes in enzyme activity were accompanied by changes in levels of G-6-P- the initial substrate in the pentose phosphate pathway. When wheat was exposed for 16 h to a nutrient solution containing aluminium, a 90% reduction in G-6-P concentration was observed. In the Al-tolerant rye cultivar, an increase and subsequently a slight decrease in G-6-P concentration was detected, and after 16 h of Al-stress the concentration of this substrate was still higher than in control plants. This dramatic Al-induced decrease in G-6-P concentration in the Al-sensitive wheat cultivar was associated with a decrease in both the concentration of glucose in the root tips as well as the activity of hexokinase, an enzyme which is responsible for phosphorylation of glucose to G-6-P. However, in the Al-tolerant rye cultivar, the activity of this enzyme remained at the level of control plants during Al-treatment, and the decrease in the concentration of glucose occurred at a much slower rate than in wheat. These results suggest that aluminium ions change cellular metabolism of both wheat and rye root tips. In the Al-sensitive wheat cultivar, irreversible disturbances induced by low doses of Al in the nutrient solution appear very quickly, whereas in the Al-tolerant rye cultivar, cellular metabolism, even under severe stress conditions, is maintained for a long time at a level which allows for root elongation to continue.Abbreviations G-6-PDH glucose-6-phosphate dehydrogenase - 6-PGDH 6-phosphogluconate dehydrogenase - G-6-P glucose-6-phosphate - TEA triethanolamine     

Haematological changes in an Antarctic teleost,Trematomus bernacchii,following stress

The effect of an acute increase in temperature, exhaustive exercise and hypoxia on the haematology of the benthic Antarctic teleost, Trematomus bernacchii was investigated. High temperature and hypoxia caused the biggest changes to the blood, with increases in haematocrit, haemoglobin concentrations and plasma chloride levels. The spleen decreased in mass. Exercise produced the smallest changes. Changes were substantially less than reported for the more active cryopelagic species Pagothenia borchgrevinki. The magnitude of the haematocrit increase is discussed in relation to life-style of fish living in the Antarctic.     

Cloning and expression analysis of an ADP-ribosylation factor from Solanum tuberosum L.

Summary A cDNA clone encoding an ADP-ribosylation factor from potato (Solanum tuberosum L.) was isolated. The nucleotide and deduced amino acid sequences show high homology to known ADP-ribosylation factor sequences from Arabidopsis, yeast, cow and man. In northern blot experiments, all tissues analysed showed expression of the corresponding mRNA. Strongest expression was found, however, in potato tubers.Abbreviations ARF, ADP ribosylation factor - BSA bovine serum albumin - EDTA ethylenediaminetetraacetic acid - SDS sodium dodecyl sulfate - SSC sodium saline citrate     

Clonal growth in woody plants: A review

Bulkiness, longevity and solidity of the body in woody plants enable the successive development of accessory shoots and adventitious roots in (1) both proximal and distal positions on organs, (2) both the above-ground and below-ground space, (3) both the aerial and soil environments. In monocotyledons, woody rhizomes play an essential role in the basic growth habit and architectural models. In dicotyledonous and a few gymnospermous trees, attached and successively disconnected ramets play a multilateral role in the pertinent life strategies. The majority of sprouts, coppice shoots and root suckers behave as opportunistic organs (a) serving as means of vegetative reproduction, (b) securing colonization of unoccupied ground, (c) increasing competitive power of the species within the community, (d) increasing survival rate of the stressed/disturbed genet in marginal habitats, (e) forming replacement for ageing or damaged organs, and (f) enabling reiteration of the genet's entire architectural model.     

Social Behaviour of the Carpenter Bee Xylocopa pubescens (Spinola)

The development of about 20 relatively small nests of Xylocopa pubescens was studied. After the first offspring had become adult, these nests reached a social stage in which there was only one egg-layer per nest. Freshly emerged (teneral) adults eat a lot of food, collected by a forager, before they fly out of the nest. This food appears to be of major importance to these bees in that it makes them fully agile. It seems therefore, that part of the food needed for the development of a young bee is not given at the larval stage, via the beebread, but at the teneral adult stage. As a result of this, a necessary overlap of generations is accomplished. Besides, less pollen has to be collected for the provision of a brood cell, so more cells can be constructed within a short period of time. There is a high degree of nest competition. Many nests were taken over by conspecific individuals (or by females of X. sulcatipes) that were searching for nesting sites within the study area. However, although more than 50% of the solitary nests were taken over sooner or later, strangers hardly ever intruded into social nests, with more than one adult. This illustrates how important it is for a reproducing female to tolerate the presence of nestmates which guard the nest in her absence. Although in most cases the foundress of a nest proceeded to produce new brood in the presence of her offspring, it happened that a daughter took over reproduction from her mother. In two of these cases, it could be observed that a mother started a new nest elsewhere after having been thrown out by her own daughter. At least in these cases, nest competition between mother and daughter started long before the mother had reached the end of her reproductive capacities. Since nesting possibilities are scarce, it seems a logical strategy to stay in the maternal nest and wait for a chance to become the egg-layer if the mother dies or if she loses her dominance. The occurrence of several social interactions among nestmates is discussed: — trophallaxis was observed often, not only under ‘forced’ conditions, but also as a form of ‘voluntary’ feeding; — nestmates were observed to groom each other.     

Meiobenthic distribution and nematode community structure in five European estuaries

Meiofauna from the intertidal zone of five European estuaries (Ems, Westerschelde, Somme, Gironde, Tagus) was investigated. Samples represented a cross section of various benthic habitats from near-freshwater to marine, from pure silts to fine-sandy bottoms. The meiobenthic community comprised everywhere a fauna strongly dominated by nematodes, with meiobenthic density increasing with increasing salinity. The Ems differed from the other estuaries due to the presence of a well developed community of Copepods, Gastrotrichs, large Ciliates and/or soft-shelled Foraminiferans in some sites. The Westerschelde stood out due to the near-absence of harpacticoid copepods and, as in the Tagus, the lower meiobenthic densities in the marine part of the estuary. For nematode community analysis, we also included data from the Tamar which were obtained from the literature (Warwick &; Gee, 1984). This resulted in the enumeration of 220 species, belonging to 102 genera, each with a characteristic distribution along the salinity, sedimentary and latitudinal gradients. Using the multivariate technique CANOCO, a zonation along these different physicochemical determinants was observed as well although salinity and sediment characteristic (scale of hundreds of meters to kilometers) proved to be more important in explaining community structure than latitudinal differences (scale of hundreds of kilometers). Nematode diversity was nearly entirely determined on the genus level and was positively related to salinity. Deviations from this general trend in the Gironde and the Tamar were attributed to sedimentary characteristics or to low macrobenthic predation. The presence of a typical opportunistic colonizing nematode species Pareurodiplogaster pararmatus in the low-salinity region of the Gironde could indicate (organic?) pollution or disturbance of the intertidal mud-flats.     

Therapy of bovine ocular squamous-cell carcinoma with local doses of interleukin-2: 67% complete regressions after 20 months of follow-up

We have tested the therapeutic potency of peritumorally injected low doses of interleukin-2(IL-2). Seventy tumours of the bovine ocular squamous-cell carcinoma (BOSCC), 1–3 cm in diameter, were treated with 5000, 20 000 or 200 000 U IL-2 from Eurocetus (Chiron) to find the optimal dose for treatment. Injections were given peritumorally on Monday to Friday on 2 consecutive weeks. The size of the tumours was measured before treatment and 1, 3, 4, 9 and 20 months after treatment. After 9 months complete regression was observed in 89% of the tumours treated with 5000 U IL-2, 80% treated with 20 000 U and 67% treated with 200 000 U. After 20 months, there was complete regression of 35%, 31% and 67% of the tumours respectively. The 9-and 20-month results of the 200 000-U treatment are significantly better than those of the 5000-U and 20 000-U treatments taken together. This protocol may be useful to treat advanced inoperable tumours (e.g. of the nasopharynx or skin) of human patients.     

Chiroptical methods in conformational analysis

CD spectra of flexible organic molecules in solution are normally very sensitive to conformation. In a system composed of two or more chromophores joined by one or more single bonds and with one fixed or strongly preferred conformation, it is often possible to reproduce the CD spectrum by semiempirical calculations based on interactions between the electronic transitions in the respective chromophores. In a system containing two or more conformations of appreciable weight, the observed CD spectrum is the superposition of those of the individual conformations and has to be analyzed in terms of the individual calculated spectra and the relative energies of the respective conformations. The effect of temperature variation on conformational equilibria and on the composite CD spectra will be discussed and exemplified. © 1995 Wiley-Liss, Inc.