Insulin pretreatment (imprinting) produces elevated capacity in the insulin binding of Tetrahymena. Different binding by the cilia of the body and oral field

Gold-labeled insulin is bound first of all to the cilia of the oral field of Tetrahymena. A primary treatment (hormonal imprinting) with insulin increases the binding capacity even after 24h and makes it more sensitive for appearance a week later, within a minute of giving insulin-gold. The food vacuoles contain insulin-gold in pretreated cells or without pretreatment as well, though in imprinted situations the label can be found in pinocytotic vesicles at the bases of cilia in the oral field. Altogether, a functional difference can be observed between the cilia of the oral and non-oral surfaces of Tetrahymena and hormonal imprinting has a specifying effect on the binding of labeled hormone.     

Chloroflexus-like organisms from marine and hypersaline environments: Distribution and diversity

We report the presence of a diverse number ofChloroflexus-like organisms in intertidal marine and submerged hypersaline microbial mats using light, infrared fluorescence, and electron microscopy. The intertidal organisms appear morphologically very similar to thermophilicC. aurantiacus while the 2 hypersaline strains are larger and have a more complex ultrastructure composed of chlorosome-bearing internal membranes that appear to arise as invaginations of the cell membrane. By comparing spectroradiometry of microbial mat layers with microscopic observations, we have confirmed that theChloroflexus-like organisms are major constituents of the hypersaline microbial mat communities. In situ studies on mat layers dominated byChloroflexus-like organisms showed that sulfide-dependent photoautotrophic activity sustained by near infrared radiation prevailed. Autoradiographic analyses revealed that autotrophy was sustained in the filaments by 750 nm radiation. Three morphologically distinct strains are now maintained in mixed culture. One of these appears to be growing photoautotrophically.     

Influence of enzyme solution on protoplast culture and transient gene expression in maize (Zea mays L.)

The influence of two enzyme solutions, differing only in the presence or absence of Macerozyme, on protoplast yield, colony formation and transient GUS (-glucuronidase) activity was studied. For all parameters tested the presence of Macerozyme during protoplast isolation had a negative influence. Using an enzyme solution without Macerozyme suspension aggregates gave up to 4.4 times higher protoplast yield and plating efficiencies were increased up to 10-fold. Further, protoplasts isolated without macerozyme showed a 5.2-fold higher GUS activity in transient gene expression. Apart from the presence of Macerozyme, longer incubation (3 compared with 1.5 h) of cell aggregates in the enzyme solution also had a negative effect on transient transformation efficiency. These data demonstrate that protoplast isolation conditions have a profound effect on transient gene expression and it is proposed that these factors will also influence stable transformation efficiency.Abbreviations CP cellulase pectolyase - CPM cellulase pectolyase Macerozyme - 2,4-d 2,4-dichlorophenoxyacetic acid     

Strong synergistic effects of gibberellins with the synthetic cytokinin N-(2-chloro-4-pyridyl)-N-phenylurea on parthenocarpic fruit set and some other fruit characteristics of apple

The induction of parthenocarpic fruit set was investigated using the apple cvs. Golden Delicious and Jonagold. The gibberellins GA₃, GA₄, GA₅ and GA₇ and the synthetic phenylurea-type cytokinin CPPU (N-(2-chloro-4-pyridyl)-N-phenylurea), were applied alone and in combination to unpollinated flowers at the end of petal fall. Gibberellins induced only a marginal final set of parthenocarpic fruits. CPPU sprays were more effective, particularly in the first year. When applied in combination, CPPU and gibberellins had a positive synergistic effect on parthenocarpic fruit set and fruit size, but a negative effect on flower induction the next year. After CPPU + GA sprays, percent fruit set was similar, or greater, compared to natural pollinated trees. The parthenocarpic fruits induced by CPPU + GA had an increased length to diameter ratio. CPPU stimulated, and GA₄ and GA₇ reduced, the russeting of the parthenocarpic fruits. The internal quality of the fruits was hardly affected, but Ca-deficiency symptoms occurred more frequently in parthenocarpic fruits.     

Interactions among juveniles of two freshwater crayfish species and a predatory fish

Two freshwater crayfish species, Astacus astacus L. and Pacifastacus leniusculus Dana, co-occur in some Swedish lakes. Observational studies indicate that the introduced, North American species P. leniusculus may gradually replace the native A. astacus, but the mechanism behind the replacement is not known. This study examined the direct effects of interspecific competition between the crayfish, and indirect effects of competitive interactions and fish (European perch, Perca fluviatilis L.) predation. Three different experiments with young-of-the-year (YOY) crayfish were performed. P. leniusculus was strongly dominant over similar-sized A. astacus in interference competition for shelter in a laboratory experiment. However, in a 35-day experiment in outdoor pools, A. astacus growth and survival were about equally affected by interactions with conspecifics and P. leniusculus. In contrast, P. leniusculus was significantly more affected by intraspecific competition than by competition with A. astacus, suggesting asymmetric competition between the two species. The presence of perch in outdoor ponds with mixed-species groups of the two crayfish species resulted in considerably higher predation rates on A. astacus than on P. leniusculus. Both species showed strong antipredator responses to perch by increasing refuge use. I suggest that higher perch predation rates on A. astacus originate from P. leniusculus being the superior species in interspecific competition for shelter. Because of displacement from refuges, A. astacus individuals become more exposed to the predator. This indirect effect of interactions among the two cray-fish species and the predator may be important in the observed in situ replacement of A. astacus by P. leniusculus.     

Herbivory on calcicolous lichens: different food preferences and growth rates in two co-existing land snails

A total of 32 calcicolous lichen species, one alga and one bryophyte were recorded on a limestone wall in the grassland Great Alvar on the Baltic island of Öland, Sweden. Fourteen (41%) of these 34 species and free-living cyanobacteria showed herbivore damage, most probably due to grazing by the land snails Chondrina clienta and Balea perversa which inhabited the limestone wall. Three laboratory experiments were conducted to examine the food preferences of individuals of C. clienta and B. perversa collected at this site and to evaluate any association between their preference and the net food quality of the lichens to the snails. Chondrina clienta and B. perversa exhibited food preferences, which differed significantly between species. Within species, variation in food choice was similar among individuals. This indicates that snail populations may be composed of polyphagous individuals with similar food preferences. Different lichen species were of different net food quality to the snails as indicated by growth rate differences. In both snail species the most preferred lichen species of the choice experiment caused the largest weight increase in juveniles, viz. Caloplaca flavovirescens for C. clienta and Aspicilia calcarea for B. perversa. This suggest that the snail species studied differ in their abilities to deal with secondary compounds and physical characteristics of certain lichens or that they can utilize the energy and nutrients of these lichens to a different extent. It is suggested that differential food preferences might reduce the intensity of interspecific competition for resources (lichens) between C. clienta and B. perversa.     

Evaluation of the palatability of chrysomelid larvae containing anthraquinones to birds

Chrysomelid larvae of the subfamily Galerucinae, tribe Galerucini, are known to contain 1,8-dihydroxylated 9,10-anthraquinones. Since nonhydroxylated 9,10-anthraquinone is the active agent in several commercial products sold to protect seeds against birds, we suggested that the naturally occurring dihydroxylated anthraquinones of galerucine larvae may also act as protective devices against bird predation. Tits (Parus spp.) are potential predators of larvae of the tansy leaf beetle, Galeruca tanaceti, and the elm leaf beetle, Xanthogaleruca luteola. To investigate the palatability of these chrysomelid larvae to birds, we offered them with mealworms and Calliphora pupae, respectively, as controls in dual choice bioassays to eight singly kept, naive tits (five P. major and three P. ater individuals). The bioassays were limited to 5 days, during which larvae were offered daily for 2 h (X. luteola) and 3 h (G. tanaceti), respectively. Every day, the birds significantly avoided uptake of G. tanaceti and X. luteola. More than 98% of the control food was consumed daily, whereas the percentage of chrysomelid larvae totally eaten never surpassed 6.6% for G. tanaceti and 51.8% for X. luteola. In order to determine whether this avoidance was due to the anthraquinones of the chrysomelid larvae, mealworms and Calliphora pupae, respectively, were treated with these compounds in concentrations equivalent to the natural ones. Dual choice bioassays with treated and untreated prey were conducted, again for 5 days with a daily 2- or 3-h test period, respectively. The tits ate all or nearly all treated and untreated food items every day. However, during the 5-day test period the tits learnt to take up the control insects significantly earlier than the treated ones; the food containing anthraquinones was not consumed as readily as the control, which suggest aversive learning based on distastefulness. The efficiency of anthraquinones in protecting galerucine larvae against bird predation is discussed with special respect to learning behavior and factors which might delay or mask learning of avoidance.