Benthic nematodes in acidified lakes: case of a neglected grazer

Abundance and composition of nematode fauna were examined in the benthic microbial mats and upper sediment layer of the littoral of acidified (pH 4.6 to 5.7) lakes. Nematodes constituted from 58% to 90% of all the invertebrates present (excluding protozoans and rotifers). In the examined material, the majority of nematodes was represented by 3 taxa of which Ironus was found specifically associated with the mats. It was concluded that the persistence of benthic mats may be linked to the metabolic activity of the associated nematode fauna.     

Phosphorylation of Synaptic Membrane Glycoproteins: The Effects of Ca2+ and Calmodulin

Synaptic membranes were incubated with [gamma-32P]ATP, and glycoproteins were isolated by affinity chromatography on concanavalin A agarose. Glycoproteins accounted for 1.5-2.5% of the total 32P incorporated into synaptic membrane proteins. Ca2+ and calmodulin enhanced the phosphorylation of synaptic membrane glycoproteins approximately threefold. In the presence of Ca2+ and calmodulin, the rate of glycoprotein dephosphorylation was also increased three- to four-fold. Gel electrophoretic analysis identified several synaptic membrane glycoproteins that incorporated 32P, with the most highly labeled glycoprotein under basal phosphorylating conditions having an apparent Mr of 205,000 (gpiii). Ca2+ and calmodulin produced a marked increase in the phosphorylation of a glycoprotein with an apparent Mr of 180,000 (gpiv) and lesser increases in the labeling of three other glycoproteins. Membranes that had been labeled with [gamma-32P]ATP were extracted with Triton X-100 under conditions that yield a detergent-insoluble residue enriched in postsynaptic structures. The Triton X-100 insoluble residue accounted for 20-25% of the 32P associated with synaptic membrane glycoproteins. Gpiv and other glycoproteins, the phosphorylation of which was stimulated by calmodulin, were located exclusively in the Triton X-100 insoluble residue, whereas gpiii and other calmodulin-insensitive glycoproteins partitioned predominantly into the Triton X-100-soluble fraction. Phosphopeptide maps and phosphoamino acid analysis of gpiv isolated from synaptic membranes and a postsynaptic glycoprotein of apparent Mr of 180,000 (gp180) isolated from synaptic junctions indicated that the former protein was identical to the previously identified postsynaptic-specific gp180. In addition to phosphoserine and phosphothreonine, gpiv also contained phosphotyrosine, identifying it as a substrate for tyrosine-protein kinase as well as for Ca2+/calmodulin-dependent protein kinase.     

Biodiversity assessment in ecological restoration above the timberline

Ecological restoration trials in high-alpine sites require sampling of indigenous plant populations. This problem is discussed briefly in relation to initial genetic diversity in the restoration material. The further part of the paper deals with restoration trials in the Swiss Alps and their assessment.The plots, set in machine-graded downhill ski runs, were revegetated with transplants of alpine species used in various combinations. Safe-site conditions were simulated with biodegradable wood-fibre mats. Surveys carried out in plots aged four to seven years focused on plant species inventory and age-state structure of mixed stands. The alpha diversity assessment included speices number and the associated aspects. The consistent increase in species number, the number of plant families represented, and range of life-forms was apparently independent of the restoration timing. The age-state structure of the mixed stands was characterized by a considerable increase in the range of age-state classes and, in particular, a regular appearance of younger variants. These changes clearly indicate development of self-sustaining plant communities influenced by reproduction of the transplants and extensive immigration. It is proposed that age-state structure be called delta diversity and included in a routine assessment of post-restoration status of both single plant populations and mixed stands.     

Effects of ionizing radiation on the growth and allyl isothiocyanate accumulation of Wasabia japonica in vitro and ex vitro

Mutations were induced in tissue-cultured wasabi (Wasabia japonica Matsumura) by treating in vitro-derived shoot tips with either γ-rays or X-rays at 0, 10, 20, 40 or 80 Gy. Doses of up to 40 Gy of either γ- or X-ray treatments resulted in a survival rate of more than 60% in culture after 3 mo. The use of γ- or X-rays at doses between 10 Gy and 40 Gy to induce mutation in W. japonica resulted in an alteration of the growth and allyl isothiocyanate (AITC) content of multiple shoots after 3 mo. in culture on Murashige and Skoog medium containing 5 μM N⁶-benzyladenine (BA). Putative mutants from the 40 Gy treatments of either γ- or X-rays exhibited a reduction in shoot weight, number, and height, whereas treatments of either γ-rays or X-rays at 10 Gy and 20 Gy doses showed no significant differences in shoot growth. All shoots treated with 80 Gy were either necrotic or irregenerable, while those treated with 40 Gy produced deformed leaves, from both types of ionizing radiation. Concentrations of AITC were measured by the use of gas chromatography-mass spectrometry (GC-MS). The accumulation of AITC was shown to decrease when doses increased in both γ- and X-ray treatments, compared with the controls. Positive responses were solely occurred at 18 mo. after transfer of in vitro rooted shoots to the shade house. The survival rate, rhizome weight and AITC content of plants derived from shoots treated with 20 Gy or 40 Gy of either γ-rays or X-rays were significantly greater than those of the controls.     

Physiological activity of 1-amino-2-phenylethylphosphonic acid,a substrate analogue of phenylalanine

1-Amino-2-phenylethylphosphonie acid (PheP) retards growth inSpirodela oligor-rhiza causing morphological malformations, inhibits chlorophyll synthesis in progeny fronds, and markedly stimulates L-phenylalanine ammonia-lyase (PAL) activityin vivo and inhibits itin vitro; in prolonged experiments ribonuclease activity is stimulated. PheP severely inhibits anthocyanin synthesis in seedlings of red cabbage, with moderate inhibition of PAL activityin vivo; chlorophyll synthesis and growth of the seedlings are little affected.     

Targeting RNA for Degradation with a (2′, 5′)-Oligoadenylate Antisense Chimera

Abstract

A novel method is described to selectively cleave RNA by harnessing the 2-5A-dependent ribonuclease.     

Binding of magnesium by proteins of the mitochondrial intermembrane compartment

The intermembrane compartment of rat liver mitochondria contains high molecular weight compounds, most likely proteins, complexing magnesium ions. Compound/s/ of about 150 000 daltons has a low affinity /K_d 0.37 mM/ and a high binding capacity of 300 ng atoms Mg/mg protein; compound/s/ of about 100 000 daltons is characterized by a very high affinity towards magnesium /K_d of the order of magnitude of 0.001 mM/ and a low capacity of about 20 ng atoms Mg/mg protein.     

Effects of Tripeptides on the Amidolytic Activities of Urokinase, Thrombin, Plasmin and Trypsin

Eight peptides of the general formula X-d-Ser-AA-Arg-Y where X = H, Ac; AA = Ala, Gly and Y = OH, NH₂ were obtained and tested for their effect on the amidolytic activities of urokinase, thrombin, plasmin, and trypsin.     

Advances in soil microbial ecology and the biodiversity

Recent studies on the colony formation of soil bacteria opened the way to categorize soil bacteria into colony forming curve (CFC) groups of different growth rates. A bacterial culture collection comprising organisms from every CFC group is called an ecocollection. Outlines of ECs of paddy soil 1992 and grassland soil 1987 and 1992 were described. Phylogenetic studies by 16S rDNA sequencing showed a great diversity of culture strains of the ecocollections (EC). A set of alternative concepts was proposed; the active and the quiescent forms of bacterial cells in soil. The former is able to be cultivated and thus counted by the plate method, while the latter is not unless it transforms into the former. Based on the results several points required for extensive cataloguing of soil bacteria were noted.     

Maturation of somatic embryos of Pinus strobus is promoted by a high concentration of gellan gum

Application of somatic embryogenesis to Pinus strobus clonal propagation and genetic improvement was hampered by the difficulty in achieving synchronous maturation of a large number of somatic embryos that would germinate and produce plants. Media containing abscisic acid (80 μ M ) and osmotic agents such as sucrose, polyethylene glycol and/or dextran did not sustain development of mature somatic embryos from plated embryonal masses. This indicated that factors other than osmotic agents might be involved in sustaining development of Pinus strobus somatic embryos to maturity. It was subsequently found that media lacking osmotica but containing a high concentration of gellan gum (1%) induced significant improvement in the development of mature somatic embryos in the presence of 80 or 120 μ M abscisic acid. This positive effect was independent of the genotype and all four tested lines displayed similar responses. Media containing gellan gum at concentrations from 0.4 to 1.2% formed gels that varied in their strength. Gel strength was proportional to the concentration of gellan gum in the specific medium but varied depending on the medium formulation. Gel strength increased with the duration of storage of the culture medium by 46% (SD 14) after 14 days of storage. Preliminary results showed that embryos matured on high gellan gum media displayed improved germination frequencies. These results indicate that in Pinus strobus the water status and possibly other medium characteristics that are influenced by increased concentration of gelling agent have stimulatory effects on maturation of somatic embryos.