Ceratophyllum demersum hampers phytoplankton development in some small Norwegian lakes over a wide range of phosphorus concentrations and geographical latitude

1. Data on submerged and floating-leafed macrophytes, phytoplankton, nutrients (N, P) and calcium were collected from twenty-four small lakes ( 1 km²) over a wide range of latitudes in Norway. The majority of the investigated lakes were mesotrophic or eutrophic, and most of the lakes were markedly affected by diffuse and point-source runoff from agriculture. According to their macrophyte species composition, the majority of the lakes can be classified as Potamogeton lakes or Chara lakes, or a combination of these.
2. This study is consistent with the 'two alternative stable states' hypothesis. We observed clearwater lakes with dense macrophyte cover over a wider range of total P concentration than has been reported previously: from 30 to more than 700 mg P m^–3. The clearwater state was only observed in lakes with mean depths of less than 1.9 m.
3. Most clear lakes with high cover of submerged vegetation showed indications of N limitation.
4. In this study nearly all the macrophyte-dominated lakes with P concentrations above 30 mg m^–3 had dense stands of Ceratophyllum demersum (L.). This indicates that Ceratophyllum may also play an important role in stabilizing and maintaining a clearwater state at high P concentrations.     

Demographic and genetic effects on reproduction as related to population size in a rare, perennial herb, Senecio integrifolius (Asteraceae)

Seed-set of the rare and threatened plant Senecio integrifolius increased significantly with population size. Experimental studies as well as field observations showed this to be due to density-dependent seed-set (Allee effect). Hand-pollination revealed lower seed-set, and a lower germination rate of inbred progeny than of outbred progeny, with great differences among populations. Contrary to general predictions in models of minimum viable population sizes, the present study indicates little negative effects of inbreeding in small populations. A genetic load model was invoked to explain the results, hypothesizing that purging of deleterious alleles in small populations has reduced inbreeding depression. However, no clear correlation between population size and genetic load was found. The results in this paper suggest that demographic and environmental factors are of greater immediate importance than population genetics in determining extinction probabilities of small plant populations.     

Seasonal Effects on Photosynthetic Electron Transport and Fluorescence Properties in Isolated Chloroplasts of Pinus silvestris

Chloroplasts were isolated from primary needles of 1-year-old seedlings and from secondary needles of a 20-year-old pine tree in a natural stand. In autumn the electron transport capacities of PSII, PSI and PS (II + I) decreased and the electron transport between PSII and PSI became inhibited in October in the 20-year-old tree. This inhibition lasted until May the following year. The partial reactions of PSI and PSII still showed low but fairly constant rates during the whole winter seedlings. Seasonal changes in the electron transport properties of 1-year-old showed the same general trends as observed in the 20-year-old tree, but the changes were less pronounced. However, in snow-covered seedlings the PSI-mediated electron transport and the electron transport from H₂O to NADP increased during the late winter when the seedlings were still covered by snow. The total chlorophyll content of the needles decreased in autumn and winter. Low temperature fluorescence ratios of F692/F680 and F726/F680 indicated more severe destruction of the chlorophyll a antennae closely associated with the two photosystems than of the light harvesting chlorophyll a/b complex. In this case, too, the changes were more pronounced in the 20-year-old tree than in the 1-year-old seedlings. The chlorophyll/P700 ratios indicated a more marked reduction in the reaction centre molecules during autumn than in the antennae chlorophyll molecules. The changes in electron transport and low temperature fluorescence properties which occurred during autumn and winter were mainly reversed during spring.     

Antidiabetic activity of a polyherbal preparation (tincture of panchparna) in normal and diabetic rats

The present work was executed to evaluate the anti-diabetic potency of a polyherbal formulation, and its influence on derangement in the metabolism of glucose and cholesterol and changes in sodium levels in serum and urine in normal and alloxan induced diabetic rats. Serum glucose and serum cholesterol levels were found to be increased in diabetic animals. Serum sodium and urinary sodium, hepatic glycogen levels are found to be decreased in diabetic state. Treatment with the polyherbal formulation (1.0 ml/kg body wt) for 30 days in diabetic animals has shown decrease in serum glucose and serum cholesterol levels in comparison to control animals, whereas in normal treated animals, the formulation does not effect the serum glucose and serum cholesterol levels. Serum sodium and urinary sodium levels were increased in both diabetic treated and the control animals. Hepatic glycogen levels were increased in diabetic treated animals, but there was no change in the control treated animals.     

Ethnobotany of Linnaea borealis (Linnaeaceae) in Norway

In Norwegian folk tradition, Linnaea borealis has a long-standing reputation as a cure for shingles ( Herpes zoster ). Numerous vernacular names reflect this use; the majority are dialectal variations of nårisle or nårislegras , literally: 'corpse rash', 'corpse rash grass'. Both are based on nårisle , the old name for shingles, derived from Norse nár , 'corpse', and risla , 'rash'. In folk medicine, Linnaea was also used to treat other kinds of rash, eczema, hives, measles, ringworms, scabies, water blisters, rheumatism and finger infections. It was applied either internally (as a decoction) or externally (as an ointment, in compresses or by exposing the patient to smoke). The use of L. borealis to treat shingles and skin diseases is almost entirely restricted to Norway. Within Norway, such tradition is widespread throughout the southern parts northwards to Trøndelag. The only reference to medicinal use of L. borealis in northern Norway dates back to the 18th century.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 437–452.     

Warming up the system: higher predator feeding rates but lower energetic efficiencies

Predictions on the consequences of the rapidly increasing atmospheric CO₂ levels and associated climate warming for population dynamics, ecological community structure and ecosystem functioning depend on mechanistic energetic models of temperature effects on populations and their interactions. However, such mechanistic approaches combining warming effects on metabolic (energy loss of organisms) and feeding rates (energy gain by organisms) remain a key, yet elusive, goal. Aiming to fill this void, we studied the metabolic rates and functional responses of three differently sized, predatory ground beetles on one mobile and one more resident prey species across a temperature gradient (5, 10, 15, 20, 25 and 30 °C). Synthesizing metabolic and functional‐response theory, we develop novel mechanistic predictions how predator–prey interaction strengths (i.e., functional responses) should respond to warming. Corroborating prior theory, warming caused strong increases in metabolism and decreases in handling time. Consistent with our novel model, we found increases in predator attack rates on a mobile prey, whereas attack rates on a mostly resident prey remained constant across the temperature gradient. Together, these results provide critically important information that environmental warming generally increases the direct short‐term per capita interaction strengths between predators and their prey as described by functional‐response models. Nevertheless, the several fold stronger increase in metabolism with warming caused decreases in energetic efficiencies (ratio of per capita feeding rate to metabolic rate) for all predator–prey interactions. This implies that warming of natural ecosystems may dampen predator–prey oscillations thus stabilizing their dynamics. The severe long‐term implications; however, include predator starvation due to energetic inefficiency despite abundant resources.     

Expression,purification and molecular modeling of the NIa protease of Cardamom mosaic virus

The NIa protease of Potyviridae is the major viral protease that processes potyviral polyproteins. The NIa protease coding region of Cardamom mosaic virus (CdMV) is amplified from the viral cDNA, cloned and expressed in Escherichia coli. NIa protease forms inclusion bodies in E.coli. The inclusion bodies are solubilized with 8?M urea, refolded and purified by Nickel-Nitrilotriacetic acid affinity chromatography. Three-dimensional modeling of the CdMV NIa protease is achieved by threading approach using the homologous X-ray crystallographic structure of Tobacco etch mosaic virus NIa protease. The model gave an insight in to the substrate specificities of the NIa proteases and predicted the complementation of nearby residues in the catalytic triad (H42, D74 and C141) mutants in the cis protease activity of CdMV NIa protease.     

RGK small GTP-binding proteins interact with the nucleotide kinase domain of Ca2+-channel beta-subunits via an uncommon effector binding domain

RGK proteins (Kir/Gem, Rad, Rem, and Rem2) form a small subfamily of the Ras superfamily. Despite a conserved GTP binding core domain, several differences suggest that structure, mechanism of action, and functional regulation differ from Ras. RGK proteins down-regulate voltage-gated calcium channel activity by binding in a GTP-dependent fashion to the Cavbeta subunits. Mutational analysis combined with homology modeling reveal a novel effector binding mechanism distinct from that of other Ras GTPases. In this model the Switch 1 region acts as an allosteric activator that facilitates electrostatic interactions between Arg-196 in Kir/Gem and Asp-194, -270, and -272 in the nucleotide-kinase (NK) domain of Cavbeta3 and wedging Val-223 and His-225 of Kir/Gem into a hydrophobic pocket in the NK domain. Kir/Gem interacts with a surface on the NK domain that is distinct from the groove where the voltage-gated calcium channel Cavalpha1 subunit binds. A complex composed of the RGK protein and the Cavbeta3 and Cav1.2 subunits could be revealed in vivo using coimmunoprecipitation experiments. Intriguingly, docking of the RGK protein to the NK domain of the Cavbeta subunit is reminiscent of the binding of GMP to guanylate kinase.     

N-helix and Cysteines Inter-regulate Human Mitochondrial VDAC-2 Function and Biochemistry

Human voltage-dependent anion channel-2 (hVDAC-2) functions primarily as the crucial anti-apoptotic protein in the outer mitochondrial membrane, and additionally as a gated bidirectional metabolite transporter. The N-terminal helix (NTH), involved in voltage sensing, bears an additional 11-residue extension (NTE) only in hVDAC-2. In this study, we assign a unique role for the NTE as influencing the chaperone-independent refolding kinetics and overall thermodynamic stability of hVDAC-2. Our electrophysiology data shows that the N-helix is crucial for channel activity, whereas NTE sensitizes this isoform to voltage gating. Additionally, hVDAC-2 possesses the highest cysteine content, possibly for regulating reactive oxygen species content. We identify interdependent contributions of the N-helix and cysteines to channel function, and the measured stability in micellar environments with differing physicochemical properties. The evolutionary demand for the NTE in the presence of cysteines clearly emerges from our biochemical and functional studies, providing insight into factors that functionally demarcate hVDAC-2 from the other VDACs.