Specificity in the inactivation of enzymes by periodate-oxidized nucleotides

Periodate-oxidized ATP (oATP) inactivates the partial reaction of aminoacyl-tRNA synthetases in which amino acid is transferred to tRNA without altering the other partial reaction in which ATP is a substrate or a product. The inactivation has been shown to be nonspecific with regard to substituents on the dialdehyde and with regard to the enzymes susceptible to inactivation; oxidized GTP and oxidized uridine react as well as oATP with aminoacyl-tRNA synthetases and all three dialdehydes also inactivate rabbit muscle aldolase.     

Differences in drifting of larval stages of Rhyacophila nubila (Trichoptera)

Larval drift of the trichopteran Rhyacophila nubila (Zett.) was studied in a West Norwegian river. The frequency distribution of different instars in the drift samples was significantly different compared with the benthic samples. The drift, measured as the number which passed a transect of the river, rised markedly in periods of high water discharge. Different instars can be arranged according to the extent in which they are drifting: 2>3>4>1>5. Instar 1 and 2 shared a neutral phototaxis. From the 2nd instar and on, the larvae became increasingly night-active with a culmination in the last instar which was highly night active, also confined by laboratory studies. It is suggested that changes in activity patterns is associated with a shift towards a more carnivorous way of life.     

Heavy metal tolerance of marine phytoplankton. III. Combined effects of copper and zinc ions on cultures of four common species

The combined effects of copper and zinc ions on the growth of three marine diatoms and one dinoflagellate in culture have been studied. The two metals were found to act synergistically to all algae except Phaeodactylum tricornutum Bohlin. With this species an antagonistic effect was observed. Addition of zinc ions reduced the inhibition of growth caused by the more toxic copper ions. Zinc toxicity to this alga increased at low concentration of magnesium, indicating a common route for divalent metal ions in general.     

Autoradiographic study on the localization of estradiol-17β in neonatal mouse uterus and cervix

Summary The uptake of ³H-estradiol-17 in the neonatal mouse uterus and cervix has been studied by an autoradiographic method. When the radio-active hormone is administered in vivo and in vitro, grains are found to be concentrated above the nuclei both in the uterine and cervical epithelium and stroma. Grain counts revealed that the nuclear concentration of grains is higher at 4 h than at 2 h after isotope injection. The cervical epithelium has a higher nuclear concentration than the uterine epithelium both in vivo and in vitro. In the stroma, this situation is reversed except after in vitro treatment of the tissues.In the cervix, more of the hormone seems to be located within the nucleus while in the uterus a higher proportion of the grains are found in the vicinity of the nuclear periphery.Although the nuclear concentration of grains is higher at 4 h than at 2 h, the number of grains above the sections is lower at 4 h. Both in vivo and in vitro, the number of grains is higher above the stromal than above the epithelial compartments of the uterus and cervix.Five days old animals showed the same labeling pattern. The differences in uptake and distribution of ³H-estradiol are discussed in relation to other known differences in the hormone responsiveness in these tissues.We are greatly indebted to Professor W.E. Stumpf and the Laboratories for Reproductive Biology, University of North Carolina Medical School for the opportunity to study the method of dry mount autoradiography. The work has been supported by the Norwegian Research Council for Science and the Humanities and by the Norwegian Cancer Society (Landsforeningen mot Kreft)     

Molecular phylogenetics of the tribeInuleae s. str.(Asteraceae), based on ITS sequences of nuclear ribosomal DNA

The sequences of the internal transcribed spacer (ITS) region of 18S–26S nrDNA for a sample of 16 taxa from theInuleae s. str. and two outgroup taxa are analysed cladistically with PAUP. A consensus tree of the four most parsimonious cladograms is presented. Three different tests of cladogram stability are conducted (Bremer support, parsimony jackknifing and bootstrapping); all tests indicate a high degree of support for the basal nodes of the tree. The ITS phylogeny of the tribe is compared with previous hypotheses based on morphological data. The position ofAnisopappus as sister group to the rest of the tribe is supported by the molecular data, but the proposed subdivision ofInuleae s. str. into a paleate grade group and an epaleate clade is not. The interpretation of the character evolution of, e.g. receptacular paleae and pappus features within the tribe is discussed.     

Climate change at northern latitudes: rising atmospheric humidity decreases transpiration, N-uptake and growth rate of hybrid aspen

At northern latitudes a rise in atmospheric humidity and precipitation is predicted as a consequence of global climate change. We studied several growth and functional traits of hybrid aspen (Populus tremula L.×P. tremuloides Michx.) in response to elevated atmospheric humidity (on average 7% over the ambient level) in a free air experimental facility during three growing seasons (2008-2010) in Estonia, which represents northern temperate climate (boreo-nemoral zone). Data were collected from three humidified (H) and three control (C) plots, and analysed using nested linear models. Elevated air humidity significantly reduced height, stem diameter and stem volume increments and transpiration of the trees whereas these effects remained highly significant also after considering the side effects from soil-related confounders within the 2.7 ha study area. Tree leaves were smaller, lighter and had lower leaf mass per area (LMA) in H plots. The magnitude and significance of the humidity treatment effect - inhibition of above-ground growth rate - was more pronounced in larger trees. The lower growth rate in the humidified plots can be partly explained by a decrease in transpiration-driven mass flow of NO(3) (-) in soil, resulting in a significant reduction in the measured uptake of N to foliage in the H plots. The results suggest that the potential growth improvement of fast-growing trees like aspens, due to increasing temperature and atmospheric CO(2) concentration, might be smaller than expected at high latitudes if a rise in atmospheric humidity simultaneously takes place.     

Carbohydrate degradation and methane production during fermentation ofLaminaria saccharina (Laminariales,Phaeophyceae)

Anaerobic digestion of the brown algaLaminaria saccharina (L.) Lamour. harvested in spring and autumn was carried out at controlled laboratory conditions in stirred fermentor systems. Due to the normal seasonal variations, the autumn material had a much higher content of carbohydrates such as mannitol and laminaran. Both batch and semi-continuous feeding conditions were investigated for periods up to 800 h, with inoculum provided from previous kelp fermentations. In batch cultures, the methane yield from the autumn material was doubled compared to that of the spring material. Semi-continuous conditions gave more similar methane yields for both raw materials, 0.22 and 0.27 l CH₄ per g VS for spring and autumn material, respectively. In all experiments, mannitol and laminaran were reduced to less than 5 of the initial values within 24–48 hours after inoculation, whereas 30 of the alginate content was detectable even after 30 days. Viscometry revealed that this material was severely depolymerized, and alginate lyase activity was found to develop rapidly in all cultures. Although mannitol and laminaran were fermented much faster than alginate, the total accumulated methane yields seemed to be determined by the total carbohydrate content of the raw material during extended semi-continuous feeding.(*author for correspondence)     

Microscope laser light scattering spectroscopy of single biological cells

A microscope laser light scattering setup was developed, allowing us to do intensity autocorrelation spectroscopy on the light scattered from a volume as small as (2 micron)3. This non-invasive technique makes cytoplasmic studies possible inside single live biological cells. The effect of osmotic swelling and shrinking on the diffusion coefficient of hemoglobin inside intact red blood cells is shown as an illustrative example of the applicability and sensitivity of this new experimental method.     

Impact of emotion on consciousness: positive stimuli enhance conscious reportability

Emotion and reward have been proposed to be closely linked to conscious experience, but empirical data are lacking. The anterior cingulate cortex (ACC) plays a central role in the hedonic dimension of conscious experience; thus potentially a key region in interactions between emotion and consciousness. Here we tested the impact of emotion on conscious experience, and directly investigated the role of the ACC. We used a masked paradigm that measures conscious reportability in terms of subjective confidence and objective accuracy in identifying the briefly presented stimulus in a forced-choice test. By manipulating the emotional valence (positive, neutral, negative) and the presentation time (16 ms, 32 ms, 80 ms) we measured the impact of these variables on conscious and subliminal (i.e. below threshold) processing. First, we tested normal participants using face and word stimuli. Results showed that participants were more confident and accurate when consciously seeing happy versus sad/neutral faces and words. When stimuli were presented subliminally, we found no effect of emotion. To investigate the neural basis of this impact of emotion, we recorded local field potentials (LFPs) directly in the ACC in a chronic pain patient. Behavioural findings were replicated: the patient was more confident and accurate when (consciously) seeing happy versus sad faces, while no effect was seen in subliminal trials. Mirroring behavioural findings, we found significant differences in the LFPs after around 500 ms (lasting 30 ms) in conscious trials between happy and sad faces, while no effect was found in subliminal trials. We thus demonstrate a striking impact of emotion on conscious experience, with positive emotional stimuli enhancing conscious reportability. In line with previous studies, the data indicate a key role of the ACC, but goes beyond earlier work by providing the first direct evidence of interaction between emotion and conscious experience in the human ACC.     

Changes in gray matter induced by learning--revisited

Background

Recently, activation-dependant structural brain plasticity in humans has been demonstrated in adults after three months of training a visio-motor skill. Learning three-ball cascade juggling was associated with a transient and highly selective increase in brain gray matter in the occipito-temporal cortex comprising the motion sensitive area hMT/V5 bilaterally. However, the exact time-scale of usage-dependant structural changes occur is still unknown. A better understanding of the temporal parameters may help to elucidate to what extent this type of cortical plasticity contributes to fast adapting cortical processes that may be relevant to learning.

Principal Findings

Using a 3 Tesla scanner and monitoring whole brain structure we repeated and extended our original study in 20 healthy adult volunteers, focussing on the temporal aspects of the structural changes and investigated whether these changes are performance or exercise dependant. The data confirmed our earlier observation using a mean effects analysis and in addition showed that learning to juggle can alter gray matter in the occipito-temporal cortex as early as after 7 days of training. Neither performance nor exercise alone could explain these changes.

Conclusion

We suggest that the qualitative change (i.e. learning of a new task) is more critical for the brain to change its structure than continued training of an already-learned task.