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PubMed2003

Low melatonin secretion associates with albedo in circumpolar environments.

To clarify how seasonal changes of environmental luminosity affect melatonin secretion in human beings, nocturnal urine samples were collected every 2 months throughout the year from 20 outdoor workers living in an area, for which exact data on solar irradiance and temperature were available (67-68 degrees N). Melatonin secretion rates, determined by melatonin-specific radioimmunoassays, were found to be twice as high in December as in April, i.e. 0.88 +/- 0.16 nmol/12 hr (mean +/- S.E.) versus 0.43 +/- 0.09 nmol/12 hr, P < 0.05. Regression analyses showed that melatonin values correlated best inversely with solar irradiance reflected off the ground (albedo). A 10-fold increase in albedo for 1-4 weeks prior to the date of urine sampling was associated with a ca. 50% reduction in melatonin secretion. Association with global irradiance was weaker and did not correlate with temperature. Thus, light reaching the eyes via snow or other reflecting surfaces appears to be most effective. These results assist us in understanding some of the mechanisms involved in certain biological phenomena that exhibit seasonal variations as, for instance, reproduction and self-destructive behavior.

Finland↗

PubMed2000

Group support interventions for women with breast cancer: who benefits from what?

Research on the benefits of social support groups has been inconclusive. One reason is that individual differences in intervention responses have rarely been examined. The authors determined the extent to which individual difference variables moderated the effects of an information-based educational group and an emotion-focused peer discussion group on the mental and physical functioning of women with breast cancer (n = 230). The authors administered the SF-36 (S.E. Ware, K.K. Snow, M. Kosinski, & B. Gandek, 1993), a multidimensional quality of life instrument, pre- and postintervention. Educational groups showed greater benefits on the physical functioning of women who started the study with more difficulties compared with less difficulties (e.g., lacked support or fewer personal resources). Peer discussion groups were helpful for women who lacked support from their partners or physicians but harmful for women who had high levels of support. Implications of these results for clinical interventions are discussed.

Adult↗

PubMed2000

Gender-linked personality traits predict mental health and functional status following a first coronary event.

Three gender-linked traits were examined with respect to adjustment to a coronary event: agency, a focus on the self; communion, a focus on others; and unmitigated communion, an extreme focus on others to the exclusion of the self. Participants (n = 65) were interviewed 1 week and 4 months after a 1st coronary event. Hypotheses were that agency should predict improved health, communion should be unrelated to health, and unmitigated communion should predict worse health over time. Outcomes included depression, anxiety, and well-being (as measured by the Profile of Mood States; D. McNair, M. Lorr, & L. Droppleman, 1971); mental and physical functioning (SF-36; J. E. Ware, K. K. Snow, M. Kosinski, & B. Gandek, 1993); and cardiac symptoms. Results confirmed hypotheses. In addition, unmitigated communion was linked with poor health behavior and negative social interactions, which partly explained the link of unmitigated communion with depression and cardiac symptoms.

Coronary Disease↗

PubMed2005

Traumatic stress, perceived global stress, and life events: prospectively predicting quality of life in breast cancer patients.

The authors investigated the relationship between stress at initial cancer diagnosis and treatment and subsequent quality of life (QoL). Women (n = 112) randomized to the assessment-only arm of a clinical trial were initially assessed after breast cancer diagnosis and surgery and then reassessed at 4 months (during adjuvant treatment) and 12 months (postadjuvant treatment). There were 3 types of stress measured: number of stressful life events (K. A. Matthews et al., 1997), cancer-related traumatic stress symptoms (M. J. Horowitz, N. Wilner, & W. Alvarez, 1979), and perceived global stress (S. Cohen, T. Kamarck, & R. Mermelstein, 1983). Using hierarchical multiple regressions, the authors found that stress predicted both psychological and physical QoL (J. E. Ware, K. K. Snow, & M. Kosinski, 2000) at the follow-ups (all ps < .03). These findings substantiate the relationship between initial stress and later QoL and underscore the need for timely psychological intervention.

Adult↗

PubMed2000

Offset of the potential carbon sink from boreal forestation by decreases in surface albedo.

Carbon uptake by forestation is one method proposed to reduce net carbon dioxide emissions to the atmosphere and so limit the radiative forcing of climate change. But the overall impact of forestation on climate will also depend on other effects associated with the creation of new forests. In particular, the albedo of a forested landscape is generally lower than that of cultivated land, especially when snow is lying, and decreasing albedo exerts a positive radiative forcing on climate. Here I simulate the radiative forcings associated with changes in surface albedo as a result of forestation in temperate and boreal forest areas, and translate these forcings into equivalent changes in local carbon stock for comparison with estimated carbon sequestration potentials. I suggest that in many boreal forest areas, the positive forcing induced by decreases in albedo can offset the negative forcing that is expected from carbon sequestration. Some high-latitude forestation activities may therefore increase climate change, rather than mitigating it as intended.

Atmosphere↗

PubMed2001

Nonlinear effects of large-scale climatic variability on wild and domestic herbivores.

Large-scale climatic fluctuations, such as the North Atlantic Oscillation (NAO), have been shown to affect many ecological processes. Such effects have been typically assumed to be linear. Only one study has reported a nonlinear relation; however, that nonlinear relation was monotonic (that is, no reversal). Here we show that there is a strong nonlinear and non-monotonic (that is, reversed) effect of the NAO on body weight during the subsequent autumn for 23,838 individual wild red deer (Cervus elaphus) and 139,485 individual domestic sheep (Ovis aries) sampled over several decades on the west coast of Norway. These relationships are, at least in part, explained by comparable nonlinear and non-monotonic relations between the NAO and local climatic variables (temperature, precipitation and snow depth). The similar patterns observed for red deer and sheep, the latter of which live indoors during winter and so experience a stable energy supply in winter, suggest that the (winter) climatic variability (for which the index is a proxy) must influence the summer foraging conditions directly or indirectly.

Animals↗

PubMed2001

Climate change. Increasing shrub abundance in the Arctic.

The warming of the Alaskan Arctic during the past 150 years has accelerated over the last three decades and is expected to increase vegetation productivity in tundra if shrubs become more abundant; indeed, this transition may already be under way according to local plot studies and remote sensing. Here we present evidence for a widespread increase in shrub abundance over more than 320 km of Arctic landscape during the past 50 years, based on a comparison of historic and modern aerial photographs. This expansion will alter the partitioning of energy in summer and the trapping and distribution of snow in winter, as well as increasing the amount of carbon stored in a region that is believed to be a net source of carbon dioxide.

Arctic Regions↗

PubMed2000

Identification and expression of isoflavone synthase, the key enzyme for biosynthesis of isoflavones in legumes.

Isoflavones have drawn much attention because of their benefits to human health. These compounds, which are produced almost exclusively in legumes, have natural roles in plant defense and root nodulation. Isoflavone synthase catalyzes the first committed step of isoflavone biosynthesis, a branch of the phenylpropanoid pathway. To identify the gene encoding this enzyme, we used a yeast expression assay to screen soybean ESTs encoding cytochrome P450 proteins. We identified two soybean genes encoding isoflavone synthase, and used them to isolate homologous genes from other leguminous species including red clover, white clover, hairy vetch, mung bean, alfalfa, lentil, snow pea, and lupine, as well as from the nonleguminous sugarbeet. We expressed soybean isoflavone synthase in Arabidopsis thaliana, which led to production of the isoflavone genistein in this nonlegume plant. Identification of the isoflavone synthase gene should allow manipulation of the phenylpropanoid pathway for agronomic and nutritional purposes.

Anthocyanins↗

PubMed2002

The hydrologic cycle in deep-time climate problems.

Hydrology refers to the whole panoply of effects the water molecule has on climate and on the land surface during its journey there and back again between ocean and atmosphere. On its way, it is cycled through vapour, cloud water, snow, sea ice and glacier ice, as well as acting as a catalyst for silicate-carbonate weathering reactions governing atmospheric carbon dioxide. Because carbon dioxide affects the hydrologic cycle through temperature, climate is a pas des deux between carbon dioxide and water, with important guest appearances by surface ice cover.

Climate↗

PubMed2004

High levels of atmospheric carbon dioxide necessary for the termination of global glaciation.

The possibility that the Earth suffered episodes of global glaciation as recently as the Neoproterozoic period, between about 900 and 543 million years ago, has been widely discussed. Termination of such 'hard snowball Earth' climate states has been proposed to proceed from accumulation of carbon dioxide in the atmosphere. Many salient aspects of the snowball scenario depend critically on the threshold of atmospheric carbon dioxide concentrations needed to trigger deglaciation. Here I present simulations with a general circulation model, using elevated carbon dioxide levels to estimate this deglaciation threshold. The model simulates several phenomena that are expected to be significant in a 'snowball Earth' scenario, but which have not been considered in previous studies with less sophisticated models, such as a reduction of vertical temperature gradients in winter, a reduction in summer tropopause height, the effect of snow cover and a reduction in cloud greenhouse effects. In my simulations, the system remains far short of deglaciation even at atmospheric carbon dioxide concentrations of 550 times the present levels (0.2 bar of CO2). I find that at much higher carbon dioxide levels, deglaciation is unlikely unless unknown feedback cycles that are not captured in the model come into effect.

Journal Article↗

PubMed2004

Recent and episodic volcanic and glacial activity on Mars revealed by the High Resolution Stereo Camera.

The large-area coverage at a resolution of 10-20 metres per pixel in colour and three dimensions with the High Resolution Stereo Camera Experiment on the European Space Agency Mars Express Mission has made it possible to study the time-stratigraphic relationships of volcanic and glacial structures in unprecedented detail and give insight into the geological evolution of Mars. Here we show that calderas on five major volcanoes on Mars have undergone repeated activation and resurfacing during the last 20 per cent of martian history, with phases of activity as young as two million years, suggesting that the volcanoes are potentially still active today. Glacial deposits at the base of the Olympus Mons escarpment show evidence for repeated phases of activity as recently as about four million years ago. Morphological evidence is found that snow and ice deposition on the Olympus construct at elevations of more than 7,000 metres led to episodes of glacial activity at this height. Even now, water ice protected by an insulating layer of dust may be present at high altitudes on Olympus Mons.

Dust↗

PubMed2005

Malaria risk: estimating clinical episodes of malaria.

Estimates of the disease burden caused by malaria are crucial for informing malaria control programmes. Snow and colleagues claim that their estimate of 515 million cases of malaria caused by Plasmodium falciparum globally is up to 50% higher than that reported by the World Health Organization (WHO), and 200% higher for areas outside Africa. However, this comparison refers to the WHO's estimates from 1990 and 1998, and not to the range of 300 million to 500 million that the WHO has used since 2000 (ref. 2). Both groups agree that the burden of malaria disease outside Africa, especially in South Asia, is greater than was estimated in the 1990s.

Animals↗

PubMed2005

Malaria risk: estimation of the malaria burden.

Accurate estimates of the global burden of malaria are important for planning, monitoring and advocacy. Snow et al. attempt to address the shortcomings of previous estimates of the incidence of malaria caused by Plasmodium falciparum by combining current and historical data. However, we believe that the design of their model and its inputs have led to a significant overestimate of the malaria burden outside Africa--as in the example of the World Health Organization (WHO) western Pacific region (WPR), for which their model predicts 60 times the 2002 incidence reported by national malaria-control programmes.

Animals↗

PubMed2005

A soft solid surface on Titan as revealed by the Huygens Surface Science Package.

The surface of Saturn's largest satellite--Titan--is largely obscured by an optically thick atmospheric haze, and so its nature has been the subject of considerable speculation and discussion. The Huygens probe entered Titan's atmosphere on 14 January 2005 and descended to the surface using a parachute system. Here we report measurements made just above and on the surface of Titan by the Huygens Surface Science Package. Acoustic sounding over the last 90 m above the surface reveals a relatively smooth, but not completely flat, surface surrounding the landing site. Penetrometry and accelerometry measurements during the probe impact event reveal that the surface was neither hard (like solid ice) nor very compressible (like a blanket of fluffy aerosol); rather, the Huygens probe landed on a relatively soft solid surface whose properties are analogous to wet clay, lightly packed snow and wet or dry sand. The probe settled gradually by a few millimetres after landing.

Journal Article↗

PubMed2002

Inflammatory pigmented paravenous retinochoroidal atrophy.

PURPOSE: To describe an active inflammatory cause of pigmented paravenous retinochoroidal atrophy. METHODS: A 54-year-old female patient presented with complaints of worsening visual acuity and poor night vision was examined. Fundus examination was performed and color fundus photographs were taken. In addition to fluorescein angiography, visual field examinations and electroretinographic tests were performed. Macular evaluation was performed with optical coherence tomography. RESULTS: Both fundi showed circumscribed patches of retinochoroidal atrophy and pigmentation along the retinal veins. She had also marked vitreous cells with snow ball opacities and cystoid macular edema in both eyes. Fluorescein angiography confirmed the presence of a hyperfluorescence due to widespread paravenous retinal pigment epithelial defect while ICG angiography disclosed hypofluorescence in all phases. The electroretinogram showed reduced responses especially in the left eye. Visual field tests showed scotomas corresponding with areas of atrophy along the retinal veins. CONCLUSIONS: This is a report of the findings in pigmented paravenous retinochoroidal atrophy that is a nonspecific degenerative disease and may occur in association with systemic infections or inflammation. Ocular inflammation with cystoid macular edema is an unusual manifestation of the disease.

Atrophy↗

PubMed2004

High Ca(2+)-phosphate transfection efficiency enables single neuron gene analysis.

Introducing exogenous genes into cells is one of the most important molecular techniques to study gene functions. Comparing to other type of cells, neurons are more difficult to transfect with cDNAs because they are very sensitive to microenvironmental changes. Among various gene transfer techniques, the Ca(2+)-phosphate transfection method is one of the most popular tools in neuroscience research because of its low cell toxicity and easiness to use. However, it is well known that the Ca(2+)-phosphate transfection efficiency in neurons is very low, typically in the range of 1-5%, which has limited its applications in gene functional analyses. Here we report a novel Ca(2+)-phosphate transfection protocol that dramatically increased the transfection efficiency by 10-fold, up to 60%, while maintaining low cell toxicity. The critical factors are the formation of homogenous snow-like precipitate with particle size about 1-3 microm and the subsequent removal of the precipitate. Using this new transfection protocol, we were able to routinely transfect single autaptic neurons in hippocampal microisland cultures and combine it with electrophysiology and fluorescent imaging methods to study gene functions. This high efficiency, low toxicity, and simple to use gene transfer method will have a broad application in gene research at the single cell level.

Animals↗

PubMed2005

To succeed globally, disperse locally: effects of local pollen and seed dispersal on tetraploid establishment.

Newly formed tetraploid plants in sympatry with their diploid progenitors should face significant obstacles to persistence and population establishment because of low-fitness triploids formed by cross-ploidy pollinations. Prior models have found restrictive conditions for a minority tetraploid subpopulation to persist. A stochastic spatial model, parameterized using snow buttercups (Ranunculus adoneus), was used to examine the influence of limited seed and pollen dispersal distances on the success of minority tetraploids and the interaction of these factors with different rates of self-pollination and tetraploid advantage. Higher rates of self-pollination and increased tetraploid advantage increase the probability of tetraploid persistence. Limiting the dispersal of seeds and pollen further increases the positive impact of any given level of self-pollination and tetraploid advantage. Taxa with short-distance seed and pollen dispersal should face much less stringent barriers to sympatric polyploid speciation than taxa with long-distance dispersal patterns. With short-distance seed and pollen dispersal, polyploid speciation should be possible in the absence of ecological differentiation or recurrent polyploid formation through unreduced gametes.

Crosses, Genetic↗

PubMed2001

Levels of lead in atmospheric deposition in a large urban agglomeration in Poland.

Lead levels in wet and dry deposition were determined within this project. A network of 10 sampling stations was established. The stations were located in areas characterized by heavy traffic volumes, but away from industrial and/or municipal pollution sources. It was assumed, therefore, that lead in the samples collected was coming primarily from automobile emissions. Measurements were carried out over a period of one year. Both rain and snow samples were collected. Lead concentrations in the samples ranged from 0.6 to 141 microg dm(-3). They depended on street topography, traffic volume, average speed of the vehicles, frequency of traffic congestion and atmospheric conditions. The highest lead levels in deposition were observed during the cold season.

Air Pollutants↗