Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Snow”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,405 records · Page 78Linked to original sources
PubMed1982

Effects of caffeine ingestion on exercise performance at low and high altitudes in cross-country skiers.

The effect of caffeine on exercise time over a specified distance (approx. 21 km) was investigated in well-trained cross-country skiers (14 subjects) both at low (300 m above sea level) and high (2900 m above sea level) altitudes. Each subject participated in two races at both altitudes--one after caffeine ingestion (6 mg/kg body weight) and one after placebo on a double-blind basis. In each race 50% of the participants were medicated with caffeine, thereby after normalization (where the mean time was set at 100%), when the influence of weather and snow conditions were minimized, the difference between the race time with caffeine and placebo could be calculated for each individual and expressed as a percentage of the mean. At low altitudes, after half the distance, the race time with caffeine was decreased 0.94% of the mean time (corresponding to approx. 33 s) as compared to placebo (P less than 0.05), whereas after the full distance the corresponding decrease was 1.7% of the mean time (corresponding to approx. 59 s) (0.05 less than P less than 0.10). At high altitudes, the race time was significantly faster with caffeine than with placebo (P less than 0.001), both after one and two laps, 2.19% and 3.18% of the mean time, respectively (corresponding to approx. 101 s and 152 s). The perceived exertion was similar at low and high altitudes independent of medication. In conclusion, there are indications that caffeine induces an increased performance capacity for cross-country skiers at low altitudes. Furthermore, an even more marked improvement after caffeine as compared to placebo was found at high altitudes.

Adult↗
PubMed1986

[Aldose reductase inhibitor--a new way for preventing diabetic lens changes?].

Increased blood sugar levels may influence the refractive power of the lens in juvenile diabetics, and can lead to the rare true diabetic cataract ("snow-storm cataract"). Surplus glucose induces accumulation of the sugar alcohol within the cells, thus generating disturbances of the osmotic balance and finally causing cataract. The enzyme aldose reductase catalyzes the formation of sorbitol. Experiments with animals have shown that aldose reductase inhibitors can prevent the formation of such opacities with streptozotocin-induced diabetes in rats. Numerous aldose reductase inhibitors are now known, but we still have insufficient knowledge to determine whether systemic or local administration is preferable. The mechanisms reported here are not relevant with respect to the frequent occurrence of senile cataract in older diabetics, which has often been described.

Aldehyde Reductase↗
PubMed1999

Scales and kinetics of granular flows.

When a granular material experiences strong forcing, as may be the case, e.g., for coal or gravel flowing down a chute or snow (or rocks) avalanching down a mountain slope, the individual grains interact by nearly instantaneous collisions, much like in the classical model of a gas. The dissipative nature of the particle collisions renders this analogy incomplete and is the source of a number of phenomena which are peculiar to "granular gases," such as clustering and collapse. In addition, the inelasticity of the collisions is the reason that granular gases, unlike atomic ones, lack temporal and spatial scale separation, a fact manifested by macroscopic mean free paths, scale dependent stresses, "macroscopic measurability" of "microscopic fluctuations" and observability of the effects of the Burnett and super-Burnett "corrections." The latter features may also exist in atomic fluids but they are observable there only under extreme conditions. Clustering, collapse and a kinetic theory for rapid flows of dilute granular systems, including a derivation of boundary conditions, are described alongside the mesoscopic properties of these systems with emphasis on the effects, theoretical conclusions and restrictions imposed by the lack of scale separation. (c) 1999 American Institute of Physics.

Journal Article↗
PubMed2000

Asthma in United States olympic athletes who participated in the 1998 olympic winter games.

BACKGROUND: About one of every 5 athletes who participated in the 1996 Summer Olympic Games in Atlanta had a past history of asthma, had symptoms that suggested asthma, or took asthma medications. No previous study has determined the prevalence of asthma in all US athletes who participated in an Olympic Winter Games. OBJECTIVES: We sought to determine how many US athletes who participated in the 1998 Olympic Winter Games had a past history of asthma, had symptoms that suggested asthma, or indicated taking a medication used to treat asthma. METHODS: We evaluated responses to questions that asked about allergic and respiratory diseases in the United States Olympic Committee Medical History Questionnaire that was completed by all 196 athletes who represented the United States at the 1998 Olympic Winter Games in Nagano, Japan. RESULTS: Forty-three (21.9%) of the 196 athletes had a previous diagnosis of asthma, and 36 (18. 4%) recorded use of an asthma medication at some time in the past. Forty-four (22.4%) reported use of an asthma medication, a diagnosis of asthma, or both (our basis for the diagnosis of asthma). Thirty-four (17.4%) of the athletes were currently taking an asthma medication at the time that they completed the questionnaire or indicated that they took these medications on a permanent or semipermanent basis and were considered to have active asthma. Athletes who participated in Nordic combined, cross-country, and short track events had the highest prevalence of having been told that they had asthma or had taken an asthma medication in the past (60.7%) in contrast with only one (2.8%) of the 36 athletes who participated in bobsled, biathlon, luge, and ski jumping. Eighteen (24%) of 75 athletes who participated in alpine, long track, figure skating, snow boarding, and curling had a previous diagnosis of asthma or recorded use of an asthma medication. CONCLUSIONS: We conclude that asthma appeared to have been more common in athletes who participated in the 1998 Winter Games than in athletes who participated in either the 1996 or 1984 Summer Games. Clearly, asthma rates vary widely among sports. This suggests that the environment in which exercise is performed is important in leading to a decrease in the amount of exercise required to trigger asthma and perhaps in causing injury to the airways.

Asthma↗
PubMed1983

The perception of depth contours with yellow goggles.

The ability of subjects to discriminate the depth of depressions in the snow was conducted at a cross-country ski area. The percentage of correct judgments on an overcast day was significantly greater with yellow goggles than with luminance-matched neutral goggles. This experiment, suggested by the chromatic-achromatic theory of color vision, indicates why yellow goggles are popular despite many previous unsuccessful attempts to prove their effectiveness.

Color Perception↗
PubMed1984

A new random-dot stereo illusion and its application to the Anstis-Howard-Rogers effect.

When the dynamic visual noise of an untuned television set is viewed with image defocusing (positive lenses) and with a narrow vertical obstruction partially blocking the pupil of one eye, the video 'snow' seems to separate into two stable surfaces at different depths, divided by a vertical discontinuity. The main features of this illusion can be quantitatively accounted for in terms of the optics of defocused images and the retinal disparities predicted from blur circles. A residual component of the illusion, however, which was perceived by a majority of subjects, cannot be readily explained by geometrical optics; it apparently reflects a more subtle aspect in the processing of visual images, corresponding to the Anstis-Howard-Rogers stereo-effect, in which local depth configurations can bias global stereopsis. Several novel aspects of that effect are described, based on use of this obstructed-pupil illusion as the evoking stimulus.

Adult↗
PubMed2002

Delayed ovulation and parturition in a viviparous alpine lizard (Niveoscincus microlepidotus): morphological data and plasma steroid concentrations.

The southern snow skink, Niveoscincus microlepidotus, exhibits an unusual biennial reproductive cycle with an extended gestation period of approximately 1 year. Morphological data were gathered on a monthly basis, providing a detailed picture of the reproductive cycle. Vitellogenesis begins in spring, immediately after parturition. Maximum follicular diameter is reached before the winter hibernation period and ovulation occurs the following spring. Embryos are fully developed and reach maximum size by early autumn. Yolk reserves are depleted before winter. Birth of between one and four young occurs the following spring. Plasma progesterone concentrations are low (2.7 +/- 0.9 ng mL(-1)) in post-partum females, begin to rise in autumn in vitellogenic females and peak (38.5 +/- 7.9 ng mL(-1)) in pre-ovulatory females after hibernation. Concentrations are high (15.4 +/- 5.9 ng mL(-1)) in early pregnancy and decline to basal levels before winter and well before birth in spring. Plasma oestradiol concentrations peak during vitellogenesis (1.0 +/- 0.3 ng mL(-1)) and decline to basal levels during pregnancy (0.2 +/- 0.03 ng mL(-1)). A second oestradiol peak occurs before parturition (0.7 +/- 0.2 ng mL(-1)). Thus, functional completion of vitellogenesis and gestation is achieved by autumn in successive years. The mechanisms that defer ovulation and parturition by a further six months are unknown.

Animals↗
PubMed2004

Temperature dependence of metabolic rates for microbial growth, maintenance, and survival.

Our work was motivated by discoveries of prokaryotic communities that survive with little nutrient in ice and permafrost, with implications for past or present microbial life in Martian permafrost and Europan ice. We compared the temperature dependence of metabolic rates of microbial communities in permafrost, ice, snow, clouds, oceans, lakes, marine and freshwater sediments, and subsurface aquifer sediments. Metabolic rates per cell fall into three groupings: (i) a rate, microg(T), for growth, measured in the laboratory at in situ temperatures with minimal disturbance of the medium; (ii) a rate, microm(T), sufficient for maintenance of functions but for a nutrient level too low for growth; and (iii) a rate, micros(T), for survival of communities imprisoned in deep glacial ice, subsurface sediment, or ocean sediment, in which they can repair macromolecular damage but are probably largely dormant. The three groups have metabolic rates consistent with a single activation energy of approximately 110 kJ and that scale as microg(T):microm(T):micros(T) approximately 10(6):10(3):1. There is no evidence of a minimum temperature for metabolism. The rate at -40 degrees C in ice corresponds to approximately 10 turnovers of cellular carbon per billion years. Microbes in ice and permafrost have metabolic rates similar to those in water, soil, and sediment at the same temperature. This finding supports the view that, far below the freezing point, liquid water inside ice and permafrost is available for metabolism. The rate micros(T) for repairing molecular damage by means of DNA-repair enzymes and protein-repair enzymes such as methyltransferase is found to be comparable to the rate of spontaneous molecular damage.

Bacteria↗
PubMed2002

Preferential maintenance of critically short telomeres in mammalian cells heterozygous for mTert.

Prolonged growth of murine embryonic stem (ES) cells lacking the telomerase reverse transcriptase, mTert, results in a loss of telomere DNA and an increased incidence of end-to-end fusions and aneuploidy. Furthermore, loss of only one copy of mTert also results in telomere shortening intermediate between wild-type (wt) and mTert-null ES cells [Liu, Y., Snow, B. E., Hande, M. P., Yeung, D., Erdmann, N. J., Wakeham, A., Itie, A., Siderovski, D. P., Lansdorp, P. M., Robinson, M. O. & Harrington, L. (2000) Curr. Biol. 10, 1459-1462]. Unexpectedly, although average telomere length in mTert(+/-) ES cells declined to a similar level as mTert-null ES cells, mTert(+/-) ES cell lines retained a minimal telomeric DNA signal at all chromosome ends. Consequently, no end-to-end fusions and genome instability were observed in the latest passages of mTert(+/-) ES cell lines. These data uncover a functional distinction between the dosage-dependent function of telomerase in average telomere-length maintenance and the selective maintenance of critically short telomeres in cells heterozygous for mTert. In normal and tumor cells, we suggest that telomerase activity insufficient to maintain a given average telomere length may, nonetheless, provide a protective advantage from end-to-end fusion and genome instability.

Animals↗
PubMed2000

Protection and storage of chlorophyll in overwintering evergreens.

How evergreen species store and protect chlorophyll during exposure to high light in winter remains unexplained. This study reveals that the evergreen snow gum (Eucalyptus pauciflora Sieb. ex Spreng.) stores and protects its chlorophylls by forming special complexes that are unique to the winter-acclimated state. Our in vivo spectral and kinetic characterizations reveal a prominent component of the chlorophyll fluorescence spectrum around 715 nm at 77 K. This band coincides structurally with a loss of chlorophyll and an increase in energy-dissipating carotenoids. Functionally, the band coincides with an increased capacity to dissipate excess light energy, absorbed by the chlorophylls, as heat without intrathylakoid acidification. The increased heat dissipation helps protect the chlorophylls from photo-oxidative bleaching and thereby facilitates rapid recovery of photosynthesis in spring.

Acclimatization↗
PubMed1972

Isolation and properties of a macromolecular, water-soluble, immuno-adjuvant fraction from the cell wall of Mycobacterium smegmatis.

Trypsin- and chymotrypsin-treated delipidated cell walls of Mycobacterium smegmatis were digested overnight with lysozyme. The water-soluble products thus obtained were filtered on a column of Sephadex G-50; the first peak, excluded from the column, has immunological adjuvant activity. The material of the excluded peak is obtained after lyophilization as a snow-white, fluffy material, soluble in water and insoluble in organic solvents. It behaves as a slightly polydisperse macromolecule in an ultracentrifuge, with an approximate molecular weight of 20,000. All the constituents of this material are typical bacterial cell-wall constituents; thus, the water-soluble adjuvant is considered to be an "oligomer" of the cell wall. When added to Freund's incomplete adjuvant with an antigen (e.g., ovalbumin) and injected into hind-foot pads of guinea pigs, this water-soluble adjuvant increases the amount of precipitating antibodies and induces hypersensitivity to ovalbumin and the biosynthesis of gamma(2)-type precipitating antibodies. The water-soluble material has a stronger adjuvant activity than equal amounts of whole bacteria, cell walls, or wax D, and seems to be the first well-defined, water-soluble, adjuvant-active fraction isolated from Mycobacteria.

Adjuvants, Immunologic↗
PubMed1975

Play: early and eternal.

A systematic 12-week investigation of development of play behavior was conducted with eight socially reared rhesus monkey infants. A new, basic and primary play form termed self-motion play or peragration was identified and examined. This behavior follows a human model which includes a wide range of pleasurable activities involving motion of the body through space, e.g., rocking, swinging, running, leaping, and water or snow skiing. It can be argued that self-motion play is the initial primate play form and because of its persistence constitutes a reinforcing agent for maintaining many complex patterns and even pastimes. Monkey self-motion play in the present study was divided into five separate patterns in order to compare the relative importance of social and individual peragration play, the role of apparatus and the overall developmental relationships between the different individual and social self-motion play patterns. The data showed that from 90 to 180 days of age self-motion play was independent of other forms of play, that individual self-motion play appeared earlier and with significantly greater increases in frequency than did social self-motion play, and that apparatus was a necessary component for significant increases in social self-motion play. Other findings were that self-motion play existed independent of locomotion and, though initiated by exploration, was separate from it. Therapeutic implications of self-motion play were discussed.

Aging↗
PubMed1976

Bedload measurements, East Fork River, Wyoming.

A bedload trap in the riverbed provided direct quantitative measurement of debris-transport rate in the East Fork River, Wyoming, a basin of 466 km(2) drainage area. Traction load moves only during the spring snow melt season. Data collected in three spring runoff seasons during which a peak flow of 45 m(3)/s occurred showed that transport rate is correlated with power expenditure of the flowing water and at high flows becomes directly proportional to power as suggested by Bagnold.

Journal Article↗
PubMed1999

The GTPase activating factor for transducin in rod photoreceptors is the complex between RGS9 and type 5 G protein beta subunit.

Proteins of the regulators of G protein signaling (RGS) family modulate the duration of intracellular signaling by stimulating the GTPase activity of G protein alpha subunits. It has been established that the ninth member of the RGS family (RGS9) participates in accelerating the GTPase activity of the photoreceptor-specific G protein, transducin. This process is essential for timely inactivation of the phototransduction cascade during the recovery from a photoresponse. Here we report that functionally active RGS9 from vertebrate photoreceptors exists as a tight complex with the long splice variant of the G protein beta subunit (Gbeta5L). RGS9 and Gbeta5L also form a complex when coexpressed in cell culture. Our data are consistent with the recent observation that several RGS proteins, including RGS9, contain G protein gamma-subunit like domain that can mediate their association with Gbeta5 (Snow, B. E., Krumins, A. M., Brothers, G. M., Lee, S. F., Wall, M. A., Chung, S., Mangion, J., Arya, S., Gilman, A. G. & Siderovski, D. P. (1998) Proc. Natl. Acad. Sci. USA 95, 13307-13312). We report an example of such a complex whose cellular localization and function are clearly defined.

Amino Acid Sequence↗
PubMed1995

The cytoplasmic domain of the Drosophila cell adhesion molecule neuroglian is not essential for its homophilic adhesive properties in S2 cells.

Drosophila neuroglian is a transmembrane glycoprotein that has strong structural and sequence homology to the vertebrate L1 gene family of cell adhesion molecules (Bieber, A.J., Snow, P.M., Hortsch, M., Patel, N.H., Jacobs, J.R., Traquina, Z.R., Schilling, J., and Goodman, C.S. (1989) Cell 59, 447-460. Two different neuroglian protein forms that are generated by a differential splicing process are expressed in a tissue-specific fashion by embryonic and larval cells (Hortsch, M., Bieber, A.J., Patel, N.H., and Goodman, C.S. (1990) Neuron 4, 697-709). The two neuroglial polypeptides differ only in their cytoplasmic domains. Both of these neuroglian species, when transfected into the expressed in Drosophila S2 cells, induce the calcium-independent, homophilic aggregation of transformed cells. A third artificial neuroglian protein form was constructed by substituting the neuroglian transmembrane segment and cytoplasmic domains with the glycosyl phosphatidylinositol attachment signal of the Drosophila fasciclin I protein. This cDNA construct generates a glycosyl phosphatidylinositol-anchored form of neuroglian, which retains the ability to induce homophilic cell aggregation when expressed in S2 cells, and was able to interact with both of the two naturally occurring neuroglian polypeptides. These results demonstrate that neuroglian mediates a calcium-independent, homophilic cell adhesion activity and that neither cytoplasmic neuroglian domains nor a direct interaction with cytoskeletal elements is essential for this property.

Amino Acid Sequence↗
PubMed1997

Abeta(1-40) prevents heparanase-catalyzed degradation of heparan sulfate glycosaminoglycans and proteoglycans in vitro. A role for heparan sulfate proteoglycan turnover in Alzheimer's disease.

Alzheimer's disease is characterized by senile plaques composed of polymeric fibrils of beta amyloid (Abeta), a 39-42-amino acid peptide formed after proteolytic processing of the amyloid precursor protein (betaAPP). Heparan sulfate proteoglycans have been shown to colocalize with Abeta in Alzheimer's disease brain, and experimental evidence indicates that the interactions between the proteoglycan and the peptide are important for the promotion, deposition, and/or persistence of the senile plaques. Studies in rat brain indicated that both the core protein and the heparan sulfate glycosaminoglycan chains are required for amyloid fiber formation and deposition in vivo (Snow, A. D., Sekiguchi, R., Nochlin, D., Fraser, P., Kimata, K. , Mizutani, A., Arai, M., Schreier, W. A., and Morgan, D. G. (1994) Neuron 12, 219-234), suggesting that one mechanism to prevent the formation of Abeta-heparan sulfate proteoglycan complexes that lead to deposition of amyloid would be to degrade the proteoglycan. Normally, heparan sulfate proteoglycans are internalized and degraded to short glycosaminoglycans by intracellular heparanases. These reactions occur in the endosomal-lysosomal pathway, which is the same intracellular location where betaAPP is processed to Abeta. Using partially purified heparanase activities from Chinese hamster ovary cells we examined whether Abeta(1-40) affects the catabolism of Chinese hamster ovary heparan sulfate glycosaminoglycans and proteoglycans in vitro. Abeta(1-40) binds to both the long heparan sulfate glycosaminoglycans attached to core proteins and the short, heparanase-derived chains in a concentration-dependent and pH-dependent manner. When Abeta(1-40) is added to heparanase assays, it prevents the partially purified activities from releasing heparan sulfate chains from core proteins and degrading them to short glycosaminoglycans; however, a large molar excess of the peptide to heparan sulfate is required to see the effect. Our results suggest that normally the levels of Abeta in the endosomal pathway are not sufficient to interfere with heparanase activity in vivo. However, once the level of Abeta-peptides are elevated, as they are in Alzheimer's disease, they could interact with heparan sulfate proteoglycans and prevent their catabolism. This could promote the formation and deposition of amyloid, since the binding of Abeta to the proteoglycan species will predominate.

Alzheimer Disease↗
PubMed1999

Quantitative analyses of schooling effects on executive function in young children.

Developmental studies have demonstrated the utility of select executive function (EF) tasks for the early diagnosis of specific learning-related problems (e.g., Snow, 1998). However, previous data demonstrating schooling effects on EF measures suggests potential pitfalls in clinical interpretation. In the present study three common EF measures, (Wisconsin Card Sort, Thurstone Word Fluency, and a mazes task) in addition to a VIQ estimating task, were administered to a cross-section of 115 children aged 7 to 9. Using a school-entrance cut-off design the unique contributions of formal schooling versus age-related changes to performance on the EF measures were examined. Schooling effects were both task and age-dependent supporting the conclusion that the proper use of EF measures with children in this age range depends upon consideration of factors beyond that usually depicted in net-effect models.

Age Factors↗
PubMed2002

Palladium--a review of exposure and effects to human health.

Palladium is a metal the output and use of which has more than doubled in the past ten years. It is used in dental appliances, chemical catalysts, electrical appliances and jewelry, but the greatest increase in Pd demand has been in automotive emission control catalysts. Studies on Pd concentrations in ancient ice and recent snow samples reflect the increase in mining, smelting and use of palladium in the last decades. Increases of palladium in the environment have been shown in air and dust samples. There is no data as yet available to assess the effect of this exposure. A major source of health concern is the sensitization risk of Pd as very low doses are sufficient to cause allergic reactions in susceptible individuals. Persons with known nickel allergy may be especially susceptible. Workers occupationally exposed to Pd include miners, dental technicians and chemical workers. The latter are exposed mainly to Pd salts several of which may cause primary skin and eye irritations. It is advised that persons with known Pd allergy should not work with Pd compounds. The general population may come into contact with palladium mainly through mucosal contact with dental restorations and jewelry containing palladium and possibly via emissions from Pd catalysts. Protection of the public from related adverse effects may be achieved by the use of alloys with high corrosion stability and thus minimal release of palladium. In general, in dental patients who are sensitive to Pd, restorations using Pd-containing materials should not be used although Pd has been used without allergic effects in some of these individuals. Further, those patients who have an allergy to nickel should be informed that use of Pd-containing dental materials may cause Pd allergy, though this risk appears to be low.

Air Pollutants↗