Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Ice Cover”

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 343 records · Page 19Linked to original sources
PubMed1995

Human in vivo cutaneous microdialysis: estimation of histamine release in cold urticaria.

A novel bioanalytical in vivo sampling technique, cutaneous microdialysis, was used to follow the chronology of skin histamine release in 3 patients with cold urticaria and in 2 healthy volunteers. Laser Doppler perfusion imaging was used simultaneously to monitor the skin circulatory response. Microdialysis samples were collected at 10-min intervals and analysed by radioimmunoassay technique. Fifty minutes after probe insertion, the ventral forearm skin in the area of the dialysis membrane was provoked for 5-15 min with a 25 x 40 mm ice cube covered with plastic foil. In the cold urticaria patients, an up to 80-fold increase of histamine was observed, with peak levels 20-30 min after challenge. Histamine levels then fell to reach "baseline" levels within 50 min. In the healthy subjects, the histamine increase was earlier, less pronounced and of shorter duration. Cutaneous microdialysis and laser Doppler imaging offer new possibilities for the chronological multiparameter assessment of inflammatory skin disorders in vivo.

Adult↗
PubMed2004

Health care in the circumpolar world: Greenland.

Greenland is part of the Kingdom of Denmark and it is the world's largest island. An ice cap covers 85% of its territory. The population is about 57,000 inhabitants, with 14,000 living in the capital Nuuk, and 10,000 in villages and other small settlements. There are pronounced regional variations in lifestyle and living conditions. The Greenland Home Rule Government assumed responsibility, for health care on 1 January 1992. Greenland's territory is divided into 16 health care districts. Queen Ingrid's Hospital in Nuuk is the national hospital and has 156 beds and numerous specialist physicians associated with it. Each health district has a health care centre with one or more physicians, nurses and other health care personnel appropriate for the number of people living in the district. Each district health centre is responsible for primary health care in towns, villages and other small settlements, and the health centres treat all common illnesses. The health centres handle uncomplicated births, minor surgery, common treatment in internal medicine and community mental health services. The centres have a number of inpatient beds proportional to the number of people in the health district. People with more complicated illnesses are referred to Queen Ingrid's Hospital in Nuuk or to specialised treatment in Denmark.

Delivery of Health Care↗
PubMed2004

Evolution of triploidy in Apios americana (Leguminosae) revealed by genealogical analysis of the histone H3-D gene.

Autotriploidy is normally considered to be maladaptive in plants because of its association with high levels of sterility. Nonetheless, triploid individuals are found in many plant species and play important roles in plant evolution, in particular as a first step toward tetraploid formation. However, few studies have addressed the evolutionary potential of triploid lineages, which may principally suffer from the impossibility of combining useful mutations in a single genome due to their low fertility. Therefore, triploids acquire genetic diversity only via recurrent evolution and somaclonal mutation. This study evaluates the potential of multiple origins of polyploidy as a source of genetic diversity in Apios americana, a North American legume that possesses both diploid and triploid populations. Ploidy level determination via flow cytometry shows that triploids are mainly restricted to the portion of eastern North America that was covered by ice during the Wisconsinan glaciation 18,000 years ago. This distribution implies that either selection or postglaciation colonization played a role in shaping this cytogeographic pattern. A haplotype network of the single copy nuclear histone H3-D gene reconstructed using statistical parsimony, together with single-strand conformational polymorphism analysis, shows that autotriploidy evolved at least three times in this species and that heterozygosity is high in triploids. The genetic diversity found in A. americana resulting from recurrent evolution and fixed heterozygosity increases the likelihood of producing successful genotypes and may give the opportunity for triploids to be better fit than diploids in new habitats. This suggests that triploid lineages can exhibit evolutionary potential of their own, and do not serve solely as a first step toward tetraploid formation.

DNA Primers↗
PubMed2004

Psychrophilic versus psychrotolerant bacteria--occurrence and significance in polar and temperate marine habitats.

The numerical dominance and ecological role of psychrophilic bacteria in bottom sediments, sea ice, surface water and melt pools of the polar oceans were investigated using isolates, colony forming units (CFU) and metabolic activities. All sediment samples of the Southern Ocean studied showed a clear numerical dominance of cold-loving bacteria. In Arctic sediments underlying the influence of cold polar water bodies psychrophiles prevailed also but they were less dominant in sediments influenced by the warm Atlantic Water. A predominance of psychrophiles was further found in consolidated Antarctic sea ice as well as in multiyear Arctic sea ice and in melt pools on top of Arctic ice floes. A less uniform adaptation response was, however, met in polar surface waters. In the very northern part of the Fram Strait (Arctic Ocean) we found bacterial counts and activities at 1 degree C exceeding those at 22 degrees C. In surface water of the Weddell Sea (Southern Ocean) psychrophiles also dominated numerically in early autumn but the dominance declined obviously with the onset of winter-water and a decrease of chlorphyll a. Otherwise in surface water of the Southern Ocean CFUs were higher at 22 degrees C than at 1 degree C while activities were vice versa indicating at least a functional dominance of psychrophiles. Even in the temperate sediments of the German Bight true psychrophiles were present and a clear shift towards cold adapted communities in winter observed. Among the polar bacteria a more pronounced cold adaptation of Antarctic in comparison with Arctic isolates was obtained. The results and literature data indicate that stenothermic cold adapted bacteria play a significant role in the global marine environment. On the basis of the temperature response of our isolates from different habitats it is suggested to expand the definition of Morita in order to meet the cold adaptation strategies of the bacteria in the various cold habitats.

Bacteria↗
PubMed2004

Environmental threats, mitigation strategies and high-mountain areas.

High-mountain areas suffer from increasing environmental threats. The causes are often global in dimension but lead to specific impacts under conditions of steep and/or high-altitude terrain with strong effects from snow and ice. This paper presents a global perspective, focussing primarily on observed and projected changes in climate and then goes on to discuss key messages of greatest relevance to the highest belts of mountain regions. The paper finishes with a brief discussion of mitigation strategies.

Altitude↗
PubMed2004

Mountains of the world: vulnerable water towers for the 21st century.

Mountains as "Water Towers" play an important role for the surrounding lowlands. This is particularly true of the world's semiarid and arid zones, where the contributions of mountains to total discharge are 50-90%. Taking into account the increasing water scarcity in these regions, especially for irrigation and food production, then today's state of knowledge in mountain hydrology makes sustainable water management and an assessment of vulnerability quite difficult. Following the IPCC report, the zone of maximum temperature increase in a 2 x CO2 state extends from low elevation in the arctic and sub-arctic to high elevation in the tropics and subtropics. The planned GCOS climate stations do not reach this elevation of high temperature change, although there are many high mountain peaks with the necessary sensitive and vulnerable ecosystems. Worldwide, more than 700 million people live in mountain areas, of these, 625 million are in developing countries. Probably more than half of these 625 million people are vulnerable to food insecurity. Consequences of this insecurity can be emigration or overuse of mountain ecosystems. Overuse of the ecosystems will, ultimately, have negative effects on the environment and especially on water resources. New research initiatives and new high mountain observatories are needed in order to understand the ongoing natural and human processes and their impacts on the adjacent lowlands.

Altitude↗
PubMed2004

Mountains: top down.

Mountainous regions offer not only essential habitat and resources, including water, to the earth's more than 6 billion inhabitants, but also insights into how the global human habitat works, how it is being changed at the moment as global climates are disrupted, and how the disruption may lead to global biotic and economic impoverishment. At least 600 million of the earth's more than 6 billion humans dwell in mountainous regions. Such regions feed water into all the major rivers of the world whose valleys support most of the rest of us. At least half of the valley dwellers receive part or all of their water from montane sources, many from the melt water of glaciers, others from the annual snow melt. Glaciers are retreating globally as the earth warms as a result of human-caused changes in the composition of the atmosphere. Many are disappearing, a change that threatens municipal water supplies virtually globally. The warming is greatest in the higher latitudes where the largest glaciers such as those of Greenland and the Antarctic Continent have become vulnerable. The melting of ice in the northern hemisphere raises serious concerns about the continued flow of the Gulf Stream and the possibility of massive climatic changes in Scandinavia and northern Europe. Mountains are also biotic islands in the sea life, rich in endemism at the ecotype level. The systematic warming of the earth changes the environment out from under these genetically specialized strains (ecotypes) which are then maladapted and vulnerable to diseases of all types. The process is systematic impoverishment in the pattern conspicuous on mountain slopes with increasing exposure to climatic extremes. It is seen now in the increased mortality and morbidity of plants as climatic changes accumulate. The seriousness of the global climatic disruption is especially clear in any consideration of mountains. It can and must be addressed constructively despite the adamancy of the current US administration.

Altitude↗
PubMed2004

[Vegetation biomass distribution characteristics of alpine tundra ecosystem in Changbai Mountains].

Climate change is one of the hotspots in global environment concerns, while alpine tundra ecosystem is most sensitive to global climate change. Because of the relatively small area of tundra, researches on alpine tundra ecosystem were much less. Based on the measurement of species biomass, dominant species organ biomass and vegetation biomass, this paper discussed the biomass spatial variation in alpine tundra ecosystem of Changbai Mountains. The results showed that among 43 species investigated, the first five species in biomass were Rhododendron chrysanthum (159.01 kg x hm(-2)), Vaccinium uliginosum var. alpinum (137.52 kg x hm(-2)), Vaccinium uliginosum (134.7 kg x hm(-2)), Dryas octopetala var. asiatica (131.5 kg x hm(-2)) and Salix rotundifolia (128.4 kg x hm(-2)), which were the dominant species in the alpine tundra ecosystem of Changbai Mountains. Along with increasing altitude, the ratio of below-/above-ground biomass and below-ground/total biomass gradually increased, while the vegetation biomass gradually decreased. The vegetation biomass showed a significant correlation with altitude in typical alpine tundra ecosystem of Changbai Mountains, and the average vegetation biomass was 2.21 t x hm(-2). Alpine tundra ecosystem is very important for microclimate regulation, soil improvement, water-holding, soil conservation, nutrient cycling, carbon fixation and oxygen production, and currently, it is the CO2 sink of Changbai Mountains.

Biomass↗
PubMedDate not supplied

[The role of antarctica in formation of the cenozoic climate and contemporary open sea abyssal fauna].

The key role of the Antarctic continent in the formation of the contemporary (Cenozoic) zonal-contrast climate and related geologically "young" (Postmesozoic) contemporary abyssal fauna of the World Ocean is discussed on the basis of the current concepts of pleitectonics, history of planetary climates, paleobiooceanology, and bioevolution. It has been shown that the flows of cold aerated near-Antarctic waters that started to descend in the open sea abyssal in the middle of Cenozoic were capable of substituting for previously (in Mesozoic) heated (up to 15-20 degrees C) abyssal waters within only 1500-2000 years. Following the descending near-Antarctic waters, the shallow and cold water oxyphilic fauna assimilated the abyssal zone that had been warm water and weakly populated.

Animals↗
PubMedDate not supplied

[Taphonomic features of Arctic pollen].

The composition of the primary pollen changes during pollen transfer and redistribution over the Earth's surface and fossilization. These processes are particularly pronounced in the tundra zone. Patterns of pollen spectra formation in the subaerial and subaqueous deposits of the tundra zone were considered and the differences in the content of palynomorphs with exine rupture were revealed. The changes in the effect of regional and local taphonomic factors on Arctic tundra slopes were traced. Pollen conservation in the deposits of the tundra zone, snowfields, and wedge ice was considered.

Arctic Regions↗
PubMed2006

[Phylogenetic diversity and cold-adaptive hydrolytic enzymes of culturable psychrophilic bacteria associated with sea ice from high latitude ocean, Artic].

The phylogenetic diversity of culturable psychrophilic bacteria associated with sea ice from high latitude sea (77 degrees 30'N - 81 degrees 12'N), Canadian Basin and Greenland sea Arctic, was investigated. A total of 37 psychrophilic strains were isolated using three different methods of ( i ) spread plate method: 100 microL of each dilution ice-melt sample was spreaded onto the surface of Marine 2216 agar (DIFCO laboratories, Detroit, MI) and incubated for 2 to 6 weeks at 4 degrees C; ( ii ) bath culture and spread plate method: 1 mL of sample was added to 9mL of NSW (unamended natural seawater, 0.2 microm prefiltered and autoclaved) and incubated for 1 months at - 1 degrees C, then spread plate method was used to isolate bacterial strains from the pre-cultured samples; ( iii ) cold shock, bath culture and spread plate method: samples were exposed to - 20 degrees C for 24h, then bacterial strains isolated by bath culture and spread plate method under aerobic conditions. Nearly half of psychrophilic strains are isolated by using method iii . 16S rDNA nearly full-length sequence analysis reveal that psychrophilic strains fall in two phylogenetic divisions, gamma-proteobacteria (in the genera Colwellia, Marinobacter, Shewanella, Thalassomonas, Glaciecola, Marinomonas and Pseudoalteromonas) and Cytophaga-Flexibacter-Bacteroides (in the genera Flavobacterium and Psychroflexus). Nine of bacterial isolates (BSi20007, BSi20497, BSi20517, BSi20537, BSi20170, BSi20001, BSi20002, BSi20675 and BSi20101) quite likely represent novel species (16S rDNA sequence similarity below 97%). One of strains (BSi20002) from Canadian Basin shows 100% sequence similarity to the Antarctic Weddell sea ice isolate Marinobacter sp. ANT8277, suggesting bacteria may have a bipolar distribution at the species level. AF283859 sequences were submitted to the BLAST search program of the National Center for Biotechnology Information website (NCBI, http://www. ncbi. nlm.nih. gov). Twenty sequences showing 100% similarity each other are retrieved from the database, eleven from Antarctic seawater bacteria, three from Antarctic sea-ice bacteria, one from Spitzbergen sea-ice bacteria, two from Chukchi Sea sea-ice bacteria, two from Canadian Basin sea-ice bacteria (in this study) and one from uncultured bacterium clone PDA-OTU11 associated with the coral Pocillopora damicornis from the Great Barrier Reef. These may indicate that the physiological and geographic barriers appear to be permeable and some bacterial species can survive in different environment. The majority of the bacterial strains are able to secrete diversity cold-adaptive hydrolytic enzymes into the medium at 4 degrees C. The isolates that are able to degrade Tween-80, glutin, and starch account for, respectively, 62.6%, 51.4% and 40.5%.

Arctic Regions↗
PubMed2006

[Hydrochemical characteristic analysis of melting water flow in Keqikaer Glacier, Tianshan (west) Mountains].

In order to study the melting water chemical characteristics in the Keqikaer Glacier, Tianshan(west)Mountains, the samples were collected from June to September in 2003. The result is found that: (1) The pH value is between 7.35-8.52, the order of which is:river water > glacier melting water > lake water on glacier > precipitation. (2) The various ionic concentrations of melting water are lower than other three kinds of samples, and average is 24% of river water. (3) Comparing and analyzing hydrochemical difference among various precipitation forms, the author found that inhomogeneous ionic concentration of rainwater is higher than the others. (4) Next, the water samples at different altitude have been analyzed, which shows that inhomogeneous ionic concentration of altitude effect is very remarkable. It is expected that if altitude is lower, the eluviation is led by glacier melting can influence the enviro-information record of ice layer.

China↗
PubMed2006

Expected coalescence times and segregating sites in a model of glacial cycles.

The climatic fluctuations of the Quaternary have influenced the distribution of numerous plant and animal species. Several species suffer population reduction and fragmentation, becoming restricted to refugia during glacial periods and expanding again during interglacials. The reduction in population size may reduce the effective population size, mean coalescence time and genetic variation, whereas an increased subdivision may have the opposite effect. To investigate these two opposing forces, we proposed a model in which a panmictic and a structured phase alternate, corresponding to interglacial and glacial periods. From this model, we derived an expression for the expected coalescence time and number of segregating sites for a pair of genes. We observed that increasing the number of demes or the duration of the structured phases causes an increase in coalescence time and expected levels of genetic variation. We compared numerical results with the ones expected for a panmictic population of constant size, and showed that the mean number of segregating sites can be greater in our model even when population size is much smaller in the structured phases. This points to the importance of population structure in the history of species subject to climatic fluctuations, and helps explain the long gene genealogies observed in several organisms.

Animals↗
PubMed1993

Scanning electron microscopy of high-pressure-frozen sea urchin embryos.

High-pressure-freezing permits direct cryo-fixation of sea urchin embryos having a defined developmental state without the formation of large ice crystals. We have investigated preparation protocols for observing high-pressure-frozen and freeze-fractured samples in the scanning electron microscope. High-pressure-freezing was superior to other freezing protocols, because the whole bulk sample was reasonably well frozen and the overall three-dimensional shape of the embryos was well preserved. The samples were either dehydrated by freeze-substitution and critical-point-drying, or imaged in the partially hydrated state, using a cold stage in the SEM. During freeze-substitution the samples were stabilized by fixatives. The disadvantage of this method was that shrinking and extraction effects, caused by the removal of the water, could not be avoided. These disadvantages were avoided when the sample was imaged in the frozen-hydrated state using a cold-stage in the SEM. This would be the method of choice for morphometric studies. Frozen-hydrated samples, however, were very beam sensitive and many structures remained covered by the ice and were not visible. Frozen-hydrated samples were partially freeze-dried to make visible additional structures that had been covered by ice. However, this method also caused drying artifacts when too much water was removed.

Animals↗