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PubMed1997

Microtubule assembly in cold-adapted organisms: functional properties and structural adaptations of tubulins from antarctic fishes.

Fishes native to the coastal waters of the Antarctic have adapted to habitat and body temperatures in the range -1.8 to +2 degrees C. Their cytoplasmic microtubules, unlike those of mammals and temperate poikilotherms, have evolved to assemble efficiently at these low temperatures. To learn about the underlying molecular adaptations, my laboratory is studying microtubule proteins [tubulin alpha beta dimers and microtubule-associated proteins (MAPs)] and tubulin genes from several Antarctic fishes, including the rockcods Notothenia coriiceps and Gobionotothen gibberifrons. We find that the assembly-enhancing adaptations of the fish microtubule proteins are intrinsic to the tubulin subunits themselves. Furthermore, microtubule formation by Antarctic fish tubulins is strongly entropy driven, due in part to an increased reliance, relative to tubulins from other species, on hydrophobic interactions. Based on analyses of tubulin polypeptides and cDNAs, we suggest that the structural adaptations of Antarctic fish tubulins most likely involve alterations in the primary sequences of tubulin isotypes. With respect to neural beta tubulins from other vertebrates, for example, the class II beta-tubulin isotype of N. coriiceps brain contains seven unique amino acid substitutions and one novel insertion in its 446-residue primary sequence. Most of these changes are located in a structural domain that forms contacts between tubulin dimers during microtubule assembly and would be expected to enhance polypeptide flexibility, thereby facilitating addition of tubulin to microtubule ends. The acidic carboxy-terminal tails of the alpha and beta tubulins, by contrast, appear not to be sites of cold adaptation of polymerization. We have also found that brain and egg tubulins from Antarctic fishes differ strikingly in their polymerization efficiencies, which demonstrates, in agreement with the multitubulin hypothesis, that tissue-specific tubulin isoforms can possess distinct functional properties. Thus, study of microtubule proteins from organisms, such as the Antarctic fishes, that have adapted to extreme thermal regimes should contribute significantly to an understanding of the quaternary interactions that control microtubule assembly in all eukaryotes.

Adaptation, Physiological↗
PubMed2000

Efficacy of the nematophagous fungus Duddingtonia flagrans in reducing equine cyathostome larvae on pasture in south Louisiana.

The effectiveness of Duddingtonia flagrans in reducing the free living third stage larvae (L(3)) of equine cyathostomes on pasture when fed to horses has been demonstrated in cold temperate climates. The objective of this experiment was to assess the efficacy of D. flagrans against equine cyathostomes in the subtropical environment of southern Louisiana. Fecal pats were prepared by mixing feces obtained from a parasite-free horse fed D. flagrans at a dose of approximately 2 x 10(6) spores kg(-1), with feces containing cyathostome eggs from a parasitized horse. Control pats contained feces from a parasite-free horse mixed with feces containing cyathostome eggs. The fecal pats were placed on pasture in six replicates at 4-week intervals from March 1997 until January 1998. Comparison of recoveries of L(3) from non-treated control pats in the field with non-treated coprocultures maintained in the laboratory indicated that L(3) survival on pasture was reduced during the months of May, June, July, August and September. The efficacy of the fungus was determined by L(3) recovery from grass surrounding the fecal pats of treated and control groups. D. flagrans significantly reduced L(3) during the months of April, May, and October 1997 to January 1998 (range 66-99% reduction, p=0.0001), and for the year as a whole (p=0.0001).

Animals↗
PubMed2003

Longspurs and snow buntings: phylogeny and biogeography of a high-latitude clade (Calcarius).

Using complete cytochrome b sequence data, we determined that the genus Calcarius, as presently recognized, is paraphyletic. Calcarius plus Plectrophenax form a highly supported clade composed of two subclades, a "snow bunting" clade comprised of Plectrophenax plus Calcarius mccownii (formerly in the monotypic genus Rhynchophanes), and a "collared" longspur clade of Calcarius lapponicus, ornatus, and pictus. Contrary to conventional thought, Calcarius is not phylogenetically close to either Calamospiza or Emberiza. Unlike these two genera, the taxonomic affinities of Calcarius appear to lie outside of the sparrow (tribe Emberizini) assemblage. Calcarius appears to be a relatively old songbird lineage, originating between 4.2 and 6.2 million years ago. Within Calcarius, pictus and ornatus form a closely related sister pair (2.9% divergent), as do Calcarius nivalis and hyperboreus (0.18% divergent). The group (Calcarius, sensu lato) is inferred to have its origins at relatively high latitudes in the New World.

Alaska↗
PubMed2000

The Irving-Scholander legacy in polar physiology.

The pioneer arctic and cold environment studies of Laurence Irving and Per Scholander, undertaken during the middle decades of the 20th century, have had a wide ranging and major influence on the direction and character of experimental research on polar species. Their investigations included comparative studies of metabolism, insulation, and acclimatization of mammals and birds in arctic Alaska and the tropics. Freezing, supercooling, and antifreeze research included fishes, insects, and plants. They examined the special problems of cooling in appendages of mammals and birds and the potential for acclimatization of these structures by repeated cold exposure. Studies of cold exposure in human populations considered possible adaptive reactions. Their research on diving mammals opened a vast new area for studies with attention to asphyxial tolerance and temperature regulation. A lesser-known accomplishment was an innovative approach to recovery of ancient atmospheric gases from polar ice fields, an approach that was stimulated by original investigations of frozen insect larvae and gas permeability through ice.

Adaptation, Physiological↗
PubMed2000

Diving physiology of birds: a history of studies on polar species.

Our knowledge of avian diving physiology has been based primarily on research with polar species. Since Scholander's 1940 monograph, research has expanded from examination of the 'diving reflex' to studies of free-diving birds, and has included laboratory investigations of oxygen stores, muscle adaptations, pressure effects, and cardiovascular/metabolic responses to swimming exercise. Behavioral and energetic studies at sea have shown that common diving durations of many avian species exceed the calculated aerobic diving limits (ADL). Current physiological research is focused on factors, such as heart rate and temperature, which potentially affect the diving metabolic rate and duration of aerobic diving.

Animals↗
PubMed2000

History of polar whaling: insights into the physiology of the great whales.

The sheer size and pelagic nature of the great whales has effectively precluded detailed studies of most of their physiological processes. The vast majority of all data for these species have come from anatomical studies conducted on specimens that were caught in commercial and native whaling operations. In both the polar regions, an incredible number of whales were hunted, but anatomical studies were not usually conducted until relatively recent times. However, the anatomical data that do exist provide a valuable insight into some of the physiological demands placed on the animals by their marine habitat. These include information on blubber and nutrition; baleen and feeding ecology; contaminant chemistry and tissue samples; diving chemistry and acoustics. Taken together, these anatomical data provide the only substantial information on how these animals dive and hunt. Recent breakthroughs in chemical techniques however, are providing even greater details on function (for example, fatty acid signature methods). Coupled with advanced methods for tracking these whales at sea (acoustic and satellite), future studies should provide significant new information on the general physiology of these difficult to study species.

Adipose Tissue↗
PubMed2000

How does the European common lizard, Lacerta vivipara, survive the cold of winter?

Although the European common lizard, Lacerta vivipara, is among the most common Eurasian reptile species, we know little about how these lizards cope with very low temperatures. In this study we examined microenvironmental conditions, body temperature, behavior, and cold strategies to see whether strategies of freezing and supercooling, while normally considered to be mutually exclusive, may in fact be adopted simultaneously by the common lizard. Following up on an earlier study of a lowland population, this time we used a mountain population (850 m) to discover differences in overwintering strategies between the two populations. Differential scanning calorimetry conducted during the hibernation period (vs. the activity period) showed that the blood of highland lizards had an increased ability to resist ice formation, confirming an ecophysiological effect most likely mediated by physical properties of the blood. Mean blood glucose level of unfrozen L. vivipara in the field increased significantly (about fourfold) from 8.5+/-0.7 mmol l(-1) in September to 33.2+/-5.6 mmol l(-1) in March. The blood glucose level then experienced a significant decline as it fell to 6. 2+/-0.8 mmol l(-1) after hibernation in April. Glucose, in conclusion, seems to play a role of cryoprotectant rather than antifreeze.

Adaptation, Physiological↗
PubMed2002

Beating the cold: the functional evolution of troponin C in teleost fish.

The sensitivity of the cardiac myocyte contractile element for Ca(2+) decreases with temperature. As myocyte contractility is regulated by changes in cytosolic [Ca(2+)], this desensitizing effect represents a challenge for temperate fish such as the rainbow trout, Oncorhynchus mykiss, living in environments where temperatures are low and variable. To allow cardiac function in a temperate environment it is thought that the comparatively high Ca(2+) sensitivity of trout cardiac myocytes compensates for the effects of low temperature on myocyte contractility. The high Ca(2+) sensitivity of the trout myocyte is due, at least in part, to changes in the amino acid sequence of the thin filament protein, cardiac troponin C (cTnC). cTnC is the Ca(2+)-activated switch that triggers myocyte contraction. The isoform of cTnC cloned from trout ventricle (ScTnC) is 92% identical to mammalian cTnC (McTnC) and is significantly more sensitive to Ca(2+). This result suggests that ScTnC has evolved in trout to allow cardiac function at low temperatures. cTnC also appears to play a role in maintaining cardiac function when temperatures change. Increasing myofibrillar pH according to alpha-stat regulation, as would occur when temperature decreases, increases Ca(2+) sensitivity. A similar increase in pH also sensitizes cTnC to Ca(2+). ScTnC therefore appears critical in maintaining cardiac function in trout at low temperatures as well as during changes in temperature.

Acclimatization↗
PubMed2002

Temperature and angiogenesis: the possible role of mechanical factors in capillary growth.

This review examines the effect of prolonged cold exposure on muscle capillary supply in mammals and fishes. In rats and hamsters, the response to a simulated onset of winter is to conserve the microcirculation and maintain a constant capillary to fibre ratio (C:F), implying either an unaltered vacular bed or angiogenesis matched by muscle hyperplasia, while chronic acclimation to low environmental temperature induces a variable degree of muscle atrophy, which in turn increases capillary density (CD). In striped bass and rainbow trout, cold-induced angiogenesis results in an increase in C:F, but also a cold-induced fibre hypertrophy that is accompanied by a powerful angiogenic response such that CD is much less sensitive to changes in fibre size. Endothelial cells can act as mechanotransducers such that angiogenesis may be initiated by changes in their physical environment. It is hypothesised that in mammals, the metabolic consequences of cold exposure increases the luminal shear stress, while in fishes the stimulus for angiogenesis is abluminal stretch following an increase in fibre size.

Acclimatization↗
PubMed2002

Metabolic cold adaptation of polar fish based on measurements of aerobic oxygen consumption: fact or artefact? Artefact!

Whether metabolic cold adaptation in polar fish, based on measurements of aerobic standard metabolic rate, is a fact or an artefact has been a dispute since Holeton asked the question in 1974. So far polar fish had been considered to be metabolically cold adapted because they were reported to have a considerably elevated resting oxygen consumption, or standard metabolic rate, compared with oxygen consumption values of tropical or temperate fish extrapolated to similar low polar temperatures. Recent experiments on arctic and Antarctic fish, however, do not show elevated resting aerobic oxygen consumption values, or standard metabolic rate, and hence it is concluded that that metabolic cold adaptation in the traditional sense is an artefact.

Acclimatization↗
PubMed1998

Submaximal exercise in the cold: does cooling potentiate the development of muscle injuries in the rat?

To test the effect of low ambient temperature on muscular strain and possible development of muscle injuries, male Sprague-Dawley rats (n = 35) were exercised at a speed of 15 m min-1 on a treadmill at a 6 degrees inclination for 1.5 h in a warm (22 degrees C) or a cold (-10 degrees C) environment. Blood and tissue samples were collected 0 and 48 h postexercise. Blood glucose, lactate, pyruvate, cortisol, epinephrine (E) and norepinephrine (NE) were determined to investigate the effect on energy metabolism. To estimate the degree of physical strain, possible muscle injury and regenerative processes of muscles in response to exercise in the cold, serum creatine kinase (CK), lactate dehydrogenase (LDH), muscle beta-glucuronidase and prolyl-4-hydroxylase (PH) activities were measured. In addition, histology of the hindlimb muscles m. soleus and m. tibialis anterior was examined. In general, the circulating level of metabolic substrates during exercise were unaffected by the exercise and independent of ambient temperature. Plasma cortisol increased significantly during exercise (P < 0.01), but was unaffected by the thermal strain. Of the myocellular enzymes, serum CK increased by 100% (P < 0.01) and LDH by 93% (P < 0.05) during exercise in the cold compared with exercise in warm, indicating a higher physical strain. However, exercise in the cold did not result in muscle injuries as judged by the unaltered muscular beta-glucuronidase, PH levels and muscle morphology. It is concluded that the exercise type and intensity used caused stress that was independent of the ambient temperature. In addition, the rats were able to maintain unaltered circulating levels of energy substrates also in the cold. Finally, exercise in the cold increased muscular strain but did not result in muscle injuries.

Animals↗
PubMed1999

Bone metabolic changes in Antarctic wintering team members.

Bone mass, bone metabolic markers, and calcium regulation hormones were measured in members of an Antarctic wintering team who stayed at the Japanese Antarctic station, Syowa (latitude: south 69 degrees 00', longitude: east 39 degrees 35') for 1 year. Subjects included 31 healthy Japanese males, aged 24-51 years (mean age 34.5 years) at the beginning of this study, ingesting 488 IU/day of vitamin D and 550.9 mg/day of calcium per person. The long-term coefficient of variation (CV) of the equipment used in the assessments of bone mass was 0.67% in single X-ray absorptiometry (SXA), 0.17% in the speed of sound (SOS) by quantitative ultrasound method (QUS), and 0.63% in broadband ultrasound attenuation (BUA) by QUS. The seasonal changes in the calcaneal bone mineral density (BMD) by SXA were not significant, whereas the SOS measured by QUS decreased during the measurement period (0.55%, p < 0.001), and BUA increased (1.9%, p < 0.01). Bone-specific alkaline phosphatase and osteocalcin levels increased significantly during summer (p < 0.001) and urinary calcium level decreased significantly during winter (p < 0.05). Urinary pyridinoline and deoxypyridinoline levels decreased significantly at the end of winter (p < 0.001). Serum 1,25(OH)2D3 level did not change significantly, whereas serum 25(OH)D3 level decreased significantly during winter (p < 0.001). Serum parathyroid hormone (PTH) level significantly increased at the end of winter (p < 0.01), although both PTH level and 25(OH)D3 level remained within the normal range. We concluded that the 25(OH)D3 level in subjects who stayed in Antarctica for 1 year decreased significantly with the reduction in duration of sunshine, but there were no clear changes in bone mass.

Adult↗
PubMed1987

Epilithic lichens in the Beacon sandstone formation, Victoria Land, Antarctica.

The epilithic lichen flora on the Beacon sandstone formation in Victoria Land consists of seven species: Acarospora gwynnii Dodge & Rudolph, Buellia grisea Dodge & Baker, B. pallida Dodge & Baker, Carbonea capsulata (Dodge & Baker) Hale comb. nov., Lecanora fuscobrunnea Dodge & Baker, Lecidea cancriformis Dodge & Baker, and L. siplei Dodge & Baker. The typification of the species is given along with descriptions and distribution in Antarctica.

Antarctic Regions↗
PubMed1998

Soil temperatures and stability of ice-cemented ground in the McMurdo Dry Valleys, Antarctica.

Year-round temperature measurements at 1600 m elevation during 1994 in the Asgard Range Antarctica, indicate that the mean annual frost point of the ice-cemented ground, 25 cm below the surface, is -21.7 +/- 0.2 degrees C and the mean annual frost point of the atmosphere is -27.5 +/- 1.0 degrees C. The corresponding mean annual temperatures are -24.9 degrees C and -23.3 degrees C. These results imply that there is a net flux of water vapour from the ice to the atmosphere resulting in a recession of the ice-cemented ground by about 0.4-0.6 mm yr-1. The level of the ice-cemented permafrost is about 12 cm below the level of dry permafrost. The summer air temperatures would have to increase about 7 degrees C for thawing temperatures to just reach the top of the subsurface ice. Either subsurface ice at this location is evaporating over time or there are sporadic processes that recharge the ice and maintain equilibrium over long timescales.

Antarctic Regions↗
PubMed1998

Dissolved gases in perennially ice-covered lakes of the McMurdo Dry Valleys, Antarctica.

Measurements of dissolved N2, O2, Ar, CO2, and CH4 were made in perennially ice-covered Lake Hoare. Results confirm previous reports that O2 concentrations in the upper water column exceed atmospheric equilibrium and that N2 and Ar are supersaturated throughout the water column. The mean supersaturation of N2 was found to be 2.0 (+/- 0.37) and Ar was 3.8 (+/- 1.1). The ratios of N2/Ar (20.3 +/- 13.8), and O2/Ar (22.5 +/- 4.0) at the ice-water interface are consistent with those previously measured, suggesting that bubble formation is the main process for removing gas from the lake. However, the saturations of N2 and Ar greatly exceed those previously predicted for degassing by bubble formation only at the ice-water interface. The data support the hypothesis that removal of gas by bubbles occurs in the water column to a depth of 11 m in Lake Hoare. CO2 concentration increases from near zero at the ice-water interface to 80-100 times saturation at and below the chemocline at c. 28 m. There is considerable variability in the gas concentrations throughout the water column; samples separated in depth by one metre may vary by more than 50% in gas content. It is likely that this phenomenon results from the lack of turbulent mixing in the water column. Methane (c. 2 micrograms l-1) was detected below the chemocline and immediately above the sediment/water interface at a depth of 30 m. Samples from lakes Vanda, Joyce, and Miers, also show supersaturations of O2, N2, and Ar at levels similar to levels found in Lake Hoare.

Antarctic Regions↗
PubMedDate not supplied

Challenges of major incident management when excess resources are allocated: experiences from a mass casualty incident after roof collapse of a military command center.

During a military exercise in northern Norway in March 2000, the snow-laden roof of a command center collapsed with 76 persons inside. Twenty-five persons were entrapped and/or buried under snow masses. There were three deaths. Seven patients had serious injuries, three had moderate injuries, and 16 had minor injuries. A military Convalescence Camp that had been set up in a Sports Hall 125 meters from the scene was reorganized as a causality clearing station. Officers from the Convalescence Camp initially organized search and rescue. In all, 417 persons took part in the rescue work with 36 ambulances, 17 helicopters, three ambulance airplanes and one transport plane available. Two ambulances, five helicopters and one transport aircraft were used. Four patients were evacuated to a civilian hospital and six to a field hospital. The stretcher and treatment teams initially could have been more effectively organized. As resources were ample, this was a mass casualty, not a disaster. Firm incident command prevented the influx of excess resources.

Cold Climate↗