The hemodynamics of the lesser circulation and blood indices in rats under long-term high-altitude hypoxia

Pulmonary hemodynamics in anesthetized rats was studied during long-term residence (2,5 and 10 months) at high altitude (3,200 m, Tien Shan). Transbronchial regional electroplethysmography and catheterization of pulmonary artery was used. It has been shown that at all periods of adaptation there was increased systolic pressure in pulmonary artery and practically unchanged diastolic one. Some regional redistributions of pulmonary blood flow and blood volume for five different lung parts were demonstrated. Hemoglobin content in erythrocytes was steadily increased while specific electric blood resistance, hematocrit, and number of erythrocytes did not change so significantly. The role of pulmonary arterial hypertension and changes of other studied indices of hemodynamics and red blood in adaptation to chronic high-altitude hypoxia are being discussed.     

Variation in russet sparrow (Passer cinnamomeus) breeding biology in relation to small-scale altitudinal differences in China

Evolution of avian life histories is typically strongly influenced by both altitude and latitude. To date, most studies have investigated the effects of extreme differences in altitude and latitude on variation in reproductive traits. Studies based on small altitude and latitude spans are needed to better understand the resolution of selective pressures. We compared several aspects of russet sparrow (Passer cinnamomeus) breeding biology between a low-altitude (200 m) and a high-altitude (1,500 m) population in China, representing a relatively small altitudinal gradient (1,300 m). High-altitude birds initiated breeding significantly later compared to their low-altitude counterparts. Interestingly, breeding season was significantly longer in the high-altitude site (57 vs. 84 d). Lowland sparrows laid larger clutches (4.92 vs. 4.09 eggs) and showed greater fledging success (4.20 vs. 3.46 fledgings) than did upland birds. Variation in life history traits thus appears to occur even along a small scale altitudinal gradient. We suggest that the longer breeding season and smaller clutch size in the highland population may be an adaptation or acclimation to compensate for the reduced annual productivity resulting from unfavourable or sub-optimal habitats for these sparrows.     

Functional capacities of lungs and thorax in beagles after prolonged residence at 3,100 m

Functional capacities of the lungs and thorax in beagles taken to high altitude as adults for 33 mo or in beagles raised from puppies at high altitude were compared with functional capacities in corresponding sets of beagles kept simultaneously at sea level. Comparisons were made after reacclimatization to sea level. Lung volumes, airway pressures, esophageal pressures, CO diffusing capacities (DLCO), pulmonary blood flow, and lung tissue volume (Vt) were measured by a rebreathing technique at inspired volumes ranging from 15 to 90 ml/kg. In beagles raised from puppies we measured anatomical distribution of intrathoracic air and tissue using X-ray computed tomography at transpulmonary pressures of 20 cm H2O. Lung and thoracic distensibility, DLCO, and Vt were not different between beagles that had been kept at high altitude for 33 mo as adults and control subjects kept simultaneously at sea level. Lung distensibility, DLCO, and Vt were significantly greater in beagles raised at high altitude than control subjects raised simultaneously at sea level. Thoracic distensibility was not increased in beagles raised at high altitude; the larger lung volume was accommodated by a lower diaphragm, not a larger rib cage.     

The influence of altitude and topography on genetic structure in the long-toed salamander (Ambystoma macrodactulym)

A primary goal of molecular ecology is to understand the influence of abiotic factors on the spatial distribution of genetic variation. Features including altitudinal clines, topography and landscape characteristics affect the proportion of suitable habitat, influence dispersal patterns, and ultimately structure genetic differentiation among populations. We studied the effects of altitude and topography on genetic variation of long-toed salamanders (Ambystoma macrodactylum), a geographically widespread amphibian species throughout northwestern North America. We focused on 10 low altitude sites (< 1200 m) and 11 high-altitude sites in northwestern Montana and determined multilocus genotypes for 549 individuals using seven microsatellite loci. We tested four hypotheses: (1) gene flow is limited between high- and low-altitude sites; and, (2) gene flow is limited among high-altitude sites due to harsh habitat and extreme topographical relief between sites; (3) low-altitude sites exhibit higher among-site gene flow due to frequent flooding events and low altitudinal relief; and (4) there is a negative correlation between altitude and genetic variation. Overall F(ST) values were moderate (0.08611; P < 0.001). Pairwise F(ST) estimates between high and low populations and a population graphing method supported the hypothesis that low-altitude and high-altitude sites, taken together, are genetically differentiated from each other. Also as predicted, gene flow is more prominent among low-altitude sites than high-altitude sites; low-altitude sites had a significantly lower F(ST) (0.03995; P < 0.001) than high altitude sites (F(ST) = 0.10271; P < 0.001). Use of Bayesian analysis of population structure (BAPS) resulted in delineation of 10 genetic groups, two among low-altitude populations and eight among high-altitude populations. In addition, within high altitude populations, basin-level genetic structuring was apparent. A nonequilibrium algorithm for detecting current migration rates supported these population distinctions. Finally, we also found a significant negative correlation between genetic diversity and altitude. These results are consistent with the hypothesis that topography and altitudinal gradients shape the spatial distribution of genetic variation in a species with a broad geographical range and diverse life history. Our study sheds light on which key factors limit dispersal and ultimately species' distributions.     

Local adaptation and cogradient selection in the alpine plant, Poa hiemata, along a narrow altitudinal gradient

Alpine environments are particularly susceptible to environmental changes associated with global warming but there is potential for alpine plants to adapt to warming if local adaptation occurs and gene flow allows genotypes adapted to low altitudes to colonize higher altitude sites. Here we examine the adaptive potential of a common alpine grass, Poa hiemata, within the restricted alpine habitat of Australian mountains, across a narrow altitudinal gradient replicated in three areas. Grasses at high altitude sites had shorter leaf lengths and larger circumferences than those at lower sites. Transplant experiments with clonal material and plants grown from seed indicated that these differences were partly genetic, with environmental and genetic factors both contributing to the differences between altitudes. Differences in altitudinal forms were also evident in a common garden experiment. Plants showed a home-site advantage in terms of survival. A fitness analysis indicated that at high altitude sites, selection favored plants with short leaves and larger circumferences, whereas these traits were selected in the opposite direction at the low altitude sites. These findings indicate cogradient selection and potential for both plastic and genotypic shifts in response to climate change in P. hiemata.     

High altitude tissue adaptation in Andean coots: capillarity,fibre area,fibre type and enzymatic activities of skeletal muscle

Capillarity, fibre types, fibre area and enzyme activities of different skeletal muscles (pectoralis, extensor digitorum longus), tibialis anterior, plantaris and the myocardium were compared in Andean coot (Fulica americana peruviana) native to high altitude (Junín, Perú, 4200 m) and the same species nesting at sea level. Numbers of capillaries per square millimeter were higher in all high-altitude muscles when compared with sea-level muscles (P<0.0001). Moreover, values for capillaries per fibre and capillaries in contact with each fibre were higher in digitorum and tibialis high-altitude muscles. Muscle fibres were classified as Type I, Type IIA or Type IIB on the basis of their myofibrillar ATPase pH lability. Pectoralis muscle of high-altitude and sea-level coots presented only fibres of Type IIA. In contrast, all the leg muscles studied showed a mosaic pattern of the three fibre types. Fibre areas were determined using a Leitz Texture Analysis System. Significant differences in fibre area were observed (P<0.01) between high-altitude and sea-level muscles. Mean muscle fibre diameters were also lower in the high-altitude group than in the sea-level group. The enzyme activities studied were hexokinase, lactate dehydrogenase, citrate synthase and 3-hydroxyacyl-CoA-dehydrogenase. The oxidative capacity, as reflected by citrate synthetase and hydroxyacyl-CoA-dehydrogenase activities, was greater for myocardial and pectoralis than for leg muscles. However, analysis of maximal enzyme activities showed that there were no significant differences between the glycolytic and oxidative enzyme activities of high-altitude and sea-level coots. These results suggest that in Andean coots genetically adapted to high altitude, changes in muscle capillarity and fibre size, in addition to high haemoglobin O₂ affinity and low haemoglobin concentration, are sufficient to allow adequate energy production without increases in enzymatic activities.Abbreviations BSA bovine serum albumin - C:F ratio Capillaries per fibre - CAF Capillaries in contact with each fibre - CD capillary density (mm^-2) - CS citrate synthetase - EDL muscularis digitorum longus - fra fraction reduction area - HA high altitude - HAD hydroxyacyl-CoA-dehydrogenase - HK hexokinase - LDH lactate dehydrogenase - P ₅₀ PO₂ at which hemoglobin is half saturated with O₂ - P _aO₂ arterial partial pressure of oxygen - PAS periodic acid-schiff - PEC muscularis pectoralis - PLA muscularis planaris - P _tO₂ mean tissue oxygen pressure - P _vO₂ mixed venous partial pressure of oxygen - SD standard deviation - SL sea level - TA muscularis tibialis anterior - TAS texture analysis system     

Granular pneumocytes and altitude: A stereological evaluation

Summary Stereological analysis demonstrates that the granular pneumocytes of mice native to high altitude (4660 m) are significantly larger than those of the same species (Phyllotis darwini) living at sea level. Such cells have larger nuclei and a significantly greater volume of mitochondria. There are both more and larger lamellar bodies in high altitude granular pneumocytes, resulting in about four times more surfactant per cell at high altitude.     

Lung volume, chest size, and hematological variation in low-, medium-, and high-altitude central Asian populations

To evaluate adaptive responses to high-altitude environment, we examined three groups of healthy adult males from Central Asia: 94 high-altitude (HA) Kirghiz subjects (3,200 m above sea level); 114 middle-altitude (MA) Kazakh subjects (2,100 m), and 90 low-altitude (LA) Kirghiz subjects (900 m). Data on chest size (chest perimeter and chest diameter), lung volume (forced expiratory volume (FEV) and forced expiratory volume in 1 sec (FEV1)), and hematological parameters (hemoglobin, erythrocytes, hematocrit, and SaO(2)) are discussed. The results show that 1) chest shape is less flat in the samples living at higher altitude. In the HA sample, chest perimeter is lower but chest excursion is high. 2) In the highlanders, forced vital capacity (FVC) and FEV1 are no higher than in the other samples, even when corrected for stature and body weight. The negative correlation between FVC-FEV1 and age decreases with increasing altitude. 3) The HA and MA samples have higher values of hemoglobin, erythrocytes, and hematocrit. The HA sample has lower SaO(2) and higher arterial oxygen content than the LA sample. No association between hematocrit and age was detected in the four samples. The results indicate that the high-altitude Kirghiz present features of developmental acclimatization to hypobaric hypoxia which are also strongly influenced by other major high-altitude environmental stresses.     

Effects of altitude and exercise on pulmonary capillary integrity: evidence for subclinical high-altitude pulmonary edema.

Strenuous exercise may be a significant contributing factor for development of high-altitude pulmonary edema, particularly at low or moderate altitudes. Thus we investigated the effects of heavy cycle ergometer exercise (90% maximal effort) under hypoxic conditions in which the combined effects of a marked increase in pulmonary blood flow and nonuniform hypoxic pulmonary vasoconstriction could add significantly to augment the mechanical stress on the pulmonary microcirculation. We postulated that intense exercise at altitude would result in an augmented permeability edema. We recruited eight endurance athletes and examined their bronchoalveolar lavage fluid (BALF) for red blood cells (RBCs), protein, inflammatory cells, and soluble mediators at 2 and 26 h after intense exercise under normoxic and hypoxic conditions. After heavy exercise, under all conditions, the athletes developed a permeability edema with high BALF RBC and protein concentrations in the absence of inflammation. We found that exercise at altitude (3,810 m) caused significantly greater leakage of RBCs [9.2 (SD 3.1)x10(4) cells/ml] into the alveolar space than that seen with normoxic exercise [5.4 (SD 1.2)x10(4) cells/ml]. At altitude, the 26-h postexercise BALF revealed significantly higher RBC and protein concentrations, suggesting an ongoing capillary leak. Interestingly, the BALF profiles following exercise at altitude are similar to that of early high-altitude pulmonary edema. These findings suggest that pulmonary capillary disruption occurs with intense exercise in healthy humans and that hypoxia augments the mechanical stresses on the pulmonary microcirculation.     

Long-Term Exposure to High Altitude Affects Conflict Control in the Conflict-Resolving Stage

The neurocognitive basis of the effect of long-term high altitude exposure on conflict control is unclear. Event related potentials (ERPs) were recorded in a flanker task to investigate the influence of high altitude on conflict control in the high-altitude group (who had lived at high altitude for three years but were born at low altitude) and the low-altitude group (living in low altitude only). Although altitude effect was not significant at the behavioral level, ERPs showed cognitive conflict modulation. The interaction between group and trial type was significant: P3 amplitude was greater in the low-altitude group than in the high-altitude group in the incongruent trial. This result suggests that long-term exposure to high altitude affects conflict control in the conflict-resolving stage, and that attentional resources are decreased to resist the conflict control in the high-altitude group.     

Functional morphology of resistant pulmonary vessels and capillaries in individual and species adaptation to high altitude]

Morphological and structural rearrangement of resistant pulmonary vessels and alveolar capillaries was assessed in lowland animals (rabbits) during high-altitude adaptation, in aboriginal high-altitude species (yaks, mountain goats) and on native highlanders. Structural adaptive developments in pulmonary vessels and capillaries of high-altitude animals contribute to maximal facilitation of gas diffusion. Similar adaptive changes in pulmonary resistant vessels and capillaries of laboratory animals and in native highlanders are associated with pathological alterations manifest in the elevation of pulmonary vascular resistance, right ventricular hypertrophy, increases in the thickness of the basal membrane of the air-blood barrier. In all the subjects studied the process of high-altitude adaptation is associated with hypertrophy of pulmonary endothelium. The intensification of pulmonary endothelium. The intensification of pulmonary endothelium metabolic activity may be directed at regulation of vascular tone.     

Ultrastructure of the Blood System in the Phoronid Phoronopsis harmeri Pixell, 1912: 1. Capillaries

Four types of blood capillaries of the phoronid Phoronopsis harmeri are described. These are capillaries of the tentacles, of the body, of the stomach plexus, and of the vasoperitoneal tissue. The wall of capillary consists of cells of the coelomic lining, a layer of extracellular matrix, and separate endothelial cells. Myoepithelial coelomic cells of tentacle capillaries contain cross-striated fibers. In capillaries of the body and the stomach plexus, the myofilaments are smooth. In the cells of the wall of vasoperitoneal tissue capillaries, myofilaments are lacking. The cells of the vessel wall of the tentacles, the body, and the vasoperitoneal tissue bear a single cilium. The cells of capillaries of the stomach plexus lack a cilium. The ultrastructure of erythrocytes and amebocytes is described. In the cytoplasm of erythrocytes, there is a basal body. It is assumed that erythrocytes originated from the ciliary cells of the wall of the blood vessels.     

Blood rheology in acute mountain sickness and high-altitude pulmonary edema.

The role of blood rheology in the pathogenesis of acute mountain sickness and high-altitude pulmonary edema was investigated. Twenty-three volunteers, 12 with a history of high-altitude pulmonary edema, were studied at low altitude (490 m) and at 2 h and 18 h after arrival at 4,559 m. Eight subjects remained healthy, seven developed acute mountain sickness, and eight developed high-altitude pulmonary edema. Hematocrit, whole blood viscosity, plasma viscosity, erythrocyte aggregation, and erythrocyte deformability (filtration) were measured. Plasma viscosity and erythrocyte deformability remained unaffected. The hematocrit level was lower 2 h after the arrival at high altitude and higher after 18 h compared with low altitude. The whole blood viscosity changed accordingly. The erythrocyte aggregation was about doubled 18 h after the arrival compared with low-altitude values, which reflects the acute phase reaction. There were, however, no significant differences in any rheological parameters between healthy individuals and subjects with acute mountain sickness or high-altitude pulmonary edema, either before or during the illness. We conclude that rheological abnormalities can be excluded as an initiating event in the development of acute mountain sickness and high-altitude pulmonary edema.     

Pulmonary vascular response of the coati to chronic hypoxia.

The unusually muscular pulmonary arteries normally present in cattle and swine residing at low altitude are associated with a rapid development of severe pulmonary hypertension when those animals are moved to high altitude. Because these species lack collateral ventilation, they appear to have an increased dependence on hypoxic vasoconstriction to maintain normal ventilation-perfusion balance, which, in turn, maintains thickened arterial walls. The only other species known to lack collateral ventilation is the coati, which, similarly, has thick-walled pulmonary arteries. We tested the hypothesis that coatis will develop severe high-altitude pulmonary hypertension by exposing six of these animals (Nasua narica) to a simulated altitude of 4,900 m for 6 wk. After the exposure, pulmonary arterial pressures were hardly elevated, right ventricular hypertrophy was minimal, there was no muscularization of pulmonary arterioles, and, most surprising of all, there was a decrease in medial thickness of muscular pulmonary arteries. These unexpected results break a consistent cross-species pattern in which animals with thick muscular pulmonary arteries at low altitude develop severe pulmonary hypertension at high altitude.     

Altitude-related shift of relative abundance from insect to sunbird pollination in Elaeagnus umbellata (Elaeagnaceae)

The evolution of floral traits has been thought to be influenced by local, effective pollinators. However, little attention has been paid to the possibility that altitudinal variation in floral traits could be mediated by local pollinator functional groups, particularly a shift from bees to birds. Plant size, floral traits, pollinators and their pollination roles were investigated in the spring-flowering shrub Elaeagnus umbellata (Elaeagnaceae) at three altitudes (1160, 1676, and 2050 m) in Minshan, Sichuan Province, on the northern rim of the Hengduan Mountains, southwest China. Compared to lower altitudes, higher-altitude plants were smaller but the floral tubes were longer, with a larger volume of nectar of lower sugar concentration but with a greater proportion of sucrose. The visitation frequency of bees decreased with altitude, whereas the sunbirds did the opposite. Birds and bees foraged for nectar but not pollen, and birds deposited more pollen grains per visit relative to bees and least were syrphid flies. Excluding birds decreased seed set at high but not at mid- or low altitude. Our study of E. umbellata revealed an association between altitudinal variation in floral traits and a change in the relative abundance of the major pollinators with altitude from majority bees to majority sunbirds. Although abiotic factors also tend to vary with altitude and can affect floral traits, nectar properties of “pro-bird” pollination were observed at high altitude.     

Are there latitudinal and altidudinal Rapoport effects in the geographic ranges of Andean passerine birds?

We analysed the range-sizes of 835 Andean passerine species (including 414 endemics and 421 non-endemics) to test for latitudinal and altitudinal Rapoport effects (LRE and ARE). We tested for positive range-size: latitude/altitude correlations using three different methods: (i) Rohde's mid-point method, (ii) species sorted out by altitude, and (iii) a phylogenetic comparative method (CAIC). Using Rohde's mid-point method, the mean latitudinal extent of species does not follow a Rapoport pattern, but the mean latitudinal occupancy of all passerines and non-endemics do increase with latitude. The latitudinal ranges of endemics sorted out by altitude follow a reverse Rapoport effect, but non-endemics support the pattern. CAIC confirms the latitudinal increase in the occupancy of non-endemics, but regressions have low coefficients of determination. The ARE is supported by the mean altitudinal extent of species, but the trend vanishes when controlling for geometric effects. Low-altitude species occupy about the same proportion of the available altitudinal space as do high-altitude ones. Our analyses suggest that latitude and altitude have low explanatory power for understanding the spatial variation in range-sizes at a continental scale. We show how different patterns can emerge from applying different criteria to the analysis of data.     

GPIHBP1: an endothelial cell molecule important for the lipolytic processing of chylomicrons

PURPOSE OF REVIEW: To summarize recent data indicating that glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1) plays a key role in the lipolytic processing of chylomicrons. RECENT FINDINGS: Lipoprotein lipase hydrolyses triglycerides in chylomicrons at the luminal surface of the capillaries in heart, adipose tissue, and skeletal muscle. The endothelial cell molecule that facilitates the lipolytic processing of chylomicrons has never been clearly defined. Mice lacking GPIHBP1 manifest chylomicronemia, with plasma triglyceride levels as high as 5000 mg/dl. In wild-type mice, GPIHBP1 is expressed on the luminal surface of capillaries in heart, adipose tissue, and skeletal muscle. Cells transfected with GPIHBP1 bind both chylomicrons and lipoprotein lipase avidly. SUMMARY: The chylomicronemia in Gpihbp1-deficient mice, the fact that GPIHBP1 is located within the lumen of capillaries, and the fact that GPIHBP1 binds lipoprotein lipase and chylomicrons suggest that GPIHBP1 is a key platform for the lipolytic processing of triglyceride-rich lipoproteins.     

Quantitative interrelationship between the parenchyma and the stroma of the rabbit myocardium in atherosclerotic cardiosclerosis]

The relative volume of myocardial fibers, connective tissue cells, capillaries, interstitial space and surface area of the myocardial fibers and capillaries per tissue volume unit of the myocardium were measured during diffuse cardiosclerosis under conditions of experimental atherosclerosis. A significant decrease in the relative volume of the myocardial fibers alone with a concomitant increase of the extracellular space of the stroma were demonstrated.     

Species Diversity and Life-Form Patterns in Steppe Vegetation along a 3000 m Altitudinal Gradient in the Alborz Mountains, Iran

Biodiversity pattern and life-form spectra were studied along a 3,000 m altitudinal gradient from a semi-desert area to the alpine peak of Tochal Mountain. The gradient is located on the southern slopes of Central Alborz with a Mediterranean continental climate. DCA ordination was applied to 1,069 relevés and 7 quantitative variables to discover the relation of diversity and altitude. A biodiversity pattern was obtained by relating values for species richness and Shannon-Wiener’s index to 100-m altitudinal sections. Altitude was determined as the major ecological gradient. Both diversity indices are negatively correlated with altitude and show a decreasing trend beyond a peak in species richness at 1,800–1,900 m a.s.l. towards a very low diversity in the high alpine zone. The biodiversity peak does not match with the potential tree line in the area (2,500–3,000 m a.s.l.). The high diversity in foothills can be related to habitat heterogeneity, longer suitable climatic conditions, and diverse disturbance factors, while unfavorable conditions at high-altitude alpine and low-altitude desert areas reduce the number of species at both extremes. Life-form patterns clearly change along altitudinal gradient. Annuals with decreasing trend, and hemicryptophytes and chamaephytes with increasing trend along the altitudinal gradient are notable patterns of life form in the area. Temperature, soil moisture and nutrients are the main factors that explain the ecological influence of altitude on species diversity and life-form patterns in the semi-arid steppe vegetation of the area.     

Searching for Altitudinal Zonation: Species Distribution and Vegetation Composition in the Superpáramo of Volcán Iliniza, Ecuador

Altitudinal variation of the zonal superpáramo vegetation was studied between 4300 and 4630 m to test a possible occurrence of a fine altitudinal zonation within the superpáramo belt. A rectangular grid of 1 m² sample plots was established; 25 replicate plots separated by a 3 m space were located along a 100 m long transect parallel to the contours, and there were 17 such transects separated by 20 m of altitude. Species were scored using a 7-grade cover scale and basic environmental data were gathered for each sample. Major changes occur over a short altitudinal range, at around 4400 m, which corresponds to a transition between the lower and upper superpáramo. Species richness sharply declines but species turnover (per altitude) increases along the altitudinal gradient. The correlation between richness and bare ground or rock cover is negative, but the correlation to rocks becomes positive above 4500 m. Species from lower altitudes tend to have narrower altitudinal range, although a large number of species appear to be indifferent to altitude. Direct ordination analyses indicate that high-altitude species show stronger correlation to environmental variables, especially rock, than species from lower altitudes. TWINSPAN cluster analysis delimited 15 groups of samples. There is a change in the clustering pattern along the altitudinal gradient from a horizontal (i.e., within altitude) to vertical (i.e., across altitude) arrangement of the cluster groups, although this pattern is partly obscured at the highest altitudes due to a large number of empty samples. MANOVA tests for samples from adjacent altitudinal levels indicate two distinct altitudinal breaks at lower altitudes, corresponding to the Loricaria-belt in lower superpáramo and the transition between lower and upper superpáramo, while no indication of a zonation was found in upper superpáramo.