Environment Of Plateau Research Articles

Variations in Genome Size of Turnip Landraces from Two High-altitude Environments

Brassica rapa var. rapa (turnip) is considered a main source of food for the inhabitants of the Qinghai-Tibetan Plateau (QTP) and its adjacent highlands when other crops are scarce. The QTP ranges from lat. 25.59°N to 39.49°N and from long. 73.29°E to 104.40°E, whereas the Yunnan Plateau ranges from lat. 20.00°N to 29.16°N and from long. 96.00°E to 110.19°E. A comparison between the turnip landraces of two different plateau environments can provide a mechanistic insight into plant adaptation in highlands. The aim of this investigation was to understand the patterns in variation in genome size (GS) between the turnip landraces of two plateau environments. We used a well-established protocol to count chromosome number and performed propidium iodide flow cytometry to measure GS. No polyploidy was detected among the turnip landraces tested, and 15.5% variation in GS was observed between the landraces. No consistent pattern pertaining to GS variation emerged after the environmental variables were considered. Thus, we propose that such pattern may reflect the indirect effect of selection, random process, genetic drift, or some other factors on GS through interaction of life-form and phenotypic traits.

Detours in long-distance migration across the Qinghai-Tibetan Plateau: individual consistency and habitat associations.

Migratory birds often follow detours when confronted with ecological barriers, and understanding the extent and the underlying drivers of such detours can provide important insights into the associated cost to the annual energy budget and the migration strategies. The Qinghai-Tibetan Plateau is the most daunting geographical barrier for migratory birds because the partial pressure of oxygen is dramatically reduced and flight costs greatly increase. We analyzed the repeated migration detours and habitat associations of four Pallas’s Gulls Larus ichthyaetus across the Qinghai-Tibetan Plateau over 22 migration seasons. Gulls exhibited notable detours, with the maximum distance being more than double that of the expected shortest route, that extended rather than reduced the passage across the plateau. The extent of longitudinal detours significantly increased with latitude, and detours were longer in autumn than in spring. Compared with the expected shortest routes, proximity to water bodies increased along autumn migration routes, but detour-habitat associations were weak along spring migration routes. Thus, habitat availability was likely one, but not the only, factor shaping the extent of detours, and migration routes were determined by different mechanisms between seasons. Significant between-individual variation but high individual consistency in migration timing and routes were revealed in both seasons, indicating a stronger influence of endogenous schedules than local environmental conditions. Gulls may benefit from repeated use of familiar routes and stopover sites, which may be particularly significant in the challenging environment of the Qinghai-Tibetan Plateau.

Transcriptome profile and unique genetic evolution of positively selected genes in yak lungs.

The yak (Bos grunniens), which is a unique bovine breed that is distributed mainly in the Qinghai-Tibetan Plateau, is considered a good model for studying plateau adaptability in mammals. The lungs are important functional organs that enable animals to adapt to their external environment. However, the genetic mechanism underlying the adaptability of yak lungs to harsh plateau environments remains unknown. To explore the unique evolutionary process and genetic mechanism of yak adaptation to plateau environments, we performed transcriptome sequencing of yak and cattle (Bos taurus) lungs using RNA-Seq technology and a subsequent comparison analysis to identify the positively selected genes in the yak. After deep sequencing, a normal transcriptome profile of yak lung that containing a total of 16,815 expressed genes was obtained, and the characteristics of yak lungs transcriptome was described by functional analysis. Furthermore, Ka/Ks comparison statistics result showed that 39 strong positively selected genes are identified from yak lungs. Further GO and KEGG analysis was conducted for the functional annotation of these genes. The results of this study provide valuable data for further explorations of the unique evolutionary process of high-altitude hypoxia adaptation in yaks in the Tibetan Plateau and the genetic mechanism at the molecular level.

Retinal changes following rapid ascent to a high-altitude environment

PurposeTo determine what impact rapid ascension to a high-altitude environment has on the retina with the aim of preventing and treating high-altitude oculopathy.Patients and methodsParticipants in the study were members of the Chinese military assigned to the high-altitude environment of the Tibetan plateau. Ninety-one participants were enrolled in the study. Optical coherence tomography was used to measure the thickness of retina-related indicators. Measurements were taken before and after exposure to the high-altitude environment and upon return to the baseline altitude.ResultsFollowing exposure to the high-altitude environment in Tibet, there was a significant increase in retinal nerve fiber layer (RNFL) thickness in the temporal and nasal quadrants of the optic disc, whilst a significant decrease in RNFL thickness in the inferior optic disc was also observed. A significant increase in RNFL thickness in the superior and inferior macula was also evident, along with a significant increase in the ganglion cell layer thickness in the superior macula. Upon return to the baseline altitude, all measurements returned to baseline levels except for the RNFL of the inferior macula, which was significantly thicker. Pathological changes were also documented in the eyes of nine participants upon returning to baseline altitude, including ischemic optic neuropathy, myopia, and cortical amaurosis.ConclusionsThe high-altitude environment can have a negative impact on the health of the retina and may contribute to the incidence of various eye diseases. This study deepens the understanding of what impact a high-altitude environment has on retina and provides reliable data for blindness prevention and treatment.

Metabolic Alterations of Qinghai-Tibet Plateau Pikas in Adaptation to High Altitude.

Cao, Xue-Feng, Zhen-Zhong Bai, Lan Ma, Shuang Ma, and Ri-Li Ge. Metabolic alterations of Qinghai-Tibet plateau pikas in adaptation to high altitude. High Alt Med Biol. 18:219-225, 2017.-To determine specific metabolic alterations in the myocardium of plateau pikas (Ochotona curzoniae) and potential metabolic biomarkers involved in their adaptation to the high-altitude environment of the Qinghai-Tibet Plateau. Ten pikas were captured by traps in the Kekexili Reserve (4630 m a.s.l; n = 5) and at the foot of the Laji Mountain (2600 m a.s.l; n = 5) on the Qinghai-Tibet Plateau, Qinghai Province, China. Metabolite levels were determined by gas chromatography time-of-flight mass spectrometry (GC-TOF-MS) metabolomics, and multivariate statistical analysis was performed. Several metabolites involved in carbohydrate, fat, energy, and redox homeostasis pathways were significantly altered in pikas living at 4630 m. In addition, those pikas showed increased levels of lactic acid, sarcosine, 4-hydroxybutyrate, methionine, tartaric acid, ribose, tyrosine, pentadecanoic acid, 2-monoolein, 3,5-dihydroxyphenylglycine, trehalose-6-phosphate, succinic acid, myoinositol, fumaric acid, taurine, 2-hydroxybutanoic acid, gluconic acid, citrulline, and glutathione, but decreased levels of oleic acid and 2'-deoxyadenosine 5'-monophosphate. Metabolic activity is significantly altered in the myocardium of pikas in the high-altitude areas of the Qinghai-Tibet Plateau. This study provides important insights into metabolic biomarkers related to the adaptation of pikas to high-altitude hypoxia.

Genome-Wide Identification and Functional Analysis of the Calcineurin B-like Protein and Calcineurin B-like Protein-Interacting Protein Kinase Gene Families in Turnip (Brassica rapa var. rapa)

The calcineurin B-like protein (CBL)–CBL-interacting protein kinase (CIPK) complex has been identified as a primary component in calcium sensors that perceives various stress signals. Turnip (Brassica rapa var. rapa) has been widely cultivated in the Qinghai–Tibet Plateau for a century as a food crop of worldwide economic significance. These CBL–CIPK complexes have been demonstrated to play crucial roles in plant response to various environmental stresses. However, no report is available on the genome-wide characterization of these two gene families in turnip. In the present study, 19 and 51 members of the BrrCBL and BrrCIPK genes, respectively, are first identified in turnip and phylogenetically grouped into three and two distinct clusters, respectively. The expansion of these two gene families is mainly attributable to segmental duplication. Moreover, the differences in expression patterns in quantitative real-time PCR, as well as interaction profiles in the yeast two-hybrid assay, suggest the functional divergence of paralog genes during long-term evolution in turnip. Overexpressing and complement lines in Arabidopsis reveal that BrrCBL9.2 improves, but BrrCBL9.1 does not affect, salt tolerance in Arabidopsis. Thus, the expansion of the BrrCBL and BrrCIPK gene families enables the functional differentiation and evolution of some new gene functions of paralog genes. These paralog genes then play prominent roles in turnip's adaptation to the adverse environment of the Qinghai–Tibet Plateau. Overall, the study results contribute to our understanding of the functions of the CBL–CIPK complex and provide basis for selecting appropriate genes for the in-depth functional studies of BrrCBL–BrrCIPK in turnip.

Bacterial community in the rumen of Tibetan sheep and Gansu alpine fine-wool sheep grazing on the Qinghai-Tibetan Plateau, China.

The rumen microbiome plays a vital role in ruminant nutrition and health, and its community is affected by environmental factors. However, little is known about the rumen bacterial community of ruminants living in the special ecological environment of the Qinghai-Tibetan Plateau (QTP) of China. The objectives of this study were to investigate the rumen bacterial community of the typical plateau sheep (Tibetan sheep, TS, and Gansu alpine fine-wool sheep, GS) grazing on the QTP, using 16S rRNA gene sequence analysis, and to evaluate the relationship between the rumen bacterial community and the QTP environment. A total of 116 sequences (201 clones) were examined and divided into 53 operational taxonomic units (OTUs) in the TS library and 46 OTUs in the GS library. Phylogenetic analysis showed that the sequences that belonged to the Firmicutes were the most predominant bacteria in both TS and GS libraries, representing 79.4% and 62.8% of the total clones, respectively. The remaining sequences belonged to Bacteroidetes, Proteobacteria, Actinobacteria, or were unclassified bacteria. Sequence analysis revealed that the TS and GS rumens harbored many novel sequences associated with uncultured bacteria that accounted for 63.6% and 46.8% of the total clones, respectively. Comparison of the composition and diversity of the TS and GS rumen bacteria revealed few overlapping known bacteria between the two breeds, and a higher diversity in TS. The rumen bacteria of the plateau sheep showed higher percentages of bacteria that belonged to Firmicutes and novel species compared with the low-elevation sheep. The unique bacterial community in the plateau sheep rumens is perhaps one of the major reasons that they can adapt to the harsh plateau environment. These results can help identify the rumen bacterial community of the ruminants in the QTP, and provide bacteria resources and basic data to improve ruminant productivity.

A novel open chest method of right ventricular hemodynamics measurement in pulmonary hypertensive mice

Objective: Right heart catheterization is the gold-standard for measurement of right ventricular hemodynamics. However, it is difficult to perform in mice. We thus aimed to establish a new open chest method to record and analyze the right ventricular hemodynamic parameters in intubated mice connected to a respirator under anesthesia. Methods: Eight-week old male C57BL/6 mice were divided into the control group, and the hypoxia group using completely random method. Mice in the hypoxia group were exposed in low pressure oxygen chamber, which simulated the environment of plateau (5 500 m altitude, 10% oxygen) for 3 weeks. Mice in the control group were exposed in normal pressure and oxygen environment. The mice were intratracheally intubated and connected to a respirator, chest was opened, right ventricular hemodynamics were measured with a needle (0.7 mm×19 mm) punctured into right ventricle (5 mm in death), which was connected to the measuring equipment. Results: The open chest procedure could be finished within 5-10 minutes. The successful rate was 100%. There was no significant difference in heart rate between control group and hypoxia group under anesthetia ((306.4±11.5) bpm vs.(320.4±16.0) bpm, P>0.05). Compared with the control group, both the right ventricular systolic pressure (RVSP) and the mean right ventricular pressure(mRVP)were increased in hypoxia group ((17.1±1.0)mmHg(1 mmHg=0.133 kPa) vs. (22.6±1.0) mmHg, P<0.01; (9.6±0.8) mmHg vs.(12.4±0.3) mmHg, P<0.01). Moreover, the absolute value of the maximal rate of increase in right ventricular pressure (dp/dtmax) and the maximal rate of decrease in right ventricular pressure (dp/dtmin) were higher in the hypoxia group ((421.3±30.6)mmHg/s vs.(639.7±47.7)mmHg/s, P<0.01; (-324.3±24.0)mmHg/s vs. (-496.5±40.6) mmHg/s, P<0.01), indicating the pathological status after hypoxia treatment. Conclusions: Right ventricular hemodynamics measurement with this open chest technique is easy to handle and can accurately reflect the right ventricular pressure in mice under physiological and pathological conditions.

Actual ET modelling based on the Budyko framework and the sustainability of vegetation water use in the loess plateau.

Jointly influenced by the natural factors and the artificial protection measures, the ecological environment of Loess Plateau has been significantly improved in recent years, but which has already brought about some water-related problems. To maintain the balance between precipitation and water consumption is an important foundation for sustainable development of the ecology remediation. This study used Budyko Framework to simulate the actual water consumption of 161 sub-basins from 1990 to 2014. Based on the simulation results, the research also analyzed the evolution characteristics of water balance in Loess Plateau from 1990 to 2014. Results show that, with the increase of vegetation coverage, the regional precipitation and actual evapotranspiration were both showing a significant increasing trend, and the increasing rate of precipitation was 1.91mm/a on average, which was greater than the increasing rate of actual evapotranspiration of 1.34mm/a. To further demonstrate the water balance regime in Loess Plateau, the evapotranspiration coefficient (ECC) was used to quantitatively indicate the ratio of the vegetation water consumption and the total precipitation. The average values of ECC were 0.868, 0.863, 0.851 and 0.837 respectively in four sub-periods of 1990-1999, 2000-2004, 2005-2009 and 2010-2014. The above analyses indicate that with the vegetation recovery and ecological restoration, the percentage of evapotranspiration in the total precipitation is keeping decreasing and in turn the percentage of water yield in the total precipitation is keeping increasing. Consequently, it seems more sustainable for vegetation water use in most areas of Loess Plateau currently.

Prospect of Tourism Development on the Mambilla Plateau: Lessons From Obudu Mountain Resort, Nigeria

&lt;div&gt;&lt;p&gt;&lt;em&gt;Tourism provides one of the most important avenues to achieve economic diversification in Taraba State and Nigeria in particular in the face of the present economic challenges all over the world. This study examines the prospect of tourism development on the Mambilla plateau of Taraba State Nigeria and the lessons that can be drawn from the Obudu Mountain Resort. The data used in this study was generated from &lt;/em&gt;&lt;em&gt;existing sources of data, journal articles, relevant textbooks, online materials, field trips and interviews with government officials and individuals from the study area. The findings of the study shows that despite the rich tourism potentials of the area, traffic flow has been very low owing to a number of challenges. Some of these challenges include inaccessibility of most of the important tourist sites, poor transportation network and connectivity, lack of awareness and poor infrastructural development. The findings of the study also shows striking similarity in the physical environment of Obudu mountain and Mambilla plateau and some of the advantages of the Mambilla plateau over Obudu mountain. Based on the findings of this study, there is need for the government to be more proactive towards tourism development in the area. The state can do well by completing the design of the state tourism development master plan that started many years back. This will provide the required roadmap to tourism development in the state.&lt;/em&gt;&lt;/p&gt;&lt;/div&gt;

Cloning of oligopeptide transport carrier PepT1 and comparative analysis of PepT1 messenger ribonucleic acid expression in response to dietary nitrogen levels in yak () and indigenous cattle () on the Qinghai-Tibetan plateau.

The gastrointestinal lumen can directly absorb all di- and tripeptide protein degradation products, and oligopeptide absorption depends on the specific peptide transport carriers, which are located in gastrointestinal epithelial cells on the brush border membrane. Yak () use N more efficiently than cattle do, which implies that yak have a specific mechanism of nonprotein utilization including a peptide absorption mechanism. However, this mechanism has not been clarified. Our objective was to explore whether yak possess any adaptive mechanisms of peptide absorption to survive in the harsh foraging environment of the Qinghai-Tibetan plateau. Twelve castrated males of each of 2 genotypes, yak () and indigenous cattle (), were fed diets of various N levels. The yak PepT1 (yPepT1) cDNA was cloned in omasum epithelial tissue. Our results showed that the full-length yPepT1 cDNA contains 2,805 bp, and a 2,121-bp open reading frame encodes a putative protein of 707 AA residues. The yPepT1 AA sequence identified 5 putative extracellular N-glycosylation sites (Asn, Asn, Asn, Asn, and Asn), 2 putative intracellular protein kinase A sites (Ser and Thr), and 3 intracellular putative protein kinase C sites (Ser, Ser, and Ser). The yPepT1 AA sequence was 99, 95, 86, and 83% identical to PepT1 from cattle (), sheep (), pigs (), and humans (), respectively. The relative PepT1 mRNA expression for indigenous cattle was greater than yak in the rumen, omasum, duodenum, ileum, and liver ( < 0.001); however, it was lower in jejunum tissue ( < 0.01). The relative PepT1 mRNA expression in response to increasing dietary N for both genotypes were linear in the rumen and jejunum ( < 0.10); quadratic or cubic in the reticulum ( < 0.01); linear or quadratic in the duodenum, ileum, and liver ( ≤ 0.01); and linear, quadratic, or cubic in the omasum ( < 0.001). Moreover, there were significant interactions between genotype and dietary N in rumen, reticulum, omasum, duodenum, jejunum, ileum, and liver tissues. In conclusion, the PepT1 profile and expression in gastrointestinal epithelial cells of yak varied from those of cattle, implying that yak have evolved a peptide transport mechanism to adapt the environment of the Qinghai-Tibetan plateau.

Sediment and State in Imperial China: The Yellow River Watershed as an Earth System and a World System

China’s Yellow River is the most sediment laden water course in the world today, but that came to be the case only about a thousand years ago. It is largely the result of agriculture and deforestation on the fragile environment of the loess plateau in the middle reaches of the watershed. This article demonstrates that the long term environmental degradation of the Yellow River was primarily anthropogenic, and furthermore, it explains how the spatial organization of state power in imperial China amplified the likelihood and consequences of landscape change.

Reconstruction of biological drought conditions during the past 2847 years in an alpine environment of the northeastern Tibetan Plateau, China, and possible linkages to solar forcing

In this study we reconstructed the moisture condition of the eastern Qaidam Basin of the northeastern Tibetan Plateau based on a 3585-year tree ring chronology. The growth environment of Qilian juniper (Sabina przewalskii Kom.) on the mountains in the eastern Qaidam Basin was first determined by comparing precipitation and temperature estimates from two spatial datasets (PRISM and World Climate). Moisture balance was calculated as the sum of simulated moisture deficit (negative) and surplus using a modified Thornthwaite water balance model, and used as a proxy of biological drought conditions. Using data during 1956–2005, we established the transfer function to reconstruct a 2847-year series of January–June moisture balance (843 BCE–2004 CE). With an adjusted R2 value of 0.654 of the transfer function and strong performance in validation, the reconstructed January–June moisture balance can be considered an excellent indicator of biological drought conditions for the study region. The reconstructed series showed strong correlations with reconstructed PDSI in the monsoon Asian region, representing a region of 10° latitudes by 20° longitudes. Using the reconstructed series, we identified centennial-scale dry periods since 843 BCE: 381–277 BCE, 425–520 CE, 1108–1212 CE, 1428–1516 CE, and 1634–1743 CE. Additionally it had statistically significant negative correlations with a monsoon intensity proxy based on oxygen stable isotope from southwestern China (Dongge Cave). Further analyses identified significant relationships with solar activity, especially during the last 700years. We confirmed the ~200-year cyclic pattern in the reconstructed moisture balance series, which matched the known 210-year de Vries solar cycle and peaked during the Little Ice Age. However, the cyclic patterns of the reconstructed moisture balance series and solar activity were decoupled for the period prior to approx. 1300 CE.

Heterogeneous Fault Mechanisms of the 6 October 2008 MW 6.3 Dangxiong (Tibet) Earthquake Using Interferometric Synthetic Aperture Radar Observations

Most current crustal deformation models do not account for topographic effects, crustal lateral variations, and complex fault geometries. To overcome these limitations, we apply finite element models constrained by interferometric Synthetic Aperture Radar (InSAR) images of co-seismic displacements to the 2008 Mw 6.3 Dangxiong earthquake that occurred in Yadong–Gulu rift, southern Tibet. For mountainous plateau environments, InSAR observations are advantageous for studying crustal deformation and crustal medium structure. We evaluate the effect of topography and variations in Poisson’s ratio and elastic moduli on estimation of coseismic deformation from InSAR observations. The results show that coseismic surface displacements are more sensitive to variations in Young’s modulus than to variations in topography and Poisson’s ratio. Therefore, with constant Poisson’s ratio and density, we change the Young’s modulus on each side of the fault to obtain the model that best fits the observations. This is attained when the Young’s moduli in the eastern and western sides of the fault were 2.6 × 1010 Pa and 7.8 × 1010 Pa, respectively. The result is consistent with previous field surveys that the medium on either side of the fault is different.

The genus Scoparia (Lepidoptera, Crambidae) from Galongla Snow Mountain of China, with DNA barcoding and descriptions of three new species

Four species from Galongla Snow Mountain, southeastern Tibet of China are revealed as members of the genus Scoparia by combining DNA barcoding (658 bp of the mitochondrial gene cytochrome c oxidase subunit I, COI) and morphological characters. Three species are described as new to science: S. varians Li, sp. nov., S. nussi Li, sp. nov. and S. lii Li, sp. nov. The female of S. simplicissima Li is described for the first time. All species are described and illustrated, including the habitat, characters of intraspecific variability and sexual dimorphism. A map showing the localities on the Tibetan Plateau, where more than 40% of Chinese Scoparia species are endemic, is also provided. The results suggest the genus Scoparia has high species diversity on the Tibetan Plateau and may exhibit potential for specific adaptation to high plateau environments.

A biogeographic perspective on early human colonization of the Tibetan Plateau

Whence came the early human colonizers of the Tibetan Plateau? Recent genomic research of modern Tibetan gene pool diversity provides evidence of numerous different founding haplogroups among populations. Age estimates suggest that much of the Tibetan gene pool is the product of Holocene migration and admixture, but at least one distinct ancestral haplotype may pre-date the last glacial maximum. Key genes conferring high-altitude adaptation to Tibetan populations suggest that those populations diverged from Han Chinese ancestors between ~8–18calka BP. Diverse Upper Paleolithic technological packages existed in different regions around the margins of the Plateau that could have been carried up by potential early colonizers. However, archeological evidence of early (pre-Neolithic) occupation on the Plateau itself is remarkably uniform, consisting of small short-term camps with a mixed lithic technology featuring simple flakes and shatter, microblades and microcores, larger blades or bladelets, discoidal tablet cores, and occasional bipolar pebble cores; well-dated sites are all post-glacial in age. A simple biogeographic model, the “up from the north” hypothesis, asserts that human groups best suited to colonizing the harsh alpine Plateau environments would have been those adapted to life typical of higher latitudes, and those advantaged northern-latitude colonizers routinely carried microlithic technology with them in hunting the same Palearctic steppe fauna found on the Plateau. The archeological record of early colonizers on the Plateau should therefore be dominated by the north Asian epi-Paleolithic technological package in which microblades were a key component. Complications to this simple model, and possible scenarios addressing the disparity between the evidence from historical genetics and the archeological record, are considered.

Transcriptome sequencing of Crucihimalaya himalaica (Brassicaceae) reveals how Arabidopsis close relative adapt to the Qinghai-Tibet Plateau

The extreme environment of the Qinghai-Tibet Plateau (QTP) provides an ideal natural laboratory for studies on adaptive evolution. Few genome/transcriptome based studies have been conducted on how plants adapt to the environments of QTP compared to numerous studies on vertebrates. Crucihimalaya himalaica is a close relative of Arabidopsis with typical QTP distribution, and is hoped to be a new model system to study speciation and ecological adaptation in extreme environment. In this study, we de novo generated a transcriptome sequence of C. himalaica, with a total of 49,438 unigenes. Compared to five relatives, 10,487 orthogroups were shared by all six species, and 4,286 orthogroups contain putative single copy gene. Further analysis identified 487 extremely significantly positively selected genes (PSGs) in C. himalaica transcriptome. Theses PSGs were enriched in functions related to specific adaptation traits, such as response to radiation, DNA repair, nitrogen metabolism, and stabilization of membrane. These functions are responsible for the adaptation of C. himalaica to the high radiation, soil depletion and low temperature environments on QTP. Our findings indicate that C. himalaica has evolved complex strategies for adapting to the extreme environments on QTP and provide novel insights into genetic mechanisms of highland adaptation in plants.

青藏高原特有种黄绿卷毛菇的地理分布与生态环境的相关性

青藏高原特有种黄绿卷毛菇的地理分布与生态环境的相关性

Effect of atmospheric pressure on air content and air void parameters of concrete

The effects of atmospheric pressure changes on the air-entraining capability of air-entraining admixtures and the air void parameters of hardened concrete are studied using a low-pressure test chamber to simulate plateau environments with thin air and low atmospheric pressure. Results indicate that the atmospheric pressure of the environment significantly affects the performance of air-entraining admixtures. The air content of fresh concrete decreases by approximately 20–49% when the atmospheric pressure is 50 kPa with respect to when at normal atmospheric pressure (101 kPa). The air content of fresh concrete decreases linearly as atmospheric pressure drops. The air void parameters of concrete mixed when atmospheric pressure is low are worse than when it is mixed under normal atmospheric pressure. However, when the air content of hardened concrete reaches a certain value (4%) as the dosage of air-entraining admixtures is increased, the spacing factor could achieve freezing–thawing resistance (300 μm). The enhanced surface tension of liquids at low atmospheric pressure may contribute to the decreased air-entraining capability of air-entraining admixtures.

Intermittent cold exposure results in visceral adipose tissue “browning” in the plateau pika (Ochotona curzoniae)

The plateau pika has developed tolerance to cold and hypoxia in order to adapt to living in the extreme environment of the Qinghai-Tibetan Plateau. One mammalian mechanism for cold adaptation is thermogenesis by brown adipose tissue (BAT), but the degree to which pika exploits this mechanism or how it may be modified by the additional stresses of high altitude is not known. Intermittent Cold Exposure (ICE) is an approachable method to study cold adaptation in rodents. To investigate the role of adipose tissue in the adaptation of pika to cold temperatures, we have studied pika during ICE. We find that pika kept in warm temperatures has little classical brown fat, but “browning” of white adipose tissues is observed rapidly upon cold exposure. This is demonstrated by the increased expression of several markers of brown fat differentiation including uncoupling protein 1 (UCP-1). Surprisingly, this occurs mainly in visceral rather than epididymal adipose tissue. In addition, ICE increases the expression of several general adipose differentiation markers at both the mRNA and protein levels. These substantial changes in the distribution of fat are accomplished without changes in weight or blood levels of glucose and triglycerides, suggesting that the adaptable changes are coordinated and self-compensated. Together, our results demonstrate that ICE promotes recruitment of BAT in pika, and unlike small mammals in at lower altitudes, pika can activate visceral WAT to adapt to cold stress without major changes overall energy balance.