Purpose
The high altitude area is characterized by low pressure and hypoxia, and rapidly entering the high altitude area will cause a series of damage to the body. Some studies have shown that ...hypoxia can cause damage to the reproductive system. In recent years, researchers have been paying attention to the effects of hypoxia on hormone level, ovarian reserve, embryonic development, testicular development, sperm motility level, and have begun to explore its injury mechanism, but its mechanism is not clear. In this paper, the mechanism of hypoxia on the reproductive system is reviewed, which is expected to provide a new idea for solving the problem of the low fertility rate of humans and animals at high altitudes.
Methods
A comprehensive PubMed search was conducted, selecting all relevant peer-reviewed English papers published before January 2022. Other relevant papers were selected from the list of references.
Results
Studies have shown that the complete fertility rate of people living at low altitudes is 7.7, and the complete fertility rate of people living at high altitudes is 4.77, and the hypoxic environment at high altitudes reduces fertility. At the same time, high-altitude, low-oxygen environments are associated with increased infant mortality and post-neonatal mortality. To date, most studies seem to point to a correlation between anoxic exposure at high altitudes and low fertility in humans and animals.
Conclusion
Although the molecular mechanisms are not fully understood, the effects of hypoxia at high altitude on hormonal level, ovarian reserve, embryonic development, testicular development, and sperm motility and levels require further research to investigate this complex topic.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The Qinghai-Tibetan Plateau is a very large land unit and an important terrestrial ecosystem within the Eurasian continent. Because of the harsh climate associated with the high altitude, alpine ...meadows on the plateau are susceptible to degradation from overgrazing. For this region, and for other alpine meadow pastures internationally, there is a need to define the sustainable stocking rate, to develop sound policy pertaining to future land use. Here we report biomass and liveweight gain per animal and per ha for pastures grazed by yaks at high, medium, or low stocking rates over 4 growing seasons from 2010 to 2013. Measures of herbage nutritive value are reported. The influence of inter-year variation in precipitation on standing herbage biomass was also evaluated. Higher precipitation increased standing herbage biomass and herbage nutritive value, indicating that vegetation suffered summer water deficit even in this environment. The sustainable stocking rate in this environment was determined to be approximately 1 yak ha-1 (grown from 80 kg to 120 kg liveweight in 90 d). At this stocking rate, yak weight gain per ha was 88% of that achieved at higher stocking rates typically used by farmers, but with little or no evidence of land degradation.
Full text
Available for:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In 2020, the monitored AQI (Air Quality Index) in plateau-Tibet varied from 24 to 98 and averaged 48, while the PM_(2.5) concentration ranged between 3.0 and 31 μg m^(-3) and with an average of 10 μg ...m^(-3). The plateau-Tibet, had a good air quality, but with a lower atmospheric pressure and low oxygen concentration. As the important characteristic of plateau atmospheric environment, hypobaric hypoxia (HBH) is the key risk factor causing high altitude pulmonary edema (HAPE). It has been reported that the abnormal platelet function caused by HBH is an important pathogenesis of HAPE. In this preliminary study, male Sprague-Dawley rats were randomly divided into control group and HBH 24, 48, and 72-hour exposed groups. A multi-functional hypoxic chamber was used to simulate HAPE model with an altitude of 6000 m, oxygen concentration of 9.46% and partial oxygen pressure of 9.6 KPa. We measured pulmonary wet to dry (W/D) weight ratio, MT-Cox1, MT-Cox2 and MT-Cox3 methylation levels by pyrosequencing on blood samples from all rats and the levels of plasma inflammatory mediators by Luminex liquid chip technology. Results showed that the W/D ratio increased in the HBH-48h and HBH-72h exposed groups significantly (p ＜ 0.05). The mtDNA methylation levels in all HBH exposed groups were lower than pre-exposure (all p value ＜ 0.05). The levels of MT-Cox1, MT-Cox2_Pos2 and MT-Cox2_Pos3 methylation were correlated with W/D ratio significantly (r = 0.16-0.20, p ＜ 0.05). And a strong correlation was found between some inflammatory cytokines (IL 4, IL 6, IL 10 and IL 12p70) and MT-Cox2 methylation levels (r = 0.09-0.30, p ＜ 0.05). In conclusion, HBH exposures can induce alterations in platelet mtDNA methylation in HAPE, which may be related to unfavorable effects on HAPE caused by the inflammation through the regulation of inflammatory response.
The cold and hypoxic conditions at high altitude necessitate high metabolic O
demands to support thermogenesis while hypoxia reduces O
availability. Skeletal muscles play key roles in thermogenesis, ...but our appreciation of muscle plasticity and adaptation at high altitude has been hindered by past emphasis on only a small number of muscles. We examined this issue in deer mice (
). Mice derived from both high-altitude and low-altitude populations were born and raised in captivity and then acclimated as adults to normoxia or hypobaric hypoxia (12 kPa O
for 6-8 wk). Maximal activities of citrate synthase (CS), cytochrome
oxidase (COX), β-hydroxyacyl-CoA dehydrogenase (HOAD), hexokinase (HK), pyruvate kinase (PK), and lactate dehydrogenase (LDH) were measured in 20 muscles involved in shivering, locomotion, body posture, ventilation, and mastication. Principal components analysis revealed an overall difference in muscle phenotype between populations but no effect of hypoxia acclimation. High-altitude mice had greater activities of mitochondrial enzymes and/or lower activities of PK or LDH across many (but not all) respiratory, limb, core and mastication muscles compared with low-altitude mice. In contrast, chronic hypoxia had very few effects across muscles. Further examination of CS in the gastrocnemius showed that population differences in enzyme activity stemmed from differences in protein abundance and mRNA expression but not from population differences in CS amino acid sequence. Overall, our results suggest that evolved increases in oxidative capacity across many skeletal muscles, at least partially driven by differences in transcriptional regulation, may contribute to high-altitude adaptation in deer mice.
Most previous studies of muscle plasticity and adaptation in high-altitude environments have focused on a very limited number of skeletal muscles. Comparing high-altitude versus low-altitude populations of deer mice, we show that a large number of muscles involved in shivering, locomotion, body posture, ventilation, and mastication exhibit greater mitochondrial enzyme activities in the high-altitude population. Therefore, evolved increases in mitochondrial oxidative capacity across skeletal muscles contribute to high-altitude adaptation.
High-altitude electromagnetic pulse (HEMP) has the competence to produce extensive and even eternal disruption when interacting with modern power grid. In order to provide a better protection of ...power grid, it is necessary to understand the influence. In this article, the power grid is analyzed using a dynamical model based on Kuramoto-like oscillators, and the HEMP is considered as a wide-range interference source. It generates transient high-voltage interference through the transmission line coupling, which may damage the transformer. Failure of the transformer will change the connection of power grid, which may lead to a frequency deviation of 10 Hz at each node for the considered IEEE 57-node model. The oscillation of nodes can lead to the failure of the power grid. Those results reveal the impact of HEMP on synchronous stability of complex power grid. By modeling and analyzing the effect of HEMP on the power grid, the power quality and stability of the power grid can be comprehensively evaluated, which provides important information that supports the optimization of the power system facing wide-rage electromagnetic interference.
Aim
We examined the effects of chronic hypoxia on diaphragm function in high‐ and low‐altitude populations of Peromyscus mice.
Methods
Deer mice (P. maniculatus) native to high altitude and ...congeneric mice native to low altitude (P. leucopus) were born and raised in captivity to adulthood and were acclimated to normoxia or hypobaric hypoxia (12 or 9 kPa, simulating hypoxia at 4300 and 7000 m) for 6‐8 weeks. We then measured indices of mitochondrial respiration capacity, force production, and fatigue resistance in the diaphragm.
Results
Mitochondrial respiratory capacities (assessed using permeabilized fibres with single or multiple inputs to the electron transport system), citrate synthase activity (a marker of mitochondrial volume), twitch force production, and muscle fatigue resistance increased after exposure to chronic hypoxia in both populations. These changes were not well explained by variation in the fibre‐type composition of the muscle. However, there were several differences in diaphragm function in high‐altitude mice compared to low‐altitude mice. Exposure to a deeper level of hypoxia (9 kPa vs 12 kPa) was needed to elicit increases in mitochondrial respiration rates in highlanders. Chronic hypoxia did not increase the emission of reactive oxygen species from permeabilized fibres in highlanders, in contrast to the pronounced increases that occurred in lowlanders. In general, the diaphragm of high‐altitude mice had greater capillary length densities, produced less force in response to stimulation and had shorter relaxation times. The latter was associated with higher activity of sarcoplasmic reticulum Ca2+‐ATPase (SERCA) activity in the diaphragm of high‐altitude mice.
Conclusion
Overall, our work suggests that exposure to chronic hypoxia increases the capacities for mitochondrial respiration, force production and fatigue resistance of the diaphragm. However, many of these effects are opposed by evolved changes in diaphragm function in high‐altitude natives, such that highlanders in chronic hypoxia maintain similar diaphragm function to lowlanders in sea level conditions.
Full text
Available for:
DOBA, FSPLJ, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
Steady gamma-ray emission up to at least 200 GeV has been detected from the solar disk in the Fermi-LAT data, with the brightest, hardest emission occurring during solar minimum. The likely cause is ...hadronic cosmic rays undergoing collisions in the Sun’s atmosphere after being redirected from ingoing to outgoing in magnetic fields, though the exact mechanism is not understood. An important new test of the gamma-ray production mechanism will follow from observations at higher energies. Only the High Altitude Water Cherenkov (HAWC) Observatory has the required sensitivity to effectively probe the Sun in the TeV range. Using 3 years of HAWC data from November 2014 to December 2017, just prior to the solar minimum, we search for 1–100 TeV gamma rays from the solar disk. No evidence of a signal is observed, and we set strong upper limits on the flux at a few 10−12 TeV − 1 cm − 2 s − 1 at 1 TeV. Our limit, which is the most constraining result on TeV gamma rays from the Sun, is ∼ 10 % of the theoretical maximum flux (based on a model where all incoming cosmic rays produce outgoing photons), which in turn is comparable to the Fermi-LAT data near 100 GeV. The prospects for a first TeV detection of the Sun by HAWC are especially high during the solar minimum, which began in early 2018.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UM
Abstract
Background
Species living at high altitude are subject to strong selective pressures due to inhospitable environments (e.g., hypoxia, low temperature, high solar radiation, and lack of ...biological production), making these species valuable models for comparative analyses of local adaptation. Studies that have examined high-altitude adaptation have identified a vast array of rapidly evolving genes that characterize the dramatic phenotypic changes in high-altitude animals. However, how high-altitude environment shapes gene expression programs remains largely unknown.
Findings
We generated a total of 910 Gb of high-quality RNA-seq data for 180 samples derived from 6 tissues of 5 agriculturally important high-altitude vertebrates (Tibetan chicken, Tibetan pig, Tibetan sheep, Tibetan goat, and yak) and their cross-fertile relatives living in geographically neighboring low-altitude regions. Of these, ∼75% reads could be aligned to their respective reference genomes, and on average ∼60% of annotated protein coding genes in each organism showed FPKM expression values greater than 0.5. We observed a general concordance in topological relationships between the nucleotide alignments and gene expression–based trees. Tissue and species accounted for markedly more variance than altitude based on either the expression or the alternative splicing patterns. Cross-species clustering analyses showed a tissue-dominated pattern of gene expression and a species-dominated pattern for alternative splicing. We also identified numerous differentially expressed genes that could potentially be involved in phenotypic divergence shaped by high-altitude adaptation.
Conclusions
These data serve as a valuable resource for examining the convergence and divergence of gene expression changes between species as they adapt or acclimatize to high-altitude environments.
Neonatal pulse oximetry screening (POS) algorithms for critical congenital heart disease (CCHD) have contributed towards decreasing neonatal mortality but cannot be applied at high altitudes. New POS ...algorithms at high altitudes are needed.
This observational, prospective study included newborns born at different altitudes from 0 to 4380 meters above the sea level in Peru. Healthy newborns underwent neonatal preductal and postductal oximetry, echocardiography and telephonic follow-up up to 12 months of age. Newborns with CCHD underwent preductal and postductal oximetry at the time of telemedicine evaluation while located at the high-altitude hospital where they were born, and their diagnoses were confirmed with echocardiography locally or after arriving to the referral center. Two new algorithms were designed using clinically accepted neonatal oximetry cutoffs or the 5th and 10th percentiles for preductal and postductal oximetry values.
A total of 502 healthy newborns and 15 newborns with CCHD were enrolled. Echocardiography and telephonic follow-up were completed in 227 (45%) and 330 healthy newborns (65%), respectively. The algorithm based on clinically accepted cutoffs had a sensitivity of 92%, specificity of 73% and false positive rate of 27% The algorithm based on the 5th and 10th percentiles had a sensitivity of 80%, specificity of 88% and false positive rate of 12%.
Two algorithms that detect CCHD at different altitudes had adequate performance but high false positive rates.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
High‐altitude indoctrination (HAI) trains individuals to recognize symptoms of hypoxia by simulating high‐altitude conditions using normobaric (NH) or hypobaric (HH) hypoxia. Previous studies suggest ...that despite equivalent inspired oxygen levels, physiological differences could exist between these conditions. In particular, differences in neurophysiological responses to these conditions are not clear. Our study aimed to investigate correlations between oxygen saturation (SpO2) and neural responses in NH and HH. We recorded 5‐min of resting‐state eyes‐open electroencephalogram (EEG) and SpO2 during control, NH, and HH conditions from 13 participants. We applied a multivariate framework to characterize correlations between SpO2 and EEG measures (spectral power and multiscale entropy MSE), within each participant and at the group level. Participants were desaturating during the first 150 s of NH versus steadily desaturated in HH. We considered the entire time interval, first and second half intervals, separately. All the conditions were characterized by statistically significant participant‐specific patterns of EEG–SpO2 correlations. However, at the group level, the desaturation period expressed a robust pattern of these correlations across frequencies and brain locations. Specifically, the first 150 s of NH during desaturation differed significantly from the other conditions with negative absolute alpha power–SpO2 correlations and positive MSE–SpO2 correlations. Once steadily desaturated, NH and HH had no significant differences in EEG–SpO2 correlations. Our findings indicate that the desaturating phase of hypoxia is a critical period in HAI courses, which would require developing strategies for mitigating the hypoxic stimulus in a real‐world situation.
It is still unknown whether there are differences in neurophysiological responses to normobaric and hypobaric hypoxia, as normobaric hypoxia is often used as a proxy for hypobaric hypoxia during research and hypoxia awareness courses. We collected 5‐min of eyes‐open resting‐state data with an electroencephalogram (EEG) and oxygen saturation (SpO2) monitor from 13 participants during normobaric hypoxia, hypobaric hypoxia, and normobaric normoxia. We found that there is less variability in the spatiotemporal patterns of EEG–SpO2 correlations during the desaturation phase of normabric hypoxia when compared to a stable desaturated phase.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
You have reached the maximum number of search results that are displayed.
For better performance, the search offers a maximum of 1,000 results per query (or 50 pages if the option 10/page is selected).
Consider using result filters or changing the sort order to explore your results further.
PDF
