A redução no número de variedades comerciais disponíveis, a partir da liberação de cultivares transgênicas de milho, compromete a autonomia e a consolidação de sistemas orgânicos de produção. ...Objetivou-se avaliar, em duas localidades com altitudes distintas, características agronômicas e componentes de produção de cinco variedades comerciais (AL Avaré, AL Bandeirante, Cativerde 02, AL Piratininga e UFVM 200 - Soberano) e duas variedades crioulas (Santa Rita 1 e Santa Rita 2), em sistema orgânico de produção. O experimento foi conduzido em esquema fatorial 2x7, sendo o primeiro fator dois locais com altitudes distintas (Muzambinho/MG, 1100 m de altitude e Araras/SP, 665 m de altitude) e o segundo fator composto por sete variedades de milho, em delineamento de blocos casualizados, com quatro repetições. Avaliou-se diâmetro de colmo, altura de plantas, altura de inserção e número de folhas acima da espiga superior, índice de clorofila total Falker, teor de nitrogênio foliar, número de fileiras por espiga, de grãos por fileira e de grãos por espiga, acamamento, estande final, peso de 1000 grãos e produtividade. O ambiente, principalmente os efeitos da altitude, temperatura média noturna e diurna e a distribuição da precipitação pluviométrica, mostrou-se o fator mais importante para o rendimento de grãos de milho. O comportamento agronômico de todas as variedades foi superior em Muzambinho. A variedade AL Piratininga apresentou adequado desempenho agronômico tanto em alta quanto em baixa altitude e, em ambos os locais, as variedades crioulas apresentaram desempenho semelhante ao das convencionais.
Individuals ascending rapidly to altitudes >2500 m may develop symptoms of acute mountain sickness (AMS) within a few hours of arrival and/or high-altitude pulmonary edema (HAPE), which occurs ...typically during the first three days after reaching altitudes above 3000-3500 m. Both diseases have distinct pathologies, but both present with a pronounced decrease in oxygen saturation of hemoglobin in arterial blood (SO
). This raises the question of mechanisms impairing the diffusion of oxygen (O
) across the alveolar wall and whether the higher degree of hypoxemia is in causal relationship with developing the respective symptoms. In an attempt to answer these questions this article will review factors affecting alveolar gas diffusion, such as alveolar ventilation, the alveolar-to-arterial O
-gradient, and balance between filtration of fluid into the alveolar space and its clearance, and relate them to the respective disease. The resultant analysis reveals that in both AMS and HAPE the main pathophysiologic mechanisms are activated before aggravated decrease in SO
occurs, indicating that impaired alveolar epithelial function and the resultant diffusion limitation for oxygen may rather be a consequence, not the primary cause, of these altitude-related illnesses.
High-altitude illnesses (HAIs) result from acute exposure to high altitude/hypoxia. Numerous molecular mechanisms affect appropriate acclimatization to hypobaric and/or normobaric hypoxia and curtail ...the development of HAIs. The understanding of these mechanisms is essential to optimize hypoxic acclimatization for efficient prophylaxis and treatment of HAIs. This review aims to link outcomes of molecular mechanisms to either adverse effects of acute high-altitude/hypoxia exposure or the developing tolerance with acclimatization. After summarizing systemic physiological responses to acute high-altitude exposure, the associated acclimatization, and the epidemiology and pathophysiology of various HAIs, the article focuses on molecular adjustments and maladjustments during acute exposure and acclimatization to high altitude/hypoxia. Pivotal modifying mechanisms include molecular responses orchestrated by transcription factors, most notably hypoxia inducible factors, and reciprocal effects on mitochondrial functions and REDOX homeostasis. In addition, discussed are genetic factors and the resultant proteomic profiles determining these hypoxia-modifying mechanisms culminating in successful high-altitude acclimatization. Lastly, the article discusses practical considerations related to the molecular aspects of acclimatization and altitude training strategies.
Denisovans are members of a hominin group who are currently only known directly from fragmentary fossils, the genomes of which have been studied from a single site, Denisova Cave
in Siberia. They are ...also known indirectly from their genetic legacy through gene flow into several low-altitude East Asian populations
and high-altitude modern Tibetans
. The lack of morphologically informative Denisovan fossils hinders our ability to connect geographically and temporally dispersed fossil hominins from Asia and to understand in a coherent manner their relation to recent Asian populations. This includes understanding the genetic adaptation of humans to the high-altitude Tibetan Plateau
, which was inherited from the Denisovans. Here we report a Denisovan mandible, identified by ancient protein analysis
, found on the Tibetan Plateau in Baishiya Karst Cave, Xiahe, Gansu, China. We determine the mandible to be at least 160 thousand years old through U-series dating of an adhering carbonate matrix. The Xiahe specimen provides direct evidence of the Denisovans outside the Altai Mountains and its analysis unique insights into Denisovan mandibular and dental morphology. Our results indicate that archaic hominins occupied the Tibetan Plateau in the Middle Pleistocene epoch and successfully adapted to high-altitude hypoxic environments long before the regional arrival of modern Homo sapiens.
Aims
Alpine ecosystems are important terrestrial carbon (C) pools, and microbial decomposers play a key role in cycling soil C. Microbial metabolic limitations in these ecosystems, however, have ...rarely been studied. The objectives of this study are to reveal the characteristics of microbial nutrient limitation, and decipher the drivers in the alpine ecosystems.
Methods
Models of extracellular enzymatic stoichiometry were applied to examine and compare the metabolic limitations of the microbial communities in bulk and rhizosphere soils along an altitudinal gradient (2800–3500 m a.s.l.) under the same type of vegetation (
Abies fabri
) on Gongga Mountain, eastern Tibetan Plateau.
Results
The soil microbial communities suffered from relative C and phosphorus (P) limitations in the alpine ecosystem despite of high soil nutrient contents here. Partial least squares path modelling (PLS-PM) revealed that the limitations were directly regulated by soil nutrient stoichiometry, followed by nutrient availability. The C and P limitations were higher at the high altitudes (3000–3500 m) than that at the low altitude (2800 m), which mainly attribute to changes of soil temperature and moisture along the altitudinal gradient. This suggested that global warming may relieve microbial metabolic limitation in the alpine ecosystems, and then is conducive to the retention of organic C in soil. Furthermore, the C and P limitations varied significantly between the bulk and rhizosphere soils at the high altitudes (3200–3500 m), but not at the low altitudes. This indicated the influences of vegetation on the microbial metabolisms, while the influences could decrease under the scenario of global warming.
Conclusions
Our study suggests that the alpine ecosystems with high organic C storage harbour abundant microbial populations limited by relative C and P, which have sensitive metabolic characteristics. This could thus potentially lead to large fluctuations in the soil C turnover under climate change. The study provides important insights linking microbial metabolisms to the environmental gradients, and improves our understanding of C cycling in alpine ecosystems.
Acute mountain sickness (AMS) affects more than 25% of individuals ascending to 3500 m (11 500 ft) and more than 50% of those above 6000 m (19 700 ft). AMS may progress from nonspecific symptoms to ...life-threatening high-altitude cerebral edema in less than 1% of patients. It is not clear how to best diagnose AMS.
To systematically review studies assessing the accuracy of AMS diagnostic instruments, including the visual analog scale (VAS) score, which quantifies the overall feeling of sickness at altitude (VASO; various thresholds), Acute Mountain Sickness-Cerebral score (AMS-C; ≥0.7 indicates AMS), and the clinical functional score (CFS; ≥2 indicates AMS) compared with the Lake Louise Questionnaire Score (LLQS; score of ≥5).
Searches of MEDLINE and EMBASE from inception to May 2017 identified 1245 publications of which 91 were suitable for prevalence analysis (66 944 participants) and 14 compared at least 2 instruments (1858 participants) using a score of 5 or greater on the LLQS as a reference standard. To determine the prevalence of AMS for establishing the pretest probability of AMS, a random-effects meta-regression was performed based on the reported prevalence of AMS as a function of altitude.
AMS prevalence, likelihood ratios (LRs), sensitivity, and specificity of screening instruments.
The final analysis included 91 articles (comprising 66 944 study participants). Altitude predicted AMS and accounted for 28% of heterogeneity between studies. For each 1000-m (3300-ft) increase in altitude above 2500 m (8200 ft), AMS prevalence increased 13% (95% CI, 9.5%-17%). Testing characteristics were similar for VAS(O), AMS-C, and CFS vs a score of 5 or greater on the LLQS (positive LRs: range, 3.2-8.2; P = .22 for comparisons; specificity range, 67%-92%; negative LRs: range, 0.30-0.36; P = .50 for comparisons; sensitivity range, 67%-82%). The CFS asks a single question: "overall if you had any symptoms, how did they affect your activity (ordinal scale 0-3)?" For CFS, moderate to severe reduction in daily activities had a positive LR of 3.2 (95% CI, 1.4-7.2) and specificity of 67% (95% CI, 37%-97%); no reduction to mild reduction in activities had a negative LR of 0.30 (95% CI, 0.22-0.39) and sensitivity of 82% (95% CI, 77%-87%).
The prevalence of acute mountain sickness increases with higher altitudes. The visual analog scale for the overall feeling of sickness at altitude, Acute Mountain Sickness-Cerebral, and clinical functional score perform similarly to the Lake Louise Questionnaire Score using a score of 5 or greater as a reference standard. In clinical and travel settings, the clinical functional score is the simplest instrument to use. Clinicians evaluating high-altitude travelers who report moderate to severe limitations in activities of daily living (clinical functional score ≥2) should use the Lake Louise Questionnaire Score to assess the severity of acute mountain sickness.
Villafuerte, Francisco C., and Noemí Corante. Chronic mountain sickness: clinical aspects, etiology, management, and treatment. High Alt Med Biol. 17:61-69, 2016.-Millions of people worldwide live at ...a high altitude, and a significant number are at risk of developing Chronic Mountain Sickness (CMS), a progressive incapacitating syndrome caused by lifelong exposure to hypoxia. CMS is characterized by severe symptomatic excessive erythrocytosis (EE; Hb ≥19 g/dL for women and Hb ≥21 g/dL for men) and accentuated hypoxemia, which are frequently associated with pulmonary hypertension. In advanced cases, the condition may evolve to cor pulmonale and congestive heart failure. Current knowledge indicates a genetic predisposition to develop CMS. However, there are important risk factors and comorbidities that may trigger and aggravate the condition. Thus, appropriate medical information on CMS is necessary to provide adequate diagnosis and healthcare to high-altitude inhabitants. After reviewing basic clinical aspects of CMS, including its definition, diagnosis, and common clinical findings, we discuss aspects of its etiology, and address its epidemiology, risk factors, and treatment.
Intraocular pressure changes at high altitude Mayhook‐Walker, India; Westwood, Jessica; Simpkins, Ciaran ...
Acta ophthalmologica (Oxford, England),
December 2022, 2022-12-00, 20221201, Volume:
100, Issue:
S275
Journal Article
Peer reviewed
Purpose: The effect of altitude on Intraocular Pressure has been debated for decades. The literature is unclear, encompassing exertional and non‐exertional ascents, as well as simulated ascents, with ...most finding a decrease in IOP, but some finding no change or an increase. Additionally, several papers have previously corrected IOP for Central Corneal Thickness, further confounding efforts to draw conclusions from the literature. The Imperial Remote Medicine BSc's Morocco expedition aimed to assess changes in IOP and CCT during an exertional winter ascent of Mount Toubkal (4167 m) which to our knowledge is the first exertional study conducted partially in sub‐zero temperatures.
Methods: IOP, CCT, clinical parameters and Lake Louise Score (LLS) were recorded daily in 9 participants before, 1 month after and during the expedition. Participants flew into Marrakesh, ascended to Imlil (1886 m) by car, and ascended from there on foot, stayed at the Nelter refuge for 3 nights (3037 m). All measurements were taken in the evening. IOP was measured using an iCare ic200 tonometer. Total IOP and CCT per participant per day was used to assess more fully the overall change in IOP and CCT across the expedition. Differences between eyes were also assessed.
Results: No significant change in IOP was seen. CCT increased significantly at altitude. IOP was significantly positively correlated with LLS and headache, and significantly negatively correlated with SpO2. In line with current clinical practice, IOP was not adjusted for CCT. There was no difference in IOP or CCT between contact users and non‐contact users.
Conclusions: The increase in CCT is in line with the existing literature. The lack of significant change in IOP has precedence, and we propose that it is the interplay of physiological changes at altitude, alongside other factors such as exertion and temperature that alter IOP rather than IOP changes simply being a function of altitude.
Multi- and hyperspectral cameras on drones can be valuable tools in environmental monitoring. A significant shortcoming complicating their usage in quantitative remote sensing applications is ...insufficient robust radiometric calibration methods. In a direct reflectance transformation method, the drone is equipped with a camera and an irradiance sensor, allowing transformation of image pixel values to reflectance factors without ground reference data. This method requires the sensors to be calibrated with higher accuracy than what is usually required by the empirical line method (ELM), but consequently it offers benefits in robustness, ease of operation, and ability to be used on Beyond-Visual Line of Sight flights. The objective of this study was to develop and assess a drone-based workflow for direct reflectance transformation and implement it on our hyperspectral remote sensing system. A novel atmospheric correction method is also introduced, using two reference panels, but, unlike in the ELM, the correction is not directly affected by changes in the illumination. The sensor system consists of a hyperspectral camera (Rikola HSI, by Senop) and an onboard irradiance spectrometer (FGI AIRS), which were both given thorough radiometric calibrations. In laboratory tests and in a flight experiment, the FGI AIRS tilt-corrected irradiances had accuracy better than 1.9% at solar zenith angles up to 70°. The system's low-altitude reflectance factor accuracy was assessed in a flight experiment using reflectance reference panels, where the normalized root mean square errors (NRMSE) were less than ±2% for the light panels (25% and 50%) and less than ±4% for the dark panels (5% and 10%). In the high-altitude images, taken at 100–150 m altitude, the NRMSEs without atmospheric correction were within 1.4%–8.7% for VIS bands and 2.0%–18.5% for NIR bands. Significant atmospheric effects appeared already at 50 m flight altitude. The proposed atmospheric correction was found to be practical and it decreased the high-altitude NRMSEs to 1.3%–2.6% for VIS bands and to 2.3%–5.3% for NIR bands. Overall, the workflow was found to be efficient and to provide similar accuracies as the ELM, but providing operational advantages in such challenging scenarios as in forest monitoring, large-scale autonomous mapping tasks, and real-time applications. Tests in varying illumination conditions showed that the reflectance factors of the gravel and vegetation targets varied up to 8% between sunny and cloudy conditions due to reflectance anisotropy effects, while the direct reflectance workflow had better accuracy. This suggests that the varying illumination conditions have to be further accounted for in drone-based in quantitative remote sensing applications.
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•We propose a direct reflectance workflow for drone hyperspectral imaging.•A novel atmospheric correction method for direct reflectance workflows•Radiometric calibration of the hyperspectral camera and the irradiance sensor•The tilt-corrected onboard irradiances had accuracy better than 1.9%.•The reflectance factors had a max error of 2.6% in VIS bands and 5.3% in NIR bands.
To provide guidance to clinicians about best practices, the Wilderness Medical Society (WMS) convened an expert panel to develop evidence-based guidelines for prevention, diagnosis, and treatment of ...acute mountain sickness, high altitude cerebral edema, and high altitude pulmonary edema. Recommendations are graded based on the quality of supporting evidence and the balance between the benefits and risks/burdens according to criteria put forth by the American College of Chest Physicians. The guidelines also provide suggested approaches for managing each form of acute altitude illness that incorporate these recommendations as well as recommendations on how to approach high altitude travel following COVID-19 infection. This is an updated version of the original WMS Consensus Guidelines for the Prevention and Treatment of Acute Altitude Illness published in Wilderness & Environmental Medicine in 2010 and the subsequently updated WMS Practice Guidelines for the Prevention and Treatment of Acute Altitude Illness published in 2014 and 2019.
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