Left ventricular strain changes at high altitude in rats: a cardiac magnetic resonance tissue tracking imaging study

BACKGROUND

Long-term exposure to a high altitude environment with low pressure and low oxygen could cause abnormalities in the structure and function of the heart. Myocardial strain is a sensitive indicator for assessing myocardial dysfunction, monitoring myocardial strain is of great significance for the early diagnosis and treatment of high altitude heart-related diseases. This study applies cardiac magnetic resonance tissue tracking technology (CMR-TT) to evaluate the changes in left ventricular myocardial function and structure in rats in high altitude environment.

METHODS

6-week-old male rats were randomized into plateau hypoxia rats (plateau group, n = 21) as the experimental group and plain rats (plain group, n = 10) as the control group. plateau group rats were transported from Chengdu (altitude: 360 m), a city in a plateau located in southwestern China, to the Qinghai-Tibet Plateau (altitude: 3850 m), Yushu, China, and then fed for 12 weeks there, while plain group rats were fed in Chengdu(altitude: 360 m), China. Using 7.0 T cardiac magnetic resonance (CMR) to evaluate the left ventricular ejection fraction (EF), end-diastolic volume (EDV), end-systolic volume (ESV) and stroke volume (SV), as well as myocardial strain parameters including the peak global longitudinal (GLS), radial (GRS), and circumferential strain (GCS). The rats were euthanized and a myocardial biopsy was obtained after the magnetic resonance imaging scan.

RESULTS

The plateau rats showed more lower left ventricular GLS and GRS (P < 0.05) than the plain rats. However, there was no statistically significant difference in left ventricular EDV, ESV, SV, EF and GCS compared to the plain rats (P > 0.05).

CONCLUSIONS

After 12 weeks of exposure to high altitude low-pressure hypoxia environment, the left ventricular global strain was partially decreased and myocardium is damaged, while the whole heart ejection fraction was still preserved, the myocardial strain was more sensitive than the ejection fraction in monitoring cardiac function.

Altitude-associated trends in bacterial communities in ultrahigh-altitude residences

BACKGROUND

Indoor bacterial communities may change with altitude because their major contributors, outdoor bacterial communities, vary with altitude. People's health effects from bacteria inhalation exposure can also vary with altitude because human respiratory physiology changes with oxygen content in air. Accordingly, adjusting indoor bacterial communities may help to acclimate newcomers from low-altitude environments to ultrahigh-altitude environments. To lay the groundwork for further research, we aimed to first elucidate the bacterial communities in ultrahigh-altitude residences and the effects of altitude on these communities. We collected 187 environmental samples from residential communities at ultrahigh altitudes of 3811-4651 m in Ngari, China and sequenced bacterial 16S rRNA genes.

RESULTS

On one hand, when abundant genera in ultrahigh-altitude residences and those reported by previous studies on low-altitude residences were compared, nine genera were shared, whereas other five genera were abundant only at ultrahigh altitudes. On the other hand, when the bacterial communities of residences at different ultrahigh altitudes were further compared, the bacterial composition in indoor surface samples varied significantly with altitude. The relative abundance of five bacterial genera in indoor air samples and 10 genera and three phyla in indoor surface samples varied monotonically with altitude.

CONCLUSIONS

Altitude may be a long-neglected factor that shapes residential bacterial communities and thus warrants attention.

Low CO2 concentration, a key environmental factor for developing plateau adapted rapeseed

BACKGROUND

Photosynthesis is a fundamental process that underlies the formation of crop yield, wherein light serves as the driving force and carbon dioxide (CO2) as the raw material. These two factors have a direct influence on the progress and efficiency of photosynthesis in crops. Rapeseed is one of the four major oilseed crops worldwide. Plateau rapeseed has now become a research hotspot. However, the lack of high-yielding rapeseed germplasm resources on the plateau and the highly efficient strategy for screening them severely affect the development of rapeseed industry in plateau.

RESULTS

In the rapeseed experimental fields located on the plateau (Lhasa, Tibet), we measured abundant sunlight, characterized by an average daily photosynthetically active radiation (PAR) of 1413 μmol m-2 s-1. In addition, the atmospheric CO2 concentrations range from 300 to 400 ppm, which is only two-thirds of that in the plain (Chengdu, Sichuan). We found that under different measurement conditions of light intensity and CO2 concentration, different rapeseed genotypes showed significant differences in leaf photosynthetic efficiency during the seedling stage. Moreover, the rapeseed materials with high photosynthetic efficiency under low CO2 concentrations rather than high light intensity, exhibited significant advantages in biomass, yield, and oil content when cultivated on the plateau, indicating that the CO2 is the key environmental factor which limited rapeseed production in plateau. Based on photosynthetic efficiency screening under low CO2 concentrations, six rapeseed varieties SC3, SC10, SC25, SC27, SC29 and SC37, shown significantly higher yields in plateau environment compared to local control variety were obtained. In addition, the adaptability of rapeseed to plateau was found to be related to the activities of key Calvin cycle enzymes and the accumulation of photosynthetic products.

CONCLUSIONS

This study established a screening strategy for plateau high-yielding rapeseed materials, obtained six varieties which were suitable for plateau cultivation, explored the mechanism of rapeseed response to the plateau environment, and thus provides a feasible strategy for plateau-adapted rapeseed breeding.

The prone posteromedial approach to the knee revisited: a safe and effective strategy for posterior tibial plateau fractures

PURPOSE

To compare outcomes of patients with posterior tibial plateau fractures who underwent repair indirectly with an anterior approach to those who underwent direct repair with a prone "Lobenhoffer" operative approach.

METHODS

A total of 44 patients with a posterior column tibial plateau fracture that underwent repair were identified. Twenty-two patients with 22 tibial plateau fractures were fixed using a prone Lobenhoffer approach. They were compared to 22 patients treated with an indirect reduction using a supine approach for similar fracture patterns. Data collection at minimum 1 year included: patient-reported outcome scores (SMFA), patient-reported pain, knee range of motion, complications and need for reoperation. Radiographs were reviewed for knee alignment, residual depression and fracture healing.

RESULTS

All demographics were similar between the groups except BMI, which was lower in the prone group (P < 0.05). Fracture type according to age, Schatzker and three-column classification was matched between cohorts. There was no difference in outcomes including: pain, radiographic knee alignment, residual articular depression, functional outcome (SMFA), complications and need for reoperations. Knee flexion at 1 year was greater in the prone group (127.8 vs. 115.8; P = 0.018). In addition, surgical time was less in the prone group (mean 73.7 min vs. 82.3 min; P = 0.015).

CONCLUSION

The Lobenhoffer approach with direct reduction of posterior fracture fragments for complex tibial plateau fractures is an excellent option for these injuries. It allowed for faster surgery with improved ultimate knee range of motion in posterior column tibial plateau fractures.

Comprehensive viewpoints on heart rate variability at high altitude

OBJECTIVES

Hypoxia is a physiological state characterized by reduced oxygen levels in organs and tissues. It is a common clinicopathological process and a major cause of health problems in highland areas.  Heart rate variability (HRV) is a measure of the balance in autonomic innervation to the heart. It provides valuable information on the regulation of the cardiovascular system by neurohumoral factors, and changes in HRV reflect the complex interactions between multiple systems. In this review, we provide a comprehensive overview of the relationship between high-altitude hypoxia and HRV. We summarize the different mechanisms of diseases caused by hypoxia and explore the changes in HRV across various systems. Additionally, we discuss relevant pharmaceutical interventions. Overall, this review aims to provide research ideas and assistance for in-depth studies on HRV. By understanding the intricate relationship between high-altitude hypoxia and HRV, we can gain insights into the underlying mechanisms and potential therapeutic approaches to mitigate the effects of hypoxia on cardiovascular and other systems.

METHODS

The relevant literature was collected systematically from scientific database, including PubMed, Web of Science, China National Knowledge Infrastructure (CNKI), Baidu Scholar, as well as other literature sources, such as classic books of hypoxia.

RESULTS

There is a close relationship between heart rate variability and high-altitude hypoxia. Heart rate variability is an indicator that evaluates the impact of hypoxia on the cardiovascular system and other related systems. By improving the observation of HRV, we can estimate the progress of cardiovascular diseases and predict the impact on other systems related to cardiovascular health. At the same time, changes in heart rate variability can be used to observe the efficacy of preventive drugs for altitude related diseases.

CONCLUSIONS

HRV can be used to assess autonomic nervous function under various systemic conditions, and can be used to predict and monitor diseases caused by hypoxia at high altitude. Investigating the correlation between high altitude hypoxia and heart rate variability can help make HRV more rapid, accurate, and effective for the diagnosis of plateau-related diseases.

Effect of different hypoxic and hypobaric interventions on blood gas and erythrocyte-related indicators in rats

OBJECTIVES

To explore the effects of hypoxic and hypobaric conditions on blood gas and erythrocyte-related indicators in rats.

METHODS

SD male rats were exposed to low-pressure hypoxic conditions simulating an altitude of 6500 m in a small or a large experimental cabin. Abdominal aortic blood samples were collected and blood gas indicators, red blood cells (RBCs) count, and hemoglobin (Hb) content were measured. The effects of exposure to different hypoxia times, different hypoxia modes, normal oxygen recovery after hypoxia, and re-hypoxia after hypoxia preconditioning on blood gas indicators, RBCs count and Hb content were investigated.

RESULTS

The effect of blood gas indicators was correlated with the length of exposure time of hypoxia and the reoxygenation after leaving the cabin. Hypoxia caused acid-base imbalance and its severity was associated with the duration of hypoxia; hypoxia also led to an increase in RBCs count and Hb content, and the increase was also related to the time exposed to hypoxia. The effects of reoxygenation on acid-base imbalance in rats caged in a small animal cabin were more severe that those in a large experimental cabin. Acetazolamide alleviated the effects of reoxygenation after leaving the cabin. Different hypoxia modes and administration of acetazolamide had little effect on RBCs count and Hb content. Normal oxygen recovery can alleviate the reoxygenation and acid-base imbalance of hypoxic rats after leaving the cabin and improve the increase in red blood cell and hemoglobin content caused by hypoxia. The improvement of hypoxia preconditioning on post hypoxia reoxygenation is not significant, but it can alleviate the acid-base imbalance caused by hypoxia in rats and to some extent improve the increase in red blood cell and hemoglobin content caused by hypoxia.

CONCLUSIONS

Due to excessive ventilation and elevated RBCs count and Hb content after hypoxia reoxygenation, oxygen partial pressure and other oxygenation indicators in hypoxic rats are prone to become abnormal, while blood gas acid-base balance indicators are relatively stable, which are more suitable for evaluating the degree of hypoxia injury and related pharmacological effects in rats.

Update on the Obesity Epidemic: After the Sudden Rise, Is the Upward Trajectory Beginning to Flatten?

PURPOSE OF REVIEW

To provide an update on current obesity prevalence trends and summarize the available evidence suggesting a possible plateau or stabilization in obesity rates after the previous sudden global rise.

RECENT FINDINGS

The escalating global obesity epidemic represents one of the most serious public health challenges. There have been some indications that in high-income populations, the rate of obesity increase in adults has been stabilized after the decade 2000-2010, suggesting a possible plateau. Current evidence also suggests that obesity rates have been stabilized in children and adolescents of most economically advanced countries since 2000, which is possibly related to healthier dietary habits and increased levels of physical activity. On the other hand, there is a steady uninterrupted rise in low-income nations, and the universal trend is obesity escalation rather than slowdown, mainly driven by sharp increases in the obesity prevalence of low-income populations. Furthermore, an increasing number of high- and middle-income countries are currently experiencing an epidemic of severe obesity. In high-income populations, severe obesity is expected to double its prevalence from 10 to 20% between 2020 and 2035, posing an enormous threat for healthcare systems. Even if transiently stabilized, the obesity prevalence remains globally at unacceptably high levels, and there is no guarantee that the current stability (if any) will be maintained for long. In this review, we explore the underlying drivers of the global obesity epidemic; we provide possible explanations for the reported slowdown of the obesity rates in some countries; and we overall take a critical perspective on the obesity plateau hypothesis, emphasizing the urgent need for immediate effective actions at population and regional level in order to halt the alarming obesity escalation and its serious health risks.

Perception and level of satisfaction with the quality of antenatal care services among pregnant women attending antenatal clinic at plateau state specialist hospital, Jos, Nigeria

Objective

This study evaluated pregnant women's perception and level of satisfaction with quality of antenatal care received at Plateau State Specialist Hospital.

Materials and Methods

The study employed a hospital-based cross-sectional design. Convenience sampling was used to select two hundred and thirty-eight (238) women attending antenatal clinic at the Plateau State Specialist Hospital. A validated semi-structured interviewer-administered questionnaire with a Cronbach's Alpha score of 0.83 was used for data collection. Respondent's perception was measured on a 36-point rating scale and the level of satisfaction on a 9-point rating scale. Data was subjected to descriptive analysis and Pearson's correlation was used to test for hypothesis.

Results

The mean age was 28.79 years. Most of the respondents were married (81.9%), twenty-eight percent of the respondents had two children. The respondent's perception of quality of antenatal care shows a mean score of 25.0± 4.61 which indicates that the respondents had positive perception of the quality of antenatal care (69.4%). Also, the respondent's level of satisfaction with the quality of antenatal care received shows a mean score of 6.50 ± 1.8 indicating that they were very satisfied (72.2%) with quality of antenatal care. There was a significant relationship between the respondent's perception of the quality of antenatal care and level of satisfaction of the quality of antenatal care service (r= 0.43; p< 0.003).

Conclusion

The respondents had positive perception and are satisfied with the quality of antenatal care services received. A Periodic patient satisfaction survey should be established as part of the antenatal evaluation to provide feedback for continuous quality improvement.

Effects of L-carnitine Administration on Sperm and Sex Hormone Levels in a Male Wistar Rat Reproductive System Injury Model in a High-Altitude Hypobaric Hypoxic Environment

The plateau environment impacts male reproductive function, causing decreased sperm quality and testosterone levels. L-carnitine can improve the semen microenvironment. However, the role of L-carnitine in a high-altitude environment remains unclear. In our study, we investigated the effects of L-carnitine administration in a male Wistar rat reproductive system injury model in the context of a simulated high-altitude environment. Rats were randomly divided into a normal control group (group A1, A2-low dose and A3-high dose) and high-altitude model groups (group B, C-low dose and D-high dose) with 20 rats in each group. With the exception of the normal control group exposed to normoxic conditions, the other groups were maintained in a hypobaric oxygen chamber that simulated an altitude of 6000 m for 28 days. In the experimental period, the low-dose groups (A2 and C) were administered 50 mg/kg L-carnitine via intraperitoneal injection once a day, and the high-dose groups (A3 and D) were given 100 mg/kg. After the feeding period, blood samples were collected to assess blood gas, serum hormone levels and oxidative stress. Sperm from the epididymis were collected to analyse various sperm parameters. After obtaining the testicular tissue, the morphological and pathological changes were observed under a light microscope and transmission electron microscopy (TEM). The impact of the simulated high-altitude environment on the rat testis tissue is obvious. Specifically, a decreased testicular organ index and altered indices of arterial blood gas and serum sex hormone levels caused testicular tissue morphological damage, reduced sperm quality, increased sperm deformity rate and altered malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) concentrations. The results demonstrate that L-carnitine can be administered as a preventive intervention to reduce the reproductive damage caused by high-altitude hypobaric and hypoxic environments and improve semen quality in a rat model.

Open lower extremity fractures in the geriatric population

INTRODUCTION

Open fractures in the elderly are distinct compared to younger populations. The purpose of this study is to follow a series of open fractures of the lower extremity in the geriatric population to better prognosticate outcomes.

METHODS

We performed a retrospective chart review of patients over the age of 65 years old who were treated for an open, lower extremity fracture across two level I trauma medical systems. Patients were included if they had documented wound healing problems in the postoperative period, or 6 months of follow-up, or if they had a definitive radiographic outcome. Sixty-four patients were included of an average age of 76.23, of whom 73.4% were female.

RESULTS

The fracture types were midshaft femur in 3, distal femur in 9, patella in 2, proximal tibia in 3, proximal fibula in 1, midshaft tibia in 14, distil tibia in 8, ankle in 23, and talar neck/calcaneus in 1. Forty-two fractures were the result of low energy mechanism and 22 fractures were from high energy mechanism. Fourteen fractures were type 1, 32 were type 2, 11 were type 3A, 6 were type 3B, and 1 was type 3C. At final follow-up, 13 wounds were well healed, 39 wounds were healed following a delay of more than 6 weeks to achieve healing, 3 were infected, 3 had been treated with amputation, 2 had chronic ulceration, 2 with active draining, and 2 had draining sinuses.

DISCUSSION

Open lower extremity fractures are serious injuries with high rates of morbidity. Such risks are even higher in the geriatric population, particularly with regard to wound healing. This study provides important prognostic information in counseling geriatric patient with an open lower extremity fracture, as well as informs treatment in terms of wound surveillance and care in the postoperative period.

Comparison of the prevalence of sarcopenia in geriatric patients in Xining based on three different diagnostic criteria

BACKGROUND

Sarcopenia is an age-related decline in skeletal muscle mass, which depends on an assessment of muscle strength and muscle mass. The diagnostic definition of sarcopenia varies by region.

AIM

To determine the optimal diagnostic criteria for sarcopenia in a plateau population. Cut off values for the components of diagnostic algorithms for sarcopenia in plateau populations should consider altitude.

METHODS

One hundred and fifty subjects aged > 60 years attending a tertiary comprehensive hospital in the city of Xining (elevation: 2260 m) between October and December 2018 were enrolled. Handgrip strength, muscle mass, and physical performance were measured. Sarcopenia was diagnosed according to the Asian Working Group for Sarcopenia (AWGS) 2019 criteria, Beijing criteria, and Lasha criteria.

RESULTS

Across diagnostic criteria, there were significant differences in the prevalence of sarcopenia in the overall population and stratified by gender. The prevalence of sarcopenia measured by the AWGS 2019 or Lasha criteria was significantly higher in female compared to male subjects. In males, the prevalence of sarcopenia measured by the Beijing criteria was significantly higher in subjects who identified as Han compared to Minority. In females, there were no significant differences in the prevalence of sarcopenia by ethnicity according to any criteria.

CONCLUSION

The Lasha criteria provided a lower prevalence of sarcopenia (males, 8.7%; females, 22.41%; overall, 14%) and were able to differentiate between males and females. The Lasha criteria are likely most appropriate for detection of sarcopenia in this plateau population. We recommend the Lasha criteria for detection of sarcopenia in Xining.

Effects of orientation and distance of goats on blast lung injury characteristics on a plateau above 4500 m

PURPOSE

High explosives are used to produce blast waves to study their biological effects. The lungs are considered as the critical target organ in blast-effect studies. The degree of lung hemorrhaging is related to both the explosive power and the increased lung weight. We studied the characteristics of the biological effects from an air explosion of a thermobaric bomb in a high-altitude environment and the lethality and lung injury severity of goats in different orientation and distances.

METHODS

Goats were placed at 2.5, 3, 4, and 5 m from the explosion center and exposed them to an air blast at an altitude of 4700 m. A group of them standing oriented to the right side and the other group seated facing the explosion center vertically. The lung injuries were quantified according to the percentage of surface area contused, and using the pathologic severity scale of lung blast injury (PSSLBI) to score the 4 injury categories (slight, moderate, serious and severe) as 1, 2, 3, and 4, respectively. The lung coefficient (lung weight [g]/body weight [kg]) was the indicator of pulmonary edema and was related to lung injury severity. Blast overpressure data were collected using blast test devices placed at matching locations to represent loadings to goats. All statistical analyses were performed using SPSS, version 26.0, statistical software (SPSS, Inc., Chicago, IL, USA).

RESULTS

In total, 127 goats were involved in this study. Right-side-standing goats had a significantly higher mortality rate than those seated vertical-facing (p < 0.05). At the 2.5 m distance, the goat mortality was nearly 100%, whereas at 5 m, all the goats survived. Lung injuries of the right-side-standing goats were 1-2 grades more serious than those of seated goats at the same distances, the scores of PSSLBI were significantly higher than the seated vertical-facing goats (p < 0.05). The lung coefficient of the right-side-standing goats were significantly higher than those of seated vertical-facing (p < 0.05). Mortality, PSSLBI, and the lung coefficient results indicated that the right-side-standing goats experienced severer injuries than the seated vertical-facing goats, and the injuries were lessened as the distance increased. The blast overpressure was consistent with these results.

CONCLUSION

The main killing factors of the thermobaric bomb in the high-altitude environment were blast overpressure, blast wind propulsions and burn. The orientation and distances of the goats significantly affected the blast injury severity. These results may provide a research basis for diagnosing, treating and protecting against injuries from thermobaric explosions.

Effects of high-altitude environment on pharmacokinetic parameters of gliquidone in rats

OBJECTIVE

To investigate the effect of high-altitude hypoxia on the pharmacokinetics parameters of gliquidone.

METHODS

Twelve healthy male Wistar rats were randomly divided into plain group and high-altitude group with 6 rats in each group. Blood samples were collected after intragastric administration of gliquidone (6.3 mg/kg). Ultra-fast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS) was used to determine the concentration of gliquidone in rat plasma samples. And the expression of CYP2C9 in rat liver tissues was determined by Western blotting.

RESULTS

Compared with the plain group, the peak concentration of gliquidone in the high-altitude rats was significantly increased, the absorption rate constant was decreased, the elimination rate constant and the absorption half-life were increased, the elimination half-life was shortened, the mean residence time and apparent volume of distribution were decreased (all P<0.05). Western blotting showed that the expression of CYP2C9 was significantly up-regulated in the liver tissues of high altitude group rats, compared with the plain group (4.18 ±0.06 vs. 2.13±0.06, t=11.57, P<0.01).

CONCLUSION

Under the high-altitude hypoxia environment, the absorption of gliquidone in rats was reduced and the metabolism was accelerated in rats, which may be related to the up-regulation of CYP2C9 expression in liver tissues.

Two-level fixation with headless compression screws for tibial plateau fractures

PURPOSE

Reduction and fixation of tibial plateau fractures associated with small, "floating" intra-articular fragments proposes a challenge. We use fully threaded headless compression screws for (interfragmentary) fixation of such fragments before final plate fixation when standard fixation of intra-articular fragments with k-wires or lag screws is deemed insufficient. Our aim is to describe our technique and clinical experience of this two-level fixation.

METHODS

Between 2006 and 2021, 29 patients with a comminuted tibial plateau fracture were treated with this two-level fixation in this retrospective case series. Clinical baseline and surgical variables were collected for all patients. Clinical outcome variables were available for 28 patients with a median follow-up of 16.5 months (IQR 5-24). Functional outcomes were measured with the Knee Injury and Osteoarthritis Outcome Score (KOOS) and reported by 22 patients at a median of 5.2 years (IQR 3.5-9.8).

RESULTS

Reduction was anatomic or good in 82% of cases, fair in 14%, and a malreduction in 4%. Arthrosis was graded as grade 0 in 25% of cases, 1 in 39%, 2 in 21%, and 3 in 14%. Flexion was 110 degrees (IQR 100-130). Five patients had an extension deficit of 5 to 10 degrees. Median KOOS for symptoms and stiffness was 69 points (IQR 45-78), for pain 71 (IQR 45-88), for ADL 85 (IQR 52-95), for sports 30 (IQR 11-55), and for quality of life 34 (IQR 19-56).

CONCLUSION

The use of fully threaded headless compression screws is a simple and helpful addition in the treatment of comminuted tibial plateau fractures.

Can linear regression confirm VO2max was attained in middle-aged and older adults?

PURPOSE

Evaluate the efficacy of a regression method for identifying a VO₂ plateau to confirm the attainment of VO₂max compared to a verification trial in middle-aged and older adults.

METHODS

Eleven men and ten women (age 61.0 ± 8.1, VO₂max 21.8-50.3 ml/kg/min, n = 21) completed an individualized ramp graded exercise test (GXT) on the cycle ergometer, and one hour later, a verification trial at 105% of their maximal work rate (WR) achieved during the GXT. A plateau in VO₂ was used to confirm VO₂max was attained. VO₂ plateau was identified using the difference between the highest VO₂ between the two trials and a linear regression analysis of the VO₂-WR relationship during the GXT. McNemar's test of marginal homogeneity was used to detect differences in the proportion of paired data of individuals' attainment of VO₂max criteria.

RESULTS

Of the 21 participants, 15 (71.4%) met the verification criterion while 6 (28.6%) did not, compared to the regression method where 16 (76.2%) achieved the regression criterion while 5 (23.8%) did not. McNemar's test revealed no significant difference between participants' ability to achieve the regression and verification criteria (p = 0.999).

CONCLUSION

The regression method is an effective strategy for confirming VO₂max was attained with middle-aged and older adults on a cycle ergometer. This time-efficient regression method is comparable with the verification criterion but does not require a second maximal test, which may be advantageous for those where the verification trial may not be practical.

Community chlorophyll quantity determines the spatial variation of grassland productivity

Plant functional traits are considered a potential approach to explain the spatial variation of ecosystem productivity on a large scale, but how to involve traits in models to predict productivity is still a challenge. Here, we propose a novel trait-based productivity (TBP) framework, as a core of plant community traits in land areas, to interpret the variation in productivity. We assumed that productivity in TBP is determined by a three-dimensional combination of "efficiency × quantity × growth length" and tested it using data regarding leaf chlorophyll traits (scaling-up community weighted mean) in three grassland transects of the Tibetan, Mongolian, and Loess Plateaus in China. The results showed that 52%, 54%, and 67% of the variations in gross primary productivity, net primary productivity, and aboveground net primary productivity, respectively, were captured by the TBP framework in all grassland transects, indicating that it was applicable for the three environmentally distinct plateaus. Furthermore, it was more fitted to the environmentally stressful Tibetan plateau, with an explanatory power of up to 83%. Compared with "chlorophyll efficiency", the "chlorophyll quantity" which is regulated by climate or regional limiting factors, has dominant roles in influencing the spatial variation of grassland productivity. The TBP framework emphasises the connotation of traits behind community functions and seemed as a potential in ecological estimations and predictions; however, multiple traits should be considered for further improvement in the future.

[Discussion on the application of ventilatory threshold in classification of physical workload in plateau]

Objective: To explore the application of the first ventilatory threshold (VT1) and the second ventilatory threshold (VT2) in the classification of physical workload for plateau workers, to provide reference for formulating the classification in plateau. Methods: In August 2018, 88 male workers from substations at different altitudes (500 m, 2000 m, 3000 m and 4000 m) of a company were selected as study subjects by cluster sampling. They were divided into plain group and plateau groups.The intensities of workload were simulated by power bicycle, and physiologic parameters, including VO(2), heart rate (HR) and energy metabolic rate per body surface area (E/BSA) , were recorded in test system when reaching VT1, VT2 and peak oxygen uptake (VO(2)Peak) . The ratios of VT1, VT2 and VO(2)Peak to the quiet and work potential at different altitudes were compared. Results: In a quiet state, compared with the plain group, the HR and E/BSA of the workers in the 2000 m and 3000 m groups increased, and the differences were statistically significant (P<0.05) . At VT2, compared with the plain group, the HR of the workers in the 4000 m group decreased, the difference was statistically significant (P<0.05) . VO(2) and E/BSA of workers in each plateau group were lower than those in the plain group at VO(2)Peak, and the differences were statistically significant (P<0.05) . At VT2 and VO(2)Peak, the ratios of VO(2), HR, and E/BSA relative to the quiet state of the workers in each plateau group were lower than those of the plain group, and the differences were statistically significant (P<0.05) . In the quiet state and VT1, compared with the plain group, the remaining percentages of VO(2) and E/BSA of workers in each plateau group decreased, and the differences were statistically significant (P<0.05) . Taking VT1, VT2 and VO(2)Peak as cut-off points and VO(2), HR and E/BSA as indicators, the physical workload in plateau could be divided into four levels, namely medium, heavy, extremely heavy and extreme physical workload. Conclusion: It is practicable to use ventilatory threshold to classification of physical workload. VT1 and VT2 can be applied to the classification in plateau to supplement and optimize current national standard of physical workload.

Application of 7.0 T ultra-high-field MRI in evaluating the structure and function of the right ventricle of the heart in rats under a chronic hypoxic environment at high altitude

Background

Long-term exposure to a high-altitude environment with low pressure and low oxygen can cause abnormalities in the structure and function of the heart, in particular the right ventricle. Monitoring the structure and function of the right ventricle is therefore essential for early diagnosis and prognosis of high-altitude heart-related diseases. In this study, 7.0 T MRI is used to detect cardiac structure and function indicators of rats in natural plateau and plain environments.

Methods

Rats in two groups were raised in different environments from 6 weeks of age for a period of 12 weeks. At 18 weeks of age both groups underwent 7.0 T cardiac magnetic resonance (CMR) scanning. Professional cardiac post-processing software was used to analyze right ventricular end-diastolic volume (RVEDV), right ventricular end-systolic volume (RVESV), right ventricular stroke volume (RVSV), right ventricular ejection fraction (RVEF), Right ventricular end-diastolic myocardial mass (RV Myo mass, diast), Right ventricular end-systolic myocardial mass (RV Myo mass, syst), tricuspid valve end-diastolic caliber (TVD), tricuspid valve end-systolic caliber (TVS), right ventricular end-systolic long-axis (RVESL) and right ventricular end-diastolic long-axis (RVEDL). Prior to the CMR scan, blood was collected from the two groups of rats for evaluation of blood indicators. After the scan, the rats were sacrificed and the myocardial tissue morphology observed under a light microscope.

Results

In the group of rats subject to chronic hypoxia at high altitude for 12 weeks (the plateau group), red blood cell (RBC) count, hemoglobin (HGB) and hematocrit (HCT) increased (P<0.05); RVEDV, RVESV, RVSV, RV Myo mass (diast), RV Myo mass (syst), TVS, RVESL, and RVEDL also increased (P<0.05). Observation of the right ventricle of rats in the plateau group using a light microscope mainly showed a slightly widened myocardial space, myocardial cell turbidity, vacuolar degeneration, myocardial interstitial edema, vascular congestion and a small amount of inflammatory cell infiltration.

Conclusions

The importance of ultra-high-field MRI for monitoring the early stages of rat heart injury has been demonstrated by studying the changes in the structure and function of the right ventricle of rats subject to chronic hypoxia at high altitude over a period of 12 weeks.

Controlled backfill in oncology dose-finding trials

The use of backfill in early phase dose-finding trials is a relatively recent practice. It consists of assigning patients to dose levels below the level where the study is at. The main reason for backfilling is to collect additional pharmacokinetic, pharmacodynamic and response data, in order to assess whether a plateau may exist on the dose-efficacy curve. This is a possibility in oncology with molecularly targeted agents or immunotherapy. Recommending for further study a dose level lower than the maximum tolerated dose could be supported in such situations. How to best allocate backfill patients to dose levels is not yet established. In this paper we propose to randomise backfill patients below the dose level where the study is at. A refinement of this would be to stop backfilling to lower dose levels when these show insufficient efficacy compared to higher levels, starting at dose level 1 and repeating this process sequentially. At study completion, data from all patients (both backfill patients and dose-finding patients) is used to estimate the dose-response curve. The fit from a change point model is compared to the fit of a monotonic model to identify a potential plateau. Using simulations, we show that this approach can identify the plateau on the dose-response curve when such a plateau exists, allowing the recommendation of a dose level lower than the maximum tolerated dose for future studies. This contribution provides a methodological framework for backfilling, from the perspective of both design and analysis in early phase oncology trials.

Case series of COVID-19 patients from the Qinghai-Tibetan Plateau Area in China

BACKGROUND

Coronavirus disease 2019 (COVID-19) is a serious infection caused by the new coronavirus severe acute respiratory syndrome coronavirus 2. The disease was first identified in December 2019 and has caused significant morbidity and mortality worldwide.

AIM

To explore the clinical characteristics and treatments for COVID-19 in the Qinghai-Tibetan Plateau Area in China.

METHODS

We retrospectively analyzed the blood cell counts (neutrophils and lymphocytes), blood gas analysis, and thoracic computed tomography changes of patients from Qinghai Province before, during, and after treatment (January 23, 2020 to February 21, 2020). In addition, we summarized and analyzed the information of critical patients. All data were analyzed using SPSS 17.0 (SPSS Inc., Chicago, IL, United States). The quantitative and count variables are represented as the mean ± SD and n (%), respectively.

RESULTS

The main symptoms and signs of patients with COVID-19 were fever, dry cough, cough with phlegm, difficulty breathing, and respiratory distress with a respiration rate ≥ 30 times/min, finger oxygen saturation ≤ 93% in the resting state, and oxygenation index less than 200 but greater than 100 (after altitude correction). Eighteen patients with COVID-19, of whom three were critical, and the others were in a mild condition, were included. The main manifestations included fever, dry cough, and fatigue. Three patients developed difficulty breathing and had a fever. They were eventually cured and discharged. Adjuvant examinations showed one case with reduced white cell count (6%) (< 4 × 109/L), six with reduced count of lymphocytes (33%) (< 0.8 × 109/L), and one with abnormal blood glucose level. All 18 patients were discharged, and no death occurred.

CONCLUSION

Our findings provide critical insight into assessing the clinical diagnosis and treatment for COVID-19 in the Tibetan plateau area.

Sarcopenia in geriatric patients from the plateau region of Qinghai-Tibet: A cross-sectional study

BACKGROUND

Sarcopenia is an age-related decline in skeletal muscle mass, which depends on an assessment of muscle strength and muscle mass. It has been reported that the prevalence of sarcopenia in non-hospitalized elderly people was 9.0%-18.5% in the lowland plains. However, epidemiological investigations of sarcopenia in plateau regions are limited. The city of Xining in Qinghai Province (altitude 2260 m) is the sole point of access to the Qinghai-Tibet plateau. We hypothesized that the diverse ethnicities or dietary habits of the people living in the plateau may influence the prevalence of sarcopenia.

AIM

To investigate the prevalence and risk factors of sarcopenia in geriatric patients from the Qinghai-Tibet plateau region.

METHODS

From October to December 2018, 150 hospitalized geriatric patients (72.4 ± 5.60 years) from Xining City (altitude 2260 m) in Qinghai Province were recruited. Collected data included demographics, history of fall, nutritional status, self-care ability, depression, handgrip, muscle mass, and 6-m gait speed. Sarcopenia was diagnosed based on the 2014 criteria of the Asian Working Group for Sarcopenia.

RESULTS

The overall rate of sarcopenia was 20% (8.7 and 11.3% in men and women, respectively). Binary logistic regression analysis indicated that widowhood was associated with sarcopenia, while higher body mass index and beef and mutton consumption were protective.

CONCLUSION

The prevalence of sarcopenia in hospitalized geriatric patients in the Qinghai-Tibet plateau region was higher than that in the plain region and in non-hospitalized geriatric people (reported elsewhere). Specific cultural features of the region, including ethnicity, brewed tea and ghee consumption, were not significantly associated with sarcopenia. Higher body mass index and consumption of beef and mutton were protective, while patients who were widowed was at increased risk.

Spatial distribution of gut microbes along the intestinal duct

We studied the spatial pattern of two microbial strains along the intestinal duct. Probiotic bacteria acidify the environment and suppress their competitors, non-probiotic bacteria. Food resources are supplied from the proximal end, and there exists a flow from the proximal end to the distal end. In the steady state, we observed three major patterns. In the "standard" pattern (ST), the abundance of probiotic bacteria was high in the proximal end, and it decreased toward the distal end; in contrast, the abundance of non-probiotic bacteria was low in the proximal end, and it increased toward the distal end. In the "proximal reversion" pattern (PR), non-probiotic bacteria were dominant and probiotic bacteria were suppressed in the proximal portion of the duct. Subsequently, the abundance values of the two competitors switched, followed by a spatial pattern similar to ST. In the "distal suppression" pattern (DS), the pattern was similar to ST in the proximal portion; however, toward the distal end, the abundance of probiotic bacteria remained at an intermediate level and suppressed the abundance of non-probiotic bacteria, resulting in a peak abundance of non-probiotic bacteria in the middle portion of the duct. We additionally discuss the nonmonotonic increase in the abundance of non-probiotic bacteria in ST and the transition of the spatial pattern from one type to another due to changes in the resource abundance in the influx.

Does heart rate response confirm the attainment of maximal oxygen uptake in adults 45 years and older?

PURPOSE

To test the efficacy of a plateau in heart rate (HR_plat) as an effective indicator for confirming [Formula: see text]max attainment in a middle-aged to older sample.

METHODS

Nine men and eleven women (age 60 ± 8.5 years, [Formula: see text]max 35.9 ± 9.4 ml/kg/min, N = 20) completed a single [Formula: see text]max test on both the treadmill and cycle ergometer.[Formula: see text]max was confirmed using a plateau in [Formula: see text] ([Formula: see text]_plat) of ≤ 150 ml/min, a verification bout, and HR_plat (≤ 4 bpm).

RESULTS

[Formula: see text]_plat occurred in 100% and 95% of participants on the treadmill and cycle ergometer, respectively. Verification criteria ([Formula: see text]max during verification ≤ 2% of [Formula: see text]max during incremental test) were met by 80% of participants on both modalities. HR_plat was achieved by 90% and 70% of participants on the treadmill and cycle ergometer, respectively.

CONCLUSION

These results suggest that a verification bout is reliable for confirming [Formula: see text]max in older adults on both modalities. In our sample of middle-aged and older adults, [Formula: see text]_plat was the most robust method to assess [Formula: see text]max when indirect calorimetry is available. Although more research is warranted, when indirect calorimetry is not available, a HR_plat of ≤ 4 bpm may be a useful alternative to get an accurate representation of maximal effort in middle-aged and older adults.

Seed germination and early seedling survival of the invasive species Prosopis juliflora (Fabaceae) depend on habitat and seed dispersal mode in the Caatinga dry forest

Background

Biological invasion is one of the main threats to tropical biodiversity and ecosystem functioning. Prosopis juliflora (Sw) DC. (Fabales: Fabaceae: Caesalpinioideae) was introduced in the Caatinga dry forest of Northeast Brazil at early 1940s and successfully spread across the region. As other invasive species, it may benefit from the soils and seed dispersal by livestock. Here we examine how seed dispersal ecology and soil conditions collectively affect seed germination, early seedling performance and consequently the P. juliflora invasive potential.

Methods

Seed germination, early seedling survival, life expectancy and soil attributes were examined in 10 plots located across three habitats (flooding plain, alluvial terrace and plateau) into a human-modified landscape of the Caatinga dry forest (a total of 12,000 seeds). Seeds were exposed to four seed dispersal methods: deposition on the soil surface, burial in the soil, passed through cattle (Boss taurus) digestive tracts and mixed with cattle manure and passed through mule (Equus africanus asinus × Equus ferus caballus) digestive tracts and mixed with mule manure. Seeds and seedlings were monitored through a year and their performance examined with expectancy tables.

Results

Soils differed among habitats, particularly its nutrient availability, texture and water with finely-textured and more fertile soils in the flooding plain. Total seed germination was relatively low (14.5%), with the highest score among seeds buried in the flooding plain (47.4 ± 25.3%). Seed dispersal by cattle and mule also positively impacted seed germination. Early seedling survival rate of P. juliflora was dramatically reduced with few seedlings still alive elapsed a year. Survival rate was highest in the first 30 days and declined between 30 and 60 days with stabilization at 70 days after germination in all seed treatments and habitats. However, survival and life expectancy were higher in the flooding plain at 75 days and lower in the plateau. Prosopis juliflora seedling survival and life expectancy were higher in the case seeds were mixed with cattle manure.

Synthesis

Prosopis juliflora seeds and seedlings are sensitive to water stress and habitat desiccation. Therefore, they benefit from the humid soils often present across human-disturbed flooding plains. This plant also benefits from seed deposition/dispersal by livestock in these landscapes, since cattle manure represents a nutrient-rich and humid substrate for both seeds and seedlings. The quality of the seed dispersal service varies among livestock species, but this key mutualism between exotic species is due to the arillate, hard-coated and palatable seeds. Prosopis juliflora traits allow this species to take multiple benefits from human presence and thus operating as a human commensal.

Tibetan patients with hepatic hydatidosis can tolerate hypoxic environment without incident increase of pulmonary hypertension: an echocardiography study

Use of echocardiography to evaluate the characteristics of right heart and pulmonary artery of Tibetans with hepatic hydatidosis living in a high plateau area. We recruited 222 Tibetan adults diagnosed with hydatidosis from June 2016 to June 2017 in Shiqu and Seda areas of Tibet; 40 healthy control from the same area, denoted as the high plateau group. We also include 755 Healthy adults of Han nationality living in the plain from the EMINCA study as the low altitude group. Compared to high plateau group, hydatidosis individuals showed decreased RVADed, RVTDed, increased E(T)/A(T) and reduced RVFAC and TAPSE (p < 0.05). The 2 groups did not differ in the incidence rate of tricuspid regurgitation (TR) and pulmonary regurgitation (PR) (63.9% vs. 55.0%, p = 0.281 and 15.3% vs. 5.0%, p = 0.135, respectively) or incidence of pulmonary hypertension (PH) (13.9% vs. 20.5%, p = 0.167). PH risk did not differ between hydatidosis individuals and high plateau controls (OR 0.559, 95% CI 0.243-1.287). The RVADed and TAPSE were higher and E(T)/A(T) was lower for high plateau group than low altitude group (p < 0.05). The decreased right ventricular size and reduced diastolic and systolic function were found in Tibetans with hydatidosis. Hepatic hydatidosis had no significant effect on the incidence of pulmonary hypertension in Tibetans. Healthy Tibetans showed increased right ventricular size, decreased diastolic function, and increased systolic function compared to the Han counterparts.

Vitamin D nutritional status in the adult population in Colombia - An analytical cross-sectional study

Background

The key role of Vitamin D is to maintain an adequate calcium and phosphorus metabolism. Vitamin D plays an antagonistic role with the parathyroid hormone. 25 OH Vitamin D is the major circulating form and the best indicator to monitor Vitamin D levels.

Methods

A cross-sectional study was conducted in 1339 individuals ≥18 years old. The main objective was to establish the nutritional status of Vitamin D and its association with PTH and ionized calcium levels. Other objectives were to compare the levels of 25 OH Vitamin D based on sun exposure habits, and to identify the minimum cut-off point for the levels of 25 OH Vitamin D that could give rise to a concomitant increase in PTH and ionized calcium levels.

Results

14.2% of participants presented Vitamin D deficiency, and 28.8% presented insufficiency; ≥89% of the participants with deficiency or insufficiency were exposed to sunlight <30 minutes per week. A value of 25 OH Vitamin D >30 ng/mL was associated with a more stable and "flat" PTH value. The median of 25 OH Vit-D associated with hypercalcemia was <10 ng/mL.

Conclusion

In Colombia, low 25 OH Vitamin D values are highly prevalent; this may be accounted for by poor sun-exposure habits and frequent use of sunscreen. Just as in other similar trials, the lower the levels of 25 OH Vit-D, the higher the effect on PTH and ionized calcium elevation.

High-Complexity Plasmodium falciparum Infections, North Central Nigeria, 2015-2018

The mass migration that occurred during 2009–2013 and after the insurgency in northeastern Nigeria could have increased malaria incidence and Plasmodium falciparum genetic diversity in North Central Nigeria. To determine P. falciparum sequence diversity in this region, we screened 282 samples collected in regional clinics during 2015–2018 for Plasmodium spp. and, with positive samples, determined P. falciparum infection complexity and allele diversity using PCR. Of 34 P. falciparum–positive samples, 39 msp1, 31 msp2, and 13 glurp alleles were detected, and 88% of infections were polyclonal. We identified trimorphic and dimorphic allele combinations in a high percentage of samples, indicative of a high infection complexity in the study population. High genetic diversity is a catalyst for the evolution of drug-resistant alleles. Improved measures (e.g., better drug quality, diagnostics) are needed to control P. falciparum transmission and reduce the potential for the emergence of drug resistance in Nigeria.

Genetic changes in the EPAS1 gene between Tibetan and Han ethnic groups and adaptation to the plateau hypoxic environment

In the Chinese Han population, prolonged exposure to hypoxic conditions can promote compensatory erythropoiesis which improves hypoxemia. However, Tibetans have developed unique phenotypes, such as downregulation of the hypoxia-inducible factor pathway through EPAS1 gene mutation, thus the mechanism of adaption of the Han population should be further studied. The results indicated that, under plateau hypoxic conditions, the plains population was able to acclimate rapidly to hypoxia through increasing EPAS1 mRNA expression and changing the hemoglobin conformation. Furthermore, the mutant genotype frequencies of the rs13419896, rs1868092 and rs4953354 loci in the EPAS1 gene were significantly higher in the Tibetan population than in the plains population. The EPAS1 gene expression level was lowest in the Han population carrying the A-A homozygous mutant of the rs13419896 locus but that it increased rapidly after these individuals entered the plateau. At this time, the hemoglobin content was lower in the homozygous mutant Han group than in the wild-type and heterozygous mutant populations, and the viscosity of blood was reduced in populations carrying the A-A haplotypes in rs13419896 and rs1868092 Among Tibetans, the group carrying homozygous mutations of the three SNPs also had lower hemoglobin concentrations than the wild-type. The Raman spectroscopy results showed that exposure of the Tibetan and Han population to hypoxic conditions changed the spatial conformation of hemoglobin and its binding ability to oxygen. The Tibetan population has mainly adapted to the plateau through genetic mutations, whereas some individuals adapt through changes in hemoglobin structure and function.

Clinicopathological characteristics and health care for Tibetan women with breast cancer: a cross-sectional survey

Background

The healthcare system (HCS) improved in Tibet Autonomous Region (TAR), China. The present study aimed to investigate whether these improvements might alter the clinicopathological characteristics of a Tibetan female with breast cancer (BC) in TAR.

Methods

This was a single-center cross-sectional study conducted at TAR People’s Hospital. All Tibetan adult women were treated for BC in this hospital between January 1, 1973 and December 31, 2015. The inclusion criteria were as follows: (1) Tibetan adult woman living in Tibet; (2) Histopathology or cytopathology or both confirming primary BC; (3) All the treatments were finished in this hospital. χ² test and logistic regression were applied, using age group and census register as the two covariates.

Results

A total of 273 patients with BC were included in the final analysis. Of these, 14 patients were in the free HCS, 183 patients had medical insurance combined with a new rural cooperative HCS, and 76 were in a rural and urban integration HCS. Currently, a rural and urban integration HCS is an improved system. Consequently, an increase in the proportion patients in the T1–3 stage was observed (0.198; 0.046 to 0.852) between the rural and urban integration HCS and free HCS. The proportion of patients in early (I + II) stage cancer (0.110; 0.019–0.633) also increased between these two HCSs.

Conclusion

This was the first report about Tibetan women with BC in Tibet. Some clinicopathological characteristics at the presentation of Tibetan women with BC may improve during different HCSs. The cancer awareness, early detection, and the overall management in patients with advanced stage BC might improve the prognosis of BC in the rural and urban integration HCS.

[Analysis of eight-year follow-up data of plateau workers by color doppler echocardiography]

Objective: To analyze the heart rate changes and risk factors, as a result of high altitude. Methods: Retrospective analysis of echocardiographic data of plateau workers at a railway maintenance company from 2006 to 2013. The survival curve method was used to analyze the abnormal rate of the heart. Kaplan-Meier method and Cox proportional hazards regression model were used to analyze the influencing factors. Results: In the first occurrence of cardiac abnormalities, the main types of abnormalities were right atrium enlargement (53.47%) , right ventricle enlargement (17.36%) , and tricuspid regurgitation (16.67%) . Cox regression analysis showed that workplace altitude and first physical examination age are two influencing factors of cardiac abnormalities, and their relative risk was 1.661 and 1.039. At high altitudes (3 600~4 000 m) , nearly 40% of workers heart has not changed. But this adaptation does not observed in the ultra-high altitudes (≥4 000 m) . Conclusion: There are individual differences in human adaptability to high altitude. We should take more stringent measures of health care for older people and those who work at more than 4000m. And we should abide by the rotation system for railways that are suitable for the plateau.

Tibia plateau fracture mapping and its influence on fracture fixation

Background

Tibial plateau fracture classifications are based on anteroposterior radiographs. Precontoured locking plates are commonly used to treat such fractures. The aims of this study are to: (1) describe tibial plateau fracture anatomy in the axial plane and (2) assess whether current plating systems allow screws to be placed suitably.

Materials and methods

A graphical tibial plateau template was developed. One hundred twenty-five tibial plateau fractures (four bilateral) were reviewed (80 men, 41 women; average age 45.5 years, range 21–77.7 years). The axial computed tomography (CT) slice 0.3–0.5 mm below the medial articular surface was reviewed in all cases. Fracture lines were drawn on the template. Four lateral locking plates were placed against a cadaveric adult tibia. Based on the projected screw directions, suitable fracture patterns were identified. Fractures were considered “suitable” if the screws passed 90 ± 22° to the fracture line.

Results

Two hundred sixty-one different fracture lines were identified. One hundred thirty-four fractures involved the lateral plateau; 96 were suitable for lateral plating. Ninety fractures involved the medial plateau, 82 were treatable using the various plate positions on medial-posterior aspect of the medial plateau. Thirty-seven fractures were bicondylar; 20 were treatable with a posteromedial plate.

Conclusions

Tibial plateau fractures follow consistent patterns, with most lateral and medial plateau fracture lines being in the sagittal plane, although there is greater variation medially. Positioning of modern locking plates will deal effectively with 72 % of all lateral plateau fractures and 91 % of medial plateau fractures.

Level of evidence

Level 3.

Malreduction of tibial articular width in bicondylar tibial plateau fractures treated with circular external fixation is associated with post-traumatic osteoarthritis

Objectives

We aimed to report outcomes of Bicondylar Tibial Plateau (BTP) fractures treated using Ilizarov fixation, and identify risk factors for developing post-traumatic radiographic osteoarthritis (ROA).

Methods

Retrospective study of 80 BTP fractures managed with Ilizarov fixation.

Results

All fractures united, with only 3 cases of deep infection. ROA was evident in 12.5% at average 13 months post-injury. Increased tibial articular-widening associated with risk of developing ROA (p = 0.02).

Conclusion

Ilizarov fixation is safe and reliable in the management of BTP fractures. Restoration of tibial articular-width at fixation associated with reduced risk of developing radiographic OA.

Vegetation and soil nutrient restoration of cut slopes using outside soil spray seeding in the plateau region of southwestern China

Outside soil spray seeding (OSSS) is used widely for road cut revegetation, and the artificial soil used in OSSS can improve slope soil conditions and nutrients, and help promote plant growth and succession. Three different slopes was investigated to evaluate the effectiveness of OSSS for restoration, including a natural slope (NS), a cut slope without any artificial recovery treatment (CSW) and a cut slope treated with OSSS (CSO). The recovery of cut slopes was determined by evaluating a number of factors, including indices associated with plants on the slopes, soil enzyme activities (urease and sucrase), and soil nutrient content (soil organic matter (SOM), total phosphorous (TP), total potassium (TK), available nitrogen (AN), available phosphorous (AP), available potassium (AK), potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), and sulphate (SO₄^2-)). The results indicated that the vegetation and soil conditions differed between the three slopes. The Shannon-Wiener index (H), the Simpson index (D), and the Margalef index (R) values from the CSO and NS were lower than those of the CSW, whilst the Pielou index (E) value and vegetation canopy cover were higher for the CSO and NS than for the CSW. The content of SOM and AN in soil from the CSO was lower than in soil from the NS and CSW, and content of many nutrients were higher in soil from the CSO than in soil from the NS and CSW. This suggests that the restoration of vegetation and soil nutrients on the CSO was relatively successful. Our results indicated that the use of OSSS to restore cut slopes is effective in plateau areas. However, despite improvements in soil nutrient levels, there were still nutritional imbalances. Therefore, more attention should be paid to balancing nutrients in the later stage of OSSS implementation for the recovery of cut slopes at high altitudes.

Staged Treatment of Bicondylar Tibial Plateau Fracture (Schatzker Type V or VI) Using Temporary External Fixator: Correlation between Clinical and Radiological Outcomes

Purpose

This study is to investigate clinical and radiological results of staged treatment using a temporary external fixator in bicondylar tibial plateau fractures (TPFs) and to evaluate correlation between prognostic factors and postoperative clinical outcomes.

Materials and Methods

Twenty-four bicondylar TPF patients were selected. All patients were operated by a temporary external fixator first and then open reduction and internal fixation with dual plating. Clinical and radiological outcomes were evaluated.

Results

The mean American Knee Society score (AKSS) was 85.3. The mean Western Ontario and McMaster Universities Osteoarthritis index was 11.2. The mean range of motion (ROM) was 123.4°. The mean medial tibial plateau angle (mTPA) was 88.3°, and the mean proximal posterior tibial angle (PPTA) was 8.4°. Compared with the uninjured limb, the mean difference of mTPA was 1.5° and that of PPTA was 4.0°. The difference of PPTA and the AKSS demonstrated negative correlation (p=0.007). Patients with normal mTPA showed better ROM than those with abnormal mTPA (p=0.041).

Conclusions

Staged treatment using a temporary external fixator in bicondylar TPFs showed good clinical and radiological outcomes. Surgeons should evaluate the reduction status intraoperatively by fluoroscopy and also refer to the uninjured limb radiologically.

The Maximal Oxygen Uptake Verification Phase: a Light at the End of the Tunnel?

Commonly performed during an incremental test to exhaustion, maximal oxygen uptake (V̇O_2max) assessment has become a recurring practice in clinical and experimental settings. To validate the test, several criteria were proposed. In this context, the plateau in oxygen uptake (V̇O₂) is inconsistent in its frequency, reducing its usefulness as a robust method to determine “true” V̇O_2max. Moreover, secondary criteria previously suggested, such as expiratory exchange ratios or percentages of maximal heart rate, are highly dependent on protocol design and often are achieved at V̇O₂ percentages well below V̇O_2max. Thus, an alternative method termed verification phase was proposed. Currently, it is clear that the verification phase can be a practical and sensitive method to confirm V̇O_2max; however, procedures to conduct it are not standardized across the literature and no previous research tried to summarize how it has been employed. Therefore, in this review the knowledge on the verification phase was updated, while suggestions on how it can be performed (e.g. intensity, duration, recovery) were provided according to population and protocol design. Future studies should focus to identify a verification protocol feasible for different populations and to compare square-wave and multistage verification phases. Additionally, studies assessing verification phases in different patient populations are still warranted.

Measurement of Posterior Tibial Slope Using Magnetic Resonance Imaging

BACKGROUND

Posterior tibial slope (PTS) is an important factor in the knee joint biomechanics and one of the bone features, which affects knee joint stability. Posterior tibial slope has impact on flexion gap, knee joint stability and posterior femoral rollback that are related to wide range of knee motion. During high tibial osteotomy and total knee arthroplasty (TKA) surgery, proper retaining the mechanical and anatomical axis is important. The aim of this study was to evaluate the value of posterior tibial slope in medial and lateral compartments of tibial plateau and to assess the relationship among the slope with age, gender and other variables of tibial plateau surface.

METHODS

This descriptive study was conducted on 132 healthy knees (80 males and 52 females) with a mean age of 38.26±11.45 (20-60 years) at Imam Reza hospital in Mashhad, Iran. All patients, selected and enrolled for MRI in this study, were admitted for knee pain with uncertain clinical history. According to initial physical knee examinations the study subjects were reported healthy.

RESULTS

The mean posterior tibial slope was 7.78± 2.48 degrees in the medial compartment and 6.85± 2.24 degrees in lateral compartment. No significant correlation was found between age and gender with posterior tibial slope (P≥0.05), but there was significant relationship among PTS with mediolateral width, plateau area and medial plateau.

CONCLUSION

Comparison of different studies revealed that the PTS value in our study is different from other communities, which can be associated with genetic and racial factors. The results of our study are useful to PTS reconstruction in surgeries.

Responses of trophic structure and zooplankton community to salinity and temperature in Tibetan lakes: Implication for the effect of climate warming

Warming has pronounced effects on lake ecosystems, either directly by increased temperatures or indirectly by a change in salinity. We investigated the current status of zooplankton communities and trophic structure in 45 Tibetan lakes along a 2300 m altitude and a 76 g/l salinity gradient. Freshwater to hyposaline lakes mainly had three trophic levels: phytoplankton, small zooplankton and fish/Gammarus, while mesosaline to hypersaline lakes only had two: phytoplankton and large zooplankton. Zooplankton species richness declined significantly with salinity, but did not relate with temperature. Furthermore, the decline in species richness with salinity in lakes with two trophic levels was much less abrupt than in lakes with three trophic levels. The structural variation of the zooplankton community depended on the length of the food chain, and was significantly explained by salinity as the critical environmental variable. The zooplankton community shifted from dominance of copepods and small cladoceran species in the lakes with low salinity and three trophic levels to large saline filter-feeding phyllopod species in those lakes with high salinity and two trophic levels. The zooplankton to phytoplankton biomass ratio was positively related with temperature in two-trophic-level systems and vice versa in three-trophic-level systems. As the Tibetan Plateau is warming about three times faster than the global average, our results imply that warming could have a considerable impact on the structure and function of Tibetan lake ecosystems, either via indirect effects of salinization/desalinization on species richness, composition and trophic structure or through direct effects of water temperature on trophic interactions.

Identification of reference genes in blood before and after entering the plateau for SYBR green RT-qPCR studies

BACKGROUND

Tibetans have lived at high altitudes for thousands of years, and they have unique physiological traits that enable them to tolerate this hypoxic environment. However, the genetic basis of these traits is still unknown. As a sensitive and highly efficient technique, RT-qPCR is widely used in gene expression analyses to provide insight into the molecular mechanisms underlying environmental changes. However, the quantitative analysis of gene expression in blood is limited by a shortage of stable reference genes for the normalization of mRNA levels. Thus, systematic approaches were used to identify potential reference genes.

RESULTS

The expression levels of eight candidate human reference genes (GAPDH, ACTB, 18S RNA, β2-MG, PPIA, RPL13A, TBP and SDHA) were assessed in blood from hypoxic environments. The expression stability of these selected reference genes was evaluated using the geNorm, NormFinder and BestKeeper programs. Interestingly, RPL13A was identified as the ideal reference gene for normalizing target gene expression in human blood before and after exposure to high-altitude conditions.

CONCLUSION

These results indicate that different reference genes should be selected for the normalization of gene expression in blood from different environmental settings.

Return to sport following tibial plateau fractures: A systematic review

AIM

To systemically review all studies reporting return to sport following tibial plateau fracture, in order to provide information on return rates and times to sport, and to assess variations in sporting outcome for different treatment methods.

METHODS

A systematic search of CINAHAL, Cochrane, EMBASE, Google Scholar, MEDLINE, PEDro, Scopus, SPORTDiscus and Web of Science was performed in January 2017 using the keywords “tibial”, “plateau”, “fractures”, “knee”, “athletes”, “sports”, “non-operative”, “conservative”, “operative”, “return to sport”. All studies which recorded return rates and times to sport following tibial plateau fractures were included.

RESULTS

Twenty-seven studies were included: 1 was a randomised controlled trial, 7 were prospective cohort studies, 16 were retrospective cohort studies, 3 were case series. One study reported on the outcome of conservative management (n = 3); 27 reported on the outcome of surgical management (n = 917). Nine studies reported on Open Reduction Internal Fixation (ORIF) (n = 193), 11 on Arthroscopic-Assisted Reduction Internal Fixation (ARIF) (n = 253) and 7 on Frame-Assisted Fixation (FRAME) (n = 262). All studies recorded “return to sport” rates. Only one study recorded a “return to sport” time. The return rate to sport for the total cohort was 70%. For the conservatively-managed fractures, the return rate was 100%. For the surgically-managed fractures, the return rate was 70%. For fractures managed with ORIF, the return rate was 60%. For fractures managed with ARIF, the return rate was 83%. For fractures managed with FRAME was 52%. The return rate for ARIF was found to be significantly greater than that for ORIF (OR 3.22, 95%CI: 2.09-4.97, P < 0.001) and for FRAME (OR 4.33, 95%CI: 2.89-6.50, P < 0.001). No difference was found between the return rates for ORIF and FRAME (OR 1.35, 95%CI: 0.92-1.96, P = 0.122). The recorded return time was 6.9 mo (median), from a study reporting on ORIF.

CONCLUSION

Return rates to sport for tibial plateau fractures remain limited compared to other fractures. ARIF provides the best return rates. There is limited data regarding return times to sport. Further research is required to determine return times to sport, and to improve return rates to sport, through treatment and rehabilitation optimisation.

Rapid response of arbuscular mycorrhizal fungal communities to short-term fertilization in an alpine grassland on the Qinghai-Tibet Plateau

BACKGROUND

The Qinghai-Tibet Plateau (QTP) is home to the vast grassland in China. The QTP grassland ecosystem has been seriously degraded by human land use practices and climate change. Fertilization is used in this region to increase vegetation yields for grazers. The impact of long-term fertilization on plant and microbial communities has been studied extensively. However, the influence of short-term fertilization on arbuscular mycorrhizal fungal (AMF) communities in the QTP is largely unknown, despite their important functional role in grassland ecosystems.

METHODS

We investigated AMF community responses to three years of N and/or P addition at an experimental field site on the QTP, using the Illumina MiSeq platform (PE 300).

RESULTS

Fertilization resulted in a dramatic shift in AMF community composition and NP addition significantly increased AMF species richness and phylogenetic diversity. Aboveground biomass, available phosphorus, and NO3 (-) were significantly correlated with changes in AMF community structure. Changes in these factors were driven by fertilization treatments. Thus, fertilization had a large impact on AMF communities, mediated by changes in aboveground productivity and soil chemistry.

DISCUSSION

Prior work has shown how plants often lower their reliance on AMF symbioses following fertilization, leading to decrease AMF abundance and diversity. However, our study reports a rise in AMF diversity with fertilization treatment. Because AMF can provide stress tolerance to their hosts, we suggest that extreme weather on the QTP may help drive a positive relationship between fertilizer amendment and AMF diversity.

Medial meniscal cyst as a cause of painful erosion of the tibial plateau

Medial cysts are rarely encountered as a cause of bone erosion. It is thought meniscal cysts are present in up to 22 % of meniscal tear operations. MRI is the gold standard for visualisation of meniscal cysts. Decompression is often guided by careful study of the pre-operative MRI scans in multiple planes. This is the first case report demonstrating erosion of the medial tibial plateau due to an incarcerated meniscal cyst highlighting the potential for bone damage if left untreated. Level of evidence IV.

On the analysis and interpretation of late-life fecundity in Drosophila melanogaster

Late-life plateaus have been described in both cohort and individual trajectories of fecundity in Drosophila melanogaster females. Here I examine life history data recently analyzed by Le Bourg and Moreau (2014) and show that non-linearity in the cohort trajectory of fecundity is largely explained by heterogeneity in the duration of reproductive life spans. A model specifying linear post-peak decline of fecundity in individual flies provides a better fit to the data than one that combines linear decline with late-life fecundity plateaus. Using repeated measures analysis of variance, I show that age-dependent trends in individual fecundity are mostly linear, while among the most longevous individuals up to 20% of the variation in trends is non-linear. Plateaus in individual trajectories might be explained by evolutionary processes or by random environmental variation. The dominant role of environmental variation is supported by several observations, including the high variability of late-life fecundity, the occurrence of occasional individual plateaus in inbred lines, and the observation of plateaus in only a fraction of the population. Plateau and non-plateau flies identified by Le Bourg and Moreau (2014) have, on average, the same total fecundity and the same fecundity trajectories. The available evidence suggests that the environmental variance for late-life fecundity is sufficiently large to produce occasional individual trajectories that resemble plateaus but are not heritable.

Hypovitaminosis D in a sunny country: time trends, predictors, and implications for practice guidelines

The aim of the current study is to investigate the prevalence of hypovitaminosis D in Lebanese subjects, its robust predictors, evaluate the relationship between 25 hydroxy vitamin D [25(OH)D] and parathyroid hormone levels, and derive desirable vitamin D levels, based on a large hospital laboratory database spanning all age groups. Data from a large representative digitized database of 9147 subjects, mostly outpatients, evaluated between 2000-2004 and 2007-2008, in whom information on age, gender, service, and time of the year, was analyzed. The PTH-25(OH)D relationship was studied in a subset of 657 adult subjects, in whom such data were available. At a 25(OH)D cut-off of<20 ng/ml, the prevalence of hypovitaminosis D ranged between 58% and 62% in pediatric subjects, 44% and 60% in adults, and 41% and 62% in elderly, in the 2 study periods. At a cut-off <30 ng/ml, the prevalence was above 78%, in most sub-groups. Regardless of cut-off used, the only significant predictors of high mean 25(OH)D levels were the male gender in the pediatric group, and female gender in adults and elderly, summer/fall seasons, out-patient status, as well as study period. Curve fitting of the PTH-25(OH)D relationship, in adults and elderly, revealed a plateau at 25(OH)D levels of 17-21 ng/ml, depending on sub-study group. Hypovitaminosis D is prevalent in our sunny country, even using a conservative population-derived cut-off of 20 ng/ml, and thus the need for a public health strategy for supplementation.

[Arterial hypertension in Dakar: Prevalence, awareness, treatment, and control]

The aim of this study was to determine prevalence, awareness, treatment, and control of hypertension, and its risk factors in Dakar. Six hundred people aged 20 and older, living in the city of Dakar were interviewed. This sample was constructed using the combined quota method in order to strive to representativeness of the target population. Prevalence of hypertension was 27.50%. Quarter of those suffering from high blood pressure were aware of their problem, and among the latter, 61% said they were on treatment. However, of these, only 32% had controlled arterial blood pressure, that is less than 6% of those suffering from hypertension. Two factors were associated with hypertension, awareness, and treatment: age and the frequency of doctor visits. These results indicate that hypertension already constitutes a major health concern in the Senegalese capital. Detection can be considerably improved given that only a quarter of the hypertensives are aware of this problem. Compliance with treatments also appears particularly problematic. Public health policies should be quickly set up to minimize the consequences of this emerging burden.

Narrowing of the wide nasal dorsum in the 'minimal-hump' nose: A simplified universal approach

The operative procedure frequently used to narrow the nasal pyramid in the context of a regular rhinoplasty is well known to all rhinoplastic surgeons. It consists of hump removal, followed by lateral osteotomies and medialization of the nasal bones. However, narrowing of a wide nasal pyramid, in the absence of an appreciable dorsal hump, as in the case of an ideal dorsal height or a mild hump, presents a different challenge. The present article describes a simplified approach to the 'nasal plateau resection', a technique that allows the creation of an open nasal roof, without hump removal and without compromising dorsal projection. This permits the medialization of the lateral nasal bones and the subsequent narrowing of the wide pyramid, while preserving the height of the nasal dorsum as viewed in profile.

Late-life fecundity plateaus in Drosophila melanogaster can be explained by variation in reproductive life spans

Population trajectories of age-specific fecundity in Drosophila melanogaster typically decline with increasing age and then exhibit an upward inflection, or "plateau", at the oldest ages. This pattern has been interpreted as evidence of an evolved and physiologically distinct life history stage in late life. While low levels of fecundity are common in the last few days of life of individual flies, it is unclear that defining a single age as the beginning of a period of low fecundity for the entire cohort is useful, since reproductive life spans vary substantially from fly to fly. Here I analyze published data on survival and reproduction of individual female flies and show that non-linearities in late-life fecundity trajectories arise from a type of demographic selection that occurs when sub-groups with different reproductive life spans (RLS) are mixed. For groups of flies stratified by RLS late-life fecundity declines linearly with age. A simulation incorporating strictly linear decline of individual fecundities and realistic levels of variation in RLS produces late-life plateaus similar to those observed in experiments. Existing population heterogeneity is a sufficient explanation, and no special evolutionary argument is required. For these data survival and reproduction are governed by positive correlations.

Research advances in plateau hypoxia and gut barrier injury

Gut barrier function is an important feature of the intestinal tract. It consists of mechanical barrier, immune barrier, chemical barrier and organism barrier. Each barrier has different structures, molecular regulatory mechanisms and biologic functions, which are connected organically via their own signal paths simultaneously to protect the host from intruding of foreign antigen. The injury to these barriers in the plateau environment is a complex and inter-related process with many changes of inflammatory mediators and pathologic procedure. In this review, we focus on the barrier injury mechanisms under this special environment.