Forestry Applications of Space-Borne LiDAR Sensors: A Worldwide Bibliometric Analysis

The 21st century has seen the launch of new space-borne sensors based on LiDAR (light detection and ranging) technology developed in the second half of the 20th century. Nowadays, these sensors offer novel opportunities for mapping terrain and canopy heights and estimating aboveground biomass (AGB) across local to regional scales. This study aims to analyze the scientific impact of these sensors on large-scale forest mapping to retrieve 3D canopy information, monitor forest degradation, estimate AGB, and model key ecosystem variables such as primary productivity and biodiversity. A worldwide bibliometric analysis of this topic was carried out based on up to 412 publications indexed in the Scopus database during the period 2004-2022. The results showed that the number of published documents increased exponentially in the last five years, coinciding with the commissioning of two new LiDAR space missions: Ice, Cloud, and Land Elevation Satellite (ICESat-2) and Global Ecosystem Dynamics Investigation (GEDI). These missions have been providing data since 2018 and 2019, respectively. The journal that demonstrated the highest productivity in this field was "Remote Sensing" and among the leading contributors, the top five countries in terms of publications were the USA, China, the UK, France, and Germany. The upward trajectory in the number of publications categorizes this subject as a highly trending research topic, particularly in the context of improving forest resource management and participating in global climate treaty frameworks that require monitoring and reporting on forest carbon stocks. In this context, the integration of space-borne data, including imagery, SAR, and LiDAR, is anticipated to steer the trajectory of this research in the upcoming years.

What does the freshwater clam, Corbicula largillierti, have to tell us about chlorothalonil effects?

Chlorothalonil (CLT) is a broad spectrum, and non-systemic fungicide applied in foliar structures to prevent and treat pathogens. This compound reaches to aquatic environments and affects the biota. In this context, the main goal of this study was to assess the effects of CLT at biochemical, tissular, and individual levels of biological organization using the invasive bivalve Corbicula largillierti as a bioindicator species. Clams were exposed to different sublethal concentrations (0, 10, 20 and 50 µg. L^-1 CLT) for 96 h. At biochemical level, the enzymatic activity (Glutathione-s-Transferase, Catalase, Acetyl-, Butiryl- and Carboxyl-esterases) and lipid peroxidation were measured in gills and the visceral mass. Also, the digestive gland morphometry through quantitative histological indexes was registered at the tissular level. Finally, filtering activity and burial behavior at the individual level were measured. At the highest CLT concentration, the most significant changes were observed in enzymatic activity (except for butyrylcholinesterase), lipid peroxidation and in digestive gland morphometry. It was also registered increases of the filtering activity and the latency time to burial. Most of the biomarkers assessed showed significant responses under CLT exposure. Therefore, taking into account that C. largillierti was affected by CLT, it can be expected that other species could be in a potential risk if this fungicide is present in freshwater systems.

Intensity profile during an ultra-endurance triathlon in relation to testing and performance

We examined the heart rate (HR)-based intensity profile during an ultra-endurance triathlon (UET) estimated from the individual HR-oxygen uptake (˙VO2) relationship during specific graded tests, relating it to race performance. 9 male ultra-endurance triathletes completed the study. Before racing, subjects performed graded exercise tests involving cycle (C) ergometry, treadmill running (R) and free swimming (S) for peak ˙VO2 and HR at ventilatory thresholds (VT). Exercise-specific HR-˙VO2 regression equations were developed. Mean race HR was higher during S (149.2 (10.1) bpm) than during C (137.1 (5.7) bpm) and R (136.2 (10.5) bpm). During C and R, HR was below both VT (11% and 27-28%). HR differences between S and C correlated with C, R and final times. The greatest differences between S and C were related to the worst times in the next stages. These ultra-endurance triathletes performed S at a higher relative intensity, which was inversely correlated with performance in the following stages. The best predictors of final racing time (81%) were weight-adjusted ˙VO2max and HR difference between C and S. A more adequate characterization of the time pattern during the whole race, especially during S, adds new information concerning the intensity profile and cardiovascular demands of an UET race.

Physiological demands of young women's competitive gymnastic routines

The objective of this study was to investigate the physiological indices of competitive routines in women's artistic gymnastics by characterizing post-exercise heart rate (HR), oxygen uptake (VO₂) and peak blood lactate concentration (L_max) in a group of eight young elite-oriented female gymnasts. HR was continuously monitored with Polar RS400 monitors during the test event simulating a competition environment. Within 5 s of the end of each routine, the breath-by-breath gas analyser mask was placed on the face to record VO₂. VO₂max was calculated by the backward extrapolation method of the VO₂ recovery curve. L_max was obtained during recovery (min 1, 3, 5, 7 and 10) subsequent to each event. One week later, HR, VO₂ and L_max were measured during an incremental continuous treadmill test. The treadmill test was confirmed as the assessment with the highest physiological demand. The gymnasts reached their highest values of HR (183-199 beats · min^-1), VO₂/Bm (33-44 ml · kg^-1 · min^-1) and L_max (7-9 mmol · l^-1) in the floor and uneven bars exercises. The vault was the event with the lowest HR (154-166 beats · min^-1) and L_max (2.4-2.6 mmol · l^-1), and the balance beam had the lowest VO₂ (27-35 ml · kg^-1 · min^-1). The mean relative peak intensities attained in the different events, which ranged from 65 to 85% of the individual VO₂max and HRmax recorded in the laboratory, suggest that cardiorespiratory and metabolic demands are higher than previously indicated. The high percentage of VO₂ measured, particularly after the floor event, suggests that aerobic power training should not be neglected in women's artistic gymnastics.

Usefulness and metabolic implications of a 60-second repeated jumps test as a predictor of acrobatic jumping performance in gymnasts

Gymnastics floor exercises are composed of a set of four to five successive acrobatic jumps usually called a “series”. The aims of the study were: 1) to relate the acrobatic gymnastics performance of these series with a repeated jumps test of similar duration (R60), 2) to study the relation between R60 and physiological parameters (heart rate and blood lactate), and the performance obtained in different kinds of jumps, 3) to confirm whether R60, executed without a damped jumping technique, can be considered an anaerobic lactic power test. Twenty male and twenty-four female gymnasts performed three repeated jumps tests for 5 s (R5), 10 s (R10) and 60 s (R60) and vertical jumps, such as drop jumps (DJ), squat jumps (SJ) and countermovement jumps (CMJ). We assessed heart rate (HR) and blood lactate during R10 and R60. The average values of the maximal blood lactate concentration (L_max) after R10 (males = 2.5±0.6 mmol · l⁻¹; females = 2.1±0.8 mmol · l⁻¹) confirm that anaerobic glycolysis is not activated to a high level. In R60, the L_max (males = 7.5±1.7 mmol · l⁻¹ females = 5.9±2.1 mmol · l⁻¹) that was recorded does not validate R60 as an anaerobic lactic power test. We confirmed the relation between the average power obtained in R60 (R60Wm) and the acrobatic performance on the floor. The inclusion in the multiple regression equation of the best power in DJ and the best flight-contact ratio (FC) in R5 confirms the influence of other non-metabolic components on the variability in R60 performance, at least in gymnasts.

Influence of sludge retention time and temperature on the sludge removal in a submerged membrane bioreactor: comparative study between pure oxygen and air to supply aerobic conditions

Performance of a bench-scale wastewater treatment plant, which consisted of a membrane bioreactor, was monitored daily using pure oxygen and air to supply aerobic conditions with the aim of studying the increases of the aeration and sludge removal efficiencies and the effect of the temperature. The results showed the capacity of membrane bioreactor systems for removing organic matter. The alpha-factors of the aeration were determined for six different MLSS concentrations in order to understand the system working when pure oxygen and air were used to supply aerobic conditions in the system. Aeration efficiency was increased between 30.7 and 45.9% when pure oxygen was used in the operation conditions (a hydraulic retention time of 12 h and MLSS concentrations between 4,018 and 11,192 mg/L). Sludge removal efficiency increased incrementally, from 0.2 to 1.5% when pure oxygen was used at low sludge retention time and from 1.5% to 15.4% at medium sludge retention time when temperature conditions were lower than 20°C. Moreover, the difference between calculated and experimental sludge retention time was lesser when pure oxygen was used to provide aerobic conditions, so the influence of the temperature decreased when the pure oxygen was used. These results showed the convenience of using pure oxygen due to the improvement in the performance of the system.

Comparative analysis of the enzyme activities and the bacterial community structure based on the aeration source supplied to an MBR to treat urban wastewater

A comparative analysis was performed in a pilot-scale membrane bioreactor (MBR) treating urban wastewater supplied with either pure oxygen (O2) or air, to assess the influence of each aeration source on the diversity and activity of the bacterial communities in the sludge. The MBR was operated in three experimental stages with different concentrations of volatile suspended solids (VSS) and temperature, and under both aeration conditions. α-Glucosidases, proteases, esterases and phosphatases were tested as markers of organic matter removal in the sludge, and the diversity of the bacterial community was analysed by fingerprinting (temperature-gradient gel electrophoresis of partially-amplified 16S-rRNA genes). Redundancy analysis (RDA) revealed that temperature and VSS concentration were the only factors that significantly influenced the levels of enzyme activities and the values of both the Shannon-Wiener diversity index (H') and the functional organisation index (Fo), while the bacterial community structure experienced significant changes depending on the aeration source supplied in each experimental stage.

Comparative study of the use of pure oxygen and air in the nitrification of a MBR system used for wastewater treatment

A MBR (membrane bioreactor) was performed to quantify the improvement in nitrogen removal terms when pure oxygen and air were used to supply the aerobic conditions at different HRT (hydraulic retention time) and mixed liquid suspended solids concentrations. The improvement in the efficiency was 8.0% and 13.5% when pure oxygen was used with 12h and 18 h of HRT respectively. The ammonium utilization rates with HRT of 18 h with pure oxygen was 1.23 mg N(t)/(L h) and with air 0.66 mg N(t)/(L h) and with HRT of 12h was 1.14 mg N(t)/(L h) and 1.18 mg N(t)/(L h) respectively. Model simulation (DESSAS software) confirmed the validity for nitrogen removal, hydrolysis constant was increased (106% and 184%), decay constant was decreased and Monod's constant was increased (190.4% to 324.1%), and a multivariate analysis with CANOCO v4.5 demonstrated that temperature and HRT have the higher influence in kinetics.

New indices for quantification of the power spectrum of heart rate variability time series without the need of any frequency band definition

This paper presents a new family of indices for the frequency domain analysis of heart rate variability time series that do not need any frequency band definition. After proper detrending of the time series, a cumulated power spectrum is obtained and frequencies that contain a certain percentage of the power below them are identified, so median frequency, bandwidth and a measure of the power spectrum asymmetry are proposed to complement or improve the classical spectral indices as the ratio of the powers of LF and HF bands (LF/HF). In normal conditions the median frequency provides similar information as the classical indices, while the bandwidth and asymmetry can be complementary measures of the physiological state of the tested subject. The proposed indices seem to be a good choice for tracking changes in the power spectrum in exercise stress, and they can guide in the determination of frequency band limits in other animal species.

Kinetic study and oxygen transfer efficiency evaluation using respirometric methods in a submerged membrane bioreactor using pure oxygen to supply the aerobic conditions

The performance of a wastewater bench-scale ultrafiltration membrane bioreactor (MBR) treatment plant using pure oxygen to supply the aerobic conditions for 95 days was studied. The results showed the capacity of the MBR systems to remove organic material under a hydraulic retention time of 12h and a sludge retention time of 39.91 days. Aeration represents its major power input; this is why the alpha-factor of the aeration and kinetic parameters (design parameters) were determined when the mixed liquid suspended solids (MLSS) was increased from 3420 to 12,600 mg/l in order to understand the system. An alpha-factor in the range 0.462-0.022 and the kinetic parameters measured with the respirometric method (K(M) of 73.954-3.647 mg/l, k(d) of 0.0142-0.104 day(-1), k(H) of 0.1266-0.655 day(-1), and the yield mean coefficient of 0.941) were obtained. Our study suggested significant changes in the behaviour of the biological system when the concentration of MLSS was increased.

Spectral and temporal modulation tradeoff in the inferior colliculus

The cochlea encodes sounds through frequency-selective channels that exhibit low-pass modulation sensitivity. Unlike the cochlea, neurons in the auditory midbrain are tuned for spectral and temporal modulations found in natural sounds, yet the role of this transformation is not known. We report a distinct tradeoff in modulation sensitivity and tuning that is topographically ordered within the central nucleus of the inferior colliculus (CNIC). Spectrotemporal receptive fields (STRFs) were obtained with 16-channel electrodes inserted orthogonal to the isofrequency lamina. Surprisingly, temporal and spectral characteristics exhibited an opposing relationship along the tonotopic axis. For low best frequencies (BFs), units were selective for fast temporal and broad spectral modulations. A systematic progression was observed toward slower temporal and finer spectral modulation sensitivity at high BF. This tradeoff was strongly reflected in the arrangement of excitation and inhibition and, consequently, in the modulation tuning characteristics. Comparisons with auditory nerve fibers show that these trends oppose the pattern imposed by the peripheral filters. These results suggest that spectrotemporal preferences are reordered within the tonotopic axis of the CNIC. This topographic organization has profound implications for the coding of spectrotemporal features in natural sounds and could underlie a number of perceptual phenomena.

Influence of a medium-impact aquaerobic program on health-related quality of life and fitness level in healthy adult females

AIM

The aim of the study was to examine the influence of a medium-impact aquaerobic program on the health-related quality of life (HRQoL) and health-related fitness (HRF) level of middle-aged healthy female subjects.

METHODS

Twenty apparently healthy women (mean age: 43.1 [standard deviation: 9.7] years) participated in the study. Criteria for inclusion were absence of diagnosed illnesses, as well and signs and symptoms of disease as evaluated by the Physical Activity Readiness Questionnaire. Participants carried out a medium-impact aquaerobic exercise program consisting of 2 weekly sessions of 60 min during 8 months. Before and after the exercise program, HRQoL was assessed by the 36-item short form health survey (SF-36) questionnaire, and HRF was measured using a simplified version of the AFISAL-INEFC HRF test battery.

RESULTS

Following the exercise program, an increase in all domains of HRQoL, except general health and role-emotional, was observed. Total body mass and body fat percentage decreased, and estimated aerobic power increased.

CONCLUSION

Completion of a medium-impact aquaerobic program (2 weekly sessions of 60 min during 8 months) improves HRQoL in most domains, particularly bodily pain and vitality, and shows to be among the most effective programs for improving perceived quality of life. Moreover, this exercise program proved to have a positive influence on the body composition and functional capacity of the subjects, being effective in reducing fat body mass and improving cardiorespiratory function.

Acclimatization near home? Early respiratory changes after short-term intermittent exposure to simulated altitude

OBJECTIVE

With the ultimate goal of finding a straightforward protocol for acclimatization at simulated altitude, we evaluated the early effects of repeated short-term exposure to hypobaric hypoxia on the respiratory response to exercise in hypoxia.

METHODS

Nine subjects were exposed to a simulated altitude of 5000 m for 2 hours a day for 14 days. Arterial oxygen saturation (SaO2), expired volume per minute (VE), respiratory rate, tidal volume (VT), and heart rate were measured during rest and during exercise (cycloergometer, at 30% of maximum oxygen consumption at sea level), both in normoxia and at 5000 m of simulated altitude on the first and 15th days. On the same days, blood samples were obtained for hematological tests.

RESULTS

During exercise in hypoxia, SaO2 rose from 65 to 71% (P = .02), and VE rose from 55.5 to 67.6 L.min-1 (P = .02) due to an increase in VT from 2 to 2.6 L (P = .003). No significant differences were found in any of the variables studied at rest either in normoxia or in hypoxia or in exercise in normoxia after the exposure program. In the second week, changes in packed cell volume and blood hemoglobin concentration were nonsignificant.

CONCLUSIONS

After short-term intermittent exposure to hypobaric hypoxia, subjects increased their ventilatory response and SaO2 during exercise at simulated altitude. These changes may be interpreted as acclimatization to altitude. The monitoring of ventilatory response and SaO2 during moderate exercise in hypobaric hypoxia may be used to detect the first stages of acclimatization to altitude.

Erythropoietin acute reaction and haematological adaptations to short, intermittent hypobaric hypoxia

This study aimed to determine whether brief hypoxic stimuli in a hypobaric chamber are able to elicit erythropoietin (EPO) secretion, and to effectively stimulate erythropoiesis in the short term. In two different experiments, a set of haematological, biochemical, haemorheological, aerobic performance, and medical tests were performed in two groups of healthy subjects. In the first experiment, the mean plasma concentration of EPO ([EPO]) increased from 8.7 to 13.5 mU.ml-1 (55.2%; P < 0.01) after 90 min of acute exposure at 540 hPa, and continued to rise until a peak was attained 3 h after the termination of hypoxia. In the second experiment, in which subjects were exposed to a simulated altitude of up to 5500 m (504 hPa) for 90 min, three times a week for 3 weeks, all haematological indicators of red cell mass increased significantly, reaching the highest mean values at the end of the programme or during the subsequent 2 weeks, including packed cell volume (from 42.5 to 45.1%; P < 0.01), red blood cell count (from 4.55 x 10(6) to 4.86 x 10(6).l-1; P < 0.01), reticulocytes (from 0.5 to 1.4%; P < 0.01), and haemoglobin concentration (from 14.3 to 16.2 g.dl-1; P < 0.01), without an increase in blood viscosity. Arterial blood oxygen saturation during hypoxia was improved (from 60% to 78%; P < 0.05). Our most relevant finding is the ability to effectively stimulate erythropoiesis through brief intermittent hypoxic stimuli (90 min), in a short period of time (3 weeks), leading to a lower arterial blood desaturation in hypoxia. The proposed mechanism for these haematological and functional adaptations is the repeated triggering effect of EPO production caused by the intermittent hypoxic stimuli.

Maximal oxygen uptake and cardiorespiratory response to maximal 400-m free swimming, running and cycling tests in competitive swimmers

BACKGROUND

This study compared the cardiorespiratory response of trained swimmers to 400-m unimpeded front crawl swimming (SW), treadmill running (TR) and ergometer cycling (EC) maximal exercise tests, and evaluated the validity and specificity of a method to measure maximal aerobic power in swimming.

METHODS

Two series of experiments were conducted. In series A (n=15), comparisons were made between VO2peak and other cardiorespiratory variables in three maximal tests: after 400-m SW, and during incremental TR and EC. In series B, VO2 peak and related variables were measured after SW and during EC (n=33).

RESULTS

No significant differences were observed between VO2peak and VE in the three modes of exercise, although SW values tended to be higher. After SW, maximal ventilatory response was characterized by higher tidal volumes (VT) and lower respiratory rates (fR) as compared with TR and EC. The highest heart rate values (fH) were also observed in TR, followed by EC and SW. In series B, no significant differences were observed either in peak VO2 or VE, but fH was also lower in SW.

CONCLUSIONS

A maximal 400-m unimpeded freestyle SW test yields essentially equal or nonsignificantly higher peak VO2 and VE values than during maximal TR or EC tests in trained swimmers. The specific maximal cardiorespiratory response to the SW test is characterized by higher VT, lower fR, and lower fH. Breath-by-breath measurements during the immediate recovery after a 400-m voluntary maximal swim is proposed as a valid and specific test for directly measuring maximal metabolic parameters and evaluating specific maximal aerobic power in swimming.

[Comparation of the antero-lateral and posterior approaches in primary total hip arthroplasty]

Comparison between the antero-lateral and posterior approaches in primary total hip arthroplasty. In this retrospective study, 184 patients were enrolled, 95 submitted to the anterolateral (Watson jones) and 89 to the posterior approach (Moore) from June 1993 to June 1997. The outcomes assessed were perioperative data (operative time, hospital stay, time from surgery until hospital discharge, surgical bleeding and the need for blood transfusion), as well as late complications (deep venous thrombosis DVP, pulmonary embolism, periopheral nerve injury, prothesis instability and others). Both groups did not differ in terms of preoperative parameters. Those submitted to the posterior approach had shorter operative times (p < 0.001), as well as reduced bleeding (p < 0.05) and need for blood transfusion (p < 0.001) during surgery. The outcomes, such as late complications, had similar reduced frequency in both groups. The posterior approach has been successfully applied in our service and proves to be an excellent alternative surgical access to the total hip arthroplasty.

Intermittent hypobaric hypoxia induces altitude acclimation and improves the lactate threshold

The physiological responses to short-term intermittent exposure to hypoxia in a hypobaric chamber were evaluated. The exposure to hypoxia was compatible with normal daily activity. The ability of the hypoxia program to induce hematological and ventilatory adaptations leading to altitude acclimation and to improve physical performance capacity was tested. Six members of a high-altitude expedition were exposed to intermittent hypoxia and low-intensity exercise (in cycle-ergometer) in the INEFC-UB hypobaric chamber over 17 d, 3-5 h x d(-1), at simulated altitude of 4,000 m to 5,500 m. Following this hypoxia exposure program, significant increases were found in packed cell volume (41 to 44.6%; p<0.05), red blood cells count (4.607 to 4.968 10(6) cells x microL(-1); p<0.05), and hemoglobin concentration (14.8 to 16.4 g x dL(-1); p<0.05), thus implying an increase in the blood oxygen transport capacity. Significant differences in exercise blood lactate kinetics and heart rate were also observed. The lactate vs. exercise load curve shifted to the right and heart rate decreased, thus indicating an improvement of aerobic endurance. These results were associated with a significant increase in the ventilatory anaerobic threshold (p<0.05). Significant increases (p<0.05) in pulmonary ventilation, tidal volume, respiratory frequency, O2 uptake, CO2 output and ventilatory equivalents to oxygen (VE/Vo2) and carbon dioxide (VE/co2) were observed at the ventilatory threshold and within the transitional zone of the curves. We conclude that short-term intermittent exposure to moderate hypoxia, in combination with low-intensity exercise in a hypobaric chamber, is sufficient to improve aerobic capacity and to induce altitude acclimation.

Intermittent hypobaric hypoxia stimulates erythropoiesis and improves aerobic capacity

PURPOSE

The purpose of the study was to examine the effect of a very short intermittent exposure to moderate hypoxia in a hypobaric chamber on aerobic performance capacity at sea level and the erythropoietic response. The effects of hypobaric hypoxia alone and combined with low-intensity exercise were also compared.

METHODS

Seventeen members of three high-altitude expeditions were exposed to intermittent hypoxia in a hypobaric chamber over 9 d at simulated altitude, which was progressively increased from 4000 to 5500 m in sessions ranging from 3 to 5 h x d(-1). One group (N = 7; HE group) combined passive exposure to hypoxia with low-intensity exercise on a cycle ergometer. Another group (N = 10; H group) was only exposed to passive hypoxia. Before and after the exposure to hypoxia, medical status, performance capacity, and complete hematological and hemorheological profile of subjects were evaluated.

RESULTS

No significant differences were observed between the two groups (HE vs H) in any of the parameters studied, indicating that hypoxia alone was responsible for the changes. After the acclimation period, a significant increase in exercise time (mean difference: +3.9%; P < 0.01), and maximal pulmonary ventilation (+5.5%; P < 0.05) was observed during the maximal incremental test at sea level. Individual lactate-velocity curves significantly shifted to the right (P < 0.05), thus revealing an improvement of aerobic endurance. A significant increase was found in PCV (42.1-45.1%; P < 0.0001), RBC count (5.16 to 5.79 x 10(6) x mm(-3); P < 0.0001), reticulocytes (0.5 to 1.1%; P < 0.0001) and hemoglobin (Hb) concentration (14.2 to 16.7 g x dL(-1); P < 0.002).

CONCLUSIONS

It was concluded that short-term hypobaric hypoxia can activate the erythropoietic response and improve the aerobic performance capacity in healthy subjects.

New evidence from magnetic resonance imaging of brain changes after climbs at extreme altitude

The aim of the present study was to look for anatomical changes in climbers' brains, using magnetic resonance imaging (MRI), after extremely high-altitude climbs and to relate them to possible associated risk factors. Clinical history, neurological examinations and MRI were carried out on a group of nine climbers before and after climbing to over 7500 m without the use of supplementary oxygen. None of the subjects showed any neurological dysfunctions. In five climbers MRI abnormalities (high signal areas, cortical atrophy) were observed before the expedition. After the descent, two of them showed new high intensity signal areas recorded by MRI. Both subjects suffered severe neurological symptoms during the climb. The present study suggested that the brain changes observed by MRI could be related to the severity of clinical events at high altitude. However, we do not know the exact meaning of such MRI findings or the reason for their location, predominantly in posterior regions of the brain. The new evidence that a high percentage of climbers show MRI brain abnormalities, and especially the appearance of changes after the ascent, reinforces the possibility of a potential neurological risk in high-altitude climbing.

Cortical atrophy and other brain magnetic resonance imaging (MRI) changes after extremely high-altitude climbs without oxygen

The purpose of the present study is to detect by means of MRI any structural changes in the brain and their correlation with the clinical history of climbers who have ascended to extremely high altitudes without supplementary oxygen. Clinical history, neurological examinations and brain MRI were obtained from a group of 26 climbers who ascended to over 7000 m without supplementary oxygen, and the results were compared with a control group (n = 21) of healthy subjects. All the MRI studies were carried out between 26 days and 36 months after return to sea level. Significant neuropsychological disorders were experienced by all climbers during the ascent with residual neurobehavioural impairment after returning to sea level in 58% of them. The neurological examination was normal in all subjects. Almost half of the climbers showed MRI abnormalities (46%). Characteristic signal patterns of cortical atrophy were detected in five subjects. Periventricular hyperintensity lesions in the T2-weighted images were observed in other five climbers. Both types of lesions were found in two subjects. These pathological findings did not correlate with age, sex, clinical symptoms, maximal altitude reached, or length of exposure to extreme altitude. The exact long-term pathological significance of these MRI abnormalities is as yet unknown.

A comparative study of blood lactate analytic methods

Three different blood lactate analytic methods were tested for precision, accuracy, linearity, and intermethod comparison: a photoenzymatic assay (PHE), and three electroenzymatic (EE) semiautomatic assays (EE1, EE2, EE3). Reference standards and duplicate capillary blood samples from the earlobe were used. Precision and accuracy of the three techniques, when measuring L-lactate standards, were good in the whole range of measurement (mean variation coefficient, VC = 1.78-3.38%; mean difference = 1.81-3.38%). Correlation between the three methods was high (r = 0.913-0.946), but all three electroenzymatic techniques systematically measured lower values as compared to the PHE tests. The differences ranged from 0.1-1.2 (5 mmol.l-1 PHE level), to 3.4-5.7 (20 mmol.l-1 PHE level). These differences were drastically reduced when a hemolyser and a glycolytic inhibitor were added to the sample prior to the assay. The measurements obtained in capillary blood by the three techniques are not equivalent. The differences are partially attributed to the fact that the PHE technique measures total blood lactate, while the EE methods only measure plasmatic-extraerythrocytic lactate. Some regression equations are presented that may be used to convert values measured by the PHE technique, to EE values and vice versa.