Le globule rouge drépanocytaire : données fonctionnelles: The sickle red blood cell: functional data.

Sickle cell anemia is a genetic disorder that affects hemoglobin leading to the production of an abnormal hemoglobin, called HbS. HbS has the property to polymerize under deoxygenated conditions, causing a mechanical distortion of red blood cells; a phenomenon called sickling. These sickle red blood cells are more fragile and rigid, leading to chronic hemolytic anemia and painful vaso-occlusive crises, as well as chronic vascular complications that can affect many organs. The abnormal functional properties of these sickle red blood cells are responsible for a wide range of clinical expression of the disease. HbS polymerization can be influenced by many factors, such as the hydration state of the red blood cells or the affinity of hemoglobin for oxygen. Moreover, the rheological characteristics of red blood cells, including their deformability and aggregation properties, are associated with specific clinical phenotypes. The pro-inflammatory and pro-oxidant state, as well as the repeated polymerization of HbS, accelerate the senescence of sickle red blood cells, promoting the release of microparticles and contributing to vascular dysfunction. Patients' red blood cells also have molecular characteristics that promote their adhesion to the endothelium and other circulating cells, contributing to the onset of vascular complications. Massive intravascular hemolysis, due to increased erythrocyte fragility, is also responsible for chronic vascular complications. These different alterations are privileged therapeutic targets, leading to the emergence of new specific treatments. © 2023 Société nationale française de médecine interne (SNFMI). Published by Elsevier Masson SAS. All rights reserved.

Early effects of acetazolamide on hemoglobin mass and plasma volume in chronic mountain sickness at 5100 m.

INTRODUCTION AND OBJECTIVES: Chronic Mountain Sickness (CMS) syndrome, combining excessive erythrocytosis and clinical symptoms in highlanders, remains a public health concern in high-altitude areas, especially in the Andes, with limited therapeutic approaches. The objectives of this study were to assess in CMS-highlanders permanently living in La Rinconada (5100-5300 m, Peru, the highest city in the world), the early efficacy of acetazolamide (ACZ) and atorvastatin to reduce hematocrit (Hct), as well as the underlying mechanisms focusing on intravascular volumes. MATERIALS AND METHODS: Forty-one males (46±8 years of age) permanently living in La Rinconada for 15 [10-20] years and suffering from CMS were randomized between ACZ (250 mg once-daily; N = 13), atorvastatin (20 mg once-daily; N = 14) or placebo (N = 14) uptake in a double-blinded parallel study. Hematocrit (primary endpoint) as well as arterial blood gasses, total hemoglobin mass (Hbmass) and intravascular volumes were assessed at baseline and after a mean (±SD) treatment duration of 19±2 days. RESULTS: ACZ increased PaO2 by +13.4% (95% CI: 4.3 to 22.5%) and decreased Hct by -5.2% (95% CI: -8.3 to -2.2%), whereas Hct remained unchanged with placebo or atorvastatin. ACZ tended to decrease Hbmass (-2.6%, 95% CI: -5.7 to 0.5%), decreased total red blood cell volume (RBCV, -5.3%, 95% CI: -10.3 to -0.3%) and increased plasma volume (PV, +17.6%, 95% CI: 4.9 to 30.3%). Atorvastatin had no effect on intravascular volumes, while Hbmass and RBCV increased in the placebo group (+6.1%, 95% CI: 4.2 to 7.9% and +7.0%, 95%CI: 2.7 to 11.4%, respectively). CONCLUSIONS: Short-term ACZ uptake was effective to reduce Hct in CMS-highlanders living at extreme altitude >5,000 m and was associated with both an increase in PV and a reduction in RBCV.

Strenuous exercise in warm environment is associated with improved microvascular function in sickle cell trait.

PURPOSE: Sickle cell trait is characterized by the presence of both normal and abnormal haemoglobin in red blood cells. The rate of exertional collapse is increased in athletes and military recruits who carry the trait, particularly in stressful environmental conditions. The aim of the present study was to investigate microvascular function and its determinants in response to intense exercise at control and warm environmental temperatures in carriers (AS) and non-carriers (AA) of sickle cell trait. METHODS: Nine AS and 11 AA, all healthy physically active young men, randomly participated in four experimental sessions (rest at 21 °C and 31 °C and cycling at 21 °C and 31 °C). All participants performed three exercises bouts as follows: 18-min submaximal exercise; an incremental test to exhaustion; and three 30-s sprints spaced with 20-s resting intervals. RESULTS: Skin Blood Flow (SkBF) was similar at rest between AA and AS. SkBF for all participants was higher at 31 °C than 21 °C. It was significantly higher in the AS group compared to the AA group immediately after exercise, regardless of the environmental conditions. No significant differences in hemorheological parameters, muscle damage or cardiac injury biomarkers were observed between the two groups. Our data also suggest higher oxidative stress for the AS group, with high superoxide dismutase (P = 0.044 main group effect). CONCLUSION: A specific profile is identified in the AS population, with increased microvascular reactivity after maximal exercise in stressful environment and slight pro-/antioxidant imbalance.

Automatic depletion with Spectra Optia allows a safe 16% reduction of red blood cell pack consumption in exchanged sickle cell anemia patients.

BACKGROUND: Chronic red blood cell exchanges (RBCXs) are frequently used to prevent complications in patients with sickle cell anemia, but the scarcity of matched red blood cell packs (RBCPs) is a serious concern. The main goal of this study was to compare the number of RBCPs used during RBCXs between the Spectra Optia (SO) device (with the automatic depletion step) and the former Cobe Spectra (CSP) device. STUDY DESIGN AND METHODS: The performances and safety of 300 SO sessions using the automatic depletion step (SO/DE) in 50 patients with sickle cell anemia under a chronic transfusion program over a 1-year period were prospectively analyzed. The numbers of RBCPs saved using this protocol compared to the SO device without depletion and to the CSP device were determined. RESULTS: The SO/DE protocol appeared to be safe, as only 5% and 17% of the sessions were characterized by a significant decrease in blood pressure and increase in heart rate (grade 2 adverse events), respectively. Postapheresis hematocrit and fraction of cells remaining reached expected values. The SO/DE protocol required 16% fewer RBCPs compared to SO without depletion, allowing a mean saving of 12 RBCPs per patient and per year and 13% fewer compared to CSP device. Interestingly, the saving was more important for patients with high total blood volume and/or high preapheresis hematocrit. CONCLUSION: The SO/DE protocol is an efficient, safe and cost-effective procedure for patients with sickle cell anemia under a chronic transfusion program.

Eryptosis and hemorheological responses to maximal exercise in athletes: Comparison between running and cycling.

We compared the effects of cycling and running exercise on hemorheological and hematological properties, as well as eryptosis markers. Seven endurance-trained subjects randomly performed a progressive and maximal exercise test on a cycle ergometer and a treadmill. Blood was sampled at rest and at the end of the exercise to analyze hematological and blood rheological parameters including hematocrit (Hct), red blood cell (RBC) deformability, aggregation, and blood viscosity. Hemoglobin saturation (SpO2), blood lactate, and glucose levels were also monitored. Red blood cell oxidative stress, calcium content, and phosphatidylserine exposure were determined by flow cytometry to assess eryptosis level. Cycling exercise increased blood viscosity and RBC aggregation whereas it had no significant effect on RBC deformability. In contrast, blood viscosity remained unchanged and RBC deformability increased with running. The increase in Hct, lactate, and glucose concentrations and the loss of weight at the end of exercise were not different between running and cycling. Eryptosis markers were not affected by exercise. A significant drop in SpO2 was noted during running but not during cycling. Our study showed that a progressive and maximal exercise test conducted on a cycle ergometer increased blood viscosity while the same test conducted on a treadmill did not change this parameter because of different RBC rheological behavior between the 2 tests. We also demonstrated that a short maximal exercise does not alter RBC physiology in trained athletes. We suspect that exercise-induced hypoxemia occurring during running could be at the origin of the RBC rheological behavior differences with cycling.

Sickle cell disease: selected aspects of pathophysiology.

Sickle cell disease (SCD), a genetically-determined pathology due to an amino acid substitution (i.e., valine for glutamic acid) on the beta-chain of hemoglobin, is characterized by abnormal blood rheology and periods of painful vascular occlusive crises. Sickle cell trait (SCT) is a typically benign variant in which only one beta chain is affected by the mutation. Although both SCD and SCT have been the subject of numerous studies, information related to neurological function and transfusion therapy is still incomplete: an overview of these areas is presented. An initial section provides pertinent background information on the pathology and clinical significance of these diseases. The roles of three factors in the clinical manifestations of the diseases are then discussed: hypoxia, autonomic nervous system regulation and blood rheology. The possibility of a causal relationship between these three factors and sudden death is also examined. It is concluded that further studies in these specific areas are warranted. It is anticipated that the outcome of such research is likely to provide valuable insights into the pathophysiology of SCD and SCT and will lead to improved clinical management and enhanced quality of life.

Ventilatory and lactic thresholds in subjects with sickle cell trait.

This study investigated 1) whether ventilatory and lactic thresholds (VT and LT, respectively) are different in sickle cell trait carriers (SCTc) and subjects with normal hemoglobin (control group), and 2) whether the first LT and VT and the second LT and VT are respectively coincident in the two populations. Seven SCTc and 8 control subjects performed an incremental exercise test (IET). Blood lactate concentration and cardioventilatory variables were analyzed at rest and during IET. No significant difference in the ventilatory parameters (notably, maximal oxygen uptake [VO (2max)] and the ventilatory thresholds) or the lactic thresholds was observed between the two groups. In both SCTc and control subjects, the LTs and VTs did not occur at the same exercise intensity. The first VT did not coincide with the first LT, in contrast with the second VT and the second LT, which coincided in both groups. In conclusion, SCTc exhibited normal ventilatory and lactic responses during a progressive and maximal exercise test assessing aerobic physical fitness.

Does the pattern of repeated sprint ability differ between sickle cell trait carriers and healthy subjects.

Sickle cell trait (SCT) is a genetic abnormality affecting the synthesis of normal haemoglobin [Hb] and is the heterozygous form of sickle cell anaemia. The aim of the present study was to compare the ability to repeat maximal cycling sprints (RSA; repeated sprint ability) between SCT carriers (SCT group, n = 7) and a control group with normal haemoglobin [Hb] (n = 7). The two groups performed a 10-s maximal cycling sprint in order to determine the peak power output (P(peak10)). They then performed an RSA test that consisted of five 6-s maximal cycling sprints interspersed with 24 s of passive recovery. For each sprint, the peak power output (P(peak6)) and the work over the 6-s (W6) were calculated. The sum of each W6 developed during the test was considered to be the total work (W(tot)). The decrements over the repeated sprints for P(peak6) (P(6dec)) and W6 (W(6dec)) were also determined. We found no difference in P(peak10), W(tot) and W(6dec) between the two groups. However, the drop in P(peak6) and W6 during the RSA test appeared earlier in the SCT group and the decrease in P(peak6) over the RSA test was greater in the SCT group than in the control group (p < 0.05). In conclusion, we found that: 1) maximal anaerobic performance determined during a single sprint was not altered by SCT, but 2) repeated sprint ability was different in SCT carriers compared with sportsmen with normal Hb.

Oxygen uptake kinetics during heavy submaximal exercise: Effect of sickle cell trait with or without alpha-thalassemia.

Sickle cell trait (SCT) is a genetic disease affecting the synthesis of normal hemoglobin (Hb) marked by the heterozygous presence of HbA and HbS. It is thought that exercise tolerance and aerobic capacity could be limited in SCT carriers, but that the co-existence of alpha-thalassemia with SCT (SCTAT) could improve exercise response. To examine these issues, we compared the characteristics of VO2 kinetics during a constant heavy exercise among athletes carrying either the SCT (n = 6), the SCTAT (n = 9), or the normal Hb (control group; n = 10). After determination of maximal power output (Ppeak), all subjects underwent a constant heavy cycling exercise lasting 9 min at approximately 70 % Ppeak. Pulmonary VO2 and cardio-respiratory parameters were measured breath-by-breath and the VO2 response was modelled using non-linear regression techniques. The time constant of the VO2 primary component and oxygen deficit were not significantly different among the three groups. The VO2 slow component was 28 % and 33 % higher (p < 0.05) in SCT and SCTAT than in the control groups, respectively. Altogether, athletes with the SCT and the SCTAT had higher heart rate at the beginning (+ 5.2 %) and the end (+ 7.4 %) of the slow component compared to the control group (p < 0.05). These results suggest that SCT and SCTAT subjects are not limited during the first exercise minutes, but are prone to exercise intolerance and to lower aerobic capacity thereafter, due to a higher VO2 slow component, and that alpha-thalassemia does not improve exercise response. The finding of a higher slow component in SCT and SCTAT athletes was possibly due to the loss of O2 availability to muscles, additional fiber recruitment and/or higher cardiac load with time.

Lactate distribution in the blood compartments of sickle cell trait carriers during incremental exercise and recovery.

Whether or not whole blood lactate concentration is the same during a ramp exercise test in subjects with sickle cell trait (AS) as in normal subjects remains a point of controversy in the literature. Some studies have shown that the ability to produce or clear circulating lactate might differ between AS and subjects with normal haemoglobin (AA). If this is indeed so, the lactate distribution in the blood compartments should also differ. To test this hypothesis, lactate concentrations in the whole blood, plasma and red blood cells of AS and AA were compared at rest and in response to exercise. Eight AS and 8 AA performed an incremental exercise test. Whole blood, plasma and red blood cell lactate concentrations, the red blood cell : plasma lactate concentration ratio, the plasma-to-red blood cell lactate gradient, haematocrit and cardiorespiratory variables were analysed at rest and during an incremental exercise test and active recovery. Maximal oxygen uptake and ventilatory thresholds were similar in the two groups. No significant difference in whole blood, plasma or red blood cell lactate concentrations was observed between the two groups at rest, during exercise, or during the immediate recovery. Neither the red blood cell : plasma lactate concentration ratio nor the plasma-to-red blood cell lactate gradient differed between groups. Lactate distribution in the blood compartments did not differ between the two groups and this finding suggests that lactate production and/or clearance is quite similar during exercise in AS and AA.

Effect of endurance training on lung function: a one year study.

OBJECTIVE: To identify in a follow up study airway changes occurring during the course of a sport season in healthy endurance athletes training in a Mediterranean region. METHODS: Respiratory pattern and function were analysed in 13 healthy endurance trained athletes, either during a maximal exercise test, or at rest and during recovery through respiratory manoeuvres (spirometry and closing volume tests). The exercise test was conducted on three different occasions: during basic endurance training and then during the precompetition and competitive periods. RESULTS: During the competitive period, a slight but non-clinically significant decrease was found in forced vital capacity (-3.5%, p = 0.0001) and an increase in slope of phase III (+25%, p = 0.0029), both at rest and after exercise. No concomitant reduction in expiratory flow rates was noticed. During maximal exercise there was a tachypnoeic shift over the course of the year (mean (SEM) breathing frequency and tidal volume were respectively 50 (2) cycles/min and 3.13 (0.09) litres during basic endurance training v 55 (3) cycles/min and 2.98 (0.10) litres during the competitive period; p < 0.05). CONCLUSIONS: This study does not provide significant evidence of lung function impairment in healthy Mediterranean athletes after one year of endurance training.

Is hemoglobin desaturation related to blood viscosity in athletes during exercise?

Several studies have suggested that athletes with low hemoglobin saturation during exercise may experience impaired pulmonary blood gas exchange during maximal exercise. Blood viscosity may be implicated in exercise-induced pulmonary hemorrhage in race horses. We hypothesized that blood rheology may contribute to impaired gas exchange and reduced hemoglobin saturation during exercise in humans. A group of 20 highly trained endurance athletes participated in this study, 9 with low hemoglobin saturation during exercise (Low-SpO (2) group) and 11 with normal hemoglobin saturation (High-SpO (2) group). All subjects performed a progressive exercise test conducted to V.O (2max). Venous blood was sampled at rest, 50 % V.O (2max) and maximal exercise. Blood viscosity (etab) was measured at very high shear rate (1000 s (-1)) and 37 degrees C with a falling ball viscometer. The erythrocyte rigidity coefficient, "Tk", was calculated using the Dintenfass equation. At rest, no significant difference in etab was observed between the two groups (3.00 +/- 0.08 mPa . s vs. 3.01 +/- 0.04 mPa . s for the Low-SpO (2) and High-SpO (2) group, respectively). At 50 % V.O (2max) and maximal exercise, etab was higher in Low-SpO (2) (p < 0.01). Tk decreased in High-SpO (2) (p < 0.01) but remained unchanged in the other group during testing. The greater increase in etab in the Low-SpO (2) group during exercise may therefore have been due to the lack of reduction in Tk. As suggested by previous studies, the greater increase in blood viscosity in athletes with low hemoglobin saturation may lead to vascular shear stress. Whether this could impair the blood gas barrier and result in exercise-induced hypoxemia requires further study.

Fiber-linked telescope array: description and laboratory tests of a two-channel prototype.

We present a complete two-telescope version of a fiber-linked coherent array that is meant to be used for mounting on the dish of a radio telescope. This was built with 20-cm amateur telescopes and includes three different servo subsystems for guiding, nulling of the air path difference, and fiber length control. Laboratory tests of the fully integrated system in front of a star simulator are described.

Interferometric control of fiber lengths for a coherent telescope array.

Single-mode fibers have been proposed for connecting telescopes to mixing stations in coherent telescope arrays intended for image synthesis. We describe a laser-controlled servosystem that keeps the fiber-optical length differences stable and permits passage of wide-bandwidth astronomical beams from an unlimited number of telescopes. Initial laboratory results are presented.

Infrared Fourier spectrometer for airborne and ground-based astronomy.

A unique high resolving power near-infrared, astronomical Fourier spectrometer has been constructed foruse at both ground-based and airborne telescopes. Its capabilities include a limiting resolution of 0.01 cm(-1) and spectral coverage over the InSb detector sensitivity region (0.8-5.6 microm). The instrument is optimized for operation in environments inaccessible to other high-resolution Fourier spectrometers, namely, the Cassegrain focuses of conventional telescopes and the NASA Kuiper Airborne Observatory's 91-cm telescope. Details of the spectrometer are discussed, and various astronomical and laboratory spectra are presented.

Of Fourier, Pasteur, and sundry others.

Twenty years of Fourier spectroscopy revival may be long enough to present some reminiscences and general comments. It is necessary to read the text to ascertain how Pasteur fits in.