Increased core body temperature in astronauts during long-duration space missions.

Humans' core body temperature (CBT) is strictly controlled within a narrow range. Various studies dealt with the impact of physical activity, clothing, and environmental factors on CBT regulation under terrestrial conditions. However, the effects of weightlessness on human thermoregulation are not well understood. Specifically, studies, investigating the effects of long-duration spaceflight on CBT at rest and during exercise are clearly lacking. We here show that during exercise CBT rises higher and faster in space than on Earth. Moreover, we observed for the first time a sustained increased astronauts' CBT also under resting conditions. This increase of about 1 °C developed gradually over 2.5 months and was associated with augmented concentrations of interleukin-1 receptor antagonist, a key anti-inflammatory protein. Since even minor increases in CBT can impair physical and cognitive performance, both findings have a considerable impact on astronauts' health and well-being during future long-term spaceflights. Moreover, our findings also pinpoint crucial physiological challenges for spacefaring civilizations, and raise questions about the assumption of a thermoregulatory set point in humans, and our evolutionary ability to adapt to climate changes on Earth.

Changes in the haemostatic system after thermoneutral and hyperthermic water immersion.

Warm water bathing is a popular recreational activity and is frequently used in rehabilitation medicine. Although well tolerated in most cases, there are reports indicating an increased risk of thrombotic events after hot tub bathing. The effects of a 45 min thermoneutral bath followed by a 50 min bath with increasing water temperature (maximum 41 degrees C) until reaching a body core temperature of 39 degrees C on factors of blood coagulation and fibrinolysis were studied in eight healthy male volunteers. Blood was obtained after a 45-min resting period as control and after the thermoneutral and hyperthermic bath as well as after another 45 min recovery period at the end of the study. Hyperthermic immersion (HI) lead to a shortening of activated partial thromboplastin time (aPTT) (P < 0.05). Fibrinogen concentration decreased immediately after HI (P < 0.05) but increased during recovery (P < 0.05). Plasminogen activator inhibitor (PAI) activity decreased during HI (P < 0.05), D-dimer concentration was not found to change. Thrombocyte count increased (P < 0.05) during HI. The increases in tissue-type plasminogen activator concentration as well as leucocyte count during HI were due to haemoconcentration. Prothrombin time, PAI-activity and granulocyte count decreased during thermoneutral immersion (P < 0.05). Warm water bathing leads to haemoconcentration and minimal activation of coagulation. The PAI-1 activity is decreased. A marked risk for thrombotic or bleeding complications during warm water bathing in healthy males could not be ascertained.

Rapid identification of iron deficiency in blood donors with red cell indexes provided by Advia 120.

BACKGROUND: A new generation of automated hematology analyzers allows the rapid determination of various red cell (RBC) indexes, including the percentage of hypochromic mature RBCs (HYPOm) and the hemoglobin (Hb) content of reticulocytes (CHr). These indexes have not yet been validated as measures for the detection of iron deficiency in blood donors. STUDY DESIGN AND METHODS: Iron status was evaluated in a total of 1142 unselected prospective blood donors based on measurement of serum ferritin, soluble transferrin receptor, and Hb compared to RBC indexes provided by an automated hematology analyzer (Advia 120, Bayer HealthCare) including HYPOm and CHr. RESULTS: Assuming that the most precise measure for body iron storage is related to the logarithm of the ratio of soluble transferrin receptor to ferritin, the sensitivity of ferritin for the diagnosis of iron depletion was 89 percent compared to 57 percent for HYPOm and CHr, respectively, to 69 percent for the combination of both RBC indexes, and to 26 percent for Hb concentration. CONCLUSION: The RBC indexes HYPOm und CHr are significantly better screening measures for identification of iron depletion in blood donors than Hb.

Concentraciones de hierro en atletas de resistencia / Iron status in endurance athletes

Numerous reports have described a poor iron status in endurance athletes (especially in females). However, the traditionally applied indicators of iron status may not truly reflect the iron status. Therefore the newly developed indicators for iron status (soluble transferrin receptor, reticulocyte indices or hypochromic red blood cells) should be applied to control iron status in endurance athletes.

Numerosos informes describen bajas concentraciones de hierro en los atletas de resistencia (especialmente en mujeres). Sin embargo, los indicadores tradicionalmente utilizados en la evaluación de los niveles de hierro podrían no reflejar claramente esta carencia. Por lo tanto, los recientemente descubiertos indicadores de las concentraciones de hierro (el receptor soluble de transferrina, los índices reticulocitarios y los glóbulos rojos hipocrómicos) podrían emplearse para controlar los niveles de hierro en los atletas de resistencia.

Daily doses of 20 mg of elemental iron compensate for iron loss in regular blood donors: a randomized, double-blind, placebo-controlled study.

BACKGROUND: A considerable number of regular blood donors develops an iron deficiency, and the exact amount of iron required to compensate for the iron loss from whole-blood donation in males and females is still unknown. STUDY DESIGN AND METHODS: A total of 526 regular blood donors (289 male and 237 female) were randomly assigned to treatment with either 40 mg, 20 mg, or 0 mg per day of elemental iron as ferrous gluconate for a period of 6 months, during which one unit of whole blood was collected on four occasions (males) or three occasions (females). Hemoglobin level, serum ferritin, and soluble transferrin receptor levels were measured before each donation. RESULTS: Daily doses of either 40 mg or 20 mg of elemental iron adequately compensated for iron loss in males, who gave blood at 2-month intervals, but did not result in a positive iron balance or an increase in storage iron as reflected by the logarithm of the ratio of transferrin receptor to ferritin concentration. In females, who donated at 3-month intervals, the same daily doses not only restored the iron balance but also led to an increase in storage iron. The number of gastrointestinal side effects due to iron supplementation (12%) was only slightly higher in both iron groups than in the placebo group. CONCLUSION: The results of this study indicate that 20 mg of elemental iron per day can adequately compensate for iron loss in males and females who donate whole blood up to four (females) or six times per year (males).

Iron supplementation and 2-unit red blood cell apheresis: a randomized, double-blind, placebo-controlled study.

BACKGROUND: The benefits of 2-unit red blood cell (RBC) apheresis are evident, but iron depletion may be a limiting factor in using this technology. Regular iron supplementation may allow a better utilization of this technique. STUDY DESIGN AND METHODS: In this study, 260 regular blood donors donated 2-unit RBCs on each of a total of seven visits at intervals of 8 to 10 weeks. The volunteers were randomly assigned to receive 100 mg of iron(II) or placebo daily. Group A received iron capsules after the first three donations, and Group B after the second three donations, respectively. Hemoglobin, serum ferritin, and serum iron were measured before each donation. RESULTS: Mean serum ferritin concentration decreased after each donation in the placebo phase of both treatment groups, but it remained largely constant during the iron phase in Group A, and even increased during the iron phase in Group B. CONCLUSION: Regular iron supplementation prevents iron depletion in the majority of donors after 2-unit RBC apheresis within an 8- to 10-week period.

Austrian Moderate Altitude Study (AMAS 2000) - fluid shifts, erythropoiesis, and angiogenesis in patients with metabolic syndrome at moderate altitude (congruent with 1700 m).

It was hypothesized that subjects with metabolic syndrome (hypertension, obesity, hyperlipidemia, diabetes mellitus): (1) develop measurable peripheral edema at moderate altitude and (2) might show differences on erythropoiesis, iron status and vascular endothelial growth factor (VEGF) in comparison to healthy subjects during and after a long-term stay (3-week exposure) at moderate altitude (congruent with 1700 m). Twenty-two male subjects with metabolic syndrome were selected. Baseline investigations (t1) were performed in Innsbruck (500 m). All participants were transferred by bus to 1700 m (Alps) and remained there for 3 weeks with examinations on day 1 (after the first night at altitude, t2), day 4 (t3), day 9 (t4) and day 19 (t5). After returning to Innsbruck, post-altitude examinations were conducted after 7-10 days (t6) and 6-7 weeks (t7), respectively. Body mass was decreased from t1 to t7 (P<0.01). Total body water was decreased at t2 (P<0.01), returned to control level (t3, t4), and was found elevated at t7 (P<0.01). Lean body mass did not change, but body fat decreased during the study (P<0.01). Tissue thickness at the forehead decreased during and after altitude exposure (P<0.01), whereas tissue thickness at the tibia did not alter. Erythropoietin (EPO) was elevated as early as t2 and remained increased until t5. Reticulocyte count was increased at t3 and remained above pre-altitude values. VEGF levels were unchanged. After a 3-week exposure to moderate altitude, patients with metabolic syndrome had reduced their body mass, mainly because of a reduction in body fat. The moderate altitude was found to stimulate erythropoiesis in these patients but this was not sufficient to increase serum VEGF concentration.

Influence of endurance exercise (triathlon) on circulating transferrin receptors and other indicators of iron status in female athletes.

Numerous reports have described a poor iron status in female endurance athletes. However, the traditionally applied indicators of iron status (hemoglobin, ferritin, transferrin) may not truly reflect the iron status. Therefore we studied the newly developed soluble transferrin receptor and other indicators of iron status in twelve female endurance athletes before and after a triathlon race. Resting values showed a poor iron status in the participants of the race. Serum TfR concentration increased slightly after the race. However, if the values are corrected for hemoconcentration no change could be found. Hemoglobin, serum ferritin and transferrin values were increased after the race.