K. Kirsch

Fluid shifts into and out of superficial tissues under microgravity and terrestrial conditions

SummaryThe microgravity environment can be expected in man to induce a swelling of facial tissues and a shrinking of the tissues in the lower limbs together with a loss in body weight. To quantitate fluid shifts into and out of superficial tissues an ultrasound A-mode method was used in one cosmonaut during a 7-day spaceflight. Measurements were taken from frontal and tibia tissues, where the underlying bone provides a good backwall echo. During the spaceflight the cosmonaut showed a swelling of facial tissues during the first 3 days. At the same time the superficial tissues of the caudal areas shrank by 20%. In space he lost 7.7% of body weight. After the spaceflight the superficial tissues were dried out but regained their water content within the next 4 days even before body weight returned to control level. Per kilogram of body weight an increase of 400 cm3 entered the superficial tissue layers of the body. It is concluded that water loss as well as wasting of tissues contribute to the loss in body weight during space flight.

Effects of sustained intrathoracic vascular distension on body fluid distribution and renal excretion in man

SummaryIntrathoracic blood volume was increased by prolonged immersion in thermo-indifferent (34δ C) water. Urinary excretion patterns of free water and electrolytes during immersion were compared with those for an identical period of the previous day when the subjects were performing routine activity. Plasma volume changes during immersion were compared with the concomitant urine volume which under these conditions can be equated with total fluid loss. The nature of the immersion diuresis depended on the state of hydration. Normally hydrated subjects showed a rise in free water clearance whereas a hydropenic group increased urine volume by an augmentation of osmolar clearance. Sodium excretion during immersion rose from 118±48 (SD) to 180±51.7 (SD) μeq./h×kg in normally hydrated subjects (p>0.05) and from 66.8±22.5 (SD) to 152±43.3 (SD) μeq./h×kg (p<0.01) in the hydropenic group.Immersion led to plasma volume reduction in all cases. Plasma volume reduction constituted a much greater percentage of the urine volume in hydropenic subjects (98.8±35.4 (SD)%) than in the normally hydrated ones (19.3±8.56 (SD)%). It is concluded that engorgement of the intrathoracic volume-sensitive vascular areas may not only lead to increased fluid elimination by the kidney but at the same time to a shift of fluid from plasma into the interstitial space. Both effects serve the homeostatic control of blood volume.

Vascular endothelial growth factor in exercising humans under different environmental conditions

Abstract It was the aim of this study to investigate the time course of changes in the serum concentrations of vascular endothelial growth factor (VEGF) during a regular survival training programme combined with food and fluid deprivation and during a high altitude marathon run. We studied soldiers of the Austrian Special Forces performing survival training at sea-level and marathon runners of the Posta Atletica who crossed the border between Chile and Argentina at altitudes up to 4722 m. Baseline data collected before the 1-week of survival training showed that the soldiers had normal VEGF [n=8, 246.7 (SD 118.5) pg · ml−1] serum concentrations which remained unchanged during the course of the study. Before the high altitude marathon the subjects showed normal VEGF serum concentrations [178 (SD 84.5) pg · ml−1]. After the run VEGF concentrations were found to be significantly decreased [41.0 (SD 41.6) pg · ml−1, P < 0.01]. It was concluded that prolonged physical stress during normobaric-normoxia did not alter the VEGF concentrations whereas during severe hypobaric-hypoxia decreased VEGF serum concentrations were measured, at least temporarily, after prolonged physical exercise which might have been due to changes in production, release, removal and/or binding of circulating VEGF.

Feeding patterns of endurance athletes

SummaryFeeding pattern was studied in 13 long distance runners, eight cyclists and eight sedentary men. The timing of the food and fluid intakes, the kind and the amount of food and fluids taken, the body weight (BW), and the exercise schedules were recorded on 3 or 4 successive days under ad libitum conditions of feeding and drinking. The subjects remained in energy and water balance, since the BW measured in the morning during the observation periods did not change significantly. The total caloric intake was 13 876 kJ per day in the runners and 26 282 kJ per day in the cyclists, exceeding the estimated basic metabolic rate by 103% and 250% respectively. The total water intakes were 33 and 36 ml·kg−1·24 h−1. The athletes consistently showed a nibbling pattern, characterized by frequent eating and drinking (average 8–10 per day). In the runners 63% of eating and drinking were synchronized, in the cyclists only 49% (p<0.01). In both groups drinking occurred most frequently in the morning, at noontime and in the evening. After 8 p.m. 45% of the total daily fluid intake occurred. In all likelihood the fluid intake followed an underlying circadian rhythm. The total intake frequency was determined by the total caloric needs.

NEW DATA ON THE DIMENSIONS OF BRACHIOSAURUS BRANCAI AND THEIR PHYSIOLOGICAL IMPLICATIONS

There are highly divergent data on the body m a s s (mb) of Brachiosaurus (B.). The range of the body-mass estimations lies between 14900 and 102000 kg for this giant dinosaur [1-6] . This is mainly due to the fact that different specimens and varying techniques are used for the volume (V) estimations, such as equations from the circumferences of femur and humerus [4] or from the volume of models [5]. The precise determination of Vis important for calculating the body surface area (SA) as well as for allometric equations, which are often based on Mb. Herewith, we present a photogrammetric method to determine the metrical dimensions of giant sauropods such as B. The data presented here are based on the skeleton of B. brancai from the Upper Jurassic of Tendaguru (East Africa, Tanzania), mounted and exhibited at the Museum of Natural History in Berlin (Germany). The major part of the skeleton belongs to one single specimen of B. brancai recovered from the Middle Saurian Bed at Tendaguru. The tail originates from another individual of the same species of similar size found in the Upper Saurian Bed. In addition, skeletal remains of B. brancai excavated in different sites in the surroundings of the Tendaguru hill were used for the mounting, partly original and partly modeled. The presacral vertebral column (cervicals, dorsals) and the skull have been replaced by plaster copies modeled from originals of the main skeleton due to their extreme fragility and weight. The right shoulder blade, four dorsal ribs, and some bones of the left forefoot have been modeled in plaster according to counterparts of the other body side. Some missing elements are substituted by bones belonging to individuals of the same size such as the right ilium, the right ischium, and the left lower leg. Other missing items have been replaced by originals (e.g., left femur) or copies of bones from different-sized animals (e.g., sacrum, most hindfoot bones). At the very end of the tail four small pieces were added. Like the missing first caudal vertebra, most of the hemapophyses (chevrons) are plaster imitations [6]. As can be seen in Fig. 1, we divided the presumable shape of B. brancai into XI parts. Each part was separately calculated and the Vi-xi are given in Table 1. From the V found, the Mb was calculated assuming a density of 1000 kg per m 3 tissue [5, 7]. On the basis of the above findings, we investigated further whether the presumable organ volumes derived by allometric equations could be fitted into the anatomical dimensions given by the skeleton. The advantage of the photogrammetrical approach is that when the values are taken from a specimen, the complete shape of the animal is stored in the computer. This allows later derivation of other forms and dimensions, which is almost impossible from a model. In the case of a small model being built from the data and later becoming enlarged, the smallest deviation is multiplied by a factor of 10-50 depending on the size of the model. Therefore, regardless of the size of a model, it is defined by these exact basal metric values. The anatomical data of B. brancai derived by stereophotogrammetry and the presumable physiological data calculated after equations given for endotherms are summarized in Table1, Table2, and Fig. 2. According to these, the Mb of B. braneai is ca. 74420 kg (skeleton 11480 kg). Accordingly, the M b estimations in [1] are similar to our findings, whereas those in [2, 4 6 ] are far too low. It is not clear whether the estimation in [3] for B. refers to the Berlin specimen. If so, it is far too high. The S A (Table 2) was found to be at least (without any skin-

Plasma volume, albumin and globulin concentrations and their intravascular masses. A comparative study in endurance athletes and sedentary subjects.

Plasma volume, hematocrit, intravascular protein concentration, colloid osmotic pressure and the intravascular mass of proteins were measured in 49 sedentary subjects and 40 endurance athletes (long-, middle distance runners, cyclists).The plasma volume in sedentary subjects was 42.7 (35.8–51.7) ml/kg body weight (BW) as compared to 54.6 (46.7–65.9) ml/kg BW in athletes. The protein concentrations were 71.0 (66.5–77.1) g/l in sedentary subjects and 69.0 (64.8–75.2) g/l in athletes. The respective numbers for the hematocrit were 44.6 (40.1–49.25)% and 42.8 (38.2–49.6)%, for the colloid osmotic pressure 38.0 (36.0–40.5) cm H2O (n = 35) and 30.0 (25.0–34.4) cm H2O (n = 31), for the intravascular mass of proteins 3.09 (2.45–4.01) g/kg BW and 3.75 (3.31–4.67) g/kg BW. All differences were statistically significant at least on the 5% level.The physiological consequences for athletes of having a lower hematocrit and lower protein concentration but a higher intravascular mass of proteins (+22%) for their waterbalance as well as for their dietary protein intake are discussed. Endurance exercise stimulates mainly the synthesis of albumin and globulins produced by the liver resulting in an expansion of the PV. The protein synthesis of the RES does not seem to respond to exercise stimulus.

Formation of edema and fluid shifts during a long-haul flight

BACKGROUND More than 1.5 billion passengers travel by aircraft every year. Leg edema, as a sign of venous stasis, is a well-known problem among passengers during and after long-haul flights. Until now, no studies have been done on the development of leg edema and fluid shifts under real flight conditions. The aim of our study was to evaluate edema formation in the leg and to investigate possible fluid shifts to the interstitial space under real flight conditions. METHODS Twenty participants, 10 without risk and 10 with moderate risk for venous thrombosis, were selected. They flew from Vienna to Washington, flight time 9 h, and returned 2 days later. Investigations were done 48 h before the flight, between the fifth and eighth flight hour on board to Washington and back to Vienna, immediately after arrival in Vienna, and 1 and 3 days after arrival. Plethysmographic measurements were carried out using an optoelectronic scanner system (Perometer). Thickness of the skin was measured at the forehead and in front of the tibia. RESULTS There were no differences in all measurements between both groups. The volume of the leg increased from 8242 +/- 1420 mL to 8496 +/- 1474 mL after the flight (p <.001). Volume accumulation was distributed to the lower leg as well as to the thigh. Skin thickness in front of the tibia increased significantly during the flight (p <.05), and remained elevated 1 day after arrival. CONCLUSION We have demonstrated that long-haul flights induce significant fluid accumulation in the lower extremity, involving the lower leg and thigh. This increase in tissue thickness was maintained for some days after the flights.

Distribution and circulation of extracellular fluid and protein during different states of hydration in the cat

Summary1.Determinations of plasma volume (PV) and circulating protein in 13 anaesthetized cats before and after dehydration by deprivation of water for 48 h revealed an 11.5% decrease of PV and a 13.5% decrease of circulating protein, the plasma protein concentration and the albumin/globulin ratio remaining essentially constant. Extracellular fluid volume (ECFV) was reduced by 13.8% in 9 dehydrated animals as compared to 10 control animals.2.The fractional disappearance rate of radio albumin revealed that half a pool of albumin is exchanging with the extravascular space in 10 h in control animals as well as in dehydrated animals. The observation that lymph flow and lymph protein transport from the thoracic duct were closely correlated with the state of filling of the interstitial space explains why half a pool of plasma albumin was returned to the blood stream in 16.5 h in dehydrated animals as compared to 10 h in controls. The reduction of plasma albumin due to dehydration was calculated to result from the disturbance of the dynamic equilibrium between transcapillary albumin shift and lymphatic return.3.During rehydration by saline infusion, dehydrated animals kept larger percentages of the infused fluid inside the intravascular space demonstrating a decrease of net transcapillary fluid shift. The increase of lymph flow during infusion was shown to be closely correlated with the filtration rate. There was an increase of transcapillary protein shift and a decrease of transport rates for lymph protein during infusion.

Erythropoietin in 29 men during and after prolonged physical stress combined with food and fluid deprivation

The study investigated the influence of prolonged physical stress during survival training with food and fluid deprivation on the serum concentrations of erythropoietin (EPO). A group of 29 male subjects [mean age 22.2 (SD 2.8) years, height 1.78 (SD 0.06) m, and body mass (mb) 73.5 (SD 8.6) kg] were studied for 5 days of multifactorial stress including restricted water intake (1] H2O · day−1) and food intake (628 kJ day−1) combined with physical exercise (estimated energy expenditure approximately 24 000 kJ · day−1) and sleep deprivation (20h within 5 days). Blood samples were taken before (T1), after 72 h (T2) and 120h (T3) of physical stress, and after 48h, (T4) and 72 h (T5) of recovery. The samples were analysed for EPO, and concentrations of serum iron (Fe), haptoglobin (Hapto), transferrin (Trans), ferritin (Fer), haemoglobin (Hb) and packed cell volume (PCV). The mb had decreased by 6.77 kg at T3 (P <0.01) and 0.68 kg at T5. The EPO and Hapto decreased during the survival training (P <0.01) and increased during the recovery period (P <0.01). The Fe increased during the survival training (P <0.01) and remained above the control concentrations during recovery (P <0.01). The Hapto decreased during the survival training (P <0.01) and remained below control concentration at T4 and T5 (P <0.01). The Trans decreased continuously over the week (P <0.01). The Fer increased during the survival training (P <0.01) and returned to control concentration at T5. The Hb increased from T1 to T2 (P <0.01) and had decreased significantly at T5 (P <0.01). The PCV increased from T1 to T2 (P <0.01) and remained below control levels afterwards (P <0.01). From our study it was concluded that, in humans, prolonged physical stress with food and fluid deprivation induces a marked EPO decrease, which is followed by a rapid increase during recovery to restore the reduced OZ transport capacity.

Fluid distribution and tissue thickness changes in 29 men during 1 week at moderate altitude (2,315 m)

To quantify fluid distribution at a moderate altitude (2,315 m) 29 male subjects were studied with respect to tissue thickness changes [front (forehead), sternum, tibia], changes of total body water, changes of plasma volume, total protein concentrations (TPC), colloid osmotic pressure (COP), and electrolytes. Tissue thickness at the forehead showed a significant increase from 4.14 mm to 4.41 mm 48 h after ascent to the Rudolfshuette (2,315 m) (P < 0.05). At 96 h after ascent the tissue thickness at the tibia was decreased to 1.33 mm compared to the control value of 1.59 mm (P < 0.01). Body mass increased from 75.5 kg (control) to 76.2 kg on the last day (P < 0.05) and body water from 44.21 to 45.01 during the week (P < 0.01). The accumulation fluid in the upper part of the body was paralleled by a decrease in TPC and COP. At 48 h after the ascent COP dropped from 29.5 mmHg to 27.5 mmHg (P < 0.01). After 96 h at moderate altitude COP was still significantly decreased compared to the control level. At 1.5 h after the return from the Rudolfshuette in Saalfelden (744m) COP was back to the control values. The TPC also showed an initial drop from 7.75 g · dl−1 to 7.48 g · dl−1 after 48 h at altitude and remained below the control value during the whole week (P < 0.01). It seems from our study that even with exposure to moderate altitude measurable fluid shifts to the upper part of the body occurred which were detected by our ultrasound method.