Biphasic voltage relaxation pattern observed in cells of Eremosphaera viridis after injection of charge-pulses of short duration: detection of tip clogging of intracellular microelectrodes by charge-pulse technique.

Charge pulse experiments performed on the peat-bog alga Eremosphaera viridis revealed an unusual voltage relaxation behaviour. Injection of charge pulses of 1 microseconds duration resulted in an immediate charging of the membranes (time constant of the order of 40 ns). Nevertheless, the potential-measuring microelectrode recorded an exponential increase in membrane voltage with a time constant of about 1.3 ms. The maximum voltage value was recorded after about 3 ms, followed by an exponential decay with a time constant of about 9.6 ms. This biphasic time course was independent of the amplitude of the injected charge and of the location of the impaled microelectrodes in the vacuole. Centrifuged cells in which the chloroplasts and the other organelles were pelleted in one part of the cells showed the same electrical response. Electrical breakdown of the cell membranes resulted in the disappearance of the biphasic voltage response. In this case only the decaying relaxation process could be recorded with a time constant of 3 ms. After resealing of the membranes the original biphasic relaxation response was restored. Increasing concentrations of KCl in the bathing medium reduced both time constants almost correspondingly. The experimental findings were evaluated with an electrical equivalent circuit. Theoretical analysis with reference to the experimental data suggested that the delayed voltage response of the potential-recording electrode resulted from a membrane seal across the tip of this electrode. The resistance of this seal was calculated to be about 400 M omega. The specific resistances and capacitances of tonoplast and plasmalemma membranes were calculated from the decaying part of the biphasic relaxation curves. The average values were found to be 2.58 omega.m2 and 5 mF.m-2. The investigations reported here suggest that charge pulse experiments can be generally used for the detection of membrane and cytoplasmic material clogging of the tip of intracellular microelectrodes, a problem with which most electrophysiologists are faced when interpreting data obtained from impaled microelectrodes.

Low plasma glutamine in combination with high glutamate levels indicate risk for loss of body cell mass in healthy individuals: the effect of N-acetyl-cysteine.

Skeletal muscle catabolism, low plasma glutamine, and high venous glutamate levels are common among patients with cancer or human immunodeficiency virus infection. In addition, a high glycolytic activity is commonly found in muscle tissue of cachectic cancer patients, suggesting insufficient mitochondrial energy metabolism. We therefore investigated (a) whether an "an-aerobic physical exercise" program causes similar changes in plasma amino acid levels, and (b) whether low plasma glutamine or high glutamate levels are risk factors for loss of body cell mass (BCM) in healthy human subjects, i.e., in the absence of a tumor or virus infection. Longitudinal measurements from healthy subjects over longer periods suggest that the age-related loss of BCM occur mainly during episodes with high venous glutamate levels, indicative of decreased muscular transport activity for glutamate. A significant increase in venous glutamate levels from 25 to about 40 microM was seen after a program of "anaerobic physical exercise." This was associated with changes in T lymphocyte numbers. Under these conditions persons with low baseline levels of plasma glutamine, arginine, and cystine levels also showed a loss of BCM. This loss of BCM was correlated not only with the amino acid levels at baseline examination, but also with an increase in plasma glutamine, arginine, and cystine levels during the observation period, suggesting that a loss of BCM in healthy individuals terminates itself by adjusting these amino acids to higher levels that stabilize BCM. To test a possible regulatory role of cysteine in this context we determined the effect of N-acetyl-cysteine on BCM in a group of subjects with relatively low glutamine levels. The placebo group of this study showed a loss of BCM and an increase in body fat, suggesting that body protein had been converted into other forms of chemical energy. The decrease in mean BCM/body fat ratios was prevented by N-acetyl-cysteine, indicating that cysteine indeed plays a regulatory role in the physiological control of BCM.

Individual variation in the erythropoietic response to altitude training in elite junior swimmers.

OBJECTIVES: Inter-individual variations in sea level performance after altitude training have been attributed, at least in part, to an inter-individual variability in hypoxia induced erythropoiesis. The aim of the present study was to examine whether the variability in the increase in total haemoglobin mass after training at moderate altitude could be predicted by the erythropoietin response after 4 h exposure to normobaric hypoxia at an ambient Po(2) corresponding to the training altitude. METHODS: Erythropoietin levels were measured in 16 elite junior swimmers before and after 4 h exposure to normobaric hypoxia (Fio(2) 0.15, approximately 2500 m) as well as repeatedly during 3 week altitude training (2100-2300 m). Before and after the altitude training, total haemoglobin mass (CO rebreathing) and performance in a stepwise increasing swimming test were determined. RESULTS: The erythropoietin increase (10-185%) after 4 h exposure to normobaric hypoxia showed considerable inter-individual variation and was significantly (p<0.001) correlated with the acute erythropoietin increase during altitude training but not with the change in total haemoglobin mass (significant increase of approximately 6% on average). The change in sea level performance after altitude training was not related to the change in total haemoglobin mass. CONCLUSIONS: The results of the present prospective study confirmed the wide inter-individual variability in erythropoietic response to altitude training in elite athletes. However, their erythropoietin response to acute altitude exposure might not identify those athletes who respond to altitude training with an increase in total haemoglobin mass.

Changes in bone turnover induced by aerobic and anaerobic exercise in young males.

Physical activity is considered an important factor in attaining bone mass. However, the mechanisms by which exercise affects bone metabolism are not completely understood. The present study was performed to investigate the effects of aerobic and anaerobic exercise on bone turnover. Twenty healthy young males (aged 20-29 years) were followed through an 8-week program of aerobic (n = 10) and anaerobic training (n = 10). Ten age-matched individuals served as controls. Serum bone-specific alkaline phosphatase (BAP), serum osteocalcin (OC), and urinary pyridinoline (Pyd) and deoxypyridinoline (Dpd) were determined as indices of bone metabolism. After 4 weeks of aerobic training, serum BAP and OC (p < 0.01), and urinary Pyd (p < 0.001) and Dpd (p < 0.01) were significantly reduced. After 8 weeks, BAP and OC levels had returned to baseline values, whereas the urinary cross-link excretion remained low. In the anaerobic training group, elevated levels of BAP (p < 0.05 vs. week 4), OC (p < 0.05 vs. week 4), and Pyd (p < 0. 01 vs. week 0) were observed after 8 weeks of exercise. Changes in urinary Pyd and Dpd (week 0 vs. week 8) were positively correlated with changes in the mean power level in the Wingate test, a parameter of the anaerobic performance capacity (r = 0.50 and r = 0. 55, p < 0.01, respectively). In the controls, no significant changes in biochemical markers were observed. We conclude that aerobic and anaerobic training excert different effects on bone metabolism. While aerobic training led to changes compatible with reduced bone resorption activity, anaerobic training seems to result in an overall accelerated bone turnover. Therefore, the impact of physical activity on bone turnover may depend on the kind of exercise performed.

Effects of iron repletion on blood volume and performance capacity in young athletes.

PURPOSE: The purpose of this study was to find out whether iron repletion leads to an increase in red blood cell volume (RBV) and performance capacity in iron-deficient nonanemic athletes. METHODS: 40 young elite athletes (13-25 yr) with low serum ferritin (< 20 microg.L-1) and normal hemoglobin (males > 13.5 g.dL-1, females > 11.7 g.dL-1) were randomly assigned to 12-wk treatment with either twice a day ferrous iron (equivalent to 2 x 100 mg elemental iron) or with placebo using a double blind method. Before and after treatment, hematological measures and parameters of iron status were determined in venous blood. RBV, blood volume (BV), and plasma volume (PV) were measured by CO rebreathing. For determination of the aerobic and anaerobic capacity (maximal accumulated oxygen deficit, MAOD), the athletes performed an incremental as well as a highly intensive treadmill test. RESULTS: After 12 wk, ferritin levels were within the normal range in the iron-treated group (IG) with a significant (P < 0.001) mean increase by 20 microg.L-1 opposed to a slight nonsignificant decrease in the placebo group (PG). RBV did not change significantly in either group nor did any of the hematological measures. However, only in IG there were significant increases in VO2max and in O2 consumption in the MAOD test. MAOD and maximal capillary lactate concentration remained unchanged in both treatment groups. CONCLUSIONS: The results indicate that in young elite athletes with low serum ferritin and normal hemoglobin concentration iron supplementation leads to an increase in maximal aerobic performance capacity without an augmentation of RBV.

Effect of severe exercise on plasma catecholamines in differently trained athletes.

OBJECTIVE: In the present study we investigated whether plasma catecholamine (CA) responses to short-term severe exercise (SX) are affected by different training regimen and whether this test will increase plasma catecholamine sulfates. METHODS: Nine anaerobically (ANTA) and eight aerobically trained male athletes (ATA) performed a severe treadmill exercise test (SX) at similar oxygen demands, leading to exhaustion within 2-3 min. RESULTS: The anaerobic contribution to energy supply was higher in ANTA than in ATA as indicated by the higher maximal accumulated oxygen deficit (37.5+/-3.5 vs. 22.7+/-4.4 mL x kg(-1) x min(-1)) (means +/- SE) (P<0.009) and blood lactate concentration after exercise (19.4+/-2.4 vs. 15.0+/-1.9 mmol x L(-1)) (P<0.005). In both groups plasma norepinephrine (NE), norepinephrine sulfate (NE-S), epinephrine (EPI), and epinephrine sulfate (EPI-S) increased significantly (P<0.05) during exercise with higher increments (P<0.05) in ANTA than in ATA (NE: 87.5+/-9.7 vs. 60.8+/-7.1 nmol x L(-1), P<0.034; EPI: 16.6+/-3.3 vs. 6.9+/-1.2 nmol x L(-1), P<0.009). CONCLUSION: Data suggest that during this type of exercise the sympathoadrenergic system is more activated in ANTA than in ATA and seems related to the higher anaerobic contribution to energy supply in ANTA. The short duration of SX was sufficient to increase plasma NE-S and EPI-S concentration.

Lack of effect of oral Mg-supplementation on Mg in serum, blood cells, and calf muscle.

UNLABELLED: Magnesium (Mg) is important for regulating ion transport and cellular metabolism in all body tissues. In skeletal muscle Mg is involved in the neuromuscular activity, excitation, and muscle contraction. Mg deficiency can cause muscle weakness and muscle cramps. Less than 1% of total body Mg is found in serum, yet the serum Mg concentration is used to assess the body's Mg status. PURPOSE: The purpose of this study was to determine whether an oral Mg supplementation (500 mg Mg-oxide.d-1 for 3 wk) affects exercise performance, clinical symptoms, and the Mg concentration in various body compartments in athletes with low-normal serum Mg levels (N = 10 in each group). METHODS: In a double-blind, placebo-controlled study, correlation analysis between the Mg concentration in serum, blood cells, and skeletal muscle was performed to establish a measure for muscle cell Mg. RESULTS: The data indicate that a 3-wk Mg supplementation did not affect exercise performance, neuromuscular activity, or muscle related symptoms. Also, the supplementation did not increase the Mg concentration in serum or any cellular compartment studied. However, in the placebo group the renal Mg clearance decreased, whereas it increased in the subjects receiving Mg supplementation. Correlation analysis revealed that serum Mg only correlated with red cell Mg and that only leukocyte Mg correlated with the nuclear magnetic resonance (NMR)-measured muscle cell Mg concentration. CONCLUSIONS: These results indicate that Mg supplementation in athletes with low-normal serum Mg did not improve performance and failed to increase the body's Mg stores. Serum Mg appears to be a poor indicator for Mg in skeletal muscle or most other cellular compartments, but the concentration of Mg in mononuclear leukocytes might be used as an indicator of skeletal muscle Mg when NMR is not available.

Coagulation and thrombomodulin in response to exercise of different type and duration.

PURPOSE: The present study was conducted to evaluate the role of the duration of exercise and the impact of the exercise type for exercise-induced activation of coagulation. METHODS: Eleven male triathletes were subjected to stepwise maximal (17 min) and 1-h maximal exercise in swimming, cycling, and running. Changes of hemostatic variable sand of plasma thrombomodulin, a marker of endothelial cell activation, were monitored. RESULTS: Irrespective of the type of exercise, alterations in markers of thrombin (prothrombin fragment 1 + 2, thrombin-antithrombin III complexes) and fibrin formation (fibrinopeptide A) were more pronounced after 1-h exercise than after stepwise maximal exercise. Hemostatic parameters rose to the highest levels after running resulting in substantial fibrin formation as indicated by fibrinopeptide A increasing from 1.33 ng.mL-1 to 2.25 ng.mL (P < 0.05) after 1-h exercise testing. Significant changes of plasma thrombomodulin were detected exclusively after running with increases from 38.2 ng.mL-1 to 44.2 ng.mL-1 (1 h, P < 0.01). CONCLUSIONS: The data demonstrated that prolonged exercise is necessary for exercise-induced activation of coagulation resulting in thrombin and fibrin formation and suggested that endothelial cell activation possibly due to mechanical factors associated with running might play a role.

Balanced activation of coagulation and fibrinolysis after a 2-h triathlon.

To examine whether exercise-induced thrombin formation is accompanied by increased in vivo plasmin formation, we measured molecular markers and neoantigens of the hemostatic system in 10 male subjects (mean 29 yr. range 19-38) before, immediately after, and 2, 8, and 21 h after a triathlon lasting 128-163 min. Thrombin-antithrombin (TAT) complexes, fibrinopeptide A (FPA), and tissue plasminogen activator (t-PA) antigen were maximally increased immediately after exercise and decreased thereafter rapidly. Prothrombin fragment 1 + 2 (PTF1 + 2), fibrin degradation products (FbDP) and plasmin-antiplasmin (PAP) complexes rose to a similar extent 0 and 2 h after exercise decreased thereafter. The maximal levels of PTF1 + 2, TAT, FPA, and FbDP were 1.5-, 2.1-, 1.8-, and 1.9-fold above baseline, respectively. This investigation shows that strenuous prolonged exercise leads to a moderate activation of blood coagulation resulting in thrombin and fibrin formation which is accompanied by a greatly enhanced plasmin generation. It is concluded that the hemostatic of healthy individuals is well kept in balance when stimulated by prolonged strenuous exercise.

The blood volume and splenic red cell pool in hairy cell leukemia.

Investigating the splenic red cell pool in 7 patients with hairy cell leukemia we have found unusually high values of retained erythrocytes (means 527 ml, SD 264) with a range from 300 to 998 ml. This amount represents on average 26% of the total red cell mass. The blood volume in these patients ws 26% greater than predicted by NADLER et al. Following splenectomy, the hemoglobin improved with 49.3% (SD 29.1).

[A brief account of the 130 year history of the First Czech Internal Medicine Clinic]. / Utrzky ze stotricetileté historie I. ceské (interní) kliniky.

The first Czech medical clinic in Prague was founded in 1871 during the period of Czech revival by prof. Bohumil Eiselt. Since that time the clinic was headed by eight professors, each of them being an impressive and outstanding personality contributed significantly to its future development. The clinic keeps its immense vitality and represents the place of an outstanding curative and research activity.

[The importance of iron in humans]. / Význam zeleza v lidském organismu.

The authors submitted a very brief review of some biological properties of iron in particular protein-bound iron and on the immense amount of iron which surrounds us (it is the fourth most frequent element). In the human organism there is no physiological system for iron elimination. Therefore its absorption is regulated and restricted. Some substances promote its absorption, other inhibit it. An important factor in the regulation of iron absorption are the iron reserves of the organism, the amount of dietary iron and the enhanced erythropoiesis (incl. the ineffective one), while reduced erythropoiesis does not affect iron absorption. Ascorbic acid forms chelates with iron and thus remains soluble and can be absorbed despite the alkaline pH in the duodenum. Unbound trivalent iron remains insoluble. An important asset to rational iron therapy are Lauberger's discovery of ferritin (1936), assessment of the iron plasma level (Heilmeyer and Plötner, 1937), Laurell's discovery of transferrin (1947), and Addison's RIA method for assessment of the serum ferritin level (1974). Sideropenia remains the most widespread deficiency in human pathology, sideropenic anaemia the most readily diagnosed anaemia which is, however, most wrongly treated.

[Hypercalcemia as the first manifestation of bone marrow T-cell lymphoma]. / Hyperkalcémie jako první manifestace drenového T lymfomu.

The authors describe the case of a 20-year-old patient where the first leading symptom was hypercalcaemia. A similar case was not published so far in the Czech literature. The disease took a fulminant course and proved fatal nine days after the first symptoms of the disease. The correct diagnosis was established only by necropsy. The adverse course of the disease could not be influenced by repeated haemodialysis nor by the administration of disodium pamidronate (Aredia) and calcitonin. The authors discuss differential diagnostic problems of hypercalcaemias and the pathogenesis of hypercalcaemia in malignant diseases of the haematopoietic system.

[Diagnosis of performance capacity and guided training for physical endurance]. / Leistungsdiagnostik und Trainingssteuerung im Ausdauerbereich.

The evaluation of the aerobic capacity is of great importance for athletes as well as for patients with cardiac and pulmonary diseases. For objective measurements of cardiorespiratory and metabolic responses heart rate, lactate concentration in capillary blood and ventilatory gas exchange are determined during incremental exercise tests either on different ergometers in a laboratory or under training conditions in the field. Besides the maximal O2-uptake (VO2max) several ventilatory and lactate thresholds have been proposed as reliable values for assessing the aerobic capacity and giving training recommendations. For interpretation of the results the training and nutrional behaviour in the previous days have to be considered as especially the lactat thresholds are influenced by the glycogen content of the muscles. Furthermore, training recommendations cannot always be easily transferred from test to training conditions as these can be very different from each other.

[Trephine biopsy of the bone marrow in hematologic tumors]. / Trepanobiopsie kostní drene pri hematologických nádorech.

A group of 1000 random trephine biopsies were evaluated according to their usefulness for typing and staging of haematological tumours. Trephine biopsy contributed someway to clinical data in half the cases. Primary medullary processes showed an excellent correspondence of clinical and bioptical data. Biopsy contributed substantially to specification of myeloproliferations and myodysplasias. There were only 24% of negative results (descriptive inconclusive). Malignant lymphomas presented situation analogical to leucaemias. Peripherical malignant lymphomas in medulla mostly did not follow diversity of lymph node phenomena and did not contribute to more detailed typing but enabled satisfactory staging. Malignant lymphomas were located, unlike leucaemia, intertrabeculary or peritrabeculary and often induced reactive myeloproliferation or scarring. Biopsy was usually good for separation of medullary carcinosis. Remarks to technology of getting and processing of bioptical sample were discussed.

[Pseudo-anemia caused by sports]. / Pseudoanämie durch Sport.

Regular physical training leads to an increase of plasma volume by 10-20 percent. Therefore, hemoglobin concentration slightly below normal values in the presence of low-normal serum ferritin levels in athletes are usually due to a dilutional "pseudoanemia". Several cross sectional studies indicate that true iron deficiency anemia is not more frequent in athletes than in the general population. Since regular physical activity, especially extensive, running increases iron loss, mild iron deficiency (abnormal serum ferritin and normal hemoglobin concentration) and sometimes true iron deficiency anemia can occur especially when nutritional iron intake is insufficient and iron demand is increased because of growth (children, adolescents) or additional iron loss (menstruation). Several controlled studies indicate that iron supplementation (recommended dose 2 x 100 mg elementary iron/day) improves performance only when hemoglobin concentration increases, i.e. when iron deficiency anemia is present. On the contrary, iron supplementation has no measurable effects on performance when hemoglobin concentration cannot be increased, i.e. in mild iron deficiency.

[Glanzmann thrombasthenia--a defect in the surface membrane of platelets]. / Glanzmannova trombastenie--defekt povrchové membrány krevních desticek.

The authors present a clinical description, detailed platelet function analysis, and certain biochemical parameters in two siblings with Glanzmann thrombasthenia (G. t.). The isolated occurrence of this disorder in the family corresponds with its autosomal recessive inheritance. In both cases blood platelets completely failed to aggregate. In contrast, the platelet interaction with ristocetin, reflecting their ability to adhere to the subendothelium, the so-called "shape change", the storage granule contents and their release and arachidonic acid metabolism were unaffected. Further, the aggregation abnormality was accompanied by marked procoagulant activity and clot retraction defects; these functions, similarly as aggregation, are implemented on the platelet surface. The analysis of blood platelet proteins, using two dimensional polyacrylamide electrophoresis, confirmed the absence of glycoprotein GP IIb and IIIa and a decrease of the fibrinogen content. The analysis of these findings in G. t. led to the contemporary concept that GP IIb and IIIa on the platelet surface act as receptors for platelet aggregation.