Myofibril and sarcoplasmic reticulum changes with exercise and growth

Summary The intent of this study was to observe the effects of different treadmill running programs upon selected biochemical properties of soleus muscle from young rats. Young 10 day litter-mates were assigned to endurance (E), sprint (S) and control (C) groups. Each was partitioned into either 21 or 51 day exercising groups and 10 day controls. For C the myofibril ATPase activity at 21 and 51 days were lower than 10 day activity (p0.05). In the 51 day E group ATPase activity (0.378±0.009 mol Pi·mg^–1·min^–1) was greater than at 10 and 21 days (0.307±0.006 and 0.323±0.008 mol Pi·mg^–1·min^–1) (p0.05). No change occurred in the S group from 10 to 21 and 51 days (p0.05). Both the 21 and 51 day S (0.318±0.011 and 0.399±0.010 mol Pi·mg^–1·min^–1) and E (0.323±0.008 and 0.378±0.009 mol Pi·mg^–1·min^–1) groups had higher activity compared to the C group (0.193±0.029 and 0.172±0.031 mol Pi·mg^–1·min^–1) (p0.05). Maturation (10–51 day) resulted in a lowered sarcoplasmic reticulum (SR) yield and Ca²⁺ binding (p0.05) while Ca²⁺ uptake ability did not change (p0.05). SR yield, Ca²⁺ binding and uptake were not altered with S training (p0.05). The E training resulted in greater Ca²⁺ uptake at 51 days compared to C and S (p0.05), with no change in Ca²⁺ binding (p0.05). The data suggest that E training alters the normal development pattern of young rat soleus muscle.Supported by grants A-6449 and A-0425 from the Natural Sciences and Engineering Research Council of Canada     

Variations in serum myoglobin after a 2-min isokinetic exercise test and the effects of training

Summary Serum-myoglobin was measured after the completion of three different types of exercise i.e., dynamic, isometric, and isokinetic. The maximal rises in serum-myoglobin levels were 20%, 70%, and 300%, respectively. On the basis of this finding a 2-min isokinetic test was developed and standardized for the purpose of studying conditions in vivo that may affect myoglobin leakage from skeletal muscle cells.Fourteen healthy men performed the 2-min isokinetic test. Blood lactate increased on average eight times with maximal levels obtained 4 min after completed work. S-Myoglobin was raised approximately five times after 2 h. The rise in S-myoglobin was significantly (P<0.01) related to the loss in muscle strength (torque decline) during the test. After a training period of 3 weeks comprising 4 min of maximal isokinetic exercise three times a week the rise in S-myoglobin after a 2-min isokinetic test was reduced from on average 240 g·l^–1 to 96 g·l^–1 (P<0.001). The rise in blood lactate was not related to the variations in S-myoglobin or affected by training.The 2-min isokinetic exercise test is an easily standardized exercise test which in combination with measurements of serum-myoglobin should prove valuable in the study of conditions affecting leakage from muscle cells.     

Collagen of slow twitch and fast twitch muscle fibres in different types of rat skeletal muscle

Summary The appearance of collagen around individual fast twitch (FT) and slow twitch (ST) muscle fibres was investigated in skeletal muscles with different contractile properties using endurance trained and untrained rats as experimental animals. The collagenous connective tissue was analyzed by measuring hydroxyproline biochemically and by staining collagenous material histochemically in M. soleus (MS), M. rectus femoris (MRF), and M. gastrocnemius (MG). The concentration of hydroxyproline in the ST fibres dissected from MS (2.72±0.35 g·mg^–1 d.w.) was significantly higher than that of the FT fibres dissected from MRF (1.52±0.33 g·mg^–1 d.w.). Similarly, the concentration of hydroxyproline was higher in ST (2.54±0.51 g·mg^–1 d.w.) than in FT fibres (1.60±0.43 g·mg^–1 d.w.), when the fibres were dissected from the same muscle, MG. Histochemical staining of collagenous material agreed with the biochemical evidence that MS and the slow twitch area of MG are more collagenous than MRF and the fast twitch area of MG both at the level of perimysium and endomysium. The variables were not affected by endurance training. When discussing the role of collagen in the function of skeletal muscle it is suggested that the different functional demands of different skeletal muscles are also reflected in the structure of intramuscular connective tissue, even at the level of endomysial collagen. It is supposed that the known differences in the elastic properties of fast tetanic muscle compared to slow tonic muscle as, e.g., the higher compliance of fast muscle could at least partly be explained in terms of the amount, type, and structure of intramuscular collagen.This study was supported by grants from the Finnish Research Council for Physical Education and Sport (Ministry of Education) and the Academy of Finnland     

Vascular fluid shifts and endocrine responses to exercise in the heat

Summary This study examines the relationships between vascular changes and endocrine responses to prolonged exercise in the heat, associated with dehydration and rehydration by fluids of different osmolarity. Five subjects were exposed, in a 34 C environment for 4 h of intermittent exercise on a cycle ergometer at 85±12 Watts (SD). Fluid regulatory hormones and cortisol were analysed in 3 experimental sessions: one without any fluid supplement (NO FLUID), and two with progressive rehydration, either by spring water (WATER) or isotonic solution (ISO), given after 70 min of exercise. Results were expressed in terms of differences between the mean values observed at the end of the exercise and the first hour values taken as references.Dehydration (NO FLUID) elicited a 4.0±0.8% (SE) decrease in plasma volume (PV) and an increase in osmolarity (8.4±3.1 mosmol · l^–1). Concomitantly, plasma aldosterone (PA), renin activity (PRA), arginin vasopressin (AVP) and cortisol (PC) levels increased greatly in response to exercise in the heat (PA: 37.2+-10.8 ng. 100 ml^–1; PRA: 13.4±2.5 ng · ml^–1 · h^–1; AVP: 3.8±1.3 pg · ml^–1; PC: 12.2±2.7 g · 100 ml^–1). Rehydration with water led to decreased osmolarity (–8.2±2.1 mosmol · l^–1) with no significant changes in PV. With ISO, PV increased by 6.0±1.3% and the decrease in osmolarity was –5.8±1.8 mosmol · l^–1. With both modes of rehydration, the increases in PRA, AVP and cortisol were blunted; only ISO prevented the rise in PA.These data indicate that prolonged exercise in moderate heat is extremely effective in increasing cortisol and fluid-electrolyte regulatory hormones in dehydrated subjects. Progressive rehydration with water or isotonic solution, in the absence of osmotic and volemic stimuli, prevents the hormonal increases.     

Neuronal composition and interneuronal connection of area 5 in the cat parietal association cortex

Area 5 of the cat cortex was studied by Nissl's method and by Golgi's chromate-silver impregnation method. Its typical six-layered structure with well-developed layers of pyramidal cells was revealed. The characteristic features of area 5 are: predominance of pyramidal cells in layers II–III and the presence of large forms (40×26) among them (in layer III); giant pyramidal neurons (70×23) arranged singly or nidally in layer V; large (diameter 25–30) and giant (diameter 40–45) stellate cells with radial dendrites, arranged singly or in groups in layers V–VI; infrequent efferent fusiform neurons (40×20) in layers V–VI. Stellate cells connecting pyramidal neurons in the same or in different layers were found in layers II–VI. Some stellate cells in layers II–III form long horizontal connections within area 5. Interneuronal connections are effected by axosomatic and axodendritic terminals, the latter being more numerous; Dendrodendritic and axoaxonal synapses are less common.Translated from Neirofiziologiya, Vol. 11, No. 1, pp. 35–42, January–February, 1979.     

The responses of the catecholamines and β-endorphin to brief maximal exercise in man

Summary The responses to brief maximal exercise of 10 male subjects have been studied. During 30 s of exercise on a non-motorised treadmill, the mean power output (mean±SD) was 424.8±41.9 W, peak power 653.3±103.0 W and the distance covered was 167.3±9.7 m. In response to the exercise blood lactate concentrations increased from 0.60±0.26 to 13.46±1.71 mmol·l^–1 (p<0.001) and blood glucose concentrations from 4.25±0.45 to 5.59±0.67 mmol·l^–1 (p<0.001). The severe nature of the exercise is indicated by the fall in blood pH from 7.38±0.02 to 7.16±0.07 (p<0.001) and the estimated decrease in plasma volume of 11.5±3.4% (p<0.001). The plasma catecholamine concentrations increased from 2.2±0.6 to 13.4±6.4 nmol·l^–1 (p<0.001) and 0.2±0.2 to 1.4±0.6 nmol·l^–1 (p<0.001) for noradrenaline (NA) and adrenaline (AD) respectively. The plasma concentration of the opioid-endorphin increased in response to the exercise from <5.0 to 10.2±3.9 p mol·l^–1. The post-exercise AD concentrations correlated with those for lactate as well as with changes in pH and the decrease in plasma volume. Post-exercise-endorphin levels correlated with the peak speed attained during the sprint and the subjects peak power to weight ratio. These results suggest that the increases in plasma adrenaline are related to those factors that reflect the stress of the exercise and the contribution of anaerobic metabolism. In common with other situations that impose stress,-endorphin concentrations are also increased in response to brief maximal exercise.     

Lactate after exercise in man: IV. Physiological observations and model predictions

Summary Following earlier papers that established the mathematical form of the time dependence of lactate concentrations during recovery from several types of exercise, and that set up a two-compartment model predicting the same time dependences, the present work applies the model to obtain parameters of specific physiological processes. Satisfactory agreement between predictions of the model and our experiment and literature data is obtained in the cases where comparisons can be made, as in the muscular lactate time evolution measured from biopsy samples, in blood flows through the active muscle at the end of exercise or at rest and their evolution during recovery, as well as in the volume of the active muscle compartment. The model prediction that lactate efflux from the muscles to the blood can reduce to zero during recovery is verified experimentally.List of Abbreviations and Symbols A ₁, A ₂ Amplitudes of the two exponential terms fitted to arterial lactate concentrations (mol·1^–1) - ₁₂, ₂₁ Transfer coefficients from (M) to (S) and (S) to (M) respectively (min^–1) - A _D Area of the body according to Dubois (m²) - BM Body mass (kg) - C ₁, C ₂ Amplitudes of the exponential terms of L _m (t) (mol·1^–1) - c ₁, d ₁ Rates of lactate production in (M) and (S), respectively (mol·min^–1) - c ₂, d ₂ Coefficients of lactate disappearance in (M) and (S) respectively (min^–1) - F ₁ Field of validity of the model (see [32]) - ₁, ₂ Velocity constants of the exponential terms fitted to arterial lactate concentrations (min^–1) - L _a (t) Arterial lactate concentration at time t (mmol·1^–1 or mol·1^–1) - L _a max Maximum arterial lactate concentration of the recovery (mmol·1^–1) - L _fv (t) Femoral venous blood lactate concentration at time t (mmol·^–1) - L _M (t), L _S (t) Lactate concentrations in (M) and (S), respectively at time t (mmol·1^–1 or mol·1^–1) - (M) Working or active muscle space - q(t) Blood flow through (M) at time t (ml·100 ml^–1·min^–1) - _MS (t) Rate of net lactate release from (M) to (S) at time t (mmol·min^–1) - Rate of net lactate release from (M) to (S) at t(mol·min^–1) - (S) Remaining lactate space - t Time after the end of exercise (min) - , Moments at which the net lactate release from (M) to (S) becomes zero (min) - ₂ Moment of the intersection of the arterial and brachial venous blood lactate curves (min) - _fa1, _fa2 Moments of the intersection of the arterial and femoral venous blood lactate curves (min) - V _M , V _s , V _TLS Volume of (M), (S), and (TLS), respectively, [1] - (TLS) Total lactate space - Difference between L _M () and L _s ()     

The effect of training on responses of Β-endorphin and other pituitary hormones to insulin-induced hypoglycemia

Summary We studied whether the previously reported intensified -endorphin response to exercise after training might result from a training-induced general increase in anterior pituitary secretory capacity. Identical hypoglycemia was induced by insulin infusion in 7 untrained (Skeletal muscle enzyme activity, fiber composition and in relation to distance running performance 49±4 ml · (kg · min)^–1, mean and SE) and 8 physically trained (Skeletal muscle enzyme activity, fiber composition and in relation to distance running performance 65±4 ml · (kg · min)^–1) subjects. In response to hypoglycemia, levels of -endorphin and prolactin immunoreactivity in serum increased similarly in trained (from 41±2 pg · ml^–1 and 6±1 pg · ml^–1 before hypoglycemia to 103±11 pg · ml^–1 and 43±9 pg · ml^–1 during recovery, P<0.05) and untrained (from 35±7 pg · ml^–1 and 7±2 pg · ml^–1 to 113±18 pg · ml^–1 and 31±8 pg · ml^–1 P<0.05) subjects. Growth hormone (GH) was higher 90 min after glucose nadir in trained (61±13 mU · l^–1) than in untrained (25±6 mU · l^–1) subjects (P<0.05). Levels of thyrotropin (TSH) changed in neither of the groups. It is concluded that, in contrast to what has been formerly proposed, training does not result in a general increase in secretory capacity of the anterior pituitary gland. TSH responds to hypoglycemia neither in trained nor in untrained subjects. Finally, differences in -endorphin responses to exercise between trained and untrained subjects cannot be ascribed to differences in responsiveness to hypoglycemia.     

Ca2+ influx induced by store release and cytosolic Ca2+ chelation in HT29 colonic carcinoma cells

Cl^– secretion in HT₂₉ cells is regulated by agonists such as carbachol, neurotensin and adenosine 5-triphosphate (ATP). These agonists induce Ca²⁺ store release as well as Ca²⁺ influx from the extracellular space. The increase in cytosolic Ca²⁺ enhances the Cl^– and K⁺ conductances of these cells. Removal of extracellular Ca²⁺ strongly attenuates the secretory response to the above-mentioned agonists. The present study utilises patch-clamp methods to characterise the Ca²⁺ influx pathway. Inhibitors which have been shown previously to inhibit non-selective cation channels, such as flufenamate (0.1 mmol·l^–1, n=6) and Gd³⁺ (10 mol·l^–1, n=6) inhibited ATP (0.1 mmol·l^–1) induced increases in whole-cell conductance (G _m). When Cl^– and K⁺ currents were inhibited by the presence of Cs₂SO₄ in the patch pipette and gluconate in the bath, ATP (0.1 mmol·l^–1) still induced a significant increase in G _m from 1.2±0.3 nS to 4.7±1 nS (n=24). This suggests that ATP induces a cation influx with a conductance of approximately 3–4 nS. This cation influx was inhibited by flufenamate (0.1 mmol·l^–1, n=6) and Gd³⁺ (10 mol·l^–1, n=9). When Ba²⁺ (5 mmol·l^–1) and 4,4-diisothiocyanatostilbene-2-2-disulphonic acid (DIDS, 0.1 mmol·l^–1) were added to the KCl/K-gluconate pipette solution to inhibit K⁺ and Cl^– currents and the cells were clamped to depolarised voltages, ATP (0.1 mmol·l^–1) reduced the membrane current (I _m) significantly from 86±14 pA to 54±11 pA (n=13), unmasking a cation inward current. In another series, the cation inward current was activated by dialysing the cell with a KCl/K-gluconate solution containing 5–10 mmol·l^–1 1,2-bis-(2-aminoethoxy)ethane-N,N,N,N-tetraacetic acid (EGTA) or 1,2-bis-(2-aminophenoxy) ethane-N,N,N,N-tetraacetic acid (BAPTA). The zero-current membrane voltage (V _m) and I _m (at a clamp voltage of +10 mV) were monitored as a function of time. A new steady-state was reached 30–120 s after membrane rupture. V _m depolarised significantly from –33±2 mV to –12±1 mV, and I _m fell significantly from 17±2 pA to 8.9±1.0 pA (n=71). This negative current, representing a cation inward current, was activated when Ca²⁺ stores were emptied and was reduced significantly (I _m) when Ca²⁺ and/or Na⁺ were removed from the bathing solution: removal of Ca²⁺ in the absence of Na⁺ caused a I _m of 5.0±1.2 pA (n=12); removal of Na⁺ in the absence of Ca²⁺ caused a I _m of 12.8±3.5 pA (n=4). The cation inward current was also reduced significantly by La³⁺, Gd³⁺, and flufenamate. We conclude that store depletion induces a Ca²⁺/Na⁺ influx current in these cells. With 145 mmol·l^–1 Na⁺ and 1 mmol·l^–1 Ca²⁺, both ions contribute to this cation inward current. This current is an important component in the agonist-regulated secretory response.     

Effect of high intensity interval training on 2,3-diphosphoglycerate at rest and after maximal exercise

Summary The purpose of this study was to examine the effect of intense interval training on erythrocyte 2,3-diphosphoglycerate (2,3-DPG) levels at rest and after maximal exercise. Eight normal men, mean ± SE=24.2±4.3 years, trained 4 days·week^–1 for a period of 8 weeks. Each training session consisted of eight maximal 30-s rides on a cycle ergometer, with 4 min active rest between rides. Prior to and after training the subjects performed a maximal 45-s ride on an isokinetic cycle ergometer at 90 rev·min^–1 and a graded leg exercise test (GLET) to exhaustion on a cycle ergometer. Blood samples were obtained from an antecubital vein before, during and after the GLET only. Training elicited significant increases in the amount of work done during the 45-s ride (P<0.05), and also in maximal oxygen uptake ( max: Pre=4.01±0.13; Post=4.29±0.07 l·min^–1;P<0.05) during exercise and total recovery (Pre=19.14±0.09; Post=21.45±0.10 l·30 min^–1;P<0.05) after the GLET. After training blood lactate was higher, base excess lower and pH lower during and following the GLET (P<0.05 for all variables). Training caused no significant differences in erythrocyte 2,3-DPG levels at rest (Pre=11.8±0.7; Post=12.1±0.7 mol·g^–1 hemoglobin (Hb);P>0.05), at exhaustion (Pre=12.0±0.8; Post=11.2±0.8 mol·g^–1 Hb;P>0.05) or during 30 min of recovery from the GLET. Additionally, acute exercise (pre-training GLET) did not effect any change in 2,3-DPG at exhaustion or during recovery from exercise compared to resting values. The higher max and total recovery values observed after training appear to be unrelated to 2,3-DPG levels. Under the present conditions, the role, if any, of 2,3-DPG in enhancing tissue oxygenation during increased metabolic demand remains obscure.Supported by grants from Miles Laboratories, Elkhart, Indiana, and the Ball State Graduate Student Research Fund     

Premières observations sur deux Microsporidies hyperparasites d'Acanthocéphales de Poissons marins et lagunaires

Résumé Microsporidium acanthocephali n. sp. et Microsporidium propinqui n. sp. sont deux espèces de Microsporidies hyperparasites du syncytium tégumentaire d'Acanthocéphales de Poissons marins et lagunaires. Leur étude ultrastructurale met en évidence des caractères communs: mérontes et spores à diplocaryons, filament polaire anisofilaire, mais aussi une vacuole parasitaire autour des mérontes et quelques stades sporogoniques de l'espèce Microsporidium acanthocephali. Les spores des deux parasites sont oviformes; celles de M. acanthocephali, géantes, mesurent 12–14 m de longueur sur 6–7 m de largeur, celles de M. propinqui seulement 3–4 m X 1,25–1,50 m. La méconnaissance de certains aspects de la sporogonie empÊche une assignation générique de ces deux parasites qui peuvent cohabiter chez un mÊme Acanthocéphale.Au cours de recherches sur les Acanthocéphales de Poissons marins et lagunaires (Buron 1986), deux Microsporidies hyperparasites de ces Helminthes ont été observées chez des Poissons Gobiidae et Pleuronectiformes. Les Microsporidies sont déjà connues pour Être des hyperparasites de Grégarines, de Myxosporidies et d'autres Helminthes (Cestodes, Trématodes, Nématodes) (Sprague 1977). Il semble cependant, chez les Acanthocéphales, n'avoir été recensé jusqu'à présent que des «psorospermies» par Moniez (1879) que Balbiani (1884) interprète comme étant des Grégarines (in Dollfus 1946).Le présent travail propose donc de décrire quelques stades du cycle biologique des deux premières Microsporidies indiscutables d'Acanthocéphales.

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Preliminary observations on two microsporidian hyperparasitic in Acanthocephalan of salt water fishes

Microsporidium acanthocephali n. sp. and Microsporidium propinqui n. sp. are two microsporidian species hyperparasitic in the tegumentary syncytium of salt-water fishes. Their ultrastructural study shows that both species have diplocaryotic meronts and spores, anisofilar polar filaments; meronts and some sporogonic stages of M. acanthocephali are surrounded by a parasitic vacuole. Spores of both parasites are oviform; those of M. acanthocephali are gigantic, 12–14 m long and 6–7 m broad, those of M. propinqui are only 3–4 m X 1.25–1.50 m. A poor knowledge of some sporogonic aspects prevents us from all precise generic assigning of these two parasites which may coexist in the same Helminth.

     

Elektronenmikroskopische Befunde Über Kleinformen der Sarcosporidien

Zusammenfassung In elektronenmikroskopischen Bildern von Sarcosporidien werden 2 Arten von Kleinformen gefunden und als Makro-Tomonten (250 bis 500) und Mikro-Tomonten (100–200) beschrieben.Die Elektronenbilder sind mit dem Siemens-Elektronenmikroskop der Forschungsstelle für Mikromorphologic der Max-Planck-Gesellschaft aufgenommen worden.     

The anthropometrical and physiological characteristics of elite water polo players

In order to examine the physical and physiological demands of water polo, we assessed the profile of elite water polo players. Nineteen male professional water polo players (age: 25.5±5.0 years, height: 184.5±4.3 cm body mass: 90.7±6.4 kg) underwent body composition assessment by dual-energy X-ray absorptiometry. We also evaluated peak oxygen consumption O_2peak, lactate threshold (LT), energy cost of swimming (C_s), anaerobic capacity and isokinetic shoulder strength. Body fat (%) was 16.8±4.4, lean mass (LM) 75.1±4.9 kg and bone mineral density (BMD) 1.37±0.07 g·cm^–2 . O_2peak was 57.9±7 ml·kg^–1· min^–1 . LT was identified at 3.9±0.7 mmol·l^–1 at a swimming velocity (v) of 1.33±0.05 m·s^–1 with a heart rate of 154±7 bpm, corresponding to an intensity of 83±9 of O_2peak. The average C_s of swimming at the LT was 1.08±0.04 kJ·m^–1 . C_s at LT was correlated to body mass index (BMI) (r=0.22, P=0.04) and to swimming performance at 400 m (r=0.86, P=0.01) and 4×50 m (r=0.84, P<0.01). Internal rotator muscles were stronger compared to the external rotators by a 2:1 ratio. This study provides a quantitative representation of both physical and physiological demands of water polo and proposes a comprehensive battery of tests that can be used for assessing the status of a team.     

Ultrastructural effect of penicillin and cycloheximide onChlamydia trachomatis strain HAR-13

The effect of cycloheximide and penicillin on the ultrastructural morphology ofC. trachomatis strain HAR-13 was examined by electron microscopy. HAR-13 infected McCoy cells were either treated with cycloheximide (1g/ml) or cycloheximide (1g/ml) plus penicillin G (100 U/ml). The studies revealed that cycloheximide alone induced no morphological alterations into the ultrastructure of HAR-13. Both HAR-13 developmental forms, the elementary body and reticulate body, were present inside the treated McCoy cells. The elementary bodies contained the central dense nucleoid and were about 0.3m in diameter, while the reticulate bodies were of typical gram negative bacterial morphology and were from 0.5–1.0m in diameter. Cycloheximide in combined treatment with penicillin produced giant, swollen reticulate bodies that were 2–4m in diameter and in some cases vacuolated. Elementary bodies were noticeably absent. These results indicate that cycloheximide does not alter the morphology of HAR-13. This system is a useful model for studying the ultrastructural morphology ofC. trachomatis strain HAR-13.     

Life cycle and ultrastructure of Adelina tenebrionis (Sporozoea: Adeleidae) from Heteronychus arator (Coleoptera: Scarabaeidae)

The coccidian from the black beetle, Heteronychus arator (Fabricius), in New Zealand was identified as Adelina tenebrionis Sautet 1930. Its development occurs in the fat body of the host. Merogony produces bundles of 8–19 vermiform merozoites, which range in length from 12.0 to 24.1 m. Spherical macrogametocytes and small, vermiform microgametocytes fuse to form a zygote. Sporogony produces an oocyst 29.2–45.0 m in diameter, containing 3–13 sporocysts, 12.3–14.0 m in diameter. The life cycle takes about 46 days in an alternative host, Planotortrix excessana (Lepidoptera: Tortricidae), at 22 C. Electron micrographs of merozoites and gametocytes are presented.     

Effect of exercise training on aortic collagen content in spontaneously hypertensive rats (SHR)

Summary We investigated the effects of exercise training on the amount of aortic collagen and systolic blood pressure in spontaneously hypertensive rats (SHR). Ten-week old SHR were trained either by forced treadmill running (26.8 m·min^–1 h·day^–1, five times a week, 0% incline) or by voluntary running in revolving wheels (7,800 m·day^–1 at peak) for 8 weeks. Succinate dehydrogenase (SDH) activity measured as a marker of an endurance training effect was 13% higher (P<0.01) in the soleus of forced-exercised animals than in that of sedentary ones. (6.56±0.17 mol·g^–1·min^–1; mean ± SEM), whereas SDH activity in that of voluntarily-exercised group was found to be at the same level as in sedentary animals. The systolic blood pressure after training increased by 26.4 in sedentary, 21.1 in voluntarily-exercised, and 33.9 mm Hg in forced-exercised rats, when compared with the value of each group at the beginning of the training programm. A significant difference was observed in the increment of blood pressure only between the voluntarily- and forced-exercised groups (P<0.05). The amount of aortic collagen in voluntarily-trained rats (96.5±2.0 mg·g tissue^–1, 39.8±0.7 mg·100 mg protein^–1) was significantly less than that in forced-trained rats (P<0.05). These results suggest that voluntary, mild exercise training may be more effective in the reduction of collagen accumulation in the aorta associated with the suppression of blood pressure increase than forced, vigorous exercise training in SHR.     

Comparison of the buffer capacity of endocytotic vesicles,lysosomes and cytoplasm in cells derived from the proximal tubule of the kidney (opossum kidney cells)

During transepithelial acid-base transport cells of the proximal tubule of the kidney have to maintain a relative constant intracellular pH. Herein cellular buffer capacity plays an important role. We measured vesicular buffer capacity in proximal tubule-derived opossum kidney cells and compared it with cytoplasmic buffer capacity to determine the possible importance of vesicular buffer capacity for cellular pH homeostasis. Under HCO₃ ^–-free conditions endocytotic vesicular buffer capacity was 43±4 mmol·l^–1·pH-unit^–1 (n=7) and exceeded cytoplasmic buffer capacity (19±3 mmol·l^–1 ·pH-unit^–1; n=7) significantly. Lysosomal buffer capacity was 19±6 mmol·l^–1·pH-unit^–1; (n=5). Inhibition of vesicular H⁺-ATPase using bafilomycin A₁ led to a dramatic increase of vesicular pH but to a decrease of cytoplasmic pH indicating the importance of organellar buffer systems. We estimated that endocytotic buffer capacity accounts for 23% of cellular buffer capacity under our experimental condition and thus, impairment of endosomal acidification may affect cytoplasmic pH indeed. From our results we conclude that endocytotic vesicles have a large buffer capacity and might play a role in cellular pH homeostasis.     

Effect of auranofin on antibody-dependent cellular cytotoxicity (ADCC) mediated by rat peripheral blood polymorphonuclear leukocytes and mononuclear cells

Auranofin and other clinically used gold compounds were evaluated in vitro for effects on antibody-dependent cellular cytotoxicity (ADCC)of L929 fibroblast target cells mediated by adjuvant rat peripheral blood PMNs or mononuclear cells. Auranofin (10M) was found to be a potent inhibitor of PMNADCC. In contrast, gold sodium thiomalate (10–100M), gold thioglucose (10–1000M, and nongold substructures of auranofin (10M) were not inhibitory. In continuous culture, gold sodium thiomalate and relatively low concentrations of auranofin (1 M) significantly enhanced PMNADCC. Results of pretreatment studies indicate that auranofin's inhibitory activity of PMNADCC is caused by a noncytotoxic effect on PMN function which is not associated with alteration of PMN-target cell contact. In contrast to its inhibitory activity on PMNADCC, auranofin pretreatment of mononuclear cells resulted in enhanced target cell destruction which appeared to correlate with increased mononuclear cell-target cell contact.SK&F D-39162 (2,3,4,6-tetra-O-acetyl-l-thio--d-glucopyranosato-S)triethylphosphine gold.     

Uptake of 3H-leucine into different fractions of rat skeletal muscle following acute endurance and sprint exercise

Summary In order to study the specificity of the protein synthetic response to different acute exercise loads, 48 male rats served as non-exercised controls or ran at either 0.5 m·s^–1 for 1 h or 1.5 m·s^–1, 10 s20 s workrest, for 1h. Animals were killed and red and white vastus muscles excised from the controls or at 0, 2, 18, 24, or 48 h post-exercise. Muscle slices were incubated in a medium containing 10 Ci l-[4,5-³H]leucine for 30 min. Incorporation of the radionuclide was measured by liquid scintillation (dpm·mg^–1 protein) in the whole homogenate and in four subcellular fractions. The endurance exercise elicited increased uptakes into the mitochondrial fractions of both red and white vastus at 2 and 18 h respectively. However, the mitochondrial uptake was depressed at 24 h in the red and at 2 h in the white vastus. Only in red vastus was incorporation into the soluble protein elevated following endurance exercise. The sprint protocol elicited increased uptake into soluble protein at 2 and 18 h in both red and white vastus and into mitochondrial protein at 18 and 24 h in the white vastus. The shifts in uptake in white vastus occurred in conjunction with depressed uptakes in the total homogenate. These data indicate that both the changes in the type of protein and the time course of amino acid incorporation following acute exercise are related to both the metabolic characteristics of the muscle fibres and the intensity of the exercise.This study was supported by Grants from the Natural Sciences and Engineering Research Council (NSERC A0424 and NSERC A6436)     

Effect of calcium,furosemide and chlorothiazide on net volume reabsorption and basolateral membrane potential of the distal tubule

In the distal tubule of the isolated kidney of Amphiuma net volume reabsorption (split-oil droplet method) and basolateral membrane potential ( _b ) were measured. Luminal perfusion solution could be changed rapidly from 108 mmol·l^–1 NaCl plus 0.1 mmol·l^–1 calcium to solutions containing 103 or 97 mmol·l^–1 NaCl plus 3.6 or plus 7.2 mmol·l^–1 calcium. Furthermore, 10^–4 mol·l^–1 furosemide or chlorothiazide were applied luminally. (1) Addition of 7.2 mmol·l^–1 calcium hyperpolarized _b from –73.4 mV to –108.3 mV and inhibited net volume reabsorption. (2) Similarly, when furosemide was injected, _b was hyperpolarized and net volume reabsorption reduced. Application of both high calcium and furosemide further inhibited volume reabsorption. (3) The effects of chlorothiazide were similar to those of furosemide. However, when both high calcium and chlorothiazide were administered _b and volume reabsorption were almost normalized. (4) The data are consistent with the hypothesis that calcium and the diuretics interfere primarly with chloride uptake across the luminal membrane and thus reduce sodium chloride transport. When chlorothiazide in the presence of high luminal calcium almost normalized chloride transport, it is likely that its effects were by stimulating calcium transport and thus increasing intracellular calcium activity.Supported by Deutsche Forschungsgemeinschaft (Wi 328)The paper was presented, in part, at the XXVIIth Int. Congr. Physiol. Sci., Paris 1977, Proc. Vol. 13:304