Showing papers in "Acta Physiologica Scandinavica in 1967"

Diet, Muscle Glycogen and Physical Performance

Abstract: The muscle glycogen content of the quadriceps femoris muscle was determined in 9 healthy subjects with the aid of the needle biopsy technique. The glycogen content could be varied in the individual subjects by instituting different diets after exhaustion of the glycogen store by hard exercise. Thus, the glycogen content after a fat ± protein (P) and a carbohydrate-rich (C) diet varied maximally from 0.6 g/100g muscle to 4.7 g. In all subjects, the glycogen content after the C diet was higher than the normal range for muscle glycogen, determined after the mixed (M) diet. After each diet period, the subjects worked on a bicycle ergometer at a work load corresponding to 75 per cent of their maximal O2 uptake, to complete exhaustion. The average work time was 59, 126 and 189 min after diets P, M and C, and a good correlation was noted between work time and the initial muscle glycogen content. The total carbohydrate utilization during the work periods (54–798 g) was well correlated to the decrease in glycogen content. It is therefore concluded that the glycogen content of the working muscle is a determinant for the capacity to perform long-term heavy exercise. Moreover, it has been shown that the glycogen content and, consequently, the long-term work capacity can be appreciably varied by instituting different diets after glycogen depletion.

Muscle glycogen during prolonged severe exercise.

Abstract: 10 well trained and 10 untrained subjects worked to complete exhaustion on a bicycle ergometer with work loads averaging 77 (76–87) per cent of their individual maximal aerobic power. Determinations of glycogen used by working muscles (biopsy of lateral portion of the quadriceps femoris muscles) and of combusted carbohydrate (Vo2 and RQ) were performed at certain intervals from the start of work to exhaustion. At a combustion rate of about 3 g carbohydrate per minute (RQ around 0.9 or higher) and at average values for glycogen in resting muscle of 1.6 (1.1–2.5)g/100 wet muscle, the effective work time was around 85 min for the untrained and 90 min for the trained subjects. At the end of the exhaustive exercise the glycogen content averaged 0.06 g in the untrained and 0.12 g/100 g wet muscle in the trained subjects. A close relationship between utilized glycogen and combusted carbohydrate was found, and it seems highly probable that at high relative workloads primarily the glycogen stores in the exercising muscles will limit the capacity for prolonged strenuous work.

The Effect of DOPA on the Spinal Cord 6. Half‐centre organization of interneurones transmitting effects from the flexor reflex afferents

Abstract: JANKOWSKA, E., M. G. M. JUKES, S. LUND and A. LUNDBERG. The effect of DOPA on the spinal cord. 6. Half- centre organization of interneurones transmitting effects from theyexor rejex aferents. Acta physiol. scand. 1967. 70. 389-402. In unanaesthetized spinal cats a systematic microelectrode exploration has been made in the lumbosacral spinal cord in order to find interneurones that may transmit the late longlasting reflex effects that volleys in the FRA (flexor reflex afferents) evoke after an intravenous injection of DOPA. Interneurones that may transmit these late effects are found in the lateral part of Rexed’s layer VII and three main types are identified: A) cells activated from the ipsilateral FRA and inhibited from the contralateral FRA, B) cells activated from the contralateral FRA and inhibited from the ipsilateral FRA, C) cells activated from both the ipsilateral and contralateral FRA. The receptive fields and other criteria employed suggest that type A and B transmit excitatory action to flexor and extensor motoneurones respectively, and type C depolatization to Ia afferent terminals. The functional organization of these pathways is discussed mainly in relation to the mechanisms responsible for the long latency and duration of the discharge.

The Effect of DOPA on the Spinal Cord 5. Reciprocal organization of pathways transmitting excitatory action to alpha motoneurones of flexors and extensors

Abstract: In unanaesthetized spinal cats, injected with L-DOPA, volleys in the flexor reflex afferents (FRA) evoke a long-latency, longlasting discharge in ipsilateral flexor and contralateral extensor motoneurones. It is postulated that this discharge is transmitted by a neuronal pathway which is inhibited in the normal acute spinal cat, presumably from the pathway, which in this state transmits the shortlatency effect from the FRA to motoneurones. The organization of the pathway released by an injection of DOPA has been analyzed by recording the discharges in efferents to flexors and extensors and with intracellular records from motoneurones. Combined stimulation of ipsilateral and contralateral FRA reveals a reciprocal organization in that either flexor or extensor motoneurones are activated. Transmission from the ipsilateral FRA to flexor motoneurones can be inhibited by volleys in the contralateral FRA, and transmissiqn from the contralateral FRA to extensor motoneurones by volleys in the ipsilateral FRA. These inhibitory effects are neither produced postsynaptically in the motoneurones nor presynaptically by depolarization of primary afferents and are hence exerted at an interneuronal level. The organization of reciprocal innervation at an interneuronal level is discussed in relation to the primary afferent depolarization evoked in Ia afferent terminals after DOPA and to rhythmic alternating movements.

Extraneuronal binding of catecholamines and 3,4-dihydroxyphenylalanine (dopa) in salivary glands.

Abstract: In vivo and in vitro studies using the histochemical fluorescence technique of Falck and Hillarp were made on the submaxillary and sublingual glands of the rat after the administration of catecholamines or dopa, or the incubation of slices of the glands with the same drugs. Catecholamines and in all probability also L-dopa were found to be bound extraneuronally in the salivary gland parenchyma under the conditions of the experiments. It is probable that the present experiments visualize the same type of extraneuronal binding as has been found with biochemical techniques. It appears that a certain activity of the parenchyma is necessary for the binding to occur. Apart from being a source of error in the evaluation of biochemical measurements, extraneuronal binding may be of importance related to transmitter mechanisms.

Muscle Glycogen and Muscle Electrolytes during Prolonged Physical Exercise1

Abstract: Nine volunteers have been examined during prolonged physical exercise to exhaustion at a load of about 60 per cent of W170. Ordinary circulatory parameters were measured as well as the quantities of glycogen, water and electrolytes in muscle tissue obtained by needle biopsy. In a separate study 6 subjects were examined for respiratory quotient under similar exercising conditions. The muscle glycogen fell considerably from a mean of 6.9 per 100g glycogen and fat-free solids to a mean of 1.7 g at the end of exercise. The quantity of muscle glycogen used was correlated both to total energy developed during exercise and also to duration of exercise. The electrolyte and water content in muscle tissue showed only small changes. Some increase was found in muscle sodium and chloride, and also in the chloride space. The potassium content fell significantly by about 4 per cent of the basal value. None of the circulatory parameters measured showed changes of such magnitude as to have a limiting effect on performance. Two subjects were examined also with glucose infusion during the exercise. The reduction of glycogen, as also the performance of these two subjects, was of the same order of magnitude with and without infusion of glucose. The results suggest that the capacity for prolonged work is directly correlated to the glycogen store in the working muscles.

An improved method for the fluorimetric determination of 5-hydroxytryptamine in tissues.

Abstract: In the method described where the fluorescence of 5-hydroxytryptamine (5-HT) is read in 3 N HCl, tissue blanks are produced by means of UV-irradiation in the presence of potassium ferricyanide. This treatment destroys only the 5-HT but no other substance fluorescing at 295/545 mμ. With this new type of blank and by reduction of the volumes of the eluate and the reagents the sensitivity of the method is improved so that 25 ng (1 ng = 10-9 g) in an extract can be demonstrated and 50 ng determined quantitatively. The stability of 5-HT in 0.4 N perchloric acid extract is increased by adjustment of the pH almost to neutrality and by addition of ascorbic acid and ethylenediamine tetraacetate. The recovery and reproducibility are satisfactory.

Degranulation and histamine release, two consecutive steps in the response of rat mast cells to compound 48-80.

Abstract: Isolated rat peritoneal mast cells were exposed to compound 48/80 in A isotonic salt solution and in B isotonic sucrose solution. In both cases degranulation and histamine release occurred. In A all the released histamine appeared dissolved in the suspension medium, the discharged granules having lost their histamine. In B the discharged granules were show to retain histamine. These granules released their histamine when suspended in a NaC1-containing medium. Depleted granules could be refilled with histamine by suspension in a histamine-containing medium and again depleted of the amine by exposure to sodium chloride. The proposal is made that the histamine release induced by compound 40/80 is a two stage process, a primary energy-requiring transport of histamine-containing granules to the outside of the mast cell and a secondary nonenergy-requiring physico-chemical process, an extracellular cation exchange in the shed granules between histamine and cations, mainly sodium in the tissue fluid.

Circulatory and Respiratory Adaptation during Prolonged Exercise of Moderate Intensity in the Sitting Position

Abstract: Circulatory and respiratory adaptation during prolonged exercise of moderate intensity in the sitting position were studied with heart catheterization technique in 6 healthy young men of ordinary, physical fitness. The work load was chosen so that they worked at a level of 57.3 per cent of the rate of work they could perform at a pulse rate of 170 beats/min. This load gav a mean heart rate of 126.7 beats/min after 10 min and 138.5 beatslmin after 60 min of work. The circulatory changes under these experimental conditions were characterized by a constant cardiac output with a continuous increase in heart rate and a continuously falling stroke volume. The systemic arterial mean blood pressure fell slightly but significantly and the mean pulmonary arterial pressure also decreased significantly from 10 to 40 min work. The total blood volume decreased 7.2 per cent from rest to 10 min work and then remained unchanged. The respiratory response was characterized by a numerical increase (P<0.1) in total ventilation, dead space ventilation and an unchanged alveolar ventilation. The respiratory quotient increased from rest to the beginning of the exercise and then decreased significantly. The observed changes during prolonged exercise may be explained by a decreased vasomotor tone with a change in the compliance of the capacity vessels and the distribution of the blood volume. The relative level of work intensity seems to be more important than the body position to maintain a steady state.

A possible role played by central monoamine neurones in thermo-regulation.

Abstract: The effect of a cold and warm environment on the activity of the central catecholamine (CA) and 5-hydroxytryptamine (5-HT) neurones has been studied with the help of a combined biochemical and histochemical approach using inhibitors of the tyrosine and tryptophane hydroxylase. The central noradrenaline (NA) and 5-HT neurones of rats kept at: 40d C were found to increase their state of neuronal activity. whereas the 5-HT but not the CA neurones of rats kept at ± 3d C showed a decreased neuronal activity. These results indicate that the central NA and 5-HT neurones participate in thermo-regualtion.

The effect of calcium on the mechanical response of single twitch muscle fibres of Xenopus laevis.

Abstract: The effect of altered external calcium concentration on potassium-induced contractures in single twitch muscle fibres of Xenopus laezis was studied. It was found that an increase in [Ca] shifted the curve relating peak tension to membrane potential to lower potential values and that the rate of relaxation was decreased. Decreased [Ca]° shifted the peak tension-membrane potential curve in the opposite direction and made relaxation quicker. The relation between inactivation of the contractile system and membrane potential was also affected by changes in [Ca]°; increased [Cal]° shifted the curve towards more positive potential values and decreased [Ca]° caused a large shift in the opposite direction. Small effects of altered [Ca]° were seen on the recovery of twitches after a preceding contracture in 190 m M-K The refractory period was shortened by an increase in [Ca]° and lengthened by a decrease in [Ca]° The rate of action of altered [Ca]° was found to be high, both on twitch amplitude and contracture height, the effects of a change in [Ca]° being seen in less than one second. The results can be satisfactorily explained by assuming that the site of action for these calcium effects is the cell membrane.

Histamine Release from Isolated Rat Peritoneal Mast Cells Induced by Adenosine‐5‘‐Triphosphate

Abstract: Histamine release from isloated rat mast cell is induced by ATP (10-5 — 3 × 10-5 M). The activity found in an ADP-perepatation was shown to be due to contamination with ATP, purified ADP has no activity. AMP, 3′ 5′ AMP, PCr and PEP were without histamine releasing activity. Histamine release induced by ATP was compared with that caused by compound 48/80 with respect to the influence of Ca++, Mg++, Zn++, ouabain, DNP, oligomaycin and glucose. The results are interpreted to indicate that ATP and compoundf 48/80 release histamine by mechanisms that in certain respects differ from each other. The histamine releasing effect of ATP is discussed in relation to the enery-requiring mechanism that iis known to be involved in histamine release by compound 48/80.

Effects of some monovalent anions on fluxes of Na and K, and on glucose metabolism of ouabain treated human red cells.

Abstract: The present work deals with the effects of the anions Cl, Br, NO3, I, SCN, and HCO3 on Na and K fluxes, and on glucose metabolism of human red cells suspended in isotonic electrolyte media at 38d C and pH 7.40 in the presence of ouabain. When 120 m M Cl of the isotonic medium was substituted by the anion concerned, Na influx and K efflux were unaffected by Br, increased about 30 per cent by NO3 and I, but increased 200 to 250 per cent in the presence of SCN. Substitution of 120 mM Cl by HCO3 increased Na influx into red cells by 250 per cent. In contradistinction K efflux was reduced by 25 per cent. The increase of Na influx was linearly related to HCO3 concentration at pH 7.40. At intracellular Na concentrations between 10 and 35 meq/kg cell water the rate constant of Na efflux was close to 0.15 h-1 in the presence of all 6 anions studied. At external K concentrations from 5 to 7.6 meq/l potassium influx into ouabain treated cells suspended in a chloride medium was thrice as big as the influx calculated from the flux ratio equation M1/M0=K0/K1. exp (-zEF/RT). A similar condition was found in the presence of Br. In all other media studied (NO3.l, SCN, and HCO3) the ratio between the measured fluxes of potassium agreed with the calculated values of flux ratio for passive, independent fluxes. A net flux of water into the cells was observed in cells suspended in SCN and HCO3 media. In the same media the gain of Na in cells exceeded K loss. The relation of water net flux to the net gain of cations was 6.5–7.3 g water per meq. The rate of glycolysis was unaffected by the substitution of Cl by HCO3, was reduced by 15 per cent in the presence of Br, NO3, and I, and decreased by 30 per cent in the presence of SCN.

The Relationship between Active Constriction and Passive Recoil of the Veins at Various Distending Pressures

Abstract: The vasoconstrictor fibre influence on veins, exposed to varying distending pressures, was analysed with respect to the relative contribution of active venoconstruction and passive venous recoil, respectively, to total venous blood mobilization. The results indicate that active venoconstriction can produce only a minor reduction of venous capacity when venous transmural pressure is low but a considerable diminution of the capacity at higher venous pressures, provided the pressure is not so high as to “overstretch” the muscle elements. — The passive emptying of blood at vasoconstrictor fibre stimulation is very pronounced in the low pressure range, but becomes small at higher pressures, in accordance with the pressure-volume characteristics of the veins, demonstrating an apparently very high distensibility at low pressures. This high “distensibility” is mainly due to changes of vessel geometry, associated with the collapse, and does not reflect true wall distensibility. … Consequently, when venous pressure is low, venous function is primarily governed by passive factors, while active shortening of venous smooth muscles will play a dominant role first when the vessels are kept well distended. — The implications of these findings for venous control is discussed, with special respect to man, where venous pressure varies greatly with body position. Some methods earlier used for assessing venous tone changes are critically analysed.

Effect of Prolonged Heavy Exercise on Renal Function and Urinary Protein Excretion

Abstract: The urinary proteins in normal men participating in an 85–kilometre ski race held in 1964 and 1965 were examined by electrophoresis, immunoelectrophoresis and gel filtration. The urinary escretion of protein, glucose, ribonuclease and α-amino acid-N was also studied. In conjunction With the 1965 race additional studies were made of urine flow, free water clearance, creatinine clearance sodium, phosphorus and potassium exeretion and examination of urinary sediment. There was a significant increase in total protein and albumin excretion during the race. The protein excretion varied considerably from one individual to another. In 9 subjects who participated in both years the protein excretion, and also the peremtage albumin found by electrophorcsis, showed a significant correlation between the two years. The excretion of glucose and α-amino acids, which are freely filtrable in the glomerule, was not significantly changed. Sor was the exeretion of the low molecular wright protein, ribonuclease. which may be expected to be almost completely filtrable. This suggests that tubular reabsorption is mainly unchanged during exercise, but that glomerular prmirability for relatively large molecules is increased. Creatinine clearance decreased during the race. Urine flow and sodium exeretion decreased slightly during exercise. Potassium exeretion increased both during and after the ski race. Urinary sediment showed increased amounts of red and white cells, and hyalinc casts.

The relation between blood flow in an isolated muscle measured with the Xe133 clearance and a direct recording technique.

Abstract: To allow a critical evaluation of the Xe133 clearance technique this method was compared with directly metered blood flow in the isolated gastrocnemius muscle of cats at different flow levels between rest and maximum exercise dilatation. Whether the Xe133 was applied by close intraarterial injection or intramuscularly the clearance curve had a multiexponential course. This was ascribed partly to local variations of the affinity of the tissues to the gas but mainly to an uneven perfusion of the muscle. When the first phase of the clearance curve was approximated by a monoexponential curve and was taken to represent blood flow a significant correlation to metered flow was found. With i.a. injections the calculated flow amounted to an average of 93 per cent of the drop counter flow while after i.m. injections it only averaged 62 per cent. The difference in results is ascribed to the different microcirculatory conditions created by the two modes of injections. The relative volume of the well-perfused part of the tissue was estimated by noting at which level of activity the curve deviated from the first phase of rapid clearance. The well-perfused fraction increased at higher blood flows. It is concluded that the Xe133 clearance technique may give valuable information about the local circulation provided the limitations of the method are considered.

Effects of "diving" on cardiac output in ducks.

Abstract: Arterial and central venous pressures (AP and CVP), cardiac output (CO) and heart rate (HR) were recorded, and stroke volume (SV) computed, in awake ducks before, during and after submersion, special attention being paid to the time course and extent of the induced changes. During rest CO was 1509 ml/min (S.D. 245), HR 244/min (S.D. 83) and SV 6.6 ml (S.D. 1.6). Immediately upon submersion CO and HR fell slightly and then showed a more gradual, up to twenty fold reduction within 1–2 min; SV decreased moderately despite a 10–20 mm Hg increase in CVP. During the immediate 1–2 sec postdive period HR increased to 300–500/min, with a sharp rise in AP while CVP fell. Within 10–15 sec a profound vasodilatation was established, AP and CVP returning towards normal. CO now reached 2500–4000 ml/min and SV increased beyond resting level. Thus, at the shift from submersion to emersion CO could increase up to fiftyfold within 10–15 sec; CO then returned towards control in 6–8 min. Results with vagal and sympathetic blocking agents suggest the following neurogenic events: During submersion inhibited sympathetic activity to the heart is coupled with a greatly intensified vagal discharge. reducing also ventricular contractility; the sympathetic vasoconstrictor fibre discharge is sharply increased. On emersion a complete reversal of this intense and differentiated pattern takes place within 1–2 sec. The receptors and central mechansims involved are briefly discussed.

The Effect of DOPA on the Spinal Cord 7. Reflex activation of static γ‐motoneurones from the flexor reflex afferents

Abstract: In unanaesthetized spinal cats reflex activation of γ-motoneurones (to a flexor muscle) from the flexor reflex afferents (FRA) has been assessed from the discharge recorded in muscle spindle afferents. After injection of L-DOPA the resting discharge frequency increases in afferents with secondary endings and volleys in the FRA evoke a longlasting acceleration of the discharge in these afferents. On the basis of previous experiments showing that spindle afferents with secondary endings are activated from static but not from dynamic γ-motoneurones it is inferred that static γ-motoneurones are spontaneously active and reflexly activated from the FRA after an injection of DOPA. It has been confirmed that in the acute spinal cat, not treated with DOPA, there is no or little evidence for reflex activation of static γ-motoneurones from the FRA and it is postulated that the reflex pathway to static γ-motoneurones is inhibited in this preparation. The results are discussed in relation to other reflex effects evoked from the FRA.

Studies on the time course of histamine release and morphological changes induced by histamine liberators in rat peritoneal mast cells.

Abstract: The histamine release process in rat peritoneal mast cells, exposed to histomine liberators, can be terminated by the addition of ice-cold salt solution. This was taken advantages of for studies on the time course of histamine release and concomitant morphological changes induced by compound 48/80, bee venom and n-decylamine. After addition of compound 48/80 or bee venom, histamine was released in about 10 sec at 37/dG C and about 30 sec at 22/dG C. independently of the liberator concentration. AT 22/dG C the release was preceded by a lag period, which was shorter with higher liberator concentrations. The enzyme inhibitors potssium cyanide and N-ethylmaleimide did not alter the duration of the reaction induced by compound 48/80 or bee venom, although they lowered the final release. The release curve showed a different shape when histamine was released by n-decylamine. The morphological changes, studied both in the light and electron microscope, were found to be correlated to the histamine release.

Spread of excitation in the smooth muscle of the rat portal vein.

Abstract: The longitudinal musculature of the rat portal vein is characterized by spontancous, rhythmic contractions indicating effective intercellular conduction in this vascular smooth muscle. The present study was done in order to evaluate the relative importance of neurogenic and myogrnic mechanisms for the spread of excitation in an isolated preparation of this vessel. A local anesthetic agent, in concentrations which blocked impulse transmission in autonomic nerves, failed to interfere with conduction in the smooth muscle of the portal vein whereas hyperosmolarity. which is considered to preclude electro tonic spread of action potentials between muscle cells (Barr. Dewey and Rerger 1965), caused desynchronization of the contractile activity. It is concluded that conduction in this vascular smooth muscle is myogenic in nature. The fact that the portal vein, in contrast to most other vessels, is equipped with a “double plexus” of adrenergic nerve fibres (Fuxe. personal communication) does not seem to be important for coordination of its spontaneous contractions. The influence of the hyperosmotic environment on the electrical and mechanical activity of the portal vein is illustrated by experiments with a sucrose-gap technique. The mode of action of hyperosmotic solutions is discussed.

The Interaction of Secretin and Pancreozymin on the External Pancreatic Secretion in Dogs

Abstract: The pancreatic secretion of fluid, bicarbonate and protein in 4 dogs with chronic Thomas type fistulae, has been studied in response to secretin (1U/kg b.w.), pancreozymin (1U/kg b.w.) and combined secretin-pancreozymin (1U/kg b.w. of each). The secretion rates of fluid, bicarbonate and protein after combined, submaximal stimulation were highly reproducible, as indicated by the coefficients of variation 1.7 per cent (fluid), 3.9 per cent (bicarbonate) and 5.1 per cent (protein). The secretion rates of fluid and bicarbonate obtained after the combined stimulation with secretin-pancreozymin (1U/kg b.w. of each) were very close to those obtained after isolated stimulation with maximal doses of secretin. Secretin and pancreozymin are shown to have a potentiating effect on the pancreatic secretion of bicarbonate, but only an additive effect on the secretion of protein.