Showing papers in "Acta Physiologica Scandinavica in 1973"

Muscle Metabolism and Enzyme Activities after Training in Boys 11–13 Years Old

Abstract: The effect of training on the skeletal muscle metabolism of 11-to 13-year-old boys was examined. In one experiment changes in blood lactate, and muscle lactate, CP, ATP, and glycogen were determined at rest and following exercise before and after 4 months of training. The concentrations of glycogen, CP and ATP at rest were higher (P<0.01) following training. Blood and muscle lactate were 23 and 56 % higher after maximal work following training. A greater reduction in muscle glycogen occurred during maximal work after training but the pattern for ATP and CP depletion was unchanged. In a second experiment boys trained by pedalling a bicycle ergometer an average of 30 min 3 times a week for 6 weeks. Biopsy samples of the vastus lateralis were examined for oxidative (succinate dehydrogenase) and anaerobic (phosphofructokinase) capacity before and after training. The fiber composition and relative oxidative capacity in the fibers was determined histochemically. Succinate dehydrogenase and phosphofructokinase activities increased 30 and 83 %, respectively, following training. Fiber distribution was unchanged by training but the oxidative capacity of both fiber types appeared to increase.

On the descending control of the lumbosacral spinal cord from the "mesencephalic locomotor region".

Abstract: Continuous stimulation (60 c/s) of a region below the inferior coliculus can induce locomotion on the treadmill of precollicular, postmammilar cats. This study aims at revealing what changes occur in the spinal cord, when the “locomotor region” is stimulated. This stimulation enables the cat to walk if the treadmill is moved. After controlling the threshold for evoking good locomotion, the cats were curarized. Stimulation at a strength that evoked walking prior to curarization induced a depression of inhibitory short-latency reflex effects to α-motoneurones from cutaneous, and high threshold muscular afferents without changing the direct excitability of α-motoneurones. The threshold for evoking longlasting reciprocally organized discharges was lowered. The results suggest that the effects are induced by a slow fiber system, that releases the activity of the spinal stepping generating neurones. The results would be explained if the noradrenergic reticulospinal system was activated from the mesencephalic locomotor region.

The effect of stimulation of the cervical sympathetic chain on retinal oxygen tension and on uveal, retinal and cerebral blood flow in cats.

Abstract: The effects of stimulation of the cervical sympathetic chain on blood flow through the retina, the different parts of the uvea, different parts of the brain and some other tissues were studied in cats. 5 Hz reduced the oxygen tension in the vitreous body close to the retina in 5 expts. of 6. 15 μm labelled microspheres were used for quantitative determinations of blood flow. Unilateral stimulation at 10 Hz was performed for 1 min in 9 normocapnic and in 4 hypercapnic cats and for 15–30 min in 5 normocapnic cats. The results suggest that blood ffow through the innermost layers of the retina is influenced by sympathetic stimulation. The vascular resistance within the uvea was much increased in all three groups with no indications for “autoregulatory escape”. The effect was most pronounced in the ciliary processes and least in the ciliary muscle. “Autoregulatory escape” was seen in the parotid gland, the tongue and the masseter muscle, where 1 min stimulation caused mean reductions in blood flow by 82–99% compared to 6–56% after 15–30 min stimulation. Cerebral blood flow showed no statistically significant reductions in either group indicating a quantitatively minor role for the sympathetics in regulation of total cerebral blood flow in cats.

Glyoxylic Acid Condensation: A New Fluorescence Method for the Histochemical Demonstration of Biogenic Monoamines

Abstract: A new methodological approach to the fluorescence microscopical visualization of biogenic monoamines, based on condensation with gaseous glyoxylic acid, is presented. Glyoxylic acid treatment seems both to be more sensitive for the well-known biogenic catecholamines and indolamines, and to allow the detection of other biogenic amines—such as melatonin—which are not demonstrable with available techniques.

Glycogen depletion pattern in human muscle fibres during distance running.

Abstract: Costill, D. L., P. D. Gollnick, E. D. Jansson, B. Saltin and E. M. STEIN. Glycogen depletion pattern in human muscle fibres during distance running. Acta physiol. scand. 1973. 89. 374–383. Muscle biopsy and venous blood samples were taken from 9 subjects before and after a 30 km race. Additional measurements were made when 8 subjects ran 20.5 km of the course 2-3 weeks later. Information about total metabolism and the glycogen depletion pattern in the fibres of the thigh muscle during prolonged running has been obtained from these measurements. The average oxygen uptake and respiratory exchange ratio were 4.7 1×min-1 (83 % ot maximal oxygen uptake) and 0.90, respectively. An average intramuscular tryglyceride reduction of 2.2 mmoles×kg-1 (30 %) accounted for only part of the lipid combusted. Muscle glycogen declined 56 % (from 98 to 42 mmoles of glucose units × kg-1) during the race. Histochemical staining of the muscle for glycogen revealed a marked depletion in the slow twitch fibres. Only a small glycogen depletion occurred in the fast twitch fibres. This suggests a primary reliance upon slow twitch fibres during prolonged running. The results also point to the limitations of assessing substrate utilization or availability in working fibres from muscle samples with mixed fibre populations.

Antidromic activation of Renshaw cells and their axonal projections.

Abstract: Antidromic invasion of Renshaw cells following stimulation of their axons was found always to produce only a single spike in contrast to repetitive synaptic discharges. A systematic exploration of the spinal cord in a search for sites from which single Renshaw cells could be activated antidromically revealed that their axons: 1) can project to distances over 12 mm, 2) run in the ventral funiculus. 3) are likely to terminate both within motor nuclei (mainly at short distances) and in an area dorso-medial and medial to them, and 4) have a maximal conduction velocity of about 30 mls.

Protein concentration of interstitial fluid collected from rat skin by a wick method.

Abstract: A new method has been developed for studying interstitial fluid protein concentration: A 3 cm long and 0.5 mm thick nylon thread was sewn into subcutaneous tissue of ether anesthetized rats and left for equilibration with interstitial fluid for 35 to 240 min. The wick was then pulled out, both ends cut off, and the middle part quickly transferred to a tared vial containing 2 ml saline and weighed. Blood-stained wicks, about 1 out of 5, were discarded. After 24 h elution the wick was removed, dried and weighed, allowing calculation of wick fluid volume. Total protein, albumin and hemoglobin concentrations were measured in the eluate. Hemoglobin concentration was less than 0.2 g/100 ml in all but one wick. Implantation of 73 wicks in 24 rats for 35 to 120 min gave an average albumin concentration of 2.10 (S.D. 0.24) g/100 ml, or 63% of plasma albumin concentration. Total protein concentration in 80 wicks averaged 3.44 (S.D. 0.30) g/100 ml, 56% of plasma. The concentrations did not change during this time interval and were reduced by less than 10% by antihistamine/antiserotonin treatment. An irregular rise in concentrations after more than 2 h implantation was delayed by antihistamine/antiserotonin.

Effect of physical training on hemodynamic response during submaximal and maximal exercise in 11-13-year old boys.

Abstract: Nine healthy boys, mean age 11.7 years (11.0–13.0), height 150.4 cm and weight 45.1 kg, were examined with determinations of maximal oxygen uptake (1.85 1×min-1), heart volume (499 ml) and total hemoglobin (391 g). Cardiac output was determined at rest and during exercise, including maximal exercise, using the dye-dilution technique and i.a. pressures were recorded. Cardiac output was approximately 2 1×min-1 lower and the systemic a-v oxygen difference (AVD) was correspondingly higher than for young adult men at the same sub-maximal oxygen uptake. At maximal exercise cardiac output was 12.5 1×min-1, stroke volume 67 ml, AVD 14.2 ml × 100 ml-1, systolic, diastolic and mean blood pressure 160, 71 and 105 mm Hg respectively and total peripheral resistance 8.6 mm Hg×1–1×min. After a training period of 4 months a normal increase in height was found in all boys, but body weight was unchanged. Maximal oxygen uptake increased to 2.21 1×min-1 (p < 0.01), almost entirely due to increased stroke volume (80 ml), resulting in a maximal cardiac output of 14.6 1×min-1. No significant increase in AVD was found. Mean blood pressure at maximal exercise increased significantly, total peripheral resistance was unchanged. Both heart volume and total hemoglobin showed minor increases, but the changes found were not significantly larger than expected from body growth. The hemoglobin concentration was normal (13 g%) for the age and unaffected by training.

Repetitive Impulse Firing: Comparisons between Neurone Models Based on ‘Voltage Clamp Equations' and Spinal Motoneurones

Abstract: Repetitive impulse firing was elicited in neurone models by steady stimulating currents of abrupt onset. The neurone models were based on the Frankenhaeuser—Huxley equations (1964) for voltage clamp data from the amphibian peripheral nerve. A frequency-current curve (‘f-I curve’), initial adaptation, and minimum firing rate similar to those of cat spinal motoneurones were obtained in the Frankenhaeuser—Huxley model if it were provided with (i) a long-lasting after-hyperpolarization due to potassium permeability changes, and (ii) a decreased subthreshold sodium inactivation. For detailed comparisons to the repetitive impulse firing of spinal motoneurones, model versions were used in which the subthreshold sodium inactivation was very slight, and the passive membrane properties as well as the afterpotentials resembled those of spinal motoneurones. In their repetitive behaviour, these models were quantitatively similar to spinal motoneurones. In the motoneurone-like model versions, initial adaptation was due to a kind of ‘summation’ of the potassium permeability changes underlying the after-hyperpolarizations of consecutive spikes. The slope of the f-I curve was markedly affected by modifications of the size or time course of the potassium permeability changes responsible for the after-hyperpolarization.

Sequential Exocytosis of Storage Granules during Antigen-Induced Histamine Release from Sensitized Rat Mast Cells in vitro An electron microscopic study

Abstract: The morphological changes appearing in sensitized rat mast cells incubated with antigen at 25° C for times ranging from 30 s to 10 min were studied using light and electron microscopy. Histamine release was assayed in parallel. After a latent period of 30 s, during which no histamine release or morphological changes occurred, degranulation and histamine release commenced and increased progressively with time. The first changes were seen in the most peripherally-located granules, and consisted of a fusion of the cell membrane with the perigranular membrane and a swelling and a reduction of the electron-density of the granules. With increasing time these changes were seen to spread deeper into the cells, resulting in the formation of labyrinthic cavities contatining changed granules; such granules were also seen outside the cells. Using the extracellular tracer lanthanum these apparently intracellular cavities were demonstrated to be in unbroken communication with the extracellular milieu. Thus when sensitized rat mast cells are incubated with antigen sequential exocytosis of histamine-storing granules take place. The results agree with the hypothesis that histamine release takes place by ion exchange between histamine and extracellular cations both in granules expelled from the cells and in those retained in cavities open to the exterior.

Circulatory Responses to Stimulation of Medullated and Non-medullated Afferents in the Cardiac Nerve in the Cat

Abstract: Recordings of the evoked compound potentials in the right main cardiac nerve in the cat demonstrated the presence of both medullated and non-medullated fibres. The circulatory responses to afferent stimulation of these two fibre populations were followed in terms of changes in blood pressure, heart rate and skeletal muscle and renal flow resistances. A selective stimulation of the medullated afferents, which probably arise mainly from atrial receptors, induced a moderate reflex rise of blood pressure, an increased heart rate and a vasoconstriction in the skeletal muscle and kidney. Clearcut effects were observed first with high stimulation frequencies, and then only in case the buffering influences from other receptor sites were minimized. Stimulation of the non-medullated fibres, which probably emanate from ventricular receptors, caused a very marked reflex blood pressure fall, slowing of the heart and vasodilatation in the muscle and the kidney, already with very low stimulation rates. These results suggest that the powerful reflex influence from cardiac receptors on the cardiovascular system is exerted by receptors with non-medullated afferents, while endings firing in medullated pathways as e.g. atrial receptors, have very small direct effects on the cardiovascular system and then rather of an excitatory nature.

Mucosal hemodynamics in the small intestine of the cat during reduced perfusion pressure.

Abstract: This study was performed with an indicator-dilution technique that allowed quantitative and separate investigation on the cat small intestine, of the “mucosal” as well as of the “villous” intravascular flows and volumes. When reducing arterial inflow pressure from about 100 to about 30 mm Hg “villous” plasma volume and mean transit time increased while “villous” plasma flow remained largely unaltered. Concomitantly, total intestinal blood flow decreased significantly indicating that a larger fraction of total plasma flow was diverted to the villi at low inflow pressure. When intestinal blood flow was reduced by increasing venous outflow pressure villous hemodynamics was largely unaffected. “Mucosal” red cell and plasma flows were affected in the direction of and, generally speaking, in proportion to total intestinal blood flow. These results suggest that the autoregulatory capacity of the villous vessels is larger than that of the vessels in the deeper parts of the mucosa.

Prostaglandins in Human Burn Blister Fluid

Abstract: Acidic lipids with smooth muscle stimulating activity were isolated from human burn blister fluid. Analysis by silicic acid chromatography and thin-layer chromatography indicated the presence of prostaglandin E and F compounds. Prostaglandin E2 (about 1.9 ng/ml of blister fluid) was identified and quantitatively determined by gas-liquid chromatography—mass spectrometry. No metabolic conversion of tritium-labelled prostaglandin E1 incubated with blister fluid was observed.

Cerebral blood flow in ischemia caused by carotid artery ligation in the rat.

Abstract: In order to study if bilateral ligation of the carotid arteries, either alone or combined with moderate arterial hypotension is accompanied by a macroscopically uneven brain perfusion, the regional cerebral blood flow (rCBF) was measured using the antipyrine-14C method with direct counting of the radioactivity in the tissue. Ligation of the carotid arteries at normal blood pressure decreased blood flow in the frontal-parietal regions by about 50 % in both hemispheres. At a mean blood pressure of 100 mm Hg, the ligation caused a further reduction in flow but the results were variable and gross differences often occurred between the hemispheres. At 70 mm Hg in blood pressure carotid occlusion drastically reduced the frontal-parietal rCBF but flow in the occipital and basal temporal regions was usually better upheld. It is concluded that in the rat, combined carotid artery ligation and moderate hypotension gives rise to a macroscopically inhomogenous reduction in rCBF, and that regions of nonperfusion may coexist with adequately perfused areas.

Mucosal Lesions in the Small Intestine of the Cat during Low Flow

Abstract: The mucosal changes, produced at the villous tips of the cat small intestine during a mimicked shock situation (regional hypotension at 30 mm Hg during nervous vasoconstrictor fibre activation), were examined macro-and microscopically. Macroscopically, petechial bleedings and ulcerations were regularly seen in the mucosa after a 2 h hypotensive period. The microscopic findings were characterized by epithelial lifting of various degrees at the tips of the villi and in some cases by a complete denudation of the villous tips. Intraluminal perfusion of a segment with oxygenated saline during the hypotension prevented or greatly reduced the mucosal lesions compared to control segments. On the other hand, intraluminal perfusion with nitrogenated saline did not change the mucosal lesions as compared with control. This strongly indicates that hypoxia per se plays an important role in the pathogenesis of the mucosal lesions, while the intestinal content (e.g. energy substrates or enzymes) does not appear to be of any great importance. It is suggested that the hypoxia is caused by an extravascular shunting of oxygen in the intestinal countercurrent exchanger.

Osmotic fluid transfer from tissue to blood during hemorrhagic hypotension.

Abstract: Jarhult, J. Osmotic fluid transfer from tissue to blood during hemorrhagic hypotension. Acta physiol. scand. 1973. 89. 213–226. Arterial and venous plasma osmolality and glucose concentration, and net transcapillary fluid movements were studied in the cat lower leg muscles during hemorrhagic hypotension (50 mm Hg). Arterial plasma osmolality increased rapidly after bleeding and exceeded after 20 min the control value by about 20 mOsm/kg H2O, a level maintained during the remainder of the 90 min observation period. Popliteal venous osmolality rose much more slowly and did not reach the arterial level until some 50 min after the bleeding. Studies of plasma glucose concentration showed that the arterial and regional venous hyperosmolality almost entirely could be ascribed to a concomitant hyperglycemia, in particular during the first 30 min of hemorrhage. A clearcut arterio-venous osmolar difference in the muscle (reflecting a transcapillary osmolar gradient) was thus present in the early (≅50 min) stages of bleeding. In the sympathectomized muscle region an absorption of extravascular fluid to the blood stream occurred as long as this arterio-venous osmolar difference existed, strongly indicating that the fluid transfer was caused by osmosis. Comparative studies on the innervated and the sympathectomized muscle region showed that the extravascular fluid absorption due to reflex decrease of hydrostatic capillary pressure was most prominent in the early (< 20 min) stages of bleeding, whereas the osmotic fluid absorption was maintained for a more prolonged period of time. Both mechanisms no doubt are important for plasma volume restoration after hemorrhage.

Analysis of threshold currents during microstimulation of fibres in the spinal cord.

Abstract: W. J. Roberts and D. O. Smith. Analysis of threshold currents during micro-stimulation of fibres in the spinal cord. Acta physiol. scand. 1973. 89. 384- 394. Fillies within the dorsal spinocerebellar tract of the cat were stimulated with current pulses from a mirroelertrode. With precise tracking, single nodes of Rainier of a fibre could be localized and the current required for activation studied as a function of the electrode position. The threshold stimulus amplitude was found to increase nonlinearly with distance from the node. The rate of increase in threshold was found to be less pronounced when the position of the electrode tip was changed axially rather than transversely to the node. The rates of increase with distance tended to decrease as the estimated fibre diameter became larger.

Role of cyclic AMP and Ca ++ in mechanical and metabolic events in isometrically contracting vascular smooth muscle.

Abstract: In bovine mesenteric artery catecholamines stimulated simultaneously adrenergic α-and β-receptors. The relaxation induced by a specific adrenergic β-receptor stimulation was associated with an increased content of cyclic AMP, a phosphorylase a activation and a decrease of the content of ATP and creatinephosphate (CrP). No effect on the high energy phosphate compounds was present in the Ca++-poor artery, but the effect on cyclic AMP and phosphorylase was still evident. Sotalol blocked all the actions induced by adrenergic β-receptor stimulation. The contracting action induced by selective adrenergic α-receptor stimulation was initially associated with a decrease of the cyclic AMP content, but when the tension was maximally developed, after 120 s, the cyclic AMP content was increased and the phosphodiesterase activity reduced. In Ca++-poor artery a cyclic AMP decreasing effect was still present after 120 s and there was no reduction of the phosphodiesterase activity. The mechanical and metabolic effects induced by α-receptor stimulation were blocked by dibenamine. Histamine, which increased the artery tension, significantly reduced the cyclic AMP content after 15 s, but after 5 min the level of cyclic AMP had increased and phosphorylase a was activated. The mechanical and metabolic effects of histamine were blocked by promethazine, an antihistaminic drug. The role of cyclic AMP in relaxation and contraction of vascular smooth muscle is discussed.

Electrophysiological Study of the Gustatory Effects of the Sweet Proteins Monellin and Thaumatin in Monkey, Guinea Pig and Rat

Abstract: The afferent activity of the facial portion of the chorda-lingual nerve, the chorda tympani proper, and the glossopharyngeal nerves was recorded during the application of 0.02 % and 0.005 % solutions of Monellin (2times 10-5 and 5times 10-6 M) and Thaumatin (10-5 and 2.1) × 10 -6 M) and of 0.5 M sucrose, 0.3 M NaCl and 0.03 M citric acid, representing the three taste qualities sweet, salt and acid. Monellin and Thaumatin, which give a sweet sensation in man, elicited a significant electrophysiological response in the monkey which showed several characteristics that could be related to psychophysical observations in man. In guinea pig and rat little or no response could be recorded.

Colonic motility in the cat. II. Extrinsic nervous control.

Abstract: Rostad. H. Colonic motility in the cat. III. Influence of hypothalamic and mesencephalic stimulation. Acta physiol. scand. 1973. 89. 104–115. Colonic motility recorded with sensitive extraluminal strain gage transducers was studied in lightly anesthetized cats following electrical stimulation of hypothalamic, and mesencephalic structures. Stimulation of various structures of the hypothalamus produced the following: 1) The sympatho-inhibitory area in the anterior hypothalamus increased colonic activity concomitantly with a fall in blood pressure. 2) The ventral anterior and lateral hypothalamus produced excitatory colonic effects, but these were usually associated with a rise in blood pressure. Similar effects were obtained from the dorsal part of the ventromedial hypothalamic nucleus. 3) Stimulation of the ventral part of the hypothalamus, mainly corresponding to the course of the medial forebrain bundle, and the ventral part of the ventromedial nucleus, resulted in inhibitory colonic effects. Stimulation of various structures of the mesencephalon produced the following: 1) The central gray substance, red nucleus and reticular substance elicited increased colonic effects, most conspicuous in the proximal part of the colon. These responses were usually associated with a blood pressure rise. 2) Points within the central tegmental tract and the medial lemniscus resulted in inhibition of colonic motility. The. functional significance of the results and their relation to behavioural patterns are discussed.

Autoregulation of blood flow in human cutaneous tissue.

Abstract: The presence of autoregulation of blood flow was investigated in human cutaneous tissue of the skin fold between thumb and forefinger by means of die method of epicutaneous atraumatic application of gaseous xenon-133. 49 studies were performed on 3 healthy subjects. Blood pressure changes were obtained by passive displacement of the skin fold to various test levels above and below the reference level, the jugular notch. Blood flow remained constant for all subjects in an interval around the reference level. The range of autoregulatory ability showed variation. In extreme positions a decrease of blood flow was observed for some subjects. The significance of these findings is discussed.