bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Changes in Plasma Volume and Osmolarity on Thermoregulation during Exercise
Authors: Nielsen Bodil
Published: December 2008

Plateau values of deep body temperature were diminished during work after intake of 1 1/2 1 water, they were increased after intake of 2–3 % sodium chloride solution and after dehydration in a sauna by 1 1/2 kg. The shifts in plateau values were related to plasma osmolarity, not to plasma volume. In rest and during work at low temperature (7° C), when there was virtually no sweating, the effect of plasma osmolarity on body temperature disappeared. The rate of increase in sweating at the start of work was faster than normal after intake of water and slower after intake of sodium chloride solution and dehydration. The mechanism by which the changes in temperature were brought about is the increase in sweating at the start of work. Plasma osmolartiy may cause these changes either by a peripheral effect on the sweat glands or a central effect on the thermoregulatory centres.
The Effect of Glucagon on Hepatosplanchnic Hemodynamics, Functional Capacity, and Metabolism of the Liver in Gats
Authors: Krarup Niels , Larsen Jens Anker
Published: December 2008

Glucagon in doses of 0.1, 0.5, and 5.0, μg/kg/min infused i.v. caused a marked increase in portal blood flow (up to 300 %) due to a dose‐dependent increase in conductance‐of gastrointestinal vessels, and an increase in the conductance in the hepatic low pressure vessels (up to 30 %), but only slight changes in hepatic arterial conductance and flow. Glucagon caused a decrease in the hepatic extraction of Indocyanine Green (ICG), no change in ICG clearance, an increase in bile acid secretion, but only minor changes in bile flow and ICG excretion. The splanchnic glucose output and ketone production were increased by glucagon. The cytoplasmic redox level was not affected, but the mitochondrial redox level was changed to a more oxidized state together with a 30 % rise in hepatic oxygen consumption and a correlated increase in ethanol elimination. These last effects were not dose‐dependent. It is concluded that the marked changes in splanchnic hemodynamics found during glucagon infusions, are not a consequence of the metabolic effects of the hormone on the liver, but rather a direct effect of non‐physiological concentrations of glucagon on gastrointestinal vessels. The results exclude any marked influence of glucagon on the intrahepatic distribution of blood flow and functional liver mass.
Effects of Ethanol, tert. Butanol, and Clomethiazole on Net Movements of Sodium and Potassium in Electrically Stimulated Cerebral Tissue
Authors: Wallgren H. , Nikander P. , Boguslawsky P. von , Linkola J.
Published: December 2008

The sodium and potassium contents of rat brain cortex slices incubated in bicarbonate medium were measured and the intracellular quantities estimated on the basis of the inulin distribution. Ethanol (109 mM) did not affect the ion content of unstimulated tissue during passive leakage in cold medium or aerobic incubation at 37oC.

The effects of ethanol (109 mM), tert. butanol (34 mM) and clomethiazole (0.39 mM) were tested on the response to electrical stimulation (entry of sodium and loss of potassium in the non‐inulin space) as well as on the restoration of the ionic gradients occurring after a period of stimulation. All agents selectively inhibited the entry of sodium on stimulation with very little effect on potassium loss. The result is considered compatible with preferential action of the drugs on the activation step of the sodium channel controlling movement of sodium during the excitation cycle, and presumably located on the outside of the membranes. During recovery, no inhibition of sodium expulsion was observed, whereas both alcohols‐ but not clomethiazole‐slightly decreased the accumulation of potassium. Considered together with other observations, this finding suggests a special affinity of ethanol for the potassium binding site in the ion transport system.
Plasma Hyperosmolarity and Pulmonary Capacitance Vessels
Authors: Piene H. , Aarseth P. , Bo G.
Published: December 2008

Changes in pulmonary blood volume have been looked for during increased plasma osmolality. Two different techniques, one involving freezing of whole rats, and the other with removal of separate lung lobes from cats, have been used. In both cases lung blood volume was calculated from content of 123I‐plasma albumin and 51Cr‐erythrocytes. Plasma osmolarity was increased 10–23 % by intravenous infusions of hyperosmolar solutions of NaCl or glucose. In the cat lung experiments vascular pressures and cardiac output were followed during i.v. infusions of 3 M NaCl or 3–5 M glucose solutions. The pulmonary vascular resistance decreased upon the injections, but no significant changes in pulmonary vascular volume could be detected. The extravascular lung water content decreased markedly during the hypertonic infusions. Also in the rat experiments the pulmonary blood volume seemed to be unchanged during hyperosmolarity.
Disappearance of 133Xenon and 125Iodide and Extraction of 86Rubidium in Subcutaneous Adipose Tissue during Sympathetic Nerve Stimulation
Authors: Linde Birgitta , Gainer John L.
Published: December 2008

Effects of sympathetic nerve stimulation on the disappearance rates of 133Xenon and 125Iodide from a local depot as well as on the extraction of 86Rubidium from blood have been studied in the subcutaneous adipose tissue of dogs during constant blood flow perfusion. Resting mean k‐values for 133Xenon were 0.0040 min‐1(n = 10) and for 125Iodide 0.0386 min‐1(n = 5) while the PS‐products for 86Rubidium had a mean value of 2.5 ml × min‐1X 100 g‐1(n = 17). During sympathetic nerve stimulation a frequency dependent decrease of disappearance rates and PS‐products was found. The latter were reduced by an average of 30 % while the reductions of the disappearance rates were twice as large and similar for 133Xenon and 125Iodide. These results suggest a decrease in the perfused capillary surface area during sympathetic nerve stimulation.
The Action Potential in End‐Plate and Extrajunctional Regions of Rat Skeletal Muscle1
Authors: Thesleff S. , Vyskoil F. , Ward M. R.
Published: December 2008

In the innervated rat diaphragm muscle, the maximum rate of rise of the action potential was approximately 20 % greater in the end‐plate region as compared to non‐junctional areas. This difference in rate of rise was maintained for a period of at least 14 days after denervation. Desensitization of the post‐junctional membrane by carbachol or irreversible blockade of the cholinergic receptor system by use of a toxin from Naja naja siamcnsis failed to reduce this difference. When TTX (10‐6M) was added to the bathing fluid, action potentials could no longer be elicited from innervated fibres; a sodium‐dependent local response remained in most fibres, however, but only in the end‐plate region. After surgical denervation, the action potential becomes partially resistant to the blocking action of TTX, and it was found that the action potential in the end‐plate region was more resistant than that in non‐junctional areas. The results show the presence of TTX‐insensitive ionophores situated in the postjunctional membrane of innervated and denervated muscle fibres. It is suggested that these TTX‐insensitive sites contribute to the observed greater rate of rise of action potentials elicited from these areas.
Method for Gravimetric Registration of Changes in Tissue Volume
Authors: Grände P.‐O. , Järhult J. , Mellander S.
Published: December 2008

A technique is described by which changes of tissue volume of a muscle region enclosed in a plethysmograph can be followed in terms of water displacements measured with an electronic gravimetric transducer. Experimental tests show that the method provides accurate recordings of vascular capacitance responses and of transcapillary fluid movements.
Action of Drugs on the Innervated and Denervated Urinary Bladder of the Rat
Authors: Elmer Mats
Published: December 2008

In the normally innervated rat bladder methacholine, acetylcholine, adrenaline and phenylephrine elicited contraction of the detrusor musclein situ,while isoprenaline caused relaxation. The response to noradrenaline varied but was most often relaxation. Experiments with dihydroergotamine and propranolol indicated the presence of both excitatory a‐receptors and inhibitory β‐receptors in the detrusor muscle. The bladder developed supersensitivity to parasympathomimetic agents and in the case of a‐receptor mediated effects also to sympathomimetic agents after parasympathetic decentralization and denervation, and after sympathetic denervation. Regarding the adrenergic β‐receptor effects, however, no supersensitivity developed after any of the denervation procedures. Parasympathetic denervation or decentralization uncovered a contractile response to noradrenaline most often masked by predominant relaxation in the normal bladder.
Characteristics and Distribution of Spinal Focal Synaptic Potentials Generated by Group II Muscle Afferents
Authors: Fu T. C. , Santini M. , Schomburg E. D.
Published: December 2008

The location of the segmental relays of group II afferents in the spinal cord was investigated by recording extracellular “focal synaptic potentials” (FSP), generated by group II afferents in the gastrocnemius‐soleus nerve. Three types of group II FSPs were differentiated by their location and latency. (1) The “dorsal group II FSP” was located in the dorsal horn dorsolateral to the intermediate nucleus. Its short latency from the incoming group II volley (0.6‐1.0 ins; led to the conclusion that at least the onset is monosynaptically generated. (2) The “ventral group II FSP” was found between the intermediate nucleus and the motor nucleus. This type of FSP had a longer central latency ranging from 1.2‐2.5 ms, which made it difficult to decide whether the linkage was monosynaptic or disynaptic. However, when considering other results (Fu and Schomburg 1974) it seems probable that the ventral FSPs in the low range of central latencies were generated monosynaptically. (3) The “late group II FSP” had a long and varying central latency and was found over a wider region although less regularly than the other FSPs. Presumably the late FSP represents the postsynaptic effect in second and third order neurones. It seems likely that at least the main part of the investigated dorsal and ventral group II FSPs was generated by secondary afferents from muscle spindles.
Protein Concentration and Colloid Osmotic Pressure of Rat Skeletal Muscle Interstitial Fluid
Authors: Aukland K. , Johnsen H. M.
Published: December 2008

Protein concentration and colloid osmotic pressure (COP) were estimated in the fluid contained in nylon wicks after implantation in skeletal muscle of rats for 1 to 3 h. After 1 and 2 h implantation wick fluid showed an albumin/total protein ratio of 0.44, compared to 0.61 in plasma. Average concentrations relative to that of plasma were 0.37 for albumin, 0.52 for total protein, and 0.76 (calculated by difference) for non‐albumin protein. After 3 h implantation these ratios had increased significantly to 0.49, 0.69 and 1.07 respectively, presumably indicating beginning inflammation. The unexpected “excess” of non‐albumin wick fluid protein had an electrophoretic mobility like that of plasma β‐globulins, but its origin,‐from plasma or muscle‐is uncertain. Wick fluid COP averaged 8.7 mm Hg, as compared to a plasma COP of 18.9 mm Hg.
Storage of Elastic Energy in Skeletal Muscles in Man
Authors: Asmussen Erling , Bonde‐Petersen Flemming
Published: December 2008

The question, if muscles can absorb and temporarily store mechanical energy in the form of elastic energy for later re‐use, was studied by having subjects perform maximal vertical jumps on a registering force‐platform. The jumps were performed 1) from a semi‐squatting position, 2) after a natural counter‐movement from a standing position, or 3) in continuation of jumps down from heights of 0.23, 0.40, or 0.69 m. The heights of the jumps were calculated from the registered flight times. The maximum energy level, Eneg, of the jumpers prior to the upward movement in the jump, was considered to be zero in condition 1. In condition 2 it was calculated from the force‐time record of the force‐platform; and in condition 3 it was calculated from the height of the downward jump and the weight of the subject. The maximum energy level after take‐off, Ep0s, was calculated from the height of the jump and the jumper's weight. It was found that the height of the jump and Epos increased with increasing amounts of Eneg, up to a certain level (jumping down from 0.40 m). The gains in Epos over that in condition 1, were expressed as a percentage of Eneg and found to be 22.9 % in condition 2, and 13.2, 10.5, and 3.3 % in the three situations of condition 3. It is suggested that the elastic energy is stored in the active muscles, and it is demonstrated that the muscles of the legs are activated in the downward jumps before contact with the platform is established.
Glycogen Utilization in Leg Muscles of Men during Level and Uphill Running
Authors: Gostill D. L. , Jansson E. , Gollnick P. D. , Saltin B.
Published: December 2008

Glycogen depletion was followed in the soleus, gastrocnemius, and vastus lateralis muscles of 3 men during 2 h of treadmill running on the level and uphill (+6o). One subject also ran downhill (‐4.5o). Running speed was adjusted in each condition to require 75% of the subjects' Vo2 max. Glycogen concentrations were similar in all 3 muscles at rest. From PAS staining glycogen appeared to be evenly distributed between slow and fast twitch fibres. A glycogen depletion of 17, 33, and 44 mmol of glucose units X kg‐1 wet weight occurred in the vastus lateralis, soleus, and gastrocnemius muscles, respectively, after running on the level. These values were 55, 46, and 60 mmol X kg‐1, respectively, after uphill running. Glycogen depletion in the soleus and gastrocnemius muscles after downhill running was similar to that after running on the level, however, in the vastus lateralis it was intermediate to that for uphill and level running. A loss of PAS stain was observed first in the slow twitch fibres in all conditions. The results support the concept of a differential involvement of the leg muscles during running which can be modified by running either uphill or downhill. Thus it is of importance for the representativity of a sample that it is taken from a particular muscle when the local response to exercise or physical training is studied.
Middle Ear Muscle Effects on Cochlear Responses to Bone‐conducted Sound
Authors: Irvine D. R. F. , Wester K. G.
Published: December 2008

Contractions of the stapedius and tensor tympani muscles were elicited by electrical stimulation of their motor nerves or of the muscles themselves in anesthetized cats. The effects of these contractions on cochlear microphonic responses to air‐ and bone‐conducted sound were examined. Stapedius contractions that produced changes in air conduction similar to those observed under physiological conditions had almost identical effects on bone conduction. Tensor tympani effects on bone conduction were of similar magnitude but greater complexity than those on air, and varied as a function of the location of the bone conductor on the skull. Control observations established that the effects were attributable to the middle ear muscles and not to other consequences of the experimental procedures, and that they did not reflect modification of an air‐conduction component of the bone‐conduction stimulus. The functional significance of these effects is discussed in terms of protection against masking of environmental sounds by self‐generated bone‐conducted sound.
Transcapillary Passage of Plasma Proteins in Experimental Burns
Authors: Ganrot Karin , Jacobsson Sten , Rothman Ulf
Published: December 2008

The “leakage” of proteins from plasma to interstitial fluid in burns was studied experimentally in dogs. The concentration of orosomucoid, α1‐antitrypsin, albumin, haptoglobin, IgG, β1C‐globulin and α2‐macroglobulin were determined in plasma and in lymph from the leg before and after scalding of the paw. The lymph/plasma ratio of all proteins except that of α2‐macroglobulin increased after scalding, indicating an increased capillary permeability to proteins with molecular weights up to 300,000.
DDT and Related Substances: Effects on Permeability Properties of Myelinated Xenopus Nerve Fibre. Potential Clamp Analysis
Authors: ÅRhem By Peter , Fraxkexhaeuser Berxhard
Published: December 2008

An analysis was made of the effect of DDT and related substances on the membrane currents associated with step changes of the membrane potential. The substances tested are: DDT, DDD, DDE, DDMU, DDA, DDCN, bis‐(p‐chlorophenyl)‐acetamide and polychlormated bi‐phenyls (PCB). DDT. DDA and bis‐(p‐chlorophenyl)‐acetamide had acute effects on permeability parameters of the nerve membrane. The effects of the substances differed drastically from each other. DDT affected the turn off process of the sodium permeability mechanism after a positive potential step; the effect was large on fibres from Rana pipiens but negligible on fibres from Xenopus laeris. DDA affected the turn off process of the potassium permeability mechanism while bis‐“p‐chlorophenyl‘‐acetamide affected sodium and potassium permeability constants, Pxa and PK. The other substance; tested had no or only marginal acute effects. The main effect of DDA may be described as a specific effect on the rate constant βn. The obvious differences in effects of the substances on the permeability parameters were thus related to defined minute molecular differences of the studied substances.
Changes in Pulmonary Vascular Volumes after Induced Intravascular Aggregation of Blood Platelets
Authors: Vaage J. , Aarseth P. , Enge I. , Hognestad J.
Published: December 2008

The volumes of intra‐ and extravascular fluid compartments in lungs have been studied in cats after intravascular aggregation of blood platelets induced by collagen infusions. Such infusions give marked pulmonary pressor responses. A biopsy‐technique with removal of isolated lobes after isotopelabelling of the blood, indicated an increased vascular volume during the response to a collagen‐infusion, while the extravascular water content remained unchanged. Angiographic observations revealed that the increased vascular volume is due to distension of large arteries, while the veins have a somewhat reduced dimension. These findings are interpreted as being caused by a precapillary vasoconstriction, no marked changes on capillary pressure, and with passive arterial dilatation upstreams to the constricted segments. Venous narrowing might be active or due to some passive recoil.
The Influence of Arterial Hypoxia and Unilateral Carotid Artery Occlusion upon Regional Blood Flow and Metabolism in the Rat Brain
Authors: Salford Leif G. , Siesjö Bo K.
Published: December 2008

The influence of marked arterial hypoxia combined with unilateral carotid artery clamping upon regional cortical metabolites and blood flow was studied in the rat brain. When the arterial Po, was reduced to about 20 mm Hg the hemisphere on the clamped side showed a marked lactic acidosis and a fall in phosphocreatine but the adenylate energy charge remained close to normal. In this hemisphere, the cortical blood flow increased about 4‐fold. On the clamped side there was an excessive lactic acidosis and a marked fall in energy charge. However, since the levels of glucose, glucose‐6‐phosphate and pyruvate did not fall below normal, and since the regional blood flow was at least doubled, it is concluded that the derangement of the energy metabolism was due to cellular hypoxia, exaggerated by the relative ischemia induced by the carotid artery clamping. The biochemical lesion was most pronounced in the distribution territory of the middle cerebral artery that also showed the largest degree of relative ischemia. It is suggested that the pronounced lactic acidosis may contribute to the neuronal damage observed with this model of hypoxia and relative ischemia.
Effects of Alpha‐ and Beta‐Receptor Blocking Agents on Catecholamine and 5‐Hydroxytryptamine Induced Peroxidase and Amylase Secretion from Guinea Pig Submandibular Gland
Authors: Carlsoo Bengt , Danielsson Ake , Marklund Stefan , Stigbrand Torgny
Published: December 2008

Enzyme secretion from incubated guinea pig submandibular gland slices was induced by adrenaline, noradrenaline, dopamine, 5‐hydroxytryptamine or dibutyryl cyclic AMP combined with theophylline. Effects of alpha‐ and beta‐blocking agents on stimulated peroxidase and amylase discharge were studied. Propranolol (beta‐blocker), but not phenoxybenzamine (alpha‐blocker), markedly inhibited the secretion of both enzymes induced by adrenaline or noradrenaline. Dopamine and 5‐hydroxytryptamine were found to be potent enzyme secretagogues. Both propranolol and phenoxybenzamine antagonized the effects of these two amines. The secretagogic effect of dibutyryl cyclic AMP in combination with theophylline was not affected by either propranolol or phenoxybenzamine. L‐DOPA and 5‐hydroxytryptophan were without effect on enzyme secretion. It is concluded that peroxidase and amylase are secreted in parallel from guinea pig submandibular gland and that enzyme release is mainly mediated via the beta‐adrenergic receptor.
Transient and Steady State Effects of C02 on Mechanisms Determining Rate and Depth of Breathing
Authors: Bradley G. W. , Euler C. von , Marttila Irja , Roos B.
Published: December 2008

Breath‐by‐breath analysis of tidal volume, VT, inspiratory duration, Tr, and expiratory duration, TE, was performed on cats under light pentobarbitone anesthesia or after decerebra‐tion before and after vagotomy. In response to step changes in inspired CO2 VT changes earlier and more rapidly than the corresponding changes in the timing. The VT–Tj points may thus form a ‘hysteresis loop’ embracing the volume threshold curve of Clark and Euler (1972). The transient responses were present also after peripheral chemodenervation and after bilateral vagotomy. In contrast to earlier papers vagotomized cats under pentobarbitone anesthesia often showed some decrease of T(with increased steady state CO2 levels. In decerebrate vagotomized cats T[was more independent of variations in steady state PCO2 levels, but after administration of pentobarbitone Ti showed some steady state shortening of Tj with increased CO2. It is concluded that the controller of depth and rate of breathing contains at least 2 functional components which depend on PCO2 in such a way that they exert opposite effects on Ti which cancel out to a great extent and that this relative match can be disturbed by pentobarbitone. It is postulated that the transient increase in mismatch is due to the fact that the 2 (or more) CO2 effects have slightly different dynamic features.
Steady State Effects of CO2 and Temperature on the Relationship between Lung Volume and Inspiratory Duration (Hering‐Breuer Threshold Curve)
Authors: Bradley G. W. , Euler C. von , Marttila Irja , Roos B.
Published: December 2008

The time course of the volume threshold curve for the inspiratory off‐switch, i.e. the relationship between volume, (Vx) and inspiratory duration (Tj) with intact vagus nerves, was determined in steady conditions at different inspired CO2 concentrations and body temperatures in lightly anesthetized cats by means of ‘ramp’‐shaped inflations and deflations of different rise times. With intact vagal feedback the Vx–TT data points could be very well fitted to hyperbolas in all conditions studied. Changes in steady state FACO2 never caused any detectable influence on the volume threshold curves. Changes in body temperatures, in a range below the panting threshold, caused pronounced effects on the volume threshold curve which could best be characterized as a shift of the whole curve along the volume axis to lower values with increased temperature. Thus, at each rate of volume expansion the threshold for inspiratory off‐switch was reached earlier the higher the temperature. Also in the absence of vagal volume feed‐back Ti became correspondingly shorter with increased temperature which indicates that these temperature effects are mainly of central origin. The mechanisms for the CO2 and temperature effects on tidal volume and inspiratory duration are discussed.
Single‐Nephron Filtration during Hemorrhagic Hypotension in the Conscious Rat
Authors: Clausen Gunnar , Tyssebotn Ingvald
Published: December 2008

To decide whether redistribution of filtrate between superficial (S) and deep (D) nephrons takes place when GFR is reduced by hemorrhagic hypotension (HH) the amount of filtered 14C ferrocyanide precipitated as Prussian blue in single S and D nephrons was determined in rats during HH of 80, 65 and 50 mm Hg mean arterial pressure (AP). Marked filtration and urine flow persisted only in the AP 80 mm Hg group, whereas the major fraction of nephrons had ceased filtration in four out of live rats at AP 50 mm Hg. The distribution of radioactivity between S and D proximal tubules was not altered in any of the HH groups as compared to normotensive controls.
Afferent G Units Responding to Mechanical, Thermal and Chemical Stimuli in Human Non‐Glabrous Skin
Authors: Torebjörk H. Erik
Published: December 2008

C unit activity was recorded with microelectrodes from intact sensory fascicles in the human peroneal nerve. The analysis includes 46 afferent units with receptive fields predominantly on the dorsum of the foot and ankle. 16 units were tested quantitatively. Another 30 units were tested qualitatively by a combination of electrical and natural stimuli in the skin. This method was valuable for a reliable identification of activity in individual afferent C elements, when several C units with similar potential amplitudes responded to testing in the skin. The units were not spontaneously active at normal skin temperatures but one unit showed a low frequency discharge at a skin temperature of 22o C. Cooling by ether evaporation was an inefficient stimulus except for 2 units. Gentle mechanical stimuli did not activate any of the units, whereas afferent C unit impulses were induced by moderately intense mechanical stimuli, noxious heat and various chemical irritants. The sensations produced by stimuli inducing intense afferent C unit activity were reported as “burning or delayed pain”, whereas stimuli eliciting low frequency activity often were reported as “itch”. It is concluded that polymodal C receptors, similar with “polymodal nociceptors” in the cat and monkey, are numerous in skin areas sparsely covered with hairs on the dorsum of the foot and ankle in man, whereas no low threshold C mechanoreceptors were identified. The experiments do not exclude the possibility that both delayed pain and burning itch sensations may be mediated by different impulse patterns from polymodal C receptors.
A Serum Factor Influencing the Physiological Activity of Thyrotropin‐Releasing Hormone (TRH) I. Studies with human serum
Authors: Virkkunen Pekka
Published: December 2008

Thyrotropin‐releasing hormone was incubated at 2° C, 37° C and 60° C with varying dilutions of human serum and with serum fractions obtained by gel filtration. The amount of TRH left after incubation was measured by bioassay. The inactivation of TRH was shown to be complete by 90 min, the half‐time being 18 min. Dilution of serum more than 1: 16 did not abolish TRH. Binding of TRH to serum proteins could not be detected. Instead of this evidence is submitted for the enzymic nature of the serum protein which inactivates TRH. In gel filtration this protein migrates between the globulins and albumin, which suggests a molecular weight of about 100,000.
The Effect of Angiotensin on Isosmotic Fluid Absorption by the Rabbit Gail‐Bladder In Vitro
Authors: Leyssac P. P. , Kristensen L. Østergaard , Christensen P. , Frederiksen O.
Published: December 2008

The rabbit gall‐bladder in vitro preparation was used for studying the effect of angiotensin‐11 on isosmotic fluid transport. Angiotensin inhibited net fluid transfer at serosal concentrations between 10‐9‐10‐8 M. Maximum inhibition (about 25 %) was obtained at a concentration of 5 times 10˜* M. No significant effect was demonstrable at concentrations of 10‐10 M or lower, and the effect disappeared at higher concentrations (10 and 20 × 10‐9 M). The inhibitory effect was due to a depression of the unidirectional Na+‐efflux (from mucosal to serosal side); Na+‐influx (from serosal to mucosal side) was unaffected. Maximum effective doses of angiotensin had no effect on transepi‐thelial potential difference (PD), while ohmic resistance (R) increased slightly (about 10 %). The inhibitory effect of angiotensin was significantly reduced by incubating gall‐bladders with indomethacin (10 μg/ml) which effectively blocks prostaglandin biosynthesis. Addition of indo‐methacin alone had no effect on either net fluid transfer rate, PD, or R. It is concluded that angiotensin inhibits isosmotic fluid transport in the gall‐bladder by an effect on the active component of the transfer process; and the data suggest that the effect is indirect and mediated, in part at least, by release of endogenous prostaglandins. Alternatively indomethacin might interfere with the angiotensin receptor.
A Serum Factor Influencing the Physiological Activity of Thyrotropin‐Releasing Hormone (TRH) II. Studies with rat serum in vivo and in vitro
Authors: Virkkunen Pekka , Lybeck Harry , Ranta Tapio , Leppäluoto Juhani
Published: December 2008

The mid‐fractions in gel filtration of rat serum proteins were shown to be the most potent in abolishing the biological activity of TRH during incubation in vitro. The kidneys were not able, in vitro or in vivo, to restore the biological activity of inactivated TRH. Biologically active TRH, labelled TRH and serum‐inactivated labelled TRH were excreted in the urine in equal amounts.
Pulmonary Responses to Intravascular Platelet Aggregation in the Cat
Authors: Vaage J. , Bø G. , Hognestad J.
Published: December 2008

Platelet aggregation has been induced in cats by intravenous infusions of ADP, collagen or platelet antiserum, and the airway and pulmonary vascular responses subsequent to such infusions have been studied. Dynamic lung compliance (dyn CL), pulmonary resistance (RL) and the number of circulating platelets were followed together with pulmonary vascular resistance (PVR). Induction of platelet aggregation caused temporary and parallel increases in PVR and in RL and a simultaneous decrease in dyn CL. The major part of these effects was apparently due to active smooth muscle constriction. It could be shown that airway and vascular responses declined and finally disappeared in a characteristic way after repeated episodes of platelet aggregation. The total number of circulating platelets is apparently not the key factor in this connection. The way in which aggregation is induced, as well as the functional state of the circulating platelets, appear to be more important factors. It may be that the platelet release recation is mandatory for the lung responses to intravascular platelet aggregation.
Comparative Studies on the Effects of Bradykinin and Vagal Stimulation on Motility in the Stomach and Colon
Authors: Fasth S. , Hultén L. , Jahnberg T. , Martinson J.
Published: December 2008

The effect of bradykinin on gastric and colonic motility was studied in anaesthetized cats with volume recording devices and compared with the effects of vagal nerve stimulation. When administered intra‐arterially bradykinin caused a profound and prolonged gastric relaxation. Simultaneously there was a marked and likewise prolonged colonic contraction. The gastric relaxation closely mimicked the atropine resistant relaxation elicited by vagal nerve stimulation. These effects could not be blocked by antiadrenergic drugs and it is suggested that bradykinin and the unknown transmittor substance(s) released on vagal stimulation act in a similar way on the gastric smooth muscles and that a kinin mechanism may be involved in the vagal response. As regards the colonic motor response it was shown that bradykinin does not reproduce the vagal motility effects on colon smooth muscle but mimicks closely the atropine resistant expulsive contraction elicited by activation of the pelvic nerves.
Circulatory Effects Evoked by ‘Physiological’ Increases of Arterial Osmolality
Authors: Jkrhult Johannes , Hillman Jan , Mellander Stefan
Published: December 2008

The effects of moderate arterial hyperosmolality (+ 20 mOsm/kg H2O), produced by short term intravenous hypertonic infusion, on vascular resistance in skin, skeletal muscle, intestine, and kidney were analysed in the anesthetized cat. Vascular resistance decreased in all four regions in response to the hypertonicity both before and after regional sympathectomy and the effects were not significantly altered by β‐adrcno‐ceptor blockade. Arterial blood pressure rose during the hypertonic infusion despite the decreased vascular resistance and an unchanged heart rate, indicating an increased stroke volume and cardiac output. Similar increases of arterial osmolality are known to occur in heavy exercise and in hemorrhage. The present results may therefore suggest that blood borne hyperosmolality is a factor which can contribute to the overall cardiovascular adjustments in these situations.
Relationship between Isometric Endurance and Fibre Types in Human Leg Muscles
Authors: Hultén B. , Thorstensson A. , Sjödin B. , Karlsson J.
Published: December 2008

Relationship between isometric endurance performance at 50% of maximal voluntary isometric contraction (MVC) and skeletal muscle fibre composition has been elucidated in 19 physical education students. This was found to be linear and the equation corresponded to: y=9.35 + 1.093x; r= 0.70 (endurance time expressed in seconds and fibre composition as percent slow twitch muscle fibres (ST) of the vastus lateralis muscle). As it is assumed from previous studies that similar isometric tensions preferentially recruit fast twitch muscle fibres (FT) and that the muscle at the point of exhaustion exhibits maximal values for lactate accumulation, it is suggested that lactate formed in FT fibres is released and stored in nonrecruited ST fibres. The ability to sustain similar isometric tension would then be depending on how large the fraction of ST fibres is that can serve as a lactate recipient for lactate producing FT fibres.
Acid‐Base Changes and Excitation‐Contraction Coupling in Rabbit Myocardium. I. Effects on Isometric Tension Development at Different Contraction Frequencies
Authors: Jóhannsson M. , Nilsson E.
Published: December 2008

The effects of changes in acid‐base parameters on the active force of isolated rabbit papillary muscles were studied at contraction frequencies of 12, 60 and 120/min. When extracellular pH was lowered from 7.4 to 7.0 and 6.7 in a bathing solution buffered with 10 mM histidine, the active force decreased at all contraction frequencies studied. After parallel increases of HCO3concentration (up to 47 mM) and Pco2at a constant extracellular pH of 7.4 the active force of the muscle increased at low and decreased at high contraction frequencies. None of these effects can be attributed to catecholamine release or to altered extracellular concentration of ionized calcium. The inotropic effects produced by bicarbonate were not reproducible by methyl sulfate (47 mM) or propionate (47 mM). It is concluded that: 1. a lowering of the extracellular pH has a negative inotropic effect at all frequencies, 2. HCO3has a positive inotropic effect that is most pronounced at low contraction frequencies and 3. CO2has a negative inotropic effect exceeding that produced by the mere reduction in extracellular pH. The cellular mechanisms involved in the various inotropic effects are discussed.
Signal Characteristics of EMG with Special Reference to Reproducibility of Measurements
Authors: Viitasalo Jukka H. T. , Komi Paavo V.
Published: December 2008

Reliability and constancy of recordings of EMG signal characteristics were investigated from the measurements taken with minitature size surface electrodes during submaximal and maximal contraction of the rectus femoris muscle. The following EMG variables were studied: integrated EMG (IEMG) various band‐widths of the power spectral density function, mean power frequency (MPF), and rise time, amplitude and number of spikes of the averaged motor unit potential (AMUP). The results indicated that for most of the variables studied the reproducibility of measurements was better within the test session (reliability) than between the different test days (constancy). The reliability values for IEMG, MPF and AMUP amplitude were rather high (r = 0.77–0.92). MPF and number of spikes in AMUP showed good constancy values (r=0.73–0.93) and it is suggested that these parameters can be recommended for use in EMG studies where recordings are repeated over a period of several days.
Biogenic Amines in Carotid Body of Adult and Infant Rats —a Gas Chromatographic‐Mass Spectrometric Assay
Authors: Hellstrom Sten , Koslow Stephen H.
Published: December 2008

A gas chromatographic‐mass spectrometric method was used for the determination of biogenic amines in carotid body of adult and 10 days old rats. The method is ideally suited for this measurement since only small amounts of tissue were available (dry weight carotid body: adult 8.3 μg;infant 5.6 μg). In adult carotid body large amounts of dopamine (1 950 pmol/mg protein) and norepinephrine (1 140 pmol/mg protein) were found together with a comparatively small concentration of serotonin (505 pmol/mg protein). The carotid bodies of infant rats contained 1 065 pmol dopamine/mg protein and 410 pmol norepinephrine/ mg protein. Epinephrine could not be detected. Surgical sympathetic denervation and chemical sympathectomy (6‐hydroxydopamine) of adult carotid bodies did not significantly change the catecholamine content as compared to the controls. Reserpine depleted the catecholamines dosedependently. Administration of L‐Dopa and pargyline (a monoamineoxidaseinhibitor) drastically increased the concentration of catecholamines. Treatment with a dopamine‐β‐hydroxylase‐inhibitor resulted in a decreased amount of norepinephrine without a simultaneous increase of dopamine. This may indicate that certain storage sites in this tissue may store dopamine while in other sites dopamine is a precursor of norepinephrine. Probably most of the dopamine and norepinephrine are stored in different cells.
Inefficiency of Isoprenaline to Induce Drinking in the Goat
Authors: Olsson Kerstin , Rundgren Mats
Published: December 2008

Isoprenaline, which acts as a potent dipsogen in water‐satiated rats and dogs, did not elicit water intake when infused intravenously at 0.1 or 0.3μg/kgmin‐1in non‐hydrated goats. Even the low dose of the drug caused a marked reduction of parotid salivary flow. The possibility is discussed that reduced salivary secretion might be the particular effect which makes isoprenaline dipsogenic in prandially drinking species. The intravenous infusion of isoprenaline at the high dose level caused an inhibition of the water diuresis of hydrated goats, concomitant with reduced renal Na+excretion and a marked, sustained fall in the arterial blood pressure. Significant amounts of ADH were recovered from the urine secreted during the antidiuresis. This ADH‐release was apparently not due to central β‐adrenergic stimulation since no inhibition of the water diuresis was observed during intraventricular infusions of isoprenaline. Rather, the ADH‐release appears to have been secondary to the isoprenaline‐induced fall in arterial blood pressure.
Reduced Urinary Noradrenaline Excretion during Rest, Exercise and Cold Stress in Trained Rats: a Comparison between Physically‐Trained Rats, Cold‐Acclimated Rats and Warm‐Acclimated Rats
Authors: ÖStman Ingegerd , Sjöstrand Nils O.
Published: December 2008

Physically trained rats were compared with cold‐acclimated rats. Trained as well as cold‐acclimated rats showed cardiac and adrenal hypertrophy. Cardiac noradrenaline (NA) content was increased in both groups of rats but only the trained rats had an increased cardiac NA concentration. The adrenal NA content was increased in both groups but only the trained rats had an increased adrenal content of adrenaline (A). The spleen of trained rats had an increased NA content, while that of cold‐acclimated rats had a decreased NA content. The submandibular glands of cold‐acclimated rats were enlarged and had an increased NA content. Trained as well as cold‐acclimated rats had lower urinary NA excretions during rest, after exercise and during cold stress when compared with controls. However, only the trained rats had a reduced net increment in NA excretion after exercise, whereas there was no difference between the increments of cold‐acclimated and control rats. Six months after cessation of training, ex‐trained rats still had an increased heart ratio and a reduced urinary NA excretion after exercise. It is suggested that physical training induces “cross tolerance” to cold stress, while cold‐acclimation does not lead to “cross tolerance” to acute exercise.
Effects of Hypoxia of 10–45 Seconds Duration on Energy Metabolism in the Cerebral Cortex of Unanesthetized and Anesthetized Rats
Authors: Norberg Karin , Quistorff Björn , Siesjö Bo K.
Published: December 2008

Glycolytic and citric acid cycle intermediates, as well as organic phosphates, were measured in the cerebral cortex of unanesthetized rats following arterial hypoxia (administration of 6–8 % 0,) of 10 and 20 s duration. There were decreases in glucose‐6‐phosphate and fructose‐6‐phosphate, and increases in fructose‐1,6‐diphosphate, dihydroxyacetone phosphate and 3‐phosphoglycerate, even before pyruvate accumulated. Since measurements of the lactate concentration showed that there was an increased glycolytic rate, the results demonstrate that phosphofructokinase was activated. The glycolytic changes were accompanied by, and probably due to, minor changes in phosphocreatine, ATP, ADP and AMP. Experiments of anesthetized animals showed that hypoxia for 45 s was accompanied by signs of phosphofructokinase activation, even if tissue Pco2 was kept constant. It is concluded that, irrespective of the tissue CO2 tension, hypoxia is accompanied by activation of phosphofructokinase which, at least initially, is responsible for the increased glycolytic rate.
Rubrospinal Control of Static and Dynamic Fusimotor Neurones
Authors: Appelberg B. , Jeneskog T. , Johansson H.
Published: December 2008

Rubrospinal effects on about 60 extracellularly recorded γ‐motoneurones were studied in anesthetized cats. All cells were antidromically identified from various muscle nerves. 23 cells were regarded as dynamic as they were activated from a mesencephalic region previously known to influence selectively muscle spindle dynamic sensitivity. The pattern of rubrospinal influence on static fusimotor neurones to different muscles closely followed that previously demonstrated for α‐motoneurones with predominantly excitation of flexor neurones and excitation or inhibition in equal amounts of extensor cells. Dynamic fusimotor neurones were influenced in a strictly reciprocal manner with excitation of flexor cells and inhibition of extensor cells except for a few neurones which could not be reached from nucleus ruber. Evidence was also obtained indicating that the shortest path from nucleus ruber to static fusimotor neurones involves one interneurone.
Pulsatile Secretion of ACTH, GH, LH and TSH in Man
Authors: Leppäluoto J. , Laisi U. , Lybeck H. , Partanen J. , Ranta T. , Virkkunen P.
Published: December 2008

Blood samples were taken every 4 min for 80 min from 5 healthy subjects. Plasma ACTH, GH, LH and TSH were estimated by radioimmunoassays. The mean peak intervals were11, 12, 13 and 14 minutes respectively and mean peak amplitudes were 25 pg, 1.1 ng, 11 ng and 5.3 μU. Mean durations of ascending and descending limbs of the plasma patterns of these hormones were also measured. The timing of the different hormone peaks appeared to be independent.
Non‐Hyperbolic Force‐Velocity Relationship in Single Muscle Fibres1
Authors: Edman K. A. P. , Mulieri L. A. , Scubon‐Mulieri B.
Published: December 2008

The force‐velocity relation has been studied in sixteen single fibres from frog semitendinosus muscle with particular attention to the high‐force portion of the curve. The force‐velocity curve was hyperbolic except for a reversal of curvature near 80 % measured isometric tension (P0). Rectangular hyperbolas fitted (linear, least‐squares method) these data well only when values below 0.78 P0 were considered. Extrapolation of these hyperbolas above 0.78 P0 gave predicted isometric tensions (P*0) which averaged 32±6% above the measured P0 values. Hill's constants (1.84°C) for these hyperbolas were: a/P*0=0.177±0.021, b = 0.329±0.035 M.L./sec, Vmax=1.91±0.074 M.L./sec. The reversal of curvature persisted when force‐velocity data were obtained using: 1 or 60 min response intervals, afterloaded isotonic responses, grid stimulation, electrically induced contractures and bundles of fibres. The reversal of curvature diminished when force‐velocity data were obtained from slightly stretched fibres (about 2.3 μm sarcomere length as compared to 2.1 μm in the control). The results indicate that sarcomere length redistributions probably do not account for the non‐hyperbolic force‐velocity relation. An explanation for the behavior based on the geometry of the contractile filament lattice is discussed.
The Effect of Serotonin and Transcapillary Pressure on the Capillary Permeability in therete mirabileof the Eel (Anguilla vulgarisL.)
Authors: Myhre Kjell , Steen Johan B. , Stray‐Pedersen Sverre
Published: December 2008

Measurements of transcapillary exchange of high‐molecular dextrans, K+ and THO in therete mirabileof eel (Anguilla vulgaris L.) have been made under steady‐state conditions while the transcapillary pressure was varied and pharmaca added to the perfusates. Raising the transcapillary input pressure increased the exchange of dextrans and K+ but lowered that of THO. Histamine and ouabain had no effect on the transcapillary exchange of the test molecules. The highest dose (100 μg/ml) of serotonin reversibly increased the capillary permeability of D‐75 000, K+and THO while the medium dose (50 μg/ml) only raised the transcapillary exchange of K+and THO. The lowest dose (10 μg/ml) had no permeability effect. Our main conclusion is that serotonin reversibly increases the area of the intercellular pores by affecting the capillary wall directly.
Plasma Renin Activity Following Central Infusion of Angiotensin II and Altered CSF Sodium Concentration in the Conscious Goat
Authors: Eriksson Lea , Fyhrquist Frej
Published: December 2008

To study central influences on the renal release of renin, angiotensin II was infused into the lateral cerebral ventricle of conscious hydrated goats. CSF sodium concentration was increased or lowered by similar infusions of hypertonic NaCl or of isotonic fructose solution. Infusion of anglotensin II in doses from 0.5 to 1 μgcaused a drop in plasma renin activity (PRA) and elicited a rise in blood pressure, antidiuresis, natriuresis, and thirst. Intraventricular infusion of hypertonic NaCl also suppressed PRA, induced anti‐diuresis, natriuresis, and an inconsistent rise in blood pressure. Lowering of CSF [Na+] by infusion of isotonic fructose caused a rise in PRA and was followed by a water diuresis in the non‐hydrated animal. The fructose infusions caused some decrease in renal K+excretion but no consistent change in renal Na+excretion. The results indicate that angiotensin II and changes in sodium balance modulate renal renin release alsoviathe central nervous system.