bluuebunny/crossref_metadata_2025 huggingface dataset:
The Influence of Mechanical Factors on the Response Characteristics of the Frog Muscle Spindle
Authors: Husmark Ivan
Published: December 2008

Husmark, I. The influence of mechanical factors on the response characteristics of the frog muscle spindle. Acta physiol. scand 1973. 89. 395–405.

The impulse response of the muscle spindle in situ was related to lengthening and tension of the whole muscle during stretch. The results were compared with the impulse response as related to lengthening and tension ohtained from stretches of the isolated encapsulated sensory region (isolated spindle). The aim was to find out if the force‐transmitting structures distorted the stretch stimulus and also to see if the adaptation of the spindle in situ was causally related to the extrafusal tension changes. The results indicate that during stretch the extra‐ and intrafusal fibres develop tension changes, which have the same general characteristics and which are related to the impulse response in a regular way. In some spindles the impulse response did not reflect the general tension of the muscle. This fact lends support to the hypothesis that most of the mechanical deformation of the sensory endings as revealed by the impulse responses is produced by the lengthening of the intrafusal fibres. Furthermore, only a small part of the adaptive decline of the response can be ascribed to the extrafusal tissue tension.
Vagal Relaxation of the Stomach Induced from the Gastric Antrum
Authors: Abrahamsson Hasse
Published: December 2008

Abrahamsson, H.Vagal relaxation of the stomach induced from the gastric antrum.Acta physiol scand. 1973.89.406–414.

The effect of mechanical stimulation of the gastric antrum on gastric (corpus‐fundus) motility was studied in anesthetized cats. Antral distension elicited a pronounced corpus‐fundus relaxation which was not blocked by atropine, guanethidine or by cervical spinal cord transection but was abolished by blockade of the vagal nerves. The “threshold stimulus” for eliciting the reflex response was an antral distension pressure between 5 and 10 cm H2O. Stepwise increases of antral distension produced correspondingly increased corpus‐fundus relaxations. A steady antral distension could keep the corpus‐fundus part relaxed for at least 10 min. La. infusion of acetylcholine to the antrum produced antral contractions followed by a marked corpus‐fundus relaxation which persisted after guanetnidine. Electric afferent stimulation of antral nerve branches elicited a gastric relaxation similar to the corpus‐fundus response to antral distension.‐It is concluded that activation of slowly adapting “tension receptors”, located in the antral gastric wall and with vagal afferents, elicits gastric relaxation by a reflex activation of the vagal non‐adrenergic rclaxatory fibres to the stomach. These reflex mechanisms are suggested to be involved in the control of gastric reservoir function (receptive relaxation) and gastric emptying. Some effects of vagotomy on gastric motility are discussed in relation to the present findings.
Effect of Acute Exposure to Cold on Blood Thyrotrophin (TSH) and Corticosterone Concentrations in the Rabbit
Authors: Leppäluoto J. , Lybeck H. , Ranta T. , Virkkunen P.
Published: December 2008

Leppäluoto, J., H. Lybeck, T. Ranta and P. Virkkunen. Effect of acute exposure to cold on blood thyrotrophin (TSH) and corticosterone concentrations in the rabbit. Acta physiol. scand. 1973. 89. 423–428.

Rabbits were exposed to various degrees of cold and plasma TSH concentration was measured by the McKenzie bioassay method (McKenzie 1958) and plasma corticosterone by a fluoro‐metric method. After the transfer of 19 rabbits to a cold room (10o C) no consistent change (p > 0.05) in the plasma TSH level could be seen up to 3 h, whereas the plasma corticosterone level rose transiently from 6.8 to 15.8 μg/100 ml (p<0.01) at 1 h but then fell to the initial level. After immersion of anesthetized rabbits (18 cases) in ice‐cold water for 10 min, the colonic temperature fell from 38 to 30o C. By 2 h plasma TSH levels were again unchanged (p > 0.05) and plasma corticosterone levels had risen from 5.9 to 27.4 μg/100 ml (p < 0.001, 10 cases), or were unchanged (p > 0.05) but high i nanimals pretreated with stereotactically around the preoptic area provoked a decrease in hypothalamic temperature by 3o C (8 cases), while plasma TSH fell to an undetectable level adn corticosterone rose from 18.7 to 26.2 (p < 0.05) μg/100 ml. We conclude that in the rabbit the hypothalamus is refractory to cold stimulus, possibly through a mechanism associated with the secretion of ACTH.
Ionic Fluxes in the Rat Portal Vein and the Applicability of the Goldman Equation in Predicting the Membrane Potential from Flux Data
Authors: Wahlström Bo A.
Published: December 2008

Wahlstrom, B. A. Ionic fluxes in the rat portal vein and the applicability of the Goldman equation in predicting the membrane potential from flux data. Acta physiol. scand. 1973. 89. 436–448.

The sodium, potassium and chloride effluxes from the rat portal vein were measured using radioactive tracer ions. It was found that the sodium efflux attributable to an intracellular compartment was very slow, with a rate constant of 4.66×10‐4 s‐1, and the corresponding intracellular sodium only 3.0 mmol/kg wetweight. The intracellular potassium exchanged with a rate constant of 2.15×10‐4 s‐1 and contained 45.5 mmol/kg wetweight. The intracellular chloride content was 14.7 mmol/kg wetweight, exchanging with a rate constant of 10.55 × 10‐4 s‐1. From these data the permeabilities of Na, K and CI were calculated to 0.130, 3.81 and 3.11 ×10‐8 cms‐1 respectively. The relative permeabilities PK: PNa: PC1 were 1: 0.034: 0.816, and from these values the Goldman equation predicted a membrane potential of ‐42.3 mV. The actual membrane potential, measured by glass microelectrodes, was ‐ 45 mV. It was concluded that the membrane potential in the rat portal vein in normal solution can be predicted from the permeabilities and distribution of K and CI, while Na plays an insignificant part.
Contraction Properties of Cat Facial Muscles
Authors: Lindquist By Christer
Published: December 2008

The contraction properties of some facial muscles of the cat have been investigated. The contraction time of a maximal isometric twitch is 8.5 ms for the orbicularis oculi. 24 ins for the depressor conchae and 33 ms for the orbicularis oris. It is suggested that a slower decay of the active state may be one factor explaining the longer contraction time of the orbicularis oris as compared to the orbicularis oculi. The duration of a maximal compound action potential is also longer for the orbicularis oris than for the orbicularis oculi (8.5 and 2.8 ms respectively). Muscle length is more critical for the twitch amplitude of the orbicularis oculi than for the orbicularis oris. Summation of individual twitches occurs at a stimulus frequency of minimum 20–22 Hz for the orbicularis oculi and at 10–12 Hz for the orbicularis oris. Apparent fusion occurs at 100 Hz for the orbicularis oculi and at 60 Hz for the orbicularis oris. The rate of tension development increases for both muscles with stimulus frequencies up to 200 Hz. Average tetanus/twitch ratios are 4.5 for the orbicularis oris and 7.0 for the orbicularis oculi.
Histochemical Fiber Composition of Some Facial Muscles in the Cat in Relation to their Contraction Properties
Authors: Edström Lars , Lindquist Christer
Published: December 2008

A histochemical analysis has been performed of the activity of myofibrillar ATPase, succinic dehydrogenase. NADH2 tetrazolium reductase and phosphorylase and of the content of glycogen and fat in the orbicularis oculi, orbicularis oris and the depressor conchae muscles in the cat. All three muscles contain fibers with a low activity (type I) and such with a high activity (type II) of myofibrillar ATPase. The type II fibers predominate. In general, the type II fibers of the orbicularis oris have a higher activity of oxidative enzymes than those of the other two muscles. Differences in contraction times in relation to fiber composition are discussed. Stimulation of the orbicularis oculi at 5 Hz causes a contractile fatigue of 22–48 % in a 10 min period, which is related to a depletion of glycogen in muscle fibers with a low activity of succinic dehydrogenase. The orbicularis oris fatigues very little (2–21 %) during such a period and no significant glycogen depletion is seen. This is explained by a higher activity of oxidative enzymes in this muscle.
Electrophysiological Study of the Gustatory Effects of the Sweet Proteins Monellin and Thaumatin in Monkey, Guinea Pig and Rat
Authors: Brouwer J. N. , Hellekant G. , Kasahara Y. , Wel H. van der , Zotterman Y.
Published: December 2008

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.
Cardiovascular Effects of Blood Borne Material Released from the Gat Small Intestine during Simulated Shock Conditions
Authors: Haglund Ulf , Lundgren Ove
Published: December 2008

Cardiac performance was studied in the cat during and after a mimicked shock situation in the small intestine (regional hypotension at 35 mm Hg during nervous vasoconstrictor fibre activation). Aortic blood flow was measured with an electromagnetic flow probe around the ascending aorta and, in some experiments, maximal dP/dt of the left ventricle was also followed. Upon restoration of intestinal perfusion pressure after a 2 h “shock” period a rapid reduction of aortic flow occurred due to a decreased stroke volume. Concomitantly maximal dP/dt was reduced in the face of an unchanged central venous pressure and left end diastolic pressure. This decline of cardiac performance could be prevented by substituting, during the first posthypotensive min, the intestinal venous blood with fresh blood from a healthy donor animal. However, when the shed intestinal venous blood was retransfused, a rapid decline of cardiac performance was evident. The reduced cardiac function was accompanied by an unchanged or slightly elevated total peripheral resistance. It is proposed that substances released front the “shocked” intestine cause a rapid and pronounced depression of cardiac function.
Countercurrent Multiplication of Sodium in Intestinal Villi during Absorption of Sodium Chloride
Authors: Haljamäe Hengo , Jodal Mats , Lundgren Ove
Published: December 2008

The sodium and the potassium concentrations in the villous tissue, expressed as g Na or K per nig tissue protein, were determined in vivo along the villous length during the absorption of isotonic saline solutions. The sodium concentrations was found to be 3 4 times higher at the tip than at the villous base. The addition of 30 mmol glucose to the incubation medium resulted in a significant increase of the sodium concentration along villous length, while this gradient was drastically decreased by ischemia or intense vasodilatation as well as by intraarterial infusion of ouabain. The intracellular sodium and potassium concentrations at the villous base were calculated to 21 and 125 mEq/1, respectively, during isotonic saline absorption. The extracellular sodium concentration at the villous tip was estimated to 300–900 mEq/1, corresponding to an interstitial osmolarity of 600–1600 mOsm/1. It is proposed that a counter‐current multiplication of sodium occurs in the villi resulting in a high interstitial osmolarity at the villous tip. The functional importance of the countercurrent multiplication of sodium for the absorption of water is discussed.
A Study of Plasma and CSF Potassium Relationship during Postnatal Development in the Cat
Authors: Cullheim By Stakfan
Published: December 2008

The concentration of potassium in plasma and cerebrospinal fluid obtained from the cistcina magna was determined in anesthetized kittens and adult cats before and after elevation of the potassium concentration in blood by means of 1) i.v. isotonic KCl‐infusion for 2 h arid 2) feeding with isotonic KC1 for 12 h. The results suggest that in anesthetized animals a slight decrease in CSF potassium concentration occurs postnatally. Elevation of the potassium concentration in blood caused a rise in CSF potassium concentration which was very slight in all age groups but was somewhat larger in the kittens than in the adults.
The Force‐Velocity Relation in Phasic Contractions of Venous Smooth Muscle
Authors: Hellstrand Per , Johansson Börje
Published: December 2008

The force‐velocity relation of the rat portal vein has been studied during regular spontaneous contractions induced by elevated levels of [K+]0 and [Ca2+]0. No satisfactory description of the force‐velocity relation was obtained by measuring shortening velocity in afterloaded isotonic contractions. Therefore the method of isotonic quick release was used, as this permits mechanical studies at specified instants of the contraction‐relaxation cycle. The temporal development of the force‐velocity relation in the phasic response was investigated. During a time interval in the rising phase of the contraction, at about the time for maximal dP/dt, the force‐velocity curves were practically identical, suggesting a plateau in the intensity of active state. At later stages of the twitch the curves were progressively displaced towards the origin, the intercepts on both the force and the velocity axis becoming smaller. At the time of the isometric peak the maximal shortening velocity had declined relatively more than the isometric force. This is presumably caused by inhomogeneous activation of the muscle at the beginning of relaxation. The maximal force‐velocity relation in the rising phase of the contraction can be described by Hill's (1938) equation with the following parameters (at 37°C): a/Po= 0.73±0.04, b = 0.5±0.04 lengths/s, Vmax= 0.74±0.02 lengths/s (n = 7, mean ± S.E.). The force‐velocity relation of the portal vein in comparison with other kinds of muscle is discussed.
Isometric and Isotonic Relaxation in Venous Smooth Muscle
Authors: Johansson Borle , Hellstrand Per
Published: December 2008

The time course of relaxation under isometric and isotonic conditions was studied in preparations of rat portal vein which maintained regular phasic contractions in solutions with increased [K+] and [Ca2+]. It was found that the smooth muscle during isotonic lengthening was able to carry the afterload for a period of time which was longer than expected from the control isometric response. The difference was largest for afterloads corresponding to about half the isometric peak force. The terminal decline in force was identical in afterloaded and purely isometric responses. Inhibitory influences of isotonic shortening causing increased rates of relaxation, as reported for striated muscles, were not observed. The differences in the course of relaxation between isotonic and isometric responses of portal vein could not be attributed to variations in membrane excitation. It also appears that the differences are not due to changes in release or uptake of activator calcium, or to presence of viscous elements in the tissue. It is suggested that the ability of the smooth muscle to carry load over a relatively long period during isotonic relaxation may be attributed to the characteristics of the instantaneous force‐velocity relations in the force range above P0.
Carbon Monoxide as a Degradation Product of Cytochrome C and of Ascorbic Acid
Authors: Westman Gunnar
Published: December 2008

Cytochrome c has been incubated with 4 different reducing agents at 37°C for 24 h at pH 7.0, and the spectral changes and the production of carbon monoxide have been followed. Only with hydrazine hydrate cytochrome c produced some carbon monoxide. Accidentally, carbon monoxide formation from ascorbic acid was found, amounting to about 0.1 μmol from 15 μmol of ascorbic acid in 24 h under the above conditions.
The Heat Production of Pancreatic β‐Cells Stimulated by Glucose
Authors: Gylfe Erik , Hellman Bo
Published: December 2008

A recently developed batch microcalorimeter was used for studying heat production in β‐cell‐rich pancreatic islets isolated from obese‐hyperglycemic mice. In the absence of glucose, the rate of heat production was 50 nW/islet increasing to 90 nW/islet when the islets were exposed to 20 mM glucose. The data obtained are consistent with an increase in the caloric value of oxygen with glucose concentration, as might be expected when the β‐cells utilize proportionally more carbohydrate as a source of energy.
A Compact Perfusion System for Studies on the Control of Metabolic Processes in Isolated Organs from Small Animals
Authors: Eriksson Hakan
Published: December 2008

A compact apparatus for perfusion of isolated organs from small animals is described. The system is based on a module principle making it useable both in low and high pressure perfusions. 40–80 ml of heparinized, diluted rat blood used as liver‐perfusion medium, is recirculated in the system, which is temperature controlled by means of a water jacket. A new type of capillary membrane oxygenator is used for oxygenation. The system permits rapid measurements of perfusate flow, vascular resistance, bile production (when the isolated liver is used), urinary production (when the isolated kidney is used), gas tensions, oxygen consumption, pH and perfusion pressure. Descriptions of the techniques used for operation and perfusion of isolated livers and kidneys from rats are given. By the generally accepted criteria of viability the isolated rat liver remains almost normal for the test period of 3 h. Liver functions were normal as judged by formation of glucose, respiratory rate, urea and bile production and gross morphology. There was very little leakage of liver enzymes into the perfusate. The transformation and elimination of labelled corticosterone were studied to test the steroid metabolizing activity of the isolated rat liver preparation.
Frequency Dependent Changes in the Amplitude of the Cochlear Microphonic Potential of the Pigeon Ear during Transient Anoxia
Authors: Jørgensen Finn Ove
Published: December 2008

The effect of transient anoxia on the cochlear microphonic potential at different sound frequencies was investigated. The microphonic potential was recorded with glass microelectrodes in the ductus cochlearis of the pigeon ear. Transient anoxia had different effects, related to frequency, on the amplitude and the relative phase angle of the microphonic potential recorded from one place in the ductus cochlearis. At frequencies equal to and higher than the best frequency the amplitude of the microphonic potential was more sensitive to anoxia than it was at lower frequencies. Microphonic potential at 1 kHz lower than the best frequency was often enlarged in amplitude during transient anoxia. The results suggest that this frequency‐dependent effect is a positional one. Changes in the phase were largest around the best frequency. It is inferred that anoxia causes complex changes in the pattern of vibration in the cochlear partition. The observed changes in amplitude and also changes in phase are caused by the combined effects of reduction of the endolymphatic potential and changes in vibration pattern.
Transcapillary Fluid Movements in Sympathectomized Intestine and Skin during Hemorrhagic Hypotension
Authors: Järhult Johannes , Grände Per‐Olof
Published: December 2008

Net transcapillary fluid exchange in skin tissue (paw) and small intestine was observed during a 90 min period of hemorrhagic hypotension at 50 mm Hg in the cat. Reflex fluid transfer was prevented by regional sympathectomy and α‐adrenergic blockade. Early in hemorrhage, fluid absorption from the extravascular space occurred in both tissues, apparently caused by osmosis. The process was thus co‐ordinated in time with a positive arterio‐venous osmolar difference, in turn caused by a marked arterial hyperosmolality. Experimental arterial hyperosmolality of similar magnitude, created by i.v. infusion of hypertonic glucose in non‐bled animals, led to transcapillary fluid absorption in both intestine and skin and at rates similar to those in bleeding. Regional hypotsionen per se caused no fluid absorption. Later in hemorrhage (> 30 min), plasma fluid moved into the extravascular space both in skin and intestine, apparently due to a gradual increase of capillary hydrostatic pressure. It is concluded that the arterial hyperosmolality during bleeding can cause transcapillary fluid absorption in intestinal and skin tissues, as previously shown for skeletal muscle (Järhult 1973). The hemodynamic significance of this process for plasma volume regulation in hemorrhage is, however, much greater in skeletal muscle than in intestine and skin, mainly due to the much larger total mass of the muscle tissue.
The Effect of ATP and Related Compounds on Spontaneous Mechanical Activity in the Rat Portal Vein
Authors: Sjöberg Björn , Wahlström Bo A.
Published: December 2008

The effects of ATP, ADP, AMP and adenosine were studied on the spontaneous mechanical activity of the rat portal vein. It was found that ATP and ADP, in concentrations higher than 300 μM, caused a transient tetanus, followed by inhibition, and at lower concentrations an increase in the frequency and amplitude of the spontaneous contractions. AMP and adenosine on the other hand, inhibited spontaneous activity, by reducing the amplitude of contractions and increasing their frequency. The effects were dose‐dependent. ATP was found to be 2.2 times more potent than ADP, while AMP and adenosine were equipotent. Weak inhibitory effects were obtained with GMP, guanosine and adenine, while GTP, 3′5′‐cyclic AMP and guanine had no effect. ATP and ADP increased the K‐contracture, while AMP and adenosine relaxed it. The effects of ATP were augmented in Mg‐free solutions and partially inhibited in Mg‐high solutions in the normally polarized muscle, while Mg had no influence on the ATP‐induced contraction in the depolarized muscle. Theophylline potentiated the inhibitory response to AMP and adenosine. Adrenergic and cholinergic blockers had no influence on the response to ATP, ADP, AMP or adenosine. It is suggested that the effects of ATP and ADP are linked with Ca++ movements across the membrane, while AMP and adenosine might stimulate intracellular metabolism causing increased intracellular Ca++ binding.
Incorporation of Choline, Serine, Ethanolamine and Inositol into Phospholipids of Isolated Rat Mast Cells
Authors: Strandberg Kjell , Sydbom Anita , Uvnäs Börje
Published: December 2008

The incorporation of labelled phospholipid precursors, [Me‐14C]‐choline, L‐[3‐14C]‐serine, [2‐14C]‐ethanol‐amine and [2‐3H]‐myoinositol into the phospholipids of isolated rat mast cells was studies. The label from the different precursors were found to be essentially associated with compounds with the t.l.c.‐motility of the respective phospholipids. Whereas the incorporation of [Me‐14C]‐choline and L‐[3‐14C]‐serine showed evidence of saturation, the incorporation of [2‐14C]‐ethanolamine was linear with time (2 h) and it was not saturated by increasing the concentration from 0.07 mM to 2.07 mM. The incorporation of [2‐3H]‐myoinositol was stimulated by Ca2+ (1 mM) or Mg2+ (1 mM), while the incorporation of the other precursors was stimulated only in the presence of both Ca2+ and Mg2+ (1 mM). Antimycin A (1 μM), an inhibitor of the respiratory chain, significantly inhibited the incorporation of [Me‐14C]‐choline, L‐[3‐14C]‐serine and [2‐3H]‐myoinositol but not that of [2‐14C]‐ethanolamine. The experimental system used might be a useful model for studies on the turnover of membrane phospholipids during histamine release
Influences on Colonic and Small Intestinal Motility by the Cerebellar Fastigial Nucleus
Authors: Martner Jan
Published: December 2008

The fastigial influence on intestinal motility was investigated in acute experiments on chloralosed casts. Motility was recorded both from the small and large intestine. Electrical stimulation of the rostral fastigial pole produced, in combination with a blood pressure rise, increased motor activity in ileum and colon while jejunum could respond with either increased or decreased mobility. The intestinal responses were neither secondary to changes in intestinal blood flow, nor to baroreceptor reflexes induced by the increased blood pressure. The excitatory responses were not due to increased parasympathetic activity since sectioning of such pathways failed to abolish the responses. Insted, interruption of adrenergic sympathetic discharge, accomplished either by guanethidine or by sectioning of relevant nerves, did eliminate the responses, indicating that the fastigial effects were mediated by suppression of prevailing adrenergic tone. Noxious stimuli to the abdomen, including laparotomy, inhibit intestinal motility by a reflex increase in adrenergic discharge. It is suggested that fastigial influence on intestinal motility is mainly due to suppression of this reflex.
Influences on the Defecation and Micturition Reflexes by the Cerebellar Fastigial Nucleus
Authors: Martner Jan
Published: December 2008

The influence of the cerebellar fastigial nucleus on the defecation and micturition reflexes was investigated in chloralosed cats with recordings of colonic blood flow and motility, intravesical and intraabdominal pressures. Whenever effective, topical fastigial stimulation regularly suppressed both somatomotor and autonomic components of the defecation reflex, to the extent that the straining movements as well as the colonic vasodilatator and motor responses associated with defecation could be completely inhibited. Bladder motility could either be suppressed or enhanced, depending both on prevailing bladder tone and on the fastigial site stimulated. The autonomically conveyed inhibitory responses were in both cases independent of the adrenergic sympathetic pathways, since they were unaffected both by sympathetic nerve sectioning and by adrenergic blocking drugs but eliminated by pelvic nerve section. It is suggested that the mentioned fastigial inhibitory influences are exerted on the spinal parasympathetic reflexes controlling the bladder and colon. Parallels between fastigial control of autonomic and somatomotor mechanisms are discussed.
Optimal Parameters for Eliciting Cardio‐Acceleration by Electrical Stimulation of the Ventromedial Hypothalamus
Authors: Johansson G. , Kalimo R. , Pääkkönen T. , Ruusunen S.
Published: December 2008

The ventromedial hypothalamus of the unrestrained cat was stimulated electrically through permanent electrodes. The stimulation parameters, amplitude, duration and frequency of the square wave pulses were combined to produce a 20% increase of the resting heart rate value. The total electric charge for each parametric combination was calculated. The charge per stimulation (10 s) varied from about 1 to 100 micro‐coulombs, depending on the parametric combination used. The response could therefore not be expressed as a function of the charge but depended on the individual parametric combinations. The relation among the stimulation parameters and the total amount of electric charge of the pulses was estimated by the correlation technique. The results suggested that about 60% of the variation in the electric charge resulting in the constant response was due to the variation of the pulse repetition frequency. The optimal parameters for eliciting cardio‐acceleration in the cat by stimulation of the ventromedial hypothalamus seem to be pulse durations between 0.1 and 0.5 ms and pulse repetition frequencies below 100 P/s, with pulse amplitude as the dependent variable.
Facilitation from Contralateral Primary Afferents of Interneuronal Transmission in the la Inhibitory Pathway to Motoneurones
Authors: Fedina L. , Hultborn H. , Illert M.
Published: December 2008

The action of volleys in contralateral primary afferents on transmission in the la inhibitory pathways to motoneurones was investigated with intracellular recording from motoneurones. Ia IPSPs in flexor as well as most extensor motoneurones were regularly facilitated by volleys in contralateral high threshold muscle, cutaneous and joint afferents in spinal cats under chloralose anaesthesia. In decerebrate cats with a low pontine lesion transmission in la inhibitory pathways was not facilitated but rather depressed by volleys in these afferents. The recurrent effects from motor axon collaterals were investigated on inhibitory transmission from different contralateral afferents to motoneurones. Previous investigations have shown that the interneurones mediating the reciprocal la inhibition receive recurrent inhibition via motor axon collaterals and Renshaw cells. Now a strong positive correlation was revealed between recurrent depression of IPSPs evoked from different contralateral afferents and facilitation of la IPSPs by the same afferent volleys. These results suggest that the recurrent depression of IPSPs from different contralateral primary afferents depends on their excitatory convergence onto the la inhibitory interneurones, which then partly mediate the IPSP evoked in the motoneurone from these afferents.
Circulatory and Respiratory Effects Evoked by Hypertonic Ventriculo‐Cisternal Perfusion
Authors: Mellander Stefan , Hillman Jahn
Published: December 2008

The cerebral ventricular system of anesthetized dogs was perfused with synthetic isotonic CSF and, for 80 s intervals, with hypertonic CSF of various compositions. Hypertonic perfusion evoked centrally mediated marked increases in arterial blood pressure, heart rate, respiratory rate, and ventilation and, after some delay, an excitatory resembling arousal. The responses were coordinated in time with the induced CSF hypertonicity, graded in relation to its magnitude, and reversible on return to isotonicity. The effects, which seemed to be elicited from periventricular structures in the brain stem, were more pronounced and consistent when CSF hypertonicity was produced by adding NaCl or Na‐lactate than monosacharides to the isotonic CSF solution. Analysis of the cardiovascular responses indicated that they were caused by increased sympathetic vasoconstrictor and cardiac accelerance fibre activity and by inhibition of vagal discharge to the heart. The described pattern of response much resembles that evoked by physical exercise, a state which might lead to osmolar changes in the brain and CSF of a similar kind to that in the present study as a consequence of the pronounced work‐induced arterial hyperosmolality. It is suggested that such an osmotic mechanism might constitute a “metabolic link” in the centrally mediated circulatory and respiratory adjustments in exercise.
Effect of Insulin on Albumin Production and Incorporation of 14C‐leucine into Proteins in Isolated Parenchymal Liver Cells from Normal Rats.
Authors: Dich J. , Gluud C. N.
Published: December 2008

Parenchymal rat liver cells were isolated by a modification of the collagenase method of Quistorff, Bondesen and Grunnet. The cells secreted albumin into the medium and incorporated 14C‐leucine both into cell proteins and proteins secreted into the medium. Albumin production measured from the immunologically determined increment in the incubation medium was 1.7 ± 0.2, μg albumin/min per g liver wet wt. This is about 30% of the rate of production in the perfused liver. Addition of insulin (10‐6‐10‐10 M) enhanced albumin production (50‐17%), and incorporation of 14C‐leucine both into albumin (50‐8%), secreted proteins (40‐9%) and cell proteins (20‐8%). Insulin does not increase the production of albumin by depleting the cells. The effect of insulin on albumin production is compatible with an effect on the rate of synthesis as the specific activity of albumin is unaffected by addition of insulin.
Prostaglandin Synthesis in Membrane Fractions from the Rabbit Renal Medulla
Authors: Bohman Sven‐Olof , Larsson Carin
Published: December 2008

In order to investigate the subcellular location of the prostaglandin synthesizing enzyme complex (prostaglandin synthetase) the distribution of this enzyme was analysed in membrance fractions from the rabbit renal medulla using an improved radioactive asay with arachidonic acid as a substrate. 3 membrane fractions were isolated and the subcellular origin of the membranes was determined by electron microscopy and by their contents of different marker enzymes. Fraction I was a plasma memberane fractin, II was a cytomembrane fraction, mainly derived from the endoplasmic reticulum and fraction III was a mitochodrial fraction. The specific activity of prostaglandin synthetase in the homogenate of rabbit renal mitochondrial fraction. The specific activity of prostaglandin synthetase in the homogenate of rabbit renal medulla was 0.1 nmol arachidonic acid converted/min per mg protein. In fraction II, the cytomembrane fraction, the specific activity was increased 2.4 times over the homogenate, the plasma membrane fraction and the mitochondrial fraction having lower activities. The results suggest that prostaglandin synthetase is located in the endoplasmic reticulum of renal medullary cells.
Membrane Potential and Conductance during Piocytosis Induced in Amoeba proteus with Alkali Metal lons
Authors: Josefsson Jan‐Owe , Holmer Nils‐Gunnar , Hansson S. Elisabeth
Published: December 2008

An investigation of the relationshi between the polarized state of the membrane adn the onset and the intensity of pinocytosis was made in Amoeba proteus. Membrane potential and input resistance was in all instance found to decrease in approximate proportion to the number of channels when pinocytosis was induced by a variety of alkali metal ions at varying pH. channels began to appear when the membrane was depolarized to–30 mV by the inducer of pinocytosis. With all inducers the maximum pinocytosis was encountered at membrane potentials close to zero. No positive potentials were recorded when the chloride salts of the inducing cations were used. At high concentration of alkali ions a transient increase of the chloride permeability caused short‐lasting hyperpolarizations of the membrane. Inhibition of pinocytosis by Ca++ was accompanied by an increase of input resistance and membrance potential. The selectivity of the membrane to different alkali metal ions observed as changes in pinocytosis intensity, membrane potential and input resistance was found to vary with the concentration of the inducer and with the Ca++concentration of the extracellular solution. Displacement of membrane bound Ca++appeared to decrease the field strength of charged groups in the membrane altering its selectivity among alkali cations. The formation of pinocytotic channels in suggested to require translocation of Ca++from the membrane into the cell and would therefore be closely related to the electrical properties of the amoeba.
A Theoretical Study of Restricted Convention‐Diffusion as Applied to Blood‐Tissue Barrier Exchange
Authors: ÅBerg Bo
Published: December 2008

This paper handles a model of the capillary function in the exchange of uncharged molecules between the blood and the tissue. The capillary system is subdivided into a filtering and a reabsorbing part. The exchange is assumed to occur through channels which are described in operational terms as pores. Through these pores there is a transport of solutes by concomitantly acting convection and diffusion influenced by a steric hinderance (restricted convection‐diffusion). The outflux of glucose and raffinose is enhanced in the filtering pores, raffinose relatively more than glucose. In the reabsorbing pores the outward diffusion is hindered to some extent, raffinose relatively more than glucose. It is shown that the net effect of filtration and reabsorption is to increase the outflux of raffinose as compared to that of glucose. This mechanism may explain why glucose and raffinose and other small molecules appear to pass across capillary walls in proportion to their free diffusion coefficients and not in proportion to their restricted diffusion coefficients.
Integrated Somatomotor, Cardiovascular and Gastrointestinal Adjustments Induced from the Cerebellar Fastigial Nucleus
Authors: Lisander Börn , Martner Jan
Published: December 2008

Behavioural, cardiovascular and gastric responses induced by fastigial stimulation wereobserved in conscious cats with gastric fistulas, indwelling fastigial electrodes and arterial catheters. Fastigial stimulation elicited oral behaviours, e.g. grooming and chewing, together with tachycardia and pressor responses, while gastric motility was unaffected in most cases as was gastric hydrochloric secretion. In subsequent experiments on the anesthetized animals it was found that the same fastigial area could suppress the intestino‐gastric inhibitory reflex. Fastigial influences on small intestinal motility were investigated in anesthetized cats, well recovered from surgical isolation of intestinal loops whose motility could therefore be recorded without laparotomy. Fastigial stimulation either depressed or did not influence ileal motility before laparotomy but after this procedure excitatory responses were uniformly recorded. This reversal is explained by a fastigial suppression of inhibitory intestinal reflexes, elicited by the laparotomy.
Rapid Transport of Noradrenaline in Adrenergic Axons of Rat Sciatic Nerve Distal to a Crush1
Authors: Häggendal J. , Dahlsträm A. , Larsson P. A.
Published: December 2008

The transport of NA in the rat sciatic nerve distal to a crush was studied in 5 mm segments. The disappearance of a NA fraction in consecutive segments with time after crushing (0–12 h) was interpreted to indicate a proximo‐distal migration of a NA fraction into further distal parts of the nerve. This transportable NA fraction was found to be about 45% of the NA in normal sciatic nerves and migrated at a rate of approximately 8 mm/h. The apparently non‐mobile fraction (55%) was probably mainly located in vaso‐constrictor nerve terminals of the blood vessels supplying the nerve. This non‐mobile NA fraction does not contribute to the NA accumulations proximal to a crush. Thus, when calculating the rate of transport of any substance from accumulation experiments, corrections for a non‐mobile fraction must always be considered.
Synaptosomes Containing Large Agranular Vesicles Isolated from Developing Rat Brain
Authors: Kanerva L. , Hervonen A. , Tissari A. H.
Published: December 2008

Using the subcellular fractionation technique the fine structure of the isolated nerve endings (synaptosomes) from the hemispheres and brain stem of the 1–day old and adult rat was examined. In the synaptosomal fractions of the brain of 1–day old rats we observed a new type of nerve endings containing predominantly large agranular vesicles about 1 000 Å in diameter. After incubation with a‐methylnoradrenaline or 5–hydroxydopamine these vesicles remained agranular. It is assumed that the new type of large vesicles represent developing synaptic vesicles. References
The Effect of Ca++, Mg++ and H+ on the Capillary Permeability of the rete mirabile of the Eel, Anguilla vulgaris L.
Authors: Stray‐Pedersen Sverre
Published: December 2008

The effects of EDTA, and of varying pH on the capillary permeability in the rete mirabile have been investigated: EDTA had to be added to the perfusate in excess to the total content of Ca++ and Mg++ in plasma in order to elicit changes in the permeability. When exposed to sufficient amounts of EDTA, the capillary permeability to hydrophilic molecules increased several fold whereas the permeability to THO and lipid‐soluble molecules remained unchanged. The increase in the permeability to high‐molecular dextrans was delayed. When the EDTA‐effect was maximal the mutual relationship between the permeabilities of THO and the lipid‐insoluble molecules became close to the ratio between the corresponding free diffusion coefficients in water. During exposure to EDTA the content of K+ and Na+ of the rete tissue (mostly endothelial cells) became very similar to that of plasma. Similar effects were obtained when the rete was perfused with plasma having a pH below 4 or above 9. The EDTA‐effect was reversible during its initial stage. Perfusions with plasma in which Ca and Mg had been removed by dialysis at pH 3.5 were performed. When an EDTA‐effect had been induced with this type of perfusates, it could be reversed by addition of equimolar amounts of either Ca++ or Mg++. This indicates Ca++ and Mg++ to be equally important in order to assure normal permeability properties of the capillary membrane.
Changes in Renal Hemodynamics and Sodium Excretion during Saline Infusion in Lambs
Authors: Aperia Anita , Broberger Ove , Herin Peter
Published: December 2008

The renal response to a progressive isotonic extracellular volume (ECV) expansion was studied in 13 lambs of two age groups (5–28 days and 48–57 days). Changes in renal hemodynamics induced by the ECV expansion were followed. Intraenal blood flow was determined by the microsphere method. For determination of the glomerular filtration rate (GFR) standard clearance techniques were used. Recordings were made during control conditions and when normal saline had been infused in amounts up to 4.5% of the body weight. During the infusion there was an increase in sodium excretion both in absolute values and in relationship to GFR. The increase was, however, much less pronounced in the younger lambs. The GFR did not change significantly during saline infusion. The cortical blood flow increased only in the older lambs. As a consequence the quotient between GFR and cortical blood flow decreased in the older lambs. The possibility of a causal relationship between the fall in filtration fraction so obtained and the more pronounced natriuretic response in the older lambs is discussed. The inner to outer cortical blood flow ratio increased more in the younger lambs during saline infusion. The functional significance of an age related blood flow redistribution is, however, not clear.
On the Noradrenaline Loading in Axonal Amine Storage Granules in Rat Crushed Sciated Nerves1
Authors: Dahlström A. , Häggendal J. , Larsson P. A.
Published: December 2008

The increase of NA in rat sciatic nerve above a crush was investigated. The transported amounts of NA did not increase quite linearly with time, but more NA was found above the crush at 6 and 12 h than would be expected from the 3 h value. One possible reason for this phenomenon—an increased NA loading of the accumulated axonal granules—was investigated by 2 types of double crush experiments. One type involved simultaneous double crushes 1‐1.5 cm apart. The increase in NA in the isolated segment 6 h after crushing indicated that the axonal amine storage granules had increased their NA load by about 70%. In the second type (“delayed double crushes”) a distal crush was made 6 h before a second crush, 1‐1.5 cm proximal to the first crush. 1–12 h after the second high crush the NA content of the isolated segment was assayed. The results indicated an increased NA content in the axonal granules of 75% already 3–4 h after the isolation of the segment, remaining constant up to 9 h after the second crush. The results indicate that axonal storage granules may increase their NA content by a factor of about 2 (1.7) while being transported distally in the axons. This information together with the information from the preceding article of a mobile NA fraction of 45%, was used to calculate the rate of transport of NA granules proximal to a crush. The value obtained was 9 mm/h which is in good agreement with the value obtained for transport distal to a crush (8 mm/h) in the preceding article.
Indomethacin Blockade of Renal PGE‐Synthesis: Effect on Total Renal and Tubular Function and Plasma Renin Concentration in Hydropenic Rats and on Their Response to Isotonic Saline
Authors: Leyssac P. P. , Christensen P. , Hill R. , Skinner S. L.
Published: December 2008

The effects of indomethacin (I), a blocker of prostaglandin (PG)‐synthetase, was studied in rats in an attempt to elucidate the physiological role of renal PGE. Plasma‐I‐concentrations of 13–14 μg/ml reduced renal venous plasma PGE‐concentration significantly from 216 to 85 pg/ml within 45 min. Urine flow and solute excretion decreased by 42% and 20%, respectively, while urine osmolality increased 450 mOsm. Inulin clearance (CIN) and proximal reabsorption rate was unaffected, while renal plasma flow (RPF) decreased by 18%. Plasma renin concentration decreased slightly but significantly. An i.v. saline load equal to 1% b.wt. given to I‐treated rats failed to elevate significantly either urine flow, solute excretion, CIN, RPF or proximal reabsorption rate, but plasma renin decreased further. The normal inverse relationship between plasma renin and proximal reabsorption rate was absent. The data are consistent with the concept that intrarenal PGE plays a role in adjustment of renal vascular resistance, and support the concept of a physiological role of intrarenal PGE in regulating salt and water excretion. The data do not support any major physiological role of PGE in regulating proximal tubular function.
The Biliary Excretion of 3H‐Inulin and 3H‐Terbutaline in the Unanesthetized Rat
Authors: Eriksson Hans , Hellström Wera , Ryrfeldt ÅKe
Published: December 2008

An animal model which permits sampling of arterial blood and bile from unanesthetized rats with uninterrupted enterohepatic circulation is described. Pharmacokinetic data concerning inulin (0.2 μmol kg‐1) and terbutaline (1.8 μmol kg‐1) after intraarterial injection are presented. The following values for inulin were obtained Vdβ= 0.25 ml g‐1 plasma clearance = 2.3 ml min‐1 kg‐1 and bile clearance = 0.03‐0.04 ml min‐l kg‐1, which mainly are in agreement with data from the literature. For terbutaline the corresponding values were 0.58 ml g‐l, 5.2 ml min‐l kg‐l and 0.12‐0.98 ml min‐1 kg‐1, respectively.
Potentiation by Prostaglandins E1, E2, and F2αof the Contraction Response to Transmural Stimulation in the Bovine Iris Sphincter Muscle
Authors: Gustafsson Lars , Hedqvist Per , Lagercrantz Hugo
Published: December 2008

The contraction response to transmural stimulation in the bovine iris sphincter muscle was abolished by atropine but was left virtually unchanged by hexamethonium, and by adrenergic neuron and receptor blockers, indicating activation of postganglionic cholinergic nerve fibres. Low doses of prostaglandins E1, E2and F2α(0.1–5.0 ng/ml) consistently and apparently in a dose‐dependent manner enhanced the contraction response to transmural stimulation. Prostaglandins E1and E2were equipotent while F., was at least 10 times less active. Within the same dose range the prostaglandins also enhanced the contraction response to exogenous acetylcholine, indicating that part of the enhancing effect of the prostaglandins on neuromuscular transmission was due to a postjunctional action. A spontaneous increase in tone of the preparation commonly occurred about 1 h after the beginning of the experiment. SC 19220, a potent antagonist of prostaglandin action, reduced the tone and the contraction responses as well as the enhancing effect of the prostaglandins. It is concluded that prostaglandins might serve the function of controlling neuroeffector transmission and muscular tone in the sphincter muscle of the bovine iris.