bluuebunny/crossref_metadata_2025_split huggingface dataset:
Countercurrent Multiplication of Sodium in Intestinal Villi during Absorption of Sodium Chloride
Authors: Haljamäe Hengo , Jodal Mats , Lundgren Ove 
Published: December 2008

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractCytochrome 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

AbstractA 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

AbstractA 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

AbstractThe 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

AbstractNet 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractParenchymal 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

AbstractIn 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.