bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effects of Intestinal Vasodilator Mechanisms on the Rate of 85Kr Absorption in the Cat
Authors: Biber Björn
Published: December 2008

The absorption rate of 85Kr from the small intestine of the cat was estimated during intestinal vasodilatation induced by transmural electrical field stimulation or by local i.a. infusions of cholecystokinin and secretin. As blood flow increased, a considerably augmented rate of absorption was observed, the absorption rate being increased in excess of that observed during corresponding hyperemia induced by isopropylnoradrenaline. An increased fraction of the intramural blood flow became fully equilibrated with luminal contents during the vasodilatory procedures.
Some Chemical and Biological Properties of a Protein Fraction from Nigerseed (Guizotia Abyssinica Cass.) Soluble in Hot Aqueous Ethanol
Authors: Eklund Anders
Published: December 2008

A nigerseed protein fraction soluble in a hot water‐ethanol solution of sodium chloride was isolated. It contained high levels of cystine and chlorogenic acid and inhibited the proteolytic digestion of casein by trypsin in vitro. Weanling male rats failed to grow when fed on this protein fraction as the sole source of protein. Histo‐pathological examinations of the main animal organs did not show any abnormalities.
Rates of Transvascular Fluid Filtration in Lungs from Normal and Thrombocytopenic Rabbits
Authors: Aursnes I. , Hauge A. , Waaler B. A.
Published: December 2008

The rate at which fluid is filtered out of the vessels on standardized elevations of left atrial pressure (Pla) has been tested in isolated lungs from normal and thrombocytopenic rabbits. Higher filtration rates were found in the lungs from normal than in the lungs from thrombocytopenic animals both during plasma and during blood perfusion. The filtration rates from the two groups of lungs were significantly different both at Pla elevations of 10 mm Hg (p = 0.008, two‐sided test) and at Pla elevations of 15 mm Hg. The reason for this difference is not clear. One possibility is that lungs in thrombocytopenic animals may be protected against changes occurring during the surgical procedures necessary for removal of the organ.
Effect of TRH, and Short‐term Exposure to Experimental Stress or Cold on the Serum Immunoassayable TSH Concentration in the Rat
Authors: Leppäluoto J. , Ranta T. , Lybeck H. , Varis R.
Published: December 2008

The influence of TRH, transfer and sampling stress and cold on the blood TSH level was studied in female rats using a specific radioimmunoassay for rat TSH. The maximum response to TRH increased with the dose of TRH and occurred at 5 min with 10 and 50 ng. With a TRH dose of 250 ng the niaxirnum response occurred at 10 min. Transfer stress caused a significant rise in serum TSH level at 5 min. After this, the serum TSH level gradually decreased and the decrease at 30 min was significant compared with 5 min value. Sampling stress caused a slight increase in the serum TSH level at 5 min, and at 30 and 60 min the serum TSH level was significantly lower than ir. controls. The maximum effect of cold on the blocd TSH level was seen in animals kept for 30 min at 5° C. These studies clearly demonstrate the effect of TRH on the serum TSH level in rats. The activation of the secretion of TSH in the cold is physiologically relevant, and the inhibition of TSH secretion in response to stress refutes the hypothesis that stressful stimuli activate the thyroid gland.
The Neuromuscular Blocking Action of an Isolated Toxin from the Elapid (Oxyuranus scutellactus)
Authors: Kamenskaya Marina A. , Thesleff S.
Published: December 2008

Intravenous administration of the neurotoxin (taipoxin) to mice caused after a latent period death by respiratory paralysis. The length of the latent period varied with dose, the dose‐response relation being bilogarithmic. Taipoxin failed to affect the resting membrane potential and the action potential of muscle. It caused a slight reduction in the acetylcholine sensitivity of the muscle membrane. The main effect of taipoxin on neuromuscular transmission was to reduce spontaneous and evoked transmitter release. The frequency of spontaneous miniature end‐plate potentials (m.e.p.p.s) was reduced to complete stop and depolarization of nerve terminals by a high potassium concentration (20 mM) failed to cause a marked and sustained increase in m.e.p.p. frequency. With nerve stimulation the amplitude of end‐plate potentials (e.p.p.s.) was reduced and with repetitive stimulation the amplitude of e.p.p.s. rapidly fell to a low level. Post‐tetanic facilitation of m.e.p.p. frequency and of e.p.p. amplitude were absent. The shape of evoked e.p.p.s. indicated asynchronous release of transmitter quanta. The effects of the toxin on neuromuscular transmission progressed even when the muscle was removed from the animal and placed in toxin‐free bathing fluid. In vitro experiments showed that the rate of onset of neuromuscular block depended on the temperature of the bathing solution and on the degree of activity at the neuromuscular junction. Thus, incubation in toxin solution during 4 hr at 28° C failed to produce a neuromuscular block while at 37° C the block was complete within 1 h. With nerve stimulation at 10 Hz for 2 s every 2 min the rate of blockade was more rapid than in unstimulated preparations, similarly 20 mM potassium in the bathing fluid enhanced the rate of blockade.
Lactate Production and Anaerobic Work Capacity after Prolonged Exercise
Authors: Asmussen E. , Klausen K. , Nielsen L. Egelund , Techow O. S. A. , Tønder P. J.
Published: December 2008

It has been found that previous heavy or long‐lasting exercise results in a diminished ability to raise the blood lactate concentration by exhaustive supermaximal work (Hedman 1957, Astrand et al. 1963, and others). No definitive explanation for this phenomenon has been given. It was the purpose of the present experiments to throw light on the question whether a diminishing store of carbohydrates in the body could be the cause for the declining ability to liberate energy anaerobically by breakdown of glycogen to lactic acid. In 3 subjects the stores of glycogen were presumed to be varied 1) by repeated bouts of supermaximal and submaximal exercise on the bicycle‐ergometer, and 2) by diet after previously depleting the carbohydrate stores by exercise. It was found that in all cases the ability to work anaerobically and to produce lactate decreased with decreasing amounts of available carbohydrate. Disturbances in water or electrolyte balance were avoided. It is tentatively suggested that the velocity of the enzymatic process glycogen—glucose‐1‐phosphate is the limiting factor, and that this process is slowed down by lactic acid accumulation, the more the lower the substrate (glycogen) concentration is. Glucose, which enters the glycogenolytic chain as glucose‐6‐phosphate, can partly restore the ability for lactate production.
Changes in the Concentration and Fatty Acid Composition of Phospholipids in Rat Skeletal Muscle during Postnatal Development
Authors: Bruce ÅKe
Published: December 2008

Rat skeletal muscle was analysed at different ages, from birth to 90 days, for its concentration of phospholipids and individual phosphoglycerides, and for the fatty acid pattern of cardiolipin, choline phosphoglyceride (CPG), ethanolamine phosphoglyceride (EPG), inositol phospho‐glyceride and serine phosphoglyceride (SPG). The concentration of phospholipids was found to increase between birth and two weeks of age, after which it decreased slightly to 14 μmol/g fresh weight at the age of 90 days. The relative amount of CPG and EPG varied but little with age, while that of cardiolipin increased to three times its original value. The concentration of polyenoic acids increased with age in all phosphoglycerides except SPG. The concentration of the sum of the fatty acids of the linoleic acid series in CPG increased rapidly during the first weeks of life, while that of the linolenic acid series increased throughout the period studied. In EPG the concentration of the sum of the fatty acids of the linolenic acid series increased, while that of the linoleic acids decreased and the concentration of linoleic acid in cardiolipin increased. In the muscles of 90‐day‐old rats, the fatty acid pattern of cardiolipin showed a high level of linoleic acid and no fatty acids of the linolenic acid series. The fatty acid pattern of CPG was characterized by rather high levels of both linoleic and arachidonic acids and that of EPG by a high concentration of the fatty acids of the linolenic acid series.
Glycogen Storage and Glycogen Synthetase Activity in Trained and Untrained Muscle of Man
Authors: Piehl K. , Adolfsson S. , Nazar K.
Published: December 2008

Bilateral biopsies from “one‐leg” trained subjects were analysed for glycogen content (G), total glycogen synthetase activity (GST), synthetase I‐form (GSI) and hexokinase (HK). Histochemical estimations were made of G, GST and GSI in slow twitch (ST) and fast twitch (FT) muscle fibres. Samples from the trained (T) and the untrained (U) legs were taken before and after acute exhaustive exercise and at different intervals during a 46 h recovery period when a carbohydrate enriched diet was given. Prior to exercise G levels were higher (32 %) in T‐leg than in U‐leg. Throughout the experiment T‐leg showed higher activity for GST (35%) and HK (18%). In both U‐ and T‐legs GSI activity increased (from 16 to 48 %) after exercise. The increase in GSI was histochemically found mainly in ST fibres in both T‐ and U‐leg, while the staining intensity for GST was similar in ST and FT fibres. During the recovery period, G was restored and GSI gradually declined to resting values. The rate of synthesis was the same in T‐ and U‐legs and in the two fibre types.
Regional Cerebral Blood Flow in the Rat Measured by the Tissue Sampling Technique; a Critical Evaluation Using Four Indicators C14‐Antipyrine, C14‐Ethanol H3‐Water and Xenon133
Authors: Eklöf B. , Lassen N. A. , Nilsson L. , Norberg K. , Siesjö B. K. , Torlöf P.
Published: December 2008

The validity of the assumptions inherent in the tissue sampling technique for measuring cerebral blood flow was tested in the rat, using the 4 indicators C14‐antipyrine, C14‐ethanol, H3‐water and Xenon133. Each one of the indicators was infused i.v. during either 30, 60 or 120 s and the blood flow was calculated from the integrated arterial curve and from the tracer concentration in the tissue. The calculated flows varied with the time of infusion, and at high perfusion rates all tracers gave flow values that were lower than those obtained with the Kety and Schmidt technique. For C14‐antipyrine, the method gives an error already at normal perfusion rates. It is concluded that the cerebral uptake of the tracers is diffusion‐limited, and that the tissue sampling technique cannot be used for quantitative measurement of cerebral blood flow in high flow situations. However, the error of the method is considerably reduced if C14‐ethanol is used and if the time of infusion is limited to 30 s.
Distribution of Renal Cortical Blood Flow during Hemorrhagic Hypotension in Conscious Dogs
Authors: Kirkebö A. , Tyssebotn I.
Published: December 2008

The effect of hemorrhagic hypotension on distribution of renal cortical blood flow was investigated in 9 conscious dogs. 6 platinum electrodes were chronically implanted in inner and outer renal cortex and local cortical blood flow measured by hydrogen clearance. Urine was collected through a catheter implanted in the split bladder and total renal blood flow f RBF) determined by PAH clearance. In anesthetized dogs control blood flow averaged 3.72 ± 0.74 ml/min‐g in outer cortex and 3.60 ± 0.53 ml/rnin g in inner cortex. Local blood flow in conscious dogs fell to 30–60 % of control in the course of 11 days after implantation of the electrodes, though RBF was almost constant and filtering glomeruli were demonstrated in the small fibrotic zone (20–50 μ) close to the electrode tip. No change in local flow was found by induction of Nembutal anesthesia. Bleeding of conscious dogs 1–3 days after implantation, to mean arterial pressure 50 mm Hg, reduced local blood flow to 10–30 % of prebleeding control. The local blood flow in outer and inner cortex decreased near proportionately. Typically, flow at all electrode sites in outer and inner cortex showed a similar fall. A marked redistribution of cortical blood flow during hemorrhagic hypotension was never observed. Bilateral clamping of carotid arteries at normal and at low arterial pressures did not change outer or inner cortical blood flow.
Autoregulation of Capillary Hydrostatic Pressure in Skeletal Muscle during Regional Arterial Hypo‐ and Hypertension
Authors: Järhult Johannes , Mellander Stefan
Published: December 2008

Net transcapillary fluid movements in the sympathectomized cat skeletal muscle were observed in response to regional mean arterial pressure variations in the range from 30 to 170 mm Hg. The transcapillary Starling fluid equilibrium prevailing at normal perfusion pressure was found to be roughly maintained over the entire range of arterial hypo‐ and hypertensions, indicating an approximate constancy of capillary hydrostatic pressure (pc). This “autoregulation of pe” was mainly due to active changes of vascular tone in the precapillary resistance vessels causing a resetting of the pre‐ to postcapillary resistance ratio (ra/rv), but disappeared after abolition of vascular tone by papaverine. In the lowest pressure range, a passive rise of postcapillary resistance contributed to the resetting of ra/rv. By this autoregulation of pc the muscle tissue is protected against undue redistributions of fluid between the intra‐ and extravascular spaces when arterial pressure per se is changed.
Effect of Lowered CSF Sodium Concentration on the Central Control of Fluid Balance
Authors: Eriksson Lea
Published: December 2008

Isotonic and hypertonic non‐electrolyte solutions were slowly infused into the cerebral ventricular system of conscious goats in normal water balance. Infusions of all the isotonic solutions induced water diuresis. When the infusions were made into the anterior part of the lateral ventricle, the response was more delayed than when the solutions were infused into the third ventricle. Also, hypertonic (0.45 M or 0.6 M) solutions of d‐glucose, d‐fructose, glycerol, and sucrose turned renal CH2O positive. Hypertonic urea, instead, gave inconsistent responses. The observed increase in renal CH2O obviously resulted from an inhibition of the normal release of ADH. Firstly, there was no increase in renal C0sm; and secondly, intravenous injection of ADH interrupted this water diuresis. No obvious changes occured in renal electrolyte excretion, blood pressure, and heart rate during infusions. After infusions, when CH2O returned to the preinfusion level, there was sometimes a slight increase in sodium excretion and blood pressure. Infusions of isotonic saccharides in physiologic saline did not induce water diuresis under infusions, but after infusions there was (in 4 out of 6 cases) some increase in urine flow and CH2O could become positive for 10 to 20 min.

These results indicate that, instead of osmolality, the ionic composition of CSF is important for ADH release, and support the concept of a Na+ sensitive receptor system near the third ventricle.
The Effect of Glycerol on the Postexercise Lactate Clearance
Authors: Olsen Christian , Petersen Ebbe Strange
Published: December 2008

The effect of increased glycerol concentrations induced by peroral intake of glycerol on the concentrations of lactate and pyruvate in blood was investigated in 7 young adults at rest and after exercise. 10 mill of work on a bicycle ergometer induced a small but statistically significant rise in the glycerol concentration. The concentration of lactate at rest was significantly higher after than before glycerol intake. The lactate/pyruvate ratio was significantly higher after than before glycerol intake both at rest and after 15 min of recovery and onwards. The metabolic clearance of lactate after exercise was reduced by the glycerol intake to about 70% of the control value. The effect of glycerol on the metabolic clearance of lactate was the same whether estimated at rest or after exercise. These observations are in accordance with the concept, that glycerol metabolism influences the lactate/pyruvate ratio in the liver and thereby reduces the clearance of lactate.
Morphology and Storage Properties of Rat Mast Cell Granules Isolated by Different Methods
Authors: Anderson Per , Röhlich Pál , Slorach Stuart A. , Uvnäs Börje
Published: December 2008

Pure granule fractions were obtained from rat mast cells by sonication in sucrose for different times and at different amplitudes. Two types of mast cell granule were found. One type appeared dark blue in the light microscope when stained with toluidine blue–azur A and was homogeneous, electron dense and surrounded by a trilaminar membrane when observed in the electron microscope; thus this type had the same appearance as mast cell granulesin situ.The second type appeared pink after staining with the above dye and had a swollen, reticular appearance with a reduced electron density and no surrounding membrane when observed in the electron microscope. With increasing sonication time and amplitude there was an increase in the proportion of the swollen, less electron dense granules with no surrounding membrane and a concomitant decrease in the amount of histamine retained (as shown by the histamine/ heparin and histamine/protein ratios) after washing in isotonic sodium chloride. Granules isolated from water‐lysed mast cells or mast cells treated with compound 48/80 were all of the second type with no perigranular membrane: they released their histamine when suspended in isotonic sodium chloride solution.
The Effect of Barbiturate on Retinal Functions. II. Effects on the c‐wave of the Electroretinogram and the Standing Potential of the Sheep Eye
Authors: Knave Bengt , Persson Hans E. , Nilsson Sven Erik G.
Published: December 2008

The present work is the second in a series of investigations on the effect of barbiturate on retinal functions. The changes in the c‐wave of the conventional ERG and in the standing potential (SP) of the intact sheep eye were studied after i.v. administration of an ultra‐short‐acting barbiturate, thiopental. The c‐wave was transiently decreased or abolished after a small dose (< 10 mg/kg), whereas a negative shift could be observed in the SP. Larger doses resulted in negative‐positive cyclic variations of the c‐wave amplitude and the SP resembling damped oscillations. There was an increase of the a‐ and b‐waves after barbiturate administration, not related to the SP‐changes. The effect of barbiturate on the components of the conventional ERG and the SP was also studied after selective blocking of the function of the pigment epithelial cells with sodium iodate. Hereby, the barbiturate induced changes of the c‐wave and the SP disappeared, whereas those of the a‐ and b‐waves remained. On the basis of these results, the possibility that barbiturate has a dual site of action on the retina, namely on the neuroretina and on the pigment epithelial cells, cannot be excluded.
The Effect of Barbiturate on Retinal Functions. III. Effects on the Isolated Receptor Responses and the Inner Nuclear Layer Components in the Low‐intensity Electroretinogram of the Sheep Eye
Authors: Knave Bengt , Persson Hans E.
Published: December 2008

The present study is the third in a series of investigations on the effects of barbiturate on retinal functions. The changes in the isolated receptor responses and inner nuclear layer components of the low‐intensity electroretinogram (ERG) of the intact sheep eye were studied after i.v. administration of an ultra‐short‐acting barbiturate, thiopental. The low‐intensity ERG, i.e. the electroretinographic responses below the b‐wave threshold, have recently been shown to consist of a slow corneanegative receptor potential and two d.c. responses of opposite polarity presumably generated in the inner nuclear layer. The administration of small doses of thiopental (5 mg/kg) had no effect on the receptor response, whereas larger doses (10 mg/kg) increased its amplitude. The most striking effect of thiopental was an enhancement of the positive d.c. response, which could be observed already at barbiturate doses of 5 mg/kg. The results are consistent with the assumption that barbiturates primarily influence the cells of the inner nuclear layer and secondly the receptors. It is suggested that the functional mechanism behind the barbiturate effect on the inner nuclear layer (as expressed in the increase of the positive d.c. component) constitutes an intraretinally mediated disinhibition of the “on‐type”‘ bipolar cells i.e. the presumed generators of the positive d.c. component.
Parallel Activation of Dynamic Fusimotor Neurones and a Climbing Fibre System from the Cat Brain Stem. I. Effects from the Rubral Region
Authors: Jeneskog Torgny
Published: December 2008

Climbing fibre activity in the cerebellar paramedian lobule as well as hind limb dynamic fusimotor activation, caused by electrical stimulation in the rubral region, were studied in halothane anesthetized cats. A dorsal stimulating region, which was somatotopically arranged, could evoke climbing fibre activity in 3 longitudinal projection areas. This stimulating region was situated in the dorsal parts of the red nucleus and at caudal levels also dorsally to this structure. It was suggested that a synapse was interposed in this descending pathway at rostral rubral levels. From a ventral region, situated in the ventral parts of, but also extending ventrally and caudally to the red nucleus, only a hind limb projection area could be activated. The two pathways relay through the inferior olive and share olivary climbing fibres with each other and with ascending spino‐olivocerebellar paths. A marked similarity in the extent of stimulating areas activating hind limb dynamic fusimotor neurones and climbing fibres to one hind limb zone is demonstrated, as well as a close similarity in minimum stimulating thresholds for the two effects. The results are discussed in relation to a current hypothesis on the role of climbing fibre systems in motor control.
Titratable Acid, Pco2, Bicarbonate and Ammonium Ions along the Rat Proximal Tubule
Authors: Karimark Bertil , Danielson Bo G.
Published: December 2008

The proximal tubule of cortical nephrons of male albino rats were studied. The intratubular pH was measured with antimony microelectrodes. The concentrations of bicarbonate ions, the ammonium ions and titratable acid were measured in the same free flow samples from single tubules, using a recently developed ultramicroanalytical system, which also permits the estimation of intratubular Pco2. The concentration of titratable acid, which is thought mainly to emanate from phosphate, was found to be constant, about 1 mM, along the proximal tubule. This is explained as a gradient limited transport process for phosphate as well as for hydrogen ions. The concentration of ammonium ions was found to be about 2 mM along the convoluted proximal tubule in spite of water reabsorption, indicating some reabsorptive mechanisms for ammonium or the base, ammonia. Furthermore the present investigation indicates a high Pco2 in the untreated proximal tubule which could explain the phenomenon of disequilibrium pH.
Long‐term Treatment with Antihypertensive Drugs in Spontaneously Hypertensive Rats (SHR). Effects on Blood Pressure, Survival Rate and Cardiovascular Design
Authors: Weiss Lilian
Published: December 2008

Three age groups of SHR were treated orally with hydralazine and guanethidine. The first “prehypertensive” group was treated from 2.5 until 8 months of age, and thereafter pressure was followed for another 6 months. A delayed and quite modest pressure increase then occurred and average life span was prolonged compared with untreated SHR or SHR treated only from 12 months of age. ‐ The second, 8 months old group, representing “established” hypertension, was treated for 5, 10 or 20 weeks, the last subgroup being followed for another 2 weeks without treatment. Arterial pressure, left ventricular weight and design of the resistance vessels as explored by quantitative hemodynamic analyses, were studied at these intervals. After 5 weeks pressure was normalized with some regression of hypertrophic vascular changes, particularly in females, though the increased wall/lumen ratio appeared to remain and heart weight was only slightly reduced. After 20 weeks with and 2 weeks without treatment, cardiac and vascular design were still the same as during treatment but pressure had now risen considerably. ‐ The third, 14 months old group with “advanced” hypertension was treated for 13 weeks, causing only modest pressure reduction and vascular regression. ‐ This suggests that early treatment has great advantages, that females exhibit more regression of vascular structural changes than males and that late treatment gives less regression, presumably due to addition of less reversible wall components like collagen.
Effects of Barbiturates on Synthesis and Rapid Axonal Transport of Protein in vitro in the Sciatic System of the Frog
Authors: Edstrom Anders , Larsson Håkan
Published: December 2008

The effects of hexobarbital, pentobarbital, methohexital and thiopental (0.5 mil and 2 mM) on the synthesis and fast axonal transport of 3H‐leucine‐labeIled proteins were studied in vitro in the sciatic system of the frog. The methodology used made it possible to discriminate between effects on synthesis and transport. All 4 drugs arrested the transport, pentobarbital being the most, and thiopental the least, potent one. The transport inhibiting effect of 0.5 mil pentobarbital was reversible but not that of the higher concentration. These drugs, at concentrations (2 mM) which inhibited axonal transport, did not influence the uptake of 3H‐leucine into ganglionic cell bodies, whereas pentobarbital, methohexital and thiopental, but not hexobarbital, depressed subsequent steps of protein synthesis. Pentobarbital lacked effect on protein synthesis at a concentration (0.5 mM), which arrested axonal transport by 50%. The results indicate that rapid axonal transport shows higher sensitivity than protein synthesis to the barbiturates tested. Fairly high concentrations of barbiturates were required to inhibit axonal transport and still higher to depress protein synthesis in the present study. Normal anesthesia by barbiturates is therefore hardly likely to affect these mechanisms.
Electrical Activity and Isometric Tension in Motor Units of the Cat's Inferior Oblique Muscle
Authors: L.Ennerstrand Gunnar
Published: December 2008

Single motor units of the cat's inferior oblique muscle were isolated by partial denervation of the muscle and threshold stimulation of split motor nerve filaments. With electrical tests singly innervated (SI) units, multiply innervated conducting (MIC) units and multiply innervated non‐conducting (MIXC) units could be differentiated. SI units conducted impulse activity faster (2.93 m/s) than MIC units (1.72 m/s). Singly innervated units contracted faster than multiply innervated units. Fusion frequency was found the most useful parameter for a mechanical separation; most SI units fused above 200 pps, most MIC units between 100 and 200 pps and the MIXC units below 100 pps. Tetanic tension was higher in fast (SI) than in slow (MIC and MIXC) units, but there was a considerable overlap. The range for the whole material was 25–425 mg. In fast units fusion fequency and the rate of stimulation for maximal tetanic tension coincided. In slow units maximal tetanic tension was reached at stimulus rates of 150–200 pps irrespective of the fusion frequency of the unit. Resistance to fatigue was high in the slow units and in the majority of the fast units.

The contractile properties fit into the motor unit activity pattern determined through motoneuron recordings in alert animals.
Maximal Work Performance at Raised Air and Helium‐Oxygen Pressures
Authors: Fagraeus By Lennart
Published: December 2008

To study the influence of increased air pressure and gas density on maximal work performance, cardiorespiratory measurements were made on 8 subjects who performed maximal exercise until exhaustion on a cycle ergometer while breathing air at ambient pressures of 1.0 (control), 3.0, and 6.0 ATA, and a mixture of 79 % helium and 21 % oxygen (He‐O2) at 3.0 ATA (same density as air at 1.0 ATA). Exposure to air at 3.0 and 6.0 ATA caused no consistent changes in maximal oxygen uptake (Vo2max), peak blood lactate (LA), or endurance time, whereas pulmonary ventilation (VE) and carbon dioxide elimination (Vco2) decreased significantly with a consequent rise of end‐tidal PCo2 from 35 mm Hg at 1.0 ATA, to 56 mm Hg at 6.0 ATA. Maximal heart rate (HRmax) decreased from a mean control value of 192 beats‐min‐1to 183 beats‐min‐1at 6.0 ATA. With exposure to He‐O2 at 3.0 ATA, as compared to control, Vo2max and endurance time increased by 13 % and 14 %, respectively, whereas VE and HRmax decreased, Vco2 and LA remained unchanged, and end‐tidal Pco2 rose to 39 mm Hg. It is concluded that the beneficial effect that hyperoxia exerts on Vo2max and endurance time at normal gas density is offset when the gas density is high enough to cause ventilatory impairment with concomitant CO2 retention. The results also suggest that maximal work performance was more closely related to the LA concentration than to the Pco2 or pH levels existing in the working muscles at the point of exhaustion.
Metabolic State and Blood Flow in Rat Cerebral Cortex, Cerebellum and Brainstem in Hypoxic Hypoxia
Authors: Magmillan V. , Salford L. G. , Siesjö B. K.
Published: December 2008

In order to study the effect of hypoxic hypoxia upon regional cerebral metabolism and blood flow the arterial Poa of lightly anaesthetized rats was lowered to about 35, 29 and 23 mm Hg, respectively, with subsequent measurements of labile metabolites and of blood flow in cerebral cortex, cerebellum and brain stem. The metabolites, which included organic phosphates, carbohydrate substrates and amino acids, were measured with enzymatic, fluorometric techniques after freezing the tissue in situ and the regional blood flow was estimated from the tissue uptake of 14C‐ethanol. In all 3 regions marked hypoxia (Poa 23) gave rise to small increases in the ADP concentration, but since neither ATP nor AMP was changed from the normal it is concluded that the energy state remained essentially unaltered. The increase in lactate concentration was similar in all three regions and the substrate patterns were essentially the same. Since the regional blood flow also increased to a similar extent in the three regions it is concluded that brain regions show similar metabolic and circulatory changes in hypoxic hypoxia. The results thus give no support to the view that different brain areas show selective vulnerability to hypoxia, at least not in forms of hypoxia that are uncomplicated by absolute or relative ischemia.
Intrarenal Filtrate Distribution, during Saline Infusion in Rats with Unilateral Ureteral Ligation
Authors: Clausen G.
Published: December 2008

Six days after unilateral ureteral ligation (UL) the contralateral kidney had increased GFR by 66 % in conscious rats. The average relative single nephron filtration rate (gfr) of superficial nephrons, as measured by the 14C ferrocyanide single injection technique, was 75 % of deep nephron gfr in UL rats compared to 90 % in intact rats. Thus hyperfiltration was more pronounced in deep nephrons. Isotonic saline infused i.v. (15 % BW in 60 min) in a second group of UL rats increased GFR by average 36 % compared to preinfusion GFR. Higher single nephron GFR and lower fractional sodium reabsorption enabled the UL rats to excrete sodium and water at practically the same absolute rates as compared to intact rats previously studied during identical saline infusion experiments. Saline infusion increased superficial gfr in UL rats from 75 % to 96 % of deep gfr. Provided superficial nephrons constitute 70 % of total nephron number these results imply that filtration rate rose by 48 % in superficial and by 16 % in deep nephrons. It is suggested that maximally one third of total sodium excretion in the saline infused UL rats might be due to superficial nephrons not being able to reabsorb their disproportionately increased filtered load.
Role of Tissue Hyperosmolality in Functional Vasodilatation in the Submandibular Gland
Authors: Lundvall By J. , Holmberg J.
Published: December 2008

Parasympathetic activation of the submandibular gland in the cat was found to cause considerable regional tissue hyperosmolality concomitant with the functional hyperemia response. The hyperosmolality, as traced in the venous effluent, was present at all rates of chorda nerve stimulation (0.25‐20 Hz). Osmolality was clearly raised already during the initial phase of the dilator response and reached plateau values during the later, steady state hyperemia response. In the latter phase it could exceed the resting control level by as much as 50 mOsm/kg H2O. There was a direct relation between the degree of venous hyperosmolality and the dilator response during low and moderate rates of chorda stimulation. Experimental hyperosmolality in die resting gland, produced by intra‐arterial infusion of hypertonic solutions, evoked a pattern of dilator response resembling that observed during chorda stimulation. Graded experimental hyperosmolality of magnitudes similar to those seen during chorda stimulation evoked progressively increasing dilatations of the resistance vessels. Comparison of the dilator effects during chorda stimulation and during hypertonic infusion at comparable levels of venous hyperosmolality indicated that tissue hyperosmolality contributed significantly to both the initial and maintained functional hyperemia response in the gland. The factor seemed to be of special importance at low and moderate rates of chorda excitation. This conclusion was supported by a separate series of experiments in which the effects of atropine on the functional hyperemia response and on the hyperosmolality were studied.
In Vitro Release of Corticosteroids from Adrenal Glands of Obese‐Hyperglycemic Mice (Gene Symbol ob)
Authors: Naeser By Peter
Published: December 2008

The adrenal function of obese‐hyperglycemic mice of various ages was investigated by measurements of the corticosteroid release from hemisectioned adrenal glands incubated in vitro. Glands from lean litter mates were used as controls. The corticosteroid release was strongly stimulated by ACTH and this stimulated release remained constant throughout the experiments. The ACTH effect was blocked when nitrogen was substituted for oxygen in the gas phase. In all investigated age groups the adrenals of obese mice displayed a higher release of corticosteroids than those of the lean controls when incubated without addition of ACTH. In the presence of ACTH the adrenal halves of obese mice showed a similar release of corticosteroids to those of the lean mice, except for the 2‐month‐old group, in which there was a smaller release from the adrenals of the obese animals. Insulin had no stimulating effect on the corticosteroid release and was even slightly inhibitory in the absence of ACTH in the medium. It is suggested that the increased size and steroid production of the adrenal glands of the obese‐hyperglycemic mice may reflect a continuous functional stimulation such as could be exerted by ACTH.
Bile Acids as Inhibitors of the Liver‐like Anion Transport System in the Rabbit Kidney, Uvea and Choroid Plexus
Authors: Bárány By Ernst H.
Published: December 2008

Slices of rabbit kidney cortex, pieces of lateral choroid plexus and of ciliary body with iris were incubated in a potassium‐rich medium containing iodipamide and o‐iodohippurate labelled with different isotopes as test substances for the L‐and the H‐system respectively. Cholic, deoxycholic, chenodeoxycholic, lithocholic and dehydrocholic acids and their glycine and taurine conjugates were added as inhibitors and their ability to suppress iodipamide uptake preferentially compared. The most selective inhibitor was free chenodeoxycholic acid, followed by deoxycholic. Considerable inhibition was caused at 100, μM by the dihydroxy acids. At this concentration uptake of quaternary cations as “toxicity indicators” was hardly affected. Non‐ionic detergents were unselective inhibitors. Thus, bile acids have affinity for the liverlike anion transport system in the kidney, eye and choroid plexus.
Composite Transport Systems for Iodipamide and Iodohippurate out of the Cerebrospinal Fluid in the Rat
Authors: Lundberg By Viveka
Published: December 2008

The mechanism for the removal of iodohippurate and iodipamide from the CSF in rats was studied by ventriculo‐cisternal perfusion and by uptake experiments with choroid plexusin vitro. In agreement with finclings in other species excised plexus from the lateral ventricles accumulates131I‐o‐iodohippurate and125I‐iodipamide, and the process is at least partly saturable. Ventriculo‐cisternal perfusions were performed on pentobarbital anesthetized rats with a fluid containing131I‐o‐iodohippurate,125I‐iodipamide and14C‐inulin. A considerable loss of iodohippurate and iodipamide, but not of inulin, from the CSF was observed during the perfusion. When sodium hippurate and/or non‐labelled iodipamide were added in excess to the infusion fluid the loss of labelled iodohippurate and iodipamide was reduced. In concentrations which reduced iodohippurate loss equally, hippurate and iodipamide had different effects on iodipamide loss: hippurate had less effect. This indicates that iodohippurate and iodipamide are removed from the CSF partly by saturable and presumably active transport, and that iodipamide is transported both by the same system as iodohippurate and also by a separate hippurate‐insensitive one. Choroid plexus can be one locus of this transport.
Effects of Ethanol on Urine Sodium and Potassium Concentrations and Osmolality in Water‐Loaded Rats
Authors: Linkola By Jaakko
Published: December 2008

The effects of ethanol on urine sodium, potassium and osmolality were investigated in rats kept in a positive water balance produced by prior consecutive water loaclings. Ethanol loacling was followed by rapid rises in urine output, sodium concentration and osmolality and a somewhat slower rise in potassium concentration. Presumably water loacling led to an increased glomerular filtration rate, which, with the inhibition of ion reabsorption caused by ethanol, was responsible for this rise.
Motor and Secretory Effects of Autonomic Nerves and Drugs in the Rat Submaxillary Gland
Authors: Thulin By Anders
Published: December 2008

The effect of autonomic nerves and drugs on duct pressure and salivary flow was investigated in rat submaxillary gland. The results showed that it is possible to separate motor responses, probably exerted by activation of myoepithelial cells, from secretion. It is concluded that both divisions of the autonomic nervous system evoke motor responses and that the sympathetic motor effect is mediated via α‐receptors.
Effects of Sympathetic Stimulation on Facial Muscle Contractions
Authors: Lindquist Christer
Published: December 2008

Low‐frequency stimulation (1–10 Hz) of the cervical sympathetic nerve is shown to increase twitch tension in the non‐fatigued orbicularis oculi and oris muscles by up to 15 % and to increase contraction and half‐relaxation times. The effect sets in 15–45 s following start of sympathetic stimulation, reaches a peak in 50–100 s and outlasts the stimulation by up to 90 s. The potentiating effect is not accompanied by any signs of changes in neuromuscular transmission or conduction. It is blocked by the /ff‐blocker propranolol. The mechanism of sympathetic action is discussed as well as its possible physiological significance.

The possible presence of non‐twitch fibers of the slow tonic type in facial muscles is tested by i.v. injections of suxamethonium and decamethonium. Even relatively small doses not affecting neuromuscular transmission may produce long‐lasting contractions in the orbicularis oculi and oris. It is concluded that these contractions suggest specific properties of the twitch fibers rather than pointing to the presence of slow tonic muscle fibers.
Synthesis of Serum Albumin in Isolated Rat Liver Perfused by a Synthetic Medium with Fluorocarbon FG–80 Emulsion as Oxygen Carrier
Authors: Nováková Vera , Birke G. , Plantin L.‐O.
Published: December 2008

A fluorocarbon emulsion FC‐80 has been used as a substitute for erythrocytes in a synthetic nutrition medium in in vitro perfusions of isolated rat livers. The rate of albumin synthesis was estimated. After the first hour albumin was synthesised at a constant rate of 0.52 + 0.17 mg/h per 100 g of the body weight of the liver donor. 14C‐lysine was incorporated into the circulating proteins linearly after the first hour. Other parameters tested were: levels of circulating proteins, urea nitrogen, glucose, glutamic‐pyruvic transaminase, excretion of bile, weight changes of the liver, and level of glycogen in liver tissue after perfusion. Histological examinations were also performed. The function of the liver was comparable with the findings of other investigators who used whole blood as the perfusate. As far as we are aware this is the first time that a rat liver has been maintained in good functional condition for over 6 hours during in vitro perfusions with a synthetic medium that included an erythrocyte substitute. The method seems to offer great advantages for the study of metabolic processes.
Single Unit Sympathetic Activity in Human Skin Nerves during Rest and Various Manoeuvres
Authors: Hallin Rolf G. , Torebjork H. Erik
Published: December 2008

Single unit activity in sympathetic nerve fibres was studied in microelectrode recordings from intact cutaneous nerves in alert man. 4 units exhibited a “spontaneous” discharge of very low frequency (not exceeding 15 imp/min) during resting conditions, whereas 4 other units were silent. Mental concentration and arousal stimuli of different types caused an increase in impulse frequency of spontaneously active units, and previously silent units started firing. In reflex responses to electrical shocks, deep breathing and loud noises, single units often fired repeatedly in bursts, the maximal instantaneous frequency observed being 35 imp/s. Intense reflex responses to electrical stimulation were sometimes followed by a suppression of spontaneous activity for 1–2 s. Some of the units probably had a sudomotor function, since the unit activity correlated well with changes in galvanic skin resistance recorded within the innervation zone of the explored nerve fascicle. The conduction velocity measured for 6 sympathetic units ranged 1.0–0.58 m/s.
Methods to Differentiate Electrically Induced Afferent and Sympathetic C Unit Responses in Human Cutaneous Nerves
Authors: Hallin Rolf G. , Torebjörk H. Erik
Published: December 2008

C unit responses to intradermal electrical stimulation were recorded with tungsten micro‐electrodes inserted percutaneously into intact human cutaneous nerves. An increase in discharge frequency was associated with a decrease in conduction velocity in unmyelinated fibres, and this phenomenon was used to identify afferent C units which responded to both electrical and natural stimuli in the skin. Antidromic impulses in efferent, sympathetic fibres were also elicited by electrical stimulation in the skin as judged by latency changes or signs of collisions in the C responses associated with activity in sympathetic fibres. In this way, conduction velocities in distal segments of both afferent and sympathetic C fibres can be estimated. Furthermore, the possibility to differentiate afferent and sympathetic C units is of obvious importance for the study of their respective discharge characteristics and in psychophysiological studies in alert man.
Effect of 2, 3‐Diphosphoglycerate on the Oxygen Affinity and on the Proton‐ and Carbamino‐Linked Oxygen Affinity of Hemoglobin in Human Whole Blood
Authors: Arturson G. , Garby L. , Wranne B. , Zaar B.
Published: December 2008

Oxygen binding curves were determined, at two plasma pH values in the range 7.0–7.5, each at two pCOa values of 22 and 77 mm Hg, respectively, on human whole blood where the red cell 2,3‐diphosphoglycerate (DPG) concentration had been decreased to about 1 mmol/1 of packed cells and increased to about 9 mmol/1 of packed cells. Numerical values are given for the oxygen‐saturation‐dependant ligand interaction coefficients AlogpOzl ApH, AiogpOzl/llog/>C02 and /llog/)02//llogDPG and their dependance on pH, PCO2 and DPG, respectively.
Microvascular Flow Velocity in Cat Omental Adipose Tissue as Affected by Sympathetic Nerve Stimulation
Authors: Rosell Sune , Intaglietta Marcos , Tuma Ronald F. , Arfors Karl‐E.
Published: December 2008

The effect of sympathetic nerve stimulation on the microvascular red blood cell flow velocity was measured in cat omental adipose tissue. Electrical impulses of 10 V, 0.5–6 Hz were utilized to stimulate the appropriate branch of the splenic nerve. Microvascular velocities were measured in the transilluminated omental bursa in arterioles, capillaries and venules, on‐line, by means of a dual window television system. The responses noted were: 1) decrease in flow (75% of vessels); 2) no response (7%); and 3) increase (18%). The magnitude of the responses were in proportion to the stimulatory frequency. The disparity of responses may be related to previous morphologic observations on the non‐uniformity of innervation of canine subcutaneous adipose tissue. It is proposed that the various vascular reactions reflect the presence of compartments, in the same tissue, endowed with different sympathetic controls. Indexable words. Sympathetic activity, adipose tissue, capillary flow, lipolysis, television microscopy.
Potentiation and Inhibition of Noradrenaline Induced Contractions of the Rat Portal Vein in Anion Substituted Solutions
Authors: Wahlström Bo A. , Svennerholm Bo
Published: December 2008

The effect of anion substitution on spontaneous mechanical activity and noradrenaline induced excitation of the rat portal vein was studied. When chloride was substituted by nitrate and bromide the spontaneous activity was increased, while pyruvate, isethionate and benzenesulphonate decreased it. When noradrenaline was given initially the response was potentiated in all solutions. The order of potency was benzenesulphonate > isethionate > pyruvate ≥ Br−≥ NO−3. When dose‐response curves for noradrenaline were made in normal solution and in anion‐substituted solutions it was found that NO−3 and Br− increased the sensitivity of the muscle cells to noradrenaline, while in isethionate and benzenesulphonate solutins the responsivenss was reduced. Stepwise substitution of CI− by NO−3 or Br− showed that the effect of noradrenaline was inversely related to [C1−]0. When the membrane was depolarized by solutions with excess [K.+]0 the response to noradrenaline gradually fell, although about 15 % was still present in high K+solution. It is concluded from the experiments that the distribution and permeability of anions greatly influence the excitatory effect of noradrenaline on the rat portal vein.