bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dehydration‐Induced Reductions in Total Blood Volume and in Pulmonary Blood Volume in Rats
Authors: Aarseth P. , Klug D. 
Published: December 2008

AbstractGroups of rats were exposed to water deprivation and/or food deprivation for 24 h periods. The degree of dehydration obtained was evaluated by weight examinations of the differently treated rats. The plasma and erythrocyte volumes were estimated by the use of i.v. injected isotopes. It was found that on water deprivation the intravascular fluid compartment was reduced relatively more than the total body water content. The blood content in the lungs was estimated from the organ content of isotopes after the rats had been rapidly frozen in liquid nitrogen. When dehydration had caused an 8 % reduction in the total blood volume, the pulmonary blood volume was found to be reduced by 30 %. The pulmonary vascular compartment thus appears to function as an important blood depot in this connection.
Effects of Alterations in Calcium Concentrations on Secretion and Protein Synthesis in Cat Submandibular Salivary Gland
Authors: Gautvik K. M. , Kriz M. , Lund‐Larsen Kari 
Published: December 2008

AbstractThe effects of low Ca++concentrations on secretory responses induced by injections of nor‐adrenaline to the perfused cat submandibular salivary gland have been investigated. Particular attention has been paid to the release of kininogenase (a kinin‐forming enzyme). Kininogenase activity was measured in saliva, in effluent perfusate and in gland homogenate. When perfusion media containing no added Ca++was used, a reduced amount of saliva with a normal concentration of kininogenase was secreted. Additional reduction to near zero of [Ca++] in perfusion fluid by the use of EGTA blocked saliva secretion. However, a fall in remaining kininogenase activity was still observed in homogenates from activated glands, although less marked than in the activated control glands. Low perfusate [Ca++] also reduced the incorporation of14C‐L‐Leucine into proteins of non‐activated glands by an average of 52 per cent. It is concluded that the secretion of water and ions is blocked and that the release, and probably also the synthesis, of glandular kininogenase is reduced under conditions of low concentrations of Ca++in the perfusate.
Effect of Training on Esterified Fatty Acids and Carnitine in Muscle and on Lipolysis in Adipose Tissue in Vitro
Authors: Fröberg Sven O. , ÖStman Ingegerd , Sjöstrand Nils O. 
Published: December 2008

AbstractThe concentration of triglycerides, phospholipids and carnitine was determined in red and white parts of the gastrocnemius muscle from rats with and without a period of training by running. Also the rate of lipolysis in adipose tissue was determined with and without stimulation in vitro. The concentration of triglycerides was reduced in the red and white muscle tissue but positively correlated to each other in white muscle tissue. This suggests that the white muscle tissue. Correlation analysis revealed no direct relationship between the spontaneous or stimulated rate of lipolysis in vitro and the triglyceride concentration in either type of muscle tissue. This suggests that the level of muscle triglycerides was influenced or deter‐mined by other factors than the rate of mobilization of fatty acids from the adipose tissue per se. The concentrations of carnitine and triglycerides were negatively correlated in red muscle tissue but positively correlated to each other in white muscle tissue. This suggests that the metabolic role of carnitine with regard to triglyceride metabolism differed between the two muscle types. The possibility was discussed that the capacity of the intracellular carnitine transport system for fatty acids into mitochondria of red muscle tissue increased in the course of physical training as part of an adaptation towards enhanced oxidative metabolism.
Regulation of Middle Ear Sound Transmission in the Nonanesthetized Rabbit
Authors: Borg Erik 
Published: December 2008

AbstractThe regulation of sound transmission through the middle ear of nonanesthetized rabbits was quantitatively investigated by comparing the excitation of the cochlea before and after surgical inactivation of m. stapedius and/or m. tensor tympani in the stimulated ear. The crossed middle ear reflex was used as a measure of the excitation of the cochlea to stimulation with pure tones in the range from 0.5 to 8.0 kHz at intensities up to 125 dB SPL. Sounds through this frequency range were attenuated above a level of 90 to 100 dB SPL. Low frequency tones (0.5 kHz) were attenuated by all levels of activity in the m. stapedius and m. tensor tympani. High frequencies were attenuated only by m. stapedius activity at high intensity levels above reflex threshold (20–30 dB). The m. tensor tympani had no influence on high frequencies, above 2.0 kHz. Improved sound transmission due to reflex activity was not regularly found. The efficiency of the regulation was regarded as high: a 1.0 dB increase in sound level in the ear canal gave only a 0.3 dB increase in the excitation of the cochlea (i.e. the regulating efficiency of the closed‐loop system was 0.7 dB attenuation per 1.0 dB increase in stimulus sound intensity). The regulating efficiency of the open‐loop system was about 2 dB/dB. The open‐loop gain was estimated to 4 during steady‐state. The oscillations in the middle ear reflex response were found to be generated in the m. stapedius feed‐back loop regulating the sound transmission through the middle ear. It was concluded that the function of the acoustic middle ear reflexes can be described as extending the dynamic range of the cochlea and adaptation and it may also be compared with the effect of lateral inhibition.
Production and Removal of Lactate during Exercise in Man
Authors: Hermansen Lars , Stensvold Inger 
Published: December 2008

AbstractBlood lactate concentration (LA) was measured in 4 female and 3 male well‐trained subjects before and during 30 min of continuous treadmill running at 4 different speeds, demanding about 30, 60, 70 and 80% of the individuals' maximal oxygen uptake (Vo2 max). The same subjects also performed in another series of experiments where maximal intermittent exercise preceded 30 min of running at the same 4 speeds, or resting in a chair. During continuous running, starting from resting conditions, the blood LA increased only slightly up to a critical Ievel (i.e. 60—80%) of Vo2‐max. From then on, a pronounced lactate production may occur. During the maximal intermittent exercise, blood LA increased to 130—220 mg/100 ml. In the recovery period, i.e. continuous running at the same 4 speeds, or resting in a chair, blood LA decreased towards resting values. The lactate removal rate was calculated from the rectilinear part of the curves describing the changes in LA with time, and expressed as mg/100 ml X min. The lactate removal rate was higher during exercise than during rest, and increased with increasing work load up to the same critical level (i.e. 60—80% of Vo2 max), beyond which a reduction was observed. The highest removal rate was 8 mg lactate/100 ml x min at 63% of Vo2 max (average values). These results indicate that human skeletal muscle possesses a pronounced capacity to oxidize lactate. Therefore, a production of lactate is possible even with no increase in the blood LA. These results also indicate that the skeletal muscle, rather than the liver, may be regarded as the main site for lactate removal during exercise.
Low Flow States in the Microvessels of Skeletal Muscle in Cat
Authors: Eriksson Elof , Lisander Björn 
Published: December 2008

AbstractWith the tenuissimus muscle exposed for vital microscopy, the effects on macro‐ and micro‐circulation of aortic compression and of arterial bleeding were studied in cats anesthetized with chloralose. In the first case, arterial pressure in the hindlimbs was kept at 50 mm Hg for 2 ½ h and in the latter, the animal was rapidly bled with 40% of its total volume, and then observed for up to 4 h. — During aortic compression arterioles of 25 μm internal diameter increased their dimensions with about 40% and arteries of 70 μm with about 15%. The diameters of the venules showed a slight decrease. Linear flow rates in the capillaries decreased but there was an even distribution of the blood flow. No formation of thrombi was seen. — At arterial bleeding all the vessels first reduced their diameters during 10—20 min. Then arterioles of 25 μm diameter dilated, while the diameters of the other vessels remained reduced. In average the cats survived for 2 ½ h. Within a few minutes after the bleeding there was an adhesion of white cells to the venular walls and in later stages aggregates of red cells, platelets and white cells started to occlude most venules and capillaries leading to extensive “functional shunting” at the capillary level.
Coding of Amplitude and Frequency Modulated Sounds in the Cochlear Nucleus of the Rat
Authors: Møller Aage R. 
Published: December 2008

AbstractThe responses of single units in the cochlear nucleus of the rat to sinusoidally amplitude‐ and frequency‐modulated tones and amplitude‐modulated broadband noise were studied. The distribution of discharges within a cycle of modulation was determined from cycle histograms locked to the modulation wave. In response to amplitude‐modulated tones and broadband noise, all units investigated showed a peak in the degree of modulation of the spike frequency within the modulation frequency range from 50 to 200 Hz. In many units the relationship between the degree of modulation of the stimulus sound and of the modulation of the resulting spike train was almost unchanged over a wide range of sound intensities. In other units, enhancement of modulation within a certain range of modulation frequency became more pronounced when the sound intensity was increased. This was mainly due to a suppression of modulation at lower modulation frequencies. The shape of the histograms was nearly sinusoidal even at modulation depths which resulted in nearly 100% modulation of the neural discharge frequency. The amount of modulation of the discharge frequency in response to frequency‐modulated tones was dependent on the frequency of the tone in relation to the CF of the unit.
Lipid Biosynthesis from DL (2‐14C) Mevalonic Acid in Intact Mice and Rabbits
Authors: Edgren Bo , Hellström Kjell 
Published: December 2008

AbstractDL‐mevalonate‐2‐14C was administered parenterally to 2 rabbits and 5 groups of mice. In the rabbits the amount of labelled material recovered in the non‐saponifiable lipids of the kidneys exceeded that of the liver. Most of the renal radioactivity was found in the squalene, lanosterol and methostenol fractions whereas the major part of the labelled material in the liver was present as radioactive cholesterol. The distribution of radioactivity within the kidney and the liver in the mice varied with the size of the administered dose. The smaller the dose, the larger the proportion of label recovered in the kidneys. In all experiments most of the radioactivity of the liver was transformed to cholesterol. The conversion of squalene to cholesterol proceeded more slowly in the kidneys and 30 min after the administration of the mevalonate substantial amounts of radioactivity was recovered as labelled squalene and lanosterol. The importance of circulating mevalonate as substrate in the cholesterol synthesis of the kidney will be discussed.
Functional Dependence of the Ciliary Epithelium ATPase Activity and Intraocular Pressure on the Autonomic Nervous System
Authors: Härkönen Matti , Palkama Arto , Uusitalo Risto 
Published: December 2008

AbstractRegulation of intraocular pressure by autonomic nerves of the eye was studied using three types of denervation: sympathectomy, ciliarectomy or coagulation of the parasympathetic nerves (around the optic nerve). Intraocular pressure, inflow and outflow were registered manometrically using a constant pressure infusion technique. ATPase activities in the ciliary processes were demonstrated histochemically and assayed fluorometrically. Special attention was paid to the biochemical characteristics of the ciliary body NaK‐ATPase activity. A kinetic fluorometric method for NaK‐ATPase was developed. Intraocular pressure decreased after ciliarectomy simultaneously with a decrease in inflow of the aqueous humour. Ciliary body‐iris NaK‐ATPase activity also decreased. The changes in the ocular fluid dynamics after coagulation of the parasympathetic nerves tended to be the same. Intraocular pressure decreased as well as NaK‐ATPase activity. Sympathectomy, however, did not change ocular fluid dynamics or NaK‐ATPase activity. The ciliary body‐iris NaK‐ATPase activity seemed to have the characteristics of the transport enzyme found in other organs. It was activated by Na+, K+ Mg++ could be inhibited by ouabain. Activity was optimum when the Mg++/ATP ratio was about 1 and the optimal pH both for Mg‐ and NaK‐ ATPase was 8.1. The results give further support to the theory that intraocular pressure is under nervous control. This regulation is mediated by decreased inflow, which in turn is reflected by a lowered NaK‐ATPase activity in the ciliary processes.
Response to Submaximal and Maximal Exercise at Different Levels of Carboxyhemoglobin
Authors: Ekblom Björn , Huot Roger 
Published: December 2008

AbstractFive subjects performed submaximal and maximal bicycle and maximal treadmill exercise in normalcy and after carbon monoxide inhalation, giving different levels of carboxyhemoglobin (COHb) in the blood. During maximal treadmill exercise work time on a fixed work load and maximal oxygen uptake were decreased with increasing level of COHb (r = 0.79 and r = 0.85, respectively). Peak blood lactate concentration and pulmonary ventilation were unchanged. Highest measured heart rate was lower in parallell with the increased COHb level compared to control studies. During submaximal work heart rate was increased and oxygen uptake was unchanged at the various levels of COHb. At low submaximal work loads blood lactate concentrations and oxygen deficit was unchanged but increased as work load and COHb‐level increased.
Augmented Noradrenaline Release Following Nerve Stimulation after Inhibition of Prostaglandin Synthesis with Indomethacin
Authors: Pham‐Huu‐Chanh  , Junstad Marianne , Wennmalm ÅKe 
Published: December 2008

AbstractThe effect of inhibition of prostaglandin synthesis on the release of noradrenaline induced by sympathetic nerve stimulation was studied in the isolated perfused rabbit heart. It was found that indomethacin (Indomeé®, Merck, Sharp and Dohme), a drug known to inhibit prostaglandin synthesis, decreased the outflow of prostaglandins normally induced by nerve stimulation. Simultaneously the outflow of noradrenaline in response to nerve stimulation was augmented. Since indomethacin neither caused any release of noradrenaline heart in the absence of nerve stimulation, nor affected the uptake of exogenous noradrenaline, it is concluded, that the increased noradrenaline release reflects disinhibition of a feed‐back mechanism, using endogenously formed prostaglandins for limitation of noradrenaline release.
The Effect of Hypercapnic Acidosis upon the Energy Metabolism of the Brain in Arterial Hypotension Caused by Bleeding
Authors: Eklöf Bo , MacMillan Vernon , Siesjö Bo K. 
Published: December 2008

AbstractThe effect of hypercapnia upon the sensitivity of the cerebral energy metabolism to low perfusion pressures was studied by decreasing the mean arterial blood pressure to 60 and 45 mm Hg, respectively, in rats maintained at arterial CO2 tension of 60–65 mm Hg. The hypercapnia gave rise to a moderate extra‐and intracellular acidosis. The cerebral venous Pco2 rose and remained above 50 mm Hg even in the hypotensive groups. In spite of this venous hyperoxia a reduction of the mean arterial blood pressure to 60 mm Hg gave rise to slight but consistant changes in the tissue concentrations of adenine nucleotides. At a pressure of 45 mm Hg there was a major derangement of the energy state of the tissue in 4 out of 6 animals. It is concluded that hypercapnic acidosis adversely affects the cerebral energy metabolism in hypotensive states, probably by inducing a flow pattern which leads to regional ischemia.
Nonlinear Dynamic Properties of a Somatomotor Reflex System. A Model Study
Authors: Borg Erik 
Published: December 2008

AbstractThe time course of polysynaptic reflex responses is known to exhibit two prominent non‐linearities, one dependent on the amplitude of the stimulus and the other dependent on the direction of change of the stimulus. Both nonlinearities were demonstrated in the open‐loop responses of the acoustic middle ear reflex and simulated in a piecewise linear model. Their significance for stability of the closed‐loop feed‐back system was investigated. In this model the source of nonlinearity was a pool of “reflex units” with various thresholds and time constants. The mode! responses were studied in the time domain and the frequency domain. The amplitude dependent nonlinearity could be simulated when low threshold reflex units were made slow and tonic and high threshold units fast and tonic or when some of the high threshold units were phasic. A decrease in transport delay at increased input step amplitude was seen under these conditions but also when all units mere made equal. Both types of nonlinearities were found to improve the stability of the model system without decreasing its bandwidth (a measure of the speed of action). The nonlinearities were suggested to be important in systems with high values of transport delay.
Reflex Bradycardia Elicited from Left Ventricular Receptors during Acute Severe Hypoxia in Gats
Authors: Thorén Peter 
Published: December 2008

AbstractIn chloralose anesthetized cats blood pressure, heart rate and left ventricular pressure were measured as well as changes in ventricular volume by means of a cardiometer. Hypoxia was induced by ventilating the animal with a gas mixture containing 3 % O2. 1–2 min after the onset of hypoxia cardiac volume started to increase and simultaneously a bradycardia developed. The bradycardia was eliminated by vagal cooling indicating that it was elicited by nervous mechanisms rather than by local myocardial factors. After injection of procaine (0,3–0,5 %) into the cardiometer the afferent vagal fibres from the ventricles could be blocked, leaving the efferent fibres to the sinus node intact. Such selective denervation of the ventricular receptors markedly reduced the bradycardia during hypoxia, suggesting that it is mainly a reflex response emanating from ventricular receptors.
Dual Effects on the Sphincter of Oddi and Gallbladder Induced by Stimulation of the Right Great Splanchnic Nerve
Authors: Persson Carl G. A. 
Published: December 2008

AbstractThe right great splanchnic nerve was stimulated in 15 anesthetized cats. Effects on gallbladder pressure, resistance to flow through the sphincter of Oddi, and (in 6 cats) intramural duodenal pressure were evaluated. By nerve stimulation, the sphincter was consistently contracted and the intestine relaxed. The gallbladder showed variable slight responses, except in 3 cats where consistent relaxation was obtained. Cholecystokinin (i.v.) relaxed the sphincter and contracted the gallbladder. During the action of the hormone, the nervous response was counteracted in the sphincter; in the gallbladder, relaxation was obtained in all cats. Noradrenaline (i.v.) mimicked the responses induced by adrenergic nerve stimulation. The contraction of the sphincter induced by nerve stimulation and by noradrenaline was inhibited by phenoxybenz‐amine and atropine. The relaxation of the gallbladder was prevented by propranolol. It is concluded that the adrenergic splanchnic nerves, as well as i.v. noradrenaline, mainly activated α‐receptors in the sphincter of Oddi (inducing contraction) and β‐receptors in the gallbladder (inducing relaxation). Results obtained with the nerve stimulation and the 3 blocking agents also confirmed the presence of contraction‐mediating atropine‐sensitive cholinoceptors in the sphincter and the gallbladder, contraction‐mediating α‐receptors in the gallbladder, and relaxation‐mediating β‐receptors in the sphincter.
Effect of Prolonged Nerve Blockage on the Development of the Myoneural Junction
Authors: Juntunen J. , Teräväinen H. 
Published: December 2008

AbstractThe electrical conductivity of the sciatic nerve was locally blocked by repeatedly injecting long‐acting local anesthetic (Marcaine®‐adrenaline) dorsally to the collum femoris of newborn rat for 7 days. Structural alterations of the postsynaptic muscle fibre membrane occurring during the development were followed with a light microscope after the activity of myoneural acetylcholinesterase (E.C.3.1.1.7) enzyme was histochemically demonstrated. Unlike anatomical denervation by cutting the sciatic nerve, nerve blockage with the anesthetic did not prevent structural development of the myoneural junction from occurring as in normal untreated muscles. The observations would seem to indicate that chemical agents other than acetylcholine are responsible for the regulatory effect of the nerve on the structural alterations of the postsynaptic part of the muscle fiber membrane.
Interaction between the Fastigial Pressor Response and the Defence Reaction
Authors: Lisander Björn , Martner Jan 
Published: December 2008

AbstractExperiments were performed on chloralosed cats with recording of blood pressure, heart rate and regional blood flows. Electrical stimulation of the fastigial nucleus produced a pressor response. During stimulation of the hypothalamic defence area, fastigial stimulation decreased the muscle vasodilation and augmented the concomitant vasoconstriction in the skin and intestinal beds. These effects from fastigial stimulation could be accounted for by activation of α‐adrenergic mechanisms. However, a fastigial inhibition of hypothalamically induced cholinergic vasodilation was also observed in the innervated, cross‐circulated limb in which adrenergic blocking drugs had been administered. This suggests that fastigial stimulation can interfere with the activation of the dilator fibres at some level within the central nervous system as well as in the periphery. Both defence area and fastigial stimulation can also cause an adrenomedullary activation. The defence reaction may include a weak activation of the adrenergic outflow to the, muscles which is not readily apparent, because of the baroceptor activation secondary to the widespread systemic adrenergic activation.
Intramural Blood Flow and Blood Volume in the Small Intestine of the Gat as Analyzed by an Indicator‐Dilution Technique
Authors: Biber Björn , Lundgren Ove , Svanvik Joar 
Published: December 2008

AbstractThe mucosal red cell and plasma flow and volume in the cat small intestine were studied at various levels of smooth muscle vascular tone by means of an indicator‐dilution technique. 32P‐labelled red cells and plasma particles as well as 198Au‐labelled colloid particles were used. The monitored tissue region includes when using 32P most of the mucosa, while only the villi were “seen” with 198Au. During “rest” (total intestinal blood flow about 25 ml/min × 100 g) “mucosal” plasma flow was somewhat lower than total intestinal blood flow while “villous” plasma flow was of the same order of magnitude. “Mucosal” and “villous” plasma volumes measured about 2.0 and 1.5 ml/100 ml, respectively. As the intestinal vascular bed was maximally dilated (total intestinal blood flow 200–250 ml/min × 100 g) by an i.a. infusion of isopropylnoradrenaline, “villous” plasma flow increased to 275 ml/min × 100 ml tissue while “mucosal” blood flow was the same as total intestinal flow. Concomitantly, “mucosal” and “villous” plasma volumes increased to 3.0 and 4.0 ml/100 ml, respectively. Mean transit time through the villous hairpin loop decreased from 5–6 s at rest to about 1 s at maximal vasodilatation.