bluuebunny/crossref_metadata_2025 huggingface dataset:
The Fate of Intravenously Administered Radioactive Cholesterol Dispersion in the Rat
Authors: Viikari J. , Saarni H. , Ruuskanen O. , Nikkari T.
Published: December 2008

The present work was aimed at studying the first stages of disappearance of particulate cholesterol from the circulation. The distribution of radioactivity in blood, liver, spleen, lungs and kidneys was determined at different time intervals after i.v. injections of aqueous‐ethanolic dispersions of radioactive cholesterol to rats. More than 95% of the dose disappeared from the circulation in 10 min. From 71 to 93% of the dose was found in the liver 5 min‐2 h after the injection. According to autoradiography, most of the particulate cholesterol was immediately taken up by the liver parenchymal cells. There were only few grains over the Kupffer cells. 2 min to 6 h after the injection the highest specific radioactivity was in the free cholesterol fraction of the liver. The specific activity of liver esterified cholesterol was 54 % of that of the free cholesterol at 1 h. They both declined gradually and reached the same level in 1–2 days. There was a gradual rise of the specific activities of plasma free and esterified cholesterol starting 30 min after the injection. Both reached a maximum in 6–16 h, when the curve of plasma esterified cholesterol intersected that of liver esterified cholesterol. The radioactivity reappearing in plasma was associated with lipoproteins and red cells; the cholesterol of the high density lipoproteins had the highest specific activity. The results indicate that particulate cholesterol is taken up chiefly by the parenchymal cells of the liver and is subsequently incorporated into the plasma lipoproteins, most rapidly into the high density lipoproteins. A large fraction of plasma esterified cholesterol originates in the liver.
Small Airway Constriction and Closure after Induced Intravascular Platelet Aggregation
Authors: Vaage Jarle , Hauge Anton
Published: December 2008

The aim of this study was to investigate the function of the peripheral airways after intravascular platelet aggregation induced by i.v. infusions of collagen in open chest anesthetized cats, ventilated with constant tidal volume. Lung compliance was examined under static conditions (stat CL) and under dynamic conditions (dyn CL) at ventilation frequencies of 5, 24 and 50/min. In the control situation dyn CL 24 was approximately 90 % of stat CL. Collagen infusions resulted in a pronounced frequency‐dependence of lung compliance. When dyn CL 24 had decreased by approximately 40 % a reduction in stat CL could also be detected. When dyn CL 24 decreased even more a concurrent reduction in stat CL was evident. These findings indicate that the initial event after induced intravascular platelet aggregation is small airway constriction. With more pronounced changes airway closure and reduction in lung volume occurs. We suggest that these functional changes in peripheral airways result in the impaired gas exchange known to occur after intravascular platelet aggregation.
Inhibition of Gastric and Intestinal Motor Activity in Dogs by (Gln4) Neurotensin
Authors: Andersson S. , Rosell S. , Hjelmquist U. , Chang D. , Folkers K.
Published: December 2008

The action of (Gln4)‐neurotensin was studied on the spontaneous motor activity in isolated canine fundic, antral and intestinal pouches. All pouches had been prepared more than 6 months prior to the experiments. Spontaneous motor activity was recorded for at least 1 h before the (Gln4)‐neurotensin was infused i.v. for 30 min in doses ranging between 6.3 and 100 ng × kg‐1× min‐1. In the vagally denervated fundic pouches (Gln4)‐neurotensin inhibted motor activity in doses above 25 ng × kg‐1× min‐1. The vagally innervated antral pouches were more sentitive than the vagally denervated fundic pouches to the action of (Gln4)‐neurotensin. Thus motor inhibition was induced by doses as low as 6.3 ng × kg‐1× min‐1. The effect of (Gln4)‐neurotensin on motor activity in intestinal pouches was inconsistent. Inhibition was seen in 1 out of 7 expts. The present results show that the gastric motor activity is the most sensitive function to (Gln4)‐neurotensin so far studied.
Blood Volume and Extravascular Water Content in the Rat Lung during Acute Alveolar Hypoxia
Authors: Aarseth P. , Karlsen J.
Published: December 2008

Values for pulmonary blood volume and extravascular lung water (estimated as wet weight of lung tissue) were arrived at in intact, anesthetized rats by labelling of blood constituents with isotopes and rapidly freezing the whole animals in liquid nitrogen. On ventilating the animals with 10% O2 in N2/N2O. a reduction in lung blood content could be demonstrated. The degree of reduction depended on the type of anesthesia and ventilation used. In some animals the volume reduction was so marked that both arterial, venous and capillary blood compartments have most probably been involved. The water content of the lung tissue was also rapidly and markedly reduced during hypoxia. Increased plasma osmolarity in mixed venous blood could partly be responsible for this tissue water reduction.
Is Capillary Micropinocytosis of any Significance for the Transcapillary Transfer of Plasma Proteins?
Authors: Rippe B. , Kamiya A. , Folkow B.
Published: December 2008

It has been repeatedly suggested that micropinocytosis plays a decisive role in the transfer of macromolecules across capillary walls. The evidence for this hypothesis is, however, only indirect. Thus physiological data (e.g. Carter et al. 1974, Renkin et al. 1974) cannot exclude that macromolecular transfer takes place by way of diffusion and/or filtration through e.g.“large pores” (cf. Landis and Pappenheimer 1963, Crone 1974). Ultramicroscopic pictures (e.g. Simionescu et al. 1973, 1975, Jennings and Florey 1967) no doubt illustrate uptake of macromolecular tracers within endothelial micropinocytotic vesicles, and their rapid appearance in the interstitial fluid space. It should be stressed, however, that such pictures cannot alone be taken as proof of any directed transendothelial vesicle passage and here opinions, also among experts on ultrastructure, seem to differ somewhat. The tracer appearance in the interstitial fluid may, for example, be the result of diffusion and/or filtration through nearby pores which, because they make out such a minor fraction of capillary walls, are very difficult to visualize. In fact, the ultrastructural pictures might rather illustrate e.g. an endothelial “phagocytotic activity”, of great importance in its own right but without relevance for “active”transcapillary passage.
Effect of Teasing and Sham Feeding on Plasma Glucagon Concentration in Dogs
Authors: Nilsson Göran , Uvnäs‐Wallensten Kerstin
Published: December 2008

Plasma glucagon concentration was determined by radioimmunoassay during fasting and following teasing and sham feeding. Teasing and sham feeding for 1–10 min raised the plasma glucagon concentration which then within a short period of time returned to the basal level. Atropinization (0.2 mg/kg) almost abolished the glucagon response to 10 min of sham feeding. Glucose concentration was slightly elevated in response to 10 min of sham feeding. The results show that physiological stimulation that is induced by the smell. sight and taste of food releases glucagon in the dog. The release is mediated by a cholinergic mechanism.
Pressure‐Independent Inhibition of Sympathetic Activity by Noradrenaline: Role of Baroreceptor C Fibres*
Authors: Akre Stein , Aars Harald
Published: December 2008

The effect of i.v. infusion of noradrenaline on activity in the renal sympathetic nerve was studied in rabbits anesthetized with chloralose and urethane. Noradrenaline (3–8 μg/kg·min) initially increased mean arterial pressure 20–40 mmHg and consequently reduced renal nerve activity. However, studies over a wide range of pressures—obtained by changing the blood volume, revealed that noradrenaline after a few minutes had induced a pressure‐independent reduction of sympathetic discharge. The effect disappeared with baroreceptor denervation. An unchanged relationship between arterial pressure and integrated activity in the whole left aortic nerve (which is largely a measure of activity in A fibres) suggested that the sympathetic depression was due to excitation of aortic nerve C fibres. This conclusion was supported by studies of sympathetic responses to selective stimulation of aortic nerve A and C fibres at equal pressures before and during infusion of noradrenaline. Compared to the reflex activity from A fibres, C fibre stimulation was invariably less effective in suppressing renal nerve activity during the infusion. Our studies indicate that noradrenaline may effect a negative feedback control of sympathetic discharge through activation of baroreceptor C fibres.
Comparative Study of Some Isolated Mammalian Smooth Muscle Effectors of Penile Erection
Authors: Klinge Erik , Sjöstrand Nils O.
Published: December 2008

Spontaneous rhythmic activity, responses to drugs and effects of field stimulation of nerves of the retractor penis (rp) and/or corpus cavernosum urethrae (ceu) of macaque, rabbit, guinea‐pig, rat, dog, cat, horse, boar, elk, bull, ram and goat, as well as of the penile artery (pa) of bull were studied. A basic property of all these muscles was automaticity. Their responses to 5‐hydroxytryptamine, histamine, adenosine triphosphate, prostaglandins E1, E2 and F2α, oxytocin, vasopressin, substance P, bradykinin and angiotensin exhibited considerable species variations. Their excitatory innervation seems to be adrenergic. They also have an inhibitory innervation. In spite of comprehensive pharmacological analysis the inhibitory mediator remains obscure. The frequency‐response relationship to inhibitory nerve stimulation was characterized by a rapidly achieved maximum at low frequencies, indicating high efficiency of the neuroeffector unit.
The Importance of the Intestinal Countercurrent Exchanger for 85Kr Absorption from the Feline Gut
Authors: Jodal Mats , Svanvik Joar , Lundgren Ove
Published: December 2008

The rate of 85Kr absorption from the feline gut was studied at varying intestinal blood flows induced by i.a. infusions of a vasodilator drug or by lowering arterial inflow pressure. The effects on rate of absorption of distending the intestine by increasing intraluminal pressure from 0–1 to 5–7 cm H2O as well as of augmenting the rate of luminal perfusion of the 85Kr solution were also investigated. Distending the small bowel increased rate of 85Kr absorption at all levels of intestinal blood flow except at the very low and the very high blood flow rates. Decreasing blood flow by lowering of arterial perfusion pressure decreased the rate of absorption from the distended gut while it had no effect in the collapsed small intestine. Increasing the rate of luminal perfusion enhanced the rate of 85Kr absorption at all blood flow levels except at the lowest ones. The results are discussed with regard to villous hemodynamics, intestinal countercurrent exchange and intraluminal concentration gradients in the lumen. It is concluded that the countercurrent exchanger represents, under physiological conditions, the major limiting factor for the absorption of lipophilic solutes such as 85Kr.
Absence of Restricted Diffusion in Adipose Tissue Capillaries
Authors: Paaske William P.
Published: December 2008

Capillary permeability in adipose tissue for57Co‐cyanocobalamin (57Co‐B12) was determined by the single injection, external registration method. The capillary diffusion capacity, CDC, (the permeability‐surface area product, PS) was 1.1 ml/100 g·min at a capillary extraction of 0.21 and a plasma flow of 6.7 ml/100 g·min. Results were compared to51Cr‐EDTA data from a previous study with similar method and preparation. As CDC(51Cr‐EDTA)/CDC (57Co‐B 12) was 1.81 and as D(51Cr‐EDTA)/D(57Co‐B 12), the ratio between the free diffusion coefficients in water at 37°C, was 1.79, it is concluded that restricted diffusion does not occur in cutaneous tissue for57Co‐B 12 as compared to51Cr‐EDTA,i.e.,51Cr‐EDTA and57Co‐B 12 diffuse across the capillary membrane of adipose tissue at rates proportional to their respective free diffusion coefficients in water. The Pappenheimer equivalent pore radius estimate of 30 Å and the Karnovsky interendothelial 40 Å slit width are both defective in explaining the experimental data. The transendothelial channel system of fused vesicles (Simionescu, Simionescu and Palade 1975) is a possible structural equivalent for the present findings. The results support the hypothesis that capillaries of continuous type exhibit similar permeation characteristics regardless of the tissue in which they are located.
Effect of Carotid Sinus Stimulation on Cardiac Output and Peripheral Vascular Resistance during Changes in Blood Volume Distribution in Man
Authors: Bevegård Sture , Castenfors Jan , Lindblad Lars Erik
Published: December 2008

In ten healthy subjects (mean age 29.6 years) the hemodynamic response to carotid sinus stimulation (neck suction ‐ 40 mmHg) was studied under control conditions and during peripheral pooling of blood (lower body negative pressure). Heart rate, arterial and central venous pressure, cardiac output and forearm blood flow were measured. The time sequence of the heart rate response was studied separately in six healthy subjects. During control conditions, carotid sinus stimulation induced a significant decrease in arterial pressure and heart rate. The blood pressure decrease mainly reflected a reduction in cardiac output, total peripheral vascular resistance being essentially unchanged. However, in the skeletal muscle, represented by a forearm segment, vascular resistance decreased significantly. During lower body negative pressure (LBNP) the same stimulation of the carotid sinus induced a significantly greater fall in mean arterial pressure even though the reduction in cardiac output was slightly smaller on the average than in the control condition. The heart rate increased, probably secondary to a time dependent increase in heart rate elicited by the continuous LBNP stimulus. Total peripheral vascular resistance decreased significantly during LBNP, the reaction likewise differing significantly from that in the control condition. Thus the augmented blood pressure response was due to a more pronounced vasodilatation when the carotid sinus was stimulated during lower body negative pressure. The results indicate that the hemodynamic changes elicited by carotid sinus stimulation are modified by changes in the distribution of blood volume and in the tone of resistance vessels.
Adenosine in Rat Cerebral Cortex: Its Determination, Normal Values, and Correlation to AMP and Cyclic AMP during Shortlasting Ischemia
Authors: Nordström C.‐H. , Rehncrona S. , Siesjö B. K. , Westerberg Eva
Published: December 2008

It has recently been suggested that adenosine is a metabolic coupling factor responsible for an increased cerebral blood flow during hypoxia or increased functional activity. However, tissue adenosine concentrations have been reported to increase in situations previously shown to be unassociated with changes in tissue AMP concentrations. The present experiments were undertaken to assess cerebral cortex concentrations of adenosine under normal circumstances, and to relate changes in adenosine, AMP and cyclic AMP during shortlasting ischemia. Following freezing and extraction of tissue, adenosine was measured using high pressure liquid chromatography. In paralyzed and anaesthetized (70% N2O) rats, freezing of tissue through intact skull bone gave an adenosine concentration of 0.9 ± 0.1 μmol·kg‐1(mean±S.E.M). With freezing through the exposed dura the concentration was 3 times as high with a large scatter. When special precautions were taken to avoid tissue trauma during craniotomy, the adenosine concentration was 1.1 ± 0.1 μmol·kg‐1. It is concluded that previously reported values are erroneously high. During the first 60 s of total ischemia there was a linear correlation between increase in AMP and in adenosine concentration (as well as between adenosine and cyclic AMP concentrations). It is concluded that increases in tissue adenosine concentration only occur if AMP accumulates. However, since (relative) changes in adenosine concentrations are at least twice those of AMP, analyses of adenosine may provide sensitive measures of a change in phosphorylation state.
Dependence on External Calcium for the Noradrenaline Contractility of the Resistance Vessels in Spontaneously Hypertensive and Renal Hypertensive Rats, as Compared with Normotensive Controls
Authors: Folkow Björn , Hallbäck Margareta , Jones John V. , Sutter Morley
Published: December 2008

Isolated hindquarters of rats were perfused at constant flow with a plasma substitute so that pressor responses to various concentrations of noradrenaline (NA) could be measured in consecutive sections of the vascular bed with normal (>1.5 mM) or low (0.2 mM) Ca2+in the perfusate. The animals used were 6‐week‐old spontaneously hypertensive rats of the Okamoto strain (SHRY), normotensive controls of the same age (NCRY); 6–7‐month‐old SHR (SHRA) and NCR (NCRA); and rats made hypertensive by clipping of one renal artery (RHR) plus matched normotensive controls (NCRB). Concentration‐response curves to NA showed that constrictor responses to NA become more dependent on external calcium as one proceeds peripherally in the vascular system in both SHRA and NCRA, with responses in proximal vessels being least and small pre‐and postcapillary vessels being most dependent in both cases. In low calcium SHRA retained their responses better than NCRA, whereas RHR retained their responses to NA poorer than did NCRB. No significant differences in responses in low calcium were observed in SHRT compared to NCRY though a trend in the same direction as in SHRA could be traced. It is concluded that there is no evidence that altered handling of calcium initiates vascular hyperreactivity in SHR, but that the handling of vascular calcium in SHR differs from RHR and both differ from NCR.
Motility of the Urinary Bladder in Cats during Filling at Physiological Rates II. Effects of Extrinsic Bladder Denervation on Intramural Tension and on Intravesical Pressure Patterns
Authors: Klevmark Bjørn
Published: December 2008

The influence of extrinsic innervation on bladder wall tension (tonus) and on intravesical pressure patterns was studied with a new cystometric procedure (Controlled Slow Cystometry, CSC) and during natural filling. After parasympathectomy, but not after sympathectomy, the basal intravesical pressure was markedly increased. At low filling rate the partial or completely denervated bladder was filled from small initial volumes without any increase in intravesical pressure. At higher rates of filling a pressure rise occcurred, and this reaction was not affected by either parasympathectomy or sympathectomy. As in the intact cat, the new pressure level was retained when the filling rate was gradually reduced. The various intravesical pressure patterns observed during filling were preserved in the partial or completely denervated organ. Thus, bladder adaptation during natural filling occurs independently of extrinsic innervation.
Fatigue and EMG of Repeated Fast Voluntary Contractions in Man
Authors: Nilsson J. , Tesch P. , Thorstensson A.
Published: December 2008

A fatigue test consisting of repeated fast maximal contractions of the left quadriceps muscle in an isokinetic apparatus was performed by 12 healthy male subjects (19–25 yrs). EMG signals were recorded from the surface of the left vastus lateralis muscle, from which also biopsies were obtained for muscle fibre classification. Only minor changes were observed in the EMG variables despite a decrease in muscle strength performance, in terms of peak torque, work and power to about 50% of initial values after 100 contractions. The concomitantly obtained positive correlation between the increase in EMG/torque ratio and the individual percentage of fast twitch (FT) muscle fibres indicated that local factors in the muscle, primarily in the FT fibres, were causing the development of fatigue during repeated dynamic contractions with high power outputs.
Methodological Aspects of Testicular Blood Flow Measurements in Rats
Authors: Damber Jan‐Erik , Janson Per Olof
Published: December 2008

3 techniques for the measurement of testicular blood flow in anesthetized adult rats were compared. Direct measurement of testicular venous outflow yielded values more than 3 times lower than those obtained by Xe‐133 clearance and radioactive microsphere techniques due to the surgical procedures involved in spermatic venous cannulation. There was an agreement between flow values obtained with Xe‐133 clearance (17.8 ± 3.5 ml/100 g×min) and radioactive microspheres (19.9 ± 5.5 ml/100 g×min). A homogeneous distribution of microspheres to different segments of the testis indicates that Xe‐133 clearance is an adequate technique for testicular blood flow measurements. However, for some experimental purposes the radioactive microsphere technique is more versatile than Xe‐133 clearance because of its capacity of measuring several organ flows simultaneously.
Direct Antilipolytic Effect of Acidosis in Isolated Rat Adipocytes
Authors: Hjemdahl Paul , Fredholm Bertil B.
Published: December 2008

The possibility that acidosis inhibits lipolysis indirectly by causing ionic shifts or by favouring the accumulation of an inhibitor has been tested in isolated fat cells. Lipolysis induced by 3 μM noradrenaline (NA) was inhibited by 40–60% and that induced by 1 mM theophylline (THEO) by about 75% when the pH was reduced to 6.6. Lipolysis induced by NA+THEO was inhibited by 20–30%. Changing the concentration of Ca++or Mg++did not alter the degree of inhibition. Reducing the K+‐ion concentration enhanced the inhibitory effect of low pH on lipolysis induced by NA or NA + THEO, whereas cyclic AMP accumulation was uninfluenced. Omitting glucose from the incubation medium caused a slight enhancement of pH‐induced inhibition of lipolysis (from 60 to 70%, p<0.01). Reducing the concentration of albumin, which binds inhibitory substances such as FFA, reduced lipolysis more at normal than at reduced pH. At high FFA/albumin ratios (5 or above) lipolysis was similar at normal and reduced pH. The antilipolytic effect of decreased pH was equally pronounced in perifused fat cells, where inhibitory substances are not allowed to accumulate. Our results suggest that the antilipolytic effect of acidosis is mainly a direct effect of the increase in H+ion concentration. The inhibitory effect of acidosis on various responses to β‐adrenoceptor stimulation may be caused by a decreased formation of cyclic AMP in turn caused directly by the decrease in pH.
Release of3H‐Acetylcholine from Isolated Guinea Pig Ileum. A Radiochemical Method for Studying the Release of the Cholinergic Neurotransmitter in the Intestine
Authors: Wikberg Jarl
Published: December 2008

Innervated strips of longitudinal muscle of guinea pig ileum were incubated with3H‐choline in the presence of physostigmine, after which the efflux of tritiated metabolites was studied. Under resting conditions3H‐acetylcholine,3H‐choline and other tritiated metabolites were released into the incubation medium. Analysis of the kinetics of the release of the metabolites indicated that the release occurred from at least 2 different compartments. Under the unstimulated conditions used, between 72 and 78% of the radioactivity remained in a third, non‐releasable compartment. The release of3H‐acetylcholine showed spontaneous fluctuations which were positively correlated to spontaneous variations of the isometric tension of the preparation. Electrical field stimulation at low frequency (0.5 Hz) consistently increased the release of3H‐acetylcholine. The release of3H‐choline was increased only slightly or not at all by the electrical stimulation. For studying stimulation‐evoked release of3H‐acetylcholine, it is suggested that the measurement of the total quaternary amine release is of similar value to measurement of3H‐acetylcholine itself. This approach considerably simplified the method. During 5 consecutive stimulation periods of 150 pulses each, the increase in the release of total quaternary amines diminished with time. By taking into account the reduction of the stores of radioactivity in the tissue during the experiment, correction for the negative trend could be made. When the preparation was stimulated with between 30 and 3 000 pulses a close correlation was found between the increase in the release of total quaternary amines and the number of pulses delivered. The volley output of the quaternary amines was not constant, however, but diminished by increasing stimulation frequency.
Serum Testosterone Compared with Serum Zinc in Man
Authors: Hartoma R.
Published: December 2008

Serum zinc was measured in 154 male and 95 female blood donors. Men had higher serum zinc levels than women, the difference being statistically significant (p < 0.001). The correlations between serum zinc and serum testosterone, serum zinc and serum FSH and serum zinc and serum LH were studied in 40 men aged 28–60 years and a statistically significant positive correlation was found only between serum zinc and serum testosterone in men of age 36–60 years (p < 0.005). These results do not support the theory that slight zinc deficiency primarily effects pituitary gonadotropins but indicate that it would rather act on testicular level.
Regional Brain Uptake of Noradrenaline Following Mechanical or Osmotic Opening of the Blood‐Brain Barrier
Authors: Hardebo J. E. , Edvinsson L. , Mackenzie E. T. , Owman Ch.
Published: December 2008

The passage of noradrenaline from the cerebrovascular circulation into the brain (vessel walls and parenchyma) was studied quantitatively and regionally by a modification of Oldendorf's technique for determination of brain uptake index. Using14C‐ethanol as the highly diffusible internal standard, the index for noradrenaline varied between 2.7 and 4.5% in different regions, confirming the poor penetration of this neurotransmitter. The barrier was impaired transiently as evidenced by Evans blue extravasation, through osmotic opening by internal carotid injection of a hyperosmolar urea solution or mechanical disruption by a short‐lasting elevation of the intracarotid hydrostatic pressure. This resulted in a 3–4‐fold increase in the passage of noradrenaline from the circulation into the brain.
K+‐Permeability of the Blood‐Brain Barrier, Investigated by Aid of a K+‐Sensitive Microelectrode
Authors: Hansen Anker Jon , Lund‐Andersen Henrik , Crone Christian
Published: December 2008

The K+‐permeability of the blood‐brain barrier at the capillary level was estimated from determinations of brain extracellular K+‐concentration in response to an isotonic bolus containing KC1 injected into the carotid artery. A very low permeability appeared from the fact that the extracellular K+‐concentration—measured by aid of K+‐sensitive microelectrodes—remained unchanged during the passage of the bolus. An upper limit for the blood‐brain barrier K.+‐permeability in the rat was estimated to be 2.8 7times; 10‐7 cm · s‐1.
Sustained Water Diuresis in Anesthetized Dogs: Antidiuresis in Response to Intravenous and Bilateral Intracarotid Infusion of Hyper‐Osmolar Solutions of Sodium Chloride
Authors: Bie Peter
Published: December 2008

The function of the suggested hypothalamic osmoreceptors was re‐examined in dogs during light chloralose anesthesia. The body weight of the dogs was increased to—and maintained at—102.0% of the initial value by i.v. infusion of a hypo‐osmolar solution of glucose and urea. During the water diuresis renal free water clearance (CH2O) remained approximately constant for more than 3 h during which infusion of physiological amounts of vasopressin (5 or 10 μU/(kg b.wt. · min)) was associated with a dose‐dependent, reversible decrease in CH2O. Infusion of hyper‐osmolar sodium chloride solution (90μmol/(kg b.wt. · min) for 60min) was performed either through a central venous catheter or through needles placed in both common carotid arteries. After an initial increase in CH2O these infusions elicited antidiuresis (negative CH2O) and increase in the rates of excretion of sodium (100‐fold) and potassium (3‐fold). Left atrial pressure and renal clearance of inulin and PAH did not change significantly. The renal effects of NaCl infusion were independent of the mode of infusion. It is concluded that the results are inconsistent with the hypothesis that the area supplied by the common carotid arteries includes an osmoreceptor which is capable of changing —within seconds—the rate of secretion of vasopressin, although they support the view that the renal excretion of water is strongly influenced by a receptor which is sensitive to osmolality or concentration of sodium. In addition it appeared that an increase of a few per cent in the concentration of sodium in plasma was associated with a substantial increase in the rate of excretion of sodium without measurable changes in central venous pressure or in glomerular filtration rate.
Electrophysiological Membrane Properties of the Frog Muscle Fibre: Effects of Detergents in the Triton Series
Authors: Rydqvist Bo
Published: December 2008

The effect of the nonionic detergent Triton X‐100 on the membrane properties of frog sartorius muscle fibres was studied using intracellular microelectrode technique. The effect of Triton X‐100 was compared with that of Triton X‐45 and Triton N‐101. At 40 μM Triton X‐100 had little effect on the specific membrane resistance (Rm), membrane capacitance (Cm) and the resting membrane potential (Er) while the action potential (AP) was markedly reduced. At 160 μM AP was completely abolished and Er was diminished linearily with time. The effect on the maximum rate of rise (Va) of the AP was dose‐dependent and the apparent dissociation constant (KDapp) and KD were found to be about 40 μM. The Hill coefficient was 1.6 indicating a deviation from a first order reaction. The effect of Triton X‐100 on Er may be accounted for by a reduction of the Na‐K pumping activity. The effect of Triton X‐100 on the AP is suggested to be due to a perturbation of a protein‐system either by a drug‐receptor interaction involving two or more sites, or an unspecific binding of Triton X‐100 to hydrophobic loci on the protein.
Intra‐ and Extracellular Activity of Ciliated Cells
Authors: Huberman D. , Hakansson C. H. , Mercke U. , Toremalm N. G.
Published: December 2008

A method permitting simultaneous recording in vitro of the intracellular and extracellular (=mucociliary) activity of respiratory ciliated mucous membrane is presented. Using this method the influence of different temperature levels (20°, 30°, 40°C) upon the tracheal mucous membrane of 15 rabbits has been investigated. It is shown 1) that the extracellular (= mucociliary) activity increases with rising temperatures whereas the intracellular activity is unaffected and remains constant, indicating a temperature influence upon the respiratory tract mucus rather than a change of the intracellular “pace‐maker” mechanism; 21 that the restraining effect of the mucus decreases with rising temperatures but is still 10% of the intracellular frequency at body temperature; 3) that the presented method should be useful for future investigations concerning the effect of air‐pollution and pharmacological substances upon respiratory mucous membranes.
Regulation of the Heart of a Teleost,Gadus morhua,by Autonomic Nerves and Circulating Catecholamines
Authors: Holmgren Susanne
Published: December 2008

The cod heart regulation has been investigated by anatomical studies, fluorescent histochemistry, nerve stimulation and drug effects on the perfused heart and electrically paced strips. The effect on the heart of catecholamine release from the head kidney has been studied in a perfused head kidney and heart preparation. Branches of the vagi and the fused 1st and 2nd spinal nerves innervate the heart. Specifically fluorescent fibres were found in these nerve branches, in the ducts of Cuvier, all parts of the heart, bulbus arteriosus and the ventral aorta. Weakly autofluorescent ganglion cells surrounded by specifically fluorescent varicose fibres were present in the walls of the sinus venosus. Vagal stimulation caused bradycardia altered after atropine to tachycardia. Spinal nerve and sympathetic chain stimulation also induced tachycardia, as did provoked catecholamine release from the head kidney. The tachycardia could be blocked by propranolol. Atropine increased and propranolol decreased basic heart rate and contraction force. Adrenergic drugs accelerated and acetylcholine retarded the perfused heart. A positive inotropic effect was obtained with adrenergic drugs on isolated heart strips, while acetylcholine produced a negative inotropic effect on atrial but not ventricular strips. It is concluded from this study that the cod heart has an inhibitory cholinergic nerve supplyviathe vagi and an excitatory adrenergic supplyviaboth the vagi and the first spinal nerves. Sympathetically controlled release of catecholamines from the chromaffin tissue in the head kidney may also play an important role in the heart regulation.
Coacervate‐like Membrane Structures and Olfactory Transduction
Authors: Sperber G. O.
Published: December 2008

Current theories concerning the olfactory transduction process are discussed. A hypothesis is formulated, according to which the olfactory receptor membrane contains regions where it has the structure of a lipid‐protein coacervate. Such structures may well occur in living cells. Such a membrane would have the ability to change its permeability in response to odorants and a sensitivity comparable to that of the sense of smell. The model also explains the fact that different receptor cells have different sensitivity patterns towards odorants. The model is consistent with the results of experiments that seek to establish the locus of odorant action.
Localization of Adrenergic Receptors in Guinea Pig Ileum and Rabbit Jejunum to Cholinergic Neurons and to Smooth Muscle Cells
Authors: Wikberg Jarl
Published: December 2008

The localization of adrenergic receptors mediating a relaxing action was investigated in innervated and denervated longituclinal muscle strips from guinea pig ileum and rabbit jejunum. Denervated preparations were contracted by drugs that had a direct effect on smooth muscle cells, such as acetylcholine and histamine, but not by stimuli acting on cholinergic neurons, such as electrical field stimulation or nicotine. After blockade of β‐adrenoceptors, norepinephrine relaxed the innervated guinea pig ileum contracted by electrical field stimulation, by stimulating α‐adrenoceptors. Norepinephrine in low concentrations did not relax denervated preparations contracted by agents acting directly on smooth muscle. In high concentrations, it relaxed denervated preparations by a nonadrenergic mechanism, resistant to α‐ and/or β‐receptor blockade, but which was also activated by l‐(3,4‐dihydroxyphenyl) ethanol. Phenylephrine only had a weak agonistic effect on the electrically stimulated innervated preparation and did not relax the denervated one. The denervated rabbit intestine contracted by acetylcholine was relaxed by norepinephrine and phenylephrine by stimulation of α‐adrenoceptors. In the innervated preparations both drugs were more effective in inhibiting contractions induced by electrical field stimulation or eserine than those induced by exogenous acetylcholine. Both the denervated guinea pig and rabbit intestine were relaxed by stimulation of β‐adreno‐ceptors. It is suggested that in the guinea pig ileum α‐adrenoceptors mediating relaxation are located only in cholinergic neurons, whereas in rabbit jejunum they are located both in these neurons and in the smooth muscle cells. Beta‐adrenoceptors are located in the smooth muscle cells of both organs.
Actomyosin ATPase, Myokinase, CPK and LDH in Human Fast and Slow Twitch Muscle Fibres
Authors: Thorstensson Alf , Sjödin Bertil , Tesch Per , Karlsson Jan
Published: December 2008

The enzyme activities of Mg2+ stimulated ATPase, creatine phosphokinase (CPK), myokinase (MK) and lactate dehydrogenase (LDH) were determined in pooled fast twitch (FT) and slow twitch (ST) human skeletal muscle fibres, dissected out from freeze‐dried muscle biopsy material. All enzymes investigated demonstrated higher activities in FT fibres. The ratio in enzyme activity between fibre types was greatest for Mg2+ stimulated ATPase (3:1) and smallest for CPK (1.3: 1). In addition, the isozyme patterns of CPK, MK and LDH were studied by means of isoelectric focusing (CPK and MK) and discelectrophoresis (LDH). A difference was observed between fibre types with respect to the isozyme distribution of MK and LDH, whereas the CPK isozyme pattern was similar in both fibre types. These results on separated human FT and ST fibres were essentially in conformity with what has earlier been indicated from experiments on mixed muscle homogenates.
Vasodilator Fibres to the Tongue in the Chorda Tympani Proper Nerve
Authors: Hellekant Göran
Published: December 2008

Electrical stimulation of the chorda tympani proper nerve (CT) causes vasodilatation in the constant‐flow perfused tongue. It has been suggested, as an explanation for this, that the vasodilatation is the result of antidromic impulses in sensory fibres of the CT. However, after degeneration of the efferent fibres in the CT in the rat it was found that electrical stimulation of the CT caused no vasodilatation. Since, by all criteria available, the sensory fibres remained, the result indicates that antidromic impulses could not be the cause of the vasodilatation observed in tongues with intact nerve supply. Further, since there are no glands in the part of the tongue innervated by the CT and the circulation of the large salivary glands is separate from the tongue in the rat, it is concluded that the vasodilatation was not a secondary effect of glandular activity, but was caused by vasodilator fibres in the CT.
Blood Pressure and Heart Rate Regulating Capacity of the Carotid Sinus during Changes in Blood Volume Distribution in Man
Authors: Bevegård Sture , Castenfors Jan , Erik Lindblad Lars , Tranesjö Jussi
Published: December 2008

The influence of changes in blood volume distribution on the carotid baroreflex was studied in 18 subjects. Blood volume distribution was changed by varying the pressure around the lower body above and below ambient, thereby varying the amount of blood pooled in this region and exerting a secondary influence on the central blood volume. The carotid arterial stretch receptors were stimulated by varying the pressure in an air‐tight box enclosing the neck. To obtain a standardized carotid sinus stimulus (SCS) the pressure in the box was varied sinusoidally between ‐10 and ˜ 40 mmHg with a fixed frequency of 0.03 Hz. The effects on heart rate and blood pressure were assessed by harmonic analysis performed off‐line on a digital computer. During lower body negative pressure of –40 mmHg (LBNP ‐ 40), i.e. during a procedure known to reduce the central blood volume, SCS induced an augmented effect on the blood pressure regulating capacity but not on the heart rate response. Expressing the blood pressure regulating capacity as peak‐to‐peak changes in systolic arterial pressure, the response during LBNP 40 mmHg was almost twice the control value. The opposite stimulus–lower body positive pressure–influenced the SCS‐induced effects only slightly but on the average a minor reduction in both blood pressure and heart rate regulating capacity was found compared with the control condition, though the difference did not reach significant levels.

The results support the hypothesis that changes in blood volume distribution modify the function of the carotid baroreflex, possibly via intrathoracic receptors sensitive to changes in central blood volume and/or central venous pressure.
Effect of Sodium Pentobarbital on the Apparent Turnover of Acetylcholine in Different Brain Regions
Authors: Nordberg Agneta , Sundwall Anders
Published: December 2008

The turnover rate of acetylcholine (ACh) was measured in six different brain regions in the mouse following pulse injection of radioactive choline (Ch) and killing of the animals by microwave irradiation of the head (0.25 s, 5 kW). The time course of the change in3H‐ACh/3H‐Ch ratio was linear 0–60 s in all brain regions after administration of3H‐Ch. Plots of the specific radioactivities (SA) of ACh and Ch versus time indicate a precursor‐product relationship in all brain regions except the cerebellum both in control and sodium pentobarbital anesthesized animals. The turnover was highest in the striatum (55 nmol g‐1min‐I), while in the cortex and hippocampus this value was approximately half (27 and 21 nmol‐g‐1‐min‐1). In the midbrain and medulla oblongata the turnover rates were only 11 and 10 nmol gr‐1min‐1. Sodium pentobarbital anesthesia reduced specifically the turnover in the cortex and hippocampus to about 60 to 70 per cent.
Lower Body Negative Pressure and Effects of Autonomic Heart Blockade on Cardiovascular Responses
Authors: Bjurstedt H. , Rosenhamer G. , Tydén G.
Published: December 2008

Heart rate, arterial pressure and cardiac output were recorded in eight healthy male volunteers during exposure to 80 mmHg of lower body negative pressure (LBNP) in the supine position before and after beta‐adrenergic and combined beta‐adrenergic and parasympathetic blockade of the heart as induced by the i.v. administration of propranolol 0.25 mg/kg b.wt. and atropine 0.04 mg/kg b.wt. After propranolol, heart rate response to LBNP averaged 48 % of that observed without blockade indicating that LBNP‐induced cardioacceleration is of both sympathetic and parasympathetic origin. Tolerance to LBNP was reduced by beta‐adrenergic blockade, since the decrease in mean arterial pressure during LBNP was exaggerated by such blockade. Although the addition of atropine markedly elevated mean arterial pressure and cardiac output in the control situation, tolerance to LBNP was not enhanced by this drug as judged from the arterial pressure response. Post‐LBNP overshoot in mean arterial pressure was strikingly augmented by combined cardiac effector blockade and was in part due to a lingering elevation of total peripheral resistance, cardiac output remaining decreased for more than 110 s after release of LBNP.
The Compliance Curve for the Flow Limiting Segments of the Airway. I. Model Studies
Authors: Pedersen Ole Find , Nielsen Tage Mors
Published: December 2008

By means of a pitot‐static tube airway compliance curves describing the cross‐sectional area (A) as a function of transmural pressure (Ptm) were constructed for several locations in the elastic airway of a mechanical model of the lung. From these curves local relations between elastic recoil pressure of the lung (Pel) and maximal expiratory flow (V̇max) were calculated and compared with the experimentally determined Pel‐V̇max curve for the entire airway, i.e. all parts in series. Theory and experiments showed that the latter was the lower borderline of all the local Pel‐v̇max curves. This means that the maximal flow through the entire airway at a given Pel is determined by the segment of the airway, having the smallest v̇max, just as the maximal strength of a chain is determined by its weakest link. The relation between the critical transmural pressure (Ptm‘) and the corresponding cross‐sectional area (A’) was derived from theexperimental Pel‐V̇max curve. This Ptm‘‐A’ curve had a composed appearance, which was found to reflect parts of the different local Ptm‐A curves and transitions between them because of movement of the flow limiting site within the airway. The Ptm‘‐A’ curve depends on the elastic properties of the flow limiting segment, and the slope of this curve (dA‘/dPtm’) is the compliance of the flow limiting segment. Significant frictional pressure losses upstream from the site of flow limitation caused underestimation of both A‘ and dA’/dPtm“, but downstream pressure losses had no influence on the Ptm‘‐A’ curve.
Effect of the Polyene Antibiotic Filipin on the Permeability of the Inward‐ and the Outward‐facing Membranes of the Isolated Frog Skin (Rana temporaria)
Authors: Nielsen Robert
Published: December 2008

The effect of the polyene antibiotic filipin on the electrical properties and the passive permeability of the cell membranes was investigated. The addition of filipin to the outside bathing solution has the following effects: 1. it results in a drastic reduction in the transepithelial resistance and potential, 2. it causes a 10–20 times increase in the passive transepithelial chloride, sodium and sucrose flux, 3. it results in the formation of an amiloride insensitive sodium pathway in the outward facing membrane, 4. it results in an active outward transport of potassium, 5. it results in a highly significant swelling of all the cells in the epithelium. The addition of filipin to the inside bathing solution has the following effects 1. it results in an activation of the active sodium transport, 2. it causes a slight increase in the passive transepithelial chloride and sodium permeabilities but has no effect on the sucrose permeability, 3. it has no effect on the amiloride inhibition of the short‐circuit current, 4. it has no effect on the volume of the cells in the epithelium. It is suggested that the addition of filipin to the outside bathing solution increases the direct sodium flow from cell to cell in neighbour layers. Furthermore these experiments indicate that the outward facing membrane of the isolated frog skin has a high cholesterol content as compared with the cholesterol content of the inward facing membrane.
Alpha‐Receptor Subsensitivity of Isolated Atria from Rats Following Physical Training or Repeated ACTH‐Injections
Authors: Siltovuori Anneli , Tirri Rauno , Harri Mikko N. E.
Published: December 2008

Decreased chronotropic and inotropic sensitivity of isolated atria to phenylephrine but not to isoprenaline was found in rats following repeated physical training by swimming or repeated ACTH‐injections. These changes were induced within a week of subjection of animals to these treatments. It is concluded, that these effects are mediated by increased adrenergic activity which results in this subsensitivity of alpha‐receptors.
The Effect of 6‐Aminonicotinamide Blockade of the Pentose Phosphate Pathway on Catecholamines in the Rat Adrenal Medulla, Superior Cervical Ganglion, Hypothalamus and Synaptosome Fractions
Authors: Jansson S.‐E. , Gripenberg J. , Harkonen M.
Published: December 2008

The effect on tissue catecholamines of blockade of the pentose phosphate pathway with 6‐aminonicotinamide (6‐AN) was studied in the rat. 6‐AN at 35–50 mg kg‐1persistently lowered the adrenaline content in the adrenal gland to less than 10% of control values and caused a 50% loss of noradrenaline, which recovered. When the amine turnover rate was increased by a preceding period of drum stress, 6‐AN also consistently depressed noradrenaline in the gland. 6‐AN was without significant effect on the noradrenaline concentration in heart tissue, hypothalamus and superior cervical ganglion and did not affect the uptake or release of catecholaminesin vitro.The possibility is discussed that 6‐AN interferes with the biosynthesis of catecholamines, when it blocks the pentose phosphate pathway, by decreasing the supply of reducing equivalents in the form of NADPH which are necessary for the tetrahydropteridine cofactors of tyrosine hydroxylase.