bluuebunny/crossref_metadata_2025 huggingface dataset:
Absence of Restricted Diffusion in Cutaneous Capillaries
Authors: Paaske William P.
Published: December 2008

Capillary permeability in cutaneous 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 2.3 ml/100 g·min. Capillary extraction was 0.48 at a plasma flow of 4.1 ml/ 100 g·min. Results were compared to51Cr‐EDTA data from a previous study with identical method and preparation. As CDC(51Cr‐EDTA)/CDC(51Co‐B12) was 1.61 and as D(51Cr‐EDTA)/D(51Co‐B12), the ratio between the free diffusion coefficients in water at 37deg;C, was 1.79 it is concluded that restricted diffusion does not occur in cutaneous tissue for57Co‐B12 as compared to51Cr‐EDTA,i.e.51Cr‐EDTA and57Co‐B12 diffuse across the capillary membrane of cutaneous 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 patent 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.
Responses of Reindeer to Water Loading, Water Restriction and ADH
Authors: Valtonen Maija , Eriksson Lea
Published: December 2008

Two female reindeer were hydrated by administration of (10% of b.wt.) water into the rumen. The diuretic response was very fast and strong but the urea and electrolyte excretion were little affected. Dehydration was carried out by not giving the reindeer water for 48 h. This water deprivation caused a loss of up to 20% of their body weight. The urine osmolality did not exceed 840 mosm/kg H2O, although the plasma osmolality rose from 300 to 346 and 368 mosm/kg H2O respectively. The plasma and urine urea concentrations were elevated during dehydration, while the urine urea excretion did not increase. Urine sodium concentration did not increase. When the urine flow rate, after two days of water deprivation, decreased to half of the original, the urine Na+ concentration, instead of increasing, went down to half of the original. So did the potassium excretion. When ADH was injected intravenously into hydrated animals a dose of 30 mU of ADH was needed to induce antidiuresis or increased excretion of potassium. The resistance to ADH and the low relative thickness of the medulla confirm the limited capacity of reindeer kidney to concentrate urine or to excrete a solute load. On the other hand, reindeer is able rapidly to excrete surplus water without affecting the electrolyte or nitrogen balance.
Suppression of the Excitatory Adrenergic Neurotransmission; a Possible Role of Cholinergic Nerves in the Retractor Penis Muscle
Authors: Klinge Erik , Sjöstrand Nils O.
Published: December 2008

The excitatory adrenergic response to transmural nerve stimulation of the isolated retractor penis (rp) of dog, rat, cat, horse, boar, elk, bull, ram and goat, as well as the evoked release of 3H from dog rp preloaded with 3H‐noradrenaline were studied. In untreated preparations a low concentration of scopolamine could markedly increase the excitatory adrenergic response. On the contrary, physostigmine per se suppressed this response and so did acetylcholine. Scopolamine or atropine totally prevented these suppressions. They also immediately restored the suppressed responses in spite of continuous presence of physostigmine and/or acetylcholine. In the rat rp there was no suppression of the response by physostigmine. Physostigmine decreased the evoked release of 3H and this effect was counteracted by scopolamine. The rp of dog, gelding, boar, hog, bull and ram contained considerable amounts of noradrenaline and also of acetylcholine. It is suggested that one action of cholinergic nerves in the rp is muscarinic suppression of the excitatory adrenergic neurotransmission.
Electrical Activity of the Rat Uterus during Early Pregnancy and Abortion
Authors: Talo A. , Kärki A. E.
Published: December 2008

Electrical activity of the rat uterus was recorded for 1 h daily on days 2–9 of pregnancy with 6 electrodes chronically implanted in the left uterine horn. In 10 untreated and 7 ergocornine treated rats, activity decreased in frequency and intensity during the first days of pregnancy. After day 3 activity was present in only about 30 % of electrodes as compared to 85 % on day 2. Abortion was induced by ergocornine injected on day 5. In these rats the frequency of bursts increased on days 8 and 9. During the peak of activity the majority of bursts spread in the cervical direction.
Evidence of Decarboxylation of Lysine by Mammalian Ornithine Decarboxylase
Authors: Persson Lo
Published: December 2008

In enzymic preparations from mouse kidney stimulated with the anabolic steroid Durabolin (nandrolone phenpropionate) lysine and ornithine were shown to inhibit the decarboxylation of each other competitively. The Michaelis constants for the decarboxylations were approximately equal to the inhibition constants of the two amino acids. The pH optima of the decarboxylation of lysine and ornithine were found to be identical. Chromatographic studies of the enzyme preparation on a Sephadex G‐150 Superfine column did not bring about a separation of the two enzyme activities. The ratio of the decarboxylating activities was practically the same during the elution. Lysine decarboxylating activity was also shown to be present in growth hormone stimulated rat liver. The results are in agreement with the assumption that the decarboxylation of lysine and ornithine is carried out by the same enzyme.
In Vitro Studies of Frog Mucous Glands
Authors: Skoglund C. R. , Sjöberg E.
Published: December 2008

The ionic outflow, mainly consisting of Na+ and Cl‐, from the mucous glands in an excised nerve‐skin preparation of frog has been determined by recording the conductance changes occurring in a fluid layer covering a small area of the skin surface. In the main series of experiments the glands were activated by stimulation of sympathetic nerve fibers in the skin nerve. The relationship between the ionic outflow and the number of nerve volleys was studied over a wide range. The outflow per impulse was found to be fairly constant during the first tens of impulses but diminished gradually with increasing number of stimuli up to a certain maximum value—varying in different preparations—after which the outflow ceased completely. During the initial phase of stimulation the outflow is most likely caused by an ejection of preformed secretion due to the contractions of the glandular myoepithelium. The continued outflow in the later stages of the stimulation periods must be due to production of new secretion. Since the glandular epithelium is devoid of nerve terminals a nervous control of the ionic secretion can only be explained by an indirect influence mediated either by transmitter diffusion from the myoepithelial nerve endings or by a close electric coupling between the contractile and the secretory gland cells. Adrenaline and noradrenaline induce ionic outflows which like those evoked by nerve stimulation are inhibited by the β‐adrenoreceptor blocker propranolol, α‐adrenoreceptor blockers being without effect. A serendipitous finding of tonus changes in the frog skin during nerve stimulation is also described.
Capillary Permeability in Skeletal Muscle
Authors: Paaske William P.
Published: December 2008

Capillary permeability in skeletal muscle was investigated by applying the single injection, external registration method to the autoperfused cat gastrocnemius preparation.51Cr‐EDTA (MW: 341.2) and57Co‐B12 (MW: 1353.5) served as simultaneously injected indicators. At a plasma flow of 7 ml/100 g×min and an assumed capillary surface area, S, of 70 cma/g the permeability coefficients Pd(51Cr‐EDTA) and Pd(57Co‐B12) were 0.74 × 10‐5cm/s and 0.45×10‐6cm/s, respectively. However, correction for the recruitment of perfused capillaries yields Pd(51C‐EDTA)‐ 1.5 × 10‐5cm/s and Pd(57Co‐B12) = 0.9 × 10‐5cm/s. The results indicate that the permeability of a muscle capillary for hydrophilic solutes is similar to that of continuous capillaries in other tissues. The Pappenheimer pore radius estimate of 30 Å, the Karnovsky 40 Å interendothelial slit width, and pinocytotic transport are defective in accounting for the results as51Cr‐EDTA and57Co‐B12 diffuse across the capillary membrane at rates proportional to their free diffusion coefficients in water (CDC(51Cr‐EDTA)/CDC(57Co‐B12) = D(51Cr‐EDTA)/D(57Co‐B12)= 1.79). The intraendothelial patent channel system of fused vesicles might be the pathway for transcapillary exchange of hydrophilic molecules as this system alone could account for the experimental results. Only 1–2 open channels per μm capillary length are necessary to account for the observed permeabilities. For both indicators CDC was a linear function of plasma flow and CDC increased 3‐3.5 fold when plasma flow increased from 4 to 52 ml/100 g× min. Assuming constant permeability coefficients, the CDC increase with plasma flow reflects an increase in capillary surface area indicating a 3‐3.5 fold recruitment of capillaries. A constant ratio of CDC(51Cr‐EDTA)/CDC(57Co‐B12) within the perfusion range indicates that51Cr‐EDTA and57Co‐B12 can be employed at plasma flow > 4 ml/100 g× min without risk of early back‐diffusion resulting in underestimation of permeability.
Release of Thiamine and Formation of a Methylthiamine‐Like Substance in the Phrenic Nerve‐Diaphragm Preparation of the Rat
Authors: Waldenlind Lennart
Published: December 2008

An increased formation of a radioactive methylthiamine‐like substance (MTLS) in the end plate region of the rat diaphragm muscle and a release of radioactivity chromatographed as thiamine into the bath medium after a subcutaneous injection of35S‐thiamine were found after stimulation of the phrenic nerve. There was also an increased formation of the radioactive methylthiamine‐like substance in the denervated diaphragm preparation incubated with radioactive acetylcholine (ACh) in comparison with the innervated diaphragm.
Plasma Protein Dynamics: Albumin and IgG Capillary Permeability, Extravascular Movement and Regional Blood Flow in Unanesthetized Rabbits
Authors: Bill Anders
Published: December 2008

The turnover rate constants for extravascular albumin and immunoglobulin‐G (IgG) and the turnover rates and extravascular spaces for the proteins and regional blood flow were determined in different tissues in unanesthetized rabbits. The turnover rate constant in percent per minute for extravascular albumin was 1.9 in the kidney cortex and 1.4 in the kidney medulla, about 0.8‐1.4 in the lung, small intestine, choroid plexus and heart muscle and about 0.2‐0.6 in the skeletal muscle, stomach wall and gall bladder. The turnover rate constants for IgG were similar or lower. The plasma equivalent extravascular albumin space was 145 μl/g in the kidney medulla, about 100 μ1/g in the gall bladder, heart muscle, choroid plexus and small intestine, 30–70 μl/g in the kidney cortex, lung, stomach wall and triceps muscle. The extravascular IgG spaces were similar or smaller. In the liver, spleen and adrenals where extravascular spaces could not be determined, the ratios total IgG space/total albumin space were about 1.3‐1.5. Extraction of albumin defined as turnover rate of extravascular albumin/regional plasma flow could not be determined in the liver, spleen and adrenals. It was zero in the brain cortex, about 0.001 % in the lung and around 0.01‐0.05 % in most other tissues. The results suggest that in the walls of the capillaries of the kidney cortex, stomach wall, skeletal muscle and gall bladder there was convection of the proteins with pinocytosis and/or through large pores, diffusion playing little role. The albumin and the IgG passed through the tissues and were drained essentially by bulk flow. In the heart muscle, choroid plexus, lung and small intestine there seemed to be some diffusion of albumin through the capillary wall in addition to convection. Accumulation of IgG in the liver, spleen and adrenals was probably caused by adsorption to cells belonging to the RES.
Influence of Age on Sensitivity and Effector Mechanisms of the Carotid Baroreflex
Authors: Lindblad Lars Erik
Published: December 2008

In 30 healthy subjects aged 20–48 years the hemodynamic response to carotid sinus stimulation (neck suction ‐40 mmHg) was studied. Heart rate, arterial pressure and cardiac output (dye dilution technique) were measured. In order to evaluate the effect of age on carotid sinus function the material was subdivided into two arbitrary subgroups, aged up to 30 years (n = 15) respectively 30 years and above (n = 15). Carotid sinus stimulation induced a significantly greater reduction in mean arterial pressure in the younger group compared to the older group. The heart rate reduction was, on the average, slightly greater in the younger group though the difference was not significant. In both groups a significant decrease in cardiac output contributed to the demonstrated reduction in mean arterial pressure. As the decrease in cardiac output was, on the average, slightly smaller in the younger group, the results indicate that the greater blood pressure response in the younger group was due to a greater reduction in peripheral vascular resistance. This is further supported by the finding of a significant correlation between changes in total peripheral vascular resistance, elicited by carotid sinus stimulation and age.
Choline Acetyltransferase Activity in the Denervated Urinary Bladder of the Rat
Authors: Ekström Jörgen , Elmér Mats
Published: December 2008

After extirpation of the pelvic ganglia the choline acetyltransferase activity decreased markedly indicating that most of the postganglionic cholinergic neurones of the bladder take this route. A small decrease in the activity of this enzyme was found after section of the hypogastric nerves, showing that these nerves contribute to some extent to the cholinergic innervation. The residual enzyme activity found after a combination of the two surgical procedures suggests that neurones relay distal to the level of the section of the hypogastric nerves and pass outside the pelvic ganglia and (or) that neurones pass the pelvic ganglia and relay distal to them. Electrical stimulation of the hypogastric nerves after extirpation of the pelvic ganglia and the use of blocking drugs showed on the existence of cholinergic neurones passing outside the pelvic ganglia, some of them relaying distal to the point of stimulation.
Capillary Permeability to Albumin in Normotensive and Spontaneously Hypertensive Rats
Authors: Rippe Bengt , Folkow Björn
Published: December 2008

Transcapillary passage of plasma proteins is enhanced in man's primary hypertension and it is debated whether this reflects increased permeability or merely a raised capillary pressure. To elucidate this problem, maximally vasodilated hindquarters of spontaneously hypertensive rats (SHR) and normotensive controls (NCR) were perfused in parallel at constant flow with dextran, horse serum or mixtures of the two, using labelled albumin as indicator of capillary permeability to macromolecules. By equal increases of venous pressure modest filtration was maintained during one hour, after which the edema and its albumin content were determined. — There was less edema in SHR, reflecting a slightly lower postcapillary resistance and a much higher precapillary resistance compared with NCR, which here resulted in a lower capillary pressure in SHR. In both SHR and NCR the presence of dextran slightly enhanced the capillary filtration coefficient but increased albumin permeability up to tenfold, also after antihistamine drugs. However, for each perfusate the SHR capillaries were, if anything, slightly less permeable to albumin than the NCR ones. — The results suggest that the enhanced transcapillary passage of plasma proteins in primary hypertension reflects an increased capillary pressure in some circuit(s), probably mainly skeletal muscle, resulting from the functional balance in vivo between the pre‐ and postcapillary resistances.
Vascular Responses to Mechanical Stimulation of the Mucosa of the Cat Colon
Authors: Fasth S. , Hultén L. , Lundgren O. , Nordgren S.
Published: December 2008

Mechanical stimulation of the mucosa of the proximal colon evoked a hyperemia which also could be elicited when severing the autonomic fibres to the colon. Mechanical stimulation of the distal colon produced a hyperemia which, on the other hand, was abolished by cutting the pelvic nerves. Afferent pelvic nerve stimulation evoked a response similar to that seen when stimulating the distal colon. Adrenergic and cholinergic receptor blockers did not affect the studied colonic vasodilatations. Dihydroergotamine, given in doses abolishing the vascular effects of i.a. injected 5‐hydroxytryptamine, abolished the hyperemia to mechanical stimulation of the proximal colon but not that of the pelvic stimulation. It is concluded that a local nervous vasodilator reflex exists in the proximal colon similar to that earlier demonstrated in the small bowel (Biber et al. 1971) and that the reflex vasodilatation evoked by mechanical stimulation in the distal colon is mediated via the pelvic nerves. Hence, the vascular control differs in the proximal and in the distal parts of the colon.
Reflex Plasma Hyperglycemia and Hyperosmolality Evoked by Unloading of the Carotid Baroreceptors
Authors: Järhult Johannes , Holmberg Jan , Lundvall Jan
Published: December 2008

Hemorrhage is usually accompanied by a considerable increase in the plasma osmolality and glucose concentration due to an augmented release of glucose from the liver. In the present cat experiments an attempt was made to investigate the possible role of different vascular receptors in mediating this hyperglycemic (hyperosmolar) response. Bilateral vagotomy or stimulation of the carotid chemoreceptors by perfusion of the carotid sinus with venous blood at normal pressure only slightly increased the arterial plasma glucose concentration. On the other hand, when the sinus nerves were cut in the vagotomized animal, thereby simulating complete unloading of the carotid baroreceptors, the arterial plasma glucose concentration rose by about 8 mM/L and the arterial plasma osmolality by about 10 mOsm/kg H2O. Perfusion of the carotid baroreceptors with arterial blood at different levels of hypotension showed that the baroreceptor‐induced hyperglycemia was graded in relation to the pressure level. Regional hypotension of the liver, pancreas, intestine, kidneys or brain did not significantly affect plasma glucose concentration or osmolality. We conclude that the reflex release of glucose from the liver during hemorrhage mainly is initiated from the unloading of arterial baroreceptors.
The Role of Intramural Noradrenaline in the Potassium Induced Contracture of Non‐Estrogenized Smooth Muscle
Authors: Bengtsson Bengt
Published: December 2008

The influence of intramural noradrenaline on potassium induced contractures was studied in isolated preparations of the uterus and the portal vein of the rat. Uterine strips of oophorectomized rats responded with contraction followed by transient relaxation when immersed in a medium containing 127 mM potassium chloride. Reserpinization or blockade of β‐adrenoceptors with propranolol greatly diminished the transient relaxation. In the isolated portal vein, both noradrenaline depletion with reserpine and α‐adrenoceptor blockade (phentolamine) reduced the active tension produced in response to the isotonic potassium solution. These results suggest that intramural noradrenaline plays a significant role in the development of contractures evoked by potassium in the uterus and the portal vein of the rat. In the uterus, the released noradrenaline counteracts the development of active tension, whereas in the portal vein, noradrenaline has a contractile effect which is added to that of potassium. Estrogen treatment reduced (portal vein) or abolished (rat uterus) the contractile effects of intramural noradrenaline. The adrenolytic effect of estrogen is possibly due to reduction in the release of noradrenaline from the sympathetic nerve‐endings.
Effects of Intraventricular 6‐Hydroxydopamine on Cerebrovascular CO2Reactivity in Anesthetized Rats
Authors: Edvinsson Lars , Hardebo Jan Erik , MacKenzie Eric T.
Published: December 2008

Regional cerebral blood flow was measured by the14C‐ethanol technique in anesthetized rats before and after intraventricular injection of 6‐hydroxydopamine. This treatment reduced the fluorescence of the central noradrenaline and dopamine nerve terminals, as well as of the perivascular nerve terminals in cerebral vessels. The administration of 6‐hydroxydopamine had no significant effect on cerebral blood flow at normocapnia. The cerebrovascular reactivity to hypercapnia was significantly increased in the 6‐hydroxydopamine treated animals. The results indicate an involvement of central catecholamine pathways in the cerebrovascular reactivity to hypercapnia.
Neuronal and Extraneuronal Outflow of3H‐Noradrenaline Induced by Electrical‐Field Stimulation of an Isolated Blood Vessel
Authors: Schrold Jørgen , Nedergaard Ove A.
Published: December 2008

The adrenergic neuronal selectivity of3H‐outflow elicited by electrical‐field stimulation of rabbit isolated pulmonary artery preloaded with3H‐(‐)‐noradrenaline (3H‐NA) was examined. Following incubation (45 min) of arterial rings at 37°C with3H‐NA (10‐6M) and a 100 min wash‐out period, the sympathetic neurones were stimulated selectively and supramaximally, as regards tension development, with a constant current (250 mA; 300 monophasic pulses; 10 Hz; 0.3 ms). The initial stimulation‐induced3H‐outflow was higher than the subsequent 5 outflows, which remained almost constant (39, 20, 19, 17, 16 and 16 pmol g‐1, respectively).3H‐NA and3H‐O‐methylated plus deaminated metabolites constituted 11% and 74%, respectively, of the total3H‐outflow induced during the initial stimulation period, but 38% and 38%, respectively, during the second stimulation period. Omission of Ca2+in the physiological salt solution reduced the 6 stimulation‐induced outflows to 67, 40, 35, 24, 21 and 21%, respectively, of the untreated preparations. Bretylium (3 × 10‐5M) or tetrodotoxin (10‐6M) reduced the3H‐outflow to approximately the same extent. Stimulation‐induced outflows from artery rings preloaded with3H‐NA in the presence of cocaine (10‐3M) or in the cold (3°C) approximated the Ca2+, bretylium and tetrodotoxin‐insensitive release. These treatments all completely blocked the neurogenic contractile response. When artery rings were preloaded with3H‐NA in the presence of normetanephrine (10‐4M), the stimulation‐induced Ca2+‐insensitive outflows were markedly reduced. The results suggest that the field stimulation‐induced release of3H‐NA is in part of extraneuronal origin.
Experimental Cardiac Hypertrophy and the Synthesis of Poly(A) Containing RNA and of Myocardial Proteins in the Rat: The Effect of Digitoxin Treatment
Authors: Turto Heikki
Published: December 2008

The synthesis of poly(A) containing RNA was increased in heart of non‐digitalized and digitalized rats after aortic constriction, the increase being of the same degree as that of the RNA lacking this sequence. No differences were found, either in the absence or presence of polyuridylic acid, in the incorporation of radioactivity into protein by cardiac ribosomes isolated from animals treated differently. It may be concluded, that after the constriction of the aorta the synthesis of mRNA proceeds at a similar rate as that of the bulk RNA, and that the treatment of the animals with digitoxin does not abolish the stimulus for hypertrophy.
Relationship between Sarcomere Length and Active Force in Rabbit Papillary Muscle1
Authors: Wohlfart B. , Grimm A. F. , Edman K. A. P.
Published: December 2008

Isometric peak twitch force (stimulation frequency 0.5/s; 29.5–30.5°C) was correlated with sarcomere length in isolated papillary muscles of the rabbit. Sarcomere length was measured from photographic recordings (1.5 ms exposure time) performed at rest between contractions and at the time of isometric peak twitch force. The sarcomere length at rest was found to be relatively uniform throughout the preparation and to be linearly related to the overall muscle length within the range Lmax‐ 0.85 Lmax. The distribution of sarcomere lengths increased considerably as the muscle went from rest to activity. Studies of surface markers showed different degrees of shortening (or elongation) of individual segments along the length of the preparation. The mean resting sarcomere length at Lmax (the optimum muscle length for force production) was 2.44±0.01 μm (grand mean ± S.E., 7 muscles). The mean active sarcomere length at Lmax was 2.29 ± 0.04 /μm. Active force declined steeply as the muscle length was reduced below Lmax. At a resting sarcomere length of 2.0 μm, active force was approximately 1/3 of the maximum. The observed differences between the length‐tension relationships in myocardium (twitch responses) and skeletal muscle (tetanic contractions) are discussed on the basis of a length dependency of the activation process in cardiac muscle.
Effect of Atropine and SC‐15396 on Stimulated Gastric Acid Secretion in the Atlantic Cod, Gadus morhua
Authors: Holstein Björn
Published: December 2008

Gastric acid secretion was measured in swimming codfish surgically equipped with a catheter draining the stomach. Gastric acid secretion was stimulated by histamine (5 or 15μg/kg‐h) or by carbachol (5μg/kg‐h). Pretreatment with atropine (1 μmol/kg‐h) completely prevented the acid secretion induced by carbachol, but did not influence the secretion induced by histamine. Atropine had marked effects on the motor functions of the stomach, and seriously reduced the volume draining from the stomach. Infusion of phenol red indicated that the decrease in volume was due to a decrease in recovery of ingested water. SC‐15396, “antigastrin”, significantly depressed acid secretion induced by histamine, and reduced carbachol‐stimulated secretion, although the latter was statistically insignificant. The effects of SC‐15396 is discussed with reference to the absence of receptors for gastrin related to gastric acid secretion in the codfish stomach.
Frequency‐Dependence of3H‐Noradrenaline Secretion from Human Vasoconstrictor Nerves: Modification by Factors Interfering with α‐ or β‐Adrenoceptor or Prostaglandin E2Mediated Control
Authors: Stjärne L. , Brundin J.
Published: December 2008

Isolated superfused field stimulated human omental arteries and veins, preincubated with3H‐(‐)‐nor‐adrenaline (NA) were used to study the frequency dependence of NA secretion and of the mechanisms for its local feedback control.3H‐NA secretion per shock was found to be basically a simple hyperbolic function of the stimulation frequency from 1 to 30 Hz, as long as secretion was restricted by prostaglandin E2(PGE2). In the absence of restriction, or during facilitation,3H‐NA secretion per shock reached its maximum at 10 Hz and then declined at 30 Hz, indicating ‘overload’ in some link in the secretory mechanism.3H‐NA secretion was depressed by exogenous NA and by PGE2, and enhanced by isoprenaline, phentolamine and by blockade of PGE2formation. Most of these effects were inversely related to the stimulation frequency. Attempts were made to study interactions between the different control mechanisms and to evaluate possiblein vivoconsequences of disturbance of adrenergic neuroeffector transmission by interference with the local control of the secretory mechanisms.
Effects of Sympathetic Nerve Stimulation in the Presence of a Slow Parasympathetic Secretion in the Parotid and Submaxillary Glands of the Rabbit
Authors: Gjörstrup Per
Published: December 2008

Sympathetic secretory responses from the parotid and the submaxillary glands of the rabbit were studied; sympathetic excitation occurred either alone or during a slow parasympathetic background secretion, imitating the resting secretion normally present. The fairly rapid sympathetically evoked flow of saliva from the parotid gland was, in the background secretion, further increased and obtained at low frequencies, which at sympathetic stimulation alone were subthreshold. The effects, which could be repeated with sympathomimetic drugs in a pilocarpine induced secretion, were abolished by αand βadrenoceptor blockade in combination. The submaxillary gland gave a very scanty secretion on sympathetic excitation, the effects being mediated via β‐adrenoceptors. The responses were not increased in a background secretion but the main effect of sympathetic activation was to retard the salivary flow. The retardation was attributed to vasoconstriction accompanying sympathetic excitation. Eliminating the vasoconstrictor responses, while retaining the sympathetic secretory effects, did not reveal any increase of the sympathetic salivary responses in the submaxillary gland.
Cardiac Receptors Activated during the Hypothalamic Defence Reaction
Authors: Wennergren Goran , Thorén Peter , Lisander Björn
Published: December 2008

The increases of arterial blood pressure, cardiac inotropy and venous return seen during the hypothalamic defence reaction are likely to lead to concomitant excitation of left ventricular receptors with nonmedullated afferents. The integrated efferent pattern of response resulting from the central interaction between the defence reaction and influences from the mentioned cardiac receptors was recently analyzed. These two, essentially opposing influences on the circulation were then seen to interact in such a way as to produce an optimal cardiovascular response with respect to increases in cardiac output and blood supply to the skeletal muscles. However, direct electrophysiological recordings from nonmedullated cardiac afferents during defence area stimulation have hitherto been lacking. The present experiments, performed on chloralose‐anesthetized cats and utilizing electrophysiological recordings, clearly demonstrate that the left ventricular receptors are activated by the cardiovascular readjustments induced by the defence reaction. Defence area stimulation increased the activity of these receptors, which work within a very narrow, low frequency range, from 1.1 ± 0.3 imp/s to 2.7 ± 0.7 imp/s associated with rises in systolic blood pressure (afterload) and heart rate. Normally such a receptor activation would induce considerable bradycardia and sympathetic inhibition, but particularly the reflex bradycardia is centrally suppressed by a concomitant defence area activation. The marked bradycardia often seen immediately upon interruption of the defence area stimulation is, however, probably to a great extent initiated from the excited ventricular receptors.
Effects of Low Tissue Temperature on Peripheral Vascular Control Mechanisms
Authors: Reite Ola B. , Millard Ronald W. , Johansen Kjell
Published: December 2008

Influence of low temperatures on vascular effects produced by adrenaline, noradrenaline and vasoconstrictor nerve stimulation was studied in the feet of ducks. Observations were made on isolated preparations as well as on intact ducks with one or both feet immersed in ice‐water. Isolated preparations were perfused with physiological solution and information on changes in vascular resistance obtained by direct measurement of flow changes during perfusion at constant pressure or by measuring changes in perfusion pressure during perfusion at constant flow. In intact ducks changes in blood flow were recorded as changes in digital subcutaneous tissue temperature. The study revealed that in the duck foot a relatively large fraction of the resistance to blood flow is found in the arteries of the proximal part of the foot. During cooling of the foot the influence of vasoconstrictor nerve stimulation and low doses of adrenaline and noradrenaline on vascular resistance is gradually lost, and it is negligible at temperatures below 8°C. At these low temperatures the blood vessels stay dilated and blood flow through the web seems to be determined by the digital arterial blood pressure.
Effect of Dehydration on Renal Blood Flow in Dog
Authors: Kirkebø A. , Tyssebotn I.
Published: December 2008

The effect of dehydration on intrarenal blood flow was investigated in 11 dogs, using polarographic determination of H2‐gas desaturation for measuring local blood flow in inner cortex (ICF) and outer cortex (OCF). Dehydration was induced by 48 h water deprivation + 2–300 mg ethacrynic acid (EA) per os the day before the experiment. Compared to a control group (n = 9) ICF was markedly reduced to 2.40 ± 0.47 ml/min×g (control 3.23 ± 0.64) whereas OCF 3.29 ± 0.80 ml/min×g was nearly unchanged (control 3.59±0.85). The ratio OCF/ICF was increased to 1.37 (1.11). Further dehydration by hypertonic peritoneal dialysis for 3 h increased Hct to 60 ± 4 and further reduced OCF and ICF, without significant change of the OCF/ICF‐ratio. At Hct above 55 sudden and intermittent changes in local cortical blood flow were recorded randomly at individual electrode sites, showing ischemic periods lasting for 1 to 60 min. Such flow changes were observed in 13 of 14 expts. and were not accompanied by changes in RBF. It is concluded that moderate dehydration causes a greater reduction of ICF than of OCF. Severe dehydration gives in addition rise to patchy, intermittent ischemia in both cortical layers.
Circulatory Reflex Responses during the Initial Stage of Feline Endotoxin Shock
Authors: Halinen M. O. , Hakumäki M. O. K. , Sarajas H. S. S.
Published: December 2008

Cardiovascular and autonomic nervous responses to an injection of E. coli endotoxin were followed for up to 15 min. in cats anesthetized with chloralose and given artificial respiration. Within 60 seconds, endotoxin induced a drop of aortic pressure, with simultaneous cardiac acceleration and slight central venous hypertension. There was an associated, almost complete cessation of the aortic arch baroreceptor afferentation. The cardiac sympathetic efferentation increased up to 1.4 times the control level at its maximum. The splenic sympathetic efferentation increased up to 10.6 times the control level at the end of the 15 min period, when the other parameters studied showed a trend to control level. The sympathetic autonomic system seems to be activated through cardiovascular receptors sensing hemodynamic changes touched off by endotoxin‐induced release of vasoactive substances.
Influence of Muscle Length on the Force‐Velocity Relation of K+‐contractures in Smooth Muscle from Rabbit Urinary Bladder
Authors: Uvelius Bengt
Published: December 2008

Force‐velocity relations of K+‐contractures of longitudinal smooth muscle from rabbit urinary bladder were studied by isotonic quick release at 37°C. In order to minimize the influence of parallel elasticity the study was limited to the rising part of the length‐tension curve. The force‐velocity data fitted well with Hill's equation. The in situ length of the strip at a bladder volume of 10 ml is called L10. This length is 50% of that at which maximum active tension is developed. At L10 Vmax was 0.29 muscle lengths per second and it was estimated to be 0.36 lengths/s at optimum length. Constant b in Hill's equation had a value of 0.052 L10/s and it was unaffected by length changes over the interval 0.69 L10‐ 1.44 L10. At L10 a/Po was 0.17. In the interval given above, a/Po decreased with increasing length in proportion to the increase in Po, indicating that a was also length independent. According to Hill's equation [V = b(Po ‐ P)/(P + a)], V should increase in proportion to (Po ‐ P) when the muscle length is increased if a and b are constants. Such a linear relation was found at shorter lengths but at lengths close to or at the length for maximum active tension, V increased more than (Po ‐ P). Two possible explanations were considered; firstly that b/(P+a) increased, and secondly that the load on the contractile element could be less than P due to an influence of the considerable tension in the parallel elastic element at these lengths. The series elastic recoil of the active muscle amounted to 3–4% of the muscle length when released to zero tension.
Characteristics of Aortic Baroreceptors with Non‐medullated Afferents Arising from the Aortic Arch of Rabbits with Chronic Renovascular Hypertension
Authors: Jones John V. , Thorén Peter N.
Published: December 2008

The characteristics of 47 non‐medullated and 54 medullated fibres arising from the aortic arches of 6 hypertensive rabbits have been investigated. The threshold for activation of the aortic C‐fibres lay between 78 and 190 (mean 122) mmHg. The threshold for activation of 54 medullated aortic baroreceptors in the same animals was from 70 to 140 (mean 109) mmHg. At the awake mean arterial blood pressure (MABP) of these hypertensive rabbits (143 mmHg) all the medullated fibres were active as were 78% of the C‐fibres. In contrast in a group of normotensive animals 91% of the medullated and only 28% of the non‐medullated fibres were active. Pressure response curves were constructed for 19 C‐fibres and 12 medullated fibres from the hypertensive animals. At a MABP of 110 mmHg the firing in the non‐medullated fibres was 2.0 Hz as compared with 19.0 Hz in the medullated fibres and at the awake MABP mean firing was 9.0 Hz in the non‐medullated fibres and 48.0 Hz in the medullated fibres. The firing at awake MABP was considerably higher in the hypertensives (9.0 Hz) as compared with the normotensives (1.1 Hz). Thus these data indicate that although the aortic C‐fibres are reset in chronic hypertension, they are reset less than the medullated aortic baroreceptors from the same animal. It is suggested that arterial baroreceptor C‐fibres may have an important role in the tonic control of the circulation in hypertension.
Effect of Endurance Training on the Capacity of Red and White Skeletal Muscle of Mouse to Oxidize Carboxyl‐14C‐labelled Palmitate
Authors: Salminen Antero , Vihko Veikko , Pilström Lars
Published: December 2008

Three groups of mice were trained for 1, 4 and 5 months according to different running programs on a motor driven treadmill and the fatty acid oxidation capacity (FAO) and the activities of some enzymes of energy metabolism (cytochrome c oxidase, malate dehydrogenase, triosephosphate dehydrogenase, and lactate dehydrogenase) were determined from m. quadriceps femoris (MQF). Endurance training increased the FAO [5‐month training, 4 days/week, 30 min/day 22% (p<0.05); 1‐month training, 7 days/week, 150 min/day 37% (p<0.001); 4‐month training, 5 days/week, 60 min/day 24% (p<0.05)]. The activities of cytochrome c oxidase and malate dehydrogenase increased approx. 30% (p< 0.001) whereas triosephosphate dehydrogenase and lactate dehydrogenase activities were not prominently influenced by training. The predominantly red part of MQF of untrained animals oxidized palmitate four times faster than the predominantly white part. The activities of cytochrome c oxidase and malate dehydrogenase were two times higher showing pronounced FAO in the red part. Endurance training increased the FAO and activities of oxidative enzymes in the red and white parts and in the whole muscle relatively equally resulting in similar differences between the muscle types after training. The absolute increase in the FAO of the red muscle was, however, manyfold when compared in chemical units to the white muscle.
Difference in Sensitivity of Parotid Glands brought about by Disuse and Overuse
Authors: Ekström Jörgen , Templeton David
Published: December 2008

The sensitivity to methacholine of the parotid glands in rats maintained on a liquid diet (aiming at sensitization) for a period of 2 weeks or 3–4 weeks was compared with that of the parotid glands in rats on a pelleted bulk diet (aiming at desensitization). In the rats on the liquid diet, it was found that the dose needed to evoke a just perceptible secretion of saliva was smaller, that the secretion started earlier and continued over a longer time period, and further that the amount of saliva secreted expressed per gland weight in response to submaximal doses of the sialogogue drug was bigger when compared with the rats on the pelleted bulk diet. These findings are interpreted as signs of a higher degree of sensitivity of the glands in the rats on the liquid diet than of those in the rats on the pelleted bulk diet.
Low Intensity Training, Inactivity and Resumed Training in Sedentary Men
Authors: ÖRlander Jan , Kiessling Karl‐Heinz , Karlsson Jan , Ekblom Björn
Published: December 2008

The effects of a low intensity training regimen, consisting of two 7‐week periods with an interspersed 8‐week inactivity period were investigated in 16 sedentary men. A follow‐up was made on 7 subjects after 38 additional weeks' training. Systemic as well as local effects were studied using exercise tests and leg muscle biopsies. The two 7‐week training periods both resulted in a 6% increase in Vo2 max and a lowered heart rate during submaximal work. No persisting training effects were detected by exercise tests after inactivity. In skeletal muscle, however, striking differences in enzyme activity pattern and ultrastructure were observed between the two periods, indicating that some training effect of importance for muscle metabolic adaptation might have persisted during inactivity. It is suggested that such an effect might be associated with the local oxygen supply. During the 38‐week training period there was a large increase in muscle metabolic capacity, but no change in maximal oxygen uptake. This separation of systemic and local training effects indicates a lack of a direct causal relationship between muscle metabolic potential and maximal oxygen uptake. It is suggested that the elevated muscle oxidative capacity is of importance for an increased endurance capacity.
Impulse Dependent Adaptation in Helix Pomatia Neurones: Effect of the Impulse on the Firing Pattern
Authors: Colding‐Jørgensen Morten
Published: December 2008

In neurones of the ventral ganglion of Helix pomatia an adaptation type is demonstrated, where the impulses contribute to the adaptation, as if a slowly changing outward current were associated to every impulse. The current appears to be accumulated from impulse to impulse and the accumulated current to decrease towards zero in the interval between the impulses. This type of adaptation is called impulse dependent. A method to distinguish between impulse dependent adaptation and impulse independent adaptation is described. Typical adaptation curves for the impulse dependent adaptation are shown. With a strong adaptation there is a linear relation between the steady state frequency and the applied stimulus. When stimuli of short duration are applied repetitively, neurones with impulse dependent adaptation respond with spikes on an increasing fraction of the stimuli as the stimulus strength is increased. A simplified model of the adaptation is proposed, and the firing pattern of the cells is compared with that of the model. In this way numerical values of the model parameters have been estimated.
Impulse Dependent Adaptation in Helix Pomatia Neurones: Demonstration of the Adaptation Conductance
Authors: Colding‐Jørgensen Morten
Published: December 2008

By conventional voltage clamp methods an increase in membrane conductance after a depolarizing pulse is demonstrated in neurones of Helix pomatia. This increase decays exponentially with a time constant in the range of 5–20 s. The rise of the conductance during the depolarization can be represented by 3 exponentials with time constants from 12 ms to 1 s. The steady state value of the conductance depends on the membrane potential in a sigmoid manner. The conductance gives rise to an outward current, which appears to be carried by potassium ions. The firing pattern of the cell is governed by the conductance. A short, rectangular potential change, a pulse clamp, is used to disturb the firing pattern of the freely firing cell. The effect on the firing pattern depends on the height and duration of the clamp pulse in the same manner as the conductance increase. The normal firing produces similar changes in the membrane conductance.
Angiotensin II: Intratubular and Renal Capillary Pressure Regulation in the Rat Kidney
Authors: Steven Kenneth , Thorpe Darrell H.
Published: December 2008

Experiments were designed to test the hypothesis that angiotensin II, in its action on receptor sites in vascular smooth muscle and the proximal tubule, acts homeostatically to stabilize hydrostatic pressure in the proximal tubule, and as a consequence, maintains a constant flow of fluid to the distal tubule. Infusion, at 20 n1 min‐1, of Ileu5‐angiotensin II [(Ileu5)‐A II] (20 ng m1‐1) into peritubular capillaries adjacent to a proximal tubule was found to be accompanied by an increase in hydrostatic pressure in both the infused capillaries and the proximal tubule and by a decrease in the rate of proximal fluid reabsorption (RPFR). RPFR was derived from timed quantitative collections of tubular fluid from the last superficial proximal segments. Tubular pressure before infusion and pressures in noninfused capillaries were not related to plasma renin activity (PRA). 1‐Sarcosine, 8‐alanine‐angiotensin II [(Sar1, Ala8)‐A II] is known to be a competitive antagonist to the action of angiotensin II on vascular smooth muscle and on adrenocortical zona glomerulosa cells. Infusion, at 20 n1 min‐1, of (Sar1, Ala8)‐A II (333 ng m1‐1) into peritubular capillaries caused a decrease in hydrostatic pressure in the peritubular capillaries and adjacent proximal tubules. The most striking fall in pressure (‐4 cmH2O) occurred in rats with high levels of PRA. No pressure change resulted from infusion with a mixture of (Ileu5)‐A II and (Sar1, Ala8)‐A II. (Sar1, Ala8)‐A II in this mixture blocked the inhibitory effect of (Ileu5)‐A II on RPFR, but infusion of the angiotensin antagonist alone did not influence RPFR. It is concluded that angiotensin II is a physiological regulator of hydrostatic pressure in both the proximal tubule and the peritubular capillaries.
In Vivo Turnover Rate of Acetylcholine in Rat Brain Parts at Elevated Steady‐State Concentration of Plasma Choline
Authors: Eckernäs Sven‐Åke , Sahlström Lena , Aquilonius Sten‐Magnus
Published: December 2008

Cortical and striatal turnover rates of acetylcholine TRAchwere estimated by applying steady‐state tracer kinetics in rats killed by microwave irradiation following a constant i.v. infusion of3H‐Ch. In control rats TRAChwas 3.6 nmol · g‐1· min‐1in the cortex and 23.8 nmol · g‐1· min‐1in the striatum. When steady‐state plasma concentrations of Ch were increased from 17 to 140 μmol · 11by a 15‐min infusion of unlabeled Ch the corresponding TRAChwere 3.6 nmol · g‐1· min‐1and 21.4 nmol · g‐1· min‐1, respectively. These results indicate that increased plasma levels of Ch are not accompanied by increased synthesis of brain ACh.
Effect of the Preceding Day's Energy Intake on the Total Energy Cost of Light Exercise
Authors: Garby Lars , Lammert Ole
Published: December 2008

The effect of a variation in the preceding day's dietary energy intake‐4, 10 and 18 MJ‐on the oxygen consumption and respiratory quotient at rest and at work before and after a test meal (4 MJ) was investigated. 7 normal male subjects were studied at 3 different experimental situations. During the first day the subjects had an energy intake of 10 MJ and normal activity. The following morning measurements of V̇o2 and V̇co2 were performed at rest and at work on a bicycle ergometer (36 W) before and after the test meal. The same measurements were performed on the following day but the dietary intake between the two sets of measurement was then either 6, 0 or 14 MJ. No significant effect was found of the preceding day's dietary energy intake on the oxygen consumption or on the energy transformed during rest, during exercise before and after the test meal. The results do no support the conclusions of previously published studies, proposing a significant feed‐back mechanism tending to control the body energy content by regulation of the energy expenditure through chemical or mechanical uncoupling.