bluuebunny/crossref_metadata_2025 huggingface dataset:
Capillary Pressure in Deep and Superficial Glomeruli of the Rat Kidney
Authors: Aukland K. , Tønder K. Heyeraas , Næss G.
Published: December 2008

A new technique has been developed to make deep renal cortical structures in rats accessible for micro‐puncture: The left kidney is dissected free and immobilized in a lucite cup. A lense‐shaped slice, 1–2 mm thick and about 5×5 mm wide, is cut off from the dorsal aspect of the kidney. Blood oozing from the cut surface is removed by flushing with saline and suction by microsponges. The bleeding stops in 1–3 min and causes none or only transient fall in arterial pressure (PA). Up to 40 glomeruli become visible and remain circulated for several hours, as shown by injection of dye or silicone rubber. Glomerular capillary pressures (PG), measured with servocontrolled counter pressure (Wiederhielm), showed no consistent change with time and no correlation to PA. Average PG± S.E. in mmHg (number of glomeruli in parantheses) were: Wistar rats (WR), Inactin anesthesia, 57.8 ± 1.4 (41), Membumal anesthesia, 58.1 ± 1.3 (13). Sprague Dawley rats, Inactin, 58.1 ± 1.7 (14). In WR, PG was lower in deep than in midcortical glomeruli: ≤ 0.4 mm below kidney surface, 57.9 ± 1.8 (20); 0.5‐0.9 mm: 60.5+1.5 (20) and ≥ 1.0 mm: 53.8 ± 2.5 (13). Pressure in Bowman's capsule: 11.2 ± 0.6 (30). The observed PG is higher than previously reported on the Munich mutant strain of WR, and suggests that glomerular filtration equilibrium is not reached.
Catecholamines and Pancreatic Hormones during Autonomic Blockade in Exercising Man
Authors: Galbo H. , Christensen N. J. , Holst J. J.
Published: December 2008

The importance of autonomic nervous activity for the pancreatic hormonal response to exercise in man was studied. 7 men ran at 58% of V̇o2max (determined without administration of drugs) to exhaustion during a‐adrenergic blockade with phentolamine (P), during parasympathetic blockade with atropine (A), or without drugs (C). At rest phentolamine increased the plasma concentrations of both insulin and norepinephrine. During exercise norepinephrine concentrations increased and were in P experiments 3 times the concentrations in C experiments. Insulin always declined during exercise but in P experiments never decreased below basal levels. At identical times neither glucagon nor glucose differed significantly in the different expts. Thus during exercise α‐adrenergic blockade increased insulin concentrations but did not diminish the glucagon response. Nor was this response increased when β‐receptor stimulation in P experiments was intensified by the particularly high catecholamine concentrations. The concentrations of FFA, glycerol and lactate were highest in P experiments and identical in A and C experiments. These findings indicate that during prolonged moderate exercise in man insulin secretion is depressed by stimulation of α‐adrenergic receptors whereas glucagon secretion is not influenced by adrenergic receptors. Stimulation of β‐adrenergic receptors enhances lipolysis but neither lipolysis nor pancreatic hormonal secretion is influenced by cholinergic activity during exercise.
Transmembrane Potential Measurements as an Indicator of Heterogeneous Distribution of Nutritive Blood Flow in Skeletal Muscle during Shock
Authors: Haljämae Hengo , Jennische Eva , Medgeård Alf
Published: December 2008

The heterogeneity of nutritive skeletal muscle blood flow during shock was studied in terms of cellular transmembrane potential variations. Shock was induced in dogs by exteriorization of the small intestine for 3 h, whereafter the intestine was replaced and the dogs were studied for another 3–4 h. Transmembrane potentials of single skeletal muscle cells were recorded by the use of modified Ling‐Gerard microelectrodes. The mean resting transmembrane potential in control animals was ‐90.4 mV ± 0.7. The variation in transmembrane potential between adjacent fibers was small. During shock there was a significant decrease in the mean transmembrane potential and at the same time there was an increasing variation of up to 29 mV in the values between adjacent fibers. To exclude metabolic differences between red and white fibers as the main reason for this increasing heterogeneity of transmembrane potentials of adjacent fibers, complete tourniquet ischemia was also studied. The total tissue ischemia resulted in a marked reduction of the transmembrane potential in all cells with only small differences between adjacent fibers. After release of the tourniquet a marked spread of resting membrane potentials, with variations of 17–25 mV between adjacent fibers, occurred. This variation was similar to that observed during shock. It is concluded that repeated transmembrane potential registrations may reveal the variable state of adjacent cells subjected to a heterogeneous nutritive blood flow in shock.
Apnoea and Bradycardia from Submersion in “Chronically” Decerebrated Cats
Authors: Martner Jan , Wadenvik Hans , Lisander Björn
Published: December 2008

In “chronically” but not in acutely decerebrated cats, submersion of the head caused apnoea and marked bradycardia, associated with a maintained or slightly raised arterial pressure. Since these reflex adjustments, though very reproducible, occurred with a varying latency and could be induced also by nasal injection of water, they appeared to be, at least in part, elicited from the upper respiratory passages. Thus, a terrestrial mammal, reputed to shun any form of immersion, can exhibit adjustments during head submersion, similar to those in habitually diving species. This response pattern is basically organized at the lower brainstem level.
Role of the Adrenergic Nervous System in Development of Training‐Induced Bradycardia
Authors: Sigvardsson K. , Svanfeldt E. , Kilbom Å.
Published: December 2008

Sprague‐Dawley rats, normal and chemically sympathectomized with 6‐hydroxy‐dopamine, were trained by treadmill running. The normal rats, unlike the sympathectomized animals, showed reduction of the exercise heart rate after the training period. Compared to a sedentary control group the sympathectomized rats showed no difference in intrinsic heart rate after pithing and denervation and no increase in heart weight. The increase of the heart weight/body weight ratio after training was smaller in the sympathectomized group than in the normal one. The results show that a functioning adrenergic nervous system is necessary for an efficient adaptation to physical training. Administration of noradrenaline to pithed trained and untrained rats showed that betaadrenergic receptor sensitivity was not altered by physical training. The intrinsic heart rate of normal trained rats was lower than that of normal control rats.
Local Reflex in Microcirculation in Human Skeletal Muscle
Authors: Henriksen O. , Sejrsen P.
Published: December 2008

The effect of venous stasis of 40 mmHg upon blood flow in human skeletal muscle was studied in four normal subjects and in two chronically sympathectomized patients. Blood flow in skeletal muscle was measured by the local 133Xenon washout technique. Blood flow decreased about 30 per cent during venous stasis of 40 mmHg. In a “passive vascular bed” induced by means of histamine, blood flow decreased only by 16 per cent, indicating that the decrease in blood flow is due to a vasoconstrictor response to increase in vascular transmural pressure. The vasoconstrictor response was unaffected by a spinal sympathetic blockade, but was blocked in areas infiltrated with lidocaine or with phentolamine. The vasoconstrictor response was present in the nonoperated limbs used as a control, but abolished in the denervated arms in the two chronically sympathectomized patients. The findings strongly suggest that the vasoconstrictor response in skeletal muscle is due to a local nervous mechanism involving adrenergic fibres. Thus a local reflex mechanism, most likely a sympathetic axon reflex, seems to be present in human skeletal muscle as in cutaneous and subcutaneous tissue. This indicates that about 45 per cent of the change in total vascular conductance, when a person changes from supine to upright position, is due to this local reflex mechanism operating independently of the central nervous system.
Efflux of 5‐Hydroxytryptamine from Synaptosomes of Rat Cerebral Cortex
Authors: Ross Svante B. , Kelder Diana
Published: December 2008

The efflux of3H‐5‐HT from a crude synaptosome preparation of the cerebral cortex of reserpinized rats was examined. The synaptosomes were loaded with3H‐5‐HT by pre‐incubation of the homogenate in presence of pargyline and desipramine in order to inhibit deamination of 5‐HT and uptake into noradrenergic neurones. The synaptosomes were collected by centrifugation, washed and resuspended in 0.25 M sucrose. No spontaneous efflux of 5‐HT was detectable at 0°C but marked efflux was observed at 27°C and 37°C. 4‐Chloroamphetamine, low external Na+concentration, ouabain and the depolarizing agent veratridine markedly accelerated the initial (5 min) efflux. Inhibitors of the neuronal 5‐HT uptake,e.g.chlorimipramine, H 102/09 and A 23189, antagonized the 5‐HT efflux evoked by these means, whereas desipramine, which is a poor inhibitor of the 5‐HT uptake, had only slight effect on the 5‐HT efflux. It is suggested that 5‐HT can be actively transported out from the synaptosomes by the reversed 5‐HT uptake mechanism.
The Effect of Teeth Amputations on the Choline Aeetyltransferase Activity of Rat Submaxillary Glands
Authors: Ekström Jörgen
Published: December 2008

The choline aeetyltransferase activity in parasympathetically decentralized glands was unaffected by repeated teeth amputations over a period of 2 weeks, while after the same period of time the treatment caused the enzyme activity to increase in innervated glands. It appears that the enzyme in the postganglionic nerve is for its activity dependent on an intact connection with the central nervous system. The increase in enzyme activity is attributed to an enhanced reflex stimulation of the glands from pulpal receptors.
Carbonic Anhydrase in the Intestinal Tract of the Guinea‐pig
Authors: LöNNERHOLM GUDMAR
Published: December 2008

The distribution of carbonic anhydrase activity in the intestinal tract of the guinea‐pig was studied by the histochemical method of Hansson. Enzyme activity was demonstrated in epithelial cells, erythrocytes and capillary walls. In the gastric mucosa parietal cells, surface mucous cells and neck mucous cells were highly active. In the small intestine only a few epithelial cells on the villi and in the upper part of the crypts showed enzyme activity. They seemed to be randomly scattered among inactive ones. It is not clear at present if they represent a distinct cell type or specialized absorptive cells. In the proximal colon most surface epithelial cells were highly active (goblet cells were inactive), whereas the surface cells in the distal colon showed less activity with a more varying degree of staining. In the cecum enzyme activity was found in the surface epithelium and in the upper part of the crypts, the staining being most marked at the luminal border of the surface cells. The staining reaction was completely inhibited in all tissues by 10 μM acetazolamide, except for the luminal staining of the cecum, which was inhibited only by 100 μM acetazolamide. This indicates the presence of high concentrations of carbonic anhydrase, probably of the “low activity” form, at this locus. Mucosal scrapings were taken from the intestinal tissues, homogenized and assayed for carbonic anhydrase activity by a changing‐pH indicator method. The results confirm those of previous studies and correlate well with the histochemical findings.
Potentiation by Carbachol and Aminophylline of Histamine‐ and db‐cAMP‐Induced Parietal Cell Activity in Isolated Gastric Glands
Authors: Berglindh Thomas
Published: December 2008

The response to combinations of gastric acid secretagogues was studied in isolated glands from the rabbit gastric mucosa in terms of changes in oxygen consumption and accumulation of the weak base aminopyrine (AP). The latter reflects the acid secreting status of the glands. The following secretagogues were investigated: histamine, carbachol, aminophylline and db‐cAMP. The histamine respiratory dose‐response curve was shifted to the left in the presence of the phosphodiesterase inhibitor aminophylline. Both ED‐50 and maximum response were significantly increased. Histamine‐induced AP accumulation was also strongly enhanced by aminophylline (5 × 10‐4 M). These results are consistent with the hypothesis that histamine stimulation of acid secretion is mediated by cyclic AMP. Carbachol‐stimulated oxygen consumption could not be potentiated by aminophylline and the combined effect was only additive. The response to a combination of histamine and carbachol was a significant increase in oxygen consumption above what could be expected from an additive effect alone. Carbachol addition to glands prestimulated with histamine gave a rapid increase in the respiratory rate resulting in a new steady state level within 10–15 min, as compared with a time constant of about 40 min when both drugs were added simultaneously. Likewise AP accumulation increased more rapidly and reached a higher value after addition of histamine + carbachol as compared with histamine alone. The db‐cAMP‐stimulated oxygen consumption was in all respects equally affected by carbachol as was histamine stimulation. This indicates that the well known cholinergic potentiation of histamine stimulation is not due to an increased sensitivity of the histamine receptor but is of a more general nature. A mechanism involving intracellular availability of Ca2+ is proposed as one possible explanation of this potentiation.
The Effect of Plasma Proteins on the Capillary Permeability in the rete mirabile of the Eel (Anguilla vulgaris L.)
Authors: Myhre Kjell , Steen Johan B.
Published: December 2008

Measurements of transcapillary exchange of high‐molecular dextrans, K+ and THO in the rete mirabile of the eel (Anguilla vulgaris L.) have been made under steady‐state conditions while varying the amounts of plasma proteins in the perfusates. When the perfusates contained 20% or less horse serum the permeabilities of D‐75 000. K. and THO increased significantly. The effect on the K+ permeability was irreversible while that on D‐75 000 and THO was not. The permeability was unaffected when the perfusate contained 30% serum or more. Adding 1.3g/100 ml bovine albumin to the perfusate maintained the D‐75 000 and THO permeabilities unchanged while that of K˜ appeared to increase. At an albumin content of 0.33 g/100 ml the effect was similar to that produced by low serum perfusates. Our main conclusion is that lack of the albumin fraction of the plasma proteins reversibly increases the intercellular pore area and irreversibly changes the K permeability of the cell membrane.
Skeletal Muscle Fiber Splitting Induced by Weight‐Lifting Exercise in Cats
Authors: Gonyea W. , Ericson G. C. , Bonde‐Petersen F.
Published: December 2008

Adult skeletal muscle hypertrophy induced by exercise has been thought to be exclusively related to an increase in cross‐section area of individual muscle fibers and not to an increase in the number of muscle fibers. Recent experiments using surgical intervention to cause muscle overload have induced an increase in fiber numbers; however, the muscle also exhibited pathological alterations. The purpose of this study was to determine if an exercise regimen also induced hyperplasia. Cats were trained to lift weights with their right forelimb to receive a food reward. After 19–46 weeks of training, the flexor carpi radialis muscle (FCR) was removed and prepared for histochemical examination. The total number of muscle fibers of the right exercised FCR increased significantly (19.3%) when compared with that of the unexercised left FCR (p < 0.05). This increase was found to be due to muscle fiber splitting.
Influence of Acetate on the Metabolism of β‐Hydroxybutyrate in the Perfused Hind‐Quarter of the Rat
Authors: Karlsson N. , Fellenius E. , Kiessling K.‐H.
Published: December 2008

The effect of acetate, at concentrations normally found during ethanol combustion in intact animals and man in vivo, on the uptake and oxidation of β‐hydroxybutyrate by the perfused rat hind‐quarter was studied. The addition of acetate did not significantly affect the total uptake of β‐hydroxybutyrate, but caused a 40 % decrease in the oxidation of β‐hydroxybutyrate to CO2. The oxidation of 14CO2‐hydroxybutyrate to 14CO2 accounted for about 10 % of the total oxygen consumption by the perfused muscle in the absence of acetate. In the presence of acetate this figure was reduced to about 5 %. The addition of β‐hydroxybutyrate did not significantly affect the metabolic fate of 14C‐acetate. It is concluded that acetate is preferred as oxidative substrate to β‐hydroxybutyrate. The inhibited oxidation of β‐hydroxybutyrate by acetate did not affect the concentration ratio between β‐hydroxybutyrate and acetoacetate in the medium at the end of the perfusion, indicating that the ability of the muscle tissue to restore an increased redoxlevel, “exported” from the liver during ethanol combustion to extrahepatic tissues, was not impaired by acetate.
Flow and Composition of Leg Lymph in Normal Men during Venous Stasis, Muscular Activity and Local Hyperthermia
Authors: Olszewski W. , Engeset A. , Icger P. M. , Sokolowski J. , Theodorsen L.
Published: December 2008

Changes in normal human leg lymph protein concentration, output, and lymph flow/lymph protein concentration relationship, as well as lactate dehydrogenase and alkaline phosphatase activity were followed during procedures known to increase capillary filtration as venous stasis, muscular exercise and warming of tissues. Lymph flow increased by 83% during two hour ergometer cycling, and by 117% during two hour warm water foot bath. During a two hour period of venous stasis lymph flow dropped by 50%. There was an increase in lymph flow during the rest period following all three types of experiment, most pronounced after foot warming. An inverse relationship between the lymph flow rate and lymph protein concentration was found. Lymph enzymes followed the same pattern of changes as total protein.
Influence of Acetate on the Metabolism of Palmitate in the Perfused Hind‐Quarter of the Rat
Authors: Karlsson N. , Fellenius E. , Kiessling K.‐H.
Published: December 2008

The metabolism of l‐14C‐palmitate and its metabolic interaction with U‐14C‐acetate were studied in the perfused hind‐quarter of the rat. 9% of l‐14C‐palmitate taken up was oxidized to 14CO2 accounting for 7% of total oxygen consumption by the perfused tissue. Most label from l‐14C‐palmitate was found in the lipid fraction of the muscle tissue. In spite of a 40% inhibition of palmitate oxidation, acetate only caused minor changes in the overall metabolism of palmitate. U‐14C‐acetate was mainly oxidized to 14CO2 and the oxygen consumption due to oxidation of acetate accounted for 20–30% of the total oxygen uptake. Minor amounts of 14C‐acetate were found in muscle lipids. The addition of palmitate did not alter the metabolism of acetate. It is concluded that the presence of palmitate did not affect 14C‐acetate metabolism, while the presence of acetate inhibited 14C‐palmitate oxidation. The possible sites of interaction are discussed. The found interaction will probably not contribute to any major extent to the disturbed lipid metabolism found in animals and man during ethanol intake. No major changes in the tissue content of high‐energy phosphate compounds were found in the presence of palmitate or acetate or both.
Contractile Responses to Noradrenaline: Varying Dependence on External Calcium of Consecutive Vascular Segments of Perfused Rat Hindquarters
Authors: Sutter Morley C. , Hallback Margareta , Jones John V. , Folkow Björn
Published: December 2008

To study the dependency of vascular smooth muscle contractions, produced by noradrenaline, on the concentration of extracellular calcium, experiments were performed on adult male Wistar rats. The hemodynamic characteristics of the isolated, perfused hindquarters were investigated from maximal dilatation up to maximal, noradrenaline‐induced constriction under constant flow conditions. Pressor responses to noradrenaline in the consecutive segments of the vascular bed (“proximal” and “distal” precapillary resistance vessels and postcapillary resistance vessels) were determined at low (0.2 mM) and at normal (1.5‐2.0 mM) Ca++ concentrations in the perfusate. Dependence on external calcium is much greater peripherally. The smallest pre‐ and postcapillary resistance vessels are the most dependent while the larger, “proximal” precapillary resistance vessels are the least dependent on the availability of external calcium. The results illustrate the considerable differentiation of smooth muscle, depencling on its location along the vascular circuit. They further indicate that it is likely that the hemodynamically so important microvessels are highly dependent on extrinsic Ca++ sources not only concerning their involvement of remote adrenergic control, but also in their maintenance of normally pronounced “myogenic” tone.
Rate‐dependent Myogenic Response of Vascular Smooth Muscle during Imposed Changes in Length and Force
Authors: Sigurdsson Stefan B. , Johansson Börje , Mellander Stefan
Published: December 2008

A recent study of electrical and mechanical responses to stretch in isolated vascular smooth muscle revealed a clear‐cut and graded influence of the rate of change in length, dL/dt (Johansson and Mellander, 1975). This myogenic “dynamic” response at high rates of stretch was much more pronounced than the “static” response to constant, increased (+ 40%) length. In this previous study the mechanical responses were recorded as active force. In view of the fact that myogenic reactions in vivo must be associated with changes in vessel caliber, it was considered of interest to investigate the responses to stretch also in smooth muscle undergoing active shortening. In the present study, as in the one referred to above, electrical and mechanical activity in the isolated rat portal vein was studied by the sucrose gap method. However, in the present experiments the mechanical responses were recorded not only as active force but also as active shortening, making possible a comparison of the myogenic responses under these two types of smooth muscle contraction. Dynamic passive stretch was found to be associated with marked increases in spike discharge and mechanical activity under both these experimental conditions and the quantitative relation between spike discharge and rate of passive stretch (or shortening) was similar. Thus, active shortening of the smooth muscle did not interfere with the ability of the vessel to respond myogenically to passive stretch. A further analysis of the results suggested that, for the preparations as a whole, the dynamic excitatory response was more closely related to the rate of change of passive force, dP/dt, than to dL/dt.
Cardiovascular Control in the Milan Strain of Spontaneously Hypertensive Rat (MHS) at “Rest” and during Acute Mental “Stress”
Authors: Hallbäck Margareta , Jones John V. , Bianchi Giuseppe , Folkow Björn
Published: December 2008

The cardiovascular responses to acute mental “stress” were compared in the Milan strain of spontaneously hypertensive rats (MHS) and in normotensive control rats (NR). Blood pressure and heart rate were followed in pairs of awake MHS and NR, while defence reactions were provoked by alerting stimuli (noise, vibration). No differences were noted between the two groups in response to “stress” although resting heart rate in MHS was lower than in NR. Administration of atropine or propranolol to MHS and NR showed the MHS to have a higher resting vagal tone and lower sympathetic tone than the NR. Subsequent (at least two weeks later) hemodynamic investigation, under nembutal anesthesia, showed no difference in cardiac output between MHS and NR but a higher stroke volume, presumably related to the lower heart rate in MHS. Thus, total peripheral resistance was increased in MHS as was the ratio left ventricular weight/body weight, and in good proportion to the blood pressure rise. Thus MHS differ substantially in both their responses to “stress” and also hemodynamically from the Okamoto strain of spontaneously hypertensive rat (SHR), being the so far most studied and best known model of essential hypertension in man. In MHS the hypertension is more of a systolic type and is of primarily renal origin. As such, MHS provide another model for investigating the polygenic nature of hypertension in man.
Effects of Carbachol and Calcium on the Cyclic Guanosine‐3‘,5’‐Monophosphate (Cyclic GMP) Metabolism in Intestinal Smooth Muscle
Authors: Nilsson Karin B. , Andersson Rolf G. G.
Published: December 2008

In a submaximal concentration carbachol contracted the rabbit colon muscle and increased the cyclic GMP level. The cyclic AMP level was reduced. In a Ca++‐depleted muscle carbachol reduced the cyclic GMP level while the effect on the cyclic AMP content of the muscle was unchanged. Carbachol had no effect on the guanylate cyclase activity of the “plasma membrane fraction” (the 35–45% fraction). In the homogenate and the microsomal fractions Ca++ had no effect on the guanylate activity while it stimulated the enzyme in a soluble fraction. In the “plasma membrane fraction” cyclic GMP released Ca++ from the preloaded fraction and inhibited the Ca++ accumulation. These effects were not found in the vesicular microsomal fraction (the 35% fraction). In both fractions, however, cyclic GMP counteracted the stimulating effect of cyclic AMP. These results indicate that cyclic AMP and cyclic GMP may have antagonistic roles on the Ca++ metabolism in the colon muscle. It is suggested that cyclic GMP may act as some kind of positive feedback mechanism which may have a modulating effect on the release of Ca++ from one pool to another in rabbit colon.
The Effect of Oxygen on Peripheral Airways
Authors: Nielsen Tage Mors , Pedersen Ole Find
Published: December 2008

In ten normal young subjects four alveolar O2‐concentration levels ranging from about 7 % to 95 % were obtained by breathing different concentrations of oxygen in nitrogen at a constant alveolar CO2‐con‐centration of about 5%. Maximum expiratory flows at 60% TLC were measured at each level and corrected for the influence of the expired gas density on flow. The corrected maximum flows were not significantly different, which is taken as evidence of no effect of oxygen on tone of peripheral bronchi.
Spatial Distribution of the EOG in the Rat; a Variation with Odour Quality
Authors: Thommesen G. , Doving K. B.
Published: December 2008

The spatial distribution of olfactory receptors in the rat has been studied by simultaneous recordings of the electroolfactograms (EOGs) from areas of the olfactory mucosa. The potentials were recorded from the dorsal surface of the cribriform plate, leaving the mucosa and the nasal cavities intact. The ratio between the peak amplitude of the EOG potentials served as a measure of the relative sensitivity of one area against the other. The results obtained by stimulating with 31 substances at 38 positions demonstrate a non‐homogeneous distribution of different receptors. Each substance gives a spatial pattern of response efficiency. The response distributions are mapped on the cribriform plate for the different odours.
Changes in ATP and Cyclic Nucleotide Levels during Sympathetic Nerve Stimulation in Canine Subcutaneous Adipose Tissue in situ
Authors: Fredholm Bertil B. , Belfrage Erik , Blaschke Eleonora
Published: December 2008

Subcutaneous adipose tissue in fed, female dogs was isolated. Biopsies of the tissue (30–150 mg) were taken and rapidly frozen in liquid nitrogen before, during and after nerve stimulation (3–4 Hz). In unstimulated adipose tissue the levels of ATP1were 74 ± 7 nmol/g, of cyclic AMP 90 ± 12 pmol/g and of cyclic GMP 18 ± 3 pmol/g (mean + S.E.). During sympathetic nerve stimulation the levels of ATP and cyclic GMP fell by 30 and 50% respectively (p < 0.01), while the cyclic AMP content increased by 50 % (p < 0.05). After nerve stimulation there was a marked increase in glycerol release, and the levels of all three nucleotides returned to control. The fall in ATP during nerve stimulation was essentially eliminated by prior adrenergic a‐receptor blockade. It is concluded that 1) sympathetic nerve stimulation induces a rapid, reversible fall in tissue ATP content, which may be related to hypoxia secondary to the vasoconstriction, and 2) lipolytic responses to sympathetic nerve stimulationin vivoare preceeded by small increases in the tissue cyclic AMP level, and a 3‐fold increase in the cyclic AMP/cyclic GMP ratio.
Renal Na‐K‐ATPase Activity during Saline Infusion in the Rabbit
Authors: Sejersted Ole M.
Published: December 2008

During saline infusion, sodium reabsorption (RNa) in the diluting segment (thick ascending limb of Henle's loop) increases acutely. The mechanism for this higher pumping rate of outer medullary Na‐K‐ATPase is unknown. Following left‐sided nephrectomy, immediate i.v. infusion of hypertonic saline increased RNain the remaining whole right kidney by 28 ± 14% (p < 0.05). Na‐K‐ATPase activity in outer medulla was raised by (A) 23 + 4% above the left kidney (p < 0.05), whereas cortical activity was unchanged. The mechanism for this increase in Na‐K‐ATPase activity was explored. The catalytic rate per enzyme did not differ in the two kidneys and equalled 5 340 min‐1. The increase was therefore due to higher tissue concentration of active enzyme. The response was fully developed during continuous infusion within 20 min, and of equal magnitude whether protein synthesis had been inhibited by cycloheximide (Δ= 23 ± 7%) or stimulated by unilateral nephrectomy 6 days earlier combined with saline infusion for 2 h (Δ= 34+ 10 %). Thus, during hypertonic saline infusion, the increased RNain the outer medulla was partly accounted for by the activation of latent Na‐K‐ATPase. High delivery of sodium to the diluting segment for more than 20 min during hypertrophy caused no further activity change.
Slow Action of Ca on Myelinated Nerve Fibres of Xenopus laevis
Authors: Brismar Tom
Published: December 2008

Single myelinated nerve fibres were isolated and the nodal currents were recorded with potential clamp technique. Rapid solution changes were performed by use of a recording chamber so shaped that it had a minimal dead space. A volume ten times larger than the dead space flowed past the node within about 20 ms. The half‐time of the change in Na current (INa) amplitude associated with changes between solutions of different [Na]:s was 100–150 ms, whereas the half‐time of the change in INa associated with changes between solutions of different [Ca]:s was 200–300 ms. The external [Ca] affects INa through its action on the Na permeability properties of the nodal membrane. The difference in rate of effect between changes in [Na] and [Ca] was also noticeable when simultaneous changes were performed. These findings are discussed with regard to the properties of the nodal gap.
Quantitative Evaluation of the Blood‐Brain Barrier Capacity to Form Dopamine from Circulating L‐DOPA
Authors: Hardebo J. E. , Edvinsson L. , Owman Ch. , Rosengren E.
Published: December 2008

The ability of the blood‐brain barrier to form dopamine from increasing doses of systemically administered L‐DOPA has been studied in rats by a combination of chemical determination of dopamine, and histo‐chemical and cytofluorometric measurements of L‐DOPA and dopamine. The break‐through of L‐DOPA from the circulation into the brain parenchyma via the enzymatic blood‐brain barrier was estimated by comparing the amount of newly formed dopamine in the caudate nucleus‐putamen and in the cerebellum. The capillaries were found to efficiently trap L‐DOPA in their walls, and an upper limit was reached (at an administered i.p. dose of 100 mg/kg of L‐DOPA). It could be estimated that approximately 3 % of the total dose of L‐DOPA given was decarboxylated by the blood‐brain barrier. The possible influence by the regional differences in perfusion of the two regions seen after administration of L‐DOPA was ruled out in measurements of local cerebral blood flow using the14C‐ethanol technique.
Evidence for a Rate‐Sensitive Regulatory Mechanism in Myogenic Microvascular Control
Authors: Grände Per‐Olof , Lundvall Jan , Mellander Stefan
Published: December 2008

To reveal a possible rate‐sensitive component in the myogenic control, changes of total and segmental vascular resistances in sympathectomized skeletal muscle in response to alteration of vascular transmural pressure (extravascular pressure) by 40 mmHg were compared when the pressure change was applied at two distinctly different rates (15 and 120 s). The papaverine‐dilated vascular bed showed an entirely passive behaviour, whereas the normal, myogenically reactive vascular bed responded with active constriction upon transmural pressure increase and active dilation upon pressure decrease. These responses were especially pronounced in the microvessels where a clearcut two‐component effector response was observed. The magnitude of the initial component was distinctly correlated to the rate at which the transmural pressure stimulus was applied, whereas the later steady state component during the static pressure change was rate‐independent. At the high rate of pressure increase, the initial rate‐dependent microvascular constrictor response was some ten times larger than the steady state response. These observations indicate the existence of a rate‐sensitive as well as a static component in the myogenic response to changed transmural pressure, an interpretation strongly supported by a previous analogous study on isolated single‐unit vascular smooth muscle (Johansson and Mellander 1975). It is concluded that the microvessels in skeletal muscle are highly responsive to myogenic stimuli and that emphasis should be placed on the dynamic rather than the static characteristics of the stimulus. Such rate‐sensitivity in myogenic control would seem to facilitate prompt and proper vascular adjustments, for instance in myogenic autoregulation.
Characteristics of Aortic Baroreceptor C‐Fibres in the Rabbit
Authors: Thoren Peter , Jones John V.
Published: December 2008

The characteristics of 40 C‐fibres arising from the aortic arches of 15 normotensive rabbits have been investigated. The conduction velocity of the fibres varied between 0.5‐1.8 m/s (0.91±0.05, mean ± S.E.). The activation threshold for all the fibres lay between 70–140 mmHg. 32 medullated fibres from the same animals had thresholds between 35 and 90 mmHg. After correction for the time delay in conduction the firing in the C‐fibres occurs in early systole. Pressure response curves were constructed for 10 medullated and 18 C‐fibres. The mean activity at 100 mmHg was, for the C‐fibres 5.0 Hz and for the medullated fibres 34 Hz. At 130 mmHg the activity in the C‐fibres was 13 Hz and in the medullated fibres 68 Hz. Thus C‐fibres from the aortic baroreceptor regions are activated at higher pressures than the medullated fibres and have lower discharge frequencies. Noradrenaline did not influence the pressure response curves of the C‐fibres. It is concluded that the arterial baroreceptor C‐fibres may exert a weak tonic influence on the vasomotor centre at normal pressures but are likely to be of greater importance when the arterial pressure rises acutely.
Contractility, Muscle Mass and Agonist Sensitivity of Isolated Portal Veins from Normo‐ and Hypertensive Rats
Authors: Sutter Morley C. , Ljung Bengt
Published: December 2008

Properties of the longitudinal smooth muscle of portal veins from normotensive Wistar rats, adult (NCR) and young (NCRy); spontaneously hypertensive Okamoto rats, adult (SHR) and young (SHRy); and adult Wistar rats with renal hypertension (RHR) were studied in vitro and histologically. Some aortic strips from SHR and SHRywere compared with controls. In response to noradrenaline (NA) and acetylcholine (ACh) greater maximum force was developed by veins from all hypertensive groups than by those from control rats. Cross‐sectional area of the longitudinal muscle of veins from SHR but not SHR nor RHR was greater than control. Maximum stress in response to agonists was greater in both SHR and RHR than NCR. EDso‐values for NA and ACh were lower in portal veins from SHR than NCR but not from RHR nor SHRycompared to controls. Denervation did not abolish any of the differences between SHR and NCR. Aortic strips from SHR developed less maximum force to NA and ED50was greater than those from NCR.i.e.opposite to the findings in portal veins. Low levels of external Ca2‐reveal altered calcium handling in veins from SHR compared to controls.

It is concluded that portal veins from hypertensive rats are functionally different from those of normotensive rats and differ in SHR compared to RHR. It is suggested that the altered functional properties of portal vein, but not of aorta, in several respects resemble those of arterial resistance vessels. The implications of these findings are discussed in terms of mechanisms of hypertension in these animal models.
Effect of Atropine and Methiamide on Vagally Induced Gastric Acid Secretion and Gastrin Release in Anesthetized Cats
Authors: Uvnäs‐Wallensten Kerstin , Andersson Harriet
Published: December 2008

Gastrin release and HC1 secretion was induced by electrical vagal stimulation in anesthetized cats. Both atropine (0.1‐0.3 mg/kg) and methiamide (4–20 mg/kg) inhibited the HC1 secretion (by˜60 and˜80%). On the other hand, neither atropine (0.2‐2 mg/kg) nor methiamide (20 mg/kg) inhibited the vagally induced gastrin release. Possible explanations of the atropine resistance of the vagal gastrin release mechanism are discussed.
Effect of Hypercapnia and Hypocapnia on Tryptophan and Tyrosine Hydroxylation in Rat Brain
Authors: Carlsson A. , Holmin T. , Lindqvist M. , Siesjo B. K.
Published: December 2008

The effects of induced hypo‐ and hypercapnia upon the rate of hydroxylation of tryptophan and tyrosine in the rat brain were studied by measuring the accumulation of 5‐HTP and DOPA following administration of the aromatic L‐aminoacid decarboxylase inhibitor 3‐hydroxybenzylhydrazine HC1 (NSD 1015). The results suggest that the hydroxylation of tryptophan varies directly with the tissue Po2‐ On the other hand, the hydroxylation of tyrosine did not show a simple relationship to Po2 but appeared to be influenced by pH changes.
Properties of a conductive cellular chloride pathway in the skin of the toad (Bufo bufo)
Authors: Larsen Erik Hviid , Kristensen Poul
Published: December 2008

Two types of chloride current response to a step‐wise hyperpolarization of the toad skin is demonstrated: (1) An “instantaneous” response observed immediately upon voltage change, and (2) a subsequent slow response, the time course of which is sigmoidal. The slow response is due to an increase of a transcellular conductance which is specific to chloride ions. The time constant of the conductance increase is dependent on the amplitude of the transepithelial voltage displacement, the smallest time constants are obtained for the highest amplitudes and are in the order of 30 s. The voltage dependences of the steady‐state conductance and the steady‐state chloride current reveal that the chloride pathway has maximum conductance for V≅‐80 mV (outside of the skin being negative) and approaches a non‐conducting state for V > 0 mV. This strong outward going rectification is a steady‐state phenomenon: In skins hyperpolarized for a few minutes, the “instantaneous” I‐V curves show that the chloride pathway in the conducting state allows a large inward chloride current (outward chloride flux) to pass in the voltage range 40 mV > V > 0 mV. Calculations based on a three‐compartment model indicate that the strong steady‐state chloride current rectification cannot be obtained if only the intracellular chloride concentration and the membrane potentials are allowed to vary (“Goldman‐rectification”). It is suggested, therefore, that the permeability of the chloride pathway varies reversibly with the transepithelial potential difference. The variable which controls the chloride permeability may be a membrane potential or the concentration of an intracellular ion.
On the neuromuscular effects of pindolol and sotalol in the rat
Authors: Larsen Andreo
Published: December 2008

The effects of pindolol and sotalol on neuromuscular transmission were tested using intracellular micro‐electrode recording of resting membrane potentials, miniature end‐plate potentials and end‐plate potentials, and recording of muscle contractions upon nerve stimulation of rat phrenic nerve‐hemidiaphragm preparations. Both pindolol and sotalol reduced the amplitudes of miniature end‐plate potentials and end‐plate potentials in a dose‐dependent manner without significantly affecting their time‐courses. Pindolol, but not sotalol, also increased the frequency of the miniature end‐plate potentials and decreased the number of acetylcholine quanta released by nerve impulses. Neither of the drugs significantly affected resting membrane potentials of the muscle fibres or excitability of the motor nerve to electric stimulation.
Cardiovascular reactivity and design in rats with experimental “neurogenic hypertension”
Authors: Jones John Vann , Hallbäck Margareta
Published: December 2008

The arterial baroreceptors were denervated in 20 normotensive Wistar rats. 2 1/2 months after the operation their cardiovascular responses to “mental stress” were compared to those of matched control rats (NCR). At the time of investigation the blood pressure of the baroreceptor denervated rats (BDR) was increased some 15 per cent above that of the control group. There was, however, no difference in response to “mental stress” between groups, if anything the BDR responded with less pronounced tachycardia. Two months subsequent to the stress‐test the mean blood pressure of the BDR was still significantly above normal levels, but the BDR did not exhibit structural cardiovascular adaptation, which has been documented in most types of stable hypertension as a response to the increased mean blood pressure. The results imply that hypertension induced by baroreceptor denervation is not of a stable and persistent type in which case structural changes in the cardiovascular system would have developed within the observation period (approximately 4 months). Emotional stimuli, however, do not seem to contribute to periodic blood pressure increases at the time of measurement, as earlier suggested.
Ultrastructure of synaptosomes from fetal rat brain
Authors: Kanerva Lasse , Hervonen Antti , Tissari Anja H.
Published: December 2008

The crude mitochondrial fraction P2 and subfractions of P2 were prepared from the brain stem, hemispheres and whole brain of 19‐day‐old fetal rats. Samples were fixed in glutaraldehyde‐osmium, NaMnO4 or by Tranzer's triple fixation method (aldehyde‐chromate‐dichromate‐osmium) and examined by electron microscopy. The C‐fraction from whole brain was the main synaptosome fraction, containing 3.2 % presynaptic terminals as counted from all membrane bound particles. The brain stem showed more presynaptic terminals than the hemisphere (2.8% versus 0.9%) suggesting a caudal‐rostral maturation gradient for synaptogenesis. The maturity of the nerve endings obtained was very variable in contrast to the rather uniform synaptosomes derived from adult tissue. They varied from profiles without any substructures to mature synaptosomes displaying asymmetric synaptic junctions. Monoamine synaptosomes containing small granular vesicles were not detected in the present study, suggesting immaturity of the granular monoamine pool at this stage of development.
Effect of chronic hypoxia on hepatic triacylglycerol concentration and mitochondrial fatty acid oxidizing capacity in liver and heart
Authors: Kinnula Vuokko L. , Hassinen Ilmo
Published: December 2008

The effect of moderate hypoxia (50.5 kPa air) and severe hypoxia (40.8 kPa air) in vivo on liver and heart triglyceride concentration and mitochondrial respiration rates was studied. Liver triglyceride concentrations increased in severe hypoxia from 7.3 μmol/g wet weight to 23.3 μmol/g wet weight over 7 days. After the period of seven days in severe hypoxia, the palmitate, octanoate and palmitoylcarnitine oxidation rates of mitochondrial suspensions were significantly reduced when the citric acid cycle was operative. No decrease in the fatty acid, fatty acyl‐CoA or carnitine derivative oxidation was observed when only the β oxidation system was studied. Mitochondria isolated from the heart or liver after seven days in severe hypoxia showed reduced respiratory control ratios, the decrease being from the normal 4.9 to 1.9 in the liver mitochondria using succinate as substrate. The reduction in respiratory control was mainly due to lowered State 3 respiration rates. Some reduction in the ratio was also observed in the fasting controls, from 5.8 to 3.4 with succinate. The respiratory control ratio could be partially normalized by the addition of albumin to the isolation medium for the liver mitochondria after severe hypoxia. Under these conditions, however, the State 4 respiration of the mitochondria from the hypoxic animals was higher than that for the controls.
Efflux of phenylalanine and tryptophan from cerebral cortex slices of adult and 7‐day‐old rats
Authors: Laakso M.‐L.
Published: December 2008

An equation of two exponential terms was found to adequately describe the efflux of phenylalanine and tryptophan from cerebral cortex slices of adult and 7‐day‐old rats. These exponential terms described two forms (components) of efflux taking place at different rates. The fast component of efflux was more prominent in the slices from young rats than in those from adults. In both age groups the contribution of the fast component increased with an increasing amino acid concentration in the superfusate, but there were no changes in the rate constants. The rate constants of the fast components were equal in all experimental conditions in both age groups. The rate constants for the slow components of both amino acids were lower in the slices from adult rats than in those from young rats. The reason for efflux occurring at two different rates is discussed. The fast component probably consisted of the amino acid originating from the extracellular space of the slices and of the intracellular amino acid released by exchange. The slow component consisted of the amino acid released from the cells by other mechanisms, e.g. by diffusion through the membranes or by some active efflux processes. The cerebral cortex slices from adult rats have greater ability to concentrate aromatic amino acids than the slices from young rats. This may partly be dependent on the more effective influx and partly on the slower efflux of amino acids in the slices from adults.