bluuebunny/crossref_metadata_2025 huggingface dataset:
Relation between chloride exchange diffusion and a conductive chloride pathway across the isolated skin of the toad (Bufo bufo)
Authors: Kristensen Poul , Larsen Erik Hviid
Published: December 2008

Substitution of chloride in the outside bathing medium of the toad skin with bromide, iodide, nitrate and sulphate leads to a reduction in the apparent exchange diffusion of chloride across this tissue, and also to a reduction of the chloride current recorded during hyperpolarization. A series of inhibitors (thiocyanate, furosemide, phloretin, and acetazolamide) also affects chloride exchange diffusion, hyperpolarization current as well as chloride influx during hyperpolarization. Although in some cases, effects on short circuit current were also observed, none of the effects on chloride transport systems could be explained as secondary effects due to a primary interaction with the sodium transport mechanisms. A correlation was found between the clamping current recorded during hyperpolarization and the efflux of chloride under short circuit conditions with chloride Ringer's on both sides. On the basis of these findings, and the results reported in the previous paper (Hviid Larsen and Kristensen 1977) it is considered probable that the membrane molecules responsible for chloride exchange diffusion under short circuit conditions, are rearranged under the influence of a hyperpolarizing clamping voltage, thereby forming channels allowing charge transferring transport of chloride.
Fall in choline acetyltransferase activity in the ventricles of the rat heart after treatment with a ganglion blocking drug
Authors: Ekström Jörgen
Published: December 2008

The choline acetyltransferase activity was found to be 27% lower in the ventricles of rats which had been given the ganglion blocking drug chlorisondamine than in those of untreated rats. Since the weight of the ventricles were also lower in the treated rats than in the untreated ones, it was wondered whether a change in the muscle mass as such affected the activity of the enzyme: isoprenaline treatment was found to cause the weight to increase markedly, while it left the enzyme activity unchanged. The decrease in enzyme activity observed after the prolonged ganglion blockade is interpreted as being the consequence of a reduced traffic of impulses along the postganglionic parasympathetic nerves of the ventricles. Thus, the results of the present investigation give further support for the idea of a vagal innervation of this part of the heart.
Kidney volume expansion and prostaglandin release by bradykinin. The effect of indomethacin pretreatment
Authors: Olsen Uffe Bang
Published: December 2008

100 ng/kg/min bradykinin was infused into the left renal artery in anaesthetized dogs which were loaded with 10% mannitol in saline to produce a diuresis of approximately 1 ml/min. Bradykinin initially increased renal blood flow (70%), kidney volume (20%), subcapsular pressure (85%), urine PG‐excretion (410%), diuresis (80%) and decreased urine osmolarity (20%). Kidney volume, diuresis and urine osmolarity remained equally changed during continuous kinin infusion, while other parameters subsided toward the control levels. When renal blood flow was maintained constant during the infusion of bradykinin, urine PG‐excretion increased (330%), the glomerular filtration decreased (60%) and this was accompanied by decreased kidney volume, diuresis/natriuresis with unchanged urine osmolarity. Indomethacin treatment (2.5 mg/kg i.v.) decreased renal blood flow (35%) and inhibited urine PG‐excretion. Bradykinin after indomethacin showed effects which were very similar to those observed before indomethacin treatment. It is concluded that increased intratubular volume is a main determinant of bradykinin induced increase of whole kidney volume. The accompanying increase of intrarenal pressure does not apparently contribute to the kinin induced PG‐release. The vasodilation by bradykinin seems independent of released prostaglandins. The diuresis/natriuresis and decreased urine osmolarity are probably of hemodynamic origin.
A quantitative study of the insulin release induced by vagal stimulation in anesthetized cats
Authors: Uvnäs‐Wallensten Kerstin , Nilsson Göran
Published: December 2008

Insulin was released by vagal stimulation in anesthetized and eviscerated cats. The plasma insulin concentration and blood flow in the portal vein were determined concomitantly and the insulin output was calculated. Stimulation of either the right or the left cervical vagus released the same amount of insulin, whereas bilateral stimulation released twice as much. Following a stimulation that depleted the “vagally‐releasable pool”, a recovery period of 15–20 min was needed before the same maximal output could be obtained again. With shorter interstimulatory periods the amounts of insulin released were reduced. When less than 2–3 000 impulses were applied during a stimulation period, the amount of insulin released per impulse was constant. Atropine (0.2–2 mg/kg) did not reduce the vagally‐induced insulin release.
The effects of cholera toxin on intramural blood flow distribution and capillary hydraulic conductivity in the cat small intestine
Authors: Cedgård Sture , Hallbäck Dan‐Axel , Jodal Mats , Lundgren Ove , Redfors Staffan
Published: December 2008

Blood flow distribution to the mucosa‐submucosa and to the muscularis in the cat small intestine was investigated with a85Kr elimination technique before and after exposing the intestinal mucosa for 30 min to cholera enterotoxin. In all experiments the toxin induced an intestinal secretion. Concomitantly, total intestinal blood flow was increased to a level 50 per cent above control 3 h after exposure. This vasodilatation reflected a doubling of mean blood flow in the mucosa‐submucosa while muscularis blood flow remained unchanged. In another series of experiments the effect of cholera toxin on intestinal capillary hydraulic conductivity was investigated by determining the capillary filtration coefficient (CFC). A slight increase in CFC was noted during the 3 h observation period but this was not more pronounced than would have been expected from the concomitant vasodilatation. It is concluded that hemodynamic changes in the intestinal mucosa may be one of the several factors that probably are involved in the pathogenesis of cholera.
Prostaglandin content in blood and lung tissue during alveolar hypoxia
Authors: Wiberg Terje , Vaage Jarle , Bjertnæs Lars , Anton Hauge  , Gautvik Kaare M.
Published: December 2008

The aim of the present work was to investigate whether prostaglandins (PGs) are synthetized and released from isolated blood‐perfused rat and cat lungs secondary to vasoconstriction induced by alveolar hypoxia. The lungs were perfused with autologous blood with constant volume inflow via the pulmonary artery in a recirculating system. They were ventilated with constant volume positive pressure, and acute alveolar hypoxia was induced by ventilation with a gas containing 2% O2. A superfusion bioassay technique was used to measure PG‐like activity in the perfusate from the lungs, the blood being re‐oxygenated before reaching the assay tissues. The oxygenator prevented the perfusate hypoxia induced by ventilation hypoxia to affect the bioassay tissues. The assay tissues were rat stomach strip, rat colon and chick rectum. They were sensitive to calibrating doses of 0.5–1 ng/ml PGE2 and 1–2 ng/ml PGF2α. In another series of experiments PGs of the F‐series were measured in lung tissue from normoxic and hypoxic lungs with radioimmunoassay technique. No increase in PG‐like activity could be detected in the venous effluent by means of bioassay during hypoxia, nor was the lung tissue content of immunoactive PGF increased by hypoxia. The present findings indicate that alveolar hypoxia does not stimulate PG‐synthesis in lungs, refuting that PGs are important mediators of the pulmonary vasoconstrictor response to alveolar hypoxia. It is concluded that PGs play no significant role in producing the pressor response to alveolar hypoxia.
Effect of adenosine, adenosine analogues and drugs inhibiting adenosine inactivation on lipolysis in rat fat cells
Authors: Fredholm Bertil B.
Published: December 2008

It has been suggested that adenosine may be a physiologically important modulator of lipolysis. In the present study it was found that adenosine inhibited lipolysis stimulated by low (0.03 μM) concentrations of noradrenaline (NA). Lipolysis stimulated by higher concentrations (0.3 and 3 μM) of NA was inhibited to a minor degree or not at all. Theophylline (1 mM)‐induced lipolysis was inhibited by adenosine (IC60˜ 10μM). Inhibition of theophylline‐induced lipolysis was tested for several analogues of adenosine. Some N6‐sub‐stituted adenosine analogues and 2‐Cl‐adenosine were more potent inhibitors. Adenine‐nucleotides (ATP, ADP, AMP) were about equipotent with adenosine. Several adenosine analogues, including its breakdown products were considerably less potent or ineffective. None of the analogues tested inhibited the action of adenosine. Dipyridamol, dilazep and papaverine, which inhibit the uptake of adenosine into cells, caused only a slight enhancement of the antilipolytic effect of adenosine. None of the analogues inhibited the effect of adenosine. It is concluded that adenosine can inhibit lipolysis due to low, “physiological” concentrations of noradrenaline and of low concentration of theophylline via an action on a receptor structure on the cell surface which exhibits structural specificity.
Prostaglandin‐mediated inhibition of noradrenaline release: II. Dual mechanism behind its frequency‐dependence
Authors: Wennmalm ÅKe
Published: December 2008

Sympathetically innervated, isolated rabbit hearts were perfused according to Langendorff and the nerves were stimulated at 2, 5 or 10 Hz by equally long trains of pulses. The outflows of prostaglandin‐like substances (PLS) and of noradrenaline (NA), induced by the nerve stimulations, were followed. The sensitivity of the process of NA release to exogenous PGE1 (2–6 × 10‐8 M) at 2, 5 and 10 Hz was assayed. The outflow of PLS was found to be frequency‐dependent, being greater at 2 Hz than at higher discharge rates, while the outflow of NA was similar at the different frequencies. The inhibitory action of PGE, on the NA release process was more pronounced at 2 than at 10 Hz. It is concluded that the frequency‐dependence of the endogenous PGE‐mediated inhibition of the release of NA from discharging sympathetic nerves is based on 2 independent, frequency‐related mechanisms: a) a higher synthesis rate of PLS/impulse, and b) a more pronounced sensitivity of the process of NA release, at low compared to higher impulse frequencies.
Characteristics of static and dynamic regulatory mechanisms in myogenic microvascular control
Authors: Per‐Olof Grände  , Mellander Stefan
Published: December 2008

The recently described static and dynamic components in myogenic microvascular control (Grände, Lundvall and Mellander 1977) were analysed in this study with regard to their stimulus‐effector characteristics. Total and microvascular resistance responses in the sympathectomized vascular bed of skeletal muscle were analysed during graded changes of vascular transmural pressure (PT) applied at different rates (dPT/dt) in the range from +7.5 to ‐7.5 mmHg/s. The dynamic microvascular resistance responses, developing during the phase of changing PT, were pronounced and distinctly graded in relation to the magnitude of the dPT/dt stimulus, both with regard to amplitude of resistance response and rate of resistance change per unit time (dRmicro/dt). The static responses, revealed in the steady state phase of constant increased PT, were comparatively small and graded in relation to the amplitude of the PT increase. Rate‐sensitivity in microvascular myogenic control was bi‐directional, eliciting excitatory effects (constriction) in response to positive, and inhibitory effects (dilation) in response to negative, values of dPT/dt. The dynamic constrictor response to a given dPT/dt stimulus increased with increasing amplitude of PT and, thereby, increased duration of the dynamic stimulus. This effect might be explained by successive activation of myogenic “receptor units” with different thresholds. The described rate‐sensitivity in the myogenic control system seems to increase its rapidity, stability, and sensitivity and thereby can contribute efficiently to well‐adapted and refined microvascular adjustments.
Anticholeretic effect of substance P in anesthetized dogs
Authors: Holm Inger , Thulin Lars , Hellgren Margareta
Published: December 2008

Nine anesthetized dogs were provided with acute common duct fistulas after exclusion of the gallbladder. Synthetic Substance P was administered as caval infusions in a dosage of 0.5–20 ng × kg‐1× min‐1, duration 10 min. The output of hepatic bile, sodium and amylase decreased during infusion by 40–52 per cent at the highest doses. After termination of infusion all 3 parameters increased by 19–60 per cent above the basal level. The biliary concentration of sodium was constant, while that of amylase increased during infusion. The responses were dose‐related. The anticholeresis induced by Substance P might be due to inhibition of the canalicular bile fraction, which presumably is mediated by active sodium transport and independent of bile salt excretion.
Maturation of circulating red blood cells in young baltic salmon (Salmo salar L.)
Authors: Härdig Jan
Published: December 2008

The maturation of circulating red blood cells (RBC) in salmon (Salmo salar L.) has been studied. A developmental RBC series of 6 classes based on morphological criteria was proposed. After a single dose of iron (55Fe) given to 5–6 months old salmon the incorporation of radioactivity in maturing RBC was followed by autoradiography on blood smears. The relative distribution of labelled RBC between the 6 classes in specimens taken 15, 20, 41, and 52 days after the injection of iron showed that the RBC matured along the proposed series. The projected area of the RBC increased by 100% during the maturation. This RBC growth was caused by an elongation of the RBC. Thus the ratio between short and long axes of the RBC decreased with maturation and can be used as a measure of the degree of maturation. The uptake of radioactive iron measured as grain count per RBC or per projected area of the RBC increased during the maturation in classes II‐IV. Radioactive iron was not incorporated by mature RBC. The maturation time from class I to class VI was shorter than 41 days. RBC iron bound to non‐haemoglobin proteins as a possible restriction in estimations of the haemoglobin concentrations of developing RBC is discussed.
Effects of pindolol, sotalol and the optical isomers of propranolol on muscle action potentials and depolarization‐secretion coupling in the rat
Authors: Larsen Andreo
Published: December 2008

Muscle action potentials and miniature end‐plate potential frequency were studied in different concentrations of pindolol,d‐andl‐propranolol and sotalol using intracellular microelectrode recording from rat phrenic nerve‐diaphragm preparations,d‐andl‐propranolol at concentrations of 10 to 40 mg/1 and pindolol at 20 to 100 mg/1 slowed down the rate of rise, prolonged rise and half‐decay times and reduced the overshoot of the muscle action potentials. Sotalol had similar effects but only at higher concentrations (100 to 200 mg/1). The drugs had no effect on the increase in the miniature end‐plate potential frequency obtained with depolarization by increased extracellular potassium concentration.
Effect of the nonionic detergent Triton X‐100 on sodium permeability of the myelinated nerve fibre ofXenopus laevis
Authors: Brismar Tom , Rydqvist Bo
Published: December 2008

The effect of the nonionic detergent Triton X‐100 (TX‐100) on the Na permeability (PNa) properties of the nodal membrane in myelinated nerve fibres ofXenopus laeviswas analysed with potential clamp technique. Application of TX‐100 caused a rapid initial decrease in PNathat was reversible at wash out as well as a slow irreversible block. Both effects depended on [TX‐100] and duration of exposure. The reversible reduction of PNaat the steady state was 50% at 40–60µM TX‐100. The slope of the Hill plot for the reaction was 1.75 indicating a deviation from a first order reaction. The equilibrium dissociation constant (KD) for n = 1.75 was 0.9 × 10‐7(M1.75). KDcalculated from the rate constants for onset and offset of the reversible reaction (KD= k2/k1) was 1.5 × 10‐7(M1.75). The possibility that the action of TX‐100 involves membrane proteins is discussed.
Dose‐dependent inhibition of sensory nerve activity in the feline dental pulp by anti‐inflammatory drugs
Authors: Ahlberg Karin Forssell
Published: December 2008

The aim of the present study was to investigate whether substances known to antagonize algogenic agents can block an experimentally induced increased sensory nerve activity in the dental pulp of the cat. Increased neural activity following repeated brief heat stimulation has been shown to be characteristic of the individual cat and can be utilized for intraindividual comparative studies on such increased activity. When indomethacin, diclofenac sodium or naproxen were given intravenously as a pretreatment prior to stimulation, a consistent blocking effect on expected impulse activity as compared to the impulse activity in the control teeth was produced. Indomethacin produced a dose‐dependent inhibition (ID500.04–0.2 mg/kg). Diclofenac sodium (5 mg/kg) inhibited nerve activity by 51–91% and naproxen (15 mg/kg) by 92–95%. Methysergide (0.02–0.08 mg/kg) did not show such blocking effect. When the drugs were administered during a state of established increased neural activity no effect on the current impulse activity was obtained. The present results suggest that prostaglandins may be involved in certain stages of heat induced pulp inflammation and act as mediators of increased intradental sensory nerve excitability.
Fluid transfer from skeletal muscle to blood during hemorrhage Importance of beta adrenergic vascular mechanisms
Authors: Lundvall Jan , Hillman Jahn
Published: December 2008

Vascular reactions in the cat lower leg muscles in response to short‐term (10 min) hemorrhagic hypotension (˜80 mmHg) were studied before and after regional blockade of the β‐adrenoceptors. In the muscle region with intact β‐adrenoceptors, hemorrhage raised vascular resistance by about 80% and caused a dilatation of the precapillary sphincters, the latter effect evidenced in terms of a 35% increase of the capillary filtration coefficient. Concomitantly, an absorption of extravascular fluid to the blood stream occurred, a process tending to compensate for the reduction of intravascular fluid volume. After regional β‐blockade there was quite a marked augmentation of the hemorrhage induced increase of vascular resistance whereas the inhibition of precapillary sphincter tone and the transcapillary fluid absorption were almost abolished. These observations indicate that bleeding is associated with a significant β‐adrenergic dilator influence in both the resistance vessels and precapillary sphincters of skeletal muscle and that the β‐dilator mechanism may be essential for the important, compensatory fluid gain from the extravascular to the intravascular space during hemorrhage. The observed β‐adrenergic mediation of the net transcapillary fluid absorption could be ascribed to resetting of the pre‐/postcapillary resistance ratio, leading to decreased capillary hydrostatic pressure, and to the dilator influence in the precapillary sphincters, leading to an increased number of the patent capillaries available for the transcapillary fluid exchange.
Comparison of β‐adrenoceptors mediating vasodilatation in canine subcutaneous adipose tissue and skeletal muscle
Authors: Belfrage Erik
Published: December 2008

Blood flow changes in response to various drugs in simultaneously autoperfused canine subcutaneous adipose tissue and gracilis muscle were compared to study the vascular β‐adrenoceptors. Compared to isoprenaline the β2‐selective agonist salbutamol was 4–6 times more potent as a vasodilator in the muscle than in adipose tissue. Furthermore two β1‐selective agonists (Tazolol and H80/62) caused vasodilatation in adipose tissue but not in the gracilis muscle. When given by close i.a. injection after β‐adrenoceptor blockade, adrenaline was a more potent vasoconstrictor than noradrenaline in both tissues. Before β‐blockade, however, noradrenaline was the more potent vasoconstrictor in the gracilis muscle whereas adrenaline was more potent in adipose tissue. Intravenous infusion of adrenaline in doses causing vasodilatation in the muscle caused vasoconstriction in adipose tissue whereas intravenous infusion of noradrenaline caused vasoconstriction in both tissues. The present findings suggest that the β‐adrenoceptors mediating vasodilatation in skeletal muscle are mainly of the β2‐type, whereas β1‐adrenoceptors seem to predominate in subcutaneous adipose tissue. Since adrenaline is a much more potent β2‐ than β1‐agonist, these differences point to different roles of intravascular adrenaline in the two sites. In skeletal muscle circulating adrenaline is mainly a vasodilator whereas in subcutaneous adipose tissue it mainly acts as a vasoconstrictor.
The in vivo transport of 14C‐α‐aminoisobuturic acid into mouse blastocysts during activation for implantation
Authors: Lindqvist Inger , Einarsson Barbro , Nilsson Ove , Ronquist Gunnar
Published: December 2008

The in vivo transport of 14C‐AIB (14C‐α‐aminoisobuturic acid) into mouse blastocysts was studied during activation for implantation. Mice, kept in experimentally delayed implantation, were given estrogen to induce implantation and then injections of 14C‐AIB i.v. at 0, 4 and 8 h after the estrogen. After in vivo incubation times for 1/3 or 4 h with the labeled amino acid the blastocysts were flushed out of the uterus and collected. A distinct uptake of 14C‐AIB occurred in the blastocysts 8 h (the highest uptake) and 12 h after the induction, provided that the in vivo incubation time was 4 h. At these times the blastocysts are lying free in the uterine lumen and consequently there is a transport of 14C‐AIB from the epithelium via the uterine secretion into the blastocysts. This uptake indicates that amino acids transported by the system A are important nutrients during early activation. The uptake and retention of 14C‐AIB in the uterus was tested at 4 and 8 h after the induction of implantation. The highest uptake was observed when the labeled amino acid was given at 8 h while the longest retention time occured when 14C‐AIB was given at 4 h. Since the transport ratio between the blastocysts and the uterine tissue is not maintained constant it is concluded that the metabolic rates for 14C‐AIB transport are different for the uterus and the blastocysts. The AIB transport into uterine tissue proceeds that into the blastocysts. The AIB transport into the blastocysts is maintained as long as they have a negative surface charge.
Capillary supply of the muscle fibre population in hindlimb muscles of the cat
Authors: Myrhage Rhagnar
Published: December 2008

Comparative analyses of the fibre content (FG, FOG, and SO fibres) and the capillary density (the number of capillaries surrounding individual fibres and the capillary/fibre ratio) were performed in hind limb muscles of the cat. Cross‐sections from the tenuissimus, the biceps femoris, the lateral head (LG) and the medial head (MG) of the gastrocnemius and the soleus were cut in a cryostat. The sections were stained histochemically for the NADH2‐diaphorase and alkaline (pH 9.4) actomyosin ATPase activity, which enables differentiation of different types of fibres. The endothelium of the capillaries was identified via staining for unspecific alkaline ATPase activity. The number of capillaries surrounding each individual muscle fibre had a positive correlation, first to the oxidative capacity and secondly to the average diameter of the fibres. The thin tenuissimus muscle did not differ in this respect from the thicker muscles. The highest proportion of SO fibres was found in the soleus and the MG muscles. FG fibres of two different types were dominating the fibre mass in the biceps femoris and the LG muscles, while the tenuissimus contained more FOG fibres than these muscles. In general the FG fibres had a larger diameter than the FOG and the SO fibres. The soleus and the MG muscles contained larger fibres than the other examined muscles. FG fibres were surrounded by fewer capillaries than FOG and SO fibres. The soleus and the MG muscles, with a higher percentage of SO fibres and also larger fibres, had the largest number of capillaries around the fibres and the highest capillary/fibre ratio.
Influence of local noxious heat stimulation on sensory nerve activity in the feline dental pulp
Authors: Ahlberg Karin Forssell
Published: December 2008

The present investigation was undertaken to develop an experimental model in which noxious heat stimulation was used to produce increased intradental sensory nerve activity in canine teeth of anesthetized cats. Two techniques were evaluated in which both the method of recording and the nature of the stimulus varied. Slow heating (approx 1 °C/s) to 47°C of the tooth surface (combined with recording from electrodes in open dentinal cavities) did not produce any persistent nerve activity. Repeated periods of brief intense heating (approx 60°C/s) (combined with recording from amalgam electrodes placed on cavity floors) resulted in an immediate response and an afterdischarge (phase 3) generally persisting for 20–60 min. Maximum phase 3 activity was characteristic for the individual cat and ranged from 0.2 to 50.2 imp/s, mean value 10.6 imp/s (S.D. + 9.2). A systematically higher phase 3 activity was recorded in lower compared to upper canine teeth (p < 0.05). The maximum phase 3 response generally occurred after 3–8 stimulations; the median number of required stimuli was 3. Repeated brief heat stimulations combined with the closed cavity recording technique may be used as an experimental model by which the mechanisms behind increases in intradental sensory nerve activity associated with tissue damage can be studied.
The influence of dietary sodium on urinary prostaglandin excretion
Authors: Davila D. , Davila T. , Oliw E. , Anggard E.
Published: December 2008

The influence of dietary sodium chloride on the urinary excretion of prostaglandins (PGs) was studied in unanesthetized female rabbits housed in metabolic cages. Urinary PG levels were determined by radioimmunoassay. bioassay and gas chromatography‐mass spectrometry. In the first experiment rabbits were fed at high (2.5%) and later a low (0.25%) sodium chloride diet ad libitum. A 2–5 fold increase in excretion of immunoreactive PGF2α (iPGF α) and iPGE2 was noticed when animals were given the low salt diet. Since it could not be excluded that dietary factors other than sodium chloride contributed to the changes a second, more controlled, experiment was undertaken. Rabbits were fed 30 g/kg per day of diets differing only in the content of sodium chloride, 2 % and 0.37 % respectively. On the high salt diet the rabbits excreted 0.1 ± 0.04 μg/day of PGE, and 2.0 ± 0.5μg/day of iPGF‐2α. After equilibration on the low salt diet the PGE2 excretion rate increased to 1.5 ± 0.3 μg/day (p < 0.001) and that of iPGF2α to 3.4 + 0.4 μg/day (p < 0.01). These results thus point to an inverse relationship between renal sodium excretion and the activity of the renal prostaglandin system.
The postnatal development of the inferior oblique muscle of the cat: II. Effects of repetitive stimulation on isometric tension responses
Authors: Lennerstrand By Gunnar , Hanson Jerker
Published: December 2008

The changes with postnatal age in post‐tetanic potentiation (PTP) and fatigue of the inferior oblique muscle have been studied in the cat. PTP of the twitch amplitude increased steadily with age up to 20 weeks after birth. Twitch contraction time (ct) and half relaxation time (hrt) was not significantly changed. The potentiation of the tetanic response also became more prominent with age. The young muscles (10 weeks and below) were slightly more susceptible to fatigue than older muscles, but recovery was rapid in muscles of ail ages. Intensive stimulation induced post‐tetanic depression of twitch responses in muscles older than 1 week, but none in the muscles of new‐born cats. Ct and hrt were greatly prolonged in muscles above six weeks of age. In these muscles, but never in the very youngest, repetitive firing could be observed in response to post‐tetanic single nerve stimulation. The results are compared with those obtained in similar experiments on hind‐limb muscles by other workers. They further support the idea, raised in a previous paper, that slow eye muscle fibres develop quicker and reach maturity earlier than fast fibres.
Binding of thiamine to nicotinic acetylcholine receptor in Torpedo marmorata and the frog end plate
Authors: Waldenlind Lennart , Elfman Lena , Rydqvist Bo
Published: December 2008

Thiamine was found to bind to the isolated nicotinic receptor (nAChR) from Torpedo marmorata (KD ‐ 3 ‐5 10‐5 M). The binding was reversible and inhibited by α‐neurotoxin from Naja naja siamensis. Acetylcholine binding was not inhibited by thiamine. When thiamine (5 × 10‐4 M) was applied to frog sartorius muscles a decrease of miniature end plate potential amplitudes was seen. This effect was readily reversible after the perfusion fluid of the muscle was changed to normal Ringer solution. Thus both biological and electrophysiological studies indicated a binding of thiamine to the nAChR.
Pharmacological properties of curare‐sensitive receptors mediating post‐tetanic potentiation in rat masseter muscle
Authors: Waldenlind Lennart
Published: December 2008

Post‐tetanic potentiation (PTP) of single muscle twitches after “tetanic” stimulation at 1 to 20 Hz in rat masseter muscle has been studied. PTP was inhibited by d‐tubocurarine (2–6 μg/kg), hexamethonium (1.75‐2.25 mg/kg), succinylcholine(5–7μg/kg), prostigmin (1.0–1.5μg/kg), lidocain (3–4 mg/kg) and ouabain (215–240 μg/kg). The doses did not affect the control twitches. Prostigmin could not reverse the blocking effect on the PTP caused by these drugs. Atropin was without any effect on the PTP. The nicotinic receptors mediating PTP differ from both end‐plate and ganglionic receptors since drugs blocking both types of receptors are effective. The sensitivity to the blocking agents is higher or the same (in the case of hexamethonium) as for the two other types of nicotinic receptors. Thus the PTP is dependent on activity of a “nicotinic” receptor active during physiological conditions, suggesting the presence of an additional mechanism for neuromuscular transmission in rat twitch fibres.
Rabbit lung plasma and erythrocyte volumes. Lung hematocrit in relation to total body hematocrit
Authors: Aarseth P. , Waaler B. A. , Nicolaysen G.
Published: December 2008

The total body hematocrit has been reported to be 85–90% of packed cell volume (PCV) in several species. We have found similar values in rabbits. An “extra” plasma volume must exist somewhere in the vascular bed to explain this observation. We have looked for such an extra plasma volume in the pulmonary vasculature. The dynamic hematocrit was estimated in isolated, perfused rabbit lungs from distribution volumes for plasma and erythrocyte tracers. Estimation was also obtained from indicator‐dilution curves using bolus‐injections of such tracers avoiding their recirculation. It was thus possible to calculate mean transit times for the tracers from their dilution curves directly or applying monoexponential extrapolation from the first part of the downslope of the curves. The dynamic hematocrit of the lung vessels was about 94% of perfusate PCV and there was no difference between the results obtained by the different methods. We concluded that in the rabbit only a very small part of the extra plasma volume is located in the lung vessels. The lung plasma volume is not underestimated by the indicator‐dilution technique.
Histochemical fiber composition of lumbar back muscles in the cat
Authors: Carlson Hans
Published: December 2008

A histochemical analysis has been performed of the activity of myofibrillar ATPase, NADH2tetrazolium‐reductase, succinic dehydrogenase and phosphorylase and of the content of fat and glycogen in the muscles of the cat's lumbar back region. The correlation between the fiber composition and the previously studied contraction properties of the muscles was analyzed. All muscles contain fibers with a low activity (type I) and such with a high activity (type II) of myofibrillar ATPase following preincubation at pH 9.4. Type II fibers showed either a low (type II A) or an intermediate (type II B) reaction when stained for ATPase, preincubation at pH 4.6. Type 1 fibers have a high, II A an intermediate‐high and II B fibers a low activity of oxidative enzymes. The longissimus, iliocostalis and sacrocaudalis dorsalis lateralis muscles are characterized by high percentages of type II B fibers and low proportions of type I and type II A fibers. The central region of the longissimus which is connected to a well developed intermuscular septum is composed of a high proportion of type I fibers. The multifidi, interspinales and intertransversarii mediales muscles have higher proportions of type I and type II A fibers than the other muscles in the region.
The release of serotonin from rat duodenal enterochromaffin cells by adrenoceptor agonists studied in vitro
Authors: Pettersson Gösta , Dahlström Annica , Larsson Inger , Lundberg Jan M. , Ahlman Häkan , Kewenter Jan
Published: December 2008

The serotonin (5‐HT) content of enterochromaffin cells (EC) was studied by a cytofluorimetric method in biopsies from rat duodenal mucosa after in vitro incubation with different adrenoceptor agonists and antagonists and acetylcholine (ACh). Noradrenaline (NA), Adrenaline (A) and Isoprenaline (IP) caused a decrease of 5‐HT in EC down to 40–60% and for NA and A this effect was concentration‐dependent. The effect was antagonized by d,1‐propranolol but not by d‐propranolol, metoprolol, phentolamine or phenoxy‐benzamine indicating that the 5‐HT release from EC is probably mediated via a true β‐adrenoceptor mechanism possibly of the β2 type. ACh also decreased the 5‐HT content of EC but was much less potent than the adrenergic substances. Dopamine (DA) had no effect.
Aspects of temperature regulation in harp seal pups evaluated by in vivo experiments and computer simulations
Authors: ØRitsland Nils A. , Ronald Keith
Published: December 2008

Temperature regulation in harp seal pups (Pagophilus groenlandicus) has been studied by in vivo measurements of oxygen consumption, body temperatures and in vitro determinations of the thermal values of a fur sample. The experimental animals were restrained and exposed to natural weather conditions. Solar irradiance above 600 W/m (global radiation) caused hyperthermia. Computer simulations based on the thermal values of the fur indicated that heat dissipation from primarily the limbs is a prerequisite for avoiding hyperthermia under natural weather conditions. Further simulations showed that the lower critical temperature of a lean newborn harp seal pup with standard metabolism is only – 1oC while it is depressed to –59oC as the pup grows, aquire a 10 cm thick layer of blubber and the metabolism increases to 1.5 times standard. High metabolism and tolerance to low deep body temperatures (35oC) seems a prerequisite for thermal balance in the harp seal pup under cold conditions.
Intra‐abdominal pressure changes during natural movements in man
Authors: Grillner Sten , Nilsson Johnny , Thorstensson Alf
Published: December 2008

The weight of the upper part of the trunk is partially transmitted to the pelvis via the vertebral column. If the muscle walls around the abdominal cavity are contracted, a high pressure can be generated within the cavity (>200 mmHg). The abdominal space can then transmit part of the weight to, e.g., the upper part of the body. Intra‐abdominal pressure recordings have been performed during locomotion and other natural movements with intragastric pressure recordings. With each step, there is a phasic variation in pressure, with its peak coinciding with that of the peak vertical force exerted by the leg against the ground. The peak values increase progressively with the speed of walking/running up to a mean of 38 mmHg and with trough values of 16 mmHg. The phasic variations with each step is due to a phasic activation of the abdominal muscles, with an EMG activity starting 50 ms or more before foot contact. If an extra load is put on the back, the posture changes and at the highest speed of running the pressure values are significantly higher than without this additional load. After a jump down from a moderate height of 0.4 m, the average increase is 89 mmHg and can often exceed 100 mmHg. These pressure changes are large and will presumably act to unload the spine under the prevailing biomechanical conditions and, in addition, there will no doubt be an effect on the circulatory system.
Phosphoryl group transfer from Ehrlich cells prelabeled in vivo with (32P)‐orthophosphate and (14C)‐glucose to unlabeled glioma cells
Authors: ÅGren Gunnar , Ronquist Gunnar
Published: December 2008

A transfer of (32P)‐labeled phosphoryl groups has been demonstrated to occur between prelabeled Ehrlich cells (donor cells) and glioma cells (acceptor cells). The Ehrlich cells were generally prelabeled in vivo by an intraabdominal injection of (32P)‐orthophosphate 24 hours prior to scarifice of the tumor‐bearing mice. In some experiments two injections of (14C)‐glucose were given to the animals in addition to the injection of (32P)‐orthophosphate prior to sacrifice. The prelabeled Ehrlich cells were mixed with the glioma cells, that were still attached to the culture plates, and incubation took place in vitro. Labeled (32P)‐phosphoryl (14C)‐serine was isolated from the glioma cells as well as from the Ehrlich cells. The 32P/14C‐ratio of (32P)‐phosphoryl (14C)‐serine of the glioma cells (acceptor cells) was significantly higher than found for the Ehrlich cells (donor cells). This was indicative of an interactive mechanism between the cells partly due to binding of membrane fragments from the Ehrlich cells on to the surface of the glioma cells and partly due to a phosphoryl group transfer between the two types of cells. Interaction experiments with a plasma membrane fraction prepared from the prelabeled Ehrlich cells vis à vis the glioma cells clearly showed that the phosphoryl group transfer mechanism between the cells was dominating and only a minor part of the interaction was due to adhesion. This transphosphorylation reaction represents a new type of interaction between cells. It was not influenced by either adenosine 3′,5′‐monophosphate or adenosine 5‐diphosphate.
Electrochemical forces for chloride transport in the proximal tubules of the rat kidney
Authors: Sohtell Morgan
Published: December 2008

The electrochemical forces for chloride transport in the proximal tubule of the rat kidney were studied using micropuncture techniques. Electrical transmembrane potentials were recorded in randomly punctured tubules with Ling‐Gerhard electrodes. Chloride activities in the luminal, cellular and interstitial compartments were measured with ion selective micro‐electrodes. Electrical potential measurements between cell to interstitium and lumen to interstitium were ‐72.1 ± 2.6 mVand ± 0.5±1.4mV(mean ± S.D.)respectively. The calculated chloride concentrations for lumen, cell and interstitium were 133.0±10.3 mM, 8.5±1.0 mM and 99.1 ± 3.2 mM (mean ± S.D.) respectively. The net electrochemical forces, qualitatively, offer a passive chloride ion pathway through the tubular wall and a chloride equilibrium over the luminal membrane seems to exist.
Different effects of the ionophore A‐23187 and D‐glucose on 45Ca2+ fluxes in isolated islets of ob/ob‐mice
Authors: Tamarit‐Rodriguez Jorge
Published: December 2008

Fluxes of 45Ca2+ were studied in β‐cell rich islets of non‐inbred ob/ob‐mice, using LaCl3 to wash out extracellular and superficially bound 45Ca2+. The ionophore A‐23187 (10,μM) increased the 45Ca2+ uptake in islets both at 3 and 20 mM D‐glucose, the effect being more pronounced after 10 min than after 120 min of incubation. In incubations for 120 min, 20 mM D‐glucose induced a higher uptake of 45Ca2+ than did A‐23187. The ionophore enhanced the unidirectional efflux of 45Caa+ from preloaded islets. Pretreatment of islets with 20 mM D‐glucose in non‐radioactive medium inhibited the subsequent D‐glucose‐induced 45Ca2+ uptake. Similar pretreatment with A‐23187 increased the subsequent ionophore‐induced 45Ca2+ uptake. The results suggest that A‐23187 acts by catalyzing Ca2+ fluxes across the β‐cell plasma membrane. The different effects of D‐glucose and A‐23187 on 45Ca2+ fluxes suggest that the two agents act through different mechanisms in the β‐cells.
A modified Sperber technique for direct estimation of true renal tubular excretion fraction
Authors: Odlind Bo
Published: December 2008

The Sperber technique in the hen is particularly suitable for the study of renal tubular secretion. However, results obtained with this technique vary considerably, due to an unpredictable and highly variable shunting of renal portal blood. In an attempt to get a total and stable renal perfusion by portal blood from the leg, appropriate shunt vessels were ligated. This procedure was found to force all portal blood from the leg to perfuse the ligated kidney, without affecting the symmetry of glomerular filtration or renal clearance of 125‐I‐Na‐o‐iodohippurate between the kidneys. In conclusion, the abolition of renal portal shunt flow allows use of the Sperber technique for a direct estimation of the true tubular excretion fraction (TTEF) of a substance. Thus, TTEFPAH, a measure of the tubular excretion efficiency of para‐amino‐hippuric acid, was found to be about 70%. The stable renal perfusion in ligated animals will also facilitate comparative studies of renal tubular excretion in the hen. Moreover, no animal has to be rejected due to a low renal perfusion of portal blood. Furthermore, the use of ligated hens makes it unnecessary to use markers for the renal perfusion of portal blood when steady‐state experiments are performed. Finally, the total renal perfusion of portal blood in ligated animals will facilitate the demonstration of a secretory component in the renal handling of substances with a low affinity for the renal transport system.
Glycogen depletion of different fibre types in human skeletal muscle during intermittent and continuous exercise
Authors: Essén Birgitta
Published: December 2008

Muscle biopsies from the vastus lateralis were obtained from thirteen healthy subjects at rest and at intervals during continuous and intermittent exercise. After freeze‐drying of the muscle sample, fragments of single fibres were dissected out and stained for myofibrillar ATPase with preincubation at pH 10.3, 4.6 or 4.3 to identify type 1, II A and II B fibres respectively. The remaining part of each fragment was used for quantitative glycogen analyses. At rest, mean glycogen content was significantly higher in type II fibres (402 mmol/kg dry weight) than in type 1 (344 mmol/kg dry weight). After 60 min continuous exercise at moderate work load a more pronounced glycogen depletion had occurred in type I (277 mmol/kg dry weight) than in type II (A‐r B) fibres (113 mmol/kg dry weight). With 60 min intense intermittent exercise a significant and similar depletion occurred in both type I (213 mmol/kg dry weight) and type II (A + B) fibres (203 mmol/kg dry weight). With continuous intense exercise to exhaustion (4–6 min), glycogen depletion was more marked in type II (A‐ B) (1 !8 mmol/kg dry weight) than type I fibres (74 mmol/kg dry weight). These data imply that the glycogen depletion pattern in muscle fibres is determined mainly by the work intensity but the lower glycogen depletion per unit time in intermittent compared with continuous intense exercise indicates that the mode and duration of exercise is important, too.
A study of permanent adipsia induced by medial forebrain lesions
Authors: Rundgren Mats , Fyhrquist Frej
Published: December 2008

Cerebral lesions involving most of the anterior wall of the third ventricle, and the medial part of the septal region, induced a permanent loss of thirst in two goats. The ventral part of the lamina terminalis remained intact in one of the animals. Pronounced dehydration (10–13% loss of b.wt.) developed during periods (3–7 days) when water supplementation was omitted. Determinations of plasma arginine vasopressin in one of the animals revealed that the dehydration did not cause any significant increase in the secretion of antidiuretic hormone. However, the water deficit induced a considerable rise in plasma renin activity and tachycardia. If anything, the carotid blood pressure became slightly elevated towards the end of 7 d dehydration periods. The lesions obviously inactivated a cerebral sensory mechanism controlling water balance. It may have been due mainly to destruction of juxtaventricular receptors in the anterior hypothalamic region, but perhaps also to a disruption of afferents from such receptors located posterior to this cerebral level.
Efferent innervation of the small intestine by adrenergic neurons from the cervical sympathetic and stellate ganglia, studied by retrograde transport of peroxidase
Authors: Lundberg Jan M. , Dahlström A. , Larsson I. , Pettersson G. , Ahlman H. , Kewenter J.
Published: December 2008

The nervous pathways between the small intestine of cat and guinea pig and various sympathetic ganglia were investigated by the retrograde horse‐radish peroxidase (HRP) technique. HRP was injected at multiple sites in the wall of the duodenum and the first third of the jejunum. At 1–5 days after (he injections. the HRP reaction product was searched for in various sympathetic ganglia. Not only the coeliac and nodose ganglia, but also the superior cervical, medial cervical, stellate and thoracic ganglia contained HRP‐positive nerve cells. Crushing the cervical vagal nerve prevented the occurrence of HRP‐reaction in the cervical ganglia, indicating that the HRP was transported from the gut to the cervical ganglia bia axons in the vagal nerve. The results demonstrate that the sympathetic ganglia in the neck (sup. and med. cerv. ganglia and stellate ggl.) send efferent fibres to the small intestine.
Triton detergents and the frog neuromuscular end‐plate: An electrophysiological and ultrastructural study
Authors: Rydqvist Bo
Published: December 2008

The effects of the nonionic detergents Triton X‐45 and Triton X‐100 were studied in the frog muscle end‐plate, by intracellular recordings of spontaneous miniature end‐plate potentials (m.e.p.p.'s) and the potential changes produced by iontophoretic application of acetylcholine (ACh‐potentials). In addition, the ultra‐structural changes produced by Triton X‐100 were studied by transmission electron microscopic and freeze‐fracture techniques. It was found that Triton X‐45 and Triton X‐100 caused a rapidly developing reduction of the amplitude of the m.e.p.p.'s. The response lo iontophoretic application of acetylcholine was reduced by Triton X‐100. Following return to normal Ringer solution the ACh‐potentials recovered, although not completely. The dissociation constant calculated from the rate constants for onset and offset of the reaction (KD= k2/kl) was 5–50 μM depending on the type of stoichiometric reaction presumed to occur between Triton X‐100 and the cholinergic receptor. The ultrastructural changes observed indicate that the nerve terminal plasma membrane and mitochondria are affected by Triton X‐100. Leakage of Ca2+from the latter may therefore be the cause of the increase in m.e.p.p. frequency. It is concluded that the influence on the amplitude of the m.e.p.p.'s and the ACh‐potentials can be attributed to a direct effect of the detergent upon the acetylcholine receptor protein.