bluuebunny/crossref_metadata_2025 huggingface dataset:
Importance of molecular charge for the passage of endogenous macromolecules across continuous capillary walls, studied by serum clearance of Lactate Dehydrogenase (LDH) isoenzymes
Authors: HARALDSSON B. , EKHOLM C. , RIPPE B.
Published: December 2008

Electrostatic capillary barrier characteristics was studied in the isolated maximally vasodilated rat hindquarter by use of a modified “tissue uptake” technique (Rippe et al. 1979). The hindquarters were artificially perfused with oxygenated horse serum at isogravimetry. As tracers two isoenzymes of lactate dehydrogenase (LDH) were used, having indentical size (41 Å, Mw˜ 140000) but with differing molecular charge and labelled with two separable isotopes. LDH‐H4 (125I) is negatively charged and LDH‐M4 (131I) slightly positive, at physiological pH. The negatively charged protein LDH‐H4 was more retarded in its transcapillary passage than LDH‐M4. Net clearance of H4 was 0.0242±0.0045 ml/min × 100 g and that of M4 was 0.0748±0.0092 ml/min × 100 g (n= 11, p<0.001). This difference is suggested to be due to an interaction of the polyanionic tracer with a barrier of negative molecular charge, most effective at the small pore equivalent. Clearance data for H4 and for albumin (Rippe et al. 1979) are compatible with an equivalent large pore radius of 520 Å. Neither vesicular transport (Palade 1953) nor the impact of fibre pore matrix (Michel 1980) is considered to be involved in the transcapillary passage of proteins. Negatively charged proteins probably pass through the large pore equivalent exclusively, while neutral macromolecules also utilize part of the small pore equivalent, for their transcapillary passage.
Hydraulic permeability of the peritubular and glomerular capillary membranes in the rat kidney
Authors: LARSON M. , HERMANSSON K. , WOLGAST M.
Published: December 2008

The hydraulic conductivity of the peritubular capillary membrane was calculated from I) single nephron fluid reabsorption and 2) net driving force, i. e. from hydrostatic and colloid osmotic pressures in renal interstitium and peritubular capillary blood, as determined by a micropuncture technique and with use of a computer‐based model.

Under control conditions the net driving force was estimated to be 15.4 mmHg and the hydraulic conductivity 1.04 nl/(mmHg) per 100 g rat. During extracellular volume expansion with 0.15 M saline, 4% and 10% of body weight, the net driving force decreased to 12.5 mmHg and 6.4 mmHg, respectively, whereas the conductivity increased to 1.85 and 3.14 nl/(min‐mmHg) per 100 g rat. The reduction in net driving force was compensated by an increased hydraulic conductivity. In the glomeruli the net driving force for filtration increased from 14.2 mmHg under control conditions to 21.2 mmHg and 25.3 mmHg during saline expansion 4% and 10%, whereas the corresponding hydraulic conductivity decreased from 1.13 nl/(min‐mmHg) per 100 g rat to 1.03 and 0.80 nl/(min‐mmHg) per 100 g rat during the two expansions. During saline expansion the water permeability of the glomerular capillaries is decreased while that of the peritubular capillaries is increased. These changes in the water permeability will lead to retarded excretion of the excess fluid.
Influence of pancreatic duct ligation on endocrine and exocrine rat pancreas
Authors: ISAKSSON GUNNAR , IHSE INGEMAR , LUNDQUIST INGMAR
Published: December 2008

A parallel investigation into endocrine and exocrine pancreatic function, after duct‐ligation in the rat, was performed to study the effect of reduced intestinal trypsin levels on insulin secretion and glucose tolerance. Animals with only a slight exocrine insufficiency displayed a normal insulin secretion and a normal glucose tolerance 4 weeks after operation. At 4–5 months these animals showed a slight increase in glucose‐induced insulin release when compared with control rats. However, animals operated on with a more complete ligation of the pancreatic ducts, who showed a marked exocrine insufficiency accompanied by decreased levels of intestinal trypsin, displayed a markedly increased insulin secretory response to intravenous glucose and an increased glucose tolerance. The results lend further support to our previous suggestion that, in the rat, the levels of intestinal trypsin may influence insulin secretory processes via complex feed‐back mechanisms which may involve cholecystokinin and/or other intestinal hormones.
On the interaction between intragastric pH and electrical vagal stimulation in causing gastric acid secretion and intraluminal release of gastrin and somatostatin in anesthetized rats
Authors: ALIÑO SALVADOR F. , GARCIA DOLORES , UVNÄS‐MOBERG KERSTIN
Published: December 2008

The effect of electrical vagal stimulation (5 V, 2 ms, 2, 5 and 10 Hz) on gastric acid secretion and on the intragastric release of gastrin and somatostatin was studied in anesthetized rats. The gastric lumen was perfused with Dextrane T 70 (21 g/1) at 3 different rates (2.0, 0.15 and 0.035 ml/min). pH as well as gastrin and somatostatin levels were measured in the perfusate. At a perfusion rate of 2 ml/min electrical vagal stimulation (10 Hz) reduced pH of the perfusate from 3.8 to 2.6. Neither gastrin nor somatostatin levels were influenced. At a perfusion rate of 0.15 ml/min pH fell to 1.87 during vagal stimulation at 10 Hz. During this period the somatostatin levels in the perfusate increased approximately 7‐fold. No effect on gastrin release was observed. When the stomach was perfused with Dextrane at a rate of 0.035 ml/min. pH was lowered to 1.20 during vagal stimulation at 5 Hz. The somatostatin level increased approximately 14‐fold and the gastrin levels 6‐fold. In order to study the effect of low pH per se the stomach was perfused with 0.1 M HCl. Perfusion of the stomach with 0.1 M HCI (pH1.2) at a rate of 0.035 ml/min caused a small (3‐fold) increase in somatostatin levels. In conclusion, electrical vagal stimulation or low antral pH alone had minor effects on somatostatin or gastrin release. However, when intragastric pH was <2, electrical vagal stimulation increased the intraluminal release of somatostatin and to a lesser extent that of gastrin. We suggest that both somatostatin and gastrin cells are activated by vagal stimulation at low antral pH. Less gastrin was found to be released in comparison to somatostatin, which may be due to inhibition of the gastrin cells by the somatostatin simultaneously released.
Separation of different cell populations of rat liver by density gradient centrifugation in a vertical rotor with self‐generated Percoll gradients
Authors: SINGH B. , BORREBAEK B. , OSMUNDSEN H.
Published: December 2008

A procedure is described which, with good resolution, separates viable rat liver parenchymal cells from other cell populations present in crude suspensions of liver cells. Fractionation is carried out by vertical rotor centrifugation in a self‐generated Percoll gradient. Kupffer cells can be separated from other sinusoidal cells, resulting in a separate peak of peroxidase negative non‐parenchymal cells, composed mainly of endothelial cells.
Bidirectional axonal transport of thallium in frog sciatic nerve
Authors: BERGQUIST JAN‐ERIK , EDSTRÖM ANDERS , HANSSON PER ANDERS
Published: December 2008

Bidirectional axonal transport of radioactivity was demonstrated in frog sciatic nerve in vitro and in vivo after local application of the thallium isotope 204Tl+1 to the nerve. The transport rate was similar in both directions and about 30 mm/day at 18°C. The transport was depressed by 2.4‐DNP, low‐temperature and vinblastine. A somewhat larger amount of radioactivity was transported in the retrograde than in the anterograde direction. The possibility that K+ is in part replaced by Tl+, which is transported bound to organelles, e. g. mitochondria, will be considered. Thallium might be a useful tool for future studies of axonal transport.
A note on the elimination of polyneuronal innervation of skeletal muscles in neonatal rats
Authors: TAXT TORFINN , DING RONALD , JANSEN JAN K. S.
Published: December 2008

The elimination of the polyneuronal innervation was reinvestigated in normal rats from the tenth day after birth. The extent of polyneuronal innervation was measured by intracellular recordings in cut muscle fibre preparations (Barstad 1962). This preparation has the advantage that it favours the recording of small signals. With this increased sensitivity we detected a class of small end‐plate potentials which may represent nerve terminal function in the course of elimination. These small potentials were always observed in fibres with an additional large end‐plate potential and were occassionally present even in one‐month old rats.
Motor unit numbers, motor unit sizes and innervation of single muscle fibres in hyperinnervated adult mouse soleus muscle
Authors: TAXT TORFINN
Published: December 2008

The sural and the lateral plantar nerves were implanted simultaneously into the denervated soleus muscle of adult mice. Each of these nerves contained approximately the normal number of soleus motor axons. This procedure therefore allowed a study of how an initial excessive number of motor axons provided by two different, foreign nerves and terminating into the soleus muscle affected the final pattern of muscle innervation. In muscles examined two months or more after the implantation of the foreign nerves all muscle fibres were innervated. The fraction of the muscle innervated by either nerve varied widely from one preparation to another. However, all the motor axons which were implanted into the muscle appeared to make permanent synapses. Moreover, the distribution of motor unit sizes of each foreign nerve relative to the total number of muscle fibres innervated by that nerve was similar to the distribution of motor unit sizes in muscles cross‐innervated by that nerve alone, although the absolute motor unit sizes were reduced. Estimated by intracellular recording, 20–30% of the muscle fibres were polyneuronally innervated. A similar fraction of teased muscle fibres stained for acetylcholinesterase had more than one endplate.
Chronic treatment with I‐dopa plus carbidopa in hemitransected rats: Preferential effects at intact dopamine synapses leading to behavioural signs of dopamine receptor supersensitivity
Authors: AGNATI LUIGI F. , FUXE KJELL , CALZA LAURA , ZINI ISABELLA , BENEFENATI FABIO , FARABEGOLI COSTANZA , GOLDSTEIN MENEK
Published: December 2008

Chronic i. p. treatment with 1‐dopa‐carbidopa for 3 weeks in hemitransected male rats leads on one hand to tolerance to l‐dopa induced turning behaviour and on the other hand to behavioural and biochemical signs of dopamine (DA) receptor supersensitivity on the intact side. Thus, the apomorphine induced ipsilateral turning behaviour is enhanced and the Kdvalues of the3H‐spiperone binding sites linked to DA receptors of the D2type on the intact, but not on the denervated side are reduced by 40%. However, the number of3H‐spiperone binding sites is reduced by 20% in striatal membranes on the intact side after this type of treatment. Therefore, chronic treatment with a catecholamine (CA) precursor leads to selective adaptive changes at intact striatal DA synapses with certain signs of the expected development of DA receptor subsensitivity, but above all with signs of paradoxical development of DA receptor supersensitivity. A hypothesis is introduced to explain these results.
Intravenous injections of nicotine induce very rapid and discrete reductions of hypothalamic catecholamine levels associated with increases of ACTH, vasopressin and prolactin secretion
Authors: ANDERSSON KURT , SIEGEL RICHARD , FUXE KJELL , ENEROTH PETER
Published: December 2008

The present findings show that nicotine given i. v. can within minutes induce increases of ACTH, vasopressin and prolactin secretion in the male rat, giving further evidence for the existence of nicotine‐like cholinergic receptors involved in the regulation of these hormones. These changes were associated with rapid reductions of NA levels in the subependymal layer of the median eminence, in the nuc dorsomedialis hypothalami and in the anterior and posterior periventricular hypothalamic area as revealed by quantitative micro‐fluorimetrical measurements of CA fluorescence. Intraindividual correlations indicate the involvement of an inhibitory noradrenergic mechanism in the subependymal layer of the median eminence in the regulation of ACTH secretion, the involvement of noradrenergic mechanisms in the posterior periventricular area in the regulation of prolactin secretion and the involvement of dopaminergic mechanisms in the medial palisade zone of the median eminence in the regulation of prolactin secretion. A rapid rise of prolactin secretion seems to be associated mainly with a reduction of NA levels in the posterior periventricular area indicating the existence of a possible facilitatory noradrenergic mechanism in this region regulating prolactin secretion.
“Structural autoregulation” of blood flow and GFR in the two renal vascular beds from two‐kidney, one‐clip renal hypertensive rats, as compared with kidneys from uni‐nephrectomized and intact normotensive rats
Authors: GÖTHBERG G. , FOLKOW B.
Published: December 2008

Both kidneys from two‐kidney, one‐clip renal hypertensive rats (RHR) and the hypertrophied kidney of uni‐nephrectomized rats (UNR) were investigated during artificial perfusion with 2% Dextran solution and kerosene at maximal vasodilatation, and studied with respect to organ weight, vascular resistance, preglomerular/postglomerular resistance ratio and glomerular filtration capacity. Paired perfusions were throughout used, isolated kidneys from age‐matched normotensive rats serving as controls. The untouched, “high‐pressure” RHR kidney had increased 40% in weight/100 g b. w. while its vascular resistance at maximal dilatation had increased almost 60%/g organ weight. Glomerular filtration capacity and preglomerular/postglomerular resistance ratio remained, however, largely unchanged.—The clipped “low‐pressure”, RHR kidney was reduced 40% in weight and 45% in renal vascular resistance/g organ weight. It also showed a reduced pre/postglomerular resistance ratio and some reduction of filtration capacity.—The remaining hypertrophied kidney in UNR had increased 40% in weight, while its vascular resistance and filtration capacity/g organ weight, as well as its pre/postglomerular resistance ratio were unchanged. It is concluded that the kidney in renovascular hypertension rapidly adapts structurally not only in tissue mass, but also concerning total vascular resistance and pre/postglomerular resistance ratio, so as to chronically “autoregulate” GFR to match the altered pressure situation. Likewise, after unilateral nephrectomy the remaining, normotensive kidney increases in mass, with matched increases in blood flow and glomerular filtration capacity, while total resistance/g organ weight and the pre/postglomerular resistance ratio remain at normotensive levels.
Rotation of synergistic activity during isometric jaw closing muscle contraction in man
Authors: HELLSING GUSTAF , LINDSTRÖM LARS
Published: December 2008

5 healthy subjects were studied during 10–15 min of isometric jaw elevator contraction above fatigue threshold level. Bite force was measured between upper and lower front teeth and electromyographic (EMG) activity recorded from the right temporal and masseter muscles. Of the two muscles only the masseter was active at the start of the test and usually during the whole test. When the test was repeated, however, great relief from the pain in the fatigued masseter was sometimes experienced and the temporalis took over the load. All subjects experienced this “switch” phenomenon after a varying number of tests, one of them already during his first test. The mechanism seemed to be completely out of voluntary control and showed facilitation at repeated tests.
Inhibition of antidromically induced stimulation of gastric motility by substance P receptor blockade
Authors: DELBRO D. , FÄNDRIKS L. , ROSELL S. , FOLKERS K.
Published: December 2008

Electrical stimulation of the feline vagal or splanchnic nerves after hexamethonium blockade of nicotinic ganglionic transmission produces gastric contractions, suggesting antidromic activation of thin afferents. The present experiments were performed to examine whether substance P is involved as a transmitter in such gastric responses. Cats were anesthetized with chloralose, laparotomized and the adrenals were ligated. The left greater splanchnic nerve, proximal to the celiac ganglion, and the left or right cervical vagal nerve were dissected, cut and placed on electrodes for peripheral stimulation. Gastric motility was monitored with a balloon. Hexamethonium was administered i.v. as well as i.a. to the stomach. Nerve stimulations produced powerful gastric contractions, which were antagonized by large doses (˜0.8 μmol) of substance P administered i.a. to the stomach. Similarly, the gastric contractions elicited by vagal or splanchnic nerve stimulations were reduced to at least 60% of control by the specific substance P antagonist (D‐Pro2, D‐Trp7,9)‐SP administered i.a. (0.4–1.3 μmol). The present results support the concept that substance P is associated with gastric excitatory motor responses, possibly elicited by antidromic activation of thin afferent nerve fibres.
The influence of dantrolene, diazepam, pentobarbital and 4‐aminopyridine on shortening induced depression in isolated muscle fibres of the frog
Authors: EKELUND M. C.
Published: December 2008

The influence of dantrolene, diazepam, pentobarbital and 4‐aminopyridine on the depressant effect of active shortening during twitch and tetanus was investigated in isolated muscle fibres of the frog. These drugs are all presumed to alter the kinetics of the release and re‐uptake of activator calcium during the excitation‐contraction process. The shortening induced depression was calculated as the difference in redeveloped force after a small (control) and a larger (test) release step and was expressed in per cent of the control. The depressant effect in response to a given amount of shortening during twitch contraction as well as during the plateau of a tetanus was approximately doubled after addition of 10 μM dantrolene. In contrast, diazepam (150 μM) reduced the shortening effect during the twitch to about one tenth of the value obtained in ordinary Ringer solution, while the force depression by shortening during tetanic stimulation remained essentially unaltered. Pentobarbital (1.0 mM) reduced the shortening induced depression during the twitch by 95–100%. 4‐aminopyridine (3.0 mM) completely abolished the depressant effect of shortening obtained during the twitch and approximately halved the shortening effect during tetanic contraction.
Comparative vascular effects of stimulation continuously and in bursts of the sympathetic nerves to cat skeletal muscle
Authors: ANDERSSON P. O.
Published: December 2008

Recent electrophysiological studies indicate that sympathetic vasoconstrictor fibre di‐charge in vivo usually occurs in intermittent high frequency bursts, increased activity beeing established by raised intra‐burst frequency or, more commonly, by shortened burst intervals. The present study describes the responses of the resistance and capacitance vessels in cat skeletal muscle to electrical vasoconstrictor fibre stimulation with characteristics simulating the discharge pattern in vivo. Stimulation in bursts (1 s duration) was applied either at varying intra‐burst impulse rates (from 5 to 160 Hz) at constant burst interval (5 or 10 s), or at varying burst intervals (from 32 to 2 s) at constant intra‐burst frequency (16 or 32 Hz). For comparison, continuous stimulation was made at rates from 0.5 to 16 Hz. Both types of burst stimulation were capable of evoking maintained constrictions in the resistance and capacitance vessels, graded in relation to the total number of impulses/unit time. Stimulation in bursts at varying intervals was as effective as continuous stimulation with maximal constriction reached at 32 Hz bursts at 4 s intervals. The responses to stimulation in bursts at varying impulse rates peaked at 40 Hz, higher intraburst frequencies being less effective, at least in the resistance vessels. The data suggests that the resistance and capacitance vessels are gradedly responsive to sympathetic discharge rates up to about 40 Hz provided excitation occurs in bursts and, that an effective control can be achieved especially by shortening the burst interval. Sympathetic firing in skeletal muscle may thus well exceed 10 Hz, previously believed to be the upper physiological discharge range.
Separation and purification of blood plasma arginine vasopressin on Sephadex G‐50M for subsequent radioimmunoassay
Authors: LISHAJKO F.
Published: December 2008

A gel filtration method has been developed for purification and separation of plasma arginine vasopressine (AVP) from proteins interfering with RIA‐determination of AVP. The method involves filtration of 1 ml of plasma on a Sephadex G‐50M gel column and the eluant used is 100 mM borate buffer. This rapid, and relatively simple method gives rather complete separation of plasma protein and AVP with an AVP recovery of about 90% at normal or elevated plasma AVP levels. Since 30 plasma samples may be run simultaneously, the method has potential value for routine laboratory use.
Effects of acetylcholine, isoprenaline, phenylephrine and dibutyryl‐cAMP on the contractility of isolated myocytes of the rat heart ventricles
Authors: VORNANEN M. , TIRRI R.
Published: December 2008

Single ventricular myocytes were isolated by enzymatic dissociation from the rat heart. The myocytes showed two types of spontaneous contractions: action potential dependent ‘electric’ contractions which occurred as short bursts, and slowly propagating contraction waves, i.e. phasic contractions. Electric contractions were normally found only in some of the myocytes, but in about 85% of the cells these could be induced by isoprenaline (ISO), phenylephrine (PHE), dibutyryl‐cAMP (DB‐cAMP) or acetylcholine (ACh). The inducing potency of the drugs was ACh<PHEDB‐cAMP. When electric contractions were blocked with verapamil, the frequency of phasic contractions was increased by ISO and DB‐cAMP, whereas PHE and ACh had not this effect. In 45 min. ISO increased the frequency tenfold. High concentrations (10‐4 and 10‐5 M) of ISO lead to steady contracture of the myocytes in about 40% of the cells. The effect of DB‐cAMP was weaker being only about 20% of that of ISO and it never caused steady contractures. The results suggest that alpha receptor activation by PHE does not affect the intracellular calcium movements but that ISO through beta receptor activation and DB‐cAMP directly may increase the rate of calcium accumulation by sarcoplasmic reticulum (SR).
The effect of lumbar sympathectomy on fiber composition, contractility of skeletal muscle and regulation of central circulation in dogs
Authors: KARLSSON J. , SMITH H.J.
Published: December 2008

It has been speculated upon that the sympathetic activity might be of significance for fiber composition in skeletal muscle and by similar features indirectly affecting muscle contractility and regulation of circulation. To further study this hypothesis unilateral lumbar sympathectomy from L‐2 and down was applied on 5 female beagle dogs. After 14 weeks the gracilis muscle on the sympathectomized and the control side as well were examined for their muscle fiber compositions, endurance capacity and how heart rate and blood pressure responses were affected. Muscle fiber composition decreased to 28% slow twitch fibers as compared to 41 % on the control side (p<0.01). The relative cross‐sectional area of the fast twitch fibers increased simultaneously from 57 (control side) to 71 % (p<0.05). Endurance performance measured as contraction time at 50% of peak tension decreased from 55 to 29 s (p<0.05). On an individual bases including both control and sympathectomized muscles it was found that heart rate increased with percent fast twitch muscle fibers (p<0.01) and a tendency was present for a similar relationship between blood pressure and fiber types (p<0.1)
Effects of antidromic trigeminal nerve stimulation in relation to parasympathetic vasodilation in cat nasal mucosa
Authors: LUNDBLAD L. , ÄNGGÅRD A. , LUNDBERG J.M.
Published: December 2008

High threshold stimulation of the trigeminal nerve in sympathectomized cats caused an atropine and hexamethonium resistant vasodilation in the nasal mucosa. Stimulation of efferent parasympathetic neurons to the nose caused a partially atropine sensitive vasodilation which was abolished by hexamethonium. Combined trigeminal and parasympathetic nerve stimulation did not reveal any obvious functional interactions between these two systems. Local intra‐arterial infusions of substance P, VIP and acetylcholine caused a dose dependent vasodilation in the nasal mucosa. The relative vasodilatory potencies were substance P VIP > acetylcholine. Local infusions of capsaicin, known to release substance P from nerve endings, caused a marked longlasting biphasic vasodilation which was atropine and hexamethonium resistant. In conclusion, the present findings illustrate the presence of two vasodilator mechanisms of different nervous origin in the nasal mucosa. The trigeminal response is probably mediated via release of substance P, while the parasympathetic effect seems to be caused by acetylcholine and VIP.
Influence of adenosine on the vascular responses to sympathetic nerve stimulation in the canine subcutaneous adipose tissue
Authors: SOLLEVI ALF , FREDHOLM BERTIL B.
Published: December 2008

Adenosine appears to regulate resting blood flow in canine subcutaneous adipose tissue. Sympathetic nerve stimulation has been shown to enhance the adenosine production in this tissue. This study therefore tested the possibility that adenosine may influence the vascular responses to sympathetic nerve stimulation. Intraarterial infusion of adenosine (5–20 μM in arterial blood) increased the resting vascular conductance (from 0.048 ± 0.007 to 0.095 ± 0.013 ml ± min‐1100 g‐1± mmHg‐1) and the percental reduction in vascular conductance due to sympathetic nerve stimulation (4 Hz) by 34 per cent (p<0.05) and to i. a.noradrenaline by 27 per cent (p<0.05). The vasodilator response due to nerve stimulation after α‐blockade was reduced by adenosine. Dipyridamole (0.5–1.5 μM) + EHNA (3–10 μM), which increases plasma adenosine levels, had similar effects to adenosine, while theophylline (30–80 μM) decreased the vasoconstrictor response. The vasoconstrictor escape was enhanced by EHNA alone and in combination with dipyridamole, but was reduced by theophylline. On the other hand, the poststimulatory hyperemia was unaffected by adenosine, dipyridamole and EHNA, and theophylline. The results show that adenosine does not reduce the magnitude of the initial vasoconstrictor response in proportion to the increase in resting blood flow. The autoregulatory escape in adipose tissue during nerve stimulation appears to be mediated both by adenosine and by noradrenaline acting on β‐adrenoceptors. Poststimulatory hyperemia does not seem to be greatly influenced by exogenous or endogenous adenosine
Orthostatic reactions during recovery from exhaustive exercise of short duration
Authors: BJURSTEDT H. , ROSENHAMER G. , BALLDIN U. , KATKOV V.
Published: December 2008

We studied the responses of six healthy volunteers to standard 70° head‐up tilt tests before exhaustive exercise of short duration (control) and after 5, 25, 50, 80, and 110 min of recovery, all tests lasting for 6 min except when impending syncope (IS) necessitated premature termination of a test. Marked impairment of orthostatic tolerance was apparent during the first half‐hour of recovery as manifested by symptoms of IS in five subjects in one or both of the first two postexercise tilt tests. In none of the subjects who developed symptoms of IS did central venous pressure fall to a lower level than it did in the control test. From the central venous and arterial pressure reactions we conclude that when IS developed, declining systematic resistance rather than diminished cardiac filling was the responsible factor. The increased tendency for orthostatic collapse occurred during a period of recovery marked by persistent postexercise acidemia and hyperthermia suggesting interference of these conditions and associated events with the normal ability to vasoconstrict during orthostasis
Slow EEG potentials preceding self‐paced plantar flexions of hand and foot
Authors: HARI R. , ANTERVO A. , SALMI T.
Published: December 2008

Slow EEG shifts preceding voluntary self‐paced plantar flexions of hand and foot were studied in five healthy right handed subjects. The EEG was recorded from a coronal electrode chain at the central areas. The movements were preceded by slow negative shifts beginning even as early as one second before the movement and culminating in fast slopes during the early EMG activity at the onset of the movements. The EEG shifts preceding hand and foot movements were differently distributed over the scalp: hand movements were preceded by contralaterally maximal shifts a few hundred milliseconds before the movement, whereas the potential distributions preceding foot movements were symmetrical or ipsilaterally dominant. It is suggested that the differences in the scalp distributions are due to the different orientation of the current dipoles at the cortical motor areas of hand and foot
Dopamine release from the porcine myocardium
Authors: ILEBEKK ARNFINN , ANDERSEN FRANK ROBERT , KJELDSEN SVERRE ERIK , EIDE IVAR
Published: December 2008

Dopamine is a catecholamine with profound influence on cardiac function and known to be present in adrenergic nerve terminals as a precursor of noradrenaline. However, no previous study has examined whether dopamine is produced by myocardial tissue. During stable hemodynamic conditions in 13 young, thoracotomized pigs with the heart in situ, we found a net release of dopamine into the coronary sinus amounting to 1.39 ± 0.36 ng/min ± 100 g of left ventricular muscle mass (p<0.01). Dopamine was released from the myocardium whether the v‐a difference for noradrenaline was positive or negative. This observation indicates a release of dopamine from the heart independent of sympathetic noradrenergic activity. Regulation of myocardial dopamine release remains unknown.
The effect of prolonged skeletal muscle stretch‐shortening cycle on recoil of elastic energy and on energy expenditure
Authors: BOSCO CARMELO , RUSKO HEIKKI
Published: December 2008

The enhancement of performance in stretch‐shortening exercises has been attributed to the recoil of elastic energy stored during the stretching phase. If the time between stretching and shortening (coupling time) is too long the stored elastic energy can be wasted. In the present study, coupling time was increased by asking ten male subjects to run on a treadmill at different speeds (2.2–5.2 m × s‐1) using special soft shoes in addition to normal shoes. The results indicated that running with soft shoes required greater energy consumption than running with normal shoes except at slow speed (2.2 m × s‐1). When the running speed was increased the extra energy consumed using soft shoes was parallelly enhanced (0.4 J × kg‐1/step at 5.2 m × s‐1). It was suggested that the effect of coupling time as limiting factor for recoil of elastic energy was relevant in fast twitch (FT) fibers, which were progressively recruited when the running speed was increased. This is consistent to the fact that cross‐bridge life time in FT fibers is very short, and therefore more sensitive to coupling time. At slow running speed (2.2 m ×s s‐1) only slow twitch (ST) fibers were recruited and the enhancement of coupling time was not long enough to provocate detachment of cross‐bridges of ST fibers, which possess a long cross‐bridge life time. It was concluded that the different recruitment of ST and FT fibers influenced the pattern of recoil of elastic energy which was dependent on the running speed.
Regional cerebral, ocular and peripheral vascular effects of naloxone and morphine in unanesthetized rabbits
Authors: KOSKINEN LARS‐OWE , BILL ANDERS
Published: December 2008

Effects of morphine and naloxone were investigated on cerebral, ocular and peripheral blood flow in unanesthetized rabbits. Blood flow measurements were performed with the labelled microsphere method. Cervical sympathotomy was performed on one side the day before the flow determination. Naloxone 2 mg/kg b. w.i. v.had no consistent effect on cerebral, ocular or peripheral blood flow or on mean arterial blood pressure. Morphine 2 mg/kg b. w.i. v.caused a rise in PaCO2of 0.9 kPa and tended to increase cerebral blood flow in all parts investigated. In the hippocampal region, caudate nucleus and collicles the increase in flow was about 30% which is more than expected from the rise in PaCO2· Blood flow in the retina increased while the other parts of the eye showed no consistent changes in blood flow. Morphine reduced the blood flow in the duodenum by 60%. Mean arterial blood pressure did not change after morphine. No effect of the cervical sympathotomy was detected on cerebral or ocular blood flow before or after morphine or naloxone. Thus, we found no evidence for a tonically operating opioid system controlling cerebral, ocular or peripheral blood flow. However, exogenously administrated opiate can influence blood flows in these areas.
Neonatal treatment with 6‐OH dopamine and the elimination of polyneuronal innervation of skeletal muscle in the rat
Authors: TAXT TORFINN , TØNNESEN HAAVARD , JANSEN JAN K.S.
Published: December 2008

The polyneuronal innervation of skeletal muscles of newborn rats was eliminated completely in spite of virtually complete destruction of the sympathetic nervous system with 6‐OH dopamine (6‐OHDA).There was, however, a moderate delay in the elimination of redundant nerve terminals which is probably a secondary effect of the treatment.
Effect of elevated substrates on substrate oxidation in normal and diabetic aorta
Authors: DAHLKVIST H.H. , ARNQVIST H.J. , NORRBY K.
Published: December 2008

The influence of elevated substrates (glucose, β‐hydroxybutyrate and palmitate) on the gated. The oxidation of 14C‐glucose to 14CO2 was depressed in diabetic aorta at a glucose concentration of 5.6 mM in the incubation medium. The glucose oxidation in normal and diabetic aorta was not affected by raising the glucose concentration of the medium to 22.2 mM. The oxidation of 14C‐β‐hydroxybutyrate (0.5 and 1.5 mM) to 14CO2 was impaired in diabetic aorta, while the oxidation of 14C‐palmitate (0.5 and 1.0 mM) to 14CO2 was unaltered. The oxidation of both substrates was concentration dependent. The glucose oxidation in normal rat aorta was reduced by addition of 3.0 and 6.0 mM of β‐hydroxybutyrate to the incubation medium, while 1.5 mM palmitate had no effect on the glucose oxidation. After incubation of normal rat aorta in MEM with glucose (20.0 mM) for 46 h the subsequently determined glucose oxidation was not influenced in comparison to the aorta incubated in 5.6 mM glucose. Incubation with 6.0 mM β‐hydroxybutyrate or 1.5 mM palmitate did not affect the aortic glucose oxidation. In rats which were infused for 24 h with glucose or β‐hydroxybutyrate to obtain diabetic levels of these substrates, there was no change in the aortic glucose oxidation compared to saline‐infused controls. The present results suggests that the lowered glucose oxidation in diabetic vascular tissue is not caused by hyperglycemia or high concentrations of ketone bodies or free fatty acids in the diabetic state.
Gangliosides increase the survival of lesioned nigral dopamine neurons and favour the recovery of dopaminergic synaptic function in striatum of rats by collateral sprouting*
Authors: AGNATI LUIGI F. , FUXE KJELL , CALZA LAURA , BENFENATI FABIO , CAVICCHIOLI LUCIO , TOFFANO GINO , GOLDSTEIN MENEK
Published: December 2008

The effects of chronic ganglioside treatment GM‐1 (10 mg/kg, i. p., once daily for 56 days) have been evaluated on the degenerative and regenerative features of nigrostriatal dopamine (DA) neurons following a partial lesion by tyrosine hydroxylase immunocytochemistry in combination with morphometrical analysis and by quantitative DA receptor autoradiography. Chronic GM‐1 treatment resulted in the maintenance in the number of DA cell bodies, terminals and striatal area on the lesioned side and also increased dendrite length of the DA nerve cells in the zona reticulata on that side. The lesion induced DA receptor supersensitivity was counteracted by chronic treatment with GM‐1 and the apomorphine induced rotational behaviour was significantly reduced. The hypothesis is introduced that following ganglioside treatment some lesioned DA nerve cells do not degenerate, but elongate their dendrites to give increased trophic support to DA cell bodies with intact DA axons. These increased dendro‐dendritic interactions may enable the unlesioned DA cells to increase the density of their striatal nerve terminal networks via collateral sprouting leading to recovery of dopaminergic synaptic function as evidenced in the receptor autoradiographical and behavioural analysis. Gangliosides may therefore possibly represent a new type of drug in the treatment of Parkinson's disease and aging processes in DA systems.
Changes in segmental reflexes following chronic spinal cord hemisection in the cat:
Authors: HULTBORN H. , MALMSTEN J.
Published: December 2008

The effect of a chronic spinal cord hemisection on segmental reflex transmission was studied in cats. Recordings of ventral root responses were made after a terminal transection below the initial lesion to eliminate descending influence through the intact spinal half. Procedures to ensure comparability between sides, that are lacking in earlier work on this experimental model, were introduced in the present work. It was demonstrated that there was an increase in reflex size on the lesioned (left) side, relative to the other side, of both mono‐and polysynaptic reflexes. The reflex changes were found at all survival times studied (from 2 to 515 days).In control animals mono‐and polysynaptic reflexes were found to be larger on the right side. It is discussed that side symmetry of reflex size is not to be presupposed even in a normal population. Detailed clinical examinations of lesioned animals were not performed, but a tendency for enhancement of the ipsilateral knee‐jerk was found. There was no syndrome of spasticity and general motor recovery was very good.
Atropine‐resistant secretion of parotid saliva on stimulation of the auriculo‐temporal nerve
Authors: EKSTRÖM J. , MÅNSSON B. , TOBIN G. , GARRETT J.R. , THULIN A.
Published: December 2008

Non‐adrenergic non‐cholinergic parasympathetic secretory responses in parotid glands of rats have been demonstrated by electrical stimulation of the auriculo‐temporal nerve after appropriate blocking drugs and compared with secretion in the absence of these drugs. After atropine +/‐ adrenergic blocking drugs secretion was greatly reduced but some secretion was always evident at frequencies of 5 Hz and higher. The time taken for secretion to appear was greatly increased and this may relate to an absence of accompanying myoepithelial contraction. Continuous stimulation always produced greater flows of saliva than intermittent bursts of stimulation at higher frequencies both in the absence and in the presence of blocking drugs. Thus it is likely in vivo that secretion is induced by relatively steady nerve‐impulse traffic at moderate frequencies rather than by bursts of high frequency stimulation. Possible transmitters contributing to the atropine‐resistant secretion are considered.
Relationship between arterial and venous adenosine levels and vasodilatation during ATP‐and adenosine‐infusion in dogs
Authors: SOLLEVI ALF , LAGERKRANSER MICHAEL , ANDREEN MAGNA , IRESTEDT LARS
Published: December 2008

The hemodynamic effects of ATP and adenosine (i.v. infusions) were studied in dogs in parallel with quantitative determination of purines in plasma by HPLC. In two experiments, infusion were performed during treatment with dipyridamole, an uptake inhibitor of adenosine. A 50–60% reduction of mean arterial blood pressure (MABP) was induced by both ATP and adenosine at infusion rates ranging between 17–290 μmoles/min. Cardiac output was unaffected by the purine infusions, indicating that the reduction of MABP was caused by a reduction of the systemic vascular resistance. Elevated ATP and adenosine concentrations were seen in venous plasma (pulmonary artery) during infusion, while only approximately 10% recovered ATP had been degraded to adenosine. On the other hand, in arterial plasma, virtually all nucleotides had been eliminated whereas the adenosine concentrations in plasma ranged between 5 and 20 μM. The magnitude of the vasodilatation was strictly related to the arterial plasma adenosine level irrespective of whether ATP or adenosine was infused. Thus, adenosine probably mediates the vasodilatory effect of ATP.
Ability to judge lung volumes at different CO2‐drives for ventilation and the possible influence of such a judgment on the ventilatory CO2‐responsiveness
Authors: KATZ‐SALAMON MIRIAM
Published: December 2008

Possible influences of changes in the CO2‐respiratory drive on the ability to judge lung volumes and the possible effects of such judgments on the ventilatory CO2‐responsiveness were studied in healthy subjects. The psychophysical relationships between objective and subjective magnitudes of lung volumes were determined at normocapnia, at three different levels of hypercapnia (breathing 1–3% CO2 in air) and at hypocapnia (after volitional hyperventilation). The relationships, expressed by a power function with the mean exponent 1.5 (SD±0.3), were analyzed with respect to slope, intercept and correlation coefficient of the regression lines. None of these parameters was affected by variations in end‐tidal PCO2 or by the concomitant changes in ventilation. In the ‘attentive’ pre‐judgment breathing (APJB) the ventilatory response to CO2 was lower than during non‐attentive breathing in three or four subjects. It is speculated that in these subjects the CO2‐responsiveness was depressed by the increased attention during APJB. The question whether volitional hyperventilation gave rise to any specific post‐hyperventilatory breathing pattern was analyzed. The results showed that the majority of post‐hyperventilatory breathing pattern was apnoeic or hypopnoeic in character.
The reno‐renal reflex; evaluation from renal blood flow measurements
Authors: HERMANSSON K. , ÖJTEG G. , WOLGAST M.
Published: December 2008

Stimulation of the intact renal nerve bundle at a frequency of 5 Hz was found to affect not only the blood flow of the ipsilateral kidney, but also the contralateral kidney responded with a 15% reduction in its total and regional renal blood flow. If the nerves were cut proximal to the stimulation electrodes, the ipsilateral kidney, as before, responded with a reduction in its blood flow, but now the contralateral kidney remained almost unaffected. If, on the other hand, the nerves were cut distal to the stimulation electrode, meaning that only efferent nerve fibres will be activated, the contralateral kidney responded with the same 15% fall in its blood flow. If the afferent fibres of the ipsilateral kidney were stimulated as before, but the contralateral kidney was denervated, no reduction of the blood flow of the contralateral kidney could be established. It was furthermore noted that stimulation of afferent fibres resulted in a prompt rise in the systemic blood pressure with subsequent normalization after interruption of the stimulus. It is concluded that the general sympathetic tone is determined also by receptors within the kidneys. The signals reach the central nervous system via afferent fibres, and act to increase the sympathetic tone with concotnittant rise in the systemic blood pressure and increased efferent renal nerve activity with subsequent reduction of the renal blood flow.
Effect of tubocurarine on static and dynamic muscle contractions in man
Authors: SECHER N. H. , PETERSEN S. , GRIMBY G.
Published: December 2008

The effect of a bolus injection of tubocurarine (0.1 mg × kg‐1 i.v.) was followed in six young subjects by registration of static, and slow (30°Xs‐1) and fast (15°Xs‐1) dynamic (isokinetic) maximal voluntary leg extensions. Mechanograms from both unblocked and curarized muscle contractions showed a “notch” after about 440 ms separating two relative maxima. The mechanograms were divided by an arbitrary straight line connecting the starting point of the contraction curve and the notch. The line separated an area (NmXs) above and to the left (α‐component) from an area below and to the right (β‐component) of the line. Tubocurarine affected the β‐component selectively until about 70% reduced in the static contractions. With further curarization the α‐component was also reduced in size. The α‐component was equally affected during the three types of contractions, while the faster the contraction the more the β‐component was reduced. The results suggest that static as well as dynamic human muscle contractions can be divided into two parts with a different sensitivity for tubocurarine, one of which seems to have a sensitivity which depends on the contraction velocity.
Active transepithelial potassium transport in frog skin via specific potassium channels in the apical membrane
Authors: NIELSEN R.
Published: December 2008

In frog skin bathed in Cl‐‐Ringer's solution the short circuit current (SCC) is equal to the net Na+ flux. In the present study Na+ and K+ transport across frog skin have been investigated in skins bathed in a solution where all Cl has been substituted by the impermeable anion gluconate. In this solution the net Na+ flux (9.22±0.72 nmole/cm2/min) was significantly higher than the SCC (7.61±0.63) nmole/cm2/min). Measurement of the transepithelial K+ influx and K+ efflux showed that the discrepancy between the net Na+ flux and the SCC was caused by an active outwards going transepithelial K+ transport. The K+ but not the Na+ transport could be blocked by adding the K+ channel blocking agent Ba++ to the apical solution. Thus, the K+ transport occurs via a K+ specific pathway in the apical membrane. Ouabain blocked both the Na+ and the K+ transport, whereas the presence of the Na+ channel blocking agent amiloride in the apical solution blocked the Na+ transport and reduced the K+ transport. In the presence of amiloride in the apical solution the SCC and the transepithelial potential difference (PD) reversed so that the outside (the apical side) of the frog skin became positive with respect to the basolateral side. The inverted SCC was carried by an active transepithelial K+ transport, this K+ transport required the presence of Na+ in the basolateral solution. The experiments show that frog skin can insert or activate K+ channels in the apical membrane, indicating that the frog may regulate its K+ content by varying the K+ permeability of the apical membrane.
Effect of clonidine at steady state on blood pressure in spontaneously hypertensive rats: Interaction of various alpha‐adrenoceptor antagonists
Authors: FRISK‐HOLMBERG MARIANNE
Published: December 2008

The influence of various α‐adrenoceptor antagonists (phentolamine, yohimbine, R 28935, prazosine, terazosine) on clonidine's blood pressure effects at different steady state plasma concentrations was investigated in awake spontaneous hypertensive rats. Clonidine's threshold (>10 mmHg,<20 mmHg) antihypertensive effect was potentiated by phentolamine but opposed by centrally acting antagonists as was the maximal antihypertensive effect. The pressor response on the other hand was blocked by peripherally acting α‐1‐and α2‐antagonists. The effect of clonidine on blood pressure thus seems a consequence of both the tissue distribution and the α‐adrenoceptor affinity. At low steady state plasma concentrations of clonidine a peripheral action could be a part of the antihypertensive mechanism.