bluuebunny/crossref_metadata_2025 huggingface dataset:
Membrane and biochemical alterations after denervation and during reinnervation of mouse skeletal muscle
Authors: SELLIN L. C. , LIBELIUS R. , LUNDQUIST I. , TÅGERUD S. , THESLEFF S.
Published: December 2008

Denervation of the extensor digitorum longus (EDL) muscle of the mouse by either nerve crush or nerve section produced: a reduction of the resting membrane potential (Em), alterations in the properties of muscle fibre action potentials and the development of tetrodotoxin (TTX)‐resistant action potentials. These changes in membrane electrical properties were accompanied by an increase in the endocytic activity of the muscle and an increase in the activities of the lysosomal enzymes cathepsin D and N‐acetylglucos‐aminidase (NAGA). Reinnervation of muscle was indicated at 9 days after nerve crush by the presence of miniature end‐plate potentials. The recovery of membrane electrical properties, beginning with the onset of reinnervation, were not temporally related. The Em increased in two stages: an early rapid repolarization and a later slower repolarization. The muscle fibers were sensitive to the blocking action of TTX by 12 days after nerve crush, whereas the rate of rise (dV/dt) of the action potential did not approach values of innervated muscles until 21 days. Reinnervation resulted in a decrease in endocytosis and a decrease in the activities of cathepsin D and NAGA toward innervated values by 21 days after nerve crush. The results suggest that membrane alterations after denervation and during reinnervation may occur by endo‐ and exocytosis of membrane constituents and that the lysosomal system may play a role in the breakdown and/or recycling of these structures.
Post‐ischemic coma in rat: effect of different pre‐ischemic blood glucose levels on cerebral metabolic recovery after ischemia
Authors: SIEMKOWICZ EUGENIUSZ , GJEDDE ALBERT
Published: December 2008

Hyper‐, normo‐, and hypoglycemic rats were exposed to 10 min of complete cerebral ischemia. Regional cerebral blood flow (CBF), blood‐brain glucose transfer, and cerebral consumption of oxygen and glucose were measured before, as well as three and 60 minutes after ischemia. Three min after ischemia, no differences were observed between the 3 groups of rats. One h after ischemia, the hyperglycemic rats in comparison to those of the other groups had similar whole‐brain CBF and glucose consumption but appreciately lower oxygen consumption, indicating continued non‐oxidative use of glucose in the hyperglycemic group. In general, regional CBF values exceeded the control value by 100–200% 3 min after ischemia and were reduced to 50% of control at 1 h after ischemia, at which time the rats were still comatose. In the brain stem of hyperglycemic rats, blood flow, however, remained elevated after ischemia. Thus, the significantly increased mortality observed in rats hyperglycemic before, during and after ischemia (Siemkowicz & Hansen 1978) was the result, not of impaired postischemic CBF, but of ischemic or postischemic damage to brain cells. We suggest that the damaging factor in the hyperglycemic group is increased lactacidosis associated with prolonged anaerobic glycolysis.
Endometrial cholinergic secretory responses during estrous cycle, pregnancy and after estrogen and/or progesterone treatment of the guinea‐pig
Authors: HAMMARSTRÖM MARGARETA
Published: December 2008

During estrous cycle as well as during pregnancy and after treatment with estrogen and/or progesterone uterine mucus secretory responses were studied as amount of carbohydrate released from everted guinea‐pig uteri after transmural nerve stimulation or carbachol administration. In estrous cycle both stimuli increased secretion by about 20% except for the late diestrus phase, when no secretory responses were seen. In pregnancy a secretory response was noted at implantation time. From mid pregnancy and onwards secretory responses of increasing magnitude were obtained. Secretory responses persisted post partum. Evidence of an adrenergic inhibitory influence on the neurogenic cholinergic responses during metestrus was noted. Both stimuli increased carbohydrate release by about 50% above resting level in uteri from animals receiving combined hormone treatment. In uteri of animals receiving estrogen only the increase was about 20%. No definite secretory response was obtained in uteri from animals receiving progesterone only. It is suggested that both hormones are necessary for full cholinergic secretory response to nerve stimulation or muscarinic drugs. It is concluded that muscarinic stimulation of the endometrium results in mucus secretion during all crucial events during the reproductive cycle. Furthermore a cholinergic secretory innervation seems to be present at all these times.
Taste and chewing as stimuli for the secretion of amylase from the parotid gland of the rabbit
Authors: GJÖRSTRUP PER
Published: December 2008

Reflex secretion of amylase was studied in response to feeding pellets and carrots. Section of the ipsilateral glossopharyngeal nerve but not of the lingual nerve reduced the secretion of amylase with carrots but not with pellets. The fluid secretion was unaffected by the nerve sections. Larger volumes were secreted with pellets than with carrots, indicating that the hardness of the food, via chewing, is the main stimulus for fluid secretion. Sweet, salty, sour and bitter taste stimuli did not produce any fluid secretion in concentrations normally used for gustatory stimulation in rabbits. In a background flow of parasympathetically secreted saliva sweet stimuli regularly caused a large increase in the amylase output, salty stimuli usually had a small effect and sour and bitter stimuli seemed to have only exceptionally a small effect. Citric acid in a high concentration caused fluid secretion, at the most at a rate of about 50% of maximum; this saliva had a high content of amylase. The results support the view that during feeding the sympathetic secretory nerves can be activated via both taste stimulation and chewing, while the parasympathetic activity is mainly influenced by chewing.
Dissociation of electrical and mechanical activity caused by vibrations in the spontaneously active smooth muscle of the rat portal vein
Authors: SJÖQVIST A. , LJUNG B.
Published: December 2008

The effects of vibrations on the electrical membrane discharge and on the contractile force of the spontaneously active smooth muscle of isolated rat portal vein were studied. The electrical activity was recorded extracellularly and quantitatively related to the mean active force. Sinusoidal vibrations (40 Hz, 2.5–3.0% tissue length peak to peak), applied in the logitudinal direction of the smooth muscle, caused prompt and reversible reduction of active force but neither the pattern of the phasic contractions nor the electrical membrane discharge was altered. The degree of inhibition of mechanical activity increased with vibration amplitude, activity being 50% of control at a vibration amplitude of 12±4% (mean ± S.D., n=8). It is concluded that the induced length changes caused prompt dissociation between electrical membrane discharge and mechanical force development in the vascular smooth muscle. This finding adds support to the previously forwarded hypothesis that vibrations cause inhibition of contracting muscle by direct action on the contractile process.
Nervous control of pancreatic endocrine secretion in pigs
Authors: HOLST JENS J. , GRØNHOLT RIKKE , de MUCKADELL OVE B. SCHAFFALITZKY , FAHRENKRUG JAN
Published: December 2008

The increases in the concentrations of insulin and pancreatic glucagon in portal venous and arterial plasma in response to electrical stimulation of the vagus nerves were studied in anesthetized splanchnicotomized young pigs. The responses were frequence dependent; threshold frequency was below 1 Hz and maximum response was reached at 8–12 Hz. With maximal stimulation responses of magnitudes comparable to the responses to maximal arginine (glucagon) and glucose stimulation (insulin) were observed. However, both the insulin and the glucagon response were critically dependent on the blood glucose concentration during the stimulation: the glucagon response was inversely correlated to blood glucose, whereas the insulin response was positively correlated to blood glucose at concentrations above 4.5 mmol · 1‐1. Below this glucose concentration there was no detectable insulin response and above 8.0 mmol ·‐1 no glucagon response to vagal stimulation. A stimulated secretion of glucagon as well as insulin was maintained for up to 30 min stimulation, but insulin secretion tended to decrease, whereas glucagon secretion tended to increase. Above blood glucose concentrations of 4 mmol · 1‐1, blood glucose concentrations increased slightly in response to vagal stimulation, whereas no change was noted during stimulations performed at lower blood glucose concentrations.
Nervous control of pancreatic endocrine secretion in pigs
Authors: HOLST JENS J. , de MUCKADELL OVE B. SCHAFFALITZKY , FAHRENKRUG JAN , LINDKÆR STEEN , NIELSEN OLE VAGN , SCHWARTZ THUE W.
Published: December 2008

We studied the effect of intraarterial administration of acetylcholine on insulin and glucagon secretion in anesthetized splanchnicotomized pigs and on insulin, glucagon, and pancreatic polypeptide secretion from the isolated perfused porcine pancreas and the isolated perfused duodeno‐pancreatic block of pigs and dogs. In the pigs acetylcholine stimulated insulin and glucagon secretion in a glucose dependent manner similar to vagal stimulation; however, the response was completely resistant to hexamethonium and abolished by atropine. Acetylcholine stimulated insulin and pancreatic polypeptide secretion of the isolated perfused porcine pancreas, and inhibited glucagon secretion, whether the duodenum was present or not, whereas the glucagon secretion of the isolated perfused canine pancreas was stimulated by acetylcholine.
Influence of exogenous substrates on adenosinetriphosphate (ATP) concentration in normal and diabetic rat aorta in vitro
Authors: CARLSSON MARIA , ARNQVIST HANS J.
Published: December 2008

In diabetic rat aorta glucose metabolism is impaired and changes in the activities of several enzymes are found. The aim of this study was to investigate whether the metabolic alterations in diabetic vascular tissue influence energy production. Aortas of normal and diabetic male Sprague‐Dawley rats were incubated in vitro for up to 120 min with various substrates added to the incubation medium. Diabetes was induced by streptozotocin and the rats were used after a diabetes duration of two weeks. When normal and diabetic aorta were incubated in the presence of 5.6 mmol/1 glucose no significant difference in ATP‐concentration was found after 60 min while after 120 min the ATP‐concentration was lowered in diabetic aorta. Addition to the incubation medium of a substrate mixture containing amino acids in the same concentrations as in rat plasma, 3 mmol/1 DL‐β‐hydroxybutyrate and 1.5 mmol/1 palmitate increased the ATP‐concentration, measured after 120 min, in diabetic aorta but not in normal aorta. No significant difference in ATP‐concentration was found between normal and diabetic aorta incubated in a medium containing all substrates. When diabetic aorta was incubated with each substrate separately β‐hydroxybutyrate but not glucose, palmitate or amino acids, increased the ATP‐concentration to about the same level as the complete substrate mixture. The results suggest that the ability to utilize glucose for ATP production is impaired in diabetic vascular tissue and that other substrates such as ketone bodies are of importance for energy production in diabetic vessels.
The in vitro transport of 14C‐α‐aminoisobuturic acid into blastocysts from mice in delay and after activation for implantation
Authors: LINDQVIST INGER , NILSSON B. OVE , RONQUIST GUNNAR
Published: December 2008

The uptake of 14C‐AIB (14C‐α‐aminoisobuturic acid) into mouse blastocysts was studied in vitro. The flushed blastocysts fell into two size categories, namely large or “expanded” and small or “contracted”. The arithmetic mean volume for the large blastocysts grew from 0.58 nl for delayed blastocysts to 0.76 nl for 8 h activated ones, while both delayed and activated small blastocysts had a mean volume of 0.22 nl. Delayed and 8 h activated large blastocysts showed an enhanced uptake of 14C‐AIB with time of incubation, the uptake increasing 3‐fold from 15 min to 60 min. The small blastocysts generally showed a higher uptake than the large ones, but the activated small blastocysts were atypical in that they unexpectedly displayed a 3‐fold decrease in uptake at 60 min incubation as compared with 15 min. The early peaks of 14C‐AIB uptake in vivo by uterine tissue and blastocysts were shown to be well correlated to the uptake in vitro. The presence of a working System A carrier in the activated blastocysts was demonstrated by showing that the uptake of AIB was sodium dependent and could be inhibited by N‐methyl‐AIB. Ultrastructural studies by scanning and transmission electron microscopy revealed that the trophoblast of large blastocysts was elongated and covered by numerous microvilli on a slightly bulging surface. The small blastocysts on the other hand displayed cuboidal trophoblast cells, sometimes in a pseudostratified arrangement, with the outer surface covered by many small ridges.
Increase in choline acetyltransferase activity in surgically isolated postganglionic parasympathetic neurones of the urinary bladder of adult rats
Authors: EKSTRÖM JÖRGEN
Published: December 2008

In the urinary bladder of adult male rats the choline acetyltransferase activity in postganglionic neurones isolated from the central nervous system was shown to increase markedly and rapidly following section of the contralateral postganglionic neurones. The enzyme activity of the operated bladder was 32% of the control 3 days postoperatively, while at the last observation, 25 days postoperatively, it was 86%. As judged from additional studies on totally denervated bladders and on totally decentralized bladders the increase found in the enzyme activity was not due to ingrowth of nerves from outside or to unspecific acetylcholine synthesis neither was it due to increase in bladder wall tension or to increase in tissue mass.
Interrelationships between electromyographic, mechanical, muscle structure and reflex time measurements in man
Authors: VIITASALO JUKKA T. , KOMI PAAVO V.
Published: December 2008

Reaction time (TRT) with its premotor (PMT) and motor time (MT) components, patellar reflex time (TRfT) with its latency (LAT) and motor time (RfMT) were studied together with isometric force production and relaxation time variables in one leg isometric knee extension. These variables were intercorrelated together with muscle biopsy variables taken from m. vastus lateralis. From these computations MT proved to demonstrate significant correlations to rate of isometric force development (RFD) (P<0.001), maximum force (P0) (P<0.001) and per cent distribution of ST fibers (P<0.001). It is speculated that these relationships are determined by the pattern of the motor unit recruitment and by different characteristics of the slow and fast twitch muscle fibers to trigger the excitation‐contraction coupling.
Basic contraction properties of the avian stapedius muscle
Authors: COUNTER S. A. , BORG E. , LÄNNERGREN J.
Published: December 2008

The basic contraction properties of the solitary avian middle ear muscle, the M. stapedius, was investigated in chicken, Callus gallus, by a sensitive tension transducer. Previous experimental studies on the in situ muscle preparation revealed both fast and slow components in the muscle's physiological responses. In the present study, brief electrical stimulus pulses delivered to the “isolated” M. stapedius elicited rapid twitch contractions with average tension levels of 46 mN for maximal stimulation. The contraction time was 15 ms, the half relaxation time was 15 ms and the total twitch time was 54 ms. Repetitive stimulation (2.5–200 Hz) revealed minimal summation of responses at 10–20 Hz and apparent complete fusion at 160 Hz. Peak tension at 160 Hz ranged from 150 mN to 200 mN. The twitch tetanus ratio was found to be 0.25. In earlier experiments with an in situ preparation, a slow component was observed in the physiological responses. However, this slow component was not seen in the single twitch responses or the response to repetitive stimulation in the present study. The M. stapedius of Gallus gallus was found to be a “fast” muscle by conventional terminology. Its contraction time is slightly shorter than the contraction times of the M. stapedius in mammals such as the cat (21 ms) and the rabbit (22 ms). These findings are consistent with earlier morphological studies which show the M. stapedius of Gallus gallus to have the features of a fast twitch muscle.
Long‐lasting cardiovascular depressor response to somatic stimulation in spontaneously hypertensive rats.
Authors: YAO T. , ANDERSSON S. , THORÉN P.
Published: December 2008

It has been known that a short‐lasting stimulation of the somatic afferent nerves elicits either a depressor or a pressor response depending on the stimulus parameters (Johansson 1962). In the present study cardiovascular responses were observed during and after a long‐lasting sciatic nerve stimulation in conscious spontaneously hypertensive rats (SHR) and their normotensive controls, the Wistar Kyoto rats (WKR).
Effect of lower body negative pressure upon local regulation of blood flow in human subcutaneous tissue
Authors: SKAGEN K. , HENRIKSEN O. , BONDE‐PETERSEN F.
Published: December 2008

Local regulation of subcutaneous blood flow in the forearm was studied during lower body negative pressure (LBNP) in 7 young healthy male subjects in supine position. Blood flow was measured on the forearm by the local133Xe washout technique. LBNP of ‐40 and ‐60 mmHg induced a decrease in the133Xe washout rate of 34 and 50% respectively. This response to LBNP could be blocked by proximal nervous blockade indicating that the vasoconstriction observed was due to a central sympathetic reflex mechanism. The vasoconstrictor response to increase in venous transmural pressure induced by lowering the arm (veno‐arteriolar reflex mechanism) could not be demonstrated during 40 mmHg LBNP. The abolishment of this reflex is most likely due to centrally elicited increase in sympathetic activity as a normal veno‐arteriolar reflex was elicited following proximal nervous blockade.
Tissue concentration and release of substance P‐like immunoreactivity in the dental pulp
Authors: BRODIN ERNST , GAZELIUS BERTIL , OLGART LEIF , NILSSON GÖRAN
Published: December 2008

The concentration of substance P‐like immunoreactivity (SPLI) was determined in dental pulps from cat, dog and man by radioimmunoassay. Pulps from mature cats showed the highest SPLI‐levels (mean 32 pmol/g); these are comparable to or higher than those found in any other organ outside the central nervous system. The SPLI concentrations were lower in pulp from immature teeth. The immunological and chromatographic behav behaviour of the pulpal SPLI from cat and man resembled that of synthetic substance P (SP), indicating that the assayed substance is closely related to or identical with SP. Release of pulpal SPLI in canine teeth ws evoked by stimulation of the inferior alveolar nerve in anaesthetized cats. In 9 of 16 experiments the amounts of SPLI found in pulp suprafusates following stimulation (4–31 fmol) were larger than those in unstimulated controls (0–7 fmol). Stimulation also reduced the pulpat tissue concentration of SPLI to 60% of that in homologous control pulps. The high concentration of SPLI found in the dental pulp and the demonstration of nerve‐induced release strengthen the hypothesis that SP serves some function in the dental pulp.
Formation of ectopic neuromuscular junctions in adult rats
Authors: SOMMERSCHILD H.
Published: December 2008

The formation of ectopic neuromuscular junctions between a transplanted foreign nerve (the superficial fibular nerve) and the denervated soleus muscle was examined in adult rats. Formation of new junctions was induced by denervating the soleus muscle by cutting the tibial nerve. Junctional transmission began 3 days after denervation when denervation was done 3 weeks after transplantation of the foreign nerve, and progressively later when denervation was done 8, 16 and 24 weeks after transplantation. The rate at which the transmission, once started, acquired mature characteristics was approximately the same in each case. Initially, spontaneous m. e.p. p.s were infrequent, long lasting with a skewed amplitude distribution. The e. p.p. s evoked by stimulation of the foreign nerve were then commonly below threshold for eliciting action potentials and were occasionally no larger than the size of the spontaneous m. e.p. p.s. M.e. p.p. characteristics became normal in the 2nd week after transmission had started. Fully effective evoked transmission with every innervated fibre responding with overshooting action potential occurred 1–3 months after onset of transmission.
Motor responses in the human trunk due to load perturbations
Authors: CARLSON H. , NILSSON J. , THORSTENSSON A. , ZOMLEFER M. R.
Published: December 2008

The trunk constitutes an integral part of the motor system and represents a large part of the total body mass. An adequate control of trunk movements and posture is therefore a prerequisite for the maintenance of the body equilibrium during various motor tasks. There is, however, little experimental data on how such a control is executed in different situations. During locomotion, phasic variations of the pressure within the abdominal cavity resulting from preprogrammed abdominal wall muscle activity occur and may be one important factor stabilizing the trunk (Grillner et al. 1978). Simultaneous bilateral phasic activation of different parts of the lumbar back muscles is another factor which may govern the stiffness of the spine in repetitive motor activities like walking and running (Carlson et al. 1979). In experiments on postural control associated with voluntary arm movements it has been found that different trunk muscles are activated in a specific order and prior to the execution of the actual movement of the extremity (Belenki et al. 1967, Weiss & Hayes 1979). This type of preactivation may give rise to a preparatory stabilization of the trunk.
Secretory effects of cholecystokinins on the isolated perfused porcine pancreas
Authors: JENSEN STEEN LINDKÆR , REHFELD JENS F. , HOLST JENS J. , NIELSEN OLE VAGN , FAHRENKRUG JAN , De MUCKADELL OVE B. SCHAFFALITZKY
Published: December 2008

Three different molecular forms of cholecystokinin (CCK‐39, ‐33, and ‐8) were used in concentrations from 10‐11 to 10‐8 mol/l to stimulate the endocrine and exocrine secretion from the isolated perfused porcine pancreas. During perfusion with a glucose concentration of 7.5 mmol/1 CCK‐39 in the highest concentration increased the insulin secretion slightly. No significant effect was observed at lower glucose concentrations (5.0 and 3.5 mmol/l). CCK‐33 and ‐8 did not stimulate the secretion of insulin significantly, and neither of the cholecystokinins increased the secretion of glucagon and bicarbonate. All three molecular forms stimulated the secretion of fluid and protein in concentrations above 10‐11 mol/l in a dose‐dependent manner and with equal potency. We conclude that the effect of these three cholecystokinins on the endocrine pancreas is without physiological significance, whereas all three are sufficiently potent to play a role in the control of pancreatic protein secretion.
Load‐dependent activation of calcium turnover and cardiac performance in isolated rat atria
Authors: METSÄ‐KETELÄ T. , PARANTAINEN J. , VAPAATALO H.
Published: December 2008

The effects of increasing load on developed tension (DT) and its second derivative, 45Ca uptake, as well as on the levels of cAMP, cGMP, PGE and PGF2α were investigated in spontaneously beating isolated rat atria. Gradually increasing loads augmented, parallelly, both DT and 45Ca uptake into the atria. The levels of cAMP, cGMP, PGE and PGF2α were not altered. Indomethacin (1 μM) did not antagonize the effect of loading on DT. It is concluded that activation of calcium mobilization is involved in the length‐tension relationship of the heart. This mobilization is not connected with changes in tissue concentrations of cAMP or of prostaglandins.
Effect of orthostatic blood pressure changes upon capillary filtration‐absorption rate in the human calf
Authors: SEJRSEN PER , HENRIKSEN OLE , PAASKE WILLIAM P.
Published: December 2008

The effect of postural changes upon fluid filtration rate in the calf was studied in 3 healthy subjects placed in supine position. Volume changes in the calf were measured by a water plethysmograph. Relative changes in blood flow in subcutaneous tissue and anterior tibial muscle were measured by the local 133Xe washout technique. Lowering the calf from 5–25 cm caused a linear increase in filtration rate whereas blood flow in subcutaneous tissue of the segment studied and anterior tibial muscle remained constant. Based on this average CFC was about 0.0012 ml min‐1 100 g‐1 mmHg‐1 Further lowering of the calf caused a decrease in blood flow in subcutaneous tissue and skeletal muscle by about 50% corresponding to an increase in total vascular resistance by about 100%. During these circumstances the increase in filtration rate was reduced by about 33%. The results indicate that the local veno‐arteriolar reflex responsible for the observed vasoconstriction in the tissue under study together with intrinsic vascular mechanisms reduces transcapillary fluid filtration in the lowered position. The mechanism appears to be mainly due to a reduction of the increase in mean capillary pressure whereas CFC seems to remain almost constant.
Circulatory effects of carotid sinus stimulation and changes in blood volume distribution in hypertensive man
Authors: LINDBLAD L. E. , BEVEGÅRD S. , CASTENFORS J. , TRANESJÖ J.
Published: December 2008

In 8 patients with moderate hypertension and 8 normotensive subjects an attempt was made to study the circulatory effects of high and low pressure baroreceptor stimulation. Intrathoracic low pressure receptors were stimulated by changes in blood volume distribution using lower body negative pressure (LBNP) and lower body positive pressure (LBPP). The carotid sinus was stimulated by sinusoidal neck suction. Blood pressure, central venous pressure, heart rate, cardiac output and forearm blood flow were recorded. During LBNP and LBPP changes in central blood volume, reflected in changes in central venous pressure, induced significantly greater changes in cardiac output and forearm blood flow in the hypertensive subjects. In both normotensive and hypertensive subjects mean arterial blood pressure was essentially unchanged during LBNP and a slight increase was found during LBPP. Heart rate and blood pressure response to stimulation of the carotid sinus decreased with increasing resting mean arterial pressure. The results suggest impairment of reflex adjustments, via arterial baroreceptors, possibly in particular to dynamic stimuli, rather than via intrathoracic “low pressure” baroreceptors in subjects with moderate hypertension.
The occurrence of Gastrin‐17 in the heart
Authors: GERSL VLADIMIR , GOINY MICHEL , UVNÄS‐WALLENSTEN KERSTIN
Published: December 2008

Radioimmunoassay revealed gastrin‐like immunoreactivity in extracts of the heart muscle from cat, guinea pig, rabbit and hog. The immunoreactivity was unevenly distributed, the highest levels being observed in extracts from the atria of the cat heart: in the right atrium ˜1000 pg/g or 450 pmol/kg and in the left atrium ˜4400 pg/g or 2000 pmol/kg. In extracts from the cat atria the gastrin‐like immunoreactivity was identified as Gastrin‐17. The preponderant localization of gastrin to the atria is suggested to be due to the distribution of gastrin containing vagal fibres and nerve terminals in that area, even if a possible localization to specific receptors, Purkinje fibres etc. cannot be excluded. A modulating action on the vagal influence on the heart, either on neurotransmission or on the receptor level, or a direct (perhaps trophic) effect on biochemical processes in the muscle are suggested as possible biological functions of the heart gastrin.
Vascular effects of slow reacting substance (SRS) in the cat nasal mucosa and the appearance of a SRS‐like principle in cat nasal secretion on nerve stimulation
Authors: ÄNGGÅRD ANDERS , STRANDBERG KJELL
Published: December 2008

Stimulation of parasympathetic secreto‐vasomotor nerve fibres in cat nasal mucosa produced nasal secretions with biological activity similar to cat paw SRS. The biologically active principle was purified by ethanol extraction, Amberlite XAD‐2 and anion exchange chromatography. It had elution characteristics common with cat paw SRS but different to those of prostaglandin F2α. The biological activity on the guinea pig ileum was antagonized by FPL 55712. In the cat intraarterial administration of cat paw SRS resulted in a dose‐dependent but modest increase in nasal blood flow whereas local blood content was not affected. Provided SRS has similar effects on human nasal blood flow the importance for SRS as a mediator for nasal congestion in allergic rhinitis or parasympathetically induced vasomotor rhinitis seems less likely.
Effect of membrane potential on the passive transport of TI+ in human red blood cells
Authors: SKULLSKII I. A. , MANNINEN V.
Published: December 2008

It was earlier found that TI+ can easily penetrate the red cell membrane. The main finding of this work is that TI+ can be used for studying alterations in the membrane potential of human red blood cells exposed to various experimental conditions. It was shown that after inhibiting active transport by ouabain, both the rate of transmembrane movement and the cell/medium distribution of TI+ were in a good agreement with the expected changes in membrane potential. Alterations in membrane potential were induced by modifying the cation permeability of the red cell membrane and by varying the cation concentration gradient across the membrane, which were achieved: 1) by incubation in an electrolyte‐free sucrose solution, 2) by addition of valinomycin or 3) by addition of propranolol. Changes in cation permeability were followed by means of 86Rb tracer. Hyperpolarization of the red cell membrane led to accelerated influx and retarded efflux of TI+. The opposite effect was obtained by depolarization. Quantification of the results was made using the Nernst equation and the cell/medium concentration ratio of TI+ at equilibrium. The calculations show that the membrane potential of the propranolol‐treated cells increased to about ‐20 mV, negative inside. The mechanism of the propranolol effect is briefly discussed.
Aggressive behaviour in mice provokes a marked increase in both plasma epidermal growth factor and renin
Authors: NEXØ EBBA , HOLLENBERG MORLEY D. , BING JENS
Published: December 2008

The plasma concentration of epidermal growth factor (EGF) in normal, nephrectomized and sialectomized mice is about 0.5 nmol/1. Aggressive behaviour results in a parallel increase in both plasma EGF and plasma renin for both normal and nephrectomized mice. The plasma concentration of EGF increases around 300‐ and 150‐fold respectively; no increase is observed in sialectomized mice, suggesting that the submaxillary gland is an important source of liberated EGF. Virtually all the EGF is found in plasma as a low molecular species that behaves as pure EGF, when examined by radioimmuno‐ and radioreceptor assays.
Capillary supply and lipoprotein‐lipase activity in skeletal muscle in man
Authors: LITHELL H. , LINDGÄRDE F. , NYGAARD E. , SALTIN B.
Published: December 2008

Circulating plasma triglycerides cannot be taken up by different tissues until they have been hydrolysed by lipoprotein lipase (Robinson 1970). The enzyme is located on the intraluminal surface of the capillaries (Scow et al. 1976). It is synthesised in adipocyte (Scow et al. 1976) and (heart) muscle cells (Chohan & Cryer 1978, Bagby et al. 1977) and transferred to the surface of the capillary endothelial cells, migrating over this surface to reach the intraluminal area (Olivecrona et al. 1976). Hydrolysis by lipoprotein lipase is a rate‐limiting step in the removal process of plasma triglycerides and is therefore a determining factor for the plasma triglyceride concentration (Robinson 1970).
Influence of ethanol and acetaldehyde on electro‐mechanical coupling of skeletal muscle fibres
Authors: KHAN A. RAUF.
Published: December 2008

The effects of ethanol were studied on the time course of the isometric twitch and tetanus of isolated semitendinosus muscle fibres ofRana temporaria(at 2.8‐4.5°C). Ethanol in concentrations between (0.1‐0.4 M) suppressed the isometric twitch without significantly affecting the tetanus amplitude. A further increase in ethanol concentration (0.5 M) depressed the tetanic tension as well. The maximum rate of force development both of twitch and tetanus was reduced. These changes were fully reversible when ethanol was removed from the bathing fluid. In presence of ethanol there was a reduction, although not statistically significant, in the resting membrane potential and in the maximum rate of rise of the action potential. The overshoot and the maximum rate of fall of the action potential were significantly lowered leading to a prolongation of the duration of the action potential. Acetaldehyde in relatively low concentrations (0.9‐1.8 mM) caused a marked potentiation of the twitch without significantly affecting the tetanic amplitude. These changes were, to a great extent, reversible. Higher concentrations (18 mM) of acetaldehyde reduced both the twitch and the tetanic tension and these effects were not reversible on removal of drug from the bathing solution. No detectable effects of the drug (1.8 mM) were observed on resting or action membrane potentials of the muscle fibre. The data presented supports the idea that ethanol suppresses the twitch response by inhibiting the calcium release mechanism and uncouples the excitation‐contraction process. The twitch potentiation by acetaldehyde seems to be due to enhancement of calcium release from the storage sites.
Effect of vasoactive intestinal polypeptide on cerebral blood flow in the goat
Authors: LARSEN JENS‐JØRGEN , BOECK VITA , OTTESEN BENT
Published: December 2008

The effect of vasoactive intestinal polypeptide (VIP) on the cerebral blood flow was investigated in the goat. An electromagnetic flow probe was placed around the internal maxillary artery for continuous measurement of ipsilateral blood flow. Intraarterial injection of VIP resulted in a dose‐dependent increase in the cerebral blood flow. The effect was not antagonized by any of the antagonists atropine, propranolol, phentolamine and naloxone administered intraarterially 1 min before VIP. It is discussed that VIP may play a physiological role in the local blood flow regulation in the CNS.
Effects of prostaglandin E1, E2, and F2α on isolated pial arteries of cat
Authors: USKI TORE K. , EDVINSSON LARS , OWMAN CHRISTER
Published: December 2008

Responses to prostaglandin (PG), E1, E2, and F2α were studied on isolated feline middle cerebral arteries. At resting state PGF2α produced strong dose‐dependent contractions. PGE2 elicited weak relaxations at low concentrations, followed by powerful contractions at higher doses. PGE1 had little effect on resting pial vessels. The relative constrictory potency was PGF2α > PGE2 > PGE1. During active tone, induced by administration of either potassium, norepinephrine, or 5‐hydroxytryptamine, relaxations induced by PGE1 were enhanced, whereas PGE2‐induced relaxations were unaffected. PGE1 induced relaxations were more pronounced when the active tension had been produced by administration of PGF2α than with either of the vasoactive amines or potassium. This study demonstrates the importance of smooth muscle tone, and by what means this is achieved, when examining the responses of PG's on cerebral blood vessels.
The role of left atrial receptors in the regulation of renin release in anesthetized dogs
Authors: HOLDAAS HALLVARD , DIBONA GERALD F.
Published: December 2008

Experiments were performed on anesthetized dogs to further define the role of left atrial cardiopulmonary receptors in the reflex neural control of renin release. Non‐hypotensive arterial hemorrhage produced reversible decreases in left atrial pressure and increases in renin release without significant changes in mean arterial pressure or renal blood flow. When non‐hypotensive arterial hemorrhage was performed, while keeping left atrial pressure constant via left atrial balloon inflation, no increase in renin release was observed. These experiments indicate that changes in blood volume unaccompanied by changes in arterial pressure are sensed by left atrial cardiopulmonary receptors, which results in renin release mediated by a neural reflex arc involving in the vagus as the afferent pathway and the renal sympathetic nerves as the efferent pathway.
Chemical design of antagonists of substance P
Authors: FOLKERS KARL , HÖRIG JOACHIM , ROSELL SUNE , BJÖRKROTH ULLA
Published: December 2008

Since the elucidation of the structure of substance P (Arg ‐ Pro ‐ Lys ‐ Pro ‐ Gin ‐ Gin ‐ Phe ‐ Phe ‐ Gly ‐ Leu ‐Met ‐ NH2) by Chang, Leeman & Niall (1971), many SP‐analogs have been described and have provided important information about the sequence‐activity relationships of SP. These studies have revealed the importance of chain length and of Phe7, Leu10 and Met11 for SP smooth muscle activity (Bergmann et al. 1974, Rosell et al. 1977). Thus, the smooth muscle stimulating activity is confined to the hexa‐peptide sequence at the C‐terminal. The (IIe7)‐SP analog showed little or no smooth muscle stimulating activity (Leban et al. 1979). Yamaguchi et al. (1979) synthesized (D‐Phe7)‐SP which was found to be a weak partial agonist on the guinea‐pig ileum. Likewise, (D‐Pro2)‐SP and (D‐Leu8, D‐Phe9)‐SP exerted some SP‐antagonism. A series of newly designed SP‐analogs has been tested for possible SP‐antagonism. We have found that (D‐Pro2, D‐Phe7, D‐Trp9)‐SP is an inhibitor of SP both on isolated organs and in vivo.
Uptake of (3H)‐ADTN into dopaminergic neurons in the rabbit retina
Authors: EHINGER BERNDT
Published: December 2008

6,7‐ADTN (2‐amino‐6,7‐dihydroxytetrahydronaphthalene) has been introduced as a potent dopaminergic agonist (McDermed, McKenzie & Phillips 1975, Cannon et al. 1977) which could possibly be used as a false neurotransmitter for dopamine. However, direct morphological evidence of the cellular localization of (3H)‐ADTN is lacking. This can readily be obtained in the retina where the dopaminergic neurons are well recognizable. We have therefore injected 20 μCi (3H)‐ADTN (2‐(5,8‐3H)‐ amino ‐6,7‐dihydroxy‐1,2,3,4‐ tetrahydronaphthalene, specific activity 35.5 Ci/mol, New England Nuclear, Dreieichenhain, West Germany) into rabbit eyes. After 4 h, the retina was obtained, freeze‐dried, fixed in formaldehyde gas at 80°C for 1 h, embedded in vacuo in plastic (Durcopan Fluka) without immersion in any intermediary solvents, cut at 4 μm and covered with autoradiographic stripping film (Kodak AR 10). The auto‐radiograms were developed after 3 months. Rabbit retina was also incubated at 37°C for 15 min in a balanced salt solution (Ames, Parks & Nesbett 1980) with 2.5 μCi (3H)‐ADTN/ml. After washing for 2°5 min at 0°C the tissue pieces were processed for autoradiography as above.
Interstitial fluid volume, colloid osmotic and hydrostatic pressures in rat skeletal muscle. Effect of venous stasis and muscle activity
Authors: REED ROLF K.
Published: December 2008

The effect of 24 h caval/iliac venous obstruction on interstital fluid volume (IFV), hydrostatic (P|) and colloid osmotic (COP1) pressure in hindlimb skeletal muscle was studied in three groups of rats: Group I (GI), Intact innervation, unrestricted motor activity. Group II (GII), Sympathectomized, unrestricted. Group III (GIII), Motoric and sympathetic denervation + immobilization of the hindlimbs. Subcutaneous edema was present in all groups at femoral venous pressure (Pv) exceeding 13 mmHg. Skeletal muscle edema was seen in G III at Pv above 12 mmHg, in two rats in G II at Pv of 18 and 23 mmHg, but in no rats in G I. Whithout venous obstruction, control COP1 was 8–10 mmHg in all groups. With increasing Pv, COP fell moderately in GI and GII: ΔCOP1/APv= 0.22. In GIII, COP, fell from a control of 8.2 to 3.5 mmHg at a Pv of 12 mmHg (ACOP1/APv=0.52), but remained constant with further rise in Pv P1 was about 0 mmHg in controls and 1–2 mmHg in rats with muscle edema. IFV rose by 6% per mmHg increase in Pv in G III, and 2% in G I and G II. This expansion of IFV may explain about 70% of the fall in COP1, the remaining being due to lymphatic washout of interstitial proteins. It is concluded that normal muscle activity together with dilution and washout of interstitial proteins constitute the main edema preventing mechansms in skeletal muscle.
Plasma Na+‐ion concentration or pH as regulator of pancreatic HCO‐3 secretion
Authors: RÆDER MORTEN , MATHISEN ØYSTEIN
Published: December 2008

Pancreatic HCO‐3 secretion is caused by proton flux from pancreatic cells to interstitial fluid which, hypothetically, may be driven by a Na‐pump or a proton pump. A Na‐pump would reabsorb protons from pancreatic duct in proportion with plasma Na+ concentration (PNa+). A proton pump would cause passive HCO‐3 flux into pancreatic ducts that would vary with pancreatic jive HCO‐3 concentration (CHCO3‐). Because pancreatic ducts are water‐permeable, CHCO3‐ varies with plasma osmolarity. This phenomenon allows testing of the two hypotheses. Intravenous infusion of hypotonic salt solution to 5 anesthetized, secretin infused pigs (2.7 C.U./kg b. wt. H‐1) lowered PNa+ by 20±2 mmol/l and CHC03‐ by 20±4 mmol/1 and increased pancreatic HCO‐3 secretion by 71±15 μmol/min. Intravenous infusion of hypertonic salt solutions to 5 other pigs raised PNa+ by 52±3 mmol/l and CHC03‐ by 54±3 mmol/1 and reduced HCO‐3 secretion by 86±26 μmol/min. Istonic glucose infusion lowered PNa+ by 27±2 mmol/l and did not change CHC03‐ nor HCO‐3 secretion rate in 5 pigs. These findings comply with the proton pump hypothesis and are at variance with the Na‐pump hypothesis of pancreatic HCO‐3 secretion.
Effects of autonomic blockade by methylatropine and optical isomers of propranolol on plasma insulin levels in the basal state and after stimulation
Authors: AHRÉN BO , LUNDQUIST INGMAR
Published: December 2008

The effects of autonomic blockade on plasma concentrations of immunoreactive insulin in the basal state and after stimulation with 4 different secretagogues were investigated in vivo in conscious mice. The muscarinic blocker methylatropine slightly depressed basal insulin, and almost totally abolished the insulin response to the cholinergic agonist carbachol, whereas the insulin response to glucose and glucagon was unaffected. Contrary to these findings, the insulin response to the β2‐adrenoceptor agonist terbutaline was potentiated, by about 75%. The β‐adreneceptor blocker l‐propranolol depressed basal insulin by about 60%, and totally abolished the insulin responses to glucagon and terbutaline. The insulin response to glucose was slightly reduced and that to carbachol was unaffected by l‐propranolol. The stereoisomer d‐propranolol which is devoid of β‐adrenoceptor blocking activity but exerts local anaesthetic effect of the same potency as the lpisomer, was without effect on basal insulin levels and the insulin responses to the different secretagogues. It is concluded that basal concentrations of immunoreactive insulin is substantially dependent on intact β‐adrenoceptros and more moderately dependent on intact muscarinic receptors. The insulin responses to terbutaline and glucagon are closely connected to the β‐adrenoceptors, and the response to carbachol to the muscarinic receptors. Glucose‐induced insulin response seems largely unaffected by autonomic receptor blockade although a slight reduction after β‐adrenoceptor blockade is demonstrable.
Responses to catecholamines and nerve stimulation of the perfused rete tibiotarsale and associated blood vessels in the hind limb of the Mallard (Anas platyrhynchos)
Authors: MIDTGÅRD UFFE , BECH CLAUS
Published: December 2008

The rete tibiotarsale, which is a functional arterio‐venous heat exchanger, and its associated blood vessels were perfused in situ and the responses to epinephrine (E), norepinephrine (NE), and perivascular nerve stimulation (NS) were studied. The vasoconstrictor response of the arterial shunt, which bypasses the rete, was significantly greater than in adjacent segments of the same artery. The constrictor responses to E, NE, and NS were reversibly blocked by the alpha‐blocker phentholamine. The rete arteries were also capable of vasoconstriction, but during simultaneous perfusion of the arterial shunt and the rete arteries, stimulation with NE and E stopped perfusate flow in the shunt while the flow in the rete arteries increased. Segments of the large vein and rete veins were unresponsive to NE, E, and NS. The results support the previously reported morphological evidences for a sphincteric action of the shunt artery, but not of the shunt vein.
Effect of isotonic volume expansion on proximal tubular reabsorption of Na and fluid in the developing rat kidney1
Authors: ELINDER GÖRAN
Published: December 2008

Young rats (aged 22–24 days) and adult rats (aged 40–42 days) were studied during hydropenia (HP) and during volume expansion (VE) in order to clarify the role of the proximal tubule of the immature kidney in the blunted natriuretic response seen in young mammals during VE. The position of the last accessible site for micropuncture of the proximal tubular segment was determined. The disadvantages of using lissamine green as a marker of different tubular segments were investigated. Tubular function was ascertained by micropuncture of superficial proximal nephrons. Measurements of tubular length were made from latex casts of the proximal tubule. No side‐effects of lissamine green were detected, when small quantities were used (20–30 μl) and at least 20 min elapsed between the infusions of the dye and tubular samplings. The last accessible proximal tubule available for micropunction was found to be similarly located in young and adult rats. Fractional reabsorption during HP remained constant during development. An equivalent degree of VE induced an increase in tubular load in both age groups, but it was more marked among younger rats. Absolute proximal reabsorption in both young and old rats in HP paralleled that of the tubular load. Fractional reabsorption, however, decreased slightly during VE but to the same extent in both age groups. This indicates a great flexibility in the immature proximal tubule under various tubular loads although it had been thought that this part of the nephron was in the later stages of development. The results imply that the proximal tubule does not create the blunted sodium response in the immature kidney during VE.
The effect of a small stretch on the latency relaxation and the short‐range elastic stiffness in isolated frog muscle fibres
Authors: HAUGEN P. , STEN‐KNUDSEN O.
Published: December 2008

The amplitude of the latency relaxation and the stiffness of the short‐range elastic component (SREC) were determined in single muscle fibres before and immediately after subjecting the fibre to a sudden small stretch at constant velocity. After the stretch the amplitude of the latency relaxation was reduced compared to the value obtained before the stretch provided that the velocity of stretch exceeded about 1 nm · ms‐1per half‐sarcomere and that the amplitude of the stretch was sufficient to reach the stationary response of the SREC. The effect of the stretch on the amplitude of the latency relaxation subsided after about 4 ms. A reduction of the amplitude of the latency relaxation was accompanied by a reduction of the short‐range elastic stiffness. This result is discussed in terms of the various hypotheses put forward to account for the generation of the latency relaxation.