bluuebunny/crossref_metadata_2025 huggingface dataset:
Sympathetic denervation affects the choline acetyltransferase activity in decentralized parasympathetic neurones of the submaxillary gland of the rat
Authors: EKSTRÖM JÖRGEN
Published: December 2008

Parasympathetic decentralization of the rat submaxillary gland caused the activity of the acetylcholine forming enzyme, choline acetyltransferase, to decrease. No such decrease in the enzyme activity was observed when parasympathetic decentralization was combined with sympathetic denervation and further, if the two types of operation were carried out in sequence the enzyme activity could be shown to increase from a reduced level. Thus in contrast to previous concept the present study shows that the activity of choline acetyltransferase in the postganglionic nerves can be influenced by sympathetic denervation in spite of the fact that these nerves are not in contact with the central nervous system. The choline acetyltransferase activity was not affected by preganglionic sympathetic denervation.
Effects of age and prolonged running on proteolytic capacity in mouse cardiac and skeletal muscles
Authors: SALMINEN A. , VIHKO V.
Published: December 2008

Male NMRI‐mice, aged 3, 6, 9, and 12 months, were made to run for a period of 4 h at a speed of 13.5 m/min on a motor‐driven treadmill. 5 days after exertion, selected enzymatic estimates of acid and alkaline proteolytic as well as energy metabolic capacities were analyzed from the cardiac muscle and from the red and white parts of m. quadriceps femoris (MQF). The activities of alkaline and myofibrillar proteases increased most considerably in skeletal muscles with age. Cathepsin D and β‐glucuronidase activities were less affected in both muscles. Prolonged running increased the activities of cathepsin D, dipeptidyl aminopeptidase I and β‐glucuronidase in the white and, especially, in the red part of MQF. This stimulation of acid hydrolytic capacity was more prominent at the ages of 3 and 6 months than in the older animals. The estimates of alkaline proteolytic or energy metabolic capacities were not affected by prolonged running. In cardiac muscle, no significant changes were recorded in acid hydrolytic or energy metabolic capacity. Histological observation showed no necrosis or other pathological phenomena in the proximal part of m. rectus femoris after exertion. We suggest that the increased acid proteolytic capacity is involved in subcellular regenerative processes of skeletal muscle fibres. The smaller lysosomal response of older mice may indicate a reduced potential capacity for cellular repair.
The dependence of the short‐range elasticity on sarcomere length in resting isolated frog muscle fibres
Authors: HAUGEN P. , SEN‐KNUDSEN O.
Published: December 2008

The tension response of a resting muscle fibre to a sudden small stretch (ca. I % of the fibre length) at constant velocity was analyzed according to a mechanical model in which two components are arranged in parallel: (i) The parallel elastic component (PEC) which is responsible for the resting tension of the fibre. (ii) The short‐range elastic component (SREC) which has a highly non‐linear tension response: Initially, the tension increases linearly with stretch, but with further stretch the increase in tension subsides and a steady tension level is attained. Both the initial short‐range elastic stiffness and the steady state tension level increased with increasing sarcomere length up to 2.9‐3.3 pm where both variables reached maximum values. The maximum value of the steady tension level was about 1 % of the maximum twitch tension. With further increase of sarcomere length both the short‐range elastic stiffness and the steady tension level demased and approached zero at a sarcomere length of about 3.7 pm. The structural basis for the SREC is considered to be myosin heads which are cross‐linking the thick and the thin fdaments even in the resting state of the fibre.
Methylprednisolone and adrenergic mechanisms in vascular smooth muscle
Authors: BENGTSSON B.
Published: December 2008

The influence of methylprednisolone on noradrenaline‐indicted contractions and3H‐noradrenaline release was investigated in isolated preparations of rat aorta and portal vein. 20–200 μM of methylprednisolone had a slight inhibitory effect on the contractions of the aorta but had no effect in the portal vein. The EC50‐values for noradrenaline were about 10‐6M in both vessels; methylprednisolone did not change it. The steroid changed neither spontaneous nor potassium (127 mM) induced release of3H‐noradrenaline. The potassium (127 mM) induced contracture in the portal vein had 2 phases; the second, at least partly, was produced by released intramural noradrenaline as it was depressed by reserpinization of the animal. Injection of methylprednisolone to the animal 2 h before sacrifice induced a better maintained second phase of the potassium contracture in the portal vein. Although this could mean the release of increased amounts of noradrenaline, other explanations are also possible.
Effect of apomorphine on peripheral venous gastrin and insulin levels in conscious dogs
Authors: UVNÄS‐WALLENSTEN KERSTIN , GOINY MICHEL
Published: December 2008

Apomorphine 0.001, 0.005, 0.05 and 0.1 mg/kg were given i. v. to conscious dogs and gastrin and insulin levels were measured in peripheral venous blood. The lowest dose of apomorphine (0.001 mg/kg) did not change gastrin levels but some times caused a decrease of insulin levels, whereas the higher doses (0.005–0.1 mg/kg) induced a dose dependent increase of both hormone levels. The peak shaped release responses appeared within a few minutes and the basal values were reached again within 20 to 30 min. Apomorphine within the dose range which induced a response of insulin and gastrin also caused nausea and vomiting. Añer pretreatment with haloperidol (0.1 mg/kg) no signs of sickness were observed and the response of gastrin to 0.01 and 0.05 mg/kg of apomorphine was almost completely blocked, whereas the insulin response to both these doses was inhibited to ˜50%. We conclude that the release of gastrin and insulin can be activated by stimulation of dopaminergic receptors, the anatomical location of which is not clear. Possible sites for the dopaminergic receptors are the hypothalamic region or the vagal centres in the medulla oblongata.
Peripheral and central vascular compliances in conscious normotensive and spontaneously hypertensive rats
Authors: RICKSTEN S. E. , YAO T. , THORÉN P.
Published: December 2008

Changes of left atrial (LAP) and right atrial pressure (RAP) upon 10% and 20% blood volume expansion were studied in conscious spontaneously hypertensive rats (SHR) and normotensive Wistar‐Kyoto rats (WKR) with intact nervous cardiovascular control. In a separate series the changes of central (CBV) and peripheral (PBV) blood volumes upon similar increases of total blood volume (TBV) were measured as well, throughout using male, adult SHR and WKR in both series. During volume expansion both LAP and RAP increased significantly more in SHR than in WKR, as did CBV, while PBV increased significantly less in SHR than in WKR. Total ‘effective’ vascular compliance, defined as ΔTBV/ΔRAP, was significantly lower in SHR. From the two series of measurements central (CBV/LAP) and peripheral (PBV/RAP) vascular compliances could be separately deduced. Central vascular compliance was nearly 50% lower in SHR than in WKR. However, ‘unstressed’ volume of the peripheral compartment appeared to be rather normal in SHR compared to WKR. It is therefore suggested that the decreased total vascular compliance seen in essential hypertension and in SHR is mainly due to a decreased distensibility of the systemic capacitance vessels.
Outgrowth of cholinergic nerves in the rat urinary bladder either partially denervated or partially denervated and decentralized
Authors: ALM PER , EKSTRÖM JÖRGEN
Published: December 2008

Unilateral excision of the pelvic ganglion caused a loss in the number of AChE‐positive nerves in the rat urinary bladder both on the operated side and on the contralateral side, thus indicating a bilateral intramural distribution of cholinergic nerves derived from the pelvic nerve. In the course of the subsequent observation period (3–28 days) the AChE‐positive nerves increased in number and in staining intensity and further, the nerves became ramified and twisted. Similar events were found to occur in the urinary bladder decentralized on one side and denervated on the other. The morphological findings indicate an outgrowth of cholinergic nerves by collateral sprouting. These findings are discussed in relation to previous physiological studies.
Effects of facial nerve section and stimulation on cerebral and ocular blood flow in hemorrhagic hypotension
Authors: UNDER JAN
Published: December 2008

Albino rabbits were anesthetized and artificially ventilated. In two groups of animals the facial nerve on one side was sectioned and/or electrically stimulated at the internal acoustic pore. Hemorrhagic hypotension was induced to reveal a possible parasympathetic vasodilator mechanism, normally masked. The labelled microsphere method was used for flow determinations. Section of the facial nerve did not produce any difference between sectioned and intact side, concerning cerebral, ocular and mandibular gland blood flows at normal or low blood pressures. Stimulation of the facial nerve at arterial hypotension produced significant ipsilateral increases in the choroidal and the mandibular gland blood flows. Regional and total cerebral blood flow remained unaffected. The results indicate no or only minimal contribution of the facial nerve to the cerebral vascular tone under conditions of general anestheisa. Further evidence is given in this study for a vasodilator pathway to the eye via the facial nerve, but the resting vasodilator tone under general anesthesia seems to be very low at normotensive as well as hypotensive states.
Further studies on beta‐adrenergic control of transcapillary fluid absorption from skeletal muscle to blood during hemorrhage
Authors: HILLMAN JAHN
Published: December 2008

During hemorrhage fluid is absorbed from the extravascular space of skeletal muscle into the intravascular compartment in order to compensate for the blood loss. In a previous report (Lundvall & Hillman 1978) this process was found causally linked to reflex, β‐adrenergic control of the capillary hydrostatic pressure (via adjustment of pre‐/postcapillary resistance) and of the capillary exchange area (via adjustment of ‘precapillary sphincter’ tone). The present study extends the experimental evidence for such β‐adrenergic control of plasma volume in bleeding, showing that it operates for prolonged periods of time and in a graded manner over a wide range of hemorrhagic hypovolemia. The investigation also provides information about the quantitative importance of the fluid gain from muscle to blood for plasma volume restoration in hemorrhage. Thus, during moderate bleeding (10 ml × kg b. wt.‐1) the cumulative (45 min) fluid gain from muscle to blood averaged 1.4 ml × 100 g muscler.‐1 This implies, when calculated for the total muscle mass, that about 2/3 of the shed blood volume will be replaced by interstitial fluid within less than one hour.
Sodium and calcium action potentials in cells derived from a rat medullary thyroid carcinoma
Authors: SAND O. , OZAWA S. , GAUTVIK K. M.
Published: December 2008

Primary monolayer cultures were made from a rat medullary thyroid carcinoma. All the cultures produced calcitonin throughout the 4 week experimental period. Two different parenchyma! cell types could be distinguished, based on a marked size difference. Only the group of smaller cells was electrically excitable. The membrane potential and resistance of these cells were 55.3±15.4 mV and 623±275 Mü (mean ± S.D., n=23), and current injections produced regenerative responses in all the cells. All‐or‐none action potentials were recorded in both normal and Na+‐free solution. In Na+‐free solution the maximum rate of rise of the action potential was reduced by about 70%, and the action potential was reversably blocked by D‐600. It is concluded that the action potentials have both a Na+ and a Ca2+ component, and circumstantial evidence suggests that our recordings were obtained from the calcitonin‐producing cells.
Development and validation of a radioimmunoassay for beta‐endorphin‐related peptides
Authors: VUOLTEENAHO OLLI , LEPPÄLUOTO JUHANI , VAKKURI OLLI , KARPPINEN JARO , HÖYHTYÄ MATTI , LING NICHOLAS
Published: December 2008

A radioimmunoassay method suitable for measuring levels of B‐endorphin, B‐lipotropin and proopiocortin in tissue and plasma extracts was developed and the method was evaluated by using 3 independently prepared antisera. Of the several variables tested the choice of assay buffer and test tubes and the purification of tracer were found to be the most critical in the successful performance of B‐endorphin radioimmunoassay. The prevention of degradation of tracer during incubation was also necessary when crude tissue extracts or plasma were assayed. The sensitivities of the assays obtained with the 3 antisera utilized (Bendo 2, K 2 and RB 100) were 1, 2.8 and 4 fmol B‐endorphin per tube. All the antisera crossreacted equimolarly with B‐lipotropin. The method was employed to measure the levels of B‐endorphin immunoreactivity in rat pituitary and plasma by separating the different immunoreactants by gel filtration. It was found that both pituitary and plasma contain significant amounts of proopiocortin, B‐lipotropin and B‐endorphin, the molar proportions being 10:33:57 in pituitary and 15:15:70 in plasma, respectively. Both anterior and posterior lobes of rat pituitary were found to contain all the three immunoreactants. However, anterior lobe contained mostly the larger molecules, while posterior lobe was rich in B‐endorphin. No absolute levels of the immunoreactants could be obtained due to the heterologous system used. Moreover the elution pattern of the immunoreactivity was found to be dependent on the conditions used for elution in gel filtration: higher proportion of the immunoreactivity eluted like B‐endorphin when the elution was done in dissociating conditions (6M urea) compared to elution with ordinary buffers.
Augmented vasoconstrictor response to changes in vascular transmural pressure in patients with essential arterial hypertension
Authors: HENRIKSEN O. , SKAGEN K. , AMTORP O. , HARTLING O.
Published: December 2008

The vasoconstrictor response to increase in venous transmural pressure in subcutaneous tissue was studied in 9 patients with essential arterial hypertension. Subcutaneous blood flow was measured on the distal part of the forearm and at the lateral malleolus by the local133Xe washout technique. Increase in venous transmural pressure was obtained by lowering the area under study 40cm below midaxillary line in the recumbent subject. Average mean arterial pressure ± 1 S.E. was 133 ± 6 mmHg. The fractional increase in vascular resistance induced by arteriolar constriction was more pronounced in the hypertensive patients than in a normotensive control group. “Minimal vascular resistance” in the papaverine relaxed vascular bed was higher in the hypertensive patients than in the controls. Distensibility of the papaverine relaxed resistance vessels was diminished in the patients. Follow‐up studies after 6–18 months of anti‐hypertensive treatment indicate that the vasoconstrictor response as well as “minimal vascular resistance” are normalized, whereas the distensibility of the papaverine relaxed arterioles remained unaltered in the hypertensive patients. The results indicate that the arteriolar smooth muscle cells of hypertensive patients are subjected to reversible hypertrophy whereas the reduced distensibility of the resistance vessels is due to irreversible structural changes.
Ocular responses to antidromic trigeminal stimulation, intracameral prostaglandin E1 and E2, capsaicin and substance P
Authors: MANDAHL AGNETA , BILL ANDERS
Published: December 2008

The role of nerve conduction was studied in acute experimental uveitis caused by antidromic trigeminal nerve stimulation, prostaglandin E1 and E2 (PGE1 and PGE2), capsaicin and substance P (SP). Systemic indomethacin was used to prevent formation of endogenous prostaglandins, and intracameral injection of tetrodotoxin (TTX) was used to block nerve conduction. 10μg TTX prevented the miosis and reduced the rise in intraocular pressure (IOP) usually caused by antidromic trigeminal nerve stimulation. At a low dose of PGE1 the IOP rise was blocked by TTX. At higher doses of PGE1 and PGE2 the pressure effect was not blocked by TTX; the miotic effect was markedly diminished. Capsaicin caused a rise in IOP that was almost totally blocked by TTX, while the miosis at high doses seemed unaffected. At low doses, capsaicin‐induced miosis could be abolished by TTX. SP caused miosis in TTX treated eyes similar to that in untreated eyes; the IOP rise was delayed by TTX. The results indicate that nerve conduction plays a role in the IOP reaction caused by low doses of PGE1 and by capsaicin and SP. The mechanism suggested is an axon reflex, elicited in the anterior uvea and resulting in transmitter release in the ciliary processes. Nerve conduction with release of SP or a similar substance in the iris seems to be required for the miotic effects of PGE1 and PGE2. SP and capsaicin are similar in not requiring nerve conduction to cause miosis, but the capsaicin effect probably requires presence of nerves, since denervated eyes—which respond to SP—have been reported not to respond to capsaicin doses similar to those used here.
Effects of hypoxia and fasting on the cytochrome concentration in intestinal epithelial villous cell mitochondria: Role of changes in the life‐span of the cells
Authors: KINNULA VUOKKO L. , HASSINEN ILMO E.
Published: December 2008

The effects of hypoxia in vivo (40.8 kPa barometric pressure up to 120h) and fasting on the characteristics of intestinal epithelial villous cell mitochondria and the turnover of epithelial villous cells and mitochondria were studied in rats. Using cells and mitochondria isolated in the isotonic mannitol medium, it was found that 24‐h hypoxia or fasting did not alter the mitochondrial cytochrome content, but 48‐h hypoxia or fasting led to increases of 70% and 37% in the cytochrome aa3 concentration in the hypoxic and fasting animals respectively. The turnover of intestinal epithelial cells was studied by observing the labelling kinetics of the cells with 3H‐thymidine and the turnover of the cell and mitochondrial proteins with (guanido‐14C)‐arginine or 3H‐leucine. The decay in thymidine radioactivity obeyed exponential kinetics from which half‐lives of 1.15, 1.31 and 1.53 days were calculated in the control, fasting and hypoxic animals respectively. The half‐lives for total cellular protein were 1.31, 1.54 and 1.54 days respectively when calculated from the (guanido‐14C)‐arginine experiments, or 0.69, 0.75 and 0.99 days when calculated from the leucine experiments. The labelling experiments with (guanido‐14C)‐arginine indicated that the turnover of mitochondrial proteins in intestinal epithelial cells is the same as that of the cells themselves. Since the turnover of mitochondrial proteins in other tissues is known to be a relatively slow process, the increase in the cytochrome concentration in the intestinal cells of the hypoxic rats must be due to the longer life of the cells, which allows for the synthesis of larger amounts of the mitochondrial components.
The effect of temperature elevation on the cerebrovascular response to noradrenaline and 5‐hydroxytryptamine
Authors: HARDEBO J. E. , HINDFELT B.
Published: December 2008

Fever frequently complicates stroke and subarachnoid haemorrhage. A transient rise in transmitter monoamine levels of plasma and cerebrospinal fluid occurs in these diseases. The present study demonstrates an enhanced vasoconstrictor response of cerebral vessels to noradrenaline—but not 5‐hydroxytryptamine—following a rise in temperature. The augmented response is more likely due to an impaired inactivation (re‐uptake) of the amine than to an altered sensitivity of the post‐synaptic α‐adrenergic receptor, since it could be reproduced by pretreatment with cocaine. The finding indicates that it may be important to combat fever in these patients.
Insulin secretion induced by glucose and by stimulation of β2‐adrenoceptors in the rat. Different sensitivity to somatostatin
Authors: AHRÉN BO , JÄRHULT JOHANNES , LUNDQUIST INGMAR
Published: December 2008

The effects of somatostatin on insulin secretion stimulated by glucose or by the selective β2‐adrenoceptor agonist terbutaline were studied in vivo in the anaesthetized rat. Infusion of low doses of glucose (5mg/min) or terbutaline (2 μg/min) caused slight stimulation of insulin secretion, whereas infusion of higher doses of glucose (12.5mg/min) or terbutaline (200 μg/min) yielded higher rates of insulin release. In both instances plasma insulin concentrations were of comparable magnitudes immediately prior to somatostatin infusion. Somatostatin (0.1 μg/min) inhibited the insulin response to glucose and terbutaline, both at the low and high secretory rates. However, the inhibitory effect of somatostatin was much more pronounced on insulin release during glucose infusion than during infusion of terbutaline. Thus, at the high rate of insulin secretion somatostatin depressed plasma insulin by 46% during glucose and by 22% during terbutaline infusion. The results at the low rate of insulin secretion were 66% and 48%, respectively. Both at high and low secretory rates somatostatin depressed plasma insulin levels more potently during glucose infusion than during terbutaline infusion (P < 0.001 and P < 0.05, respectively). Furthermore, the plasma insulin levels during inhibition by somatostatin following terbutaline stimulation stabilized after approximately 10min of somatostatin infusion, whereas following glucose stimulation the insulin levels continued to decline. The results suggest that somatostatin inhibits insulin secretion via mechanisms that are more closely related to the insulin secretory pathway induced by glucose than to that induced by β‐adrenoceptor agonists.
Responses to ions and vasoconstrictor agents and changes of potassium fluxes in vascular smooth muscle during hypoxia
Authors: SIGURDSSON STEFAN B. , ORLOV RATMIR S. , HELLSTRAND PER , JOHANSSON BÖRJE
Published: December 2008

An inhibitory effect of hypoxia (PO2<5mmHg) on electrical and mechanical activity of the smooth muscle of the rat portal vein has been described by Hellstrand, Johansson & Norberg (1977). The present study using the sucrose gap method confirmed their finding that spontaneous activity was completely (or almost completely) abolished by the low PO1. Increased [K+]0from 6 to 24 mM or decreased [Na+]0from 137.5 to 76.5 mM reinitiated electrical and mechanical activity during hypoxia. If muscle activity had already been increased by 24 mM K+ or 76.5 mM Na+ solutions in the aerobic situation, switching to hypoxia caused only partial inhibition. In hypoxic solutions of such altered ionic composition a gradual increase in muscle activity with time was seen especially in the low Na+‐solution. Stimulating agents such as noradrenaline, acetylcholine, 4‐aminopyridine, and Ba2+could reinitiate spike activity and contractions under hypoxic conditions. Ouabain stimulated the activity in normoxia but no effect was seen in hypoxia. Uptake and washout of42K+ was studied. No difference in uptake was found between normoxic and hypoxic conditions. The rate of42K+ efflux was decreased under hypoxia. A similar decrease was produced by Mn2+(0.4 mM) which, like hypoxia abolished phasic muscle activity. In both cases the reduction in42K+ efflux may just reflect the elimination of action potentials. It is concluded from these results that profound hypoxia exerts its inhibitory effect on the smooth muscle to a large extent through membrane mechanisms responsible for pacemaker activity or spike generation. The electrophysiological response may be secondary to change in intracellular [Na+] or [Ca2+].
Cyclic AMP‐dependent and independent effects of prostaglandins on the contraction‐relaxation cycle of spontaneously beating isolated rat atria
Authors: METSÄ‐KETELÄ TIMO
Published: December 2008

The effects of prostaglandin (PG) F2α, E2, E1and I2on the amplitude, duration of the contraction‐relaxation cycle (CRC), the second derivative of developed tension and the cyclic adenosine‐3′,5′‐monophosphate (cAMP) level and on45Ca uptake were studied in isolated spontaneously beating rat atria. The order of capacity to generate positive inotropic effects was PGF2α>PGE2>PGE1˜PGI2. Only PGI2and PGE1decreased the duration of CRC. PGF2αproduced an increase during the first 2.5min, whereafter the duration returned to the initial level. PGE2had no significant effect on the shape of the CRC. The ratios of the maximum and minimum of the second derivative of the developed tension were reduced by PGI2and PGF2α2.5 and 5 min after administration, respectively. The45Ca uptake was stimulated equally by all of the tested PGs, but only PGI2and PGE1could significantly increase the cAMP level. The results do not support the conception that cAMP could mediate the positive inotropic effect of PGs. Rather the contrary, cAMP, increased by PGE1or PGI2, could be responsible for increased relaxation, which might prevent the full development of tension.
Early changes in ATP and cyclic AMP levels in experimental critical skin flaps
Authors: JURELL GÖRAN , FREDHOLM BERTIL B.
Published: December 2008

A cranially based pedicle skin flap, 2 cm wide and 7 cm long, was prepared in the midline of the rat dorsum. The contents of ATP and cyclic AMP were determined in the proximal, middle and distal parts of the flap. The basal level of ATP was 1.3±0.1 nmol/g dry weight. Following the operation the level of ATP fell rapidly. The fall was more marked in those parts of the flap that eventually do not survive. During the first 12 h the level of cyclic AMP fell at least as rapidly. However, thereafter the cyclic AMP level remained constant or even increased while the ATP showed a further decrease. It is suggested that the rapid fall in ATP may be used to assess the eventual survival of skin flap. The results are also compatible with the opinion that a period of metabolic stimulation in the skin flap starts 12–18 h after operation, i.e. at the time when the adrenergic nerves in the flap degenerate.
The uptake index method applied to studies on the blood‐retinal barrier II. Transport of several hexoses by a common carrier
Authors: ALM ALBERT , TÖRNQUIST PER , MÄEPEA OLAV
Published: December 2008

The uptake index method was used for studies on the passage of various monosaccharides across the blood‐retinal and the blood‐brain barriers in albino rats. The results indicate large similarities for the hexose transport through the two barriers. Thus a stereo‐specific, saturable transport of glucose was observed for both barriers. The carriers involved showed measurable affinity for 2‐deoxy‐D‐glucose, 3‐0‐methyl‐D‐glucose, D‐mannose and D‐galactose, but not for L‐glucose, D‐fructose or D‐ribose. The relative affinities of the various hexoses to the carriers were similar. Phloretin and phloridzin both reduced retinal and brain uptake of D‐glucose.
Effects of neurotensin, substance P and methionine‐enkephalin on colonic motility
Authors: HELLSTRÖM PER M. , ROSELL SUNE
Published: December 2008

The influence of neurotensin, substance P and methionine‐enkephalin (met‐enkephaline) on proximal and distal colonic motility was studied in anesthetized cats. When administered i.v. at a dose of 14 pmol × kg‐1× min‐1, neurotensin increased basal smooth muscle tone and antiperistaltic activity in the proximal colon. After higher doses of neurotensin the basal muscle tone also increased in the distal colon. Substance P at a dose of 17 pmol × kg‐1× min‐1selectively and powerfully stimulated the distal colon, thus causing a mass contraction pattern with a concomitant decrease in peristaltic amplitude. In the proximal part of the colon 17 pmol × kg‐1× min‐1of substance P exerted an inhibitory action on the peristaltic amplitude in animals with a high level of spontaneous activity. In addition, the basal muscle tone was slightly decreased. In animals with sluggish spontaneous activity, however, no effects were detected in the proximal colon. With increasing doses of substance P forceful contractions of the proximal colon were also registered. Met‐enkephalin at a dose of 40 pmol × kg‐1× min‐1increased the smooth muscle basal tone with no effect on the peristaltic activity in the proximal or distal segments. The effect on basal tone was blocked by naloxone. Thus, neurotensin, substance P and met‐enkephalin have distinct motor actions on the colon. At low doses neurotensin may stimulate the churning and mixing functions of the proximal colon. Substance P exerts its major effects on the distal part with a mass contraction response and met‐enkepahlin increases the basal muscle tone equally in the proximal and distal parts of the colon.
Evidence that substance P is a mediator of antidromic vasodilatation using somatostatin as a release inhibitor
Authors: GAZELIUS B. , BRODIN E. , OLGART L. , PANOPOULOS P.
Published: December 2008

The effect of somatostatin on nerve‐induced vasodilatation and the release of substance P (SP) was studied in the dental pulp of anesthetized cats. Changes in pulpal blood flow were determined by measuring the rate of disappearance of a local depot of radioactive tracer. The release of SP was studied indirectly by determining the residual amounts of substance P‐like immunoreactivity (SPLI)in the pulps by radioimmunoassay. Electrical stimulation (3 min at 10 V, 15 Hz and 5 ms) of the distal end of the cut inferior alveolar nerve (IAN) increased pulpal blood flow. After pretreatment (10 min) with somatostatin (30 pmol/min) similar nerve stimulation was without effect on pulpal blood flow. Intra‐arterial infusion of somatostatin (30 pmol/min) had no effect on pulpal blood flow and did not influence the vasodilator response to SP. Following IAN stimulation (3–45 min) and subsequent incubation (30 min, 37°C) of the lower canine teeth, the SPLI levels in ipsilateral pulps were significantly lower (47.5% reduction) than those in contralateral, unstimulated controls. In cats pretreated with somatostatin (30 pmol/min for 10 min, i.a.) similar nerve stimulation (3 min) did not reduce the pulpal SPLI levels as compared to controls. The results show that nerve‐induced vasodilatation and release of SPLI are inhibited by somatostatin. They are consistent with the hypothesis that vasodilatation in the cat dental pulp produced by stimulation of the IAN is mediated by substance P.
Electrical properties of isolated demyelinated rat nerve fibres
Authors: BRISMAR TOM
Published: December 2008

Isolated large rat nerve fibres with diphtheria toxin induced paranodal demyelination were investigated. These fibres had increased membrane time constant of the demyelinated nodal segment, related to a large increase in capacitance (5 to 50 times). The resting conductance was less increased (2 to 3 times), meaning that the internodal axolemma has considerably higher resting resistance than the nodal membrane. A large variation in action potential amplitude was found which was unrelated to the size of the nodal widening and the passive electrical properties.
Vasoactive intestinal polypeptide (VIP): Effect on rabbit uterine smooth muscle in vivo and in vitro
Authors: OTTESEN BENT
Published: December 2008

The effect of vasoactive intestinal polypeptide (VIP) on uterine smooth muscle electrical and mechanical activity in non‐pregnant estradiol‐treated rabbits was investigated using in vivo and in vitro methods. The studies were performed on spontaneous, oxytocin‐, car‐bachol‐, and prostaglandin‐F2α‐induced activity. VIP had a dose‐related inhbitory effect on both myoelectrical and mechanical activity. The concentration needed for 50% inhibition (ID50) was 2xl0−10mol VIP 1−1(in vivo), and 6xl0−8mol VIP‐ l−1(in vitro). This inhibition was unaffected by the presence of atropine (10−5mol‐ I−1), propranolol (10−5), phentolamine (10−5), naloxone (10−5), apamin (10−4), and tetrodotoxin (10−5). These findings indicate that VIP may act via a specific receptor on the smooth muscle and supports the hypothesis that VIP may be a neurotransmitter involved in the local nervous control of uterine smooth muscle activity.
Effects of ACTH and Alprenolol treatments on muscle and brown fat enzyme activities and weights in the rat
Authors: HARRI M.
Published: December 2008

Chronic ACTH treatment (3 IU/kg daily for 8 days) caused an increase in wet weight of the interscapular brown adipose tissue (ISBAT) in the rat without affecting the enzyme activities of the cardiac or skeletal muscles or of ISBAT. On the other hand, chronic β‐blockade (alprenolol 10 mg/kg daily for 8 days) induced elevated activities in the oxidative enzymes of the ISBAT but not of the muscle tissues measured. Combined ACTH and alprenolol treatment also increased significantly the citrate synthase and malate dehydrogenase activities and protein concentration, but decreased the weight of ISBAT to normal. The results suggest that, although a direct antagonism between the β‐blockers and ACTH has not been demonstrated, β‐blockers can abolish the ACTH‐induced weight gain of the ISBAT.
Acute effects of gonadotrophins and cyclic AMP on protein synthesis and progesterone production by isolated rat granulosa cells
Authors: NORDENSTRÖM KNUT , NILSSON LARS , HAMBERGER LARS
Published: December 2008

Amino acid uptake, protein synthesis and progesterone production were studied in rat granulosa cells, isolated from follicles of different stages of development. The amino acid uptake in granulosa cells from prepubertal rats was rapid with a distribution ratio above 1 within 10 min. No significant effects of gonadotrophins were observed on this parameter. The acute influence of exogenous LH and FSH or dibutyryl cyclic AMP (dbcAMP) on incorporation of 3H‐leucine or 3H‐phenylalanine was investigated as a measure of the rate of protein synthesis. In most experiments progesterone production was determined concomitantly. Both FSH (10μg/ml or 100 /μg/100 g b. wt.) and dbcAMP (1 mM) stimulated (1.6‐1.8 fold) the incorporation of leucine into granulosa cell proteins from prepubertal rats while LH was without effect. Progesterone production in these granulosa cells was very low and neither the gonadotrophins nor dbcAMP were stimulatory. Similarly designed experiments were performed on granulosa cells isolated from preovulatory rat follicles. It was then found that both FSH (10 μg/ml or 100 μg/199 g bwt.) and dbcAMP (1 and 5 mM) as well as LH (10 μg/ml or 100 μg/100 g bwt.) significantly (1.2‐2 fold) stimulated protein synthesis. Furthermore, basal progesterone production was higher and was markedly stimulated (3–6 fold) by all three substances tested. The observations that the protein synthesis in immature granulosa cells is increased by exposure to FSH and dbcAMP while progesterone production is not, whereas both these parameters are stimulated with FSH, LH and dbcAMP in the preovulatory granulosa cells suggest that there might be certain differences in the nature of the proteins synthesized by immature and preovulatory granulosa cells.
Oxygen dependence and energy turnover in normal and hypertrophic rat portal vein
Authors: ARNER ANDERS , UVELIUS BENGT
Published: December 2008

Oxygen consumption (J02), lactate production (JLA), and active force were studied on rat portal veins that had hypertrophied in response to a 5 days period of increased transmural pressure. The vessels were mounted in vitro at optimum lengths for force development. The walls of the hypertrophic (H) veins had in comparison to their controls (C) an increased cross‐sectional area (1.14plusmn;0.05 vs. 0.46±0.03 mm2, S.E., n= 12). The H veins had a diminished or absent spontaneous contractile activity in contrast to C. The influence of surrounding PO2 on amplitude of K+‐induced contractures was studied in an open organ bath. For both Cand H veins a decline in force was seen at PO2levels around 275 mmHgand below. Energy metabolism was studied in a closed glass chamber (volume 1.2 ml) at a PO2of 290 mmHg. In comparison to recordings at 690 mmHg, JLA and active force were unaltered in both groups indicating a sufficient O2 supply. For veins relaxed in Ca2+‐free solution JO2and JLA were higher in H veins compared to C if expressed per unit vessel length (JO2: 0.47±0.03 vs. 0.20±0.02, JLA: 0.66±0.09 vs. 0.22±0.03 nmol/min×mm, n= 6). When the comparisons were made per unit weight JO2 was similar, about 0.38 μmol/min×g whereas JLA was higher in the H group (0.53±0.04 vs. 0.38±0.05 μmol/min×g). Contractures were elicited in high‐K+solutions with varied amounts of Ca2+added. Maximal force per unit area was lower for H veins compared to C (9.5 ± 1.6 vs. 16.3±3.3 mN/mm2). For both groups JO2 increased with active force. JLA increased with force for C but was unaltered for H veins. The relation between calculated ATP production and force was less steep for H indicating a lower metabolic tension cost.
A barbiturate‐induced potassium permeability increase in the myelinated nerve membrane
Authors: ÅRHEM P. , KRISTBJARNARSON H.
Published: December 2008

Effects of the highly lipid soluble barbiturates methohexital and thiopental on potential clamped myelinated nerve fibres were analysed. Both were found to affect the potassium as well as sodium transport system. The methohexital effect on the potassium system was complex. At low potential values it reduced the permeability, while at high values it increased the permeability as well as slowed down the kinetics. It antagonized the rectification of 1K at high potential values caused by increased axoplasmic [Na+]. The effect may be described as a combination of a decreased permeability constant (P̄K) and a methohexital induced potassium permeability with a potential and time dependence different to the ordinary potassium system. Thiopental reduced P̄K only. The effect on the sodium system was similar for the studied barbiturates and similar to that described for other barbiturates: a decrease of the permeability constant (P̄Na) and a shift of the h∞‐U relation in negative direction along the potential axis.
Drinking in goats as effect of simultaneous intravenous infusions of angiotensin (I or II) and hypertonic NaCl or mannitol
Authors: ERIKSSON S. , APPELGREN B. , RUNDGREN M. , JÓNASSON H.
Published: December 2008

Drinking during the simultaneous intravenous infusion of angiotensin I (Al) or II (AII) and hypertonic NaCl or mannitol was studied in the goat, and was compared to the dipsogenic responses to the separate infusion of each of these four factors. Approximately the same amount of water was drunk during the infusion of AI/NaCl, AI/mannitol and AII/NaCl. The amount was roughly equal to the sum of the amounts taken when each of two paired stimuli was infused separately. Significantly less water was drunk in response to AII/mannitol. Somewhat more water was drunk during the separate AI than during the separate AII infusion. Administration of an AI converting enzyme inhibitor completely abolished the AI contribution to drinking during the AI/NaCl infusion but did not reduce AII/NaCl drinking, indicating that the response to Al was entirely due to its conversion into AII. The possibility is discussed that the considerable difference between AI/mannitol and AII/mannitol drinking might have been the result of choroidal and/or ependymal AI converting enzyme activity.
On caecal synthesis and absorption of amino acids and their importance for nitrogen recycling in willow ptarmigan [Lagopus lagopus lagopus)1
Authors: MORTENSEN A. , TINDALL A.
Published: December 2008

The willow ptarmigan has two large caeca housing dense populations of microorganisms. Urine, containing uric acid, is transported from the cloaca into the caeca when these are filled. Here the uric acid is rapidly broken down, suggesting that the caeca take part in a recycling of excretory nitrogen. In this work it is shown that ammonia produced by the uric acid decomposition is incorporated into new amino acids in a glutamic dehydrogenase catalyzed reaction. We have, however, not been able to detect any absorption of amino acids from the caeca, indicating that nitrogen recycling via the amino acid route does not occur.
Metabolism of putrescine in the pregnant rat
Authors: ANDERSSON ANNE‐CHARLOTTE , HENNINGSSON STIG
Published: December 2008

The in vivo metabolism of14C‐putrescine injected to rats before, during and after pregnancy was studied. Within 30 min of the administration of the isotope 9–12% of the injected radioactivity was recorded as14CO2in the expired air and after 5 h 60% was expired. The radioactivity excreted in the urine during the first day following the14C‐putrescine administration consisted of unmetabolized putrescine, γ‐aminobutyric acid (GABA) and some unidentified compound(s). No radioactive polyamines were detected in the urine. After treatment of pregnant rats with the diamine oxidase inhibitor aminoguanidine the expiration of14CO2was almost completely inhibited. In the urine increased amounts of unmetabolized putrescine were excreted while the excretion of GAB A and the unidentified compound(s) were decreased. In addition14C‐spermidine appeared in the urine. The in vitro metabolism of putrescine was determined by the incubation of different tissues of pregnant and non‐pregnant rats with14C‐putrescine. The14C‐metabolites derived via the diamine oxidase pathway (δ1‐pyrroline, GABA, some unidentified compound(s) and carbon dioxide) varied in magnitude with the tissue investigated. GABA was found to be a main metabolite of putrescine in several tissues of the pregnant rat. The content of putrescine and spermidine was elevated in several tissues as well as the blood on the 19th day of pregnancy in rats treated with aminoguanidine, while the content of spermine was unchanged.
Regulation of subcutaneous blood flow during head‐up tilt (45°) in normals
Authors: SKAGEN KNUD , BONDE‐PETERSEN FLEMMING
Published: December 2008

Local and remote regulation of subcutaneous blood flow in the forearm and leg was studied during head‐up tilt (45°) in 6 young healthy male subjects. Relative blood flow was estimated by the local 133Xe washout technique. Lowering of a leg lead to a 51 % decrease in its subcutaneous blood flow due to a veno‐arteriolar reflex elicited by the increase in venous transmural pressure. During head‐up tilt subcutaneous blood flow in the arm remaining at heart level decreased by 27%, in the leg blood flow decreased by 50%. Following proximal nervous blockade, head‐up tilt did not induce vasoconstriction in forearm at heart level, but blood flow in distal leg decreased by 45%. Thus there was no difference in the vasoconstrictor response in the leg to head‐up tilt or lowering of the labelled area by 40 crn. Since head‐up tilt caused neurogenically mediated vasoconstriction in subcutaneous tissue, subcutaneous blood flow in the extremities seems to be regulated by remote (baroreceptor) as well as local sympathetic reflex mechanisms (veno‐arteriolar reflex).
Osmotic control of plasma vasopressin in anesthetized dogs
Authors: BIE P. , PETERSON T. V. , SHARE L. , GILMORE J. P.
Published: December 2008

The relation between plasma osmolality (pOsm) and the concentration of immunoreactive vasopressin in plasma from an external jugular vein (pAVP) was studied in dogs prepared with carotid loops and anesthetized with chloralose‐pentobarbital. Control meail pAVP was 0.6–1.0 μU/ml, after 24 h of dehydration pAVP was tripled. Isosmotic volume expansion for 10 min elicited a decrease in pAVP in all cases not associated with low control values of pAVP. I.v. hyperosmotic infusions (A pOsm: 9 or 18 mOsm/kg in 10 min) increased pAVP. No significant alterations in pAVP occurred in relation to infusions during which the head or the remainder of the body was selectively supplied by hyperosmotic blood. Statistically, the distribution of the pAVP values suggests the existence of two populations, in euhydrated animals high concentrations (>8 μU/ml) were found in a small fraction of the samples. It is concluded that (i) in chloralose‐anesthetized, non‐traumatized dogs pAVP is very similar to values found in venous plasma from conscious dogs, (ii) the pAVP measurements support the concept of an episodic secretion of vasopressin, and (iii) under the present circumstances, an ubiquitous increase in pOsm is a more effective stimulus for vasopressin release than a similar but selective increase in the osmolality of the blood flowing towards the head.
The relation between carotid solute concentration and renal water excretion in conscious dogs
Authors: DIETZ J. R. , BIE P. , GILMORE J. P. , SHARE L. , ZUCKER I. H.
Published: December 2008

Verney's hypothesis of cerebral osmoreceptors controlling the renal excretion of water via vasopressin was reinvestigated in conscious trained dogs provided with bilateral skin loops containing the common carotid arteries. In multiple experiments in two dogs, bilateral intracarotid injections (0.25 ml.(kg b. wt.)‐1 per artery in 10 s) of a hyperosmotic solution of sodium chloride (0.257 mol/l) during transient water diuresis failed to produce an antidiuretic response, although it is estimated that the injections elevated the osmolality of the carotid blood by 12–15%. In another 5 dogs, bilateral intracarotid infusions of hyperosmotic saline (45 μmol. (kg b. wt. min)‐1 per artery for 10 min) during sustained water diuresis resulted in a 3% increase in jugular venous osmolality and an antidiuretic response without detectable changes in heart rate or mean arterial pressure. Equal intravenous hyperosmotic or intracarotid isosmotic infusions were not associated with antidiuretic responses. Analysis of the concomitant concentrations of vasopressin in plasma fell short of supporting the hypothesis that the antidiuretic response to intracarotid hyperosmotic infusions was exclusively or mainly due to liberation of vasopressin. although the renal response could be mimicked by exogenous vasopressin. It is concluded that the present results—although discordant with several of Verney's results and assumptions—nevertheless support the concept of a cerebral solute receptor influencing the rate of renal water excretion.
Some aspects of calcium uptake by human myometrial mitochondria and microsomes relevant to relaxation
Authors: BATRA SATISH
Published: December 2008

Calcium uptake by mitochondria and microsomes isolated from the human myometrum was studied at physiological Ca++ concentrations. The initial rates as well as the maximum velocity of Ca uptake by mitochondria were 10–20 times higher than those by microsomes. The Ca++ concentration for half‐maximal transport in the mitochondria and microsomes was about 1 μM and 0.5 μM, respectively. The Ca uptake capacity of mitochondria measured after 20 min of uptake (1 μM Ca++ in the medium) was 10–30 times higher than that of microsomes. The capacity but not the initial rates of Ca uptake by microsomes was increased in the presence of 5 mM oxalate. There was only minor differences in the Ca uptake kinetics of subcellular fractions isolated from the pregnant and non‐pregnant myometria. The results of this study reinforce the argument for a domineering role of mitochondria in the relaxation of the human myometrium.