bluuebunny/crossref_metadata_2025 huggingface dataset:
Oxygen supply, oxygen consumption, and endocrine and exocrine secretions of the isolated, perfused, porcine pancreas
Authors: HOLST JENS J. , JENSEN STEN LINDKÆR , NIELSEN O. VAGN. , SCHWARTZ THUE W.
Published: December 2008

We studied the effect of varying oxygen supply on the endocrine and exocrine secretions of the isolated perfused porcine pancreas utilizing completely synthetic perfusion medium with and without the addition of erythrocytes. With synthetic medium oxygenated to a Po2 of 500 mmHg, oxygen consumption was constant for How rates at or above 0.5 ml×min‐1×g‐1 (wet weight). Addition of erythrocytes to the medium did not increase oxygen consumption at flow rates above this level. Furthermore, the secretion of fluid, bicarbonate and protein in response to secretin and acetylcholine was not influenced by addition of erythrocytes. Similarly, the secretion of insulin, glucagon, pancreatic polypeptide, and somatostatin in response to arginine and acetylcholine was unchanged; arginine stimulated the secretion of all four peptides, whereas acetylcholine stimulated the secretion of insulin and pancreatic polypeptide and inhibited glucagon and somatostatin secretion. The results indicate that the porcine pancreas is respiring adequately, when perfused with a completely synthetic perfusion medium at flows above about 0.5 ml × min‐1× g‐1 and Po2 about 500 mmHg, and that addition of erythrocytes is not necessary for the study of its secretory functions.
Changes in blood volume and extravascular watt content in isolated perfused rat lungs during ventilation hypoxia
Authors: AARSETH P. , BJERTNÆS L. , KARLSEN J.
Published: December 2008

Isolated rat lungs were perfused with homologous blood at constant volume inflow. The effect of ventilation hypoxia on pulmonary vascular resistance, preparation weight and reservoir volume (vascular capacitance) were studied. In some experiments also wet/dry weight ratio of the preparation was estimated (extravascular water content). There was no difference in this last parameter between hypoxic and normoxic lungs, thus alveolar hypoxia had no effect on tissue water content as previously described in intact rats. With forward perfusion small and transient changes in either direction were seen in preparation weight and reservoir volume, even though inflow pressure exceeded 5 kPa during alveolar hypoxia. With backward perfusion marked weight increases were seen, and if inflow pressure in this situation was above 3.5 kPa, the weight change was irreversible, thus indicating outward fluid filtration. It is concluded that the vessels responding to alveolar hypoxia are located on the arterial side of the pulmonary vasculature.
Rapid post‐ejaculatory inhibitory effect of seminal plasma on sperm nuclear chromatin decondensation ability in man
Authors: KVIST U.
Published: December 2008

The stability of the nuclear chromatin in human spermatozoa soon after ejaculation was studied by exposing the cells to sodium dodecyl sulphate (SDS) one to 20 min after ejaculation. Semen samples were obtained both from men with apparently normal, and from men with impaired prostatic secretion (=subnormal seminal plasma [Zn]). The sperm nuclear resistance to decondensation in SDS increased in both groups during the first 15 min after ejaculation, but was significantly lower in the semen samples with subnormal [Zn]. This fast post‐ejaculatory increment in sperm SDS resistance was significantly reduced by a 5‐fold saline dilution of the semen at the time of ejaculation. It is discussed if the observed stabilization with time was illusory and that a prostatic component instead counteracted an intrinsic nuclear chromatin decondensation (NCD) process initiated by SDS derangement of spermatozoal membranes.
Reversible inhibition of nuclear chromatin decondensation (NCD) ability of human spermatozoa induced by prostatic fluid
Authors: KVIST U.
Published: December 2008

In semen from donors with adequate secretory function of the prostate, spermatozoa in the first (“prostatic”) portion of the ejaculate were more resistant to nuclear swelling in sodium dodecyl sulphate (SDS) than spermatozoa from the second (“vesicular”) portion. No such difference was revealed by a donor with severely impaired prostatic function. This demonstrates that some sperm nuclear chromatin stabilizing factor(s) is present in normal prostatic fluid. The chromatin stabilizing factor(s) could largely be removed by washing the spermatozoa in saline containing albumin. Spermatozoa sensitized to SDS in this manner regained their SDS resistance upon exposure to normal (zinc‐rich) “prostatic fluid”. Such exposure also induced a high degree of resistance in natively SDS sensitive spermatozoa. The possibility is discussed that zinc of prostatic or other origin reversibly inhibits a nuclear chromatin decondensation ability (NCD‐ability). It is suggested that such a mechanism may be of essential importance for male genome transfer.
Recovery of choline acetyltransferase activity in the rat urinary bladder deprived of half of its innervation
Authors: BANNS HEATHER , EKSTRÖM JÖRGEN , MANN STEPHEN P.
Published: December 2008

In the urinary bladder of the rat, partially denervated by unilateral removal of the pelvic ganglion 3 days in advance, the activity of the acetylcholine‐forming enzyme, choline acetyltransferase, measured by a radiolabelling method, was reduced to 58% of the control. A gain in enzyme activity of 28% was found to have occurred when the bladders were examined 25 days postoperatively; the main part of this increase took place during the period 3 to 6 days after the operation and beyond 25 days no further gain in enzyme activity was found. The present findings are compared with previous observations of a transient supersensitivity and an increased motor response to electrical stimulation of the intact pelvic nerve of such a partially denervated bladder.
Interaction of Substance P with dispersed pancreatic acinar cells from the guinea pig. Binding of radioiodinated peptide1
Authors: SJÖDIN LARS , BRODIN ERNST , NILSSON GÖRAN , CONLON THOMAS P.
Published: December 2008

Tyr8‐SP has been radioactively labeled with 125I to a specific activity of 200 μCi/μg. This tracer has been found to be rapidly and reversibly bound in a specific way to dispersed pancreatic acinar cells. The specific binding is saturable and dependent on incubation temperature. At 37°C 125I‐tyr8‐SP is bound to a less degree than at lower temperatures since the peptide is rapidly degraded at 37°C. Native SP inhibits binding of tracer. Results have been analyzed according to Scatchard and suggest 2 functionally distinct types of binding sites; a small number of sites with high affinity and a larger number of sites with low affinity for SP. SP‐sites also bind eledoisin and physalaemin which are peptides similar to SP in terms of chemical structure and biological activities. The concentration range in which SP, physalaemin, and eledoisin inhibit binding of 125I‐tyr8‐SP correlates well with the range in which these peptides stimulate biochemical processes like outflux of 45Ca, accumulation of cyclic GMP and release of amylase from acinar cells.
Interaction of Substance P with dispersed pancreatic acinar cells from the guinea pig. Stimulation of calcium outflux, accumulation of cyclic GMP and amylase release
Authors: SJÖDIN LARS , CONLON THOMAS P. , GUSTAVSON CARIN , UDDHOLM KRISTINA
Published: December 2008

In dispersed acinar cells from the guinea pig pancreas, substance P (SP) was found to stimulate outflux of 45Ca, cellular accumulation of cyclic GMP, and release of amylase. Maximal effects on accumulation of cyclic GMP and release of amylase were obtained with 3 × 10‐8 M of SP. 10‐7 M of SP caused maximal outflux of 45Ca. These effects corresponded to 30–50% of the maximal effects obtained with caerulein, a cholecystokinin‐like decapeptide. The concentrations of SP required for stimulation of 45Ca outflux, accumulation of cyclic GMP, and release of amylase corresponded well with those which affect binding of 125I‐tyr8‐SP to pancreatic acinar cells.
A method to improve the size uniformity of microspheres
Authors: SPERBER G. O. , JOHANSSON ALF
Published: December 2008

When microspheres are used to measure blood flow, the amount that may be injected is limited by side effects, primarily a rise in arterial pressure. It is therefore desirable that the proportion of spheres that actually get stuck in the capillaries is as large as possible. Too small spheres, which pass through the capillaries, as well as too large spheres, which may be held up in the arterioles, should be avoided. This is especially the case if blood flow is measured in small tissue segments, since the spheres found may be so few that the statistical variability of the result becomes embarrassing. From this point of view, commercially available microspheres, in particular the more inexpensive varieties, tend to have too wide size ranges. Also, in developing automatic methods for sphere counting, uniform sphere size may be advantageous.
A simple and efficient method for studying neurotransmitter release in vitro by a radiotracer technique
Authors: WIKBERG J. E. S. , AXELSSON K. L.
Published: December 2008

A method which allows measurement of neurotransmitter release from isolated preparations has been developed. With this method release of 3H‐acetylcholine from guinea pig ileum and rabbit jejunum could be studied after preincubation of the preparations with 3H‐choline. The release of noradrenaline from guinea pig vas deferens could also be measured after preincubation with 3H‐noradrenaline. The method is based on a device which allows experiments on 4 preparations at the same time, including incubation, field stimulation and collection of fractions for counting of radioactivity. With the purpose of obtaining a simple and inexpensive device for stimulating the tissue preparations electrically, a physiological stimulator distributor (PSD) was constructed. It is concluded that the described method constitutes an inexpensive simple and quick means of studying neurotransmitter release from isolated tissues.
Effect of sensitization and non‐antibody IgE on 48/80 induced histamine release from isolated rat mast cells
Authors: SYDBOM A. , KARLSSON T. , UVNÁS B.
Published: December 2008

Histamine release from isolated rat mast cells from non‐immunized and immunized Hooded Lister rats was induced by compound 48/80. The histamine release was decreased with a lower maximum at the optimal concentration of 48/80 when using cells from immunized rats compared to non‐immunized control rats. The stimulation of IgE antibody production, after immunization using B. pertussis as an adjuvant was also accompanied by an elevation of total serum IgE. The 48/80 induced histamine release from Sprague Dawley mast cells was not inhibited by immunization. Non‐antibody IgE showed a non‐competitive inhibition of 48/80 induced histamine release when myeloma IgE was incubated with mast cells from both Hooded Lister and Sprague Dawley rats. The results indicate the existence of different receptors for IgE and 48/80.
ATP, β‐γ‐methylene‐ATP, and adenosine inhibit non‐cholinergic non‐adrenergic transmission in rat urinary bladder
Authors: DAHLÉN S.‐E. , HEDQVIST P.
Published: December 2008

ATP and adenosine caused a dose‐dependent and reversible inhibition of the atropine‐resistant contraction response to transmural nerve stimulation in the rat urinary bladder. Both purines also inhibited contraction responses to acetylcholine and direct muscle stimulation, indicating a postjunctional effect on the transmission. It seems as ATP per se inhibits the excitatory transmission, because the stable ATP‐analogue β‐γ‐methylene‐ATP was inhibitory as well, and because exogenous adenosine deaminase annulled the inhibition by adenosine but not that by ATP or β‐γ‐methylene‐ATP. Blockade of purine in‐activation enhanced the inhibitory action of ATP and adenosine, and by itself inhibited the transmission. These results are consistent with the possibility that endogenous purines may modulate non‐cholinergic non‐adrenergic excitatory transmission in the rat urinary bladder.
Effects of metabolic inhibitors on the efflux of 5‐hydroxytryptamJne from pancreatic β‐cells
Authors: GYLFE ERIK
Published: December 2008

The influence of glucose and metabolic inhibitors on the efflux of tritiated 5‐hydroxytrypt‐amine (5‐HT) was studied in perifused β‐cell‐rich ob/ob mouse islets loaded with trace amounts of 3H‐5‐hydroxytryptophan. Glucose stimulated exocytotic release of 5‐HT but the effect was rapidly inhibited by 2,4‐dinitrophenol, antimycin A or N‐ethylmalemide. This inhibition was followed by a marked stimulation of 5‐HT efflux. The later phenomenon was reversible when 2,4‐dinitrophenol was used but appeared irreversible with antimycin A or N‐ethylmalemide. The results show that the maintenance of 5‐HT within the β‐cell depends on energy. It is suggested that both inhibitory and stimulatory effects of 5‐HT on insulin secretion depend on release of calcium from the secretory granules after short‐circuiting a proton pump across the granule membrane.
Serotonin metabolism in neonatal rat brain during asphyxia and recovery
Authors: HEDNER THOMAS , LUNDBORG PER
Published: December 2008

Neonatal rats were exposed to 20 or 30 min of total or partial oxygen deprivation. During asphyxia and subsequent recovery the endogenous levels of tryptophan and 5‐hydroxytryptamine (5‐HT, serotonin) were measured. The activity of tryptophan hydroxylase, the first and rate limiting enzyme in the 5‐HT synthesis pathway, was studied in vivo by measuring the accumulation of 5‐hydroxytryptophan (5‐HTP) after inhibition of aromatic L‐amino acid decarboxylase with NSD 1015. During asphyxia there was a decrease in tryptophan hydroxylase activity in the whole brain and various brain regions studied. The levels of tryptophan, 5‐HTP and 5‐HT all increased after 30 min of recovery from asphyxia. In the whole brain, 5‐HTP and 5‐HT levels were normal 2 h after anoxia while tryptophan levels normalized more slowly to reach control values after 6 h. In the regional brain study, the 5‐HTP levels returned quickly to control levels after asphyxia in the striatum and midbrain but not in the brainstem and hemispheres regions. The whole brain 5‐HTP and 5‐HT levels did not differ from controls 24 and 48 h after the asphyxia. Although the neonatal nervous system exhibits a great resistance to asphyxia, the metabolism of the neurotransmitter 5‐HT is affected already during a short period of asphyxia and subsequent recovery. As 5‐HT is ascribed important neurotransmitter functions, this might be relevant to the neurological sequelae of human asphyxia neonatorum.
Relationship between plasma pH and pancreatic HCO3‐ secretion at different intravenous secretin infusion rates
Authors: RÆEDER MORTEN , MO ARVE , AUNE SNORRE , MATHISEN ØYSTEIN
Published: December 2008

The relationship between pancreatic HCO3‐ secretion and plasma pH during acute systemic acid‐base changes was investigated in 6 anesthetized, artificially ventilated pigs (20–25 kg) at 2 different, i.v. secretin infusion rates. At 0.45 C.U./kg b.wt. h‐1 secretin infusion and plasma pH 7.40±0.01 pancreatic HCO3‐ secretion averaged 61±12 μmol/min. Stepwise lowering of plasma pH through i.v. infusion of HCI and CO2 administration to inspired air proportionately reduced secretion rate; estimated zero HCO3‐ secretion occurring at plasma pH 7.01. Subsequent i.v. secretin infusion at 2.70 C.U./kg b.wt. h‐1 increased HCO3‐ secretion to 249±42 μmol/min at plasma pH 7.33+0.04; stepwise lowering of plasma pH proportionately reduced HCO3‐ secretion to estimated zero at plasma pH 6.71. A reduction of plasma pH by 0.1 pH unit reduced HCO3‐ secretion during low and high rate of i.v. secretin infusion by 18±3 μmol/min and 35±8 μmol/min, respectively. Secretin infusion rate did not affect pancreatic chloride excretion. These findings support the view that secretin increases HCO3‐ secretion, and hence proton transport to the interstitial fluid, by augmenting the proton motive force developed by HCO3‐ secreting cells.
Simultaneous determinations of metabolic and hormonal responses, heart rate, temperature and oxygen uptake in running rats
Authors: SONNE B. , GALBO H.
Published: December 2008

We have developed a tiny metabolism chamber, including a treadmill, for the study of exercising rats. The effects of work time, speed and inclination of running on V̇o2, heart rate (HR), respiratory exchange ratio (R) and rectal temperature (TR) were determined. During prolonged running V̇o2, HR, R and catecholamine concentrations in arterial plasma drawn through chronically implanted catheters displayed an initial “overshooting”, which did not diminish during the four times the rats within 10 days participated in experiments. When graded exercise was performed after a pre‐test run of low intensity V̇o2, HR, R and TRincreased with increasing running speed but did not vary with inclination. During 45 min of running, the plasma concentration of glucagon increased and that of insulin remained unchanged in spite of a marked increase in blood glucose. Conclusions: In exercise studies in rats it is necessary to introduce a 20 min pre‐test period, during which unspecific stress responses disappear. This pre‐test period cannot be replaced by “habituation runs” on 3 preceding days. Furthermore, using rats, running speed rather than inclination has to be changed in order to establish physiologically significant differences in work intensity. The chamber makes it possible to carry out sophisticated studies of adaptations to exercise of a wide range of intensities in untrained rats and to relate the responses to V̇o2.
Stimulation of gastric acid secretion and suppression of VIP‐like immunoreactivity by bombesin in the Atlantic codfish, Gadus morhua
Authors: HOLSTEIN B. , HUMPHREY C. S.
Published: December 2008

Cods were equipped with cannulae for drainage of the stomach and for separate perfusion of the stomach (pure sea‐water) and intestine (diluted sea‐water). Acidity and volume of gastric effluence were measured. Plasma immunoreactive gastrin and vasoactive intestinal polypeptide (VIP) were assayed in some experiments. The high rate of “basal” acid secretion was further elevated by i.m. administration of bombesin, but not by pentagastrin. Exogenous VIP inhibited acid secretion. Following 5 h of bombesin infusion, plasma gastrin‐IR was unaffected while VIP‐IR was depressed compared to saline‐treated controls. The possibility that bombesin stimulates acid secretion by inhibiting VIP‐release is discussed.
Dilatation of pial arterial vessels in hypercapnia and in acute hypertension
Authors: AUER LUDWIG M. , JOHANSSON BARBRO B.
Published: December 2008

Pial arterial vessels were inspected in hypercapnia (PaCO2 97±9 (S.E.) mmHg) and in acute hypertension induced by 5 μg kg‐1 noradrenaline i.v. (mean arterial pressure 210±5 mmHg) by means of a cranial window. The diameter of arterial vessels with a resting diameter of 10 to 150 μm was measured either from photographs or by aid of an image splitting eyepiece. Arterioles with a resting diameter ≫30 μm exhibited the highest degree of dilatation both in hypercapnia and acute hypertension. The mean dilatation was higher in hypertension than in hypercapnia in vessels of all sizes, the difference being statistically significant in arterioles up to 50 μm resting diameter.
Patchy, intermittent ischemia in renal cortex during tourniquet shock in dog
Authors: TYSSEBOTN I. , KIRKEBØ A.
Published: December 2008

The effect of bilateral hindlimb occlusion on the distribution of renal cortical blood flow was investigated in anesthetized dogs. Local blood flow in outer cortex (OCF) and in inner cortex (ICF) was measured by 6 platinum electrodes recording hydrogen gas clearance. Renal blood flow fell unsignificantly while hematocrit (Hct) rose from 37 to 47% during the 4 h tourniquet period. After the release of the tourniquets average arterial blood pressure fell to about 75% of control, whereas OCF and ICF were proportionately reduced towards 30—40% of control. Hct increased to 58%. Patchy, intermittent ischemia in outer and inner cortex was irregularly observed after release of the tourniquets when Hct had increased markedly, as previously found during dehydration and endotoxin shock. The sudden shifts in washout rates from single electrodes were not accompanied by corresponding variations in total renal blood flow. Heparinization or α‐receptor blocking did not suppress the appearance of abrupt flow changes in this period. However, sudden shifts in local flow were also seen shortly after application of the tourniquets, before Hct had increased, in this phase possibly induced by an increased renal nervous tone. In conclusion: OCF and ICF fell to the same degree during tourniquet shock. Patchy, intermittent ischemia was observed in the renal cortex, most frequently at high Hct, but also before Hct did rise.
Simultaneous measurements of capillary filtration and diffusion capacities during graded infusions of noradrenaline (NA) and 5‐hydroxytryptamine (5‐HT) into the rat hindquarter vascular bed
Authors: RIPPE B. , FOLKOW B.
Published: December 2008

The relationships between capillary diffusion capacity (PS) for Cr‐EDTA respective capillary filtration capacity (CFC) and vascular resistance during graded intraarterial infusions of NA and 5‐HT into the artificially constant flow perfused rat hindquarter vascular bed were investigated. During maximal vasodilatation PS for Cr‐EDTA was some 5.5‐5.7 m//min × 100 g, CFC some 0.04 ml/min × mmHg × 100 g, while vascular resistance was 2.8 mmHg × ml‐1× min × 100 g (PRU100) and isogravimetric capillary pressure 12.8 mmHg on an average. Setting out from maximal vasodilatation, increasing doses of NA and 5‐HT produced graded reductions in capillary surface area as reflected by progressive decreases in both PS for Cr‐EDTA and CFC. These changes occurred simultaneously with progressive increases in both pre‐ and postcapillary resistances, causing elevations in both arterial and capillary hydrostatic pressures and hance in capillary fluid filtration at constant flow. Capillary hydrostatic pressure increased maximally to 45 mmHg (calculated for NA) and vascular resistance to some 21 mmHg × ml‐1× min × 100 g on an average. PS for Cr‐EDTA decreased maximally to some 0.7‐1 ml/min × 100 g for both NA and 5‐HT and, furthermore, the relationships between PS for Cr‐EDTA and PRU100for NA respective 5‐HT were almost identical. This was taken to indicate that capillary surface area for nutritional exchange is affected similarly by both drugs. However, the CFC‐PRU100relationship was shifted towards some 30–50% higher CFC values for 5‐HT than for NA at almost every level of vasoconstriction. This might suggest that 5‐HT besides reducing capillary surface area also induces moderate increases in capillary permeability through increases in number and/or radius of large pores (gaps) (cf. Rippe, Kamiya& Folkow 1978). Even during NA‐induced vasoconstriction, when virtually no changes in capillary permeability occurred, PS for Cr‐EDTA was reduced to a relatively greater extent than CFC, the discrepancy being most pronounced during marked vasoconstriction. The significance of this finding is discussed.
Effects of purified macrophage RNases on granuloma fibroblasts with reference to silicosis
Authors: AHO S. , LEHTINEN P. , KULONEN E.
Published: December 2008

Two alkaline RNases, designated RNase 1 and RNase 2, were isolated from the culture media of silica‐treated and non‐treated macrophages. The yield of RNase from the medium of silica‐treated macrophages was 30% of that from the non‐treated control. The effects of these RNases on cultured granuloma fibroblasts and on granulation‐tissue nuclei were studied. RNase 1 inhibited thymidine incorporation into fibroblasts except at low concentrations, where it was observed to be stimulatory. RNase 1 also inhibited the protein synthesis of fibroblasts. The incorporation of cytidine into RNA in cultured fibroblasts was not affected by RNase 1, but the incorporation into isolated nuclei was decreased. In pulse chase experiments RNase 1 increased the release of cytidine, but not that of thymidine, from the cells. RNase 2 had no effect on the protein or nucleic acid metabolism of the fibroblasts or on the RNA metabolism of isolated nuclei, perhaps because of impermeability. These experiments confirm that macrophage RNase activity is able to regulate the metabolism of granulation‐tissue fibroblasts by increasing RNA degradation. Through this action it also regulates DNA and protein synthesis and other metabolic functions of those cells.
Effects of chronic nerve conduction block on formation of neuromuscular junctions and junctional AChE in the rat
Authors: CANGIANO A. , LØMO T. , LUTZEMBERGER L. , SVEEN O.
Published: December 2008

The development of ectopic n.m.j.s. between the transplanted superficial fibular nerve and the soleus muscle has been studied in adult rats. Impulse conduction in the sciatic nerve was blocked chronically and synapse formation between the blocked fibular nerve and the paralysed soleus was compared with synapse formation between non‐blocked fibular nerves and denervated soleus muscles. Nerves with conduction block readily made new n.m.j.s. Thus 6 and 10–14 days after the onset of the block the number of newly innervated muscle fibres, the percentage of innervated fibres responding with action potentials and the frequency of m.e.p.p.s. at new junctions were comparable to that observed during innervation by non‐blocked nerves. Muscle fibres innervated by both the original soleus nerve and the foreign fibular nerve were regularly encountered in the impulse blocked preparations. Junctions formed by impulse blocked fibular nerves had either no or very little AChE activity 10–15 days after the onset of the block. The evidence for this was 1) weak staining for ChE; 2) prolonged rise time and ½ decay time of m.e.p.p.s.; 3) positive correlation between m.e.p.p. amplitude and ½ decay time and 4) insensitivity to anticholinesterases. In contrast, junctions formed by non‐blocked fibular nerves had strong AChE activity by these criteria at corresponding times. AChE activity at the original soleus endplates was much reduced 10–15 days after the onset of conduction block.
Low threshold facilitation of inspiration by lung volume increments
Authors: DIMARCO A. F. , VON EULER C. , ROMANIUK J. R. , YAMAMOTO Y.
Published: December 2008

Vagally mediated, volume dependent excitatory effects on phrenic nerve activity have been recently described in anesthetized dogs and pigs, but could not be ascertained in rabbits and baboons (Bartoli et al. 1975, Huszczuk et al. 1977, Cross et al. 1980, Karczewski et al. 1980). Results presented here on cats confirm and further characterize a volume dependent facilitatory effect on inspiratory intercostal and phrenic activity in this species.
In vitro studies on a two‐pool storage of adrenaline and noradrenaline in granule material from bovine adrenal medulla
Authors: UVNAÄS B. , ÅBORG C.‐H.
Published: December 2008

Adrenal medullary granules were isolated by millipore filtration according to Poisner & Trifaró (1967) and then lysed in deionized water. In a perfusion system the influence of concentration and pH was studied on the uptake of biogenic amines (PhEA, TA, DA, NA, A, Ach and Hi) and sodium ions by lysed and by dialyzed material. The results suggest a two‐pool storage of A and NA in the granules. A minor pool with cation exchanger properties binds unselectively organic (biogenic amines) and inorganic cations with a Umaxof 400–500 nmol/mg granules dry‐weight. This minor pool (pool 1) was fully charged at amine concentrations >10 mM. A larger pool binds selectively A and NA‐possibly stereospecifically L‐NA and L‐A—with a Umax˜1500 nmol/mg granules. This larger pool (pool 2) required A and NA concentrations ˜200–300 mM for maximal filling. In pool 2 CA+ions are assumed to be electrostatically linked to carboxyl groups, which become available as hypothetical COO‐—+H3N salt bridges are successively forced open by increasing CA concentrations (>10–30 mM). ATP‐ions become attached to the concomitantly unmasked+NH3groups.
In vitro studies on a cation dependent catecholamine release from a two‐compartment storage in bovine adrenal medullary granules
Authors: UVNÄS B. , ÅBORG C.‐H.
Published: December 2008

Perfusion of adrenal medullary granules, isolated according to Poisner & Trifaró, with isotonic cation‐containing solutions (NaCl, KCl, LiCl) caused a concentration dependent release of CA. The course of the release indicated the existence of a two‐compartment storage of CA. The minor compartment (pool 1) with a Umaxof ˜500 nmol/mg granule dry weight showed the characteristics of a cation exchanger and was assumed to be depleted on exposure to cations, e.g. sodium ions, as an ion exchange Na‐← CA+. The major compartment (pool 2) with a Umaxof ˜1000 nmol/mg stored both CA and ATP. It was assumed to empty via the cation exchanger pool. The total storage capacity of the two compartments ˜1500 nmol/mg matched the in vivo storage capacity for CA (˜1300 nmol/mg according to Hillarp 1960).
Plasma concentration of neurotensin‐like immunoreactivity (NTLI) and lower esophageal sphincter (LES) pressure in man following infusion of (GIn4)‐neurotensin
Authors: ROSELL S. , THOR K. , RÖKAEUS Å. , NYQUIST O. , LEWENHAUPT A. , KAGER L. , FOLKERS K.
Published: December 2008

(GIn4)‐neurotensin was infused i.v. for 5 to 70 min at 3 different infusion rates (6, 12 and 18 pmol×kg‐1×min‐1, respectively) in 19 male volunteers, aged 26–47. The plasma concentration of neurotensin‐like immunoreactivity (NTLI), the lower esophageal sphincter (LES) pressure, blood pressure, heart rate, ECG and blood glucose concentration were measured. The volunteers did not report any subjective effects during the infusion. Following infusion periods of 30 min or more the volunteers often reported bowel movements starting 5 min or more after cessation of the infusion. Neither blood pressure nor heart rate changed significantly. No changes were noted in the continuous ECG or in the blood glucose concentration. Apparent steady state levels of about 300 pM NTLI were reached at about 40 min during infusion of 12 pmol×kg‐1×min‐1 (GIn4)‐neurotensin. In all volunteers the LES pressure was significantly reduced within 5 min of starting the infusion. In 6 volunteers 12 pmol×kg‐1×min‐1 (GIn4)‐neurotensin was infused i. v. for 5 min. The LES pressure decreased significantly (P<0.01) from 13.7±1.3 mmHg to 5.3±0.8 mmHg. The decrease in the LES pressure occurred at plasma NTLI concentrations of approximately 50 pM, i. e. at levels below those obtained in man after a meal or the ingestion of fat. The present data further support the hypothesis that in man plasma neurotensin, or a neurotensin metabolite is an endocrine hormone involved in the postprandial regulation of the motor functions of the gastrointestinal tract.
Firing behaviour in nerve cell models with a two‐state pore system
Authors: SKAUGEN ERIK
Published: December 2008

The firing behaviour of simple nerve cell models with a two‐state pore system was investigated by computer simulation. The pores were assumed to open and close randomly, with the probabilities for opening and closing calculated from the equations found by Hodgkin and Huxley for the squid giant axon. The cell models had a cell body and an axon with an initial segment with a smaller diameter. Both the case of a uniform membrane with constant pore densities all over the cell, and the case of a cell body membrane with only a leakage conductance (a ‘passive’ membrane) were investigated. The results indicate that the firing behaviour of a small nerve cell may be significantly influenced by the finite number of pores in the initial segment. In contrast to the original Hodgkin‐Huxley equations which give a very non‐linear frequency‐current relationship in such nerve cell models, a fairly linear relationship over a large current range was found in many cases. It was estimated that the diameter of the initial segment must be less than approximately 1μm and the length larger than half a space constant, in order to obtain a current frequency relationship significantly different from that predicted by the original Hodgkin‐Huxley equations.
A simulation study of a neuron in a simple muscle control system
Authors: LIESTØL KNUT , NJÅ ARILD , WALLØE LARS
Published: December 2008

The mechanism underlying signal transmission through the accessory neuron of the muscle receptor organ in the crayfish abdomen was examined experimentally and by computer simulation. The mathematical model of the accessory neuron and its synaptic inputs was based, in part, on previous neuronal models studied by Stein (1965) and Rail (1964). The model predicted with considerable accuracy the behaviour of the experimental system in a number of situations. It was possible to determine in some detail the mechanisms underlying the frequency response characterized by a threshold and an approximately linearly increasing response for stimulus intensities above threshold. Furthermore, we were able to explain the observation that the accessory cell transforms a regular input train from a stretch receptor into an irregular output train. The highly branched structure of the dendritic tree, combined with a firing threshold in the dendrites which prevents action potentials from invading large parts of the dendritic tree, seems essential in determining these properties.
On the sympathetic innervation to the cat's liver and its role for hepatic glucose release
Authors: JÄRHULT J. , ANDERSSON P.‐O. , HOLST J. , MOGHIMZADEH E. , NOBIN A.
Published: December 2008

Morphology and function of the adrenergic innervation of the liver were studied in cats. Fluorescence microscopy revealed a dense network of adrenergic nerve fibres in association with interlobular vessels and a sparse, but unequivocal innervation of the hepatocytes. These parenchymal adrenergic nerve fibres were more frequent in kittens (2 months old) than in adult cats. Electrical stimulation of the hepatic sympathetic nerves in the adult adrenalectomized cat evoked a small but insignificant increment (1–2 mM) of arterial plasma glucose concentration. When both hepatic and pancreatic sympathetic nerves were stimulated simultaneously, arterial plasma glucose concentration increased significantly by about 6 mM. We conclude that the pronounced hyperglycemic effect of activation of the sympathetic nervous system in the cat is mediated mainly via an adrenergic influence on the release of insulin and glucgon from the pancreas. The sympathetic innervation of the cat liver parenchyma seems to contribute to the hyperglycemia to a minor extent only.
The effect of chronic nicotine and withdrawal on intra‐neuronal dynamics of acetylcholine and related enzymes in a preganglionic neuron system of the rat
Authors: DAHLSTRÖM A. , BÖÖJ S. , HEWALL P.‐O. , LARSSON P.‐A.
Published: December 2008

The effect of chronic nicotine treatment, given in the drinking water for 8–10 weeks in a dose equivalent to that of a heavy cigarette smoker, and of withdrawal 2 days on acetylcholine (ACh), choline acetyltransferase (CAT) and ACh‐esterase (AChE) activities in the preganglionic cervical nerve and the superior cervical ganglia (SCG) of rats, were studied. Control rats were housed and handled as the nicotine rats. After cutting the preganglionic nerve 7–19 h before dissection, ACh, CAT and AChE accumulated in the nerve part proximal to the cut (relative to the nerve cell bodies in the spinal cord). A clearance of these substances was observed in the nerve distal to the cut. This indicates that all 3 substances are transported proximo‐distally in this preganglionic cholinergic nerve. In the SCG, ACh was decreased already by 7 h (to about 60%), while CAT and AChE‐activities were lowered to 60% and 80%, respectively, at 19 h after cutting the nerve. Chronic nicotine treatment caused an increased ACh accumulation (by about 35 %) and a decreased CAT accumulation (by about 20%) in the cut nerve, while the ganglionic levels of all 3 substances were essentially unchanged. Withdrawal of nicotine for 2 days prior to the final experiments caused a reduced ACh‐accumulation (by about 30%) in the nerve and normalized the CAT accumulation. The AChE‐activity of intact nerve was markedly increased to about 175% of control, and the transportable fraction of AChE (clearance distal to the cut) was about twice as large as in control. In the SCG withdrawal caused marked changes in the ACh content, which was decreased to 62% of control. CAT‐activity was increased to 117% of control while AChE was unchanged. Our hypothesis to explain the results is that chronic nicotine treatment and in particular withdrawal of nicotine may cause marked alterations in the activity of the preganglionic neuron. This may induce changes in the intra‐axonal transport of the 3 substances and an increased turnover of ACh in the nerve terminals of the SCG after withdrawal of nicotine.
Contraction of the rat portal vein in hypertonic and isotonic medium: mechanical properties and effects of Mg2+
Authors: HELLSTRAND PER , ARNER ANDERS
Published: December 2008

The contracture elicited in the rat portal vein by hyperosmotic solutions (HC) has been investigated with respect to its Mg2+‐dependence and its mechanical properties. Comparison was made with K+‐induced contractures (KC) of similar force. In contrast to its relative resistance to Ca2+‐depletion, HC is entirely abolished after depletion of both Ca2+ and Mg2+ ions. After readdition of Mg2+ alone, HC can be partially restored again. Isotonic quick release expts were performed on muscles in HC, KC and after passive stretch (PS) to a similar total tension and the length responses following the releases were analyzed. The immediate elastic response showed that stiffness was markedly higher in HC than in KC. whereas in PS it was much lower. After the elastic response a quickly decaying exponential component could be distinguished from the later more steady length change. The time constant of this transient response was 40–50 ms (KC) or 25–30 ms (HC). On release to a minimal afterload the amplitude of the transient response was about 1 % (KC) or 0.5 % (HC) of the initial muscle length, decreasing with increasing afterload. A corresponding transient lengthening response was seen after a step to a force greater than the isometric tension. Transient length responses in PS were much smaller than in KC or HC following force steps producing similar elastic recoils. The late shortening in HC and KC, interpreted as the isotonic response of the contractile system, could be fitted to Hill's eq. Vmax in KC ([Ca2+]=0.5 mM) was 0. 25times;0.02 and in HC 0.05×0.01 (SE, n=6) lengths/s. The results of this investigation support the conclusion that HC originates in the contractile system of the muscle. The quantitative differences in mechanical properties are discussed against possible alterations in HC of cross‐bridge behaviour and/or filament structure.
Contraction of the rat portal vein in hypertonic and isotonic medium: rates of metabolism
Authors: ARNER ANDERS , HELLSTRAND PER
Published: December 2008

The contracture induced by hyperosmolality (HC) in the rat portal vein has been investigated with respect to its metabolic properties. Oxygen consumption (Jo2) and lactate production (JLA) were measured. Comparison was made with K+‐induced contractures (KC). Variation in active force was produced for both kinds of contracture by alteration of muscle length. Measurements were also made in normal isotonic solution, where the muscle is spontaneously active, and in Ca2+‐free isotonic solution. At short muscle lengths, where no active tension was produced, Jo2 was lower in HC than in KC. In contrast, JLA was greatly enhanced in HC, so that calculated ATP turnover (Jatp) was almost the same in both kinds of solution. Comparison of metabolic rates at long and short muscle length and correlation to force development allowed calculation of tension‐dependent metabolism. In normal solution (spontaneous activity) tension‐dependent metabolic rate was much greater than in either kind of contracture. No difference in tension‐dependent Jo2, Jla or JATP could be detected between HC and KC. In nominally Ca2+‐free solution, force development and metabolic rates in HC did not differ from those in Ca2+‐containing solution. Glucose removal abolished lactate formation in HC. The temporal variations of Jo2 and active force during 30 min of HC and KC were followed. In HC, force development increased with time, whereas in KC it decreased. Tension‐independent Jo2 declined with time in HC but stayed constant in KC. On the other hand, tension‐dependent Jo2 was unchanged in HC but declined in KC. The results of this study indicate that despite alterations in overall cell metabolism caused by the hypertonic solution, the energetic aspects of cross‐bridge operation may be similar in HC and KC, despite prominent differences in dynamic mechanical properties.
Reflex inhibition of sympathetic activity during volume load in awake normotensive and spontaneously hypertensive rats
Authors: RICKSTEN S.‐E. , THOREN P.
Published: December 2008

The reflex inhibition of the sympathetic activity in the splanchnic nerves was recorded upon volume expansion with blood in awake spontaneously hypertensive rats (SHR) and in normotensive Wistar‐Kyoto rats (WKR) at an age of 16–20 weeks. At 10% blood volume expansion SHR showed a significantly greater nerve inhibition (43 %) in comparison with WKR (33 %). This augmented reflex response was not caused by the arterial baroreceptors, because the sensitivity of the arterial baroreceptor reflex arch, if anything, tended to be lower in SHR and the increase in arterial blood pressure upon volume load was also lower in SHR. It is suggested that the reason for this increased reflex inhibition in SHR is an augmented low pressure receptor response. The mechanism behind this is discussed. The most likely explanation is a decreased distensibility of the venous system, the systemic andlor the pulmonary veins.
Changes in cerebral blood flow during hyperventilation and CO2‐breathing measured transcutaneously in humans by a bidirectional, pulsed, ultrasound doppler blood velocitymeter
Authors: HAUGE ANTON , THORESEN MARIANNE , WALLØE LARS
Published: December 2008

We have used a bidirectional pulsed ultrasound doppler system which measures the instantaneous mean velocity across the lumen of a blood vessel in order to determine the relationship between alveolar Pco2 (Paco2) and blood flow in the four arteries supplying the brain in humans. Both high and low Paco2values were explored. Six subjects, 3 males and 3 females (22–40 years) were studied by use of this non‐invasne technique. To increase the Paco2 the subjects were breathing 4. 6 and 8% CO2 in air. Paco2 was reduced by voluntary hyperventilation down to a chosen end‐expiratory Pc value of about 2.2 kPa. We found a linear relationship between arterial blood flow expressed as a percentage of control level and Paco2 in the range from 3.3 to 7.3 kPa. At the very lowest Paco2 values a levelling off of the response, with flow values of 40 to 45%, was observed. The CO2‐reactivities in the 6 persons varied between 28.1 and 30.0%/kPa. The time course and the magnitude of the flow response were similar in all four arteries.
Morphological and histochemical properties of tongue muscles in cat
Authors: HELLSTRAND ERIC
Published: December 2008

The morphology of the tongue muscles was studied by in situ dissection as well as by histological and histochemical methods. By means of the latter an anatomical reassessment of attachments and fiber courses was made. The histochemistry was studied in sections stained for myofibrillar adenosine triphosphatase (mATPase), succinic dehydrogenase. NADH diaphorase, phosphorylase, esterase, glycogen and lipids. Fibers of type I and type II were identified, and the latter were subdivided into II1 (highly glycolytic), II12 (intermediately glycolytic and lipolytic) and II123 (highly lipolytic). In the extrinsic muscles, the fibers were 19–25% type I (mean diameter 27 μm) and 75–81 % type II (37 μm); the three type II subgroups appeared in equal proportions, each accounting for 22–30% of the total fiber amount. Pars longitudinalis superior m. hyoglossi and pars longitudinalis inferior m. styloglossi contained only type II fibers, mainly type II12 (67% and 46%, respectively), of diameters like those in m. hyoglossus and m. styloglossus. The intrinsic muscles also consisted entirely of type II fibers (23 μm). II123 fibers predominated in m. verticalis (83%), which has only 10% H12 and 6% II1, whereas the fiber composition of m. transversus was more balanced: 37% type II1, 32% II12 and 31 % II123.
Cellular calcium as a determinant of action potential duration in rabbit myocardium
Authors: JÓHANNSSON MAGNÚS , WOHLFART BJÖRN
Published: December 2008

It has been suggested that the amount of calcium in the myocardial cell determines force production as well as the duration of the action potential. We have examined two factors proposed to determine the action potential duration: (I) the inotropic state of the muscle and (2) the preceding stimulation interval. The experiments were performed on isolated papillary muscles from rabbits. The preparations were stimulated to contract isometrically at a temperature of 37°C and intracellular recordings of action potentials were made. An increased inotropic state produced either by raised external calcium concentration or by increased stimulation frequency was associated with shortened action potentials, confirming factor (1) above. The dependence of the action potential duration on the preceding stimulation interval (factor (2) above) disappeared over a wide range of intervals when the preparation was exposed to 4 μM D600. The action potential duration was, however, still dependent on the preceding stimulation interval when the extracellular calcium concentration had been lowered from 2.0 mM to 1.0 and 0.5 mM respectively. The results are discussed in terms of a model which postulates an inverse relationship between the amount of calcium in a membrane compartment and the action potential duration.
Distribution of blood flow in the dog kidney
Authors: CLAUSEN G. , HOPE A. , KIRKEBØ A. , TYSSEBOTN I. , AUKLAND K.
Published: December 2008

While 15 μm microspheres (Ms) in principle provide a measure of glomerular flow, uptake rate of inert diffusible tracers indicates “effective” or “nutrient” flow, i.e. essentially postglomerular capillary flow. Paired measurements of glomerular and postglomerular flow were made in tissue samples from outer, middle and inner cortex (C1, C2, C3) and medullary zones. After a control Ms injection, renal vascular conductance (RVC) was altered in one kidney whereupon a second Ms injection was made, immediately followed by infusion of the125I‐iodoantipyrine and tritiated water. RVC was increased maximally byLa. infusion of acetylcholine with and without reduced renal arterial pressure, whereas moderate vasodilation was produced by lowering renal arterial or rising ureteral pressure. RVC was reduced by i.a. or i.v. infusion of angiotensin II. Within a mean RVC range of 50 to 180% of control the fractional distribution of zonal postglomerular flow remained unaltered, in agreement with previous results obtained from local H2gas desaturation rate. Glomerular flow was about 20% higher in C1, equal in C2and 40% lower in C3as compared to postglomemlar flow in control kidneys. This disparity nearly disappeared during maximal vasodilation and tended to increase during vasoconstriction. The results might suggest a variable net postglomerular effective flow in radial direction through the renal cortex. Alternatively, the fractional redistribution of Ms might reflect a variable degree of Ms skimming at the afferent arteriolar inlets along the interlobular arteries.