bluuebunny/crossref_metadata_2025_split huggingface dataset:
Potassium permeability of the mesothelium of the frog mesentery
Authors: Frøkjær‐Jensen J. , Christensen Ove 
Published: December 2008

AbstractThe mesothelium of the mesentery is a single cell layer described to offer no or every little hindrance to diffusion of small water soluble solutes. We have measured the potassium permeability of the mesothelium of the frog mesentery both in vivo and in vitro. The permeability measured in vivo–using K+–sensitive microelectrodes is 2.4 times 10‐5 cm s‐1. In vitro measurements using conventional tracer flux technique on isolated mesentery yields a K+‐permeability of 5.7 times 10‐5 cm s_1. These values are 15–30 times smaller than values previously reported from in vitro experiments on rat and rabbit mesentery. Also, the permeability is 12–15 times lower than the K+‐permeability of the capillary wall determined on single capillaries in the frog mesentery. In the frog mesentery the mesothelium thus represents an important diffusion barrier compared to the capillary wall. This may be critical in experiments where filtration and reflexion coefficients of the capillaries are determined from measurements of fluid exchange across the capillary wall in response to application of hypertonic solutions on the surface of the mesentery.
The Spitzbergen reindeer‐a winter‐dormant ungulate?
Authors: RINGBERG TATA 
Published: December 2008

AbstractSeasonal changes in serum levels of growth hormone, Cortisol and thyroxine in calves and adult Spitzbergen reindeer (Rangifer taranilus platyrynehus) were measured and compared to those previously found in Norwegian reindeer (R.t. tarandus). Cortisol did not differ significantly between summer and winter, or between the subspecies. Growth hormone and thyroxine exhibited highly significant seasonal changes and subspecific differences: winter levels of growth hormone were much higher than summer levels in the Spitzbergen reindeer, while Norwegian reindeer differed very little from season to season. Both Spitzbergen and Norwegian reindeer had markedly reduced thyroxine levels during winter, but the values from the former were much lower than those from the latter. In summer, however, the levels were equal. The high levels of growth hormone and low levels of thyroxine in the Spitzbergen reindeer during winter are indicative of high lipolytic activity and a reduced metabolic rate, respectively.
The effect of propranolol on cerebral oxygen consumption and blood flow in the rat: measurements during normocapnia and hypercapnia
Authors: HEMMINGSEN RALF , HERTZ MARIANNE M. , BARRY DAVID I. 
Published: December 2008

AbstractThe cerebral blood flow (CBF) and cerebral oxygen consumption (CMRO,) in the rat during normocapnia and hypercapnia were investigated by means of the intraarterial 133Xenon injection technique; measurements were performed during normocapnia and hypercapnia and the effect of propranolol upon CBF and CMRO2 was studied. The CBF technique applied to rat yield reliable results even in high flow situations. A steady state period of only 10–15 s is all that is necessary to obtain the initial slope of the 133Xenon clearance curve from which CBF is calculated and measurements may be repeated within minutes. Hypercapnia caused an increase in CMRO2 of 35% which confirms the findings of other investigators. The beta‐adrenergic receptor blocker propranolol (2 rag per kg i.v.) prevented this increase and could eliminate an increase in CMRO2 already induced; this indicates that CO2 affects adrenergic mechanisms. Although propranolol eliminated the CMRO2 response to hypercapnia, it only reduced the CBF response; this dissociation of CBF and CMRO2 response occurred probably because the beta‐receptor blockage only eliminated a CBF increase mediated through an increased CMRO2 (cellular response) whereas a direct CO2 effect upon the arterioles (vascular response) persisted.
Hepatic portal vein infusion of glucose on sodium excretion in the rat
Authors: BLAKE WILLIAM D. , ULFENDAHL H. R. 
Published: December 2008

AbstractAnesthetized rats were prepared with catheters in the hepatic portal (HPV) and femoral (FEM) veins and in the bladder or ureters. In some experiments the left kidney was denervated. HPV infusion of 1 M glucose at 2 ml/h for 20 min increased Na excretion by the kidney when given as a second infusion. Bilateral cervical vagotomy eliminated the increase in Na excretion during glucose infusion and uncovered a delayed decrease in Na and K excretion. Renal denervation attenuated the increase in Na excretion to HPV glucose. FEM infusion of glucose had variable effects, increasing Na excretion only after vagotomy. The results are interpreted to suggest that central and vagal receptors tend to enhance Na excretion whereas splanchnic nerve afferents and humoral mediator(s) have the opposite effect.
Determination oi 6‐keto‐prostaglandin Flα in rabbit kidney and urine and its relation to sodium balance
Authors: OLIW ERNST , LUNDÉN INGER , SJÖQUIST BIRGITTA , ÄNGGÅRD ERIK 
Published: December 2008

AbstractThe occurrence of 6‐keto‐prostaglandin Flα (6‐keto‐PGF1α) was demonstrated in rabbit kidney medulla and cortex by mass‐spectrometry. The post‐mortem accumulation of 6‐keto‐PGF1α was studied by mass‐fragmentography in regions of the rabbit kidney using (3,3,4,4,‐2H4) 6‐keto‐PGFlα as an internal standard. The cortex contained 1.4 + 0.3 μMg/g, the medulla 2.1 ± 0.6 μg/g and the papilla 3.7 ± 0.7 (S.E.) μg/g. The accumulation of 6‐keto‐PGF1α is thus about 5 fold higher in the cortex than reported for PGE2 and PGF2α, whereas accumulation of PGE2 and PGF2α dominates over 6‐keto‐PGFlα in the medulla and the papilla. The occurrence of 6‐keto‐PGFlα in rabbit urine was demonstrated by mass‐fragmentography. On a low salt diet unanesthetized, female rabbits (n = 6) excreted Na+ 0.09 ± 0.01 (S.E.) mmol/day, 6‐keto‐PGFlα 11.8 ± 2.2 μg/day and immunoreactive PGF2α (iPGF2α) 2.0 ± 0.6 μg/day. Two days treatment with acetylsalicylic acid (30 mg/kgx 2) reduced urinary excretion of 6‐keto‐PGFlα and iPGF2α by 71 and 85%, respectively (both p < 0.05), but sodium excretion was unchanged. On the same diet supplemented with NaCl, the rabbits excreted Na+ 27.5 ± 3.4 mmol/day (p < 0,05), 6‐keto‐PGFlα 13.3 ± 4.6 μg/day (p > 0.05) and iPGF2α 0.63 ± 0.10 μg/day (p < 0.05). 6‐keto‐PGFlα is a major metabolite of prostacyclin (PGI2). The occurrence of 6‐keto‐PGFlα in kidney and urine indicates a considerable synthesis of PGI2 in the kidney. The data on urinary PG excretion indicate that intrarenal synthesis of PGI2, in contrast to PGF2α, is not influenced by dietary variations in NaCl.
Effects of calcium and pH on the mechanical performance of heart muscle in the frog, Rana temporaria, during anoxia and subsequent recovery
Authors: LAGERSTRAND GUNNEL , POUPA OTAKAR 
Published: December 2008

Heart ventricular muscle strips from Rana temporaria recover their isometric contractile tension completely within 20 min of reoxygenation following an anoxic period of 60 min in a physiological solution at pH 7.6. Corresponding recovery at pH 6.6 is only 43% of pretreatment values. High calcium concentration during the period of anoxia at pH 6.6 and subsequent recovery, returns contractile tension to almost pre‐anoxic values within 1 h. If, however, the calcium concentration is increased at the moment of reoxygenation, contractile tension is restored even faster than if high calcium levels were present during anoxia. The loss of contractile tension caused by anoxia is the same at both pH 7.6 and 6.6 with the same calcium concentration.Comparison of the velocity parameters between high and low calcium experiments always shows a greater difference for the contraction velocities than for the corresponding relaxation velocities, independently of the pH. The quotient of these two velocities is used as an index of their relative rate of change. The results are interpreted in terms of calcium and hydrogen ion competition at various subcellular structures and the different influences these ions may have on contractile tension and both contraction and relaxation velocities.
Effect of varying exercise intensity on glycogen depletion in human muscle fibres
Authors: VØLLESTAD NINA KØPKE , BLOM PER C S. 
Published: December 2008

VØLLESTAD, N.K. & BLOM P.C.S. 1985. Effect of varying exercise intensity on glycogen depletion in human muscle fibres. Acta Physiol Scand125, 395–405. Received 15 December 1984, accepted 30 April 1985. ISSN 0001–6772. Institute of Muscle Physiology, Oslo, Norway.Glycogen depletion of muscle fibre types I, II A, IIAB and IIB was studied during bicycle exercise at 43% (π= 5), 61% (π= 7) and 91% (π= 5) of Vo2 max Glycogen content in individual fibres from vastus lateralis muscles was quantified as optical density of periodic acid‐Schiff (PAS) stain. After 60 min at the lowest intensity, glycogen depletion was observed in almost all type I fibres and in about 20% of type IIA fibres. After 60 min exercise at 61 % of Vo2max, glycogen breakdown was observed in all type I fibres and in about 65% of type IIA fibres. During the first part of exercise at 91% of Vo2 max, glycogen breakdown was observed in all type I and IIA and in about 50% of type IIAB and IIB fibres. Muscle lactate concentration increased during the first 5 min of exercise at 91% of Vo2max to 15 mmol kg‐1 (w/w) and remained thereafter at this level. From start of exercise the average rates of glycogen depletion in type I fibres were about 1.0,2.0 and 4.3 mmol glucosyl units kg‐1 (w/w) min‐1 at 43%, 61 % and 91 % of Vo2max The depletion rates were almost constant with time at the two lower intensities. The results indicate that the number of fibres activated from the start increase gradually in response to increased exercise intensity. The rates of glycogen depletion in type I fibres suggest a progressive tension output of these fibres with increasing intensity.
The control of granule movement in fish melanophores
Authors: GRUNDSTRÖM N. , KARLSSON J. O. G. , ANDERSSON R. G. G. 
Published: December 2008

GRUNDSTRÖM, N., KARLSSON, J.O.G. & ANDERSSON, R.G.G. 1985. The control of granule movement in fish melanophores. Acta Physiol Scand125, 415–421. Received 4 December 1984, accepted 8 May 1985. ISSN 0001–6772. Departments of Pharmacology and Biology, Linkoping University, Sweden.The effects of electrical field stimulation, alpha‐2‐adrenoceptor activation and manipulation of the intracellular machinery on aggregation and dispersion of melanosomes within melanophores of Labrus ossifagus were studied. Neither melatonin nor MSH exerted any direct effects on the melanophores, and furthermore MSH alone did not affect the responses elicited by electrical stimulation or by noradrenaline. Omitting extracellular Ca2+ blocked the nerve‐mediated aggregation but was without effect on noradrenaline‐induced aggregation. Colchicine and demecolcine inhibited the melano‐some aggregation induced by noradrenaline. The characteristics of aggregation and dispersion were found to diverge in several ways. In melanophores made permeable by using saponin, cyclic AMP caused dispersion. The dynein‐ATP‐ase inhibitor vanadate prevented the melanosome aggregation within saponin‐treated melanophores, while vandate was without effect on the cyclic AMP‐induced dispersion. The melanosome transport in saponin‐treated melanophores could be activated even in the absence of Ca2+, indicating that the melanosome movements were completely Ca2+‐independent.
Endothelial negative surface charge areas and blood‐brain barrier function
Authors: HARDEBO J. E. , KÅHRSTRÖM J. 
Published: December 2008

HARDEBO, J.E. & KÅHRSTRÖM, J. 1985. Endothelial negative surface charge areas and blood‐brain barrier function. Acta Physiol Scand 125, 495–499. Received 30 January 1984, revised 26 March, 1985. ISSN 0001–6772. Departments of Histology and Neurology, University of Lund, Sweden.Recent evidence points to the negative surface charge of the luminal endothelial membrane of brain vessels as one determinant for morphologic blood‐brain barrier function. The present study evaluates, in awake rats, how barrier function is affected by the polycation protamine to neutralize the negatively charged groups. High local doses of protamine, as infused intracarotideally, are able to substantially impair barrier capacity against albumin and inulin, which normally do not pass the blood‐brain barrier. Evidence is presented that it is the positive charge of protamine that is a major factor underlying the barrier opening. However, when comparing the barrier opening obtained by corresponding concentration of the polycation lysine, it was obvious that another property of protamine contributed. This property was not linked to hyperosmolar, hypertensive or vasodilatory barrier opening, but may be a direct, cytotoxic effect of protamine. It is discussed whether barrier opening through transendothelial vesicular or channel transport occurs only at locations on the cell membrane deprived of negative surface charge areas.
Lymphatic drainage from subcutaneous tissue in the foot and leg in the sitting human
Authors: ASA M. , SKRETTING A. , ENGESET A. , WESTGAARD R. , NICOLAYSEN G. 
Published: December 2008

AAS, M., SKRETTING, A., ENGESET, A., WESTGAARD, R., NICOLA YSEN, G. 1985. Lymphatic drainage from subcutaneous tissue in the foot and leg in the sitting human. Acta Physiol Scand 125, 505–511. Received 27 March 1985, accepted 22 May 1985. ISSN 001–6772. The Norwegian Radium Hospital, Montebello 0310, Oslo 3, Norway, Institute of Work Physiology, Oslo and Institute of Physiology, University of Oslo.To determine how fast lymph is drained from the foot in the sitting, completely relaxed position, we injected 99mTc‐labelled human serum albumin subcutaneously between the first and second toe of both feet in three subjects sitting with legs down. Radioactivity appeared in the calf within the first 30 s, in the thigh within 1 min and in the blood between 2 and 5 min after injection. A scintigram of the calves showed distinct strands of activity. Radioactivity was found in the inguinal lymph nodes and in no other lymph nodes. The radioactivity in the segments of the calf showed rhythmic variations. EMGs showed minimal muscular activity during the examination. We conclude that interstitial fluid is drained by way of the lymphatics against gravity and most probably as a result of the intrinsic contractions of the lymphatics.
Inhibition of shivering in man by thermal stimulation of the facial area
Authors: MEKJAVIC I. B. , EIKEN O. 
Published: December 2008

MEKJAVIC, I. B. & EIKEN, O. 1985. Inhibition of shivering in man by thermal stimulation of the facial area. Acta Physiol Scand 125, 633–637. Received 26 April 1985, accepted 28 May 1985. ISSN 0001–6772. Department of Kinesiology, Simon Fraser University, Burnaby, Canada, and Department of Environmental Medicine, Karolinska Institutet, Stockholm, SwedenThe contribution of the facial thermoreceptors to thermoregulatory shivering was studied. Seven subjects were exposed to – 3 °C ambient air for 1 h. Radiant heat was applied to the facial area during 30 s periods at 10 min intervals and the effects on the integrated electromyographic activity (IEMG) in the brachial biceps, trapezius and femoral rectus muscles, and on the heart rate (HR) were studied. During cold‐air exposure mean skin temperature as measured at four sites decreased by 15.5±0.6 °C (mean ± SE) while rectal temperature remained virtually unchanged. During the radiant heat exposures IEMG activity decreased by 18.9 ± 2.3%; HR decreased by 11± 1 beats min‐1. The changes in IEMG occurred within or slightly below the range of maximum cold receptor sensitivity (20–30 °C) and coincided with the maximum rate of change in chin temperature. The observed inhibition of shivering IEMG during locally applied facial heat stimulation suggest that the trigeminal region contributes an important input to the overall thermoregulatory responses.
Neuromodulation by adenine nucleotides, as indicated by experiments with inhibitors of nucleotide inactivation
Authors: WIKLUND N. PETER , GUSTAFSSON LARS E. 
Published: December 2008

The adenine nucleotides AMP, ADP and ATP (3 × 10‐7M AND above) inhibited contractile responses to transmural nerve stimulation in guinea‐pig ileum longitudinal muscle via a prejunctional action. Nucleotides assumed to inhibit the degradation of adenine nucleotides were employed to determine whether inhibition of contractile responses was elicited by adenine nucleotidesper se, or required breakdown to adenosine.The IMP or 2′‐deoxy AMP enhanced the prejunctional inhibitory effect elicited by AMP. A similar enhancementofthe inhibitory effect of ADP and ATP was seen after administration of IDP and ITP, respectively. The inhibitory effect of adenosine was not enhanced by inosine, IMP or IDP.The 5′‐nucleotidase inhibitor, TDP enhanced inhibition elicited by ADP. In contrast, α, β‐meADP did not influence the prejunctional inhibitory effect elicited by the adenine nucleotides. However, the combination of α, β‐meADP and IMP enhanced the inhibitory effect of ATP. The postjunctional contractile effect elicited by ADP and ATP was enhanced by pretreatment with inosine nucleotides, α,β‐meADP or TDP, indicating decreased inactivation of ADP and ATP during concurrent nucleotide administration. The fact that the prejunctional effect of adenine nucleotides can be enhanced by forms of pretreatment known to antagonize the breakdown of adenine nucleotides, constitutes strong evidence for prejunctional actionper seby adenine nucleotides.
Comparative effects of some calcium‐channel blockers on human peripheral arteries and veins
Authors: SJÖBERG T. , ANDERSSON K.‐E. , NORGREN L. , STEEN S. 
Published: December 2008

Comparative effects of some calcium‐channel blockers on human peripheral arteries and veins. Acta Physiol Scand 130, 419–427. Received 5 December 1986, accepted 9 February 1987. ISSN 0001–6772. Departments of Surgery and Clinical Pharmacology, Lund University, Sweden.We investigated the effects of five different calcium‐channel blockers (CCBs), verapamil, nifedipine, diltiazem, flunarizine and lidoflazine, on contractions evoked an vitro by noradrenaline (NA) in small human arteries and veins from the epigastric region. Vessels were obtained from patients without obvious vascular diseases undergoing surgery because of inguinal hernias. The human superficial epigastric artery has previously been shown to contain mainly α1‐adrenoceptors, whereas in the vein α2‐adrenoceptors predominate. In experiments where NA (10‐5 m) was added non‐cumulatively, it was found that nifedipine was the most potent relaxant agent in both arteries and veins, but that this drug showed no preference for any type of vessel. In contrast verapamil (10‐6 m) and (10‐5 m) diltiazem, flunarizine and lidoflazine inhibited the NA‐induced contractions to a significantly greater extent in the arteries than in the veins. Comparison between diltiazem and nifedipine on contractions induced by cumulative addition to NA showed that both drugs had significantly more depressive effects on arteries than on veins if the vessels were contracted by relatively high concentrations of NA (10‐‐6 and 10‐‐5 m). The results thus confirm the clinical finding that CCBs have more pronounced effects on the arterial than on the venous side of the circulation. They do not support the view that CCBs are more effective inhibitors of α2‐‐ than α1‐adrenoceptor mediated contraction in isolated human blood vessels.
Localization of K‐NPPase and Li+ secretion in the exocrine pancreas of the pig
Authors: BUANES T. , GROTMOL T. , LANDSVERK T. , RÆDER M. G. 
Published: December 2008

Localization of K‐NPPase and Li+ secretion in the exocrine pancreas of the pig. Acta Physiol Scand 130, 457–466. Received 30 October 1986, accepted 9 February 1987, ISSN 0001–6772. University of Oslo, Institute for Experimental Medical Research and Surgical Department, Ullevaal Hospital and Department of Pathology, The Norwegian College of Veterinary Medicine, Oslo, Norway.To study the mode of transepithelial Na+ transport into pancreatic ducts during secretindependent NaHCO3 secretion, Na, K‐ATPase was first localized within the exocrine pancreas of the pig using a cytochemical reaction for K‐dependent p‐nitrophenylphosphatase (K‐NPPase). K‐NPPase staining was confined to the lateral cell membrane bordering the intercellular spaces between ductal cells, negating the possibility of primary active, transcellular Na+ transport into pancreatic ducts. To assess how transepithelial Na+ transport may be coupled to HCO‐3 secretion, net flux of Li+ into pancreatic juice was measured following intravenous systemic Li+ loading of 12 secretin infused, anaesthetized pigs. At plasma Li+ 32 (23–35) mmol I‐1, Li+ displaced Na+ as accompanying cation to secreted HCO3‐‐, and Li+/Na+ in pancreatic juice matched Li+/Na+ in arterial plasma. During superimposed inhibition of pancreatic water flux by hyperglycaemia, Li+ and Na+ were both transported against a transepithelial concentration gradient. Li+ reduced pancreatic HCO3‐ secretion rate by 14 (‐2 to‐20)%, as well as Na, K‐ATPase activity in a separate in vim assay. The finding that Li+ substituted for Na+ in the secretion even during reduced osmotic water flow suggests that Na+ and Li+ are transported together with secreted HCO3‐ into pancreatic juice by an electrogenic mechanism in addition to solvent drag and diffusion.
Influence of oxygen tension and substrates on basal and luteinizing hormone stimulated progesterone production and energy metabolism by isolated corpora lutea of adult pseudopregnant rats
Authors: GÅFVELS M. , SELSTAM G. , DAMBER J.‐E. 
Published: December 2008

Influence of oxygen tension and substrates on basal and luteinizing hormone stimulated progesterone production and energy metabolism by isolated corpora lutea of adult pseudopregnant rats. Acta Physiol Scand 130, 475–482. Received 8 January 1987, accepted 23 February 1987. ISSN 0001–6772. Departments of Physiology and Urology & Andrology, University of Umeå, Sweden.The effect of substrate reduction on in vitro progesterone production by isolated corpora lutea of pseudopregnant rats was studied. Pseudopregnancy was induced by mating adult females with vasectomized males. The rats were killed at different luteal ages and the corpora lutea of pseudopregnancy were identified, dissected free and incubated for 3 h. Six‐day‐old corpora lutea were incubated in the presence of different oxygen tensions as well as different glucose and amino acid concentrations and basal as well as luteinizing hormone (LH)‐stimulated progesterone production was studied. When the oxygen tension was reduced, both basal and LH‐stimulated progesterone production was decreased. At 6 and o kPa, the stimulatory effect of LH on progesterone production was abolished. Lowering the oxygen tension decreased the levels of adenosine‐5′‐triphosphate (ATP) in the tissue and increased lactic acid accumulation in the medium. Omitting both glucose and amino acids while maintaining oxygen tension at 100 kPa abolished the stimulatory effect of LH on progesterone production and decreased the levels of ATP. The present study shows that the corpus luteum in vitro is dependent on a high oxygen tension for maintenance of its progesterone production and LH responsiveness. It is suggested that the amount of ATP available is critical to the degree of LH response. Hypoxia increased luteal glycolysis, but this could only marginally compensate for a low oxygen tension.