bluuebunny/crossref_metadata_2025 huggingface dataset:
Total and local renal blood flow and filtration in the rat during reduced renal arterial blood pressure
Authors: HOPE A. , CLAUSEN G. , ROSIVALL L.
Published: December 2008

Discrepancies concerning the lower pressure limit of renal blood flow (RBF) autoregulation, different autoregulatory adjustments in deep and superficial renal zones and dissociation of RBF and filtrate production stimulated the present study. Autoregulation of renal blood flow was investigated at reduced renal arterial blood pressure (RAP) in Sprague‐Dawley rats using 4 different flow methods: uptake of125I‐iodoantipyrine (I‐Ap) and86Rb, local detection of hydrogen gas washout rate (H2) and, in the autoperfused kidney, electromagnetic flowmetry (FM). With I‐Ap and86Rb, RBF was maintained at a RAP as low as 80 mmHg, compared to contralateral RBF. However, with the other two methods where each kidney serves as its own control, a 15% RBF reduction was obtained at this RAP. This discrepancy (p<0.001) infers a contralateral renal vasoconstriction during ipsilateral renal hypotension and vasodilation. Arterial blood pressure increased during unilateral renal hypotension, suggesting that contralateral renal constriction was part of a general increase in total body vascular resistance. Following abrupt RAP reduction RBF was immediately readjusted (2–3 s) and maintained for up to 40 min. No significant change in intrarenal blood flow distribution was observed with I‐Ap. Superficial and deep cortical single nephron glomerular filtration rates were equally reduced at lowered RAP as determined by the ferrocyanide technique. However, a dissociation between the autoregulation of RBF and glomerular filtration rate (GFR) in the direction of less well maintained GFR was observed. Renal arterial acetylcholine infusion increased RBF by about 40% and effectively abolished RBF autoregulation.
Distribution of blood flow in the dog kidney III. Local uptake of 10 μ and 15 μ microspheres during renal vasodilation and constriction
Authors: CLAUSEN G. , TYSSEBOTN I. , KIRKEBØ A. , ØFJORD E. S. , AUKLAND K.
Published: December 2008

Recent studies indicate that intrarenal distribution of blood flow measured with microspheres (Ms) during control conditions depends on Ms size. We therefore compared local flow in outer and middle cortex (C1 and C2) and inner cortex plus the medulla (C3M) using 10.5–12.0 and 13.9–15.0 μm Ms (Ms 10 and Ms 15). One pair of Ms 10 and Ms 15 was injected during control and a second pair at 80% increased or 50% decreased total renal vascular conductance (RVC), as induced by infusion of acetylcholine (Ach) and angiotensin II (Ang) or noradrenaline (NA). All zones participated in dilation and constriction, as indicated by both Ms sizes. Ms 15 underestimated C3M flow as compared to Ms 10, by 19% during control or Ang, and by 3 % during Ach (P<0.02). The C3M flow fractions increased during Ach and decreased during Ang, whereas NA gave greatly variable results, on average no change. Renal Ms extraction averaged 97.0±3% for Ms 10, 98.6±2.4% (S.D.) for Ms 15. About 8% of Ms 10 and less than 1 % of Ms 15 were located in peritubular capillaries in each cortical zone. Neither total Ms extraction nor zonal extraglomerular Ms fraction changed over the present RVC range. Thus, the Ms 10 to Ms 15 differences as well as the observed redistribution must be due to differences in local entry of Ms into the afferent arterioles. However, steric restriction of Ms at arteriolar inlets did not play a significant role. The measured redistribution of fractional flow could in part be due to skimming of Ms at arteriolar inlets along the interlobular arteries (i.l.a.), depending on the C3M flow fraction, Ms size and i.l.a. diameter. If the observed fractional flow redistributions were solely due to variable Ms skimming, Ms 15 underestimatèd C3M flow by 53%, Ms 10 by 43%, during Ang as compared to Ach. Although Ms 10 and Ms 15 may correctly indicate the direction of fractional glomerular flow redistribution, at least Ms 15 overestimates this phenomenon quantitatively.
Distribution of blood flow in the dog kidney IV. Reversed net inward postglomerular capillary flow in the cortex after blocking interlobular arteries by 50 μm microspheres
Authors: CLAUSEN G. , KIRKEBØ A. , TYSSEBOTN I. , ØFJORD E. S. , AUKLAND K.
Published: December 2008

Simultaneous measurement of glomerular flow by 15 μm microspheres (Ms) and postglomerular capillary flow by 125I‐iodoantipyrine (I‐Ap) suggest that about 10% of total RBF flow inward through the entire cortex in the postglomerular capillaries of the dog kidney. This flow fraction might be variable (Clausen et al. 1978, 1980) and perhaps even reversible. To test this possibility we injected 50 μm Ms into the renal artery in order to obstruct interlobular arteries and produce a selective reduction of outer cortical glomerular blood flow and postglomerular pressure. The 50 μm Ms reduced total RBF by 50%. In the outer cortex, postglomerular flow measured by I‐Ap was significantly less reduced than glomerular flow as measured by 15 μm Ms: Whereas the inward flow fraction from inner cortex to the medulla was maintained, about 5% of RBF now drained from midcortex to outer cortex. This observation support the theory of a variable net postglomerular capillary flow of radial direction in the cortex of the dog kidney.
Pulmonary diffusing capacity of the bullfrog (Rana catesbeiana)
Authors: GLASS MOGENS L. , BURGGREN WARREN W. , JOHANSEN KJELL
Published: December 2008

Carbon monoxide diffusing capacity of the lungs (DLCO) was measured in bullfrogs, Rana catesbeiana (mean body weight 260 g) along with oxygen uptake, pulmonary perfusion and lung volume. The measurements were all performed by methods depending on mass‐spectrometry. Pulmonary oxygen uptake, DLCO and perfusion all increased with body temperature. At 20°C O2‐uptake was 0.49 ml STPD·kg‐1 · min‐1 at rest and DLCO was 0.022 ml STPD · kg‐1 · min‐1 · ‐Torr‐1. At 30°C the values for O2‐uptake and DLCO approximately doubled. Lung volume was large (90 ml · kg‐1) and independent of body temperature. Oxygen uptake and DLCO of the bullfrog were small compared to values for a similar‐sized mammal but the ratios of DLCO to O2‐uptake quite similar. Analysis of available data on DLCO and O2‐uptake in ectotherms also suggests a close correlation between O2‐uptake and DLCO.
Changes in nodal function in nerve fibres of the spontaneously diabetic BB‐Wistar rat: Potential clamp analysis
Authors: BRISMAR TOM , SIMA ANDERS A. F.
Published: December 2008

Single myelinated nerve fibres were isolated from the sciatic nerves of the spontaneously diabetic BB‐Wistar rat after 17–185 days of overt diabetes. Pronounced demyelination and paranodal changes were found in one rat (diabetes duration 185 days), the others had no structural changes that could be detected light‐microscopically. Potential clamp analysis of these fibres showed a decreased Na equilibrium potential (UNa), decreased Na currents caused by large inactivation, and a specific increase in the K‐permeability. Measurements with high‐K solution outside the node revealed that the decreased UNa was caused by high axoplasmic [Na]. Fibres with increased K‐permeability had, in addition, increased nodal leak conductance. Decreased excitability was found in the majority of the fibres and was related to the permeability changes. The present findings indicate that axonal dysfunction (Na‐accumulation and inactivation of the Na‐permeability) precede the changes (increased K‐permeability) related to paranodal demyelination.
Plasma vasopressin concentration and renin in the rat: Effect of hydration and hemorrhage
Authors: FYHRQUIST FREJ , TIKKANEN ILKKA , LINKOLA JAAKKO
Published: December 2008

In order to investigate effects of hydration state, different techniques of collecting blood samples, and of acute, stepwise hemorrhage, we studied plasma vasopressin (AVP) concentration, and plasma renin activity (PRA) in 80 female Wistar rats. Plasma AVP was decreased following hydration with 10 ml of water (1.0±0.3 pg/ml, mean ± S.E.M.) as compared to controls (6.1±2.0 pg/ml), while withdrawal of water for 48 hours stimulated AVP release (29±8 pg/ml). AVP values in jugular venous blood during light ether anesthesia (9.6±4 pg/ml) were slightly higher than in trunk blood following decapitation (2.7±0.7 pg/ml). There was no effect of sham gastric lavage on AVP. PRA was slightly increased in trunk blood, and in jugular venous blood following ether anesthesia, and 5‐fold increased following 48 h of water withdrawal. In aortic blood obtained during ether anesthesia, AVP‐levels were 12‐ to 560‐fold those in control trunk blood. Rapid hemorrhage, 2.0 ml stepwise, resulted in corresponding increases of AVP blood concentration, presumably due to hypothalamohypophyseal ischemia. PRA values showed a similar, albeit less pronounced increase. These results show the importance of controlling conditions of blood sample collection for AVP and PRA analysis, and demonstrate massive release of AVP in response to acute hemorrhage. The amount of AVP released is well about the treshold for pressor activity, and may be of importance in vasoconstrictive adaptation to acute hypovolemic hypotension.
Efferent renal nerve activity during intracarotid and intracerebroventricular infusions of hypertonic sodium chloride solutions and isotonic volume expansion in the rat
Authors: A.‐C ERICSON , SJÖQUIST M.
Published: December 2008

The change in renal nerve activity under conditions known to increase renal sodium excretion was studied. In adult Sprague Dawley rats, anaesthetized with Inactin®, nor‐motonic and hypertonic NaCl solutions were infused into 1) a vein, 2) a carotid artery and 3) the third ventricle. The left kidney was freed and placed in a plastic cup. A renal nerve was dissected free and placed on a stainless bipolar electrode. The nerve was cut distal to the electrode. The nerve signals were amplified and recorded on a tape recorder. Simultaneously integrated nerve signals and also arterial and venous pressures were recorded. Intracarotid infusion of a 1 M NaCl solution increased sodium output and temporarily decreased renal nerve activitv by some 35%. Corresponding intravenous (i.v.) infusion gave an increase in renal nerve activity and also in sodium output. The latter increase was delayed compared with that caused by the intracarotid infusion. No variations in blood pressure were noted. In control experiments with a slow i.v. infusion of physiological saline, renal nerve activity increased throughout the experiment, while sodium excretion remained constant. During infusion of a 1 M NaCl solution into the third ventricle, renal nerve activity decreased in about half of the cases. This reduction was often accompanied by an increased arterial blood pressure and an increased sodium output. Arterial blood pressure increases were especially pronounced at the highest infusion rate, i.e. 800 nl‐min‐1. Isotonic volume expansion of 2% of the body weight resulted in a transient decrease in renal nerve activity by about 30%. Venous blood pressure rose and sodium output increased six‐fold. The decrease in nerve activity was observed both when the vagal nerves were intact and when they were cut.
Effect of regional hypoxia and blood flow on capillary permeability in canine myocardium
Authors: HAUNSØ STIG
Published: December 2008

The effect of hypoxia and blood flow on the capillary permeability‐surface area product (PS) of51Cr‐EDTA was investigated in canine myocardium of open chest anesthetized dogs at constant aortic pressure, heart rate, and cardiac output. PS was determined by bolus injection of51Cr‐EDTA into the left anterior descending coronary artery (LAD) and external registration of the response curve. Vascular conductance (G) and PS were measured: (1) during pump perfusion of LAD with arterial blood (control state), and (2) during vasodilation obtained by LAD perfusion with deoxygenated blood at same blood flow as in control state, and (3) during increased blood flow with deoxygenated blood. Mean value of G in control state was 1.31 ml. min‐l. (100 g)‐1(mmHg)‐1. The ratio G‐hypoxialG‐control used to assess the extent of vasodilation was 2.42 (range 1.67–3.56) during hypoxia and unchanged flow and 2.82 (range 1.81447) during hypoxia and increased flow. Mean value of PS in control state was 36 ml. (100 g)‐1. min‐1. With maximum vasodilation and constant blood flow PS increased to 47.3 ml.(100 g)‐1.min‐1(37%) and during increased blood flow to 69.0 ml.(100 g)‐1. min‐1(96%). The increase in PS most likely reflects an increase in capillary surface area available for exchange of51Cr‐EDTA indicating a 1.4– to 2‐fold recruitment of capillaries.
The effect of prostaglandin inhibition on renal function in the developing anesthetized lamb
Authors: HERIN PETER , APERIA ANITA
Published: December 2008

The importance of prostaglandin (PG) compounds for renal function in the developing kidney was studied by comparing renal blood flow (RBF), glomerular filtration rate (GFR) and fractional sodium (Na) excretion in control lambs and lambs treated with a PG synthesis inhibitor, indomethacin. The lambs were 1–2 and 4–6 weeks old and they were studied either during hydropenia (HP) or volume expansion (VE). lndomethacin significantly decreased Na excretion in both groups of hydropenic lambs. lndomethacin also completely blunted the natriuretic response to VE in the older lambs but had no effect on Na excretion in the volume expanded younger lambs. It is concluded that partial lack of PG inhibiting action on tubular Na transport will contribute to the poor natriuretic response to VE in neonatal lambs. Since PG will act locally rather than being blood‐borne messengers, the divergent PG action in younger and older lambs might be explained by local differences in maturation of PG metabolism as well as by local differences ir the maturation of PG sensitivity.
Effects of vagotomy and glossopharyngectomy on respiratory response to dopamine‐agonists
Authors: LUNDBERG DAG , MUELLER ROBERT A. , BREESE GEORGE R.
Published: December 2008

In normal rats lightly anesthetized with halothane apomorphine increased both resting and CO2‐‐dependent minute ventilation (VM) by stimulating respiratory frequency (RF) whereas tidal volume (VT) was slighly decreased. Acute bilateral glossopharyngectomy, which impaired carotid body function, did not change the apomorphine effects in contrast to bilateral vagotomy, which abolished the RF response of the drug, but now increased VT. Intravenous infusion of dopamine increased VM, by elevating RF, and this effect was only slightly blunted by bilateral glossopharyngectomy but nearly abolished by vagotomy and totally eliminated by the combined procedures. The respiratory response to dopamine was depressed in rats with chronically destroyed central catecholaminergic neurons. These findings indicate that there may be two different dopaminergic stimulatory mechanisms that modulate RF—one peripheral and one central—and both depend upon afferent vagal activity. With impaired vagal function, however, two other dopaminergic stimulatory mechanisms effecting V., are evident—one central, and one peripheral which involves the carotid body.
Adrenergic and cholinergic induced contractions of tracheal smooth muscle in the rabbit as demonstrated by a new in vivo method
Authors: MUSTAFA K. Y. , ELKHAWAD A. O. , BICIK V. , MARDlNI I. A. , THULESIUS O.
Published: December 2008

An in vivo tracheal muscle preparation in the rabbit was developed which enabled us to measure changes in the isometric tension of the trachealis muscle in response to electrical stimulation of autonomic nerves and to i.v. administration of autonomic agonists and antagonists. The preparation was very sensitive to injections of carbachol, and showed graded contractions to stimulation of the caudal end of the cut cervical vagus as frequency and strength of stimulation were increased. Stimulation of the rostral end of the cut cervical sympathetic nerve fibres produced contractions in all preparations. This effect was mimicked by the α‐adrenoceptor agonist, phenylephrine. The effects of both sympathetic stimulation and phenylephrine were blocked by phentolamine and not inhibited by pre‐treatment with atropine or propranolol. Sympathetic stimulation produced contraction of the trachealis muscle whether the initial tone was normal or actively increased by carbachol, while adrenaline produced relaxation when the initial tone was high. Using this new in vivo trachealis muscle preparation in the rabbit, we could show that sympathetic stimulation produced contractions of the trachealis muscle. This effect is consistent with the existence of smooth muscle activating alpha adrenoceptors.
Effects of liver ischemia on hepatic protein synthesis in vitro and in vivo
Authors: HASSELGREN PER‐OLOF , FORNANDER JÖRGEN , JAGENBURG RUDOLF , SUNDSTRÖM ELISABETH
Published: December 2008

When an in vitro system is used to study the influence of ischemia on hepatic protein synthesis, an important question is whether alterations observed in vitro reflect changes in vivo. In the present study the effects of liver ischemia on protein synthesis were investigated in rats both in vitro and in vivo. Liver ischemia was induced by hepatic artery ligation. Protein synthesis in vitro was determined from leucine incorporation into proteins in liver slices incubated in a medium containing 14C‐leucine (0.5 mmol/l) and in vivo from leucine incorporation into hepatic proteins after intraportal injection of a tracer dose of 14C‐leucine. Leucine incorporation rate in non‐ischemic liver was 0.16 pmol * g pror1 h‐1 in vitro and 19.6 μmol g prot‐1. h‐1 in vivo. After hepatic artery ligation protein synthesis in vitro was reduced by about 60% and in vivo by about 80%. Thus, the relative changes were of the same magnitude in vitro and in vivo. This indicates that an in vitro system can be used to evaluate the effects of liver ischemia on hepatic protein synthesis.
Increase of resistance to stretch during the latent period in single muscle fibres of the frog
Authors: HAUGEN P.
Published: December 2008

The time from stimulation to the first change of the extensibility in an isolated skeletal muscle fibre was measured by subjecting the fibre to a rapid, small stretch at various times during the latent period. The experiments were performed at constant temperatures in the range 1–16°C. Irrespective of the temperature, the first increase of the resistance to stretch occurred after the onset of the latency relaxation. At a temperature of 10°C and a sarcomere length of 3 μm the resistance started to increase 5.5 ms after stimulation, i.e. 1.5–2 ms after the onset of the drop in tension, and then increased nearly linearly with time. Corresponding to the end of the latent period, i.e. when the tension recrosses the resting level, the amplitude of the response was about 1.5 times its resting value. There was an interval between the onset of increase of the resistance to stretch and the time when the rate of drop in tension had passed its maximum value. The results are compatible with the hypothesis that the latency relaxation arises from a minute lengthening of the thin filaments as proposed by Haugen & Sten‐Knudsen, and that attachment and generation of force take place at separate steps of the cross‐bridge cycle.
Amounts and distribution of intracellular magnesium and calcium in pancreatic β‐cells
Authors: ANDERSSON TOMMY , BERGGREN PER‐OLOF , GYLFE ERIK , HELLMAN BO
Published: December 2008

β‐Cell‐rich pancreatic islets were incubated for 60–120 min in the presence of 1 mM or 20 mM glucose and analysed with regard to their contents of magnesium and calcium and how these elements were distributed among subcellular fractions. The islets contained 42 mmol magnesium per kg protein with as much as 70 mmol per kg protein in the microsomal fraction. Both the total amount and intracellular distribution of magnesium remained unaffected after raising the glucose concentration of the incubation medium. The islet content of calcium was twice as high as that of magnesium, the mitochondria and secretory granules accounting for most of the calcium in the sedimentable fractions. In both organelles a substantial fraction of calcium was exchangeable as indicated from the incorporation of 45Ca during 90 min of incubation of the islets. When raising the glucose concentration to 20 mM the percentage exchange of calcium increased from 10 to 27 in the mitochondria and from 13 to 28 in the secretory granules. The glucose stimulation of 45Ca uptake was not associated with a statistically significant increase in the total amounts of calcium. However, in addition to stimulating calciumkalcium exchange, it cannot be excluded that glucose also induces a net accmulation of intracellular calcium in the β‐cells.
Plasma levels of somatostatin following a test meal in dogs Initial atropine resistant vagally mediated decrease of somatostain levels and increase of gastrin and insulin levels
Authors: UVNÄS‐WALLENSTEN KERSTIN UVNÄS‐MOBERG , ANDERSON BARBRO , POSLONCEC BRANKA
Published: December 2008

Plasma levels of somatostatin like immunoreactivity (SLI), below referred to as somatostatin levels, were measured in peripheral plasma of conscious dogs. Basal somatostatin levels averaged 49±10 pM. Somatostatin as well as gastrin and insulin plasma levels were measured before and after feeding with and without prior atropinization. During the first 10 min after feeding somatostatin levels fell from 49±10 to 23±9 pM, whereas gastrin and insulin levels rose from 9±2 and 140±14 pM to 48±11 and 370±91 pM respectively. Atropine 0.01 or 0.1 mg/kg did not inhibit these responses. After the initial decrease, somatostatin levels rose again and peaked at around 60 min after feeding (110±24 pM). This secondary rise was completely abolished by atropine in both doses tried. Gastrin and insulin levels remained elevated throughout the experiments with and without atropine. It is suggested that gastrin release and HCI secretion are inhibited by a tonic outflow of gastric somatostatin during basal conditions. The process of feeding induces an atropine resistant, vagally mediated decrease in somatostatin release from the gastrointestinal tract and this decreased output of somatostatin facilitates initiation of meal‐related endocrine and exocrine gastric secretions.
Effects of nifedipine on potassium‐induced contraction and noradrenaline release in cerebral and extracranial arteries from rabbit
Authors: HÖGESTÄTT E. D. , ANDERSSON K.‐E. , EDVINSSON L.
Published: December 2008

The present study was designed to evaluate the effects of the calcium antagonist nifedipine on potassium‐evoked contractions and release of noradrenaline from sympathetic nerves in rabbit basilar and facial arteries. Contractions were measured isometrically in a small volume organ bath. While noradrenaline (NA) produced strong contractions in facial arteries, the majority of the basilar arteries responded only to the highest concentrations of NA employed (> 10 μM) with weak contractions. Prazosin (1 μM) and phentolamine (1–10 μM) effectively antagonized the responses to NA in both types of vessel. In contrast, contractions evoked by potassium (K+, 124 mM) were only slightly reduced by the alpha‐adrenoceptor blocking agents, indicating that the participation of endogenous NA in maintaining the contractile response to K+is either small or negligible in the vessel types studied. Nifedipine concentration‐dependently inhibited K+‐induced contractions in basilar and facial arteries, the former being significantly more affected as evidenced by the maximum inhibitions (˜ 80% compared to ˜60%) and IC50values (˜ 10 nM vs. ˜ 30 nM). A combination of nifedipine (0.3 μM) and prazosin (1 μM) or phentolamine (1 μM) further suppressed the K+‐evoked contractile response in facial arteries, but failed to do so in basilar arteries, when compared with the effect of nifedipine alone. The depressant effect of the alpha‐adrenoceptor blockers was, however, still obtainable after reserpine treatment of the facial artery in vitro. Fluorescence histochemical demonstration of noradrenaline revealed a dense network of adrenergic nerve fibres in the walls of the basilar and facial artery. The vessels were also shown to accumulate3H‐NA and release it upon depolarization with K+. The uptake and subsequent release of3H‐NA were significantly reduced by desipramine (10 μM). Nifedipine (0.3–3.0 μM) failed to alter the K+‐evoked3H‐NA efflux from sympathetic nerves in neither of the two vessel types. It may be concluded that nifedipine effectively inhibits K+‐evoked contractions in isolated basilar and facial arteries from rabbit without interfering with nerve‐mediated NA release. Possible explanations for this selective effect of nifedipine on muscle contraction are discussed.
Neural beta‐adrenergic dilatation of the facial vein in man Possible mechanism in emotional blushing
Authors: MELLANDER STEFAN , ANDERSSON PER‐OLOF , AFZELIUS LARS‐ERIK , HELLSTRAND PER
Published: December 2008

Ring preparations of the superficial buccal segment of the human facial vein, taken from extirpated tissue in 12 patients during neck surgery, were studied in vitro. The vein developed a maintained intrinsic myogenic tone in response to passive stretch and was supplied with α‐ as well as β‐adrenoceptors, both of which could be influenced by transmural nerve stimulation (TNS) and noradrenaline. These unusual characteristics for a vein are basically similar to the ones described for the rabbit facial vein by Pegram, Bevan & Bevan (1976). In man there seemed to be an inter‐individual difference with regard to the abundance of ‘innervated’α‐ and β‐adrenoceptors. Facial vein specimens from some subjects thus responded with prompt and pronounced net dilatation to TNS with maximum at 4 Hz and those from others with net constriction with maximum at 16 Hz. The latter showed a reversal into neural β‐adrenergic dilatation after α‐adrenergic blockade. The human external jugular vein was devoid of intrinsic tone and β‐adrenoceptors. It is tentatively proposed that a β‐adrenergic neuro‐effector mechanism in superficial ramifications of the facial vein in man might be involved in the emotional blushing reaction.
Effect of stress and dexamethasone on immunoreactive β‐endorphin levels in rat hypothalamus and pineal
Authors: VUOLTEENAHO OLLI , LEPPÄLUOTO JUHANI , MÄNNISTÖ PEKKA
Published: December 2008

In response to mild stress the levels of immunoreactive β‐endorphin in rat anterior pituitary, hypothalamus and pineal fell within 10 minutes from 210 to 129 pmol/lobe, 1.47 to 0.89 pmol/mg protein and 2.53 to 0.41 pmol/gland, respectively. No alterations were found to take place in β‐endorphin levels in posterior pituitary or plasma. Dexamethasone pre‐treatment given 18 h prior to stress resulted in significantly greater reduction of β‐endorphin levels in hypothalamus and pineal than stress alone—hypothalamic levels fell to 0.73 pmol/mg protein and pineal to 0.07 pmol/gland. Plasma β‐endorphin levels in dexamethasone pretreated stressed rats were significantly lower than in intact rats (42 fmol/ml vs. 98 fmol/ml). The almost complete disappearance of β‐endorphin from the pineal in response to stress and dexamethasone suggests that pineal does not itself synthesize the hormone but only utilizes and/or stores it. Gel filtration analysis of the β‐endorphin im‐munoreactivity in tissue extracts and plasma showed that anterior pituitary and plasma contain three immunoreactive components, eluting like β‐endorphin,βP‐Epotropin and pro‐opiocortin, whereas only β‐endorphin‐like material was detected in posterior pituitary, hypothalamus and pineal.
Effects of conditioning vibratory stimulation on pain threshold of the human tooth
Authors: EKBLOM ANDERS , HANSSON PER
Published: December 2008

The effect of mechanical vibratory stimulation on the human tooth pain threshold has been studied in 4 healthy naive subjects. Vibration at 10 and 100 Hz was applied to a maxillary incisor and the electrical pain threshold was measured in an adjacent tooth. During the conditioning stimulation the pain threshold increased 1.2–1.8 times the unconditioned values. The present study indicates that mechanical vibratory stimulation applied to human teeth elevates the pain threshold in adjacent teeth.
Increased concentration of neurotensin‐like immunoreactivity (NTLI) in rat plasma after administration of bombesin and bombesin‐related peptides (porcine and chicken gastrin‐releasing peptides)1
Authors: RÖKAEUS Å. , YANAIHARA N. , McDONALD T. J.
Published: December 2008

The present experiments in the rat were designed to study the effect of bombesin on plasma concentrations of neurotensin‐like immunoreactivity (NTLI), to localize the gastrointestinal site(s) of bornbesin‐induced NTLI release and to compare the effects of bombesin and mammalian and avian bombesin‐related peptides (porcine and chicken gastrin‐releasing peptides) on the plasma concentrations of NTLI. Tail vein injections of bombesin (7.8–500 pmol X kg‐l) increased plasma NTLI in a dose‐related fashion and a peak concentration was obtained one min after the injection. Bombesin was injected into the arteries supplying certain vascular beds. A significant increase in plasma NTLI was found only after injection into the cranial mesenteric artery—the artery which supplies the intestinal area containing the highest concentration of NTLI. lntralurninal instillation of bombesin (1.25 nmol × kg‐1) into the distal part of the small intestine had no effect upon plasma NTLI. but intraperitoneal injection of bombesin (1.25 nmol × kg‐1) caused a significant increase in plasma NTLI. Intravenous injection of natural porcine and chicken gastrin‐releasing peptides and of synthetic porcine gastrin‐releasing peptide caused similar increases in plasma NTLI as bombesin. Chronic bilateral vagotomy did not change the effect of bombesin on plasma NTLI. The results show that the administration of bombesin and mammalian and avian bombesin‐related peptides markedly elevates the plasma concentration of NTLl in the rat and suggest that this elevation is largely due to release of NTLI from the area of the intestine supplied by the cranial mesenteric artery, i.e. jejunum and ileum.
Renal medullary blood flow studied with the 86‐Rb extraction method Methodological considerations
Authors: KARLBERG LARS , KÄLLSKOG ÖRJAN , ÖJTEG GÖRAN , WOLGAST MATS
Published: December 2008

The 86‐Rb extraction method was applied for a study of regional renal blood flow. In the cortex, a samling time of 30 s led to an underestimation by about 15% as compared with the microsphere method. This was due to incomplete cortical cellular extraction of rubidium with subsequent rapid wash‐out the tracer. In the renal medulla, a sampling of 30–60 s gave valid data with almost complete extraction. A sampling time of only 10 s, i. e. a time similar to the intravascular transit time, gave rise to a 50% underestimation of the inner medullary blood flow. Errors due to transport of rubidium by the tubular fluid were investigated in detail. A theoretical analysis based on equilibrium data revealed a maximal error of about 5%. Studies with micropuncture of distal tubules and studies of the urinary transport showed no or negligible contamination from tubular urine. Under control antidiuretic conditions the blood flow in the cortex was 5.2±0.2 ml‐min± g± (mean±SE, n=16), in the outer stripe of the outer zone 2.2±0.1, in the inner stripe 1.5±0.1 and in the inner zone 0.69±0.06.
Specificity and distribution of receptor cells in the olfactory mucosa of char (Salmo alpinus L.)
Authors: THOMMESEN GEORG
Published: December 2008

Olfactory receptor activity was studied in the char by two methods: (a) recording of the electro‐olfactogram (EOG) with two electrodes simultaneously in the olfactory pit and (b) recordings from the olfactory bulb during olfactory stimulation and progressive removal of lamellae in the olfactory rosette. As stimuli were used methionine representing the amino acids and dilute char bile representing the bile salts. By cross‐adaptation studies it was demonstrated that receptors sensitive to each of these two stimuli are functionally independent. The results show further that both types of receptors may be found on all lamellae, but differentially distributed within each lamella. Receptors sensitive to methionine are located closer to the raphe than receptors sensitive to bile. The spatial differentiation persists regardless of stimulus concentration. The results are discussed in relation to the projection and growth of primary nerve fibres into the olfactory bulb, and the existence of receptor cells with microvilli and with cilia.
Renal function and sympathetic activity during mental stress in normotensive and spontaneously hypertensive rats
Authors: LUNDIN S. , THORÉN P.
Published: December 2008

The aim of the present study was to explore the role of the renal sympathetic nerves in the urinary sodium excretion response to ‘mental stress’ in spontaneously hypertensive rats (SHR). In conscious male SHR and male Wistar Kyoto rats (WKY) urinary sodium excretion and renal function were measured both during ‘rest’ and during a 20 min period of ‘mental stress’. Experiments were also performed on renal denervated rats. In addition, renal sympathetic activity was measured in a separate group of rats. Urinary sodium excretion, similar at rest in SHR and WKY, decreased significantly more during the stress period in SHR (‐64±5%) than in WKY (‐34±7%), despite a greater arterial pressure increase in SHR. Renal sympathetic nerve activity which already at rest was higher in SHR than in WKY, also increased much more in SHR during stress than in WKY. The more intense renal sympathetic activation during stress may explain the greater reduction in urinary sodium excretion in SHR, because renal denervation almost abolished this latter response. Thus, during ‘mental stress’ the increased renal sympathetic activity reduces urinary sodium excretion in SHR despite the pressure rise, perhaps explaining why renal denervation delays the rise in arterial pressure in young SHR. The tachycardia response in SHR gradually subsided towards the end of the stress period, while renal sympathetic activity remained elevated. This indicates that neurogenic heart rate increases if anything underestimate the extent of sympathetic activation to e. g. the renal and splanchnic regions during increased alertness.
Latency relaxation in frog skeletal muscle under hypertonic conditions
Authors: BARTELS E. M. , JENSEN P.
Published: December 2008

The effect of exposure to hypertonic conditions on latency relaxation (LR), twitch tension and resting tension in frog toe muscle was studied. Measurements were carried out in standard and hypertonic conditions (1 to 3.6 times standard tonicity) and following transversal stimulation. In hypertonic conditions, the LR showed increased duration and decreased amplitude. Both time course and amplitude showed the same dependency on sarcomere length as in standard conditions. The fall in amplitude and extension of the time course was proportional to the increase in tonicity up to 2.2 times the tonicity of the standard. At higher tonicities the time course extended earlier and diverged from the linear dependency, the amplitude falling later with increasing tonicity. The LR was abolished at tonicities exceeding 3 times the standard. In hypertonic conditions the twitch tension was reduced and extended, but showed the same dependency on sarcomere length as in standard conditions. The amplitude showed the same dependency on tonicity as the LR amplitude. The time course extended in a non‐linear way with growing tonicity. In hypertonic conditions the resting tension was higher than or the same as in standard conditions, and the dependency on sarcomere length was the same.
On the extensive contact between veins and arteries in the human ovarian pedicle
Authors: BENDZ A. , HANSSON H.‐A. , SVENDSEN P. , WIQVIST N.
Published: December 2008

The human ovarian arteries and their anatomical relation to the utero‐ovarian venous plexus were studied in surgical specimens using roentgen angiography and corrosion casts. The arteries were in close contact with the veins, had a tortuous shape and sometimes a helical folding of inner layers of the wall. The results obtained are similar to the findings in a number of animal species and may represent the morphological basis for a counter‐current exchange mechanism.
Zinc and zinc ligands in human seminal plasma
Authors: ARVER STEFAN , ELIASSON RUNE
Published: December 2008

The zinc binding properties of whole human seminal plasma and various fractions of split ejaculates were analysed with gel chromatographic and dialysis methods. The proportion of dialyzable zinc was strongly correlated to the zinc/fructose ratio in the seminal plasma, i. e. correlated to the relative contributions by the prostate and seminal vesicles, respectively. Zinc originates, however, almost entirely from the prostate gland. The non‐diffusible zinc ligands thus seemed to originate from the seminal vesicles. This could also be confirmed in experiments with split ejaculates. The high molecular weight (HMW) zinc ligands from the seminal vesicles have also a higher affinity for zinc than the low molecular weight (LMW) ligands from the prostate. A redistribution of zinc therefore takes place after ejaculation. The HMW zinc ligands from the seminal vesicles were found to have an isoelectric point at 6.1–6.7, to be glucoproteins, and to have an apparent molecular weight of 250000. The possible physiological implications of a redistribution of zinc after the ejaculation is discussed in view of the fact that zinc is of importance for many functional properties of the human spermatozoa.
A model study of the tubuloglomerular feedback mechanism: effector site and influence on renal autoregulation
Authors: JENSEN PETER KOCH , STEVEN KENNETH
Published: December 2008

The effector site of the macula densa tubuloglomerular feedback mechanism was determined with a mathematical model of glomerular ultrafiltration. The feedback response was found to be mediated by an increase in the hydraulic resistance of the afferent arteriole, possibly accompanied by a slight decrease in the ultrafiltration coefficient of the glomerular membrane. The contribution of the tubuloglomerular feedback mechanism to the autoregulation of renal blood flow and GFR during increased arterial blood pressure was evaluated with a mathematical model of the kidney. The tubuloglomerular feedback system of the superficial nephron was found to be a less efficient regulator of renal blood flow and GFR than the remainder of the autoregulatory mechanism.
Blood flow in human adipose tissue after infusion of (Gln4‐neurotensin
Authors: LINDE B. , ROSELL S. , RÖKAEUS Å.
Published: December 2008

(Gln4)‐neurotensin, 18pmol±kg‐1±min‐1, was infused i. v. during 20 min in 10 healthy male volunteers. Adipose tissue blood flow was continuously monitored by measuring the disappearance rate of 99mTc‐pertechnetate injected s. c. on the abdomen and thigh. Heart rate and blood pressure were measured and calf blood flow studied by venous occlusion plethysmography. Neurotensin‐like immunoreactivity (NTLI) in serum was determined. Infusion of isotonic saline served as control. During intravenous infusion of (Gln4)‐neurotensin the first order rate constants of 99mTc‐pertechnetate from the abdomen decreased by 21.9±5.9% from a basal value of 8.3±0.5% min‐1 (p<0.01). The reduction in blood flow started after a latent period of 5–10 min and persisted throughout the thirty minute observation period following infusion. A significant correlation (r=0.87, p<0.001) was found between the percentage decrease in blood flow from abdominal fat and the body fat content of the subjects as determined from the sum of four skinfolds. Blood flow from thigh fat did not change significantly, nor did heart rate, blood pressure or calf blood flow. During infusion of (Gln4)‐neurotensin plasma neurotensin‐like immunoreactivity (NTLI) increased successively. Ten minutes after starting the infusion the mean plasma NTLI level had increased from 20±5 pM to 302±31 pM; at 20 min it was 473±51 pM. These concentrations are within the range found after eating a fatty meal. The results indicate that neurotensin plays a physiological role in the regulation of human adipose tissue blood flow and may be of importance for the postprandial uptake of substrates in adipose tissue in certain regions. We suggest that neurotensin deserves consideration as an endocrine hormone affecting the regional deposition of fat postprandially.
Effects of water deprivation and hyperhydration in pregnant and lactating goats
Authors: OLSSON K. , BENLAMLIH S. , DAHLBORN K. , FYHRQUIST F.
Published: December 2008

The response to 30 h water deprivation was studied in 7 goats during the last month of pregnancy and during lactation with anestrus as the control period. Plasma osmolality and plasma Na concentration increased by about 4% in pregnant and lactating goats and by about 2% in anestral goats. Plasma AVP concentration rose by about 7 pg/ml in pregnant and lactating goats, but only by about 3 pg/ml during anestrus. PRA was elevated in pregnant animals, but dehydration caused only a minor further rise. Total plasma protein concentration was low in pregnant goats and did not increase during water deprivation, but it did so in lactating animals. Neither the hematocrit nor the plasma K concentration changed in response to dehydration. GFR fell by about 24% in pregnant goats and by 22% in lactating animals, but remained unchanged during anestrus. ERPF fell by 20% in lactating animals, but no consistent effect of the dehydration was seen during pregnancy and anestrus. Urine flow decreased by about 75% during pregnancy, 55% during lactation and 65% during anestrus with the highest urine osmolality observed during anestrus. Milk production was only slightly reduced, but the milk osmolality increased in parallel with that of the blood plasma. When allowed to drink at the end of the water deprivation period, pregnant goats immediately drank 2.5±0.5 litres, lactating goats 3.3±0.9 litres and anestral goats 1.1±0.3 litres. When hyperhydrated, pregnant goats excreted the excessive water more readily and showed less response to exogenous AVP than lactating and anestral animals. In conclusion, pregnant and lactating goats are obviously more susceptible to a shortage of water supply than anestral animals but can easily excrete an excess of water.
Atropine modulates changes in striatal muscarinic receptor binding sites in barbital abstinence in the rat
Authors: NORDBERG AGNETA , WAHLSTRÖM GÖRAN
Published: December 2008

We have previously reported that cholinergic mechanisms in the brain are involved in tolerance and physical dependence as expressed in the abstinence after 30–40 weeks forced chronic treatment with barbital to rats (for reviews see Nordberg & Wahlström 1980, 1981a). In the first part of the abstinence period the turnover of acetylcholine (ACh) seems to be increased in different areas of the brain since both decreased content of endogenous ACh and increased biosynthesis of ACh have been recorded (Nordberg & Wahlström 1977, 1979). These changes have been observed at peak abstinence when there is a maximal tolerance to hexobarbital and a maximal number of spontaneous convulsions. Some changes in cholinergic parameters may prevail in late abstinence as illustrated by reduced content of endogenous ACh in the striatum which is still present after 80 days of abstinence (Nordberg & Wahlström 1981b). The muscarinic receptors also undergo changes in the abstinence (Nordberg et al. 1980). In the striatum an increased number of binding sites has been measured on day 0 to 3 in the abstinence. Increases, but with different time courses, are seen also in other brain areas (Nordberg & Wahlström 1982).
Body mass, temperature and cost of walking in polar bears
Authors: HURST RICKI J. , ØRITSLAND NILS A. , WATTS PAUL D.
Published: December 2008

Body temperatures and oxygen consumption of three sub‐adult polar bears (Ursus maritimus) during treadmill exercise are presented. Comparisons are also made with results from prior studies of polar bear locomotion. The increase in body temperature and the metabolic cost were unexpectedly high, particularly in young animals. An equation describing the cost of locomotion versus body mass shows a negative, and apparently linear relationship. A significant correlation between body temperature and oxygen consumption may permit the use of body temperature telemetry to estimate activity metabolism of free‐ranging polar bears.
Analysis of mechanical alternans in rabbit papillary muscle
Authors: WOHLFART BJÖRN
Published: December 2008

Isometric force and action potentials were recorded in rabbit papillary muscles. It was found that the monophasic decline of the contractile potentiation that was recorded after an extrasystole (ES) was replaced by transient mechanical alternans (TMA) when temperature and calcium concentration of the perfusion medium had been lowered (from 37° to 27°C and from 2.0 to 0.5 mM, respectively). TMA in response to ES was also seen when the preparation was exposed to 2 mM 4‐aminopyridine. Furthermore, TMA could be induced by a shortening step during activity. Mechanical restitution curves were recorded by relating max. rate of force development of a test contraction to the duration of the preceding stimulus interval. It was found that the alternating contractions during TMA were associated with shifts of the mechanical restitution curve along the force axis. The duration of the action potential was inversely related to force development during TMA. It is proposed that TMA is due to a reduced damping of a regulatory feedback system between inotropic state and intake of activator calcium during the action potential. The following sequence of events are suggested: The abbreviated action potential accompanying a potentiated contraction is associated with reduced intake of activator calcium. This leads to depression of the subsequent contraction. The latter contraction is associated with increased calcium intake due to prolongation of the action potential. This will lead to potentiation of the next beat and the sequence is repeated. It is proposed that recirculation of calcium between heart beats will act as a damping factor of this system.
Effects of Ca2+ on the contractility and Sr2+ accumulation in the quail oviductal smooth muscle
Authors: ARJAMAA O.
Published: December 2008

There occur strong spontaneous contractions in the avian oviduct, which are considered to effect the locus of the ovum during ovum transport. Previously it has been shown that stretch regulates these contractions by means of some unknown mechanisms in this tissue. When a transversal strip, cut from the proximal magnum of the oviduct, was first kept at the length (L0= length in situ) and then stretched to the length 200% L0 the total integrated area of contractions increased 3.67±0.63 (6) times greater (p<0.01) than the contractility at the length Lo. Ca2+ concentration of 5 mM increased the total integrated area of the contractions 1.42±0.22 (7) greater than the control while the increase at 8 mM was only 1.17±0.30 (7). 0.5 mM Ca2+ decreased the contractility to 0.72±0.15 (7). In a 50 μM EGTA containing solution, the contractility decreased in a few minutes. Sr2+ used as an indirect tracer of Ca2+ accumulated both in control and stretched strips in the sarcoplasmic reticulum, the mitochondria, and the sarcolemma. The electron‐dense deposits were, however, most clearly seen in the sarcolemma. Compared to the Sr2+ accumulating sites in erythrocytes, deposits were on the outer side of the cell membrane, thus suggesting the glycocalyx as an important site for Ca2+ exchange in this smooth muscle. The sarcolemmal invaginations, caveolae, accumulated Sr2+ similarly to other parts of the sarcolemma. During ovum transport, stretch changes the Ca2+ accessibility to muscle cells, and at structural level, this takes place in the sarcolemma.