bluuebunny/crossref_metadata_2025 huggingface dataset:
On a cholinergic motor innervation of the rat urethra
Authors: EKSTRÖM JÖRGEN , MALMBERG LARS
Published: December 2008

Choline acetyltransferase activity was demonstrated in the proximal part of the male rat urethra, indicating a cholinergic innervation of this tissue. The cholinergic nerve fibres emanated evidently from the pelvic nerves, since bilateral removal of the pelvic ganglion caused a major fall in the activity of this enzyme. The muscle activity of the circular layer of the proximal urethra was recorded in vitro. The basal activity of this segment was low. The parasympathomimetics acetylcholine and methacholine, evoked rapid and marked contractile responses; the maximal responses to these drugs were 36 and 44%, respectively, of that to potassium. The corresponding figures for phenylephrine and noradrenaline were found to be 79 and 88%, respectively. The responses evoked by the parasympathomimetics were unaffected by the ganglion blocker hexamethonium, the α‐adrenoceptor blocker dihydroergotamine and the β‐adrenoceptor blocker propranolol. Atropine, however, abolished the responses completely. Following degeneration of adrenergic or cholinergic nerves of the urethra the parasympathomimetics still evoked contractions. Taken together these findings indicate that the parasympathomimetics exert their contractile effect through a direct action on muscarinic receptors. Parasympathectomy but not sympathectomy (caused by 6‐hydroxydopamine treatment) gave rise to a supersensitivity to methacholine, as judged by a leftward shift of the dose‐response curve for this drug, the ED50‐value being ten times less than that of the controls. The observations seem to suggest that the proximal urethra normally is under the influence of cholinergic activity beside that of adrenergic activity previously demonstrated.
The acyl‐amino‐alkyl benzoic acid residue and the sulfonylurea containing residue of glibenclamide affect different aspects of β‐cell function
Authors: NORLUND LENA , SEHLIN JANOVE
Published: December 2008

HB 699 is a non‐sulfonylurea acyl‐amino‐alkyl benzoic acid derivative, corresponding to a major part of the glibenclamide molecule. Basal insulin release (3mmol/1 glucose) as well as glucose‐induced release (10 mmol/1 glucose) were stimulated by 25 μmol/1 and 200 μmol/1 HB 699. HB 699 (200 μmol/1) had no effect on the osmotic swelling induced by hypoosmolarity (180 mosm/1). The results indicate that the glibenclamide‐induced insulin release can be resolved in a “high‐affinity” component, which correlates with increased osmotic resistance in the β‐cells and a “low‐affinity” component not associated with increased osmotic resistance. It is suggested that the latter component may be due to the part of the glibenclamide molecule that corresponds to HB 699.
Enzyme activities of energy metabolism in skeletal muscle, and in the uterus, during late pregnancy in the mouse
Authors: ÖRLANDER JAN
Published: December 2008

Three hindleg muscles (white and red quadriceps, soleus), and uterine tissue, from late pregnant NMRI mice were analyzed for selected enzyme activities of energy metabolism. In addition, skeletal muscle fibre type distribution and fibre diameters were estimated in some animals. No differences between pregnant and non‐pregnant animals were found for any enzyme in any of the tissues. Neither were there any differences in muscle morphology. It was concluded, that the increased work load, and altered plasma substrate profile, during late pregnancy do not induce metabolic or morphological adaptations in skeletal muscle. Furthermore, the smooth muscle of the murine myometrium does not increase its metabolic capacity in preparation for parturition, suggesting that the base‐line metabolic capacity is sufficient for the work involved. The morphological and metabolic characteristics of the three skeletal muscles were similar to those in the rat. Compared with these muscles, the uterus had a low metabolic capacity, and appeared to rely predominantly on fatty acid oxidation.
Further evidence for the presence of subepithelial nerve cells in the rat ileum—an immunohistochemical study
Authors: DAHLSTRÖM A. , NEWSON B. , NAITO S. , UEDA T. , AHLMAN H.
Published: December 2008

Earlier we observed electronmicroscopically an unidentified but neuron‐like subepithelial cell in the crypts of the rat ileum. We have now studied some immunocytochemical characteristics of similar cells in the fluorescence microscope by indirect immunofluorescence. Three markers for neuronal tissues were used: 1) Monoclonal Thy‐1‐antibodies, demonstrated previously to recognize surface antigens of thymus‐derived cells and nervous tissue; 2) Tetatus toxin, which binds to the GTI ganglioside receptor of nerve cells, and to some other neuronal receptor; and 3) Anti‐Protein I‐IgG, which is monospecific for Protein I located in synaptic vesicle membranes. The various antisera used for secondary incubations all reacted with leucocytes and other connective tissue cells in the villous cores. When the specific primary antisera of Thy‐1 and Protein I, and tetanus toxin, were included, a small number of spindle‐shaped cells with two processes, extending just beneath the basal lamina of the epithelium, was observed. These cells had a similar location and appearance as the neuron‐like cells observed electronmicroscopically and may be identical with these cells. These results give further evidence that cells with neuron‐like characteristics are present in the mucous layer of the small intestine.
The ability of human subjects to detect small changes in breathing volume
Authors: KATZ‐SALAMON MIRIAM
Published: December 2008

Human ability to detect small changes in the inspired volume was tested in four healthy subjects. The tested volume changes were achieved by: 1) displaying breathing volume continuously to the subject on the screen of an oscilloscope, the vertical gain of which was changed by the experimenter, and 2) breathing small amounts of CO2 (0.02–2.0%) in air. The subject was asked to signal, by pressing a button, every time two consecutive breaths differed from the reference level. The six tested volume changes corresponded to 15–65% of the reference, when changes in eupneic tidal volume were tested, and to 15–45% when changes in three reference volume levels, 1.0, 1.5, and 2.0 times the resting tidal volume, were tested. The just noticeable difference (JND) was defined as the volume change detected in 50% of the trials. The obtained results showed that the JND for volume corresponds to a volume change of 120–160 ml (23–28% of the reference) when the resting tidal volume was used as the reference. For the three reference volumes, the JND was found to be a nearly constant fraction (0.25–0.29) of the reference volume and thus followed the ‘classical’ Weber law (JND/reference stimulus = constant).
Assessment of ventilation and respiratory rate by healthy subjects
Authors: KATZ‐SALAMON MIRIAM
Published: December 2008

Ability to judge ventilation (V̇1) and respiratory rate (RR) was examined in healthy subjects using the standard psychophysical technique of magnitude production. The relationships between objective and subjective magnitudes of V̇1 could be adequately described by power function with the mean exponent 1.9. The mean deviation from the regression line was 3.0%. The requested levels of V̇1 were produced either by changing tidal volume (VT) or RR. Changes in VT resulted in higher exponents of V̇1 judgment. When requesting the subjects to keep V̇1 constant by matching either VT with the imposed changes in RR or vice versa, the lesser acuity was found in adjusting RR to VT than in matching VT with RR. The results indicate that V̇1 is judged on the basis of either VT or RR and is not treated as a concept in its own power. The ‘RR’ experiments consisted of assessment of RR and breath duration. The relationships between objective and subjective magnitudes of these two parameters were characterized by power functions with the exponents 1.0 and 1.2 respectively and mean deviation from the regression line of 13%. It is speculated that difficulties in adjusting RR to VT depended on a lesser precision in RR judgment.
Diurnal profile of plasma somatostatin in man
Authors: BURHOL PER G. , JORDE ROLF , JENSSEN TROND G. , LYGREN IDAR , FLORHOLMEN JON
Published: December 2008

Plasma somatostatin was followed for 24 h in 6 healthy young males having 4 regular meals with water allowed freely, and performing their normal daily activities. Plasma somatostatin rose significantly after each meal, it returned towards the basal level before the next meal, and it rose higher and stayed significantly elevated longer after the evening meal than after any of the other meals. A possible physiological circadian rhythm of plasma somatostatin is discussed.
Cation exchange—a common mechanism in the storage and release of biogenic amines stored in granules (vesicles)?
Authors: UVNÄS BÖRJE , ÅBORG CARL‐HUGO
Published: December 2008

The matrices of the amine storing granules in mast cells, chromaffin cells and noradrenergic nerves show properties reminiscent of cation exchanger materials. In vitro, the amines are released from their granule storage sites on exposure of the granules to cations, e.g. sodium ions. The proposal is made that also in vivo the release of transmitter amines is the result of cation exchange Amine+⇌ Na+ ions and that the release of transmitter amines occurs as a nonexocytotic fractional release engaging multiple granules instead of exocytotic emptying of a few. Some physiological and pharmacological implications of a fractional transmitter release are discussed.
Activation of monoamine oxidase by high molecular weight fractions of human plasma
Authors: WAHLUND LARS‐OLOF , SÄÄF JAN , ROSS SVANTE B. , WETTERBERG LENNART
Published: December 2008

The activation of human platelet monoamine oxidase (MAO) and rat brain mitochondrial MAO (RBM‐MAO) by human plasma were studied. The deamination of two different substrates, tyramine and phenethylamine (PEA) was investigated. The increase in MAO activity in the presence of human plasma can be explained by the observed decrease in the apparent Km for the amine (tyramine, PEA). This activation pattern was the same both for human platelet MAO and RBM‐MAO. The activating properties of human plasma were recovered in high molecular weight fractions after gel filtration.
Effect of glibenclamide on the osmotic resistance of pancreatic β‐cells
Authors: NORLUND LENA , SEHLIN JANOVE
Published: December 2008

The effect of glibenclamide on the osmotic resistance of β‐cells was measured using isolated β‐cells fromob/ob‐mice. The β‐cells were incubated at different osmolarity and the diameters of the approximately spherical β‐cells were measured at 22°C or at 37°C with the aid of a screw micrometer eyepiece fitted to a light microscope. A near linear decrease of β‐cell diameter was found with increasing osmolarity (111–617 mosm/l). Control experiments showed that the membrane stabilizers, imipramine (0.1 mmol/l) or tetracaine (I mmol/l), strongly reduced the osmotic swelling induced by low osmolarity (180 mosm/l). Glibenclamide (0.001 or 0.2 mmol/l) did not affect the β‐cell diameter at normal osmolarity (317 mosm/l) but reduced the swelling induced by hypoosmolarity (180 mosm/l) and the shrinking induced by hyperosmolarity (617 mosm/l). It is suggested that glibenclamide increases the osmotic resistance of isolated β‐cells by changing transmembrane flow of ions.
Force development in muscle strips of the disused and nondistended rat urinary bladder
Authors: EKSTRÖM J. , MALMBERG L. , EKELUND M. C.
Published: December 2008

In rats the flow of urine was diverted from the bladder over a period of 7–10 days. Active length‐tension curves of muscle strips of such disused bladders did not differ from those of controls, provided lengths were related to optimum length for force development. When, however, lengths were related to length in situ the active length‐tension curves were shifted to the left. The muscle strips of the disused bladders showed a higher degree of stiffness than those of controls. The present findings are related to previous ones made on disused but distended bladders showing changes in the opposite direction. Taken together they demonstrate the importance of filling and periodic emptying for the preservation of normal length‐tension relations in the bladder.
Cardiovascular responses to face immersion and apnea during steady state muscle exercise: A heart catheterization study on humans
Authors: BJERTNÆS L. , HAUGE A. , KJEKSHUS J. , SØYLAND E.
Published: December 2008

The cardiovascular adjustments to face immersion and apnea (FIA) in human beings during steady‐state muscle exercise (163 and 98 watt) have been investigated. Using a triple lumen flow directed catheter inserted into the pulmonary artery we were able to measure cardiac output (CO) by thermodilution technique, pulmonary arterial pressure (PPA) right atrial pressure (PRA) and left ventricular filling pressure (PAD). Phasic arterial blood pressure (BP) was measured via a cannula in the radial artery. A 12 lead ECG was recorded continuously. FIA caused an immediate rise in BP (median 61 %), the highest level being 25.33 kPa. CO during the last half of FIA was reduced by 49% (range 46–59, n=7) systemic vascular resistance increased by median 200% (range 111–280). Myocardial oxygen demand determined by the heart rate pressure double product fell from median 33.6 to 16.8 (163 W) and 28.5 to 19.1 (98 W) given as beats/min · kPa ·4 102. Mean reduction was by 42%. PPA and PRA immediately increased and remained constant until a further pronounced increase was seen towards the end of FIA when pulmonary vascular resistance (PVR) went up. PACO2 and PAO2 at the end of 30 sec FIA (163 W) was 10.0 and 5.6 kPa, respectively, values which expectedly would cause pulmonary vasoconstriction. Our findings demonstrate that humans are able to make principally the same cardiovascular adjustments to diving as aquatic mammals, although the response patterns are slower and less efficient. The marked increase in systemic arterial blood pressure which we observed is in contrast to that in e.g. diving seals. In humans the rises in SVR and PVR is not so closely adjusted to the reduction in CO. This will reduce the oxygensaving potential by causing a rise in cardiac afterloads.
Effects of synthetic porcine GIP on the PP release in healthy subjects
Authors: JORDE ROLF , BURHOL PER G.
Published: December 2008

Six healthy subjects were given 30 min intravenous infusions of synthetic procine GIP in doses of 0.52, 1.04 and 1.56 μg·kg‐1·h‐1 on one occasion and a bolus injection of 1 μg·kg‐1 on another. The GIP infusions gave physiological GIP levels which did not affect plasma PP, whereas the GIP injection giving supraphysiological GIP levels evoked a significant elevation in plasma PP.
Effect of ambient temperature on rectal temperature in normal and malnourished rats during early postnatal development
Authors: CONRADI NILS G. , MÜNTZING KRISTINA , SOURANDER PATRICK , HAMBERGER ANDERS
Published: December 2008

Information on body temperature is frequently lacking in metabolic studies on normal and malnourished suckling rats although differences in their thermoregulatory efficiency may be expected. The aim of the present study was to evaluate the effect of different ambient temperatures on the rectal temperature of litters of normal and protein deprived rats to establish the ambient temperatures at which a normal rectal temperature can be expected at various postnatal ages. The offspring of normal rats and rats subjected to a dietary reduction of 50% of the protein intake were examined 10 days to 30 days postnatally. The pups were transferred from the nest cage to an incubator: the rectal temperature was measured immediately after transfer to the incubator and 30 and 60 min later at ambient temperatures of 35, 30 and 25°C. Up to 15 days of age control pups showed a fall in rectal temperature after the short exposure to room temperature (22°C) needed for transfer. A similar fall of rectal temperature was recorded in the malnourished pups up to 25 days age. The effects of the ambient temperatures on the malnourished pups indicated a delay in the control of body temperature of some 10 days. This is in agreement with a previous report on semi‐starved rats (Heim & Szelenyi 1965). The conditions for the maintenance of a normal rectal temperature in litters of normal and malnourished suckling rats separated from their mother are out‐lined.
Cigarette smoking potentiates fat‐induced elevation of neurotensin‐like immunoreactivity in human plasma
Authors: RÖKAEUS ÅKE , THOR KJELL , ROSELL SUNE
Published: December 2008

The aim of the present study in man was to investigate the influence of cigarette smoking on basal plasma concentrations of neurotensin‐like immunoreactivity (p‐NTLI), as well as on fat‐induced elevation of p‐NTLI levels. On three separate occasions, habitual tobacco smokers either ingested fat (55 ml Intralipid 20%) or smoked three cigarettes, or ingested fat and smoked. The subjects were fasted overnight and told no to smoke during the fasting period. Smoking of one cigarette at one hour intervals (0, 60, and 120 min) did not change the p‐NTLI levels (n=6). Ingestion of fat caused a significant increase (n=16) and when these two procedures were combined (n=16), the mean integrated p‐NTLI response (nM0–180 min) was 56% larger than the response after fat ingestion alone. The results show that cigarette smoking potentiates the fat‐induced elevation of p‐NTLI levels, whereas cigarette smoking per se has no effect.
Effects of hemorrhage on intramural blood flow distribution, villous tissue osmolality and fluid and electrolyte transport in the cat small intestine
Authors: REDFORS S. , HALLBÄCK D.‐A. , SJÖVALL H. , JODAL M. , LUNDGREN O.
Published: December 2008

The hemodynamic response in the parallel‐coupled vascular sections of the cat small intestine were studied before, during and after a two hour period of hemorrhage (about 30 per cent of estimated blood volume). Fluid and electrolyte transport and villous tissue osmolality were also measured. Biopsies for histology were taken at the end of all experiments. The animals were divided in two groups, undamaged and damaged, according to the degree of mucosal damage observed. The hemodynamic reactions were investigated with a method that made it possible to study total intestinal, absorptive site (“villous”), nonabsorptive site (“crypt”) and muscle layer blood flows. Total intestinal blood flow was lower in the damaged as compared to the undamaged group during hypovolemia. No difference in absorptive site blood flow was observed between the two groups during hypovolemia. Furthermore, no decrease of red blood cell flow in the “villi” was recorded in either group after hemorrhage. Consequently, mucosal lesions developed despite an unchanged oxygen transport capacity to the villi. The pathophysiology of the mucosal lesions is briefly discussed. Net fluid and sodium absorption was after hemorrhage increased in the undamaged group reflecting a decrease in the tissue to lumen transport of sodium. After retransfusion net fluid and sodium absorption returned to control. In the damaged group, however, net fluid and sodium absorption was decreased after hemorrhage. The increased rate of fluid and electrolyte transport observed in the undamaged small intestine after hemorrhage, is proposed to be an important mechanism for fluid replacement after hemorrhage.
Is protease activity involved in fast axonal transport?
Authors: EDSTRÖM ANDERS , EKSTRÖM PER , KANJE MARTIN
Published: December 2008

N‐a‐p‐Tosyl‐L‐Lysine Chloromethyl Ketone (TLCK), a protease inhibitor, was found to irreversibly inhibit rapid axonal transport of protein in vitro in the frog sciatic nerve. TLCK exerted its action at the axonal level and seemed to depress the rate rather than the amount of transported protein. The efficiency of TLCK as a protease inhibitor was demonstrated by polyacrylamide gel electrophoresis, which showed that degradation of high molecular weight proteins (presumably neurofilament subunits) into a 25 000 dalton protein could be induced by exposing the frog nerves to triton‐X and prevented by the presence of TLCK. Findings that TLCK, at a transport inhibiting concentration (0.1 mM), had little or no effects on either protein synthesis or ATP levels, suggest that TLCK did not affect transport due to general cytotoxic properties. The effects of TLCK is discussed in relation to possible roles of protease activity in axonal transport.
Vasoactive intestinal polypeptide (VIP): Effects in the eye and on regional blood flows
Authors: NILSSON SIV F. E. , BILL ANDERS
Published: December 2008

The effect of vasoactive intestinal polypeptide (VIP) on regional blood flows was studied with labeled microspheres in albino rabbits. Intravenous injection of 500 ng VIP/kg b. w. during 100 s did not change the arterial blood pressure significantly, but caused a rise in intraocular pressure (IOP) and an increase in the choroidal blood flow by 35%, while the blood flow through the anterior uvea was unaffected. The most pronounced vasodilation was observed in the pancreas, the thyroid gland and the parotid gland. In these tissues local blood flow increased by more than 100%. Other tissues, in which this dose of VIP produced vasodilation, were the submandibular gland, the eyelids, the nictitating membrane, the choroid plexus and the heart muscle. Ganglionic or muscarinic blockade had little or no effect on the VIP‐induced vasodilation in most of the tissues. Intracameral injection of VIP (1 μg) produced vasodilation in the iris and the ciliary body, but did not affect IOP. VIP had no apparent effect on the pupil size or the blood‐aqueous barrier. In experiments with direct blood flow determination from an opened vortex vein intravenous infusion of VIP, 100 ng. kg‐1 .min‐1 b. w., during five minutes reduced the uveal vascular resistance by about 50%. This study shows that VIP is a potent vasodilator in many tissues at doses hardly affecting the arterial blood pressure and supports the suggestion, that VIP is responsible for the non‐cholinergic vasodilation in the eye caused by facial nerve stimulation.
Vasopressin release in response to acute hypotension induced at different time intervals in the conscious sheep
Authors: RUNDGREN M. , JÓNASSON H. , APPELGREN B. , ERIKSSON S. , LEKSELL L. G.
Published: December 2008

The renal arginine Vasopressin (AVP) excretion in response to acute systemic hypotension induced by intravenous infusion of sodium nitroprusside (SNP) (30–40 μg/kg min‐1) at different experiment intervals (0, 2, 4, 7 and >12 days) was studied in the conscious hyperhydrated sheep. During the first post‐infusion hour, 2.5 times more AVP was excreted in response to hypotension induced at >12 day intervals than that observed at intervals of 0–7 days. No interexperimental time dependence of the AVP response to SNP infusion was seen with intervals of 0–7 days. The attenuated AVP release obtained with reduced experiment intervals (0–7 days) was accompanied by shorter antidiuresis and a less accentuated natriuresis during the post‐hypotensive period in comparison to what was observed with >12 day experiment intervals. There were no interval‐dependent differences in maximal fall of mean arterial pressure, or onset and recovery of the hypotension induced by SNP administration. It is suggested that acute systemic hypotension causes such a massive AVP release that more than one week is needed for complete restoration of a releasable neurohypophyseal pool of the hormone.
The effect of 2 hours of complete unilateral ureteral obstruction on tubuloglomerular feedback control
Authors: PERSSON A. ERIK G. , WAHLBERG JAN , SAFIRSTEIN ROBERT , WRIGHT FRED S.
Published: December 2008

The mechanisms affecting renal blood flow and filtration during and after unilateral ureteral obstruction (UUO) are incompletely understood. Since ureteral obstruction leads to changes in interstitial pressure and volume, and since we have previously shown that interstitial pressure conditions can modulate the sensitivity of the tubuloglomerular feedback (TGF) control system, we sought in the present study to define the contribution of the TGF system to changes in GFR during and after UUO, and to observe associated changes in pressures in vessels, tubules and the interstitial space. Interstitial pressures and glomerular filtration rate (GFR) were measured in one group of Sprague Dawley rats. Interstitial hydraulic pressure was determined with a thin catheter placed in the subcapsular space. Interstitial oncotic pressure was estimated from the protein concentration in collected hilar lymph. In a second group of rats proximal tubule pressure (PT) and stop‐flow pressure (PSF) were measured during the first three hours of UUO and after 24 h UUO. In a third group of rats PSF was measured while the loop of Henle was perfused at different rates. The sensitivity of the TGF system was determined from the maximal drop in stop‐flow pressure (APsF) and the turning point (TP)‐the tubule perfusion rate at which 50% of this maximal stop‐flow pressure response was obtained. In a fourth group of rats proximal tubule flow‐rate was measured after release of 2 hrs UUO. The results show that PT and PSF are both increased during the first three hours of obstruction and that they return to normal or sub‐normal levels after 24 h of UUO. Interstitial hydraulic pressure increased to 7 mmHg (control 3 mmHg), and oncotic pressure in the interstitial space decreased to ‐2 mmHg (control ‐3 mmHg) during obstruction. In this situation feedback sensitivity was reduced or abolished. After release of obstruction, interstitial hydraulic pressure fell to zero and oncotic pressure returned to ‐3 mmHg. In this situation feedback sensitivity was increased considerably, with a TP of 12.5 nl/min (control 20.0 nl/min) and a ΔPSF of 12.6 mmHg (control 8.2 mmHg). Thus the present experiments show that during UUO the feedback response is abolished. Diminution of feedback mediated vasoconstriction may contribute to the vasodilation seen during the first hours of ureteral obstruction. Furthermore, after release of UUO an increase feedback sensitivity may be a factor causing the observed reduction in GFR.
Hyperplasia and hypertrophia in the denervated and distended rat urinary bladder
Authors: EKSTRÖM J. , HENNINGSSON A.‐C. , HENNINGSSON S. , MALMBERG L.
Published: December 2008

The parasympathetically denervated and distended rat urinary bladder was found to have increased fourfold in weight when examined 3 weeks postoperatively. Both in muscularis and mucosa of such a bladder the synthesis of proteins, RNA and DNA was increased severalfold. An increase in the polyamines putrescine, spermidine and spermine was also found; these polyamines are usually linked to protein synthesis. The results suggest that the cells of the two layers increase both in size and number. Hyperplasia was, in a previous study, suggested as a possible explanation for a right‐ward shift of the active length‐tension curve of muscle strips in the denervated rat urinary bladder.
Changes in noradrenaline release and in beta receptor number in rat hippocampus following long‐term treatment with theophylline or L‐phenylisopropyladenosine
Authors: FREDHOLM BERTIL B. , JONZON BROR , LINDGREN EVA
Published: December 2008

The administration of a stable adenosine analogue, L‐N6‐phenylisopropyladenosine (LPIA, 0.3 mg/kg i. p.), caused a decrease in the accumulation of L‐DOPA in the rat hippocampus after blockade of aromatic amino acid decarboxylase by NSD 1015 (150 mg/kg). Conversely, the adenosine receptor antagonist theophylline (15 mg/kg) increased the L‐DOPA accumulation. In slices from rat hippocampus L‐PIA causes an inhibition of the stimulation‐evoked release of [3H]‐noradrenaline (NA). The magnitude of this effect was enhanced after 1 week treatment with theophylline (15 mg/kg/day). The number of beta‐adrenoceptors in the rat hippocampus, measured by binding of [3H]‐dihydroalprenolol was significantly reduced after theophylline treatment, and tended to be higher after LPIA treatment. The results show that activation of adenosine receptors in vivo causes a decreased synthesis of NA in the rat hippocampus. The reason may be a reduced firingrate of the NA‐neurons. Theophylline, by contrast, enhanced the synthesis, possibly indicating a role for endogenous adenosine in the regulation of NA‐turnover. Long‐term treatment with these drugs caused adaptive changes in the presynaptic adenosine receptor activity and in the number of beta‐adrenoceptors.
Breathing pattern and occlusion pressure during moderate and heavy exercise
Authors: LIND F. , HESSER C. M.
Published: December 2008

We studied changes in breathing pattern and mouth occlusion pressure (P0. 1) in 11 healthy subjects performing graded steady‐state exercise on a cycle ergometer up to the maximal load sustainable for 4 min. With increasing work intensity both the tidal volume (VT) and end‐inspiratory volume relations to inspiratory (TI) and expiratory (TE) durations were linear in the moderate work load range; in the high load range VT and end‐inspiratory volume tended to plateau with further decreases in TI and TE. The ratio of TI to total breath duration (TI/Ttot) increased with work intensity. Intraindividual coefficients of variation for VT, breathing frequency (f), mean inspiratory flow (VT/TI), and other respiratory variables decreased with increasing work intensity, indicating that breath‐tobreath variations in breathing pattern became smaller as the level of ventilation increased. P0,1 rose with VT/TI as a power function with an exponent averaging 1.5 (range 1.3‐1.9), indicating that the ratio P0, 1(VT/TI), an index of respiratory system impedance, increased with VT/TI and work intensity. We conclude that in moderate and heavy exercise (1) the work of inspiration at a given ventilation is reduced because of the increase in TI/Ttot, (2) the impedance of the respiratory system increases with work intensity because of both an increase in f and a flow‐dependent rise in airway resistance, and (3) the neuromuscular inspiratory activity is reflexly augmented because of internal flow‐resistive loading.
Structural and mechanical adaptations in rat aorta in response to sustained changes in arterial pressure
Authors: ARNER ANDERS , MALMQVIST ULF , UVELIUS BENGT
Published: December 2008

Structural and mechanical adaptations in response to sustained changes in arterial pressure were studied on abdominal aorta of the male rat. Two models were used: 1. Aortic ligature (L), immediately below the renal arteries producing hypotension distal to the knot (duration before sacrifice 6 weeks or 3 months). 2. One‐clip renal hypertensive rats (H) (duration 6 weeks). Normotensive sham‐operated rats (C) served as controls. At sacrifice mean tail artery pressure was L: 58±1, C: 110±3, and H: 163±5 mmHg (SE, n=6). Segments of abdominal aorta were mounted in vitro for determination of their length–tension relations (activation: High‐K+ solution with 2.5 mM Ca2+). At end of experiments the vessels were supramaximally stimulated at optimal circumference (Io) for active force (activation: High‐K+ solution with 10 mM Ca2+, and 10‐5 M noradrenaline), and then fixated for light and electron microscopy. Passive and active length–tension relations were shifted towards lower and higher circumference values for hypo‐ and hypertensive vessels, respectively. The Io values were L: 3.60±0.13, C: 4.44±0.19, and H: 4.91±0.29 mm. The media thickness at I0 was reduced in L: 56.0±3.3, and increased in H: 81.3±2.4 compared to C: 73.4±1.8 μm. Maximal active wall stress was L: 46.6±9.8, C: 74.2±7.0, and H: 83.8±7.7 mN/mm2. Intracellular volume (ICV) in the media was L: 30±2, C: 45±3, and H: 44±1% (n=4 for each). The results indicate that the vascular smooth musle in the H group has an unaltered force generating ability. The low active stress in L could to a large extent be explained by the decreased ICV. In conclusion, the arterial vessel wall of these animals, with no genetic predisposition for hypertension, adjusts smooth muscle content and length–force relations in a characteristic way in response to sustained alterations in transmural pressure.
The influence of tubulo‐glomerular feedback on the autoregullation of filtration rate in superficial and deep glomeruli
Authors: SJÖQUIST M. , GÖRANSSON A. , KÄLLSKOG Ö. , ULFENDAHL H. R.
Published: December 2008

Single nephron glomerular filtration rate (SNGFR) of superficial and juxtamedullary nephrons were measured at normal and reduced perfusion pressure in the left kidney of young Sprague Dawley rats. Perfusion pressure was lowered by constricting the aorta proximal to the branching of the left renal artery. The influence of the tubulo‐glomerular feedback mechanism on SNGFR was quantitated by measuring SNGFR during intact and interrupted urine flow to the macula densa region. By using a modified Hanssen technique, SNGFR was measured under free‐flow conditions. In other experiments, the urine flow to the distal nephron was blocked by a micropuncture technique, which was used for collection of the tubular fluid for measuring the filtration rate. All nephron populations autoregulated SNGFR from 70–80 to 130 mmHg, which was the upper limit of this investigation, when urine flow throughout the nephron was intact. The autoregulation in this pressure range was lost when tubular fluid was prevented from reaching the distal nephron. It was shown that the influence of negative feedback on SNGFR by the macula densa mechanism at normal blood pressure is greater in deep nephrons than in superficial ones.
Fatigue of voluntary contractions in normal and myasthenic human subjects
Authors: SECHER N. H. , PETERSEN S.
Published: December 2008

The effect of fatigue developed during 96 repeated rapid maximal voluntary finger muscle contractions (MVC), 12 contractions per minute, was followed in 4 control subjects and 4 myasthenic patients. The tension‐time integral (T‐TI) was determined during either the first 1 or 1.25 s of each contraction. Fatigue decreased the T‐TI by 21% in the control subjects and by 65% in the patients. While ordinary MVC showed a slow rate of rise of tension and gradually increasing electromyographic activity, rapid MVC from both groups showed a steep rate of rise of tension, a ‘notch’ after about 0.3‐0.4 s separating two relative maxima and a larger electromyographic activity during the first half second of the contraction. The mechanograms from rapid MVC were divided by an arbitrary straight line connecting the starting pint of the contraction curve and the notch. The line separated an area (N x s) above and to the left (a‐component) from an area below and to the right (β‐component) of the line. Fatigue affected the β‐component selectively in both control subjects and myasthenic patients. Only when the α‐component was reduced by more than 80%, was a reduction of the α‐component also seen. At any time during a sustained contraction, the patients could briefly increase their instantaneous strength, but for only about one half second. The results suggest that human muscle contractions can be divided into two parts with a different sensitivity to fatigue in both control subjects and myasthenic patients.
Increase in neurotensin‐like immunoreactivity in rat plasma after administration of calcium, bombesin and fat and its inhibition by somatostatin
Authors: RÖKAEUS ÅKE
Published: December 2008

Neurotensin‐like immunoreactivity (NTLI) is released from the small intestine into the blood after enteral administration of fat and systemic administration of bombesin. The purpose of the present investigation in the rat was to study the effect of intravenously (i. v.) administered CaCl2 on the plasma concentration of NTLI (pNTLI) and to investigate the effect of i. v. infusion of somatostatin on basal NTLI release, as well as that stimulated by fat, bombesin and CaCl2. Administration of CaCl2 (5–25 mgxkg‐) increased p‐NTLI levels in a significant and dose‐dependent manner. In contrast, somatostatin 25–200 ngxmin‐1) reduced the basal p‐NTLI levels, as well as the increase in p‐NTLI levels induced by CaCl2 (10 and 25 mgxkg‐1), fat (oleic acid, 0.5 ml) and bombesin (25 and 125 pmolxkg‐1), in a dose‐related manner. Injection of bombesin released immunoreactive material that was indistinguishable from synthetic bovine neurotensin (1–13) upon gel‐filtration. This material seemed to be rapidly converted to the more stable metabolite neurotensin (1–8).
Inhibitory effect of pentobarbital anesthesia on venous stasis induced arteriolar vasoconstriction in the dog hindleg
Authors: BÜLOW JENS , HENRIKSEN OLE , AMTORP OLE
Published: December 2008

The effect of close intrarterial administration of pentobarbital in the concentration of about 2times10‐4mol/1 on the venous stasis induced arteriolar constriction in the dog hindleg was studied in 6 neurolept anesthetized dogs. It was found that the blood flows and vascular resistances in the legs before pentobarbital infusion were equal and the vasoconstrictor responses to venous stasis were the same. Pentobarbital infusion into the femoral artery in one of the legs increased the total leg blood flow compared to the control leg and abolished the increase in vascular resistance during venous stasis. In another experimental series the effect of general pentobarbital anesthesia on the vasoconstrictor activity in response to venous stasis locally in subcutaneous and muscle tissue in the hind limb was examined in 6 dogs. It was found that during the first 2–3 h of anesthesia the vasoconstrictor response was present in both tissues although the response in muscle tissue exhibited a great variation between the dogs during this period. However, after 4–5 h of anesthesia the response was abolished in both tissues. During neurolept anesthesia with fentanyl/N2O the same vasoconstrictor response was demonstrated in the hindleg 1 h and 5 h after induction of the anesthesia. It is concluded that pentobarbital anesthesia abolishes the arteriolar constriction induced by venous stasis. The mechanism may be blockade of the local sympathetic vasoconstrictor fibres or interference with myogenic vasoconstrictor mechanism of the vascular smooth muscle cells or both. It is suggested that fentanyl/N2O anesthesia is better suited for this kind of studies.
Static contraction of the quadriceps muscle in man: Cardiovascular control and responses to one‐legged strength training
Authors: LEWIS STEVEN , NYGAARD ELSE , SANCHEZ JORGE , EGEBLAD HENRIK , SALTIN BENGT
Published: December 2008

Knee extension strength training of one leg (ST) (120 maximal contractions per day, 5 days per week for 9 weeks) was performed by 9 healthy young men. Before and after ST, biopsies were obtained from the vastus lateralis muscle of each leg and static quadriceps contractions (SQC) lasting 2 min were performed with each leg under control conditions and after combined vagal and β‐adrenergic blockade with atropine and metoprolol. Maximal voluntary contraction strength (MVC) increased more for the trained leg (TL) than for the untrained leg (UTL) but thigh circumferences and muscle fibre diameters gave little evidence for muscle hypertrophy. In pre‐ vs. post‐training comparisons during SQC at the same relative force (40% of MVC) mean blood pressure (MBP), heart rate (HR) and smoothed rectified electromyographic activity were similar for TL and UTL. Similar findings were obtained for MBP after attenuation of the HR response by autonomic blockade, indicating that MBP, per se, was closely linked to the relative force of SQC. Pre‐to post‐training reductions in MBP and HR during SQC with each leg at an absolute force of 40% of pre‐training MVC were likely due to changes in the pattern of motor unit activation. A lower MBP response to SQC and TL than of UTL after training correlated with a greater capillary density and a lower muscle lactate level for TL.
Progesterone distribution in the brain of the PMSG treated female rat
Authors: BIXO MARIE , BÄCKSTRÖM TORBJÖRN , WINBLAD BENGT
Published: December 2008

The uptake of progesterone in the intact female rat brain was studied in 25, immature, female rats which were given an injection of 4 IU PMSG on the 25th day of life. The rats were killed 53–55 h after their first ovulation. Amounts of progesterone were measured in seven brain areas, peripheral fat and muscle tissue and blood plasma. The analyses were done by radioimmunoassay after extraction with ethanol or diethylether. The highest mean concentration was found in the cerebral cortex, followed by the hypothalamus, the hippocampus, the striatum, the midbrain, the cerebellum and the medulla oblongata (mean ± SE pg/mg 29±2.0, 27±5.2, 19±2.4, 15±1.8, 14±2.0, 12±1.7 and 11±1.9). The concentration of progesterone in the cerebral cortex was significantly higher than in all other areas except the hypothalamus (p<0.001). The cerebral cortex, the hypothalamus and the hippocampus had progresterone levels that were significantly higher than in peripheral fat tissue (p<0.01). The plasma progesterone level correlated positively with that in the cerebral cortex (r=0.62, p<0.01). Some earlier studies have shown high accumulation in the hypothalamus, but low in the cerebral cortex. One reason for the different results might be the nonphysiological models used in the earlier studies.
The influence of mechanical vibratory stimulation and transcutaneous electrical nerve stimulation on experimental pruritus induced by histamine
Authors: EKBLOM A. , FJELLNER B. , HANSSON P.
Published: December 2008

The effect of conditioning mechanical vibratory stimulation and transcutaneous electrical nerve stimulation (TENS) on experimentally induced pruritus was studied on 12 healthy subjects. Pruritus was provoked by intradermal injection of histamine on the upper arm. Vibration at 10, 100 and 200 Hz and TENS at 2 and 100 Hz were applied (i) over or (ii) proximal (in the same dermatome) to the pruritic area for a period of 5 min following itch elicitation. In addition the influence of a 5 min pre‐stimulatory regimen of the injection area was investigated (iii). The results obtained were compared with unconditioned values and with those obtained following a placebo conditioning procedure (i, ii). It was found that vibratory as well as electrical stimulation, for all frequencies used, reduced subjective itch intensity. Vibration at 100 Hz was the most effective mode of stimulation especially when applied directly to the pruritic area. Conditioning with 100 Hz vibration was also the most effective mode for reducing the duration of the itch response as well as the total experience of pruritus (estimated as a total itch index). Induction time to partial and maximal itch alleviation was shortest for 100 Hz vibration. The results indicate that treatment of pruritic conditions with conditioning stimulation, especially vibration, may be of therapeutic interest.
Taurine and hypotaurine transport by a single system in cultured neuroblastoma cells
Authors: HOLOPAINEN I. , KONTRO PIRJO
Published: December 2008

The kinetics of mutual inhibition of taurine and hypotaurine uptake were studied using neuroblastoma C1300 cells as neuronal model. Hypotaurine and GABA inhibited taurine uptake competitively, increasing the apparent Km. High‐affinity uptake of hypotaurine was completely abolished and the low‐affinity component competitively inhibited by taurine. GABA affected noncompetitively low‐affinity hypotaurine uptake, whereas the effect on high‐affinity uptake was competitive, with an increase in the apparent Km. All structural analogues tested inhibited taurine and hypotaurine uptakes similarly. The most potent inhibitors were β‐alanine and 2‐guanidinoethanesulphonic acid. The mutual inhibition and similar specificity profiles of taurine and hypotaurine uptakes showed that these amino acids employ a single transport system in neuroblastoma cells. Competitive inhibition by GABA of the high‐affinity uptake of taurine and hypotaurine further suggests that also GABA uses the same carrier system.
Stimulation by calcium and barium of somatostatin release. Evidence for lower sensitivity of D‐ vis‐à‐vis B‐ and A‐cells
Authors: GRILL VALDEMAR , EFENDIĆ SUAD
Published: December 2008

To address the question whether a “second messenger” function of calcium differs between D‐cells and other cells of the endocrine pancreas, we compared effects of calcium and barium (a calcium substitute) on somatostatin secretion to effects on insulin and glucagon secretion from the perfused pancreas of the rat. 6.5 mmol/l of calcium, when administered early during perfusion, failed to stimulate somatostatin release. 0.05 mmol/l of barium, when added to calcium‐deprived media failed to affect somatostatin secretion while 0.5 induced a slight and 2.0 mmol/l a marked and sustained response. Barium‐induced insulin release was left‐shifted in relation to the somatostatin response, since 0.05 mmol/l of barium stimulated and 0.5 mmol/l evoked a near‐maximal insulin response. All concentrations of barium evoked diphasic glucagon responses, i. e. a small (1 min) stimulation followed by sustained inhibition. Addition of 0.5 mmol/l of EGTA to calcium‐deprived media abolished D‐ as well as B‐ and A‐cell secretion. Reintroduction of 0.5–6.5 mmol/l of calcium stimulated somatostatin release; the secretory response was proportionate to the calcium concentration. In contrast, addition of calcium stimulated insulin and glucagon secretion maximally already at 0.5 mmol/l of calcium. We conclude that the D‐cell is less sensitive than B‐ and A‐cells to a regulatory effect on secretion exerted by extracellular calcium or barium.
Effect of graded 15(R)15 methyl prostaglandin E2 and of indomethacin on the gastric secretory and plasma gastrin response to modified shamfeeding
Authors: JOHANSSON C. , BEFRITS R. , WISÉN O. , KALLNER A.
Published: December 2008

Vagal stimulation by modified shamfeeding in healthy subjects induced about fourfold increases of gastric outputs of acid, chloride, sodium and potassium. Prior oral 15(R)15 methyl prostaglandin E2 inhibited dose‐dependently the peak and total gastric acid response to modified shamfeeding by lowering both the secreted volumes and the acidity. The inhibition by 15 μg of the analogue exceeded 50% and the suppression was submaximal by 140 μg. Gastric output of chlorides decreased in a dose‐related way. The hydrogen ion output was proportionally more reduced than the chlorides. The analogue did not affect the gastric output of sodium. Potassium decreased in a dose‐related way. Indomethacin was without effect on the gastric acid response to shamfeeding but reduced the sodium output compared to in controls and in series with the analogue. Plasma gastrin was slightly but significantly elevated by the shamfeeding procedure. This elevation was absent or even reversed by 15(R)15 Me PGE2. No effect was recorded by indomethacin pretreatment. Vagal stimulation augments both the parietal and non‐parietal components of the gastric secretion. Low doses of oral 15(R)15 Me PGE2 were effective in suppressing the vagally stimulated acid secretion. Neutralization by the gastric non‐parietal secretion can contribute to reduce the acid response. Blocking of the prostaglandin biosynthesis decreased gastric sodium output, suggesting indirectly that endogenous prostaglandins may be involved in modulating the gastric non‐parietal secretion.