bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of propranolol on cerebral oxygen consumption and blood flow in the rat: measurements during normocapnia and hypercapnia
Authors: HEMMINGSEN RALF , HERTZ MARIANNE M. , BARRY DAVID I.
Published: December 2008

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

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

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

Diaphragmatic and renal blood flow were measured with Ytterbium–169 and Scandium–46 labelled 15 μm microspheres in sodium pentobarbitone anesthetized rabbits. The first measurement was performed during spontaneous breathing of air and the second measurement after 15 min of breathing 2–6% carbon dioxide in oxygen. The lung ventilation as well as the diaphragmatic blood flow increased significantly during breathing of the carbon dioxide–oxygen mixture. Arterial blood pressure and renal blood flow were not significantly altered by the induced hyperventilation. No significant correlation was found between the magnitude of lung ventilation and diaphragmatic blood flow. The results of the present study indicate that consecutive measurements of diaphragmatic blood flow with radioactive microspheres at various levels of breathing effort is an appropriate method for further exploration of the relationship between diaphragmatic perfusion and working performance.
Continuous measurement of flow rate and volume in the nanoliter range
Authors: JENSEN PETER KOCH
Published: December 2008

A simple transducer which is based on changes of electrical capacity with volume is described. The system accomodates fluid volumes of several microliters and the resolution is below one nanoliter. The response time of the transducer is about 10 ms. The system is applicable for continuous recording of flow rates in renal collecting tubules. Pulsatile flow in the duct of Bellini is demonstrated.
Release of3H‐nucleosides from3H‐adenine labelled hypothalamic synaptosomes
Authors: FREDHOLM BERTIL B. , VERNET LOUISE
Published: December 2008

[3H]adenine was taken up by a crude hypothalamic synaptosomal fraction and incorporated into mainly nucleotides. The synaptosomes were superfiTsed and after the initial washout a steady fractional release rate of 0.5‐1 % of the content/min was found. Electrical pulses (2 ms, 50 Hz, 10–20 mA, 4 min) and veratridine (10 μM, 4 min) induced a Ca++‐dependent increase in purine release rate. K+(30 mM, 4 min) caused a largely Ca++independent increase. Most of the released material co‐chromatographed with adenosine, inosine and hypoxanthine, while little or no nucleotide material was detected. Release of endogenous adenosine, inosine and hypoxanthine was detected by high performance liquid chromatography. However, following hypo‐osmotic shock most of the released material was in nucleotides. The removal of glucose from the medium increased the fractional release rate 2–3 fold. Histamine, acetylcholine and glutamate were without effect. High amounts of noradrenaline caused an EGTA‐inhibited release of purines, which was un‐af‐fected by propranolol or phentolamine. It is suggested that purines are released from neuronal structures and that the release reflects increased energy consumption and/or decreased energy production.
Measurements of cardiac output and organ blood flow in rats using 99Tcm labelled microspheres
Authors: HAFSTRÖM LARSOLOF , PERSSON BERTIL , SUNDQVIST KAJ
Published: December 2008

The cardiac output and regional blood flow have been simultaneously determined in the anesthetized rat by using the reference organ method. 99Tcm labelled dextran 15 μm microspheres were injected in the left ventricle while simultaneously an arterial reference sample was drawn at constant known rate. The values calculated regarding cardiac output agree well with previously recorded series. Regional organ blood flow in the rat is presented as ml. min‐1. g‐1 tissue and values do agree with those reported by others. The results indicate that the reference organ method can be used in the rat for the study of cardiac output and regional blood flow.
The time course of the latency relaxation as a function of the sarcomere length in frog and mammalian muscle
Authors: BARTELS E. M. , SKYDSGAARD J. M. , STEN‐KNUDSEN O.
Published: December 2008

In a comparative study the isometric twitch tension and the latency relaxation were correlated to the sarcomere length in frog and mammalian muscle, the latter only in the length range from 2.4 to 3.1 μm since at higher degrees of stretch the sarcomere lengths became increasingly non‐uniform along the fibres. The location of the triads in mammalian muscle fibres was examined by means of electron microscopy. During stretch the location of the triads was gradually changed from the overlap zone at sarcomere lengths below 2.6 to 2.7 jim to the I‐band at sarcomere lengths above 3.0 to 3.1 μm, their centres (T‐tubules) being equally distributed between the overlap zone and the I‐band at sarcomere lengths around 2.9 μm. In both types of muscle the maximum amplitude of the latency relaxation (of about equal relative size) occurred at a sarcomere length of about 3.1 μm; and both twitch tension and latency relaxation were dependent upon the presence of a zone of overlap between the thin and thick filaments. In neither of the two types of muscles did the time, t1, from stimulation to the onset of tension drop depend upon the sarcomere length. At room temperature (22oC) t1 was about 1 ms in mammalian muscle and 2 ms in frog muscle. In mammalian muscle the time, t2, from the stimulus to the maximum drop in tension and the time, t3, to positive tension development were both substantially uninfluenced by changes in sarcomere length in the range 2.4 to 2.9 μm, whereas in frog muscle both t2 and t3 increased linearly with increasing sarcomere length in the above range. These findings are discussed in the light of the different locations of the triads in frog and mammalian muscle. It is concluded that the theory of Sandow (1966)–extended by Mulieri (1972)–and that of Haugen & Sten‐Knudsen (1976), which both have the virtue of being able to account for the increase of the latent period with stretch in frog muscle, also would be applicable to mammalian muscle provided that a time lag of 0.5 to 1.0 ms exists from the time of the binding of Ca2+‐ions to the troponin molecules inside the zone of overlap until the attached cross bridges start to move and develop tension.
The effects of changes in the carotid sinus baroreceptor activity on splanchnic blood flow in anesthetized man
Authors: TYDÉN G. , SAMNEGÅRD H. , THULIN L.
Published: December 2008

In 9 patients being subjected to abdominal surgery, electromagnetic blood flow measurements were obtained from the hepatic, mesenteric and iliac beds while the carotid sinus baroreceptors were stimulated by carotid sinus massage. Carotid sinus stimulation produced an average maximum decrease in mean arterial pressure of 21%. Hepatic and mesenteric blood flows decreased by 15% and calculated vascular resistances were not significantly changed in these vascular beds. Iliac blood flow, on the other hand, showed a slight increase and iliac vascular resistance was decreased by 29%. It is concluded that the splanchnic vascular bed is of less importance in the carotid sinus baroreflex control of systemic arterial pressure in anesthetized man.
Principal mechanisms controlling penile retraction and protrusion in rabbits
Authors: SJÖSTRAND NILS O. , KLINGE ERIK
Published: December 2008

The effects on penile volume of nerve stimulations and drugs injected into the systemic circulation were studied plethysmographically. Dilator responses at selective perfusion of the penile artery were studied by measuring the perfusion pressure. The main results and conclusions are: The penis has an adrenergic vasoconstrictor supply coming from the sacrococcygeal parts of the sympathetic chains. A very low (0.2 Hz) vasomotor tone keeps the penis relaxed. If this tone is interrupted the penis will protrude but autoregulation will soon take over and eventually produce hyperinvolution of the penis. Two vasodilator paths, both with pelvic ganglionic relays, were found. I) The pelvic parasympathetic nerves, probably having mainly non‐cholinergic postganglionic neurons and operating quite effectively at low frequencies. 2) The sympathetic hypogastric nerves, presumably having at least partly cholinergic postganglionic neurons which, apart from muscarinic dilation of minute inflow resistance vessels to the erectile tissue, may also work by suppression of excitatory adrenergic neurotransmission. The pelvic and hypogastric vasodilator outflows work synergistically. The vasoconstrictor nerves are very strong and efficient antagonists of the vasodilator nerves.
Gastric acid secretion and drinking in the Atlantic cod (Gadus mothua) during acidic or hyperosmotic perfusion of the intestine
Authors: HOLSTEIN BJÖRN
Published: December 2008

Cods were equipped with cannulae for drainage of the stomach and for separate perfusion of the stomach and intestine. Acidity, volume, and osmolality of the gastric outflow were measured. During perfusion of the intestine with a near‐isosmotic saline (1 part sea‐water, 2 parts distilled water, '33% SW) and the stomach with pure (‘100%’) SW, gastric acid output was high and volume output slightly above the infused volume. The osmolality of the gastric perfusate decreased during passage of the stomach. It was concluded that no drinking occurred, and that the decreased osmolality was due to dilution by gastric secretions and osmotically lost water. When substituting the isosmotic intestinal perfusion to a dehydrating perfusion (100% SW), gastric acid secretion was depressed but volume output was unaffected. Also perfusion of the intestine with acidified 33% SW depressed gastric acid secretion and in addition increased volume and osmolality of the gastric outflow. The results suggest that perfusion of the intestine depresses the drinking reflex and that this depression is surmounted by intestinal acidification. Possible mediators of the intestinal feed‐back mechanism for the inhibition of gastric acid secretion are discussed.
Muscle strength and muscle characteristics in monozygous and dizygous twins
Authors: KARLSSON J. , KOMI P. V. , VIITASALO J. H. T.
Published: December 2008

Muscle strength and electrical activity were investigated on 31 pairs of young male and female monozygous (MZ) and dizygous (DZ) twins. The measurements included leg forces, force‐time, running velocity, muscular power, maximal integrated electromyographic activity (IEMG) and chronaximetry of the quadriceps muscle group. In each parameter the intrapair variance was computed and the differences were tested between the MZ and DZ twins. The variance ratio (MZ vs. DZ) was statistically significant only for muscular power confirming an earlier finding which has demonstrated a genetic component for the variable. In addition to the various performance variables several key enzymes involved in ATP turnover during muscle contraction and in glucose residue metabolism were analyzed from the muscle biopsy samples (m. vastus lateralis). A genetic component could not be observed in any of their activities or their relationships to performance variables.
Renal cortical blood flow distribution measured by hydrogen clearance during dopamine and acetylcholine infusion. Effect of electrode thickness and position in cortex
Authors: TYSSEBOTN I. , KIRKEBØ A.
Published: December 2008

Blood flow distribution in the renal cortex was investigated in control and during i.a. infusion of dopamine (DA) and acetylcholine (Ach) in dogs. Local blood flow in outer cortex (OCF) and in inner cortex (ICF) was measured by platinum electrodes detecting hydrogen washout rate in tissue. Mean cortical blood flow measured by hydrogen washout rate in the renal vein (CFV) was compared with renal arterial blood flow (RAF) measured by electromagnetic flowmeter. With electrodes of 0.05–0.2 mm diameter control blood flow rates in outer and inner cortex were 4.57± (S.D.) 1.73 ml/min g and 4.35±0.57 ml/min g, which is higher than found using 0.2–0.5 mm electrodes in this and previous studies. OCF and ICF increased proportionally during intraarterial infusion of DA or Ach. The increase in local blood flow per unit volume was about 20% less than the increase in RAF, most likely due to an increase in renal volume and a reduced vasodilatory response in the surrounding of some electrodes. CFV rose almost to the same degree as RAF, showing a diffusion equilibrium for hydrogen gas even at maximal flow rate. During vasoconstriction induced by high doses of DA, OCF and ICF fell proportionately. Thus, equal vascular responses in outer and inner cortex were observed during both vasodilator and vasoconstrictor infusion. This indicates that changes in sodium excretion with renal blood flow may not be associated with a redistribution of cortical peritubular blood flow.
Conversion of arachidonic acid to prostaglandins in homogenates of human skeletal muscle and kidney
Authors: BERLIN T. , CRONESTRAND R. , NOWAK J. , SONNENFELD T. , WENNMALM Å.
Published: December 2008

The capacity of human skeletal muscle and kidney homogenates to synthetize prostaglandins (PGs) from exogenous precursor was investigated. Low–speed supernatants of muscle as well as renal medullary and cortical homogenates were incubated with 14C–labelled arachidonic acid (14C–AA) prepared as a sodium salt. 14C–PGs in the incubates were extracted, separated with thin–layer chromatography (TLC) and quantified by radioscanning. In the skeletal muscle incubates 14C–AA was converted into 14C–PGs with a time–dependent yield, most effectively after 10–15 min incubation. Well–defined radiopeaks parallel to unlabelled standards of PGD2, PGE2, PGF2α and 6–keto–PGF1α were obtained in the chromatograms. PGE2 was the main PG formed, constituting over 50% of 14C–activity, whereas 6–keto–PGF1α, PGD2 and PGF2α were found in considerably lower proportions. In the renal medullary incubates, PGE2 likewise accounted for the largest part of 14C–PGs formed, but significant relative amounts of PGF2α and PGD2 were also found. A minor peak, corresponding to 6–keto–PGF,a and thus indicating formation of PGI2, was also obtained. In contrast to the medulla, no 14C–PGs could be found in the renal cortical incubates. The results demonstrate the existence of a considerable tissue specificity in the quantitative and qualitative expression of PG biosynthesis in man.
Potentiation of the mechanical behavior of the human skeletal muscle through prestretching
Authors: BOSCO CARMELO , KOMI PAAVO V.
Published: December 2008

Force–velocity and power–velocity curves in a vertical jump involving movements around several joints were derived from vertical ground reaction forces and knee angular velocities. The jumps were performed with weights from 10 to 160 kg added on the shoulders. The obtained curves from a semi–squatting static starting position resembled those reported for isolated muscles or single muscle groups. Vertical jumps were also performed in the conditions where the shortening of the leg extensors was preceded by prestretching of the active muscles either through a preparatory counter–movement or dropping down on the force–platform from the various heights ranging from 20 to 100 cm. Prestretching modified through a range of velocities the force–velocity and power–velocity curves by increasing both the ground reaction forces and the calculated mechanical power. Thus the results are similar to those reported in isolated muscles. In studies with isolated muscle preparation the nervous connections have not been intact and therefore it is suggested that increase in the performance of the skeletal muscles through prestretching, in the conditions of the present study, was attributed to the combined effects of the utilization of stored elastic energy and the reflex potentiation of muscle activation.
Inhibitory actions from low and high threshold cutaneous afferents on groups II and III muscle afferent pathways in the spinal cat
Authors: JENESKOG TORGNY
Published: December 2008

The inhibitory effects caused by volleys in cutaneous afferents on the transmission through some polysynaptic segmental pathways activated by high threshold muscle afferents were studied in chloralose anesthetized, spinal cats. Pathways studied were groups II and III to motoneurones as well as group II to primary afferents. The results suggested that two different mechanisms were involved. One mechanism, with a very slow time course (duration more than 400 ms), is suggested to be an example of presynaptic inhibition between different primary afferent systems. This mechanism required high threshold (≥ 1.6T) conditioning shocks, and appeared simultaneously with the component II dorsal root potential being evoked by the cutaneous afferent volley. The other mechanism, with a faster time course (duration always below 300 ms), was dependent upon low threshold (≥ 1.5T) cutaneous conditioning volleys. This inhibitory interaction could not be ascribed to the same presynaptic mechanism, but is suggested to be an example of postsynaptic inhibition at an interneuronal level. The presumed disynaptic excitatory pathway from group II muscle afferents to flexor motoneurones was not inhibited by cutaneous conditioning shocks, but could on the contrary be facilitated by activity in low threshold cutaneous afferents, probably at the only intemeurone involved in this group II pathway.
Fibre types in human abdominal muscles
Authors: HÄGGMARK T. , THORSTENSSON A.
Published: December 2008

Histochemical muscle fibre composition was studied in biopsies from the four different muscles of the abdominal wall (rectus abdominis, RA, obliquus externus, OE, obliquus internus, OI, and transversus abdominis, Tr) in 13 normal human subjects (9 females and 4 males, age 24–55 years) undergoing gall‐bladder surgery. Muscle fibres were classified as Type I, II A, II B or II C on the basis of their myofibrillar ATPases' pH lability. There were large inter‐individual variations in fibre composition, whereas, in general, the differences between the different muscles were minor or non‐existent. Mean fibre distribution ranges were 55–58% I, 15–23% II A, 21–28% II B, and 0–1% II C fibres. The least fibre diameters were similar for all types and muscles (range of means 50–54 μm) except for Tr in which the Type II fibres were smaller (mean 45 μm). There was a high correlation in the size of Type I vs. II fibres and Type II A vs. II B fibres in all layers. The oxidative potential (NADH‐diaphorase staining intensity) appeared high in Type I fibres and low in Type II fibres, irrespective of subgroups. Thus, based on histochemical fibre composition, the different abdominal muscles appear to have a similar functional capacity. However, functional differences between individuals were indicated by the large inter‐individual variation in muscle fibre distribution.
Firing behaviour in a stochastic nerve membrane model based upon the Hodgkin—Huxley equations
Authors: SKAUGEN ERIK , WALLØE LARS
Published: December 2008

A nerve membrane model with a two‐state pore system was investigated by computer simulation in the uniform (space‐clamped) case. Both sodium and potassium conducting pores were modelled, each pore having four independent gates which switched randomly between the open and the closed position, governed by the assumed rate constants. Each pore conducted only when all the gates were open. The model was based upon the Hodgkin‐Huxley equations for the giant axon in squid, and in the limit of an infinite number of pores it was identical to these. The firing behaviour of this model as a function of the number of pores and the injected current were investigated. The mean firing frequency and the distribution of interspike intervals were mainly used in the presentation of the results. It was found that for pore numbers less than about 20000 the main effects due to a finite number of pores were a lowering of the current threshold for firing and a more linear frequency current relationship relative to that of the original H‐H equations. For higher pore numbers an increase in the current threshold and a pronounced burst firing close to the threshold were found.
Behaviour of mature anadromous char (Salmo alpinus L.) towards odorants produced by smolts of their own population
Authors: SELSET ROLF , DØVING KJELL B.
Published: December 2008

Mature anadromous char (Salmo alpinus L.) of a specific population were tested in behaviour experiments with respect to attraction effects of smolts of the same population, smolt material, and chemical fractions of that material. The char reaction indicated preference for intestinal contents and possibly bile from own population over skin mucus material and food. Chemical fractions isolated from the intestinal contents were tested for attraction at a concentration of 1.5 × 10‐9 g per 1. One of the fractions attracted the mature char. The results are discussed in relation to the “migration pheromone” hypothesis proposed by Nordeng (1971) as being crucial for the return of anadromous salmonids to their home river's spawning grounds.
Effect of a pressure barrier on retrograde axoplasmic transport in vitro. A study in the motor neurons of the rabbit vagus
Authors: HAHNENBERGER RUDOLPH W.
Published: December 2008

Retrograde axoplasmic transport, demonstrated by the “double ligature method” was studied in vitro in the motor neurons of rabbit vagus nerve, labelled with 3H‐leucine. When a pressure barrier with a maximal pressure of 30 mmHg, induced by a fluid jet, was applied to a small section of the nerve at 38°C, retrograde flow was partially inhibited. More radioactivity was found in front of the barrier (with respect to direction of flow) than immediately behind it. This observation differs from findings in anterograde transport at the same pressure and tested with a similar technique, where most radioactivity was detected immediately behind the barrier (Hahnenberger 1978).
Control of tissue environment during vital microscopy of the microcirculation in the m. tenuissimus in cat
Authors: AMUNDSON BJÖRN , BAGGE ULF , HALJAMÄE HENGO
Published: December 2008

The physiological preservation of the tenuissimus muscle preparation in cat during vital microscopy of the microcirculation is assessed, comparing the originally described technique with a modified approach. Differences in the compared techniques include modes of dissection and transillumination, room‐air exposure and moisturizing procedures. The original technique involves extensive dissection, inadequate temperature control and irrigation in open air. The modified technique involves less surgery due to a new illumination system, controlled heating and a Mylar foil cover on the preparation to minimize room‐air influences. Temperature measurements and analyses of energy metabolism (ATP, CP, glucose, G6‐P and lactate) are used as objective criteria of tissue normalcy. The microcirculation and metabolism are evaluated during anesthesia (α‐chloralose) at rest as well as in hemorrhagic shock. In the resting state, muscle temperature drops to 28°C with the irrigation technique, whereas the Mylar technique keeps the temperature at 34–35°C. Neither technique causes deviations in normal metabolism. In shock, however, the temperature in the irrigated tenuissimus muscle falls 8–9°C below deep muscle temperature and there is a significantly attenuated metabolic response to ischemia, while the Mylar preparation follows the changes of unexposed muscle, both in temperature and metabolism.
Vasodilatation in the dental pulp produced by electrical stimulation of the inferior alveolar nerve in the cat
Authors: GAZELIUS BERTIL , OLGART LEIF
Published: December 2008

The effects of nerve stimulation on blood flow were studied in the dental pulp of anesthetized cats. Changes in iodide disappearance rate (k‐value) from dentinal cavities were used to determine changes in pulpal blood flow. Electrical stimulation of the distal end of the cut inferior alveolar nerve after α‐adrenoceptor blockade (phentolamine, 3 mg/kg) consistently resulted in a rapid increase in disappearance rate. The first stimulation produced the greatest response (an average increase in k‐values of 60%) and repeated stimulations showed a successive attenuation in response, the fourth stimulation usually having no effect. A progressive decrease in resting k‐values was observed after the first stimulation, indicating an impaired exchange function of the capillary vessels. Systemic pretreatment with propranolol (0.5–1 mg/kg), atropine (3 mg/kg), mepyramine (3 mg/kg) and cimetidine (3 mg/kg) did not influence the rapid increase in k‐values produced by the nerve stimulation. The experiments show that Vasodilatation in the cat dental pulp produced by stimulation of the inferior alveolar nerve is not mediated by common efferent vasodilatory mechanisms and strengthen the hypothesis that the sensory nerve axon reflex mechanism is involved.
Characterization of the in vitro uptake of monoamines into brain microvessels
Authors: HARDEBO J. E. , OWMAN CH.
Published: December 2008

The ability of brain microvessels to take up and metabolize transmitter monoamines (DA, NA, A and 5‐HT) was studied in tissues from several species (rat, rabbit, guinea‐pig, cat, dog, baboon, man) in vitro. Following incubation, slices were analyzed by fluorescence histochemistry and isolated microvessels by measurement of radioactivity from tritiated amine. Provided the MAO activity was inhibited a strong accumulation, similar for all animals tested, occurred in the wall (endothelial cells and pericytes) of capillaries and venules—but not in larger vessels—of all species. The degree of amine uptake and accumulation and the conditions under which it was inhibited suggested that it reflected a saturable, energy‐dependent process, with characteristics of both the extraneuronal and neuronal type of uptake processes. The mechanism may serve as an inactivation of transmitter monoamines at the blood—brain interphase, thereby assisting in the control of transmitter levels in the cerebral extracellular compartment.
Effects of calcium and pH on the mechanical performance of heart muscle in the frog, Rana temporaria, during anoxia and subsequent recovery
Authors: LAGERSTRAND GUNNEL , POUPA OTAKAR
Published: December 2008

Heart ventricular muscle strips from Rana temporaria recover their isometric contractile tension completely within 20 min of reoxygenation following an anoxic period of 60 min in a physiological solution at pH 7.6. Corresponding recovery at pH 6.6 is only 43% of pretreatment values. High calcium concentration during the period of anoxia at pH 6.6 and subsequent recovery, returns contractile tension to almost pre‐anoxic values within 1 h. If, however, the calcium concentration is increased at the moment of reoxygenation, contractile tension is restored even faster than if high calcium levels were present during anoxia. The loss of contractile tension caused by anoxia is the same at both pH 7.6 and 6.6 with the same calcium concentration.

Comparison of the velocity parameters between high and low calcium experiments always shows a greater difference for the contraction velocities than for the corresponding relaxation velocities, independently of the pH. The quotient of these two velocities is used as an index of their relative rate of change. The results are interpreted in terms of calcium and hydrogen ion competition at various subcellular structures and the different influences these ions may have on contractile tension and both contraction and relaxation velocities.
Relationship between local changes in cortical blood flow and extracellular K+ during spreading depression*
Authors: HANSEN ANKER JON , QUISTORFF BJØRN , GJEDDE ALBERT
Published: December 2008

Change of local cerebral blood flow in response to a single cortical spreading depression of Leäo was studied in the brain. During a spreading depression, potassium briefly accumulates in the brain extracellular space. The cortical blood flow was normal during the maximal rate of increase of the extracellular potassium concentration. The blood flow doubled during the subsequent period of normalization of potassium and remained high for one minute thereafter. Thus, potassium cannot be the immediate mediator of the blood flow increase.
Severe hypoglycemia leads to accumulation of arachidonic acid in brain tissue
Authors: AGARDH CARL‐DAVID , WESTERBERG EVA , SIESJÖ BO K.
Published: December 2008

It is now well known that brain tissues only contain a small pool of free fatty acid (FFA), of which the polyenoic arachidonic and docosahexanoic acids comprise a minor part (see Bazan 1976, Marion & Wolfe 1979). This pool increases rapidly in ischemia and, under those circumstances, the polyenoic acids form the major part of the pool. Accordingly, it has been concluded that ischemia preferentially activates phospholipase A2.
Effects of castration and testosterone substitution on body composition and muscle metabolism in rats
Authors: KROTKIEWSKI M. , KRAL J. G. , KARLSSON J.
Published: December 2008

Male weanling Wistar rats were castrated or sham‐operated and followed for 12 weeks without substitution or with large (2 mg‐ 14 days‐1) or small (0.2 mg 14 days‐1) intramuscular dose of testosterone enantate. Castration without substitution was associated with lower body weight and smaller fat cell sizes in different adipose tissue depots. The epididymal and caudal subcutaneous depots were the most sensitive to castration. The percentage of fast‐twitch high‐oxidative (type II A) muscle fibers decreased in the non‐substituted castrated animals. There was a decrease in phosphorylase and lactate dehydrogenase activities in the white portion of the gastrocnemius muscle of the castrates. These changes were reversed by the large dose of testosterone. Removal of testosterone by castration thus seems to “feminize” male rats with respect to body composition and muscle metabolism.
Local cerebral blood flow in the brain during bicuculline‐induced seizures and the modulating influence of inhibition of prostaglandin synthesis
Authors: INGVAR MARTIN , NILSSON BENGT , SIESJÖ B. K.
Published: December 2008

The purpose of this study was to measure changes in local cerebral blood flow (1‐CBF) during generalized seizures, and to study whether or not formation of prostaglandins or related substances contributes to the increased flow rates. Seizures were induced in ventilated rats maintained on 70% N2O and 30% O2 by the i. v. injection of the GABA receptor blocker bicuculline (1.2 mg‐kg‐1). Formation of prostaglandins was inhibited by the administration of the fatty acid cyclo‐oxygenase inhibitor indomethacin (10 mg · kg‐1)‐Local CBF in 21 defined brain structures was measured autoradiographically with HC‐iodoantipyrine as the diffusible tracer. After 20 min of continuous seizure activity 1‐CBF increased 1.5‐5‐fold, the smallest increases (<200% of control) being observed in frontal and auditory cortex and in the caudoputamen, and the largest (>400% of control) in substantia nigra, thalamus, visual cortex, lateral geniculate and hypothalamus. In general, the largest increases in 1‐CBF occurred in sensory and limbic systems (and hypothalamus) while motor systems showed a pronounced variability. In the majority of structures examined indomethacin failed to modify the CBF response during seizures. Although this result suggests that seizures, in contrast to hypercapnia, lead to an increased CBF by other mechanisms than those related to prostaglandin formation, some structures (nucleus ruber, cerebellum, and superior colliculus) showed a clearly reduced 1‐CBF in indomethacin‐treated animals.
Characteristics and rate of occurrence of spontaneous and provoked augmented breaths
Authors: CHERNIACK N. S. , von EULER C. , GLOGOWSKA MARIA , HOMMA I.
Published: December 2008

The tidal volume and corresponding efferent phrenic activity of spontaneously occurring and provoked ‘augmented’ breaths, AB, and the subsequent post‐augmented breaths were studied in cats anesthetized with pentobarbitone during hypercapnia and hypoxia. The augmentation phase (phase II) begins at, or close to, the crest of what appears as a ‘normal’ inspiration (phase I). The amplitude and duration of phase II remained fairly constant whereas the amplitude and the duration of phase I changed with the chemical drive just as in control breaths. The smaller amplitude and shorter duration of post‐augmented breaths as compared to control breaths seems to be due to both a lower‐than‐normal inspiratory ‘off‐switch’ threshold following the AB and an increased rate of rise of inspiratory activity. With increasing hypercapnia and hypoxia both the time interval between AB and the refractory period following an AB during which a new AB cannot be provoked were reduced. Following bilateral vagotomy AB was temporarily abolished but reappeared after 1–2 h. The relatively low rates of occurrence after vagotomy still showed the same type of dependence on chemical stimuli. The refractory period was not abolished although usually decreased by gallamine paralysis or high thoracic spinalization.
Contraction times of the cat's tongue muscles measured by light reflection. Innervation of individual tongue muscles
Authors: HELLSTRAND E.
Published: December 2008

The contraction times of the cat's tongue muscles were measured by recording the fine movements of their surfaces and movements of the tongue's surfaces. The recordings were made by means of a commercial, high‐sensitive light reflection transducer (Fairchild FPLA 850) which could be operated without any mechanical loading of the tongue. The contraction times of the intrinsic muscles (including pars longitudinalis superior m. hypoglossi and pars longitudinalis inferior m. styloglossi) measured about 22 ms, while the extrinsic muscles were somewhat slower, around 33 ms. The data are considered in the light of the recently reported histochemical composition of these muscles. The study of the hyoglossal nerve supply to individual tongue muscles revealed that, contrary to earlier reports, the medial nerve sends branches to the intrinsic muscles not only at its distal end but during its entire course through the tongue. The transversal and vertical muscles were found to receive numerous fibers innervating small units of their muscle fibers.
Blood flow in “red” and “white” calf muscles in cats during isometric and isotonic exercise
Authors: BONDE‐PETERSEN F. , JR C. H. ROBERTSON
Published: December 2008

Muscle blood flow was measured with the radioactive microspheres technique in plantar flexors of seven cats. Right leg performed rhythmic isotonic and left leg sustained isometric contractions. Flows were determined at rest, during stimulation periods, and immediately after 90 sec of high frequency stimulation. During isotonic contraction, flow to m. soleus (a “red muscle”) increased progressively as stimulation increased: 0.06±0.02, 0.21±0.05, 0.41±0.12, and 0.26±0.06 ml/min/g during rest, 10 Hz, 50 Hz, and after 50 Hz stimulation frequencies, respectively. Corresponding values for gastrocnemius medialis were 0.06±0.01, 0.38±0.05, 0.27±0.03, and 0.28±0.06 (x± S.E.). These last values were characteristic also for the other “white” muscles investigated: gastrocnemius lateralis, and plantaris. During sustained isometric exercise at 5 and 25 Hz stimulation frequency the patterns were similar, except that higher flows were observed, and during recovery flows actually increased again in the “white” muscles. Blood pressure did not change. Resting flows were similar in innervated and denervated muscles. These data demonstrate that during isotonic as well as isometric exercise there is an increased resistance to flow with increasing muscle tension in “white” but not in “red” muscles. This supports the notion that a condition of relative ischaemia exists in “white” muscles during both isometric and isotonic contractions which is more pronounced during isometric exercise. The results corroborate previous studies on isometric exercise and suggest that the pattern during isotonic exercise is similar.
Skeletal muscle fibre characteristics in young women
Authors: NYGAARD E.
Published: December 2008

Muscle samples were obtained by needle biopsy from the lateral vastus muscle of 54 healthy female subjects, 18 to 40 years of age. 25 subjects were classified as sedentary, 20 as active, and 9 as endurance trained. In 33 of the subjects, the deltoid muscle was biopsied as well. The lateral vastus muscle of runners and the deltoid muscle of swimmers contained 60% slow twitch fibres (ST) and none or few fast twitch b fibres (FTb). Otherwise the percentage of fibre types was 50% ST fibres, 30% to 35% FTa fibres, and 15% to 20% FTb fibres. In the lateral vastus muscle ST fibres were larger than FT fibres, whereas in male skeletal muscles FT fibres tend to be larger than ST fibres. The capillarization was linearly related to maximal oxygen uptake, as is also the case in male subjects. The activity of biochemically determined phosphofructokinase (PFK) was the same in both muscles and in all groups; succinate dehydrogenase activity (SDH) was closely related to maximal oxygen uptake. The activities of PFK and SDH were lower than in male subjects; the ratio between the activities indicated that the relative contribution of oxidative metabolism was higher than in males. The morphological and biochemical differences between female and male skeletal muscle are found in sedentary and trained subjects, and may be due both to the influence of sex hormones, and to differences in the daily activity pattern.
Testicular blood flow measured with a laser Doppler flowmeter: acute effects of catecholamines
Authors: DAMBER JAN‐ERIK , LINDAHL OLOF , SELSTAM GUNNAR , TENLAND TORSTEN
Published: December 2008

Laser Doppler flowmetry was used to continuously measure testicular blood flow in rats. The method was found applicable on surgically exposed testes. Regular oscillations in blood flow, with a periodicity of 8.6±0.7 cycles per minute (mean ± SD), were observed in recordings from 22 of 23 rats. Clamping of the testicular artery reduced the blood flow signal to background values. Effects of catecholamines administered into the tail artery on testicular blood flow together with systemic effects on mean arterial blood pressure and heart rate were measured. It was found that noradrenaline as well as adrenaline caused a significant decrease in blood flow when 10 μg was injected. Only noradrenaline decreased the blood flow when 1 μg was given. The large oscillations detected in the blood flow recordings disappeared quickly when 10 or 1 μg of both hormones was administered. It was concluded that catecholamines can exert rapid effects on testicular blood flow.
Quantitative physiological and morphological aspects of microvascular permeability changes induced by histamine and inhibited by terbutaline
Authors: SVENSJÖ E. , ADAMSKI S. W. , SU K. , GREGA G. J.
Published: December 2008

Histamine induced changes in microvascular permeability to macromolecules were studied in two models, the hamster cheek pouch and the canine forelimb preparation. Fluoresceinlabelled dextran FITC‐dextran. Mw=70000 and 150000 was used as tracer of permeability increases. Studies in the hamster showed that morphological changes as indicated by intravital microscopy of FITC‐dextran leakage at postcapillary venules were accompanied by an increased concentration of FITC‐dextran in the superfusion solution for the cheek pouch. Following histamine challenge during 4 min the cheek pouch microcirculation was normalized 30 min later both with regard to number of leakage sites and the concentration of FITC‐dextran in the superfusion solution. Pretreatment of the cheek pouch with terbutaline (3.6 × 10‐6M) for 1 h resulted in total inhibition of both morphologically and fluorometrically recorded changes from continuous histamine superfusion. When terbutaline and histamine were given at the same time, there was a significant inhibition of the histamine induced increase in the number of leakage sites to 10% of the pre‐terbutaline response. The fluorometrically detected efflux of FITC‐dextran was 65% of the preterbutaline value. The dynamics of interendothelial cell gap formation and closure was also studied in the dog. Intra‐arterial infusions of histamine into forelimbs perfused at a constant pump controlled flow rate produced decreases in perfusion pressure, increases in lymph flow, lymph protein concentration, total protein transport and weight. FITC‐dextran was given as an i. v. injection 30 min before and 0, 30 and 60 min after the start of a 90 min arterial infusion of histamine into the brachial artery of the forelimb. Lymph (CL) and plasma (Cp) concentrations of FITC‐dextran were determined and CL/Cp‐ratios showed that the permeability increasing effect lasted less than 30 min although histamine was given for further 60 min. The results of both hamster and forelimb experiments suggest that leakage sites or interendothelial cell gaps in postcapillary venules are closed within 30 min from the first exposure to histamine, probably within 15 min and that there is little indication of any remaining increase in macromolecular permeability via any other route (vesicular) following closure of gaps.
Store and recoil of elastic energy in slow and fast types of human skeletal muscles
Authors: BOSCO C. , TIHANYI J. , KOMI P. V. , FEKETE G. , APOR P.
Published: December 2008

Stretch‐shortening cycle refers to the mechanical condition in which store and recoil of elastic energy occur in the skeletal muscle. This leads to a greater work output when compared to a simple shortening contraction. The subjects performed vertical jumps with and without preliminary counter‐movement and with small and large knee angular displacement. The results indicated that those subjects who had more fast twitch (FT) fibers benefited more from the stretching phase performed with high speed and short angular displacement. The amounts of elastic energy stored in this phase were 30 and 26 N × kgBW‐1, respectively, for FT and slow twitch (ST) type subjects. The recoil of elastic energy was proportional to the amount of energy storage. In large amplitude jumps where transient period between stretch and shortening is long the both types of subjects demonstrated similar amount of storage of elastic energy (17 and 16 N × kgBW‐1, respectively). However, the re‐use of this elastic energy was greater in ST group (24%) as compared to the FT group (17%). The results can be interpreted through differences in sarcomere cross‐bridge life times between fast and slow muscle fibers. The slow type muscle may be able to retain the cross‐bridge attachment for a longer period of time and therefore it may utilize elastic energy better in a slow type ballistic motion.
Resetting of aortic baroreceptors with non‐myelinated afferent fibers in spontaneously hypertensive rats
Authors: THOREN P. , ANDRESEN M. C. , BROWN A. M.
Published: December 2008

The phenomenon of resetting and the possible mechanisms responsible for it were investigated in aortic baroreceptors having unmyelinated axons. Recordings were obtained from 31 aortic baroreceptor C‐fibers in 20 normotensive Wistar Kyoto rats (WKY) and 37 baroreceptor C‐fibers in 11 spontaneously hypertensive rats (SHR). The recordings were obtained from the left aortic nerve of an in vitro aortic nerve‐aortic arch preparation. The thresholds for activation of baroreceptor C‐fibers were not different between SHR's and WKY's at 16 weeks of age (139±7 and 133±5 mmHg, respectively). However, the thresholds for activation in SHR at 36 weeks of age were considerably higher (163±4 mmHg) indicating resetting of the receptors in the older rats. The pressure‐discharge curves were not different between SHR's and WKY's at 16 weeks of age and WKY's at 35 weeks of age, but were shifted to the right for SHR's at 36 weeks of age. The receptors showed greater responses to pulsatile pressures than to steady state pressures at the same mean level of pressure. We found that aortic C‐fibers were not reset during the early established phase of hypertension in SHR's because of enhanced receptor strain sensitivity. This is likely to be of importance for tonic vasomotor control at this time. In later stages of hypertension and despite enhanced strain sensitivity the endings were reset to higher pressures probably due to an increased collagen content in the aortic wall.