bluuebunny/crossref_metadata_2025 huggingface dataset:
Renal nerve activity and exaggerated natriuresis in conscious spontaneously hypertensive rats
Authors: RICKSTEN S. E. , YAO T. , BONA G. F. DI , THORÉN P.
Published: December 2008

Exaggerated natriuresis upon volume loading occurs in both human and animal hypertension and is mainly due to suppressed tubular reabsorption. To explore whether altered renal sympathetic activity contributes to this response, conscious male spontaneously hypertensive rats (SHR) were exposed to isotonic saline loading in comparison with normotensive male Wistar Kyoto rats (WKR). After a 60 min control hydropenic period, during which mean arterial pressure, heart rate, renal sympathetic nerve activity and urinary sodium excretion were followed, a 60 min period of intravenous volume expansion with isotonic saline (0.2 ml/minx 100 g b. w.) was started followed by a 60 min hydropenic recovery period. Already during the control period sodium excretion was significantly higher in SHR. During the volume load and subsequent recovery period a clearly exaggerated natriuresis occurred in SHR compared with WKR. Further, volume loading reduced renal sympathetic nerve activity in all animals, but significantly more in SHR. Moreover, volume loading reduced mean arterial pressure and heart rate in both groups. It is suggested that the accentuated reflex inhibition of renal sympathetic activity in SHR upon volume loading emanates from cardiac mechanoreceptors and partly explains the exaggerated natriuresis in SHR. This augmented ‘volume’ reflex response is probably due to reduced systemic venous compliance in SHR with a consequently increased central filling and cardiac receptor activation.
Binding of14C‐spermidine to melanin in vivo and in vitro
Authors: TJÄLVE HANS , NILSSON MONICA , LARSSON BENGT
Published: December 2008

It has been shown that melanin has the properties of a polyanion and may in vivo and in vitro bind inorganic cations and drugs which are positively charged at physiological pH by a cation‐exchange mechanism. In the present study, we explored if the organic aliphatic polycation spermidine would bind to melanin in vivo after administration of14C‐spermidine to pigmented mice and in vitro at incubations with pigment from beef‐eyes. The results showed a high labelling of the pigmented tissues in the mice after the administration of14C‐spermidine. At long survival intervals, the radioactivity in the melanin was higher than in any other tissue. A strong melanin affinity of14C‐spermidine was found in vitro. An analysis of the binding by the method of Scale hard showed that the data could be best fitted by the assumption of two classes of binding sites. The in vivo bound material could be displaced by in vitro incubation in solutions containing inorganic cation‐chloride salts or HCI and HC1 was also very effective in inhibiting the melanin‐binding of14C‐spermidine in vitro. The results indicate that an electrostatic interaction between spermidine and melanin will occur both in vivo and in vitro.
Concentration of substance P‐like immunoreactivity (SPLI) in tissues of dog, rat and mouse1
Authors: BRODIN ERNST , NILSSON GÖRAN
Published: December 2008

The distribution of SPLI in various tissues from dog, rat and mouse was determined by radioimmunoassay. The gastrointestinal, urogenital and tracheobronchial tracts were found to contain SPLI with marked differences in levels in different parts of these tracts. Glandular tissues, such as salivary glands and pancreas, as well as eye, tongue and skin also contain SPLI. Species differences were encountered both in absolute amounts and the distribution of SPLI. The highest concentrations of SPLI were generally found in mouse followed by dog and rat. The present results are in agreement with those of previous studies in which SP was demonstrated by bioassay technique, but due to the greater sensitivity of the radioimmunoassay it was possible to show a much wider distribution of SP. Virtually all organs in which an effect of SP has been demonstrated also contain SPLI.
Leg blood flow during exercise in man in relation to muscle fibre composition
Authors: FRISK‐HOLMBERG MARIANNE , JORFELDT LENNART , JUHLIN‐DANNFELT ANDERS , KARLSSON JAN
Published: December 2008

Fibre composition in the vastus lateralis muscle, leg blood flow, oxygen uptake and respiratory exchange ratio were determined in 12 healthy male volunteers during submaximal exercise (50% of VO2 max). The percentage of slow‐twitch fibres varied from 26 to 66. Mean leg blood flow during exercise was 4.68 ± 0.191 · min‐1. The blood flow and respiratory exchange ratio correlated positively to the percentage of slow‐twitch fibres in the vastus muscles. No correlation was found between the muscle fibre composition and either oxygen uptake heart rate or mechanical efficiency. The results with a dependence of muscle blood flow and carbon dioxide release to muscle fibre composition support the view that the arrangement of the vascular bed and blood supply differ between fast‐twitch and slow‐twitch muscle fibres in humans.
Further studies on properties of renin granules isolated from rat kidney cortex
Authors: MÄNNISTÖ P. T. , POISNER A. M.
Published: December 2008

The properties of renin granules isolated from rat renal cortex were studied. Renin granules were thermolabile since in 10 min at 0°C twice as much renin was released as at +37°C. Addition of Ca++ (10‐6M‐10‐2M) did not affect the spontaneous release at +37°C, pH 6.5, during 10 or 30 min incubation. However, when pH was elevated to above 7, renin release was significantly increased by Ca++ (10‐3M). Additions of various amounts of KCl, NaCl or MgCl2, which increased the osmolality less than 20 mOsm/kg, did not affect the stability of the renin granules. Mg‐ATP (0.5 and 5 mM) as well as Mg‐GTP (5 mM) stabilized renin granules at +37°C, pH 6.5, but the corresponding nitrogen analogues Mg‐AMP‐PNP and Mg‐GMP‐PNP (0.5 and 5 mM) were not effective. Neither did Mg‐AMP (5 mM) nor ATP (5 mM) without Mg++ affect the renin release. No stabilization was observed by Mg‐ATP and Mg‐GTP in the purified granule preparations. The results suggest the importance of the cleavage of the terminal phosphate in the stabilization process. When the granules prepared at 300 mOsm/kg were first kept at hyperosmotic medium (range 300–1650 mOsm/kg) and then moved back to 300 mOsm/kg, the granules tend to lyse the more the greater was the reduction of the osmolality. The granules were more stable in isotonic sucrose than in isotonic ionic medium.
Length‐tension relations of smooth muscle from normal and denervated rat urinary bladders
Authors: EKSTRÖM JÖRGEN , UVELIUS BENGT
Published: December 2008

Urinary bladders of rats were denervated by bilateral excision of the pelvic ganglion and removed 10 days after the operation. They were filled with 0.75 ml saline and a longitudinal muscle strip was marked out, measured and dissected out. Strips from normal bladders filled with the same volume were used as controls. Denervated bladders were 4–5 times heavier than control bladders. Muscle strips from denervated bladders showed, in contrast to controls, marked phasic spontaneous contractions which were unaffected by tetrodotoxin, indicating a myogenic origin. Active tension in response to AC stimulation was measured at different lengths. In relation to the in situ length (Lin situ) at 0.75 ml the denervated strips had to be stretched to much greater extent than controls in order to reach optimum length (L0) for force development. Furthermore, the denervated strips shortened less in relation to Lin situ than the controls. If active length‐tension relations were expressed in relation to Lo, the difference between denervated and control strips was abolished. Maximal active force was the same for denervated and control strips. Water content increased significantly in denervated bladders. The results suggest a remodelling of the smooth muscle structure in denervated bladders; the characteristics of the contractile machinery seem, however, to be unaltered.
Structurally reduced distensibility of cardiovascular ‘low‐pressure’ compartments in primary hypertension, as studied in spontaneously hypertensive rats (SHR)
Authors: HARALDSSON B. , NILSSON H. , FOLKOW B.
Published: December 2008

Adult male spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY) were compared to explore to what extent venous ‘unstressed’ volume, compliance and wall distensibility are structurally altered in primary hypertension. The perfused, maximally vasodilated hindquarters and the entire, completely relaxed cardiovascular system during cardiac arrest were used for comparisons of ‘initial’ volumes and pressure‐volume characteristics of the respective low‐pressure compartments. In both preparations SHR and WKY showed identical ‘unstressed’ venous volumes, computed by extrapolation to zero pressure from initial volumes and the nearly linear pressure‐volume relationships, while venous compliance (Δ/ΔP) was in each case about 20% reduced in SHR. Consequently, the structurally determined wall distensibility of the low‐pressure compartment, calculated as the square root of volume compliance/unstressed (or initial) volume, was significantly reduced in SHR; about 10%. Such venous ‘structural resetting’ has important hemodynamic consequences, not least because it reinforces increase of venous return and cardiac filling pressure in SHR, caused by given sympathetic activations. Evidently, not only resistance, cardiac and barostat functions but also the venous capacitance function are structurally reset early in primary hypertension, implying a redesign of the entire cardiovascular system to operate at a higher pressure equilibrium.
Evidence for a function of calcium influx in the stimulation of hormone release from the parathyroid gland in the goat
Authors: HOVE K. , SAND O.
Published: December 2008

The acute effects of various drugs on the release of parathyroid hormone (PTH) in goats were studied by local infusions in vivo. Infusions of Ca2+ or Sr2+ reduced the PTH secretion rate, whereas hypocalcemia induced by EDTA increased the PTH release. Blockers of voltage sensitive Ca2+ channels (verapamil, D‐600 and nifedipine) lowered the PTH secretion rate, while infusion of 4‐aminopyridine, which is a blocker of voltage sensitive K+ channels, increased the PTH release. These effects were not due to altered βadrenergic tonus, since the effects persisted when the drugs were administered during contineous infusion of the β‐blocker propranolol. We suggest that the parathyroid cells possess voltage sensitive K+ and Ca2+ channels, and that exocytosis of stored PTH depends on the influx of extracellular Ca2+ as in other secretory cells. In order to explain the inverse relationship between the plasma Ca2+ level and the PTH release, we postulate a suppressive effect of the plasma Ca2+ on the membrane permeability to Ca2+ in parathyroid cells.
The uptake index method applied to studies on the blood‐retinal barrier I. A methodological study
Authors: ALM ALBERT , TÖRNQUIST PER
Published: December 2008

The validity of the uptake index method for studies on passage through the blood‐retinal barrier was evaluated. Data for the brain were also obtained for comparison. A rapid intracarotid injection of 0.2 ml buffered Ringer solution in rats did not result in a measurable increase in the permeability to EDTA for either the blood‐retinal or the blood‐brain barriers, while a markedly hypertonic solution caused an immediate osmotic breakdown of both barriers. For determinations of the retinal uptake index (RUI) 3HOH was found to be a suitable reference substance. A more diffusible reference, such as 14C‐ethanol, resulted in a lower net extraction, probably due to a more rapid wash‐out by the choroidal blood flow. Clearance of both reference and test substances from the retina was considerably faster than from the brain. For this reason a 5‐s interval between the intracarotid injection and the enucleation was used as routine for determinations of RUI. With this technique RUI for the transported monosaccharide 3‐0‐methyl‐D‐glucose was significantly larger than for L‐glucose, 53.8 and 14.2% respectively. The RUI for L‐glucose was mainly due to L‐glucose confined to extravascular choroidal fluid adhering to the retinal tissue samples. By prolonging the interval between injection and enucleation, and subtracting the activity due to recirculation, this extraretinal contamination could be practically eliminated. It is concluded that the uptake index method can be a useful tool in studies on transport of metabolic substrates through the blood‐retinal barrier.
Preponderance for either α or β‐adrenoceptor mediated sensitization in the rat submaxillary gland
Authors: EKSTRÖM JÖRGEN , MALMBERG LARS
Published: December 2008

The sensitivity of the rat submaxillary gland was examined 3–4 weeks after either parasympathetic decentralization or sympathetic decentralization or denervation. The threshold doses for secretion of saliva of parasympathomimetic (methacholine) and sympathomimetic (noradrenaline, adrenaline, phenylephrine and isoprenaline) drugs were estimated and the amount of saliva secreted in response to supraliminal doses of these drugs was measured. Each type of operation caused the development of a supersensitivity that involved all three types of receptors, i.e. muscarinic cholinoceptors, alpha;‐adrenoceptors and β‐adrenoceptors. Following parasympathetic decentralization the sensitization was predominantly mediated via α‐adrenoceptors, and also via cholinoceptors. Following sympathetic decentralization or denervation the postjunctional sensitization was predominantly mediated via β‐adrenoceptors; most of the supersensitivity to noradrenaline, adrenaline and phenylephrine found after sympathetic denervation was of the prejunctional type. An increase in receptor density and an intracellular arrangement where the response of cholinoceptors and α‐adrenoceptors is mediated via one pathway and the response of β‐adrenoceptors via another are suggested as factors that may be of importance for the development of the postjunctional supersensitivity. The present study shows that the traffic of secretory impulses in the sympathetic nerve is of importance for the level of sensitivity of the secretory cells. Since postjunctional supersensitivity following sympathetic denervation did not exceed that following sympathetic decentralization it is suggested that under normal conditions a continuous release of noradrenaline from the nerve endings is of little importance for the level of sensitivity.
Nicotine‐induced increases of noradrenaline turnover in discrete noradrenaline nerve terminal systems of the hypothalamus and the median eminence of the rat and their relationship to changes in the secretion of adenohypophyseal hormones
Authors: ANDERSSON KURT , ENEROTH PETER , AGNATI LUIGI F.
Published: December 2008

The effects of acute single doses (0.3 and 1 mg/kg) of nicotine on various hypothalamic catecholamine nerve terminal systems and on the secretion of adenohypophyseal hormones in the rat were studied. Nicotine, in a dose of 1.0 mg/kg, increased noradrenaline turnover in the median eminence and in the peri‐ and paraventricular hypothalamic regions. The dopamine and noradrenaline nerve terminal systems in the median eminence and the dorsomedial hypothalamic nucleus respectively were unaffected. Serum GH levels were decreased and serum prolactin levels increased after a dose of 1 mg/kg. In the presence of tyrosine hydroxylase inhibition, nicotine in a dose of 1 mg/kg, instead increased GH and also LH secretion. It is suggested that the preferential increases of noradrenaline turnover in various hypothalamic noradrenaline nerve terminal systems by nicotine may be partly responsible for the nicotine induced increases of serum prolactin, GH and LH levels observed.
The inactivation of prostaglandin E2and 5‐hydroxytryptamine in isolated perfused fetal and neonatal rabbit lungs
Authors: SIMBERG N. , TOIVONEN H. , HARTIALA J. , BAKHLE Y. S.
Published: December 2008

The inactivation of prostaglandin E2(PGE2) and 5‐hydroxytryptamine (5‐HT) was studied in isolated perfused lungs from fetal and neonatal rabbits. PGE2inactivation was considerable already at the 28th day of fetal life, as only 11 % of injected substrate survived passage through the pulmonary circulation. However, the inactivation increased significantly during the last 3 prenatal days (4% survival) and remained at this level when analyzed one week postnatally. In contrast to PGE2‐metabolism, 5‐HT inactivation was relatively stable during the studied fetal period (47–49% inactivation), but was decreased significantly on the 7th day postnatally when compared to newborn litters. The results indicate that pulmonary prostaglandin and amine metabolism reach maturity at different times during the perinatal period.
Complementary role of vasoactive intestinal polypeptide (VIP) and acetylcholine for cat submandibular gland blood flow and secretion I. VIP release
Authors: LUNDBERG JAN M. , ÄNGGÅRD ANDERS , FAHRENKRUG JAN
Published: December 2008

The effects of parasympathetic and sympathetic nerve stimulation on VIP release in relation to blood flow and secretion were studied in the cat submandibular salivary gland. Parasympathetic nerve stimulation caused a marked VIP overflow (over thousand fold increase in VIP output) into the venous effluent from the gland which was simultaneous with profuse salivation and an about 10–15 fold increase in blood flow. The VIP output was dependent on the stimulation frequency, the duration of the stimulation period as well as the glandular blood flow. At 15 Hz maximal VIP output (about 4 fmol per impulse) was obtained after about 5 min of stimulation simultaneously with the maximum of the maintained phase of vasodilation. About 50 pmol VIP was recovered in the venous effluent from the gland during 1 h of maximal nerve stimulation. The VIP output after 1 h, was only about 20% of maximal, however, suggesting that the storage reserves and/or resupply of VIP might be running out. Under physiological conditions (frequencies ≤ 6 Hz) it was estimated that the axonal transport mechanism should be sufficient for replacement of VIP. At lower frequencies (2 and 6 Hz) the VIP output was parallel to vasodilation and secretion, while at a high frequency (15 Hz) a much more pronounced VIP output was seen. The increased overflow at 15 Hz may either be due to an actual increase in release or to a saturation of local VIP inactivating mechanisms. When stimulated simultaneously, the parasympathetic vasodilator mechanism seemed much more potent than sympathetic vasoconstriction. Since VIP may be present in cholinergic neurons, data from the literature concerning acetylcholine release are discussed in relation to the observed VIP output.
Complementary role of vasoactive intestinal polypeptide (VIP) and acetylcholine for cat submandibular gland blood flow and secretion II. Effects of cholinergic antagonists and VIP antiserum
Authors: LUNDBERG JAN M. , ÄNGGÅRD ANDERS , FAHRENKRUG JAN
Published: December 2008

The effects of atropine and hexamethonium on submandibular vasodilation, secretion and VIP release in response to parasympathetic nerve stimulation were studied in cats. It was found that salivary secretion was completely atropine sensitive at all frequencies. The vasodilatory response was characterized by an initial phase (most marked at lower frequencies) followed by a maintained phase (most pronounced at high frequencies). Atropine reduced the initial phase at all frequencies while the maintained phase was reduced only at low stimulation frequencies. At 15 Hz the maintained blood flow response was paradoxically increased after atropine, particularly with regard to the duration. The increase in blood flow after atropine was accompanied by an about eight fold increase in VIP output as compared to control stimulations at 15 Hz. This may suggest that the acetylcholine levels regulate the VIP release in a feed‐back system via muscarinic auto‐receptors. No increase in VIP output by atropine was, however, observed at 2 Hz while a small but significant increase was found at 6 Hz. Treatment with VIP antiserum reduced both phases of the vasodilation as well as the secretion in response to stimulation at 2 Hz. Thus, VIP and acetylcholine seem to be important for both phases of vasodilation as well as for salivary secretion. The relative contributions of VIP and acetylcholine are, however, hard to evaluate since atropine appears to increase VIP release. This fact complicates the characterization of cholinergic and noncholinergic vasodilator mechanisms by the use of atropine. Hexamethonium treatment abolished both the vasodilation, the secretion and the VIP release seen during parasympathetic nerve stimulation implying that it was preganglionic and that the preganglionic transmitter is acetylcholine which activates postganglionic neurons via nicotinic receptors. Somatostatin had no blocking effect on parasympathetic mechanisms in the cat submandibular gland.
A rapid method of visualizing the pancreatic islets for studies of islet capillary blood flow using non‐radioactive microspheres
Authors: JANSSON LEIF , HELLERSTRÖM CLAES
Published: December 2008

A technique is described for visualization of the pancreatic islets in the rat by simple dark field illumination of pieces of the frozen and thawed pancreas. By using this method, microspheres, injected for studies of the capillary blood flow, can be readily located and counted in both the islets and the exocrine parenchyma. The procedure could be useful both for rapid estimations of the total number of islets and for studies of their microcirculation.
The importance of carbonic anhydrase B and C for the unloading of CO2 by the human erythrocyte
Authors: WISTRAND PER J.
Published: December 2008

Carbonic anhydrase (carbonate dehydratase, EC 4.2.1.1) isoenzymes HCA B and HCA C from human erythrocytes were purified by affinity chromatography and characterized kinetically at 37°C in 25 mM N‐methylimidazole buffer, 1=0.15, pH 7.1, using a pH‐indicator stopped‐flow technique. The rate constants for the uncatalyzed hydration of CO2 and dehydration of H2CO3 were 0.12·s‐1 and 58 · s‐1, respectively. Km and turnover numbers in the hydration reaction were 14.0 mM and 19.1 · 105 · s‐1 for HCAC and 3.3 mM and 0.56 · 105·s‐1 for HCA B. Km and turnover numbers in the dehydration reaction were 70 mM and 5 · 105·s‐1 for HCA C and 16.8 mM and 0.27 · 105 · s1 for HCA B. Ki for chloride was 14 mM for HCA B and > 200 mM for HCA C. Ki for acetazolamide was 0.9 μM against HCA B and 16 nM against HCA C. The rates of hydration of CO2 in hemolysates with known concentration sof HCA B and HCA C., and in mixtures of purified HCA B and HCA C with concentrations near those in the erythrocyte, were similar to the rates calculated from the kinetic parameters of each isoenzyme. HCA B is 86 % inhibited by chloride in vivo. This strong inhibition, together with the low specific activity, explains why HCAB only accounts for 10% of the total carbonic anhydrase activity of the erythrocyte, en spite the cellular concentration HCAB is 8 times higher than that of HCAC. HCAB and HCA C can together accelerate the intracellular CO2‐reaction 23 000‐fold, which gives a margin of 25‐fold over physiological needs in hard work and 50‐fold at rest. Perceptible physiological effects on respiration should therefore be seen when total carbonic anhydrase activity of erythrocytes is 96 to 98% inhibited. These degrees of inhibition are achieved when plasma concentrations of acetazolamide reach 2 and 5 muM, respectively.
Extracellular ion concentrations during spreading depression and ischemia in the rat brain cortex
Authors: HANSEN ANKER JON , ZEUTHEN THOMAS
Published: December 2008

We compared interstitial ion concentrations in rat brain cortex during two conditions where pronounced changes are observed: spreading depression and ischemia. Initially, during the two phenomena, an increase of [K+]e from 3 to approximately 10 mM were observed, but only small changes of the other ion concentrations. Hereafter, [K+]e exhibited a rapid increase (2–3 s) to 55 mM, whereas [Na+]e rapidly decreased to 60 mM, [Cl‐]e to 75 mM, and [Ca++]e to 0.08 mM. The changes were accompanied by a rapid negative shift in the local electrical potential. However, there were differences in the ionic events during the two phenomena. In spreading depression, the initial [K+]e increase took place in 5–10 s, but in ischemia it lasted 1–2 min. The ionic perturbations were spontaneously reverted in SD, but in ischemia they proceeded further and reached after 5 min (mM): [K+]e 75, [Na+]e 50, [Cl‐]e 72, and [Ca++]e 0.06. The similar chain of ionic events during spreading depression and ischemia suggests a common mechanism for the ionic changes, probably involving changes of ionic permeability of brain cells.
Cerebral and ocular blood flow during α2‐blockade: evidence for a modulated sympathetic response
Authors: LINDER JAN
Published: December 2008

The effect upon regional blood flows of α2‐blockade by yohimbine was investigated in albino rabbits before and during unilateral cervical sympathetic stimulation. The combined effects of i.v. angiotensin, α2‐blockade and sympathetic stimulation were also investigated. Regional blood flows were determined using the labelled microsphere method. Yohimbine produced high flow rates in the eyes, the dura, the choroid plexus and in the peripheral organs. Sympathetic stimulation during α2‐blockade caused significant blood flow reductions in the brain, the eye and in all other tissues investigated. In the brain the flow reduction was 20–25% in several structures. Angiotensin caused marked reductions in blood flow in the dura and in most peripheral tissues. The effects of sympathetic stimulation were not appreciably changed. The results suggest that vascular α2‐receptors affect the vascular tone in some organs and that presynaptic α2‐receptors modulate the response to sympathetic stimulation in the brain, the optic nerve and in the choroid plexus.
On the significance of the respiratory exchange ratio after different diets during exercise in man
Authors: JANSSON E.
Published: December 2008

Total respiratory exchange ratio (R) was compared to the respiratory exchange ratio over the legs (RQL) during exercise after different diets, to evaluate if R (which represents a mean for the whole body) can be used to estimate the relative proportions of fat and carbohydrate oxidation in exercising muscle. One important prerequisite for this is a steady state acid base balance. 7 subjects were studied at rest and during the later part of a 25 min exercise (65% of Vo2 max) on two occasions, the first preceded by a fat rich diet and the second by a carbohydrate rich diet. Oxygen uptake, R and arterial‐femoral venous differences for [O2]. [CO2], PCO2 and pH and arterial concentrations for lactate and β‐hydroxybutyrate were measured. Respiratory exchange ratio over the exercising legs (RQL) and ventilationloxygen uptake were calculated. Arterial pH, PCO2, lactate and β‐hydroxybutyrate as well as specific ventilation attained steady levels during the later part of exercise after both diets. Although arterial lactate and β‐hydroxybutyrate differed between the diets. the arterial pH and specific ventilation were the same. Both R and RQL were higher after the carbohydrate than after the fat diet and there was no systematic difference between R and RQL. Therefore, it seems likely that R estimates the proportion of fat and carbohydrate oxidation in skeletal muscle during submaximal exercise after extreme diets.
Blood flow in the rabbit tenuissimus muscle Influence of preparative procedures for intravital microscopic observation
Authors: LINDBOM L. , TUMA R. F. , ARFORS K.‐E.
Published: December 2008

LINDBOM, L., TUMA, R. F. & ARFORS, K.‐E.: Blood flow in the rabbit tenuissimus muscle: Influence of preparative procedures for intravital microscopic observation. Acta Physiol Scand 1982,114:121–127. Received 21 April 1981. ISSN 0001–6772. Department of Experimental Medicine, Pharmacia AB, Uppsala, Sweden.

The tenuissimus muscle in the rabbit and the cat is a suitable tissue for intravital microscopic investigation of skeletal muscle blood flow. In this study the influence of surgical procedures necessary for direct microscopic observation on the physiological state of the rabbit tenuissimus muscle was assessed by means of blood flow measurements. Mean resting blood flow was 2.8±0.8 (mean ± S.D.) ml. min‐1. 100 g‐1in the left tenuissimus muscle when prepared for microscopic observation as determined by the radioactive microsphere method. This value was not significantly different from that in the intact unexposed muscle in the contralateral leg, 3.3 ±1.1 ml. min‐1. 100 g‐1. Exposure of the muscle to atmospheric oxygen tension resulted in a reduction of blood flow to 0.7±0.4 ml. min‐l. 100g‐l, suggesting that local metabolic control mechanisms were active. The normal range of vascular control seemed to be maintained, as demonstrated by an increase in blood flow to 64.2± 18.8 ml. min‐1. 100 g‐lduring “maximal” vasodilation induced by topical application of PGE1. The tenuissimus muscle showed a marked sensitivity to mechanical stimulation. Slight stretching of the muscle, similar to what may occur during surgical preparation, resulted in an increase in blood flow to 17.5±5.7 ml. min‐1. 100 g‐1. Flow values calculated from data obtained by direct microscopic measurements in the tenuissimus muscle agreed well with those obtained by the microsphere method.
Effects of excessive caloric intake and caloric restriction on body weight and energy expenditure at rest and light exercise
Authors: LAMMERT OLE , HANSEN ERIK STEEN
Published: December 2008

The individual response to overeating and semistarvation on energy expenditure at rest and light work before and after a test meal was investigated. This response was related to the change in dry body weight, measured as weight (W) minus total body water (TBW). Experiments were performed on 9 non‐obese subjects: (a) with a normal habitual energy intake; (b) (overfeeding) with an extra energy intake of 12 MJ per day for two weeks; and (c) (semistarving) with an energy intake of only 2.1 MJ per day for 2 weeks. Measurements of VO2, VCO2. W and TBW were obtained at the end of each of the three periods. It was found that the perturbation in energy intake from normal to 20–25 MJ per day increased the energy expenditure. The magnitude of this increase was highly individual and inversely related to the change in dry body weight. Energy expenditure, measured under the four standardized conditions, after 2 weeks of semistarvation was lower than that obtained after the preceding overeating period. This decrease was also roughly inversely related to the change in dry body weight. The results support the idea that part of the regulation of body energy content takes place by way of a change in the efficiency of energy utilization and that the response to a perturbed energy intake varies considerably between subjects.
Sympathetic effects on cerebral and ocular blood flow in rabbits pretreated with indomethacin
Authors: BEAUSANG‐LINDER MARIANNE
Published: December 2008

The effects of unilateral stimulation of the cervical sympathetic chain on cerebral and ocular blood flow was investigated in 8 rabbits anesthetized with pentobarbital sodium and pretreated with indomethacin in order to inhibit the formation of prostaglandins. Blood flow determinations were made with the labelled microsphere method during normotension and acute arterial hypertension. Hypertension was induced by ligation of the thoracic aorta. Evans blue was given as a tracer for protein leakage during hypertension. Sympathetic stimulation had no significant effect on the blood flow in the brain under the two conditions studied. In the uvea marked effects of sympathetic stimulation were obtained at normotension as well as at hypertension. There were no indications of breakdown of the blood‐brain barrier or the blood‐aqueous barrier. Thus, there was no evidence for any prostaglandin‐mediated inhibition of sympathetic effects in the brain or the eye.
Contributions of blood drainage from the liver, spleen and intestines to cardiac effects of aortic occlusion in the dog
Authors: STOKLAND OLAV , THORVALDSON JØRGEN , ILEBEKK ARNFINN , KIIL FREDRIK
Published: December 2008

By occluding the descending thoracic aorta, blood transferred from the lower to the upper part of the body increases left ventricular end‐diastolic volume and maintains stroke volume despite a rise in systolic left ventricular pressure (LVP) of about 60 mmHg. Seventy percent of the blood drained stems from the splanchnic circulation. To examine which splanchnic organs contribute to the cardiac effects, selective occlusions were performed during ultrasonic measurements of spleen and liver dimensions and left ventricular myocardial chord length (MCL) in atropinized, open‐chest dogs. Drainage of 15±2 ml from the spleen accounted for 18±4% of the increase in end‐diastolic MCL, whereas liver dimensions remained unaltered. Similar results were obtained during aortic occlusion at high inotropy (isoproterenol infusion). it was ascertained by occlusion of the coeliac and mesenteric arteries that about 50% of the cardiac response to aortic occlusion was due to drainage from the intestines and the aorta. Liver blood volume could be reduced by combined occlusion of the aorta and portal vein or coeliac and mesentenc arteries and was sensitive to changes in pressure in the inferior vena cava, but did not contribute to the cardiac response to aortic occlusion.
Effects of cervical sympathetic stimulation on cerebral and ocular blood flows during hemorrhagic hypotension and moderate hypoxia
Authors: LINDER JAN
Published: December 2008

The effect of cervical sympathetic stimulation upon regional blood flows was investigated in albino rabbits during graded hemorrhagic hypotension and mild to moderate hypoxic hypoxia. Regional blood flows were determined using labelled microspheres. Cerebral blood flow (CBF) decreased in response to progressive hypotension and increased considerably during hypoxia (100–200%). Unilateral sympathetic stimulation did not change the ipsilateral cerebral flow responses under either condition. There was a greater tendency to autoregulate down to lower blood pressures in deep than in superficial cerebral structures. During hypoxia cortical gray matter blood flow increased relatively more than did white matter blood flow. Blood flow in different parts of the eye decreased during hypotension and tended to increase during hypoxia. Unilateral sympathetic stimulation reduced tlow rates on the stimulated side (10–50% of control side) under both conditions. The vasoconstrictory effect upon retinal blood flow tended. however, to be less during hypoxia. Dural blood flow showed a poor autoregulation and also no consistent vasodilatory response upon hypoxia. Sympathetic stimulation had a very marked effect. The results suggest that the cervical sympathetic nerves do not have any appreciable effect upon cerebral circulation during profound hypotensive and moderate hypoxic states. Dural and most ocular blood flows seem. however. to be clearly affected by sympathetic stimulation even under these extreme conditions.
Gastric atropine‐sensitive excitation by peripheral vagal stimulation after hexamethonium. Antidromic activation of afferents?
Authors: DELBRO D. , FÄNDRIKS L. , LISANDER B. , ANDERSSON S. A.
Published: December 2008

Experiments were performed in chloralosed cats with ligated adrenals with redording of arterial blood pressure, heart rate and gastric volume, the latter with a balloon method. Electric activation of the peripheral cut vagus at low and high intensity induced gastric excitatory and relaxatory responses, respectively. Hexamethonium blocked the stimulation‐bound bradycardia but now high intensities induced excitatory gastric responses, resistant to a‐ and fi‐adrenergic blocking agents and naloxone but sensitive to atropine. Heating of the intact vagus, to selectively activate thin afferents, resulted in gastric inhibition, due to vago‐vagal reflex activation. When the nerve had been proximally cut, local nerve heating induced excitatory gastric responses, with the same pharmacological chnracteristics as those caused by electric nerve stimulation. The observations suggest that the hexamethonium‐resistant gastric excitatory responses to peripheral vagal stimulation are due to antidromic activation of thin afferents which are proposed to function in axon reflexes affecting gastric motility.
A mean distance of more than 100 Å separates the surfaces of lipoproteins and rat erythrocytes
Authors: BOJESEN ElGIL , BOJESEN INGE NORBY
Published: December 2008

The distribution volumes of125l‐labelled IgG (γ‐immunoglobulin).32P‐labelled VLDL (very light density lipoproteina) (d< l 016). or32l‐labelled HDL (high density lipoproteins) (1.11 < d <1.16) and [3H] inulin in packed erythrocytes from rats were measured by the dilution technique. in two sudsequent steps using approximately 5‐fold dilutions of the trapped extracellular volume. initially louded with the tracers. The total cell area. the Stoke radius of inulin and the distribution volume of inulin together define in each experiment a surface of reference not necessarily identical with the cell surface. Centrifugation of a standard cell concentration 10000xg tor 30. 60 or 90 s produced fractional distribution volumes of inulin between 85 and 37mU/g. The discoid form of the cells was preserved in the expermiental medium and the total cell area of the packed cells was calculated from the volume to surface area ratio eatimated to 6024 A. The minimum average distance between the surface of reference and the protein or a lipoprotein particle was calculated on the basia of the difference in distribution volumea of each of these substances and inulin. The distance was 138±9.5 A (n= 8) (mean ±SD) for IgG independent of the bize of the inulin space. For VLDL and HDL the calculated distances varied significantly with the fractional inulin space of an average thickness less than 140 A in excess of the maximum levels of 299±20 A (n=13) and 191±15 A (n=12) for the lipoproteins respectively. Subtractions of the Stoke radii of the protein and the particles from these distances indicate that the surfaces of IgG. VLDI, and HDL are spaced from the surface of reference by about 87 A. 100 A and 125 A respectively. The distances to the true cell surface are greater in so far as the inulin concentration of the pericellular space is diminished by the fibers of the glycocalyx. Together with lack of affinity of the particles to the cell surface the data make an exchange of molecules by contact unlikely.
Regional tissue fluid pressure in rat calf muscle during sustained contraction or stretch
Authors: KIRKEBØ A. , WISNES A.
Published: December 2008

The tissue fluid equilibration pressure in central and peripheral regions of rat calf muscles has been measured by needles with large smoothed sideholes. Short equilibration periods were normally achieved although saline was not infused. Tissue fluid pressure during rest remained constant at ‐2 to 0 mmHg. During sustained isometric contraction the average tissue fluid pressure rose almost linearly with increasing force of contraction. The average pressure in the central inner zone of the muscle reached 220±80 mmHg during maximal force, whereas the average pressure in the outer peripheral zone increased to 85±56 mmHg, markedly less than in the central zone. Thus, this difference in regional tissue pressure may possibly explain the greater impediment to blood flow in central than in peripheral regions during contraction shown previously by Wisnes & Kirkebø (1976). Although a corresponding regional pressure difference was observed during passive stretch of the muscle, the absolute tissue pressures were much smaller. However, the heterogeneous pattern of muscle fiber directions and relative displacement of various muscle elements during work, may induce shear forces causing focal vessel obstructions that are different during contraction and stretch.
Combined effect of elastic energy and myoelectrical potentiation during stretch‐shortening cycle exercise
Authors: BOSCO C. , VIITASALO J. T. , KOMI P. V. , LUHTANEN P.
Published: December 2008

In addition to the utilization of muscle's elastic energy enhancement of performance in exercise involving stretch‐shortening cycle might be also due to simultaneous increase of myoelectrical activity. This hypothesis was tested by examining three athletes during jumping exercise on force‐platform. Vertical jumps were performed with and without preliminary counter‐movement, and the jumps were called counter‐movement jump (CMJ) and squatting jump (SJ), respectively. In both conditions several jumps were performed also with extra loads on the shoulders (15–220% of b. wt.). Additional droppingjumps (DJ) were executed from different heights (20–100 cm). During jumping exercise myoelectrical activity of selected muscles from the quadriceps femoris was monitored with surface electrodes. The results obtained were similar to those reported in isolated muscle and as expected, the prestretch in CMJ shifted the force‐velocity curve of concentric work to the right. In two cases enhancement of performance was attributed primarily to restitution of elastic energy because myoelectrical activity was similar to that observed in SJ. In one subject increased myoelectrical activity was observed during the concentric phase of CMJ. In DJ condition the EMG activity during eccentric phase was much higher than in SJ. Therefore the high performance in this condition was attributed to both elastic energy and reflex potentiation. In eccentric work of CMJ the average force decreased with the increase of stretching speed. This phenomenon was associated with a light increase of EMG activity. The observed results emphasize that both elastic energy and reflex potentiation may operate effectively during stretch‐shortening cycle activity.
On periodic sweating from the human skin during rest and exercise
Authors: NILSSON A. L. , NILSSON G. E. , ÖBERG P. A.
Published: December 2008

The rhythmic variations in the water evaporation rate (gm 2 h 11 from the dorsal side of the forearm have heen studied. The evaporaition rate is estimated by calculating the difference between the vapour pressures at two distinet points on a line perpendicular to the evaporative surface. Using autocorrelation technique it is found that the evaporation rate is periodie with a period of around 0.7 s. This value is consistent. al rest as well as prior to profuse sweating in exercise. for all the subjects included in the investigation. During profuse swesting the period becomes slightly longer. It is suggested that the variations in the evaporation rate reflect the periodie activity in the sudomotor nerves.
Adrenergic responses in different sections of rat airways
Authors: VORNANEN M.
Published: December 2008

Effects of adrenergic agonists on 4 different preparations (trachea, bronchus, bronchiole and parenchymal strip) of rat airway smooth muscle were studied. Phenylephrine, an alpha‐agonist, contracted the trachea, bronchus and parenchymal strip but had no effect on the bronchiole. Similarily adrenaline, both a beta‐ and an alpha‐agonist, contracted the trachea, bronchus and parenchymal strip, but neither contracted nor relaxed the bronchiole. These results suggest that the rat trachea and bronchus contain alpha receptors but the bronchiole does not. Alpha response of the parenchymal strip preparation seems to originate from the vascular smooth muscle. Isoprenaline, a nonselective beta‐agonist, could not elicit any response on resting airways, but caused a relaxation of all four preparations after being contracted by carbacholine. Expressed in%of maximal carbacholine contractions. the relaxations were: 21% in the trachea, 45% in the bronchus, 92% in the bronchiole and 141 % in the parenchymal strip. This shows that beta response is weak in the large central airways but becomes stronger towards the small peripheral airways, when measured against cholinergic contraction.
Inactivation of the potassium transport system of myelinated nerve in the presence of a cyclic ionophore
Authors: ÅRHEM P. , FRANKENHAEUSER B. , KRISTBJARNARSON H.
Published: December 2008

A potassium carrying ionophore dicyclohexano‐18‐crown‐6 was found to affect the specific ionic currents in the node of Ranvier. Its presence caused an inactivation of the potassium permeability mechanism and a decrease of the sodium permeability. The rate of inactivation of the potassium permeability depended on crown ether concentration, on membrane potential and on temperature. At large concentrations, the rate of inactivation was of the same order of size as the normal rate of activation. The recovery from the inactivated state was slow, it took a few seconds, and recovery time depended on holding potential. The inactivation was caused by potential steps in positive direction. The un‐complexed crown ether is uncharged and does not move due to a potential gradient. The mechanism by which the crown ether makes the inactivation potential dependent remains obscure. A few other ionophores were tested but they did not affect the membrane currents.
Effect of diazepam on cerebral monoamine synthesis during hypoxia and hypercapnia in the rat
Authors: SAKABE TAKEFUMI , DAHLGREN NILS , CARLSSON ARVID , SIESJÖ BO K.
Published: December 2008

In view of the fact that diazepam has been shown to prevent an increase in catecholamine synthesis and/or turnover rates in stressful situations, and to modify the cerebral metabolic (and circulatory) response to hypoxia and hypercapnia, the influence of the drug on synthesis rates of DOPA and 5‐HTP in three regions of the rat brain were studied under normoxic‐normocapnic conditions, as well as in hypoxia and hypercapnia. In order to exclude a modifying influence of variations in tissue pO2during hypercapnia, cerebral venous pO2was kept at control values by moderate arterial hypoxia. When compared to the control state (paralyzed animals maintained on 70% N2O) normoxic and normocapnic animals given diazepam (in the absence of N2O) showed a slightly enhanced DOPA synthesis in limbic structures and reduced 5‐HTP synthesis in limbic structures and striatum. In hypoxia, the drug considerably curtailed DOPA synthesis in limbic structures and striatum but had no effect on synthesis rate in cortex. The drug also appeared to exaggerate the generalized reduction in 5‐HTP synthesis observed under 70% N2O. In hypercapnia, diazepam reduced the enhanced rate of DOPA synthesis (observed under 70% N2O) in striatum but left that in the cortex unchanged. The drug prevented the hypercapnia‐induced increase in 5‐HTP synthesis, observed under 70% N2O. It is concluded that diazepam significantly alters dopamine and serotonin synthesis in hypoxia and hypercapnia. Probably an indirect action, perhaps related to the stress‐alleviating effect of diazepam, is involved. The results suggest that the effect of the drug on cerebral metabolic rate and blood flow in hypoxia and hypercapnia is unrelated to changes in noradrenaline synthesis or turnover. Furthermore, although the results demonstrate that diazepam modulates dopamine metabolism in hypoxia and hypercapnia it seems questionable that this influence can explain the metabolic and circulatory effects of diazepam in these conditions.