bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of 1,3‐diaminopropane on testosterone induced hypertrophy and polyamine synthesis in mouse kidney
Authors: CAMERON ROBERT , HENNINGSSON STIG , PERSSON LO , ROSENGREN ELSA
Published: December 2008

The effects of prolonged treatment with 1,3‐diaminopropane, a structural analogue of putrescine, on polyamine metabolism and growth in kidney tissue, were studied in mice in which renal hypertrophy was induced by testosterone treatment. Injections of 1,3‐diaminopropane resulted in an almost total suppression of the testosterone induced stimulation of ornithine decarboxylase activity and prevented the accumulation of putrescine and spermidine in the kidneys. Renal spermine concentration was even lowered. Administration of 1,3‐diaminopropane effectively prevented the testosterone induced increase in renal weight and RNA. In mice receiving 1,3‐diaminopropane proteinuria was observed and histological examination revealed renal damage. Due to the nephrotoxic action of 1,3‐diaminopropane caution is essential in relating the prevention of renal hypertrophy and the inhibition of polyamine synthesis.
Human forearm and kidney conversion of arachidonic acid to prostaglandins
Authors: NOWAK J. , WENNMALM Å.
Published: December 2008

The capacity of the human forearm and kidney to synthetize different prostaglandins (PGs) was studied, together with the quantitative relationship between the various PGs formed in these organs. 14C‐labelled arachidonic acid (14C‐AA) was infused in healthy male volunteers at a constant rate into the brachial or the renal artery, with simultaneous sampling of regional venous blood. The venous plasma content of 14C‐PGs was extracted, separated with thin‐layer chromatography (TLC) and quantified using fractionated liquid scintillation spectrometry. Most of the 14C‐AA infused was metabolized and radiopeaks parallel to unlabelled standards of PGD2, PGE2, PGFja, 6‐keto‐PGF, and 13,14‐dihydro‐15‐keto‐PGEj (Me) were obtained. The chromatograms of both the forearm and the kidney plasma contained all the peaks described, but the relative distribution of the I4C‐PGs differed between the two tissues. In the cubital venous plasma, the main PG (apart from Me) was 6‐keto‐PGFla, indicating a considerable synthesis of PGI2 in the forearm. In the renal venous plasma, on the other hand, PGD2 accounted for the largest part of the authentic 14C‐PGs found. Besides the tissue differences, large inter‐individual variations were observed. The results demonstrate the existence of both a considerable tissue specificity and an appreciable inter‐individual variation in the local conversion of AA to PGs in man.
Ribonuclease activities in developing experimental granulation tissue with reference to polysomes
Authors: AHO SIRPA , KULONEN EINO
Published: December 2008

The Mg2+‐precipitable polysomes in experimental granulation tissue increase up to three weeks and decrease slowly thereafter. Polysomes from young granulation tissue are, on a weight basis, more active in cell‐free protein synthesis than polysomes from old granulation tissue. RNase activity is highest in polysomes from 1‐week tissue. The polysomes contain both acid and alkaline RNase, but the alkaline RNase is in latent form, manifested by the addition of p‐chloromercuribenzoate (pCMB). The high RNase activity of granulation tissue renders the analysis of polysomal patterns and functions of the polysomes difficult. In the post‐polysomal supernatant of granulation tissue the RNase activity is highest in 2–4 week old tissue; it is maximal at pH 7–8 and only slightly influenced by pCMB.
Changes in penile volume during some cardiovascular reflexes and reactions in rabbit
Authors: SJÖSTRAND NILS O. , KLINGE ERIK
Published: December 2008

The effect of various cardiovascular reflexes and reactions on the plethysmographically recorded penile volume in rabbit was investigated. Stimulation of the aortic nerve or direct stimulation of the carotid sinus produced increase in penile volume, while carotid occlusion produced decrease. Brief volume load or protoveratrine given into the right atrium produced increase in penile volume. Asphyxia, hypercapnia, hypoxia, cyanide and lobeline produced decrease in penile volume, while hypocapnia increased it. Moderate blood taps decreased penile volume. With the exception of the response to asphyxia all these reactions required intact vasomotor nerves. Clonidine increased penile volume if vasomotor nerves were intact but decreased it if the penis was decentralized. Penile volume decreased in shivering animals but increased on warming. Carotid occlusion impaired erectile responses to hypogastric and pelvic nerve stimulation. In certain experiments this effect was more pronounced in the latter case. It is concluded that the medullary neuron pool responsible for penile vasomotor tone participates in general reflex cardiovascular homeostasis and that this may have implications for normal erectile responses.
Intramural blood flows and flow distribution in the feline small intestine during arterial hypotension
Authors: CASSUTO JEAN , CEDGÅRD STURE , HAGLUND ULF , REDFORS STAFFAN , LUNDGREN OVE
Published: December 2008

The vascular reactions of the parallel‐coupled vascular sections of the small intestine were studied during hypotension at two different levels of intestinal arterial inflow pressure, using a 85Kr elimination technique. The regional hypotension was accomplished by partially occluding the superior mesenteric artery with a clamp and maintained for 2 h. At the higher level (50–55 mmHg) total intestinal blood flow decreased but not to the same relative extent as blood pressure due to the autoregulatory capactiy of the intestinal vascular bed. The flow autoregulation was also reflected in a decreased blood flow resistance. The distribution of blood to the muscularis and mucosa‐submucosa layer, respectively, did not change significantly during or after hypotension as compared to the prehypotensive level, since the relative flow decrease was the same in the mucosa‐submucosa and in the muscularis. At the lower arterial pressure level (30–35 mmHg) a more marked decrease of intestinal blood flow and flow resistance was observed as compared to the experiments performed at the 50–55 mmHg pressure level. Moreover, muscularis blood flow was relatively more decreased than blood flow in the mucosa‐submucosa implying the fraction of total blood flow diverted to the muscularis was significantly decreased. Despite this redistribution of blood flow, a histological damage was apparent only in the mucosa, particularly at the villous tips.
Studies on ocular blood flow and retinal capillary permeability to sodium in pigs
Authors: TÖRNQUIST P. , ALM A. , BILL A.
Published: December 2008

A surgical technique was developed in pigs that permits access to the retinal venous plexus surrounding the optic nerve. The effect of surgery on ocular blood flow and capillary permeability was evaluated. Blood flow, determined by the labelled microsphere technique, did not differ significantly between operated and control eyes. Increased intraocular pressure in the operated eye reduced blood flow through the choroid and the anterior uvea in proportion to the reduction in perfusion pressure, while in the retina a smaller reduction in blood flow occurred indicating that autoregulatory mechanisms are involved in the control of retinal blood flow. The capillary permeability to sodium was studied by the single injection technique, using albumin as a reference substance. The fractional initial extractions from the choroidal and the retinal vessels were 0.77 and ‐0.001 respectively. The absence of a sodium extraction from the retinal vessel indicates that this part of the blood‐retinal barrier was intact and that the blood drained by the retinal plexus is not mixed with blood from other sources.
Retinal and choroidal contribution to retinal metabolism in vivo. A study in pigs
Authors: TÖRNQUIST P. , ALM A.
Published: December 2008

The glucose metabolism of the retina was studied in vivo, by determining glucose, oxygen and lactate a‐v differences for choroidal and retinal blood in pigs at different levels of intraocular pressure. At normal intraocular pressure the choroidal a‐v differences were 0.07 and 0.11 mmol/1 for glucose and oxygen respectively. The corresponding figures for the retina were 0.44 and 2.15. At increased levels of intraocular pressure the choroidal and retinal glucose and choroidal oxygen a‐v differences increased, thus at least partly compensating for reduced blood flow. A major part of the oxygen and glucose consumed by the retina was delivered by the choroid. The total amount of oxygen extracted from choroidal and retinal blood could only account for complete oxidation of 37% of the extracted glucose. The results obtained in determinations of lactate a‐v differences indicate that part of the remaining glucose is used for anaerobic glycolysis.
Effect of vagus nerve stimulation on the secretory‐granule volume of the principal cells of the mouse gallbladder epithelium
Authors: WAHLIN T. , HULLIGER M. , AXELSSON H.
Published: December 2008

Experiments in mice were performed in order to investigate whether vagal activity could affect glycoprotein secretion from gallbladder principal cells. This cell type was studied with the electron microscope in control animals and after electric stimulation of the right or left nervus vagus. The volume density of glycoprotein containing granules was determined using morphometry. It was found that stimulation of the left vagus nerve significantly reduced the relative cellular volume of secretory granules in the principal cells of the gallbladder. Right vagus stimulation was accompanied by a weak but insignificant increase in secretory granule content. It is suggested that the left vagus nerve may exert a direct influence on glycoprotein secretion from gallbladder principal cells.
A study on the role of endogenous prostaglandins in the development of exercise‐induced and post‐occlusive hyperemia in human limbs
Authors: NOWAK J. , WENNMALM Å.
Published: December 2008

The contribution of endogenous PGs to the development of functional (exercise‐induced) and reactive (post‐occlusive) hyperemia was investigated in healthy volunteers. Leg blood flow during dynamic leg exercise was estimated by an indicator dilution technique. Forearm blood flow during supine leg exercise and forearm and calf blood flow following 5 min of arterial occlusion were measured plethysmographically. All subjects were examined before and after pretreatment with indomethacin, a PG synthesis inhibitor. During leg exercise, and in the absence of indomethacin, a 10‐fold rise in leg blood flow was observed. Forearm blood flow increased moderately. Both these blood flow effects of exercise were unaffected by indomethacin. Following arterial occlusion a marked hyperemia developed in the forearm and the calf. Indomethacin significantly reduced the magnitude of the reactive hyperemia both in the forearm and in the calf, decreasing both the peak value and the duration of the vasodilation. These data reveal differences between the mechanisms behind functional and reactive hyperemia in man, suggesting an appreciable contribution of endogenous PGs to post‐occlusive vasodilation only.
Delayed hypoperfusion in the cerebral cortex of the rat in the recovery period following severe hypoglycemia
Authors: SIESJÖ BO K. , ABDUL‐RAHMAN ALI
Published: December 2008

Male Wistar rats were starved for 24 h before being injected with insulin (Novo Actrapid®) in a dose of 40 Iukg‐1 i.p. They were then anesthetized with 2–3% halothane, tracheotomized, immobilized with tubo‐curarine chloride (1.5 mg‐kg‐1, i.v.) and connected to a respirator delivering nitrous oxide‐oxygen (3:1). Femoral arterial catheters were inserted for blood pressure recording and blood sampling, and a femoral vein was cannulated for infusions. Goldplated screws were inserted in the skull bone for frontoparietal recording of EEG. Arterial PCO2was adjusted to 35–40 mmHg and body temperature was maintained close to 37oC.

Local cerebral blood flow (1‐CBF) was measured with the autoradiographic 14C‐iodoantipyrine technique of Sakurada et al. (1978) as described in detail in a previous communication (Abdul‐Rahman et al. 1979). Measurements were performed in animals in which the spontaneous EEG activity had ceased for 30 min, as well as in those that had been allowed recovery periods of either 5, 30 or 90 min. Recovery was induced by i.v. injection of 0.5 ml of a 50% (w/v) glucose solution in saline followed by i.v. infusion (1 ml/h).
A metabolic basis for the selective vulnerability of neurons in status epilepticus
Authors: SIESJÖ BO K. , ABDUL‐RAHMAN ALI
Published: December 2008

Unstarved, male Wistar rats (290–410 g) were anesthetized with 2–3% halothane, tracheotomized, and connected to a respirator delivering 70% N20 and 30% 02. Catheters were placed in the femoral arteries and in one femoral vein. Gold‐plated screws were inserted in the skull bone for recording of (frontoparietal) EEG. When the operative procedures were completed, halothane supply was discontinued. Arterial PCO2 was adjusted to 35–40 mmHg, and body temperature was maintained close to 37oC.

The animals were allowed a steady state period of about 30 min before seizures were induced by the i.v. injection of bicuculline (1.2 mg‐kg‐1, see Chapman et al. 1977). Just before the injection the animals were bled to a mean arterial blood pressure of about 120 mmHg to avoid too excessive an increase in pressure at the onset of seizures. Local CMRg1 was determined with the method described by Sokoloff et al. (1977). In summary, after 20 min of seizure activity 1 ml of a 14C‐deoxyglucose solution (New England Nuclear), containing 30 μCi, was injected i. v. Over the next 30 min, repeated arterial blood samples were taken for determination of plasma glucose concentration (hexokinase method) and ,4C activity (liquid scintillation counting). At the end of this period, the animals were decapitated and the brains were prepared for quantitative autoradiography. Local CMRgl was calculated from the integrated plasma activity and from the 14C activity in tissue. The latter was determined from the X‐ray films by microdensitometry, either manually (see Abdul‐Rahman et al. 1979) or, in one case, with the automatic microscanning equipment developed in the Laboratory of Cerebral Metabolism, NIMH, Bethesda (courtesy of Dr Louis Sokoloff).
Capillary permeability in cat choroid, studied with the single injection technique (II)
Authors: TÖRNQUIST P.
Published: December 2008

Transcapillary movements of 22Na, 51Cr–EDTA and 125I–myogIobin were studied in the cat choroid by means of the single injection technique, using labelled albumin as the reference tracer. By an external shunting of blood, recirculation of tracer was delayed and complete venous outflow curves became available for analysis. The initial extractions observed were 0.66, 0.35 and 0.08 respectively. The extractions decreased with time. Within 20–25 s the extracted fractions of the tracers had almost completely returned to the blood. The results indicate high permeability coefficients and small extravascular volumes of distribution. The retinal pigment epithelium seems to have a very low permeability to all three substances. Extraction of tritiated water at 20–25 s was about 0.30 probably due to rapid penetration of labelled water into the retina. Evidence for a stereo–specific transport system for glucose in the retinal pigment epithelium was found in experiments with labelled D–glucose and 3–O–methyl–D–glucose. The total amount of glucose delivered by the choroid was calculated from measurements of the a–v differences for unlabel led glucose.
Hemodynamic changes during the development of sodium–induced hypertension in subtotally nephrectomized rats
Authors: YLITALO P. , GROSS F.
Published: December 2008

Hemodynamic changes during the development of sodium–induced hypertension were investigated in male Sprague–Dawley rats after about 70% of the renal mass was removed. Throughout the four experimental weeks, subtotally nephrectomized rats on a high sodium diet (750 mEq/kg) showed a continuous rise in blood pressure up to the mean value of 178±9 mmHg. In sham–operated animals on the high sodium supply the blood pressure did not increase, as compared to sham–operated controls on the standard sodium diet (150 mEq/kg). In the hypertensive group, the primary changes were urea retention and a concomitant increase of serum osmolality, but the serum sodium concentration remained at the normal level. These changes were followed by sustained enlargement of extracellular fluid and relative intravascular volumes, together with a simultaneous increase of heart rate and blood pressure. During high sodium intake, the plasma renin activity in subtotally nephrectomized rats was suppressed to one fifth of that in sham–operated animals, but the renin substrate activity did not increase markedly.
Shortening velocity, active force and homogeneity of contraction during electrically evoked twitches in smooth muscle from rabbit urinary bladder
Authors: UVELIUS BENGT
Published: December 2008

Force–velocity relations obtained by the quick release technique were studied at different times during the twitch at 25oC in electrically stimulated longitudinal smooth muscle from rabbit urinary bladder. The results show that maximal shortening velocity (Vmax) and maximal tension (P0) reach their highest values during the rising phase of the twitch. Maximum Vmax was calculated to be 0.3010.04 1/s (S.E., n=9). Vmax declines rapidly with time and at the peak of the twitch it is only about 70% of the maximum value. On the other hand Poat the peak does not differ significantly from its maximum value during the rising phase. In the relaxation phase of the twitch, both Vmax and Podecrease progressively. Photographic studies of preparations marked with charcoal grains did not show any considerable inhomogeneity of contraction during isometric twitches, maximum movement of grains never exceeding 4 % of total muscle length. No yield at the ends of the preparations were seen. The different time course of Vmax and Po can therefore not be explained by longitudinal inhomogeneity of activation or deactivation of the preparations.
Quantitative changes in regional cerebral blood flow of rats induced by alpha‐and beta‐adrenergic stimulants
Authors: EDVINSSON L. , LACOMBE P. , OWMAN C.H. , REYNIER‐REBUFFEL A.‐M. , SEYLAZ J.
Published: December 2008

Cerebral blood flow was measured with the14C‐ethanol technique in 8 regions (frontal, parieto‐temporal and occipital cortex, caudate nucleus, thalamus, cerebellum, mesencephalon, and pons) of rats. The highest flow values (83–89.5 ml/100 g/min) were found in cortical areas, whereas pons had the lowest flow (48 ml/100 g/min). Intravenous infusion of noradrenaline or adrenaline markedly reduced rCBF (by 22–48% of control levels) in all regions except thalamus, mesencephalon, and pons. The noradrenaline‐induced reduction was blocked, and the effect of adrenaline reversed, after pretreatment with the alpha‐receptor antagonist, phentolamine. Isoprenaline infusion markedly augmented rCBF in thalamus, mesencephalon, pons, and also in the caudate nucleus. The response was reduced by the beta‐receptor antagonist, propranolol. The experiments show the presence and heterogenous distribution in the cerebrovascular bed of alpha‐and beta‐adrenoceptors that can be activated by sympathomimetics given systematically. If noradrenaline was allowed to pass the blood‐brain barrier after osmotic opening with urea, an increased regional flow was obtained, probably due to a mechanism where the vasodilator effect secondary to activation of cerebral metabolism predominated over the direct vasoconstrictor effect of the amine.
Morphological and mechanical properties of small mesenteric arteries and veins in spontaneously hypertensive rats
Authors: AALKJæR C. , MULVANY M. J.
Published: December 2008

Segments of small mesenteric arteries (—150 μm lumen diameter) and of corresponding veins were taken from 5‐month‐old spontaneously hypertensive rats (SHR) and from age matched Wistar Kyoto (WKY) controls. The segments were mounted on a myograph which enabled their mechanical and morphological parameters to be investigated simultaneously. Compared with the WKY arteries the lumen diameter of the SHR arteries was smaller while the media thickness and active wall tension response were greater. On the other hand there were no differences between the corresponding veins from SHR and WKY animals although, compared with the arteries, the veins had a greater lumen diameter, a smaller media thickness and a smaller tension response. The findings suggest that the morphological and mechanical differences seen in arteries from SHR are not found on the venous side.
Modification of human pain threshold by specific tactile receptors
Authors: PERTOVAARA ANTTI
Published: December 2008

The effects of conditioning vibrotactile stimulation of particular tactile receptor groups on thresholds to painful electric stimuli were studied in seven healthy adults. Preferentially Pacinian afferents were activated with conditioning sinusoidal vibration of 240 Hz at 20 and 200μm amplitudes and preferentially non‐Pacinian tactile fibers were activated with conditioning sinusoidal vibration of 20 Hz at 200 and 400 μm amplitudes. None of the subjects showed pain threshold elevation during activation of non‐Pacinian tactile fibers. However, 6 of the 7 subjects showed significant pain threshold elevation with conditioning vibratory stimulus of 240 Hz at 200 μm amplitude, and 4 subjects showed significantly elevated pain thresholds with conditioning stimulus of 240 Hz at 20 μm amplitude. It is concluded that the activation of Pacinian afferents causes inhibition of pain conducting pathways.
Efflux of cyclic AMP, prostaglandin E2 and F2 and thromboxane B2 in leg lymph of rabbits after scalding injury
Authors: JONSSON CARL‐EVERT , SHIMIZU YASUYUKI , FREDHOLM BERTIL B. , GRANSTRÖM ELISABETH , OLIW ERNST
Published: December 2008

Leg lymph was collected from pentobarbital anaesthetized rabbits before and after scalding injury of the paw (75°C for 20 s), and the contents of cyclic AMP (cAMP), prostaglandin E2 (PGE2) and PGF2α and thromboxane B2 (TXB2) in lymph were determined. After injury lymph flow increased about four times. The maximal rate of flow was found between 30 and 60 min after scalding. The efflux of cAMP and immunoreactive iPGE2, iPGF2α and iTXB2 also increased. The maximum values were detected at approximately 0–30, 30–60, 30–60 and 180–240 min, respectively, after the injury. The output of cAMP, iPGE2 and iPGF2α and iTXB2 in lymph of the contralateral non‐scalded paw remained low throughout the experiments. When rabbits were injected with indomethacin (2.5 mg/kg) or diclofenac sodium (2.5 mg/kg) immediately after the scalding injury, the efflux of cAMP, iPGE2 and iPGF2α were low. Lymph flow was markedly reduced after treatment with diclofenac sodium; treatment with indomethacin did not significantly affect lymph flow. The results suggest a prostaglandin‐dependent formation of cAMP following scalding injury which may be related to the initial responses to scalding.
Carotid baroreflex heart rate control during the active and the assisted breathing cycle in man
Authors: MELCHER ANDERS
Published: December 2008

The interaction between the phase of the breathing cycle and the carotid baroreflex heart rate control was studied in fifteen healthy subjects with special reference to respiratory sinus arrhythmia (RSA). Carotid baroreceptors were stimulated by neck suction. With a standardized breathing pattern, two types of experiment were performed. (A) Neck suction applied in counter phase with the respiratory arterial pressure variations; this reduced the amplitude and shifted the phase of the transmural carotid arterial pressure oscillations but did not influence the RSA. (B) During active as well as ventilator assisted breathing, brief periods of neck suction were applied during either inspiration (insufflation) or expiration. Neck suction during active inspiration did not change the amplitude of the RSA but when applied during expiration, increased it by 6.8 beatsXmin‐1 (P < 0.001). In the ventilator experiments, neck suction during insufflation and expiration augmented the RSA equally, by 5.3 beatsXmin‐1 (P < 0.05). The results indicate a decreased sensitivity of the carotid arterial baroreflex during active inspiration, with no equivalent during assisted breathing, and suggest that the change in baroreflex sensibility is a prerequisite for the rise of the RSA.
Connective tissue of “fast” and “slow” skeletal muscle in rats…effects of endurance training
Authors: KOVANEN VUOKKO , SUOMINEN HARRI , HEIKKINEN EINO
Published: December 2008

The connective tissue of two skeletal muscles having different contractile properties was investigated in trained and untrained rats. The animals to be trained were put to run on a treadmill 5 days a week for 4 weeks. The “slow” m. soleus (MS) showed higher malate dehydrogenase activity but lower lactate dehydrogenase activity compared to the “fast” m. rectus femoris (MRF). When whole muscles were taken into account, the concentrations of both hydroxyproline and hexosamines were higher for MS compared to MRF. In the middle section of MS there were more hexosamines than in that of MRF, but no similar difference existed in hydroxyproline. The histochemical staining of collagen, however, suggested that there is also more internal collagen for MS as against MRF. It can be supposed that collagen of MRF and MS is differently distributed in different muscle connective tissue components. Compared to MS, the solubility of collagen was higher in MRF, whereas no significant difference between the muscles existed in the prolyl hydroxylase activity. The concentrations of hydroxyproline and hexosamines or the solubility of collagen were not affected by the training given, but the activity of prolyl hydroxylase was increased in MS suggesting that the metabolism of collagen may be accelerated by physical training.
Priority of blood flow to splanchnic organs in humans during pre‐ and post‐meal exercise
Authors: ERIKSEN M. , WAALER B. A.
Published: December 2008

Cardiac output and superior mesenteric arterial flow in five healthy young men were followed using Doppler ultrasound techniques at rest and during 4 min bouts of bicycle exercise in both a pre‐ and a post‐meal situation. The meal given was mixed and heavy, with an energy content (related to body size) of about 1400–1600 kcal (5.9‐6.9 MJ). Two levels of exercise, 50–65 W and 150–200 W (about 75% of Votmax), were tested, with the subjects cycling in a reclining position.

Superior mesenteric arterial flow increased threefold, to about 1.11 min‐1, after the meal. During exercise in the fasting situation there were only modest changes in splanchnic vascular conductance, and moderate increases in superior mesenteric arterial flow were actually recorded. Exercise in the post‐prandial state caused appreciable reductions in splanchnic vascular conductance, and a 38% reduction was observed during the most heavy exercise. However, not even such a decrease in conductance resulted in any definite reduction in superior mesenteric arterial blood flow, which was maintained at the pre‐exercise level.

Cardiac output increased by about 1.3 1 min‐1 after the meal. The exercise‐induced increases in cardiac output were of the same order in the fasting and in the post‐prandial state. Variance analyses showed the high cardiac output levels reached during postprandial exercise to be no different from levels that would be reached by pure summation of the changes caused by eating alone and by exercise alone.

It is concluded that blood flow to the splanchnic organs in reclining man retains its high pre‐ and post‐prandial priority during short exercise bouts of up to 75% of VoSmax.
Haemorrhage‐induced splenic vasodilation in the rat is mediated by sympathetic vasomotor nerves
Authors: IVERSEN P. O. , BENESTAD H. B. , NICOLAYSEN G.
Published: December 2008

A marked decrease in splenic vascular resistance, with an increase in blood flow to the spleen, occurs already 5 min after an acute and severe hypotensive bleeding in awake rats. This response is virtually abolished in rats pretreated with a β‐adrenergic blocking agent. We have now studied the contribution of the sympathetic vasomotor innervation and of adrenal gland‐derived catecholamines to the splenic vasodilation.

Splenic blood flow was determined with the microsphere method in heavily bled (1.5% of body weight) awake rats. The sympathetic neurones in one group of rats had been chemically destroyed with 6‐hydroxydopamine. In another group of rats we had removed the adrenal glands.

In the control and in sympathectomized rats, splenic vascular resistance fell to 35 and 64%, respectively, of baseline 5 min after bleeding. Splenic blood flow about doubled during this period in the control rats, and then declined gradually to baseline over the next 24 h. In the sympathectomized rats, splenic blood flow decreased gradually over the first 12 h to reach 66% of baseline. The removal of the adrenal glands did not appreciably influence the splenic vascular response to bleeding.

We conclude that an increased activity in the splenic sympathetic vasomotor neurones is a prerequisite for the observed vasodilation and concomitant large increase in splenic blood flow after haemorrhage in intact, awake rats. Catecholamines from the adrenal glands did not contribute detectably to the splenic vasodilation.
Responses of noradrenergic nerves in rabbit ear‐artery before and after experimental frost‐bite
Authors: Aas PÅl
Published: December 2008

Experiments were designed to determine the effects of sub‐zero temperatures on the function of the noradrenergic innervation of a peripheral blood‐vessel. The central ear‐artery of the rabbit was used for this purpose. The ear was exposed to temperatures of – 6, –9 or –18 oC in vivo for 15 min. After 1 day (24 h) or 6 days in vivo, the central ear‐artery was dissected free, incubated in [3H]‐noradrenaline (NA) and stimulated in vitro with high potassium (75 mM) for 5 min to evoke release of [3H]‐NA. The release of [3H]‐NA was Ca2+‐dependent. One day after exposure to –6, –9 or –18 CC, increases of 45–57 and 44–72% and a reduction of 12–35% were observed, respectively, in three successive potassium‐evoked NA‐releases. After 6 days in vivo an increase of 30–34% was observed following exposure to –6 oC, while no alteration was observed after exposure to –9 oC. A reduction of 84–89% was recorded after exposure to – 18 oC. Following this exposure to – 18 oC, there was also a great reduction in the evoked release of [3H]‐NA compared with the spontaneous release, whereas this correlation did not change after exposure to – 6 and – 9 oC. The total uptake of [3H]‐NA was unchanged after freezing the tissue at – 6 oC, but was substantially reduced after exposure to –9 and –18 oC. A short period of in vivo restoration (6 days, enhanced the uptake of [3H]‐NA. Rapid thawing, within approximately 3 min, after freezing at – 9 oC (1 day in vivo) resulted in a normal, potassium‐evoked, release of [3H]‐NA and a higher uptake of [3H]‐NA than after a longer, standardized, thawing procedure of approximately 10 min. These results demonstrate that both the evoked and the spontaneous releases of [3H]‐NA from the sympathetic nerves were increased after freezing at moderate freezing temperatures (±– 9 oC), while rapid thawing resulted in a normalization of the potassium evoked released of [3H]‐NA. Exposure to –18 oC reduced both the uptake and release of neurotransmitter. Restoration in vivo for 6 days improved the uptake, but not the release, of [3H]‐NA.
AMP deaminase in skeletal muscle of healthy males quantitatively determined by new assay
Authors: NORMAN B. , HELLSTEN‐WESTING Y. , SJODIN B. , ANSSON E. J.
Published: December 2008

A new, sensitive assay for the quantitative determination of AMP deaminase activity in human skeletal muscle is presented. The method is based on the determination of the direct product of the AMP deaminase reaction, the formed IMP, by high performance liquid chromatography (HPLC). In order to evaluate the relationship between AMP deaminase activity on the one hand and the contractile and metabolic characteristics of the muscle and the physical performance on the other, muscle biopsies were taken from 20 male subjects. The subjects also performed a 30 s sprint test on a cycle ergometer. The inter‐individual variation in AMP deaminase activity was large, ranging from 5.4 to 27.4 μkat g‐1 dry muscle. AMP deaminase was positively correlated with phosphofructokinase (PFK), the marker of the glycolytic capacity of the muscle, but there was no correlation with enzymes of oxidative metabolism, such as 3‐hydroxyacyl‐CoA dehydrogenase and citrate synthase, or with the activity of myokinase and lactate dehydrogenase. There was no significant correlation between AMP deaminase activity and the proportion of the different muscle fibre types. A weak positive correlation was found between the sprint performance and the AMP deaminase activity. In conclusion, the HPLC assay was found to be a fast, sensitive and reliable method for the quantitative determination of AMP deaminase activity in muscle. A direct relationship between AMP deaminase activity on the one hand and glycolytic capacity and sprint performance on the other was found. However, no relationship to oxidative capacity or contractile properties was found.
Oxygen or low concentrations of nitric oxide reverse pulmonary vasoconstriction induced by nitric oxide synthesis inhibition in rabbits
Authors: PERSSON M. G. , KALZÉN H. , GUSTAFSSON L. E.
Published: December 2008

The objective of this study was to investigate the role of nitric oxide and oxygen in the regulation of pulmonary vascular resistance, especially by means of substitution with nitric oxide after inhibition of endogenous nitric oxide formation. In artificially ventilated open‐chest rabbits pulmonary vascular resistance at normoxic ventilation (F102= 21%) was 56±6cmH2O ml‐1 mim‐1 1000‐1 (mRUL). Nw‐nitro‐L‐arginine methyl ester (l‐NAME, 30 mg kg‐1), an inhibitor of NO synthase, increased pulmonary vascular resistance to 122±17 mRUL at normoxic ventilation. In response to l‐NAME there was also an increase in mean arterial blood pressure. Exogenous nitric oxide (0.014‐9 p.p.m. in the inhaled air) dose‐dependently and reversibly counteracted the effect of l‐NAME on pulmonary vascular resistance at normoxic ventilation, without affecting systemic blood pressure. In addition, the L‐NAME‐induced vasoconstriction was critically dependent on oxygen. Thus, during hypoxic ventilation (F1O2= 10%) the pulmonary vascular resistance was increased approximately four‐fold by the presence of L‐NAME (30 mg kg‐1), and increments in F,02 (21–100%) dose‐dependently and reversibly counteracted the effect of L‐NAME on pulmonary vascular resistance.

Taken together these findings demonstrate that inhalation of low doses of NO may act as a replacement when endogenous NO synthesis is inhibited, and that pulmonary vasoconstriction induced by NO synthesis inhibition is likely to be the result of interference with oxygen‐dependent regulatory mechanisms. Endogenous NO cooperates with oxygen to evoke a vasodilator component of the pulmonary hypoxic pressor response, balancing a hitherto unknown constrictor mechanism.
Histamine release and its effects in ischaemia‐reperfusion injury of the isolated rat heart
Authors: VALEN G. , KASZAKI J. , SZABO I. , NAGY S. , VAAGE J.
Published: December 2008

Histamine is released from the heart during ischaemia‐reperfusion injury. As histamine has cardiac effects, we investigated the role of histamine in ischaemia‐reperfusion injury of isolated rat hearts. A Langendorff‐model with 30 min global (37 oC) ischaemia followed by 60 min reperfusion was employed. The effects of ischaemia alone (n= 10, group 1.1+n = 10, group 2.1, 2 different series), and ischaemia with H1‐ and H2‐receptor blockade with cimetidine (10 μM, n= 10), chlorpheniramine (10 μm, n= 8), terfenadine (10 μM, n= 8), and promethazin (10 μM, n= 9), or both cimetidine and chlorpheniramine (n = 8), were studied. Histamine was measured in the coronary effluent and cardiac tissue of group 1.1. Release of histamine increased from 6.5 ± 1 pmol min‐1 before ischaemia to 19 ± 3 pmol min‐1 at the start of reperfusion. Ischaemia decreased left ventricular developed pressure to 18 ± 11 % (1.1) and 50 ± 11 % (2.1) of initial value (mean ± SEM) at the start of reperfusion. Left ventricular end‐diastolic pressure increased from 0 to 79 ± 8 mmHg (1.1) and 39 ± 9 (2.1) mmHg, while left ventricular systolic pressure was unchanged (101 ± 12% in 1.1 and 101 ± 10% in 2.1). Severe arrhythmias were induced in 90 (1.1) and 30 (2.1)% of the hearts, while coronary flow decreased during reperfusion. H2‐blockade did not modify the changes in left ventricular pressures, coronary flow, or heart rate induced by ischaemia. Three different Hj‐blockers increased left ventricular systolic pressure, inhibited the decrease of developed pressure, attenuated the increase of end‐diastolic pressure, and totally inhibited reperfusion arrhythmias. The effect of both blockers together was similar to that of H1‐blockers alone. Coronary flow was increased during reperfusion in two of the groups with Hj‐blocker compared with ischaemic controls. Increased release of histamine from ischaemic‐reperfused rat hearts concurred with depression of left ventricular function and arrhythmias during early reperfusion. Cardiac dysfunction during reperfusion was attenuated by three different Hj‐receptor blockers.
Inefficiency of intracerebroventricular ANP to alter haemodynamic, plasma vasopressin and renin responses to haemorrhage in sheep
Authors: GUNNARSSON U. , RUNDGREN M.
Published: December 2008

Whether intracerebroventricular (i.e.v.) infusion of atrial natriuretic peptide (human‐ANP, 1–28) 25 pmol min‐1 influences the tolerance to blood loss and haemorrhage induced cardiovascular, vasopressin and renin responses were studied in five conscious sheep. The i.e. v. infusion was started 60 min prior to a slow (0.7 ml kg‐1 min‐1) venous haemorrhage, was run concurrently with bleeding, and for 90 min thereafter. Venous blood was removed until the mean systemic arterial pressure suddenly fell to about 50 mmHg. There were no statistically significant differences in either the bleeding volume necessary to induce the sudden decrease in blood pressure, or in cardiovascular parameters measured by venous heart thermodilution catheterization, compared with control experiments with i.e.v. infusion of artificial CSF. The plasma protein and vasopressin concentrations and renin activity were unaffected by the i.c.v. infusion of ANP as were the changes in these parameters occurring during the subsequent haemorrhage. The same negative findings were obtained with a three times higher dose of ANP(l‐28) (75 pmol min‐1), tested in three of the animals. Thus the i.c.v. infusion of ANP(l‐28), in amounts expected to elevate the CSF concentration far above basal levels does apparently not influence normal blood pressure regulation or alter haemodynamic, vasopressin and renin responses to haemorrhage in conscious sheep.
Ionic selectivity of the mechano‐electrical transduction channels in the hair cells of the frog sacculus
Authors: Jørgensen F. , Kroese A. B. A.
Published: December 2008

In the isolated saccular macula of Ratio, esculenta extracellular hair cell receptor currents evoked by mechanical stimulation of the otolithic membrane were recorded under transepithelial voltage clamp conditions. The ionic selectivity of the mechano‐electrical transduction channels of the hair cells was determined by examining the effects of different concentrations of Ca2+ and K+ in the apical solution on the transepithelial voltage at which the extracellular receptor current was zero (Vrev).

Changing the concentration of Ca2+ from 0.26 mM to 0.026 and to 2.6 mM at a constant K+ concentration caused changes in Vrev of – 15 + 7 mV (mean±SD; n= 9) and 20±6mV (n= 13), respectively. The relative ionic permeabilities of the transduction channels were estimated from a modified Goldman, Hodgkin and Katz equation, assuming that 80% of the transepithelial resistance is located in the apical membranes of the hair cells. The permeability of the transduction channels for Ca2+ was found to be two orders of magnitude larger than that for K+. The measured effects on Vrev of changing the concentration of K+ at constant ionic strength and at different constant Ca2+ concentrations were well predicted by the same equation.

These results indicate that the transduction channels of the frog saccular hair cells are highly selective to Ca2+.
Regional cerebral oxidative and total glucose consumption during rest and activation studied with positron emission tomography
Authors: BLOMQVIST G. , SEITZ R. J. , SJÖGREN I. , HALLDIN C. , STONE‐ELANDER S. , WIDEN L. , SOLIN O. , HAAPARANTA M.
Published: December 2008

The relationship between regional oxidative and total rCMR in five healthy volunteers in activated and non‐activated areas of the brain has been investigated with positron emission tomography (PET). The tracers [l‐uC]‐D‐glucose and [2‐18F]2‐fluoro‐2‐deoxy‐D‐glucose were used. A previous study has shown that the former may be used to measure the rate of glucose oxidation while the latter tracer is used to measure the total rate of glucose consumption. Regional activation was performed (voluntary finger movements). Use of a computerized brain atlas enabled comparison between the regional oxidative and total rCMRglc in each volume element of the brain for the group of subjects.

The values of total and oxidative rCMRgle, when calculated for each volume element of the brain and displayed in a scatter plot, were found to be symmetrically grouped around a straight line which passes close to the origin. The slope of this line varied between the subjects. This indicates that, on the average, the fraction of non‐oxidative glucose utilization is constant within each subject, regardless of the value of rCMRgle and, further, that the fraction of non‐oxidative glucose utilization varies between subjects.

The total and oxidative CMRglc in the activated left hand area were 23.4 + 0.9% (mean + SEM) and 11.7 + 0.3%, respectively, higher than in the contralateral homologous non‐activated area. Our interpretation of the difference is that regional activation increases the fraction of non‐oxidative glucose consumption. This interpretation is supported by a previous PET study using [150]Oa, and by studies using MRS technique.
Effect of NPPB on chloride (CI) transport in distal colon of potassium (K+) adapted rats
Authors: VERON D. , MARTIN R. S. , ESCOBAR E. , TUFARO D. , VISCONTI P. , TEZON J. G. , ARRIZURIETA E. E.
Published: December 2008

Secondary hyperaldosteronism enhances the rate of K secretion in distal colon, at least in part, through the stimulation of Na+‐K+‐Cl‐ cotransport across the basolateral membrane. To maintain a constant intracellular Cl‐ activity an increase in Cl‐ transport out of the cell must be assumed. We explored, under amiloride 10‐4 M and short circuited conditions, conductive pathways for Cl‐ exit in the distal colon of K+‐adapted rats by means of a putative Cl‐ channel blocker, NPPB (5‐nitro‐2(3‐phenyl‐propylamino‐benzoate. Results prior to NPPB showed an increase in JClras after K+ loading from 5.84 + 0.66 to 8.33 ±0.86 and JCl8m from 4.77 ±0.55 to 8.16±0.96/μEq h“1 cm”2 (P < 0.001), when compared with controls. Net fluxes were not different between groups. Luminal NPPB in K+ adaptation resulted in a decrease of JClsm, from 7.85 ±1.5 to 6.69 ± 1.5 μEq h‐1 cm‐2 (P < 0.05). There were no changes in both unidirectional Cl‐ fluxes in controls under luminal NPPB and in potential difference (V) and short‐circuit current (I‐.) under any condition. Finally, K+ adaptation resulted in an increase of luminal cyclic AMP (cAMP) concentration (0.09 ±0.02 to 0.20 ±0.03 pmol 100 μ‐1, P < 0.05), when compared with control rats.

The data may suggest a transcellular recycling of Cl‐ and an activated NPPB inhibitable serosal to mucosal Cl‐ pathway on luminal membrane in the K+ adapted state, possibly mediated by an increase in cAMP production.
Skeletal muscle and skin as targets for powerful homeostatic vasomotor baroreflexes in humans during prolonged circulatory stress: a study on the innervated and nerve blocked forearm
Authors: EDFELDT H. , LUNDVALL J.
Published: December 2008

Flow (vascular resistance) was followed in the innervated and axillary nerve blocked arm during prolonged low to high and barely tolerated circulatory stress [15–85 mmHg LBNP (lower body negative pressure) for 10min; room temperature 24.8–25.7oC]. With intact innervation LBNP caused initial graded and potent forearm vasoconstriction. At low LBNP, however, there was soon significant and maintained partial (50%) abolition of the early response. At high LBNP, the initial striking vasoconstriction remained constant throughout 10 minofpronounced circulatory stress [marked tachycardia; fall in systolic pressure but mean arterial pressure (MAP) normal]. Flow decreased in steady state by 15 + 4, 38 + 5, 63 + 2 and by pronounced 78 + 3 % at 15, 40, 70, and 85 mmHg LBNP (resistance raised 27±7, 78+16, 192+18, and 387±55% above control), alterations ascribed to constriction in both muscle and skin. Comparison of LBNP responses with intact and blocked innervation revealed that the vasoconstriction was neurogenic with little or no humoral contribution. The overall observations show that under normal comfortable (thermoneutral) conditions the resistance vessels in muscle and skin, with haemodynamically important large tissue mass and great tolerance to even drastic and prolonged ischaemia, indeed are important targets in the homeostatic sympathetic control, especially when cardiovascular homeostasis is challenged by marked stress with urgent need for strong, maintained compensatory vasoconstriction. The study also demonstrated > three‐fold (4.1 +0.5 to 13.1 + 1.9 ml min‐1100 ml‐1) forearm flow increases upon blockade of resting nervous vasoconstrictor tone. It thus appears that the sympathetic nerves not only can elicit prominent and maintained baroreflex limb vasoconstriction but also that, in humans, reflex inhibition of resting tone might allow surprisingly large resistance decline.
CGRP (8–37) reduces the duration but not the maximal increase of antidromic vasodilation in dental pulp and lip of the rat
Authors: KEREZOUDIS N. P. , OLGART L. , EDWALL L.
Published: December 2008

In this study the newly developed blockers of substance P (CP‐96,345) and calcitonin gene‐related peptide (CGRP8 37) were used to examine whether substance P and CGRP are involved in the afferent nerve induced vasodilation in the rat lower incisor pulp and lip. Electrical stimulation of the inferior alveolar nerve (10 V, 2 ms, 10 Hz, 30 s) in the presence of phenoxybenzamine (3 mg kg1) induced an immediate vasodilation in the pulp and lip (52 and 186% increase in blood flow respectively, n = 12) with a long duration. Infusion of 2 mg kg‐1 CP‐96,345, a dose that inhibited the vasodilator effects of substance P (5–25 ng kg‐1) in oral tissues, did not have any effect on antidromic vasodilation in either tissue. After infusion of CGRP8 37 (0.3 mg kg‐1) the duration of the antidromic vasodilation in the pulp and lip was significantly reduced by 72 and 67% respectively (P < 0.05, n= 4), whereas the maximal increase of the response was unaffected. The blocking effect of the drug was short‐lasting. When combined infusions of CP‐96,345 and CGRP8 37 were given, a similar reduction in the duration of antidromic vasodilation in the pulp and lip occurred but in this case the amplitude of vasodilation in the pulp was reduced (from 35 + 9 to 12 + 3%, P < 0.05, n= 4). However, in the lip, the amplitude of vasodilation was not significantly reduced. The present findings indicate an involvement of CGRP in the mediation of the late phase of antidromic vasodilation in rat oral tissues and a role of substance P in the initiation of antidromic vasodilation in the incisor pulp.