bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of intravenous calcitonin gene‐related peptide (CGRP) and substance P on the blood–aqueous barrier in the rabbit
Authors: ANDERSSON S.E. , BILL A. 
Published: December 2008

The irritation response of the rabbit eye to trigeminal nerve stimulation, which includes a breakdown of the blood–aqueous barrier (BAB), seems to be due to the release of substance P (SP) and calcitonin gene‐related peptide (CGRP). In order to assess the relative importance of these two peptides for the barrier effect, and the role of arachidonic acid metabolites (AAM) in the response, we have studied the effects of intravenous injections of the peptides on the permeability of the blood vessels of the anterior uvea and the BAB using labelled albumins. At a dose of 120 pmol kg‐1 there was marked leakage of labelled albumin into the aqueous humour in animals under pentobarbital anaesthesia. The leakage was enhanced by sympathotomy. In conscious animals 5 pmol kg‐1 CGRP caused enhanced leakage from the blood vessels of the ciliary processes in those pre‐treated with biperiden in order to abolish the cholinergic vasoconstrictor tone in the anterior uvea. 24 and 120 pmol kg‐1 CGRP caused marked leakage of albumin and a breakdown of the epithelial part of the BAB. These effects were not modified by biperiden pre‐treatment, but markedly reduced by pre‐treatment with indomethacin. The protecting effect of indomethacin was lost when biperiden was given as well.SP did not cause a leakage with 5 nmol kg‐1 and only moderate leakage with 25 nmol kg‐1. This effect was abolished by pre‐treatment with indomethacin but not if indomethacin was combined with biperiden. The results indicate that the effects of CGRP and SP on the blood–aqueous barrier are dependent on the tone of the uveal blood vessels, and suggest that the two neuropeptides tend to release vasodilating AAM. CGRP is likely to play a much greater role than SP in the neurogenic breakdown of the blood–aqueous barrier since the two peptides seem to be released in comparable amounts.
Comparison of tactile discrimination ability of visually deprived and normal monkeys
Authors: CARLSON S. , TANILA H. , LINNANKOSKI I. , PERTOVAARA A. , KEHR A. 
Published: December 2008

The tactile discrimination ability of visually deprived and normal monkeys was tested to study whether loss of vision would improve the utilization of the tactual sense. Three normally sighted monkeys and three monkeys that had been deprived of vision during the first year of their life were trained in two tactile discrimination tasks by using a reward system in which the animals received a raisin or half a peanut under a correctly chosen wooden block. Discrimination was based on the gradual roughness or size of various blocks. When the monkeys had learned the tasks to the criterion, discrimination thresholds were determined.All monkeys improved their performance in both tasks with time, but no statistically significant differences between the performance of the two groups of monkeys were obtained. These results suggest that although the representation of the tactual sense in the cortical association areas has been shown to increase as a result of visual deprivation during the early sensitive period of life, increased representation does not improve the tactual discrimination ability of simple tactual stimuli.
Effects of growth hormone on skeletal muscle. II. Studies on regeneration and denervation in adult rats
Authors: ULLMAN M. , ALAMEDDINE H. , SKOTTNER A. , OLDFORS A. 
Published: December 2008

The effects of human recombinant growth hormone (rhGH) on regenerating skeletal muscle after ischaemic necrosis and on denervated skeletal muscle were studied in normal adult rats. One group of rats was treated with 4 IE rhGH daily by subcutaneous injections, while control rats were injected with saline. The treatment with rhGH resulted in increased levels of insulin‐like growth factor‐I (IGF‐I) in serum.Ischaemic necrosis was achieved in the extensor digitorum longus (EDL) muscle by cutting the supplying vessels and nerve fascicles at the entrance into the muscle. The wet weight and DNA:protein ratio in the regenerating muscle were determined 2 and 4 weeks after the operation. The weight of the regenerating muscles in the rats treated with rhGH during the period of study was larger than in the control rats, while the DNA:protein ratio did not differ significantly between the groups.Denervation of the EDL and soleus muscles followed by subsequent reinnervation was obtained by freezing the sciatic nerve with a forceps chilled in liquid nitrogen. Rats treated with rhGH during the period of denervation and reinnervation, i.e. during the 4 weeks after the freezing of the sciatic nerve, revealed increased weight of both the reinnervated and normal muscles compared to corresponding muscles of control rats.Denervation of the EDL and soleus muscles without subsequent reinnervation was achieved by cutting the sciatic nerve at the level of the thigh. Four weeks after denervation the muscles showed atrophy, mainly affecting type 2 fibres in the EDL muscle and both type 1 and type 2 fibres in the soleus muscle. Both denervated and normal muscles of rats treated with rhGH during the 4 weeks after denervation showed significantly higher weight than the corresponding muscles of control rats.It is concluded that rhGH administered to normal adult rats results in growth of normal muscle, increased growth of regenerating skeletal muscle after ischaemic necrosis and diminished atrophy of skeletal muscle after denervation.
Motor patterns of a fast voluntary postural task in man: trunk extension in standing
Authors: ODDSSON L. 
Published: December 2008

The co‐ordination between muscles controlling the primary movement and associated postural adjustments during fast trunk extension movements was studied in six male subjects. Myoelectrical activity (EMG) was recorded from antagonistic muscle pairs at the trunk, hip, knee and ankle. Horizontal displacements of the upper trunk, hip and knee were recorded with an opto‐electronic system (Selspot).A backward displacement of the trunk was accompanied by a forward displacement of the hip and knee. In general, the trunk started to move 30 ms before the hip and knee. Muscle activity first appeared in the ankle extensors (soleus/gastrocnemius) up to 150 ms prior to onset of prime mover muscles (trunk extensor, erector spinae; and hip extensors/knee flexors, hamstrings). This pre‐activation was seldom followed by any detectable ankle joint movement. Prime mover muscles were activated simultaneously followed by the hip extensor gluteus maximus. Time to activation of muscles braking the movement (rectus abdominis, rectus femoris and vastus lateralis) was correlated with the amplitude of the primary movement (r = 0.63–0.75, P 0.01). Onset of activity in vastus lateralis was highly correlated with the amplitude of the forward displacement of the knee (r= 0.93, P 0.01). An associated postural adjustment appeared as an ankle flexion accompanied by activity in the ankle flexor tibialis anterior, and often also in the ankle extensors. This co‐activation of antagonistic ankle muscles can under certain conditions have interesting functional implications for the control of posture.
Aldosterone secretion during acute respiratory acidosis and NH4CI‐induced metabolic acidosis in the goat
Authors: AUGUSTINSSON O. , FORSLID A. 
Published: December 2008

Acute respiratory acidosis was induced in goats by inhalation of 6% or 8% CO2 in air for 30 min. The lower CO2 concentration caused a significant rise in plasma Cortisol (PC), but had no appreciable influence upon plasma aldosterone (PA), and did not affect the arterial blood pressure (aBP).A more pronounced PC response was observed in association with the inhalation of 8% CO2, but also here without concomitant increase in PA. However, the aBP became elevated by about 30% during the CO2 exposure with a simultaneous increase in glomerular filtration rate and a water diuresis, suggesting that the release of arginine vasopressin temporarily became inhibited.It was confirmed that metabolic acidosis induced by duodenal NH4Cl administration is preceded by a transient rise in PA. Dexamethasone‐induced feedback inhibition of the ACTH secretion blocked the PA response, which possibly reflects NH4 ion stimulation of the ACTH release.The combined results of the CO2 and NH4Cl experiments seem to justify the conclusion that increases in PA seen in conjunction with acidosis do not reflect a direct hydrogen ion stimulation of the adrenal glomerulosa cells.
Electrical and mechanical responses to inhibition of cell respiration in vascular smooth muscle of the rat portal vein
Authors: EKMEHAG B.L. 
Published: December 2008

Metabolic regulation of contractility in vascular smooth muscle was studied in the spontaneously active rat portal vein using respiratory depression by cyanide (0.2–2.0 mm) as a model for tissue hypoxia. Intracellular recordings of electrical activity were done with concomitant registration of force development. Average membrane potential in the absence of cyanide was ‐ 61 ± 1 mV (n = 27). Addition of cyanide to normal Krebs solution resulted in a reduction of force amplitude and the number of action potentials per burst, with a relatively more pronounced effect on the mechanical activity. At moderate levels of inhibition of force amplitude the frequency of spontaneous bursts of action potentials transiently increased concomitant with a slight depolarization, but after prolonged (15–20 min) exposure to cyanide the membrane repolarized to the level prior to cyanide addition and the burst frequency decreased to be equal to or lower than that in the absence of cyanide. Higher concentrations of cyanide totally inhibited spontaneous mechanical and electrical activity. In contrast to the results with glucose, it was found that when p‐hydroxybutyrate was used as substrate the addition of 2 mm cyanide led to a marked hyperpolarization (13 ± 1 mV) after total inhibition of spontaneous activity. The hyperpolarization was not prevented by administration of 4‐aminopyridine (2.5 mm) or tetraethylammonium (44 mm) prior to the addition of cyanide. To investigate the effects of increased metabolic demand on the relation between force and membrane potential in cyanide‐treated muscle, high‐K+ (40 mm) contractures were studied. Contractures were associated with depolarization of 34 ± 3 mV (n = 5). I mm cyanide reduced the amplitude of the contractures to about 904 of control with a moderate reduction in the amount of depolarization (28 ± 1 mV, n= 5).Ihd is concluded that the decrease of mechanical activithd during respiratory inhibition may partly reflect a reduction in the number of spikes per burst but that other mechanisms, independent of membrane activity, also contribute to the inhibition. The increase of glycolysis during respiratory inhibition seems to prevent more pronounced changes in membrane potential.
Evidence for a countercurrent exchanger in the intestinal villi of suckling swine
Authors: BUSTAMANTE S. A. , JODAL M. , NILSSON N. J. , LUNDGREN O. , Köhlin Thorvald 
Published: December 2008

The possible existence of a countercurrent exchanger (multiplier) in the intestinal villi of suckling swine was investigated with three different methods:

Comparing venous appearance of oxygen and red cells ihd the mesenteric vein after close i. a. injection of a blood sample equilibrated with pure oxygen and containing methaemoglobinaemic red cells.
Determining sodium (μg) over protein (mg) ratios along villi.
Estimating tissue osmolality in the villus tissue frohd measurements of freezing‐point depression.

It was observed that oxygen appeared earlier than red cells in the mesenteric vein after i. a. injection. Furthermore, both the chemical measurements of sodium/protein ratios in the villi and the estimations of tissue osmolality indicate that there exists a gradient of osmolalities along the villus length, the villus tip being hyperosmolar as compared to the villus base. We conclude that a countercurrent exchanger (multiplier) exists in the villi of suckling swine. Its possible pathophysiological significance is discussed.,
Fluid balance and arterial blood pressure during intracarotid infusions of atrial natriuretic peptide (ANP) in water‐deprived goats
Authors: OLSSON K. , DAHLBORN K. , NYGREN K. , KARLBERG R. E. , ANDÉN N.‐E. , ERIKSSON L. 
Published: December 2008

The aim of this study was to investigate if atrial natriuretic peptide (ANP) plays a role in the control of water balance in goats and whether ANP affects the increase in mean arterial blood pressure (MAP) which accompanies drinking in water‐deprived animals. Bilateral intracarotid infusions werc made in female adult goats deprived of water for 48 h. ANP (1.5 μg min‐1, n = 5, or 4.75 μg min‐1, n = 5) was infused for 40 min. In control experiments isotonic saline (n= 7) was infused. The goats got access to water 35 min after the start of the infusions. During saline infusions they drank 2.9 ± 0.4 litres, during the low dose of ANP 1.9 ± 0.6 litres (ns. vs saline), and during the high dose of ANP 0.6 ± 0.2 litres (P < 0.01 vs saline). Plasma vasopressin conccntration did not change during saline infusions until after drinking, when it decreased. The vasopressin concentration increased in one goat after infusion of the low dose of ANP and in two goats after the high dose of ANP. The low dose of ANP caused no change in hlAP in four goats, but MAP dropped in the one in which vasopressin concentration increased. MAP fell in all goats infused with the high dose (P < 0.01), with the largest changes occurring in animals showing increased vasopressin concentration.Dhdring the act of drinking a temporary increase of MAP wahd observed when saline or the low dose of ANP was infused, hut this response was attenuated during infusions of the high dose. Plasma adrenaline concentration did nut change during the infusions until the animals drank, when it tended to increase. In connection with drinking, plasma noradrenaline concentration increased during both doses of ANP, hut not during saline. Mean plasma protein concentration increased by 16.5% and 12.5% during low and high doses of ANP respectively. The renal Na excretion increased by about three times during the low dose of ANP, and by about 10 times during the high dose of ANP. The K excretion increased for both doses of ANP.In conclusion, our results indicate that pharmacological doses of ANP are needed to attenuate water intake in dehydrated goats and that even such high doses do not decrease the plasma vasopressin Concentration. Instead, no change or a large increase in the vasopressin concentration was observed, the latter probably secondary to a fall in MAP. We have confirmed in goats that drinking in water‐deprived animals is accompanied by a transient increase in MAP, and hake shown that this increase is diminished when infusions of ANP cause reduced water consumption.,
Effects of intravenous calcitonin gene‐related peptide (CGRP) on local blood flow in the cat
Authors: ANDERSSON S. E. 
Published: December 2008

The effects of i. v. calcitonin gene‐related peptide (CGRP) on regional blood flow, vascular resistance, heart rate and cardiac output in cats were studied using the microsphere method. Three series of experiments were performed. In the first there was no pre‐treatment of the animals. In the second the animals were pre‐treated with indomethacin (5 mg kg‐1) in order to prevent the formation of prostaglandins. In the third series the ganglionic blocking agent hexamethonium bromide (80 mg kg‐1) was given in order to prevent autonomic reflexes. CGRP was given as an i. v. infusion. Two doses were tested in each series. Animals with no pre‐treatment and those pre‐treated with indomethacin received first 60 pmol kg‐1infused over a 5‐min period and then 180 pmol kg‐1infused over a 3‐min period. Animals under ganglionic blockade received the same dose as the total infusions in the other series (240 pmol kg‐1) infused over 4 min and a second infusion of 1.2 nmol kg‐1over 5 min.Vhdsodilatory effects were observed in most of thhd tissues tested, but there were marked differences in sensitivity. The most sensitive tissues seemed to be the lacrimal, submandibular and parotid glands, the nictitating membrane, the tongue and the gallbladder. The patterns of sensitivity were similar in all the series, indicating that neither prostaglandins nor autonomic reflexes were involved in the effects.In experiments with animals under ganglionic blockade, an increase in blood pressure, concomitant with an increase in heart rate, was seen 5 min after the infusions ended. Thus, it is likely that the peptide exerts a direct positive chronotropic effect on the feline heart.,
Beta‐adrenoceptor agonists and hypoxia in sheep fetuses
Authors: DAGBJARTSSON A. , HERBERTSSON G. , STEFANSSON T. S. , KJELD M. , LAGERCRANTZ H. , ROSEN K. G. 
Published: December 2008

Sheep fetuses, near term, were studied to test the influence of a tocolytic β agonist, terbutaline, on fetal responses to hypoxia. After fetal exteriorization the drug was administered intravenously to the mother in three different doses: The max group comprised 11 ewes receiving 67–134 μg min‐1. Seven ewes were given 30 μg min‐1 and eight ewes were infused with 10 μg min‐1. Seventeen fetuses served as controls. Hypoxia was induced by intermittent complete occlusions of the maternal abdominal aorta. Maternal terhutaline levels were high (range 50–748 nmol I‐1) in the max group and the 30–μg group, whereas those in the 10–μg group were in the clinical range (range 11–58 nmol I‐1).Fhdtuses in the max and 30–μg groups reacted thd moderate hypoxia with excessive responses of heart rate, blood pressure myocardial contractility and ST waveform changes and a 50%) mortality rate during severe hypoxia as compared with 12% in the control animals. Ten pg min‐1 did not decrease the survival but caused an increase in myocardial workload and a negative energy balance during severe hypoxia.,
Potential‐dependent potassium currents in the slowly adapting stretch receptor neuron of the crayfish
Authors: RYDQVIST R. , ZHOU J.‐Y. 
Published: December 2008

The outward current in the stretch receptor neuron of the crayfish Pucifastacus leniusculus was analysed using a two‐micropipette potential‐clamp technique. The outward current was shown to be carried by K+. When the sodium‐dependent inward current was blocked by tetrodotoxin a fast‐activating potassium current was revealed, resembling the delayed rectifier. The time‐course of activation (Tn) was dependent on potential and had a mean value of 1 ms at potential steps of to mV. The activation followed a second‐order process according to the Hodgkin‐Huxley model. The potential dependence of activation (nα) followed a sigmoid curve, nα= 1/{1 +exp [(E ‐ En) / a]} with half‐maximal activation potential En= ‐31 mV and a= ‐13 mV.When long pulses were applied, the potassium current showed marked inactivation with a fast time constant of 0.5 s that was potential independent and a slow component that was slightly potential dependent. The minimum value for the slow time constant was 4 s for steps to about o mV. The potential dependence of inactivation followed a sigmoid function kα= 1/{1 +exp [(E ‐ Ek)/a]} with Ek= ‐ 39 mV and a= 11 mV. No transient potassium outward current (IA) was found in the crayfish stretch receptor neuron. In experiments on tail currents after depolarizing potential steps of different duration, it was found that the reversal potential changed in the positive direction when the duration of the pre‐pulse increased. This could be due to K+ accumulation in a space close to the neuronal membrane. The potassium current during depolarizing potential steps in the crayfish stretch receptor is similar to the delayed current found in other cells, for example the frog myelinated nerve, but different from many other invertebrate neurons.
Electrical stimulation of the gastrocnemius muscle in the spontaneously hypertensive rat increases the pain threshold: role of different serotonergic receptors
Authors: HOFFMANN P. , SKARPHEDINSSON J. O. , DELLE M. , THORÉN P. 
Published: December 2008

In a previous study, prolonged low‐frequency muscle stimulation in the hind leg of the fully conscious spontaneously hypertensive rat (SHR) was shown to induce a long‐lasting reduction of blood pressure. It was also shown that opioid and serotonergic (5‐HT) systems were involved. More recently, we have shown that the 5‐HT1 receptors are involved in the post‐stimulatory decrease in blood pressure.In the present study, the influence of this type of muscle stimulation on the pain threshold was investigated. Pain perception was measured as the squeak threshold to noxious electric pulses. After cessation of the stimulation, an analgesic response was elicited within 60 min and peak analgesia developed after 120 min, being 139 ±10% (P < 0.01) of the prestimulatory control value. The increased pain threshold lasted for another 2 h.One group of SHR was pretreated with PCPA, a serotonin synthesis blocker, which completely abolished the post‐stimulatory analgesia. To analyse further the involvement of different serotonin systems, drugs with selective affinity for 5‐HT receptors were used. In one group a prestimulatory dose of metitepine maleate (a 5‐HT1&2 receptor antagonist) abolished the post‐stimulatory elevation of the pain threshold. The prolonged analgesic response was still present after prestimulatory treatment with ritanserin or ICS 205–930 (5‐HT2 and 5‐HT3 blocking agents respectively).In another group of experiments, the serotonin receptor antagonists were administered post‐stimulation to animals with fully elicited analgesia. None of the antagonists used could reverse the elevation of pain threshold towards prestimulatory levels.Thus, intact 5‐HT systems were necessary to elicit the analgesia to muscle stimulation and the response was mediated by the 5‐HT1 receptor. However, the results indicate that serotonin is not required to maintain the analgesia once it has been elicited.
Uptake of ascorbic acid by freshly isolated cells and secretory granules from the intermediate lobe of ox hypophyses
Authors: ZHOU A. , MATSUMOTO T. , FARVER O. , THORN N. A. 
Published: December 2008

Mechanically isolated cells from the intermediate lobe of ox hypophyses contained 40.6 ± 3.7 nmol mg‐1 protein (mean ± SE, n = 5) of ascorbic acid. They accumulated radioactivity time dependently, on incubation with L‐[14C]ascorbic acid in an ionic medium dominated by NaCl. No definite saturation of uptake occurred when mechanically isolated cells were incubated with increasing ascorbic acid concentrations up to 0.6 mM. But if such cells were purified on a Percoll gradient, a clear saturation of uptake could be observed. Acetylsalicylic acid reduced the uptake markedly. When cells loaded with L‐[14C]ascorbic acid were homogenized and placed on a Percoll gradient, the radioactivity was recovered in several subcellular fractions. Decrease of the Na+ concentration or presence of ouabain in the medium did not cause noticeable changes in uptake by non‐purified cells, whereas uptake by purified cells was clearly sodium‐dependent. Phloridzin inhibited uptake.Secretory granules from pars intermedia contained 40.0 ± 3.8 nmol mg‐1 protein of ascorbic acid (mean ± SE, n = 3) and could accumulate L‐[14C]ascorbic acid rapidly in a KCl‐dominated medium. The uptake was not saturable with ascorbic acid concentration and was not influenced by the presence of 1 mM ATP + 1 mM Mg2+ in the medium.The concentration of copper and iron in isolated cells was comparable to that in isolated neurohypophysial nerve terminals, whereas the concentration of zinc was considerably higher in the pars intermedia cells. The concentration of Cu, Zn, Fe and Co in secretory granules from pars intermedia was higher than in secretory granules from neurohypophyses.