bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Reducing Submandibular Blood Flow on Secretory Responses to Parasympathetic Stimulation in Anaesthetized Cats
Authors: Hanna S. J. , Brelen M. E. , Edwards A. V. 
Published: May 2004

SUMMARYSubmandibular secretory responses to stimulation of the parasympathetic chorda‐lingual nerve were investigated in five anaesthetized cats before, during and after withdrawal of blood (ca 20 ml kg−1) in order to investigate the consequences of a reduced blood flow through the gland. Stimulation at different frequencies (2, 4, 6 and 8 Hz) evoked a frequency‐dependent increase in the flow of submandibular saliva, sodium concentration, electrolyte and protein output. When the blood pressure was reduced (by about 50%) there was a significant reduction in submandibular blood flow and the secretion of both saliva and protein during stimulation. Under each set of conditions the flow of saliva was linearly related to the blood flow through the gland. It is concluded that submandibular secretory responses to electrical stimulation of the parasympathetic innervation can be significantly attenuated when the blood flow through the gland is reduced under the conditions employed in this study.
Vagotomy Suppresses Cephalic Phase Insulin Release in Sheep
Authors: Herath C. B. , Reynolds G. W. , Mackenzie D. D. S. , Davis S. R. , Harris P. M. 
Published: May 2004

SUMMARYThe effect of selective vagotomy of the abomasum, pylorus, duodenum and liver on insulin release during the cephalic phase of digestion was investigated in wethers and lactating ewes. Electrical stimulation of the cervical vagus nerves was carried out to test the completeness of the vagotomies performed. In experiment 1, using wethers, the abomasal, pyloric and duodenal branches (ADV; n= 7) or the hepatic, abomasal, pyloric and duodenal branches (HADV; n= 10) of the ventral and/or dorsal vagus nerves were cut; a third group of wethers underwent sham‐operation (SO; n= 8). In experiment 2, vagotomy (ADV; n= 5) or sham‐operations (SO; n= 5) were carried out in lactating ewes. Jugular blood was drawn before and after presentation of food for glucose and insulin determination (experiments 1 and 2) or before, during and after the electrical stimulation of the peripheral ends of the cut cervical vagus nerves in randomly selected lactating ewes (experiment 3: ADV = 3, SO = 3) and wethers (experiment 4: ADV = 4, HADV = 4, SO = 4), for determination of insulin only. Presentation of food caused an immediate and significant (P < 0.05) rise in plasma insulin levels in SO animals compared with ADV or HADV wethers (experiment 1) or ADV ewes (experiment 2) without any significant change in blood glucose concentrations. In comparison with the SO group the baseline‐corrected areas under the insulin response curve were significantly (P < 0.05) smaller for the respective vagotomized groups for periods 1‐2, 2‐4 and 4‐6 min (experiment 1) and 1‐2 and 2‐4 min (experiment 2) after presentation of food. Total area under the response curve for 10 min was significantly (P < 0.05) lower (experiment 1) and tended (P < 0.10) to be lower (experiment 2) for the vagotomized groups compared with that of the control groups. Direct electrical stimulation of the cervical vagus nerves raised plasma insulin concentrations to significantly (P < 0.05) higher levels in the SO ewes but not in the ADV ewes (experiment 3). It was also evident that in experiment 1, HADV did not have any additive effect over that achieved by ADV alone. These results indicate that the vagal innervation of the gut mediates insulin release during the cephalic phase of feeding in sheep. It is concluded that insulin secretion from the pancreatic β‐cells in response to either food‐related reflex activation of the vagal nuclei in the hypothalamus or direct cervical vagus nerve stimulation is mediated through the vagal efferent fibres carried in the abomasal, pyloric and duodenal branches of the vagus nerves in sheep.
L‐Arginine Transport at the Fetal Side of Human Placenta: Effect of Aspirin in Pregnancy
Authors: Acevedo C. G. , Rojas S. , Bravo I. 
Published: May 2004

SUMMARYl‐Arginine transport by the fetal side of human placenta was investigated through the characterization of l‐[3H]arginine uptake in isolated perfused cotyledon. Competitive inhibition experiments suggest the presence of at least two transport systems: a Na+‐independent, pH‐insensitive system inhibitable by cationic amino acids, similar to system y+, and a Na+‐dependent system which recognizes both cationic and neutral amino acids only in the presence of Na+, i.e. a Bo,+‐like system. The kinetic analysis of l‐arginine uptake in the presence of Na+ revealed that the process is mediated by saturable components: a high‐affinity system (Km= 167 ± 18.0 μM; Vmax= 0.174 ± 0.012 μmol min−1) and a low‐affinity carrier (Km= 980 ± 112 μM; Vmax= 1.60 ± 0.12 μmol min−1). In the absence of Na+, l‐arginine uptake was fitted by one model with a Michaelis‐Menten constant of 200 ± 24.8 μM. These results suggest that the high‐affinity component corresponds to the Na+‐independent system y+, whilst the low‐affinity system may represent the activity of the Na+‐dependent Bo,+ transporter. Kinetic studies in placentae taken from aspirin‐treated pregnancies showed that l‐arginine is transported with a significantly higher affinity (Km= 42.5 ± 5.7 μM), but with a lower capacity (Vmax= 0.064 ± 0.003 μmol min−1) than in the non‐treated group. The latter finding suggests that aspirin would facilitate the uptake of the NO precursor only at very low arginine concentrations.
Effects on L‐Type Calcium Current of Agents Interfering with the Cytoskeleton of Isolated Guinea‐Pig Ventricular Myocytes
Authors: Pascarel Caroline , Brette Fabien , Cazorla Olivier , Le Guennec Jean‐Yves 
Published: May 2004

SUMMARYWe studied the effects of an external acute 10 min application of cytoskeletal interfering agents on cardiac L‐type calcium current (ICa,L). We found that colchicine, taxol and cytochalasin D had no direct effect on the L‐type calcium channel as indicated by the absence of effect on voltage‐dependent parameters. Phalloidin induced a shift in the I‐V curve which renders it difficult to use in excitation‐contraction coupling studies. Microfilaments of actin did not seem to regulate cardiac ICa,L as indicated by the lack of effect of cytochalasin D on ICa,L amplitude and inactivation kinetics. On the contrary, microtubules seem to be involved in the calcium‐dependent inactivation of ICa,L. This involvement might be direct, i.e. a physical link between the microtubules and some part of the channel protein, or it could be indirect, i.e. the calcium chelating properties and physical obstacle of microtubules in the space between the sarcolemma and the SR.
Training‐Induced Alterations in Lactate Dehydrogenase Reaction Kinetics in Rats: A Re‐Examination
Authors: Favero Terence G. , Stavrianea Stasinos S , Klug Gary A. 
Published: May 2004

SUMMARYThe kinetics and the isozyme composition of lactate dehydrogenase (LDH) were measured in rat plantaris muscle during a 26 week endurance‐training program. Alterations in the LDH isozyme pattern were detectable after 6 weeks as the percentage of the M4 isozyme was reduced from 89 to 76% and the total percentage of M subunits compared with H subunits declined by 8%. At 16 weeks, M4 accounted for only 62% of the total. The replacement of M with H subunits continued when training was prolonged as M4 represented only 52% of the total isozymes at 26 weeks. Conversely, training for 6 and 16 weeks produced no changes in either Vmax or Km. At 26 weeks, these values declined for both the forward (pyruvate to lactate) and backward reactions. The rate constants for both reactions were also reduced. These data suggest that changes in LDH isozyme pattern do not contribute significantly to the enhancement of lactate oxidation that may occur after training. They also suggest that the functional significance of alterations in LDH structure and/or function are best determined from analysis of the overall reaction kinetics as opposed to individual characteristics such as the isozyme pattern, Km or Vmax.
Ion Currents in Smooth Muscle Cells from Human Small Bronchioles: Presence of an Inward Rectifier K+ Current and Three Types of Large Conductance K+ Channel
Authors: Snetkov V. A. , Ward J. P. T. 
Published: May 2004

SUMMARYBronchoconstriction of small bronchioles plays a major role in the increase in airway resistance following agonist challenge. There is evidence that the airway smooth muscle (ASM) of small bronchioles differs functionally from that in larger airways. Little is known however about the electrophysiology of small bronchioles. Ion currents were therefore studied in airway smooth muscle cells freshly dissociated from human intralobular bronchioles, with a diameter between 0·3 and 1·0 mm. As previously reported for human large airways, the major outward current in these cells was due to activity of large conductance K+ (BK) channels, with a relatively minor component due to a voltage‐gated delayed rectifier current (IDR), which was only observed in ∼30% of cells. Three distinct types of iberiotoxin‐ and TEA‐sensitive large conductance K+ channel contributed to large conductance K+ current (IBK). These included a highly voltage‐ and Ca2+‐sensitive 200 pS channel previously reported in human large airways, and two smaller channels of 150 and 100 pS previously seen only in human fetal or cultured ASM. In contrast to large airways, ASM cells from bronchioles also demonstrated a voltage‐gated inward rectifier current (IIR). IIR was activated by hyperpolarisation below the K+ equilibrium potential and could be blocked by submillimolar concentrations of Cs+ or Ba2+, and partially by physiological concentrations of Na+. Corresponding single channels with a conductance of ∼17 pS could also be recorded in the cell‐attached configuration. A small voltage‐independent current was also observed which was resistant to classic K+ and Cl− channel blockers but which could be abolished by replacement of Na+ with the impermeant cation N‐methyl‐D‐glucamine (NMDG+). Corresponding non‐selective single channels of ∼20 pS could be seen in inside‐out mode. These results demonstrate that ASM from small bronchioles differs in terms of ion currents and channels from ASM derived from large airways, with possible implications for function.
Inhibition of Baroreflex Vagal Bradycardia by Selective Stimulation of Arterial Chemoreceptors in Rats
Authors: Murata Tomohiro , Otsu Kazuya , Kobayashi Masayoshi , Nosaka Shoichiro 
Published: May 2004

SUMMARYWe reported recently that hypoxia inhibits baroreflex vagal bradycardia (BVB) in rats and that this inhibition persists following chemoreceptor denervation. However, since it is possible that hypoxia also affects the central processing of chemoreceptive input, the existence of chemoreceptor‐mediated inhibition of BVB cannot be ruled out. Therefore, we have studied whether selective chemoreceptor activation affects BVB in normoxic conditions. In pentobarbital‐urethane‐anaesthetized, succinylcholine‐immobilized, artificially ventilated rats, BVB was provoked by electrical stimulation of the aortic depressor nerve. Arterial chemoreceptors were selectively activated by intracarotid injection of a minute amount of sodium cyanide. Cyanide injection consistently increased blood pressure while changing heart rate variably. BVB was inhibited in a dose‐dependent manner. This inhibition, as well as changes in blood pressure and heart rate, was abolished following transection of the carotid sinus nerve (CSN) ipsilateral to the injection. Spinal cord transection at the C2 level did not affect the inhibition. On the other hand, intracarotid cyanide had no effect on bradycardia elicited by electrical stimulation of a peripheral cut end of the cervical vagus nerve. We conclude that chemoreceptor activation definitely inhibits BVB and that this inhibition is mediated by the CSN, and predominantly occurs in the central nervous system. The possibility is suggested that severe hypoxia suppresses not only BVB but also the chemoreceptor‐mediated inhibition of BVB, both via the direct, central action.
Effect of Captopril in L‐Name‐Induced Hypertension on the Rat Myocardium, Aorta, Brain and Kidney
Authors: Bernátová Iveta , Pechánová Ol'Ga , Simko Fedor 
Published: May 2004

SUMMARYLong‐term administration of NG‐nitro‐L‐arginine methyl ester (L‐NAME) induces development of hypertension and hypertrophy of the left ventricle in rats. The aim of the present study was to demonstrate the effect of chronic L‐NAME treatment on DNA and RNA concentration, and protein synthesis in the rat heart, aorta, brain and kidney and to determine the effect of angiotensin converting enzyme (ACE) inhibitor captopril on these potential alterations. Four groups of rats were investigated: control, L‐NAME (40 mg kg−1 day−1), captopril (100 mg kg−1 day−1), and L‐NAME (40 mg kg−1 day−1) + captopril (100 mg kg−1 day−1). NO synthase activity in the heart, aorta, brain and kidney was found to be decreased in the L‐NAME group. In the group of rats treated with L‐NAME + captopril, captopril did not affect NO synthase inhibition. Captopril, however, completely prevented development of hypertension and left ventricular hypertrophy in this group. In the L‐NAME group, DNA and RNA concentrations, as well as [14C]leucine incorporation, were significantly increased in all the tissues investigated. In the L‐NAME + captopril group, captopril completely prevented the enhancement of DNA and RNA concentrations and [14C]leucine incorporation in all tissues compared to the L‐NAME group. Moreover, a significant decrease in RNA concentration and [14C]leucine incorporation below control values was found in the captopril group as well as the L‐NAME + captopril group in all the tissues investigated. We conclude that captopril prevented the development of hypertension and increase in nucleic acid concentration and protein synthesis in the heart, aorta, brain and kidney in rats treated with L‐NAME + captopril. However, this protective effect of captopril was not associated with increased NO synthase activity in this model of hypertension.
Exhaled Nitric Oxide Increases During High Frequency Oscillatory Ventilation in Rabbits
Authors: Artlich Andreas , Adding Christofer , Agvald Per , Persson Magnus G. , Lönnqvist Per‐Arne , Gustafsson Lars E. 
Published: May 2004

SUMMARYThis study compared the effects of high frequency oscillatory ventilation (HFOV) and intermittent mandatory ventilation (IMV) on the homeostasis of nitric oxide (NO) in the lower respiratory tract of healthy rabbits. The mechanisms underlying a putative stretch response of NO formation in the airways were further elucidated. Male New Zealand White rabbits were anaesthetized, tracheotomized and ventilated with IMV or HFOV in random order. Total NO excretion increased from 9·6 ± 0·8 nl min−1 (mean ±s.e.m.) during IMV to 22·6 ± 2·7 nl min−1 during HFOV (P < 0·001). This increase was not explained by changes of functional residual capacity (ΔFRC). A similar increase in NO excretion during HFOV was seen in isolated buffer‐perfused lungs under constant circulatory conditions (P < 0·05, n= 4). Intratracheal mean CO2 and NO concentrations, measured at 2·5, 5, 7·5 and 10 cm below tracheostomy, increased significantly with increasing distance into the lung during both IMV and HFOV (P < 0·001 for each comparison). At every intratracheal location of the sampling catheter, particularly low in the airways, both CO2 and NO concentrations were significantly higher during HFOV than during IMV (P < 0·01 for each comparison). We conclude that HFOV increases pulmonary NO production in healthy rabbits. Increased stretch activation of the respiratory system during HFOV is suggested as a possible underlying mechanism. The increase in mean airway NO concentrations may have biological effects in the respiratory tract. Whether it can account for some of the benefits of HFOV treatment needs to be considered.
Temperature Effect on the Rates of Isometric Force Development and Relaxation in the Fresh and Fatigued Human Adductor Pollicis Muscle
Authors: de Ruiter C. J. , Jones D. A. , Sargeant A. J. , de Haan A. 
Published: May 2004

SUMMARYThe purpose of the present study was to investigate the effect of temperature on the rates of isometric force development and relaxation in electrically activated fresh and fatigued human adductor pollicis muscle. Following immersion of the lower arm for 20 min in water baths of four different temperatures, muscle temperatures were approximately 37, 31, 25 and 22°C. Maximal isometric force was reduced by 16.8 ± 1.5% at 22°C. The stimulation frequency‐force and ‐rate of force development relationships were shifted to the left at lower temperatures. Q10 values for the maximal rates of force development and relaxation, and the times for 100 to 50% and 50 to 25% force relaxation, were about 2.0 between 37 and 25°C and about 3.8 between 25 and 22°C. However, the time for 50 to 25% force relaxation had a relatively high Q10 value between 25 and 22°C (6.9) and this parameter also appeared to be more sensitive to fatigue compared to the other indices of relaxation. Nevertheless, the effect of fatigue on all parameters decreased with cooling over the entire (37‐22°C) temperature range.
Bidirectional Neurones in the Cervical Enlargement of the Cat Spinal Cord with Axons Descending to Sacral Segments and Ascending to the Cerebellum and the Lateral Reticular Nucleus
Authors: Grottel K. , Krutki P. , Mrówczynski W. 
Published: May 2004

SUMMARYNeurones located in cervical segments (C6/C7) of the spinal cord were investigated electrophysiologically in cats deeply anaesthetized with α‐chloralose. Extracellular recordings of antidromic action potentials were performed in order to establish whether long descending propriospinal neurones projecting to sacral segments could have collateral axonal branches ascending to supraspinal centres. The effects of stimulation of the lateral reticular nucleus (LRN) and the inferior cerebellar peduncle (restiform body, RB), as well as the thirteenth thoracic (Th13) and sacral (S1/S2) segments of the spinal cord were tested in 93 cells. Two main groups of cells were identified: 54% of the total sample were classified as purely propriospinal and 46% as bidirectional neurones. Various patterns of projections, as well as the ipsi‐, contra‐ or bilateral courses of axons in the lateral funiculi of the spinal cord, enabled several types of neurones to be distinguished within the above groups. Comparison between particular types showed no significant difference with respect to location in the grey matter (predominantly Rexed's laminae VII‐VIII) and the conduction velocities of descending axons. However, the mean axonal conduction velocities of branches ascending to LRN and/or RB were significantly lower in comparison to those measured for spinal collaterals. The hypothetical function of the neurones examined is discussed. Since the same information can be conveyed simultaneously by these branching neurones to lower spinal segments and supraspinal centres, an integrative role in the system of motor control is suggested.
Adrenocortical Response Profiles to Corticotrophin‐Releasing Hormone and Adrenocorticotrophin Challenge in the Chronically Catheterized Adult Guinea‐Pig
Authors: Liu Li , Matthews Stephen G. 
Published: May 2004

SUMMARYThe guinea‐pig has been used extensively to investigate adrenal steroidogenesis. However, very little is known about adrenocortical responses to corticotrophin‐releasing hormone (CRH) and adrenocorticotrophin (ACTH) in this species, in vivo. In the present study, we have developed a stress‐free sampling system, in the chronically catheterized adult guinea‐pig, that has allowed us to investigate basal and activated adrenocortical activity. Indwelling carotid artery and jugular vein catheters were surgically implanted into female guinea‐pigs (n= 5). Each animal was treated with vehicle, human CRH (0·2 or 2 μg kg−1) and ACTH1‐24 (0·2 or 2 μg kg−1), and serial plasma samples removed for analysis of ACTH and cortisol concentrations by radioimmunoassay. There was no effect of serial sampling on pituitary‐adrenocortical activity, indicating that the animals remain in an unstressed state. Basal plasma ACTH and cortisol concentrations were 703·9 ± 24·5 pg ml−1 and 117·9 ± 5·2 ng ml−1, respectively. Both CRH and ACTH significantly increased adrenocortical activity in a dose‐dependent manner. ACTH (2 μg kg−1) was the most potent activator leading to plasma cortisol concentrations of 647 ± 116 ng ml−1. In conclusion, we have shown that basal plasma cortisol concentrations in the guinea‐pig are low compared to those obtained in previous studies by cardiac puncture or following decapitation. However, plasma ACTH concentrations are high compared to other species. We have also shown that human CRH and ACTH1‐24 act as potent activators of the guinea‐pig pituitary‐adrenocortical axis, leading to response profiles consistent with mild cortisol resistance.
Membrane Oestrogen Receptors on Rat Pituitary Tumour Cells: Immuno‐Identification and Responses to Oestradiol and Xenoestrogens
Authors: Watson Cheryl S. , Campbell Celeste H. , Gametchu Bahiru 
Published: May 2004

SUMMARYOur laboratory has identified plasma membrane oestrogen receptors on a GH3/B6 rat pituitary tumour cell line and several sublines which produce rapid (within minutes), non‐genomic responses to oestrogens. Oestrogen receptors have been identified by their binding to nine different antibodies (Abs) which together recognize at least seven epitopes on the oestrogen receptor‐α. GH3/B6/F10 cells, a membrane oestrogen receptor‐enriched subline, elevate intracellular calcium levels in response to 10 nM oestradiol. Prolactin release in these cells is triggered by both 1 pM and 1 nM oestradiol and diethylstilbestrol (DES). A membrane oestrogen receptor‐α immunocyto‐chemical signal rapidly disappears (at 3 min) and reappears (at 12‐15 min) when 1 nM oestradiol, 10 nM diethylstilbestrol, or 10 nM nonylphenol is applied to the cells. This suggests that both oestrogens and xenoestrogens can utilize this alternative pathway for oestrogenic action. Xenoestrogens, which have so far shown weak effects in genomic assay systems, should now be retested for activity in eliciting membrane‐initiated oestrogenic responses.