bluuebunny/crossref_metadata_2025 huggingface dataset:
Localization of cAMP‐ and aldosterone‐induced K+ secretion in rat distal colon by conductance scanning
Authors: Grotjohann I. , Gitter A. H. , Köckerling A. , Bertog M. , Schulzke J. D. , Fromm M.
Published: September 2004

Aldosterone‐ and adrenaline‐induced K+ secretion were investigated in rat late distal colon using conductance scanning and Ussing chamber techniques. K+ secretion was unmasked by the K+ channel blocker tetraethylammonium (TEA). Electrogenic Na+ absorption was inhibited by amiloride. Rb+ net fluxes consistently measured about 80 % of K+ secretion estimated using change in short‐circuit current (ΔISC) measurements.

Partial block of K+ absorption by mucosal ouabain did not change TEA‐sensitive K+ secretion. Thus, K+ absorption and K+ secretion are not coupled.

Additivity of Rb+ fluxes as well as ΔISC caused by 3 nM aldosterone (6 h in vitro incubation) and, subsequently, adrenaline suggested additivity of aldosterone‐induced and cAMP‐mediated K+ secretion in the presence of amiloride.

Conductance scanning under control conditions revealed a small TEA‐sensitive K+ conductivity in surface epithelium (0.3 ± 0.2 mS cm−2) but not in crypts, as well as a small basal K+ secretion in surface epithelium (ΔISC= 0.3 μmol h−1 cm−2), which increased during sham incubation.

Aldosterone (3 nM, 6 h in vitro incubation) resulted, after correction for the basal K+ secretion, in a K+ secretion of ΔISC= 0.9 μmol h−1 cm−2. Aldosterone induced a TEA‐sensitive conductivity of 1.1 ± 0.3 mS cm−2 in surface epithelium, but not in crypts.

Adrenaline (5 μm) caused, in fresh tissue, a K+ secretion of ΔISC= 1.2 μmol h−1 cm−2 and equal conductivity changes in crypts (0.7 ± 0.2 mS cm−2) and surface epithelium (0.7 ± 0.1 mS cm−2).

We conclude that K+ secretion induced by aldosterone in physiological concentration is restricted to surface epithelium, whereas cAMP‐mediated K+ secretion is located equally in crypts and surface epithelium.
Electrical characteristics and responses to jejunal distension of neurons in Remak's juxta‐jejunal ganglia of the domestic fowl
Authors: Smith Terence K. , Lunam Christine A.
Published: September 2004

Remak's nerve is a ganglionated nerve trunk found only in birds that runs parallel to the gut from the duodenal‐jejunal junction to the cloaca. We report the first electrophysiological characterization of these neurons and their responses to gut distension.

A segment of chicken jejunum with attached Remak's nerve was pinned in an electrophysiological chamber. Neurons in Remak's ganglia were impaled with microelectrodes. The adjacent segment of gut was distended with fluid.

One hundred and thirty neurons were characterized into three electrophysiological classes: (i) tonic neurons (74 %) fired action potentials spontaneously (frequency 3.5 Hz) and continuously (up to 40 Hz) throughout a depolarizing current pulse; (ii) AD neurons (22 %) fired a brief burst of action potentials (1‐10), which were followed by a prolonged after‐depolarization (AD) of duration 2.8 ± 0.3 s; and (iii) phasic neurons (4 %) fired an initial burst of action potentials followed by an after‐hyperpolarization (duration, 520.0 ± 32.0 ms). Tetrodotoxin (1 μM) abolished action potentials in tonic and AD neurons as well as the after‐depolarization.

Spontaneous fast excitatory postsynaptic potentials (FEPSPs) occurred in all classes of neurons; they were not observed, however, in ganglia isolated from the jejunum.

Intracellular injection of biocytin revealed that neurons could be characterized into four morphological classes. Tonic neurons, which had long and extensive dendritic trees, were Remak's Type I, II and IV neurons. AD neurons also comprised Remak's type II neurons. Phasic neurons were Remak's Type III neurons. Most neurons had axons that projected orally along Remak's nerve.

Distension of the jejunum evoked FEPSPs and action potentials in tonic neurons, and repetitive bursts of action potentials (1‐4) followed by an after‐depolarization in AD neurons. All responses to distension were blocked by hexamethonium (300 μM) and tetrodotoxin (1 μM).

In conclusion, neurons in Remak's juxta‐jejunal nerve appear to regulate gut motility. Three distinct electrophysiological classes of neurons were observed, all of which appear to be activated by distension sensitive cholinergic intestinofugal neurons in the jejunum.
Effect of hydrogen peroxide and dithiothreitol on contractile function of single skeletal muscle fibres from the mouse
Authors: Andrade Francisco H. , Reid Michael B. , Allen David G. , Westerblad Håkan
Published: September 2004

We used intact single fibres from a mouse foot muscle to study the role of oxidation‐reduction in the modulation of contractile function.

The oxidant hydrogen peroxide (H2O2, 100‐300 μM) for brief periods did not change myoplasmic Ca2+ concentrations ([Ca2+]i) during submaximal tetani. However, force increased by 27 % during the same contractions.

The effects of H2O2 were time dependent. Prolonged exposures resulted in increased resting and tetanic [Ca2+]i, while force was significantly diminished. The force decline was mainly due to reduced myofibrillar Ca2+ sensitivity. There was also evidence of altered sarcoplasmic reticulum (SR) function: passive Ca2+ leak was increased and Ca2+ uptake was decreased.

The reductant dithiothreitol (DTT, 0.5‐1 mM) did not change tetanic [Ca2+]i, but decreased force by over 40 %. This was completely reversed by subsequent incubations with H2O2. The force decline induced by prolonged exposure to H2O2 was reversed by subsequent exposure to DTT.

These results show that the elements of the contractile machinery are differentially responsive to changes in the oxidation‐reduction balance of the muscle fibres. Myofibrillar Ca2+ sensitivity appears to be especially susceptible, while the SR functions (Ca2+ leak and uptake) are less so.
The influence of nerves on the secretion of immunoglobulin A into submandibular saliva in rats
Authors: Carpenter G. H. , Garrett J. R. , Hartley R. H. , Proctor G. B.
Published: September 2004

The influence of sympathetic and parasympathetic nerve stimulations on salivary secretion of immunoglobulin A (IgA) was studied in the submandibular glands of anaesthetized rats by stimulating the nerve supplies with bipolar electrodes.

Although the flow of saliva from sympathetically stimulated glands was only 23 % of that from parasympathetically stimulated glands the output of IgA was over 2‐fold greater. This difference was attributable to influences of the nerves on IgA secretion through the epithelial cell polymeric immunoglobulin receptor‐mediated pathway, as Western blotting with specific antibodies to IgA and secretory component revealed that secretory IgA (SIgA) dominated in all saliva samples.

Study of saliva secreted in sequential periods of nerve stimulation or following rest pauses suggested that SIgA secretion occurred in the absence of stimulation but this was upregulated 2.6‐ and 6‐fold by parasympathetic and sympathetic nerve stimulations, respectively, compared with the calculated unstimulated rate.

The IgA content of extensively stimulated glands was 77 % of levels in unstimulated contralateral control glands despite a secretion into saliva equivalent to almost 90 % of the glandular IgA content. The IgA may be synthesized and secreted by glandular plasma cells at a rate which exceeds demand and/or such synthesis may be upregulated by nerve impulses.

The results indicate that salivary secretion of SIgA is upregulated by nerve impulses and that sympathetic nerves induce a greater effect than parasympathetic nerves.
Regulation of intracellular pH during H+‐coupled oligopeptide absorption in enterocytes from guinea‐pig ileum
Authors: Hayashi Hisayoshi , Suzuki Yuichi
Published: September 2004

The mechanisms for regulating the intracellular pH (pHi) level during oligopeptide absorption were investigated in the enterocytes from guinea‐pig ileum by identifying the acid‐base transporters responsible for extruding H+ that enters the cell through the H+‐oligopeptide cotransporter.

The pHi level was measured by microfluorometry in an isolated villus tip loaded with the pH‐sensitive fluoroprobe 2′7’‐bis(2‐carboxyethyl)‐5(6)‐carboxyfluorescein (BCECF). The oligopeptide‐induced increment in the short‐circuit current (Isc) was determined in a mucosal sheet in Ussing chambers. A CO2/HCO3−‐buffered solution was used.

The superfusion of glycylglycine (Gly‐Gly, l0 mM) caused a decrease in pHi level, which returned to the basal level after removing Gly‐Gly. This pHi recovery was strongly dependent on extracellular Na+. Amiloride partially inhibited the pHi recovery rate with an IC50 value of 41 μM, the maximum inhibition being approximately 70 %. In the presence of amiloride at its maximum concentration (0.3 mM), the addition of 0.6 mM DIDS caused a further decrease, but did not abolish the pHi recovery rate. In the absence of CO2 and HCO3−, the pHi recovery was almost completely abolished by 0.3 mM amiloride.

The intracellular H+ accumulation induced by 0.3 mM amiloride or by 0.6 mM DIDS, as estimated from the pHi decrease and buffer capacity, was significantly greater during Gly‐Gly superfusion than under resting conditions.

The increase in Isc induced by luminal glycylproline was attenuated by either removing serosal Na+ or by adding 0.5 mM amiloride or 0.6 mM DIDS to the serosal side.

We conclude that both Na+‐dependent, amiloride‐sensitive acid extrusion, probably by the Na+‐H+ exchanger, and Na+‐ and HCO3−‐dependent, DIDS‐sensitive acid extrusion, possibly by the Na+‐HCO3− cotransporter, are involved in extruding H+ that enters cells by the H+‐oligopeptide cotransport. It is proposed that these acid extrusion (or base loading) mechanisms are present in the basolateral membrane and are important for maintaining oligopeptide absorption, as well as the acid extrusion mechanism in the apical membrane.
Effect of nitric oxide on single skeletal muscle fibres from the mouse
Authors: Andrade Francisco H. , Reid Michael B. , Allen David G. , Westerblad Håkan
Published: September 2004

Single skeletal muscle fibres from a mouse foot muscle were used to investigate the effects of nitric oxide on contractile function.

We measured force production and myoplasmic free Ca2+ concentration ([Ca2+]i) in single fibres exposed to the nitric oxide donors S‐nitroso‐N‐acetylcysteine (SNAC) and nitroprusside.

The nitric oxide donors reduced myofibrillar Ca2+ sensitivity, whereas [Ca2+]i transients were increased during submaximal tetani. Force was largely unchanged. SNAC did not change maximum shortening velocity, the rate of force redevelopment, or force production at saturating [Ca2+]i.

The guanylyl cyclase inhibitor LY83583 increased tetanic [Ca2+]i but had no effect on Ca2+ sensitivity. LY83583 did not prevent the decrease in myofibrillar Ca2+ sensitivity in response to SNAC. The oxidizer sodium nitrite increased tetanic [Ca2+]i and decreased myofibrillar Ca2+ sensitivity.

We conclude that under our experimental conditions nitric oxide impairs Ca2+ activation of the actin filaments which results in decreased myofibrillar Ca2+ sensitivity.
Vestibulocollic reflexes evoked by short‐duration galvanic stimulation in man
Authors: Watson S. R. D. , Colebatch J. G.
Published: September 2004

Vestibular‐dependent responses in leg muscles following transmastoid galvanic stimulation have been well characterized. Here we describe the properties of vestibulocollic responses evoked by transmastoid galvanic stimulation.

In twelve healthy human subjects we examined the averaged responses in unrectified sternocleidomastoid (SCM) EMG evoked by transmastoid stimulation using current pulses of 4 mA intensity and 2 ms duration. In ten subjects we also examined the effects of unilateral vestibular stimulation with the indifferent electrode at the vertex. In further experiments we studied the effects of different levels of background muscle activation, head position, current intensity and current duration. We compared these responses with click‐evoked vestibulocollic responses in SCM.

A clearly defined biphasic response, beginning with a surface positivity, was recorded in the SCM ipsilateral to the side of cathode placement in all subjects. We refer to this as the p13/n23 [g] (galvanic) response, given the close similarity, in terms of waveform and latencies, to the previously described click‐evoked p13/n23 vestibulocollic response. The amplitude of this response was linearly related to background muscle activation, current intensity and current duration, but independent of head position. Unilateral galvanic stimulation revealed the p13/n23 [g] response to be solely generated by the cathode.

A biphasic response beginning with a surface negativity (n12/p20 [g]) contralateral to the cathode was seen in all subjects and was generated by both the cathode contralaterally and the anode ipsilaterally.

Both the p13/n23 [g] and n12/p20 [g] potentials were abolished by selective vestibular nerve section and unaffected by severe sensorineural deafness.

We conclude that galvanic stimulation evokes short‐latency vestibulocollic reflexes. These vestibulocollic reflexes have properties that are distinct from those described for galvanic‐evoked vestibular reflexes in leg muscles, and which may be related to their differing physiological roles.
The regulation of lung liquid absorption by endogenous cAMP in postnatal sheep lungs perfused in situ
Authors: Stephens R. H. , Benjamin A. R. , Walters D. V.
Published: September 2004

The lungs of two groups of lambs aged 0–2 weeks and 6–12 weeks were artificially perfused in situ with warmed and oxygenated sheep blood. The airspaces of the lungs were filled with liquid containing an impermeant tracer to allow estimation of net liquid movement across the pulmonary epithelium at rest and after administration of certain drugs.

Dibutyryl cAMP (dB‐cAMP, 10−4 M) stimulated the rate of lung liquid (LL) absorption in the lungs of four neonatal sheep aged 9–12 days, from −1.43 ± 0.2 to −2.75 ± 0.3 ml h−1 (kg body wt)−1 (P < 0.05, comparison of regression lines by Student's t test), but had no effect in four juvenile sheep aged 6–12 weeks (P > 0.10).

Theophylline, a non‐selective phosphodiesterase (PDE) inhibitor (5 × 10−4 M), increased LL absorption from a resting rate of −1.55 ± 0.3 to −3.62 ± 0.5 ml h−1 kg−1 in the lungs of four sheep aged 1–12 days and from −1.47 ± 0.3 to −3.73 ± 0.4 ml h−1 kg−1 in four sheep aged 6–12 weeks (P < 0.05, Student's paired t test).

The β‐adrenergic antagonist sotalol (10−4 M) reduced LL absorption rate from −1.47 ± 0.1 to −1.22 ± 0.1 ml h−1 kg−1 (P < 0.01) in the lungs of four sheep aged 4–13 days, while theophylline given after sotalol had no effect. In four sheep aged 6–12 weeks, sotalol had no effect on LL absorption rate, whereas theophylline given after sotalol increased LL absorption rate from −1.06 ± 0.1 to −1.92 ± 0.2 ml h−1 kg−1 (P < 0.05).

The A1/A2 purinergic receptor blocker 7‐(β‐chloroethyl) theophylline (CET; given at 5 × 10−6 M and 10−4 M) had no effect on LL absorption rate in the lungs of four sheep aged 6–12 weeks, confirming that theophylline produced its effect of increasing LL absorption by inhibiting PDE hydrolytic activity.

The selective PDE IV (cAMP‐specific) PDE inhibitor rolipram was given in the perfused lungs of seven sheep aged 6–12 weeks at doses between 10−8 and 10−4 M, increasing LL absorption rate at concentrations of 10−6 M and above; the half‐maximal effective concentration was estimated to be 5.9 × 10−7 M.

Rolipram (10−5 M) increased LL absorption rate from −1.99 ± 0.2 to −3.18 ± 0.5 ml h−1 kg−1 in the perfused lungs of four sheep aged 6–11 days, and from −1.21 ± 0.4 to −3.45 ± 0.3 ml h−1 kg−1 in the perfused lungs of four sheep aged 6–12 weeks (P < 0.05). Sotalol (10−4 M) reduced LL absorption rate from −3.39 ± 0.8 to −2.18 ± 0.4 ml h−1 kg−1 (P < 0.05) in four sheep aged 10–14 days, while rolipram given after sotalol had no effect. In four sheep aged 6–12 weeks, sotalol had no effect on resting LL absorption rate, whereas rolipram given after sotalol increased absorption rate from −1.27 ± 0.1 to −2.02 ± 0.6 ml h−1 kg−1 (P < 0.05).

We conclude that cAMP mediates a component of LL absorption postnatally, and that while β‐adrenergic stimulation was the sole source of endogenous cAMP in neonates, this was not the case in juveniles, in whom cAMP originated, at least in part, from other sources.
Induction of histidine decarboxylase in skeletal muscle in mice by electrical stimulation, prolonged walking and interleukin‐1
Authors: Endo Yasuo , Tabata Takayoshi , Kuroda Hiroshi , Tadano Takeshi , Matsushima Kouji , Watanabe Makoto
Published: September 2004

In normal non‐exercised skeletal muscles in mice, the activity of histidine decarboxylase (HDC), the enzyme which forms histamine, was very low.

HDC activity in the quadriceps femoris muscle was markedly elevated following contractions evoked by even a few minutes of direct electrical stimulation, peaking at 8‐12 h following contraction lasting 10 min, and gradually decreasing during the 24 h following contraction. The elevation in HDC activity depended on the duration and strength of stimulation.

Direct electrical stimulation induced a quantitatively similar elevation of HDC activity in the muscles of mast‐cell‐deficient mice (W/Wv mice).

Prolonged walking at a speed of 6 m min−1 for up to 6 h with a 30 min rest period at 3 h also elevated muscle HDC activity, the magnitude of the elevation being related to the duration of the walking. Repeated exercise (training) for several days diminished the elevation of muscle HDC activity induced by walking. In contrast, starvation augmented the elevation of muscle HDC activity induced by walking.

Intraperitoneal injection of interleukin‐1β (IL‐1β) also elevated muscle HDC activity in a dose‐dependent manner, as little as 1 μg kg−1 of IL‐1 producing a significant elevation of muscle HDC activity.

IL‐1β was immunohistochemically detected in normal non‐exercised quadriceps femoris muscle. We could not detect a significant increase in IL‐1β after exercise in the muscle or in serum: it may be below the level of detection.

On the basis of these results, together with those reported previously and the known actions of histamine, we propose that an elevation of HDC activity and generation of histamine occur in skeletal muscle following muscle contraction possibly as a result of induction by IL‐1β and that the histamine may be involved in fatigue in skeletal muscle as part of a defence mechanism preventing damage to the muscle.
Energy metabolism of the gastrocnemius and soleus muscles during isometric voluntary and electrically induced contractions in man
Authors: Ratkevicius Aivaras , Mizuno Masao , Povilonis Edward , Quistorff Bjørn
Published: September 2004

Phosphocreatine (PCr) and intracellular pH detected by 31P NMR in the gastrocnemius and soleus muscles were evaluated in order to compare the anaerobic ATP costs of voluntary and electrically induced exercise. Continuous isometric contraction at 40 % of maximum force and repeated isometric contractions at approximately 75 % of maximum force (contraction plus relaxation period of 0.5 s plus 2 s) were studied.

Anaerobic ATP turnover in soleus and gastrocnemius muscles was slower during continuous voluntary contraction than during continuous electrically induced contraction (0.36 ± 0.04 versus 0.63 ± 0.05 mmol (kg wet wt)−1 s−1, P < 0.05, in soleus; 0.19 ± 0.03 versus 1.04 ± 0.04 mmol (kg wet wt)−1 s−1, P < 0.001, in gastrocnemius).

There was no significant difference in anaerobic ATP turnover between voluntary and electrically induced exercise when repeated brief contractions were performed (0.22 ± 0.05 and 0.30 ± 0.04 mmol (kg wet wt)−1 s−1, respectively, for the soleus muscle and 0.57 ± 0.03 and 0.66 ± 0.07 mmol (kg wet wt)−1 s−1, respectively, for the gastrocnemius muscle).

During continuous voluntary contraction, in contrast to continuous stimulated contraction, anaerobic ATP turnover was slower (P < 0.05) in the gastrocnemius than in the soleus muscle, which also showed a higher electromyogram amplitude (41.1 ± 1.1 % of maximum) than the medial gastrocnemius muscle (21.4 ± 3.6 % of maximum, P < 0.001).

Anaerobic ATP turnover was faster (P < 0.05) in the gastrocnemius than in the soleus muscle during brief voluntary and brief electrically induced contractions.

The results show that the anaerobic ATP costs were higher for electrically induced exercise than for voluntary exercise when continuous submaximal contraction was performed but not when brief high‐intensity contractions were performed. The gastrocnemius muscle contributes to total force production relatively less than the soleus muscle during continuous voluntary plantar flexion at 40 % of the maximum voluntary contraction.
Stimulation of pulmonary rapidly adapting receptors by inhaled wood smoke in rats
Authors: Lai C. J. , Kou Y. R.
Published: September 2004

The stimulation of pulmonary rapidly adapting receptors (RARs) by wood smoke was investigated. Impulses from seventy RARs were recorded in fifty‐nine anaesthetized, open‐chest and artificially ventilated rats; responses to delivery of 6 ml of wood smoke into the lungs were studied in sixty‐one receptors whereas responses to histamine (10 or 100 μg kg−1, i.v.) were studied in the other nine.

Delivery of wood smoke stimulated fifty‐two of the sixty‐one RARs studied. When stimulated, an intense burst of discharge was evoked within 1 or 2 s of smoke delivery. This increased activity quickly peaked in 1‐3 s (Δ= 15.8 ± 1.6 impulses s−1; n= 61; mean ± s.e.m.), then declined and yet remained at a level higher than the baseline activity. The mean duration of the stimulation was 25.1 ± 2.7 s. In contrast, smoke delivery did not affect tracheal pressure.

Peak responses of RARs to wood smoke were partially reduced by removal of smoke particulates and were largely attenuated by pretreatment with dimethylthiourea (DMTU, a hydroxyl radical scavenger), indomethacin (Indo, a cyclo‐oxygenase inhibitor), or both DMTU and Indo (DMTU + Indo). Conversely, the peak responses of RARs were not significantly affected by pretreatment with isoprenaline (a bronchodilator) or vehicle for these chemicals. Additionally, pretreatment with DMTU, Indo, or DMTU + Indo did not significantly alter the RAR sensitivity to mechanical stimulation (constant‐pressure lung inflation; 20 cmH2O).

Of the nine RARs tested, six were stimulated by histamine and their sensitivity to this chemical irritant was not altered by pretreatment with DMTU + Indo.

The results suggest that both the particulates and gas phases are responsible for, and both the hydroxyl radical and cyclo‐oxygenase products are involved in, the stimulation of RARs by wood smoke. Furthermore, changes in lung mechanics following smoke delivery are not the cause of this afferent stimulation.
The effect of transcranial magnetic stimulation on the soleus H reflex during human walking
Authors: Petersen Nicolas , Christensen Lars O. D. , Nielsen Jens
Published: September 2004

The effect of transcranial magnetic stimulation (TMS) on the soleus H reflex was investigated in the stance phase of walking in seventeen human subjects. For comparison, measurements were also made during quiet standing, matched tonic plantar flexion and matched dynamic plantar flexion.

During walking and dynamic plantar flexion subliminal (0.95 times threshold for a motor response in the soleus muscle) TMS evoked a large short‐latency facilitation (onset at conditioning‐test interval: −5 to −1 ms) of the H reflex followed by a later (onset at conditioning‐test interval: 3–16 ms) long‐lasting inhibition. In contrast, during standing and tonic plantar flexion the short‐latency facilitation was either absent or small and the late inhibition was replaced by a long‐lasting facilitation.

When grading the intensity of TMS it was found that the short‐latency facilitation had a lower threshold during walking than during standing and tonic plantar flexion. Regardless of the stimulus intensity the late facilitation was never seen during walking and dynamic plantar flexion and the late inhibition was not seen, except for one subject, during standing and tonic plantar flexion.

A similar difference in the threshold of the short‐latency facilitation between walking and standing was not observed when the magnetic stimulation was replaced by transcranial electrical stimulation.

The lower threshold of the short‐latency facilitation evoked by magnetic but not electrical transcranial stimulation during walking compared with standing suggests that cortical cells with direct motoneuronal connections increase their excitability in relation to human walking. The significance of the differences in the late facilitatory and inhibitory effects during the different tasks is unclear.
Vasodilator component in sympathetic nerve activity destined for the skin of the dorsal foot of mildly heated humans
Authors: Sugenoya Junichi , Iwase Satoshi , Mano Tadaaki , Sugiyama Yoshiki , Ogawa Tokuo , Nishiyama Tetsunari , Nishimura Naoki , Kimura Tomomi
Published: September 2004

Skin sympathetic nerve activity (SSNA) was recorded in seven male subjects from the peroneal nerve by microneurography, and the temporal correspondence of spontaneously occurring SSNA bursts with vasodilatation and sweating responses on the dorsal foot was studied during a mild body heating at rest.

Some SSNA bursts were followed by a sweat expulsion with a latency of 2.4 ± 0.4 s, and some bursts by a transient vasodilatation with a latency of 2.2 ± 0.4 s (means ± s.d.). SSNA bursts followed both by a sweat expulsion and by a vasodilatation response (Type 1), those followed only by a sweat expulsion (Type 2) and those followed only by a vasodilatation response (Type 3) were 70 %, 10 % and 1 % of the total bursts examined, respectively.

For Type 1 bursts, there was a significant, but weak linear relationship among the burst amplitude, the amplitude of the corresponding vasodilatation and the amplitude of the corresponding sweat expulsion.

It was concluded that SSNA contains vasodilatory activity which is synchronous with sudomotor nerve activity. The results suggest that such vasodilatory activity contributes to sustaining the sweat gland function by supplying sufficient blood.
Antidiuretic hormone and angiotensin II plasma concentrations in febrile Pekin ducks
Authors: Gray David A. , Maloney Shane K.
Published: September 2004

The objective of this study was to determine the changes in plasma concentrations of the hormones arginine vasotocin (AVT) and angiotensin II (AII) associated with lipopolysaccharide (LPS)‐induced fever in Pekin ducks.

LPS, intravenously administered into conscious birds at doses of 1, 10 and 100 μg kg−1, caused dose‐dependent and monophasic increases in body temperature, with fever index values of 3.5, 7.0 and 10.6, respectively.

Plasma AVT concentrations also increased with the progression of the fever, with the largest elevation (from 8.4 ± 1.6 to 25.2 ± 3.2 pg ml−1; means ± s.e.m., n= 7) being caused by the highest dose of LPS.

Plasma AII concentrations did not significantly change from basal values (mean of 45.5 ± 6.3 pg ml−1 for all groups) during the acute phase of the fever response.

The osmotic status of the birds, as indicated by plasma osmolality and electrolyte values, did not significantly change in any of the experimental animals.

The elevation of AVT in avian fever leads to speculation about a possible antipyretic action of this hormone, which would have particular relevance to understanding the evolution of fever.
Galvanic vestibular stimulation modulates voluntary movement of the human upper body
Authors: Cauquil Alexandra Séverac , Day Brian L.
Published: September 2004

We have investigated whether vestibular information plays a role in the control of voluntary movement of the upper body. Movement consisted of a lateral tilt of the upper body in the frontal plane through an angle of about 8 deg. The influence of vestibular input was assessed from the effect of long duration (3–6 s), low‐intensity (0.7 mA) galvanic vestibular stimulation (GVS) applied at different times relative to the movement.

GVS always produced a tilt of the body in the frontal plane but the response was larger and more prolonged when the onset of stimulation coincided with the cue to start moving compared with when it was applied some seconds after movement onset (i.e. while the subject was stationary in a tilted posture).

When the stimulus began 2 s before the voluntary movement the response consisted of two distinct components separated in time, one that was linked to the onset of GVS and another that was linked to onset of the voluntary movement. The large response observed when GVS onset coincided with the movement cue resembled the sum (after realignment in time) of these two separate components.

We suggest that these two components of the response to GVS relate to two different uses of vestibular information for whole‐body control: first, to help maintain balance of the body, and second, to help guide and improve the accuracy of voluntary movements involving motion of the head in space.
Intracellular and extracellular skeletal muscle triglyceride metabolism during alternating intensity exercise in humans
Authors: Rico‐Sanz Jesús , Hajnal Joseph V. , Thomas E. Louise , Mierisová Ŝárka , Ala‐Korpela Mika , Bell Jimmy D.
Published: September 2004

The main purpose of this study was to evaluate non‐invasively with magnetic resonance spectroscopy (1H‐MRS) changes in the concentrations of intracellular (IT) and extracellular (between muscle fibres) triglycerides (ET) in skeletal muscles of trained males (age range: 24–38 years) during two standard exercise protocols of alternating velocities.

Protocol 1 consisted of locomotion in a shuttle manner between two lines 30 m apart at four different velocities (1, 2, 3 and 4 m s−1) which were alternated every minute in a standard routine for 90 min, whereas Protocol 2 included locomotion between two lines 20 m apart at only three velocities (2, 2.7 and 4 m s−1) until volitional exhaustion. The heart rate during both protocols fluctuated between 140 and 200 beats min−1.

Using pre‐exercise muscle water to quantify individual total creatine (TCr) that was utilized as an internal standard and assuming that TCr does not change during exercise, subjects’ mean IT and ET concentrations in soleus (Sol) muscle before Protocol 1 (n= 8) were 45.8 ± 4.8 mmol (kg dry weight)−1 (mean ± s.e.m.) and 93.1 ± 14.1 mmol (kg dry weight)−1, respectively. After the exercise, the concentrations of IT and ET were not significantly different from the values at rest. Before Protocol 2 (n= 4), IT concentrations in Sol, gastrocnemius (Gast) and tibialis (Tib) muscles were 46.4 ± 13.6, 35.0 ± 12.1 and 23.1 ± 4.8 mmol (kg dry weight)−1, respectively, and were not affected by the exhaustive exercise. The ET concentrations in Sol, Gast and Tib were 136.4 ± 38.1, 175.3 ± 86.5 and 79.3 ± 20.0 mmol (kg dry weight)−1, respectively, and they did not change significantly after exhaustion.

The study showed that levels of IT and ET were not affected by alternating intensity exercise to fatigue. This suggests that IT and ET in human Sol, Gast and Tib muscles do not contribute significantly to the energy turnover during this type of exercise. Energy for this type of muscle contraction may arise primarily from muscle phosphocreatine (PCr) and glycogen breakdown, circulating glucose and fatty acids from triglycerides other than those encountered within and between muscle cells.
In vivo observations of the intramural arterioles and venules in beating canine hearts
Authors: Hiramatsu Osamu , Goto Masami , Yada Toyotaka , Kimura Akihiro , Chiba Yoko , Tachibana Hiroyuki , Ogasawara Yasuo , Tsujioka Katsuhiko , Kajiya Fumihiko
Published: September 2004

To evaluate the effects of cardiac contraction on intramyocardial (midwall) microvessels, we measured the phasic diameter change of left ventricular intramural arterioles and venules using a novel needle‐probe videomicroscope with a CCD camera and compared it with the diameter change in subepicardial and subendocardial vessels.

The phasic diameter of the intramural arterioles decreased from 130 ± 79 μm in end‐diastole to 118 ± 72 μm (mean ± s.d.) in end‐systole by cardiac contraction (10 ± 6 %, P < 0.001, n= 21).

The phasic diameter in the intramural venules was almost unchanged from end‐diastole to end‐systole (85 ± 44 vs. 86 ± 42 μm, respectively, 2 ± 6 %, n. s., n= 14).

Compared with intramural vessels, the diameters of subendocardial arterioles and venules decreased by a similar extent (arterioles: 10 ± 8 %, P < 0.001; venules: 12 ± 10 %, P < 0.001) from end‐diastole to end‐systole, respectively, whereas the diameter of the subepicardial arterioles changed little during the cardiac cycle, and subepicardial venule diameter increased by 9 ± 8 % (P < 0.01) from end‐diastole to end‐systole. These findings are consistent with our previous report.

We suggest that the almost uniform distribution of the cardiac contractility effect and arteriolar transmural pressure between the subendocardium and the midmyocardium, which together constitute the systolic vascular compressive force, accounts for the similarity in the arteriolar diameter changes in both myocardial layers. The smaller intravascular pressure drop from deep to superficial myocardium relative to the larger intramyocardial pressure drop explains the difference in the phasic venular diameter changes across the myocardium.
Direct evidence for the partial reflection of hyaluronan molecules by the lining of rabbit knee joints during trans‐synovial flow
Authors: Scott D. , Coleman P. J. , Mason R. M. , Levick J. R.
Published: September 2004

In synovial joints hydraulic and turnover studies indicate that the synovial lining may partially reflect large macromolecules like hyaluronan, despite discontinuities in the lining cell layer. The reflection hypothesis was tested directly in the present study.

Solutions of high molecular weight hyaluronan were infused at controlled pressures into the cavity of rabbit knees under anaesthesia, at concentrations of 0.2 g l−1 (n= 5), 2 g l−1 (n= 5) and 4 g l−1 (n= 6). Time‐averaged trans‐synovial flows were 9.6, 4.8 and 2.9 μl min−1, respectively. After 5 h infusion the intra‐articular fluid was mixed and sampled. Hyaluronan concentration was determined by size‐exclusion chromatography.

In all sixteen experiments the hyaluronan concentration in the aspirate was greater than that in the infusate (P= 0.0001, Student's paired t test). The increases averaged 2.28 ± 0.04 times at high filtration rates (0.2 g l−1 infusates; mean ± s.e.m.), 1.60 ± 0.09 times at intermediate filtration rates (2 g l−1 infusates) and 1.26 ± 0.08 times at low filtration rates (4 g l−1 infusates).

Between 48 and 95 % of the hyaluronan in the filtrand was retained in the joint cavity. The greater retention at 2 g l−1, viz.95 %, than at 0.2 g l−1, viz.48 %, was attributed to interactions between overlapping molecular domains in the more concentrated solution.

It is concluded that synovial interstitial matrix can partially reflect hyaluronan molecules, and thus conserve intra‐articular lubricant.
Habituation of the initial responses to cold water immersion in humans: a central or peripheral mechanism?
Authors: Tipton Michael J. , Eglin Clare M. , Golden Frank St C.
Published: September 2004

The initial respiratory and cardiac responses to cold water immersion are thought to be responsible for a significant number of open water deaths each year. Previous research has demonstrated that the magnitude of these responses can be reduced by repeated immersions in cold waterwhether the site of habituation is central or peripheral.

Two groups of subjects undertook two 3 min head‐out immersions in stirred water at 10 °C of the right‐hand side of the body (R). Between these two immersions (3 whole days) the control group (n= 7) were not exposed to cold water, but the habituation group (n= 8) undertook a further six 3 min head‐out immersions in stirred water at 10 °C of the left‐hand side of the body (L).

Repeated L immersions reduced (P < 0.01) the heart rate, respiratory frequency and volume responses. During the second R immersion a reduction (P < 0.05) in the magnitude of the responses evoked was seen in the habituation group but not in the control group, despite both groups having identical skin temperature profiles.

It is concluded that the mechanisms involved in producing habituation of the initial responses are located more centrally than the peripheral receptors.
A defect in skeletal muscle sodium channel deactivation exacerbates hyperexcitability in human paramyotonia congenita
Authors: Featherstone David E. , Fujimoto Esther , Ruben Peter C.
Published: September 2004

Paramyotonia congenita (PC) is a human hereditary disorder wherein missense mutations in the skeletal muscle sodium channel lead to cold‐exacerbated muscle hyperexcitability. The most common site for PC mutations is the outermost arginine of domain IV segment 4 (human R1448, rat R1441).

We examined the rat homologues of two PC mutants with changes at this site: R1441P and R1441C. The R→P mutation leads to the most clinically severe form of the disease. Since PC has so far been attributed to defects in fast inactivation, we expected the R→P substitution to have a more dramatic effect on fast inactivation than R→C. Both mutants (R1441P and R1441C), however, had identical rates and voltage dependence of fast inactivation and activation.

R1441P and R1441C also had slowed deactivation, compared with wild‐type, raising the possibility that slowed deactivation, in combination with defective fast inactivation, might be a contributing cause of paramyotonia congenita. Furthermore, deactivation was slower in R1441P than in R1441C, suggesting that the worse phenotype of the human R→P mutation is due to a greater effect on deactivation, and supporting our hypothesis that slowed sodium channel deactivation contributes to paramyotonia congenita.

We show that the downstroke of the muscle action potential produced a sodium tail current, and thus slowed deactivation opposes repolarization and therefore leads to hyperexcitability. Hyperexcitability due to slowed deactivation, which has previously been overlooked, also predicts the temperature sensitivity of PC, which has otherwise not been adequately explained.
Regulation of distal nephron K+ channels (ROMK) mRNA expression by aldosterone in rat kidney
Authors: Beesley A. H. , Hornby D. , White S. J.
Published: September 2004

The expression of ROMK mRNA isoforms in rat kidney was measured using competitive polymerase chain reaction. Under basal conditions the expression of ROMK2 and 3 mRNA was significantly higher than that of ROMK1 or 6.

Administration of aldosterone for a period of 1 week significantly increased the mRNA expression not only of the α1‐subunit of the Na+‐K+‐ATPase, but also of ROMK2, 3 and 6.

These data not only provide evidence that ROMK K+ channels may be involved with mineralocorticoid‐sensitive K+ secretion in the distal nephron, but also demonstrate for the first time that ROMK6 may be involved in this process.
Colour processing in the primate retina: recent progress
Authors: Martin Paul R.
Published: September 2004

Colour vision in the majority of humans is trichromatic, relying on a comparison of the quantal absorption in three different types of cone photoreceptors. The first steps in this comparison process take place at an early level of the visual system, in the retina. This topical review will highlight recent experiments which have advanced our understanding of how cone signals are compared to generate cone‐opponent responses in the primate retina.
Modulation of guinea‐pig cardiac L‐type calcium current by nitric oxide synthase inhibitors
Authors: Gallo Maria Pia , Ghigo Dario , Bosia Amalia , Alloatti Giuseppe , Costamagna Costanzo , Penna Claudia , Levi Renzo C.
Published: September 2004

Electrophysiological (whole‐cell clamp) techniques were used to study the effect of NO synthase (NOS) inhibitors on guinea‐pig ventricular calcium current (ICa), and biochemical measurements (Western blot and citrulline synthesis) were made to investigate the possible mechanisms of action.

The two NOS inhibitors, NG‐monomethyl‐L‐arginine (L‐NMMA, 1 mM) and NG‐nitro‐L‐arginine (L‐NNA, 1 mM), induced a rapid increase in ICa when applied to the external solution. D‐NMMA (1 mM), the stereoisomer of L‐NMMA, which has no effect on NOS, did not enhance ICa.

Western blot experiments gave no indication of the presence of inducible NOS protein (iNOS) in our cell preparation, neither immediately after dissociation nor after more than 24 h. Statistically, there was no significant difference between electrophysiological experiments performed on freshly dissociated cells and experiments performed the next day. Moreover cells prepared and kept in the presence of dexamethasone (3 μM), to inhibit the expression of iNOS, gave the same response to L‐NMMA as control cells.

The stimulatory effect of L‐NMMA (1 mM) on basal ICa was reversed by competition with higher doses (5 mM) of externally applied L‐arginine, the natural substrate of NOS. The effect of L‐NMMA was also eliminated by L‐arginine in the patch pipette solution.

Intracellular perfusion with GDPβS (0.5 mM), which stabilizes the G‐proteins in the inactive state, did not affect the L‐NMMA‐induced stimulation of ICa.

Carbachol (1 μM) reduced the ICa previously stimulated by L‐NMMA, and intracellular cGMP (10 μM) prevented L‐NMMA enhancement.

Simultaneous treatment with L‐NMMA and isoprenaline (1 μM) induced a non‐cumulative enhancement of ICa that could not be reversed by carbachol (1 μM).

NO synthesis, measured by the formation of [3H]citrulline from L‐[3H]arginine during a 15 min incubation, showed a relatively high basal NO production, which was inhibited by L‐NMMA but not affected by carbachol.

These results suggest that inhibitors of NOS are able to modulate the basal ventricular ICa in the absence of a receptor‐mediated pathway, and that NO might be required for the muscarinic reduction of ICa under isoprenaline stimulation, even if NO production is not directly controlled by the muscarinic pathway.
Laminar difference in GABA uptake and GAT‐1 expression in rat CA1
Authors: Engel Dominique , Schmitz Dietmar , Gloveli Tengis , Frahm Christiane , Heinemann Uwe , Draguhn Andreas
Published: September 2004

The axonal plexus of most hippocampal interneurons is restricted to certain strata within the target region. This lamination suggests a possible functional heterogeneity of inhibitory synapses between different interneurons and CA1 pyramidal cells.

We therefore compared inhibitory postsynaptic potentials (IPSPs) and currents (IPSCs) in CA1 pyramidal cells, which were evoked from two stimulation sites (stratum oriens and stratum radiatum). Stimulation in stratum oriens yielded faster decaying IPSPs and IPSCs than stimulation in stratum radiatum.

IPSP and IPSC kinetics were regulated by GABA uptake in both layers as indicated by the prolongation of the signals under tiagabine, a GAT‐1 (neuronal GABA plasma membrane transporter)‐specific GABA‐uptake blocker. However, the effect of tiagabine was significantly more pronounced following stimulation in stratum radiatum than in stratum oriens (prolongation of IPSC half‐decay time by 167 vs. 115 %, respectively).

In situ hybridization with antisense mRNA for the GABA‐synthesizing enzyme glutamate decarboxylase (GAD65/67) and the GABA transporter GAT‐1 showed that the proportion of interneurons expressing GAT‐1 was lower in stratum oriens than in stratum radiatum/lacunosum‐moleculare.

From these functional and molecular data we conclude that the regulation of IPSP and IPSC kinetics in CA1 pyramidal cells by neuronal GABA uptake differs between layers. Our findings suggest that this laminar difference is caused by a lower expression of GAT‐1 in interneurons in stratum oriens than in stratum radiatum/lacunosum‐moleculare.
The role of bradykinin in the regulation of blood flow to hindlimb muscle groups of the anaesthetized cat
Authors: Poucher S. M. , Garcia S. , Brooks R.
Published: September 2004

Male cats were anaesthetized with alphaxalone‐alphadolone and breathed spontaneously following tracheotomy. Using coloured microspheres, muscle blood flow was measured at rest and during two periods of contraction elicited by simultaneous stimulation of the left sciatic and femoral nerves at 3 Hz for 10 min. In one group, the hindlimb blood flow was allowed to increase during muscle contraction and in another group the perfusion of the hindlimb was limited by a stenosis on the left external iliac artery.

In the absence of flow restriction, soleus muscle blood flow increased from 18.9 ± 3.8 to 30.4 ± 3.3 ml min−1 (100 g tissue)−1 (n= 6; P < 0.02) and gastrocnemius muscle blood flow increased from 24.8 ± 5.9 to 61.6 ± 12.8 ml min−1 (100 g tissue)−1 (n= 6; P < 0.01) during contraction. The bradykinin (BK) antagonist HOE 140 (1 mg kg−1, i.v.) did not affect the response in either the soleus (37.7 ± 7.3 ml min−1 (100 g tissue)−1; n= 6; n.s.) or the gastrocnemius (62.9 ± 7.9 ml min−1 (100 g tissue)−1; n= 6; n.s.) muscles.

In the stenosis group, soleus muscle blood flow increased from 9.8 ± 2.3 to 22.9 ± 4.9 ml min−1 (100 g tissue)−1 (n= 6; P < 0.01) and gastrocnemius muscle blood flow increased from 15.8 ± 3.4 to 36.4 ± 5.5 ml min−1 (100 g tissue)−1 (n= 6; P < 0.01) during contraction. Following administration of HOE 140, functional hyperaemia in the soleus muscle was unaffected (blood flow, 17.8 ± 2.2 ml min−1 (100 g tissue)−1; n= 6; n.s.) whilst blood flow in the gastrocnemius muscle was reduced to 21.8 ± 6.0 ml min−1 (100 g tissue)−1 (n= 6; P < 0.05).

The results show that BK does not contribute to functional hyperaemia associated with twitch contraction at 3 Hz when blood flow is unrestricted, but may contribute up to 40 % of the vasodilatation of predominantly glycolytic muscle groups such as the gastrocnemius when flow is restricted. BK plays no role in hyperaemia associated with twitch contraction of oxidative muscle groups such as the soleus.
Functional contribution of the α7 subunit to multiple subtypes of nicotinic receptors in embryonic chick sympathetic neurones
Authors: Yu C. Ron , Role Lorna W.
Published: September 2004

Many studies of the α7 subunit of the neuronal nicotinic acetylcholine receptor (nAChR) family have demonstrated that this α‐bungarotoxin (α‐BgTx)‐binding neuronal receptor can participate in ACh‐gated channels. Heterologous expression studies reveal that α7 subunits form homomeric channels of unusually high Ca2+ permeability. However, the physiological role of the α7 subunit in native neuronal nAChR channels is less clear.

We present evidence that the α7 subunit contributes to the function of at least three subtypes of native nAChR expressed by embryonic chick sympathetic neurones. These subtypes are functionally distinct from heterologously expressed homomeric α7 nAChRs as well as homomeric‐like currents described in studies of hippocampal and parasympathetic neurones.

The proposed nAChRs differ from one another and from homomeric α7 nAChRs in their sensitivity to block by α7 subunit‐specific antagonists: α‐BgTx and methyllycaconitine (MLA). While MLA blocks 60 % of the macroscopic ACh response, α‐BgTx inhibits a small component of the macroscopic current described by slow‐on and slow‐off kinetics.

Functional deletion of the α7 subunit by antisense oligonucleotide treatment eliminates the susceptibility of the nAChRs to block by both MLA and α‐BgTx.

Single channel recordings combined with pharmacological and antisense‐mediated ‘deletion’ techniques reveal that α‐BgTx‐sensitive α7‐containing nAChRs have a small unitary conductance (18 pS), brief open time kinetics and relatively low open probability (Po). MLA‐sensitive α7 nAChRs are characterized by a conductance of ≈35 pS, intermediate burst duration, and a relatively high Po.

The third nAChR subtype deleted by α7 antisense treatment is characterized by a unitary conductance of 50 pS and prolonged opening duration.

We propose that these three populations of native α7‐containing nAChRs are distinct heteromeric complexes that include other α and/or β nAChR subunits.