bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.