摘要:

To determine the relationship between hyperosmolality and immunoreactive atrial natriuretic peptide of heart atrial plasma six healthy men were given 0.06 ml kg‐1min‐1855 mmol 1‐1NaCI, i.v., for 2 h. The right atrial pressure and atrial plasma atrial natriuretic peptide were measured. During the infusion, right atrial pressure was kept constant by lowering the legs of the subject in a supine position downwards if any increase in the pressure was seen. There was a significant and linear increase in atrial serum osmolality, from 288 ± 3.3 to 307 ± 3.2mOsm kg‐l(P<0.001). No statistically significant changes in right atrial pressure were seen. Regression analysis revealed that there was a statistically significant correlation between serum osmolality and plasma ANP in three subjects (responders) (r2: 0.5241, 0.8965, 0.6695). In three other subjects (nonresponders), there was no correlation between osmolality and ANP. The mean basal osmolality of responders was 280 mOsm kg‐1and the mean basal osmolality of nonresponders was 295 mOsm kg‐1. In contrast, all subjects responded with an increase in plasma ANP (P<0.05) after RAP had been increased by tilting the legs of the subject upwards for 30 min.We conclude that the right atrial pressure regulates the release of atrial natriuretic peptide. Serum hyperosmolality may also contribute to the the regulation of atrial natriuretic peptide independently of the right atrial pr

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09275.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

To study the mechanisms of alcohol‐induced diuresis, the plasma concentration of immunoreactive atrial natriuretic peptide and arginine vasopressin, serum sodium and osmolality, plasma renin activity and aldosterone, urinary sodium and volume, free water clearance, blood pressure and heart rate were measured in seven healthy men after oral intake of ethanol (1.5 g kg‐1in 6 h). Serum ethanol levels increased to 27 ± 4 mmol 1‐l(mean ± SD) in 30 min and remained detectable for 14 h. Serum osmolality rose from 280±10 to 340 ± 4 mosm kg‐1in 2 hours (P<0.01) and was 300 ± 4 at 14 h (P<0.01). Formation of hypotonic urine began after the alcohol intake and resulted in a net loss of 0.9 ± 0.1 kg water in 2 h. Free water clearance increased from ‐3.4 ± 1.4 to 2.8 ± 1.5ml min‐lin 2 h (P<0.01). Plasma immunoreactive arginine vasopressin decreased from 5.7 ± 2.1 to 3.3 ± 1.3 ng 1‐1(P =0.05) in 30 min and increased to 17 ± 25 and 12±10 ng 1‐1at 6 and 12 h, respectively (P<0.05 for both). Plasma immunoreactive atrial natriuretic peptide levels decreased from 17 ± 9 to the minimum of 11 ± 3 ng 1‐1in 2 h (P<0.01) and returned to the initial levels in 6 h. Serum sodium, plasma renin activity and plasma aldosterone increased maximally by 4 ±2, 165 ± 153 and 143 ± 101 % (P<0.01 each) during 1–6 h. No changes in blood pressure were observed during the ingestion period, but the heart rate rose significantly from 70 min‐1at 6 p.m. to 95 min‐1at 12 p.m.We conclude that ethanol intake in relation to serum ethanol levels caused in the first phase a rapid increase in osmolality which was associated with a decrease in plasma immunoreactive arginine vasopressin. This caused hypotonic diuresis and increased free water clearance followed by volume contraction which evidently led to decreased plasma immunoreactive atrial natriuretic peptide. Serum osmolality was significantly elevated during the whole experiment and serum sodium 1–2 h after the ethanol intake. This was associated with the return of plasma immunoreactive atrial natriuretic peptide to initial levels after 6 h, the increase in plasma immunoreactive arginine vasopressin levels and reduced diuresis after 2 h. Our results suggest that ANP is not responsible for

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09276.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Age‐related plasma noradrenaline and neuropeptide Y were evaluated in seven young (mean ± SD, 28 ± 3 years) and seven elderly (64 ± 8 years) normal subjects during rest and different work loads on a cycle ergometer. In the supine and the sitting position plasma noradrenaline and neuropeptide Y were almost identical in the two groups. Plasma neuropeptide Y did not increase during exercise at 100 W for 15 min. At this load plasma noradrenaline levels were higher in the older subjects (mean ± SEM, 0.97 ± 0.12vs. 0.60 ± 0.09 ng ml‐l). There was a significant correlation between plasma noradrenaline and the relative work load at 100 W (r =0.794,P =0.0007). At 75% of maximal work load plasma noradrenaline and neuropeptide Y were higher in the young group (1.84 ± 0.16vs. 1.26 ± 0.13 ng ml‐l(noradrenaline) and 38 ± 4vs. 22 ± 5 pmol 1‐1(neuropeptide Y)). In the elderly group plasma neuropeptide Y did not increase during exercise and showed a tendency to fall below basal level 5 min post‐exercise. It is concluded, that plasma noradrenaline does not increase more in older subjects during exercise when correcting for the generally lower physical fitness in this group compared to younger subjects, and that plasma neuropeptide Y does not increase during exercise in older subjects, suggesting an age‐reduced ca

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09277.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The rates of glycogen breakdown during exhaustive intense exercise of three different intensities were determined in type I and subgroups of type II fibres. The exercise intensity corresponded to 122 ±2, 150 ± 7 and 194 ± 7% ofVo2max. Muscle biopsies were taken from both legs before and immediately after exhaustion. Muscle lactate concentration increased by 27 ±1, 27 ± 1 and 20 ± 2 mmolkg‐1wet wt during the exercise at122, 150 and 194%Vo2max, respectively. The rates of glycogen depletion increased in all fibre types with increasing intensity, and the decline in type I fibres was 30–35% less than in type II fibres at all intensities. No differences were observed between the glycogen depletion rates in subgroups of type II fibres (IIA, IIAB and IIB). During the exercise at 194% Vo2max, the rates of glycogen breakdown were 0.35 ± 0.03 and 0.52 ± 0.05 mmol s‐1kg‐1wet wt in type I and type II fibres, respectively. For both fibre types, the rates were 32 and 69% lower during the exercise at 150 and 12296 VO2max. These data indicate that the glycolytic capacity of type I fibres is 30–35% lower than the capacity of type II fibres, in good agreement with the differences in phosphorylase and phosphofructokinase activities (Essénet al. 1975, Harriset al. 1976). The data also indicate that both fibre types contribute significantly to the anaerobic energy release at powers up till

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09278.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Single motor units in the fast‐twitch tibialis anterior muscle were functionally isolated by stimulation of microdissected ventral root filaments. The muscle fibres of 35 fast‐twitch single motor units (motor unit fibres), 18 units from 3 to 6–month‐old and 17 units from 20 to 24–month‐old male rats, were identified by glycogen depletion. Measurements were made of staining intensities for intermyofibrillar succinate dehydrogenase, using microphotometric techniques, and of cross‐sectional areas of the motor unit fibres. The average coefficients of variation for succinate dehydrogenase activity of the muscle fibres within each unit, between the different units and for repeated measurements of the same fibre in 10 consecutive cross‐sections stained on different glasses were26, 72 and 14%, respectively. The average coefficients of variation for cross‐sectional fibre areas within each unit, between the different units and for repeated measurements were21, 53 and774, respectively. Further, the succinate dehydrogenase activity of muscle fibres within the motor unit differed significantly depending on the position of the fibre along the superficial‐deep axis of the muscle. The average succinate dehydrogenase activity in the 35 motor units was 21% lower (P<0.001) in the superficial as compared with the deep motor unit fibres. In order to eliminate the influence of altered motoneurone properties related to a transformation process or an age‐related motoneurone dysfunction as indicated by a non‐homogeneous myosin heavy chain composition in motor unit fibres, cross‐sectional fibre areas and enzyme activities were also compared in motor units with a uniform myosin heavy chain composition in young animals. However, the same regional differences were observed in these 16 units as when all the 35 units were pooled together. Thus, in conformity with previous reports, the variability in enzyme activities within single motor unit fibres is small but too Iarge for a motor unit homogeneity to be accepted. In addition, the present results demonstrate that the systematic differences in succinate dehydrogenase activities of motor unit fibres along the superficial‐deep axis of the tibialis anterior muscle represent a biological rather than

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09279.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Tactile directional sensibility is probably functionally important and deserves attention as it is known to be sensitive to many different disturbances of the somatosensory system. Therefore, the ability of healthy adults to determine the direction of motion of a light tactile stimulus travelling proximally or distally along a straight line on depilated, hairy skin of the forearm was examined with two‐alternative, forced‐choice technique. The aim was to investigate the relative importance of different types of afferent information which may be used for this purpose. A test was started with the moving stimulus covering a distance of no less than 2.5 mm, which was subsequently increased until the subject could report the direction of motion reliably.Afterwards, the distance was decreased until the subject could no longer do so. Three different stimulation conditions were used and for a point stimulator touching the skin it was found that the necessary distance decreased to 2.5 mm after a moderate increase of the vertical contact load. No such decrease was found when a frictionless air‐stream point stimulator was used instead. The distances which had to be covered by the point stimulator touching the skin increased to values which were comparable to those obtained with the air‐stream stimulator after the lateral extensibility of the skin had been diminished. This was achieved by attaching a surgical sticky plaster around the stimulated skip area. The present findings consequently indicated that optimal, tactile, directional sensitivity depends on peripheral afferent messages which signal the direction of lateral stretching of t

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09280.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The neuropeptide neurokinin A was injected intrathecally and its effect on the spinal nocifensive flexor reflex was examined. The reflex, which was evoked by electrical, thermal or mechanical stimulation of the foot and was recorded from the ipsilateral hamstring muscles, was substantially facilitated by 7 pmol intrathecally injected neurokinin A. The facilitatory effect of neurokinin A to thermal stimulation was, however, significantly stronger than to electrical or mechanical stimuli. Furthermore, co‐administration of neurokinin A with substance P induced a significant synergistic facilitation of the reflex. It is suggested that neurokinin A, like substance P, may be released in association with activation of polymodal C‐nocicept

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09281.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Previous results indicated the possibility of abolishing the orienting reaction to light tactile stimulation of specific areas below lesions encompassing three sectors of the transverse spinal plane, if all sectors were transected simultaneously. Hence presumably interrupting three different ascending pathways. Two sectors corresponded to the sites of the well known, somatosensory, dorsal column and spino‐cervical pathways. Single stage lesion technique now has been used to pinpoint the site of the third pathway.Immediate orienting reactions to both sides were seen before surgery. The orienting reactions remained postoperatively to stimuli applied on the hind limb contralateral to the dorsal column and the spino‐cervical lesions. When the hind limb ipsilateral to the dorsal column and the spino‐cervical lesions was stimulated five cats showed an absence of orienting reactions. The cats' lesions included the dorsal column and the spino‐cervical on one side and the border area between the lateral and ventral funiculi on the other side of the cord. The remaining cats showed either partial or no deficiency of the orienting reactions. These cats' spinal lesions spared the area between the ventral and lateral funiculi.The findings show the possibility of abolishing the tactile orienting reactions from one hind limb with single stage lesions, which include the dorsal column and the spino‐cervical pathway on one side, and a pathway located in the border area between the contralateral lateral, and ventral funiculi. This site corresponds to the morphological position of ascending spino‐mesencephalic and/or spino‐thalamic fibres. Consequently, all of these pathways might provide alternative routes for information about the place of tactile stimuli, which may evoke orient

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09282.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Neuronal activity in the spinal trigeminal subnucleus oralis in response to electrical tooth stimulation was recorded in the anaesthetized cat in order to compare the eiectrophysiological characteristics of the oralis neurons with those of subnucleus caudalis and interpolaris neurons recorded in previous studies. The most sensitive oralis neurons had lower thresholds and shorter latencies than the most sensitive caudalis and interpolaris neurons. The thresholds of the oralis neurons were lower and their strength‐duration curves flatter than those depicting liminal dental pain in man but similar to those depicting liminal jaw reflexes in the cat. Noxious conditioning stimulus elevated the threshold of only 1 of 10 neurons tested. The converging input from the skin and oral mucosa was from low‐threshold mechanoreceptors. The results indicate that the response properties of the subnucleus oralis neurons differ significantly from those of other spinal subnuclei. Human pain thresholds cannot be explained by the liminal response properties of oralis neurons. These neurons might be important in the mediation of liminal reflex events evoked by dental stim

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09283.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

This study examine the regulation Na+, K+‐ATPase activity in the medullary thick ascending limb of Henle Na+, K+‐ATPase activity was determined in medullary thick ascending limb of Henle (mtal) segments dissected from rat kidneys. The sodium concentration in the medium (Na,) was 20 or 70 mM. Since the segments were permeabilized, intracellular Na+(Na,) was assumed to be the same as Na2. Dibuturyl cyclic adenosine monophosphate (dbcAMP) and forskolin inhibited Na+, K+‐ATPase activity independently of Nam. Arginine vasopressin (AVP) receptors coupled to adenylate cyclase have been identified in the medullary thick ascending limb of Henle. At Nam= 20 mMAVP caused a dose‐dependent inhibition of Na+, K+‐ATPase activity with a maximal effect (49%) at 10‐8m. This inhibition was abolished in the presence of the adenylate cyclase inhibitor 2,5‐dideoxyadenosine (2, 5‐DDA). AVP had no effect on Na+, K+‐ATPase activity in the mTAL at Nam= 70 mM. The guanosine‐diphosphate analogue GDPβS inhibited Na+, K+‐ATPase activity at Nam= 70 mM but not at Nam= 20 mM.We conclude that increased cyclic adenosine monophosphate (CAMP) levels inhibit Na+, K+, ATPase activity in mTAL. AVP can, depending on Na2produce this effect by adenylate cyclase activation. The guanonine nucleotide binding protein G‐protein might be th

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09284.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY