ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09868.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Rat medial gastrocnemius (GM) muscle is a compartmentalized muscle. The functional properties and fibre type composition of the most proximal and most distal compartment were studied inin situpreparations. The proximal compartment contained predominantly fast twitch oxidative fibres. The distal compartment was mainly composed of fast twitch glycolytic fibres. With the use of two small electrodes placed around the primary nerve branches, both compartments could be separately stimulated within the same muscle. The length‐force relationship was less broad and maximal twitch and tetanic forces were obtained at lower muscle lengths for the proximal compartment. The differences (mm) were 0.9 ± 0.2 and 1.2 ± 0.2 for maximal twitch and tetanic force (120 Hz) production, respectively (P<0.001). The shortening velocity for maximal power production was lower (P<0.001) for the proximal compartment (proximal: 57.1 ± 2.7 mm s‐1, distal: 73.1 ± 3.0 mm s‐1). During a standard fatigue test the fatiguability was significantly lower for the proximal compared with the distal fibres. Our findings suggest that the proximal compartment is likely to be activatedin vivoduring activities requiring relatively low power outputs for longer time periods. In contrast the distal compartment is probably recruited only during high power demanding short lasting activities. The presented model makes it possible to study fatigue related changes in power production of the ‘red’ and ‘white’ areas of the GM separately in a way that is probably meaningful with respect

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09869.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The effects of 2,3‐butanedione monoxime (BDM) on the forcevelocity relaion were studied in single fibres from the anterior tibialis muscle ofRana temporaria(2.2 μm sarcomere length, temperature 1.9‐2.4 d̀C). BDM (1.0 and 1.8 mM) suppressed the maximum tetanic force (Po) and the maximum speed of shortening (Vmax), and increased the main curvature of the force‐velocity relation. The biphasic shape of the forcevelocity curve was maintained well in the presence of BDM, but the interrelation between the two portions of the forcevelocity relation was significantly changed. Caffeine (0.5 mM) added in the presence of BDM increased the initial rate of rise of force during twitch and tetanus, increased the twitch amplitude, but did not affect the maximum tetanic force. The latter finding suggests that the contractile system was fully activated during tetanus in the presence of BDM. The results support the view that BDM affects the cross‐bridge function by exerting a direct action upon the contractile apparatus. The decrease in tetanic force and the change of the force‐velocity relation induced by BDM may be interpreted to show that a larger fraction of the attached cross‐bridges is in a state of low force production under the influence of BDM. This view is further supported by the observation that the instantaneous stiffness of the muscle fibre is reduced proportionally less by BDM than the

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09870.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

In eight subjects luminal diameter of the resting limb radial and dorsalis pedis arteries was determined by high‐resolution ultrasound (20 MHz). This measurement was followed during rest and during 2 min of static handgrip or of one‐leg knee extension at 30% of maximal voluntary contraction of another limb. Static exercise increased heart rate and mean arterial pressure, which were largest during one‐leg knee extension. After exercise heart rate and mean arterial pressure returned to the resting level. No changes were recorded in arterial carbon dioxide tension, and the rate of perceived exertion was ˜ 15 units after both types of exercise. The dorsalis pedis arterial diameter was 1.50±0.20 mm (mean and SE) and the radial AD 2.45±0.12 mm. During both types of contractions the luminal diameters decreased ˜ 3.5% within the first 30 s (P<0.05), and during one‐leg knee extension they continued to decrease to a final exercise value 7.6±1.1% lower than at rest (P<0.05). Thus, they became smaller than during the handgrip. After exercise resting values were reestablished. When the arterial diameter was expressed in relation to mean arterial pressure for the radial and dorsalis pedis artery was 22±3 and 28±3% lower during handgrip than the relation during rest, respectively. After one‐leg knee extension both arteries reached 30±4% lower values. This study demonstrated arterial constriction in the resting limbs within the first 30 s of static exercise, and continued constriction during one‐leg knee extension. These results support to the hypothesis that central command and/or muscle mechano‐ receptors influence arterial tone, and that the exercise pressor reflex becomes important with the involvement o

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09871.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Distribution of pulmonary blood flow has traditionally been regarded as determined by gravity. This view has been challenged recently by reports describing marked gravity‐independent distribution of flow. These reports were based on experiments in which local blood flow was measured by methods that have not been thoroughly evaluated. In the present study, we showed that in the goat lung regional trapping of i. v. infused microspheres (Ø= 15 um) correlated to endothelial uptake of a simultaneously i. v. infused diamine (r = 0.99, region size ˜ 1.5 cm3, dry weight ˜ 40 mg). This indicates that the deposition of microspheres reflects true regional pulmonary blood flow. Using the microsphere method, we found a marked gravity‐independent heterogeneity in blood flow (coefficient of variation ˜ 40%) in the awake goat. We could find no pattern related to anatomy that could account for this variability. We re‐examined the influence of gravity by analysing the distribution of pulmonary blood flow in anaesthetized goats both in prone and supine positions. The dorsal to sternal distribution of flow appeared to be inverted when the animals were turned from prone to supine recumbency, indicating that gravity influenced the distribution of pulmonary blood flow along this axis. However, along the gravitational axis, distribution of blood flow varied considerably from lung to lung. It appears that in awake goats the distribution of pulmonary blood flow is the result of several different det

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09872.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The effects of arterial pressure on cerebral reactive hyperaemia were studied in anaesthetized goats measuring electromagnetically middle cerebral artery flow and performing arterial occlusions of 5–30 s. Under normotension (mean arterial pressure, MAP = 11± 0.3 kPa), reactive hyperaemia (peak hyperaemic flow to control flow and repayment to debt ratios) increased, and cerebrovascular resistance during peak hyperaemic flow decreased, as ischaemia duration lengthened; the virtual maximal changes were obtained after 20 s ischaemia. During hypertension by aorta constriction (MAP = 18 ± 0.7 kPa) or by i. v. infusion of noradrenaline (MAP = 19 ± 0.8 kPa) middle cerebral artery flow did not change significantly and cerebrovascular resistance increased 25 and 46%, respectively (P<0.05). During both types of hypertension reactive hyperaemia was over 50% higher, and the decrement in cerebrovascular resistance during peak hyperaemic flow was also higher, than under normotension. During hypotension by constriction of the inferior vena cava (MAP = 5 ±.5 kPa) or by i. v. infusion of isoproterenol (MAP = 6±.5 kPa), middle cerebral artery flow decreased 35% or did not change, and cerebrovascular resistance decreased 41 and 45 %, respectively (P<0.05). In these conditions, reactive hyperaemia and the decrement in cerebrovascular resistance during peak hyperaemic flow were reduced SOY, and it was similar in both types of hypotension. The absolute levels of cerebrovascular resistance obtained during peak hyperaemia were similar during normotension, hypertension and hypotension. Thus, arterial pressure is a main determinant of postocclusive cerebral reactive hyperaemia, and myogenic mechanisms may be of significance in determining the early stage of cerebral reactive hyperaemia after brief ischaemias. Adrenergic mechanisms might be of minor significance in this type of cerebral reactive hype

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09873.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The aim was to investigate whether prostaglandins affect HCI‐induced permeability and to elucidate the role of mucosal bicarbonate secretion in protection. Proximal duodenum of anaesthetized rats were perfused with hydrochloric acid and the effect on luminla alkalinization, mucosal permeability and morphology examined in the absence in the presence of prostaglandin E2and/or indomenthacin. Luminal alkalinzation was determined by back titration of the perfusate and mucosal permeability assessed by measuring the clearance of51Cr‐labelled ethylenediaminetetraacetat (51Cr]EDTA) from blood‐to‐intestinal lumen. Perfusilon with 100mM HCI for adiministration of PGE2at a concentration of 10‐6M ahd no effect whereas 10‐4M increased alkalinization by 100% but neither concentration affected the HCI‐induced increase in mucosal permeability. PGE2(10‐4M), however, improved the ability of the doudenal mucosa to recover form teh HCI‐induced in mucosal permeability. Indomethacin (5 mg kg‐1, i. v.) increased alkalinmization, augmented HCI‐induced mucosal permeability and aggrvated mucosal injury. In anikmals pre‐treated with PGE2plus indomethacin, the HCI‐induced increase in mucosal permeability were lower and was found between the rate of alkalinization and the HCI‐induced increase imcosal permeability. It is concluded that endogenous prostaglandins reduced the extent of 100 mM HCI‐induced duodenal mucosal damage by la mechanism other than the stim

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09874.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Invivocalibration of microdialysis catheters with [3H]glucose as internal reference was done in rat (n= 17) and human (n= 12) subcutaneous tissue. The estimated interstititial glucose level was compared owth the glucose concentration in venous plasma which, in turn, has been shown to be identical to the interstitial glucose concentration. In subcutaneous tissue of anaesthetized male Sprageue‐Dawley rats, interstitial glucose was significantly overestimated (43%,P<0.005,n= 8, and 19%, P<0.005,n=9, in nornoglycaemic and hyperglycaemic animals, respectively). Furthermore, fractional outflux of [3H]glucose decreased continuously during prolonged perfusion of the microdialysis catheter. Incontrast, in human subcutaneous tissue microdialysed with two catheters, correct measurements of interstitial glucose could be achieved and the precision was comparableto that obtained with equilibration calibratonin vivo. The average relative error of the mean result of two catheters was 8.9% at a perfusate flow rate of 1 μL min‐1.It may be suggested that calibration inin vivoof microdialysis catheters with internal references may be used in human subcutaneous tissue. However, it is necessary to validate the calibration technique in each different tissue under reproducible experimental conditions since accumulation of the reference substance in the tissue may create artefactual res

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09875.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

In pentobarbitone‐anaesthetized cats, responses were recorded as surface positive potentials in the motor cortex on forelimb and brachium conjunctivum stimulation. In such a preparation, the forelimb nerve responses are mediated via the spino‐cervical tract and the dorsal column‐lemniscal pathway. Lesions of the sensory cortex (sparing only the depth of the coronary sulcus) abolished or reduced short‐latency peripheral responses, in the motor cortex, on both skin and muscle nerve stimulation to less than 10% of control, while brachium conjunctivum responses were unchanged. Lesions of the second somatosensory area alone reduced the motor cortex responses on peripheral nerve stimulation by 10–20%. When the sensory cortex were abolished before the spreading depression reached the recording point, as judged from the brachium conjunctivum response. The depth distribution of positive and negative field potentials, constituting the early componentsof a peripheral response in the motor cortex, closely resembled that of a cortico‐cortical response evoked on stimulation in area 3. It differed from that of thalamo‐cortical response evoked in brachium conjunctivum stimulation. These data suggest that most, if not all, sensory input through the dorsal column and spino‐cervical tract to the motor cortex is mediatd via the

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09876.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09877.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY