Tissue Electrolytes in the Rabbit Following Chronic Dietary Potassium Depletion

Ward, Jeremy

doi:10.1113/expphysiol.1988.sp003210

Cited by 3 publications

(6 citation statements)

References 4 publications

(7 reference statements)

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“…These observations are consistent with functional studies on rat myocytes (Fry et al 1984). Using a water content of 76% (von Zglinicki & Bimmler, 1986) (Ward, 1988). The results presented here show a somewhat higher [Na+]i than that reported for whole tissue 20 mm [Na+] but this value reflects an upward bias due to some cells with very high Na+.…”

Section: Pcontrasting

confidence: 54%

Proceedings of the Physiological Society, 10‐11 February 1989, Royal College of Surgeons, London, Meeting: Communications

1989

The Journal of Physiology

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The human motor cortex can be excited by both electromagnetic and percutaneous electrical stimulation. The latencies of EMG responses in arm muscles are 1P4-2-7 ms longer with electromagnetic stimulation. The reason for this difference remains unclear; it has been proposed that electromagnetic stimulation indirectly excites corticospinal neurones, whilst electrical stimulation activates them directly (Day et al. 1987; see also Amassian et al. 1987). We have examined the corticospinal volleys excited by electromagnetic stimulation in the macaque monkey.In the first experiment, a monkey was anaesthetized with alfentanil (150 mg/kg per h) combined with midazolan (1 mg/kg per h, i.v.). Tungsten electrodes were placed in the hand area of the left motor cortex and in the left medullary pyramid.The cervical (C7) and thoracic (T9) spinal segments were exposed by laminectomy and electrodes placed on the right dorsolateral funiculus (DLF). After surgery the monkey was paralysed with Flaxedil (20 mg/h) and ventilated. The anaesthetic iinfusion was maintained at the same rate and the level of anaesthesia assessed from heart rate and blood pressure. The left motor cortex was activated with a Novametrix MagStim 200 stimulator with the coil tangential to the scalp. The latencies of the evoked volley were as follows: left pyramid at 0 7 ms; right DLF at C7, 1-4 ms and right DLF at T9, 2-6 ms. The corticospinal origin of this volley was confirmed by its collision with volleys evoked from the pyramid (1 shock, 300 PsA) 0-14 ms before the electromagnetic stimulus. The latency of the antidromic volley from C7 to cortex was 1-4 ms. No significant indirect responses (I-waves) were seen after electromagnetic stimulation.The second experiment was conducted on a conscious monkey which had previously had tungsten electrodes implanted in the left pyramidal tract under full Halothane anaesthesia (Lemon et al. 1986). While the monkey performed a precision grip task with the right hand, electromagnetic stimuli were delivered to the cortex with the coil held tangentially above the head. A volley was evoked in the pyramid at 0-8 ms. Clear responses were observed in the EMG of forearm muscles (latencies 7-0-775 ms) and of intrinsic hand muscles (10-0-10-4 ms). The latencies of EMG responses following single shock (200 ,sA) stimulation of the pyramid were 6-5 and 9-5 ms in forearm and hand, respectively.We conclude that in these experiments tangential electromagnetic stimulation of the cortex activated corticospinal neurones directly.

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Section: Pcontrasting

confidence: 54%

Proceedings of the Physiological Society, 10‐11 February 1989, Royal College of Surgeons, London, Meeting: Communications

1989

The Journal of Physiology

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“…However, direct comparison with other techniques is difficult, as values are expressed in terms of mass of the area analysed. Previous studies (for example, Ward, 1988) have shown that total cardiac muscle electrolytes are unchanged following K depletion, and although the present results for Na, Mg and, in the mitochondria, K are consistent with this, there was a significant reduction in myofibrillar K. This relatively small (15 %) fall may well be masked in analyses of whole tissue by a lack of change in other regions of the cell (e.g. mitochondria), but it suggests that any adaptation to K depletion is not as effective as previously thought.…”

Section: Discussionmentioning

confidence: 98%

“…Male New Zealand White rabbits, with an average weight of 2-3 kg, were fed either a control or a K-deficient diet (< 0 1 mmol K/100 g; SDS Ltd) for 25 days as previously described (Ward, 1988(Ward, , 1990. The animals were anaesthetized with pentobarbitone (50 mg/kg) and the heart removed.…”

Section: Methodsmentioning

confidence: 99%

“…Isolated cardiac myocytes were preIare by collagenase disaggregation, using a dification of the method described for rat by Fry, Powell, Twist & Ward (1984). The heart was perfused through the aorta at 70 mmHg and 37 oC with HEPES-buffered physiological saline (pH (Ward, 1988(Ward, , 1990. Solutions were equilibrated with 02.…”

Section: Methodsmentioning

confidence: 99%

“…Chronic dietary potassium depletion in the rabbit results in severe electrolyte disturbances of plasma and skeletal muscle, whereas the heart, brain and liver show little change (Ward, 1988). In the heart this protection has been ascribed to adaptive changes in Na+ pump density (Ward & Cameron, 1984).…”

Section: Introductionmentioning

confidence: 99%

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Subcellular elemental composition in isolated cardiac myocytes from rabbit following chronic potassium depletion and acute repletion, studied by X‐ray microanalysis

Ward

Warley²

1990

Experimental Physiology

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SUMMARYX-ray microanalysis was used to estimate K, Na, Cl, Mg, P and S within the mitochondria and the myofibrillar regions of cardiac myocytes from rabbits, following dietary potassium depletion. K depletion caused no changes in mitochondrial K, but myofibrillar K was reduced. There were no changes in Na, Mg or Cl. Both areas showed increases in P but decreases in S. Acute K repletion resulted in a significant overshoot of K in both areas, coupled with a profound decrease in Cl. P was reduced in the mitochondria alone. These results may be partly explained by adaptive changes in Nae pump activity.

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X-Ray Microanalysis of Freshly Isolated Cells in Suspension

Warley

1989

Electron Probe Microanalysis

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Tissue Electrolytes in the Rabbit Following Chronic Dietary Potassium Depletion

Cited by 3 publications

References 4 publications

Proceedings of the Physiological Society, 10‐11 February 1989, Royal College of Surgeons, London, Meeting: Communications

Proceedings of the Physiological Society, 10‐11 February 1989, Royal College of Surgeons, London, Meeting: Communications

Subcellular elemental composition in isolated cardiac myocytes from rabbit following chronic potassium depletion and acute repletion, studied by X‐ray microanalysis

X-Ray Microanalysis of Freshly Isolated Cells in Suspension

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