The diffusion of oxygen and lactic acid through tissues

The diffusion of dissolved substances through cells and tissues is a determining factor in many vital processes. The slowness of diffusion on the scale of ordinary sensible objects gives to the unaided imagination an imperfect realisation of its speed and importance in systems of the dimensions of the living cell. The diffusion constant k is expressed in terms of the number of unit quantities of substance which diffuse per minute across an area of 1 sq. cm. in a gradient of concentration per cm. of 1 unit quantity per c. c. For aqueous solutions of ordinary substances k is usually of the order of 2 to 10 times 10 -4 . The diffusion constant is of the dimensions L 2 T -1 , 2 in length, -1 in time. Expressing it in units of 1μ (0·0001 cm.) instead of 1 cm., and of 1σ (0·001 sec.) instead of minutes, k is of the order of unity, instead of multiple of 10 -4 . Thus the diffusion constant is a fairly large quantity for systems involving distances of the order of 1μ and times of the order of 1σ. A cylinder 1 cm. in diameter composed of material similar to frog's nerve, if suddenly placed in oxygen, would take 185 minutes to attain 90 per cent. of is full saturation with that gas. An actual nerve 0·7 mm. thick would take 54 seconds for the same stage of saturation to be reached. A single nerve fiber 7μ thick would take only 5·4 σ. Again, the rapidity of diffusion attainable in systems of small dimensions is the basis of the capillary circulation, and therewith of the whole design of the larger animals; and the rate at which diffusion an supply oxygen to a fatigued muscle for the removal of lactic acid is an important factor in determining the speed at which recovery can occur.

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Pressure-clamped single-fiber recording technique: A new recording method for studying sensory receptors

Molecular Pain ◽

10.1177/1744806920927852 ◽

2020 ◽

Vol 16 ◽

pp. 174480692092785 ◽

Cited By ~ 1

Author(s):

Mayumi Sonekatsu ◽

Hiroshi Yamada ◽

Jianguo G Gu

Keyword(s):

Nerve Fiber ◽

Single Unit ◽

Single Fiber ◽

Single Unit Recording ◽

Sensory Receptors ◽

Unit Recording ◽

Recording Technique ◽

C Fibers ◽

Recording Method ◽

Single Nerve

An electrophysiological technique that can record nerve impulses from a single nerve fiber is indispensable for studying modality-specific sensory receptors such as low threshold mechanoreceptors, thermal receptors, and nociceptors. The teased-fiber single-unit recording technique has long been used to resolve impulses that are likely to be from a single nerve fiber. The teased-fiber single-unit recording technique involves tedious nerve separation procedures, causes nerve fiber impairment, and is not a true single-fiber recording method. In the present study, we describe a new and true single-fiber recording technique, the pressure-clamped single-fiber recording method. We have applied this recording technique to mouse whisker hair follicle preparations with attached whisker afferents as well as to skin-nerve preparations made from mouse hindpaw skin and saphenous nerves. This new approach can record impulses from rapidly adapting mechanoreceptors (RA), slowly adapting type 1 mechanoreceptors (SA1), and slowly adapting type 2 mechanoreceptors (SA2) in these tissue preparations. We have also applied the pressure-clamped single-fiber recordings to record impulses on Aβ-fibers, Aδ-fibers, and C-fibers. The pressure-clamped single-fiber recording technique provides a new tool for sensory physiology and pain research.

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The formation of lactic acid in desiccated amphibian muscles

Proceedings of the Royal Society of London. Series B, Containing Papers of a Biological Character ◽

10.1098/rspb.1930.0016 ◽

1930 ◽

Vol 106 (742) ◽

pp. 122-131 ◽

Cited By ~ 5

Keyword(s):

Lactic Acid ◽

Chloride Solution ◽

Sartorius Muscle ◽

Silk Thread ◽

Experimental Procedure ◽

The Third ◽

Uniform State ◽

Cent Sodium ◽

Geometrical Form ◽

Determining Factor

The present paper is the third of a series dealing with the effects of freezing and drying on living amphibian muscle (1, 2). In this paper it is shown that simple drying of muscles causes the production of lactic acid, in amount identical with that produced by the corresponding degree of freezing (2). This finding confirms the view expressed in the earlier communications that the effects of freezing and drying are identical, the determining factor in each case being the removal from the muscle of a certain amount of water. Experimental Procedure . To ensure even drying throughout, it was necessary to use a thin muscle of regular geometrical form. The sartorius muscle of the frog was therefore chosen. The frogs were precooled for some hours at zero. The muscles were then carefully removed at their insertions, wiped on filter paper, and each individual muscle suspended by a silk thread of known weight (see later) in a stoppered bottle, over 0·72 per cent, sodium chloride solution. After standing at 0° C. for 24 hours, to allow of the removal of the lactic acid formed during the manipulation, the muscles were weighed, and rapidly dried by being suspended in bottles over solid calcium chloride. It has already been shown that this method of drying produces a uniform state throughout the muscle (1, p. 187). They were removed at intervals for weighing.

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