INFLUENCE OF AGEING ON INORGANIC HYDROPHILE COLLOIDS, CELLS AND COLLOIDS I N T H E A N M A L BODY N. R. DHAR
I n a previous paper’ I have advanced the view that old age is associated with marked decrease in the catalytic activity of the body enzymes and cells. Consequently in old age there is an appreciable decrease in the metabolism in the animal body. Observations on the metabolism of human beings of different ages show that the metabolism expressed per square nletre of the body surface or kilogram of the body weight is less in old age than in childhood or youth. Moreover a certain minimum quantity of heat is necessary for the maintenance of the body temperature. I am of the opinion that when the amount of oxidation in the body is just less than the minimum necessary to keep up the body temperature, death is likely to follow. Animal life is assumed to depend essentially on the activity of the cells and enzymes. I n this paper I shall bring forward further evidence in support of the above views and show that the phenomenon of ageing is common both to inorganic and organic colloids and precipitates. I n publications* from these laboratories we have shown that the activity, adsorptive power, stability and viscosity of hydrophobe colloids decrease with time. On the other hand, with hydrophile colloids, the viscosity and the amount of hydration increase up to limiting value on ageing. I n a recent communication we have shown that the viscosity of a sol of ceric hydroxide prepared in the cold goes on increasing with time up to a limiting value and then it sets to a stiff jelly. Now if the jelly is kept in a stoppered bottle the viscosity decreases and the sol becomes mobile again. The electric conductivity of the sol goes on decreasing up to a minimum value and then i t increases. Exactly similar results are obtainable with a sol of vanadium pentoxide. I n this case we prepared a concentrated sol and measured the conductivity and viscosity day to day and found that the viscosity goes on increasing up to a limiting value and then it decreases with time. The electrical conductivity, on the other hand, goes on decreasing up to a minimum and then it increases again. These two sols behave as typical hydrophile colloids. With silicic acid some interesting results have been obtained. The sol prepared both in the cold and hot conditions show increased viscosity with time and on keeping the silicic acid sets to a jelly. I n course of time the jelly is broken and a portion of the liquid is given out. Exactly similar behaviour is observable with animal cells and protoplasm. From ultramicroscopic observations it can be clearly concluded that amoeba J. Phys. Chem., 30, 378 (1926). 2. anorg. allgem. Chem., 162, 237; 164, 63 (1927); Kolloid-Z., 42,
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(1927).
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consists of colloidal particles. Similar conclusions are drawn by Matt' from observations on living nerve cells by the same method. As a general rule the small granules often seen in living cells do not show active Brownian movement indicating that protoplasm is often of considerable viscosity. This is in harmony with the fact that it can often be drawn into long sticky threads. The degenerative changes which precede the death of a cell are accompanied by a liquefaction of the protoplasm and by the appearance of small granules in active Brownian movement. These granules become larger in course of time whilst the Brownian movement ceases and this indicates that the protoplasm has irreversibly coagulated. The protoplasm of young cells is often homogeneous, whilst that of the mature cell may show a definite structure. Thus immature eggs of Echinoderms are quite clear and transparent, whilst in the mature eggs, Chambers* distinguishes two kinds of particles visible in the ordinary microscope-very small ones, and larger ones, macrosomes. The former are stable and the latter very sensitive to injury. Mitochondria are granules apparently composed of albumin and lecithin which stain with dyes containing di-ethyl safranin. They are present in the living cell and modify the activities of the cell. It appears therefore that the protoplasm of young cells behaves like a freshly prepared colloidal solution and in the mature egg partial separation of the solid and increased capacity are observable due to ageing. This behaviour of protoplasm is similar to that observed with a sol of silicic acid. Fischer has shown that the same type of change takes place with proteins. Gelatine jelly, as well as other protein media, as the familiar blood serum of the bacteriologists all squeeze off fluid on standing. The more highly hydrated the protein gel or jelly, the more liquid is squeezed off. Hence it appears that in course of time the body proteins have a tendency to lose their adsorptive power and activity. This is one of the important factors that lead to old age and death. The cells of the tissues are like other living beings dependent for their life and activity upon a constant and abundant supply of food, and oxygen and an equally adequate removal of their waste products. Now the utilization of food and oxygen is possible because of the existence of catalysts in the body. I n course of time the activity of the enzymes as well as that of the cells is decreased and hence the metabolism is decreased. In previous communications from these laboratories we have shown that hydrophobe colloids like ferric hydroxide, aluminium hydroxide, etc. , show greater conductivity on ageing and their viscosity becomes less and less with time. Now the particles of these colloids in course of time grow into bigger ones and hence the surface of the particles becomes less and less and along with the decrease in the surface the adsorptive power, the amount of hydration and the viscosity decrease. The adsorbed electrolyte is thus given out and the conductivity of the sol taken as a whole is increased. Exactly similar behaviour is observable with solutions of ferric chloride, aluminium nitrate, 1
“The Brain and the Voice in Speech and Song,”
2
J. Exp. Zool., 23, 483 (19x7).
IIZ (1912).
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thorium nitrate, alums etc. All these salts when dissolved in water are hydrolysed into a base which is sparingly soluble and this base will exist in a colloidal state by the adsorption of the acid and the metallic salt solution. The particles of this colloid in course of time will agglomerate and lose part of its adsorbed electrolyte and hence the electrical conductivity will increase and the viscosity and stability will decrease. I n the case of solutions of sodium or potassium palmitate, stearate, etc., by hydrolysis we get an acid which is sparingly soluble, I n these cases also the particles of the sparingly soluble acid will lose a part of their free surface and the adsorbed electrolyte. But the particles of sodium or potassium stearate, palmitate etc. have great a f i i t y for water and hence in course of time these particles will be more and more hydrated and the viscosity will increase up to a maximum value. The electrical conductivity will decrease up to a limiting value and then it will increase again. I n the case of vanadium pentoxide the sol shows increased viscosity and decreased conductivity with time up to a limiting value. This is because vanadium pentoxide has a great affinity for water, and it will combine with more and more water and hence the viscosity will increase and along with it the electrical conductivity will decrease up to a limiting value. This hydration tendency of substances like vanadium pentoxide, ceric hydroxide, silicic acid, etc., depends upon the affinity of the substances for water and is possibly controlled by those forces which make substances dissolve in water. Now when the chemical affinity of the particles of vanadium pentoxide, ceric hydroxide, etc.: for water is satisfied and the maximum hydration and viscosity are reached, the particles on further ageing begin to agglomerate and partially lose their adsorptive power, stability, and hydration tendency. Our experimental results on the viscosity of gelatine show that the viscosity goes on increasing with time up to limiting value and then i t decreases. Hence with gelatine the viscosity and the hydration tendency increase up to maximum and then they fall off due to ageing. Typical animal products like albumin, gelatin, protoplasm, cells etc. also behave in a similar manner as has already been mentioned. From the above results it will be clear that there is no essential difference between inorganic hydrophile colloids and typical animal products like albumin, protoplasm etc. The ageing phenomenon is similar in both these groups of substances. It is well known that Dony-Hknault prepared artificial laccase, which is an oxidising enzyme by alcoholic precipitation of a solution containing gum arabic, manganese formate and sodium bicarbonate. This precipitate can be redissolved in water and reprecipitated by alcohol. It is undoubtedly an adsorption compound with gum and colloidal manganese hydroxide. This artificial enzyme will age in course of time and partly lose its activity. In publication from these laboratories we have shown that iron salts and colloidal ferric hydroxide can act as active catalytic agents in oxidation reactions. Thus the oxidation of tartaric acid, starch, etc., by hydrogen peroxide can be largely increased by ferric or ferrous salts or colloidal ferric hydroxide and in this way we have explained the internal use of iron in medi-
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cine. Now it is well known that animal blood contains iron and that a good deal of oxidation of food material takes place in blood. It seems likely that in course of time the iron compound present in adult animal blood will lose a part of its catalytic influence and the amount of oxidation in the animal body is likely to decrease with age. Moreover the inorganic salts which are present in the body as adsorbed by the protein matter are likely to be partly given up due to the ageing of the protein particles. Kow the body cells, enzymes, hormones, internal secretions, etc., are likelyto act with the help of theadsorbed inorganic andorganic substances; but in course of time the adsorbed substances are likely to be given up and hence the activity of the cells, the enzymes etc. will decrease. The cartilages, connective tissues, bone cells, etc., which consist mainly of calcium carbonate and phosphate will also age in course of time and partially lose their activity and adsorptive power. I n a foregoing paper' I have suggested that bone formation takes place by the adsorption of calcium phosphate and calcium carbonate existing in the colloidal state in the body by the solid or semi-solid cartilages, bones, etc. S o w in the course of time the adsorbents, like cartilages, bones, etc., will partly lose their adsorptive power and would not be able to adsorp the requisite amounts of sols of calcium phosphate and carbonate from the body and hence bone formation would be difficult in old age. Whenever an electric stimulus is sent through an Amoeba it is made to draw itself together, so that its surface shall be the least possible, in fact it becomes more or less spherical. I n a recent csmmunication from this laboratory, it has been proved mathematically that when the charge on the colloid particles is increased the particles tend to be more and more spherical. I n this respect an amoeba behaves exactly like a sol. With the establishment of the cellular nature of the tissues it may well have been that the ultimate unit of life had been reached and that no minuter element need be considered, Indeed our doctrine of pathology is essentially a cellular one, although we realise that the cell in all cases is a vastly complicated structure within which there are elaborate mechanisms developed in almost infinite variety, and within which too, we can discern evidence of the accomplishment of the chemical processes which in complexity and ingenuity of combination surpass anything which can be carried on in a laboratory. From the foregoing pages it will be clear that the cells in the animal body lose their adsorptive power, hydration tendency and activity with time. It has already been mentioned that the protodasm in the mature egg consists of two kinds of particles, small and large. The former are stable and the latter very sensitive to injury. It appears therefore, that on ageing the cells in the animal body become comparatively powerless and sensitive to injury and bacteria. summary
The hydration tendency and viscosity of vanadium pentoxide and ceric hydroxide increase with time up to a limiting value and then decrease I)
' Z . anorg. allgem. Chem., 162,243 (1927).
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and this behaviour depends on the chemical affinity of these substances for water. When the chemical affinity for water is satisfied and the maximum hydration and viscosity are reached, the particles on further ageing begin to agglomerate and partially lose their adsorptive power, stability and hydration tendency. Gelatin, albumin, etc., behave like the above two inorganic hydrophile colloids. 2) Silicic acid sol prepared in hot and cold conditions shows increased viscosity with time and on keeping the silicic acid sets t o a jelly. I n course of time the jelly is broken and a portion of the adsorbed liquid is given out. Similar behaviour is observable with the animal cells and protoplasm. The degenerative changes which precede the death of a cell are accompanied by the partial liquefaction of the protoplasm and by the appearance of granules. Protoplasm of young cells behave like a feshly prepared sol and in the mature egg partial separation of the solid and increased capacity are observable due t o ageing. Gelatine jelly and other protein media squeeze off fluid on standing. Hence it appears that there is no essential difference in the phenomenon of ageing between inorganic hydrophile colloids and the typical animal products like albumin, protoplasm etc. 3) It appears that the enzymes, blood cells, etc., containing inorganic and organic substances will partially lose their activity on ageing and hence metabolism will decrease. The bone cells containing mainly calcium phosphate and carbonate will age with time and partially lose their adsorptive power and hence formation of new bones is difficult in old age. 4) I t appears that on ageing the cells in the animal body become comparatively powerless and sensitive to injury and bacteria. Chenizcal Laboratory, Allahabad l'nzisrsity, Allahabad, I n d i a . October 6 , 1927.
