Peptone

“ Peptones are truly formed, and many times in large amount, but never under any circumstances have I been able to effect a complete transformation of any proteid into true peptone by pepsin-proteolysis; there is always found a certain amount of proteoses more or less resistant to the further action of the ferment. Obviously, the nature and proportion of the individual products formed in any digestive experiment are dependent greatly upon the attendant conditions ”

“ Dilution is only effected in order to make the best use of the costly material.
Standardization of the Peptone.—Let us assume that we have to deal with placenta peptone. This is mixed with the serum of individuals, who are certainly not pregnant, and then there should be no alteration of the original rotation. Should this not be the case, then the peptone is certainly not free from sulphuric acid or barium. With the serum of pregnant individuals a decomposition is bound to take place. At first, readings are taken every hour, and tests are made with many sera. ”

“ Pep′tōne, one of a class of albumenoids formed by the action of the chemical ferment pepsin and hydrochloric acid, the latter first converting into a syntonin or acid protein, the former converting this syntonin into peptone—they are soluble in water, are not coagulated by boiling, and pass readily through an animal membrane, being therefore easily absorbed ”

“ When using the optical method, we allow the decomposition, produced by the ferments present in the serum, to set in later, than in the dialysation process. We remove part of the decomposition from the influence of the ferment, when we convert albumen into peptone in the test-tube. It must be our aim to maintain the peptone mixture in as high a molecular state as is possible, as experience has shown, that decomposites of too low molecularity are not attacked by some kinds of serum, which decompose more highly molecular peptones. ”

“ The terms peptone and albumose include bodies of very uncertain composition, and their suitableness as food substances depends largely on how they are prepared. Animal experiments have shown that nitrogen equilibrium may be maintained, for a time at least, by use of enzymic hydrolytic products of the proteins, even where the hydrolysis has been carried far beyond the so-called peptone stage, but it appears to be likewise true that the mixtures secured by acid or high temperature steam hydrolysis have no such value. ”

“ Weigh out Witté's peptone, 20 grammes (= 2 per cent.) , and emulsify with 200 c.c. distilled water previously warmed to 60°C.
2. Weigh out sodium taurocholate (commercial) , 5 grammes (= 0.5 per cent.) , and glucose, 5 grammes (= 0.5 per cent.) , and dissolve in the peptone emulsion.
3. Wash the peptone emulsion into a flask with 800 c.c. distilled water, and heat in the steamer at 100° C. for twenty minutes.
4. Filter through Swedish filter paper into a sterile flask.
5. Add sterile litmus solution sufficient to colour the medium to a deep purple, usually 13 per cent. required. ”

“ The deutero-body, on the other hand, once formed is more rapidly converted into peptone, but even this is in no sense a rapid process. Hence, in the artificial digestion of proteids with pepsin-hydrochloric acid, solubility of the proteids may be quite rapid, and even complete in a very short time, but the resultant products will be mainly proteoses and not peptones. ”

“ Pepsin, in the presence of hydrochloric acid, acts on proteids, and changes them into proteoses Peptone and proteoses and peptone. Comparatively little food is completely peptonized in gastric digestion. Proteoses are intermediate products between food proteids and peptone, being the principal product of the action of the gastric juice. Thus it is seen that this stomach-action is only preparatory for the digestive processes of the intestines. ”

“ Far more probable is it that retrogression or transformation of peptone by the substance of the intestine, is due to the vital activity of some or all of the epithelial cells of the intestinal mucosa; a characteristic possibly shared by some or all of the hepatic cells of the liver. The kidney-cells certainly do not possess this power, but we can see a special fitness in the liver-cells being endowed with the ability to quickly break down, or transform, any peptone or proteose that might by chance escape unaltered from the intestinal tract. ”

“ Loew considered the ferment to be a true peptone, but in view of our present knowledge regarding the albumoses, I think we are justified in assuming it to be an albumose-like body rather than a true peptone. At the same time it may be well to again emphasize the fact that our only “means of determining the presence of an enzyme is that of ascertaining the change which it is able to bring about in other substances, and since the activity of the enzymes is extra­ordinarily great, a minute trace suffices to produce a marked effect. ”

“ Now, we understand why proteoses and peptone are not normally present in the circulating blood, even of the portal vein. We see that it is no longer necessary to assume a construction of blood proteins from absorbed proteoses and peptone. The old dictum, so often quoted, that the proteins of our muscle tissue, for example, are simple transformation products of the various food proteins no longer satisfies us, since it is so out of harmony with observed facts. We see opening up before us a totally different conception of the process of digestion so far at least as it relates to protein food. ”

“ The reagent is prepared by dissolving 30 grains of flesh peptone, 4 grains of salicylic acid, and 30 minims of strong acetic acid, in sufficient water to produce 8 fluid oz. of solution. Thus prepared, the peptone shows no signs of decomposition on keeping. To use the test, mix 1 fluid drachm of the reagent with 20 minims of urine, previously diluted to a standard specific gravity of 1.003. A haze is produced, which will be found to be more or less distinct, according to the proportion of bile salts present. ”

“ The peptone solution must never be strongly evaporated, until we have repeatedly satisfied ourselves, that it is actually free from sulphuric acid and barium. With very dilute solutions traces of these compounds may escape detection. During the concentration of the solution, that of the sulphuric acid and barium hydroxide naturally increases, so that we may eventually get an hydrolysis of the peptone mixture. ”

“ The general character of these interesting results was confirmed by Fano,151 who found that the injection of so-called peptone in the proportion of 0.3 gramme per kilo. of body-weight was sufficient to bring about complete narcosis, together with loss of coagulability on the part of the blood. Very suggestive, however, was the fact that Fano, on trying similar experiments with the peptone formed by pancreatic digestion, viz., with antipeptone, which presumably contained a far smaller proportion of proteoses, failed to obtain like results ”

“ At the same time, if complete peptonization is characteristic of pepsin-proteolysis in the stomach, and failure to obtain such results in an artificial digestion is due to lack of withdrawal of the diffusible products formed, then certainly the experiments carried on in dialyzer tubes, with abundant opportunity for diffusion, and with a large excess of free hydrochloric acid, should show some indications of increased peptone-formation. But none were obtained.
It is more than probable that the rate of absorption of diffusible products from the stomach has been overestimated. ”

“ Once the normal alterations of rotation of the serum peptone mixture are known, then the readings for the diagnosis of normal cases need only be taken every four to six hours. If one has a special object in view, then the readings are taken more often. ”

“ It is to be remembered, however, that the very nature of the proteid molecule precludes the possibility of anything like a complete decomposition into crystalline or other simple products. Full fifty per cent. of the peptone formed must be antipeptone, which cannot be further changed by trypsin under any circumstances, so that, whether the amount of proteid in the intestine be large or small, or whether it is exposed for a longer or shorter period to trypsin-proteolysis, there will always be a fairly large amount for absorption. ”

“ Furthermore, in considering absorption as it occurs in the living stomach, we must necessarily give due weight to the selective power of the epithelial cells, a power which may be far more potent even than we suppose. Hence, without attempting at this point to draw any broad deductions from our experiments we may simply lay stress upon the facts themselves, viz., that the primary products of pepsin-proteolysis are diffusible, and, like true peptones, are capable of passing through animal and vegetable membranes, although to a less extent. ”

“ In general properties and reactions, pepsin and trypsin may be closely related; both are products of the katabolic action of specific protoplasmic cells, but the inner nature or structure of the two must be quite different. Pepsin, as we have seen, is powerless to produce any change in proteid bodies unless acids are present to lend their aid. Furthermore, pepsin is limited in its action to the production of proteoses and peptones, while trypsin gives rise to a series of hydrolytic cleavages which result in the ultimate formation of comparatively simple bodies. ”

“ In pepsin-proteolysis we have to deal, in my opinion, with a series of progressive hydrolytic changes in which peptones are the final products of the transformation. Commencing with the formation of acid-albumin or syntonin, hydrolysis and cleavage proceed hand in hand, under the guiding influence of the proteolytic enzyme, and each onward step in the process is marked by the appearance of a new body corresponding to the extent of the hydrolysis ”

“ In a general way, the products of pepsin-proteolysis may be divided into three main groups, viz., bodies precipitated by neutralization and represented mainly by the so-called syntonin or acid-albumin; bodies precipitated by saturation of the neutralized fluid with ammonium sulphate and represented by proteoses; bodies non-precipitable by saturation with ammonium sulphate and represented by amphopeptones. The relationship of the individual products may be clearly seen from the following scheme, arranged after the plan suggested by Neumeister. ”

“ Examine the tubes carefully for visible growth, especially delicate pellicle formation, which if present should be examined microscopically for vibrios, both by stained preparations or by fresh specimens with dark ground illumination.
4. Inoculate fresh tubes of peptone water from such of the tubes as exhibit pellicle formation—from the pellicle itself—and incubate at 37° C. for twenty-four hours.
5. Test the peptone water itself for the presence of indol and nitrite by the addition of pure concentrated H2SO4. ”

“ Stated in different language, it is apparently the purpose of digestion, through the enzymes, pepsin, trypsin and erepsin, to thoroughly dismember the protein molecule so that no vestige of its original structure remains; while out of the many fragments or chemical groups so split apart the body can reconstruct proteins adapted to its own particular needs. This means synthesis of a most marked kind, quite different in character from that implied by the hypothetical transformation of absorbed proteoses and peptone in the mucous membrane of the intestine. ”

“ By further decomposition peptones yield peptides, a certain number of which have been synthesized by Emil Fischer and his collaborators. Albumoses and peptones are white powders, readily soluble in water, with the exception of the hetero-albumoses—a subdivision of primary albumoses. They give the biuret and xanthoproteic reactions, and form salts with both acids and bases. Albumoses and peptones are obtained by peptic digestion, the latter being termed peptic-peptones; tryptic digestion also produces peptones. Acids and moist heat induce similar changes. ”

“ In accord with this theory, true peptones always show a marked difference in composition from that of the mother-proteid, the most striking feature being the greatly diminished content of carbon, which may be taken as a measure, in part at least, of the extent of the hydrolytic change. And it is to be noticed that the crystallized phytovitellins are no exception to the general rule; the secondary vitelloses and peptones resulting from proteolysis bear essentially the same relationship to the mother-proteids that the albumoses from egg-albumin do. ”

“ Proteins undergo peptonization, but that does not change them sufficiently. The mere splitting into peptones, formerly thought sufficient, is now known to be quite inadequate. Recent researches have shown that the complex protein molecule has to be quite crushed into a heterogeneous assemblage of fragments, from which those suitable for building up into the body protein are selected for that purpose, the remainder being used as fuel; that is, as a source of energy. In the case of the other food principles, fats and starches, the chemical processes are much simpler. ”

“ Peptones are especially characterized by non-precipitation with the ordinary precipitants for proteid bodies, and especially by the fact that they are wholly indifferent to saturation with ammonium sulphate either in neutral, acid, or alkaline fluids. This reaction, which constitutes the main, and perhaps the only absolute method of separating peptones from proteoses must be carried out with great thoroughness in order to insure a complete precipitation of deutero­proteose. ”

“ When substances, that are out of harmony with the plasma, are introduced into the plasma or serum of a given animal, we always find developed a special power of decomposing bodies belonging to the protein series, especially protein itself and its peptones. A specific activity of the injected substrates could be traced only so far as that, after the injection of proteins and peptones, ferments appeared in the plasma which were able to chemically reduce the derivatives of this group, but not, for instance, fats or carbohydrates. ”