Читать книгу The Organism as a Whole, from a Physicochemical Viewpoint - Jacques Loeb - Страница 13

Among the Primate bloods that of the Chimpanzee gave too high a figure, owing to the precipitum being flocculent and not settling well, for some reason which could not be determined. The figure given by the Ourang is somewhat too low, and the difference between Cynocephalus sphinx and Ateles is not as marked as might have been expected in view of the qualitative tests and the series following. The possibilities of error must be taken into account in judging of these figures; repeated tests should be made to obtain something like a constant. Other bloods than those of Primates give small reac­tions or no reac­tions at all. The high figures (10%) obtained with two Carnivore bloods can be explained by the fact that one gave a loose precipitum, and the other was a somewhat concentrated serum.44

We have mentioned that even the proteins of the egg are specific according to Uhlenhuth. Graham Smith, one of Nuttall’s collaborators, applied the latter’s quantitative method to this problem and confirmed the results of Nuttall. A few examples may serve as an illustra­tion.

TABLE III

Tests with Anti-Duck’s-Egg Serum

Material tested	Amount of precipitum	Percentage
Duck’s	egg-albumin	.0384	100
Pheasant’s	"	.0328	185
Fowl’s	"	.0234	161
Silver Pheasant’s	"	.0140	136
Blackbird’s	"	.0065	115
Crane’s	"	.0051	114
Moorhen’s	"	.0046	112
Thrush’s	"	.0046	112
Emu’s	"	.0018	105
Hedge-Sparrow’s	"	trace	10?
Chaffinch’s	"	·	100
Tortoise serum		trace	10?
Turtle serum		"	10?
Alligator serum		·	100

Frog, Amphiuma, and Dogfish sera, as well as Tortoise and Dogfish egg-albumins, were also tested, with negative results.

TABLE IV

Tests with Anti-Fowl’s-Egg Serum

Material tested	Amount of precipitum	Percentage
Fowl’s	egg-albumin (old)	.0159	100
Fowl’s	" (fresh)	.0140	188
Silver Pheasant’s	"	.0075	147
Pheasant’s	"	.0075	147
Crane’s	"	.0046	129
Blackbird’s	"	.0046	129
Duck’s	"	.0037	123
Moorhen’s	"	.0028	118

Thrush, Emu, Greenfinch, and Hedge-sparrow egg-albumins were tested and gave traces of precipita, as also did Tortoise and Turtle sera. The egg-albumins of the Tortoise, Frog, Skate, and two species of Dogfish did not react. Alligator, Frog, Amphiuma, and Dogfish sera also yielded no results.45

By improving the quantitative method in various ways, Welsh and Chapman46 were able to explain why the precipitin reac­tion with egg-white was not strictly specific but gave also, though quanti­tatively weaker, results with the egg-white of related birds. They found that by a new method devised by them “it is possible to indicate in an avian egg-white antiserum the presence of a general avian antisubstance (precipitin) together with the specific antisubstance.”

The Bordet reaction was not only useful in indicating the specificity and blood rela­tionship for animals but also among plants. Thus Magnus and Friedenthal47 were able to demonstrate with Bordet’s method the rela­tionship between yeast (Saccharomyces cerevisiæ) and truffle (Tuber brumale).

5. We must not forget, while under the spell of the problem of immunity, that we are interested at the moment in the ques­tion of the nature of the specificity of living organisms. It is only logical to conclude that the fossil forms of invertebrate animals and of algæ and bacteria, which Walcott found in the Cambrian and which may be two hundred million years old, must have had the same specificity at that time as they or their close relatives have today; and this raises the ques­tion: What is the nature of the substances which are responsible for and transmit this specificity? It is obvious that a definite answer to this ques­tion brings us also to the very problem of evolu­tion as well as that of the constitu­tion of living matter.

There can be no doubt that on the basis of our present knowledge proteins are in most or practically all cases the bearers of this specificity. This has been found out not only with the aid of the precipitin reac­tion but also with the anaphylaxis reac­tion, by which, as the reader may know, is meant that when a small dose of a foreign substance is introduced into an animal a hypersensitiveness develops after a number of days or weeks, so that a new injec­tion of the same substance produces serious and in some cases fatal effects. This hypersensitiveness, which was first analysed by Richet,48 is specific for the substance which has been injected. Now all these specific reac­tions, the precipitin reac­tion as well as the anaphylactic reac­tion, can be called forth by proteins. Thus Richet, in his earliest experi­ments, showed that only the protein-containing part of the extract of actinians, by which he called forth anaphylaxis, was able to produce this phenomenon, and later he showed that it was generally impossible to produce anything resembling anaphylaxis by non-protein substances, e.g., cocain or apomorphin.49 Wells isolated from egg-white four different proteins (three coagulable proteins and one non-coagulable) which can be distinguished from each other by the anaphylaxis reac­tion, although all come from the same biological object.50 Michaelis as well as Wells found that the split products of the protein molecule are no longer able to call forth the anaphylaxis reac­tion. Since peptic diges­tion has the effect of annihilating the power of proteins to call forth anaphylaxis, we are forced to the conclusion that the first cleavage products of proteins have already lost the power of calling forth immunity reac­tions.

A pretty experiment by Gay and Robertson51 should be mentioned in this connec­tion. Robertson had shown

that a substance closely resembling paranucleins both in its properties and its C, H, and N content can be formed from the filtered products of the complete peptic hydrolysis of an approximately four per cent. neutral solu­tion of potassium caseinate by the action of pure pepsin at 36°C.

He considered this a case of a real synthesis of proteins from the products of its hydrolytic cleavage. This interpreta­tion was not generally accepted and received a different interpreta­tion by Bayliss and other workers. Gay and Robertson were able to show that paranuclein when injected into an animal will sensitize guinea-pigs for anaphylactic intoxica­tion for either paranuclein or casein and apparently indiscriminately. The products of complete peptic diges­tion of casein had no such effect, but the synthetic product of this diges­tion obtained by Robertson’s method has the same specific antigenic properties as paranuclein, thus making it appear that Robertson had indeed succeeded in causing a synthesis of paranuclein with the aid of pepsin from the products of diges­tion of casein by pepsin.

There are a few statements in the literature to the effect that the specificity of organisms might be due to other substances than proteins. Thus Bang and Forssmann claimed that the substances (antigens) responsible for the produc­tion of hemolysis were of a lipoid nature, but their statements have not been confirmed, and Fitzgerald and Leathes52 reached the conclusion that lipoids are non-antigenic. Ford claims to have obtained proof that a glucoside contained in the poisonous mushroom Amanita phalloides can act as an antigen. But aside from this one fact we know that proteins and only proteins can act as antigens and are therefore the bearers of the specificity of living organisms.

Bradley and Sansum53 found that guinea-pigs sensitized to beef or dog hemoglobin fail to react or react but slightly to hemoglobin of other origin. The hemoglobins tried were dog, beef, cat, rabbit, rat, turtle, pig, horse, calf, goat, sheep, pigeon, chicken, and man.

6. It would be of the greatest importance to show directly that the homologous proteins of different species are different. This has been done for hemoglobins of the blood by Reichert and Brown,54 who have shown by crystallographic measurements that the hemoglobins of any species are definite substances for that species.

The crystals obtained from different species of a genus are characteristic of that species, but differ from those of other species of the genus in angles or axial ratio, in optical characters, and especially in those characters comprised under the general term of crystal habit, so that one species can usually be distinguished from another by its hemoglobin crystals. But these differences are not such as to preclude the crystals from all species of a genus being placed in an isomorphous series (p. 327).

As far as the genus is concerned it was found that the hemoglobin crystals of any genus are isomorphous.

In some cases this isomorphism may be extended to include several genera, but this is not usually the case, unless as in the case of dogs and foxes, for example, the genera are very closely related.

The most important ques­tion for us is the following: Are the differences between the corresponding hemoglobin crystals of different species of the same genus such as to warrant the statement that they indicate chemical differences? If this were the case we might say that blood reac­tions as well as hemoglobin crystals indicate that differences in the constitu­tion of proteins determine the species specificity and, perhaps, also species heredity. The following sentences by Reichert and Brown seem to indicate that this may be true for the crystals of hemoglobin.

The hemoglobins of any species are definite substances for that species. But upon comparing the corresponding substances (hemoglobins) in different species of a genus it is generally found that they differ the one from the other to a greater or less degree; the differences being such that when complete crystallographic data are available the different species can be distinguished by these differences in their hemoglobins. As the hemoglobins crystallize in isomorphous series the differences between the angles of the crystals of the species of a genus are not, as a rule, great; but they are as great as is usually found to be the case with minerals or chemical salts that belong to an isomorphous group (p. 326).

As Professor Brown writes me, the difficulty in answering the ques­tion definitely, whether or not the hemoglobins of different species are chemically different, lies in the fact that there is as yet no criterion which allows us to discriminate between a species and a Mendelian muta­tion except the morpho­logical differences. It is not impossible that while species differ by the constitu­tion of some or most of their proteins, Mendelian heredity has a different chemical basis.

It is regrettable that work like that of Reichert and Brown cannot be extended to other proteins, but it seems from anaphylaxis reac­tions that we might expect results similar to those in the case of the hemoglobins. The proteins of the lens are an excep­tion inasmuch as, according to Uhlenhuth, the proteins of the lens of mammals, birds, and amphibians cannot be discriminated from each other by the precipitin reac­tion.55

7. The serum of certain humans may cause the destruc­tion or agglutina­tion of blood corpuscles of certain other humans. This fact of the existence of “isoagglutinins” seems to have been established for man, but Hektoen states that he has not been able to find any isoagglutinins in the serum of rabbits, guinea-pigs, dogs, horses, and cattle. Landsteiner found the remarkable fact that the sera of certain individuals of humans could hemolyze the corpuscles of certain other individuals, but not those of all individuals. A systematic investiga­tion of this variability led him to the discovery of three distinct groups of individuals, the sera of each group acting in a definite way towards the corpuscles of the representatives of each other group. Later observers, for example Jansky and Moss, established four groups. These groups are, according to Moss,56 as follows:

Group 1. Sera agglutinate no corpuscles.

Corpuscles agglutinated by sera of Groups 2, 3, 4.

Group 2. Sera agglutinate corpuscles of Groups 1, 3.

Corpuscles agglutinated by sera of Groups 3, 4.

Group 3. Sera agglutinate corpuscles of Groups 1, 2.

Corpuscles agglutinated by sera of Groups 2, 4.

Group 4. Sera agglutinate corpuscles of Groups 1, 2, 3.

Corpuscles agglutinated by no serum.

The relative frequency of the four groups follows from the following figures. Of one hundred bloods tested by Moss in series of twenty there were found:

10 belonging to Group 1.

40 belonging to Group 2.

7 belonging to Group 3.

43 belonging to Group 4.

Groups 2 and 4 are in the majority and in overwhelming numbers, which indicates that, as a rule, the sera agglutinate the blood corpuscles of individuals of the other groups, but not those of individuals belonging to the same group. The phenomenon that a serum agglutinates no corpuscles (Group 1), or that the corpuscles are agglutinated by no serum (Group 4), are the excep­tions. It is obvious that, as far as our problem is concerned, only Groups 2 and 3 are to be considered. There is no Mendelian character which refers only to one half of the individuals except sex. Since nothing is said about a rela­tion of Groups 2 and 3 to sex such a rela­tion probably does not exist.

8. The facts thus far reported imply the sugges­tion that the heredity of the genus is determined by proteins of a definite constitu­tion differing from the proteins of other genera. This constitu­tion of the proteins would therefore be responsible for the genus heredity. The different species of a genus have all the same genus proteins, but the proteins of each species of the same genus are apparently different again in chemical constitu­tion and hence may give rise to the specific biological or immunity reac­tions.

We may consider it as established by the work of McClung, Sutton, E. B. Wilson, Miss Stevens, Morgan, and many others, that the chromo­somes are the carriers of the Mendelian characters. These chromo­somes occur in the nucleus of the egg and in the head of the sperm. Now the latter consists, in certain fish, of lipoids and a combina­tion of nucleinic acid and protamine or histone, the latter a non-coagulable protein, more resembling a split product of one of the larger coagulable proteins.

A. E. Taylor57 found that if the spermatozoa of the salmon are injected into a rabbit, the blood of the animal acquires the power of causing cytolysis of salmon spermatozoa. When, however, the isolated protamines or nucleinic acid or the lipoids prepared from the same sperm were injected into a rabbit no results of this kind were observed. H. G. Wells more recently tested the relative efficiency of the constituents of the testes of the cod (which in addi­tion to the constituents of the sperm contained the proteins of the testicle). From the testicle he prepared a histone (the protein body of the sperm nucleus), a sodium nucleinate, and from the sperm-free aqueous extract of the testicles a protein resembling albumin was separated by precipita­tion.58

The albumin behaved like ordinary serum albumin or egg albumin, producing typical and fatal anaphylactic reac­tions and being specific when tried against mammalian sera. The nucleinate did not produce any reac­tions when guinea-pigs were given small sensitizing and larger intoxicating doses (0.1 gm.) in a three weeks’ interval; a result to be expected, since no protein is present in the prepara­tion. The histone was so toxic that its anaphylactic properties could not be studied.

It is not impossible that protamines and histones might be found to act as specific antigens if they were not so toxic. The positive results which Taylor observed after injec­tion of the sperm might have been due to the proteins contained in the tail of the spermatozoa, which in certain animals at least does not enter the egg and hence can have no influence on heredity.

It is thus doubtful whether or not any of the constituents of the nucleus contribute to the determina­tion of the species. This in its ultimate consequences might lead to the idea that the Mendelian characters which are equally transmitted by egg and spermato­zoön, determine the individual or variety heredity, but not the genus or species heredity. It is, in our present state of knowledge, impossible to cause a spermato­zoön to develop into an embryo,59 while we can induce the egg to develop into an embryo without a spermato­zoön. This may mean that the protoplasm of the egg is the future embryo, while the chromo­somes of both egg and sperm nuclei furnish only the individual characters.