Chemical pathology : being a discussion of general pathology from the standpoint of the chemical processes involved / by H. Gideon Wells.

  • Wells, H. Gideon (Harry Gideon), 1875-1943.
Date:
1920
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Licence: In copyright

Credit: Chemical pathology : being a discussion of general pathology from the standpoint of the chemical processes involved / by H. Gideon Wells. Source: Wellcome Collection.

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    Globulins also occur in all cells, but in small amounts in most animal cells except the muscles, whose chief protoins belong to this or a closely related group. The globulins are quite similar to the albumins, so that there is really no sharp line between the two groups. Their insolubility in water separates them from albu- mins, and their solubility in dilute neutral salt solutions from the more complex proteins. An important feature of the globulins is the low temperature at which they coagulate—some so low that Halliburton4 believes it possible that they may be coagulated within the cells during high fevers. Hammarsten has long maintained that simple proteins form a relatively in- significant part of the cytoplasm, in opposition to the once-prevalent view that, the nucleo-proteins were limited to the nucleus, and that the cytoplasm was chiefly albumin and globulin. The general trend of opinion as influenced by the results of researches has been favorable to his contentions, and we shall probably not be far wrong in accepting his statement that—“The chief mass of the protein sub- stances of the cells does not consist of proteins in the ordinary sense, but consists of more complex phosphorized bodies, and that the globulins and albumins are to be considered as nutritive materials for the cells or as destructive products in the chemical transformation of the protoplasm.”5 Nucleo-proteins are considered to be the most important constituents of the cell, both in quantity and in relation to cell activity. In structure the nucleo- proteins are very complex, as indicated by the different products yielded on hydro- lytic cleavage of the molecule. Furthermore, there are many varieties, depending both upon the nature and proportions of the component parts. They may be described as consisting of two primary constituents—(1) nucleic acid and (2) a protein body, in chemical combination with each other like a salt. The term nucleic acid covers a large group of substances, which are characterized, on the one hand, by their frequent occurrence bound with proteins, and, on the other hand, by their yielding phosphoric acid and purine bases, pyrimidines and pentoses or hexoses on cleavage. Diagrammatically the manner of cleavage of the nucleo- proteins may be indicated as follows: Nucleo-protein nuclein6 protein nucleic acid protein phosphoric acid purine bases, pyrimidines and carbohydrates. In the cell the nucleo-proteins probably exist partly as solid structures, e. g., the chromatin framework of the nucleus, and partly dissolved in the plasma. An interesting phenomenon is the alteration in the chromatin nucleo-proteins during cell division, when they seem to lose part of the combined protein and approach more nearly pure nucleic acid—just as inorganic salts occur with the acids and bases saturating each other more or less incompletely, e. g., mono-, di-, and tri- basic phosphates. In this we have a chemical explanation of the intensity of the staining of dividing nuclei by basic dyes.7 Phosphoproteins resemble nucleo-proteins to the extent that they also yield phosphoric acid, and are somewhat similar in solubility and digestibility. They are essentially different, however, in that they do not yield nucleic acid or purine bases on cleavage. Probably members of this group are also constant components of cells. Glycoproteins (or gluco-proteins) and phospho-glycoproteins are also believed to- occur frequently or constantly in protoplasm. They are compounds of proteins with a sugar or sugar-like group, which probably usually contains nitrogen, thus differing from the ordinary hexoses and pentoses. 4 Halliburton and Mott, Archives of Neurology, 1903 (2), 727; also see Halli- burton’s “Chemistry of Muscle and Nerve.” 5 See Kossel, Munch, med. Woch., 1911 (58), 65. 6 Probably nuclein should be considered as merely one variety of nucleoprotein, with less protein than the other varieties. 7 The chemistry of the nucleo-proteins is discussed in the chapter on Uric Acid Metabolism and Gout, Chap, xxiii.