Читать книгу On Digestive Proteolysis - R. H. Chittenden - Страница 3
PREFACE
ОглавлениеThe present volume, as explained by the title, consists mainly of a reprint of the Cartwright Lectures for 1894. These lectures were originally printed in the current numbers of the Medical Record, but so many requests have been made for their publication in a more convenient and accessible form that they are now re-issued, through the courtesy of the publishers of the Record, in book-form.
It is hoped that these lectures may prove of value not only in calling attention to some of the fundamental chemico-physiological facts of digestion, but in stimulating closer investigation of the many questions which are so intimately associated with a proper understanding of the processes concerned in the digestion and utilization of the proteid food-stuffs.
R. H. CHITTENDEN.
LECTURE I.
The general nature of Proteolytic Enzymes and of Proteids.
| Introductory observations, | 1 |
| Early history of gastric digestion, | 3 |
| The proteolytic power of the pancreatic juice, | 7 |
| The general nature of proteolytic enzymes, | 8 |
| Origin of proteolytic enzymes, | 8 |
| Preparation of pepsin, | 10 |
| Reactions and composition of proteolytic enzymes, | 13 |
| The proteid nature of enzymes, | 15 |
| Conditions modifying the action of enzymes, | 17 |
| The influence of temperature on proteolytic action, | 18 |
| The influence of acids, alkalies, and other substances on the activity of enzymes, | 20 |
| Action of chloroform on pepsin, | 21 |
| Theories of enzyme action with special reference to catalysis, | 22 |
| The general nature of Proteids, | 27 |
| Classification of proteids, | 29 |
| Chemical composition of some of the more prominent proteids occurring in nature, | 31 |
| Chemical constitution of proteids, | 33 |
| The presence of hemi- and anti-groups in all typical proteids, | 34 |
| Cleavage of the albumin-molecule with dilute sulphuric acid, | 34 |
| Hydration and cleavage of albumin by the action of superheated water, with formation of atmid-albumoses, etc., | 37 |
| Action of powerful hydrolytic agents on proteid matter, | 39 |
| Initial action of pepsin-acid on proteids, | 40 |
| Scheme of the general line of proteolysis as it occurs in pepsin-digestion, with a view to the structure of the albumin-molecule, | 41 |
LECTURE II.
Proteolysis by pepsin-hydrochloric acid, with a consideration of the general nature of proteoses and peptones.
| Proteolysis by pepsin-acid, | 44 |
| Formation of hydrochloric acid in the gastric glands, | 45 |
| Liebermann’s theory regarding the formation of the acid of the gastric juice, | 46 |
| Differences in the action of free and combined acid, | 47 |
| Proteolysis in the presence of combined acid, | 49 |
| The combining power of various forms of proteid matter with hydrochloric acid, | 51 |
| Quantitative estimation of the affinity of the products of digestion for acid, | 53 |
| Richet’s theory regarding the conjugate character of the acid of the gastric juice, | 54 |
| Proteolysis in the presence of amido-acids, | 55 |
| Necessity for knowing the amount of combined acid in the stomach-contents, | 57 |
| Antiseptic action of the hydrochloric acid of the gastric juice, | 58 |
| The maximum action of pepsin exerted only in the presence of free hydrochloric acid, | 59 |
| Division of the products of pepsin-proteolysis into three main groups, | 60 |
| Detection of the products of digestion, | 61 |
| Separation of proteoses and peptones from a digestive mixture or from the stomach-contents, | 62 |
| Some of the chemical properties of peptones, | 64 |
| The so-called propeptone a mixture of proteoses, | 65 |
| Pepsin-proteolysis synonymous with a series of progressive hydrolytic changes, | 66 |
| Chemical composition of proteoses and peptones, | 67 |
| Pepsin-proteolysis a true hydrolytic and cleavage process, | 71 |
| Schützenberger’s results on the formation of fibrin-peptone, | 72 |
| Amphopeptones the final products of gastric digestion, but proteolysis never results in complete peptonization, | 73 |
| Solution of a proteid by pepsin-acid not synonymous with peptonization, | 75 |
| Influence of the removal of the products of digestion on the activity of the ferment, | 75 |
| Lack of complete peptonization by pepsin-acid not due to accumulation of the products of digestion, | 76 |
| The diffusibility of proteoses and peptones, | 77 |
| Absorption of peptones from the living stomach, | 79 |
| Differences between natural digestion in the stomach and artificial proteolysis, | 80 |
| Relative formation of proteoses and peptones in the living stomach, | 81 |
| Gastric digestion merely a preliminary step in proteolysis, | 81 |
| Intestinal digestion alone capable of accomplishing all that is necessary for the complete nourishment of an animal, | 82 |
| Some physiological properties of proteoses and peptones, | 83 |
| The experiments of Schmidt-Mülheim and Fano on the action of peptones when injected into the blood, | 84 |
| Physiological action of albumoses, | 85 |
| Introduction of albumoses into the blood, | 87 |
| Proteose-like nature of the poisons produced by bacteria, | 89 |
| The acrooalbumoses formed by the tubercle-bacillus, | 90 |
| Toxic nature of proteoses and peptones, | 91 |
LECTURE III.
Proteolysis by trypsin—Absorption of the main products of proteolysis.
| Proteolysis by trypsin, | 93 |
| Comparison of pepsin and trypsin, | 94 |
| Trypsin especially a peptone-forming ferment, | 95 |
| The primary products of trypsin-proteolysis, | 95 |
| Scheme of trypsin-digestion, showing the relationship of the products formed, | 96 |
| The fate of hemi-groups in trypsin-proteolysis, | 97 |
| The primary products of trypsin-digestion mainly antibodies, | 98 |
| Character and composition of antipeptones, | 99 |
| Antialbumid as a product of pancreatic digestion, | 100 |
| The peculiar action of trypsin in the formation of amido-acids, etc., | 101 |
| Formation of lysin and lysatin in pancreatic digestion, | 103 |
| The relationship of lysatin to urea, | 105 |
| Formation of tryptophan or proteinochromogen by trypsin, | 105 |
| Appearance of ammonia in trypsin-proteolysis, | 107 |
| Relationship between artificial pancreatic digestion and proteolysis in the living intestine, | 109 |
| Leucin and tyrosin products of the natural pancreatic digestion in the intestine, | 112 |
| The physiological significance of leucin and tyrosin, | 113 |
| Absorption of the main products of proteolysis, | 116 |
| Absorption of acid-albumin, alkali-albuminate, etc. | 117 |
| Absorption limited mainly to the intestine, very little absorption from the stomach, | 119 |
| The change which the primary products of proteolysis undergo in the process of absorption, | 120 |
| Peptones not present in the circulating blood, | 121 |
| The change which peptones and proteoses undergo by contact with the living mucous membrane of the small intestine, | 122 |
| Retrogression of peptones by contact with other living cells, etc., | 125 |
| Functional activity of leucocytes in absorption, | 128 |
| Digestive leucocytosis incited by nuclein, | 131 |
| Shore’s experiments on the ability of lymph-cells to assimilate either proteoses or peptones, | 133 |
| Lymph a true secretion from the blood-vessels, | 134 |
| Direct excitatory effect of peptones when present in the blood on the endothelial cells, | 136 |
| Selective activity of endothelial cells, | 137 |
DIGESTIVE PROTEOLYSIS
