Studies on the Nutrition of Blow-Fly Larvae

1931 ◽  
Vol 8 (2) ◽  
pp. 109-123 ◽  
Author(s):  
R. P. HOBSON
Keyword(s):  
Proteolytic Enzymes ◽  
Anterior Segment ◽  
Posterior Segment ◽  
Ion Concentration ◽  
Gut Contents ◽  
Middle Segment ◽  
Hydrogen Ion Concentration ◽  
Alkaline Reaction ◽  
Bacterial Action ◽  
Hind Gut

1. The mid-gut in Lucilia larvae can be divided into three distinct regions (termed anterior, middle and posterior segments). 2. Histologically the anterior and posterior segments are similar. In a feeding larva the cells are highly vacuolated and contain fat; in a starved larva the cells are deeply staining and non-vacuolated. In the middle segment the cells are always deeply staining and free from vacuoles and fat, whatever the state of nutrition. 3. The hydrogen-ion concentration varies along the gut and with the nature of the food. With liquefied meat as food, the pH is 7.5-8.0 in the crop, 7.5 in the anterior segment, 3.0-3.5 in the middle segment, 7.5-8.3 in the posterior segment, and 8.0-8.5 in the hind-gut. With fresh gelatine (pH 7.0) as food, the values are the same except in the crop and anterior segment, for which the figures are respectively pH 7.0 and 6.5. 4. It has been suggested that the acidity in the middle segment may be due to an acid secretion, the most likely component being phosphoric acid. The alkaline reaction in other parts of the gut is probably caused by ammonia, which is present in the gut-contents and excreta. 5. Tryptase, peptidase and lipase are present in the mid-gut, the enzymes being concentrated in the anterior and posterior segments. The proteolytic enzymes persist in the excreta and some extra-intestinal digestion, therefore, can occur without the aid of micro-organisms. Carbohydrate-splitting enzymes are absent except for a feeble secretion of amylase in the salivary gland. 6. By combining the evidence from various sources, I have attempted to obtain a complete picture of the process of digestion, which I suggest is as follows: The food is stored unchanged in the crop and, passing into the mid-gut, is rapidly forced into the middle segment. Some absorption of water and simple products of bacterial action occurs along the anterior segment, the concentration of the food being completed in the middle segment where the acidity prevents digestion. The food, by now of a pasty constituency, passes into the posterior segment, dissolves in the alkaline fluid and is digested and absorbed. The digestive enzymes are secreted in the anterior and posterior segments, but digestion does not progress far in the anterior segment owing to the rapid passage of the food.

scholarly journals PROTEOLYTIC ENZYMES

1946 ◽  
Vol 29 (4) ◽  
pp. 219-247 ◽  
Author(s):  
David Grob
Keyword(s):  
Proteolytic Enzymes ◽  
Reducing Agents ◽  
Sulfhydryl Groups ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Oxidizing Agents ◽  
Neutral Ph ◽  
Oxidation Reduction ◽  
Antiproteolytic Activity ◽  
Sulfhydryl Compounds

1. The literature on conditions affecting the activity of proteolytic enzymes has been reviewed. 2. Experimental data on the control of the activity of trypsin, leucoprotease, papain, serum antiprotease, leucopeptidase, and pancreatic peptidase have been presented. These data indicate that: (a) The polymorphonuclearleucocytes of the cat contain abundant proteinase and peptidase active at neutral pH; those of the rabbit lack proteinase active at neutral pH. (b) Reducing agents, including several biologically important thiol-sulfhydryl compounds and ascorbic acid, inhibit the activity of leucoprotease and trypsin. For each reductant the degree of inhibition is proportional to the reducing capacity of the medium. (c) p-Aminobenzoic acid, sulfonamides (especially sulfathiazole), and many diphenyl sulfones inhibit the activity of leucoprotease. (d) Serum, plasma, several heavy metals, ammonium salts, asparagine, thiourea, heparin, glutamic acid, tyrothricin, calcium chloride, and bile salts and bile acids also inhibit the activity of leucoprotease, and in most cases of trypsin too. (e) Preparations of tryptic digests of proteins, and egg white trypsin inhibitor, inhibit trypsin to a much greater degree than leucoprotease. (f) Mild oxidizing agents increase the activity of leucoprotease and trypsin. (g) Oxidizing agents and some inhibitors of sulfhydryl groups inhibit the antiproteolytic activity of the serum. It is suggested that serum antiprotease may consist (chiefly) of reducing agents, including thiol-sulfhydryl peptides which exert their antiproteolytic activity by virtue of the presence of sulfhydryl groups. (h) The antiproteolytic activity of the serum is progressively weakened by exposure to a hydrogen ion concentration below pH 6.5 or above pH 9.7. Because of this the pH optima of leucoprotease and trypsin are shifted in the presence of serum from pH of 7 and 8 to pH of 6 to 6.5, and the range of activity of these enzymes is slightly widened, in both acid and alkaline reactions. (i) Reducing agents increase the activity of leucopeptidase and pancreatic peptidase. Serum, sulfathiazole, and thiourea have little or no effect. 3. The significance of the oxidation-reduction system in the control of the activity of leucoprotease, trypsin, serum antiprotease, leucopeptidase, and pancreatic peptidase has been emphasized.

Studies on the Nutrition of Blow-Fly Larvae

1932 ◽  
Vol 9 (4) ◽  
pp. 359-365
Author(s):  
R. P. HOBSON
Keyword(s):  
Muscle Tissue ◽  
Proteolytic Enzymes ◽  
Liquid Food ◽  
Blow Fly ◽  
Insoluble Protein ◽  
Alkaline Reaction ◽  
Bacterial Action ◽  
Chief Factors ◽  
Fly Larvae ◽  
Structural Parts

1. Investigation of the feeding of Lucilia larvae on meat suggested that the chief factors involved are mechanical maceration and the alkaline reaction which results in the first place from bacterial action. 2. Larvae suck the fluid serum from acid muscle; they ingest semi-liquid food only when the reaction is alkaline or the free liquid has been removed. 3. Predigestion of the muscle substance is apparently not essential, as the crop contents often consist of insoluble protein. 4. The proteolytic enzymes in the larval excreta, which include a collagenase, probably serve to digest the structural parts of muscle tissue.

scholarly journals STUDIES ON THE PNEUMOCOCCUS

1922 ◽  
Vol 35 (5) ◽  
pp. 703-706 ◽  
Author(s):  
Frederick T. Lord ◽  
Robert N. Nye
Keyword(s):  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Alkaline Reaction

Dissolution of pneumococci takes place most rapidly in bile at a slightly alkaline reaction. This is probably due to death of the organisms and activation of the endocellular enzyme at its optimum hydrogen ion concentration.

The Instability of Hevea Latex

1941 ◽  
Vol 14 (1) ◽  
pp. 133-136
Author(s):  
Paul Stamberger
Keyword(s):  
Specific Conductivity ◽  
Chemical Compounds ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Specific Substance ◽  
Bacterial Action ◽  
Sodium Pentachlorophenate ◽  
Bacterial Decomposition ◽  
Colloidal State ◽  
Serum Components

Abstract In a study made on plantations in Malaya, it was found that the cause of instability is not the same for both fresh and preserved latex. The autocoagulation of fresh latex, as it will be shown, is not caused by the acid formed by bacterial action on the serum components (autoacidification). Coagulation takes place, in fact, when decomposition of the serum components is prevented by the addition of strong antiseptics. These experiments, carried out in 1938 and 1939 in Malaya, support Whitby's view that autocoagulation is not due to autoacidification, but is probably caused by enzyme action on the protein or other serum components of the latex. The behavior of preserved latex is entirely different. Coagulation on storage was found to be due to acid formation and neutralization of the preserving agent applied. Decomposition of serum components was found in cases when coagulation did not take place, which would naturally influence the further behavior of latex. The action of the preserving agents is not a simple one. Inhibiting bacterial growth and preventing decomposition are not enough to keep the latex in the liquid, colloidal state. In addition to antiseptics, chemical compounds which act specifically as coagulation preventatives must be present. Rhodes recommends 0.1 per cent ammonia in addition to sodium pentachlorophenate. This small quantity of ammonia, as it was found, is the specific substance, probably an enzyme poison, which prevents coagulation. A number of additional substances in combination with sodium pentachlorophenate were tried, and it was found that adjusting the hydrogen ion concentration on the alkali side was not sufficient to prevent coagulation, although bacterial decomposition was inhibited. Observing the changes in the specific conductivity of latex during storage was the most satisfactory method found to measure the value of preserving agents or combinations of preserving agents. An increase in the specific conductivity of latex was found after a few days' storage, provided that the preserving agent did not inhibit decomposition of the serum components. From this increase in conductivity on storage, it could be predicted whether or not the preserving agent tested would give satisfactory results, or whether or not the concentration of the preserving agent was sufficiently high.

scholarly journals THE SIGNIFICANCE OF THE HYDROGEN ION CONCENTRATION FOR THE DIGESTION OF PROTEINS BY PEPSIN

1920 ◽  
Vol 3 (2) ◽  
pp. 211-227 ◽  
Author(s):  
John H. Northrop
Keyword(s):  
Enzyme Preparation ◽  
Proteolytic Enzymes ◽  
Quantitative Agreement ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Enzyme Preparations ◽  
Weak Bases ◽  
Strong Acids ◽  
Hydrolysis Of

The experiments described above show that the rate of digestion and the conductivity of protein solutions are very closely parallel. If the isoelectric point of a protein is at a lower hydrogen ion concentration than that of another, the conductivity and also the rate of digestion of the first protein extends further to the alkaline side. The optimum hydrogen ion concentration for the rate of digestion and the degree of ionization (conductivity) of gelatin solutions is the same, and the curves for the ionization and rate of digestion as plotted against the pH are nearly parallel throughout. The addition of a salt with the same anion as the acid to a solution of protein already containing the optimum amount of the acid has the same depressing effect on the digestion as has the addition of the equivalent amount of acid. These facts are in quantitative agreement with the hypothesis that the determining factor in the digestion of proteins by pepsin is the amount of ionized protein present in the solution. It was shown in a previous paper that this would also account for the peculiar relation between the rate of digestion and the concentration of protein. The amount of ionized protein in the solution depends on the amount of salt formed between the protein (a weak base) and the acid. This quantity, in turn, according to the hydrolysis theory of the salts of weak bases and strong acids, is a function of the hydrogen ion concentration, up to the point at which all the protein is combined with the acid as a salt. This point is the optimum hydrogen ion concentration for digestion, since the solution now contains the maximum concentration of protein ions. The hydrogen ion concentration in this range therefore is merely a convenient indicator of the amount of ionized protein present in the solution and takes no active part in the hydrolysis. After sufficient acid has been added to combine with all the protein, i.e. at pH of about 2.0, the further addition of acid serves to depress the ionization of the protein salt by increasing the concentration of the common anion. The hydrogen ion concentration is, therefore, no longer an indicator of the amount of ionized protein present, since this quantity is now determined by the anion concentration. Hence on the acid side of the optimum the addition of the same concentration of anion should have the same influence on the rate of digestion irrespective of whether it is combined with hydrogen or some other ion (provided, of course, that there is no other secondary effect of the other ion). The proposed mechanism is very similar to that suggested by Stieglitz and his coworkers for the hydrolysis of the imido esters. Pekelharing and Ringer have shown that pure pepsin in acid solution is always negatively charged; i.e., it is an anion. The experiments described above show further that it behaves just as would be expected of any anion in the presence of a salt containing the protein ion as the cation and as has been shown by Loeb to be the case with inorganic anions. Nothing has been said in regard to the quantitative agreement between the increasing amounts of ionized protein found in the solution (as shown by the conductivity values) and the amount predicted by the hydrolysis theory of the formation of salts of weak bases and strong acids. There is little doubt that the values are in qualitative agreement with such a theory. In order to make a quantitative comparison, however, it would be necessary to know the ionization constant of the protein and of the protein salt and also the number of hydroxyl (or amino) groups in the protein molecule as well as the molecular weight of the protein. Since these values are not known with any degree of certainty there appears to be no value at present in attempting to apply the hydrolysis equations to the data obtained. It it clear that the hypothesis as outlined above for the hydrolysis of proteins by pepsin cannot be extended directly to enzymes in general, since in many cases the substrate is not known to exist in an ionized condition at all. It is possible, however, that ionization is really present or that the equilibrium instead of being ionic is between two tautomeric forms of the substrate, only one of which is attacked by the enzyme. Furthermore, it is clear that even in the case of proteins there are difficulties in the way since the pepsin obtained from young animals, or a similar enzyme preparation from yeast or other microorganisms, is said to have a different optimum hydrogen ion concentration than that found for the pepsin used in these experiments. The activity of these enzyme preparations therefore would not be found to depend on the ionization of the protein. It is possible of course that the enzyme preparations mentioned may contain several proteolytic enzymes and that the action observed is a combination of the action of several enzymes. Dernby has shown that this is a very probable explanation of the action of the autolytic enzymes. The optimum hydrogen ion concentration for the activity of the pepsin used in these experiments agrees very closely with that found by Ringer for pepsin prepared by him directly from gastric juice and very carefully purified. Ringer's pepsin probably represents as pure an enzyme preparation as it is possible to prepare. There is every reason to suppose therefore that the enzyme used in this work was not a mixture of several enzymes.

scholarly journals THE ROLE OF MYCOBACTERIA AND THE EFFECT OF PROTEOLYTIC DEGRADATION OF THYROGLOBULIN ON THE PRODUCTION OF AUTOIMMUNE THYROIDITIS

1969 ◽  
Vol 130 (2) ◽  
pp. 243-262 ◽  
Author(s):  
W. O. Weigle ◽  
Gloria J. High ◽  
R. M. Nakamura
Keyword(s):  
Autoimmune Thyroiditis ◽  
Proteolytic Enzymes ◽  
Ion Concentration ◽  
Experimental Autoimmune Thyroiditis ◽  
Hydrogen Ion Concentration ◽  
Initial Event ◽  
Local Areas ◽  
Experimental Autoimmune

Data are presented which suggest that the initial event involved in experimental autoimmune thyroiditis following injection of rabbits with homologous thyroglobulin in complete Freund's adjuvant is alteration of the thyroglobulin. Alteration of the thyroglobulin does not occur during incorporation into the adjuvant or in vitro storage in the adjuvant, and the mycobacteria in the adjuvant have no direct effect on the thyroglobulin. Most likely, the alteration results from an increase in hydrogen ion concentration within cells or local areas in the granuloma and the subsequent action of proteolytic enzymes. These conditions are probably established in the granuloma as the result of neutrophilic response to the mycobacteria in the adjuvant. Rabbits injected with aqueous preparations of homologous thyroglobulin partially degraded in vitro with pepsin at acid pH produced antibody to native thyroglobulin and developed thyroiditis. Most of these rabbits responded to a subsequent injection of native thyroglobulin given 1 month later.

Digestion in the Tsetse-Fly: A Study of Structure and Function

Parasitology ◽  
1929 ◽  
Vol 21 (3) ◽  
pp. 288-321 ◽  
Author(s):  
V. B. Wigglesworth
Keyword(s):  
Epithelial Cells ◽  
Salivary Glands ◽  
Digestive Enzymes ◽  
Anterior Segment ◽  
Posterior Segment ◽  
Tsetse Fly ◽  
Peritrophic Membrane ◽  
Middle Segment ◽  
Columnar Cells ◽  
Blood Pigment

The anatomy, histology and digestive enzymes of the mid-intestine of the tsetse-fly have been investigated, and an attempt has been made to determine the functions of the various parts and to observe the changes to which they are subject during the digestion of blood.Histologically the mid-gut of Glossina consists of three regions:(i) An anterior segment of small, pale-staining, irregularly columnar cells, which comprises about half the total length of the mid-gut. The zone of giantcells containing bacteroids, which is very limited in extent, lies at about the middle of this region.(ii) A middle segment of large, deeply staining cells, heaped together in the resting state, which is separated abruptly from the anterior segment.(iii) A posterior segment, arising by gradual transition from the middle segment, composed of regular columnar cells.After a meal the blood is concentrated by the removal of fluid in the anterior segment but it shows no other change in this region. The giant-cells are greatly flattened but they do not regularly discharge the bacteroids which they contain and there is no evidence that these organisms play any part in the digestion of blood. Their possible function has been discussed.During digestion the cells in the middle segment contain globules of secretion, and vacuolated buds of cytoplasm are set free and disintegrate in the lumen. The blood shows an abrupt change on reaching this region; it turns black where it is in contact with the epithelium and amorphous masses of altered blood pigment are deposited.In the posterior segment, the epithelial cells become greatly vacuolated later in digestion and are probably concerned chiefly in absorption.The distribution of digestive enzymes agrees with these histological observations. The salivary glands and proventriculus contain no digestive enzymes, and the anterior and posterior segments of the mid-gut also are practically inactive. But the middle segment produces a very active tryptase which agrees in its pH-activity curve and other properties with the tryptase of the cockroach. A peptidase also is present but, except for a very weak amylase, enzymes acting upon carbohydrates are absent. The contents of the mid-gut are always slightly acid (about pH 6·5) and the tryptase present is well adapted to work at this reaction.These findings have been contrasted with those in a non-blood-sucking muscid (Calliphora). Here the salivary glands secrete an active amylase and the mid-gut is rich in amylase, invertase and maltase, whereas the proteolytic enzymes are extremely weak.Some observations have been made upon the tracheal supply to the walls of the gut. The epithelial cells of the middle segment have been shown to contain a very rich supply of intracellular tracheoles. These are usually difficult to make out in the resting cells but after a large meal the surface of the cells is ruptured and blood pigment enters the tracheoles and may extend to the sub-epithelial tracheoles and tracheae or even to quite large tracheal trunks. As the epithelial cells are flattened by the pressure of the meal, this pigment is set free in the lumen in the form of dark rods of haematin, which often bear a superficial resemblance to bacteria. The pigment in the deeper tubes appears to be slowly absorbed later. Intracellular tracheoles similar to these are present also in the mid-gut of Calliphora.The proventriculus in Glossina is a complex and has always been a puzzling structure. It has been shown that it acts as a sphincter between the fore-gut and mid-gut and that it is responsible for the production of the peritrophic membrane. This membrane, which is composed of chitin but contains a small quantity of protein, is secreted in the form of a fluid by the ring of large epithelial cells at the base of the proventriculus. The fluid is pressed and condensed to form a uniform membrane by being drawn through the cleft between the wall of the proventriculus and the funnel-shaped invagination of the fore-gut.The function of the peritrophic membrane has been discussed and it has been shown that it is freely permeable to digestive enzymes and to haemoglobin.

scholarly journals Laser microbeam study of a rotary motor in termite flagellates. Evidence that the axostyle complex generates torque.

1978 ◽  
Vol 78 (1) ◽  
pp. 76-92 ◽  
Author(s):  
S L Tamm
Keyword(s):  
Dynamic Properties ◽  
Anterior Part ◽  
Anterior Segment ◽  
Rotation Velocity ◽  
Posterior Segment ◽  
Velocity Data ◽  
Middle Segment ◽  
Laser Microbeam ◽  
Free Running ◽  
Rotary Motor

A rotary motor in a termite flagellate continually turns the anterior part of the cell (head) in a clockwise direction. Previous descriptive observations implicated the noncontractile axostyle, which runs through the cell like a drive shaft, in the motile mechanism. This study demonstrates directly that the axostyle complex generates torque, and describes serval of its dynamic properties. By laser microbeam irradiation, the axostyle is broken into an anterior segment attached to the cell's head, and a posterior segment which projects caudally as a thin spike, or axostylar projection. Before lasing, both head and axostylar projection rotate at the same speed. After breaking the axostyle, the rotation velocity of the head decreases, depending on the length of the anterior segment. Head speed is not a linear function of axostyle length, however. In contrast, the rotation velocity of the axostylar projection always increases about 1.5 times after lasing, regardless of the length of the posterior segment. Turning the head is thus a load on the axostylar rotary motor, but the speed of the posterior segment represents the free-running motor. A third, middle segment of the axostyle, not connected to the head or axostylar projection, can also rotate independently. No ultrastructural differences were found along the length of the axostyle complex, except at the very anterior end; lenth-velocity data suggest that this region may not be able to generate torque. An electric model of the axostylar rotary motor is presented to help understand the length-velocity data.

Sign in / Sign up

Export Citation Format

Share Document