THE STABILITY OF BACTERIAL SUSPENSIONS : V. THE REMOVAL OF ANTIBODY FROM SENSITIZED ORGANISMS.

1. The removal of antibody from Bacillus typhosus is no more complete at pH 3 than at pH 7. 2. Approximately twelve agglutinating doses are firmly combined with the organisms. Immune body in excess of this amount is easily removable by distilled water. 3. A method of testing for the presence of immune body on the organism is described which depends on the difference in the acid agglutination of sensitized and unsensitized organisms. 4. Repeated washing in distilled water will serve to remove all the immune body from sensitized bacteria.     

HYDROGEN ION CONCENTRATIONS IN THE BLOOD OF INSECTS

The range of pH values for the blood of grasshoppers and of houseflies is 7.2 to 7.6. The range of values for roaches is 7.5 to 8.0. The range for Malacosoma americanum is 6.4 to 7.4; and the range for Bombyx mori is 6.4 to 7.2. From the work of other investigators and from the writer''s results, it is apparent that the pH of insect blood, in general, may vary between 6.4 and 8.0. In the forms observed no correlation exists between blood pH and age, nor between pH and metamorphosis.     

HYDROGEN ION CONCENTRATIONS WITHIN THE ALIMENTARY TRACT OF INSECTS

Larvæ of Psychoda and of Chironomus (diptera) maintained in solutions of appropriate indicators show that the typical acidities (pH) prevailing within the several regions of the digestive tract are: esophagus 7.1; cardiac chamber 6.2; mesenteron 7.5; the latter being functionally an intestine. The acidity of the hindgut, pH 6.4, is due to the discharge of the malphigian tubules.     

THE STABILITY OF BACTERIAL SUSPENSIONS : II. THE AGGLUTINATION OF THE BACILLUS OF RABBIT SEPTICEMIA AND OF BACILLUS TYPHOSUS BY ELECTROLYTES.

1. Measurements have been made of the potential and of the cohesive force at the surface of Bacillus typhosus and the bacillus of rabbit septicemia in solutions of various salts and acids. 2. Electrolytes in low concentration (0.01 N) affect primarily the potential, and in high concentration decrease the cohesive force. 3. As long as the cohesive force is not affected, agglutination occurs whenever the potential is reduced below about 15 millivolts. 4. When the cohesive force is decreased the critical potential is also decreased, and in concentrated salt solution no agglutination occurs even though there is no measurable potential.     

THE STABILITY OF BACTERIAL SUSPENSIONS : III. AGGLUTINATION IN THE PRESENCE OF PROTEINS,NORMAL SERUM,AND IMMUNE SERUM.

1. The addition of proteins or serum to suspensions of bacteria, (Bacillus typhosus or rabbit septicemia) at different pH widens the acid agglutination zone and shifts the isoelectric point to that of the added substance. 2. The amount of serum required to agglutinate is much less near the acid agglutination point of the organisms. 3. The addition of immune serum prevents the salt from decreasing the cohesive force between the organisms, and agglutination therefore is determined solely by the potential, provided excess immune body is present. Whenever the potential is decreased below 15 millivolts the suspension agglutinates.     

THE COMBINATION OF ENZYME AND SUBSTRATE : I. A METHOD FOR THE QUANTITATIVE DETERMINATION OF PEPSIN. II. THE EFFECT OF THE HYDROGEN ION CONCENTRATION.

1. A quantitative method for the determination of pepsin is described depending on the change in conductivity of a digesting egg albumin solution. 2. The combination of pepsin with an insoluble substrate has been followed by this method. 3. The amount of pepsin removed from solution by a given weight of substrate is independent of the size of the particles of the substrate. 4. There is an optimum zone of hydrogen ion concentration for the combination of enzyme and substrate corresponding to the optimum for digestion. 5. It is suggested that the pepsin combines largely or entirely with the ionized protein.     

猪和牛轮状病毒抗原和抗体的检测

应用ELISA直接双抗体夹心法检查轮状病毒抗原,24份仔猪和29份犊牛的腹泻粪样,分别有12和16份阳性。用病毒RNA电泳分析检查阳性粪样,各出现两种病毒RNA电泳型,用中和试验检查17份成年牛和16份成年猪血清,分别有16和15份病毒抗体阳性。将其与ELISA间接法和结合法进行了比较。     

THE STABILITY OF BACTERIAL SUSPENSIONS : VI. THE INFLUENCE OF THE CONCENTRATION OF THE SUSPENSION ON THE CONCENTRATION OF SALT REQUIRED TO CAUSE COMPLETE AGGLUTINATION.

1. The concentrations of various salts required to agglutinate different concentrations for a suspension of typhoid bacilli sensitized with immune serum have been determined. 2. The electrolytes may be divided into two classes; (1) those with which the concentration required to agglutinate is independent of the concentration of the suspension; and (2) those with which the agglutinating concentration increases in proportion to the concentration of the suspension. 3. The salts comprised under (1) do not reverse the sign of the charge of the suspension. 4. The salts of Class (2) (with the exception of ZnSO₄) do reverse the sign of the charge.     

CHANGES IN THE STABILITY AND POTENTIAL OF CELL SUSPENSIONS : II. THE POTENTIAL OF ERYTHROCYTES.

1. Human and sheep erythrocytes, when placed in 0.01 N buffer solutions at reactions more acid than pH 5.2, undergo a progressive change in potential, becoming less electronegative or more electropositive. This change usually occurs within 2 hours at ordinary room temperatures. It did not occur when rabbit erythrocytes were used. 2. This change is due primarily to the liberation of hemoglobin from some of the cells. 3. Hemoglobin, even in very low concentrations, markedly alters the potential of erythrocytes in the more acid reactions. This is due to a combination between the electropositive hemoglobin and the erythrocytes. The effect of the hemoglobin is most marked in the more acid solutions; it occurs only on the acid side of the isoelectric point of the hemoglobin. 4. The isoelectric point of erythrocytes in the absence of salt, or in the presence of salts having both ions monovalent, occurs at pH 4.7. This confirms the observations of Coulter (1920–21). Divalent anions shift the isoelectric point to the acid side. 5. The effect of salts on the potential of erythrocytes is due to the ions of the salts, and is analogous in every way to the effect of salts on albumin-coated collodion particles, as discussed by Loeb (1922–23).     

THE EFFECT OF HYDROGEN ION CONCENTRATION UPON THE INDUCTION OF POLARITY IN FUCUS EGGS : III. GRADIENTS OF HYDROGEN ION CONCENTRATION

1. Gradients of hydrogen ion concentration across Fucus eggs growing in sea water determine the developmental polarity of the embryo. 2. Gradients may determine polarity even if removed before the morphological response begins. 3. The rhizoid forms on the acid side of the egg unless this is too acid, in which case it develops on the basic side of the egg. 4. Since gradients of hydrogen ion concentration in sea water produce gradients of CO₂ tension, as a result of chemical action on the carbonate buffer system, it is not proven whether the physiological effects are due to the hydrogen ions, or to the CO₂ which they produce in the medium. 5. The developmental response of the eggs to gradients of hydrogen ion (or CO₂) concentration provides an adequate but not an exclusive explanation of the group effect in Fucus. 6. Hydrogen ions may exert their effect by activating growth substance. Hydrogen ions or CO₂ probably also affect the underlying rhizoid forming processes in other ways as well.     

EFFECT OF THE HYDROGEN ION CONCENTRATION ON THE PHAGOCYTOSIS AND ADHESIVENESS OF LEUCOCYTES

1. Immediately after coming into contact with glass, leucocytes are most adhesive at pH 8.0 or > 8.0. 2. Agglutination of leucocytes increases with increasing H ion concentration from pH 8.0 to 6.0. 3. In phagocytosis experiments where leucocytes creep about on the slide picking up articles the optimum pH is 7.0. Here ameboid movement is probably the limiting factor. 4. The optimum for phagocytosis of quartz from suspension is on the acid side of neutrality at or near pH 6.7. 5. Phagocytosis of quartz increases with the acidity, while adhesiveness of leucocytes to glass increases with the alkalinity.     

THE CAMBIUM AND ITS DERIVATIVE TISSUES : VI. THE EFFECTS OF HYDROGEN ION CONCENTRATION IN VITAL STAINING

It should be emphasized, in conclusion, that the writers'' investigation is a reconnaissance, and was initiated primarily in searching for more adequate techniques for the study of cytological problems. Crude as many of the data undoubtedly are, they are of some significance in outlining future trends of more intensive investigation. The occurrence of two distinct types of vacuoles within the same cell provides a valuable check upon generalizations concerning the penetration of certain dyes. The A-type vacuole affords a means of determining that a number of dyes do penetrate living plant cells readily and rapidly from acid buffers. The recognition of two distinct categories of vacuoles—which are widely distributed throughout the higher plants—and a study of their staining reactions in Group I, Group II, and Group III dyes, indicate that certain discrepancies in the literature are due to the fact that different investigators are concerned with different vacuoles and with different dyes. For an accurate visualization of the physico-chemical mechanisms of the penetration and accumulation of dyes in living cells a much wider range of reliable data is essential, both as regards the purely biological variables and the physico-chemical variables in techniques employed in their investigation. Until such data are available, generalizations from limited induction should be reduced to a minimum.     

THE EFFECTS OF HYDROGEN ION CONCENTRATION UPON THE METAMORPHIC PATTERN OF THYROXIN- AND IODINE-TREATED TADPOLES

1. It has been shown quantitatively that the degree of response of the hind limbs of tadpoles to the action of thyroxin is dependent upon the lengths of the limbs at the beginning of treatment. 2. Both the potency of the inducing substance and the rate of penetration of the substance into the animal might be involved in the effects of hydrogen ion concentration on induced development. 3. Changes in hydrogen ion concentration affect the inducing power of thyroxin and iodine differently. With thyroxin, it is the rate of penetration of the molecule which determines the amount of growth, but with iodine it is the chemical form in which the substance has entered the animal which is of prime importance. 4. The hydrogen ion concentration of thyroxin solutions does not affect their potency when they are injected into tadpoles. 5. Change in hydrogen ion concentration of the environment does not affect the potency of thyroxin injected into tadpoles. 6. When thyroxin is administered in the environmental solution its effects, as measured by increase in hind limb length are greater at higher than at lower hydrogen ion concentrations in the range tested. 7. Since the potency of thyroxin is unaffected by change in hydrogen ion concentration when the thyroxin solution is injected, the above fact (point 6) seems explicable only on the basis of differences in the rate of penetration of thyroxin into the animals at the different hydrogen ion concentrations. 8. These differences in penetration of the thyroxin at different hydrogen ion concentrations may be the result of a differential effect of hydrogen ion concentration upon the rate of metabolism of the animal. The metabolic rate is significantly greater when the tadpoles are kept in solutions of higher hydrogen ion concentration than when they are kept in solutions of low hydrogen ion concentration. It is postulated that the rate of metabolism, since it controls the rate of intake of the environmental fluid and therefore of dissolved thyroxin, also controls the amount of thyroxin-induced development. 9. Change in hydrogen ion concentration of iodine solutions affects their potency when injected into tadpoles. A peak of effectiveness is reached at about the neutral point, with a lowered efficiency as the hydrogen ion concentration is either increased or decreased from this point. 10. Change in hydrogen ion concentration of the environment affects the potency of iodine injected into tadpoles. The effect is similar to that noted in point 9. 11. The hydrogen ion concentration of the environment seems to affect the chemical nature of the iodine in solution in the environment. If this is so, it is possible that the differences in the metamorphic effects of iodine at different hydrogen ion concentrations are dependent upon the chemical form of iodine present. 12. The effect of hydrogen ion concentration on normal development is similar to that on thyroxin-induced development; an effect on the rate of metabolism of the animal causes increased growth in more acid solutions.     

THE INFLUENCE OF ELECTROLYTES ON THE CATAPHORETIC CHARGE OF COLLOIDAL PARTICLES AND THE STABILITY OF THEIR SUSPENSIONS : I. EXPERIMENTS WITH COLLODION PARTICLES.

1. When collodion particles suspended in water move in an electric field they are, as a rule, negatively charged. The maximal cataphoretic P.D. between collodion particles and water is about 70 millivolts. This is only slightly more than the cataphoretic P.D. found by McTaggart to exist between gas bubbles and water (55 millivolts). Since in the latter case the P.D. is entirely due to forces inherent in the water itself, resulting possibly in an excess of OH ions in the layer of water in contact and moving with the gas bubble, it is assumed that the negative charge of the collodion particles is also chiefly due to the same cause; the collodion particles being apparently only responsible for the slight difference in maximal P.D. of water-gas and water-collodion surfaces. 2. The cataphoretic charge of collodion particles seems to be a minimum in pure water, increasing as a rule with the addition of electrolytes, especially if the cation of the electrolyte is monovalent, until a maximal P.D. is reached. A further increase in the concentration of the electrolyte depresses the P.D. again. There is little difference in the action of HCl, NaOH, and NaCl or LiCl or KCl. 3. The increase in P.D. between collodion particles and water upon the addition of electrolyte is the more rapid the higher the valency of the anion. This suggests that this increase of negative charge of the collodion particle is due to the anions of the electrolyte gathering in excess in the layer of water nearest to the collodion particles, while the adjoining aqueous layer has an excess of cations. 4. In the case of chlorides and at a pH of about 5.0 the maximal P.D. between collodion particles and water is about 70 millivolts, when the cation of the electrolyte present is monovalent (H, Li, Na, K); when the cation of the electrolyte is bivalent (Mg, Ca), the maximal P.D. is about 35 to 40 millivolts; and when the cation is trivalent (La) the maximal P.D. is lower, probably little more than 20 millivolts. 5. A reversal in the sign of charge of the collodion particles could be brought about by LaCl₃ but not by acid. 6. These results on the influence of electrolytes on the cataphoretic P.D. between collodion particles and water are also of significance for the theory of electrical endosmose and anomalous osmosis through collodion membranes; since the cataphoretic P.D. is probably identical with the P.D. between water and collodion inside the pores of a collodion membrane through which the water diffuses. 7. The cataphoretic P.D. between collodion particles and water determines the stability of suspensions of collodion particles in water, since rapid precipitation occurs when this P.D. falls below a critical value of about 16 millivolts, regardless of the nature of the electrolyte by which the P.D. is depressed. No peptization effect of plurivalent anions was noticed.