CHANGES OF APPARENT IONIC MOBILITIES IN PROTOPLASM : III. SOME EFFECTS OF GUAIACOL ON HALICYSTIS

Lowering the pH of sea water from 8.2 to 6.4 lowers the positive P.D. of Halicystis reversibly (this does not happen with Valonia). Exposure to sea water at pH 6.4 does not affect the apparent mobility of Na+ or of K+ (this agrees with Valonia). Guaiacol makes the P.D. of Halicystis less positive (in Valonia it has the opposite effect). Exposure to guaiacol does not reverse the effect of KCl in Halicystis which in this respect differs from Valonia. The P.D. can be changed from 66 mv. positive to 23 mv. negative by the combined action of KCl and guaiacol. Exposure to guaiacol affects Halicystis and Valonia similarly in respect to their behavior with dilute sea water. Normally the dilute sea water makes the P.D. more negative but after sufficient exposure to guaiacol dilute sea water either produces no change in P.D. or makes it more positive. In the latter case we may assume that the apparent mobility of Na+ has become greater than that of Cl- as the result of the action of guaiacol. (Normally the apparent mobility of Cl- is greater than that of Na+.) In Halicystis, as in Valonia and in Nitella, an organic substance can greatly change the apparent mobilities of certain inorganic ions (K+ or Na+)

PACEMAKERS IN NITELLA : III. ELECTRICAL ALTERNANS

An electrical impulse traveling along a Nitella cell may produce a complete or a partial response. The two kinds of response may occur in regular alternation. The partial response varies greatly and may be so far reduced as to appear as a local thickening in the upstroke of the action curve, usually accompanied by a more or less pronounced hump. In consequence a considerable variety of action curves is produced. The observations show that different regions of the cell may react differently

THE KINETICS OF PENETRATION : I. EQUATIONS FOR THE ENTRANCE OF ELECTROLYTES

When the only solute present is a weak acid, HA, which penetrates as molecules only into a living cell according to a curve of the first order and eventually reaches a true equilibrium we may regard the rate of increase of molecules inside as See PDF for Equation where PM is the permeability of the protoplasm to molecules, Mo, denotes the external and Mi the internal concentration of molecules, Ai denotes the internal concentration of the anion A- and See PDF for Equation (It is assumed that the activity coefficients equal 1.) Putting PMFM = VM, the apparent velocity constant of the process, we have See PDF for Equation where e denotes the concentration at equilibrium. Then See PDF for Equation where t is time. The corresponding equation when ions alone enter is See PDF for Equation. where K is the dissociation constant of HA, PA is the permeability of the protoplasm to the ion pair H+ + A-, and Aie denotes the internal concentration of Ai at equilibrium. Putting PAKFM = VA, the apparent velocity constant of the process, we have See PDF for Equation and See PDF for Equation When both ions and molecules of HA enter together we have See PDF for Equation where Si = Mi + Ai and Sie is the value of Si at equilibrium. Then See PDF for Equation VM, VA, and VMA depend on FM and hence on the internal pH value but are independent of the external pH value except as it affects the internal pH value. When the ion pair Na+ + A- penetrates and Nai = BAi, we have See PDF for Equation and See PDF for Equation where PNaA is the permeability of the protoplasm to the ion pair Na+ + A-, Nao and Nai are the external and internal concentrations of Na+, See PDF for Equation, and VNa is the apparent velocity constant of the process. Equations are also given for the penetration of: (1) molecules of HA and the ion pair Na+ + A-, (2) the ion pairs H+ + A- and Na+ + A-, (3) molecules of HA and the ion pairs Na+ + A- and H+ + A-. (4) The penetration of molecules of HA together with those of a weak base ZOH. (5) Exchange of ions of the same sign. When a weak electrolyte HA is the only solute present we cannot decide whether molecules alone or molecules and ions enter by comparing the velocity constants at different pH values, since in both cases they will behave alike, remaining constant if FM is constant and falling off with increase of external pH value if FM falls off. But if a salt (e.g., NaA) is the only substance penetrating the velocity constant will increase with increase of external pH value: if molecules of HA and the ions of a salt NaA. penetrate together the velocity constant may increase or decrease while the internal pH value rises. The initial rate See PDF for Equation (i.e., the rate when Mi = 0 and Ai = 0) falls off with increase of external pH value if HA alone is present and penetrates as molecules or as ions (or in both forms). But if a salt (e.g., NaA) penetrates the initial rate may in some cases decrease and then increase as the external pH value increases. At equilibrium the value of Mi equals that of Mo (no matter whether molecules alone penetrate, or ions alone, or both together). If the total external concentration (So = Mo + Ao) be kept constant a decrease in the external pH value will increase the value of Mo and make a corresponding increase in the rate of entrance and in the value at equilibrium no matter whether molecules alone penetrate, or ions alone, or both together. What is here said of weak acids holds with suitable modifications for weak bases and for amphoteric electrolytes and may also be applied to strong electrolytes

ABNORMAL PROTOPLASMIC PATTERNS AND DEATH IN SLIGHTLY HYPERTONIC SOLUTIONS

Some interesting properties of protoplasm are revealed when slightly hypertonic solutions of sugars or of electrolytes are applied to Nitella. The chloroplasts contract and the space between them increases and forms a characteristic pattern consisting of clear areas extending lengthwise along the cell and tapering off at both ends. The development of these areas is irreversible from the start. If the cell is returned to water after plasmolysis begins these areas continue to enlarge in much the same fashion as when no change is made in the external solution. The cell soon dies whether returned to water or left in the plasmolyzing solution. Similar results are obtained with other sugars, with NaCl, CaCl2, and sea water. Similar reactions are also brought about by strong ingoing or outgoing currents of water. This suggests that mechanical action may be chiefly responsible for the result and this idea is in harmony with other facts. It seems possible that the retraction of the protoplasm from the cellulose wall may disturb the delicate non-aqueous film which covers the outer surface of the protoplasm and thus produce injury. Such an effect might take place even without visible retraction if the injury occurred in protoplasmic projections extending into the cellulose wall. A study of this behavior may throw light on the nature of the protoplasmic surface and on the properties of protoplasmic gels as well as on the process of death. An understanding of the mechanism involved may help to explain the action of hypertonic solutions in other cases as, for example, in the artificial parthenogenesis of marine eggs

A COMPARISON OF PERMEABILITY IN PLANT AND ANIMAL CELLS

Quantitative studies show a striking agreement between frog skin and plant tissues in respect to certain important aspects of permeability, antagonism, injury, recovery, and death

CHANGES OF APPARENT IONIC MOBILITIES IN PROTOPLASM : IV. INFLUENCE OF GUAIACOL ON THE EFFECTS OF SODIUM AND POTASSIUM IN NITELLA

In Nitella, as in Halicystis, guaiacol increases the mobility of Na+ in the outer protoplasmic surface but leaves the mobility of K+ unaffected. This differs from the situation in Valonia where the mobility of Na+ is increased and that of K+ is decreased. The partition coefficient of Na+ in the outer protoplasmic surface is increased and that of K+ left unchanged. Recovery after the action current is delayed in the presence of guaiacol and the action curves are "square topped.

NATURE OF THE ACTION CURRENT IN NITELLA : VI. SIMPLE AND COMPLEX ACTION PATTERNS

The experiments indicate that the protoplasm of Nitella consists of an aqueous layer W with an outer non-aqueous surface layer X and an inner non-aqueous surface layer Y. The potential at Y is measured by the magnitude of the action curve and the potential at X by the distance from the top of the action curve to the zero line. These potentials appear to be due chiefly to diffusion potentials caused by the activity gradients of KCl across the non-aqueous layers X and Y. The relative mobilities of K+ and Cl- in X and in Y can be computed and an estimate of the activity of KCl in W can be made. In the complete resting state the mobilities of K+ and Cl- in X are not very different from those in Y. The action curve is due to changes in Y which suddenly becomes very permeable, allowing potassium to move from the sap across Y into W, and thus losing its potential. A gradual loss may be due to changes in ionic mobility in Y. When recovery is incomplete and Y has not yet regained its normal potential a stimulus may cause a loss of the potential at Y giving an action curve of small magnitude. The magnitude may vary in successive action curves giving what is called a complex pattern in contrast to the simple pattern observed when recovery is complete and all the action curves are alike. Complex patterns occur chiefly in cells treated with reagents. Untreated cells usually give simple patterns. A variety of complex action patterns is discussed. It is evident that the cells of Nitella show much more variation than such highly specialized cells as muscle and nerve which give stereotyped responses. In some cases it may be doubtful whether the all-or-none law holds

CALCULATIONS OF BIOELECTRIC POTENTIALS : VI. SOME EFFECTS OF GUAIACOL ON NITELLA

Values have been calculated for apparent mobilities and partition coefficients in the outer non-aqueous layer of the protoplasm of Nitella. Among the alkali metals (with the exception of cesium) the order of mobilities resembles that in water and the partition coefficients (except for cesium) follow the rule of Shedlovsky and Uhlig, according to which the partition coefficient increases with the ionic radius. Taking the mobility of the chloride ion as unity, we obtain the following: lithium 2.04, sodium 2.33, potassium 8.76, rubidium 8.76, cesium 1.72, ammonium 4.05, ½ magnesium 20.7, and ½ calcium 7.52. After exposure to guaiacol these values become: lithium 5.83, sodium 7.30, potassium 8.76, rubidium 8,76, cesium 3.38, ammonium 4.91, ½ magnesium 20.7, and ½ calcium 14.46. The partition coefficients of the chlorides are as follows, when that of potassium chloride is taken as unity: lithium 0.0133, sodium 0.0263, rubidium 1.0, cesium 0.0152, ammonium 0.0182, magnesium 0.0017, and calcium 0.02. These are raised by guaiacol to the following: lithium 0.149, sodium 0.426, rubidium 1.0, cesium 0.82, ammonium 0.935, magnesium 0.0263, and calcium 0.323 (that of potassium is not changed). The effect of guaiacol on the mobilities of the sodium and potassium ions resembles that seen in Halicystis but differs from that found in Valonia where guaiacol increases the mobility of the sodium ion but decreases that of the potassium ion

DECREASE OF PERMEABILITY AND ANTAGONISTIC EFFECTS CAUSED BY BILE SALTS

Sodium taurocholate is able to produce a decrease in permeability and to antagonize NaCl. This confirms the hypothesis that antagonistic relations can be predicted from studies on the permeability of pure substances

A METHOD OF STUDYING RESPIRATION

An apparatus is described which makes it possible to measure rapidly and accurately small amounts of CO2 given off by organisms of all kinds. The apparatus can also be used to measure photosynthesis