THE EFFECT OF RADIOACTIVE RADIATIONS AND X-RAYS ON ENZYMES : IV. THE EFFECT OF RADIATIONS FROM RADIUM EMANATION ON SOLUTIONS OF INVERTASE.

The radiochemical inactivation of invertase by beta radiation from the radioactive products in equilibrium with radium emanation can be explained quantitatively on the same basis as that of trypsin and pepsin previously reported; namely, the rate of change in the logarithm of the concentration of the active enzyme with respect to the variable, W, is constant, under the conditions of irradiation described, when the volume of solution exposed is constant. When, within the limits stated in this paper, this volume (V) is varied, the rate of radiochemical change is inversely proportional to V; i.e., See PDF for Equation     

THE EFFECT OF RADIO-ACTIVE RADIATIONS AND X-RAYS ON ENZYMES : I. THE EFFECT OF RADIATIONS FROM RADIUM EMANATION ON SOLUTIONS OF TRYPSIN.

A quantitative study has been made of the radiochemical decomposition of trypsin by the radiations from radium emanation. The following equation accounts quantitatively for the experimental results presented. See PDF for Equation It follows from this that the amount of trypsin decomposed by the radiations from radium emanation depends on the concentration of trypsin present and is proportional to the quantity of emanation expressed in millicuries and to the time of irradiation expressed in hours. It would seem that it is the active or undissociated trypsin that is affected. Evidence has been found which suggests that the beta radiations produce the decomposition observed for which the above statement holds. Qualitative evidence has been found which suggests that x-rays, gamma rays, and beta rays produce identical effects in dilute trypsin solutions.     

THE EFFECT OF RADIOACTIVE RADIATIONS AND X-RAYS ON ENZYMES : III. A UNIT OF MEASURE OF ACTIVITY FOR RADIUM EMANATION.

In this communication we have introduced a unit to express activity or power of a given preparation of radium emanation. We have named this unit the curie-power and defined it as the activity of 1 curie of radium emanation and its radioactive products in equilibrium with it. We suggest the introduction of this unit in order that we may make a more comprehensive statement of our experimental observation. In the radiochemical reaction effected by the radiations (beta and gamma) from radium emanation in which enzymes are inactivated the chemical change in a given system is a function of the product of two variables; namely, the average activity of the radium emanation, P_a, expressed in terms of the unit millicurie-power, and time, t, expressed in hours. This product has the dimensions of energy and is identical with W which is measured in terms of the energy unit, millicurie-power hours.     

THE EFFECTS OF RADIATIONS ON BIOLOGICAL SYSTEMS : I. INFLUENCE OF HIGH-FREQUENCY X-RAY RADIATION UPON THE DURATION OF THE PREPUPAL PERIOD OF DROSOPHILAE

The effect of high-frequency x-ray irradiation in prolongation of the larval stage of Drosophila melanogaster has been studied further, and evidence presented of the attainment of a maximum effect followed by a decrease to an almost level plateau in the course curve of average (median) prepupal period (φ) as a function of the period of irradiation (t) under otherwise fixed conditions. The variation of effects of the experimental treatment with age of the larvae at the time of irradiation has been demonstrated in both control and irradiated lots, and a strikingly decreased effect observed when ventilation was not supplied as usual. Means of employment of a living system of this type as an indicator of effectiveness of radiation as in phantom depth or other distributional experiments have been presented and their use illustrated.     

THE EFFECT OF RADIATIONS FROM A MERCURY ARC IN QUARTZ ON ENZYMES : I. THE EFFECT OF ULTRA-VIOLET RADIATION ON PEPSIN IN SOLUTION.

Pepsin in solution is inactivated by the radiations from a mercury arc in quartz. It would seem that the effective radiations are those in the ultra-violet region of the spectrum. The form of the curve describing the course of the inactivation is the same as that found for monomolecular chemical change.     

THE EFFECT OF RADIATIONS FROM A MERCURY ARC IN QUARTZ ON ENZYMES : II. THE EFFECT OF ULTRA-VIOLET RADIATION ON AMYLASE IN SOLUTION

Amylase in solution is inactivated by the radiations from a mercury arc in quartz, in a manner similar to that previously reported for pepsin. The reaction was followed to a point where more than 88 per cent change had taken place, the course being that of mono-molecular radiochemical change. Apparently, this reaction is due to the influence of ultra-violet radiation alone.     

THE EFFECT OF LIGHT ON THE PERMEABILITY OF PARAMECIUM

1. The permeability of Paramecium to NH₄OH is greater when the cells are exposed to light than it is when they are in darkness. 2. This change can be demonstrated in cells exposed to monochromatic red light, though it is small. It becomes greater as the wave lengths shorten, and is greatest in the near ultra-violet. 3. The permeability increases as the duration of exposure to light is prolonged. 4. These experiments demonstrate the necessity of controlling the illumination when using Paramecium in physiological tests.     

THE EFFECTS OF RADIATIONS ON BIOLOGICAL SYSTEMS : II. IMMEDIATE AND SUBSEQUENT EFFECTS OF X-RAY IRRADIATION UPON RESPIRATION OF DROSOPHILA LARVAE

By means of measurement of CO₂ respiratory rates it has been possible to observe immediate and latent effects of x-ray irradiations upon Drosophila larvae. The observations were extended over a period of several days, the duration of the prepupal period being observed also. In every instance a significant decrease in the rate of CO₂ respiration was observed immediately after irradiation. This decrease was univariant with the period of irradiation within the experimental limits.     

COMPARATIVE STUDIES ON RESPIRATION : IV. THE EFFECT OF ETHER ON THE RESPIRATION OF WHEAT.

These experiments show that 7.3 and 3.65 per cent ether solutions cause an increase in respiration followed by a decrease. The results agree with those of Haas on Laminaria, of Gustafson on higher fungi, and of Mrs. Brooks on bacteria. They do not agree with the theory of Verworn that anesthesia is a kind of asphyxia and that it decreases respiration.     

THE EFFECT OF ULTRAVIOLET LIGHT ON PHOTOSYNTHESIS

1. An unidentified unit in the mechanism of the photosynthesis of Chlorella pyrenoidosa is rendered inactive by the absorption of one quantum of ultraviolet light (2537 Å wave length). 2. The same irradiation has no effect on the normal respiration of Chlorella pyrenoidosa. Experiments have not yet been made on the respiration inhibitable by HCN. 3. No chemical change was detected in the chlorophyll extracted from irradiated cells.     

THE EFFECT OF AUXINS ON PROTOPLASMIC STREAMING. II

1. A further study has been made of the effect of indole-3-acetic acid (auxin) on protoplasmic streaming in the epidermal cells of the Avena coleoptile. 2. The transient nature of the effect of auxin, both in accelerating and retarding streaming, is due to the temporary exhaustion of carbohydrate from the tissues. In presence of 1 per cent fructose or some other sugars the acceleration or retardation of streaming by auxin is not transient, but is maintained for at least 2 hours. 3. The retardation of streaming brought about by concentrations of auxin above 0.5 mg. per liter is due to oxygen deficiency This has been confirmed in several ways. 4. It follows that the effect of auxin is to increase the respiration of the coleoptile tissue. 5. Younger coleoptiles, 3 cm. long, are sensitive to lower concentrations of auxin than those 5 cm. long, and more readily exhibit oxygen deficiency as a result of the action of auxin. However, after decapitation their response to auxin more closely resembles that of 5 cm. coleoptiles. 6. The retardation of streaming in such coleoptiles, resulting from oxygen deficiency, is delayed by very dilute solutions of histidine. On this basis an explanation is suggested for the results of Fitting on streaming in Vallisneria leaves. 7. The mean rate of streaming in control untreated coleoptiles in pure water varies with the time of year, but not with the time of day. 8. The results support the view that auxin accelerates an oxygen-consuming process which controls the rate of protoplasmic streaming, and that the latter controls growth. The substrate for this process is probably sugar. 9. It is suggested that auxin also accelerates another oxygen-consuming process, which may withdraw oxygen from the process which controls streaming rate and hence cause retardation of the latter.     

THE EFFECT OF CERTAIN RESPIRATORY INHIBITORS ON THE RESPIRATION OF CHLORELLA

Chlorella, when made heterotrophic by means of certain sugars, respires like other heterotrophic cells when subjected to the respiratory inhibitors, hydrocyanic acid, hydrogen sulfide, and carbon monoxide. Whether the case of Chlorella is typical for green cells in general remains to be seen. Experiments with various other green organisms are being carried out, in hope of settling this point.     

THE EFFECT OF AGRONOMIC PHOTOSYSTEM-II HERBICIDES ON LICHENS

The sensitivity ofHypogymnia physodes,Lobaria pulmonariaandPeltigera aphthosaH. physodesto six photosystem II herbicides and to DBMIB was tested in the laboratory by chlorophyll flouresence and oxygen-exchange measurements. in addition, experiments with freshly isolated photobiont cells fromH. physodesandL. pulmonariawere performed. Generally, the lichens were most sensitive to the urea herbicides diuron and isoproturon, whereas the triazines atrazine, terbuthylazine, and simazine and the triazinone metamitron wre less inhibitory. Among the three lichen species invesigated,H. physodeswas the most sensitive to the urea herbicides. For the other agents, no signifiant differences between lichen species could be found. The highest pI₅₀values obtained from dose response curves were around 6.5 for isolated photobionts, but most values for lichen thalli were in the range 5-6. Thus, there is no particular sensitivity of green algal lichen photobionts to photosytem II herbicides as compared to other algae, higher plant chloroplasts or protoplasts. In nature, we observed recovery from (damaging) treatment with 10⁻⁵mol diuron 1⁻¹forH. physodeswithin weeks. Therefore, damage to lichens fromt he use of photosystem-II herbicides in agriculture is probably only of very local occurence.     

STUDIES ON THE REGULATION OF OSMOTIC PRESSURE : II. THE EFFECT OF INCREASING CONCENTRATIONS OF ALBUMIN ON THE CONDUCTIVITY OF A SODIUM CHLORIDE SOLUTION.

Egg albumin, like gelatin, influences the conductivity of a 0.6 per cent NaCl solution in two ways: (a) At an hydrogen ion concentration of about pH 3.0, increasing concentrations increase the conductivity. (b) Near the isoelectric point of albumin and at the pH of the blood, increasing concentrations of albumin decrease the conductivity of the NaCl solution.     

STUDIES ON THE REGULATION OF OSMOTIC PRESSURE : I. THE EFFECT OF INCREASING CONCENTRATIONS OF GELATIN ON THE CONDUCTIVITY OF A SODIUM CHLORIDE SOLUTION.

1. In pure gelatin solutions the conductivity of the solution increases with increasing concentrations, regardless of the hydrogen ion concentration. The actual value of the specific conductivity is greater at that reaction where the degree of ionization is greater. 2. The addition of gelatin in increasing concentrations to a 0.6 per cent sodium chloride solution affects the conductivity of that solution in two ways: (a) At pH 3.3, (where gelatin is highly ionized) the conductivity increases with each added increment of gelatin. (b) At pH 5.1 and 7.4 (where gelatin is less highly ionized) the conductivity decreases with each added increment of gelatin. A similar study is being made of crystalline egg albumin.     

THE EFFECT OF AUXINS ON PROTOPLASMIC STREAMING. III

1. A new method is described which gives a continuous record of the absolute rate of protoplasmic streaming in epidermal cells of the Avena coleoptile. 2. With this method a study was made of the influence of malate and iodoacetate on streaming velocity, in order to make correlations with the previously established effects of these substances on growth and respiration. 3. In the presence of optimum concentrations of indole-3-acetic acid in freshly cut sections, malate had no effect on streaming. In the presence of very low concentrations of the auxin, however, malate increased the range of response, so that the threshold of auxin sensitivity was lowered some ten times by the malate. Malate alone had no effect on streaming. 4. In coleoptile sections, soaked overnight in sugar solution or in water, the acceleration of streaming normally caused by auxin almost disappears, but the presence of malate causes large accelerations of streaming by the auxin. 5. Similarly, in sections from old coleoptiles, which no longer show acceleration of streaming by auxin, the acceleration is restored when malate is added together with the auxin. 6. Malate does not enter the cell as rapidly as does auxin, but easily detectable amounts penetrate within 30 minutes. 7. Iodoacetate in the concentration which inhibits growth (5 x 10^–5 M) completely inhibits the acceleration of streaming by auxin. In still lower concentrations iodoacetate slightly accelerates streaming. Higher concentrations, up to 2 x 10^–4 M, did not reduce the rate of streaming below that of controls without auxin. The effect of iodoacetate is therefore to inhibit the acceleration caused by auxin and not to affect the basal streaming rate. 8. It is concluded that, just as for growth and respiration, malate is necessary for the response to auxin shown by acceleration of streaming. This further strengthens the triple parallel between the effects of auxin on streaming, growth, and respiration, all of which are apparently mediated by the 4-carbon acid system.     

THE EFFECT OF VALENCE OF IONS ON CELLULAR PERMEABILITY TO WATER

1. Permeability to water in unfertilized eggs of the sea urchin, Arbacia punctulata, was studied by measuring the rate of swelling in hypotonic dextrose solution. 2. Permeability is greatly affected by addition of electrolytes in low concentration. 3. A decrease in permeability to water was found with increasing valence of the cation, using a series of cobaltammine chlorides in which the valence of the cation ranged from 1 to 6. 4. Conversely, an increase in permeability to water was found with increasing valence of the anion, using two series of potassium salts in which the valence of the anion ranged from 1 to 4, and 1 to 3, respectively. 5. It is concluded that the effect of electrolytes on permeability to water depends chiefly on the sign and the number of charges on the ion, in the sense that positive ions decrease permeability to water, while negative ions increase permeability to water; and the effectiveness of the ion is greater the higher its valence. 6. Antagonism has been demonstrated between cations and anions in their effect on permeability, and the method employed permits quantitative study of such antagonism.     

COMPARATIVE STUDIES ON RESPIRATION : III. THE EFFECT OF ETHER ON THE RESPIRATION AND GROWTH OF BACILLUS SUBTILIS.

1. In all the concentrations of ether studied (from 0.037 to 7.3 per cent) there is an increase in the rate of respiration of Bacillus subtilis followed by a decrease. 2. In 7.3 per cent ether in tap water there is an extraordinary increase in the output of CO₂ (amounting to 50 times the normal). This does not occur when 0.85 per cent NaCl is added, which indicates antagonism between ether and NaCl. 3. Ether is toxic in low concentrations (0.037 to 1.1 per cent) and high concentrations (3.65 to 7.3 per cent) but in intermediate concentrations (1.1 to 3.65 per cent) stimulates growth.