bluuebunny/crossref_metadata_2025_split huggingface dataset:
EFFECTS OF CORTISONE ON REGENERATING RAT LIVER
Authors: Einhorn Stanley L. , Hirschberg Erich , Gellhorn Alfred 
Published: May 2004

The effects of continuous administration of cortisone on the metabolism of regenerating rat liver have been studied. Whereas the restoration of the weight of the liver after partial hepatectomy was not markedly affected by cortisone, the multiplication of cells was reduced to a significant degree after the first 2 days of regeneration. Liver restoration in terms of nucleic acids was similarly inhibited by cortisone. The results are consistent with the interpretation that the inhibition of cell multiplication in this system is dependent on and keeps pace with the inhibition of nucleic acid synthesis by this drug. At almost any time after hepatectomy, the nucleic acid content of the liver cells was the same in treated and in untreated animals.
In ancillary studies, it was shown that cortisone caused the cells of regenerating liver to be increased in size and weight through the increased infiltration of lipids. Changes in water, protein, and carbohydrate content of the liver cells did not contribute to this increase in the weight of the cells.
Since all animals were treated with cortisone for 5 days before hepatectomy, data were also obtained on the effect of this agent on the resting liver. This course of treatment brought about a significant decrease in the number of cells per unit wet weight and in the water content of the livers. The nucleic acid content of the cells at hepatectomy, on the other hand, was unchanged.
PHOTOSYNTHESIS BY PROTOPLASM EXTRUDED FROM CHARA AND NITELLA
Authors: Tolbert N. E. , Zill L. P. 
Published: May 2004

(a) Photosynthesis with protoplasm isolated from Chara or Nitella as measured by C14 fixation has been obtained at a rate 12 to 15 per cent of that of the whole cells.
(b) Photosynthesis by cut cells of Chara or Nitella with the vacuolar sap removed was at a rate comparable to that of the whole cells.
(c) Both the protoplasm and the cut cells reduced CO2 in the light to sucrose and hexose phosphates. Other products formed were also detected by paper chromatography. In contrast, dark controls fixed the C14 into products associated with plant respiration.
(d) An important difference in the products from the extruded protoplasm was the absence of C14-labelled pentoses or sedoheptulose which were formed, however, by the whole or cut cells. This suggests that the most sensitive site affected by disruption of the cells may be the steps involved in the regeneration of the "C-2 acceptor" for CO2 fixation in photosynthesis.
THE EFFECT OF ACTH AND ADRENAL STEROIDS ON K TRANSPORT IN HUMAN ERYTHROCYTES
Authors: Streeten D. H. P. , Solomon A. K. 
Published: May 2004

The effect of ACTH and adrenal steroids on K transport in human erythrocytes has been studied. A new method of calculation has revealed that in normal human erythrocytes the K transport is not independent of external K concentration as had previously been thought. The equation describing the relationship is,
K influx (m.eq./liter cells hour) = [K]pi/(0.697 + 0.329 [K]pi)
in which [K]pi refers to the plasma K concentration at the beginning of the experiment. At the physiological plasma K concentration of 4.65 m.eq./liter, K influx is 2.09 m.eq./liter cells hour; K efflux is 1.95 m.eq./liter cells hour and is independent of plasma K concentration.
The effect of the infusion of ACTH and adrenal steroids on the K content of the erythrocytes was also studied. Infusions of ACTH or cortisone do not cause the expected loss in erythrocyte K content and may well cause a gain.
Infusions of ACTH and cortisone decrease the rate of K influx and efflux slightly at all stages of the infusion, as measured in vitro in blood samples drawn at various times during and following the infusion. However, the erythrocytes incubated in vitro do not exhibit the same changes in K content as are found in vivo. Hydrocortisone added to normal cells in vitro also decreases both influx and efflux of K, without affecting the K content of the cells.
THE EFFECT OF FORMALDEHYDE ON THE OXYGEN EQUILIBRIUM OF HEMOGLOBIN
Authors: Guthe Karl F. 
Published: May 2004

1. When formaldehyde (0.10 M) is added to solutions of human hemoglobin, the oxygen affinity of the hemoglobin increases considerably (more than tenfold near pH 7). The interaction between hemes of the same hemoglobin molecule decreases, as shown by a drop in the value of n in Hill's equation from 2.9 to 1.5 or less.
2. In the presence of formaldehyde, both n and the oxygen pressure for half-saturation fall gradually as the pH rises in the range from pH 6.2 to 7.2.
3. Some of the effect of formaldehyde on the oxygen equilibrium may be due to combination with sulfhydryl groups of the protein, but nitrogenous groups are probably also involved.
ELECTRICAL STUDIES ON THE COMPOUND EYE OF LIGIA OCCIDENTALIS DANA (CRUSTACEA: ISOPODA)
Authors: Ruck Philip , Jahn Theodore L. 
Published: May 2004

The ERG of the compound eye in freshly collected Ligia occidentalis, in response to high intensity light flashes of ⅛ second or longer duration, begins with a negative on-effect quickly followed by an early positive deflection, rapidly returns to the baseline during illumination, and ends with a positive off-effect. As the stimulus intensity is decreased the early positivity progressively decreases and the rapid return to the baseline is replaced by a slowing decline of the negative on-effect. Responses were recorded with one active electrode subcorneally situated in the illuminated eye, the reference electrode in the dark eye.
The dark-adapted eye shows a facilitation of the amplitude and rates of rise and fall of the on-effect to a brief, high intensity light stimulus. This facilitation may persist for more than 2 minutes.
Following light adaptation under conditions in which the human eye loses sensitivity by a factor of almost 40,000 the Ligia eye loses sensitivity by a factor of only 3.
The flicker fusion frequency of the ERG may be as high as 120/second with a corneal illumination of 15,000 foot-candles.
Bleeding an otherwise intact animal very rapidly results in a decline of amplitude, change of wave form, and loss of facilitation in the ERG.
When the eye is deganglionated without bleeding the animal the isolated retina responds in the same manner as the intact eye.
Histological examination of the Ligia receptor layer showed that each ommatidium contains three different retinula cell types, each of which may be responsible for a different aspect of the ERG.
RELATION OF FUNCTION TO DIAMETER IN AFFERENT FIBERS OF MUSCLE NERVES
Authors: Hunt Carlton C. 
Published: May 2004

1. A method of isolation of individual afferent fibers from muscle has yielded a representative sample of the fibers which comprise groups 1 (12 to 20 µ) and II (4 to 12 µ) of the afferent fiber diameter distribution of muscle nerves in cat.
2. Afferent fibers from muscle stretch receptors account for groups I and II of the afferent diameter spectrum of muscle nerves to soleus and medial gastrocnemius. Fibers from tendon organs are largely confined to the diameter range above 12 µ. This fiber group, which has a simple one-peak diameter distribution, is termed group IB. Fibers from muscle spindles show a bimodal diameter distribution and account for the remainder of fibers in the 12 to 20 µ group (termed IA) and substantially all of group II (4 to 12 µ).
3. No significant difference has been found in the receptor characteristics of the large (group IA) and intermediate sized (group II) spindle afferent fibers other than a slightly higher threshold of the latter to steady external stretch.
THE BEHAVIOR OF ISOLATED HEARTS OF THE GRASSHOPPER, CHORTOPHAGA VIRIDIFASCIATA, AND THE MOTH, SAMIA WALKERI, IN SOLUTIONS WITH DIFFERENT CONCENTRATIONS OF SODIUM, POTASSIUM, CALCIUM, AND MAGNESIUM
Authors: Barsa Mary C. 
Published: May 2004

1. The blood of Chortophaga viridifasciata was analyzed. The average concentrations of inorganic cations expressed as milligrams per cent are: sodium, 250.66; potassium, 13.52; calcium, 11.40; and magnesium, 51.15. The osmotic pressure of the blood at 0°C. is 10.7 atmospheres. Protein and non-protein nitrogen, expressed as milligrams per cent, are 253.4 and 140.0, respectively.
2. The blood of Samia walkeri has an osmotic pressure of 13.36 atmospheres at 0°C. Its protein nitrogen is 628.58, and its non-protein nitrogen, 441.20 milligrams per cent.
3. The effects of isotonic chloride solutions of sodium, potassium, calcium, and magnesium and of distilled water on the heart beat of these two species were determined. The heart of the grasshopper failed to beat in isotonic solutions of KCl, MgCl2, or in distilled water. For both insects, sodium was found to be the least toxic ion. In the case of the grasshopper, calcium ranks next in order. In the case of the moth, potassium ranks next after sodium and is followed by calcium and magnesium.
4. The ratio of sodium to potassium in milligrams per cent, necessary for maintaining the normal heart beat of Chortophaga viridifasciata is 3 to 1, but it may be increased to at least 34 to 1 without any appreciable effects. The ratio of potassium to calcium necessary for maintaining the normal heart beat of this insect is 1 to 1, and may be increased to as much as 3 to 1.
5. The ratio of sodium to potassium, in milligrams per cent, necessary for maintaining the normal heart beat of Samia walkeri was found to be equal to or to exceed 1 to 13.8. The sodium content may be increased so that the ratio of sodium to potassium is 34 to 1 without any toxic effects. The ratios of potassium to calcium required for normal heart beat in this insect may be 1 to 1, 2 to 1, or 3 to 1.
6. The hearts of the grasshoppers beat normally in isotonic solutions having an osmotic pressure of 10.7 atmospheres. They beat equally well in solutions having an osmotic pressure of 13.4 atmospheres. The hearts of the cynthia pupae beat normally in isotonic solutions having an osmotic pressure of 13.36 atmospheres. However, they also beat normally in solutions having an osmotic pressure of 10.02 atmospheres. Therefore, although the blood of the cynthia moth and of the grasshopper have different osmotic pressures, their hearts are tolerant to solutions having the same tonicity. Because of this, and since the ratios of potassium to calcium necessary for maintaining normal heart beats of both insects are the same, solutions favorable to the grasshopper may also be favorable to the cynthia moth.
RELAXATION IN EXTRACTED MUSCLE FIBERS
Authors: Bozler Emil 
Published: May 2004

1. Ethylenediamine tetraacetic acid (EDTA) in low concentrations imitates all the known effects of the relaxation factor ("Marsh factor"). In extracted muscle fibers which have contracted in a solution containing adenosinetriphosphate (ATP), the addition of EBTA causes relaxation, the subsequent addition of CaCl2, contraction.
2. In fibers which have been briefly immersed in 5 MM EDTA, ATP causes rapid relaxation if Mg is also present. These fibers have essentially the same properties as briefly extracted fibers. Brief immersion into a solution containing CaCl2 restores at once the original condition. It is concluded that EDTA produces its action by firmly combining with bound Ca, thereby inactivating it.
3. In relaxed muscle fibers not only Ca, but also lowering the concentration of Mg below a critical level, causes contraction. In such fibers Mg in the lowest effective concentrations increases contraction, but the effect reverses above a certain concentration.
4. At 0° Mg in the presence of ATP has a relaxing effect without the relaxation factor.
5. The results indicate that Mg has two distinct effects in the presence of ATP. It causes contraction at low concentrations, but above a critical concentration its relaxing action prevails. The last of these effects is blocked by bound Ca. If the latter is inactivated by EDTA, Mg in sufficiently high concentrations causes relaxation. The action of the relaxation factor can similarly be explained by assuming that it acts as a complexing agent which inactivates bound Ca.
6. Previous evidence that the relaxed state depends on the formation of an enzymatically inactive ATP-protein complex was confirmed. It was found that PP in low concentrations strongly increases the relaxing effect of ATP in briefly extracted fibers.
ENZYMATIC BREAKDOWN OF THREONINE BY THREONINE ALDOLASE
Authors: Lin Shih-Chia C. , Greenberg David M. 
Published: May 2004

1. The enzyme which splits threonine to acetaldehyde and glycine has been partially purified from rat liver (five- to sixfold purification) and the name threonine aldolase proposed for it.
2. The general properties of threonine aldolase have been studied. The enzyme is unstable to a pH below 5. The pH optimum of the enzyme reaction is at 7.5–7.7. The initial rate of production of acetaldehyde is proportional to the enzyme concentration, and when the enzyme concentration is constant, the production of acetaldehyde is proportional to the time, provided that the substrate is in excess. The enzyme is inhibited by the carbonyl group reagent, hydroxylamine. Attempts to demonstrate that pyridoxal phosphate is a cofactor were unsuccessful.
3. The enzyme splits only L-allothreonine and L-threonine and is inactive against the D-forms of these amino acids.
4. The enzyme reaction on DL-allothreonine follows first order kinetics. From the first order velocity constants and the initial rates of the rates of the reaction at various substrate concentrations the Michaelis constant, Ks, for this substrate has been evaluated. Michaelis constants have also been determined for threonine.
5. The optimum temperature for the enzymatic breakdown of DL-allothreonine at pH 7.65 was found to be 50°C. in phosphate buffer and 48°C. in tris-maleate buffer. The rate of thermal inactivation of the enzyme threonine aldolase obeys a first order reaction. The heat of thermal inactivation was calculated by the aid of the van't Hoff-Arrhenius equation to be 43,000 cal. per mole for the temperature range 41.2–46.6°C.
6. Equivalent amounts of acetaldehyde and glycine were formed from DL-allothreonine and the enzymatic breakdown of DL-allothreonine was found to be irreversible.
BIOELECTRIC EFFECTS OF IONS MICROINJECTED INTO THE GIANT AXON OF LOLIGO
Authors: Grundfest Harry , Kao C. Y. , Altamirano Mario 
Published: May 2004

1. A technique is described for recording the bioelectric activity of the squid giant axon during and following alteration of the internal axonal composition with respect to ions or other substances.
2. Experimental evidence indicates that the technique as described is capable of measuring changes in local bioelectric activity with an accuracy of 10 to 15 per cent or higher.
3. Alterations of the internal K+ or Cl- concentrations do not cause the change in resting potential expected on the basis of a Donnan mechanism.
4. The general effect of microinjection of K+ Rb+, Na+, Li+, Ba++, Ca++, Mg++, or Sr++ is to cause decrease in spike amplitude, followed by propagation block.
5. The resting potential decreases when the amplitude of the spike becomes low and block is incipient.
6. The decrease in resting potential and spike amplitude may be confined to the immediate vicinity of the injection.
7. At block, the resting potential decreases up to 50 per cent, but injection of small quantities of divalent cations may cause much larger localized depolarization.
8. The blocking effectiveness of K+, Na+, and Ca++ expressed as reciprocals of the relative amounts needed to cause block is approximately 1:5:100. Rb+ has the same low effectiveness as does K+. Li+ resembles Na+. Ba++ and Mg++ are approximately as effective as Ca++.
9. Microinjection of Na+ may cause marked prolongation of the spike at the injection site as well as decrease in its amplitude.
10. The anions used (Cl-, HCO3-, NO3-, SO4-, aspartate, and glutamate) do not seem to exert specific effects.
11. A tentative explanation is offered for the insensitivity of the resting potential to changes in the axonal ionic composition.
12. New data are presented on the range of variation, in a large sample, of the magnitude of the resting potential and spike amplitude.
THE EFFECT OF NUTRITIONAL STATE ON PHOTOREVERSAL OF ULTRAVIOLET INJURIES IN DIDINIUM NASUTUM
Authors: Brandt C. L. , Shepard D. C. , Giese A. C. 
Published: May 2004

1. The effect of the nutritional state of Didinium nasutum on its resistance to short ultraviolet (UV) radiation (2654 A) and its recovery from the injury following illumination with visible light (4350 A, blue) was studied.
2. The resistance of a didinium to UV is considerably increased by feeding it a paramecium 15 to 60 minutes before exposure to UV. If fed just before exposure to UV, the resistance is less than that of an unfed control.
3. Photoreversal is only slightly greater in didinia fed after irradiation with UV but before exposure to visible light as compared to those fed after exposure to visible light.
4. Irradiated paramecia are eaten by didinia, provided they have not started to cytolyze. Didinia fed on irradiated paramecia divide at about the same rate as controls or slightly faster.
5. The available stock of Didinium declines in vigor with lapse of time after excystment, as measured by the time required for division. The sensitivity of Didinium to UV did not change essentially during the 5 month period over which tests were made.
6. The theoretical implications of the results are considered.
TRANSMISSION IN FRACTIONATED MONOSYNAPTIC SPINAL REFLEX SYSTEMS
Authors: Lloyd David P. C. , Hunt Carlton C. , McIntyre A. K. 
Published: May 2004

A study has been made of conditions that support monosynaptic reflex transmission from afferent fibers of one part of a synergic muscle mass to motoneurons of another part. Heteronymous response so called can be brought on by prior tetanization of the afferent pathway and by asphyxiation to a critical stage. The response is facilitated by cooling and may appear in the cold preparation without need for prior tetanization.
By appropriate asymmetrical subdivision of a monosynaptic reflex system an afferent inflow can be obtained that is sufficiently powerful to secure heteronymous transmission without the need for prior tetanization or cooling. Each junction between a monosynaptic afferent fiber and a motoneuron possesses some degree of potentiality for transmitting. Transmitter potentiality of an afferent fiber at its several junctions with motoneurons varies widely. Reasons are advanced for supposing the variation to be graded rather than stepwise, and quantitative rather than qualitative.
HISTONES WITH HIGH LYSINE CONTENT
Authors: Daly M. M. , Mirsky A. E. 
Published: May 2004

1. The preparation and properties of lysine-rich histones, which differ in a number of respects from the classical arginine-rich histones, have been described.
2. Lysine-rich histones, like those previously known, are located in cell nuclei.
3. Lysine-rich histones dissociate more readily from combination with nucleic acid than do other histones.
INACTIVATION OF BACTERIOPHAGES BY DECAY OF INCORPORATED RADIOACTIVE PHOSPHORUS
Authors: Stent Gunther S. , Fuerst Clarence R. 
Published: May 2004

The inactivation of the phages T1, T2, T3, T5, T7, and λ by decay of incorporated P32 has been studied. It was found that these phages fall into two classes of sensitivity to P32 decay: at the same specific activity of P32 in their deoxyribonucleic acid (DNA), T2 and T5 are inactivated three times as rapidly as T1, T3, T7, and λ. Since the strains of the first class were found to contain about three times as much total phosphorus per phage particle as those of the second) it appears that the fraction of all P32 disintegrations which are lethal is very nearly the same in all the strains. This fraction α depends on the temperature at which decay is allowed to proceed, being 0.05 at –196°C., 0.1 at +4°C., and 0.3 at 65°C.
Decay of P32 taking place only after the penetration of the DNA of a radioactive phage particle into the interior of the bacterial cell can still prevent the reproduction of the parental phage, albeit inactivation now proceeds at a slightly reduced rate. T2 phages inactivated by decay of P32 can be cross-reactivated; i.e., donate some of their genetic characters to the progeny of a mixed infection with a non-radioactive phage. They do not, however, exhibit any multiplicity reactivation or photoreactivation.
The fact that at low temperatures less than one-tenth of the P32 disintegrations are lethal to the phage particle and the dependence of the fraction of lethal disintegrations on temperature can be accounted for by the double stranded structure of the DNA macromolecule.
THE INACTIVATION OF DILUTE SOLUTIONS OF CRYSTALLINE TRYPSIN BY X-RADIATION
Authors: McDonald Margaret R. 
Published: May 2004

The proteolytic activity of dilute solutions of clystalline trypsin is destroyed by x-rays, the amount of inactivation being an exponential function of the radiation dose. The reaction yield increases steadily with increasing concentration of trypsin, varying, as the concentration of enzyme is increased from 1 to 300 µM, from 0.068 to 0.958 micromole of trypsin per liter inactivated per 1000 r with 0.005 N hydrochloric acid as the solvent, from 0.273 to 0.866 with 0.005 N sulfuric acid as the solvent, and from 0.343 to 0.844 with 0.005 N nitric acid as the solvent. When the reaction yields are plotted as a function of the initial concentration of trypsin, they fall on a curve given by the expression Y α XK, in which Y is the reaction yield, X is the concentration of trypsin, and K is a constant equal to 0.46, 0.20, and 0.16, respectively, with 0.005 N hydrochloric, sulfuric, and nitric acids as solvents. The differences between the reaction yields found with chloride and sulfate ions in I to 10 µM trypsin solutions are significant only in the pH range from 2 to 4.
The amount of inactivation obtained with a given dose of x-rays depends on the pH of the solution being irradiated and the nature of the solvent. The reaction yield-pH curve is a symmetrical one, with minimum yields at about pH 7. Buffers such as acetate, citrate, borate and barbiturate, and other organic molecules such as ethanol and glucose, in concentrations as low as 20 µM, inhibit the inactivation of trypsin by x-radiation. Sigmoid inactivation-dose curves instead of exponential ones are obtained in the presence of ethanol.
The reaction yields for the inactivation of trypsin solutions by x-rays are approximately 1.5 times greater when the irradiation is done at 26°C. than when it is done at 5°C., when 0.005 N hydrochloric acid is the solvent. The dependence on temperature is less when 0.005 N sulfuric acid is used, and is negligible with 0.005 N nitric acid.
The difficulties involved in interpreting radiation effects in aqueous systems, and in comparing the results obtained under different experimental conditions, are discussed.