The Journal of General Physiology 

About: The Journal of General Physiology is an academic journal published by Rockefeller University Press. The journal publishes majorly in the area(s): Membrane potential & Gating. It has an ISSN identifier of 0022-1295. It is also open access. Over the lifetime, 8713 publications have been published receiving 502882 citations. The journal is also known as: Journal of General Physiology & J Gen Physiol.

The metabolism of tumors in the body.

Abstract: In this contribution we discuss the question of whether tumor cells in living animals can be killed off through lack of energy, and the related question of how the tumors are supplied with oxygen and glucose in the body. We assume it is understood that tumor cells obtain the energy required for their existence in two ways: by respiration and by fermentation. In respiration they burn organic materials to carbon dioxide and water; in fermentation they split glucose to lactic acid. All tumors so far tested behave fundamentally alike. There is no essential difference between the cancer cells of transplanted rat tumors and spontaneous tumors, sarcoma and carcinoma cells, and the tar carcinoma, and Rous sarcoma produced by filtrate. The fermentation of tumors was first found with cut pieces of tumor in vitro. I C. and G. Cori 2 demonstrated it in living animals as well. They determined the glucose and lactic acid in the axillary veins of hens having in one wing a Rous sarcoma, and found in 100 cc. of blood 23 mg. less glucose and 16 rag. more lactic acid on the tumor side than on the normal side. A corresponding experiment with a human fore-arm tumor showed in 100 cc. of blood 12 rag. less glucose and 9 rag. more lactic acid on the tumor side. In experiments on the nourishment of tumors through the blood stream, we, like Cori, determined the glucose and lactic acid in tumor veins. Our procedure differed from Cori's in that we compared tumor veins and arteries, not tumor veins and corresponding normal veins. Our differences were greater than Cori's because we went closer to

The estimation of pepsin, trypsin, papain, and cathepsin with hemoglobin.

Abstract: In the hemoglobin method for the estimation of proteinase, denatured hemoglobin is digested under standard conditions, the undigested hemoglobin is precipitated with trichloracetic acid, and the amount of unprecipitated protein split products, which is a measure of the amount of proteinase present, is estimated with the phenol reagent which gives a blue color with tyrosine and tryptophane. Hemoglobin, unlike casein and gelatin, is a reproducible substrate. Different batches of hemoglobin are digested at the same rate by a given proteinasesolution. Even when peptidase is present in addition to proteinase, the formation of products not precipitable by trichloracetic acid is due so far as is known to proteinase alone. Hemoglobin methods have been described for pepsin (Anson and Mirsky, 1932), trypsin (Anson and Mirsky, 1933), papain (Anson, 1937a), and cathepsin (Anson, 1937 b). Since the methods were first worked out several minor errors have been corrected, the preparation of the hemoglobin substrates has been simplified, and the estimation procedures have been standardized. Rather than point out the numerous changes which have been made I have considered it simpler and more useful to describe completely the procedures as they are now used in this laboratory. To avoid confusion about results already published no radical changes have been made. The pepsin, trypsin, and papain substrates are the same in composition as those originally described. The cathepsin substrate now contains 0.001 M ammonium sulfate which increases the rate of digestion. In the case of the estimation of pepsin the procedure for the estimation 79

Potential, impedance, and rectification in membranes

Abstract: Impedance and potential measurements have been made on a number of artificial membranes. Impedance changes were determined as functions of current and of the composition of the environmental solutions. It was shown that rectification is present in asymmetrical systems and that it increases with the membrane potential. The behavior in pairs of solutions of the same salt at different concentrations has formed the basis for the studies although a few experiments with different salts at the same concentrations gave results consistent with the conclusions drawn. A theoretical picture has been presented based on the use of the general kinetic equations for ion motion under the influence of diffusion and electrical forces and on a consideration of possible membrane structures. The equations have been solved for two very simple cases; one based on the assumption of microscopic electroneutrality, and the other on the assumption of a constant electric field. The latter was found to give better results than the former in interpreting the data on potentials and rectification, showing agreement, however, of the right order of magnitude only. Although the indications are that a careful treatment of boundary conditions may result in better agreement with experiment, no attempt has been made to carry this through since the data now available are not sufficiently complete or reproducible. Applications of the second theoretical case to the squid giant axon have been made showing qualitative agreement with the rectification properties and very good agreement with the membrane potential data.

Crystalline soybean trypsin inhibitor : ii. general properties.

Abstract: A study has been made of the general properties of crystalline soybean trypsin inhibitor. The soy inhibitor is a stable protein of the globulin type of a molecular weight of about 24,000. Its isoelectric point is at pH 4.5. It inhibits the proteolytic action approximately of an equal weight of crystalline trypsin by combining with trypsin to form a stable compound. Chymotrypsin is only slightly inhibited by soy inhibitor. The reaction between chymotrypsin and the soy inhibitor consists in the formation of a reversibly dissociable compound. The inhibitor has no effect on pepsin. The inhibiting action of the soybean inhibitor is associated with the native state of the protein molecule. Denaturation of the soy protein by heat or acid or alkali brings about a proportional decrease in its inhibiting action on trypsin. Reversal of denaturation results in a proportional gain in the inhibiting activity. Crystalline soy protein when denatured is readily digestible by pepsin, and less readily by chymotrypsin and by trypsin. Methods are given for measuring trypsin and inhibitor activity and also protein concentration with the aid of spectrophotometric density measurements at 280 mmicro.

ATPase Activity of Myosin Correlated with Speed of Muscle Shortening

Abstract: Myosin was isolated from 14 different muscles (mammals, lower vertebrates, and invertebrates) of known maximal speed of shortening. These myosin preparations were homogeneous in the analytical ultracentrifuge or, in a few cases, showed, in addition to the main myosin peak, part of the myosin in aggregated form. Actin- and Ca++-activated ATPase activities of the myosins were generally proportional to the speed of shortening of their respective muscles; i.e. the greater the intrinsic speed, the higher the ATPase activity. This relation was found when the speed of shortening ranged from 0.1 to 24 muscle lengths/sec. The temperature coefficient of the Ca++-activated myosin ATPase was the same as that of the speed of shortening, Q10 about 2. Higher Q10 values were found for the actin-activated myosin ATPase, especially below 10°C. By using myofibrils instead of reconstituted actomyosin, Q10 values close to 2 could be obtained for the Mg++-activated myofibrillar ATPase at ionic strength of 0.014. In another series of experiments, myosin was isolated from 11 different muscles of known isometric twitch contraction time. The ATPase activity of these myosins was inversely proportional to the contraction time of the muscles. These results suggest a role for the ATPase activity of myosin in determining the speed of muscle contraction. In contrast to the ATPase activity of myosin, which varied according to the speed of contraction, the F-actin-binding ability of myosin from various muscles was rather constant.