Frog Liver Research Articles

Cellular lipoproteins: IV. The insoluble lipoproteins of various tissues

1. 1. The insoluble lipoprotein was prepared from the liver, kidney, lung, brain, muscle, and red cell membranes of the rabbit and rat and in the livers of bull frogs and trout. 2. 2. The insoluble lipoproteins prepared from the various tissues differ from each other. 3. 3. There is a species difference in the insoluble lipoprotein prepared from the same tissues from different animals. 4. 4. The lipoprotein prepared from red cell membranes seems to be an excellent one to study the protein, lipid, and carbohydrate components comprising the lipoprotein.

Insulin stimulus of leucine incorporation into frog liver protein

Slices prepared from livers of bull frogs ( Rana catesbiana), pancreatectomized and/or hypophysectomized 7 days before, were incubated 2 hr in frog Ringer-bicarbonate solution at 25 C. Incorporation of leucine-1-C14 into protein was subnormal in the pancreatectomized series. The addition of insulin in vitro, with glucose also present in the medium, produced a significant ( P < 0.01) stimulation of amino acid incorporation in the following series: livers from normal fed animals; livers from animals pancreatectomized 7 days before; and livers from animals pancreatectomized and hypophysectomized 7 days before. Neither insulin nor glucose alone gave a significant effect. These results therefore confirm and extend those obtained with rat liver slices showing that insulin can stimulate amino acid incorporation into protein when added directly to liver. The effect is relatively greatest with livers from animals pancreatectomized 7 days before; the insulin effect does not depend on the presence of the pituitary, as it is obtainable with livers from animals hypophysectomized and pancreatectomized 7 days previously.

Lack of species specificity of antibody to an enzyme.

Antibodies to crystalline bovine hepatic L-glutamic dehydrogenase were induced in rabbits. These antibodies inhibited the bovine glutamic dehydrogenase used as antigen, and also inhibited glutamic dehydrogenases from rat, rabbit, human, pigeon, and frog livers, as well as frog renal and muscle glutamic dehydrogenase. The antibody did not inhibit yeast glutamic dehydrogenase which differs from the animal enzymes in cofactor requirement. The kinetic characteristics of the inhibition of the bovine glutamic dehydrogenase indicate mixed competitive and non-competitive inhibition, suggesting reaction with multiple antigenic sites; the data indicate competitive inhibition of the enzyme from other species, suggesting reaction with the catalytic site.

Excretion of nitrogen compounds by perfused frog liver.

The differences in excretion of nitrogen compounds in the perfused livers of summer and winter frogs ( Rana esculenta) are related to temperature change of environment. From the results obtained it was established that in summer (over 15 C) the nitrogen metabolism was about five times more intensive than in winter (below 10 C).

Studies on dehydrogenase activities during amphibian metamorphosis

The levels of activity of glutamic acid, lactic acid, glucose 6-phosphate, and malic acid dehydrogenases in prematamorphic tadpole liver and adult frog liver were determined. The level of glutamic acid dehydrogenase activity is six times higher in adult frog liver than in tadpole liver. Adult frog liver has slightly higher malic acid dehydrogenase, but lower glucose 6-phosphate and lactic acid dehydrogenase activities than tadpole liver. During thyroxine-induced metamorphosis (immersion of tadpoles in 2.6 · 10 −8 M thyroxine), the glutamic acid dehydrogenase activity of tadpole liver increased 150% after 20 days; lactic acid dehydrogenase and glucose 6-phosphate dehydrogenase activities decreased to 50–60% and to 75–80%, respectively, of the premetamorphic values. Tadpole and frog liver glutamic acid dehydrogenase is active with both DPN with the H 2O 2-generating system and 10 −6 M KI, for 2 or more minutes prior to addition of 131I, iodinating activity was destroyed (Table II). KI (10 −5 M) and tyrosine (10 −3 M) present during the incubation protected the enzyme (Table III).

Amino acid activating enzymes and pyrophosphatase in frog and tadpole liver

Amino acid activating enzymes were studied in the soluble fraction, in the isolated nuclei, and in a particulate fraction of frog and tadpole liversusing the ATP-[ 32P]PP i exchange method. The soluble fraction was found to possess the highest specific activity. Lysine, leucine, and valine activating enzymes were the most active in both the frog and tadpole liver supernatant fraction. A glutamic acid activating enzyme was found to be present in the soluble fraction which had a pH optimum of 5.2. Mg 2+ and to a greater extent Mg 2+ together with ATP were found to increase the heat stability of certain of the amino acid activating enzymes. Certain amino acid activating enzymes were studied in both the soluble and the particulate fraction during thyroxine-induced metamorphosis. No change in activity during metamorphosis was observed. Pyrophosphatase in frog liver supenatant fraction was found to be 2 to 2.5 times higher than in tadpole liver supernatant fraction.

Physical and Kinetic Properties of Carbamyl Phosphate Synthetase from Frog Liver

Physical and Kinetic Properties of Carbamyl Phosphate Synthetase from Frog Liver

Histochemical localization of L-gulonolactone oxidase activity in tissues of several species.

SummaryA histochemical method was described which localized the activity of L-gulonolactone oxidase, the final oxidative step in synthesis of ascorbic acid from glucose. The enzyme was found to be active in the centrilobular cells of the rat liver and in selected portions of the mesonephric tubules of the frog kidney. It was absent from guinea pig kidney and liver, and from frog liver.

The effects of hydrocortisone on glycogen storage and phosphorylase activity of frog liver.

The effects of hydrocortisone on glycogen storage and phosphorylase activity of frog liver.

Biochemistry of amphibian oocytes. I. Method of isolation and nucleic acid content of nuclei

A procedure for the mass isolation of frog mature ovarian egg nuclei is described. Chemical analyses of these nuclei indicate they contain approximately 800 times more DNA and roughly 3600 times more RNA than frog liver nuclei. Because of the extraordinary DNA content, the mature ovarian egg nucleus is apparently an exception to the general rule of DNA constancy in nuclei of a species. Regardless of its remarkable DNA content, the nucleus contributes only about one-sixth to one-tenth of the total DNA found in the egg. These measurements support the suggestion that DNA of mature ovarian egg nucleus is metabolically highly active.

Monoamine oxidase, thyroid activity and hyperglycaemia in the frog.

SUMMARY 1. Estimations of monoamine oxidase (m.o.) activity in suspensions of frog liver taken at monthly intervals showed that activity was relatively constant during the greater part of the year (mean value 8·6 ± 0·332 μl. O2/15 min/mg colloid nitrogen), but it rose to a significantly higher level from August to November inclusive (mean 11·7 ± 0·513 μl. O2/15 min/mg colloid nitrogen). 2. The pattern of seasonal variation in enzyme activity showed no correspondence with the annual cycle of change in the thyroid gland, nor was there any correlation between m.o. activity of the liver and the histological appearance of the thyroid in individual frogs. 3. Inhibition of m.o. in vivo by iproniazid elicited a hyperglycaemic response to excitement in previously unresponsive frogs which was almost identical with that obtained after treatment with thyroxine and iproniazid. 4. There was no evidence that treatment with thyroxine led to any alteration in the activity of liver m.o. 5. It is concluded that m.o. is not an important factor in the inactivation of catechol amines in the strongly stimulated frog, but the possibility is discussed that under natural conditions of lower stress the high enzyme activity from August to November might be one factor tending to limit mobilization of liver glycogen.

Influence of 31-Mev X-Rays on Excretion of Nitrogen Compounds in Isolated Liver of Irradiated Frogs

Numerous authors have studied the changes brought about in the liver by wholebody irradiation with ionizing rays. Pohle and Bunting (1), Rhoades (2), and others hold that the liver is morphologically relatively resistant. Patt and Brues (3) are of the opinion that this resistance is partly due to the remarkable regenerative capacity of the liver. Rhoades (2) considers the changes in the liver parenchyma caused by irradiation as the secondary effect of an over-all intoxication. Experiments carried out in this laboratory do not support this view. The effect of ionizing rays on the functional ability of the liver is controversial. Schwartz et al. (4) established that the change of serum proteins irradiated with ionizing rays is not due to fundamental changes in the liver functions. Sherman and Forssberg (5), on the contrary, are of the opinion that the liver is radiosensitive. Gabrieli and Cuttler (6) likewise hold that the Kupfer cells are extremely sensitive to ionizing rays. The aim of this study was to determine, by means of the perfusion of frog liver, the level of nitrogen compounds excreted by Rana esculenta irradiated with X-rays. These experiments afford an opportunity of indirectly studying the effect of irradiation on the liver and on the protein metabolism therein. Gustafson and Koletsky (7) have established an increased nitrogen excretion through the kidneys of the irradiated animals. In this process the liver might play an important role. Williams et al. (8), Krise et al. (9), Kay et al. (10), Jackson and Entenman (11), and Hunter (12) have also established an increased excretion of nitrogen compounds through the urine after irradiation. Further it was found (13-18) that the activity of some enzymes in the liver is not, or is only slightly, changed. The experiments discussed below refer to the increased excretion of nitrogen compounds by isolated liver.

Effects of iodoacetate on potassium, glucose and lactic acid metabolism in isolated perfused frog liver.

Iodoacetate (IAA) caused a decreased lactic acid production and increased glucose and potassium losses in the isolated perfused frog liver. These effects of IAA are compared to those of epinephrine which increased lactic acid production as well as causing glucose and potassium losses. Interpretation of these results is based on the assumption that both agents will cause an increase in the concentration of hexosemonophosphates, an event which may be associated with potassium loss from the liver.

Decrease in thermal stability of frog liver carbamyl phosphate synthetase by substrates and cofactors

Decrease in thermal stability of frog liver carbamyl phosphate synthetase by substrates and cofactors

Blockade of hyperkalemia and hyperglycemia induced by epinephrine in frog liver and in cats.

Dihydroergotamine (DHE) and Dibenamine are both known to block the hyperkalemic response to intravenously injected epinephrine. By simultaneously sampling blood from the hepatic vein and from the carotid artery it was possible to demonstrate that these blocking agents act directly on the liver. DHE is also known to decrease the hyperglycemic response to epinephrine, an observation confirmed in the present work. Although Dibenamine is said by some to be ineffective in this respect, we found that it significantly decreased the hyperglycemia. Various dosage combinations of DHE were ineffective in changing the potassium or glucose losses induced by different concentrations of epinephrine administered to the isolated perfused frog liver. Dibenamine also exhibited no effect on the response of the frog liver.

Effects of epinephrine on lactic and keto-acid production, phosphate balance and pH changes in the isolated perfused frog liver.

The study of the isolated perfused frog liver has been extended to show that epinephrine will cause an increase in lactic acid and keto-acid production. This reaction is brief and corresponds to the period of potassium loss. A decrease in the pH of the effluent was noted. The duration of this change mimics the course of increased glucose production. No change in the phosphate balance could be detected. These results are discussed as they relate to the present views of epinephrine action.

Purification of Carbamyl Phosphate Synthetase from Frog Liver

Purification of Carbamyl Phosphate Synthetase from Frog Liver

Observations on epinephrine and glucagon-induced glycogenolysis and potassium loss in the isolated perfused frog liver.

In the isolated perfused frog liver, epinephrine and glucagon produced potassium and glucose losses. Potassium loss preceded the glucose loss and the potassium loss ceased as glucose loss reached a maximum rate. After stimulation and after glucose loss begins to decrease, the liver was able to regain potassium. Both the potassium and glucose losses were influenced by the potassium concentration of the perfusion medium. Potassium loss was accompanied by sodium loss. The dose response to epinephrine in this preparation was similar for both the potassium loss and glycogenolysis.

THE ROLE OF THE LIVER IN THE INACTIVATION OF THE MELANOCYTE STIMULATING HORMONE IN THE BODY

WHEN melanocyte stimulating hormone (MSH) is injected into an animal, the blood level of MSH decreases rapidly thereafter (1). As only a small portion of injected MSH is excreted in the urine (2), the hormone is either rapidly destroyed or bound by tissue in the body. As the inactivation of posterior pituitary hormones (3, 4) and gonadotrophic hormone (5, 6) by the liver has been reported previously, the role of liver in the rapid disappearance of MSH from the circulation has been studied. Previously Eser and Tuzunkam (7) reported the inactivation of MSH by the liver of rat, pigeon and frog in vitro but Durlach and Cachin (8) could not observe the inactivation of MSH by the liver in vivo. In the present study MSH was administered to hepatectomized dogs and to dogs with injured liver and the disappearance rate of injected MSH from the circulation in the dogs was compared with that in normal dogs.

Inactivation of insulin by the isolated liver of the bullfrog.

Experiments are presented in which insulin solutions were perfused through isolated frog livers in order to study the inactivation of this hormone by liver tissue. The solutions were recirculated many times and aliquots were tested biologically at various intervals for hypoglycemic activity. While insulin retains its activity after a single frog liver perfusion, it is gradually inactivated with increasing numbers of reperfusions. This result is in accord with the inactivation of insulin by liver slices and liver brei as reported by others. The relatively slow inactivation of insulin when perfused through the isolated frog liver is in contrast to the inactivation of glucagon which, as previously reported, loses its hyperglycemic activity after a single perfusion through this preparation. The general significance of this finding is discussed.