摘要:

AbstractThere are two types (M and H) of lactic dehydrogenase that are found in most animals. The M‐type is found largely in the more anaerobic tissues, such as voluntary skeletal muscles; the H‐type is found in aerobic tissues, such as cardiac muscle. In the immature uterus, the level of M units is considerably less than that found in the mature uterus. Injection of estradiol leads to a marked increase in M units in the immature uterus, but there is no significant change in the concentration of the H form. Testosterone and progesterone, in contrast, promote a proportional increase in the two lactic dehydrogenases in the immature uterus. Testosterone, however, induces a selective synthesis of M units in the seminal vessels of the immature rat. Hypophysectomy leads to a decrease in M units of skeletal muscle. The effects of various hormones on the composition of lactic dehydrogenase of the rat and chicken will be summari

ISSN:0095-9898    

DOI:10.1002/jcp.1030660403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1965

数据来源: WILEY

摘要:

AbstractGlucocorticoid administration produces an increase in precursor incorporation into rat liver glutamic‐alanine transaminase in the whole animal and in liver preparations incubatedin vitro. The augmented incorporating ability was present in both the microsomal and cell sap fractions. The effect bothin vivoandin vitrowas specific, with little or no increase observed in the total soluble protein pool of the cell. From these results, together with information obtained from measurements of the biological half‐life of the enzyme, it is concluded that the increase in tissue level of the enzyme consequent to glucocorticoid administration results from an increased rate of biosynthesis. The possible role of environmental control of enzyme levels in cells through effects on degradation rates is discussed. The increased rate of precursor incorporation into liver glutamic‐alanine transaminasein vivowas aleady at a maximum value 12 hours after initiation of hormone administration, in contrast to the enzymelevelwhich had not increased by 12 hours and reached a peak only after 5 days. These findings suggest the possibility that there is a simultaneous induction by glucocorticoids of all the liver enzymes responsive to the ho

ISSN:0095-9898    

DOI:10.1002/jcp.1030660404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1965

数据来源: WILEY

摘要:

AbstractGlucokinase synthesis and degradation in rat liver have been studiedin vivoand in slices incubatedin vitro.Glucokinase induction in fasted rats can be obtained by administration of either glucose or insulin, although the amount of enzyme that accumulates in the latter case is small. There is an apparent lag of about 2 hours from administration of external inducer to detectable increase of glucokinase in liver. The results of delayed administration of actinomycin and puromycin indicate that formation of messenger RNA starts within 1 hour, and that completion of active enzyme rapidly follows polypeptide synthesis. An incubation system for liver slices has been developed with which glucokinase can be studiedin situfor several hours. Glucose, but not insulin, stabilizes the enzyme. Net synthesis of glucokinase has been obtained in slices of liver taken from the animal shortly after the apparent induction lag. Messenger RNA for glucokinase seems to be fairly stable; its half‐life appears to be greater than 8 hours. Actinomycin has a paradoxical effect on the disappearance of glucokinase by fasting; during the first day it prevents the normal decrease and even increases glucokinase in liver. A model of regulation of the level of glucokinase in liver is proposed in which insulin induces enzyme synthesis, high glucose concentration favors accumulation by slowing down its degradation, and glucagon prevents enzyme accumulation at a still undefined level. The rapid decrease of liver hexokinase activity in actinomycin‐treated animals is also repor

ISSN:0095-9898    

DOI:10.1002/jcp.1030660405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1965

数据来源: WILEY

摘要:

AbstractEnzymes of the gluconeogenic pathway in animals adapt so as to exhibit increased activity during fasting, in diabetes, and following the administration of glucocorticoids. Many investigators have shown that these changes result from the synthesis of new enzyme protein rather than activation of latent forms of these enzymes. Glucocorticoids appear to induce the formation of several gluconeogenic enzymes, but the available evidence indicates this is a secondary rather than a primary response. Insulin appears to suppress formation of these enzymes, but experimental evidence indicates that insulinper seis not a repressor, nor is liver glycogen level. It is more likely that suppression of liver gluconeogenic enzymes by insulin is mediated by the latter's effect on availability of glucose to peripheral tissue. In liver and adipose tissue, enzymes that participate in lipogenesis (for example, citrate cleavage enzyme and malic enzyme) increase in activity following insulin administration. These enzymes are induced by available carbohydrate, and the induction is suppressed by fat.

ISSN:0095-9898    

DOI:10.1002/jcp.1030660406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1965

数据来源: WILEY

摘要:

AbstractAddition of gibberellic acid to barley endosperm evokes the formation of α‐amylase and of other hydrolases. Protein synthesis inhibitors–notably cycloheximide–inhibit the production of the hydrolases and the incorporation of labeled amino acids into proteins. Isolation, purification, and “fingerprinting” of the gibberellic acid‐induced α‐amylase indicate that it is formed byde novosynthesis. RNA synthesis inhibitors–notably actinomycin D–also inhibit the production of α—amylase and of the other hydrolases. Gibberellic acid enhances the incorporation of labeled RNA precursors into RNA. These data are consistent with the idea that gibberellic acid controls the level of α‐amylase and of other enzymes by controlling the synthesis of specific RNA's which in turn control the synt

ISSN:0095-9898    

DOI:10.1002/jcp.1030660407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1965

数据来源: WILEY

摘要:

AbstractEcdysone is the molting hormone of insects. It is a steroid; its chemistry and physiology are briefly reviewed. One of its most interesting physiological actions is the production of “puffs” in the salivary gland chromosomes of the midgeChironomus. Since puffs are generally believed to represent activity structures of genes, the implications of gene activation have been investigated. In the blowflyCalliphora, the synthesis of messenger RNA has been demonstrated; this messenger carries the information for the enzyme dopa decarboxylase. This enzyme is inducedin vivoby ecdysone; this induction can be inhibited by actinomycin, puromycin, and other inhibitors of RNA and protein synthesis. Dopa decarboxylase is one of the key enzymes in the process of sclerotization, in which tyrosine metabolites are incorporated into the cuticle, resulting in tanning. Thus, all steps from gene activation through RNA and protein synthesis to the final physiological response have been demonstrated experimenta

ISSN:0095-9898    

DOI:10.1002/jcp.1030660408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1965

数据来源: WILEY

摘要:

AbstractThe isolated interphase chromosomes or chromatin of higher plants and animals can act as template for the conduct of DNA‐dependent RNA synthesis catalyzed by RNA polymerase. Such polymerase may be either the endogenous enzyme present in the chromatin or added exogenous enzyme purified from a different organism, asE. coli.Only a portion of the DNA of chromatin is available for transcription by RNA polymerase, the remainder being inert, repressed. The physical agents of repression are proteins of the class known as histones. Removal of histone from chromosomal DNA causes derepression of genetic material previously repressed. Analysis of a particular gene, that which supervises the synthesis of pea seed globulin, shows that the state of repression characteristic of the chromatin in life is preserved in the isolated material. That hormones which bring about increases in rate of RNA and protein synthesis in life do so by causing derepression of previously repressed genes is indicated by the fact that the template activity for RNA synthesis of chromatin isolated from organs after appropriate hormone treatment is greater than is the case without such treatmen

ISSN:0095-9898    

DOI:10.1002/jcp.1030660409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1965

数据来源: WILEY

摘要:

AbstractEstrogen action in the rat uterus can be arbitrarily considered as occurring in three steps. The first step is the interaction of the estrogen with the target tissue. This appears to be of stereospecific interaction with a receptor that is sensitive to proteinases and extremes of pH and insensitive to ribonuclease and deoxyribonuclease. The second step involves a change in the biological activity of this receptor protein due to the interaction with estrogen, a mechanism about which we have no definitive information at present. Eventually, this primary function does bring about an increase in glucose metabolism and an increase in lipid and RNA synthesis, as well as a number of other responses. The fact that these responses are all blocked by inhibitors of RNA and protein synthesis at a time when no effect on overall protein synthesis is noted suggests that the synthesis of specific enzymes may be involved. Certain complications in this interpretation are discussed. The events of the third, or amplification, step of estrogen action arise as a consequence of the first two events, and appear to include a number of metabolic changes which contribute to the increase in overall protein synthesis occurring between 2 and 4 hours after estrogen administration.

ISSN:0095-9898    

DOI:10.1002/jcp.1030660410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1965

数据来源: WILEY

摘要:

AbstractA survey is given of experimental studies on the influence of treatment with androgenic hormonesin vivoon various intermediary reactions involved in ribonucleic acid (RNA) and protein synthesis in the prostate gland and seminal vesicle, with particular reference to the control of the growth and functional differentiation of these organs by testosterone and related steroids. Studies on the influence of androgens on RNA metabolism and protein biosynthesis in mouse kidney, certain muscles, and some other extragenital tissues are also considered.

ISSN:0095-9898    

DOI:10.1002/jcp.1030660411

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1965

数据来源: WILEY

摘要:

AbstractIncreased synthesis of hepatic enzymes due to hydrocortisone is preceded by an increase in the rate of synthesis of nuclear RNA. Pulse‐labeled RNA from liver nuclei was fractionated by a differential thermal phenol procedure, and the labeled RNA of each fraction was characterized by sucrose gradient centrifugation and base composition analysis. Hormone treatment increases the rate of synthesis of three types of RNA: (1) the nuclear precursor to ribosomal RNA, (2) a rapid turnover component with base composition similar to the tissue DNA, and (3) transfer RNA. Much of the total isotope incorporation into transfer RNA can be traced to turnover of the terminal adenylate residue, but this type of labeling is insensitive to the hormone. The steroid also stimulates isotope incorporation into tissue precursor pools. This effect is abolished by actinomycin and thus is secondary to the hormonal stimulation of RNA synthesis. Growth hormone stimulates RNA synthesis in both intact and adrenalectomized rats, but induces the rapid turnover enzymes (tyrosine transaminase and tryptophan pyrrolase) only in the presence of functional adrenals. It therefore seems that glucocorticoids initiate both a generalized increase in synthesis of RNA and a selective induction of specific enzyme

ISSN:0095-9898    

DOI:10.1002/jcp.1030660412

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1965

数据来源: WILEY