Metabolic block

2013 ◽  
Vol 13 (7) ◽  
pp. 440-441
Author(s):  
Sarah Seton-Rogers
Keyword(s):  
Metabolic Block

Metabolic block at early stages of the glycolytic pathway activates the Rcs phosphorelay system via increased synthesis of dTDP-glucose in Escherichia coli

2003 ◽  
Vol 51 (4) ◽  
pp. 1117-1128 ◽  
Author(s):  
Waleed El-Kazzaz ◽  
Teppei Morita ◽  
Hideaki Tagami ◽  
Toshifumi Inada ◽  
Hiroji Aiba
Keyword(s):  
Escherichia Coli ◽  
Glycolytic Pathway ◽  
Early Stages ◽  
Metabolic Block

THE DIAGNOSIS OF MAPLE SYRUP URINE DISEASE (Branched-chain Ketoaciduria)

PEDIATRICS ◽  
1963 ◽  
Vol 32 (2) ◽  
pp. 234-238
Author(s):  
Joseph Dancis ◽  
Joel Hutzler ◽  
Mortimer Levitz
Keyword(s):  
Amino Acids ◽  
Maple Syrup Urine Disease ◽  
Oxidative Decarboxylation ◽  
Maple Syrup ◽  
Peripheral Leukocyte ◽  
Metabolic Block ◽  
Urine Disease ◽  
Branched Chain ◽  
Normal Leukocyte

The metabolism of the three branched-chain amino acids has been investigated in vitro, using the peripheral leukocyte. The normal leukocyte can transaminate and decarboxylate the three amino acids. These functions are demonstrable at birth. Five cases of maple syrup urine disease (branched-chain ketoaciduria) were studied. The peripheral leukocyte could transaminate the three amino acids, but decarboxylation was greatly reduced or absent. This confirms the site of metabolic block in maple syrup urine disease, and suggests an early and specific approach to diagnosis. Oxidative-decarboxylation of the branched-chain ketoacids involves an enzyme common to all three ketoacids.

THE PATHOGENESIS AND TREATMENT OF VIRILIZING ADRENAL HYPERPLASIA

PEDIATRICS ◽  
1956 ◽  
Vol 17 (3) ◽  
pp. 418-427
Author(s):  
Melvin M. Grumbach ◽  
Lawson Wilkins
Keyword(s):  
Adrenal Cortex ◽  
Significant Rise ◽  
Clinical Effects ◽  
Adrenal Hyperplasia ◽  
Adrenal Androgen ◽  
Metabolic Block ◽  
Low Levels ◽  
17 Hydroxyprogesterone ◽  
Androgenic Steroids ◽  
Excessive Quantity

SINCE the discovery by wilkins et al., in 1950, that in virilizing adrenal hyperplasia the clinical effects and the increased excretion of androgenic steroids can be suppressed by cortisone treatment, our knowledge of the primary metabolic disturbance underlying this disease has been advanced significantly through the work of a number of investigators. Considerable evidence has been obtained to support the observation of Bartter et al., in 1950, that in this disorder the ability of the adrenal cortex to synthesize gluconeogenetic hormone, or compound F, is impaired. This results in the increased secretion of ACTH in an attempt to provide sufficient compound F for homeostasis and secondarily leads to hyperplasia of the adrenal glands and the production of excessive quantities of adrenal androgen. In contrast to the normal, generally low levels of 17-hydroxycorticoids are found in plasma, and usually no significant rise occurs after the administration of ACTH. An excessive amount of endogenous ACTH is present in the blood which can be decreased readily by the administration of cortisone. Important advances in clarification of the series of transformations by which the adrenal cortex synthesizes compound F or hydrocortisone from precursors have been made by Hechter and his associates and [SEE FIG 1 IN SOURCE PDF] others. Jailer suggested that in virilizing adrenal hyperplasia there is a metabolic block in this synthetic pathway between 17-hydroxyprogesterone and hydrocortisone (Fig. 1). The observation by Bongiovanni of an excessive quantity of pregnanetriol, a metabolite of 17-hydroxyprogesterone, in the urine of patients with this disease contributed substantial evidence to the support of such and hypotheses.

CHOLESTEROL BIOSYNTHESIS: THE STARVATION BLOCK

1957 ◽  
Vol 35 (1) ◽  
pp. 615-623
Author(s):  
J. F. Scaife ◽  
B. B. Migicovsky
Keyword(s):  
Experimental Evidence ◽  
Rat Liver ◽  
Biosynthetic Pathway ◽  
Glutaric Acid ◽  
Cholesterol Biosynthesis ◽  
Metabolic Block ◽  
Liver Homogenates ◽  
Acidic Compound

Partial localization of the metabolic block in cholesterol biosynthesis from acetate by starved rat liver homogenates has been achieved. Experimental evidence indicates that this block is located in the biosynthetic pathway between β-hydroxy-β-methyl glutaric acid and squalene. Fractionation and comparative chromatographic examination of incubated homogenates from starved and normal rats failed to reveal any accumulation of an appreciably radioactive intermediate as a result of the blocked biosynthetic pathway in the starved animal. A strongly labelled acidic compound has been isolated in minute amounts from incubated homogenates of both starved and normal rats. This is readily incorporated into cholesterol by liver homogenates from normal, but not from starved rats. Its identity has as yet not been established.

scholarly journals Reciprocal Relationship of Hemoglobins A2 and F in Beta Chain Thalassemias, a Key to the Genetic Control of Hemoglobin F

Blood ◽  
1961 ◽  
Vol 17 (4) ◽  
pp. 393-408 ◽  
Author(s):  
WOLF W. ZUELZER ◽  
ABNER R. ROBINSON ◽  
CLIFFORD R. BOOKER
Keyword(s):  
Genetic Control ◽  
Adult Life ◽  
Fetal Hemoglobin ◽  
Thalassemia Major ◽  
Reciprocal Relationship ◽  
Hemoglobin F ◽  
Multiple Alleles ◽  
Metabolic Block ◽  
Relationship Of ◽  
Β Chain

Abstract Two pedigrees, each exhibiting the presence of two distinct thalassemia genes are described. Though indistinguishable by their hematologic stigmata the genes in each pedigree differed in their effect on the quantitative behavior of the minor hemoglobin components A2 and F. One gene produced the usual pattern of elevated values for the A2 fraction with minimal if any increases in the proportion of hemoglobin F. Another gene failed to produce increases in the A2 fraction but gave rise to substantial increments in the amounts of fetal hemoglobin. Still another gene produced a similar pattern but with less marked elevations of hemoglobin F though still well above the usual levels for thalassemic heterozygotes. There were intrafamilial similarities with respect to these features. In one family, the combination of two dissimilar genes had produced the picture of thalassemia major in the propositus. For the particular thalassemia genes observed a reciprocal relationship in the quantitative behavior of the two minor components could be shown on the basis of comparisons including a larger case material studied by the authors. The apparent vagaries in the quantitative behavior of fetal hemoglobin in thalassemic heterozygotes could thus be explained as related to the presence or absence of an elevated A2 fraction. In general, levels of fetal hemoglobin in the former type rarely exceed 3.5 per cent, in the latter they are rarely below 4.0 per cent. In accordance with other genetic information the findings are compatible with the assumption that both types of thalassemia genes represent mutations of β genes affecting the synthesis of β chains and thus represent a series of multiple alleles at the β chain locus. This interpretation fits the hypothesis of Ingram and Stretton regarding the nature of the defect in thalassemia. The factor determining whether predominantly δ or γ chains and consequently hemoglobin A2 or hemoglobin F (or still other fractions) are formed appears to be the nature of the particular amino-acid substitutions in the anomalous β chain, resulting in the utilization of one or another metabolic pathway leading to the formation of different by-products of a metabolic block. The genetic implications of this hypothesis are presented with a view to establishing that current genetic theory does not yet fully account for the observations. The interpretation of γ chains of fetal hemglobin as primitive β chains produced under the control of the same pair of genes which in normal adult life regulate the synthesis of β chains is offered as the basis for a unifying concept concerning the nature and genetic control of fetal hemoglobin. If valid, this concept appears applicable to all conditions thus far known, normal or abnormal, in which fetal hemoglobin occurs.

scholarly journals PGC1α drives a metabolic block on prostate cancer progression

2016 ◽  
Vol 18 (6) ◽  
pp. 589-590 ◽  
Author(s):  
Martina Wallace ◽  
Christian M. Metallo
Keyword(s):  
Prostate Cancer ◽  
Cancer Progression ◽  
Prostate Cancer Progression ◽  
Metabolic Block

Position of the metabolic block for gibberellin biosynthesis in mutant b1-41a of Gibberella fujikuroi

1974 ◽  
Vol 13 (6) ◽  
pp. 911-917 ◽  
Author(s):  
John R. Bearder ◽  
Jake MacMillan ◽  
Colin M. Wels ◽  
Marion B. Chaffey ◽  
Bernard O. Phinney
Keyword(s):  
Gibberella Fujikuroi ◽  
Gibberellin Biosynthesis ◽  
Metabolic Block

ON THE MECHANISM OF THE ADRENAL GLAND RESPONSE TO ADRENOCORTICOTROPHIC HORMONE IN HYPOPHYSECTOMIZED RATS

1965 ◽  
Vol 50 (1) ◽  
pp. 55-64 ◽  
Author(s):  
M. Staehelin ◽  
P. Barthe ◽  
P. A. Desaulles
Keyword(s):  
Ascorbic Acid ◽  
Adrenal Gland ◽  
Acid Output ◽  
Adrenocorticotrophic Hormone ◽  
Considerable Time ◽  
Corticosterone Secretion ◽  
Metabolic Block ◽  
Hypophysectomized Rats ◽  
Dose Dependent

ABSTRACT The adrenal gland response to natural or synthetic adrenocorticotrophic hormone was studied at various periods after hypophysectomy. Adrenal ascorbic acid depletion was observed following the administration of ACTH at all intervals up to 10 days. In contrast, the capacity to respond to ACTH by an increase in corticosterone secretion was rapidly lost. Experiments with rat adrenal slices in vitro showed that the capacity to form corticosteroids following the addition of ACTH or 3′,5′-cyclic-AMP is rapidly lost after hypophysectomy, but that the adrenal slices are still capable of producing corticosterone if NADP and glucose-6-phosphate are added to the medium. It is concluded that the adrenal gland is still capable of responding to the action of ACTH for a considerable time after hypophysectomy, but that due to a metabolic block prior to the formation of NADPH, the adrenal is no longer capable of reacting by a further increase in corticosterone production. In addition, it was found that the effects of ACTH on blood flow and ascorbic acid output were parallel. Both effects were dose-dependent, but independent of any concomitant corticosterone secretion, and persisted during the whole period studied after hypophysectomy.

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