Showing papers on "Steroid biosynthesis published in 1974"
TL;DR: The tissue of resting plant storage organs can be activated by slicing into thin disks and incubation of these fragments in a moist atmosphere for different periods of time (“aging”) and a vigorous synthesis of various enzymes and structural proteins which enable the cell to greatly enhanced metabolic activities.
Abstract: The tissue of resting plant storage organs such as carrots, red beets, sugar beets or potato tubers can be activated by slicing into thin disks and incubation of these fragments in a moist atmosphere for different periods of time (“aging”). Activation comprises the turning-on of various genes with subsequent synthesis of transfer-, ribosomal and messenger RNAs and their transport into the cytoplasm. The immediate consequence of all these primary reactions is a vigorous synthesis of various enzymes and structural proteins which enable the cell to greatly enhanced metabolic activities. Thus, degradation of storage polymers and the procession of the resulting products through glycolysis, the pentose phosphate shunt and the shikimateprephenate-pathway and cellulose biosynthesis occur. Deinhibition of the tricarboxylic acid cycle opens the flow of metabolites into fatty acid, phospholipid and steroid biosynthesis, simultaneously providing the respiratory chain with electrons. In spite of functional modifications within the electron transport chain, the enhanced respiration of tissue slices serves as an energy source for the various energy-dependent reactions of the cell such as syntheses and the uptake of solutes. All of these activities accompany a concomitant dedifferentiation process and ultimately lead to renewed redifferentiation of the tissue slice cell.
132 citations
122 citations
TL;DR: Radioimmunoassay techniques indicate the presence of testosterone and possibly estrogens in the gonad of the mussel at two different stages in its gametogenic cycle.
121 citations
TL;DR: The kinetic mechanism of cytoplasmic thiolase is discussed in terms of its proposed role in steroid biosynthesis and the Ping Pong mechanism for acetoacetyl-CoA thiolysis is confirmed.
Abstract: 1. Cytoplasmic acetoacetyl-CoA thiolase was highly purified in good yield from rat liver extracts. 2. Mg2+ inhibits the rate of acetoacetyl-CoA thiolysis but not the rate of synthesis of acetoacetyl-CoA. Measurement of the velocity of thiolysis at varying Mg2+ but fixed acetoacetyl-CoA concentrations gave evidence that the keto form of acetoacetyl-CoA is the true substrate. 3. Linear reciprocal plots of velocity of acetoacetyl-CoA synthesis against acetyl-CoA concentration in the presence or absence of desulpho-CoA (a competitive inhibitor) indicate that the kinetic mechanism is of the Ping Pong (Cleland, 1963) type involving an acetyl-enzyme covalent intermediate. In the presence of CoA the reciprocal plots are non-linear, becoming second order in acetyl-CoA (the Hill plot shows a slope of 1.7), but here this does not imply co-operative phenomena. 4. In the direction of acetoacetyl-CoA thiolysis CoA is a substrate inhibitor, competing with acetoacetyl-CoA, with a Ki of 67μm. Linear reciprocal plots of initial velocity against concentration of mixtures of acetoacetyl-CoA plus CoA confirmed the Ping Pong mechanism for acetoacetyl-CoA thiolysis. This method of investigation also enabled the determination of all the kinetic constants without complication by substrate inhibition. When saturated with substrate the rate of acetoacetyl-CoA synthesis is 0.055 times the rate of acetoacetyl-CoA thiolysis. 5. Acetoacetyl-CoA thiolase was extremely susceptible to inhibition by an excess of iodoacetamide, but this inhibition was completely abolished after preincubation of the enzyme with a molar excess of acetoacetyl-CoA. This result was in keeping with the existence of an acetyl-enzyme. Acetyl-CoA, in whose presence the overall reaction could proceed, gave poor protection, presumably because of the continuous turnover of acetyl-enzyme in this case. 6. The kinetic mechanism of cytoplasmic thiolase is discussed in terms of its proposed role in steroid biosynthesis.
77 citations
48 citations
TL;DR: Evidence is presented to suggest that the latter steroid may be a physiological regulator of C 19 steroid biosynthesis from pregnenolone and progesterone in boar testis.
34 citations
TL;DR: Genuine concern for potential side effects during gestation may be warranted in regard to the unusual association of amino-glutethimide administration with pregnancy, owing to this drug's relationship to thalidomide, another glutarimide.
Abstract: To the Editor.— We have recently observed the unusual association of amino-glutethimide administration with pregnancy. Amino-glutethimide is a potent inhibitor of steroid biosynthesis. It may soon be released for treatment of adrenocortical hyperfunction with excess cortisol or aldosterone secretion. The drug creates a partial block at the cholesterol desmolase reaction converting cholesterol to pregnenolone. Other blocks occur at the 21 and 11 hydroxylation reactions. 1,2 Genuine concern for potential side effects during gestation may be warranted in regard to the above effects, owing to this drug's relationship to thalidomide, another glutarimide. Also, the first block described is very similar to the complete defect seen in congenital lipoid adrenal hyperplasia, a fatal form with deficiencies of all steroids. Report of a Case.— A 22-year-old patient was referred for pregnancy termination at 27 weeks' gestation. A diagnosis of Cushing disease had been made elsewhere prior to conception, and she was treated with
26 citations
01 Jan 1974
TL;DR: Monolayer cultures of mouse adrenal cortex tumors have been used to investigate the effects of Ca2+ on the binding of 125I-labelled s1-24-ACTH peptide to the cell, ACTH-stimulated cyclic-AMP and steroid biosynthesis, suggesting that they are products of a common pool of ATP.
Abstract: Monolayer cultures of mouse adrenal cortex tumors have been used to investigate the effects of Ca2+ on the binding of 125I-labelled s1-24-ACTH peptide to the cell, ACTH-stimulated cyclic-AMP and steroid biosynthesis. Stimulation with ACTH results in increased intracellular cyclic-AMP levels and release of cyclic-AMP into the medium. The specific activities of intracellular and extracellular cyclic-AMP produced by cells incubated with 3H-adenine are the same, suggesting that they are products of a common pool of ATP. ACTH-stimulated cyclic-AMP release continues after intracellular cyclic-AMP levels have decreased and reflects continuing cyclic-AMP biosynthesis. In incubations of two hours or less with 5.0 mM Ca2+, maximum steroidogenesis occurs with 0.1 milliunit/ml ACTH. Further increases in cyclic-AMP production are elicited with higher concentrations of ACTH. In the absence of Ca2+, both cyclic-AMP and steroid syntheses are attenuated, maximum steroidogenesis requiring > 10 milliunits/ml ACTH.The propor...
18 citations
17 citations
TL;DR: Intercellular distribution of several enzymes related to steroidogenesis in rat testicular tissue was examined and activities of 17α-hydroxylase and C 17 -C 20 lyase were located in the interstitial tissue, while 20-hydroxysteroid dehydrogenase was concentrated in the seminiferous tubules.
15 citations
TL;DR: FSH acted primarily as a stimulator of general growth: it largely induced increases in enzyme activities in proportion to the general increase in protein and the protein per mg tissue did not increase.
Abstract: Most evidence indicates that FSH alone does not stimulate estrogen biosynthesis in immature ovaries in spite of increased follicular growth. We studied the influence of FSH free of biological LH activity compared with the same dose of FSH supplemented by LH on the intermediate steps of steroid biosynthesis in the immature mouse ovary. The steroidogenic profile in the immature ovary revealed very active hydroxysteroid dehydrogenases, moderately active Δ4-reductases and low activities of mixed function oxidases. The Δ4-rather than the Δ5-pathway was shown to be the predominant route of androgen formation from pregnenolone, and Δ4-androstenedione was preferred to testosterone as androgen precursor of aromatization to estrogens. FSH acted primarily as a stimulator of general growth: it largely induced increases in enzyme activities in proportion to the general increase in protein and the protein per mg tissue did not increase. FSH † LH caused marked differential increases in cholesterol side-chain splitting, ...
TL;DR: It is concluded that fetal adrenals can form neutral steroid sulfates of the 3 β -hydroxy-5-ene series from endogenous precursors in vitro from endogenous preservatives in vitro.
TL;DR: It is suggested that certain cases of the ovarian hypoplasia represent a part of the broader spectrum of regressive ovarian condition, appearing as “pure gonadal dysgenesis” in its most severe form.
Abstract: 30 patients with the 46,XX gonadal dysgenesis or with a severe primary ovarian hypoplasia are described. In 13 of them the gonadal histology and the patterns of the steroid biosynthesis in vitro are given. The gonads could be divided into three groups: A) “gonadal dysgenesis” without any follicular apparatus, B) “severe ovarian hypoplasy”, C) “hypoplastic sclerocystic ovaries”. Gradual transitions between all these groups and familial occurrence of both hypoplasia and sclerocystic ovaries suggest that certain cases of the ovarian hypoplasia represent a part of the broader spectrum of regressive ovarian condition, appearing as “pure gonadal dysgenesis” in its most severe form.
TL;DR: The results indicate that the in vitro transformation of C-27 or C-21 radioactive substrate by lizard adrenals is similar to the other reptiles studied, however, it appears to possess 17β-hydroxysteroid oxido-reductase, though the adrenal tissue itself lacks 17α-hydroxylase activity.
TL;DR: The results seem to give additional support to the possibility of direct action of the drug on the steroidogenic organs in vivo.
Abstract: The side chain cleavage of cholesterol and of pregesterone in rat testis preparations is stimulated in vitro by 0.5–2.0 × 10−3 M clomiphene citrate. The mechanism is thought to be analogous with that demonstrated by Hagerman and co-workers (1966) for the stimulation of placental ring A aromatization. The results seem to give additional support to the possibility of direct action of the drug on the steroidogenic organs in vivo.
TL;DR: Analysis of plasma progesterone, urinary estriol and 19 plasma and 27 urinary neutral steroid sulfates indicated that progesteronesynthesis and the biosynthesis of certain maternal adrenal steroids was partly inhibited by p-Aminoglutethimide treatment.
Journal Article•
TL;DR: In this article, the incubation of terminally modified squalene 2,3-oxide analogs with the enzyme preparation of hog liver yielded the corresponding lanosterol analogs, respectively, at different conversion rates.
Abstract: The incubation of terminally modified squalene 2,3-oxide analogs with the enzyme preparation of hog liver yielded the corresponding lanosterol analogs, respectively, at different conversion rates. The interaction of 2,3-oxidosqualene cyclase with the substrates has thus been found to be influenced by the bulk of the terminal moiety.