Showing papers on "Steroid biosynthesis published in 1973"

Steroid biosynthesis in vitro by dysgenetic ovaries induced by neonatal thymectomy in mice.

Abstract: The small dysgenetic gonads which are induced in mice by neonatal thymeetomy are characterized by predominance of interstitial cells and absence of corpora lutea and follicles. In addition, the animals have stimulated uteri and masculinization of the salivary gland. Since these latter features suggested an abnormal pattern of steroid formation in vitro, ovarian steroid biosynthesis was studied. When 10 nmoles of 3H-3β hydroxy- pregn-S-en-20-one, 14C-progesterone or 14C-17-hydroxyprogesterone was incubated with 5 or 10 mg of ovarian homogenates, androstenedione and testosterone were synthesized by the dysgenetic ovaries, while much less of these C19- steroids was formed by control ovaries of normal mice. Enzyme activities related to steroid conversion were also estimated. In homogenates, the activity of 20α-hydroxysteroid dehydrogenase per g tissue was found to be about 15 times higher in the control ovaries than in the dysgenetic ovaries, while 3β-hydroxysteroid dehydrogenase activity per g tissue was sim...

The reproductive cycle of the firetail gudgeon, Hypseleotris galii I. Seasonal histological changes in the ovary

Abstract: Seasonal histological changes in the ovary of H. galii are described. Oogenesis occurs in January and February, at the end of the breeding season. Evidence suggests that oogenesis continues in senile (post-reproductive) fish. Oocytes in the primary growth phase grow throughout the winter months. Vitellogenesis commences in August, and fish mature by November. During the breeding season (November-January) females ovulate and spawn repeatedly. Mature oocytes remaining after the breeding season become atretic. The fate of follicular derivatives and their possible role in steroid biosynthesis is discussed.

Activities of enzymes responsible for steroid biosynthesis and cholesterol ester metabolism in rabbit ovarian interstitial tissue and corpora lutea. A comparison of enzyme activities with flow rates.

Abstract: A method involving the use of isolated cholesterol ester-storage granules as substrate is described for the assay of cholesterol esterase in rabbit ovarian tissues. Activities of cholesterol esterase 100–200-fold higher than those previously reported in ovarian tissues were measured by using this method. In addition to that of cholesterol esterase, activities of cholesterol ester synthetase, cholesterol side-chain cleavage enzyme and 3β-hydroxy steroid dehydrogenase were determined in rabbit ovarian interstitial tissue and corpora lutea. Activities of these enzymes are in general compatible with the flows through them measured under a variety of conditions both in vivo and in vitro . It is concluded that, in the rabbit ovarian tissues investigated, these enzymes are capable of catalysing the conversions usually attributed to them.

Impaired renin responsiveness with secondary hypoaldosteronism.

Abstract: The existence of a syndrome of "primary aldosteronopenia" was postulated by Conn in 1956, 1 and the first patient was described by Hudson et al in 1957. 2 Since then, several other cases have been reported. 3-15 The condition is characterized by deficiency of aldosterone production, with normal secretion of cortisol. The patients are usually asymptomatic, but they may develop symptomatic hyperkalemia 7 and cardiac arrhythmias, 2, 4 particularly during a low sodium diet when requirements of aldosterone increase. Plasma renin activity has not been evaluated extensively in these patients, and it has been believed generally that the primary abnormality is defective steroid biosynthesis within the adrenal cortex. 9 This report describes the cases of two men with selective hypoaldosteronism, both of whom had inadequate sodium conservation and who developed hyperkalemia when given a low sodium diet. Of particular interest is the finding of impaired renin responsiveness, which is postulated

Effects of aminoglutethimide (Elipten Ciba), a steroid biosynthesis blocking agent, on adrenal glands in Cushing's syndrome.

Abstract: Seven adrenal glands removed from 4 patients suffering from a central-type Cushing's syndrome after various periods of aminoglutethimide (AGL) treatment were subjected to conventional morphological and histochemical, particularly enzyme histochemical, studies and to biochemical incubation studies

Steroid biosynthesis. relative efficiencies of enzymic transformation of terminally modified squalene 2,3-oxide analogs into lanosterol analogs by 2,3-oxidosqualene cyclase

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.

The gonadotropin-primed rat: a model for testing agents that influence steroid biosynthesis.

Abstract: Immature female rats were injected with 50 IU pregnant mare serum gonadotropin (PMSG) on day 0 and 25 IU human chorionic gonadotropin (hCG) on day 3. Plasma progestin rose to concentrations ranging from 350 to 625 ng/ml from day 5 to day 17. Expression of plasma progestin concentrations in ng/ml/mg ovary weight showed maximal concentrations of approximately 3 ng/ml/mg ovary weight on days 7 to 11 followed by a gradual decrease through day 19. Although the pituitary glands of D5GPR were significantly larger (5.20 mg ± 0.49 mg SE) than controls (3.65 mg ± 0.15 mg SE), radioimmunoassay indicated serum LH levels were not different than controls. Administration of LHreleasing factor (LRF) to D5GPR caused a significant increase in serum LH and a significant decrease in plasma progestin concentrations 20 min after LRF administration. Injection of ergocornine methanesulfonate did not alter serum LH or plasma progestin concentrations. A minimum iv dose of 3 to 5 μg prostaglandin F2α caused a maximal decrease (appr...

Les cellules secretrices testiculaires du poussin de la caille japonaise: differenciation de leur ultrastructure et rapports avec leurs potentialites steroidogenes

Abstract: The differentiation of the Quail testis progresses slowly after hatching. The Leydig cells, not yet typical, store up lipids which indicate already their future capacities; Δ5–3β HSDH activity being rather low, the conversion from pregnenolone into progesterone is restricted. However, differentiation accelerates from the third week on, after the beginning of germ cell meiosis. Interstitial cells become hypertrophied and acquire the typical features of active steroidogenic cells: smooth endoplasmic reticulum develops, mitochondria swell and take on specific structures, lipids become progressively less abundant; steroid biosynthesis through Δ5–4 pathway increases rapidly. These characteristics continue to develop. At the same time, smooth endoplasmic reticulum forms in Sertoli cells; it probably represents the morphological basis of some metabolic activities necessary for the harmonious functionning of seminiferous tubules. The ultrastructure of the Quail testis, after hatching, confirms its low steroidogenic potentialities, compared to those of the adult.

Steroid biosynthesis. the absolute configuration of the enzymatically active enantiomer of 2,3-oxidosqualene participating in its cyclization to lanosterol

Abstract: The absolute configuration of the enzymatically active enantiomer of 2,3-oxidosqualene participating in its enzymatic cyclization to lanosterol has been first established experimentally to be 3S on the basis of circular dichroism measurements of a Eu(DPM)3 complex of (+)-2,3-dihydroxysqualene derived from the recovered oxidosqualene unchanged.

Role of the adrenal cortex in maturation of the lymphoid system and immunological competence; the effects of aminoglutethimide in suckling mice

Abstract: Newborn rats and mice have rudimentary peripheral lymphoid tissues and are immunologically incompetent. The lymphoid system matures late in the third week after birth, shortly before weaning. The adrenal cortex also is relatively inactive neonatally and begins to secrete glucocorticoids in a mature fashion two weeks after birth. These experiments were designed to test the hypothesis that adrenal glucocorticoids induce maturation of the lymphoid system and immunological competence during the third postnatal week. Mice 10–12 days old were injected daily for 4–11 days with aminoglutethimide, an inhibitor of steroid biosynthesis. The adrenal glands and lymphoid tissues were prepared for histological examination 24 hours after the last injection and evaluated without knowledge of the treatment received. Aminoglutethimide caused adrenal dysplasia with a frequency proportional to dose. Effective doses also inhibited growth, and slightly larger doses were fatal. Therefore it was concluded that large doses of aminoglutethimide caused adrenal insufficiency, but the completeness of this insufficiency in surviving animals was not ascertained. Three phases in postnatal maturation of the lymphoid system were identified by examination of untreated littermate controls and reference to previous work. During the first week after birth, the thymus-dependent lymphoid tissues grow by immigration of thymus-derived cells that soon have the capacity for cell-mediated immunity. During the second postnatal week, a new population of wandering lymphoid cells, presumptively derived from bone marrow, settles in lymphoid organs in response to antigenic stimulation, to form primary lymphoid nodules and a few plasma cells. Late in the third week after birth the machinery for humoral antibody synthesis matures with the appearance of germinal centers and numerous plasma cells, coincident with a great increase in production of immunoglobulin. This third phase of maturation was retarded in mice injected with near-fatal doses of aminoglutethimide. Because these mice suffered neither involution of lymphoid tissue nor suppression of proliferation in thymus or thymus-dependent lymphoid-tissue, it was concluded that the effects of aminoglutethimide upon the development of germinal centers and plasma cells were selective and specific. Therefore these experiments support the hypothesis that glucocorticoid secretion plays a decisive role in maturation of immunological competence during the third week after birth in mice. This role appears to be the potentiation of cellular proliferation and differentiation of B cells in response to antigens, culminating in antibody synthesis. Maturation of adrenal glucocorticoid synthesis has also been implicated in the initiation of physiological involution of the thymus and cessation of intestinal absorption of antibodies during the third postnatal week in rats and mice.

The reproductive cycle of the firetail gudgeon

Abstract: Seasonal histological changes in the ovary of H, galii are described. Oogenesis occurs in January and February, at the end of the breeding season. Evidence suggests that oogenesis continues in senile (post-reproductive) fish. Oocytes in the primary growth phase grow throughout the winter months. Vitellogenesis commences in August, and fish mature by November. During the breeding season (November-January) females ovulate and spawn repeatedly. Mature oocytes remaining after the breeding season become atretic. The fate of follicular derivatives and their possible role in steroid biosynthesis is discussed. Hypseleotris galii is a small freshwater fish occuring in coastal streams along the central eastern coast of Australia. According to the classification of Greenwood et al. (1966), this fish is placed in the family Gobiidae. The fish derives its common name from the bright red coloration of the dorsal, anal, and tail fins of mature male fish, of which the body is a grey-black colour. These colours are present throughout the year, but intensify with the approach of the breeding season. In mature females and juvenile fish of both sexes, the body wall and fins are transparent. Mature females can be readily identified, however, by the presence of a heavily pigmented black ovipositor. Female fish are smaller than males, rarely exceeding 40 mm in total length, while males of 50-55 mm are common. Like most temperate freshwater teleosts, H. galii has an annual breeding cycle. Breeding takes place from November to January. Young fish mature after 1 yr growth, when they are 30-35 mm (female) and 35-40 mm (male) in length. Fish maintained in the laboratory grew and reproduced for two years in succession, and a third year of reproductive life seems likely from the size of mature fish captured from the river. Occasionally large female fish (> 50 mm in length) were captured, but these fish were non-reproductive. The ovipositor had lost its characteristic dark

Steroid biosynthesis and the brain-testis axis

Abstract: textThe significanee of testicular tunetion was shown as l early as 1849 by Berthold when he observed atrophy of the comb in castrated cockerels, which could be restored by implantation of a testis in the abdomen. It was only in the beginning of the twentieth century, however, that Bouin and Ancel postulated the formation of certain horrnonal principles in distinct cell types of the testis. The identification of testasterene as the biologically active andregen of the bull testis in 1935 rnarked the beginning of biochemical studies of testis function. The measurement of testicular horrnonal products has been difficult for a long time because only small quantities are produced. However, present techniques such as radioimmunoassay permit the measurement of picogram quantities of testosterone4. Parallel with the development of these techniques, insight has been gained into the endocrine function of the testis.