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A Chabab

Publications and source records attributed to A Chabab.

10 recordsLinked to original sources
PubMed1986

Aromatase activity in human skin fibroblasts: characterization by an enzymatic method.

Human skin fibroblasts were incubated for 24 h with 10(-6) M androstenedione and the estrone + estradiol released in the culture medium were measured by an enzymatic assay. Aromatase activity was expressed as pmol (estrone + estradiol) formed in the medium per mg cell protein per day. Using this method we were able to investigate the kinetic properties of aromatase in different cell strains and its stimulation by dexamethasone. Values of 92 nM and 9.1 pmol/mg protein/day were obtained respectively for Km and Vmax in cultured fibroblasts derived from genital skin of normal prepubertal subjects. In patients with complete androgen insensitivity syndrome CAIS, the Km was 156 nM and the Vmax 42 pmol/mg protein/day. Aromatase activity varied from 7.9 +/- 1.2 pmol/mg protein/day (mean +/- SD; n = 19) in normal prepubertal boys to 24.5 +/- 4.7 pmol/mg protein/day (mean +/- SD; n = 11) in those from normal postpubertal boys. The values were even higher in fibroblasts cultured from genital skin of prepubertal patients with CAIS. Cell concentrations did not modify the pattern of estrogen formation and aromatase activity did not vary with serial subcultures. The stimulatory effect of dexamethasone on aromatase activity in cultured fibroblasts was measured after preincubation of the cells for 48 h with dexamethasone, by determining estrogen formation after 24 h incubation of the cells with androstenedione 10(-6) M using this enzymatic method. This data suggest that aromatase activity measured in cultured fibroblasts could be a useful tool for studying extraglandular estrogen formation in physiological and pathological conditions.

Adipose Tissue↗
PubMed1986

Stimulation of aromatase activity by dihydrotestosterone in human skin fibroblasts.

In order to study the regulation of aromatase activity by androgens in cultured fibroblasts derived from genital skin of normal prepubertal boys, aromatase activity was evaluated in the presence of various concentrations of non-aromatizable androgen DHT(5 alpha-dihydrotestosterone). The estrogen formation was assayed by an enzymatic method, after 24 h incubation of the cells with 10(-6) M androstenedione. Aromatase activity was stimulated 3- to 20-fold by DHT at concentrations 10(-10) and 10(-9) M. It was necessary to preincubate the cells with DHT for 48 h in order to bring about this stimulation. The stimulatory effect was not significant after preincubation for only 24 h. The basal value of aromatase activity was in the range of 8 +/- 1.2 pmol/mg protein/day (mean +/- SEM), while the maximal stimulation 1043 +/- 46 pmol/mg protein/day was obtained at the concentration of 10(-8) M DHT. This stimulation was partially blocked with cyproterone acetate at level of 20 +/- 4 pmol/mg protein/day; stimulation of aromatase activity by DHT could thus be mediated by the androgen receptor. This stimulatory effect was prevented by incubation of the cells with cycloheximide or actinomycin D, suggesting that DHT acts to increase aromatase activity in cultured fibroblasts by inducing the synthesis of new proteinaceous material. In vitro regulation of aromatase activity by androgens could contribute to a new approach to the extraglandular formation of estrogen.

Aromatase↗
PubMed1986

Follicular steroids in relation to oocyte development and human ovarian stimulation protocols.

Oocytes of pre-ovulatory follicles were collected by laparoscopy for in-vitro fertilization in 118 women. Patients were treated either during the natural cycle, or after induction of ovulation with clomiphene citrate, or with human menopausal gonadotrophin (HMG), or clomiphene citrate combined with HMG. The oestrogens (oestrone + oestradiol) and total aromatizable androgens (androstenedione, testosterone and dehydroepiandrosterone and its sulphate) were assayed in follicular fluids using an enzymatic method. The levels of progesterone, 17 alpha OH-progesterone, thromboxane, and prostaglandins (PGE2 and PGF2 alpha) were determined by radioimmunoassay. The best follicular fluid indicator of oocyte fertilization in vitro was the A/E ratio, which was less than 1 when the oocyte was fertilized in vitro and led to a pregnancy. The lowest value for the A/E ratio was obtained with spontaneous ovulation protocols. Regardless of oocyte development, the progesterone level was always greater than 2000 ng/ml, and the PGE2/PGF2 alpha ratio was greater than 1 in all stimulated cycles. Our investigations show that a combination of clomiphene citrate and HMG provides the best stimulation, on the basis of follicular fluid analysis and the outcome of fertilized oocytes.

Androgens↗
PubMed1986

[Stimulation of ovulation by pure FSH for in vitro fertilization. Study of the route of administration].

Pulsatile injection of FSH to stimulate ovulation for in vitro fertilization was undertaken in order to compare the intramuscular route with the pulsatile subcutaneous route in two groups of 6 patients each selected at random. The patients were selected in such a way as to reduce as far as possible the parameters that would make it difficult to interpret the results. Both from the point of view of the numbers of patients who responded to stimulation of ovulation as well as the numbers of pregnancies that were obtained, the intramuscular route seems to be preferable.

Adult↗
PubMed1985

Increased peripheral aromatase activity in prepubertal children with partial androgen insensitivity syndrome.

It has been suggested that rate of estrogen formation was higher in patients with androgen insensitivity syndrome (AIS). This work was designed to find out if peripheral aromatase activity could be related to a defect in androgen action in prepubertal children with male pseudohermaphroditism. Fibroblast estrogen production was assayed by a highly specific enzymatic determination. Foreskin fibroblast strains were raised from 17 children with partial androgen insensitivity (PAIS) as defined by dihydrotestosterone binding activity in cells. Results are expressed as pmol estrogens/mg proteins synthetized/day when cultured fibroblasts are incubated with D4-androstenedione. In normal prepubertal boys (n = 19), aromatase activity ranged between 5 and 10 pmol estrogens/mg proteins/day, while in postpubertal boys it varied between 15 and 34 pmol estrogens/mg proteins/day. In prepubertal boys with PAIS (n = 17) aromatase activity is highly elevated: 19.4 +/- 8.4 pmol/mg proteins/day. These results show that (a) peripheral aromatase activity is low before puberty and (b) fibroblast estrogen synthesis is significantly (p less than 0.001) increased in prepubertal children with PAIS. Our data suggest that low utilization of androgens by target cells stimulates the production of estrogen. Peripheral aromatase activity can thus be considered as a 'marker' of androgen insensitivity in prepubertal children with male pseudohermaphroditism.

Androgens↗
PubMed1985

[Enzymatic determination of urinary estrogens. A 5-year experience in a hospital milieu].

The enzymatic method for urinary estrogens determination from Nicolas et al. has become a useful tool for the management of infertility problems. It can be used for: investigation of ovarian by establishing the urinary estrogens profile during menstrual cycle, useful to: understand anomalies of the spontaneous cycle, explain some therapeutic failures during IVF attempts or artificial inseminations (AID or AIC); prediction of failures during IVF attempts during spontaneous cycles, and monitoring ovarian response during stimulated cycles in order to determine the trigger with hCG; monitoring ovulation during induction of ovulation in anovulatory patients stimulated with various drugs (clomiphene citrate, pure FSH combination of FSH and LH, GnRH ou analogs...) under various conditions of prescription and administration (oral, IM, intermittent pulsatile administration with portable pump with or without hypophyseal down regulation). This technique allows also exploration of androgens after changing main androgens (delta 4 A, T, DHEA, DHEA S) into estrogens through the action of placental aromatase, as well as appreciation of aromatase activity of some tissues in the presence of androgenic substrates. This paper gives the conclusions after 5 years of practice with this method and summaries different works published by the biologists who developed the method and by the clinicians who used its results.

Adolescent↗
PubMed1985

[Various protocols for determining estrogens by the enzymatic method using estradiol dehydrogenase. Respective procedures and advantages].

Up to now, more than 40.000 determinations of urinary estrogens (E1 + E2) have been carried out in routine clinical analysis by the enzymatic method using estradiol dehydrogenase. This method makes use of the transhydrogenating activity of the placental enzyme: this enzyme transfers hydrogen from NADP to NAD with recycling of the specific substrate (E1 + E2). For several years the necessary reagents have been commercially available in the form of a kit. Nonetheless, various improvements have been made to the measurement of reduced NAD, which accumulates in the reaction medium and is directly proportional to the concentration of the two estrogens. Three protocols are available at present: Spectrophotometric measurement at 340 nm (initial technique); Colorimetric measurement at 492 nm. The pink colour measured arises from the reduction of a tetrazolium salt (INT) by reduced NAD in a coupled system using diaphorase; Measurement by bioluminescence of the light energy liberated on the reduction of flavin derivatives by NADH. The reaction is mediated by various enzymes isolated from marine bacteria (FMN oxidoreductase and luciferase) in the presence of an aliphatic aldehyde (decanal). The procedure for each of these protocols is described as well as the means for controlling the linearity of the reaction. The choice of protocol is determined by the biological fluid available, the speed of response desired and the cost of the analysis.

17-Hydroxysteroid Dehydrogenases↗
PubMed1985

[Pregnancies by fertilization in vitro. Biochemistry of the follicular fluid].

Fifty four follicular fluids containing 41 oocytes were sampled from 6 patients in which at least one pregnancy was obtained after IVF. Their biochemical composition has been correlated with the follicle maturity and oocyte quality. Three components have been assayed: steroids, prostanoids, proteolytic enzymes. Determinations of estrogens and total aromatisable androgens were carried out by the enzymatic technic of Nicolas and al.; progesterone and 17 OH progesterone by RIA. Development of in vitro cultured and fertilized oocytes appears to be improved when progesterone and estrogens concentrations in the follicular fluid are above 2 000 and 600 ng/ml respectively, with an A/E ratio under 1. On the other hand, prostanoids (T X B2, PGE2, PGF2 alpha determined by RIA) and proteolytic enzymes : (collagenolytic and kallikrein type activities) seemed related to ovulatory activity rather than to oocyte quality.

Androgens↗
PubMedDate not supplied

[Male pseudohermaphroditism caused by partial insensitivity to androgens. Clinical and biochemical heterogeneity].

Male pseudohermaphroditism due to partial androgen insensitivity (PAI) may be suspected clinically in case of incomplete masculinization of external genitalia in spite of age related plasma androgen levels. In 25 children or adolescents in whom PAI was suspected, the 5 alpha-reductase activity of external genitalia fibroblasts, the number of androgen receptor sites (Bmax) and the affinity of receptors for dihydrotestosterone (Kd) were studied. Clinical expression of PAI is highly polymorphic (Prader's type I to type IV), when most children (18/25) were considered as males. In a single patient the very low 5 alpha-reductase activity permitted the diagnosis of 5 alpha-reductase deficiency. The number of receptor sites (fmoles/mg DNA) varied from 0 to 730. Mean Bmax of patients (282 +/- 187 fmoles/mg DNA) was statistically lower than that of normal subjects (642 +/- 220 fmoles/mg DNA), p less than 0.05. The 5 cases in whom receptor concentrations were normal may be related to a qualitative abnormality of the androgen receptor or to a "post-receptor" defect. On the contrary no significant differences in Kd values were found. Correlation between sexual ambiguity and the number of measured receptors was not possible. These results emphasize the clinical and biochemical heterogeneity of PAI. Nevertheless, the decrease in number of androgen receptor sites remains the major data for the biochemical diagnosis of PAI. Study of post-receptor "markers" (3 alpha-reductase activity, aromatase, collagen) might allow better analysis of cases with PAI in whom androgen receptor concentrations are normal.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗