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R J Hackett

Publications and source records attributed to R J Hackett.

9 recordsLinked to original sources
PubMed1992

Steroid sulfatase in the human ovary and placenta: enzyme kinetics and phosphate inhibition.

In 5 placental homogenates the Km of steroid sulfatase for DHEA sulfate increased from 15.4 in Tris buffer to 26.8 microM in phosphate (both buffers 0.1 M, pH 7.4), P less than 0.05. In 3 pooled ovarian preparations the Km increased from 14.3 microM in Tris to 33.0 microM in phosphate, P less than 0.01. There was no significant difference between the ovarian and placental values for Km in either Tris or phosphate (P greater than 0.5), and the increase in the Km produced by phosphate in ovarian tissue was not significantly different from that in the placenta (P greater than 0.5). In the placentas the Vmax in Tris was 1420 pmol/min/mg protein and this fell to 523 pmol/min/mg protein in phosphate (P less than 0.005). The Vmax was 50-fold higher in the placenta than in the ovary in either Tris or phosphate (both P less than 0.001). In the ovary, the Vmax was 27.6 pmol/min/mg protein in Tris and 11.0 pmol/min/mg protein in phosphate (P less than 0.05). The reduction of Vmax produced by phosphate in the ovary was not significantly different from that in the placenta (P greater than 0.5). The slope of the 1/v vs 1/S plot (Km/Vmax) increased 4.7-fold in the placentas and 5.8-fold in the ovaries in phosphate over that in Tris (both P less than 0.001); the increase in the placentas was not significantly different from that in the ovaries (P greater than 0.5). Phosphate ion acts as a mixed inhibitor of both placental and ovarian steroid sulfatase.

Arylsulfatases↗
PubMed1991

Metabolic clearance rate of dehydroepiandrosterone sulfate, its metabolism to testosterone, and its intrafollicular metabolism to dehydroepiandrosterone, androstenedione, testosterone, and dihydrotestosterone in vivo.

At the time of surgery, women were infused with [3H]dehydroepiandrosterone sulfate ([3H]DS)/[14C]testosterone ([14C]T) for 6 h; blood samples were obtained from an artery the ovarian veins, and a peripheral vein; and fluid was obtained from ovarian follicles. Both blood and follicular fluid samples were analyzed for radioactivity as DS, dehydroepiandrosterone (D), androstenedione (delta 4A). T, and dihydrotestosterone (DHT), and the blood was also analyzed for the concentration of nonisotopic DS by RIA. In other subjects the concentrations of D and DS were measured in paired samples of blood and follicular fluid. From these data, values of 13.6 +/- 0.69 L/day four (mean +/- SE; n = 4) for MCRDS, 607 +/- 90 L/day (n = 3) for MCRT, and 0.0190 +/- 0.0089 (n = 3) for [p]DS-T (fraction of plasma DS metabolized to plasma T) were obtained. The ratio of the concentration of the tracer-labeled steroid in the follicular fluid to the concentration in the arterial plasma sample was elevated significantly above 1 for three 3H-labeled and three [14C-labeled metabolites: [3H]D (21-fold; P less than 0.001), [3H]T (81-fold; P less than 0.001), [3H]DHT (19-fold; P less than 0.001), [14C]T (4-fold; P less than 0.025), [14C]DHT (21-fold; P less than 0.01), and [14C]delta 4A (50-fold; P less than 0.001). The estimated concentrations of steroids in follicular fluid derived from DS based on specific activity calculations were as follows: [geometric mean (95% confidence limits; n)]: DS, 5600 (4800-6500 nmol/L; 12); D, 370 (88-1500 nmol/L; 10); delta 4 A, 120 (67-220 nmol/L; 12); T, 130 (39-450 nmol/L; 10); and DHT, 64 (35-120 nmol/L; 8). Comparison of these data to known follicular fluid steroid concentrations shows that DS from the intravascular pool can be used as an ovarian prehormone.

Adult↗
PubMed1991

Metabolism of dehydroepiandrosterone sulfate (DS) in normal women and women with high DS concentrations.

In order to determine the contribution of serum dehydroepiandrosterone sulfate (DS) to estrone (E1) production in normal women and the effect of chronic elevation of the serum DS concentration on DS metabolism, four normal women and four women with high endogenous serum DS were infused with [3H]DS and [14C]E1 or [14C]testosterone for 6 h. Blood samples were analyzed for radioactivity as DS, dehydroepiandrosterone (D), androstenedione, testosterone, and dihydrotestosterone. Urine was collected for analysis of creatinine, 17-ketosteroids (17-KS), and radioactivity as estrone (E1). The serum DS of 12.4 +/- 1.44 mumol/L (mean +/- SE) in the group with high DS was higher than that of 3.96 +/- 1.0 mumol/L (1.46 +/- 0.37 micrograms/mL) in the normals (P less than 0.005). Those with high DS also had increased 17-KS (13.2 +/- 2.0 vs. 5.68 +/- 0.68 mg/day, P less than 0.025) and a higher blood production rate of DS (PBDS) (126 +/- 21 (n = 3) vs. 54.3 +/- 13.8 mmol/day, P less than 0.05) but a lower MCRDS (10.94 +/- 0.61 (n = 3) vs. 13.8 +/- 0.27 L/day, P less than 0.01) than that in normals. In the four normal women the fraction of infused DS converted to estrone ( [rho]BMDS E1) was 0.00078 +/- 0.00018, the amount of E1 produced from serum DS was 41.3 +/- 15 nmol/day, the basal plasma E1 was 102 +/- 18 pmol/L, the MCRE1 was 1340 +/- 181 L/day, the value for blood production of E1 (PBE1) was 129 +/- 12 nmol/day, and the portion of E1 derived from DS was 30.4 +/- 9.4%. Correlation analysis of the data from these eight subjects showed that 17-KS, PBDS, and the serum DS were all correlated with body surface area, body weight, and ponderal index and that 17-KS excretion, PBDS, and serum DS were all correlated with one another. The most important predictors of 17-KS excretion were serum DS (P less than 0.001) and the ponderal index (P less than 0.05).

17-Ketosteroids↗
PubMed1990

Steroid sulphatase activity in the human ovarian corpus luteum, stroma, and follicle: comparison to activity in other tissues and the placenta.

Steroid sulfatase activity was measured in 89 human samples, using dehydroepiandrosterone sulfate (DHEAS) as substrate. The lowest activity was that of follicular fluid which was significantly lower than that of other tissues tested (each P less than 0.01). The steroid sulfatase activity of ovarian tissue taken collectively (corpus luteum, stroma, and follicles) was higher than that of other tissues taken collectively (abdominal skin, uterus, and fallopian tube) (P less than 0.001), and the steroid sulfatase activity of either the follicle (P less than 0.01) or the stroma (P less than 0.05) was significantly greater than that of the corpus luteum. The geometric mean steroid sulfatase activity of the placenta was significantly higher than other tissues tested (each P less than 0.01) and was 22-fold higher than that of the follicle, the tissue with the next highest activity. These data indicate that the human ovary (particularly the stroma and follicle) is capable of utilizing DHEAS, an adrenal product, as a substrate for production of other androgens such as dehydroepiandrosterone (DHEA), androstenedione, and testosterone.

Arylsulfatases↗
PubMed1988

Comparative effects of tumor necrosis factor-alpha and IL-1 beta on mitogen-induced T cell activation.

The effect of rTNF-alpha on human T cell function was examined and compared with that of rIL-1 beta by assessing the ability of each cytokine to support mitogen-induced proliferation, IL-2 production, and IL-2R expression. TNF-alpha and IL-1 beta each enhanced DNA synthesis induced by PHA or immobilized mAb to the CD3 molecular complex. In addition, each cytokine increased the number of cells entering the G1 phase of the cell cycle and augmented IL-2R expression. The combination of optimal concentrations of these factors supported these responses to a greater extent than either cytokine alone, suggesting that T cell responsiveness is independently regulated by the action of at least two separate monocyte derived cytokines. Whereas TNF-alpha had little effect, IL-1 beta augmented IL-2 mRNA expression and IL-2 production by mitogen-stimulated cells. Furthermore, IL-1 beta enhanced proliferation with increasing length of culture. Whereas TNF-alpha also enhanced proliferation late in culture, it was less effective in this regard than IL-1 beta. Thus, IL-1 beta and TNF-alpha augment mitogen-induced T cell proliferation by increasing the number of cells initially activated and by promoting subsequent cell cycle progression. They differ, however, in their capacity to promote IL-2 mRNA and IL-2 production and therefore ongoing T cell proliferation.

Antibodies, Monoclonal↗
PubMed1988

Effects of fetal sex, stage of gestation, dibutyryl cyclic adenosine monophosphate, and gonadotropin releasing hormone on secretion of human chorionic gonadotropin by placental explants in vitro.

Explants from 16 term and 6 midtrimester placentas were cultured for 6 days. Statistically significant increases in secretion of human chorionic gonadotropin occurred in control medium cultures of both term and midtrimester explants during the 6-day culture period (p less than 0.01). Statistically significant increases in secretion of human chorionic gonadotropin were produced by 2 mmol/L dibutyryl cyclic adenosine monophosphate in both the term (p less than 0.01) and the midtrimester (p less than 0.01) explants. There was no effect of gonadotropin releasing hormone. The ratio of human chorionic gonadotropin secretion from midtrimester explants to that from term explants varied under different conditions, dropping from twentyfold in day 1 cultures to elevenfold for maximum secretion produced after culture in control medium for up to 6 days. A further drop in the ratio to fourfold was observed for the maximal response to 2 mmol/L dibutyryl cyclic adenosine monophosphate treatment. Explants from term female infants produced significantly more human chorionic gonadotropin than those from term male infants (p less than 0.05), but the sex difference disappeared after stimulation with 2 mmol/L dibutyryl cyclic adenosine monophosphate.

Bucladesine↗