Rates in the SN2 and E2 reactions of a series of β-substituted ethyl chloride (RCH2CH2Cl, R=Et, MeO, PhO, Gl, and H) in aqueous solutions have been measured at temperatures ranging from 90 to 150°C, using sodium acetate as a nucleophile. The mild rate-retarding effect of β-subtituents in the SN2 reactions, observed in the rate order, H>Et>MeO>Cl>PhO, may be attributed to the steric effects. In a similar fashion, the retardation of E2 reaction rates by the β-substituents, which is in the rate sequence H>MeO>Et>PhO>Cl, may be ascribed to the steric effects, which outweigh the electronic effects. The β-substituent effects of several other substituents, which are known in the literature, have also been discussed.
Marked fluctuations in mobility, known as the on-off phenomenon, frequently emerge during the course of chronic treatment with levodopa in patients with Parkinson's disease. Similar fluctuations in mobility and mental status have been observed in a 10-year-old Japanese girl with tetrahydrobiopterin deficiency (BH4 deficiency) while receiving neurotransmitter and biopterin supplement. In order to define the underlying mechanisms for the phenomenon in our patient, we studied the temporal relationship between plasma levodopa levels and clinical status during oral (2.0 mg/kg per day) and continuous intravenous (2.0 mg/kg per 12 h) administration of the drug. Following each oral levodopa dose, the plasma concentration of levodopa peaked at 60-90 ng/ml within 60 min and fell to 5-15 ng/ml within 2 h. The clinical state of the patient varied acutely in parallel with the plasma levodopa concentrations. The clinical swings completely disappeared when the plasma levodopa concentrations were stabilized between 120-150 ng/ml by continuous infusion. Paradoxically, on awakening from sleep, she was invariably ambulatory despite very low plasma levodopa levels (less than 10 ng/ml). These observations indicate that the on-off phenomenon in our patient reflect the fluctuations of plasma levodopa levels as demonstrated in Parkinson's disease, but there may be substantial differences in levodopa transport across the blood-brain barrier and/or striatal dopamine-receptor interaction between Parkinson's disease and BH4 deficiency.
Abstract. To investigate the changes in the serum androgen concentrations and the Free Androgen Index (FAT) in women during danazol therapy, we measured the serum concentrations of adrenal steroids and danazol metabolites, and then examined the effects of danazol metabolites on assays for serum androgens. Thirteen women who had endometriosis were treated with danazol (300 or 400 mg/day) for 8 to 16 weeks. Blood samples were taken before, during, and after the medication. During the danazol therapy, serum testosterone (T), cortisol (F), and sex-hormone binding globulin (SHBG) significantly decreased (P<0.05); but serum dehydroepiandrosterone-sulfate (DHEAS) and FAT increased (P<0.05). The serum concentrations of danazol metabolites were: danazol, 209.0±28.3 (ng/mL, mean ± SEM); A'-2-hydroxymethyl ethisterone, 114.4±8.4; and 2-hydroxymethyl ethisterone, 660.0±54.2. There was considerable cross-reaction between danazol metabolites and androgens [T, androstenedione (A), and dehydroepiandrosterone (DHEA)] in the direct assays. As for the ratios of adrenal steroids in serum, the DHEAS/F, DHEAS/DHEA, and 11-deoxycortisol (S)/F ratios increased (P<0.05). We conclude that the increase in FAT and DHEAS represents increased native androgenic activity with danazol, and the changes in adrenal steroid ratios in serum indicate the inhibition of 11 f3-hydroxylase and sulfatase activities during danazol therapy.
To investigate the physiological importance of inhibin in the regulation of FSH secretion in prepubertal bulls, animals (6-month-old) were passively immunized against inhibin. Five animals were given an i.v. bolus injection of 50 ml inhibin antiserum raised against bovine 32 kDa inhibin in a castrated male goat, and four bulls were given the same amount of castrated male goat serum (control serum) as controls. Treatment with the inhibin antiserum resulted in a marked increase (P < 0.01) in plasma concentrations of FSH within 12 h compared with control animals, and FSH levels in immunized animals remained high until 168 h after the injection. Concentrations of plasma LH and testosterone in the immunized animals were not different from those in the control animals. The present findings provide strong evidence that inhibin plays an important role in the inhibitory regulation of FSH secretion in prepubertal bulls.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.