Reovirus type 3 and [125I]-iodocyanopindolol bind to distinct domains on the beta-adrenergic like receptor

Antireceptor antibodies have been developed as a probe to study the cellular receptor for reovirus type 3. Using this probe, a glycoprotein with a molecular weight of 65-67 kilodaltons and a pI of 5.8-6.0 was isolated and identified as the reovirus receptor. This protein was also structurally similar to the affinity-purified beta-adrenergic receptor from calf lung. In this report, we employ [125I]-iodocyanopindolol, a high affinity beta-adrenergic antagonist, to further characterize this protein. We show that R1.1, a murine thymoma cell line, possesses about 2,000 receptors per cell with high affinity for ICYP (kD = 3.3 X 10(-11) M). Competitive inhibition studies suggest that the receptor is of the beta-2 subtype. Solubilized receptor proteins from R1.1 cells bound to the antireceptor antibody were further purified by SDS-PAGE and electroelution from the gel. Five percent of the proteins thus obtained could bind ICYP with high affinity (kD = 1.6 X 10(-10) M). This suggests that the purification procedure produced a collection of forms of this 65- to 67-kilodalton protein, some of which retained the conformation for binding the beta ligands. We also demonstrate that the isolated receptor protein was able to bind ICYP even when the virus binding site was occupied by the anti-idiotype, suggesting that reovirus type 3 and the beta ligands bind to distinct domains on the receptor protein.

Effects of an antiprogesterone (RU486) on the hypothalamic-hypophyseal-ovarian-endometrial axis during the luteal phase of the menstrual cycle

The impact of the antiprogesterone RU486 [17 beta-hydroxy-11 beta-(4-dimethylaminophenyl) 17 alpha-(1-propynyl)estra- 4,9-dien-3-one] on the hypothalamic-pituitary-ovarian-endometrial axis was examined in normal cycling women during the mid (MLP)- and late (LLP) luteal phases. During the MLP, 10 women received 3 mg/kg RU486 for 3 days. During the LLP, a single dose of 600 mg RU486 was administered to 4 women, and in another 4 women a single dose of 3 mg/kg was given during corpus luteum rescue by hCG. Longitudinal studies with daily and frequent blood samples (every 10 min for 10 h) were conducted during 3 consecutive cycles (control-treatment-recovery). During the MLP, RU486-induced uterine bleeding occurred in all 10 women 36-72 h after the first dose. No histological evidence of endometrial breakdown was found in endometrial biopsies taken 12-24 h before the onset of bleeding. Significant decreases in LH secretion (P less than 0.001) and LH pulse amplitude (P less than 0.006) and blunted pituitary responses to GnRH (P less than 0.01) were evident by the last treatment day, but LH pulse frequency did not change. Complete luteolysis occurred in 2 of the 10 women. Incomplete luteolysis occurred in 8 women and was associated with an initial decline of serum estradiol (P less than 0.001), but not progesterone levels, followed by rebound increases (P less than 0.001) in LH, estradiol, and progesterone levels 3 days later, which may have reversed the luteolytic processes and prolonged corpus luteum function. Spontaneous luteolysis ensued 3-5 days later with the onset of second episodes of uterine bleeding. For serum FSH, an early rise occurred during the luteal phase in advance of the onset of the second episodes of uterine bleeding. This rise may have resulted in early follicle recruitment and accounted for the shorter duration of the follicular phase during recovery cycles. During the LLP, the single RU486 dose resulted in significant decreases in LH pulse amplitude (P less than 0.03), frequency (P less than 0.05), and secretion (not significant) within 12 h. The recovery cycle was entirely normal. Corpus luteum rescue with incremental doses of hCG did not prevent uterine bleeding after RU486 treatment. These findings indicate that RU486 operates at multiple sites and implies that progesterone is important in the control of luteal function. Further, our data provide a basis for exploring the potential use of RU486 as a once a month birth control agent.

Ionic and permeability requirements for exocytosis in vitro in sea urchin eggs

We study exocytosis in the planar isolated cortex of the egg of the sea urchin Lytechinus pictus. Solutions bathing the exocytotic apparatus need not contain appreciable amounts of ions: fusion follows addition of submicromolar calcium to solutions containing only nonelectrolyte. We examine the effects of altering the granule membrane permeability to small molecules with ionophores and digitonin. Introducing holes in the secretory granule membrane to the extent of allowing free passage of small molecules does not cause secretion in vitro. We add the amphipathic compound digitonin at 12 to 15 microM concentrations and demonstrate that the granule membrane can become permeable to lucifer yellow, yet that granules remain intact. Granules still undergo exocytosis after digitonin treatment at such concentrations upon subsequent addition of calcium. Higher concentrations of digitonin lead to granule content swelling and vesicle bursting. We conclude that cortical granule hydration during exocytosis is not mediated by small ionic channels.

Treatment of uterine fibroids with agonist analogs of gonadotropin-releasing hormone

Agonist analogs of GnRH were used to effect a "medical castration" in 14 patients with uterine fibroids, presenting with either an enlarged uterus, recurrent menometrorrhagia, and/or infertility. This study confirms prior reports of a reduction in uterine size and cessation of menometrorrhagia in patients with fibroids following treatment with GnRHa. Of interest, however, was the successful use of GnRHa as either the sole treatment for uterine fibroid-associated infertility, or as a preoperative adjunct in infertility patients scheduled for myomectomy. Three of the five infertility patients in this study achieved intrauterine pregnancies. Further study of the role of GnRHa treatment in infertility patients with uterine fibroids appears warranted.

The effect of berbamine derivatives on activated Ca2+-stimulated Mg2+-dependent ATPase in erythrocyte membranes

Ca2+-stimulated Mg2+-dependent ATPase (Ca2+ + Mg2+-ATPase) stimulated by calmodulin, by partial proteolysis or by oleic acid in erythrocyte membranes was inhibited by various derivatives of the naturally occurring alkaloid berbamine. The ability of these derivatives to inhibit trypsin-activated Ca2+ + Mg2+-ATPase correlated well with their ability to inhibit the calmodulin-stimulated enzyme. Inhibition of the trypsin-activated Ca2+ + Mg2+-ATPase by O-4-(ethoxybutyl)berbamine (EBB) was competitive with respect to ATP. The Ki for inhibition was about 8 microM. These results suggest that the binding site of EBB on the activated Ca2+ + Mg2+-ATPase may bear structural similarity to that on calmodulin, and may be closely related to the ATP-binding site on the enzyme.

Vessel imaging using dual-energy tomosynthesis

A method has been developed that combines dual-energy subtraction and tomosynthesis for vessel imaging in intravenous angiography. This paper describes the procedure for doing tomosynthesis on a fan-beam rotational-motion system and gives the point responses of the imaging system. Phantom studies show that dual-energy tomosynthesis improves the visualization of desired vessels lying on a selected plane. The results may be feasible for some applications such as clinical diagnosis of coronary artery diseases.

Immunochemical probing of the N-terminus of the myosin heavy chain

The reactivity of myosin subfragment 1 (S-1) towards site specific polyclonal anti-N-terminus antibodies was examined in competitive ELISA titrations. Tryptic digestion of S-1 and specifically the cleavage at the 25/50K junction greatly increased the accessibility of the N-terminus region to the antibodies. The binding of actin to S-1 did not change significantly the reactivity of either tryptic or intact S-1 towards anti-N-terminus antibodies. These results suggest the interdependence of the N-terminus and 25/50K junction regions on S-1.

Proteolysis and binding of myosin subfragment 1 to actin

Rates of proteolytic cleavage of myosin subfragment 1 were measured in the absence and presence of different amounts of actin. The rates of tryptic digestion at the 50K/20K junction and papain digestion at the 25K/50K junction of the myosin head were progressively inhibited with increasing substoichiometric molar ratios of actin to myosin subfragment 1. The percentage inhibitions of digestion reactions corresponded precisely to the molar compositions of actin-subfragment 1 solutions and demonstrated that equimolar complexes of these proteins were responsible for the observed changes in the proteolysis of myosin heads.