Kiyoshi Sakai

Endocrine profiles in the females of a twice-annually spawning strain of rainbow trout

Abstract Endocrine profiles of the reproductive phases in individual females were studied using forty-four 2.5-year-old fish for 1 year following their first ovulation in winter. Ovulation occurred from 24 April to 28 July and from 14 December to 26 January, in 24 individuals (68.6%) and 33 individuals (94.3%), respectively, out of 35 females which survived the whole experimental period. Ovulation occurred over a few months in the summer breeding season, whereas it was rather concentrated in the winter breeding season. In the fish that were successful ovulators in the summer, plasma estradiol-17β rapidly increased in January, attaining the highest values from March to May and then decreased before ovulation. Plasma gonadotropin (GtH) gradually increased from January followed by a second increase just before ovulation in summer. In the fish that failed to mature in summer, plasma estradiol and GtH showed little increase from January to February, and synchronously decreased in March. Lengthening daylength in spring probably inhibited GtH secretion in the once-spawners, but not in the twice-spawners which already had high plasma estradiol and GtH at the critical period between late February and late March. In almost all females, synchronous increases in plasma estradiol and GtH occurred in July, probably triggered by the shortening daylength. The highest values for estradiol were attained in October.

Endocrine profiles in the males of a twice-annually spawning strain of rainbow trout, Salmo gairdneri

The male reproductive cycles of a twice-annually spawning strain of rainbow trout were studied by monitoring the plasma gonadotropin (GtH) and steroid hormone levels in individual fish for more than a year using thirty-five 2.5-year-old mature males. Twenty-five males survived the whole experimental period and were divided into four groups according to the amount of milt and endocrine profiles. In the summer breeding season, milt amount was negligible in Group I and small in Group II with low plasma testosterone, 11-ketotestosterone (11-KT), and 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17 alpha,20 beta-diOH-P) levels, whereas both groups showed a large amount of milt and a distinct increase in steroid levels in the winter breeding season (November-January). Group III expelled a large amount of milt in both the summer and winter breeding seasons, and plasma testosterone, 11-KT, and 17 alpha,20 beta-diOH-P showed a clear peak in each breeding season. In Group IV, milt was expelled from December to July, and plasma steroid levels remained high until June before declining to the basal levels; however, these fish failed to mature in the ensuing winter breeding season. Plasma GtH levels in Groups III and IV were significantly higher than those in Groups I and II in the summer breeding season. These results clearly indicate that fish in Group III are twice-annual spawners.

Effects of bergenin on experimental ulcers—Prevention of stress induced ulcers in rats

Abstract 1. 1. The effects of bergenin on various experimental ulcers were tested. Bergenin is a constituent of folk medicines for gastritis and gastric ulcers. 2. 2. It was effective in preventing stress-induced gastric ulcers (30 mg/kg i.v.). 3. 3. One of the mechanisms of its effectiveness may be inhibition of acetylcholine release, which induces gastric acid secretion and enhances gastric motility, both being well known ulcerogenic factors.

Ovarian steroid synthesis during oocyte maturation and ovulation in Japanese catfish (Silurus asotus)

Abstract Several aspects of the endocrine regulation of final oocyte maturation (FOM) and ovulation in Japanese catfish ( Silurus asotus ), was investigated. These were: (1) potency of various steroids on inducing FOM in vitro, (2) steroid production stimulated with human chorionic gonadotropin (hCG) in vitro, (3) effectiveness of hCG administration in vivo on inducing FOM and ovulation, and (4) plasma sex steroids profiles in female catfish during FOM and ovulation induced by hCG injections. Among steroids tested, 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) was the most potent steroid in inducing FOM and 17,20β,21-trihydroxy-4-pregnen-3-one (20β-S) was the second most effective. 17α-xa0hydroxyprogesterone (17α-P) and 11-deoxycortisol (11-DC) did not induce FOM even at the highest dose tested. Both ovarian 17,20β-P and 20β-S production were induced by hCG in vitro and the 17,20β-P production was higher than 20β-S production. The ovarian fragments cultured in vitro did not convert 17α-P to 17,20β-P unless they were treated with hCG. hCG injection increased plasma 17,20β-P and 20β-S levels, causing FOM and partial ovulation. In addition, this hCG-induced 17,20β-P production was higher than the 20β-S production in vivo. These data suggest that 17,20β-P appears to be a major maturation-inducing steroid (MIS) in Japanese catfish and that MIS production may be regulated by GTH-induced activation or synthesis of 20β-hydroxysteroid dehydrogenase.

Effect of papaverine on Ca2+ uptake by a mitochondrial fraction isolated from rat uterine smooth muscle

A mitochondrial fraction was isolated from rat uterine smooth muscle. The effect of papaverine (3 X 10(-6), 10(-5), 3 X 10(-5), 10(-4) M) on Ca2+ accumulation by the fraction was studied. The effect of papaverine was changed by using different substrates for Ca2+ accumulation. Papaverine inhibited the Ca2+ accumulation supported by glutamate plus ATP concentration-dependently. The Ca2+ accumulation supported by ATP alone was also inhibited. On the other hand, the Ca2+ accumulation supported by succinate and ATP was increased by papaverine. The effect was not concentration-dependent; papaverine (3 X 10(-5) M) was the most effective concentration for the effect with a shorter incubation (2 min).

Effect of quinidine on microsomal ATPase from rabbit taenia coli.

Quinidine inhibits the relaxation of intestinal smooth muscle in response to 8-stimulants, a-stimulants, antispasmodics or non-adrenergic inhibitory stimulation (Burnstock, Campbell & others, 1970; Tomiyama, Takayanagi & Takagi, 1975). Its inhibitory action implies that it interferes with basic mechanisms of relaxation of the smooth muscle and Tomiyama & others (1975) demonstrated that it inhibits ATP-dependent uptake of Ca2+ ions into intestinal microsomes. Thus quinidine depresses intracellular Ca2+-sequestration and reduces the effects of relaxants that lower the intracellular concentration of Ca2+ ions. As this sequestration is supported by ATP, we have examined the effect of quinidine on microsomal ATPase to obtain information on Ca2+ ion pumping mechanisms in smooth muscle. Inhibitors of Ca2+-pumps, such as ruthenium red do not affect relaxation of intact muscle (Tomiyama & others, 1975). Therefore quinidine is useful for studies on the underlying mechanisms of the Ca*+ ion pump in smooth muscle. Male rabbits, 2-3 kg, were killed by exsanguination after a blow on the head. Then the taeniae coli were rapidly removed, washed with ice-cold 0.25 M sucrose solution, cut into small pieces and homogenized in 9 volumes of ice-cold 0.25 M sucrose solution in a Polytron (PT 10, Brinkman) at rheostat setting 6 for three 5 s periods. The homogenate was centrifuged at 15 000 g for 30 rnin and the supernatant was further centrifuged at 40 000 g for 60 min. The resulting microsomal fraction is the fraction reported by Takayanagi, Hongo & Kasuya (1977) to consist mainly of plasma membrane vesicles. Contaminating actomyosin-ATPase was removed by washing the microsomal fraction twice with 0.6 M KCI. ATPase activity was measured in 20 mM imidazole buffer (pH 7.2) containing 0.1 M KCI, 3 mM Na,ATP, 0.1 mM ouabain and 5 mM sodium azide. Ouabain (0.1 mM) was added to block the activity of Na+-, K+-, Mg2+-ATPase, and sodium azide ( 5 mM) was used to block the contaminating mitochondria1 Ca2+-, Mg2+ATPase. To the reaction mixture a specified amount of Mg2+ and/or Ca2+ ions were added. ATPase activity in the presence of Mg2+ ions alone was denoted as Mg2+ATPase, that in the presence of Ca2+ ions alone as Ca2+-ATPase, and the activation of Mg2+-ATPase by further addition of Ca2+ ion, as Ca2+-, Mg2+-ATPase. The free concentration of Ca2+ ions was adjusted with EGTA and calculated as described by Ogawa (1968) assuming that Kapp = 3.16 x l @ ~ l (at pH 7.20). The reaction was started by adding a suspension of the