Hormonal sex reversal of wild-spawned tilapia in India

The effectiveness of methyltestosterone (MT) for sex reversal and growth promotion in Oreochromis mossambicus was studied in culture experiments in India. Wild-spawned fry were treated with 30 μg MT g⁻¹ diet for 30 or 60 days at two feeding levels (initially 20% or 10% of body weight daily). The fish were grown on for 66–96 days after the hormone treatment period in fertilized cement ponds without supplementary feeding. Tilapia treated with MT for 60 days attained an average weight of 29.0 g compared to 18.8 g for untreated fish reared under similar conditions. The percentage of males among the untreated tilapia was 58%, MT treatment for 30 days significantly increased this percentage at the higher feeding level (79% male), but not at the lower feeding level (51%). More than 90% of the tilapia in both 60 day MT treatment groups were male; 3% of all the fish reared showed an intersex condition. The experiments demonstrated that the anabolic and sex reversal effects of MT on tilapia are proportional to the duration of treatment and quantity of hormone administered. The possible application of monosex tilapia culture in tropical countries is noted.     

Phenotypic variation in seasonal adjustments of testis size, body weight, and food intake in deer mice: role of pineal function and ambient temperature

We investigated pineal function as well as reproductive and energetic characteristics in male deer mice (Peromyscus maniculatus) that differentially respond to short photoperiod with full, partial or no gonadal regression. In mice at both high (23 °C) and low temperature (1 °C), these phenotypic differences in reproductive responses to short days were not reflected by differences in urinary excretion of 6-sulphatoxy-melatonin, the main metabolite of pineal melatonin. Neither duration nor amplitude or phase-angle of nocturnal peaks in 6-sulphatoxymelatonin significantly differed between reproductive phenotypes at either temperature. Differences in testis size were, however, associated with different energy requirements. In gonadally regressed males only, food intake and body weight were significantly (P < 0.01) reduced by up to 29% and 13% respectively. Chronic cold exposure (5 °C) had no effect on the proportion of males undergoing testicular regression under short days, but caused a general elevation in body weights among all mice (P < 0.05). Phenotypic differences in body weight and food intake were maintained in the cold. Together, these results suggest that within-population variation of reproductive responses in male deer mice is based on post-pineal differences in the regulation of gonadal function, and that phenotypic characteristics in reproductive and energetic responses to short days are largely unaffected by ambient temperature. Accepted: 2 October 1995     

The mRNA expression of P450 aromatase, gonadotropin beta-subunits and FTZ-F1 in the orange-spotted grouper (Epinephelus Coioides) during 17alpha-methyltestosterone-induced precocious sex change

The orange-spotted grouper Epinephelus coioides is a protogynous hermaphroditic fish, but the physiological basis of its sex change remains largely unknown. In the present study, the 2-year-old orange-spotted grouper was induced to change sex precociously by oral administration of 17alpha-methyltestosterone (MT, 50 mg/Kg diet, twice a day at daily ration of 5% bodyweight) for 60 days. The serum testosterone levels were significantly elevated after MT treatment for 20 and 40 days as compared to control, but the levels of serum estradiol (E(2)) remained unchanged. The expression of P450aromA in the gonad significantly decreased after MT treatment for 20, 40, and 60 days. Accordingly, the enzyme activity of gonadal aromatase was also lower. The expression of FSHbeta subunit in the pituitary was significantly decreased after MT treatment for 20 days, but returned to the control levels after 40 and 60 days; however, the expression of LHbeta subunit was not altered significantly by MT treatment. The expression of FTZ-F1 in the gonad also decreased significantly in response to MT treatment for 40 and 60 days, but its expression in the pituitary was not altered significantly. Interestingly, when tested in vitro on ovarian fragments, MT had no direct effect on the expression of P450aromA and FTZ-F1 as well as the activity of gonadal aromatase, suggesting that the inhibition of gonadal P450aromatase and FTZ-F1 by MT may be mediated at upper levels of the brain-pituitary-gonadal axis. Taken together, these results indicated that FSH, P450aromA, FTZ-F1, and serum testosterone are associated with the MT-induced sex change of the orange-spotted grouper, but the cause-effect relationship between these factors and sex change in this species remains to be characterized.     

Effects of temperature, age and body size on moulting and growth in the freshwater amphipods Gammarus fossarum and G. roeseli

1. The total body length, cephalic length, wet weight and dry weight was measured in juveniles, males and females of Gammarus fossarum and G. roeseli kept in the laboratory. Numbers of flagellar segments on the first and second pairs of antennae of G. fossarum and G. roeseli were quantitatively related to body size and in stars. The addition of segments cannot be used to identify particular instars of individuals or to determine their ages in natural populations. 2. At experimental temperatures ranging from 3.8 to 20.2°C, the number of moults, duration of intermoults, maturation times and specific growth rates were studied from birth in isolated specimens. Sexual maturity was reached after 9 or 10 moults, at a mean wet weight of c. 5mg for females and c. 7mg for males of G. fossarum, and at c. 10 mg for females and c. 13 mg for males of G. roeseli. At 3.8°C neither species reached sexual maturity within 550 days. 3. The mean interval between moults was observed from birth to sexual maturity and was linearly related to moult number and exponentially related to age. The relationship between each intermoult interval, or the maturation time, and the experimental water temperature was described by a power function. Maturation times increased from 96 days at 20.2°C to 355 days at 7.9°C in G. fossarum, and 85 days to 403 days in G. roeseli. 4. Over the range 3.8–20.2°C there was a log—log relationship between temperature and specific growth rates. Growth was maximal at 20.2°C in newborn animals as well as in small sexually mature animals; interspecific differences were highly significant. 5. Increase in body wet weight of G. fossarum and G. roeseli fed ad libitum on a constant mixture of autumn-shed, naturally decaying, tree leaves and aquatic macrophytes was followed to senescence and death. The instantaneous or specific growth rate was maximal near birth, at c. 7.98% wet weight day^?1 in G. fossarum and 9.03% in G. roeseli. At ≥12°C, growth conformed to a logistic curve; maximum absolute increments in weight occurred about half-way through a life span of 280–300 days at 20°C, 380–420 days at 16°C and 550–600 days at 12°C. Some individuals lived longer than 850 days at ≤12°C. The wet weight at birth was 0.112mg for G. fossarum and 0.123mg for G. roeseli. Asymptotic mean body weights of males and females were, respectively, 61 and 41 mg for G. fossarum and 87 and 58 mg for G. roeseli. However, G. roeseli reached the inflection point of the logistic curve significantly faster than G. fossarum. In the latter species, growth and maturation were relatively faster at temperatures below 12°C, whereas they were faster in G. roeseli at 16–20°C. Thus G. fossarum is adapted to summer-cool streams and G. roeseli is adapted to summer-warm streams.     

性逆转石斑鱼性腺差异表达基因的克隆和筛选

以 17α 甲基睾丸酮 (17α MT)饲喂 2～ 4龄赤点石斑鱼 (Epinephelusakaara) ,成功地促使其性转变为具有生殖功能的雄鱼 .应用抑制性差减杂交 (SSH)技术构建了石斑鱼性反转前后性腺组织的SMARTcDNA文库及其cDNA差减文库 ,从中随机挑取 12 0 0个克隆进行了PCR和斑点杂交筛选 ,得到 12 0个差异表达cDNA片段 .挑选 71个cDNA克隆测序 ,将所测序列经GenBank检索和生物信息学比较 ,发现有 5 1个cDNA片段序列无明显的同源性 ,2 0个片段与报道的基因有较高同源性 .在这 2 0个具同源性的片段中有 3个片段可能是与性别分化密切相关的重要功能基因 ,它们是钙调蛋白基因、活性蛋白激酶C受体基因和一氧化氮合酶蛋白抑制剂基因 .这 3个基因被分别命名为鱼钙调蛋白基因 (GenBankaccession :AY2 8136 3)、鱼活性蛋白激酶C受体基因 (GenBankaccession :AY2 8136 4)和鱼一氧化氮合酶蛋白抑制剂基因 (GenBankaccession :AY2 8136 5 ) .     

Reduced incidence of retained placenta with induction of parturition in the cow

Two experiments were designed to determine whether pretreatment with Opticortenol (OPT), a long-acting corticosteroid, prior to induction of parturition with 25 mg of dexamethasone (DEX) alone or in combination with 500 mug cloprostenol (CLO) would result in a reduced incidence of retained placenta. In Experiment 1, 70% of the cows pretreated with 25 mg OPT on Day 270 of gestation calved before or within 24 hours of the scheduled induction treatment on Day 277. Cows induced to calve with DEX plus CLO without OPT pretreatment had an increased rate of placental retention (P<0.05), whereas, cows that received OPT were not different from the controls. In Experiment 2, cows received either 1 mg/25 kg OPT (high dosage) or 1 mg/50 kg OPT (low dosage) on Day 270 of gestation and were induced with DEX plus CLO on either Day 274 (4 days) or Day 276 (6 days). Cows claved 29.0 to 31.8 hours after induction treatment with 95% beginning to calve between 0700 and 1900 hours. The interval from calving to placental release and the incidence of retained placenta was not different between the high dosage 6-day group (29.4+/-8.2 hours, 29%) and the non-induced control cows (16.1+/-10.7 hours, 5%). When three cows in the high dosage 6-day group that retained their placentas for 30 to 36 hours were considered as not retained, the incidence of placental retention for that group was reduced still further to 17%. First service conception rates and pregnancy rates were lower in cows with retained placentas. Differences were significant (P<0.01) in Experiment 1 but not in Experiment 2. It was concluded that pretreatment with 1 mg/25 kg OPT 6 days prior to induction of parturition with DEX plus CLO in combination results in a predictable calving time, high calf viability, and a low incidence of placental retention.     

Developmental toxicity assessment of thermoresponsive poly(N-isopropylacrylamide-co-acrylamide) oligomers in CD-1 mice

BACKGROUND: Although polymers and hydrogels are used successfully in biomedical applications, including implants and drug delivery devices, smaller molecular weight oligomers, such as those investigated here, have not been extensively studied in vivo. Poly(N‐isopropylacrylamide‐co‐acrylamide), or P(NIPAAm‐co‐AAm), has a unique thermoresponsive behavior and is under investigation as a novel drug delivery system for metastatic cancer treatment. To date, no studies have been published regarding the safety of P(NIPAAm‐co‐AAm) to the conceptus. METHODS: From gestation days (GD) 6–16, pregnant CD‐1 mice were dosed via i.p. injection with aqueous solutions containing 500, 750, or 1,000 mg/kg/d P(NIPAAm‐co‐AAm). Dams were sacrificed on GD 17 and their litters were examined for abnormalities. RESULTS: P(NIPAAm‐co‐AAm) caused no statistically significant difference in maternal weight gain or percent resorbed or dead fetuses compared to control values, but fetal weight was significantly decreased in the two highest dosage groups. CONCLUSIONS: At the highest dosages employed, maternal exposure to P(NIPAAm‐co‐AAm) was associated with decreased fetal weight. However, as the estimated human exposure levels for persons using this system would be some 1,500‐fold lower than the lowest dosage administered in this study, the authors feel that this oligomer was not shown to pose a biologically significant risk at relevant human dosages. Birth Defects Res (Part B), 2008. © 2008 Wiley‐Liss, Inc.     

Comparison of cold hardiness and sugar content between diapausing and nondiapausing pupae of the cotton bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae)

Abstract. To understand overwintering of the cotton boll worm Helicoverpa armigera, cold hardiness and sugar content are compared between diapausing and nondiapausing pupae. Diapausing and nondiapausing pupae reared at 20 °C under short and long photoperiods are acclimatized with a reduction of 5 °C per 5 days to 0 °C. When the acclimation temperature reaches 0 °C, the survival of diapausing pupae is assessed. The survival gradually decreases as the period of treatment progresses and approximately half survive for 112 days. However, nondiapausing pupae survive only 14 days after exposure to 0 °C. The surpercooling points of nondiapausing, diapausing and acclimatized pupae are approximately −17 °C. The major sugars contained in pupae are trehalose and glucose. Even though trehalose contents in diapausing pupae (initial level: 0.6 mg 100 mg⁻¹ fresh weight) increase significantly during cold acclimation and continue increasing until 58 days after exposure to 0 °C (maximum level: 1.8 mg 100 mg⁻¹), glucose is maintained at low levels (0.02 mg 100 mg⁻¹) for 56 days at 0 °C. However, glucose contents increase (maximum level: 0.8 mg 100 mg⁻¹) with decreasing contents of trehalose 84 days after exposure to 0 °C. Glycogen content gradually decreases during cold acclimation. When nondiapausing pupae are acclimatized with a reduction of 5 °C per 5 days to 5 °C from the beginning of pupation until the eyespots move, trehalose content increases (maximum level: 1.0 mg 100 mg⁻¹). Glucose contents in nondiapausing pupae increase before eclosion (0.09 mg 100 mg⁻¹). From these results, diapausing pupae of H. armigera can overwinter in regions where average winter temperatures are higher than 0 °C, but nondiapausing pupae cannot.     

Effects of short- and long-term cold acclimation on morphology,physiology, and exercise performance of California mice (Peromyscus californicus): potential modulation by fatherhood

California mice (Peromyscus californicus) differ from most other mammals in that they are biparental, genetically monogamous, and (compared with other Peromyscus) relatively large. We evaluated effects of cold acclimation on metabolic rate, exercise performance, and morphology of pair-housed male California mice, as well as modulation of these effects by fatherhood. In Experiment 1, virgin males housed at 5° or 10 °C for approximately 25 days were compared with virgins housed at standard vivarium temperature of 22 °C. Measures included resting metabolic rate (RMR), maximal oxygen consumption (\(\dot{V}{\text{O}}_{2}\)max), grip strength, and sprint speed. In Experiment 2, virgin males housed at 22 °C were compared with three groups of males housed at 10 °C: virgins, breeding males (housed with a female and their pups), and non-breeding males (housed with an ovariectomized, estrogen- and progesterone-treated female) after long-term acclimation (mean 243 days). Measures in this experiment included basal metabolic rate (BMR), \(\dot{V}{\text{O}}_{2}\)max, maximal thermogenic capacity (\(\dot{V}{\text{O}}_{2}\)sum), and morphological traits. In Experiment 1, virgin males housed at 5° and 10 °C had higher RMR and \(\dot{V}{\text{O}}_{2}\)max than those at 22 °C. In Experiment 2, 10 °C-acclimated groups had shorter bodies; increased body, fat, and lean masses; higher BMR and \(\dot{V}{\text{O}}_{2}\)sum, and generally greater morphometric measures and organ masses than virgin males at 22 °C. Among the groups housed at 10 °C, breeding males had higher BMR and lower \(\dot{V}{\text{O}}_{2}\)max than non-breeding and/or virgin males. Overall, we found that effects of fatherhood during cold acclimation were inconsistent, and that several aspects of cold acclimation differ substantially between California mice and other small mammals.

     

Combined effect of dimethylnitrosamine and a lysine-restricted diet on O6-methylguanine-DNA methyltransferase levels in mouse tissues

O6-Methylguanine is a lesion produced in DNA after exposure of animals to the procarcinogen dimethylnitrosamine. The lesion may lead to mutagenesis or carcinogenesis if not repaired. Repair is accomplished by the protein O6-methylguanine-DNA methyltransferase (MT). The methyl group is transferred to a cysteine residue of the protein, which is not regenerated. In mice, after exposure to alkylating agents, the synthesis of the protein is non-inducible. The inactivation of MT as a result of the transmethylation makes new synthesis of the protein molecules necessary for further dealkylation reactions. Protein synthesis activity correlates well with dietary protein quality. Nutritional conditions of amino acid restriction will limit the number of MT molecules synthesized. Continuous exposure of mice to dimethylnitrosamine will further diminish the pool of the protein. In this study, mice were fed a diet low in lysine and simultaneously given dimethylnitrosamine in the drinking water at concentrations resulting in dosages of zero, 0.4 mg or 1.2 mg/kg body weight/day. After 6 days MT was assayed in liver, kidney and lung. In liver and kidney, lysine restriction provoked a decrease in MT levels per mg of tissue DNA which was intensified by the presence of dimethylnitrosamine in the drinking water. Recovery from lysine restriction with respect to MT levels was achieved within 2 days. In lung, moderate effects on MT levels were observed when dietary lysine restriction was combined with the highest dosage of dimethylnitrosamine used (1.2 mg/kg body weight/day). The data strongly emphasize the importance of an adequate amino acid mixture in the diet, to support protein synthesis and to allow for high MT levels and repair of DNA lesions at the O-6 position of guanine during the exposure of the animals to alkylating agents.     

In vivo depression of reserve albumin binding capacity by cadmium: a preliminary evaluation

The effect of cadmium upon the depression of reserve albumin binding capacity (%RABC) was investigated in male, New Zealand white rabbits at daily dosages of 0.65 mg and 0.90 mg Cd/kg body weight. Correlations of % RABC to the duration of exposure were strongest at the higher dosage. After 30-35 days exposure, the decline in % RABC was partially reversed. Levels of total protein in urine increased sharply within a few days after the % RABC had been reduced by cadmium to their lowest values.     

Life cycle of Ornithodoros rostratus (Acari: Argasidae) under experimental conditions and comments on the host-parasite relationship in the Pantanal wetland region, Brazil

The genus Ornithodoros is represented by 15 species in Brazil, on which no detailed life cycle studies have been published, except for O. talaje and O. mimon. The aim of the present study was to evaluate life cycle parameters of O. rostratus based on ticks collected in the Pantanal wetland region of the state of Mato Grosso do Sul, Brazil, using domestic rabbits as experimental hosts. The periods of pre-attachment and feeding of the larvae lasted an average of 39 min (range 15–76 min). Five or six nymphal instars were found. The emergence of adults started with N3 in the following sequence: N3—two males; N4—13 males; N5—three males and 16 females; and N6—two females. Mean weight of N4 that molted to males was 31.7 ± 13.6 mg, whereas mean weight of N5 that molted to females was 100.1 ± 36.2 mg. The overall sex ratio was 1:1. Oviposition lasted 14 days, with a sharp decline beginning with the 7th day. The overall duration of the life cycle of O. rostratus ranged from approximately 66 to 136 days. Comments on the tick-host relationship in the Pantanal region are offered.     

A new progestin (Sa 45.249) for cycle control in pigs communication I: Hormonal activities and dosage

Sa 45.249 was applied for 12 days to groups of ten gilts each. A daily dose of 3, 6, 12 or 24 mg inhibited cyclic functions effectively; estrus was observed 4.5 ± 0.8, 4.8 ± 0.8, 5.2 ± 0.9 and 6.1 ± 0.6 days after cessation of treatment, respectively. All animals were slaughtered 8 days after induced estrus. Only animals treated with 3 mg showed a high incidence of ovarian cysts simultaneously with the occurrence of corpora lutea. In animals treated with higher dosages, only one (6 mg) had 4 cystic follicles, but simultaneously 12 corpora lutea. In another study, the effectiveness of Sa 45.249, applied at different doses, for differing time periods, and starting at different days of the cycle, was investigated. Doses ranged from 3 to 9 mg/day, duration of treatment from 8 to 16 days and treatments commenced on days 2, 5, 10, 15 or 19 of the cycle. An increase in the daily doses of 1 mg resulted in a delay of estrus of less than 0.1 day. Of 99 gilts, 93 showed an estrus 6.5 ± 1.7 days after cessation of treatment. None of the variables studied had a significant effect on the occurrence of estrus or the interval between treatment and the onset of heat.     

External genitalia abnormalities in male rats exposed in utero to finasteride, a 5 alpha-reductase inhibitor

A series of studies was conducted to determine the developmental toxicity of the 5 alpha-reductase inhibitor finasteride (MK-0906) in rats. This compound was administered orally once daily to pregnant rats during various extended treatment periods during gestation. F1 offspring were evaluated on Day 20 of gestation as well as postnatally through mating to produce an F2 generation. MK-0906 treatment induced dosage-related incidences of hypospadias (penischisis) in male offspring with a threshold dosage level near 0.1 mg/kg/day and a 100% effect level of 100 mg/kg/day (with dosing through Day 20 of gestation). MK-0906 also caused decreased anogenital distance in male offspring. The dosage response for this effect (ranging from a 4.2% decrease at 0.003 mg/kg/day to a 38% decrease at 100 mg/kg/day) was more shallow than that for hypospadias. The decreases in anogenital distance were at least partially reversible postnatally with essentially complete recovery at dosages up to 0.1 mg/kg/day. There was also a dosage-related, temporary induction of nipples in F1 males. All of these effects were apparent following treatment on Days 6 through 17 of gestation but were more pronounced when dosing extended to Day 20 of gestation. Slight maternal toxicity consisting of minor decreases in body weight gain occurred only at dosages of 3 mg/kg/day and higher, indicating the selective nature of the developmental toxicity. The 5 alpha-reductase enzyme located in the rat fetal genital tubercle was studied in vitro and compared to that in the adult ventral prostate. The values for Km, Vmax, and IC50 for inhibition by MK-0906 were similar in the two tissues, suggesting that the enzymatic proteins in the genital tubercle and ventral prostate may be similar.     

Cold hardiness and sugar content in photo‐insensitive individuals of the cotton bollworm Helicoverpa armigera

Abstract A proportion of Helicoverpa armigera collected from fields in Okayama Prefecture (Western Japan; 34.6°N, 134.1°E) does not enter diapause when reared under a short days at 20 °C during the larval stages. However, diapause in such photo‐insensitive individuals can be induced when they are reared at moderately low temperatures, such as 15 °C, regardless of photoperiod. To determine whether such photo‐insensitive individuals can survive overwintering in fields, the present study compares the cold hardiness and sugar content between nondiapausing and diapausing pupae of photo‐insensitive individuals selected over several generations at 20 °C under a short day photoperiod (LD 10 : 14 h). Diapausing and nondiapausing pupae are obtained under the short days by rearing at 15 and 20 °C, respectively, during larval and pupal stages. These pupae are stepwise acclimated at a reduction of 5 °C every 5 days to 0 °C. Maximum survival periods of nondiapausing and diapausing pupae at 0 °C are approximately 30 and 90 days, respectively. Trehalose content in diapausing pupae increases, reaches a maximum level (1.95 mg 100 mg^?1 in males and 2.1 mg 100 mg^?1 in females) 28 days after exposure to 0 °C and then decreases. On the other hand, glucose content in diapausing pupae increases (maximum level: 0.32 mg 100 mg^?1 in males and 0.21 mg 100 mg^?1 in females) with decreasing trehalose content 42 days after exposure to 0°C. The decrease in trehalose content and the increase in glucose content may be linked to termination of diapause in H. armigera. These results suggest that, in Japan, the photo‐insensitive individuals can only survive in the mild winters of southern regions, and not in the severe winters of northern regions.     

Sex differentiation in the European eel: histological analysis of the effects of sex steroids on the gonad

The effects of sex steroids on sex differentiation in the European eel were studied. The steroids, 17α-methyltestosterone (MT) and 17α-ethynylestradiol (EE), were given in the diet to 6–8 cm elvers and to 15–18 cm and 22–25 cm yellow eels. In our rearing conditions a very large percentage of the untreated eels developed as males. No masculinizing effect of MT could be demonstrated. The EE, administered at a dose of 10 mg kg^-1 of diet to 6–8 cm elvers and 15–18 cm eels, induced ovarian differentiation in about 90 and 65% of eels respectively, while in the control <5% of females was recorded. In 22–25 cm yellow eels a moderated feminizing effect was observed.
Histological analysis of the gonads of treated eels showed that sex steroids affect the gonadal structure. The androgen stimulates hypertrophy of compact connective tissue, early differentiation of Leydig cells, Sertoli cells and early formation of the spermatic duct. Oestrogen inhibits the differentiation of these structural components and stimulates the differentiation of follicular cells and an ovarian structure.
The involvement of gonadal structural components is discussed in relation to the effect of steroid treatment and to the peculiarities of sex differentiation in the European eel.     

Effects of 17α‐methyltestosterone on the growth performance,development, and reproduction of gynogenetic topmouth culter (Culter alburnus Basilewsky)

This study investigated the effects of 17α‐methyltestosterone (17α‐MT) on the physiological properties of gynogenetic topmouth culter (Culter alburnus). Five 17α‐MT concentration (0, 10, 25, 40, and 60 μg/g) groups were set up in Experiment 1, and three treatment and recovery methods of the above five concentrations were studied in Experiment 2. In Experiment 3, fish were fed with increasing concentrations of 17α‐MT (from 40 μg/g to 140 μg/g) in an outdoor pond. In Experiment 1, growth was promoted during the initial 60 days in the 10 μg/g group, whereas inhibition was first observed at 20 days after treatment in the 60 μg/g group. Increased concentration (40–60 μg/g) of 17α‐MT significantly inhibited the expression of FOXL2 and CYP19a gene but significantly activated the expression of AMH and DMRT1 gene. The levels of superoxide dismutase, estradiol, testosterone, growth hormone, and tetraiodothyronine in the 40 and 60 μg/g groups were significantly higher than those in the other concentration groups at 40 days after treatment. In Experiment 2, almost all indexes detected besides the expression of reproduction‐related genes in the 17α‐MT treatment groups were recovered to those in the control groups. All gonads observed in Experiments 1 and 2 remained in a primordial state after treatment with different concentrations of 17α‐MT. In Experiment 3, 100% of the detected gonads developed into testes at 126 and 460 days post‐fertilization after three‐month outdoor 17α‐MT induction. These results suggest that 17α‐MT affects the physiological processes related to sexual differentiation in topmouth culter and that feeding 17α‐MT with increasing dose in an outdoor pond provides an effective protocol for producing neo‐male topmouth culter.     

Water and carbohydrate levels at different developmental stages and dynamics in hibernating pupae of Pieris melete (Lepidoptera: Pieridae)

For insight into the physiological indicators of diapause in Pieris melete, water and carbohydrate (glycogen and trehalose) levels were measured under both natural and laboratory conditions. The highest water content (3.71–3.79 mg/mg dry weight) was found in larvae and developing pupae, which was substantially higher than in diapausing pupae (2.59 mg/mg dry weight). Water content was almost stable during diapause, except for individuals approaching diapause termination (3.43–3.58 mg/mg dry weight). The total carbohydrate level was significantly higher in pre‐pupae (47.41 μg/mg) compared to larvae (22.80 μg/mg) and developing pupae (21.48 μg/mg). The highest level of trehalose was detected in winter diapausing pupae, and no trehalose was found in larvae or developing pupae. Levels of glycogen were highest in pre‐pupae and lowest in diapausing pupae. Levels of total carbohydrate decreased as diapause proceeded, and no significant changes were found in trehalose levels for diapausing pupae under natural conditions or treated for 60–90 days at 5°C. Pupae treated at 20°C for 60–90 days had significantly lower levels of trehalose than those treated for 30 days. Glycogen content was relatively stable at 5°C, but increased after treatment under natural conditions and 20°C for more than 60 days. These results suggest that the dynamics of water and carbohydrate levels are potential physiological diapause indicators, which show metabolic differences between trehalose and glycogen during diapause development.     

Post-harvest age-induced seed dormancy of Acer ginnala and its alleviation by growth regulator and low temperature treatments

One-month-old fruits of Acer ginnala with winged pericarp attached gave 44% germination and this was not increased by cold treatment at 4°C for 0, 10, 20, or 30 days, gibberellic acid treatment at 0, 1, 10, 100 or 1000 mg litre^-1, or ethephon treatment at 0, 2, 20, 200 or 2000 mg litre^-1. After 6 months of storage at 20–25 °C, germination of untreated fruits fell to 5% but could be restored to that of 1-month-old fruits by incubation at 4 °C for 30 days. After 9 months storage, no germination occurred in untreated fruits. Cold treatment (30 days at 4 °C partially restored germination (26%). Treatment with either gibberellic acid (1000 mg litre^-1) and 30 days at 4 °C (40%) or ethephon (100 mg litre^-] and 30 days at 4 °C improved germination (69%). The combination of all three treatments, i.e. 100 mg litre^-1 gibberellic acid, 100 mg litre^-1 ethephon and 30 days at 4 °C, optimised germination (86%). Thus, dormancy of A. ginnala developed during storage but could be reversed by a combination of treatment with low temperature and growth regulators. The highest germination (86%) was achieved after low temperature and growth regulator treatment of stored fruit.     

Critical period of androgen-inducible sex differentiation in a teleost fish, the European sea bass

Twenty-day exposures to 17α-methyltestosterone (MT) (10 mg kg-©¹ food) starting at 86 or 106 days post fertilization (DPF) resulted in a complete masculinization of sea bass Dicentrarchus labrax , as opposed to 46% females present in the controls. Earlier exposures failed to suppress ovarian development, resulting in a variable number of females (range 10·5–49·5%). All treatments assayed between 110 and 210 DPF induced a complete masculinization, regardless of the androgen or the dose tested. However, a dose dependent increase in the number of fish with intratesticular oocytes was observed after MT but not after 17α-methyldihydrotestosterone (MDHT) administration. This might be a reflection of the capability of MT and not of MDHT to be converted into oestradiol by the action of aromatase. One hundred-day exposures to either of the androgens (10 mg kg©¹ food) starting at 60 or 160 DPF resulted in a total suppression of ovarian development and a partial induction of sterility. Complete sterility was accomplished after 200 days of exposure starting at early ontogenesis (60–260 DPF). These deleterious effects on gonadal development were later confirmed by a dramatic reduction of the gonadosomatic index. In addition, around the first year of age, growth was significantly depressed in all groups except those for which treatments started at the latest (160–260 DPF; experiment 1) or the earliest and shortest (46–66 DPF; experiment 2). Hence, the critical period of androgen-inducible masculinization is located between 96 and 126 DPF and coincides with a rapid proliferation of primordial germ cells in the sexually undifferentiated gonad.