4-Nitro-3-phenylphenol has both androgenic and anti-androgenic-like effects in rats

To investigate the effect of endocrine disruption of 4-nitro-3-phenylphenol (PNMPP) on immature male Wistar-Imamichi rats, the rat pituitary was exposed to PNMPP (10^–5–10^–9 M) for 24 h with or without gonadotropin-releasing hormone (GnRH) in experiment I. In addition, the Leydig cells (10^–5–10^–9 M) were exposed to PNMPP for 24 h with or without human chronic gonadotropin (hCG) in experiment II. Our results showed that the PNMPP at 10^–5–10^–7 M suppressed follicle-stimulating hormone (FSH) and luteinizing hormone (LH) productions from GnRH-stimulated pituitary cells. At the same time, PNMPP 10^–5–10^–7 M induced an increase in testosterone production from the Leydig cells treated with or without hCG. Based on our results, it can be concluded that that PNMPP might have both androgen agonist action by decreasing FSH and LH production in the pituitary and anti-androgenic action by increasing testosterone production in the Leydig cell.     

Experimental approach to prezygotic chromosome screening using only a single pair of gametes in mice

During in vitro embryo production, chromosome screening is essential to prevent pregnancy losses caused by embryonic chromosome aberrations. When the chromosome screening is completed before fertilization, gametes are effectively utilized as genetic resources. The aim of this study was to investigate whether chromosome screening of gametes accompanied by fertilization would be feasible using a single mouse spermatozoon and oocyte. Metaphase II oocytes were divided into a cytoplast and a karyoplast. For genome cloning of the gametes, androgenic and gynogenic embryos were produced by microinjection of sperm into cytoplasts and parthenogenetic activation of karyoplasts, respectively. Pairs of blastomeres from androgenic and gynogenic embryos were fused electrically to produce diploid embryos, which were transferred into pseudopregnant surrogate mothers to examine fetal development. Blastomeres from androgenic and gynogenic embryos were individually treated with calyculin A—a specific inhibitor of type 1 and 2A protein phosphatases—for 2 h to induce premature chromosome condensation. Thereafter, chromosome analysis of blastomeres, reflecting the genetic constitution of individual spermatozoa and oocytes, was performed, and we confirmed that most of the androgenic and gynogenic 2-cell embryos had a haploid set of chromosomes in their sister blastomeres. The reconstructed embryos from blastomeres of androgenic and gynogenic 2-cell embryos could be implanted and develop into live fetuses, albeit at low efficiency. This study indicates that prezygotic chromosome screening and embryo production using a single pair of gametes may be practicable.     

Seasonality of serum levels of vitellogenin in male Japanese whiting, Sillago japonica, reared under natural temperature and photoperiod

ABSTRACT:   Because blood vitellogenin (Vg) has been considered a biomarker for environmental estrogens, the basal levels of Vg and 17β-estradiol (E₂) were determined in male Japanese whiting reared under natural conditions. Serum levels of Vg and E₂ were measured and gonadal development was assessed by gonadosomatic index (GSI) and histological observation in 8–10 male fish at monthly intervals throughout the annual reproductive cycle. Serum E₂ was <60 pg/mL throughout the study period. In contrast, serum Vg exhibited seasonal changes: serum levels of Vg gradually increased from April to May (mean 63 ± 13 ng/mL and 124 ± 48 ng/mL in April and May, respectively), and then reached a peak value (mean 352 ± 68 ng/mL) in June. Thereafter, serum Vg gradually decreased, reaching undetectable levels (<50 ng/mL) in October. Serum levels of Vg tended to increase in the male fish in which the GSI was >1%. Histological observation revealed that testes in such male fish were in active spermatogenesis and then all of the testes of male fish in which serum Vg decreased to ND levels were regressed. These results suggest that Vg productive potency (sensitivity to estrogens) may increase in the spermatogenic stage, resulting in production of Vg in response to very low levels of natural or xenobiotic estrogens.     

Balancing protein ingredients in carp feeds to limit dischargeof phosphorus and nitrogen into water bodies

ABSTRACT:   Through a series of experiments, it has been demonstrated successfullythat an appropriate choice of ingredients is primary for achievinga reduction in phosphorus (P) and nitrogen (N) loading from carpculture. In this final study, four multi-ingredient diets were examined.In addition to the basal ingredients (fish meal 15%, corngluten meal 8%, defatted soybean meal 10%, blood meal3–5%), three of the test diets (PF, MM, and SP)contained 6% each of either poultry feather meal, meatmeal or soy protein concentrate, respectively, and the fourth diet(PMS) had each of the three aforementioned ingredients includedat 3%. These diets had crude protein < 35%,digestible energy > 3.5 kcal/g,available P between 0.65 and 0.66% and total P rangingfrom 1.26 to 1.36%. The diets were fed to juvenile carpduring a 12-week feeding trial. The highest growth was obtained forfish fed the MM diet. The absorption and retention rates of P werehigher for the PF diet, whereas these values for N did not showtreatment-related differences. The total discharges per ton fish productionwere estimated to range between 7.8 and 9.2 kg for P andbetween 39.1 and 40.7 kg for N. These were lower than thefigures for Lake Kasumigaura, a main carp culture site, indicatingthat proper balancing of protein ingredients aids in efficientlylowering emissions from aquaculture.     

Feeding habits of Pacific pomfret Brama japonica inthe transition zone of the central North Pacific

ABSTRACT:   We examined the diets of three size groups of the Pacific pomfret Bramajaponica collected in April and May 2000 in the transition zoneof the central North Pacific. Amphipods, cephalopods and fish werethree of the most common prey groups of pomfret. Of the three size groups,small pomfret (11.0–19.9 cm standard length (SL))preyed mainly on amphipods and occasionally on cephalopods (mainlytransitional species Onychoteuthis borealijaponica ) and fish.(These prey amphipods and fish could not be identified to lowertaxonomic levels because they were too digested.) Medium and largepomfret (20.0–30.9 and 31.0–40.9 cm SL,respectively) preyed mainly on cephalopods (mainly O. borealijaponica ,but also on two subarctic species, namely Berryteuthis anonychus and Gonatopsisborealis ), suggesting that these cephalopod species ensure energyfor the northward migration of these two size groups in the transitionzone in the spring. The next most common prey for medium pomfretwas amphipods (mainly subtropical species Phronima sedentaria and Platyscelusovoides ), followed by fish (mainly Bathylagus sp.). However,in the case of large pomfret, fish (mainly Paralepididae sp. 'A')were the next most common prey, followed by amphipods (mainly P.sedentaria and P. ovoides ), indicating that the importanceof fish as prey increases with growth for medium and large pomfret.     

A laboratory-based assessment of phosphorus and nitrogen loading from currently available commercial carp feeds

ABSTRACT: To clarify the total phosphorus (P) and nitrogen (N) loading from carp culture, five commercial diets were selected from a major location in Japan, Lake Kasumigaura, for a 12-week feeding trial. These diets were prepared as per the 'Kasumigaura Feed Standard' (crude protein < 35% and digestible energy > 3.5kcal/g), and total P ranged from 1.4% to 2.0%. However, for most of the diets the P available was lower than the requirement level. A control diet was formulated with 25% fishmeal to comply with that standard and contain adequate available P. Duplicate groups of juvenile carp were fed the aforementioned diets to satiation, three times a day, six days a week throughout the trial. Growth performance was significantly higher for the control group and values of P absorption (20.4–47.0%) and retention (14.0–36.3%) varied widely among the groups. Consequently, the total P loading (kg/t production) values based on retention fluctuated from 14.8 to 26.4 among the commercial diet groups compared with the low level of 8.5 for the control group. Similarly, the total N loading (kg/t production) values varied from 30.9 to 86.0 and was lowest for the control group. A higher whole body lipid and lower bone P and Ca confirmed the deficiency of the dietary available P in commercial diets. Better growth and comparatively less P and N loading rates were observed in the diet that had sufficient available P, not to mention that the control diet ranked best. It was concluded that an inadequacy of available P among the commercial diets affects the growth of carp and produces high P and N loading into the water. Therefore, if the commercial diets do not supply adequate levels of available P to carp, growth is negatively affected and may result in greater waste loading.