Carcinogen-induced Thyroid Proliferative Lesions in Wistar Hannover GALAS Rats with Thyroid Dysplasia

Incidences and morphological features of thyroid proliferative lesions induced by carcinogens in Wistar Hannover GALAS rats (GALAS rats) showing normal growth with or without thyroid dysplasia were examined. All thyroid tissue samples were obtained from our recently conducted study using male GALAS rats treated with 5 carcinogens according to the medium-term multiorgan carcinogenicity bioassay protocol (called DMBDD treatment). In the DMBDD-treated rats, thyroid dysplasia was found in 9 out of 114 rats. Follicular cell adenomas were found in 5 out of 9 rats with thyroid dysplasia and in 7 out of 105 rats without thyroid dysplasia. The incidence of adenoma was significantly increased in rats with thyroid dysplasia (55.6%) compared with that in rats without thyroid dysplasia (6.7%). Adenomas in rats with thyroid dysplasia were observed as single or multiple nodules, well demarcated and composed of variously sized vacuolated cells or unvacuolated cells. These histopathological features and staining profiles of luminal colloid for PAS and thyroglobulin, together with PCNA-positive cells, were fundamentally similar to those of rats without thyroid dysplasia. On the other hand, the luminal colloid in adenomas of rats with thyroid dysplasia had a tendency to be poorly stained for T(4) compared with that of rats without thyroid dysplasia. From these findings, it appears that dysplastic thyroids of rats showing normal growth are more sensitive to carcinogens than normal thyroids. In addition, the morphological features of carcinogen-induced thyroid proliferative lesions in GALAS rats with thyroid dysplasia were fundamentally similar to those of rats without thyroid dysplasia, except for the vacuoles and T(4) staining profile.     

Minimum alveolar concentration for blunting adrenergic responses (MAC-BAR) of sevoflurane in dogs

It is well known that heart rate or arterial blood pressure may increase in response to surgical stimulation despite the absence of a purposeful movement. However, there is limited information regarding anesthetic requirement for blunting adrenergic response in dogs. This study was designed to compare the minimum alveolar concentrations of sevoflurane required to prevent autonomic response (MAC-BAR) and purposeful movement (MAC) in dogs. Sevoflurane MAC-BAR and MAC were determined in 5 beagle dogs by judging dogs' response to a noxious electrical stimulus applied to the gingiva. The sevoflurane MAC-BAR was significantly higher than MAC (3.33 ± 0.48 vs 2.10 ± 0.28%, P=0.005). These results suggested that autonomic responses occurred at sevoflurane anesthetic concentrations at which purposeful movements were absent.     

Age related decreases in neural sensitivity to NaCl in SHR-SP

To determine whether neurophysiological taste responses of young and old rats are different, recordings were made from the whole chorda tympani nerve which innervates taste buds on the anterior tongue. SHR-SP (Stroke-Prone Spontaneously Hypertensive Rats) in two age groups were studied. Chemical stimuli included single concentrations of 250 mM NH(4)Cl, 100 mM NaCl, 100 mM KCl, 500 mM sucrose, 20 mM quinine-hydrochloride, 10 mM HCl, 10 mM monosodium glutamate (MSG), 10 mM L- glutamic acid (L-Glu) and an NaCl concentration series. The magnitude of the neural response (response ratio) was calculated by dividing the amplitude of the integrated response by the amplitude of the spontaneous activity that preceded it. Substantial neural responses to all chemicals were obtained at both ages. The responses to KCl, sucrose, quinine-hydrochloride, HCl, monosodium glutamate (MSG) and glutamic acid (Glu) did not change with age, but the response to NaCl did decrease significantly. The profile of the response/concentration function for NaCl differed with age. In particular, the responses to solutions more concentrated than 100 mM NaCl were significantly weaker in aged than in young SHR-SPs. We also observed that recovery from amiloride treatment on the tongue of SHR-SPs was faster in aged rats than in young ones, suggesting that there is some functional difference in the sodium-specific channels on the taste cell. These results suggest that aged SHR-SP may be less able than young SHR-SPs to discriminate among higher concentrations of NaCl solutions.     

Formation process of staining-type hypermelanosis in Japanese flounder juveniles revealed by examination of chromatophores and scales

Staining-type hypermelanosis, defined as blind-side melanosis occurring after completion of metamorphosis, reduces commercial value in hatchery-produced flatfishes. Detailed characterization was performed on the stained area of juvenile Japanese flounder Paralichthys olivaceus to physiologically understand this phenomenon. From 80 to 120 days after hatching, juveniles were reared in sandy and sandless tanks. By classifying the staining degree into 7 levels, about 2 times higher occurrence of middle-level staining was reconfirmed in sandless tank (about 80 %) than in sandy tank (about 40 %). In the stained area, we found 3 types of chromatophores (melanophore, xanthophore, and iridophore) and ctenoid scales, which would be typically observed on the normal ocular side. Detailed examination on the melanophores revealed further similarity between the stained area and the normal ocular side, in terms of the distribution at 2 layers (shallower and deeper than scale), and the densities in both layers (about 1000 cells/mm² above scale and 200 cells/mm² beneath scale). These results strongly suggest that the staining is a status change in the body surface conditions from the blind side to that on the ocular side, and not a simple darkening caused by disordered proliferation of melanophores on the blind side.     

Self-feeding behavior of yellowtail, Seriola quinqueradiata, in net cages: diel and seasonal patterns and influences of environmental factors

The self-feeding pattern of yellowtail, Seriola quinqueradiata, maintained in floating net cages was examined throughout a year, and the influence of seasonal changes of the photoperiod and water temperature on the feeding pattern was investigated. Two groups of 50 yellowtail (initial mean body weight about 50 and 80 g, respectively) were kept in two experimental net cages (2×3×4 m deep), with a self-feeding device installed on each. It was possible to maintain yellowtail in net cages using a self-feeder throughout almost a year. The number of daily food demands was greatly affected by the seasonal changes in water temperature. Yellowtail showed high self-feeding activity, above 18 °C; depressing water temperatures did not influence the activity when the water temperature was over 18 °C. However, the activity decreased when the water temperature fell below 18 °C. The feeding pattern in a 24-h period was greatly affected by the temporal changes in light intensity. Annual observations revealed that yellowtail showed generally crepuscular plus nocturnal feeding behavior and had two peaks of feeding activity a day. These peaks appeared at dawn and dusk; moreover, a clear association between the most active time of self-feeding and the period of the greatest change in light intensity was observed. The results suggest that a change in light intensity might stimulate the appetite of yellowtail or that there is a light level at which yellowtail prefer to eat.     

Age, growth, and reproductive characteristics of dolphinfish Coryphaena hippurus in the waters off west Kyushu, northern East China Sea

The growth and reproductive characteristics of dolphinfish Coryphaena hippurus collected in the waters off western Kyushu from May 2008 to April 2011 were determined based on scale and otolith readings and gonad histological examinations, respectively. Based on annual increments in scales and daily increments in sagittal otoliths, the von Bertalanffy growth curves in male and females were determined as $ FL_{t} = 1049[1 - \exp \{ - 0.835(t + 6.975 \times 10^{ - 14} )\} ] $ and $ FL_{t} = 938[1 - \exp \{ - 1.029(t + 6.975 \times 10^{ - 14} )\} ] $ , respectively, where FL _t is the mean fork length (mm) at age t. The spawning period was found to last from June to August for dolphinfish, based on an examination of the monthly changes in the gonadosomatic index and histological observations. Therefore, based on the relationship between the fork length and the developmental stage of the testes or ovaries, male and female dolphinfish were found to reach sexual maturity by the following spawning season after hatching in the northern East China Sea.     

Highly efficient induction of triploid Pacific abalone <Emphasis Type="Italic">Haliotis discus hannai</Emphasis> by caffeine treatment

ABSTRACT:   In order to develop a highly efficient method for mass production of triploid Pacific abalone Haliotis discus hannai , caffeine treatment that is safe and inexpensive was optimized. To suppress the first meiotic division, fertilized eggs were exposed to either a 10- or 15-mM caffeine solution for 24 min beginning at 12 min after fertilization. In most treated batches, the rates of cleaved eggs showed no significant difference from the control batches. However, in most treated batches, the rates of occurrence of normal larvae and the survival rates of the early juveniles were significantly lower than those of the controls. The triploid rates at 6 days to 11 months after settlement in all the treated batches were extremely high (91–100%). There was no significant difference in the mean triploid rates between 10- and 15-mM caffeine treatments. These results suggest that both treatment conditions were conducive to triploid abalone production. One live 2n/3n mosaic specimen was found in the treated batches. However, since the frequency of mosaic was extremely low, the mosaicism would probably not have an adverse effect on the stable production of triploid abalones.