Spatial relationships among the cellular tapetum,visual streak and rod density in dogs

The dog visual system is well suited to dim light conditions due to rod-dominated retina and the reflective tapetum. The topographical distributions of rods and thickness of the tapetum of the dog were quantified in retinal whole mounts stained with thionine, and spatial relationships among the tapetum, rod density and visual streak of high ganglion cell density were elucidated. The relationship between the retina and tapetum was analyzed in parasagittal sections stained with thionine or hematoxylin-eosin. The tapetum was thick in its center, and the thickest part consisted of 9 to 12 tapetal cell layers. Rod density ranged from 200,000 to 540,000/mm². Maximum rod density was found in the area dorsal to the visual streak, and the density in that area was significantly higher than the rod density in the visual streak and accorded spatially with the thickest part of the tapetum. The horizontal visual streak was found over the horizontal line through the optic disc in the temporal half and extended slightly into the nasal half. The central area of the highest density of ganglion cells was approximately located midway between the nasal and temporal ends of the visual streak. The visual streak was located within the tapetal area, but ventrally to the thick part of the tapetum.     

Morphological and habitat characteristics of settling and newly settled Roughscale Sole Clidoderma asperrimum collected in the coastal waters of northeastern Japan

This report first describes the morphological and habitat characteristics of larval and juvenile Roughscale Sole Clidoderma asperrimum. Five metamorphosing larvae (22.1–31.7 mm standard length, SL) and 12 juveniles (23.7–46.4 mm SL) were collected from two locations in coastal waters of northeastern Japan, Shizugawa Bay (rocky habitats, 6–12 m depth) and Iwaki (sandy habitats, 10–50 m depth), respectively, using a hand net while SCUBA diving and a small trawl net during May–August in 2008 and 2010. Underwater observation in Shizugawa Bay revealed that metamorphosing larvae and juveniles that had settled on rocks or stones showed transparent and variegated body coloration, which is cryptic to a rocky habitat. Juveniles in Iwaki showed monotonic coloration. The settlement would occur during metamorphosis because the same larva observed on a stone subsequently swam with a left-lateralized body posture. The larval morphology was characterized by a dense covering of fine spines on the whole body surface. Spines on the ocular side developed steadily, gradually forming bony tubercles with growth, whereas those on the blind side regressed with development and finally disappeared in metamorphosed juveniles. Our results indicate that Roughscale Sole can settle and adapt to rocky and sandy habitats in coastal waters with wide depth range.     

Effect of dietary high amount of calcium and phosphorous on reducing the prevalence of morphological deformities in GH-transgenic Nile tilapia

To satisfy the world’s growing need for animal protein, it is important to develop or select fish species which are suitable for optimal cultivation in closed recirculating aquaculture systems (CRASs) as an environment-friendly aquaculture technology for providing safe and secure aquaculture food products. We have developed an ‘all fish’ growth-hormone (GH)-transgenic Nile tilapia Oreochromis niloticus (GHTi) which appears to be a predominant candidate for CRAS since it has been found to exhibit two important characteristics, namely, a shorter rearing duration to a market size and lowered N and P discharge load. However, these fish have undergone morphological changes, resulting in a short body which is less acceptable to consumers as an edible fish. One possible solution to reducing the prevalence of such morphological deformities is to determine the association between changes in the nutritional conditions of these fish. To this end, we first calculated the ideal total calcium (Ca) and phosphorous (P) intake (g/kg), ideal daily Ca and P intake and retention (g/kg/day) and ideal daily feeding rate (%) for the fourth filial (F₄) offspring of GHTi. Our hypothesis was that GHTi would achieve the same total retention of Ca (14.6 g/kg) or P (7.69 g/kg) during a 69-day shorter rearing period as their production-matched pedigree common domestic strain (CTi). We estimated that when GHTi were fed conventional commercial diets to satiety, those with a body weight (BW) of more than approximately 230 g could not retain sufficient Ca, while those with a BW of more than approximately 429 g could not retain sufficient P. We then attempted to reduce the prevalence of morphological deformities in GHTi via dietary compound regulation by supplying a high amount of dietary Ca [6.82 % in the diet with Ca supplementation (Ca-S)] or P [4.75 % in the diet with P supplementation (P-S)]. Both the Ca-S and P-S diet improved mineral retention, while those fed on a Ca-S diet showed a lower prevalence of deformities, close to the size-matched CTi. These results suggest that the requirements of dietary Ca and P were significantly higher in GHTi than in CTi and, consequently, that the conventional levels of Ca and P in commercial diets for CTi cannot meet the mineral requirement of GHTi. We therefore propose to develop an optimal feed to meet the altered nutritional requirements of GH-transgenic Nile tilapia for growth-promoting optimization. This may become prerequisite for rearing this GHTi line in CRASs.     

Immunological effects of glucan and <Emphasis Type="Italic">Lactobacillus rhamnosus</Emphasis> GG,a probiotic bacterium,on Nile tilapia <Emphasis Type="Italic">Oreochromis niloticus</Emphasis> intestine with oral <Emphasis Type="Italic">Aeromonas</Emphasis> challenges

The present study histologically examined the effects of glucan-containing and Lactobacillus rhamnosus GG (LGG)-containing diets on intestinal damages inflicted on Nile tilapia by Aeromonas challenges. Tilapia were fed control, glucan, and LGG diets for 2 weeks and were subsequently challenged with Aeromonas. The intestines were then histologically examined at 1, 7, 14, and 21 days post-infection. Mortality following the challenge was lower for the fish fed the glucan and LGG diets. The intestines of these groups also showed increased inflammatory cell infiltration and reduced intestinal damage from Aeromonas. Moreover, inflammatory cell infiltration occurred more rapidly in the glucan-fed than in the LGG-fed fish following the challenge. Before the challenge, the dominant mucous cell was the acid type in all the tests. After the challenge, the main mucus cell type in the proximal intestine of the glucan-fed fish shifted to AB-PAS double-staining cells, while in the LGG-fed fish, it remained the acid type throughout the test period, and the number of double-staining cells was smaller than in the control fish after the challenge. Thus, the different mucous cell and inflammatory cell responses show that glucan and LGG might have different immunostimulative effects, although they both reduced the intestinal damage following Aeromonas challenges.     

Xanthophyll levels in foxtail millet grains according to variety and harvesting time

Foxtail millet grains usually contain carotenoids, which are yellow pigments that are important for human health. Yellow grains are preferred by distributors and consumers, and special cultivars and cultivation methods are desired for a stable supply of yellow millet. We investigated the level of pigment fluctuation in several foxtail millet accessions, including the yellow grain cultivar ‘Yuikogane’ from Iwate Prefecture, using high-performance liquid chromatography. Most yellow grains primarily contained xanthophylls, including approximately 1 mg/100 g lutein and 0.2 mg/100 g zeaxanthin. These pigments were rare in the bran and grain husks but were readily detected in polished grains, indicating that xanthophylls accumulate in the endosperm. We examined ‘Yuikogane’ to investigate the relationship between xanthophyll accumulation and grain ripening. During the ripening stage, xanthophyll levels gradually increased, but they rapidly decreased in response to over-ripening. Xanthophyll accumulation was estimated using a colorimetric assay of yellow pigmentation, which could be a useful method for determining the proper harvesting time for foxtail millet.     

Transgenic medaka with brilliant fluorescence in skeletal muscle under normal light

ABSTRACT:   Green fluorescent protein ( GFP ) and red fluorescent protein ( RFP ) genes regulated by the medaka skeletal muscle actin promoter were microinjected into fertilized d-rR medaka eggs to establish transgenic medaka lines. Intense fluorescence was detected in skeletal muscle. During development, GFP and RFP became detectable in anterior somites at the 12- and 30-somete stages, respectively. After hatching, intense fluorescence in skeletal muscle enabled individual fish to be identified under normal lighting without fluorescent microscopy. Fluorescence was also observed in the gills and esophagus of the adult fish. These data indicated that medaka lines are convenient not only for the study of skeletal muscle but also for the identification of cells or individuals in various studies.