Three cone opsin genes and cone cell arrangement in retina of juvenile Pacific bluefin tuna <Emphasis Type="Italic">Thunnus orientalis</Emphasis>

ABSTRACT:   In bluefin tuna aquaculture, collision of juveniles with the tank or net walls is a major cause of high mortality. This problem may be related to color sensibility of the visual mechanisms of this species. As a first step in understanding of color vision of Pacific bluefin tuna Thunnus orientalis , we applied a molecular technique and histology to study cone cell distribution in the retina of juvenile fish. We isolated three cone opsin genes encoding one blue-sensitive ( SWS2 ) and two green-sensitive ( RH2 ) visual pigments. In situ hybridization revealed that SWS2 mRNA is localized in the single-cone photoreceptors. The localization of the two RH2 signals in distinct cone cells was not determined, probably because of the high homology between the two RH2 genes. Single-cone photoreceptors appeared frequently in the ventral–temporal retina in approximately 80-mm fish and in the temporal retina in approximately 230-mm fish. These cone distributions may define a visual field with best color contrast vision in front and above the fish with a short wavelength (blue) reflecting target (sensed by single cones), and may be enhanced against the longer wavelength (green) background when fish see a target below them (sensed by double cones).     

Repeatable immersion infection with <Emphasis Type="Italic">Photobacterium damselae</Emphasis> subsp. <Emphasis Type="Italic">piscicida</Emphasis> reproducing clinical signs and moderate mortality

Pseudotuberculosis is a bacterial septicaemia caused by Photobacterium damselae subsp. piscicida in several marine fish species. Yellowtail Seriola quinqueradiata is the most sensitive fish species to this disease. The internal organs of naturally infected yellowtail exhibit whitish spots, tubercle-like tissue structures, consisting of bacterial accumulations. There have been many trials for experimental infection, however adequate method of infection that reproduces moderate mortality and primary clinical signs has not yet established. Present investigation evaluated an immersion infection method by using logarithmic culture-phase bacteria resulting in higher mortality than that using stationary culture-phase bacteria. Typical white spots on the spleen and kidney were also observed constantly in dead fish. Transmission electron microscopy and fluorescent antibody microscopy showed bacterial clusters not only in the spleen and kidney but also in the blood channels in the secondary gill filaments. These results were confirmed repeatedly by plural experiments. The use of logarithmic-phase bacteria in immersion infection is an appropriate technique to reproduce moderate mortality and primary clinical signs, which will be a reliable infection method also for the challenge test of pseudotuberculosis vaccine.     

Progression of the dose-related effects of estrogenic endocrine disruptors, an important factor in declining fertility, differs between the hypothalamo-pituitary axis and reproductive organs of male mice

For the purpose of investigation of working mechanisms in endocrine disruptors, we evaluated the dose-related effects of fetal and/or neonatal exposure to an estrogenic compound on the male reproductive organs in adult mice, particularly with respect to gene expression of steroidogenic acute regulatory protein (StAR). The pregnant ICR mice were given subcutaneous injections of 10 micro g/day/animal of diethylstilbestrol (DES) to subject the fetal mice to in utero exposure (IUE). Subsequently, the newborn male mice were subjected to neonatal exposure (NE) by treatment with vehicle or 0.1-10 micro g/day/animal of DES. Fertility rates of each group were as follows: control, 100%; IUE only, 60%; IUE+NE 0.1 micro g, 25%; IUE+NE 1 micro g, 0%; IUE+NE 10 micro g, 0%. In general histology, germ cell layers in the seminiferous tubules were thinned in the group of IUE+NE 10 micro g. Hypoplasia of the Leydig cells, in which the staining intensity of eosin was diminished, was also observed in the groups of IUE+NE 0.1-10 micro g. The androgen receptor (AR) and estrogen receptor alpha (ERalpha) immunoexpression in the Leydig cells of IUE+NE 1-10 micro g was slightly lower than that in the controls. Long-term dysfunction of the hypothalamo-pituitary-testicular axis, including sustained hypoproduction of gonadotropin and testosterone, and altered expressions of steroid hormone receptors and StAR genes were observed. The hypothalamo-pituitary control of gonadotropin secretion may be affected by the smaller doses of estrogenic agents than the reproductive organs. Furthermore, the fertility rate in the male mice exposed to this estrogenic agent was closely correlated with the testosterone levels, and even more so with the rate-limiting factor of steroidogenesis, StAR. This finding suggests that endocrine disruptors have an important pronounced effect on StAR gene expression.     

Lymphoma in Miniature Dachshunds: A retrospective multicenter study of 108 cases (2006‐2018) in Japan

BackgroundMiniature Dachshunds (MD) are predisposed to lymphoma with disease onset of young age and long‐term survival.ObjectivesTo compare clinical features and survival time of lymphoma in MD and non‐MD.AnimalsOne hundred and eight MDs with lymphoma and 149 non‐MD breed dogs with lymphoma were included in the study.MethodsThis was a retrospective multicenter observational study. Lymphoma was classified based on signalment, histopathology/cytology, and anatomical site of the disease. For each type of lymphoma, median survival time was analyzed by Kaplan‐Meier estimates and life table analysis. Prognostic factors for large‐cell gastrointestinal lymphoma (LGIL) were analyzed using Cox regression.ResultsGastrointestinal lymphomas were more common in MDs (53/108) compared to non‐MDs (41/149). The multicentric lymphoma was most common in non‐MD breed dogs (74/149) compared to MDs (33/108). The median age that dog developed lymphoma in MD and non‐MD were both 10 years old; however, lymphomas were more frequently observed in younger dogs (<4 years) in MDs (20/108) compared to non‐MDs (9/149; P = .002). Seventy percent were diagnosed with B‐cell with median age of diagnosis was 3 (1‐14) years. Mott cell differentiation was observed in 6 dogs. Age <4 years and B‐cell phenotype were significant factors for longer survival time in MD with LGIL.Conclusions and Clinical ImportanceLymphomas in MDs involved gastrointestinal lesions at higher frequency compared to other dog breeds examined. B‐cell lymphoma was more common in early‐onset LGIL in MD and cases that involved Mott cell differentiation were observed. Awareness of this specific presentation of lymphoma in dogs will possibly affect the treatment decision process for the owners of MD with LGIL.     

Determination of Damaged Starch and Diastatic Activity in Wheat Flour Using a Flow-Injection Analysis Biosensor Method

The determination of damaged starch and diastatic activity in flour was studied using a flow-injection analysis (FIA) biosensor system. The system consisted of an oxygen electrode and an immobilized enzyme column containing purified glucoamylase and glucose oxidase immobilized on activated aminopropyl glass beads. The biosensor system has an optimum pH between 6.5 and 7.5 and an optimum temperature of 35°C for glucose measurement. The response of the FIA biosensor was linear up to 1.000 g/L of glucose with a lower detection limit of 0.025 g/L. Each assay took about 20 min, and the system showed good reproducibility (r = 0.998, n = 8). When applied to the measurement of damaged starch and diastatic activity in wheat flour, the results obtained agreed with those obtained using the conventional methods of measurement. This biosensor system is a rapid practical alternative for the measurement of damaged starch and diastatic activity in wheat flour.