Characteristics of prolactin-releasing response to salsolinol in vivo in cattle

The aims of the present study were to clarify the effect of salsolinol (SAL), a dopamine (DA)-derived endogenous compound, on the secretion of prolactin (PRL) in cattle. The experiments were performed from April to June using calves and cows. A single intravenous (i.v.) injection of SAL (5 mg/kg body weight [BW]) or sulpiride (a DA receptor antagonist, 0.1 mg/kg BW) significantly stimulated the release of PRL in male and female calves (P < 0.05), though the response to SAL was smaller than that to sulpiride. The secretory pattern of PRL in response to SAL or sulpiride in female calves resembled that in male calves. A single i.v. injection of SAL or sulpiride significantly stimulated the release of PRL in cows (P < 0.05). There was no significant difference in the PRL-releasing response between the SAL- and sulpiride-injected groups in cows. A single intracerebroventricular injection of SAL (10 mg/head) also significantly stimulated the release of PRL in castrated calves (P < 0.05). These results show that SAL is involved in the regulatory process for the secretion of PRL, not only in male and female calves, but also in cows. The results also suggest that the potency of the PRL-releasing response to SAL differs with the physiological status of cattle.     

Capsule thickness and amounts of a 39 kDa capsular protein of avian Pasteurella multocida type A strains correlate with their pathogenicity for chickens

Capsule thickness of avian Pasteurella multocida type A strains was determined by transmission electron microscopy after labeling with polycationic ferritin and compared with their pathogenicity for chickens. The capsule thickness of P. multocida strains Pm-18 and X-73 was 81.4 and 50.1 nm on average, respectively. These strains were highly virulent for chicken, whereas the less virulent strains Pm-1 and Pm-3 had a thin and irregular capsule, 21.0 and 29.8 nm on average, respectively. However, the thickest capsule was observed in strain P-1059, 101.2 nm on average, and the strain revealed moderate virulence. The noncapsulated variant P-1059B, which was derived from strain P-1059, revealed low virulence. The six P. multocida strains were examined with regard to protein content on the capsule of organisms. Amounts of total proteins of crude capsular extract (CCE) from capsulated strains were approximately twice those of the noncapsulated strains. The amount of an antigenic 39 kDa protein in the CCE were found to correlate with the capsule thickness, since heavily capsulated strains exhibited the greatest amount, whereas noncapsulated strains including noncapsulated and low virulent variant P-1059B possessed little 39 kDa protein. The results demonstrated that the capsule thickness and the quantity of a 39 kDa capsular protein of avian P. multocida type A strains correlated with their pathogenicity for chickens.     

Characterization of a 39kDa capsular protein of avian Pasteurella multocida using monoclonal antibodies

The role of a 39kDa protein of avian Pasteurella multocida in pathogenesis of fowl cholera was investigated using monoclonal antibodies (Mabs). Mabs were prepared by immunization of BALB/c mice with a crude capsular extract (CCE) of P. multocida strain P-1059 (serovar A:3). Totally eight hybridomas producing Mab were obtained. Immunoblot analysis of the hybridomas revealed that all the Mabs recognized a 39kDa protein of CCE. Treatment of CCE antigen with proteinase K or periodic acid indicated that the epitope recognized was proteinaceous. The Mabs reacted with a major 39kDa protein of CCE from encapsulated strains but not with any protein of non-capsulated strains indicating that a direct correlation between encapsulation and the 39kDa protein. Immunoelectron microscopy on strain P-1059 and the non-capsulated derivative P-1059B (serovar -:3) reacting with the Mabs and gold-labeled anti-mouse IgG indicated that the protein is associated with the capsule. The Mabs significantly inhibited the adherence of encapsulated P. multocida strains to chicken embryo fibroblast cells, but only slightly that of non-capsulated strains. Mice passively immunized with the Mabs were protected from lethal challenge with virulent strains P-1059 and X-73 (serovar A:1). Thus the capsular 39kDa protein was determined to be an adherence factor and a cross-protective antigen of avian P. multocida type A strains.     

Muscle growth in full-cycle cultured Pacific bluefin tuna Thunnus orientalis from early larval to juvenile stage: histochemical,immunohistochemical and ultrastructural observation

With the development of successful aquaculture techniques, the Pacific bluefin tuna (PBT) has become the most important fish species in Japan. Early muscle growth and cellularity of muscle fibers have a profound effect on ultimate body size and meat quality of fish. Larvae and juveniles of full-cycle cultured PBT were sampled at 3, 15, 29, 41, 70, 128 and 218 days post hatch (dph). Transverse body sections until 41 dph and muscle sections from 41 dph thereafter from dorso-cranial or caudal areas were stained for muscle fiber morphological and morphometric analysis and muscle sections from the dorso-cranial region were used for ultra-structural observation. Red muscle fibers appeared by 15 dph at the horizontal septum both in epaxial and hypaxial regions. Other than a single layer of superficial red fibers and those at the horizontal septum, existence of red muscle fibers was apparent in the PBT myotome. The muscle fiber diameters varied in their size even in adjacent myotomes of PBT. Overall, growth throughout the various stages was a result of both hyperplasia and hypertrophy of muscle fibers. Muscle fiber diameters were greater in the dorso-cranial than in dorso-caudal region at 41, 70 and 128 dph. These results provide additional characterization of PBT growth, which may assist with managing fish production efficiency, harvest age and eating quality.     

Exposure Time‐Dependent Bactericidal Activities of Amoxicillin Against Actinobacillus pleuropneumoniae; an In Vitro and In Vivo Pharmacodynamic Model

The pharmacodynamic effects of amoxicillin against Actinobacillus pleuropneumoniae at exposure concentration above and below minimum inhibitory concentration (MIC) were evaluated in both in vitro and in vivo. In vitro, the growth and morphological change of A. pleuropneumoniae in culture medium was observed. In vivo, the efficacy of amoxicillin on experimentally induced A. pleuropneumoniae infection in disease‐free pigs was evaluated. Fifteen pigs were divided into three groups (n = 5 per group). After the onset of clinical respiratory disease symptoms, 6 h post‐infection, amoxicillin sustained‐release injectable formulation was injected intramuscularly at 7.5 mg/kg/day (group I) and 15 mg/kg/day (group II). Then the serum concentration of amoxicillin was measured. An untreated infected group served as controls. In each amoxicillin administration group, if symptoms were not absent after 48 h, the pig was injected with the amoxicillin sustained‐release injectable formulation again using the same dosage. In vitro, the growth of A. pleuropneumoniae inhibited by amoxicillin exposure at the concentration above the MIC (1.28 × MIC), and the inhibition time was in directly proportion to the time of amoxicillin exposure. Moreover, all the cells were lysed. Whereas the bacterial growth inhibition at the amoxicillin exposure concentration below the MIC (0.25 × MIC) was not done, and the shape of cells were normal or long filamentous. In vivo, the group I clinical and pathological score was higher than the group II, and the group I weight gain was significantly less than the group II. Performance with respect to weight gain corresponded with clinical signs. The infected control group was severely affected with an 80% (4/5) mortality rate 24–96 h post‐challenge. The duration of time above MIC (T > MIC) of serum amoxicillin concentration in the group I was less than group II. The present studies suggest that amoxicillin has exposure time‐dependent bactericidal activity against A. pleuropneumoniae.     

Olfactory neuroepithelioma in a dog: an immunohistochemical and electron microscopic study

A case of olfactory neuroepithelioma was investigated electron microscopically and immunohistochemically. The tumor mass was found in the nasal cavities of a 10-year-old female dog, which showed epistaxis, nasal discharge and facial swelling. The tumor tissue consisted of tubular structure of cuboidal to columnar cells and compactly arranged nests of small cells surrounded by a fibrovascular stroma. Mitotic figures were frequently observed. Immunohistochemically, the tumor cells frequently showed positive for neurofilament protein, synaptophysin and/or carnosine in addition to keratin. Ultrastructurally, tight junction was observed between the tumor cells. No dense-cored secretory granules were shown in the tumor cells. These findings indicated that the present tumor had neuronal and epithelial features probably originating from the olfactory epithelium.     

Cross protection of mice and swine inoculated with culture filtrate of attenuated Erysipelothrix rhusiopathiae and challenge exposed to strains of various serovars

Mice and swine inoculated subcutaneously with culture filtrate vaccine prepared from acriflavine-fast attenuated Erysipelothrix rhusiopathiae strain Koganei 65-0.15 (serovar 2), were challenge exposed to 20 pathogenic strains of E rhusiopathiae of 18 serovars and type N. Vaccinated mice survived after challenge exposure to serovars 1b, 2, 8 (strain Goda), and type N, but mortality occurred in vaccinated mice challenge exposed to other strains: 20% to 30% mortality in mice challenge exposed to serovars 1a, 11, 12, 15, 16, or 21; 40% to 50% mortality in mice challenge exposed to serovars 4, 5, 6, 7, or 8 (strain 911); and 60% to 80% mortality in mice challenge exposed to serovars 9, 10, 18, or 19. All vaccinated mice died after challenge exposure with strain 2553 (serovar 20). Non-vaccinated control mice died after challenge exposure to all strains. Of 2 vaccinated swine challenge exposed to strain 2553, 1 developed a local urticarial lesion at the site of intradermal exposure. Vaccinated swine challenge exposed to serovars 1a, 1b, 2, 4, 5, 6, 7, 8, 9, 10, 11, 12, 15, 16, 18, 19, 21, or type N did not have clinical signs of acute erysipelas. Nonvaccinated control swine developed acute generalized erysipelas or localized urticarial lesions at the site of intradermal exposure.     

Acid Dissolution of Olivines, Feldspars and Dunite

We have treated feldspars (orthoclase, albite, anorthite), JF-1 (a mixture of orthoclase and albite), olivines (fayalite, forsterite) and JP-1 (dunite: an olivine-rich rock) with HNO₃ solution at pH 2 for 10 – 1200 min. The resultant changes in surface composition were assessed by X-ray photoelectron spectroscopy (XPS). The XPS data for fayalite, notably shifts in the Si 2s and O 1s binding energies, indicate preferential dissolution of Fe and formation of a Si-rich surface layer composed of amorphous silica. A Si-rich layer also forms on the surface of the other minerals as the result of acid treatment but the changes in binding energies are relatively small. Forsterite and anorthite dissolved almost congruently in acid solutions, and the Si-rich surface layer is poorly developed. Unlike forsterite, JP-1 shows preferential leaching of Mg relative to Si. Although forsterite is the major constituent of JP-1, this rock also contains some talc and orthopyroxene. These minor mineral constituents appear to influence the behavior of JP-1 in acid solutions. On the other hand, the dissolution and resultant surface alteration of JF-1 were comparable to those of its constituent minerals. The extent of Si-rich surface layer formation followed the order of albite = orthoclase > anorthite for the feldspars, and fayalite > forsterite for the olivines.     

Effects of feeding conditions and size differences on aggressive behaviour and cannibalism in the Pacific bluefin tuna Thunnus orientalis (Temminck and Schlegel) larvae

We examined the effects of feeding conditions and size differences on the aggressive behaviour and cannibalism in Pacific bluefin tuna (PBT) Thunnus orientalis larvae. In a 24 h experiment, restricted feeding alone was found to remarkably increase the frequency of aggressive behaviour, which was further elevated by differences in fish size. In a 4‐day rearing experiment, while aggressive behaviour was increased by restricted feeding alone, the frequency of cannibalism did not change significantly. Although the frequency of aggressive behaviour did not increase with difference in size factor, small fish in this group gradually tended to die over 4‐day period. In the restricted feeding and size difference group, large fish were observed to bite the small fish, and almost all the small fish died on the day after the start of the experiment. These results suggest that the aggressive behaviour of PBT larvae is chiefly increased by the shortage of live food; however, deaths related to cannibalism mainly occurred in small larvae and rapidly increased with food restriction and differences in fish size.