Spectral sensitivity of juvenile chub mackerel (<Emphasis Type="Italic">Scomber japonicus</Emphasis>) in visible and ultraviolet light

Although chub mackerel (Scomber japonicus) is widely distributed all over the world, the relevance of its visual sensitivity to its ecology is not yet fully understood. We investigated spectral sensitivity in juvenile chub mackerel in the range of ultraviolet (UV) to visible light (369–652 nm) by electroretinogram (ERG) using light-emitting diodes (LEDs). Sensitivity peaked at a wavelength of approximately 482 nm in dark-adapted fish and 525 nm in light-adapted fish. A secondary sensitivity peak in the UV range at approximately 382 nm was found in both dark- and light-adapted fish. The UV sensitivity of chub mackerel may be attributable to UV transmissibility of the optical media and to the presence of a beta-band of visible light-sensitive visual pigments, and not to an alpha-band of UV visual pigments. This UV sensitivity may be useful for feeding or communication with other fishes.     

ATP depletion inhibits retraction of chromatophores induced by GABA in cephalopod Todarodes pacificus

Color changes in cephalopods are generated by the expansion or retraction of chromatophores located under the dermis. The behavior of the chromatophores is regulated by neurotransmitters; l-glutamate (l-Glu) is an excitatory transmitter that causes the chromatophores to expand. To date, serotonin [5-hydroxytryptamine (5-HT)] is the only neurotransmitter known to stimulate retraction of chromatophores. We found that the chromatophores in the Japanese squid Todarodes pacificus were regulated by γ-aminobutyric acid (GABA), an inhibitory neurotransmitter, and that GABA caused expanded chromatophores to retract. We also found that adenosine 5′-triphosphate (ATP) concentrations in skin samples remained stable at their initial values for more than 24 h after the death of each squid; therefore, the chromatophores could respond to both l-Glu and GABA during that period. Furthermore, we attempted to reduce the levels of ATP by storing skin sample in sodium azide solution. The chromatophores in sodium azide-treated skin samples were induced to expand by l-Glu, but these expanded chromatophores could not be induced to retract by GABA. Based on these observations, we conclude that ATP is essential for retraction, but not expansion, of chromatophores.     

Novel method for improving the antioxidative properties of fish meat by direct injection of sodium l-ascorbate into the blood vessels of live fish

The color of the red muscle of pelagic fish is used as an indicator of freshness, and sustaining a bright red color is important for maintaining the commercial value of pelagic fish. Feeding fish with antioxidant compounds can delay metmyoglobin (metMb) formation, but the process requires long-term feeding. Live cultured Japanese horse mackerel Trachurus japonicus were used in this study. After anesthetization, 2 ml of blood was drawn from blood vessels, and a parenteral solution including an antioxidant compound was injected. Browning, metMb formation, and lipid oxidation of dark muscle during chilled storage were delayed by injecting sodium l-ascorbate as an antioxidant compound in the blood vessels of live fish.     

Cytokinin signaling and its inhibitor AHP6 regulate cell fate during vascular development

The cell lineages that form the transporting tissues (xylem and phloem) and the intervening pluripotent procambial tissue originate from stem cells near the root tip. We demonstrate that in Arabidopsis, cytokinin phytohormones negatively regulate protoxylem specification. AHP6, an inhibitory pseudophosphotransfer protein, counteracts cytokinin signaling, allowing protoxylem formation. Conversely, cytokinin signaling negatively regulates the spatial domain of AHP6 expression. Thus, by controlling the identity of cell lineages, the reciprocal interaction of cytokinin signaling and its spatially specific modulator regulates proliferation and differentiation of cell lineages during vascular development, demonstrating a previously unrecognized regulatory circuit underlying meristem organization.     

Immune response during the onset of coliform mastitis in dairy cows vaccinated with STARTVAC®

The immune response during the onset of coliform mastitis in vaccinated cows was investigated by measuring lactoferrin (LF), interleukin-8 ( IL-8), and interleukin-1β (IL-1β) concentrations and somatic cell counts in 28 milk samples at the onset of acute coliform mastitis (ACM) and 73 milk samples at the onset of peracute coliform mastitis (PCM). Vaccinated ACM, unvaccinated ACM, and vaccinated PCM showed significantly higher values for LF and IL-1β levels than unvaccinated PCM (p < .01). The IL-8 concentration was lower in vaccinated PCM than in unvaccinated PCM (p < .05). There was no significant difference in somatic cell counts for each parameter. There were no significant differences in the parameters between vaccinated and unvaccinated ACM cows, or vaccinated ACM and PCM cows. From the above results, it is suggested that mastitis vaccination improved the early immune response, particularly at the onset of PCM, and played a large role in host defense against the initial infection.     

Analysis of neutral glycosphingolipids from Trypanosoma brucei

Neutral glycosphingolipids (GSLs) were isolated from Trypanosoma brucei and analyzed by thin-layer chromatography (TLC), TLC/secondary ion mass spectrometry (TLC/SIMS), and liposome immune lysis assay (LILA). Three species of neutral GSLs, designated as N-1, -2, and -3 were separated on TLC. N-1 GSL migrated very close to glucosylceramide (GlcCer) and N-2 GSL showed the same mobility as lactosylceramide (LacCer). On the other hand, the mobility of N-3 GSL on the TLC plate was slower than globotetraosylceramide (Gb4). In order to characterize the molecular species of neutral GSLs from T. brucei, N-1, -2 and -3 GSLs were analyzed by TLC/SIMS. The TLC/SIMS analysis of N-1 of the parasites revealed a series of (M–H)⁻ ions from m/z 698 to 825 representing the molecular mass range of ceramide monohexoside (CMH) (GlcCer or galactosylceramide). On the other hand, the TLC/SIMS spectra of N-2 GSL revealed a series of (M–H)⁻ ions from m/z 944–987 indicating the molecular mass range of LacCer. In the TLC/SIMS analysis of N-3 GSL, however, the characteristic molecular ions that can elucidate the structure of N-3 GSL were not obtained. In order to confirm the results obtained from TLC/SIMS, N-1, -2, and -3, GSLs were tested by LILA with specific antibodies against GlcCer, LacCer, and Gb4, respectively. N-1 GSL had reactivity to anti-GlcCer antibody and N-2 GSL reacted with the antibody against LacCer. However, N-3 GSL was not recognized by anti-Gb4 antibody. Using anti-GlcCer and anti-LacCer antibodies, furthermore, we studied the expression of GlcCer and LacCer in T. brucei parasites. Both GlcCer and LacCer were detected on the cell surface of T. brucei.     

Detection of fungi producing infection-inhibiting metabolites against <Emphasis Type="Italic">Alternaria alternata</Emphasis> Japanese pear pathotype from fungi inhabiting internal tissues of Japanese pear shoots

Fungi inhabiting Japanese pear were isolated from internal tissues of cv. Nijisseiki, and culture filtrates (CFs) of 100 isolates were evaluated for their inhibitory activity against infection by Alternaria alternata Japanese pear pathotype. CFs of 11 isolates inhibited lesion formation on the pear by the pathogen. Among these isolates, CFs of five isolates inhibited spore germination. CFs of the six other isolates inhibited appressorial formation, infection hypha formation, AK-toxin production, or a combination of these actions. Analysis of sequence homology in the rDNA ITS1 regions of these isolates showed that most isolates had high homology with some fungal endophytes.