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.     

Integrated pest management in western flower thrips: past,present and future

Western flower thrips (WFT) is one of the most economically important pest insects of many crops worldwide. Recent EU legislation has caused a dramatic shift in pest management strategies, pushing for tactics that are less reliable on chemicals. The development of alternative strategies is therefore an issue of increasing urgency. This paper reviews the main control tactics in integrated pest management (IPM) of WFT, with the focus on biological control and host plant resistance as areas of major progress. Knowledge gaps are identified and innovative approaches emphasised, highlighting the advances in ‘omics’ technologies. Successful programmes are most likely generated when preventive and therapeutic strategies with mutually beneficial, cost‐effective and environmentally sound foundations are incorporated. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

The in vitro efficacy of oxytetracycline against re‐isolated pathogenic Aeromonas hydrophila carrying the cytolytic enterotoxin gene through hybrid catfish,Clarias macrocephalus (Günther, 1864) × Clarias gariepinus (Burchell, 1822) in Thailand

Aeromonas hydrophila is a pathogen infecting farmed hybrid catfish, Clarias macrocephalus (Günther, 1864) × Clarias gariepinus (Burchell, 1822) which incurs substantial economic losses in Thailand. The study aimed at a genetic tracking of A. hydrophila infection and the in vitro assessment of the efficacy of antibiotics against its virulent strains. Five clinical strains from catfishes and Nile tilapia were employed. They were 3‐passage re‐isolated through healthy hybrid catfish and the cytolytic enterotoxin gene (AHCYTOEN) of individuals was traced. Each of the re‐isolates at a dose of ~6.67 × 10⁵ CFU/g was intraperitoneally injected into ~15 g‐healthy hybrid catfish and their pathogenicity were observed for 7 days. It was found that AHCYTOEN was carried over whereas typical signs of motile aeromonas septicaemia were found in the specimens. The bacterial strains of Nile tilapia origin did not induce mortality but those of catfish origins (80%–100% rate of mortality). The strains were susceptible to the tetracycline antibiotics, and oxytetracycline produced MIC₅₀ and MBC as low as 0.007–0.031 μg/ml and 1–8 μg/ml respectively. As oxytetracycline specifically inhibited pathogenic A. hydrophila in vitro, it is recommended that an appropriate dosage regimen of the drug should be established.     

Factors affecting methane production and mitigation in ruminants

Methane (CH₄) is the second most important greenhouse gas (GHG) and that emitted from enteric fermentation in livestock is the single largest source of emissions in Japan. Many factors influence ruminant CH₄ production, including level of intake, type and quality of feeds and environmental temperature. The objectives of this review are to identify the factors affecting CH₄ production in ruminants, to examine technologies for the mitigation of CH₄ emissions from ruminants, and to identify areas requiring further research. The following equation for CH₄ prediction was formulated using only dry matter intake (DMI) and has been adopted in Japan to estimate emissions from ruminant livestock for the National GHG Inventory Report: Y = −17.766 + 42.793X − 0.849X², where Y is CH₄ production (L/day) and X is DMI (kg/day). Technologies for the mitigation of CH₄ emissions from ruminants include increasing productivity by improving nutritional management, the manipulation of ruminal fermentation by changing feed composition, the addition of CH₄ inhibitors, and defaunation. Considering the importance of ruminant livestock, it is essential to establish economically feasible ways of reducing ruminant CH₄ production while improving productivity; it is therefore critical to conduct a full system analysis to select the best combination of approaches or new technologies to be applied under long-term field conditions.     

A direct time-resolved fluoroimmunoassay (TR-FIA) for measuring plasma estradiol-17beta concentrations in cattle

A direct Time-Resolved Fluoroimmunoassay (TR-FIA) system for measuring estradiol-17beta (E(2)) in bovine plasma was developed and evaluated. A 100 microl sample of bovine plasma was used for a TR-FIA without prior extraction and purification. The dose-response curves of reference standards ranged from 0.0625 to 10 pg/well. The minimum detectable concentration of this assay system was 0.625 pg/ml, and 19 pg/ml of E(2) caused a 50% reduction of maximum binding. The intra- and inter-assay coefficients of variation were 10.2 and 17.4%, respectively. The plasma E(2) concentrations measured by direct TR-FIA correlated closely with those measured after extraction (r=0.939). The results in the present study indicate that the TR-FIA reagent for E(2), designed for human research can also be utilized, with some modification, for direct assaying in bovine plasma. This assay type seems to fulfill the requirements for safety, sensitivity, specificity, reproducibility and practical convenience.     

Relationships between tropomyosin and myosin heavy chain isoforms in bovine skeletal muscle

The composition of tropomyosin (TPM) and myosin heavy chain (MyHC) isoforms was analyzed in 10 physiologically different bovine muscles ( masseter , diaphragm, tongue, semispinalis, pectoralis profundus , biceps femoris, psoas major , semimembranosus, longissimus thoracis and semitendinosus ) to clarify the relationships between TPM and MyHC isoforms in different muscle fiber types. The content of TPM1 and TPM3 was different in muscles according to their function in muscle contraction, although the content of TPM2 was constantly about 50% of the total TPM in all muscles. The content of TPM1 was higher in semimembranosus , longissimus thoracis and semitendinosus, while that of TPM3 was higher in masseter and diaphragm. The high positive correlation between MyHC-slow content and TPM3 content ( r  = 0.92) suggested a coexpression of TPM3 and MyHC-slow isoforms in a muscle fiber. MyHC-slow and TPM3 were expressed at the same level in masseter and diaphragm, whereas there was more TPM3 than MyHC-slow in tongue and semispinalis , so it appears that the excess TPM3 in tongue and semispinalis is expressed with other MyHC isoforms. MyHC-2a was the only fast type isoform expressed in tongue and semispinalis . Therefore, the excess TPM3 was composed of myofibrils with MyHC-2a. The results suggested that a fiber expressing MyHC-2a would be regulated delicately by changing the TPM isoform types.     

Denaturation mode of carp myofibrils when affected by temperature and salt concentration

ABSTRACT: Heating temperatures of 30–40°C and KCl concentrations of 0.1–0.5 M altered the denaturation mode of carp myofibrils. In 0.1 M KCl medium, heating temperature affected the denaturation of rod more significantly than of subfragment-1 (S-1), and a slow decrease in solubility at 30°C was accompanied by a slow denaturation of rod. KCl concentration at heating altered the denaturation mode differently at 30°C and 40°C. Increased KCl concentrations for heating reduced the rod denaturation rate at 40°C, but it was increased at 30°C. At concentrations above 0.3*Τ*M KCl, the denaturation rate for rod became identical to that for S-1 at both temperatures. Upon heating of chymotryptic digest of myofibrils, S-1 denaturation was similarly detected as in intact myofibrils, whereas practically no rod denaturation was detected. Thus, it was concluded that myosin structure connecting S-1 and rod has an important role in the denaturation process.     

Preparation of heavy meromyosin from the autolyzed squid mantle muscle homogenate

ABSTRACT:   Incubation of squid mantle muscle homogenate caused a selective cleavage of myosin into heavy meromyosin (HMM) and light meromyosin (LMM). HMM was isolated from the incubated homogenate by using ammonium sulfate fractionation. The purified HMM retained two types of light chain components. Its Mg²⁺-ATPase activity with or without F-actin showed a Ca-sensitivity. HMM was cleaved into subfragment-1 and subfragment-2 upon chymotryptic digestion with or without Ca²⁺, possessing different light chain composition. Two types of light chain component were kept intact when digested in the presence of Ca²⁺. Ca²⁺ stabilized HMM especially in a bound form to F-actin.