Method for underwater measurement of the auditory brainstem response of fish

ABSTRACT:   The auditory brainstem response (ABR) of fishes is commonly measured by bringing the heads of the fishes out of the water in a small tank. However, this method is inapplicable to experiments for large fishes that are economically important in large spaces such as the sea or in a large tank. This paper describes a method of recording, the ABR for fishes in water, without exposing the fish heads to air, by using a waterproof, insulated electrode. To evaluate the effectiveness of this method, the goldfish Carassius auratus was investigated, and the ABR waveform and auditory thresholds measured in water were compared with those measured on the surface. Both ABR waveforms and auditory thresholds showed similar trends between the two methods. The underwater ABR method is useful to measure the auditory thresholds of larger fish in natural or on-site environments such as the sea, net enclosures and large aquaria in which precise positioning of the fish is not possible. However, more improvement is needed to apply this method to large fishes.     

Changes in mRNA of immune factors expressed by milk somatic cells of Holstein cows with hypocalcemia after calving

Changes in immune factors expressed by milk somatic cells from Holstein cows with hypocalcemia after calving were investigated in this study. Fourteen multiparous Holstein cows after their 3rd or 4th calving in one farm were used. The cows were divided into 2 groups: 7 cows needing treatment due to onset of hypocalcemia (hypocalcemia group; age = 5.53 ± 0.27 years, parity = 3.14 ± 0.14) and 7 cows without health problems (control group; age = 5.88 ± 0.31 years, parity = 3.57 ± 0.26). Milk samples were collected aseptically using a cannula and mRNA of immune factors expressed by milk somatic cells were analyzed. Milk samples (50 mL) were collected from the right rear mammary gland of cows before milking at day 1 and weeks 1, 2, 4, and 8 after calving. All milk samples showed a negative reaction to the California Mastitis Test. Levels of relative interleukin (IL)-6 and cathelicidin in the hypocalcemia group were lower than those in the control group in weeks 1 to 8. A significant difference in relative IL-6 levels was found in week 4 (P < 0.05). These results suggest that levels of IL-6 expressed by milk somatic cells may be affected by hypocalcemia in dairy cows.     

Molecular detection of filarial nematode parasites in Japanese black bears (Ursus thibetanus japonicus) from Iwate Prefecture, Japan

This study aimed to detect filarial parasites in blood samples of Japanese black bears (Ursus thibetanus japonicus) collected from Iwate Prefecture, Japan. Positive amplicons were obtained from 26 out of 30 samples by nested PCR targeting 18S ribosomal RNA gene and first internal transcribed spacer regions. DNA sequences of Mansonella sp. close to M. ozzardi and Dirofilaria sp. were detected for eight and 11 positive amplicons, respectively. Co-infection was detected for the remaining seven amplicons. Dirofilaria sp. was identified as D. ursi by further genetic analysis of 5S ribosomal RNA gene sequence. The results of this study will contribute to further investigations of Japanese black bears for monitoring their risk as a reservoir of possible zoonotic filarial parasites.     

Formation of a one-dimensional array of oxygen in a microporous metal-organic solid

We report the direct observation of dioxygen molecules physisorbed in the nanochannels of a microporous copper coordination polymer by the MEM (maximum entropy method)/Rietveld method, using in situ high-resolution synchrotron x-ray powder diffraction measurements. The obtained MEM electron density revealed that van der Waals dimers of physisorbed O2 locate in the middle of nanochannels and form a one-dimensional ladder structure aligned to the host channel structure. The observed O-O stretching Raman band and magnetic susceptibilities are characteristic of the confined O2 molecules in one-dimensional nanochannels of CPL-1 (coordination polymer 1 with pillared layer structure).     

Epidemic progress of beet necrotic yellow vein virus: Evidence from an investigation in Japan spanning half a century

Beet necrotic yellow vein virus (BNYVV) is the causal agent of rhizomania, the most serious sugar beet disease worldwide. Since the first finding in Japan in 1969, BNYVV became widespread throughout Hokkaido in a few decades and led to the introduction of Rz1-resistant sugar beet cultivars in the 1990s. Here, we report the historical progress of the BNYVV epidemic in Hokkaido from 1969 to 2019. Previous analysis on samples from 1991 showed that BNYVV isolates were classified into three strains (named O, D, and T) based on the RNA3-encoded p25 gene. The O-type viruses were widely detected in Hokkaido, while the D- and T-type viruses were detected in limited areas. The RNA5, encoding the p26 gene, was initially contained in some D- and O-type isolates but not in any T-type isolates. Interestingly, recent sample analysis revealed that RNA5-containing T-type viruses, seemingly more virulent than the other two strains, were widely detected in Hokkaido. Additionally, a small group of virus isolates harbouring a new p25 gene (named C) was found in limited areas. These results suggest that the T-type viruses, which accompanied RNA5, have been preferentially spread from a limited area to other districts over the last few decades and that this spread might be strongly associated with the recent introduction of Rz1-resistant sugar beet cultivars. BNYVV-positive samples also contained mainly beet soil-borne virus and traces of beet virus Q, both of which are the first to be recorded in Japan.     

Neuronal pathway from the liver modulates energy expenditure and systemic insulin sensitivity

Coordinated control of energy metabolism and glucose homeostasis requires communication between organs and tissues. We identified a neuronal pathway that participates in the cross talk between the liver and adipose tissue. By studying a mouse model, we showed that adenovirus-mediated expression of peroxisome proliferator-activated receptor (PPAR)-g2 in the liver induces acute hepatic steatosis while markedly decreasing peripheral adiposity. These changes were accompanied by increased energy expenditure and improved systemic insulin sensitivity. Hepatic vagotomy and selective afferent blockage of the hepatic vagus revealed that the effects on peripheral tissues involve the afferent vagal nerve. Furthermore, an antidiabetic thiazolidinedione, a PPARg agonist, enhanced this pathway. This neuronal pathway from the liver may function to protect against metabolic perturbation induced by excessive energy storage.     

Effect of thinning and shade removal on green stem disorder in soybean

Green stem disorder (GSD) in soybean (Glycine max (L.) Merrill) retains green stems and leaves as the pods mature, thereby reducing the harvest efficiency and impairing seed quality. In order to elucidate the causes of GSD, the factors that promote GSD need to be identified. In our experiments, we adjusted plant density at the developmental growth stage R1 (the beginning of flowering) or at R5 (the beginning of seed filling), from dense (22.2 plants m^–2) to sparse (5.56 plants m^–2) by thinning. We found that GSD occurrence was increased when plant density was changed, compared to the treatments that were maintained under either dense or sparse conditions. GSD was promoted more strongly when thinning was conducted at R5 than at R1 stage. Shading equipment surrounding plants, except for their upper-most leaves, was implemented to determine the association of shading and GSD. The results of the shade experiment revealed that GSD occurrence generally increased in treatments subjected to shade removal, compared to those that were shaded until R8 stage (full maturity) or never shaded since the time of sowing. GSD was strongly promoted by shade removal at R5 than at R1 stage. The shading results coincide with the results of the plant density experiment, indicating that an increase in light availability enhances source activity relative to sink at R5 stage, thereby promoting GSD occurrence in soybean. Thinning is expected to be used as an easy experimental method to create GSD for research purpose.     

Natural variation in photoperiodic flowering pathway and identification of photoperiod-insensitive accessions in wild wheat, <Emphasis Type="Italic">Aegilops tauschii</Emphasis>

The D-genome progenitor of hexaploid wheat, Aegilops tauschii Coss., has a wide natural species range in central Eurasia and possesses wide natural variation in heading and flowering time. Here, we report identification of two Ae. tauschii accessions insensitive to short day length. Similarly to a loss or reduced degree of vernalization requirement, the photoperiod-insensitive mutations were found only in the early flowering sublineage (TauL1b) of Ae. tauschii. Quantitative trait locus (QTL) analyses using two F₂ mapping populations showed that a QTL for heading time on the long arm of chromosome 5D was related to the early heading phenotype of the photoperiod-insensitive accessions under short-day conditions. In the photoperiod-insensitive accession, expression patterns of two flowering-related genes were altered under short-day conditions compared with the patterns in photoperiod-sensitive accessions. This study indicates that analysis of natural variations in the Ae. tauschii population is useful to find novel genetic loci controlling agronomically important traits.