Net depth response of a depth-controllable (towed) gillnet for fish sampling

SUMMARY: Flume-tank experiments were performed to examine the depth response of a new type of depth-controlled gillnet. Variations of net depth were investigated as the warp was paid out and wound up for different changes of warp length, main sinker weights, and winch speeds. In most experiments, when the warp finished paying out, the net continued to descend and then ascended slightly to an equilibrium depth (overshoot phenomenon). The overshoot distance was nearly constant when the warp was wound up and increased linearly with increasing winch speed when the warp was paid out. An increase in winch speed reduced net settling time, which converged on a constant value for both paying out and winding up.     

Powdery Mildew of Prairie Gentian: Characteristics,Molecular Phylogeny and Pathogenicity

In March 1999, we found prairie gentian (Eustoma grandiflorum) infected with powdery mildew in a greenhouse in Oita Prefecture, Japan. Morphological observation revealed that the causal fungus belongs to the mitosporic genus Oidium subgenus Pseudoidium [teleomorph: Erysiphe sensu Braun and Takamatsu (2000)]. Precise taxonomic position of the fungus, however, is uncertain due to lack of the perfect stage. We determined the nucleotide sequence of the rDNA ITS region of the fungus. Comparison of the sequence with those obtained from DNA databases of this fungal group revealed that the sequence is identical to those of powdery mildews from garden four-o'clock (Mirabilis jalapa) and broad bean (Vicia faba). Inoculation of an isolate from garden four-o'clock caused mildew on prairie gentian and broad bean, suggesting that the prairie gentian mildew originates from garden four-o'clock or broad bean. Molecular phylogenetic analysis indicated a close relationship of this fungus to Erysiphe baeumleri on Vicia spp. and E. trifolii on Trifolium pratense. From these results, we propose that prairie gentian mildew diverged from a Fabaceae-parasitic ancestor. Received 14 March 2002/ Accepted in revised form 28 May 2002     

Simultaneous detection of multiple mycotoxins in broiler feeds using a liquid chromatography tandem-mass spectrometry

Mycotoxins are secondary fungal metabolites that are typically present in grain and feed ingredients used for animal feeds. An analytical method using LC-ESI-MS/MS was developed to quantify nine mycotoxins, consisting of aflatoxin B₁ (AFB₁), AFB₂, AFG₁, AFG₂, T-2 toxin, deoxynivalenol (DON), nivalenol (NIV), zearalenone (ZEA) and ochratoxin A (OTA) in broiler feeds. In total, 100 samples of broiler feeds were collected from poultry farms in Central Thailand. The survey found that AFB₁ and ZEA were the most prevalent mycotoxins in the feed samples at percentages of 93% and 63%, respectively. The limit of detections (LODs) of investigated mycotoxins was 0.20–0.78 ng/g. AFB₂, DON, AFG₁, NIV and T-2 toxin were also detectable at low contamination levels with percentages of 20%, 9%, 7%, 5% and 1%, respectively, whereas OTA and AFG₂ were not detected in any of the feed samples. These results suggest that there is a very low level of risk of the exposure to mycotoxins in feeds obtained from broiler farms in Central Thailand.     

Involvement of microaerophilic iron-oxidizing bacteria in the iron-oxidizing process at the surface layer of flooded paddy field soil

Journal of Soils and Sediments - To reveal whether microaerophilic Fe(II)-oxidizing bacteria (FeOB) participate in the Fe(II) oxidation at the oxic-anoxic interface in flooded paddy field soil,...     

Growth and morphologic response of rumen methanogenic archaea and bacteria to cashew nut shell liquid and its alkylphenol components

The growth and morphology of rumen methanogenic archaea (15 strains of 10 species in 5 genera, including 7 strains newly isolated in the present study) and bacteria (14 species in 12 genera) were investigated using unsupplemented in vitro pure cultures and cultures supplemented with cashew nut shell liquid (CNSL) and its phenolic compound components, anti-methanogenic agents for ruminant animals. Growth of most of the methanogens tested was inhibited by CNSL and alkylphenols at different concentrations ranging from 1.56 to 12.5 μg/ml. Of the alkylphenols tested, anacardic acid exhibited the most potent growth inhibition. Three gram-negative bacterial species involved in propionate production were resistant to CNSL and alkylphenols (>50 μg/ml). All the methanogens and bacteria that were sensitive to CNSL and alkylphenols exhibited altered morphology; disruption of the cell surface was notable, possibly due to surfactant activity of the tested materials. Cells division was inhibited in some organisms, with cell elongation and unclear septum formation observed. These results indicate that CNSL and alkylphenols, particularly anacardic acid, inhibit both rumen bacteria and methanogens in a selective manner, which could help mitigate rumen methane generation.     

Effects of extracerebral dopamine on salsolinol‐ or thyrotropin‐releasing hormone‐induced prolactin (PRL) secretion in goats

The aim of the present study was to clarify the effect of extracerebral dopamine (DA) on salsolinol (SAL)‐induced prolactin (PRL) secretion in goats. An intravenous injection of SAL or thyrotropin‐releasing hormone (TRH) was given to female goats before and after treatment with an extracerebral DA receptor antagonist, domperidone (DOM), and the PRL‐releasing response to SAL was compared with that to TRH. DOM alone increased plasma PRL concentrations and the PRL‐releasing response to DOM alone was greater than that to either SAL alone or TRH alone. The PRL‐releasing response to DOM plus SAL was similar to that to DOM alone, and no additive effect of DOM and SAL on the secretion of PRL was observed. In contrast, the PRL‐releasing response to DOM plus TRH was greater than that to either TRH alone or DOM alone and DOM synergistically increased TRH‐induced PRL secretion. The present results demonstrate that the mechanism involved in PRL secretion by SAL differs from that by TRH, and suggest that the extracerebral DA might be associated in part with the modulation of SAL‐induced PRL secretion in goats.     

Enhancement of antigen-specific immunoglobulin G production in mice by co-administration of L-cystine and L-theanine

Supplementation with both cystine and glutamic acid increases the synthesis of glutathione (GSH), which has a marked effect on immune cell function, as compared with supplementation with either amino acid alone in human macrophages in vitro. As dietary glutamic acid is metabolized during intestinal transport, oral administration of L-theanine (gamma-glutamylethylamide), which is metabolized to glutamic acid mainly in the liver, may act as a glutamic acid donor in vivo. The present study was performed to investigate the effects of oral administration of L-cystine and/or L-theanine on GSH levels and immune responses. Co-administration of L-cystine (200 mg/kg) and L-theanine (80 mg/kg) for 11 days before immunization significantly increased the levels of total GSH in the liver 6 hr after immunization as compared with the levels in control mice. To examine the effects of administration of L-cystine and/or L-theanine on the balance of T helper (Th) 1/Th2 cell responses, the serum ratios of the Th1 cytokine, interferon (IFN)-gamma, and the Th2 cytokine, interleukin IL-10, were investigated. At 24 hr after immunization, co-administration significantly increased the IL-10/IFN-gamma ratio compared with the ratios of the control and single-administration mice. Furthermore, co-administration before primary immunization significantly enhanced serum antigen-specific IgG levels. Taken together, these findings suggest that co-administration of L-cystine and L-theanine enhances antigen-specific IgG production partly through augmentation of GSH levels and Th2-mediated responses.     

Involvement of granulin in estrogen-induced neurogenesis in the adult rat hippocampus

Recent studies have demonstrated the presence of neurogenesis in the adult mammalian hippocampus, and it has been suggested that estrogen and various growth factors influence the processes of adult neurogenesis. The present study assessed cell proliferation in the dentate gyrus and the mRNA expression levels of granulin, insulin-like growth factor-I (IGF-I), and brain-derived neurotrophic factor (BDNF) in the hippocampus 4 h after treatment with estradiol benzoate (EB) in 3- and 12-month old ovariectomized rats. At 3 months of age, mRNA expression of granulin precursor and cell proliferation were increased by EB treatment, although the mRNA expressions of IGF-I and BDNF remained unchanged. At 12 months of age, however, neither mRNA expression of the three genes nor cell proliferation in the dentate gyrus were affected by EB treatment. In addition, 17beta-estradiol enhanced the proliferation of neural progenitor cells derived from hippocampal tissue of 3-month-old female rats in vitro; this was inhibited by neutralization of granulin with specific antibody. These results suggest that estrogen induces granulin gene expression in the hippocampus and that the product of this gene is involved in the mitogenic effects of estrogen in the dentate gyrus, although the responses to estrogen decline with age.     

Phytogeny and Cross-infectivity of Powdery Mildew Isolates (Podosphaera fuliginea s. lat.) on Cosmos and Cucumber

To clarify the relationship between the phylogeny and infectivity of isolates of Podosphaera fuliginea s. lat. (= Sphaerotheca fuliginea s. lat.) from cosmos and cucumber, more than 50 powdery mildew isolates from these two plants were subjected to nucleotide sequencing or PCR-RFLP analysis of the rDNA internal transcribed spacer (ITS) region and cross-inoculation tests. The isolates from both cosmos and cucumber are genetically monotypic, and there are six nucleotide substitutions in the rDNA ITS region between isolates from cosmos and cucumber. Cross-inoculation tests of these isolates revealed that isolates from cosmos are not pathogenic on cucumber. Although isolates from cucumber produced conidia on leaves of cosmos in the laboratory, the conidial density was much lower than that from isolates from cosmos. This result, as well as the fact that the cucumber strain was not isolated from cosmos in fields, suggests that isolates from cucumber do not infect cosmos in the field. Therefore, powdery mildews on cosmos and cucumber can be regarded to have become specialized for their hosts both genetically and pathogenically. The present study reconfirms the close relationship between phylogeny and infectivity of powdery mildew fungi. Host specialization may be a trigger that causes genetic divergence of powdery mildew fungi. Received 28 June 2000/ Accepted in revised form 4 September 2000