Absorption, translocation and metabolism of -DOPA in barnyardgrass and lettuce: their involvement in species-selective phytotoxic action

-DOPA (-3,4-Dihydroxyphenylalanine) is one of the most highly active allelochemicals. -DOPA is exuded from the roots of velvetbean [Mucuna pruriens (L.) DC. var. utilis] into soil, and causes growth inhibition of other species. In order to highly clarify the phytotoxic mechanism of -DOPA, its effect on 32 species was surveyed, and absorption, translocation and metabolism in a tolerant species, barnyardgrass (Echinochloa crus-galli L.), and susceptible species, lettuce (Lactuca sativa L. cv. Great lakes 366), were examined at the germination stage. The species tested showed distinctly different responses to -DOPA, with root elongation being more suppressed than that of shoots. Barnyardgrass was 77-fold more tolerant than lettuce based on the GR₅₀ values determined 5 days after treatment. Absorption of -DOPA in barnyardgrass and lettuce increased continuously during a 5 day exposure period, however,barnyardgrass absorbed a larger amount of -DOPA than lettuce. The translocation of radioactivity derived from ¹⁴C--DOPA to shoots was greater in lettuce than in barnyardgrass 3 and 5 days after treatment. Although the -DOPA absorbed was metabolized in the roots of both species, the percentage of radioactive ¹⁴C--DOPA increased in lettuce continuously but decreased in barnyardgrass over 5 days. In lettuce roots, a continuous increase of -DOPA but not other metabolites was observed. However, the concentration of -DOPA was higher in barnyardgrass roots compared with lettuce roots throughout the exposure period. These results suggest that -DOPA itself is the active form, and the species-selective phytotoxicity of -DOPA is at least partly due to metabolism and not due to absorption or translocation.     

Identification of aquarium-raised muraenid leptocephali, <Emphasis Type="Italic">Gymnothorax minor</Emphasis>

Leptocephalus larvae of Gymnothorax minor collected from eastern Kyushu were identified by observation of metamorphosis procedure. The leptocephali were characterized by 135–142 total myomeres (31–42 predorsal, 87–95 preanal) and the last vertical blood vessel between myomeres 77–85. Diagnostic pigments were apparent on the head, the somatic (below intestine) and splanchnic (along pronephric ducts) regions, before the dorsal fin origin, ventrally on the spinal cord, and along the dorsal and anal fin bases. Such pigments were suitable for species identification of metamorphosing larvae because of their persistence during that process.     

β‐carotene suppresses Porphyromonas gingivalis lipopolysaccharide‐mediated cytokine production in THP‐1 monocytes cultured with high glucose condition

Periodontitis is associated with development of diabetes mellitus. Although lipopolysaccharide (LPS) of Porphyromonas gingivalis (Pg), a major pathogen of periodontitis, may lead the progression of diabetes complications, the precise mechanisms are unclear. We, therefore, investigated the effects of β‐carotene on production of Pg LPS‐induced inflammatory cytokines in human monocytes cultured high glucose (HG) condition. THP‐1 cells were cultured under 5.5 mM or 25 mM glucose conditions, and cells were stimulated with Pg LPS. To investigate the productivity of TNF‐α, IL‐6, and MCP‐1, cell supernatants were collected for ELISA. To examine the effects of NF‐kB signals on cytokine production, Bay11‐7082 was used. HG enhanced Pg LPS‐induced production of TNF‐α, IL‐6, and MCP‐1 via NF‐kB signals in THP‐1. β‐carotene suppressed the enhancement of the Pg LPS‐induced cytokine production in THP‐1 via NF‐κB inactivation. Our results suggest that β‐carotene might be a potential anti‐inflammatory nutrient for circulating Pg LPS‐mediated cytokine production in diabetic patients with periodontitis.     

Competition for Space Is Controlled by Apoptosis-Induced Change of Local Epithelial Topology

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Distinct roles for U‐type proteins in iron–sulfur cluster biosynthesis revealed by genetic analysis of the Bacillus subtilis sufCDSUB operon

The biosynthesis of iron–sulfur (Fe–S) clusters in Bacillus subtilis is mediated by the SUF‐like system composed of the sufCDSUB gene products. This system is unique in that it is a chimeric machinery comprising homologues of E. coli SUF components (SufS, SufB, SufC and SufD) and an ISC component (IscU). B. subtilis SufS cysteine desulfurase transfers persulfide sulfur to SufU (the IscU homologue); however, it has remained controversial whether SufU serves as a scaffold for Fe–S cluster assembly, like IscU, or acts as a sulfur shuttle protein, like E. coli SufE. Here we report that reengineering of the isoprenoid biosynthetic pathway in B. subtilis can offset the indispensability of the sufCDSUB operon, allowing the resultant Δsuf mutants to grow without detectable Fe–S proteins. Heterologous bidirectional complementation studies using B. subtilis and E. coli mutants showed that B. subtilis SufSU is interchangeable with E. coli SufSE but not with IscSU. In addition, functional similarity in SufB, SufC and SufD was observed between B. subtilis and E. coli. Our findings thus indicate that B. subtilis SufU is the protein that transfers sulfur from SufS to SufB, and that the SufBCD complex is the site of Fe–S cluster assembly.     

Location,size and age at onset of metamorphosis in the Japanese eel Anguilla japonica

This study clarifies the location, size and age at the onset of metamorphosis in Japanese eels Anguilla japonica through oceanic surveys, rearing experiments and analyses of the morphology and otoliths of leptocephali and glass eels. Twenty‐eight metamorphosing leptocephali were collected in the mesoscale eddy region to the east of Taiwan during research expeditions in 2004. Rearing experiments showed that the total length (L_T) of leptocephali decreased by an average of 12·5% during metamorphosis and 13·9% during the 2–12 h after death. Thus, the mean back‐calculated L_T at the onset of metamorphosis for 630 glass eels from Taiwan and Japan was estimated at 67·8 ± 2·7 mm (mean ± S.D.). The estimated mean ante‐mortem size of the fully grown pre‐metamorphic leptocephali collected in 2004 was 64·6 ± 3·4 mm, which was consistent with the L_T estimate for glass eels. Otolith analysis showed that the mean age at the onset of metamorphosis was 137 ± 15 days and indicated that Japanese eels may have a recruitment route through the mesoscale eddies to the east of Taiwan in addition to the direct transfer route from the North Equatorial Current to the Kuroshio Current.     

Distribution pattern of Polar cod (<Emphasis Type="Italic">Boreogadus saida</Emphasis>) larvae and larval fish assemblages in relation to oceanographic parameters in the northern Bering Sea and Chukchi Sea

Polar cod, Boreogadus saida, is a key species in the Arctic Ocean ecosystem. We examined the distribution pattern of B. saida and other fish larvae in relation to oceanographic parameters, including sea surface temperature and salinity (SST and SSS), the mode of temperature and salinity within the water column (F _temp and F _sal), and the temporal duration between the date of sea ice retreat and the date of field surveys (dSRT) in the northern Bering Sea and Chukchi Sea during the summers of 2008 and 2013. Sampling was conducted onboard the T/S Oshoro-Maru using a bongo net for 2 years. At sampling stations, the temperature and salinity were measured using conductivity-temperature-depth profiler casts. We calculated dSRT from satellite derived polar gridded sea ice concentration data. A total of 1186 individuals comprising 7 families and 16 species were collected, with B. saida (35 %) and Ammodytes hexapterus (27 %) dominating the catch in number. Based on the species composition (cluster analysis), the sampling stations were divided into four groups. Pleuronectidae dominated group A, which was characterized by relatively high temperature (SST and F _temp), while B. saida dominated group B, characterized by low temperatures. A. hexapterus dominated group C and D, which had similar temperatures and salinities, but group C had a shorter dSRT than group D. The latter was also differentiated by the presence of Lumpenus sp. B. saida, which were most abundant in regions where temperatures ranged from ?2 to 0.5 °C. These results, the geographical variation of group B sampling stations, suggest there are two separate spawning areas characterized by similar fish communities and related to consistently cold bottom temperatures. Moreover, stations with a higher abundance of smaller sized larval B. saida were characterized by a short dSRT, whereas stations with a lower abundance and a larger size were characterized by a long dSRT.     

Theoretical calculation of triazolam hydroxylation and endogenous steroid inhibition in the active site of CYP3A4

CYP3A4 has unusual kinetic characteristics because it has a large active site. CYP3A4 produced more 4-hydroxytriazolam than alpha-hydroxytriazolam at concentrations of more than 60 muM triazolam, and different steroids had different inhibitory effects on the system. To clarify these interesting observations, the interactions between substrate and substrate/steroid were investigated by theoretical calculations. When two triazolam molecules were docked into the active site, the distance between the O-atom and the 4-hydroxylated site was less than the distance to the alpha-hydroxylated site because of interaction between the two triazolam molecules. Estradiol inhibited both alpha- and 4-hydroxytriazolam formation by 50%. Dehydroepiandrosterone (DHEA) inhibited alpha-hydroxylation more than 4-hydroxytriazolam formation, whereas aldosterone had no effect. When one triazolam molecule and one steroid molecule were simultaneously docked, estradiol increased the distance between the O-atom and the two hydroxylated sites, DHEA only increased the distance between the O-atom and alpha-hydroxylated site, and aldosterone did not change the distances. The relevant angles of Fe-O-C in the hydroxylated site of triazolam also widened, together with increased distance. These findings indicate that formation of a substrate and substrate/effector complex in the active site may be a factor for determining the enzyme kinetic parameters of CYP3A4.     

Difference in nucleocytoplasmic shuttling sequences of rat and human constitutive active/androstane receptor

Fluorescence recovery after photobleaching (FRAP) in spontaneous multinuclear cells shows that both rat and human constitutive active/androstane receptors (CARs) are shuttling proteins with both nuclear localization signals (NLSs) and nuclear export signals (NESs). We previously identified two NLSs in rat CAR: NLS1 in the hinge region (residues 100-108) and NLS2 in the ligand-binding domain (residues 111-320). In the present study, we compared the intracellular localization signals between rat and human CARs. There was a marked difference in their intracellular localization in COS-7 cells because, unlike rat CAR, human CAR does not contain NLS1 due to an amino acid change at position 106. A CRM1-dependent leucine-rich NES, which is sensitive to an inhibitory effect of leptomycin B, was found in the cytoplasmic retention region previously identified within the ligand-binding domain of rat CAR (residues 220-258). We found that human CAR instead has a NES in the ligand-binding domain between residues 170 and 220. Also, we detected CRM1-independent C-terminal NESs between residues 317-358 of rat and human CARs. Removal of NLS1 by N-terminal truncation and mutation of xenochemical response signal caused rat CAR to localize in the cytoplasm of COS-7 cells, which we suspect is due to the masking of NLS2.     

Maintenance of Bone Homeostasis by DLL1‐Mediated Notch Signaling

Adult bone mass is maintained through a balance of the activities of osteoblasts and osteoclasts. Although Notch signaling has been shown to maintain bone homeostasis by controlling the commitment, differentiation, and function of cells in both the osteoblast and osteoclast lineages, the precise mechanisms by which Notch performs such diverse and complex roles in bone physiology remain unclear. By using a transgenic approach that modified the expression of delta‐like 1 (DLL1) or Jagged1 (JAG1) in an osteoblast‐specific manner, we investigated the ligand‐specific effects of Notch signaling in bone homeostasis. This study demonstrated for the first time that the proper regulation of DLL1 expression, but not JAG1 expression, in osteoblasts is essential for the maintenance of bone remodeling. DLL1‐induced Notch signaling was responsible for the expansion of the bone‐forming cell pool by promoting the proliferation of committed but immature osteoblasts. However, DLL1‐Notch signaling inhibited further differentiation of the expanded osteoblasts to become fully matured functional osteoblasts, thereby substantially decreasing bone formation. Osteoblast‐specific expression of DLL1 did not alter the intrinsic differentiation ability of cells of the osteoclast lineage. However, maturational arrest of osteoblasts caused by the DLL1 transgene impaired the maturation and function of osteoclasts due to a failed osteoblast‐osteoclast coupling, resulting in severe suppression of bone metabolic turnover. Taken together, DLL1‐mediated Notch signaling is critical for proper bone remodeling as it regulates the differentiation and function of both osteoblasts and osteoclasts. Our study elucidates the importance of ligand‐specific activation of Notch signaling in the maintenance of bone homeostasis. J. Cell. Physiol. 232: 2569–2580, 2017. © 2016 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals Inc.