A low trophic position of Japanese eel larvae indicates feeding on marine snow

What eel larvae feed on in the surface layer of the ocean has remained mysterious. Gut contents and bulk nitrogen stable isotope studies suggested that these unusual larvae, called leptocephali, feed at a low level in the oceanic food web, whereas other types of evidence have suggested that small zooplankton are eaten. In this study, we determined the nitrogen isotopic composition of amino acids of both natural larvae and laboratory-reared larvae of the Japanese eel to estimate the trophic position (TP) of leptocephali. We observed a mean TP of 2.4 for natural leptocephali, which is consistent with feeding on particulate organic matter (POM) such as marine snow and discarded appendicularian houses containing bacteria, protozoans and other biological materials. The nitrogen isotope enrichment values of the reared larvae confirm that the primary food source of natural larvae is consistent only with POM. This shows that leptocephali feed on readily available particulate material originating from various sources closely linked to ocean primary production and that leptocephali are a previously unrecognized part of oceanic POM cycling.     

Nucleosides and Nucleotides. 192. Toward the Total Synthesis of Cyclic ADP-Carbocyclic-Ribose. Formation of the Intramolecular Pyrophosphate Linkage by a Conformation-Restriction Strategy in a Syn-form Using a Halogen Substitution at the 8-Position of the Adenine Ring

Abstract

The synthesis of cyclic ADP-carbocyclic-ribose (2), as a stable mimic for cyclic ADP-ribose, was investigated. Construction of the 18-membered backbone structure was successfully achieved by condensation of the two phosphate groups of 19, possibly due to restriction of the conformation of the substrate in a syn-form using an 8-chloro substituent at the adenine moiety. SN2 reactions between an optically active carbocyclic unit 8, which was constructed by a previously developed method, and 8-bromo-N ⁶-trichloroacetyl-2′,3′-O-isopropylideneadenosine 9c gave N-1-carbocyclic derivative, which was deprotected to give 5′,5′-diol derivatives 18. When 18 was treated with POCl₃ in PO(OEt)₃, the bromo group at the 8-position was replaced to give N-1-carbocyclic-8-chloroadenosine 5′,5′-diphosphate derivative 19 in 43% yield. Treatment of 19 with 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride gave the desired intramolecular condensation product 20 in 10% yield. This is the first chemical construction of the 18-membered backbone structure containing an intramolecular pyrophosphate linkage of a cADPR-related compound with an adenine base.     

Crystal structure of the C-terminal domain of Mu phage central spike and functions of bound calcium ion

Bacteriophage Mu, which has a contractile tail, is one of the most famous genus of Myoviridae. It has a wide host range and is thought to contribute to horizontal gene transfer. The Myoviridae infection process is initiated by adhesion to the host surface. The phage then penetrates the host cell membrane using its tail to inject its genetic material into the host. In this penetration process, Myoviridae phages are proposed to puncture the membrane of the host cell using a central spike located beneath its baseplate. The central spike of the Mu phage is thought to be composed of gene 45 product (gp45), which has a significant sequence homology with the central spike of P2 phage (gpV). We determined the crystal structure of shortened Mu gp45Δ1-91 (Arg92–Gln197) at 1.5 Å resolution and showed that Mu gp45 is a needlelike structure that punctures the membrane. The apex of Mu gp45 and that of P2 gpV contained iron, chloride, and calcium ions. Although the C-terminal domain of Mu gp45 was sufficient for binding to the E. coli membrane, a mutant D188A, in which the Asp amino acid residue that coordinates the calcium ion was replaced by Ala, did not exhibit a propensity to bind to the membrane. Therefore, we concluded that calcium ion played an important role in interaction with the host cell membrane.     

Induction of ornithine decarboxylase by sialagogues in a human parotid gland adenocarcinoma cell line.

Ornithine decarboxylase in a human parotid gland adenocarcinoma cell line was induced by both cholinergic (carbachol) and beta-adrenergic (isoproterenol) sialagogues. The enzyme protein level, measured with anti-peptide antiserum, as well as the enzyme activity, was found to be high in unstimulated cells and to increase approximately 2-fold on stimulation, while the mRNA level increased 3-4 fold, as revealed by Northern hybridization. The rise in activity was completely blocked by the simultaneous addition of antagonists or actinomycin D. These results suggest that receptor-mediated stimulation of ornithine decarboxylase activity by sialagogues involves alterations in the level of mRNA and that the proliferative responses of human parotid cells to these sialagogues resemble those of the murine parotid gland.     

Recessive and dominant genes controlling inducible sexual agglutinability in Saccharomyces cerevisiae

Summary We have characterized the two dominant genes, IND 1 and IND 2, responsible for inducible sexual agglutinability. The strains carrying these genes differ from the inducible strains carrying the recessive gene, saa 1 in the following points. The former strains produce agglutination substance at 22°, 28°, and 37° C only in response to sex pheromone of the opposite mating type, but the latter strains produce the substance constitutively without the pheromone at 22° C, only in response to the pheromone at 28° C, and do not produce the substance, even in the presence of the pheromone, at 37° C.We suggest that strains carrying one of the dominant, inducible genes are wild type and have a pheromone-controlled regulatory system of sexual agglutinability.     

Ionophores and weak bases inhibit phagolysosomal proteolysis in Paramecium

In a recent report we showed that ionophores and weak bases inhibit digestive vacuoles (DV) acidification primarily and lysosome-DV fusion secondarily but have no effect on lysosome-DV fusion when acidification is normal. In this study we attempted 1) to show that fluorescein isothiocyanate (FITC)-albumin taken up by phagocytosis could be used for a sensitive proteolytic assay, 2) to use this assay to determine the effect of ionophores and weak bases on proteolysis and 3) to learn how an inhibition of acidification and/or lysosome-DV fusion would affect proteolysis. When cells were pulsed with FITC-albumin and latex beads for 3 min and chased, the amount of albumin degraded increased linearly from 9 to 27 min, reaching a plateau by 30 min, and was inhibited by leupeptin and pepstatin A by 47 to 89%. These results showed that the degradation of FITC-albumin occurred in the phagolysosomes. When added before acidification had commenced, carbonyl cyanide p-trifluoro-methoxyphenyl hydrazone (FCCP), monensin and NH4Cl partially inhibited lysosome-DV fusion (25-50%) and strongly inhibited proteolysis by 64 to 79%. Added between acidification and lysosome-DV fusion, fusion was unaffected while proteolysis was reduced by 40 to 50%. Added after lysosome-DV fusion was completed, proteolysis was still reduced by the same amount. Chloroquine at 0.25 mM had no effect on proteolysis except when added before acidification, it inhibited fusion by 22% and proteolysis by 16%. These data, together with those published recently, showed that 1) ionophores and weak bases inhibited acidification first, lysosome-DV fusion second and proteolysis third, but they also inhibited proteolysis directly and independent of the prior steps and 2) the proteolysis inhibitory effects were additive.     

Osteopontin Deficiency Accelerates Spontaneous Colitis in Mice with Disrupted Gut Microbiota and Macrophage Phagocytic Activity

Background

Osteopontin (OPN) is a multifunctional protein expressed in a variety of tissues and cells. Recent studies revealed increased OPN expression in the inflamed intestinal tissues of patients with inflammatory bowel disease (IBD). The role of OPN in the pathophysiology of IBD, however, remains unclear.

Aims

To investigate the role of OPN in the development of intestinal inflammation using a murine model of IBD, interleukin-10 knock out (IL-10 KO) mice.

Methods

We compared the development of colitis between IL-10 KO and OPN/IL-10 double KO (DKO) mice. OPN expression in the colonic tissues of IL-10 KO mice was examined by fluorescence in situ hybridization (FISH) analysis. Enteric microbiota were compared between IL-10 KO and OPN/IL-10 DKO mice by terminal restriction fragment length polymorphism analysis. The effect of OPN on macrophage phagocytic function was evaluated by phagocytosis assay.

Results

OPN/IL-10 DKO mice had an accelerated onset of colitis compared to IL-10 KO mice. FISH analysis revealed enhanced OPN synthesis in the colonic epithelial cells of IL-10 KO mice. OPN/IL-10 DKO mice had a distinctly different enteric bacterial profile with a significantly lower abundance of Clostridium subcluster XIVa and a greater abundance of Clostridium cluster XVIII compared to IL-10 KO mice. Intracellular OPN deletion in macrophages impaired phagocytosis of fluorescence particle-conjugated Escherichia coli in vitro. Exogenous OPN enhanced phagocytosis by OPN-deleted macrophages when administered at doses of 1 to 100 ng/ml, but not 1000 ng/ml.

Conclusions

OPN deficiency accelerated the spontaneous development of colitis in mice with disrupted gut microbiota and macrophage phagocytic activity.