Inhibitory effect of chicken gonadotropin-releasing hormone II on food intake in the goldfish, Carassius auratus

Gonadotropin-releasing hormone (GnRH) is an evolutionarily conserved neuropeptide with 10 amino acid residues, which possesses some structural variants. A molecular form known as chicken GnRH II ([His⁵ Trp⁷ Tyr⁸] GnRH, cGnRH II) is widely distributed in vertebrates, and has recently been implicated in the regulation of sexual behavior and food intake in an insectivore, the musk shrew. However, the influence of cGnRH II on feeding behavior has not yet been studied in model animals such as rodents and teleost fish. In this study, therefore, we investigated the role of cGnRH II in the regulation of feeding behavior in the goldfish, and examined its involvement in food intake after intracerebroventricular (ICV) administration. ICV-injected cGnRH II at graded doses, from 0.1 to 10 pmol/g body weight (BW), induced a decrease of food consumption in a dose-dependent manner during 60 min after treatment. Cumulative food intake was significantly decreased by ICV injection of cGnRH II at doses of 1 and 10 pmol/g BW during the 60-min post-treatment observation period. ICV injection of salmon GnRH ([Trp⁷ Leu⁸] GnRH, sGnRH) at doses of 0.1-10 pmol/g BW did not affect food intake. The anorexigenic action of cGnRH II was completely blocked by treatment with the GnRH type I receptor antagonist, Antide. However, the anorexigenic action of cGnRH II was not inhibited by treatment with the corticotropin-releasing hormone (CRH) 1/2 receptor antagonist, α-helical CRH₍₉₋₄₁₎, and the melanocortin 4 receptor antagonist, HS024. These results suggest that, in the goldfish, cGnRH II, but not sGnRH, acts as an anorexigenic factor, as is the case in the musk shrew, and that the anorexigenic action of cGnRH II is independent of CRH- and melanocortin-signaling pathways.     

Alpha-melanocyte-stimulating hormone mediates melanin-concentrating hormone-induced anorexigenic action in goldfish

In goldfish, intracerebroventricular (ICV) administration of melanin-concentrating hormone (MCH) inhibits feeding behavior, and fasting decreases hypothalamic MCH-like immunoreactivity. However, while MCH acts as an anorexigenic factor in goldfish, in rodents MCH has an orexigenic effect. Therefore, we examined the involvement of two anorexigenic neuropeptides, alpha-melanocyte-stimulating hormone (alpha-MSH) and corticotropin-releasing hormone (CRH), in the anorexigenic action of MCH in goldfish, using an alpha-MSH receptor antagonist, HS024, and a CRH receptor antagonist, alpha-helical CRH((9-41)). ICV injection of HS024, but not alpha-helical CRH((9-41)), suppressed MCH-induced anorexigenic action for a 60-min observation period. We then examined, using a real-time PCR method, whether MCH affects the levels of mRNAs encoding various orexigenic neuropeptides, including neuropeptide Y (NPY), orexin, ghrelin and Agouti-related peptide (AgRP), in the goldfish diencephalon. ICV administration of MCH at a dose sufficient to inhibit food consumption decreased the expression of mRNAs for NPY and ghrelin, but not for orexin and AgRP. These results indicate that the anorexigenic action of MCH in the goldfish brain is mediated by the alpha-MSH signaling pathway and is accompanied by inhibition of NPY and ghrelin synthesis.     

Histology of the hormone-producing glands in the damp-wood termite <Emphasis Type="Italic">Hodotermopsis sjostedti</Emphasis> (Isoptera,Termopsidae): A focus on soldier differentiation

Caste differentiation in termites depends on complex hormonal changes during postembryonic development. Juvenile hormone (JH) is a central player in this process. The present study examined histological changes in the main hormone-producing endocrine glands, the corpora allata and molt glands, in the Japanese dampwood termite Hodotermopsis sjostedti. We focused on the soldier caste differentiation pathway, which can be induced artificially using an analogue of JH. The corpora allata exhibited volumetric changes during soldier induction, reflecting variations in the quantity of cytoplasm. Corpora allata from alates and neotenics clearly showed differentiation accompanied by cell proliferation, preparing for the high-level JH production necessary for reproduction. However, the volume increase of corpora allata was not always correlated to high JH titers. In contrast, molt glands degenerated in the reproductive castes. The JH analogue induced hypertrophy of the molt glands, along with the formation of lacunae, possibly related to ecdysteroid production. The JH analogue effect, inducing soldier differentiation, was suggested to require both mimic of high JH titers and stimulation of the molt glands. Received 12 November 2007; revised 2 June 2008; accepted 14 July 2008.     

A novel GDP-dependent pyruvate kinase isozyme from Toxoplasma gondii localizes to both the apicoplast and the mitochondrion

We previously reported a cytosolic pyruvate kinase (EC 2.7.1.40) from Toxoplasma gondii (TgPyKI) that differs from most eukaryotic pyruvate kinases in being regulated by glucose 6-phosphate rather than fructose 1,6-diphosphate. Another putative pyruvate kinase (TgPyKII) was identified from parasite genome, which exhibits 32% amino acid sequence identity to TgPyKI and retains pyruvate kinase signature motifs and amino acids essential for substrate binding and catalysis. Whereas TgPyKI is most closely related to plant/algal enzymes, phylogenetic analysis suggests a proteobacterial origin for TgPyKII. Enzymatic characterization of recombinant TgPyKII shows a high pH optimum at 8.5, and a preference for GDP as a phosphate recipient. Catalytic activity is independent of K+, and no allosteric or regulatory effects were observed in the presence of fructose 1,6-diphosphate, fructose 2,6-diphosphate, glucose 6-phosphate, ribose 5-phosphate, AMP, or ATP. Unlike TgPyKI, native TgPyKII activity was exclusively associated with the membranous fraction of a T. gondii tachyzoite lysate. TgPyKII possesses a long N-terminal extension containing five putative start codons before the conserved region and localizes to both apicoplast and mitochondrion by immunofluorescence assay using native antibody and fluorescent protein fusion to the N-terminal extension. Further deletional and site-directed mutagenesis suggests that a translation product from 1st Met is responsible for the localization to the apicoplast, whereas one from 3rd Met is for the mitochondrion. This is the first study of a potential mitochondrial pyruvate kinase in any system.     

Stereoselective synthesis of a new muscarinic M3 receptor antagonist, J-104129.

A diastereoselective synthesis of J-104129 (1) was developed. A key step of this synthesis was Michael addition of enolate generated from cis-chiral dioxolane 2 to cyclopentenone, followed by hydrogenolysis of the resultant enol triflate 4. A mixture of cyclopentyldioxolane (5, 6) was hydrolyzed with sodium hydroxide to yield carboxylic acid 7 in 86% ee.     

Characteristics and inhibition by flavonoids of 20alpha-hydroxysteroid dehydrogenase activity in mouse tissues

Progesterone was stereoselectively reduced to a metabolite 20alpha-hydroxy-4-pregnen-3-one in the cytosolic fraction from the liver of male mice, indicating that the reduction of progesterone is catalyzed by 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD). The cytosolic 20alpha-HSD activity was observed not only in the liver, but also in the kidney and lung. In liver cytosol, both NADPH and NADH were effective as cofactors for 20alpha-HSD activity, although NADPH was better than NADH for the enzyme activity. On the other hand, 20alpha-HSD activity in kidney cytosol required only NADPH as a cofactor. No significant sex-related difference of 20alpha-HSD activity was observed in liver and kidney cytosols. Flavonoids have been reported to inhibit the biosynthesis and metabolism of steroids. However, little is known about inhibitory effects of flavonoids on 20alpha-HSD activity. Thus, the effects of 16 flavonoids on 20alpha-HSD activity were examined, using liver cytosol of male mice. Among flavonoids tested, fisetin, apigenin, naringenin, luteolin, quercetin and kaempferol exhibited high inhibitory potencies for the 20alpha-HSD activity. We propose the possibility that these flavonoids augment progesterone signaling by inhibiting potently 20alpha-HSD activity in non-reproductive tissues.     

The role of OsBRI1 and its homologous genes, OsBRL1 and OsBRL3, in rice

Since first identifying two alleles of a rice (Oryza sativa) brassinosteroid (BR)-insensitive mutant, d61, that were also defective in an orthologous gene in Arabidopsis (Arabidopsis thaliana) BRASSINOSTEROID INSENSITIVE1 (BRI1), we have isolated eight additional alleles, including null mutations, of the rice BRI1 gene OsBRI1. The most severe mutant, d61-4, exhibited severe dwarfism and twisted leaves, although pattern formation and differentiation were normal. This severe shoot phenotype was caused mainly by a defect in cell elongation and the disturbance of cell division after the determination of cell fate. In contrast to its severe shoot phenotype, the d61-4 mutant had a mild root phenotype. Concomitantly, the accumulation of castasterone, the active BR in rice, was up to 30-fold greater in the shoots, while only 1.5-fold greater in the roots. The homologous genes for OsBRI1, OsBRL1 and OsBRL3, were highly expressed in roots but weakly expressed in shoots, and their expression was higher in d61-4 than in the wild type. Based on these observations, we conclude that OsBRI1 is not essential for pattern formation or organ initiation, but is involved in organ development through controlling cell division and elongation. In addition, OsBRL1 and OsBRL3 are at least partly involved in BR perception in the roots.     

An Emulsion of Sulfoquinovosylacylglycerol with Long-Chain Alkanes Increases Its Permeability to Tumor Cells

The α-anomer form of sulfoquinovosyl-monoacylglycerol with a saturated C18 fatty acid (α-SQMG-C_18:0) is a natural sulfolipid that is a clinically promising antitumor agent. It forms vesicles, micelles or an emulsion in water, depending on several physicochemical conditions. The type of aggregate formed appears to strongly influence the bioactivity level. Thus, we investigated the nature of the aggregates in relation to their bioactivities. The structure of the α-SQMG-C_18:0 assembly was greatly affected by the type of additive used in the preparation. Emulsification with ethanol and n-decane might be more effective at inhibiting tumor cell growth than the micelle or vesicle preparations. α-SQMG-C_18:0 formed an “emulsion-like-aggregate” in ethanol containing an n-decane concentration in the range of 1.03–103 mM. These ethanol/n-alkane/α-SQMG-C_18:0 aggregates inhibited cell growth in a dose-dependent manner, under optimum conditions (i.e., ethanol containing 103 mM of n-decane or n-dodecane dispersed in phosphate-buffered saline or culture medium). Based on these data, we discuss the relationship between the molecular action of and antitumor activity by α-SQMG-C_18:0.     

Expression and distribution of JNK/SAPK-associated scaffold protein JSAP1 in developing and adult mouse brain

The c-Jun N-terminal kinase (JNK) is one of the three major mitogen-activated protein kinases (MAPKs) playing key roles in various cellular processes in response to both extracellular and intracellular stimuli. JNK/SAPK-associated protein 1 (JSAP1 also referred to as JIP3) is a JNK-associated scaffold that controls the specificity and efficiency of JNK signaling cascades. Here we studied its expression in mouse brains. JSAP1 mRNA was expressed in developing and adult brains, showing spatial patterns similar to JNK1-3 mRNAs. In embryos, JSAP1 immunolabeling was intense for progenitor cells in the ventricular zone throughout the brain and in the external granular layer of the cerebellum, and for neurons and glial cells differentiating in the mantle zone. In adults, JSAP1 was distributed in various neurons and Bergmann glia, with higher levels in striatal cholinergic interneurons, telencephalic parvalbumin-positive interneurons and cerebellar Purkinje cells. In these neurons, JSAP1 was observed as tiny particulate staining in spines, dendrites, perikarya and axons, where it was often associated with the smooth endoplasmic reticulum (sER) and cell membrane. Immunoblots revealed enriched distribution in the microsomal fraction and cytosolic fraction. Therefore, the characteristic cellular expression and subcellular distribution of JSAP1 might be beneficial for cells to efficiently link external stimuli to the JNK MAPK pathway and other intracellular machineries.