Binding sites for melanin-concentrating hormone in the human brain

Binding sites for melanin-concentrating hormone (MCH) in human brain were investigated and characterized by radioligand binding. Specific binding sites for MCH were present in every region of human brain (cerebral cortex, cerebellum, thalamus, hypothalamus, pons, and medulla oblongata) obtained at autopsy. alpha-Melanocyte stimulating hormone or ACTH was a poor inhibitor of (125)I-MCH binding (IC(50) 1 microM) compared with MCH (IC(50) = 0.3 +/- 0.07 nM, mean +/- SEM, n = 3). Scatchard plots of (125)I-MCH binding in human brain (thalamus) gave a dissociation constant of 0.2 +/- 0.06 nM and maximal binding of 5.8 +/- 0.3 fmol/mg protein (n = 3). These findings suggest that specific MCH binding sites that differ from the melanocortin receptors exist in human brain.     

Menaquinol oxidase activity and primary structure of cytochrome bd from the amino-acid fermenting bacterium Corynebacterium glutamicum

Cytochrome d was spectroscopically detected in membrane fractions of the amino-acid-fermenting, high-G+C gram-positive bacterium Corynebacterium glutamicum. Inhibition of NADH oxidase activity in the membranes by cyanide suggested that the main terminal respiratory oxidase during the stationary phase was a type of cytochrome bd. Cytochrome bd-type quinol oxidase, purified from the membranes, was composed of two subunits. Its reduced form showed absorption peaks at 627, 595, and 560 nm, which were due to haem d, high-spin protohaem, and low-spin protohaem, respectively. The air-oxidised form showed a peak at 645 nm, which might be due to oxygenated ferrous haem d. The spectral features and the size of subunit I are more similar to the properties of cytochromes bd from Proteobacteria, such as Escherichia coli, than to those of cytochrome bd from low-G+C gram-positive bacteria, such as Bacillus stearothermophilus. The menaquinol oxidase activity of the purified cytochrome bd was low, but was enhanced about fivefold by pre-incubating the enzyme with menaquinones. The order of effectiveness of quinols as oxidase substrates was clearly different from that of quinones as the activators of enzyme activity. Furthermore, activation was destroyed by ultraviolet irradiation of the pre-incubated enzyme and then restored by a second incubation with menaquinone. These results indicate that the enzymatic properties of this new oxidase are more similar to the properties of cytochromes bd from low-G+C gram-positive bacterial than to those of proteobacterial counterparts. They also suggest that the enzyme has a second quinone-binding site essential for full activity, in addition to the active centre for substrate oxidation. By using probes based on partial peptide sequences of the subunits, the genes for the two subunits of C. glutamicum cytochrome bd were cloned. The deduced amino acid sequence demonstrated that subunit I lacks the C-terminal half of the Q loop and that the primary structure of C. glutamicum cytochrome bd is more similar to that of other gram-positive bacteria than to proteobacterial cytochromes bd.     

The Receptor-like Cytoplasmic Kinase BIK1 Localizes to the Nucleus and Regulates Defense Hormone Expression during Plant Innate Immunity

1. Download high-res image (205KB)
2. Download full-size image

     

Reciprocal regulation of cholesterol excretion in apolipoprotein E-null mice by angiotensin II type 1 and type 2 receptor deficiency

AimsThe effects of AT₁ and AT₂ receptor deficiency on the intake and excretion of cholesterol were examined using atherosclerotic apolipoprotein E-null (ApoEKO) mice.Main methodsApoEKO, AT₁a/ApoEKO and AT₂/ApoEKO mice received a high-cholesterol diet (HCD: 1.25% cholesterol) for 10 days before sampling.Key findingsPlasma total cholesterol level was lower in AT₁a/ApoEKO mice and higher in AT₂/ApoEKO mice than in ApoEKO mice with a high cholesterol intake. In these mice, cholesterol content in feces was higher in AT₁a/ApoEKO mice and lower in AT₂/ApoEKO mice than in ApoEKO mice. Moreover, cholesterol content in bile tended to be higher in AT₁a/ApoEKO mice and lower in AT₂/ApoEKO mice than in ApoEKO mice, while a significant difference was observed only between AT₁a/ApoEKO and AT₂/ApoEKO mice. Cholesterol content and expression of HMG-CoA reductase and LDL receptor in liver were not different among the groups. Similar but weaker changes were also observed with a normal standard diet. Treatment with an AT₁ receptor blocker, irbesartan, increased cholesterol content in bile and tended to increase cholesterol excretion into feces in ApoEKO mice with HCD.SignificanceThese results suggest that AT₁ and AT₂ receptor stimulation was involved in the regulation of cholesterol excretion into bile and feces, and that the regulation acted reciprocally in a cholesterol overload condition with HCD.     

The T-Cell Antigen Receptor: A Logical Response to an Unknown Ligand

The immune system can be roughly divided into innate and adaptive compartments. The adaptive compartment includes the B and T lymphocytes, whose antigen receptors are generated by recombination of gene segments. The consequence is that the creation of self-reactive lymphocytes is unavoidable. For the host to remain viable, the immune system has evolved a strategy for removing autoimmune lymphocytes during development. This review discusses how T lymphocytes are generated, how they recognize antigens, and how their antigen receptor directs the removal of self-reactive T cells.     

Indirect sperm transfer and male mating strategies in soil invertebrates

Summary

Many soil invertebrates transfer their sperm indirectly by means of spermatophores. Among the different taxa there is great variation in spermatophore architecture, auxiliary structures and behaviour. The behaviour, ranging from elaborate courtship rituals to seemingly indifferent scattering of spermatophores, can roughly be classified as association and dissociation. Which of the two is adaptive depends on many factors which can be summarized in a simple functional response model showing that in some cases the best choice depends on density.     

Artificial model of photosynthetic oxygen evolving complex: Catalytic O2 production from water by di-μ-oxo manganese dimers supported by clay compounds

Adsorption of [(OH₂)(terpy)Mn(μ-O)₂Mn(terpy)(OH₂)]³⁺ (terpy = 2,2′:6′,2?-terpyridine) (1) onto montmorillonite K10 (MK10) yielded catalytic dioxygen (O₂) evolution from water using a Ce^IV oxidant. The Mn K-edge X-ray absorption near edge structure (XANES) of the 1/MK10 hybrid suggested that the oxidation state of the di-μ-oxo Mn₂ core could be Mn^III-Mn^IV. However the pre-edge peak in the XANES spectrum of 1 adsorbed on MK10 is different from the neat 1 powder. The kinetic analysis of O₂ evolution showed that the catalysis requires cooperation of two equivalents of 1 adsorbed on MK10. The reaction of the [(bpy)₂Mn(μ-O)₂Mn(bpy)₂]³⁺ (bpy = 2,2′-bipyridine) (2)/MK10 hybrid with a Ce^IV oxidant evolved O₂. However, the turnover number value was less than unity for 2/MK10, showing that 2 adsorbed on MK10 does not work as a catalyst. The terminal water ligands could be an important for the catalysis by adsorbed 1. The mechanism of O₂ production by photosynthetic oxygen evolving complex is discussed based on catalytic O₂ evolution by 1 adsorbed on MK10.     

Systematic Analysis of Fly Models with Multiple Drivers Reveals Different Effects of Ataxin-1 and Huntingtin in Neuron Subtype-Specific Expression

The fruit fly, Drosophila melanogaster, is a commonly used model organism for neurodegenerative diseases. Its major advantages include a short lifespan and its susceptibility to manipulation using sophisticated genetic techniques. Here, we report the systematic comparison of fly models of two polyglutamine (polyQ) diseases. We induced expression of the normal and mutant forms of full-length Ataxin-1 and Huntingtin exon 1 in cholinergic, dopaminergic, and motor neurons, and glial cells using cell type-specific drivers. We systematically analyzed their effects based on multiple phenotypes: eclosion rate, lifespan, motor performance, and circadian rhythms of spontaneous activity. This systematic assay system enabled us to quantitatively evaluate and compare the functional disabilities of different genotypes. The results suggest different effects of Ataxin-1 and Huntingtin on specific types of neural cells during development and in adulthood. In addition, we confirmed the therapeutic effects of LiCl and butyrate using representative models. These results support the usefulness of this assay system for screening candidate chemical compounds that modify the pathologies of polyQ diseases.     

A novel ring-expanded product with enhanced tyrosinase inhibitory activity from classical Fe-catalyzed oxidation of rosmarinic acid, a potent antioxidative Lamiaceae polyphenol

The iron-ion catalyzed oxidation of the ethanol solution of rosmarinic acid, a potent antioxidant polyphenol of Lamiaceae (Labiatae) plants, afforded a highly tyrosinase-inhibitory active product. The structure of the active product in the oxidation product mixture was determined using extensive NMR spectroscopy to have a novel oxygen-containing seven-membered ring system. The formation mechanism of the unique ring structure from the catechol part of the rosmarinic acid was proposed.     

Cochlear Cell Modeling Using Disease-Specific iPSCs Unveils a Degenerative Phenotype and Suggests Treatments for Congenital Progressive Hearing Loss

1. Download high-res image (168KB)
2. Download full-size image