Regional Distribution and Relative Abundance of Serotonin2c Receptors in Human Brain: Effect of Suicide

Abnormalities in serotonin receptor subtypes have been observed in the postmortem brain of suicide victims. We examined the regional distribution of serotonin (5HT)(2C) receptor mRNA in several areas of the human brain and also compared its protein and mRNA expression in the prefrontal cortex (PFC), hippocampus, and choroid plexus between suicide victims and normal control subjects. 5HT(2C) receptors were found to be distributed in several areas of the human brain (in order of abundance): highly concentrated and richest in choroid plexus; hypothalamus; nucleus accumbens; with the lowest abundance in PFC and cerebellum. Comparison of 5HT(2C) receptors between suicide victims and control subjects showed higher protein levels in the PFC but not the hippocampus or choroid plexus of suicide victims. However, there were no significant differences in mRNA levels between suicide victims and control subjects in these brain areas. These results suggest that 5HT(2C) receptors are richly distributed throughout the brain with the highest level in the choroid plexus and that abnormalities in protein expression of 5HT(2C) receptors in the PFC may be associated with suicide.     

First confirmed case of pseudocopulation in terrestrial orchids of South America: Pollination of Geoblasta pennicillata (Orchidaceae) by Campsomeris bistrimacula (Hymenoptera, Scoliidae)

The attraction of male pollinating insects by sexual deception is known for several orchids from the Mediterranean, Australia, South Africa and South America. The sexual delusion may be so enticing in some species that it elicits males to attempt copulation with insect-like structures of the labellum. Pollination by such a pseudocopulation mechanism is reported here for the terrestrial orchid Geoblasta penicillata (Chloraeinae) from subtropical South America. Observations of the pollination process were carried out in two wild populations 560 km distant from each other. The only pollinators seen in both populations were male Campsomeris bistrimacula (Scoliidae) wasps. They attempted copulation with the insect-like labellum by directing the genitalia to its base whereby pollinia got attached to the dorsal surface of the metasoma. The present case of pseudocopulation, which is in South America the second known and the first recorded in wild populations, represents a striking parallel to the Australian Calochilus campestris also pollinated by male scoliid wasp of the genus Campsomeris.     

Guttural pouches, brain temperature and exercise in horses

Selective brain cooling (SBC) is defined as the lowering of brain temperature below arterial blood temperature. Artiodactyls employ a carotid rete, an anatomical heat exchanger, to cool arterial blood shortly before it enters the brain. The survival advantage of this anatomy traditionally is believed to be a protection of brain tissue from heat injury, especially during exercise. Perissodactyls such as horses do not possess a carotid rete, and it has been proposed that their guttural pouches serve the heat-exchange function of the carotid rete by cooling the blood that traverses them, thus protecting the brain from heat injury. We have tested this proposal by measuring brain and carotid artery temperature simultaneously in free-living horses. We found that despite evidence of cranial cooling, brain temperature increased by about 2.5 degrees C during exercise, and consistently exceeded carotid temperature by 0.2-0.5 degrees C. We conclude that cerebral blood flow removes heat from the brain by convection, but since SBC does not occur in horses, the guttural pouches are not surrogate carotid retes.     

TLR9 signaling in B cells determines class switch recombination to IgG2a

Although IgG2a is the most potent Ab isotype in the host response to viral and bacterial infections, the regulation of class switch recombination to IgG2a in vivo is not yet well understood. Recognition of pathogen-associated molecular patterns by dendritic cells expressing TLRs, like TLR7, recognizing ssRNA, or TLR9, recognizing DNA rich in nonmethylated CG motifs (CpG), favors induction of Th1 responses. It is generally assumed that these Th1 responses are responsible for the TLR-mediated induction of IgG2a. Using virus-like particles loaded with CpGs, we show here that TLR9 ligands can directly stimulate B cells to undergo isotype switching to IgG2a. Unexpectedly, TLR9 expression in non-B cells did not affect isotype switching in the Ab response against virus-like particles. Thus, TLR9 can regulate isotype switching to IgG2a directly by interacting with B cells rather than indirectly by inducing Th1 responses.     

Remote loading of doxorubicin into liposomes driven by a transmembrane phosphate gradient

This study examines a new method for the remote loading of doxorubicin into liposomes. It was shown that doxorubicin can be loaded to a level of up to 98% into large unilamellar vesicles composed of egg phosphatidylcholine/cholesterol (7/3 mol/mol) with a transmembrane phosphate gradient. The different encapsulation efficiencies which were achieved with ammonium salts (citrate 100%, phosphate 98%, sulfate 95%, acetate 77%) were significantly higher as compared to the loading via sodium salts (citrate 54%, phosphate 52%, sulfate 44%, acetate 16%). Various factors, including pH-value, buffer capacity, solubility of doxorubicin in different salt solutions and base counter-flow, which likely has an influence on drug accumulation in the intraliposomal interior are taken into account. In contrast to other methods, the newly developed remote loading method exhibits a pH-dependent drug release property which may be effective in tumor tissues. At physiological pH-value doxorubicin is retained in the liposomes, whereas drug release is achieved by lowering the pH to 5.5 (approximately 25% release at 25 degrees C or 30% at 37 degrees C within two h). The DXR release of liposomes which were loaded via a sulfate gradient showed a maximum of 3% at pH 5.5.     

Interaction between nitric oxide and ethylene in the induction of alternative oxidase in ozone-treated tobacco plants

The higher plant mitochondrial electron transport chain contains, in addition to the cytochrome chain, an alternative pathway that terminates with a single homodimeric protein, the alternative oxidase (AOX). We recorded temporary inhibition of cytochrome capacity respiration and activation of AOX pathway capacity in tobacco plants (Nicotiana tabacum L. cv BelW3) fumigated with ozone (O(3)). The AOX1a gene was used as a molecular probe to investigate its regulation by signal molecules such as hydrogen peroxide, nitric oxide (NO), ethylene (ET), salicylic acid, and jasmonic acid (JA), all of them reported to be involved in the O(3) response. Fumigation leads to accumulation of hydrogen peroxide in mitochondria and early accumulation of NO in leaf tissues. Although ET accumulation was high in leaf tissues 5 h after the start of O(3) fumigation, it declined during the recovery period. There were no differences in the JA and 12-oxo-phytodienoic acid levels of treated and untreated plants. NO, JA, and ET induced AOX1a mRNA accumulation. Using pharmacological inhibition of ET and NO, we demonstrate that both NO- and ET-dependent pathways are required for O(3)-induced up-regulation of AOX1a. However, only NO is indispensable for the activation of AOX1a gene expression.     

Carbonic anhydrase inhibitors: Valdecoxib binds to a different active site region of the human isoform II as compared to the structurally related cyclooxygenase II "selective" inhibitor celecoxib

The high resolution X-ray crystal structure of the adduct of human carbonic anhydrase (CA, EC 4.2.1.1) isoform II (hCA II) with the clinically used painkiller valdecoxib, acting as a potent CA II and cyclooxygenase-2 (COX-2) inhibitor, is reported. The ionized sulfonamide moiety of valdecoxib is coordinated to the catalytic Zn(II) ion with a tetrahedral geometry. The phenyl-isoxazole moiety of the inhibitor fills the active site channel and interacts with the side chains of Gln92, Val121, Leu198, Thr200, and Pro202. Its 3-phenyl group is located into a hydrophobic pocket, simultaneously establishing van der Waals interactions with the aliphatic side chain of various hydrophobic residues (Val135, Ile91, Val121, Leu198, and Leu141) and a strong offset face-to-face stacking interaction with the aromatic ring of Phe131 (the chi1 angle of which is rotated about 90 degrees with respect to what was observed in the structure of the native enzyme and those of other sulfonamide complexes). Celecoxib, a structurally related COX-2 inhibitor for which the X-ray crystal structure was reported earlier, binds in a completely different manner to hCA II as compared to valdecoxib. Celecoxib completely fills the entire CA II active site, with its trifluoromethyl group in the hydrophobic part of the active site and the p-tolyl moiety in the hydrophilic one, not establishing any interaction with Phe131. In contrast to celecoxib, valdecoxib was rotated about 90 degrees around the chemical bond connecting the benzensulfonamide and the substituted isoxazole ring allowing for these multiple favorable interactions. These different binding modes allow for the further drug design of various CA inhibitors belonging to the benzenesulfonamide class.     

The fusogenic state of mayaro virus induced by low pH and by hydrostatic pressure

Mayaro virus is an enveloped virus that belongs to the Alphavirus genus. To gain insight into the mechanism involved in Mayaro virus membrane fusion, we used hydrostatic pressure and low pH to isolate a fusion-active state of Mayaro glycoproteins. In response to pressure, E1 glycoprotein undergoes structural changes resulting in the formation of a stable conformation. This state was characterized and correlated to that induced by low pH as measured by intrinsic fluorescence, 4,4′-dianilino-1,1′-binaphthyl-5,5′-disulfonic acid, dipotassium salt fluorescence, fluorescence resonance energy transfer, electron microscopy, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In parallel, we used a neutralization assay to show that Mayaro virus in the fusogenic state retained most of the original immunogenic properties and could elicit high titers of neutralizing antibodies.     

Linking organism groups – major results and conclusions from the STAR project

Here we summarize results of the EU funded research project STAR concerning the suitability of different organism groups (fish, benthic invertebrates, macrophytes, diatoms) for monitoring European rivers. In a general way, the suitability of the organism groups is classified by monitoring type, stress type, river type, temporal scale and taxonomic resolution. For example, although all organism groups are affected by acidification, the relatively low species richness of fish and macrophytes in small mountain streams makes these two groups less suitable, and, hence, we argue that benthic diatoms and/or invertebrates may be considered as more robust indicators. Similar, lines of reasoning are given for a number of stressor and stream types.