The impact of species concept on biodiversity studies

Species are defined using a variety of different operational techniques. While discussion of the various methodologies has previously been restricted mostly to taxonomists, the demarcation of species is also crucial for conservation biology. Unfortunately, different methods of diagnosing species can arrive at different entities. Most prominently, it is widely thought that use of a phylogenetic species concept may lead to recognition of a far greater number of much less inclusive units. As a result, studies of the same group of organisms can produce not only different species identities but also different species range and number of individuals. To assess the impact of different definitions on conservation issues, we collected instances from the literature where a group of organisms was categorized both under phylogenetic and nonphylogenetic concepts. Our results show a marked difference, with surveys based on a phylogenetic species concept showing more species (48%) and an associated decrease in population size and range. We discuss the serious consequences of this trend for conservation, including an apparent change in the number of endangered species, potential political fallout, and the difficulty of deciding what should be conserved.     

Loss of AtPIN1 does not influence the <Emphasis Type="Italic">in vitro</Emphasis> morphogenic potential of <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> suspension cultures

Suspension cultures from Arabidopsis thaliana wild type and AtPIN1-deficient lines were initiated and maintained for more than 3 years. A protocol for efficient regeneration from long-term suspension cultures was established. Arabidopsis wild-type and respectively AtPIN1 mutant plants have been regenerated from these cultures and characterized. Additionally, transgenic suspension cultures expressing the uidA ( -glucuronidase) reporter gene under the control of AtPIN1 promoter have been used for morphogenic studies. Our studies suggest that a lack of AtPIN1 function affects shoot differentiation and development, but does not influence in vitro regeneration of plants.     

Synthesis and radioiodination of selective ligands for the dopamine D3 receptor subtype

Starting from FAUC 365, a series of iodine substituted heteroaryl carboxamides has been synthesized revealing high affinity and selectivity for the dopamine D3 receptor. Binding data showed a 15-560-fold selectivity for the dopamine D3 over D2. A 2,3-dichloro substitution pattern on the phenylpiperazine moiety led to the highest subtype selectivity, whereas the 2-methoxy substituted compounds showed superior D3 affinity. Suitable precursors were radioiodinated with high radiochemical yields (53-85%) leading to potential imaging agents for the D3 receptor by SPET.     

Synthesis, structural investigations and biological evaluation of novel hexahydropyridazine-1-carboximidamides, -carbothioamides and -carbothioimidic acid esters as inducible nitric oxide synthase inhibitors

Local excess of nitric oxide (NO) has been implicated in beta-cell damage, thus, a possible approach to the treatment of autoimmune IDDM is the selective inhibition of inducible nitric oxide synthase (iNOS). A series of variously substituted hexahydropyridazine-1-carbothioamides, -carbothioimidic acid esters and -carboximidamides was synthesized and dose-dependently evaluated as potential inhibitors of iNOS. The screening of the title compounds was performed with insulin-producing RIN-5AH cells and a combination of IL1-1 beta and IFN-gamma as inducers of cellular NO production. The structure-activity analysis revealed that the variation of substituents in the position 1 of the hexahydropyridazine strongly influences the inhibitory activity to iNOS as well as being critical for RIN cell survival. Among the compounds tested, the hexahydropyridazine-1-carbothioamides showed particularly significant inhibitory effects. However, for an efficient iNOS inhibition substitution at the nitrogen of the 1-carbothioamide group is important. Thus, the introduction of aliphatic chains such as propyl or butyl and of cyclic moieties such as cyclohexyl, 3-methoxyphenyl, and 4-methoxyphenyl (IC(50): 0.5-2.1 mM), respectively, provided compounds with similar inhibitory activity to aminoguanidine (IC(50): 0.3 mM), a common standard substance used for the selective inhibition of iNOS. However, the 1-carboximidamides, which represent more structurally related semicyclic derivatives of aminoguanidine, caused only incomplete iNOS inhibition. The hexahydropyridazine-1-carbothioimidic acid esters caused dose- and substituent-dependent damage of RIN-5AH cells. The toxicity of the synthesized compounds increased markedly if aliphatic substituents at the exocyclic N atom(s) were replaced by variously substituted aromatic rings.     

Taurine supplementation induces multidrug resistance protein 2 and bile salt export pump expression in rats and prevents endotoxin-induced cholestasis

The effect of oral taurine supplementation on endotoxin-induced cholestasis was investigated in rat liver. At 12h following lipopolysaccharide (LPS) injection (4mg/kg body weight i.p.) bile flow and bromosulfophthalein (BSP) and taurocholate (TC) excretion were determined in the perfused liver and the expression of the canalicular transporters multidrug resistance protein 2 (Mrp2) and bile salt export pump (Bsep) was analyzed. Injection of LPS induced a significant decrease of bile flow ( 2.2+/-0.2 microl/g liver wet weight/min vs 3.3+/-0.1 microl/g liver wet weight in controls), biliary BSP excretion (10.8+/-2.2 nmol/g/min vs 21.0+/-3.8 nmol/g/min), and biliary TC excretion (114+/-23 nmol/g/min vs 228+/-8 nmol/g/min). These effects were due to transporter retrieval from the canalicular membrane and downregulation of Mrp2 and Bsep expression. In taurine-supplemented rats bile flow was 30% higher than that in untreated rats and the expression of Mrp2 and Bsep protein was increased two- to threefold. In taurine-supplemented rats there was no significant reduction of bile flow or of BSP and TC excretion at 12h following LPS injection. This protective effect of taurine was due to higher Mrp2 and Bsep protein levels compared to nonsupplemented LPS-treated rats, whereas relative Mrp2 retrieval from the canalicular membrane induced by LPS was not significantly different. LPS-induced tumor necrosis factor alpha and interleukin-1beta release were lower in taurine-fed rats; however, downregulation of Mrp2 and Bsep expression by LPS was delayed but not prevented. The data show that oral supplementation of taurine induces Mrp2 and Bsep expression and may prevent LPS-induced cholestasis.     

Carotenoid cleavage products modify respiratory burst and induce apoptosis of human neutrophils

Carotenoid supplementation in the treatment of diseases associated with oxidative stress has been recently questioned because of the cell damage and the increased risk of lung cancer in male smokers. Because of the complex role of neutrophils in lung diseases, we investigated whether carotenoid derivatives could affect respiratory burst and apoptosis of human neutrophils purified from peripheral blood. Stimulation of superoxide production was induced by nanomolar and micromolar concentrations of carotenoid cleavage products with aliphatic chains of different length, but not by carotenoids lacking the carbonyl moiety. The stimulatory effect of carotenoid cleavage products was observed in cells activated by phorbol myristate acetate (PMA), while a slight inhibition of superoxide production was noticed with cells activated by the chemotactic tripeptide N-formyl-Met-Leu-Phe (f-MLP). At higher concentrations, carotenoid cleavage products inhibited superoxide production in the presence of both PMA and f-MLP. In the presence of 20 microM carotenoid cleavage products, inhibition of superoxide production was accompanied by DNA fragmentation and increased level of intracellular caspase-3 activity.     

Genistein can modulate channel function by a phosphorylation-independent mechanism: importance of hydrophobic mismatch and bilayer mechanics

Genistein, a generic tyrosine kinase inhibitor, has been used extensively as a tool to investigate the possible regulation of membrane function by tyrosine phosphorylation. Genistein, in micromolar concentrations, alters the function of numerous ion channels and other membrane proteins, but only in few cases has it been demonstrated that the changes in membrane protein (ion channel) function are due to changes in a protein's phosphorylation status. The major common denominator characterizing proteins that are modulated by genistein seems to be that they are imbedded into, and span, the bilayer component of the plasma membrane. We therefore explored whether genistein could alter ion channel function by a bilayer-mediated mechanism and examined genistein's effect on gramicidin A (gA) channels in planar phospholipid bilayers. gA channels form by transmembrane dimerization of two nonconducting subunits, and genistein potentiates gA channel activity by increasing the appearance rate and prolonging the lifetime of bilayer-spanning gA dimers. That is, genistein shifts the equilibrium between nonconducting monomers and conducting dimers in favor of the bilayer-spanning dimers; the changes in channel activity therefore cannot be due to changes in bilayer fluidity. To obtain further insights into the mechanism underlying this modulation of gA channel function, we examined the effects of genistein on channels formed by gA analogues that differ in amino acid sequence. For a given channel length, the effects of genistein on gA dimerization do not depend on the specific sequence, or the chirality, of the channel-forming gA analogues. In contrast, when we change the channel length (by decreasing or increasing the number of amino acid residues in the sequence), or the bilayer thickness (by changing methylene groups in the acyl chains), the magnitude of genistein's effect increases with increasing hydrophobic mismatch between the channel length and the bilayer thickness. These results strongly suggest that genistein alters bilayer mechanical properties, which in turn modulates channel function. This bilayer-mediated mechanism is likely to apply to other pharmacological reagents and membrane proteins.