Relationships between plant diversity,vegetation cover,and site conditions: implications for grassland conservation in the Greater Caucasus

Overgrazing, land use abandonment and increasing recreational activities have altered the vegetation of high-montane and subalpine grassland of the Caucasus. The failure of previous restoration efforts with unsuitable and exotic plant species indicates the need for information on the present vegetation and in which way it might change. Within the Greater Caucasus, we have described and quantified the mountain grassland which develops under characteristic overgrazed and eroded site conditions. Further, we have proposed potential native plant species for revegetation to restore and conserve valuable mountain grassland habitats. We used non-metric dimensional scaling ordination and cluster comparison of functional plant groups to describe a gradient of grassland vegetation cover. For our study region, we identified four major vegetation types with increasing occurrence of ruderal pasture weeds and tall herb vegetation on abandoned hay meadows within the subalpine zone. Within high-montane grassland a decline of plant diversity can be observed on sites of reduced vegetation cover. Due to a low potential of the grassland ecosystem to balance further vegetation cover damage, the long-term loss of diverse habitats can be expected. We conclude with management recommendations to prevent erosion and habitat loss of precious mountain grasslands.     

Ala31-Aib32: identification of the key motif for high affinity and selectivity of neuropeptide Y at the Y5-receptor

The turn-inducing sequence Ala-Aib introduced into positions 31 and 32 of neuropeptide Y (NPY) and its analogues has been identified as the key structure for Y(5)-receptor selectivity. Analogues of NPY and PP/NPY chimera containing the motif Ala-Aib were prepared; these peptides turned out to be selective for the Y(5)-receptor. The affinity of the NPY-based peptides was in the range of 6-150 nM, while the affinity of three (Ala-Aib)-containing PP/NPY chimera was in the range of 0.2-0.9 nM. The circular dichroism spectra of the Aib analogues in aqueous solution were all characteristic of an alpha helix; however, they had different intensities of the two negative bands at 220 and 208 nm. Affinity and selectivity for the Y(5)-receptor were correlated with the ratio of the ellipticity at 220 nm versus the one at 208 nm (R), which indicates the presence of a pronounced helix (R > 1) versus a less stabile one (R < 1). When R was in the range 0.74-0.96, the affinity at the Y(5)-receptor was in the range >5 nM, while there was complete loss of affinity at the Y(4)-receptor. R > 1.15 was associated with very high affinity at the Y(5)-receptor and weak affinity at the Y(4)-receptor. These results suggest that the selectivity of the Ala(31)-Aib(32) motif for the Y(5)-receptor derives from a specific conformation that must be correlated with the bioactive conformation of NPY at this subtype.     

Late pregnancy suppresses relapses in experimental autoimmune encephalomyelitis: evidence for a suppressive pregnancy-related serum factor

Women with multiple sclerosis have significantly diminished disease activity during pregnancy. The purpose of our study was to identify the underlying mechanism for the diminished disease activity. We found that during the period of late pregnancy there is protection against paralysis, during both the induction and effector phases of relapsing experimental autoimmune encephalomyelitis, a mouse model of multiple sclerosis. We did not find any changes in the cytokine secretion profiles or the proliferative activity of autoreactive T cells from mice induced during late pregnancy compared with virgin controls. In mice mated after disease onset, the inflammatory histologic lesions did not clear, despite marked clinical improvement during pregnancy. We found evidence for a serum factor present in late pregnancy that suppresses T cell activation. In the presence of sera taken from mice late in pregnancy, the proliferative response and IL-2 production of proteolipid protein p139-151-specific T cells were significantly diminished as compared with stimulation in the presence of normal mouse sera. In conclusion, serum from late pregnancy has the capacity to down-regulate T cell responses and might be associated with the amelioration of disease activity in experimental autoimmune encephalomyelitis.     

Non-imidazole heterocyclic histamine H3 receptor antagonists

Continued exploration of the SAR around the lead imidazopyridine histamine H(3) antagonist 1 has led to the discovery of several related series of heterocyclic histamine H(3) antagonists. The synthesis and SAR of indolizine, indole and pyrazolopyridine based compounds are now described.     

Genomewide linkage analysis identifies polymorphism in the human interferon-gamma receptor affecting Helicobacter pylori infection

Helicobacter pylori is considered the most prevalent infectious agent among humans, and it causes gastric inflammation, gastroduodenal ulcers, and a risk of gastric cancer. We performed a genomewide linkage analysis among Senegalese siblings phenotyped for H. pylori-reactive serum immunoglobulin G. A multipoint LOD score of 3.1 was obtained at IFNGR1, the gene that encodes chain 1 of the interferon-gamma (IFN-gamma) receptor. Sequencing of IFNGR1 revealed -56C-->T, H318P, and L450P variants, which were found to be associated with high antibody concentrations. The inclusion of these in the linkage analysis raised the LOD score to 4.2. The variants were more prevalent in Africans than in whites. Our findings indicate that IFN-gamma signaling plays an essential role in human H. pylori infection, and they contribute to an explanation of the observations of high prevalences and relatively low pathogenicity of H. pylori in Africa. Moreover, they provide further support for the value of genomewide linkage studies in the analysis of susceptibility to infection and other complex genetic traits.     

A Kdp-like,high-affinity,K+-translocating ATPase is expressed during growth of Rhodobacter sphaeroides in low potassium media

Cells of the purple non-sulphur bacterium Rhodobacter sphaeroides express a high-affinity K⁺ uptake system when grown in media with low K⁺ concentrations. Antibodies againts the catalytic KdpB protein or the whole KdpABC complex of Escherichia coli crossreact with a 70.0 kDa R. sphaeroides protein that was expressed only in cells grown in media with low K⁺ concentrations. In membranes derived from R. sphaeroides cells grown with low K⁺ concentrations (induced cells), a high ATPase activity could be detected when assayed in Tris-HCl pH 8.0 containing 1 mM MgSO₄. This ATPase activity increased upon addition of 1 mM KCl from 166 to 289 mol ATP hydrolysed x min^-1 x g protein^-1 (1.7-fold stimulation). The K⁺-stimulated ATPase activity was inhibited approximately 93% by 0.5 mM vanadate but hardly by N,N-dicyclohexylcarbo-diimide (DCCD). These results indicate that the inducible K⁺-ATPase in R. sphaeroides resembles the Kdp K⁺-translocating ATPase of Escherichia coli. This Kdp-like transport system is also expressed in R. capsulatus and Rhodospirillum rubrum during growth in media with low K⁺ concentrations suggesting a wide distribution of this transport system among phototrophic bacteria.Abbreviations electrical potential difference across the cytoplasmic membrane - pH pH difference across the cytoplasmic membrane - BSA bovine serum albumine - PAGE polyacrylamide gel electrophoresis - HEPES 4-(2-hydroxyethyl)-1-piperazine-ethanesulfonic acid - PMSF phenyl-methyl-sulfonyl fluoride - DCCD N,N-dicyclohexylcarbodiimide - AIB 2--aminoisobutyric acid - TMG methyl--d-thiogalactopyranoside     

Minimizing growth regulators in shoot culture of an endangered plant,Hackelia venusta (Boraginaceae)

Summary Hackelia venusta (Boraginaceae) is an endangered perennial herb endemic to the interior northwestern United States. Because of seed scarcity, micropropagation (anex situ conservation strategy) could produce true-to-type plantlets suitable for reintroduction. We hypothesized that clones of predetermined size could be rapidly produced by supplementing multiplication and rooting media with minimal levels of cytokinin and auxin. Microshoots derived from shoot expants were cultured on Murashige and Skoog (1962) media supplemented with 1% (wt/vol) agar and 0.0001 to 10 μM benzyladenine. Inverse regression estimates on 3 genotypes predicted that a target of 2.5 axillary microshoots per explant would require a minimal level of 0.04±0.02 μM benzyladenine. Culture of 25 genotypes with 0.04 μM benzyladenine resulted in an average of 2.3±0.1 axillary microshoots per explant. Elongated microshoots were transferred to media supplemented with 0.1 to 25 μM indoleacetic acid. Clones rooted from 36% to 100% success after 4 wk in 2.0 μM indoleacetic acid. Plantlets transplantedex vitro with three or more roots survived at 84% versus 46% of plantlets with fewer roots. Up to 84% of the plantlets survived in a planting trial. The data suggest that shoot culture ofHackelia venusta, with minimal growth regulators, can produce axillary microshoots for reintroduction.