Pigment dynamics and autumn leaf senescence in a New England deciduous forest,eastern USA

The leaves of woody plants at Harvard Forest in Central Massachusetts, USA, changed color during senescence; 70% (62/89) of the woody species examined anatomically contained anthocyanins during senescence. Anthocyanins were not present in summer green leaves, and appeared primarily in the vacuoles of palisade parenchyma cells. Yellow coloration was a result of the unmasking of xanthophyll pigments in senescing chloroplasts. In nine red-senescing species, anthocyanins were not detectable in mature leaves, and were synthesized de novo in senescence, with less than 20µg cm^–2 of chlorophyll remaining. Xanthophyll concentrations declined in relation to chlorophyll to the same extent in both yellow- and red-leaved taxa. Declines in the maximum photosystemII quantum yield of leaves collected prior to dawn were only slightly less in the red-senescing species, indicating no long-term protective activity. Red-leaved species had significantly greater mass/area and lower chlorophylla/b ratios during senescence. Nitrogen tissue concentrations in mature and senescent leaves negatively correlated to anthocyanin concentrations in senescent leaves, weak evidence for more efficient nitrogen resorption in anthocyanic species. Shading retarded both chlorophyll loss and anthocyanin production in Cornus alternifolia, Acer rubrum, Acer saccharum, Quercus rubra and Viburnum alnifolium. It promoted chlorophyll loss in yellow-senescing Fagus grandifolia. A reduced red:far-red ratio did not affect this process. Anthocyanins did not increase leaf temperatures in Q.rubra and Vaccinium corymbosum on cold and sunny days. The timing of leaf-fall was remarkably constant from year to year, and the order of senescence of individual species was consistent.     

Lipopeptides: adjuvanticity in conventional and genetic immunization

Synthetic lipopeptides derived from the bacterial cell wall component lipoprotein activate B-lymphocytes and macrophages/monocytes in vitro. In vivo they constitute potent immunoadjuvants for a broad range of different antigens and species comparable or superior to Freund's adjuvant. Here, we demonstrate that P(3)CSK(4), representing a highly active lipopentapeptide derivative in vitro, significantly enhances and accelerates the humoral immune response to tetanus toxoid. P(3)CSK(4) could substitute for up to 90% of the antigen without any decrease in the specific IgG level, and the presence of the lipopeptide resulted in a prolonged production of specific IgG in time. Investigations using P(3)CSK(4) as an adjuvant in genetic immunization confirmed earlier data demonstrating that lipopeptides constitute adjuvants for low-immunogenic DNA constructs and/or for application routes resulting in weak immune responses. We monitored a lipopeptide-dependent shift from a Th1-type to Th2-type response, when DNA immunization was followed by i.p. administration of the lipopeptide adjuvant.     

Recombinant expression and antigenic properties of a 31.5-kDa keratinolytic subtilisin-like serine protease from Microsporum canis

A secreted 31.5-kDa keratinolytic subtilase (SUB3; AJ431180) is thought to be a Microsporum canis virulence factor and represents a candidate for vaccination trials. In this study, the recombinant keratinase (r-SUB3) was produced by the Pichia pastoris expression system and purified to homogeneity. Recombinant SUB3 displayed identical biochemical properties with the native protease. Experimentally cutaneously infected guinea pigs showed specific lymphoproliferative response towards r-SUB3, while no specific humoral immune response was induced except for one animal. The heterologous expression of SUB3 provides a valuable tool for addressing further investigations on the role of this keratinase in the specific cellular immune response and on its use in vaccination trials in the cat.     

Interactions of the pyridine-2-carboxaldehyde isonicotinoyl hydrazone class of chelators with iron and DNA: implications for toxicity in the treatment of iron overload disease

Iron chelation therapy for the management of iron-overload disease is dominated by desferrioxamine (DFO). However, treatment using DFO is very arduous. Recently, novel Fe chelators of the pyridine-2-carboxaldehyde isonicotinoyl hydrazone (PCIH) class have shown high chelation efficacy and the potential to replace DFO. A critical consideration in the design of alternatives to DFO is that the chelator forms a redox-inert Fe complex. In the present study, the participation of Fe complexes in redox reactions has been investigated. Ascorbate oxidation in the presence of Fe(III) or benzoate hydroxylation in the presence of Fe(II) was not enhanced by the PCIH analogues. However, redox-induced DNA strand breaks were observed with these ligands under highly oxidizing conditions in the presence of Fe(II) and hydrogen peroxide. Experiments then examined the interactions of the PCIH analogues with DNA, and this was found to be weak. Considering this, we suggest that under extreme conditions seen in the DNA-strand break assay, weak DNA-binding may potentiate the redox activity of the PCIH analogues. However, importantly, in contrast to naked plasmid DNA, DNA damage by these chelators using intact human cells was not significant. Collectively, our results support the potential of the PCIH analogues for the treatment of Fe overload.     

Archaeobotanic evidence of the preincaic Chiribaya culture. Determination of capsaicinoids in archaeological samples of Capsicum frutescens and votive foods

The lack of Capsicum species or paprika (a basic ingredient of Peruvian foodstuff) in preincaic archaeological samples and votive foods, as evidenced by archaeobotanic studies, has stimulated the chemical analyses of these samples by HPLC methods. The results confirmed the absence of capsaicinoids in these samples whereas they were detected in more ancient fossil fruit.     

Antimicrobial activity of Mitracarpus scaber extract and isolated constituents

The antimicrobial activity of a methanol extract and isolated constituents of Mitracarpus scaber, a species used in folk medicine by West African native people, was evaluated against Staphylococcus aureus and Candida albicans strains. The mitracarpus methanol extract possesses both antibacterial and antimycotic activities (minimum inhibitory concentration-MIC 31.25 and 62.50 microg ml-, respectively). This extract was subsequently fractioned and monitored by bioassays leading to the isolation of seven compounds screened for antibacterial and antimycotic activities. Among these compounds, gallic acid and 3,4,5-trimethoxybenzoic acid inhibited the growth of Staph. aureus (MIC 3.90 and 0.97 microg ml-). 4-Methoxyacetophenone and 3,4,5-trimethoxyacetophenone effectively inhibited C. albicans (MIC 1.95 microg ml-). The other compounds (kaempferol-3-O-rutinoside, rutin and psoralen) which were also isolated showed low antibacterial and antimycotic activities (125-500 microg ml-).     

Systematic study of high molecular weight compounds in Amazonian plants by high temperature gas chromatography-mass spectrometry

The fractions of hexane and dichloromethane extraction from marupá (Simaruba amara) and (Bertholletia excelsa) leaves were analyzed by HT-HRGC (high temperature high resolution gas chromatography) and HT-HRGC coupled to mass spectrometry (HT-HRGC-MS). Several compounds can be characterized including unusual high molecular weight compounds.