Induction kinetics of delayed fluorescence of sun and shade leaves ofFagus sylvatica in the ms-range

Summary Induction kinetics of luminescence (=delayed chlorophyll fluorescence or delayed light emission) were measured with sun and shade leaves of a tall beech tree (Fagus sylvatica pendula, weeping beech). The kinetics detected in the ms-range are contrasted for the upper and the lower leaf side. The influence of the following parameters is demonstrated: time of dark-adaptation prior to the measurement, intensity of the excitation light and photoinhibitory treatment. The effects are discussed with respect to chlorophyll concentration, absorption of the excitation light, reabsorption of the luminescence and photosynthetic activity of the leaf tissue. It is shown that the luminescence signal and its kinetic are determined mainly by the properties of the mesophyll parenchyma facing the detector. Thus the more densely packed palisade parenchyma at the upper leaf side exhibits a lower luminescence and a slower kinetic than the spongy parenchyma at the lower leaf side, which is characterized by many aerial interspaces. Our study shows that luminescence kinetics can be applied to interpret the physiological state of a specific leaf tissue. They may serve as an indicator of disorders in the photosynthetic function.     

Agar yield and quality of Gracilaria chilensis (Gigartinales,Rhodophyta) in tank culture using fish effluents

Tank cultivation of Gracilaria using fish effluents has permitted a production of 48 kg m^–2 yr^–1 and can reduce the dissolved nitrogen loads in the seawater. We report the yield, gel strength, gelling and melting point of agar from Gracilaria cultivated in tanks with seawater previously utilized in intensive, land-based salmon cultures and compared to a control using directly pumped seawater, over a study period of 22 months. The results show that the highest agar yield (20 to 22%) was obtained when Gracilaria was cultivated with pure seawater as compared to the fish effluents. The gel strength, gelling and melting point were higher in the agar obtained from algae cultured with fish effluents. During the spring, the gel strength, gelling and melting point increased in tanks with fish effluents and decreased in tanks with a supply of pure seawater.     

Effects of hypercalcemia-producing tumor extract and parathyroid hormone on osteoclast ultrastructure

Hypercalcemia is a frequent complication of cancer. Recently, parathyroid hormone-related protein has been isolated from tumors associated with this syndrome. In the present study, the effects of tumor-derived hypercalcemic factor and bovine parathyroid hormone (PTH) on bone were compared in an organ culture system using calvarial bones from newborn mice. Mouse calvaria were incubated for 72 h with control medium or media containing 0.15 mg/m tumor extract (TE) or 2 x 10(-9) M PTH. Bone resorption, as assessed by the amount of calcium released into the medium and the number of osteoclasts counted on light microscopy, was increased by both PTH and TE. On electron microscopy, areas for cytoplasm, ruffled border and clear zone were statistically increased in PTH- and TE-treated calvaria as compared to control. These values were not significantly different between PTH- and TE-treated calvaria. The study therefore demonstrates that the ultrastructural changes in osteoclasts induced by the hypercalcemia-producing TE are similar to those induced by PTH.     

Biomarkers Reveal Diverse Microbial Communities in Black Smoker Sulfides from Turtle Pits (Mid-Atlantic Ridge,Recent) and Yaman Kasy (Russia,Silurian)

The steep biogeochemical gradients near deep sea hydrothermal vents provide various niches for microbial life. Here we present biosignatures of such organisms enclosed in a modern and an ancient hydrothermal sulfide deposit (Turtle Pits, Mid-Atlantic Ridge, Recent; Yaman Kasy, Russia, Silurian). In the modern sulfide we found high amounts of specific bacterial and archaeal biomarkers with δ¹³C values between ?8 and ?37‰ VPDB. Our data indicate the presence of thermophilic members of the autotrophic Aquificales using the reductive tricarboxylic acid (rTCA) cycle as well as of methanogenic and chemolithoheterotrophic Archaea. In the ancient sample, most potential biomarkers of thermophiles were obscured by compounds derived from allochthonous organic matter (OM), except for an acyclic C₄₀ biphytane and its C₃₉ breakdown product. Both samples contained high amounts of unresolved complex mixtures (UCM) of hydrocarbons. Apparently, OM in the sulfides had to withstand high thermal stress, indicated by highly mature hopanes, steranes, and cheilanthanes with up to 41 carbon atoms.     

VEGF and therapeutic opportunities in cardiovascular diseases

In the past ten years, alternative revascularization strategies have come from bench to bedside focusing on the growth of new vessels to replace the old. Hypoxia and vascular endothelial growth factor may induce capillary growth; however, atherosclerosis affects large conductance vessels, which can only be replaced by functional collateral arteries.     

Phenylpropanoids, phenylalanine ammonia lyase and peroxidases in elicitor-challenged cassava (Manihot esculenta) suspension cells and leaves

BACKGROUND AND AIMS: Control of diseases in the key tropical staple, cassava, is dependent on resistant genotypes, but the innate mechanisms are unknown. The aim was to study phenylpropanoids and associated enzymes as possible defence components. METHODS: Phenylalanine ammonia-lyase (PAL), phenylpropanoids and peroxidases (POD) were investigated in elicited cassava suspension cells and leaves. Yeast elicitor was the most effective of several microbial and endogenous elicitors. Fungitoxicity was determined against the cassava pathogens Fusarium solani, F. oxysporum and the saprotroph Trichoderma harzianum. KEY RESULTS: A single and rapid (> or =2-3 min) oxidative burst, measured as hydrogen peroxide, occurred in elicited cells. PAL activity was induced maximally at 15 h and was preceded by PAL mRNA accumulation, which peaked at 9 h. Symplasmic POD activity increased four-fold in cells, 48 h post-elicitation. POD isoforms (2-7 isoforms, pI 3.1-8.8) were detected in elicited and unelicited cells, extracellular medium and leaves but two extracellular isoforms were enhanced post-elicitation. Also expression of a cassava peroxidase gene MecPOD1 increased in elicited cells. Only anionic forms oxidized scopoletin, with highest activity by isoform pI 3.6, present in all samples. Unidentified phenolics and possibly scopolin increased post-elicitation, but there was no enhancement of scopoletin, rutin or kaempferol-3-O-rutinoside concentration. Fungal germ tube elongation was inhibited more than germination by esculetin, ferulic acid, quercetin and scopoletin. T. harzianum was generally more sensitive than the pathogens and was inhibited by > or =50 microg mL(-1) of ferulic acid and quercetin and > or =10 microg mL(-1) of scopoletin. CONCLUSIONS: Phenolic levels in cells were not enhanced and were, theoretically, too low to be inhibitory. However, in combination and when oxidized they may contribute to defence, because oxidation of esculetin and scopoletin by peroxidase and of esculetin by tyrosinase enhanced their fungitoxicity up to 20-fold.     

Oxidative stress responses during cassava post-harvest physiological deterioration

A major constraint to the development of cassava (Manihot esculenta Crantz) as a crop to both farmers and processors is its starchy storage roots’ rapid post-harvest deterioration, which can render it unpalatable and unmarketable within 24–72 h. An oxidative burst occurs within 15 min of the root being injured, that is followed by the altered regulation of genes, notably for catalase and peroxidase, related to the modulation of reactive oxygen species, and the accumulation of secondary metabolites, some of which show antioxidant properties. The interactions between these enzymes and compounds, in particular peroxidase and the coumarin, scopoletin, are largely confined to the vascular tissues where the visible symptoms of deterioration are observed. These, together with other data, are used to develop a tentative model of some of the principal events involved in the deterioration process.     

The asymmetry of transient response in compression versus release for cartilage in unconfined compression

Observations in compression tests of articular cartilage have revealed unequal load increments for compression and release of the same amplitude applied to a disk with an identical previously imposed compression (in equilibrium). The mechanism of this asymmetric transient response is investigated here using a nonlinear fibril-reinforced model. It is found that the asymmetry is predominantly produced by the fibril stiffening with its tensile strain. In addition, allowing the hydraulic permeability to decrease significantly with compressive dilatation of cartilage increases the transient fibril strain, resulting in a stronger asymmetry. Large deformation also enhances the asymmetry as a consequence of stronger fibril stiffening.     

Tailor-made dyes for fluorescence correlation spectroscopy (FCS)

Two new fluorescent labels are presented that are optimized for excitation with He/Ne laser and red diode lasers. Application in FCS and labeling of proteins and oligomers are demonstrated. A strong rise of quantum yield and emission life time upon binding to biomolecules are characteristic features of the dyes.