Telomere length in fibroblasts and blood cells from healthy centenarians

Several lines of evidence indicate that telomere shortening during in vitro aging of human somatic cells plays a causal role in cellular senescence. A critical telomere length seems to be associated with the replicative block characterizing senescent cells. In this paper we analyzed the mean length of the terminal restriction fragments (TRF) in fibroblast strains from 4 healthy centenarians, that is, in cells aged in vivo, and from 11 individuals of different ages. No correlation between mean TRF length and donor age was found. As expected, telomere shortening was detected during in vitro propagation of centenarian fibroblasts, suggesting that in fibroblasts aged in vivo telomeres can be far from reaching a critical length. Accordingly, chromosome analysis did not show the presence of telomeric associations in early passage centenarian fibroblasts. In blood cells from various individuals, the expected inverse correlation between mean TRF length and donor age was found. In particular, a substantial difference (about 2 kb) between telomere length in the two cell types was observed in the same centenarian. Expression analysis of three senescence-induced genes, i.e., fibronectin, apolipoprotein J, and p21, revealed for only the fibronectin expression levels a clear positive correlation with donor age. Our results suggest that (1) telomere shortening could play a different role in the aging of different cell types and (2) the characteristics of fibroblasts aged in vitro might not be representative of what occurs in vivo.     

The role of ascorbic acid role in the differentiation of sclerotia in Sclerotinia minor

Sclerotinia minor in culture produces ascorbic acid in levels dependent on oxidative growth conditions and stage of development. During differentiation reduced/oxidized ascorbate ratio decreased by 12 and 6 fold at high and low oxidative stress, respectively. Exogenous ascorbate caused a concentration-dependent decrease of oxidative stress (lipid peroxidation), inhibition of sclerotial differentiation (up to 100%) and delay of differentiatlon (up to 10 days). Ascorbic acid may be produced to help the fungus reduce oxidative stress during growth. The data of this study support our theory proposing that oxidative stress is the inducing factor of sclerotial differentiation in fungi.This revised version was published online in October 2005 with corrections to the Cover Date.     

Terpenes from Inula verbascifolia

The aerial parts of Inula verbascifolia afforded two new xanthanes and a new germacranolide derivative, together with the known compounds inusoniolide, 4-O-dihydroinusoniolide and 9beta-hydroxyparthenolide. The structures were determined by spectral methods (IR, HRMS,1H NMR, 13C NMR, DEPT, 1H-1H COSY, HMQC and HMBC).     

Site-dependent differences in transmittance and UV-B-absorbing capacity of isolated leaf epidermes and mesophyll in Urginea maritima (L.) Baker

The spectral transmittance of isolated 'intact' upper and lower epidermes as well as the extractable UV-B-absorbing capacity of epidermes and mesophyll were studied in the leaves of exposed and deeply shaded, field-grown plants of Urginea maritima (L.) Baker. Epidermal transmittance in the visible part of the spectrum was high (>80%) in all cases. Transmittance in the UV-B (280-320 nm) was comparatively high (c. 14%) in both the upper and lower epidermes of shaded plants, but more than an order of magnitude lower in exposed plants, with the lowest values observed on the upper leaf epidermis. UV-B transmittance was negatively correlated with the methanol extractable UV-B-absorbing capacity of the epidermes, but was independent of epidermal thickness. The UV-B-absorbing capacity of the mesophyll, when expressed on an area basis, was not affected by exposure. However, it was significantly higher in shaded plants, when expressed on a dry mass basis. The results indicate that although the concentrations of the UV-B-absorbing components of the whole leaf or its epidermis fluctuate according to the site-dependent radiation stress, the opposite is evident for the mesophyll. Therefore, high irradiance in U. maritima, apart from inducing an increase in UV-B-absorbing compounds on a whole leaf basis, also caused a change in the distribution of these compounds between epidermis and mesophyll.     

Reduction of ambient UV-B radiation does not affect growth but may change the flowering pattern of Rosmarinus officinalis L.

The effects of sub-ambient levels of UV-B radiation on the shrub Rosmarinus officinalis L. were investigated in a field filtration experiment in which the ambient UV-B was manipulated by a combination of UV-B transmitting and UV-B absorbing filters. As a result, the plants were receiving near-ambient or drastically reduced UV-B radiation doses. Drastic reduction of UV-B radiation had no effect on mean, total and maximum stem length, number of stems per plant, dry mass of leaves, stems and roots and leaf nitrogen and phenolic contents. However, flowering was more pronounced under reduced UV-B radiation during the winter period which coincides with ascending ambient UV-B radiation. In contrast, during autumn and early winter, a period which coincides with descending ambient UV-B radiation, flowering was unaffected by reduced UV-B radiation. We can conclude that natural UV-B radiation does not affect growth of Rosmarinus officinalis, but its reduction could influence the flowering pattern of the species.     

Nectar Amount, Pollinator Visit Duration and Pollination Success in the Mediterranean Shrub Cistus creticus

We have re-examined the nectar status of Cistus creticus, aplant that was previously thought to be an almost exclusivepollen donor. Although attempts to extract nectar with the microcapillarymethod failed, rinsates of the flower interior yielded considerableamounts of sugar, yet with high interplant variation. Enzymaticmicroassays revealed that secreted sugar is adsorbed onto thesurfaces of the numerous filaments surrounding the nectary,on the dense pubescence of the ovary surrounded by the nectaryand on the yellow base of the purplish-pink, free, obovate petals.The conclusion that C. creticus is an efficient nectar donorwas further strengthened by video recording the behaviour ofbees and by the high frequency of nectar thieves. We proposethat the shallow flower shape and the overheating caused bysolar tracking facilitate evaporative concentration of nectar.Alternatively (or in addition), the morphological proximityof the nectary to the filaments and the ovary pubescence facilitatesadsorption and the capillary action of the cell walls worksantagonistically to glass microcapillaries precluding nectarcollection. Addition of artificial nectar in the field had noeffect on bee visit frequency but it increased visit durationsignificantly and decreased abortion rates. In addition, seedyield was increased, especially under insect-limited conditions.We conclude that C. creticus is a nectar donor, and that nectarvariation in the field may modify pollinator behaviour and affectpollination success and the fitness of the plant. Copyright2000 Annals of Botany Company Cistus creticus, insect behaviour, nectar manipulation, pollination success, visit duration     

The transiently pubescent young leaves of plane (Platanus orientalis) are deficient in photodissipative capacity

We have analyzed reflectance changes and carotenoid composition of young and mature leaves of Platanus orientalis L. in order to test the hypothesis that the transient occurrence of highly absorptive and reflective leaf hairs of young leaves (M. Ntefidou and Y. Manetas 1996, Aust. J. Plant Physiol. 23: 535–538) may be correlated to a weakly developed photodissipative capacity in the chloroplast. Compared to mature leaves, young leaves showed negligible reflectance changes at 530 nm upon sudden illumination, possibly indicating a limited production of zeaxanthin. In addition, actual pigment analysis confirmed lower pools of xanthophyll cycle components and reduced capacity for violaxanthin photoconversion in young leaves. Accordingly, the epoxidation state at saturating photon fluence rates was particularly high. A notable feature of xanthophyll cycle interconversions in young leaves was the inability to drive the system to complete de-epoxidation, as antheraxanthin in the light was always higher than zeaxanthin. Among the rest of the carotenoids, the levels of β-carotene were particularly low. Moreover, most of the photosynthetic pigments were considerably bleached when young leaves were exposed to high light. The above results strongly suggest that young leaves possess a limited photodissipative capacity and therefore, the presence of leaf hairs affords protection against excess light. When the leaf has matured and presumably the concentrations of photoprotective compounds are adequate, the loss of hairs is not of consequence. In fact, their presence on mature leaves may reduce the photosynthetically active radiation to non-saturating levels for photosynthesis.     

The effects of UV-B radiation on European heathland species

The effects of enhanced UV-B radiation on three examples of European shrub-dominated vegetation were studied in situ. The experiments were in High Arctic Greenland, northern Sweden and Greece, and at all sites investigated the interaction of enhanced UV-B radiation (simulating a 15% reduction in the ozone layer) with artificially increased precipitation. The Swedish experiment also involved a study of the interaction between enhanced UV-B radiation and elevated CO₂ (600 ppm). These field studies were supported by an outdoor controlled environment study in the United Kingdom involving modulated enhancement of UV-B radiation in combination with elevated CO₂ (700 ppm). Effects of the treatments on plant growth, morphology, phenology and physiology were measured. The effects observed were species specific, and included both positive and negative responses to the treatments. In general the negative responses to UV-B treatments of up to three growing seasons were small, but included reductions in shoot growth and premature leaf senescence. Positive responses included a marked increase in flowering in some species and a stimulation of some photosynthetic processes. UV-B treatment enhanced the drought tolerance of Pinus pinea and Pinus halepensis by increasing leaf cuticle thickness. In general, there were few interactions between the elevated CO₂ and enhanced UV-B treatments. There was evidence to suggest that although the negative responses to the treatments were small, damage may be increasing with time in some long-lived woody perennials. There was also evidence in the third year of treatments for effects of UV-B on insect herbivory in Vaccinium species. The experiments point to the necessity for long-term field investigations to predict the likely ecological consequences of increasing UV-B radiation.     

Fatty acid-related modulations of membrane fluidity in cells: detection and implications

Abstract

Metabolic homeostasis of fatty acids is complex and well-regulated in all organisms. The biosynthesis of saturated fatty acids (SFA) in mammals provides substrates for β-oxidation and ATP production. Monounsaturated fatty acids (MUFA) are products of desaturases that introduce a methylene group in cis geometry in SFA. Polyunsaturated fatty acids (n-6 and n-3 PUFA) are products of elongation and desaturation of the essential linoleic acid and α-linolenic acid, respectively. The liver processes dietary fatty acids and exports them in lipoproteins for distribution and storage in peripheral tissues. The three types of fatty acids are integrated in membrane phospholipids and determine their biophysical properties and functions. This study was aimed at investigating effects of fatty acids on membrane biophysical properties under varying nutritional and pathological conditions, by integrating lipidomic analysis of membrane phospholipids with functional two-photon microscopy (fTPM) of cellular membranes. This approach was applied to two case studies: first, pancreatic beta-cells, to investigate hormetic and detrimental effects of lipids. Second, red blood cells extracted from a genetic mouse model defective in lipoproteins, to understand the role of lipids in hepatic diseases and metabolic syndrome and their effect on circulating cells.