Erratum

Untypical ageing off-ßavour and masking effects due to long-term nitrogen fertilizationVitis 46 (1), 33-38 (2007

Untypical ageing off-flavour and masking effects due to long-term nitrogen fertilization

The off-flavour UTA (untypical ageing) of wines produced from the vintages 1996-1999 within the scope of a long-term N fertilization experiment was compared to the o-aminoacetophenone (AAP) concentrations found in these wines. The wines were made of plants treated with 0, 60 and 150 kg N ha-1·N fertilization led to higher UTA intensities and AAP concentrations in aged wines; due to stronger fruity aromas with increasing N fertilization, young wines were able to mask AAP. Controls had a stronger masking effect in older wines, caused by antioxidants (phenols) and possibly higher alcohols. Moreover, at the same AAP level, wines from the vintages 1996 and 1998 exhibited lower UTA intensity than wines from 1997 and 1999. This is influenced by N supply, yield and time of harvest which can not be separated from each other.

Ambivalence of the influence of nitrogen supply on o-aminoacetophenone in 'Riesling' wine

AAP (o-aminoacetophenone) is the aroma substance responsible for the untypical ageing off-flavour (UTA). The impact of nitrogen supply on the formation of AAP was investigated between 1994 and 1999. The experiment was carried out in the Rheingau (Germany) with six fertigation treatments of annual quantities of N (0, 30, 60, 90, 150 kg·N·ha-1). Results indicated that the long-term varied N fertilization affected AAP concentration in wine as much as the year. Whereas a better N supply of the grapes due to effects of the year coincided with lower AAP values, the fertilization effect was reversal: higher N fertilization increased the concentrations of AAP. AAP did not correlate with its precursor IAA and only slightly with antioxidative capacity. Neither varying yield nor soluble solids could explain the high variance of AAP. An indicator for potential AAP formation could not be found, neither in must nor in wine.

Fundamental differences in patterns of retinal ageing between primates and mice

Photoreceptors have high metabolic demands and age rapidly, undermining visual function. We base our understanding mainly on ageing mice where elevated inflammation, extracellular deposition, including that of amyloid beta, and rod and cone photoreceptor loss occur, but cones are not lost in ageing primate although their function declines, revealing that primate and mouse age differently. We examine ageing primate retinae and show elevated stress but low inflammation. However, aged primates have a >70% reduction in adenosine triphosphate (ATP) and a decrease in cytochrome c oxidase. There is a shift in cone mitochondrial positioning and glycolytic activity increases. Bruch’s membrane thickens but unlike in mice, amyloid beta is absent. Hence, reduced ATP may explain cone functional decline in ageing but their retained presence offers the possibility of functional restoration if they can be fuelled appropriately to restore cellular function. This is important because as humans we largely depend on cone function to see and are rarely fully dark adapted. Presence of limited aged inflammation and amyloid beta deposition question some of the therapeutic approaches taken to resolve problems of retinal ageing in humans and the possible lack of success in clinical trials in macular degeneration that have targeted inflammatory agents

Endogenous VEGF Is Required for Visual Function: Evidence for a Survival Role on Müller Cells and Photoreceptors

Vascular endothelial growth factor (VEGF) is well known for its role in normal and pathologic neovascularization. However, a growing body of evidence indicates that VEGF also acts on non-vascular cells, both developmentally as well as in the adult. In light of the widespread use of systemic and intraocular anti-VEGF therapies for the treatment of angiogenesis associated with tumor growth and wet macular degeneration, systematic investigation of the role of VEGF in the adult retina is critical.Using immunohistochemistry and Lac-Z reporter mouse lines, we report that VEGF is produced by various cells in the adult mouse retina and that VEGFR2, the primary signaling receptor, is also widely expressed, with strong expression by Müller cells and photoreceptors. Systemic neutralization of VEGF was accomplished in mice by adenoviral expression of sFlt1. After 14 days of VEGF neutralization, there was no effect on the inner and outer retina vasculature, but a significant increase in apoptosis of cells in the inner and outer nuclear layers. By four weeks, the increase in neural cell death was associated with reduced thickness of the inner and outer nuclear layers and a decline in retinal function as measured by electroretinograms. siRNA-based suppression of VEGF expression in a Müller cell line in vitro supports the existence of an autocrine role for VEGF in Müller cell survival. Similarly, the addition of exogenous VEGF to freshly isolated photoreceptor cells and outer-nuclear-layer explants demonstrated VEGF to be highly neuroprotective.These results indicate an important role for endogenous VEGF in the maintenance and function of adult retina neuronal cells and indicate that anti-VEGF therapies should be administered with caution

Understanding the retinal basis of vision across species

The vertebrate retina first evolved some 500 million years ago in ancestral marine chordates. Since then, the eyes of different species have been tuned to best support their unique visuoecological lifestyles. Visual specializations in eye designs, large-scale inhomogeneities across the retinal surface and local circuit motifs mean that all species' retinas are unique. Computational theories, such as the efficient coding hypothesis, have come a long way towards an explanation of the basic features of retinal organization and function; however, they cannot explain the full extent of retinal diversity within and across species. To build a truly general understanding of vertebrate vision and the retina's computational purpose, it is therefore important to more quantitatively relate different species' retinal functions to their specific natural environments and behavioural requirements. Ultimately, the goal of such efforts should be to build up to a more general theory of vision