Changes in humus forms and soil animal communities in two developmental phases of Norway spruce on an acidic substrate.

This study focuses on the relationships between forest dynamics and changes in humus forms and animal communities in three areas of spruce forest at two developmental phases: two areas with 24-year-old trees (mean age) and one area with 136-year-old trees located in the Italian Alps. Mesofauna and macroarthropods were identified at the level of zoological group, order, super-family or family, when possible. They were then classified into morphotypes on the basis of features observable under a magnifying glass. The humus form varied from amphimull to dysmull in the 24-year-old spruce stands (regeneration), and was a dysmoder under the 136-year-old trees (adult). Results of correspondence analysis and ANOVA indicated that soil pH was higher in regeneration stands, where animal communities were mainly characterized by high densities of collembola, centipedes, and macrofauna. The diversity of zoological (and functional) groups was also higher in regeneration stands. The two regeneration stands differed only in the abundance of gamasids and Protura. Soil carbon and nitrogen contents increased in the mature spruce stand, as did the C/N ratio. The abundance of animals increased due to higher densities of mites, particularly oribatids while collembola, macrofauna, zoological diversity and the rate of disappearance of the litter decreased. The comparison of morphotype assemblages by hierarchical agglomerative clustering indicated that the shift between 24-year-old and 136-year-old trees, observed for humus forms, also occurred for animal communities. Differences in soil characteristics and animal communities between the two phases of the forest cycle corresponded to those generally observed between mull and moder, except for collembola which are generally more abundant in the thick organic layers of moder soils. Our findings confirm the change in humus form previously noted by other authors in the French Alps, but are inconsistent with data on humus forms and collembola and oribatid mite populations from Northern Europe. We conclude that changes in invertebrate communities, particularly arthropods, with the growth phases of spruce may be attributed to (1) soil impoverishment, due to the increased rate of nutrients and water uptake by growing trees; and (2) increase in recalcitrant litter input, mostly transformed by oribatid mites. Our data indicated that animal communities and humus forms could be a reliable means of assessing functional characteristics of the ecosystem corresponding to each growth phase of spruce. # 2006 Elsevier B.V. All rights reserved

Digital implementations for determination of temporal light artefacts of LED luminaires

Flicker and stroboscopic effects caused by a temporally modulated light source may be harmful for the human visual system. Standardized measurement methods have been developed for the related temporal light artefacts of LED luminaires. It was found out that the performance of the International Electrotechnical Commission (IEC) recommended flickermeter implementation is highly dependent on sampling frequency. Novel digital implementations for the flickermeter and stroboscopic effect visibility measure (SVM) were created to remove any inaccuracies. The performance of the novel Aalto implementations does not depend on the sampling frequency when running the test waveforms of the IEC standard through the implementations. As compared with the IEC recommended digital implementations, Aalto flickermeter decreases the average error related to the test waveforms from −0.05 to +0.003, and Aalto SVM meter also decreases the average error by almost two orders of magnitude.</p

Overlapping and distinct pRb pathways in the mammalian auditory and vestibular organs

Retinoblastoma gene (Rb1) is required for proper cell cycle exit in the developing mouse inner ear and its deletion in the embryo leads to proliferation of sensory progenitor cells that differentiate into hair cells and supporting cells. In a conditional hair cell Rb1 knockout mouse, Pou4f3-Cre-pRb™/™, pRb™/™ utricular hair cells differentiate and survive into adulthood whereas differentiation and survival of pRb™/™ cochlear hair cells are impaired. To comprehensively survey the pRb pathway in the mammalian inner ear, we performed microarray analysis of pRb™/™ cochlea and utricle. The comparative analysis shows that the core pathway shared between pRb™/™ cochlea and utricle is centered on e2F, the key pathway that mediates pRb function. A majority of differentially expressed genes and enriched pathways are not shared but uniquely associated with pRb™/™ cochlea or utricle. In pRb™/™ cochlea, pathways involved in early inner ear development such as Wnt/β-catenin and Notch were enriched, whereas pathways involved in proliferation and survival are enriched in pRb™/™ utricle. Clustering analysis showed that the pRb™/™ inner ear has characteristics of a younger control inner ear, an indication of delayed differentiation. We created a transgenic mouse model (ER-Cre-pRbflox/flox) in which Rb1 can be acutely deleted postnatally. Acute Rb1 deletion in the adult mouse fails to induce proliferation or cell death in inner ear, strongly indicating that Rb1 loss in these postmitotic tissues can be effectively compensated for, or that pRb-mediated changes in the postmitotic compartment result in events that are functionally irreversible once enacted. This study thus supports the concept that pRb-regulated pathways relevant to hair cell development, encompassing proliferation, differentiation and survival, act predominantly during early development

Sox2 and Jagged1 Expression in Normal and Drug-Damaged Adult Mouse Inner Ear

Inner ear hair cells detect environmental signals associated with hearing, balance, and body orientation. In humans and other mammals, significant hair cell loss leads to irreversible hearing and balance deficits, whereas hair cell loss in nonmammalian vertebrates is repaired by the spontaneous generation of replacement hair cells. Research in mammalian hair cell regeneration is hampered by the lack of in vivo damage models for the adult mouse inner ear and the paucity of cell-type-specific markers for non-sensory cells within the sensory receptor epithelia. The present study delineates a protocol to drug damage the adult mouse auditory epithelium (organ of Corti) in situ and uses this protocol to investigate Sox2 and Jagged1 expression in damaged inner ear sensory epithelia. In other tissues, the transcription factor Sox2 and a ligand member of the Notch signaling pathway, Jagged1, are involved in regenerative processes. Both are involved in early inner ear development and are expressed in developing support cells, but little is known about their expressions in the adult. We describe a nonsurgical technique for inducing hair cell damage in adult mouse organ of Corti by a single high-dose injection of the aminoglycoside kanamycin followed by a single injection of the loop diuretic furosemide. This drug combination causes the rapid death of outer hair cells throughout the cochlea. Using immunocytochemical techniques, Sox2 is shown to be expressed specifically in support cells in normal adult mouse inner ear and is not affected by drug damage. Sox2 is absent from auditory hair cells, but is expressed in a subset of vestibular hair cells. Double-labeling experiments with Sox2 and calbindin suggest Sox2-positive hair cells are Type II. Jagged1 is also expressed in support cells in the adult ear and is not affected by drug damage. Sox2 and Jagged1 may be involved in the maintenance of support cells in adult mouse inner ear