Despite being a harsh environment, sand dunes are rich in invertebrates, with about 30% (188 species) of the British spider fauna represented (Duffey, 1968), and 53 species being strongly associated with coasts (Ratcliffe, 1977). Arachnologists have examined spider communities in relation to the seral succession of plant communities on sand dunes (e.g. Lowrie, 1948; Barnes, 1953; Perttula, 1984...

Changes in freshwater inflow can cause changes in the distribution and diversity of marsh vegetation in estuarine habitats. In the fall of 2002 bankside vegetation was surveyed along the 24 km length of the Altamaha River estuary (n= 14 sites). Sites were quantified for multiple plant and edaphic parameters, including plant density, height, and tiller diameter. In this paper we present the char...

We have developed a perfusion bioreactor system that allows the formation of steady state oxygen gradients in cell culture. In this study, gradients were formed in cultures of rat hepatocytes to study the role of oxygen in modulating cellular functions. A model of oxygen transport in our flat-plate reactor was developed to estimate oxygen distribution at the cell surface. Experimental measureme...

In the process of morphogenesis primordia of lateral organs, like leaves or flowers, are formed at the shoot apical meristem (SAM). In order to maintain the ability to organ formation, the SAM itself has to be self-perpetuated, i.e. its general shape and size have to be maintained, despite the fact that portions of SAM periphery are continuously used up for lateral organ formation. Thus growth ...

In mammals, aldosterone is produced in the zona glomerulosa (zG), the outermost layer of the adrenal cortex, whereas glucocorticoids are produced in adjacent zona fasciculata (zF). However, the cellular mechanisms controlling the zonal development and the differential hormone production (i.e. functional zonation) are poorly understood. To explore the mechanisms, we defined zone-specific transcr...

Heterogeneous zonation of hepatic protein expression over the liver lobule has been recognized by using several analytical techniques, including microdissection, selective cell isolation, immunohistochemistry and hybridization of mRNA in situ. We previously employed the technique of dual-digitonin-pulse perfusion for the highly selective collection and analysis of periportal and perivenous solu...

The theoretical basis of the use of the multiple indicator dilution technique to account for the heterogeneous distribution (or zonation) of enzymes in the liver was explored. The microcirculation was assumed to consist of identical capillaries perfused in parallel, with enzymatic activities for drug metabolism being distributed uniformly over the upstream half (periportal or pp) or the downstr...