Epidermal tumourigenesis can be achieved in rodents by the application of a single subthreshold dose of a carcinogen (initiation) followed by repeated applications of a tumour promoter such as 12-0-tetradecanoyl phorbol, 13-acetate (TPA). TPA induces terminal differentiation in the majority of epidermal keratinocytes in vitro. However, transformed keratinocytes respond weakly to this terminal d...

H abitat change and invasions of alien species are usually listed as the two biggest causes of biodiversity loss. When the two coincide, the results can be devastating, because altered habitat often favors alien species adapted to the changed conditions. This is particularly true in streams and rivers of North America, where homogenization of fish faunas through extinction of native species and...

~ Organic matter from aquatic and terrestrial sources provides the carbon energy that 'drives' aquatic food webs. Most streams and rivers are heterotrophic — that is, more carbon is consumed (e.g. by animals and bacteria) than is produced within the system by aquatic plants. However, despite the presence of vast amounts of carbon in streams and rivers, only a small proportion of the total is tr...

Bankfull discharge was identified in some 30 gravel-bed rivers representing in total c. 40 gauging stations. The catchment sizes vary from 4km2 to nearly 2700km2. Bankfull discharge value increases with basin size. In the case of gravel-bed rivers developed on an impermeable substratum, the following equation emerges: Qb=0·087 A 1·044. Bankfull discharge recurrence interval was determined by fi...

Convergent evolution is characterized by the independent evolution of similar phenotypes within similar selective environments. Previous work on Trinidadian killifish, Rivulus hartii, demonstrated repeatable life-history differences across communities that differ in predation intensity. These studies were performed in rivers located on the south slope of Trinidad's Northern Range Mountains. The...

Given recent focus on large rivers as conduits for excess nutrients to coastal zones, their role in processing and retaining nutrients has been overlooked and understudied. Empirical measurements of nutrient uptake in large rivers are lacking, despite a substantial body of knowledge on nutrient transport and removal in smaller streams. Researchers interested in nutrient transport by rivers (dis...

The sediment fluxes of the Moulouya and the Sebou Rivers – the two largest rivers in Morocco – were estimated on the basis of suspended sediment loads carried by these rivers towards the coastal zone. The high rate of the specific sediment yield of the Sebou (995 t km year), which is one of the highest in Africa, is probably due to the fact that the drainage basin is characterized by young moun...

We sampled 6 rivers of the piedmont region of Venezuela during the dry seasons of 1997 and 1998 to compare physical, chemical, and biological features and evaluate the influence of natural and anthropogenic differences in their watersheds. These 6 watersheds lie in a northeast-to-southwest transect along the interior slope of the Andes. Human disturbance declines and elevation of river origin i...

Chlorophyll-a and nutrient concentrations were monitored at weekly intervals across 21 river sites throughout the River Thames basin, southern England, between 2009 and 2011. Despite a 90% decrease in soluble reactive phosphorus (SRP) concentration of the lower River Thames since the 1990s, very large phytoplankton blooms still occur. Chlorophyll concentrations were highest in the mid and lower...