Expression of α2-macroglobulin receptor-associated protein in normal human epidermal melanocytes and human melanoma cell lines

α₂-Macroglobulin receptor/low-density lipoprotein receptor-related protein is a multifunctional cell surface receptor known to bind and internalize a large number of ligands. α₂-Macroglobulin receptor-associated protein acts as an intracellular “chaperone” for this receptor, and it has been shown to inhibit binding of all its known ligands. In this paper, we characterize the expression of the receptor-associated protein in both normal human epidermal melanocytes and in six different human melanoma cell lines, by the use of flow cytometry and Western blotting analysis. We show that all the melanoma cell lines and the normal melanocytes express the receptor-associated protein at similar levels, with most located intracellularly. No receptor-associated protein was detected at the cell surface in the melanocytes or in three of the cell lines. However, in two of the melanoma cell lines, large amounts of receptor-associated protein were found on the cell surface, these having the largest amounts of it reported to date; in a further melanoma cell line, there was a small amount at the cell surface. We have also shown that the melanocytes and all the melanoma cell lines express the receptor itself at a wide range of levels, the highest levels of both the cell surface receptor and the cell surface receptor-associated protein being found in one particular melanoma cell line. By growing the cell lines under controlled conditions, we have demonstrated that, although the total cellular content of the receptor is markedly increased at high cell culture density, this treatment has no effect on the level of expression of the receptor-associated protein. J. Cell. Biochem. 71:149–157, 1998. © 1998 Wiley-Liss, Inc.     

The changing face of genus Homo

Since its introduction in the 18th century, the genus Homo has undergone a number of reinterpretations, all of which have served to make it a more inclusive taxon. In this paper, we trace this trend towards greater inclusiveness, and explain how it has affected the way Homo is defined. We then demonstrate that the current criteria for identifying species of Homo are difficult, if not impossible, to operate using paleoanthropological evidence. We discuss alternative, verifiable, criteria, and show that when these new criteria are applied to Homo, two species, Homo habilis and Homo rudolfensis, fail to meet them. We contend that the lowest boundary of Homo should be redrawn so that the earliest species in the genus is Homo ergaster, or early African Homo erectus. The appearance of this species at around 1.9 Myr appears to mark a distinct shift in hominin adaptive strategy involving morphological and behavioral innovations.     

Persistence of historical population structure in an endangered species despite near‐complete biome conversion in California's San Joaquin Desert

Genomic responses to habitat conversion can be rapid, providing wildlife managers with time‐limited opportunities to enact recovery efforts that use population connectivity information that reflects predisturbance landscapes. Despite near‐complete biome conversion, such opportunities may still exist for the endemic fauna and flora of California's San Joaquin Desert, but comprehensive genetic data sets are lacking for nearly all species in the region. To fill this knowledge gap, we studied the rangewide population structure of the endangered blunt‐nosed leopard lizard Gambelia sila, a San Joaquin Desert endemic, using restriction site‐associated DNA (RAD), microsatellite and mtDNA data to test whether admixture patterns and estimates of effective migration surfaces (EEMS) can identify land areas with high population connectivity prior to the conversion of native xeric habitats. Clustering and phylogenetic analyses indicate a recent shared history between numerous isolated populations and EEMS reveals latent signals of corridors and barriers to gene flow over areas now replaced by agriculture and urbanization. Conflicting histories between the mtDNA and nuclear genomes are consistent with hybridization with the sister species G. wislizenii, raising important questions about where legal protection should end at the southern range limit of G. sila. Comparative analysis of different data sets also adds to a growing list of advantages in using RAD loci for genetic studies of rare species. We demonstrate how the results of this work can serve as an evolutionary guidance tool for managing endemic, arid‐adapted taxa in one of the world's most compromised landscapes.     

Macroinvertebrate community composition and diversity in ephemeral and perennial ponds on unregulated floodplain meadows in the UK

Ponds are common and abundant landscape features in temperate environments, particularly on floodplains where lateral connectivity with riverine systems persists. Despite their widespread occurrence and importance to regional diversity, research on the ecology and hydrology of temperate ephemeral and perennial floodplain ponds lags behind that of other shallow waterbodies. This study examines the aquatic macroinvertebrate diversity of 34 ponds (20 perennial and 14 ephemeral) on two unregulated riverine floodplain meadows in Leicestershire, UK. Perennial ponds supported nearly twice the diversity of ephemeral ponds. Despite frequent inundation of floodwater and connectivity with other floodplain waterbodies, ephemeral ponds supported distinct invertebrate communities when compared to perennial ponds. When the relative importance of physical, chemical, biological and spatial characteristics was examined, physical and chemical characteristics were found to account for more variation in community composition than biological or spatial variables. The results suggest that niche characteristics rather than neutral colonisation processes dominate the structure of invertebrate communities of floodplain ponds. The maintenance of pond networks with varying hydroperiod lengths and environmental characteristics should be encouraged as part of conservation management strategies to provide heterogeneous environmental conditions to support and enhance aquatic biodiversity at a landscape scale.