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(6) strongly supported this latter possibility. Thus EBV-positive Burkitt lymphoma (BL) cell lines displaying the latency I form of infection, in which only the nuclear antigen EBNAl is expressed, could readily be induced into apoptosis by signals such as serum withdrawal or treatment with calcium ionophore (5). In contrast BL lines that had progressed on serial passage to a latency III form of infection, with expression of the full spectrum of latent proteins, including nuclear antigens EBNAs 1, 2, 3A, 3B, 3C, and LP and the latent membrane proteins (LMPs) 1 and 2, showed enhanced cell survival under such conditions. Gene transfers into apoptosis-sensitive B-cell lines mapped this protective effect to LMP1 and indicated a likely mechanism, namely, LMPl-mediated up-regulation of the cellular protein Bcl-2 (7). Importantly Bcl-2, a membrane-associated protein with a distinctive pattern of cytoplasmic localization (8, 9), not only enhances cell survival in a variety of experimental situations (7, 9-15) but also appears to be involved in the physiological selection of B cells into memory (16 (Fig. 1).Transfections. Transient transfections into COS-1 cells using DEAE-dextran and stable transfections into the EBVpositive BL cell lines Wan-BL (23), Akata-BL (24), and Raji-BL (25) by using electroporation were performed as described (7,26). For the latter, selection was in hygromycin B at 300 ug/ml (pHEBO-based constructs) or G418 at 2.5 mg/ml ref. 27

Epstein-Barr virus (EBV), a human herpesvirus, establishes a persistent asymptomatic infection of the circulating B-lymphocyte pool. The mechanism of virus persistence is not understood but, given the limited lifespan of most B cells in vivo, it seems most likely that EBV-infected cells must gain access to the long-lived memory B-cell pool. Here we show in an in vitro system that EBV, through expression of the full set of eight virus-coded 'latent' proteins, can protect human B cells from programmed cell death (apoptosis), the deletion mechanism which normally restricts entry into memory. We have found that EBV-positive Burkitt's lymphoma (BL) cell clones retaining the original tumour cell phenotype and expressing only one of the virus latent proteins, the nuclear antigen EBNA 1, are extremely sensitive to apoptosis; in this respect they resemble the tumour's normal cell of origin found in the germinal centres of lymphoid tissue. By contrast, isogenic BL cell clones which have activated expression of all eight EBV latent proteins are resistant to the induction of apoptosis. The EBV latent proteins should therefore be seen not just as activators of B-cell proliferation but, perhaps more importantly, as mediators of enhanced B-cell survival.

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Indeed, in vitro-transformed LCLs also grow when inoculated into SCID mice, the frequency of tumor outgrowth correlating with the in vitro growth phenotype ofthe LCL which is itself determined by the identity of the transforming virus (i.e., type 1 or type 2 EBV). Histologically the PB1.r derived hu-SCID tumors resemble the EBV + large cell lymphomas that develop in immunosuppressed patients and, like the human tumors, often present at multiple sites as individual monoclonal or oligoclonal foci. The remarkable efficiency oftumor development in the hu-SCID model suggests that lymphomagenesis involves direct outgrowth of EBVtransformed B cells without requirement for secondary genetic changes, and that selection on the basis of cell growth rate alone is sufficient to explain the monoclonal/oligoclonal nature of tumor foci. EBV + large cell lymphoma of the immunosuppressed may arise in a similar way. T he C.B-17 scid/scid mutant strain ofmouse (hereafter referred to as the SCID mouse) exhibits a severe combined immunodeficiency characterized by the absence of mature B and T lymphocytes (1) ; indeed, the mutation is thought to affect a component of the recombinase enzyme system involved in Ig and TCR gene rearrangements (2-4). The unexpected finding that mice carrying the SCID mutation could be grafted successfully with human (hu) haematopoietic cells has opened the way to the use ofthe hu-SCID chimeric mouse as a model for studying human immune-function in vivo (5-7). In addition, one of the original papers describing such engraftment showed that SCID mice reconstituted with high numbers of(hu-PBIJSCID mice) often developed lymphomas of B cell origin ifthe donor lymphocytes were from individuals with serological evidence of infection with EBV; these tumors were shown to carry EBV DNA but were otherwise poorly characterized (5) . It was immediately apparent from these studies that SCID mice could provide a potentially interesting in vivo model of human B lymphomagenesis involving an important viral pathogen .EBV is a human herpesvirus that in vitro has potent growth transforming activity for resting B lymphocytes but that in vivo is carried as an asymptomatic and persistent infection by >90% of adults worldwide . The virus is, however, consistently associated with two types of B cell malignancies: (a) large cell lymphomas which arise in immunocompromised individuals such as post-transplant patients (8, 9), and (b) the high incidence, or "endemic," form of Burkitt's lymphoma (BL)t which is geographically restricted to equatorial regions of Africa and Papua New Guinea where malaria is holoen-1 Abbreviations used in this paper. BL, Burkitt's lymphoma ; LCL, lymphoblastoid cell lines ; NGS, normal goat serum; NRS, normal rabbit serum ; VCA, viral capsid antigen complex .

Short CommunicationMapping terrestrial anthropogenic degradation on the inhabited islands of the Galapagos Archipelago J a m e s W a t s o n , M a n d y T r u e m a n , M a r t a T u f e t , S c o t t H e n d e r s o n and R a c h e l A t k i n s o n Abstract The Galapagos Archipelago is renowned for its high endemism but little effort has been made to quantify the human disturbance that compromises the islands' ecological integrity. We provide a quantitative assessment of anthropogenic degradation, which we define as areas either transformed by direct human activity or heavily invaded by four of the most prevalent alien plant species (Psidium guajava, Rubus niveus, Cinchona pubescens and Syzygium jambos). We assessed how the amount of degraded area varied among the six major vegetation zones (bare ground, littoral, arid, transition, humid and very humid) across five inhabited or formerly inhabited islands. Overall, we found that 37,833 ha (5.5%) of the Archipelago have been completely degraded. The islands that have suffered the greatest human impact (13,000-14,000 ha each) are Santa Cruz (the most populous) and Isabela (the largest). When vegetation type is considered the humid and very humid vegetation zones have been most affected by humans (29 and 45%, respectively). On San Cristobal and Santa Cruz 100 and 76%, respectively, of the very humid zone and 94 and 88%, respectively, of the humid zone have been transformed. These results are underestimations as mapping of the anthropogenic change in some vegetation zones (e.g. on Floreana) is poor, and the analysis did not take into account the effects of introduced animals. Nevertheless, this research points to an urgent need to prioritize restoration efforts in humid and very humid vegetation zones and to improve spatial mapping across the Archipelago to obtain a better understanding of the impacts of humans.

Comparisons between historical and recent ecological datasets indicate that shallow reef habitats across the central Galapagos Archipelago underwent major transformation at the time of the severe 1982/1983 El Niñ o warming event. Heavily grazed reefs with crustose coralline algae ('urchin barrens') replaced former macroalgal and coral habitats, resulting in large local and regional declines in biodiversity. Following recent threat assessment workshops, a total of five mammals, six birds, five reptiles, six fishes, one echinoderm, seven corals, six brown algae and nine red algae reported from coastal environments in Galapagos are now recognized as globally threatened. The 2008 International Union for the Conservation of Nature (IUCN) Red List includes 43 of these species, while two additional species (Galapagos damsel Azurina eupalama and 24-rayed sunstar Heliaster solaris) not seen for 425 years also fulfil IUCN threatened species criteria. Two endemic species (Galapagos stringweed Bifurcaria galapagensis and the damselfish A. eupalama) are now regarded as probably extinct, while an additional six macroalgal species (Dictyota galapagensis, Spatoglossum schmittii, Desmarestia tropica, Phycodrina elegans, Gracilaria skottsbergii and Galaxaura barbata) and the seastar H. solaris are possibly extinct. The removal of large lobster and fish predators by artisanal fishing probably magnified impacts of the 1982/1983 El Niñ o through a cascade of indirect effects involving population expansion of grazing sea urchins. Marine protected areas with adequate enforcement are predicted to ameliorate but not eliminate ecosystem impacts caused by increasing thermal anomalies associated with El Niñ o and global climate change.

Aim To quantify general differences in reef community structure between wellenforced and poorly enforced marine protected areas (MPAs) and fished sites across the Eastern Tropical Pacific (ETP) regional seascape Location The Pacific continental margin and oceanic islands of Costa Rica, Panama, Colombia and Ecuador, including World Heritage sites at Galapagos, Coiba, Cocos and Malpelo Methods Densities of reef fishes, mobile and sessile invertebrates, and macroalgae were quantified using underwater visual surveys at 136 'no-take' and 54 openly fished sites associated with seven large MPAs that encompassed a range of management strategies. Spatial variation in multivariate and univariate community metrics was related to three levels of fishing pressure (high-protection MPAs, limited-protection MPAs, fishing zones) for both continental and oceanic reefs.Results High-protection MPAs possessed a much greater biomass of higher carnivorous fishes, lower densities of asteroids and Eucidaris spp. urchins, and higher coral cover than limited-protection MPAs and fished zones. These results were generally consistent with the hypothesis that overfishing of predatory fishes within the ETP has led to increased densities of habitat-modifying macroinvertebrates, which has contributed to regional declines in coral cover. Major differences in ecological patterns were also evident between continental and oceanic biogeographic provinces.Main conclusions Fishing down the food web, with associated trophic cascades, has occurred to a greater extent along the continental coast than off oceanic islands. Poorly enforced MPAs generate food webs more similar to those present in fished areas than in well-protected MPAs.