Abstract. A database of 15,617 point measurements of dimethylsulfide (DMS) in surface waters along with lesser amounts of data for aqueous and particulate dirhethylsulfoniopropionate concentration, chlorophyll concentration, sea surface salinity and temperature, and wind speed has been assembled. The database was processed to create a series of climatological annual and monthly 1øxl ø latitude-longitude squares of data. The results were compared to published fields of geophysical and biological parameters. No significant correlation was found between DMS and these parameters, and no simple algorithm could be found to create monthly fields of sea surface DMS concentration based on these parameters. Instead, an annual map of sea surface DMS was produced using an algorithm similar to that employed by Conkright et al. [1994]. In this approach, a first-guess field of DMS sea surface concentration measurements is created and then a correction to this field is generated based on actual measurements. Monthly sea surface grids of DMS were obtained using a similar scheme, but the sparsity of DMS measurements made the method difficult to implement. A scheme was used which projected actual data into months of the year where no data were otherwise present.

Significant dimethyl sulfide (DMS) production is confined to a few classes of marine phytoplankton, mainly the Dinophyceae (dinoflagellates) and the Prymnesiophyceae (which includes the coccolithophores). One hundred and twenty-three individual clones of phytoplankton representing twelve algal classes were examined in exponential growth for intra-and extracellular DMS (and its precursor DMSP). There is a strong correlation between the taxonomic position of the phytoplankton and the production of DMS. Although the Dinophyceae and Prymnesiophyceae predominate, other chromophyte algae (those possessing chlorophylls a and c) also contain and release significant amounts of DMS, including some members of the Chrysophyceae and the Bacillariophyceae (the diatoms). The chlorophytes (those algae possessing chlorophylls a and b) are much less significant producers of DMS with the exception of a few very small species. Other classes, including the cryptomonads and the cyanobacteria, are minor producers.The oceans are a significant source of organic sulfur compounds that are implicated in acid precipitation and the production of atmospheric aerosols which affect global climate. These compounds are largely biogenic in origin, the most important being dimethyl sulfide (DMS) produced by marine phytoplankton (1-4). Although the distribution of DMS is broadly similar to that of primary productivity (5.6). attempts to directly correlate DMS P roduction to primary production have been only moderately successful (e.g., ). This is mainly because only certain groups of algae are known to produce significant amounts of DMS. Thus, correlations of DMS with chlorophyll a measurements are often poor and need to be supplemented with information on species composition. Field observations nave implicated the colonial prymnesiopnyte, Phaeocystis sp., with high levels of DMS (4.8.9). Coccolithophores (members of the Prymnesiophyceae) and some dinoflagellates (Dinophyceae) have also been suspect (4.9).Until recently, no comprehensive survey of DMS production by phytoplankton has been made. Single clones of various marine species have been examined and of these, the coccolithophore, Hymenomonas (ex. Cricosphaera, Syracosphaera) carterae had the highest DMS levels (10.11).

A medium (K) developed for culturing fastidious oceanic phytoplankton has been tested using recently isolated ultraphytoplankton clones representing at least seven different algal classes. The medium was designed to satisfy as completely as possible the nutritional requirements of this diverse group of phytoplankters. Important aspects are the addition of selenium, the inclusion of both nitrate and ammonium, an increased level of chelation and a moderate level of pH buffering. The seawater‐based version of this medium has been tested on 200 clones of which 186 grew reliably. A synthetic counterpart (AK) was tested on 40 of the more difficult clones and 27 grew well; 13 grew not all. While neither medium meets the exacting nutritional needs of all the ultraphytoplankton forms tested, they are excellent for most oceanic clones and are very successful for the isolation and establishment in culture of new oceanic phytoplankton clones.

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Inactivation of the tumor suppressor gene RASSF1A by promoter hypermethylation represents a key event underlying the initiation and progression of lung cancer. RASSF1A inactivation is also associated with poor prognosis and may promote metastatic spread. In this study, we investigated how RASSF1A inactivation conferred invasive phenotypes to human bronchial cells. RNAi-mediated silencing of RASSF1A induced epithelialto-mesenchymal transition (EMT), fomenting a motile and invasive cellular phenotype in vitro and increased metastatic prowess in vivo. Mechanistic investigations revealed that RASSF1A blocked tumor growth by stimulating cofilin/PP2A-mediated dephosphorylation of the guanine nucleotide exchange factor GEF-H1, thereby stimulating its ability to activate the antimetastatic small GTPase RhoB. Furthermore, RASSF1A reduced nuclear accumulation of the Hippo pathway transcriptional cofactor Yes-associated protein (YAP), which was reinforced by RhoB activation. Collectively, our results indicated that RASSF1 acts to restrict EMT and invasion by indirectly controlling YAP nuclear shuttling and activation through a RhoB-regulated cytoskeletal remodeling process, with potential implications to delay the progression of RASSF1-hypermethylated lung tumors. Cancer Res; 76(6);

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