Myc and Max: molecular evolution of a family of proto-oncogene products and their dimerization partner.

The myc gene family encodes a group of transcription factors that regulate cell proliferation and differentiation. These genes are widely studied because of their importance as proto-oncogenes. Phylogenetic analyses are described here for 45 Myc protein sequences representing c-, N-, L-, S-, and B-myc genes. A gene duplication early in vertebrate evolution produced the c-myc lineage and another lineage that later gave rise to the N- and L-myc lineages by another gene duplication. Evolutionary divergence in the myc gene family corresponds closely to the known branching order of the major vertebrate groups. The patterns of sequence evolution are described for five separate highly conserved regions, and these analyses show that differential rates of sequence divergence (= mosaic evolution) have occurred among conserved motifs. Further, the closely related dimerization partner protein Max exhibits significantly less sequence variability than Myc. It is suggested that the reduced variability in max stems from natural selection acting to preserve dimerization capability with products of myc and related genes.

Organic properties of sediments and amino acids in iterstitial waters of ODP Holes 111-677A and 111-678B

The basement at Ocean Drilling Program (ODP) Sites 677 and 678 originated from the Galapagos spreading center of the Costa Rica Rift and has moved about 200 km over the last 6 m.y. (Fig. 1) (Shipboard Scientific Party, 1987, 1988; Scientific Drilling Party, 1987). Sediments about 300 m thick cover basement so young that basal sediments at Sites 677 and 678 have been reheated up to 60?-70?C at Site 677 and altered to limestone and/or chert (Shipboard Scientific Party, 1988). Sediments from both sites indicate (1) a high sedimentation rate (about 48 m/m.y.) and (2) biogenic silica and carbonate as the main constituents of sediments (Table 1) (Shipboard Scientific Party, 1988). Heatflow observations and measurements of interstitial water chemistry around the sites show that Site 677 is in a lower heatflow zone (166 mW/m**2; 1°12.14'N, 83°44.22'W) whereas Site 678 is located in a zone of higher heat flow (250 mW/m**2; 1°13.01'N, 83°43.39'W) (Langseth et al., 1988; Shipboard Scientific Party, 1988). In the flank hydrothermal systems, circulating solution is moving upward through the sedimentary column in zones of higher heat flow while it is moving downward in zones of lower heat flow (Anderson and Skilbeck, 1981). The chemistry of the interstitial waters is modified by several processes such as (1) diagenetic reactions and (2) advective and (3) diffusive transports of dissolved constituents. Analyses of Ca2+ and Mg2+ in interstitial waters from Sites 677 and 678 show that their profiles are mainly controlled by advective transport (Shipboard Scientific Party, 1988). In contrast, the interstitial-water profiles for NH4+, Si, and PO4[3-] are highly affected by reactions in the sediments. Site 677 offers a good opportunity to investigate amino acids in the interstitial waters because sediments of similar compositions have been deposited at constant rates of sedimentation. There are few previous works on amino acid distributions in interstitial waters (Henrichs and Parrington, 1979; Michaelis et al., 1982; Henrichs et al., 1984; Henrichs and Farrington, 1987; Ishizuka et al., 1988). In this chapter, we report (1) Rock-Eval analysis and (2) the composition of total hydrolyzable and dissolved free amino acids (THAA and DFAA, respectively) in the interstitial waters. Our objectives are to discuss (1) the possible origin of organic materials, (2) the characteristics of THAA and DFAA, and (3) their relationships in interstitial waters.

(Table 3) Textural and bulk mineralogy of Pliocene and Pleistocene sediments from ODP Hole 161-976B

The Pliocene and Pleistocene deposits recovered at Site 976 from the northwestern Alboran Sea at the Málaga base-of-slope include five main sedimentary facies: hemipelagic, turbidite, homogeneous gravity-flow, contourite, and debris-flow facies. The thickness and vertical distribution of these facies into lithostratigraphic Units I, II, and III show that the turbidites and hemipelagic facies are the dominant associations. The Pliocene and Pleistocene depositional history has been divided into three sedimentary stages: Stage I of early Pliocene age, in which hemipelagic and low-energy turbidites were the dominant processes; Stage II of early Pleistocene/late Pliocene age, in which the dominant processes were the turbidity currents interrupted by short episodes of other gravity flows (debris-flows and homogeneous gravity-flow facies) and bottom currents; and Stage III of Pleistocene age, in which both hemipelagic and low-energy gravity-flow processes occurred. The sedimentation during these three stages was controlled mainly by sea-level changes and also by the sediment supply that caused rapid terrigenous sedimentation variations from a proximal source represented by the Fuengirola Canyon.

Abundance of copepods from multinet samples during POLARSTERN cruise ANT-XXII/2 (ISPOL)

The mesozooplankton community, with special emphasis on calanoid copepods, was studied with respect to its species composition, abundance, vertical distribution and developmental structure during the ISPOL expedition to the ice covered western Weddell Sea. Stratified zooplankton tows were carried out nine times between December 1, 2004 and January 2, 2005 with a multiple opening-closing net between 0 and 1000 m depth. Copepods were by far the most abundant taxon contributing more than 94% of the total mesozooplankton. Numerical dominants were cyclopoid copepods, mostly Oncaea spp. A total of 66 calanoid copepod species were identified, but the calanoid copepod community was characterised by the dominance of only a few species. The most numerous species was Microcalanus pygmaeus, which comprised on average 70% of all calanoids. Calanoides acutus and Metridia gerlachei represented other abundant calanoid species contributing an average of 8 and 7%, respectively. All other species comprised less than 3%. The temporal changes in the abundance and population structure of M. pygmaeus and M. gerlachei were small while a shift in the stage frequency distribution of C. acutus was observed during the study: CIV dominated the C. acutus population with 48 to 50% during the first week of December, while CV comprised 48% in late December. CI and CII of C. acutus were absent in the samples and males occurred only in very low numbers in greater depths. In M. gerlachei, CI was not found, whereas all developmental stages of M. pygmaeus occurred throughout the study. All three species showed migratory behaviour, and they occurred in upper water layers towards the end of the investigation. This vertical ascent was most pronounced in C. acutus and relatively weak in the other two species. In M. pygmaeus and M. gerlachei, copepodite stages were responsible for the upward migration in late December, while the vertical distribution of adults did not change. In C. acutus all abundant developmental stages (CIV, CV and females) ascended to upper water layers. Almost exclusively (93%) medium- and semi-ripe females of C. acutus and M. gerlachei were found, and only 3 - 4% of the ovaries were ripe. The absence of CI and the low number of ripe females indicate that the main reproductive period had not started in C. acutus and M. gerlachei until the end of our study in early January. In contrast, the high portion of CI and CII of M. pygmaeus suggests that reproduction of this species had started in October-November and hence, before the onset of the phytoplankton bloom in the water. The community structure did not differ between stations with one exception on December 26, when the station was strongly influenced by the continental shelf.

Stable carbon and oxygen isotope ratios of benthic and planktic foraminifera from the Atlantic Ocean

Benthonic foraminifera in late Pleistocene deep-sea cores show significant variation in delta 13C with depth in sediment. This, and the report by Sommer et al., (in prep) of delta 13C variations in planktonic foraminifera, indicate that the delta13C in dissolved oceanic CO2 undergoes a significant change in a few thousand years. This is in apparent contradiction to the estimated 300 ka residence time for carbon in the ocean. It is suggested that this is a consequence of changes in the terrestrial plant biomass, which has a delta13C of about -25?. Postulated changes in world vegetation, particularly in tropical rainforests during the Late Pleistocene, were sufficient to produce change of the magnitude observed. Rapid expansions of forests between 13 ka and 8 ka ago may have resulted in the striking accumulation of aragonite pteropods in Atlantic Ocean sediments of the age. Rapid deforestation during an interglacial-glacial transition probably caused the intense carbonate dissolution which is observed in Equatorial Pacific Ocean sediments deposited over this interbal. The current rate of injection of fossil fuel CO2 into the atmosphere is substantially greater than the rate at which it was added during post-interglacial aridification in the tropics.

(Table 1) Soil density and concentration of 10Beryllium and 26Aluminium in samples from two ash deposits in the McMurdo Dry Valleys

The McMurdo Dry Valleys, Antarctica (MDV) are among the oldest landscapes on Earth, and some landforms there present an intriguing apparent contradiction such that millions of years old surface deposits maintain their meter-scale morphology despite the fact that measured erosion rates are 0.1-4 m/Ma. We analyzed the concentration of cosmic ray-produced 10Be and 26Al in quartz sands from regolith directly above and below two well-documented ash deposits in the MDV, the Arena Valley ash (40Ar/39Ar age of 4.33 Ma) and the Hart ash (K-Ar age of 3.9 Ma). Measured concentrations of 10Be and 26Al are significantly less than expected given the age of the in situ air fall ashes and are best interpreted as reflecting the degradation rate of the overlying sediments. The erosion rate of the material above the Arena Valley ash that best explains the observed isotope profiles is 3.5 ± 0.41 x 10**-5 g/cm**2/yr (~0.19 m/Ma) for the past ~4 Ma. For the Hart ash, the erosion rate is 4.8 ± 0.21 x 10**-4 g/cm**2/yr (~2.6 m/Ma) for the past ~1 Ma. The concentration profiles do not show signs of mixing, creep, or deflation caused by sublimation of ground ice. These results indicate that the slow, steady lowering of the surface without vertical mixing may allow landforms to maintain their meter-scale morphology even though they are actively eroding.

Down-core distribution of live and dead benthic foraminifera in deep sea sediments from the Weddell Sea and the Californian continental borderland

Five short cores sub-sampled from box cores from three sites in the eastern Weddell Sea off Antarctica and in the eastern Pacific off southern California, covering a range in water depth from 500 to 2000 m, were analysed for the down-core distribution of live (stained with Rose Bengal) and dead benthic foraminifera. In the California continental borderland, Planulina ariminensis, Rosalina columbiensis and Trochammina spp. live attached to agglutinated polychaetes tubes that rise above the sedimentwater interface. Bolivina spissa lives exclusively in or on the uppermost sediment. Stained specimens of Chilostomella ovoidea are found down to 6 cm within the sediment and specimens of Globobulimina pacifica down to a maximum of 8 cm. Delta13C values of live G. pacifica decrease with increasing depth from the sediment surface down to 7 cm core depth, indicating that this infaunal species utilizes13C-depleted carbon from pore waters. In the dead, predominantly calcareous benthic forminiferal assemblage, selective dissolution of small delicate tests in the upper sediment column causes a continuous variation in species proportions. In the eastern Weddell Sea, the calcareous Bulimina aculeata lives in a carbonate corrosive environment exclusively in or on the uppermost sediment. The arenaceous Cribrostomoides subglobosum, Recurvoides contortus and some Reophax species are frequently found within the top 4 cm of the sediment, whereas stained specimens of Haplophragmoides bradyi, Glomospira charoides and Cribrostomoides wiesneri occur in maximum abundance below the uppermost 1.5 cm. Species proportions in the dead, predominantly arenaceous, benthic foraminiferal assemblage change in three distinct steps. The first change is caused by calcite dissolution at the sediment-water interface, the second coincides with the lower boundary of intense bioturbation, and the third results from the geochemical shift from oxidizing to reducing conditions below a compacted ash layer.