Marine saline ponds as sedimentary archives of late Holocene climate and sea-level variation along a carbonate platform margin: Lee Stocking Island, Bahamas

A 1500-year, late Holocene history of coastal and lacustrine carbonate sedimentation is preserved in shallow ponds on Lee Stocking Island, Exuma Cays, Bahamas. Details of environmental change have been extracted by integrating lithostratigraphy, biostratigraphy (macrobiota, foraminifers, ostracodes), and chemical stratigraphy (C, O isotopes of foraminiferal and molluscan skeletal carbonate; MgO wt% of ostracode calcite) with a well defined ¹⁴C AMS radiocarbon chronology. Carbonate deposition began within physically restricted, euryhaline coastal embayments, with several pronounced changes in salinity defined by biotic and calculated salinity variation (from MgO wt% in shells of Cyprideis americana). By about 700–740 yr B.P., embayment closure occurred possibly related to changed longshore deposition associated with sea level rise and/or regional change in climate (previously documented). With closure, the initial euryhaline foraminifer assemblage was replaced by a predominant hypersaline biofacies (e.g., Triloculina sp.); with progressive basin fill, ostracode assemblages, calculated salinities, and variation in abundance of the gastropod Cerithidea sp. may resolve higher-order (and some extreme) salinity fluctuations throughout the remaining history of saline pond development. Foraminiferal isotope stratigraphy is compatible with that expected for hydrologically closed lake basins. Carbonate accumulation was effectively shut-down <200 years ago, replaced by stromatolitic growth. Present-day salinities vary according to water balance governed by rainfall and evaporation. A centuries-scale (300–400 year) flux of abraded (reworked), marine-derived bioclasts, admixed with skeletal remains of indigenous biota, is also preserved in these ponds. Allochthonous sediment was transported by hurricane storm surges or related to abrupt transgressive events superimposed on an overall gradual rise in global sea level. We discuss evidence for both as controls on sedimentation. Our study illustrates that saline ponds on Bahamian islands are excellent sedimentary archives of local, regional, and possibly global paleoclimatic events of late Holocene age.     

Effect of Mg2+ concentration, polyamines, streptomycin, and mutations in ribosomal proteins on the accuracy of the two-step selection of aminoacyl-tRNAs in protein biosynthesis

Discrimination against the binding of noncognate aminoacyl (aa)-tRNAs by mRNA-programmed ribosomes is the outcome of two selection steps, one involving an aa-tRNA.EFTu.GTP complex, which occurs prior to and includes GTP hydrolysis, the other involving the aa-tRNA alone, which follows GTP hydrolysis. Conditions which lead to errors in protein synthesis have been found to influence the accuracy of one or both selection steps in a system measuring poly(U)-directed binding of Leu-tRNA2Leu. Streptomycin has a large effect only on the discrimination process following GTP hydrolysis, but the other pertubations of recognition studied, high [Mg2+], polyamines, the strA1 and ram1 mutations, affect both discrimination processes. The general result is consistent with the view that proofreading of aa-tRNA by ribosomes for the most part uses the same specificity determinants used in the initial selection of a ternary complex.     

Anhydrobiosis and Freezing-Tolerance: Adaptations That Facilitate the Establishment of Panagrolaimus Nematodes in Polar Habitats

Anhydrobiotic animals can survive the loss of both free and bound water from their cells. While in this state they are also resistant to freezing. This physiology adapts anhydrobiotes to harsh environments and it aids their dispersal. Panagrolaimus davidi, a bacterial feeding anhydrobiotic nematode isolated from Ross Island Antarctica, can survive intracellular ice formation when fully hydrated. A capacity to survive freezing while fully hydrated has also been observed in some other Antarctic nematodes. We experimentally determined the anhydrobiotic and freezing-tolerance phenotypes of 24 Panagrolaimus strains from tropical, temperate, continental and polar habitats and we analysed their phylogenetic relationships. We found that several other Panagrolaimus isolates can also survive freezing when fully hydrated and that tissue extracts from these freezing-tolerant nematodes can inhibit the growth of ice crystals. We show that P. davidi belongs to a clade of anhydrobiotic and freezing-tolerant panagrolaimids containing strains from temperate and continental regions and that P. superbus, an early colonizer at Surtsey island, Iceland after its volcanic formation, is closely related to a species from Pennsylvania, USA. Ancestral state reconstructions show that anhydrobiosis evolved deep in the phylogeny of Panagrolaimus. The early-diverging Panagrolaimus lineages are strongly anhydrobiotic but weakly freezing-tolerant, suggesting that freezing tolerance is most likely a derived trait. The common ancestors of the davidi and the superbus clades were anhydrobiotic and also possessed robust freezing tolerance, along with a capacity to inhibit the growth and recrystallization of ice crystals. Unlike other endemic Antarctic nematodes, the life history traits of P. davidi do not show evidence of an evolved response to polar conditions. Thus we suggest that the colonization of Antarctica by P. davidi and of Surtsey by P. superbus may be examples of recent “ecological fitting” of freezing-tolerant anhydrobiotic propagules to the respective abiotic conditions in Ross Island and Surtsey.     

Blood lymphocyte volumes and diameters in patients with chronic lymphocytic leukemia and normal controls

The electronic modal lymphocyte volumes of 151 patients with chronic lymphocytic leukemia (CLL) and 305 normal controls were determined by the hydrodynamically focused multi-channel Coulter TF analyser. The mean volumes of the normally distributed groups were 166 +/- 19.3 (range 126-216) fl in patients with CLL and 206 +/- 14.4 (range 126 +/- 246) fl in normal controls. The calculated cell diameters were 6.8 (6.2-7.4) micron and 7.3 (6.8-7.8) micron respectively. Our data do not support previous reports about relations between cell size and clinical stages of the Rai and Binet classifications.