A comparative analysis of the diatom flora on the snail Ampullaria cuprina from the Goshen Ponds, Utah

Seventeen genera and 60 species of diatoms were identified from four different substrates in a warm spring - fed pond near Goshen, Utah. The diatom forms sampled included both plankton and periphyton. A minimum of 400 individuals were counted from each sample. Diversity and similarity indices were calculated, and substrate relationships were identified on their basis.     

Effect of natural iron fertilization on carbon sequestration in the Southern Ocean

The availability of iron limits primary productivity and the associated uptake of carbon over large areas of the ocean. Iron thus plays an important role in the carbon cycle, and changes in its supply to the surface ocean may have had a significant effect on atmospheric carbon dioxide concentrations over glacial-interglacial cycles. To date, the role of iron in carbon cycling has largely been assessed using short-term iron-addition experiments. It is difficult, however, to reliably assess the magnitude of carbon export to the ocean interior using such methods, and the short observational periods preclude extrapolation of the results to longer timescales. Here we report observations of a phytoplankton bloom induced by natural iron fertilization--an approach that offers the opportunity to overcome some of the limitations of short-term experiments. We found that a large phytoplankton bloom over the Kerguelen plateau in the Southern Ocean was sustained by the supply of iron and major nutrients to surface waters from iron-rich deep water below. The efficiency of fertilization, defined as the ratio of the carbon export to the amount of iron supplied, was at least ten times higher than previous estimates from short-term blooms induced by iron-addition experiments. This result sheds new light on the effect of long-term fertilization by iron and macronutrients on carbon sequestration, suggesting that changes in iron supply from below--as invoked in some palaeoclimatic and future climate change scenarios--may have a more significant effect on atmospheric carbon dioxide concentrations than previously thought.     

bicoid RNA localization requires specific binding of an endosomal sorting complex

bicoid messenger RNA localizes to the anterior of the Drosophila egg, where it is translated to form a morphogen gradient of Bicoid protein that patterns the head and thorax of the embryo. Although bicoid was the first localized cytoplasmic determinant to be identified, little is known about how the mRNA is coupled to the microtubule-dependent transport pathway that targets it to the anterior, and it has been proposed that the mRNA is recognized by a complex of many redundant proteins, each of which binds to the localization element in the 3' untranslated region (UTR) with little or no specificity. Indeed, the only known RNA-binding protein that co-localizes with bicoid mRNA is Staufen, which binds non-specifically to double-stranded RNA in vitro. Here we show that mutants in all subunits of the ESCRT-II complex (VPS22, VPS25 and VPS36) abolish the final Staufen-dependent step in bicoid mRNA localization. ESCRT-II is a highly conserved component of the pathway that sorts ubiquitinated endosomal proteins into internal vesicles, and functions as a tumour-suppressor by removing activated receptors from the cytoplasm. However, the role of ESCRT-II in bicoid localization seems to be independent of endosomal sorting, because mutations in ESCRT-I and III components do not affect the targeting of bicoid mRNA. Instead, VPS36 functions by binding directly and specifically to stem-loop V of the bicoid 3' UTR through its amino-terminal GLUE domain, making it the first example of a sequence-specific RNA-binding protein that recognizes the bicoid localization signal. Furthermore, VPS36 localizes to the anterior of the oocyte in a bicoid-mRNA-dependent manner, and is required for the subsequent recruitment of Staufen to the bicoid complex. This function of ESCRT-II as an RNA-binding complex is conserved in vertebrates and may clarify some of its roles that are independent of endosomal sorting.     

Diatoms of Oregon Caves National Monument, Oregon

The diatom flora of the Oregon Caves National Monument, Josephine Co., Oregon, was investigated. Diatoms were distributed throughout the cave system with abundance and species diversity depending upon moisture, light, availability of mineral nutrients, and proximity to cave openings. Twenty-six taxa were identified and described.     

Cloning and characterization of a new intercellular adhesion molecule ICAM-R.

The human intercellular adhesion molecules ICAM-1, ICAM-2 and their counter-receptors, the beta 2 or leukointegrins, mediate a variety of homotypic and heterotypic leukocyte and endothelial cell-cell adhesions central to immunocompetence. It has been found that cell-cell adhesion which is dependent on expression of the leukocyte function-associated antigen LFA-1 is not always blocked completely by antibodies raised against ICAM-1 and ICAM-2. Other leukointegrin ligands therefore probably exist, such as a glycoprotein of M(r) 124K that binds LFA-1 and has been designated ICAM-3 on the basis of this function. We have molecularly cloned a new member of the ICAM family, ICAM-R, which is related to ICAM-1 and ICAM-2. The complementary DNA encoding ICAM-R is 1,781 base pairs long and the protein has five extracellular immunoglobulin-family type domains. The mature cell-surface form of the ICAM-R protein has an M(r) which varies from 116 to 140K in a cell type-specific fashion. Overall identities in protein sequence with ICAM-1 and ICAM-2 are 48% and 31% respectively, with the degree of similarity varying between individual domains. The high level of expression of ICAM-R on resting leukocytes of all lineages and its lack of expression on either resting or cytokine-activated endothelial cells indicates a pattern of expression distinct from ICAM-1 and ICAM-2. In common with ICAM-1 and ICAM-2, ICAM-R is a ligand for the beta 2-integrin CD11a/LFA-1 (CD18).     

Genetic evidence for a novel familial Alzheimer's disease locus on chromosome 14.

Familial Alzheimer's disease (FAD) has been shown to be genetically heterogeneous, with a very small proportion of early onset pedigrees being associated with mutations in the amyloid precursor protein (APP) gene on chromosome 21, and some late onset pedigrees showing associations with markers on chromosome 19. We now provide evidence for a major early onset FAD locus on the long arm of chromosome 14 near the markers D14S43 and D14S53 (multipoint lod score z = 23.4) and suggest that the inheritance of FAD may be more complex than had initially been suspected.     

Molecular cloning, expression and regional distribution of rat ciliary neurotrophic factor

Ciliary neurotrophic factor (CNTF) was originally characterized as a survival factor for chick ciliary neurons in vitro. More recently, it was shown to promote the survival of a variety of other neuronal cell types and to affect the differentiation of E7 chick sympathetic neurons by inhibiting their proliferation and by inducing the expression of vasoactive intestinal peptide immunoreactivity (VIP-IR). In cultures of dissociated sympathetic neurons from newborn rats, CNTF induces cholinergic differentiation as shown by increased levels of choline acetyltransferase (ChAT). This increase is paralleled by a reduction of tyrosine hydroxylase (TH) activity. Moreover, CNTF promotes the differentiation of bipotential 02A progenitor cells to type-2-astrocytes in vitro. To help establish which, if any, of these functions CNTF exerts in vivo, it is necessary to determine its primary structure, cellular expression, developmental regulation and localization. The complementary DNA-deduced amino-acid sequence and subsequent expression of cDNA clones covering the entire coding region in HeLa-cells indicate that CNTF is a cytosolic protein. This, together with its regional distribution and its developmental expression, show that CNTF is not a target-derived neurotrophic factor. CNTF thus seems to exhibit neurotrophic and differentiation properties only after becoming available either by cellular lesion or by an unknown release mechanism.