Ribosomal DNA shows extremely low genetic divergence in a world-wide distributed,but disjunct and highly adapted marine protozoan (Virgulinella fragilis,Foraminiferida)

Virgulinella fragilis can be mainly observed in different, separated, oxygen-depleted and sulfide-enriched environments around the world and seems to be well adapted to such extreme habitats. Dispersal mechanisms behind this geographical distribution pattern are not yet understood. To analyze the genetic differentiation of geographically isolated populations, we conducted molecular phylogenetic analyses of the small subunit (SSU) ribosomal DNA (rDNA) and internal transcribed spacers (ITS) of rDNA nucleotide sequences in populations of V. fragilis collected in the South Atlantic (upwelling area off Namibia) and in the Pacific (Wellington Harbor, New Zealand, and Namako-ike, Japan). Our molecular analyses revealed SSU rDNA and ITS sequences strikingly similar or identical among these three disjunct populations. Such a low molecular genetic differentiation, a fixation rate converging to zero, could either arise from rapid dispersal, ultraslow mutation rates due to a strictly asexual mode of reproduction, unlimited genetic exchange between populations or the existence of a resting stage for survival under unfavorable conditions. We discuss each explanation and conclude that V. fragilis might possibly represent a protozoan trapped in evolutionary stasis.     

Glycemic control reverses increases in urinary excretions of immunoglobulin G and ceruloplasmin in type 2 diabetic patients with normoalbuminuria.

To examine whether urinary excretions of plasma proteins with molecular radii of 45-55 A and different isoelectric points such as IgG (pI = 7.4) and ceruloplasmin (pI = 4.4) increase selectively in normoalbuminuric type 2 diabetic patients, urinary albumin excretion rate (AER), renal clearances of IgG, ceruloplasmin and alpha2-macroglobulin, and creatinine clearance (Ccr) were studied in timed overnight urine samples of 36 diabetic outpatients and 16 control subjects. Furthermore, to examine effect of glycemic control on these urinary protein excretions, the same analysis was performed before and after glycemic control in 17 diabetic inpatients admitted for glycemic control. Renal clearances of IgG and ceruloplasmin were significantly higher in diabetic outpatients than in the control group, whereas AER and renal clearance of alpha2-macroglobulin did not differ. Glycemic control caused significant decreases in renal clearances of IgG and ceruloplasmin, accompanied with tendency for Ccr to decrease (p = 0.055). The present results, together with our previous finding of selectively increased urinary excretions of 45-55 A sized plasma proteins in parallel with enhanced glomerular filtration rate after acute protein loading, led us to conclude that enhanced intraglomerular hydraulic pressure may cause increases in clearances of IgG and ceruloplasmin, and that this change can be reversed by strict glycemic control in normoalbuminuric diabetic patients.     

A novel anticancer ribonucleoside, 1-(3-C-ethynyl-beta-D-ribo-pentofuranosyl)cytosine, enhances radiation-induced cell death in tumor cells

1-(3-C-Ethynyl-beta-D-ribo-pentofuranosyl)cytosine (ECyd, TAS106) is a newly developed anti-tumor agent that targets RNA synthesis. We report here that a low dose of ECyd induces radiosensitization of caspase-dependent apoptosis and reproductive cell death in cells of the gastric tumor cell lines MKN45 and MKN28 and murine rectum adenocarcinoma Colon26. Flow cytometry demonstrated that TAS106 induced the abrogation of the X-ray-induced G(2)/M checkpoint. Western blot analysis showed that X rays increased the expression of cyclin B1, phospho-Cdc2 and Wee1, whereas co-treatment with X rays and TAS106 decreased the expression of these cell cycle proteins associated with the G(2)/M checkpoint. Furthermore, TAS106 was shown to decrease the radiation-induced expression of survivin but not Bcl2 and BclX(L) regardless of TP53 status and cell type. Overexpression of wild-type survivin in MKN45 cells inhibited the induction of apoptosis induced by co-treatment with X rays and TAS106. These results suggest that TAS106 enhances X-ray-induced cell death through down-regulation of survivin and abrogation of the cell cycle machinery.     

Biogeochemical processes in the saline meromictic Lake Kaiike, Japan: implications from molecular isotopic evidences of photosynthetic pigments

Stable carbon and nitrogen isotopic compositions were determined for individual photosynthetic pigments isolated and purified from the saline meromictic Lake Kaiike, Japan, to investigate species-independent biogeochemical processes of photoautotrophs in the natural environment. In the anoxic monimolimnion and benthic microbial mats, the carbon isotopic compositions of BChls e and isorenieratene related to brown-coloured strains of green sulfur bacteria are substantially ( approximately 10 per thousand) depleted in (13)C relative to those found in the chemocline. In conjunction with 16S rDNA evidence reported previously, it strongly suggests that Pelodyctyon luteolum inhabited and photosynthesized in the anoxic monimolimnion and benthic microbial mats by using (13)C-depleted regenerated CO(2). By contrast, both Chl a and BChl a in the monimolimnion and microbial mats have similar isotopic compositions as they do in the chemocline, implying that the source organisms live only in the chemocline. In the chemocline, the nitrogen isotopic compositions of BChl e homologues ranges from -7.7 to-6.5 per thousand, whereas that of BChl a is -2.1 per thousand. These isotopic compositions suggest that green sulfur bacteria Chlorobium phaeovibrioides would conduct nitrogen fixation in the chemocline, whereas purple sulfur bacteria Halochromatium sp. and cyanobacteria Synechococcus sp. may assimilate nitrite.     

Distribution of chloropigments in suspended particulate matter and benthic microbial mat of a meromictic lake, Lake Kaiike, Japan

We investigated the distribution of chloropigments in a small meromictic lake, Lake Kaiike, south-west Japan. In the water-column, concentrations of Chl a related to cyanobacteria, BChl a related to purple sulphur bacteria, and three types of BChl e homologues (BChls e1, e2 and e3) related to brown-coloured green sulphur bacteria, were maximal at the redox boundary. Below the redox boundary, absolute concentrations of Chl a and BChl a gradually decreased with depth, whereas BChls e remained rather constant. Suspended particulate matter (SPM) at the deeper region of the anoxic water-column was enriched in highly alkylated BChl e homologues compared with SPM at the redox boundary. The shift in the relative content of highly alkylated BChl e homologues beneath the boundary was associated with community related adaptation of brown-coloured green sulphur bacteria to changes in light quality/quantity, resulting from the optical absorption and reflectance of SPMs in the overlying water-column. Benthic microbial mats were characterized by high abundances of BChls e, in which highly alkylated homologues were substantially abundant. This suggests that the BChls e in the microbial mat may be derived from the low-light adapted brown-coloured green sulphur bacteria forming the bacterial mat.     

Autophagy is involved in anti-viral activity of pentagalloylglucose (PGG) against Herpes simplex virus type 1 infection in vitro

Pentagalloylglucose (PGG) is a natural polyphenolic compound with broad-spectrum anti-viral activity, however, the mechanisms underlying anti-viral activity remain undefined. In this study, we investigated the effects of PGG on anti-viral activity against Herpes simplex virus type 1 (HSV-1) associated with autophagy. We found that the PGG anti-HSV-1 activity was impaired significantly in MEF-atg7^–/– cells (autophagy-defective cells) derived from an atg7^–/– knockout mouse. Transmission electron microscopy revealed that PGG-induced autophagosomes engulfed HSV-1 virions. The mTOR signaling pathway, an essential pathway for the regulation of autophagy, was found to be suppressed following PGG treatment. Data presented in this report demonstrated for the first time that autophagy induced following PGG treatment contributed to its anti-HSV activity in vitro.     

Vertical niche partitioning between cryptic sibling species of a cosmopolitan marine planktonic protist

A large portion of the surface‐ocean biomass is represented by microscopic unicellular plankton. These organisms are functionally and morphologically diverse, but it remains unclear how their diversity is generated. Species of marine microplankton are widely distributed because of passive transport and lack of barriers in the ocean. How does speciation occur in a system with a seemingly unlimited dispersal potential? Recent studies using planktonic foraminifera as a model showed that even among the cryptic genetic diversity within morphological species, many genetic types are cosmopolitan, lending limited support for speciation by geographical isolation. Here we show that the current two‐dimensional view on the biogeography and potential speciation mechanisms in the microplankton may be misleading. By depth‐stratified sampling, we present evidence that sibling genetic types in a cosmopolitan species of marine microplankton, the planktonic foraminifer Hastigerina pelagica, are consistently separated by depth throughout their global range. Such strong separation between genetically closely related and morphologically inseparable genetic types indicates that niche partitioning in marine heterotrophic microplankton can be maintained in the vertical dimension on a global scale. These observations indicate that speciation along depth (depth‐parapatric speciation) can occur in vertically structured microplankton populations, facilitating diversification without the need for spatial isolation.     

Cytologic and Genetic Characteristics of Endobiotic Bacteria and Kleptoplasts of Virgulinella fragilis (Foraminifera)

The benthic foraminifer Virgulinella fragilis Grindell and Collen 1976 has multiple putative symbioses with both bacterial and kleptoplast endobionts, possibly aiding its survival in environments from dysoxia (5–45 μmol‐O₂/L) to microxia (0–5 μmol‐O₂/L) and in the dark. To clarify the origin and function of V. fragilis endobionts, we used genetic analyses and transmission electron microscope observations. Virgulinella fragilis retained δ‐proteobacteria concentrated at its cell periphery just beneath the cell membranes. Unlike another foraminifer Stainforthia spp., which retains many bacterial species, V. fragilis has a less variable bacterial community. This suggests that V. fragilis maintains a specific intracellular bacterial flora. Unlike the endobiotic bacteria, V. fragilis klepto‐plasts originated from various diatom species and are found in the interior cytoplasm. We found evidence of both retention and digestion of kleptoplasts, and of fragmentation of the kleptoplastid outer membrane that likely facilitates transport of kleptoplastid products to the host. Accumulations of mitochondria were observed encircling endobiotic bacteria. It is likely that the bacteria use host organic material for carbon oxidation. The mitochondria may use oxygen available around the δ‐proteobacteria and synthesize adenosine triphosphate, perhaps for sulfide oxidation.     

Domains of receptor mobility and endocytosis in the membranes of neonatal human erythrocytes in the membranes of neonatal human erythrocytes and reticulocytes are deficient in spectrin

It has previously shown (Schekman, R., and S.J. Singer, Proc. Natl. Acad. Sci. U.S.A. 73:4075-4079) that receptors in the membranes of neonatal human erythrocytes show a restricted degree of lateral mobility, whereas in adult human erythrocytes the receptors are essentially immobile. This restricted mobility is exhibited, for example, when concanavalin A (Con A) induces a limited clustering of its receptors in the neonatal erythrocyte membrane, resulting in the formation of invaginations and endocytic vesicles. This does not happen with adult cells. By the use of indirect immunoferritin labeling of ultrathin frozen sections of Con A-treated neonatal blood cells, we now show that the invaginations and endocytotic vesicles do not stain for spectrin, whereas the adjacent unperturbed membrane is heavily stained. The reticulocytes in the neonatal cell population undergo substantially more Con A-induced invagination and endocytosis than do the erythrocytes. These results lend strong support to the hypothesis that specialized discrete domains exist, or are induced, in the membranes of these neonatal cells, in which receptors are laterally mobile, whereas in the remaining (and predominant) part of the membrane the receptors are immobile. Such mobile domains are characterized by an absence of spectrin. During the maturation of the neonatal reticulocyte to erythrocyte, it is proposed that these domains are in large part, but not completely, eliminated.