Pseudodeflectusin, a novel isochroman derivative from Aspergillus pseudodeflectus a parasite of the sea weed, Sargassum fusiform, as a selective human cancer cytotoxin

A new isochroman derivative named pseudodeflectusin was isolated from a culture broth of Aspergillus pseudodeflectus. The structure was determined by spectroscopic means as 9-hydroxy-7-methyl-2-(methylethylidine)-furano[3,2-H]isochroman-3-one. This compound exhibited cytotoxicity for several human cancer cell lines from the stomach (NUGC-3), cervix (HeLa-S3), and peripheral blood (HL-60), but did not affect those from the lung (A549) or colon (DLD-1). The LD50 value of this compound for HL-60 cells was 39 microM.     

Mitochondria and autoimmunity in primary biliary cirrhosis

Primary biliary cirrhosis is an enigmatic autoimmune liver disease that predominantly affects women and is characterized by antimitochondrial antibodies and specific destruction of small bile ducts. Interestingly, patients with this disease not only have high titer antibodies to mitochondria, but also highly directed, liver-specific CD4 and CD8 cells directed at the same mitochondrial autoantigens. These mitochondrial autoantigens are all members of the 2-oxo dehydrogenase complex family and include the E2 component of pyruvate dehydrogenase as the major autoantigen. Moreover, the epitopes recognized by CD4, CD8 T cells and autoantibody, are all directed within the same region, namely the lipoyl domain of pyruvate dehydrogenase complex-E2. All cells in the body have mitochondria but there appear to be specific destruction of biliary cells. We believe that this specific destruction is secondary to a highly directed mucosal response that focuses on biliary cells because of the involvement of a polymeric immunoglobulin receptor, the presence of immunoglobulin A in mucosal secretions, and the unique apoptotic properties of biliary epithelium.     

CLIP-170 family members: a motor-driven ride to microtubule plus ends

CLIP-170 family proteins regulate microtubule plus end dynamics. Two reports published in this issue of Developmental Cell show that Bik1 and tip1p, the CLIP-170-like proteins of budding and fission yeast, are carried to microtubule plus ends by kinesin motor proteins. These findings indicate a complex interplay between microtubule-associated proteins and suggest a novel mechanism by which kinesin proteins stabilize microtubules.     

Effect of irradiance on the partitioning of assimilated carbon during the early phase of grain filling in rice

Low irradiance in the early phase of grain filling in rice often results in a low grain yield, but its effects on the partitioning of previously or recently assimilated carbon within the plant or panicle have not been seriously examined. The objective of this study was to demonstrate the effect of shading during the different stages in the early phase of grain filling on the partitioning of previously or recently assimilated carbon among constituent organs and into superior and inferior spikelets of the panicle in rice (Oryza sativa L. 'Sasanishiki') plants using 13C as a tracer. Plants were grown either under low (shading) or moderate (non-shading) irradiance (120 and 800 micromol quantum m(-2) s(-1)) for 3 or 4 d before or after the 13CO2 feeding at heading, full-heading or milky stages during the early phase of grain filling. Four days after the 13CO2 feeding, the proportion of labelled (previously assimilated) carbon partitioned into the panicle was 17% higher in plants grown under low irradiance compared with plants grown under moderate irradiance at the full-heading stage (7-11 d after heading), while the proportion partitioned into the culm was 13% lower. The light treatments for 3 d were conducted before the 13CO2 feeding and partitioning of the labelled (recently-assimilated) carbon into spikelets was examined 6 h after feeding. The amount of labelled carbon partitioned into the spikelets of the secondary branch (inferior grains) in the plants grown under low irradiance was only 31% when compared with plants grown under moderate irradiance at the full-heading stage, although the partitioning of labelled carbon into the apical spikelets of the primary branch (superior grains) was not affected by the light treatments. These results clearly indicate that preferential partitioning of assimilated carbon into the panicle occurs under low irradiance at around 7-11 d after heading and that the priority of superior spikelets for assimilated carbon intensifies. This phenomenon is thought to be an important strategy for such rice cultivars as used in this study to achieve a certain proportion of ripened grains even under light limited conditions.     

A series of immune responses leading to the induction ofT cell IL-12/IL-18 responsiveness in patientswith relatively large tumor burdens

The induction of interleukin-12 (IL-12) responsiveness in T cells depends on T cell receptor (TCR) triggering, and is regarded as a parameter of recently TCR-sensitized T cells. Here, we investigated whether IL-12 responsiveness could be detected in freshly prepared T cells from tumor-bearing patients, and if so whether such patients exhibited additional immunological parameters related to IL-12 responsiveness. CD4(+) and CD8(+) T cell populations from an appreciable proportion of tumor-bearing patients exhibited high levels of IL-12 responsiveness as evaluated by IL-12-stimulated interferon-gamma (IFN-gamma) production. T cell populations with high IL-12 responsiveness were observed in the group of patients with moderate to large tumor mass or tumor metastases rather than in patients with small tumors. The frequency of such a T cell population was also lower in post-surgery tumor-free patients, showing the correlation between IL-12 responsiveness and the presence of a certain extent of tumor burden. More importantly, a higher incidence of IL-12 responsiveness was observed in tumor-bearing patients exhibiting detectable plasma IL-12 levels, and correlated with IL-18 responsiveness. T cell IL-12 and IL-18 responsiveness is induced by TCR triggering and subsequent IL-12 stimulation respectively. Furthermore, TCR-triggered T cells stimulate antigen-presenting cells (APC) to produce IL-12. Therefore, the present observations suggest that an immune response loop from TCR sensitization to the induction of IL-12/IL-18 responsiveness via IL-12 production operates in tumor-bearing patients, particularly in those with relatively large tumor burdens.     

Macrophage-tropic simian/human immunodeficiency virus chimeras use CXCR4, not CCR5, for infections of rhesus macaque peripheral blood mononuclear cells and alveolar macrophages

After the nearly complete and irreversible depletion of CD4(+) T lymphocytes induced by highly pathogenic simian/human immunodeficiency virus chimeric viruses (SHIVs) during infections of rhesus monkeys, tissue macrophages are able to sustain high levels (>10(6) viral RNA copies/ml) of plasma viremia for several months. We recently reported that the virus present in the plasma during the late macrophage phase of infection had acquired changes that specifically targeted the V2 region of gp120 (H. Imamichi et al., Proc. Natl. Acad. Sci. USA 99:13813-13818, 2002); some of these SHIV variants were macrophage-tropic (M-tropic). Those findings have been extended by examining the tropic properties, coreceptor usage, and gp120 structure of five independent SHIVs recovered directly from lymph nodes of late-stage animals. All of these tissue-derived SHIV isolates were able to infect alveolar macrophages. These M-tropic SHIVs used CXCR4, not CCR5, for infections of rhesus monkey PBMC and primary alveolar macrophages. Because the starting highly pathogenic T-tropic SHIV inoculum also utilized CXCR4, these results indicate that the acquisition of M-tropism in the SHIV-macaque system is not accompanied by a change in coreceptor usage. Compared to the initial T-tropic SHIV inoculum, tissue-derived M-tropic SHIVs from individual infected animals carry gp120s containing similar changes (specific amino acid deletions, substitutions, and loss of N-linked glycosylation sites), primarily within the V1 and/or V2 regions of gp120.     

Characterization of nucleotide pyrophosphatase-5 as an oligomannosidic glycoprotein in rat brain

Membrane glycoproteins of neural cells play crucial roles in axon guidance, synaptogenesis, and neuronal transmission. We have here characterized membrane glycoproteins containing terminal alpha-mannose residues in rat brain membranes. Affinity purification using Galanthus nivalis agglutinin, that is highly specific for terminal alpha-mannose residues, revealed a 50-kDa protein as well as 80-kDa SHPS-1 and 45-kDa beta2 subunit of Na,K-ATPase in rat brain membranes. Combination of N-terminal peptide sequencing and mass spectrometry indicated that the 50-kDa protein was rat nucleotide pyrophosphatase-5 (NPP-5). In contrast to other NPPs, NPP-5 was a type-I transmembrane protein. Northern blot analysis showed that NPP-5 was highly expressed in brain, but also expressed in other peripheral tissues. However, we could not detect either the NPP activity or the lysophospholipase D activity in the immunoprecipitates with antibodies to NPP-5 from rat brain membranes. These data, therefore, suggest that NPP-5 is a neural oligomannosidic glycoprotein that may participate in neural cell communications.     

A novel DNA polymerase inhibitor and a potent apoptosis inducer: 2-mono-O-acyl-3-O-(alpha-D-sulfoquinovosyl)-glyceride with stearic acid

Sulfo-glycolipids in the class of sulfoquinovosyl diacylglycerol (SQDG) including the stereoisomers are potent inhibitors of DNA polymerase alpha and beta. However, since the alpha-configuration of SQDG with two stearic acids (alpha-SQDG-C(18)) can hardly penetrate cells, it has no cytotoxic effect. We tried and succeeded in making a permeable form, sulfoquinovosyl monoacylglycerol with a stearic acid (alpha-SQMG-C(18)) from alpha-SQDG-C(18) by hydrolysis with a pancreatic lipase. alpha-SQMG-C(18) inhibited DNA polymerase activity and was found to be a potent inhibitor of the growth of NUGC-3 cancer cells. alpha-SQMG-C(18) arrested the cell cycle at the G1 phase, and subsequently induced severe apoptosis. The arrest was correlated with an increased expression of p53 and cyclin E, indicating that alpha-SQMG-C(18) induced cell death through a p53-dependent apoptotic pathway.