Behavior of the groundwater in a riverine-type mangrove forest

The behavior of groundwater and physical properties of bottom sediment in a riverine-type mangrove forest which is composed of a tidal creek and fringing mangrove swamps were investigated through field observations at Iriomote Island, Japan. After the tidal water ebbed from the swamp surface to the creek, groundwater levels at swamp sites near the creek fell by up to 15 cm by the next flood tide, although the fall was negligible at sites far from the creek and at the open coast outside the mangrove forest. The amount of groundwater discharged to the creek from the swamp depended strongly both on the tidal range and the presence of the steep bank which separates the tidal creek from the fringing mangrove swamp. Based on the fall of groundwater level, the bulk hydraulic conductivity of the swamp was estimated to be 1.5×10⁻² cm/s. This value is two to three orders of magnitude larger than that measured in a laboratory using small scale sediment core samples collected in the swamp. These results suggest that the presence of crowded, intricate and large animal burrows as well as sediment layers rich in mangrove humus increases permeability in the mangrove swamp. Further, it is suggested that the mangrove topography with the steep bank of the tidal creek plays an important role which enhances material exchanges through groundwater between the mangrove swamp and the adjacent offshore waters.     

Coastal erosion due to long-term human impact on mangrove forests

A coast in southern Vietnam, which is located in a wide and flat alluvial fan and neighbors tidal rivers fringed by wide mangrove swamps, has been eroded continuously by approximately 50 m/year since the early 20th century. Based on field observations and numerical experiments, it is inferred that this large scale erosion is caused by the transition of mangrove vegetation resulting from the long-term impact of humans since the late 19th century. This eroded coast is not in direct contact with mangrove swamps, but is strongly affected by the existence of mangrove forests through the intermediation of neighboring tidal rivers. Thus, with a view to coastal protection, it is argued that the mangrove vegetation in adjacent areas should be managed more sensitively.     

Modes of overinitiation, dnaA gene expression, and inhibition of cell division in a novel cold-sensitive hda mutant of Escherichia coli

The chromosomal replication cycle is strictly coordinated with cell cycle progression in Escherichia coli. ATP-DnaA initiates replication, leading to loading of the DNA polymerase III holoenzyme. The DNA-loaded form of the beta clamp subunit of the polymerase binds the Hda protein, which promotes ATP-DnaA hydrolysis, yielding inactive ADP-DnaA. This regulation is required to repress overinitiation. In this study, we have isolated a novel cold-sensitive hda mutant, the hda-185 mutant. The hda-185 mutant caused overinitiation of chromosomal replication at 25 degrees C, which most likely led to blockage of replication fork progress. Consistently, the inhibition of colony formation at 25 degrees C was suppressed by disruption of the diaA gene, an initiation stimulator. Disruption of the seqA gene, an initiation inhibitor, showed synthetic lethality with hda-185 even at 42 degrees C. The cellular ATP-DnaA level was increased in an hda-185-dependent manner. The cellular concentrations of DnaA protein and dnaA mRNA were comparable at 25 degrees C to those in a wild-type hda strain. We also found that multiple copies of the ribonucleotide reductase genes (nrdAB or nrdEF) or dnaB gene repressed overinitiation. The cellular levels of dATP and dCTP were elevated in cells bearing multiple copies of nrdAB. The catalytic site within NrdA was required for multicopy suppression, suggesting the importance of an active form of NrdA or elevated levels of deoxyribonucleotides in inhibition of overinitiation in the hda-185 cells. Cell division in the hda-185 mutant was inhibited at 25 degrees C in a LexA regulon-independent manner, suggesting that overinitiation in the hda-185 mutant induced a unique division inhibition pathway.     

Towards a mutant map of the mouse – new models of neurological, behavioural, deafness, bone, renal and blood disorders

With the completion of the first draft of the human genome sequence, the next major challenge is assigning function to genes. One approach is genome-wide random chemical mutagenesis, followed by screening for mutant phenotypes of interest and subsequent mapping and identification of the mutated genes in question. We (a consortium made up of GlaxoSmithKline, the MRC Mammalian Genetics Unit and Mouse Genome Centre, Harwell, Imperial College, London, and the Royal London Hospital) have used ENU mutagenesis in the mouse for the rapid generation of novel mutant phenotypes for use as animal models of human disease and for gene function assignment (Nolan et al., 2000). As of 2003, 35,000 mice have been produced to date in a genome-wide screen for dominant mutations and screened using a variety of screening protocols. Nearly 200 mutants have been confirmed as heritable and added to the mouse mutant catalogue and, overall, we can extrapolate that we have recovered over 700 mutants from the screening programme. For further information on the project and details of the data, see http://www.mgu.har.mrc.ac.uk/mutabase.     

Intravascular insulin gene delivery as potential therapeutic intervention in diabetes mellitus

We assessed therapeutic potential of intravascular insulin gene delivery in a diabetic murine model. The rat proinsulin-1 gene cDNA engineered to harbor furin consensus cleavage sequences was inserted into EBV-based plasmid vectors that contained CAG promoter or multimerized rat insulin promoter (RIP). Normal or streptozotocin (STZ)-induced diabetic mice were given an injection of the plasmids via the tail vein under high pressure. Transfection of the CAG-proinsulin construct markedly improved hyperglycemia of diabetic mice, accompanied by a considerable increase in serum insulin concentrations. Although the RIP-plasmid failed to reduce fasting blood glucose, the glucose tolerance test and RT-PCR analysis revealed that insulin production was regulated in the liver in a blood glucose level-dependent manner. The present results suggest a potential therapeutic means of controlling DM.     

Polyethylenimine-mediated suicide gene transfer induces a therapeutic effect for hepatocellular carcinoma in vivo by using an Epstein-Barr virus-based plasmid vector

The present study aimed to establish a novel efficient nonviral strategy for suicide gene transfer in hepatocellular carcinoma (HCC) in vivo. We employed branched polyethylenimine (PEI) and combined it with Epstein-Barr virus (EBV)-based plasmid vectors. The HCC cells transfected with an EBV-based plasmid carrying the herpes simplex virus-1 thymidine kinase (HSV-1 Tk) gene (pSES.Tk) showed up to 30-fold higher susceptibilities to ganciclovir (GCV) than those transfected with a conventional plasmid vector carrying the HSV-1 Tk gene (pS.Tk). The therapeutic effect in vivo was tested by intratumoral injection of the plasmids into HuH-7 hepatomas transplanted into C.B-17 scid/scid mutant (SCID) mice and subsequent GCV administrations. Treatment with pSES.Tk, but not pS.Tk, markedly suppressed growth of hepatomas in vivo, resulting in a significantly prolonged survival period of the mice. These findings suggest that PEI-mediated gene transfer system can confer efficient expression of the suicide gene in HCC cells in vivo by using EBV-based plasmid vectors.     

Intracellular interferon triggers Jak/Stat signaling cascade and induces p53-dependent antiviral protection

Intracellular interferons (IFNs) exert biological functions similar to those of extracellular IFNs, but the signal transduction pathway triggered by the intracellular ligands has not been fully revealed. We investigated the signaling cascade by sequence-specific knockdown of signaling molecules by means of the RNA interference. Truncated IFN-beta gene was constructed so that the N-terminal secretory signal sequence was deleted (SD.IFN-beta). Cells transfected with this construct showed phosphorylation and activation of the STAT1 without any detectable secretion of the cytokine. The MHC class I expression was significantly augmented, while the augmentation was suppressed by short interfering RNA duplexes specific for JAK1, TYK2, and IFN-alpha/beta receptor (IFNAR) 1 and 2c chains. The SD.IFN-beta also induced p53 and phosphorylation of p53 at Ser(15). Specific silencing of p53 abrogated the antiviral effect of SD.IFN-beta, suggesting that the tumor suppressor is critically involved in antiviral defense mediated by intracellular IFN.     

The identification of inhibitors in bromelin one-stage irregular antibody screening techniques

Human sera contain bromelin inhibitors in irregular antibody screening techniques. In order to identify and purify these inhibitors, pooled human sera were precipitated with ammonium sulfate, followed by DEAE-cellulose and Sephadex G-150 column chromatography. Proteinase activity and inhibitory activity to bromelin were observed in two protein fractions, these were identified as alpha 2-macroglobulin and the S-2 thiol proteinase inhibitor.     

Genetic variability of the mTOR pathway and prostate cancer risk in the European Prospective Investigation on Cancer (EPIC)

The mTOR (mammalian target of rapamycin) signal transduction pathway integrates various signals, regulating ribosome biogenesis and protein synthesis as a function of available energy and amino acids, and assuring an appropriate coupling of cellular proliferation with increases in cell size. In addition, recent evidence has pointed to an interplay between the mTOR and p53 pathways. We investigated the genetic variability of 67 key genes in the mTOR pathway and in genes of the p53 pathway which interact with mTOR. We tested the association of 1,084 tagging SNPs with prostate cancer risk in a study of 815 prostate cancer cases and 1,266 controls nested within the European Prospective Investigation into Cancer and Nutrition (EPIC). We chose the SNPs (n = 11) with the strongest association with risk (p<0.01) and sought to replicate their association in an additional series of 838 prostate cancer cases and 943 controls from EPIC. In the joint analysis of first and second phase two SNPs of the PRKCI gene showed an association with risk of prostate cancer (OR_allele = 0.85, 95% CI 0.78–0.94, p = 1.3×10⁻³ for rs546950 and OR_allele = 0.84, 95% CI 0.76–0.93, p = 5.6×10⁻⁴ for rs4955720). We confirmed this in a meta-analysis using as replication set the data from the second phase of our study jointly with the first phase of the Cancer Genetic Markers of Susceptibility (CGEMS) project. In conclusion, we found an association with prostate cancer risk for two SNPs belonging to PRKCI, a gene which is frequently overexpressed in various neoplasms, including prostate cancer.