Ecology of deepwater rice-fields in Bangladesh 4. Nitrogen fixation by blue-green algal communities

1. Aquatic macrophytes formed dense beds in fallow areas during the four and a half months of the flood season in all but one deepwater rice-growing location in Bangladesh; these included several types of life-form, but the fine-leaved species, Myriophyllum sp., Najas indica, Utricularia stellaris were often especially abundant. The same species grew inside deepwater rice fields, but at much lower densities. A similar contrast occurred for the algae, although deepwater rice often developed dense masses of epiphytes on aquatic roots, stems and leaf sheaths, when plants were growing in isolated, well-illuminated situations.
2. Two widespread algae, Aulosira fertilissima and Scytonema mirabile, were equally successful on soil in the period prior to the arrival of floodwaters and floating on the surface of the water during the flood season. Other species common during the flood season differed from those common on soil.
3. Most blue-green algae inside deepwater rice fields were heterocystous; the only species not so, but forming distinct colonies, was Aphanothece stagnina. However only non-heterocystous forms were found at one location in south Bangladesh (Phaltita) and a change from heterocystous to non-heterocystous forms was noted at the main research site (near Sonargaon) during late September in at least one year. The water column at the former was almost entirely anoxic, while the change at the latter occurred at a time when the water sometimes became anoxic during the night. It is suggested that differences in ability to tolerate anoxic periods may be a key factor in determining the success of the algal and vascular plant species in the different micro-habitats within these DWR-growing areas.
4. Although diatoms were quantitatively only a minor component of the algal biomass, they became more frequent later in the season when the water became microaerobic or anoxic for part of the day. Navicula confervacea was overall the most abundant species at the two main research locations.

     

An Integrated Approach for Analysis of the DNA Damage Response in Mammalian Cells: NUCLEOTIDE EXCISION REPAIR,DNA DAMAGE CHECKPOINT,AND APOPTOSIS*

DNA damage by UV and UV-mimetic agents elicits a set of inter-related responses in mammalian cells, including DNA repair, DNA damage checkpoints, and apoptosis. Conventionally, these responses are analyzed separately using different methodologies. Here we describe a unified approach that is capable of quantifying all three responses in parallel using lysates from the same population of cells. We show that a highly sensitive in vivo excision repair assay is capable of detecting nucleotide excision repair of a wide spectrum of DNA lesions (UV damage, chemical carcinogens, and chemotherapeutic drugs) within minutes of damage induction. This method therefore allows for a real-time measure of nucleotide excision repair activity that can be monitored in conjunction with other components of the DNA damage response, including DNA damage checkpoint and apoptotic signaling. This approach therefore provides a convenient and reliable platform for simultaneously examining multiple aspects of the DNA damage response in a single population of cells that can be applied for a diverse array of carcinogenic and chemotherapeutic agents.     

Stromal upregulation of lateral epithelial adhesions: Gene expression analysis of signalling pathways in prostate epithelium

Background  

Stromal signalling increases the lateral cell adhesions of prostate epithelial cells grown in 3D culture. The aim of this study was to use microarray analysis to identify significant epithelial signalling pathways and genes in this process.     

Vibrio cholerae Cytolysin Causes an Inflammatory Response in Human Intestinal Epithelial Cells That Is Modulated by the PrtV Protease

Background

Vibrio cholerae is the causal intestinal pathogen of the diarrheal disease cholera. It secretes the protease PrtV, which protects the bacterium from invertebrate predators but reduces the ability of Vibrio-secreted factor(s) to induce interleukin-8 (IL-8) production by human intestinal epithelial cells. The aim was to identify the secreted component(s) of V. cholerae that induces an epithelial inflammatory response and to define whether it is a substrate for PrtV.

Methodology/Principal Findings

Culture supernatants of wild type V. cholerae O1 strain C6706, its derivatives and pure V. cholerae cytolysin (VCC) were analyzed for the capacity to induce changes in cytokine mRNA expression levels, IL-8 and tumor necrosis factor-α (TNF-α) secretion, permeability and cell viability when added to the apical side of polarized tight monolayer T84 cells used as an in vitro model for human intestinal epithelium. Culture supernatants were also analyzed for hemolytic activity and for the presence of PrtV and VCC by immunoblot analysis.

Conclusions/Significance

We suggest that VCC is capable of causing an inflammatory response characterized by increased permeability and production of IL-8 and TNF-α in tight monolayers. Pure VCC at a concentration of 160 ng/ml caused an inflammatory response that reached the magnitude of that caused by Vibrio-secreted factors, while higher concentrations caused epithelial cell death. The inflammatory response was totally abolished by treatment with PrtV. The findings suggest that low doses of VCC initiate a local immune defense reaction while high doses lead to intestinal epithelial lesions. Furthermore, VCC is indeed a substrate for PrtV and PrtV seems to execute an environment-dependent modulation of the activity of VCC that may be the cause of V. cholerae reactogenicity.     

Cisplatin‐Induced Testicular Toxicity in Rats: The Protective Effect of Arjunolic Acid

In the present study, the effect of arjunolic acid on testicular damage induced by intraperitoneal injection of rats with 7 mg/kg cisplatin was studied. Cisplatin induced a significant reduction in testicular weights, plasma testosterone, and testicular reduced glutathione levels in addition to a significant elevation of testicular malondialdehyde levels and testicular gene expressions of inducible nitric oxide synthase (iNOS), tumor necrosis factor‐α (TNF‐α), and p38 mitogen‐activated protein kinase (MAPK) when compared with the control group (p < 0.05). Lower tubular diameters and depletion of germ cells and irregular small seminiferous tubules with Sertoli cells only were observed in the cisplatin group. Arjunolic acid administration significantly corrected the changes in both biochemical and histopathological parameters. Arjunolic acid plays a significant protective role against cisplatin‐induced testicular injury by attenuating oxidative stress parameters along with downregulation of iNOS, TNF‐α, and p38‐MAPK testicular expressions.     

(A)BC excinuclease: the Escherichia coli nucleotide excision repair enzyme

Nucleotide excision repair is the major pathway for removing damage from DNA. (A)BC excinuclease is the nuclease activity which initiates nucleotide excision repair in Escherichia coli. In this review, we focus on current understanding of the structure-function of the enzyme and the reaction mechanism of the repair pathway. In addition, recent biochemical studies on preferential repair of actively transcribed genes in E. coli are summarized.     

Peripheral blood gene expression profiling for cardiovascular disease assessment

Whole blood gene expression profiling has the potential to be informative about dynamic changes in disease states and to provide information on underlying disease mechanisms. Having demonstrated proof of concept in animal models, a number of studies have now tried to tackle the complexity of cardiovascular disease in human hosts to develop better diagnostic and prognostic indicators. These studies show that genomic signatures are capable of classifying patients with cardiovascular diseases into finer categories based on the molecular architecture of a patient's disease and more accurately predict the likelihood of a cardiovascular event than current techniques. To highlight the spectrum of potential applications of whole blood gene expression profiling approach in cardiovascular science, we have chosen to review the findings in a number of complex cardiovascular diseases such as atherosclerosis, hypertension and myocardial infarction as well as thromboembolism, aortic aneurysm, and heart transplant.