Epstein-Barr Virus Latent Membrane Protein 2 Induces Autophagy To Promote Abnormal Acinus Formation

Epstein-Barr virus latent membrane protein 2A (LMP2A) induces many characteristics of carcinoma, including transformation, migration, invasion, and impaired differentiation. The MCF10A cell line differentiates to form hollow acini when grown in Matrigel, and expression of LMP2A inhibited differentiation and anoikis induced by loss of matrix attachment. LMP2A-infected cells formed large, lobular structures rather than hollow acini. Autophagy inhibitors impaired this abnormal growth and induced caspase 3 activation and acinus formation. LMP2A also increased autophagosome formation and expression of proteins in the autophagosome pathway. These findings suggest that LMP2A may inhibit anoikis and luminal clearance in acini through induction of autophagy.     

Nitrogen uptake in two frontal areas in the Greenland Sea

Summary During late spring, 1987, observations were made of nitrate and ammonium uptake in two regions of the Greenland Sea, the Arctic Front and the Polar Front. In the area of the Arctic Front, mixed layers were relatively deep (generally below 100m), and the 1% isolume averaged 35 m. Ambient nitrate concentrations were always greater than 6 M, whereas ammonium levels were always less than 0.6 M. Surface nitrate and ammonium specific uptake rates averages 4.4 and 2.3×10^–3 h^–1, respectively. The Polar Front generally coincided spatially with the location of the ice edge, and vertical mixed layers were shallow (pycnocline depth ranged from 8–14 m), and the 1 % isolume averaged 37 m. Nitrate concentrations were somewhat lower than in the Arctic Front, but remained above 3 M at all times. Ammonium levels reached 1.2 M. Nitrate and ammonium specific uptake rates at the surface averaged 4.8×10^–3 and 10×10^–3 h^–1, respectively. Integrated water column f-ratios for the Arctic and Polar Front regions averaged 0.63 and 0.31, and the ammonium relative preference indices at all depths within each study area were always greater than 8, indicating that ammonium remained the preferred nitrogen source for phytoplankton. New production in the two regions was approximately equal, but the Polar Front had a substantially greater amount of regenerated production, and hence total production as well. Irradiance (and not nutrient concentration) seems to be the most important environmental factor in controlling nitrogen uptake. The spatial variability observed within the Greenland Sea suggest that inclusion of this region in global carbon models will require increased spatial resolution of both the models and the data included.     

Protein expression from synthetic genes: selection of clones using GFP

Construction of synthetic genes is today the most elegant way to optimize the heterologous expression of a recombinant protein. However, the selection of positive clones that incorporate the correct synthetic DNA fragments is a bottleneck as current methods of gene synthesis introduce 3.5 nucleotide deletions per kb. Furthermore, even when all predictable optimizations for protein production have been introduced into the synthetic gene, production of the protein is often disappointing: protein is produced in too low amounts or end up in inclusion bodies. We propose a strategy to overcome these two problems simultaneously by cloning the synthetic gene upstream of a reporter gene. This permits the selection of clones devoid of frame-shift mutations. In addition, beside nucleotide deletion, an average of three non-neutral mutations per kb are introduced during gene synthesis. Using a reporter protein downstream of the synthetic gene, allows the selection of clones with random mutations improving the expression or the folding of the protein of interest. The problem of errors found in synthetic genes is then turned into an advantage since it provides polymorphism useful for molecular evolution. The use of synthetic genes appears as an alternative to the error-prone PCR strategy to generate the variations necessary in protein engineering experiments.     

A gentle introduction to SNP analysis: resources and tools

Bioinformatics is the use of informatics tools and techniques in the study of molecular biology, genetic, or clinical data. The field of bioinformatics has expanded tremendously to cope with the large expansion of information generated by the mouse and human genome projects, as newer generations of computers that are much more powerful have emerged in the commercial market. It is now possible to employ the computing hardware and software at hand to generate novel methodologies in order to link data across the different databanks generated by these international projects and derive clinical and biological relevance from all of the information gathered. The ultimate goal would be to develop a computer program that can provide information correlating genes, their single nucleotide polymorphisms (SNPs), and the possible structural and functional effects on the encoded proteins with relation to known information on complex diseases with great ease and speed. Here, the recent developments of available software methods to analyze SNPs in relation to complex diseases are reviewed with emphasis on the type of predictions on protein structure and functions that can be made. The need for further development of comprehensive bioinformatics tools that can cope with information generated by the genomics communities is emphasized.     

Atypical memory phenotype T cells with low homeostatic potential and impaired TCR signaling and regulatory T cell function in Foxn1Delta/Delta mutant mice

Foxn1Delta/Delta mutants have a block in thymic epithelial cell differentiation at an intermediate progenitor stage, resulting in reduced thymocyte cellularity and blocks at the double-negative and double-positive stages. Whereas naive single-positive thymocytes were reduced >500-fold in the adult Foxn1Delta/Delta thymus, peripheral T cell numbers were reduced only 10-fold. The current data shows that Foxn1Delta/Delta peripheral T cells had increased expression of activation markers and the ability to produce IL-2 and IFN-gamma. These cells acquired this profile immediately after leaving the thymus as early as the newborn stage and maintained high steady-state proliferation in vivo but decreased proliferation in response to TCR stimulation in vitro. Single-positive thymocytes and naive T cells also had constitutively low alphabetaTCR and IL7R expression. These cells also displayed reduced ability to undergo homeostatic proliferation and increased rates of apoptosis. Although the frequency of Foxp3+CD4+CD25+ T cells was normal in Foxn1Delta/Delta mutant mice, these cells failed to have suppressor function, resulting in reduced regulatory T cell activity. Recent data from our laboratory suggest that T cells in the Foxn1Delta/Delta thymus develop from atypical progenitor cells via a noncanonical pathway. Our results suggest that the phenotype of peripheral T cells in Foxn1Delta/Delta mutant mice is the result of atypical progenitor cells developing in an abnormal thymic microenvironment with a deficient TCR and IL7 signaling system.     

Adenovirus-mediated hepatic overexpression of scavenger receptor class B type I accelerates chylomicron metabolism in C57BL/6J mice

The function of scavenger receptor class B type I (SR-BI) in mediating the selective uptake of HDL cholesteryl esters is well established. In SR-BI-deficient mice, we recently observed a delayed postprandial triglyceride (TG) response, suggesting an additional role for SR-BI in facilitating chylomicron (CM) metabolism. Here, we assessed the effect of adenovirus-mediated hepatic overexpression of SR-BI (Ad.SR-BI) in C57BL/6J mice on serum lipids and CM metabolism. Infection of 5 x 10(8) plaque-forming units per mouse of Ad.SR-BI significantly decreases serum cholesterol (>90%), phospholipids (>90%), and TG levels (50%), accompanied by a 41.4% reduction (P < 0.01) in apolipoprotein B-100 levels. The postprandial TG response is 2-fold lower in mice treated with Ad.SR-BI compared with control mice (area under the curve = 31.4 +/- 2.4 versus 17.7 +/- 3.2; P < 0.05). Hepatic mRNA expression levels of genes known to be involved in serum cholesterol and TG clearance are unchanged and thus could not account for the decreased plasma TG levels and the change in postprandial response. We conclude that overexpression of SR-BI accelerates CM metabolism, possibly by mediating the initial capture of CM remnants by the liver, whereby the subsequent internalization can be exerted by additional receptor systems such as the LDL receptor (LDLr) and LDLr-related protein 1.     

Flow rate and vertical position influence ingestion rates of colonial zebra mussels (Dreissena polymorpha)

1. Zebra mussels aggregate to form dense colonies where, depending on the flow rate, individuals in different vertical locations within the colony may experience restricted food availability. 2. Using ³²P‐labelled Chlamydomonas angulosa, we found ingestion rates of individual mussels located at the surface to exceed those in the bottom of a 6 cm thick colony by up to 75%. 3. Higher velocities (10 and 20 cm s^?1) increased algal delivery to the colony's middle layer (2–4 cm depth), subsequently increasing ingestion rates to equal those in the surface layer, while increasing ingestion only for the smallest mussels in the bottom (4–6 cm). 4. At all vertical locations within the colonies, smaller mussels showed higher ingestion rates per unit mass than larger mussels, particularly at higher flow rates.