Alterations in the spatiotemporal expression pattern and function of N-cadherin inhibit cellular condensation and chondrogenesis of limb mesenchymal cells in vitro

Cartilage formation in the embryonic limb is presaged by a cellular condensation phase that is mediated by both cell-cell and cell-matrix interactions. N-Cadherin, a Ca(2+)-dependent cell-cell adhesion molecule, is expressed at higher levels in the condensing mesenchyme, followed by down-regulation upon chondrogenic differentiation, strongly suggesting a functional role in the cellular condensation process. To further examine the role of N-cadherin, we have generated expression constructs of wild type and two deletion mutants (extracellular and intracellular) of N-cadherin in the avian replication-competent, RCAS retrovirus, and transfected primary chick limb mesenchymal cell cultures with these constructs. The effects of altered, sustained expression of N-cadherin and its mutant forms on cellular condensation, on the basis of peanut agglutinin (DNA) staining, and chondrogenesis, based on expression of chondrocyte phenotypic markers, were characterized. Cellular condensation was relatively unchanged in cultures overexpressing wild type N-cadherin, compared to controls on all days in culture. However, expression of either of the deletion mutant forms of N-cadherin resulted in decreased condensation, with the extracellular deletion mutant demonstrating the most severe inhibition, suggesting a requirement for N-cadherin mediated cell-cell adhesion and signaling in cellular condensation. Subsequent chondrogenic differentiation was also affected in all cultures overexpressing the N-cadherin constructs, on the basis of metabolic sulfate incorporation, the presence of the cartilage matrix proteins collagen type II and cartilage proteoglycan link protein, and alcian blue staining of the matrix. The characteristics of the cultures suggest that the N-cadherin mutants disrupt proper cellular condensation and subsequent chondrogenesis, while the cultures overexpressing wild type N-cadherin appear to condense normally, but are unable to proceed toward differentiation, possibly due to the prolonged maintenance of increased cell-cell adhesiveness. Thus, spatiotemporally regulated N-cadherin expression and function, at the level of both homotypic binding and linkage to the cytoskeleton, is required for chondrogenesis of limb mesenchymal cells.     

Fas/Fas ligand-mediated death pathway is involved in oxLDL-induced apoptosis in vascular smooth muscle cells

Oxidizedlow-density lipoprotein (oxLDL) is a potent inducer ofapoptosis for vascular cells. In the present study, wedemonstrate that the expression of death mediators, including p53, Fas,and Fas ligand (FasL) was substantially upregulated by oxLDL incultured vascular smooth muscle cells (SMCs). The induction of thesedeath mediators was time dependent and was accompanied by an increase in apoptotic death of SMCs following oxLDL treatment. Twooxysterols, 7-hydroxycholesterol and 25-hydroxycholesterol, werealso effective to induce the expression of death mediators andapoptosis. -Tocopherol and deferoxamine significantlyattenuated the induction of death mediators and cell death induced byoxLDL and oxysterols, suggesting that reactive oxygen species areinvolved in triggering the apoptotic event. Incubation of cellswith FasL-neutralizing antibody inhibited the oxLDL-induced cell deathup to 50%. Furthermore, caspase 8 and caspase 3 activities wereinduced time dependently in SMCs following oxLDL treatment.Collectively, these data suggest that the Fas/FasL death pathway isactivated and responsible for, at least in part, the apoptoticdeath in vascular SMCs upon exposure to oxLDL.

     

The effect of rice seeding rate and fish stocking on the floodwater ecology of the rice field in direct-seeded,concurrent rice-fish systems

Concurrent, rice-fish systems in the Mekong Delta, Vietnam, are characterized by a rice field surrounded by a trench. Rice is direct seeded and fish are reared in polyculture. The most common species for polyculture are silver barb Barbodes gonionotus (Bleeker), common carp Cyprinus carpio L. and Nile tilapia Oreochromis niloticus (L.). In a 1996–97 rice-fish experiment, the effects of (1) absence or presence of such a polyculture, and (2) different rice-seeding rates (100 and 300 kg pre-germinated rice per ha) on the field floodwater ecology were studied. Fish obtained from local nurseries were stocked in six out of 12 rice-fish plots at the Co Do experimental rice-fish station (10°10 N and 105°20 E). Silver barb, common carp and Nile tilapia were stocked in polyculture at densities of 3150, 310 and 550 fish ha^–1, respectively. About 50% of the observed variation in the floodwater could be attributed to the fish stocked and to rice-seeding rate. The above-ground dry weight of the rice plants increased in the presence of fish and by an increase in rice-seeding rate. Greater shading by denser plants resulted in changes in variables related to aquatic primary production, including the amount of chlorophyll-a, dissolved oxygen concentration and pH. The presence of fish quadrupled the ammonium concentration, but decreased that of ortho-phosphate. Though fish increased the ammonium concentration, this did not result in a higher aquatic photosynthesis. Light, not ammonium, was the most limiting factor. However, increased ammonium concentrations in the presence of fish did have a positive effect on the density of Euglenophyta and the amount of chlorophyll-a, though only at the lower rice-seeding rate. At the higher rice-seeding rate, light seemed to be lacking. At the lower rice-seeding rate, fish also had a significant effect on the Cladocera–Rotifera ratio. Rotifera numbers increased as fish stimulated phytoplankton. We also demonstrated that fish most probably do not reduce ammonia volatilization losses. The lower rice-seeding rate seemed better for fish production than the higher rate: at the lower rate, dissolved oxygen concentrations were higher throughout the rice cycle. In addition, the amount of chlorophyll-a and the density of Euglenophyta were higher at the lower rice-seeding rate. Finally, we could show that even at high rice-seeding rates, fish had an impact on the aquatic environment. Fish access to the field is not hindered by dense rice stands.     

Larval Settlement: The Role of Surface Topography for Sessile Coral Reef Invertebrates

For sessile marine invertebrates with complex life cycles, habitat choice is directed by the larval phase. Defining which habitat-linked cues are implicated in sessile invertebrate larval settlement has largely concentrated on chemical cues which are thought to signal optimal habitat. There has been less effort establishing physical settlement cues, including the role of surface microtopography. This laboratory based study tested whether surface microtopography alone (without chemical cues) plays an important contributing role in the settlement of larvae of coral reef sessile invertebrates. We measured settlement to tiles, engineered with surface microtopography (holes) that closely matched the sizes (width) of larvae of a range of corals and sponges, in addition to surfaces with holes that were markedly larger than larvae. Larvae from two species of scleractinian corals (Acropora millepora and Ctenactis crassa) and three species of coral reef sponges (Luffariella variabilis, Carteriospongia foliascens and Ircinia sp.,) were used in experiments. L. variabilis, A. millepora and C. crassa showed markedly higher settlement to surface microtopography that closely matched their larval width. C. foliascens and Ircinia sp., showed no specificity to surface microtopography, settling just as often to microtopography as to flat surfaces. The findings of this study question the sole reliance on chemical based larval settlement cues, previously established for some coral and sponge species, and demonstrate that specific physical cues (surface complexity) can also play an important role in larval settlement of coral reef sessile invertebrates.     

Finasteride Concentrations and Prostate Cancer Risk: Results from the Prostate Cancer Prevention Trial

ObjectiveIn the Prostate Cancer Prevention Trial (PCPT), finasteride reduced the risk of prostate cancer by 25%, even though high-grade prostate cancer was more common in the finasteride group. However, it remains to be determined whether finasteride concentrations may affect prostate cancer risk. In this study, we examined the association between serum finasteride concentrations and the risk of prostate cancer in the treatment arm of the PCPT and determined factors involved in modifying drug concentrations.MethodsData for this nested case-control study are from the PCPT. Cases were drawn from men with biopsy-proven prostate cancer and matched controls. Finasteride concentrations were measured using a liquid chromatography-mass spectrometry validated assay. The association of serum finasteride concentrations with prostate cancer risk was determined by logistic regression. We also examine whether polymorphisms in the enzyme target and metabolism genes of finasteride are related to drug concentrations using linear regression.

Results and Conclusions

Among men with detectable finasteride concentrations, there was no association between finasteride concentrations and prostate cancer risk, low-grade or high-grade, when finasteride concentration was analyzed as a continuous variable or categorized by cutoff points. Since there was no concentration-dependent effect on prostate cancer, any exposure to finasteride intake may reduce prostate cancer risk. Of the twenty-seven SNPs assessed in the enzyme target and metabolism pathway, five SNPs in two genes, CYP3A4 (rs2242480; rs4646437; rs4986910), and CYP3A5 (rs15524; rs776746) were significantly associated with modifying finasteride concentrations. These results suggest that finasteride exposure may reduce prostate cancer risk and finasteride concentrations are affected by genetic variations in genes responsible for altering its metabolism pathway.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00288106","term_id":"NCT00288106"}}NCT00288106     

Buried Effects of Surface Plasmon Resonance Modes for Periodic Metal–Dielectric Nanostructures Consisting of Coupled Spherical Metal Nanoparticles with Cylindrical Pore Filled with a Dielectric

We numerically investigate the buried effects of surface plasmon resonance (SPR) modes for the periodic silver-shell nanopearl dimer (PSSND) array and their solid counterparts with different buried depths in a silica substrate by means of finite element method with three-dimensional calculations. The investigated PSSND array is an important novel geometry for plasmonic metal nanoparticles (MNPs), combining the highly attractive nanoscale optical properties of both metallic nanoshell and cylindrical pore filled with a dielectric. Numerical results for SPR modes corresponding to the effects of different illumination wavelengths, absorption spectra, pore–dielectric, electric field components and total field distribution, charge density distribution, and the model of the induced local field or an applied field of the PSSND array are reported as well. It can be found that the buried MNPs with cylindrical pore filled with a dielectric in a substrate exhibit tunable SPR modes corresponding to the bonding and antibonding modes that are not observed for their solid counterparts.     

Emerging and divergent roles of pyrophosphorylated nucleotides in bacterial physiology and pathogenesis

Bacteria inhabit diverse environmental niches and consequently must modulate their metabolism to adapt to stress. The nucleotide second messengers guanosine tetraphosphate (ppGpp) and guanosine pentaphosphate (pppGpp) (collectively referred to as (p)ppGpp) are essential for survival during nutrient starvation. (p)ppGpp is synthesized by the RelA-SpoT homologue (RSH) protein family and coordinates the control of cellular metabolism through its combined effect on over 50 proteins. While the role of (p)ppGpp has largely been associated with nutrient limitation, recent studies have shown that (p)ppGpp and related nucleotides have a previously underappreciated effect on different aspects of bacterial physiology, such as maintaining cellular homeostasis and regulating bacterial interactions with a host, other bacteria, or phages. (p)ppGpp produced by pathogenic bacteria facilitates the evasion of host defenses such as reactive nitrogen intermediates, acidic pH, and the complement system. Additionally, (p)ppGpp and pyrophosphorylated derivatives of canonical adenosine nucleotides called (p)ppApp are emerging as effectors of bacterial toxin proteins. Here, we review the RSH protein family with a focus on its unconventional roles during host infection and bacterial competition.