Identification of Novel Thymic Epithelial Cell Subsets Whose Differentiation Is Regulated by RANKL and Traf6

Thymic epithelial cells (TECs) are critical for the normal development and function of the thymus. Here, we examined the developmental stages of TECs using quantitative assessment of the cortical and medullary markers Keratin 5 and Keratin 8 (K5 and K8) respectively, in normal and gain/loss of function mutant animals. Gain of function mice overexpressed RANKL in T cells, whereas loss of function animals lacked expression of Traf6 in TECs (Traf6ΔTEC). Assessment of K5 and K8 expression in conjunction with other TEC markers in wild type mice identified novel cortical and medullary TEC populations, expressing different combinations of these markers. RANKL overexpression led to expansion of all medullary TECs (mTECs) and enlargement of the thymic medulla. This in turn associated with a block in thymocyte development and loss of CD4⁺CD8⁺, CD4⁺ and CD8⁺ thymocytes. In contrast, Traf6 deletion inhibited the production of most TEC populations including cortical TECs (cTECs), defined by absence of UEA-1 binding and LY51 expression, but had no apparent effect on thymocyte development. These results reveal a large degree of heterogeneity within the TEC compartment and the existence of several populations exhibiting concomitant expression of cortical, medullary and epithelial markers and whose production is regulated by RANKL and Traf6.     

Nutrient Limitation to Primary Productivity in a Secondary Savanna in Venezuela1

We examined nutrient limitation to primary productivity in a secondary savanna in the interior branch of the Coastal Range of Venezuela, which was converted from forest to savanna more than 100 years ago. We manipulated soil nutrients by adding nitrogen (+N), phosphorus and potassium (+PK), and nitrogen, phosphorus, and potassium (+NPK) to intact savanna. Eleven months after fertilization, we measured aboveground biomass and belowground biomass as live fine roots in the top 20 cm of soil, and species and functional group composition in response to nutrient additions. Aboveground biomass was highest in the NPK treatment ([mean g/m2]; control = 402, +N = 718, +PK = 490, +NPK = 949). Aboveground production, however, appeared to be limited primarily by N. Aboveground biomass increased 78 percent when N was added alone but did not significantly respond to PK additions when compared to controls. In contrast to aboveground biomass, belowground biomass increased with PK additions but showed no significant increase with N (depth 0–20 cm; [mean g/m2]; control = 685, +N = 443, +PK = 827, +NPK = 832). There was also a 36 percent increase in root length with PK additions when compared to controls. Whole savanna shoot:root ratios were similar for control and +PK (0.6), while those for +N or +NPK fertilization were significantly higher (1.7 and 1.2, respectively). Total biomass response (above + belowground) to nutrient additions showed a strong N and PK co‐limitation ([mean g/m2]; control = 1073, +N = 1111, +PK = 1258, +NPK = 1713). Aboveground biomass of all monocots increased with N additions, whereas dicots showed no response to nutrient additions. Trachypogon spp. (T. plumosus+T. vestitus) and Axonopus canescens, the two dominant grasses, made up more than 89 percent of the total aboveground biomass in these sites. Trachypogon spp. responded to NPK, whereas A. canescens, sedges, and the remaining monocots only responded to N. Even though nutrient additions resulted in higher aboveground biomass in N and NPK fertilized plots, this had little effect on plant community composition. With the exception of sedges, which responded positively to N additions and increased from 4 to 8 percent of die plant community, no changes were observed in plant community composition after 11 months.     

Effect of insoluble extracellular matrix molecules on fas expression in epithelial cells

Fas, which functions to initiate a signal causing apoptosis, is expressed in epithelia, thus, suggesting a role in controlling cell number during states of cell and matrix turnover. In view of this, we hypothesized that cell-matrix interactions may be an important determinant of Fas expression in epithelial cells. To investigate this, we examined the effect of insoluble extracellular matrix molecules on Fas expression in murine lung epithelial (MLE) cells, a transformed mouse lung epithelial cell line. We report that (1) insoluble extracellular matrices increased Fas mRNA in a time and concentration-dependent manner; (2) induced increases in Fas mRNA were associated with concomitantly increased Fas protein; and (3) nonspecific adherence to a polylysine substrate did not induce Fas mRNA. Consistent with these findings, Fas-induced apoptosis was significantly enhanced in cultures plated on type IV collagen. Employing rat hepatocytes, we confirmed that the insoluble extracellular matrix also increases Fas expression in primary epithelial cells. By amplifying Fas-mediated apoptosis, these data suggest a mechanism whereby the extracellular matrix regulates the fate of specific epithelial cell populations. J. Cell. Physiol. 174:285–292, 1998. © 1998 Wiley-Liss, Inc.     

New Electropositive Filter for Concentrating Enteroviruses and Noroviruses from Large Volumes of Water

The U.S. Environmental Protection Agency''s information collection rule requires the use of 1MDS electropositive filters for concentrating enteric viruses from water, but unfortunately, these filters are not cost-effective for routine viral monitoring. In this study, an inexpensive electropositive cartridge filter, the NanoCeram filter, was evaluated for its ability to concentrate enteroviruses and noroviruses from large volumes of water. Seeded viruses were concentrated using the adsorption-elution procedure. The mean percent retention of seeded polioviruses by NanoCeram filters was 84%. To optimize the elution procedure, six protocols, each comprising two successive elutions with various lengths of filter immersion, were evaluated. The highest virus recovery (77%) was obtained by immersing the filters in beef extract for 1 minute during the first elution and for 15 min during the second elution. The recovery efficiencies of poliovirus, coxsackievirus B5, and echovirus 7 from 100-liter samples of seeded tap water were 54%, 27%, and 32%, respectively. There was no significant difference in virus recovery from tap water with a pH range of 6 to 9.5 and a water flow rate range of 5.5 liters/min to 20 liters/min. Finally, poliovirus and Norwalk virus recoveries by NanoCeram filters were compared to those by 1MDS filters, using tap water and Ohio River water. Poliovirus and Norwalk virus recoveries by NanoCeram filters from tap and river water were similar to or higher than those by the 1MDS filters. These data suggest that NanoCeram filters can be used as an inexpensive alternative to 1MDS filters for routine viral monitoring of water.Viruses that primarily infect and replicate in the gastrointestinal tract are known as enteric viruses. More than 140 different enteric viruses are known to infect humans. These include the enteroviruses, rotaviruses, hepatitis A virus, noroviruses, adenoviruses, and reoviruses, among others. Enteric viruses are capable of causing a wide range of illnesses, including gastroenteritis, paralysis, aseptic meningitis, herpangina, respiratory illness, fevers, myocarditis, etc. Given the potential public health impact of the enteric viruses, enteroviruses (echovirus and coxsackievirus), adenoviruses, and caliciviruses are on the U.S. Environmental Protection Agency''s contaminant candidate list 2 for regulatory consideration for drinking water (11). Within the Caliciviridae family, noroviruses are the primary viruses of concern for drinking water.Contaminated drinking water is considered to be a potential transmission route, and an infectious dose in humans may consist of only a small number of virus particles. Enteric viruses are introduced in aquatic environments through natural or human activities, such as leaking sewage and septic systems, urban runoff, landfills, injection of treated wastewater into aquifers, wastewater discharge, sewage outfall, etc. These viruses have been found in surface water, groundwater, and drinking water (1, 6, 13, 22, 26). Between 1971 and 2004, 789 drinking water outbreaks and 575,207 cases of illness were reported in the United States, and 8% of the reported outbreaks were due to enteric viruses (2, 5, 28, 29, 30, 46).The levels of enteric viruses in natural waters are often low, and as such, typical virus sampling involves a primary concentration of viruses from large volumes of water (hundreds to thousands of liters). Unlike other waterborne pathogens (such as bacteria and parasites), viruses are smaller, and thus, size exclusion filtration is often not practical, especially for turbid waters. In addition, viruses are negatively charged in natural environments and can be adsorbed onto a number of different matrices by electrostatic and hydrophobic interactions (16). Consequently, different types of matrices have been used to isolate enteric viruses from water. These include negatively and positively charged membranes or cartridge filters (10, 17, 32, 34, 35, 39), gauze pad (31), and glass powder or glass wool (14, 27). Of all of these methods, electronegative and electropositive filters are most commonly used. In the case of electronegative filters, the acidification of the water and addition of multivalent cations are required for optimal virus adsorption. Because of this need to condition the water to attain acceptable recoveries, it is difficult to use electronegative filters for field sampling. In contrast, electropositive filters do not require conditioning of the water. Among all the filters, 1MDS electropositive filters (Cuno, Meriden, CT) are the most commonly used filter for fresh and drinking water sampling; however, they are not cost-effective for routine viral monitoring of water and require pH adjustment for waters with pH values exceeding 8.0 (12).Viruses adsorbed on the filter are usually eluted and recovered using 1 to 1.6 liters of eluting solution (6, 12). Many different procedures are described in the literature to elute viruses from filters. These procedures include the use of different eluting solutions, such as 0.3%, 1.5% or 3% beef extract, urea-arginine phosphate buffer, glycine buffer, etc. (10, 12, 24, 37). There are also different elution processes, such as single elution, recirculation of eluents, or successive elution of filters (6, 8, 15, 43). Sobsey and Hickey (40) used only one elution with 0.3% beef extract in 50 mM glycine. Sobsey et al. (43) suggested that 1 liter of 1.5% beef extract be recirculated through the filters for 5 min. Dahling and Wright (8) reported that the highest virus recoveries were obtained by three elutions, each using 1.6 liters of 3% beef extract. Dahling (6) reported that the highest virus recoveries were obtained with two separate beef extract elutions, one being an overnight filter immersion in beef extract.Although methods for concentration of many enteric viruses have been developed, limited studies have been conducted for concentrating noroviruses from water. Huang et al. (21) described a norovirus concentration method using porcine calicivirus (Pan-1) as a surrogate. Pan-1 was sensitive to the high pH (9.5) of the eluting solution, which is commonly used. Myrmel et al. (33) described a method of norovirus concentration using feline calicivirus as a surrogate organism. The method used electronegative filters, and the recovery of virus was 5 to 10%. Many other studies reported detection of human noroviruses in environmental waters (18, 19, 25); however, none of these studies evaluated the recovery efficiencies of human noroviruses from large volumes of water.The objective of this study was to evaluate the NanoCeram (Argonide, Sanford, FL) cartridge filter for the concentration of enteroviruses and noroviruses from large volumes of water. NanoCeram filters have an active component of nano alumina (AlOOH) fibers, which give them a naturally occurring electropositive charge.     

Acute Stress Increases Sex Differences in Risk Seeking in the Balloon Analogue Risk Task

Background

Decisions involving risk often must be made under stressful circumstances. Research on behavioral and brain differences in stress responses suggest that stress might have different effects on risk taking in males and females.

Methodology/Principal Findings

In this study, participants played a computer game designed to measure risk taking (the Balloon Analogue Risk Task) fifteen minutes after completing a stress challenge or control task. Stress increased risk taking among men but decreased it among women.

Conclusions/Significance

Acute stress amplifies sex differences in risk seeking; making women more risk avoidant and men more risk seeking. Evolutionary principles may explain these stress-induced sex differences in risk taking behavior.     

A revision of the genus Lomaantha, with the description of a new species

Lomaantha phragmitis sp. nov. is described and illustrated from a specimen collected on dead culms of Phragmites communis in southern China. The fungus differs from other described Lomaantha species in its conidiophores, conidiogenous cells and conidial appendages. Conidial morphology and presence or absence of percurrent proliferation of conidiogenous cells are the main characters distinguishing species within this genus. We provided a key and synoptic table of morphological characters of all three Lomaantha species.