Archive for April, 2008
Peat Accumulation of a Sphagnum Poor Fen in Temperate East Pennsylvania during the Holocene
Climate change can greatly affect the carbon balance of peatlands by influencing production and decomposition. Studying boreal peatlands along the edge of their southern range may provide insight into boreal peatland responses to warmer climates. Here we present results of AMS dating (n=9), 268 bulk density measurements and macrofossil analysis of a 10.7-m peat core from Tannersville Bog, one of the southernmost (41N) low altitude (277 m) Sphagnum peatlands along the eastern seaboard of North America. Results indicate a concave peat-age pattern over the last ~11 cal ka, similar to patterns documented in oceanic bogs but different from those of continental fens. The peat-addition rate of ~120 g per square meter per year was higher than most boreal peatlands, but catotelm decomposition rate was similar (0.0002 yr-1) to other peatlands. Apparent accumulation rates ranged from 13 to 109 gC per square meter per year, with a time-averaged mean of 28 gC per square meter per year. This relatively high accumulation rate may have been caused by high primary production (rather than low acrotelm decomposition) associated with a warmer and wetter climate. Plant macrofossil data indicate a major transition from rich fen to poor fen at ~1.2 cal ka, possibly triggered by a dry and/or variable climate as documented at other sites in the region. Our results imply that a warmer and wetter climate may increase carbon storage in some regions for certain types of peatlands.
Functional Distribution of Hamster Sperm Associated alpha-L-fucosidase: a role in fertilization?
Sperm associated alpha-L-fucosidases have been identified in diverse organisms. The wide-spread distribution of this enzyme is consistent with the importance of carbohydrates during fertilization. Characterization of human sperm membrane associated alpha-L-fucosidase (SMALF) by our lab has demonstrated its cryptic subcellular distribution, with enrichment in the equatorial segment (Venditti et al. 2007). More recently we have reported SMALFs in situ stability with enzyme activity detectable up to 72 hours post ejaculation; consistent with the timeline for a successful fertilization event to occur. Previous studies provide direct evidence supporting roles for fucose containing polysaccharides and/or fucosidases during fertilization; however the roles and molecular mechanisms of SMALF remain to be defined. If SMALF is present in Syrian hamster sperm an in vitro model system to evaluate its role during stages of fertilization could be developed. Cauda epididymal contents (CEC) were collected from adult male Syrian hamsters and suspended in Human Sperm Medium (HSM). For capacitation, CEC were incubated in HSM supplemented with 3% BSA and 1 mM hypotaurine for 3 hours at 37C, 5% CO2. Acrosome reaction was induced by incubating capacitated cells with 10 M BrA23187 ionophore for 30 minutes at 37C, 5% CO2. Enzyme assays using the fluorogenic substrate 4-MU-fuc were performed as previously described (Venditti et al. 2007), with measurements recorded over a 30 minute time period. Enzymatic studies have revealed the presence of hamster sperm associated alpha-L-fucosidase. Activity was detectable in both the sperm pellet and soluble fraction. An increase in sperm associated alpha-L-fucosidase activity was evident following capacitation and acrosome induction. All hamster alpha-L-fucosidase activity was inhibitable by inclusion of L-fucose or deoxyfuoconjirimycin (DFJ) a known, specific competitive inhibitor. Western blot analysis showed detectable alpha-L-fucosidase bands comparable to those found in human semen. Preliminary IVF experiments using Syrian hamster sperm and oocytes have shown successful zona pellucida (ZP) binding and penetration by sperm, demonstrating a reasonable model system to evaluate the role of alpha-L-fucosidase during fertilization.
Aggression & Courtship Behaviors of Beaugregory Damselfish on Different Quality Territories: Correlated Behaviors, But Not a Syndrome
Personalities, temperaments, or behavioral types have long been the interest of scientists and have been studied in more than 60 species, from ants to zebrafish. The behavioral syndrome hypothesis suggests that individual animals within a population behave differently because of their specific behavioral type or temperament and these behavioral types should be consistent across behaviors or in different situations. In contrast, when animals live within an environment in which territory quality can change over time, natural selection should have favored animals that show behavioral flexibility and modulate the cost of defense of the area in relation to territory quality. This would require assessment of the territory followed by displays of appropriate types and intensities of behavior. We examined the territorial behavior of male beaugregory damselfish by enhancing territory quality using artificial breeding sites and comparing their behavior to males on natural sites. Males on artificial sites reproduce at a higher level than males on natural sites. We found that when male fish were defending high quality artificial territories, they had higher levels of aggression toward male conspecifics and courtship toward females than when on low quality natural territories. We also found that behaviors were correlated on natural sites, but not artificial. Behaviors were not correlated when males switched from natural to artificial territories or from artificial to natural territories. These results indicate that males assess their current territories and adjust behaviors accordingly.
Representing the Yellow ‘Other’: Japan and China in American Popular Culture 1924-1942
The National Origins Act of 1924 effectively ended Japanese immigration into the United States. The act was a response to pressures from Progressive eugenicists and West Coast agricultural interests who feared competition from Japanese migrant workers. The passage of the National Origins Act also ended a period in which American political leaders saw Japanas a close partner and protg to the United States, and began a slow process in which the American people othered Japan. American filmmakers, writers, artists and other popular culture figures were deeply involved in othering Japan and the Japanese, and ultimately rehabilitating the image of China and the Chinese, who had, up until that time, been seen as the great yellow peril and much more of a threat than the Japanese, who were seen as much more like Americans. Ultimately, those similarities would prove to be Japanese-Americans undoing. › Continue reading