Use of single versus multiple biotic communities as indicators of biological integrity in northern prairie wetlands

AbstractAs much as 70% of prairie wetlands in Canada have been lost. Although further degradation of natural wetlands is considered to be somewhat offset by wetland construction and restoration, Canada lacks bioassessment tools that can track ecosystem health in prairie wetlands. Indices of biological integrity (IBIs) use one or more biotic communities to compare the biological condition of a particular site to conditions found in least-impacted reference sites. Using the IBI approach, we evaluated the potential of 5 biotic communities to assess wetland health in northern prairie wetlands in Canada. Vegetation in the wet meadow, emergent and open-water zones as well as wetland-dependent songbirds and waterbirds were sampled at 81 semi-permanent/permanent natural and compensation wetlands spanning an environmental stress gradient. Metrics with strong linear relationships to the stress gradient (R2>0.2) were combined into an IBI for each biotic community and were subsequently validated at a suite of test sites. After validation, the entire data set was combined and each IBI was evaluated based on its linear relationship to environmental stress. Wet meadow zone vegetation was a strong indicator of environmental stress (R2=0.68, p<0.001), as was the wetland-dependent songbird community (R2=0.59, p<0.001). The emergent zone vegetation community was a relatively weak and inconsistent indicator of environmental stress, while the open-water zone vegetation and waterbird communities were poor indicators. To evaluate whether monitoring more than one biotic community provided additional information about a site's biological and environmental condition, we produced a two-taxon IBI that combined wet meadow zone vegetation and wetland-dependent songbird metrics. The two-taxon IBI had a marginally stronger linear relationship to the stress gradient (R2=0.72, p<0.001) than any single biotic community alone, although we argue that this added information would not warrant the extra cost, effort, and logistical barriers of sampling both plants and birds. The wet meadow zone vegetation and wetland-dependent songbird IBIs were strong surrogates of one another (R2=0.57), suggesting that wet meadow zone vegetation can be used to predict the health of wetland-dependent songbirds, and visa versa. Our results suggest that habitat for healthy wet meadow zone vegetation and wetland-dependent songbird communities is being degraded as compensation sites are replacing their natural analogs

Effect of Estradiol-17β on Placental Size

Meishan embryos transferred to recipient females on day 2.5 are larger, contain greater numbers of trophectoderm cells, and secrete greater amounts of estradiol-17β when gestated in a Yorkshire compared with Meishan uterus to day 12. Additionally, placentae of Meishan conceptuses are larger when gestated in a Yorkshire compared with Meishan uterus throughout gestation. Embryonic estradiol-17β secretion during elongation on day 12 to 13 of gestation is temporally associated with endometrial secretion of growth factors, including IGF-I, which has been shown to increase mitotic rate in the trophectoderm of pig embryos. This experiment was conducted to determine if estradiol-17β administration to Meishan females at the time of conceptus elongation would increase placental size at term. Meishan females (n=12) were checked twice daily for estrus (0700 and 1900), and each bred to a Meishan boar at 0 and 24 h after the onset of estrus (day 0). Females were randomly assigned in equal numbers to receive injections of sesame oil (VEH) starting on day 12 (CONTROL), 1 mg of estradiol-17β in VEH starting on day 12 (E212), or 1 mg of estradiol-17β in VEH starting day 13 (E213). The injections were initiated at 0700 or 1900 (corresponding to the time of day they first exhibited estrus) and continued at 6-hour intervals for 48 hours, resulting in 8 mg of estradiol-17β given in eight injections. Pregnant females were killed on day 112 of gestation and ovulation rate, litter size, implantation site length, fetal weight, crown-rump length, placental weight, and placental surface area were quantified. There were no differences among E212, E213, and CONTROL females in ovulation rate or litter size, which averaged 16.3 ± .7 and 11.8 ± .7, respectively. Fetal weight and crown-rump length were not different (P\u3e.10) among E212, E213, and CONTROL females, averaging 802 ± 26 g and 24.3 ± .3 cm. Placentae were markedly heavier (176 ± 14 and 174 ± 16 g vs. 134 ± 10 g,

Glycan Engineering for Cell and Developmental Biology

Cell-surface glycans are a diverse class of macromolecules that participate in many key biological processes, including cell-cell communication, development, and disease progression. Thus, the ability to modulate the structures of glycans on cell surfaces provides a powerful means not only to understand fundamental processes but also to direct activity and elicit desired cellular responses. Here, we describe methods to sculpt glycans on cell surfaces and highlight recent successes in which artificially engineered glycans have been employed to control biological outcomes such as the immune response and stem cell fate

Synthetic probes of glycosaminoglycan function

Glycosaminoglycans (GAGs) participate in many critical biological processes by modulating the activities of a wide range of proteins, including growth factors, chemokines, and viral receptors. Recent studies using synthetic oligosaccharides and glycomimetic polymers have established the importance of specific structural determinants in controlling GAG function. These findings illustrate the power of synthetic molecules to elucidate glycan-mediated signaling events, as well as the prospect of further advancements to understand the roles of GAGs in vivo and explore their therapeutic potential

The Experience of using Facebook as an Educational Tool

Social Networking Sites (SNS) such as Facebook are widely used by student populations and are increasingly used by the population generally. Researchers have considered the benefits of using SNS for educational purposes. This qualitative study involved interviews with seven academic members of staff at one UK university who currently use Facebook in their teaching. The study provides a unique insight into the views of teaching staff who use Facebook in their classroom, gaining an understanding of their experience and views of using SNS as part of their teaching

Properties of PAN Fibers Solution Spun into a Chilled Coagulation Bath at High Solvent Compositions

In this work, multifilament, continuous polyacrylonitrile (PAN) fiber tow was solution spun mimicking industrial processing at the small pilot scale (0.5 k tow), while carefully altering the composition of the coagulation bath, in order to determine the effect on the resulting fiber shape, density, orientation, and tensile properties at varying points in the spinning process. Novel here are the abnormally high coagulation bath solvent compositions investigated, which surpass those often reported in the literature. In addition, the coagulation bath was maintained at a slightly chilled temperature, contrary to reported methods to produce round fibers. Further, by altering the composition of the bath in a step-wise fashion during a single spinning run, variations in all other process parameters were minimized. We found that with increasing solvent composition in the coagulation bath, the fibers not only became round in cross section, but also became smaller in diameter, which persisted down the spin line. With this decrease in diameter, all else equal, came an accompanying increase in apparent fiber density via a reduction in microvoid content. In addition, molecular orientation and tensile properties also increased. Therefore, it was found that inadequate understanding of the coagulation bath effects, and spinning at low coagulation bath solvent compositions, can hinder the ability of the fiber to reach optimum properties

The Effect of Uterine Environment on Meishan and Yorkshire Fetal Development and Placental Size and Vascularity

When Meishan (M) and Yorkshire (Y) embryos were cotransferred to Y recipients that were then allowed to farrow, it was observed that the birth weights of M and Y littermates were similar averaging 1.15 ± .06 kg. In contrast, placentae matched to M piglets were markedly smaller (.70% lighter) and more vascular (.two-fold) than Y placentae. To investigate the effect of uterine environment on conceptus development to term, M and Y embryos were cotransferred to M recipients (n=3) that were slaughtered one day before expected parturition (day 113). Fetal weight, placental weight, and placental surface area were recorded. Additionally, a section of the intact maternal placental interface was excised, fixed, embedded, sectioned, and stained to allow quantitation of the placental vascular density (PVD). As observed when M and Y fetuses were cogestated by Y recipients, littermate M and Y fetuses gestated in M uteri were similar in weight (1.04 ± .03 vs. 1.03 ± .05 kg) at term. Further, M conceptuses exhibited markedly reduced (P\u3c.03) placental weights (170 ± 19 vs. 249 ± 10 g) and surface areas (1017 ± 70 vs. 1506 ± 96 cm 2 ) compared with their Y littermates. As was the case for conceptuses gestated in Y uteri, the similarity in fetal weight between the two breeds with very different placental sizes appears to result from an increased (P\u3c.09) M PVD compared with littermate Y fetuses (2.5 ± .3 vs. 1.4 ± .4%). These data indicate that in both the M and Y uterine environment, the reduced size of the M compared with Y placenta is compensated for by an increase in PVD. Currently it is unknown whether M placentae contain a greater amount of vasculature (total volume) or a similar amount of vasculature simply squeezed into a smaller space. To investigate breed differences in total placental vasculature we have perfused placentae of M and Y conceptuses cogestated in M uteri on d 113 of gestation with vascular casting material and will compare the volumes of the corrosion casts

Role of Vascular Endothelial Growth Factor in Placental Vascularization

The ratio of a fetus’s weight to that of its placenta has been used in our laboratory as an estimate of placental efficiency, which defines the number of grams of placenta required to support a gram of fetus. Because the pig placenta is noninvasive, nutrients from the mother must diffuse from uterine blood vessels to placental blood vessels at the placental-endometrial interface. A pig placenta can respond to increasing fetal nutrient demands by either increasing in size, and thus surface area in contact with the endometrium, or by increasing the number of blood vessels per unit area at the fetal-maternal interface. Previous studies from our laboratory have shown Meishan and Yorkshire conceptuses gestated in a Meishan uterus had markedly smaller placentae than Meishan or Yorkshire conceptuses gestated in a Yorkshire uterus whereas fetal weights across the two uterine environments were much more similar. These data suggested that conceptuses in a Meishan uterine environment have a greater vascular density at the placentalendometrial interface. Greater densities of blood vessels can be achieved by either vasodilation (increasing the diameter of existing blood vessels) or angiogenesis (growth of new vessels from preexisting ones). Hypoxia, or inadequate oxygen transport, has been shown to increase angiogenic factors, such as vascular endothelial growth factor (VEGF), which stimulate blood vessel development. It is possible that VEGF may be important in stimulating increased blood vessel density in the pig placenta, as it has been to shown to do in the ovine placenta. Our objective was to determine if VEGF mRNA expression was associated with placental and/or endometrial vascular density, placental efficiency, and litter size during late gestation. We observed a positive association of both placental vascular density (r=0.37, p\u3c0.05) and VEGF mRNA levels (r=0.35; P\u3c.05) with placental efficiency . There was also a positive correlation between VEGF mRNA levels and the number of conceptuses in a litter (r=0.42; P\u3c.05) on day 70, 90, and 110 of gestation. Although Yorkshire uteri exhibited greater endometrial vascular density than Meishan uteri on day 70 of gestation, placentae of conceptuses gestated in a Meishan uterus had greater amounts of VEGF mRNA than placentae of conceptuses gestated in a Yorkshire uterus. The greater amounts of placental VEGF mRNA of conceptuses gestated in a Meishan uterus on day 70 may have resulted in the increased placental vascular density observed on day 90. We conclude that the increased litter size of the Meishan female may stem from her having smaller, more vascular placentae than placentae of conceptuses gestated in the uterus of a Yorkshire female, to allow for efficient nutrient delivery to the fetus. The increased placental vascular density of a conceptus gestated in the uterus of a Meishan female may result from increased placental VEGF mRNA production induced from an endometrial induced hypoxia on day 70 of gestation

Use of Asynchronous Embryo Transfer to Investigate the Role of Uterine-embryo Timing on Placental Size

The ability of the uterus to accommodate a finite amount of placental tissue appears to be a major limitation to litter size. Meishan preimplantation conceptuses contain fewer cells, produce less estradiol-17β, elongate to a shorter length, and exhibit a reduced placental size throughout gestation than Yorkshire conceptuses. Uterine luminal embryonic estradiol-17β and growth factor content are positively associated at elongation. Based on these data, we have argued that growth factor quantity regulates the length an embryo attains at elongation, and ultimately limits placental size. Recently, we injected Meishan gilts every 6 hours with estradiol-17β on day 12 and 13 of gestation, resulting in a 40% increase in placental size at term compared with vehicle-injected Meishan gilts. This study was conducted to determine if transfer of embryos into the oviducts of asynchronous females (more or less advanced uterine environments) would alter fetal and/or placental size at term. Embryos (1 to 4 cells) were flushed from the oviducts of each donor gilt on day 2.5 of gestation and transferred in equal numbers to the oviducts of a recipient gilt on day 1.5, 2.5, or 3.5 of their estrous cycle. Gilts were slaughtered on day 112 of gestation and fetal and placental weight, placental surface area, and implantation site lengths were determined. Although litter sizes were similar (8.4 ± 1.1), conceptuses transferred to day 3.5 recipients had heavier fetuses (1.57 ± .09 vs. 1.23 ± .04 kg, P\u3c.001), larger placental surface area (1812 ± 106 vs. 1458 ± 43 cm 2 , P\u3c.01) and occupied longer implantation site length (34 ± 3 vs. 25 ± 1 cm, P\u3c.001) than those transferred to recipients on day 1.5 or 2.5. These data demonstrate that oviductal transfer of embryos to a reproductive tract as little as 24 hours more advanced can result in dramatic alterations in placental growth and function during gestation