An investigation of factors determining growth and form of bacterial colonies

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Sex Determination And Differentiation In The Common Snapping Turtle - A Reptile With Temperature-Dependent Sex Determination

Temperature-dependent sex determination (TSD) was first discovered in an African lizard over 40 years ago. TSD has since been shown to be exhibited by many vertebrates including some fish and amphibians, numerous lizards, turtles, and all crocodilians studied to date. Although numerous questions surround TSD, a major question focuses on understanding the genetic, physiological and molecular mechanisms underlying this process. However, the molecular mechanisms underlying TSD are not well known and the gene(s) that transduces a signal for ovary or testis development is not known in any species. Furthermore, it is well established that sex steroid hormones, androgens and estrogens, are important for sex determination and differentiation in TSD species. Yet, the role of androgens in these processes is not well understood. This dissertation addresses these questions in two parts. First, to identify unique, thermo-sensitive, genes involved in TSD and secondly, determine the role of androgens in sex determination and differentiation in the common snapping turtle, a reptile with TSD. I used differential-display PCR to clone a candidate gene involved in TSD, the cold-inducible RNA binding protein (Cirbp). The temporal and spatial patterns of Cirbp mRNA and protein expression during and after sex determination were determined using quantitative real-time PCR, in situ hybridization, and immunohistochemistry. I used next-generation Illumina sequencing to identify small nucleotide polymorphisms (SNPs) to test for associations between Cirbp genotype, mRNA expression, and sex ratios. To determine the role of androgens in sex determination and differentiation, snapping turtle embryos were treated with the androgen, dihydrotestosterone (DHT), the anti-androgen, flutamide, or a vehicle (ethanol) control. Whole mount in situ hybridization and immunohistochemistry were used to determine the effect of the treatments on sex differentiation of the male reproductive tracts. Quantitative real-time PCR was used to measure expression patterns of ovary-specific genes, testis-specific genes and steroidogenic genes in gonads from embryos treated with vehicle, DHT, or flutamide. I found Cirbp was induced at a high female-producing temperature, but not at a low female-producing temperature. Cirbp is associated with TSD and expression of alternative Cirbp alleles is capable of transducing temperature differently for establishing a signal that directs ovaries versus testes development. I observed allelic specific expression and differences in allele frequencies between turtle embryos from northern and southern Minnesota, suggesting genetic adaptation to local thermal regime. I also found significant genetic associations between Cirbp genotype, Cirbp expression and sexual phenotype in a study that produced mixed sex ratios. Androgens were capable of inducing ovarian development even at an all-male producing temperature, presumably by inducing aromatase expression and increasing endogenous estrogen production. I also observed among clutch variation in androgen responsiveness to produce females, suggesting there is a genetic basis for the response. My findings provide the strongest evidence to date for a unique gene involved in TSD. Additional studies are required to define the functional role of Cirbp in sex determination. Androgens appear critical for ovarian development, but ongoing research is needed to understand androgen signaling and the genetic variation underlying this process

Northern Bobwhite Densities in Burned and Unburned Redberry Juniper Rangelands

We estimated northern bobwhite (Colinus virginianus) densities in 4- and 8-year-old burned and unburned redberry juniper (Juniperus pinchottii) dominated pastures. The 4-year-old burned (800 ha), 8-year-old burned (1,200 ha), and unburned (1,200 ha) treatment sites had 8.6, 14.4, and 22.3% woody canopy coverage, respectively. Fall bobwhite densities were estimated from 122 flushes of quail coveys on 592.8 km of transects. Data histograms indicated that bobwhite were harder to detect in the unburned area than in the 8-year-old burn or the 4-year-old burn. Probability detection functions were smaller in the old burn than the new burn (P = 0.05) or unburned area (P = 0.02). Bobwhite densities of 43.3, 55.1, and 60.5 birds/100 ha in the 4-year-old burn, 8-year-old burn, and unburned sites, respectively, were similar (P \u3e 0.10). Prescribed burning to control redberry juniper and manage bobwhite should be designed to maintain intermittent shrub coverage

Buried narratives : representations of pregnancy and burial in South African farm novels

This dissertation examines the way in which South African colonial texts may be read for the historical signs they inadvertently reveal. The history of land acquisition in South Africa may be read through the representation of burial and illegitimate pregnancy in South African farm novels. Both burial and illegitimate pregnancy are read as signifiers of illegitimacy in the texts, surfacing, by indirection, the question of the illegitimacy of land acquisition in South Africa. The South African farm novel offers a representational form which seeks (or fails) to mediate the question of land ownership and the relationship between colon and indigene. In the four texts under discussion, Olive Schreiner's The Story of an African Farm, Florence Ethel Mills Young's The Bywonner[sic], Pauline Smith's The Beadle and Daphne Rooke's Mittee, the representation of burial and illegitimate pregnancy is problematic and marked by narrative displacements and discursive breakdowns. KEY TERMS burial, colonial discourse, farm novel, illegitimacy, illegitimate pregnancy, land, postcolonial theory, representationEnglishM.A. (English

What\u27s New in Plant Pathology

Changes to the Disease Management Section of the 2016 Guide for Weed, Disease, and Insect Management in Nebraska Biological control Products Trivapro Fungicide Priaxor D. Fungicide Table 1. Foliar products for disease control that were updated in the 2016 Guide for Weed, Disease and Insect Management in Nebraska. Table 2. Seed treatment products for disease control that were updated in the 2016 Guide for Weed, Disease and Insect Management in Nebraska. Table 3. Seed treatment nematicide product that was updated in the 2016 Guide for Weed, Disease and Insect Management in Nebraska

Corn Disease Profiles: Diseases Favored by Wet Conditions

Extension Circular 1909 (EC1909) Extreme weather events are predicted to become increasingly common and could bring periods of more intense rainfall. Wet conditions are favorable for many plant pathogens and the development of diseases. Seasonal timing when these conditions occur, as well as other factors such as temperature, impact which diseases develop and when. Listed, described, and illustrated are some common corn diseases favored by wet conditions: Pythium Root Rot, Eyespot, Northern Corn Leaf Blight, Gray Leaf Spot, Physoderma Brown Spot, Rust Diseases (Puccinia spp.), Stalk and Crown Rot Diseases (such as those caused by Fusarium and Diplodia spp.), and Ear Rot Diseases (such as those caused by Fusarium, Gibberella, and Diplodia spp.)

Corn Disease Profiles: Diseases Favored by Dry Conditions

Extension Circular 1910 (EC1910) Extreme weather events are predicted to become increasingly common and could bring periods of drought as well as intense rainfall events. Wet conditions are favorable for many plant pathogens and the development of diseases, but some diseases may also develop during or following dry weather. The timing during the season when dry conditions occur, as well as other factors, such as temperature, impact which diseases develop and when. The list summarizes some of the most common corn diseases that can develop during dry conditions: Seedling Root Rot Diseases, Nematodes, Common Smut, Rust Diseases Charcoal Rot, Stalk and Crown Rot Diseases, and Aspergillus Ear Rot. (Illustrated with photographs.

Corn Disease Profiles: Diseases Favored by Wet Conditions

Extension Circular 1909 (EC1909) Extreme weather events are predicted to become increasingly common and could bring periods of more intense rainfall. Wet conditions are favorable for many plant pathogens and the development of diseases. Seasonal timing when these conditions occur, as well as other factors such as temperature, impact which diseases develop and when. Listed, described, and illustrated are some common corn diseases favored by wet conditions: Pythium Root Rot, Eyespot, Northern Corn Leaf Blight, Gray Leaf Spot, Physoderma Brown Spot, Rust Diseases (Puccinia spp.), Stalk and Crown Rot Diseases (such as those caused by Fusarium and Diplodia spp.), and Ear Rot Diseases (such as those caused by Fusarium, Gibberella, and Diplodia spp.)

Effects of Human Choices on Characteristics of Urban Ecosystems

Most urban ecology in cities remains an ecology in cities rather than an ecology of cities. Accomplishing the latter requires the inclusion of humans within the concept of ecosystem, both how humans alter the properties of urban ecosystems and how these alterations in turn influence human well-being. These influences are both direct (e.g., physiological and psychological influences on the human organism) and indirect, by influencing ecosystem sustainability. For the 2007 ESA meeting, Larry Baker, Loren Byrne, Jason Walker, and Alex Felson organized a symposium to address the relationships among human choices and urban ecosystems. In the introductory talk of this symposium, these authors discussed how the cumulative effect of individual household choices can have major effects on the properties of urban ecosystems