Showing 861 - 870 of 5701 Items
“I felt so untrustworthy of my ability to get pregnant”: Women’s Embodied Uncertainties and Decisions to Become Pregnant
Date: 2020-01-01
Creator: Theodora K. Hurley
Access: Open access
- This paper identifies “embodied uncertainties”—possibilities of aging and infertility lodged within the body—as informing women’s conceptualizations of their reproductive bodies and their decisions about and approaches to getting pregnant. Using data from semi-structured interviews with a small sample of highly educated, professional, white women who had given birth within 18 months prior, this paper argues that (bio)medicalized risk discourses and neoliberal logics of responsible choice-making lodge uncertainty and the possibility of failure within women’s reproductive bodies. As they attempt to reconcile childbearing with professional and financial constraints, women may identify their bodies as laden with embodied uncertainties and may subsequently adopt strategies for becoming pregnant that seek to mitigate those embodied uncertainties, such as by trying to conceive before feeling completely ready for a pregnancy. Ultimately, (bio)medicalization and neoliberalism have transformed reproductive aging and infertility into individualized concerns and foreclosed recognition of the institutional failures that create conflicts of aging, careers, and childbearing in women’s lives.
Beyond Urban Bias: Peasant Movements and the State in Africa
Date: 2019-05-01
Creator: Connor Rockett
Access: Open access
- Focusing on sub-Saharan Africa, this study tests the hypothesis that state intervention in agrarian economies causes peasant movements to engage in broad-based contention, on regional and national levels. The study traces the connections between government land and agricultural institutions and the characteristics of rural movements that make claims on them. Case studies of regions of Tanzania, Senegal, Côte d’Ivoire, and Ethiopia show the ways in which rural movements are constructed in response to the political and social environments in which they arise. That is, the comparisons demonstrate that the character of political authority and social organization are important determinants of the form taken by peasant movements.
Active and Passive Spatial Learning and Memory in Human Navigation
Date: 2019-01-01
Creator: Caroline Rice
Access: Open access
- Previous studies show that active exploration of an environment contributes to spatial learning more than passive visual exposure (Chrastil & Warren, 2013; Chrastil & Warren, 2015). Active navigation and cognitive decision-making in a novel environment leads to increased spatial knowledge and memory of location compared to a passive exploration that removes the decision-making component. There is evidence of theta oscillations present in electroencephalography (EEG) recordings from the hippocampus and pre-frontal cortex (PFC). These low-frequency waves could reflect spatial navigation and memory performance, suggested by their involvement in communication between the formerly named brain regions. Through communication with the hippocampus, theta oscillations could be involved in the integration of new spatial information into memory. While undergoing EEG, subjects in this study either actively or passively explored a virtual maze, identified as the “Free” or “Guided” groups, respectively. After exploring, subjects’ spatial memory of the maze was tested through a task that required navigation from a starting object to a target object. Behavioral data show increased spatial memory for the Free group, indicated by significantly greater navigation to the correct target object in the memory task. EEG results indicate significantly greater theta oscillations in frontal regions for the Free group during the exploration phase. These results support those found in previous studies and could indicate a correlation between frontal theta oscillations during learning of novel environments and spatial memory.
Quantification and Characterization of AST-C Peptides in Homarus americanus Using Mass Spectrometry
Date: 2014-08-01
Creator: Amanda Howard
Access: Open access
- Neuropeptides are small signaling molecules found throughout the nervous system that are responsible for influencing animal behavior. They consist of short amino acid chains and interact with cell-membrane receptors in order to regulate behavioral responses (Fig. 1a). The American lobster, Homarus americanus, has proven to be a strong model organism in which to study such activity due to the simplicity of the system and the wealth of existing knowledge about the animal. One neuropeptide found in H. americanus is a C-type allatostatin (AST-C). Allatostatins are a family of neuropeptides originally identified in insects that inhibits juvenile hormone production. The H. americanus AST-C has a pyroglutamate blocked N-terminus and an unmodified C-terminus (Fig. 1b). In addition to AST-C, a different, yet structurally similar neuropeptide has been found in H. americanus. This peptide has an unmodified N-terminus and an amidated C-terminus (Fig. 1c). Both forms of AST-C (referred to as ASTC-real and ASTC-like) also have a disulfide bond between their two cysteine residues. In the lobster, both peptides influence cardiac muscle contraction patterns and have been found in various tissues throughout the nervous system [1, 2]. In order to establish the purpose of the observed post-translational modifications, this study aims to find whether these peptides exist in other forms in the lobster and to determine their relative and absolute concentrations.Liquid chromatography-mass spectrometry (LC-MS) and tandem mass spectrometry (MS/MS) are often used in analytical chemistry to characterize complex samples and identify neuropeptides. First, sample components are separated by chromatography based on properties such as size and hydrophobicity. Using mass spectrometry (MS), peptides are protonated (positively charged) and their mass is determined from their measured mass-to-charge ratios. These peptides are lastly fragmented into many ions using MS/MS, which ultimately allows them to be sequenced in order to determine their identity. This summer, standards of the two AST-C peptides have been characterized by LC-MS/MS. The reduced forms of both peptides have been synthesized by chemically reducing the disulfide bond and were also analyzed by MS/MS. As expected, the structural stability provided by the disulfide bond prevented fragmentation during MS/MS analysis; that is, there was evidence of more fragmentation in the reduced forms than in the fully processed forms (Fig. 2). When looking for other forms of ASTC, these findings will facilitate the identification of the reduced forms in crustacean tissue.To assess the accuracy of the detection method used, detection limits were assessed by analyzing sample matrices augmented with known amounts of peptide standards. The smallest amount of peptide detected from a single injection was 25 fmol (2.5·10-14 mol) peptide. There appeared to be a strongly linear relationship between the amount of ASTC-real injected and the instrument response (chromatographic peak area) (R2=0.996, n=6). However, the relationship between the amount of ASTC-like injected and the instrument response was less linear (R2=0.802, n=5), and the calibration slope was more shallow, indicating that this peptide is more difficult to detect. This is possibly because ASTC-real, unlike ASTC-like, contains an arginine (R) and a histidine (H) residue, two basic amino acids susceptible to protonation. Therefore, it seems that ASTC-real is more easily protonated during the ionization process in MS analysis, causing it to be more readily detected.Lastly, ASTC-real has been identified in the pericardial organ (PO), a tissue responsible for delivering neuropeptides manufactured in the thoracic ganglion to the heart in order to control muscle contraction. ASTC-like is also believed to be present in the PO based on previous work in the Dickinson lab (E. Dickinson, unpublished data), but it is likely that it has not yet been detected in this study due to the detection limitations described above. To address these issues, more tissues will be pooled to increase the amount of peptide in each sample analyzed.Currently, tissue extraction methods are being optimized to eliminate phospholipid contamination and to maximize detection sensitivity. Specifically, two separate extraction solvents as well as a chloroform delipidation procedure are being tested. Future goals include quantifying peptide levels by adding a known amount of internal standard to the samples and comparing instrument responses for ASTC and for internal standard. Additionally, known amounts of peptide standard will be brought through the extraction process to determine the amount of peptide loss throughout this procedure. During the upcoming academic year, this study will be continued as an Honor’s project. Further research in these areas will ultimately help explain how neuropeptides interact to regulate behavior within the lobster and in more complex systems. Final Report of research funded by the Henry L. and Grace Doherty Charitable Foundation Coastal Studies Research Fellowship.
The letter of the law: Administrative discretion and Obama's domestic unilateralism
Date: 2014-04-01
Creator: Andrew Rudalevige
Access: Open access
- In his 2014 State of the Union address Barack Obama pledged to act without Congress on a variety of fronts, following up his "we can't wait" campaign of unilateralism before the 2012 election. The partisan furor this engendered tended to obscure the longstanding efforts of presidents to "faithfully execute" the law in a manner that aligns with their policy preferences. This paper examines the broad logic of those efforts, and delineates five areas where the Obama administration has been particularly aggressive: in its (1) recess appointments; (2) refusal to defend federal law (notably, the Defense of Marriage Act) in court; (3) use of prosecutorial discretion in declining to pursue violations of immigration and drug laws; (4) use of waivers; and (5) its utilization of the regulatory process to interpret the meaning of statutes, as with the Clean Air Act and the Affordable Care Act. Presidents do have flexibility in many cases; but this ends where they seek to alter the plain "letter of the law.".
The capacity to act in trans varies among drosophila enhancers
Date: 2016-05-01
Creator: Amanda J. Blick, Ilana Mayer-Hirshfeld, Beatriz R. Malibiran, Matthew A. Cooper, Pieter A., Martino, Justine E. Johnson, Jack R. Bateman
Access: Open access
- The interphase nucleus is organized such that genomic segments interact in cis, on the same chromosome, and in trans, between different chromosomes. In Drosophila and other Dipterans, extensive interactions are observed between homologous chromosomes, which can permit enhancers and promoters to communicate in trans. Enhancer action in trans has been observed for a handful of genes in Drosophila, but it is as yet unclear whether this is a general property of all enhancers or specific to a few. Here, we test a collection of well-characterized enhancers for the capacity to act in trans. Specifically, we tested 18 enhancers that are active in either the eye or wing disc of third instar Drosophila larvae and, using two different assays, found evidence that each enhancer can act in trans. However, the degree to which trans-action was supported varied greatly between enhancers. Quantitative analysis of enhancer activity supports a model wherein an enhancer’s strength of transcriptional activation is a major determinant of its ability to act in trans, but that additional factors may also contribute to an enhancer’s trans-activity. In sum, our data suggest that a capacity to activate a promoter on a paired chromosome is common among Drosophila enhancers.