• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 19
  • 15
  • 3
  • 1
  • 1
  • 1
  • Tagged with
  • 49
  • 49
  • 16
  • 13
  • 12
  • 9
  • 9
  • 8
  • 7
  • 7
  • 7
  • 7
  • 7
  • 6
  • 6
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Manipulation of the A mating type genes of Coprinus cinereus

Owusu, Rachel Asante January 1995 (has links)
No description available.
2

A study to identify the factors of influence on headteachers when considering whether or not to include sex education in the primary curriculum

Fidge, Roy January 1998 (has links)
The study examines factors which influence primary heads' decisions whether or not to include sex education in the curriculum. This is done using a questionnaire of 83 statements based on factors thought likely to discriminate between heads who support sex education and those who do not. The questionnaire was developed using statements from a small group of primary heads who were asked whether or not they had sex education in their schools and their reasons for this. These statements together with others from the literature were examined and analysed, reduced from a pool of about 170 to the final 83, and presented to a larger group of heads In another area. Influences upon heads' sex education decision-making were identified from the responses to these statements. The study was undertaken in 1990 in The North Kent Area where all 77 heads of all primary schools were invited to contribute. 54 heads did so, (response rate of 70.1%). 26 schools were junior, 28 were Junior mixed and infant. 37 were county schools, 11 Church of England and 6 Roman Catholic. 31 schools included sex education, 21 did not and 2 gave no indi, cation of status. 16 heads were women, 34 were men and 4 remained anonymous. The main hypothesis is that heads are main; y influenced by a few factors from the whole possible range which are said to influence curriculum development, and these will be close to, or within the school, in terms of their strength of influence. These will include factors which are personal to the head, with others relating to the staff and school, parents and families and the head's perception of children's needs and development. Two methods of analysis were applied to the data. The main method was by factor analysis, together with the use of cross-tabulation analysis. These methods combined to identify 33 statements in the questionnaire which discriminated between Sex Education and Ron-Sex Education heads. The main hypothesis was supported, that heads were influenced by factors in or close to the school. Heads regard themselves as occupying a significant position of influence over sex education decisions and expect theirs and the governors' decisions to be the sane. Sex Education Heads were more consistent in responding as anticipated and displayed higher levels of agreement/disagreement with the statements than Non-Sex Education Heads. Non-Sex Education Heads displayed a higher degree of ambivalence and ambiguity in their responses, Sex Education Heads showed greater personal commitment to their position compared with Non-Sex Education Heads. The 33 discriminating statements have been used to form a 'Sex Education Inventory' which could have various applications. It shows that many of the reasons for-against sex education in the literature have little influence on heads' decisions. It identifies those factors which are influential. It informs the sex education debate of the basic factors which need to be addressed to gain heads' support. It provides a means of determining where heads are on the for-against sex education continuum. It gives a sound starting point to those providing training, advice or support for the introduction, implementation and development of primary school sex education. The study provides a conceptual analysis of the factors which influence and shape sex education decisions.
3

Reproductive effects in two species of native freshwater gastropod mollusc exposed to 17β-oestradiol or an environmentally relevant mixture of oestrogenic chemicals in outdoor mesocosms

Baynes, Alice Louise January 2009 (has links)
Recent evidence suggests that molluscs may be sensitive to the effects of endocrine disrupting chemicals (EDCs) in a similar manner to vertebrates, such as fish. Despite this (with the exception of TBT-induced imposex in marine gastropods), molluscs have been largely overlooked in the field of endocrine disruption. Life-cycle studies were conducted in which two species of native UK freshwater gastropod molluscs (the hermaphrodite Planorbarius corneus and the gonochorist Viviparus viviparus) were exposed to either 17β-oestradiol or environmentally relevant mixtures of chemicals known to be oestrogenic to vertebrates and to be present in UK treated sewage effluents (TSE) and rivers. Adult snails were exposed for four months in outdoor mesocosms, fed by river water, over the spring and summer (breeding season) in order to examine effects on reproductive output, growth and mortality. Furthermore, offspring (F1s) were also developmentally exposed over the same period. F1 juvenile snails were then depurated in river water for nine months (over winter) after which time their growth, survival, and reproductive success were measured in further un-dosed river water mesocosm studies in the following spring/summer. Histopathology was used to determine immediate effects of chemical exposure on adult and F1 snails’ reproductive health. Histopathology was also used to determine long lasting effects of chemical exposure on depurated F1s. Exposure to oestrogenic chemicals resulted in a range of effects, including modulated fecundity and growth in F0 adults, to retardation of growth, sexual development and fecundity in developmentally exposed F1s. Exposure to mixtures of oestrogenic chemicals also resulted in possible modulation of the immune system, resulting in increased parasitism and over winter mortality of exposed F1s compared to snails exposed to river water alone. Differences in sensitivity and response to exposure between the two species and the generations were also observed.
4

Identification of genes regulated by the A mating type of Coprinus cinereus

Kingsnorth, Crawford January 1996 (has links)
No description available.
5

Unisexual Reproduction in Cryptococcus: Evolutionary Implications, Virulence and RNA Silencing

Feretzaki, Marianna January 2013 (has links)
<p>Sexual development enables microbial pathogens to purge deleterious mutations from the genome and drives genetic diversity in the population. <italic>Cryptococcus neoformans</italic> is a human fungal pathogen with a defined sexual cycle. Nutrient-limiting conditions and pheromones induce a dimorphic transition from unicellular yeast to multicellular hyphae and the production of infectious spores. <italic>C. neoformans</italic> has a defined <bold>a</bold>&ndash;&alpha; opposite sexual cycle (bisexual reproduction); however, >99% of clinical and environmental isolates are of the &alpha; mating type. Interestingly, &alpha; cells can undergo &alpha;&ndash;&alpha; unisexual reproduction, even involving genotypically identical cells. A central question is why would cells mate with themselves given that sex is costly and typically serves to admix pre-existing genetic diversity from genetically divergent parents? Sexual reproduction generates abundant spores that following inhalation, they penetrate deep into the alveoli of the lung, germinate, and establish a pulmonary infection growing as budding yeast. Therefore sex has been linked with virulence; however, hyphal development has been previously associated with reduced virulence and thus the roles of morphogenesis in virulence have not been extensively analyzed. To further understand the role of unisexual reproduction in <italic>C. neoformans</italic> we will investigate the evolutionary implications of &alpha;&ndash;&alpha; mating, explore its role in pathogenesis, and we will dissect the signaling pathway that regulates sexual development.</p><p>We isolated &alpha;&ndash;&alpha; unisexual reproduction progeny from the hyperfilamentous strain XL280 and subjected to a variety of phenotypic and genotypic assays (including whole genome sequencing and CGH). We found that unisexual and bisexual reproduction frequently generates phenotypic and genotypic diversity de novo, including aneuploidy. Aneuploidy was responsible for the observed phenotypic changes, as chromosome loss restoring euploidy results in a wild-type phenotype. Other genetic changes, including diploidization, chromosome length polymorphisms, SNPs, and indels, were also generated. Our study suggests that the ability to undergo unisexual reproduction may be an evolutionary strategy for eukaryotic microbial pathogens, enabling de novo genotypic and phenotypic plasticity and facilitating rapid adaptation to novel environments, such as the mammalian host.</p><p>Interestingly aneuploidy strains that were fluconazole resistant were as virulent as the WT parental strain XL280. Although XL280 belongs to the serotype D lineage that exhibits limited pathogenicity, in further studies we found that is hypervirulent in the murine model. It can grow inside the lung of the host, establishing a pulmonary infection, and then disseminates to the brain to cause cryptococcal meningoencephalitis. Surprisingly, this hyperfilamentous strain triggers an immune response polarized towards Th2-type immunity, which is characterized by less protective immunity and is usually observed in the highly virulent sibling species <italic>C. gattii</italic>, responsible for the Pacific Northwest outbreak. These studies: 1) provide a technological advance that will facilitate analysis of virulence genes and attributes in <italic>C. neoformans</italic> var. <italic>neoformans</italic> (serotype D), and 2) reveal the virulence potential of serotype D that is broader and more dynamic than previously appreciated.</p><p>Bisexual and unisexual reproduction are governed by shared components of the conserved pheromone-sensing Cpk1 MAPK signal transduction cascade and by Mat2, the major transcriptional regulator of the pathway. However, the downstream targets of the pathway are largely unknown, and homology-based approaches have failed to yield downstream transcriptional regulators or other targets. To address this question we applied an insertional mutagenesis via <italic>Agrobacterium tumefaciens</italic> transkingdom DNA delivery to identify mutants with unisexual reproduction defects. In addition to elements known to be involved in sexual development (Crg1, Ste7, Mat2, and Znf2), three key regulators of sexual development were identified by our screen: Znf3, Spo11, and Ubc5. Spo11 and Ubc5 promote sporulation during both bisexual and unisexual reproduction. Genetic and phenotypic analyses provide further evidence implicating both genes in the regulation of meiosis. Phenotypic analysis of sexual development showed that Znf3 is required for hyphal development during unisexual reproduction and also plays a central role during bisexual reproduction. Znf3 governs cell fusion and pheromone production through a pathway parallel to and independent of the pheromone signaling cascade. Surprisingly, Znf3 participates in transposon silencing during unisexual reproduction and may serve as a link between RNAi silencing and sexual development. In further studies we found that Znf3 is required for sex- and mitotic-induced (SIS and MIS). SIS is less efficient in <italic>znf3</italic> unilateral matings and is abolished in <italic>znf3</italic> x <italic>znf3</italic> bilateral matings, similar to the phenotypes of <italic>rdp1</italic> mutants (the RNA-dependent RNA-polymerase of RNAi pathway). Znf3 is also required for transgene-induced mitotic silencing; <italic>znf3</italic> mutations abrogate silencing of repetitive transgenes during vegetative growth. Znf3 tagged with mCherry is localized in the cytoplasm in bright, distinct foci. Co-localization of Znf3 with the P-body marker Dcp1-GFP further supports the hypothesis that Znf3 is a novel element of the RNAi pathway and operates to defend the genome during sexual development and vegetative growth. In concussion our studies provide further understanding of unisexual reproduction as an evolutionary successful strategy.</p> / Dissertation
6

Nutrition, metabolic hormones, and sexual development in bulls

Brito, Leonardo Fonseca Castro de 03 April 2006
A series of experiments was conducted to evaluate the effects of nutrition during calfhood (defined as the period from 10 to 26-30 wk of age) and peripubertal period (defined as the period from 27-31 to 70-74 wk of age) on sexual development and reproductive function in beef bulls. The overall objective of these experiments was to evaluate the effects of nutrition on endogenous metabolic hormones (leptin, insulin, GH, and IGF-I), gonadotropins and testosterone concentrations, sexual development, sperm production, and semen quality in bulls. The results of these experiments demonstrated that nutrition affected GnRH secretion and sexual development in bulls. Increased nutrition during calfhood resulted in a more sustained increase in LH pulse frequency during the early gonadotropin rise and greater testicular development at maturity. On the other hand, low nutrition during calfhood suppressed LH secretion during the early gonadotropin rise and resulted in delayed puberty and reduced testicular development at maturity. When low nutrition was accomplished by restricted feed intake, hypothalamic and pituitary function were compromised and LH secretion was more severely affected. Temporal associations between LH secretion patterns and circulating IGF-I concentrations implied that IGF-I is a possible signal to the central metabolic sensor involved in translating body nutritional status to the GnRH pulse generator. Nutrition also affected testicular steroidogenesis (testosterone concentrations), indicating effects on the number or function of Leydig cells, or both. Age-related increases in physiological and GnRH-stimulated circulating testosterone concentrations were hastened in bulls receiving high nutrition and delayed in bulls receiving low nutrition; these effects were probably mediated by both LH secretion and IGF-I concentrations. Circulating leptin and insulin may have only permissive roles on GnRH secretion, but may enhance testicular development. Growth hormone concentrations decreased concomitantly with increasing IGF-I concentrations during sexual development in bulls, suggesting that the testes could contribute considerable amounts of circulating IGF-I. In conclusion, management strategies to optimize reproductive function in bulls should focus on increasing nutrition during calfhood.
7

Nutrition, metabolic hormones, and sexual development in bulls

Brito, Leonardo Fonseca Castro de 03 April 2006 (has links)
A series of experiments was conducted to evaluate the effects of nutrition during calfhood (defined as the period from 10 to 26-30 wk of age) and peripubertal period (defined as the period from 27-31 to 70-74 wk of age) on sexual development and reproductive function in beef bulls. The overall objective of these experiments was to evaluate the effects of nutrition on endogenous metabolic hormones (leptin, insulin, GH, and IGF-I), gonadotropins and testosterone concentrations, sexual development, sperm production, and semen quality in bulls. The results of these experiments demonstrated that nutrition affected GnRH secretion and sexual development in bulls. Increased nutrition during calfhood resulted in a more sustained increase in LH pulse frequency during the early gonadotropin rise and greater testicular development at maturity. On the other hand, low nutrition during calfhood suppressed LH secretion during the early gonadotropin rise and resulted in delayed puberty and reduced testicular development at maturity. When low nutrition was accomplished by restricted feed intake, hypothalamic and pituitary function were compromised and LH secretion was more severely affected. Temporal associations between LH secretion patterns and circulating IGF-I concentrations implied that IGF-I is a possible signal to the central metabolic sensor involved in translating body nutritional status to the GnRH pulse generator. Nutrition also affected testicular steroidogenesis (testosterone concentrations), indicating effects on the number or function of Leydig cells, or both. Age-related increases in physiological and GnRH-stimulated circulating testosterone concentrations were hastened in bulls receiving high nutrition and delayed in bulls receiving low nutrition; these effects were probably mediated by both LH secretion and IGF-I concentrations. Circulating leptin and insulin may have only permissive roles on GnRH secretion, but may enhance testicular development. Growth hormone concentrations decreased concomitantly with increasing IGF-I concentrations during sexual development in bulls, suggesting that the testes could contribute considerable amounts of circulating IGF-I. In conclusion, management strategies to optimize reproductive function in bulls should focus on increasing nutrition during calfhood.
8

Normal Childhood Sexual Development

Langenbrunner, Mary R. 03 December 2008 (has links)
No description available.
9

How Do Individuals View Their Own Experiences with Risky Sexual Behaviour?: A Narrative Inquiry

Moore, Elizabeth L Unknown Date
No description available.
10

Narratives of Racial Sexual Preference in Gay Male Subculture

Crockett, Jason Lee January 2010 (has links)
My dissertation uses multiple methods to introduce the novel concept of racial sexual preference - individuals’ preferences for a sexual or romantic partner based on race. This project builds on an insight from Daryl Bem’s “Exotic Becomes Erotic” theory of sexual development: a diverse set of sexual preferences exists beyond gender. I argue the very real social consequences of race make preferences in regard to it (sexual or otherwise) an important area for systematic study. I focus on gay male subculture, which has uniquely developed a terminology for expressing racial preferences. I investigate how racial preference is understood and organized within this subculture by collecting gay men’s sexual history narratives of cross-race preferences through interviews, as well as collecting archival materials from the national organization Black and White Men Together (BWMT) that pertain to racial sexual preference. I find that racial sexual preferences are experienced early in the life course and are consistent over time, similarly to experiences of gendered sexual orientation, though generally less exclusive. Unlike gendered sexual orientation, identities are unlikely to form in relation to racial sexual preferences because there is little ideological structure to support expression of cross-race racial preferences. Even within the organizational structure of BWMT, founded to support racial sexual preferences, over time I find a decrease in discourse and identity related to racial sexual preference (in favor of a colorblind ideal of preferences). I end my study by using the concept of racial sexual preference, supported by the findings from interviews and case study, to build on and challenge the theoretical work of Daryl Bem, Lisa Diamond, and James Giles in the area of sexual development and desire.

Page generated in 0.0825 seconds