Tracing ancient evolutionary divergence in parasites

For parasitic platyhelminths that generally lack a fossil record, there is little information on the pathways of morphological change during evolution. Polystomatid monogeneans are notable for their evolutionary diversification, having originated from ancestors on fish and radiated in parallel with tetrapod vertebrates over more than 425 million years. This study focuses on the genus Polystomoides that occurs almost worldwide on freshwater chelonian reptiles. Morphometric data show a major divergence in structural adaptations for attachment; this correlates with a dichotomy in micro-environmental conditions in habitats within the hosts. Species infecting the urinary tract have attachment organs with large hamuli and small suckers; species in the oro-nasal tract differ fundamentally, having small hamuli and large suckers. Zoogeographical and molecular evidence supports ancient separation of these site-specific clades: a new genus is proposed – Uropolystomoides – containing urinary tract species distinct from Polystomoides sensu stricto in oro-nasal sites. Aside from differences in attachment adaptations, body plans have probably changed little over perhaps 150 million years. This case contrasts markedly with polystomatids in other vertebrate groups where major morphological changes have evolved over much shorter timescales; the chelonian parasites show highly stable morphology across their global distribution over a long period of evolution, exemplifying ‘living fossils’

Spherical alterations of handles: embedding the manifold plus construction

A key tool in our earlier work on ends of manifolds high-dimensional manifolds was an ability to embed cobordisms provided by the Quillen Plus Construction into those ends. Here we develop a `spherical modification' trick which provides a constructive approach to obtaining such embeddings. More importantly, this approach allows for more general embedding results. In this paper we develop generalizations of the plus construction and show how the corresponding cobordisms can be embedded in manifolds satisfying appropriate fundamental group properties. Results obtained here play an important role in our ongoing study of noncompact manifolds.Comment: This final version will appear in Algebraic & Geometric Topology. Small corrections, including a fix to the statement of Theorem 5.3. 22 pages, 4 figure

Molecular Recognition Profiles of Molecular Cocrystals

The manner in which molecules recognize each other holds critical importance to nearly every area of science. This significance stems from the key underpinning of molecular assembly to our most basic understanding of chemical processes. Whether these interactions relate to small-molecule catalytic transformations or complex physiological processes, the structural features responsible for molecular association play into the well-known adage that form follows function where material property arises from the collective structural features of the molecular components. Because the form of chemical systems is derived from a complex blend of covalent and non-bonded contacts, codifying each contributor has become essential for recognizing the functions and potential applications of materials. While considerable progress in this area has been realized by isolating and identifying molecular contacts and the structural details of their conditional exceptions, insight to the entire landscape of molecular associations remains an ongoing effort. This thesis explores the molecular recognition process from two uniquely different perspectives. The first is from cocrystalizing a variety of benzoic acids with the pharmaceutical agent sulfamethazine and the second area investigates how molecular shape controls quasiracemate formation. Sulfamethazine is an active pharmaceutical ingredient (API) with a strong ability to form hydrogen bonds due to its donor and acceptor groups. The chemical structure of this API allows it to exist in more than one tautomer. The cocrystallization of this molecule with a coformer has the ability to influence which tautomer is present in the crystal structure. This thesis provides data that defines the relationship of coformer acidity to tautomer formation in sulfamethazine. A total of eighteen cocrystals of sulfamethazine with benzoic acid derivatives were synthesized and the tautomeric form to coformer acidity was analyzed. The cocrystallization of APis is a classic example of molecular recognition between two or more compounds. Studies that seek to design these materials and others often focus on strong non-bonded contacts (e.g. hydrogen bonds) as a means to generate desired supramolecular architectures. Less well studied, but no less important to the overall molecular recognition process, are chemical features that produce less manageable motifs via ill-defined or weak contacts. Molecular shape is one such feature. This thesis exploits quasiracemates — i.e., near racemic materials — to probe the role molecular topology plays in the recognition process. A diverse set of diarylamide quasienantiomers that differ incrementally in substituent size and molecular framework has been prepared. Mixing of pairs of these quasienantiomers in the melt using video-assisted host stage microscopy provided a robust diagnostic tool for detecting new quasiracemic crystalline phases. Data retrieved using this virtual melting-point phase method not only draws considerable attention to the role of topological features to supramolecular assemblies, but also the structural boundaries of these co-crystalline systems. This investigation synthetically explores the broad structure space towards the identification of new isostructural building blocks and highlights important molecular relationships responsible for molecular recognition that may serve in the design of new functional materials

Molecular Recognition Profiles of Molecular Cocrystals

The manner in which molecules recognize each other holds critical importance to nearly every area of science. This significance stems from the key underpinning of molecular assembly to our most basic understanding of chemical processes. Whether these interactions relate to small-molecule catalytic transformations or complex physiological processes, the structural features responsible for molecular association play into the well-known adage that form follows function where material property arises from the collective structural features of the molecular components. Because the form of chemical systems is derived from a complex blend of covalent and non-bonded contacts, codifying each contributor has become essential for recognizing the functions and potential applications of materials. While considerable progress in this area has been realized by isolating and identifying molecular contacts and the structural details of their conditional exceptions, insight to the entire landscape of molecular associations remains an ongoing effort. This thesis explores the molecular recognition process from two uniquely different perspectives. The first is from cocrystalizing a variety of benzoic acids with the pharmaceutical agent sulfamethazine and the second area investigates how molecular shape controls quasiracemate formation. Sulfamethazine is an active pharmaceutical ingredient (API) with a strong ability to form hydrogen bonds due to its donor and acceptor groups. The chemical structure of this API allows it to exist in more than one tautomer. The cocrystallization of this molecule with a coformer has the ability to influence which tautomer is present in the crystal structure. This thesis provides data that defines the relationship of coformer acidity to tautomer formation in sulfamethazine. A total of eighteen cocrystals of sulfamethazine with benzoic acid derivatives were synthesized and the tautomeric form to coformer acidity was analyzed. The cocrystallization of APis is a classic example of molecular recognition between two or more compounds. Studies that seek to design these materials and others often focus on strong non-bonded contacts (e.g. hydrogen bonds) as a means to generate desired supramolecular architectures. Less well studied, but no less important to the overall molecular recognition process, are chemical features that produce less manageable motifs via ill-defined or weak contacts. Molecular shape is one such feature. This thesis exploits quasiracemates — i.e., near racemic materials — to probe the role molecular topology plays in the recognition process. A diverse set of diarylamide quasienantiomers that differ incrementally in substituent size and molecular framework has been prepared. Mixing of pairs of these quasienantiomers in the melt using video-assisted host stage microscopy provided a robust diagnostic tool for detecting new quasiracemic crystalline phases. Data retrieved using this virtual melting-point phase method not only draws considerable attention to the role of topological features to supramolecular assemblies, but also the structural boundaries of these co-crystalline systems. This investigation synthetically explores the broad structure space towards the identification of new isostructural building blocks and highlights important molecular relationships responsible for molecular recognition that may serve in the design of new functional materials

Environmental constraints influencing survival of an African parasite in a north temperate habitat: effects of temperature on egg development

SUMMARYFactors affecting survival of parasites introduced to new geographical regions include changes in environmental temperature. Protopolystoma xenopodis is a monogenean introduced with the amphibian Xenopus laevis from South Africa to Wales (probably in the 1960s) where low water temperatures impose major constraints on life-cycle processes. Effects were quantified by maintenance of eggs from infections in Wales under controlled conditions at 10, 12, 15, 18, 20 and 25°C. The threshold for egg viability/ development was 15°C. Mean times to hatching were 22 days at 25°C, 32 days at 20°C, extending to 66 days at 15°C. Field temperature records provided calibration of transmission schedules. Although egg production continues year-round, all eggs produced during >8 months/ year die without hatching. Output contributing significantly to transmission is restricted to 10 weeks (May-mid-July). Host infection, beginning after a time lag of 8 weeks for egg development, is also restricted to 10 weeks (July-September). Habitat temperatures (mean 15·5°C in summer 2008) allow only a narrow margin for life-cycle progress: even small temperature increases, predicted with 'global warming', enhance infection. This system provides empirical data on the metrics of transmission permitting long-term persistence of isolated parasite populations in limiting environments

Environmental constraints influencing survival of an African parasite in a north temperate habitat: effects of temperature on development within the host

The monogenean Protopolystoma xenopodis has been established in Wales for >40 years following introduction with Xenopus laevis from South Africa. This provides an experimental system for determining constraints affecting introduced species in novel environments. Parasite development post-infection was followed at 15, 20 and 25 °C for 15 weeks and at 10 °C for51 year and correlated with temperatures recorded inWales. Development was slowed/arrested at410 °C which reflects habitat conditions for >6 months/year. There was wide variation in growth at constant temperature (body size differing by >10 times) potentially attributable in part to genotype-specific host-parasite interactions. Parasite density had no effect on size but host sex did: worms in males were 1·8 times larger than in females. Minimum time to patency was 51 days at 25 °C and 73 days at 20 °C although some infections were still not patent at both temperatures by 105 days p.i. In Wales, fastest developing infections may mature within one summer (about 12 weeks), possibly accelerated by movements of hosts into warmer surface waters. Otherwise, development slows/stops in October–April, delaying patency to about 1 year p.i., while wide variation in developmental rates may impose delays of 2 years in some primary infections and even longer in secondary infections

Faculty Pressures and Professional Self-Esteem: Life in Texas Teacher Education

Studies of the beliefs of teacher educators record high levels of professional self-esteem, but also document the perceived lack of professional regard from colleagues in other areas, informing and redirecting our professional needs assessment. The literature documents that a general disregard for teacher educators as professionals has become a part of the academic culture at many institutions of higher learning in the US. With all of the external pressures on teacher educators, from governmental and accrediting agencies, the public, and professional organizations, perhaps we should address the attitudes of our academic colleagues as one area in which faculty pressures might be lightened

Sex-specific routes to immune senescence in Drosophila melanogaster

Animal immune systems change dramatically during the ageing process, often accompanied by major increases in pathogen susceptibility. However, the extent to which senescent elevations in infection mortality are causally driven by deteriorations in canonical systemic immune processes is unclear. We studied Drosophila melanogaster and compared the relative contributions of impaired systemic immune defences and deteriorating barrier defences to increased pathogen susceptibility in aged flies. To assess senescent changes in systemic immune response efficacy we injected one and four-week old flies with the entomopathogenic fungus Beauveria bassiana and studied subsequent mortality; whereas to include the role of barrier defences we infected flies by dusting the cuticle with fungal spores. We show that the processes underlying pathogen defence senescence differ between males and females. Both sexes became more susceptible to infection as they aged. However, we conclude that for males, this was principally due to deterioration in barrier defences, whereas for females systemic immune defence senescence was mainly responsible. We discuss the potential roles of sex-specific selection on the immune system and behavioural variation between males and females in driving these different senescent trends

Chemical Abundance Constraints on White Dwarfs as Halo Dark Matter

We examine the chemical abundance constraints on a population of white dwarfs in the Halo of our Galaxy. We are motivated by microlensing evidence for massive compact halo objects (Machos) in the Galactic Halo, but our work constrains white dwarfs in the Halo regardless of what the Machos are. We focus on the composition of the material that would be ejected as the white dwarfs are formed; abundance patterns in the ejecta strongly constrain white dwarf production scenarios. Using both analytical and numerical chemical evolution models, we confirm that very strong constraints come from Galactic Pop II and extragalactic carbon abundances. We also point out that depending on the stellar model, significant nitrogen is produced rather than carbon. The combined constraints from C and N give $\Omega_{WD} h < 2 \times 10^{-4}$ from comparison with the low C and N abundances in the Ly$\alpha$ forest. We note, however, that these results are subject to uncertainties regarding the nucleosynthesis of low-metallicity stars. We thus investigate additional constraints from D and $^4$He, finding that these light elements can be kept within observational limits only for \Omega_{WD} \la 0.003 and for a white dwarf progenitor initial mass function sharply peaked at low mass (2$M_\odot$). Finally, we consider a Galactic wind, which is required to remove the ejecta accompanying white dwarf production from the galaxy. We show that such a wind can be driven by Type Ia supernovae arising from the white dwarfs themselves, but these supernovae also lead to unacceptably large abundances of iron. We conclude that abundance constraints exclude white dwarfs as Machos. (abridged)Comment: Written in AASTeX, 26 pages plus 4 ps figure