• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 101
  • 99
  • 22
  • 11
  • 6
  • 5
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 316
  • 91
  • 34
  • 29
  • 28
  • 27
  • 24
  • 21
  • 20
  • 19
  • 18
  • 17
  • 16
  • 15
  • 14
  • 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.
131

Determination Of Polymorphism Of Pgm, Hk, Pgi, And G6pd In Different Developmental Stages Of Honey Bee (apis Mellifera L.) And Its Relation With Pgm Activity And Glycogen Content

Yeni, Filiz 01 May 2010 (has links) (PDF)
In this study, three subspecies of Apis mellifera L. (A. m. caucasica, A. m. carnica, and A. m. syriaca) from different climatic regions were evaluated electrophoretically at ontogenetic level by means of four enzymes, namely Phosphoglucomutase (PGM), Hexokinase (HK), Phosphoglucose isomerase (PGI) and Glukose-6-phosphate dehydrogenase (G6PD). It is determined that only Pgm and Hk loci were polymorphic. Allele and genotype frequencies at Pgm locus changes seasonally whereas Hk locus does not exhibit seasonal variation. Within the scope of this study we investigated at which developmental stage shifting to heterozygotes prior to winter occurs. It is found that there is a seasonal fluctuation throughout the year in Pgm genotype frequencies at each developmental stage studied and correlated with enzyme activity and glycogen content. As the studied enzymes have crucial v roles in insect energy metabolism, results of this study provided further information about the relationship between carbohydrate metabolism and enzyme polymorphism of honey bees.
132

Age-related differences in cocaine place conditioning and cocaine-induced dopamine

Badanich, Kimberly A 01 June 2005 (has links)
In humans, adolescent exposure to illicit drugs predicts the onset of adult drug abuse and suggests that early drug use potentiates adolescent vulnerability to drug addiction. In experiment 1, it was hypothesized that adolescent rats would show a CPP for a low cocaine dose if in fact adolescents are more vulnerable to cocaine's rewarding effects. Place preferences were measured in early adolescent [postnatal day (PND) 35], late adolescent (PND 45) and young adult (PND 60) rats by injecting either 0, 5 or 20 mg/kg cocaine and conditioning them to environmental cues in a 2-chamber place conditioning apparatus. Significant cocaine preferences were found for all ages at the high dose. Interestingly, PND 35's were the only age group to have a CPP at the low dose suggesting that PND 35 rats are more sensitive than late adolescent and young adult rats to cocaine's rewarding effects. In Experiment 2, it was hypothesized that age-related differences in cocaine CPP may be mediated by differences in the mesolimbic dopaminergic (DA) system throughout development. Extracellular DA levels in the nucleus accumbens septi (NAcc) of early adolescent, late adolescent and adult rats were measured via quantitative microdialysis. PND 35, PND 45 and PND 60 rats were injected daily with either 5 mg/kg/ip or saline for 4 days, surgically implanted with a microdialysis probe aimed at the NAcc. Rats were perfused with either 0, 1, 10 or 40 nM DA and the extracellular DA concentration was measured. Our results show that adolescents differ from adults in basal DA with PND 35 rats having low basal DA (0.4 nM), PND 45 rats having high basal DA (1.8 nM) and PND 60 rats having intermediate basal DA (1.3 nM). PND 45 cocaine treated rats showed a 58% decrease in basal DA. All cocaine treated rats, regardless of age, showed a significant increase in DA over baseline in response to a cocaine challenge. Additionally, there were age-related differences in the extraction fraction (Ed), an indirect measure of DA reuptake, with PND 45 and PND 60's showing a decrease in basal Ed, an effect absent in PND 35's. Together these findings suggest that there are substantial ontogenetic differences in extracellular DA and DA reuptake and that these differences may provide an explanation for adolescent vulnerability to addiction. Future research should investigate DA supply and degradation processes in naïve and cocaine treated adolescent rats and vulnerability to addiction.
133

An integrated evaluation of costs and benefits of corticosterone secretion through development

Wada, Haruka 28 August 2008 (has links)
Not available / text
134

The evolution of skeletal development in early tetrapods : anatomy and ontogeny of microsaurs (Lepospondyli)

Olori, Jennifer Catherine 15 July 2011 (has links)
Because the ancestry of extant amphibians remains highly controversial, under traditional perspectives, amphibians and amniotes often are distinguished by differences in developmental mode rather than their evolutionary relationships. Resolution of relationships is important, however, because phylogeny affects interpretations of biology, including the evolution of development. To address those issues, I documented the growth and development of two extinct lepospondyls, Microbrachis pelikani and Hyloplesion longicostatum, and compared the patterns in those taxa to data from other tetrapods. I quantified allometry in the skeleton using both measurement-based and geometric morphometric analyses. I applied Ontogenetic Sequence Analysis (OSA), a size-independent method, to the reconstruction of ossification sequences based on fossils. I also documented skeletal morphogenesis and used Parsimov Analysis and Parsimov-based Genetic Inference of ossification sequence data to evaluate the three hypotheses of extant amphibian ancestry, the Lepospondyl (LH), Temnospondyl (TH), and Polyphyletic (PH) hypotheses. Skeletal growth in Microbrachis pelikani and Hyloplesion longicostatum is primarily isometric. Comparisons with data from other Paleozoic taxa suggest that isometry was the ancestral pattern of growth in tetrapods. All regression analyses had a linear fit indicating lack of an abrupt metamorphosis. Absence of metamorphosis is also supported by the possession of lateral lines in both taxa throughout ontogeny, and Microbrachis pelikani additionally retained gills. However, ossification of the skeleton was completed at small body size. The greatest resolution in ossification sequence reconstruction was achieved with OSA, but results from all reconstruction methods indicated advanced ossification of the pubis and delayed ossification of the scapula in the lepospondyls. In terms of total number of sequence shifts optimized across each hypothesis of amphibian relationships, the TH had the shortest tree length. However, the values for the three hypotheses did not differ significantly, demonstrating that none was supported strongly. Based on my synthesis of new developmental data, I propose that Microbrachis pelikani and Hyloplesion longicostatum expressed a mosaic pattern of skeletal development. That pattern included a gradual transition to an adult morphology, and a lack of an amphibian-like metamorphosis. A similar pattern is common to most early tetrapods and Eusthenopteron, supporting the hypothesis that metamorphosis is not ancestral for Tetrapoda. / text
135

An integrated evaluation of costs and benefits of corticosterone secretion through development

Wada, Haruka, 1976- 19 August 2011 (has links)
Not available / text
136

Ontogenetic Patterns of Positional Behavior in Cebus Capucinus and Alouatta Palliata

Bezanson, Michelle January 2006 (has links)
Positional behavior is the measurable and observable link between the biology and behavior of an animal in its environment. In this dissertation, I examine ontogenetic patterns of positional behavior in infant, juvenile, and adult white-faced capuchins (Cebus capucinus) and mantled howling monkeys (Alouatta palliata) inhabiting the same tropical forest in Costa Rica. During growth and development ontogenetic changes in body size, limb proportions, and motor skills are likely to influence locomotion and posture through the arboreal canopy. I collected data on positional behavior, activity, prehensile-tail use, branch size, branch angle, and crown location during a 12 month period at Estación Biológica La Suerte in northeastern Costa Rica. The data set is comprised of 401.3 hours of data on Cebus capucinus and 554.3 hours of data on Alouatta palliata totaling 955.7 hours of data or 57,344 individual activity records.Life history timing and differences in rates of growth did not predictably influence the development of adult-like positional behaviors in Cebus and Alouatta. In both species, infancy was characterized by high proportions of dorsal, ventral, and side riding on the mother with smaller proportions of independent positional modes observed during play, explore, active posture, and feed/forage. Young Cebus resembled the adult pattern of positional behavior by six months of age while howlers exhibited significant differences in several positional behavior categories through 24 months of age. The positional repertoire of both species revealed similarities in the types of modes used during feed/forage and travel in juveniles and adults. For example, in juvenile and adult age categories of Cebus, feeding and foraging included high proportions of quadrupedal walk, sit, and squat in conjunction with climbing, leaping, and suspensory behaviors. In howlers, the degree to which coordination and increases in body mass during ontogeny as limiting factors in the development of adult-like positional competence is unclear. Data presented here suggest that the environment exerts different pressures on growing Cebus and Alouatta that may relate to diet, energy expenditure, foraging skill, and/or social learning.
137

Addressing key conservation priorities in a data poor species

Cook, Adam 14 August 2012 (has links)
Conserving biodiversity is suggested to be one of the most important challenges being faced by the global community. The field of conservation biology has been developed to examine the threats that drive species to low abundance, the dynamics of species in low abundance and the methods to rebuild abundance. Typically, assessing these issues requires substantial data inputs; however we are often faced with situations where little information exists. In this thesis, I addressed several key conservation priorities in the endangered Atlantic Whitefish (Coregonus huntsmani), a data poor species, which has been restricted to one watershed for most of the past century. Using molecular genetic markers Atlantic Whitefish were determined to be a distinct and basal species within the genus. Population size was suggested to be low and the incidence of inbreeding high as genetic effective population size was among the lowest of any fish species examined and genetic diversity was 2-6 times lower than regional congeners. Through laboratory experiments environmental threats to the persistence of Atlantic Whitefish were examined. Overall, Atlantic Whitefish were tolerant to a broad range of environmental conditions and were capable of surviving in harsher environments than many other regional species. Furthermore, their persistence in current habitats will likely not be influenced by the assessed environmental conditions. As part of this work, a suite of methods and metrics to compare thermal sensitivity across a range of finfish species were assessed. In order to inform recovery efforts, I developed simulation models to evaluate habitat suitability for translocation of Atlantic Whitefish. As part of this work, I examined the role of incorporating variability in species response, environment and / or life history into simulations. The results showed that the inclusion of multiple sources of variability altered the perception of optimal habitats; however, several watersheds offered suitable translocation habitats. Throughout this thesis I explored novel tools to address some of the key issues facing conservation programs of data poor species. This work is not only applicable to the conservation of Atlantic Whitefish, but also outlines some of the potential tools useful in addressing conservation priorities in other species.
138

Infant Development and Maternal Strategies in the Two Largest Lemurs: The Diademed Sifaka (Propithecus diadema) and the Indri (Indri indri).

Weir, Jody Suzanne 22 August 2014 (has links)
At least half of the world’s primate species are currently threatened with extinction. Slow life histories combined with rapid habitat loss and hunting in recent years has heightened the extinction risk for many species, including the two largest extant lemurs, the diademed sifaka (Propithecus diadema) and the indri (Indri indri). Both species belong to the taxonomic family Indriidae, have similar adult weights, and occur in sympatry in certain areas of the montane rainforests of eastern Madagascar. Both species are adapted for folivory however I. indri spend considerably more time feeding on leaves than do P. diadema resulting in several energy-saving adaptations in I.indri. In this dissertation, I explore infant development and maternal strategies of these critically endangered primates with the goal of increasing our knowledge of reproduction and ontogeny in both species. Although previous studies have elucidated key differences in adult behaviour, there is a dearth of information on infants and lactating females in either of these two species. Between June and December of 2011 and 2012, I collected continuous time focal animal data, in Maromizaha forest, to examine behavioural patterns of 12 infants and their mothers from 0 – 33 weeks. In addition, I developed a framework to define and quantify the weaning process and facilitate comparisons across different species and studies. P. diadema infants developed feeding competency and independent locomotion faster than did I. indri infants however both species were consistently feeding independently more than they were suckling by week 20. The process of feeding ontogeny in I. indri was likely accelerated by coprophagy, as all infants of this species consumed their mother’s feces regularly from 10 – 15 weeks old. Lactating females of both species spent more time feeding in mid-lactation when maternal investment was the highest. The prolonged inter-birth interval in I. indri is suggested as another adaptation that reduces energetic expenditures. In addition, the protracted period of close contact with their mother may offer infant I. indri more time for social learning of the mother’s diet and the group song and for developing competency in vertical clinging and leaping without a tail for balance and support. / Graduate
139

Patterns in ontogeny of human trabecular bone from SunWatch Village in the prehistoric Ohio Valley

Gosman, James Howard, January 2007 (has links)
Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 328-378).
140

Stoichiometry and the relative importance of autochthonous and allochthonous food sources for a dominant detritivorous fish

Pilati, Alberto. January 2007 (has links)
Thesis (Ph. D.)--Miami University, Dept. of Zoology, 2007. / Title from second page of PDF document. Includes bibliographical references.

Page generated in 0.0854 seconds