Thesis (M.A.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / Serotonin (5-hydroxytryptamine), one of the biologically active amines, has been found in rather large quantities in the dorsal skin of Rana pipiens. Quantitative determination of the endogenous levels of the amine in the whole dorsal skin homogenate extracts were made on a Farrand spectroflourometer, and ranges of 120-200 micrograms per gram of fresh tissue were established. Comparison of whole skin homogenates and homogenates of just the dorsal cutaneous ridges, or dermal plicae, indicated that the amine is localized in these ridges. Acid treatment of the denser more fibrous portions of the homogenate prior to extraction more then noublcc the yields of serotonin. This result showed that the amine is found primarily in the deeper portions of the skin, very likely in the poison glands which are concentrated in the dermal plicae. Skin homogenates were also studied to determine if serotonin is actually synthesized in the skin. A precursor of the amine, 5-hydroxytryptophan, decarboxylates in tne presence of 5-hydroxytryrtophan decarooxylase to produce the amine. 5-hydroxytryrtophan was incubated with the homogenate, under nitrogen, for two hours to determine enzymic activity. Under the conditions of the experiment, no enzymic activity could be shown, indicating that serotonin is not produced in the skin of the frog in detectable amounts. The fact that serotonin levels are so high, and the lack of enzymic activity indicates that once synthesized serotonin is stored in an inactive form or is synthesized elsewhere and transnorted to the skin. / 2031-01-01

No description available.

This study was undertaken to determine the effects of beryllium nitrate on regeneration in the tail of Rana Pipiens larvae. The tails were amputated approximately 3 rom from the tips. Some were then treated with different concentrations of beryllium nitrate (0.5 N, 0.7 N, and 1.0 N). Normal regeneration of untreated amputated tails was fulfilled in an orderly manner. In the animals treated with beryllium nitrate, general tissue regeneration was inhibited. Considerable degeneration was observed in all tissues of the tail stumps. Holfever, the elastic lamella of the notochordal sheath was stimulated to stretch, oftentimes breaking the continuity of the fibrous lamella. The elastic layer appeared highly ravelled within the degenerated tissues of the tail, and, in some cases, extended for 3 to 4 inches from the tail stump due to a break in the covering epithelium.

Host-pathogen investigations have conceptually evolved during the last two decades, from a basic and descriptive approach to a current hypothesis-driven and a more theoretical discipline shaped by evolutionary biology. Our deeper understanding of the elements influencing the mutual selective pressures that the host and the pathogens exert on each other, together with recent conceptual advances, currently position this field of research at the frontier between ecology and evolution. Recent theoretical considerations define hostpathogens systems as an evo-eco mosaic comprised of evolutionary and ecological attributes in turn underlying the context-dependent nature of the system dynamic. Therefore, investigations of host-pathogen interactions should integrate the diversity of the systems drivers by using an integrative approach in order to elucidate both coevolutionary trajectory and epidemiological dynamic of the system. In this thesis, such a framework is used to investigate Amphibian/ranavirus interactions. Ranaviruses are emerging pathogens known to have caused amphibian die-offs on five continents with the greatest number of reported mortality events documented in North America and Europe. Despite an increasing understanding of ranaviral disease properties, ranavirus disease dynamics in the environment remain poorly understood. For instance, the influence of potential abiotic and biotic mechanisms including temperature, local landscape features, larval developmental stages, host density and genetic variability as well as genotypic interactions between the host and the pathogen has on the prevalence and virulence of the virus remains to be elucidated. In order to improve our knowledge regarding these specific determinants of ranaviral disease, I designed a combination of manipulative laboratory experiments and a field mensurative survey using the ranid amphibian Lithobates (Rana) pipiens as the host model for this system. I observed that populations of amphibian hosts inhabiting urbanized landscapes suffered from significant decline in genetic diversity in turn promoting the accrued infection by the ranavirus (manuscript 1). Complementary analysis using two amphibian host species, L.pipiens and L.sylvaticus, and three ranavirus strains revealed significant variation among hosts for their susceptibility to ranavirus, and significant variation among ranavirus strains for infectivity. I also showed that specific amphibian/ranavirus interactions might have a tighter coevolutionary history than other combinations, resulting in sharper mutual coadaptations and the potential for frequency-dependent selection to operate in this system. However, the coevolutionary trajectories in this host-pathogen system are dependent on the temperature conditions in which the interaction takes place. Amphibian/ranavirus interactions outcomes iv are therefore temperature, host, and pathogen genotype-dependent suggesting that the range of infection outcomes in this system is potentially large (manuscript 2). Further, I observed that increasing animal holding density is detrimental for host fitness as mortality rate is higher, day of death earlier, development longer, and growth rate significantly lower when tadpoles are experimentally exposed to ranavirus in high holding density situations. These results paralleled a linear increase of detrimental effects when ranavirus doses increased in low density conditions, with control tadpoles having a significantly higher overall relative fitness. However, this pattern was not observed in high density conditions, where the effects of increasing ranavirus dose were limited, revealing non-trivial density-dependence of virulence expression (manuscript 3). Finally, ranavirus infection rate varied with the host developmental stage as the host immune system clears the infection over the course of individual host development. However the intensity of the clearing depends on both the timing and number of ranavirus exposures (manuscript 4). Overall the results described in my thesis suggest that ranavirus virulence depends on a diversity of ecological, epidemiological, and evolutionary determinants. The underlying complexity of ranavirus

Thesis (Ph.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / Quantitative relationships between blood flow velocity, vessel diameter, width of the peripheral plasma layer and induction of thrombus formation were studied in small blood vessels of the retrolingual membrane and intestinal mesentery of the frog, Rana Pipiens, and of the cheek pouch of the golden hamster, Mesocricetus auratus. Blood flow velocity was measured by a modification of the technique described by Hugues (Arch. Int. de Physiol. 61: 565, 1953). Internal vessel diameters and widths of the total peripheral plasma layer were measured with an ocular micrometer. Thrombus thresholds were determined by graded electrical stimulation. Determinations were made on 202 vessels in retrolingual membranes of frogs prepared by single pithing. In 95 arterioles (diameters from 10 to 40 microns), the mean flow velocity was 2.84 mm/sec. and the mean volume flow rate, 1.68xl0-3 cu mm/sec. The mean width of the total peripheral plasma layer was 3.6 microns and its ratio to mean vessel diameter was 1:6. In 107 venules (diameters from 10 to 50 microns), the mean flow rate was 1.20 mm/sec. The mean volume flow rate was 1.02x10-3 cu mm/sec. The mean width of the total peripheral plasma layer was 4.1 microns and its ratio to mean vessel diameter was 1:7.4. The ratios of mean arterial to mean venous velocity and volume flow were 1:2.3 and 1:1.6 respectively. Measurements were made on 100 mesenteric vessels of frogs prepared by single pithing. In 50 arterioles (diameters from 15 to 45 microns), the mean velocity was 3.77 mm/sec. The mean volume flow was 3.05xlo-3 cu mm/sec. The mean width of the total peripheral plasma layer was 2. 7 microns and its ratio to mean vessel diameter was 1:11.5. In 50 venules (diameters from 20 to 50 microns), the mean velocity was 1.55 mm/sec. and the mean volume flow rate, 1.76x10-3 cu mm/sec. The mean width of the total peripheral plasma layer was 6.7 microns and its ratio to mean vessel diameter was 1:5.3. The ratios of mean arterial to mean venous velocity and volume flow were 1:2.3 and 1:1.7 respectively. A total of 109 mesenteric vessels were studied in frogs anesthetized with urethane. In 55 arterioles (diameters from 15 to 45 microns), the mean velocity was 3.28 mm/sec. The mean volume flow was 2.87x10-3 cu mm/sec. The mean width of the total peripheral plasma layer was 3.2 microns and its ratio to mean vessel diameter was 1:9.3. In 54 venules (diameters from 20 to 50 microns), the mean flow rate was 1.61 mm/sec. and the mean volume flow, 1.83x10-3 cu mm/sec. The mean width of the total peripheral plasma layer was 5.6 microns and its ratio to mean vessel diameter was 1:5.9. The ratios of mean arterial to mean venous velocity and volume flow were 1:2.0 and 1:1.5 respectively. In these three series of studies in the frog, no relationship was clearly apparent between velocity and either vessel diameter or width of the peripheral plasma layer in arterioles. Suggestions of a direct relationship between velocity and peripheral plasma layer in veins, however, were evident. In all cases, and in both arterioles and venules, vessel diameter and peripheral plasma layer were clearly and directly related. The effects of flow velocity changes on width of the total peripheral plasma layer in individual vessels were studied in 26 arterioles of the hamster cheek pouch. Blood flow was varied by means of a cuff described by Copley (Biorheology 1: 3, 1962). A direct relationship between velocity and width of the peripheral plasma layer was clearly demonstrated. Thrombus thresholds were determined in mesenteric vessels of the frog. In 103 arterioles (diameters from 20 to 140 microns), the mean strength of stimulus necessary to produce a platelet thrombus was 24.8 volts with an amperage of 0.18 milliamperes. In 100 venules (diameters from 20 to 140 microns), the mean strength of stimulus necessary was 20.7 volts with an amperage of 0.12 milliamperes. Possible relationships of thrombus thresholds to flow velocity in mesenteric arterioles and venules are discussed. / 2031-01-01

Leopard frogs (Rana pipiens) rely on vision to recognize behaviorally meaningful aspects of their environment. The optic tectum has been shown to mediate the frog's ability to recognize and respond to moving prey and looming objects. Nonetheless, atectal frogs are still able to appropriately respond to non-moving aspects of their environment. There appears to be independent visual systems operating in the frog: one system for recognizing moving objects; and another system for recognizing stationary objects. Little is known about the neural mechanisms mediating the recognition of stationary objects in frogs. Our laboratory showed that a retino-recipient area in the anterior lateral thalamus--the NB/CG zone--is involved in processing visual information concerning stationary aspects of the environment. This thesis aims to characterize the frog's responses to a range of stationary stimuli, and to elucidate the thalamic visual system that mediates those responses. I tested leopard frogs' responses to different stationary stimuli and found they respond in stereotypical ways. I discovered that leopard frogs are attracted to dark, stationary, opaque objects; and tested the extent of this attraction under different conditions. I found that frogs' preference to move toward a dark area versus a light source depends on the intensity of the light source relative to the intensity of ambient light. Unilateral lesions applied to the NB/CG zone of the anterior lateral thalamus resulted in temporary deficits in frogs' responses to stationary stimuli presented in the contralateral visual field. Deficits were observed in response to: dark objects, entrances to dark areas, light sources, and gaps between stationary barriers. However, responses to moving prey and looming stimuli were unaffected. Interestingly, these deficits tended to recover after about 6 days in most cases. Recovery time ranged from 2 - 28 days. The NB/CG zone is anatomically and functionally connected to a structure in the posterior thalamus called the "PMDT." The PMDT has no other connections in the brain. Thus, I have discovered a "satellite" of the NB/CG zone. Preliminary evidence suggests that the PMDT is another component of the visual system mediating stationary object recognition in the frog. / Biology

This thesis deals with a study on the ability of Rana pipiens and Rana clamitans to perceive acoustic stimuli. The research has been carried out in three parts: conditioning to sound; recording of the respiratory rate in response to sound; observation on the threshold of sound perception. A review of the available literature on hearing in frogs, a description of the methods used and the results obtained are presented, followed by a general discussion and conclusions. / Thesis / Master of Science (MSc)

Despite a thorough understanding of the proximate mechanisms that drive genetic diversity, we are still very poor at predicting the genetic diversity of natural populations. Understanding patterns of genetic diversity is important for many reasons, including predicting species' adaptation to climate change and predicting the spread of invasive species, but it is particularly important for species that are declining. This dissertation attempts to explain patterns in genetic diversity at multiple spatial scales across the range of the Northern Leopard Frog, Rana pipiens, which is declining across large portions of its range. Genetic diversity is often lower in edge populations than in central populations. Genetic diversity may be reduced in edge populations per se, or populations that occur at the edge of the species' range may have low diversity because they have recently expanded into new habitat and thus show signs of founder effects. In Chapter 2, we tested several alternative hypotheses to explain genetic diversity across the species' range, and to explain why some edge populations may not show reduced genetic diversity. We found that genetic diversity was reduced in edge populations relative to central populations, but was not reduced in populations in previously glaciated areas relative to previously unglaciated areas; therefore position at range edge had a stronger effect in reducing diversity than recent colonization of new habitat. We found that genetic diversity declined linearly towards the range edge in one of two transects from range center to range edge. We concluded that genetic diversity in this species is generally reduced by position at the range edge, but that this effect may differ among edges. In Chapter 3, we tested the hypothesis that eastern and western populations were genetically distinct. We found two distinct clades that introgress in some markers but are distinct and defined by narrow boundaries in the eastern Great Lakes region in others. We concluded that genetic diversity in the Mississippi River region was elevated by the introgression of descendants from two Pleistocene refugia. In Chapter 4, we analyzed genetic diversity within populations throughout Arizona to assess potential source populations for reintroductions. We also analyzed mitochondrial DNA to determine whether any populations contained genetic material not native to the region. Populations in one area had high genetic diversity and high gene flow among populations, but also contained evidence of introduction of eastern frogs. We conclude that supplementing genetic diversity in other populations with translocations from this area is not recommended.

The purpose of this investigation was first, to make a histological and cytological study of the testis of male frogs, Rana pipiens, and to determine if there were tissue or cellular changes as well as physiological effects caused by fish pituitary-extract injections. Second, to determine if injections of fish pituitary extract into immature female white mice caused histological changes in the ovaries and uteri.