Rodents cause significant damage to agricultural crops throughout the world, including rice, the staple food for the increasing population of Southeast Asia. Little is known about the ecology of pest rodent species, resulting in much effort being concentrated on ineffective, time consuming control practices. This research was designed to understand the demography and habitat use of the major pest rodent (Rattus tanezumi) of the Banaue rice terraces in order to identify the most efficient time and location to undertake pest control. Rodent crop damage and associated yield loss was also assessed in order to provide information for a cost : benefit analysis of rodent control practices. And the beliefs, perceptions and practices of Banaue rice farmers were investigated to assist in identifying future compatible rodent control programs. Replicated cage trapping was undertaken for a twelve month period over the entire rice cropping season in two study sites in the Municipality of Banaue Philippines. The breeding season of R. tanezumi corresponded with periods of food availability from the transplanted to ripening stages of the rice crop. A non-breeding season occurred from the fallow to seedling stages. The distinct breeding season occurred within the rice fields and adjacent village and scrub habitats. Radio-tracked and spool-and-line tracked R. tanezumi moved from adjacent habitats into the rice field during the breeding season, and individuals persisted in all habitat types, including the rice field, during the fallow, nonbreeding season. Overall rice yield was significantly greater (43%) in areas where rodents were excluded by fencing compared to areas where rodents were not excluded. More rodent damage to rice tillers occurred at the booting than at the ripening stage of the rice crop. These results suggest that to prevent rodent damage, control should be undertaken at the end of the R. tanezumi non-breeding season (prior to transplanting), before rodent numbers multiply and crop damage occurs. Further, the cost-benefit analysis of non-chemical rodent control programs in Banaue, suggests that benefits accrue once yield loss is likely to exceed 5%.

The effect of delayed freezing on muscle glycogen and lactate was investigated to determine the rate of change following excision of samples from an intact muscle. The plantaris muscle was removed and a portion frozen as quickly as possible to establish a zero time reference point. The remaining portion of the plantaris was exposed to room atmosphere for a specific time interval, either 1.00, 4.00, 5.00, 6.00, 10.00, 15.00 minutes, after which they were immediately frozen. he glycogen and lactate values for the timed intervals were subtracted from the zero or initial value. In this way the results could be reported as the net increase or decrease per time interval. The muscle glycogen analysis indicated no difference in the timed intervals (P<0.05) 1.00, 2.00, 4.00, 5.00, 6.00, but at the ten and fifteen minute intervals, significant differences were noted for a net decrease of 9.94 and 10.18 μmoles/g, respectively. In muscle lactate analysis, no significant differences were noted for any of the time intervals. The rate of utilization of glycogen was calculated as 0.523 μmoles/g/min., and lactate formation as 0.214 μmoles/g/min. This study indicates that freezing muscle biopsy specimens may be delayed as long as six minutes after removal from the subject with no significant changes.Ball State UniversityMuncie, IN 47306

Leishmaniasis is caused by infection with protozoan parasites within the genus Leishmania and, in the New World, is transmitted by the bites of female sand flies within the genus Lutzomyia. The occurrence of leishmaniasis in rodent species, the geographic distribution of sand fly species in Nicaragua, and environmental factors associated with the distribution of human cases of typical cutaneous leishmaniasis were investigated. Three hundred ninety five rodents representing 17 species were collected from 13 localities from August 2001–March 2006 and screened for Leishmania infections. One Heteromys desmarestianus and one Peromyscus mexicanus were found to be positive for leishmanial infections by PCR. This is the first report of Leishmania infections in rodents in Nicaragua. Five hundred fifty six sand flies representing 12 species were collected from 8 localities, including Lutzomyia hartmanni, a new record for this species in Nicaragua. The predominant sand fly species captured in western Nicaragua were Lutzomyia longipalpis and Lutzomyia evansi. The predominant species captured in central and eastern Nicaragua was Lutzomyia cruciata. The geographic distribution of sand flies in this study provides additional support to previouslypublished reports of suspected vectors of Leishmania species that cause typical and atypical forms of cutaneous leishmaniasis in Nicaragua. Distribution data of human cases of typical cutaneous leishmaniasis obtained from the Nicaraguan Ministry of Health, along with GIS and remotely sensed data of elevation, precipitation, temperature, soil types and land use/cover classes, were used to develop predictive logistic regression models for the presence or absence of human cases within 151 municipalities. Mean annual precipitation and land use/cover were determined to be the best environmental variable predictors for the occurrence of typical cutaneous leishmaniasis.

Thesis (Ph. D.)--University of Missouri--Columbia, 2000. / "December 2000." Typescript. Vita. Includes bibliographical references (leaves 95-112). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri--Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 95-112). Also available on the Internet.

Magnetic Resonance Imaging (MRI) is a non-ionizing imaging modality that can provide images with excellent soft tissue contrast at high resolution. In particular, molecular and cellular MRI is a powerful imaging method that could provide a non-invasive way for assessing specific biological processes in vivo in living organisms. The ability to monitor and track biological structures and processes down to molecular and cellular level and the possibility to probe the development, survival, migration, and differentiation of cells in vivo, has opened up new ways for scientists to investigate the fundamental mechanisms of health and diseases. In this dissertation, novel applications of conventional MR contrast agents to study specific biological structures and processes are demonstrated. First, the potential of manganese enhanced MRI (MEMRI) for in vivo tract tracing and assessment of neuroarchitecture was investigated. Manganese was intracortically infused into the visual cortex along the border of the primary and secondary visual cortex and then imaged 8 and 24 hours later. A dynamic migratory path of manganese from the infusion site through the corpus callosum to the contralateral hemisphere was observed. Also, layer specific enhancement on the contralateral cortex and the connection of the visual cortex with other brain structures were shown and the results were consistent with established anatomical data. Secondly, MEMRI was performed to probe in vivo neuronal changes in the rodent brain following 72-hour rapid eye movement sleep deprivation. Significant reduction in manganese uptake was observed in the cortical and hippocampal region in the sleep deprived animals when compared to the normal group. In particular, the dentate gyrus substructure in the hippocampus exhibited the least uptake. This indicated the functional vulnerability of the hippocampus and the cortex to sleep deprivation. Lastly, in vivo tracking of endogenous neural stem and progenitor cell migration during neurogenesis in neonatal rat brain was performed by micron sized iron oxide particles (MPIO) labeling. Susceptibility weighted imaging was used for image processing to highlight the susceptibility contrast induced by the iron oxide particles. MPIO-labeled cells induced contrast was clearly enhanced in the susceptibility weighted images, particularly at day 3 after MPIO injection in which the MPIO-labeled NPCs became more dispersed in the olfactory bulb. The ventral migratory pathway of endogenous neural stem and progenitor cells, which could not be easily observed in conventional T2*W imaging, couldalsobe detected. Overall, various biological systems and processes have been successfully interrogated using MR contrast agents. Through these studies, the versatility and power of molecular and cellular MRI have been demonstrated. Looking ahead, the rapid development and combination of different molecular and cellular imaging techniques would certainly revolutionize the way we study health and diseases. In the end, this could foster our understanding of basic life sciences and hence improve the quality of healthcare. / published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

No description available.

No description available.

Studies conducted for this dissertation utilized a rodent model exposed to single or multiple short duration heat loads in an effort to: 1) elucidate the changes in energy metabolism occurring at the tissue and whole-body level in response to hyperthermia, 2) characterize specific aspects of glucose utilization and hepatic glucose production following a heat load and 3) determine if aspects of mitochondrial function and/or dysfunction might play a role in the metabolic changes that occur in response to heat stress. Study 1 was conducted to determine if rodents exposed to heat stress shared similarities using a bovine heat stress model. Specifically, we were interested in identifying changes in blood metabolites and hormones, as well as gene expression and protein abundance of enzymes associated with energy metabolism in skeletal muscle (type I and type II), liver and adipose tissue. Previous bovine data indicates glucose may be preferentially utilized during heat stress, suggesting alterations in energy metabolism. This study provided evidence that tissue-specific changes occur in response to a heat load and that full glucose oxidation might be reduced, specifically in skeletal muscle where abundance of PDK4 mRNA was increased. Within skeletal muscle, glucose transporters (GLUTs 1 and 4) also tended to be increased in rats exposed to a heat load. Increases in skeletal muscle AMPK-α and PGC-1α as well as increased expression of energy substrate transporters suggests heat stress may impose a cellular energy deficit and/or increased energy demands which subsequently leads to changes in energy metabolism. Few changes were noted in either hepatic or adipose tissue in response to acute heat stress in this pilot study. Study aim of Chapter 3 was to further characterize the effects of heat stress on energy metabolism at the tissue and whole-body level in rats exposed to either 1 or 2 bouts of heat. Rats exposed to a 6 h heat load tended to have higher plasma glucose but reduced insulin levels, compared to thermal neutral controls, suggesting decreased glucose uptake or increased hepatic glucose output. Additionally, although heat stress likely increases whole-body energy demand, plasma NEFA levels were blunted in the early hours following onset of heat, suggesting increased adipocyte insulin sensitivity. Gene expression of enzymes associated with oxidative energy metabolism were increased in the TA (which is comprised primarily of glycolytic muscle fibers) following 2 bouts and in liver following a single bout of heat, while expression of oxidative enzymes were decreased within the soleus (a primarily oxidative muscle type). AMPK mRNA was increased following a single bout of heat in hepatic tissue and after 2 bouts of heat in type I skeletal muscle. AMPK mRNA abundance remained the same following 1 bout but was reduced following 2 bouts of heat within type II skeletal muscle. In the TA, phosphorylated AMPK protein abundance was reduced by HS. Abundance of PGC-1α mRNA was increased in types I and II skeletal muscle but was only numerically increased in liver following heat exposure. These data suggest differences at the transcription level in how heat effects energy metabolism within types I and II skeletal muscle as well as between muscle and hepatic tissue and also suggests a cellular attempt to increase energy production (by all mechanisms) in response to heat exposure. Study 3 (Chapter 4) focused on the effect of a heat load on glucose utilization in skeletal muscle and hepatic glucose production capacity. Similar to study 1, PDK4 expression was increased in types I and II skeletal muscle, while PDK2 expression was increased in hepatic tissue. Within skeletal muscle, increases in PDK expression paralled the increased protein abundance of PDHE1α following heat exposure, implying a decrease in oxidative glucose metabolism. Within the liver, protein abundance of PDH-E1α was reduced following a single heat load, but returned to TN levels after a 2nd heat exposure, suggesting that glucose oxidative metabolism is increased above normal levels after an initial heat exposure, but reduced following multiple heat bouts. Hepatic mRNA abundance for gluconeogenic enzymes were increased, implying an increase in hepatic glucose output capacity. The purpose of Study 4 (Chapter 5) was to determine if heat stress elicits changes on mitochondrial function/dysfunction (i.e. oxidative stress), that may account for changes observed in energy metabolism. Expression of genes associated with antioxidant defense were increased by heat stress, but differed between types I and II skeletal muscle as well as between muscle, hepatic tissue and WBCs. The abundance of mRNA for antioxidant enzymes was increased the greatest, and expression of DNA repair enzymes were also upregulated the most within hepatic tissue due to heat exposure, suggesting either increased damage at the level of hepatocytes or greater defensive capacity following an environmental insult. Taken together, this data provides evidence that heat alters energy metabolism, but these changes are tissue-specific and may be reflective of where damage is occurring, or which tissues are able to adapt and/or compensate for increased energy demands imposed by an environmental insult.

No description available.