No description available.

No description available.

M.S. / Molecular Biology / Neurospora crassa arg-2 encodes the small subunit of Arg-specific carbamoyl phosphate synthetase and is negatively regulated by arginine. This regulation is mediated by a 24-codon upstream open reading frame (uORF). The sequence of this uORF is critical for Arg-specific regulation. Six mutated templates were used to examine which residues of the uORF are important for this regulation. Mutations were created using megaprimer PCR and a luciferase gene was used as a reporter in the in vitro translation studies. Mutations of Asp 12, Asp 16, and Ser 10 eliminate Arg-specific regulation. Leaky scanning is thought to be involved, and a hypothetical ribosome stalling model that mediates Arg-specific attenuation of translation is proposed.

Previous studies in the population genetics of the oyster drill Thais clavigera show that snails from the west coast of Taiwan belong to the same population. However, the genotype frequency of arginine kinase (Ark) in large snails is different among sites in the west coast. In general, changes of temperature and desiccation caused by tidal cycle are the most important twp environmental factors affect genetic variation of intertidal organisms. In the present study, the relationship between the frequency of Ark genotype and tide was evaluated through the following experiments. It has been found that the frequencies of Ark genotype of snails, collected in August with the size range of 25-35mm, were correlated to tides. A higher grequency of Ark63/100 (0.47~0.56) was in the upper intertidal and a higher frequency of Ark63/63 (0.49~0.66) was at the lower end. Moreover, the genotype frequency also varied with size, i.e. more Ark63/63 in small snails (<25mm) and more Ark63/100 in large snails (>35mm). Laboratory desiccative experiments indicated that snails with genotype of Ark63/100 preferred in the areas of high water level and Ark63/63 in areas of low water level. The laboratory results were consistent with the field data. To compare the enzyme activity, there was no difference among the genotypes of Ark63/63, Ark63/100 and Ark100/100at temperatures of 18, 24 and 30¢J. In summary, the frequencies of Ark genotype varied with tide and size and factors such as temperature, desiccation and reproduction may play important roles in the relationship.

Thesis (M.S.)--Missouri University of Science and Technology, 2009. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed December 23, 2009) Includes bibliographical references (p. 39-44).

Thesis (Ph. D.)--OGI School of Science & Engineering at OHSU, 2003. / Includes bibliographical references (leaves 115-148).

No description available.

Maintenance of body temperature is one of the first and most important physiological processes that must be initiated after birth. Failure to sustain homeothermy leads to hypothermia and death. Indeed, in sheep, 40% of non-predator lamb deaths are attributed to cold and cold-related causes. Brown adipose tissue (BAT) is an essential mediator of thermogenesis in many species and is responsible for 50% of the heat generated in the newborn lamb despite comprising only 2% of body weight. Previously, we found that maternal arginine supplementation increased fetal peri-renal BAT by 62%. This observation led us to test the hypothesis that increased the amount of fetal BAT will enhance neonatal thermogenesis at birth and thus combat the effects of cold stress. Thirty-one multiparous Suffolk ewes gestating singletons and twins were assigned to receive either intravenous injections of L-arginine (27 mg/kg bodyweight; n=17) or sterile saline (n=14) three times daily from Day 75 to Day 125 of gestation (term=147). Following parturition lambs were removed from their dams, placed in a thermoneutral environment, and fed artificial colostrum on a per body weight basis. At 4 hours of age, lambs were cold challenged at 0 degrees C for 2 hours. Rectal temperatures were recorded at 15 minute intervals. At 6 hours of age all singletons and one lamb of each twin pair was sacrificed. The remaining twin lamb was challenged again at 22 hours of age for an additional 2 hours prior to necropsy. Rectal temperature was greater for the duration of both cold challenges in lambs from arginine-treated ewes than lambs from saline-treated ewes (P<0.050). Interestingly, at time of necropsy, BAT weight did not differ (P>0.10) between treatments. UCP1 mRNA levels were not affected by treatment or age (P>0.10). However, TEK, PPARGC1A, NRF1, NRF2, PPARG, ADRB3, ARG2, RPS6KA1, EIF4EBP1, ODC1 were not affected by treatment (P>0.10) but were upregulated (P<0.05) by age; being greater at 24 hours of age versus 6 hours of age. Results indicate that maternal arginine treatment results in increased neonatal thermogenesis after birth. Although the underlying mechanisms remain to be elucidated, the data reported herein represent the first step in improving neonatal survival in response to cold.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--Illinois State University, 1992. / Title from title page screen, viewed February 6, 2006. Dissertation Committee: Brian J. Wilkinson (chair), Radheshyam Jayaswal, Herman E. Brockman, Robert L. Preston, Philip D. Morse. Includes bibliographical references (leaves 107-112) and abstract. Also available in print.