Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2007. / Human African Trypanosomiasis (HAT) is a disease that threatens more then 60 million men, woman and children in Africa. It is known that the inhibition of the enzyme, ornithine decarboxylase (ODC) leads to cell arrest and subsequent death of Trypanosoma brucei, the parasite that causes the disease. The fluorinated ornithine analogue, DFMO (difluoromethylornithine or eflornithine) is a known inhibitor of ODC. Although various syntheses for DFMO exist they have some practical drawbacks which prevent the cost effective production of this compound as a drug for HAT treatment. This work focuses on the synthetic preparation of the fluorinated ornithine analogue DFMO as well as the fluorinated ornithine analogues 2-MFMO, 3-fluoro-ornithine and 3,3-difluoro-ornithine. Our chosen synthetic methodology focused on the introduction of the fluorine functionality using a simpler, safer and more convenient method than current direct fluorination techniques, or those that rely on the use of CFCs. Instead we decided to develop and optimise a fluorodehydroxylation method based on the transformation of hydroxylated ornithine analogues. The fluorodehydroxylation method substitutes a hydroxyl group to the corresponding fluorine and can also be used to transform an aldehyde or ketone to the corresponding difluoro group. Application of this fluorination method requires the synthesis of appropriate ...

The effects of TCDD on hepatic ornithine decarboxylase (ODC) activity and endocrine function in rats were investigated. Sixteen hours after partial hepatecomy, rats which had been pretreated with TCDD for one week exhibited a 3- to 4-fold increase in ODC activity, while vehicle controls exhibited an 8- to 10-fold increase. ODC induction after either aminophylline or dexamethasone administration, agents which act via cAMP-mediated and direct nuclear events, respectively, also was inhibited by pretreatment with TCDD. RNA polymerase I activity, which positively correlates to ODC activity in growth and development, decreased concomitant with decreased induction of ODC. In unstimulated liver, RNA polymerase I activity, as well as protein, DNA and RNA levels, remained unchanged one week after TCDD. However, TCDD administration resulted in decreased liver concentrations of putrescine and spermidine, but not spermine. Within 2 days following administration of TCDD (45 or 90 μg/kg), rats exhibited hypothermia, hypothyroidism and decreased growth rate compared to pair-fed controls and rats fed ad libitum. Within 2 weeks of the administration of 90 μg TCDD/kg, body temperature had fallen to below 35°C with a low mean value 34.5°C recorded on day 16. Mean body temperatures for control rats ranged from 36.8°C to 37.5°C. One week after the administration of TCDD (45 μg/kg) to rats, serum thyroxine (T₄) and triiodothyronine (T₃) levels declined to 42% and 82% of control, respectively. Mild hypoglycemia occurred subsequent to hypothyroidism and hypothermia. At 1 week after administration of 45 μg TCDD/kg to rats, serum and pancreatic insulin levels were reduced to 25% and 76% of control, respectively. Hypophagia was determined to be responsible for decreased growth rate and hypoinsulinemia, but it could not account for hypothyroidism, hypothermia or hypoglycemia following administration of TCDD. No changes in glucagon or pancreatic, hepatic or serum somatostatin levels were found. Decreased somatostatin in the gastric antrum coincided with a 29% increase in stomach weight. The delayed toxicity of TCDD may be related to these striking hormonal alterations.

published_or_final_version / Biochemistry / Master / Master of Philosophy

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 61-73). Also available via the Internet.

No description available.

The developmental profiles of mRNA and protein expression for ornithine decarboxylase (ODC), the Na$ sp+$-dependent glucose co-transporter (SGLT1), sucrase isomaltase (SI), and the Na$ rm sp+K sp+$ ATPase $ alpha sb1$ and $ beta sb1$ subunit isoforms in the postnatal rat small intestine, as well as the effects of exogenous spermidine on their precocious development, were examined. Postnatal age had a significant effect with all enzymes and the nutrient transporter maturing around weaning. Consecutive exposure to exogenous spermidine during suckling precociously induced ODC mRNA, SI protein, and SGLT1 gene expression in the proximal and distal small intestine. Levels of Na$ rm sp+K sp+$ ATPase $ alpha sb1$ and $ beta sb1$ subunit isoform mRNA were precociously induced in the proximal small intestine only. These findings show that exposure to exogenous spermidine can promote precocious alterations in intestinal enzyme and nutrient transporter expression; however, it appears that spermidine must be continuously supplied for these alterations to persist in suckling rats.

In all mammalian species examined thus far, the ovaries produce a burst of ornithine decarboxylase (ODC) and putrescine during ovulation or after application of a bolus of human chorionic gonadotropin (hCG). Aged mice are deficient in this peri-ovulatory ODC and putrescine burst. Moreover, peri-ovulatory putrescine supplementation in aged mice increases egg quality and reduces miscarriage rates. These studies suggest that peri-ovulatory putrescine supplementation may be a simple and effective therapy for reproductive aging for women. However, putrescine has never been used in humans and, currently no pure source of putrescine is suitable for human trials. Given that ODC is highly expressed in the ovaries during ovulation but otherwise exhibits low activity in most tissues, we hypothesized that L-ornithine, the substrate of ODC, might be a better alternative. In this study, we have demonstrated that systemic application of L-ornithine increased ovarian putrescine levels; the increase was restricted to animals that had been injected with hCG. Furthermore, L-ornithine specifically increased ovarian putrescine levels without affecting putrescine levels in most other tissues. Unfortunately, thus far peri-ovulatory L-ornithine supplementation in mouse drinking water produced mixed effects on reproductive outcome in aged mice. Therefore, our studies demonstrated the potential of L-ornithine supplementation as a possible therapy for aging-related infertility, but further work is required to produce an effective application method.

Malaria is one of the most serious tropical infectious diseases affecting mankind. The prevention of the disease is hampered by the increasing resistance of the parasite to existing chemotherapy and -prophylaxis drugs. The need for novel therapeutic targets and drugs is therefore enormous and the understanding of the biochemistry of the parasite is imperative. The aim of this study was the identification and molecular characterisation of the eDNA of one such metabolic target protein, ornithine decarboxylase (ODC), in the human malaria parasite P. falciparum. The P. falciparum ODC eDNA was isolated by means of a modified RT-PCR technique, RACE. No sequence data were available and the primers used were based on consensus areas identified in the protein sequences from other related organisms. The isolation and identification of the eDNA with degenerate primers was successful in 3' -RACE, but necessitated the optimisation of the eDNA synthesis protocol and the use of total RNA as starting material. The sequence obtained facilitated the application of 5' -RACE with ODC-specific primers based on the 3' -RACE sequence data. The full-length ODC eDNA sequence was obtained by overlap-alignment of various segments. A novel suppression PCR technology was applied during the 5' -RACE in order to create an uncloned eDNA library of amplified cDNAs representing only the mRNA population. The P. falciparum ODC eDNA contains an open reading frame of ---2847 bp and translates to a large 939 amino acid protein. The protein contained large internal insertions and was extended by '""273 N-terminal residues compared to ODCs from other organisms. Several possible signature motifs were identified for phosphorylation, glycosylation and transamidation. The P. falciparum ODC protein seems to contain more hydrophilic and a-helix forming residues. These characteristics should be further investigated after expression of the recombinant protein. The isolation of the P. falciparum ODC eDNA facilitates the validation of this protein as an antimalarial target. / Dissertation (MSc)--University of Pretoria, 1998. / gm2014 / Biochemistry / unrestricted

Ornithine is an amino acid of which the side chain contains three pairs of diastereotopic protons. The diastereotopic protons are chemically nonequivalent. The NOEDIF spectra of ornithine were obtained in an acid solution to assign the individual chemical shifts of the β diastereotopic protons with the aid of the theoretical calculation of conformation distribution. The β Pro-S resonance was found to be at a higher field than β pro-R proton. (S,S)-Ethylenediamine-N,N'-disuccinic acid (EDDS) was found to be a good chiral chemical shift reagent ligand in water solution. The Ytterbium complex of EDDS was used to distinguish L-ornithine and D-ornithine. For the α protons, the enantiomeric shift difference was affected by the pH of the solution and the substrate : Yb(EDDS)’ ratio. The association constants between Yb(EDDS)’ and L- or D-ornithine were found to be slightly different. Yb(EDDS)’ may also be useful to distinguish between the diastereotopic protons in ornithine and other molecules in NMR spectra.

No description available.