APOBEC3 proteins, in particular APOBEC3G/F, are important innate host factors that contribute to protection from HIV-1 infection by inducing high levels of guanine to adenine nucleotide substitutions (termed hypermutation) during HIV-1 viral replication. These nucleotide substitutions occur at different rates and locations across the HIV-1 genome and are thought to be particularly more frequent in the pol region. The virus has evolved ways to counteract these host factors by inducing degradation of APOBEC3G/F proteins through protein interactions with HIV-1 Vif. The aim of this thesis is to characterize and investigate the role of APOBEC3G/F-mediated hypermutation in the HIV-1 genome. We identified a subset of women from the Pumwani Commercial Sex Worker (CSW) cohort with significantly higher rates of hypermutated proviruses in pol. This degree of hypermutation correlated to less severe HIV disease progression as measured by CD4+ T cell count. This was in agreement with previous studies that evidence of APOBEC-mediated hypermutation correlate with reduced disease progression, confirming APOBEC3G/F proteins role in HIV-1 disease. Furthermore, we investigated the in vitro and ex vivo interaction between HIV-1 Vif and APOBEC3G from subjects infected with hypermutated and non-hypermutated proviruses. In vitro studies indicated that HIV-1 Vif protein expression in subjects with hypermutated proviruses were quite divergent and levels of APOBEC3G also differed between subjects. Ex vivo studies in subjects with hypermutated proviruses indicated that endogenous APOBEC3G expression was greater than in subjects with hypermutated proviruses. Both studies suggest that host and viral factors such as APOBEC3G and HIV-1 Vif are playing an influential role in HIV-1 pathogenesis. Further investigations into these interactions may lead to novel strategies into the development of therapeutic drugs for the fight against HIV-1.

Objective: Serpins are serine protease inhibitors that are involved in a wide variety of biological functions in nature. They are known to regulate inflammation processes as well as provide host defense against microorganisms. Recent evidence has associated many types of mucosal serpins with a protective phenotype against HIV infection in women. Our hypothesis is that serpins with known antiviral activity against HIV-1 are correlated with protection in a group of HIV exposed seronegative individuals (HIV-resistant) from the Pumwani sex worker cohort. Study design: Cervico-vaginal lavage (CVL) fluid was collected from 66 HIV-positive, 82 HIV-negative and 84 HIV-resistant sex workers from the cohort. Clinical and epidemiological information was recorded at the time of sample collection. CVL protein levels were determined by BCA assay and serpin (A1 and A3) concentrations by a commercially available ELISA kit. Mucosal serpin concentrations were compared against clinical and epidemiological factors as well as sexual practices. Results: Serpin A1 was significantly higher in the HIV-resistant group compared to the HIV-negative controls (Anova: p=0.0470*). Total concentration of serpin A3 did not reach statistical significance between groups. Serpins did not correlate with age, sexual practices, contraceptive use or number of pregnancies. Serpins were differentially abundant during different stages of the menstrual cycle whereas serpin A1 was elevated during the proliferation phase but not in secretory phase (p=0.0275*). Conclusion: Serpin A1 was correlated with HIV-protection in this group of HESN women. This work will contribute to a more complete understanding of mechanisms of resistance and susceptibility to HIV infection.

No description available.

This thesis project was designed to investigate the phenotypic and genotypic variability of human immunodeficiency virus type 1 (HIV-1) drug-naive clade C reverse transcriptase (RT) and its potential impact in the development of resistance against inhibitors of RT. Five treatment-naive HIV-1 Ethiopian isolates were classified as subtype C on the basis of env gene heteroduplex mobility assays (HMA) profile and phylogenetic analysis of RT sequences. In subtype C RT, a specific KVEQ motif of silent mutations (amino acid 65, 106, 138, 161) at resistance sites was present. Two Ethiopian strains were naturally resistant to non-nucleoside RT inhibitors (NNRTI), as well as to zidovudine (ZDV), based on the natural polymorphisms of G190A and K70R, respectively. The final drug concentration that selected for NNRTI primary resistance mutations in tissue culture assays was significantly higher for clade B than clade C for each of nevirapine (NW) (10 muM versus 2 or 4 muM), efavirenz (EFV) (1muM versus 0.01muM) and delaviridine (DLV) (10muM versus 1 or 4muM), respectively. In the middle of the selection period with all the NNRTIs, subtype B viruses were harboring a mixture of both wild type and mutated forms, whereas in clade C viruses, primary resistance mutations were fully generated. Thus, we have found that clade C isolates developed more rapidly resistance (8 or 9 weeks with NVP or DLV and 13 weeks with EFV) as compared with clade B controls (at least 15 weeks with NW or DLV and 30 weeks with EFV). Odd mutations were detected during selection with NNRTIs, such as S98I, and two mutations (A62V and V75E), at sites associated to multi-drug resistance against nucleoside inhibitors (NRTIs). The substitution A62V was initially observed as a drug-naive silent mutation A62A. NW and DLV mutants were broadly cross-resistants. Following in vitro selection for drug-resistance with NNRTIs (NVP, DLV and EFV) and NRTIs [lamivudine (3TC) and ZDV], RT immunodominant regions of 14 HIV-1 s

Cardioprotective effects of glucagon-like peptide-1 (GLP-1), the GLP-1 receptor (GLP-1R) agonist exendin-4 (Ex-4), and GLP-1(9-36), a cleavage product of GLP-1, were examined in ischemia-reperfusion (I/R) models of both isolated mouse hearts and cultured cardiac myocytes (CMs) using both wild-type (WT) and GLP-1R knockout (Glp1r-/-) mice. In WT hearts, GLP-1 and Ex-4 significantly improved left ventricular functional recovery vs. untreated controls following I/R, whether the drugs were administered prior to ischemia (pre-ischemia) or during reperfusion (post-ischemia). Surprisingly, the cardioprotective effects of pre- and post-ischemia treatments with GLP-1, but not Ex-4, remained evident in Glp1r-/- hearts. Although pre-ischemia infusion of GLP-1(9-36) induced lower functional recovery than untreated controls, post-ishemia infusion of GLP-1(9-36) augmented functional recovery and reduced infarct size to a similar extent to that of GLP-1 and Ex-4 in hearts from both WT and Glp1r-/- mice. Mass spectrometry was used to assay conversion of GLP-1 to GLP-1(9-36) in coronary effluents of isolated mouse hearts. Within 15 min of infusing GLP-1, significant amounts of GLP-1(9-36) were generated by the heart. By 30 min, only trace amounts of intact GLP-1 remained in coronary effluents indicating the heart rapidly converts GLP-1 to GLP-1(9-36). In CMs undergoing simulated I/R injury in vitro, both GLP-1(9-36) and Ex-4 significantly improved cell viability, LDH release and caspase-3 activation. These effects were significantly attenuated by co-treatments with LY294002, PD98059 and Ex(9-39), inhibitors of PI3K, ERK1/2, and GLP-1R respectively. The actions of Ex-4, but not GLP-1(9-36), were lost in CMs isolated from Glp1r-/- mice and only GLP-1(9-36), but not Ex-4, improved the survival of human aortic endothelial cells (HAEC) undergoing simulated I/R injury. Of note, both GLP-1 and GLP-1(9-36) treatments also demonstrated potent vasodilatory effects, as manifested by increased coronary flow rates in isolated hearts and increased diameters of pre-constricted mesenteric arteries isolated from both WT and Glp1r-/- mice. The cardioprotective effects on isolated hearts and vasodilatory effects on isolated mesenteric arteries, induced by GLP-1 was blunted by co-treatment with a dipeptidyl peptidase-4 (DPP-4) enzyme inhibitor known to block conversion of GLP-1 to GLP-1(9-36). Together, these data suggest that the beneficial effects of GLP-1 in I/R injury are mediated in part by GLP(9-36) and support the existence of a GLP-1(9-36) responsive, but Ex(9-39)-sensitive cardioprotective signaling pathway distinct from that associated with the classical GLP-1R.

Many environmental stress factors have been identified that increase square and boll abscission and thus result in reduced cotton (Gossypium hirsutum L.) yield. Under stress conditions, ethylene, an endogenous hormone, is elicited. Ethylene peaks before abscission to promote the formation of the abscission layer and plays a major role in early season square and boll abortion. In addition, ethylene stimulates the leaf senescence process. Thus, it is desirable to protect a crop from ethylene-induced fruit loss and premature leaf senescence under stress conditions. The overall objective of this study was to test the hypothesis that the ethylene inhibiting compound 1-methylcyclopropene (1-MCP) treatment can have a beneficial effect on the physiology, biochemistry and yield traits of cotton plants under abiotic stress conditions under field and controlled environment studies. The growth chamber studies were conducted in 2011 using a randomized complete design with six replications. Cotton plants were exposed to stress conditions (heat and drought) and 1-MCP treatment at the seven-true-leaf stage. The heat stress study consisted of two 1-MCP rates (0 and 10 g a.i. ha-1) and two temperature regimes (optimum temperature: 30/20 ºC (day/night temperature) and high temperature: 40/25 ºC). The drought study consisted of two water regimes (well-watered and water-stressed) was exposed to two rates of 1-MCP (0 and 10 g a.i. ha-1). Both of the field studies were conducted with a randomized complete block design with four replications in 2010 and 2011 at the Texas A&M AgriLIFE Research Farm in Burleson County, TX. The objective of the first field study was to evaluate the ability of 1-MCP to protect cotton plants against abiotic stress imposed by a foliar treatment of ethephon. Eight treatments consisted of two 1-MCP rates (0 and 10 g a.i. ha-1) in combination of four ethephon rates (0, 146, 292, and 438 mL ha-1) were imposed at the first flower (FF) stage of crop development. The second field study investigated the effect of 1-MCP on boll development and the corresponding subtending leaves, and consisted of two 1-MCP rates (0 and 10 g a.i. ha-1) applied at 20 days after flowering. In the growth chamber study examining heat and drought, application of 1-MCP resulted in reductions of lipid peroxidation, membrane leakage, and soluble sugar content as well as increased chlorophyll content, compared to the untreated plants under stress conditions. In the field study to evaluate the effect of 1-MCP under ethephon stress, 1-MCP increased plant height and number of main stem nodes in both years. In addition, 1-MCP treated plants exhibited greater membrane integrity and increased photosystem II quantum efficiency, and thus delayed senescence in both years. This potential for yield increase was realized in 2011 with 1-MCP treatment exhibiting a higher lint yield. In 2012, although 1-MCP treatment increased number of open fruit and open fruit weight per plant, no significant yield increase was detected. In the field study to test the effect of 1-MCP on boll development and subtending leaf conditions, 1-MCP treatment increased cotton boll weight at 20 days after flowering. One probable explanation for the enhanced boll size was the healthier subtending leaves: 1-MCP-treated subtending leaves exhibited decreased membrane damage and lipid peroxidation, and higher chlorophyll content and photosynthetic efficiency.

This project investigated the effects of exercise and epinephrine on the mRNA expression of peroxisome proliferator activated receptor gamma coactivator-1 alpha (PGC-1 alpha), a master regulator of mitochondrial biogenesis, in rat adipose tissue. Rats that swam 2 hours daily for 4 weeks had increased mitochondrial marker proteins and PGC-1 alpha mRNA expression in epididymal and retroperitoneal adipose tissue (p<0.05). Adipose tissue organ culture treatment with epinephrine increased (p<0.05) PGC-1 alpha mRNA expression in both depots, but only epididymal adipose responded to a supra-physiological dose. Beta blockade attenuated the effects of an acute bout of exercise on PGC-1 alpha mRNA expression in epididymal, but not in retroperitoneal adipose tissue. This is the first study to demonstrate that rat white adipose tissue PGC-1 alpha mRNA expression is increased by acute and chronic exercise and epinephrine. Increases in circulating catecholamine levels might be one potential mechanism mediating exercise induced increases in PGC-1 alpha mRNA expression in rat abdominal adipose tissue. / Nutrition and Metabolism

In New Zealand, it is common for young people to mix 1-benzylpiperazine (BZP) containing 'party pills' and ethanol (drinking alcohol). However, there is no scientific literature which compares the individual and combined long-term effects of these substances. Therefore, the aim of this study was to provide a comparison of BZP and ethanol's individual and combined effects on adulthood behaviour following repeated adolescent exposure. To investigate this 40 male and 40 female adolescent rats received daily exposure (post natal days 41 - 50) to BZP (10 mg/kg) and/or ethanol (2 g/kg) or saline vehicle (1 ml/kg) via intraperitoneal injection. Animals were tested in a Y maze, light/dark emergence box, and an open field during early adulthood (PND 78 - 81) and again during mid-adulthood (PND 117 - 120). Results found females treated with alcohol ambulated less in the open field. Interestingly, no other behavioural differences between the treatment groups were observed. Overall, it appeared that adolescent exposure to BZP and/or alcohol did not have long-term behavioural consequences, at least in rats. This finding was most likely due to the narrow range of testing ages adopted in the study.

Zugl.: Potsdam, Univ., Diss., 2006

Universiẗat, Diss., 2004--Kassel. / Gedr. Ausg. im Verl. Franzbecker, Hildesheim, erschienen.