Life Sciences Commons^™

A Characterization Of Extractable, Hydroxylated Fatty Acid Bearing Components In Legionella Pneumophila, Jonathan R. Lane

Electronic Theses and Dissertations

Extraction of the lipids of Legionella pneumophila yields phases unlike those produced from other Gram-negative bacteria. A viscous interface forms between the aqueous (wash) and organic phases. More than half of the hydroxylated fatty acids were found distributed between the aqueous phase and the interfacial material, fractions in which such constituents have not been reported in other Gram-negative species. It was further observed that after the material from the aqueous/interfacial phase was dissolved in methanol or chloroform/methanol (2:1 (V/V)), the addition of acetone would create a white, flocculent precipitate. Analyses showed that the supernatant contained fatty acids that were nonhydroxylated …

Nitric Oxide Production: A Mechanism For Inhibition Of Chlamydia Trachomatis Replication, Bojun Chen

Electronic Theses and Dissertations

Chlamydia trachomatis (CT) replicates in macrophages, but is inhibited by IFN-$\gamma$ or LPS. IFN-$\gamma$ and/or LPS induced nitrite production in mouse peritoneal macrophages, macrophage cell lines (RAW264.7 and J774A.1) and McCoy cells. Kinetic studies indicated that peak production occurred 48 hours post-treatment. CT infection itself was insufficient to induce nitrite production, but resulted in enhancement of nitrite production in IFN-$\gamma$-treated cells. Treatment with IFN-$\gamma$ or LPS resulted in significant inhibition of CT replication in these cells. Strong correlation between nitrite production and inhibition of CT replication was observed in RAW264.7 and J774A.1 cells (correlation coefficients: $-$0.93 and $-$0.94, p $<$ 0.001). N$\sp{\rm g}$- monomethyl-L-arginine (L-NMMA) specifically inhibited nitrite production and partially reversed inhibition of CT replication in macrophage cell lines. NOS mRNA was measured in RAW264.7 cells by Northern blot and Dot blot hybridization. Strong correlation between NOS mRNA expression and inhibition of CT replication (correlation coefficient: $-$0.97, p $<$ 0.05) was observed. Anti-TNF-$\alpha$ antibody completely neutralized the biological activity of TNF-$\alpha$ secreted by LPS-treated RAW264.7 cells, yet the antibody neither reduced nitrite production nor restored CT replication. Combination of the antibody and L-NMMA significantly enhanced restoration of CT replication. In peritoneal macrophages, inhibition of CT replication induced by IFN-$\gamma$ was partially restored by L-NMMA or anti-TNF-$\alpha$ antibody. In McCoy cells, inhibition of CT replication induced by IFN-$\gamma$ and LPS was not significantly restored by L-NMMA. Great restoration of CT replication by 1 mM L-NMMA was observed in LPS-treated J774A.1 cells (31%), but not in IFN-$\gamma$-treated cells (5%). Our data indicate that (1) NO production is one of the mechanisms for inhibition of CT replication in IFN-$\gamma$-activated peritoneal macrophages and RAW264.7 cells; (2) NO plays a significant role in CT inhibition in LPS-treated macrophage cell lines, but not peritoneal macrophages; (3) TNF-$\alpha$ may be associated with inhibition, but the mechanism(s) may not involve NO production; (4) NO production may not be the mechanism for CT inhibition in McCoy cells treated with IFN-$\gamma$ and LPS.

Suppressive Effects Of Transforming Factor-Β And Interleukin-10 On The Cytolytic Activity Of Murine Macrophages And Reversal By Cytokines, Chin-Hung Lin

Loma Linda University Electronic Theses, Dissertations & Projects

In this study, the suppressive effects of transforming growth factor-β (TGF-β) and interleukin-10 (IL-10) on peritoneal macrophage killing of H238 target cells and the potential for reversal of the immunosuppressive effect by IL-4 and interferon-γ (IFN-γ) were investigated. The responsiveness of naive and peptone-activated macrophages was compared. The cytolytic activity for tumor cells of these effector cells was measured by percent lysis of ³H-thymidine labeled Herpes simplex virus type 2-transformed tumor cells (H238). After 18-24 hours of incubation with TGF-β or IL-10, the cytolytic activity of macro-medium alone. The immunosuppressive effect of TGF-β or IL-10 on non-activated macrophages was …

Thymic Peptide Modulates Glutathione Redox Cycle And Antioxidant Enzymes In Macrophages, Choon Sil Park

Loma Linda University Electronic Theses, Dissertations & Projects

The effect of a 6-kDa thymic peptide (TP) on the oxidative burst of a murine macrophage cell line J774 was determined. TP (12.5-200 μg/ml) was incubated with 5 x 10⁵ J774 cells at 37° C and 5% C0₂ for 18 h and oxidative burst was triggered by zymosan; chemiluminescence was amplified by luminol and measured in an automated luminometer. TP exhibited a concentration-dependent inhibition of oxidative burst. To study the mechanisms involved in TP’s inhibition of oxidative burst, its effect on the glutathione (GSH) redox cycle, GSH biosynthesis, and antioxidant enzymes was investigated. TP was shown to increase …

A Continuous Culture Model To Examine Factors That Affect Transduction Among Pseudomonas Aeruginosa, Jean Replicon

Dissertations

No abstract provided.

Mechanisms Of Complement Resistance By Pathogenic Naegleria Fowleri Amoebae, Denise Marie Toney

Theses and Dissertations

The genus Naegleria is composed of a distinct group of free-living amoeboflagellates that include both pathogenic and nonpathogenic species. N. fowleri, the only pathogenic species of Naegleria to be isolated from humans, is the etiological agent of primary amoebic meningoencephalitis, a rare but rapidly fatal disease of the central nervous system in humans and in laboratory animals. The mechanisms of pathogenicity and the determinants of virulence of N. fowleri are unknown. Both pathogenic and nonpathogenic Naegleria activate the alternative complement pathway, however pathogenic N. fowleri are complement-resistant and nonpathogenic N. gruberi are complement-sensitive. The ability to resist complement-mediated lysis …

Identification Of Regulatory Mechanisms Of Genes Encoding Citrate Synthase In The Yeast Saccharomyces Cerevisiae, Christine Smith Kell

Theses and Dissertations

The major aim of this research was to investigate the molecular mechanisms of regulation of transcription of CIT1 and CIT2, the genes encoding citrate synthase in yeast. Specifically addressed are the questions of (1) localization of cis-acting sites required for expression or regulation, (2) the roles of HAP1 and HAP2,3,4 in expression of both genes, (3) identification of other trans-acting factors involved in expression of either gene, (4) localization of cis-acting sites involved in up regulation of CIT2 in response to disruption of CIT1 or rho° status (Liao et al., 1991; Liao and Butow, 1993).

I show here that mutations …

Characterization Of A Promoter Rearrangement And A Second Promoter In The Human C-Myb Proto-Oncogene, Sarah Margaret Jacobs

Theses and Dissertations

The human cellular proto-oncogene c-myb has been implicated as important in the regulation of hematopoietic cell growth and differentiation. Aberrant expression of this gene and chromosomal aberrations near the c-myb locus have been associated with a number of carcinogenic processes. An alternatively spliced CDNA clone of c-myb, pMbm-2, contains unique 5’ sequences which replace exon 1. The existence of this 5’ divergent CDNA clone led us into a study of the promoter activity of the c-myb gene.

Intron 1 of c-myb is highly conserved between human and mouse throughout the intron, while only those sequences directly adjacent to exons …

Immunomodulatory Effects Of Transforming Growth Factor-Β On T Lymphocytes, Thomas Harris Inge

Theses and Dissertations

Transforming growth factor-β1 (TGFβ) is a peptide cytokine implicated in control of growth, adhesion, and differentiation of cells in numerous tissues. TGFβ has potent inhibitory effects on many lymphocyte responses; we also found that TGFβ could inhibit in vitro generation of tumor-specific CTL. Suppression was largely reversed with exogenous IL-2. Proliferation of memory-stage CTL clones was also inhibited by TGFβ, while the upregulation of cytotoxicity was not inhibited by TGFβ. These studies suggested that TGFβ limited anti-tumor CTL responses via both an indirect effect on IL-2 production, and by a direct effect on proliferation of memory CTL.

In CTLL-2 cells, …

The Distribution And Occurrence Of Aerobic Heterotrophic Antimicrobic-Producing Bacteria Isolated From The Lower Chesapeake Bay, Linda Lea Gilmer

Biological Sciences Theses & Dissertations

Three different estuarine microenvironments in the lower Chesapeake Bay were investigated for the occurrence and geographical distribution of antimicrobic-producing bacteria. Samples were taken from the water column, fish skin, and algal surfaces. A total of 1472 bacterial isolates were assayed for antimicrobial activity against fungal, Gram-negative and Gram-positive bacterial test organisms. Of the total bacterial isolates assayed, 5. 2% were active antimicrobic producers. Algal surf aces were shown to have a higher incidence of antimicrobic-producing bacteria than the water column or fish skin. No antimicrobic activity was demonstrated by bacteria isolated from the flounder fish skin. The majority of the …