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Articles 1 - 8 of 8
Full-Text Articles in Life Sciences
Nitric Oxide Production: A Mechanism For Inhibition Of Chlamydia Trachomatis Replication, Bojun Chen
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.
A Molecular Basis For Erythromycin Sensitivity And Resistance In Escherichia Coli, Harold S. Chittum
A Molecular Basis For Erythromycin Sensitivity And Resistance In Escherichia Coli, Harold S. Chittum
Electronic Theses and Dissertations
The effect of erythromycin on the 50S ribosomal subunit during cell growth has been extensively investigated. Sucrose density gradient analysis of ribosomes formed in the presence and absence of the drug revealed a 50S specific assembly defect is partially responsible for erythromycin's inhibitory effects on wild type cells. Examination of two erythromycin-resistant mutants of E. coli (N281 and N282) revealed that mutant N281 (L22 mutant) but not N282 (L4 mutant) was assembly defective in the presence of the drug, although only at much higher drug concentrations (300 ug/ml vs. 75 ug/ml for wild type cells). The altered genes from each …
A Characterization Of Extractable, Hydroxylated Fatty Acid Bearing Components In Legionella Pneumophila, Jonathan R. Lane
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 …
Unusual Structure Of A Human Middle Repetitive Dna, Duminda D. Ratnasinghe
Unusual Structure Of A Human Middle Repetitive Dna, Duminda D. Ratnasinghe
Electronic Theses and Dissertations
The L2Hs sequences are a polymorphic, interspersed, middle repetitive DNA family unique to human genomes. Genomic fingerprinting indicates that these DNAs vary from one individual to another and between tissues of the same individual. Sequence analysis reveals that they are AT-rich (76%) and contain many unusual sequence arrangements (palindromes, inverted and direct repeats). These sequence properties confer on the L2Hs elements the potential to fold into non-B-form structures, a characteristic of recombination hot spots. To test this hypothesis carbodiimide, osmium tetroxide and S$\sb1$ nuclease were used as single-strand specific probes to study a recombinant plasmid, pN6.4.39, containing a single L2Hs …
Co-Sensitization Of Dopamine And Serotonin Receptors Occurs In The Absence Of A Change In The Dopamine D1 Receptor Complex After A Neonatal 6-Ohda Lesion, Li Gong
Electronic Theses and Dissertations
To test whether SKF 38393 could ontogenetically sensitize dopamine (DA) D$\sb1$ receptors and whether this sensitization would be associated with biochemical changes, intact and neonatal 6-hydroxydopamine (6-OHDA)-lesioned rats (200 $\mu$g i.c.v.) were treated daily from birth with SKF 38393 (3.0 mg/kg i.p. x 28 days) or its vehicle. In DA D$\sb1$ neonatally sensitized 6-OHDA rats, enhanced locomotor responses were observed with the first SKF 38393 challenge dose (3.0 mg/kg i.p.) at 6 weeks. This response increased further with weekly SKF 38393 treatments. Enhanced stereotyped behaviors were seen in both lesioned and sensitized rats at 8 weeks. There was no change …
Mechanisms Of T Cell-Mediated Macrophage Activation: Role Of Antigen Specific And Antigen Nonspecific Cognate Interactions, Xiang Tao
Electronic Theses and Dissertations
Macrophages play an important role in host antimicrobial immunity and in non-septic inflammatory reactions. Most studies on macrophage activation have focused on the roles of the T cell-produced cytokine, interferon-$\gamma$ (IFN$\gamma)$ and bacterial product, lipopolysaccharide (LPS). T cell-macrophage interaction is a critical step in initiating both specific and nonspecific immune responses to antigenic stimulation. The current study examines the role of cognate T cell-macrophage interaction in activation of macrophage effector functions and induction of macrophage early activation gene expression. Viable resting T$\sb{\rm H}$2 clone cells can activate IFN$\gamma$-primed macrophages to produce reactive nitrogen intermediates (RNI) or express cytostatic activity. The …
Human Lung Mast Cell Tryptase Isozymes: Separation And Examination Of Structural And Functional Differences, Susan S. Little
Human Lung Mast Cell Tryptase Isozymes: Separation And Examination Of Structural And Functional Differences, Susan S. Little
Electronic Theses and Dissertations
Tryptases are trypsin-like enzymes found in mast cell granules. Although in vivo substrates have not been positively identified, tryptases cleave a limited number of potential physiological substrates in vitro, including high molecular weight kininogen (HMWK) and vasoactive intestinal peptide (VIP). Purified human lung mast cell tryptase (HLT) apparently exists as a tetramer with an M$\sb{\rm r}$ of 135-144 kDa by gel filtration, whereas SDS-PAGE yielded two bands of M$\sb{\rm r}$ 29 Kda and 33 Kda. Tryptases are resistant to inhibition by most natural trypsin inhibitors and display some affinity for heparin. The existence of tryptase isozymes has been implied from …
Probing Protein-Protein Interactions Among Proteins Of A Nonaggregated Fatty Acid Synthetase From Euglena Gracilis Variety Bacillaris, Sande G. Williams
Probing Protein-Protein Interactions Among Proteins Of A Nonaggregated Fatty Acid Synthetase From Euglena Gracilis Variety Bacillaris, Sande G. Williams
Electronic Theses and Dissertations
Enoyl-acyl carrier protein (ACP) reductase from chloroplast nonaggregated fatty acid synthetase (FAS) of Euglena gracilis variety bacillaris was purified to a single band on a denaturing polyacrylamide gel. The enzyme was partially characterized with respect to substrate specificity, reduced nucleotide requirement, and the effect of ACP and Ca$\sp{++}$ on enzyme activity. Antibodies against the purified protein were raised in hens and isolated from eggs. ACP was purified from Euglena in yields of about 1mg/100g (wet weight) of cells. Antibodies were raised against the purified protein. ACP antibodies inhibited the Euglena chloroplast FAS using Euglena or E. coli ACP as a …