Biomedical subjects

Mary J O'Connell

Publications and source records attributed to Mary J O'Connell.

7 recordsLinked to original sources

PubMed2006

Early detection and measurement of urothelial tumors in mice.

OBJECTIVES: To establish reliable noninvasive in vivo methods to detect, measure, and monitor experimentally induced urothelial tumors in mice. METHODS: UPII-SV40T transgenic mice reliably develop bladder tumors by expression of simian virus 40 large T antigen specifically in bladder urothelium through the use of the uroplakin II promoter. Two wild-type and 10 UPII-SV40T transgenic mice were monitored for microhematuria two to three times weekly using dipstick analysis. A unique flat panel detector-based cone beam computed tomography (FPD-CBCT) system imaged the urinary tracts of anesthetized mice after tail vein injection of an iodinated contrast agent (Omnipaque) that is excreted in urine. Within 10 seconds, the FPD-CBCT system acquired 290 two-dimensional images, which produced three-dimensional volumes with true isotropic resolution (180 microm)3 using a filtered back projection-based modified Feldkamp reconstruction algorithm. Amira, version 3.1.1-1, for MacOSX was used for data analysis and advanced visualization of the three-dimensional reconstructed FPD-CBCT images. RESULTS: Hematuria was present in UPII-SV40T transgenic mice at 32 days of age; the wild-type animals exhibited no hematuria. Filling defects, associated with histologically confirmed tumors, in the bladders of the UPII-SV40T transgenic mice were visualized in the reconstructed FPD-CBCT images 1 to 45 minutes after contrast agent injection. Longitudinal FPD-CBCT imaging sessions showed the tumor position, volume, and growth. CONCLUSIONS: The combination of early detection of hematuria and high-resolution in vivo FPD-CBCT imaging of murine bladder tumors enabled accurate longitudinal assessment of tumor growth and progression in individual animals. This approach could provide an important alternative to serial sacrifice experimental designs, while refining statistical power and reducing animal use.

Animals↗

PubMed2005

Gamma chain receptor interleukins: evidence for positive selection driving the evolution of cell-to-cell communicators in the mammalian immune system.

The interleukin-2 receptor (IL-2R) gamma chain, or common gamma chain (gammac), is the hub of a protein interaction network in the mammalia that is central to defense against disease. It is the indispensable subunit of the functional receptor complexes for a group of interleukins known as the gamma-chain-dependent interleukins (IL-2, IL-4, -7, -9, -15, and -21). The gammac links these proteins through their interaction with it and their competition for its recruitment. The gammac-dependent interleukins also interact with each other to either enhance or suppress expression through manipulation of expression of receptor subunits. Given the influence of protein-protein interactions on evolution, such as those documented for many genes including the reproductive proteins of the sperm and egg coat, here we have asked whether there is a common thread in the evolution of these interleukins. Our findings indicate that positive selection has acted by fixing a large number of amino acid replacement mutations in every single one of these interleukins, this adaptive evolution is also observed in a lineage-specific manner. Crucially, however, there does not appear to have ever been an instance of adaptive evolution in the gammac chain itself, thereby providing an insight into the evolution of this hub protein. These findings highlight the importance of adaptive evolutionary events in the evolution of this central network in the immune system and suggest underlying causes for differences in defense responses in the mammalia.

Animals↗

PubMed2005

Adaptive evolution of the human fatty acid synthase gene: support for the cancer selection and fat utilization hypotheses?

Cancer may act as the etiological agent for natural selection in some genes. This selective pressure would act to reduce the success of neoplastic lineages over normal cell lineages in individuals of reproductive age. In addition, human's relatively larger brain and longer lifespan may have also acted as a selective force requiring new genotypes. One of the most important proteins in both processes is the fatty acid synthase (FAS) gene involved in fatty acid biosynthesis. A variety of other proteins, including PTEN, MAPK1, SREBP1, SREBP2 and PI are also involved in the regulation of fatty acid biosynthesis. We have specifically analysed variability in selective pressure across all these genes in human, mouse and other vertebrates. We have found that the FAS gene alone has signatures indicative of adaptive evolution. We did not find any signatures of adaptive evolution in any of the other proteins. In the FAS gene, we have detected an excess of non-synonymous over synonymous substitutions in approximately 6% of sites in the human lineage. Contrastingly, the substitution process at these sites in other available vertebrates and mammals indicates strong purifying selection. This is likely to reflect a functional shift in human FAS and correlates well with previously observed changes in FAS biochemical activities. We speculate that the role played by FAS either in cancer development or in human brain development has created this selective pressure, although we cannot rule out the various other functions of FAS.

Biological Evolution↗

PubMed2005

Evidence for heterogeneous selective pressures in the evolution of the env gene in different human immunodeficiency virus type 1 subtypes.

Recent studies have demonstrated the emergence of human immunodeficiency virus type 1 (HIV-1) subtypes with various levels of fitness. Using heterogeneous maximum-likelihood models of adaptive evolution implemented in the PAML software package, with env sequences representing each HIV-1 group M subtype, we examined the various intersubtype selective pressures operating across the env gene. We found heterogeneity of evolutionary mechanisms between the different subtypes with a category of amino acid sites observed that had undergone positive selection for subtypes C, F1, and G, while these sites had undergone purifying selection in all other subtypes. Also, amino acid sites within subtypes A and K that had undergone purifying selection were observed, while these sites had undergone positive selection in all other subtypes. The presence of such sites indicates heterogeneity of selective pressures within HIV-1 group M subtype evolution that may account for the various levels of fitness of the subtypes.

Amino Acid Sequence↗

PubMed2004

Does a tree-like phylogeny only exist at the tips in the prokaryotes?

The extent to which prokaryotic evolution has been influenced by horizontal gene transfer (HGT) and therefore might be more of a network than a tree is unclear. Here we use supertree methods to ask whether a definitive prokaryotic phylogenetic tree exists and whether it can be confidently inferred using orthologous genes. We analysed an 11-taxon dataset spanning the deepest divisions of prokaryotic relationships, a 10-taxon dataset spanning the relatively recent gamma-proteobacteria and a 61-taxon dataset spanning both, using species for which complete genomes are available. Congruence among gene trees spanning deep relationships is not better than random. By contrast, a strong, almost perfect phylogenetic signal exists in gamma-proteobacterial genes. Deep-level prokaryotic relationships are difficult to infer because of signal erosion, systematic bias, hidden paralogy and/or HGT. Our results do not preclude levels of HGT that would be inconsistent with the notion of a prokaryotic phylogeny. This approach will help decide the extent to which we can say that there is a prokaryotic phylogeny and where in the phylogeny a cohesive genomic signal exists.

Bacteria↗

PubMed2004

Interstitial cystitis antiproliferative factor (APF) as a cell-cycle modulator.

BACKGROUND: Interstitial cystitis (IC) is a chronic bladder disorder of unknown etiology. Antiproliferative factor (APF), a peptide found in the urine of IC patients, has previously been shown to decrease incorporation of thymidine by normal bladder epithelial cells. This study was performed to determine the effect of APF on the cell cycle of bladder epithelial cells so as to better understand its antiproliferative activity. METHODS: Explant cultures from normal bladder biopsy specimens were exposed to APF or mock control. DNA cytometry was performed using an automated image analysis system. Cell cycle phase fractions were calculated from the DNA frequency distributions and compared by two-way analysis of variance (ANOVA). RESULTS: APF exposure produced statistically significant increases in the proportion of tetraploid and hypertetraploid cells compared to mock control preparations, suggesting a G2 and/or M phase cell cycle block and the production of polyploidy. CONCLUSIONS: APF has a specific effect on cell cycle distributions. The presence of a peptide with this activity may contribute to the pathogenesis of interstitial cystitis through disruption of normal urothelial proliferation and repair processes.

Adult↗

PubMed2003

Grade progression and regression in recurrent urothelial cancer.

PURPOSE: Recurrent urothelial cancers are reported to have characteristics similar to those of the primary tumor, with 10% to 25% of low grade tumors recurring as high grade disease. We determined how often grade progression and regression occur and whether abnormalities in p53 protein expression in original tumors are preserved in recurrences. MATERIALS AND METHODS: Two groups of patients treated for recurrent stages Ta/T1 urothelial bladder cancers with at least 1 tumor-free examination between the index and recurrent tumors were reviewed. Group 1 included 115 patients in whom the first available tumor was compared with the last recurrence and group 2 included 42 in whom the initial tumor was compared with the first recurrence. Immunohistochemical analysis of p53 expression was performed on a subset of 34 tumor pairs. RESULTS: In group 1, 33 grade 3 tumors (45%) recurred as grade 1 or 2 tumors, while 9 of 82 grades 1 and 2 tumors (11%) recurred as grade 3 tumors. Five of 7 group 2 grade 3 tumors (71%) recurred as grade 1 or 2 disease, while 1 of 35 grades 1 and 2 tumors (3%) recurred as grade 3 disease. In the 34 pairs studied immunohistochemically 6 of 14 grade 3 tumors recurred at lower grades. Nuclear p53 over expression occurred in 21 index tumors (12 of 14 grade 3, 8 of 17 grade 2 and 1 of 3 grade 1) and in 9 recurrences (6 of 10 grade 3, 2 of 17 grade 2 and 1 of 7 grade 1). Only 7 of 21 p53 positive and 2 of 12 p53 negative index tumors were p53 positive on recurrence. CONCLUSIONS: While progression from low to high grade occurred in less than 15% of patients, grade regression was observed in almost 50%. The loss of p53 positivity in regressing tumors indicates that these recurrences are molecularly distinct from the corresponding initial tumor.

Aged↗