Comparative studies of Hox genes in mammalian limb and vertebral pattern formation

Divergence of anterior-posterior (AP) limb pattern and differences in vertebral column morphology are the two main examples of mammalian evolution. The Hox genes (homeobox containing gene) have been implicated in driving evolution of these structures. However, regarding Hox genes, how they contribute to the generation of mammalian morphological diversities, is still unclear. Implementing comparative gene expression and phenotypic rescue studies for different mammalian Hox genes could aid in unraveling this mystery. In the first part of this thesis, the expression pattern of Hoxd13 gene, a key Hox gene in the establishment of the limb AP pattern, was examined in developing limbs of bats and mice. Bat forelimbs exhibit a pronounced asymmetric AP pattern and offer a good model to study the molecular mechanisms that contribute to the variety of mammalian limbs. The data showed that the expression domain of bat Hoxd13 was shifted prior to the asymmetric limb plate expansion, whereas its domain in mice was much more symmetric. This finding reveals a correlation between the divergence of Hoxd13 expression and the AP patterning difference in limb development. The second part of this thesis details a phenotypic rescue approach by human HOXB1-9 transgenes in mice with Hoxb1-9 deletion, The mouse mutants displayed homeosis in cervical and anterior thoracic vertebrae. The human transgenes entirely rescued the mouse mutants, suggesting that these human HOX genes have similar functions to their mouse orthologues in anterior axial skeletal patterning. The anterior expressing human HOXB transgenes such as HOXB1-3 were expressed in the mouse embryonic trunk in a similar manner as their murine orthologues. However, the anterior boundary of human HOXB9 expression domain was more posterior than that of the mouse Hoxb9 by 2-3 somites. These data provide the molecular support for the hypothesis that Hox genes are responsible for maintaining similar anterior axial skeletal architectures cervical and anterior thoracic regions, but different architectures in lumbar and posterior thoracic regions between humans and mice. ^

RELATION OF TYPE OF REPORTED ILLNESSES TO PATTERN OF USE OF THE STUDENT HEALTH CENTER BY THE INTERNATIONAL STUDENTS AT TEXAS SOUTHERN UNIVERSITY, HOUSTON, TEXAS

The state of knowledge on the relation of stress factors, health problems and health service utilization among university students is limited. Special problems of stress exist for the international students due to their having to adjust to a new environment. It is this latter problem area that provides the focus for this study. Recognizing there are special stress factors affecting the international students, it is first necessary to see if the problems of cultural adaptation affect them to any greater degree than American students attending the same university.^ To make the comparison, the study identified a number of health problems of both American and international students and related their frequency to the use of the Student Health Center. The expectation was that there would be an association between the number of health problems and the number of life change events experienced by these students and between the number of health problems and stresses from social factors. It was also expected that the number of health problems would decline with the amount of social support.^ The population chosen were students newly enrolled in Texas Southern University, Houston, Texas in the Fall Semester of 1979. Two groups were selected at random: 126 international and 126 American students. The survey instrument was a self-administered questionnaire. The response rate was 90% (114) for the international and 94% (118) for the American students.^ Data analyses consisted of both descriptive and inferential statistics. Chi-squares and correlation coefficients were the statistics used in comparing the international students and the American students.^ There was a weak association between the number of health problems and the number of life change events, as reported by both the international and the American students. The study failed to show any statistically significant association between the number of stress from social factors and the number of health problems. It also failed to show an association between the number of health problems and the amount of social support. These findings applied to both the international and the American students.^ One unexpected finding was that certain health problems were reported by more American than international students. There were: cough, diarrhea, and trouble in sleeping. Another finding was that those students with health insurance had a higher level of utilization of the Health Center than those without health insurance. More international than American students utilized the Student Health Center.^ In comparing the women students, there was no statistical significant difference in their reported fertility related health problems.^ The investigator recommends that in follow-up studies, instead of grouping all international students together, that they be divided by major nationalities represented in the student body; that is, Iranians, Nigerians and others. ^

Correlation of tuberculosis and human immunodeficiency virus in Harris County, Texas from 2009 through 2010 using Geographic Information Systems

A population based ecological study was conducted to identify areas with a high number of TB and HIV new diagnoses in Harris County, Texas from 2009 through 2010 by applying Geographic Information Systems to determine whether distinguished spatial patterns exist at the census tract level through the use of exploratory mapping. As of 2010, Texas has the fourth highest occurrence of new diagnoses of HIV/AIDS and TB.[31] The Texas Department of State Health Services (DSHS) has identified HIV infected persons as a high risk population for TB in Harris County.[29] In order to explore this relationship further, GIS was utilized to identify spatial trends. ^ The specific aims were to map TB and HIV new diagnoses rates and spatially identify hotspots and high value clusters at the census tract level. The potential association between HIV and TB was analyzed using spatial autocorrelation and linear regression analysis. The spatial statistics used were ArcGIS 9.3 Hotspot Analysis and Cluster and Outlier Analysis. Spatial autocorrelation was determined through Global Moran's I and linear regression analysis. ^ Hotspots and clusters of TB and HIV are located within the same spatial areas of Harris County. The areas with high value clusters and hotspots for each infection are located within the central downtown area of the city of Houston. There is an additional hotspot area of TB located directly north of I-10 and a hotspot area of HIV northeast of Interstate 610. ^ The Moran's I Index of 0.17 (Z score = 3.6 standard deviations, p-value = 0.01) suggests that TB is statistically clustered with a less than 1% chance that this pattern is due to random chance. However, there were a high number of features with no neighbors which may invalidate the statistical properties of the test. Linear regression analysis indicated that HIV new diagnoses rates (β=−0.006, SE=0.147, p=0.970) and census tracts (β=0.000, SE=0.000, p=0.866) were not significant predictors of TB new diagnoses rates. ^ Mapping products indicate that census tracts with overlapping hotspots and high value clusters of TB and HIV should be a targeted focus for prevention efforts, most particularly within central Harris County. While the statistical association was not confirmed, evidence suggests that there is a relationship between HIV and TB within this two year period.^