STUDIES ON THE PATTERNS OF NUCLEOTIDE AND AMINO ACID SUBSTITUTION (ELECTROPHORESIS, MUTATION RATE, SELECTION, BASE, COMPOSITION)

Theoretical and empirical studies were conducted on the pattern of nucleotide and amino acid substitution in evolution, taking into account the effects of mutation at the nucleotide level and purifying selection at the amino acid level. A theoretical model for predicting the evolutionary change in electrophoretic mobility of a protein was also developed by using information on the pattern of amino acid substitution. The specific problems studied and the main results obtained are as follows: (1) Estimation of the pattern of nucleotide substitution in DNA nuclear genomes. The pattern of point mutations and nucleotide substitutions among the four different nucleotides are inferred from the evolutionary changes of pseudogenes and functional genes, respectively. Both patterns are non-random, the rate of change varying considerably with nucleotide pair, and that in both cases transitions occur somewhat more frequently than transversions. In protein evolution, substitution occurs more often between amino acids with similar physico-chemical properties than between dissimilar amino acids. (2) Estimation of the pattern of nucleotide substitution in RNA genomes. The majority of mutations in retroviruses accumulate at the reverse transcription stage. Selection at the amino acid level is very weak, and almost non-existent between synonymous codons. The pattern of mutation is very different from that in DNA genomes. Nevertheless, the pattern of purifying selection at the amino acid level is similar to that in DNA genomes, although selection intensity is much weaker. (3) Evaluation of the determinants of molecular evolutionary rates in protein-coding genes. Based on rates of nucleotide substitution for mammalian genes, the rate of amino acid substitution of a protein is determined by its amino acid composition. The content of glycine is shown to correlate strongly and negatively with the rate of substitution. Empirical formulae, called indices of mutability, are developed in order to predict the rate of molecular evolution of a protein from data on its amino acid sequence. (4) Studies on the evolutionary patterns of electrophoretic mobility of proteins. A theoretical model was constructed that predicts the electric charge of a protein at any given pH and its isoelectric point from data on its primary and quaternary structures. Using this model, the evolutionary change in electrophoretic mobilities of different proteins and the expected amount of electrophoretically hidden genetic variation were studied. In the absence of selection for the pI value, proteins will on the average evolve toward a mildly basic pI. (Abstract shortened with permission of author.) ^

Inherited and noninherited sources of variation in metastasis and the growth rate of tumors: Implications for tumor evolution and therapy

I have undertaken measurements of the genetic (or inherited) and nongenetic (or noninherited) components of the variability of metastasis formation and tumor diameter doubling time in more than 100 metastatic lines from each of three murine tumors (sarcoma SANH, sarcoma SA4020, and hepatocarcinoma HCA-I) syngeneic to C3Hf/Kam mice. These lines were isolated twice from lung metastases and analysed immediately thereafter to obtain the variance to spontaneous lung metastasis and tumor diameter doubling time. Additional studies utilized cells obtained from within 4 passages of isolation. Under the assumption that no genetic differences in metastasis formation or diameter doubling time existed among the cells of a given line, the variance within a line would estimate nongenetic variation. The variability derived from differences between lines would represent genetic origin. The estimates of the genetic contribution to the variation of metastasis and tumor diameter doubling time were significantly greater than zero, but only in the metastatic lines of tumor SANH was genetic variation the major source of metastatic variability (contributing 53% of the variability). In the tumor cell lines of SA4020 and HCA-I, however, the contribution of nongenetic factors predominated over genetic factors in the variability of the number of metastasis and tumor diameter doubling time. A number of other parameters examined, such as DNA content, karyotype, and selection and variance analysis with passage in vivo, indicated that genetic differences existed within the cell lines and that these differences were probably created by genetic instability. The mean metastatic propensity of the lines may have increased somewhat during their isolation and isotransplantation, but the variance was only slightly affected, if at all. Analysis of the DNA profiles of the metastatic lines of SA4020 and HCA-I revealed differences between these lines and their primary parent tumors, but not among the SANH lines and their parent tumor. Furthermore, there was a direct correlation between the extent of genetic influence on metastasis formation and the ability of the tumor cells to develop resistance to cisplatinum. Thus although nongenetic factors might predominate in contributing to metastasis formation, it is probably genetic variation and genetic instability that cause the progression of tumor cells to a more metastatic phenotype and leads to the emergence of drug resistance. ^

An examination of the rate of high school completion experienced by handicapped and nonhandicapped students in the state of Texas

This research examines the graduation rate experienced by students receiving public education services in the state of Texas. Special attention is paid to that subgroup of Texas students who meet Texas Education Agency criteria for handicapped status. The study is guided by two research questions: What are the high school completion rates experienced by handicapped and nonhandicapped students attending Texas public schools? and What are the predictors of graduation for handicapped and nonhandicapped students?^ In addition, the following hypotheses are explored. Hypothesis 1: Handicapped students attending a Texas public school will experience a lower rate of high school completion than their nonhandicapped counterparts. Hypothesis 2: Handicapped and nonhandicapped students attending school in a Texas public school with a budget above the median budget for Texas public schools will experience a higher rate of high school completion than similar students in Texas public schools with a budget below the median budget. Hypothesis 3: Handicapped and nonhandicapped students attending school in large Texas urban areas will experience a lower rate of high school completion than similar students in Texas public schools in rural areas. Hypothesis 4: Handicapped and nonhandicapped students attending a Texas public school in a county which rates above the state median for food stamps and AFDC recipients will experience a lower rate of high school completion than students living in counties below the median.^ The study will employ extant data from the records of the Texas Education Agency for the 1988-1989 and the 1989-1990 school years, from the Texas Department of Health for the years of 1989 and 1990, and from the 1980 Census.^ The study reveals that nonhandicapped students are graduating with a two year average rate of.906, while handicapped students following an Individualized Educational Program (IEP) achieve a two year average rate of.532, and handicapped students following the regular academic program present a two year average graduation rate of only.371. The presence of other handicapped students, and the school district's average expense per student are found to contribute significantly to the completion rates of handicapped students. Size groupings are used to elucidate the various impacts of these variables on different school districts and different student groups.^ Conclusions and implications are offered regarding the need to reach national consensus on the definition and computation of high school completion for both handicapped and nonhandicapped students, and the need for improved statewide tracking of handicapped completion rates. ^

Adherence to a lifestyle physical activity program: Trends over time and associations with processes of change and physical activity

Research on lifestyle physical activity interventions suggests that they help individuals meet the new recommendations for physical activity made by the Centers for Disease Control and Prevention (CDC) and the American College of Sports Medicine (ACSM). The purpose of this research was to describe the rates of adherence to two lifestyle physical activity intervention arms and to examine the association between adherence and outcome variables, using data from Project PRIME, a lifestyle physical activity intervention based on the transtheoretical model and conducted by the Cooper Institute of Aerobics Research, Dallas, Texas. Participants were 250 sedentary healthy adults, aged 35 to 70 years, primarily non-Hispanic White, and in the contemplation and preparation stages of readiness to change. They were randomized to a group (PRIME G) or a mail- and telephone-delivered condition (PRIME C). Adherence measures included attending class (PRIME G), completing a monthly telephone call with a health educator (PRIME C), and completing homework assignments and self-monitoring minutes of moderate- to vigorous physical activity (both groups). In the first results paper, adherence over time and between conditions was examined: Attendance in group, completing the monthly telephone call, and homework completion decreased over time, and participants in PRIME G were more likely to complete homework than those in PRIME C. Paper 2 aimed to determine whether the adherence measures predicted achievement of the CDC/ACSM physical activity guideline. In separate models for the two conditions, a latent variable measuring adherence was found to predict achievement of the guideline. Paper 3 examined the association between adherence measures and the transtheoretical model's processes of change within each condition. For both, participants who completed at least two thirds of the homework assignments improved their use of the processes of change more than those who completed less than that amount. These results suggest that encouraging adherence to a lifestyle physical activity intervention, at least among already motivated volunteers, may increase the likelihood of beneficial changes in the outcomes. ^

Evaluation of the causal pathways through which subjective norms influence mammography intention and stage of change in a national sample of women veterans

Few studies have investigated causal pathways linking psychosocial factors to each other and to screening mammography. Conflicting hypotheses exist in the theoretic literature regarding the role and importance of subjective norms, a person's perceived social pressure to perform the behavior and his/her motivation to comply. The Theory of Reasoned Action (TRA) hypothesizes that subjective norms directly affect intention; while the Transtheoretical Model (TTM) hypothesizes that attitudes mediate the influence of subjective norms on stage of change. No one has examined which hypothesis best predicts the effect of subjective norms on mammography intention and stage of change. Two statistical methods are available for testing mediation, sequential regression analysis (SRA) and latent variable structural equation modeling (LVSEM); however, software to apply LVSEM to dichotomous variables like intention has only recently become available. No one has compared the methods to determine whether or not they yield similar results for dichotomous variables. ^ Study objectives were to: (1) determine whether the effect of subjective norms on mammography intention and stage of change are mediated by pros and cons; and (2) compare mediation results from the SRA and LVSEM approaches when the outcome is dichotomous. We conducted a secondary analysis of data from a national sample of women veterans enrolled in Project H.O.M.E. (H&barbelow;ealthy O&barbelow;utlook on the M&barbelow;ammography E&barbelow;xperience), a behavioral intervention trial. ^ Results showed that the TTM model described the causal pathways better than the TRA one; however, we found support for only one of the TTM causal mechanisms. Cons was the sole mediator. The mediated effect of subjective norms on intention and stage of change by cons was very small. These findings suggest that interventionists focus their efforts on reducing negative attitudes toward mammography when resources are limited. ^ Both the SRA and LVSEM methods provided evidence for complete mediation, and the direction, magnitude, and standard errors of the parameter estimates were very similar. Because SRA parameter estimates were not biased toward the null, we can probably assume negligible measurement error in the independent and mediator variables. Simulation studies are needed to further our understanding of how these two methods perform under different data conditions. ^

Assessing residents' readiness to screen for domestic violence: Utilizing the transtheoretical model - stages of change, decisional balance and self-efficacy

Domestic violence is a major public health problem, yet most physicians do not effectively identify patients at risk. Medical students and residents are not routinely educated on this topic and little is known about the factors that influence their decisions to include screening for domestic violence in their subsequent practice. In order to assess the readiness of primary care residents to screen all patients for domestic violence, this study utilized a survey incorporating constructs from the Transtheoretical Model, including Stages of Change, Decisional Balance (Pros and Cons) and Self-Efficacy. The survey was distributed to residents at the University of Texas Health Science Center Medical School in Houston in: Internal Medicine, Medicine/Pediatrics, Pediatrics, Family Medicine, and Obstetrics and Gynecology. Data from the survey was analyzed to test the hypothesis that residents in the earlier Stages of Change report more costs and fewer benefits with regards to screening for domestic violence, and that those in the later stages exhibit higher Self-Efficacy scores. The findings from this study were consistent with the model in that benefits to screening (Pros) and Self-Efficacy were correlated with later Stages of Change, however reporting fewer costs (Cons) was not. Very few residents were ready to screen all of their patients.^

Stages of change and carotene intake in the Paso del Norte region: Que Sabrosa Vida

Understanding a population's dietary behavior is important to promote behaviors which have the most beneficial impact on health. The most recent Dietary Guidelines for Americans (2005) identifies carotenoids as a key nutrient to be consumed through increased intake of fruits and vegetables (FV). While some studies have included or focused on the Hispanic population, few have focused only on Mexican-American populations and staged its intake of FV. Stage of change behavior theory has been used to understand the adoption and promotion of healthy behaviors such as increased intake of FV. It has been shown to effectively aid interventionists' understanding of dietary behavior. Intake patterns of FV of older women, rural residents, and adolescents of Mexican American descent have been conducted but not by stages of change. This study aimed to determine the relationship between stages of change for fruits and vegetables (SOC-FV) and total carotene intake to assess the quality of SOC-FV as a surrogate measure of total carotene. ^ Data from the 2000 Qué Sabrosa Vida Community Nutrition Survey (QSV-CNS) were analyzed to identify the SOC-FV and sources of carotenes in a Mexican American population 18-60 yrs. of the Paso del Norte region. A 107 item interviewer administered food frequency questionnaire (FFQ) specifically calibrated for a Mexican American population was used to collect usual intake of total carotene. The QSV survey study population included 963 participants, 590 (61.3%) women and 373 (38.7%) men. A statistically significant mean difference in caloric intake between men and women was found (p-value = <0.01). When total carotene intake was adjusted for energy, there were significant differences between men and women (p-value = <0.0001) with women consuming a higher amount of total carotene (406 RE/kcal 1,000) than men (332 RE/kcal 1000). The food sources of total carotene for both genders included many items found in a traditional Mexican American diet. Chile, after carrots, was the highest contributor of dietary carotene. Total carotene intake was not associated with stages of change among women or men and their distributions were not linear. Mean differences of total carotene by stages of change were significant for women for pre-contemplation/contemplation (p-value = 0.04) and preparation (p-value = 0.0004) but not for men. ^ SOC-FV may serve as a surrogate measure for dietary carotene intake. This study's Mexican American population had a high carotene quality diet derived from traditional food items irrespective of their stage of change for fruits and vegetables. To better understand this population's dietary intake a measure for acculturation should be included. Interventions aimed at Mexican American populations should aim to promote traditional diets consistent with cultural practices.^ ^

The contribution of change in ethnic composition to prevalence of obesity and overweight

Objective. The prevalence of overweight and obesity differs substantially among children of different ethnic origin in the United States. The objective of this project is to estimate to what extent changes in ethnic composition since 1980 have contributed to the current general “obesity epidemic” in the childhood population of the United States.^ Methods. Populations by single year of age, 0 to 19, male and female, for Hispanics, non-Hispanic whites, and non-Hispanic blacks, from the US Census’ July estimates for 1985, 1990, 1995, 2000 and 2005 were taken and compared to the population and percentage of those groups from 1980. Age, sex, and ethnicity specific prevalence rates for overweight in 1980 were then applied to the populations by age for the specified year and differences in expected and actual overweight populations were assessed.^ Result. The results from this investigation provide estimates of the contribution that different ethnic groups have made to the overall prevalence of overweight and obesity in the childhood population of the United States. Assuming that the 1976-1980 prevalence rates had remained unchanged, and then comparing the population had there been no change in ethnic composition with the population given the actual change in ethnicity, the percentage increase was 1.06% in 1985, 1.72% in 1990, 2.57% in 1995, 3.95% in 2000, and 4.39% in 2005.^ Conclusion. The changes in ethnic composition of the population, independent of changes in ethnicity-specific prevalence, have contributed substantially to the current overall prevalence of obesity in the United States childhood population. There are a number of factors that may be responsible for the apparent susceptibility of Mexican-Americans and non-Hispanic blacks to overweight and obesity. Further research is needed on specific characteristics of those populations.^

Literature review of estimation of prevalence rate of HIV/AIDS in India using population survey and sentinel surveillance based data

HIV/AIDS is a treatable although incurable disease that presents immense challenges to those infected including physical, social and psychological effects. As of 2009, an estimated 2.4 million people were living with HIV or AIDS in India, 0.3% of the country's population. In India, it is difficult to not only treat but also to track because it is associated with socio-economic factors such as illiteracy, social biases, poor sanitation, malnutrition and social class. Nevertheless, it is important to know the prevalence of HIV/AIDS for several reasons. At the individual level, the quality of life of people living with HIV/AIDS is markedly lower than their counterparts without the disease and is associated with challenges. At the community level, it is important to identify high risk groups, monitor prevention efforts, and allocate appropriate resources to target programs for the reduction of transmission of HIV. ^

TURNOVER RATE OF THE NEURONAL CONNEXIN CX36 IN HELA CELLS

Electrical synapses formed of the gap junction protein Cx36 show a great deal of functional plasticity, much dependent on changes in phosphorylation state of the connexin. However, gap junction turnover may also be important for regulating cell-cell communication, and turnover rates of Cx36 have not been studied. Connexins have relatively fast turnover rates, with short half-lives measured to be 1.5 to 3.5 hours in pulse-chase analyses of connexins (Cx26 and Cx43) in tissue culture cells and whole organs. We utilized HaloTag technology to study the turnover rate of Cx36 in transiently transfected HeLa cells. The HaloTag protein forms irreversible covalent bonds with chloroalkane ligands, allowing pulse-chase experiments to be performed very specifically. The HaloTag open reading frame was inserted into an internal site in the C-terminus of Cx36 designed not to disrupt the regulatory phosphorylation sites and not to block the C-terminal PDZ interaction motif. Functional properties of Cx36-Halo were assessed by Neurobiotin tracer coupling, live cell imaging, and immunostaining. For the pulse-chase study, transiently transfected HeLa cells were pulse labeled with Oregon Green (OG) HaloTag ligand and chase labeled at various times with tetramethylrhodamine (TMR) HaloTag ligand. Cx36-Halo formed large junctional plaques at sites of contact between transfected HeLa cells and was also contained in a large number of intracellular vesicles. The Cx36-Halo transfected HeLa cells supported Neurobiotin tracer coupling that was regulated by activation and inhibition of PKA in the same manner as wild-type Cx36 transfected cells. In the pulse-chase study, junctional protein labeled with the pulse ligand (OG) was gradually replaced by newly synthesized Cx36 labeled with the chase ligand (TMR). The half-life for turnover of protein in junctional plaques was 2.8 hours. Treatment of the pulse-labeled cells with Brefeldin A (BFA) prevented the addition of new connexins to junctional plaques, suggesting that the assembly of Cx36 into gap junctions involves the traditional ER-Golgi-TGN-plasma membrane pathway. In conclusion, Cx36-Halo is functional and has a turnover rate in HeLa cells similar to that of other connexins that have been studied. This turnover rate is likely too slow to contribute substantially to short-term changes in coupling of neurons driven by transmitters such as dopamine, which take minutes to achieve. However, turnover may contribute to longer-term changes in coupling.

Behavioral decision making and the levels of change: An application of the transtheoretical model to prenatal smoking in low -income women

Despite continued research and public health efforts to reduce smoking during pregnancy, prenatal cessation rates in the United States have decreased and the incidence of low birth weight has increased from 1985 to 1991. Lower socioeconomic status women who are at increased risk for poor pregnancy outcomes may be resistant to current intervention efforts during pregnancy. The purpose of this dissertation was to investigate the determinants of continued smoking and quitting among low-income pregnant women.^ Using data from cross-sectional surveys of 323 low-income pregnant smokers, the first study developed and tested measures of the pros and cons of smoking during pregnancy. The original decisional balance measure for smoking was compared with a new measure that added items thought to be more salient to the target population. Confirmatory factor analysis using structural equation modeling showed neither the original nor new measure fit the data adequately. Using behavioral science theory, content from interviews with the population, and statistical evidence, two 7-item scales representing the pros and cons were developed from a portion (n = 215) of the sample and successfully cross-validated on the remainder of the sample (n = 108). Logistic regression found only pros were significantly associated with continued smoking. In a discriminant function analysis, stage of change was significantly associated with pros and cons of smoking.^ The second study examined the structural relationships between psychosocial constructs representing some of the levels of and the pros and cons of smoking. The cross-sectional design mandates that statements made regarding prediction do not prove causation or directionality from the data or methods analysis. Structural equation modeling found the following: more stressors and family criticism were significantly more predictive of negative affect than social support; a bi-directional relationship was found between negative affect and current nicotine addiction; and negative affect, addiction, stressors, and family criticism were significant predictors of pros of smoking.^ The findings imply reversing the trend of decreasing smoking cessation during pregnancy may require supplementing current interventions for this population of pregnant smokers with programs addressing nicotine addiction, negative affect, and other psychosocial factors such as family functioning and stressors. ^