Natural variation in life history and aging phenotypes is associated with mitochondrial DNA deletion frequency in Caenorhabditis briggsae

<p>Abstract</p> <p>Background</p> <p>Mutations that impair mitochondrial functioning are associated with a variety of metabolic and age-related disorders. A barrier to rigorous tests of the role of mitochondrial dysfunction in aging processes has been the lack of model systems with relevant, naturally occurring mitochondrial genetic variation. Toward the goal of developing such a model system, we studied natural variation in life history, metabolic, and aging phenotypes as it relates to levels of a naturally-occurring heteroplasmic mitochondrial <it>ND5 </it>deletion recently discovered to segregate among wild populations of the soil nematode, <it>Caenorhabditis briggsae</it>. The normal product of <it>ND5 </it>is a central component of the mitochondrial electron transport chain and integral to cellular energy metabolism.</p> <p>Results</p> <p>We quantified significant variation among <it>C. briggsae </it>isolates for all phenotypes measured, only some of which was statistically associated with isolate-specific <it>ND5 </it>deletion frequency. We found that fecundity-related traits and pharyngeal pumping rate were strongly inversely related to <it>ND5 </it>deletion level and that <it>C. briggsae </it>isolates with high <it>ND5 </it>deletion levels experienced a tradeoff between early fecundity and lifespan. Conversely, oxidative stress resistance was only weakly associated with <it>ND5 </it>deletion level while ATP content was unrelated to deletion level. Finally, mean levels of reactive oxygen species measured <it>in vivo </it>showed a significant non-linear relationship with <it>ND5 </it>deletion level, a pattern that may be driven by among-isolate variation in antioxidant or other compensatory mechanisms.</p> <p>Conclusions</p> <p>Our findings suggest that the <it>ND5 </it>deletion may adversely affect fitness and mitochondrial functioning while promoting aging in natural populations, and help to further establish this species as a useful model for explicit tests of hypotheses in aging biology and mitochondrial genetics.</p

The Educational Goals and Degree Objectives of Community College Students: Implications for Planning Instructional Programs and Student Services.

Community colleges have been judged as being low quality institutions because they have "high dropout rates." An alternative explanation is that community college students have a variety of goals, and not all involve degree completion. Attrition research has produced an increasingly sophisticated general literature on attrition that has not included a consideration of students' goals, and a very simplistic literature that has focused on these goals. The present study was designed to begin an integration between the two, by: (1) Demonstrating that a relationship exists between student choices of goal and goal achievement method, and student re-enrollment decisions. (2) Exploring how these goals and methods operate as intervening variables which help to explain the relationship between demographic variables and attrition. A causal model was designed to test this latter relationship: Age Selection of Selection of Decision to Sex Educational (--->) Method of (--->) Re-enroll or Ethnicity Goal Achieving Not to Educational Re-enroll Goal ("Status") This model was tested by analyzing the relationship between the goal choices stated by 5,981 students at Washtenaw Community College in Jauary 1980, and their status at the college in September 1980. Both bivariate and multivariate analyses were used. The first purpose of the study was supported: students' choices of goals and goal achievement methods at one point in time are related significantly to later re-enrollment decisions. However, the data did not support the simple causal model which was proposed, in that age, sex, and ethnicity were not significantly related to the selection of an educational goal. The most interesting finding was unanticipated: that goals functioned as a suppressor variable in the relationship between race and attrition: the difference between blacks' and whites' attainment of their stated goals at Washtenaw is more substantial than a traditional measure of "dropout" would indicate. The results of this study have specific implications for attrition researchers and for those who judge community colleges on the basis of their "dropout rates." The diversity of student goals has more general implications in m and ating a continuing diversity in college responses to those students in instruction, student services, and other areas of college practice.Ph.D.Community college educationUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/159050/1/8225010.pd

Black Like Malcolm: Grace Halsell’s Rewriting of Black Like Me (1961) in Soul Sister (1969)

This essay compares Grace Halsell’s under-examined and now out-of-print memoir Soul Sister (1969) to its precursor, John Howard Griffin’s Black Like Me (1961), in order to demonstrate that Halsell attempts to revise Black Like Me’s focus on a portrait of black powerlessness, pathos, and lack of voice. While Griffin evacuates political context, Halsell fills her text with male and female voices from the Civil Rights and Black Power Movements; in so doing she forwards a multivalent and plural construct of black subjectivity and black political struggle. Ultimately, Halsell depicts herself moving into the political subjectivity of Malcolm X, although she also reaches towards what she sees as his final vision in which a stark black-white racial binary is transcended. Second, the essay also argues that at key junctures Halsell’s text turns back onto itself as an exploration of the formation of white racial identity as well as the privileges according to white femininity; the intersectional oppression she experiences while passing forces her to interrogate the construction of categories not only of race, but also of sex and class. Taken together, these texts therefore enable an examination of what is at stake in the genre of the white passing narrative—as well as why the modes of looking at blackness present in these texts so often fail. While the genre of the white passing narrative has been critically derided, this essay seeks to show that such works allow an examination of the formation and transformation of categories of white racial (and to a lesser extent) gendered identity, as well as the way whiteness remains the fulcrum of personal, social, and political privilege

An Interview with Martha J. Cutter, editor of MELUS

NANO assistant editor Rebecca Devers interviews Martha J. Cutter, the former editor of MELUS, about the complexities of processing, reviewing, and publishing a journal that receives in over 300 submissions each year. An Interview with Martha J. Cutter, editor of MELUS by Rebecca Devers