University of Missouri

About: University of Missouri is a education organization based out in Columbia, Missouri, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 41427 authors who have published 83598 publications receiving 2911437 citations. The organization is also known as: Mizzou & Missouri-Columbia.

Two Pleiotropic Classes of daf-2 Mutation Affect Larval Arrest, Adult Behavior, Reproduction and Longevity in Caenorhabditis elegans

Abstract: The nematode Caenorhabditis elegans responds to overcrowding and scarcity of food by arresting development as a dauer larva, a nonfeeding, long-lived, stress-resistant, alternative third-larval stage. Previous work has shown that mutations in the genes daf-2 (encoding a member of the insulin receptor family) and age-1 (encoding a PI 3-kinase) result in constitutive formation of dauer larvae (Daf-c), increased adult longevity (Age), and increased intrinsic thermotolerance (Itt). Some daf-2 mutants have additional developmental, behavioral, and reproductive defects. We have characterized in detail 15 temperature-sensitive and 1 nonconditional daf-2 allele to investigate the extent of daf-2 mutant defects and to examine whether specific mutant traits correlate with each other. The greatest longevity seen in daf-2 mutant adults was approximately three times that of wild type. The temperature-sensitive daf-2 mutants fell into two overlapping classes, including eight class 1 mutants, which are Daf-c, Age, and Itt, and exhibit low levels of L1 arrest at 25.5 degrees. Seven class 2 mutants also exhibit the class 1 defects as well as some or all of the following: reduced adult motility, abnormal adult body and gonad morphology, high levels of embryonic and L1 arrest, production of progeny late in life, and reduced brood size. The strengths of the Daf-c, Age, and Itt phenotypes largely correlated with each other but not with the strength of class 2-specific defects. This suggests that the DAF-2 receptor is bifunctional. Examination of the null phenotype revealed a maternally rescued egg, L1 lethal component, and a nonconditional Daf-c component. With respect to the Daf-c phenotype, the dauer-defective (Daf-d) mutation daf-12(m20) was epistatic to daf-2 class 1 alleles but not the severe class 2 alleles tested. All daf-2 mutant defects were suppressed by the daf-d mutation daf-16(m26). Our findings suggest a new model for daf-2, age-1, daf-12, and daf-16 interactions.

The possibilistic C-means algorithm: insights and recommendations

Abstract: Recently, the possibilistic C-means algorithm (PCM) was proposed to address the drawbacks associated with the constrained memberships used in algorithms such as the fuzzy C-means (FCM). In this issue, Barni et al. (1996) report a difficulty they faced while applying the PCM, and note that it exhibits an undesirable tendency to converge to coincidental clusters. The purpose of this paper is not just to address the issues raised by Barni et al., but to go further and analytically examines the underlying principles of the PCM and the possibilistic approach, in general. We analyze the data sets used by Barni et al. and interpret the results reported by them in the light of our findings.

The Glass Ceiling Effect

Abstract: The popular notion of glass ceiling effects implies that gender (or other) disadvantages are stronger at the top of the hierarchy than at lower levels and that these disadvantages become worse later in a person's career. We define four specific criteria that must be met to conclude that a glass ceiling exists. Using random effects models and data from the Panel Study of Income Dynamics, we examine gender and race inequalities at the 25th, 50th, and 75th percentiles of white male earnings. We find evidence of a glass ceiling for women, but racial inequalities among men do not follow a similar pattern. Thus, we should not describe all systems of differential work rewards as "glass ceilings." They appear to be a distinctively gender phenomenon.

The Health Benefits of Writing about Life Goals

Abstract: In a variation on Pennebaker’s writing paradigm, a sample of 81 undergraduates wrote about one of four topics for 20 minutes each day for 4 consecutive days. Participants were randomly assigned to write about their most traumatic life event, their best possible future self, both of these topics, or a nonemotional control topic. Mood was measured before and after writing and health center data for illness were obtained with participant consent. Three weeks later, measures of subjective well-being were obtained. Writing about life goals was significantly less upsetting than writing about trauma and was associated with a significant increase in subjective well-being. Five months after writing, a significant interaction emerged such that writing about trauma, one’s best possible self, or both were associated with decreased illness compared with controls. Results indicate that writing about self-regulatory topics can be associated with the same health benefits as writing about trauma.