Quantifying Distances Between Non-Elliptical Clusters to Enhance the Identification of Meaningful Emotional Reactivity Subtypes.

Coordinated emotional responses across psychophysiological and subjective indices is a cornerstone of adaptive emotional functioning. Using clustering to identify cross-diagnostic subgroups with similar emotion response profiles may suggest novel underlying mechanisms and treatments.However, many psychophysiological measures are non-normal even in homogenous samples, and over-reliance on traditional elliptical clustering approaches may inhibit the identification of meaningful subgroups. Finite mixture models that allow for non-elliptical cluster distributions is an emerging methodological field that may overcome this hurdle. Furthermore, succinctly quantifying pairwise cluster separation could enhance the clinical utility of the clustering solutions. However, a comprehensive examination of distance measures in the context of elliptical and non-elliptical model-based clustering is needed to provide practical guidance on the computation, benefits, and disadvantages of existing measures. We summarize several measures that can quantify the multivariate distance between two clusters and suggest practical computational tools. Through a simulation study, we evaluate the measures across three scenarios that allow for clusters to differ in location, scale, skewness, and rotation. We then demonstrate our approaches using psychophysiological and subjective responses to emotional imagery captured through the Transdiagnostic Anxiety Study. Finally, we synthesize findings to provide guidance on how to use distance measures in clustering applications.

Genomics of Parallel Experimental Evolution in Drosophila.

What are the genomic foundations of adaptation in sexual populations? We address this question using fitness-character and whole-genome sequence data from 30 Drosophila laboratory populations. These 30 populations are part of a nearly 40-year laboratory radiation featuring 3 selection regimes, each shared by 10 populations for up to 837 generations, with moderately large effective population sizes. Each of 3 sets of the 10 populations that shared a selection regime consists of 5 populations that have long been maintained under that selection regime, paired with 5 populations that had only recently been subjected to that selection regime. We find a high degree of evolutionary parallelism in fitness phenotypes when most-recent selection regimes are shared, as in previous studies from our laboratory. We also find genomic parallelism with respect to the frequencies of single-nucleotide polymorphisms, transposable elements, insertions, and structural variants, which was expected. Entirely unexpected was a high degree of parallelism for linkage disequilibrium. The evolutionary genetic changes among these sexual populations are rapid and genomically extensive. This pattern may be due to segregating functional genetic variation that is abundantly maintained genome-wide by selection, variation that responds immediately to changes of selection regime.

The effect of superoxide dismutase alleles on aging in Drosophila.

The effects of superoxide dismutase on aging were tested using two different experimental approaches. In the first, replicated populations with postponed aging were compared with their controls for frequencies of electrophoretic alleles at the SOD locus. Populations with postponed aging had consistently greater frequencies of the allele coding for more active SOD protein. This allele was not part of a segregating inversion polymorphism. The second experimental approach was the extraction of SOD alleles from different natural populations followed by the construction of different SOD genotypes on hybrid genetic backgrounds. This procedure did not uncover any statistical effect of SOD genotype on longevity or fecundity. There were large effects on longevity and fecundity due to the family from which a particular SOD genotype was derived. To detect the effects of SOD genotypes on longevity with high probability would require a ten-fold increase in the number of families used.

Population density effects on longevity.

Population density, or the number of adults in an environment relative to the limiting resources, may have important long and short term consequences for the longevity of organisms. In this paper we summarize the way in which crowding may have an immediate impact on longevity, either through the phenomenon known as dietary restriction or through alterations in the quality of the environment brought on by the presence of large numbers of individuals. We also consider the possible long term consequences of population density on longevity by the process of natural selection. There has been much theoretical speculation about the possible impact of population density on the evolution of longevity but little experimental evidence has been gathered to test these ideas. We discuss some of the theory and empirical evidence that exists and show that population density is an important factor in determining both the immediate chances of survival and the course of natural selection.

The costs of reproduction and dietary restriction: parallels between insects and mammals.

Dietary restriction increases life span in mammals. This essay connects the dietary restriction response to evolutionary life history theory and experiments related to it. Evolutionary biologists have shown mathematically that aging is an inevitable consequence of age-specific natural selection acting on species with somata separate from germ lines. Empirical tests of this prediction currently point to its general validity. Two specific genetic mechanisms are known which could underlie the evolution of aging under these conditions: age-specificity of gene effects and antagonistic pleiotropy between early and late ages. The antagonistic pleiotropy theory assumes that some genes with beneficial effects on early life fitness will have deleterious effects upon fitness in later life. Experimental work in insects, particularly selection experiments in Drosophila melanogaster, has tested these ideas. The negative genetic correlation between longevity and reproductive effort produced by selection has been shown to be paralleled, in some cases, by environmental manipulation. Thus the increase in life span caused by dietary restriction might be explained as an incidental consequence of lower reproductive effort. This response also could have been an adaptation that enhanced fitness in some species that faced uncertain food supplies, a condition that may have evolved independently in a wide variety of taxa. Several schools of research, besides that of the evolutionary biologists concerned with genetic correlations, have produced corroborations of this hypothesis in insects and mammals: the gerontological work on life span extension, reproductive physiologists concerned with factors that affect fertility, and various life history studies.

Selection on stress resistance increases longevity in Drosophila melanogaster.

Tests for the causal involvement of specific physiological mechanisms in the control of aging require evidence that these mechanisms can be used to increase longevity or reproductive lifespan. Selection for later reproduction in Drosophila has been shown to lead to increased longevity, as well as increased resistance to starvation and desiccation stresses. Selection for increased resistance to starvation and desiccation in Drosophila melanogaster is here shown to lead to increased longevity, indicating that alleles that increase stress resistance also may increase longevity. The responses of desiccation and starvation resistance to selection are partly independent of each other, indicating a multiplicity of physiological mechanisms involved in selectively postponed aging, and thus aging in general.

What evolutionary biology can do for gerontology.

Evolutionary biologists have shown mathematically that aging is an inevitable consequence of age-specific natural selection acting on species with somata separate from germ lines. Two specific genetic mechanisms are known which could underlie the evolution of aging under these conditions: age-specificity of gene effects and antagonistic pleiotropy between early and late ages. Comparative evidence indicates that senescence occurs only when the stipulations of the evolutionary theory are met. Laboratory experiments with Drosophila indicate that prolonging the action of natural selection leads to the evolution of postponed senescence. The genetic variation involved in such postponed senescence exhibits both age-specificity and antagonistic pleiotropy. These theories and empirical findings together suggest that the best general theory of aging now available is the evolutionary theory. In addition, this work has yielded Drosophila stocks with postponed senescence that are being used to unravel physiological mechanisms of senescence.

Localizing genes that defer senescence in Drosophila melanogaster.

Selection for age-specific reproduction has produced replicate stocks in which life span exceeds that in short-lived controls by about 30 per cent, in unpaired individuals. Crosses between a selected long-lived (L) stock, short-lived (S) stock and a strain with balancer chromosomes were used to create all possible combinations of their chromosomes. The longest and shortest-lived genotypes are found to be (LSL) and (SLS), with other combinations distributed between them approximately according to their first and third chromosomes. Longevity appears to be under polygenic control with contributing elements on all chromosomes. The third chromosome is by far the most influential, accounting for 66 to 72 per cent of the observed variation in females. The first chromosome is less effective. Epistatic interactions are more important in males than females, but are significant only in measurements of single individuals. Some controlling elements for longevity appear to differ in males and females. Crosses of selected stocks with known P and M-cytotype strains show no effect on either sterility or longevity.

Issues in family planning clinic management.

PIP: Describes the use of a patient flow analysis (PFA) technique for improving the efficiency of family planning clinic sessions. Using the PFA technique, 883 clinic sessions were studied. The most common problems identified were long patient waits and inefficient use of staff. The causes of these problems were identified, and included inadequate patient scheduling, failed appointment rates and inadequate sequencing of clients through the clinic. Solutions to the problems are discussed.^ieng

Computerized patient-flow analysis of local family planning clinics.

PIP: The Center for Disease Control, in cooperation with the Illinois Family Planning Council and the Tennessee Department of Public Health, has created a computerized method of patient flow analysis (PFA) to meet the need for a simply operated, easily understood and inexpensively performed technique. PFA is a self administered time and motion study performed during 1 clinic session, relating characteristics of the clinic setting, staff, and patient population to the amount of time each staff member spends with each patient. Output consists of an easily read flowchart and a detailed statistical report showing how patient and staff time is used, and presents a brief cost analysis of services provided. Using these data, clinic managers can compare staff activity with patient movement and spot probable causes of inefficiency and bottle necks in patient flow. The operation of PFA is described fully, together with its use in a 5 step problem solving process. Its use in a publicly funded family planning clinic is described, where patient waiting time was reduced nearly an hour and costs per visit reduced by 1 dollar.^ieng