Evolution of MHC class IIB in the genome of wild and ornamental guppies, Poecilia reticulata.

This is the first study to quantify genomic sequence variation of the major histocompatibility complex (MHC) in wild and ornamental guppies, Poecilia reticulata. We sequenced 196-219 bp of exon 2 MHC class IIB (DAB) in 56 wild Trinidadian guppies and 14 ornamental strain guppies. Each of two natural populations possessed high allelic richness (15-16 alleles), whereas only three or fewer DAB alleles were amplified from ornamental guppies. The disparity in allelic richness between wild and ornamental fish cannot be fully explained by fixation of alleles by inbreeding, nor by the presence of non-amplified sequences (ie null alleles). Rather, we suggest that the same allele is fixed at duplicated MHC DAB loci owing to gene conversion. Alternatively, the number of loci in the ornamental strains has contracted during >100 generations in captivity, a hypothesis consistent with the accordion model of MHC evolution. We furthermore analysed the substitution patterns by making pairwise comparisons of sequence variation at the putative peptide binding region (PBR). The rate of non-synonymous substitutions (dN) only marginally exceeded synonymous substitutions (dS) in PBR codons. Highly diverged sequences showed no evidence for diversifying selection, possibly because synonymous substitutions have accumulated since their divergence. Also, the substitution pattern of similar alleles did not show evidence for diversifying selection, plausibly because advantageous non-synonymous substitutions have not yet accumulated. Intermediately diverged sequences showed the highest relative rate of non-synonymous substitutions, with dN/dS>14 in some pairwise comparisons. Consequently, a curvilinear relationship was observed between the dN/dS ratio and the level of sequence divergence.

Time-keeping system of the eel pout, Zoarces viviparus.

Observations on the rhythmic activity of 71 juvenile specimens of the inter-tidal blenny Zoarces viviparus reveal an endogenous pattern of swimming at three different periodicities. Circatidal swimming, with activity peaks phased to high water or the ebb of the subjective 12.4-h tides, was found in 50 fish and was the predominant pattern seen immediately after collection, when the rhythm generally persisted for between 3 and 12 cycles. Discrete activity peaks, with a free running period of approximately 24 h were also evident in the swimming pattern of eight fish. A circadian influence was also manifest as a modulation in amplitude, phase shifts and changes in free-running period of the circa-tidal rhythm. Overall, the activity level declined with time but those fish that remained active long enough showed a semi-lunar rhythm, with maximum activity at the time of the spring tides. A comparison of the behavior of animals collected at different times of the year suggests a seasonal variation in the persistence of circatidal swimming. The results are consistent with a control system involving circatidal, circadian, and semi-lunar oscillators.

Reported response rates to mailed physician questionnaires.

OBJECTIVE: To examine response rate information from mailed physician questionnaires reported in published articles. DATA SOURCES/STUDY SETTING: Citations for articles published between 1985 and 1995 were obtained using a key word search of the Medline, PsychLit, and Sociofile databases. STUDY DESIGN: A 5 percent random sample of relevant citations was selected from each year. DATA COLLECTION/EXTRACTION METHODS: Citations found to be other than physician surveys were discarded and replaced with the next randomly assigned article. Selected articles were abstracted using a standardized variable list. PRINCIPAL FINDINGS: The average response rate for mailed physician questionnaires was 61 percent. The average response rate for large sample surveys (> 1,000 observations) was 52 percent. In addition, only 44 percent of the abstracted articles reported a discussion of response bias, and only 54 percent reported any type of follow-up. CONCLUSIONS: (1) Response rates have remained somewhat constant over time, and (2) researchers need to document the efforts used to increase response rates to mailed physician questionnaires.

Knowledge of and attitudes toward aging among non-elders: gender and race differences.

Although the aging process begins at birth, fears about late adulthood can foster anxiety in younger cohorts about this time of life. This study examines the relationship between non-elderly subjects' (n = 884, 18-55 years) knowledge of and anxieties regarding personal aging and their gender and race. We hypothesized that non-elderly women and persons of color, those who will experience multiple jeopardy in their own late life, would report greater anxiety about their own aging process than did men and majority group members. Women did report lower income and education levels, less knowledge of aging, greater anxiety related to their own aging process, and more time involved in caregiving activities. People of color also differed from Caucasians in certain dimensions of knowledge and anxiety. Implications from these results include the creation of public educational strategies and the organization of women and minorities to more actively address the development and shape of age-related policies.

Adequacy of discharge plans and rehospitalization among hospitalized dementia patients.

Because of the rapid growth of the elderly population and the decreasing number of days that patients are able to remain in the hospital, the task of discharge planning has become increasingly critical and challenging. This article reports on a study undertaken to examine the adequacy of discharge plans developed for dementia patients and to investigate factors related to inadequate plan development and patient readmission. Study results suggest that a sizeable proportion of dementia patients are discharged without adequate aftercare plans and are at risk of rehospitalization. The findings of this study point to significant family and resource-related factors that compromise discharge plan adequacy for dementia patients. Implications for practice, education, and policy are discussed.

Ethical dilemmas in discharge planning for patients with Alzheimer's disease.

Because of an increase in the older population in the United States, hospital social workers are faced with the task of developing discharge plans for patients with Alzheimer's disease. The nature of the disease creates the potential for complex situations that can complicate the discharge-planning process. This article explores the ethical dilemmas that arise in discharge planning for patients with Alzheimer's disease and examines how the nature of these dilemmas evolves as the illness progresses. A clinical model is proposed to help practitioners identify, organize, and evaluate information relevant to discharge planning and determine an appropriate course of action.