3 resultados para Laying on of Hands
em National Center for Biotechnology Information - NCBI
Resumo:
Mating triggers behavioral and physiological changes in the Drosophila melanogaster female, including an elevation of egg laying. Seminal fluid molecules from the male accessory gland are responsible for initial behavioral changes, but persistence of these changes requires stored sperm. Using genetic analysis, we have identified a seminal fluid protein that is responsible for an initial elevation of egg laying. This molecule, Acp26Aa, has structural features of a prohormone and contains a region with amino acid similarity to the egg-laying hormone of Aplysia. Acp26Aa is transferred to the female during mating, where it undergoes processing. Here we report the generation and analysis of mutants, including a null, in Acp26Aa. Females mated to male flies that lack Acp26Aa lay fewer eggs than do mates of normal males. This effect is apparent only on the first day after mating. The null mutation has no other detectable physiological or behavioral effects on the male or the mated female.
Resumo:
Because it is widely accepted that providing information online will play a major role in both the teaching and practice of medicine in the near future, a short formal course of instruction in computer skills was proposed for the incoming class of students entering medical school at the State University of New York at Stony Brook. The syllabus was developed on the basis of a set of expected outcomes, which was accepted by the dean of medicine and the curriculum committee for classes beginning in the fall of 1997. Prior to their arrival, students were asked to complete a self-assessment survey designed to elucidate their initial skill base; the returned surveys showed students to have computer skills ranging from complete novice to that of a systems engineer. The classes were taught during the first three weeks of the semester to groups of students separated on the basis of their knowledge of and comfort with computers. Areas covered included computer basics, e-mail management, MEDLINE, and Internet search tools. Each student received seven hours of hands-on training followed by a test. The syllabus and emphasis of the classes were tailored to the initial skill base but the final test was given at the same level to all students. Student participation, test scores, and course evaluations indicated that this noncredit program was successful in achieving an acceptable level of comfort in using a computer for almost all of the student body.
Resumo:
Brood parasitism by brown-headed cowbirds (Molothrus ater) reduces reproductive success in many passerines that nest in fragmented habitats and ecological edges, where nest predation is also common. We tested the hypothesis that parasitism and predation are often linked because cowbirds depredate nests discovered late in the host's nesting cycle to enhance future opportunities for parasitism. Over a 20-year study period, brood parasitism by cowbirds was a prerequisite to observing marked inter- and intraannual variation in the rate of nest failure in an insular song sparrow (Melospiza melodia) population. Nest failure increased with the arrival and laying rate of cowbirds and declined when cowbirds ceased laying. The absence or removal of cowbirds yielded the lowest nest failure rates recorded in the study. The absence of cowbirds also coincided with the absence of an otherwise strong positive correlation between host numbers and the annual rate of nest failure. Host numbers, cowbird parasitism, and nest failure may be correlated because cowbirds facilitate nest failure rather than cause it directly. However, an experiment mimicking egg ejection by cowbirds did not affect nest failure, and, contrary to the main prediction of the predation facilitation hypothesis, naturally parasitized nests failed less often than unparasitized nests. Higher survival of parasitized nests is expected under the cowbird predation hypothesis when female cowbirds defend access to hosts because cowbirds should often depredate unparasitized nests but should not depredate nests they have laid in. Where female cowbirds have overlapping laying areas, we expect parasitized nests to fail more often than others if different cowbirds often discover the same nests. We suggest that nest predation by cowbirds represents an adaptation for successful parasitism and that cowbirds influence host demography via nest predation.