Genetic variation of resistance to mercury poisoning in steelhead (Oncorhynchus mykiss) alevins.

Newly hatched steelhead alevins were obtained from the factorial breeding of 24 male and 10 female steelhead trout, Oncorhynchus mykiss. Each set of offspring were in a separate cell. They were tested for resistance to intoxication by methylmercuric chloride (CH3HgCl) in water at a nearly constant mercury concentration of 8 microg l(-1). High mortality (81% of the tested alevins) occurred within 2 weeks. Resistance to intoxication, as measured by the time to death, as well as by the survival rate, shared high paternal and maternal variation with negligible interaction. Heritability of time to death was 0.59 +/- 0.17; heritability of survival (all-or-none trait) was lower (0.26 +/- 0.09). Mercury in dead alevins increased with time to death, exhibiting a large environmental variation and (comparatively) negligible genetic influence. At the end of the bioassay, the mercury content in survivors varied widely (3-21 microg g(-1) wet weight). The content was greater than, but correlated with that of dead alevins from the same cells, and it showed little relation with survival rate. Thus, it seems that resistance to poisoning implies a tolerance to high levels of mercury rather than a limitation of its accumulation.

Familial external angular dermoid: evidence for a genetic link?

Congenital craniofacial dermoid cysts are hamartomas of ectodermal and mesodermal origin, made up of keratinizing epithelium lining a cavity containing dermal skin appendages. They usually present as an asymptomatic, firm, round mass, usually noticed at birth or in the first year. They are thought to occur as a result of ectodermal sequestration at lines of fusion during embryological development. Although nasal and epibulbar dermoid cysts have occurred in families and have been associated with inheritable gene defects, there has previously been no evidence for a similar etiology in external angular cases. We present the first description of external angular dermoids occurring in siblings suggesting that this subgroup may, in some instances, also have a genetic origin.

A comparative study of the learning style preferences of students with learning disabilities and students who are gifted.

The purpose of this study was to investigate whether significant group, gender, and grade differences existed in the learning style preferences of students with learning disabilities and students who are gifted, using the Learning Style Inventory (LSI) (Dunn, Dunn, & Price, 1987). Subjects consisted of 53 students with learning disabilities and 64 gifted students randomly selected from two large public high schools. They were 10th-, 11th-, and 12th-grade students, aged 15 to 17. A three-way analysis of variance on the LSI raw scores revealed significant group differences in preferences for light, design, and kinesthetic modality, and in motivation, persistence, responsibility, parent motivation, and teacher motivation. Significant gender and grade differences were found in preferences for mobility and learning in the afternoon, respectively. A stepwise discriminant analysis revealed six variables that significantly discriminated between the two groups. Findings imply that incorporating the learning styles of students with learning disabilities and students who are gifted is important for individualizing educational programming.

Comparison of self-concepts of students identified as gifted and regular students.

The purpose of the present study was to compare the self-concepts of 40 eighth grade students identified as gifted and 40 regular eighth grade students using the Piers-Harris Children's Self-concept Scale. A t test indicated a significant group difference on the behavior component only and no significant differences by gender. More similarities than differences were noted in self-concepts of these students identified as gifted and regular students.