Construction of meaning in the authentic science writing of deaf students.

This study examines how students construct meaning through writing during authentic science activities. To determine how well students understood science concepts, we analyzed 228 writing samples from deaf students in grades 6 through 11 as well as the explanatory and reflective comments of their teachers. The analyses indicate that certain process writing strategies were differentially useful in helping deaf students to construct meaning and in allowing teachers to evaluate the constructed meaning. Three instructional conditions and two teacher variables were found to play roles in determining the accuracy and adequacy of the writing: (1) the writing prompts the teachers used, (2) the focus for the writing, (3) follow-up to the initial writing activity, (4) the teacher's content knowledge, and (5) the teacher's ability to interpret student writing. The authors recommend future applications of writing-to-learn strategies and suggest directions for further research and changes in teacher education.

Critical teaching incidents. Recollections of deaf college students.

In interviews with 56 deaf college students, we collected accounts of 839 "critical incidents" describing effective and ineffective teaching. From those incidents, 33 specific teaching characteristics were derived and were analyzed in relation to teacher, student, and course variables. Our primary goal was to identify the teaching characteristics underlying deaf students' recollections about their classroom learning experiences. The most frequently mentioned characteristics are similar to those found in studies of hearing college students, particularly within the domain of Teacher Affect. The teacher's ability to communicate clearly in sign language, however, was not only a characteristic unique to deaf college students but also the most frequently occurring characteristic of effective teaching in this study.

Characteristics of effective teachers.

We designed and administered rating and ranking instruments to examine the perceptions about teaching characteristics held by administrators, academic department chairpersons responsible for evaluating teaching, instructional faculty, and deaf college students. The differences in perceptions found between supervisors and teachers about characteristics of effective teaching indicate a need for ongoing dialogue. In addition, teachers and deaf college students were found to differ in their views of the importance of certain characteristics, and we suggest teachers discuss these perceptions with students. We also recommend additional research on particular characteristics of effective teaching.

Macromolecular conjugates of transport inhibitors: new tools for probing topography of anion transport proteins.

Macromolecular-conjugated, water-soluble, membrane-impermeant compounds were designed and assessed as topological probes for chloride-transporting agencies. The novel compounds were derivatives of either disulfonic stilbene (DS) and benzylaminoethylsulfonate (BS), "classical" inhibitors of erythrocyte chloride-bicarbonate exchange, or of phenylanthranilates (PA), high-affinity blockers of epithelial chloride channels. Covalent reactive derivatives of various DS, BS, and PA were synthesized and coupled either directly to polyethylene glycol or via spacer arms of different lengths to dextrans. The macromolecular conjugates were demonstrably inhibitory to red blood cell anion exchange when the ligands were appropriately coupled: inhibitory efficacy strongly depended on the chemical structure of the coupled ligand and the spacer length between the inhibitory moiety and the macromolecule. Mechanistic studies indicated that impermeant DS and PA derivatives acted exofacially on sites, which although different in their affinity for chloride, shared geographical proximity. BS derivatives were unique in that they affected transport from either surface. The results suggest asymmetric aqueous access routes leading to the functional domain of the anion transporter from either membrane surface.

The development of the static vestibulo-ocular reflex in the southern clawed toad, Xenopus laevis. II. Animals with acute vestibular lesions.

Acute hemilabyrinthectomized tadpoles of the Southern Clawed Toad (Xenopus laevis), younger than stage 47 (about 6 days old), perform no static vestibulo-ocular reflex (Fig. 1). Older acute lesioned animals respond with compensatory movements of both eyes during static roll. Their threshold roll angle, however, depends on the developmental stage. For lesioned stages 60 to 64, it is 75 degrees while stage 52 to 56 tadpoles respond even during a lateral roll of 15 degrees (Figs. 1 and 2). Selective destruction of single macula and crista organs revealed that the static vestibulo-ocular reflex is evoked by excitation of the macula utriculi (Figs. 3 and 4) even in young tadpoles. The results demonstrate that bilateral projections of the vestibular apparatus must have developed at the time of occurrence of the static VOR, that during the first week of life the excitation of a single labyrinth is subthreshold (Fig. 1). We discuss the possibility whether the loss of the static VOR during the prometamorphic period of life (Fig. 2) is caused by increasing formation of multimodal connections in the vestibular pathway.

The development of the static vestibulo-ocular reflex in the southern clawed toad, Xenopus laevis. I. Intact animals.

In the clawed toad, Xenopus laevis, the static vestibulo-ocular reflex appears in 3 days old tadpoles (developmental stage 42) (Fig. 2). The amplitude and gain of this reflex increase up to stage 52, and then decrease to an almost constant value at stage 60 and older tadpoles (Fig. 3). The most effective roll angle gradually increases during development (Fig. 4). The size of the sensory epithelia reaches the final value at the end of the premetamorphic period (stage 56) (Fig. 5). The small-cellular medial ventral vestibular nucleus (VVN) reaches its maximal number of neurons before the large-cellular lateral VVN. Cell death is more pronounced in the medial than in the lateral part of the VVN. In the dorsal vestibular nucleus (DVN), the numerical development of the small and large neurons is similar to that in the small-cellular medial and large-cellular lateral portion of the VVN (Fig. 7). The results demonstrate that labyrinth and oculomotor centres are anatomically connected before the labyrinth and the vestibular nuclei are fully developed. We discuss the possibility that the ciliary polarity pattern of the sensory epithelium is radial during the first period of life, and changes to the vertebrate fan-type pattern during the second week of life. According to the increase of gain during the first three weeks of life, an increase of the spontaneous activity of vestibular neurons may occur during this period.