William A. Harris

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PROBLEM Priority health-risk behaviors contribute to the leading causes of morbidity and mortality among youth and adults. Population-based data on these behaviors at the national, state, and local levels can help monitor the effectiveness of public health interventions designed to protect and promote the health of youth nationwide. REPORTING PERIOD(More)
In the developing frog visual system, topographic refinement of the retinotectal projection depends on electrical activity. In vivo whole-cell recording from developing Xenopus tectal neurons shows that convergent retinotectal synapses undergo activity-dependent cooperation and competition following correlated pre- and postsynaptic spiking within a narrow(More)
In the United States, 71% of all deaths among persons aged 10-24 years result from 4 causes: motorvehicle crashes, other unintentional injuries, homicide, and suicide. Results from the 2005 national Youth Risk Behavior Survey (YRBS) indicated that during the 30 days preceding the survey, many high school students engaged in behaviors that increased their(More)
We examined the function of basic-helix-loop-helix (bHLH) transcription factors during retinal neurogenesis. We identified Xath5, a Xenopus bHLH gene related to Drosophila atonal, which is expressed in the developing Xenopus retina. Targeted expression of Xath5 in retinal progenitor cells biased the differentiation of these cells toward a ganglion cell(More)
Populations of Drosophila were trained by alternately exposing them to two odorants, one coupled with electric shock. On testing, the flies avoided the shock-associated odor. Pseudoconditioning, excitatory states, odor preference, sensitization, habituation, and subjective bias have been eliminated as explanations. The selective avoidance can be(More)
Xenopus embryos injected with tritiated thymidine throughout the stages of embryonic retinal neurogenesis showed that more than 95% of the embryonic retinal cells are born within a 25 hr period. While there are shallow central to peripheral, dorsal to ventral, and interlaminar gradients of neurogenesis in these eyes, throughout most of this 25 hr period,(More)
Xotch is a Xenopus homolog of Notch, a receptor involved in cell fate decisions in Drosophila. Using an extracellular deletion construct, Xotch delta E, we show that Xotch has a similar role in Xenopus embryos. Broad expression causes the loss of dorsal structures and the expansion and disorganization of the brain. Single blastomere injections of Xotch(More)
The ciliary marginal zone is a perpetually self-renewing proliferative neuroepithelium at the perimeter of the retina in amphibians and fish. In the ciliary marginal zone (CMZ), cells are spatially ordered with respect to cellular development, deep stem cells being most peripheral and differentiating retinal progenitors being most central. This spatial(More)
Several eye-field transcription factors (EFTFs) are expressed in the anterior region of the vertebrate neural plate and are essential for eye formation. The Xenopus EFTFs ET, Rx1, Pax6, Six3, Lhx2, tll and Optx2 are expressed in a dynamic, overlapping pattern in the presumptive eye field. Expression of an EFTF cocktail with Otx2 is sufficient to induce(More)
Three mutations which eliminate specific types of photoreceptors in Drosophila were characterized. Of the eight photoreceptors in each facet, two mutations delete the outer six (R 1-6). The third eliminates R 7, one of the two central photoreceptors. Double mutants can be constructed in which only photoreceptor R 8 is present. The spectral sensitivities,(More)