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John Houston

Publications and source records attributed to John Houston.

4 recordsLinked to original sources
PubMed2005

Flexible-dose clinical trials: predictors and outcomes of antipsychotic dose adjustments.

In a new approach to the interpretation of data from flexible-dose studies, we examined the safety and efficacy measurements that preceded and followed dose changes, to identify clinical factors that predict dose change as well as subsequent outcome of clinical status with dose change. This was a post hoc analysis of 3 flexible-dosed olanzapine studies: acutely ill bipolar I patients with an index manic episode (N = 452) who received olanzapine (5-20 mg/d) or haloperidol (3-15 mg/d); acutely ill patients with schizophrenia (N = 339) who received olanzapine (10-20 mg/d) or risperidone (4-12 mg/d) for 28 weeks; and remitted bipolar I patients (N = 361) who received olanzapine (5-20 mg/d) or placebo for 48 weeks. The major findings of this analysis were: an increase in dose was predicted by baseline illness severity in the acute studies, and a decrease in dose was predicted by illness symptom improvement or worsening of adverse events. Dose decrease was followed by significantly decreased efficacy for patients with acute mania treated with olanzapine or haloperidol, and olanzapine dose increases were followed by improved efficacy. Treatment-emergent extrapyramidal symptom adverse events and akathisia typically predicted dose decreases. Techniques used in this analysis may prove to be useful in assessing the relationship between dose change and safety and efficacy measures.

Adult↗
PubMed2003

Sonic hedgehog cascade is required for penile postnatal morphogenesis, differentiation, and adult homeostasis.

The penis is unique in that it undergoes morphogenesis and differentiation primarily in the postnatal period. For complex structures such as the penis to be made from undifferentiated precursor cells, proliferation, differentiation, and patterning are required. This process involves coordinated activity of multiple signals. Sonic hedgehog (Shh) forms part of a regulatory cascade that is essential for growth and morphogenesis of many tissues. It is hypothesized that the penis utilizes regulatory mechanisms similar to those of the limb and accessory sex organs to pattern penile postnatal morphogenesis and differentiation and that the Shh cascade is critical to this process. To test this hypothesis, Shh, BMP-4, Ptc, and Hoxa-10 localization and function were examined in Sprague-Dawley rat penes by means of quantitative reverse transcription polymerase chain reaction, in situ hybridization, immunohistochemistry, and Western blotting. These genes were expressed in the penis during postnatal morphogenesis in a spatially and temporally restricted manner in adjacent layers of the corpora cavernosal sinusoids. The function of Shh and BMP-4 is to establish and maintain corpora cavernosal sinusoids. The data suggest that Ptc and Hoxa-10 are also important in penile morphogenesis. The continuing function of Shh and targets of its signaling in maintaining penile homeostasis in the adult is significant because disruption of Shh signaling affects erectile function. This is the first report that demonstrates the significant role that Shh plays in establishing and maintaining penile homeostasis and how this relates to erectile function. These studies provide valuable insight that may be applied to improve treatment options for erectile dysfunction.

Aging↗
PubMed2002

Revising the Competitiveness Index using factor analysis.

The Competitiveness Index is a 20-item true-false measure designed to assess the desire to win in interpersonal situations. To develop a more psychometrically sound form of the scale, 213 undergraduates were administered the original form and a modified version containing a 5-point Likert-type scale. An initial principal component analysis using a varimax rotation of the modified version yielded a four-factor solution accounting for 54.5% of the explained variance. Based on a subsequent reliability analysis. six items were dropped from the modified scale. A second analysis produced a two-factor solution accounting for 54.1% of the explained variance. Both factors (Enjoyment of Competition and Contentiousness) formed reliable subscales. The 14-item Revised Competitiveness Index had high internal consistency and was positively correlated with the original Competitiveness Index, the competitiveness subscales of the Work and Family Orientation Questionnaire, the Sports Orientation Questionnaire, and the Nach Naff measure of Need for Achievement.

Adolescent↗