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The objective of this study was to perform a study of fragile X syndrome (FXS) in São Luís, Maranhão, in males residing in five specialized institutions. Two hundred thirty-eight males with intel-lectual disability of unknown etiology participated in this study. Blood samples were processed and stored until DNA extraction. Screening for FMR1 gene mutations was performed using non-isotopic polymerase chain reaction amplification and DNA sequencing using an ABI Prism 3130 automated sequencer. Two individuals (0.84%) were positive for FMR1 mutations. One had a mutation due to expansion of the CGG repeat beyond normal levels and the other had a deletion in exon 1 of the FMR1 gene, which was confirmed by sequencing. Both probands were over 18 years old, which demonstrates the late diagnosis of the condition in these individuals and reinforces the need to implement ef-fective programs for early diagnosis of FXS in the state of Maranhão. We found that FXS might be transmitted in the families of the two indi-viduals bearing the mutation, and that it is important to understand the mutation dynamics to provide better counseling to the family members of these two individuals.

Ffteen Sprague-Dawley rats were administered sodium nitrite 0.13% or 0.15% solutions in their drinking water from the age of 45 days to the end of the study. Six control rats received only tap water. At 80 days of age, rats were trained to bar press for food pellets on a CRF schedule. After reaching criterion performance the rats were switched to a DRL-20 for a period of 6 days to test for response inhibition, which was measured as a ratio of responses to reinforcements. Results indicated no significant differences between groups for response inhibition. All groups showed significant increases in learning as reflected by a decrease in ratios and an increase in total reinforcements over days. However, sodium nitrite rats compared to controls obtained significantly fewer reinforcements over sessions and a greater number of no responding periods (time-outs). One interpretation discussed was the possibility that sodium nitrite produced an increase in responding to distractible (non-task related) cues.