Long-term effects of cochlear implants in children.

OBJECTIVE: Since 1987, when the use of multichannel cochlear implants was initiated in children, candidacy has expanded; many thousands of children have received these devices, and results have revealed a wide range of performance. However, few long-term studies exist on a large population of these children. There have been concerns expressed that cochlear implant function might degrade over time, that devices and electrodes might migrate and extrude in the growing child, or that there might even be a deleterious effect of long-term stimulation of the cochlear nerve. The purpose of this study was to explore the long-term effects of implantation as a function of performance over time, reimplantation, and educational factors. STUDY DESIGN AND SETTING: We studied 81 children who received implants at a major academic medical center and were followed for 5 to 13 years. RESULTS: Results revealed significant gains in speech perception, use of oral language, and ability to function in a mainstream environment. There was no decrease in performance over time and no significant incidence of device or electrode migration or extrusion, and device failure did not cause a deterioration in long-term outcome. CONCLUSIONS: Multichannel cochlear implants in children provide perception, linguistic, and educational advantages, which are not adversely affected by long-term electrical stimulation.     

Wisconsin Card Sorting Test performance in schizophrenia: remediation of a stubborn deficit.

OBJECTIVE: Schizophrenic patients typically perform poorly on the Wisconsin Card Sorting Test, which is a putative index of prefrontal functioning. The authors attempted to remediate the deficits of schizophrenic patients on this measure by giving detailed instructions and monetary reinforcement. METHOD: Forty-six inpatients with chronic schizophrenia and 20 control subjects with other psychiatric illnesses were given the Wisconsin Card Sorting Test under four conditions that varied in monetary reinforcement and level of instructions. The schizophrenic patients were given the Brief Psychiatric Rating Scale (BPRS) and three information processing measures (the Continuous Performance Test, Span of Apprehension, and Pin Test). RESULTS: Schizophrenic patients performed worse than psychiatric control subjects across most conditions. Monetary reinforcement had little effect on performance, but detailed instructions significantly improved the scores for both groups. When instructions were withdrawn and monetary reinforcement was maintained, both groups continued to show improved performance over baseline. Symptoms were not significantly associated with Wisconsin Card Sorting Test performance. One measure (the Pin Test) correlated significantly with performance on the Wisconsin Card Sorting Test. CONCLUSIONS: The results suggest the importance of combining motivational with instructional factors for training psychiatric patients in problem solving.     

Morphogen gradients, positional information, and Xenopus: interplay of theory and experiment.

The idea of morphogen gradients has long been an important one in developmental biology. Studies with amphibians and with Xenopus in particular have made significant contributions to demonstrating the existence, identity, and mechanisms of action of morphogens. Mesoderm induction and patterning by activin, nodals, bone morphogenetic proteins, and fibroblast growth factors have been analyzed thoroughly and reveal recurrent and combinatorial roles for these protein growth factor morphogens and their antagonists. The dynamics of nodal-type signaling and the intersection of VegT and beta-catenin intracellular gradients reveal detailed steps in early long-range patterning. Interpretation of gradients requires sophisticated mechanisms for sharpening thresholds, and the activin-Xbra-Gsc system provides an example of this. The understanding of growth factor signal transduction has elucidated growth factor morphogen action and provided tools for dissecting their direct long-range action and distribution. The physical mechanisms of morphogen gradient establishment are the focus of new interest at both the experimental and theoretical level. General themes and emerging trends in morphogen gradient studies are discussed.     

Bionomics of Anopheles maculatus complex and their role in malaria transmission in Thailand

The bionomics of Anopheles maculatus complex and its role in malaria transmission were conducted in Pakchong and Sadao districts, Nakhon Ratchasima and Songkhla provinces, respectively, from January 1984 to July 1985. In Pakchong, An. maculatus species A was the most dominant species, followed by species B form F and species C which was rare. The densities of species A and species B form F were high between July and November, with their peaks in October. Biting activities of both species occurred through out the night, with a major peak during the first quarter of the night on all seasons. In Sadao, only An. maculatus species B form E was detected with peak densities between February and June. Biting activities of this species varied according to seasons. The prevalence of mosquitoes was influenced by monthly rainfall, relative humidity and air-temperature. All species of female An. maculatus complex studied prefered to feed on animal rather than on human, and tended to bit human more outdoors than indoors, and thus exhibiting a zoophilic and exophagic behaviour. Life expectancies of An. maculatus species A ranged from 1.6 to 6.6 days, species B form F from 1.1 to 8.1 days, and species B form E from 0.7 to 21.2 days. The natural malaria infection rate was very low. Out of 4,430 guts dissected, only 0.23% were found infected with oocysts. There were no sporozoites detected in the 4,472 dissected salivary glands.