Sporotrichosis in Peru: description of an area of hyperendemicity.
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Sporotrichosis is a sporadic and rare mycotic infection in most of the developed world. In many parts of the developing world, sporotrichosis is much more commonly recognized, but epidemiological data are generally lacking from these regions. We report epidemiological, clinical, and treatment data from 238 cases of culture-proven sporotrichosis occurring in a relatively remote area of the south central highlands of Peru that were retrospectively collected during 1995-1997. Most cases (60%) occurred in children aged +info)
The zebrafish colourless gene regulates development of non-ectomesenchymal neural crest derivatives.
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Neural crest forms four major categories of derivatives: pigment cells, peripheral neurons, peripheral glia, and ectomesenchymal cells. Some early neural crest cells generate progeny of several fates. How specific cell fates become specified is still poorly understood. Here we show that zebrafish embryos with mutations in the colourless gene have severe defects in most crest-derived cell types, including pigment cells, neurons and specific glia. In contrast, craniofacial skeleton and medial fin mesenchyme are normal. These observations suggest that colourless has a key role in development of non-ectomesenchymal neural crest fates, but not in development of ectomesenchymal fates. Thus, the cls mutant phenotype reveals a segregation of ectomesenchymal and non-ectomesenchymal fates during zebrafish neural crest development. The combination of pigmentation and enteric nervous system defects makes colourless mutations a model for two human neurocristopathies, Waardenburg-Shah syndrome and Hirschsprung's disease. (+info)
Neural systems underlying the recognition of familiar and newly learned faces.
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Memory for famous faces can be used to examine the neural systems underlying retrieval from long-term memory. To date, there have been a limited number of functional neuroimaging investigations examining famous face recognition. In this study, we compared recognition of famous faces to recognition of newly learned faces. Whole-brain, event-related functional magnetic resonance imaging was used to image regional changes in neural activity in 11 subjects during the encoding of unfamiliar faces and during familiarity judgments for: (1) newly learned faces, (2) unfamiliar face distractors, and (3) famous faces. Image analyses were restricted to correct recognition trials. Recognition accuracy and response time to famous and recently learned faces were equivalent. Recognition of famous faces was associated with a widespread network of bilateral brain activations involving the prefrontal, lateral temporal, and mesial temporal (hippocampal and parahippocampal regions) regions compared to recognition of recently encoded faces or unfamiliar faces seen for the first time. Findings are discussed in relation to current proposals concerning the neural regions thought to participate in long-term memory retrieval and, more specifically, in relation to retrieval of information from the person identity semantic system. (+info)
Cognitive response profile of the human fusiform face area as determined by MEG.
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Activation in or near the fusiform gyrus was estimated to faces and control stimuli. Activation peaked at 165 ms and was strongest to digitized photographs of human faces, regardless of whether they were presented in color or grayscale, suggesting that face- and color-specific areas are functionally separate. Schematic sketche evoked approximately 30% less activation than did face photographs. Scrambling the locations of facial features reduced the response by approximately 25% in either hemisphere, suggesting that configurational versus analytic processing is not lateralized at this latency. Animal faces evoked approximately 50% less activity, and common objects, animal bodies or sensory controls evoked approximately 80% less activity than human faces. The (small) responses evoked by meaningless control images were stronger when they included surfaces and shading, suggesting that the fusiform gyrus may use these features in constructing its face-specific response. Putative fusiform activation was not significantly related to stimulus repetition, gender or emotional expression. A midline occipital source significantly distinguished between faces and control images as early as 110 ms, but was more sensitive to sensory qualities. This source significantly distinguished happy and sad faces from those with neutral expressions. We conclude that the fusiform gyrus may selectively encode faces at 165 ms, transforming sensory input for further processing. (+info)
Complementary neural mechanisms for tracking items in human working memory.
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Recognition of a specific visual target among equally familiar distracters requires neural mechanisms for tracking items in working memory. Event-related functional magnetic resonance imaging revealed evidence for two such mechanisms: (i) Enhanced neural responses, primarily in the frontal cortex, were associated with the target and were maintained across repetitions of the target. (ii) Reduced responses, primarily in the extrastriate visual cortex, were associated with stimulus repetition, regardless of whether the stimulus was a target or a distracter. These complementary neural mechanisms track the status of familiar items in working memory, allowing for the efficient recognition of a currently relevant object and rejection of irrelevant distracters. (+info)
Different roles for Pax6 in the optic vesicle and facial epithelium mediate early morphogenesis of the murine eye.
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Chimaeric mice were made by aggregating Pax6(-/-) and wild-type mouse embryos, in order to study the interaction between the optic vesicle and the prospective lens epithelium during early stages of eye development. Histological analysis of the distribution of homozygous mutant cells in the chimaeras showed that the cell-autonomous removal of Pax6(-/-) cells from the lens, shown previously at E12.5, is nearly complete by E9.5. Most mutant cells are eliminated from an area of facial epithelium wider than, but including, the developing lens placode. This result suggests a role for Pax6 in maintaining a region of the facial epithelium that has the tissue competence to undergo lens differentiation. Segregation of wild-type and Pax6(-/-) cells occurs in the optic vesicle at E9.5 and is most likely a result of different adhesive properties of wild-type and mutant cells. Also, proximo-distal specification of the optic vesicle (as assayed by the elimination of Pax6(-/-) cells distally), is disrupted in the presence of a high proportion of mutant cells. This suggests that Pax6 operates during the establishment of patterning along the proximo-distal axis of the vesicle. Examination of chimaeras with a high proportion of mutant cells showed that Pax6 is required in the optic vesicle for maintenance of contact with the overlying lens epithelium. This may explain why Pax6(-/-) optic vesicles are inefficient at inducing a lens placode. Contact is preferentially maintained when the lens epithelium is also wild-type. Together, these results demonstrate requirements for functional Pax6 in both the optic vesicle and surface epithelia in order to mediate the interactions between the two tissues during the earliest stages of eye development. (+info)
Three-dimensional shape and two-dimensional surface reflectance contributions to face recognition: an application of three-dimensional morphing.
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We measured the three-dimensional shape and two-dimensional surface reflectance contributions to human recognition of faces across viewpoint. We first divided laser scans of human heads into their two- and three-dimensional components. Next, we created shape-normalized faces by morphing the two-dimensional surface reflectance maps of each face onto the average three-dimensional head shape and reflectance-normalized faces by morphing the average two-dimensional surface reflectance map onto each three-dimensional head shape. Observers learned frontal images of the original, shape-normalized, or reflectance-normalized faces, and were asked to recognize the faces from viewpoint changes of 0, 30 and 60 degrees. Both the three-dimensional shape and two-dimensional surface reflectance information contributed substantially to human recognition performance, thus constraining theories of face representation to include both types of information. (+info)
Masseter muscle volume measured using ultrasonography and its relationship with facial morphology.
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The aims of this study were to measure the volume, cross-sectional area, thickness, width, and length of contracted masseter muscles in a sample of adults, four males and six females, using three-dimensional (3D) ultrasonography, and to correlate these measurements with the variations in facial morphology of the sample. The scans were carried out bilaterally using a hand-held probe carrying a magnetic positional sensor, which enabled a computer to reconstruct the images into a 3D array of slices. Measurements were made by the computer from the reconstructed images using specially written software. Cephalometric analysis initially involved seven angular, eight linear, and two proportional variables, but as these were strongly inter-dependent, the variables were reduced to four principal components prior to statistical comparison with the mean muscle variables. The values found for muscle volume, cross-sectional area, and thickness were broadly consistent with those of previous investigators. Volume showed a significant, negative correlation with mandibular inclination including gonial angle (P < or = 0.001), and a significant, positive correlation with total posterior face height and ramus height (P < or = 0.001), and lower posterior face height percentage (P < or = 0.01). Weaker correlations were found for length and thickness. While the results support existing evidence that large masticatory muscles are associated with brachycephalism and vice versa, a cautious interpretation is necessary in view of the small sample size. The 3D ultrasonography system is at an experimental stage and requires further development and evaluation. (+info)