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Sensory Tracts (sensory + tract)
Selected AbstractsPhenotypic plasticity in number of glomeruli and sensory innervation of the antennal lobe in leaf-cutting ant workers (A. vollenweideri)DEVELOPMENTAL NEUROBIOLOGY, Issue 4 2010Christina Kelber Abstract In the leaf-cutting ant Atta vollenweideri, the worker caste exhibits a pronounced size-polymorphism, and division of labor is dependent on worker size (alloethism). Behavior is largely guided by olfaction, and the olfactory system is highly developed. In a recent study, two different phenotypes of the antennal lobe of Atta vollenweideri workers were found: MG- and RG-phenotype (with/without a macroglomerulus). Here we ask whether the glomerular numbers are related to worker size. We found that the antennal lobes of small workers contain ,390 glomeruli (low-number; LN-phenotype), and in large workers we found a substantially higher number of ,440 glomeruli (high-number; HN-phenotype). All LN-phenotype workers and some small HN-phenotype workers do not possess an MG (LN-RG-phenotype and HN-RG-phenotype), and the remaining majority of HN-phenotype workers do possess an MG (HN-MG-phenotype). Using mass-staining of antennal olfactory receptor neurons we found that the sensory tracts divide the antennal lobe into six clusters of glomeruli (T1,T6). In LN-phenotype workers, ,50 glomeruli are missing in the T4-cluster. Selective staining of single sensilla and their associated receptor neurons revealed that T4-glomeruli are innervated by receptor neurons from the main type of olfactory sensilla, the Sensilla trichodea curvata. The other type of olfactory sensilla (Sensilla basiconica) exclusively innervates T6-glomeruli. Quantitative analyses of differently sized workers revealed that the volume of T6 glomeruli scales with the power of 2.54 to the number of Sensilla basiconica. The results suggest that developmental plasticity leading to antennal-lobe phenotypes promotes differences in olfactory-guided behavior and may underlie task specialization within ant colonies. © 2009 Wiley Periodicals, Inc. Develop Neurobiol 70: 222,234, 2010. [source] Rapid assessment of internodal myelin integrity in central nervous system tissueJOURNAL OF NEUROSCIENCE RESEARCH, Issue 4 2010Daniel A. Kirschner Abstract Monitoring pathology/regeneration in experimental models of de-/remyelination requires an accurate measure not only of functional changes but also of the amount of myelin. We tested whether X-ray diffraction (XRD), which measures periodicity in unfixed myelin, can assess the structural integrity of myelin in fixed tissue. From laboratories involved in spinal cord injury research and in studying the aging primate brain, we solicited "blind" samples and used an electronic detector to record rapidly the diffraction patterns (30 min each pattern) from them. We assessed myelin integrity by measuring its periodicity and relative amount. Fixation of tissue itself introduced ±10% variation in periodicity and ±40% variation in relative amount of myelin. For samples having the most native-like periods, the relative amounts of myelin detected allowed distinctions to be made between normal and demyelinating segments, between motor and sensory tracts within the spinal cord, and between aged and young primate CNS. Different periodicities also allowed distinctions to be made between samples from spinal cord and nerve roots and between well-fixed and poorly fixed samples. Our findings suggest that, in addition to evaluating the effectiveness of different fixatives, XRD could also be used as a robust and rapid technique for quantitating the relative amount of myelin among spinal cords and other CNS tissue samples from experimental models of de- and remyelination. © 2009 Wiley-Liss, Inc. [source] The extent of axonal loss in the long tracts in hereditary spastic paraplegiaNEUROPATHOLOGY & APPLIED NEUROBIOLOGY, Issue 6 2004G. C. DeLuca Hereditary spastic paraplegia (HSP) comprises a group of inherited neurodegenerative disorders with the shared characteristics of progressive weakness and spasticity predominantly affecting the lower limbs. Limited pathological accounts have described a ,dying back' axonal degeneration in this disease. However, the distribution and extent of axonal loss has not been elucidated in a quantitative way. We have studied post-mortem material from six HSP patients and 32 controls in detail. The population of axons was examined quantitatively in the corticospinal tracts from the medulla to the lumbar spinal cord and the sensory tracts from the lumbar to upper cervical spinal cord. Myelin and axon-stained sections were employed to estimate the notional area and axonal density, respectively, of both tracts. Our results indicate that in the corticospinal tracts there is a significant reduction in area and axonal density at all levels investigated in HSP compared to controls. In the corticospinal tracts, the ratio of medulla and lumbar total axonal number was significantly greater in HSP cases compared to controls suggesting more pronounced axonal loss in the distal neuraxis in HSP than in controls. The sensory tracts in HSP, in contrast, showed a significant reduction in area and axonal density only in the upper regions of the spinal cord. Similar to the corticospinal tracts, the ratio of lumbar and upper cervical cord total axonal number in the sensory tracts was increased in HSP cases compared to controls. These findings are consistent with a length-dependent ,dying back' axonopathy. Nerve fibre loss was not size-selective with both small and large diameter fibres affected. In HSP, axonal loss is widespread and symmetrical and its extent tract-specific. The characterization of the nature of axonal loss in HSP, where this is a primary phenomenon, may help the interpretation of axonal loss in conditions such as multiple sclerosis where the sequence of events is less clear. [source] Complete mapping of glomeruli based on sensory nerve branching pattern in the primary olfactory center of the cockroach Periplaneta americanaTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 19 2010Hidehiro Watanabe Abstract Glomeruli are structural and functional units in the primary olfactory center in vertebrates and insects. In the cockroach Periplaneta americana, axons of different types of sensory neurons housed in sensilla on antennae form dorsal and ventral antennal nerves and then project to a number of glomeruli. In this study, we identified all antennal lobe (AL) glomeruli based on detailed innervation patterns of sensory tracts in addition to the shape, size, and locations in the cockroach. The number of glomeruli is ,205, and no sex-specific difference is observed. Anterograde dye injections into the antennal nerves revealed that axons supplying the AL are divided into 10 sensory tracts (T1,T10). Each of T1,T3 innervates small, oval glomeruli in the anteroventral region of the AL, with sensory afferents invading each glomerulus from multiple directions, whereas each of T4,T10 innervates large glomeruli with various shapes in the posterodorsal region, with a bundle of sensory afferents invading each glomerulus from one direction. The topographic branching patterns of all these tracts are conserved among individuals. Sensory afferents in a sub-tract of T10 had axon terminals in the dorsal margin of the AL and the protocerebrum, where they form numerous small glomerular structures. Sensory nerve branching pattern should reflect developmental processes to determine spatial arrangement of glomeruli, and thus the complete map of glomeruli based on sensory nerve branching pattern should provide a basis for studying the functional significance of spatial arrangement of glomeruli and its developmental basis. J. Comp. Neurol. 518:3907,3930, 2010. © 2010 Wiley-Liss, Inc. [source] | ||||||||||