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81.
82.
Antje Neugebauer 《Bioscience Hypotheses》2009,2(5):298-301
The medial longitudinal fascicle and the optic nerve are often affected in multiple sclerosis which causes internuclear ophthalmoplegia and optic neuritis. During prenatal development axons of both neuronal pathways are subjected to midline crossing in the central nervous system. Transmembrane receptor proteins like robos and dcc that interact with the chemorepellents and attractants slit and netrin are expressed in developing axons that cross the midline and are likely to play a role postnatally. It is hypothesized and discussed that these receptor proteins represent a specific antigen targeted by autoimmune processes in multiple sclerosis. 相似文献
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86.
Antennal sensilla of grasshoppers (Orthoptera: Acrididae) in relation to food preferences and habits
The external structure, i.e. number and distribution of sensillae on male and female antennae of 12 species of grasshoppers
belonging to Pamphaginae, Catantopinae, Oedipodinae and Gomphocerinae in the grasslands of Inner Mongolia was investigated
using scanning electron microscopy. Five major types of antennal sensillae were detected - trichoid, long basiconic, short
basiconic, slender and short basiconic, and coeloconic sensillae. Total number of antennal sensillae varied among different
sexes, subfamilies, feeding groups, life forms and eco-forms. Males showed significantly more sensillae than females, due
to presence of more short basiconic and coeloconic sensillae. Species under Catantopinae showed more long basiconic sensillae
than the others. The Oedipodinae had the highest number of slender and short basiconic sensillae and coeloconic sensillae,
followed by Catantopinae and Gomphocerinae; while Pamphaginae had the fewest. The total number of sensillae showed the same
trend for these two types amongst the subfamilies as well, species which prefer habits on the ground possessed fewer antennal
sensillae than species which prefer to stay on plants. The maximal number of antennal sensillae were observed in hygrophytous
species,Chorthippus albomarginatus, in the 12 grasshopper species investigated, although the data is not statistically significant. The general trend which
emerged was that species feeding on grass possessed more antennal sensillae, particularly coeloconic sensillae, compared to
other feeding group species. 相似文献
87.
Dual function of Slit2 in repulsion and enhanced migration of trunk,but not vagal,neural crest cells
Neural crest precursors to the autonomic nervous system form different derivatives depending upon their axial level of origin; for example, vagal, but not trunk, neural crest cells form the enteric ganglia of the gut. Here, we show that Slit2 is expressed at the entrance of the gut, which is selectively invaded by vagal, but not trunk, neural crest. Accordingly, only trunk neural crest cells express Robo receptors. In vivo and in vitro experiments demonstrate that trunk, not vagal, crest cells avoid cells or cell membranes expressing Slit2, thereby contributing to the differential ability of neural crest populations to invade and innervate the gut. Conversely, exposure to soluble Slit2 significantly increases the distance traversed by trunk neural crest cells. These results suggest that Slit2 can act bifunctionally, both repulsing and stimulating the motility of trunk neural crest cells. 相似文献
88.
Development of phenotypic differences in sensillum populations on the antennae of a grasshopper,Schistocerca americana 总被引:1,自引:0,他引:1
Chapman RF 《Journal of morphology》2002,254(2):186-194
The development of diet-induced phenotypic differences in numbers of sensilla on the antennae of the grasshopper Schistocerca americana was studied using the exuviae produced at each molt. This made it possible to follow changes within an individual insect. In the first instar, insects had similar numbers of four sensillum types: uniporous trichoid sensilla, coeloconic sensilla, and large and small multiporous basiconic sensilla. Rearing on lettuce resulted in sixth instars with greater numbers of three sensillum types than siblings reared on an artificial diet. The first statistically significant differences between treatments in numbers of trichoid sensilla and large basiconic sensilla occurred in the third and fourth instars, respectively. No major reductions in sensillum numbers occurred at any time and the phenotypic differences resulted from differences in the numbers added at each molt. 相似文献
89.
Processing of mechanosensory information from gustatory receptors on a hind leg of the locust 总被引:1,自引:0,他引:1
P. L. Newland M. Burrows 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1994,174(4):399-410
Gustatory receptors (basiconic sensilla) on the legs of the desert locust, Schistocerca gregaria, are innervated by chemosensory afferents and by a mechanosensory afferent. We show, for the first time, that these mechanosensory afferents form an elaborate detector system with the following properties: 1) they have low threshold displacement angles that decrease with increasing stimulus frequency in the range 0.05–1 Hz, 2) they respond phasically to deflections of the receptor shaft and adapt rapidly to repetitive stimulation, 3) they encode the velocity of the stimulus in their spike frequency and have velocity thresholds lower than 1°/s, and 4) they are directionally sensitive, so that stimuli moving proximally towards the coxa elicit the greatest response.The mechanosensory afferents, but not the chemosensory afferents, make apparently monosynaptic connections with spiking local interneurones in a population with somata at the ventral midline of the metathoracic ganglion. They evoke excitatory synaptic potentials that can sum to produce spikes in the spiking local interneurones. Stimulation of the single mechanosensory afferent of a gustatory receptor can also give rise to long lasting depolarizations, or to bursts of excitatory postsynaptic potentials in the interneurones that can persist for several seconds after the afferent spikes. These interneurones are part of the local circuitry involved in the production of local movements of a leg. The mechanosensory afferents from gustatory receptors must, therefore, be considered as part of the complex array of exteroceptors that provide mechanosensory information to these local circuits for use in adjusting, or controlling locomotion. 相似文献
90.
The type II microtrich sensilla on the lotic amphipod Gammarus pseudolimnaeus Bousfield enable it to control body orientation while swimming, as animals with their sensilla masked spent significantly more time swimming on their sides. These sensilla appear to be involved in the behavioural process that allows the animal to orient into the current (positive rheotaxis), as significantly fewer masked animals were able to turn into novel current flows compared with controls. The sensilla do not appear to play a role in detecting gravity. Results suggest that the sensilla transmit hydromechanical sensory information to the animal, and it is thought that the individual sensilla act in unison as a kinetic sensory organ. The sensilla are well adapted for such a hydromechanical role, as they would likely only be stimulated by currents hitting them broadside on. The sensilla are grouped, with each sensillum facing in a different direction, and the groups are located at appropriate positions for detecting current flows. The sensilla do not play a role in the detection of vibrations. Nor do they play a chemosensory role in the detection of food or predators; however, a role in conspecific chemodetection cannot be ruled out. 相似文献