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Results for “Fasciculation”

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At least 271 records · Page 15Linked to original sources
PubMed1986

Fasciculation in the early mouse trigeminal nerve is not ordered in relation to the emerging pattern of whisker follicles.

Detailed reconstructions of lengths of the embryonic mouse maxillary nerve were made from serial light and electron microscope sections to determine whether there is any correspondence between the arrangement of fasciculi in the developing nerve and the emerging pattern of whisker follicles on the snout. There was neither correspondence nor obvious pattern in the arrangement of fasciculi at either E11, when trigeminal nerve fibers first contact the presumptive whisker pad, or at E12, when the pattern of developing whisker follicles becomes apparent. Fasciculi merged and branched to form an intricate plexus. Furthermore, the ratio of the number of nerve fibers in one fasciculus to the number in another prior to their merger differed significantly from the ratio of fiber numbers in the two fasciculi after their separation, which indicates that nerve fibers are freely exchanged between fasciculi. Our findings suggest that the somatotopic representation of the whisker follicle pattern in the brainstem does not develop by nerve fiber growth augmenting an initially ordered pattern of fasciculi.

Animals↗
PubMed1984

[Automatic retroversion of the femur neck during fasciculated nailing of pertrochanteric fractures by the Ender method].

The shape of the standard Ender nail may result in malunion in external rotation in intertrochanteric fractures treated with this device. The nail is curved in one plane, and is usually introduced into the femur without making allowance for the bowing of the diaphysis and the anteversion present in the neck. We have measured radiographically the anteversion of the femoral neck in three groups of patients after operation using Ender nails, and also assessed the anteversion of the unoperated hip for comparison. In Group I normal Ender nails were used. The operated hip showed an average of 12 degrees of retroversion compared with the opposite side. In Group II the nails were bent anteriorly at their upper end, but an average retroversion of 14 degrees was produced compared with the other hip. In Group III the nails were bent to produce anterior bowing as well as proximal anteversion. The group showed retroversion of only 1 degree compared with the normal side. We therefore recommend that Ender nails be bent in this manner in order to reduce rotatory malunion when used for intertrochanteric fractures of the neck of the femur.

Aged↗
PubMed2003

Multi-fasciculated anterior talo-fibular ligament: reassessment of normal findings.

The aims of this study were to (a) provide an accurate description of the anterior talo-fibular ligament (ATFL) multifasciculated feature by means of cadaver study, and (b) to further delineate contour and signal variations on MR images related to this feature in a group of asymptomatic subjects. After MR imaging, three cadaveric feet were frozen and cut in the coronal plane. The ATFL were harvested and sent to pathology. Another cadaveric foot was dissected. The MR imaging was performed in 3 healthy volunteers and 19 patients without pathology of the ATFL. For both cadaveric feet and subjects, MR imaging protocol consisted of axial and coronal proton-density (PD) and T2-weighted turbo-spin-echo (TSE) sequences (TR/TE: 3500 ms/17-119 ms). On MR images, ATFL signal and fascicle numbers were assessed, respectively, in the axial and coronal planes. Gross anatomy and pathology confirmed the ATFL bifasciculated aspect. On cadaveric coronal MR images, 3 of 4 ATFLs were bifasciculated and one of four was striated. On patients' coronal MR images, 2 of 22 of the ATFL were monofasciculated, 12 of 22 bifasciculated, and 8 of 22 striated. On axial MR images, 16 of 22 of the ATFL demonstrated a low signal intensity and 8 of 22 an intraligamentous subtle increased signal intensity. Two of 22 of the ATFL had contour irregularities. Isolated anterior talo-fibular intraligamentous signal abnormalities or contour irregularities on axial PD and T2-weighted MR images with an otherwise normal ATFL aspect on coronal MR images and no other MRI criteria for ankle sprain may reflect normal anatomy.

Ankle Injuries↗
PubMed1997

Modeling an extracellular environment for axonal pathfinding and fasciculation in the central nervous system.

An increasing number of extracellular matrix molecules has been identified in the brain over the last couple of years. Various interactions have been identified between some of these molecules, indicating that they are components of an organized matrix. In this review, an attempt is made to arrive at a model for such a matrix, based on the current knowledge of the structure and interactions of these molecules.

Animals↗
PubMed1992

Tract formation and axon fasciculation of molecularly distinct peripheral neuron subpopulations during leech embryogenesis.

In leech, the central projections of peripheral sensory neurons segregate into specific axonal tracts, which are distinguished by differential expression of surface antigens recognized by the monoclonal antibodies Lan3-2 and Lan4-2. Lan3-2 recognizes an epitope expressed on axons that segregate into three distinct axon fascicles. In contrast, the Lan4-2-positive axons selectively project into only one of the Lan3-2-positive axon tracts. These observations provide evidence for a hierarchy of guidance cues mediating specific pathway formation in this system. Since the Lan3-2 antibody has been shown to perturb this process and since, as shown here, the Lan3-2 and Lan4-2 antigens are closely molecularly interrelated, these antibodies may help define molecules and epitopes mediating neuronal recognition and axonal guidance.

Afferent Pathways↗
PubMed2003

Diffusible signals and fasciculated growth in reticulospinal axon pathfinding in the hindbrain.

We have addressed the control of longitudinal axon pathfinding in the developing hindbrain, including the caudal projections of reticular and raphe neurons. To test potential sources of guidance signals, we assessed axon outgrowth from embryonic rat hindbrain explants cultured in collagen gels at a distance from explants of midbrain-hindbrain boundary (isthmus), caudal hindbrain, or cervical spinal cord. Our results showed that the isthmus inhibited caudally directed axon outgrowth by 80% relative to controls, whereas rostrally directed axon outgrowth was unaffected. Moreover, caudal hindbrain or cervical spinal cord explants did not inhibit caudal axons. Immunohistochemistry for reticular and raphe neuronal markers indicated that the caudal, but not the rostral projections of these neuronal subpopulations were inhibited by isthmic explants. Companion studies in chick embryos showed that, when the hindbrain was surgically separated from the isthmus, caudal reticulospinal axon projections failed to form and that descending pioneer axons of the medial longitudinal fasciculus (MLF) play an important role in the caudal reticulospinal projection. Taken together, these results suggest that diffusible chemorepellent or nonpermissive signals from the isthmus and substrate-anchored signals on the pioneer MLF axons are involved in the caudal direction of reticulospinal projections and might influence other longitudinal axon projections in the brainstem.

Animals↗
PubMed2002

Neuropilin-2 mediates axonal fasciculation, zonal segregation, but not axonal convergence, of primary accessory olfactory neurons.

The mechanisms that underlie axonal pathfinding of vomeronasal neurons from the vomeronasal organ (VNO) in the periphery to select glomeruli in the accessory olfactory bulb (AOB) are not well understood. Neuropilin-2, a receptor for secreted semaphorins, is expressed in V1R- and V3R-expressing, but not V2R-expressing, postnatal vomeronasal neurons. Analysis of the vomeronasal nerve in neuropilin-2 (npn-2) mutant mice reveals pathfinding defects at multiple choice points. Vomeronasal sensory axons are severely defasciculated and a subset innervates the main olfactory bulb (MOB). While most axons of V1R-expressing neurons reach the AOB and converge into distinct glomeruli in stereotypic locations, they are no longer restricted to their normal anterior AOB target zone. Thus, Npn-2 and candidate pheromone receptors play distinct and complementary roles in promoting the wiring and patterning of sensory neurons in the accessory olfactory system.

Animals↗