The mechanisms controlling axon guidance are of fundamental importance in understanding brain development. Growing corticospinal and somatosensory axons cross the midline in the medulla to reach their targets and thus form the basis of contralateral motor control and sensory input. The motor and sensory projections appeared uncrossed in patients with horizontal gaze palsy with progressive scoliosis (HGPPS). In patients affected with HGPPS, we identified mutations in the ROBO3 gene, which shares homology with roundabout genes important in axon guidance in developing Drosophila , zebrafish, and mouse. Like its murine homolog Rig1/Robo3, but unlike other Robo proteins, ROBO3 is required for hindbrain axon midline crossing.

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Among 1685 patients who sustained a hip fracture at the island of Crete (Greece) in a 4-year period we found 106 patients with bilateral noncontemporary hip fractures. Pathologic hip fractures and fractures that emerged from high energy trauma were excluded. To investigate the possible factors predisposing to the later fracture in the sound hip, we studied these 106 patients and compared them with the 1579 patients who sustained a single hip fracture (control group). There was no significant difference between the mean age of the bilateral group at the time of the first hip fracture (78.3 +/- 7.4 years, range 52-94 years) and the mean age of the control group (77.3 +/- 11.9 years, range 50-101 years). We found no significant difference in the bone status between the two groups, using both lumbar spine dual photon absorptiometry (DXA) and calcaneus broadband ultrasound attenuation (BUA). Falls, which were the main cause of all the hip fractures, were much more common in the bilateral group. The second hip fracture was of the same location (trochanteric or cervical) in 92% of the trochanteric and 68% of cervical fractures and a tendency to greater displacement or instability was observed. Of the second hip fractures 75% happened in the first 48 months after the first one. The mean interval time was much longer (160 months) when a neck fracture was followed by a trochanteric one.

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Broadband ultrasound attenuation (BUA) on the os calcis has been proposed as a safe and reliable technique for evaluating skeleted status. The present study provides preliminary normative BUA results on 93 female subjects divided into five age groups. These data can be used as a guide for comparing the results of individual studies. The diagnosis of osteoporosis was determined from lateral calcaneus and spine radiographs. Postmenopausal osteoporotic female subjects had significantly lower BUA values than normal women (P less than 0.001). There was a significant negative linear relationship between BUA and age in the postmenopausal subjects. No correlation was found between body size parameters (weight, height, and body mass index) and ultrasound attenuation. These results indicate that BUA may be a useful technique for detection of persons at risk.