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81.
Lucio RA; Garcia JV; Ramon Cerezo J; Pacheco P; Innocenti GM; Berbel P 《Cerebral cortex (New York, N.Y. : 1991)》1997,7(4):303-316
Previous studies have shown that hypothyroidism modifies the development of
callosal connections. In particular, adult hypothyroid rats have fewer
callosally projecting neurons in layers II-III of the auditory cortex and
more in layer V. This might be due to disturbance in the
stabilization/elimination of juvenile callosal axons, or to abnormal
neuronal migration during cortical histogenesis. To distinguish between
these possibilities we have studied the distribution of callosally
projecting auditory neurons at different postnatal ages using retrogradely
transported tracers, and the cortical neurogenetic gradients using DNA
labelling with 5-bromo-2'- deoxiuridine. In hypothyroid rats, injected at
postnatal day 5 (P5) and killed at P18-20, most of the neurons retrogradely
labelled from the contralateral hemisphere are distributed between layers
IV and VI, as in older rats. In hypothyroid rats, many neurons are at
locations inappropriate for their birthdate, including the subcortical
white matter, resulting in more diffuse radial neurogenetic gradients.
These results indicate that early induced hypothyroidism alters neuronal
migration and prevents the establishment of callosal connections from
cortical layers II-III.
相似文献
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BACKGROUND: Medium chain acyl-CoA dehydrogenase (MCAD) deficiency is a common disorder of fatty acid oxidation in north west Europe. It is very variable in its clinical consequences and is believed to be considerably underdiagnosed. OBJECTIVE: To investigate the diagnosis and outcome of MCAD deficiency in the UK. METHOD: A prospective surveillance study through the British Paediatric Surveillance Unit. RESULTS: Of 62 affected individuals identified, 57 were from England, giving an incidence of 4.5 cases/100,000 births. Forty six cases presented with an acute illness (10 of whom died), 13 cases were identified because of family history, and three for other reasons. Six of the survivors were neurologically impaired. CONCLUSIONS: Despite increased clinical awareness, the mortality and morbidity from MCAD deficiency remain high. The frequency and severity of the disease support the case for the introduction of universal neonatal screening in England and Scotland. 相似文献
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Simon JH; Foster TH; Ketonen L; Totterman S; Szumowski J; Kido DK; Manzione JV Jr; Joy SE 《Radiology》1989,172(3):771-775
A decrease in the magnetic resonance (MR) imaging bandwidth can be used to increase the signal-to-noise ratio (S/N) at constant imaging time or to maintain the S/N for reduction of imaging time. The effect of bandwidth reduction from the default value of 16 kHz to 8 kHz was evaluated prospectively in 50 patients referred for MR imaging of the head. On intermediate (2,000/30 [repetition time msec/echo time msec]) and more T2-weighted (2,000/90) studies, there were no definite missed diagnoses and no diagnostically important changes in lesion characteristics when the reduced-bandwidth technique was used to obtain half- or quarter-time studies, excluding differences attributable to unintentional changes in patient position between image acquisitions. Chemical shift misregistration artifacts associated with reduced bandwidth are easily recognized with experience and do not interfere with diagnosis, as the artifacts occur in characteristic locations and diminish in most anatomic locations with increasing echo time. This study suggests the feasibility of reduced-bandwidth techniques in clinical MR imaging of the head at high field strength to achieve an increased S/N, to decrease imaging time, or to obtain images in additional projections. 相似文献
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Radiation tolerance of the cervical spinal cord 总被引:2,自引:0,他引:2