The last decade has witnessed the identification of single-gene defects associated with an impressive number of mental retardation syndromes. Fragile X syndrome, the most common cause of mental retardation for instance, results from disruption of the FMR1 gene. Similarly, Periventricular Nodular Heterotopia, which includes cerebral malformation, epilepsy and cognitive disabilities, derives from...

A number of families have been reported in which mental retardation appeared to be segregating as an X-linked recessive (Martin and Bell, 1943; Allan, Herndon, and Dudley, 1944; Losowsky, 1961; Renpenning et al, 1962; Dunn et al, 1962/1963; Neuhauser et al, 1969; Snyder and Robinson, 1969; Neuhauser and Zerbin-Rudin, 1970). We reported 5 such families (Turner, Turner, and Collins, 1971b) in whi...

Isolated mitotic apparatuses (MA) of clam and sea urchin eggs were investigated by polarizing and electron microscopy. Examination of fixed MA in oils of different refractive index revealed that at least 90% of the retardation of isolated MA is due to positive, form birefringence, the remaining retardation deriving from positive, intrinsic birefringence. Electron micrographs reveal the isolated...

Introduction: Congenital hypothyroidism is the most common cause of mental retardation in the world. The presence of hypothyroidism in fetal is lead to abnormalities in major organs, including nervous system and central skeleton. Aim of this study was to investigate epidemiologic situation of neonatal hypothyroidism in Ilam province between 2005 -2011. Materials and methods: This was a cross-s...