rf Spectroscopy with a single Ba+ ion.

We have employed the method of shelving to measure Zeeman resonances of a single trapped Ba+ ion. We use optical pumping to place the ion in a selected magnetic sublevel of either the 6S(1/2) ground state or the 5D(3/2) metastable state. The ion is exposed to an rf field, and a probing/shelving mechanism detects whether spin-flip transitions have taken place. We have observed rf transitions with linewidths of 15 Hz, limited by magnetic-field noise. We have also observed the shift in the Zeeman frequency when the ion is illuminated by off-resonant light. A simultaneous measurement of such light shifts in two atomic states of Ba+ will permit a precise determination of the ratio of transition matrix elements.

"Baltic" myoclonus epilepsy: hereditary disorder of childhood made worse by phenytoin.

A survey of 15 families in the USA with Baltic myoclonus epilepsy showed that the 27 individuals who were affected had the following clinical picture from about the age of 10: photosensitive, occasionally violent, myoclonus, usually worse upon waking; generalised tonic-clonic seizures, sometimes associated with absence attacks; and light-sensitive, generally synchronous, spike-and-wave discharges on EEG that preceded clinical manifestations. Necropsy revealed marked loss of Purkinje cells of the cerebellum, but no inclusion bodies. Since the disease was confined to sibs and consanguinity was present in two families, autosomal recessive inheritance is probable. The disease progressed more rapidly in these families than it did in the early cases, seen in the Baltic region. This difference could be due to a toxic effect of phenytoin because phenytoin given alone or with other antiepileptic drugs was associated with progressive motor and intellectual deterioration, marked ataxia, and even death. Treatment with valproic acid, and the concomitant reduction or elimination of phenytoin, has been associated with marked improvement in at least 8 patients. Baltic myoclonus epilepsy must be distinguished from Lafora body disease, which is invariably fatal and discernible on clinical grounds.

Central neurofibromatosis with bilateral acoustic neuroma: genetic, clinical and biochemical distinctions from peripheral neurofibromatosis.

Neurofibromatosis includes the common "peripheral" form and a recently documented "central" form. We describe the central form in 130 cases from 9 kindreds personally studied and 15 reported kindreds. Central neurofibromatosis with bilateral acoustic neuroma is an autosomal dominant disorder beginning about 20 years of age, accompanied by mild skin changes. In three kindreds with central neurofibromatosis, we measured nerve growth factor in serum by radioimmunoassay and radioreceptor assay. Only the antigenic activity of nerve growth factor was increased. In contrast, in peripheral neurofibromatosis, only the functional activity of nerve growth factor has been reported increased. Central and peripheral forms of neurofibromatosis are closely related but discrete diseases which appear to have separate alterations in nerve growth factor activity.