Sex determining gene on the X chromosome short arm: Dosage sensitive sex reversal

The present review article summarizes current knowledge concerning the sex determining gene on Xp21, termed DSS (dosage sensitive sex reversal). The presence of DSS has been based on the finding that, in the presence of SRY, partial active Xp duplications encompassing the middle part of Xp result in sex reversal, whereas those of the distal or proximal part of Xp permit male sex development. Because Klinefelter patients develop as males, it is believed that DSS is normally subject to X-inactivation, and that two active copies of DSS override the function of SRY, resulting in gonadal dysgenesis because of meiotic pairing failure. It may be possible that DSS encodes a target sequence for repressing function of SRY or that DSS is involved in an X chromosome-counting mechanism. Molecular approaches have localized DSS to a 160 kb region and isolated candidate genes such as DAX-1 and MAGE-Xp, but there has been no formal evidence equating the candidate gene with DSS. In addition to its clinical importance, the exploration of DSS must provide a useful clue to phylogenetic studies of sex chromosomes and dosage compensation.     

Effect of Intraatrial Reentry on Initiation of Atrioventricular Reentrant Tachycardia

We studied the effect of intratrial reentry (IAE) on initiation of orthodromic reentrant tachycardia (ORT) in 150 patients with Wolff-Parkinson-White syndrome using His-bundle recording and the atrial extrastimulus technique. IAR was initiated by premature atrial stimulation in 44 patients (29%), and it was followed by ORT in 16 patients (11%). In 8 patients (5%), IAR promoted the initiation of ORT, whereas in 5 patients (3%), IAR inhibited the initiation of ORT. These findings suggest that ORT is frequently induced following IAR. IAR, which was frequently observed during electrophysiological studies, seems to play an important role in the initiation of ORT.     

Autoradiographic Distribution of 131I-Clioquinol in Canine and Feline

To elucidate the absorption, intracellular location and pathogenicity of clioquinol, micro-autoradiographic studies were done. ¹³¹I-clioquinol was administered under different methods to 6 mongrels, 2 inbred beagles and a cat. Shortly after i.v.- or i.p.-injections of the substance to the mongrels and cat, a high concentration of radioactive grains was seen in the following nervous system: Nerve cells of the spinal root ganglia, spinal grey matter and nuclei in the brain stem; peripheral nerves; capsular cells of the spinal root ganglia; glial cells in the spinal cord, brain stem and periventricular region of the cerebrum. Though in lesser degree, orally administered radioactive clioquinol was also detected in the nervous system of the mongrels. I.p.-injected beagles showed, however, a low concentration of the grains in the nervous system. This may indicate strain-difference of dogs for the neurotoxicity of clioquinol.