A double point mutation in PCL-gamma1 (Y509A/F510A) enhances Y783 phosphorylation and inositol phospholipid-hydrolyzing activity upon EGF stimulation

Growth factor stimulation induces Y783 phosphorylation of phosphoinositide-specific PLC-gamma1, and the subsequent activation of this enzyme in a cellular signaling cascade. Previously, we showed that a double point mutation, Y509A/F510A, of PLC-gamma1, abolished interactions with translational elongation factor 1-alpha. Here, we report that the Y509A/F510A mutant PLC-gamma1 displayed extremely high levels of Y783 phosphorylation and enhanced catalytic activity, compared to wild-type PLC-gamma1, upon treatment of COS7 cells with EGF. In quiescent COS7 cells, the Y509A/F510A mutant PLC-gamma1 exhibited a constitutive hydrolytic activity, whereas the wild-type counterpart displayed a basal level of activity. Upon treatment of COS7 cells with EGF, the Y783F mutation in Y509A/F510A PLC-gamma1 (Y509A/F510A/Y783F triple mutant) cells also led to an enhanced catalytic activity, whereas Y783F mutation alone displayed a basal level of activity. Our results collectively suggest that the Y509A/F510A mutant is more susceptible to receptor tyrosine kinase-induced Y783 phosphorylation than is wild-type PLC-gamma1, but no longer requires Y783 phosphorylation step for the Y509A/F510A mutant PLC-gamma1 activation in vivo.

A Case of Hyponatremia with Generalized Convulsion Following Sinus Surgery / 대한이비인후과학회지

Post-operative hyponatremia is associated with fluid overload and inappropriate secretion of antidiuretic hormone (ADH), which is related to stress, pain and others. Hyponatremia is a frequently encountered condition in clinical practice but severe post-operative hyponatremia has rarely been reported. Hyponatremia is curable; but severe hyponatremia is a fatal and emergency. Therefore, we should be aware of this phenomenon, diagnosis and management. We experienced one case of severe hyponatremia with generalized convulsion and neurologic symptoms in post-operative period.

Clinical Implication and Therapeutic Efficacy of Tinnitus Retraining Therapy / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Tinnitus retraining therapy (TRT) has been presented as a new approach to tiniutus management. The aim of this paper is to show the clinical implication method of TRT in our clinic and to evaluate the therapeutic efficacy of TRT based on questionnaires and tinnitograms. MATERIALS AND METHODS: Using the clinical implication method of TRT, 60 patients with tinnitus, who visited Tinnitus Clinic, Kangnam St. Mary's Hospital from May, 1999 to July, 2001, and who had received TRT for their tinnitus, were included for the evaluation of therapeutic efficacy of TRT. Their psychoacoustic characteristics of tinnitus and changes of subjective tinnitus were analyzed. RESULTS: Loudness, awareness, annoyance and effect on life of tinnitus decreased after TRT. Tinnitus handicap score also significantly decreased (p<0.05). Forty-eight patients among the sixty patients (80%) showed relief of their tinnitus in more than 2 of 4 subjective parameters (loudness, awareness, annoyance and effect on life of tinnitus). CONCLUSION: TRT has been shown to be effective in the treatment of subjective tinnitus. Modification of TRT may be necessary for easy application of this therapy in Korea.