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Articles by M. C Chen
Total Records ( 2 ) for M. C Chen
  M. C Chen , J. P Hamilton and I. H. Gotlib

Context  Researchers have documented that the hippocampus is smaller in individuals with depression than in those without. The temporal or causal association of this reduction in hippocampal volume in depression, however, is not known.

Objective  To test the hypothesis that reduced hippocampal volume precedes and therefore may be implicated in the onset of depression.

Design  We used magnetic resonance imaging to examine brain structure volume in individuals at high and low familial risk of depression. Anatomic images from magnetic resonance imaging were analyzed using both whole-brain voxel-based morphometry and manual tracing of the bilateral hippocampus.

Setting  A research university.

Participants  Fifty-five girls aged between 9 and 15 years: 23 daughters of mothers with recurrent episodes of depression in the daughter's lifetime (high risk) and 32 age-matched daughters of mothers with no history of psychopathology (low risk). None of the girls had any past or current Axis I psychopathology.

Main Outcome Measures  Group differences in voxel-based morphometry brain matter density estimates and traced hippocampal volume.

Results  Voxel-based morphometry analyses indicated that individuals at high risk of depression had significantly less gray matter density in clusters in the bilateral hippocampus (P < .001) than low-risk participants. Tracing yielded a volumetric reduction in the left hippocampus in the high-risk participants (P < .05).

Conclusions  Compared with individuals at low familial risk of the development of depression, high-risk individuals have reduced hippocampal volume, indicating that neuroanatomic anomalies associated with depression may precede the onset of a depressive episode and influence the development and course of this disorder.

  M. C Chen , H Lin , F. N Hsu , P. H Huang , G. S Lee and P. S. Wang

The signaling mechanisms underlying cell differentiation have been extensively studied with the use of rat PC12 cells as a model system. Nerve growth factor (NGF) is a trophic factor inducing PC12 cell differentiation through the activation of the p35/cyclin-dependent kinase 5 (Cdk5) complex. It has been reported that adenylyl cyclase activation and cAMP production may be involved in NGF-dependent actions. Our previous results indicate that cAMP activates the p35/Cdk5 complex in reproductive cells. Therefore, the role of cAMP in NGF-triggered p35/Cdk5 activation and PC12 differentiation was interesting to explore. Our results indicate that roscovitine, a molecular inhibitor of Cdk5, blocks cAMP-triggered PC12 differentiation, which was evaluated by neurite initiation, a decrease in proliferation, and cell cycle G1 arrest. The following data show that cAMP treatment increased Cdk5 activity through p35 upregulation. cAMP downstream components, protein kinase A (PKA) and phosphorylated cAMP response element binding protein (CREB), are involved in this regulation. The immunocytochemical results indicate that PKA inhibition disrupted cAMP-triggered p35/Cdk5 localization in PC12 cells. In addition, adenylyl cyclase inhibition was found to diminish NGF-induced intracellular cAMP production, CREB phosphorylation, and p35 expression. The cAMP antagonist and the PKA inhibitors reduced NGF-induced p35 expression. Finally, NGF-triggered PC12 differentiation was partially decreased by adenylyl cyclase or PKA inhibitors. In conclusion, these results demonstrate that cAMP may play a role in NGF-p35/Cdk5-dependent PC12 differentiation.

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