State-dependent activity dynamics of hypothalamic stress effector neurons.

The stress response necessitates an immediate boost in vital physiological functions from their homeostatic operation to an elevated emergency response. However, the neural mechanisms underlying this state-dependent change remain largely unknown. Using a combination of in vivo and ex vivo electrophysiology with computational modeling, we report that corticotropin releasing hormone (CRH) neurons in the paraventricular nucleus of the hypothalamus (PVN), the effector neurons of hormonal stress response, rapidly transition between distinct activity states through recurrent inhibition.

Neuronal hypertrophy dampens neuronal intrinsic excitability and stress responsiveness during chronic stress.

Key Points: The hypothalamic-pituitary-adrenal (HPA) axis habituates to repeated stress exposure. We studied hypothalamic corticotropin-releasing hormone (CRH) neurons that form the apex of the HPA axis in a mouse model of stress habituation using repeated restraint. The intrinsic excitability of CRH neurons decreased after repeated stress in a time course that coincided with the development of HPA axis habituation.

Coordination structure and extraction behavior of a silver ion with N-substituted-9-aza-3,6,12,15-tetrathiaheptadecanes: significant effect of Ph-C-N framework on the extractability.

N-Substituted-9-aza-3,6,12,15-tetrathiaheptadecanes having Ph-C-N frameworks (N-R-ATH; R = benzyl (N-Bn-ATH), 4-nitrobenzyl (N-NO2Bn-ATH), and diphenylmethyl (N-Ph2CH-ATH)) were synthesized, and their Ag(i) complexes were structurally characterized. X-Ray crystal structure analyses of [Ag(N-R-ATH)](BF4) (R = Bn and Ph2CH) revealed monomeric tetra-S-coordinated complex cation structures without the N-coordination, and a benzene ring of the N-R group covered over the amine nitrogen atom. The precise extraction analyses of a Ag(i) ion with ATH derivatives (L = N-R-ATHs and N-H-ATH) associated with the (1)H NMR analyses of the [Ag(L)](+) complexes in polar and non-polar solvents revealed that the introduction of the N-substituent significantly enhanced the extractability of Ag(+), due to the "hydrophobic cover" effect by the Ph-C-N framework in the [Ag(N-R-ATH)](+) complexes.

Studies on a unique organelle localization of a liver enzyme, serine:pyruvate (or alanine:glyoxylate) aminotransferase.

Serine:pyruvate (or alanine:glyoxylate) aminotransferase (SPT or AGT) in the liver is unique in that its subcellular distribution is entirely peroxisomal in man and herbivores, and largely mitochondrial in carnivores. In rats, this enzyme is located in both mitochondria and peroxisomes and only the mitochondrial activity is markedly induced by glucagon. The mechanism of the species-specific dual organelle localization is either transcription of the gene from two different start sites or loss of upstream translation initiation ATG codon by mutations.

Assay of alanine:glyoxylate aminotransferase in human liver by its serine: glyoxylate aminotransferase activity.

We have examined assay methods and conditions for human liver alanine:glyoxylate aminotransferase (AGT). This enzyme shows not only the AGT activity but also serine:pyruvate and serine: glyoxylate aminotransferase (SPT and SGT) activities. In the assay of AGT activity using crude enzyme preparations, there is the complication that glutamate:glyoxylate aminotransferase (GGT) also contributes to AGT activity, but at present no other enzyme is known to catalyze transamination between L-serine and glyoxylate or pyruvate.