Kazumi Yoshioka

Long-term potentiation and depression in layer III and V pyramidal neurons of the cat sensorimotor cortex in vitro.

Synaptic plasticity of the cat sensorimotor cortex was examined intracellularly in vitro. After tetanic stimulation of the white matter, layer III and V pyramidal neurons showed long-term potentiation (LTP) of EPSPs in high incidence without GABA(A) antagonist. The incidence and magnitude of LTP were very conspicuous in layer V cells. After an NMDA receptor antagonist application, the synaptic potentiation was blocked completely in layer III but not in layer V cells. Long-term depression (LTD) of the evoked EPSPs was also induced by the same stimulation in some layer III cells, where a transient hyperpolarization of the membrane potential was observed during tetanus.

The burst firing in the layer III and V pyramidal neurons of the cat sensorimotor cortex in vitro.

We identified the burst and single-spiking cells, and the repetitive bursting cells in layers III and V of the cat sensorimotor cortex with intracellular recording and staining techniques. Both types of the bursting cells were found in 22.7% of the recorded layer V neurons and in 23.1% of the recorded neurons in layer III. The bursting cells were characterized by the prominent afterdepolarization (ADP) which was usually reaching the threshold depolarization. Intracellular staining revealed that the morphology of the bursting cells was not so different from that of the regular-spiking cells in the cat.

Human Colon Cancer Cells Undergo Apoptosis by Theaflavin Digallate, Epigallocatechin Gallate, and Oolong Tea Polyphenol Extract

ABSTRACT The effects of theaflavin digallate, a main component of black tea theaflavins; epigallocatechin gallate, a main component of green tea catechins; and polyphenol extract, containing an OTP trimer as a major component of oolong tea, was tested on human colon cancer COLO 205 cells and normal lymphocytes. Treatment with theaflavin digallate, epigallocatechin, and polyphenol extract resulted in growth inhibition and induced apoptosis in the COLO 205 cells, but not in normal human lymphocytes. Morphological examination of the tissue showed apoptotic bodies in cells treated with the chemical compounds. DNA fragmentation and the formation of oligonucleosomal-sized fragments in treated cells, characteristic of apoptosis, were concentration and time dependent. The data provide the first evidence that tea extracts induce apoptosis in human colon cancer cells.