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G G Chen

Publications and source records attributed to G G Chen.

27 records · Page 2Linked to original sources
PubMed1987

Rat lactotrophs isolated by fluorescence-activated cell sorting are electrically excitable.

Lactotrophs (prolactin-containing cells) from the anterior pituitary of the adult female rat were labeled by a cell-surface reaction with anti-prolactin antibodies and then isolated by fluorescence-activated cell sorting (FACS). FACS-isolated pituitary cells were maintained in culture 1-9 days, after which their excitable membrane properties were examined using the whole-cell patch recording technique. Comparisons between lactotrophs sorted at different laser-power settings on the FACS showed that although the electrical excitability of the sorted lactotrophs was acutely altered by exposure to high laser power, excitability comparable to unsorted cells was retained by the use of minimal laser power (10 mW). Recordings were made from 67 cells that had been isolated using the low laser power. These cells had resting membrane potentials ranging from -22 mV to -60 mV. More than 80% of the cells responded to depolarizing current injections with regenerative, full-amplitude, overshooting action potentials. Approximately 20% of these cells exhibited spontaneous 20-30 mV fluctuations in the level of resting membrane potential, the majority of which did not overshoot 0 mV. Both the action potentials and the spontaneous fluctuations involved Na+ and Ca2+ ion conductance mechanisms.

Action Potentials↗
PubMed1987

The influence of skeletal muscle on the electrical excitability of dorsal root ganglion neurons in culture.

Dorsal root ganglion (DRG) neurons from embryonic mice grown in coculture with dissociated skeletal muscle or in skeletal muscle conditioned medium (CM) showed an increased incidence of repetitive firing of action potentials when injected with sustained (60-100 msec) depolarizing current. This is in contrast to DRG neurons grown in monoculture and normal medium, which exhibit such behavior far less frequently. The first action potential showed less sensitivity to block with TTX and more sensitivity to Ca2+ channel blockers than the subsequent action potentials. The increased incidence of repetitive firing occurred when CM was added after as few as 2 or as many as 22 d in culture and with as little as 1-7 hr exposure to CM. This effect of CM cannot be mimicked by NGF or by coculture with cells from embryonic spinal cord (Peacock et al., 1973), can be eliminated by heating the CM at 56 degrees C for 30 min, and partially reversed following short exposure to CM. These results indicate that skeletal muscle releases some heat-labile factor(s) that can cause repetitive firing and, in addition, significant decrease in input resistance in the CM-treated neurons and a depression of the anomalous rectification, neither of which could account for the increase in repetitive firing.

Action Potentials↗
PubMed1984

A prosencephalic neuronal circuit possibly involved in modulation of pain.

Both anatomical and physiological studies in cats substantiated the existence of a thalamus-cortex-thalamus neuronal circuit in which neurons in the centre median send fibers to wide areas of the cerebral cortex and the cerebral cortex, the motor cortex in particular, may send the fibers back to the parafascicular nucleus. The cortical neurons concerned tend to discharge spontaneously and constantly. These spontaneous discharges can be readily inhibited by the corticopetal impulses from the centre median, which itself can be activated by general afferent impulses. On the basis of this observation it is assumed that constantly discharging corticothalamic neurons may exert a tonic excitatory influence on the pain-receiving center, parafascicular nucleus, so as to keep it in a state of constant alertness to the tissue-damaging danger signals and that the inhibitory action of the ascending fibers from centre median would serve to suspend the excitatory action of the cortex on the parafascicular nucleus, resulting in relief of pain. The corticofugal fibers in this forebrain circuit terminating in the centromedian nucleus may reinforce the inhibitory action of the centromedian neurons so as to inhibit the spontaneous discharges of the cortical neurons . A self-regulating mechanism is thus formed by which a stabilized state of brain excitability can be maintained.

Animals↗
PubMedDate not supplied

Pharmacokinetics of Astragaloside IV in rats by liquid chromatography coupled with tandem mass spectrometry.

Pharmacokinetics of Astragaloside IV (AGS-IV) in rats was studied by high performance liquid chromatography coupled with tandem mass spectrometry. The concentration in plasma was determined after i.v. administration of 1, 2, 4 mg/kg and p.o. administration of 20 mg/kg of AGS-IV. The AUC were linearly correlated to doses. Recoveries of AGS-IV in bile, urine and feces were also analyzed following i.v. dose of 2 mg/kg. Cumulative recovery of AGS-IV in bile reached 30.8% in 24h. Cumulative recovery of AGS-IV in urine and feces was 52.14%, which indicates that about 50% of AGS-IV was metabolized in vivo. The bioavailability of AGS-IV after p.o. administration was found to be 3.66%. These findings provide useful information for the research and development of AGS-IV and other potential agents.

Administration, Oral↗
PubMedDate not supplied

Induction of thyroid papillary carcinoma cell proliferation by estrogen is associated with an altered expression of Bcl-xL.

PURPOSE: One of the features of thyroid carcinoma is its predilection for women of reproductive age relative to men. An increased risk has also been documented in women who have used estrogens for gynecologic reasons. The aim of this study was to explore the mechanism by which sex hormones contribute to the development of thyroid carcinoma, which is not well understood at present. MATERIALS AND METHODS: In this study, we investigated the effects of estradiol and testosterone on cell proliferation in a human thyroid papillary carcinoma cell line (KAT5) by MTT assay. We also studied the expression of estrogen receptors and the levels of anti-apoptotic Bcl-xL protein, pro-apoptotic Bax protein, and messenger RNA in the cells by Western blot and reverse transcriptase polymerase chain reaction analysis. RESULTS: The results showed that estradiol promotes cell proliferation when compared with cells treated with testosterone and untreated cells, and that the growth-promoting effect of estradiol was attenuated by tamoxifen. The expression of Bcl-xL was markedly increased in a dose-dependent manner, resulting in an elevated ratio of Bcl-xL to Bax. DISCUSSION: We conclude that estradiol promotes KAT5 cell proliferation and that the underlying mechanism may be associated with up-regulation of Bcl-xL expression. The data provide insight into the molecular mechanism underlying the epidemiologic data that shows a two- to threefold increased prevalence of thyroid carcinoma in women relative to men. From the therapeutic point of view, the finding that estradiol enhances anti-apoptotic signaling pathways may be significant in the search for novel prevention and treatment strategies of thyroid carcinomas.

Blotting, Western↗