Search PubMed⌕ Search

Biomedical subjects

J J Liu

Publications and source records attributed to J J Liu.

116 records · Page 7Linked to original sources
PubMedDate not supplied

Activation of Stat3 by v-Src is through a Ras-independent pathway.

V-Src induces tyrosine phosphorylation of various cellular proteins and activates a number of signaling molecules including the Jak family of proteins tyrosine kinases and Stat (signal transducers and activators of transcription) proteins. Many cellular effects elicited by v-Src are mediated through Ras, a molecular switch linking growth factor receptors and non-receptor tyrosine kinases to many downstream effectors. In this report, we demonstrated that v-H-Ras and v-Src both induced cellular transformation. However, the activation of Jak1 and Stat3 were only observed in v-Src transformed cells. Using reporter gene assays, we further showed that activation of Stat3 and possibly of Jak1 by v-Src were mediated through a Ras-independent pathway. As Stat3 activation has recently been shown to be required for cellular transformation by v-Src, our results suggest that activation of the Jak-Stat pathway may serve as a modulator in some but not all transformation processes.

3T3 Cells↗
PubMedDate not supplied

Auditory 40-Hz responses in the guinea pig.

Auditory evoked potentials in response to tone bursts repeated at a rate of 40 per second (auditory 40-Hz responses) were studied in the guinea pig. The potentials, consisting of a sequence of 40-Hz waves with a periodicity of about 25 msec, were distributed widely over the skull, and the largest potentials were recorded from the vertex (midline) and the temporal area contralateral to the stimulated ear. Administration of pentobarbital did not affect the midline response but reduced the amplitude of the contralateral response. Investigations of the effects of acute lesions demonstrated that the auditory 40-Hz responses from the contralateral temporal area were eliminated by aspiration of the contralateral cerebral cortex, whereas the responses from the midline continued to appear after bilateral aspiration of the cerebral cortex. The response from the midline was maintained after bilateral aspiration of the inferior colliculi, and the basic 40-Hz rhythm was still observed after decerebration. These data suggest different generation areas for the midline and contralateral 40-Hz responses in the guinea pig.

Acoustic Stimulation↗
PubMedDate not supplied

Effects of hyperosmotic solutions on endolymphatic pressure.

Hydrostatic pressure changes in endolymph as well as perilymph and cerebrospinal fluid (CSF) following intravenous injection of glycerol, urea, and mannitol were studied in the guinea pig using a servo-controlled micropipet system. After the initial rise in pressure observed during and immediately after injection of each hyperosmotic agent, all pressures fell below baseline levels for about 20 minutes. The largest reductions in pressure with each of the hyperosmotics showed no significant difference between CSF and labyrinth. In the glycerol and urea studies, labyrinthine pressures stabilized at their minimum levels 20 to 40 minutes after injection, while CSF pressure recovered slowly. However, alteration of labyrinthine pressures induced by mannitol paralleled that of CSF. These results may suggest a possible osmotic dehydration effect in the labyrinth for glycerol and urea, but an ambiguous effect for mannitol.

Animals↗
PubMedDate not supplied

Activation of neutral sphingomyelinase participates in ethanol-induced apoptosis in Hep G2 cells.

The mechanism underlying ethanol-induced apoptosis in liver cells is not clear. Sphingomyelin (SM) metabolism is a novel signal transduction pathway that has an impact on apoptosis in many cell types. We investigated whether the SM pathway is involved in ethanol-induced apoptosis in the liver. Hep G2 cells were treated with ethanol followed by assaying apoptosis, sphingomyelinase (SMase) activity, caspase-3 activity, and the changes of SM content in the cells. We found that ethanol dose-dependently increased apoptosis and the effect was accompanied by increases of caspase-3 activity and neutral SMase activity. At concentrations of 80 and 160 mM, ethanol significantly increased caspase-3 activity by 120% and neutral SMase activity by 24%. The activity of acid SMase was only slightly increased without statistical significance. C(2)-ceramide, the exogenous SM metabolite, mimicked the effects of ethanol on apoptosis and caspase-3 activation. When the SM content was determined 24 h after treatment with ethanol, its level was 15% lower than that of controls. The results indicate that metabolism of SM triggered by neutral SMase participates in ethanol-induced apoptosis in Hep G2 cells and activation of caspase-3 is involved in the apoptotic pathway.

Apoptosis↗
PubMedDate not supplied

Anti-proliferative effects of oridonin on SPC-A-1 cells and its mechanism of action.

Oridonin, an extract from the Chinese herb Rabdosia rubescens, is currently one of the most important traditional Chinese herbal medicines. We investigated the anti-proliferative effect of oridonin on the lung cancer cell line SPC-A-1 and its mechanism of action. Growth inhibition was measured using a microculture tetrazolium assay and apoptosis was measured by several standard methods. Western blot analysis measured the expression of bcl-2 and bax proteins. Oridonin (> 28 micromol/l) inhibited the growth of SPC-A-1 cells and induced apoptosis. Marked morphological changes indicative of apoptosis were observed, especially in cells treated with oridonin for 48 - 60 h. Western blot analysis revealed downregulation of bcl-2 and upregulation of bax proteins following treatment with oridonin for 48 h. We conclude that oridonin demonstrated anti-proliferative and apoptosis-inducing effects on SPC-A-1 cells in vitro, and that changes in bcl-2 and bax protein levels may play an important role in its mechanism of action.

Apoptosis↗