Biomedical subjects

Tim Jacob

Publications and source records attributed to Tim Jacob.

7 recordsLinked to original sources

PubMed2005

Involvement of regulatory volume decrease in the migration of nasopharyngeal carcinoma cells.

The transwell chamber migration assay and CCD digital camera imaging techniques were used to investigate the relationship between regulatory volume decrease (RVD) and cell migration in nasopharyngeal carcinoma cells (CNE-2Z cells). Both migrated and non-migrated CNE-2Z cells, when swollen by 47% hypotonic solution, exhibited RVD which was inhibited by extracellular application of chloride channel blockers adenosine 5'-triphosphate (ATP), 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) and tamoxifen. However, RVD rate in migrated CNE-2Z cells was bigger than that of non-migrated cells and the sensitivity of migrated cells to NPPB and tamoxifen was higher than that of non-migrated cells. ATP, NPPB and tamoxifen also inhibited migration of CNE-2Z cells. The inhibition of migration was positively correlated to the blockage of RVD, with a correlation coefficient (r) = 0.99, suggesting a functional relationship between RVD and cell migration. We conclude that RVD is involved in cell migration and RVD may play an important role in migratory process in CNE-2Z cells.

Adenosine Triphosphate↗

PubMed2004

Activation of chloride current and decrease of cell volume by ATP in nasopharyngeal carcinoma cells.

Whole-cell patch clamp and cell volume measurement techniques were used to investigate the ATP-activated chloride current and the ATP effect on cell volume in nasopharyngeal carcinoma cells. Extracellular application of ATP in micromolar concentrations activated a current with the properties of modest outward rectification and negligible time-dependent inactivation in a dose-dependent manner. The current reversed at a potential [(-0.05+/-0.03) mV] close to the Cl- equilibrium potential (-0.9 mV). Substitution of Cl- with gluconate in the extracellular solution decreased the ATP-activated current and shifted the reversal potential positively. NPPB, one of the chloride channel blockers, inhibited the current by (81.03+/-9.36)%. The current was also depressed by the P2Y purinoceptor antagonist, reactive blue 2, by (67.39+/-5.06)%. ATP (50 micromol/L) decreased the cell volume under the isotonic condition. Depletion of extracellular and intracellular Cl- abolished the ATP effect on cell volume. The results suggest that extracellular ATP of micromolar scales can induce a chloride current associated with cell volume regulation by activation of chloride channel through binding to purinoceptor P2Y.

Adenosine Triphosphate↗

PubMed2004

Volume-activated Cl- current in migrated nasopharyngeal carcinoma cells.

The transwell chamber migration assay and the patch-clamp technique were used to investigate the volume-activated Cl(-) current (I(Cl.vol)) in migrated nasopharyngeal carcinoma cells (CNE-2Z). 47% hypotonic solution activated a ICl.vol in the migrated CNE-2Z cells. Compared with the control cells (non-migrated), the properties of this current and the sensitivity to Cl(-) channel blockers were changed. The current density in migrated CNE-2Z cells was higher than that in non-migrated cells. The current was almost completely inhibited by extracellular application of adenosine-5'-triphosphate (ATP, 10 mmol/L), 5-nitro-2-3-phenylpropylamino benzoic acid (NPPB, 100 mmol/L) and tamoxifen (30 mmol/L) in all voltage steps applied. The inhibition of NPPB and tamoxifen on the current was stronger in migrated cells than that in non-migrated cells. The permeability sequence of the four anions was Br(-)>Cl(-)> I (-)>Gluconate. The sequence was different from that of the non-migrated cells (I(-)> Br(-)> Cl(-)> Gluconate). The results suggest that volume-activated chloride channels may be involved in the CNE-2Z cell migration.

Carcinoma↗

PubMed2004

ClC-3 expression in the cell cycle of nasopharyngeal carcinoma cells.

The immunofluorescence approach, the confocal microscopy and the patch-clamp technique were used to investigate the expression of ClC-3 (one of the candidates of volume-activated chloride channels) and its relationships with the volume-activated chloride current and the capacity of regulatory volume decrease (RVD) in the cell cycle of nasopharyngeal carcinoma cells (CNE-2Z cells). The results indicated that CNE-2Z cells expressed ClC-3. ClC-3 was located predominantly inside the cells but not in the membrane. Both the expression level and the distribution of ClC-3 were cell cycle dependent. ClC-3 expression was low in G1 but high in S phase. The cells in G2/M phase possessed an intermediate level of the expression. ClC-3 expression level was negatively correlated to the RVD capacity and amplitude of the volume-activated chloride current in the cell cycle. The results suggest that ClC-3 may be an important factor in the regulation of cell cycle progression, but that it is probably not the chloride channel associated with RVD in these cancer cells.

Adenosine Triphosphate↗

PubMed2004

Evidence for peripheral plasticity in human odour response.

Of those people who are anosmic to androstenone, a proportion can acquire sensitivity to it by repeated exposure and even those who are able to smell it can lower their threshold with this treatment. Using olfactory threshold testing, intranasal electrophysiology and EEG we show for the first time that: (1) the subjects' detection threshold is proportional to the amplitude of the olfactory evoked potential (EOG) recorded inside the nose; (2) the EOG amplitude is correlated with the amplitude of the olfactory event-related potential (OERP) recorded on the scalp; and (3) with repetitive exposure, human subjects acquire a reduced threshold for androstenone and, as they do so, their EOG and OERP increase. These observations support the existence of odourant-specific plasticity in the peripheral olfactory system.

Adolescent↗

PubMed2004

A new non-invasive method for recording the electro-olfactogram using external electrodes.

OBJECTIVE: The aim of this investigation was to explore the possibility of recording the electro-olfactogram (EOG) using external electrodes placed on the root of the nose on either side of the bridge and at the medial termination of the eyebrows. The EOG is considered to be the summated generator potential of olfactory receptor cells and therefore represents peripheral olfactory events. Recording of human EOG is technically difficult due to poor access to the olfactory mucosa and the nasal irritation is tolerated by few subjects. METHODS: The evoked potentials at these sites in response to two odourants, n-amyl acetate and benzaldehyde, were recorded simultaneously with the EOG, recorded conventionally with an intranasal electrode, and the olfactory event-related potential (OERP) recorded using scalp electrodes. RESULTS: The extranasal potential recorded at the root of the nose, 0.5-1 cm below the nasion, 1 cm from the ridge and ipsilateral with the stimulus, had the highest degree of correlation with the intranasal EOG. We refer to this site as N1 (left side) and N2 (right side). Further analysis demonstrated that the latency, the time constant of the rising phase and the amplitude of the evoked potential recorded at N1 also had a higher correlation coefficient with the EOG than did those potentials recorded at other sites. Statistical analysis indicated that the latency and time constant of the response recorded externally at N1 were the same as those of the EOG recorded intranasally. CONCLUSIONS: We conclude that an olfactory evoked potential, with many of the characteristics of the EOG recorded from the olfactory mucosa, can be recorded externally at a site close to the bridge of the nose. SIGNIFICANCE: This non-invasive method of recording the EOG will have benefits for the objective assessment of olfactory function.

Adult↗

PubMed2002

The role of MDR1 gene in volume-activated chloride currents in pigmented ciliary epithelial cells.

The role of multidrug resistance (MDR1) gene in the activation of volume-activated chloride currents in bovine pigmented ciliary epithelial (PCE) cells was investigated by the patch-clamp technique, the antisense approach, the immunofluorescent technique and the confocal microscopy. PCE cells express P-glycoprotein (P-gp, the product of MDR1 gene). An MDR1 antisense oligonucleotide suppressed MDR1 expression (93% reduction of P-gp immunofluorescence), delayed the activation of a volume-activated chloride current (latency prolonged by 109%), reduced the activation rate by 62% and decreased the peak value of the current by 56%. The transfection reagent lipofectin and the mismatch control oligonucleotide did not significantly affect the current. The data indicate that the volume-activated chloride current is associated with the endogenous expression of MDR1 gene in PCE cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗