Yuk-Keung Lo

Association of cognitive impairment, depressive symptoms and sarcopenia among healthy older men in the veterans retirement community in southern Taiwan: A cross-sectional study

To evaluate the association of cognitive impairment, depressive mood and sarcopenia among older men living in the veterans retirement community in southern Taiwan

Stimulation of the BKCa channel in cultured smooth muscle cells of human trachea by magnolol

Background: Magnolol, a compound isolated from the cortex of Magnolia officinalis, has been found to possess anti-allergic and anti-asthmatic activity. Methods: The effect of magnolol on ionic currents was studied in cultured smooth muscle cells of human trachea with the aid of the patch clamp technique. Results: In whole cell current recordings magnolol reversibly increased the amplitude of K+ outward currents. The increase in outward current caused by magnolol was sensitive to inhibition by iberiotoxin (200 nM) or paxilline (1 μM) but not by glibenclamide (10 μM). In inside out patches, magnolol added to the bath did not modify single channel conductance but effectively enhanced the activity of large conductance Ca2+ activated K+ (BKCa) channels. Magnolol increased the probability of these channel openings in a concentration dependent manner with an EC50 value of 1.5 μM. The magnolol stimulated increase in the probability of channels opening was independent of internal Ca2+. The application of magnolol also shifted the activation curve of BKCa channels to less positive membrane potentials. The change in the kinetic behaviour of BKCa channels caused by magnolol in these cells is the result of an increase in dissociation and gating constants. Conclusions: These results provide evidence that, in addition to the presence of antioxidative activity, magnolol is potent in stimulating BKCa channel activity in tracheal smooth muscle cells. The direct stimulation of these BKCa channels by magnolol may contribute to the underlying mechanism by which it acts as an anti-asthmatic compound.

Ceramide Inhibits the Inwardly Rectifying Potassium Current in GH3 Lactotrophs

The effects of ceramide on ion currents in rat pituitary GH(3) cells were investigated. Hyperpolarization-elicited K(+) currents present in GH(3) cells were studied to determine the effect of ceramide and other related compounds on the inwardly rectifying K(+) current (I(K(IR))). Ceramide (C(2)-ceramide) suppressed the amplitude of I(K(IR)) in a concentration-dependent manner, with an IC(50) value of 5 microM. Ceramide caused a rightward shift in the midpoint for the activation curve of I(K(IR)). Pretreatment with PD-98059 (30 microM) or U-0126 (30 microM) did not prevent ceramide-mediated inhibition of I(K(IR)). However, the magnitude of ceramide-induced inhibition of I(K(IR)) was attenuated in GH(3) cells preincubated with dithiothreitol (10 microM). TNF alpha (100 ng/g) also suppressed I(K(IR)). In the inside-out configuration, application of ceramide (30 microM) to the bath slightly suppressed the activity of large conductance Ca(2+)-activated K(+) channels. Under the current clamp mode, ceramide (10 microM) increased the firing of action potentials. Cells that exhibited an irregular firing pattern were converted to those displaying a regular firing pattern after application of ceramide (10 microM). Ceramide also suppressed I(K(IR)) in neuroblastoma IMR-32 cells. Therefore, ceramide can produce a depressant effect on I(K(IR)). The blockade of this current by ceramide may affect cell function.

Rutaecarpine-induced block of delayed rectifier K+ current in NG108-15 neuronal cells

The effects of rutaecarpine on ionic currents of NG108-15 neuronal cells were investigated in this study. Rutaecarpine (2-100 microM) suppressed the amplitude of delayed rectifier K+ current (I(K(DR))) in a concentration-dependent manner. The IC50 value for rutaecarpine-induced inhibition of I(K(DR)) was 11 microM. I(K(DR)) present in these cells is sensitive to the inhibition by quinidine and dendrotoxin, yet not by E-4031. The presence of rutaecarpine enhanced the rate and extent of I(K(DR)) inactivation, although it had no effect on the initial activation phase of I(K(DR)). Recovery from block by rutaecarpine (5 microM) was fitted by a single exponential with a value of 2.87 s. Crossover of tail currents in the presence of rutaecarpine was also observed. Cell-attached single-channel recordings revealed that rutaecarpine decreased channel activity, but it did not alter single-channel amplitude. With the aid of the binding scheme, a quantitative description of the rutaecarpine actions on I(K(DR)) was provided. However, rutaecarpine (20 microM) had no effect on L-type Ca2+ current. Under current-clamp configuration, rutaecarpine prolonged action potential duration in NG108-15 cells. These results show that rutaecarpine is a blocker of the K(DR) channel. The increase in action potential duration induced by rutaecarpine can be explained mainly by its blocking actions on I(K(DR)).

Tamoxifen-induced increases in cytoplasmic free Ca2+ levels in human breast cancer cells.

Tamoxifen has been shown to increase cytoplasmic free Ca2+ levels [Ca2+]i in renal tubular cells and bladder cancer cells, and to alter Ca2+ signaling in MCF-7 breast cancer cells. The present study examined the effect of tamoxifen on [Ca2+]i in ZR-75-1 human breast cancer cells using fura-2 as an indicator. Tamoxifen increased [Ca2+]i at a concentration above 2 μM with an EC50 of 5 μM. Removing extracellular Ca2+ reduced the response by 48 ± 2%. In Ca2+-free medium, after tamoxifen-induced [Ca2+]i increased had returned to baseline, adding 3 mM Ca2+ increased [Ca2+]i in a concentration-dependent manner. Further, pretreatment with 10 μM tamoxifen abolished the [Ca2+]i increase induced by 1 μM thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor); and conversely, pretreatment with thapsigargin prevented tamoxifen from releasing more Ca2+. Tamoxifen (10 μM)-induced Ca2+ release was not changed by inhibiting phospholipase C activity with 2 μM U73122. Trypan blue exclusion assay revealed that tamoxifen (1–10 μM) did not alter viability after 1 min of incubation, but killed 10% of cells after 3–10 min of incubation. Together, this study shows that tamoxifen (>2 μM) induced a significant, immediate increase in [Ca2+]i in ZR-75-1 breast cancer cells. Tamoxifen acted by releasing Ca2+ from the endoplasmic reticulum Ca2+ stores in a manner independent of phospholipase C activity, and by inducing Ca2+ entry from extracellular medium. Tamoxifen may be of mild cytotoxicity after acute exposure.

Mechanisms of histamine-induced intracellular Ca2+ release and extracellular Ca2+ entry in MG63 human osteosarcoma cells

The effect of histamine on intracellular free Ca2+ levels ([Ca2+](i)) in MG63 human osteosarcoma cells was explored using fura-2 as a Ca2+ dye. Histamine increased ([Ca2+](i)) in a concentration-dependent fashion with an EC(50) value of 0.5 microM. Extracellular Ca2+ removal inhibited the ([Ca2+](i)) signals. Histamine failed to increase ([Ca2+](i)) in Ca2+-free medium after cells were pretreated with thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor). Addition of Ca2+ induced concentration-dependent ([Ca2+](i)) increases after preincubation with histamine in Ca2+-free medium. Histamine-induced intracellular Ca2+ release was abolished by inhibiting phospholipase C with 1-(6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione (U73122). The ([Ca2+](i)) increase induced by histamine in Ca2+ medium was abolished by cimetidine, but was not altered by pyrilamine, nifedipine, verapamil, and La(3+). Together, this study shows that histamine increased in ([Ca2+](i)) in osteosarcoma cells by stimulating H2 histamine receptors. The Ca2+ signal was caused by Ca2+ release from the endoplasmic reticulum in a phospholipase C-dependent manner. The Ca2+ release was accompanied by Ca(2+) influx.

Differential effects of quercetin, a natural polyphenolic flavonoid, on L-type calcium current in pituitary tumor (GH3) cells and neuronal NG108-15 cells.

The effects of quercetin, a natural polyphenolic compound, on voltage‐dependent L‐type Ca2+ current (ICa,L) in rat pituitary GH3 cells were investigated with the aid of the whole‐cell voltage‐camp technique. Quercetin (0.5–200 μM) stimulated ICa,L in a concentration‐dependent manner. The current–voltage (I–V) relationship of ICa,L was slightly shifted to more negative potentials in the presence of quercetin. The EC50 value of the quercetin‐induced stimulation of ICa,L was about 7 μM. The presence of quercetin (5 μM) shifted the steady state inactivation curve of ICa,L to a more negative potential by approximately −10 mV. Although quercetin might increase intracellular cyclic AMP, sp‐cAMPS did not affect ICa,L. In addition, neither flavone nor wortmannin had any effect on the amplitude of ICa,L, while epicatechin and genistein slightly suppressed it. Quercetin (50 μM) decreased the amplitude of tetrodotoxin‐sensitive Na+ current in GH3 cells. Under current‐clamp configuration, quercetin could increase the firing frequency of actions potentials. Conversely, in NG108‐15 neuronal cells, quercetin suppressed the amplitude of ICa,L. The quercetin‐induced inhibition of ICa,L was abolished in NG108‐15 cells preincubated with t‐butyl hydroperoxide (1 mM). Quercetin‐mediated stimulation of ICa,L in GH3 cells was presumably not associated with the level of intracellular cyclic AMP, or with the activity of tyrosine or phosphoinositide 3‐kinases. Therefore, the effects of quercetin on ion currents may, at least in part, contribute to the underlying mechanisms through which it affects neuronal or neuroendocrine function.

Impact of nutritional status on long-term functional outcomes of post-acute stroke patients in Taiwan

Nutritional status is important in stroke care, but little is known regarding to the prognostic role of nutritional status on long-term functional outcomes among stroke survivors. The main purpose of this study was to evaluate to the prognostic role of nutritional status on long-term functional outcomes among stroke survivors. Data of acute stroke registry in Kaohsiung Veterans General Hospital were retrieved for analysis. Overall, 483 patients (mean age = 70.7 ± 10.3 years) with first-ever stroke were found. Among them, 95 patients (19.7%) were malnourished at admission, 310 (mean age = 70.4 ± 10.1 years, 63.5% males) survived for 6 months, and 244 (78.7%) had good functional outcomes. Subjects with poor functional outcomes were older (74.7 ± 8.9 vs. 69.0 ± 10.1 years, p < 0.001), more likely to be malnourished (56.2% vs. 26.6%, p < 0.001), to develop pneumonia upon admission (23.3% vs. 12.7%, p = 0.027), had a longer hospital stay (23.5 ± 13.9 vs. 12.5 ± 8.2 days, p < 0.001), had a higher National Institutes of Health Stroke Scale (NIHSS) score (12.9 ± 9.3 vs. 4.9 ± 4.3, p < 0.001), poorer stroke recovery (NIHSS improvement: 6.9% vs. 27.4%, p = 0.005), and poorer functional improvement (Barthel index = BI improvement in the first month: 31.4% vs. 138%, p < 0.001). Older age (odds ratio = OR) = 1.07, 95% confidence interval (CI = 1.03-1.11, p<0.001), baseline NIHSS score (OR = 1.23, 95%CI = 1.15-1.31, p < 0.001) and malnutrition at acute stroke (OR = 2.57, 95%CI: 1.29-5.13, p<0.001) were all independent risk factors for poorer functional outcomes. In conclusion, as a potentially modifiable factor, more attentions should be paid to malnutrition to promote quality of stroke care since the acute stage.

Effect of timosaponin A-III, from Anemarrhenae asphodeloides Bunge (Liliaceae), on calcium mobilization in vascular endothelial and smooth muscle cells and on vascular tension

The effects of timosaponin A-III (TA-III), from Rhizoma Anemarrhenae, on Ca(2+) mobilization in vascular endothelial cells and smooth muscle cells and on vascular tension have been explored. TA-III increased intracellular Ca(2+) concentrations ([Ca(2+)](i)) in endothelials cells at a concentration larger than 5 microM with an EC(50) of 15 microM, and increased [Ca(2+)](i) in smooth muscle cells at a concentration larger than 1 microM with an EC(50) of 8 microM. Within 5 min, the [Ca(2+)](i) signal was composed of a gradual rise, and the speed of rising depended on the concentration of TA-III. The [Ca(2+)](i) signal was abolished by removing extracellular Ca(2+) and was recovered after reintroduction of Ca(2+). The TA-III-induced [Ca(2+)](i) increases in smooth muscle cells were partly inhibited by 10 microM nifedipine or 50 microM La(3+), but was insensitive to 10 microM verapamil and diltiazem. TA-III (10-100 microM) inhibited 0.3 microM phenylephrine-induced vascular contraction, which was abolished by pretreatment with 100 microM N(omega)-nitro-L-arginine (L-NNA) or by denuding the aorta. TA-III also increased [Ca(2+)](i) in renal tubular cells with an EC(50) of 8 microM. Collectively, the results show for the first time that TA-III causes [Ca(2+)](i) increases in the vascular system. TA-III acted by causing Ca(2+) influx without releasing intracellular Ca(2+). TA-III induced relaxation of phenylephrine-induced vascular contraction via inducing release of nitric oxide from endothelial cells.

Urinary incontinence: An under-recognized risk factor for falls among elderly dementia patients†‡

Elderly people with dementia are at increased risk of falls and intervention trials to prevent falls have failed to demonstrate clinical effectiveness in this population. This study evaluates the role of urinary incontinence as a fall risk factor in older patients with dementia, with the aim of developing relevant intervention strategies.