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J K Huang

Publications and source records attributed to J K Huang.

At least 19 recordsLinked to original sources
PubMed2006

Effect of riluzole on Ca2+ movement and cytotoxicity in Madin-Darby canine kidney cells.

Riluzole is a drug used in the treatment of amyotrophic lateral sclerosis; however, its in vitro action is unclear. In this study, the effect of riluzole on intracellular Ca2+ concentration ([Ca2+]i) in Madin-Darby canine kidney (MDCK) cells was investigated using the Ca2+ -sensitive fluorescent dye, fura-2. Riluzole (100-500 microM) caused a rapid and sustained increase of [Ca2+]i in a concentration-dependent manner (EC50 = 150 microM). Some 40 and 50% of this [Ca2+]i increase was prevented by the removal of extracellular Ca2+ and the addition of La3+, respectively, but was unchanged by dihydropyridines, verapamil and diltiazem. In Ca2+ -free medium, thapsigargin - an inhibitor of the endoplasmic reticulum (ER) Caz+ -ATPase--caused a monophasic [Ca2+]i increase, after which the increasing effect of riluzole on [Ca2+]i was attenuated by 70%; in addition, pre-treatment with riluzole abolished thapsigargin-induced [Ca2+]i increases. U73122, an inhibitor of phospholipase C (PLC), abolished ATP (but not riluzole)-induced [Ca2+]i increases. At concentrations of 250 and 500 microM, riluzole killed 40 and 95% cells, respectively. The cytotoxic effect of riluzole (250 microM) was unaltered by pre-chelating cytosolic Ca2+ with BAPTA. Collectively, in MDCK cells, riluzole rapidly increased [Ca2+]i by stimulating extracellular Ca2+ influx via an La3+ -sensitive pathway and intracellular Ca2+ release from the ER via, as yet, unidentified mechanisms. Furthermore, riluzole caused Ca2+ -unrelated cytotoxicity in a concentration-dependent manner.

Animals↗
PubMed2006

Spectral karyotyping and fluorescence in situ hybridization analysis of de novo partial trisomy 7p (7p21.2-->pter) and partial monosomy 12q (12q24.33-->qter).

An 8-year-old boy presenting with hypotonia, moderate mental retardation, developmental delay, and psychomotor retardation is reported. Magnetic resonance imaging of the brain at age 3 years revealed a Dandy-Walker variant. Cytogenetic analysis of the peripheral blood revealed a derivative chromosome 12 with unknown additional material attached to the distal region of the long arm of chromosome 12. The parental karyotypes were normal. Spectral karyotyping (SKY) using the 24-color SKY probes and fluorescence in situ hybridization (FISH) using the specific 7p, 7q, 12p, and 12q telomeric probes confirmed a duplication of distal 7p and a deletion of terminal 12q. The karyotype of the proband was designated as 46,XY.ish der(12)t(7;12) (p21.2;q24. 33)(SKY+, 7pTEL+, 12qTEL-). The present case provides evidence for the association of partial trisomy 7p (7p21.2-->pter) and partial monosomy 12q (12q24.33-->qter) with a cerebellar malformation and the usefulness of SKY and FISH in the identification of a de novo aberrant chromosome resulting from an unbalanced translocation.

Child↗
PubMed2006

Direct transmission of the 18q- syndrome from mother to daughter.

A 34-year-old mother presented moderate mental retardation, short stature, microcephaly, and characteristic facial dysmorphism. Her 12-year-old daughter manifested moderate mental retardation, short stature, microcephaly, dysplastic external ear canals, hearing impairment, and characteristic facial dysmorphism. Cytogenetic analysis of the family revealed a normal karyotype, 46,XY, in the father, and a 46,XX,del(18)(q22.2) karyotype in both mother and daughter. Molecular marker analysis determined direct transmission of the distal 18q deletion from mother to daughter. The present case provides evidence of fertility of the affected females and a mother-to-daughter direct transmission in the familial 18q- syndrome. Identification of affected females with the 18q- syndrome should include genetic counseling of possible direct transmission and consideration of birth control or prenatal genetic testing at reproductive age.

Abnormalities, Multiple↗
PubMed2005

Effect of celecoxib on Ca2+ fluxes and proliferation in MDCK renal tubular cells.

The effect of celecoxib on renal tubular cells is largely unexplored. In Madin Darby canine kidney (MDCK) cells, the effect of celecoxib on intracellular CaCa2+ concentration ([Ca2+]i) and proliferation was examined by using the Ca(2 +)-sensitive fluorescent dye fura-2 and the viability detecting fluorescent dye tetrazolium, respectively. Celecoxib (> or =1 micro M) caused an increase of [CaCa2+]i in a concentration-dependent manner. Celecoxib-induced [CaCa2+]i increase was partly reduced by removal of extracellular CaCa2+. Celecoxib-induced CaCa2+ influx was independently suggested by MnCa2+ influx-induced fura-2 fluorescence quench. In Ca(2 +)-free medium, thapsigargin, an inhibitor of the endoplasmic reticulum Ca(2 +)-ATPase, caused a monophasic [CaCa2+]i increase, after which celecoxib only induced a tiny [CaCa2+]i increase; conversely, pretreatment with celecoxib completely inhibited thapsigargin-induced [CaCa2+]i increases. U73122, an inhibitor of phospholipase C, abolished ATP (but not celecoxib)-induced [CaCa2+]i increases. Overnight incubation with 1 or 10 micro M celecoxib decreased cell viability by 80% and 100%, respectively. These data indicate that celecoxib evokes a [CaCa2+]i increase in renal tubular cells by stimulating both extracellular CaCa2+ influx and intracellular CaCa2+ release and is highly toxic to renal tubular cells in vitro.

Animals↗
PubMed2005

Econazole induces increases in free intracellular Ca2+ concentrations in human osteosarcoma cells.

Econazole is an antifungal drug with different in vitro effects. However, econazole's effect on osteoblast-like cells is unknown. In human MG63 osteosarcoma cells, the effect of econazole on intracellular Ca2+ concentrations ([Ca2+]i) was explored by using fura-2. At a concentration of 0.1 microM, econazole started to cause a rise in [Ca2+]i in a concentration-dependent manner. Econazole-induced [Ca2+]i rise was reduced by 74% by removal of extracellular Ca2+. The econazole-induced Ca2+ influx was mediated via a nimodipine-sensitive pathway. In Ca2+ -free medium, thapsigargin, an inhibitor of the endoplasmic reticulum Ca+ -ATPase, caused a [Ca2+]i rise, after which the increasing effect of econazole on [Ca2+]i was abolished. Pretreatment of cells with econazole to deplete Ca2+ stores totally prevented thapsigargin from releasing Ca2+. U73122, an inhibitor of phospholipase C, abolished histamine (an inositol 1,4,5-trisphosphate-dependent Ca2+ mobilizer)-induced, but not econazole-induced, [Ca2+]i rise. Econazole inhibited 76% of thapsigargin-induced store-operated Ca2+ entry. These findings suggest that in MG63 osteosarcoma cells, econazole increases [Ca2+]i by stimulating Ca2+ influx and Ca2+ release from the endoplasmic reticulum via a phospholipase C-independent manner. In contrast, econazole acts as a potent blocker of store-operated Ca2+ entry.

Antifungal Agents↗
PubMed2004

De novo satellited 21q associated with corpus callosum dysgenesis, colpocephaly, a concealed penis, congenital heart defects, and developmental delay.

De novo satellited 21q associated with corpus callosum dysgenesis, colpocephaly, a concealed penis, congenital heart defects, and developmental delay: We present clinical and cytogenetic data on an infant with de novo satellited 21 q. A 3-month-old boy was found to have microcephaly, developmental delay, hypertelorism, down-slanting palpebral fissures, large low-set ears, a prominent nose, a broad philtrum, a concealed penis, interventricular septal defects, corpus callosum dysgenesis, colpocephaly, ventriculomegaly, and a de novo karyotype of 46,XY,21qs. Standard Ag-NOR staining and FISH studies confirmed a satellite and a deletion on the long arm of a chromosome 21. Quantitative-fluorescent polymerase chain reaction using the polymorphic small tandem repeat markers specific for chromosome 21 determined a maternal origin of the deletion and the breakpoint between D21S156 (21q22.1) (present) and D21S53 (21q22.3) (absent), centromeric to the known minimal holoprosencephaly critical region, D21S13-21qter. The present case provides evidence of the correlation of a distal region of chromosome 21 to the phenotypic effects of monosomy 21.

Abnormalities, Multiple↗
PubMed2002

Effect of triethyltin on Ca2+ movement in Madin-Darby canine kidney cells.

The effects of the environmental toxicant, triethyltin, on Ca2+ mobilization in Madin-Darby canine kidney (MDCK) cells have been examined. Triethyltin induced an increase in cytosolic free Ca2+ levels ([Ca2+]i) at concentrations larger than 2 microM in a concentration-dependent manner. Within 5 min, the [Ca2+]i signal was composed of a gradual rise and a sustained phase. The [Ca2+]i signal was partly reduced by removing extracellular Ca2+. In Ca(2+)-free medium, pretreatment with thapsigargin (1 microM), an endoplasmic reticulum Ca2+ pump inhibitor, reduced 50 microM triethyltin-induced [Ca2+]i increase by 80%. Conversely, pretreatment with triethyltin abolished thapsigargin-induced Ca2+ release. Pretreatment with U73122 (2 microM) to inhibit phospholipase C-coupled inositol 1,4,5-trisphosphate formations failed to alter 50 microM triethyltin-induced Ca2+ release. Incubation with triethyltin at a concentration (1 microM) that did not increase basal [Ca2+]i for 3 min did not alter ATP (10 microM)- and bradykinin (1 microM)-induced [Ca2+]i increases. Collectively, this study shows that triethyltin altered Ca2+ movement in renal tubular cells by releasing Ca2+ from multiple stores in an inositol 1,4,5-trisphosphate-independent manner, and by inducing Ca2+ influx.

Animals↗
PubMed2001

The presynaptic particle web: ultrastructure, composition, dissolution, and reconstitution.

We report the purification of a presynaptic "particle web" consisting of approximately 50 nm pyramidally shaped particles interconnected by approximately 100 nm spaced fibrils. This is the "presynaptic grid" described in early EM studies. It is completely soluble above pH 8, but reconstitutes after dialysis against pH 6. Interestingly, reconstituted particles orient and bind PSDs asymmetrically. Mass spectrometry of purified web components reveals major proteins involved in the exocytosis of synaptic vesicles and in membrane retrieval. Our data support the idea that the CNS synaptic junction is organized by transmembrane adhesion molecules interlinked in the synaptic cleft, connected via their intracytoplasmic domains to the presynaptic web on one side and to the postsynaptic density on the other. The CNS synaptic junction may therefore be conceptualized as a complicated macromolecular scaffold that isostatically bridges two closely aligned plasma membranes.

Animals↗
PubMed2001

Mechanism of bifonazole-induced [Ca2+]i increases in MDCK renal tubular cells.

The effect of the antifungal drug bifonazole on Ca2+ homeostasis in Madin Darby canine kidney (MDCK) cells was investigated. Cell suspensions were loaded with the Ca2+-sensitive dye fura-2, and the fluorescence changes were measured with a spectrofluorophotometer. At concentrations between 10-80 microM bifonazole increased cytosolic free Ca2+ levels ([Ca2+]i) in a concentration-dependent manner. The Ca2+ signals were partly inhibited by removing extracellular Ca2+. Bifonazole (40 microM) released Ca2+ from the store sensitive to 1 microM thapsigargin, an endopolasmic reticulum Ca2+ pump inhibitor. Bifonazole (40 microM) per se induced capacitative Ca2+ entry while reduced 1 microM thapsigargin-induced capacitative Ca2+ entry. Inositol 1,4,5-trisphosphate may be involved in bifonazole-induced Ca2+ release because inhibiting phospholipase C with 2 microM U73122 partly reduced the bifonazole response. Together, bifonazole increased [Ca2+]i in renal tubular cells by inducing intracellular Ca2+ release and extracellular Ca2+ influx.

Adenosine Triphosphate↗
PubMed2001

Mechanisms of diethylstilbestrol-induced calcium movement in MG63 human osteosarcoma cells.

The effect of the estrogen diethylstilbestrol (DES) on cytosolic free Ca(2+) levels ([Ca(2+)](i)) in MG63 human osteoblasts was explored by using fura-2 as a Ca(2+) indicator. DES at concentrations between 5--20 microM induced an immediate increase in [Ca(2+)](i) in a concentration-dependent manner with an EC(50) of 10 microM. Removing extracellular Ca(2+) reduced the Ca(2+) signal by 70%. Pretreatment with 50 microM La(3+) or 10 microM of nifedipine, verapamil and diltiazem did not change 20 microM DES-induced [Ca(2+)](i) increases. Addition of 3 mM Ca(2+) increased [Ca(2+)](i) in cells pretreated with 20 microM DES in Ca(2+)-free medium. Pretreatment with 1 microM thapsigargin (an endoplasmic reticulum Ca(2+) pump inhibitor) to deplete the endoplasmic reticulum Ca(2+) store partly inhibited 20 microM DES-induced Ca(2+) release, but addition of carbonylcyanide m-chlorophenylhydrazone (CCCP; a mitochondrial uncoupler) and thapsigargin together abolished DES-induced Ca(2+) release. Conversely, pretreatment with 20 microM DES abrogated CCCP- and thapsigargin-induced Ca(2+) release. Inhibition of phospholipase C activity with 2 microM U73122 did not alter 20 microM DES-induced Ca2+ release. Another estrogen 17beta-estradiol also increased [Ca(2+)](i) in a concentration-dependent manner with an EC50 of 7 microM. Together, the data indicate that in human osteoblasts, DES increased [Ca(2+)](i) via causing Ca(2+) release from both mitochondria and the endoplasmic reticulum in a phospholipase C-independent manner, and by causing Ca(2+) influx.

Calcium↗
PubMed2001

Mechanism of estrogens-induced increases in intracellular Ca(2+) in PC3 human prostate cancer cells.

BACKGROUND: The effect of estrogens (diethylstilbestrol [DES], 17 beta-estradiol) on intracellular Ca(2+) concentrations ([Ca(2+)](i)) in hormone-insensitive PC3 human prostate cancer cells was examined. METHODS: [Ca(2+)](i) changes in suspended cells were measured by using the Ca(2+)-sensitive fluorescent dye fura-2. RESULTS: Estrogens (1--20 microM) increased [Ca(2+)](i) concentration-dependently with DES being more potent. Ca(2+) removal inhibited 50 +/- 10% of the signal. In Ca(2+)-free medium, pretreatment with 20 microM estrogens abolished the [Ca(2+)](i) increases induced by 2 microM carbonylcyanide m-chlorophenylhydrazone (CCCP, a mitochondrial uncoupler) and 1 microM thapsigargin (an endoplasmic reticulum Ca(2+) pump inhibitor), but pretreatment with CCCP and thapsigargin did not alter DES-induced Ca(2+) release and partly inhibited 17 beta-estradiol-induced Ca(2+) release. Addition of 3 mM Ca(2+) increased [Ca(2+)](i) in cells pretreated with 1- 20 microM estrogens in Ca(2+)-free medium. Pretreatment with 1 microM U73122 to block phospholipase C-coupled inositol 1,4,5-trisphosphate formation did not alter estrogens-induced Ca(2+) release. The effect of 20 microM estrogen on [Ca(2+)](i) was not affected by pretreatment with 0.1 microM estrogens. CONCLUSIONS: Estrogen induced significant Ca(2+) release and Ca(2+) influx in an inositol 1,4,5-trisphosphate-independent manner in PC3 cells. These effects of estrogens on Ca(2+) signaling appear to be nongenomic. Prostate 47:141-148, 2001.

Antineoplastic Agents, Hormonal↗
PubMed2001

Linoleamide, a brain lipid that induces sleep, increases cytosolic Ca2+ levels in MDCK renal tubular cells.

Linoleamide is an endogenous lipid that has been shown to induce sleep in cats, rats and humans. However, its physiological function remains unclear. In this study the effect of linoleamide on cytosolic free Ca2+ concentrations ([Ca2+]i) in Madin Darby canine kidney (MDCK) tubular cells was examined, by using fura-2 as a Ca2+ probe. In a concentration-dependent manner, linoleamide induced increases in [Ca2+]i between 10-500 microM with an EC50 of 20 microM. The signal comprised a slow rise and a persistent phase, and was a result of internal Ca2+ release and external Ca2+ influx because it was partly inhibited by external Ca2+ removal. In Ca2+-free medium, depletion of the endoplasmic reticulum Ca2+ store with 1 microM thapsigargin abolished 100 microM linoleamide-induced internal Ca2+ release, and conversely, pretreatment with linoleamide prevented thapsigargin from releasing internal Ca2+. This demonstrates that the internal source of linoleamide-induced [Ca2+]i increase is located in the endoplasmic reticulum. This discharge of internal Ca2+ caused capacitative Ca2+ entry because after incubation with 100 microM linoleamide in Ca2+-free medium for 8 min readmission of 3 mM CaCl2 induced increases in [Ca2+]i. After the formation of inositol-1,4,5-trisphosphate (IP3) was blocked by the phospholipase C inhibitor U73122 (1 microM), linoleamide still induced an increase in [Ca2+]i but the shape of the increase was altered. Similar results were found for another sleep-inducing lipid 9,10-octadecenoamide. Together, the present study shows that the endogenous sleep-inducing lipid linoleamide was able to cause significant increases in [Ca2+]i in renal tubular cells, by releasing the endoplasmic reticulum Ca2+ store and triggering capacitative Ca2+ entry in a manner independent of IP3.

Animals↗
PubMed2001

Mechanism underlying histamine-induced intracellular Ca2+ movement in PC3 human prostate cancer cells.

The effect of histamine on intracellular free Ca2+ levels ([Ca2+]i) in PC3 human prostate cancer cells and the underlying mechanism were evaluated using fura-2 as a Ca2+ dye. Histamine at concentrations between 0.1 and 50 microM increased [Ca2+]i in a concentration-dependent manner with an EC50 value of 1 microM. The [Ca2+]i response comprised an initial rise and a slow decay, which returned to baseline within 3 min. Extracellular Ca2+ removal inhibited 50% of the [Ca2+]i signal. In the absence of extracellular Ca2+, after cells were treated with 1 microM thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor), 10 microM histamine did not increase [Ca2+]i. After pretreatment with 10 microM histamine in a Ca2+-free medium for several minutes, addition of 3 mM Ca2+ induced [Ca2+]i increases. Histamine (10 microM)-induced intracellular Ca2+ release was abolished by inhibiting phospholipase C with 2 microM 1-(6-((17 beta-3- methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione (U73122), and by 10 microM pyrilamine but was not altered by 50 microM cimetidine. Collectively, the present study shows that histamine induced [Ca2+]i transients in PC3 human prostate cancer cells by stimulating H1 histamine receptors leading to Ca2+ release from the endoplasmic reticulum in an inositol 1,4,5-trisphosphate-dependent manner, and by inducing Ca2+ entry.

Calcium↗
PubMed2001

Tamoxifen-induced Ca2+ mobilization in bladder female transitional carcinoma cells.

This study examined the effect of tamoxifen, an anti-breast cancer drug, on Ca2+ handling in bladder female transitional cancer cells. Changes in cytosolic free Ca2+ levels were recorded by using the Ca2+-sensitive dye fura-2. In a dose-dependent manner, tamoxifen induced intracellular free Ca2+ concentrations ([Ca2+]i) increases between 5 and 20 microM with an EC50 of 10 microM. External Ca2+ removal reduced the response by 60+/-6%. Addition of 3 mM Ca2+ caused a [Ca2+]i increase after pretreatment with 10 microM tamoxifen in Ca2+-free medium. In Ca2+-free medium, pretreatment with 10 microM tamoxifen abolished the [Ca2+]i increase induced by 1 microM thapsigargin, an endoplasmic reticulum Ca2+ pump inhibitor. Conversely, pretreatment with 1 microM thapsigargin prevented tamoxifen from releasing more Ca2+. Inhibition of phospholipase C-dependent inositol 1,4,5-tris-phosphate formation with 2 microM U73122 did not alter 10 microM tamoxifen-induced Ca2+ release. The [Ca2+]i increase induced by 5 microM tamoxifen was not altered by 10 microM La3+, nifedipine, verapamil, and diltiazem. Collectively, it was found that tamoxifen increased [Ca2+]i in bladder cancer cells by releasing Ca2+ from the endoplasmic reticulum Ca2+ stores in a manner independent of phospholipase C activity, and by inducing Ca2+ entry from external medium.

Anticarcinogenic Agents↗
PubMed2001

Fluoxetine-induced Ca2+ signals in Madin-Darby canine kidney cells.

The effect of fluoxetine on Ca2+ signaling in Madin-Darby canine kidney (MDCK) cells was investigated by using fura-2 as a Ca2+ probe. Fluoxetine increased [Ca2+]i concentration-dependently between 5 microM and 200 microM with an EC50 value of 40 microM. The response was reduced by external Ca2+ removal by 30%40%. In Ca2+-free medium pretreatment with 1 microM thapsigargin, an inhibitor of the endoplasmic reticulum Ca2+ pump, abolished 100 microM fluoxetine-induced Ca2+ release. Addition of 3 mM Ca2+ to Ca2+-free medium increased [Ca2+]i when cells were pretreated with 100 microM fluoxetine. Suppression of 1,4,5-trisphosphate (IP3) formation by 2 microM U73122 (a phospholipase C inhibitor) did not affect 100 microM fluoxetine-induced Ca2+ release. Fluoxetine (5-100 microM) also increased [Ca2+]i in neutrophils, prostate cancer cells and bladder cancer cells from human and rat glioma cells.

Adenosine Triphosphate↗
PubMed2001

Fendiline, an anti-anginal drug, increases intracellular Ca2+ in PC3 human prostate cancer cells.

BACKGROUND: The effects of the anti-anginal drug fendiline on intracellular Ca2+ concentrations ([Ca2+]i) in human PC3 prostate cancer cells were examined. METHODS: [Ca2+]i was measured using the fluorescent dye fura-2. RESULTS: Fendiline (0.5-100 microM) increased [Ca2+]i in a concentration-dependent manner. Ca2+ removal partly inhibited the Ca2+ signals. In Ca2+-free medium, pretreatment with 100 microM fendiline inhibited most of the [Ca2+]i increase induced by 1 microM thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor), and pretreatment with thapsigargin abolished the fendiline-induced [Ca2+]i increases. Adding 3 mM Ca2+ increased [Ca2+]i in cells pretreated with 0.5-200 microM fendiline in Ca2+-free medium. Pretreatment with 1 microM U73122 to block the formation of inositol-1.4.5-trisphosphate (IP3) did not alter fendiline-induced internal Ca2+ release. CONCLUSIONS: The anti-anginal drug fendiline induced internal Ca2+ release and external Ca2+ entry. Because prolonged increases in [Ca2+]i may lead to cell injury and death, the long-term effect of fendiline on the function of prostate cancer cells should be investigated.

Adenosine Triphosphate↗
PubMed2001

Organizing principles of the axoglial apparatus.

On axonal surfaces that flank the node of Ranvier and in overlying glial paranodal loops, proteins are arranged within circumscribed microdomains that defy explanation by conventional biosynthetic mechanisms. We postulate that the constraint of proteins to these loci is accomplished in part by discriminative membrane-embedded molecular sieves and diffusion barriers, which serve to organize and redistribute proteins after delivery by vesicular transport to neural cell plasma membranes. One sieve likely comprises a moveable, macromolecular scaffold of axonal and glial cell-derived transmembrane adhesion molecules and their associated cytoplasmic binding partners, located at the ends of each elongating myelin internode; this sieve contributes to restricting the sodium channel complexes to the node. We also anticipate the existence of a passive paranodal diffusion barrier at the myelin/noncompact membrane border, which prohibits protein diffusion out of contiguous paranodal membranes.

Animals↗