Biomedical subjects

Fenghua Li

Publications and source records attributed to Fenghua Li.

10 recordsLinked to original sources

PubMed2006

Synthesis, characterization and biological activity of complexes of lanthanum(III) with 2-(1'-phenyl- 2'-carboxyl-3'-aza-n-butyl)-1,10-phenanthroline and 2-(1'-p-phenol-2'-carboxyl-3'-aza-n-butyl)-1,10-phenanthroline.

Two novel ligands 2-(1'-phenyl-2'-carboxyl-3'-aza-n-butyl)-1,10-phenanthroline (L1) and 2-(1'-p-phenol-2'-carboxyl-3'-aza-butyl)-1,10-phenanthroline (L2), and their La(III) complexes of La(III)L1, La(III)(L1)(2), La(III)L2, and La(III)(L2)(2), were synthesized and characterized by (1)H NMR, elemental analysis, IR, thermal analysis and conductance measurement. All complexes have been assayed for anticancer activity in vitro against HL-60 (human leukocytoma) cells, PC-3MIE8 (human prostate carcinoma) cells, BGC-823 (human stomach carcinoma) cells, MDA-MB-435 (human galactophore carcinoma) cells, Bel-7402 (human liver carcinoma) cells, and HeLa (human cervix carcinoma) cells. Results showed that the two complexes La(III)L1 and La(III)(L1)(2) exhibited good cytotoxic activity against different cell lines in general; and La(III)(L1)(2) is more effective than cisplatin against all six cell lines. DNA-binding studies indicated that, besides the intercalation, the complexes bind to DNA by the other interaction(s).

Aza Compounds↗

PubMed2006

Orientational coupling amplification in ferroelectric nematic colloids.

We investigated the physical properties of low concentration ferroelectric nematic colloids, using calorimetry, optical methods, infrared spectroscopy, and capacitance studies. The resulting homogeneous colloids possess a significantly amplified nematic orientational coupling. We find that the nematic orientation coupling increases by approximately 10% for particle concentrations of 0.2%. A manifestation of the increased orientational order is that the clearing temperature of a nematic colloid increases by up to 40 degrees C compared to the pure liquid crystal host. A theoretical model is proposed in which the ferroelectric particles induce local dipoles whose effective interaction is proportional to the square of the orientational order parameter.

Journal Article↗

PubMed2005

Relative abundance of alpha2 Na(+) pump isoform influences Na(+)-Ca(2+) exchanger currents and Ca(2+) transients in mouse ventricular myocytes.

In the mouse, genetic reduction in the Na(+), K(+)-ATPase alpha1 or alpha2 isoforms results in different functional phenotypes: heterozygous alpha2 isolated hearts are hypercontractile, whereas heterozygous alpha1 hearts are hypocontractile. We examined Na(+)/Ca(2+) exchange (NCX) currents in voltage clamped myocytes (pipette [Na(+)]=15 mM) induced by abrupt removal of extracellular Na(+). In wild-type (WT) myocytes, peak exchanger currents were 0.59+/-0.04 pA/pF (mean+/-S.E.M., n=10). In alpha1(+/-) myocytes (alpha2 isoform increased by 54%), NCX current was reduced to 0.33+/-0.05 (n=9, P<0.001) indicating a lower subsarcolemmal [Na(+)]. In alpha2(+/-) myocytes (alpha2 isoform reduced by 54%), the NCX current was increased to 0.89+/-0.11 (n=8, P=0.03). The peak sarcolemmal Na(+) pump currents activated by abrupt increase in [K(+)](o) to 4 mM in voltage clamped myocytes in which the Na(+) pump had been completely inhibited for 5 min by exposure to 0 [K(+)](o) were similar in alpha1(+/-) (0.86+/-0.12, n=10) and alpha2(+/-) myocytes (0.94+/-0.08 pA/pF, n=16), and were slightly but insignificantly reduced relative to WT (1.03+/-0.05, n=24). The fluo-3 [Ca(2+)](i) transient (F/F(o)) in WT myocytes paced at 0.5 Hz was 2.18+/-0.09, n=34, was increased in alpha2(+/-) myocytes (F/F(o)=2.56+/-0.14, n=24, P=0.02), and was decreased in alpha1(+/-) myocytes (F/F(o)=1.93+/-0.08, n=28, P<0.05). Thus the alpha2 isoform rather than the alpha1 appears to influence Na(+)/Ca(2+) exchanger currents [Ca(2+)](i) transients, and contractility. This finding is consistent with the proposal that alpha2 isoform of the Na pump preferentially alters [Na(+)] in a subsarcolemmal micro-domain adjacent to Na(+)/Ca(2+) exchanger molecules and SR Ca(2+) release sites.

Animals↗

PubMed2004

Catalysis of phosphoryl transfer from adenosine-5'-triphosphate (ATP) by trinuclear "chelate" complexes.

The chelate ligand 2,9-di(6'-alpha-phenol-n-2',5'-diazahexyl)-1,10-phenanthroline (L) was synthesized and fully characterized. This ligand formed six protonated species in the solution. The bindings of the ligand to the nucleotide anions ATP, ADP and AMP were described in detail, with equilibrium constants given for each species formed. The strength of binding increased with the number of protons, corresponding to an increase in the number of hydrogen bonds and an increase in the coulombic attractive forces. At the same time, the coordination properties of the ternary complexes formed from the chelate ligand above, M (M=Zn(2+), Cd(2+)) and adenosine-5'-triphosphate (ATP) were studied. The metal complexes of the chelate recognize the nucleotides via multiple interactions similar to those occurring in the center of enzymes. The hydrolysis of ATP was studied with the mononuclear and trinuclear chelate complexes.

Adenosine Triphosphate↗

PubMed2004

[Induction and culture of hairy-root by Agrobacteriun rhizogenes in Dendrobium nobile].

OBJECTIVE: To obtain the hairy-roots of Dendrobium nobile. METHODS: The hairy-root were obtained by infecting different explants with Agrobacteriun rhizogenes A4 and culture conditions of hariy root were optimized. RESULT: The best conditions of hairy root culture were 1/2MS medium with sucrose (3%) as carbon material and lactalbumin hydrolyze (1g/L) as nitron material.

Alkaloids↗

PubMed2003

Saxitoxin blocks L-type ICa.

Saxitoxin (STX) and tetrodotoxin (TTX) are frequently used to selectively block sodium channels. In this study, we provide evidence that commercial STX also inhibits L-type Ca2+ currents (I(Ca,L)) in adult mouse ventricular myocytes (VMs) and tsA-201 cells that were transiently cotransfected with three calcium channel subunits. We measured inhibition of sodium currents (INa) in mouse VMs, of I(Ca,L) in mouse VM and tsA-201 cells, and intracellular calcium concentration ([Ca2+]i) transients in single mouse VMs. STX or TTX was abruptly applied before the test voltage pulse using a rapid solution switcher device. STX (10 microM; Calbiochem) and TTX (60 microM; Sigma-Aldrich) completely blocked INa in mouse VMs. However, STX at 10 microM also reduced I(Ca,L) in mouse VM by 39% (P < 0.0001; n = 14), whereas TTX at 60 microM had no effect on I(Ca,L). STX (10 microM; Calbiochem) reduced the amplitude of the [Ca2+]i transients in mouse VMs by 36% (P < 0.0001; n = 10). In contrast, TTX (60 microM; Sigma-Aldrich) only reduced the amplitude of the [Ca2+]i transients by 9% (P = 0.003; n = 5). STX (10 microM) obtained from Sigma-Aldrich showed a similar inhibitory effect on I(Ca,L) (33%) (P < 0.0001; n = 5) in mouse VMs. STX (Calbiochem) inhibited the calcium currents of tsA-201 cells in a dose-dependent manner. This inhibition was voltage-independent. The current-voltage relationship of calcium currents in tsA-201 cells was not altered by STX. These results indicate that STX partially blocks L-type Ca2+ channels and thus provide further evidence that its effects are not specific for Na+ channels.

Animals↗

PubMed2003

Comparison of sarcoplasmic reticulum Ca2+-ATPase function in human, dog, rabbit, and mouse ventricular myocytes.

It has been reported that sarcoplasmic reticulum (SR) Ca(2+) uptake is more rapid in rat than rabbit ventricular myocytes, but little information is available on the relative SR Ca(2+) uptake activity in others species, including humans. We induced Ca(2+) transients with a short caffeine pulse protocol (rapid solution switcher, 10 mM caffeine, 100 ms) in single ventricular myocytes voltage clamped (-80 mV) with pipettes containing 100 microM fluo-3 and nominal 0 Ca(2+), in 0 Na(+)(o)/0 Ca(2+)(o) solution to inhibit Na/Ca exchange. SR in non-paced human, dog, rabbit, and mouse ventricular myocytes could be readily loaded with Ca(2+) under our experimental conditions with a pipette [Ca(2+)] = 100 nM. Resting [Ca(2+)](i) was similar in four types of ventricular myocytes. Activation of the Ca(2+)-release channel with a 100-ms caffeine pulse produced a rise in [caffeine](i) to slightly above 2 mM, the threshold for caffeine activation of Ca(2+) release. This caused a similar initial rate of rise and peak [Ca(2+)](i) in the four types of ventricular myocytes. However, there were significant differences in the duration of the plateau (top 10%) [Ca(2+)](i) transients and the time constant of the [Ca(2+)](i) decline (reflecting activity of the SR Ca(2+)-ATPase), with values for human > dog > rabbit > mouse. In paced myocytes under physiologic conditions, SR Ca(2+) content was greater in mouse than in rabbit myocytes, while peak I(Ca,L) was smaller in mouse. These findings confirm substantial species difference in SR Ca(2+)-ATPase activity, and suggest that the smaller the animal and the more rapid the heart rate, greater the activity of the SR Ca(2+)-ATPase. In addition, it appears that substantial species differences exist in the degree of SR Ca(2+) loading and I(Ca,L) under physiologic conditions.

Animals↗

PubMed2003

Ca2+ sparks induced by Na/Ca exchange.

Whether Ca(2+) influx on the Na/Ca exchanger (NCX) can trigger elementary sarcoplasmic reticulum (SR) Ca(2+) release events (Ca(2+) sparks) is controversial. We imaged [Ca(2+)](i) (Nipkow confocal microscope and fluo-3) in left ventricular myocytes isolated from wild type (WT) and transgenic (TG) mice overexpressing NCX 2.5-fold. Sudden activation of Ca(2+) influx via NCX induced by abrupt exposure to "0" [Na(+)](o)/normal [Ca(2+)](o) solution by means of a rapid solution switcher-induced Ca(2+) sparks in NCX TG myocytes in 425+/-17 ms, n=21. The diameter and amplitude (F/F(0)) of these sparks (2.74+/-0.14 microm, F/F(0)=2.16+/-0.06, n=18) were similar to those induced by field stimulation of myocytes in the presence of 20 microM nifedipine (2.70+/-0.10 microm, F/F(0)=1.98+/-0.08, n=17). In WT myocytes no Ca(2+) sparks were observed within the first 600 ms after abrupt removal of extracellular Na. In parallel experiments, voltage clamp current measurements (-80 mV) showed that the Na/Ca exchange current (I(NCX)) began within 60 ms of activation of the switcher, and peaked at 312+/-57 pA in TG myocytes within 300-500 ms. I(Ca,L) in 20 microM nifedipine was 10.3+/-4.3 pA, n=7. These results indicate that Ca(2+) entering the myocyte via NCX can cause Ca(2+) sparks which are similar to those elicited by electrical stimulation. However, Ca(2+) influx on NCX is much less efficient in inducing Ca(2+) sparks than Ca(2+) influx via I(Ca,L).

Animals↗

PubMed2003

Effects of FK506 on [Ca2+]i differ in mouse and rabbit ventricular myocytes.

FK506 binding proteins (FKBPs 12 and 12.6) interact with ryanodine receptor (RyR) and modulate its functions. FK506 binds to and reverses effects of FKBP on RyR, thus increasing RyR sensitivity to Ca2+, decreasing RyR cooperativity, and increasing RyR open probability. FK506 would thus be expected to have an effect on excitation-contraction coupling, but which of these FK506 effects predominates and how the [Ca2+]i transient would be altered are difficult to predict. FK506 has been reported to increase the [Ca2+]i transient in rat myocytes, but effects in other species have not been described. We compared the effects of FK506 on [Ca2+]i transients, L-type Ca2+ channel and Na/Ca exchange currents, membrane potential, and sarcoplasmic reticulum (SR) Ca2+ content in adult mouse and rabbit ventricular myocytes (VM). FK506 (10 microM) increased the [Ca2+]i transient in mouse VM (656 +/- 116 to 945 +/- 144 nM, p < 0.001) but decreased the amplitude of [Ca2+]i transients in rabbit VM (627 +/- 61 to 401 +/- 37 nM, p < 0.001). Similar effects were observed with rapamycin. The effects of FK506 and rapamycin on [Ca2+]i transients in VM of both species were reversible upon washout. FK506 did not alter SR Ca2+ content in mouse VM (0.79 +/- 0.1 versus 0.78 +/- 0.1 pC/pF) but reduced the SR Ca2+ content in rabbit VM (0.43 +/- 0.05 versus 0.30 +/- 0.04 pC/pF, P < 0.05) [pC = the integral (pA. s) of the caffeine-induced inward I(Na/Ca) normalized by cell capacitance (pF)]. FK506 had no effects on membrane potential, I(Ca,L) and outward I(Na/Ca) in either mouse or rabbit VM. These results indicate that alteration of the functions of RyR by FK506-mediated dissociation of FKBP from RyR has different species-dependent effects on SR Ca2+ load and thus [Ca2+]i transients. This difference may result from the fact that [Na+]i is low in rabbit myocytes, allowing extrusion by Na+/Ca2+ exchange of Ca2+ released by FK506-induced dissociation of FKBP12.6 from SR RyR.

Animals↗

PubMed2002

[Role of hepatic sinusoidal endothelium injury in hepatic fibrogenesis induced by dimethylnitrosamine in rats].

OBJECTIVE: To study the role of hepatic sinusoidal endothelium injury during hepatic fibrogenesis induced by dimethylnitrosamine (DMN) in rats. METHODS: Hepatic fibrosis of rats was induced by administration of DMN intraperitoneally three times a week for 4 weeks. The animals were harvested on day 2 and week 1, 2, 3, 4, 5, 6, 8, 12, and 24. The formation of liver fibrosis and hepatic sinusoid capillarization were successively observed by morphological observation and other methods. RESULTS: Two days after treated with DMN, there was no obvious changes in the liver, but the fenestration of the sinusoidal endothelial cells decreased, and it became more obvious after one week. After four weeks, there was a large necrotic area and a number of pseudolobes appeared. The HA in the serum was lower than that of control (231.30 ng/ml +/- 143.80 ng/ml vs 56.50 ng/ml +/- 18.10 ng/ml; t=3.14, P<0.05), but the hydroxyproline content was obviously higher than that of control (223.04 microg/g +/- 37.09 microg/g vs 61.55 microg/g +/- 20.85 microg/g; t=8.28, P<0.05). Hepatic sinusoid capillarization was gradually formed and defenestration of the hepatic sinusoidal endothelium preceded the appearance of serious hepatocellular damage, hepatic fibrosis and basement membrane. CONCLUSIONS: The damage and phenotypic alteration of the hepatic sinusoidal endothelium may be a vital issue triggering the liver fibrosis induced by DMN.

Actins↗