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Biomedical subjects

J F Lu

Publications and source records attributed to J F Lu.

At least 19 recordsLinked to original sources
PubMed2001

Antioxidant properties of phenolic diterpenes from Rosmarinus officinalis.

AIM: To investigate the inhibition capacities of carnosol, rosmanol, and epirosmanol, which are phenolic diterpenes from Rosmarinus officinalis, to oxidized low-density lipoprotein (LDL) formation in human blood and detect their scavenging activities to lipid free radical and superoxide anion in vitro. METHODS: The antioxidant activities which were expressed with the inhibilities to lipid free radicals in the membrane lipid of cell and oxidized LDL formation were evaluated by TBARS assay and ESR method. The inhibition on the Cu2+-mediated oxidization of apo B formation in LDL was investigated by fluorescence spectroscopy. RESULTS: Carnosol, rosmanol, and epirosmanol had an inhibitory activity to lipid peroxidation and oxidized apo B formation in human bloods LDL. The IC50 were 7-10 micromol/L. The antioxidant mechanism was related to the scavenging activities to lipid free radical. CONCLUSION: carnosol, rosmanol, and epirosmanol showed the activity in inhibiting LDL oxidation.

Abietanes↗
PubMed2000

Arsenite, arsenate and vanadate affect human erythrocyte membrane.

Effects of arsenite, arsenate and vanadate on human erythrocyte membrane have been assessed according to their routes passing through the membrane, their binding modes to the membrane and their influences on membrane proteins and lipids. The uptake of arsenate (1.0 mM) by cells approached a limit with intracellular arsenic of about 0.2 mM in 5 h, and was strongly inhibited (approximately 95%) by 4,4'-diisothiocyano-2,2'-disulfonic stilbene (DIDS), indicating that arsenate, similar to vanadate, passed across the membrane through the anion exchange protein, band 3. Arsenite (1.0 mM) influx reached a maximum of about 0.4 mM in 30 min, and was not inhibited by DIDS. The transformed species of arsenite bound to the membrane from cytosol. In contrast, arsenate bound rapidly from the outside, followed by releasing and re-binding. The binding to the membrane via sulfhydryl was indicated by the decrease of the sulfhydryl level of membrane proteins. Polyacrylamide gel electrophoresis in sodium dodecyl sulfate (SDS-PAGE) analysis revealed that the proteins, bands 1-3, were among the targets of arsenite, arsenate and vanadate. Their binding to the membrane also induced changes in the fluidity of membrane lipids and in the negative charge density in the outer surface of the membrane.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed2000

Population pharmacokinetics of tobramycin in hospitalized patients receiving once-daily dosing regimen.

The population pharmacokinetics of tobramycin was investigated in a group of 327 adult hospitalized patients receiving once-daily administration of tobramycin at a dose of 7 mg kg(-1). The patients had an average age of 57+/-18 y and an average weight of 65+/-14 kg; 153 of the patients were female. Data, comprised of 575 serum concentrations, were analyzed using a nonlinear mixed-effect model (NONMEM) with a first-order conditional estimation method and were best described with a one-compartment model. The patient covariates including body weight, gender, age and creatinine clearance (CL(CR)) were added in a stepwise fashion to identify their potential influences on tobramycin pharmacokinetics. Results showed that tobramycin clearance (CL) was linearly correlated with CL(CR) (proportionality constant: 0.066+/-0.002 x CL(CR) (ml min(-1))) and the volume of distribution (Vd) was linearly related to body weight (proportionality constant: 0.40+/-0.024 x body weight (1 kg(-1))). The mean population estimates for CL and Vd were 4.53 l h(-1) and 27.3 l, respectively. The half-life of tobramycin was estimated to be 4.2 h. The inter-individual variability in CL and Vd were 37.0 and 28.5%, respectively. The residual error was 1.2 mg l(-1). Based on the results, optimal dosing intervals for renal impaired patients were calculated and were comparable with the intervals derived from the previous established nomogram.

Adolescent↗
PubMed2000

Disruption of a yeast very-long-chain acyl-CoA synthetase gene simulates the cellular phenotype of X-linked adrenoleukodystrophy.

X-linked adrenoleukodystrophy (X-ALD) is characterized biochemically by elevated levels of saturated very long-chain fatty acids (VLCFAs) in plasma and tissues. In X-ALD, peroxisomal very-long-chain acyl-CoA synthetase (VLCS) fails to activate VLCFAs, preventing their degradation via beta-oxidation. However, the product of the defective XALD gene (ALDP) is not a VLCS, but rather a peroxisomal membrane protein (PMP). Disruption of either or both of two yeast PMP genes related to the XALD gene did not produce a biochemical phenotype resembling that found in X-ALD fibroblasts. The authors identified a candidate yeast VLCS gene (the FAT1 locus) by its homology to rat liver VLCS. Disruption of this gene decreased VLCS activity, but had no effect on long-chain acyl-CoA synthetase activity. In FAT1-disruption strains, VLCS activity was reduced to 30-40% of wild-type in both a microsome-rich 27,000 g supernatant fraction and a peroxisome- and mitochondria-rich pellet fraction of yeast spheroplast homogenates. Separation of the latter organelles by density gradient centrifugation revealed that VLCS activity was peroxisomal and not mitochondrial. VLCS gene-disruption strains had increased cellular VLCFA levels, compared to wild-type yeast. The extent of both the decrease in peroxisomal VLCS activity and the VLCFA accumulation in this yeast model resembles that observed in cells from X-ALD patients. Characterization of the gene(s) responsible for the residual peroxisomal VLCS activity may suggest new therapeutic approaches in X-ALD.

Adrenoleukodystrophy↗
PubMed2000

Magnesium sulfate in eclampsia and pre-eclampsia: pharmacokinetic principles.

Magnesium sulfate (MgSO4) is the agent most commonly used for treatment of eclampsia and prophylaxis of eclampsia in patients with severe pre-eclampsia. It is usually given by either the intramuscular or intravenous routes. The intramuscular regimen is most commonly a 4 g intravenous loading dose, immediately followed by 10 g intramuscularly and then by 5 g intramuscularly every 4 hours in alternating buttocks. The intravenous regimen is given as a 4 g dose, followed by a maintenance infusion of 1 to 2 g/h by controlled infusion pump. After administration, about 40% of plasma magnesium is protein bound. The unbound magnesium ion diffuses into the extravascular-extracellular space, into bone, and across the placenta and fetal membranes and into the fetus and amniotic fluid. In pregnant women, apparent volumes of distribution usually reach constant values between the third and fourth hours after administration, and range from 0.250 to 0.442 L/kg. Magnesium is almost exclusively excreted in the urine, with 90% of the dose excreted during the first 24 hours after an intravenous infusion of MgSO4. The pharmacokinetic profile of MgSO4 after intravenous administration can be described by a 2-compartment model with a rapid distribution (a) phase, followed by a relative slow beta phase of elimination. The clinical effect and toxicity of MgSO4 can be linked to its concentration in plasma. A concentration of 1.8 to 3.0 mmol/L has been suggested for treatment of eclamptic convulsions. The actual magnesium dose and concentration needed for prophylaxis has never been estimated. Maternal toxicity is rare when MgSO4 is carefully administered and monitored. The first warning of impending toxicity in the mother is loss of the patellar reflex at plasma concentrations between 3.5 and 5 mmol/L. Respiratory paralysis occurs at 5 to 6.5 mmol/L. Cardiac conduction is altered at greater than 7.5 mmol/L, and cardiac arrest can be expected when concentrations of magnesium exceed 12.5 mmol/L. Careful attention to the monitoring guidelines can prevent toxicity. Deep tendon reflexes, respiratory rate, urine output and serum concentrations are the most commonly followed variables. In this review, we will outline the currently available knowledge of the pharmacokinetics of MgSO4 and its clinical usage for women with pre-eclampsia and eclampsia.

Animals↗
PubMed2000

[The effect of melatonin on enhancing immune function and inhibiting the ability of NO over-release in morphine dependent mice].

AIM: To observe the effects and mechanism of melatonin (MT) on the immune function of morphine dependent mice. METHODS: A physical dependent mice model was established by repeated subcutaneous injection of morphine. The intensity of morphine withdrawal syndrome was evaluated according to the weight of immune organs, the proliferation reaction of stimulated splenic lymphocytes by Con A, the phagoindex of blood primed macrophages and the content of NO induced in the peritoneal macrophage (pM phi). RESULTS: MT reversed the inhibitory effect of morphine on the proliferation ability of splenic lymphocytes and enhanced the phagocytosis of macrophages of morphine dependent mice obviously and prevented the over-release of NO from pM phi. The enhancing effects of MT on the phagocytosis can be prevented by naloxon. CONCLUSION: MT can significantly enhance the immune function of morphine dependent mice and inhibit NO excessive release from pM phi.

Adjuvants, Immunologic↗
PubMed1999

X-linked adrenoleukodystrophy: genes, mutations, and phenotypes.

X-linked adrenoleukodystrophy (X-ALD) is a complex and perplexing neurodegenerative disorder. The metabolic abnormality, elevated levels of very long-chain fatty acids in tissues and plasma, and the biochemical defect, reduced peroxisomal very long-chain acyl-CoA synthetase (VLCS) activity, are ubiquitous features of the disease. However, clinical manifestations are highly variable with regard to time of onset, site of initial pathology and rate of progression. In addition, the abnormal gene in X-ALD is not the gene for VLCS. Rather, it encodes a peroxisomal membrane protein with homology to the ATP-binding cassette (ABC) transmembrane transporter superfamily of proteins. The X-ALD protein (ALDP) is closely related to three other peroxisomal membrane ABC proteins. In this report we summarize all known X-ALD mutations and establish the lack of an X-ALD genotype/phenotype correlation. We compare the evolutionary relationships among peroxisomal ABC proteins, demonstrate that ALDP forms homodimers with itself and heterodimers with other peroxisomal ABC proteins and present cDNA complementation studies suggesting that the peroxisomal ABC proteins have overlapping functions. We also establish that there are at least two peroxisomal VLCS activities, one that is ALDP dependent and one that is ALDP independent. Finally, we discuss variable expression of the peroxisomal ABC proteins and ALDP independent VLCS in relation to the variable clinical presentations of X-ALD.

Adrenoleukodystrophy↗
PubMed1999

Effect of verbascoside on decreasing concentration of oxygen free radicals and lipid peroxidation in skeletal muscle.

AIM: To detect the effects of verbascoside on decreasing the concentration of oxygen free radicals (OFR) and lipid peroxidation in skeletal muscle resulting from exhaustive exercise. METHODS: Electron spin resonance (ESR) technique and thiobarbituric acid reaction (TBAR) method were used to detect the concentration of OFR in intact gastrocnemius muscle and the contents of milondialdehyde (MDA) in muscle homogenate. RESULTS: Verbascoside decreased the concentration of OFR (P < 0.05) and the level of lipid peroxidation (P < 0.05) in muscle caused by exercise. CONCLUSION: Verbascoside has the effects of reducing oxidative stress in muscle caused by exhaustive exercise by decreasing the concentration of free radicals and the level of lipid peroxidation.

Animals↗
PubMed1998

Disruption of the Saccharomyces cerevisiae FAT1 gene decreases very long-chain fatty acyl-CoA synthetase activity and elevates intracellular very long-chain fatty acid concentrations.

Activation of fatty acids to their coenzyme A derivatives is necessary for subsequent metabolism. Very long-chain fatty acids, which accumulate in tissues of patients with X-linked adrenoleukodystrophy, are activated by very long-chain acyl-CoA synthetase (VLCS) normally found in peroxisomes and microsomes. We identified a candidate yeast VLCS gene (FAT1), previously identified as encoding a fatty acid transport protein, by its homology to rat liver peroxisomal VLCS. Disruption of this gene decreased, but did not abolish, cellular VLCS activity. Fractionation studies showed that VLCS activity, but not long-chain acyl-CoA synthetase activity, was reduced to about 40% of wild-type level in both 27,000 x g supernatant and pellet fractions. Separation of organelles in the pellet fraction by density gradient centrifugation revealed that VLCS activity was associated with peroxisomes and microsomes but not mitochondria. FAT1 deletion strains exhibited decreased growth on medium containing dextrose, oleic acid, and cerulenin, an inhibitor of fatty acid synthesis. FAT1 deletion strains grown on either dextrose or oleic acid medium accumulated very long-chain fatty acids. Compared with wild-type yeast, C22:0, C24:0, and C26:0 levels were increased approximately 20-, 18-, and 3-fold in deletion strains grown on dextrose, and 2-, 7-, and 5-fold in deletion strains grown on oleate. Long-chain fatty acid levels in wild-type and deletion strains were not significantly different. All biochemical defects in FAT1 deletion strains were restored to normal after functional complementation with the FAT1 gene. The level of VLCS activity measured in both wild-type and deletion yeast strains transformed with FAT1 cDNA paralleled the level of expression of the transgene. The extent of both the decrease in peroxisomal VLCS activity and the very long-chain fatty acid accumulation in the yeast FAT1 deletion model resembles that observed in cells from X-linked adrenoleukodystrophy patients. These studies suggest that the FAT1 gene product has VLCS activity that is essential for normal cellular very long-chain fatty acid homeostasis.

Adrenoleukodystrophy↗
PubMed1998

Gene redundancy and pharmacological gene therapy: implications for X-linked adrenoleukodystrophy.

As more functional redundancy in mammalian cells is discovered, enhanced expression of genes involved in alternative pathways may become an effective form of gene therapy. X-linked adrenoleukodystrophy (X-ALD) is a peroxisomal disorder with impaired very-long-chain fatty acid metabolism. The X-ALD gene encodes a peroxisomal membrane protein (ALDP) that is part of a small family of related peroxisomal membrane proteins. We show that 4-phenylbutyrate treatment of cells from both X-ALD patients and X-ALD knockout mice results in decreased levels of and increased beta-oxidation of very-long-chain fatty acids; increased expression of the peroxisomal protein ALDRP; and induction of peroxisome proliferation. We also demonstrate that ALDP and ALDRP are functionally related, by ALDRP cDNA complementation of X-ALD fibroblasts. Finally, we demonstrate the in vivo efficacy of dietary 4-phenylbutyrate treatment through its production of a substantial reduction of very-long-chain fatty acid levels in the brain and adrenal glands of X-ALD mice.

ATP Binding Cassette Transporter, Subfamily D↗
PubMed1998

Genetic analysis of N-acetyltransferase polymorphism in a Chinese population.

AIM: To study the genetic basis of N-acetylatransferase polymorphism in Chinese. METHODS: Genotypes in 120 healthy Han volunteers from 19 provinces of China were assayed. The 3 common mutant alleles (M1, M2, M3) and one normal wild-type (WT) allele of the N-acetyltransferase (NAT2) gene were detected by allele-specific polymerase chain reaction technique. RESULTS: The NAT2 allele frequencies in 120 Chinese (WT = 0.625, M1 = 0.0458, M2 = 0.188, M3 = 0.142) were different (P < 0.01). The NAT2 genotype distribution for all detected combinations of NAT2 alleles in 120 Chinese subjects was consisitent with Hardy-Weinberg equilibrium (chi 2 = 7.27, nu = 8, 0.7 > P > 0.5). Fifty subjects (41.7%) were homozygous wildtypes, 50 subjects (41.7%) were heterozygous mutants, and 20 subjects (16.7%) were homozygous mutants. CONCLUSION: The lower frequency of mutant M1 allele compared with that of Caucasians explains the low frequency of slow acylators in Chinese.

Acetyltransferases↗
PubMed1997

A mouse model for X-linked adrenoleukodystrophy.

X-linked adrenoleukodystrophy (X-ALD) is a peroxisomal disorder with impaired beta-oxidation of very long chain fatty acids (VLCFAs) and reduced function of peroxisomal very long chain fatty acyl-CoA synthetase (VLCS) that leads to severe and progressive neurological disability. The X-ALD gene, identified by positional cloning, encodes a peroxisomal membrane protein (adrenoleukodystrophy protein; ALDP) that belongs to the ATP binding cassette transporter protein superfamily. Mutational analyses and functional studies of the X-ALD gene confirm that it and not VLCS is the gene responsible for X-ALD. Its role in the beta-oxidation of VLCFAs and its effect on the function of VLCS are unclear. The complex pathology of X-ALD and the extreme variability of its clinical phenotypes are also unexplained. To facilitate understanding of X-ALD pathophysiology, we developed an X-ALD mouse model by gene targeting. The X-ALD mouse exhibits reduced beta-oxidation of VLCFAs, resulting in significantly elevated levels of saturated VLCFAs in total lipids from all tissues measured and in cholesterol esters from adrenal glands. Lipid cleft inclusions were observed in adrenocortical cells of X-ALD mice under the electron microscope. No neurological involvement has been detected in X-ALD mice up to 6 months. We conclude that X-ALD mice exhibit biochemical defects equivalent to those found in human X-ALD and thus provide an experimental system for testing therapeutic intervention.

Adrenoleukodystrophy↗
PubMed1997

The chirality selectivity in the uptake of platinum (II) complexes with 1,2-cyclohexanediamine isomers as carrier ligand by human erythrocytes.

The uptake kinetics of cisplatin analogs of 1,2-cyclohexanediamine(dach) isomers with various leaving groups, by human erythrocytes in plasma isotonic buffer, were studied. The experimental results showed that the uptake rate constants (k values) decrease with the change of leaving group in the sequence: chloride (Cl) > squaric acid (SA) > oxalate (OX) > demethylcantharic acid (DA), with the same dach isomer as carrier group. It is noteworthy that for the platinum (II) complexes with the same leaving group, the k values always reduce as: 1R, 2R-dach > 1R, 2S-dach > 1S, 2S-dach. This result reflects the chirality selectivity. No differences in reactivity to protein thiols and effects on membrane permeability were found for the R,R-, R,S-, S,S-isomeric complexes. It is proposed that the chirality selectivity in uptake is due to the recognition of the chirality of the platinum complexes by the erythrocyte membrane. The interactions between the chiral platinum complexes and the head groups of the membrane phospholipid molecules are probably involved.

Cell Membrane Permeability↗
PubMed1997

[Determination of caffeine metabolite for the evaluation of N-acetyltransferase, CYP1A2 and xanthine oxidase activities].

Caffeine was used as a metabolic probe to measure, in 120 healthy volunteers, the activities of three enzymes, deduced to be N-acetyltransferase(NAT2), CYP1A2 and xanthine oxidase (XO). The caffeine metabolites of 5-acetylamino-6-formylamino-3-methyluracil (AFMU), 1-methylxanthine(1X), 1-methyluric acid(1U), 1, 7-dimethylxanthine(17X), and 1, 7-dimethyluric acid(17U) in urine were determined with HPLC after 4-5 hours of caffeine drink. The ratios of AFMU/1X or AFMU/(AFMU + 1X + 1U), (AFMU + 1X + 1U)/17X or (AFMU + 1X + 1U)/17U, and 1U/1X or 1U/(1X + 1U) were used as the index of NAT2, CYP1A2, and XO activities respectively. Frequency distribution analysis of the metabolic ratios of NAT2 indicated two distinct group with 20 slow acetylators and 100 rapid acetylators. Similar CYP1A2 activity was found in Chinese compared with European volunteers. Frequency analysis of CYP1A2 indicated the log normal distribution in 120 Chinese. The CYP1A2 index was much higher in smokers than that in nonsmokers. But no obvious difference was observed between young and old volunteers. The XO index also showed log normal distribution and has the similar value compared with European volunteers. The concentration variations of 1X and 1U in young volunteers were much lower than that in old volunteers.

Adolescent↗
PubMed1997

[HPLC determination of five caffeine metabolites].

An HPLC method for the determination of caffeine metabolites in urine was established. Shim Pack CLC-ODS column (5 microns) was eluted with the mobile phase of methanol--acetonitrile--0.05% acetic acid = 12:1:87 (v/v) at a flow rate of 1.2 ml.min-1, and the ultraviolet absorbance was monitored at 280 nm. The 13 caffeine metabolites and caffeine were well separated and the concentrations of the five metabolites, AFMU, 1U, 1X, 17U, and 17X, were determined. The recoveries of the five metabolites were above 87%, the inter- and intra-day variations were less than 3%. The concentrations of the five metabolites in 120 volunteers were determined. The ratios of the metabolites were employed for the assessment of CYP1A2, NAT, and XO enzymes successfully.

Caffeine↗
PubMed1996

Heterologous expression and site-directed mutagenesis studies on the activation mechanism and the roles of the basic residues in the prosegment of aspergillopepsinogen I.

To study the structure/function relationship of the prosegment of aspartic proteinase, a putative proform of aspergillopepsin I (or proteinase B) from Aspergillus niger var. macrosporus was expressed by Escherichia coli, refolded in vitro, and purified. The conversion of the purified proenzyme (aspergillopepsinogen I, proproteinase B) into the active mature form occurred at pH < or = 4.5 and was completely inhibited by pepstatin A, a specific inhibitor for aspartic proteinase, suggesting autoprocessing. The N-terminus of this mature form was Glu67 (numbering in preproform), which was different from the N-terminal Ser70 of native proteinase B although there was no significant difference in enzymatic activity. During the conversion, two intermediates were observed on SDS/PAGE, indicating a stepwise mechanism. The Lys56-Phe57 sequence seems to be a counterpart of the Lys-Tyr pair highly conserved in the prosequences of aspartic proteinases. When the mutant proenzyme (K56N), in which Lys56 was replaced with Asn by site-directed mutagenesis, was allowed to refold under various conditions, no significant potential activity could be obtained. Proproteinase B was also expressed by Bacillus brevis HPD31. This system required no in vitro refolding to obtain potentially active proenzyme, which was secreted into the culture medium (30-120 mg/l) and had the same properties with that obtained by the E. coli system. The K56N mutant prepared by this system also had no potential activity, and was rapidly digested by incubation with native proteinase B, suggesting that the mutant did not fold correctly. On the other hand, the K56R mutant (Lys56-Arg) was potentially active. These results indicated that Lys56 is essential for the folding through electrostatic interaction with the catalytic Asp residues in the active site although it may be replaced with Arg. In the presence of a low concentration of pepstatin A, an incompletely processed form with N-terminal Ser53 was obtained. Further, the R52Q (Arg52-->Glin) mutant showed no processing but was converted to the active mature form by incubation with the native enzyme. Therefore, the cleavage between Arg52 and Ser53 is considered to be the initial and essential step of the autoactivation. The R26Q, K27Q, R36Q, K40Q, R42Q, and K66Q mutants were also potentially active. The K66Q mutant was processed to a form with N-terminal Ala55.

Amino Acid Sequence↗
PubMed1995

The effect of cisplatin and transplatin on the conformation and association of F-actin.

The effects of cisplatin and transplatin on the conformation and association of F-actin were studied by ESR, turbidimetry and CD measurement. The results indicate that the major component affecting F-actin secondary conformation is derived from their effect on the tertiary or quaternary conformation and association states of F-actin. The effect of platinum is seen by the fact that binding of cisplatin causes first an increase in molecular size followed by a later decrease. The induction time for the association depended on the concentration of cisplatin. Transplatin was able to reach the target site more readily, resulting in the dissociation of F-actin even at a very low concentration.

Actins↗