Biomedical subjects

J Feng

Publications and source records attributed to J Feng.

At least 217 records · Page 12Linked to original sources

PubMed1996

The study of DNA oxidative damage in benzene-exposed workers.

Peripheral blood lymphocyte 8-hydroxy-2-deoxyguanosine (8-OHdG), were detected in 87 benzene-exposed and 30 control subjects by high performance liquid chromatograph coupled with an electrochemical detector system (HPLC-EC). The air concentration of benzene and its homologes in the workplace, urinary trans,trans-muconic acid (TTMA) as an internal dose of benzene exposure, were examined. The lymphocyte micronuclei (MN) as genotoxic and white blood cell (WBC) count as well as the myelotoxic markers of benzene were examined. Exposure to low, medium and high concentrations of benzene resulted in increased levels of 8-OHdG, which were 4.67, 26.12 and 29.89/10(5) dG, respectively, However, the 8-OHdG level observed in the control group was 3.738/10(5) dG). A good correlation between 8-OHdG formation and the groups exposed to external and internal benzene was observed (r = 0.77, 0.64, respectively). There was also a correlation between 8-OHdG and MN formation (r = 0.50). WBC levels were within normal range in all benzene-exposed subjects. It may be concluded that: benzene induced DNA oxidative damage in occupational exposure workers. The major factors influencing blood the 8-OHdG level were sex and toluene.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed1996

Regulation of myosin phosphatase by Rho and Rho-associated kinase (Rho-kinase)

The small guanosine triphosphatase Rho is implicated in myosin light chain (MLC) phosphorylation, which results in contraction of smooth muscle and interaction of actin and myosin in nonmuscle cells. The guanosine triphosphate (GTP)-bound, active form of RhoA (GTP.RhoA) specifically interacted with the myosin-binding subunit (MBS) of myosin phosphatase, which regulates the extent of phosphorylation of MLC. Rho-associated kinase (Rho-kinase), which is activated by GTP.RhoA, phosphorylated MBS and consequently inactivated myosin phosphatase. Overexpression of RhoA or activated RhoA in NIH 3T3 cells increased phosphorylation of MBS and MLC. Thus, Rho appears to inhibit myosin phosphatase through the action of Rho-kinase.

3T3 Cells↗

PubMed1996

Determination of dihydroetorphine in biological fluids by gas chromatography-mass spectrometry using selected-ion monitoring.

A method for the determination of dihydroetorphine hydrochloride, a powerful anaesthetic and analgesic drug, in biological fluids by GC-MS with selected-ion monitoring using etorphine as internal standard was established. Dihydroetorphine was extracted from human blood and urine with dichloromethane and then derivatized with N-heptafluorobutyrylimidazole after concentration to dryness. A dihydroetorphine monoheptafluorobutyl derivative was formed which showed good behavior on GC-MS with electronic-impact ionization. The main fragment, m/z 522, which is the base peak, was selected as the ion for quantitation and the corresponding ion, m/z 520, was selected for monitoring the internal standard, etorphine. The recoveries and coefficients of variation of the whole procedure were determined with five controlled dihydroetorphine-free urine and plasma samples spiked with different concentrations of dihydroetorphine. The concentration of dihydroetorphine for quantitation was in the range 1-20 ng/ml for urine and 2.5-250 ng/ml for plasma. The correlation coefficients of the standard curves are sufficient to determine the dihydroetorphine. The accuracy for quantitation of dihydroetorphine in urine and plasma is less than 10.6%.

Analgesics, Opioid↗

PubMed1996

Replication of plasmid R6K gamma origin in vivo and in vitro: dependence on IHF binding to the ihf1 site.

The gamma origin of plasmid R6K requires the specific initiator protein pi for initiation of replication. However, increased pi concentrations inhibit replication. The host-encoded integration host factor (IHF) protein permits gamma origin replication at otherwise inhibitory pi levels. IHF is thought to mediate this positive effect by directly binding to the gamma origin. In this study we demonstrate that IHF binding to one IHF site in the gama origin, ihf1, but not to the other side, ihf2, is necessary for the gamma origin to replicate at high pi protein levels. We also show that in vitro replication of the gamma origin plasmid requires IHF binding to the ihf1 site. Finally, we demonstrate both in vivo and in vitro that, when mutant pi proteins (hyperactive) are provided instead of wild-type pi, gamma origin plasmids can replicate in the absence of IHF. This supports a previously proposed hypothesis that the pi mutants can bypass the IHF requirement for gamma origin replication.

Bacterial Proteins↗

PubMed1996

Effects of in vivo treatments of nicotine and benzo[a]pyrene on the epidermal growth factor receptor in hamster buccal pouch.

This study was conducted to investigate the effects of two major ingredients in cigarette smoke, benzo-alpha-pyrene (BP) and nicotine (Nic), on epidermal growth factor (EGF) receptor in hamster buccal pouch. Adult male Syrian hamsters were treated by apically swabbing the buccal pouch with mineral oil (Control), 0.5 microgram/ml of BP, Nic or BP+Nic in mineral oil, twice a day, 5 days a week for 4 weeks. The BP+Nic treatment resulted in a significant reduction of submandibular gland (SG) EGF (Control vs. BP+Nic, 6.93 +/- 1.31 vs. 4.77 +/- 0.26* ng/g wet tissue, mean +/- S.D., n=5,*P < 0.05). Treatment with BP or Nic also caused a reduction, although not statistically significant, of EGF in SG extract. For the receptor study, all treatments significantly increased [125I]EGF binding to membrane preparations of buccal pouch as compared to Control (Control, BP, Nic, BP+Nic; 12.2 +/- 0.9, 20.5 +/- 2.2*, 17.0 +/- 1.3*, 21.2 +/= 1.6* fmol/mg prot. (mean +/- S.E.M.), n=5, P < 0.05). Scatchard analysis revealed that the higher EGF binding to the BP+Nic-treated sample was due to the higher number of receptors, but not higher affinity. Data from protein kinase study indicate that EGF stimulated phosphorylation of 170- and 150-kDa proteins in buccal membrane preparations. Treatment of BP+Nic resulted in reductions in EGF-stimulated phosphorylation of 170- and 150-kDa proteins by 19 and 72%, respectively. The present study has established an animal model which will benefit investigation of the mechanism by which tobacco alters the EGF receptor in oral buccal mucosa.

Animals↗

PubMed1996

Water vapour-treated hydroxyapatite coatings after plasma spraying and their characteristics.

A novel way to enhance the ability of hydroxyapatite (HA) coatings in resisting degradation was revealed. The as-received plasma sprayed HA coatings were kept in water vapour at 125 degrees C, with a pressure of 0.15 MPa for 6 h; most of the amorphous phase in the coating was converted into crystalline HA and enhanced the crystallinity significantly. Meanwhile, the alpha-tricalcium phosphate, tetracalcium phosphate and CaO which decomposed from HA during plasma spraying were also transformed into crystalline HA. The dissolution experiment in distilled water at room temperature showed that the post-water vapour-treated coatings were more stable than post-heat-treated ones. The average interfacial tensile bond strength between HA and substrate before and after water vapour treatment was 45.0 and 39.1 MPa, respectively.

Biocompatible Materials↗

PubMed1996

Effect of particle size on molten states of starting powder and degradation of the relevant plasma-sprayed hydroxyapatite coatings.

Crystallinity of hydroxyapatite (HA) coatings is an important parameter to evaluate their stability. Variation of the size distribution of the starting powder is one way to alter crystallinity of coatings. The fundamental reason might be the variation of molten states of HA powders with different particle sizes. In the experiments, HA particles sized between 1 and 180 microns were divided into six groups by sieving. It was observed that the trend of crystallinity of coatings on particle size is not linear but fluctuates. The fluctuation of crystallinity was caused by the alteration of molten states of HA powders with different size distributions. It is concluded that the molten state of starting powder also fluctuated with particle size but the trend was different from that of crystallinity. Coatings sprayed with different particle sizes were immersed in deionized water for 1 month. After immersion, severe degradation and break-up were observed on the surface of coatings with the highest crystallinity, which were sprayed with large sized HA powders. It may be the high porosities in these coatings that cause the severe degradation. This shows that high crystallinity is not necessarily related to high stability of coatings and microstructure is of great importance when stability of coatings is considered.

Biocompatible Materials↗

PubMed1996

Prostaglandin E1 (PGE1) reduces cardiac-derived TXA2 release in ischaemic arrest in isolated working rat heart.

To determine whether PGE1 plays a beneficial role in crystalloid cardioplegia in the isolated working rat heart, twenty isolated rat hearts were studied. The hearts were subjected to 90 min cardioplegic arrest under hypothermia (25 degrees C) and 30 min reperfusion. Prior to ischaemic arrest, the amount of TXA2 in coronary effluent, left ventricular developed pressure (LVDP), left ventricular end diastolic pressure (LVEDP), coronary flow (CF), aortic flow (AF) and cardiac output (CO) did not differ between the control and PGE1 treated rats (28 nmol/l). However, at 30 min reperfusion, the recovery of LVDP, LVEDP, CF, AF, CO and SV in hearts from PGE1 treated rats was more than in control hearts. TXA2 levels from coronary effluent were increased during reperfusion in control rats. On the other hand, PGE1 (28 nmol/l) inhibited the release of TXA2 at reperfusion. The present studies confirm that the cardiac-derived TXA2 are increased after ischaemia/reperfusion. Infusion of cardioplegia solution containing PGE1 results in the inhibition of release of cardiac-derived TXA2 and in a better preservation of cardiac function after ischaemic arrest.

Alprostadil↗

PubMed1996

The NMDA receptor antagonist MK-801 differentially modulates mu and kappa opioid actions in spinal cord in vitro.

We have examined the interactions between NMDA receptors and opioid effects in isolated neonatal rat spinal cord. Electrical stimulation of a lumbar dorsal root evoked a nociceptive-related slow ventral root potential (sVRP) recorded at the corresponding ipsilateral ventral root. The kappa opiate receptor agonist U69,593 (2.5 nM-1 microM) depressed sVRP area by a maximum of 80%, EC50 was approximately 33 nM. Both the non-specific antagonist naloxone and the kappa-specific antagonist nor-binaltorphimine (nor-BNI) antagonized the effects of U69,593. Morphine, a mu agonist, (1 nM-1 microM) depressed sVRP area with an approximate EC50 of 90 nM. The effects of both mu and kappa opioid agonists were selective for the very slow metabotropically mediated components of the sVRP, compared to the relatively fast NMDA receptor-mediated components. The non-competitive N-methyl-D-aspartate (NMDA) antagonist MK-801 (20 nM) had no effect on sVRP area when applied alone but co-applied with morphine significantly potentiated the depressant effects of morphine. In contrast, MK-801 either had no effect on or slightly antagonized the depressant effects of U69,593. Naloxone following morphine produced a significant increase in sVRP area above pre-morphine control values; the increase lasted 30 min or more. Neither naloxone nor nor-BNI was associated with an increase in sVRP area when given alone or following U69,593. MK-801 co-applied with morphine blocked the rebound increase in sVRP area following naloxone. These results suggest that (1) both mu and kappa receptor agonists exert similar selective depressant effects on spinal nociceptive neurotransmission; (2) mu but not kappa agonists exert prolonged excitatory effects that oppose the depression; and (3) NMDA receptors play a role in determining opioid analgesic potency and naloxone-precipitated hyperresponsiveness. The results may be related to initial steps in the development of acute tolerance to mu opioids, and suggest that tolerance to kappa opioids may have a different mechanism.

Analgesics↗

PubMed1996

Epidermal growth factor in gingival crevicular fluid and its binding capacity in inflamed and non-inflamed human gingiva.

Epidermal growth factor (EGF) is a pro-inflammatory small peptide (6000 Da) with a variety of biological activities including stimulation of cell differentiation and mediation of proteolysis by binding to its specific receptor on the cell surface. The purpose of this study was to determine the levels of EGF in gingival crevicular fluid (GCF) and the EGF-binding capacity to its receptor in gingival tissue. The GCF samples were collected from six patients by inserting paper strips into shallow (< 5 mm) and deep pockets (> or = 5 mm) for 30 s. The strips were soaked in 0.2 M acetate for extraction and the EGF in the supernatants was analysed by radioimmunoassay. To determine the binding capacity of EGF to its receptor, inflamed gingival tissues (pocket depth > or = 5 mm, Gingival Index = 1, 2 or 3) were collected during periodontal flap surgery and non-inflamed gingival tissues (pocket depth < 5 mm, Gingival Index = 0) were collected during surgical "crown lengthening' for aesthetic purposes. The tissues were pooled by group, homogenized for membrane preparation and the supernatants obtained after centrifugation were used in a 125IEGF binding assay. To determine the effect of inflammation on gingival EGF receptor, inflamed and non-inflamed gingival tissues were collected from six patients and prepared similarly to the binding assay. Gingival preparations were then electrophoresed for Western blot analysis with EGF receptor antiserum. The EGF level in GCF was significantly lower (P < 0.05) in the samples collected from pockets > or = 5 mm (0.9 +/- 0.6 ng/ml) than in those from pockets < 5 mm (2.4 +/- 2.1 ng/ml). The average Gingival Index was higher (2.6 +/- 0.6) in pockets > or = 5 mm than in pockets < 5 mm (1.4 +/- 1.0). Specific binding of 125I-EGF to its receptor in inflamed gingiva was 2.7-fold higher than in non-inflamed gingiva (14.4 +/- 4.9 vs 5.4 +/- 1.8 fmol/g wet tissue). Western blot analysis showed two major immunoreactive bands (180 and 120 kDa), which represent EGF receptor and its degradation products, in inflamed gingiva. The findings show that inflammation activates EGF binding capacity in gingiva and that the up-regulation of EGF receptor in inflamed gingiva might be associated with a lowered concentration of EGF in GCF produced adjacent to inflamed gingiva. This up-regulation of EGF receptor during inflammation might be an important mechanism in the pathogenesis of periodontal disease.

Blotting, Western↗

PubMed1996

Beneficial effects of iloprost cardioplegia in ischemic arrest in isolated working rat heart.

To determine whether the prostacyclin analog iloprost plays a beneficial role in crystalloid cardioplegia in isolated working rat hearts, 20 isolated rat hearts were studied after sustaining 90 min of cardioplegic arrest under hypothermia (20 degrees C). The findings indicated that thromboxane A2 (TXA2) levels in coronary effluent were increased during reperfusion. Iloprost (12 nm/l) inhibited the release of TXA2 and improved the recovery of cardiac hemodynamics after ischemia. These data demonstrated that cardiac-derived TXA2 appeared to mediate reperfusion injury after prolonged aortic clamp or cardiac transplantation and iloprost cardioplegic infusion resulted in the inhibition of release of cardiac-derived TXA2 and in a better preservation of cardiac function after ischemic arrest.

Animals↗

PubMed1996

Pretreatment with tetramethylpyrazine increases the release of PGI2 and decreases TXA2 release in isolated rat heart.

We investigated the release of PGI2 and TXA2 by measuring their stable metabolites of 6-keto-PGF1a and TXB2 in the perfusate in the isolated rat heart after pretreatment with tetramethylpyrazine (TMP). Pretreatment with TMP (12 mg/kg, i.p.) 7 days before preparation produced a significant elevation of 6-keto-PGF1a from 2.30 +/- 0.65 ng/min/g of untreated controls to 3.8 +/- 0.77 ng/mir/g (p < 0.05). Pretreatment with TMP also decreased TXB2 release (p < 0.05 versus control).

6-Ketoprostaglandin F1 alpha↗

PubMed1996

Synergistic interactions between midazolam and alfentanil in isolated neonatal rat spinal cord.

Benzodiazepines, which may themselves have analgesic properties, display complex interactions with opioids. This study was designed to investigate the effects of midazolam on nociceptive neurotransmission in isolated neonatal rat spinal cord, and the interactions between midazolam and alfentanil. Slow ventral root potentials (sVRP) were recorded from a lumbar root of spinal cords isolated from 1-7-day-old rats and superfused at 27-28 degrees C. Midazolam (35 nmol litre-1 to 15 mumol litre-1) significantly (P < 0.05) depressed sVRP area in a concentration-dependent manner. Midazolam depression was antagonized by flumazenil, bicuculline and naloxone. Midazolam and alfentanil interacted synergistically, as determined by a combination index of less than 1. Midazolam blocked the rebound hyperexcitability observed when alfentanil was reversed by naloxone. The results of the study are relevant to benzodiazepine-opioid analgesia and to the effectiveness of benzodiazepines in mitigating the development of opioid tolerance and dependence.

Alfentanil↗

PubMed1996

Bi-directional dideoxy fingerprinting (Bi-ddF): a rapid method for quantitative detection of mutations in genomic regions of 300-600 bp.

There is a great need for rapid screening methods that detect essentially all mutations. Dideoxy fingerprinting (ddF) is a highly sensitive screening method that is performed by electrophoresing one lane of a Sanger dideoxy termination reaction through a nondenaturing gel. Mutations may produce an extra segment or eliminate a segment from the termination products (informative dideoxy component). In addition, mutations can be detected by the altered mobility of one or more termination segments (informative SSCP component). To screen larger segments with virtually 100% sensitivity, bi-directional ddF (Bi-ddF) was developed. Bi-ddF is a 'second generation ddF' in which the dideoxy termination reaction is performed simultaneously with two opposing primers. Bi-ddF has two important advantages over ddF: (i) the dideoxy component can detect 10 of the 12 types of possible single-base substitutions; and (ii) the SSCP component is enhanced because alterations of mobility can be detected in either the downstream or upstream direction. As a result, Bi-ddF can screen larger regions of genomic DNA with virtually 100% sensitivity. Bi-ddF detected 100% of 28 single-base substitutions in a 494 bp segment containing exons B and C of the human factor IX gene and 100% of 42 single-base substitutions and one microdeletion present in a 577 bp region containing exon H. In a blinded analysis in which 39 wildtype samples were randomly mixed with 51 mutant samples, all mutations were detected with no false positives. Bi-ddF requires essentially the same effort as ddF, yet twofold more DNA sequence can be screened reliably per unit effort.

DNA↗

PubMed1996

Bovine natural resistance associated macrophage protein 1 (Nramp1) gene.

The Bcg/Ity/Lsh locus is a major gene controlling early phases of infection with intracellular parasites in mice. Natural resistance associated macrophage protein 1 (Nramp1) has been shown to be the Bcg gene in mice. Analysis of a bovine cDNA homolog of murine Nramp1, designated as bovine NRAMP1, predicted a 548-amino-acid protein with hydrophobic domains, an amino-terminal SH3-binding domain, and a conserved consensus transport motif. Northern blotting indicated that bovine NRAMP1 was expressed primarily in macrophages and tissues of the recticuloendothelial system. Bovine NRAMP1 was mapped to BTA 2 within syntenic loci conserved on HSA 2q and MMU 1.

Amino Acid Sequence↗

PubMed1996

Transmembrane chloride currents in human atrial myocytes.

The present study was designed to evaluate the presence of basal, swelling-induced, and cAMP-dependent Cl- currents in human atrial myocytes studied with the whole cell patch-clamp technique. Under basal conditions, a small outwardly rectifying background conductance was noted that reversed close to 0 mV and was not altered by Cl- replacement. Isoproterenol (1 microM), forskolin (3 microM), and 8-bromoadenosine 3',5'-cyclic monophosphate (50 microM) did not increase membrane conductance, even when responsiveness to isoproterenol was confirmed by an increase in Ca2+ current and when perforated-patch techniques (nystatin) were used. Exposure to hyposmotic solutions increased cell volume and induced a whole cell conductance that showed outward rectification, was inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (100 microM), and responded to changes in Cl- gradient in a fashion consistent with a Cl(-)-selective conductance, with estimated relative permeabilities of 1, 0.25, and 0.07 for Cl-, methanesulfonate, and aspartate, respectively. The results suggest that human atrial cells lack basal and adenosine 3',5'-cyclic monophosphate-dependent Cl- current but manifest a substantial Cl- conductance in the presence of cell swelling.

Animals↗

PubMed1996

Properties of sodium and potassium currents of cultured adult human atrial myocytes.

Cultured cell systems are valuable for the study of regulation of phenotypic expression, but little is known about the electrophysiological properties of human cardiac tissues in culture. The present studies were designed to determine the feasibility of maintaining human atrial myocytes in primary culture and to assess changes in Na+ (INa) and K+ (Ito, transient outward, and Ikur, ultra-rapid delayed rectifier) currents. Within 24 h of culture, cells assumed an avoid shape, which they maintained for up to 7 days. The voltage dependence, kinetics, and density of INa were unchanged in culture. The activation properties of Ito (kinetics and voltage dependence) were not altered, but Ito density (current normalized to cell capacitance) was reduced and inactivation properties were altered (negative shift in voltage dependence and slowed kinetics) in cultured compared with fresh cells. The absolute current amplitude, kinetics, voltage dependence, and 4-aminopyridine sensitivity of IKur were unchanged, but current density was increased. All changes in ionic currents occurred within 24 h of culture and remained stable for the next 4 days. We conclude that human atrial myocytes can be maintained in primary culture, that the qualitative properties of INa, Ito, and IKur remain constant but that some quantitative changes occur, and that cultured human atrial myocytes may be valuable for studies of the molecular mechanisms and regulation of cardiac channel function in humans.

4-Aminopyridine↗

PubMed1996

Transient outward and delayed rectifier currents in canine atrium: properties and role of isolation methods.

Although the dog is the principal species used for in vivo studies of atrial arrhythmias, little is known about currents governing canine atrial repolarization. Cells were isolated from dog atria by exposure to collagenase of tissue in vitro ("chunk cells") and by arterial perfusion ("perfusion cells"). Whole cell voltage clamp revealed transient outward K+ current (Ito1), Ca(2+)-dependent Cl- current (Ito2), and delayed rectifier K+ current (IK). Ito1 recovered rapidly and showed little frequency dependence. Two components of IK were present as follows: a rapidly activating E-4031-sensitive current with marked inward recitification and a slower-activating E-4031-insensitive component. Ito1 and IK resembled corresponding currents previously described in human atrium. Transient outward currents were similar in chunk and perfusion cells, but IK was seen in 4% of chunk cells vs. 99% of perfusion cells (P < 0.001). Suppression of each identified current retarded canine action potential repolarization. We conclude that Ito1, Ito2, and both components of IK are present in dog atrium, IK is much more sensitive to the isolation method than Ito1 or Ito2, and the properties of two important repolarizing currents (Ito1 and IK) previously described in human atrium are similar to those in dog atrium.

Action Potentials↗