Biomedical subjects

L Fan

Publications and source records attributed to L Fan.

At least 37 records · Page 2Linked to original sources

PubMed2001

An adaptive template-matching method and its application to the boundary detection of brachial artery ultrasound scans.

We developed an adaptive template-matching method for vessel wall boundary detection in brachial artery ultrasound (US) scans. The computer-aided identification of lumen-intima and media-adventitia boundaries of the brachial artery US scan is a critical step for flow-mediated vasodilator response measurement, which has become an increasingly important tool in both clinical and research applications. The adaptive template we propose in this paper is a combination of two parameterized Gaussian envelopes that approximates the US pulse envelope. The algorithm for template matching is cast as a constrained nonlinear least squares problem. A best match between the template and the observed US scan line signal results in a set of optimum parameters of the adaptive template, and the location of the boundaries is directly computed from these parameters. We present the results of applying our method to synthetic and clinical data, showing that the adaptive template-matching method provides superior accuracy in detecting the media-adventitia boundaries of both the near wall and the far wall of the vessel to that of conventional edge-detection methods.

Algorithms↗

PubMed2001

Automated embolus identification using a rule-based expert system.

Transcranial Doppler ultrasound (US) can be used to detect microemboli in the cerebral circulation, but is still limited because it usually relies on "human experts" (HEs) to identify signals corresponding to embolic events. The purpose of this study was to develop an automatic system that could replace the HE and, thus, make the technique more widely applicable and, potentially, more reliable. An expert system, based around a digital signal-processing board, analysed Doppler signal patterns in both the time domain and frequency domain. The system was trained and tested on Doppler signals recorded during the dissection and recovery phases of carotid endarterectomy. It was tested with 74 separate 2.5-min recordings that contained at least 575 artefacts in addition to 253 s of diathermy interference. The results were compared with the results obtained by three HEs. Using a "gold-standard" that classified any event detected by the majority of HEs as an embolus, the automatic system displayed a sensitivity of 94.7% and a specificity of 95.1% for 1151 candidate events 7 dB or more above the clutter (signal-to-clutter ratio, SCR, > or = 7 dB), and 89.6% and 95.3%, respectively, for 2098 candidate events with SCR > or = 5 dB. The system had a very similar performance to individual HEs for SCR > or = 7dB, and was only marginally worse for SCR > or = 5 dB.

Artifacts↗

PubMed2001

Molecular cloning and characterization of hNP22: a gene up-regulated in human alcoholic brain.

An improved differential display technique was used to search for changes in gene expression in the superior frontal cortex of alcoholics. A cDNA fragment was retrieved and cloned. Further sequence of the cDNA was determined from 5' RACE and screening of a human brain cDNA library. The gene was named hNP22 (human neuronal protein 22). The deduced protein sequence of hNP22 has an estimated molecular mass of 22.4 kDa with a putative calcium-binding site, and phosphorylation sites for casein kinase II and protein kinase C. The deduced amino acid sequence of hNP22 shares homology (from 67% to 42%) with four other proteins, SM22alpha, calponin, myophilin and mp20. Sequence homology suggests a potential interaction of hNP22 with cytoskeletal elements. hNP22 mRNA was expressed in various brain regions but in alcoholics, greater mRNA expression occurred in the superior frontal cortex, but not in the primary motor cortex or cerebellum. The results suggest that hNP22 may have a role in alcohol-related adaptations and may mediate regulatory signal transduction pathways in neurones.

Adult↗

PubMed2001

Characterization of acute inhibition of Na/H exchanger NHE-3 by dopamine in opossum kidney cells.

BACKGROUND: Dopamine (DA) is a principal natriuretic hormone that defends extracellular fluid volume from a Na load. Natriuresis is effected partly through inhibiting the proximal tubule Na/H exchanger NHE-3. Changes in NHE-3 phosphorylation is one mechanism by which NHE-3 activity is regulated. METHODS: We used opossum kidney (OK) cells to characterize the differential and synergistic effects of DA receptor subtype-1 (DA1) and -2 (DA2) agonists and the effect of blockade of protein kinase A (PKA) or protein kinase C (PKC) on NHE-3 activity and phosphorylation. RESULTS: DA and DA1 agonists inhibited NHE-3 activity, and DA1 antagonist blocked the effect of either DA or DA1 agonist. DA2 agonist alone had no effect, but DA2 antagonist reduced the DA effect on NHE-3 activity. DA1 and DA2 agonists together were more potent than DA1 alone. PKA inhibition eliminated the effect of DA1 agonist and partially blocked the effect of DA on NHE-3 activity. PKC inhibition did not block the DA effect. DA1 agonist and PKA activation phosphorylated NHE-3 on identical sites. Despite lack of effect on NHE-3 activity, DA2 agonists increased NHE-3 phosphorylation. DA-induced NHE-3 phosphorylation was distinct from DA1 and PKA but closely resembled DA2. CONCLUSION: We postulate the following: (1) DA modifies NHE-3 phosphorylation by activating PKA through DA1 and by other kinases/phosphatases via DA2. (2) DA1 is sufficient to inhibit NHE-3, while DA2 is insufficient but plays a synergistic role by altering NHE-3 phosphorylation.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

PubMed2001

The inhibition and selectivity of bacterial topoisomerases by BMS-284756 and its analogues.

Analogues of BMS-284756, a novel des-F(6)-quinolone, were synthesized and evaluated in order to determine the effects of modification of substituents on in vitro target inhibition. BMS-340281 (stereoisomer of BMS-284756), BMS-340280 (C-6 fluorinated analogue of BMS-284756), BMS-340278 (C-8-H derivative), BMS-433366 (C-8 methoxy analogue) and fluoroquinolone comparators were evaluated for antibacterial activity. The MICs of BMS-284756 were generally found to be within two-fold of the MICs of BMS-284756 analogues against a panel of Gram-positive and -negative organisms. BMS-284756 had MICs of 0.03-0.125 mg/L against Streptococcus pneumoniae strains with GyrA and ParC mutations, and was the most active quinolone. BMS-284756 and its analogues had similar activity compared with ciprofloxacin and moxifloxacin against topoisomerase IV decatenation, but were three times more active than levofloxacin. The IC(50) of BMS-284756 for human topoisomerase II (hTopo II) was 3000 times higher than its IC(50) for DNA gyrase, and no whole-cell cytotoxicity was noted. Two analogues, BMS-340280 and BMS-340278, demonstrated moderate inhibition against hTopo II and cytotoxicity in the cellular assay. BMS-284756 demonstrated greater Gram-positive antibacterial activity and similar inhibition of targets compared with other fluoroquinolones, and more favourable selectivity compared with the other BMS-284756 analogues.

Anti-Infective Agents↗

PubMed2001

ET(B) receptor activation causes exocytic insertion of NHE3 in OKP cells.

Endothelin-1 (ET-1) activates sodium/hydrogen exchanger 3 (NHE3) in opossum kidney clone P (OKP) cells expressing ET(B) receptors. ET-1 (10(-8) M) caused a two- to threefold increase in apical membrane NHE3 (assessed by surface biotinylation), in the absence of a change in total cellular NHE3. A maximal effect was achieved within 15 min. The increase in apical NHE3 was not blocked by cytochalasin D but was blocked by latrunculin B, which also prevented the ET-1-induced increase in NHE3 activity. Endocytic internalization of NHE3, measured as protection of biotinylated NHE3 from the membrane-impermeant, sulfhydryl-reducing agent MesNa was minimal within 35 min and was not regulated by ET-1. Exocytic insertion of NHE3, measured as the appearance of biotinylated NHE3 after the blockade of reactive sites with sulfo-NHS-acetate, was increased in response to ET-1. These studies demonstrate that ET-1 induces net trafficking of NHE3 to the apical membrane that is mediated by enhanced exocytic insertion and is required for increased NHE3 activity.

Alkaline Phosphatase↗

PubMed2001

Brachial flow-mediated vasodilator responses in population-based research: methods, reproducibility and effects of age, gender and baseline diameter.

BACKGROUND: Brachial artery ultrasound has been proposed as an inexpensive, accurate way to assess cardiovascular risk in populations. However, analysis and interpretation of these data are not uniform. METHODS: We analysed the relationship between relative and absolute changes in brachial artery diameter in response to flow-mediated dilation and age, gender and baseline diameter among 4,040 ultrasound examinations from subjects aged 14 to 98 years. RESULTS: Reproducibility studies demonstrated intra- and interreader and intrasubject correlations from 0.67 to 0.84 for repeated measures of per cent change in diameter. Per cent change in diameter after flow stimulus was 3.58 +/- 0.10% (mean +/- standard deviation). Corresponding values for baseline diameter and absolute change in diameter were 4.43 +/- 0.87 mm and 0.15 +/- 0.01 mm, respectively. Baseline diameter and its variance were inversely related to per cent change in diameter (P< 0.001). In contrast, absolute change in diameter was more uniform throughout the range of baseline diameters. Baseline diameter was directly related, and per cent change in diameter inversely related, to age (P < 0.001 for all three measures). Time to maximum vasodilator response increased with age (P < 0.001). Women (n=2,315) had significantly larger per cent change in diameter than men (n=1,725) (P < 0.001). However, after adjustment for age and baseline diameter, per cent and absolute change were 5% smaller in women than men (P < 0.05 for both). In multivariate analysis, age was overwhelmingly the most important determinant of absolute change in diameter (P < 0.001). CONCLUSIONS: Automated analysis of brachial flow-mediated vasodilator responses is both feasible and reproducible in large-scale clinical and population-based research.

Adolescent↗

PubMed2001

mGluR5 antagonists 2-methyl-6-(phenylethynyl)-pyridine and (E)-2-methyl-6-(2-phenylethenyl)-pyridine reduce traumatic neuronal injury in vitro and in vivo by antagonizing N-methyl-D-aspartate receptors.

The effect of selective group I metabotropic glutamate receptor subtype 5 (mGluR5) antagonists 2-methyl-6-(phenylethynyl)-pyridine (MPEP) and (E)-2-methyl-6-(2-phenylethenyl)-pyridine (SIB-1893) on neuronal cell survival and post-traumatic recovery was examined using rat in vitro and in vivo trauma models. Treatment with MPEP and SIB-1893 showed significant neuroprotective effects in rat cortical neuronal cultures subjected to mechanical injury. Application of the antagonists also attenuated glutamate- and N-methyl-D-aspartate (NMDA)-induced neuronal cell death in vitro. Intracerebroventricular administration of MPEP to rats markedly improved motor recovery and reduced deficits of spatial learning after lateral fluid percussion-induced traumatic brain injury. Lesion volumes as assessed by magnetic resonance imaging were also substantially reduced by MPEP treatment. Although we show that MPEP acts as a potent mGluR5 antagonist in our culture system, where it completely blocks agonist-induced phosphoinositide hydrolysis, electrophysiological and pharmacological studies indicate that MPEP and SIB-1893 also inhibit NMDA receptor activity at higher concentrations that are neuroprotective. Taken together, these data suggest that MPEP and SIB-1893 may have therapeutic potential in brain injury, although the mechanisms of neuroprotective action for these drugs may reflect their ability to modulate NMDA receptor activity.

Animals↗

PubMed2001

[Malformed macrocephalous sperm with polytails and chromosomal aberrance].

OBJECTIVE: To investigate the relationship between sperm anomalies and chromosomal aberrance and to further understand the pathological changes of anomalous spermatozoa. METHODS: Light and electronic (SEM or TEM) microscopes were used for morphological analysis. Fluorescence in situ hybridization(FISH) with chromosome X-, Y-specific probes were used for aneuploidy detection in sperms of the patient. RESULTS: Ninety eight point seven five per cent of the Papanicolaou stained sperms were observed to be abnormal; 100% of the sperm heads were abnormal, measured under oil objective (1000 times); 60.25% of the sperms had two or more tails (the maximum being eight tails). SEM and TEM demonstrated that the heads contained a large amount of cytoplasmic structure, the surfaces of heads were uneven, the nuclei were of much irregular shape; besides aberrance in quantity, anomalies occurred with centromeres, mitochondria and flagella in the tails. The results of FISH showed that the aneuploidy rate of sex chromosomes was 61.41% which was parallel to the rate of polytails. CONCLUSION: Even though the chromosomes in somatic cells are normal, the chromosomes in anomalous sperms may be abnormal.

Adult↗

PubMed2001

[Correction of occipito-posterior by maternal postures during the process of labor].

OBJECTIVE: To investigate the effect on correction of occipito-posterior (OP) by changing maternal posture during labor. METHODS: One hundred normal primigravida with head OP position in the latent phase of labor were randomly divided into 2 groups: Group A (n = 50), women were instructed to lay on the same lateral posture with the fetal spine during labor in order to correct the fetal position from OP to occipito anterior (OA); Group B (n = 50) lay on the opposite side to the fetal spine. The OP position was diagnosed by vaginal examination or B ultrasound, and the course of labor and mode of delivery were observed. RESULTS: Thirty-four women delivered vaginally (68%) in group A, with 27 of them turned to OA position (54%); spontaneously while they were 22 (44%) and 12 (24%) in group B respectively, a significant difference was shown (P < 0.005). The average time interval for the 1st stage was (13.5 +/- 6.5) hour and (17.1 +/- 7.2) hour for group A and B respectively, also a significant difference was noted (P < 0.01). CONCLUSION: To instruct women in labor to take the lateral recumbent position with the same side of fetal spine for correcting OP to OA is an effective method. It may increase vaginal deliveries and shorten the first stage of labor, thus reduce dystocia due to OP position. This method is simple and effective, and maybe adopted in most obstetric units.

Adult↗

PubMed2001

[Gene dispersal risk of transgenic plants].

Gene flow is a key problem and top topic in risk assessment and management of transgenic plants. Five major study areas of gene dispersal in transgenic plants were reviewed in this paper, which include gene flow from transgenic plant to its wild species, characteristics of gene flow based on pollen, methods of doing experiment and risk assessment for gene flow, safety standards of risk assessment of transgenic plants, and long-term ecological impact of gene flow in the future. Some areas needed to be studied further were also proposed.

Ecosystem↗

PubMed2001

[Analysis on HLA-E polymorphism in Shanghai Han population].

OBJECTIVE: To investigate the distribution of HLA-E alleles in Chinese Han in Shanghai area. METHODS: HLA-E alleles were assigned by using a PCR/SSO method in 201 random healthy individuals from Shanghai region. HLA-A,-B antigens typing was carried out with NIH standard microlymphocytoxicy method. RESULTS: Three alleles of HLA-E could be detected in this population. The E*0101 is the most common allele with a frequency of 42.29%, followed by E*01032 and E*01031 with 32.84% and 24.88% respectively. No E*0102 and E*0104 could be detected in all of the individuals. The analysis of linkage on two loci between HLA-E and HLA-A or -B showed that no significant difference could be found between expected frequencies and observed frequencies excepting B15/E*01032 and A2/E*01032. CONCLUSION: The allele frequencies of HLA-E are 42.29% for E*0101, 24.88% and 32.84% for E*01031 and E*01032 respectively in Shanghai Chinese. No extensive linkage disequilibrium was found between HLA-E and HLA-A or -B locus.

Alleles↗

PubMed2000

Acute regulation of Na+/H+ exchanger NHE3 by parathyroid hormone via NHE3 phosphorylation and dynamin-dependent endocytosis.

Parathyroid hormone (PTH) is a potent inhibitor of mammalian renal proximal tubule Na(+) transport via its action on the apical membrane Na(+)/H(+) exchanger NHE3. In the opossum kidney cell line, inhibition of NHE3 activity was detected from 5 to 45 min after PTH addition. Increase in NHE3 phosphorylation on multiple serines was evident after 5 min of PTH, but decrease in surface NHE3 antigen was not detectable until after 30 min of PTH. The decrease in surface NHE3 antigen was due to increased NHE3 endocytosis. When endocytic trafficking was arrested with a dominant negative dynamin mutant (K44A), the early inhibition (5 min) of NHE3 activity by PTH was not affected, whereas the late inhibition (30 min) and decreased surface NHE3 antigen induced by PTH were abrogated. We conclude that PTH acutely inhibits NHE3 activity in a biphasic fashion by NHE3 phosphorylation followed by dynamin-dependent endocytosis.

Animals↗

PubMed2000

The role of tyrosine 15 in erythropoietin action.

The results of iodination inactivation of erythropoietin suggest that tyrosine 15 is required for biological activity. This was confirmed by site-directed mutagenesis. Substitution of tyrosine by alanine or isoleucine resulted in mutants with no biological activity, whereas substitution by phenylalanine yielded an active mutein. Protein footprinting using trypsin showed that the N-terminal residues 1 to 46 and the C-terminal residues 155 to 165 linked by the 7 to 161 disulfide bond, includes one active site of the hormone.

Antibodies, Monoclonal↗

PubMed2000

Ventricular preexcitation sensitive to flecainide in late stage chick embryo ECGs: 2,3,7,8-tetrachlorodibenzo-p-dioxin impairs inotropic but not chronotropic or dromotropic responses to isoproterenol and confers resistance to flecainide.

ECGs free of movement artefacts were obtained without anesthesia in 16- to 18-day-old chick embryos close to hatching and used to study the effect of the environmental toxin 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) on cardiac rhythm and conduction. The ECGs of normal late stage chick embryos exhibited short PR intervals, frequent nonisoelectric PR segments, delta waves, and inverted T waves. Those ECG characteristics are found in patients with the Wolff-Parkinson-White syndrome (WPW) in which they reflect ventricular preexcitation associated with the use of accessory conduction pathways and arrhythmias. Isoproterenol (30 microg/egg) did not alter the ECG preexcitation characteristics. Flecainide, a sodium channel blocker used clinically to suppress WPW accessory pathway activity, at 0.5 to 5 mg per egg diminished the preexcitation and caused atrioventricular (AV) block, supporting the use of accessory pathways together with AV-nodal conduction in normal late stage chick embryos. The findings challenge the dogma that accessory pathways are entirely replaced by AV conduction pathways in late fetal development. TCDD, at 1-2 nmol per egg for 48 h, did not affect heart rate, the increase in heart rate by isoproterenol, or the ECG characteristics, suggesting that short-term TCDD treatment did not affect sinus node function or cardiac conduction. The latter results taken together with prior findings indicate that TCDD differentially impairs the inotropic and lusitropic effects but not the chronotropic or dromotropic effects of isoproterenol. In TCDD-treated embryos, flecainide, tested at 5 mg per egg, caused much less inhibition of preexcitation or production of AV block than in the untreated or solvent-treated controls. The resistance to flecainide represents a new TCDD effect consistent with the reported increase of cardiac myocyte [Ca(2+)](i) by TCDD treatment.

Animals↗

PubMed2000

Cutting edge: ectopic expression of the chemokine TCA4/SLC is sufficient to trigger lymphoid neogenesis.

To test whether accumulation of naive lymphocytes is sufficient to trigger lymphoid development, we generated mice with islet expression of the chemokine TCA4/SLC. This chemokine is specific for naive lymphocytes and mature dendritic cells (DC) which express the CCR7 receptor. Islets initially developed accumulations of T cells with DC, with scattered B cells at the perimeter. These infiltrates consolidated into organized lymphoid tissue, with high endothelial venules and stromal reticulum. Infiltrate lymphocytes showed a naive CD44low CD25- CD69- phenotype, though half were CD62L negative. When backcrossed to RAG-1 knockout, DC were not recruited. Interestingly, islet lymphoid tissue developed in backcrosses to Ikaros knockout mice despite the absence of normal peripheral nodes. Our results indicate that TCA4/SLC can induce the development and organization of lymphoid tissue through diffential recruitment of T and B lymphocytes and secondary effects on stromal cell development.

Animals↗

PubMed2000

Inhibition of transplant vasculopathy in a rat aortic allograft model after infusion of anti-inflammatory viral serpin.

BACKGROUND: Transplant vasculopathy remains a difficult therapeutic problem, resulting in the majority of late cardiac graft losses. This chronic vascular disease is thought to be triggered by alloantigen-dependent and alloantigen-independent inflammatory factors. Despite improved 1-year survival, the incidence of transplant vasculopathy has not improved with current immunosuppressive protocols. Highly effective strategies have evolved in the large DNA viruses that shield infecting viruses from host inflammatory responses. Serp-1 is a secreted myxoma virus anti-inflammatory serine proteinase inhibitor. Serp-1 inhibits plasminogen activators in a manner similar to plasminogen activator inhibitor (PAI-1), a vascular protein that plays a pivotal regulatory role in vascular wound healing. In this study, we tested the ability of purified Serp-1 protein to ameliorate posttransplant vasculopathy after rat aortic allograft surgery. METHODS AND RESULTS: Serp-1 protein or controls were infused into 98 rats immediately after segmental aortic allograft transplantation. After either late (28 days, 64 rats) or early (12 to 48 hours, 24 rats) follow-up, transplanted aortic segments were harvested for morphological and immunohistochemical analysis. Significant reductions in intimal plaque growth (P<0.002) and mononuclear cell invasion (P<0.033) were detected after Serp-1 infusion at nanogram doses. Serp-1 reduced early macrophage (P<0.0016) and nonspecific lymphocyte (P<0.0179) invasion into medial and adventitial layers and inhibited associated depletion of medial smooth muscle cells (P<0.0006). CONCLUSIONS: Infusion of a viral anti-inflammatory serpin, Serp-1, significantly reduces early inflammatory responses and later luminal occlusion in a rat aortic allograft model.

Animals↗

PubMed2000

Differences in the effects of HMG-CoA reductase inhibitors on proliferation and viability of smooth muscle cells in culture.

We investigated the influence of lovastatin, simvastatin and pravastatin on proliferation and viability of vascular smooth muscle cells (SMC) in vitro and studied the effects of lovastatin on a mouse SMC line transgenic for a temperature-sensitive mutant of SV40 large T antigen (TAg), known to inhibit the function of p53 and pRb family members. We found that lovastatin and simvastatin inhibited cell proliferation by provoking G0/G1 phase arrest with concomitant depression of the proliferation antigen Ki-67/MIB-1. Lovastatin at high concentrations of 20 micromol/l caused cell death in the presence of serum but not under serum starved conditions, which was verified on the basis of increased DNA strand breaks, decreased DNA content and morphological alterations seen by electron microscopy. Cell death was also found for simvastatin, whereas pravastatin did not exhibit antiproliferative or cytotoxic effects. Mouse SMC transgenic for TAg did not show any impaired sensitivity to the antiproliferative and cell death inducing effect of lovastatin, but both effects could be antagonized by the supplementation of mevalonate. The data indicate that antiproliferative and cytotoxic effects of lovastatin are caused by the using up of products of mevalonate metabolism and do not require the presence of p53 or pRb.

Animals↗