Biomedical subjects

J Lu

Publications and source records attributed to J Lu.

At least 343 records · Page 19Linked to original sources

PubMed1998

The histone acetylase PCAF is a nuclear receptor coactivator.

Whereas the histone acetylase PCAF has been suggested to be part of a coactivator complex mediating transcriptional activation by the nuclear hormone receptors, the physical and functional interactions between nuclear receptors and PCAF have remained unclear. Our efforts to clarify these relationships have revealed two novel properties of nuclear receptors. First, we demonstrate that the RXR/RAR heterodimer directly recruits PCAF from mammalian cell extracts in a ligand-dependent manner and that increased expression of PCAF leads to enhanced retinoid-responsive transcription. Second, we demonstrate that, in vitro, PCAF directly associates with the DNA-binding domain of nuclear receptors, independently of p300/CBP binding, therefore defining a novel cofactor interaction surface. Furthermore, our results show that dissociation of corepressors enables ligand-dependent PCAF binding to the receptors. This observation illuminates how a ligand-dependent receptor function can be propagated to regions outside the ligand-binding domain itself. On the basis of these observations, we suggest that PCAF may play a more central role in nuclear receptor function than previously anticipated.

3T3 Cells↗

PubMed1998

High-performance liquid chromatographic method for measurement of cytochrome P450-mediated metabolism of 7-ethoxy-4-trifluoromethylcoumarin.

An HPLC method for analysis of deethylation of 7-ethoxy-4-trifluoromethylcoumarin (ETFMC), a substrate of various enzymes of the cytochrome P450 superfamily, was developed. ETFMC was incubated at 37 degrees C with human hepatic microsomes or microsomes prepared from a lymphoblastoid cell line that expresses human CYP2B6. Under these conditions, the highly fluorescent metabolite 7-hydroxy-4-trifluoromethylcoumarin (HTFMC) is formed. The metabolite was analyzed by reversed-phase HPLC with fluorescence detection. The limits of detection of the metabolite were 5.0 fmol per injection, a sensitivity at least one order of magnitude greater than the standard method, which does not involve HPLC. This method will be of great utility when quantities of microsomal protein from cell lines expressing human CYP enzymes are limited.

Adult↗

PubMed1998

1H NMR studies of azide binding to cytochrome c.

The binding of azide ion to the heme iron of ferricytochrome c in D2O is studied using 1H NMR methods at pH 7.0 and 300 K or 315 K. Some hyperfine shifted resonances arising from heme peripheral protons and resonances of side-chain protons of some amino acid residues in N3-cyt c have been assigned using 2D EXSY and DQF-COSY methods. The majority of the heme pocket side-chain proton signals have been identified. The 1D nuclear overhauser effect (NOE) difference spectra and 2D NOESY spectrum are presented and changes in NOE patterns between the heme and certain residues, and several residues around the axial ligand are interpreted in terms of changes in the pocket structure. Interpretation of NOE data indicates that conformation changes are obvious on the Met80 side of the heme cavity in the environment of the axial ligand in N3-cyt c. In addition, kinetics analysis of azide binding to cyt c is studied using 2D EXSY method.

Animals↗

PubMed1998

cDNA cloning reveals two mouse beta5 integrin transcripts distinct in cytoplasmic domains as a result of alternative splicing.

The integrin beta5 subunit has only been found to form a heterodimer with subunit alphav which acts as a vitronectin receptor. Integrin alphavbeta5 has been implicated in cell migration and growth factor-induced angiogenesis. In the present study, a mouse liver cDNA library was screened using a human beta5 cDNA fragment obtained by reverse transcriptase PCR (RT-PCR). Three of the clones (MB5, MB15 and MB17) overlapped to give an open reading frame, called beta5A, which is homologous to the human beta5 subunit. The sequence of another clone (MB26), called beta5B, was identical with beta5A, except for a deletion of 29 bp near the 3' end of the open reading frame. The 29 bp deletion resulted in an open-reading-frame shift and a completely different C-terminal sequence in beta5B. beta5A and beta5B were shown, by RT-PCR, to be co-expressed in most mouse tissues tested, although beta5B mRNA was detected at much lower levels than beta5A. beta5A and beta5B mRNAs were also detected in the mouse monocytic cell line, J774, and in isolated mouse peritoneal macrophages. Adhesion of peritoneal macrophages has been shown to up-regulate the expression of both beta5A and beta5B mRNAs. The 29 bp sequence begins with a putative intron-splicing donor site (GTGAT...). A 3' fragment of the mouse integrin beta5 gene was cloned by PCR and sequenced showing that the 29 bp sequence was also immediately followed by an intron. Therefore, the 29 bp sequence was apparently expressed as part of the beta5A mRNA but was spliced out as part of the downstream intron in beta5B. Since the cytoplasmic domains of the integrin beta subunits are important in cytoskeleton attachment and signalling, the two alternatively spliced beta5 isoforms may have distinct roles in cell adhesion and other cellular functions.

Alternative Splicing↗

PubMed1998

Disruption of cellular translational control by a viral truncated eukaryotic translation initiation factor 2alpha kinase homolog.

Phosphorylation of eukaryotic translation initiation factor 2alpha (eIF2alpha) is a common cellular mechanism to limit protein synthesis in stress conditions. Baculovirus PK2, which resembles the C-terminal half of a protein kinase domain, was found to inhibit both human and yeast eIF2alpha kinases. Insect cells infected with wild-type, but not pk2-deleted, baculovirus exhibited reduced eIF2alpha phosphorylation and increased translational activity. The negative regulatory effect of human protein kinase RNA-regulated (PKR), an eIF2alpha kinase, on virus production was counteracted by PK2, indicating that baculoviruses have evolved a unique strategy for disrupting a host stress response. PK2 was found in complex with PKR and blocked kinase autophosphorylation in vivo, suggesting a mechanism of kinase inhibition mediated by interaction between truncated and intact kinase domains.

Animals↗

PubMed1998

Origin, nature, and some functional considerations of intraventricular macrophages, with special reference to the epiplexus cells.

Intraventricular macrophages encompass the supraependymal, free-floating, and epiplexus (Kolmer) cells; the supraependymal cells lie in close apposition to the ventricular ependyma, the epiplexus cells are closely associated with the choroid plexus epithelium, and the free-floating cells are at a variable distance from the epithelial surface. Although the three cell types are regarded as one cellular entity, the epiplexus cells preponderate. On scanning electron microscopy, the epiplexus cells display diverse morphological forms, ranging from round to bipolar to stellate, and bear a variable number of cytoplasmic processes. Transmission electron microscopy shows the presence of large numbers of lysosomes. The phagocytic nature of epiplexus cells is shown by their intense staining for nonspecific esterase and active uptake of tracers, e.g., horseradish peroxidase and rhodamine isothiocynate, administered intravenously or intraperitoneally. The mode of entry of these tracers in the cerebral ventricles is by way of transepithelial transport. In rats, the population of intraventricular macrophages increases steadily after birth until 17 days of age; thereafter, their cell population remains relatively unchanged. The early upsurge is attributed to proliferation of residential cells and/or influx of circulating monocytes/stromal macrophages through the process of "emperipolesis." The immunophenotypic features of intraventricular macrophages are consistent with other mononuclear phagocytes being immunoreactive for OX-42, OX-18, OX-6, and OX-1 and ED1 for the detection of CR3 receptors, MHC class I and II antigens, leucocyte common antigen, and macrophage antigen, respectively. The expression of these antigens is noticeably enhanced following the injection of lipopolysaccharide (LPS) into postnatal rats. Remarkably, the intraventricular macrophages are induced to express MHC class II (Ia) antigen after LPS or interferon-gamma injections. Furthermore, the expression of transferrin receptors as detected with OX-26 is also upregulated after these treatments. Epiplexus cells are also elicited to display a de novo expression of nitric oxide synthase-like immunoreactivity following intracerebral injection of LPS. They also respond vigorously to a single nonpenetrative blast. Results of our series of studies suggest that, besides their primary function as scavenger cells, the intraventricular macrophages partake in possible immunological responses and iron regulation in the ventricular system or the brain as a whole.

Animals↗

PubMed1998

Human L-ficolin: plasma levels, sugar specificity, and assignment of its lectin activity to the fibrinogen-like (FBG) domain.

Ficolins are characterised by the presence of collagen-like and fibrinogen-like (FBG) sequences. Human L-ficolin is synthesised in the liver and secreted into blood circulation. In previous studies, it was shown to bind to N-acetyl-D-glucosamine (GlcNAc). In the present study, its detailed sugar specificity and binding site have been investigated. It was found to bind to GlcNAc and GalNAc (N-acetyl-D-galactosamine) while showing no significant affinity for the precursor sugars. The structure in these molecules which is recognised by L.-ficolin has been deduced to include an amide (-CO-NH-) or similar group. L-Ficolin was digested with collagenase and the collagenase resistant FBG domain was shown to bind to GlcNAc. Its levels in adult and cord blood-derived human plasma were also determined and showed that adult plasma contains approximately three times more L-ficolin than that of newborn babies.

Adult↗

PubMed1998

Anatomic considerations of C2 nerve root ganglion.

STUDY DESIGN: Dissection and observation of the dorsal root ganglion of the second cervical spinal nerve bilaterally. OBJECTIVES: To determine the position of the C2 dorsal root ganglion and the heights of the C2 ganglion and its corresponding foramen. SUMMARY OF BACKGROUND DATA: The dorsal root ganglion has been well studied in the middle and lower cervical spine and in the lumbar spine. In no previous study are the position and height of the C2 dorsal root ganglion and its corresponding foramen described. METHODS: Fifteen cadaveric cervical spines were exposed posteriorly. The C2 nerve roots and ganglia were dissected between the arch of the atlas and the lamina of the axis. The heights of the C2 ganglion and foramen were measured. The location of the C2 ganglion was also macroscopically observed. RESULTS: The heights of the C2 ganglion and foramen are 5.7 +/- 0.8 mm and 7.7 +/- 1.2 mm, respectively. The C2 ganglion occupies 76% of the foramen height. All C2 dorsal root ganglia are confined within foramens between the arch of the atlas and the lamina of the axis. CONCLUSIONS: The C2 dorsal dorsal root ganglia are all proximally placed and occupy most of the foramen height, which may render the C2 ganglion vulnerable to entrapment.

Cadaver↗

PubMed1998

Structure-function study of the extracellular domain of the human IFN-alpha receptor (hIFNAR1) using blocking monoclonal antibodies: the role of domains 1 and 2.

We have performed a structure-function analysis of extracellular domain regions of the human IFN-alpha receptor (hIFNAR1) using mAbs generated by immunizing mice with a soluble hIFNAR1-IgG. Five mAbs described in this study recognize different epitopes as determined by a competitive binding ELISA and by alanine substitution mutant analyses of the hIFNAR1-IgG. Two mAbs, 2E1 and 4A7, are able to block IFN-stimulated gene factor 3 (ISGF3) formation and inhibit the antiviral cytopathic effect induced by several IFN-alpha (IFN-alpha 2/1, -alpha 1, -alpha 2, -alpha 5, and -alpha 8). None of these anti-IFNAR1 mAbs were able to block activity of IFN-beta. mAb 4A7 binds to a domain 1-hIFNAR1-IgG but not to a domain 2-hIFNAR1-IgG, which suggests that its binding region is located in domain 1. The binding of the most potent blocking mAb, 2E1, requires the presence of domain 1 and domain 2. The most critical residue for 2E1 binding is a lysine residue at position 249, which is in domain 2. These findings suggest that both domain 1 and domain 2 are necessary to form a functional receptor and that a region in domain 2 is important. IFN-beta recognizes regions of the hIFNAR complex that are distinct from those important for the IFN-alpha.

Alanine↗

PubMed1998

The reaction of lanthanide ions with n-doxyl stearic acids and its utilization for the ESR study on the permeability of lipid-bilayer of erythrocyte membrane to gadolinium ions.

The reaction of lanthanide ions with n-doxyl stearic acid (nDS) spin labels (n = 5,7,12,16) was investigated by the electron spin resonance technique in aqueous solution. Among the lanthanides, the Gd3+, Tb3+, Tm3+ and Ce3+ ions strongly quenched the ESR signal of spin labels, but the effects of La3+, Eu3+ and Lu3+ are very weak. The quenching effects are featured by: (1) the dependence on the concentration of lanthanide ions; (2) no obvious changes of the ESR line shape in the presence of lanthanide ions; (3) the quenching constant decreases in the order: Gd3+ > Tb3+ > Tm3+ > Ce3+; (4) the quenching effects of lanthanide ions are found to strikingly correlate with their magnetic properties. These findings indicate that the interaction of lanthanide ions with nitroxide oxygen leading to the reduction of ESR signal amplitude is dominated by their magnetic characteristics rather than the coordination effect. By labeling erythrocyte membrane with nDS, n = 5,7,12,16 at different depths, we studied the diffusion of Gd3+ into the lipid-bilayer of erythrocyte membrane by monitoring the reduction processes of the ESR signals of nitroxide spin labels located at different depths of membrane lipid-bilayer after addition of Gd3+. These results revealed that the Gd3+ ions can penetrate into the lipid-bilayer, though the entry rate is slow. It was shown that the Gd3+ ions bind to the membrane and enhance the permeability of extracellular ascorbate into erythrocyte membrane. The transport mechanism of Gd3+ ions through the lipid-bilayer might be involved in the Gd3+ cation-induced pore formation in the surface of membrane.

Ascorbic Acid↗

PubMed1998

Role of p53 in the regulation of irradiation-induced apoptosis in neuroblastoma cells.

Wild-type p53 plays a crucial role in the control of apoptosis following ionizing radiation (IR); conversely, mutant p53 is associated with IR resistance. Although wild-type p53 is expressed in virtually all neuroblastoma tumors, treatment failures secondary to inadequate local control with radiotherapy are a problem in patients with advanced stage disease. This apparent paradox is the focus of our interest. The Shep-1 neuroblastoma cell line is highly resistant to IR. This cell line contains a wild-type p53 gene and is an ideal model for studying the mechanism of IR resistance in this disease. Following high-dose IR, cell fractionation demonstrated that p53 is induced and targeted to the nucleus. The induced p53 is functional as p53-responsive genes (Waf-1 and MDM-2) are appropriately induced following IR. Intriguingly, overexpression of p53 could reverse the inherent IR resistance of Shep-1 cells. Multiple cell lines expressing variable levels of exogenous temperature-sensitive p53 were generated. Pulse induction of p53 alone did not affect Shep-1 cell viability, while induction of p53, followed by IR, resulted in cell death and DNA fragmentation proportional to the dose of IR and the level of p53 expression. These findings demonstrate that p53 overexpression renders Shep-1 cells IR-sensitive and suggest that large quantities of exogenous p53 can overcome the factors inhibiting p53-mediated, IR-induced apoptosis.

Apoptosis↗

PubMed1998

Anatomic basis of dorsoradial approach for radioulnar synostosis.

The object of this study was to identify the best approach for exposing the radioulnar interosseous membrane while protecting the posterior interosseous n. (PIN). Twenty paired upper limbs were used to obtain measurements of the PIN and expose the distal two-thirds of the interosseous membrane in the forearm through a dorsoradial approach. The length of the PIN from the radial head to the arcade of Frohse (AF) was 26.5 +/- 1.6 mm in males and 25.3 +/- 1.1 mm in females. The length of the PIN between the radial head and the point where the PIN exits from the supinator was 66.7 +/- 4.7 mm in males and 64.0 +/- 2.5 mm in females. The length of the PIN covered by the supinator was 44.0 +/- 0.5 mm in males and 37.0 +/- 0.5 mm in females. The distance between the point where the PIN exits from the supinator and the lateral margin of the radius was 15.0 +/- 0.9 mm in males and 14.5 +/- 0.9 mm in females. The distance between the exit point of the PIN from the supinator and the lateral margin of the ulna was 18.2 +/- 0.6 mm in males and 17.9 +/- 0.7 mm in females. The distance from the point where the most lateral branch of the PIN entered the abductor pollicis longus (APL) to the lateral margin of the radius was 3.5 +/- 0.5 mm. In 20 cadaveric upper limb, the middle and distal portions of the interosseous membrane were exposed through the interval between the extensor carpi radialis brevis (ECRB) and extensor digitorum communis (EDC) m., after the origin of the extensor pollicis brevis (EPB), and extensor pollicis longus (EPL) mm. had been elevated from the lateral margin of the radius. The present study suggests that using dorsoradial approach facilitates exposure of the middle and distal portions of the interosseous membrane.

Aged↗

PubMed1998

Cervical uncinate process: an anatomic study for anterior decompression of the cervical spine.

Morphometric evaluation of 54 dry cervical spines from C3 to C7 (a total of 270 cervical vertebrae) was performed to determine the bony boundaries of the uncinate process for resection of the uncinate process for access to posterolateral osteophytes or herniated disks at the time of anterior cervical diskectomy. The uncinate processes were significantly higher (p < 0.01) at the C4-C6 levels (5.8 +/- 1.1 mm to 6.1 +/- 1.3 mm) than at the C3 or C7 levels. The distance between the medial and lateral margins of the base of the uncinate process was significantly smaller (p < 0.01) at the C3 level (4.9 +/- 0.7 mm) than at the C7 level (6.3 +/- 0.7 mm). The anteroposterior diameter of the medial margin of the uncinate process decreased gradually from the C5 (12.5 +/- 1.5 mm) to C7 levels (11.6 +/- 1.3 mm) (p < 0.05). The inter-uncinate distance widened from the C3 (19.2 +/- 1.5 mm) to the C7 (24.6 +/- 2.1 mm) levels (p < 0.01). The mid-anteroposterior diameter of vertebral body increased gradually from the C3 (14.7 +/- 1.1 mm) to the C7 levels (16.1 +/- 1.5 mm) (p < 0.01). The width of the vertebra increased gradually from C3 to C7 (from 19.2 +/- 1.8 mm at C3 to 25.6 +/- 2.0 mm at C7) (p < 0.01). Knowledge of all the aforementioned data may be helpful during anterolateral cervical uncosectomy or uncoforaminotomy.

Cadaver↗

PubMed1998

Anterior tibial artery and its actual projection on the lateral aspect of the tibia: a cadaveric study.

The anterior tibial artery (ATA) is at risk of injury during high tibial osteotomy, Ilizarov wire placement, pin placement in external fixation, or proximal locking screw insertion, as the artery is not visualized intraoperatively. The ATA is anchored to the oval foramen of the interosseous membrane on the proximal tibia by the deep fascia and recurrent genicular vascular branches. Segment 1 (from the bifurcation of the popliteal artery to the level of the interosseous foramen) and the proximal part of segment 2 (from the interosseous foramen to the level where the artery crosses the anterior border of the tibia) may be damaged when pin, wire or screw placement is directed posterolaterally at that level. Distally, a straight mediolateral pin or Ilizarov wires may lacerate the artery. Segment 2 of the ATA descends against the interosseous membrane in its proximal part, which is projected on the posterior third of the tibia relative to the sagittal plane; in its middle part, it runs close to the lateral cortex of the tibia, it is projected on the middle third of the tibia; in its distal part it runs gradually towards the anterior third of the tibia and contacts with the anterior third of the tibial cortical surface. This information may help reduce risk of injury to the ATA during high tibial osteotomy, external fixation and pin placement or insertion of locking screws.

Bone Nails↗

PubMed1998

Anatomic basis of the anterior surgery on the cervical spine: relationships between uncus-artery-root complex and vertebral artery injury.

Vertebral artery injury is a serious complication during anterior surgery on the cervical spine. However, little information is available in the literature concerning the mechanism of vertebral artery laceration during the procedures of the anterior cervical decompression. In the current study twenty-eight cadavers were dissected to determine the location and relationships of the fibro-ligamentous tissues to the uncinate process, vertebral artery and nerve roots from the C3 to C6 levels. The vertebral artery and nerve root are encased by a fibro-ligamentous band at the level of the intertransverse space. This fibro-ligamentous band is attached to the lateral aspect of the uncinate process and uncovertebral joint, which combines the vertebral artery, nerve root and uncinate process to form a complex or unit. The fibro-ligamentous tissues between the uncovertebral joint and vertebral artery may explain the propensity to vertebral artery laceration during resection of the uncinate process or an osteophyte projecting from the uncovertebral joint. For this reason, the authors recommend that before resection of the uncinate process or uncovertebral joint is performed, it is necessary to thoroughly dissect the fibro-ligamentous tissues off the uncinate process.

Aged↗

PubMed1998

Cytostatic and apoptotic effects of paclitaxel in human breast tumors.

PURPOSE: We have previously reported incomplete cytotoxic responses of other human solid tumors (bladder, head and neck, ovarian and prostate) to paclitaxel. This finding is qualitatively different from the nearly complete response observed in monolayer cultures of human cancer cell lines. The present study examined the pharmacodynamics of paclitaxel in human breast tumors. METHODS: Three-dimensional histocultures of patient tumors were used. The cytostatic effect was evaluated by measurement of the inhibition of 48-h cumulative bromodeoxyuridine (BrdUrd) incorporation. The apoptotic effect was evaluated in terms of morphological changes and by in situ DNA end labeling. RESULTS: Paclitaxel produced partial cytostasis (approximately 30% maximum) and induced apoptosis (maximum apoptotic index of 3.3% to 29%) in all 15 tumors. More than 95% of apoptotic cells were BrdUrd labeled, but not all BrdUrd-labeled cells were apoptotic. The maximal apoptotic indices in the tumors were significantly correlated with the BrdUrd labeling index of untreated controls (r2 = 0.63, P < 0.01). The maximum apoptotic effect was observed at a tenfold lower drug concentration (0.1 microM) compared to the maximum cytostatic effect (1 microM). Neither of these effects was enhanced by increasing the drug concentration to 10 microM. CONCLUSIONS: The pharmacodynamics of paclitaxel in human breast tumors are comparable to those found in other human solid tumors. The labeling of apoptotic cells by BrdUrd and the correlation between the proliferation index and apoptosis suggest that drug-induced apoptosis is linked to cell proliferation and is completed after DNA synthesis. The finding that maximal cytostatic and apoptotic effects of paclitaxel were achieved at or below the clinically achievable concentration of 1 microM suggests further increasing the dose to elevate plasma concentration beyond 1 microM may not improve treatment outcome.

Adolescent↗

PubMed1998

The bidirectional effect of vanadyl ion on the oxygen affinity of human hemoglobin.

The bidirectional effects of vanadyl on the oxygen affinity of hemoglobin depend on the mole ratio of vanadyl to Hb(R). In low R, the vanadyl ion increases Hb's oxygen affinity due to DPG hydrolysis. The lowered oxygen affinity in higher R is mainly due to the reactive-oxygen-species, probably superoxide, induced oxidation of Fe(II)-Hb to Fe(III)-Hb. The conformation change due to vanadyl binding contribute also to the lowered oxygen binding, but is monotonously decreasing with increasing of R values.

Circular Dichroism↗

PubMed1998

Ficolins and the fibrinogen-like domain.

Ficolins are a group of proteins containing collagen-like and fibrinogen-like (FBG) sequences and they have a similar overall structure to C1q and the collectins. There are two types of ficolin in man: L-ficolin and M-ficolin. L-ficolin is synthesized in the liver and secreted into the plasma. It binds to several apparently unrelated structures including sugar residues and enhances phagocytosis of bound bacteria. M-ficolin is synthesized mainly in monocytes and is detected on the monocyte surface. The polypeptide sequences of ficolins, the collectins and C1q diverge mainly in their C-terminal globular regions which are, respectively, FBG domains, Ca(2+)-dependent carbohydrate recognition domains (C-type CRD), and collagen-related sequences. The FBG domain consists of 220-250 residues and is found in a number of proteins besides fibrinogen and ficolins. The crystal structure of the FBG domain has been characterized and the elucidation of its binding properties should provide essential insights into its role in ficolins and other proteins.

Amino Acid Sequence↗