Biomedical subjects

Z Lu

Publications and source records attributed to Z Lu.

At least 289 records · Page 16Linked to original sources

PubMed1997

A natural motif approach to protein design: a synthetic leucine zipper peptide mimics the biological function of the platelet factor 4 protein.

The design of smaller functional mimics of large proteins has long been an important challenge. In this study we use the natural leucine zipper as a structural template to design a 31-residue peptide analog that mimics the function of the larger platelet factor 4 (PF4) protein. The heparin binding activity of PF4 has been introduced into an unrelated leucine zipper sequence only by virtue of incorporating four lysines of PF4. Circular dichroism and binding experiments have shown that the designed leucine zipper peptide adopts a stable helical conformation and shows significant PF4-like heparin binding activity. These results strongly suggest that the lysine residues play an important role in the binding of PF4 to heparin. The de novo generation of the PF4 function in a designed leucine zipper peptide demonstrates that the leucine zipper motif is a useful scaffold for the design of functional peptides and proteins.

Amino Acid Sequence↗

PubMed1997

Preparation of Liposomes with a Controlled Assembly Procedure

A method of liposome preparation that involves two experimental steps is demonstrated. First, water in oil (W/O) emulsions are prepared by sonication. Then, due to centrifugal force, water droplets in the emulsion contact the monolayer at the oil/water interface and transform into liposomes after the monolayer has enwrapped the droplets. This procedure results in liposomes with diameters in the range 50-200 nm. Advantages of this procedure include relatively high (60%) encapsulation efficiency, direct preparation of liposomes in an aqueous medium different from the entrapped phase, and no leakage of the encapsulated chemicals during preparation. This relatively simple and rapid method may be useful in the encapsulation of drugs, enzymes, and other macromolecules as well as in the study of membrane properties.

Journal Article↗

PubMed1997

Association between v-Src and protein kinase C delta in v-Src-transformed fibroblasts.

In response to the kinase activity of v-Src there is an increase in the membrane association of the novel protein kinase C (PKC) isoform PKC delta (Zang, Q., Frankel, P., and Foster, D. A. (1995) Cell Growth Differ. 6, 1367-1373). We report here that in v-Src-transformed cells PKC delta co-immunoprecipitates with v-Src and is phosphorylated on tyrosine. The tyrosine-phosphorylated PKC delta had reduced enzymatic activity relative to the non-tyrosine-phosphorylated PKC delta from v-Src-transformed cells. The association between Src and PKC delta was dependent upon both an active Src kinase and membrane association. The association between c-Src Y527F and PKC delta was substantially enhanced by mutating a PKC phosphorylation site at Ser-12 in Src to Ala indicating that PKC delta phosphorylation of Src at Ser-12 destabilizes the interaction, possibly in a negative feedback loop. These data demonstrate that upon recruitment of PKC delta to the membrane in v-Src-transformed cells there is the formation of a Src.PKC delta complex in which PKC delta becomes phosphorylated on tyrosine and down-regulated.

Animals↗

PubMed1997

A BIR motif containing gene of African swine fever virus, 4CL, is nonessential for growth in vitro and viral virulence.

An African swine fever virus (ASFV) gene with similarity to viral and cellular inhibitor of apoptosis genes (iap) has been described in the African isolate Malawi Lil-20/1 (ORF 4CL) and a cell-culture-adapted European virus, BA71V (ORF A224L). The similarity of the ASFV gene to genes involved in inhibiting cellular apoptosis suggested the gene may regulate apoptosis in ASFV-infected cells and thus may function in ASFV virulence and/or host range. Sequence analysis of additional African and European pathogenic isolates demonstrates that this gene is highly conserved among both pig and tick ASFV isolates and that its similarity to iap genes is limited to the presence of a single IAP repeat motif (BIR motif) in the ASFV gene. To study gene function, a 4CL gene deletion mutant, delta 4CL, was constructed from the pathogenic Malawi Lil-20/1 isolate. Growth characteristics of delta 4CL in swine macrophage cell cultures were indistinguishable from those of parental virus. Infected macrophage survival time and the induction and magnitude of apoptosis in virus-infected macrophages were comparable for cells infected with either delta 4CL or parental virus. In infected swine, delta 4CL exhibited an unaltered Malawi Lil-20/1 virulence phenotype. These data indicate that, although highly conserved among ASFV isolates, the 4CL gene is nonessential for growth in macrophage cell cultures in vitro and for pig virulence. Additionally, despite its limited similarity to JAP genes, 4CL exhibits no anti-apoptotic function in infected macrophage cell cultures. The high degree of gene conservation among ASFV isolates, together with the apparent lack of function in the swine host, suggests 4CL may be a host range gene involved in aspects of infection in the arthropod host, ticks of the genus Ornithodoros.

African Swine Fever↗

PubMed1997

VLA-4 integrin cross-linking on human monocytic THP-1 cells induces tissue factor expression by a mechanism involving mitogen-activated protein kinase.

Adhesion molecules such as VLA-4 are important not only for monocyte adhesion to extracellular matrix proteins, but also for subsequent cell activation. Monocyte adherence to fibronectin or engagement of VLA-4 has been demonstrated to stimulate production of potent inflammatory mediators such as tumor necrosis factor-alpha, interleukin-1, and the procoagulant tissue factor protein. However, the intracellular signaling cascades leading to gene expression have not been elucidated. Using the human monocytic THP-1 cell line, VLA-4 cross-linking by monoclonal antibodies directed against its alpha4 and beta1 subunits produced a time-dependent increase in tyrosine phosphorylation of a broad range of cellular proteins. Using Western blot analysis directed against the phosphorylated form of the extracellular signal-related kinase (ERK) mitogen-activated protein (MAP) kinase proteins, as well as immunoprecipitation and in vitro kinase assays, we found that VLA-4 cross-linking increased ERK1/ERK2 tyrosine phosphorylation and activity. In conjunction, integrin cross-linking also increased NF-kappaB nuclear translocation and 4-h expression of tissue factor. Inhibition of tyrosine kinase activity with genistein (10 microg/ml) as well as selective MAP kinase inhibition with the MEK-1 inhibitor PD98059 abolished the VLA-4-dependent ERK tyrosine phosphorylation, inhibited NF kappaB nuclear binding, and abrogated tissue factor expression induced by both VLA-4 cross-linking and adhesion to fibronectin in THP-1 cells and human peripheral blood monocytes. These studies point to the involvement of the MAP kinase pathway in the activation of monocytic cells during transmigration to inflammatory sites.

Calcium-Calmodulin-Dependent Protein Kinases↗

PubMed1997

Expression of chemokine receptors by subsets of neurons in the central nervous system.

IL-8 is expressed by activated and neoplastic astrocytes and enhances the survival of hippocampal neurons in vitro. Since mRNA encoding chemokine receptors have been demonstrated in brain, the expression of chemokine receptors by specific cell types in anatomic regions of the central nervous system (CNS) was investigated. Archival tissues from various regions of the CNS were stained with specific mAbs to the Duffy Ag/receptor for chemokines, a promiscuous receptor that binds selected chemokines; the specific receptor for IL-8 (CXCR1); and the receptor (CXCR2) shared by IL-8 and melanoma growth stimulatory activity. The Duffy Ag/receptor for chemokines was expressed exclusively by Purkinje cells in the cerebellum. Chemokine binding and radioligand cross-linking confirmed the presence of a high affinity, promiscuous chemokine receptor in the cerebellum. Although CXCR1 was not expressed in the CNS, CXCR2 was expressed at high levels by subsets of projection neurons in diverse regions of the brain and spinal cord, including the hippocampus, dentate nucleus, pontine nuclei, locus coeruleus, and paraventricular nucleus, and in the anterior horn, interomediolateral cell column, and Clarke's column of the spinal cord. Fibers that express CXCR2 included those in the superior cerebellar peduncle and the substantia gelatinosa. Immunohistochemical analysis of the involved brain tissues from patients with Alzheimer's disease revealed expression of CXCR2 in the neuritic portion of plaques surrounding deposits of amyloid. These data suggest that chemokines may play a role in reactive processes in normal neuronal function and neurodegenerative disorders.

Antigens, CD↗

PubMed1997

High-performance liquid chromatographic determination of 9-(3-pyridylmethyl)-9-deazaguanine (BCX-34) in biological fluids.

9-(3-Pyridylmethyl)-9-deazaguanine (BCX-34), a new purine nucleoside phosphorylase inhibitor, has selective immunosuppressive activity with potential therapeutic value in T-cell-mediated disease. We now report a sensitive, specific and reproducible method for measurement of 9-(3-pyridylmethyl)-9-deazaguanine in biological fluids using high-performance liquid chromatography (HPLC). 9-(3-Pyridylmethyl)-9-deazaguanine was extracted from plasma using perchloric acid precipitation followed by passage through Sep-Pak C18 cartridges (average extraction efficiency, 64.6%). Standard curves were linear over the range of interest (28-1120 ng/ml in plasma and 200-4000 ng/ml in urine, r2 > 0.999). Within-day and between-day coefficients of variation were less than 8%. The limit of quantitation was 28 ng/ml in plasma and 200 ng/ml in urine. This HPLC method should be useful in future clinical studies with this drug.

Administration, Oral↗

PubMed1997

Cloning and origin of the two forms of chicken vitamin D receptor.

The cDNA for the chicken vitamin D receptor (VDR) has been cloned in full length by screening cDNA libraries from chicken intestine and chicken kidney. The chicken kidney cDNA library constructed by both oligo(dT) and random primer methods yielded several full-length clones. These contained a 66-bp additional coding sequence at the 5' end in comparison to the cDNAs of human, rat, and mouse VDR. The Japanese quail VDR cDNA was also cloned in full length. We found that the 5' coding sequence reported previously had been artifactually inverted. Both chicken and quail cDNAs have three conserved ATG sites for translation initiation with the 3' one corresponding to the only ATG site found in the mammalian cDNAs. Northern blot analysis showed that the VDR gene is expressed as a single 2.69-kb transcript in chicken intestine and kidney. An analysis of the avian multiple ATG sites revealed that the first ATG is in a suboptimal context of TCCATGT, while the second ATG is in AGC-ATGG, matching the optimal context: R-3NNATGG+4. As a result, the two forms of chicken VDR (cVDR) (form A, 60.3 kDa; form B, 58.6 kDa) likely arise from the first and second ATG sites of a single mRNA during translation. Mutational analysis confirmed this belief. The wild-type construct starting from the first ATG site with its original context was subcloned into pCMV5 expression vector and expressed in COS-1 cells. Two receptor proteins, exactly comigrating with the form A and form B cVDRs isolated from chicken intestine, were detected by immunoblotting. Point mutations optimizing the first ATG context led to exclusive production of form A, while knocking out the first ATG site resulted in the sole generation of form B. Form A translated from the first ATG site has 451 amino acids, and form B from the second ATG has 437 amino acids. Comparison between avian and mammalian VDRs indicated that VDR is essentially conserved in DNA binding and ligand binding domains. The significant difference especially at the N-terminus demonstrates divergence of this receptor during evolution of these species.

Amino Acid Sequence↗

PubMed1997

Effects of cement creep on stem subsidence and stresses in the cement mantle of a total hip replacement.

In cemented total hip prostheses, the role of creep of the acrylic cement (polymethyl methacrylate, [PMMA]) in increasing or decreasing the chance of failure of the cement mantle is a subject of ongoing controversy. In the present study we used a three-dimensional finite-element model of a cemented stem to assess the influence of cement creep on subsidence of the stem, and on the stress and strain in the cement under cyclic load, both in the short and long term. The cement layer was assigned the shear and bulk creep moduli of Zimmer regular PMMA cement, which were obtained experimentally. The stem-cement interface was modeled either as (1) completely bonded, (2) completely debonded with friction, or (3) completely debonded and frictionless. Under the cyclic load some cement creep occurred with all three bonding conditions, allowing additional subsidence of the stem and a decrease in the stress components within the cement. During the unloaded period the full recovery of the preload conditions could be reached with the completely bonded and with the frictionless interfaces. With the frictional interface there was residual cement creep, residual stresses within the cement, and residual subsidence of the stem during the unloaded period; however, the reduction of the stress was at most 13% and the subsidence was about 0.46 mm. The much larger subsidence of debonded stems that is often observed clinically might be attributed to the factors which were not included in the present model, such as circumferential bone remodeling.

Biocompatible Materials↗

PubMed1997

Anti-inflammatory activity of the aqueous extract from Rhizoma smilacis glabrae.

Our previous paper has reported that the aqueous extract from Rhizoma smilacis glabrae (RSG) (RSG ext) selectively inhibited the effector phase of delayed-type hypersensitivity (DTH) without suppressing humoral immune response. In the present study, a remarkable inhibitory activity was exhibited by the extract against both primary and secondary hind paw swelling of adjuvant arthritis in rats. RSG ext also significantly reduced the inflammatory edema induced by carrageenan in either naive or bilaterally adrenalectomized rats, suggesting the independence of the anti-inflammatory action on the function of pituitary-adrenal axis. The PGE2 content in the carrageenan-induced inflammatory tissue was also decreased remarkably by the extract. Furthermore, RSG ext showed a distinct inhibition on the formation of cotton-induced granuloma formation. However, as compared with a steroidal agent, prednisolone, the extract did not affect the vitamin C content in adrenal gland as well as the weights of some organs. These results suggest that RSG ext may act as a therapeutic agent of immunoinflammatory diseases through a selective suppression on the cellular immune response involved in inflammations as well as through a direct anti-inflammatory mechanism including inhibiting PGE2.

Adrenal Glands↗

PubMed1997

Bipolar esophageal electrocardiography by using standard limb leads.

The ear-xiphisternum distance (EXD, the distance from the low edge of the ear to the xiphisternal basis in supine position) was used as a reference value for esophageal catheter insertion. ECGs recorded in the esophagus with bipolar electrocardiography using standard limb lead (ESLL) and conventional unipolar lead (ECUL) were compared. 112 patients with sinus rhythm and 76 patients during paroxysmal supraventricular tachycardia (PSVT) whose P-wave and QRS complex did not overlap were studied. The results suggested that in sinus rhythm the amplitude of the P-wave in ESLL was larger and the T-wave was smaller than in ECUL. During PSVT, the P-wave was much clear and higher in each lead of ESLL than that in ECUL. The ideal range of esophageal ECG recording was situated between the end of EXD and 6.5 cm proximal to it.

Adolescent↗

PubMed1997

Discrete cleavage patterns of pseudorabies virus immediate early protein (IE180) seen in some cell lines upon extraction after cycloheximide reversal.

Pseudorabies virus (PrV) encodes for a single and essential immediate early phosphoprotein designated IE180. In this study, IE180 was examined in lysates from various cell lines infected at high multiplicities under cycloheximide inhibition of protein synthesis and subsequent reversal. Three distinct protein patterns of IE180 which were cell-specific and dependant on the extraction procedure were revealed. Detergent lysates of PrV infected MDBK cells yielded almost exclusively wild type IE molecule (180 kDa). In contrast, SSG/94 cells, VERO or CV-1 cells did not yield 180 kDa molecules but predominantly a shorter variant of approximately 60 kDa in molecular mass. Additional bands of about 50/55 kDa were also detected in lysates of SSG/94 and VERO cells by immunoprecipitation. Lysates of CV-1 and MDBK cells also yielded a 120 kDa molecule. The smaller molecular mass bands occurred in the presence of PMSF and aprotinin however, cleavage was blocked completely by addition of N alpha-p-Tosyl-L-lysine chloromethyl ketone (TLCK) into the lysis buffer. Moreover, an ability of the shorter IE180 variants to bind heparin was also revealed in the study. These data provide useful insights on protease profiles encountered among different PrV susceptible cells and indicates the use of appropriate protease inhibitors such as TLCK to protect IE180 under these experimental conditions.

Animals↗

PubMed1997

Presence of two signaling TGF-beta receptors in human pancreatic cancer correlates with advanced tumor stage.

Transforming growth factor-beta (TGF-beta) signal transduction is mediated via specific cell surface signaling TGF-beta receptors, most notably the type I ALK5 (TbetaR-I[ALK5]) and the type II (TbetaR-II). We evaluated TbetaR-I(ALK5) and TbetaR-II expression in 41 human pancreatic cancer tissue samples and correlated these findings with clinical data of the patients. Northern blot analysis indicated that, in comparison with the normal pancreas, pancreatic adenocarcinomas exhibited 8.0-fold and 4.5-fold increases (P < 0.01), respectively, in mRNA levels encoding TbetaR-I(ALK5) and TbetaR-II. In situ hybridization showed that both TbetaR-I(ALK5) and TbetaR-II mRNA were highly expressed in the majority of pancreatic cancer cells. Immunohistochemical analysis of TbetaR-I(ALK5) and TbetaR-II revealed positive immunostaining in 73% and 56% of the tumors, respectively. Both receptors were concomitantly present in 54% of the pancreatic cancer samples. The presence of TbetaR-I(ALK5) or TbetaR-II and the concomitant presence of TbetaR-I(ALK5) and TbetaR-II in the cancer cells was associated with advanced tumor stage (P < 0.01). These findings show that in many human pancreatic cancers, increased levels of the two signaling TbetaRs are present. The presence of the signaling TbetaRs in advanced tumor stages indicates a role in disease progression.

Adenocarcinoma↗

PubMed1997

Use of transport mutants to examine the identity and expression of GLUT isoforms in rat cardiac myoblasts.

Two different spontaneous glucose transport (GLUT) mutants were used to examine the identity and properties of proteins involved in rat cardiac myoblast glucose transport processes. The parental clone, H9C2, possessed a high (HAHT) and a low (LAHT) affinity hexose transport process, and the GLUT 1, 3 and 4 isoforms. Mutant RCM was devoid of HAHT, the GLUT 3 transcript, and a 41 kDa protein recognizable by an anti-mouse GLUT 3 Ab. Mutant EZ-4 was impaired in the GLUT 3 and 4 isoforms, and in HAHT and LAHT. These studies demonstrated a close association of the GLUT 3 and 4 isoforms with the HAHT and LAHT processes, respectively. Both GLUT 3 and 4 isoforms were regulated in opposite ways during myogenesis, and both GLUT 3 mutants were impaired in myogenesis. Despite its normal GLUT 1 transcript level, mutant EZ-4 was devoid of an efficient carrier-mediated glucose transport process, thus suggesting that the GLUT 1 transporter was inoperative in rat cardiac myoblasts. Unlike the rat skeletal. L6 GLUT 1 isoform, expression of the rat cardiac GLUT 1 isoform was not affected by glucose starvation, and was not reduced in multinucleated myotubes. These studies demonstrated the usefulness of transport mutants in determining the identity, expression and property of GLUT isoforms and their association with specific transport processes.

Animals↗

PubMed1997

Tumor promotion by depleting cells of protein kinase C delta.

Tumor-promoting phorbol esters activate, but then deplete cells of, protein kinase C (PKC) with prolonged treatment. It is not known whether phorbol ester-induced tumor promotion is due to activation or depletion of PKC. In rat fibroblasts overexpressing the c-Src proto-oncogene, the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) induced anchorage-independent growth and other transformation-related phenotypes. The appearance of transformed phenotypes induced by TPA in these cells correlated not with activation but rather with depletion of expressed PKC isoforms. Consistent with this observation, PKC inhibitors also induced transformed phenotypes in c-Src-overexpressing cells. Bryostatin 1, which inhibited the TPA-induced down-regulation of the PKCdelta isoform specifically, blocked the tumor-promoting effects of TPA, implicating PKCdelta as the target of the tumor-promoting phorbol esters. Consistent with this hypothesis, expression of a dominant negative PKCdelta mutant in cells expressing c-Src caused transformation of these cells, and rottlerin, a protein kinase inhibitor with specificity for PKCdelta, like TPA, caused transformation of c-Src-overexpressing cells. These data suggest that the tumor-promoting effect of phorbol esters is due to depletion of PKCdelta, which has an apparent tumor suppressor function.

Animals↗

PubMed1997

Frictional heating of bearing materials tested in a hip joint wear simulator.

In a hip simulator wear test using bovine serum as a lubricant, the heat generated by ball-cup friction may cause precipitation of the proteins from the lubricant. The resultant accumulation of a solid layer of precipitated protein between the ball and cup could artificially protect the bearing surfaces from wear, in a manner that does not occur in vivo. Alternatively, the gradual depletion of the soluble proteins could interfere with their ability to act as boundary lubricants on the bearing surfaces, thereby artificially increasing the wear rate. Because the rate of protein precipitation may depend on the maximum temperature at the bearing surfaces during sliding, rather than the mean temperature of the bulk lubricant, this study determined the transient surface temperatures using an array of thermocouples embedded in acetabular cups of GUR 415 ultra-high molecular weight polyethylene (UHMWPE) and femoral balls of metal or ceramic, in conjunction with a finite element model of the temperature distribution. The prostheses were tested at one cycle/s under a Paul-type, physiological load profile with 2030 N maximum force, with the load cycle synchronized to the motion cycle. The steady state temperatures of the bulk lubricant were 38 degrees C for the zirconia balls, 36 degrees C for the cobalt-chromium and 33 degrees C for the alumina. However, the corresponding surface temperatures of the polyethylene, calculated with the finite element model, were 99 degrees C with zirconia ceramic, 60 degrees C with cobalt-chromium alloy, and 45 degrees C with alumina ceramic. The rank order of the surface temperatures corresponded to the relative amounts of protein that were precipitated in the test chambers during wear tests with these materials.

Animals↗

PubMed1997

[Clinical study of polymerase chain reaction technique in the diagnosis of bone tuberculosis].

OBJECTIVE: To evaluate the clinical value of polymerase chain reaction (PCR) technique in diagnosis of bone tuberculosis. METHODS: PCR, standard light-microscopy and standard culture technique were used to detect Mycobacterium tuberculosis in samples obtained from 60 patients with bone tuberculosis and 20 patients without bone tuberculosis. In the meantime, some factors affecting PCR result were analysed and methods to deal with them were discussed. RESULTS: In the group of 60 patients with bone tuberculosis, the positive rate was 83% in PCR technique, 3% in standard light-microscope technique and 7% in the standard culture technique. A statistically obvious difference was seen (P < 0.005). In the group of 20 patients without bone tuberculosis, 2 cases showed positive in PCR technique, none in the other methods. Specificity of PCR technique in a blind comparison study indicated 100%. The whole process of PCR amplification is fully automatic and can be finished within several hours, and the detection time is considerably reduced. CONCLUSIONS: PCR technique is a rapid, specific, sensitive and simple method for detection of mycobacterium tuberculosis in sample of bone tuberculosis, and it is of great value in the diagnosis of bone tuberculosis and differentiating bone tuberculosis from other bone diseases.

Adolescent↗

PubMed1997

[Determination of airway reactivity in the conscious and unrestrained guinea pigs].

A simple, stable determining system in the conscious and unrestrained guinea pigs was established that can quantitatively analyse the airway reactivity (AR). In this model, the response to histamine (His) or acetylcholine (ACh) aerosol was concentration-dependent with EC50 effective concentration causing 50% animals wheezing) of 53.3 mumol/m3 and 269 mumol/m3 respectively.

Acetylcholine↗