Biomedical subjects

N Liu

Publications and source records attributed to N Liu.

At least 127 records · Page 7Linked to original sources

PubMed1999

[Specific immune responses in H-2d mice after DNA immunization of HBV core gene].

OBJECTIVE: To observe the specific immune responses in H-2d mice after DNA immunization of HBV core gene. METHODS: The DNA vaccine (pJW4303/HBc) was constructed by inserting HBV core gene fragment into the reading frame of plasmid pJW4303. Both methods of gene gun and intramuscular immunization were used in this experiment. Anti-HBc (IgG) and its isotypes (IgG1, IgG2a) in mice sera were detected by ELISA. HBcAg specific cytotoxic T lymphocyte (CTL) activity was measured by 51Cr release assay. RESULTS: The expression of HBcAg was confirmed by ELISA and Western-blot in 293T cells transfected with pJW4303/HBc. The end-point titers of serum anti-HBc in immunized mice were 1: 328,050 (gene gun method) and 1:109,350 (intramuscular method). In both groups of gene gun and intramuscular immunization IgG2a level was slightly higher than IgG1. HBcAg specific CTL activities were 51. 1% in gene gun group and 55.2% in intramuscular group. CONCLUSION: In this experiment the DNA vaccine of pJW4303/HBc shows strong antigenecity in both cellular and humoral immunity.

Animals↗

PubMed1999

[An extensive matrilineal nonsyndromic sensorineural deafness family and mtDNA 12SrRNA gene mutation].

OBJECTIVE: To investigate the possible cause and molecular genetic mechanism of matrilineal nonsyndromic sensorineural deafness, the authors analyzed an extensive matrilineal nonsyndromic sensorineural deafness family. METHODS: PCR amplification of the nt1555 and nt7445 of the mitochondrial DNA, combined with PCR-SSCP, PCR-RFLP and sequence to analyze the family. RESULTS: The authors found a homoplasmic A to G transition at position 1555(A1555G) of the mitochondrial 12SrRNA gene from all the patients, and four matrilineal relatives of this family, but the mutation was not found in the normal spouses of the family and controls (100 normal persons). CONCLUSION: The A1555G mutation may be one of the major factors that cause deafness in this family.

DNA, Mitochondrial↗

PubMed1999

[MRI features of lymphedema of the lower extremity: comparison with lymphangioscintigraphy].

OBJECTIVE: To investigate the features of chronic lymphedema of the extremity. METHODS: Magnetic resonance imaging (MRI) and lymphangioscintigraphy (LAS) examinations were performed on 12 patients with peripheral lymphedema. RESULTS: MRI characteristically showed diffusive subcutaneous edema, reticular lymphangiectasis and "channels" with sequestered lymph. MRI scan clearly displayed the proliferative and extended lymphatic vessels, trunks and chylocyst. LAS showed dermal diffusion (dermal backflow) or retention at the injection site of the tracer with poorly defined lymphatic trunks and delayed or no visualization of regional lymph nodes. CONCLUSION: MRI can visualise peripheral lymph trunks, lymph nodes and soft tissue. LAS is more helpful in ascertaining the condition of obstruction of lymphatic system. Using these two imaging modalities together is helpful for anatomical diagnosis and delineating the disarranged pattern of lymphedema.

Adolescent↗

PubMed1999

[Role of neuronal nitric oxide synthase in dynorphin spinal neurotoxicity and analgesia in rats].

OBJECTIVE: To investigate the different role of neuronal constitutive nitric oxide synthase (nc-NOS) in dynorphin (Dyn) A(1-17) spinal neurotoxicity and analgesia. METHODS: The cNOS activity in ventral and dorsal spinal cord in rats was measured with H-L-arginine conversion, and ncNOS immunoreactivity(IR) was observed with strepavidin-peroxidase immunohisto-chemistry. RESULTS: Intrathecal administration of Dyn A(1-17) produced dose-dependent paralysis of hindlimbs and tail as well as inhibition of tail flick (TF) and foot flinch (FF) reflexes. Dyn A(1-17) 10 nmol induced only transient paralysis and apparently reduced the ncNOS-IR in the superficial dorsal horn but did not induce any change of ncNOS-IR in the ventral horn cells as compared with saline control. Dyn A(1-17) 20 nmol produced permanent paraplegia with irreversible spinal cord damage, characterized by central and progressive necrosis. Dyn A(1-17) 20 nmol remarkedly induced the expression of ncNOS-IR in the ventral horn cells whereas inhibited ncNOS-IR in the superficial dorsal horn. Dyn A(1-17) 20 nmol also significantly increased the activities of cNOS in the ventral spinal cord but did not affect cNOS activities in the dorsal spinal cord. Intrathecal pretreatment with 7-nitroindazole (7-NI) 1 mumol, a selective ncNOS inhibitor 10 min prior to i.t. Dyn A(1-17) 20 nmol significantly ameliorated Dyn-induced neurological outcome, but TF and FF remained inhibited. 7-nitroindazole also significantly antagonized the increases of cNOS activities and ncNOS-IR in the ventral spinal cord at 4 h after i.t. Dyn A(1-17) 20 nmol, but did not affect or even potentiated Dyn-induced inhibition of cNOS activity and ncNOS-IR in the dorsal spinal cord. CONCLUSIONS: Over-expression or over-activation of ncNOS in the ventral spinal cord may be involved in Dyn spinal neurotoxicity, whereas as the reduction of ncNOS activities in the dorsal spinal cord might reflect Dyn spinal analgeisia or pain modulation.

Analgesics↗

PubMed1999

[The sarcoplasmic reticulum Ca2+ handling protein and left ventricular hypertrophy in SHR].

OBJECTIVE: To elucidate the role of myocardial angiotensin II and sarcoplasmic reticulum (SR) Ca2+ handling protein (ryanodine receptor and Ca2+ ATPase) in the process of left ventricular hypertrophy. METHODS: The myocardial angiotensin II level, Bmax and Kd value of ryanodine receptor and calcium ATPase activity in SR were determined among 3 groups: spontaneously hypertensive rats (SHR), SHR treated with perindopril and WKY. RESULTS: The blood pressure (BP) of the SHR group, the ratio of left ventricular weight to body weight (LVW/BW) and the myocardial angiotensin II level were higher than those of the WKY group (P < 0.01), Perindopril decreased the BP(P < 0.01) and the myocardial angiotensin II level, and reversed the LVW/BW of the SHR group (P < 0.05). Compared to the WKY group, the Bmax value of cardiac ryanodine receptor in the SHR group was increased (232 +/- 27) fmol.mg-1 vs (173 +/- 18) fmol.mg-1, (P < 0.01), but there was no difference in Kd value (P > 0.05). The SR calcium ATPase activity was also decreased in the SHR group [(0.52 +/- 0.11) mumol.g-1.min-1 vs (1.03 +/- 0.22) mumol.g-1.min-1, P < 0.01]. In the SHR perindopril treatment group, the Bmax of ryanodine receptor was decreased [(191 +/- 23) fmol.mg-1, P < 0.05]. There was no difference in Kd value. The calcium ATPase activity was increased [(0.82 +/- 0.28) mumol.g-1.min-1, P < 0.05)]. CONCLUSION: The left ventricular hypertrophy is closely related to the myocardial angiotensin II and the SR calcium handling protein.

Angiotensin II↗

PubMed1999

[Humoral and cellular immunogenecity of genetic vaccine on core gene of hepatitis B virus in mice].

OBJECTIVE: To observe the specific humoral and cellular immunogenecity of genetic vaccine based on core gene of hepatitis B virus in both C57BL/6(H-2b) and BALB/c(H-2d) mice. METHODS: The in vitro expressing product of genetic vaccine of HBV core antigen (HBcAg) was identified by Western-blot. Both methods of gene gun and intramuscular immunization were used. Anti-HBc(IgG) and its isotypes (IgG1, IgG2a) in mice sera were detected by indirect ELISA. HBcAg specific cytotoxic T lymphocyte(CTL) activity was measured by 51Chromium release assay. RESULTS: The expression of HBcAg was confirmed by Western-blot. High titers of serum anti-HBc(1:328,050 by gene gun method and 1:109,350 by intramuscular method) were raised in both H-2b and H-2d mice after immunization with genetic vaccine of HBcAg. The levels of IgG2a isotype were generally higher than those of IgG1 in all groups of mice with both immunization methods. IgG2a was predominant in C57BL/6 mice after intramuscular immunization. These results suggested the Th1 type of immune response in mice after HBcAg genetic vaccination. HBcAg specific CTL activities were more than 50% in both species of mice with both immunization methods. CONCLUSION: This genetic vaccine of HBcAg shows strong antigenecity in both cellular and humoral immunity. The possibility of its clinical application needs to be further investigated.

Animals↗

PubMed1999

[The diagnostic significance of antineutrophil cytoplasmic antibodies in ulcerative colitis].

OBJECTIVE: To inquire into the diagnostic significance of antineutrophil cytoplasmic antibodies (ANCA) in ulcerative colitis (UC). METHODS: Serum ANCA from 58 UC patients, 43 non-UC patients and 58 healthy donors were detected with indirect immunofluorescence (IIF), enzyme linked immunosorbent assay (ELISA)and Western blot. RESULTS: The sensitivity and specificity of the presence of ANCA in the diagnosis of UC were 37.93% and 100% respectively. In the group of UC, patients with mild, moderate and severe clinical manifestations had positive ANCA rates of 17.65%, 41.67% and 52.94% respectively. The occurrence rates of mucosal vasculitis and grade III-V mucosal inflammation were 78.95% and 78.95% respectively in ANCA-positive group, but 37.04% and 44.44% in ANCA-negative group. The levels of the binding of the five kinds of ANCA antigens i.e. myeloperoxidase (MPO), bactericidal/permeability increasing protein (BPI), lactoferrin (LF), cathepsin G (CG) and proteinase-3 (PR-3) with the serum of UC patients were 13.99%, 13.79%, 10.34% 10.34% and 8.62% respectively. Specific protein strips were observed in 48.28% of the UC patients with Western blot technique, 47,000 polypeptide being the most common and making up 22.41% of them. CONCLUSION: The detection of ANCA was an auxiliary method for the diagnosis of UC. At present, UC-associated target antigens were not yet clarified, 47,000 polypeptide may be one of them. ANCA may participate in the pathogenesis of UC.

Adolescent↗

PubMed1999

[A clinicopathological study of pancreatoblastoma].

OBJECTIVE: To investigate the clinicopathological, immunohistochemical features and the histogenesis of pancreatoblastoma (PB) in 14 pediatric cases, including 9 male and 5 female patients, their age ranged from 1.5 to 8 years with a mean of 4.4 years. METHODS: Routine pathological, histochemical, and immunohistochemical methods were utilized to analyse the PB specimens. RESULTS: Tumors of 6 patients had metastasized to the liver, spleen and lymph nodes, 8 patients were alive 10 months to 105 months after diagnosis. Histologically, the tumors were composed of dense epithelial elements separated by fibro-stromal tissue, resulting in a nesting or organoid pattern. Immunohistochemically and histochemically, the tumors exhibited acinar, endocrine and ductal differentiation. The positive rates for were: CK 100%, EMA 86%, NSE 79%, CEA 71%, SYN 64%, CgA 43%, alpha1-AT 57%, PAS 100% and mucicarmine 57%. CONCLUSIONS: PB is the most common malignant pancreatic neoplasm of childhood. PB arises from primitive pluripotential cells capable of differentiating into 3 pancreatic cell types: acinar, endocrine and ductal. The prognosis is better than pancreatic carcinoma in adults.

Carcinoembryonic Antigen↗

PubMed1999

[Influence of functional groups of huatanyuxin decoction on Ca2+ transmembrane influx in rat aorta].

OBJECTIVE: To study the Ca2+ antagonistic effect of functional groups of Huatanyuxin decoction. METHOD: The 45Ca transmembrane influx technique was used to measure the Ca2+ blocking effect of leak, receptor-operated Ca2+ channel (ROC) and potential-dependent Ca2+ channel (PDC) in rat aorta. RESULT: ROC and PDC could be blocked when the complex prescription was used at concentrations of 0.5-5 mg/ml. Among the functional groups, Huoxue group (activating blood) and Xinqi group (promoting and normalizing flow of vital energy) showed better Ca2+ antagonistic effect. CONCLUSION: The mechanism of therapeutic effect of Huatanyuxin decoction may be related to its Ca2+ blocking effect similar to verapamil.

Animals↗

PubMed1999

[Double resonance multiphoton spectrum of high excited state of iodine].

The F0u(+) ion-pair state of I2 was studied in detail by using optical-optical double resonance multiphoton ionization spectroscopy technique. The OODR-MPI spectra were analyzed and identified based on the molecular constants published. The progression with a spacing of 37 cm(-1) at T(e) = 52 400 cm(-1) is identified to be the highly vibrational levels of F0u(+) state, and the transition pathway of excitation and ionization by multiphoton was determined.

English Abstract↗

PubMed1998

Release of the neuregulin functional polypeptide requires its cytoplasmic tail.

Based on both in vivo and in vitro studies, we have shown previously that the intracellular domain of a membrane-bound isoform of the growth factor, neuregulin, regulates proteolytic release of its extracellular domain ErbB receptor-activating ligand. To investigate the mechanism(s) involved in this regulation, a series of intracellular domain mutants were constructed and tested for susceptibility to proteolytic processing after transient transfection in COS-7 cells. These studies revealed that regulation of extracellular domain cleavage by the intracellular domain is sequence-specific and involves three distinct 30-60-residue segments. The presence of any two of these three segments is both necessary and sufficient for proteolytic processing, and resistance to proteolysis is not due to an alteration in cellular localization or transport. Evidence was also obtained that regulation of extracellular domain processing involves initial intracellular domain dimerization. Thus, with expression of a construct encoding only the intracellular domain, dimerization could be demonstrated in cross-linking experiments. Furthermore, resistance to proteolytic processing of a construct lacking a large portion of the intracellular domain was rescued with a chimera, in which the intracellular domain was replaced with a spontaneously dimerizing Fc fragment. Taken together these studies indicate that intracellular domain interactions are critically involved in the spacial and temporal control of growth and development by membrane-bound neuregulin isoforms.

Animals↗

PubMed1998

Inhibitory effect of acidic pH on OmpC porin: wild-type and mutant studies.

By use of the patch clamp technique, we have compared the electrophysiological signature of OmpC porin channels at neutral and acidic pH. The perfusion of pH 5.4 buffer to the periplasmic side of excised patches promoted the closure or block of approximately 20% of the open porins present in the patch without changes in their single channel conductance. Besides this effect on the main, long-lived open state, lowering the pH also suppressed the spontaneous transitions of channels to another distinct short-lived open state. The inhibitory effect on the opening kinetics was particularly visible in two mutants (K16Q and E109Q) in which transitions to the short-lived open state are enhanced by the mutations themselves at pH 7.2. On the other hand, the R124Q mutant responded to acidic pH by an increased gating to the short-lived open state. The results suggest that acidic pH stabilizes a closed state of OmpC porin, and that the pH sensitivity might be conferred in part by R124, but not by K16 or E109.

Electrophysiology↗

PubMed1998

A unique form of proliferating cell nuclear antigen is present in malignant breast cells.

Despite extensive research efforts to identify unique molecular alterations in breast cancer, to date, no characteristic has emerged that correlates exclusively with malignancy. Recently, it has been shown that the multiprotein DNA replication complex (synthesome) from breast cancer cells has a significantly decreased replication fidelity compared to that of nonmalignant breast cells. Proliferating cell nuclear antigen (PCNA) functions in DNA replication and DNA repair and is a component of the synthesome. Using two-dimensional PAGE analysis, we have identified a novel form of PCNA in malignant breast cells. This unique form is not the result of a genetic alteration, as demonstrated by DNA sequence analysis of the PCNA gene from malignant and nonmalignant breast cells. This novel form is most likely the result of an alteration in the post-translational modification of PCNA in malignant breast cells. These findings are significant in that it is now possible to link changes in the fidelity of DNA replication with a specific alteration of a component of the DNA synthetic apparatus of breast cancer cells. The novel form of PCNA may prove to be a new signature for malignant breast cells.

Animals↗

PubMed1998

GFP expression in Drosophila tissues: time requirements for formation of a fluorescent product.

We analyzed the acquisition of fluorescence of a GFP fusion protein expressed from gene constructs designed to regulate either the time of translation of the protein or the time of gene transcription. Both gene constructs expressed a fusion protein with wild-type GFP appended to the N-terminus of the Bicoid (Bcd) transcription factor. One gene construct, P[gfp-bcd] expressed an mRNA that was initially translated at the time of egg deposition. GFP-Bcd fluorescence could first be detected in anterior nuclei in the embryo at syncytial blastoderm stage, within 1.5-2.5 h after translation commenced. The second gene construct, P[hs-gfp-bcd], utilized the hsp70 promoter to regulate the induction of gene expression. In larval salivary glands, GFP-Bcd fluorescence could first be detected in nuclei after a 40-min recovery period following a 10-min heat shock induction of gene expression. These estimates of the time required for the acquisition of a fluorescent GFP product in Drosophila tissues are less than suggested by previously published reports.

Animals↗

PubMed1998

A new model of cell cycle-regulated transcription: repression of the cyclin A promoter by CDF-1 and anti-repression by E2F.

Cell cycle regulation of the cyclin A gene is determined by a bipartite repressor binding site in the region of the basal promoter, termed CDE-CHR, which also controls the expression of cell cycle genes upregulated in S or G2 (such as cdc25C). The CDE-CHR in the cyclin A promoter is recognized by both E2F complexes and CDF-1, but the contribution of each of these factors in cell cycle regulation is unknown. In the present study, we have introduced mutations into the cyclin A promoter which lead to either a loss or enhancement of E2F binding, while having only marginal effects on the interaction with CDF-1. Unlike mutants deficient for CDF-1 binding, promoter variants lacking E2F binding showed an unchanged repression in G0, thus identifying CDF-1 as the principal repressor of the cyclin A gene. The same mutants did show, however, a delayed derepression while a mutation leading to increased E2F binding resulted in premature up-regulation. These findings clearly suggest that E2F contributes to the correct timing of cyclin A transcription, presumably by acting as an anti-repressor. In agreement with this conclusion, we find that the cyclin A promoter only poorly interacts with E2F-4, which is the major E2F family member in G0 cells, while a clear binding is seen with E2F-1 and -3, which are up-regulated in late G1.

3T3 Cells↗

PubMed1998

Effect of the RF cavity temperature on low-energy injection at HLS.

The resonant frequency shift caused by the temperature of the RF cavity at the Hefei Light Source has been measured and the results analysed. The effect of this frequency shift on low-energy injection with a low cavity voltage is discussed, and a new injection mode is proposed.

Journal Article↗

PubMed1998

Mechanism of the dynorphin-induced dualistic effect on free intracellular Ca2+ concentration in cultured rat spinal neurons.

In order to study the different mechanisms of dynorphin spinal analgesia and neurotoxicity at low and high doses, the effects of various concentrations of dynorphin A-(1-17) on the free intracellular Ca2+ concentration ([Ca2+]i) in the cultured rat spinal neurons were studied using single cell microspectrofluorimetry. While dynorphin A-(1-17) 0.1-100 microM had no significant effect on basal [Ca2+]i, dynorphin A-(1-17) 0.1 and 1 microM significantly decreased the high KCl-evoked peak [Ca2+]i by 94% and 83% respectively. Dynorphin A-(1-17) 10 and 100 microM did not affect the peak [Ca2+]i following K+ depolarization, but in all these neurons there was a sustained and irreversible rise in [Ca2+]i following high-K+ challenge. Pretreatment with the specific kappa-opioid receptor antagonist nor-binaltorphimine 10 microM, but not the competitive NMDA receptor antagonist, DL-2-amino-5-phosphonovalerate (APV) 10 microM, significantly blocked the inhibitory effect of dynorphin A-(1-17) 0.1 microM on peak [Ca2+]i. However, APV 10 microM and nor-binaltorphimine 10 microM significantly antagonized the sustained rise in [Ca2+]i induced by a high concentration of dynorphin A-(1-17) 10 microM. Furthermore, in the presence, and following the addition, of increasing concentrations of dynorphin A-(1-17) (0.1, 1, 10 and 100 microM), the high concentrations of dynorphin A-(1-17) failed to produce a sustained rise in peak [Ca2+]i. These results suggested that dynorphin exerted a dualistic modulatory effect on [Ca2+]i in cultured rat spinal neurons, inducing a sustained and irreversible intracellular Ca2+ overload via activation of both NMDA and kappa-opioid receptors at higher concentrations, but inhibiting depolarization-evoked Ca2+ influx via kappa-opioid but not NMDA receptors at lower concentrations. Serial addition of graded concentrations of dynorphin A-(1-17) prevented the effect of high concentrations of dynorphin A-(1-17) on [Ca2+]i.

Animals↗

PubMed1998

Synthesis, physicochemical characterization, and crystallization of a putative retro-coiled coil.

An artificial HIV enhancer-binding polypeptide has recently been dimerized by covalently linking it to the leucine zipper motif of the yeast transcriptional activator GCN4 (Liu N et al., 1997, Eur Biophys J 25:399-403). Although it seemed that the dimerization of this peptide could be best achieved by the use of the retro sequence of the leucine zipper, this approach was not implemented in the original construct. As the first step toward the synthesis of a basic region-retro leucine zipper HIV enhancer-binding fusion protein, we have now prepared the retro version of the leucine zipper (r-LZ35) and performed initial physicochemical characterization. Circular dichroism and sedimentation equilibrium studies showed that, at concentrations < 100 microM, the retro peptide was an unstructured monomer. At higher concentrations, however, the monomer was in equilibrium with a tetramer and, at 1 mM, the retro peptide was almost fully helical. N-terminal extension of the retro peptide by the tripeptide Cys-Gly-Gly resulted in a 38-residue polypeptide that could be covalently dimerized by forming a disulfide bond between two chains to give the peptide (r-LZ38)2. Even in the low micromolar concentration range peptide (r-LZ38)2 formed a stable, noncovalent, helical dimer as revealed by circular dichroism and sedimentation equilibrium in the presence and absence of guanidinium chloride. (r-LZ38)2 has been crystallized and X-ray structural analysis is under way. The disulfide-crosslinked retro-leucine zipper may lend itself to interesting protein structural studies, including protein design. The present work also highlights the structural and functional potential of retro proteins in general.

Amino Acid Sequence↗