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C Liang

Publications and source records attributed to C Liang.

At least 91 records · Page 5Linked to original sources
PubMed1999

[Relationship between expression of P16 protein and prognosis in carcinoma of nasopharynx].

We observed the relationship between p16 gene and the occurrence, development and prognosis of carcinoma of nasopharynx by means of LSAB immunohistochemistry method and investigated the expression of protein P16 in 73 cases of carcinoma of nasopharynx and 10 cases of epithelia of chronic inflammation of nasopharynx. The results showed that P16 positive rate was 100% for the epithelia of chronic inflammation of nasopharynx. It was significantly higher than the P16 positive rate for the carcinoma of nasopharynx (38.4%, P < 0.01). There was significant difference of P16 positive expression in differentiation of nasopharyngeal carcinoma (poor differentiation versus undifferentiation), clinical staging (I-II versus IV) and grading of tumor (T1-T2 versus T3, T4) (P < 0.01). There was no correlation between P16 expression and metastatic lymph node (P > 0.05). The 3-year survival rates were 88.9% and 72.9% in P16 expression (+) and (-) patients respectively (P < 0.05). These findings suggested that P16 might play an important role in the process of carcinogenesis and development of nasopharyngeal carcinoma, and P16 might be used as a valuable marker for assessment of the biological behavior and prognosis of nasopharyngeal carcinoma.

Adolescent↗
PubMed1999

[Magnetic resonance imaging in 40 cases of optic neuritis].

OBJECTIVE: To explore the clinical value of magnetic resonance imaging (MRI) in optic neuritis. METHODS: Forty patients with optic neuritis were examined with the spectral presaturation inversion recovery and fluid attenuated inversion recovery. RESULTS: The lesion was frequently seen in orbital portion (86.7%) and intracanalicular portion (29.3%), and primarily in the axial part (49.3%) and transverse section (38.7%) of the optic nerve. The longitudinal extent of lesion was from 2 to 35 mm (mean, 12.6 mm), the visual acuity of patients with optic neuritis was related to the site of the lesion, and negatively correlated with the longitudinal extent of lesion of logarithm curve. A poor visual acuity (< 0.01) was significantly associated with lesion of greater extent > 10 mm and the transverse or axial lesion, but the good visual acuity (>or= 0.3), with the lesion of smaller extent < 10 mm and the axial or peripheral lesion. In addition, paramagnetic contrast-medium, Gd-DTPA, enhancement scanning was carried out in 11 cases of optic neuritis, of them the visual acuity was increased in 10 cases after administration of corticosteroid, and in one case, visual improvement was not seen. CONCLUSION: MRI is a new and useful equipment which is helpful in the diagnosis and treatment of optic neuritis.

Adolescent↗
PubMed1999

[Expression of P53 protein in premalignant lesion and carcinoma of larynx].

To investigate the expression of P53 protein in the premalignant lesion and carcinoma of laryngeal epithelium, the authors used DO-7, an antibody to wild and mutant type P53 protein. Eleven cases of simple hyperplasia of epithelium (SHE), 32 cases of atypical hyperplasia of epithelium (AHE) and 42 cases of laryngeal squamous cell carcinoma (LSCC) were examined by ABC technique. The results showed that the overexpression of P53 protein were 0%, 31.25% and 52.38% in SHE, AHE and LSCC, respectively. The positive rate of P53 protein were 0%, 33.33% and 75.00% in mild, moderate and severe AHE, respectively. In well, moderately and poorly differentiated carcinomas of larynx, the positive rates were 62.50%, 76.92% and 15.39%, respectively. There were highly significant differences (P < 0.01). No correlation was found between the P53 protein overexpression and the clinical stages, neck lymph node metastasis, local recurrence and, survival of LSCC. The results suggest that the overexpression of P53 protein may play a role in the pathogenesis and development of LSCC.

Carcinoma, Squamous Cell↗
PubMed1998

Enhanced impairment of chain elongation by inhibitors of HIV reverse transcriptase in cell-free reactions yielding longer DNA products.

We have studied the relationship between the length of HIV-1 reverse transcriptase (RT)-mediated nucleotide polymerization and inhibitors of these reactions in cell-free RT assays performed in the presence of either of two dideoxynucleoside triphosphates (ddNTPs), i.e. AZTTP or 3TCTP, or nevirapine, a non-nucleoside RT inhibitor. These reactions employed a heterologous RNA template and three DNA oligonucleotide primers, i.e. pAR, dPR and PA, that yielded distinct full-length products of 65, 192 and 376 nt, respectively, in the absence of inhibitor. We now show that the extent of inhibition of RT activity was greatest with use of the PA primer, which normally yielded the longest reaction product, and that lesser degrees of inhibition were noted in the reactions that generated shorter products. For example, at a concentration of 5 microM AZTTP, the extent of inhibition was 75% with the PA primer but only 40% and <10% when reactions were primed by the dPR and pAR primers, respectively. Similar results were obtained when either a mutated form of HIV RT (i.e. M184V), associated with resistance to 3TC, was tested in the presence of 3TCTP or when RT derived from Moloney murine leukemia virus (M-MuLV) was tested in the presence of AZTTP.

Cell-Free System↗
PubMed1998

Characterization of human immunodeficiency virus type-1 (HIV-1) particles that express protease-reverse transcriptase fusion proteins.

We have selectively mutagenized specific residues at the junction between the protease (PR) and reverse transcriptase (RT) genes of human immunodeficiency virus type 1 (HIV-1) to study the effects of PR-RT fusion proteins in the context of a full-length, infectious proviral construct. Mutant viruses derived from COS-7 cells transfected with this construct were analyzed in regard to each of viral replication, maturation, and infectivity. Immunoblot analysis revealed that the mutation prevented cleavage between the PR and RT proteins and that both existed as a PR-RT fusion protein in each of cellular and viral lysates. Interestingly, intracellular PR that existed within the PR-RT fusion protein remained functionally active, whereby HIV-1 precursor proteins were processed efficiently. Furthermore, the RT component of the fusion protein also retained its enzymatic activity as shown in RT assays. Electron microscopy revealed that the mutant viruses containing the PR-RT fusion protein possessed wild-type morphology. These viruses also displayed wild-type sensitivities to inhibitors of each of the HIV-1 PR and RT activities. However, viruses containing the PR-RT fusion protein were 20 times less infectious than wild-type viruses. This defect was further pronounced when mutated Gag-Pol proteins were overexpressed as a consequence of an additional mutation that interfered with frameshifting. Thus, unlike cleavage site mutations at the N terminus of PR, a cleavage site mutation between PR and RT did not affect the enzymatic activities of either PR or RT and viruses containing PR-RT fusion proteins were viable.

Animals↗
PubMed1998

Overexpression of nerve growth factor in the heart alters ion channel activity and beta-adrenergic signalling in an adult transgenic mouse.

1. The electrophysiological and pharmacological properties of cardiac myocytes from the hearts of adult transgenic mice engineered to overexpress nerve growth factor (NGF) in the heart were studied. 2. There was a 12% increase in the ventricular myocyte capacitance in NGF myocytes consistent with cardiac hypertrophy, and action potential duration at 90% repolarization (APD90) was prolonged by 142 % compared with wild-type (WT) myocytes. This was due, at least in part, to a decrease in the density of two K+ currents, Ito and IK(ur), which were significantly reduced in NGF mice with no change in their electrophysiological characteristics. We found no change in the current density or electrophysiological properties of the L-type Ca2+ current. 3. The effect on Ito and IK(ur) of TEA and 4-aminopyridine (4-AP) was not different in cells isolated from WT and NGF mice. The prolongation of APD observed in NGF cells was mimicked in WT cells by exposure to 1 mM 4-AP, which partially blocked Ito, completely blocked IK(ur) and increased APD90 by 157%. 4. The isoprenaline-induced increase in ICa was significantly smaller in NGF myocytes than in WT myocytes. This was not due to a decrease in beta-adrenergic receptor (beta-AR) density, as this was increased in NGF tissue by 55%. Analysis of beta-AR subtypes showed that this increase was entirely due to an increase in beta2-AR density with no change in beta1-ARs. 5. The response of the beta-AR-coupled adenylyl cyclase system to isoprenaline, Gpp(NH)p and forskolin was studied by measuring cAMP production. In NGF tissue, isoprenaline elicited a significantly smaller response than in WT myoyctes and this was not due to reduced adenylyl cyclase activity as the responses of NGF tissue to guanylylimidodiphosphate (Gpp(NH)p) and forskolin were unaffected. 6. In conclusion, the overexpression of NGF in the mouse heart resulted in a decrease in the current density of two K+ channels, which contributed to the prolongation of the cardiac action potential. Despite an increase in beta2-AR density in the hearts of the NGF mice, the response to isoprenaline was diminished, and this was due to an uncoupling of the beta-ARs from the intracellular signalling cascade. These potentially pathological changes may be involved in the occurrence of ventricular arrhythmias in cardiac hypertrophy and failure, and this mouse provides a novel model in which to study such changes.

Action Potentials↗
PubMed1998

Dominance of the E89G substitution in HIV-1 reverse transcriptase in regard to increased polymerase processivity and patterns of pausing.

The substitution of a glycine for glutamic acid at position 89 in human immunodeficiency virus-1 (HIV-1) reverse transcriptase (RT) (E89G) confers resistance to several nucleoside and non-nucleoside inhibitors of RT. As residue 89 contacts the template strand, it has been suggested that this mutation may modulate the conformation of the RT.template/primer complex. In addition, certain mutations in RT that confer resistance to nucleoside analogs, such as M184V, are located near the polymerase active site. To characterize further these substitutions, we performed processivity assays alongside an analysis of pausing profiles with wild-type (wt) RT and recombinant RTs containing substitutions at E89G, M184V, or both. We now show that E89G RT has higher processivity than wt enzyme as well as a different pattern of pausing sites. Similar findings were obtained with the doubly mutated RT, although enzyme containing only the M184V mutation had lower processivity than wt. Consistent with these observations, and from a mechanistic standpoint, both E89G-containing as well as doubly mutated RT had decreased dissociation constants from a complex consisting of RT and template-primer, in comparison with either wt RT or M184V-containing RT. No significant differences were observed among the various enzymes in regard to Km values for the heteropolymeric RNA template used in these studies. Viruses containing the E89G mutation synthesized longer strand DNA products than either wt viruses or viruses containing only the M184V mutation in endogenous RT assays. Thus, the E89G substitution is a dominant determinant in regard to each of the koff values from an RT.template/primer complex, RT processivity, and specific patterns of pausing during DNA polymerization.

Amino Acid Substitution↗
PubMed1998

Mechanistic studies of early pausing events during initiation of HIV-1 reverse transcription.

We have investigated the role of sequences that surround the primer binding site (PBS) in the reverse transcriptase-mediated initiation of (-) strand DNA synthesis in human immunodeficiency virus type 1. In comparisons of reverse transcription initiated from either the cognate primer tRNALys.3 or a DNA primer D-Lys.3, bound to PBS sequences, we observed that a +3 pausing site occurred in both circumstances. However, the initiation reaction with tRNALys.3 was also characterized by a pausing event after incorporation of the first nucleotide. Alteration of sequences at the 5'-end instead of the 3'-end of the PBS resulted in elimination of the +3 pausing site, suggesting that this site was template sequence-dependent. In contrast, the pausing event at the +1 nucleotide position was still present in experiments that employed either of these mutated RNA templates. The mutations at the 5'-end of the PBS also caused a severely diminished rate of initiation and the strong arrest of reactions at the +1 stage when tRNALys.3 was used as primer. Therefore, we propose that the +1 pausing event is an initiation-specific event in regard to reactions primed by tRNALys.3 and that sequences at the 5'-end of the PBS may facilitate the release of reverse transcription from initiation to elongation.

Base Sequence↗
PubMed1998

Endogenous reverse transcriptase assays reveal synergy between combinations of the M184V and other drug resistance-conferring mutations in interactions with nucleoside analog triphosphates.

Resistance of HIV-1 reverse transcriptase (RT) to nucleoside analogs (e.g. AZT, ddC and 3TC) is conferred by various amino acid substitutions or combinations thereof on the RT molecule. The M184V mutation, that confers high and low-level resistance to 3TC and ddC, respectively, can restore sensitivity to AZT when introduced into RT against a background of AZT-resistance. The K65R mutation, that confers low level resistance to both 3TC and ddC, can also restore sensitivity to AZT. This information is of potential utility in choosing combinations of anti-viral drugs for clinical use. To explore this subject further, we have used an endogenous RT reaction to study mutated viruses containing M184V alone or M184V combined with each of the K65R, E89G or both the M41L and T215Y substitutions. Endogenous assays possess the advantage of utilizing genomic RNA as template in a reaction mixture that includes each of tRNALys.3 and viral nucleocapsid protein, necessary for specific initiation of reverse transcription, as well as all other viral proteins that might impact on this process. We now show that viruses containing both M184V and K65R displayed synergistic resistance to 3TC triphosphate (3TCTP), while the same combination yielded the same level of resistance to ddC triphosphate (ddCTP) as that manifested by K65R alone. The combination of M184V and E89G displayed synergistic resistance against ddCTP but not 3TCTP, while viruses containing only E89G were highly resistant to 3TCTP and displayed low-level resistance to ddCTP. The results show that endogenous RT assays can reveal variable synergistic, antagonistic, or neutral effects in regard to drug sensitivity, depending on the presence of specific amino acid substitutions in RT itself.

Anti-HIV Agents↗
PubMed1998

Toxicity of intraocular lidocaine and bupivacaine.

PURPOSE: To study the toxicity of intraocular lidocaine, bupivacaine, and a combination of the two anesthetics. METHODS: The right eyes of 34 rabbits were divided into eight groups, and each was injected intravitreally with 0.2 ml of lidocaine hydrochloride in a 2%, 1%, 0.5%, or 0.25% concentration, or bupivacaine hydrochloride in a 0.75%, 0.5%, or 0.25% concentration, or a 1:1 mixture of lidocaine 2% and bupivacaine 0.75%. The left eyes of four of these rabbits received an injection of balanced saline solution. Electroretinograms were recorded before injection and 30 minutes, 90 minutes, 3 hours, 6 hours, 24 hours, and 1 week after injection. The amplitude and the implicit time were analyzed. The rabbits were killed 1 week after injection and the eyes evaluated histologically. RESULTS: No adverse clinical reaction and no histologic abnormality was observed in any of the nine groups after injection. The a- and b-waves of the electroretinograms in the control group injected with balanced saline solution, and the a-waves of the experimental groups that received injections of lidocaine, bupivacaine, or the mixture, were normal. The b-waves of the experimental groups demonstrated a marked decrease in the amplitude and an increase (P < .05) in the implicit time after intravitreal injection. Electroretinogram responses recovered within 24 hours. CONCLUSIONS: Intravitreal injection of 0.2 ml of lidocaine up to 2%, or of bupivacaine up to 0.75%, and the mixture of lidocaine 2% and bupivacaine 0.75%, induced reversible electroretinogram changes in the rabbit retina. No histologic abnormalities were observed.

Anesthetics, Local↗
PubMed1998

An evaluation of methylated collagen as a substitute for vitreous and aqueous humor.

PURPOSE: To evaluate ocular tolerance of methylated collagen gel injected intravitreally and into the anterior chamber. METHODS: Methylated collagen (type I/III) was tested in New Zealand white rabbits. Vitreous cavity: After pars plana vitrectomy, methylated collagen gel was injected intravitreally. The eyes were examined clinically; electroretinogram recordings were made before and after surgery. Vitreous samples were taken for immunological analysis for the presence of the injected collagen. The rabbits were sacrificed 6 months after surgery; the retina was evaluated by light microscopy. Anterior chamber: In another group of rabbits, methylated collagen gel (0.2 ml, 0.1 ml, or 0.05 ml) was injected into the anterior chamber after paracentesis. The eyes were examined with a slit lamp; intraocular pressure was measured postinjection. The rabbits were sacrificed after 4 months; the corneas were evaluated histologically. RESULTS: Vitreous cavity: The fundus view was clear for 6 months after intravitreal injection. Scotopic and photopic electroretinograms were normal in 6/7 eyes; one eye experienced a mild decrease one month postoperatively. No abnormal changes were found in the retinal histology. Anterior chamber: Some corneas were hazy and edematous around the injection site for one week. The injected collagen appeared in bundles, patches, and little pieces in the anterior chamber with precipitates on the corneal endothelium, pupillary margin, and the anterior capsule of the lens. The collagen diminished gradually, without causing permanent opacity. Histologically, the corneal endothelium in the eye which received 0.2 ml collagen showed a mild distention of the mitochondriae and vesicle formation between endothelial cells under transmission electron microscope. CONCLUSION: Methylated collagen gel was tolerated by the eye after intravitreal injection. Localized temporary clinical and mild ultrastructural corneal changes were observed after anterior chamber injection.

Animals↗
PubMed1998

Toxicity and efficacy of intravitreal injection of spartanamicin B in the treatment of Candida endophthalmitis.

AIMS/BACKGROUND: We evaluated the retinal toxicity of spartanamicin B and its efficacy in a rabbit model of Candidal endophthalmitis. METHODS: Toxicity. Fourteen albino rabbit eyes were injected intravitreally with spartanamicin B (1, 2, 5, 10, 25, 50, and 100 microg); 2 eyes received the vehicle alone. Efficacy. Ten rabbit eyes were inoculated with 3000 Candida organisms which caused endophthalmitis in 24 hours. Eight eyes were treated with intravitreal spartanamicin B in doses of 1, 2, 5, or 10 microg/0.1 ml; 2 untreated eyes served as controls. RESULTS: Toxicity. The eyes injected with < or =10 microg and the control group eyes exhibited no clinical, histological, or electroretinographic evidence of retinal toxicity. Doses >10 microg caused vitritis. Efficacy. Clinical examination of the treated eyes showed a gradual improvement over 3-6 days; mild opacities remained until day 14. Results of cultures performed 15 days after infection were negative in all treated eyes. CONCLUSIONS: Intravitreally injected spartanamicin B (10 microg) is nontoxic to the retina, effective against C. albicans in the endophthalmitis model in the rabbit eye and caused no discernible histological changes in the retina.

Animals↗
PubMed1998

Roles of the human immunodeficiency virus type 1 nucleocapsid protein in annealing and initiation versus elongation in reverse transcription of viral negative-strand strong-stop DNA.

To study the initiation of human immunodeficiency virus type 1 reverse transcription, we have used the viral nucleocapsid protein (NC7) to anneal tRNA3Lys primer onto viral genomic RNA and have then eliminated NC7 from this primer-template complex by digestion with proteinase K and phenol-chloroform extraction of residual protein. Our data show that saturating concentrations of NC7 resulted in the formation of an active tRNA-template complex that yielded enhanced production of full-length negative-strand strong-stop DNA [(-)ssDNA] and that this complex remained active even after the elimination of NC7. While both of the two Zn finger motifs found within NC7 were essential for efficient elongation, NC protein that contained a point mutation in the first Zn finger or that was devoid of both Zn fingers yielded primer-template complexes that could still be initiated in 1-base-extension assays. In contrast, the use of heat annealing to produce primer-template complexes resulted in proportions of full-length (-)ssDNA lower than those seen with NC protein, and the addition of NC protein to such preformed primer-template complexes was able to reverse this defect only to a marginal extent.

Capsid↗
PubMed1998

Compensatory point mutations in the human immunodeficiency virus type 1 Gag region that are distal from deletion mutations in the dimerization initiation site can restore viral replication.

The dimerization initiation site (DIS), downstream of the long terminal repeat within the human immunodeficiency virus type 1 (HIV-1) genome, can form a stem-loop structure (SL1) that has been shown to be involved in the packaging of viral RNA. In order to further determine the role of this region in the virus life cycle, we deleted the 16 nucleotides (nt) at positions +238 to +253 within SL1 to generate a construct termed BH10-LD3 and showed that this virus was impaired in viral RNA packaging, viral gene expression, and viral replication. Long-term culture of these mutated viruses in MT-2 cells, i.e., 18 passages, yielded revertant viruses that possessed infectivities similar to that of the wild type. Cloning and sequencing showed that these viruses retained the original 16-nt deletion but possessed two additional point mutations, which were located within the p2 and NC regions of the Gag coding region, respectively, and which were therefore named MP2 and MNC. Site-directed mutagenesis studies revealed that both of these point mutations were necessary to compensate for the 16-nt deletion in BH10-LD3. A construct with both the 16-nt deletion and the MP2 mutation, i.e., LD3-MP2, produced approximately five times more viral protein than BH10-LD3, while the MNC mutation, i.e., construct LD3-MNC, reversed the defects in viral RNA packaging. We also deleted nt +261 to +274 within the 3' end of SL1 and showed that the diminished infectivity of the mutated virus, termed BH10-LD4, could also be restored by the MP2 and MNC point mutations. Therefore, compensatory mutations within the p2 and NC proteins, distal from deletions within the DIS region of the HIV genome, can restore HIV replication, viral gene expression, and viral RNA packaging to control levels.

Amino Acid Sequence↗
PubMed1998

Health effects of indoor fluoride pollution from coal burning in China.

The combustion of high fluoride-content coal as an energy resource for heating, cooking, and food drying is a major exhaust emission source of suspended particulate matter and fluoride. High concentrations of these pollutants have been observed in indoor air of coal-burning families in some rural areas in China. Because airborne fluoride has serious toxicological properties, fluoride pollution in indoor air and the prevalence of fluorosis have been analyzed in a fluorosis area and a healthy nonfluorosis area in China and in a rural area in Japan. For human health, fluoride in indoor air has not only been directly inhaled by residents but also has been absorbed in stored food such as corn, chilies, and potatoes. In the fluorosis area in China, concentrations of urinary fluoride in the residents have been much higher than in the nonfluorosis area in China and in the rural area in Japan. In the fluorosis area, almost all elementary and junior high school students 10-15 years of age had dental fluorosis. Osteosclerosis in the skeletal fluorosis patients was very serious. Urinary deoxypyridinoline in rural residents in China was much higher than in rural residents in Japan. Data suggest that bone resorption was extremely stimulated in the residents in China and that fluoride may stimulate both bone resorption and bone formation. Because indoor fluoride from combustion of coal is easily absorbed in stored food and because food consumption is a main source of fluoride exposure, it is necessary to reduce airborne fluoride and food contamination to prevent serious fluorosis in China.

Adolescent↗
PubMed1998

[Evaluation on the effects of water defluoridation measures in China. Research Group Evaluation on the Effects of Water Defluoridation Measures in China].

In order to find out the situation of management and application of water defluoridation measures, as well as the effects on the prevention of endemic fluorosis in 10 provinces and cities with heavy endemic fluorosis from the drinking water sources, 1960 water engineering projects accounting for about 10% of all projects were investigated. The authors applied uniform method, criteria and forms to carry out the retrospective investigation. The data were entered into the computer database and analyzed statistically. The results demonstrate that all the defluoridation projects have significant effectiveness on the prevention of endemic fluorosis. The concentrations of water fluoride were below 1 mg/L. The prevalences of dental fluorosis were 30%-40% and the main type was light dental fluorosis. But with the time prolonging, less attention has been paid in man.

China↗
PubMed1998

[Free jejunal grafts for reconstruction of pharynx and cervical esophasgus].

Eleven patients with hypopharyngeal carcinoma were treated surgically and the pharynx and cervical esophagus were reconstructed with free jejunal grafts through the technique of microvascular anastomosis. The microvascular anastomosis were all successful and the patients all survived the operations. The operations were performed at one time with only a few complications. There were 2 cases of pharyngeal fistula and 1 case of bleeding from the anastomotic site. The patients could eat by their mouths and swallow very well just 15 days after the operation. The 3-year suvival rate was 36%. The main causes of death were the recurrence and the metastasis to the cervical lymph nodes. We came to the conclusion that the operation is safe with high success rate and no mortality during operation, and it is less injurious than the gastropharyngeal anastomosis. The key point of the operation is the surgeon's mastery of the microvascular anastomosis technique.

Aged↗