Biomedical subjects

C Liang

Publications and source records attributed to C Liang.

At least 73 records · Page 4Linked to original sources

PubMed2000

[Experimental studies on exons 5-8 of p53 gene mutation in laryngeal squamous cell carcinoma].

This study was designed to detect the point mutations of exons 5-8 of p53 gene in laryngeal squamous cell carcinoma (LSCC) and analyze their relationship. The detection of fresh tumor samples from LSCC patients was performed using silver staining PCR-SSCP method. From among 60 patients samples, 47 were positive in SSCP. Mutation rate was 78.3% (47/60). The results showed that the prevalence of p53 mutations in LSCC subjected to silver staining PCR-SSCP test were 50% (30/60) in exon 5, 11.67%(7/60) in exon 6, 41.6%(25/60) in exon 7, and 25%(15/60) in exon 8. The majority of the mutations were found in exon 5 and exon 7. Exon 5 and exon 7 of p53 gene may be the mutation hotspot in LSCC; they may be the critical position easily attacked by some carcinogen factors relating to LSCC.

Carcinoma, Squamous Cell↗

PubMed2000

[Detection of bcl-2/JH gene rearrangement by semi-nested polymerase chain reaction from fresh tumor samples in patients with laryngeal squamous cell carcinomas].

OBJECTIVE: To evaluate the clinical implications of bcl-2/JH gene rearrangement in laryngeal squamous cell carcinomas (LSCC). METHODS: Bcl-2/JH gene rearrangement analysis in fresh tumor samples was performed in 60 patients with LSCC by semi-nested polymerase chain reaction(PCR). RESULTS: The results showed that bcl-2/JH gene rearrangement was found in 37 out of 60 patients. The breakpoint was located within the major breakpoint region(mbr) in 33 of the 60 patients and the remaining patients had bcl-2 translocation within the minor cluster region(mcr). The results of the study showed that the rearrangement rate of bcl-2 gene was not related to the grade of differentiation, clinical stage, and neck lymph-node metastasis (P > 0.05), and it was related to heavy smoking (P < 0.05). CONCLUSION: Detection of bcl-2/JH gene rearrangement could reveal that bcl-2/JH fusion gene in LSCC is an important molecular biological marker and has a significant role in occurrence and development of LSCC.

Adult↗

PubMed2000

[Detection of bacterial DNA in blood with three pairs of primers].

OBJECTIVE: To develop a stable and sensitive method to detect gut-derived bacterial DNA present in the blood. METHODS: Blood culture and PCR were performed simultaneously when temperature of patients (n = 23) was higher than 38.5 degrees C after laparotomy. PCR was performed after DNA extraction, target genes being beta-lactosidase gene of Escherichia coli(E. coli), glutamine synthase gene of Bacteroides Fragilitas, and 16SrRNA gene of most pathogenic bacteria. DNA of standard strains of E. coli and Bacteroides Fragilitas served as positive controls, blank control as negative controls, and healthy volunteers (n = 20) served as normal controls. We performed PCR twice with part of the samples (n = 20) in order to test the repetition of this method. RESULTS: The repetition rate of PCR was 95%. Three of blood cultures were positive (13.0%, 3/23), the corresponding positive ratio of PCR was 43.5% (10/23) which was higher than that of the blood culture (P = 0.016). CONCLUSION: PCR is more sensitive than blood culture in detection of bacteremia.

Bacterial Translocation↗

PubMed2000

[Photoluminescent properties of organic film in flat optical microcavity].

The microcavity is sandwiched between a quarterwavelength distributed Bragg reflector(DBR) and a metal Ag reflective mirror. A single layer of a Tris(8-quinolinolato) aluminum (Alq) film was used as the light-emitting layer. The photoluminescent properties of the optical microcavity and that of the Alq film were studied at the same excitation condition. Compared with the Alq film, the significantly narrowed spectral emission linewidth from 90 nm to 10 nm was observed, the PL emission intensity of the microcavity at the resonant mode is enhanced by the order of 1. The spectral narrowing and intensity enhancement of the microcavity is attributed to the microcavity effect.

English Abstract↗

PubMed1999

Design, synthesis, and evaluations of substituted 3-[(3- or 4-carboxyethylpyrrol-2-yl)methylidenyl]indolin-2-ones as inhibitors of VEGF, FGF, and PDGF receptor tyrosine kinases.

Receptor tyrosine kinases (RTKs) have been implicated as therapeutic targets for the treatment of human diseases including cancers, inflammatory diseases, cardiovascular diseases including arterial restenosis, and fibrotic diseases of the lung, liver, and kidney. Three classes of 3-substituted indolin-2-ones containing propionic acid functionality attached to the pyrrole ring at the C-3 position of the core have been identified as catalytic inhibitors of the vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), and platelet-derived growth factor (PDGF) RTKs. Some of the compounds were found to inhibit the tyrosine kinase activity associated with isolated vascular endothelial growth factor receptor 2 (VEGF-R2) [fetal liver tyrosine kinase 1 (Flk-1)/kinase insert domain-containing receptor (KDR)], fibroblast growth factor receptor (FGF-R), and platelet-derived growth factor receptor (PDGF-R) tyrosine kinase with IC(50) values at nanomolar level. Thus, compound 1 showed inhibition against VEGF-R2 (Flk-1/KDR) and FGF-R1 tyrosine kinase activity with IC(50) values of 20 and 30 nM, respectively, while compound 16f inhibited the PDGF-R tyrosine kinase activity with IC(50) value of 10 nM. Structural models and structure-activity relationship analysis of these compounds for the target receptors are discussed. The cellular activities of these compounds were profiled using cellular proliferation assays as measured by bromodeoxyuridine (BrdU) incorporation. Specific and potent inhibition of cell growth was observed for some of these compounds. These data provide evidence that these compounds can be used to inhibit the function of these target receptors.

Drug Design↗

PubMed1999

The Cdc6p nucleotide-binding motif is required for loading mcm proteins onto chromatin.

Cdc6p has an essential function in the mechanism and regulation of the initiation of DNA replication. Budding yeast Cdc6p binds to chromatin near autonomously replicating sequence elements in late M to early G1 phase through an interaction with Origin Recognition Complex or another origin-associated factor. It then facilitates the subsequent loading of the Mcm family of proteins near autonomously replicating sequence elements by an unknown mechanism. All Cdc6p homologues contain a bipartite Walker ATP-binding motif that suggests that ATP binding or hydrolysis may regulate Cdc6p activity. To determine whether these motifs are important for Cdc6p activity, mutations were made in conserved residues of the Walker A and B motifs. Substitution of lysine 114 to alanine (K114A) in the Walker A motif results in a temperature-sensitive phenotype in yeast and slower progression into S phase at the permissive temperature. A K114E mutation is lethal. The Cdc6(K114E) protein binds to chromatin but fails to promote loading of the Mcm proteins, suggesting that ATP binding is essential for this activity. The mutant arrests with a G1 DNA content but retains the ability to restrain mitosis in the absence of DNA replication, unlike depletion of Cdc6p. In contrast, Cdc6p containing a double alanine mutation in the Walker B motif, DE(223, 224)AA, is functional, and the mutant exhibits an apparently normal S phase. These results suggest that Cdc6p nucleotide binding is important for establishing the prereplicative complex at origins of DNA replication and that the amino terminus of Cdc6p is required for blocking entry into mitosis.

Adenosine Triphosphate↗

PubMed1999

Zinc exposure in Chinese foundry workers.

BACKGROUND: Inhalational exposure to zinc oxide fumes is associated with metal fume fever, a self-limited but very uncomfortable condition closely resembling influenza. Very little is known regarding the toxicokinetics of inhaled zinc, making the interpretation of zinc measurements in serum and urine problematic. METHODS: Twenty workers in a zinc foundry in Baiyin, Peoples' Republic of China, were investigated with serial examinations by a physician, chest radiographs, and spirometry. Exposure assessment consisted of the measurement of zinc in serum, urine, and personal air samples. RESULTS: No cases of metal fume fever were observed during the study period despite exposures to as high as 36.3 mg/m3 over less than 4 hr. In addition, no radiographic or functional changes were noted. Serum zinc levels of all workers were within the reference range and did not correlate with external exposure measurements. However, elevations were noted in urinary zinc levels, which showed a significant association (Spearman's correlation coefficient = 0.47, P = 0.04) between exposure to zinc and urine zinc. CONCLUSIONS: These results provide exposure measurements for zinc at which workers demonstrate tolerance to the development of metal fume fever. Furthermore, they suggest that urine may be the preferred biological medium for the assessment of zinc exposure.

Adult↗

PubMed1999

Sustained hemodynamic effects of an infusion of nesiritide (human b-type natriuretic peptide) in heart failure: a randomized, double-blind, placebo-controlled clinical trial. Natrecor Study Group.

OBJECTIVES: The goal of this study was to further define the role of nesiritide (human b-type natriuretic peptide) in the therapy of decompensated heart failure (HF) by assessing the hemodynamic effects of three doses (0.015, 0.03 and 0.06 microg/kg/min) administered by continuous intravenous (IV) infusion over 24 h as compared with placebo. BACKGROUND: Previous studies have shown beneficial hemodynamic, neurohormonal and renal effects of bolus dose and 6-h infusion administration of nesiritide in HF patients. Longer term safety and efficacy have not been studied. METHODS: This randomized, double-blind, placebo-controlled multicenter trial enrolled subjects with symptomatic HF and systolic dysfunction (left ventricular ejection fraction < or =35%). Central hemodynamics were assessed at baseline, during a 24-h IV infusion and for 4 h postinfusion. RESULTS: One hundred three subjects with New York Heart Association class II (6%), III (61%) or IV (33%) HF were enrolled. Nesiritide produced significant reductions in pulmonary wedge pressure (27% to 39% decrease by 6 h), mean right atrial pressure and systemic vascular resistance, along with significant increases in cardiac index and stroke volume index, with no significant effect on heart rate. Beneficial effects were evident at 1 h and were sustained throughout the 24-h infusion. CONCLUSIONS: The rapid and sustained beneficial hemodynamic effects of nesiritide observed in this study support its use as a first-line IV therapy for patients with symptomatic decompensated HF.

Atrial Natriuretic Factor↗

PubMed1999

Study of a molecular imprinting polymer coated BAW bio-mimic sensor and its application to the determination of caffeine in human serum and urine.

A bio-mimic bulk acoustic wave (BAW) sensor was fabricated by coating the caffeine (CAF) template molecular imprinting polymer (MIP). This sensor exhibited high selectivity and a sensitive mass response to CAF. The response range of the sensor was between 5.0 x 10(-9) and 1.0 x 10(-4) M with a detection limit of 5.0 x 10(-9) M at pH 8.0. Recoveries were 96.1-105.6%. Influencing factors were investigated in detail and optimized. When employed to detect real samples, the proposed method proved to be a convenient method with the advantages of high sensitivity, good selectivity and ease of handling.

Biosensing Techniques↗

PubMed1999

Experimental prophylaxis of Staphylococcus aureus endophthalmitis after vitrectomy: the use of antibiotics in irrigating solution.

PURPOSE: To test the efficacy of clindamycin and gentamicin in irrigating solution during vitrectomy to prevent experimental Staphylococcus aureus endophthalmitis. MATERIALS AND METHODS: Thirty-six New Zealand white rabbits were divided into six groups. Vitrectomy using two different irrigating solutions was followed by intravitreal injection of S. aureus: Group 1, balanced salt solution (BSS) followed by 1,000 colony-forming units (CFU) S. aureus; Group 2, BSS fortified with clindamycin, 10 microg/mL, and gentamicin, 8 microg/mL (CGBSS), followed by intravitreal injection of 1,000 CFU S. aureus; Group 3, BSS followed by 2,000 CFU S. aureus; Group 4, CGBSS followed by 2,000 CFU S. aureus; Group 5, BSS followed by 4,000 CFU S. aureus; and Group 6, CGBSS followed by 4,000 CFU S. aureus. The eyes were examined clinically after surgery. Vitreous samples were cultured and histologic studies were performed. RESULTS: Severe endophthalmitis developed in all eyes in Groups 1, 3, and 5 (not given antibiotics). No endophthalmitis developed in Group 2. In Group 4, five of the six eyes were normal and one eye had endophthalmitis. In Group 6, one eye had clear vitreous and fundus, three eyes had moderate vitreous haze, and the other four eyes demonstrated severe endophthalmitis. Bacterial growth in Groups 1, 2, 3, 4, 5, and 6 were 4/4, 0/4, 6/6, 1/6, 4/6, and 2/8 eyes, respectively. CONCLUSION: When 1,000 to 2,000 CFU S. aureus were injected after vitrectomy, clindamycin and gentamicin in the irrigating solution significantly diminished the intraocular inflammation and the rate of positive bacterial culture. Clindamycin and gentamicin in the irrigating solution were not significantly effective when 4,000 CFU bacteria was injected; however, the degree of inflammation was less severe than in the control group.

Acetates↗

PubMed1999

Tolerance of extended-term vitreous replacement with perfluoro-n-octane and perfluoroperhydrophenanthrene mixture (phenoctane).

PURPOSE: To improve the surface visibility of perfluoroperhydrophenanthrene, we added various percentages of perfluoro-n-octane. METHODS: Twenty New Zealand white rabbit eyes underwent gas vitrectomy. One milliliter of balanced salt solution was injected into each Group 1 eye as control. Perfluoro-n-octane was added to perfluoroperhydrophenanthrene in ratios of 15:85, 25:75, and 50:50; 1 mL of each mixture was injected into the vitreous cavities of Groups 2, 3, and 4, respectively. Eyes were examined clinically and electroretinograms were performed before and 4 and 8 weeks after injection, when the rabbits were killed. Eyes were processed for light and transmission electron microscopy (TEM). RESULTS: The indices of refraction of the 15:85, 25:75, and 50:50 mixtures were 1.3275, 1.3191, and 1.3026, respectively, and the mixtures were visible in the vitreous cavity. Emulsification and mild-to-moderate dust-like opacities were observed in eyes from Groups 2 through 4; vitreous strands formed in four of the Group 4 eyes. The retinae were attached. Electroretinographic responses were normal, except in one eye with cataract. Light microscopy showed normal retinal architecture, with some macrophages with intracytoplasmic vacuoles on the surface of the inferior retina or in the vitreous cavity. Fingerprint disfigurement of photoreceptor outer segments was seen in some Group 3 and 4 eyes under TEM. CONCLUSIONS: Minimal changes were induced by the 15:85 mixture in the rabbit eye. The mixtures of 25:75 and 50:50 produced some ultrastructural changes of the retina. The mixtures were visible under water.

Animals↗

PubMed1999

Ocular toxicity of intravitreal clarithromycin.

OBJECTIVE: To investigate the ocular toxicity and clearance of intravitreal clarithromycin lactobionate (Klaricid) and to determine the highest nontoxic dose. MATERIALS AND METHODS: To evaluate toxicity, 24 New Zealand white rabbits were divided into six groups (four rabbits each). Rabbits were examined preoperatively and electroretinography (ERG) was performed. The left eyes of the animals served as controls and received intravitreal injection of 0.1 mL sterile water. Klaricid (0.1 mL) was injected into the midvitreous cavity of the right eyes at concentrations of 25 microg, 250 microg, 500 microg, 1.0 mg, 2.0 mg, and 4.0 mg/0.1 mL. The animals were followed up to 15 days postinjection by clinical examination and ERG. The animals were killed and the eyes were enucleated and processed for light microscopy. Ten New Zealand rabbits were used for the vitreous clearance study as drug test rabbits and two additional rabbits were used to generate control retina and vitreous. The highest nontoxic dose (1 mg) was injected into the vitreous and the concentration of clarithromycin in the vitreous was determined using high-performance liquid chromatography at various time intervals after injection. RESULTS: Cataract occurred after intravitreal doses of 2.0 and 4.0 mg. Electroretinography showed decreasing b-wave amplitude with both dark- and light-adapted stimulus in the 4.0-mg group; it was normal in other groups. Histopathologic sections showed localized retinal necrosis and disorganization with the 2.0 and 4.0 mg dosage. No histologic changes were found in the other groups. The half-life of intravitreal clarithromycin was found to be 2 hours. No metabolites of clarithromycin were observed in the vitreous samples. CONCLUSION: Intravitreal clarithromycin lactobionate is nontoxic to rabbit eyes up to a dose of 1.0 mg. Because of its broad-spectrum antibiotic effect and appropriate half-life in the vitreous, it may be a good choice for intravitreal treatment of susceptible organisms.

Animals↗

PubMed1999

Evaluation of toxicity of intravitreal ceftazidime, vancomycin, and ganciclovir in a silicone oil-filled eye.

PURPOSE: To evaluate the toxicity of intravitreal drugs in an eye filled with silicone oil for prolonged internal retinal tamponade. METHODS: Vitrectomy was performed in 21 rabbit eyes, and the vitreous was replaced with silicone oil. Different concentrations of various drugs (ceftazidime, vancomycin, and ganciclovir) were injected intravitreally. RESULTS: Silicone oil increased the toxicity of these drugs, which were injected in previously determined nontoxic doses, possibly because of a reduction of the preretinal space. Injecting one quarter of the known nontoxic dose failed to show any toxicity. CONCLUSIONS: Nontoxic concentrations of intravitreal drugs can cause toxicity in a silicone-filled eye.

Animals↗

PubMed1999

Deletion mutagenesis within the dimerization initiation site of human immunodeficiency virus type 1 results in delayed processing of the p2 peptide from precursor proteins.

Previous work has shown that deletions of genomic segments at nucleotide (nt) positions +238 to +253, i.e., construct BH10-LD3, or nt positions +261 to +274, i.e., construct BH10-LD4, within the human immunodeficiency virus type 1 (HIV-1) dimerization initiation site (DIS) destroyed DIS secondary structure and dramatically reduced viral replication capacity. Surprisingly, two point mutations located within the viral peptide 2 (p2) and nucleocapsid (NC) protein termed MP2 and MNC, respectively, were able to compensate for this defect. Since the MP2 mutation involves an amino acid substitution near the cleavage site between p2 and NC, we investigated the effects of the above-mentioned deletions on the processing of Gag proteins. Immunoprecipitation assays performed with monoclonal antibodies against viral capsid (CA) (p24) protein showed that p2 was cleaved from CA with less efficiency in viruses that contained the LD3 and LD4 deletions than in wild-type viruses. The presence of the two compensatory mutations, MP2 and MNC, increased the efficiency of the cleavage of p2 from CA, but neither mutation alone had this effect or was sufficient to compensate for the observed impairment in infectiousness. A virus that contained both of the above-mentioned deletions within the DIS was also impaired in regard to processing and infectiousness, and it could likewise be compensated by the MP2 and MNC point mutations. These results suggest that the DIS region of HIV-1 RNA plays an important role in the processing of Gag proteins.

Animals↗

PubMed1999

Reverse transcriptase inhibitors can selectively block the synthesis of differently sized viral DNA transcripts in cells acutely infected with human immunodeficiency virus type 1.

We have recently reported that the in vitro inhibition of human immunodeficiency virus type 1 (HIV-1) reverse transcription by inhibitors of reverse transcriptase (RT) occurred most efficiently when the expected DNA products of RT reactions were long (Quan et al. , Nucleic Acids Res. 26:5692-5698, 1998). Here, we have used a quantitative PCR to analyze HIV-1 reverse transcription within acutely infected cells treated with RT inhibitors. We found that levels of minus-strand strong-stop DNA [(-)ssDNA] formed in acutely infected MT2 cells were only slightly reduced if cells were infected with viruses that had been generated in the presence of either azidothymidine or nevirapine (5 microM) and maintained in the presence of this drug throughout the viral adsorption period and thereafter. Control experiments in which virus inoculation of cells was performed at 4 degrees C, followed directly by cell extraction, showed that less than 1% of total (-)ssDNA within acutely infected cells was attributable to its presence within adsorbed virions. In contrast, synthesis of intermediate-length reverse-transcribed DNA products decreased gradually as viral DNA strand elongation took place in the presence of either of these inhibitors. This establishes that nucleoside and nonnucleoside RT inhibitors can exert similar temporal impacts in regard to inhibition of viral DNA synthesis. Generation of full-length viral DNA, as expected, was almost completely blocked in the presence of these antiviral drugs. These results provide insight into the fact that high concentrations of drugs are often needed to yield inhibitory effects in cell-free RT assays performed with short templates, whereas relatively low drug concentrations are often strongly inhibitory in cellular systems.

Anti-HIV Agents↗

PubMed1999

Mutations within four distinct gag proteins are required to restore replication of human immunodeficiency virus type 1 after deletion mutagenesis within the dimerization initiation site.

Human immunodeficiency virus type 1 (HIV-1) genomic RNA segments at nucleotide (nt) positions +240 to +274 are thought to form a stem-loop secondary structure, termed SL1, that serves as a dimerization initiation site for viral genomic RNA. We have generated two distinct deletion mutations within this region, termed BH10-LD3 and BH10-LD4, involving nt positions +238 to +253 and +261 to +274, respectively, and have shown that each of these resulted in significant diminutions in levels of viral infectiousness. However, long-term culture of each of these viruses in MT-2 cells resulted in a restoration of infectiousness, due to a series of compensatory point mutations within four distinct proteins that are normally cleaved from the Gag precursor. In the case of BH10-LD3, these four mutations were MA1, CA1, MP2, and MNC, and they involved changes of amino acid Val-35 to Ile within the matrix protein (MA), Ile-91 to Thr within the capsid (CA), Thr-12 to Ile within p2, and Thr-24 to Ile within the nucleocapsid (NC). The order in which these mutations were acquired by the mutated BH10-LD3 was MNC > CA1 > MP2 > MA1. The results of site-directed mutagenesis studies confirmed that each of these four substitutions contributed to the increased viability of the mutated BH10-LD3 viruses and that the MNC substitution, which was acquired first, played the most important role in this regard. Three point mutations, MP2, MNC, and MA2, were also shown to be sequentially acquired by viruses that had emerged in culture from the BH10-LD4 deletion. The first two of these were identical to those described above, while the last involved a change of Val-35 to Leu. All three of these substitutions were necessary to restore the infectiousness of mutated BH10-LD4 viruses to wild-type levels, although the MP2 mutation alone, but neither of the other two substitutions, was able to confer some viability on BH10-LD4 viruses. Studies of viral RNA packaging showed that the BH10-LD4 deletion only marginally impaired encapsidation while the BH10-LD3 deletion caused a severe deficit in this regard.

Amino Acid Sequence↗

PubMed1999

[A new explanation for shadow bands on denaturing PAGE for products of STRS--the difference between sense and antisense strands in electrophoresis].

OBJECTIVE: To explore the mechanism of shadow bands on denaturing PAGE for PCR products of STR sequences and try to eliminate them. METHODS: PCR and asymmetric PCR were employed. The amplified fragments were separated on denaturing PAGE and visualized by silver stain. RESULTS: By asymmetric PCR, half of shadow bands of dinucleotide repeats were eliminated and there was only one band for each allele for tetranucleotide sequence. A different migration between the sense strand and antisense strand was identified. CONCLUSION: The difference between sense and antisense strands in electrophoresis is one of the causes in shadow bands, and these shadow bands can be eliminated by asymmetric PCR partly or totally.

Electrophoresis, Polyacrylamide Gel↗

PubMed1999

[nm23-H1 protein expression and its clinical significance in human laryngeal carcinoma].

The Objective of the study on the expression of nm23-H1 protein in human laryngeal carcinoma, was to explore the role of nm23 gene in lymph node metastasis and invasion. The expression of nm23-H1 protein was immunohistochemically examined in 86 resected human laryngeal carcinomas. Anti-nm23-H1 monoclonal antibody was used. The results showed that 66.3%(57/86) of the cases were positive for nm23-H1 protein expression in the primary lesions. The positive staining rate (90.5%, 38/42) of the patients without regional lymph node metastasis, was significantly higher than that of patients with nodal involvement (43.2%, 19/44). Inverse relationship were found between the nm23-H1 protein expression in the primary lesions and the depth of tumor invasion or the advance of clinical stage. Expression of nm23-H1 protein was positively associated with the ascending histological grade of the lesion, and the relationship was significant. The above data suggest that nm23 gene plays an important role in the control of lymph node metastasis and invasion in laryngeal carcinomas.

Adult↗