Biomedical subjects

C Liang

Publications and source records attributed to C Liang.

At least 37 records · Page 2Linked to original sources

PubMed2001

Partial restoration of replication of simian immunodeficiency virus by point mutations in either the dimerization initiation site (DIS) or Gag region after deletion mutagenesis within the DIS.

We used the simian immunodeficiency virus (SIV) molecular clone SIVmac239 to generate a deletion construct, termed SD2, in which we eliminated 22 nucleotides at positions +398 to +418 within the putative dimerization initiation site (DIS) stem. This SD2 deletion severely impaired viral replication, due to adverse effects on the packaging of viral genomic RNA, the processing of Gag proteins, and viral protein patterns. However, long-term culture of SD2 in either C8166 or CEMx174 cells resulted in restoration of replication capacity, due to two different sets of three compensatory point mutations, located within both the DIS and Gag regions. In the case of C8166 cells, both a K197R and a E49K mutation were identified within the capsid (CA) protein and the p6 protein of Gag, respectively, while the other point mutation (A423G) was found within the putative DIS loop. In the case of CEMx174 cells, two compensatory mutations were present within the viral nucleocapsid (NC) protein, E18G and Q31K, in addition to the same A423G substitution as observed with C8166 cells. A set of all three mutations was required in each case for restoration of replication capacity, and either set of mutations could be substituted for the other in both the C8166 and CEMx174 cell lines.

Base Sequence↗

PubMed2001

An intact U5-leader stem is important for efficient replication of simian immunodeficiency virus.

Previous work has shown that four deletions in simian immunodeficiency virus (SIV), termed SD1a, SD1b, SD1c, and SD6, which eliminated sequences at nucleotide positions 322 to 362, 322 to 370, 322 to 379, and 371 to 379, respectively, located downstream of the primer binding site, impaired viral replication capacity to different extents. Long-term culturing of viruses containing the SD1a, SD1b, and SD6 deletions led to revertants that possessed wild-type replication kinetics. We now show that these revertants retained the original deletions in each case but that novel additional mutations were also present. These included a large deletion termed D1 (nt +216 to +237) within the U5 region that was shown to be biologically relevant to reversion of both the SD1a and SD1b constructs. In the case of SD6, two compensatory point mutations, i.e., A+369G, termed M1, located immediately upstream of the SD6 deletion, and C+201T, termed M2, within U5, were identified and could act either singly or in combination to restore viral replication. Secondary structure suggests that an intact U5-leader stem is important in SIV for infectiousness and that the additional mutants described played important roles in restoration of this motif.

Base Sequence↗

PubMed2001

Role for human immunodeficiency virus type 1 Tat protein in suppression of viral reverse transcriptase activity during late stages of viral replication.

We have examined the role of the human immunodeficiency virus type 1 (HIV-1) Tat protein in the regulation of reverse transcription. We show that a two-exon but not a one-exon form of Tat markedly suppressed cell-free reverse transcriptase (RT) activity. Conversely, viruses expressing two-exon Tat (pNL43 and pNL101) showed rapid replication kinetics and more efficient endogenous RT activity compared with viruses expressing one-exon Tat (pM1ex). The pM1ex virions, as well as pM1ex-infected cells, also contained higher levels of viral DNA than did either the pNL43 or pNL101 viruses, indicating that reverse transcription might have continued during later stages of viral replication in the absence of the second Tat exon. Moreover, degradation of viral genomic RNA was more apparent in the pM1ex virions. Accordingly, we propose that the two-exon Tat may help augment viral infectivity by suppressing the reverse transcription reaction during late stages of viral synthesis and by preventing the synthesis of potentially deleterious viral DNA products.

Cell Line↗

PubMed2001

Novel, live attenuated simian immunodeficiency virus constructs containing major deletions in leader RNA sequences.

We have constructed a series of simian immunodeficiency virus (SIV) mutants containing deletions within a 97-nucleotide (nt) region of the leader sequence. Deletions in this region markedly decreased the replication capacity in tissue culture, i.e., in both the C8166 and CEMx174 cell lines, as well as in rhesus macaque peripheral blood mononuclear cells. In addition, these deletions adversely affected the packaging of viral genomic RNA into virions, the processing of Gag precursor proteins, and patterns of viral proteins in virions, as assessed by biochemical labeling and polyacrylamide gel electrophoresis. Different levels of attenuation were achieved by varying the size and position of deletions within this 97-nt region, and among a series of constructs that were generated, it was possible to rank in vitro virulence relative to that of wild-type virus. In all of these cases, the most severe impact on viral replication was observed when the deletions that were made were located at the 3' rather than 5' end of the leader region. The potential of viral reversion over protracted periods was investigated by repeated viral passage in CEMx174 cells. The results showed that several of these constructs showed no signs of reversion after more than 6 months in tissue culture. Thus, a series of novel, attenuated SIV constructs have been developed that are significantly impaired in replication capacity yet retain all viral genes. One of these viruses, termed SD4, may be appropriate for study with rhesus macaques, in order to determine whether reversions will occur in vivo and to further study this virus as a candidate for attenuated vaccination.

5' Untranslated Regions↗

PubMed2001

Effect of long-term exposure to fluoride in drinking water on risks of bone fractures.

Findings on the risk of bone fractures associated with long-term fluoride exposure from drinking water have been contradictory. The purpose of this study was to determine the prevalence of bone fracture, including hip fracture, in six Chinese populations with water fluoride concentrations ranging from 0.25 to 7.97 parts per million (ppm). A total of 8266 male and female subjects > or =50 years of age were enrolled. Parameters evaluated included fluoride exposure, prevalence of bone fractures, demographics, medical history, physical activity, cigarette smoking, and alcohol consumption. The results confirmed that drinking water was the only major source of fluoride exposure in the study populations. A U-shaped pattern was detected for the relationship between the prevalence of bone fracture and water fluoride level. The prevalence of overall bone fracture was lowest in the population of 1.00-1.06 ppm fluoride in drinking water, which was significantly lower (p < 0.05) than that of the groups exposed to water fluoride levels > or =4.32 and < or =0.34 ppm. The prevalence of hip fractures was highest in the group with the highest water fluoride (4.32-7.97 ppm). The value is significantly higher than the population with 1.00-1.06 ppm water fluoride, which had the lowest prevalence rate. It is concluded that long-term fluoride exposure from drinking water containing > or =4.32 ppm increases the risk of overall fractures as well as hip fractures. Water fluoride levels at 1.00-1.06 ppm decrease the risk of overall fractures relative to negligible fluoride in water; however, there does not appear to be similar protective benefits for the risk of hip fractures.

Aged↗

PubMed2001

[Corrosion and haemocompatibility of 316L stainless steel with electroplated Rh film].

In this study, surface modification by electroplating Rh on 316L stainless steel was carried out in order to improve the corrosion resistance and blood compatibility of implants. XPS was used to characterize the Rh film. The corrosion behavior of 316L stainless steel with electroplated Rh and non-treated was studied in Tyrode's biological solution. Additionally, the haemocompatibility of 316L stainless steel with electroplated Rh was evaluated by preliminary hemolysis test. The results showed that the corrosion resistance of 316L stainless steel with electroplated Rh was improved, and hemolysis decreased, which indicated that electroplating Rh can improve the blood compatibility of 316L stainless steel.

Animals↗

PubMed2001

[Toxicity of different pesticides to Haemadipsa hainana and its control].

Laboratory determination on the toxicity of sumicidin, isoprocarb, dicofol, thiocyclam, dimethoate and glyphosate to Haemadipsa hainana showed that LD50 for the six pesticides followed the order of sumicidin > isoprocarb > dicofol > thiocyclam > dimethoate, but glyphosate was not virulent. "Glyphosate + sumicidin" had much more toxicity. The susceptibility of H. hainana to sumicidin differed in the order of adult > juvenile > subadult. Field tests showed that the control effect of 1.5% sumicidin to H. hainana was 95.08% of total number of its population. Applied tests showed that the control effect of "Glyphosate + 0.5% sumicidin" was 94.7%, and "glyphosate + 1% isoprocarb" was 90.5%. "Glyphosate + pesticides" was more effective both in controlling H. hainana and in destroying its habitat weed.

Animals↗

PubMed2001

[Anaerobic hydrolysis of terramycin crystallizing mother solution].

The terramycin crystallizing mother solution contained high organics and high nitrogen. There were many kinds of bioinhibition in it but not enough electronic donor. Anaerobic hydrolysis of terramycin crystallizing mother solution was completed with up anarobic sludge bed in order to improve the biodegradability of wastewater and electronic donor in it. The variations of pH, COD, NH4+, and SO4(2-) were monitored. The COD removal was in a narrow range between 10% and 16.4% even when the HRT of the reactor was changed from 1.5 h to 6 h. pH increased because of formation of NH3 and reduction of SO4(2-). Most of SO4(2-) was reduced to S2- when the HRT was longer than 2 h. Batch experiments on hydrolyzed wastewater demonstrated that reaction rates of nitrification and denitrification increased by 90.9% and 45.2%, respectively.

Anaerobiosis↗

PubMed2001

[Effect of fibrinogen on corrosion behavior of stainless steel in artificial blood solution].

The effect of fibrinogen on corrosion behavior of SUS316L and SUS317L stainless steel in artificial blood PBS solution has been investigated with electrochemical technology. The results showed that the corrosion potential (Ec) of stainless steel shifted negatively, the passivated current (ip) became less and the pitting corrosion potential (Eb) shifted negatively with the existence of fibrinogen in PBS. These indicate that samples become more sensitive to corrosion under this circumstance. SEM pictures demonstrated that stainless steel adsorbed fibrinogen on its surface.

Adsorption↗

PubMed2001

[Soil and water loss from cultivated slope land derived from granite under different cropping systems in Three-Gorges reservoir areas].

The water and soil loss caused by cultivation on slope land derived from granite under different cropping systems in the Three-Gorges reservoir area was analyzed based on the data from localized observation. The results showed that in this area, proximately 60% of total annual rainfall, distributed in May to August, and 60% of soil erosion occurred in these four months, with 50% in June and July. The coverage rates under different cropping systems differed significantly, e.g., triple-cropping systems and inter-croping system with perennial plants (grass and day lily) had a bigger covering than double-cropping systems. The soil loss under cropping system with peanut was much lower than that with sweet potato, because the covering rate of the former was higher than that of the latter in summer raining season. The sequence of soil and nutrient loss for different cropping systems was rape (wheat) sweet potato > rape(wheat)/corn/sweet potato > rape(wheat)/corn/peanut/rape(wheat)/grass/peanut/rape(wheat)/day lily/peanut. It was concluded that soil loss from cultivated slope land could be controlled below a permissible value, if rational cropping and management systems were adopted.

Agriculture↗

PubMed2001

[Mitochondrial DNA mutations in matrilineal nonsyndromic deafness pedigrees of southwest China].

OBJECTIVE: To identify the incidence of the 1555A-->G mutation and explore the audiological features of pedigrees with matrilineal non-syndromic deafness in Southwest of China so as to provide the theoretical evidence for establishing the method of gene diagnosis. METHODS: Six pedigrees with 102 members were evaluated audiologically and clinically. DNA was extracted from their blood samples. All subjects were screened for mitochondrial DNA 1555A-->G mutation by Alw 26I restriction endonuclease digestion. RESULTS: Seventeen maternal relatives of aminoglycoside antibiotic induced deafness (AAID) pedigree 1 and pedigree 2, carried 1555A-->G mutation. 10 maternal relatives of Non-AAID pedigree 6 also carried 1555A-->G mutation. No mutation was found among paternal relatives and pedigrees 3, 4 and 5. CONCLUSION: The same audiological features of these pedigrees are: bilateral and symmetrical progressive sensorineural hearing loss with variable age of onset. The 1555A-->G mitochondrial mutation is one of the hereditary factors for this disorder. 4 Aminoglycoside antibiotic plays an important role in developing deafness. The incidence of the 1555A-->G mutation in AAID and matrilineal non-syndromic deafness pedigrees is fairly high. Screening for mitochondrial 1555A-->G mutation may be of great clinical use fullness.

Aminoglycosides↗

PubMed2001

[Pilot study on mutations of p53 gene in laryngeal carcinoma].

OBJECTIVE: To determine the characteristic and frequency of the point mutation of p53 gene. METHODS: 22 cases of laryngeal squamous cell carcinoma (LSCC) with positive expression of mutant p53 protein and 2 cases of normal laryngeal epithelium as control were examined by means of polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP), single strand conformation polymorphism (SSCP) and DNA sequencing analyses. RESULTS: 3 cases of LSCC had the point mutation on codons 248, 250 and 254 of exon 7 in p53 gene. None of the cases had the point mutation on codon 249. CONCLUSION: These findings suggest that the point mutation on codon 249 of exon 7 in p53 gene may be uncommon in LSCC. SSCP and DNA sequencing analyses are sensitive and rapid methods for detecting p53 gene mutation.

Adult↗

PubMed2001

[IL-2 gene and cisplatin combined therapy for head and neck squamous cell carcinoma].

OBJECTIVE: The objective of this study is to assess the efficacy of IL-2 gene and cisplatin combined therapy on murine HNSCC models. METHODS: HNSCC tumors were established in murine models. The sizes of tumors were measured before and after combined IL-2 and cisplatin treatment, and the results were evaluated by comparing different single treatment groups and the control IL-2 expression was measured after IL-2 gene transfer. Cytotoxic T-lymphocyte (CTL) and natural killer (NK) assays were also performed. RESULTS: HNSCC tumor growth was significantly inhibited following combined IL-2 gene and cisplatin therapy, when compared with that of the control. The levels of IL-2 protein expressions were increased in combined and single IL-2 treated groups. The activities of cytotoxic T-lymphocytes and natural killers in both the combined treatment group and the IL-2 treated group are higher than those of the controlled group. CONCLUSION: Combined IL-2 gene and cisplatin therapy can significantly inhibit HNSCC tumor growth in the murine models, and efficiently induces anti-tumor immune reaction of hosts.

Animals↗

PubMed2001

[The diagnosis and treatment of isolated sphenoid sinus disease].

OBJECTIVE: To detail the underlying symptoms and signs of patients with isolated sphenoid sinus inflammatory disease and enhance the initial diagnostic accuracy. METHOD: 49 patients with isolated sphenoid sinus inflammatory disease were reviewed, and the outcomes of the endoscopic surgery were compared with the non-endoscopic surgery. RESULT: In patients who underwent endoscopic sphenoidotomy, 31 were virtually free from symptoms and 5 still experienced mild headache and hyposmia but their radiographic finding had become normalized. None of them need re-operation within 6-48 months follow-up. However, in patients with non-endoscopic sinus irrigation, only one was free from the symptoms and 5 patients underwent re-operation because of recurrence. CONCLUSION: Nasal endoscopy and CT/MRI scan could provide a precise diagnosis for isolated sphenoid sinus disease and endoscopic surgery is valuable in its treatment.

Adolescent↗

PubMed2001

[Observations of the curative effect with various liquid for post operative irrigation of ESS of treating chronic sinusitis and nasal polyps].

OBJECTIVE: To explore the influence of liquid for post-operative irrigation on the effect of ESS. METHOD: 192 cases with chronic sinusitis and/or nasal polyps of groupIIstageII who had undergone the ESS from September, 1998 to June, 1999 and completed a 3-month follow-up were divided randomly into 3 groups to accept 3 different kinds of irrigation liquid. The evaluation of curative effect was according to the index of HaiKou ESS-97. RESULT: The curative effect of Herba Houttuyniae group was better than the other two. CONCLUSION: The post-operative care is important and the irrigation liquid can affect the effect of ESS.

Adolescent↗

PubMed2001

[Research on the relationship between populations' long-term exposure to fluoride in drinking water and bone fracture in China].

There are contradictory reports on the prevalence of bone fractures associated with long-term fluoride exposure from drinking water. The prevalence of bone fracture in six rural areas of China and the exposure of fluoride in drinking water was investigated. The data including medical history and demographic information, bone fractures, fluoride content in drinking water, physical activity, cigarette smoking, alcohol consumption and dietary intakes were collected. A retrospective epidemiological study by using the same design, method, quality control and the same questionnaire was conducted. A total of 8266 male and female over 50 years of age were divided into 6 groups by the fluoride concentrations in drinking water. The subjects in each group exposed to different levels of fluoride (0.25-0.34, 0.58-0.73, 1.00-1.06, 1.45-2.19, 2.62-3.58 and 4.32-7.97 mg/L) were 1363, 1407, 1370, 1574, 1051 and 1501 respectively. It has been confirmed that drinking water was the only major source of fluoride exposure in the studied populations. The total bone fracture rates were 7.41%, 6.40%, 5.11%, 6.04%, 6.09% and 7.40% in each group. Natural bone fracture rates in each group were 3.01%, 2.21%, 1.31%, 1.65%, 1.43% and 3.66% respectively. The prevalence of bone fracture and water fluoride level appeared a U-shaped relationship. The prevalence of total bone fracture and natural bone fracture in the population with fluoride 1.00-1.06 mg/L in drinking water was the lowest, compared with the groups exposed to fluoride higher than 4.32 mg/L and lower than 0.73 mg/L. The highest prevalence of hip fracture was in the group with higher water fluoride (4.32-7.97 mg/L) exposure. In general, the prevalence of hip fracture was lower and stable up to 1.06 mg/L of fluoride in drinking water, and then it appeared to rise. Based on the data collected in this investigation, it is concluded that the long-term fluoride exposure from drinking water higher than 4.32 mg/L might increase the risk of overall fractures as well as hip fractures. The risk of overall fractures and natural fractures might be lower while the water fluoride level is at 1.00-1.06 mg/L, however, no protective benefits of fluoride for the risk of hip fracture was observed.

Aged↗

PubMed2001

[The protein expression of p53 and bcl-2 in laryngeal squamous cell carcinoma].

OBJECTIVE: To detect the relationship of p53 and bcl-2 gene to laryngeal carcinoma. METHODS: p53 and bcl-2 protein expressions were examined in the specimens of 60 laryngeal carcinomas and 8 vocal cord polyps by immunohistochemistry method. RESULTS: Overexpressions of p53 and bcl-2 were found in the laryngeal carcinoma specimens; the positive rates of p53 and bcl-2 protein expression were 61.7%(37/60) and 43.3%(26/60), respectively. Negative results were observed in all the vocal cord polyp specimens. The positive rates of p53 and bcl-2 expression were related to the histological grade and cervical lymphatic metastasis of laryngeal carcinoma but not related to clinical stage and tumor types. CONCLUSION: The results of this study support the hypothesis that p53 and bcl-2 gene may be involved in the apoptosis of laryngeal carcinoma and they may play an important role in the pathogenesis of laryngeal cancer.

Adult↗

PubMed2001

[Adenovirus-mediated Rb gene transfect for head and neck cancer].

OBJECTIVE: To evaluate the efficacy of Rb gene therapy in head and neck carcinoma. METHODS: We investigated the adenovirus-mediated Rb (Ad-Rb) gene transfect into human oral squamous cell carcinoma cell line (012) in both in vitro and in vivo models. RESULTS: The cells growth curve for 012 tumor cells transfect with Ad-Rb became lower after two days transfection and declined slightly by six days. Tumor growth in nude mice was also significantly retarded following Ad-Rb injection when compared with controls. Ad-Rb expression was identified by Western blotting in those tumors injected with Ad-Rb. CONCLUSION: These results implicated that the recombinant Rb gene adenovirus vector could efficiently transfect and inhibit oral squmous cell carcinoma. It might be an important candidate for gene therapy in head and neck cancer.

Adenoviruses, Human↗