Biomedical subjects

C Liang

Publications and source records attributed to C Liang.

At least 109 records · Page 6Linked to original sources

PubMed1998

[Relationship between tumor cell proliferating activity and biological behavior, prognosis in laryngeal carcinoma].

Using PC 10, an antibody to proliferating cell nuclear antigen (PCNA) and a standard immunohistochemical staining the authors examined 11 cases of simple hyperplasia of epithelium (SHE), 32 cases of atypical hyperplasia of epithelium (AHE) and 42 cases of laryngeal squamous cell carcinoma (LSCC) for expression of PCNA, a protein associated with DNA polymerase dalta and DNA replication, a marker for tumor cell proliferation. The results revealed that PCNA indices in SHE, AHE and LSCC were 9.5%, 27.33% and 68.05%, respectively. The PCNA indices were 63.68%, 69.57%, 71.18% in the well, moderately and poorly differentiated LSCC, respectively, there were significant differences. The PCNA indices were 63.88%, 70.82%, 66.20% and 69.04%, respectively in stages I, II, III, and IV of LSCC; no significance was found. There was a strong negative correlation betwee survival time and the tumor cell proliferative activity (r = 0.6243). PCNA might provide a useful tool for studying cell proliferation in situ under normal and pathological condition.

Adult↗

PubMed1998

[The experimental study of the facial nerve regeneration in silicone chamber: the influence of nerve growth factor].

OBJECTIVE: To elucidate the role of NGF in the regeneration of facial nerve. METHODS: The superior buccal division of facial nerve of adult New Zealand rabbit was transected and a nerve growth chamber created. The chamber of the experimental side was filled with NGF/normal saline and that of the control side with normal saline alone. Four and eight weeks after operation, the regenerated nerves in the chambers were dissected for histological studies. RESULTS: Four weeks after operation, the average thickness of myelin sheath and the average number of myelinated axons were 0.779 +/- 0.475 micron, 2.024 +/- 1.999 (n = 11) in experimental group and 0.413 +/- 0.132 micron, 368 +/- 171 (n = 8) in control sides respectively. There was significant difference between the experimental sides and control sides (P < 0.05). Eight weeks after operation, the regenerated nerve appeared more mature. There were significant difference in the average diameters, the thickness of myelin sheath and the number of myelinated axons between the experimental and control sides (P < 0.05). CONCLUSION: NGF within a silicone chamber enhanced facial nerve regeneration in New Zealand rabbits.

Animals↗

PubMed1998

[Observation on platelet aggregative ability in patients with malignant tumors of head and neck by electron microscope].

OBJECTIVE: To investigate the relationship between the platelet aggregative ability and malignant tumors of head and neck. METHOD: Platelet aggregative ability was detected by electron microscopy (EM) in 37 patients with malignant tumors of head and neck(Group C), 10 patients with non-neoplastic diseases(Group A) and 10 patients with benign tumors of head and neck(Group B) as the control group, with the ratio of aggregative type platelets as the index. Twenty-five of 37 patients with malignant tumors except 8 cases of nasopharyngeal carcinoma were included in the follow-up study 4-6 months after operations. RESULTS: 1. The mean ratio of aggregative type platelets in patients from Group C was significantly higher that that of Group A or Group B patients (P < 0.05); 2. In Group C, the mean ratio of aggregative type platelets increased significantly with the development of clinical staging(P < 0.05); 3. In follow-up study, the mean ratio of aggregative type platelets of 17 patients without metastasis and recurrence was significantly lower than that before-operation, while the results of 8 patients with metastasis or recurrence was totally opposite. CONCLUSIONS: 1. The aggregative ability of platelets increased in patients with malignant tumors of head and neck; 2. The ratio of aggregative type platelets detected by EM has an important potential value in judging the development, therapeutic effects and prognosis of the malignant tumors of head and neck.

Adult↗

PubMed1998

[Application of stress urethral pressure profile for diagnosis and treatment of stress incontinence].

OBJECTIVE: To apply the stress urethral pressure profile (SUPP) to diagnose the genuine stress incontinence (GSI) and to evaluate the results of treatment. METHOD: 22 patients with GSI underwent SUPP and rest urethral pressure profile (RUPP) using Dantec Menuet. RESULT: The results showed that the pressure transmission ratio (PTR) was 0.68 +/- 0.06, and urethral close pressure (UCP) was -0.62 +/- 0.22 kPa in 22 patients. PTR and UCP raised significantly after operation in 5 patients, P < 0.01. The results of SUPP were compared with those RUPP. CONCLUSION: SUPP is important in both diagnosis and evaluation of GSI, although some limitation exists. To improve the level of diagnosis, it should be combined with other method in clinical use.

Adult↗

PubMed1998

Subretinal semiconductor microphotodiode array.

BACKGROUND AND OBJECTIVE: To examine the function of a semiconductor microphotodiode array (SMA) surgically implanted in the subretinal space. MATERIALS AND METHODS: Positive-intrinsic layer-negative (PiN) or negative-intrinsic layer-positive (NiP) SMAs were surgically placed into the subretinal space of rabbits through a pars plana incision and a posterior retinotomy. The implants required no external connections for power and were sensitive to light over the visible and infrared (IR) spectrum; IR stimuli were used to isolate implant-mediated responses from the activity of native photoreceptors. A stimulator ophthalmoscope was used to superimpose IR stimuli on the implant and adjacent retinal areas, and responses were recorded during the postoperative recovery period. SMA responses were also evaluated in vitro. The animals were given lethal anesthetic overdoses, and the retinas were examined histologically. RESULTS: The in vitro implant response consisted of an electrical spike, followed by a small-amplitude DC offset that followed the time course of the IR stimulation, and an overshoot at the stimulus offset. The SMAs placed in the subretinal space retained a stable position and continued to function throughout the postoperative period. The SMA responses recorded in vivo included additional slow-wave components that were absent from the in vitro recordings. These responses reverted to the in vitro configuration following the death of the animal. There was a significant loss of retinal cells in areas overlying the implant, and the retina appeared normal away from the implant and surgical site. CONCLUSION: SMAs can be successfully implanted into the subretinal space and will generate current in response to light stimulation during an extended period of time.

Animals↗

PubMed1997

Persistent initiation of DNA replication and chromatin-bound MCM proteins during the cell cycle in cdc6 mutants.

Faithful inheritance of genetic information requires that DNA be copied only once each cell cycle. Initiation of DNA replication involves the establishment of a prereplication complex (pre-RC) and subsequent activation by CDK/cyclins, converting the pre-RC to a post-RC. The origin recognition complex (ORC), Cdc6p, and the MCM proteins are required for establishing the pre-RC. We show that all six ORC subunits remain bound to chromatin throughout the cell cycle, whereas the MCM proteins cycle on and off, corresponding precisely to transitions of the RC. A newly isolated cdc6 mutant displays promiscuous initiation of DNA replication, increased nuclear DNA content, and constant MCM protein association with chromatin throughout the cell cycle. This gain-of-function cdc6 mutant ignores the negative controls imposed normally on initiation by the CDK/cyclins, suggesting that Cdc6p is a key mediator of once-per-cell-cycle control of DNA replication.

CDC28 Protein Kinase, S cerevisiae↗

PubMed1997

Topological chirality of iron-sulfur proteins.

An examination of x-ray structures of single-cluster [4Fe-4S] proteins in the Protein Data Bank has revealed that all redox proteins and the glutamine 5-phosphoribosyl-l-pyrophosphate amidotransferase from Bacillus subtilis have a topological configuration arbitrarily designated as D, whereas the DNA repair enzyme endonuclease III from Escherichia coli has the opposite topological configuration L. This is the first example in which both senses of topological chirality have been observed in a class of proteins.

Iron-Sulfur Proteins↗

PubMed1997

Sequence elements downstream of the human immunodeficiency virus type 1 long terminal repeat are required for efficient viral gene transcription.

We investigated the role of a 54-nucleotide region (+200 to +253) located downstream of the HIV-1 long terminal repeat (LTR) on virus gene expression and found, using RT-PCR and p24 CA analysis, that deletion of this region inhibited synthesis of both viral RNA and protein. CAT assays showed that these results were attributable to decreased transcription efficiency of the HIV-1 LTR and not to the stability of the RNA transcripts produced. Further deletional analysis and transfection studies showed that the most important sequences with regard to proviral DNA expression were located between nucleotide positions +218 and +237. Furthermore, substitutional mutational analysis showed that a CTCTCTC sequence at positions +227 to +233, homologous to the pyrimidine-rich initiator (Inr) region found in several promoters, was required for efficient production of both viral RNA and protein. Deletion of the sequence +200 to +217, homologous to the interferon-stimulated response element (ISRE), resulted in impaired LTR promoter activity and decreased synthesis of viral RNA and protein. However, when the latter region was replaced by homologous ISRE sequences from an interferon-stimulated gene (ISG-54), an even more severe effect on HIV gene expression and replication was observed, suggesting that ISRE-like sequences in HIV act differently from homologous sequences in interferon-responsive cellular genes.

Animals↗

PubMed1997

Synthesis of L-ribofuranosyl C-nucleosides.

C-Nucleosides, 4-amino-8-(beta-L-ribofuranosyl)pyrazolo[1, 5-a]-1,3,5-triazine (12) and 4-amino-7-(beta-L-ribofuranosyl)-5H-pyrrolo[3,2-d]pyrimidine (L-9-deazaadenosine, 22), were synthesized from the key intermediate, 3-dimethylamino-2-(2,3-O-isopropylidene-5-O-trityl-L-ribofuranosyl) acrylonitrile (8), which was prepared from L-xylose in 11 steps.

Anti-HIV Agents↗

PubMed1997

The roles of the human immunodeficiency virus type 1 Pol protein and the primer binding site in the placement of primer tRNA(3Lys) onto viral genomic RNA.

Factors that modulate the placement of primer tRNA(3Lys) onto the viral RNA genome in human immunodeficiency virus type 1 (HIV-1) were investigated through analysis of reverse-transcribed products that are extended from the tRNA(3Lys) primer. Mutations were introduced into the HIV-1 pol gene to result in the appearance of a stop codon in the open reading frame of the reverse transcriptase (RT) gene. These constructs, BH10-RT1 and BH10-RT2, yielded viruses with truncated Pol proteins. Alternatively, we altered the sequences involved in frameshifting by generating the construct BH10-FS. With each of these mutated viruses, we found that the primer tRNA(3Lys) that was placed onto viral genomic RNA was present in an unextended state. In contrast, as expected, tRNA(3Lys) in the case of wild-type BH10 virus had been extended by 2 bases. Furthermore, the amount of tRNA(3Lys) that was placed onto viral RNA in mutated viruses was significantly less than that placed in the wild-type virus. We also generated a mutant within the polymerase-active site of RT (D185H) (Asp-->His) that eliminated RT polymerase activity. We found that the placement of primer tRNA(3Lys) onto viral genomic RNA was independent of enzyme function; however, the tRNA(3Lys) that was placed was present in an unextended state due to the loss of RT activity. In contrast, the elimination of protease activity through a D25A (Asp-->Ala) point mutation in the protease-active site (construct BH10-PR) did cause a drop in the efficiency of tRNA(3Lys) placement. In this situation, a proportion of the placed tRNA(3Lys) was found to be extended by 2 bases, although not to the extent found with wild-type virus (BH10), due to a decrease in RT activity associated with unprocessed Gag-Pol protein that could not be cleaved because of the loss of protease activity. We also investigated the role of the primer binding site (PBS) in the placement of tRNA(3Lys) through a series of 2-, 4-, and 8-nucleotide (nt) deletions at the 3' end of the PBS, i.e., BH10-PBS2, BH10-PBS4, and BH10-PBS8, respectively. In mutated viruses BH10-PBS2 and BH10-PBS4, the 2-base-extended form of tRNA(3Lys) was still detected. However, less primer tRNA(3Lys) was placed onto viral genomic RNA as more nucleotides were deleted until the percentage of placement seen with wild-type BH10 virus dropped to only 4% in the virus with 8 nt deleted (BH10-PBS8). Consistently, these mutated viruses possessed decreased initial replication capacity compared with that of the wild-type virus, with the extent of incapacity corresponding to the size of the deletion. However, after several days, an increase in replication potential was accompanied by a reversion to a wild-type PBS.

Animals↗

PubMed1997

Mutations in the kissing-loop hairpin of human immunodeficiency virus type 1 reduce viral infectivity as well as genomic RNA packaging and dimerization.

A stem-loop termed the kissing-loop hairpin is one of the most highly conserved structures within the leader of human immunodeficiency virus type 1 (HIV-1) and chimpanzee immunodeficiency virus genomic RNA. Because it plays a key role in the in vitro dimerization of short HIV-1 RNA transcripts (M. Laughrea and L. Jette, Biochemistry 35:1589-1598, 1996, and references therein; M. Laughrea and L. Jette, Biochemistry 35:9366-9374, 1996, and references therein) and because dimeric RNAs may be preferably encapsidated into the HIV-1 virus, alterations of the kissing-loop hairpin might affect the in vivo dimerization and encapsidation processes. Accordingly, substitution and deletion mutations were introduced into the kissing-loop hairpin of an infectious HIV-1 molecular clone in order to produce viruses by transfection methods. The infectivity of the resulting viruses was decreased by at least 99%, the amount of genomic RNA packaged per virus was decreased by 50 to 75%, and the proportion of dimeric genomic RNA was reduced from >80 to 40 to 50%, but the dissociation temperature of the genomic RNA was unchanged. There is evidence suggesting that the deletion mutations moderately inhibited CAp24 production but had no significant effect on RNA splicing. These results are consistent with the kissing-loop model of HIV-1 RNA dimerization. In fact, because intracellular viral RNAs are probably more concentrated in transfected cells than in cells infected by one virus and because the dimerization and encapsidation processes are concentration dependent, it is likely that much larger dimerization and encapsidation defects would have been manifested within cells infected by no more than one virus.

Animals↗

PubMed1997

The importance of the A-rich loop in human immunodeficiency virus type 1 reverse transcription and infectivity.

Nucleotide segment (+169)AAAA(+172) constitutes an A-rich loop within human immunodeficiency virus type 1 (HIV-1) (HXB2D) RNA and is able to interact with the anticodon loop (33)/USUU(36) of primer tRNA3(Lys). We have shown that the deletion of this A-rich loop resulted in diminished levels of infectivity and reduced synthesis of viral DNA in MT-2 cells and cord blood mononuclear cells. Endogenous reverse transcriptase (RT) assays revealed that the mutated viruses, termed HIV/del-A, generated fewer cDNA products than did wild-type virus, designated HIV/WT. We also employed in vitro RT assays with in vitro-synthesized viral RNA templates, recombinant HIV-1 RT(p66/51), and natural tRNA3(Lys) as primers to show that the mutated RNA templates, designated PBS/del-A, generated less minus-strand strong-stop DNA product than did the wild-type RNA template, designated PBS/WT. The initiation efficiency of reverse transcription from the mutated RNA template was significantly impaired compared with that from the wild-type RNA template when a single-base extension assay from the tRNA3(Lys) primer was employed. However, RT reactions performed with DNA oligonucleotides complementary to the primer binding site (PBS) as primers did not yield differences between the mutated PBS/del-A and wild-type RNA templates. Long-term culture of HIV/del-A in MT-2 cells resulted in the replacement of two G's at nucleotide positions 167 and 168 by two A's that possessed the same relationship to the 5' end of the PBS as did the wild-type A's at positions 171 and 172. In vitro RT assays performed with recombinant enzyme with tRNA3(Lys) as the primer showed that the RNA template thus generated, termed PBS/A2, yielded levels of minus-strand strong-stop DNA product similar to those yielded by the wild-type RNA template. Coincidentally, viruses containing A's at positions 167 and 168 were able to replicate with efficiencies similar to those of the wild-type viruses. Thus, the (+169)AAAA(+172) A-rich loop plays a key role in the synthesis of viral DNA.

Animals↗

PubMed1997

Identification of sequences downstream of the primer binding site that are important for efficient replication of human immunodeficiency virus type 1.

Reverse transcription of retroviruses is initiated from an 18-nucleotide (nt) primer binding site (PBS), located within the 5' region of viral genomic RNA, to which the host cell-derived tRNA primer is annealed and also involves viral genomic sequences outside the PBS. We constructed proviral DNA clones of human immunodeficiency virus (HIV) that had selective deletions of either a 7-nt segment found immediately downstream of the PBS or an extended nontranslated 54-nt stretch located immediately downstream of the PBS and containing the aforementioned 7-nt segment. Synthesis of minus-strand strong-stop DNA was assessed with MT-4 cells infected with viruses derived from COS-7 cells that had been transfected with these various constructs. We found that similar levels of minus-strand strong-stop DNA as well as DNA produced after template switching were expressed in MT-4 cells infected with COS-7-derived wild-type viruses or with viruses that had the 7-nt segment deleted. In contrast, significantly lower levels of viral DNA were detected in MT-4 cells after infection with viruses that had deletions of the 54-nt stretch. Furthermore, the molecular clone containing the 7-nt deletion was able to replicate with wild-type kinetics, while that containing the 54-nt deletion displayed a significantly diminished capacity in this regard. Further deletion analysis showed that a 16-nt segment at the 3' end of this 54-nt segment was largely responsible for these effects. We also conducted studies to determine levels of viral mRNA in COS-7 cells that had been transfected with equivalent amounts of DNA derived from either a wild-type HIV construct or our various deletion mutants. In the case of transfections performed with the 7-nt deletion mutant and wild-type HIV DNA, high levels of viral mRNA transcripts were detected, which was not the case for the 54 nt-deletion mutant. However, these various mRNAs possessed similar stabilities, as shown through studies in which transcript formation was arrested by treatment of cells with actinomycin D. Thus, the 54-nt segment of 5' nontranslated RNA, located downstream of the PBS, is involved in efficient expression of each of viral DNA, mRNA, and infectious virus.

Binding Sites↗

PubMed1997

[99mTc-MIBI myocardial perfusion imaging in patients with diabetes].

Seventy-four patients with diabetes were taken on both stress and rest 99m-Tc-MIBI SPECT imaging: 44 patients (59.5%) were found having myocardial ischemic disorders, including 28 cases of myocardial ischemia, 7 cases of myocardial infarction and 9 cases of both conditions. 113 segments were involved and 46% were located in the posterior and inferior walls, indicating that the right coronary artery is most susceptive to ischemia. Diabetic patients complicated hypertension and/or hyperlipidemia were at higher risk of either early occurrence of coronary disease. 99mTc-MIBI SPECT imaging is helpful in early diagnosis and therefore is significant in directing.

Adult↗

PubMed1997

[Conventional and ambulatory urodynamic study on patients with chronic prostatitis syndrome].

To study the urodynamic findings of chronic prostatitis syndrome (CPS), 58 patients with chronic prostatitis and prostatodynia were subjected to the urodynamic investigation that included conventional medium filling urodynamic (CMG) tests (urethral pressure profile, filling cystometry, voiding pressure-flow study) and ambulatory urodynamic monitoring (AM) by using Dantec Menuet and Urodec 500 AM system. 55 BPH patients and 20 normal men were taken as control groups. CPS patients had function bladder outflow obstruction (FBOO). FBOO resulted in the detrusor instable (DIS, 12.1%), detrusor-sphincter dysnergia (DSD, 100%) and detrusor dysconstractility (DDC, 6.9%), and resulted in clinical symptoms. FBOO resulted from the urethal sphincter spasm and DSD.

Adolescent↗

PubMed1997

[Qualitative grading of detrusor contractility in benign prostatic hyperplasia patients].

To grade qualitatively detrusor contractility in benign prostatic hyperplasia (BPH), we studied 120 BPH patients aged from 58 to 89 years. The pressure-flow studies were performed. The passive urethral resistance relation (PURR) and Schäfer diagram were used to analyse the results. The detrusor contractility was divided into 4 classes: very weak (VW), weak (W), normal (N), and strong (ST). The types of pressure-flow were high pressure--low flow (HP-LF), high pressure--high flow (HP-HF), low pressure--low flow (LP-LF) and low pressure--high flow (LP-HF) type. The results showed that the incidence of VW, W, N and ST class was 12.5%, 26.7%, 47.5% and 13.3% respectively; the incidence of HP-LF, HP-HF and LP-LF type was 55%, 1.7% and 43.3% respectively. The weak detrusor strength could become powerful by the surgery treatment of bladder outflow obstruction (BOO) and the function training of detrusor. The detrusor strength class of a BPH patient was improved from W before surgery to N after surgery in our studies. The principles of the fluid dynamics and urodynamic and the clinical application of the qualitative grading of detrusor contractility were discussed.

Aged↗

PubMed1997

[Application of electronic larynx in speech rehabilitation after laryngectomy].

An electronic larynx has been developed at this center and used among laryngectomees for speaking rehabilitation. The phonation rate was 98% in 4,520 patients from all over the country. The frequency characteristics of the artificial larynx is close to that of human sound. Other advantages of the electronic larynx are: the best sound conducting point at the neck; natural phonation actions; and on/off switch synchronized with speaking attempts. The electronic larynx is easy to use and worth to be recommended as an alternative to surgical intervention in speech rehabilitation after laryngectomy.

Adult↗

PubMed1997

[In vitro expression of wild type and precore mutant woodchuck hepatitis virus].

Hepatitis B virus (HBV) precore 1896 and 1898 G-->A mutations are regarded as hot spots to study. Such mutants have been considered associating with molecular and biological changes of HBV and causing chronic hepatitis and severe forms of hepatitis, including fulminant hepatitis. Using oligonucleotide-directed mutagenesis, we have conducted the same point mutations in the precore gene of an infectious clone of woodchuck hepatitis virus (WHV-8). Transfection of mutant WHV DNA, 1896 mutant (WHV-M1) or both 1896 and 1898 mutants (WHV-M2) resulted in WHV replication. Southern blot and Northern blot tests showed that wild type and mutants both had similar DNA replication and transcription. It was concluded that the precore gene of the WHV genome is not essential for virus replication.

Animals↗