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Biomedical subjects

L F Chen

Publications and source records attributed to L F Chen.

At least 37 records · Page 2Linked to original sources
PubMed1997

Measurement of polyethylene wear in cementless total hip arthroplasty.

We made a clinical study of polyethylene wear in 240 hips of 187 patients having primary total hip arthroplasties from 1989 to 1990, using uncemented Osteonics components, with a head size of 26 mm. We excluded cups with anteversion of over 20 degrees and measured linear wear by a new method using a digitiser and special software of our design. Follow-up was from two to five years (mean 4.3). The mean age at operation was 50.3 years, with more men than women (1.4:1). The mean linear wear per year was 0.15 mm; this did not increase with the longevity of the prosthesis (p = 0.54). In 59 hips showing evidence of osteolysis, the mean linear wear rate was significantly higher at 0.23 mm/year (p <0.001). The mean linear wear rate also correlated significantly with age at the time of operation (p = 0.008), but we found no significant correlations with body-weight, gender, aetiology of the disease, thickness of polyethylene, or cup position. Our new method of measurement is time-saving and reproducible. The results confirm the greater rate of linear wear of polyethylene in patients showing osteolysis and in those who are younger.

Adult↗
PubMed1996

Introduction and expression of foreign DNA in isolated spinach chloroplasts by electroporation.

An electroporation-mediated method for the study of foreign gene expression within chloroplasts has been developed. The chloroplast expression vector pHD203-GUS, which consists of coding regions for beta-glucuronidase (GUS) and chloramphenicol acetyltransferase (CAT) separated by a double psbA promoter fragment from pea (in opposite orientation) was electroporated into spinach chloroplasts and the transient gene expression was examined. Conditions for the expression of the reporter genes have been optimized. Both CAT and GUS activities were detected in chloroplasts electroporated with pHD203-GUS, but not with nuclear expression vector pBI221 or negative control pUC18. No GUS activity was detected when pHD203-GUS was electroporated into spinach protoplasts. Dot immunoblot analysis using anti-GUS antibody confirmed the existence of GUS protein in chloroplasts electroporated with chloroplast-specific vector but not the negative controls, excluding the possibilities of endogenous GUS or bacterial contamination. The expression of GUS protein in treated chloroplasts was further confirmed by Western blot analysis.

Cell Fractionation↗
PubMed1996

Characterization of the light-responsive promoter of rice chloroplast psbD-C operon and the sequence-specific DNA binding factor.

The transcription of rice plastid psbD-psbC genes encoding photosystem II reaction center protein D2 and chlorophyll alpha-binding protein CP43 is closely regulated by light. To elucidate the sequence requirement for the light-responsive promoter of psbD-psbC operon, transcriptional analysis of the rice promoter was performed with deleted mutants and site-directed mutants in vitro. Deletion of -546 approximately -100 upstream sequences resulted in 4- to 5-fold decrease in the transcription rate. Further deletion of -99 approximately -40 conserved region of repeated sequences resulted in 2-fold decrease in the transcription rate. The core light-responsive promoter requires "-10" element but not "-35" element for accurate initiation of basal transcription. No downstream promoter element was found in the +4 approximately +111 region. The competitive gel-retardation experiments revealed the presence of DNA-binding protein in the rice chloroplasts, which interacts specifically with the -60 approximately -37 repeated sequences. Southwestern blot analysis further demonstrated that the binding factor is composed of 36-kDa polypeptide(s).

Base Sequence↗
PubMed1994

The effect of cell density on the production of xylitol from D-xylose by yeast.

The rate of xylitol production from D-xylose increased with increasing yeast cell density. The optimal temperature for xylitol production is 36 degrees C, and the optimal pH range is from 4.0 to 6.0. At high initial yeast cell concentration of 26 mg/mL, 210 g/L of xylitol was produced from 260 g/L of D-xylose after 96 h of incubation with an indicated yield of 81% of the theoretical value.

Candida↗
PubMed1994

[Inhibition of protein kinase C by stilbenoids].

The effect of 15 stilbenoids on protein kinase C (PKC) was studied in order to search for naturally occurring PKC inhibitors. All these compounds were isolated from Chinese medicines. Three oligomeric stilbenes from Caragana sinica, alpha-viniferin, kobophenol A and miyabenol C, were shown to intensely inhibit the activity of partially purified rat brain PKC with IC50 values of 62.5, 52.0, and 27.5 mumol.L-1, respectively. Kinetic analyses revealed that that inhibition was noncompetitive. The other compounds also showed the effect. Monomer stilbenes exhibited PKC inhibitory activity at higher mumol.L-1 concentrations than oligomeric stilbenes. Whenever they are methylated or acetylated perfectly, the inhibition weakens or disappears.

Animals↗
PubMed1993

A method of dynamic analysis of iodine-123-metaiodobenzylguanidine scintigrams in cardiac mechanical overload hypertrophy and failure.

Cardiac sympathetic neuronal degeneration accompanies mechanical overload heart failure. We hypothesized that sympathetic nerve and myocyte failure share a common etiology and that 123I-metaiodobenzylguanidine (MIBG) might provide a precise method of detecting failure in chronic mechanical overload. Our aim was to develop a method for the dynamic analysis of 123I-MIBG scintigrams which could yield a quantitative index of myocardial sympathetic neuronal function in this condition. We performed serial 123I-MIBG scintigraphy in 33 volunteers, 10 orthotopic cardiac transplant recipients and 26 patients with chronic mechanical overload of the left ventricle. We constructed a compartmental model in which total heart activity represents the sum of cardiac sympathetic vesicular and cytosolic pools. Patients with antecedent mechanical overload heart failure or myocardial dysfunction had accelerated myocardial egress of tracer that we ascribed to a specific impairment in vesicular storage rather than to a more rapid turnover of an intact vesicular pool.

3-Iodobenzylguanidine↗
PubMed1991

A research for the relationship between human papillomavirus and human uterine cervical carcinoma. I. The identification of viral genome and subgenomic sequences in biopsies of Chinese patients.

Biopsies from 318 cases with squamous cell carcinoma of the uterine cervix, 48 with cervical and vulvar condylomata, 14 with cervical intraepithelial neoplasia (CIN), 34 with chronic cervicitis and 24 with normal cervical epithelium were collected from different geographic regions with different cervical cancer mortalities. The DNA.DNA dot-blot and Southern blot hybridization results show that there is a close relationship between HPV-16 and the uterine cervical squamous cell carcinoma in China. One very interesting observation is that the finding of HPV-16-homologous DNA differs significantly among five geographic regions, and corresponds with the mortalities from cervical cancer of these five regions. HPV-11 was found mainly in benign lesions. The rate of detection of HPV-16 in Chinese women increased from 8.3% in normal cervical epithelium to 20% in chronic cervicitis, 28% in cervical condyloma, 50% in CIN and 60.4% in cervical cancer. It is suggested that HPV-16 infection may be an etiological factor in the development of human cervical carcinoma. From the results of Southern blot hybridization, it appeared that HPV-16 DNA had been integrated into the genome of the host cell in cervical cancer. Whereas the HPV-16 DNA sequence was only present as an episome in normal cervical epithelium and cervical benign lesions. The rate of occurrence of E6-E7 genes is the highest (88.9%) compared with that of other subgenomic fragments of HPV-16 in specimens of human cervical cancer in China. This implies that E6 and E7 may be the oncogenic genes of HPV-16 and play an important role in the carcinogenesis of human cervical epithelial cells. The amplification and rearrangement of the c-myc protooncogene are closely associated with the occurrence of cervical cancer. The results presented here revealed that the activated c-myc oncogene may cooperate with HPV-16 in the carcinogenic processes.

Biopsy↗
PubMed1991

A research for the relationship between human papillomavirus and human uterine cervical carcinoma. II. Molecular genetic and ultrastructural study on the transforming activity of recombinant retrovirus containing human papillomavirus type 16 subgenomic sequences.

In order to elucidate the role of HPV-16 in the development of genital cancer, NIH3T3 cells were transfected by HPV-16 whole genome and its two early genes, E6-E7. Besides ordinary calcium phosphate/DNA coprecipitation technique, a newly designed recombinant retrovirus containing the HPV-16 genome or subgenomes was used to infect cells for transfer of the target genes. The transforming activities have been demonstrated to be most efficient when a bioengineering technique of this kind is used. HPV-16 DNA was proved to have transforming potential for NIH3T3 cells, and the DNA of HPV-16 was proved to undergo multisite integration into transformed cells and nude mice tumour cells. The E6-E7 open reading frames are sufficient for transforming NIH3T3 cells independently in vitro, which implies that E6-E7 open reading frames are transforming genes or even viral oncogenes of HPV-16. The RNA transcribed by the E6-E7 of HPV-16 was expressed in transformed cells and in tumour cells of nude mice. The use of a recombinant retrovirus for gene transfer in this study is much more efficient than that of calcium phosphate/DNA coprecipitation. The lack of a tissue-culture system suitable for HPV replication in vitro makes HPV gene recombination into a specially engineered retrovirus for viral-mediated gene transfer of particular significance for the possible application of viral carcinogenesis, both in vitro and in vivo, for basic and clinical research.

Animals↗
PubMed1991

Porous-coated acetabular component. Quantitative assessment of normal radiophosphate uptake as a function of implant age.

A computer-assisted quantitative analysis was undertaken of normal radiophosphate bone uptake adjacent to the porous-coated acetabular component in asymptomatic patients. Implants ranged from 1.6 to 49 months of age. In 62 hips, it was found that implants newer than 12 months of age had uptakes that were significantly greater than those 12 months or older. Between 12 and 49 months, there was no correlation with age, indicating a stabilization of the remodeling process.

Acetabulum↗
PubMed1990

[Free skin flap for wound infection].

Since 1979, free skin flaps (FSF) have been used for repairing infected wounds in 32 cases with the sequence of 31 cases succeeded and 1 case failed. Among them, 27 cases (84%) were I stage healing and 4 cases (12.5%) were II stage healing. The patients whose infectious surface of wound with exposure of bone, articulation and tendon can not repair with skin grafting or near skin flap were chosen to have this operation. However, the blood vessels in the surface of wound which can be supplied to anastomosis were also necessary. The most important thing for the operation was determination of the opportunity making out the major bacteria infected and debridement entirely. The bigger the blood vessel calibre of FSF selected, the better the surface of wound healing. In this group, 4 cases appeared crisis of blood vessels. Whether it is associated with inflammation of wound is discussed.

Adolescent↗