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Biomedical subjects

T M Chen

Publications and source records attributed to T M Chen.

At least 55 records · Page 3Linked to original sources
PubMed1997

Recipient bed vascularity and the survival of ischaemic flaps.

The purpose of this study was to identify the length of the ischaemic period required to induce the 'no-reflow' phenomenon in a rat epigastric flap on an avascular recipient site. The vascularity of the recipient bed may affect flap survival in the early postischaemic stage after flap transfer. Initially, we designed epigastric flaps in 300-350 g Sprague-Dawley rats and separated the rats into four groups of 5 rats each (total 20 rats). In groups 1, 2, 3, the flaps were made ischaemic for 1 hour, 6 hours and 10 hours, respectively, by temporarily clipping the epigastric artery and vein. In group 4, the epigastric artery and vein were divided to create permanent ischaemia. In groups 1, 2 and 3, ischaemia was ended by removing the clips. After the ischaemic flaps were reperfused, their viability was studied by measuring the flap survival rate at postoperative day 7. Flap survival was studied by direct observations, laser Doppler flowmeter measurement of flap blood flow, histopathology, and carbon particle perfusion of the flap vasculature. Ischaemic flaps of groups 1 and 2 recovered almost completely after reperfusion due to the short period of ischaema. In a second series of experiments, in order to evaluate the contribution to flap survival of the recipient vascularised bed, another four groups of epigastric flaps (of 5 animals each, using the same time periods as above) were raised and a piece of Biobrane was interposed between the flap and the recipient bed before the flap wound was closed, to eliminate all nutrient supply from the recipient bed. THe results showed that the combined effect of the reperfused flap vasculature plus the metabolic contribution of the recipient bed significantly (P < 0.01) increased the extent of flap survival of the 6- and 10-hour ischaemic flaps as well as the divided pedicle flaps, which were never reperfused. An absolute 'no-reflow' rat model flap for further flap salvage studies was also developed.

Animals↗
PubMed1997

Comparative analyses of the latency-associated transcript promoters from herpes simplex virus type 1 strains H129, +GC and KOS-63.

We have analyzed the activity of a specific portion of the latency-associated transcript (LAT) promoter of three strains of herpes simplex virus type 1 (HSV-1) in neuronal and non-neuronal cell types. Restriction fragments containing the LAT promoter sequences and the 5'-end of the LATs were isolated from HSV-1 strains H129, +GC and KOS-63, sequenced and cloned into a chloramphenicol transferase (CAT) plasmid vector. These vectors were separately assayed for CAT production in human (SknSH) and mouse (C-1300) neuroblastoma cell lines and a human continuous cell line (HeLa). Strain KOS-63 contained a C to T base substitution within the LAT promoter binding factor element upstream of the cAMP response element binding sequence. In replicate experiments, in which the construct DNA was used for transfection, the CAT constructs from strains H129 and +GC functioned equally well in all three cell lines. In contrast, the strain KOS-63 CAT construct functioned significantly better in HeLa cells than in neuroblastoma cell lines and better than the identical CAT constructs from strains H129 and +GC. In addition, the construct from strain KOS-63 functioned less well in the human neuroblastoma cell line than in HeLa or C-1300 neuroblastoma cells. When LAT expression was examined directly in vivo by in situ hybridization, strain KOS-63 produced slightly less LAT RNA than strain H129 within trigeminal ganglionic neurons of latently infected rabbits. However, utilizing competitive gel-shift assays, DNA fragments containing the LAT promoter binding element from all three strains bound equivalent amounts of HeLa cell nuclear proteins. Together, these results suggest that the activity expressed by the strain KOS-63 LAT promoter in vivo and in vitro may relate to positive or negative effects of DNA binding proteins on LAT transcription, and that these effects are cell-type dependent.

Animals↗
PubMed1997

Use of a porcine dermis template to enhance widely expanded mesh autologous split-thickness skin graft growth: preliminary report.

To answer the question whether a xenograft dermal substitute could enhance skin grafting, we used porcine dermis as a template for a widely expanded mesh autologous split-thickness skin (ASTS) graft in a rat model. Four groups of rats had received widely expanded meshed skin autografts to cover an excised back wound. Group 1 had a bed of autologous dermis, group 2 had porcine xenograft dermis, group 3 had widely expanded meshed autograft alone, and group 4 had no graft with the wound healing by contraction alone. Wounds were studied by clinical inspection for texture and contraction, and by histologic and immunofluorescent techniques. At 2 weeks, there was acceptable ASTS graft take, and most of the wound healed completely by 3 weeks. The integrity of this complex skin graft was maintained for 4 months but wound contraction gradually decreased overall wound size. Size was maintained better in the ASTS-autodermis and ASTS-xenodermis groups at postgraft 4, 5, and 6 weeks when compared with the ASTS graft, and there was no difference between the ASTS-autodermis and ASTS-xenodermis groups. Thus both allodermis and xenodermis provided a similar template to enhance widely expanded mesh skin growth and delay wound contraction. The pathologic studies indicate that the xenodermis collagen was replaced either by fibrosis or by biodegradation to rat collagen. The immunofluorescent study also reflected that anti-porcine antibody activity was hugely diminished in the ASTS-xenodermis graft wound after long-term follow-up. In conclusion, either autodermis or xenodermis enhances widely expanded mesh ASTS survival in a rat model, and could significantly maintain the original wound size better than ASTS graft without a template. In a long-term follow-up study, the porcine dermis was replaced either by fibrosis or biodegradation to rat dermis.

Animals↗
PubMed1997

Volume-activated taurine transport is differentially activated in human cervical cancer HT-3 cells but not in human papillomavirus-immortalized Z183A and normal cervical epithelial cells.

1. Previous studies demonstrate that volume-sensitive chloride currents are distinctly activated in cervical cancer cells, but not in human papillomavirus (HPV)-immortalized and normal cervical cells. In the present study, the Na(+)-independent volume-activated transport of taurine in three cervical cell types was investigated. 2. Osmotic swelling of cervical cancer HT-3 cells suspended in Na(+)-free hypotonic medium led to increased membrane uptake of taurine. This taurine uptake was effectively blocked by various Cl- channel blockers with a similar potency in blocking volume-sensitive Cl- channels: 1,9-dideoxyforskolin > 5-nitro-2-(3-phenyl-propylamino)-benzoic acid (NPPB) > 4-acetamido-4'-isothiocyanastilbene-2,2'-disulphonic acid (SITS) > 4,4'-diisothio-cyanatostilbene-2,2-disulphonic acid (DIDS) > furosemide. The taurine influx was also abolished by pertussis toxin. In contrast, Na(+)-independent volume-activated taurine transport was not significantly activated in HPV-immortalized Z183A cells and in normal cervical cells. 3. Exposure of HT-3 cells to hypotonic medium also resulted in a marked increase in taurine efflux. The volume-activated taurine efflux was osmolarity dependent and the pattern of pharmacological inhibition by Cl- channel blockers was indistinguishable from that for taurine uptake. 4. These results suggest that volume-sensitive Cl- channels in HT-3 cells can mediate the transport of amino acids. In addition, the pertussis toxin-sensitive G-protein is linked with the activation of this transport mechanism.

Biological Transport, Active↗
PubMed1997

Effects of insulin on glucose uptake by rat hearts during and after coronary flow reduction.

We tested the hypothesis that low-flow ischemia increases glucose uptake and reduces insulin responsiveness. Working hearts from fasted rats were perfused with buffer containing glucose alone or glucose plus a second substrate (lactate, octanoate, or beta-hydroxybutyrate). Rates of glucose uptake were measured by 3H2O production from [2-3H]glucose. After 15 min of perfusion at a physiological workload, hearts were subjected to low-flow ischemia for 45 min, after which they were returned to control conditions for another 30 min. Insulin (1 mU/ml) was added before, during, or after the ischemic period. Cardiac power decreased by 70% with ischemia and returned to preischemic values on reperfusion in all groups. Low-flow ischemia increased lactate production, but the rate of glucose uptake during ischemia increased only when a second substrate was present. Hearts remained insulin responsive under all conditions. Insulin doubled glucose uptake when added under control conditions, during low-flow ischemia, and at the onset of the postischemic period. Insulin also increased net glycogen synthesis in postischemic hearts perfused with glucose and a second substrate. Thus insulin stimulates glucose uptake in normal and ischemic hearts of fasted rats, whereas ischemia stimulates glucose uptake only in the presence of a cosubstrate. The results are consistent with two separate intracellular signaling pathways for hexose transport, one that is sensitive to the metabolic requirements of the heart and another that is sensitive to insulin.

3-Hydroxybutyric Acid↗
PubMed1997

Inhibition of growth factor mitogenicity and growth of tumor cell xenografts by a sulfonated distamycin A derivative.

Interference with growth factor-receptor interactions may have particular relevance in efforts to intervene clinically in both autocrine and paracrine aspects of malignancy. Suramin is a synthetic anticancer agent that works, in part, by blocking the binding of growth factors to their receptors. While initial clinical trials have been encouraging, its use in clinical applications is associated with significant toxicities. Suradista is a novel sulfonated distamycin derivative that is also effective at complexing and inactivating growth factors and cytokines while remaining relatively nontoxic. The goal of this study was to compare the antineoplastic properties of suramin and Suradista. To achieve this, the effects of these compounds on growth factor induced mitogenesis in normal mouse fibroblasts and human umbilical vein endothelial cells were examined, as well as their ability to inhibit the growth of NIH/3T3 cells that had been transformed by the introduction of a fibroblast growth factor (FGF) 1 coding region (residues 1-154) fused to the signal peptide of the hst/KS3 gene (sp-hst/KS3:FGF1-154). In each case, Suradista was more effective than suramin in inhibiting mitogenesis in normal cells, as well as the growth of the transformed cells. Furthermore, Suradista was also shown to be as effective as suramin at inhibiting the growth of sp-hst/KS3:FGF1-154-transformed NIH/3T3 xenografts grown in athymic nude mice when given at only 50% the dosage used for suramin (50 mg/kg for Suradista versus 100 mg/kg for suramin). In summary, these results indicate that novel compounds acting like suramin may be developed as effective antineoplastic agents and may also prove to be of clinical benefit.

3T3 Cells↗
PubMed1997

Endoscopic sinus surgery for the treatment of frontoethmoidal mucocele complicated with orbital abscess: a case report.

Mucoceles may develop after several decades following sinus surgery. They can progressively expand over many years and destroy the surrounding bones, which may result in severe complications such as orbital infection or intracranial lesions. A 68-year-old woman was hospitalized with the chief complaints of exacerbated right orbital swelling and progressive visual loss for one week in May 1995. Under the impression of the right frontoethmoidal mucocele complicated with orbital abscess, she underwent endoscopic sinus surgery for marsupialization and wide drainage of the mucocele. The symptoms subsided one week post-operatively without ophthalmological sequelae. There has been no recurrence one-year post-operatively. Endoscopic sinus surgery is an effective treatment for frontoethmoidal mucocele.

Abscess↗
PubMed1997

The preliminary study and tentative animal study on the sintered PDLLA/TCP composites as bone fracture internal fixation.

Polyesters based on the lactic acid have been reported safety and biodegradation in the human beings for two decades. The greatest advantage of the material is its degradation only conducted by the hydrolysis, where the ester backbones are supposed to be unchained in the aqueous condition. The final degradable products are carbon dioxide and water which can be metabolized and digested in the physiological environment. The goal of this study was aimed to develop a composite sintered with poly-DL-lactide (PDLLA) and tricalcium phosphate (TCP) ceramic particles as orthopedic application. The TCP particles in a range of 30-60 wt% (with 5 wt% increment) were doped into the PDLLA matrix for the reinforcement, which were prepared by the melting and hot pressing techniques. The basic mechanical strength, biodegradable behavior, and biological response of the composites will be investigated in the study. Various techniques, such as pH meter, UV, FTIR, XRD ect., were used to examine and record the degradable process of the composites soaked in the saline for 1-16 weeks. The rabbit femur condyle fracture fixation test was used to evaluate the tissue compatibility and the effects of bone fracture fixation of the composites. The histological observation and x-ray photography were applied for investigating assistance. In the histological evaluation of rabbit femur condyle fracture fixation test, the surface of the composite with 50 wt% TCP addition was attached by the new generated bone without fibrous tissue around after 8 weeks implantation. The fracture bone was gradually healing and the composite always firmly and properly fixed on the fracture area during the implanted period, which provided a breeding environment for normal bone remodeling. The developed composite was thought to be an alternative material for orthopedic application in the future, especially in bone screw and bone plate.

Animals↗
PubMed1996

Differential effects of progestins and estrogens on long control regions of human papillomavirus types 16 and 18.

We have studied effects of a series of progestins and estrogens on regulation of human papillomavirus (HPV) types 16 and 18 gene expression via long control region (LCR), using a transient expression assay which represented the episomal state of HPVs in precancerous lesions. Results showed that HPV gene expression induced by these steroid analogs were diverse. Gene expression via HPV16-LCR was upregulated 2-3 fold under treatment with 10(-7) M estriol, 17 beta-estradiol, and several progestins including pregnenolone, 17 alpha-hydroxy-progesterone, norethynodrel and cyproterone acetate. However, transcription via HPV18-LCR was not or weakly stimulated by these analogs. Our results can divide these analogs into HPV-enhancing and HPV-nonenhancing groups and accordingly impact the relative risk of individual oral contraceptive ingredient in cervical carcinogenesis.

Base Sequence↗
PubMed1996

Establishment and characterization of a human-papillomavirus negative, p53-mutation negative human cervical cancer cell line.

A human cervical cancer cell line, CX, was established from a patient with squamous cell carcinoma of the uterine cervix. The CX cells were epithelial in morphology with relatively large vesicular nuclei, and prominent nucleoli. Cytoplasmic organelles were generally sparse but tonofilaments were relatively abundant. The cells grew as a compact sheet with close membrane approximation interconnected by desmosome-like junctions. CX cells contained cytokeratin, but not vimentin. Elevated levels of squamous cell carcinoma antigen and carcinoembryonic antigen were detected in the cell supernatants. Population doubling time was estimated to be about 20 h. CX cells were not able to grow in soft agar and not tumorigenic in nude mice. Chromosome analysis revealed that CX cells were heterogeneous and mainly had a female diploid karyotype. Unlike cervical cancer cell lines published previously, CX cells were demonstrated to be human papillomavirus-negative, p53 mutation-negative. Based on the distinct characteristics, CX cell line may prove to be a useful tool for the study of human cervical carcinogenesis.

Antigens, Neoplasm↗
PubMed1996

The expression of the human chorionic gonadotropin beta subunit gene depends on negative control.

Transcription of the human chorionic gonadotropin (hCG) genes begins in the very early embryo stage and decreases or even disappears in nonplacental tissues. We have studied the regulation of hCG-beta genes by cell fusion and by the reverse transcription-polymerase chain reaction (RT-PCR). The choriocarcinoma cell lines, JAR and JEG-3, express high levels of the hCG-beta subunit while HeLa cells express extremely low levels of it. Most HeLa x JAR and HeLa x JEG-3 fusion clones expressed only a trace of the hCG-beta subunit mRNA, while JAR x JEG-3 fusion clones still expressed high levels of the hCG-beta subunit. Most transcripts of the hCG-beta subunit genes in JAR and JEG-3 came from the hCG-beta 5 subunit. Even the trace amount of hCG-beta transcripts from fusion clones came mainly from the beta-5 gene. The results suggest that the expression of the hCG-beta subunit genes depends on negative control. Probably when embryonic cells differentiate to form nonplacental tissues, specific inhibitors may appear and inhibit the expression of the hCG-beta subunit genes.

Cell Fusion↗
PubMed1996

Factors influencing tumor cell kinetics in cervical cancer.

Fresh tumor tissues instead of paraffin-embedded sections were used to study the clinical significance of the tumor cell kinetics in cervical carcinomas by flow cytometry. We analyzed specimens from 153 women with cervical cancer, and DNA aneuploidy was found in 61 cases (39.9%). The mean age of patients with aneuploid tumors was significantly higher than the age of patients with diploid tumors (P < 0.001). The mean proliferation index for aneuploid tumors was significantly higher than those for diploid tumors. There was a significant correlation between the proliferation index and age. However, tumor cell kinetics is not related to the status of human papillomavirus, herpes simplex virsuses I and II, lymph nodes, histology or tumor size. The mean age and S-phase fraction for stage-II tumors were significantly higher than those for stage-I tumors (P < 0.01). The tumors of menopausal patients exhibited a relatively higher rate of lymph node metastasis, and significantly higher aneuploidy rate and proliferation index than tumors of premenopausal patients. In summary, age and, what is more important, menopausal status may significantly influence DNA ploidy and cell kinetics of tumors, and subsequently influence clinical stage and lymph node metastasis. However, tumor cell kinetics is of limited value in the prediction of lymph node metastasis and prognosis.

Adult↗
PubMed1996

Synthesis and blood compatibility evaluation of segmented polyurethanes based on cholesterol and phosphatidylcholine analogous moieties.

New segmented polyurethanes based on cholesterol and phosphatidylcholine analogous moieties were synthesized. The soft segments used in this study were the poly(butadiene), poly(isoprene) or hydrogenated poly(isoprene) glycols; the hard segments of these segmented polyurethanes were composed of 4,4'-methylenediphenyl diisocyanate, 2-[bis(2-hydroxyethyl)methylammonio]ethyl 5-cholesten-3 beta-yl phosphate and 1,4-butanediol. The blood compatibilities of synthesized segmented polyurethanes were evaluated by platelet-rich plasma contact studies and scanning electron microscopy observation using glass as the reference. The results show that the blood compatibilities of the synthesized segmented polyurethanes have great difference between the glass contact side and air exposed side for the same cast films. Generally, the hydrogenated poly(isoprene)-based segmented polyurethane is the best surface in terms of platelet adhesion, and the morphology of adhered platelets undergoes the lowest degree of variation among the segmented polyurethanes investigated in this study.

Biocompatible Materials↗
PubMed1996

Acceleration of skin graft healing by growth factors.

A special local burn wound treatment, using a healing promotion factor, attempted to achieve earlier wound closure. Clinically it is not difficult to harvest autologous human platelet-derived wound healing factor (HPDWHF) from burn patients. Another study has proved that porcine pituitary extract (PPE) could be one of the supplements for growing human keratinocytes in vitro (Wang HJ, Chen TM, Tung YM et al. Burns 1995). Initially, using the ELISA immunoassay, we detected titres of platelet-derived growth factor heterodimer AB (PDGF-AB) and epidermal growth factor (EGF) in HPDWHF and PPE. After elevating a 6 X 9 cm2 flap on the backs of Sprague-Dawley (SD) rats 1 ml of heterologous HPDWHF and PPE were sprayed topically on the wound and followed by grafting six pieces of 1 cm2 autologous full-thickness skin. The flap wound was then closed with a piece of large-pore Biobrane interposed between the skin graft wound and the flap. On postgraft day 7, the wound was reopened to measure the area of the full-thickness skin graft (FTSG) using micrographic paper; the results are reported as the percentage of graft expansion beyond the original size. In the cytokine study, we found that the concentrations of PDGF-AB dimer in HPDWHF and PPE were 5222 +/- 102 and 375 +/- 12 pg/ml (both values are reported after a 1:10 dilution) (n = 3), whereas the EGF concentration was 245 +/- 9 pg/ml, and undetectable in undiluted PPE (n = 3), thereby proving that the PDGF-AB and EGF fibres in the HPDWHF were significantly higher than in the PPE Both the HPDWHF (n = 6, with each animal grafted with six skin graft samples) and PPE (n = 7) demonstrated significant accelerations of FTSG growth, with 14.41 +/- 1.08 per cent and 13.16 +/- 3.25 per cent increases in the FTSG size when compared to the sham control group 1.39 +/- 3.26 per cent (n = 5) (P < 0.05). Comparisons between the treatment groups showed no evidence to indicate that the HPDWHF is superior to the PPE in accelerating FTSG growth (P > 0.05). This supports the hypothesis that PDGF appears to transduce its signal through wound macrophages and may trigger the induction of positive autocrine feedback loops and synthesis of endogenous wound PDGF and other growth factors, thereby enhancing the cascade of tissue repair (Pierce GF, Mustoe TA, Altrock B et al. 1991; J Cell Biochem 1991; 45: 319-326), and the effect that PDGF-AB on wound healing is not dose dependent (Mustoe TA, Cutler NR, Allman RM et al. Arch Surg 1994; 129: 213-219). In future studies we expect to show that autologous HPDWHF and heterologous PPE will promote skin graft wound healing in burn patients since they contain a high concentration of PDGF-AB.

Adult↗
PubMed1996

Central-type eight-toed polydactyly associated with ipsilateral complex renogluteal agenesis: a case report with 8 years' follow-up.

At birth, a baby girl was found to have central-type eight-toed polydactyly of the left foot associated with ipsilateral nonvisualization of the kidney and atrophy of the gluteal maximum muscle. X-ray examination showed eight completely developed metatarsal and digit bones, and a chromosome study showed a normal 46, XX karyotype. She received ray amputation of the extra toes when she was 1 year old. Follow-up examination at age 9 showed unchanged renogluteal anomalies and a slightly smaller left foot. In addition, a bony defect over the posterior iliac spine and a wide femoral neck-shaft angle were found on the radiograph. Her left leg was found to be 1 cm shorter than the right, but there was no evidence of valgus or varus. Presently she can walk and run quite well, and there is no callus formation over her sole. The timing and options for excision of the supernumerary digits are discussed and this rare disease reviewed.

Abnormalities, Multiple↗
PubMed1996

Surgical management of axillary bromidrosis--a modified skoog procedure by an axillary bipedicle flap approach.

We developed a modified Skoog procedure to treat axillary bromidrosis and hyperhidrosis that creates a bipedicle flap over the axillary fold with two parallel incisions to achieve a complete excision of the sweat glands. If necessary, the flap can be extended by making another parallel incision for a larger axillary hair-bearing area. Between 1988 and 1992, 110 patients were operated on using this method, but only 92 of the 110 patients, with an average follow-up period of 29.5 months, were available for this follow-up study. In this series, 86.9 percent of patients gave a family history of axillary bromidrosis. This follow-up review demonstrated that 93.5 percent of patients experienced no odor or occasional very mild axillary odor postoperatively. Postoperative scar formation was either nonvisible or excellent in 95.1 percent of patients, and 82.6 percent of patients reported either a hairless axilla or a marked decrease of axillary hair. Most importantly, 92.4 percent of patients reported a marked decrease in axillary sweat. Four axillary fossae developed postoperative subcutaneous hematomas, and six wounds had mild dehiscence. All of the wounds eventually healed satisfactorily after minor procedures. We concluded that for the treatment of extensive axillary apocrine bromidrosis, this new method achieves complete excision of the sweat glands and provides excellent functional and cosmetic results.

Adolescent↗