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Biomedical subjects

H C Chen

Publications and source records attributed to H C Chen.

At least 199 records · Page 11Linked to original sources
PubMed1998

Primary insertion of osseointegrated dental implants into fibula osteoseptocutaneous free flap for mandible reconstruction.

Twelve patients with segmental mandibular defects were reconstructed with fibula osteoseptocutaneous flaps and simultaneous placement of osseointegrated implants. Decision to perform this procedure was based on the facts that all patients had benign diseases, did not require postoperative radiotherapy, were in good general and oral conditions, and were psychologically motivated. A total of 34 fixtures was inserted in the first stage. Eight patients underwent second stage surgery, which consisted of connection of the implant abutments to the fixtures and the use of palatal mucosal grafts around the implants. Final dental prostheses were fixed 1 month later in seven patients, at this time. All flaps survived after surgery, and no implant failure was observed after a mean follow-up period of 25 months. Only one fixture was not used during the subsequent stage and was left as a sleeper. Fixed dental prostheses were used in five patients and removable overlay prostheses in the other two. Chewing function was recovered between 4 and 6 weeks after the start using the definitive dental prosthesis. In contrast to previous results, we conclude that excellent results can be achieved when this combined procedure is used in carefully selected patients. In addition, it is confirmed that the fibula osteoseptocutaneous flap is a versatile, reliable composite tissue that facilitates primary placement of osseointegrated dental implants during mandible reconstruction, thus allowing full oral rehabilitation in a shorter period of time.

Adolescent↗
PubMed1998

Free transverse colon transplantation for functional reconstruction of intra-oral lining: a clinical and histologic study.

A variety of free-tissue transplantations are available for oropharyngeal (lining) reconstruction. The most commonly used flap, the radial forearm flap, is relatively thin, adaptable, and reliable but does not provide lubrication. In this study, the potential of the transverse colon to provide a lubricating tissue for replacement of oral lining was investigated. Eleven patients requiring replacement of oral lining received transverse colon flap transplantation between November of 1993 and December of 1995. There was one complete flap loss and one partial loss. Flap size used for reconstruction averaged 40.4 cm2, and average vessel length and diameter were 7 cm and 2.0 mm, respectively. In a follow-up period from 15 to 48 months, all colon flaps proved to be durable with continuous lubrication function. Histologic assessment of the transplanted colon flaps at various postoperative times showed an adequate amount of mucus-secreting goblet cells even after irradiation. There was no donor-site morbidity. The main disadvantage seemed a tendency to transplant too much tissue, which resulted in formation of redundant pockets affecting food handling. Thus, 8 out of 10 patients with flap survival required one to three debulking procedures. Given an accurate estimation of the area of mucosa defect and adequate trimming of the colon flaps, the transverse colon flap offers a good alternative for reconstruction of the oral lining, especially when lubrication is desirable in cases with large defects and preoperative or postoperative irradiation, or in case a radial forearm flap is not available.

Adult↗
PubMed1998

Effect of isovolaemic haemodilution on visual outcome in branch retinal vein occlusion.

AIMS: To assess the efficacy of isovolaemic haemodilution therapy (IHT) in the treatment of patients with branch retinal vein occlusion (BRVO). METHODS: Patients presenting with BRVO between 1 July 1991 and 31 August 1993 were eligible for inclusion and randomised into treatment and control groups. Patients randomised to receive IHT were treated for 6 weeks with venesection and volume replacement using hydroxyethylstarch, a plasma expander. The target haematocrit was 35%. Follow up was for 1 year. RESULTS: The baseline visual acuity of the two groups was similar at 0.74 and 0.75 logMAR units (Snellen 6/36), for the IHT and control groups, respectively. At 6 weeks, visual acuity in the IHT group had improved by 0.20 logMAR units (2 lines on the Bailey-Lovie chart) (p = 0.0001). Vision was unchanged in the control group. At 1 year, the IHT group exhibited an improvement of 0.43 logMAR units. By comparison, the improvement in the control group at 1 year was significantly less at 0.17 logMAR units (p = 0.03). The final visual acuity in the IHT and control groups was 0.30 (Snellen 6/12) and 0.60 (Snellen 6/24) logMAR units, respectively. CONCLUSIONS: The results support the theory that IHT has a positive effect on the visual outcome in patients with BRVO.

Adult↗
PubMed1998

Agonist-induced phosphorylation of the endogenous AT1 angiotensin receptor in bovine adrenal glomerulosa cells.

A polyclonal antibody was raised in rabbits against a fusion protein immunogen consisting of bacterial maltose-binding protein coupled to a 92-amino acid C-terminal fragment of the rat AT1b angiotensin II (Ang II) receptor. The antibody immunoprecipitated the photoaffinity-labeled bovine AT1 receptor (AT1-R), but not the rat AT2 receptor, and specifically stained bovine adrenal glomerulosa cells and AT1a receptor-expressing Cos-7 cells, as well as the rat adrenal zona glomerulosa and renal glomeruli. The antibody was employed to analyze Ang II-induced phosphorylation of the endogenous AT1-R immunoprecipitated from cultured bovine adrenal glomerulosa cells. Receptor phosphorylation was rapid, sustained for up to 60 min, and enhanced by pretreatment of the cells with okadaic acid. Its magnitude was correlated with the degree of ligand occupancy of the receptor. Activation of protein kinase A and protein kinase C (PKC) also caused phosphorylation of the receptor, but to a lesser extent than Ang II. Inhibition of PKC by staurosporine augmented Ang II-stimulated AT1-R phosphorylation, suggesting a negative regulatory role of PKC on the putative G protein-coupled receptor kinase(s) that mediates the majority of AT1-R phosphorylation. The antibody should permit further analysis of endogenous AT1-R phosphorylation in Ang II target cells.

Angiotensin II↗
PubMed1998

Lexical and conceptual processing in Chinese-English bilinguals: further evidence for asymmetry.

According to the asymmetry model of bilingual representation (Kroll & Stewart, 1994), the first language (L1) lexicon is closely tied to an underlying conceptual memory, whereas second language (L2) items are mostly associated with their L1 equivalents. An outcome of this architecture is that L1-to-L2, or forward, translation must be mediated by the conceptual memory, whereas L2-to-L1 (backward) translation takes a direct lexical path. Some predictions derived from this hypothetical structure were tested in the present study, which took into account, through analysis of covariance, variations in response production time, concept retrieval time, and some other characteristics associated with the individual test items. Proficient Chinese-English bilinguals were tested on delayed production (Balota & Chumbley, 1985), picture naming, word translation, and category matching. The expected asymmetrical pattern of translation latencies (i.e., forward > backward) was demonstrated, although it could be statistically explained by the item characteristic of familiarity; matching an L1 item to a category name was faster than matching an L2 item, suggesting relatively strong L1 conceptual links. The present results are best accommodated by a form of asymmetry that allows for nondominant L2-concept linkage, the use of which is conditional upon the familiarity of the test item to the bilingual.

Analysis of Variance↗
PubMed1998

Chest physiotherapy does not exacerbate gastroesophageal reflux in patients with chronic bronchitis and bronchiectasis.

BACKGROUND: Chest physiotherapy is beneficial to patients with mucus hypersecretion. However, it is not risk-free. Chest physiotherapy may affect gastrointestinal motility and the competence of the gastroesophageal sphincter during the procedure. Our study was aimed to investigate whether gastroesophageal reflux is exacerbated or induced by chest physiotherapy. MATERIALS AND METHODS: Thirty-two adult patients with chronic bronchitis or bronchiectasis received chest physiotherapy. An esophageal pH meter was placed 5 cm above the gastroesophageal junction and monitored the reflux episodes from 8 AM on the first day to 12 noon on the second day. Physiotherapy was performed with the patient in three different positions on the second day for one hour. RESULTS: Thirteen patients were found to have gastroesophageal reflux disease. For the study group as a whole, neither the frequency nor the duration of having a pH < 4 during the physiotherapy was significantly different from the mean hourly frequency and mean hourly duration recorded on the first day or from those values recorded at a corresponding time on the first day. As for the patients with gastroesophageal reflux disease, the frequency and total duration of gastroesophageal reflux during physiotherapy were not significantly different from the mean hourly frequency and the mean hourly duration or from the values recorded at the corresponding time on the first day. There was no significant difference in the gastroesophageal reflux frequency or the duration in different body positions. CONCLUSION: Chest physiotherapy including postural drainage, percussion and forced expiration techniques in different positions did not induce or increase the incidence of gastroesophageal reflux in patients with chronic bronchitis and bronchiectasis.

Adult↗
PubMed1998

Fusion of the lumbar spine with a free vascularized fibular bone graft: case report.

Spinal fusion with either non-vascularized or vascularized bone grafts has been well documented for inflammatory, degenerative, post-oncological and post-traumatic reconstruction Vascularized bone graft has been proven to have more rapid healing and better clinical results. A few reports have indicated that free vascularized fibular bone grafts have been used for reconstruction of the cervical and thoracic spine with good clinical results. We report a case of a third lumbar vertebra burst fracture successfully treated with a free vascularized fibula graft after failure of an initial conventional bone graft. The neurological symptoms improved significantly. The strong and straight bone quality makes the vascularized fibula an ideal choice for reconstruction of the spine. Vascularized fibula bone graft is an option in cases with failed nonvascularized bone grafts, in cases where an iliac bone is not suitable for reconstruction, or in cases where a poor recipient bed makes having well-vascularized bone necessary. This report describes our surgical approach and demonstrates the versatility of the free fibular osteoseptocutaneous flap for reconstruction of any portion of the spine.

Adult↗
PubMed1998

Medullary cystic disease: a family study.

Medullary cystic disease of the kidney is characterized by progressive tubulointerstitial disease with medullary cyst formation and secondary glomerular sclerosis. We treated a patient with chronic renal failure and investigated the family history of renal disease. The patient, an 18-year-old woman, was admitted due to poor appetite and fatigue for several months. Findings on physical examination were normal except for a pale conjunctiva. Urinalysis revealed only mild proteinuria with clear sediment. The hemogram showed normocytic normochromic anemia with hemoglobin 86 g/L. The patient was azotemic and her creatinine clearance rate was 10.7 mL/min. Renal sonography showed contraction of both kidneys with a marked increase in cortical echogenicity. One small cyst was found in the medullary area. Computed tomography (CT) and magnetic resonance imaging revealed several medullary cysts. Percutaneous renal biopsy showed focal and periglomerular sclerosis, marked tubular atrophy, and interstitial fibrosis. Ten of her family members were examined for renal function, and by sonography and CT. Five had medullary cysts, and three of the five showed abnormal renal function. Medullary cystic disease should be considered in the differential diagnosis of patients with renal disease and a positive family history.

Adolescent↗
PubMed1998

Effects of silicon-insole socks on pressure distribution and shear force of the foot.

BACKGROUND: Many problems of the foot are due to abnormal plantar pressure and shear force, but until now shear force could not be accurately measured. Different methods can be used to reduce foot pressure, such as foot orthosis or shoe modification. The purposes of our study were to propose a method for measuring the maximum shear force of the foot and also to investigate the effect of silicone-insole socks in reducing the peak plantar pressure and shear stress of the foot. METHODS: Twenty-two healthy subjects were included in this study, each subject underwent 2 kinds of experiments to study the peak plantar pressure, the horizontal shear reaction force, and the maximum shear force under 3 conditions: barefoot, wearing 100% cotton socks, and wearing silicone-insole socks. RESULTS: Our results showed a significant decrease in midfoot peak plantar pressure while walking, and a decrease in horizontal shear reaction force and maximum shear force while wearing cotton socks and silicone-insole socks in walking and pulling. Silicone-insole socks were more significant in decreasing horizontal shear reaction force than cotton socks. CONCLUSION: Silicone-insole socks are better than cotton socks in reducing horizontal shear reaction forces and their friction coefficients. Because only normal subjects have been tested, further study is required to prove the efficacy of silicone-insole socks on different kinds of foot pathology.

Adult↗
PubMed1998

Hypertrophic osteoarthropathy in nasopharyngeal carcinoma patients: two cases report.

Hypertrophic osteoarthropathy (HOA) is a rheumatic disorder characterized by digital clubbing, bone pain, and arthralgia. HOA can be idiopathic or secondary to a variety of pulmonary, cardiogenic, or malignant disorders. We present 2 male patients, aged 46 and 42, with advanced nasopharyngeal carcinoma (NPC) who developed HOA 1-4 years after radiotherapy. Differential diagnosis between HOA and coexisting bone metastasis must be made with caution. We found bone scintigraphy to be the most sensitive tool to distinguish between these 2 disease. Intense symmetrical uptake of radioisotope along the cortex of long bones, so-called parallel tract sign, is typical. Plain radiographs demonstrating prominent periosteal reaction were also effective for this. The rheumatic manifestation of HOA was paraneoplastic and related to pulmonary metastasis. The clinical manifestation of the 2 patients suggested that pulmonary metastasis should be suspected in NPC patients when HOA appears.

Adult↗
PubMed1997

Expression and characterization of the recombinant gene encoding chitinase from Aeromonas caviae.

The gene encoding a chitinase from Aeromonas caviae was cloned by PCR techniques. Its recombinant gene expression was performed using pET20b(+) in Escherichia coli BL21 (DE3). The recombinant chitinase with the extra 33 and 13 amino acids in its N- and C-termini, respectively, was purified to near homogeneity using His-Tag affinity chromatography. The recombinant chitinase was found to be present in both the culture medium and the cytoplasm. A single protein band on the native polyacrylamide gel was confirmed by both the activity staining and protein staining. The optimum pH and temperature of the recombinant chitinase were determined to be 6.25-6.5 and 42.5 degrees C, respectively. It was stable within the pH range of 5-7. Significant activity stimulation by Cu2+ and inhibition by Fe3+ and Hg2+ were observed. Detergents such as SDS and Triton X-100 strongly inhibited the enzyme activity. Substrates such as 4-methylumbelliferyl-N,N'-diacetylchitobioside and 4-methylumbelliferyl-N,N',N"-triacetylchitotriose were hydrolyzed by the recombinant chitinase; however, 4-methylumbelliferyl-N-acetylglucosaminide was not cleaved during the activity assay periods. When chitin power was suspended in buffer with the chitinase (pH 6.5 and 42.5 degrees C), N-acetylchitooligosaccharides [(GlcNAc)n, n = 1-4] were detected at 24 h.

Aeromonas↗
PubMed1997

Mechanisms of stem cell factor and erythropoietin proliferative co-signaling in FDC2-ER cells.

Studies of hematopoietic progenitor cell development in vivo, ex vivo, and in factor-dependent cell lines have shown that c-kit promotes proliferation through synergistic effects with at least certain type 1 cytokine receptors, including the erythropoietin (Epo) receptor. Presently, c-kit is shown to efficiently support both mitogenesis and survival in the FDCP1 cell subline, FDC2. In this system, mitogenic synergy with c-kit was observed for ectopically expressed wild-type Epo receptors (wt-ER), an epidermal growth factor (EGF) receptor/Epo receptor chimera, and a highly truncated Epo receptor construct ER-Bx1. Thus, the Epo receptor cytoplasmic box 1 subdomain appears, at least in part, to mediate mitogenic synergy with c-kit. In studies of potential effectors of this response, Jak2 tyrosine phosphorylation was shown to be induced by Epo, but not by stem cell factor (SCF). In addition and in contrast to signaling in Mo7e and BM6 cell lines, in FDC2-ER cells SCF and Epo each were shown to rapidly activate Pim 1 gene expression. Recently, roles also have been suggested for the nuclear trans-factor GATA-1 in regulating progenitor cell proliferation. In FDC2-ER cells, the ectopic expression of GATA-1 had no detectable effect on Epo inhibition of apoptosis. However, GATA-1 expression did result in a selective and marked inhibition in mitogenic responsiveness to SCF and to a decrease in c-kit transcript expression. These studies of SCF and Epo signaling in FDC2-wt-ER cells serve to functionally map the ERB1 region as a c-kit-interactive domain, suggest that Pim1 might contribute to SCF and Epo mitogenic synergy and support the notion that SCF and Epo may act in opposing ways during red cell differentiation.

Animals↗
PubMed1997

Evolution of a mitochondrial tRNA PHE gene in A. thaliana: import of cytosolic tRNA PHE into mitochondria.

Previously we have described a putative tRNATyr in Arabidopsis thaliana mitochondria, the sequence of which is different from that of other plant mitochondrial tRNATyr genes. We show here that this tRNATyr gene sequence is present in several copies in the mitochondrial genome of A. thaliana. One copy of these tRNATyr gene sequences, termed here tRNATyr-1, could encode a functional tRNA. Expression analysis has shown that the tRNATyr-1 gene is cotranscribed with the downstream tRNAGlu gene, and that the corresponding mature-sized tRNA is present in mitochondria. We also show that the native tRNATyr gene, similar to the mitochondrial tRNATyr genes found in plants, is present in the A. thaliana mitochondrial genome and expressed. The tRNATyr-1 gene has been previously suggested to be derived from a tRNAPhe gene sequence. We show here that, as a consequence, there is no tRNAPhe gene in the mitochondrial genome of A. thaliana and that a cytosolic tRNAPhe is imported in A. thaliana mitochondria.

Arabidopsis↗
PubMed1997

High-dose-rate intracavitary brachytherapy (HDR-IC) in treatment of cervical carcinoma: 5-year results and implication of increased low-grade rectal complication on initiation of an HDR-IC fractionation scheme.

PURPOSE: To report the treatment results and rectal/bladder complications of cervical carcinoma radically treated with high-dose-rate intracavitary brachytherapy (HDR-IC). The current policy of using three-fraction scheme was examined. METHODS AND MATERIALS: Between November 1987 and August 1990, 173 patients with cervical carcinoma were treated with curative-intent radiation therapy. Whole pelvic irradiation was administered with 10-MV X ray. Dose to the central cervix was 40-44 Gy in 20-22 fractions, following by pelvic wall boost 6-14 Gy in three to seven fractions with central shielding. 60Co sources were used for HDR-IC, and 7.2 Gy was given to Point A for three applications, 1-2 weeks apart. Duration of follow-up was 5-7.8 years. RESULTS: Twenty-eight patients (16%) developed central-regional recurrences. Overall 5-year actuarial pelvic control rate was 83%. By stage, 5-year actuarial pelvic control rates were 94%, 87%, and 72% for Stages IB + IIA, IIB + IIIA, and IIIB + IVA, respectively. Thirty-one patients (18%) developed distant metastasis. Overall 5-year actuarial survival rate was 58%. By stage, 5-year actuarial survival rates were 79%, 59%, and 41% for Stages IB + IIA, IIB + IIIA, and IIIB + IVA, respectively. Sixty-six (38%) and 19 patients (11%) developed rectal and bladder complications, respectively. For rectal complication, the overall actuarial rate was 38% at 5 years. By grade, 5-year actuarial rectal complication rates were 24%, 15%, 4%, and 3% for Grades 1-4, respectively. Overall prevalence of rectal complications was 37% and 14% at 2 and 5 years, respectively. Prevalence of low-grade rectal complication (Grades 1 and 2) was dominant at 2 years (30%), but declined to 8% at 5 years. Prevalence of high-grade, severe rectal complication (Grades 3 and 4) remained steady at 2 and 5 years (7% and 6%, respectively). Five-year actuarial bladder complication was 9%. Five-year prevalence of bladder complication was 2%. CONCLUSION: Using a three-fraction scheme, survival rate appeared comparable with the existing results of the low-dose-rate technique. The incidence of rectal complication with this scheme remained relatively high. The increased part of rectal complication was predominantly low grade. This result suggested that therapeutic gain with this scheme may not be good enough to circumvent its biologic disadvantage. Numbers of fractions >3 must be considered in future trials.

Adenocarcinoma↗
PubMed1997

Cloning and characterization of the extreme 5'-terminal sequences of the RNA genomes of GB virus C/hepatitis G virus.

The extreme 5'-terminal sequences of the GB virus C/hepatitis G virus (GBV-C/HGV), containing elements essential for regulation of viral gene expression and replication, have not been determined. By using a RNA-ligase-mediated RACE (rapid amplification of the cDNA ends) procedure, we have cloned the extreme 5'-terminal sequences of the viral genome from the serum of three Taiwanese patients. Sequence analysis of the 5' noncoding region in alignment with one West African and two American isolates showed that (i) a consensus 5'-end sequence was cloned; (ii) about 97% of sequences were homologous among the three Taiwan isolates and also between the two American isolates, whereas about 90% of sequences were homologous among the isolates from the three different geographic areas; (iii) the sequence heterogeneity related to geographic separation is confined mainly to three domains; and (iv) a potential hairpin structure, resembling the hairpin structure found in the 5' end of hepatitis C virus genome, was detected in the 5' end of the noncoding region. Our data support the hypotheses that (i) the extreme 5' end of the hepatitis GBV-C/HGV viral genome has been cloned, (ii) there are different genotypes correlated with geographic separation, and (iii) the viral translation and replication mechanisms may be similar to that of hepatitis C virus and pestiviruses. Our data have not only shed light on the viral replication mechanism but also offer information for selection of optimal primer sequences for the detection and genotyping of the hepatitis GBV-C/HGV virus by PCR assays.

Base Sequence↗
PubMed1997

Carboxypeptidase E is a regulated secretory pathway sorting receptor: genetic obliteration leads to endocrine disorders in Cpe(fat) mice.

A proposed mechanism for sorting secretory proteins into granules for release via the regulated secretory pathway in endocrine-neuroendocrine cells involves binding the proteins to a sorting receptor at the trans-Golgi network, followed by budding and granule formation. We have identified such a sorting receptor as membrane-associated carboxypeptidase E (CPE) in pituitary Golgi-enriched and secretory granule membranes. CPE specifically bound regulated secretory pathway proteins, including prohormones, but not constitutively secreted proteins. We show that in the Cpe(fat) mutant mouse lacking CPE, the pituitary prohormone, pro-opiomelanocortin, was missorted to the constitutive pathway and secreted in an unregulated manner. Thus, obliteration of CPE, the sorting receptor, leads to multiple endocrine disorders in these genetically defective mice, including hyperproinsulinemia and infertility.

Amino Acid Sequence↗