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H C Chen

Publications and source records attributed to H C Chen.

At least 55 records · Page 3Linked to original sources
PubMed2001

mu-Opioid receptor gene expression: the role of NCAM.

We have investigated the mechanisms regulating the expression of the mu-opioid receptor, using P19 mouse embryonal carcinoma cells, which normally lack this receptor, but which can be induced to express it in aggregated cells by retinoic acid treatment. The expression level of mu-opioid receptor mRNA was found to be closely correlated with aggregation status, and more specifically by cell to cell interaction requiring neural cell adhesion molecules (NCAM). We showed that NCAM activates the mu-opioid receptor gene through a pathway involving phospholipase C-arachidonic acid-calcium channel-calcium/calmodulin kinase II. A similar pathway was previously shown to promote neurite outgrowth, however, with distinct specificity, including the role of calcium channels. Activation of L-type calcium channels elevated mu-opioid receptor expression, while N-type-channel activity had the opposite effect. The effect of anti-NCAM-antibody treatment was not due to retardation of general neural development and was specific to the mu-opioid receptor gene. Our results indicate that the P19 system is an useful model to study the expression of the mu-opioid receptor gene.

Animals↗
PubMed2001

The thermal environment of arboreal pools and its effects on the metabolism of the arboreal, oophagous tadpoles of a Taiwanese tree frog, Chirixalus eiffingeri (Anura: Rhacophoridae).

We have studied seasonal and diurnal fluctuations of water temperature in bamboo stumps and the effect of temperature on the energy metabolism of arboreal, oophagous tadpoles of Chirixalus eiffingeri. We collected tadpoles (Gosner stage 28-29) in February and August from Chitou, Taiwan and acclimated them to 12 and 22 degrees C. Using a closed system, we measured tadpole oxygen consumption (V.O(2)) at 12, 17 and 22 degrees C. The water temperature was lowest in February (11-13 degrees C), increased rapidly during March and April and was highest from May to August (20-24 degrees C). Diel fluctuations in the temperature of the pools of water in bamboo stumps mirrored fluctuations in air temperature. Tadpoles collected in February and August exhibited metabolic compensation in that tadpoles acclimated at 12 degrees C had significantly higher V.O(2) than those acclimated at 22 degrees C. There are at least two possible explanations for the presence of metabolic compensation in C. eiffingeri tadpoles. Firstly, the larval period of C. eiffingeri ranges from 40 to 78 days, a tadpole could experience relatively large fluctuations in body temperature (up to 10 degrees C) during the development. As a result, C. eiffingeri tadpoles most likely evolved metabolic compensation to maintain activity levels under different thermal environments. Secondly, because arboreal pools are small, thermally unstratified, aquatic microhabitats, tadpoles are unable to behaviorally select preferred temperatures. As a result, metabolic compensation allows tadpoles to regulate their physiological functions.

Adaptation, Physiological↗
PubMed2001

Role of alpha(3)beta(1) integrin in tubulogenesis of Madin-Darby canine kidney cells.

BACKGROUND: We isolated several Madin-Darby canine kidney (MDCK) subclones that exhibit different degrees of branching tubulogenesis in lower concentrations of collagen gel. The M634 clone formed cell aggregates in 0.3% collagen gel, but developed branching tubules vigorously in 0.1% collagen gel. In contrast, the Y224 clone formed cysts in 0.3% collagen gel and displayed fewer branching structures in 0.1% collagen gel. Morphologically, M634 cells exhibited higher levels of cell scattering as well as collagen-induced cell migration than Y224. We conducted this study to delineate the underlying mechanism of branching tubulogenesis in M634 cells. METHODS: Components of the focal contact machinery were analyzed in both cell lines, including the extracellular matrix glycoproteins fibronectin, laminin, and vitronectin; cytoskeleton-associated elements alpha-actinin, talin, and vinculin; and receptors for extracellular matrix and alpha(2), alpha(3), alpha(5), alpha(v), beta(1), and beta(3) integrins. Furthermore, we established several stable transfectants of alpha(3) integrin antisense RNA in M634 cells to examine the role of alpha(3)beta(1) integrin in branching morphogenesis directly. RESULTS: There were no obvious differences in levels of the focal adhesion complex proteins between M634 and Y224 cells, except that the content of the alpha(3) and beta1 integrins were 1.2- and 0.6-fold higher in M634 cells, respectively. The expression of alpha(3) integrin antisense RNA significantly lowered the levels of alpha(3) integrin mRNA and protein. The potential of cell scattering, migration, and branching tubulogenesis in M634 cells was inhibited according to the decrease in alpha(3) integrin expression. CONCLUSION: Our data indicate that expression of alpha(3)beta(1) integrin regulates cell scattering, migration, and branching tubulogenesis of MDCK cells, possibly via adhesion to or serving as a signaling molecule for type I collagen.

Animals↗
PubMed2001

Insulin and heparin suppress superoxide production in diabetic rat glomeruli stimulated with low-density lipoprotein.

Patients with diabetic nephropathy frequently show increased levels of circulating low-density lipoprotein (LDL) and oxidized LDL, which have been reported to be related to the generation of oxygen-free radicals. In the present study, we evaluated the effects of insulin and heparin on the superoxide production of glomeruli, which were isolated from rats with streptozotocin-induced diabetes for one week, one month, and three months, respectively, and the glomeruli were stimulated with native and oxidized LDL. LDL was isolated from normal subjects with normolipidemia, and the superoxide was measured by using a spectrophotometer. The results demonstrated that the poorly controlled diabetic rat glomeruli showed a significantly higher production of superoxide than normal glomeruli under basal status and after stimulation, and this production increased further with the progression of diabetes. Insulin suppressed both the basal and stimulated production of superoxide in diabetic glomeruli, but not in normal glomeruli. Heparin suppressed superoxide production of diabetic glomeruli stimulated by either native or oxidized LDL, and it also partly suppressed superoxide production of normal glomeruli stimulated by oxidized LDL. Our results suggest that glomerular injury in diabetics with hyperlipidemia may be mediated through enhanced generation of oxygen-free radicals, which can be partially attenuated by insulin and heparin.

Animals↗
PubMed2001

Advanced glycation end product-induced proliferation in NRK-49F cells is dependent on the JAK2/STAT5 pathway and cyclin D1.

Advanced glycation end products (AGEs) are important in the pathogenesis of diabetic nephropathy, which leads to renal fibrosis. Previously, we found that the janus kinase (JAK)/signal transducers and activators of transcription (STAT) signaling pathway is necessary for AGE-induced cellular proliferation in normal rat kidney interstitial fibroblast (NRK-49F) cells. However, a direct link between JAK/STAT and cell-cycle progression has not been well established. In this regard, STAT5 has been found to induce cyclin D1 and proliferation in hematopoietic cells. Therefore, we examined effects of AGE on STAT5 and cell-cycle-dependent mitogenesis in NRK-49F cells. We found that AGE increased cyclin D1 expression and cyclin-dependent kinase (cdk)4 activity while decreasing p21(WAF1/CIP1) expression. We also found that AGE (100 microg/mL) induced STAT5 tyrosine phosphorylation. Meanwhile, AGE induced STAT5 protein-DNA binding activity, which was reversed by AG-490 (a specific JAK2 inhibitor) and STAT5 decoy oligodeoxynucleotide (ODN). In addition, STAT5 decoy ODN reversed AGE-induced cell-cycle-dependent cellular proliferation and cyclin D1 protein expression. We concluded that AGE induced cell-cycle-dependent cellular proliferation by inducing the JAK2-STAT5-cyclin D1 and cdk4 pathways in NRK-49F cells.

Animals↗
PubMed2001

Temporal stride and force analysis of cane-assisted gait in people with hemiplegic stroke.

OBJECTIVE: To understand the underlying biomechanics of temporal stride and force in people with hemiplegic stroke during cane-assisted walking. DESIGN: Three forceplates, 6 cameras, and an instrumented cane were integrated to analyze the cane-assisted gait of people with hemiplegic stroke. Temporal-stride parameters, and peak vertical, anterior (propulsive), posterior (braking), and lateral shear forces, as well as propulsive-breaking impulses were analyzed. SETTING: Chang Gung Memorial Hospital, Medical Center, Taiwan. PARTICIPANTS: Twenty people with hemiplegic stroke. MAIN OUTCOME MEASURES: Temporal-stride and force parameters. RESULTS: All patients walked at a relatively slow speed, ranging from 4.2 to 35.8cm/s. The triple and double support occupied most of the gait cycle (GC), whereas the single support occupied only 10% of GC. The applied vertical, propulsive, braking, and lateral shear forces on either foot and the cane were 89.7% to 97.6%, 2.2% to 4.8%, 2.9% to 3.9%, and 5.5% to 6.7% body weight (BW), respectively. Patients applied less than 25% BW of peak vertical forces on the cane. They applied greater peak propulsive forces and impulses on the sound foot, while applying greater peak braking forces and impulses on the affected foot and cane. CONCLUSIONS: The cane provided support and a braking function for people with hemiplegic stroke. People with stroke walking with cane assistance rely mostly on the sound limb for propulsion, while using the affected limb and cane for braking. Data provided could be useful in assessing the nature of cane assistance and in planning therapeutic strategies for people with stroke.

Adult↗
PubMed2001

Alterations of glomerular and extracellular glutathione peroxidase levels in patients and rats with focal segmental glomerulosclerosis.

Glutathione peroxidase (GPX) is an important antioxidant that effectively scavenges hydrogen peroxide. Recent studies have revealed that plasma GPX activity is decreased in patients with chronic kidney failure. However, there have been no reports on renal and urinary GPX levels in patients with kidney disorders. Therefore in this study we have measured the plasma and urinary GPX levels and glomerular GPX immunostaining in patients with focal segmental glomerulosclerosis (FSGS) and normal kidney function as compared with those in patients with minimal change disease (MCD) and those in normal control subjects. Rats with puromycin aminonucleoside-induced FSGS were also studied. The results showed that the plasma GPX level was significantly lower in FSGS patients than in either MCD patients or normal control subjects (both P <.01). The urinary GPX level was also significantly lower in FSGS patients than in either MCD patients (P <.05) or normal control subjects (P <.01). The immunostaining score of glomerular GPX was significantly lower in FSGS patients than in normal control subjects (both P <.05). Serial examinations of glomerular GPX immunostaining in FSGS rats also demonstrate a decrease in the score with the progression of disease. Our results indicate that all the plasma, urinary, and glomerular GPX levels are decreased in FSGS patients, indicating a decreased antioxidant defense in the early stages of chronic glomerular diseases.

Adult↗
PubMed2001

Comparison of pulmonary arterial flow phenomena in spiral and Lecompte models by computational fluid dynamics.

OBJECTIVES: The transposed great arteries are simply reversed by means of a conventional arterial switch operation with the Lecompte maneuver without resumption of their spiral relationship. We seek to clarify the functional implications of the spiral relationship of the great arteries by means of mathematic modeling. METHODS: Computational fluid dynamics is used to compare flow phenomena of the spiral and Lecompte (nonspiral) models under various body surface areas. RESULTS: The velocity profile and wall-shear stress distribution are more uniform for the spiral than for the Lecompte model. The pressure drop and power loss ratio are smaller for the spiral than the Lecompte model for all the body surface areas investigated. The power loss ratio increases abruptly starting from 0.43 m2 of body surface area for the Lecompte model. At that specific stage, after arterial switch operation with the Lecompte maneuver, suprapulmonary stenoses occur most frequently. CONCLUSIONS: Reconstructing the great arteries in spiral fashion might be recommended because the blood flow patterns are more streamlined than those of the Lecompte maneuver. Initiation of stenosis might be minimized to some extent.

Angiography↗
PubMed2001

MR imaging of displaced meniscal tears of the knee. Importance of a "disproportional posterior horn sign".

PURPOSE: Meniscal tears associated with displaced fragments are clinically significant. We propose the "disproportional posterior horn sign" as a supportive criterion to identify a posterocentrally displaced meniscal fragment on MR imaging studies. If the meniscal posterior horn in the central portion appears larger than that in the peripheral section, it is considered positive for "disproportional posterior horn sign". MATERIAL AND METHODS: MR images obtained in 42 patients with 43 lesions, confirmed to have displaced meniscal tears, were included in this study. The MR images were retrospectively evaluated for the presence of the "disproportional posterior horn sign", as well as the other known signs. RESULTS: The "disproportional posterior horn sign" was seen in 9 (20.9%) of 43 lesions, including 1 lateral discoid meniscal tear, 5 lateral meniscal tears and 3 medial meniscal tears. Five of them also had other signs of a displaced meniscal fragment. However, the remaining 4 cases only exhibited the "disproportional posterior horn sign". For the other MR signs, the "absent bow tie sign" was detected in 40 (93%) of 43 lesions, the "flipped meniscus sign" in 27 (62.8%) of 43 lesions, the "double posterior cruciate ligament sign" in 17 (39.5%) of 43 lesions and the "notch fragment sign" in 22 (51.2%) of 43 lesions. CONCLUSION: The "disproportional posterior horn sign" is helpful in demonstrating a posterocentrally displaced meniscal fragment, especially when other characteristic signs are unremarkable or absent.

Adolescent↗
PubMed2001

Molecular mechanisms of sterol absorption.

Recent studies have significantly advanced our understanding of intestinal sterol absorption at the molecular level. Nuclear hormone receptors (such as liver X receptor, farnesoid X receptor and retinoid X receptor) regulate the absorption of dietary sterols by modulating the transcription of several important genes involved in cholesterol metabolism. One of these genes encodes a molecule [adenosine triphosphate-binding cassette (ABC) transporter] that transports dietary cholesterol from enterocytes back out to the intestinal lumen, thereby limiting the amount of cholesterol absorbed. ABC transporters also provide an efficient barrier against the absorption of plant sterols. Another key process that affects intestinal sterol absorption is the synthesis of cholesterol esters. Mice lacking the enzyme for cholesterol esterification in the small intestine have a reduced capacity to absorb dietary cholesterol and are protected against diet-induced hypercholesterolemia and gallstone formation. In addition to elucidating some of the molecular mechanisms of sterol absorption, these recent findings may lead to new therapeutic options to treat hypercholesterolemia.

ATP-Binding Cassette Transporters↗
PubMed2001

Enzyme-linked immunosorbent assay for the determination of p21-activated kinase activity.

An enzyme-linked immunosorbent assay (ELISA) for the measurement of p21-activated kinase (PAK) activity is described. The development of this method takes advantage of the fact that a phospho-epitope-specific antibody against the regulatory autophosphorylation site sequence of PAK was successfully produced, and after being phosphorylated by PAK, a cross-linked peptide containing the autophosphorylation site of PAK could be recognized on immunoblot by this antibody. This procedure involves coating the cross-linked peptide on microtiter plates, phosphorylating the cross-linked peptide by adding active PAK plus ATP.Mg(2+), and detecting peptide phosphorylation using the phospho-epitope-specific antibody and secondary antibody conjugated with alkaline phosphatase followed by reaction with p-nitrophenyl phosphate (for colorimetric detection) or fluorescein diphosphate (for fluorimetric detection). The PAK activity detected by this method was linearly proportional to the amount of kinase used in the reaction and to the duration of the kinase reaction. Furthermore, fluorimetric detection proved more sensitive than colorimetric detection in terms of both detection limit and signal magnitude. Kinase inhibitor assay revealed that the IC(50) value of staurosporine obtained by this ELISA was very close to that obtained in radioassay. Besides staurosporine, the inhibitory activity of several kinase inhibitors was also tested by the PAK ELISA. The results taken together demonstrate the feasibility and efficacy of this solid phase method for the measurement of PAK activity in a non-radioactive way. Development of this method can be helpful in further high-throughput screening of potential inhibitors of this kinase.

Adenosine Triphosphate↗
PubMed2001

Bilateral small radial forearm flaps for the reconstruction of buccal mucosa after surgical release of submucosal fibrosis: a new, reliable approach.

Oral submucous fibrosis is a collagen disorder affecting the submucosal layer and often severely limiting mouth opening. Previous surgical treatments have been disappointing. This article introduces a new surgical approach: reconstructing the bilateral buccal mucosa with two small radial forearm flaps. The surgical method includes the complete surgical release of fibrotic buccal mucosa and, if necessary, a bilateral coronoidectomy and temporalis muscle myotomy. From 1997 to 1999, 15 patients with moderate-to-severe trismus received reconstructive surgery, for a total of 30 small radial forearm flaps after surgical release. The flap size was between 1.5 x 5 and 2.5 x 7 cm. All donor sites were directly closed, and all flaps survived completely, except for one with partial necrosis. Six flaps required minor revisions because of size redundancy. Two patients developed buccal cancer in the area of reconstruction. At an average of 12 months' follow-up, the inter-incisal distance averaged 33 mm, an increase of 17 mm compared with the preoperative value. The donor-site morbidity was minimal, except in one heavy smoker who developed dry gangrene of his fingertips. The use of two small free forearm flaps for buccal mucosa reconstruction allows more radical release of fibrotic tissue. Coronoidectomy and temporal muscle myotomy further contribute to the effect of trismus release. The combined effects of this approach have consistently given good results. An aggressive approach toward surgical treatment of this precancerous lesion also facilitates the detection of cancer at an early stage.

Adult↗
PubMed2001

The outcome of failed free flaps in head and neck and extremity reconstruction: what is next in the reconstructive ladder?

The indications for free flaps have been more or less clarified; however, the course of reconstruction after the failure of a free flap remains undetermined. Is it better to insist on one's initial choice, or should surgeons downgrade their reconstructive goals? To establish a preliminary guideline, this study was designed to retrospectively analyze the outcome of failed free-tissue transfers performed in the authors hospital. Over the past 8 years (1990 through 1997), 3361 head and neck and extremity reconstructions were performed by free-tissue transfers, excluding toe transplantations. Among these reconstructions, 1235 flaps (36.7 percent) were transferred to the head and neck region, and 2126 flaps (63.3 percent) to the extremities. A total of 101 failures (3.0 percent total plus the partial failure rate) were encountered. Forty-two failures occurred in the head and neck region, and 59 in the extremities. Evaluation of the cases revealed that one of three following approaches to handling the failure was taken: (1) a second free-tissue transfer; (2) a regional flap transfer; or (3) conservative management with debridement, wound care, and subsequent closure by secondary intention, whether by local flaps or skin grafting. In the head and neck region, 17 second free flaps (40 percent) and 15 regional flaps (36 percent) were transferred to salvage the reconstruction, whereas conservative management was undertaken in the remaining 10 cases (24 percent). In the extremities, 37 failures were treated conservatively (63 percent) in addition to 17 second free flaps (29 percent) and three regional flaps (5 percent) used to salvage the failed reconstruction. Two cases underwent amputation (3 percent). The average time elapsed between the failure and second free-tissue transfer was 12 days (range, 2 to 60 days) in the head and neck region and 18 days (range, 2 to 56 days) in the extremities. In a total of 34 second free-tissue transfers at both localizations, there were only three failures (9 percent). However, in the head and neck region, seven of the regional flaps transferred (47 percent) and four cases that were conservatively treated (40 percent) either failed or developed complications that lengthened the reconstruction period because of additional procedures. Six other free-tissue transfers had to be performed to manage these complicated cases. Conservative management was quite successful in the extremities; most patients' wounds healed, although more than one skin-graft procedure was required in 10 patients (27 percent). In conclusion, a second free-tissue transfer is, in general, a relatively more reliable and more effective procedure for the treatment of flap failure in the head and neck region, as well as failed vascularized bone flaps in the reconstruction of the extremities. Conservative treatment may be a simple and valid alternative to second (free) flaps for soft-tissue coverage in extremities with partial and even total losses.

Extremities↗
PubMed2001

Traction avulsion amputation of the major upper limb: a proposed new classification, guidelines for acute management, and strategies for secondary reconstruction.

Major replantation of a traction avulsion amputation is undertaken with the goal of not only the reestablishment of circulation, but also functional outcome. This type of amputation is characterized by different levels of soft-tissue divisions involving crushing, traction, and avulsion injuries to various structures. Between 1985 and 1998, 27 cases were referred for secondary reconstruction following amputation of the upper extremity involving both arm and forearm. Replantation was performed by at least 12 qualified plastic surgeons using different approaches and management, resulting in different outcomes. Initial replantation management significantly affects the later reconstruction. For comparing studies and prognostic implications, the authors propose a new classification according to the level of injury to muscles and innervated nerves: type I, amputation at or close to the musculotendinous aponeurosis with muscles remaining essentially intact; type II, amputation within the muscle bellies but with the proximal muscles still innervated; type III, amputation involving the motor nerve or neuromuscular junction, thereby causing total loss of muscle function; and type IV, amputation through the joint; i.e., disarticulation of the elbow or shoulder joint. Some patients required further reconstruction for functional restoration after replantation, but some did not. Through this retrospective study based on the proposed classification system, prospective guidelines for the management of different types of traction avulsion amputation are provided, including the value of replantation, length of bone shortening, primary or delayed muscle or nerve repair, necessity of fasciotomy, timing for using free tissue transfer for wound coverage, and the role of functioning free muscle transplantation for late reconstruction. The final functional outcome can also be anticipated prospectively through this classification system.

Adolescent↗