Biomedical subjects

H C Chen

Publications and source records attributed to H C Chen.

At least 235 records · Page 13Linked to original sources

PubMed1997

Lexical tone in Cantonese spoken-word processing.

In three experiments, the processing of lexical tone in Cantonese was examined. Cantonese listeners more often accepted a nonword as a word when the only difference between the nonword and the word was in tone, especially when the F0 onset difference between correct and erroneous tone was small. Same-different judgments by these listeners were also slower and less accurate when the only difference between two syllables was in tone, and this was true whether the F0 onset difference between the two tones was large or small. Listeners with no knowledge of Cantonese produced essentially the same same-different judgment pattern as that produced by the native listeners, suggesting that the results display the effects of simple perceptual processing rather than of linguistic knowledge. It is argued that the processing of lexical tone distinctions may be slowed, relative to the processing of segmental distinctions, and that, in speeded-response tasks, tone is thus more likely to be misprocessed than is segmental structure.

Adult↗

PubMed1997

Progressive fetal axillary cystic lymphangioma with coexistent naevus flammeus.

We report the rare occurrence of a progressive fetal axillary cystic lymphangioma coexistent with an overlying naevus flammeus. The fetus at 22 weeks' gestation was found to have a 37 x 35 mm left axillary multiloculated mass without colour-flow imaging. Amniocentesis showed a normal 46,XX karyotype. Multiple fine-needle aspirations of the mass in the second and third trimesters obtained blood-stained chocolate-coloured fluid containing numerous erythrocytes and lymphocytes but proved ineffective in lessening the progressive growth of the mass. The mother underwent caesarean delivery and a healthy neonate was born with a 141 x 81 mm left axillary cystic lymphangioma and a 50 x 35 mm coexistent naevus flammeus. The neonate was well after simple excision of the lesions. Although cystic lymphangiomas arising in the axilla enlarge progressively during fetal life, our case suggests a good prognosis and except for genetic evaluation, no prenatal intervention is required.

Adult↗

PubMed1997

Cutis marmorata telangiectatica congenita associated with an elevated maternal serum human chorionic gonadotrophin level and transitory isolated fetal ascites.

A 34-year-old woman with an abnormal maternal serum screening result and a Down syndrome risk of 1:60 calculated from a maternal serum alpha-fetoprotein (AFP) value of 1.4 multiples of the median (MoM) and a human chorionic gonadotrophin (hCG) level of 4.32 MoM at 18 weeks' gestation was found to have isolated fetal ascites at 23 weeks' gestation. Spontaneous resolution occurred 10 weeks after the initial presentation. After birth, the neonate had generalized cutis marmorata telangiectatica congenita (CMTC), large vascular plaques on the scalp with superficial ulceration and crusts, a small atrial septal defect, a patent ductus arteriosus, hepatomegaly, micrognathia, seizures, an abnormal electroencephalogram, congenital retinal detachment, glaucoma and widely spaced toes. Our patient illustrates that CMTC in utero may be associated with a markedly elevated maternal serum hCG level as well as transitory isolated fetal ascites. However, such associations can be coincidental and further collaborative studies and cases will be necessary before it can be determined that a disproportionately elevated hCG level and transitory isolated fetal ascites are predictive of CMTC in utero.

Abnormalities, Multiple↗

PubMed1997

Treatment of PermCath-related sepsis in uremic patients.

Patients who use PermCath as the vascular access for long-term hemodialysis are occasionally confronted with catheter-related infections. Recently, we have treated 17 patients suffering from PermCath-related sepsis. The clinical presenting features were leukocytosis in 14/17, high fever and shaking chill during dialysis in 12/17, and signs of exit site infection in 3/17. No shock was found. All patients received clinical evaluation to exclude infection sources other than from blood and inside the catheter, such as pulmonary, genitourinary, hepatobiliary and cutaneous systems. Blood drawn from both PermCath and peripheral vein was sent for bacterial culture. Bacterial culture of the blood samples from PermCath revealed Staphylococcus sp. in 7/17, Pseudomonas sp. in 5/17, Enterobacter sp. in 4/17, Streptococcus sp. in 1/17. Fourteen blood samples from peripheral vein showed positive culture results identical to those from PermCath, but negative study were noted in three other patients. The patients were divided into two treatment groups: Group I: systemic antibiotics without PermCath removal in 7, Group II: "locked-in" retention in addition to systemic anti-biotics in 10. Antibiotics were empirically chosen according to bacteriological studies. In the "locked-in" retention treatment, antibiotics were retained into both the inflow and outflow PermCath lumens in the exact volume of each lumen for 24 hours. The antibiotics solutions were replaced on a daily basis. The same antibiotics were also given intravenously. Duration of treatment depended on clinical progression and follow-up blood culture results and ranged between 13 and 24 days. The schedule of dialysis was not changed through the period of PermCath-related sepsis. The sepsis was cured in all group II cases but not in 2 of group I and resulted in mortality in these 2 patients. The PermCaths were preserved in 5/7 in group I with two mortality cases and all except one preserved in group II patients without mortality. We suggested that "locked-in" retention in addition to systemic antibiotics is the treatment of choice for the patients with PermCath-related sepsis. This method also preserves the functional integrity of PermCath, which is the lifeline vascular access of the patients with exhausted native vessels.

Aged↗

PubMed1997

Gastric adenocarcinoma with microangiopathic hemolytic anemia and disseminated intravascular coagulation: a case report.

The case reported was a 54-year-old woman with adenocarcinoma of the stomach who developed microangiopathic hemolytic anemia (MHA) and disseminated intravascular coagulation (DIC). Clinical and laboratory data pertaining to this patient are presented. The patient died of multiple organ failure on the 12th hospital day. Since 1962, a total of 96 cases of MHA occurring in patients with malignancy have been reported. About half of them occurred in patients with gastric carcinoma. The possible pathogenesis of MHA and disseminated intravascular coagulation in patients with gastric adenocarcinoma is discussed.

Adenocarcinoma, Mucinous↗

PubMed1997

Intravenous repletion of phosphorus deficiency in the chronic renal failure patients with severe hypophosphatemia.

Severe hypophosphatemia is a potentially life-threatening medical condition and might lead to a fatal outcome in critically ill patients. The situation is further complicated by the co-morbid renal failure. We evaluated the efficacy and safety of the intravenous phosphate repletion in 15 renal failure patients with severe hypophosphatemia. Six patients with advanced renal failure and nine patients under maintenance hemodialysis, 7 males and 8 females, aged between 42 and 83 years old, were found to have serum phosphate level < 1.2 mg/dL from various medical conditions and were treated with intravenous phosphate infusion. The phosphate solution prepared from sodium dihydrogen phosphate (NaH2PO4), containing 13 mg/ml phosphate and 0.5 meq/ml sodium, in the dosage 2.5-3.0 mg phosphate/Kg body weight, was administered through the central venous lins every 6-8 hours. The infusion was discontinued once serum phosphate level reached 5.0-5.5 mg/dL. Serum ionized calcium, phosphate and intact parathyroid hormone levels were serially followed at different intervals, respectively. The hemodialyzed uremic patients received their dialysis treatment as scheduled. All patients survived the hypophosphatemic period and regained normal phosphate levels after repletion. The amount of phosphate administered to reach the target level ranged between 3438 and 9150 mg and the duration of treatment varied between six and seventeen days. Hypocalcemia (< 4.2 mg/dL) was noted at eight occasions during the whole treatment period but none was symptomatic. Eleven patients recovered from the offending illness. However, four patients expired due to reasons not directly consequent to and temporally remote from hypophosphatemia. We conclude that prompt repletion of severe hypophosphatemia and phosphate deficiency with relatively slower rate of NaH2PO4 solution intravenous infusion is a safe and effective mode of treatment for renal failure and uremic patients. The longer treatment period allowed the administered minerals full equilibration. The risk of hyperkalemia is avoided and the sodium/volume load can be eliminated by dialysis.

Adult↗

PubMed1997

New era of reconstructive microsurgery.

Hopfner performed the first successful experimental limb replantation in 1903, and Malt performed the first successful clinical replantation for an above-elbow amputation in 1962. Since then the range of applications for reconstructive microsurgery has expanded rapidly, and it is now widely used for repair of nerves, vessels and lymphatics. In 1972 the first successful case of free flap transfer was performed. Many new applications followed including: (1) coverage of extensive wound defects with exposure of bones, joints, tendons and major vessels which can not be covered with local tissue; (2) vascularized bone transfer for bone defects; (3) vascularized joint transfer for hand joints and the temporomandibular joints; (4) functioning muscle transfer to replace the muscles of the upper limbs and face; (5) toe transfer for missing fingers and thumbs; (6) reconstruction following tumor ablation; (7) reconstruction of congenital anomalies; (8) reconstruction of chest, pharynx and cervical esophagus; (9) transfer of gliding tissue, fascia and sensory flaps for certain injuries. The goals of future reconstructive microsurgery include refinement of procedures, enhancement of functional and aesthetic results, and minimization of the morbidity of donor sites. Improvements of instruments, sutures and computer imaging systems will enable surgeons to perform more accurate reconstructions. Endoscopic harvesting of flaps will be widely used. Surgery will be performed on newborns with certain congenital anomalies. Microsurgery will be increasingly used in conjunction with a prosthesis to improve the function of the prosthesis. Microarthroscopy will be used in operations involving small joints. Advances in microsurgery techniques may also change the results of vascular surgery and tumor resection.

Humans↗

PubMed1997

Preoperative ultrasound Doppler study and clinical correlation of free posterior interosseous flap.

BACKGROUND: Conventional pedicled posterior interosseous flap has a relatively high rate of partial flap loss which may result in ultimate failure to provide coverage of this important structure. The goal of this study was to delineate the posterior interosseous flap as a reliable free tissue transfer. METHODS: From 1991 to 1995, 34 patients undergoing free posterior interosseous flap had preoperative Doppler mapping to determine the point of emergence of the skin perforators of the posterior interosseous artery. This finding was correlated intraoperatively with the number of perforators nourishing the posterior interosseous flap. The anatomic variations in the posterior interosseous artery were also identified. RESULTS: These results showed (1) the main skin perforator was consistent and reliable in all of the posterior interosseous flaps both in the preoperative Doppler evaluation and intraoperative findings; (2) the main skin perforator arose from the posterior interosseous artery, the ascending interosseous recurrent artery or the common interosseous artery in 26 cases (76%), 6 cases (17.6%) or 2 cases (5.9%) respectively; (3) the success rate with the use of the free posterior interosseous flap was 97% without any partial flap loss. CONCLUSION: It is concluded that the free posterior interosseous flap is a reliable flap with adequate arterial flow from constant main skin perforators and large antegrade venous drainage. A less reliable distally based pedicle flap can be changed into a reliable free flap, with the aid of preoperative non-invasive Doppler evaluation. This principle could be applied in the design of other "free skin perforator flaps".

Arteries↗

PubMed1997

Modified reverse sural artery flap.

BACKGROUND: Reverse sural artery flap is a useful flap for defect reconstruction in the distal leg, ankle and heel. The major problem encountered with the reverse sural artery flap is its unreliability. It may be compromised by venous congestion and peripheral arterial insufficiency when the flap is transferred with its pedicle tunneled subcutaneously. METHODS: In this study we describe modifications of this procedure consisting of a wider pedicle during flap design and transferring it without passing the pedicle through a subcutaneous tunnel. The pedicle is then divided in a second-stage operation. Four patients with defects at various locations over the distal leg and heel had reconstruction with reverse sural artery flap in this fashion. RESULTS: No failure developed among these cases and the wounds healed without complication. These patients were satisfied with this procedure. CONCLUSION: Reverse flow flap vascularity is maintained and its viability is ensured with this technical modification.

Aged↗

PubMed1996

Phosphorylation of tyrosine 397 in focal adhesion kinase is required for binding phosphatidylinositol 3-kinase.

We have shown previously that cell adhesion or platelet-derived growth factor (PDGF) promotes the in vivo association of focal adhesion kinase (FAK) with phosphatidylinositol (PI) 3-kinase. In vitro experiments indicated that this interaction was mediated by the p85 subunit of PI 3-kinase and dependent on the tyrosine phosphorylation of FAK. Here we report data suggesting that the major autophosphorylation site of FAK (Tyr-397) is the binding site for the SH2 domains of p85 in vitro and is also required for the association of FAK with PI 3-kinase in vivo. We also show that Tyr-397 is responsible for the increased FAK:PI 3-kinase association upon PDGF stimulation, implying that no additional site of FAK was involved in its binding to PI 3-kinase after PDGF stimulation. Finally, we present evidence that the interaction of PI 3-kinase with Tyr-397 of FAK stimulates its activity. Together, these results suggest that FAK activation and autophosphorylation at Tyr-397 may lead to its association with PI 3-kinase through the SH2 domains of p85, which can subsequently activate PI 3-kinase during cell adhesion.

3T3 Cells↗

PubMed1996

Identification of a protein kinase C (PKC) activator, daphnoretin, that suppresses hepatitis B virus gene expression in human hepatoma cells.

We examined the antiviral activity of a crude extract prepared from a Chinese medicinal herb Wikstroemia indica C.A. Mey. One active component, daphnoretin (7-hydroxyl-6-methoxy-3,7'-dicoumarylether), was identified, which showed strong suppressive effects on the expression of the hepatitis B surface antigen (HBsAg) in human hepatoma Hep3B cells. To examine the signaling pathway of daphnoretin on the Hep3B cells, we pretreated Hep3B cells with 12-O-tetradecanoylphorbol-13-O-acetate (200 nM) for 24 hr to down-regulate intracellular protein kinase C (PKC) levels and found that the PKC-down-regulated Hep3B cells did not respond at all to daphnoretin. Furthermore, daphnoretin induced translocation of PKC from the cytosol to the membrane and down-regulated intracellular PKC levels in the Hep3B cells, indicating that it may directly activate PKC. This hypothesis was supported by the observation that daphnoretin directly competed with [3H]phorbol dibutyrate for the binding of PKC in the whole cell and activated purified PKC activity in vitro. Our results demonstrated that daphnoretin, with a structure distinct from phorbol ester, is a PKC activator and has suppressive effects on HBsAg gene expression in human hepatoma cells.

Antineoplastic Agents, Phytogenic↗

PubMed1996

Chronic osteomyelitis of the spine managed with a free flap of latissimus dorsi. A case report.

STUDY DESIGN: A patient with intractable spinal osteomyelitis who underwent surgery 12 times with persistent exposed bone is presented. OBJECTIVES: To demonstrate the effectiveness of free-flap grafting for managing difficult spinal osteomyelitis wounds. SUMMARY OF BACKGROUND DATA: Conventional procedures can usually achieve wound closure, but they may not work for advanced cases. METHODS: A free latissimus dorsi flap was transferred for reconstruction. The muscle component was used to obliterate the dead space and cover the exposed bone, and the skin component was used for tension-free closure of the wound. RESULTS: The wound healed dramatically. There was no recurrence of infection at 2-year follow-up evaluation. CONCLUSIONS: For an intractable spinal osteomyelitis wound, a free flap should be considered, although the surgery is difficult. Technical precautions in performing this operation are given.

Chronic Disease↗

PubMed1996

Time course of discriminative stimulus effects of bretazenil and chlordiazepoxide in rats.

The time course of the discriminative stimulus effects of a benzodiazepine partial agonist, bretazenil, and a benzodiazepine full agonist, chlordiazepoxide, were determined in rats after administration of two doses of either drug. As in man, bretazenil was considerably shorter-acting than chlordiazepoxide, with 0% drug-appropriate responding at the 2-h time point after the training dose of 7 mg/kg and < 20% drug-appropriate responding at 9 h after the 14 mg/kg dose. With chlordiazepoxide, responding on the water-appropriate lever did not occur in all rats until 7 h after administration of the training dose of 7 mg/kg, compared to 17 h after administration of 14 mg/kg. Although there was considerable individual variability with both drugs, it would appear that the drug discrimination procedure can be a valuable tool for studying the time course of the interoceptive effects of psychoactive drugs.

Animals↗

PubMed1996

Topographic distribution of inguinal lymph nodes metastasis: significance in determination of treatment margin for elective inguinal lymph nodes irradiation of low pelvic tumors.

PURPOSE: To study the distribution of gross inguinal lymph node metastasis and, in particular, its correlation with major pelvic bony structures on a simulation film. METHODS AND MATERIALS: Thirty-seven cases of low pelvic tumors having gross inguinal lymph node metastasis that were treated with radiation therapy between November 1987 and December 1992 were segregated for study. The patient's nodes were palpated and marked with lead wire before the simulation film was assumed to be the origin of the previously uninfested node. A total of 84 such labeled nodes was taken. The geometric center of the usually round or elliptical node on the film was obtained from these 37 cases. These centers were transferred to and mapped collectively on a new simulation film showing major pelvic bony structures of left hemipelvis and upper femur. RESULTS: Distribution of gross inguinal lymph nodes was found confined to the following area, as related to major pelvic bony structure: laterally, just abutting the tangential line that passes through lateral border of the femoral head; medially: 3 cm away from the body's midline axis; superiorly: 1 cm below the line that joins both upper borders of the femoral head; inferiorly: 2.5 cm below the low borders of ischial tuberosity. According to this rectangular boundary, three nodes were out of the field, nine nodes near the border less than 1 cm margin. This area adequately covered 86% (72 of 84) of the studied nodes. CONCLUSION: Distribution study is important in determining the treatment margin. In general, an additional 1-2 cm beyond the area described above is the recommended treatment margin for elective inguinal lymph nodes irradiation with high confidence level of coverage.

Adult↗

PubMed1996

Molecular cloning and characterization of a novel casein kinase II substrate, HASPP28, from rat brain.

HASPP28 (heat- and acid-stable phosphoprotein of 28 kDa) has been purified to near homogeneity from the acid-stable protein fraction of rat brain extract. Based on the N-terminal 40 amino acid sequence, a pair of highly degenerate primers was used to generate a 107-bp probe from rat brain RNA by RT-PCR. From the rat brain lambda gt11 library, this probe identified two positive clones that together provided a cDNA of 837 bp with an open reading frame of 546 bp. This cDNA was extended by 3'RACE to 1.2 kb that included a polyadenylation signal and a poly(A) tail. The 180-amino-acid sequence derived from the open reading frame, which did not correspond to any known protein, was predicted to have phosphorylation sites for protein kinase C, casein kinase II (CKII), and protein kinase A. Indeed, both the purified rat brain HASPP28 and the recombinant HASPP28 (rHASPP28) can be phosphorylated by these kinases. Northern blot analysis indicated that HASPP28 was present in all rat tissues tested, including those from the brain, lung, spleen, kidney, liver, heart, and muscle, in decreasing order of abundance. Phosphopeptide analysis of rHASPP28 phosphorylated in vitro by various kinases showed different tryptic patterns on two-dimensional mapping and isoelectric focusing gels. From [32P]PO4-labeled N1E115 neuroblastoma cells, HASPP28 can be immunoprecipitated with a polyclonal antiserum raised against rHASPP28. The immunoprecipitated protein showed a phosphopeptide pattern similar to that of rHASPP28 phosphorylated by CK II in vitro. Furthermore, the immunoprecipitates from cells treated with phorbol 12-myristate 13-acetate or 8-bromo-cAMP did not show any increased phosphorylation over those of untreated ones, and the phosphopeptide patterns of the immunoprecipitates again were similar to that of CK II phosphorylated protein. These results suggest that HASPP28 is a novel phosphoprotein that can be phosphorylated by several kinases in vitro. In intact cells, CK II seems to be solely responsible for the phosphorylation of HASPP28.

Amino Acid Sequence↗

PubMed1996

Specificity and kinetic studies on the cleavage of various prohormone mono- and paired-basic residue sites by yeast aspartic protease 3.

The specificity and relative efficiency of cleavage of mono- and paired-basic residue processing sites by YAP3p was determined in vitro for a number of prohormone substrates: human ACTH1 39, bovine proinsulin, porcine cholecystokinin 33, cholecystokinin (CCK) 13-33, dynorphin A(1-11), dynorphin B(1-13), and amidorphin. YAP3p generated ACTH1-15 from ACTH1-39. It cleaved proinsulin at the paired-basic residue sites of the B-C junction as well as the C-A junction. Leu-enkephalin-Arg and Leu-enkephalin-Arg-Arg were generated from dynorphin A and dynorphin B, respectively. YAP3p generated Met-enkephalin-Lys-Lys from amidorphin showing that cleavage by this enzyme can occur at a lone pair of Lys residues. CCK33 was cleaved at Lys23 and Arg9, each containing an upstream Arg residue at the P6 and P5 position, respectively. Km values were between 10(-4) and 10(-5) M for the various substrates, with the highest affinity exhibited for the tetrabasic site of ACTH1-39 (1.8 x 10(-5) M). The tetrabasic residue site of ACTH1-39 was cleaved with the highest relative efficiency (kcat/Km = 3.1 x 10(6) m-1 s-1), while that of the monobasic site of CCK13-33 and the paired-basic site of proinsulin B-C junction, were cleaved less efficiently at 4.2 x 10(4) m-1 s-1 and 1.6 x 10(4) m-1 s-1, respectively.

Adrenocorticotropic Hormone↗

PubMed1996

The association of focal adhesion kinase with a 200-kDa protein that is tyrosine phosphorylated in response to platelet-derived growth factor.

Focal adhesion kinase (FAK) is a cytoplasmic tyrosine kinase implicated in the signal transduction pathways initiated by integrins. However, we have previously found that platelet-derived growth factor (PDGF) could stimulate the association of FAK with phosphatidylinositol 3-kinase in NIH 3T3 cells [Chen, H.-C. & Guan, J.-L. (1994) J. Biol. Chem 269, 31229-31223], suggesting that FAK might participate in some of the cellular effects of the growth factors in modulating cell morphology and migration. In this report, we describe the association of FAK with a 200-kDa protein (pp200) that is tyrosine phosphorylated in response to PDGF stimulation in NIH 3T3 cells. Although the identity of pp200 is unknown at present, we have excluded the possibilities that it is the PDGF receptor beta, tension, talin, myosin or the guanosine-triophosphatase-activating-protein-associated p190 protein. Furthermore, we found that the tyrosine phosphorylation of FAK-associated pp200 upon PDGF stimulation is largely independent of cell adhesion or the integrity of the cytoskeleton. Therefore, pp200 and its interaction with FAK may also be involved in growth-factor-induced cellular effects such as the modulation of cell adhesion or cell migration via cytoskeletal reorganization or disruption of focal adhesions.

3T3 Cells↗

PubMed1996

Overexpression of protein kinase FA/GSK-3 alpha (a proline-directed protein kinase) correlates with human hepatoma dedifferentiation/progression.

Computer analysis of protein phosphorylation sites sequence revealed that transcriptional factors and viral oncoproteins are prime targets for regulation of proline-directed protein phosphorylation, suggesting an association of the proline-directed protein kinase (PDPK) family with neoplastic transformation and tumorigenesis. In this report, an immunoprecipitate activity assay of protein kinase FA/glycogen synthase kinase-3 alpha (kinase F(A)/GSK-3 alpha) (a member of PDPK family) has been optimized for human hepatoma and used to demonstrate for the first time significantly increased (P < 0.01) activity in poorly differentiated SK-Hep-1 hepatoma (24.2 +/- 2.8 units/mg) and moderately differentiated Mahlavu hepatoma (14.5 +/- 2.2 units/mg) when compared to well differentiated Hep 3B hepatoma (8.0 +/- 2.4 units/mg). Immunoblotting analysis revealed that increased activity of kinase FA/GSK-3 alpha is due to overexpression of the protein. Elevated kinase FA/GSK-3 alpha expression in human hepatoma biopsies relative to normal liver tissue was found to be even more profound. This kinase appeared to be fivefold overexpressed in well differentiated hepatoma and 13-fold overexpressed in poorly differentiated hepatoma when compared to normal liver tissue. Taken together, the results provide initial evidence that overexpression of kinase FA/GSK-3 alpha is involved in human hepatoma dedifferentiation/progression. Since kinase FA/GSK-3 alpha is a PDPK, the results further support a potential role of this kinase in human liver tumorigenesis, especially in its dedifferentiation/progression.

Calcium-Calmodulin-Dependent Protein Kinases↗