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Biomedical subjects

H C Chen

Publications and source records attributed to H C Chen.

At least 217 records · Page 12Linked to original sources
PubMed1997

Ectopic production and processing of atrial natriuretic peptide in a small cell lung carcinoma cell line and tumor from a patient with hyponatremia.

BACKGROUND: Tumors and tumor cell lines from two patients with small cell lung carcinoma (SCLC) (one with and one without hyponatremia) were studied. Ectopic production and prohormone processing of atrial natriuretic peptide (ANP) were investigated to determine if a biologically active peptide was produced in a tumor cell line from a patient with hyponatremia and no evidence of arginine vasopressin (AVP) production. METHODS: Ribonuclease (RNase) protection assays were performed on mRNA isolated from tumors and tumor cell lines established from two SCLC patients, one with and one without hyponatremia. Cellular extracts and conditioned media were studied using reversed-phase high performance liquid chromatography (HPLC) to determine the immunoreactive form of ANP. Tumor cell line sonicates were studied for subcellular localization of enzymatic activity that cleaved pro-ANP peptide substrates. RESULTS: RNase protection assays showed a 200-base pair protected fragment in the mRNA isolated from the tumor and tumor cell line from the patient with hyponatremia (Patient 4). HPLC characterization of the cellular extract and conditioned medium from the tumor and tumor cell line from Patient 4 demonstrated ANP immunoreactivity in the same fraction as ANP- (S99-Y126). The tumor cell line extract that localizes to a subcellular fraction enriched for lysosomes and secretory organelles contains a 60-kilodalton molecular weight protein with enzyme activity that hydrolyzes synthetic pro-ANP substrates and catalyzes the formation of ANP-(S99-Y126). CONCLUSIONS: A tumor cell line from a patient with hyponatremia was able ectopically to produce, process, and secrete ANP in the same immunoreactive form as the biologically active molecule. Preliminary studies show that tumor cell line NCI-H1284 contains an enzyme that can cleave precursors at the same amino acid sequences needed to produce ANP-(S99-Y126) from pro-ANP.

Atrial Natriuretic Factor↗
PubMed1997

Combined-modality therapy for squamous carcinoma of the buccal mucosa: treatment results and prognostic factors.

BACKGROUND: Reports on locoregional control and survival of squamous cell carcinoma of buccal mucosa are scarce in literature. In this study, a single institutions's experience of combined surgery and postoperative radiotherapy (RT) for buccal mucosal malignancy with favorable results was analyzed and presented. The prognostic factors on locoregional control were also discussed. METHODS: From January 1988 to July 1994, 57 patients with squamous cell carcinoma of buccal mucosa treated by surgery and RT were reviewed. The distributions according to American Joint Committee on Cancer (AJCC) staging were: stage II, 6; stage III, 21; and stage IV, 30 patients. Total dose of RT at the buccal area ranged from 45 Gy to 68.4 Gy, median 61.2 Gy. Tumor-related factors (AJCC stage, T stage, histologic grading, pathologic tumor invasion to skin of cheek, adjacent bony structures, and regional lymph nodes) and treatment-related factors (surgical margin, radiation dose, and the time interval between operation and RT) were analyzed to determine their influence on locoregional control. RESULTS: Three-year actuarial locoregional control rate, overall survival rate, and disease-specific survival rates were 64%, 55%, and 62%, respectively. Ten of these 22 patients (45%) with recurrent tumors were reoperated, but only 2 patients were successfully salvaged. Positive surgical margin and tumor invasion to skin of cheek were significantly poor prognostic factors on locoregional control by univariate analysis. In multivariate analysis, tumor invasion to skin of cheek was the only prognostic factor (p = .0014). CONCLUSIONS: Locoregional failure was the major cause of death for squamous buccal mucosa cancers managed with surgery and RT. Few recurrences could be detected early and successfully salvaged. Skin of cheek involvement is an important prognostic factor for buccal mucosa cancers.

Actuarial Analysis↗
PubMed1997

Reversible tyrosine phosphorylation/dephosphorylation of proline-directed protein kinase FA/glycogen synthase kinase-3alpha in A431 cells.

Modulation of protein kinase FA/glycogen synthase kinase-3alpha (kinase FA/GSK-3alpha) by reversible tyrosine phosphorylation/dephosphorylation was investigated. In addition to genistein, other protein tyrosine kinase (PTK) inhibitors, such as tyrphostin A47 and B42, also could induce tyrosine dephosphorylation and inactivation of kinase FA/GSK-3alpha in A431 cells, and this process was found to be reversible. Pretreatment of the cells with 100 microM orthovanadate, a protein tyrosine phosphatase (PTP) inhibitor, could diminish significantly the effects of PTK inhibitors on both enzyme activity and phosphotyrosine content of the kinase, suggesting that the PTK inhibitors induced tyrosine dephosphorylation/inactivation of this kinase is mediated by orthovanadate-sensitive PTP(s) in A431 cells. Moreover, the phosphotyrosine moiety of kinase FA/GSK-3alpha was found to be highly turned over in resting cells. Interestingly, we found that the less active, tyrosine-dephosphorylated form of kinase FA/GSK-3alpha immunoprecipitated from genistein-treated cells was able to reactivate partially with concomitant rephosphorylation of tyrosine residue in vitro. Taken together, these findings demonstrate that tyrosine phosphorylation and concomitant activation of kinase FA/GSK-3alpha can be carried out both in vitro and in vivo and an in vivo phosphatase activity may function in antagonism to PTK activation of kinase FA/GSK-3alpha.

Animals↗
PubMed1997

Examining and reexamining the structure of Chinese-English bilingual memory.

The asymmetry model of bilingual memory proposed by Kroll and Stewart assumes that translation from a first language (L1) into a second language (L2), or forward translation, is mediated by an underlying conceptual memory, whereas L2-to-L1, or backward, translation is lexical and direct. Lexical links from L2 to L1 are hypothesized to be stronger than those from L1 to L2, but conceptual links are stronger for L1 than L2. These assumptions were evaluated in this study, which used stimulus items with similar recognition thresholds. Proficient Chinese-English bilinguals were tested on picture naming, word naming, word translation and category matching. The translation asymmetry effect predicted by the model (i.e., backward being faster than forward translation) was demonstrated; matching an L1 item to a category name was also faster than matching an L2 item. This pattern of results, nevertheless, did not completely hold after an adjustment procedure which sought to control for variations in response production and concept retrieval times due to stimulus types. The present findings are consistent with previous ones which show increased L2 conceptual processing for the proficient bilingual. They also suggest that an extended version of the asymmetry model should take into account possible biasing effects associated with some conventionally used bilingual tasks.

Analysis of Variance↗
PubMed1997

Step-wise lengthening for delayed repair of avulsion of the flexor pollicis longus.

Repair of late avulsion of the flexor pollicis longus tendon at insertion is a rare but difficult problem. A 52-year-old female labourer presented with a 3-month history of inability to flex her right thumb at the interphalangeal joint. Avulsion of the flexor pollicis longus tendon at its insertion was noted on exploration. Because the tendon had contracted and could not be reinserted directly, a technique of step-wise lengthening was used for reinsertion. Two months after operation, the patient resumed her daily activities and went back to work with satisfactory use of her right thumb. This report highlights the possibility of using a simple technique when there is no other alternative.

Female↗
PubMed1997

Suppressive effects of destruxin B on hepatitis B virus surface antigen gene expression in human hepatoma cells.

Destruxin B, a cyclodepsipeptide was originally identified as a plant pathogen from the fungus, Alternaria brassicae. We examined the antiviral activity of destruxin B and found that it suppresses the expression of the hepatitis B viral surface antigen (HBsAg) gene in human hepatoma Hep3B cells which carry an integrated viral gene in its chromosome. In contrast, destruxin B shows no cytotoxic effect on the viability of the cells. Furthermore, it can be shown that destruxin B can reversibly suppress HBsAg production by Hep3B cells in a concentration-dependent manner with EC50 of 0.5 microM. Northern blot analysis indicates that the suppression of HBsAg gene expression by destruxin B is mainly at the mRNA level. Destruxin B not only suppresses the endogenously expressed HBsAg in the Hep3B cells but also suppresses the HBsAg produced either from the stable transfected HBV DNA in another human hepatoma HuH-7 cell line which carry no endogenous HBV genome. These results suggest that destruxin B may have future potential for development as a specific anti-HBV drug.

Antiviral Agents↗
PubMed1997

Effect of megestrol acetate and prepulsid on nutritional improvement in patients with head and neck cancers undergoing radiotherapy.

BACKGROUND AND PURPOSE: Anorexia is a common problem in cancer patients who receive radiotherapy. In this current study, we attempt to determine the effect of megestrol acetate and prepulsid on appetite and nutritional improvement in patients with head and neck cancers undergoing radiotherapy. MATERIALS AND METHODS: One hundred twenty-nine consecutive patients with head and neck cancers treated between July 1993 and June 1994 were prospectively randomized to receive either megestrol acetate, 40 mg qid (megace group), prepulsid, 5 mg tid (cisapride group), or a placebo treatment (control group) during radiotherapy. Before radiotherapy, body weight (kg), appetite score, performance status, biochemical parameters and hematological parameters were evaluated, and the above-noted clinical and biochemical parameters were assessed and recorded every other week. All patients received 6- 10 MV X-rays or Co-60 gamma-ray to head and neck region for a full course of radiotherapy, 61.2-75.6 Gy/7-9 weeks. RESULTS: Forty-eight patients were enrolled in the megace group, 41 patients in the cisapride group, and 40 patients in the control group. At the 2nd, 4th, 6th and 8th week, as the radiation dose escalated, the megace group had significantly less body weight loss than did the cisapride and control groups (P = 0.045, 0.024, 0.006, 0.003, respectively). The appetite scores of the megace group were significantly higher than those of the cisapride and control groups (P = 0.0001). However, there were no statistically significant differences in the change of albumin level among these three groups at the 2nd, 4th, 6th and 8th week (P > 0.05, respectively). CONCLUSIONS: Megestrol acetate can significantly decrease the degree of body weight loss, and can prevent the deterioration of appetite in patients with head and neck cancers receiving radiotherapy. However, prepulsid lacks the above-mentioned clinical benefits.

Adult↗
PubMed1997

Arsenic methylation capacity, body retention, and null genotypes of glutathione S-transferase M1 and T1 among current arsenic-exposed residents in Taiwan.

In order to elucidate the relationships among arsenic methylation capacity, body retention, and genetic polymorphisms of glutathione S-transferase (GST) M1 and T1, a total of 115 study subjects were recruited from Lanyang Basin located on the northeast coast of Taiwan. Specimens of drinking water, blood, urine, hair and toenail were collected from each study subject. Urinary inorganic and methylated arsenic were speciated by high performance liquid chromatography combined with hydride-generation atomic absorption spectrometry. Arsenic concentration in hair and toenail were quantitated by atomic absorption spectrophotometry. The polymerase chain reaction was used to determine genetic polymorphisms of GST M1 and T1. Arsenic concentrations in urine, hair, and toenail of study subjects were positively correlated with arsenic levels in their drinking water. Percentages of various arsenic species in urine (mean +/- standard error (SE) were 11.8 +/- 1.0, 26.9 +/- 1.2 and 61.3 +/- 1.4, respectively, for inorganic arsenic, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA). Men and women had similar arsenic methylation capability. No associations were observed between arsenic methylation capability and arsenic content in either drinking water or urine. Ratios of arsenic contents in hair and toenail to urinary arsenic content (mean +/- standard error) were 6.2 +/- 0.7 and 16.5 +/- 1.7, respectively. Genetic polymorphisms of GST M1 and T1 were significantly associated with arsenic methylation. Subjects having the null genotype of GST M1 had an increased percentage of inorganic arsenic in urine, while those with null genotype of GST T1 had an elevated percentage of DMA in urine. Arsenic contents in hair and toenail were significantly correlated with the increase in arsenic concentrations of drinking water and urine, while no significant associations were observed between arsenic contents in hair and toenail and polymorphisms of GST M1 and T1. The relationship between arsenic methylation capability and body retention was modified by genetic polymorphisms of GST M1 and T1. Arsenic contents in hair and toenail were negatively associated with MMA percentage and positively associated with DMA percentage among subjects having null genotypes of GST M1 and T1, but not among those with non-null genotypes.

Arsenic↗
PubMed1997

Recombinant human erythropoietin enhances superoxide production by FMLP-stimulated polymorphonuclear leukocytes in hemodialysis patients.

Recombinant human erythropoietin (rHuEPO) is a hematopoietic growth factor that has a broad spectrum of action. We have observed the in vivo and in vitro effects of rHuEPO on the superoxide production of circulating polymorphonuclear leukocytes (PMNs) in hemodialysis patients. The PMNs were separated from heparinized blood after dextran sedimentation and Ficoll-Conray centrifugation and stimulated with formyl-methionyl-leucyl-phenylalanine (FMLP), serum-treated zymosan (STZ), or phorbol myristate acetate (PMA). The in vivo study showed that rHuEPO therapy for 12 weeks enhanced the superoxide production by FMLP-stimulated PMNs (P < 0.01). However, no significant changes on superoxide production was found in either STZ- or PMA-stimulated PMNs. Simultaneous measurement of PGE2 production by PMNs in response to all three stimulants did not show any significant changes after rHuEPO therapy. The direct in vitro effect of rHuEPO on PMNs showed that rHuEPO does not enhance the superoxide production by non-stimulated PMNs. However, preincubation of rHuEPO enhanced superoxide production from FMLP- and STZ-stimulated PMNs. Our results indicate that rHuEPO enhanced FMLP-stimulated superoxide production of PMNs both in vivo and in vitro in hemodialysis patients, which may be responsible for the increased oxidant stress in hemodialysis patients after rHuEPO therapy.

Adult↗
PubMed1997

Association properties of betaB2- and betaA3-crystallin: ability to form dimers.

The beta-crystallins are a major constituent of the mammalian lens, where they associate into dimers, tetramers and higher order aggregates. Appropriate association of lens crystallins is important for lens transparency. To examine the associative properties of betaB2-crystallin, we have expressed mouse betaB2-crystallin using a baculovirus system. Recombinant mouse betaB2-crystallin has an estimated monomer molecular weight of 24 kDa by SDS-PAGE, appropriate immunoreactivity and appropriate secondary structure as assessed by circular dichroism analysis. The recombinant betaB2-crystallin associates into a homodimer with a weight average molecular mass of 39 kDa. The betaB2-crystallin homodimer has an estimated Kd of 5 x 10(-6) M, slightly greater than that of betaA3-crystallin, 0.8 x 10(-6) M. When recombinant betaB2-crystallin is combined with recombinant betaA3-crystallin, a heterodimer is formed within 10 min of incubation at room temperature. When equilibrium is reached in 4-6 h, approximately half of each crystallin associates into heterodimers. Subunit exchange between betaB2-crystallin and betaA3-crystallin occurs readily in the absence of any denaturing agents. Thus, rbetaA3-rbetaB2 heterodimer formation can occur under conditions similar to those found in the eye lens.

Animals↗
PubMed1997

Mandibular reconstruction with fibular osteoseptocutaneous free flap and simultaneous placement of osseointegrated dental implants.

Insertion of osseointegrated dental implants several months after mandibular reconstruction using vascularized composite bone grafts has proved to be a successful method to achieve mastication and complete oral rehabilitation. Theoretically with primary placement of implants into the new mandible a better access to the bone is achieved, interdental relationships are easier to determine, and oral rehabilitation can be attained in a shorter period of time. Previous results describing this approach, however, are inconclusive and controversial. This review describes our experience with primary insertion of dental implants into fibular flaps used for mandibular reconstruction during ablative surgery. Adequate selection of patients for this combined procedure depends mainly on the pathological nature of the mandible and perioperative radiotherapy. Preoperative determination of soft-tissue and bone requirements, number of osteotomies, rigid fixation method, and familiarity with the use of osseointegrated implants are important factors that must be considered for adequate surgical planning and to achieve good results.

Dental Implantation, Endosseous↗
PubMed1997

Metacarpal hand: classification and guidelines for microsurgical reconstruction with toe transfers.

Metacarpal hand refers to the hand that has lost its prehensile ability through amputation of all fingers with or without amputation of the thumb. Functional restoration can be achieved by a wide variety of microvascular toe transfer techniques. When deciding which procedure should be used, careful consideration must be given to the level of amputation of the fingers as well as the functional status of the remaining thumb. In this article we propose a classification for the various patterns of the metacarpal hand along with guidelines for selection of the proper toe transfer procedure.

Adult↗
PubMed1997

The lateral arm fascial free flap for resurfacing of the hand and fingers.

The lateral arm free flap can be harvested as a fascial flap or fasciocutaneous flap. In this report we describe the use of the lateral arm fascial flap for degloving injuries of the fingers and for skin loss on the dorsum of the hand with exposure of tendons and bones. Concomitant reconstruction of a missing phalanx with a portion of the distal humerus is also described. The use of the fascial flap allows a large area of tissue to be harvested, and still, the donor site can be closed primarily. The fascia is thin and pliable and so conforms well to the contour of the fingers. Its bulk does not interfere with finger motion, and its undersurface creates a gliding surface for tendons. Complications in the reported cases were negligible.

Adolescent↗
PubMed1997

Toe-to-hand transfer for traumatic digital amputations in children and adolescents.

In the period from July of 1990 to August of 1994, 45 toe or toe tissue transfers were performed in 28 children and adolescents with traumatic amputation of digits. The average age at the time of transfer was 12 years (range, 3 to 16 years), and the median age was 10 years. The methods of reconstruction included transfer of 6 trimmed great toes, 2 great toe pulps, 24 second toes, 1 vascularized metatarsophalangeal joint from the second toe, 2 third toes, 4 combined second and third toes. and 1 combined third and fourth toes. All of the transferred toes, except one second toe, ultimately survived. Exploration and reanastomosis were required in three cases owing to arterial insufficiency. Partial pulp loss occurred in two digits. Follow-up ranged from 1 to 5 years (average, 3 years). Bony union occurred uneventfully in all patients. Two-point discrimination averaged 5 mm (static) and 6 mm (moving). Active range of the motion averaged 69, 38, and 13 degrees at the metaphalangeal proximal interphalangeal and distal interphalangeal joints of the reconstructed fingers, respectively, and 15 degrees at the interphalangeal joint of the reconstructed thumbs. None of the children required subsequent tenolysis. Pulp plasty was performed in nine digits in seven patients. Radiologically, the transferred phalanges showed the some growth as the non-transferred ones. Trimming the great toe before transfer did not result in premature physeal closure or growth retardation. The donor foot maintained a satisfactory appearance. None of the patients complained of difficulty in running or jumping. Toe-to-hand transfer in children, performed meticulously, can provide a valuable option for reconstruction of traumatic digit loss.

Adolescent↗
PubMed1997

Different viral aetiology of hepatocellular carcinoma between two hepatitis B and C endemic townships in Taiwan.

In Taiwan, we found two hepatitis B virus (HBV)- and hepatitis C virus (HCV)-endemic townships, Paisha and Tzukuan, with an anti-HCV prevalence of 19 and 37% in men, and 26 and 38% in women, respectively. The hepatitis B surface antigen (HBsAg)-positive rates were 25 and 18%, for men and women in Paisha, and 25 and 22% in Tzukuan, respectively. According to the national death certification database (1982 to 1991), the annual age-adjusted mortality rates per 100,000 population for liver cancer among men and women were 83.0 and 13.8, respectively, in Paisha, and 55.9 and 17.0 in Tzukuan compared with 30.9 and 9.1 in Taiwan as a whole. The male-to-female ratios were 6.0 in Paisha and 3.3 in Tzukuan. Aetiology of 11 cases of hepatocellular carcinoma (HCC) from Paisha and 14 cases from Tzukuan were analysed. All HCC cases from Paisha were HBsAg positive, while 13/14 HCC cases from Tzukuan were anti-HCV positive. The endemic duration of HCV in Tzukuan seemed long enough to induce HCC, but the HCV appeared to be a newly introduced infection in Paisha.

Adult↗
PubMed1997

Fixation of various porcine arteries with an epoxy compound.

The clinical results of biological vascular grafts have been unsatisfactory. The poor results of these vascular grafts may be attributed to the fixatives, aldehydes, used in fixing tissues. In an attempt to overcome this problem, a new fixative, epoxy compound, has recently been used to fix biological vascular grafts. The study was undertaken to investigate the crosslinking characteristics, fixation index and denaturation temperature, of various porcine arteries fixed with an epoxy compound. The porcine arteries investigated in the study were the common carotid artery, internal thoracic artery, abdominal aorta, and saphenous artery. In addition, the effects of sonication on the porcine arteries before fixation on their crosslinking characteristics were analyzed. The fresh and glutaraldehyde-fixed arteries were used as controls. It was noted that glycine, proline, and alanine were the most abundant amino acids found in the porcine internal thoracic artery. In the amino acid analysis, it was observed that the amino acids in the porcine arteries reacted with epoxy compound or glutaraldehyde were lysine, hydroxylysine, histidine, and arginine. Of these amino acids, lysine was the most reactive. In general, the fixed arteries were relatively stiffer than their fresh counterparts. The fixation indices and denaturation temperatures of various porcine arteries were comparable throughout the entire fixation process. The amounts of free amino groups of the sonicated arteries were significantly lower than those of their unsonicated counterparts (p < 0.05). It is speculated that the diminishing free amino groups of the sonicated arteries may be attributed to the removal of the destroyed cell debris and adherent proteins of the arteries after sonication. However, it was learned that sonication on the porcine arteries before fixation did not seem to affect their fixation indices and denaturation temperatures. The results obtained in this study may help one in selecting the raw materials for developing a small-diameter biological vascular graft

Analysis of Variance↗
PubMed1997

The effect of T'ai Chi Chuan training on balance, kinesthetic sense, and strength.

The purpose of this study was to assess the effect of T' ai Chi Chuan training on lateral stability, kinesthetic sense, and strength of voluntary knee extension. Subjects consisted of 24 naive volunteers (12 men and 12 women) between the ages of 20 and 45 years. Pre- and 12-week posttests included lateral body stability, kinesthetic sense in the glenohumeral joint for 30 degrees, 45 degrees, and 60 degrees, and strength of knee extension. After pretest data collection, 12 subjects performed T'ai Chi Chuan three times per week for 12 weeks, learning 108 forms of T'ai Chi Chuan. A 2 x 2 analysis of variance was used to estimate significance of group differences on all of the dependent variables. Significant group differences were found in lateral body stability, kinesthetic sense at 60 degrees, and strength of the dominant knee extensor. No significant differences between the T'ai Chi and the control group were found for kinesthetic sense at 30 degrees and 45 degrees rotation of the glenohumeral joint. Film analysis indicated that the two lesser angles were not as common in the T'ai Chi training as the greater angle (60 degrees) and thus may be less practiced. It appears that T'ai Chi Chuan presents a low-stress method to enhance stability, selected kinesthetic sense, and strength of knee extension.

Adult↗