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Biomedical subjects

H C Chen

Publications and source records attributed to H C Chen.

At least 343 records · Page 19Linked to original sources
PubMed1993

Characterization of a 7.5-kDa protein kinase C substrate (RC3 protein, neurogranin) from rat brain.

A 7.5-kDa heat- and acid-stable rat brain protein kinase C (PKC) substrate was purified to near homogeneity by a two-step procedure using DEAE-cellulose and hydroxylapatite column chromatography. This 78-amino-acid protein has a sequence identical to that deduced from rat brain RC3 cDNA identified with a cortex-minus-cerebellum subtracted cDNA probe (J. B. Watson et al., J. Neurosci. Res. 26, 397-408, 1990) and exhibits extensive sequence identity to bovine brain neurogranin (J. Baudier et al., J. Biol. Chem. 266, 229-237, 1991). On sodium dodecyl sulfate-polyacrylamide gel electrophoresis this protein, RC3, migrated as a M(r) 15-18K species in the presence of reducing agent and as heterogeneous species of M(r) 13-28K in the absence of reducing agent. Phosphorylation of RC3 by PKC alpha, beta, or gamma was stimulated by Ca2+, phospholipid, and diacylglycerol. A single site, Ser36, which is adjacent to the predicted calmodulin (CaM)-binding domain, was phosphorylated by these enzymes. Phosphorylation of RC3 by PKC or PKM, a protease-degraded PKC, was inhibited by CaM. The effect of CaM apparently targets at RC3, as phosphorylation of protamine sulfate by PKM was not inhibited by CaM. In the absence of Ca2+, RC3 formed a stoichiometric complex with CaM as evidenced by an increase in the M(r) determined by gel filtration chromatography. In the presence of Ca2+, the affinity of RC3 toward CaM is greatly reduced and Ca2+/CaM becomes less inhibitory of the PKM-catalyzed phosphorylation of RC3. Phosphorylation of RC3 by PKM prevented the interaction of this protein with CaM even in the absence of Ca2+. A 20-amino-acid synthetic peptide (AS-20F-W) containing the PKC phosphorylation site and CaM-binding domain of RC3 (Ala29-Ser48) with a substitution of Phe37 with tryptophan was used to monitor the interaction of this peptide with CaM by spectrofluorometry. In the absence of Ca2+, CaM caused negligible change in tryptophan fluorescence of the peptide; however, an enhancement and blue-shift of the emission fluorescence was observed in the presence of Ca2+. It seems that this synthetic peptide, as well as RC3 holoprotein, interacts with CaM through electrostatic interaction in the absence of Ca2+ but through hydrophobic interaction in the presence of Ca2+. In rat brain homogenate, RC3 formed a stable complex with CaM in the presence of Ca2+, as demonstrated by immunoblot analysis following gel filtration chromatography.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1993

Effects of syntactic structure in the memory of concrete and abstract Chinese sentences.

Smith (1981) found that concrete English sentences were better recognized than abstract sentences and that this concreteness effect was potent only when the concrete sentence was also affirmative but the effect switched to an opposite end when the concrete sentence was negative. These results were partially replicated in Experiment 1 by using materials from a very different language (i.e., Chinese): concrete-affirmative sentences were better remembered than concrete-negative and abstract sentences, but no reliable difference was found between the latter two types. In Experiment 2, the task was modified by using a visual presentation instead of an oral one as in Experiment 1. Both concrete-affirmative and concrete-negative sentences were better memorized then abstract ones in Experiment 2. The findings in the two experiments are explained by a combination of the dual-coding model and Marschark's (1985) item-specific and relational processing. The differential effects of experience with different language systems on processing verbal materials in memory are also discussed.

China↗
PubMed1993

Microsurgical reconstruction of distal digits following mutilating hand injuries: results in 121 patients.

From 1982-1989, 152 mutilated distal digits were reconstructed with microsurgical foot tissue transfers in 121 patients. These various foot tissues included wrap-around flaps or pulp from the great toe, second toe, or third toe, as well as partial toe, nail, web space skin, and other portions of the foot. The reconstructions were carried out primarily and secondarily in 78 and 74 patients respectively. The immediate success rate was 98%. Most of the patients were satisfied with both the cosmetic appearance and the functional result. This relatively minor microsurgical foot tissue transfer proved to be an ideal reconstructive option for distal digital defects.

Adolescent↗
PubMed1993

Pretibial epidermolysis bullosa: a clinicopathologic study.

BACKGROUND: Pretibial epidermolysis bullosa (PEB) is a rare variant of dystrophic epidermolysis bullosa (DEB) that predominantly involves the pretibial skin. OBJECTIVE: We report 19 cases of DEB with pretibial predilection and our findings on anchoring fibrils. METHODS: Patients with blisters and scars that primarily involved the pretibial were selected. Blisters and noninvolved skin were studied by light and electron microscopy. Anchoring fibrils were quantified by morphometry. RESULTS: There were 19 patients from 13 families. The inheritance was autosomal dominant in 10 families and sporadic in one family, and sibling involvement was present in two families. Nail dystrophy was noted in all patients. Pruritus was a common feature. Extensive prurigo occurred in four patients. Eight patients had skin lesions that exclusively affected the legs and were diagnosed as PEB. The remaining patients also showed some albopapuloid or hypertrophic scars at sites other than the leg, features seen in the albopapuloid or Cockayne-Touraine types. These were labeled as albopapuloid PEB or Cockayne-Touraine PEB. Common ancestry and various combinations of PEB, with albopapuloid or Cockayne-Touraine type of EB, were noted in some families. Compared with normal controls, the anchoring fibrils were rudimentary and sparser in both lesional and nonpredilected normal skin, although in the latter the changes were less marked in PEB than in the albopapuloid or Cockayne-Touraine types. CONCLUSION: Common ancestry may contribute to the higher incidence of DEB, especially PEB, in Tainan, Taiwan. The abnormalities of anchoring fibrils were not restricted to the predilected site in PEB and did not distinguish PEB from other types of DEB.

Adolescent↗
PubMed1993

Proteolysis of Saccharomyces cerevisiae RNase H1 in E coli.

Expression of S cerevisiae RNase H1 in E coli leads to the formation of a proteolytic product with a molecular mass of 30 kDa that is derived from the 39-kDa full length protein. The 30-kDa form retains RNase H1 activity, as determined by renaturation gel assay. The amount of proteolysis observed depends on the procedure used in preparing the cell extracts for protein analysis. The cleavage site on the amino acid sequence of the 39-kDa RNase H1 was determined by N-terminal sequence analysis of the 30-kDa proteolytic form. The cut occurs between two arginines located at the amino terminus region of the protein. The pattern of proteolysis was examined for both the wild-type RNase H1 and a mutant RNase H1 that was constructed in this work. In the mutant the second arginine of the cleavage site was changed to a lysine. Comparisons of the expression of the wild-type and altered protein in two different E coli strains demonstrate that the protease responsible for the degradation has a specificity very similar to that of the OmpT protease. However, the proteolysis observed in an OmpT background in extracts, prepared by boiling the cells in SDS containing buffer, indicates that the protease may, unlike OH108.

Amino Acid Sequence↗
PubMed1993

Bioaccumulation and distribution of mercury in the hard clam, Meretrix lusoria (Bivalvia: Veneidae).

1. Total mercury concentration in whole soft parts of the hard clam, Meretrix lusoria, increased significantly with increasing exposure concentrations. It reached 4.247-7.084 and 9.956-13.643 micrograms T-Hg/g dry weight in 5 and 50 micrograms/l Hg mercury solution, respectively, against a background level of 1.824-0.577 micrograms T-Hg/g dry weight. 2. Bioconcentration factor was 4-6 times higher in 5 micrograms/l Hg than that of 50 micrograms/l Hg. An estimated biological half-life of 20.2 and 18.4 days in 5 and 50 micrograms/l Hg, respectively, were also obtained after 14 days uptake. 3. Accumulation of mercury in tissues of the clams was greater in the gills and viscera than in the mantle, adductor, foot, or hemolymph. 4. The amount of mercury present in the gills is related to be a linear relationship with the mercury content of viscera.

Animals↗
PubMed1993

Generation of 1-37 and 1-38 forms of adrenocorticotropin by mono- and dipeptidyl serine carboxypeptidase activities in bovine pituitary secretory vesicles.

ACTH is a 39-amino acid peptide synthesized in the pituitary as part of the precursor molecule, POMC. Analysis of bovine anterior pituitary homogenates and secretory vesicles revealed that in addition to ACTH-(1-39), ACTH-(1-37) and ACTH-(1-38) were also present in the lobe, indicating that carboxyl-terminal processing of ACTH-(1-39) occurred in vivo. Mono- and dipe;tidyl carboxypeptidase activities that cleaved ACTH-(1-39) were detected in bovine intermediate and anterior pituitary secretory vesicle membranes and characterized. The dipeptidyl carboxypeptidase activity liberated ACTH-(1-37) and the dipeptide, Glu-Phe, and the monocarboxypeptidase activity generated, to a smaller extent, ACTH-(1-38) and phenylalanine from ACTH-(1-39). Kinetic studies indicated that the formation of ACTH-(1-37) occurred within minutes, whereas the formation of ACTH-(1-38) occurred within hours. Both enzymatic activities had a pH optimum of 5.5 and a Km of 14-18 microM for ACTH-(1-39), and were inhibited by serine and some thiol, but not metallo- or aspartic protease inhibitors. These unique serine carboxypeptidase(s) may function as a converting enzyme in vivo.

Adrenocorticotropic Hormone↗
PubMed1993

Congenital short small intestine: report of three cases.

Three cases are presented in which the recognized syndrome of functional small bowel obstruction with malrotation and short small bowel was diagnosed. Each patient underwent an exploratory laparotomy for intestinal obstruction, which revealed short small intestines with malrotation, measuring 30 cm to 39 cm. Ladd's procedure was performed in each case and gastrointestinal patency was assured during the operations. Two patients received long-term parenteral nutrition and one, in addition, received bowel lengthening using Bianchi's method. However, the symptoms persisted. The third patient received a prokinetic agent (cisapride) but with no effect; the parents withdrew further management. All three patients subsequently died. Although autopsies were performed in two cases, the exact deficits of intestinal motility are unknown.

Female↗
PubMed1993

[Inhibition of the protein kinase C-alpha gene overexpression in rat preneoplastic liver by selenium].

Effect of selenium on the protein kinase c-alpha (PKC-alpha) gene expression was observed in the preneoplastic lesions in liver of S.D. rat Solt-Farber model. Overexpression of PKC-alpha was found in preneoplastic liver but not in partially hepatectomized liver. Administration of 4PPm Na2SeO3 in water 2 weeks before i.p injection of DEN (200 ng/kg bw) for 8 weeks reduced the PKC-alpha gene overexpression in preneoplastic liver and the formation of hyperplastic foci, alpha-GT-altered foci and preneoplastic lesions.

Animals↗
PubMed1993

The thermoregulation of halothane versus isoflurane in humans receiving ophthalmological surgery.

Although suppression of thermoregulatory mechanisms during anaesthesia is generally assumed, the extent to which thermoregulation may be inactive is unknown. Twenty unpremedicated, ASA physical status class I patients (17 men and 3 women) scheduled for retinal detachment surgery were studied to evaluate the different changes of core and two skin-surface temperatures during halothane or isoflurane anaesthesia. Anaesthesia was induced by mask inhalation of halothane or isoflurane in nitrous oxide 70% and oxygen and was maintained by mechanical ventilation during surgery with halothane or isoflurane in nitrous oxide 50% and oxygen only. Core temperature (rectus) and skin-surface temperatures (forearm and fingertip) were measured during surgery using three separate thermometers (Y.S.I.: Yellow springs instrument Co., Inc. G541-211-Y01-33A0). Operating room temperatures were recorded in every case. Significant vasoconstriction was prospectively defined by a skin-surface temperature gradient between two sampling sites > or = 4 degrees C. The result indicated that there was no significant difference between core temperatures and skin-surface temperature gradients during halothane anaesthesia and isoflurane anaesthesia. However, three of the ten patients had their skin-surface temperature gradients > or = 4 degrees C in the halothane group. None of the ten patients had their skin-surface temperature gradients > or = 4 degrees C in the isoflurane group.

Adult↗
PubMed1993

Effects of manidipine hydrochloride on blood pressure in hypertensive patients--a comparison with nifedipine retard.

Manidipine hydrochloride (MH) is a new calcium channel antagonist which is not yet available in Taiwan. Thus, a clinical trial was performed. The clinical effects and adverse effects of MH were compared with those of nifedipine hydrochloride retard monotherapies. Sixty-three out-patients with mild to moderate hypertension and no advanced systemic diseases were randomly divided into 2 groups. Twenty patients remained in each group after some patients withdrew from the study. Blood pressure decreased significantly after treatment in both groups (p < 0.01). In the manidipine group, systolic blood pressure (SBP) decreased from 164 +/- 14 to 140 +/- 18 mmHg and diastolic BP (DBP) decreased from 99 +/- 6 to 87 +/- 7 mmHg by the 8th week. In the nifedipine group, SBP decreased from 163 +/- 11 to 134 +/- 17 mmHg and DBP decreased from 101 +/- 10 to 88 +/- 9 mmHg by the 8th week. Pulse rates did not change significantly. Antihypertensive efficacy was 18/20 (90%) and 19/22 (86.4%) in the manidipine and nifedipine groups, respectively. There were a few adverse effects in both groups, the reaction was severe as to lead to the discontinuation of medication in two patients in the nifedipine group. No significant changes in laboratory tests were identified in either group, except for minimal decreases of lactate dehydrogenase and creatine kinase in the nifedipine group. We conclude that MH was equally safe and effective as nifedipine and it may have less severe side effects compared to nifedipine.

Adult↗
PubMed1993

[Influence of selenium-enriched malt on the elevated cGMP concentrations induced by carcinogen].

Rats were fed with selenium-enriched malt containing 1 ppm selenium. As a parameter, cyclic guanosine-3'5'-monophosphate (cGMP) was measured by RIA in the rats following treatment with AFB1. The results demonstrated that the diet containing high selenium inhibited the elevation of cGMP levels in the liver induced by multiple exposures to AFB1 (250 micrograms/kg, 10 times/2 wks), (P < 0.05). Administration of a large single dose of AFB1 (1 mg/kg i.p.) reduced the liver cGMP contents which might be due to injury to the liver. Selenium-enriched diet could prevent this from happening. In high cancer risk areas: the cGMP level in urine of population with higher selenium concentration were lower than that of population with low selenium concentration. A supplementation of 300 micrograms selenium in the form of selenium-enriched malt cakes daily to the subjects with low selenium concentration in blood for one year, the urinary cGMP excretion was significantly decreased from 0.62 mumol/g to 0.49 mumol/g creatinine (P < 0.05). These findings suggest that diet containing high selenium has a protective effect and may play a potential role in cancer chemoprevention.

Aflatoxin B1↗
PubMed1993

Systemic lupus erythematosus with pure red cell aplasia: a case report.

Pure red cell aplasia (PRCA) is an unusual early manifestation of systemic lupus erythematosus (SLE). Review of the 13 cases in literature revealed that the immune system played a significant role in disease pathogenesis. Immunosuppression has been thought to be the cause of the efficacy of corticosteroids in treatment. The case of a 28-year-old woman with SLE is described. She presented with PRCA, but has had good response to corticosteroid therapy.

Adrenal Cortex Hormones↗
PubMed1993

[Comparison between the effects of (-)- and (+)-gossypol on protein kinase C and protein kinase A].

Protein kinase C(PKC) and protein kinase A(PKA) purified from rat liver were incubated with (-)- and (+)-gossypol. The activity of PKC was significantly inhibited in a concentration-dependent manner by both (-)-gossypol and (+)-gossypol. (-)-gossypol was found to inhibit type I PKA, whereas the inhibitory action of (+)-gossypol for type I PKA was less potent. Both (-)-gossypol and (+)-gossypol showed inhibition for type II PKA only at high concentration. These results suggest that administration of gossypol might impair cellular signal transduction.

Animals↗
PubMed1993

The multicystic dysplastic kidney in children.

Multicystic dysplastic kidney (MCDK) is the most common renal cystic disease in infancy and the second most common neonatal abdominal mass. It represents an extreme form of renal dysplasia. The key features in MCDK include variability in size, loss of kidney shape, absence of function and obstruction of ureter. Current management is still controversial. The prognosis is largely depended upon the problems of associated anomalies and the condition of the contralateral kidney. From September '82 to September '91, twelve patients with multicystic kidney have been treated at Taichung Veterans General Hospital. Ten of them received elective nephrectomy. The postoperative condition was uneventful. However, there was a high frequency of associated anomalies (41.6%) and pathologic contralateral kidney (50%). Two patients who refused operation were put on close observation and follow-up with ultrasound. During the surgical patients' follow-up period, one suffered from repeated urinary tract infection and the other died of multiple congenital anomalies.

Female↗
PubMed1993

Dilatation of the biliary tract in pediatric patients.

Forty cases of dilatation of the biliary tract in infants and children were diagnosed and treated at the Veterans General Hospital, Taipei and Taichung between 1980 and 1992. The male to female ratio was 1:2.6 and the age ranged from 1 day to 14 years. Major clinical presentations were abdominal pain (57.5%), jaundice (42.5%), vomiting (37.5%) and abdominal mass (30%); the classical triad of abdominal pain, jaundice and abdominal mass occurred in only three cases (7.5%). Abnormal liver function tests included elevated bilirubin (Bil) (22/37), aminotransferase (30/40), alkaline phosphatase (Alk-P) (34/37), lactic dehydrogenase (LDH) (22/34) and gamma-glutamyl transpeptidase (GGT) (13/15). The amylase in bile was detected in 16 cases with 10 cases higher than 500 Somogyi units/dL. All cases were diagnosed correctly, using real time sonography. Technetium-labeled scintiscan (Tc-99m DISIDA scan) was interpreted correctly in 88% (15/17) and abdominal computerized tomography (CT) in 10 cases (10/10). According to Todani's classification, type I cyst was the most common (35 cases, 87.5%) and the remaining cases were type IV-A (3 cases) and type V (2 cases). Operation was performed in 38 cases except for two who had type V dilatation of biliary tract (Caroli's disease). Complications included rupture of the gall bladder in two patients and common bile duct stone in one; mortality after operation occurred in one case. Surgical specimens of the liver revealed periportal fibrosis in nine instances.

Adolescent↗