Search PubMed⌕ Search

Biomedical subjects

C C Chen

Publications and source records attributed to C C Chen.

At least 451 records · Page 25Linked to original sources
PubMed1994

Using a radioactive and non-radioactive exchangeable labeling system for laboratory diagnosis.

In this communication a safe and simple molecular diagnosis strategy was described, which can be applied for the identification of pathogens or oncogenes in clinical studies. In Southern or Northern analysis, we demonstrated the feasibility to exchange labeling probes from non-radioactive to radioactive or vice versa in a single membrane simply by stripping. We chose non-radioactive labeling because it is safe and easy to operate, but when the sensitivity is insufficient, it can be replaced by radioactive labeling. Our data show that radioactive or non-radioactive labeling is exchangeable in a single membrane and the sensitivity was comparable by either method under optimal conditions. The clinical implication is that for general hybridization starts with non-radioactive labeling, radioactive labeling is not needed unless the signals cannot be detected by non-radioactive labeling. Moreover, one membrane can be labeled repeatedly by different probes.

Blotting, Northern↗
PubMed1994

Epstein-Barr virus (EBV) infects T lymphocytes in childhood EBV-associated hemophagocytic syndrome in Taiwan.

We have reported the prevalence of a fulminant hemophagocytic syndrome (HS) in previously healthy young children in Taiwan, most of which probably represent a lethal form of primary or active Epstein-Barr virus (EBV) infection. To further confirm their EBV association, in situ EBV hybridization (ISH) was performed on tissue biopsies from 15 pediatric HS patients (median age, 3 years and 4 months) using digoxigenin-labeled RNA probes EBER1. Double labeling immunostaining and ISH was then performed to define the immunophenotype of the lymphoid cells containing the EBV transcripts. Among the 13 patients who had serological evidence of acute or active EBV infection, 9 had demonstrable EBER1 transcripts in bone marrow, liver, and/or skin biopsies. EBER1-specific signal was not detectable in the two specimens from EBV-seronegative patients. The distribution of EBV-containing cells could be extensive or scattered. To our surprise, the EBER1 transcripts existed exclusively in T lymphoid cells in all nine cases examined rather than in B cells as previously believed in infectious mononucleosis. Considering the young affected age of the HS patients and the serological response to EBV, we suggest that EBV can infect T cells in primary EBV infection and the proliferation of these EBV-infected T cells may be responsible for the ominous outcome in childhood HS patients in Taiwan.

Adolescent↗
PubMed1993

Structure of a phosphonate-inhibited beta-lactamase. An analog of the tetrahedral transition state/intermediate of beta-lactam hydrolysis.

The crystal structure of beta-lactamase from Staphylococcus aureus inactivated by p-nitrophenyl[[N-(benzyloxycarbonyl)amino]methyl]phosphonate, a methylphosphonate monoester monoanion inhibitor, has been determined and refined at 2.3 A resolution. The structure reveals a tetrahedral phosphorus covalently bonded to the O gamma atom of the active site serine, Ser70. One of the oxygen atoms bonded to phosphorus is located in the oxyanion hole formed by the two main-chain nitrogen atoms of Ser70 and Gln237, and the second bonded oxygen is solvated. The (benzyloxycarbonyl)aminomethyl group is oriented towards the active site gully such that the peptide group forms compensating electrostatic interactions with polar groups on the enzyme. The benzyl group forms a hydrophobic interaction with Ile239 and an aromatic-aromatic edge-to-face interaction with Tyr105, which has undergone a conformational transition relative to the native structure. The mode of binding supports the proposal that on reaction with the enzyme, the phosphonate generates a structure analogous to the tetrahedral transition state/intermediate associated with the acylation step of a normal substrate. The disposition of the phosphonyl group in this complex is the same as that of the corresponding phosphoryl group in the complex resulting from the inhibition of trypsin by diisopropylphosphofluoridate. The structure is consistent with a mechanism of inactivation that follows an associative pathway, proceeding via a transition state/intermediate in which phosphorus is penta-co-ordinated, forming a trigonal bipyramidal geometry with the phosphonyl donor (p-nitrophenol) and acceptor (Ser70 O gamma atom) in apical positions. A model of this transition state can be accommodated in the active site of beta-lactamase without any steric hindrance. A model of the tetrahedral transition state associated with the acylation step by benzyl penicillin has been derived. Because of the conformational rigidity of the fused rings of penicillin molecules, the orientation of the substrate is fixed once the tetrahedral carbonyl carbon and its ligands are superimposed on the phosphonate group. The outcome is that the carboxylate substituent on the thiazolidine ring forms a salt bridge with Lys234, and the preferred puckering of the ring is that observed in the crystal structure of ampicillin, the so-called "open" conformer.

Binding Sites↗
PubMed1993

Protein kinase C alpha, delta, epsilon and zeta in C6 glioma cells. TPA induces translocation and down-regulation of conventional and new PKC isoforms but not atypical PKC zeta.

Both the cytosol and membrane in C6 glioma cells express abundance of PKC alpha, delta, zeta and trace amount of PKC epsilon by Western blot analysis with isozyme-specific antibodies. These characteristics make this cell line a good model to study the properties of different classes of PKC isoforms in one cell type. Exposure of the cells to 100 nM TPA for 10 min resulted in the translocation of conventional PKC alpha (cPKC alpha) and new PKC delta (nPKC delta) and -epsilon from the cytosolic to the membrane fraction, while left atypical PKC zeta (aPKC zeta) unaffected. The extent of translocation of cPKC alpha induced by TPA was more prominent than that of nPKC delta and nPKC epsilon. alpha-TPA, the inactive phorbol ester, did not induce translocation of these isozymes. After treatment of the cells with 1 microM TPA for 17 h, cPKC alpha, nPKC delta and nPKC epsilon were almost completely down-regulated, whereas aPKC zeta was still unaffected. The natural activators of this cell line, endothelin-1 and ATP also translocated cPKC alpha and nPKC delta. However, the extent of translocation induced by these two agonists was much less than that of TPA.

Adenosine Triphosphate↗
PubMed1993

Herbicides to curb human parasitic infections: in vitro and in vivo effects of trifluralin on the trypanosomatid protozoans.

Leishmaniasis is a major tropical disease for which current chemotherapies, pentavalent antimonials, are inadequate and cause severe side effects. It has been reported that trifluralin, a microtubule-disrupting herbicide, is inhibitory to Leishmania amazonensis. In this study, the in vitro effect of trifluralin on different species of trypanosomatid protozoans was determined. In addition to L. amazonensis, trifluralin is effective against Leishmania major and Leishmania tropica, which cause cutaneous infections, Leishmania donovani, which causes visceral disease, Leishmania panamensis, which may cause mucocutaneous infection, and Trypanosoma brucei, an important human and veterinary pathogen. Moreover, most encouragingly, trifluralin is effective in vivo as a topical ointment against L. major and Leishmania mexicana murine cutaneous leishmaniasis. Thus, trifluralin is a promising lead drug for several related, prevalent tropical diseases: leishmaniasis, trypanosomiasis of animals, and, possibly, African trypanosomiasis in humans.

Animals↗
PubMed1993

Antiproliferative effect of esculetin on vascular smooth muscle cells: possible roles of signal transduction pathways.

The effect of esculetin, a coumarin derivative with lipoxygenase inhibitor activity, on the proliferation response of cultured rabbit vascular smooth muscle cells was studied. Proliferation response was determined by the uptake of tritiated thymidine. Esculetin (10(-5)-10(-4) M) dose dependently inhibited the enhanced proliferation stimulated by 5% fetal calf serum. The structure-activity relationship of esculetin and eight other coumarin derivatives indicates that two adjacent phenolic hydroxyl groups at the C-6 and C-7 positions in the coumarin skeleton are necessary for the potent antiproliferative effect. The antiproliferative effects of other lipoxygenase inhibitors, 5,8,11,14-eicosatetraynoic acid (ETYA) and ketoconazole, were comparable to the effect of esculetin. However, esculetin exhibited the greatest maximal suppression. The enhanced releases of 12-hydroxyeicosatetraenoic acid (12-HETE), prostaglandin E2 and 6-keto-prostaglandin F1 alpha in the culture medium of smooth muscle cells stimulated by 5% fetal calf serum were significantly reduced by esculetin. Furthermore, the fetal calf serum-stimulated protein tyrosine kinase activity was reduced by esculetin (10(-5)-10(-4) M) in a dose-dependent manner. In contrast, the protein kinase C activity stimulated by phorbol-12-myristate-13-acetate was not affected by esculetin (10(-6)-10(-4) M). These results suggest that the antiproliferative effect of esculetin on vascular smooth muscle cells may be partly mediated through inhibition of protein tyrosine kinase and modulated by inhibition of lipoxygenase.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1993

The cloning and nucleotide sequence of a Corynebacterium glutamicum 3-deoxy-D-arabinoheptulosonate-7-phosphate synthase gene.

The aro gene of Corynebacterium glutamicum CCRC 18310 encoding 3-deoxy-D-arabinoheptulosonate-7-phosphate (DAHP) synthase was isolated by complementation of a DAHP synthase-deficient mutant of Escherichia coli AB3257. The specific activity of DAHP synthase was increased four-fold in a C. glutamicum strain harboring the cloned aro gene. The complete nucleotide sequence of the aro gene and its 5' and 3' flanking regions has been determined. The sequence contained an open reading frame of 368 codons, from which a protein with a molecular mass of 39,340 Da could be predicted. The deduced amino acid sequence shows high identity with the aro gene products of E. coli and Salmonella typhimurium.

3-Deoxy-7-Phosphoheptulonate Synthase↗
PubMed1993

A massively parallel memory-based story system for psychotherapy.

We describe a memory-based system for psychotherapy, Dr. Bob, built to run on the data parallel processor Thinking Machines, Inc., CM-2a Connection Machine. The system retrieves, in parallel, stories of alcohol addiction and sexual abuse which can be used by psychiatrists in working with their patients as part of their work in recovering from addictive behavior and psychological trauma. The program is written in *LISP (pronounced Star LISP), a version of LISP used in programming Connection Machines.

Artificial Intelligence↗
PubMed1993

Protection from ultraviolet irradiation by melanin of mosquitocidal activity of Bacillus thuringiensis var. israelensis.

A process for production, isolation, and purification of melanin produced by the fermentation of Streptomyces lividans 66 harboring a recombinant plasmid pIJ702-bearing tyrosinase gene has been developed. The efficacy of melanin in the protection of mosquito larvacidal activity of Bacillus thuringiensis var. israelensis against uv light has been studied. Results obtained by the live cell counts and the bioassay of residual mosquitocidal activity of B. thuringiensis var. israelensis after exposure to uv radiation showed that melanin is an excellent photoprotective agent.

Aedes↗
PubMed1993

R56865, a Na(+)- and Ca(2+)-overload inhibitor, reduces myocardial ischemia-reperfusion injury in blood-perfused rabbit hearts.

The cardioprotective effects of R56865 were studied in isolated rabbit hearts, blood-perfused with a support rabbit system. The effect on ischemic injury was evaluated by comparing myocardial contracture and contents of ATP catabolites and of lactate during 60 min of normothermic ischemia in untreated hearts (group I) and in hearts treated with 0.63 mg/kg of R56865 starting 20 min before ischemia (group II; n = 5 in each group). R56865 delayed the onset, and decreased the extent of ischemic contracture, but had no effect on the myocardial content of ATP, of its catabolites of lactate. The effect on reperfusion injury was studied by monitoring left ventricular function during 80-min reperfusion after the 60-min ischemia in three groups (n = 6 in each): an untreated group (group I) and two groups treated with R56865 given either before (group II) or after ischemia (group III). Ultrastructural changes and cellular calcium distribution after reperfusion were also studied. R56865 improved the recovery of function and prevented contracture during reperfusion. Left ventricular end-diastolic pressure was 13.2 +/- 2.8 mmHg in group II and 31.3 +/- 8.1 mmHg in group III vs 45.0 +/- 2.6 mmHg in group I (P < 0.0001 for II vs I; P > 0.05 for III vs I). Left ventricular developed pressure, maximum dP/dt and minimum dP/dt recovered to 71.0 +/- 5.4%, 98.9 +/- 6.1%, 85.3 +/- 4.8% of baseline values, respectively, in group II, to 64.5 +/- 3.0% (P > 0.05), 76.8 +/- 3.0%, 70.2 +/- 4.0% in group III, vs 52.0 +/- 6.5%, 58.9 +/- 6.9% and 53.6 +/- 5.8% in untreated hearts (P < 0.05 for II or III vs I). Coronary flow was 24.5 +/- 2.2 ml/min and 19.8 +/- 1.8 ml/min in groups II and III vs 14.8 +/- 0.7 ml/min (P < 0.05) in the untreated group. On histology the myocardium in hearts treated either before or after ischemia was well protected and calcium distribution was almost normal after reperfusion, while in untreated hearts, most of the myocardium displayed irreversible damage accompanied by massive intracellular calcium accumulation. We conclude that R56865 could attenuate Ca(2+)-overload, thereby reducing myocardial ischemia-reperfusion injury after an extended period of ischemia.

Animals↗
PubMed1993

A point mutation in the chloroplast rps12 gene from Nicotiana plumbaginifolia confers streptomycin resistance.

In an effort to understand the mechanism of streptomycin resistance in Nicotiana plumbaginifolia, we have sequenced the chloroplast rps12 gene, a potential molecular target. We report that a streptomycin-resistant mutant isolated from protoplast cultures of N. plumbaginifolia contains an A-to-G transition at nucleotide position 149 in exon 2 of the chloroplast rps12 gene. The detected point mutation predicts a substitution of arginine for lysine in a phylogenetically conserved region.

Amino Acid Sequence↗
PubMed1993

The inhibitory effect of magnolol on cutaneous permeability in mice is probably mediated by a nonselective vascular hyporeactivity to mediators.

In the present study, we demonstrated the inhibitory effect of magnolol on the plasma leakage in passive cutaneous anaphylactic (PCA) reaction, neurogenic inflammation, dorsal skin and ear edema in mice. Hind-paw skin plasma extravasation caused by antidromic stimulation of the saphenous nerve was reduced in mice pretreated with magnolol, diphenydramine or methysergide, but not with indomethacin. Ear edema formation in the PCA reaction was reduced by magnolol in dose-dependent manner. In addition, histamine-, serotonin-, compound 48/80-, bradykinin- and substance P-induced ear edema in mice was also suppressed by magnolol. A dose- and time-dependency of the inhibitory effect of magnolol was demonstrated in histamine- and compound 48/80-induced dorsal skin edema. The maximal inhibitory effect produced by a single dose of magnolol (10 mg/kg) persisted for 1 h, and significant suppression lasted for at least 3 h. In compound 48/80-pretreated mice, the histamine content of the ear was greatly reduced. Bradykinin- and substance P-induced ear edema in compound 48/80-pretreated mice was less severe than that seen in normal mice, but was still significantly reduced by magnolol pretreatment. Moreover, the inhibitory effect of magnolol was more marked than that of diphenhydramine combined with methysergide. These results suggest that the inhibitory effect of magnolol on local edema formation probably occurs through a nonselective inhibition on vascular tissue to prevent the permeability change caused by various mediators.

Adrenalectomy↗
PubMed1993

Dose titration study of isradipine in Chinese patients with mild to moderate essential hypertension.

In order to assess the effective dose, tolerability, and safety of isradipine as a monotherapeutic antihypertensive agent for Chinese patients in Taiwan, an open trial was carried out. This study consisted of a 2-week, placebo, run-in period and an 8-week active treatment period, starting with isradipine 1.25 mg twice daily (bid) for the first 4 weeks, followed by 2.5 mg bid if the blood pressure was not normalized (diastole < 90 mmHg). One hundred and one patients (M/F = 48:53) were valid for efficacy analysis. Their age ranged from 30 to 64 years (mean +/- SD, 52 +/- 8). The blood pressure before active treatment was 160 +/- 2/104 +/- 1 mmHg. At the end of treatment period I (week 4), 12-14 hours after the last dose, 38 (37.6%) patients were normalized and 47 (46.5%) subjects responded (diastolic blood pressure reduction > or = 10 mmHg). At week 8, 68 (67.3%) patients were normalized and 79 (78.2%) subjects responded. Isradipine reduced both systolic and diastolic blood pressures within 2 weeks of treatment. There were no significant differences in blood pressure reduction between both genders and among age groups. Safety analysis showed two subjects with severe flushing, dizziness, and palpitation who used the dose of 1.25 mg bid. They withdrew from the study. The adverse reactions of other patients were transient, mild, and tolerable. Most of the side effects were related to vasodilatation, but edema was not found. There was no change in body weight or heart rate, nor any atrioventricular conduction disturbances.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Murine intestinal mucins inhibit rotavirus infection.

BACKGROUND: Mucin, a population of polymeric glycoproteins, constitutes the primary component of the mucus layer that overlies the gastrointestinal tract. These studies aimed to determine whether murine intestinal mucins inhibit rotavirus infection. METHODS: Murine intestinal mucins were obtained by scraping segments of mouse intestine and purification via CsCl gradient centrifugation and sepharose 4B chromatography. Inhibition of infection was determined by quantitation of immunoperoxidase-stained cells after infection with mucin-rotavirus mixtures. RESULTS: Crude and purified intestinal mucins from suckling and adult mice are potent inhibitors of replication of a simian rotavirus, rhesus rotavirus (RRV), but weak inhibitors of other rotaviruses. In all preparations, colonic mucins were more potent inhibitors of RRV than small intestinal mucins. Suckling mucins neutralized RRV more effectively than adult mucins. In a panel of rotavirus reassortants, susceptibility to mucin inhibition correlated with the ability to hemagglutinate human type O erythrocytes and with RRV gene 4. Murine intestinal mucin inhibited RRV binding to MA104 cells, suggesting inhibition of virus-cell attachment to be the mechanism for neutralization. Mercaptoethanol or neuraminidase inhibited mucins' anti-RRV activities, implying the functional importance of mucins' polymeric structure and sialic acid content. CONCLUSIONS: These findings suggest that intestinal mucins represent a barrier to certain rotavirus infections.

Animals↗
PubMed1993

Cutaneous manifestations of Epstein-Barr virus-associated T-cell lymphoma.

BACKGROUND: In addition to human T-lymphotropic virus (HTLV-I), the Epstein-Barr virus (EBV) has recently been demonstrated to be associated with cutaneous T-cell lymphoma (CTCL). OBJECTIVE: Our purpose was to investigate characteristic clinicopathologic features of the cutaneous lesions of EBV-associated T-cell malignancies. METHODS: Clinical records, laboratory data, and histopathologic sections were reviewed. Freshly frozen tumor tissues were immunophenotyped. Southern blot and in situ hybridization studies were performed to detect the EBV genomes. RESULTS: Ten of 35 CTCL biopsy specimens collected between 1985 and 1992 were found to be EBV-associated. Clonotypic proliferation of EBV genomes was demonstrated in each case, and the atypical T lymphoid cells contained EBV genomes. The cutaneous eruptions of these patients included multiple violaceous papules or nodules, chronic ulcers, and tumors on the trunk or extremities. Three distinct clinicopathologic subgroups could be recognized. The most consistent was the angiocentric T-cell lymphoma or lymphomatoid granulomatosis (type III CTCL) (four cases), presenting with chronic ulcers or violaceous papules. The second group was the T large-cell lymphoma (type II CTCL), Ki-1 antigen (CD30) (positive or negative) (four cases). Three patients with Ki-1- lymphoma had fulminant disease, whereas the remaining Ki-1+ case had a benign course. The third group was the secondary type CTCL (type V CTCL) (two cases), representing systemic EBV-associated T-cell lymphoma. The prognosis was grave. The common features of these EBV-associated CTCLs are resistance to conventional chemotherapy, poor prognosis, and the terminal manifestation of a hemophagocytic syndrome. No EBV genome could be detected in 12 cases of classic CTCL/mycosis fungoides (type I CTCL), or in three cases of HTLV-I-associated adult T-cell lymphoma (type IV CTCL). CONCLUSION: Three distinct clinicopathologic subtypes of EBV-associated CTCL were recognized, including one additional type of virus-associated CTCL.

Adult↗
PubMed1993

Natural history of prostatism: urinary flow rates in a community-based study.

Urinary flow rates were measured in a randomly selected community sample of more than 2,000 men 40 to 79 years old with no history of prostate surgery, prostate cancer or certain other diseases known to interfere with normal voiding. Peak urinary flow rates decreased from a median of 20.3 ml. per second in men 40 to 44 years old to 11.5 ml. per second for men 75 to 79 years old, while voided volumes decreased from a median of 355.5 to 222.5 ml. for the same age ranges. Peak flow rates of less than 10 ml. per second were found in 6% of the men aged 40 to 44 years, increasing to 35% among men aged 75 to 79 years. Urological standards for peak urinary flow rate should be based on community data, and should account for age and voided volume. Our study may serve as the starting point for the development of community-based flow rate normal ranges. Nomograms are given to permit estimating flow rate percentiles as a function of age and voided volume.

Adult↗
PubMed1993

Enhancement of the ocular bioavailability of topical tobramycin with use of a collagen shield.

We compared the ocular bioavailability in rabbits of 0.3% tobramycin applied with a collagen shield with eyedrop tobramycin application. Groups of rabbits received either (1) a collagen shield presoaked in tobramycin with a tobramycin drop before and after shield application (Shield) or (2) three drops of tobramycin (Drops). Postmortem samples of the cornea, conjunctiva, and aqueous humor were obtained at various intervals after shield application or drop instillation. The corneas in a second set of rabbits were anesthetized and then chemically abraded with n-heptanol before receiving the same two dosing regimens as in the groups with intact corneas. At nearly all times in all three tissues, the Shield groups had higher mean concentrations of tobramycin than the Drops groups. The area under the concentration-time curve for the Shield group relative to the Drops group was 5.0- to 16.1-fold greater for rabbits with intact corneas (P < .05), and 1.8- to 3.7-fold greater for rabbits with abraded corneas (P < .05). The use of collagen shields together with standard ophthalmic concentrations of tobramycin may be useful in achieving higher concentrations of topically delivered drugs into the anterior segment of the eye.

Alcohols↗