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Biomedical subjects

C C Chen

Publications and source records attributed to C C Chen.

At least 235 records · Page 13Linked to original sources
PubMed1998

Vertical root fracture in nonendodontically treated teeth--a clinical report of 64 cases in Chinese patients.

Vertical root fractures (VRFs) in teeth without endodontic treatment are uncommon. A clinical study was done on 64 cases of VRFs in 61 Chinese patients to define better the clinical characteristics, diagnostic signs, and possible causes. Results showed that fractures occurred most often in first molars of patients between 40 and 69 yr of age, and the incidence was two times higher in males than in females. Flat roots with smaller mesiodistal diameters were more prone to fracture. The majority (79%) of patients had intact dentition with less than four teeth missing. Fractured teeth were frequently attrited with no restorations. VRFs may result from excessive or repetitive masticatory force due to damaging chewing habits exerted on flat roots of smaller mesiodistal diameter. Nonendodontic VRFs seem to occur more frequently than earlier believed and may represent an underdiagnosed clinical entity deserving of our attention.

Adult↗
PubMed1998

Search for mutations near the alternatively spliced 8-amino-acid exon in the GABAA receptor gamma 2 subunit gene and lack of allelic association with alcoholism among four aboriginal groups and Han Chinese in Taiwan.

The alternatively spliced 8-amino-acid exon for the GABAA receptor gamma2 subunit gene (GABRC2) has been postulated to mediate behavioral actions of alcohol. A rapid search for splice-junction mutations near the 8-amino-acid exon using restriction enzymes which normally recognize sequences near or in the exon gave negative results among 217 alcoholics in four aboriginal groups (Ami, Atayal, Bunun and Paiwan) and Han Chinese in Taiwan. The role of the GABRC2 gene in alcoholism was further assessed by a comparison of allelic frequencies revealed by a NciI RFLP between case and control groups. No significant association of alcohol dependence with GABRC2 alleles was observed. These results suggest that the GABRC2 gene probably does not play an essential role in predisposition to alcoholism in the sample population.

Alcoholism↗
PubMed1998

Effects of high dose octreotide on retrograde bile salt-induced pancreatitis in rats.

The effects of somatostatin and octreotide (a long acting somatostatin analogue) in acute pancreatitis are inconclusive. This study examined the prophylactic and therapeutic effects of different doses of octreotide on retrograde sodium taurodeoxycholate-induced acute necrotizing pancreatitis in rats. The rats were divided into 4 groups receiving subcutaneous injection of saline, octreotide 10 microg/kg, 20 microg/kg at 0, 8 and 16 h and octreotide 20 microg/kg at 5, 13 and 21 h, separately. The serum levels of amylase and lipase, pancreatic histopathology, mortality and hemodynamics were examined. Octreotide significantly reduced serum levels of amylase and lipase at 12 h and the degree of pancreatic edema, necrosis and hemorrhage at 18-24 h as compared to the control group. Prophylactic octreotide 10 microg/kg significantly decreased the 24-h mortality from 100% to 44.4% (p < 0.05). The 24-h mortality further reduced to 12.5% and 10% with prophylactic and therapeutic octreotide 20 microg/kg, respectively. The decrease of mean arterial pressure at 12 h was significantly lower in octreotide groups than in the control group. We conclude that octreotide improves pancreatic histopathology and survival in acute necrotizing pancreatitis in rats.

Amylases↗
PubMed1998

Measurement of prostaglandin E2 and leukotriene B4 in the gingival crevicular fluid.

UNLABELLED: The arachidonic acid metabolites prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) are inflammatory mediators which are likely to be involved in the pathogenesis of periodontal disease. PGE2 mediates vasodilatation, increases vascular permeability, enhances pain perception by bradykinin and histamine, alters connective tissue metabolism and enhances osteoclastic bone resorption. LTB4 causes the accumulation of inflammatory cells in the inflamed sites, and degranulation of polymorphonuclear leukocytes. OBJECTIVE: To measure gingival crevicular fluid (GCF) levels of PGE2, LTB4 and periodontal health. METHODS: The periodontal condition of 24 subjects was evaluated on the basis of plaque index, gingival index, probing depth, and attachment level. GCF samples were collected from one or two site(s) of each sextant per subject and the volume was measured using Periotron 6000. Samples were then assayed for PGE2 and LTB4 using a competitive enzyme immunoassay. Mean PGE2 and LTB4 levels were determined for each subject and group means compared. RESULTS: Significant differences in the levels of PGE2 and LTB4 were found between patients with periodontitis, and non-periodontitis individuals (P < 0.001). The PGE2/LTB4 levels were positively correlated with the clinical parameters (P < 0.01) and reduced markedly after phase 1 of the periodontal treatment (P < 0.01). The total amount and concentration (ng ml-1) of LTB4 was positively correlated with the gingival index (P < 0.01). CONCLUSIONS: These results indicate that the levels of PGE2 correlated with the severity of the periodontal status, and the levels of LTB4 correlated with gingival inflammation. Thus, our data suggest that the total amounts of PGE2/LTB4 may be good indicators for periodontal inflammation.

Adult↗
PubMed1998

Mutations in microphthalmia, the mouse homolog of the human deafness gene MITF, affect neuroepithelial and neural crest-derived melanocytes differently.

The mouse microphthalmia (Mitf) gene encodes a basic-helix-loop-helix-zipper transcription factor whose mutations are associated with abnormalities in neuroepithelial and neural crest-derived melanocytes. In wild type embryos, Mitf expression in neuropithelium and neural crest precedes that of the melanoblast marker Dct, is then co-expressed with Dct, and gradually fades away except in cells in hair follicles. In embryos with severe Mitf mutations, neural crest-derived Mitf-expressing cells are rare, lack Dct expression, and soon become undetectable. In contrast, the neuroepithelial-derived Mitf-expressing cells of the retinal pigment layer are retained, express Dct, but not the melanogenic enzyme genes tyrosinase and Tyrp1, and remain unpigmented. The results show that melanocyte development critically depends on functional Mitf and that Mitf mutations affect the neural crest and the neuroepithelium in different ways.

Animals↗
PubMed1998

Formation of basement membrane-like structure terminates the cellular encapsulation of microfilariae in the haemocoel of Anopheles quadrimaculatus.

The encapsulation of microfilariae in the haemocoels of mosquitoes combines both humoral and cellular reactions: the microfilariae are first encased in an acellular layer of melanin, followed by a cellular encapsulation by plasmatocytes. In this study, we demonstrated that cellular encapsulation of Brugia pahangi microfilariae in the haemocoel of the mosquito Anopheles quadrimaculatus was terminated by the formation of a basement membrane-like structure on the outermost surface of the cellular capsule. This structure occurred in the early stage of cellular encapsulation and was evident on the exterior surface of the plasmatocyte, when the active haemocytes were attaching to the already melanized microfilariae. The termination structure appears to be laid down by releasing the vesicle inclusions of haemocytes and has similarities in ultrastructure and cationic colloidal gold staining properties with that of mosquito basement membranes.

Animals↗
PubMed1998

Molecular cloning, characterization and tissue expression of prophenoloxidase cDNA from the mosquito Armigeres subalbatus inoculated with Dirofilaria immitis microfilariae.

A cDNA encoding mosquito Armigeres subalbatus prophenol oxidase (As-pro-PO) was obtained by rapid amplification of cDNA ends-polymerase chain reaction (RACE-PCR) after Dirofilaria immitis inoculation. The 2205 bp As-pro-PO cDNA contains a 32 bp 5'-noncoding region, a 2055 bp open reading frame (685 amino acids), and a 118 bp 3'-noncoding region. Hydrophobic signal peptide for the endoplasmic reticulum targeting is not found in the NH2-terminal region. Two potential copper-binding domains, amino acids 197-245 and 345-412, are highly homologous to those of the other insect pro-POs. A 2.2 kb As-pro-PO transcript was identified by Northern blot analysis using D. immitis microfilariae-inoculated A. subalbatus. Both in situ hybridization and Northern blot analysis demonstrated that As-pro-PO mRNA was synthesized in mosquito haemocytes but not in other tissues, i.e. fat bodies, midguts and ovaries, etc.

Amino Acid Sequence↗
PubMed1998

Anti-tumor effects of d-dicentrine from the root of Lindera megaphylla.

d-Dicentrine, a naturally occurring aporphine type isoquinoline alkaloid, isolated from the root of Lindera megaphylla Hemsl. (Lauraceae), was evaluated for its potential anti-cancer activity. We found d-dicentrine significantly inhibited the growth of human hepatoma cell line HuH-7 by delaying its doubling time in tissue culture. An in vitro colony forming assay showed that d-dicentrine decreased the colony formation efficiency in both hepatoma cell lines, HuH-7 and MS-G2, used in our study. Biosyntheses of the macromolecules DNA and RNA were also strongly inhibited. An MTT assay in 21 tumor cell lines also revealed that d-dicentrine was most cytotoxic to esophageal carcinoma HCE-6, lymphoma cell lines Molt-4 and CESS, leukemia cell lines HL60 and K562, and hepatoma cell line MS-G2. An in vitro tumor growing assay in the Severe Combined immunodeficiency (SCID) mice showed that intraperitoneal injection of d-dicentrine at the dose of 100 micrograms twice a week for 4 weeks significantly inhibited the tumor incidence of leukemia cell line K562 in SCID mice. All these data indicated that d-dicentrine has potential anti-tumor applications.

Animals↗
PubMed1998

Benzodiazepine binding site-interactive flavones from Scutellaria baicalensis root.

A benzodiazepine binding assay directed separation led to the identification of 3 flavones baicalein (1), oroxylin A (2), and skullcapflavone II (3) from the water extract of Scutellaria baicalensis root. Compounds 1, 2, and 3 interacted with the benzodiazepine binding site of GABAA receptors with a Ki value of 13.1, 14.6 and 0.36 micromol/L, respectively.

Animals↗
PubMed1998

Arachidonic acid and protein synthesis inhibitor act synergistically to suppress insulin-stimulated glucose transport in 3T3-L1 adipocytes.

The effect of arachidonic acid (AA) on insulin-stimulated glucose transport by 3T3-L1 adipocytes was examined in the presence of cycloheximide. We found that AA acted synergistically with cycloheximide to suppress insulin-stimulated glucose transport, although it alone was without effect. Similar phenomena were observed while protein synthesis inhibitors other than cycloheximide were employed. Immunoblot analysis indicated that the increase in plasma membranes of the insulin-regulated glucose transporter (GLUT4) in response to insulin was decreased in cells pretreated with cycloheximide for a prolonged time, while total amount of GLUT4 was not altered. Simultaneous presence of AA with cycloheximide had no further effect on the amount of GLUT4 in either total or plasma membranes. Thus the present study suggests that AA in the presence of a protein synthesis inhibitor seems to decrease the intrinsic activity of GLUT4.

3T3 Cells↗
PubMed1998

The effects of particle charge on the performance of a filtering facepiece.

This study quantitatively determined the effect of electrostatic charge on the performance of an electret filtering facepiece. Monodisperse challenge corn oil aerosols with uniform charges were generated using a modified vibrating orifice monodisperse aerosol generator. The aerosol size distributions and concentrations upstream and downstream of an electret filter were measured using an aerodynamic particle sizer, an Aerosizer, and a scanning mobility particle sizer. The aerosol charge was measured by using an aerosol electrometer. The tested electret filter had a packing density of about 0.08, fiber size of 3 microns, and thickness of 0.75 mm. As expected, the primary filtration mechanisms for the micrometer-sized particles are interception and impaction, especially at high face velocities, while electrostatic attraction and diffusion are the filtration mechanisms for submicrometer-sized aerosol particles. The fiber charge density was estimated to be 1.35 x 10(-5) coulomb per square meter. After treatment with isopropanol, most of fiber charges were removed, causing the 0.3-micron aerosol penetration to increase from 36 to 68%. The air resistance of the filter increased slightly after immersion in the isopropanol, probably due to the coating of impurities in isopropanol. The aerosol penetration decreased with increasing aerosol charge. The most penetrating aerosol size became larger as the aerosol charge increased, e.g., from 0.32 to 1.3 microns when the aerosol charge increased from 0 to 500 elementary charges.

Aerosols↗
PubMed1998

Development of respirable aerosol samplers using porous foams.

Workplace aerosols must be sampled to assess the degree of health hazard caused by the particulate matter. By adjusting the sampling flow rate, most of the samplers can match the 50% cutoff size, but not the slope of the respirable convention defined by the American Conference of Governmental Industrial Hygienists, the International Organization for Standardization, and the European Committee for Standardization (CEN). Combinations of foams (or other porous material) of different nominal sizes (10-100 ppi) and thicknesses (5-35 mm) were employed to overcome this bias. A foam disk 25 mm in diameter was placed in an asbestos sampling cowl. Dioctylphthalate was the liquid test agent. An aerodynamic particle sizer and an Aerosizer were calibrated against a settling chamber and were employed to measure the aerosol number concentrations and size distributions upstream and downstream of the foams. The sampling efficiency data showed that the 50% cutoff size could be met for foams in series, but that the slope remained sharper than the new definition. Foams in parallel showed great flexibility and many of the parallel combinations flattened the slope, closer to that of the new international respirable convention. For instance, when the total flow rate is set at 10.1 L/min the aerosol penetration through foams in parallel (100 ppi, 20 mm thick, diameter 25 mm + 10 ppi, 20 mm thick, diameter 13 mm) nearly matched the new international standard for respirable fraction. This sampler can be further miniaturized for smaller sampling flow rates to fit the capacity of personal sampling pumps.

Aerosols↗
PubMed1998

Hierarchical organization of molecular structure computations.

The task of computing molecular structure from combinations of experimental and theoretical constraints is expensive because of the large number of estimated parameters (the 3D coordinates of each atom) and the rugged landscape of many objective functions. For large molecular ensembles with multiple protein and nucleic acid components, the problem of maintaining tractability in structural computations becomes critical. A well-known strategy for solving difficult problems is divide-and-conquer. For molecular computations, there are two ways in which problems can be divided: (1) using the natural hierarchy within biological macromolecules (taking advantage of primary sequence, secondary structural subunits and tertiary structural motifs, when they are known); and (2) using the hierarchy that results from analyzing the distribution of structural constraints (providing information about which substructures are constrained to one another). In this paper, we show that these two hierarchies can be complementary and can provide information for efficient decomposition of structural computations. We demonstrate five methods for building such hierarchies--two automated heuristics that use both natural and empirical hierarchies, one knowledge-based process using both hierarchies, one method based on the natural hierarchy alone, and for completeness one random hierarchy oblivious to auxiliary information--and apply them to a data set for the procaryotic 30S ribosomal subunit using our probabilistic least squares structure estimation algorithm. We show that the three methods that combine natural hierarchies with empirical hierarchies create decompositions which increase the efficiency of computations by as much as 50-fold. There is only half this gain when using the natural decomposition alone, while the random hierarchy suggests that a speedup of about five can be expected just by virtue of having a decomposition. Although the knowledge-based method performs marginally better, the automatic heuristics are easier to use, scale more reliably to larger problems, and can match the performance of knowledge-based methods if provided with basic structural information.

Algorithms↗
PubMed1998

Ultrastructural studies on the reproductive system of male Aedes aegypti (Diptera: Culicidae) infected with dengue 2 virus.

Dengue 2 virus was found by transmission electron microscopy to be present in the reproductive tissues of male Aedes aegypti (L) 14 d after intrathoracic inoculation. Dengue 2 particles were detected in the matrix, epithelial cells, and the peripheral fat body of the testes; secretory droplets of columnar cells of the accessory glands; and the epithelial and muscle cells of the seminal vesicles. However, none was found in the germ cells (i.e., spermatogonia, spermatocytes, spermatid, or spermatozoa). These observations indicate that fluid transfer may be the mechanism of venereal transmission of dengue 2 virus by Ae. aegypti.

Aedes↗
PubMed1998

Alcohol-related problems in Taiwan with particular emphasis on alcoholic liver diseases.

Socioeconomic development has led to a progressive increase of alcohol consumption in Taiwan, with an accompanying increase in alcohol-related psychiatric problems, traffic accidents, and liver disease. The prevalent rates of alcohol dependence for Han Chinese and Fomosan aborigines were 0.1% and 1%, respectively in 1950. The rate of alcohol dependence increased to 23% for aborigines in 1995. The number of cases of death and serious injuries due to alcohol-related traffic accident has decreased, and the number of fatalities resulting from these accidents has decreased from third to eighth since the inception of a program of random traffic stops with alcohol breath test in 1997. Alcohol liver disease (ALD) was defined as daily alcohol consumption of 60 g, for a duration of longer than 5 years. We classified ALD patients into two groups: (1) those whose average daily consumption of alcohol exceeded 120 g for a duration longer than 15 years (group A); and (2) all other patients (group B). The case records of 33 cases of biopsy-confirmed ALD were obtained for study. The average of daily alcohol consumption in these cases was 160 g. All but one of these patients were male, age ranged from 26 to 69 years, with an average of 43.1. Clinically, ill-defined gastrointestinal symptoms were the most common presentation (61%), and hepatomegaly was the main physical sign (73%). The average mean corpuscular volume values of ALD and non-ALD patients were 102.3 +/- 10.94 and 94.5 +/- 8.1, respectively (p < 0.01). The mean corpuscular volume values of group A and group B were 102.9 +/- 9.7 vs. 96.5 +/- 9.11 (p < 0.05). Result from serum SGOT/SGPT and gamma-glutamyltransferase/alkaline phosphatase for ALD and non-ALD revealed statistically significant differences between these groups. Using the avidin-biotin complex technique, tissue IgA deposition for ALD patients was found to be different from that of non-ALD patients. Ten of 13 ALD patients vs. 2 of 13 non-ALD patients had continuous-form IgA deposition. Histologically, 45.5% of ALD patients had alcoholic cirrhosis, whereas alcoholic hepatitis was present in only 9.1% of patients. Overall, 88% of cases showed various severity of fatty metamorphosis.

Adult↗
PubMed1998

Conduction properties of the crista terminalis in patients with typical atrial flutter: basis for a line of block in the reentrant circuit.

INTRODUCTION: Previous mapping studies in patients with typical atrial flutter have demonstrated the crista terminalis to be a posterior barrier of the reentrant circuit forming a line of block. However, the functional role of the crista terminalis in patients with or without a history of atrial flutter is not well known. The aim of this study was to determine whether the conduction properties of the crista terminalis are different between patients with and those without a history of atrial flutter. METHODS AND RESULTS: The study population consisted of 12 patients with clinically documented atrial flutter (group 1) and 12 patients with paroxysmal supraventricular tachycardia as well as induced atrial flutter (group 2). A 7-French, 20-pole, deflectable Halo catheter was positioned around the tricuspid annulus. A 7-French, 20-pole Crista catheter was placed along the crista terminalis identified by the recording of double potentials with opposite activation sequences during typical atrial flutter. After sinus rhythm was restored, pacing from the low posterior right atrium near the crista terminalis was performed at multiple cycle length to 2:1 atrial capture. No double potentials were recorded along the crista terminalis during sinus rhythm in both groups. In group 1, the longest pacing cycle length that resulted in a line of block with double potentials along the crista terminalis was 638 +/- 119 msec. After infusion of propranolol, it was prolonged to 832 +/- 93 msec without change of the interdeflection intervals of double potentials. In group 2, the longest pacing cycle length that resulted in a line of block with double potentials along the crista terminalis was 214 +/- 23 msec. After infusion of procainamide, it was prolonged to 306 +/- 36 msec with increase of interdeflection interval of double potentials. CONCLUSION: The crista terminalis forms a line of transverse conduction block during typical atrial flutter. Poor transverse conduction property in the crista terminalis may be the requisite substrate for clinical occurrence of typical atrial flutter.

Adult↗
PubMed1998

Conditioning effect on the long latency potentials in the lower limb to transcranial magnetic stimulation.

OBJECTIVES: We used an electrical conditioning stimulation followed by transcranial magnetic stimulation (TMS) to facilitate the occurrence of long latency potentials (LLPs) in order to study the relationship between primary motor evoked potentials (MEPs) and LLPs in the lower limbs. MATERIALS AND METHODS: The study group included 6 healthy subjects, 1 patient with right thalamic infarction, and 3 patients with spinal cord injuries. The subjects were subjected to electrical conditioning (C) stimulation delivered to the left big toe at 250 Hz in a train of pulses of 20 ms duration prior to TMS (T) from 0 to 150 ms at an increment of 10 ms. The surface electromyographic signals were recorded at the tibialis anterior and gastrocnemius medialis for 400 ms. RESULTS: The C-T test facilitated both primary MEPs and LLPs with a pattern similar to the primary MEPs of its antagonist. There was no facilitation of the primary MEPs or LLPs in the affected limb of patients with thalamic or spinal cord lesions. CONCLUSION: At appropriate C-T interval, LLPs could be consistently provoked by TMS. The LLPs were absent in the patients with thalamic infarction and spinal cord injuries. It suggests that LLPs might be provoked through a supraspinal control.

Adult↗