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Biomedical subjects

C K Chen

Publications and source records attributed to C K Chen.

At least 109 records · Page 6Linked to original sources
PubMed1992

p140trk mRNA marks NGF-responsive forebrain neurons: evidence that trk gene expression is induced by NGF.

Nerve growth factor (NGF) appears to act as a neurotrophic factor for basal forebrain and caudate-putamen cholinergic neurons. The mechanism by which NGF transduces its signal in these neurons is yet to be defined. Recent data indicate that the product of the trk gene, p140trk, is a critical component of the NGF receptor. Herein, we show that p140trk mRNA is highly restricted in its distribution in the adult rat forebrain, that it is present in cholinergic neurons, and that most if not all cholinergic neurons contain p140trk mRNA. Furthermore, induction of trk expression by NGF suggests that neurotrophin-mediated up-regulation of their receptor tyrosine kinases is an important feature of their actions and that neurotrophins may regulate the activity of responsive neurons through increasing the level of their receptors.

Animals↗
PubMed1992

N-methyl-D-aspartate-mediated injury enhances quisqualic acid-stimulated phosphoinositide turnover in perinatal rats.

Previous work in our laboratory demonstrated that ischemic-hypoxic brain injury in postnatal day 7 rats causes a substantial increase in phosphoinositide (PPI) turnover stimulated by the glutamate analogue quisqualic acid (QUIS) in the hippocampus and striatum. To examine this phenomenon in more detail, we performed similar experiments after producing injury by unilateral intracerebral injections of the glutamate analogue N-methyl-D-aspartate (NMDA). The 7-day-old rodent brain is hypersensitive to NMDA neurotoxicity and NMDA injection causes histopathology that closely resembles that produced by ischemia-hypoxia. NMDA, 17 nmol in 0.5 microliter, was injected into the right posterior striatum of 7-day-old rat pups and they were killed 3 days later. Hippocampal or striatal tissue slices were prepared from ipsilateral and contralateral hemispheres from vehicle-injected control and from noninjected control rat pups. Slices were then incubated with myo-[3H]inositol plus glutamate agonists or antagonists in the presence of lithium ions and [3H]inositol monophosphate ([3H]IP1) accumulation was measured. The glutamate agonists, QUIS, L-glutamic acid, and (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, stimulated greater [3H]IP1 release in tissue ipsilateral to the NMDA injection compared with that in the contralateral side and in control pups. The glutamate antagonists, D,L-2-amino-7-phosphonoheptanoic acid, 3-[(+)-2-carboxypiperazin-4-yl]-propyl-1-phosphoric acid, kynurenic acid, and 6,7-dinitroquinoxaline-2,3-dione did not inhibit QUIS-stimulated [3H]IP1 release. The enhanced PPI turnover in the lesioned tissue was specific to glutamate receptors because carbachol (CARB) failed to elicit preferential enhanced stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1992

Eikenella corrodens in human oral and non-oral infections: a review.

There is substantial evidence in support of the existence of distinct clinical forms of human periodontal disease. Moreover, these different forms of periodontal disease may be associated with relatively distinct subgingival microflora, often involving microaerophilic or anaerobic Gram-negative bacterial species. Eikenella corrodens is a facultative Gram-negative bacillus which is a common inhabitant of the oral cavity and the intestinal and genital tracts. Its primary ecologic niche within the oral cavity appears to be dental plaque, both in periodontally healthy individuals and in periodontitis patients. However, E. corrodens is recognized as an infrequent human pathogen capable of causing extraoral infections, either as the sole infectious agent or as part of a mixed infection, its potential role in the etiology of periodontal disease is not well understood. E. corrodens is often present in the supra- and subgingival plaque of periodontally healthy subjects. On the basis of cross-sectional and longitudinal studies, E. corrodens appears to be somewhat more prevalent in subgingival plaque samples of periodontitis subjects than periodontally healthy individuals. However, the percentage of E. corrodens in the total cultivable microflora did not vary between the two groups. Microbiologic studies attempting to define the relationship between E. corrodens and periodontal disease assume that this species is essentially homogeneous and that all strains exhibit comparable pathogenic potential. However, E. corrodens exhibits 1) variable colony morphology, biochemical and serologic reactivity; 2) marked phenotypic diversity with respect to outer membrane protein and lipopolysaccharide structure; and 3) marked diversity in the restriction patterns of total genomic DNA. Thus, it is possible that a limited number of clones of E. corrodens may be associated with periodontal disease and/or extraoral infection, while other strains are relatively harmless commensals. Additional studies, possibly employing strain-specific nucleic acid probes, may be required to define the role of E. corrodens as a human periodontal pathogen.

Animals↗
PubMed1992

Experience of six patients with Vibrio vulnificus septicemia.

Vibrio vulnificus, a halophilic lactose fermenting vibrio, is a virulent pathogen for men and is frequently associated with overwhelming infections of areas other than the gastrointestinal tract. We encountered six cases of Vibrio vulnificus septicemia in Veterans General Hospital-Taipei over the past four years. All were admitted through the emergency room and presented with urgent conditions on arrival. The patients also demonstrated preexisting liver function impairment (either hepatic disease or chronic alcohol consumption). Five subjects had an apparent history of exposure to marine environments: one fisherman with pre-existing wounds and four others with previous consumption of poorly cooked seafood. Characteristic hemorrhagic bullous lesions were found in 5 cases. In all, 4 patients (67%) died with three of the cases within 24 hours of hospitalization. Misdiagnosis and delayed treatment were the most common causes. In conclusion, when patients present with sepsis and/or characteristic cutaneous lesions, particulously those with underlying liver disease and a history of marine exposure, clinicians should be alerted to this potentially fatal infection and should commence appropriate assessment and treatment immediately.

Adult↗
PubMed1991

The severity of excitotoxic brain injury is dependent on brain temperature in immature rat.

The effect of brain temperature on the severity of excitotoxic brain injury was evaluated in perinatal rats. Postnatal day (PND) 7 rats received unilateral intrastriatal injections of 25 nmol N-methyl-D-aspartate (NMDA) and then were exposed for 2 h to one of six different ambient temperatures. Animals were sacrificed 5 days later and the severity of brain injury was assessed quantitatively by comparison of the weights of the injected and contralateral cerebral hemispheres. Injection of NMDA consistently produced extensive unilateral brain injury in rats maintained at normothermia (36 degrees C ambient temperature; 29 +/- 1.8% reduction in the weight of the injected hemisphere). In the range of ambient temperatures between 25 degrees C and 40 degrees C, there was a linear relationship between temperature and the severity of NMDA-induced injury (r2 = 0.95, P less than 0.001, linear regression). In a separate analysis, in PND 7 rats, a positive linear relationship between ambient temperature (28 degrees C and 40 degrees C) and brain temperature was observed (r2 = 0.96, P less than 0.001). These data suggest that the severity of excitotoxic brain injury is dependent upon brain temperature.

Animals↗
PubMed1991

Nephrotic syndrome associated with acquired immunodeficiency syndrome in children.

We report here the cases of 15 children in whom nephrotic syndrome developed, from among 164 children (55% male, 90% black) followed in our acquired immunodeficiency syndrome clinic from 1984 through 1990. Mean age at onset of nephrotic syndrome was 4.9 +/- 2.6 years. Fourteen patients were black and one was Hispanic. Seventy-three percent of our patients with nephrotic syndrome were girls. The mean duration of clinical acquired immunodeficiency syndrome before development of nephrotic syndrome was 1.7 +/- 1.1 years. In eight patients, nephrotic syndrome appeared between 3 and 11 months after intravenous infusions of immune globulin or albumin were administered as part of a research protocol; this incidence (8/47) was higher than the incidence of nephrotic syndrome among those who did not receive intravenous infusions (7/117, p less than 0.05). Tissue for histologic examination was available for 80% of the patients, and histologic examination demonstrated mesangial hypercellularity (5 patients), focal segmental glomerulosclerosis (4 patients), minimal change disease (2 patients), and IgM nephropathy (1 patient). Deposition of one or more immunoglobulins was noted in all but one patient studied with immunofluorescence. Corresponding electron-dense deposits were seen by electron microscopy in 78% of specimens. Prednisone did not induce a remission of nephrotic syndrome in the 13 patients treated, whereas cyclosporine did so in the 3 patients to whom it was administered. Five patients were in the end stage of renal disease within 8 months. Successful maintenance peritoneal dialysis was performed in three patients, but 80% of patients have died of human immunodeficiency virus-related complications; one patient was lost to follow-up. We conclude that immune-complex deposition is consistently seen in children with human immunodeficiency virus-associated nephrotic syndrome. This nephrotic syndrome is resistant to steroid therapy, but we observed a remission of the proteinuria with cyclosporine therapy in three patients. For patients with end-stage renal disease, maintenance peritoneal dialysis may improve the quality of life.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Molecular action of tricholin, a ribosome-inactivating protein isolated from Trichoderma viride.

An extracellular protein was isolated from a species of soil-borne fungi (Trichoderma viride) and its amino acid composition has been determined. The protein is acidic with a molecular mass of 14,200 daltons and is given the trivial name tricholin. Tricholin is a potent inhibitor of cell-free protein synthesis. When rabbit reticulocyte lysate was incubated with tricholin at a concentration of 6.3 x 10(-7) M, it completely abolished the capacity of the lysate to support protein synthesis. The inhibition appears to be due to its reaction to ribosomes, since it generates a specific cleavage product, an alpha-sarcin RNA fragment, from reticulocyte ribosomal RNA. This reaction to ribosomes mimics that of alpha-sarcin. The antibody of alpha-sarcin strongly cross-reacts with tricholin, while the antibody of tricholin shows a weak reaction with alpha-sarcin.

Cell-Free System↗
PubMed1991

Human immunoglobulin G antibody response to iron-repressible and other membrane proteins of Porphyromonas (Bacteroides) gingivalis.

The human immunoglobulin G (IgG) immune response against Porphyromonas (Bacteroides) gingivalis A7A1-28 iron-repressible membrane proteins (IRMPs) and other membrane proteins was examined by immunoblot analysis. Thirty sera from patients with adult periodontitis and 30 sera from periodontally healthy subjects were included. Iron limitation of P. gingivalis was achieved by growing bacteria in brain heart infusion broth supplemented with protoporphyrin IX and 250 microM alpha, alpha'-dypyridyl, a ferrous iron chelator. Iron-sufficient growth was achieved by growing bacteria in the same medium without alpha, alpha'-dypyridyl. Human sera, in particular those from patients with periodontitis who exhibited high levels of IgG against whole cells of P. gingivalis A7A1-28 in serum in an enzyme-linked immunosorbent assay (ELISA), commonly reacted with five membrane proteins with apparent molecular masses of 80, 67.5, 51, 40.5, and 28 kDa and four IRMPs of 46, 43, 37.5, and 22 kDa. More than 80% of the sera from patients with periodontitis and high levels of IgG against strain A7A1-28 in serum by ELISA reacted with the 46-, 43-, and 37.5-kDa IRMPs, and 40% of these subjects expressed immunoreactivity against the 22-kDa IRMP. Sera from patients with periodontitis and low levels of IgG against strain A7A1-28 in serum by ELISA and sera from periodontally healthy subjects exhibited less immunoreactivity against IRMPs and the five membrane proteins of P. gingivalis. The present study indicates that P. gingivalis IRMPs are immunogenic and that these proteins are expressed in vivo.

Antibodies, Bacterial↗
PubMed1990

Outer membrane protein and lipopolysaccharide heterogeneity among Eikenella corrodens isolates.

Outer membrane protein (OMP) and lipopolysaccharide (LPS) phenotypic diversity among 27 oral and extraoral strains of Eikenella corrodens was assessed by SDS-PAGE. Each strain exhibited one to three major protein bands in the 35- to 41.5-kDa range and one or two protein bands of lesser density in the 24.5- to 28-kDa range. Eleven OMP patterns were distinguished among the strains. While oral strains obtained from periodontally healthy and diseased subjects exhibited diverse OMP patterns, five of six strains from extraoral sites of infection expressed an identical OMP pattern. Comparison of the electrophoretic mobilities of LPS from these same strains revealed that E. corrodens LPS consists primarily of low apparent molecular mass forms. Sixteen different LPS phenotypes were differentiated among the strains, with no apparent correlation between LPS phenotype and clinical setting. Strains expressing the same OMP pattern frequently expressed variable LPS phenotypes and vice versa. Analysis of OMP or LPS pattern by SDS-PAGE may be useful in taxonomic and epidemiologic studies of E. corrodens. Additional studies assessing the potential influence of OMP composition on invasiveness of this organism appear warranted.

Bacterial Outer Membrane Proteins↗
PubMed1990

DNA homologies shared among E. corrodens isolates and other corroding bacilli from the oral cavity.

In a previous microbiological study of Eikenella corrodens, we noted the presence of E. corrodens strains with variability in colony morphology, as well as other corroding bacilli phenotypically similar to E. corrodens but which were unidentifiable on the basis of biochemical reactions. This raised questions as to whether E. corrodens constitutes a genetically heterogeneous group of organisms, and whether the unidentified corroding bacilli represent atypical E. corrodens or genetically unrelated organisms. In the present study, the genetic relationship among 14 E. corrodens isolates and 6 unidentified corroding bacilli was examined. DNA base compositions were determined from the melting temperatures of DNA samples. DNA homologies among E. corrodens and corroding bacilli were determined by DNA hybridization in solution using S1 nuclease. The % G + C content of E. corrodens strains varied from 56 to 58%, and from 56 to 60% for unidentified corroding bacilli. The DNA homologies among 12 E. corrodens isolates and 2 reference strains varied from 57 to 97%. Although these E. corrodens isolates exhibited variabilities in colony morphology and biochemical profile, no subspecies was identified. The unidentified corroding bacilli shared less than 33% homology with either of the E. corrodens reference strains. These corroding bacilli were further divided into 3 species on the basis of DNA hybridization studies using radiolabeled DNA from 2 representative corroding bacilli. One of the unidentified corroding bacilli appears to be a component of the normal flora in the human oral cavity. Our results indicate that E. corrodens is a genetically homogeneous species containing no recognizable subspecies.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteria↗
PubMed1990

Restriction endonuclease analysis of Eikenella corrodens.

Eikenella corrodens is a gram-negative facultative bacillus commonly found in the oral cavity. Although the role of E. corrodens in periodonititis is not clear, its isolation from extraoral infections attests to its pathogenic potential. Previous studies suggested that this species is phenotypically diverse. In the present study, we used restriction endonuclease analysis (REA) to assess the genetic diversity of this species and to explore the applicability of REA in studying the transmission of E. corrodens. Two groups of E. corrodens isolates were used in this study. Group 1 included 47 epidemiologically independent isolates recovered from dental plaques in periodontally healthy subjects and periodontitis patients and from extraoral infections in different geographic areas. Group 2 E. corrodens included 40 isolates recovered from two periodontitis patients and two periodontally healthy subjects. The results indicated that E. corrodens is genetically heterogeneous, as determined by REA. The majority of the group 1 E. corrodens isolates exhibited strain-specific restriction patterns. Forty restriction patterns were distinguishable among the 47 isolates. Analyses of group 2 isolates revealed that three of four subjects harbored more than one clonal type of E. corrodens. In one instance, a periodontitis patient was found to be colonized by six different clones. Furthermore, two different clonal types of E. corrodens were recovered from a single periodontal pocket in this patient. The results indicated that REA may be a useful tool in the epidemiologic investigation of E. corrodens infections.

Bacteroides↗
PubMed1990

Assessment of periodontal disease in an adult population survey in Taipei city using CPITN and GPM/T indices.

The community periodontal index of treatment needs (CPITN) has been recommended for epidemiological surveys of periodontal status and treatment needs. The prevalence of gingivitis, periodontitis and missing teeth in a study population has been determined using the CPITN and GPM/T (gingivitis: periodontitis: missing teeth) indices. In this study, a survey of periodontal disease was performed among the adult population of Taipei City using the CPITN index. A total of 673 dentated persons (male 339, 50.4%; female 334, 49.6%) were examined and surveyed. Data were then divided into five age groups, 15-19, 20-29, 30-44, 45-64 and 64+. The prevalence of periodontal disease was analyzed using the percentage or sextant from all teeth. Treatment needs were determined by the worst periodontal score per sextant. It was found that about 91% of subjects suffered from various degrees of periodontal disease in at least one tooth. Gingivitis and periodontitis were 86.9% and 33%, respectively. Among them 48.9% had missing teeth. The prevalence of periodontitis and missing teeth increased with age. Most of them involved oral hygiene instruction and scaling. About 11.0% of the subjects needed periodontal surgery. Higher proportions of attachment loss with gingival recession caused by destructive periodontal disease were found in older persons who did not require periodontal surgery. It was concluded that endemic gingivitis and calculus, a moderate prevalence of shallow pockets and a low prevalence of deep pockets were observed among adults in this group in Taipei City and that the CPITN is a practical epidemiological and public health method for screening the periodontal status and treatment needs of a population.

Adolescent↗
PubMed1989

A new protein subunit k for RNA polymerase from Xanthomonas campestris pv. oryzae.

During the purification of RNA polymerase from Xanthomonas campestris pv. oryzae, a new subunit named k was found to be associated with this enzyme. The removal of subunit k from holoenzyme by DEAE-cellulose column chromatography results in a decrease in specific activity of the enzyme. The readdition of subunit k to subunit k-depleted holoenzyme results in restoration of enzymatic activity. Subunit k increase the activity of RNA polymerase; the activation was in proportion to the concentration of subunit k added. Antiserum against holoenzyme devoid of subunit k was prepared. This antiserum did not react with purified subunit k; therefore, subunit k may not be the proteolytic fragment of the beta, beta', sigma, or alpha subunit. When this antiserum was used to precipitate RNA polymerase obtained from a crude extract of bacterial cells, subunit k was coprecipitated as determined by sodium dodecyl sulfate gel electrophoretic analysis. The molecular mass of subunit k is approximately 29 kDa, and the molar ratio of beta:beta':sigma:alpha:k was estimated to be 1:1:1:2:4. When native Xp10 DNA was used as template, subunit k stimulated subunit k-depleted holoenzyme, but not core enzyme. When the synthetic polynucleotide poly[d(A-T)] was used, subunit k activated both subunit k-depleted holoenzyme and core enzyme. Subunit k also activated the binding of RNA polymerase to template DNA.

Chromatography↗
PubMed1989

Difluorothromboxane A2 and stereoisomers: stable derivatives of thromboxane A2 with differential effects on platelets and blood vessels.

The present study reports on the selective effects on human platelets and canine saphenous veins of four stable difluorinated analogues and thromboxane A2 (TXA2), in which the characteristic 2,6-dioxa[3.1.1]bicycloheptane structure of TXA2 has been retained. The four compounds differ in their stereochemistry of the 5,6 double bond and/or the 15-hydroxyl group. Only 10,10-difluoro-TXA2 (compound I) with the natural stereochemistry of TXA2 was an agonist in both platelets and canine saphenous veins (EC50 = 36 +/- 3.6 nM and 3.7 +/- 0.8 nM, respectively). (15R)-10,10-Difluoro-TXA2 (compound II), (5E)-10,10-difluoro-TXA2 (compound III), and (5E,15R)-10,10-difluoro-TXA2 (compound IV) were antagonists of platelet aggregation stimulated by compound I (Kd = 98 +/- 46 nM, 140 +/- 42 nM, and 1450 +/- 350 nM, respectively). However, compounds II, III, and IV stimulated contraction of canine saphenous veins (EC50 = 36 +/- 4.4 nM, 31 +/- 6.8 nM, and 321 +/- 50 nM, respectively). All four compounds could displace the TXA2/prostaglandin H2 antagonist 9,11-dimethylmethano-11,12-methano-16-(3- 125I-4-hydroxyphenyl)-13,14-dihydro-13-aza-15 alpha beta-omega-tetranor-TXA2 from its platelet receptor (Kd values = 100 +/- 30 nM, compound I; 280 +/- 60 nM, compound II; 230 +/- 70 nM, compound III; and 1410 +/- 1020 nM, compound IV). These results support the existence of two subtypes of TXA2/prostaglandin H2 receptors and emphasize the importance of the stereochemical requirements of these TXA2 analogues for interaction with these receptors. These stable fluorinated TXA2 analogues should prove useful tools for the further characterization of these and other TXA2/prostaglandin H2 receptors.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1989

Eikenella corrodens in the human oral cavity.

The prevalence and distribution of the putative periodontal pathogen Eikenella corrodens in the human oral cavity was examined. A total of 508 oral bacterial samples were taken from 10 periodontally healthy adults (PH), 11 adult periodontitis patients (AP), and 6 localized juvenile periodontitis patients (LJP). From each subject, samples of supra- and subgingival plaque were obtained from six to eight teeth as well as samples from buccal mucosa, lateral and dorsal surfaces of tongue, tonsil, and saliva. E. corrodens was cultured from 70% of healthy subjects and 100% of periodontitis patients. Dental plaque appears to be the main oral ecological niche of E. corrodens in PH subjects since it was found in, respectively, 26% and 31% of supra- and subgingival plaque samples and rarely found in other oral sites in these subjects. It was found in 59% of both supra- and subgingival plaque samples from AP subjects, as well as 48% and 64% of supra- and subgingival plaque samples of LJP subjects. In contrast to healthy subjects, E. corrodens was found on the buccal mucosa, tongue, tonsil and in the saliva of patients with periodontitis. The microorganism constituted, on average, 1% to 2% of the total cultivable bacteria in supra- and subgingival plaque samples. The prevalence of E. corrodens in plaque samples was higher in AP and LJP subjects and was significantly different from PH subjects. Within the AP group, the prevalence of E. corrodens in subgingival plaque is significantly higher from sites with GI greater than or equal to 2. These data suggest that E. corrodens is an indigenous oral microorganism which may be an opportunistic pathogen associated with gingival inflammation.

Adolescent↗