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Biomedical subjects

C T Chen

Publications and source records attributed to C T Chen.

At least 127 records · Page 7Linked to original sources
PubMed1996

Muscarinic acetylcholine receptor subtype mRNAs in the human and rat vestibular periphery.

The expression of the five muscarinic acetylcholine receptor (mAChR) subtypes (m1-m5) in the vestibular end-organs and in the primary afferent vestibular ganglia of the human and rat was studied using RT-PCR from the two tissue populations from both species. In the human, although all five mAChR subtypes were expressed in brain, only the m1, m2, and m5 mAChR subtypes were amplified from both the vestibular ganglia and the vestibular end-organs, while in the rat, all five mAChR subtypes were expressed. These data suggest that the efferent cholinergic axo-dendritic and axo-somatic synapses have a muscarinic component and that there are pharmacologic implications for patients with vestibular dysfunction.

Animals↗
PubMed1996

Mediation of signal transduction in keratinocytes of human middle ear cholesteatoma by ras protein.

Immunolocalization was used to investigate the distribution of ras protein in both congenital and acquired cholesteatoma tissues. A pathological feature of middle ear cholesteatoma included accumulation of keratin debris due to active proliferation and differentiation of keratinocytes. Ras protein localized to the inner plasma membrane and cytoplasm of keratinocytes in all of the epithelial layers in both congenital and acquired cholesteatoma specimens. Keratinocytes in the basal layer were stained more intensely than their differentiated counterparts. Findings also demonstrated that receptors for epidermal growth factor, fibroblast growth factor, and plateletderived growth factor were present in the plasma membrane of keratinocytes. C-jun, a transcription factor was found in the nuclei of keratinocytes of the cholesteatoma epithelium. These findings indicate that ras protein plays a pivotal role in a signal transduction cascade between growth factor receptors in the plasma membrane and the transcription factor, c-jun, in the nuclei of keratinocytes during the growth of cholesteatoma.

Cholesteatoma, Middle Ear↗
PubMed1996

Computed tomography in the diagnosis of organic bowel obstruction.

BACKGROUND: This study examined the usefulness of computed tomography (CT) scan for cases of organic intestinal obstruction, with two simple criteria. METHODS: One hundred and thirteen patients with clinical suspicion of bowel obstruction were referred for CT scans. A line was drawn between the dilated proximal, and the collapsed distal bowels. A careful search was conducted on this line for obstructive lesions. The results were reported to be organic obstruction if there was an abrupt change of caliber (Criterion I) or a soft tissue mass around the dilated bowel (Criterion II). The judgement based on the CT findings. RESULTS: Eighty-eight cases proved to have bowel obstruction. With Criterion I, the sensitivity was 59.1%, and specificity, 88% with Criterion II, the sensitivity was 56.3% and specificity 100%. If either of them was considered to be a positive sign of organic obstruction, the sensitivity was 100%, the specificity 88% and the accuracy 97.3%. The nature of the obstructions were precisely predicted in 76 patients (86%). CONCLUSIONS: With these two simple criteria, CT scan can achieve high accuracy and is a recommendation in virtually every instance when intestinal obstruction is suspected.

Adult↗
PubMed1996

Light-induced fluorescence spectroscopy: a potential diagnostic tool for oral neoplasia.

For the early detection of oral neoplasia, light-induced fluorescence spectroscopy was used to measure the fluorescence emission of malignant (squamous cell carcinoma & verrucous carcinoma) and premalignant (epithelial dysplasia, hyperkeratosis & lichen planus) oral tissues as well as normal oral mucosa ex vivo to assess the ability of this technique to distinguish neoplastic from normal oral tissues. The emission spectra of histologically normal and neoplastic oral tissues were obtained under excitation wavelengths varied from 270 nm to 400 nm at 10-nm intervals. At 300-nm excitation, the most intensely fluorescent peak occurred at 330-nm and 470 nm emission. At 330-nm emission, the spectrum of the malignant oral tissue was significantly stronger than that of the normal oral mucosal tissue after area normalization. However, at 470-nm emission, the spectrum of the malignant oral tissue was significantly weaker than that of the normal oral mucosal tissue. A diagnostic algorithm based on the ratio of relative intensities of 330 nm to 470 nm emission within the +/-5 nm peak area of each sample was calculated and paired. The histogram of ratios showed that histologically neoplastic oral tissues could be distinguished from normal oral mucosal tissues using the 300 nm excitation wavelength. The average ratio of malignant or premalignant oral samples was significantly greater than that of the normal oral mucosal samples (p < 0.001). This ex vivo study indicated that fluorescence spectroscopy may be useful in differentiating malignant or premalignant oral tissue from normal oral mucosa.

Areca↗
PubMed1995

Immunogenicity of mastoparan B, a cationic tetradecapeptide isolated from the hornet (Vespa basalis) venom, and its structural requirements.

Mastoparan B (MP-B) is a cationic tetradecapeptide (LKLKSIVSWAKKVL-CONH2, mol. wt 1611) isolated from the black-bellied hornet (Vespa basalis) venom. The small peptide itself was capable of inducing antibodies without prior conjugation to a protein carrier in rabbits and mice. The mouse antibody was found to be of IgG1 isotype with kappa-type light chain. The peptide antigen was able to form insoluble complexes with the specific antibody, suggesting that MP-B possessed more than one epitope in its molecule. The finding that MP-B was able to bind with both mouse and rabbit antibodies in sandwich ELISA supports this contention. Synthetic MP-B analogues in which lysine at position 2, 4, 11 or 12 was replaced by neutral amino acids such as asparagine or leucine showed a significant decrease in their antibody-binding activities. Substitution of lysine at position 4 (Lys4) caused the most marked inhibition in its binding activity. However, replacing tryptophan at position 9 by tyrosine caused a relatively small reduction in its binding activity. Replacing both Lys2,4 by asparagine or removing Lys-containing segments at amino or carboxyl terminus in MP-B sequence caused a remarkable decrease in the antibody-binding and immunogenic activities of the peptide. The Lys residues located at amino and carboxyl terminal segments of MP-B, especially Lys4, appear to play a critical role in the binding interaction and the immunogenicity of the peptide.

Amino Acid Sequence↗
PubMed1995

Regulation of cholesterol side-chain cleavage cytochrome P450 in mouse testis Leydig cell line I-10.

We have characterized regulation of steroidogenesis in a mouse testis Leydig cell line, I-10. Progesterone secretion was increased in a time- and dose-dependent fashion by 8-Br-cAMP treatment. The amount of cholesterol side-chain cleavage enzyme (P450scc), the first and rate-limiting enzyme for the synthesis of steroids, as detected by immunoblotting, was also increased. The calcium ionophore A23187 decreased the amount of P450scc, but it did not interfere with cAMP stimulation of the accumulation of P450scc. This regulation of P450scc expression by cAMP and A23187 is at the post-transcriptional level because the amount of P450scc mRNA was not affected by either treatment. This result was further confirmed by direct measurement of transcription in the presence or absence of forskolin treatment. I-10, however, supported cAMP-dependent transcriptional activation of the exogenous gene, as shown by the increased expression of a reporter gene under the control of the -600 to -2,500 fragment of the P450scc gene. The ability for transcriptional activation of the exogenous but not endogenous P450scc gene makes I-10 a unique steroidogenic cell line.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1995

Actinobacillus actinomycetemcomitans pneumonia with chest wall and subphrenic abscess.

A 14-year-old girl had progressive dyspnea and right lower chest pain for about 1 1/2 months and a weight loss of 3 kg in 2 months. Chest X-ray revealed right pleural effusion and a round infiltration over the right lower chest, initially suspected to be malignant. Image study revealed consolidation in the right middle and lower lobes with abscess-like lesions around the right lower pleura and transdiaphrenic involvement to the subphrenic region. The lesion had also invaded the intercostal muscle. The pleural abscess was obtained by fiberoptic thoracoscopy, and culture of the pus grew typical colonies of Actinobacillus actinomycetemcomitans. After the causative microorganism had been identified, cefoxitin was given for 2 weeks followed by oral amoxicillin (250 mg/6 h) for a total period of 3 months. Follow-up chest X-ray revealed resolution of the lung lesions and the patient recovered gradually without any sequelae.

Abscess↗
PubMed1995

Pulmonary nocardiosis in a child with systemic lupus erythematosus: report of a case.

Nocardiosis is an uncommon complication in children with systemic lupus erythematosus (SLE). This is a case report of pulmonary nocardiosis in a 13 year-old girl with SLE, who presented with fever, chest pain and tachypnea. She had been treated with steroids and cytotoxic agents for five months. Nocardia asteroides was isolated from a surgical specimen culture. The pulmonary nocardiosis was treated by surgical excision in combination with trimethoprim-sulfamethoxazole. Nocardia sp should be considered as a possible agent of infection in immunocompromised patients, especially those treated with corticosteroids at the time of infection.

Adolescent↗
PubMed1995

Characterization of DNA extracted from archival celloidin-embedded human temporal bone sections.

The focus of the present investigation was to study, via molecular biology techniques, the character of the DNA present in individual archival celloidin-embedded human temporal bone sections. Polymerase chain reaction (PCR) amplification of 92 base pair (bp), 121 bp, and 471 bp regions of mitochondrial DNA (mtDNA) extracted from a single archival celloidin-embedded human temporal bone section was used to assess the length of the template DNA extracted. The effects of digestion time and sample motion during the extraction method on DNA concentration was also studied. These data are crucial to determine the limits of applying PCR technology to amplify specific genomic DNA targets located within the human inner ear. Further development of these methods will allow additional molecular temporal bone pathologic studies to be completed and, more specifically, hypotheses regarding the molecular etiopathogenesis of many auditory, vestibular, and facial nerve disorders, such as autoimmune hearing loss, congenital hearing losses, Meniere's disease, otosclerosis, or Bell's palsy could be tested. The results described should be of great value to those investigators extracting DNA from archival individual human temporal bone sections for PCR assays of specific genetic alterations or infectious agents associated with temporal bone pathologies.

Base Sequence↗
PubMed1995

Endogenous endothelium-derived relaxing factor inhibits platelet adhesion under whole blood flow conditions ex vivo.

In this study, we used carbachol to stimulate the endogenous endothelium-derived relaxing factor (EDRF) release in male Sprague-Dawley rats. One ml of native blood was drawn from the femoral artery and directly passed through a parallel-plate flow chamber. This system allowed us to examine ex vivo platelet adhesion to fibrinogen-coated surface under whole blood flow conditions. Our results demonstrated that 1) the intravenous administration of carbachol induced a transient decrease of blood pressure, reduction in platelet adhesion ex vivo, and elevation in platelet cGMP level; 2) coadministration of carbachol with hemoglobin, a scavenger of EDRF, inhibited these carbachol effects; 3) the administration of hemoglobin or N omega-nitro-L-arginine, an inhibitor blocking the NO synthesis pathway, caused elevated blood pressure in vivo, increased platelet adhesion ex vivo, and decreased cGMP content in platelets. We conclude that endogenous EDRF not only modulates vascular tone, but also influences platelet adhesion under flow conditions.

Animals↗
PubMed1994

Oncogenic ras stimulates a 96-kDa histone H2b kinase activity in activated Xenopus egg extracts. Correlation with the suppression of p34cdc2 kinase.

We previously showed that purified, bacterially expressed oncogenic human rasH protein blocks or delays the progression of the embryonic cell cycle into M-phase in activated Xenopus egg extracts. This block correlates with the suppression of the activation of p34cdc2 kinase (Pan, B.-T., Chen, C.-T., and Lin, S.-M. (1994) J. Biol. Chem. 269, 5968-5975). In an attempt to identify kinases that are involved in mediating the effect of oncogenic Ras on the cell cycle, we assayed aliquots of activated Xenopus egg extracts, which were incubated at 25 degrees C for various times in the absence and presence of oncogenic Ras, for their kinase activities toward a calf thymus histone fraction (Hf1). We find that the suppression of the histone H1 kinase activity of p34cdc2 by oncogenic Ras correlates with a simultaneous stimulation of a histone H2b serine kinase activity. Using a histone H2b in-the-gel kinase assay, we further show that the stimulated histone H2b kinase activity is attributed mainly to a 96-kDa kinase and slightly to p42mapk. Although Xenopus p90rsk is also activated by oncogenic Ras, we demonstrate that activated p90rsk is not responsible for the 96-kDa histone H2b kinase activity. The identity of the 96-kDa kinase remains unclear. Our data suggests that the 96-kDa kinase may be involved in mediating the effect of oncogenic Ras on the embryonic cell cycle of Xenopus.

Amino Acid Sequence↗
PubMed1994

Cardiovascular effects of mastoparan B and its structural requirements.

Mastoparan B is a cationic, amphiphilic tetradecaeptide (LKLKSIVSWAKKVL-CONH2) isolated from the venom of the hornet Vespa basalis. Intravenous injection of the peptide into rats caused a profound depression of blood pressure and cardiac function, which was inhibited by cyproheptadine, reserpine and multiple doses of compound 48/80, but not by diphenhydramine and cromolyn. Mastoparan from Paravespula lewisii showed little cardiovascular inhibitory activity. A synthetic mastoparan B analog in which lysine at position 2 was replaced by asparagine showed a marked decrease in the cardiovascular depressor effects, while replacing lysine at position 4, 11 or 12 with leucine did not cause a significant reduction in these effects. Replacing lysine at position 12 with leucine even caused a more sustained depressor effect. However, the analog in which lysines at positions 11 and 12 were replaced by leucine lost its cardiovascular inhibitory activity. Replacing tryptophan at position 9 with phenylalanine in mastoparan B did not affect its activity. It is concluded that mastoparan B is involved in the cardiovascular disturbances induced by the hornet venom. Lysine at position 2 is a critical residue for the cardiovascular effects of mastoparan B. A peptide molecule with two lysine residues, one located close to the amino terminus and the other near the carboxyl end of the peptide, appears to be the optimal structure for eliciting the cardiovascular depressor effects.

Amino Acid Sequence↗
PubMed1994

A miniature gamma camera.

We have described a mobile miniature-gamma-camera system for use in electrical trauma units and have presented images and imaging characteristics of a prototype system. The system has as its principal component a miniature gamma camera based on a PSPMT. The camera is 92 mm x 92 mm x 190 mm in size, weighs 5 kg, has a 48 mm x 48 mm field of view, and has an intrinsic resolution of approximately 3 mm FWHM and 6 mm FWTM. It is expected that devices of this type will be useful as imaging tools in electrical trauma units and laboratories where imaging studies regarding uptake mechanisms of radiopharmaceuticals for assessing tissue viability are carried out.

Electric Injuries↗
PubMed1994

Oncogenic Ras blocks cell cycle progression and inhibits p34cdc2 kinase in activated Xenopus egg extracts.

The effect of purified, bacterially expressed human RasH proteins on embryonic cell cycle progression in activated Xenopus egg extracts was studied. Bacterially expressed human oncogenic RasH protein is able to block the progression of the Xenopus embryonic cell cycle into M-phase. In contrast, the corresponding normal human Ras protein is relatively ineffective when assayed in a like manner. The observed arresting activity can be blocked by the addition of Y13-259 anti-Ras monoclonal antibody but not by nonspecific IgG. Oncogenic Ras also induces unique morphological changes in the reconstituted nuclei; the nuclei appear to be enlarged, and the chromatin partially condenses into fiber-like structures. This induced arrest is associated with suppression of p34cdc2 kinase activity, indicating that the oncogenic Ras protein induces the arrest by inactivating p34cdc2. This inactivation by oncogenic Ras protein does not result from inhibition of the synthesis of cyclin B or of the binding of the newly synthesized cyclin B to the p34cdc2.

Animals↗
PubMed1994

Distal phalanx replantation.

Microsurgical replantation has been attempted in the distal phalanx of the digits. Twenty-three complete, single digit amputations are reviewed. The patients' ages ranged from 9 months to 48 years. Viability was 78%. Sensory recovery averaged 7 mm static two-point discrimination. Range of motion in the distal interphalangeal joint of the finger and the interphalangeal joint of the thumb averaged 64 and 51 degrees, respectively. Eight of the 17 successfully replanted digits had mild to moderate atrophy. Eighty-two percent of patients were able to use the replanted digit successfully in their daily work. We feel that distal digital replantation is rewarding. In successful cases, it always preserves acceptable function and good appearance at a price of an average of 2.3 months off work.

Adolescent↗
PubMed1994

Population structure of the Japanese eel, Anguilla japonica.

Mitochondrial DNA (mtDNA) sequences that include (a) a part of the cytochrome b gene, (b) two tRNA genes, and (c) a part of the noncoding D-loop region of 31 Anguilla japonica (Japanese eel) and 1 A. marmorata collected from Taiwan, Japan, and mainland China were determined to evaluate the population structure of Japanese eel. Among 30 genotypes identified from the 31 Japanese eel mtDNAs sequenced, there are 58 variable sites, predominantly clustered at the D-loop region. The phylogenetic tree constructed by the unweighted pair-group method with arithmetic mean shows neither significant genealogical branches nor geographic clusters. Furthermore, the sequence-statistics test reveals little, if any, significant genetic differentiation. These results indicate that the 31 Japanese eels might come from a single population. Analysis of sequence variation in mtDNA by using the relationship between the number of segregating sites and the average number of nucleotide differences under the neutral mutation hypothesis reveals that neutral mutation acts as a major factor influencing the evolutionary divergence of the Japanese eel mitochondrial genome sequenced, especially in the noncoding region.

Animals↗