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Biomedical subjects

W C Chen

Publications and source records attributed to W C Chen.

At least 109 records · Page 6Linked to original sources
PubMed1998

Structures and biological activities of new wasp venom peptides isolated from the black-bellied hornet (Vespa basalis) venom.

The black-bellied hornet (Vespa basalis) is the most dangerous species of vespine wasps found in Taiwan. The hornet possesses a highly toxic venom which is rich in toxin, enzymes and biologically active peptides. Using ultrafiltration to remove the high molecular weight toxin and enzymes followed by reverse-phase HPLC, three bioactive tridecapeptides, designated "HP-1, HP-2 and HP-3" were isolated from the venom. Their amino acid sequences were determined as: HP-1: LFRLIAKTLGSLM, HP-2: LFRLLANTLGKIL, HP-3: IFGLLAKTLGNLF. The primary structures of these peptides appear to be homologous to those of chemotactic peptides isolated from other vespid venoms. However, these peptides show little chemotactic activity on human neutrophils and have distinct tripeptide sequences at the amino and carboxylic terminal sides, as compared with other hornet chemotactic peptides. The lack of Pro3 which is a characteristic structure of vespid chemotactic peptides in their sequences is most distinctive. Circular dichroism spectra of these peptides measured in 20% trifluoroethanol show a high content of alpha-helical conformation. All three peptides provoked local edema in rat hind paw, which could be inhibited by antihistamine (diphenhydramine) and drug with antiserotonin activity (cyproheptadine). These peptides also exhibited a potent hemolytic activity which was potentiated by a non-lytic dose of the hornet lethal protein, suggesting a supporting role of these peptides in the lethal effect of Vespa basalis venom.

Amino Acid Sequence↗
PubMed1998

Preparation and cytotoxic effect of ceanothic acid derivatives.

Six ceanothane and 1-norceanothane derivatives (1, 2, 8-11) were prepared from ceanothic acid dibenzyl ester. These ring-A homologues of betulinic acid exhibited cytotoxic effects. Among these, 1-decarboxy-3-oxo-ceanothic acid (2) was found to be the most cytotoxic against OVCAR-3 and HeLa cancer cell lines, with an IC50 of 2.8 and 6.6 microg/mL, respectively, and an IC50 of 11.3 microg/mL against normal cell line FS-5.

Antineoplastic Agents, Phytogenic↗
PubMed1998

Early stage nasopharyngeal carcinoma: radiotherapy dose and time factors in tumor control.

OBJECTIVE: To evaluate radiotherapy dose and length of treatment in the control of early stage nasopharyngeal carcinoma (NPC) treated with a combination of external radiotherapy and brachytherapy, MATERIALS & METHODS: We reviewed the records of 133 patients with early stage nasopharyngeal carcinoma (stage I or II, AJC/UICC staging system) who received definitive radiotherapy in Chang Gung Memorial Hospital from 1979 to 1991. The median follow-up time was 7.1 years with a minimum of 2 years. All patients were treated with megavoltage external radiotherapy to the nasopharynx area (63-72 Gy) followed by high dose rate intracavitary brachytherapy (5-16.5 Gy in one to three fractions, spaced 1-2 weeks apart). The median total dose and time of irradiation was 75 Gy (69.8-81.4 Gy) and 11.6 weeks (7.8-20 weeks) respectively. Survival analysis was used to examine the effect of several variables on prognosis. RESULTS: The 5-year rates were 86.4% for local control, 84.7% for disease free survival, 88.5% for actuarial survival and 84.2% for overall survival. The treatment group (combination of time and dose of irradiation) was the most important prognostic factor according to Cox's proportional hazard model. Patients receiving radiation at a total dose of < or = 75 Gy completed in < 12 weeks showed the best prognosis. CONCLUSION: Treatment time and total treatment dose are both important factors in treating early stage NPC. Decreasing the total radiation time to < 12 weeks and not exceeding a radiation dose of 75 Gy gave the best results.

Adult↗
PubMed1998

Elevated Fos expression in the nucleus tractus solitarii is associated with reduced baroreflex response in spontaneously hypertensive rats.

We delineated the functional role of Fos protein at the nucleus tractus solitarii in the manifestation of reduced baroreceptor reflex control of heart rate during hypertension, using spontaneously hypertensive rats (SHR), stroke-prone SHR, Wistar-Kyoto rats, or Sprague-Dawley rats. Microinjection into the bilateral nucleus tractus solitarii of an antisense oligonucleotide that targets against the initiation codon of c-fos mRNA significantly potentiated the baroreceptor reflex in response to 30 minutes of sustained increase in blood pressure. Of particular note was the restoration of both the impaired sensitivity and capacity of baroreceptor reflex in SHR and stroke-prone SHR to levels comparable to those in normotensive rats. Likewise, the number of Fos-immunoreactive nuclei evoked by the sustained increase in blood pressure in the caudal nucleus tractus solitarii of SHR and stroke-prone SHR was reduced, after this antisense c-fos treatment, to the basal level exhibited by the normotensive animals. Control treatment with the corresponding sense oligonucleotide, an antisense oligonucleotide that targets against a different portion of the coding sequence of the c-fos mRNA or artificial cerebrospinal fluid, on the other hand, elicited no discernible effect on either the baroreceptor reflex response or the induced expression of Fos protein in the nucleus tractus solitarii by baroreceptor activation. We also found that the basal level of Fos expression in the caudal nucleus tractus solitarii was significantly elevated in the SHR and stroke-prone SHR. Together, these novel findings suggest that an elevated expression of basal Fos protein in the NTS during hypertension may be associated with the dysfunction in baroreceptor reflex control of heart rate.

Animals↗
PubMed1998

Genetic variation of Porphyromonas gingivalis genes encoding gingipains, cysteine proteinases with arginine or lysine specificity.

Porphyromonas gingivalis hemagglutinating cysteine proteinases (gingipains) are considered as important virulence factors in the development of adult periodontitis. Using Southern blot analysis it was determined that genes of three distinct but related gingipains (gingipain-R1, gingipain-R2 and gingipain-K) were present in all tested strains including HG66, ATCC 33277, W50, E-20-1, EM-3, 381, A7436, and IKG5, with a region encoding a part of the hemagglutinin domain of gingipain-R1 and gingipain-K showing considerable variability. In contrast, the loci encoding gingipain-R1 (rgp1) and gingipain-R2 (rgp2) were strongly conserved excluding the concurrent occurrence of other gingipain-R-like genes such as cpgR and agp. Significantly, no evidence could be found to support the expression of a gene coding for the putative proteinase porphypain, an enzyme suggested to have both gingipain-R and gingipain-K activity.

Adhesins, Bacterial↗
PubMed1998

In vitro cytotoxic activity of 1-decarboxy-3-oxo-ceanothic acid in a human ovarian adenocarcinoma cell line.

The effect of a novel pentacyclic triterpene, 1-decarboxy-3-oxo-ceanothic acid (DOCA) on DNA synthesis, DNA degradation and programmed cell death was examined in human ovarian adenocarcinoma (OVCAR-3) cells. OVCAR-3 cells exposed to various concentrations of DOCA for 30 h displayed a dose-dependent inhibition of DNA synthesis. Morphologically, treatment with 10 microg/ml of DOCA for 24 h and 72 h resulted respectively in reduction in cell volume and condensation of nuclear structures. By agarose gel analysis, DNA fragmentation with the characteristic pattern of inter-nucleosomal ladder was observed after cells were treated with 2.5 microg/ml of DOCA for 24 h. Both cell death and DNA fragmentation caused by this compound were partially inhibited by the protein synthesis inhibitor cycloheximide, suggesting that the apoptotic process caused by DOCA requires synthesis of new proteins. On the other hand, no apparent double-stranded DNA breaks were detected after cells were incubated with 2.5 microg/ml of DOCA for 24 h, indicating that DNA damage was not a preceding event for apoptosis induced by this compound. Taken together, our results demonstrate that the cytotoxic effect of DOCA is mediated, at least in part, by the induction of apoptosis.

Adenocarcinoma↗
PubMed1998

Maximization of cholesterol oxidase production by Rhodococcus equi no. 23 By using response surface methodology.

Medium optimization for the production of cholesterol oxidase (EC 1. 1.3.6) by Rhodococcus equi no. 23 was investigated by using response surface methodology and a central composite design. Results revealed that cholesterol and yeast extract had positive effects and the interaction between any two of three factors had no significant effect on cholesterol oxidase production. The optimized medium was the basal medium with the addition of 2.30 g/l cholesterol, 8.18 g/l yeast extract and 4.10 ml/l Tween 80. The peak cholesterol oxidase production (0.242 unit/ml) after 60-72 h cultivation was approx. 4-fold that in control medium.

Carbon↗
PubMed1997

TPA induces translocation but not down-regulation of new PKC isoform eta in macrophages, MDCK cells and astrocytes.

New type protein kinase C (PKC) eta was found to be expressed in RAW 264.7 and J774A.1 macrophages, Madin-Darby canine kidney (MDCK) cells and astrocytes by Western blot analysis. Both cytosol and membrane in macrophages and astrocytes express this isoform, however, the expression in the membrane is more abundant than that in the cytosol. On the other hand, only membrane PKC eta was detected in MDCK cells. Exposure of the cells to 1 microM TPA for 10 min resulted in the translocation of PKC eta from the cytosolic to the membrane fraction. This translocation maintained at a constant level after 1.5, 3, 6 and 24 h TPA treatment. However, another new type PKC delta which expressed in the macrophages and astrocytes was down-regulated after long-term (6 and 24 h) TPA treatment. The immunoreactive band of PKC eta in J774A.1 macrophages was blocked by the control PKC eta antigenic peptide. Incubation of RAW 264.7 macrophages with UTP (1, 10 and 100 microM) resulted in the accumulation of inositol phosphates, indicating the presence of P2 receptor-coupled PLC pathway in these cells. This natural activator UTP also induced translocation of PKC eta from cytosol to the membrane in RAW 264.7 macrophages after 1, 5 or 10 min treatment. Immunofluorescence microscopy revealed that in RAW 264.7 cells, PKC eta is located in the cytoplasm organelle, plasma membrane and nuclear envelope. Stimulation of the cells with TPA resulted in translocation to the plasma membrane. This translocation of PKC eta was still apparent after 24 h treatment with TPA.

Animals↗
PubMed1997

The role of the N-terminal leucine residue in snake venom cardiotoxin II (Naja naja atra).

The N-terminal leucine residue of snake venom cardiotoxin II (CTX II) (Naja naja atra) was systematically replaced with D-leucine (CTXII-L1-D-L), glycine (CTXII-L1G) or deleted [CTXII-(2-60)] to study the role of leucine residue in CTX II molecule. CTX II, CTXL1-D-L, CTXL1G and CTX(2-60) were produced by chemical synthesis method and purified by high performance liquid chromatography. Owing to folding problem in CTXII-(2-60), only CTX II, CTXII-L1-D-L and CTXII-L1G were produced in a pure form and characterized by amino acid analysis, mass spectrometry and peptide mapping. In the structural aspect, changing the Leu-1 by D-Leu or Gly causes a drastic alteration in the whole CTX II structure as detected by circular dichroism, 1-anilino-naphthalene-8-sulfonate (ANS) fluorescence assay. In the functional aspect, both CTXII-L1-D-L and CTXII-L1G are still retained substantial biological activity of CTX II. Therefore, the results indicate that both the chirality and the side-chain of the N-terminal leucine residue of CTX II are important elements in maintaining the whole CTX II structure. In addition, this study is the first report in elucidating the reason why the first N-terminal residue of most CTXs (90.3%) is leucine residue.

Amino Acids↗
PubMed1997

Molecular cloning and characterization of Porphyromonas gingivalis lysine-specific gingipain. A new member of an emerging family of pathogenic bacterial cysteine proteinases.

The proteinases of Porphyromonas gingivalis are key virulence factors in the etiology and progression of periodontal disease. Previous work in our laboratories resulted in the purification of arginine- and lysine-specific cysteine proteinases, designated gingipains, that consist of several tightly associated protein subunits. Recent characterization of arginine-specific gingipain-1 (gingipain R1; RGP-1) revealed that the sequence is unique and that the protein subunits are initially translated as a polyprotein encoding a proteinase domain and multiple adhesin domains (Pavloff, N., Potempa, J., Pike, R. N., Prochazka, V., Kiefer, M. C., Travis, J., and Barr, P. J. (1995) J. Biol. Chem. 270, 1007-1010). We now show that the lysine-specific gingipain (gingipain K; KGP) is also biosynthesized as a polyprotein precursor that contains a proteinase domain that is 22% homologous to the proteinase domain of RGP-1 and multiple adhesin domains. This precursor is similarly processed at distinct sites to yield active KGP. The key catalytic residues in the proteinase domain of KGP are identical to those found in RGP-1, but there are significant differences elsewhere within this domain that likely contribute to the altered substrate specificity of KGP. Independent expression of the proteinase domain in insect cells has shown that KGP does not require the presence of the adhesin domains for correct folding to confer proteolytic activity.

Adhesins, Bacterial↗
PubMed1997

Allopurinol blocks shock-wave-induced rises in cytosolic calcium levels in MDCK cells.

Allopurinol has been reported to ameliorate the side effects in patients following shock wave lithotripsy (SWL); however, the mechanism has not been studied. We have examined the protective effect of allopurinol on Madin-Darby canine kidney (MDCK) cells after shock wave exposure (SWE) by determining the release of aspartate aminotransferase (ASAT) and lactate dehydrogenase (LD), and the resting cytosolic Ca2+ concentration ([Ca2+]i). In SWE-treated cells, the release of ASAT and LD increased immediately, but largely transiently, by approximately 23% and 5-fold over control, respectively. Within 1-6 h after SWE there was a gradual rise in the resting [Ca2+]i of 16-137% above control. Allopurinol did not affect the transient enzyme release but blocked the long-term rises in the resting [Ca2+]i. The transient changes in [Ca2+]i evoked by two hormones, ATP and bradykinin, and a drug that releases Ca2+ from internal Ca2+ stores, thapsigargin, were only slightly affected in allopurinol-treated cells. We conclude that the protection conferred by allopurinol on patients treated with SWL might involve a direct protection of the kidney cells by maintaining a normal resting [Ca2+]i.

Allopurinol↗
PubMed1997

P2Y receptor linked to phospholipase C: stimulation of neuro 2A cells by UTP and ATP and possible regulation by protein kinase C subtype epsilon.

Incubation of Neuro 2A mouse neuroblastoma cells with UTP and UDP results in a concentration-dependent increase in the accumulation of inositol phosphates with equal potency and maximal effect; ATP, ADP, and 2-methylthioadenosine 5'-triphosphate were much less potent, indicating the expression of P2Y receptor in these cells. The effects of UTP and ATP were not affected by pretreatment of cells with pertussis toxin, indicating that the P2Y receptor in Neuro 2A cells is coupled to pertussis toxin-insensitive Gq protein. Short-term (10 min) treatment of cells with 1 microM 12-O-tetradecanoylphorbol 13-acetate (TPA) resulted in the inhibition of the UTP and ATP effects; this inhibitory effect was gradually attenuated with increased length of TPA treatment (1.5-6 h) and was not seen after long-term (24 h) treatment. Western blot analysis showed the expression of protein kinase C (PKC) alpha, epsilon, theta, and zeta in Neuro 2A cells. Translocation of PKC alpha, epsilon, and theta from the cytosol to the membrane was seen after 10 min or 1.5 h of treatment with TPA. However, partial and complete down-regulation of both membrane PKC alpha and theta were seen after 3 and 6 h of treatment, respectively. In contrast, the TPA-induced translocation of PKC epsilon was maintained after 3-6 h of treatment, and almost complete down-regulation occurred only after a 24-h treatment. The observed TPA-induced inhibition of UTP- or ATP-stimulated phosphoinositide hydrolysis, therefore, correlated well with the extent of translocation of PKC epsilon. Phosphoinositide hydrolysis induced by AlF4-, but not Ca2+ ionophores, was inhibited by a 10-min treatment with TPA. This was not seen after a 24-h treatment, indicating that the site of action of PKC epsilon in the P2Y receptor/Gq protein/phospholipase C beta pathway might be the Gq protein. This is the first study to show the existence of the P2Y receptor in Neuro 2A cells and the possible involvement of neuronal PKC epsilon in the regulation of the receptor-mediated phosphoinositide turnover.

Adenosine Triphosphate↗
PubMed1997

Kinetic studies of the inhibitory effects of propeptides subtilisin BPN' and Carlsberg to bacterial serine proteases.

The propeptides of bacterial subtilisin BPN' and Carlsberg were synthesized to investigate their inhibitory function on the enzymes. Kinetically, pro-BPN' inhibits the proteolytic activities of subtilisin BPN' and Carlsberg separately in a slow binding mode. Pro-Carlsberg behaves as a typical rapid equilibrium competitive inhibitor for these two proteases. Functionally, pro-Carlsberg inhibits the subtilisins with moderate selectivity. The inhibition constant Ki of pro-BPN' to subtilisin BPN' is 5.0 nM, and 6.1 nM to subtilisin Carlsberg. The on-rate of pro-BPN' to subtilisin BPN' is 5.8 x 10(5) M(-1)s(-1), and the off-rate 2.9 x 10(-3) s(-1). Similarly, the on-rate of pro-BPN' to subtilisin Carlsberg is 2.2 x 10(5) M(-1)s(-1), and the off-rate 1.3 x 10(-3) s(-1). On the other hand, the Ki of pro-Carlsberg to subtilisin BPN' gives 1.3 x 10(2) nM, and 88 nM to subtilisin Carlsberg. Based on the key features of the interactions between pro-BPN' and subtilisin from X-ray crystallographic results (Gallagher et al., 1995), the correlation between the sequence of subtilisin propeptides and their inhibition abilities on the proteases are compared and discussed.

Amino Acid Sequence↗
PubMed1997

Relationships between beta-cell function and diabetic duration and albuminuria in type 2 diabetes mellitus.

To clarify whether beta-cell function deteriorates with increasing albuminuria and duration of diabetes, we investigated the insulin and c-peptide response to oral glucose tolerance test in 47 healthy subjects and 75 normoalbuminuric (group 1), 30 microalbuminuric (group 2), and 35 macroalbuminuric (group 3) Type 2 diabetes mellitus patients. The total area under the insulin curve (AUCI) values of groups 1, 2, and 3 were 245 +/- 16, 193 +/- 17, and 88 +/- 8 pmol/L.h, respectively, significantly lower than that (624 +/- 34 pmol/L.h) of the healthy group. The mean total area under the c-peptide curve (AUCC-P) values of groups 1, 2, and 3, respectively, were 2.50 +/- 0.11, 2.05 +/- 0.15, and 1.73 +/- 0.07 nmol/L.h, respectively, significantly lower than that (5.47 +/- 0.19 nmol/L.h) of the healthy controls. The mean AUCI and AUCC-P values of group 3 were significantly reduced compared to those of group 1. The mean AUCI and AUCC-P values of patients with 0-5, 5-10, 10-15, and > 15 years' duration were significantly decreased compared to those of healthy subjects. The mean AUCI and AUCC-P values of patients with > 15 years' duration were significantly lower than those of patients with 0-5 years' duration. The mean hemoglobin Alc values of the three diabetic groups were not significantly different. These data suggest that beta-cell function deterioration was associated with increasing albuminuria and diabetic duration in Type 2 diabetic patients.

Albuminuria↗
PubMed1997

Does ureteral manipulation improve the effect of extracorporeal electromagnetic shock wave treatment on impacted ureteral calculi?--an experimental study.

OBJECTIVE: We used an experimental study to evaluate the effects of ureteral manipulation on the disintegration of impacted ureteral calculi. METHODS: Fifteen urinary calculi were divided into 3 groups according to the type of ureteral manipulation. Group 1: control group, no manipulation; group 2: bypass catheterization, and group 3: below irrigation in porcine ureter. Each calculus was subjected to 500 shock wave pulses with 0.28 mJ/mm2 power density by a Siemens Lithostar II lithotriptor. RESULTS: The successful disintegration ratio for calculus sizes less than 4 and 2 mm was 79.4 +/- 13.1 and 42.2 +/- 7.5% (group 1), 82.3 +/- 5.2 and 43.5 +/- 2.4% (group 2) and 84.3 +/- 17.3 and 49.7 +/- 14.6% (group 3). There was no statistical difference among the 3 groups by Anova and the Kruskal-Wallis test. CONCLUSION: The ureteral manipulation of impacted ureteral calculi was unable to improve stone disintegration by shock wave.

Animals↗
PubMed1997

Two-dimensional electrophoretic analyses of urinary proteins in Chinese male urinary stone patients.

This study was aimed to detect the differences in soluble urinary proteins between normal Chinese male individuals and urinary stone formers by 2-dimensional electrophoresis. Twenty urine samples were obtained from normal male adults and 35 from recurrent male urinary stone formers. The stone compositions included calcium oxalate, uric acid, carbonate apatite, and brushite. Two hundred milliliters of fresh urine was collected for analysis. Each urine sample was concentrated, dialyzed, frozen and lyophilized. The samples of the same stone composition were pooled and subjected to two-dimensional electrophoresis. Comparison of protein profiles between normal individuals and stone formers revealed a number of proteins which are not present in the urine of normal individuals, 5 from calcium oxalate, 2 from uric acid, 3 from carbonate apatite and 2 from brushite. These urinary stone-associated proteins comprise proteins A (37kd), B (30kd), C (26kd), D (25kd), and E (22kd) for calcium oxalate, proteins F (63kd) and G (59kd) for uric acid, protein H (65kd), I (42kd), and J (30kd) for carbonate apatite as well as proteins K (61kd) and L (59kd) for brushite. Among them, the proteins A, I, and J exhibited charge heterogeneity.

Adult↗
PubMed1997

Acute toxicities and feasibility of altered fractionated radiotherapy in nasopharyngeal carcinoma.

BACKGROUND: Altered fractionated radiotherapy (AFR) has been used for many years in the treatment of cancer. Although AFR therapy improves tumor control, it also increases acute radiation toxicities, which may make patients withdraw from treatment. Here, we report on the efficacy of AFR in the treatment of nasopharyngeal cancer (NPC). METHODS: From September 1993 to October 1994, 68 NPC patients received AFR in Chang Gung Memorial Hospital-Linkou. The efficacy of two types of AFR were studied: (a) Hyperfractionated radiotherapy (HFT) in which irradiation was given twice a day throughout the radiotherapy course with a total radiation dose of 81.6 Gy/68 fractions in 7 weeks; and (b) Concomitant boost radiotherapy (CBT) in which additional concommitant radiotherapy was administered only during the last 2 weeks of the radiotherapy course. The total radiation dose of CBT was 72.3 Gy/42 fractions in 6 weeks. Twenty-six patients received HFT and 42 received CBT. RESULTS: The percentage of grade 3 complications was 73% in CBT and 65% in HFT. The mean number of treatment days was 57.1 in HFT (median, 53; range 48-63) and 43.9 in CBT (median, 43; range 40-60). No patient withdrew from or prolonged the treatment because of acute radiation toxicities. CONCLUSION: Our results demonstrated that NPC patients can tolerate HFT and CBT radiotherapy with sufficient psychological support. Further randomized trials will be continued in our institution.

Adolescent↗