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Biomedical subjects

D Chang

Publications and source records attributed to D Chang.

At least 55 records · Page 3Linked to original sources
PubMed1999

T-cell co-stimulation through B7RP-1 and ICOS.

T-cell activation requires co-stimulation through receptors such as CD28 and antigen-specific signalling through the T-cell antigen receptor. Here we describe a new murine costimulatory receptor-ligand pair. The receptor, which is related to CD28 and is the homologue of the human protein ICOS, is expressed on activated T cells and resting memory T cells. The ligand, which has homology to B7 molecules and is called B7-related protein-1 (B7RP-1), is expressed on B cells and macrophages. ICOS and B7RP-I do not interact with proteins in the CD28-B7 pathway, and B7RP-1 co-stimulates T cells in vitro independently of CD28. Transgenic mice expressing a B7RP-1-Fc fusion protein show lymphoid hyperplasia in the spleen, lymph nodes and Peyer's patches. Presensitized mice treated with B7RP-1-Fc during antigen challenge show enhanced hypersensitivity. Therefore, B7RP-1 exhibits co-stimulatory activities in vitro and in vivo. ICOS and B7RP-1 define a new and distinct receptor-ligand pair that is structurally related to CD28-B7 and is involved in the adaptive immune response.

Amino Acid Sequence↗
PubMed1999

Cloning and characterization of B delta, a novel regulatory subunit of protein phosphatase 2A.

Variable regulatory subunits of protein phosphatase 2A (PP2A) modulate activity, substrate selectivity and subcellular targeting of the enzyme. We have cloned a novel member of the B type regulatory subunit family, B delta, which is most highly related to B alpha. B delta shares with B alpha epitopes previously used to generate subunit-specific antibodies. Like B alpha, but unlike B beta and B gamma which are highly brain-enriched, B delta mRNA and protein expression in tissues is widespread. B delta is a cytosolic subunit of PP2A with a subcellular localization different from B alpha and may therefore target a pool of PP2A holoenzymes to specific substrates.

Amino Acid Sequence↗
PubMed1999

Changes in myocardial protein expression in pacing-induced canine heart failure.

Canine rapid ventricular pacing produces a low output cardiomyopathic state which is similar to dilated cardiomyopathy. In this study dogs were paced at 245 beats per minute (bpm) for 3-4 weeks until signs of heart failure were apparent. Unpaced dogs were used as controls. A previous study identified myocardial protein changes in the pH region 4-7 following ventricular pacing by using two-dimensional electrophoresis (2-DE) (Heinke et al., Electrophoresis 1998 19, 2021-2030). Many of these proteins were associated with mitochondria, energy metabolism within the cardiomyocyte, the cytoskeleton and calcium cycling. The present study aimed to examine the proteins migrating in the more basic region of the 2-DE pattern using immobilised pH gradient 3-10 strips to separate myocardial proteins. The expression of 31 proteins was altered in the paced myocardium: 21 were decreased and 10 increased. Following the identification of 23 of these spots by either amino acid compositional analysis or peptide mass fingerprinting or a combination of both, we confirm that many of the proteins whose expression is altered following ventricular pacing are associated with the mitochondria and energy production within the cardiomyocyte, including creatine kinase M, triosephosphate isomerase, phosphoglycerate mutase, cytochrome c oxidase, cytochrome b5, hydroxymethyl glutaryl CoA synthase, myoglobin, and 3,2-trans-enoyl-CoA transferase. Additionally, the cytoskeletal protein actin was increased in the paced hearts. These results strongly support the notion that energy production is impaired and mitochondrial dysfunction is involved in the development of heart failure in the paced dog.

Animals↗
PubMed1999

Second-look surgery after cytoreduction and intraperitoneal chemotherapy for peritoneal carcinomatosis from colorectal cancer: analysis of prognostic features.

Assuming that peritoneal carcinomatosis is a local/regional dissemination of disease, a treatment strategy utilizing cytoreductive surgery and intraperitoneal chemotherapy was developed to treat colon cancer. In an attempt to improve knowledge of the mechanisms controlling abdominal and pelvic recurrences and for better selection of patients for reoperation, we studied those patients who had a second-look surgery following cytoreduction for peritoneal carcinomatosis from colorectal cancer. A group of 18 patients with symptoms and signs of recurrent peritoneal carcinomatosis were treated with reoperative surgery after definitive cytoreduction and intraperitoneal chemotherapy. An analysis of clinical features of these patients was performed using survival as an endpoint for evaluation of prognosis. The data suggest that the clinical features to be used to select patients for a second-look procedure after prior cytoreduction were the completeness of resection at the time of initial cytoreduction (p = 0.04) and the completeness of resection at the time of the second look (p = 0.066). In addition, a limited extent of peritoneal carcinomatosis distribution found at the time of the second look predicted a favorable result. A new objective assessment of peritoneal carcinomatosis, the peritoneal cancer index, was found to be of help during patient selection (p = 0.066). We concluded that second-look surgery with potential curative intent should be considered in patients who had a complete initial cytoreduction and those in whom total removal of the recurrence is judged possible at the time of the second look. At the time of abdominal exploration, a limited distribution and volume of peritoneal carcinomatosis as defined by the peritoneal cancer index should be considered. Palliative debulking procedures should be used to alleviate symptoms in other patients.

Adult↗
PubMed1999

JC virus genotypes in a Taiwan aboriginal tribe (Bunun): implications for its population history.

The origin of Taiwanese aborigines remains obscure; it has been speculated that they may be from either mainland China or southeastern Asia. We used the JCV genotyping method to elucidate the origin of Bunun aborigines who now live in central mountain areas of Taiwan. We found that Bunun aborigines carried two major (B1-a2 and CY) and two minor JCV genotypes (B1-a1 and SC). This was contrasted with the JCV genotype profile in modern Taiwanese: one major (SC) and two minor genotypes (CY and B1-a1). It thus appears that B1-a2 and CY are indigenous to the Bunun tribe. B1-a2 was first identified in this study as a discrete cluster that contained only Bunun and Philippine JCV isolates and that was closely related to B1-a1, one of the three common JCV genotypes in China. CY predominates in North China, while SC predominates in South China and southeastern Asia. The present findings suggest that the Bunun tribe is an admixture of two ethnic groups, one carrying B1-a2 and the other carrying CY. In other words, it is likely that the Bunun tribe was established by two waves of immigrations from mainland Asia, predating those by southern Chinese which began in the 17th century.

Adolescent↗
PubMed1999

Results of treatment of 385 patients with peritoneal surface spread of appendiceal malignancy.

INTRODUCTION: In the past, peritoneal carcinomatosis, regardless of primary tumor type, has always been a lethal condition. Recently, special treatments using cytoreductive surgery with peritonectomy procedures combined with perioperative intraperitoneal chemotherapy have resulted in long-term survival. Appendiceal malignancy with a low incidence of liver and lymph node metastases may be especially appropriate for these aggressive local regional treatments. METHODS: All patients treated with surgery before January 1999 are included. Patients left with gross residual disease after surgery were not given intraperitoneal chemotherapy, but were later treated with intravenous chemotherapy. The intraperitoneal chemotherapy was given in the perioperative period, starting with mitomycin C at 12.5 mg/m2 for males and 10 mg/m2 for females. For patients whose pathology showed adenomucinosis, intraperitoneal chemotherapy was limited to treatment in the operating theater with heated mitomycin C. Patients with mucinous adenocarcinoma or pseudomyxoma/adenocarcinoma hybrid had, in addition to mitomycin C, five consecutive days of intraperitoneal 5-fluorouracil at 650 mg/m2 instilled in 1-1.5 liters of 1.5% dextrose peritoneal dialysis solution. A complete cytoreduction was defined as tumor nodules <2.5 mm in diameter remaining after surgery. The histopathology categorized the patients as having adenomucinosis, adenomucinosis/carcinomatosis hybrid, or mucinous carcinomatosis. A previous surgical score was used to estimate the extent of previous surgical procedures. RESULTS: The morbidity of treated patients was 27% and the mortality was 2.7%. In a multivariate analysis, prognostic factors for survival included the completeness of cytoreduction (P < .0001), the histopathological character of the appendix malignancy (P < .0001), and the extent of previous surgical interventions (P = .001). Patients with a complete cytoreduction and adenomucinosis by pathology had a 5-year survival of 86%; with hybrid pathology, survival at 5 years was 50%. Incomplete cytoreduction had a 5-year survival of 20% and 0% at 10 years. CONCLUSIONS: Cytoreductive surgery and perioperative intraperitoneal chemotherapy can be used to salvage selected patients with peritoneal surface spread of appendiceal primary tumors. Similar strategies for other patients with peritoneal surface malignancy such as peritoneal carcinomatosis from colon or gastric cancer, peritoneal sarcomatosis, or peritoneal mesothelioma should be pursued.

Appendiceal Neoplasms↗
PubMed1999

Morbidity and mortality analysis of 200 treatments with cytoreductive surgery and hyperthermic intraoperative intraperitoneal chemotherapy using the coliseum technique.

BACKGROUND: Peritoneal carcinomatosis from gastrointestinal cancers is a fatal diagnosis without special combined surgical and chemotherapy interventions. Guidelines for cytoreductive surgery and hyperthermic intraoperative intraperitoneal chemotherapy (HIIC) by using the Coliseum technique have been developed to treat patients with peritoneal carcinomatosis and other peritoneal surface malignancies. The purpose of this study was to analyze the morbidity and mortality of patients undergoing cytoreductive surgery and HIIC by using mitomycin C. METHODS: Data were prospectively recorded on 183 patients who underwent 200 cytoreductive surgeries with HIIC between November 1994 and June 1998. Seventeen of the 183 patients returned for a second-look surgery plus HIIC. All HIIC administrations occurred after cytoreduction and used continuous manual separation of intra-abdominal structures to optimize drug and heat distribution. Origins of the tumors were as follows: appendix (150 patients), colon (20 patients), stomach (7 patients), pancreas (2 patients), small bowel (1 patient), rectum (1 patient), gallbladder (1 patient), and peritoneal papillary serous carcinoma (1 patient). Morbidity was organized into 20 categories that were graded 0 to IV by the National Cancer Institute's Common Toxicity Criteria. In an attempt to identify patient characteristics that may predispose to complications, each morbidity variable was analyzed for an association with the 25 clinical variables recorded. RESULTS: Combined grade III/IV morbidity was 27.0%. Complications observed included the following: peripancreatitis (6.0%), fistula (4.5%), postoperative bleeding (4.5%), and hematological toxicity (4.0%). Morbidity was statistically linked with the following clinical variables: duration of surgery (P < .0001), the number of peritonectomy procedures and resections (P < .0001), and the number of suture lines (P = .0078). No HIIC variables were statistically associated with the presence of grade III or grade IV morbidity. Treatment-related mortality was 1.5%. CONCLUSIONS: HIIC may be applied to select patients with peritoneal carcinomatosis from gastrointestinal malignancies with 27.0% major morbidity and 1.5% treatment-related mortality. The frequency of complications was associated with the extent of the surgical procedure and not with variables associated with the delivery of heated intraoperative intraperitoneal chemotherapy. The technique has shown an acceptable frequency of adverse events to be tested in phase III adjuvant trials.

Adult↗
PubMed1999

Human anti-JC virus serum reacts with native but not denatured JC virus major capsid protein VP1.

The immunoreactivity of human anti-JC virus (JCV) serum against the major capsid protein VP1 of JCV was analyzed by Western blot, dot blot, and hemagglutination inhibition (HAI) assays. JCV-positive human serum reacted with native but not denatured JCV major capsid protein VP1, as demonstrated by dot blot and Western blot. Rabbit antiserum raised against native JCV capsid had immunoreactivities similar to those of human anti-JCV serum. These results indicate that the antigenecity of native and denatured JCV VP1 is different. In addition, both JCV-positive human serum and rabbit antiserum raised against native JCV capsid protein inhibited the hemagglutination activity of JCV capsid particles. In contrast, rabbit antiserum raised against denatured JCV VP1 did not inhibit hemagglutination. These findings reveal that denaturation may alter the antigenic epitopes of JCV VP1. Therefore, keeping the JCV capsid protein native appears to be essential for serological or other immunological analyses of the virus.

Animals↗
PubMed1999

Quantitative methodologies for selection of patients with recurrent abdominopelvic sarcoma for treatment.

Peritoneal sarcomatosis is a major cause of surgical treatment failure in patients with abdominal or pelvic sarcoma. In the past, patients with this condition have had a lethal outcome. In this study, 43 consecutive patients with recurrent sarcomatosis were studied in order to evaluate an aggressive reoperative approach. In all patients, the goal of surgery was to resect all recurrent sarcoma in the abdomen and pelvis. In 30 patients in whom sarcomatosis was demonstrated and in whom a complete cytoreduction could be performed, resection was associated with peri-operative intraperitoneal chemotherapy with doxorubicin or cisplatin plus doxorubicin. Using a standardised and quantitative methodology to assess local-regional recurrence and dissemination on peritoneal surfaces, the clinical features that may affect prognosis were tabulated and analysed statistically. The median survival of these 43 patients was 20 months. Clinical features that had a significant impact on survival were involvement of less than six abdominopelvic regions (P = 0.0009), an increase in the involvement of abdominopelvic regions of less than four regions (P = 0.0007), involvement of less than 10 anatomic sites (P = 0.0002), complete cytoreduction with tumour reduced to nodules < 2.5 mm (P = 0.005) and a Peritoneal Cancer Index less than 13 (P = 0.01). Histological type and grade of recurrent sarcoma were not correlated with prognosis. In the multivariate analysis, an increase in abdominopelvic regions by four or more showed a risk ratio of 18.5. The involvement of 10 or more anatomic sites showed a risk ratio of 5.9. These data suggest that selected patients with recurrent sarcoma should be considered for further treatment and that the results of aggressive reoperative surgery and peri-operative intraperitoneal chemotherapy are greatly dependent on the volume and distribution of disease, determined at the initiation of therapy. Because of the great likelihood of local-regional treatment failure, the use of peri-operative intraperitoneal chemotherapy in a randomised study in patients with primary abdominopelvic sarcoma should be considered.

Abdominal Neoplasms↗
PubMed1999

The major capsid protein, VP1, of human JC virus expressed in Escherichia coli is able to self-assemble into a capsid-like particle and deliver exogenous DNA into human kidney cells.

The full-length major capsid protein, VP1, of the human polyomavirus JC virus was cloned and expressed in Escherichia coli. VP1 protein expressed in E. coli self-assembled into capsid-like particles and caused haemagglutination of human O-type red blood cells. Caesium chloride density-gradient centrifugation analysis revealed that the capsid-like particles consisted of virion-like pseudovirion and empty capsid-like pseudocapsid populations. The morphology of pseudo-virion and pseudocapsid particles was observed under the electron microscope. The pseudovirions contained DNA and RNA molecules but the pseudocapsids did not contain any nucleic acid, as analysed by DNA extraction. DNA-binding activity of VP1 was also demonstrated by the South-Western probing method in vitro. Furthermore, pseudocapsids were able to deliver exogenous DNA into human foetal kidney epithelial cells. These results indicate that recombinant JC virus VP1 is able to self-assemble into capsid-like particles and to package DNA in the absence of the minor capsid proteins, VP2 and VP3. This prokaryotic assembly system may facilitate the investigation of maturation mechanism(s) of polyomaviruses. Furthermore, capsid-like particles of JC virus VP1 generated in E. coli potentially could be used as a human gene transfer vector.

Capsid↗
PubMed1999

Stress fractures and tibial cortical hypertrophy after tibiotalocalcaneal arthrodesis with an intramedullary nail.

Twelve patients underwent successful tibiotalocalcaneal arthrodesis using a locked intramedullary nail with posterior moldable bone grafting. Two of the patients developed a nondisplaced stress fracture around the proximal interlocking screws, which responded to immobilization at 8 and 15 months after surgery. In 7 of 12 patients, > or =2 mm of cortical hypertrophy was noted between the proximal interlocking screws along the medial and/or lateral aspect of the tibia. Although intramedullary nailing can achieve satisfactory tibiotalocalcaneal arthrodesis, the stress risers in the tibial diaphyses do result in a stress reaction in a significant number of patients.

Adult↗
PubMed1999

Dose-dependent effects of DNA-damaging agents on p53-mediated cell cycle arrest.

We examined the dose-dependent effects of DNA-damaging agents on G1 arrest in isogenic human cell lines differing in their p53 status. As expected, 5 or 20 Gy of ionizing radiation induced a p53-dependent G1 arrest. In contrast, UV light or actinomycin D induced a modest G1 arrest that was p53-dependent only at lower doses. At higher doses, cells were arrested in G1 in a p53-independent manner coinciding with inhibition of RNA synthesis and abolished cyclin E expression. Interestingly, expression of cyclin E was enhanced after exposure to moderate doses of UV light and actinomycin D, and this enhancement was suppressed by wild-type p53. We propose that agents inducing transcription-blocking DNA lesions will at higher doses inhibit the progression of cells into S phase by a p53-independent mechanism involving the attenuation of E2F-mediated transcription of genes, such as cyclin E.

Blotting, Western↗
PubMed1998

Synthesis and antitumour effect of the melanogenesis-based antimelanoma agent N-propionyl-4-S-cysteaminylphenol.

Chemotherapy of malignant melanoma is still a great challenge, as no effective drugs are available. The development of melanogenesis-based drugs is a promising area of research because melanogenesis is a unique biochemical pathway operating only in melanoma cells (and their normal counterparts) so that the tumour can be targeted. We have been using cysteinylphenol, a sulphur-containing analogue of tyrosine, and derivatives for that purpose. N-Acetyl-4-S-cysteaminylphenol was found to have the best antimelanoma effect in cell culture systems and in mice bearing B16 melanoma tumours. It also caused depigmentation of the skin, suggesting the possibility of use as a hypopigmenting agent. To improve the efficiency of the drug, we thought of replacing the acetyl group in N-acetyl-4-S-cysteaminylphenol with a propionyl group in the hope that increased hydrophobicity would increase the cellular uptake of the drug. N-Propionyl-4-S-cysteaminylphenol was synthesized by condensing 4-hydroxythiophenol with 2-ethyl-2-oxazoline. The drug showed both cytostatic and cytocidal effects in a human melanotic melanoma cell line. The drug was found to be a good depigmenting agent for the black hair follicles of C57 black mice when given s.c. for 14 days. A 10-day treatment with N-propionyl-4-S-cysteaminylphenol at 300 mg/kg body weight reduced the growth rate of B16 melanoma s.c. tumours in mice by 36%. The propionyl derivative was found to increase the life span of mice bearing melanoma more effectively than did the acetyl derivative.

Animals↗
PubMed1998

Ovotestes in B6-XXSxr sex-reversed mice.

The sex-reversed mutation Sxr results in XX males. In the absence of any other mutations, testis differentiation in XXSxr fetuses is essentially normal and only one report of an XXSxr fetus with ovotestes is in the literature. We report that 84% (21/25) of 13 days postcoitum XXSxr fetuses on the B6 inbred genomic background have ovotestes. Ovotestes were found in fetuses from both Sxra and Sxrb variants. Examination of fetuses older than 13 dpc suggests that the presence of ovotestes is transient in most fetuses. However, one overt hermaphrodite was identified after birth. The development of ovotestes is associated with the inbred background and is exacerbated by the dominant spotting oncogene allele KitW-42J. We propose that spreading of X-inactivation into the Sxr region resulting in loss of Sry expression is more extensive in B6-Sxr strains.

Animals↗
PubMed1998

Protein changes observed in pacing-induced heart failure using two-dimensional electrophoresis.

Rapid ventricular pacing in dogs results in a low output cardiomyopathic state which is similar to idiopathic dilated cardiomyopathy in man. However, the pathophysiological mechanisms which cause this failure following pacing are unknown. Five dogs underwent rapid ventricular pacing. Hearts were stimulated at 245 beats per min (bpm) for four weeks and then reduced to 190 bpm to stabilize the failure. Six unoperated dogs were used as controls. This paper compares the two-dimensional gel electrophoresis (2-DE) protein patterns of left ventricular samples from the paced myocardium with the control dogs. Changes in protein expression were analyzed qualitatively and semi-quantitatively. In the paced dog samples 69 protein spots were significantly altered of which 42 were decreased and 27 were elevated. One qualitative change was observed: elongation factor Tu was present only the control hearts. Of these proteins, 20 have been identified by a combination of N-terminal protein microsequencing, peptide mass profiling by mass spectrometry, amino acid compositional analysis, and by comparison with databases of canine and human ventricular proteins. Ten of these are associated with mitochondria and energy production, including: pyruvate dehydrogenase E1 component, isocitrate dehydrogenase subunit alpha, HSP60 and HSP70, creatine kinase M and fatty acid binding protein. The cytoskeletal protein desmin was detected in reduced quantities and a spot corresponding to a fragment of desmin was increased. These results indicate that the development of heart failure in the paced dog involves alterations in mitochondrial energy production, the cytoskeleton and calcium activation.

Animals↗
PubMed1998

Hyperthermic intraperitoneal doxorubicin: pharmacokinetics, metabolism, and tissue distribution in a rat model.

BACKGROUND: The cytotoxic effect of several anticancer agents, including doxorubicin, can be enhanced by hyperthermia. The purpose of this study was to evaluate the effect of hyperthermia on the pharmacokinetics, metabolism, and tissue distribution of intraperitoneal (i.p.) doxorubicin in a rodent model. METHODS: Doxorubicin was given i.p. to 20 Sprague-Dawley rats at a dose of 2 mg/kg over 60 min. Rats were randomized into two groups according to the temperature of the peritoneal perfusate: group NT received normothermic (37 degrees C) i.p. doxorubicin; group HT received hyperthermic (43 degrees C) i.p. doxorubicin. During the course of i.p. chemotherapy, peritoneal fluid and blood were sampled every 10 min. At the end of the procedure, rats were sacrificed and tissue samples (liver, spleen, small bowel, omentum, bladder, diaphragm, abdominal wall, heart) were collected. Concentrations of doxorubicin and its aglycone metabolites were determined in peritoneal fluid, plasma, and tissues by HPLC. RESULTS: No significant differences in areas under the curve (AUC) of peritoneal fluid doxorubicin and plasma doxorubicin were found between group NT and group HT. AUC ratios (AUC peritoneal fluid/AUC blood) were 87.9 for group NT and 82.9 for group HT. Group HT exhibited increased doxorubicin concentrations for all intraabdominal tissues. These differences were significant for spleen (P = 0.03), small bowel (P = 0.03), and omentum (P = 0.03). Doxorubicin aglycone was detected in plasma of both groups within the first 10 min of the procedure. There was a significant (P < 0.001) increase in plasma aglycone AUC for group HT when compared with group NT. Group HT exhibited increased aglycone concentration for all tissues. This difference was significant for liver (P < 0.001) and bladder (P < 0.001). CONCLUSION: Hyperthermia did not affect significantly the pharmacokinetics of i.p. doxorubicin. Tissue concentrations of doxorubicin in small bowel, omentum, and spleen were significantly increased when the drug was administered by hyperthermic i.p. perfusion. Hyperthermia increased significantly the doxorubicin aglycone concentrations in plasma, liver, and bladder.

Animals↗
PubMed1998

Effects of cisapride on QT interval in children.

Recent reports of torsade de pointes and heart block associated with prolonged QT interval in children receiving cisapride raise questions about its safety. We prospectively examined the effects of cisapride on the QT interval in children. Electrocardiography was performed on 30 children before and after cisapride was administered. An additional 71 children underwent electrocardiography only after starting cisapride. The incidence of a corrected QT (QTc) interval > 440 msec or a marked abnormality in T wave morphology was determined in all 101 children. Cisapride significantly lengthened the QTc with a mean increase of 15.5 +/- 4.6 msec (mean +/- SEM, p = 0.002 in the 30 children with baseline electrocardiographs. Twelve of the 101 patients were found to have a QTc > 440 msec, and one had a new prominent notched T wave in all leads. In these 13 (13%) patients with repolarization abnormalities, other factors that might contribute to a long QT were noted in 11 (85%) patients. We conclude that cisapride use in children is associated with a modest increase in QT interval. The incidence of QTc > 440 msec is low. Most children with long QTc have other factors that could compound the effects of cisapride.

Child↗