Hyperon weak radiative decays in chiral perturbation theory.
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Journal Article↗
Biomedical subjects
D Chang
Publications and source records attributed to D Chang.
Human leptin characterization.
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Electrophoresis, Polyacrylamide Gel↗
Proposal for Detecting Top Spin Correlation Effects at the Fermilab Tevatron.
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Journal Article↗
Biosynthesis of surfactant protein D. Contributions of conserved NH2-terminal cysteine residues and collagen helix formation to assembly and secretion.
Surfactant protein D (SP-D) is preferentially secreted as dodecamers consisting of four collagenous trimers cross-linked by disulfide bonds. In these studies, we examined the biosynthesis of wild-type rat SP-D (RrSP-D) and selected mutants by stably transfected CHO-K1 cells to determine the roles of a conserved N-linked oligosaccharide, the collagen helix, and interchain disulfide bonds in SP-D assembly and secretion. The major intracellular form of RrSP-D accumulated in the RER as complexes containing up to four trimeric subunits. Disulfide cross-link formation and RrSP-D secretion were selectively inhibited by 2,2'-dipyridyl, an inhibitor of prolyl and lysyl hydroxylase, and by 2 mM dithiothreitol, but unaffected by tunicamycin or elimination of the consensus sequence for glycosylation at Asn70. Although mutants with serine substituted for Cys15 and Cys20 (RrSP-Dser15/20) are secreted as trimeric subunits, proteins with single cysteine substitutions were retained in the cell. Surprisingly, the secretion of RrSP-Dser15/20 was unaffected by 2,2'-dipyridyl. These studies strongly suggest that the most important and rate-limiting step for the secretion of SP-D involves the association of cross-linked trimeric subunits to form dodecamers stabilized by specific inter-subunit disulfide cross-links. Interference with collagen helix formation prevents secretion by interfering with efficient disulfide cross-linking of the NH2-terminal domain.
Animals↗
Analysis of morbidity and mortality in 60 patients with peritoneal carcinomatosis treated by cytoreductive surgery and heated intraoperative intraperitoneal chemotherapy.
BACKGROUND: Peritoneal carcinoma has been regarded as a uniformly lethal clinical entity. A treatment plan combining cytoreductive surgery and heated intraoperative intraperitoneal chemotherapy (HIIC) was devised and tested to treat such patients. The purpose of this study was to evaluate the morbidity and mortality associated with this treatment approach. METHODS: Sixty patients with peritoneal carcinomatosis from adenocarcinoma of the colon or appendix were included in the study. Extensive cytoreductive surgery was combined with heated intraperitoneal mitomycin in an intraoperative lavage technique followed by one cycle of early postoperative intraperitoneal 5-fluorouracil. Eleven clinical variables were selected and statistically correlated with morbidity and mortality. RESULTS: Twenty-five complications occurred in 21 patients (morbidity = 35%). Morbidity related to gastrointestinal function included anastomotic leak (n=6), bowel perforations (n=5), bile leak (n=3), and pancreatitis (n=2). Four patients presented with severe hematologic toxicity (Grade 3 or 4). There were three cases of postoperative bleeding, one case of abdominal wound dehiscence, and one case of pulmonary embolism. Morbidity was significantly associated with three clinical factors: male sex, high intraabdominal temperature during HIIC, and duration of the surgical procedure. Enteral complications (bowel fistula and anastomotic leak) occurred in patients with a significantly higher number of peritonectomy procedures and a significantly longer operation. Three patients died within 8 weeks after the procedure (mortality = 5%). Mortality was significantly associated with age and intraabdominal temperature. CONCLUSIONS: Cytoreductive surgery combined with HIIC is associated with a 35% morbidity rate and a 5% mortality rate. Extensive surgery (duration and number of peritonectomy procedures) and high intraabdominal temperature represent the major risk factors for postoperative morbidity and mortality of patients treated with this new therapeutic approach.
Adult↗
Site-directed mutagenesis of Cys-15 and Cys-20 of pulmonary surfactant protein D. Expression of a trimeric protein with altered anti-viral properties.
Surfactant protein D (SP-D) molecules are preferentially assembled as dodecamers consisting of trimeric subunits associated at their amino termini. The NH2-terminal sequence of each monomer contains two conserved cysteine residues, which participate in interchain disulfide bonds. In order to study the roles of these residues in SP-D assembly and function, we employed site-directed mutagenesis to substitute serine for cysteine 15 and 20 in recombinant rat SP-D (RrSP-D), and have expressed the mutant (RrSP-Dser15/20) in Chinese hamster ovary (CHO-K1) cells. The mutant, which was efficiently secreted, bound to maltosyl-agarose, but unlike RrSP-D, was assembled exclusively as trimers. The constituent monomers showed a decreased mobility on SDS-polyacrylamide gel electrophoresis resulting from an increase in the size and sialylation of the N-linked oligosaccharide at Asn-70. Although RrSP-Dser15/20 contained a pepsin-resistant triple helical domain, it showed a decreased Tm, and acquired susceptibility to proteolytic degradation. Like RrSP-D, RrSP-Dser15/20 bound to the hemagglutinin of influenza A. However, it showed no viral aggregation and did not enhance the binding of influenza A to neutrophils (PMN), augment PMN respiratory burst, or protect PMNs from deactivation. These studies indicate that amino-terminal disulfides are required to stabilize dodecamers, and support our hypothesis that the oligomerization of trimeric subunits contributes to the anti-microbial properties of SP-D.
Animals↗
A simple method for detecting human polyomavirus DNA in urine by the polymerase chain reaction.
In order to develop a simple and sensitive method for detecting human polyomavirus DNA in the urine of patients by the polymerase chain reaction (PCR), it was found that the viral DNA could be released from urine by proteinase K and then amplified by PCR directly, without additional treatment such as ultracentrifugation or DNA extraction. Direct PCR amplification of viral DNA from urine was volume limited and 5 microliters of urine appeared to be the optimum amount for direct PCR amplification. When the urine volume was greater than 10 microliters, the results of PCR were inconsistent. However, the urine volume could be increased after dialysis to remove possible inhibitor(s) which may interfere with PCR. Direct PCR amplification of patient urine is convenient and eliminates several steps which can cause loss of DNA from the sample.
DNA, Viral↗
Fine-structure epitope mapping of antierythropoietin monoclonal antibodies reveals a model of recombinant human erythropoietin structure.
We have isolated and mapped the rHuEPO epitopes for three noncompeting anti-EPO monoclonal antibodies (MoAbs). The MoAb 9G8A recognizes a linear epitope that includes amino acids 13, 16, and 17. MoAb F12 recognizes a conformational epitope that includes amino acids 31 through 33, 86 through 91, and 138. MoAb D11 recognizes a conformational epitope that includes amino acids 64 through 78 and 99 through 110. MoAb D11 neutralizes rHuEPO activity which suggests that its epitope may contain the receptor binding domain. Analysis of the effect of mutations on folding allowed the identification of buried residues, alpha-helical, and non alpha-helical regions. This data along with epitope mapping data of anti rHuEPO monoclonals was used to model rHuEPO protein structure. A model consistent with the data is a 4-helix bundle with short and long interconnecting loops.
Amino Acid Sequence↗
Isolation and characterization of conformation sensitive antierythropoietin monoclonal antibodies: effect of disulfide bonds and carbohydrate on recombinant human erythropoietin structure.
We have isolated and characterized three anti-recombinant human erythropoietin (rHuEPO) monoclonal antibodies (MoAbs) that recognize nonoverlapping epitopes on rHuEPO. Anti-EPO MoAb D11 neutralizes rHuEPO activity whereas MoAbs F12 and 9G8A do not. This suggests that D11 may bind to the rHuEPO active site. MoAbs F12 and D11 recognize conformation dependent epitopes whereas 9G8A does not. Immunoassays were developed for each monoclonal. The 9G8A immunoassay was novel and useful because immunoreactivity increased when rHuEPO was denatured. Disruption of disulfide bonds or removal of carbohydrate increased 9G8A immunoreactivity, which suggests that these elements are important for rHuEPO structure or stability.
Antibodies, Monoclonal↗
B61, a ligand for the Eck receptor protein-tyrosine kinase, exhibits neurotrophic activity in cultures of rat spinal cord neurons.
Although the Eph subfamily represents the largest group of receptor protein-tyrosine kinases, the biological roles of the Eph-related receptors and their ligands are not well understood. B61 has been identified recently by receptor affinity chromatography as a ligand for the Eph-related receptor Eck (Bartley et al.: Nature 368:558-560, 1994). Here we show that Eck immunoreactivity is localized in areas of the embryonic rat spinal cord that are rich in axons, suggesting that Eck plays a role in this region of the developing nervous system. To examine the biological function of Eck, monolayer cultures of dissociated cells from embryonic rat spinal cord were treated with soluble B61. With an ED50 of approximately 10 ng/ml, B61 treatment improved the survival of the overall neuronal population. Furthermore, in the presence of B61 neurites were longer and more elaborated. B61 similarly affected survival and neurite length in cultures enriched in motor neurons. These neurotrophic effects of B61 were not observed in the presence of anti-Eck antibodies, indicating that these effects are likely to be mediated by the Eck receptor.
Animals↗
Transformation of NIH 3T3 cells by HER3 or HER4 receptors requires the presence of HER1 or HER2.
Members of the epidermal growth factor receptor (EGFR) subfamily of receptor protein tyrosine kinases have been implicated in the pathogenesis of various malignancies. The ability of one EGFR subfamily member to influence, or function synergistically with, another is likely to be a general feature of these receptors. To assess the role of receptor heterodimerization, we analyzed the ability of Neu differentiation factor (NDF) to induce cell growth and transformation of NIH 3T3 cells transfected with different combinations of the EGFR subfamily of receptors. NDF induced mitogenesis, but not transformation, of cells expressing either HER3 or HER4 alone. However, NDF-induced cell transformation was observed when either HER1 or HER2 was coexpressed with HER3 or HER4. In analogous receptor phosphorylation experiments, NDF-induced transphosphorylation appears to be correlated with synergistic transformation of NIH 3T3 cells. Interestingly, transphosphorylation between HER1 and HER4 can be stimulated by either EGF or NDF.
3T3 Cells↗
Genotypes of human polyomaviruses in urine samples of pregnant women in Taiwan.
The viral DNA of human polyomaviruses JC virus (JCV) and BK virus (BKV) was detected by the polymerase chain reaction (PCR) in urine samples from 31 pregnant women in Taiwan. A pair of appropriate primers amplified both JCV and BKV DNA of the regulatory region simultaneously in PCR. An oligonucleotide probe homologous to both JCV and BKV regulatory region was used subsequently to detect the viral DNA by Southern blotting after PCR amplification. Approximately 36% of the examined urine samples were human polyomavirus positive. The genotypes of JCV and BKV were determined by DNA sequencing of their regulatory regions. Besides CY archetype, a new strain (Taiwan-1) of JCV with a pentanucleotide (GGGAA) deletion and a new strain (Taichung-1) of BKV with two nucleotide alterations within the regulatory region were found in the urine samples. Eight of the examined samples were JCV infected, one was BKV infected, and two were JCV and BKV mix-infected. The JCV positive individuals were infected by CY archetype and Taiwan-1 strain equally. However, Taichung-1 strain was the only BKV strain found in the BKV positive individuals.
BK Virus↗
Different genotypes of human polyomaviruses found in patients with autoimmune diseases in Taiwan.
We have assayed for the presence of human polyomaviruses in urine of autoimmune disease patients, such as systemic lupus erythematosus (SLE), Sjogren's syndrome (SS), rheumatoid arthritis (RA), or dermatomyositis/polymositis (DM/PM), by PCR. The results indicate that approximately 40% of patients were JCV positive and 15% of the JCV positive patients were also infected by BKV at the same time according to Southern blot and DNA sequencing of the PCR products. Interestingly, the JCV present in autoimmune diseases patients were Taiwan-1, Taiwan-2, and Taiwan-3 strains with pentanucleotide-A (GGGAA) and/or -B (AAAGC) deletions within the regulatory region. In addition, BKV found in the examined samples were Taichung-1 and Taichung-2 strains. Taichung-1 had two nucleotide alterations and Taichung-2 had six nucleotide differences within the regulatory region when compared to WW BKV archetype. Although the examined autoimmune diseases patients included RA, SLE, PM, DM, and SS patients, there appears to be no correlation between disease and virus strains. However, Taiwan-2 strain JCV with two copies of pentanucleotide-A deletion was present in the patient with the longest period of immunosuppressive medication.
Autoimmune Diseases↗
Effect of intraperitoneal chemotherapy and fibrinolytic therapy on tumor implantation in wound sites.
Failure of surgical treatment for gastrointestinal cancers is often caused by recurrence of the tumor in traumatized peritoneal surfaces. This study examined the effect of intraperitoneal administration of doxorubicin and recombinant tissue plasminogen activator (rt-PA), a fibrinolytic agent, on incidence and volume of postoperative tumor implants in peritoneal wounds. Prior to randomization, a surgical wound was created on the right parietal peritoneum of 110 BDIX rats and 6 x 10(5) DHD/K12 colon cancer cells were inoculated intraperitoneally (ip). The control group was given an intraperitoneal injection of saline. Five groups received 1 mg/kg of ip doxorubicin at different times postoperatively: at the end of surgery (D0), 3 hr after surgery (D + 3), postoperative day 1 (D1), postoperative day 3 (D3), and postoperative day 7 (D7). In a second set of experiments, five groups of rats received, in addition to postoperative doxorubicin, 5 mg/kg of intraoperative ip rt-PA. Incidence and volume of tumor implants in peritoneal wounds were assessed for each group 20 days after the tumor inoculation. All rats of the control group (incidence = 100%) developed tumor implants in peritoneal wounds. Mean (SD) volume was 16.2 (4.7) mm3. When administered at D0, D + 3, and D1 intraperitoneal doxorubicin reduced significantly the incidence and volume of tumor implants in wounds. Postoperative administration of doxorubicin at D3 and D7 did not affect significantly the incidence and the volume of tumor implants in peritoneal wounds. When rt-PA was administered intraoperatively, ip injection of doxorubicin at any postoperative timing decreased significantly the incidence and volume of tumor implants. In conclusion, ip doxorubicin administered before postoperative D3 may act on tumor cell implanted in peritoneal wounds. Delayed (D3, D7) ip administration of doxorubicin does not prevent the development of tumor implants in peritoneal wounds. Intraoperative administration of rt-PA may significantly increase the efficacy of delayed ip chemotherapy.
Animals↗
Pathobiology of peritoneal carcinomatosis from ovarian malignancy.
A detailed analysis of the patterns of treatment failure of ovarian malignancy may lead to a more comprehensive understanding of the natural history of the disease. A hypothesis was generated that suggests treatment failure was caused by ovarian cancer persistence and by reimplantation of tumor emboli trapped within surgically traumatized tissues. Nine ovarian cancer patients who had previously undergone standard surgical removal of the primary cancer were prospectively studied at a reoperative procedure. The operative findings at the time of primary cancer surgery and reoperative surgery were scored for the presence of tumor in 9 abdominopelvic regions and 17 abdominopelvic sites. These data were then statistically analyzed. In 7 of the 9 patients ovarian cancer recurrence was associated with an increased intraperitoneal dissemination of tumor. A mean of 3.1 regions were involved at the time of the initial surgery and 5.3 were involved at reoperation. The regions most consistently involved were those in close proximity to the primary cancer. The anatomic sites that showed a preponderance of recurrence were the rectosigmoid colon, cul-de-sac of Douglas, left paracolic gutter, vagina, and abdominal incision. Traumatized sites always showed more cancer recurrence than nontraumatized sites. The vaginal cuff and abdominal incision, sites free of cancer after hysterectomy but at high risk for tumor cell entrapment, were disproportionately common sites for cancer found at reoperation. This study shows that in this reoperative setting ovarian cancer recurrence is most common in the pelvis and the left lower part of the abdomen. The cul-de-sac of Douglas and the rectosigmoid colon are anatomic sites at extreme risk for disease progression. These are sites in which ovarian cancer implants not removed by routine hysterectomy and bilateral salpingo-oophorectomy will persist. Also, sites traumatized by surgery were disproportionately involved by cancer at reoperation. These data may be interpreted to suggest that anatomic sites with cancer persistence and with cancer implantation induced by surgical trauma are the most common sites for ovarian cancer recurrence in this select group of patients.
Adult↗
Prognostic features for peritoneal carcinomatosis in colorectal and appendiceal cancer patients when treated by cytoreductive surgery and intraperitoneal chemotherapy.
Peritoneal carcinomatosis from appendical or colorectal cancer has been regarded as a fatal clinical entity. We used cytoreductive surgery and intraperitoneal chemotherapy to treat consecutive patients with peritoneal carcinomatosis. There were 43 colorectal and 104 appendiceal cancer patients. The mean follow-up was 32 months, with a range of 0-140 months. Clinical features that showed prognostic significance included appendiceal versus colorectal primary (p < 0.0001), grade I versus grades II and III histopathology (p < 0.0001), complete versus incomplete cytoreduction (p < 0.0001), lymph node-negative versus lymph node-positive primary tumor (p < 0.0001), volume of peritoneal carcinomatosis present preoperatively for colon cancer (p < 0.0002), and nonmoderate versus heavy prior surgery (p < 0.0043). Features with no statistical prognostic significance include tumor volume for appendiceal cancer, age, sex, number of cycles of chemotherapy, operative time, complications, blood loss, and institution providing treatment. From these prognostic features, four staging groups were identified and 5 year survival was estimated by the product-limit survival method. Group I patients (n = 61) were those with grade I histology, no lymph node metastases, and a complete cytoreduction (survival at 5 years = 90%). Group II (n = 20) patients are those with grade II or III histology, no lymph node metastases, and a complete cytoreduction (62%). Group III patients (n = 22) had any histology, lymph node metastases, and a complete cytoreduction (45%). Group IV patients (n = 44) had an incomplete cytoreduction (12%). Peritoneal carcinomatosis is a treatable condition in selected patients with a possibility for long-term disease-free survival.
Appendiceal Neoplasms↗
Patterns of spread of recurrent intraabdominal sarcoma.
A prominent site for recurrence of retroperitoneal and visceral sarcoma is the abdominal cavity. In an attempt to understand the causation of local and regional recurrence, 21 sarcoma patients who had previously undergone "complete" surgical removal of the primary tumor were prospectively studied. Data were obtained retrospectively from the first operation and prospectively from the reoperative procedure at the Washington Cancer Institute. At the primary and reoperative surgeries, 9 abdominopelvic regions and 21 sites were scored and then cataloged in a standardized fashion. Tumor locations and surgical resections were statistically analyzed in an attempt to establish patterns of recurrence within the abdomen and pelvis. There was a significant difference in sites of recurrence when sarcomas that involved the parietal structures were compared with those that involved small bowel. Peritoneal implants (nodular recurrences) were uniformly present in both groups. In contrast, resection site recurrences were very common with primary sarcomas invested by parietal peritoneum, while they were absent in those covered by visceral peritoneum. When primary surgeries were compared with reoperations, there was an increasing intraabdominal dissemination; the mean number of regions increased from 1.81 to 5.13. The change in distribution of sarcoma deposits at reoperation was greatest in right upper (because of liver surface) central and pelvic abdominopelvic regions and lowest in the left upper and epigastrium. The four anatomic sites that revealed a significant increase in involvement at the time of recurrence were the greater omentum, liver surface, large bowel, and the cul-de-sac of Douglas (all p < 0.002). Regions with tumor involvement or regions subjected to surgical trauma at the time of primary sarcoma resection were significantly more likely to show sarcoma deposits than to be sarcoma free at reoperation. These data taken together may suggest that sarcoma tumor emboli are frequently present in the abdomen at the time of resection of the primary cancer and that these tumor emboli are entrapped in fibrinous material at or immediately adjacent to sites of surgical trauma and along narrow margins of resection. Tumor cell entrapment of sarcoma emboli released into the peritoneal cavity prior to or at the time of sarcoma resection may help explain the distribution of nodular and fusiform recurrence of abdominopelvic sarcoma.
Abdominal Neoplasms↗
Anastomotic leak after double-stapled low colorectal resection.
PURPOSE: Anastomotic leaks after double-stapled low anterior resection were associated with a number of factors related to patient condition, level of anastomosis, and variety of surgery-related and antitumor therapy-related factors. This retrospective analysis of a group of patients with consistent length of rectal stump was undertaken to determine the risk factors of anastomotic leak after low colorectal resection related to surgery and to intraperitoneal chemotherapy. METHODS: A group of 165 patients treated with surgery only, surgery with early postoperative intraperitoneal chemotherapy, and surgery with hyperthermic intraoperative and early postoperative intraperitoneal chemotherapy. All patients underwent surgery that used the double-stapled technique with transection of the rectum through its middle third. In univariate and multivariate analysis, the relationship between anastomotic leak rate and extent of colon resection, length of residual colon, presence of left colon, and type of applied treatment was studied. RESULTS: With a full length of residual colon, leak rate was 1 percent but increased progressively with the extent of proximal colon resection. Removal of the left colon was associated with the 2.7 odds ratio for anastomotic disruption. Leak rate after surgery only was 6 percent; surgery with normothermic intraperitoneal chemotherapy was 5 percent; and surgery with heated intraperitoneal chemotherapy was 20 percent. CONCLUSIONS: In this group of patients with consistent length of residual rectum, the incidence of anastomotic disruption was related to extent of proximal colon resection. Anastomotic integrity was not compromised by normothermic intraperitoneal chemotherapy. Hyperthermic intraperitoneal chemotherapy was associated with high leak rate only when extensive resection of the colon was performed. Variables other than extent of rectal excision are important in causing a leak of colorectal anastomosis.
Anastomosis, Surgical↗