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Biomedical subjects

M C Chang

Publications and source records attributed to M C Chang.

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

Serine protease activity is essential for thrombin-induced protein synthesis in cultured human dental pulp cells: modulation roles of prostaglandin E2.

Irritations and injuries to the dental pulp usually lead to different degrees of pulpal inflammation. To investigate the roles of thrombin and prostaglandins in the healing and inflammatory processes of dental pulp as well as their effects on pulpal protein synthesis, human dental pulp cell cultures were established and their protein production was measured with or without the presence of exogenous thrombin and prostaglandins. At concentrations of 1-25 U/ml, alpha-thrombin increased the protein synthesis to 1.4-2.3 fold over the vehicle control. On the contrary, 0.1 microg/ml of prostaglandin E1 (PGE1) suppressed protein synthesis by 60%. Prostaglandin E2 (PGE2) also inhibited protein synthesis with an IC50 of 0.4 microg/ml. The stimulatory effects of thrombin (10 U/ml) can be inhibited by antithrombin III (2 U/ml) (a natural thrombin inhibitor) with heparin (2 U/ml), PPACK (D-Phe-Pro-ArgCH2Cl) (20-50 microg/ml) (a serine protease inhibitor), and PGE2 (0.5-1.0 microg/ml). Moreover, TRAP (20-40 microg/ml), a thrombin receptor agonist peptide, also exerted a stimulatory effect (1.21-1.37 fold). In conclusion, thrombin-induced protein synthesis by pulp cells is dependent on proteolytic activity, but not on binding to receptors. Both PGE1 and PGE2 exert suppressive effects on protein synthesis, indicating that interactions between thrombin and prostaglandins are important in regulating the inflammation, repair and regeneration of pulp tissue following injury.

Adult↗
PubMed1998

Isolation of broad-host-range replicons from marine sediment bacteria.

Naturally occurring plasmids isolated from heterotrophic bacterial isolates originating from coastal California marine sediments were characterized by analyzing their incompatibility and replication properties. Previously, we reported on the lack of DNA homology between plasmids from the culturable bacterial population of marine sediments and the replicon probes specific for a number of well-characterized incompatibility and replication groups (P. A. Sobecky, T. J. Mincer, M. C. Chang, and D. R. Helinski, Appl. Environ. Microbiol. 63:888-895, 1997). In the present study we isolated 1.8- to 2.3-kb fragments that contain functional replication origins from one relatively large (30-kb) and three small (<10-kb) naturally occurring plasmids present in different marine isolates. 16S rRNA sequence analyses indicated that the four plasmid-bearing marine isolates belonged to the alpha and gamma subclasses of the class Proteobacteria. Three of the marine sediment isolates are related to the gamma-3 subclass organisms Vibrio splendidus and Vibrio fischeri, while the fourth isolate may be related to Roseobacter litoralis. Sequence analysis of the plasmid replication regions revealed the presence of features common to replication origins of well-characterized plasmids from clinical bacterial isolates, suggesting that there may be similar mechanisms for plasmid replication initiation in the indigenous plasmids of gram-negative marine sediment bacteria. In addition to replication in Escherichia coli DH5alpha and C2110, the host ranges of the plasmid replicons, designated repSD41, repSD121, repSD164, and repSD172, extended to marine species belonging to the genera Achromobacter, Pseudomonas, Serratia, and Vibrio. While sequence analysis of repSD41 and repSD121 revealed considerable stretches of homology between the two fragments, these regions do not display incompatibility properties against each other. The replication origin repSD41 was detected in 5% of the culturable plasmid-bearing marine sediment bacterial isolates, whereas the replication origins repSD164 and repSD172 were not detected in any plasmid-bearing bacteria other than the parental isolates. Microbial community DNA extracted from samples collected in November 1995 and June 1997 and amplified by PCR yielded positive signals when they were hybridized with probes specific for repSD41 and repSD172 replication sequences. In contrast, replication sequences specific for repSD164 were not detected in the DNA extracted from marine sediment microbial communities.

Bacteria↗
PubMed1998

A 2.9-kilobase noncoding nuclear RNA functions in the establishment of persistent Hz-1 viral infection.

Differential viral gene expression during both productive and persistent infections of Hz-1 virus in insect cells was elucidated. Despite more than 100 viral transcripts being expressed during productive viral infection, massive viral gene shutoff was observed during viral persistency, leaving the 2.9-kb persistence-associated transcript 1 (PAT1) as the only detectable viral RNA. Persistence-associated gene 1 (pag1), which encodes PAT1, was cloned and found to contain no significant open reading frames. PAT1 is not associated with the cellular translation machinery and is located exclusively in the nucleus. Further experiments showed that PAT1 is functional in the establishment of persistent Hz-1 viral infection in the cells. All the evidence collectively indicates that PAT1 is a novel nuclear transcript of viral origin. Our results showed that although PAT1 and XIST RNA, a mammalian X-inactive specific transcript, are transcribed by different genes, they have interesting similarities.

Animals↗
PubMed1998

Areca nut extract inhibits the growth, attachment, and matrix protein synthesis of cultured human gingival fibroblasts.

Betel quid chewing is a popular oral habit in India, South Africa, and many Southeast Asian countries. The effects of areca nut (AN) extract on the growth, attachment, and protein synthesis of healthy human gingival fibroblasts (GF) were investigated to determine why betel quid (BQ) chewers have higher prevalence of periodontal disease than non-chewers. Twenty-four hour exposure of human GF to AN extract (> 200 microg/ml) in culture led to the formation of numerous intracellular vacuoles. As analyzed by modified MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide] assay, AN extract significantly suppressed the growth of GF over 5 days of incubation in a dose-dependent manner. At concentrations of 50 and 300 microg/ml, AN extract suppressed the growth of GF with 30% and 57% (P < 0.05), respectively. AN extract also significantly suppressed the synthesis of [3H]proline incorporation into trichloroacetic acid (TCA) precipitated proteins. At concentrations of 200, 400, and 600 microg/ml, AN extract suppressed the protein synthesis with 33%, 58%, and 63% of inhibition (P < 0.05), respectively. Preincubation of cells in a medium containing AN extract for 2 hours inhibits the subsequent attachment of cultured GF to type I collagen at the 50% inhibitory concentration (IC50) which is about 720 to 798 microg/ml. Considering the frequent consumption of BQ throughout the day, impairment of sequential fibroblast functions by BQ ingredients is a potential mechanism through which BQ chewing exert a deleterious effect to the gingival tissues.

Areca↗
PubMed1998

Ultrasound-guided fine needle aspiration biopsy in the diagnosis of pulmonary cryptococcosis.

The purpose of this study was to assess the safety and reliability of ultrasound-guided fine needle aspiration biopsy (US-guided FNAB) combined with modified Papanicolaou's staining in the diagnosis of pulmonary cryptococcosis. The study included 10 patients (9 men, 1 woman, 28-70 yr). Percutaneous US-guided FNAB was performed through a puncture probe with central channel guidance (n = 8) or in a 'free-hand' manner (2), depending on the size of the lesion and the experience of the operator. Sonography disclosed homogeneously hypoechoic lesions with air bronchograms over the peripheral or central portion in nine patients, and occasional heterogeneous echogenicity with necrotic tissue without air bronchogram in one. Thirteen lesions were found on the chest radiographs of the 10 patients; these could be divided into three patterns: infiltrates (2), nodules or masses (7), and consolidation (4). Using US-guided FNAB and immediate modified Papanicolaou's stain, a diagnosis of pulmonary cryptococcosis was confirmed in nine of the 10 patients. The remaining case was proven by surgical resection. No major complications developed after US-guided FNAB. We conclude that this technique, combined with modified Papanicolaou's staining, provides a safe, rapid, and reliable method for diagnosing pulmonary cryptococcosis.

Adult↗
PubMed1998

Response of Epstein-Barr virus-associated Ki-1+ anaplastic large cell lymphoma to 13-cis retinoic acid and interferon alpha.

The response of peripheral T-cell lymphoma to 13-cis retinoic acid (13-cis-RA) has been well established, especially in Ki-1+ anaplastic large cell lymphoma (ALCL) confined to the skin. Here, we report the use of 13-cis-RA in combination with interferon alpha in a patient with refractory ALCL. The patient, an 18-year-old man, suffered from retroperitoneal, hepatic, and splenic ALCL. Reactive hemophagocytic syndrome also developed. Active Epstein-Barr virus infection was demonstrated by serologic tests and in situ hybridization of Epstein-Barr virus early RNA-1. Although high-dose intravenous immunoglobulin (IgG), etoposide, and steroids were administered, only chemotherapy (methotrexate, bleomycin, doxorubicin, cyclophosphamide, vincristine, and dexamethasone) successfully controlled the progress of hemophagocytosis. However, the retroperitoneal mass and splenic tumor did not show a satisfactory response to three cycles of chemotherapy. Hence, interferon 4.5 MU/m2 every other day with 13-cis-RA 1 mg/kg/day was instituted. Abdominal computed tomogram after 58 days of treatment revealed that the tumor had significantly reduced in size. Bone marrow biopsy demonstrated alleviation of hemophagocytosis as well. However, lymphoma cells had begun to infiltrate the bone marrow. Our findings suggest that 13-cis-RA and interferon alpha may be partially effective in treating ALCL.

Adolescent↗
PubMed1998

Pancreatic injuries resulting from penetrating trauma: a multi-institution review.

Pancreatic injury from penetrating trauma continues to be a source of significant morbidity and mortality, with questions remaining regarding optimal treatment of injuries. Our goal was to evaluate current trends in the operative management of these injuries. Our patient population comprised all patients admitted to one of three Level I trauma centers over an 8-year period that had sustained penetrating pancreatic trauma. The study was a retrospective chart review. Sixty-two patients were identified. All had associated abdominal injuries, with the liver and stomach being the most commonly injured organs. There were 14 deaths (mortality 22.6%), 10 within the first 48 hours due to associated vascular injury. In the 52 patients surviving beyond 48 hours, there were 19 patients with injuries to the main pancreatic duct and 33 with parenchymal injuries only. Pancreatic resection was carried out for all patients with ductal injury except for one, who later required distal pancreatectomy for pseudocyst and pancreatic fistula. Significant pancreatic fistulae developed in five patients, three in patients treated by drainage and two in patients treated by resection. The incidence of fistula formation was significantly higher for drainage versus resection in the patients with ductal injuries. The incidences of other complications were not affected by type of pancreatic injury, associated injuries, or method of management. We conclude that the majority of deaths in patients with penetrating pancreatic trauma are due to associated organ or vascular injuries. Appropriate management of the pancreatic injury can reduce the long-term complications. These results support treating patients with suspected ductal injuries by appropriate resection. Drainage should probably be sufficient for most nonductal pancreatic injuries.

Abdominal Abscess↗
PubMed1998

Vascularized iliac bone graft for treating avascular necrosis of the femoral head.

BACKGROUND: Nontraumatic avascular necrosis of the femoral head (ANFH) is a common disorder causing disability of the hip joint. The means for optimally treating this disease are still controversial. In this study we evaluated the relatively new technique of vascularized iliac bone grafting for treating ANFH. METHODS: From March 1990 to March 1992, 17 hips (15 patients) with ANFH were treated using the vascularized iliac bone grafting technique in our hospital. The patients included 12 men and three women, with an average age of 38 years. Steinberg's classification was used to categorize the severity of hip disease. The clinical results were classified as excellent, good, fair and poor according to symptoms, hip function and roentgenographic changes after surgery. Life-table analysis was applied to assess graft survival and the log rank test was used to compare statistical differences between the steroid-related and nonsteroid-related groups. RESULTS: Cumulatively, 16 hips (14 patients), excluding one patient (one hip) lost to follow-up, were clinically evaluated for an average of 68 months. Among 12 hips at Steinberg stage II, eight progressed to stage IV, three to stage III and only one remained at stage II. Although most hips at stage II showed mild to moderate disease progression on plain radiography, 58% of the hips (7/12) that progressed to less than IVb showed good to excellent results. In the three hips at stage III, one progressed to stage IVa and two to stage V. In the two hips at stage IV, one remained at stage IV at final follow-up and the other was lost to follow-up. The steroid-related and nonsteroid-related groups did not differ with respect to clinical results. Both groups had 63% (5/8) good to excellent results (p > 0.05, log rank test). Only four hips were converted to prosthetic arthroplasties at final follow-up. Overall, 63% (10/16) of the hips had good to excellent results, 12% had fair results and 25% had poor results. Graft survival after seven years of follow-up was 63%. CONCLUSIONS: While treatment of ANFH still poses a challenge to orthopedic surgeons, the vascularized iliac bone grafting technique is a clinically acceptable option for treating the early stages of ANFH.

Adult↗
PubMed1998

Fine-needle aspiration cytology of retroperitoneal extramedullary hematopoiesis: a case report.

We report a 69 year-old man with left renal hilar tumor, which was incidentally detected and clinically suspected to be malignant. Interpretations of fine-needle aspiration (FNA) and frozen section of this tumor were not conclusive, and originally malignancy could not be ruled out. Later, correlation with the patient's history and bone marrow biopsy with cytological and histological pictures resulted in the diagnosis of a tumor of extramedullary hematopoiesis (EMH). This case shows that FNA cytology may be a useful method for diagnosing EMH. However, we also demonstrate the potential pitfall of misdiagnosing atypical megakaryocytes as malignant cells on FNA smears, or even in frozen sections, when clinical history and clinical data are not available. EMH should be considered in the differential diagnosis of patients with bone marrow disorders and mass lesions in extramedullary sites.

Aged↗
PubMed1998

Effects of thrombin on the growth, protein synthesis, attachment, clustering and alkaline phosphatase activity of cultured human periodontal ligament fibroblasts.

Previous studies have indicated that thrombin can activate pulp cells, including fibroblasts. Because pulp cells and periodontal ligament (PDL) fibroblasts can express thrombin receptor mRNA, the specific aim of this study was to determine whether thrombin can activate the growth, attachment, protein synthesis, alkaline phosphatase activities and cellular clustering of cultured human PDL fibroblasts. Thrombin can stimulate the growth of PDL fibroblasts in a dose dependent manner (as analyzed by MTT assay). At concentrations of 5 and 10 U/ml, thrombin increased the cell numbers to 141% and 153% greater than that of the control after 5 days of incubation, respectively. Thrombin (5-20 U/ml) also stimulated the protein synthesis rate (assayed by [3H]proline incorporation) to 1.88-2.13 fold that of the control. However, pretreatment of PDL fibroblasts with thrombin (1-20 U/ml) could not promote the attachment of PDL fibroblasts to type I collagen and fibronectin. Moreover, thrombin could induce clustering of PDL fibroblasts within a concentration range of 5-20 U/ml. However, thrombin (1-20 U/ml) exerted neither stimulatory nor inhibitory effect on cellular alkaline phosphatase activities. In conclusion, it appears that the presence of thrombin seems to have effects on PDL fibroblasts in terms of cell growth, protein synthesis and cell clustering. This suggests that thrombin might be important in the early healing process of periodontium following periodontal surgery.

Alkaline Phosphatase↗
PubMed1998

Computerized tomography in the diagnosis of subluxation of the distal radioulnar joint.

BACKGROUND: The diagnosis of distal radioulnar joint (DRUJ) subluxation is difficult. Routine radiographs are imprecise in clinical analysis. However, the anatomy and dynamic configuration of this articulation have been clearly defined utilizing computerized tomography (CT). Three CT criteria for the evaluation of DRUJ subluxation have been reported: Mino's criteria, the epicenter method and the congruity method. Previous reports discussed these criteria in the analysis of symptomatic DRUJ, but no clear conclusion has been reached. The purpose of this study is to investigate accurate criteria of CT in defining subluxation of the DRUJ. METHODS: Eighty distal radioulnar joints in 40 patients with suspected DRUJ subluxation underwent CT scans of both symptomatic and asymptomatic wrists. The CT scan was obtained through the DRUJ with the forearm in neutral rotation, active full supination and active full pronation. Three CT criteria were used to assess the DRUJ in all positions of unstable and normal wrists. RESULTS: Overall, 54 wrists were included in the final analysis. Seventeen symptomatic wrists had frank DRUJ instability diagnosed from true lateral radiographs, and 11 were reconfirmed from intraoperative pathology. The other 37 wrists had normal DRUJ. Among the three methods, the epicenter method had similar sensitivity to Mino's criteria and the congruity method. However, the epicenter method had much better specificity than Mino's criteria and the congruity method. CONCLUSIONS: For accurate diagnosis of subluxation of the DRUJ, CT scan through the symptomatic DRUJ in neutral rotation, active full supination, active full pronation and analysis with the epicenter method are recommended.

Adolescent↗
PubMed1997

Cloning and sequence analysis of the gene (eprA1) encoding an extracellular protease from Aeromonas hydrophila.

A gene (eprA1) encoding the extracellular protease of Aeromonas hydrophila AH1 has been cloned and sequenced. Nucleotide sequence analysis of eprA1 predicted a single open reading frame (ORF) of 1038 bp encoding a 346 amino acid (aa) polypeptide, with a potential 21-aa signal peptide. When the eprA1 gene was expressed in minicells, one major band of approx. 37 kDa was identified, while protease activity staining experiments identified a caseinolytic band of approx. 29 kDa determined by SDS-PAGE analysis of the minicells. The deduced C-terminal aa region (Arg-290 to Gly-313) showed sequence homology to partial C-terminal sequences of other zinc metalloproteases including Penicillium citrinum metalloprotease (PlnC), Aspergillus oryzae metalloprotease (NpII), Aspergillus flavus metalloprotease (MepA), and Aspergillus fumigatus metalloprotease (Mep20), particularly with respect to zinc-binding residues.

Aeromonas hydrophila↗
PubMed1997

In vivo imaging of fatty acid incorporation into brain to examine signal transduction and neuroplasticity involving phospholipids.

An in vivo method is presented that allows quantification and imaging of fatty acid incorporation into different brain phospholipids in relation to membrane synthesis, neuroplasticity, and signal transduction. The method can be used with positron emission tomography, and may help to evaluate brain phospholipid metabolism in humans with brain tumors, neurodegenerative disease, cerebral ischemia or trauma, or neurotoxic effects of drugs or other agents.

Animals↗
PubMed1997

Brain incorporation of [1-11C]arachidonate in normocapnic and hypercapnic monkeys, measured with positron emission tomography.

Positron emission tomography (PET) was used to determine brain incorporation coefficients k* of [1-11C]arachidonate in isoflurane-anesthetized rhesus monkeys, as well as cerebral blood flow (CBF) using [15O]water. Intravenously injected [1-11C]arachidonate disappeared from plasma with a half-life of 1.1 min, whereas brain radioactivity reached a steady-state by 10 min. Mean values of k* were the same whether calculated by a single-time point method at 20 min after injection began, or by least-squares fitting of an equation for total brain radioactivity to data at all time points. k* equalled 1.1-1.2 x 10(-4) ml x s(-1) x g(-1) in gray matter and was unaffected by a 2.6-fold increase in CBF caused by hypercapnia. These results indicate that brain incorporation of [1-11C]arachidonate can be quantified in the primate using PET, and that incorporation is flow-independent.

Animals↗
PubMed1997

Cloning and characterization of the gene (empV) encoding extracellular metalloprotease from Vibrio vulnificus.

A gene (empV) encoding the extracellular metalloprotease of Vibrio vulnificus CKM-1 has been cloned and sequenced. When the empV gene was expressed in minicells, a unique peptide of approx. 46 kDa was identified. Protease activity staining experiments also indicated a similar M(r) for the protease. The empV gene product (EmpV) is secreted into the periplasm of Escherichia coli, but not out of it. The crude enzyme prepared from the periplasmic fraction of recombinant E. coli was inhibited by a metalloprotease inhibitor and Zn2+ is essential for its protease activity. Nucleotide sequence analysis predicted a single open reading frame (ORF) of 1818 bp encoding a 606 amino acid (aa) polypeptide, with a potential 24 aa signal peptide followed by a long 'pro' sequence consisting of 172 aa. The N-terminal 20 aa sequence for the elastolytic protease (EepV), purified from the culture supernatant of V. vulnificus ATCC 29307, completely identified the beginning of the predicted mature protein within the deduced aa sequence except for 1 aa residue difference. The estimated pI and molecular weight of the predicted mature protein were 5.86 and 44.3 kDa, respectively, which are nearly identical to those of V. vulnificus L-180 extracellular neutral metalloprotease (EnmV) and of strain ATCC 29307 EepV. The estimated molecular weight also closely matches that determined by SDS-PAGE analysis of the minicells and by protease activity staining. The deduced aa sequence of EmpV showed high homology to V. anguillarum metalloprotease (EmpA), V. cholerae HA/protease (HprC), and V proteolyticus neutral protease (NprP), particularly with respect to active-site residues, zinc-binding residues, and cysteine residues.

Amino Acid Sequence↗