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Biomedical subjects

S C Chen

Publications and source records attributed to S C Chen.

At least 145 records · Page 8Linked to original sources
PubMed1999

Immunity obtained by gene-gun inoculation of a rotavirus DNA vaccine to the abdominal epidermis or anorectal epithelium.

We have previously shown that gene-gun delivery of murine rotavirus DNA vaccines to the epidermis induced protection against rotavirus challenge in mice. In this study, we used a rotavirus group antigen (VP6)-specific DNA vaccine to compare epidermal immunization with immunization to the anorectal epithelium for efficacy in inducing protective immunity. The vaccine was administered into cells of the abdominal epidermis or anorectal epithelium of adult BALB/c mice with an Accell gene-gun (PowderJect, Inc). Vaccines administered by either route elicited rotavirus-specific ELISA antibodies and analysis of the IgG subtypes indicated Th2-type responses were generated by both routes of administration, in contrast to Th1-type responses generated by live rotavirus. Protection against virus challenge was obtained in mice inoculated by either route, as shown by significant reduction of virus excreted in stools. The protection obtained by immunization of the anorectal epithelium was greater than that for epidermal immunization at the same vaccine dose. These results suggest that mucosal immunization of DNA vaccines may be an effective means to generate protective immunity against mucosal pathogens.

Abdomen↗
PubMed1999

Immune responses and protection obtained by oral immunization with rotavirus VP4 and VP7 DNA vaccines encapsulated in microparticles.

Protective immune responses in mice were obtained after oral immunization with rotavirus DNA vaccines encapsulated in poly(lactide-co-glycolide) (PLG) microparticles. The DNA vaccines used encoded outer capsid proteins VP4 and VP7; proteins that are the basis for rotavirus serotyping and the generation of virus neutralizing antibodies. One dose of vaccine was given to BALB/c mice by oral gavage (75 microg DNA/mouse). Rotavirus-specific serum antibodies and intestinal IgA antibodies were detectable by 6 weeks postimmunization. After challenge with homologous murine rotavirus at 12 weeks postimmunization, fecal rotavirus antigen was reduced significantly in immunized mice compared with controls. Protective immunity also was generated by oral delivery of unencapsulated VP 7 DNA vaccine but to a lesser degree. These results demonstrate that the oral route is effective for generating protective immune responses with rotavirus DNA vaccines targeting neutralization antigens.

Administration, Oral↗
PubMed1999

Extrauterine pelvic arteriovenous malformation mimicking the clinical presentation of structural heart disease.

A case is reported of an extrauterine pelvic arteriovenous malformation involving branches of the internal iliac arteries. Cardiomegaly and a rough cardiac murmur were the clinical presentations mimicking a structural heart disease. A continuous bruit could only be detected by the diaphragm of the stethoscope applied firmly to the left lower abdomen. Multiple blood samplings from inferior vena cava, and iliac and femoral veins for determination of oxygen saturation may be necessary for suspected cases. However, selective arteriography remains the best method for diagnosing the presence, extent, and multiplicity of the lesions before surgery or percutaneous arterial embolization.

Arteriovenous Malformations↗
PubMed1999

c-jun Is dispensable for developmental cell death and axogenesis in the retina.

Although a number of studies have implicated c-Jun in neuronal death and axonal regeneration, it is unknown whether Jun function is essential for either response. One approach to resolve this issue is to analyze knock-out mice. However, c-jun-null mice die at midgestation, precluding critical investigation. Therefore, a xenograft paradigm was used in which retinas from embryonic day 12.5 (E12.5) c-jun nullizygous or wild-type mice were transplanted onto the superior colliculus of newborn rats. The rats were allowed to develop, and the grafts were assayed at various times for cell death and axon growth. Histologically, grafts of both genotypes developed in identical manners and had morphological characteristics of retinas. A functional c-jun allele was not essential for axogenesis, because ganglion cells in retinal grafts from c-jun nullizygous mice developed axons that projected into the colliculus. Programmed cell death (PCD) was also evident in the age-appropriate regions of the retina in both wild-type and c-jun-null grafts. Furthermore, there were no discernible differences in the number or location of dying cells in the two genotypes. That c-jun was not essential for PCD was supported by two additional findings. First, a c-jun-lacZ reporter gene was expressed in many cells in developing and grafted retinas, although only a few of these cells were destined to die. Second, in E12.5 c-jun-null embryos there were normal levels of PCD in the trigeminal ganglion. Together, these data indicate that c-Jun is not essential for axon growth in the retina or for PCD in the retina and trigeminal ganglion.

Alleles↗
PubMed1999

Efficacy of media enriched with nonlactate-generating substrate for organ preservation: in vitro and clinical studies using the cornea model.

BACKGROUND: Using a rabbit cornea model, our recent study demonstrated that Chen Medium (CM), an isotonic media enriched with nonlactate-generating high-energy substrates, is very effective for organ preservation. In the present study, the efficacy of CM is further evaluated with human corneas METHODS: The effectiveness of CM and Optisol for preserving the endothelial integrity of human corneas in vitro was evaluated by scanning electron microscopy. Clinical efficacy was evaluated in a total of 83 patients: 10 patients with keratoconus grafted randomly with either CM- or Optisol-stored cornea of the same donor, and 73 patients with various conditions grafted with CM-stored corneas. After surgery, visual acuity and quality of the graft were monitored for up to 4.6 years. RESULTS: The scanning electron microscopic study revealed that after 11-day storage at 4 degrees C, the CM-stored cornea had only marginal disruptive changes, 9.4+/-1.1%, in endothelial cells, as opposed to 42.4+/-4.6% of the Optisol-stored cornea. All 78 CM-stored corneas, including 67 with 12.2- to 17.7-hr death-to-storage time, 3-7.6 days of storage time, and initial marginal quality before storage, were successfully transplanted. These grafts were thin and clear, with an excellent epithelial integrity and without significant changes in endothelial cell density. Five Optisol-stored corneas were also successfully grafted; one of them, however, was edematous for about 4 weeks, and all the grafts were slightly thicker with substantial endothelial cell loss. CONCLUSION: Using a cornea model, present and recent studies show that CM is very effective for preserving tissue viability and endothelial integrity. Previous study revealed that CM-stored tissues maintained high levels of ATP and metabolic function, with suppression of lactate formation and accumulation. Thus, these findings support the concept that preservation of tissue viability is closely associated with the ability of the tissues to retain metabolic activity, to generate ATP efficiently, and to prevent acidosis effectively during storage.

Adenosine↗
PubMed1999

Decreasing levels of anti-Nef antibody correlate with increasing HIV type 1 viral loads and AIDS disease progression.

To study the association between anti-Gag and anti-Nef antibody reactivities and their correlations with disease progression, 174 HIV-1/AIDS patients were followed up for 1 year after they received triple therapy. The antibody reactivities were analyzed using a Western blot test with recombinant Gag and Nef proteins. The results showed that decreasing levels of anti-Gag or anti-Nef antibody correlate with disease progression defined by HIV-1 viral loads or T4 cell counts. After receiving triple treatment for 1 year, 8 of 38 (21.1%) Nef antibody-negative patients became positive, while only 9 of 125 (7.2%) Nef antibody-positive persons lost the antibody reactivity (p < 0.01). Therefore, HIV-1 Nef may serve as a clinical marker of disease progression.

Blotting, Western↗
PubMed1999

Depentylation of [3H-pentyl]methyl-n-amylnitrosamine by rat esophageal and liver microsomes and by rat and human cytochrome P450 isoforms.

Methyl-n-amylnitrosamine (MNAN) induces esophageal cancer in rats, probably involving activation by cytochromes P450. We studied the metabolic depentylation of MNAN. [3H-4,5-pentyl]MNAN and [3H-2,3-pentyl]-MNAN were synthesized, purified, and incubated with rat esophageal microsomes (REM) or rat liver microsomes (RLM) to give [3H]pentaldehyde (depentylation), an indicator of MNAN activation. [3H]Pentaldehyde was determined by high-performance liquid chromatography of its 2,4-dinitrophenylhydrazone. Adding 5 mM semicarbazide to incubations increased the observed depentylation (except that due to CYP2E1) by >60%. MNAN depentylation by REM and uninduced and induced RLM showed Km values of 64, 610, and 170-330 microM, respectively (Vmax: 20, 220, and 160-1270 pmol/mg protein/min, respectively). The depentylation of 100 microM MNAN by REM was inhibited 98% by CO and 65% by coumarin preincubated for 15 min with REM (Ki, 120 microM) but was unaffected by antibodies inhibitory to various P450s. MNAN inhibited coumarin 7-hydroxylation by RLM and CYP2A6 (Ki, 3000 and 320 microM, respectively). REM showed slight coumarin 7-hydroxylase activity. MNAN depentylation by RLM was 41% inhibited by an antibody to CYP2C11. Km for rat CYP2E1, human CYP2E1, and human CYP2A6 was 210, 115, and 17 microM, respectively (Vmax: 900, 570, and 120 pmol/nmol P450/min, respectively). We conclude that MNAN activation by REM is probably due to a P450 related to CYP2A3, a rodent nasal P450.

Animals↗
PubMed1999

Metaplastic carcinomas of the breast.

BACKGROUND AND OBJECTIVES: Metaplastic carcinomas of the breast are rare neoplasms. The purpose of the present study is to better characterize the clinical course, treatment, and prognostic factors of metaplastic breast carcinomas. METHODS: Data of 14 patients with metaplastic breast carcinoma were retrospectively reviewed. The follow-up period ranged from 2 months to 10 years, 10 months (median 4.3 years). RESULTS: The patients' ages ranged from 38 to 66 years (median 50.5 years). The tumors were 2.5 to 18 cm (median 4.8 cm) in size. Seven patients had axillary nodal metastases at the time of diagnosis. Estrogen and progesterone receptors were positive in only one tumor. Twelve patients underwent modified radical mastectomy and two patients underwent incisional biopsy. Adjuvant chemotherapy was administered to six patients, and radiotherapy to two patients after mastectomy. Two patients received preoperative chemotherapy. Seven patients were living without evidence of disease at a median of 7.3 years after surgery. A patient died of ovarian carcinoma without recurrence or metastasis of breast cancer. Metastases occurred in five patients at 4 to 16 months (median 8 months) after initial treatment. Duration of symptoms, TNM stage, tumor size, and axillary nodal status were significant prognostic factors of survival. CONCLUSIONS: The patients with metaplastic breast carcinomas may have a favorable prognosis.

Adult↗
PubMed1999

Oral urografin in postoperative small bowel obstruction.

The aim of our study was to determine whether Urografin has the potential to offer surgeons a way of differentiating complete from partial small bowel obstruction and whether partial small bowel obstruction can be treated nonoperatively. Altogether 116 patients who had postoperative small bowel obstructions without any toxic signs underwent Urografin studies. Urografin (40 ml) mixed with 40 ml of distilled water was administrated either orally or via nasogastric tube to each patient. Serial plain abdominal radiographs were taken 2, 4, and 8 hours later. A total of 74 patients (63.8%) whose contrast medium reached the colon within the first 8 hours were considered to have partial obstruction and were successfully treated with intravenous hydration and nasogastric decompression. The remaining 42 patients (36.2%) in whom the contrast medium failed to reach the colon within the first 8 hours were regarded as having complete obstruction, and 34 of those patients (81.0%) underwent surgery; 8 (19.0%) received conservative treatment. Adhesion bands with complete bowel obstruction were observed in all 34 patients (100.0%) during laparotomy. Regardless of the presence of an air-fluid level on a plain abdominal radiograph or abdominal pain, a liquid diet followed by a soft diet could be given to those patients whose Urografin emptied into the colon. All the patients with partial bowel obstruction were treated successfully with nonoperative methods. The presence of Urografin in the colon within 8 hours of ingestion as an indicator for nonoperative treatment had a sensitivity of 90.2%, a specificity of 100%, and an accuracy of 93. 1%. Urografin, a safe and reliable water-soluble contrast medium, can be used to differentiate partial intestinal obstruction from complete intestinal obstruction. Early oral intake was found to be a major advantage of Urografin use in this study, and the potential of Urografin use to shorten the period of conservative treatment for postoperative small bowel obstruction needs further investigation.

Administration, Oral↗
PubMed1999

Molecular characterization of ribulose-1,5-bisphosphate carboxylase/oxygenase activase in rice leaves.

A full-length cDNA (designated rcaII) encoding the Rubisco activase (RCA) of rice (Oryza sativa L.) has been cloned from a cDNA library constructed with mRNA from green leaves. Sequence analysis resulted in a reading frame of 432 amino acids with a calculated molecular mass of 47.9 kDa and an estimated isoelectric point of 5.97. The deduced amino acid sequence showed 74-89% identity with other Rubisco activases from higher plants. Two highly conserved motifs were identified. Southern blot analysis suggested the presence of a single rca gene in the rice genome. The accumulation of leaf rca mRNA was found to be regulated by an oscillating circadian rhythm, in rice plants grown in a light-dark photoperiod. To purify the rice RCA protein, total soluble protein from rice green leaves was fractionated by ammonium sulfate precipitation, followed by preparative gel electrophoresis. Two polypeptides, designated RCAI and RCAII, were isolated by two-dimensional gel electrophoresis and further confirmed by N-terminal sequencing. The polyclonal antibodies prepared against rice RCAI and RCAII were found to cross-react with two RCA polypeptides present in leaf extracts of spinach and tobacco. Furthermore, two different 3' ends of rca mRNA were detected by reverse transcription-polymerase chain reaction analysis. These cDNA fragments and the related genomic DNA fragment were cloned and sequenced. The sequence of rcaI is almost identical to the corresponding sequence of rcaII, except for its having 33 additional amino acids at the C-terminal portion. It can be concluded that a novel alternative splicing mechanism for a common rca mRNA precursor near the 3' end exists in rice plants.

Alternative Splicing↗
PubMed1999

Intrahepatic cholangiocarcinoma in Taiwan.

We report our experience of the surgical treatment of intrahepatic cholangiocarcinoma (ICC) in Taiwanese patients. A total of 162 patients with histologically proven ICC were treated of whom 106 (65. 4%) had associated hepatolithiasis. Patients with hepatolithiasis were in earlier stages than those without hepatolithiasis. Two-thirds of the patients with hepatolithiasis presented with acute cholangitis, and two-thirds of those without hepatolithiasis presented with hepatomegaly. The rate of hepatic resection was 29.6% (48 of 162), and these rates were 31.1% and 26.8% for the patients with and without hepatolithiasis, respectively. Ninety-three percent of the patients with hepatolithiasis underwent common bile duct exploration, compared with 18% of those without hepatolithiasis. The surgical mortality rates were 3.7% (6/162), for all patients, and 3. 8% and 3.6% for patients with and without hepatolithiasis, respectively. The morbidity rate was much higher in the patients with hepatolithiasis (37.7% vs 16.1%). The 1-, 3-, and 5-year survival rates were 35.5%, 20.5%, and 16.5% in the patients with hepatolithiasis and 27.2%, 8.8%, and 7.8% in those without hepatolithiasis. Concomitant hepatolithiasis prevented precise diagnosis preoperatively and precipitated biliary sepsis, which affected resectability and increased postoperative morbidity. Hepatolithiasis per se did not influence long-term survival.

Adult↗
PubMed1999

Sensitivity, specificity and predictive value of intra-operative elevation of hand temperature to ensure a successful T2-sympathectomy in patients with palmar hyperhidrosis.

To appraise the validity, intra-operative elevation of hand temperature ensuring a successful T2-sympathectomy, we conducted a randomized, self-compared, case-control study on 40 consecutive patients with palmar hyperhidrosis. All patients had a postoperative follow-up of at least 18 months without recurrence. During operation, dynamic temperature changes on their thenar eminence of both the surgically treated and non-surgically treated hands were simultaneously measured just before (baseline) and after completion of T2-sympathectomy, and again 5 and 10 minutes later. An elevation of the temperature by at least 0.5 degree C from the baseline temperature was recognized as an "elevated" temperature. The relationship between sensitivity and specificity of temperature changes was compared using receiver operator characteristic (ROC) analysis. Sensitivity was defined as the proportion of temperature-elevating procedures in the group of operated hands. As a whole, post-sympathectomy elevation of hand temperature is a useful, but not an ideal, indicator for assuring a successful T2-sympathectomy due to its low sensitivity. At the 5-minute point, if the hand temperature was elevated by 1 degree C, its sensitivity, specificity and positive predictive value were 40%, 80% and 66.7%. In comparison, a 2 degrees C elevation at the 10-minute point had a sensitivity, specificity and positive predictive value of 30%, 90% and 75% (p < 0.05). We suggest that correct localization of the T2 ganglion followed by adequate ablation should be the prerequisite for use of this monitoring system.

Adolescent↗
PubMed1999

Assessing the cost of a cardiology residency program with a cost construction model.

BACKGROUND: Although the total costs of graduate medical education are difficult to quantify, this information is of great importance in planning over the next decade. METHODS AND RESULTS: A cost construction model was used to quantify the costs of teaching faculty, cardiology fellows' salaries and benefits, overhead (physical plant, equipment, and support staff), and other costs associated with the cardiology residency program at the University of Texas-Houston during the 1996 to 1997 academic year. Surveys of cardiology faculty and fellows, checked by the program director, were conducted to determine the time spent in teaching activities; access to institutional and departmental financial records was obtained to quantify associated costs. The model was then developed and examined for a range of assumptions concerning cardiology fellows' productivity, replacement costs, and the cost allocation of activities jointly producing clinical care and education. The instructional cost of training (cost of didactic, direct clinical supervision, preparation for teaching, and teaching-related administration, plus the support of the teaching program) was estimated at $73,939 per cardiology fellow per year. This cost was less than the estimated replacement value of the teaching and clinical services provided by cardiology fellows, $100,937 per cardiology fellow per year. Sensitivity analysis, with different assumptions on cardiology fellows' productivity and replacement costs, varied the cost estimates but generally represented the cardiology residency program as an asset. CONCLUSIONS: Cost construction models can be used as a tool to estimate variations in resource requirements resulting from changes in curriculum or educators' costs. In this residency, the value of the teaching and clinical services provided by cardiology fellows exceeded the cost of the resources used in the educational program.

Cardiology↗
PubMed1999

ED overcrowding in Taiwan: facts and strategies.

The objective of this study was to quantity the extent of emergency department (ED) overcrowding in Taiwan and to identify possible solutions. The ED log was reviewed for all patients who presented to the National Taiwan University Hospital's ED from January 16, 1996 through February 15, 1996. Charts from patients held longer than 72 hours were reviewed. Among 5,810 patients, 213 (3.6%) were held in the ED for more than 72 hours (7.1 patients per day). In 149 (70.0%) of them, admission was indicated but delayed (42 because more than one subspecialty were involved, 57 because of unavailability of bed, and 50 because of the disparity in admission priority between the emergency physicians and house staffs). Eighteen (8.4%) patients did not meet admission criteria (13 could have been treated in outpatient clinics, 3 needed placement in nursing homes, 2 because of personal problems). The others (22%) recovered while waiting. Significant overcrowding exists in EDs in Taiwan. Four solutions are proposed: (1) creation of a holding unit; (2) flexible ward assignment; (3) pre-established rules for admission priority-setting; and (4) active interfacility transfer. Only through these efforts can EDs in Taiwan guarantee an optimal level of care in the face of a growing patient demand.

Appointments and Schedules↗
PubMed1999

Subcutaneous emphysema and pneumomediastinum after dental extraction.

Pneumomediastinum, pneumothorax, and subcutaneous emphysema can occur occasionally after a surgical procedure. Facial swelling is a common complication of dental management. The occurrence of subcutaneous emphysema, pneumothorax, and pneumomediastinum after dental procedures is rare. We present a case with subcutaneous emphysema of the upper chest, neck, chin, and pneumomediastinum after a tooth extraction and discuss the possible mechanism of subcutaneous emphysema. To prevent these complications during dental procedures, dental hand pieces that have air coolant and turbines that exhaust air in the surgical field should not be used.

Adult↗