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Biomedical subjects

T C Chen

Publications and source records attributed to T C Chen.

At least 73 records · Page 4Linked to original sources
PubMed2000

A human skin equivalent model that mimics the photoproduction of vitamin D3 in human skin.

A human skin equivalent was prepared by culturing human keratinocytes on the surface of nylon filtration meshes containing human skin fibroblasts and by growing the epidermal cells at the air-liquid interface. This human skin equivalent model was used to mimic the photoproduction of vitamin D3 in human skin. It was found that the concentration of 7-dehydrocholesterol and its photoconversion to previtamin D3 and its subsequent thermal isomerization to vitamin D3 in the human skin equivalent was essentially identical to that of human skin. The 7-dehydrocholesterol content in the skin equivalent and human skin was 2187 +/- 296 and 2352 +/- 320 ng/cm2, respectively. The percentage of the major photoproducts of 7-dehydrocholesterol in the skin equivalent following ultraviolet B radiation (0.5 J/cm2) was 35% pre-vitamin D3, 29% lumisterol, and 6% tachysterol; 30% remained as 7-dehydrocholesterol. Similarly, in human skin they were 36%, 29%, 7%, and 28%, respectively. After incubation at 37 degrees C for 30 min, 11% and 12% of the previtamin D3 had thermally isomerized to vitamin D3 in the skin equivalent and human skin. In conclusion, compared with cultured keratinocytes or fibroblasts, the human skin equivalent model provides a superior in vitro system that better mimics the physiology and biochemistry of the photosynthesis of vitamin D3 in human skin.

Cholecalciferol↗
PubMed2000

Reduction of Campylobacter jejuni in a simulated chicken digestive tract by Lactobacilli cultures.

Studies were conducted to investigate the impact of a selected lactobacilli mixed culture on Campylobacter jejuni in simulated chicken digestive tract models. Veronal buffer solutions corresponding to the pH of successive segments of the chicken digestive tract were prepared. The lactobacilli mixtures were prepared by mixing four fresh lactobacilli cultures, including Lactobacillus acidophilus, Lactobacillus fermenentum, Lactobacillus crispatus, and Lactobacillus brevis. The C. jejuni and lactobacilli mixture were mixed with sterile poultry feed, and the previously prepared veronal buffer solutions were then added separately. The mixture was incubated at 41.1 degrees C for various lengths of time with periodic agitation. The feed passage time for five segments of the digestive tract were adopted: crop (pH 4.5), 30 min; proventriculus (pH 4.4), 15 min; gizzard (pH 2.6), 90 min; small intestine (pH 6.2), 90 min; and large intestine (pH 6.3), 15 min. The Campylobacter and lactobacilli were enumerated. An antagonistic effect on C. jejuni by the tested lactobacilli spp. was found in individual sections and the complete simulated digestive tract models. In the simulated complete chicken digestion system, no C. jejuni were found during the final incubation period when a lactobacilli mixture was present. The results of this in vitro study indicate the potential value of future in vivo studies.

Animals↗
PubMed2000

The in vitro evaluation of 25-hydroxyvitamin D3 and 19-nor-1alpha,25-dihydroxyvitamin D2 as therapeutic agents for prostate cancer.

Prostate cancer cells contain specific receptors [vitamin D receptors (VDRs)] for 1alpha,25-dihydroxyvitamin D3 (1alpha,25(OH)2D3), which is known to inhibit the proliferation and invasiveness of these cells. These findings support the use of 1alpha,25(OH)2D3 for prostate cancer therapy. However, because 1alpha,25(OH)2D3 can cause hypercalcemia, analogues of 1alpha,25(OH)2D3 that are less calcemic but that exhibit potent antiproliferative activity would be attractive as therapeutic agents. We investigated the effects of two different types of less calcemic vitamin D compounds, 25-hydroxyvitamin D3 [25(OH)D3] and 19-nor-1alpha,25-dihydroxyvitamin D2 [19-nor-1,25(OH)2D2], and compared their activity to 1alpha,25(OH)2D3 on (a) the proliferation of primary cultures and cell lines of human prostate cancer cells; and (b) the transactivation of the VDRs in the androgen-insensitive PC-3 cancer cell line stably transfected with VDR (PC-3/ VDR). 19-nor-1alpha,25(OH)2D2, an analogue of 1alpha,25(OH)2D3 that was originally developed for the treatment of parathyroid disease, has been shown to be less calcemic than 1alpha,25(OH)2D3 in clinical trials. Additionally, we recently showed that human prostate cells in primary culture possess 25(OH)D3-1alpha-hydroxylase, an enzyme that hydroxylates the inactive prohormone, 25(OH)D3, to the active hormone, 1alpha,25(OH)2D3, intracellularly. We reasoned that the hormone that is formed intracellularly would inhibit prostate cell proliferation in an autocrine fashion. We found that 1alpha,25(OH)2D3 and 19-nor-1alpha,25(OH)2D2 caused similar dose-dependent inhibition in the cell lines and primary cultures in the [3H]thymidine incorporation assay and that both compounds were significantly more active in the primary cultures than in LNCaP cells. Likewise, 25(OH)D3 had inhibitory effects comparable to those of 1alpha,25(OH)2D3 in the primary cultures. In the chloramphenicol acetyltransferase (CAT) reporter gene transactivation assay in PC-3/ VDR cells, 1alpha,25(OH)2D3 and 19-nor-1alpha,25(OH)2D2 caused similar increases in CAT activity between 10(-11)and 10(-9) M. Incubation of PC-3/VDR cells with 5 x 10(-8) M 25(OH)D3 induced a 29-fold increase in CAT activity, similar to that induced by 10(-8) M 1alpha,25(OH)2D3. In conclusion, our data indicate that 25(OH)D3 and 19-nor-1alpha,25(OH)2D2 represent two different solutions to the problem of hypercalcemia associated with vitamin D-based therapies: 25(OH)D3 requires the presence of 1alpha-hydroxylase, whereas 19-nor-1alpha,25(OH)2D2 does not. Both drugs are approved for human use and may be good candidates for human clinical trials in prostate cancer.

Calcifediol↗
PubMed2000

Tuberculosis presenting with pelvic mass, peritoneal lesions, and elevation of serum CA125 mimicking malignant tumor: a case report.

Tuberculosis is a curable infective disease which can mimic a malignant tumor. We report on a young woman who presented with abdominal fullness, body weight loss, and microcytic anemia. A pelvic mass and peritoneal lesions were found. The serum CA125 level was high. The initial gynecologic echo and abdominal CT scan revealed bilateral ovarian mass with peritoneal lesions, and malignancy was highly suspected. Diagnostic laparoscopy was performed, and peritoneal tuberculosis was pathologically proven. Combination anti-tuberculosis therapy was prescribed for one year. She was followed up in the outpatient clinic regularly with symptom improvement, body weigh gain, and improvement of anemia. We suggest that in cases of a pelvic mass and peritoneal lesions, with elevation of the serum CA125 level, tuberculosis should always be kept on the list of differential diagnoses. A tissue diagnosis should always be obtained before treatment, regardless of initial image study and laboratory findings.

Adult↗
PubMed2000

Pseudomelanosis duodeni: case report.

Pseudomelanosis duodeni is a rare benign condition. It manifests endoscopically as discrete, flat, small brown-black spots in the duodenal mucosa. It produces no symptoms and may be reversible. The cause and natural history of the pigmentation have not been clarified, although it is associated with a variety of systemic illnesses and medications. With electron microscopy and electron-probe energy dispersive X-ray analysis, the pigment corresponds principally to an accumulation of ferrous sulfide (FeS) in macrophages within the lamina propria. We report the case of a 56-year-old female patient with a past history of diabetes mellitus and hypertension. She was admitted because of nausea, vomiting, and diarrhea and underwent esophagogastroduodenoscopy because of stool occult blood test results of 3+. Endoscopy revealed diffusely scattered black spots in the bulb and second portion of the duodenum. Histological examination showed numerous pigment-laden macrophages in the lamina propria of mucosal villi. The diagnosis requires further confirmation by electron microscopy and electron-probe energy dispersive X-ray microanalysis. No special therapy is indicated for this rare lesion.

Duodenal Diseases↗
PubMed2000

Inflammatory pseudotumor of the liver mimicking a malignancy: case report.

Inflammatory pseudotumor (IPT) is a rare lesion of the liver that can be clinically indistinguishable from a malignant tumor. A 51-year-old woman was hospitalized for upper abdominal pain and a weight loss of 5 Kg in 2 months. Radiological examination showed a large heterogenous hypervascular mass in the left lobe of her liver, strongly in favor of hepatocellular carcinoma. However, an ultrasound-guided liver biopsy revealed the typical characteristics of IPT, which consist of plump spindle cells with dense inflammatory cell infiltration. A left lobectomy was performed. No microorganisms were found on stained sections. The markedly elevated eosinophil count reverted to normal postoperatively and she remained well on follow-up examination 8 months after discharge. This case exemplifies the difficulty in radiological diagnosis of hepatic IPT and underscores the importance of its histological differentiation from malignancy before laparotomy.

Female↗
PubMed2000

Ticlopidine-induced cholestatic hepatitis with anti-nuclear antibody in serum.

We describe a case of severe cholestatic hepatitis following administration of ticlopidine. A 57-year-old man without known liver disease developed jaundice approximately 3 weeks after initiation of ticlopidine for secondary prevention of stroke. Hyperbilirubinemia and abnormal liver function test values resolved 5 months after withdrawal of ticlopidine. The diagnosis of ticlopidine-induced cholestasis was made after thorough investigations had excluded other causes of jaundice. He was not retreated with ticlopidine. This case may serve to illustrate the possibility of ticlopidine hepatotoxicity, which has rarely been reported. Furthermore, to the best of our knowledge, ticlopidine-induced cholestatic hepatitis accompanied by autoantibody has not been previously reported. This case suggests that regular assessment of liver function should be performed in the initial 3 months of ticlopidine treatment due to the potential risk of adverse effects. In patients with abnormal biochemical test results, autoantibodies should be assessed.

Antibodies, Antinuclear↗
PubMed2000

Diverticulosis of the appendix with diverticulitis: case report.

Diverticulum of the appendix is rarely encountered. A case of appendiceal diverticulosis is described. A 46-year-old male patient was sent to our hospital with presentation of acute appendicitis-like symptoms. The appendix was removed by laparoscopic appendectomy, and it showed erythematous change with local peritoneal reaction and omental shift at the tip. Pathological examination revealed three diverticula in the appendix. One of them was inflamed but the appendix itself was not. All three diverticula were pseudodiverticula, lacking muscularis propria. The appendix in this case showed only focal inflammatory change, which differs from what occurs in acute appendicitis, where diffuse inflammation of the appendix is usually noted. In cases of an appendix with only focal erythematous change, minor lesions such as diverticulitis may be revealed by pathological examination, and an appendectomy is still warranted. Diverticulitis of the appendix cannot be differentiated from acute appendicitis preoperatively. Image studies including abdominal computed tomography scan, ultrasonography, and plain film cannot improve the diagnosis. To our knowledge, diverticulosis of the appendix has never been reported in Taiwan.

Appendicitis↗
PubMed2000

Partial anomalous pulmonary venous connection draining into superior vena cava--two cases reports.

Anomalous pulmonary venous connection is a relatively common associated anomaly in patients with atrial septal defect (ASD), particularly among those with the sinus venosus type. The incidence of partial anomalous pulmonary venous connection (PAPVC) is higher than 0.7% in the general population and 10% in patients with ASD. In this study, we present two cases with initial impression of ASD, the sinus venosus type in one and the secundum type in the other. The one with the sinus venosus type was found to have a PAPVC that drained into SVC, and the other was suspected of having the same problem because an abnormal shunt was found during cardiac catheterization. This speculation could not be proved, however, due to transesophageal echocardiogram failure. Because we feared the possibility of cardiac defects other than ASD, we performed a minimally invasive operation using a small midline incision instead of the submammary incision and did a full median sternotomy on the patient to look for other complicating coexistent cardiac defects. This patient and the former one were both proven intraoperatively to have a PAPVC that drained into SVC with sinus venosus ASD. The operation to correct an ASD is a rudimentary procedure, and it often becomes a common type of minimally invasive operation among young cardiac surgeons with limited experience. A submammary incision under the impression of simple ASD may meet with certain complications. Therefore, after our experience with the latter case, we do the minimally invasive operation using a small midline incision, which can be easily extended if need be.

Adult↗
PubMed2000

Discrete subaortic membranous stenosis--a case report.

Isolated subaortic stenosis is a rare type of cardiac anomaly which has been characterized as having two types: the discrete type, including membranous or fibromuscular, and the tunnel type. In the discrete type, a crescent-shaped, fibrous curtain is attached to the ventricular septum or completely encircles the left ventricular outflow tract and can be located anywhere from immediately below the aortic valve to 10 mm or more into the body of ventricle. A 22-year-old female presented at our hospital with a divided PDA, a murmur that was found by incident and progressive exertional dyspnea. Echocardiography revealed left ventricular hypertrophy, moderate aortic insufficiency, and severe aortic stenosis characterized by a thickened aortic valve and membranous type subaortic stenosis with a transmembranous high pressure gradient, 121 mmHg. An operation to replace the aortic valve and excise the membranous collar was performed with cardiopulmonary bypass support. The patient did well during the postoperative follow-up period. If the preoperative LVOT pressure gradient had been higher than 45 mmHg, the incidence of recurrent stenosis, progression of aortic regurgitation and the need for reoperation would have been higher. In order to prevent this from happening, we chose to replace the defective valve with a mechanical valve and enucleate the discrete lesion.

Adult↗
PubMed1999

Goniosurgery for prevention of aniridic glaucoma.

OBJECTIVE: To report the long-term success and complications of modified goniosurgery to prevent aniridic glaucoma, an entity that typically is difficult to control medically or surgically. DESIGN: A retrospective review of the medical charts. RESULTS: Fifty-five eyes in 33 patients who had aniridia without glaucoma and who underwent goniosurgery were identified. Ninety-one procedures were performed on the 55 eyes by 1 surgeon (D.S.W.). Each eye had an average of 1.65 procedures and an average of 200 degrees of goniosurgery. Average age at time of initial goniosurgery was 36.6 months. There were no operative complications. No eye had a decrease in visual acuity at last follow-up. All eyes had a preoperative intraocular pressure (IOP) less than 21 mm Hg. At last follow-up (average, 9 years 6 months; range, 8 months to 24 years), 49 eyes (89%) had IOPs less than 22 mm Hg without medications. The remaining 6 eyes (11%) had IOPs of 22 mm Hg or less with up to 2 types of eyedrops. CONCLUSIONS: Without prophylactic goniotomy, aniridic glaucoma may be expected in half of patients, and when it occurs, it is extremely difficult to control. Prophylactic goniosurgery in selected eyes of young patients with aniridia may be effective in preventing aniridic glaucoma.

Aniridia↗
PubMed1999

Telomerase activity is a useful marker to distinguish malignant pancreatic cystic tumors from benign neoplasms and pseudocysts.

BACKGROUND: Pancreatic serous cystadenoma, mucinous cystic neoplasms, ductal adenocarcinoma with cystic change, and pseudocysts are a spectrum of pancreatic cystic lesions. Their management strategy and prognosis are extremely diverse. Imaging study, cytology, and analysis of the tumor markers of cyst fluid are not always reliable in differentiation of these disease entities. MATERIALS AND METHODS: Fifteen patients with pancreatic cystic neoplasms (including six mucinous cystadenocarcinomas, two mucinous cystic neoplasms with borderline malignancy, two mucinous cystadenomas, and five serous cystadenomas), 4 patients with pancreatic ductal adenocarcinomas with cystic change, and 10 patients with pseudocysts were studied. Echo-guided or computed tomography-guided biopsies of pancreatic cystic lesions and their normal counterparts were conducted on all patients prior to operation or other management. The specimens were assayed for telomerase activity by using TRAP (telomere repeat amplification protocol). The level of telomerase activity in each specimen was semiquantitated as strong, moderate, weak, and none. The final diagnoses were made from histopathological examination of surgically resected or biopsied specimens. The efficacy of telomerase activity as a tumor marker to predict malignancy of pancreatic cystic lesions was evaluated. RESULTS: Three of the four pancreatic ductal adenocarcinomas with cystic change had strong or moderate telomerase activity; four of the six mucinous cystadenocarcinomas had moderate or weak telomerase activity; one of the two mucinous cystadenomas with borderline malignancy had weak telomerase activity; and none of their normal counterparts had detectable telomerase activity. In contrast, none of the two mucinous cystadenomas, five serous cystadenomas, and 10 pseudocysts had detectable telomerase activity. Based on these results, the sensitivity of telomerase activity for prediction of malignancy or premalignancy of pancreatic cystic lesions was 67%, the specificity was 100%, and the positive and negative predictive values were 1.0 and 0.81, respectively. The overall accuracy was 86%. CONCLUSIONS: The differential expressions of telomerase activity have been detected specifically in malignant and premalignant pancreatic cystic tumors, but not in benign cystic neoplasms or pseudocysts. The implications of these results are that telomerase activation takes part in the malignant transformation of pancreatic cystic neoplasms and that telomerase activity is a useful marker to distinguish malignant pancreatic cystic tumors from benign neoplasms and pseudocysts.

Adult↗
PubMed1999

A patient with bilateral primary adrenal lymphoma, presenting with fever of unknown origin and achieving long-term disease-free survival after resection and chemotherapy.

Primary adrenal lymphoma is extremely rare. We describe a 64-year-old female patient who presented with fever of unknown origin. Imaging studies demonstrated bilateral bulky adrenal masses. She underwent bilateral adrenalectomy and the pathological diagnosis was large cell immunoblastic (B-cell) lymphoma. She received adjuvant combination chemotherapy with cyclophosphamide, doxorubicin, vincristine, and prednisolone in the following 6 months. She has been relapse free for 52 months. To the best of our knowledge, this case has the longest disease-free survival among those reported. The present case indicated that primary adrenal lymphoma should be included in the differential diagnosis of fever of unknown origin and/or suprarenal mass. Chemotherapy following surgical resection may be considered the treatment of choice.

Adrenal Cortex↗
PubMed1999

Prediction of tacrolimus blood levels by using the neural network with genetic algorithm in liver transplantation patients.

The neural network (NN) is a technique using an artificial intelligent concept in predicting outcomes by using various input variables. Tacrolimus pharmacokinetics has wide inter- and intra-subject variability and it is often difficult to predict its blood concentrations by dose alone. The objectives of this study are to select the clinically significant variables and to predict the blood concentration of tacrolimus in liver transplant patients by NN combined with genetic algorithm (GA). A total of thirty-two adult liver transplant patients from the University of Iowa Hospitals and Clinics were selected and the patients' data were retrospectively collected. These patient were randomly assigned into two groups: either the training group (n = 10), or testing group (n = 22). A back propagation (BP) NN was developed which contained two hidden layers. A dynamic BP NN based on the time series concept was trained by using the current and previous data sets to predict the trough levels of tacrolimus. The mean of the NN prediction for tacrolimus blood levels was not significantly different from the observed value by a paired t-test comparison (12.05+/-2.67 ng/ml vs. 12.14+/-2.64 ng/ml, p = 0.80). The average difference of the testing sets between the observed and predicted levels was 1.74 ng/ml with a range from 0.08 to 5.26 ng/ml which is clinically acceptable range. Thirty-seven out of 44 data sets (84%) in the testing group were within 3.0 ng/ml of the observed values. This study demonstrated that tacrolimus blood concentrations are precisely predictable in liver transplant patients using patients variables by NN.

Adult↗
PubMed1999

Primary hepatic epithelioid hemangioendothelioma: case report.

Hepatic epithelioid hemangioendothelioma (HEH) is a very rare vascular tumor of the liver. It usually affects adult women and presents as multiple hepatic nodules with mainly peripheral distribution. It poses special difficulties for clinicians in its diagnosis and treatment because of its non-specific clinical manifestations and findings on imaging, and it is easy to be misdiagnosed pathologically. Its clinical course and prognosis are variable but supposed to be intermediate between hemangioma and angiosarcoma. The primary treatments of choice are radical resection or liver transplantation. We report a 62-year-old man with right upper quadrant abdominal pain of several days' duration, who was initially misdiagnosed as having a liver abscess. Finally, HEH was diagnosed on the basis of positive immunohistochemical staining for factor VIII-related antigen in tumor cells. This case could serve to highlight the pitfalls in diagnosing this rare tumor. Increasing the index of suspicion and familiarity with the radiological and histological characteristics of this tumor would facilitate the accurate diagnosis and thus avoid unnecessary interventions.

Biopsy↗