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Biomedical subjects

L Tan

Publications and source records attributed to L Tan.

At least 55 records · Page 3Linked to original sources
PubMed2000

[Preoperative chemotherapy and operation for invasive Masaoke stage III and IV a thymoma].

OBJECTIVE: To assess the effect of preoperative chemotherapy on invasive thymoma. METHODS: Fourteen patients with invasive thymoma (12 cases in Masaoka stage III and 2 cases in stage IV a) were treated with 3-4 cycles of CAVP (cyclophosphamide 600 mg/m2 D1, adriamycin 30 mg/m2 or epi-adriamycin 40 mg/m2 D1, vincristine 0.6 mg/m2 D1 or vindestine 3 mg/m2 D1, D8, cisplatin 30 mg/m2 D1, 2, 3). Following chemotherapy, patients were operated within 1-3 months. In 10 patients, sternotomy was performed and in 4 patients, anterolateral thoracotomy was performed. Radiotherapy was given with a total dose of 50-60 Gy in all patients except in those who were pathologically in complete remission. The patients were followed up for 6 months to 3 years. RESULTS: After chemotherapy, complete response was observed in 5 patients (35.7%) and partial response in 9 patients (64.3%). Nine patients received radical tumor resection and 5 patients received partial resection. Histologic/examination of the surgical specimens showed fibrosis of the remnant thymus in 5 patients. All but two patients survived in the follow-up period. Patient died from distant metastases at 18 and 24 months after treatment, respectively. CONCLUSION: Preoperative chemotherapy helps increase the resectability of stage III and IV a invasive thymoma. A longer follow-up period and more patients are needed to ascertain the impact of this treatment strategy on long-term survival.

Adult↗
PubMed2000

[Determination of simvastatin in human plasma by high performance liquid chromatography].

Simvastatin is widely used in the treatment of hypercholestero-lemia. Recently, it was reported that it is also effective in reducing lethality in coronary heart disease. A simple and sensitive reversed-phase liquid chromatographic method has been developed and validated for the analysis of simvastatin in human plasma. Simvastatin and internal standard lovastatin in plasma were extracted with cyclohexane-dichloromethane (3.5:1, V/V), and then measured by HPLC using a Lichrospher C18 column as stationary phase and an acetonitrile-water (70:30, V/V) mixture as mobile phase. The flow rate was 1.2 mL/min. Simvastatin was quantified by UV at 237 nm. The calibration curve showed a good linearity in the mass concentration range of 0.25-50.0 micrograms/L. The regression equation is: Y = 0.0364 rho + 0.00583, r = 0.9998. Intra-day and inter-day coefficients of variation of assay for simvastatin in plasma < 7.94% and < 8.58%, respectively. The recoveries of simvastatin were > 93.3%. The method has been used to determine simvastatin in plasma from 12 healthy male volunteers.

Adult↗
PubMed1999

The Drosophila CPEB homolog, orb, is required for oskar protein expression in oocytes.

The establishment of polarity axes in the Drosophila egg and embryo depends upon the localization and on-site expression of maternal mRNAs. The critical step in the targeting of posterior determinants is the localization of oskar (osk) mRNA to the pole and its on-site translation. Osk protein then recruits other posterior group gene products involved in the formation of pole plasm and in the localization and regulation of the posterior determinant, nanos. Here we have investigated the role of the Drosophila CPEB homolog, the orb gene, in the osk mRNA localization pathway. We demonstrate that the expression of Osk protein is dependent upon the orb gene. In strong orb mutants, Osk protein expression is undetectable, while in the hypomorphic mutant, orb(mel), little or no on-site expression of Osk protein at the posterior pole is observed. The defects in Osk protein accumulation in orb mutant ovaries are correlated with a reduction in the length of the osk poly(A) tails. We show that osk mRNA is in immunoprecipitable complexes with Orb protein in ovaries and that the osk 3' UTR can be UV cross-linked to Orb protein in ovarian extracts. These data suggest that Orb is required to activate the translation of osk mRNA and at that this may be accomplished by a mechanism similar to that used by the Xenopus CPEB protein to control translation of "masked" mRNAs.

3' Untranslated Regions↗
PubMed1999

Identification and characterization of endothelial glycoprotein Ib using viper venom proteins modulating cell adhesion.

The expression and function of a glycoprotein Ib (GPIb) complex on human umbilical vein endothelial cells (HUVECs) is still a matter of controversy. We characterized HUVEC GPIb using viper venom proteins: alboaggregins A and B, echicetin, botrocetin, and echistatin. Echicetin is an antagonist, and alboaggregins act as agonists of the platelet GPIb complex. Botrocetin is a venom protein that alters von Willebrand factor (vWF) conformation and increases its binding affinity for the GPIb complex. Echistatin is a disintegrin that blocks alphavbeta3. Echistatin, but not echicetin, inhibited the adhesion to vWF of Chinese hamster ovary (CHO) cells transfected with alphavbeta3. We found the following: (1) Binding of monoclonal antibodies against GPIbalpha to HUVECs was moderately increased after stimulation with cytokines and phorbol ester. Echicetin demonstrated an inhibitory effect. (2) Both echicetin and echistatin, an alphavbeta3 antagonist, inhibited the adhesion of HUVECs to immobilized vWF in a dose-dependent manner. The inhibitory effect was additive when both proteins were used together. (3) Botrocetin potentiated the adhesion of HUVECs to vWF, and this effect was completely abolished by echicetin, but not by echistatin. (4) CHO cells expressing GPIbalphabeta/IX adhered to vWF (in the presence of botrocetin) and to alboaggregins; GPIbalpha was required for this reaction. Echicetin, but not echistatin, inhibited the adhesion of cells transfected with GPIbalphabeta/IX to immobilized vWF. (5) HUVECs adhered strongly to immobilized vWF and alboaggregins with extensive spreading, which was inhibited by LJ1b1, a monoclonal antibody against GPIb. The purified alphavbeta3 receptor did not interact with the alboaggregins, thereby excluding the contribution of alphavbeta3 in inducing HUVEC spreading on alboaggregins. In conclusion, our data confirm the presence of a functional GPIb complex expressed on HUVECs in low density. This complex may mediate HUVEC adhesion and spreading on immobilized vWF and alboaggregins.

Animals↗
PubMed1999

Microfabricated filters for microfluidic analytical systems.

Solvent and reagent filters were micromachined into quartz wafers using deep reactive ion etching to create a network of intersecting 1.5 x 10 microns channels. When placed at the bottom of reservoirs with a side exit, this channel network behaved as a lateral percolation filter composed of an array of cubelike structures one layer deep. Flow through these filters was driven by electroosmotic flow (EOF). Silanol groups at the walls of channels in the network provided the requisite charge to trigger EOF when voltage was applied laterally to the filter. Adsorption of cationic proteins in this silanol-rich matrix was controlled by the application of a polyacrylamide coating prepared by bonding N-hydroxysuccinimide (NHS)-activated poly(acrylic acid) to (gamma-aminopropyl)silane-derivatized filters. Subsequent reaction of residual NHS groups in the coating with 2-(2-aminoethoxy)ethanol provided channels of low charge density and adsorptivity. These lateral percolation filters were shown to be efficacious in filtering solvents containing a variety of particulate materials, ranging from dust to cells.

Adsorption↗
PubMed1999

Saikosaponins from roots of Bupleurum scorzonerifolium.

Saikosaponin u and saikosaponin v, were isolated from the roots of Bupleurum scorzonerifolium and these saponins were identified as 3-O-[beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranosyl- (1-->3)-beta-D-fucopyranosyl]-3 beta,16 alpha,23,28-tetrahydroxy-olean- 11,13(18)-dien-30-oic acid-30-O-[pentito(1-->1)-beta-D-glucopyranosyl-(6-->)] ester and 3-O-[beta-D-glucopyranosyl-(1-->3)-beta-D-fucopyranosyl]-3 beta,16 alpha,23,28-tetrahydroxy-olean-11,13(18)-dien-30-oic acid-30-O-[pentito(1-->1)-beta-D-glucopyranosyl(6-->)] ester, respectively.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1999

Role of screening chest computed tomography in patients with advanced head and neck cancer.

OBJECTIVE: The presence of pulmonary metastases significantly alters the treatment of patients with head and neck cancers. Currently, a chest radiograph (CXR) is used as a screening examination, although a chest CT (CCT) can detect smaller lesions. The aim of this study was to evaluate the benefit of CCT as a screening tool in patients with newly diagnosed advanced head and neck cancers. METHOD: New patients with stage III and IV head and neck squamous cell carcinomas were enrolled in this prospective study from August 1994 to December 1995. Twenty-five patients underwent CXR ($71) and CCT ($597) within 2 weeks of diagnosis of the index cancer. RESULTS: In 20 patients neither the CXR nor the CCT showed any evidence of pulmonary malignancy. Two patients had normal CXRs but possible metastases on CCT. Both the pulmonary lesions resolved on follow-up evaluation. Two patients had suspicious lesions on CXR, 1 of whom had a normal CCT. The second patient underwent CT-guided biopsy which was negative for malignancy. Both the CXR and CCT of the final patient, who had a bronchogenic carcinoma, were suspicious. CONCLUSION: In 2 patients CCT detected suspicious lesions missed on CXR, although neither revealed malignancy. Three patients with suspicious CXRs would have had CCTs anyway. Thus 22 of 25 CCTs done at the additional cost of $13,314 did not add to the sensitivity of the screening for pulmonary metastasis or second lung primary.

Adult↗
PubMed1999

Diffuse alveolar damage in BCGosis: a rare complication of intravesical bacillus Calmette-Guérin therapy for transitional cell carcinoma.

Intravesical administration of bacillus Calmette-Guérin is a relatively simple procedure used in the treatment of superficial transitional cell carcinoma of the urinary bladder. It is usually well tolerated with few major side effects. In rare instances, systemic complications can result in death. The usual autopsy finding is that of caseating and non-caseating granulomata in the affected organ. We report the second case of BCGosis in which granulomata together with acute and organising phase diffuse alveolar damage were found in the lungs.

Aged↗
PubMed1999

Biomechanics of A-to-T flap design.

OBJECTIVES/HYPOTHESIS: The objective of this study was to determine the vertical height, horizontal incision width, and extent of undermining that correlated with the lowest closure tension. STUDY DESIGN: Prospective, cadaver study. METHODS: Forty "A-to-T" flaps were made on the torso and lower extremities of fresh cadavers. Ten flaps each were designed at heights of three, four, and five defect radii. Closing tensions were measured for each of these flaps initially, followed by serial base extensions. Based on the information from these first flaps, 10 additional flaps were made at the optimal height and base extensions. These flaps were then serially undermined and tension measurements taken. RESULTS: Our results suggest that making the vertical height of the "A" twice the height of the defect yields a significant decrease in tension of closure when compared with a vertical height one and a half times the defect (P < .01), while increasing the height to two and a half times the defect height provides only a minimal further reduction in closure tension. Extending the base (horizontal) incision one defect diameter in each direction offers the greatest reduction in closing tension. Undermining up to three times the diameter of the defect offers progressive improvement in the tension of closure, while further undermining confers little additional benefit. CONCLUSIONS: Our findings indicate that the ideal A-to-T flap is designed to be twice the height of the original defect, with base extensions one defect diameter in each direction, and undermined to three times the diameter of the defect.

Biomechanical Phenomena↗
PubMed1999

An integrated theory of the no-reflow phenomenon and the beneficial effect of vascular washout on no-reflow.

OBJECTIVES: No-reflow is failure of perfusion in free tissue transfer despite adequate arterial inflow. The objectives of this study were to construct a theory of interactive mechanisms of the no-reflow phenomenon and to determine whether preischemic vascular washout could increase flap ischemia tolerance. STUDY DESIGN: The evidence for the role of various mechanisms in the development of no-reflow is reviewed, and an integrated network proposed. A rat-groin free flap model is used to test preischemic vascular washout with normal saline, heparinized normal saline, lactated Ringer's solution, Tis-U-Sol, and Viaspan. METHODS: The mean ischemia tolerance of this flap without any therapeutic intervention was first determined, using 22 animals. An additional 50 animals were used to compare with the control group the ischemia tolerance of flaps washed out with the above fluids before their ischemic period. RESULTS: The critical ischemia time 50 (time after which half of the flaps are expected to survive and half, die) of the untreated flap is 23.4 hours in this model (P<.05). Flaps washed out with normal saline or lactated Ringer's solution have significantly worse ischemia tolerance (P<.0001). Flaps washed out with Tis-U-Sol or Viaspan behave similarly to the control group (P>.57). Flaps receiving preischemic washout with heparinized normal saline (4,000 units/L) had a significantly better outcome than the control group (P<.027). CONCLUSIONS: Preischemic washout with normal saline, lactated Ringer's solution, or heparinized Tis-U-Sol is detrimental for flap survival after ischemia, Tis-U-Sol- and Viaspan-treated flaps do have ischemia tolerance similar to the control group, and flaps washed out with heparinized normal saline have a survival advantage in this model.

Animals↗
PubMed1999

Interobserver variability in the measurement of internal carotid stenosis.

OBJECTIVE: To assess interobserver variability in the measurement of carotid stenoses from digital subtraction angiograms displayed in different ways (nonmagnified or magnified, white or black arteries); and to compare human readers with computer-generated densitometric measurements of vessel stenosis. METHODS: Digital subtraction angiograms of 20 proximal internal carotid artery stenoses were laser printed in the following ways: (1) Nonmagnified white artery on a black background; (2) Magnified white artery on a black background; (3) Nonmagnified black artery on a white background; (4) Magnified black artery on a white background. This resulted in 80 images of internal carotid artery stenoses. These stenoses were independently measured by 4 radiologists using the North American Symptomatic Carotid Endarterectomy Trial method. A computer-generated densitometric measurement of the black nonmagnified images was also obtained. RESULTS: The most reliable stenosis measurements were obtained from the nonmagnified black and white artery images. The interobserver variability in the measurement of internal carotid stenoses using these images was quite small. Variability increased with the use of magnification. The computer-generated stenosis measurements were consistently much higher than those of the radiologists. CONCLUSION: There was significant variability in measurements made from magnified images and between human readers and computer-generated measurements. This has great clinical significance. Readers of digital angiographic images must determine the most reliable, reproducible images generated by their equipment, as these measurements significantly affect treatment of patients with symptomatic internal carotid artery stenosis.

Absorptiometry, Photon↗
PubMed1999

Treatment of delayed partial bronchial rupture with expandable metallic stent.

Traumatic bronchial rupture is a rare entity. The severity of the trauma often causes lethal injury to other thoracic organs. The incidence in patients with blunt chest trauma admitted to the hospital ranges from 1.5% to 3%. As a rule, early diagnosis and surgical treatment are important to facilitate successful repair of the disruption. We describe an unusual case of bronchial rupture which was diagnosed 15 days after blunt chest trauma and was treated by bronchial stenting. The success of this case involving the left main bronchial rupture provides a feasible alternative to the repair of partial airway disruption and greatly reduces the morbidity.

Adult↗
PubMed1999

[Influence of nitric oxide upon cerebral infarction in 15 cases].

To study the role of the nitric oxide(NO) in patients with cerebral infarction, NO in cerebrospinal fluid was determined in cerebral infarction group(15 cases) and control group(10 cases). Infarct volume was determined by CT between the second and the 7th day after the onset of symptoms. The severity of neurological deficits was assessed with the stroke scale of Ministry of Public Healthy(China). The results showed that NO was higher in cerebral infarction group (3.12 +/- 1.60) than that in control group(1.19 +/- 1.01) (P < 0.01). The concentration of NO was positively correlated with infarction volume(r = 0.57, P < 0.05) and severity of neurological of deficits(r = 0.54, P < 0.05), respectively. The results support the conclusion that NO produced in large amounts in the postischemic tissue contributes to the progression of the brain damage, which was demonstrated in animal models of focal cerebral ischemia.

Adult↗
PubMed1999

[Survey of jugular bulb with MRA in sudden sensorineural hearing loss].

To evaluate the correlation between the size and position of the jugular bulb and the sudden sensorineural hearing loss(SSHL), the diameter and height of all jugular bulbs were measured with magnetic resonance angiography and analysed with statistics in 15 cases with SSHL and 35 cases without SSHL(as control). The ipsilateral and the contralateral bulbs of the SSHL were more asymmetrical than that of the control. The mean diameter and height of the ipsilateral bulbs of SSHL were larger than that of the dominant side bulbs of the control. It indicates that the heteroplasia of jugular bulbs which were greatly enlarged and bulgy upward might be related to SSHL.

Adult↗
PubMed1999

Feasibility study of an ultrasound contrast agent (levovist) in color Doppler imaging of liver neoplasms.

The purpose of this study was to determine the efficacy of using an ultrasound contrast agent (levovist) to enhance the color Doppler imaging of liver neoplasms. Thirty patients with hepatic tumors were enrolled in this study. After intravenous administration of levovist, the color Doppler signals of normal hepatic vessels were enhanced. In various hepatic tumors, the different patterns of tumor vascularity were observed, which had not been demonstrated in conventional non-contrast color Doppler imaging. In 11 of 16 patients with hepatocarcinoma, additional color Doppler signals were observed in the central part of the tumors. On the contrary, 3 patients with metastatic liver lesions the enhanced color Doppler signals appear only at the peripheral of tumors. A typical rim-like color enhancement was seen in 2 of the 3 cases. In six patients with hepatic hemangiomas contrast-enhanced color Doppler imaging demonstrated the blood vessels at the margin of the neoplasms. Contrast-enhanced color Doppler imaging improves the visualization of the hepatic neoplasm vascularity. This technique holds great promise for detecting small liver tumors and differentiating hepatic neoplasms.

Adult↗