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Biomedical subjects

Y Sun

Publications and source records attributed to Y Sun.

At least 1,099 records · Page 61Linked to original sources
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A new triterpene glycoside from Asterias rollentoni.

A new triterpene glycoside, rollentoside A, has been isolated from Asterias rollentoni Bell and identified as 3beta-O-{3-O-methyl-beta-D-xylopyranosyl-(1-->3)-O-beta-D-glucopyranosyl-(1-->4)-O-beta-D-quinopyranosyl-(1-->2)-O-beta-D-xylopyranosyl}-16-beta-acetoxy-23S-acetoxy-holost-7-ene (1), together with a new natural product, rollentoside B (2). The structures of compounds1 and 2 were elucidated by extensive 1D and 2D NMR investigation (1H-1H COSY, TOCSY, HSQC, HMBC, NOESY).

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A novel percutaneous barrier device that permits safe subcutaneous access.

Successful subcutaneous access is important for optimal management of internal artificial organs and treatment of many diseases. However, skin downgrowth and tissue infection are still significant problems in the use of devices that require long-term subcutaneous access. The authors developed a new percutaneous device that provides a unique biologic boundary with surrounding connective tissue while minimizing the risk of complications. This new percutaneous device is made of a circumferential, strong, thin, and flexible mesh collar with millimeter size holes for connecting the structure. It has two distinct functional portions: a connecting zone and a sealing line. The most important features of the structure are: 1) Connective tissue grows through the millimeter size pores of the connecting zone to form a strong bond between the device and healthy tissue. 2) The millimeter size pores of the connecting zone allow capillaries to grow through its entire surface, ensuring sufficient blood supply. 3) The tissue of the connecting zone and the device surface form a biosealed junction (sealing line). This sealing line is protected by the connecting zone and is free from external forces acting on local skin. 4) The device is generally functional immediately after surgical implantation. The subcutaneous perimeter of the functional dome contains extruded rigid rings of millimeter size holes permitting growth of subcutaneous tissue through the device. This functions as the minor connecting structure of the device. Four of five implanted rabbits have remained healthy 8 months postimplantation without antibiotic administration. The fifth rabbit died 4 months postimplantation for reasons unrelated to the device. Gross or histopathologic inspection revealed no signs of tissue injury or inflammation. Growth of healthy connective tissue was clearly observed. These results indicate this percutaneous device can provide a strong, stable, and effective connection to internal organs without bioboundary damage, skin downgrowth, or tissue infection.

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Umbilical cord stricture and intrauterine fetal death.

Umbilical cord stricture is an uncommon but distinctive condition associated with intrauterine fetal death. Although cases have been reported periodically since the last century, there has been considerable speculation as to whether the condition is real or a postmortem artifact. In the present study, 25 cases reported since 1925 are reviewed and 8 new cases are described. Clinically, a decrease in fetal movements is usually the only symptom during the second or third trimester of pregnancy and fetal death occurs soon after. The women's age, health, and previous history have shown no link with this condition, but a higher incidence is noted in twin pregnancies. Morphologically, most infants are macerated and an extremely narrow segment of umbilical cord is usually seen at the fetal end and rarely at the placental end or in multiple sites along the cord. Absence of Wharton's jelly, stenosis, or obliteration of cord vessels at the narrow segment and intravascular cord thrombosis are the major pathological features. The findings of this study support the view that the condition can cause fetal death and alerts both pathologists and clinicians to the important features identifying this cause of perinatal wastage.

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The challenges of automating a real-time clinical practice guideline.

OBJECTIVE: To elucidate the types of problems encountered during implementation of a World Wide Web-based clinical practice guideline to manage hyperbilirubinemia in newborn infants. DESIGN: Formative assessment of an automated clinical-practice guideline in a large-scale implementation. SETTING: Primary-care clinics and offices, inpatient clinics, and emergency department affiliated with an academic children's hospital. PARTICIPANTS: General pediatricians, neonatologists, pediatric nurses, and computer scientists. RESULTS: Existing guidelines for hyperbilirubinemia management could not be translated directly into web pages. Modifications of the original guidelines were required to represent the clinical intent of the guidelines accurately. In addition, the automated guideline was augmented to incorporate a mechanism for generating clinical encounter forms in order for the system to be accepted into the clinical work flow. Other clinical considerations that influenced the final form of the automated guideline included limitations of computer resources and time constraints during patient encounters. CONCLUSIONS: Many existing guidelines are not amenable to straightforward implementation in automated systems. Strategies to increase the efficacy of the automated guidelines included guideline modifications, as well as careful consideration of the flow of clinical work. Repeated cycles of development and pilot testing are needed to design methods to accommodate the constraints imposed by clinical use.

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Growth inhibition of nasopharyngeal carcinoma cells by EGF receptor tyrosine kinase inhibitors.

Nasopharyngeal carcinoma (NPC) is a malignancy of epithelial origin occurring with a high incidence in southern China and southeast Asia. Radiotherapy is the main treatment modality for NPC. No effective chemotherapy is available. Since prevention of EGF/EGFR binding by an EGFR specific monoclonal antibody suppressed the growth of NPC xenografts, we examined potential anti-NPC activity by a group of specific inhibitors of the EGFR family of tyrosine kinases. We found that HONE-T1 NPC cells expressed high levels of EGFR tyrosine kinase activity upon stimulation by EGF. The receptor tyrosine kinase activity was specifically inhibited by either reversible (PD158780) or irreversible (PD168393) inhibitors specific for EGFR family tyrosine kinases. This inhibition led to a dose-dependent suppression of anchorage-independent growth as determined by soft agar assays. A structural analog (PD159805) with no inhibitory activity against EGFR tyrosine kinase had no effect on HONE-T1 cell growth in agar. Furthermore, growth of HONE-T1 xenografts in SCID mice was also inhibited by treatment with PD158780 and PD 168393. This data provides an appealing application of EGFR tyrosine kinase inhibitors for the treatment of nasopharyngeal carcinomas.

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Phosphorylation status and function of P53 are inversely related to protein kinase C activation.

The role of phosphorylation in the regulation of p53 protein function is little understood. We have addressed the role of protein kinase C (PKC) in the phosphorylation. Exposure to the protein kinase inhibitor, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H7), increased the phosphorylation of wild type p53 protein, whereas exposure to the tumor promoter phorbol ester, 12-O-tetradecanoyl-phorbol-13-acetate (TPA), decreased it in vivo following 3 hours incubation with mouse epidermal JB6 cells. Exposure to the c-AMP dependent protein kinase (PKA) activator, forskolin, did not decrease the phosphorylation of p53 protein. In the transient transfection/luciferase reporter transactivation assay, H7 modestly increased the mouse double minute (MDM) 2 reporter transactivation activity of p53 protein after 24 hours treatment, and TPA completely blocked it. These results suggest that the accelerated phosphorylation of wild type p53 protein is inversely related to PKC activation, and that p53 phosphorylation may have some relation to transcription factor function.

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Inhibition of MDA-MB-231 human breast tumor xenografts and HER2 expression by anti-tumor agents GAP31 and MAP30.

GAP31 (Gelonium protein of 31 kDa) and MAP30 (Momordica protein of 30 kDa) are agents isolated from the medicinal plants Gelonium multiflorum and Momordica charantia, respectively. The current study was conducted to investigate the efficacy of GAP31 and MAP30 on estrogen-independent and highly metastatic human breast tumor MDA-MB-231 both in vitro and in vivo. The effect of these agents on the expression of breast tumor antigen HER2 (also known as neu or as c-erbB 2) was also examined. Treatment of MDA-MB-231 breast cancer cells with GAP31 and MAP30 resulted in inhibition of cancer cell proliferation as well as inhibition of the expression of HER2 gene in vitro. When MDA-MB-231 human breast cancer cells were transferred into SCID mice, the mice developed extensive metastases and all mice succumbed to tumor by day 46. Treatment of the human breast cancer bearing SCID mice with GAP31 or MAP30 at 10 micrograms/injection EOD for 10 injections resulted in significant increases in survival, with 20-25% of the mice remaining tumor free for 96 days. Thus, anti-tumor agents GAP31 and MAP30 are effective against human breast cancer MDA-MB-231 in vitro and in vivo. These agents may therefore be a potential therapeutic use against breast carcinomas.

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Microcontroller-based real-time QRS detection.

The authors describe the design of a system for real-time detection of QRS complexes in the electrocardiogram based on a single-chip microcontroller (Motorola 68HC811). A systematic analysis of the instrumentation requirements for QRS detection and of the various design techniques is also given. Detection algorithms using different nonlinear transforms for the enhancement of QRS complexes are evaluated by using the ECG database of the American Heart Association. The results show that the nonlinear transform involving multiplication of three adjacent, sign-consistent differences in the time domain gives a good performance and a quick response. When implemented with an appropriate sampling rate, this algorithm is also capable of rejecting pacemaker spikes. The eight-bit single-chip microcontroller provides sufficient throughput and shows a satisfactory performance. Implementation of multiple detection algorithms in the same system improves flexibility and reliability. The low chip count in the design also favors maintainability and cost-effectiveness.

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[Cloning and characterization of a novel mouse short-chain dehydrogenase/reductases cDNA mHsdl2#, encoding a protein with a SDR domaid and a SCP2 domain].

The short-chain dehydrogenases/reductases (SDRs) play important roles in body's metabolism. We cloned a novel mouse SDR cDNA which encodes a deduced HSD-like protein with a conserved SDR domain and a SCP2 domain. The 1.8 kb cDNA consists of 11 exons and is mapped to mouse chromosome 4B3. The corresponding gene is widely expressed in normal mouse tissues and its expression level in liver increases after inducement with cholesterol food. The predicted mouse HSDL2 protein, which has a peroxisomal target signal, is localized in the cytoplasm of NIH 3T3 cells.

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[Identification of a novel human MAST4 gene, a new member of the microtubule associated serine-threonine kinase family].

Human protein kinases make up a large superfamily of homologous proteins, which are related by virtue of their kinase domains (also known as catalytic domains). Here we report the cloning and characterization of a novel human MAST4 (microtubule associated serine/threonine kinase family member 4) gene, which locates on human chromosome 5q13. The MAST4 cDNA is 7587 base pairs in length and encodes a putative protein of 2435 amino acids which contains a serine/threonine kinase domain and a PDZ domain. MAST4 protein has 64%, 63%, 59% and 39% identical aminoacid residues with MAST1, MAST2, MAST3 and MASTL respectively. RT-PCR analysis revealed relatively high expression level of MAST4 in most normal human tissues, with an exception of in testis, small intestine, colon and peripheral blood leukocyte.

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Indoleamine 2,3-dioxygenase--a new antioxidant enzyme.

Indoleamine 2,3-dioxygenase (IDO) was first found in rabbit intestine by Hayaishi et al. in 1963. The enzyme has a broad substrate specificity for various indoleamine derivatives and utilizes the superoxide anion as an oxygen source. IDO catalyzes the oxidative cleavage of the indole ring of several important regulatory molecules including tryptophan, tryptamine, serotonin and melatonin, and produces a new type of biogenic amine that may be termed an anthraniloylalkylamine, as shown in Fig. 1.

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A closed-loop system for pressure-controlled intermittent coronary sinus occlusion.

Computer-based instrumentation of a closed-loop system for pressure-controlled intermittent coronary sinus occlusion (PICSO) is described. PICSO is a procedure for treatment of ischemic myocardium via the venous side of the coronary circulation. The coronary venous outflow is intermittently obstructed with a balloon-tip catheter positioned in the coronary sinus, with the object of washing out toxic metabolites and redistributing the blood flow in the myocardium. Because of the relatively large capacitance in the coronary venous system, a PICSO occlusion-release cycle usually lasts for several cardiac cycles to achieve a significant pressure perturbation in the coronary sinus. The PICSO cycle should be adapted to the physiologic state of the heart. The closed-loop system described monitors the coronary sinus occlusion pressure and predicts the appropriate occlusion-release timing. The system should be useful for optimizing PICSO in animal studies as well as in clinical trials.

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No point mutation but a codon 31ser-->arg polymorphism of the WAF-1/CIP-1/p21 tumor suppressor gene in nasopharyngeal carcinoma (NPC): the polymorphism distinguishes Caucasians from Chinese.

Mutational inactivation of the p53 tumor suppressor gene is an infrequent event in human nasopharyngeal carcinoma (NPC), a malignancy showing a high incidence in southern China and southeast Asia. To examine the possible involvement of an activated p53 pathway in nasopharynx carcinogenesis, we have screened primary NPC biopsies for possible point mutations in WAF-1/CIP-1/p21, an effector gene transcriptionally regulated by and functioning as a mediator of the p53 tumor suppressor gene. Mutations in WAF-1/CIP-1/p21 might mimic p53 mutations in tumors having wild-type p53 such as most NPCs. The mutational analysis of WAF/CIP/p21 by PCR-single strand conformational polymorphism-direct sequencing revealed no point mutation in 41 primary NPC biopsies. A codon 31ser-->arg polymorphism was, however, detected. A striking difference in the distribution of the serine (WAF-ser) and arginine (WAF-arg) forms of WAF-1/CIP-1/p21 was observed when normal healthy Caucasians and Chinese were compared (P < 0.0001). The majority of Caucasians examined were found to be homozygous for WAF-ser (89%, n = 65), while Chinese living in areas of high NPC incidence show a greater than 86% homozygous or heterozygous WAF-arg (Taiwan, n = 66; Hunan, n = 32). The two forms of WAF-1/CIP-1/p21 were examined for potential functional differences in their ability to inhibit cyclin-dependent kinases and tumor cell growth. No significant differences were detected. Furthermore, no association between WAF-1/CIP-1/p21 genotype and NPC risk was observed in a case-control study of 76 NPC cases and 66 normal controls conducted in Taiwan.(ABSTRACT TRUNCATED AT 250 WORDS)

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Automated performance evaluation of real-time QRS-detection devices.

This paper presents a QRS-detector error logger and the implementation of a fully automated system for evaluation of QRS-detector performance. The error logger requires a known reference, such as an electrocardiogram (ECG) database, that provides ECG data and reference pulses wherever QRS complexes occur. These reference pulses are used to validate detection pulses generated by a QRS detector in real time. Using an eight-bit microcontroller chip, the error logger was constructed at a very low materials cost. Applications include automated analysis of QRS-detector performance and optimization of parameters in QRS-detection algorithms.

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Lack of suppression of tumor cell phenotype by overexpression of TIMP-3 in mouse JB6 tumor cells identification of a transfectant with increased tumorigenicity and invasiveness.

BACKGROUND: We have recently cloned mouse tissue inhibitor of metalloproteinases-3 (mTIMP-3) by the differential display technique and found that mTIMP-3 was expressed in preneoplastic but not in neoplastic mouse JB6 epidermal cells (Sun et at. Cancer Res. 54:11139, 1994). This down regulation of the gene is attributable at least in part to alteration in gene methylation (Sun et al., J. Biol. Chem., 270:19312, 1995). METHODS: To examine the potential role of TIMP-3 in two JB6 tumor cell model, we overexpressed mouse TIMP-3 in two JB6 tumor cell lines lacking endogenous mTIMP-3 expression. Stable transfectants from each line were selected and assayed for possible changes in tumor cell phenotype. RESULTS: Our results showed overexpression of mTIMP-3 in these two tumor lines did not change their ability to grow in soft agar, an assay for anchorage-independent growth, nor in nude mice, an in vivo tumorigenicity assay, nor to penetrate matrigel, an assay for invasiveness We, however, isolated a clone which is highly malignant was demonstrated by a) very short latent period for tumor formation; b) very fast tumor growth; and c) highly invasive in the matrigel assay. CONCLUSION: We conclude from this study that although TIMP-3 is not expressed in mouse JB6 tumor cells, overexpression by DNA transfection did not reverse tumor cell phenotype, suggesting a complex role for TIMP-3 in tumorigenesis. The highly malignant transfectant isolated by this study can be used as a tool for the cloning of dominant oncogenes as well as tumor suppressor genes.

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Comparison of bacterial translocation during traumatic shock and hemorrhagic shock in rats.

UNLABELLED: Traumatic shock has been classified as a kind of hypovolemic shock similar to hemorrhagic shock. Since bacterial translocation has been observed in shock, this study investigated the difference in bacterial translocation during traumatic shock and hemorrhagic shock, and considered this effect on lung injury during sepsis. METHODS: Forty-eight male or female Sprague-Dawley rats were divided into 2 groups, hemorrhagic shock and traumatic shock. Bacterial translocation, endotoxin, and blood gas were evaluated. Alterations of the lungs morphologically and functionally were observed. RESULTS: Traumatic shock induced more bacterial translocation and endotoxemia from the gut. Blood gas analysis shows a more severe disorder in traumatic shock than in hemorrhagic shock. Pathological morphologic changes of lungs were more severe in traumatic shock than in hemorrhagic shock. CONCLUSIONS: Traumatic shock cause more bacterial translocation and endotoxemia which subsequently caused serial pathological alterations in lung morphologically and functionally than pure hemorrhagic shock does. These results suggest that this trauma activates more severe mechanism to damage lungs.

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