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Biomedical subjects

J Sun

Publications and source records attributed to J Sun.

At least 577 records · Page 32Linked to original sources
PubMed1995

Characterization of the interaction between PQQ and heme c in the quinohemoprotein ethanol dehydrogenase from Comamonas testosteroni.

Quinohemoprotein ethanol dehydrogenase from Comamonas testosteroni (QH-EDH) contains two cofactors, 2,7,9-tricarboxy-1H-pyrrolo[2,3-f]quinoline-4,5-dione (PQQ) and heme c. Since previous studies on the kinetics of this enzyme suggested that both participate in electron transfer, spectroscopic investigations were performed of the oxidized and reduced holo- and apoenzyme (without PQQ but with heme c) to reveal the nature of the interaction between the two redox centers. From this it appears that the properties of the heme in the enzyme are affected by the presence of PQQ, as judged from the shift of the maxima in the ultraviolet/visible absorption spectra of the heme moiety in both reduced and oxidized QH-EDH and the 60-mV increase of the heme midpoint redox potential caused by PQQ addition. Also 1H-NMR spectroscopy was indicative for interaction since binding of PQQ induced shifts in the resonances of the methyl groups of the porphyrin ring in the oxidized form of the apoenzyme and a shift in the methionine heme ligand resonance of the reduced form of the apoenzyme. On the other hand, resonance Raman spectra of the heme in the different enzyme forms were nearly similar. These results suggest that a major effect of PQQ binding to apo-QH-EDH is a rotation of the methionine ligand of heme c. Since no intermediate 1H-NMR spectra were observed upon titration of apoenzyme with PQQ, apparently no exchange occurs of PQQ between (oxidized) holo- and apoenzyme at the NMR time scale and at that of the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohol Oxidoreductases↗
PubMed1995

Fractal dimension of exon and intron sequences.

In this paper, the concept of fractal is applied to describe the features of nucleotide sequences. We introduce the mapping from nucleotide sequences to two-dimensional metric space. Then we use this mapping to study quantitatively the self-similarity of exon and intron sequences in different scales. We find that self-similarity exists in the geometrical range and main range of a nucleotide sequence and define the fractal dimension in these ranges. The results show that the fractal properties of exon sequences are quite different from those of introns, reflecting their difference in structure and function. The fractal dimension of the geometrical range may be used to predict the exon regions of a raw nucleotide sequence.

Animals↗
PubMed1995

Gene structure, chromosomal localization, and expression of the murine homologue of human proteinase inhibitor 6 (PI-6) suggests divergence of PI-6 from the ovalbumin serpins.

Human proteinase inhibitor 6 (PI-6) is a recently described protein belonging to the serine proteinase inhibitor (serpin) superfamily. Sequence similarity suggests that PI-6 most resembles the ovalbumin (ov) serpins which include plasminogen activator inhibitor-2, the squamous cell carcinoma antigen, monocyte/neutrophil elastase inhibitor, and maspin. Although these proteins are associated with carcinomas and inflammation, they appear to have diverse functions and little is known of their physiological roles. In this study we have characterized cDNA and genomic clones encoding mouse PI-6 in order to analyze the localization, structure, and expression of the gene. The reactive center residues (Arg-Cys) are conserved in the mouse molecule, and recombinant mouse PI-6 was shown to bind thrombin, indicating that it has similar inhibitory properties to its human counterpart. Using reverse transcriptase-polymerase chain reaction assays on RNA isolated from 15-day-old embryos and adult mice, we have shown that mouse PI-6 expression is developmentally regulated, and that, unlike human PI-6, it is absent from the placenta. The mouse homologue of the human PI-6 gene has been designated Spi3 and was mapped to chromosome 13 between the Pl1 and ctla2 alpha genes. It spans 20 kilobases, consists of 7 exons and 6 introns, and contains a TATA motif 24 nucleotides upstream of the transcriptional start site. A 680-base pair DNA fragment containing this motif and 31 nucleotides of the 5'-untranslated region of the structural gene directed transcription of a bacterial cat gene, demonstrating the presence of a functional promoter. The PI-6 gene lacks an intron present in the ovalbumin and PAI-2 genes; otherwise it is identical in terms of the numbers, position, and phasing of the intron/exon boundaries. These results suggest that PI-6 and the ov-serpin genes have diverged and do not belong to the same subgroup.

Amino Acid Sequence↗
PubMed1995

IFN-gamma and TNF-alpha induce redistribution of PECAM-1 (CD31) on human endothelial cells.

Platelet endothelial adhesion molecule-1 (PECAM-1/CD31) is a glycoprotein adhesion molecule of the Ig superfamily that is constitutively expressed on leukocytes, platelets, and endothelial cells where it concentrates at the intercellular borders of adjacent cells. Recent studies have confirmed that endothelial PECAM-1 is involved in the recruitment of neutrophils into inflammatory sites. However, the effects of inflammatory cytokines such as TNF-alpha and IFN-gamma on endothelial PECAM-1 expression are not known. We studied the effect of several inflammatory cytokines on human umbilical vein endothelial cell PECAM-1 expression. We found that TNF-alpha and IFN-gamma produced dose-dependent changes in the surface distribution of PECAM-1, with a loss of the typical staining of PECAM-1 at intercellular junctions. Because TNF-alpha and IFN-gamma did not alter PECAM-1 transcription or total surface PECAM-1, these changes in PECAM-1 localization are most consistent with a redistribution of the protein away from intercellular junctions. This cytokine-induced surface redistribution of PECAM-1 was associated with changes in PECAM-1 cytoskeletal association but did not involve the expression of different alternatively spliced variants of the molecule. Given the involvement of endothelial PECAM-1 in neutrophil recruitment, redistribution of PECAM-1 may serve as a mechanism for regulating the transmigration of leukocytes across the vascular endothelium.

Alternative Splicing↗
PubMed1995

Elevated expression of H type GDP-L-fucose:beta-D-galactoside alpha-2-L-fucosyltransferase is associated with human colon adenocarcinoma progression.

GDP-L-fucose:beta-D-galactoside alpha-2-L-fucosyltransferase (EC 2.4.1.69) is a key enzyme in the biosynthesis of fucosylated type 1 and 2 lactoseries structures, such as Lewis b and the H type 2 and Lewis Y, respectively, that are accumulated in colon adenocarcinoma. Analysis of the mRNA transcript level for the human H gene-encoded beta-D-galactoside alpha-2-L-fucosyltransferase revealed 40- and 340-fold increases in the mRNA levels in all adenocarcinomas and tumor cell lines, respectively, compared to normal colon mucosa where a low level of mRNA transcript was detected. A variable increase in mRNA transcript levels was observed in 50% of adenomatous polyps. Nucleotide sequence analysis of the protein coding region of the cDNAs derived from normal colon, adenoma, and colon adenocarcinoma revealed 100% homology, suggesting that there are no tumor-associated allelic variations within the H beta-D-galactoside alpha-2-L-fucosyltransferase cDNA. These results suggest that beta-D-galactoside alpha-2-L-fucosyltransferase expression highly correlates with malignant progression of colon adenocarcinoma.

Adenocarcinoma↗
PubMed1995

Dexamethasone inhibits ozone-induced gene expression of macrophage inflammatory protein-2 in rat lung.

To address the potential role of the chemokine macrophage inflammatory protein-2 (MIP-2) in airway inflammation, we examined whether MIP-2 may play a role in ozone-induced neutrophilic inflammation of airways and its modulation by dexamethasone in rat lung. Following ozone exposure, MIP-2 mRNA expression in the lung peaked at 2 h after exposure and slowly declined thereafter. Dexamethasone suppressed ozone-induced MIP-2 mRNA expression and neutrophil accumulation in the lung. We suggest that the MIP-2 mRNA induction may switch on the neutrophilic influx observed in this model of lung inflammation. Furthermore, the MIP-2 expression is regulated by dexamethasone which may represent one of the mechanisms by which glucocorticoids exert their potent anti-inflammatory properties.

Animals↗
PubMed1995

In vivo cytokine gene transfer by gene gun reduces tumor growth in mice.

Implantation of tumor cells modified by in vitro cytokine gene transfer has been shown by many investigators to result in potent in vivo antitumor activities in mice. Here we describe an approach to tumor immunotherapy utilizing direct transfection of cytokine genes into tumor-bearing animals by particle-mediated gene transfer. In vivo transfection of the human interleukin 6 gene into the tumor site reduced methylcholanthrene-induced fibrosarcoma growth, and a combination of murine tumor necrosis factor alpha and interferon gamma genes inhibited growth of a renal carcinoma tumor model (Renca). In addition, treatment with murine interleukin 2 and interferon gamma genes prolonged the survival of Renca tumor-bearing mice and resulted in tumor eradication in 25% of the test animals. Transgene expression was demonstrated in treated tissues by ELISA and immunohistochemical analysis. Significant serum levels of interleukin 6 and interferon gamma were detected, demonstrating effective secretion of transgenic proteins from treated skin into the bloodstream. This in vivo cytokine gene therapy approach provides a system for evaluating the antitumor properties of various cytokines in different tumor models and has potential utility for human cancer gene therapy.

Animals↗
PubMed1995

Alternans and period-doubling bifurcations in atrioventricular nodal conduction.

A theoretical model, formulated as a finite difference equation is proposed for rate-dependent conduction properties of the atrioventricular (AV) node. The AV nodal conduction time, which is defined as the time interval from the atrial activation to the activation of the bundle of His, depends on the history of activation of the node. The theoretical model, which incorporates physiological concepts of recovery, facilitation and fatigue, accurately predicts a variety of experimentally observed complex rhythms of nodal conduction. In particular, alternans rhythms, in which there is an alternation in conduction time from beat to beat, are associated with period-doubling bifurcations in the theoretical model.

Animals↗
PubMed1995

Studies on the structure and function of glycosylated and nonglycosylated neu differentiation factors. Similarities and differences of the alpha and beta isoforms.

Comparative analyses of both glycosylated and nonglycosylated neu differentiation factor (NDF) isoforms revealed significant similarities and differences of their overall structures and functions. Biophysical analyses confirmed that all NDF isoforms are monomeric, but have an extended ellipsoidal shape in solution. All full-length NDFs are similar in secondary and tertiary structures and they contain no alpha-helix but are abundant in beta-strand structures. A small NDF fragment containing only the epidermal growth factor domain is also rich in beta-strand structures, but exhibits tertiary structure different from the long NDF forms. Monoclonal antibodies that selectively recognize epidermal growth factor domains of human NDF-alpha and -beta can specifically bind the respective NDF-alpha and -beta isoforms independent of NDF origins. Western blot analysis and quantitative binding assays further identify that an NDF preparation produced naturally from Rat1-EJ cells contains both alpha and beta isoforms in a 3 to 2 ratio. In receptor-binding competition experiments, human and rat NDF-beta isoforms have higher affinity than NDF-alpha isoforms. NDF-beta isoforms can dramatically enhance the stimulation of DNA synthesis for transfected NIH3T3 cells that overexpress HER-3 and HER-4 receptors, while NDF-alpha isoforms can only stimulate proliferation of HER-4-transfected cells with lower activity. Taken together, NDF-alpha and -beta isoforms share similar gross protein conformations but are biologically distinct.

3T3 Cells↗
PubMed1995

Effect of thrombin on release of plasminogen activator inhibitor-1 from cultured primate arterial smooth muscle cells.

Plasminogen activator inhibitor-1 (PAI-1) is the major inhibitor for plasmin formation promoted by tissue and urokinase plasminogen activators. The present study demonstrates that thrombin increase PAI-1 antigen, biological activity, and gene expression in cultured baboon aortic smooth muscle cells (BASMC). Thrombin elevates PAI-1 antigen in conditioned medium of BASMC within 10 min of the treatment, with the peak increase after 30 min of the treatment. Overexpression of PAI-1 gene was detected in the cultures exposed to thrombin for at least 60 min. PAI activity in conditioned medium increased in the cultures treated with thrombin for at least 4 h. The thrombin-induced early increase of PAI-1 antigen (up to 30 min of the stimulation) was blocked by hirudin (a specific inhibitor of thrombin), mimicked by trypsin and not suppressed by cycloheximide (a protein synthesis inhibitor). The majority of metabolically labeled PAI-1 associated with BASMC was present in extracellular matrix. The level of extracellular matrix-associated PAI-1 was reduced 40% by 30 min of thrombin treatment. Our results suggest that thrombin not only increases PAI-1 transcription but also proteolytically cleaves PAI-1 from the extracellular matrix of vascular SMC. PAI-1 released by thrombin from the extracellular matrix may not alter PAI activity in extracellular fluid but may reduce the storage of PAI-1 in the extracellular matrix of vascular smooth muscle cells.

Animals↗
PubMed1995

The American bullfrog (Rana catesbeiana) exhibits differential cardiovascular responses to LTC4 after short- and long-term cold exposure.

Mean arterial pressure (MAP) and heart rate (HR) responses to leukotriene (LT)C4 have been studied in warm (W-A) and cold-acclimated (C-A) America bullfrogs, Rana catesbeiana, but nothing is known about how the length of cold treatment affects the response to LTC4 or how responses are affected by return to room temperature following cold exposure. In this study, two groups of frogs were placed at 5 degrees either for 30 days (C-A) or for 1 day (W-C) and LTC4 dose-response curves obtained at 5 degrees. After the frogs were removed from cold, the baseline MAP and HR were monitored for 120 min, and dose-response curves were repeated at 2, 24, and 48 hr. The LTC4 dose-response curves were also obtained during the three experimental days on frogs which had never been placed at cold temperature (W-A). C-A frogs showed greater MAP response than W-C frogs at 5 degrees, and also showed the greatest MAP response of the three groups 48 hr after the animals were removed from cold temperature. These data suggest that up regulation of LTC4 receptors may have occurred in C-A frogs. Cold exposure alone eliminated reflex HR response to LTC4 in both C-A and W-C groups. Longer duration of action was also observed in these groups. The results demonstrate that short-term cold exposure can affect the response to LTC4 in frogs, but that physiological adjustments occur in frogs undergoing long-term exposure.

Acclimatization↗
PubMed1995

Inhibition of allergen-induced lung eosinophilia by type-III and combined type III- and IV-selective phosphodiesterase inhibitors in brown-Norway rats.

We examined the effect of a type IV (rolipram) and a combined type III and IV (Org 20421) isoenzyme-selective phosphodiesterase inhibitor upon allergen-induced pulmonary eosinophil recruitment in sensitised Brown Norway rats. Rats were sensitised with ovalbumin intraperitoneally and later challenged with ovalbumin aerosol which induced a significant increase in the total eosinophil and neutrophil count in bronchovalveolar lavage fluid at 24 hours (from 0.38 +/- 0.12 to 1.36 +/- 0.18 x 10(6), p < 0.01 and from 0.06 +/- 0.01 to 0.33 +/- 0.07 x 10(6), p < 0.01) respectively. Pretreatment with rolipram (30 mumol/kg) and Org 20421 (30 mumol/kg) abolished the eosinophilia and neutrophilia evoked by ovalbumin. We conclude that type IV and possibly type III isozyme phosphodiesterase inhibitors may regulate, directly or indirectly, eosinophil and neutrophil activity and/or those cells responsible for attracting them into the lung.

Administration, Inhalation↗
PubMed1995

Prospective evaluation of minimal blood use for ascending aorta and aortic arch operations.

The feasibility, safety, and impact on postoperative hospital stay of performing ascending aorta and aortic arch operations without homologous blood transfusions have not been evaluated. Sixty consecutive patients, 38 (63%) of whom also had aortic valve replacements and 17 (28%) of whom also had coronary artery bypass grafting, were evaluated for participation in blood conservation measures. Of the 45 who were able to use blood conservation techniques, 87% (39/45) required no intraoperative and 69% (31/45) required no in-hospital homologous blood transfusions. The 30-day survival rate was 98.3% (59/60), and no patient sustained a new stroke, neurologic cognitive deficit, or infection. Multivariate analysis of the 60 patients showed that the predictors of in-hospital homologous transfusion were (p < 0.05) age, cardiopulmonary bypass time, and postoperative chest tube drainage. Preoperative autologous blood donation was associated with a significantly lower risk of homologous transfusion (p = 0.0006). Indeed, patients participating in blood conservation techniques had a significantly (p < 0.05) lower incidence of homologous transfusions, required less intraoperative shed blood washing, were extubated earlier, gained less weight, had shorter hospital stays, and were discharged in a better dyspnea functional class. Most major elective cardiovascular operations on the ascending aorta and aortic arch can be safely performed without homologous transfusions.

Aged↗
PubMed1995

Antegrade and retrograde continuous warm blood cardioplegia: a 31P magnetic resonance study.

BACKGROUND: Retrograde normothermic blood cardioplegia has been shown to provide myocardial protection during certain bypass procedures. However, a number of animal studies have shown less than optimal myocardial protection with this technique. METHODS: Isolated, beating porcine hearts were perfused antegradely (aortic root pressure = 75 to 95 mm Hg) for 30 minutes. Arrest was induced and maintained for 60 minutes with high K+ blood cardioplegia delivered either antegradely (n = 8) or retrogradely (n = 8) (coronary sinus pressure = 35 to 55 mm Hg). Perfusate was switched to normokalemic blood for recovery of sinus rhythm (30 minutes). Intracellular pH, creatine phosphate, inorganic phosphate, and adenosine triphosphate were monitored continuously and noninvasively with phosphorus 31 magnetic resonance spectroscopy throughout the experiment, and functional variables (rate-pressure product and the positive and negative first derivatives of left ventricular pressure) were assessed concurrently. RESULTS: Antegrade cardioplegia maintained high-energy metabolites, intracellular pH, and myocardial function. Retrograde normothermic blood cardioplegia resulted in an increase in inorganic phosphate (197% +/- 15% of control) and a decrease in creatine phosphate (51% +/- 6% of control). There was no significant difference in myocardial function between the two groups (p > 0.05). The magnetic resonance spectroscopy data indicate ischemia occurred within 2 minutes of the initiation of retrograde perfusion. CONCLUSIONS: This study suggests that retrograde normothermic blood cardioplegia causes a transition of the myocardium to ischemic metabolism in the normal porcine heart.

Adenosine Triphosphate↗
PubMed1995

Initialization of warfarin dosages using computer modeling.

OBJECTIVE: Software incorporating warfarin pharmacokinetics and pharmacodynamics, as well as a Bayesian regression method, was evaluated for accuracy in predicting steady-state dosages of warfarin during initialization of anticoagulation therapy. DESIGN: A cohort study was used to compare computer predictions with physician-determined doses during a retrospective chart review of 42 patients. PATIENTS: Forty-two patient charts were selected for monitoring anticoagulation initialization therapy. Of the 42 patients reviewed, 22 were excluded on the following bases: uncontrolled congestive heart failure; ongoing treatment with medications that interfered with warfarin metabolism or displaced warfarin from protein binding sites; recent treatment with fresh frozen plasma or vitamin K; or any bleeding disorders, sepsis, malabsorption or significant changes in liver and/or renal function. MAIN OUTCOME MEASURES: Using physician-determined International Normalized Ratios (INRs) as target levels for the software, the number of INR feedbacks needed to stabilize blood drug levels during initialization were compared between physicians and computer forecasting. Population parameters and sequentially measured INRs were used for evaluation. RESULTS: Current oral anticoagulation protocols require significantly more measured INRs than computer forecasting to achieve steady-state dosages (9.5 v 4.4, respectively, p < 0.01). Physicians showed a statistically significant pattern of underdosing patients (4.3 v 1.7 subtherapeutic INRs, respectively, p < 0.01). Computer predictions tended to overdose patients but did not significantly increase the number of supratherapeutic INRs. This study showed that five INR inputs consistently gave accurate steady-state dosage predictions, and in many ways computer modeling was more effective than clinician-determined steady-state dosing in warfarin initialization. CONCLUSIONS: Computer modeling provides a reliable means of predicting initialization dosages for warfarin anticoagulation therapy with five INR inputs and therefore has merit in the clinical setting if used with sound clinical judgment.

Adult↗
PubMed1995

Perfluorocarbon liquid in the management of retinal detachment with proliferative vitreoretinopathy.

PURPOSE: To describe the techniques and results of perfluoro-N-octane used during vitrectomy for managing retinal detachment with severe proliferative vitreoretinopathy (PVR). METHODS: The authors retrospectively studied 223 consecutive patients who underwent vitreoretinal surgery for severe PVR (93% D1-D3). Patients underwent an average of 1.72 prior vitreoretinal surgeries. Perfluoro-N-octane was used intraoperatively to flatten the retina, avoiding posterior drainage retinotomy, to identify areas of residual retinal traction and periretinal membranes, to stabilize the peripheral retina during dissection of anterior PVR, and to help determine the extent and location of relaxing retinotomies. Extended-term gas tamponade was used in 91% of eyes. All patients were followed for a minimum of 6 months. RESULTS: Seventy-eight percent of the retinas were reattached posterior to the scleral buckle after a single vitreoretinal surgery and 96% were reattached after multiple surgeries. An average of 1.24 vitrectomy surgeries were required. The final visual acuity was 20/400 or better in 74% of eyes and 20/80 or better in 30% (P = 0.004). Preoperative hypotony (intraocular pressure < or = 5 mmHg) and multiple prior vitreoretinal surgeries were associated with a poor final visual acuity (P = 0.01 and 0.02, respectively). Preoperative hypotony (intraocular pressure < or = 5 mmHg) was associated with a greater frequency of relaxing retinotomies (P = 0.02). Retained perfluoro-N-octane was observed postoperatively in the vitreous cavity in 1.3% and subretinal perfluoro-N-octane in 0.9%. CONCLUSION: Experience with perfluoro-N-octane has demonstrated its usefulness both diagnostically and therapeutically as an intraoperative tool and improved the anatomic and visual outcome for retinal detachment complicated by severe PVR.

Adolescent↗