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Biomedical subjects

P Lu

Publications and source records attributed to P Lu.

At least 145 records · Page 8Linked to original sources
PubMed1995

Biochemical characterization of lauric acid omega-hydroxylation by a CYP4A1/NADPH-cytochrome P450 reductase fusion protein.

The binding and hydroxylation of lauric acid by a genetically engineered and expressed fusion protein comprised of an N-truncated form of rat CYP4A1 linked to an N-truncated form of rat NADPH cytochrome P450 oxidoreductase (OR) (constructed by Fisher et al., (1992) Proc. Natl. Acad. Sci. USA 89, 10817-10822) has been characterized biochemically and compared to that shown by purified reconstituted rat CYP4A1 and liver microsomes from clofibrate-induced rats. In all systems lauric acid induced a Type I cytochrome P450 difference spectrum with Ks values in agreement with prior literature (range 10-18 microM). When provided with NADPH and oxygen but no other proteins or lipid, the fusion protein (called f4A1) catalyzed omega-hydroxylation of lauric acid with apparent Km and Vm of 3-4 microM and 4-5 nmol product/min/nmol P450 irrespective of buffer concentration or cation (NaPi or KPi, 25-200 mM); comparable values for reconstituted CYP4A1 and microsomes from clofibrate-induced rats are 9 microM and 34 min-1 and 5 microM and 10 min-1, respectively. (omega-1)-Hydroxylation of lauric acid was barely detectable (omega/(omega-1) = 135) with f4A1 or with reconstituted CYP4A1, but it accounted for up to 50% of total products formed by microsomes from clofibrate-induced rats. When added to the f4A1 system, OR stimulated hydroxylation up to fivefold at a OR:f4A1 ratio of 5:1; additionally, (omega-1)-hydroxylation was routinely observed as a minor process (< 4% of total product) in this system. These effects were also independent of buffer concentration. In contrast addition of cytochrome b5 (b5) caused a small (25%) decrease in omega-hydroxylation, while added phospholipid had no effect. However, the combination of OR, b5, and lipid stimulated turnover approximately 10-fold compared to f4A1 alone, and 11-hydroxylauric acid was regularly formed as a minor (3-4% of total) product. These observations indicate that the fusion protein f4A1 is functionally equivalent to reconstituted CYP4A1 with respect to binding and hydroxylation of lauric acid and suggest that it can be used as an alternative to reconstituted systems for structure-function and mechanistic studies of fatty acid omega-hydroxylation.

Animals↗
PubMed1995

Requirement of CTLA-4 counter receptors for IL-4 but not IL-10 elevations during a primary systemic in vivo immune response.

The CD28/CTLA-4 costimulatory signal is required for TCR-mediated T cell activation resulting in increased IL-2 production in vitro, but its role in IL-4 production is unclear and few studies have examined the function of CTLA-4/CD28 in the in vivo immune response. We have examined the in vivo effects of blocking the interaction of B7 with its ligands, CTLA-4 and CD28, in an IL-4 dominant in vivo immune response to goat anti-mouse IgD. This response is characterized by elevations in serum Igs preceded by elevations in IL-2 and the Th2 cytokines: IL-4, IL-9, and IL-10. The fusion protein CTLA4-Ig administered during the in vivo immune response to goat anti-mouse IgD caused an inhibition in elevations of IL-2, IL-4, and IL-9 gene expression at both day 3 and day 6 after immunization. In contrast, IL-10 cytokine gene expression as late as day 6 after immunization was not decreased. Cell sorting analysis demonstrated that TCR-alpha beta +, CD4+ T cells were the primary source of the elevated IL-10, suggesting that T cell activation leading to IL-10 gene expression may not require CTLA-4 ligand interactions. Similarly CTLA4-Ig completely blocked elevations in the number of IL-4- but not IL-10-secreting cells, as measured by ELISPOT, in both unsorted splenic cells and sorted CD4+, TCR-alpha beta+ T cells. In situ staining of spleen sections also showed inhibition of IL-4-producing cells. These results suggest that, with the notable exception of IL-10, interaction, of B7 with its ligands is required for elevated Th2 cytokine gene expression and secretion during a primary systemic IL-4-dominant response.

Abatacept↗
PubMed1995

Study on three dimensional reconstruction of transesophageal echocardiographic images.

Using biplane transesophageal echocardiography and the concept of three dimensional transthoracic echocardiography, we performed three dimensional reconstruction of transesophageal images of various clinicopathologic cases, including atrial septal defect, mitral stenosis, mitral valve prolapse and pulmonary stenosis. The hardware equipment and image processing flow chart of three dimensional reconstruction of transesophageal echocardiographic images are described. Our present study indicates that three dimensional reconstruction of transesophageal echocardiographic images could display multi-regional three dimensional structures of heart and great vessels, including superior vena cava, ascending aorta, right ventricular outflow tract, pulmonary artery and left heart, with clear, visual and stereoscopic imaging. The regional structures could be displayed at different levels of stereo-anatomic-sections and in different orientations of rotating stereo-images, which could provide accurate three dimensional anatomical information for cardiac stereo-morphological study and definition of spatial location and size of cardiac abnormalities.

Adolescent↗
PubMed1995

Role of B7 signaling in the differentiation of naive CD4+ T cells to effector interleukin-4-producing T helper cells.

Signaling through the T cell receptor must be accompanied by costimulatory signals for the differentiation of naive T cells to cytokine-producing effector T helper cells. The costimulatory signal through CD28 is required for T cell activation resulting in increased interleukin (IL)-2 production in vitro, but its role in the production of IL-4 and in the in vivo response is still unclear. We have examined the effects of blocking CTLA-4 (the CD28 homologue) ligand interactions on the in vivo development of IL-4-producing T helper effector cells during a primary mucosal immune response to the nematode parasite Heligmosomoides polygyrus and during a primary systemic immune response to immunogenic anti-IgD antibodies. Our results demonstrate that CD28 and/or CTLA-4 signaling is required for T cell priming leading to IL-4 cytokine production, B cell activation, and IgE secretion during both immune responses, suggesting that other signaling molecules do not substitute for these molecules in either of these two different immune responses. Furthermore, the CD28 ligands, B7-1 and B7-2, can substitute for each other in providing the required T cell costimulatory ligand interactions during the primary immune response to H. polygyrus. In contrast, memory T cells during the challenge immune response do not require CD28/CTLA-4 ligand interactions for IL-4 production and T helper effector function.

Abatacept↗
PubMed1995

Cloning and expression of canine interleukin-10.

We describe here the cloning of canine IL-10 cDNA (GenBank accession No. U33843) and the expression of recombinant IL-10 in a dog kidney cell line (DK6247) and Chinese hamster ovary cells (CHO). Canine IL-10 exhibits strong sequence homology to the known sequences of human, mouse, rat, and bovine genes at nucleotide and amino acid levels. The IL-10 gene, when introduced into DK and CHO cell lines, produces recombinant IL-10 that causes an inhibitory effect on allogeneic MHC-driven lymphoproliferative responses.

Amino Acid Sequence↗
PubMed1995

Immunochemical identification of fungi using polyclonal antibodies raised in rabbits to exoantigens from Aspergillus ochraceus.

Aspergillus ochraceus Wilhelm is a producer of highly toxic mycotoxin, ochratoxin A, and is known to contribute to the damage of grain on storage. Rabbit antibodies were produced against the exoantigens of A. ochraceus, and ELISA and immunoblotting procedures were used to characterize their reactivity towards fungal exoantigens of four Aspergillus, seven Penicillium, three Fusarium, one Mucor and one Alternaria species. The antibodies were specific for A. ochraceus and essentially cross-reacted neither with other fungi nor with the water-soluble grain components. These antibodies, therefore, have the potential of being utilized for the discriminative monitoring of A. ochraceus in foodstuffs and feeds.

Animals↗
PubMed1995

Analysis of spiculation in the computerized classification of mammographic masses.

Spiculation is a primary sign of malignancy for masses detected by mammography. In this study, we developed a technique that analyzes patterns and quantifies the degree of spiculation present. Our current approach involves (1) automatic lesion extraction using region growing and (2) feature extraction using radial edge-gradient analysis. Two spiculation measures are obtained from an analysis of radial edge gradients. These measures are evaluated in four different neighborhoods about the extracted mammographic mass. The performance of each of the two measures of spiculation was tested on a database of 95 mammographic masses using ROC analysis that evaluates their individual ability to determine the likelihood of malignancy of a mass. The dependence of the performance of these measures on the choice of neighborhood was analyzed. We have found that it is only necessary to accurately extract an approximate outline of a mass lesion for the purposes of this analysis since the choice of a neighborhood that accommodates the thin spicules at the margin allows for the assessment of margin spiculation with the radial edge-gradient analysis technique. The two measures performed at their highest level when the surrounding periphery of the extracted region is used for feature extraction, yielding Az values of 0.83 and 0.85, respectively, for the determination of malignancy. These are similar to that achieved when a radiologist's ratings of spiculation (Az = 0.85) are used alone. The maximum value of one of the two spiculation measures (FWHM) from the four neighborhoods yielded an Az of 0.88 in the classification of mammographic mass lesions.

Automation↗
PubMed1995

Computerized detection of clustered microcalcifications: evaluation of performance on mammograms from multiple centers.

To investigate the performance of a computerized method for the automated detection of clustered microcalcifications in digitized mammograms from a variety of screening centers, the authors invited 118 radiologists to bring up to five mammograms to their scientific exhibit at the 1993 meeting of the Radiological Society of North America (RSNA). Forty-three mammograms from 14 sites were brought to the exhibit, where they were digitized and analyzed. Results of the analysis on the RSNA cases were compared with those obtained on a standard database of 39 mammograms collected from two centers. The performance of the detection algorithm on the RSNA images was lower than that achieved on the standard database. This lower performance was due in part to the higher fraction of very subtle clustered microcalcifications in the RSNA cases, as well as the apparent dependence of the algorithm on image characteristics (eg, contrast and noise), which varied from center to center. The authors conclude that the algorithm is robust and accurate enough to undergo clinical testing. When it is implemented clinically, the computerized scheme must be customized to the image characteristics at each specific screening center to obtain optimal performance.

Breast Diseases↗
PubMed1995

[A preliminary report on diagnostic complementarity of gut-associated and egg-associated antigenemia in schistosomiasis japonica].

With Hyroxylapatite purified preparations and BACH (biotin aminocapryl hydrazide) biotinylated McAbs, 274-2H10 and 273-2H1, recognizing different egg-associated epitopes, biotin-avidin (BA) involved alkaline phosphatase (AP) ELISA with detecting sensitivities reaching nanogram levels (10(-9), were set up. The detectable limit for crude preparations of Schistosoma japonicum SEAJ-TCA in 2H10-ELISA achieved 1. 0.3. 2 ng/ml, in which only S. japonicum specific egg antigens were efficiently detected, whereas with 2H1-ELISA, which could detect SEA-TCA of both S. japonicum and S. mansoni species, an end point of detecting 3.2 ng/ml was obtained. Repeated tests with human serum groups revealed very significant differences of extinction OD readings between patients and normal individuals. For detection combinations, a previously established anti-CAA homologous AP-ELISA system was parallelly used for gut-associated antigenemia determinations. Taking the mean extinction OD reading of a parallel normal serum group plus 3 SD as corresponding cut off values, 3 patient groups (n = 82, 52, 39) from different areas of transmission intensity were subjected to accumulating determinations for egg- and gut-associated antigenemia. Improved detectabilities to variable extent were achieved in either of the 2 or 3 combinations. The study thus demonstrated that the diagnostic efficiency for human schistosomiasis could be improved by multi-epitope detections for more than one target molecule using corresponding McAbs, especially in areas where the transmission intensity of the disease is comparatively lower.

Animals↗
PubMed1995

[Comparative study of ultrasonic detection of popliteal vein reflux].

The venous valve undergoes more destruction and malfunction, and the quantity and duration of venous valvular reflux are larger and longer. On the basis of this mechanism, we detected the popliteal vein reflux duration and various influencing factors with duplex ultrasound. The reflux duration longer than 0.5 secand was verified as the evidence of primary venous insufficiency (PVI) in the detection of 40 cases. The detecting method recommended by us is that with standing position, and pneumatic compression 10. 67kPa (80mmHg) applied to calf, the reflux duration through popliteal venous valves is detected by using both pulsed-wave Doppler scanning and color-flow Doppler scanning. With the rates of sensitivity (92%), specificity (100%), and accuracy (94%), this noninvasive, quantitative, and easily handled method showed a very good diagnostic value.

Aged↗
PubMed1995

Gangliosides are potent immunosuppressors of IL-2-mediated T-cell proliferation in a low protein environment.

Gangliosides are immunosuppressive to many classes of immune cells, and shedding of these glycosphingolipids by tumour cells may regulate immune responses in cancer, and protect tumours from host immune destruction. One mechanism of immunosuppression by gangliosides in vitro involves competition with interleukin-2 receptors (IL-2R) for binding of IL-2. Previous studies on inhibition of IL-2-mediated events by gangliosides have been conducted in the presence of high levels of fetal bovine serum (FBS). However, gangliosides shed by tumours in vivo will encounter immune cells in the low protein microenvironment of the tissue fluid. In order to better mimic physiological conditions, we have examined immunosuppression by gangliosides towards IL-2-dependent HT-2 cells in a low serum-low protein medium. The ability of gangliosides to inhibit IL-2-stimulated DNA synthesis in HT-2 increased dramatically as the serum concentration in the culture medium was decreased; the 50% inhibitory concentration (IC50) value for GM1 was 13 microM under low serum conditions, 14-fold lower than the value obtained in 10% FBS. Further investigation revealed that the mechanism of immunosuppression by gangliosides in low serum-low protein medium involved interference with the IL-2/IL-2R system. Ganglioside-mediated inhibition was dependent on the continued presence of the glycolipids during the first few hours after IL-2 stimulation, and could be reversed by increasing levels of IL-2. Receptor binding experiments demonstrated that gangliosides blocked the interaction of IL-2 with high-affinity IL-2 receptors on HT-2. Taken together, these results support the view that gangliosides will act as much more potent suppressors of IL-2-dependent processes in vivo in the vicinity of a tumour.

Animals↗
PubMed1994

CTLA-4 ligands are required to induce an in vivo interleukin 4 response to a gastrointestinal nematode parasite.

The costimulatory signal provided to T cells through CTLA-4-ligand interactions is required for T cell activation resulting in increased interleukin 2 (IL-2) production in vitro, but its role in the production of IL-4 and other cytokines is unclear and few in vivo studies have been performed to confirm results of in vitro experiments. We have examined the in vivo effects of blocking CTLA-4 ligands on the T helper cell 2 (Th2)-associated mucosal immune response that follows oral infection of mice with the nematode parasite, Heligmosomoides polygyrus. CTLA-4Ig administration inhibited H. polygyrus-induced increases in mesenteric lymph node (MLN) B cell major histocompatibility complex class II expression and size and T cell-derived IL-4 gene expression. In addition, CTLA-4 immunoglobulin (Ig) partially blocked increased IL-3, IL-5, and IL-9 cytokine gene expression in Peyer's patch (PP) and MLN 8 d after primary inoculation of mice with the parasite. Increases in the number of IL-4- but not IL-5-secreting cells were also inhibited by CTLA-4Ig. H. polygyrus-induced elevations in serum IgE levels but not blood eosinophils, were markedly inhibited by CTLA-4Ig. These results suggest that stimulation of CD28 and/or CTLA-4 is required for T cell priming leading to IL-4 cytokine production, B cell activation, and IgE secretion during a Th2-like, mucosal immune response to a nematode parasite.

Abatacept↗
PubMed1994

Clinical application of three-dimensional transesophageal echocardiography.

Three-dimensional transesophageal echocardiography is a new and evolving cardiac imaging technique. We reported our experiences of its clinical applications in 59 patients. A series of special temporal longitudinal views were selected by the frame grabber. Then the computer connected each digitized endocardial surface of the longitudinal views according to their spatial position and reconstructed the three-dimensional, cardiac shaded picture with gray scale. The three-dimensional transesophageal echocardiographic images were divided into three areas. The right area was right anterior to the esophagus and included such structures as the superior vena cava, right atrium, interatrial septum, and left atrium; the size, shape, and location of an atrial septal defect could be clearly shown. In the middle area the origin and the course of the two great arteries could be visualized, thus facilitating the diagnosis of transposition of the great arteries; in patients with obstruction of the right ventricular outflow tract, the circular ridgelike narrowing in the right ventricle was clearly visualized. In the left area the contour and size of the left ventricle and left atrium and the shape and point of coaptation of the mitral valve could be demonstrated; in patients with mitral valve prolapse, part of either leaflet protruded into the left atrium and appeared as a spoonlike depression in the mitral valve. Other entities subjected to three-dimensional transesophageal echocardiographic reconstruction included cor triatriatum, left atrial myxoma, aneurysm of sinus of Valsalva, dissecting aortic aneurysm, mitral stenosis, mitral regurgitation, and mitral valve prolapse.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Three-dimensional transesophageal echocardiography in the diagnosis of mitral valve prolapse.

Because the anulus of the mitral valve is nonplanar in systole, false-positive diagnosis of mitral valve prolapse may result from two-dimensional transthoracic echocardiography. Because of the superior image quality of TEE, we used the three-dimensional TEE technique to evaluate the mitral valve in both normal subjects and patients with mitral valve prolapse and with ruptured chordae tendineae. After a conventional TEE examination, sequential images of longitudinal views were obtained by probe rotation. The images at 5-degree intervals were stored in machine cine memory loop; the special temporal images were selected with ECG gating and videorecorded. During the examination, 6 to 8 images of the left heart were recorded for later off-line, three-dimensional reconstruction. A total of 42 subjects were studied: 32 normal, 9 with mitral valve prolapse, and 1 with ruptured chordae tendineae. In normal subjects, three-dimensional TEE showed nonplanarity of the entire mitral valve, which assumes a saddle shape. In mitral valve prolapse, either the anterior or posterior leaflet protruded into the left atrium like a spoon; when both leaflets are involved, they prolapse like two spoons. The anterior and posterior leaflets coapted poorly, and there was a seam between them. In ruptured chordae tendineae the tip of the mitral leaflet protruded during systole into the left atrium far from the coaptation point and was perpendicular to the body of the mitral valve and parallel to the anterior and posterior walls of the left atrium.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

DRB, DQA, DQB and DPB nucleotide sequences of Saguinus oedipus B95-8.

We present eight new nucleotide sequences derived from the second exons of class II genes within the major histocompatibility complex of Sanguinus oedipus (cotton-top tamarin). These comprise two DRB alleles (Saoe-DRB3*0504, -DRB*w1203), two DQA1 alleles (Saoe-DQA1*2501, -DQA1*2502), two DQB1 alleles (Saoe-DQB1*2201, -DQB1*2301), one DQB2 allele (Saoe-DQB2*0101) and one DPB1 allele (Saoe-DPB1*0101).

Animals↗