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Biomedical subjects

B Wang

Publications and source records attributed to B Wang.

At least 901 records · Page 50Linked to original sources
PubMed1987

DNA repair catalyzed by Escherichia coli DNA photolyase containing only reduced flavin: elimination of the enzyme's second chromophore by reduction with sodium borohydride.

DNA photolyase from Escherichia coli contains FAD plus a partially characterized, second chromophore. In vivo, the flavin is fully reduced (FADH2), but oxidation to a stable, blue radical (FADH.) occurs during enzyme isolation. The second chromophore is irreversibly reduced by reaction of the enzyme with sodium borohydride or by photoreduction in the presence of dithiothreitol. A similar reaction occurs with the protein-free chromophore and sodium cyanoborohydride. Reduction of the second chromophore is accompanied by a complete loss of the chromophore's visible absorption and fluorescence but does not significantly affect catalytic activity. The results show that the enzyme can repair dimers by a pathway involving only FADH2. Enzyme-bound FADH2 is fluorescent and exhibits emission (505 nm) and absorption (360 nm) maxima similar to that expected for a 1,5-dihydroflavin derivative. It is proposed that dimer cleavage via the second chromophore independent pathway involves electron donation from excited FADH2 to pyrimidine dimer. Pyrimidine dimer radicals are unstable and spontaneously monomerize. Unmodified second chromophore can also act as a sensitizer in a pathway that requires FADH2. This pathway may be similar to that proposed for the second chromophore independent reaction except that excited FADH2 would be produced via energy transfer from the excited second chromophore. The fluorescence observed for enzyme-bound, unmodified second chromophore is quenched by FADH. and increases 6-fold when the latter is reduced, but the absorption spectrum (lambda max = 390 nm epsilon 390 = 12.7 x 10(3) M-1 cm-1) is independent of the redox state of the flavin.(ABSTRACT TRUNCATED AT 250 WORDS)

Borohydrides↗
PubMed1986

[Ultrasound-guided percutaneous fine-needle puncture cytology in the diagnosis of malignant tumors of the liver].

Results of ultrasound guided percutaneous fine-needle puncture cytology in 142 cases of malignant tumors of the liver are reported. The positive cytology was noted in 118 (83.1%) (10 suspicious). The primary liver cancer comprised 99 cases. In 7 lesions, equal to or less than 3 cm in diameters, 6 were positive in cytology. In 20,3-5 cm in size, 18 were positive. In 15 false-negatives, 12 were larger than 5 cm in diameter. Among 43 cases of metastatic liver cancer, 34 showed positive cytology and 9 false-negative. Among 108 cases of benign hepatic diseases, in 49.1%, it was difficult to arrive at definitive diagnosis by ultrasonography only, but in 97.2% malignancy was excluded by ultrasound guided fine-needle puncture cytology. The suspicious false-positive result occurred only in 3 cases. In this series, there were 250 cases of malignant tumors and benign diseases. The overall accurate diagnostic rate was 89.2%. All the patients had been followed for more than 6 months. The differential diagnosis between malignant and benign tumors, causes of misdiagnosis and complications are discussed.

Adolescent↗
PubMed1984

Interaction of leptospires with human polymorphonuclear neutrophils.

The role of the polymorphonuclear neutrophils (PMN) in defense against leptospires has not been adequately studied, in part, because of difficulty in quantitating pathogenic leptospires. By using pour plates to quantitate nonpathogenic leptospires and the most-probable-number procedure to quantitate the pathogenic leptospires, we examined the interactions of nonpathogenic Leptospira biflexa and pathogenic Leptospira interrogans serovar icterohemorrhagiae with human neutrophils. Phase-contrast, scanning electron, and transmission electron microscopic observations were made. Leptospires were incubated with PMN at 37 degrees C and tumbled together. There was no ingestion or killing of nonpathogenic leptospires (with no serum) or of pathogenic organisms (with 10% normal serum). However, when leptospires were incubated with PMN (without serum) in a pellet and then resuspended, 91 +/- 6% of nonpathogenic leptospires were removed from the supernatant, and 93 +/- 4% of these organisms were killed. The pathogenic leptospires became cell associated in a pellet, but were not killed by PMN even in the presence of 10% normal serum. Observations of morphological interactions indicated that PMN phagocytized the nonpathogenic leptospires in the absence of serum and that the pathogenic leptospires attached to but were not ingested by neutrophils in the presence of 10% normal serum. PMN do not seem to be an efficient defense factor for pathogenic leptospires in nonimmune hosts. The virulence of leptospires appears to be related to their ability to resist killing by serum and to resist ingestion and killing by neutrophils.

Humans↗
PubMed1984

Role of specific antibody in interaction of leptospires with human monocytes and monocyte-derived macrophages.

It has previously been shown that human neutrophils ingest and kill nonpathogenic Leptospira biflexa in the absence of serum but that pathogenic Leptospira interrogans is not ingested by neutrophils even in the presence of normal serum. We extended this study by examining the interactions of human monocytes and monocyte-derived macrophages with pathogenic L. interrogans (serovar icterohaemorrhagiae) and evaluating the opsonizing effect of serotype-specific immune serum on the phagocytosis of pathogenic leptospires by monocytes and neutrophils. Leptospires were incubated with monocytes in pellets at 37 degrees C in 5% CO2. No ingestion or killing of pathogenic leptospires occurred when 10% normal serum was used. However, when the pathogenic leptospires were pretreated with serotype-specific immune serum, monocytes or neutrophils in pellets ingested 96% of the organisms and killed 94% of those ingested. Microscopic observations of the interaction confirmed that phagocytosis of the opsonized pathogenic leptospires by monocytes, monocyte-derived macrophages, and neutrophils had occurred. The opsonizing effect of specific antibody may play an important role in the mechanism of host defense against leptospirosis.

Antibodies, Bacterial↗
PubMed1982

Kinetic studies of haemopoietic progenitor cells (CFU-C) and T-lymphocytes in the liver of human foetus.

In the development of human foetus, liver is an important haemopoietic organ. We have determined the liver weight and total hepatic nucleated cells from 24 foetuses on the one hand, and CFU-C yield, total number of CFU-C and T-lymphocytes in liver from 22 foetuses of different ages on the other. From the kinetic observations through the early developmental period of the foetuses, the maximum yield of CFU-C or the total number of CFU-C in the liver occurs at 4-5 months of gestation; during the first 5 months of gestation the percentage of T-lymphocytes in the liver is about 1-2%.

Cells, Cultured↗
PubMedDate not supplied

A brief description of I.C.E.: the integrated crystallographic environment.

We describe the current status of the program I.C.E., the Integrated Crystallographic Environment. I.C.E. is a windows-based, menu-driven image processing package mainly aimed toward crystallographic image processing, although some of its functions have been used in analyzing single particle data and helical objects. The system can take individual images of crystals through the entire process of data analysis, from windowing the raw image through to the final evaluation of defocus, symmetry and creation of projection reconstructions. Current plans are to incorporate a three-dimensional database of images and electron diffraction patterns, and 3-D merging and visualization.

Computer Simulation↗
PubMedDate not supplied

CTF determination of images of ice-embedded single particles using a graphics interface.

We implement a graphical user interface in an X-window/UNIX environment to compute and display the incoherently averaged Fourier transforms of electron images of single particles embedded in ice and the simulated contrast transfer function with or without envelope functions. This interface provides an easy and efficient operation for the determination of defocus value and the evaluation of the extent of Fourier amplitude falloff. This computational procedure is crucial for prescreening image data and performing image correction of contrast transfer function in high-resolution three-dimensional reconstruction of single particles.

Capsid↗
PubMedDate not supplied

Modulation of the contact hypersensitivity response by AE-941 (Neovastat), a novel antiangiogenic agent.

BACKGROUND: AE-941 (Neovastat) is an angiogenesis inhibitor noted to have antiinflammatory properties. OBJECTIVE: We tested Neovastat in a contact hypersensitivity (CHS) model to determine the mechanism of action of its antiinflammatory effects. METHODS: Neovastat was orally administered (200 mg/kg/day) during the sensitization and challenge phases of a murine CHS assay and inflammatory responses were measured. Subsequent assays were performed on mice treated with Neovastat or Cortisone (120 mg/kg/day, IP) and differential mRNA expression of several pro- and antiinflammatory cytokines was quantified using RT-PCR. RESULTS: Neovastat decreased inflammation by 39% when administered during sensitization but did not alter the CHS response when given during the challenge phase. Neovastat significantly induced IL-10 expression in skin and skin-draining lymph nodes (49% and 45%, respectively) and decreased IFNgamma expression in the lymph nodes (35%). CONCLUSION: Antiinflammatory effects of Neovastat observed in CHS could be linked to modulation of cytokines early in the sensitization phase.

Administration, Oral↗
PubMedDate not supplied

Immune competence involving the natural killer cell lineage promotes placental growth.

Very small placentae and absence of uterine natural killer (uNK) cells are amongst the reproductive deficits found in the natural killer (NK) cell and thymus-derived (T) cell immunodeficient mouse tgepsilon26. These defects can be reversed by grafting of adult tgepsilon26 females with bone marrow from T and B cell immunodeficient scid/scid donors. We report here that a second protocol, grafting of neonatal tgepsilon26 females with immunocompetent bone marrow pretreated with antibody to Thy-1, successfully established the uNK cell lineage and ameliorated the phenotype. Further, comparisons of mid-gestation (days 10-16) placental area measurements from tgepsilon26 and seven other immunodeficient strains to time-matched tissues from four strains of immunocompetent mice indicate that lymphocytes of the NK but not the T or B cell lineages are able to influence placental size during normal gestation and that this action is independent of interleukin 2. Area measurements of placentae produced in manipulated tgepsilon26 pregnancies (maternal bone marrow engraftment, outcrossing to immunocompetent males and reciprocal embryo transfers with an immunocompetent strain) suggest that NK cell competence is required in each of the maternal and fetal compartments to optimize placental growth.

Animals↗