Biomedical subjects

S Wu

Publications and source records attributed to S Wu.

571 records · Page 32Linked to original sources

PubMedDate not supplied

AFM imaging of bacteria in liquid media immobilized on gelatin coated mica surfaces.

Immobilization of particulates, especially biomolecules and cells, onto surfaces is critical for imaging with the atomic force microscope (AFM). In this paper, gelatin coated mica surfaces are shown to be suitable for immobilizing and imaging both gram positive, Staphylococcus aureus, and gram negative, Escherichia coli, bacteria in both air and liquid environments. Gelatin coated surfaces are shown to be superior to poly-L-lysine coated surfaces that are commonly used for the immobilization of cells. This cell immobilization technique is being developed primarily for live cell imaging of Rhodopseudomonas palustris. The genome of R. palustris has been sequenced and the organism is the target of intensive studies aimed at understanding genome function. Images of R. palustris grown both aerobically and anaerobically in liquid media are presented. Images in liquid media show the bacteria is rod shaped and smooth while images in air show marked irregularity and folding of the surface. Significant differences in the vertical dimension are also apparent with the height of the bacteria in liquid being substantially greater than images taken in air. In air immobilized bacterial flagella are clearly seen while in liquid this structure is not visible. Additionally, significant morphological differences are observed that depend on the method of bacterial growth.

Aluminum Silicates↗

PubMedDate not supplied

A topographic study of oscillatory potentials in man.

The purpose of this study was to evaluate the use of slow multifocal m-sequence stimulation in analyzing the topographic distribution and underlying mechanisms (including nonlinearities) of the retinal oscillatory potentials (OPs). In giving us access to the response topography and the nonlinear characteristics of the OPs, the m-sequence technique provides us with two important means for the identification and characterization of the signal sources. In this study, we analyzed the OPs into the first- and second-order components and investigated their topographies and luminance dependence. The distribution of both the first- and second-order OP components differed significantly from that of the flicker ERG investigated by Sutter and Tran (1992). At eccentricities and luminance levels favoring activity by both rods and cones, the second-order OPs were particularly prominent, showing the most clear-defined and complex waveform. The topographic distribution of the second-order OPs showed combined features of both rod and cone distributions. On a strong rod-bleaching background, the second-order OPs were eliminated and the first-order OPs showed a reduced amplitude and a shifted latency. These results are consistent with the notion that the second-order component of the OPs is dominated by contributions from rod-cone interactions.

Adolescent↗

PubMedDate not supplied

Polymorphism of human Ia antigens generated by reciprocal intergenic exchange between two DR beta loci.

Class II molecules encoded by the human major histocompatibility complex (MHC) are involved in regulating T-cell response to antigens. The mechanisms for generating polymorphism in products of the MHC have been studied extensively for both the murine H-2 and the human HLA complex. Such studies indicate that point mutations plus selection have a major role in the generation of polymorphisms of class I and class II MHC genes. However, a non-reciprocal gene conversion mechanism has been proposed to explain several examples of clustered sequence variation in MHC genes. In all these examples, the proposed gene conversion event is unidirectional; that is, one of the two interacting genes acts as sequence donor and the other as sequence recipient. No examples of potential reciprocal genetic exchange (as occurs in the fungal system), in which the two interacting genes act as both donor and recipient of gene fragments, have been found in the MHC system or in other multigene families of higher organisms. We sequenced two different HLA-DR beta complementary DNAs from each of two different cells all expressing the same serologically defined determinant (DR2) but different T-cell-recognized (Dw) specificities (Dw12 and MN2). Sequence comparisons of these four cDNA clones (and two DR beta amino-acid sequences from the DR2-Dw2 subtype) suggest that new coding sequences for DR beta molecules in the DR2 haplotypes are potentially generated by reciprocal intergenic exchange.

Amino Acid Sequence↗

PubMedDate not supplied

A perspective on medical infrared imaging.

Since the early days of thermography in the 1950s, image processing techniques, sensitivity of thermal sensors and spatial resolution have progressed greatly, holding out fresh promise for infrared (IR) imaging techniques. Applications in civil, industrial and healthcare fields are thus reaching a high level of technical performance. The relationship between body temperature and disease was documented since 400 bc. In many diseases there are variations in blood flow, and these in turn affect the skin temperature. IR imaging offers a useful and non-invasive approach to the diagnosis and treatment (as therapeutic aids) of many disorders, in particular in the areas of rheumatology, dermatology, orthopaedics and circulatory abnormalities. This paper reviews many usages (and hence the limitations) of thermography in biomedical fields.

Diagnostic Imaging↗

PubMedDate not supplied

A web-based database for diagnosis of haematologic neoplasms using immunophenotyping by flow cytometry.

The interpretation of immunophenotyping results by flow cytometry involves pattern recognition of different haematologic neoplasms that may have similar immunologic marker patterns. The numerous markers available in the flow cytometry laboratory make these patterns difficult to remember, especially for those of uncommon neoplasms. We describe the design and implementation of a Web-based database for diagnosis of haematologic neoplasms using results of immunophenotyping by flow cytometry. This database aims to assist pathology and haematology residents in interpreting flow cytometry data, and is designed to reach a wide base of users who use a variety of browsers on different computer platforms. Five modules are developed in this comprehensive program: (a) differential diagnosis: to generate a list of differential diagnoses that closely match the marker results in a given case; (b) display of disorders: typical results of markers for each disorder; (c) display of markers: relevant information of each immunologic marker; (d) display of archived cases for a disorder: marker results of cases previously diagnosed for a disorder; and (e) display of summary for archived cases: summary of marker results of all the archived cases for each disorder. Our experience with this Web-based database in teaching pathology residents has been very encouraging. Since the World Wide Web is increasingly more accessible to computer users, it has become an ideal medium for distribution of clinical decision-support software.

Antigens, CD↗

PubMedDate not supplied

Breast cancer resistance protein-mediated topotecan resistance in ovarian cancer cells.

Overexpression of breast cancer resistance protein (BCRP) and mitoxantrone (MX) resistance protein can confer resistance to a variety of cytostatic drugs, such as MX, topotecan (TPT), doxorubicin, and daunorubicin. This study investigates the role of BCRP in resistance of ovarian cancer to TPT treatment. We have developed TPT-resistant human ovarian cancer cell line. Intracellular concentration of fluorescent dye rhodamine 123 (Rh123) was measured by flow cytometry. The expression of several membrane transporter proteins including P-glycoprotein (P-gp), multidrug resistance protein 1 (MRP1), and BCRP were determined by reverse transcription-polymerase chain reaction and Western blotting. The Rh123 concentration in parental cells was approximately three times of those in TPT-resistant cells. In contrast to undetectable level of P-gp messenger RNA (mRNA) and minimal level of MRP1 expression in TPT-resistant cells, overexpression of both the BCRP mRNA and the protein was detected in these cells. Introduction of antisense-phosphorothioate oligonucleotide derived from BCRP mRNA into TPT-resistant cells resulted in a significant increase in the concentration of intracellular Rh123. These results suggested a novel mechanism in which a reduced intracellular drug concentration may be mediated by BCRP gene products in human ovarian cancer cells.

ATP Binding Cassette Transporter, Subfamily G, Mem↗

PubMedDate not supplied

Prevalence of Alzheimer's disease and other dementing disorders in an urban community of Beijing, China.

A door-to-door two-phase study was used to investigate the prevalence of senile dementia in an urban community of Beijing. In the study population, 5,003 individuals aged 60 years and older (>/=65 years, n = 3,728) were screened at home with the Chinese version of the MMSE. Persons who screened positive for dementia, using different cutoff scores based on degree of literacy, were further evaluated using the criteria of DSM-III-R and ICD-10. Among subjects who screened positive in phase I, 134 were diagnosed as having dementia in phase II. The prevalence ratios of dementia were 2.68% in the population aged 60 years and older, and 3.49% in the population aged 65 years and older. The prevalence rates among those aged 65 years and older were 1.85% for Alzheimer's disease, 1.37% for vascular dementia and 0.27% for other dementia (including mixed dementia). The prevalence of all dementia and AD increased steeply with advancing age and was consistently higher in women, but it was not obviously higher for VaD in women. Alzheimer's disease was the commonest type of dementia. Our prevalence figures for dementia and AD are similar to those previously reported for China.

Aged↗

PubMedDate not supplied

Late effect of external eye irradiation on choroidal circulation.

PURPOSE: To report two cases of atypical late onset radiation chorioretinopathy occurring 15 and 25 years post exposure and the indocyanine green (ICG) angiographic findings in these patients. METHODS: Clinical examination and imaging including fluorescein and ICG angiography were performed. RESULT: Fundus examination of the first patient revealed microangiopathy with intraretinal hemorrhages, lipid exudation, telangiectatic and aneurysmal capillary changes. Indocyanine green angiography showed an apparent chorioretinal anastomosis and delayed perfusion of the choriocapillaris. Fundus examination of the second patient revealed a pigment epithelial detachment and retinal pigment epithelial changes. Indocyanine green angiography showed atypical, tortuous, dilated, choroidal vessels as well as areas of hypoperfusion. Both patients had multiple dot-like hyperfluorescent spots in the midphase of the ICG angiogram. CONCLUSIONS: External radiation exposure may lead to both retinal and choroidal alterations which may be independent events and which may manifest after a long period of quiescence. Furthermore, ICG angiography appears to be a useful diagnostic tool to study the alterations of the choroid following external eye irradiation.

Brachytherapy↗

PubMedDate not supplied

Pathophysiologic role of eicosanoids in mesangial cell immune injury.

The pathophysiologic role of thromboxane and of arachidonate 5-lipoxygenation products in mediating changes in glomerular filtration rate (GFR) and renal blood flow (RBF) was investigated in a rat model of mesangial cell immune injury induced by a monoclonal antibody (ER4) directed against the mesangial cell membrane antigen, Thy 1. Following a single intravenous dose of the ER4 antibody acute decrements in GFR and RBF occurred at 1 h and were associated with enhanced glomerular leukocyte infiltration and synthesis of thromboxane A2, 12-HETE and LTB4. Pretreatment of animals with the thromboxane synthase inhibitor, Furegrelate, or the thromboxane receptor antagonist SQ-29,548 ameliorated or completely abolished the decrements in GFR and RBF without reducing glomerular leukocyte infiltration. Pretreatment with the arachidonate 5-lipoxygenase inhibitor MK-886 partially ameliorated the decrements in GFR and RBF, reduced the glomerular leukocyte infiltration and completely inhibited the glomerular LTB4 synthesis. Combined treatment with Furegrelate and MK-886 completely abolished the decrements in GFR and RBF as well as the glomerular synthesis of thromboxane, LTB4 and 12-HETE without altering glomerular leukocyte infiltration. These observations indicate that in mesangial cell immune injury thromboxane A2 and arachidonate 5-lipoxygenation products originating from infiltrating inflammatory cells mediate the decrements in GFR and RBF. Selective inhibition of these eicosanoids could be of benefit in clinical forms of mesangial nephritis.

Animals↗

PubMedDate not supplied

Microwave-enhanced immunohistochemical staining of a formalin-sensitive antigen-laminin receptor.

Many potentially useful antigens have been difficult to detect in formalin-fixed, paraffin-embedded tissues. Recently a number of pathological and research laboratories have demonstrated that some antigens masked by formalin fixation could be restored to detectability by microwave heating. Previously, we were unable to demonstrate laminin receptor in cells processed by the routine fixation. Our results showed that microwave heating together with trypsin produced the best immunohistochemical staining for this receptor. Nevertheless, no significance was found in the levels of 67 kD LR in high and low metastatic tumor cell lines.

Adenocarcinoma↗

PubMedDate not supplied

Increased immunogenicity of tumors bearing mutant p53 and P1A epitopes after transduction of B7-1 via recombinant adenovirus.

The majority of human solid tumors are likely to express protein epitopes which can act as targets for cytotoxic T cells, but these are frequently not effectively recognized. We tested whether the introduction of the costimulatory molecule B7-1 using a recombinant adenovirus (Ad-B7) can result in effective induction of epitope-specific immunity in two tumor models that express defined endogenous protein epitopes: D459, a fibroblast-derived cell line transfected with a human missense mutant p53 (C to Y at position 135), and P815, a mastocytoma expressing the endogenous tumor epitope P1A. Under the conditions studied, both of these tumors grow and kill their hosts without evidence of significant immune rejection. However, after transduction with the adenovirus containing B7-1, both of these tumors lose tumorigenicity and elicit specific cellular immunity to the mutant p53 epitope in D459 and P1A in P815. In addition, animals exposed to B7-transduced tumor cells were protected from subsequent challenge with nontransduced tumor. Adenovirus has distinct advantages for this approach, as it has high infectivity not requiring in vitro culture, low lytic potential, and transient expression of sufficient duration for immunologic effectiveness but without significant concern over permanent genetic modification. We conclude that transduction of tumor cells with Ad-B7 can increase the immunogenicity of endogenous protein epitopes and may represent a practical therapeutic approach to system human cancers.

Adenoviridae↗

PubMedDate not supplied

Comparison of closed-vessel and focused open-vessel microwave dissolution for determination of cadmium, copper, lead, and selenium in wheat, wheat products, corn bran, and rice flour by transverse-heated graphite furnace atomic absorption spectrometry.

A method is described for the determination of Pb, Cd, Cu, and Se in cereal samples. An atomic absorption spectrometer equipped with a transverse-heated graphite furnace with Zeeman background correction was used for all determinations. Sample preparation was performed by closed-vessel microwave digestion using nitric acid and focused openvessel microwave digestion using nitric acid-hydrogen peroxide. Both techniques were evaluated by using 15 cereal reference materials and comparing results with certified or reference values for each element. Cereal reference standards obtained from the Community Bureau of Reference (Europe), the National Institute of Standards and Technology (USA), the National Institute for Environmental Studies (Japan), the National Research Centre for Certified Reference Materials (People's Republic of China), and the Canadian Grain Commission were used. Application of a series of t-tests, conducted according to Sidak's modified Bonerroni t-procedure, showed that both techniques yielded accurate results for cereal reference materials. Some differences from certified and reference values, however, were found for each element.

Bread↗

PubMedDate not supplied

Electrophoretic analysis of nuclear matrix proteins in human hepatocellular carcinoma.

The nuclear matrix is the non-chromatin skeleton of the nucleus. This structure contributes to the shape of the nucleus and regulates various nuclear functions. In this study, nuclear matrix proteins of human normal liver, a liver cancer cell line, HepG2, and hepatocellular carcinomas (HCC) were investigated. Using high resolution two-dimensional polyacrylamide gel electrophoresis, the nuclear matrix proteins of 3 normal liver and 14 HCC were compared and contrasted. A high degree of similarity between normal liver, HepG2, and HCC nuclear matrix protein patterns was found. Two HCC specific nuclear matrix proteins were identified. Among these, one protein (HCC-1, Mr 62 kd, pI 5.3) appeared in all tumor samples and HCC-2 (Mr 33.25, pI 5.3-5.5) was present in 9/11 tumors, but absent in normal liver and HepG2. Our results indicate the presence of HCC specific nuclear matrix proteins. These matrix proteins may be used as markers for HCC.

Antigens, Nuclear↗