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PubMed1990

Immune complex transfer enzyme immunoassays for anti-angiotensin I IgG in serum using angiotensin I conjugates prepared by two different methods.

Anti-angiotensin I IgG in serum was measured by immune complex transfer enzyme immunoassays using angiotensin I conjugates prepared by two different methods. In the first method, angiotensin I was conjugated to dinitrophenyl bovine serum albumin and beta-D-galactosidase through covalent links. Anti-angiotensin I IgG in rabbit serum was reacted simultaneously with dinitrophenyl bovine serum albumin-angiotensin I conjugate and beta-D-galactosidase-angiotensin I conjugate, and the complex formed of the three components was trapped onto (anti-dinitrophenyl group) IgG-coated polystyrene balls. After washing, the complex was eluted from the polystyrene balls with dinitrophenyl-L-lysine and transferred to goat (anti-rabbit IgG) IgG-coated polystyrene balls. Beta-D-Galactosidase activity bound to (anti-rabbit IgG) IgG-coated polystyrene balls was assayed by fluorometry. In the second method, biotinylated angiotensin I was coupled with dinitrophenyl bovine serum albumin-avidin conjugate and Beta-D-galactosidase-avidin conjugate and substituted for the two conjugates in the first method. The detection limits of anti-angiotensin I IgG in serum were 10-30 ng/liter (0.2-0.6 pg/assay). These methods were 330 to 1,000-fold more sensitive and much less affected by serum effect than the conventional enzyme immunoassay, in which an angiotensin I-bovine serum albumin-coated polystyrene ball was incubated with anti-angiotensin I IgG in serum and, after washing, with (anti-rabbit IgG) Fab'-peroxidase conjugate. The first method was more sensitive than the second method, but the second method may be superior in applicability to the first method.

Amino Acid Sequence↗
PubMed2001

The water-equivalence of phantom materials for 90Sr-90Y beta particles.

Intravascular brachytherapy requires that the dose be specified within millimeters of the source. High dose gradients near brachytherapy sources require that the source-detector distance be accurately known for dosimetry purposes. Solid phantoms can be designed to accommodate these stringent requirements. This study reports dosimeter readings from 90Sr-90Y sources measured in water, A150, polystyrene and in an epoxy-based water-equivalent plastic. Measurements showed that while A150 and the epoxy-based plastic agreed well with water when the surface of the source contacted the detector housing, the relative response in the phantoms decreased with increasing depth in phantom, falling to approximately 0.55 those of water at a depth of 5 mm. Readings in polystyrene were within 4% of those in water between 1 and 2 mm depth. However, while polystyrene followed water more closely than the other two materials, at greater depths the relative response in polystyrene to water varied from 0.65 to 1.34. When the density of the materials is accounted for, the relative response in A150 is nearly constant with increasing areal density. Furthermore, the response in A150 shows the closest agreement with that in water of any of the solid materials for higher areal densities. For values below 0.3 g/cm2, polystyrene shows the closest agreement with water.

Angioplasty↗
PubMed2006

Pencil beam approach for correcting the energy dependence artifact in film dosimetry for IMRT verification.

The higher sensitivity to low-energy scattered photons of radiographic film compared to water can lead to significant dosimetric error when the beam quality varies significantly within a field. Correcting for this artifact will provide greater accuracy for intensity modulated radiation therapy (IMRT) verification dosimetry. A procedure is developed for correction of the film energy-dependent response by creating a pencil beam kernel within our treatment planning system to model the film response specifically. Film kernels are obtained from EGSnrc Monte Carlo simulations of the dose distribution from a 1 mm diameter narrow beam in a model of the film placed at six depths from 1.5 to 40 cm in polystyrene and solid water phantoms. Kernels for different area phantoms (50 x 50 cm2 and 25 x 25 cm2 polystyrene and 30 x 30 cm2 solid water) are produced. The Monte Carlo calculated kernel is experimentally verified with film, ion chamber and thermoluminescent dosimetry (TLD) measurements in polystyrene irradiated by a narrow beam. The kernel is then used in convolution calculations to, predict the film response in open and IMRT fields. A 6 MV photon beam and Kodak XV2 film in a polystyrene phantom are selected to test the method as they are often used in practice and can result in large energy-dependent artifacts. The difference in dose distributions calculated with the film kernel and the water kernel is subtracted from film measurements to obtain a practically film artifact free IMRT dose distribution for the Kodak XV2 film. For the points with dose exceeding 5 cGy (11% of the peak dose) in a large modulated field and a film measurement inside a large polystyrene phantom at depth of 10 cm, the correction reduces the fraction of pixels for which the film dose deviates from dose to water by more than 5% of the mean film dose from 44% to 6%.

Algorithms↗
PubMed2005

Vitreous: a barrier to nonviral ocular gene therapy.

PURPOSE: Intravitreal injection of therapeutic DNA, complexed to nonviral carriers such as cationic liposomes, may be promising in the treatment of many severe retinal eye diseases. However, after intravitreal injection, such DNA/cationic liposome complexes-called lipoplexes (LPXs)-which are typically hundreds of nanometers in size, must first diffuse through the vitreous before they can reach the retina. The aim of this study was to elucidate whether vitreous is a barrier for the LPXs and to find strategies to overcome this barrier. METHODS: Fluorescent polystyrene nanospheres and LPXs were mixed with vitreous, and their mobility was monitored by fluorescence recovery after photobleaching (FRAP), a microscopy-based technique. The stability of LPXs and naked plasmid DNA in vitreous was studied by gel electrophoresis. RESULTS: We showed that polystyrene nanospheres, in our first experiments used as a model for the LPXs, do not diffuse freely into the vitreous but adhere to fibrillar structures in the vitreous, most likely to collagen fibers. Making the surfaces of the polystyrene nanospheres hydrophilic by attaching hydrophilic polyethylene glycol (PEG) chains at their surfaces circumvented the binding to fibrillar structures in the vitreous. FRAP revealed that "pegylated" polystyrene nanospheres, as long as they are smaller than 500 nm, are indeed mobile in the vitreous. It was further demonstrated that LPXs severely aggregate in vitreous and strongly bind to biopolymers in the vitreous, which immobilizes them completely. However, as observed for the polystyrene nanospheres, coating of the LPXs with PEG averted their aggregation in the vitreous and their binding to fibrillar structures. CONCLUSIONS: Modifying the surfaces of LPXs with hydrophilic PEG chains prevents them from aggregating in vitreous. In this way, LPXs are obtained that can freely move in vitreous, an absolute criterion for reaching the retina after intravitreal injection.

Animals↗
PubMed2004

Impact of surface coating on the adherence of slime producing and nonproducing Staphylococcus epidermidis.

The ability of Staphylococcus epidermidis to grow in the form of a biofilm not only facilitates its persistence in the host, but also allows it to survive at antibiotic concentrations several orders higher than the Minimum Inhibitory Concentration (MIC). We evaluated different surface treatments of hardened polystyrene in order to develop a model system for growth of S. epidermidis as a biofilm. We assayed for biofilm growth of S. epidermidis clinical isolates on unmodified polystyrene, on polystyrene modified by chemical abrasion and on polystyrene modified by sulfonation, using either Tryptic Soya Broth or Brain Heart Infusion as a growth medium. We concluded that sulfonated polystyrene and Brain Heart Infusion provided the best growth system for predicting the ability of a clinical isolate to form biofilm (Akaike value 23.680). Using this method, biofilm formation was detected in 14 (70%) of ica-positive strains and negative in 16 (80%) of ica-negative strains.

Bacterial Adhesion↗
PubMed1998

Potential of the immune complex transfer enzyme immunoassay for antigens and antibodies to improve the sensitivity and its limitations.

In order to reduce the nonspecific signal of noncompetitive solid phase immunoassays and to improve their sensitivities, the immune complex transfer enzyme immunoassay has been developed. Antigens to be measured were reacted with 2,4-dinitrophenyl-biotinyl-antibody Fab' and antibody Fab'-beta-D-galactosidase conjugate, and antibody IgGs to be measured were reacted with 2,4-dinitrophenyl-antigen and antigen-beta-D-galactosidase conjugate. The immune complexes formed comprising the three components were trapped onto colored polystyrene beads coated with affinity-purified (anti-2,4-dinitrophenyl group) IgG. After washing, the immune complexes were eluted from the colored polystyrene beads with epsilonN-2,4-dinitrophenyl-L-lysine, and the eluates were incubated with white polystyrene beads coated with streptavidin for antigens and coated with affinity-purified (anti-human IgG gamma-chain) IgG for antibody IgGs to transfer the immune complexes. By this method, ultrasensitive enzyme immunoassays have been developed for HIV-1 p24 antigen and antibody IgGs to HIV-1 p17 and reverse transcriptase (RT). The nonspecific signals in the absence of the antigen and the antibody IgGs were reduced 300 to 15,000-fold by the immune complex transfer process, but the amounts of the immune complexes decreased only 1.8 to 3.1-fold by the immune complex transfer. As a result, the sensitivities for HIV-1 p24 antigen and antibody IgGs to HIV-1 p17 and RT were improved 100 to 5,600-fold by the immune complex transfer. The detection limit of HIV-1 p24 antigen by 20 hr assay of beta-D-galactosidase activity (10 zmol) was 4,000 to 17,000-fold lower than those obtained with currently available commercial kits. The improved sensitivities for antibody IgGs to p17 and RT by 20 hr assay of beta-D-galactosidase activity were 1 x 10(5) to 3 x 10(5)-fold higher than those of Western blotting for p17 and p66 bands. However, the nonspecific signals in the absence of antigens and antibody IgGs were enhanced to various degrees by two factors. In order to transfer the immune complexes more efficiently within shorter periods of time, the colored polystyrene beads were incubated with the white polystyrene beads in the presence of epsilonN-2,4-dinitrophenyl-L-lysine. Such direct contact between solid phases for trapping and transferring of the immune complexes significantly enhanced the nonspecific signals. In addition, the presence of human serum samples containing neither antigens to be measured nor antibody IgGs to be measured also enhanced the nonspecific signals to various extents. Namely, these two factors limited the effect of the immune complex transfer to improve the sensitivity by 20 hr assay of beta-D-galactosidase activity. By 1 hr assay of beta-D-galactosidase activity, the detection limit of HIV-1 p24 antigen using 10 microl of serum samples (0.24 pg/ml) was 40 to 80-fold lower than those obtained with currently available commercial kits using 100 to 200 microl of serum samples (10 to 20 pg/ml) and the detection limits of antibody IgGs to HIV-1 pl7 and RTwere 1 x 10(4) to 3 x 10(4)-fold lower than those by Western blotting for p17 and p66 bands. Finally, the immunoreactions involved in the immune complex transfer enzyme immunoassays--the formation, trapping, and transferring of the immune complexes--will be performed within 15 to 30 min.

Antibodies↗
PubMed1999

Ultrasensitive immune complex transfer enzyme immunoassay of HIV-1 p24 antigen with less serum interference using 2,4-dinitrophenyl-anti-HIV-1 p24 IgG and indirectly immobilized (anti-2,4-dinitrophenyl group) Fab..

In the immune complex transfer enzyme immunoassay previously reported, the immune complex consisting of 2,4-dinitrophenyl-biotinyl-bovine serum albumin-affinity-purified rabbit anti-HIV-1 p24 Fab' conjugate, HIV-1 p24 antigen and monoclonal mouse anti-HIV-1 p24 Fab'-beta-D-galactosidase conjugate was trapped on polystyrene beads coated directly with affinity-purified (anti-2,4-dinitrophenyl group) IgG and was transferred to polystyrene beads coated with biotinyl-bovine serum albumin and streptavidin. The serum volume used was limited to 10 microL due to serious serum interference, and the detection limit of HIV-1 p24 antigen was 240 fg/mL serum. In the present study, HIV-1 p24 antigen was incubated simultaneously with 2,4-dinitrophenyl-affinity-purified rabbit anti-HIV-1 p24 IgG and monoclonal mouse anti-HIV-1 p24 Fab'-beta-D-galactosidase conjugate in the presence of excess nonspecific rabbit IgG. The immune complex of the three components formed was trapped on polystyrene beads coated successively with biotinyl-bovine serum albumin, streptavidin and biotinyl-affinity-purified (anti-2,4-dinitrophenyl group) Fab'. After washing, the immune complex was eluted from the polystyrene beads with excess epsilonN-2,4-dinitrophenyl-L-lysine and transferred to polystyrene beads coated with affinity-purified goat (antirabbit IgG) IgG. The serum volume used was increased to 90 microL with only slight serum interference, and the detection limit of HIV-1 p24 antigen was lowered 9-fold to 26 fg/mL serum.

2,4-Dinitrophenol↗
PubMed1989

More sensitive and simpler immune complex transfer enzyme immunoassay for antithyroglobulin IgG in serum.

A more sensitive and simpler immune complex transfer enzyme immunoassay for antithyroglobulin IgG in serum and its use for the measurement of antithyroglobulin IgG in healthy subjects and patients with thyroid diseases are described. Antithyroglobulin IgG in test serum was reacted simultaneously with dinitrophenylthyroglobulin and thyroglobulin-beta-D-galactosidase conjugate. The complex formed of antithyroglobulin IgG, dinitrophenyl thyroglobulin, and thyroglobulin-beta-D-galactosidase conjugate was trapped onto two polystyrene balls coated with affinity-purified rabbit (antidinitrophenyl bovine serum albumin) IgG. The polystyrene balls were washed to eliminate nonspecific IgG in the test serum, and the complex was eluted from the polystyrene balls with dinitrophenyl-L-lysine and transferred to two polystyrene balls coated with affinity-purified rabbit (anti-human IgG gamma-chain) IgG. beta-D-Galactosidase activity bound to the polystyrene balls was assayed by fluorimetry using 4-methylumbelliferyl-beta-D-galactoside as substrate. As compared with the previous immune complex transfer enzyme immunoassay, the procedure was simplified by reducing one incubation step and one washing step, and the detection limit of antithyroglobulin IgG in serum (0.1 microgram/liter) was lowered 100-fold. More careful and extensive examination than in a previous study revealed the presence of antithyroglobulin IgG in a large proportion of healthy subjects and in all patients with Graves' disease and chronic thyroiditis.

Adolescent↗
PubMed1990

Novel and sensitive enzyme immunoassay (immune-complex-transfer enzyme immunoassay) for alpha-fetoprotein from hepatocellular carcinoma.

Alpha-fetoprotein in sera from patients with hepatocellular carcinoma was fractionated into three peaks by affinity chromatography on a column of Lens culinaris agglutinin-Sepharose 4B. One peak (the first peak), which passed through the column without adsorption, was found in both healthy subjects and patients with liver cirrhosis and hepatocellular carcinoma. The second and third peaks were reactive with L. culinaris agglutinin and found only in patients with hepatocellular carcinoma. For alpha-fetoprotein in the second and third peaks, a novel and sensitive enzyme immunoassay (immune-complex-transfer enzyme immunoassay) was developed. Alpha-fetoprotein in test serum was reacted with dinitrophenyl affinity-purified anti-alpha-fetoprotein IgG, and the complex formed was trapped onto affinity-purified (antidinitrophenyl bovine serum albumin) IgG-coated polystyrene balls. The polystyrene balls were washed to eliminate substance(s) other than alpha-fetoprotein in the test serum, and the complex was eluted from the polystyrene balls with dinitrophenyl-L-lysine. The eluted complex containing alpha-fetoprotein in the second and third peaks was trapped onto L. culinaris agglutinin-coated polystyrene balls and reacted with affinity-purified anti-alpha-fetoprotein Fab'-beta-D-galactosidase conjugate. Beta-D-galactosidase activity bound to the polystyrene balls was assayed by fluorimetry. The maximal volume of serum that could be used without interference was 20 microliters, which was 100-fold larger than that in the previous enzyme immunoassay.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomarkers, Tumor↗
PubMed1990

Novel and sensitive noncompetitive (two-site) enzyme immunoassay for haptens with amino groups.

A novel and sensitive noncompetitive (two-site) enzyme immunoassay for haptens with amino groups is described. L-Thyroxine (T4) was used as a model hapten. T4 was indirectly biotinylated with glutathione as spacer between T4 and biotin molecules and trapped onto anti-(T4-bovine serum albumin) IgG-coated polystyrene balls. After washing the polystyrene balls to eliminate unreacted biotin and other biotinylated substances, biotinylated T4 was eluted from the polystyrene balls with HCl and was reacted with anti-(T4-bovine serum albumin) Fab'-horseradish peroxidase conjugate. The complex formed was trapped onto streptavidin-coated polystyrene balls. Peroxidase activity bound to the polystyrene balls was assayed by fluorimetry. The detection limit of T4 was 78 fg (0.1 fmol)/tube, which was 50-fold lower than the limit by competitive enzyme immunoassay using the same antibody and T4-peroxidase conjugate. This noncompetitive enzyme immunoassay was applied to the measurement of total T4 in serum. Serum levels of total T4 in 10 healthy subjects aged 25-40 yr were 94 +/- 13 (SD) micrograms/L (range, 78-114). The principle of this noncompetitive enzyme immunoassay may allow it to measure other haptens with amino groups more sensitively than can competitive immunoassays.

Adult↗
PubMed1990

Sensitive time-resolved fluorimetric immune-complex-transfer immunoassay for antithyroglobulin IgG in serum.

A sensitive time-resolved fluorimetric immune-complex-transfer immunoassay for antithyroglobulin IgG in serum is described. Antithyroglobulin IgG in test serum was reacted with dinitrophenyl europium ion-labeled thyroglobulin. The complex formed of antithyroglobulin IgG and dinitrophenyl europium ion-labeled thyroglobulin was trapped onto two polystyrene balls coated with affinity-purified rabbit antidinitrophenyl bovine serum albumin IgG. The polystyrene balls were washed to eliminate nonspecific IgG in the test serum, and the complex was eluted from the polystyrene balls with dinitrophenyl-L-lysine and transferred to two polystyrene balls coated with affinity-purified rabbit antihuman IgG gamma-chain IgG. Europium ion bound to the polystyrene balls was measured by time-resolved fluorimetry. Antithyroglobulin IgG was demonstrated in all patients with Graves' disease and all patients with chronic thyroiditis. This immunoassay was more sensitive than the conventional enzyme immunoassay and less time-consuming than the previously described immune-complex-transfer enzyme immunoassays, although there were larger assay variations.

Adolescent↗
PubMed1991

Immune complex transfer enzyme immunoassay for (anti-human T-cell leukemia virus type I) IgG in serum using a synthetic peptide, Cys-Gag p19(100-130), as antigen.

An immune complex transfer enzyme immunoassay for (anti-human T-cell leukemia virus type I) IgG (anti-HTLV-I IgG) in serum using a synthetic peptide, cys-gag p19(100-130), is described. Anti-HTLV-I IgG in test serum, which had been incubated with excess of inactive beta-D-galactosidase to eliminate interference by anti-beta-D-galactosidase antibodies, was reacted simultaneously with 2,4-dinitrophenyl bovine serum albumin-cys-gag p19(100-130) conjugate and cys-gag p19(100-130)-beta-D-galactosidase conjugate. The complex formed of the three components was trapped onto polystyrene balls coated with affinity-purified (anti-2,4-dinitrophenyl group) IgG. After washing to eliminate nonspecific IgG in the test serum and excess of the beta-D-galactosidase conjugate, the complex was eluted from the polystyrene balls with epsilon N-2,4-dinitrophenyl-L-lysine and transferred to polystyrene balls coated with affinity-purified (anti-human IgG gamma-chain) IgG. Beta-D-Galactosidase activity bound to the (anti-human IgG gamma-chain) IgG-coated polystyrene balls was assayed by fluorometry. This assay was 100-fold more sensitive than the conventional enzyme immunoassay, in which a cys-gag p19(100-130)-bovine serum albumin-coated polystyrene ball was incubated with test serum and, after washing, with (anti-human IgG gamma-chain) Fab'-peroxidase conjugate. The degree of inhibition by preincubation of test sera with excess of cys-gag p19(100-130) in combination with an appropriate cut-off value for the fluorescence intensity of bound beta-D-galactosidase activity discriminated almost all seropositive samples from seronegative ones.

Adolescent↗
PubMed1991

Novel and sensitive noncompetitive enzyme immunoassay (hetero-two-site enzyme immunoassay) for alpha-human atrial natriuretic peptide in plasma.

A novel and sensitive noncompetitive enzyme immunoassay (hetero-two-site enzyme immunoassay) for alpha-human atrial natriuretic peptide (alpha-hANP) in plasma, which uses only one monoclonal IgG for the ring structure of alpha-hANP, is described. Plasma was filtered through polysaccharide membrane to separate peptides from proteins. The plasma filtrate was incubated with N-hydroxysuccinimidobiotin to biotinylate alpha-hANP and subsequently with a polystyrene ball coated with monoclonal IgG for the ring structure of alpha-hANP to trap biotinylated alpha-hANP. The polystyrene ball was washed to eliminate unreacted N-hydroxysuccinimidobiotin and other biotinylated substances, and biotinylated alpha-hANP was eluted from the polystyrene ball with HCl. The eluate was neutralized and incubated with horseradish peroxidase-labeled antibody IgG for the ring structure of alpha-hANP and subsequently with two streptavidin-coated polystyrene balls. Peroxidase activity bound to the streptavidin-coated polystyrene balls was assayed by fluorometry. The detection limit of alpha-hANP was 20 amol, and the assay range of plasma alpha-hANP was 0.8-1,200 ng/L using 100 microliters of plasma filtrates corresponding to 75 microliters of plasma. Plasma levels of hANP in healthy subjects were 9.8-21.5 ng/L. These values were significantly lower than those measured by a two-site enzyme immunoassay probably due to the presence of alpha-hANPs lacking some N-terminal amino acids, which were as reactive as alpha-hANP in the two-site enzyme immunoassay but less reactive in the hetero-two-site enzyme immunoassay.

Adult↗
PubMed1994

Use of microplates and fluororeader for ultrasensitive enzyme immunoassay (immune complex transfer enzyme immunoassay) of anti-HTLV-I IgG.

Previously, an ultrasensitive solid phase enzyme immunoassay (immune complex transfer enzyme immunoassay) was described to detect low levels of anti-HTLV-I IgG in serum below those detectable by conventional methods. In this method, polystyrene balls as solid phase were transferred from test tube to test tube with tweezers. This was not only tedious but also causative of false-positivity by carryover, unless tips of the tweezers were washed carefully after each transfer of polystyrene balls. Bound enzyme activities for many samples were measured one by one by fluorometry using a spectrofluorophotometer. As a result, the assay of many samples was difficult. In the present study, microplates and a fluororeader were used in place to test tubes and a spectrofluorophotometer. Polystyrene balls were transferred quickly and easily from well to well by placing a microplate upside down on that containing polystyrene balls, and turning the two plates together upside down. Tweezers were not used for transfer of polystyrene balls, minimizing the possibility of false-positivity. Fluorescence intensities of bound enzyme activities for 96 samples were measured within a minute by using a fluororeader. Thus, it became easy to test many samples, although the sensitivity was lowered to some extent.

Amino Acid Sequence↗
PubMed1998

The effect of quality and availability of foraging materials on feather pecking in laying hen chicks.

Feather pecking resulting in feather damage, injuries and mortality causes severe welfare problems in laying hens. In the present study, we tested whether there is an inverse relationship between feather pecking and foraging behaviour (exploratory and manipulative behaviour away from the feeder). Forty-eight groups of 30 or 31 chicks, Gallus gallus domesticus, were reared in pens and provided with different types of foraging material. Feather pecking and foraging behaviour were quantified when the chicks were 4 and 5 weeks of age. In experiment 1, chicks with access to long-cut straw showed more foraging behaviour and less feather pecking than chicks that were provided with the same straw but in shredded form. On the other hand, there was no difference in foraging behaviour and feather pecking between chicks reared with access to long-cut straw and polystyrene blocks. In experiment 2, the importance of the form of the foraging material was confirmed. Chicks provided with polystyrene blocks performed more foraging behaviour and less feather pecking than chicks with access to polystyrene beads. The provision of an area with a layer of wood-shavings to promote scratching behaviour had no significant effect, however, on the incidence of feather pecking. In experiment 3, polystyrene blocks and beads were offered during the whole day or only in the morning. Both the quality and the availability of the foraging materials had a significant effect on foraging behaviour and a significant but opposite effect on feather pecking. Focal animal observations showed that the chicks performed different types of foraging behaviour at polystyrene blocks and beads. This suggests that not only the quantity but also the quality of foraging behaviour elicited by a given material may be important to prevent the development of feather pecking. Feather pecking should thus be considered as redirected foraging behaviour. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1998

Bubble Formation at Porous Hydrophobic Surfaces

The bubble formation properties of various porous surfaces at low gas supersaturations were investigated. Polystyrene and silica particles with pore sizes ranging from 40 to 1000 A were used as representative surfaces for this study. Among the polystyrene particles, those with the smallest pores generated the greatest numbers of bubbles at gas supersaturations of 5 and 15 atm N2. However, at supersaturations of 50 atm N2 all three polystyrene particles generated massive numbers of bubbles, obscuring any differences attributable to pore size. The surface wettability of the silica particles was altered by chemically coating the surfaces. Three of the four different silica particles initiated significantly greater numbers of gas bubbles after being coated with a hydrophobic silane layer. Hydrostatic prepressurization of the hydrophobic silica particles dramatically decreased the number of bubbles generated, suggesting that the bubble-initiating capability of these particles was due to gas trapped by the surfaces. In sharp contrast, the porous polystyrene particles showed no change in bubble nucleation capability following exposure to hydrostatic pretreatments of up to 1000 atm for 30 min. This suggests that gas not only may be trapped in the main pores of these particles, but also may be dispersed in undefined micropores throughout the polystyrene structure which may resist collapse by hydrostatic pretreatments of the magnitudes and/or durations used in this study. Copyright 1998 Academic Press. Copyright 1998Academic Press

Journal Article↗
PubMed2006

Hepatocyte spheroid formation on a titanium dioxide gel surface and hepatocyte long-term culture.

The cell morphology and expression of differentiated functions of primary rat hepatocytes on a titanium dioxide (TiO(2)) gel surface were investigated. Polystyrene culture dishes were coated with TiO(2) gel by spin-coating an ethanol solution of titanium n-butoxide, hydrolyzing in a humidity chamber and drying with nitrogen gas. The TiO(2) gel layer formed on the polystyrene dishes was transparent and robust, and its surface was quite flat. Rat hepatocytes inoculated on the TiO(2) gel-coated polystyrene dishes gradually accumulated with increasing culture time, and then spontaneously formed many hepatocyte spheroids at 90 +/- 21 microm diameter from about 3 days of culture. The diameter of the spheroids increased during the culture, and was 151 +/- 43 microm at 14 days of culture. Ammonia removal and albumin secretion by hepatocytes on the TiO(2) gel-coated polystyrene dishes were maintained at a high level for at least 14 days of culture compared with on a type I collagen-coated dish and a non-coated polystyrene dish. These results indicate that TiO(2) gel is an adequate material for hepatocyte spheroid formation and long-term culture of spheroids.

Animals↗
PubMed1987

A novel enzyme immunoassay of anti-insulin IgG in guinea pig serum.

A novel enzyme immunoassay of anti-insulin IgG in guinea pig serum is described. Guinea pig anti-insulin serum diluted with nonspecific guinea pig serum was incubated with dinitrophenyl biotinyl nonspecific rabbit IgG-insulin conjugate and a rabbit (anti-dinitrophenyl bovine serum albumin) IgG-coated polystyrene ball. After washing to eliminate nonspecific guinea pig IgG in the diluted serum, the polystyrene ball was incubated with dinitrophenyl-L-lysine to elute the complex of anti-insulin IgG and the conjugate. The eluate was incubated with an avidin-coated polystyrene ball. Finally, the amount of guinea pig anti-insulin IgG in the complex trapped onto the avidin-coated polystyrene ball was measured by incubation with rabbit (anti-guinea pig IgG) Fab'-peroxidase conjugate. This enzyme immunoassay was 10,000-fold more sensitive than the conventional enzyme immunoassay using insulin-coated polystyrene ball and rabbit (anti-guinea pig IgG) Fab'-peroxidase conjugate.

Animals↗