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Biomedical subjects

H B Lee

Publications and source records attributed to H B Lee.

At least 109 records · Page 6Linked to original sources
PubMed1996

Blood and cell compatibility of gelatin-carrageenan mixtures cross-linked by glutaraldehyde.

Mixtures of gelatin and iota-carrageenan cross-linked by glutaraldehyde were prepared and their physical properties and blood and cell compatibility were compared to gelatin as a control material. According to scanning electron microscopic observation of fracture surfaces, the mixtures were composed of dispersed and continuous domains which might be generated by phase separation of carrageenan. The thermal degradation temperature of iota-carrageenan in the mixtures rose with increasing gelatin content. The swelling process in the mixtures proceeded slower than in gelatin. Tensile strengths of the mixtures, except that containing 50% iota-carrageenan, increased with increased amounts of iota-carrageenan in the mixtures. The iota-carrageenan contents at the surfaces of the mixtures were generally higher than those admixed originally. Static friction coefficients of the mixtures were lower than that of gelatin. Plasma recalcification times of the mixtures were longer than that of gelatin. Platelet adhesion of the mixtures was lower than that of gelatin, while cell adhesion and growth assays using Chinese hamster ovary cells showed that cell adhesion and growth were not dependent on adding iota-carrageenan. It was concluded that blood compatibility of the mixtures increased and cell compatibility did not decrease, compared to gelatin.

Animals↗
PubMed1996

Prevention of platelet adhesion on the polysulfone porous catheter by saline solution perfusion, I. In vitro investigation.

A new technique for the prevention of platelet adhesion on the polysulfone (PSf) porous catheter system by means of saline perfusion was investigated. Commercially available ultrafiltration PSf hollow fibers were used as porous catheter tubes. Sixty milliliter of citrated canine blood was circulated for 20 min through the annular catheter flow cell system in vitro. Platelet adhesion onto the PSf porous catheter tube decreased sharply with increased saline solution perfusion rate. From the semilogarithmic relationship between the number of adhered platelets and perfusion rate, the critical perfusion rate for preventing adhesion of platelets could be about 0.3 ml min-1 cm-2. After the surface of PSf porous tubes was modified by non-ionic surfactant coating and air plasma treatment for 20 seconds without saline perfusion, the number of adhered platelets was lower than that of the control tube. These modification methods may be more effective in the prevention of initial platelet adhesion if combined with saline perfusion.

Animals↗
PubMed1996

Dialysis in patients with diabetic nephropathy: CAPD versus hemodialysis.

Diabetic nephropathy has emerged as a major cause of ESRD over the past decade, being the most prevalent cause of ESRD requiring dialysis in North America (United States and Canada) and the second highest in the incidence rate in Europe, Japan, Korea, Australia, and New Zealand. A greater proportion of older patients and of patients with diabetic nephropathy and other comorbid conditions has been treated with CAPD. Despite the preferential use of CAPD to treat a high-risk group of patients, the overall and/or selection-adjusted mortality was similar between HD and CAPD groups. Among diabetic patients, selection-adjusted mortality was similar between HD and CAPD or lower in CAPD than in HD, the difference being greatest among younger patients and significant through the age of 52, or higher in CAPD than in HD with higher risk of death for older diabetics (age > or = 50 years), but with similar risk among younger diabetics (age < 50 years). Technique survival was also variably reported as similar between HD and CAPD, lower, or higher with CAPD compared to HD. Diabetic CAPD patients had more hospital admissions and more days in the hospital and higher withdrawal rates from dialysis compared to diabetic HD patients. These disparate results of patient and technique survival between HD and CAPD in diabetic patients may have resulted from patient selection criteria with different comorbid conditions on entrance to dialysis, quantity of dialysis, and other unrecognized factors. Prospective randomized studies are needed to assign a cause-and-effect relationship between the choice of dialysis modality and patient and technique survival among patients with diabetes mellitus as well as with all other diagnostic categories.

Diabetic Nephropathies↗
PubMed1996

Prevention of platelet adhesion on polysulfone porous catheter by saline solution perfusion, II. Ex vivo and in vivo investigation.

Using a custom-made PVC medical tube ateriovenous (A-V) shunt and a porous polysulfone (PSf) catheter, an ex vivo and in vivo experiment were carried out to study the effectiveness of saline solution perfusion to prevent adhesion of platelets without using anticoagulants. The critical perfusion rate for preventing adhesion of platelets onto the PSf catheter tubes is about 0.45 ml min-1 cm-2. The higher perfusion rate resulted in a lesser platelet adhesion. At the highest perfusion rate tested, 0.92 ml min-1 cm-2, the number of adhered platelets decreased by 98% in the in vivo experiment. From the results of ex vivo and in vivo canine experiments, the saline perfusion catheters can be used as a very useful clinical armamentarium to prevent platelet and blood cell adhesion without using anticoagulants.

Animals↗
PubMed1996

Radiation effects on polypropylene for sterilization.

In order to improve the resistance of gamma-radiation sterilization of polypropylene (PP), the formulations of the additives such as antioxidants, crosslinking agent, and trans-stilbene oxide (StO) have been carried out. The irradiated PP and ethylene-propylene copolymer samples with control and additives were characterized by mechanical tester, colorimetry, and Fourier transform infrared spectroscopy with total attenuated reflectance mode (FTIR-ATR). Crosslinking agent and StO formulated PP showed remarkable radiation resistance and minimum discoloration. Also, radiation resistance of ethylene-propylene copolymers with 3% of ethylene contents was better than that of PP homopolymers in the case of no additives. The proposed mechanisms of radiation stabilization with additives are also discussed.

Antioxidants↗
PubMed1996

Improved bonding strength of polyethylene/polymethylmetacrylate bone cement--a preliminary study.

The adhesion of polymethylmetacrylate (PMMA) bone cement and low density polyethylene (LDPE) substrate by means of corona discharge treatment are presented. The surfaces were characterized by water contact angle goniometer, Fourier-transform infrared spectroscopy in the attenuated total reflectance mode (FTIR-ATR), electron spectroscopy for chemical analysis (ESCA), and scanning electron microscopy (SEM) for surface morphology. The bonding strength between bone cement and LDPE with varying intensity of corona treatment was evaluated by a 180 degrees peel test. The water contact angles decreased with increasing treatment intensity from 95.0 +/- 1.8 to around 43.5 degrees. It was observed that the oxygen containing groups as hydroxyl, ether, carboxylic acid, ester, ketone or aldehyde groups were introduced on the LDPE surfaces by corona treatment. The peel strength steeply increased from 0 to 1.75 kgf/cm with increasing the intensity of corona treatment. The improved adhesion of bone cement onto LDPE substrate may be due to only secondary force such as hydrogen bonding between PMMA bone cement and hydrophilized LDPE substrate.

Adhesiveness↗
PubMed1995

Different effects of base analog substitutions in BamHI restriction site on recognition by BamHI endonuclease and BamHI methylase.

BamHI endonuclease and BamHI methylase were used to investigate their specific interaction with the common recognition sequence, GGATCC. Five derivatives of the oligonucleotide, GACGGATCCGTC, containing a variety of single-base analog substitutions within the hexameric recognition core were synthesized. Steady-state kinetics for the reaction of the endonuclease and the methylase showed that both enzymes recognize the sequences by contacting with functional groups exposed in both major and minor grooves of the site but in different ways. Removal or substitution of the 5-methyl group in thymidine blocked the endonuclease reaction completely but still allowed the methylase reaction with less efficiency. The data also showed that the methylase made a critical minor groove contact with the 2-amino group of the first G but the endonuclease did with that of the second G.

Base Sequence↗
PubMed1995

Biocompatibility of polysulfone I. Surface modifications and characterizations.

Surface treatments by nonionic surfactant (Brij) coating and air-plasma glow discharge treatment onto polysulfone have been investigated to improve its surface properties. Surface treated samples were characterized by measurement of contact angle by a goniometer, Fourier transform infrared spectroscopy in the attenuated total reflectance mode (FTIR-ATR), and electron spectroscopy for chemical analysis (ESCA). The contact angles of the nonionic surfactant coated films decreased from 66.6 +/- 2.1 degrees to nearly 0 degrees due to hydrophilic polyethylene oxide (PEO) chain segment of the nonionic surfactant, and those of air-plasma treated films also decreased from 66.6 degrees to about 22 degrees with a treatment time of less than 5 s. ESCA analysis of air-plasma treated films indicates the incorporation of oxygen molecules onto polysulfone surface lowers the water contact angle. These modified techniques can be used to prevent platelet adhesion onto polysulfone surfaces.

Adsorption↗
PubMed1995

Biocompatibility of polysulfone II. Platelet adhesion and cho cell growth.

Experimental results on the platelet adhesion, and CHO cell adhesion and growth onto nonionic surfactant which is composed of a long alkyl chain (n = 12-18) as the hydrophobic part, and a polyethyleneoxide (PEO) segment (n = 10-23) as the hydrophilic part coated and air-plasma treated PSf surfaces are presented in terms of PEOs functionality and surface wettability to improved blood- and cell-compatibility of polysulfone. Platelet adhesion experiments on surface treated PSf films were carried out with platelet enriched plasma (PRP) in the parallel flow chamber in vitro. Number and morphology of adhered platelets were observed by scanning electron microscope. The number of adhered platelets on nonionic surfactant coated surfaces decreased significantly compared to the control. Also, the adhesion of platelets on to PSf substrate decreased with increasing coating concentration of nonionic surfactant. In the dry air-plasma exposed PSf sample, the adhesion of platelets decreased independently of plasma exposure time, and significant diminution of platelet adhesion was observed below about 40 degrees of the contact angle. It is believed that less platelet adhesion is preceded by less protein adsorption due to hydrophobic dehydration interaction. In Chinese hamster ovary (CHO) cell, adhesion and growth cells grew better on the air-plasma treated PSf surfaces. From these results, it can be proposed that surface wettability of PSf is very important for cell adhesion and growth.

Adsorption↗
PubMed1994

Reconstitution of the skeletal muscle ryanodine receptor-Ca2+ release channel protein complex into proteoliposomes.

The 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid-solubilized 30 S ryanodine receptor (RyR)/Ca2+ release channel complex from rabbit skeletal muscles, purified by density gradient centrifugation, was reconstituted with an excess of phospholipid into proteoliposomes by removal of the detergent by dialysis. Reconstituted proteoliposomes were concentrated by centrifugation, frozen and thawed, and sonicated. [3H]Ryanodine binding measurements indicated close to 50% recovery of calculated binding activity following reconstitution of the purified RyR and dynamic light scattering measurements a mean vesicle diameter of approximately 150 nm. Using these values, a functional RyR was estimated to be present in only a small fraction (< 15%) of the reconstituted vesicles. SDS-polyacrylamide gel electrophoresis of trypsin-treated proteoliposomes revealed that about four-fifths of the reconstituted 30 S complex was readily accessible to proteolytic attack. Vesicle-45Ca2+ flux and fusion of proteoliposomes with planar lipid bilayers showed that the reconstituted channel complex could be activated by Ca2+ and ATP, inhibited by Mg2+ and ruthenium red, and modified by ryanodine, similarly as observed for native sarcoplasmic reticulum vesicles. These results suggest that the method described here results in the reconstitution of a functional channel and thus provides the opportunity to study the structure and function of the sarcoplasmic reticulum Ca2+ release channel under well defined conditions.

Animals↗
PubMed1994

Cell behaviour on polymer surfaces with different functional groups.

Surfaces with differently chargeable functional groups were prepared on low density polyethylene sheets by corona discharge treatment, followed by graft copolymerization of acrylic acid (-COOH, negatively chargeable) and a subsequent substitution reaction of carboxylic acid groups to hydroxyl (-CH2OH, neutral) or amide (-CONH2, neutral) groups. The amide groups grafted on the surface were further converted to amine groups (-CH2NH2, positively chargeable). The prepared surfaces were characterized by measuring the water contact angle, electron spectroscopy for chemical analysis and Fourier-transform infrared spectroscopy in the attenuated total reflectance mode. It was observed that the wettability of the different functional group-grafted surfaces largely increases compared with the control surface but is not much affected by the kind of functional groups grafted. The interaction of Chinese hamster ovary cells with the functional group-grafted surfaces was investigated. The cells adhered and grown on the surfaces were counted using an electronic cell counter and observed by a scanning electron microscope. The surface grafted with amine groups was best for cell adhesion, spreading and growth probably owing to the positively chargeable character in aqueous cell culture medium. For surfaces grafted with neutral functional groups, the surface grafted with hydroxyl groups showed better cell spreading than that grafted with amide groups.

Alcohols↗
PubMed1994

Cloning of Pseudomonas fluorescens carboxylesterase gene and characterization of its product expressed in Escherichia coli.

A gene (estC) coding for an esterase (esterase III) of Pseudomonas fluorescens was cloned into Escherichia coli JM83. DNA sequencing showed a single open reading frame with GTG as a translation initiation codon for esterase III. This was confirmed by N-terminal amino acid sequence analysis of the purified esterase III protein from an E. coli clone. The promoter sequence and a potential Shine-Dalgarno sequence were followed by the coding sequence of the estC gene. The amino acid sequence deduced from the nucleotide sequence contains the consensus active site sequence, G-X-S-X-G, of serine esterase. The esterase III expressed in an E. coli clone was purified by ion-exchange chromatography and gel filtration. The native form of the enzyme was a monomer with a molecular weight of 41,000. The results of substrate specificity and the inhibitor studies suggest that this enzyme is a carboxylesterase (EC 3.1.1.1) and a serine residue is present at the active site of the enzyme.

Amino Acid Sequence↗
PubMed1994

The effect of radiation therapy on immune function in patients with squamous cell lung carcinoma.

The immune response is impaired in patients with malignancy, and radiation therapy (RT) can exacerbate the cancer induced-attenuation of immune response. In order to search for the fine mechanisms behind the RT-induced attenuation of cell-mediated immune response, we measured the number of lymphocytes in peripheral blood, its subsets, and lymphoblast transformation induced by phytohemagglutinin (PHA), purified protein derivatives (PPD), mitogenic monoclonal antibody anti-CD3, and mitogenic combination of anti-CD2 antibodies 9-1 and 9.6 before and after RT in 19 patients with squamous cell lung cancer. Radiation therapy significantly decreased the total numbers of lymphocytes, CD-3, CD-4, and CD8-positive lymphocytes in peripheral blood. However, RT did not change the percentages of lymphocytes and its subsets. Radiation therapy increased the percentage of interleukin 2 (IL-2) receptor-positive lymphocytes, and RT significantly decreased in vitro lymphoblast transformation by PHA, PPD, or monoclonal antibodies to T-cell surface antigens (anti-CD2 or anti-CD3). In vitro incubation with IL-2 did not increase lymphoblast transformation by anti-CD3 before RT but significantly increased after RT. In conclusion, we suggest that one of the fine mechanisms behind the RT-induced suppression of immune responsiveness of patients with lung cancer is a defect in IL-2 synthesis by lymphocytes.

Adult↗
PubMed1993

Quantitative modeling of responses of anuran retina: stimulus shape and size dependency.

Teeters and Arbib presented a model of the anuran retina which qualitatively accounts for the characteristic response properties used to distinguish ganglion cell type in anurans. In this paper we test the model's ability to reproduce quantitatively tabulated data on the dependency on stimulus shape and size, with a new implementation of the model in the neural simulation language NSL. Data of Ewert and Hock relating toad R2, R3, and R4 ganglion cell responses to moving worm, antiworm, and square-shaped stimuli of various edge lengths are used to test stimulus shape and size dependency. A close match to the data can be achieved by tuning some of the model parameters while still retaining the characteristic responses to the typical stimulus types. We stress here the importance of a populational approach to the models. We place more emphasis on the variation of response properties in a population of neurons of the same class, rather than questing for the neuron of a given type. As an example of the populational approach we offer a model for the respiratory R3 response following researchers who argue that a subclass of R3 neurons are activated by stationary boundaries owing to the anuran's self induced respiratory eye movement.

Algorithms↗
PubMed1993

Soluble interleukin-2 receptor and cellular profiles in bronchoalveolar lavage fluid from patients with bronchial asthma.

BACKGROUND: To elucidate the role of T-cell activation in the physiologic changes and cellular infiltrations in the bronchial tree of patients with symptomatic bronchial asthma, we measured the concentration of soluble interleukin-2 receptor (sIL-2R), cellular compositions and IL-2R expression on cells in bronchoalveolar lavage (BAL) fluid. We also measured physiologic parameters, including a provocation concentration of histamine required to reduce the forced expiratory volume in 1 second by 20% of the prechallenge baseline (PC20). RESULTS: The concentration of sIL-2R and the ratio of IL-2R expression on CD3 positive lymphocytes were significantly higher in BAL fluid from 20 patients with symptomatic bronchial asthma than concentrations in fluid from nine healthy controls (p < 0.01) and six asymptomatic patients with bronchial asthma (p < 0.05). The concentration of sIL-2R correlated with the percentage of IL-2R expression on CD3 positive lymphocytes (rs = 0.709, p < 0.01). There was no difference in sIL-2R concentration of BAL fluid between the healthy control and the patient with asymptomatic bronchial asthma. Among the inflammatory cells recovered in BAL fluid, the percentages of eosinophils showed significant positive correlation with the concentration of sIL-2R in BAL fluid in the patients with bronchial asthma. The concentration of sIL-2R significantly correlated with forced expiratory volume one second, peak expiratory flow rate, and PC20 when observed in all study subjects, but not in the patients with bronchial asthma. CONCLUSION: We conclude that T-cell activation within the bronchial tree appears to have a role in the infiltration of eosinophils into the bronchial tree, which may lead to enhanced bronchial hyperreactivity in patients with bronchial asthma.

Adolescent↗
PubMed1993

Immobilization of proteins on poly(methyl methacrylate) films.

Polymethyl methacrylate (PMMA) films were treated by oxygen plasma discharge followed by acrylic acid (AA) grafting. The amount of carboxyl groups introduced by the grafting of AA on to the film surfaces was in the range 0.47-9.48 mumol/cm2, depending on the pressure of the plasma chamber during the discharge treatment. The carboxyl groups of the PMMA film surface previously activated with water soluble carbodiimide were coupled with bovine serum albumin, collagen and gelatin. The protein immobilization on the surface was confirmed by attenuated total reflection Fourier transform infra-red spectroscopy (ATR-FTIR) and electron spectroscopy for chemical analysis (ESCA). The amount of albumin, collagen and gelatin immobilized on the PMMA surface was 6.25, 7.25 and 13.75 micrograms/cm2, respectively, as determined by the coomassie brilliant blue-protein interaction. The water contact angle of the PMMA film was markedly decreased by oxygen plasma treatment, AA grafting or protein immobilization, indicating the increase of hydrophilicity of the surface-modified PMMA films. The protein-immobilized PMMA films may be widely used as a biocompatible material.

Biocompatible Materials↗