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Biomedical subjects

H B Lee

Publications and source records attributed to H B Lee.

At least 19 recordsLinked to original sources
PubMed1998

Anticholinesterase induces nicotinic receptor modulation.

The effects of carbamate anticholinesterases, pyridostigmine and physostigmine, on the function of the nicotinic receptor (nAChR) in TE671 cells was studied, precluding their inhibition of acetylcholine hydrolysis by carbachol usage. In radioassay, the simultaneous application of carbachol and carbamates dose-dependently decreased carbachol-induced 22Na+ influx, compared with carbachol activation alone. Increasing cell preincubation in the presence of carbamates, however, potentiated influx at low concentrations in a time-dependent manner. This facilitating effect of carbamates, even at high concentrations, was significantly increased by washing out these drugs and was blocked by pretreatment with diisopropylfluorophosphate. Similar results were also obtained in whole-cell patch-clamp study. There were insignificant changes in desensitization properties during facilitation. It is thus supposed that facilitation cannot be explained by the inhibition of acetylcholine hydrolysis. These results support a previous hypothesis that acetylcholinesterase might modulate nAChR by an unknown mechanism. In addition, the clinical effects of carbamates may be partly attributed to this facilitation.

Carbachol↗
PubMed1998

Platelet adhesion onto chargeable functional group gradient surfaces.

Functional group gradients were prepared on low-density polyethylene (PE) sheets. The surface density of grafted functional groups was gradually changed along the sample length by way of corona discharge treatment with gradually increasing power following graft copolymerization of acrylic acid (AA), sodium p-styrene sulfonate (NaSS), or N,N-dimethyl aminopropyl acrylamide (DMAPAA). AA and NaSS are negatively chargeable and DMAPAA is positively chargeable in phosphate-buffered saline or plasma solution at pH 7.3-7.4. The prepared functional group gradient surfaces were characterized by measurement of the water contact angle, by electron spectroscopy for chemical analysis, and by Fourier transform infrared spectroscopy in the attenuated total reflectance mode. All these measurements indicated that the functional groups were grafted onto the PE surfaces with gradually increasing density. The platelets adhered to the functional group gradient surfaces along the sample length were counted and observed by scanning electron microscopy. It was observed that the platelet adhesion to the gradient surfaces decreased gradually with the increasing surface density of functional groups. This may be related to the hydrophilicity of the surfaces. The DMAPAA-grafted surface showed a large amount of platelet adhesion, probably due to its positive charge character, while the AA-grafted surface, which is charged negatively, showed poor platelet adhesion. However, the NaSS-grafted surface, which is also charged negatively, showed a relatively large amount of platelet adhesion. This may be associated with the existence of an aromatic ring close to the ionizable group in NaSS. It seems that surface functional groups and their charge character, as well as wettability, play important roles for platelet adhesion.

Acrylates↗
PubMed1998

Platelet adhesion onto wettability gradient surfaces in the absence and presence of plasma proteins.

A wettability gradient was prepared on lowdensity polyethylene (PE) sheets by treating them in air with a corona from a knife-type electrode the power of which increased gradually along the sample length. The PE surfaces oxidized gradually with the increasing corona power and a wettability gradient was created on the surfaces, as evidenced by the measurement of water contact angles, Fourier transform infrared spectroscopy in the attenuated total reflectance mode, and electron spectroscopy for chemical analysis. The wettability gradient surfaces prepared were used to investigate the adhesion behavior of platelets in the absence and presence of plasma proteins in terms of the surface hydrophilicity/hydrophobicity of polymeric materials. The platelets adhered to the wettability gradient surfaces along the sample length were counted and examined by scanning electron microscopy (SEM). It was observed that the platelet adhesion in the absence of plasma proteins increased gradually as the surface wettability increased along the sample length. The platelets adhered to the hydrophilic positions of the gradient surface also were more activated (possessed more pseudo pods as examined by SEM) than on the more hydrophobic ones. However, platelet adhesion in the presence of plasma proteins decreased gradually with the increasing surface wettability; the platelets adhered to the surface also were more activated on the hydrophobic positions of the gradient surface. This result is closely related to plasma protein adsorption on the surface. Plasma protein adsorption on the wettability gradient surface increased with the increasing surface wettability. More plasma protein adsorption on the hydrophilic positions of the gradient surface caused less platelet adhesion, probably due to platelet adhesion inhibiting proteins, such as high-molecular-weight kininogen, which preferably adsorbs onto the surface by the so-called Vroman effect. It seems that both the presence of plasma proteins and surface wettability play important roles for platelet adhesion and activation.

Animals↗
PubMed1998

Sequential effects of high glucose on mesangial cell transforming growth factor-beta 1 and fibronectin synthesis.

BACKGROUND: Transforming growth factor (TGF)-beta is recognized as the final common mediator of the principal lesions of diabetic nephropathy such as renal hypertrophy and mesangial expansion. To gain better understanding of the temporal relationships between high glucose (HG) and mesangial cell (MC) TGF-beta 1 synthesis and between TGF-beta 1 and extracellular matrix (ECM) synthesis, the present study examined early and sequential effects of HG on TGF-beta 1 and fibronectin (FN) mRNA expression and protein synthesis. METHODS: Confluent primary rat MC was stimulated with 5.6 (control) or 30 (high) mM glucose after synchronizing the growth by incubation with serum-free media for 48 hours. RESULTS: Mesangial cell TGF-beta 1 mRNA expression increased significantly in six hours and continued to increase until 48 hours in response to HG. The level of TGF-beta 1 mRNA was 1.5-fold higher than that of control glucose at six hours and 1.8-fold at 48 hours. TGF-beta activity in heat-activated conditioned media under HG increased 1.5- and 1.6-fold at 24 and 48 hours, respectively, compared to control glucose. FN mRNA increased significantly at 24 and 48 hours and 1.4-fold that of control glucose at both time points. FN protein also increased 1.5-fold that of control glucose at 48 hours. Anti-TGF-beta antibody completely abolished HG-induced FN synthesis. CONCLUSIONS: The present finding demonstrate that HG stimulates TGF-beta 1 very early and prior to FN production and that HG-induced FN production is mediated by TGF-beta. This finding is consistent with the view that TGF-beta mediates increased ECM accumulation by MC under high glucose conditions.

Animals↗
PubMed1998

Comparative stereochemical analysis of glucose-binding proteins for rational design of glucose-specific agents.

There is a need for synthesizing glucose-sensitive molecules which can be used in glucose sensors and self-regulating insulin delivery devices. Currently, glucose-sensitive proteins, such as glucose oxidase and concanavalin A (Con-A), are used for detecting glucose molecules. For long-term in vivo applications, it is necessary to synthesize non-proteineous glucose-sensitive molecules which are biocompatible, nontoxic, cost-effective, and independent of environmental factors such as pH, ionic strength, or the presence of divalent cations. As a first step toward synthesizing glucose sensitive molecules, we have compared glucose-binding sites of four different types of glucose-binding proteins. They are human beta-cell glucokinase, D-xylose isomerase, lectins (Lathyrus ochrus isolectin I and Con-A), and glucose/galactose binding protein. Analysis of the glucose-binding sites of their 3-dimensional crystal structures showed that the hydrogen bonds between the hydroxyl groups of glucose and a few types of amino acid residues of proteins provided the main attraction. In some cases, the same atom was involved in multiple hydrogen bonds. Hydrophobic interactions between the pyranose ring of glucose and aromatic rings of hydrophobic amino acid residues also played an important role in the glucose specificity. A sandwich geometry was observed among the hydrophobic groups. This comparative stereochemical analysis suggests that a possible glucose binding site can be made by placing Asp and Asn around glucose for hydrogen bonding and Phe on both sides of glucose for hydrophobic interaction.

Binding Sites↗
PubMed1998

Pulp reconstruction of fingers with very small sensate medial plantar free flap.

The essence in dealing with the pulp deficit accompanying fingertip injuries lies in functional restitution of the inherent skin texture and characteristics unique to that area and sufficient preservation of digital length, along with successful restoration of fine tactile sensation indispensable to delicate and skillful maneuvers. Among various techniques used to meet such demands, the very small sensate medial plantar free flap can be considered an excellent method in view of the skin texture that allows firm grasping, durability to friction rub, a cushion effect, and adequate sensation. Six cases of finger pulp reconstruction with the very small sensate medial plantar free flap are presented. At follow-up examination (an average follow-up of 24.3 months), the patients were evaluated clinically and neurologically. The operative procedures, advantages, and results in clinical cases are presented. Satisfactory results were obtained with sufficient preservation of digital length and good sensory recovery. No functional deficit was found at the donor site.

Adult↗
PubMed1998

Effect of prolonged subcutaneous implantation of peritoneal catheter on peritonitis rate during CAPD: a prospective randomized study.

We conducted a prospective randomized controlled study to confirm our earlier observation that prolonged subcutaneous implantation of peritoneal catheter reduced peritonitis rate when compared to retrospective data from patients with catheters placed by conventional access technique. A total of 60 patients were randomized into two groups: 30 patients had catheters left implanted subcutaneously for 6 weeks (I) and the other 30 patients had catheters inserted by conventional technique and had 6 weeks of break-in period (C). Subgroups of 15 patients each with new and conventional techniques used Y-connector (IY, CY) and remaining patients used standard spikes (IS, CS). Mean age was 47.7 years (range 16-71); 61.0% were male and 44.1% diabetics. Peritonitis, exit site infection, simultaneous peritonitis and exit site infection, and complication related to Staphylococcus or Pseudomonas infections were observed for up to 2 years in each patient after initiation of bag exchange or until termination of CAPD by transfer to hemodialysis or by death. Total duration of observation was 493.2 patient-months for new access technique and 409.6 patient-months for conventional technique. Patients in IY group had the lowest incidence of peritonitis (1/14.9 patient-months) and exit site infection (1/16.8 patient-months) among four subgroups. Peritonitis rate in IY was significantly lower compared to CY or CS. The total peritonitis-free period in those patients who did not experience peritonitis during the observation period was also significantly longer in IY (120 patient-months) than in CY (26 patient-months), IS (10.6 patient-months), or CS (10.4 patient-months). Simultaneous peritonitis and exit site infection was observed in none of IY group but 3 episodes in CY, 4 episodes in IS, and 3 episodes in CS. The rates of complications related to Staphylococcus aureus and Pseudomonas infections were also significantly lower in IY than in CY, IS, or CS. Technique survival did not differ between the two groups. The present results confirm our previous observation that the new access technique reduces the incidence of peritonitis probably by reducing infection via periluminal route. The Y-connector system further reduces peritonitis rate by reducing infection via intraluminal route.

Adolescent↗
PubMed1998

Platelet adhesion on the gradient surfaces grafted with phospholipid polymer.

We have synthesized omega-methacryloyloxyalkyl phosphorylcholine (MAPC) polymers as new blood-compatible materials, with attention to the surface structure of the biomembrane and investigated their blood compatibility. The blood compatibility observed on the MAPC polymers is due to their strong affinity to phospholipids. When the blood comes in contact with the MAPC polymer, phospholipids in the plasma preferentially adsorb on the surface, compared with the plasma proteins or cells. The adsorbed phospholipids construct a biomembrane-like structure on the MAPC polymer surface. The MAPC polymers then have an excellent blood compatibility. In this study, we prepared a gradient poly(MAPC)-grafted polyethylene (PE) surface using a corona discharge treatment method to clarify the effect of the chemical structure of the MAPC unit on the blood compatibility of the MAPC polymers. The surface composition of MAPC and the hydrophilicity on the poly(MAPC)-grafted PE surface were determined by X-ray photoelectron spectroscopic (XPS) analysis and contact angle measurement with water, respectively. The phosphorus/carbon (P/C) ratio determined by the XPS analysis increased, but the water contact angle decreased with increasing corona irradiation energy. These results indicated that the surface density of the MAPC unit was increased. More than 2.5 cm from the starting point of the corona irradiation, the P/C ratio and water contact angle of the surface achieved a constant level. Thus, the surface was completely covered with the grafted poly(MAPC) chain. The effect of the methylene chain length of the MAPC unit on surface properties was also observed. The phospholipid polar group of the MAPC unit was effectively exposed on the surface as the chain length became longer. Moreover, the hydrophobicity of the surface was increased with the increase in the methylene chain length of the MAPC unit. The number of platelets adhering to the poly(MAPC)-grafted PE surface was reduced from the same point where the P/C ratio became constant.

Animals↗
PubMed1997

EGF inhibits expression of WDNM1 and sulfated glycoprotein-2 genes in mammary epithelial cells.

We have previously shown that expressions of ferritin heavy chain (FHC), WDNM1, and sulfated glycoprotein-2 (SGP-2) genes are induced at an involution stage of mammary gland. Here we studied the effect of lactogenic hormones and EGF on the expression of involution-induced genes in HC11 mammary epithelial cells. Insulin, dexamethasone, prolactin, and its combinations did not affect expression of the genes. When cells were cultured in growth medium containing EGF, expression of WDNM1 and SGP-2 genes was strongly inhibited in a dose- and time- dependent manner, whereas expression of FHC gene was not influenced by EGF. Results demonstrate that EGF inhibits expression of WDNM1 and SGP-2 genes in mammary epithelial cells.

Animals↗
PubMed1997

The 5'-upstream region of the rat phospholipase C-beta 3 gene contains two critical Sp1 sites and an HIV Inr-like element.

The 5'-upstream region of the rat phospholipase C-beta 3 gene (PLC-beta 3) has been cloned and characterized. Sequence analysis of the 5'-upstream region showed that it contains a GC-rich region (-166 to +1: 79%) and multiple binding sites for the transcription factors Sp1, AP-1 and AP-2, but does not contain a canonical TATA box. Primer extension analysis of total RNA isolated from rat glial cell C6Bul revealed that single transcription start point (tsp) is located at an initiator (Inr) element similar to that found in the HIV promoter. Gel mobility shift and competitive mobility shift assays indicated that this Inr element forms a DNA-protein complex with the HIV Inr-binding protein, LBP-1/CP2 or a homologue. In order to localize functional elements of the 5'-upstream region of the rat PLC-beta 3 gene, 5'-deletion fragments were cloned into a chloramphenicol acetyltransferase (CAT) reporter vector. Transient transfection analyses of the 5'-deletion mutants identified a crucial promoter element located at -128 to -14. Supershift mobility assays, site-directed mutagenesis and DNase I footprints indicated that Sp1 binds to three GC boxes within the sequence between -128 and -14 of the PLC-beta 3 promoter. Transient transfection analyses of promoter constructs containing site-specific mutation(s) of these three GC boxes demonstrated that two GC boxes, located proximal to the tsp, are important elements for normal promoter activity.

Animals↗
PubMed1997

Plasma protein adsorption and platelet adhesion onto comb-like PEO gradient surfaces.

Comb-like polyethylene oxide (PEO) surfaces were prepared on low-density polyethylene (PE). The comb-like PEO chain density was changed gradually along the sample lengths by corona discharge treatment with gradually increasing power and the following graft copolymerization of poly(ethylene glycol) monomethacrylate macromers (PEO-MA). The macromers with different PEO repeat unit, 1, 5, and 10, were used. The prepared comb-like PEO gradient surfaces were characterized by water contact angle, Fourier transform infrared spectroscopy in the attenuated total reflectance mode, and electron spectroscopy for chemical analysis. All these measurements indicated that the PEO chains are grafted on the PE surface with gradually increasing density of PEO. Plasma protein adsorption and platelet adhesion on the PEO gradient surfaces decreased with increasing PEO chain length and surface density. As observed by scanning electron microscopy, PEO10-MA-grafted surface with high PEO density was very effective in preventing protein adsorption and platelet adhesion and did not activate the platelets.

Adsorption↗
PubMed1997

Development and characterization of an alginate-impregnated polyester vascular graft.

Alignate gels are known to be biocompatible, degradable, and nontoxic. In this study, sodium alginate was impregnated into a porous, knitted polyester graft (Microvel double velour graft) 6 mm in diameter. The alginate-impregnated graft was investigated in vitro and in vivo to evaluate its potential for use as a new vascular graft impervious to blood, while retaining high porosity for tissue ingrowth and biological healing. For in vitro investigation, the coating weight, water permeability, morphology, and mechanical properties of the alginate-impregnated grafts were compared to those of control or commercially available collagen-impregnated (Hemashield) grafts. The water permeability of the controls (1846 mL/min.cm2 at 120 mm Hg) was reduced > 99% by the alginate impregnation, rendering the graft impervious to blood. The coating weight of the alginate was 45 mg/g of graft, producing a much lower value than that of the collagen-impregnated model (310 mg/g). For in vivo investigation, the alginate-impregnated grafts were implanted in the aorta of mongrel dogs without preclotting for scheduled periods ranging from 4 h to 6 months. The control grafts after preclotting and the collagen-impregnated grafts without preclotting were also implanted for 3 and 6 months for comparison. Gross observation of the explanted grafts and histologic examination of the representative sections were conducted for three types of grafts using a light microscope after hematoxylin-eosin staining. No significant differences were observed between the histologic appearance of the alginate-impregnated grafts and that of the preclotted and collagen-impregnated grafts in terms of the degree of inflammation, foreign-body giant cell reaction, and intimal fibrosis. Endothelial-like cells were present on the midsections of all the grafts after 3 months of implantation. The resorption rate of alginate impregnated into the graft was also examined after staining the sections with periodic acid-Schiff reagent, Toluidine blue, and Alcian blue, which are specific for alginates. The staining alginate was partially visible between the graft fabrics up to 1 month after implantation, but was completely resorbed after 3 months. This preliminary study demonstrated that the use of an alginate as a biological sealant instead of proteins such as collagen, gelatin, and albumin may be a feasible approach to developing imprevious textile arterial prostheses, since the proteins have been reported to be generally unstable, hard to obtain in pure forms, not easy to crosslink and control resorption rate, and difficult to render compatible with standard storage and sterilization procedures.

Alginates↗
PubMed1997

Interaction of cells on chargeable functional group gradient surfaces.

Functional group gradient surfaces where the surface density of grafted functional groups changes gradually along the sample length were prepared on low density polyethylene (PE) sheets by corona discharge treatment with gradually increasing power and graft copalymerization of acrylic acid (AA), sodium p-styrene sulphonate (NaSS), and N,N-dimethyl aminopropyl acrylamide (DMAPAA). AA and NaSS are negatively chargeable and DMAPAA is positively chargeable in phosphate buffered saline or cell culture medium at pH 7.3-7.4. The functional group gradient surfaces were characterized by the measurement of water contact angle, Fourier transform infrared spectroscopy in the attenuated total reflectance mode, and electron spectroscopy for chemical analysis. All these measurements indicated that the functional groups were grafted on the PE surfaces with gradual increase of their density. The interaction of Chinese hamster ovary cells with the functional group gradient surfaces along the sample length was investigated. The cells that had adhered and grown on the surfaces were counted and observed by scanning electron microscopy. It was observed that a greater quantity of the cells had adhered and grown onto the positions with moderate density of the functional groups. This may be related to the hydrophilicity of the surface. The DMAPAA-grafted surface showed a large amount of cell attachment probably owing to the positive charge character, while the AA-grafted surface, which is negatively charged, showed poor cell attachment, as expected. The NaSS-grafted surface which is also negatively charged showed a large amount of cell attachment. This may be closely associated with the existence of an aromatic ring close to the ionizable group in NaSS. It seems that surface functional groups and their charge character as well as wettability play important roles for cell adhesion, spreading, and growth.

Amines↗
PubMed1997

Chaperone-like function of lipocortin 1.

Lipocortin 1 (LC1) is a 37 kDa member of the annexin family of proteins. It has been proposed to act as a mediator of some of the actions of glucocorticoids in anti-inflammatory and immune suppressive functions. LC1 has been shown to play a role in cell proliferation, apoptosis, and differentiation. However, the exact biological functions of LC1 still remain obscure. Here it is shown that LC1 displays a chaperone-like function. Stoichiometric amounts of LC1 suppressed thermally induced inactivation and aggregation of the test enzymes citrate synthase and glutamate dehydrogenase. LC1 was also effective in refolding guanine hydrochloride-denatured glutamate dehydrogenase, as judged by circular dichroism spectroscopy.

Animals↗
PubMed1997

Unilateral multilayered musculocutaneous V-Y advancement flap for the treatment of pressure sore.

We have devised a modified technique using the gluteus maximus musculocutaneous flap as multilayered sliding V-Y advancement to cover pressure sores on the sacral area. Nine patients with relatively large (average 7 x 7 cm) sacral grade IV pressure sores underwent unilateral multilayered V-Y advancement flap. All patients were followed for a minimum of 8 weeks. The mean postoperative follow-up was 32.3 months, with a range of 24 to 39 months. Using this technique, the success of surgery, i.e., the percentage of sores that healed, was 100 percent in our patients. The advantages of this technique include sufficient advancement of the flap, coverage of large ulcer defects using only a unilateral musculocutaneous flap, and preservation of the contralateral gluteus maximus muscle for future use.

Aged↗
PubMed1997

Identification of urinary dipeptidase as the released form of renal dipeptidase.

Amphipathic and hydrophilic forms of human renal dipeptidase and urinary dipeptidase were purified by affinity chromatography using cilastatin, a dipeptidase inhibitor, as the ligand. The sequence analyses of the first ten amino acids of renal and urinary dipeptidases were shown to be identical, and they are Asp-Phe-Phe-Arg-Asp-Glu-Ala-Glu-Arg-Ile. Unambiguous results of amino acid sequencing, the molecular weight of native protein (190 kD), the molecular weight of subunit (47.7 kD) and a single band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicate that the enzymes are composed of homotetramers. This is the most direct evidence that urinary dipeptidase is the released form of renal dipeptidase. In fact, they are the same enzymes.

Amino Acid Sequence↗