De novo induction of island capsule flap by using two silastic sheets: Part 1. Generation

A new experimental model for de novo generation of an axial pattern island flap has been designed in a rat model. The purpose of this study was to make a sufficient vascular carrier, as an island capsule flap, with only vascular pedicles and addition of collagen fibers induced by foreign-body reaction. The femoral arteriovenous bundle was isolated and sandwiched between two 2.5 x 1.5 cm Silastic sheets. Eight weeks later, as a delay procedure, femoral vessels were ligated at the distal end of the Silastic sheets and the four margins of the sheets were divided except for the vascular pedicle. This capsule flap was raised as a secondary island flap connected only by its vascular pedicle, then it was sutured back in place. Ten days after the delay procedure, the upper Silastic sheet was removed and a full-thickness skin graft was performed on the capsular island flap. Animals were killed at 80 days. A total of 40 axial pattern capsulocutaneous flaps from 20 Sprague-Dawley rats were successfully achieved. Pathologic study revealed neovascularization, and abundantly impregnated vascular structures near the pedicle were observed with randomly developed collagen fibers. The skin graft took 100 percent on this newly formed capsular flap; therefore, the capsule structure was able to survive on its own and support skin grafts. This experiment, by using an isolated femoral artery and vein as the main pedicle, led to the formation of a capsule flap through a normal foreign body reaction between two Silastic sheet implants. This new flap can be used as a reliable vascular carrier for various needs with minimal donor morbidity.

Preparation and characterization of Japanese encephalitis virus vaccine loaded poly(L-lactide-co-glycolide) microspheres for oral immunization

Japanese encephalitis virus (JEV) vaccine loaded biodegradable poly(L-lactide-co-glycolide) (PLGA) microspheres (MSs) were prepared by W/O/W solvent evaporation method to study the possibility for oral vaccination. The influence of several preparation parameters as stirring rate, types and concentration of emulsifier, PLGA concentration, etc. has been observed on size, size distribution and biodegradation. The mean MSs size decreased when the agitation speed and the concentration of emulsifier were increased, and when the PLGA concentration was decreased. The surface morphology of porous and nonporous JEV vaccine loaded PLGA MSs was prepared from polyvinylalcohol and sodium dodecyl sulfate as used emulsifiers, respectively. From the assay of lactic acid and scanning electron microscope observation, it can be suggested that the rate of biodegradation of nonporous MSs was slower than that of porous surface morphology due to lower the surface area. Mechanisms of the formation of porous and nonporous surface by different types of emulsifier, and the biodegradation of MSs have been proposed. Also, the size and size distribution of JEV vaccine loaded PLGA MSs were discussed to apply oral vaccination through the Peyer's patches across the gastrointestinal tract.

Release of renal dipeptidase from rabbit renal proximal tubules and its inhibition by gentamicin

Effects of several drugs on rabbit renal proximal tubules were examined for the applicability of renal dipeptidase (RDPase, EC 3. 4. 13. 11) release as a model system to study nephrotoxicity. The proximal tubule prepared by the method of Taub (1990) released RDPase spontaneously in the control experiment which was confirmed by Western blotting. RDPase was also released from cisplatin, lipopolysaccharide (LPS), and indomethacin-treated tubules. Gentamicin inhibited RDPase release in a concentration-dependent manner. This RDPase release system may not be a general model to screen nephrotoxicity but could be a useful source of RDPase purification in a simple and inexpensive way.

Optimization of urinary FDG excretion during PET imaging

Accumulation of fluorodeoxyglucose (FDG) activity in the urine interferes with the visualization of pelvic and, sometimes, abdominal abnormalities. Although this is a major problem, there are few data on the physiological variables affecting FDG urinary excretion that are critical to minimizing urinary FDG interference during PET imaging.

METHODS

The excretion of FDG in urine was determined during 90 min in four groups of rats (n = 24) under the following conditions: normal, hydrated, hydrochlorothiazide treated and phlorizin treated. FDG clearance rates were measured in both normal and phlorizin-treated animals and compared with the glomeruler filtration rate measured with 99mTc-diethylenetriamine pentaacetic acid. We measured FDG excretion in 10 patients who had no known renal disease and were undergoing PET scanning (divided into two groups: hydrated and dehydrated) to relate the animal data to humans.

RESULTS

The hydrated and phlorizin-treated animals had the highest excretion of FDG (39.68+/-5.00 % injected dose (%ID) and 45.64+/-9.77 %ID, respectively). Animals given the hydrochlorothiazide had the highest urinary volume, but the percentage excreted was comparable with the normal rats. Measurement of the clearance of FDG in animals before and after the administration of phlorizin determined the amount of FDG reabsorbed in the proximal tubules to be 56%+/-9.15%. The hydrated patients had a higher excretion of FDG than dehydrated patients (16.98+/-1.99 %ID versus 14.27+/-1.00 %ID, P < 0.021), and the volume of urine voided was significantly higher (P < 0.020).

CONCLUSION

Hydrochlorothiazide increases urine volume without enhancing FDG excretion. The hydration of patients before PET scanning may lead to more FDG reaching the bladder. Reduction of bladder activity by more frequent voiding facilitated by increased urine volume in hydrated patients may be offset by increased delivery of FDG to the bladder. A preferable means of increasing urinary volume without increasing delivery of FDG to the bladder may be the use of a diuretic.

Nutritional status of Korean peritoneal dialysis patients

OBJECTIVES

To assess the nutritional status of Korean peritoneal dialysis (PD) patients and to compare with data from Western literature, and to elucidate independent factors determining nutritional status and death.

DESIGN

Cross-sectional single-center study.

SETTING

Kidney Center, Soon Chun Hyang University Hospital.

MATERIALS

Ninety-eight CAPD patients were included. Of these, 54 patients were male, 32 patients were diabetic, mean age was 47.9+/-13.1 years, and mean duration of CAPD was 22.3+/-21.6 months. The patients were followed until death, transfer to hemodialysis (HD) or other units, transplantation, or until 3 years had elapsed after the first evaluation.

METHODS

Nutritional status was assessed by subjective global assessment (SGA), biochemical and anthropometric measurements, fat-free edema-free (FFEF) body mass by creatinine (Cr) kinetics, protein equivalent of total nitrogen appearance (PNA), and urea kinetic studies.

RESULTS

By SGA score, 53.1% of patients were classified as normal, 44.9% with mild-to-moderate malnutrition, and 2% with severe malnutrition. Patients with malnutrition were significantly older and had higher peritonitis rates, lower serum albumin (Alb), blood urea nitrogen (BUN), serum Cr, FFEF body mass, mid arm muscle circumference, and PNA (p < 0.05). On stepwise multiple regression analysis, the SGA score was negatively correlated with age and peritonitis rate (p < 0.01). At the end of the 3-year follow-up period, 11 patients were still on CAPD, 26 had died, 51 had transferred to HD and 5 to other units, 3 patients had been transplanted, and 2 patients were lost to follow-up. Patients who died during follow-up were older and had higher peritonitis rates and lower total serum protein, Alb, Cr, and FFEF body mass when compared to those who survived (p < 0.05). Independent predictors of death were age, peritonitis rate, and serum Alb (p < 0.01).

CONCLUSION

Malnutrition was as common in Korean PD patients as reported in the Western literature. Our data suggests that, to prevent malnutrition and early death, it is important to reduce the peritonitis rate, to improve protein intake, and to prescribe an adequate dose of peritoneal dialysis.

Leukotriene D4 inhibits Na+ uptake through cAMP and PLC pathways in primary cultured renal proximal tubular cells

Leukotriene D4 (LTD4) is one of the slow-reacting substances of anaphylaxis and is reported to have a diverse response including the mediation of glomerular nephritis. However, little is known about the functions of LTD4 and its mechanisms of action in primary cultured rabbit renal proximal tubular cells (PTCs). The purpose of this study is to investigate the effect of LTD4 on Na+ uptake and its related signal transduction pathways in PTCs. LTD4 (>10(-9) M) significantly inhibited the Na+ uptake after 15 min (in nmol/mg protein: controls 431.7+/-11.4 vs. LTD4 (10(-9) M) 355.0+/-23.6; p<0. 05); and its effect was blocked by MK-571 (10(-6) M), a leukotriene receptor antagonist, in PTCs. Preincubation with cilastatin, a renal dipeptidase inhibitor, and polyclonal antibody against renal dipeptidase potentiated the inhibitory effect of LTD4 on Na+ uptake. SQ 22536 (10(-6) M), an adenylate cyclase inhibitor, and the myristoylated protein kinase A inhibitor amide 14-22 (PKI; 10(-5) M) blocked the effect of LTD4 on Na+ uptake (in nmol/mg protein: LTD4 349.9+/-18.5 vs. SQ 22536+LTD4 476.5+/-22.0 and PKI+LTD4 440.3+/-19. 3; p<0.05), and LTD4 induced an increase in cyclic adenosine monophosphate (cAMP), suggesting the involvement of cAMP in the inhibition of Na+ uptake. In addition, U 73122 (10(-6) M) and neomycin (10(-4) M), phospholipase C (PLC) inhibitors, W-7 (10(-4) M), a calmodulin antagonist, and bisindolylmaleimide I, a protein kinase C (PKC) inhibitor, blocked the LTD4-induced inhibition of Na+ uptake, strongly suggesting involvement of the PLC-PKC signal pathways in the effect of LTD4. LTD4 significantly increased [Ca2]i by 49+/-7% as compared with baseline. TMB-8 (10(-5) M) and BAPTA/AM (10(-5) M), intracellular calcium mobilization blockers, completely blocked the LTD4-induced inhibition of Na+ uptake (in nmol/mg protein: LTD4 347.6+/-19.0 vs. TMB-8+LTD4 436.4+/-22.3 and BAPTA/AM+LTD4 419.9+/-14.3; p<0.05); however, EGTA (1 mM), a calcium chelator, partially blocked the LTD4-induced inhibition of Na+ uptake. In conclusion, LTD4-induced inhibition of Na+ uptake may be involved in both cAMP and PLC-PKC signal pathways in PTCs. In addition, Ca2+, which comes from the intracellular Ca2+ mobilization, is primarily responsible for the LTD4-induced inhibition of Na+ uptake.

Simultaneous reconstruction of the Achilles tendon and soft-tissue defect using only a latissimus dorsi muscle free flap

The combined loss of the Achilles tendon and the overlying soft tissue in the young ambulant patient with expectations of a normal life is a challenging problem. These patients need not only soft tissue but also dynamic and functional reconstruction. Four cases of major defects of the Achilles tendon and overlying soft tissue after trauma are presented. In each case, the tendon and the overlying soft tissues were reconstructed using only a latissimus dorsi muscle free flap and overlying split-thickness skin graft. In conventional methods, evolved in the reconstruction of the Achilles tendon and soft tissue, the size of the defect was a limit. However, this technique can be used to reconstruct an extensive defect, including distal calf muscle to the plantar metatarsal area. In one case, the flap was harvested in a myocutaneous unit, and the skin portion was deepithelialized for the coverage and enough padding on the bony exposure area in reverse position. The purpose of the present study was to reevaluate the potential of denervated muscle flap for a force-bearing conduit as an alternative reconstructive method of the Achilles tendon. The denervated latissimus dorsi muscle in this study eventually experienced the process of atrophy and fibrosis but maintained its original length. Although there remained some atrophic muscle fibers, a fibrosis of the muscle fibers formed a tendon-like fibrous band, and so the action of the posterior calf muscle could be transmitted through the tendon-like fibrotic change of the denervated latissimus dorsi muscle. The advantages of this technique are that (1) it is a single procedure, (2) it is adaptable to a wide range of defect sizes, (3) it allows faster wound healing supported by well-vascularized tissues, (4) it produces satisfactory function of the ankle joint and a padding effect, and (5) it produces good contour of the posterior calf to the sole and an acceptable donor-site morbidity.

Expression of ICAM-1 on conjunctival epithelium and ECP in tears and serum from children with allergic conjunctivitis

BACKGROUND

Conjunctival eosinophilia may be considered to be an indicator of conjunctival allergic disease. The absence of eosinophils on conjunctival scraping, however, cannot rule out the diagnosis of allergic conjunctivitis because eosinophil infiltration may be deeper in conjunctival tissue. Eosinophil cationic protein (ECP) is a toxic product secreted by activated eosinophil as a marker of eosinophil activation. Eosinophil cationic protein concentrations in body fluids correlate with the severity of some allergic diseases. ICAM-1 promotes adhesion of leukocytes to epithelium, endothelium, and upregulates inflammation. Expression of adhesion can be modified by many extracellular and intracellular variables such as proinflammatory cytokines, extracellular matrix proteins, and viral infection.

OBJECTIVE

We investigated whether local eosinophils are only activated in conjunctival epithelium or circulating activated eosinophils are involved in peripheral blood during allergic reaction of the eye. We also demonstrated the possible expression of ICAM-1 on epithelial cells from conjunctival scraping and compared them with soluble ICAM-1 values of serum and tears in children with allergic conjunctivitis and healthy children.

METHODS

Seventeen subjects were selected on the basis of clinical manifestations, history, skin prick test, and total serum IgE. A microcapillary tube was used to collect the tears from the inner canthus. Conjunctival epithelia were obtained by scraping the upper tarsal conjunctiva. The level of ECP was measured by the CAP system, soluble ICAM-1 was measured by ELISA, and ICAM-1 on conjunctival epithelial cells were expressed by the avidine-biotin peroxide complex procedure.

RESULTS

Serum IgE and the eosinophil count were increased in 10 out of 17 patients, positive skin prick tests were positive in 11 patients (Dermatophagoides pternyssinus; 9, Dermatophagoides farinae: 8), and eosinophilia in conjunctival epithelium was in 11 patients (4 patients: >3/HPF, 7 patients: 1-3/HPF). The ECP levels in tears were significantly increased in the patient group (12.0+/-8.0 versus 3.9+/-3.8 microg/mL, P = .01), but not in serum (52.5+/-43.1 versus 28.3+/-25.9 microg/mL). There is significant correlation between the eosinophil count in peripheral blood and on conjunctival epithelium (P = .007, r = .62; n = 25). The ICAM-1 expression score on conjunctival epithelial cells was significantly different between the patient group and controls (patient group: 1.77+/-1.25 versus control: 0.13+/-0.35 ng/mL, P = .002). There was a significant correlation between ICAM-1 expression on conjunctival epithelial cells and the ECP levels of tears (P = .01, r = .58; n = 25). Soluble ICAM-1 levels in serum and tears showed no significant difference between the patient group and controls, and also, there was no correlation between sICAM-1 levels in the serum and tears.

CONCLUSION

Eosinophil cationic protein in tears and ICAM-1 expression scores on conjunctival epithelium showed a significant difference between children with allergic conjunctivitis and the healthy controls, but circulating ECP and sICAM-1 in serum were not significantly different between the two groups. These results may suggest that ICAM-1 is locally upregulated in inflammation, mediating eosinophil activation and migration to conjunctival epithelium, but is not involved as inflammatory mediators in peripheral blood during allergic response in children with allergic conjunctivitis.

Analysis of induced sputum to examine the effects of inhaled corticosteroid on airway inflammation in children with asthma

BACKGROUND

Analysis of induced sputum can be performed safely in children with asthma and is useful for both cellular and biochemical markers of inflammation. Glucocorticosteroid inhalation has become the first line therapy for chronic asthma by suppressing airway inflammation, which produces the decrease of bronchial hyperreactivity and reduces the number of eosinophil in bronchial submucosa.

OBJECTIVE

To determine the characteristics of the inflammatory cells and their markers in sputum and to examine the pharmacokinetic effects of glucocorticoid within 3 hours after inhalation therapy on FEV1 and sputum inflammatory indices in children with clinically defined chronic asthma.

METHODS

Thirty subjects with asthma included 14 current symptomatic asthmatics and 14 normal controls inhaled 4.5% hypertonic saline for 10 minutes by nebulizer. The expectorated sputum were collected from all asthmatics before and 3 hours after corticosteroid inhalation for children with asthma and were reduced by dithiotreitol. Total cell counts and differentials were determined. ECP was measured by CAP system. Interleukin-5, GM-CSF and albumin were measured by double sandwich ELISA.

RESULTS

The mean eosinophil percentage and ECP in induced sputum of asthmatics were significantly higher than that of controls. The induced sputum samples obtained after glucocorticoid inhalation showed a significant reduction in mean eosinophil percentage, but FEV1, IL-5, GM-CSF, albumin, and ECP values were not significantly decreased.

CONCLUSION

The present results in induced sputum may be interpreted to reflect direct steroid action on airways and lack of effect on bone marrow effectors at 3 hours after glucocorticoid inhalation.

Interaction of fibroblasts on polycarbonate membrane surfaces with different micropore sizes and hydrophilicity

Surface topography appears to be an important but often neglected factor in implant performance. In this study, fibroblasts were cultured on a range of porous polycarbonate (PC) membranes with well defined surface topography (track-etched micropores, 0.2-8.0 microm in diameter) and wettability gradients. The wettability gradient on the PC membrane surfaces was produced by treating the surfaces with corona from a knife-type electrode whose power increased gradually along the sample length. The PC membrane surfaces were characterized by scanning electron microscopy (SEM) and the water contact angle measurement. Fibroblasts were cultured on the corona-treated PC membrane surfaces with different micropore sizes for 1 and 2 days. The cells attached on the membrane surfaces were examined by SEM and the cell density on the surfaces was estimated by counting the number of attached cells along the wettability gradient. It was observed that the cells were adhered and grew more on the hydrophilic positions of the membrane surfaces than the more hydrophobic ones, regardless of micropore size. It was also observed that cell adhesion and growth decreased gradually with increasing micropore size of the membrane surfaces. It seems that the cell adhesion and growth were progressively inhibited as the membrane surfaces had micropores with increasing size, probably due to surface discontinuities produced by tract-etched pores. On the membrane surfaces with smaller micropore sizes, the cells seemed to override these surface discontinuities.

Environmental factors and nutritional utilization patterns affect niche overlap indices between Aspergillus ochraceus and other spoilage fungi

The total number, and the type of C source utilized in common by an ochratoxin producing strain of Aspergillus ochraceus and six other spoilage fungi varied with the range used (95, Biolog GN plates, or 18 major C sources found in maize). The niche size and niche overlap index (NOI) were markedly influenced by water availability (water activity, aw) and temperature. With freely available water (0.995 aw) there was ecological similarity between A. ochraceus, A. alternata, A. candidus and A. flavus, all exploiting the same sources at both 18 and 30 degrees C. However, under water stress, A. ochraceus had a low NOI compared with A. niger, A. flavus and A. candidus, and Eurotium spp., suggesting that there was very little niche overlap in utilization of different C sources. The NOIs were not directly related to growth rates. Niche overlap between species was shown to be in a state of flux and significantly influenced by environmental factors. This may have important implications in understanding ecological interactions, and dominance by species in a community, and for pre-emptive exclusion of specific species.

Chitin synthase II inhibitory activity of ursolic acid, isolated from Crataegus pinnatifida

Two triterpenoid compounds, ursolic acid and uvaol, were isolated from Crataegus pinnatifida Bunge leaves. Ursolic acid inhibits chitin synthase II from S. cerevisiae with an IC50 value of 0.84 microgram/ml and the inhibition appears to be selective for chitin synthase II, whereas uvaol has no inhibitory activity up to 280 micrograms/ml. Oleanolic acid, alpha-hederin hydrate, and betulic acid inhibited the chitin synthase II activity under the same conditions with an IC50 of 5.6, 64.3, and 98.7 micrograms/ml, respectively.

Platelet and cell interactions on gold sputter-deposited polymeric surfaces

Surface treatment as gold sputter-deposited treatment onto various polymeric surfaces has been investigated to improve the cell-, tissue- and blood-compatibility. Surface treated samples were characterized by measurement of contact angle goniometer and electron spectroscopy for chemical analysis (ESCA). The contact angles on the gold-coated polymeric surfaces decreased from 95-65 degrees to around 50 degrees, i.e., increased hydrophilicity due to incorporation of gold thin layer. From the results of ESCA analysis of the modified polymeric surfaces, surface modification by the gold-sputter method was successfully performed. Morphology of the adhered platelets on the gold-coated polymeric surfaces showed lesser activating than control, and the number of adhered platelets surface modified samples decreased with decreasing water contact angle. Fibroblast cell adhesion and growth on the gold-coated polymeric surfaces were more active than those of control. It seems that surface wettability and surface chemistry of gold play important roles for platelet adhesion and cell adhesion, spreading and growth.

Perfusion impairments in infantile autism on technetium-99m ethyl cysteinate dimer brain single-photon emission tomography: comparison with findings on magnetic resonance imaging

The neuro-anatomical substrate of autism has been the subject of detailed investigation. Because previous studies have not demonstrated consistent and specific neuro-imaging findings in autism and most such studies have been performed in adults and school-aged children, we performed a retrospective review in young children in search of common functional and anatomical abnormalities with brain single-photon emission tomography (SPET) using technetium-99m ethyl cysteinate dimer (ECD) and correlative magnetic resonance imaging (MRI). The patient population was composed of 23 children aged 28-92 months (mean: 54 months) who met the diagnostic criteria of autism as defined in the DSM-IV and CARS. Brain SPET was performed after intravenous injection of 185-370 MBq of 99mTc-ECD using a brain-dedicated annular crystal gamma camera. MRI was performed in all patients, including T1, T2 axial and T1 sagittal sequences. SPET data were assessed visually. Twenty patients had abnormal SPET scans revealing focal areas of decreased perfusion. Decreased perfusion of the cerebellar hemisphere (20/23), thalami (19/23), basal ganglia (5/23) and posterior parietal (10/23) and temporal (7/23) areas were noted on brain SPET. By contrast all patients had normal MRI findings without evidence of abnormalities of the cerebellar vermis, cerebellar hemisphere, thalami, basal ganglia or parietotemporal cortex. In conclusion, extensive perfusion impairments involving the cerebellum, thalami and parietal cortex were found in this study. SPET may be more sensitive in reflecting the pathophysiology of autism than MRI. However, further studies are necessary to determine the significance of thalamic and parietal perfusion impairment in autism.

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.

Determination of 17 beta-estradiol and its metabolites in sewage effluent by solid-phase extraction and gas chromatography/mass spectrometry

The paper describes a simple and quantitative method for monitoring non-conjugated 17 beta-estradiol (E2) and its metabolites estrone (E1) and estriol (E3) as environmental contaminants in municipal sewage effluents. Estrogens were preconcentrated and cleaned up by solid-phase extraction using a reversed-phase C18 cartridge. They were derivatized with pentafluoropropionic acid anhydride, and the products were analyzed by gas chromatography/mass spectrometry. Recoveries from spiked distilled water and sewage were better than 87% at fortification levels of 100 and 20 ng/L. For a 1 L sewage sample and a concentration factor of 5000, detection limits were 5 ng/L for E1 and E2 and 10 ng/L for E3. In a brief survey of Canadian wastewater, these estrogens were detected in many raw sewage and effluent samples at concentrations ranging from 6 to 109 ng/L for E1, from < 5 to 15 ng/L for E2, and from < 10 to 250 ng/L for E3.

Interaction of Different Types of Cells on Polymer Surfaces with Wettability Gradient

Gradient surfaces whose properties are changed gradually along the sample length are of particular interest for basic studies of the interaction between biological species and surfaces since the effect of a selected property can be examined in a single experiment on one surface. We prepared a wettability gradient on low density polyethylene (PE) sheets by treating them in air with the corona from a knife-type electrode whose power increases gradually along the sample length. The PE surfaces oxidized gradually with the increasing corona power, and the 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 interaction of different types of cells (Chinese hamster ovary, fibroblast, and endothelial cells) as well as serum proteins in terms of the surface hydrophilicity/hydrophobicity of polymeric materials. The cells adhered and grown on the gradient surface along the sample length were counted and observed by scanning electron microscopy. It was observed that the cells were adhered, spread, and grown more onto the positions with moderate hydrophilicity of the wettability gradient surface than onto the more hydrophobic or hydrophilic positions. The maximum adhesion and growth of the cells appeared at around water contact angles of 55 degrees, regardless of the cell types used. This result seems closely related to the serum protein adsorption on the surfaces; the serum proteins were also adsorbed more onto the positions with moderate hydrophilicity of the wettability gradient surface. Copyright 1998 Academic Press.

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.

Modeling the physiological responses of anuran R3 ganglion cells

Teeters and Arbib (Bio Cybernet 1991;64:197-207) presented a model of the anuran retina which qualitatively accounts for some of the characteristic response properties used to distinguish ganglion cell type in anurans. Teeters et al. (Vis Res 1993;33:2361-2379) tested the model's ability to reproduce data of Ewert and Hock (Exp Brain Res 1972;16:41-59) relating toad R2, R3 and R4 ganglion cell responses to moving worm, antiworm and square-shaped stimuli of various edge lengths for stimulus shape and size dependency. In this paper we provide an exhaustive analysis of the performance of the modeled R3 cells with respect to most of the known qualitative and quantitative physiological properties of natural R3 ganglion cells. We also introduce several relevant predictions of the model relating different responses of R3 cells under the effect of changes in different model components. In some cases the predictions have been tested in neurophysiological experiments.

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.

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.

The effects of ouabain and potassium on peritoneal fluid and solute transport characteristics

BACKGROUND

We reported anomalous transport characteristics of potassium during experimental peritoneal dialysis in rats and suggested that mechanisms of peritoneal potassium transport could be other than simple passive transport. Intracellular transport of potassium in cultured human mesothelial cells was reported to be regulated by three different pathways, such as channels blocked by ouabain, channels blocked by furosemide, and other.

OBJECTIVE

To investigate the effect of ouabain on peritoneal potassium and water transport characteristics.

METHODS

A single 4-hour peritoneal dwell was performed in 28 Sprague-Dawley rats. To minimize the diffusive transport of potassium, 4.5 mmol/L of KCl was added into conventional dialysis solution with 3.86% glucose [acidic peritoneal dialysis solution (APD)]. To evaluate the effect of the pH of dialysis solution on the transport of potassium and water, 4 mmol/L of NaOH was added into the potassium-containing study solutions [neutral peritoneal dialysis solution (NPD)]. To evaluate the effect of a potassium channel blocker on peritoneal potassium transport ATPase sensitive Na+-K+-transport inhibitor, ouabain (10(-5) mmol/L) was added to dialysis solutions immediately before the dwell study in eight rats with APD (APD-O) and six rats with NPD (NPD-O). Ouabain was not added in eight and six rats with APD and NPD (APD-C and NPD-C, respectively). They were used as control. Infusion volume was 30 mL. The intraperitoneal volume (V(D)) was estimated by using a volume marker dilution method with corrections for the elimination of volume marker, radioiodinated human serum albumin (RISA), from the peritoneal cavity (K(E)). The diffusive mass transport coefficient (K(BD)) and sieving coefficient (S) were estimated using the modified Babb-Randerson-Farrell model.

RESULTS

V(D) was significantly higher (p < 0.05 from 90 min to 240 min) and K(E) (0.027+/-0.018 mL/min for APD-O, 0.026+/-0.017 mL/min for NPD-O, and 0.030+/-0.022 mL/min for NPD-C, vs 0.058+/-0.030 mL/min for APD-C, p < 0.05 for each) significantly lower during dialysis with APD-O, NPD-O, and NPD-C than with APD-C. The intraperitoneal glucose expressed as a percentage of the initial amount was significantly higher with APD-O, NPD-C, and NPD-O than with APD-C (p < 0.05 from 90 min to 240 min). K(BD) for sodium was higher during dialysis with ouabain than without ouabain, while K(BD) for urea, glucose, and potassium, and S for urea, glucose, sodium, and potassium did not differ between the four groups.

CONCLUSIONS

The physiologic potassium concentration in neutral dialysis solutions and the use of ouabain decreased the intraperitoneal fluid absorption. The diffusive transport coefficient and sieving coefficient for potassium did not differ, while the diffusive transport coefficient for sodium increased during use of ouabain.