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Biomedical subjects

S Lee

Publications and source records attributed to S Lee.

At least 163 records · Page 9Linked to original sources
PubMed2002

Nanochemical surface analyzer in CMOS technology.

We have developed an atomic force microscopy (AFM) cantilever system, fabricated using a standard CMOS process and a few post-processing steps, capable of detecting the difference between hydrophilic and hydrophobic samples for the purpose of nanochemical surface analysis. The fully integrated cantilever comprises a thermal actuator for cantilever deflection and a Wheatstone bridge to sense cantilever bending, thus obviating the need for cumbersome laser detection and external piezoelectric drives. Glass microspheres have been affixed to the cantilevers and, were either modified with a self-assembled monolayer to form hydrophobic tips, or left unmodified for hydrophilic tips. Force-distance curves have been used to measure the force between the functionalized/unfunctionalized tips and hydrophobic/hydrophilic sample surfaces. In an optimization step three different Wheatstone bridge sensors have been designed and characterized; best Wheatstone bridge sensitivity is 8.0 microV/nm with a 713 nm/mW actuator efficiency.

Journal Article↗
PubMed2002

The influence of humic acids derived from earthworm-processed organic wastes on plant growth.

Some effects of humic acids, formed during the breakdown of organic wastes by earthworms (vermicomposting), on plant growth were evaluated. In the first experiment, humic acids were extracted from pig manure vermicompost using the classic alkali/acid fractionation procedure and mixed with a soilless container medium (Metro-Mix 360), to provide a range of 0, 50, 100, 150, 200, 250, 500, 1,000, 2,000, and 4,000 mg of humate per kg of dry weight of container medium, and tomato seedlings were grown in the mixtures. In the second experiment, humates extracted from pig manure and food wastes vermicomposts were mixed with vermiculite to provide a range of 0, 50, 125, 250, 500, 1,000, and 4,000 mg of humate per kg of dry weight of the container medium, and cucumber seedlings were grown in the mixtures. Both tomato and cucumber seedlings were watered daily with a solution containing all nutrients required to ensure that any differences in growth responses were not nutrient-mediated. The incorporation of both types of vermicompost-derived humic acids, into either type of soilless plant growth media, increased the growth of tomato and cucumber plants significantly, in terms of plant heights, leaf areas, shoot and root dry weights. Plant growth increased with increasing concentrations of humic acids incorporated into the medium up to a certain proportion, but this differed according to the plant species, the source of the vermicompost, and the nature of the container medium. Plant growth tended to be increased by treatments of the plants with 50-500 mg/kg humic acids, but often decreased significantly when the concentrations of humic acids derived in the container medium exceeded 500-1,000 mg/kg. These growth responses were most probably due to hormone-like activity of humic acids from the vermicomposts or could have been due to plant growth hormones adsorbed onto the humates.

Animals↗
PubMed2002

Health-related quality-of-life treatments for severe haemophilia: utility measurements using the Standard Gamble technique.

Prophylaxis for haemophilia improves outcomes, but at a substantial cost. Cost-utility analysis balances improvements seen in health-related quality of life (HRQoL) against costs, with the purpose of aiding healthcare decision-making. This analysis uses a measure of HRQoL known as utility. The objective of this study was to measure HRQoL (utility) values for states of health that result from on-demand therapy or prophylaxis. The HRQoL for different health states (including target joint bleeding, different intensities of prophylaxis, and indwelling intravenous catheters [ports]) was measured for healthy adults (n=30), parents of haemophilic children (n=30), and adults with haemophilia (n=28). Parents and patients rated health states similarly. Healthy adults gave the lowest ratings. The following rank, in order of HRQoL, was obtained: prophylaxis (low > medium > high) > on-demand therapy > prophylaxis with port> prophylaxis with infected port > on-demand therapy with development of a target joint. We conclude that: (1) haemophilia and its treatment reduce HRQoL; (2) prophylaxis is preferred to on-demand therapy; (3) intravenous ports substantially reduce HRQoL; (4) and an intravenous port to provide prophylaxis is preferable to on-demand therapy if a target joint develops.

Adult↗
PubMed2002

Comparison between the influence of the intravenous and intracerebroventricular injection of a nitric oxide donor on adrenocorticotropic hormone release and hypothalamic neuronal activity.

We investigated the ability of the nitric oxide (NO) donor 3-morpholino-sydnonimine (SIN-1) to release adrenocorticotropic hormone (ACTH) and up-regulate hypothalamic neurones following its intravenous (i.v.) injection. i.v. SIN-1 (0.2-1.8 mg/kg) produced dose-related increases in plasma ACTH levels which were blocked by prior neutralization of endogenous corticotropin-releasing factor (CRF) but not by vasopressin antibodies. In contrast, the intracerebroventricular (i.c.v.) injection of 50-microg SIN-1 released significantly larger amounts of ACTH, a response blunted by either CRF or vasopressin antibodies. While i.c.v. SIN-1 markedly up-regulated transcripts of the immediate early gene NGFI-B in the paraventricular nucleus (PVN) of the hypothalamus, no such response was observed following the i.v. injection of up to 2.0 mg/kg SIN-1. Finally, we found no evidence that the influence of the peripheral administration of SIN-1 on ACTH secretion is mediated by altered pituitary responsiveness to CRF or vasopressin. The fact that NO has a profound hypotensive influence in the periphery suggests that it may have released ACTH through this mechanism, although the absence of PVN neuronal response in regions that are activated by decreased blood pressure casts some doubt on this hypothesis. As the systemic injection of arginine derivatives that block NOS activity potently augment the ACTH response to circulating pro-inflammatory cytokines or vasopressin, the present findings indicate that the mechanisms responsible for this phenomenon are distinct from those responsible for ACTH released by i.v. SIN-1.

Adrenocorticotropic Hormone↗
PubMed2002

Usefulness of silicone plate for sellar floor reconstruction.

During the transsphenoidal approach (TSA), the proper sellar floor reconstruction plays an important role in the surgical results. The authors have evaluated the usefulness of a silicone as a substitute for bone splint in sellar floor reconstruction. Silicone plates were used in 10 patients who had 7 pituitary adenomas, 2 Rathke's cleft cysts, and 1 metastatic tumor. Among the ten cases, seven underwent standard TSAs and three received extended TSAs. The silicone plate was cut to a size slightly larger than that of bone window, inserted with a three-pronged fork, and then adjusted precisely. In nine patients, complications that related to surgical repair did not occur. A postoperative cerebrospinal fluid (CSF) rhinorrhea occurred in one pituitary macroadenoma, and no infection was observed in any case. From the authors' experience, advantages of the silicone plate are its simplicity to shape for any size of defects, and the easy detectability of the previous bone window at reoperation.

Adult↗
PubMed2002

Intramedullary fixation for pediatric unstable forearm fractures.

Forty-nine children with diaphyseal both-bone forearm fractures were treated with either both-bone intramedullary wire fixation (24), single ulnar intramedullary wire fixation (22), or single radial intramedullary wire fixation (3). Six fractures were open and 43 were closed. A limited open approach to one or both bones was necessary for insertion of the intramedullary wire in 10 of 43 closed fractures. All both-bone and single radial intramedullary wire fixations healed with less than 5 degrees angulation. Progressive reangulation of the nonfixed radial fracture after an initial satisfactory reduction was seen in seven of the 22 fractures treated with single ulnar intramedullary wire fixation. In four patients, the reangulation was controlled by a change of cast and molding of the fracture and was between 8 degrees and 12 degrees at union. In two other patients a second operative procedure was required to reduce and internally fix the radius. One fracture healed with a radial angulation of 25 degrees. Three fractures in older patients showed late reangulation after early removal of intramedullary wires at 5 weeks. The results of the current study suggest that the radius and ulna should be stabilized with intramedullary wires and that the wires should be buried to reduce the need for early removal.

Adolescent↗
PubMed2002

Impact of iron dextran on polymorphonuclear cell function among hemodialysis patients.

BACKGROUND: Polymorphonuclear cell (PMN) dysfunction and the increased use of parenteral iron may be important contributory factors to bacterial infections among patients with end-stage renal disease (ESRD) on maintenance hemodialysis (HD). We compared the in vitro impact of a commonly used parenteral iron preparation, iron dextran, on PMN function and viability between a group of HD patients with normal iron indices and healthy subjects. METHODS: Eleven patients with ESRD on HD and 10 healthy subjects were studied. PMN harvested from heparinized blood were incubated with iron dextran (0 - 20 mM) in culture medium (RPMI) for 24 hours at 37 degrees C with 5% CO2 following which function and viability were assessed by flow cytometry using appropriate fluorescent labels. RESULTS: Unstimulated, S. aureus and N-formyl-methionyl-leucyl-phenylalanine (fMLP)-stimulated hydrogen peroxide (H2O2) production was significantly higher in PMN unexposed to iron dextran from HD patients compared to those from healthy subjects. Iron dextran had no impact on unstimulated PMN H2O2 production in either group. In the healthy group, the only significant change occurred with 4-beta-phorbol 12-beta-myristate 13-alpha-acetate (PMA) stimulation, where cells exposed to 0.2 and 2.0 mM iron dextran produced less H2O2 relative to PMN unexposed to iron dextran (p < 0.05). In the HD group, all concentrations of iron dextran significantly attenuated H2O2 production stimulated by S. aureus, fMLP and PMA compared to PMN unexposed to iron dextran. Although PMN phagocytosis decreased with exposure to increasing concentration of iron dextran in both healthy subjects and HD patients, these changes did not achieve statistical significance. No significant changes in PMN viability or apoptosis were seen in either group after exposure to iron dextran. CONCLUSIONS: These results indicate that iron dextran, a standard parenteral iron preparation, attenuates PMN function in HD patients with normal iron indices at clinically relevant concentrations. Further studies are required to evaluate and compare the impact of newer preparations of parenteral iron, such as iron sucrose and ferric gluconate, on PMN function.

Adult↗
PubMed2002

Simultaneous removal of cadmium and turbidity in contaminated soil-washing water by DAF and electroflotation.

The removal of cadmium and turbidity from contaminated soil-washing water was studied by dissolved air flotation (DAF) and electroflotation at laboratory scale by using sodium lauryl sulfate (SLS) as an anionic surfactant, and calcium hydroxide (Ca(OH)2) as a coagulant. Using DAF, and in the presence of SLS or Ca(OH)2, the maximum recovery rate of cadmium obtained at a stoichiometric cadmium to collector and coagulant ratio of 1:4.5 was 51.1% and 80.8%, while the removal rate of turbidity was 18.4% and 19.2%. However, satisfactory cadmium and turbidity removal was not obtained by DAF. Much more significant removal of cadmium (100%, not detected in the residual) and turbidity (95.7%) was obtained by electroflotation using an aluminium metal plate as electrode, which generated hydroxide and aluminum ion. As a consequence, electroflotation is considered an effective method to separate cadmium and turbidity from contaminated soil-washing water. The electroflotation process may have practical applications for the removal of other hazardous metals from contaminated soil-washing water.

Air↗
PubMed2001

Dynamical spin response in semimagnetic quantum dots.

The dynamical response of a paramagnetic spin system to the exchange field of quasi-zero-dimensional electron-hole pairs in semiconductor quantum dots is investigated by time-resolved spectroscopy. The spin response time is extracted from the transient spectral shift of the photoluminescence signal caused by the dynamical spin alignment of magnetic ions incorporated in the crystal matrix. The formation of this ferromagnetically aligned spin complex is demonstrated to be surprisingly stable as compared to bulk systems, even at elevated temperatures and high external magnetic fields.

Journal Article↗