Biomedical subjects

G W Lee

Publications and source records attributed to G W Lee.

At least 19 recordsLinked to original sources

PubMed2005

In situ high-energy x-ray diffraction study of the local structure of supercooled liquid Si.

Employing the technique of electrostatic levitation, coupled with high-energy x-ray diffraction and rapid data acquisition methods, we have obtained high quality structural data more deeply into the supercooled regime of liquid silicon than has been possible before. No change in coordination number is observed in this temperature region, calling into question previous experimental claims of structural evidence for the existence of a liquid-liquid phase transition.

Journal Article↗

PubMed2004

Difference in icosahedral short-range order in early and late transition metal liquids.

New short-range order data are presented for equilibrium and undercooled liquids of Ti and Ni. These were obtained from in situ synchrotron x-ray diffraction measurements of electrostatically levitated droplets. While the short-range order of liquid Ni is icosahedral, consistent with Frank's hypothesis, significantly distorted icosahedral order is observed in liquid Ti. This is the first experimental observation of distorted icosahedral short-range order in any liquid, although this has been predicted by theoretical studies on atomic clusters.

Journal Article↗

PubMed2003

First x-ray scattering studies on electrostatically levitated metallic liquids: demonstrated influence of local icosahedral order on the nucleation barrier.

To explain the unusual stability of undercooled liquids against crystallization, Frank hypothesized that the local structures of undercooled liquids contain a significant degree of icosahedral short-range order, which is incompatible with long-range periodicity. We present here the first direct experimental demonstration of Frank's complete hypothesis, showing a correlation between the nucleation barrier and a growing icosahedral short-range order with decreasing temperature in a Ti39.5Zr39.5Ni21 liquid. A new experimental facility, BESL (Beamline Electrostatic Levitation), was developed to enable the synchrotron x-ray structural studies on deeply undercooled, reactive liquids.

Journal Article↗

PubMed2002

The effect of physiotherapy on post-temporomandibular joint surgery patients.

The purpose of this study was to investigate the effect of physiotherapy on rehabilitation of patients who had temporomandibular joint (TMJ) surgery. The treatment group consisted of 22 post-surgical patients who were treated with physiotherapy, and the non-treatment group consisted of 22 post-surgical patients who received no physiotherapy. The assessment tools were made using visual analogue scale (VAS) and craniomandibular index (CMI) which consisted of dysfunction index (DI) and palpation index (PI). All patients received follow-up for 7 months. The subjects were measured three times; before surgery, 6 weeks after surgery and 7 months after surgery. On the 6 week post-surgery assessment, DI and total CMI scores of the treatment group were significantly lower (P < 0.05) than those of the non-treatment group. On the assessment performed 7 months after surgery, all variables were significantly lower (P < 0.05) for the treatment group compared with those of the non-treatment group. The findings of the study indicate that physiotherapy has a positive effect in relieving pain and restoring TMJ function after surgery.

Adolescent↗

PubMed2001

Regeneration and tolerance factor of the human placenta induces IL-10 production.

Regeneration and tolerance factor (RTF) was originally identified in the placenta of mice and the isolated protein shown to have suppressive effects. In these studies, the gene cloned from thymus tissue was mapped to human chromosome 12. The role of recombinant RTF on cytokines was examined. In addition, we examined the human placenta by immunohistochemistry for RTF expression. RTF was expressed at the peripheral layer of cytotrophoblast in 7-9-week-old placentas. Using the RTF gene sequence, a recombinant protein was prepared and shown to induce IL-10 production. These data indicate that RTF is expressed by the tissues most intimately involved at the maternal-fetal interface, and its biological activity is capable of producing the necessary immune response for initiating and maintaining the maternal-fetal relationship.

Cells, Cultured↗

PubMed2001

Regeneration and tolerance factor is expressed during T-lymphocyte activation and plays a role in apoptosis.

Regeneration and tolerance factor (RTF) is a protein cloned from the thymus and expressed on B lymphocytes in normal pregnancy, B lymphocytic leukemia lines, and T and B lymphocytes in individuals with HIV infection. Findings, using the Jurkat T-cell model, revealed that RTF is upregulated after activation and anti-RTF antibody-induced apoptosis. In this article anti-RTF antibody-induced apoptosis of both unstimulated and activated T lymphocytes. RTF expression was examined in human PBMC or purified T lymphocytes after their in vitro activation. Kinetic studies indicated maximal RTF cell surface expression on activated T lymphocytes occurred between expression of the early activation antigen CD69 and the IL-2alpha receptor (CD25) by multiparameter flow cytometry. RTF receptor expression correlated with Fas (CD95) and CD25 receptor expression (r2 = 0.6 and 0.5, respectively). RTF surface expression was dependent on the stimuli used to activate T lymphocytes. T lymphocytes obtained maximal RTF expression when activated through the TCR signal complex using anti-CD3epsilon antibody alone when compared with T lymphocytes activated with costimulation provided by anti-CD28 antibody alone or with anti-CD28 and anti-CD3epsilon antibody. RTF is expressed under conditions of both activation and anergy. The RTFs increased concentration on the surface of anergic T cells may protect these cells from apoptosis because increased RTF concentrations inhibited anti-RTF induced apoptosis. These data further characterize the expression of RTF on activated T lymphocytes and the role of anti-RTF antibody in T-lymphocyte apoptosis.

Annexin A5↗

PubMed2000

Regeneration and tolerance factor's potential role in T-cell activation and apoptosis.

Regeneration and tolerance factor (RTF) is a novel membrane protein that has a diverse expression pattern and immunoregulatory properties. RTF is expressed in vivo on the surface of individuals with B cell chronic lymphocytic leukemia and on activated T lymphocytes of HIV infected individuals as determined by their coexpression with CD38 and HLA-DR. The unique expression patterns of this protein in vivo lead us to investigate its expression in vitro. The activation of human PBMCs through the TCR, using anti-CD3 antibody and PMA, upregulated cell surface expression of RTF from 2. 3% to 91.2% (mean channel fluorescence [MCF] increased threefold). The activation of Jurkat T cells through the TCR upregulated surface expression of RTF from 8.3% (MCF-1.3) to 58.7% (MCF-13.1). The Jurkat T-cell line was used as a model system to explore RTF's role in cellular activation. Using the Jurkat T-cell model, we found anti-RTF antibody induces apoptosis. The addition of anti-RTF antibody increased annexin V binding by threefold compared with the IgG1 kappa isotype control antibody (p < 0.00002) and activated caspase 3. These data indicate that RTF is expressed during T-cell activation and may be associated with apoptosis.

Antibodies↗

PubMed2000

Documentation of brachial plexus compression in the thoracic inlet with quantitative sensory testing.

This study evaluated the cutaneous pressure threshold of subjects with and without a clinical diagnosis of brachial plexus compression in the thoracic inlet, usually termed thoracic outlet syndrome (TOS). Sixty-one subjects (102 arms) made up the control population; 11 subjects 120 arms) made up the TOS population. Assessment by two upper-extremity specialists preceded the testing. The one-point cutaneous pressure threshold was measured with the Pressure-Specifying Sensory Device (PSSD) on the pulp of both the index and little finger (upper and lower brachial plexus distributions) with the arm in the unprovoked (adducted) and provoked (abducted 180 degrees) positions. In the control subjects, there was no significant change in the cutaneous pressure threshold between unprovoked and provoked positions. In contrast in patients with TOS, there was a significant increase in the cutaneous pressure threshold at both sites (p < .0001 ) between the unprovoked and the provoked positions. Furthermore, the cutaneous pressure threshold for patients with TOS was significantly higher in both positions than it was in the controls (p < .0001 ). It was concluded that measurement of changes in the cutaneous pressure threshold with the PSSD in distal sensory targets of the upper and lower trunk can identify patients symptomatic for compression, when the brachial plexus is provoked as part of the testing sequence.

Adult↗

PubMed1999

Ring avulsion injuries: a biomechanical study.

The biomechanics of ring avulsion injuries was studied in a cadaveric simulation model. Custom-fitted metal rings attached to a rigid frame were placed over the proximal phalanx of fresh or thawed fresh-frozen specimens. Ring avulsion injuries in 44 fingers were produced with a standardized force applied to the proximal ulna. The progress of injury was evaluated with simultaneous high-speed cinematography and continuous force measurements. The injured digits were x-rayed and categorized according to Urbaniak's classification. Continuous force measurements produced similar curves for all classes of injuries. The average maximum force resulting in class I injuries was 80 N. The average maximum force producing amputation in class III injuries was 154 N, a force much lower than expected. Force measurements for class II injuries were nearly identical to those of class III. This surprisingly minimal force resulting in digit amputation was explained by high-speed cinematography, which showed that the rings tilt on the digits concentrating disruption forces as a result of ring angulation on the finger. Incomplete amputations were due to loss of ring purchase by skin flap eversion. Finally, comparison of high-speed cinematography with force curves suggests that skin rupture rather than skeletal or tendon disruption accounted for the maximum force during ring avulsion injury.

Amputation, Traumatic↗

PubMed1999

Increased expression of regeneration and tolerance factor in individuals with human immunodeficiency virus infection.

Regeneration and tolerance factor (RTF) plays a pivotal role in successful pregnancy outcome and has potent immunomodulating properties. During pregnancy, it is abundantly expressed in the placenta and on peripheral B lymphocytes. Several lines of evidence suggest that both successful pregnancy outcome and progression from human immunodeficiency virus (HIV) infection to AIDS are associated with a Th2-type response. As a result, we hypothesized that the cellular expression of RTF may also be increased during infection with HIV. Using flow cytometric analysis, we showed a significantly (P < 0.01) increased expression of RTF on CD3(+) cells obtained from individuals with HIV over that for individuals without HIV. On average, 32.1% of the CD3(+) cells from individuals with HIV expressed high levels of RTF. In contrast, an average of only 6.7% of the CD3(+) cells from individuals without HIV expressed high levels of RTF. Similar results were obtained when CD19(+) cells from individuals with (mean, 44.1%) and without (mean, 25.8%) HIV were evaluated. Linear regression analysis suggested that high levels of RTF expression by CD3(+) cells correlated better with viral load (r value, 0.46) than with absolute CD4 count (r value, 0.09). While additional experiments are necessary to delineate the precise immunologic role of RTF, our current data suggest that RTF expression during HIV infection may be a useful marker of immune activation.

Antibodies, Monoclonal↗

PubMed1999

Inhibition of activation of nuclear factor kappaB is responsible for inhibition of inducible nitric oxide synthase expression by higenamine, an active component of aconite root.

Effects of higenamine on nitric oxide (NO) production and inducible NO synthase (iNOS) mRNA expression (RAW 264.7 cells), on vascular reactivity in vitro and in vivo (rats), and on survival rates (mice) and serum nitrite/nitrate levels (rats) were investigated by using last lipopolysaccharide (LPS) plus interferon (IFN)-gamma. Higenamine concentration-dependently inhibited NO production and inducible NO synthase mRNA in RAW 264.7 cells, in which the IC(50) was 53 microM. Higenamine (10 mg/kg i.p.) administered 90 min before LPS (5 mg/kg i.v.) prevented not only LPS-induced hypotension but also pressor response to norepinephrine (1 microgram/kg) in rats. Incubation of thoracic aorta with LPS (300 ng/ml) for 8 h in vitro resulted in suppression of the vasoconstrictor effects to phenylephrine, which was prevented by coincubation with higenamine. The survival rate to endotoxin in mice was significantly (P <.01) increased by the presence of higenamine in the LPS-treated group up to 48 h. Serum nitrite/nitrate levels were significantly (P <.05) reduced by higenamine in LPS-treated rats. Finally, higenamine inhibited the activation of nuclear factor kappaB in RAW 264.7 cells due to LPS + IFN-gamma by mobility shift assays. Taken together, these data strongly suggest that higenamine inhibits iNOS expression by inhibiting nuclear factor kappaB activation by LPS + IFN-gamma, which may be beneficial in inflammatory diseases in which enhanced formation of NO is the main causative factor. Furthermore, due to positive inotropic action, higenamine may be more effective in a condition where myocardial contractility is likely to depress, such as in septic shock and/or endotoxin-induced inflammatory disorders.

Aconitum↗

PubMed1998

Modification of Ran GTPase-activating protein by the small ubiquitin-related modifier SUMO-1 requires Ubc9, an E2-type ubiquitin-conjugating enzyme homologue.

Covalent modification of the Ran GTPase-activating protein RanGAP1 with the ubiquitin-related protein SUMO-1 promotes its association with Nup358, a component of the cytoplasmic fibrils emanating from the nuclear pore complex (1,2). In Xenopus egg extracts, Nup358 can be found in a complex with Ubc9 (3), a structural homologue of the E2-type ubiquitin-conjugating enzymes (UBCs). Here we show that a subset of the human homologue of Ubc9 (HsUbc9) colocalizes with RanGAP1 at the nuclear envelope. HsUbc9 forms thiolester conjugates with recombinant SUMO-1, but not with recombinant ubiquitin, indicating that it is functionally distinct from E2-type UBCs. Finally, HsUbc9 is required for the modification of RanGAP1 by SUMO-1. These results suggest that HsUbc9 is a component of a novel enzymatic cascade that modifies RanGAP1, and possibly other substrates, with SUMO-1.

Adenosine Triphosphate↗

PubMed1998

Imaging of huge lingual thyroid gland with goitre.

We present the CT and MRI findings in a 75-year-old woman with a huge pathologically proven lingual thyroid which underwent goitrous degeneration. CT and MRI showed a midline, tongue-based, exophytic mass with areas of necrosis and heterogeneous contrast enhancement, as seen in large goitres in the normal thyroid gland.

Aged↗

PubMed1998

Comparison of relaxations evoked by photoactivation of NO-containing compounds and nitrergic nerve stimulation in 5-hydroxytryptamine- and potassium-contracted rat gastric fundus.

1. The aim of the present study was to further investigate our earlier proposal of liberation of nitric oxide (NO) by photoactivation of molecules containing NO or NO2, which in turn relaxes gastric smooth muscle, and to determine whether presynaptic- and/or postsynaptic NO-mediated relaxation is affected differently by the degree of membrane depolarization in rat gastric fundus smooth muscle. 2. During contraction of rat gastric fundus with 5-hydroxytryptamine (5-HT, 10 microM), low (K+, 25 mM) and high potassium (K+, 65.4 mM), relaxation responses to nitrergic nerve stimulation, photo-activation of caged NO compounds (streptozotocin [STZ], N omega-nitro-L-arginine-methylacetate [L-NAME], N omega-nitro-D-arginine-methylacetate [D-NAME]), and sodium nitroprusside (SNP) were compared. 3. Nitrergic nerve (presynaptic) stimulation and photoactivation (postsynaptic) of all caged NO compounds produced rapid, transient and reversible relaxation of 5-HT and low-K(+)-contracted tissues. However, when contractions were induced by high K+, the relaxation induced by nerve stimulation was abolished, whereas relaxations induced by photoactivated NO compounds were significantly (P < 0.01) reduced. 4. The relaxation induced by sodium nitroprusside (SNP), but not papaverine, was also diminished in high-K(+)-contracted tissues. The magnitude of photoactivated NO-induced relaxation was related to the amount of NO release, light intensity and concentration of compounds. 5. The evidence that photoactivated NO-induced relaxation is mediated by cGMP comes from the observation that zaprinast, but not forskolin, potentiated the relaxation. 6. It is concluded that rat gastric smooth muscle relaxes to photoactivation of NO or NO2-carrying molecules via NO, and it appears that degree of membrane depolarization may be a critical factor in dissociating the response to presynaptic- and postsynaptic NO-mediated relaxation in this muscle.

Animals↗

PubMed1998

Differential latency testing: a more sensitive test for radial tunnel syndrome.

A modification of the standard electrodiagnostic test was developed in an effort to provide a more sensitive electrodiagnostic evaluation in radial tunnel syndrome. Radial motor nerve latency recordings were obtained in 3 different forearm positions: neutral, passive supination, and passive pronation. The maximal difference in these recordings, the differential latency, in 25 patients with radial tunnel syndrome of greater than 6 months duration (test group) was compared with those in 25 asymptomatic volunteers (control group). Differential latency recordings were obtained in all patients in the test group before and after surgery. Radial nerves that were compressed demonstrated a significantly greater differential latency (0.44+/-0.12 ms) versus controls (0.12+/-0.008 ms). Following radial nerve decompression, differential motor latencies in the test group decreased below control values, demonstrating a resolution of the provoked electrical response with a postoperative differential latency of 0.07+/-0.05 ms. Our results demonstrate the differential motor latency of the radial nerve to be a sensitive electrodiagnostic tool in patients with radial tunnel syndrome. A differential latency of > or =0.30 ms was considered indicative of radial tunnel syndrome.

Adult↗

PubMed1998

Effects of attractiveness and gender on the perception of achievement-related variables.

The present study was an examination of the effects of physical attractiveness and gender on perceptions of academic success, achievement-related traits, intelligence, initiative, and attributions of ability and effort in relation to academic success. It was hypothesized that attractive persons and men would be rated more favorably along these dimensions than would unattractive persons and women. The participants were 144 U.S. undergraduates who observed photographs of attractive and unattractive men and women and then rated the persons in the photographs on the aforementioned dimensions. Physical attractiveness had a differential effect on the dimensions within achievement. Also, being perceived as physically attractive created positive impressions of achievement-related traits for men but negative impressions for women.

Achievement↗

PubMed1997

Treatment of long-standing thoracostoma and bronchopleural fistula without pulmonary resection in high risk patients.

A chronic bronchopleural fistula and a fibrotic postthoracotomy space in a patient with poor functional respiratory reserve is a difficult problem. The classic management of bronchopleural cutaneous fistulas has been with further pulmonary resection to healthy bronchus, repair of the bronchus directly, and a thoracoplasty or myoplasty technique to obliterate the cavity. In a high risk patient, further pulmonary resection and thoracoplasty may be contraindicated. Myoplasty techniques alone without control of the fistula have limited success. In the last 4 years, we have treated six patients with right-sided thoracostomas after a primary open drainage procedure for bronchopleural fistula and empyema. The air leak was controlled with inversion of the sinus tract, fibrin glue, and muscle flap cavity obliteration. An average of two muscle flaps per patient were used, including the contralateral latissimus dorsi muscle. An 83 percent success rate has been achieved with this procedure in patients who otherwise would not be considered surgical candidates. Attention to the details described, including direct suture closure of the bronchial sinus, obliteration of the cavity by local muscle flaps, and avoidance of mechanical positive pressure ventilation, will make extended thoracotomy, pulmonary resection, and thoracoplasty unnecessary in these high risk patients.

Adult↗

PubMed1995

Molecular, biochemical, and clinical characterization of mitochondrial acetoacetyl-coenzyme A thiolase deficiency in two further patients.

The molecular basis of mitochondrial acetoacetyl-CoA thiolase (T2) deficiency was studied in two patients (GK11 and GK16). Fibroblasts from each patient had detectable immunoreactive T2 polypeptide (CRM). In pulse-chase experiments, fibroblasts from GK11 had two types of CRM: one (type I CRM) disappeared after a 24-hr chase and migrated more slowly than that of the normal control; the other (type II CRM) was detected with a small amount even after a 72-hr chase and had normal electrophoretic mobility. GK16's fibroblasts had a CRM (type III) which was also detectable even after a 72-hr chase and showed a slower mobility than type I CRM. By analyzing amplified cDNA and genomic fragments, we showed that both patients are genetic compounds; GK11 for the mutations N158D and T297M, and GK16 for the mutations A301P and IVS8 (+1). Expression analyses confirmed that mutant T2 subunits with N158D, T297M, and A301P correspond to type I, II, and III CRM, respectively. Among them, only the mutant T2 polypeptide with T297M appeared to have a detectable residual activity, in spite of its instability. Cotransfection of two cDNAs containing N158D and T297M suggested that heterotetramer formation reduces residual activity in GK11 cells.

Acetyl-CoA C-Acetyltransferase↗