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Biomedical subjects

S Lee

Publications and source records attributed to S Lee.

At least 757 records · Page 42Linked to original sources
PubMed1997

Spin Echoes after Arbitrary N Pulses

Based on the Bloch equations, the general response of a nuclear spin-½ system to multiple RF pulses with arbitrary phases and flip angles is presented. The general solution is expressed in a form including the pathway vectors specifying the magnetization paths generated by a string of pulses. The pathway vectors are useful for predicting the exact positions, magnitudes, and number of echoes. Also, these vectors make it easy to trace the physical origin of an echo formation. It is shown that the maximum number of echoes after N pulses is (3N-1 - 1)/2 using this concept.

Journal Article↗
PubMed1997

A solenoid-like coil producing transverse RF fields for MR imaging.

A solenoidal RF coil is presented that generates an RF field only perpendicular to the long axis, so that it can be used longitudinally in the usual superconducting solenoid magnet for NMR. This new design is superior to the traditional saddle coil or Helmholtz pair. Applications for the coil will include imaging of legs, arms, etc., as well as analytical application in high-resolution NMR. A tilted single-turn-solenoid, which has the plane of each loop tilted with respect to the cylinder axis, is implemented to generate an RF field with a component perpendicular to the coil-cylinder axis. The novel addition of an eddy-current coil eliminates the undesirable longitudinal component of the RF field, leaving an RF field entirely perpendicular to the coil-cylinder axis. By inserting the eddy coil, the spatial homogeneity of the transverse RF field is greatly improved, with significant increases in the H1 field strength and receiving sensitivity. Images with the eddy-coil-modified tilted solenoid are remarkably uniform in intensity over a large useful volume.

Hand↗
PubMed1997

Quantum treatment of intermolecular multiple-quantum coherences with intramolecular J coupling in solution NMR.

A recently introduced density matrix picture for dipolar effects in solution NMR (1996, J. Chem. Phys. 105, 874) gave complete solutions for intermolecular multiple-quantum coherences for single-component samples without scalar couplings. This paper, for the first time, shows that this quantum picture can lead to explicit signal expressions for multicomponent samples of molecules with internal scalar couplings (here assumed to generate a first-order spectrum) and long-range dipolar couplings. Experimental observation of a triplet in the indirectly detected dimension for a heteronuclear CRAZED sequence (13CHCl3 sample, ZQ or 2Q coherences) gives clear evidence that the coupling is due to the intermolecular dipolar coupling. We also make comparisons with classical pictures which introduce the dipolar demagnetization field in multicomponent spin systems.

Magnetic Resonance Spectroscopy↗
PubMed1997

Role of peptide YY in regulation of duodenal motility during the interdigestive period in sheep.

Temporal coordination between duodenal migrating myoelectric complexes (MMC) and pancreatic exocrine secretion, and the effects of porcine peptide YY (PYY) on gastroduodenal motility and pancreatic exocrine secretion were examined during the interdigestive period in conscious mature sheep. Fluid and enzyme secretions from the exocrine pancreas showed a periodic pattern corresponding to the phases of duodenal MMC, although these secretion rates were maintained at a high level during phase II in sheep. Intravenous continuous infusion of PYY at doses ranging from 50 to 200 pmol.kg-1.h-1 or intravenous bolus infusion of PYY at doses ranging from 50 to 200 pmol.kg-1 showed a tendency to prolong the first cycle of the duodenal MMC and significantly shorten the second cycle. However, there was almost no effect on ruminal contractions from the PYY administration. In the pancreatic exocrine secretion, PYY could inhibit only bicarbonate secretion at only the highest dose of 200 pmol.kg-1. These results imply that endogenous PYY may play a physiological role in the regulation of the duodenal MMC cycles in sheep but not in ruminal contractions. PYY seems unlikely to regulate the pancreatic exocrine secretion in normal sheep, because a supraphysiological dose of PYY was required to inhibit the pancreatic exocrine secretion.

Amylases↗
PubMed1997

Use of the QRS scoring system in the early estimation of myocardial infarct size following reperfusion.

While the QRS scoring system has been established as a convenient tool for estimating infarct size in nonreperfused patients during the chronic stage of myocardial infarction, its applicability to reperfused patients in the acute stage has not been established. To investigate whether infarct size could be estimated by the QRS scoring system soon after reperfusion, we evaluated QRS scores obtained serially 6 hours to 1 month after reperfusion, total creatine kinase release, and left ventricular ejection fraction in 126 patients with acute myocardial infarction who underwent successful reperfusion therapy. A significant correlation was observed between the QRS score obtained after 6 hours and that obtained after 1 month (r = .89). The QRS scores obtained after 6 hours and 1 month were significantly correlated with total creatine kinase release (r = -.65 and r = -.75, respectively) and left ventricular ejection fraction (r = .62 and r = .76, respectively). Thus, the QRS scoring system can be used as a simple and economical method for estimation of infarct size soon after reperfusion.

Aged↗
PubMed1997

Pancreatoblastoma.

BACKGROUND: Pancreatoblastoma is a rare pancreatic tumor with distinct acinar and squamoid cell differentiation that generally affects infants and young children. Just over 50 cases have been reported in the literature. METHODS: Five cases of pathologically proven pancreatoblastoma treated at Seoul National University Hospital from 1984 to 1994 were reviewed. There were three girls and two boys who were 2 years to 5 years of age. All cases came to medical attention because of an abdominal mass. RESULTS: Abdominal pain was observed in one case and anorexia, vomiting, and weight loss in one case. There was marked elevation of serum alpha-fetoprotein (27,000 ng/mL) in one case of liver metastases. Complete excision was performed in two cases in which the tumors were located in the tail of the pancreas. Partial excision was performed in two patients who had unresectable tumors of the head of the pancreas. One patient had an unresectable tumor at diagnosis and needle aspiration biopsy was carried out under ultrasound guidance. Electron microscopy was performed on pathological specimens of three cases and showed zymogen granules but not neuroendocrine granules. Immunocytochemical studies for alpha-fetoprotein, insulin, glucagon and somatostatin were performed in one patient, and results were all negative. Of two patients who underwent complete excision, one patient presented with liver metastases 4 months after operation and received chemotherapy, but died of tumor 6 months after operation. The other patient had local recurrence 1 year after operation. Reoperation and chemotherapy were performed, and the child is now alive without evidence of disease for 32 months. All three patients who had unresectable tumor died of tumor despite adjuvant radiotherapy and chemotherapy. CONCLUSIONS: The authors emphasize that the diagnosis of pancreatoblastoma in childhood should be suspected with palpation of an abdominal mass, and the chance for cure may be determined by complete excision of the tumor.

Child, Preschool↗
PubMed1997

Efficacy and safety of 0.3% carbomer gel compared to placebo in patients with moderate-to-severe dry eye syndrome.

PURPOSE: Carbomer gel is a water-soluble polymeric resin that has been reported to maintain the tear film in contact with the eye for an extended period. The efficacy and safety of this new artificial tear were assessed. METHODS: A multicenter, single-masked, randomized, placebo-controlled study was carried out on 123 patients with moderate-to-severe dry eyes. The placebo was a mannitol solution with benzalkonium chloride 0.008% as preservative. Patients were observed over an 8-week period, and subjective and objective changes analyzed, compared to a baseline of no therapy, after 1 to 7 days washout period from previous medication. RESULTS: All primary subjective symptoms decreased significantly in the carbomer gel-treated group compared to the placebo group (i.e., dryness, discomfort, and foreign body sensation). The carbomer gel also significantly improved the rose bengal staining score relative to placebo. When data for the primary subjective efficacy variables were stratified for disease severity, there was a statistically significant improvement from baseline by day 10 for severely affected patients and from day 42 for patients with moderate disease. Secondary subjective symptoms that improved significantly in the tear gel group compared to placebo were photophobia, erythema, tear breakup time, blurry-filmy, dry-sandy sensation, and physician impression. However, no significant improvements in the secondary subjective symptoms of tearing, itching, scaling, conjuctival discharge, palpebral conjunctival redness, bulbar conjuctival redness, conjunctival luster, relief of discomfort, ease of use, and overall acceptability were found in either group over the baseline score. In addition, neither carbomer gel nor placebo improved the baseline fluorescein staining score or the Schirmer test score. Two patients suffered local allergic reactions to the carbomer gel or its preservative, which settled on withdrawal of the medication. CONCLUSIONS: Carbomer gel was more efficacious than was placebo in improving a number of subjective and objective symptoms of moderate-to-severe dry eye syndrome. The results of this study indicate that carbomer gel was a safe as was the placebo.

Acrylic Resins↗
PubMed1997

Identification of cis-regulatory elements in the upstream regulatory region of human papillomavirus type 59.

Human papillomavirus type 59 (HPV-59) was cloned from a vulvar intraepithelial neoplasia and the complete nucleotide sequence was determined. This virus is closely related to HPV-18 and -39 (60% homology in nucleotide sequence) and is grouped with the genital HPV types. In the present paper, we demonstrate that the HPV-59 E2 transactivator represses its E6 promoter-mediated transcription. We have also analyzed cis-regulatory elements in the upstream regulatory region (URR) of HPV-59 using chloramphenicol acetyl transferase assays as well as electrophoresis mobility shift assays (EMSA). The results allow for a subdivision of the HPV-59 URR into three regions of activity: distal (nt 7149-7493), central (nt 7493-7742), and proximal (nt 7742-7748). In particular, the 250 bp (nt 7493-7742) of the central region plays an important role as a constitutive enhancer element for the maximal transcription of the E6 promoter. Our results suggest that the transcription factors AP1, Oct1, SP1 and unidentified factors bind to the HPV-59 E6 promoter region, whereas NF1, GRE and TFIID fail to bind despite the presence of putative binding sites in the DNA sequence.

DNA-Binding Proteins↗
PubMed1997

Early induction of mRNA for calbindin-D28k and BDNF but not NT-3 in rat hippocampus after kainic acid treatment.

The influence of kainic acid (KA), which induces acute seizures, on expression of mRNA for the calcium-binding protein, calbindin-D28k, brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3) and early-response genes [c-fos, zif268 (NGFI-A), nur77 (NGFI-B)] was examined in rat hippocampus by Northern blot analysis. A significant increase (3.2-fold) in BDNF mRNA was observed 1 h after KA injection (12 mg/kg i.p.) and peak expression (9.4-fold) occurred 3 h after KA. The induction of BDNF mRNA was preceded by the induction of c-fos, mRNA (30 min after KA) and was followed by the induction of calbindin-D28k mRNA (3.5-fold 3 h after KA; a maximal response was at 3-6 h after KA). Region-specific changes, analyzed by immunocytochemistry and in situ hybridization, indicated that the most dramatic increases in calbindin protein and mRNA after KA treatment were in the dentate gyrus. Although calbindin-D28k and BDNF mRNAs were induced, a 3.4-3.8-fold decrease in NT-3 mRNA was observed by Northern analysis 3-24 h after KA treatment. Calbindin-D28k gene expression was also examined in rats with a chronic epileptic state characterized by recurrent seizures established with an episode of electrical stimulation-induced status epilepticus (SE). When these animals were examined 30 days post-SE, no changes in hippocampal calbindin-D28k mRNA were observed. Our findings suggest that the induction of calbindin-D28k mRNA (which may be interrelated to the induction of BDNF mRNA) is an early response which may not be related to enhanced neuronal activity or seizures per se, but rather to maintaining neuronal viability.

Animals↗
PubMed1997

On-line medical control versus protocol-based prehospital care.

STUDY OBJECTIVE: To compare on-scene time, appropriateness of therapy, and accuracy of paramedic clinical assessments when prehospital care was provided with the use of on-line medical control (OLMC) by EMS-certified nurses from a single base station or by paramedics using chief complaint-based protocols. METHODS: We assembled a prospective before-and-after series to compare OLMC (phase 1) and protocol (phase 2) care rendered by all paramedics in a single urban municipality using a single base station. The subjects were consecutively enrolled patients who met protocol inclusion criteria and presented with altered level of consciousness, nontraumatic chest pain, or shortness of breath. For both phases, EMS and corresponding ED records were compiled; all references identifying phase were removed. After establishing interrater reliability, we randomly assigned charts to one of two reviewers for scoring. Complaint-specific scoring elements included on-scene time, assessments performed, presence or absence of indications for common treatments, treatments given, paramedic diagnosis, and emergency physician diagnosis. The percentages of inappropriate treatment decisions and paramedic diagnostic accuracy (versus that of the receiving emergency physician) were calculated. RESULTS: Phase 1 comprised 287 patients, phase 2 294. Interrater reliability between the two scorers was high. Of 2,190 elements scored jointly, the raters agreed in 97%, with kappa-values ranging from .6 to 1.0. On-scene time was 1 minute shorter during phase 2 (95% confidence interval [CI] for difference in median time, 0 to 2 minutes; P < .03). From phase 1 to phase 2 (relative risk [RR], 1.5; 95% CI, 1.0 to 2.1), inappropriate treatment decisions decreased from 7.4% to 5.1%. The percentage of cases in which paramedics and physicians were in complete diagnostic agreement was high (77% to 78%) and did not change across phases. CONCLUSION: The use of protocols resulted in small improvements in both on-scene time and the appropriateness of therapeutic decisions, without a change in agreement between paramedic and physician. Protocol care for these three chief complaints is clinically safe and, by reducing training and staffing considerations, may offer a cost-effective alternative to OLMC.

Clinical Protocols↗
PubMed1997

How lay is lay? Chinese students' perceptions of anorexia nervosa in Hong Kong.

Using a locally devised self-report questionnaire that encompassed both professional and lay explanatory models, this study explored the perceptions of anorexia nervosa (AN) in a large sample of 842 Chinese undergraduates who had little biomedical exposure to this rare condition in Hong Kong. Anorexia nervosa, or yan shi zheng, was conceived as a chronic psychiatric condition of severe weight loss (34%) that arose from mixed psychosocial etiologies. Unlike the more exact professional categorizations but consonant with the lexical meanings of yan shi and Chinese anorectic patients' illness reality, appetitive complaints, sadness and fat phobia were believed to be the main expressions of AN. The illness was seen to affect young women of affluent societies, and to call for help from mental health professionals as well as family members. Although it was not stigmatizing, it would nearly never be admired. Factor analysis revealed a discernible resemblance between lay and professional epistemologies, particularly in the configuration of anorexic symptomatology into "specific" (fat phobic) and "general" types. This implies that in psychiatric disease categories with an uncertain etiology and a substantial cultural component, lay people may package and construct knowledge in a fashion similar to that of professionals. The findings of this study question biomedicine's positivistic claim to psychopathology, and suggest that lay and professional ethnopsychiatric theories and lived anorectic experience are interdependent facets of a socially constructed world.

Adult↗
PubMed1997

Stress-wave-induced membrane permeation of red blood cells is facilitated by aquaporins.

Stress waves generated by lasers and extracorporeal lithotripters have been shown to transiently increase the permeability of the plasma membrane, without affecting cell viability. Molecules present in the medium can diffuse into the cytoplasm under the concentration gradient. Molecular uptake under stress waves correlates with the presence of functioning aquaporins in the plasma membrane.

Animals↗
PubMed1997

Visualizing nucleic acids and their complexes using electron microscopy.

Microscopic visualization of nucleic acid-protein complexes provides a means of obtaining structural information that is difficult to obtain in any other way, and of verifying conclusions derived from other approaches. The polymorphic, flexible, and irregular nature of these complexes presents particular problems in their analysis.

DNA↗
PubMed1997

Human CD8+ T cell responses to EBV EBNA1: HLA class I presentation of the (Gly-Ala)-containing protein requires exogenous processing.

Epstein-Barr virus (EBV)-induced cytotoxic T lymphocyte (CTL) responses have been detected against many EBV antigens but not the nuclear antigen EBNA1; this has been attributed to the presence of a glycine-alanine repeat (GAr) domain in the protein. Here we describe the isolation of human CD8+ CTL clones recognizing EBNA1-specific peptides in the context of HLA-B35.01 and HLA-A2.03. Using these clones, we show that full-length EBNA1 is not presented when expressed endogenously in target cells, whereas the GAr-deleted form is presented efficiently. However, when supplied as an exogenous antigen, the full-length protein can be presented on HLA class I molecules by a TAP-independent pathway; this may explain how EBNA1-specific CTLs are primed in vivo.

Alanine↗
PubMed1997

Expression and function of CCR5 and CXCR4 on human Langerhans cells and macrophages: implications for HIV primary infection.

Transmission of HIV-1 is predominantly restricted to macrophage (Mphi)-tropic strains. Langerhans cells (LCs) in mucosal epithelium, as well as macrophages located in the submucosal tissues, may be initial targets for HIV-1. This study was designed to determine whether restricted transmission of HIV-1 correlates with expression and function of HIV-1 co-receptors on LCs and macrophages. Using polyclonal rabbit IgGs specific for the HIV co-receptors cytokines CXCR4 and CCR5, we found that freshly isolated epidermal LCs (resembling resident mucosal LCs) expressed CCR5, but not CXCR, on their surfaces. In concordance with surface expression, fresh LCs fused with Mphi-tropic but not with T-tropic HIV-1 envelopes. However, fresh LCs did contain intracellular CXCR4 protein that was transported to the surface during in vitro culture. Macrophages expressed high levels of both co-receptors on their surfaces, but only CCR5 was functional in a fusion assay. These data provide several possible explanations for the selective transmission of Mphi-tropic HIV variants and for the resistance to infection conferred by the CCR5 deletion.

Amino Acid Sequence↗
PubMed1997

Difference in the expression of Fas/Fas-ligand and the lymphocyte subset reconstitution according to the occurrence of acute GVHD.

Acute graft-versus-host disease (aGVHD) remains a major barrier to a wider application of allogeneic bone marrow transplantation (BMT). Although this complication is mainly dependent on donor-derived T lymphocytes, very little information is available concerning the mechanism of lethality. In this study, we investigated both the expression of Fas/Fas-ligand (FasL) and lymphocyte subset reconstitution in patients who underwent HLA-matched related allogeneic BMT (n = 16) and normal donors (n = 10), and several distinct features were observed. First, the reconstitutions of CD3+ and CD56+ cells were different between the aGVHD+ and aGVHD- group. In particular, the percentage of CD3-CD56+ cells was significantly decreased in patients with aGVHD (P < 0.01). Second, the expansion of CD8+ (P = 0.01) and CD8+ CD28- T cells (P = 0.03) was a characteristic finding in patients with aGVHD. Finally, we found that the percentages of Fas+CD8+, Fas+HLA-DR+ and FasL+ CD8+ cells were significantly increased. Fas antigen was highly coexpressed on most of the lymphocyte subsets, especially on CD8+ cells (P < 0.01), and also, significantly higher coexpression of FasL on CD8+ cells was found in patients with aGVHD (P < 0.01). In summary, an increase in the percentage of CD8+ cells which express Fas and its ligand in patients with aGVHD after BMT points to a possible role for the Fas/FasL pathway in the effector phase of aGVHD.

Acute Disease↗