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Biomedical subjects

Y Chung

Publications and source records attributed to Y Chung.

At least 55 records · Page 3Linked to original sources
PubMed1995

Hypoglossal nerve stimulation affects the pressure-volume behavior of the upper airway.

To determine the effects of electrical hypoglossal nerve and submental stimulation on upper airway collapsibility, we examined the pressure-volume (P-V) relationships during bilateral supramaximal stimulation of the distal cut hypoglossal nerve ends over a range of frequencies from zero to 100 Hz in the sealed upper airway of 10 anesthetized supine dogs. Animals were artificially ventilated with 50% O2 and maintained under relative hyperoxia and hypocapnia during the study to eliminate the ventilatory drive output. Sealed upper airway pressures were obtained during random injections of different volumes of air from zero to 50 ml with and without hypoglossal nerve stimulation, and the upper airway P-V curves were obtained. The characteristics of the P-V curves were as follows: (1) the upper airway compliance defined as the slope of the regression of P-V curves fell from 4.07 +/- 0.33 ml/cm H2O without stimulation to 3.02 +/- 0.30 ml/cm H2O with stimulation at 50 Hz and plateaued at frequencies greater than 50 Hz, and (2) the volume at a given pressure during stimulation was larger than that without stimulation. The effects of submental stimulation on upper airway collapsibility were similar to those of hypoglossal nerve stimulation. These results suggest that the increase of upper airway muscle tone by hypoglossal nerve or submental stimulation stiffens the upper airway and that increases in muscle tone expand the upper airway.

Animals↗
PubMed1995

Randomization model methods for evaluating treatment efficacy in multicenter clinical trials.

This paper studies randomization model methods for analyzing data from a multicenter study comparing the effectiveness of two treatments. The Mantel-Haenszel mean score statistic, which can be used for continuous or ordered categorical response variables, is shown to be a useful nonparametric alternative to standard linear model methods for testing the significance of the average treatment difference. In an extensive simulation study, the mean score test performs nearly as well as the optimal linear model methods when the normal-theory assumptions are satisfied. A related estimator of the average treatment difference is also studied. This estimator, which is a weighted average of the center-specific mean differences, is analogous to the commonly used Mantel-Haenszel estimator of the average odds ratio in stratified 2 x 2 contingency tables. The proposed estimator is equivalent to the fixed-effects analysis of variance estimator from the main effects model, and valid estimation of its variance is feasible under very general assumptions.

Aged↗
PubMed1995

Phase I study of intravenous Lu-labeled CC49 murine monoclonal antibody in patients with advanced adenocarcinoma.

CC49, a murine monoclonal antibody that recognizes the tumor-associated glycoprotein 72, was conjugated to the chemical chelate 1,4,7,10-tetraaza-1-(1-carboxy-3-(4-aminophenyl) propyl)-tris-4,7,10- ((carboxy)methyl)cyclododecane that had been labeled with a beta emitter, Lu. Preclinical studies had shown that Lu-labeled CC49 caused regression of human colon adenocarcinoma xenografts in nude mice. Patients with advanced adenocarcinoma who had failed standard treatment and whose tumors expressed the tumor-associated glycoprotein 72 antigen were eligible for treatment to determine the maximum tolerated dose of Lu-labeled CC49. The starting dose of Lu was 10 mCi/m2 given i.v. with the dose of CC49 held constant at 20 mg. Pharmacokinetic sampling and immunoscintigraphy were performed over the ensuing 3 weeks. The dose of radioactive Lu was escalated by 15 mCi/m2 for each successive dose level. Unexpected bone marrow toxicity developed in patients treated at the second dose level with 25 mCi/m2 Lu; two patients developed grade 4 thrombocytopenia, while the third patient developed grade 3 thrombocytopenia. Pharmacokinetic studies showed that the plasma half-life of the immunoconjugate was 67 h; whole-body retention, however, was prolonged with a biological half-life of 258 h. Serial gamma camera imaging localized known tumor in all patients, and also demonstrated prolonged Lu retention in the reticuloendothelial system (RES). Bone marrow dosimetry estimates ranged from 4 to 5 REMS/mCi Lu based on imaging and biopsy data. Analysis of bone marrow biopsies demonstrated that most of the Lu was localized in the cellular compartment and not in the bone. No antitumor responses were observed. Intravenous administration of 15 mCi/m2 Lu-labeled CC49 to previously treated advanced cancer patients was associated with acceptable hematological toxicity and was the maximum tolerated dose. However, prolonged retention of Lu in the RES, including the bone marrow, was observed and limited the dose of Lu that could be given. Additional studies are indicated to reduce RES uptake and retention of this immunoconjugate.

Adenocarcinoma↗
PubMed1994

Myoglobin signal as an NMR tissue thermometer: implication for hyperthermia treatment of tumors.

Measuring local tissue temperature is critical in establishing a rational approach for hyperthermia treatment of tumors. We have found that the heme signals of myoglobin provide a unique basis for NMR thermometry in vivo. In particular the 5-methyl heme signal of MbCN exhibits a sharp, temperature-dependent resonance that is distinguishable in the tissue spectrum. Its calibrated chemical shift can then reflect the local tissue temperature in vivo.

Animals↗
PubMed1994

Disseminated aspergillosis in a patient with cystic fibrosis and allergic bronchopulmonary aspergillosis.

Allergic bronchopulmonary aspergillosis (ABPA) is a well-known complication of cystic fibrosis (CF), with an estimated incidence of up to 11%. In patients with CF, the diagnosis of ABPA must be based on significant elevation of Aspergillus fumigatus (Af) antibody and total serum IgE, since it is common to already have other clinical and laboratory features of ABPA (Laufer et al., J Allergy Clin Immunol. 1984; 73:44-48). Once ABPA is identified in a patient, institution of corticosteroids is standard therapy. Invasive aspergillosis is a rare occurrence in patients with CF with or without ABPA, and has been reported in only one young adult who did not have ABPA (Giudotti et al., Am J Med Sci. 1982; 283:157-160). We present a case of a 15-year-old male with CF and ABPA who developed disseminated aspergillosis.

Adolescent↗
PubMed1994

1H NMR approach to observe tissue oxygenation with the signals of myoglobin.

The myoglobin technique measures oxygen tension in myocytes. It relies on a quantitative measurement of the Val E11 and His F8 signals and an accurate value for the [O2]50 for Mb. Even though the Mb oxygen affinity in the cell is in question, the NMR results still reflect the degree of Mb oxygen saturation. Although magnetic resonance has established a variety of strategies to measure tissue oxygenation, the Mb approach is the most direct and will lead to a better understanding of oxygen's role in regulating cellular activity.

Animals↗
PubMed1994

The effect of radiation therapy on immune function in patients with squamous cell lung carcinoma.

The immune response is impaired in patients with malignancy, and radiation therapy (RT) can exacerbate the cancer induced-attenuation of immune response. In order to search for the fine mechanisms behind the RT-induced attenuation of cell-mediated immune response, we measured the number of lymphocytes in peripheral blood, its subsets, and lymphoblast transformation induced by phytohemagglutinin (PHA), purified protein derivatives (PPD), mitogenic monoclonal antibody anti-CD3, and mitogenic combination of anti-CD2 antibodies 9-1 and 9.6 before and after RT in 19 patients with squamous cell lung cancer. Radiation therapy significantly decreased the total numbers of lymphocytes, CD-3, CD-4, and CD8-positive lymphocytes in peripheral blood. However, RT did not change the percentages of lymphocytes and its subsets. Radiation therapy increased the percentage of interleukin 2 (IL-2) receptor-positive lymphocytes, and RT significantly decreased in vitro lymphoblast transformation by PHA, PPD, or monoclonal antibodies to T-cell surface antigens (anti-CD2 or anti-CD3). In vitro incubation with IL-2 did not increase lymphoblast transformation by anti-CD3 before RT but significantly increased after RT. In conclusion, we suggest that one of the fine mechanisms behind the RT-induced suppression of immune responsiveness of patients with lung cancer is a defect in IL-2 synthesis by lymphocytes.

Adult↗
PubMed1994

The clearance rate of alveolar epithelium using 99mTc-DTPA in patients with diffuse infiltrative lung diseases.

The early diagnosis of diffuse infiltrative lung disease (DILD) is important in prognosis and it is necessary to develop a noninvasive, inexpensive, and rapid diagnostic tool for suspected cases of DILD. Thus, we measured the epithelial permeability via radioisotope (99mTc-DTPA) in 22 patients with DILD for clinical application of the clearance rate (T1/2LB) of radioisotope on the early diagnosis of DILD. We divided the patients with DILD into the early and late stages according to the derangements of the diffusion capacity for carbon monoxide. The T1/2LB in patients with DILD were significantly shorter when compared with those with normal control in all lobes. However, 40 to 58 percent of T1/2LB in patients with DILD overlapped normal values (2 SDs of mean of T1/2LB of normal control) dependent on specific lung regions. The T1/2LB of patients with early-stage DILD was longer than that of patients with late-stage DILD in right upper and middle lobes. Although T1/2LB of 99mTc-DTPA, the index of alveolar epithelial permeability, was shortened in patients with DILD with normal diffusing capacity, it was difficult to detect early-stage DILD by measuring alveolar epithelial permeability because of many overlaps of T1/2LB between early-stage DILD and normal control.

Adult↗
PubMed1994

Determinations of personal carbon monoxide exposure and blood carboxyhemoglobin levels in Korea.

Determinant factors for personal carbon monoxide (CO) exposures were sought in Korea, where CO poisoning has been a major public health problem due to coal briquette (Yeontan) combustion for space heating and cooking. Personal 24-hr CO exposures of 15 housewives were measured by CO passive samplers on 2 days of the week (Wednesday and Sunday). Blood samples were taken to measure carboxyhemoglobin (COHb) just after the exposure sampling. Average CO exposure and COHb level were 5.6 ppm and 2.4%, respectively. Personal CO exposures as well as COHb levels were significantly increased by the use of Yeontan, especially on a weekday. Carboxyhemoglobin levels were closely related to the time between blood collection and replacement of Yeontan: the closer the blood collection was to replace Yeontan, the higher the COHb levels were. Assuming a background COHb of 1.34%, COHb increased on average by 1.8% with a 24-hr personal CO exposure of 10 ppm. The relationship between CO exposure and COHb level was provided by simultaneous direct measurements in real environment, although a measurement of COHb at the end of exposure could not represent previous 24-hr exposure thoroughly.

Adult↗
PubMed1993

H-NMR characterization of the human myocardium myoglobin and erythrocyte hemoglobin signals.

The 1H-NMR signal of deoxy Mb provides a unique opportunity to measure tissue oxygenation in vivo. To utilize the technique for human application, however, requires a specific spectral characterization of both human Mb and erythrocyte Hb. We report that the proximal histidyl-NH signal of human deoxy Mb resonates at 80.3 ppm at 25 degrees C and maintains a 3.9 ppm separation with the corresponding Hb A signal throughout the physiological temperature range. In the particular case of the human thenar muscle, the deoxy Mb signal is clearly detectable without any interference from Hb.

Animals↗
PubMed1993

Experimental brain stem surgery.

Few models of experimental brain stem surgery exist in the literature. Often, experiments were devised in the animal laboratory after a similar surgical procedure already had been attempted on human subjects. Many of the experiments referenced in this article were performed with the goal of delineating neuroanatomic or neurophysiologic pathways, and then this information was used to develop new techniques in the clinical arena, such as BAERs. A new model for brain stem hemorrhage is presented in this article as well as a comparison of the outcomes of open surgical evacuation, stereotactic aspiration, and control animals with pontine hemorrhages.

Animals↗
PubMed1992

1H NMR observation of redox potential in liver.

1H NMR spectral editing techniques can select the distinct signals of lactate, pyruvate, beta-hydroxybutyrate, and acetoacetate and provide a unique way to monitor the biochemical processes in vivo. These metabolite levels reflect the near-equilibrium dehydrogenase activity and therefore the cellular redox state. The quantitative comparison between the 1H NMR and biochemical assay data is in excellent agreement. Lactate/pyruvate and beta-hydroxybutyrate/acetoacetate ratios, obtained from normalized 1H NMR spectra, respond directly to changes in the cytosolic and mitochondrial redox states. Because NMR is noninvasive, our results set the groundwork for implementing these techniques to observe tissue redox states in vivo.

3-Hydroxybutyric Acid↗
PubMed1992

Phase I study of continuous-infusion soluble CD4 as a single agent and in combination with oral dideoxyinosine therapy in children with symptomatic human immunodeficiency virus infection.

To determine the safety and pharmacokinetics of recombinant soluble CD4 (sCD4) administered by continuous intravenous infusion to children with symptomatic human immunodeficiency virus type 1 infection, we conducted a phase I study at the National Cancer Institute. Three dose levels of sCD4 were evaluated: 100, 300, and 1000 micrograms/kg per day. After an initial 12 weeks of treatment with sCD4 alone, dideoxyinosine at a dose of 90 mg/m2 every 8 hours was added and subjects were observed for an additional 12 weeks. Combination therapy was continued in patients in whom it was well tolerated. In addition to toxicity and pharmacokinetic monitoring, surrogate markers of antiviral activity were evaluated. Eleven children were enrolled in the study. During the 12 weeks of treatment with sCD4 alone, and during subsequent sCD4 plus dideoxyinosine combination therapy, no significant toxic reaction attributable to sCD4 or dideoxyinosine was encountered. Low-level anti-CD4 antibodies developed in two patients. Steady-state sCD4 levels increased proportionately at higher doses. The CD4 cell counts and serum p24 antigen levels did not provide evidence of antiviral activity. We conclude that sCD4 was well tolerated at doses up to 1000 micrograms/kg per day when administered by continuous intravenous infusion; however, evidence of in vivo antiviral activity was not observed in this study.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Injection sites utilized for DPT immunizations in infants.

The purpose of this investigation was to determine the site utilized by nurses for administering Diphtheria and Tetanus Toxoids and Pertussis (DPT) injections to infants under 7 months of age. Twenty-six of the 28 agencies identified in a metropolitan area as administering DPT injections chose to participate in the study. Those individuals administering DPT injections in the agencies completed a questionnaire with a return rate of 69% (n = 55). Forty-four participants indicated that they used the anterolateral thigh, the recommended site, 100% of the time. The participants in the study administered a total of 1,453 DPT injections per month. Eighty-seven percent of those injections were administered in the anterolateral thigh, 3.6% were given in the deltoid, 5.1% were given in the dorsal gluteal, and 4% were given in the ventrogluteal. The estimated proportion of DPT injections administered at the correct site was 84.65% which is much lower than the critical value 94.06% for alpha = .05 (p less than .00001).

Diphtheria-Tetanus-Pertussis Vaccine↗
PubMed1991

Leg pain in the rural Iowa 65+ population. Prevalence, related factors, and association with functional status.

Research tabulating the existence and effects of pain and related factors in the elderly is lacking, in spite of the continued growth of the aged population. Leg pain, in particular, may interfere with activities and interpersonal interactions. This study of 3,097 rural elderly examines the prevalence of complaints of leg pain and related factors in a geographically-defined population. Findings indicate that leg pain is clearly a common experience which impacts daily activities of the elderly.

Age Factors↗