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Biomedical subjects

G Yoon

Publications and source records attributed to G Yoon.

At least 19 recordsLinked to original sources
PubMed2006

Speech and language delay are early manifestations of juvenile-onset Huntington disease.

The neurocognitive features of juvenile-onset Huntington disease (HD) are not well understood. We present three patients with onset of HD symptoms before age 10 years in whom speech delay was the first symptom. Speech delay predated motor symptoms by at least 2 years, and language function was consistently impaired on formal testing. Screening for speech delay is particularly important in children with a family history of HD.

Child↗
PubMed2006

Andersen-Tawil syndrome: definition of a neurocognitive phenotype.

BACKGROUND: The Andersen-Tawil syndrome (ATS) is a potassium ion channelopathy caused by mutations in the KCNJ2 gene. It is characterized by periodic paralysis, cardiac arrhythmias, and distinctive features; the effect of KCNJ2 mutations on the CNS has never been studied. OBJECTIVE: To define a potential CNS phenotype in ATS using standardized methods. METHODS: Ten subjects with KCNJ2 mutations and their unaffected siblings were evaluated at the University of California San Francisco General Clinical Research Center. A comprehensive battery of neurocognitive tests was administered to ATS subjects and their unaffected siblings, followed by pairwise analysis of the resultant differences in scores. An EEG was obtained for all ATS subjects. RESULTS: There was no EEG evidence of subclinical seizure activity in any subject. ATS subjects universally had more school difficulties than their siblings, despite similar IQ between the two groups. On formal neurocognitive testing, there was no difference between ATS subjects and their siblings on tests of verbal and visual memory. Assessment of executive functioning revealed ATS subjects scored 1.93 points lower than their siblings on tests of Design Fluency (95% CI -3.46, 0.01; p = 0.052) and made 1.9 more errors (95% CI 0.46, 2.54; p = 0.005). Subjects with ATS scored an average of 5 points lower than their siblings on tests of matrix reasoning (95% CI -8.67, -1.33; p = 0.008). On tests of general ability, ATS subjects achieved much lower scores than their siblings, with an average difference of 9.13 points for reading (95% CI -12.46, 3.21; p = 0.056) and 23.4 points for mathematics (95% CI -42.53, -4.22; p = 0.017). CONCLUSION: Mutations in KCNJ2 are associated with a distinct neurocognitive phenotype, characterized by deficits in executive function and abstract reasoning.

Adolescent↗
PubMed2006

Mitochondria are impaired in the adipocytes of type 2 diabetic mice.

AIMS/HYPOTHESIS: The aim of this study was to confirm a link between mitochondrial dysfunction and type 2 diabetes. MATERIALS AND METHODS: Cellular levels of mitochondrial proteins, cellular mitochondrial DNA content, and mitochondrial function and morphology were assessed by MitoTracker staining and electron microscopy, in white adipose tissue of 12-week-old male wild-type, obese (ob/ob), and diabetic (db/db) mice. RESULTS: Levels of mitochondrial proteins were found to be very similar in the livers and muscles of all the mice studied. However, levels were greatly decreased in the adipocytes of db/db mice, but not in those of the wild-type and ob/ob mice. Levels of mitochondrial DNA were also found to be considerably reduced in the adipocytes of db/db mice. MitoTracker staining and under electron microscopy revealed that the number of mitochondria was reduced in adipocytes of db/db mice. Respiration and fatty acid oxidation studies indicated mitochondrial dysfunction in adipocytes of db/db mice. Interestingly, there was an increase in mitochondria and mitochondrial protein production in adipocytes of db/db mice treated with rosiglitazone, an agent that enhances insulin sensitivity. CONCLUSIONS/INTERPRETATION: Taken together, these data indicate that mitochondrial loss in adipose tissue is correlated with the development of type 2 diabetes.

Adipocytes↗
PubMed2006

Andersen-Tawil syndrome: prospective cohort analysis and expansion of the phenotype.

Andersen-Tawil syndrome (ATS) is an autosomal dominant multisystem disorder characterized by developmental, cardiac, and neuromuscular abnormalities. Approximately 70% of patients have mutations in KCNJ2, resulting in dysfunction of the inward-rectifying potassium channel Kir2.1. Variable expression complicates the diagnosis of ATS, which in many cases, is not made until years after the first recognized symptom. To better define the distinctive clinical features of ATS and facilitate earlier diagnosis, we conducted a prospective, standardized evaluation of 10 subjects with confirmed KCNJ2 mutations. Detailed anthropometric, neurological, and cardiac evaluations were performed. Using this approach, we identified novel skeletal and dental findings and proposed additional diagnostic criteria for ATS dysmorphology.

Abnormalities, Multiple↗
PubMed2005

Robust design of finger probe in non-invasive total haemoglobin monitor.

The development of a non-invasive monitor of total haemoglobin has been reported previously. The paper presents the design and testing of a finger probe used in that optical haemoglobin monitor. When a finger is inserted into the probe, light is radiated onto the nail, and a silicon detector measures transmitted light. This finger probe can have different values or settings for design parameters such as the internal colour, detector area, the emission area of a light source and the distance between the light source and detector. Design of experiment (DOE) was introduced to select the best combination of design parameters that were robust to external conditions such as finger alignment and ambient light. An optimally designed finger probe from DOE analysis, compared with the initial design, increased the correlation coefficient from 0.696 to 0.869 and improved the standard deviation from 1.18 to 0.81 g dl(-1) in predicting total haemoglobin. This was under different conditions of finger-probe alignment. Under different ambient light conditions, the optimum design improved the correlation coefficient from 0.735 to 0.870 and reduced the standard deviation from 1.14 to 0.83 g dl(-1).

Equipment Design↗
PubMed2004

Experimental investigation of the mammary gland tumour phantom for multifrequency microwave radio-thermometers.

Microwave radiometry is a spectral measurement technique for resolving the electromagnetic radiation of matter when its temperature is above absolute zero. The radio-thermometer utilises this technique and consequently can provide temperature distributions in subcutaneous biological tissues. A new phantom was proposed that imitates a mammary gland tumour, and the brightness temperature was observed using radio-thermometers operated at different frequencies, 1.75GHz and 3GHz. The proposed phantom, simulating heat diffusion propagated by tissues around real tumours, revealed that the thermal characteristics of the tumour imitator were well matched to the heat transfer properties of a real tumour and a proportional linear relationship between the location of the tumour imitator and the brightness temperature in a homogenous medium was established. From experiments using the proposed mammary gland tumour phantom and a clinical trial on patients with breast cancer, it could be concluded that a radio-thermometer with a short wavelength (lambda = 10cm, i.e. f= 3GHz) is useful to resolve a thermal anomaly at a shallow depth in an homogenous medium such as a breast.

Adult↗
PubMed2001

Activated ras oncogene collaborates with HBx gene of hepatitis B virus to transform cells by suppressing HBx-mediated apoptosis.

The hepatitis B virus HBx protein is a promiscuous transactivator implicated in the development of hepatocellular carcinoma. The ectopic expression of HBx fails to transform both primary and immortalized rodent cells, but rather induces apoptosis. Furthermore, most transgenic mice harboring HBx do not develop liver tumors. Thus, it remains unclear whether and how HBx contributes to oncogenesis. Here, we show that HBx collaborates with activated H-ras to transform immortalized rodent cells. Indeed, REF52 cells transfected by both HBx and activated H-ras were morphologically transformed and were able to grow in soft agar. Remarkably, nude mice injected with REF52 cells transfected by both HBx and activated H-ras developed tumors, whereas the mice injected with REF52 cells transfected by either gene alone did not. Thus, we concluded that HBx could contribute to neoplastic transformation of cells in collaboration with other oncogenes, such as H-ras, that renders cells to overcome the HBx-mediated apoptosis. Further, we found that HBx mediated apoptosis was suppressed by activated H-ras through activation of the phosphatidylinositol-3 kinase and Akt pathway. Data presented here firmly established the oncogenic potential of HBx during multistage carcinogenesis. Oncogene (2001) 20, 16 - 23.

3T3 Cells↗
PubMed2001

Selective left-lobe atrophy by nodularin treatment accompanied by reduced protein phosphatase 1/2A and increased peroxisome proliferation in rat liver.

The effect of nodularin on selective atrophy of left lobes in the liver was investigated in F344 rats. Nodularin was injected for 10 weeks from the third week of initiation with saline or N-nitrosodiethylamine (DEN), grouped as S/N and D/N, respectively. Nodularin significantly decreased weights of left (LL) and caudate (CL) lobes but increased right (RL) and middle (ML) lobes in S/N rats. Activity of protein phosphatases [types 1 (PPI) and 2A (PP2A)] was more severely reduced in S/N than D/N rats; moreover, in LL compared with RL of S/N rats, activity was significantly inhibited by nodularin treatment from week 4, which corresponded to 2 weeks after nodularin injection. However, nodularin significantly induced peroxisomal palmitoyl-CoA oxidase and cytochrome P-450 4A1 expression in S/N compared with D/N rats. An effect of nodularin on apoptosis was evident since expression of Bcl-Xs was clearly induced in LL of S/N rats as opposed to various inductions of Bcl-XL. However, Bcl-XL in RL was persistently induced, with undetectable Bcl-Xs expression. These results demonstrate biochemical evidence of selective atrophy of LL by inhibition of PP1 and PP2A activity, increase of peroxisomal enzymes and induction of Bcl-Xs expression, in contrast to proliferation of RL in rats treated with nodularin alone. However, nodularin endowed DEN-altered hepatocytes with regenerating power and concomitant restoration of phosphatase activity as well as persistent expression of Bcl-XL in D/N rats.

Alkylating Agents↗
PubMed2001

Association between congenital foot anomalies and gestational age at amniocentesis.

OBJECTIVES: Our objectives were to confirm the reported association between early amniocentesis and congenital foot anomalies as well as to report, for the first time, on the outcome of amniocenteses performed during the 13th and 14th weeks of gestation. METHODS: We conducted a triple cohort retrospective study of 4457 amniocenteses. Cohort definitions: early amniocentesis (EA), 11 weeks and 0/7 days to 12 weeks to 6/7 days; early midtrimester amniocentesis (EMA), 13 weeks and 0/7 days to 14 weeks and 6/7 days; and midtrimester amniocentesis (MA), 15 weeks and 0/7 days to 19 weeks and 6/7 days. Outcome measures were obtained by searching the Alberta Congenital Anomalies Surveillance System (ACASS) database for children born with foot anomalies represented by International Classification of Diseases version 9 (ICD-9) codes 754.5, 754.6 and 754.7. RESULTS: Incidences of congenital foot anomalies were: EA 11/980 (1.1%), EMA 11/2515 (0.4%), and MA 1/962 (0.1%). There is a significant difference between the EA and EMA cohorts (p=0.019) and between the EA and MA cohorts (p=0.003); however, these data suggest there is no difference between EMA and MA cohorts (p=0.11). CONCLUSIONS: Our incidence of congenital foot anomalies of 1.1% for women who underwent EA is similar to previously reported data, which further validates this association; however, our data also suggest that the foot anomaly risk may be limited to amniocenteses performed before the 13th week of gestation.

Amniocentesis↗
PubMed2001

Translocational inefficiency of intracellular proteins in senescence of human diploid fibroblasts.

In order to investigate signal transduction pathways and related changes of actin cytoskeleton organization in cellular senescence, H-ras double mutants--V12S35, V12G37, and V12C40--were constitutively expressed in human foreskin fibroblast (HDF). Senescent HDF cells as well as the H-ras mutant expressers accumulated p-Erk1/2 in the cytoplasm with increased MEK activity and failed to translocate it to nuclei on EGF stimulation. Senescent HDF cells, V12S35 and V12G37 expressers, revealed a failure to export actin fiber from nucleus to cytoplasm and also to form stress fibers. Perinuclear expression of Rac1 was prominent in the HDF cells and V12C40 expresser; however, in the V12S35 expresser, translocation of Rac1 from perinucleus to nucleus and strong expression of RhoA were obvious. In summary, the H-ras double mutant expressers induced premature senescence through the MEK pathway, accompanied by nuclear accumulation of actin and Rac1 proteins, cytoplasmic retention of p-Erk1/2, and marked induction of RhoA expression, suggesting the translocational inefficiency of the intracellular proteins in the senescent HDF cells.

3T3 Cells↗
PubMed2001

Data preprocessing and partial least squares regression analysis for reagentless determination of hemoglobin concentrations using conventional and total transmission spectroscopy.

Visible-near infrared spectroscopy was successfully used for the determination of total hemoglobin concentration in whole blood. Absorption spectra of whole blood samples, whose hemoglobin concentrations ranged between 6.6 and 17.2 g/dL, were measured from 500 to 800 nm. Two different types of transmission were measured: conventional transmission spectroscopy which collected primarily collimated radiation transmitted through the sample, and total transmission spectroscopy which used an integrating sphere to collect all scattered light as well. Different preprocessing techniques in conjunction with a partial least squares regression calibration model to predict hemoglobin concentrations were applied to the above two types of transmission. Depending on different preprocessing methods, the standard error of predictions ranged from 0.37 to 2.67 g/dL. Mean centering gave the most accurate prediction in our particular data set. Preprocessing methods designed for compensation of the scattering effect produced the worst results contrary to expectations. For univariate analysis, better prediction was achieved by total transmission measurement than by conventional transmission measurement. No significant difference was observed for multivariate analysis on the other hand. Careful selection of the data preprocessing methods and of the multivariate statistical model is required for reagentless determination of hemoglobin concentration in whole blood.

Hemoglobins↗
PubMed2000

Cytoplasmic retention of p-Erk1/2 and nuclear accumulation of actin proteins during cellular senescence in human diploid fibroblasts.

In order to investigate the role of signal transduction and the related changes of actin cytoskeleton organization in the process of cellular senescence, H-ras double mutants--V12S35, V12G37 and V12C40--proteins were expressed constitutively in human diploid fibroblast (HDF) cells by retrovirus infection at PD26. Constitutive expression of V12S35, V12G37 and V12C40 proteins induced premature senescence at PD38, PD47 and PD50, respectively, in contrast to the control cells at PD59. Premature senescence was evidenced by the slow cellular growth rate and SA-beta-galactosidase expression accompanied by morphological changes such as flat and large cell shape. Senescent HDF cells as well as the H-ras mutant expressers accumulated p-Erk1/2 in the cytoplasm with increased MEK activity and failed to translocate it to nuclei on EGF stimulation. Senescent HDF cells as well as V12S35 and V12G37 expressers were unable to export actin fibers from nucleus to cytoplasm, form stress fibers through the MAPK and Ral.GDS pathways. Perinuclear expression of Racl was prominent in the HDF cells and V12C40 expresser, while translocation of Racl from perinucleus to nucleus and strong expression of RhoA were observed in the V12S35 expresser. In summary, the induced premature senescence by H-ras double mutants were accompanied by nuclear accumulation of actin and Racl proteins, cytoplasmic retention of p-Erk1/2 and marked induction of RhoA expression mainly through dysregulation of the MEK pathway.

Actins↗
PubMed2000

The Spanish version of the quality of life index: presentation and validation.

Latino or Spanish-speaking individuals constitute a substantial and growing population in the United States, in addition to their general presence, with cultural variations, throughout Latin America and the Iberian Peninsula. To respond to the needs of this population, a Spanish version of the Quality of Life Index (QLI-Sp) was developed. The QLI, in its various language versions, is a concise instrument for comprehensive, culture-informed, and self-rated assessment of health-rated quality of life. It is composed of 10 dimensions collated from the international literature, including aspects ranging from physical well-being to spiritual fulfillment, as well as a global perception of quality of life. Each item is to be rated on a 10-point line by Latino subjects according to their culture-informed understanding of that concept. The study samples included 60 Latino psychiatric patients (20 outpatient, 20 inpatient, and 20 partial hospitalization) and 20 Latino actively working hospital professionals. Mean time of completion was 2.4 minutes among health professionals and 3.6 minutes among patients. The vast majority of respondents (72% of patients and 1000% of professionals) judged the instrument as easy to use. The test-retest reliability correlation coefficient of the QLI-Sp mean score was .89. The discriminant validity of the QLI-Sp was documented by the highly significant difference obtained between the mean scores of the two samples selected to represent quite different levels of quality of life.

Adult↗
PubMed1995

Understanding aging in Korea.

"This study discusses demographic trends, sociocultural characteristics, and policy choices of aging in [South] Korea.... Although the proportion of the elderly was not so high as to worry about aging before 1990, it is projected that one in eight Koreans will be aged 65 or more in 2020. Because the care for the elderly is mostly expected to be provided by each family, not by the state or Korean society, the role of the family is pivotal in coping with [the] aging problem.... Although adult children currently understand that their aged parents need assistance and support from them, they want to solve the issue of support for the elderly in a way different from the traditional.... This paper examines how the changing attitude toward the old is reflected in family life in terms of living arrangement and physical contacts. This paper also describes and discusses the current situation of various welfare policies on the elderly in Korea."

Age Distribution↗
PubMed1991

Application of charge-coupled device technology for measurement of laser light and fluorescence distribution in tumors for photodynamic therapy.

Laser and fluorescence light distributions with applications for photodynamic therapy were measured in mouse tumors using a non-invasive electronic optical imaging system. The system consists of a liquid-nitrogen-cooled, charge-coupled-device (CCD) array camera under computer control with 576 x 384 detection elements having dimensions of 23 microns x 23 microns. The available dynamic range of the array is approx. 10(3), and the effective wavelength range is 400-1000 nm. An interstitially placed cylindrical diffusing optical fiber was used to provide tumor illumination. The light distribution pattern from the fiber was determined by immersing the cylindrical diffusing tip in a fluorescing solution and recording the emission image. Fluorescence imaging facilitates an accurate measurement of light intensity distribution while avoiding problems associated with the directional nature of other detection methods used with diffusing fibers. Radiation-induced fibrosarcoma tumors on C3H mice were grown to about 1 cm diameter for in vivo recording of light distribution from the tumor volume and for determination of effective light penetration distance at 18 wavelengths in the range 458-995 nm. Endogenous tumor fluorescence and Photofrin II fluorescence intensity were measured over the wavelength range 585-725 nm to investigate the possible application of CCD imaging technology for drug distribution measurements. Model experiments were begun to evaluate the relative importance of potential distortions of light distribution measurements using this approach.

Animals↗
PubMed1989

Heat generation in laser irradiated tissue.

Many medical applications involving lasers rely upon the generation of heat within the tissue for the desired therapeutic effect. Determination of the absorbed light energy in tissue is difficult in many cases. Although UV wavelengths of the excimer laser and 10.6 microns wavelength of the CO2 laser are absorbed within the first 20 microns of soft tissue, visible and near infrared wavelengths are scattered as well as absorbed. Typically, multiple scattering is a significant factor in the distribution of light in tissue and the resulting heat source term. An improved model is presented for estimating heat generation due to the absorption of a collimated (axisymmetric) laser beam and scattered light at each point r and z in tissue. Heat generated within tissue is a function of the laser power, the shape and size of the incident beam and the optical properties of the tissue at the irradiation wavelength. Key to the calculation of heat source strength is accurate estimation of the light distribution. Methods for experimentally determining the optical parameters of tissue are discussed in the context of the improved model.

Hot Temperature↗
PubMed1987

Practical models for light distribution in laser-irradiated tissue.

The distribution of light in laser-irradiated biological medium is computed using four different procedures. Values computed with Beer's law of attenuation, Kubelka-Munk theory, the diffusion approximation, and a seven-flux model are compared. The proper conditions for using each model are discussed.

Humans↗