Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Karen Y. Oh is active.

Publication


Featured researches published by Karen Y. Oh.


Endocrinology | 2011

Maternal high-fat diet disturbs uteroplacental hemodynamics and increases the frequency of stillbirth in a nonhuman primate model of excess nutrition

Antonio Frias; Terry K. Morgan; Anne E. Evans; Juha Rasanen; Karen Y. Oh; Kent L. Thornburg; Kevin L. Grove

Prepregnancy maternal obesity confers an increased risk of stillbirth, but the mechanisms are unknown. Maternal obesity is associated with placental inflammation. We considered that maternal diet may predispose to the increased risk of placental inflammation and stillbirth. We hypothesized that a chronic high-fat diet (HFD) is associated with abnormal uteroplacental circulation and placental inflammation. Here we used a nonhuman primate model to determine the effect of chronic HFD on the uterine and placental hemodynamics, placental histology, and inflammation in a prospective, observational study of 24 Japanese macaques. Overall, there was a statistically significant (38-56%) reduction in uterine volume blood flow from HFD animals, whether they were lean or obese. Consumption of a HFD, independent of obesity, increased placental inflammatory cytokines and the expression of Toll-like receptor 4. We show that HFD consumption by obese mothers with hyperinsulinemia also reduced volume blood flow on the fetal side of the placenta and significantly increased the frequency of both placental infarctions and stillbirth. These results suggest that a HFD, independent of obesity, decreases uterine volume blood flow. Maternal obesity and insulin resistance further exacerbates the placental dysfunction and results in an increased frequency of stillbirth.


Journal of Magnetic Resonance Imaging | 2010

Pharmacokinetic Mapping for Lesion Classification in Dynamic Breast MRI

Matthias C. Schabel; Glen Morrell; Karen Y. Oh; Cheryl A. Walczak; R. Brad Barlow; Leigh Neumayer

To prospectively investigate whether a rapid dynamic MRI protocol, in conjunction with pharmacokinetic modeling, could provide diagnostically useful information for discriminating biopsy‐proven benign lesions from malignancies.


NMR in Biomedicine | 2014

Intratumor mapping of intracellular water lifetime: metabolic images of breast cancer?

Charles S. Springer; Xin Li; Luminita A. Tudorica; Karen Y. Oh; Nicole Roy; Stephen Y. Chui; Arpana Naik; Megan L. Holtorf; Aneela Afzal; William D. Rooney; Wei Huang

Shutter‐speed pharmacokinetic analysis of dynamic‐contrast‐enhanced (DCE)‐MRI data allows evaluation of equilibrium inter‐compartmental water interchange kinetics. The process measured here – transcytolemmal water exchange – is characterized by the mean intracellular water molecule lifetime (τi). The τi biomarker is a true intensive property not accessible by any formulation of the tracer pharmacokinetic paradigm, which inherently assumes it is effectively zero when applied to DCE‐MRI. We present population‐averaged in vivo human breast whole tumor τi changes induced by therapy, along with those of other pharmacokinetic parameters. In responding patients, the DCE parameters change significantly after only one neoadjuvant chemotherapy cycle: while Ktrans (measuring mostly contrast agent (CA) extravasation) and kep (CA intravasation rate constant) decrease, τi increases. However, high‐resolution, (1 mm)2, parametric maps exhibit significant intratumor heterogeneity, which is lost by averaging. A typical 400 ms τi value means a trans‐membrane water cycling flux of 1013 H2O molecules s−1/cell for a 12 µm diameter cell. Analyses of intratumor variations (and therapy‐induced changes) of τi in combination with concomitant changes of ve (extracellular volume fraction) indicate that the former are dominated by alterations of the equilibrium cell membrane water permeability coefficient, PW, not of cell size. These can be interpreted in light of literature results showing that τi changes are dominated by a PW(active) component that reciprocally reflects the membrane driving P‐type ATPase ion pump turnover. For mammalian cells, this is the Na+,K+‐ATPase pump. These results promise the potential to discriminate metabolic and microenvironmental states of regions within tumors in vivo, and their changes with therapy.


Magnetic Resonance in Medicine | 2015

Using dynamic contrast-enhanced MRI to quantitatively characterize maternal vascular organization in the primate placenta

Antonio Frias; Matthias C. Schabel; Victoria H. J. Roberts; Alina Tudorica; Peta L. Grigsby; Karen Y. Oh; Christopher D. Kroenke

The maternal microvasculature of the primate placenta is organized into 10–20 perfusion domains that are functionally optimized to facilitate nutrient exchange to support fetal growth. This study describes a dynamic contrast‐enhanced magnetic resonance imaging method for identifying vascular domains and quantifying maternal blood flow in them.


Translational Oncology | 2016

Early Prediction and Evaluation of Breast Cancer Response to Neoadjuvant Chemotherapy Using Quantitative DCE-MRI

Alina Tudorica; Karen Y. Oh; Stephen Y. Chui; Nicole Roy; Megan L. Troxell; Arpana Naik; Kathleen A. Kemmer; Yiyi Chen; Megan L. Holtorf; Aneela Afzal; Charles S. Springer; Xin Li; Wei Huang

The purpose is to compare quantitative dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) metrics with imaging tumor size for early prediction of breast cancer response to neoadjuvant chemotherapy (NACT) and evaluation of residual cancer burden (RCB). Twenty-eight patients with 29 primary breast tumors underwent DCE-MRI exams before, after one cycle of, at midpoint of, and after NACT. MRI tumor size in the longest diameter (LD) was measured according to the RECIST (Response Evaluation Criteria In Solid Tumors) guidelines. Pharmacokinetic analyses of DCE-MRI data were performed with the standard Tofts and Shutter-Speed models (TM and SSM). After one NACT cycle the percent changes of DCE-MRI parameters Ktrans (contrast agent plasma/interstitium transfer rate constant), ve (extravascular and extracellular volume fraction), kep (intravasation rate constant), and SSM-unique τi (mean intracellular water lifetime) are good to excellent early predictors of pathologic complete response (pCR) vs. non-pCR, with univariate logistic regression C statistics value in the range of 0.804 to 0.967. ve values after one cycle and at NACT midpoint are also good predictors of response, with C ranging 0.845 to 0.897. However, RECIST LD changes are poor predictors with C = 0.609 and 0.673, respectively. Post-NACT Ktrans, τi, and RECIST LD show statistically significant (P < .05) correlations with RCB. The performances of TM and SSM analyses for early prediction of response and RCB evaluation are comparable. In conclusion, quantitative DCE-MRI parameters are superior to imaging tumor size for early prediction of therapy response. Both TM and SSM analyses are effective for therapy response evaluation. However, the τi parameter derived only with SSM analysis allows the unique opportunity to potentially quantify therapy-induced changes in tumor energetic metabolism.


Radiology | 2015

Gadolinium Chelate Contrast Material in Pregnancy: Fetal Biodistribution in the Nonhuman Primate

Karen Y. Oh; Victoria H. J. Roberts; Matthias C. Schabel; Kevin L. Grove; Mark Woods; Antonio Frias

PURPOSE To determine the extent to which gadolinium chelate is found in nonhuman primate fetal tissues and amniotic fluid at 19-45 hours after intravenous injection of a weight-appropriate maternal dose of the contrast agent gadoteridol. MATERIALS AND METHODS Gravid Japanese macaques (n = 14) were maintained as approved by the institutional animal care and utilization committee. In the 3rd trimester of pregnancy, the macaques were injected with gadoteridol (0.1 mmol per kilogram of maternal weight). Fetuses were delivered by means of cesarean section within 24 hours of maternal injection (range, 19-21 hours; n = 11) or 45 hours after injection (n = 3). Gadolinium chelate levels in the placenta, fetal tissues, and amniotic fluid were obtained by using inductively coupled plasma mass spectrometry. The Wilcoxon rank sum test was used for quantitative comparisons. RESULTS Gadoteridol was present in the fetoplacental circulation at much lower quantities than in the mother. At both time points, the distribution of gadolinium chelate in the fetus was comparable to that expected in an adult. The highest concentration of the injected dose (ID) was found in the fetal kidney (0.0161% ID per gram in the 19-21-hour group). The majority of the in utero gadolinium chelate was found in the amniotic fluid and the placenta (mean, 0.1361% ID per organ ± 0.076 [standard deviation] and 0.0939% ID per organ ± 0.0494, respectively). Data acquired 45 hours after injection showed a significant decrease in the gadolinium chelate concentration in amniotic fluid compared with that in the 19-21-hour group (from 0.0017% to 0.0007% ID per gram; P = .01). CONCLUSION Amounts of gadolinium chelate in the fetal tissues and amniotic fluid were minimal compared with the maternal ID. This may impact future clinical studies on the safety of gadolinium contrast agent use in pregnancy.


Cancer Prevention Research | 2015

Sulforaphane bioavailability and chemopreventive activity in women scheduled for breast biopsy

Lauren L. Atwell; Zhenzhen Zhang; Motomi Mori; Paige E. Farris; John T. Vetto; Arpana Naik; Karen Y. Oh; Philippe Thuillier; Emily Ho; Jackilen Shannon

Epidemiologic studies suggest a protective effect of cruciferous vegetables on breast cancer. Sulforaphane (SFN), an active food component derived from crucifers, has been shown to be effective in breast cancer chemoprevention. This study evaluated the chemopreventive effect of SFN on selective biomarkers from blood and breast tissues. In a 2- to 8-week double-blinded, randomized controlled trial, 54 women with abnormal mammograms and scheduled for breast biopsy were randomized to consume a placebo or a glucoraphanin (GFN) supplement providing SFN (n = 27). Plasma and urinary SFN metabolites, peripheral blood mononuclear cell (PBMC) histone deacetylase (HDAC) activity, and tissue biomarkers (H3K18ac, H3K9ac, HDAC3, HDAC6, Ki-67, p21) were measured before and after the intervention in benign, ductal carcinoma in situ, or invasive ductal carcinoma breast tissues. Within the supplement group, Ki-67 (P = 0.003) and HDAC3 (P = 0.044) levels significantly decreased in benign tissue. Pre-to-postintervention changes in these biomarkers were not significantly different between treatment groups after multiple comparison adjustment. GFN supplementation was associated with a significant decrease in PBMC HDAC activity (P = 0.04). No significant associations were observed between SFN and examined tissue biomarkers when comparing treatment groups. This study provides evidence that GFN supplementation for a few weeks is safe but may not be sufficient for producing changes in breast tissue tumor biomarkers. Future studies employing larger sample sizes should evaluate alternative dosing and duration regimens to inform dietary SFN strategies in breast cancer chemoprevention. Cancer Prev Res; 8(12); 1184–91. ©2015 AACR.


Ultrasound Quarterly | 2008

Unilateral short femur - What does this mean?: Report of 3 cases

Karen Y. Oh; Antonio E. Frias; Janice L. B. Byrne; Anne M. Kennedy

Objectives: This study aims to: (1) characterize the prenatal diagnosis of short femur; (2) describe typical findings of proximal focal femoral deficiency; and (3) review the most common differential diagnoses for short femur(s). Methods: We present 3 examples of prenatally diagnosed proximal focal femoral deficiency and briefly reviewed the differential diagnosis of short femur(s) in utero and associations such as ethnic variation, trisomy 21, and diabetic embryopathy. Results: Multiple cases are presented in which a short femur (unilateral or bilateral) is the dominant finding on prenatal ultrasound. The fetuses were extensively examined for other skeletal anomalies, and global skeletal dysplasias are excluded from the differential diagnosis. Prenatal imaging findings are correlated with postnatal history and imaging. Conclusion: Prenatal sonography is now widely used as a screening tool, and at times, subtle findings such as an isolated short femur can be seen without other significant anatomic abnormalities. Counseling for the parents can be difficult without some knowledge of the range of associations seen with short femur(s). Proximal focal femoral dysplasia should be considered in the differential diagnosis when a short femur is discovered.


Radiology | 2018

Gadolinium Chelate Safety in Pregnancy: Barely Detectable Gadolinium Levels in the Juvenile Nonhuman Primate after in Utero Exposure

Joao Prola-Netto; Mark Woods; Victoria H. J. Roberts; Elinor L. Sullivan; Christina Ann Miller; Antonio Frias; Karen Y. Oh

Purpose To determine whether gadolinium remains in juvenile nonhuman primate tissue after maternal exposure to intravenous gadoteridol during pregnancy. Materials and Methods Gravid rhesus macaques and their offspring (n = 10) were maintained, as approved by the institutional animal care and utilization committee. They were prospectively studied as part of a pre-existing ongoing research protocol to evaluate the effects of maternal malnutrition on placental and fetal development. On gestational days 85 and 135, they underwent placental magnetic resonance imaging after intravenous gadoteridol administration. Amniocentesis was performed on day 135 prior to administration of the second dose of gadoteridol. After delivery, the offspring were followed for 7 months. Tissue samples from eight different organs and from blood were harvested from each juvenile macaque. Gadolinium levels were measured by using inductively coupled plasma mass spectrometry. Results Gadolinium concentration in the amniotic fluid was 0.028 × 10-5 %ID/g (percentage injected dose per gram of tissue) 50 days after administration of one gadoteridol dose. Gadolinium was most consistently detected in the femur (mean, 2.5 × 10-5 %ID/g; range, [0.81-4.1] × 10-5 %ID/g) and liver (mean, 0.15 × 10-5 %ID/g; range, [0-0.26] × 10-5 %ID/g). Levels were undetectable in the remaining sampled tissues, with the exception of one juvenile skin sample (0.07 × 10-5 %ID/g), one juvenile spleen sample (0.039 × 10-5 %ID/g), and one juvenile brain (0.095 × 10-5 %ID/g) and kidney (0.13 × 10-5 %ID/g) sample. Conclusion The presence of gadoteridol in the amniotic fluid after maternal injection enables confirmation that it crosses the placenta. Extremely low levels of gadolinium are found in juvenile macaque tissues after in utero exposure to two doses of gadoteridol, indicating that a very small amount of gadolinium persists after delivery.


Breast Journal | 2014

Osteosarcoma of the Breast

Kari A. Thomas; Nicole Roy; Megan L. Troxell; Karen Y. Oh

along with polymorphonuclear leucocytes infiltration in the cyst wall suggesting a microruptured cyst (Fig. 2). Pathologic diagnosis of the mass to be epidermoid cyst made additional treatment procedures unnecessary in our case. The postoperative course was uneventful, and deformity and recurrence did not occur for 1 year. Epidermoid cyst in breast is an uncommon lesion, and the origin of this cyst is considered mainly to be congenital, trauma, and surgery. There was no past history of breast biopsy or trauma in our case. As we consider our prediagnosis, clinical appearances, mammographic, and sonographic features of ECs can mimic benign as well as malignant tumors therefore usually misdiagnosed as fibroadenoma, fibrocystic disease, or cancer. To the best of our knowledge, this is the first case of which epidermoid cyst of breast on the nipple.

Collaboration


Dive into the Karen Y. Oh's collaboration.

Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Researchain Logo
Decentralizing Knowledge