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Biomedical subjects

Thomas C Ho

Publications and source records attributed to Thomas C Ho.

13 recordsLinked to original sources
PubMed2006

Measuring triamcinolone acetonide in aqueous humor by gas chromatography-electron-capture negative-ion mass spectrometry.

Intravitreal triamcinolone acetonide (IVTA) injection has been used in the treatment of various posterior segment diseases. One of the side effects of IVTA is raised intraocular pressure, which may be secondary to triamcinolone acetonide (TAA)'s effects on the trabecular meshwork that affects aqueous outflow. In order to study the biological effects of TAA on the trabecular meshwork, we firstly need to reliably and accurately detect the concentration of TAA in tissue cells or fluids. In this study we have described a technique of using gas chromatography-electron-capture-negative-ion mass spectrometry (GC-NCI-MS) to develop a simple, sensitive, selective and validated method to detect TAA in aqueous humor (AH) of rabbits following IVTA and subconjunctival TAA injections. We derivatized TAA from extracted aqueous sample by acetic anhydride and BSTFA, respectively, and analyzed by GC-NCI-MS. The detection limit was 0.3ng/ml, linearity over 0.995 from 0 to 300ng/ml. The reproducibility ranged from 10.4 to 3.9 for concentrations from 3 to 300ng/ml, and recovery was over 95% for the concentrations 10, 60, and 200ng/ml. No interference was found from 159 aqueous samples. There was no TAA residue carried to the next injection from previously high concentration injection, 10,000ng/ml. We have provided an alternative, rapid, and robust method other than LC-MS-MS for TAA detection in AH.

Animals↗
PubMed2005

Sensitivity analysis of ground-level ozone concentration to emission changes in two urban regions of southeast Texas.

Air pollutant emission is one of the predominant factors affecting urban air quality such as ground-level ozone formation. This paper assesses the impact of changing emission inventory scenarios, based on combinations of point, mobile, area/non-road and biogenic sources, on the tropospheric ozone concentration in two southeast Texas urban areas, i.e. Houston-Galveston and Beaumont-Port Arthur, during the rapid ozone formation event (ROFE) on August 25, 2000. The EPA's Community Multiscale Air Quality (CMAQ) modeling system with 1999 national emission inventory (NEI99) estimates and updated SAPRC99 chemical mechanism are used in the sensitivity analysis for twelve different emission scenarios. Based on model results, it is found that the point source emission of NOx and VOC contributes the greatest ozone peak in the ROFE. Removing Texas point sources of VOC and NOx emission from the inventory results in a reduction in peak O3 concentration by 128 and 70 ppbv in Houston urban area, respectively. Similar but less drastic impact from point source is also observed in the Beaumont-Port Arthur area. The effect on peak ozone concentration due to mobile, area and non-road sources emissions are less significant compared to that of point source emission. Reducing VOC emission appears to be more effective than reducing NOx emission in lowering peak O3 concentration in the studied region. Although biogenic emission can contribute up to 37 ppbv of peak ozone level over a large area, the affected area is away from the urban region of concern, and should not be the main cause for O3 non-attainment in the two urban areas. Removing CO emission from mobile sources does not lead to significant reduction (< 1 ppbv) in ozone concentrations. The modeled data also show that the transport of O3 precursors from adjacent states can cause a significant ozone plume near Beaumont due to its proximity to the state border based on the conditions during the August 25, 2000 O3 episode.

Air Pollutants↗
PubMed2005

A comparative study of US EPA 1996 and 1999 emission inventories in the west Gulf of Mexico coast region, USA.

Emission inventory is one of the required inputs to air quality models. To assist in the urban and regional modeling efforts, United States Environmental Protection Agency (EPA) has compiled a National Emission Inventory (NEI) for criterion pollutants, and the precursors of ozone and particulate matter (PM). In December 2002, EPA released the 1999 NEI estimates (NEI99), which represent the most recent national emission data. However, the data sets are not in model-ready format for air quality simulations. This present work converts the NEI99 Final Version 2 data sets into Inventory Data Analyzer (IDA) format and processes the data using the Sparse Matrix Operator Kernel Emissions (SMOKE) modeling system to generate a gridded emission inventory in a domain covering the west Gulf Coast Region, USA. The spatial and diurnal emission characteristics of the gridded emission inventories are then assessed and compared with those of the National Emission Trend 1996 (NET96). The NEI99 database contains more complete emission records in both area and point sources. It is also found that NEI99 data exhibit greater emissions with respect to point and mobile sources but smaller emissions with respect to area sources when compared to the corresponding gridded NET96 data in the same study domain. The most distinct differences between the NEI99 and NET96 databases are CO emission of mobile sources, SO2 emissions of point sources, and VOC/PM/NH3/NOx emissions of area and non-road sources. The gridded NEI99 data show low VOC/NOx ratios (<2-5) in the urban areas of the study domain.

Air Pollutants↗
PubMed2003

Inpatient consultation of allergy/immunology in a tertiary care setting.

BACKGROUND: Few studies examine the referral patterns for allergy/immunology (A/I) inpatient consultation. OBJECTIVE: The purpose of this study was to examine the primary reason and trends for A/I inpatient consultation to improve fellowship training. METHODS: We performed a retrospective chart review of all inpatient A/I consults from July 1, 1987 to June 30, 2001 to determine the primary reason for consultation. We also reviewed trends in the total admissions and the average daily patient load compared with A/I consultation. RESULTS: A total of 1,284 A/I inpatient consults were reviewed. Thirty-six percent (460 of 1,284) of inpatient consults were for evaluation of adverse drug reactions, 21% (270 of 1,284) asthma, 21% (272 of 1,284) miscellaneous reasons, 8% (109 of 1,284) possible immunodeficiency, 7% (93 of 1,284) angioedema/urticaria, and 6% (80 of 1,284) anaphylaxis. Our results demonstrated a fall in inpatient consults that correlated with a similar fall in total hospital admissions. The ratio of A/I inpatient consults to total admissions remained constant. Additionally, the ratio of A/I consults to average daily patient load increased over the study period. There was a decrease in asthma and adverse drug reaction consults, whereas immunodeficiency and anaphylaxis referrals remained stable. CONCLUSIONS: Identifying the most common reasons for inpatient consultation provides a guide for the education of A/I fellows and primary care residents. Inpatient consultation continues to play a crucial role in A/I training as it provides unique opportunities to evaluate serious life threatening diseases. An unchanged trend of consultation for immunodeficiency and anaphylaxis reaffirms the importance of the allergist/immunologist as a valuable resource for inpatient consultation.

Adolescent↗
PubMedDate not supplied

Bilateral metastasis to the retina, choroids and optic nerve from breast cancer: a clinicopathological case.

A 39-year-old Asian woman, with a known history of breast cancer, presented with a gradual onset of painless reduction in vision in both eyes. Examination revealed visual acuity of counting fingers in the right eye and light perception in the left. There were subretinal lesions in the posterior poles of both eyes and retinal detachment in the left eye. Later she developed left proptosis and restriction in left ocular movement, most likely to be caused by metastatic extraocular spread. She subsequently died from disseminated metastatic disease. Histopathological examination confirmed tumor cells infiltrating the choroids, retina and optic nerve in both eyes. The tumor cells were arranged in lobular fashion and stained positively with Periodic Acid Schiff, suggesting the primary to be lobular adenocarcinoma type. Choroidal metastatic disease is common but bilateral retinal and optic nerve involvement with extraocular spread from breast cancer is rare.

Adult↗