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Biomedical subjects

H C Yeh

Publications and source records attributed to H C Yeh.

At least 73 records · Page 4Linked to original sources
PubMed1986

Deposition, metabolism, and excretion of 1-[14C]nitropyrene and 1-[14C]nitropyrene coated on diesel exhaust particles as influenced by exposure concentration.

Nitrated polycyclic aromatic hydrocarbons (nitro-PAH) have been detected in the environment, originating from sources such as diesel exhaust emissions and coal combustion fly ash. 1-Nitropyrene (NP) is a predominant mutagenic and carcinogenic nitro-PAH found in diesel exhaust emissions. Since inhalation of NP is a likely route of exposure in humans, it is important to determine the biological fate of inhaled NP both in its pure form and associated with particles. The purpose of this study was to determine the disposition of NP aerosols inhaled by rats. The studies described in this paper were designed to determine the deposition of [14C]NP over a range of exposure concentrations, identify the pathways and half-times for excretion of absorbed NP, and determine the distribution of inhaled NP and metabolites in tissues. Male F344 rats were exposed nose only to various concentrations of NP and NP coated on diesel exhaust particles (50-1100 ng/liter). The results indicate that, over the range of concentrations tested, pathways for excretion of [14C]NP equivalents in urine and feces were independent of the exposure concentration of NP, whether in its pure form or associated with diesel exhaust particles. In all cases, fecal excretion was the major route of elimination of [14C]NP equivalents, with about 2 times more excreted by this route than by urine. The fractional deposition of [14C]NP in the respiratory tract did not appear to be dependent on exposure concentration. Half-times for elimination of 14C in urine and feces were about 15 to 20 hr. In all exposures, 14C was widely distributed in the tissues examined. Analysis of the tissues for NP and its metabolites indicated that within 1 hr after exposure, greater than 90% of the 14C was NP metabolites. Lungs of rats exposed to [14C]NP coated on diesel exhaust particles contained nearly 5 times more 14C than lungs from rats exposed to pure aerosols of [14C]NP (148 vs 29 pmol/g lung) within 1 hr after exposure. This difference was increased to 80-fold at 94 hr after exposure (80 vs 1 pmol/g lung). Long-term clearance half-times of 14C from various tissues were similar. The results demonstrate that particle association of NP significantly alters the biological fate of inhaled NP.

Aerosols↗
PubMed1986

Studies of the temporal and spatial distribution of aerosols in multi-tiered inhalation exposure chambers.

Two multi-tiered whole body inhalation exposure chambers with nominal volumes of 1 m3 (H-1000) and 2 m3 (H-2000) were evaluated for their performance in terms of the temporal and spatial distribution of test aerosols within the chamber. Parameters investigated included chamber type, single-chamber-single-aerosol generator versus two-chamber-single-aerosol generator systems, chamber air supply and exhaust systems, particle size, and aerosol diluter type. Results indicated that: 1) particle size has an effect on chamber aerosol concentration distribution, with the larger particle resulting in a higher variation; 2) the single-chamber-single-generator system is more stable than the two-chamber-single-generator system; 3) the H-2000 chamber has a lower aerosol spatial variability than the H-1000 chamber; and 4) the aerosol distribution within the chamber could be improved with the use of a newly designed diluter.

Aerosols↗
PubMed1986

Intradecidual sign: a US criterion of early intrauterine pregnancy.

The uterine cavity appears on sonograms as a linear echo, which is usually visible during early pregnancy and remains straight until the eighth to ninth week of gestation. The early gestational sac is not enveloped by two layers of decidua, as suggested by descriptions of the double decidual sac sign; the sac (or echogenic area of early implantation) is actually located within a markedly thickened decidua on one side of the uterine cavity. The combination of these two sonographic characteristics is called the "intradecidual sign." An early implantation of 25 days gestational age can be detected by the presence of the intradecidual sign, which is sooner than a gestational sac can be seen. The implantation site can also be located by means of the intradecidual sign. In a study of 36 patients with early intrauterine pregnancy and five with ectopic pregnancy, the intradecidual sign was more sensitive (91.7% vs. 63.9%) and specific (100% vs. 60%) than the double decidual sac sign in the detection of early intrauterine pregnancy.

Female↗
PubMed1986

Floating gallstones in bile without added contrast material.

Floating gallstones can occur without the administration of contrast material to increase the specific gravity of bile. This was observed in three patients in 17 months. After a long fast, a large stone was noticed to float because of the high specific gravity of inspissated bile. This stone sank after the patient resumed food intake. In another patient, some stones floated while others sank due to their difference in specific gravity. Sonographic demonstration of a floating stone, however, requires certain strict criteria.

Bile↗
PubMed1985

Testicular lymphoma: sonographic findings.

The sonographic findings in 2 patients diagnosed as having testicular lymphoma (subsequently surgically proven) are discussed. The diagnosis should be suspected when a hypoechoic mass is identified in the testicle.

Adult↗
PubMed1984

Ultrasonography and CT of abdominal and inguinal hernias.

Forty-two patients with various abdominal wall hernias and five patients with inguinal hernias were studied with ultrasonography. Thirteen patients were studied by CT. Although hernias are usually apparent on physical examination, difficulty in diagnosis may be encountered in some patients. Ultrasonography and CT are not only capable of diagnosing hernia in such instances, they are also helpful in the clinical management of the patients by demonstrating the precise location and extent of the muscular defect. However, the hernia may simulate a mass or cyst in the ultrasonograph and CT scan and one should carefully demonstrate intraperitoneal communication through a muscular defect or a herniated bowl loop within the hernia in order to avoid misdiagnosis. Pseudohernias due to localized thinning or thickening of the rectus muscle were also observed in five patients.

Diagnosis, Differential↗
PubMed1984

Very low-density lipoprotein metabolism in an unusual case of lipoatrophic diabetes.

Complete acquired lipoatrophic diabetes (LD) is characterized by nonketotic insulin-resistant diabetes, elevated very low-density lipoprotein (VLDL) triglyceride (TG) levels, and absent subcutaneous fat. We studied a young child in whom LD atypically developed after the onset of type 1 diabetes mellitus. On uncontrolled home diet the patient had triglyceride levels over 1,000 mg/dL on multiple occasions. In order to demonstrate the effects of caloric and dietary-fat restriction on VLDL metabolism, 3H-glycerol and autologous 125I-VLDL were used to quantitate the turnover of VLDL-TG and VLDL-apolipoprotein B (apo B) during two periods of caloric restriction. Consumption of a 900-kcal 40-g fat diet resulted in a plasma triglyceride level of 1383 mg/dL (ten-fold elevation). This hypertriglyceridemia was associated with markedly increased production rates of both VLDL-TG (73.7 mg/kg/h) and VLDL-apo B (126.9 mg/kg/d). Consumption of a 900-kcal 25-g fat diet resulted in a plasma TG level of 663 mg/dL. This reduction in plasma TG was associated with a 40% decrease in VLDL-TG production rate (PR) (45.1 mg/kg/h). There was no change in the production rate (PR) of VLDL-apo B. The hypertriglyceridemia in this patient was due to marked over production of VLDL. Furthermore, the studies demonstrate: (1) the independent benefits of caloric and dietary-fat restriction in the treatment of LD, and (2) that fat restriction lowered plasma triglyceride by its effect on the VLDL-TG production rate.

Apolipoproteins↗
PubMed1984

Computed tomography of soft-tissue lesions of the extremities, pelvic and shoulder girdles: sonographic and pathological correlations.

Sixty-five patients with various soft-tissue tumours were examined by computed tomography (CT) and ultrasonography. Results were correlated with pathological findings. Although an accurate histological prediction could not be made in most cases, certain patterns appeared to be characteristic of specific types of tumours. A lipoma of uniformly low density may be differentiated from the heterogeneously denser liposarcoma. Multiple irregular linear densities with calcification are characteristic of haemangioma. An echo-free mass on the sonogram with soft-tissue density on CT suggests lymphoma or certain sarcomas. Small isodense subcutaneous lipomas or intramuscular lymphomatous masses may be clearly delineated on sonogram but not seen on CT. Our study indicates that the combined use of CT and ultrasound gives a very detailed basis for planning the surgical approach to the tumour.

Adolescent↗
PubMed1984

Characterization of diesel exhaust in a chronic inhalation study.

We describe characterization of the exposure atmosphere in a life-span study of rats and mice exposed to chronic inhalation of diluted diesel exhaust. Diesel exhaust was generated by one of two General Motors 1980 Model, 5.7-liter V8 diesel engines connected to an eddy current dynamometer/flywheel system and operated on the Federal Test Procedure urban driving cycle. Animals were exposed 7 hours/day, 5 days/week to exhaust at particle concentrations of approximately 7000, 3500, and 350 micrograms/m3 or to clean air. Throughout the 24-month study, the mean particle mass concentration remained within 5% of the target values. Measured gas concentrations of CO, CO2, NO, NO2, and hydrocarbons were roughly proportional to the dilution ratio. A combination of a Lovelace Multijet cascade impactor followed by a parallel flow diffusion battery gave mass median diameters of 0.23 to 0.26 microns averaged over complete cycles and geometric standard deviations larger than 4. The aerosol concentration profile was associated with the operating cycle. The measured diesel particle size was similar to previously reported values of particles released to the atmosphere from the same model engine.

Animals↗
PubMed1984

Ultrasonography and computed tomography in pseudomyxoma peritonei.

Three patients with pseudomyxoma peritonei were found to have quite different sonographic and CT features from those described previously. Ultrasound (US) revealed (a) a large, highly echogenic mantle consisting of numerous tiny cysts, (b) echogenic "ascites" which was actually gelatinous in nature, or (c) multiple indentations of the bowel by semi-solid masses. On CT, the large masses appeared as spaces resembling ascites but containing mottled densities, while the regions which resembled echogenic "ascites" on US had an attenuation value slightly higher than water.

Female↗
PubMed1983

Granulomatous enterocolitis: findings by ultrasonography and computed tomography.

Granulomatous enterocolitis was evaluated in 51 patients by ultrasonography, and in 14 of those patients also by computed tomography (CT). The features of granulomatous enterocolitis include abscesses in various locations and bowel loops that are matted and inflamed, dilated due to obstruction, or have thickened walls. Although the diagnostic findings of ultrasound and CT examinations are not as specific as those of barium-enhanced radiographic examinations, they are helpful in the clinical management of patients. Serial ultrasound examinations are ideal to demonstrate progression or regression of the inflamed bowel-loops and abscesses. Real-time scanning is important in the differentiation of fluid-filled or matted and inflamed bowel-loops from abscesses. However, manual scanning is usually better for the delineation of the abdominal wall and complicated retroperitoneal abscesses.

Abscess↗
PubMed1982

Ultrasonography of the extremities and pelvic girdle and correlation with computed tomography.

Ultrasonography was performed on 54 patients with lesions of the extremities and pelvic girdle. Computed tomography (CT) was employed in 8 patients. Focal space-occupying lesions such as tumors, abscesses, hematomas, aneurysms, and popliteal cysts (dissecting or otherwise) were delineated by ultrasound and their extent defined. Differentiation from diffuse changes such as lymphedema, cellulitis, or phlebitis and diagnosis of aneurysms were possible. Popliteal cysts were usually quite characteristic, while correlation with the clinical features suggested the correct diagnosis in the case of the other lesions. CT correlated well with ultrasound, except for one tumor of the forearm which was not shown by CT.

Abscess↗
PubMed1982

Ultrasonography and computed tomography of inflammatory abdominal wall lesions.

Twenty-four patients with inflammatory lesions of the abdominal wall were examined by ultrasonography. Nine of these patients underwent computed tomographic (CT) scanning as well. Both ultrasonography and CT clearly delineated the exact location and extent of abdominal wall abscesses. Abscesses were easily differentiated from cellulitis or phlegmon with ultrasound. The peritoneal line was more clearly delineated on ultrasonograms than on CT scans; abscesses were also more distinct on the ultrasonograms because of their low echogenicity compared with the surrounding structures. Gas bubbles, fat density with specific low attenuation values, and underlying inflamed bowel loops in obese patients with Crohn's disease were better delineated by CT.

Abdominal Muscles↗
PubMed1981

A model for aerosol deposition in the human tracheobronchial region.

An aerosol deposition model in the human tracheobronchial tree based on impaction and sedimentation is proposed. Using this model, a mean deposition radius of conducting airways can be obtained from in vivo T-B deposition data or from physical dimensions of human lung casts. Agreement was found between the model and deposition data for three normal healthy subjects in the literature. Contributions of sedimentation to T-B deposition is estimated to be 42 - 78% at 250 cm3/sec average inspiration flow rate, and decreased to 8-29% at 750 cm3/sec average inspiration flow rate. Mean deposition radii are estimated to be 0.33 to 0.43 cm and correlate with pulmonary functional residual capacities.

Aerosols↗