Search PubMed⌕ Search

Biomedical subjects

H C Yeh

Publications and source records attributed to H C Yeh.

At least 19 recordsLinked to original sources
PubMed2001

Intratumoral adenovirus-mediated suicide gene transfer for hepatic metastases from colorectal adenocarcinoma: results of a phase I clinical trial.

Animal studies have shown that direct injection of an adenoviral vector (Adv.RSV-tk) expressing the herpes thymidine kinase gene into established tumors in the liver, followed by systemic ganciclovir administration, was effective in inducing tumor necrosis. Toxicities were minimal at therapeutically effective vector doses, although severe hepatic necroinflammation was seen at much higher supratherapeutic doses. We conducted a clinical phase I trial in patients with metastatic colorectal adenocarcinoma in the liver to assess the safety of intratumoral Adv.RSV-tk injection (escalating doses) followed by intravenous ganciclovir (fixed dose). The vector was injected into a metastatic tumor in the liver under local anesthesia by percutaneous needle placement with concurrent ultrasonographic monitoring to prevent injection or leakage into adjacent normal liver structures. We treated 16 patients in five dose level cohorts of Adv.RSV-tk, from 1.0x10(10) to 1.0x10(13) virus particles per patient. Hepatic toxicities were low, with transient grade 1 elevations in serum aminotransferase levels in 3 of 16 patients. Other toxicities were also transient: grade 2-3 fevers in 5 of 16 patients, grade 3 thrombocytopenia in 1 of 16 patients, and grade 2 leucopenia in 3 of 16 patients. These results indicate that Adv.RSV-tk can be safely administered by percutaneous intratumoral injection in patients with hepatic metastases at doses up to 1.0x10(13) virus particles per patient, and can provide the basis for future clinical trials involving intratumoral adenoviral vector injection.

Adenocarcinoma↗
PubMed2001

The prevalence and distribution of bone defects in patients with moderate to advanced periodontitis.

BACKGROUND: Alveolar bone defect is one of the common features of periodontitis and may vary in its form, extent, and distribution among teeth and individuals. The purpose of this study was to analyze the prevalence and distribution of different forms of bone defects in Taiwanese patients with moderate to advanced periodontitis. METHODS: One hundred and thirty-seven Taiwanese patients with moderate to advanced periodontitis comprising a total sample of 3542 teeth were studied. During periodontal surgery, osseous defects were explored and classified as interproximal crater, 1-wall, 2-wall, 3-wall, hemiseptal and circumferential defects. Among them, some were also recorded as complicated defects. RESULTS: Among 3542 existing teeth, 1376 were examined surgically and 483 teeth had bone defects. There was an increase in bone defects from anterior to posterior. The frequencies of defects in anterior and posterior segments were significantly different. More defects were found on the right side than on the left side. Yet there was no difference between the maxillary and mandibular arch. Interproximal surfaces of the first and second molars had the highest prevalence of bone defects. Crater was the most common defect type (26.50%), followed by circumferential (23.40%) and 3-wall defect (20.08%). More than 40% also presented with complicated defects. CONCLUSIONS: There was an increase in bone defects from anterior to posterior. Interproximal aspects were more frequently involved than buccal or lingual aspects. Crater, circumferential and 3-wall defects were more common than other defect types. The treatment of complicated defects, which comprise over 40% of all defects, presents a challenging task for periodontists.

Adult↗
PubMed2000

Characterization of a microprocessor-controlled tubular multiple metered dose inhaler aerosol generator for inhalation exposures of pharmaceuticals.

A microprocessor-controlled tubular multiple metered dose inhaler (MDI) aerosol generator was constructed for the delivery of pharmaceutical aerosols to inhalation chambers. The MDIs were mounted in four cassettes containing one to four MDIs on a stepped end plate. The MDIs in each cassette were pneumatically activated at intervals that were controlled by the microprocessor. The cassettes permitted easy replacement of each set of MDIs with a fresh set of MDIs whenever necessary. Aerosol concentration was controlled by varying the number of active MDIs in each cassette and the frequency of activations per minute of each row. Aerosol from the MDIs flowed along the long axis of the tube, which provided a path length sufficient to diminish impaction losses. Using a light-scattering device to monitor the aerosol concentration, the pulsatile output from the MDIs in the cassettes was demonstrated to be adequately damped out provided that the dilution/mixing/aging chamber exceeded 3 ft in length. The tube diameter selected was the minimum compatible with mounting the required number of MDIs so that the linear velocity of the aerosol was adequate to efficiently transport the aerosol out of the dilution chamber. Aerosol concentration and particle size data were recorded for a nose-only rodent exposure chamber. Reproducible aerosol concentrations ranging from 0.03 to 0.6 mg/L were generated. Particle sizes ranged from 2- to 3-microm mass median aerodynamic diameter. Thus, the aerosol generated was within the size range suitable for inhalation exposures.

Aerosols↗
PubMed1999

Phase I/II study of stage III and IV non-small cell lung cancer patients taking a specific dietary supplement.

This phase I/II study evaluates the influence of selected vegetables (SV) that contain known antitumor components on the survival of stage III-IV non-small cell lung cancer (NSCLC) patients. All patients were treated with conventional therapies. SV was added to the daily diet of 5 stage I patients in the toxicity study group (TG) and 6 stage III and IV patients in the treatment group (SVG), but not to the diet of 13 stage III and IV patients in the control group (CG). Age, Karnofsky performance status (KPS), and body mass index of SVG and CG patients were comparable at entry. KPS declined in the CG patients (79 +/- 8 to 55 +/- 11) but improved in the SVG patients (75 +/- 8 to 80 +/- 13) one to three months after entry. Weight change in the CG, SVG, and TG patients was -12 +/- 5%, -2 +/- 2%, and +4 +/- 4%, respectively. The median survival time and mean survival of the CG patients were 4 and 4.8 months, but in the SVG patients they were 15.5 and 15 months (p < 0.01). No clinical signs of toxicity were found in the TG patients in the 24-month study period. Adding SV to the daily diet of NSCLC patients was found to be nontoxic and associated with improved weight maintenance, KPS, and survival of stage III and IV NSCLC patients.

Adult↗
PubMed1998

Torsion of the fallopian tube: progression of sonographic features.

Isolated torsion of the fallopian tube is a rare gynecologic condition that is difficult to diagnose preoperatively. We present the sonographic and CT findings over a 48-hour period in a case of isolated torsion of the fallopian tube. The radiologic features of isolated torsion have been described previously; however, to our knowledge, the progressive findings have not been previously reported.

Adult↗
PubMed1998

Tissue harmonic imaging sonography: evaluation of image quality compared with conventional sonography.

OBJECTIVE: The purpose of this study was to determine if tissue harmonic imaging (THI) sonography produced higher quality images than did conventional sonography. SUBJECTS AND METHODS: A prospective study was performed on 89 patients to compare the image quality of THI sonography with that of conventional sonography. Each examination was performed using THI sonography (transmitted frequency, 2.0 MHz; received frequency, 4.0 MHz) and conventional sonography at 2.5 and 4.0 MHz. The pancreatic area was studied in 60 patients, and other anatomic areas were studied in 68 patients. The images were then graded for penetration, detail, and total image quality. Graders were unaware of the sonographic technique. RESULTS: Of the 60 pancreatic examinations, THI sonography was the best technique for penetration in 45, detail in 54, and total image quality in 50. For the pancreas, THI sonography was significantly better than 2.5-MHz conventional sonography for penetration (p = .0002), detail (p < .0001), and total image quality (p < .0001). THI sonography was significantly better than 4.0-MHz conventional sonography for penetration (p < .0001), detail (p < .0001), and total image quality (p < .0001). Of the 68 examinations of other anatomic areas, THI sonography was the best technique for penetration in 42, detail in 57, and total image quality in 58. For other anatomic areas, THI sonography was significantly better than 2.5-MHz conventional sonography for penetration (p = .05), detail (p < .0001), and total image quality (p < .0001). THI sonography was significantly better than 4.0-MHz conventional sonography for penetration (p < .0001), detail (p < .0001), and total image quality (p < .0001). CONCLUSION: The THI technique improved sonographic image quality.

Aged↗
PubMed1997

An experimental method for measuring aerosol deposition efficiency in the human oral airway.

An experimental technique was developed to measure the oral deposition of aerosols by successively drawing them passively through (1) the nasal and oral passage in series, and (2) the nose and an oral bypass "extension tube" inserted into the oral cavity just anterior to the uvula. To test this technique, a replicate human upper airway cast was challenged with monodisperse aerosols ranging in diameter from 3.6 to 150.0 nm at constant flow rates ranging from 7.5 to 30 L/min. For the inhalation study, test aerosols were drawn into the nasal cavity and directed either through the laryngeal-tracheal (L-T) section or the oral passage with/without the oral extension tube. The flow was reversed for the exhalation study. Deposition fractions of aerosols in the main oral cavity were found approximately equal to those in the L-T section for both inhalation and exhalation. Following this phase of the study, experimental measurements of total particle deposition fraction for the oral inlet-tracheal outlet path were performed. The results of these measurements agreed well with the calculated oral deposition fractions based on the initial measurements. This technique has application for measuring oral deposition of larger particles encountered in occupational environments.

Aerosols↗
PubMed1997

A comparative analysis of primate nasal airways using magnetic resonance imaging and nasal casts.

The nasal cavity is an intricate part of the respiratory tract. It is not only the site of olfaction, but also serves as a filter to protect the lower respiratory tract from inhaled pollutants. A substantial fraction of inhaled particles deposit in this region and may pose potential health risks. To predict possible sites of inhaled aerosol deposition and better understand health risks associated with inhaled aerosols in this region, it is necessary to examine the morphometry of the nasal passage. Magnetic resonance imaging (MRI) of the nose was done from the anterior to the posterior, in 3-mm sections, on five anesthetized rhesus monkeys and on two nasal casts (one human and one rhesus monkey). The MRI images were analyzed for perimeter and cross-sectional areas of each section. Results indicated that the left and right nasal passages were very symmetric for the five monkeys but not for the human cast. The cross-sectional area and, consequently, the volume varied greatly among monkeys in vivo. Measurements from the monkey cast exhibited 1.4-fold differences normalized body weight in cross-sectional areas, but with smaller differences in perimeter when compared to the MRI in vivo images. The human cast exhibited a volume three times greater than that of the monkey cast, while the surface area was approximately doubled. Results from this comparison showed many similarities in the structure of the monkey and human nose suggesting that the rhesus monkey would be a good human surrogate in aerosol deposition studies.

Aerosols↗
PubMed1997

Measurements of airway dimensions and calculation of mass transfer characteristics of the human oral passage.

This paper presents measurements of the geometric shape, perimeter, and cross-sectional area of the human oral passage (from oral entrance to midtrachea) and relates them through dimensionless parameters to the depositional mass transfer of ultrafine particles. Studies were performed in two identical replicate oral passage models, one of which was cut orthogonal to the airflow direction into 3 mm elements for measurement, the other used intact for experimental measurements of ultrafine aerosol deposition. Dimensional data were combined with deposition measurements in two sections of the oral passage (the horizontal oral cavity and the vertical laryngeal-tracheal airway) to calculate the dimensionless mass transfer Sherwood number (Sh). Mass transfer theory suggests that Sh should be expressible as a function of the Reynolds number (Re) and the Schmidt number (Sc). For inhalation and exhalation through the oral cavity (O-C), an empirical relationship was obtained for flow rates from 7.5-30.0 1 min-1: Sh = 15.3 Re0.812 Sc-0.986 An empirical relationship was likewise obtained for the laryngeal-tracheal (L-T) region over the same range of flow rates: Sh = 25.9 Re0.861 Sc-1.37 These relationships were compared to heat transfer in the human upper airways through the well-known analogy between heat and mass transfer. The Reynolds number dependence for both the O-C and L-T relationships was in good agreement with that for heat transfer. The mass transfer coefficients were compared to extrathoracic uptake of gases and vapors and showed similar flow rate dependence. For gases and vapors that conform to the zero concentration boundary condition, the empirical relationships are applicable when diffusion coefficients are taken into consideration.

Absorption↗
PubMed1996

Conformational change and inactivation of membrane phospholipid-related activity of cardiotoxin V from Taiwan cobra venom at acidic pH.

The phospholipid binding activity of cardiotoxin V from Naja naja atra (CTX A5) was studied by use of Langmuir monolayers and found to exhibit pH-dependence in binding to phosphatidylcholine membrane with an apparent pKa around 6.0. Proton NMR investigation of the CTX A5 molecule in the presence of phosphatidylcholine micelles reveals a decrease in association of CTX A5 with membranes at low pH as a result of the protonation of His-4 near the membrane binding site of loop I region of CTX. The pH-dependent binding can be attributed mainly, but not solely, to the change in charge content of the CTX molecule upon His-4 protonation at the membrane/water interface. This is shown by analyzing the pH- and ionic strength dependence of binding of CTXs to phospholipid monolayers according to Gouy-Chapman theory. The protonation of the His-4 residue also results in a local conformational change in the loop I region since the chemical shifts of amide protons for the amino acid residues from Cys-3 to Thr-14 are all found to vary as a function of pH with an apparent pKa similar to that of His-4. Interestingly, the effect is relayed to other amino acid residues in the structural core of the protein such as those in C-terminal (Lys-60, Cys-61, and Asn-62) and triple-stranded antiparallel beta-sheet (Cys-22, Lys-24, Ala-25, Arg-38, and Ala-41) regions. An additional local conformational change in the molecule results around pH 5 as evidenced by circular dichroism spectroscopic studies, although this change does not affect the characteristic beta-sheet and three-finger loop structure of CTX molecule as revealed by two-dimensional NOESY 1H NMR study. The latter conformational change at acidic pH, however, completely inactivates CTX-induced aggregation/fusion activity of sphingomyelin vesicles. The results suggest that deciphering the functional sites of CTXs on the basis of structure and dynamics determined at low pH should be done with caution. Since 19 out of 44 CTX homologues with known amino acid sequence contain His-4, the effect of His-4 on the structure and function of CTX molecules is important and is discussed in terms of the diverse membrane targets of CTX subtypes. Also discussed is the pH-induced activation of snake venom proteins in the victim.

Animals↗
PubMed1996

Paraumbilical venous collateral circulations: color Doppler ultrasound features.

Using Color Doppler ultrasonography to trace the dilated paraumbilical vein to its connection with systemic veins in 27 patients, we have found four major pathways: In type 1 (63%), the vein connected with the external iliac vein via the inferior epigastric vein. In type 2 (3.7%), the vein connected with the saphenous vein via the superficial epigastric vein. In type 3 (22.2%), the vein connected with the internal thoracic vein via the superior epigastric vein. Type 4 (11.1%) is a combination of types 1 and 2. A frank caput medusa was not seen, but occult caput medusa were seen in two patients. Turbulent flow was seen at the junction between inferior epigastric and external iliac veins, paraumbilical and superficial epigastric veins, and superficial epigastric and saphenous veins in some patients. Color Doppler ultrasonography is a convenient, noninvasive method for determining the course and associated hemodynamic changes in the paraumbilical collateral circulation.

Adult↗
PubMed1996

A follow-up study of childhood nasopharyngeal radium irradiation in Washington County, Maryland.

In 1978 an epidemiologic study exploring the health consequences of nasopharyngeal radium irradiation among individuals treated for adenoid enlargement in Washington County, Maryland, found an excess risk of brain tumors and a deficit of female breast cancers. The study population included all persons first seen at the Washington County Clinic for the Prevention of Deafness in Children from 1940 to January 1, 1960. We will continue the follow-up of irradiated and nonirradiated patients to (1) assess the risk of brain tumors and other neoplasms of the head and neck developing during a 40-year period, (2) assess hormone-related disorders resulting from irradiation of the pituitary gland, and (3) compare cancer incidence and mortality rates among exposed and nonexposed groups. Of the 2135 persons eligible for this study, 93.5% have been traced, and 90% have replied to a mailed questionnaire that elicits information on demographic characteristics, reproductive and medical history, infertility, and other sources of radiation exposure. Information on cancer incidence and mortality is being obtained from the Washington County Cancer Registry and death certificate files from Washington County and the Social Security Administration. Statistical methods to be used in the data analysis include standardized mortality ratios, standardized cancer incidence ratios, and Kaplan-Meier survival analysis.

Brain Neoplasms↗
PubMed1996

Micronodulation: ultrasonographic sign of Hashimoto thyroiditis.

The purpose of this work is to assess the validity of an ultrasonographic sign, micronodulation, in the diagnosis of Hashimoto thyroiditis. Among 101 patients found to have ultrasonographic features of micronodulation, 57 patients had autoantibody test results available. Fifty-four patients were positive and three were negative for the autoantibodies. Therefore, the positive predictive value for micronodulation in diagnosing Hashimoto thyroitis is 94.7%. The micronodules were 0.1 to 0.65 cm in size, hypoechoic, and surrounded by an echogenic rim. This corresponds to accentuated lobulation on the pathologic specimen. Although micronodulation is highly diagnostic of Hashimoto thyroiditis, the ultrasonographic features of eight biopsy-proved masses caused by Hashimoto thyroiditis varied and were not specific for the disease.

Adolescent↗