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Biomedical subjects

C Yeh

Publications and source records attributed to C Yeh.

At least 37 records · Page 2Linked to original sources
PubMed1997

Theory of force transducer design optimization for die wall stress measurement during tablet compaction: optimization and validation of split-web die using finite element analysis.

PURPOSE: 1) To illustrate how computer aided engineering stress analysis can be used to improve the transducer design process for tablet press instrumentation; 2) to use these optimal design procedures for the geometric optimization of a cylindrical, segmented, and a novel split-web die design. Discussion includes the selection of optimal die wall thickness, segment cutting angle, strain gage placement, Wheatstone bridge configuration, and the influence of tablet height and position within the die on signal output. METHODS: Stress analysis was done with a finite element analysis (FEA) software package running on a personal computer. RESULTS: For the segmented die, the admissible range of die wall thicknesses depends upon cutting angle; the signal output is non-linear because the stress distribution in the die wall is influenced by tablet height and position within the die. For the split-web die, the optimal configuration consists of a 1/8 in. sensing web with a strain gage located at the peak of the sensing-web arch. This prototype had a linear calibration curve (r2 = 0.999) with no hysteresis. Radial versus axial stress transmission curves for: starch and sodium chloride were consistent with literature data. CONCLUSIONS: Finite element analysis (FEA) is a useful numerical tool for the systematic optimization of tablet press instrumentation. By enclosing the sensing web of a three layered die design in a cylinder, the split-web design can be directly mounted without modification of the die table.

Drug Design↗
PubMed1997

Erosive esophagitis and Barrett's esophagus in Taiwan: a higher frequency than expected.

In contrast to Western countries, erosive esophagitis has been considered less common, Barrett's esophagus presumed less frequent, and hiatal hernia extremely uncommon in the Orient. However, accelerated modernization and adoption of Western customs have resulted in marked life-style changes in many Asians in the Orient that may potentially affect the frequency of erosive esophagitis and Barrett's esophagus in this population. Our aim was to determine the current frequency of erosive esophagitis, Barrett's esophagus, and other gastroesophageal reflux disease complications in self-referred Chinese patients undergoing upper gastrointestinal endoscopy in Taipei, Taiwan. Between July 1991 and June 1992, 464 consecutive patients underwent endoscopy for a variety of upper gastrointestinal symptoms at a major medical center. The presence of erosive esophagitis, strictures, Barrett's esophagus, and hiatal hernia was recorded. The extent of mucosal injury was determined by using the Savary-Miller grading system. Sixty-six (14.5%) patients were found to have erosive esophagitis, 9 (2%), Barrett's esophagus, and 32 (7%) hiatal hernias. Erosive esophagitis showed a male-to-female preponderance of 3.1:1. Disease severity increased with age and peaked during the sixth and seventh decades. We concluded that in contrast to previous experience, the Chinese population in Taiwan appears to have a higher frequency of erosive esophagitis, Barrett's esophagus, and hiatal hernia. Increased fat consumption, aging, and other possible factors are suggested as possible mechanisms.

Adolescent↗
PubMed1997

Pharmacokinetics of meropenem in patients with liver disease.

Eight subjects with chronic stable alcoholic cirrhosis and eight matched controls with normal liver function were given an initial 30-minute intravenous infusion of 1 g of meropenem; beginning 24 hours later, they received five additional 1-g doses at 6-hour intervals. No statistically significant differences were found between the first dose and steady state or between groups for any plasma pharmacokinetic parameters-including the highest observed plasma concentrations, plasma concentrations at 6 hours after dosing (C6h), terminal half-life, area under the plasma concentration-time curve (AUC), area under the first moment of the curve, plasma clearance, steady-state volume of distribution, and accumulation ratios-on the basis of either AUC or C6h. There were also no statistically significant differences in any of the measured or calculated pharmacokinetic parameters of the microbiologically inactive metabolite of meropenem (ICI 213,689). A total of 11 adverse experiences (one moderate and 10 mild) were reported by four patients; nine of these experiences, including two in controls, were rated by the investigator as "possibly" drug related. It is concluded that meropenem is well tolerated with repeated intravenous dosing and that dosage adjustments are not necessary for patients with hepatic disease.

Adolescent↗
PubMed1997

The myths of emergency medical care access in the managed care era.

In this paper, we examine the perception that emergency care is unusually expensive. We discuss the myths that have fueled the ineffective and sometimes deleterious efforts to limit access to emergency care. We demonstrate the reasons why these efforts are seriously flawed and propose alternate strategies that aim to improve outcomes, including cooperative ventures between hospitals and managed care organizations. We challenge managed care organizations and healthcare providers to collaborate and lead the drive to improve the cost and clinical effectiveness of emergency care.

Cooperative Behavior↗
PubMed1996

The accuracy of the rapid urease test and 13C-urea breath test in the diagnosis of Helicobacter pylori infection.

BACKGROUND: Helicobacter pylori (H. pylori) is an important predisposing factor in peptic ulcer disease. Many tests have been proposed, but there is no generally accepted single method for the detection of H. pylori. This study compared the four available methods in the detection of H. pylori. METHODS: One hundred and thirteen patients were studied with endoscopic biopsy. Biopsy specimens were examined with modified Giemsa stain and rapid urease (CLO) test. Serology (ELISA) and 13C-urea breath test (13C-UBT) were also performed. The 13C-UBT results were expressed at an excess delta 13CO2 excretion of 5 per mil as the upper limit. Multiple breath samples were collected 15, 30 and 60 minutes following 13C-urea ingestion (t = 15, 30, 60) in the first 60 patients. Gastric inflammatory changes were graded according to the Whitehead classification. The diagnostic gold standard was defined when three or more of the four test parameters showed positive. RESULTS: According to this diagnostic gold standard, the positive rates of H. pylori were 97.9% for duodenal ulcer, 81.8% for gastric ulcer, 47.6% for symptomatic gastritis and 13.6% for asymptomatics. Rapid urease test and the 13C-UBT had better sensitivity (93.6% and 96.2%) and accuracy (93.8% and 93.8%). The specificity and positive predictive value for rapid urease test was better than 13C-UBT (94.3% v.s. 88.6%, 97.3% v.s. 94.9% respectively). Modified Giemsa stain had the lowest sensitivity (87.2%), and the ELISA test had the lowest specificity (71.4%). Severity of the gastric inflammatory processes was directly correlated with the excess delta 13CO2 (r = 0.576). CONCLUSIONS: Both the CLO and 13C-UBT had higher accuracy in the detection of H. pylori. When the CLO test result is positive, there is little additional diagnostic benefit from performing other tests. If patients refuse endoscopic examination, 13C-UBT is a good alternative for the detection of H. pylori, either during diagnosis or follow-up after therapy.

Adult↗
PubMed1994

An estimated shape function for drift in a platelet-transport model.

Prior work has shown that concentration profiles of platelets in flowing whole blood and of platelet-sized beads in flowing blood suspensions can include near-wall excesses. A model to describe this phenomenon was built about a single-component convective diffusion equation. To incorporate redistribution to preferred sites by shear flows of red cell suspensions, the model used a drift shape function (in addition to the commonly used augmented diffusion coefficient). This paper reports experiments that provide an average concentration profile from which the shape function for that model is calculated; the experiments and shape function are for the particular conditions of 40% hematocrit, platelet-sized latex beads (2.5 microns diameter), tube ID of 217 microns, and a wall shear rate of 555 s-1. Less precise estimates of the shape function obtained from data of previous studies indicate that the shape function is similar for the hematocrit of 15%.

Biophysical Phenomena↗
PubMed1994

Transient lateral transport of platelet-sized particles in flowing blood suspensions.

Concentration profiles of 2.5 microns latex beads were measured to demonstrate lateral transport of platelet-sized objects in flows of blood suspensions; the flows had equivalent Poiseuille wall shear rates (WSRs) from 250 to 1220 s-1. Each experimental trial began with a steady flow of suspension without beads in a thin-walled capillary tube (219 microns ID; 10.2 microns SD). The tube entrance was then switched to a reservoir containing suspension of equal hematocrit, but with beads, for a short interval of flow at the same WSR. This process established a paraboloidal tongue of labeled suspension with a transient concentration gradient at its surface. The tube and contents were rapidly frozen to fix the suspended particles in flow-determined locations. Segments of frozen tube were collected at distances from the entrance corresponding to 13%, 39%, and 65% of the axial extent of the ideal paraboloidal tongue. Concentration profiles were estimated from distances measured on fluorescence microscope images of cross-cut tube segments. Experiments used tubes either 40 or 50 cm long, suspension hematocrits of 0, 15, or 40%, and bead concentrations in the range of 1.5-2.2 x 10(5)/mm3. Profiles for 0% hematocrit suspension, a dilute, single-component suspension, had features expected in normal diffusive mixing in a flow. Distinctly different profiles and more lateral transport occurred when the suspensions contained red cells; then, all profiles for 13% extent had regions of excess bead concentration near the wall. Suspension flows with 40% hematocrit exhibited the largest amount of lateral transport. A case is made that, to a first approximation, the rate of lateral transport grew linearly with WSR; however, statistical analysis showed that for 40% hematocrit, less lateral transport occurred when the WSR was 250 s-1 or 1220 s-1 than 560 s-1, thus indicating that the rate behavior is more complex.

Biological Transport, Active↗
PubMed1994

Bioequivalence of 20-mg once-daily tamoxifen relative to 10-mg twice-daily tamoxifen regimens for breast cancer.

PURPOSE: We studied the bioequivalence of a new once-daily regimen of tamoxifen citrate relative to the standard twice-daily regimen of tamoxifen citrate, an established antiestrogenic treatment for breast cancer. PATIENTS AND METHODS: Of 30 women with breast cancer, 27 completed this open, two-period, crossover randomized trial. During one 3-month period, patients took one standard 10-mg tamoxifen tablet twice daily; during the preceding or following 3-month period, patients took one of the new 20-mg tablets once daily. Pharmacokinetic profiles and safety parameters were assessed at the end of each 3-month treatment period. RESULTS: Overall, measured concentrations of tamoxifen and its principal active metabolite, N-desmethyltamoxifen, remained relatively constant over the 24-hour sampling periods at the end of each treatment sequence. For both compounds, the percentage differences of the geometric means for all pharmacokinetic parameters indicated bioequivalence of the once-daily regimen of tamoxifen relative to the standard twice-daily regimen. Both treatment sequences were well tolerated; reported adverse events occurred at similar frequencies with the two treatment regimens. CONCLUSION: The 20-mg tamoxifen tablet taken once daily was bioequivalent to the 10-mg tamoxifen tablet taken twice daily, with no difference in relative risk. The once-daily treatment is a simpler regimen and may facilitate compliance, which may enhance therapeutic outcomes during long-term treatment of breast cancer.

Administration, Oral↗
PubMed1992

Helicobacter pylori, gastritis and duodenitis in the healing process of duodenal ulcer.

The occurrence of antral gastritis, duodenitis, gastric metaplasia and Helicobacter pylori (H. pylori) were compared between 63 endoscopically proven duodenal ulcer (DU) patients and 34 non-ulcer dyspepsia (NUD) patients with no ulcer history and no ulcer present as documented by endoscopy. The DU group showed a significantly higher rate of active antral gastritis (89% vs 41% p less than 0.05), a higher antral H. pylori carrying rate (76% vs 27% p less than 0.01), a higher rate of active chronic duodenitis (75% vs 32% p less than 0.05), and a higher rate of gastric metaplasia in the duodenal bulb (68% vs 27% p less than 0.05) than the NUD group. The H. pylori carrying rate in the bulb was 16% in the DU group and 0% in the NUD group. The difference is evident, although it is statistically insignificant. All 10 cases carrying H. pylori in the duodenum in the DU group had active chronic duodenitis with gastric metaplasia. Further evaluation of the variables (rate of active antral gastritis and duodenitis and the carrying rate of H. pylori in the antrum and bulb) showed no difference between different ulcer stages (active, healing, or scarred). The above findings strongly suggest a close relation between H. pylori and duodenal ulcer. However, the low occurrence rate of the bacteria in the bulb can only indicate a partial etiologic role of the bacteria in DU. No improvement in antral gastritis, duodenitis and H. pylori occurrence, despite the healing of an ulcer, is in agreement with the naturally high recurrence rate of duodenal ulcers.

Duodenal Ulcer↗
PubMed1991

Cellular characteristics of long-term cultured rat parotid acinar cells.

We have successfully maintained and biochemically characterized differentiated rat parotid acinar cells cultured for long periods (6 mo.). The cells were cultured on a reconstituted basement membrane matrix in a medium containing a variety of agents that promote cellular proliferation and differentiation. The cultured cells retain the characteristics of the parental parotid acinar cells. They exhibit both secretory granules and abundant cellular organelles required for protein synthesis and secretion. In situ hybridization and immunocytochemistry demonstrate high levels of proline-rich protein mRNA and protein, and lower levels of amylase mRNA and protein, in their cytoplasm. These findings suggest that rat parotid acinar cells can be maintained in a differentiated state in vitro for long periods, and can serve as a useful model system for studying the regulation of exocrine secretory processes.

Amylases↗
PubMed1991

Invasive thymoma presenting as aortic dissection.

We report the case of an invasive thymoma presenting as an aortic dissection in a 49-year-old woman with hypertension and a marfanoid appearance. The patient presented to the emergency department with "tearing" substernal chest pain. A chest radiograph revealed a right para-aortic bulge consistent with a dissecting aorta, but an aortogram was normal. Other disease states, including various types of mediastinal masses, have been reported to mimic aortic dissection.

Aortic Dissection↗
PubMed1990

Elevation of salivary antimicrobial proteins following HIV-1 infection.

Thirty-seven HIV-1-positive patients contributed salivary samples from individual major salivary glands. Nineteen patients were unmedicated and asymptomatic, and 18 patients had developed signs of AIDS. Salivas from 15 healthy males served as controls. Levels of four salivary antimicrobial proteins (lactoferrin, lysozyme, secretory IgA, and histatins) were determined, as well as total fluid output of the major salivary glands. Concentrations of all four salivary antimicrobial proteins were found to be increased in the stimulated submandibular/sublingual saliva of all HIV-1-positive patients as well as the subset of unmediated HIV-1-positive patients. Those patients with evidence of oral candidiasis had the highest concentrations of lysozyme and histatins, potent antifungal proteins, in their saliva. Although the etiology of these protein increases is still unknown, these results further document salivary changes following HIV-1 infection.

Acquired Immunodeficiency Syndrome↗
PubMed1988

The emergency physician's role in injury prevention.

New Mexico's successful campaign in establishing seat belt legislation is described, as is a unique program of alcohol and substance abuse prevention based in the emergency department. Results of a local study investigating hospital and emergency department costs of victims injured in automobile crashes are presented. A strategy is proposed that encourages joint efforts to influence public opinion and awareness, support necessary legislation, develop epidemiologic and intervention research, and encourage emergency medicine practitioners to act as a clearing house for outreach and prevention activities.

Alcoholism↗
PubMed1986

Cefotetan pharmacokinetics in volunteers with various degrees of renal function.

Twenty-six volunteers with various degrees of renal function were given a single 1-g dose of cefotetan intravenously over 30 min. Concentrations of cefotetan and cefotetan tautomer in plasma and urine were determined by high-performance liquid chromatography. The pharmacokinetic parameters for cefotetan were calculated according to a two-compartment open model. The mean plasma cefotetan concentration at the end of the intravenous infusion did not vary with renal function and ranged between 122 and 126 micrograms/ml. The mean terminal half-life was 4.2 h in normal volunteers and 9.9 h in volunteers with moderate renal impairment. There was a significant linear correlation between the systemic clearance of cefotetan and creatinine clearance. The cumulative amount of cefotetan excreted in the urine over 24 h in normal volunteers was approximately 49% of the dose, but this was reduced in volunteers with moderate renal impairment. The mean urinary cefotetan concentrations generally peaked during the 2- to 4-h interval after dosing. Cefotetan tautomer was sporadically detected in the plasma and urine of approximately 50% of the volunteers. The mean plasma cefotetan tautomer concentrations and mean total cumulative urinary recoveries of cefotetan tautomer were only minimal compared with those for cefotetan. The mean percentage of the dose excreted in the urine as cefotetan tautomer was not significantly affected by the degree of renal impairment. Recommendations for the dosing of cefotetan in renal-impaired patients are given.

Adolescent↗
PubMed1984

Association of Ureaplasma urealyticum in the placenta with perinatal morbidity and mortality.

We investigated the presence of ureaplasmas, mycoplasmas, chlamydiae, fungi, aerobic and anaerobic bacteria, and cytomegalovirus in fetal membranes and evaluated their association with perinatal morbidity and mortality. We cultured 801 placentas from three groups of subjects (144 who died in the perinatal period, 452 neonates admitted to the intensive-care unit, and 205 controls). Ureaplasma urealyticum, Mycoplasma hominis, or both were isolated from 21 per cent of placentas of premature and term infants who died in the perinatal period, 25 per cent of those admitted to intensive care, and 11 per cent of controls. Gestational age and birth weight were inversely related to isolation of ureaplasma, and chorioamnionitis was positively related to isolation. The presence of ureaplasmas in the placenta suggests the transcervical migration of these microorganisms from the lower genitourinary tract. These data show a strong association between ureaplasma infection of the placenta and low birth weight of the neonate and suggest that the association is causal.

Adult↗
PubMed1984

Competing risk analysis for life table data with known observation times.

"Several models have been proposed for the analysis of cohort mortality in the presence of competing risks.... This paper describes a maximum likelihood approach to the analysis of follow up data in life table format for the case of two competing risks--a specific cause and its competing complement. The model developed uses a robust survivorship assumption--the piecewise exponential--and takes into account information on time to death and time to withdrawal." (summary in GER)

Cause of Death↗