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Biomedical subjects

M L Chen

Publications and source records attributed to M L Chen.

At least 217 records · Page 12Linked to original sources
PubMed1979

Adenocarcinoma of the pancreas associated with hypoglycemia: case report and review of the literature.

The occurrence of profound hypoglycemia in a patient with metastatic adenocarcinoma of the pancreas is reported. In contrast to the four previously reported cases, no suggestion of excess insulin production was found. Metabolic studies in this patient suggest both increased peripheral glucose utilization and decreased hepatic glucose production as contributing factors which promoted the hypoglycemia.

Adenocarcinoma↗
PubMed1975

Management of parotid gland tumors in infants and children.

Seventy-four pediatric patients with parotid gland tumors were seen during a 52-year period. Seventy percent of the lesions were benign and 30% were malignant. When the primary treatment is either subtotal or total parotidectomy, the recurrence rate was 2.3%. The facial nerve should be dissected free of parotid parenchyma and preserved, except if the lesion was malignant--a situation in which the nerve might have to be sacrificed totally or in part to ensure adequate tumor removal. No patient died of a benign or malignant lesion in this series, and the morbidity after surgical removal of primary tumors of the parotid gland in children and infants was low.

Adolescent↗
PubMedDate not supplied

Pharmacokinetics of drugs in blood. I. Unusual distribution of gentamicin.

Distribution kinetics of gentamicin in whole blood were studied. After spiking human blood to an initial concentration of 20 microgram ml-1, plasma gentamicin concentrations dropped to minima at about 5 min then increased to maxima at about 15 min and remained constant afterwards. A difference of up to 36 per cent between the maximum and minimum was found. The equilibration was faster with lower initial concentrations. These unusual distribution phenomena might be attributed to the Schiff base formation between nonprotonated amino groups of gentamicin and free fatty aldehyde groups on blood cell membrane. The mean equilibrium blood cells/plasma partition ratio was about 0.1. Similar equilibration kinetics were observed with blood of rabbits after being intravenously dosed with gentamicin. Therefore, the time elapsed between the collection and centrifugation of blood samples, especially shortly after dosing, may have a significant effect on the 'measured' plasma gentamicin concentration. Distribution between plasma and blood cells may also occur in a similar manner with other drugs which have primary amino groups. It is recommended that distribution kinetics of drugs and metabolites in blood be included in pharmacokinetic studies.

Adult↗
PubMedDate not supplied

Ultrastructural studies of fibroblasts transfected with hepatitis B virus DNA.

Cultured 3T3 mouse fibroblasts transfected with cloned hepatitis B virus genome and DNA coding for methotrexate-resistant dihydrofolate reductase, produce and secrete significant amounts of hepatitis B surface antigen (HBsAg). Ultrastructural morphometry revealed that fibroblasts transfected with hepatitis B virus DNA contained significantly more lysosomes than did fibroblasts transfected with the gene coding for methotrexate resistance or normal fibroblasts. Although abundant HBsAg was found in the cytoplasm of transfected fibroblasts by immunologic methods, HBsAg particles were not detected by electron microscopy. Immunoelectron microscopy localized HBsAg to the nuclear envelope, rough endoplasmic reticulum, and endoplasmic cisternae. These findings suggest that the transfected cells produce mainly nonparticulate HBsAg or that they have a defect in intracisternal packaging of HBsAg into particles.

Animals↗
PubMedDate not supplied

Do beta-blockers affect the diagnostic sensitivity of dobutamine stress thallium-201 single photon emission computed tomographic imaging?

BACKGROUND: The effects of beta-blockers on dobutamine stress 201Tl tomographic imaging are not known. This study was undertaken to examine whether beta-blockers affect the sensitivity of dobutamine stress 201Tl imaging. METHODS AND RESULTS: One hundred ten patients without previous myocardial infarction underwent dobutamine stress 201Tl single photon emission computed tomography (SPECT) and coronary arteriography, both studies within a 1-week period. Dobutamine was infused at rates of 5, 10, 20, 30, and 40 microg/kg/min in 3-minute stages. Atropine (as much as 1 mg) was injected intravenously when the patient's heart rate was <100 beats/min. Patients in group 1 (n = 72) were receiving beta-blockers and patients in group 2 (n = 38) were not. The SPECT images in group 1 showed perfusion abnormalities in 62%, 87%, and 94% of patients with one-, two-, and three-vessel coronary artery disease (> or = 50% diameter stenosis), respectively, compared with 75%, 71% and 100% in group 2 (p not significant). The overall sensitivities were 82% (37 of 45) in group 1 and 80% (16 of 20) in group 2 (p not significant). The specificities were 81% (22 of 27) in group 1 and 83% (15 of 18) in group 2 (p not significant). The overall accuracies were the same for both groups (82%). Atropine was added more often in group 1 than in group 2 (37/72 vs 5/38, p < 0.001). CONCLUSIONS: Our results suggest that beta-blockers do not affect the sensitivity, specificity, and accuracy of dobutamine stress 201Tl SPECT imaging for detecting coronary artery disease if atropine is given when the chronotropic response is inadequate. In patients receiving beta-blockers, however, the addition of atropine to dobutamine stress is more frequently required.

Adrenergic beta-Antagonists↗
PubMedDate not supplied

Assessment of coke oven emissions exposure among coking workers.

Coking workers are regularly exposed to coke oven emissions, which consist primarily of polycyclic aromatic hydrocarbons and volatile organic compounds. This study measured the workers' exposure to the benzene soluble fraction of total particulates (BSF). The study population consisted of 88 coking workers as an exposure group and 59 referents. Personal breathing-zone samples of BSF and total particulates were taken from all study subjects for 3 consecutive days. The highest BSF concentrations were found among the topside oven workers (geometric mean; range) (microgram/m3): lidman (515; 72-18, 181), tar chaser (432; 51-4334), and larry car operator (185; 55-649). The lowest was 7 micrograms/m3 in the referents. Among the samples at the topside oven 84% exceeded the Occupational Safety and Health Administration standard (150 micrograms/m3 BSF). The percentage of BSF in total particulates varied across job classifications, ranging from 0.3% in wharfmen to 24% in tar chasers. Area sampling indicated that the BSF concentration at the topside area was sixtyfold higher than that at the administrative area, which was approximately 2 km from the coke oven plant.

Air Pollutants, Occupational↗
PubMedDate not supplied

Electrolyte loss in sweat and iodine deficiency in a hot environment.

The authors studied electrolyte loss from profuse sweating in soccer-team players and evaluated the relationship between this source of iodine loss and iodine deficiency. Thirteen male soccer-team players and 100 sedentary students from the same high school were evaluated for 8 d, during which the players were training. The authors analyzed 208 sweat samples to determine losses of iodine, sodium, potassium, and calcium in sweat. Excretion of urinary electrolytes by the subjects was also measured. The mean losses of iodine, sodium, potassium, and calcium in sweat following a 1-hr game were 52 microg, 1,896 mg, 248 mg, and 20 mg, respectively; the ratios of sweat loss to urinary daily loss of the four electrolytes were 0.75, 0.2, 1.88, and 0.92, respectively. Urinary iodine was significantly (p < .02) lower than the normal level of 50 microg/gm creatinine in 38.5% of the soccer players, compared with 2% of the sedentary students. Forty-six percent of the players had Grade I goiter, compared with a mere 1% of the sedentary students (p < .01). The results of the study suggest that loss of iodine through profuse sweating may lead to iodine deficiency, and loss of electrolytes through sweating may have a dietary significance for heat-stressed individuals or for individuals who perform heavy workloads.

Adolescent↗