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Biomedical subjects

M Lee

Publications and source records attributed to M Lee.

At least 1,225 records · Page 68Linked to original sources
PubMedDate not supplied

Experimental analysis of the influence of stenotic geometry on steady flow.

We studied the flow behavior under steady flow conditions in four models of cylindrical stenoses at Reynolds numbers from 150 to 920. The flow upstream of the constrictions was always fully developed. The constriction ratios of the rigid tubes (D) to the stenoses (d) were d/D = 0.273; 0.505; 0.548; 0.786. The pressure drop at various locations in the stenotic models was measured with water manometers. The flow was visualized with a photoelasticity apparatus using an aqueous birefringent solution. We also studied the flow behavior at pulsatile flow in a dog aorta with a constriction of 71%. The flow through stenotic geometries depends on the Reynolds number of the flow generated in the tube and the constriction ratio d/D. At low d/D ratios, (with the increased constriction), the flow separation zones (recirculation zones, so-called reattachment length) and flow disturbances increased with larger Reynolds numbers. At lower values, eddies were generated. At high Re, eddies were observed in the pre-stenotic regions. The pressure drop is a function of the length and internal diameter of the stenosis, respective ratio of stenosis to the main vessel and the Reynolds numbers. At low Re-numbers and low d/D, distinct recirculation zones were found close to the stenosis. The flow is laminar in the distal areas. Further experiments under steady and unsteady flow conditions in a dog aorta model with a constriction of 71% showed similar effects. High velocity fluctuations downstream of the stenosis were found in the dog aorta. A videotape demonstrates these results.

Animals↗
PubMedDate not supplied

Changes of host natural killer cell activity in F344 rats during gastric carcinogenesis induced by N-methylnitrosourea.

To evaluate the role of NK cells during gastric carcinogenesis, especially in early stage of tumorigenesis, the changes of NK activity was examined. Rats were given N-methylnitrosourea (MNU) at a concentration of 100 ppm in their drinking water for 15 weeks. Rats were sacrificed sequentially on week 15, 18, 20, and 40 of the experimental period. Histological changes such as mild erosion, regenerative changes, focal or severe atypical lesions and invasive adenocarcinoma were observed sequentially in the pyloric region. Adenomatous hyperplasia was induced in majority of the rat stomach in MNU-treated group and incidence of adenocarcinoma was 20% in 40 weeks of MNU-treated group. There was no difference in NK activity until week 20, however, it was increased in MNU-treated rats at 40 week, when compared to that of untreated control group. From week 15, the ratio of pepsinogen altered pyloric gland (PAPG) between untreated control and MNU-treated rats was progressively increased, but there was no significant increment in the number of PAPG in MNU-treated rats after 20 weeks. NK activity was increased in MNU-treated rats, when compared to that of untreated control group. These results suggest that PAPG is a relatively good marker for the evaluation of progression of gastric carcinogenesis and increased NK activity is shown, especially in early stage of gastric carcinogenesis.

Animals↗
PubMedDate not supplied

Susceptibility to the induction of glutathione S-transferase positive hepatic foci in offspring rats after gamma-ray exposure during gestation.

Glutathion S-transferase positive (GST-P+) hepatic foci development was used as a means of determining whether the offspring of gestating maternal rats, which were subjected to genetically-damaging levels of gamma-ray radiation, were more susceptible to the development of cancer after treatment with diethylnitrosamine (DEN), a known carcinogen. A single dose of 10, 30, 60, and 90 rads involving whole body exposure to gamma-rays was given to pregnant rats at day 14, and during postnatal week 4. DEN was intraperitoneally injected to their offspring twice in one week. Thirteen weeks after birth, the rats were sacrificed. Irradiation of maternal rats with 30 rad gamma-rays before mating significantly increased both the incidence and the size of GST-P+ foci in the livers of both male and female pups, when combined with DEN treatment, whereas other dose levels had no such effect. Using a rat-liver model, the results of this study indicate that a low dose of radiation during the embryonic stage increases the susceptibility to carcinogens. In addition, under certain circumstances low doses of radiation, an externally applied cancer-inducing stimulus, may increase the likelihood of cancer, whereas higher doses may not.

Alkylating Agents↗
PubMedDate not supplied

Standards in anterior spine surgery in pediatric patients with neuromuscular scoliosis.

The authors reviewed 111 patients with neuromuscular disease who underwent anterior spine surgery for correction of scoliosis. An overall complication rate of 44.1% was found, 21.6% major and 22.5% minor. Pulmonary complications were the most common major complications, urinary tract infections the most common minor complications. The rate of complications was greater in patients with cerebral palsy, thoracoabdominal and transthoracic approaches, staged procedures, operative blood loss >1,000 mL, or previous spine surgery. In addition, statistical analysis confirmed that curve magnitude >100 degrees degrees was a risk factor for complications.

Adolescent↗
PubMedDate not supplied

Coagulopathy in hemorrhagic fever with renal syndrome (Korean hemorrhagic fever).

The pathophysiology of bleeding manifestations in hemorrhagic fever with renal syndrome (HFRS) was elucidated by serially evaluating coagulation and fibrinolytic profiles and complement alterations in patients with HFRS. In the early stage of the disease, platelet counts, platelet survival time, and platelet aggregation in vitro decreased. Prolongation of bleeding time, prothrombin time, and activated partial thromboplastin time was noted, with decreases in coagulation factors II, V, VIII, IX, and X. Levels of fibrinogen were decreased, and those of fibrinogen-fibrin degradation products in serum and urine were increased. Concentrations of plasminogen, alpha 2-plasmin inhibitor, and antithrombin III in plasma were depressed. Procoagulant activity was present in plasma. Circulating immune complexes were found, whereas serum levels of C3 were decreased. In the early stage of HFRS, thrombocytopenia, defects in platelet function, and disseminated intravascular coagulation may play central roles in the pathogenesis of bleeding manifestations. Vasculopathy and immunologic aberrations also may play a role.

Antigen-Antibody Complex↗
PubMedDate not supplied

Granular cell ameloblastoma of the mandible with metastasis to the third thoracic vertebra. A case report.

A 62-year-old housewife had a metastasis of granular cell ameloblastoma to the third thoracic vertebra. She had suffered at least four local recurrences during the 38-year duration of the right mandibular tumor and was treated by posterior decompression of the spinal cord with instrumentation. Histologically, the granular cells appeared to be of epithelial origin. Ultrastructurally, the granules were identified as lysosomes, including some that were autophagic. Of 45 reported cases of granular cell ameloblastoma, there have been only three cases with pathologically confirmed metastasis. Their characteristics are long duration of the tumor, multiple local recurrences, and predominance in blacks.

Ameloblastoma↗