Search PubMed⌕ Search

Biomedical subjects

Y T Lee

Publications and source records attributed to Y T Lee.

At least 19 recordsLinked to original sources
PubMed1992

Column liquid chromatography and microbiological assay compared for determination of cefadroxil preparations.

A reversed-phase column liquid chromatographic method was developed for the assay of cefadroxil in bulk drugs and pharmaceutical preparations. An equation was derived showing a linear relationship between peak-area ratios of cefadroxil to dimethylphthalate (internal standard) and the cefadroxil concentration over a range of 0.02-0.8 mg/ml (r = 0.9999). Standard addition recoveries were generally greater than 97.7%. The coefficients of variation in the within-day assay were between 0.36 and 0.65, and in the between-day assay was 0.71%. The column liquid chromatographic assay results were compared with those obtained from a microbiological assay, which indicated that the proposed method is a suitable substitute for the microbiological method for potency assays and stability studies of cefadroxil preparations.

Bacillus subtilis↗
PubMed1992

Vasodilator effect of scoparone (6,7-dimethoxycoumarin) from a Chinese herb.

A possible mechanism of the vasodilator effect of scoparone was investigated. Scoparone (10(-6)-3 x 10(-5) M) dilated rat aortic rings precontracted with phenylephrine in a dose-dependent manner. The presence of endothelium facilitated the vasodilator effect. Scoparone depressed the contractile responses to phenylephrine and serotonin, but not that to potassium chloride. Both the vasoconstriction and O2- production induced by alloxan, a diabetogenic compound, were depressed by scoparone. It appears that scoparone exhibited a free radical scavenger-like effect. The dilatation elicited by acetylcholine was potentiated by scoparone. The dilator activity of scoparone was markedly inhibited by methylene blue and hemoglobin, guanylate cyclase inhibitors. Furthermore, the basal guanosine 3',5'-cyclic monophosphate (cGMP) level was elevated in the presence of scoparone. The dilator activity of scoparone was also inhibited by quinacrine (inhibitor of phospholipase A2) and indomethacin (inhibitor of cyclooxygenase). Our results showed further that the output of 6-keto-prostaglandin F1 alpha, a stable metabolite of prostacyclin, was enhanced by scoparone. It is suggested that the vasodilator effect of scoparone in rat aorta may be mediated through the enhancement of prostacyclin release, protecting against EDRF inactivation, and activating guanylate cyclase.

Animals↗
PubMed1992

Possible mechanism of immunosuppressive effect of scoparone (6,7-dimethoxycoumarin).

The possible mechanism of the immunosuppressive effect of scoparone (6,7-dimethoxycoumarin) was investigated. Human peripheral blood mononuclear cells (10(6) cells/ml) were stimulated with 0.25% phytohemagglutinin (PHA) and the proliferative response was determined from the uptake of tritiated thymidine. Scoparone (10(-6) to 3 x 10(-4) M) reduced the proliferative response in a dose-dependent manner. The proliferative response of mononuclear cells to mixed lymphocyte reaction was also reduced by scoparone (10(-5) to 10(-4) M). Interleukin-1, interleukin-2 production and interleukin-2 receptor expression were all reduced in the presence of scoparone. Scoparone (10 and 30 microM) significantly reduced the suppression elicited by the diabetogenic drug, alloxan (10 mM). The suppressive activity of scoparone was significantly reduced by quinacrine (a phospholipase A2 inhibitor), indomethacin (a cyclooxygenase inhibitor) and nordihydroguaiaretic acid (a lipoxygenase inhibitor). The levels of prostaglandin E2, prostaglandin F2 alpha, leukotriene B4 and 2,3-dinor-thromboxane B2 in culture medium of PHA-stimulated mononuclear cells, measured with an enzyme immunoassay, were elevated by scoparone treatment. We compared the effect of scoparone on the mononuclear cell response to genistein, a specific inhibitor of protein tyrosine kinase and demonstrated the non-additivity and cross-desensitization of the two compounds. Our results suggest that the immunosuppressive effect of scoparone may be exerted in part through inhibition of protein tyrosine kinase and release of arachidonic acid metabolites.

Alloxan↗
PubMed1992

Effects of dietary supplementation with fish oil on atherosclerosis and myocardial injury during acute coronary occlusion-reperfusion in diet-induced hypercholesterolemic rabbits.

We studied myocardial injury during acute coronary occlusion-reperfusion and atherosclerosis in rabbits fed a high cholesterol diet with or without fish oil supplementation. New Zealand white male rabbits were divided into 3 groups. Eight control rabbits fed with laboratory standard rabbit chow were group I. In addition to the standard chow, 15 rabbits fed with a 1% cholesterol-enriched diet for 6 weeks were group II, and 10 rabbits fed with a 1% cholesterol-enriched and 10% fish oil supplemented diet for 6 weeks were group III. Acute coronary occlusion was induced by ligating the marginal branch of the left circumflex coronary artery for 1 h, followed by reperfusion for 4 h. Myocardial injury was assessed by tissue creatine kinase activities and amino-nitrogen concentrations from the ischemic (infarct) and nonischemic (normal) myocardium, and the infarct area/risk area ratios of the left ventricle. The surface area of the atherosclerotic lesions of the aorta and pulmonary artery was measured by planimeter. There was significantly more myocardial loss of creatine kinase and amino-nitrogen in the cholesterol-fed rabbits than the controls (p less than 0.01 and 0.02, respectively). The cholesterol and fish oil-treated rabbits had a nonsignificant reduction in myocardial loss of both agents as compared to their corresponding cholesterol-fed ones. The same trend was also found in the infarct area/risk area ratio. Fish oil treated rabbits had a good effect on the reduction of atherosclerotic lesions and tissue cholesterol levels in the aorta and pulmonary artery, but not in the left ventricle.(ABSTRACT TRUNCATED AT 250 WORDS)

Amines↗
PubMed1992

Effects of dietary supplementation with fish oil on prostanoid metabolism during acute coronary occlusion with or without reperfusion in diet-induced hypercholesterolemic rabbits.

We studied the changes in myocardial and aortic concentrations of prostacyclin and thromboxane A2 during acute coronary occlusion with or without reperfusion in rabbits fed with a cholesterol-enriched diet with or without fish oil supplementation for a short (5 days) or long period (6 weeks). New Zealand white male rabbits were divided into 5 groups: Group I, 15 control rabbits fed with a laboratory standard rabbit chow. In addition to the standard chow, the 4 study groups were treated with cholesterol or fish oil. Group II, 17 rabbits fed with a 1% high cholesterol diet for 5 days. Group III, 16 rabbits fed with a diet containing 1% cholesterol and 10% fish oil for 5 days. Group IV, 17 rabbits fed with the same diet as group II for 6 weeks. Group V, 18 rabbits fed with the same diet as group III for 6 weeks. Each group of rabbits was randomly divided into the coronary occlusion or occlusion-reperfusion mode of experiment. Acute coronary occlusion was induced by ligating the marginal branch of the left circumflex coronary artery for 1 h. Subsequent reperfusion for 4 h was performed in the occlusion-reperfusion rabbits. The aortic tissue above the aortic valve and the ischemic and normal (nonischemic) areas of the left ventricle were excised for the measurement of 6-keto-PGF1 alpha and thromboxane B2 levels by radioimmunoassay. Both during coronary occlusion and occlusion-reperfusion, rabbits showed higher myocardial concentrations of 6-keto-PGF1 alpha and thromboxane B2 in the ischemic area than in the normal myocardium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

[Changes of blood viscosity in patients undergoing cardiac surgery during cardiopulmonary bypass].

The patient undergoing open-heart surgery depends on hypothermia and cardiopulmonary bypass (CPB) to maintain organ perfusion during cardiac arrest. Increased blood viscosity during hypothermic CPB might be life-threatening, so hemodilution is imperative. Fourteen open-heart patients of ASA class II-III were included in this study. Pre- and intra-CPB viscosity changes were observed. Before CPB, 6 ml blood sample was drawn out from open-heart patients after systemic heparinization and another 6 ml blood sample was drawn out from the oxygenator after CPB was established. The hematocrit and relative viscosity of each sample in different temperatures were measured. The result revealed that as the temperature decreases, the viscosity of each sample increases apparently. As compared to the pre-CPB blood sample, the hematocrit of blood obtained intra-CPB decreases from 36.81 to 27.04, (p < 0.001), and the viscosity also decreases at all different temperatures (p < 0.001). Blood viscosity obtained at 37 degrees C pre-bypass is not statistically different from the sample at 25 degrees C during bypass. Obviously, increased viscosity due to hypothermia is buffered by hemodilution after using large amount of fluid as priming solution during CPB. Therefore, the hematocrit and viscosity remain within physiologic ranges.

Adult↗
PubMed1992

Exercise thallium-201 tomographic scintigraphy in the diagnosis of coronary artery disease: emphasis on the effect of exercise level.

Exercise thallium-201 imaging using single-photon emission computed tomography (SPECT) was evaluated in 154 patients with angiographically documented coronary artery disease (CAD) and in 25 normal subjects. Of the 154 patients with CAD, 134 (87%) had abnormal thallium images. By contrast, only 77 (50%) patients had ischemic ST-segment depression (p < 0.001). Among 25 normal subjects, 20 had normal exercise SPECT images. The specificity of exercise SPECT imaging (80% or 20/25) in excluding patients with CAD was not significantly higher than that of exercise electrocardiography (76% or 19/25). For the detection of individual vessel involvement by analysis of territories of perfusion abnormalities, the sensitivity and specificity of exercise SPECT were 72% and 96% for the left anterior descending, 78% and 85% for the right coronary, and 47% and 98% for the left circumflex artery. Ninety (group 1) of the 154 patients with CAD achieved adequate exercise end points (ischemic ST-segment depression or > 85% of maximal predicted heart rate) and 64 (group 2) did not. Exercise SPECT showed significantly more perfusion abnormalities in group 1 than in group 2 (96% vs 75%, p < 0.001). We conclude that: (1) exercise SPECT thallium imaging is more sensitive than exercise electrocardiography for detecting patients with CAD; (2) the sensitivity of the test is affected by the level of exercise; and (3) it is valuable in the identification of individual vessel involvement.

Coronary Disease↗
PubMed1992

Operation Desert Storm: clinical experiences at the 13th Evacuation Hospital, a Wisconsin National Guard unit.

The 13th Evacuation Hospital, a National Guard unit, was deployed to the Persian Gulf Jan 11, 1991. We set up a 400-bed hospital and became fully functional 11 days before the ground war started. From Jan 11 to March 8, 1991, the hospital took care of 3,907 out-patients and admitted 435 patients. Approximately half the patients were admitted before the ground war began, while 88 of the 125 operations were performed after the ground war started. We admitted 61 patients for war-related injuries, and 28 required operations in our hospital. Since the ground war lasted only 100 hours, we took care of many more patients with non-war related injuries or illness. The various complaints and reasons for admission to the hospital are presented in detail.

Hospitals, Military↗
PubMed1992

[Comparison of body height and vertebral column length in Chinese parturients].

Spinal anesthesia (SA) is frequently used in parturients undergoing Cesarean sections (C/S). The body height (BH) is commonly believed to be one of the factors influencing the spread of SA, especially in patients with extremes of the BH. Recent studies, however, show that the spread of SA is not related to the BH but to the vertebral column length (VL). This study aims to evaluate the relationship between the BH and VL in Chinese parturients. 258 parturients without vertebral column abnormality undergoing C/S were included in this study. The VL (between C7 prominence and sacral hiatus) of each patient was measured in the right decubitus position. They were divided into 3 groups according to their BH (group A less than 152 cm; group B = in the range of 153-161 cm; group C greater than 162 cm). In each group correlation between the BH and VL was made by linear regression analysis. Also determined is whether there is significant difference between each two groups by unpaired Student's t-test. A p values less than 0.05 is considered as statistical significance. The results of the present study showed that although there exists correlation between the BH and VL, the correlation coefficient (r value) is small in each group (0.29, 0.13, and 0.31 in Group A, B, and C respectively; p less than 0.05). There is, also, no significant difference of the VL among the three groups. Therefore we concluded that the BH and VL did not closely correlate and therefore BH might contribute little to the spread of SA in the Chinese parturients, including those with extremes of BH.

Adolescent↗
PubMed1991

Heterotopic heart transplantation--a life-saving procedure with a size-mismatched donor.

A 32-year-old B-type male weighing 60 kg suffered from end-stage dilated cardiomyopathy. Although aggressive medical treatment with dobutamine 21 micrograms/kg/min, dopamine 17 micrograms/kg/min, digoxin 0.25 mg i.v. once daily, furosemide 40 mg i.v. every 6 h, and bumetanide 0.5 mg i.v. every 6 h were given, he was finally ventilator dependent for the last 3 weeks until a B-type donor weighing 42.5 kg was found. Because of the 29.2% weight mismatch, a heterotopic heart transplantation was performed. Posterior plication mitral annuloplasty was also performed to correct the severe mitral regurgitation of the recipient heart. Postoperatively the patient remained respirator dependent for 17 days and was finally discharged in good condition on the 46th postoperative day.

ABO Blood-Group System↗
PubMed1991

Primary malignant fibrous histiocytoma of the aorta associated with aortic dissection.

We report a unique case of primary aortic malignant fibrous histiocytoma presenting clinically as aortic dissection. To our knowledge, this occurrence is the first ever reported. The magnetic resonance imaging technique may provide superiority in the differential diagnosis between tumor and hematoma of aortic dissection. Aortic tumor, although rare, should be included among the causes of aortic dissection.

Aortic Dissection↗
PubMed1991

The clinical characteristics of acute myocardial infarction in aged patients.

Age is one of the important prognostic factors for acute myocardial infarction. This study was performed to clarify the clinical characteristics and outcome of acute myocardial infarction in Chinese geriatric patients. The study subjects included 742 patients, divided by age into 2 groups: Group A greater than or equal to 65 years, 321 cases; and Group B less than 65 years, 421 cases. The following characteristics were compared between these 2 groups: sex composition; presence of chest pain, heart failure or shock at presentation; cardiac functional status; occurrence of various complications, and follow-up data. Males were less prominent in the older group: 229 patients (71.3%) in Group A, and 371 patients (88.1%) in Group B. At onset, the older patients presented with less chest pain (72% vs 86.5%) and more heart failure (35.2% vs 20.2%), but the occurrence of shock was similar (5.9% vs 4.5%, for Groups A and B, respectively). During hospitalization, more patients in Group A showed impaired cardiac function, as evidenced by a higher percentage of patients identified as in Killip class III or IV (35.4% vs 21.1%). Concerning complications, the older group showed a higher incidence of hypotension, low cardiac output, lung edema, frequent premature ventricular beats, atrial flutter and/or fibrillation, complete heart block and intraventricular conduction defects, but ventricular septal defects, ventricular tachycardia and ventricular fibrillation did not show any difference in occurrence. Life table analysis showed that the survival rate was significantly lower for Group A during the follow-up period of 5 years.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1991

Heart diseases following radiotherapy.

Three women had cardiac complaints 10-17 years after a radical mastectomy and radiotherapy for cancer of the left breast. Their ages were 42, 43 and 57 years, respectively. The first patient had a precocious coronary artery disease (CAD). She had segmental stenosis in the middle and distal portions of the left main coronary artery and pericardial fibrosis. Symptoms and signs of severe pericardial constriction became the problem after bypass surgery. She died 1 year later due to cardiorespiratory failure. The second case had sick sinus syndrome presenting a prolonged pause for 12 seconds alternating with tachy- and bradyarrhythmias, a complete atrio-ventricular block in association with pericardial effusion plus aortic and mitral valvular regurgitation. The condition improved after the implantation of a permanent pacemaker. To date, this is a very rare complication of radiation induced panconduction disturbance. The third patient had significant stenosis in the proximal portion of the left anterior descending coronary artery and myocardial fibrosis was proven by an endocardial biopsy. She had an uneventful course after medical treatment.

Adult↗
PubMed1991

Anticardiolipin antibodies in patients with acute myocardial infarction.

Fifty-six consecutive patients, 53 males and 3 females aged from 36 to 83 with a mean age of 61.0, all with acute myocardial infarction (AMI), were screened for anticardiolipin antibodies (ACA) by single sampling at time of admission to the medical intensive care unit; results were compared with those for age-matched, healthy controls. IgM and IgG-ACA were measured by an enzyme-linked immunosorbant assay technique. IgG-ACA were detected in 9 patients (16.1%); IgM-ACA were detected in 9 patients (16.1%). Only one of the patients had raised ACA of both isotypes. There was on difference in either ACA levels or frequency of ACA elevation between patients and controls. Risk factors of coronary artery disease showed no significant difference between patients with and without ACA. Low titer of IgG-ACA was found in one of ten patients with reinfarction and/or previous cerebral infarction. In conclusion, single measurements of anticardiolipin antibodies in general AMI patients are unlikely to yield diagnostically important information. The implication of occasional significant elevation of such antibodies in a general AMI population remains to be speculated.

Adult↗
PubMed1991

Pulmonary embolism from a venous thrombosis distal to the popliteal vein.

A case of pulmonary embolism from a venous thrombosis distal to the popliteal vein is reported. This occurred despite venographic and ultrasound verification that the thrombus had not extended to the popliteal vein. The medical literature supports expectant treatment of "calf-only" venous thrombi. Our case clearly demonstrates that clinically significant pulmonary emboli can arise from calf vein thrombi without popliteal involvement.

Adult↗