PubMed Health⌕ Search

Biomedical subjects

T Yu

Publications and source records attributed to T Yu.

At least 55 records · Page 3Linked to original sources
PubMed1995

Observer performance comparison of digital radiograph systems for stereotactic breast needle biopsy.

RATIONALE AND OBJECTIVES: Two digital radiograph systems for stereotactic mammography, one using a lens to couple a Lanex Regular screen to a back-illuminated charge-coupled device (CCD) and one using a fiber-optic taper to couple a Min-R Regular-type screen to a front-illuminated CCD, were evaluated with respect to observer performance. METHODS: A contrast-detail phantom was imaged in a variety of equivalent exposure conditions on both systems. Six observers viewed images on a video monitor and recorded which objects were detected. RESULTS: Performance (percent correct detections) with the lens-coupled system using the Lanex Regular screen was significantly higher than with the fiber-optic-coupled system using the Min-R Regular-type screen. CONCLUSION: Differences in absorption efficiencies of phosphors used, as well as differences in design of the two cameras, can explain differences in observer detection performance.

Biopsy, Needle↗
PubMed1995

Tests for possible effects of selection by domestic pyrethroids for resistance in culicine and anopheline mosquitoes in Sichuan and Hubei, China.

Resistance tests, by conventional methods and by observing the time for knockdown, showed no evidence for any build up of resistance to deltamethrin in malaria vectors from areas where millions of bednets have been treated with this compound annually for up to 7 years. However, a strain of Culex quinquefasciatus which had been bred in a factory in which volatile pyrethroids are handled had developed unequivocal resistance to deltamethrin. Observation of the time for knockdown gave clearer discrimination between resistant and susceptible strains than did observation of percentage mortality after a standard exposure time.

Animals↗
PubMed1995

Inhibition of the tumor promoting action of 12-O-tetradecanoylphorbol-13-acetate by tubeimoside III isolated from Bolbostemma paniculatum.

As tubeimoside I isolated from Bolbostemma paniculatum (Maxim.) Franquet (Cucurbitaceae) has been shown to suppress tumor promoter effects, tubeimoside III from the same plant was tested in vitro and in vivo against the action of the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). Tubeimoside III, the natural analog of tubeimoside I, also had an anti-inflammatory effect on mouse ear edema induced by arachidonic acid and TPA and a potent anti-tumor promoting effect on two-stage carcinogenesis of mouse skin after topical application. However, the important difference in bioactivities between tubeimosides I and III is the non-activity of tubeimoside III as an inhibitor of tumor promotion if administered orally. Differences in metabolism connected with different routes of the compound may be one of a number of explanations of the important difference.

Animals↗
PubMed1995

[A study on the peripheral blood stem cells mobilization, collection and their effects on engraftment].

The methods of mobilization and collection of stem cells in peripheral blood stem cells transplantation (PBSCT) and the association between the number of stem cells transplanted and hematopoietic recovery were studied. The investigation was carried in 22 patients (11 acute leukemia, 6 multiple myeloma, 4 non-Hodgkin's lymphoma, 1 breast cancer). Three regimens for mobilization were carried out as follows: 1) chemotherapy + tetrahydrofolic acid + dexamethasone, 2) chemotherapy + rhGM-CSF + dexamethasone, 3) chemotherapy + rhG-CSF + dexamethasone. Besides, CD34/CD33 dual-color direct immunofluorescence flow cytometry assay was performed in 7 cases in the rhG-CSF group. The results showed: 1) The mean number of collected cells (MNC) in the rhG-CSF group was MNC (8.29 +/- 6.14) x 10(8)/kg and CFU-GM (21.35 +/- 17.24) x 10(4)/kg, being highest among the 3 groups. 2) The number of CD34+ cells correlated with MNC and CFU-GM. CD34+ cells in the peripheral blood were 0 or < 0.5% before mobilization and increased markedly 6-8 days after rhG-CSF administration. Harvesting should be started at that time and carried out every day until CD34+ cells reached 5 x 10(6)/kg. 3) The number of PBSC transplanted was the key to hematopoietic recovery.

Adolescent↗
PubMed1994

Alterations in regional brain catecholamine concentrations after experimental brain injury in the rat.

Although activation of brain catecholaminergic systems has been implicated in the cerebrovascular and metabolic changes during subarachnoid hemorrhage, cerebral ischemia, cortical ablation, and cortical freeze lesions, little is known of the response of regional brain catecholamine systems to traumatic brain injury. The present study was designed to characterize the temporal changes in concentrations of norepinephrine (NE), dopamine (DA), and epinephrine (E) in discrete brain regions following experimental fluid-percussion traumatic brain injury in rats. Anesthetized rats were subjected to fluid-percussion brain injury of moderate severity (2.2-2.3 atm) and killed at 1 h, 6 h, 24 h, 1 week, and 2 weeks postinjury (n = 6 per timepoint). Control animals (surgery and anesthesia without injury) were killed at identical timepoints (n = 6 per timepoint). Tissue concentrations of NE, DA, and E were evaluated using HPLC. Following brain injury, an acute decrease was observed in DA concentrations in the injured cortex (p < 0.05) at 1 h postinjury, which persisted up to 2 weeks postinjury. Striatal concentrations of DA were significantly increased (p < 0.05) only at 6 h postinjury. Hypothalamic concentrations of DA and NE increased significantly beginning at 1 h postinjury (p < 0.05 and p < 0.05, respectively) and persisted up to 24 h for DA (p < 0.05) and 1 week (p < 0.05) for NE. These data suggest that acute alterations occur in regional concentrations of brain catecholamines following brain trauma, which may persist for prolonged periods postinjury.

Animals↗
PubMed1994

[Reorganization of growth-plate-like tissue by isolated chondrocytes in culture].

Growth-plate cartilage is organized into four cellular zones containing resting, proliferating, maturing, and hypertrophic cells. Rabbit chondrocytes were isolated from growth-plate costal cartilage of 4-week-old New Zealand rabbits, the cells (15 x 10(4)) were suspended in 1 ml of Iscove's modified Dulbecco's medium (IMDM) with 10% fetal bovine serum, 50 micrograms ascorbic acid, and 60 micrograms kanamycin (medium A), then transferred to a 15 ml of plastic centrifuge tube, and centrifuged at 1500 rpm for 5 min. The cell pellet was incubated at 37 degrees C under 5% CO2 in air. The cultures reorganized into growth plate-like tissue which could be seen 7-14 days after cell seeding. This growth-plate, histologically, was organized longitudinally into cellular columns and horizontally into four cellular zones containing resting, proliferating, maturing and hypertrophic cells. The hypertrophic cells in the upper were large in size and round or oval in shape, the proliferating and the mature chondrocytes in the lower were small in size and spherical or elongated in shape. These chondrocytes were surrounded by an extensive matrix. Biochemically, DNA content of cultures began to rise on the 2nd day after cell seeding and reached a plateau after 10 days later. The uronic acid content increased from day 4 and reached the maximum on day 15. In contrast in the early culture, alkaline phosphatase activity was extremely low, it began to rise on day 9 and was the highest on day 20. The sequential increase of DNA, uronic acid and alkaline phosphatase contents was analogous to the in vivo changes of growth-plate chondrocytes.

Alkaline Phosphatase↗
PubMed1993

Classification of fumarate reductases and succinate dehydrogenases based upon their contrasting behaviour in the reduced benzylviologen/fumarate assay.

Reduction of fumarate by soluble beef heart succinate dehydrogenase has been shown previously by voltammetry to become increasingly retarded as the potential is lowered below a threshold potential of -80 mV at pH 7.5. The behaviour resembles that of a tunnel diode, an electronic device exhibiting the property of negative resistance. The enzyme thus acts to oppose fumarate reduction under conditions of high thermodynamic driving force. We now provide independent evidence for this phenomenon from spectrophotometric kinetic assays. With reduced benzylviologen as electron donor, we have studied the reduction of fumarate catalysed by various enzymes classified either as succinate dehydrogenases or fumarate reductases. For succinate dehydrogenases, the rate increases as the concentration of reduced dye (driving force) decreases during the reaction. In contrast, authentic fumarate reductases of anaerobic cells (and 'succinate dehydrogenase' from Bacillus subtilis) neither exhibit the electrochemical effect nor deviate from simple kinetic behaviour in the cuvette assay. The 'tunnel-diode' effect may thus represent an evolutionary adaptation to aerobic metabolism.

Animals↗
PubMed1992

Clinical and electrophysiologic studies of R61748 (transcainide): a new class Ic antiarrhythmic drug.

The electrophysiology and antiarrhythmic efficacy of R61748, a 4-OH metabolite of R54718 (transcainide), have been studied in patients and animal experiments. The results indicated that R61748 (1 mg/l) decreased the rate of rise of the transmembrane action potential (Vmax) by 40% and shortened the action potential duration (APD) by 10% in guinea-pig right ventricular papillary muscle. ERP/APD increased by 10%. The effect was dose-dependent. Clinical electrophysiologic studies (EPS) in 6 patients with ventricular premature beats showed that R61748 (0.1 mg/kg) prolonged PA duration by 30%, AH interval by 13% and HV duration by 24%. ECG revealed prolonged P duration by 16%, P-R interval by 16% and QRS duration by 17%. R61748 has also been used in 14 patients with idiopathic premature ventricular contraction (PVCs). PVCs were abolished in 6 patients and decreased more than 93% in 2 patients. The average reduction of PVCs was 80%. R61748 (0.075 mg/kg) abolished an episode of repetitive ventricular tachycardia in 1 patient. It is concluded that R61748 is a potent new class Ic antiarrhythmic agent with slow kinetics. R61748 is the 4-OH metabolite of R54718 (transcainide) (Stroobandt et al., 1987) which is a new class Ic antiarrhythmic agent. Up to now no reports have been published about R61748. This paper presents the initial studies of cellular and clinical electrophysiologic effects and the evaluation of antiarrhythmic efficacy of R61748.

Action Potentials↗
PubMed1992

[The variations of PRL, LH, FSH and testosterone in renal disease].

Blood PRL was measured with RIA in 22 males and 19 females with various degrees of renal insufficiency. At the same time, blood LH, FSH, testosterone were studied in all the male patients and 20 sex-age matched healthy subjects. The results showed that the levels of PRL and LH were increased, and the level of testosterone was decreased significantly in male uremic patients. There was a significant negative correlation between PRL and testosterone. All the above parameters were measured again 8-25 days after continuous ambulatory peritoneal dialysis (CAPD) therapy in 5 male uremic patients. The BUN and Cr levels decreased and the clinical manifestations of uremia improved, but the levels of PRL, LH, FSH and testosterone showed no significant changes. The mechanisms of these variations were discussed.

Adolescent↗
PubMed1992

Study of the relationship between the hepatotoxicity and free radical induced by 1,1,2-trichloroethane and 1,1,1-trichloroethane in rat.

The hepatotoxicity and the relationship between the hepatotoxicity and free radical induced by 1,1,2-trichloroethane (1,1,2-TCE) and 1,1,1-trichloroethane (1,1,1-TCE) were studied by whole animals test and the isolated perfused rat liver test. Enzymatic parameters measured during the test included the assay of levels of glutamic pyruvic transaminase (GPT), sorbital dehydrogenase (SDH) and glutamate dehydrogenase (GDH). The observation of the pathologic changes of the liver by the light microscope and the measurement of the relative total free radical concentration in the liver were also made. The results showed that 1,1,2-TCE caused definite pathologic changes of rat liver. It led to much higher values for GPT, SDH and GDH both in serum and perfusate than 1,1,1-TCE did (P < 0.01). The concentration of perfusate K+ caused by 1,1,2-TCE was higher than that by 1,1,1-TCE (P < 0.01). The value of the relative total free radical concentration induced by 1,1,2-TCE was also greater than that by 1,1,1-TCE (P < 0.05). The results suggested that the hepatotoxicity of 1,1,2-TCE was stronger than that of 1,1,1-TCE. The free radical concentration was increased proportionally to the increase of the hepatotoxicity of 1,1,2-TCE and 1,1,1-TCE. It appeared that free radical may play an important role in the mechanism of the hepatic injury induced by 1,1,2-TCE.

Alanine Transaminase↗
PubMed1980

Potential organ- or tumor-imaging agents XIX: radioiodinated antiarrhythmic drugs as potential myocardial imaging agents.

Iodinated and radioiodinated analogs of propranolol and N,N-dimethylpropranolol were synthesized wherein an iodophenyl moiety replaced the naphthalene ring of the parent drug. These new compounds were evaluated not only for their beta-adrenergic blocking and antiarrhythmic activities but also for their ability to accumulate selectively in myocardial tissue. Like propranol, the iodinated analogs displayed comparable beta-blocking and antiarrhythmic activity, and the order of potency was ortho- > meta- > para-iodophenyl. Quaternization of propranolol and the iodinated analogs eliminated the beta-adrenergic blocking activity but retained the antiarrhythmic property of the secondary amine precursors. Among the quaternary salts, the antiarrhythmic potency was meta- > ortho- > para-iodophenyl. Tissue distribution of the radioiodinated derivatives revealed that only the quaternary derivatives were selectively accumulated in myocardial tissue. These results demonstrate that an iodophenyl ring can substitute for th naphthalene ring in propranolol and its quaternary salt without significant alteration of pharmacological properties. The radioiodinated quaternary derivatives may be useful pharmacological tools in experiments aimed at relating antiarrhythmic activity to myocardial uptake.

Adrenergic beta-Antagonists↗
PubMed1978

Adrenal imaging agents: rationale, synthesis, formulation and, metabolism.

In this introductory paper on radionuclide adrenal imaging, the rationale, synthesis, formulation, and metabolism of two clinically well-established and one promisinmg adrenocortical imaging agents are reviewed. Their present clinical utility is reviewed in a separate presentation in this issue. Progress to date in developing a positive imaging agent of the adrenal medulla and tumors of chromaffin tissue will be given brief consideration because there is, as yet, no clinically successful radiolabeled adrenal medulla imaging agent.

Adrenal Glands↗