Biomedical subjects

B Lu

Publications and source records attributed to B Lu.

275 records · Page 16Linked to original sources

PubMedDate not supplied

Evaluation of coronary artery bypass graft patency using three-dimensional reconstruction and flow study on electron beam tomography.

OBJECTIVES: To establish and evaluate two protocols for the noninvasive visualization and assessment of coronary artery bypass graft (CABG) patency on electron beam tomography (EBT). METHODS: Two hundred fourteen consecutive patients who underwent CABG surgery were scanned using both EBT angiography with three-dimensional reconstruction and EBT flow study with time-density curve analysis. RESULTS: There was a total of 589 CABGs evaluated in this study (10 grafts were excluded because of artifacts); 133 (98.5%) of 135 arterial grafts were patent, 345 (77.7%) of 444 saphenous vein grafts were patent. Within 5 years or 5-10 years after surgery, arterial graft patency exceeded venous graft patency (p<0.001). Three-dimensional EBT angiography achieved higher sensitivity, specificity, and accuracy (97.7%, 94.1%, and 96.7%, respectively) than EBT flow study (88.4%, 82.4%, and 85.2%, respectively) for evaluating occlusion or patency of CABGs. The intragraft flow of patent arterial and venous grafts were 4.9+/-2.2 ml/min/g and 6.9+/-2.8 ml/min/g, respectively (p<0.001). CONCLUSION: The combination of EBT three-dimensional reconstruction and flow study can be more effectively performed in the assessment of CABG anatomy and quantification of patent CABG flow.

Coronary Angiography↗

PubMedDate not supplied

Co-localization of histamine and dopamine-beta-hydroxylase in sympathetic ganglion and release of histamine from cardiac sympathetic terminals of guinea-pig.

1. The aim of this study was to investigate the co-localization of histamine and dopamine-beta-hydroxylase in the superior cervical ganglion of guinea-pig and release of histamine from cardiac sympathetic terminals in guinea-pig isolated atrium. 2. Histidine decarboxylase (a histamine-synthesizing enzyme) mRNA signals were detected in the neurones of superior cervical ganglion of guinea-pig by in situ hybridization. The results of double-labelled immunofluorescence further confirmed the co-localization of histamine and dopamine-beta-hydroxylase in the large principle neurons and small intensely fluorescent cells in the superior cervical ganglion. The immunoreactivities of both histamine and dopamine-beta-hydroxylase were significantly attenuated after 6-hydroxydopamine-induced lesion of sympathetic nerves. 3. The refractory electrical field stimulation caused the release of histamine from cardiac sympathetic terminals of guinea-pig isolated atria (112.14 +/- 40.34 ng x ml(-1)), which was significantly attenuated to 35 +/- 15.57 ng x ml(-1) by reserpine pretreatment. Following administering compound 48/80, a mast cell degranulator, electrical field stimulation induced a dramatic increase of endogenous histamine release from isolated atria (303.57 +/-72.93 ng x ml(-1)). When compound 48/80 was added to the reserpine-treated atria, the release of histamine induced by field stimulation was decreased to 207.14 +/- 76.39 ng x ml(-1). 4 These results provide novel evidence that histamine co-exists with noradrenaline in sympathetic nerves and might act as a neurotransmitter to modulate sympathetic neurotransmission.

Animals↗

PubMedDate not supplied

Gamma irradiation: effects on biomechanical properties of human bone-patellar tendon-bone allografts.

Sixty 10-mm bone-patellar tendon-bone allografts from young human donors were placed into four test groups, a control fresh-frozen group and three fresh-frozen irradiated groups. The irradiated groups were exposed to 2.0, 3.0, or 4.0 Mrad of gamma irradiation. The specimens were tested to tensile failure. The initial biomechanical strength of fresh-frozen allografts was reduced up to 15% when compared with fresh-frozen controls after 2.0 Mrad of irradiation. Maximum force, strain energy, modulus, and maximum stress demonstrated a statistically significant reduction after 2.0 Mrad of irradiation (P < 0.01). Stiffness, elongation, and strain were reduced but not with statistical significance. A 10% to 24% and 19% to 46% reduction in all biomechanical properties were found after 3.0 (P < 0.005) and 4.0 (P < 0.0005) Mrad of irradiation, respectively. After irradiation with a 4.0 Mrad dose, the ultimate load was below that of reported values for the human anterior cruciate ligament. It is clinically important to observe and document changes in human ligaments that result from currently used doses of gamma irradiation. The results from this study provide important information regarding the initial biomechanical properties of fresh-frozen human bone-patellar tendon-bone allografts after bacterial sterilization with gamma irradiation. The current accepted dose for sterilization is between 1.5 and 2.5 Mrad. There appeared to be a dose-dependent effect of irradiation on all the biomechanical parameters studied. Four of seven parameters were found to be reduced after 2.0 Mrad of irradiation. Reductions were found in all parameters after 3.0 and 4.0 Mrad of irradiation.

Biomechanical Phenomena↗

PubMedDate not supplied

Role of neurotrophins in synapse development and plasticity.

Neurotrophic factors are traditionally viewed as secretory proteins that regulate long-term survival and differentiation of neurons. The role of neurotrophic factors in the structural integrity of the nervous system makes them attractive candidates as therapeutic agents for neurodegenerative diseases. However, the fact that expression of many neurotrophic factors in the central nervous system is rapidly enhanced by neuronal activity suggests a new role for these factors in activity-dependent processes, such as synaptic development and plasticity. A series of recent studies has provided strong evidence for this novel function of neurotrophic factors. The neurotrophin family of proteins has been shown to acutely potentiate synaptic transmission at the neuromuscular junction and in the brain. These factors are also involved in the maturation of the neuromuscular synapses and in the development of synapses in the visual system. Gene targeting and physiological experiments demonstrate that brain-derived neurotrophic factor (BDNF) plays an important role in long-term potentiation (LTP), a cellular model for learning and memory. These findings have brought together two hotly pursued areas of neuroscience, namely, the function of neurotrophic factors and the mechanisms for synaptic plasticity. Continuous studies in this new field will help understand how synapses develop and function in the brain, and may have significant implications in treating learning disorders in both children and adults.

Adult↗

PubMedDate not supplied

Signaling mechanisms mediating BDNF modulation of synaptic plasticity in the hippocampus.

Although recent studies indicate that brain-derived neurotrophic factor (BDNF) plays an important role in hippocampal synaptic plasticity, the underlying signaling mechanisms remain largely unknown. Here, we have characterized the signaling events that mediate the BDNF modulation of high-frequency synaptic transmission. Mitogen-associated protein kinase (MAPK), phosphotidylinositol-3 kinase (PI3K), and phospholipase C-gamma (PLC-gamma) are the three signaling pathways known to mediate neurotrophin signaling in other systems. In neonatal hippocampal slices, application of BDNF rapidly activated MAPK and PI3K but not PLC-gamma. BDNF greatly attenuated synaptic fatigue at CA1 synapses induced by a train of high-frequency, tetanic stimulation (HFS). Inhibition of the MAPK and PI3K, but not PLC-gamma, prevented the BDNF modulation of high-frequency synaptic transmission. Neurotrophin-3 (NT-3), a close relative of BDNF, did not activate MAPK or PI3K and had no effect on synaptic fatigue in the neonatal hippocampus. Neither forskolin, which activated MAPK but not PI3 kinase, nor ciliary neurotrophic factor (CNTF), which activated PI3K but not MAPK, affected HFS-induced synaptic fatigue. Treatment of the slices with forskolin together with CNTF still had no effect on synaptic fatigue. Thus, although the activation of MAPK and PI3K is required, the two together are not sufficient to mediate the BDNF effect. Inhibition of new protein synthesis by anisomycin or cycloheximide did not prevent the BDNF effect. These data suggest that BDNF modulation of high-frequency transmission is independent of protein synthesis but requires MAPK and PI3K and yet another signaling pathway to act together in the hippocampus.

Animals↗