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S He

Publications and source records attributed to S He.

329 records · Page 19Linked to original sources
PubMedDate not supplied

Distinguishing direction selectivity from orientation selectivity in the rabbit retina.

Direction selectivity and orientation selectivity were examined in the direction-selective (DS) and orientation-selective (OS) ganglion cells in the rabbit retina. Spike activities were recorded in vivo using tungsten-in-glass electrodes. Three types of visual stimuli (flashing slit, moving edges behind a slit, and whole-field drifting gratings) were used to distinguish these attributes. Fourier analysis was performed on data obtained using drifting gratings as proposed by Worgotter and Eysel (1987). Results from both angular and Fourier (polar angle frequency) domains were consistent. DS cells had strong directional components and varying strength of orientational components; they also had intact inhibitory surrounds. The phase of the biased orientation did not have a consistent relationship with the preferred direction. OS cells had predominant orientational components and very weak directional components. We conclude that the orientation bias does not contribute to the generation of direction selectivity, and that the mechanism of this bias of DS cells is rather different from the mechanism that generates orientation selectivity in rabbit OS cells. There are indications that it is similar to the mechanism shown to cause orientation bias in cat concentric cells.

Action Potentials↗
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

Nucleocapsid protemn gene of Chinese isolate of Bombyx mori nucleopolyhedrovirus.

The nucleocapsid protein gene (vp39) of a Chinese isolate of Bombyx mori nucleopolyhedrovirus (BmNPV-Ch), namely an open reading frame (ORF) of 1050 bp that codes for a polypeptide of 39 K (VP39) consisting of 350 amino acids was sequenced. The homology of the nucleotide (nt) and amino acid sequences of vp39 and VP39, respectively, of BmNPV-Ch and a Japanese isolate of BmNPV (BmNPV-Ja) were found to be 97.5% and 97.1%, respectively. The BmNPV-Ch vp39 is nine nucleotides longer than that of BmNPV-Ja vp39 due to insertion of CGA at nt 625 and GTCGGC at nt 985 910. There are differences in 17 nucleotides causing a few substitutions of amino acids which slightly modify the secondary structure of BmNPV-Ch. It indicates that the main part of the secondary structure of VP39 is a folded structure containing high proportion of beta-sheet and beta-turn units. A dot blot hybridization analysis revealed the existence of a homologous transcript of BmNPV-Ch vp39 in Sf9 cells infected with Autographa californica multiple nucleocapsid nucleopolyhedrovirus (AcMNPV).

Amino Acid Sequence↗
PubMedDate not supplied

Establishing a protocol to quantify leaflet fibroblast responses to physiologic flow through a viable heart valve.

Mechanical stresses are thought to affect the metabolism of a variety of cell types. Little quantitative data exist regarding heart valve leaflet fibroblast activity after dynamic loading. The goal of this study was to examine leaflet fibroblast function and differentiation in response to flow through an intact valve. This requires the development of a flow system capable of reproducing the valve's native environment, as well as assay protocols to analyze cellular viability and protein and collagen synthesis. As a tool to expose viable tissue valves to physiologic flow, a sterilizable pulsatile flow system has been developed to recreate the dynamic flow environment of the aortic valve while preventing contamination from room air. Physiologic flow conditions [frequency 70 bpm, aortic pressure 129/82 mmHg (systolic/diastolic), cardiac output 2.3 L/min] were sustained for 71 hr without microbiologic contamination. Analytic tools for assessment of fibroblast function include a viability assay, which demonstrated that leaflet viability decreases after prolonged exposure to antibiotics. Proline incorporation studies revealed that 11 times more protein is retained by leaflet tissue than is released into the medium, and 27% of this protein is collagen. Polyacrylamide gel electrophoresis clearly resolved collagen Types I and III from both prepared standards as well as leaflet extracts. In ongoing work, the sterile flow loop will be used to expose fresh porcine aortic valves to defined flow conditions, and the viability and protein/collagen biosynthetic activity of leaflet fibroblasts in response to flow will be quantified. These experiments will provide a baseline by which to design and evaluate future tissue engineered substitutes.

Animals↗