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Biomedical subjects

K Yan

Publications and source records attributed to K Yan.

79 records · Page 5Linked to original sources
PubMed1981

Visual field topography in the frog's nucleus isthmi.

Responses to visual stimulation were extracellularly recorded with micropipettes from 125 neurons of the left nucleus isthmi in frogs, Rana nigromaculata, and 101 electrode tip positions were marked with cobalt staining. The present study indicates that: (1) the entire contralateral hemifield and the nasal 40 degree of the ipsilateral hemifield project on the nucleus isthmi topographically, and (2) there exist binocular units in this nucleus.

Animals↗
PubMed1981

Visual field topography and binocular responses in frog's nucleus isthmi.

Visual responses of 125 units have been extracellularly recorded with glass micropipettes from the left nucleus isthmi in the frog Rana nigromaculata, and 101 electrode tip positions marked with cobalt staining to reconstruct a visual field map in the nucleus. 80% of the units recorded show ON-OFF responses to a stationary spot of light and many are directionally selective in response to black or white targets moving through their receptive fields. All the cobalt-marked spots are within the nucleus, indicating that the nucleus isthmus proper is a restricted part of the frog visual system. There is a visual field map in the nucleus. The entire contralateral hemifield and the nasal 40 degrees of the ipsilateral hemifield project on the nucleus topographically. A cell-free band inside the nucleus is a boundary line separating the contralateral hemifield from the ipsilateral one. Dorsal to it is the contralateral field representation. The upper visual field projects on the rostral half of the nucleus and the central and medio-ventral portion of its caudal half. The lower field is represented on the dorsal and lateral part of the caudal half. Fifteen binocular units have been found from the nucleus, 13 of which are dominantly activated by the contralateral eye, the other two are almost equally excited by either eye. These binocular units are mainly situated in the medulla of the rostral half of the nucleus isthmus.

Animals↗
PubMedDate not supplied

Image-directed and color Doppler studies of gallbladder tumors.

Thirteen cases of primary adenocarcinoma of the gallbladder (GB), 1 of malignant fibrous histocytoma, 3 of metastatic adenocarcinoma, 5 of adenoma, 5 of polypus, 2 of xanthogranuloma, 6 of chronic cholecystitis, 4 of acute cholecystitis, and 8 of subacute cholecystitis were studied by image-directed and color Doppler ultrasonography (CDUS). All of the 14 cases of primary GB cancer (10 masses, 4 thickening wall) were found to have a high velocity arterial blood flow signal in the wall of the GB. In contrast, the 3 cases of metastatic cancer of the GB had no blood flow signal in the wall of the GB. For the 30 cases of benign lesions of the GB, only in 12 cases was a low velocity blood flow signal found. Nine of 10 cases of primary GB malignancy were found to have high velocity arterial blood flow signals in the tumor masses. No blood flow signal was observed in the masses of 13 cases (3 of metastatic adenocarcinoma, 5 of adenoma, 5 of polypus). An abnormal high velocity arterial blood flow signal observed within masses in the GB or in the GB wall is a significant feature of primary GB cancer and thus helps to differentiate primary GB cancer from metastatic and benign lesions of the GB.

Adult↗
PubMedDate not supplied

Effects of gallstone solvents on commonly used catheters.

PURPOSE: To determine what interaction and effect different cholesterol gallstone solvents have on catheters used for gallstone chemolysis. MATERIALS AND METHODS: Five types of catheters used for biliary procedures were chosen: polyethylene, Percuflex, silicon, Silitek, and polyurethane. The solvents chosen were methyl tert-butyl ether, ethyl propionate, isopropyl acetate, and N-propyl acetate. After incubation of the catheters in the solvents for 72 hours, they were air dried. Weight and area changes were determined for each catheter. Additionally, carbon-13 nuclear magnetic resonance (NMR) spectroscopy was performed for analysis of composition changes. RESULTS: Three catheters--silicone, Silitek, and polyurethane--showed changes in their physical characteristics that would make them less desirable for stone chemolysis. The silicone catheter showed changes in elastic texture as well as marked weight reduction. The Silitek and polyurethane catheters had similar, but less dramatic changes. C-13 NMR analysis of collected solvents showed that commonly used plasticizers were leached out of some catheters. CONCLUSION: These results suggest that all catheters are not suitable for use with all solvents. The choice of catheter should be made based on the solvent in use. The polyethylene catheter performed best under the conditions and endpoints used in this study.

Catheterization↗
PubMedDate not supplied

The use of fractional parameter in analyzing motor unit discharge pattern in stroke patients: a correlation with the functional independence measurement.

BACKGROUND: We have previously demonstrated that the fractional parameter has significant correlation with the muscle strength of patients with stroke. In this study, we have investigated whether fractional parameter can be used to objectively document stroke patients' functional level (using FIM scores). METHODS: Sixty motor units were recorded in abductor pollicis brevis, first dorsal interosseous, and abductor digiti minimi muscles in 18 stroke patients. Patients' FIM scores, obtained fractional parameters, and serial correlation coefficients were analyzed and statistical determination was made. RESULTS: Statistical significance was found between fractional parameters and motor items of FIMs (except selfcare category); no statistical significant correlation was found between SSC and FIM scores. CONCLUSION: Fractional parameter could be a useful tool for measuring motor function at a single motor unit level.

Activities of Daily Living↗