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Biomedical subjects

C H Feng

Publications and source records attributed to C H Feng.

33 records · Page 2Linked to original sources
PubMed1982

Tissue cryopreservation and rewarming study on giant cell tumor of bone.

An attempt has been made of cryopreservation of tissue fragments from 6 GCTB surgical specimens. They have been kept in 10% DMSO or 15% glycerol medium and stored in liquid nitrogen for periods up to 180 days. Tumor cellular components survive the process of slow freezing and rapid thawing as cellular growth is successful in subsequent culture. Though certain reversible ultrastructural changes have been detected, no apparent distinction could be found in microscopic morphology, motility, growth behavior and LDH isozyme pattern between cultured cells of the cryopreserved fragments and those of the fresh ones. Electron microscopy shows that DMSO exceeds glycerol in protecting the ultrastructure of the cells. Slow cooling and rapid thawing is recommended because ice-crystals form in the intercellular space, which causes only light damage to the cells.

Bone Neoplasms↗
PubMedDate not supplied

Temporary amnesia induced by cold anesthesia and hypoxia in Drosophila.

Memory consolidation in Drosophila was investigated using cold anesthesia- and hypoxia-induced amnesia. Individual flies were operantly trained to avoid the specific flight orientations with respect to the landmarks surrounding them when paired with heat reinforcement at a flight simulator. Cold anesthesia, introduced immediately after training, exerted a significantly diminishing effect on memory between 15 and 150 min after training. Hypoxia delivered immediately after training had a significantly diminishing effect on memory between 30 and 150 min after training. In addition, cold anesthesia disrupted memory only when introduced within the first 20 min, while hypoxia worked only when delivered within the first 2 min after training. When interpreted in the context of a four-phase model of memory consolidation, the results suggest that 1) cold anesthesia disrupts both short-term memory (STM) and anesthesia-resistant memory (ARM), 2) hypoxia disrupts ARM specifically, 3) both of them leave long-term memory (LTM) intact, and 4) LTM may be independent of availability of STM and ARM in flies.

Amnesia↗
PubMedDate not supplied

Conditioned visual flight orientation in Drosophila: dependence on age, practice, and diet.

Orientation preferences for visual patterns can be conditioned in tethered flies (Drosophila melanogaster) at the flight simulator. In a reversal conditioning procedure using heat as reinforcement, flies can be trained to successively prefer different flight orientations with respect to the patterns. As in many learning paradigms, conditioned responses are highly variable. Although during training most flies reliably avoid the heat and the corresponding flight orientations, in subsequent learning tests without heat some show no consistent preference for the permissive orientations. We have started to investigate the interindividual differences in learning performance and describe here three significant variables: the age of the animals, their experience in the flight simulator prior to the experiment, and the composition of the fly food. Flies learn more reliably at 3-4 days than at 1-2 days of age but learning indices do not increase further in even older flies. Learning is improved if flies are allowed to become familiar with the flight simulator before the start of the conditioning procedure. Most important, poor nutrition causes complete amnesia within three or four generations. The reverse shift from poor to nutritious food restores learning ability with an even longer delay.

Aging↗
PubMedDate not supplied

Principal component analysis. A factor analytical technique for the determination of interobserver variation in histomorphologic tumor grading.

The insufficient interobserver reproducibility limits the practical use of histomorphological tumor grading in daily routine pathology. In this study, the reasons for the quite low rates of agreement between different observers have been investigated by the application of a factor analytical technique, i.e. principal component analysis with varimax rotation, on a tumor grading system. Grading results from 44 cases of G1 and G2 giant cell tumors of the bone (GCT), graded by three different observers according to the five criteria of Jaffe, were taken as an example. It could be proven that the single criteria were used in an observer-specific way. Two criteria, for example, which are scored highly correlated by one observer, may be used independently by another. The resulting observer-specific different recognition patterns may provide an explanation for their quite different grading results, which were identical in only 48.6% to 54.1% (mean: 50.9%) of the cases. No correlation of GCT grading with recurrence was found in 31 cases which had been treated by intralesional surgery.

Adult↗