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Biomedical subjects

T Z Han

Publications and source records attributed to T Z Han.

7 recordsLinked to original sources
PubMed1999

[A quantitative study on the synaptic ultrastructural alterations in visual cortex in the maintenance of LTP].

The ultrastructure of synapses three hours after formation of long-term potentiation (LTP) was examined in the local microslices of visual cortical brain slices of 18-20 d rats. Slices without potentiating stimulation which were similarly incubated served as controls. The following structural changes were examined using a graph analyzer: (1) synaptic cleft width; (2) thickness of the postsynaptic densities(PSD); (3) length of the active zones; and (4) curvature of the synaptic interface. The number of synapses of different types in layer II/III of visual cortex was quantified by double-blind scoring procedures. The various counts were converted to the number of synapses per unit volume using stereological quantitation method. Analysis of variance was used for statistical evaluation. Our results suggest that field potentials reached their peak values at about one and a half hours after tetanus and could be maintained as long as three hours without decay. In comparison with the control groups, synaptic cleft width, thickness of PSD, surface density per unit volume(Sv) of the active zones, curvature of the synaptic interface, numeric density per unit volume (Nv) of all synapses, spine synapses and the Nv of perforated synapses were all increased significantly. These data suggest that the increase of Sv of active zones and the increase of the curvature of synaptic interface may be the morphological feature characterizing the maintenance of LTP, in addition to the formation of perforated synapses.

Animals↗
PubMed1989

Induction of LTP in rat primary visual cortex: tetanus parameters.

Long-term potentiation (LTP), intensively studied in the hippocampus as a possible mnemonic device, has begun to be studied in the neocortex. In this study the effects of varying tetanic stimulus parameters on LTP of field potentials recorded from layer II/III induced by white matter stimulation in the in vitro rat visual cortical slice were examined. Low intensity tetanus was more effective in producing LTP than high-intensity tetanus, although single pulses of very high intensity reliably resulted in LTP. LTP consistently occurred following 2 Hz-60 min, or 100 Hz-10 min tetanus; whereas, 10 min of 7 and 25 Hz tetanus usually resulted in long-lasting depression. Although no obvious rule related tetanus frequency and duration to the incidence of LTP, an inverted-U relationship was found between tetanus frequency and LTP magnitude.

Animals↗
PubMed1989

[A retrospective study of 115 cases of fungal pneumonia].

115 cases of immunocompromised patients complicated with fungal pneumonia treated during the period from April 1968 to December 1986 were retrospectively studied. 96 were male and 19 female. Their age ranged from 6 to 84. The incidence increased significantly in recent years especially after 1983. Severe liver disease was the underlying disease in 102 (88.7%) patients. 108 (93.9%) had received antibiotics and 55 (47.9%) corticosteroids. Fungi species isolated were candida in 107 (54.9%), aspergillus in 82 (36.9%), penicillium in 7 (3.6%), mucormycetes in 6 (3%) and reotrichum in 3 (1.5%). Fever, cough, expectoration, moist rales diminished breath sounds and increase of W. B. C. and neutrophils were the important clinical features. The roentgenologic findings vary with the nature and extent of the pathologic process. Disseminated mycoses were found in 9 of the 18 autopsied cases. The characteristic pathologic findings were inflammation, abscess formation, vasculitis, infarction and hemorrhage. Extrapulmonary features such as enteritis, purulent nephritis, abnormal EKG, encephalopathy and rash were present. 93 cases received antifungal therapy including garlicin, clotrimazole, amphotericin B, nystatine, miconazole, 5-fluctosine and ketoconazole. Because these drug combinations were so complex, it is difficult to evaluate their efficiency. However the survival rate was somewhat elevated in recent years. The mortality rate of this series was 80.9%.

Adolescent↗