Biomedical subjects

T Jiang

Publications and source records attributed to T Jiang.

114 records · Page 7Linked to original sources

PubMed1992

Production of a toxic, novel mammalian metabolite of N-methylcarbazole predicted by a fungal cell model of mammalian metabolism.

The formation of N-hydroxymethylcarbazole (NHMC), carbazole, 1-hydroxy-N-methylcarbazole, 2-hydroxy-N-methylcarbazole, and 3-hydroxy-N-methylcarbazole as products of mammalian liver microsomal metabolism of N-methylcarbazole (NMC) has been documented by several investigators. In previous studies in our laboratory, the fungus Cunninghamella echinulata (ATCC 9244) produced two new metabolites, 3-hydroxy-N-hydroxymethylcarbazole (3-OH-NHMC), and 3-hydroxycarbazole (3-OH-carbazole), in addition to the known mammalian metabolites, NHMC and carbazole. One of the two novel metabolites isolated from the microbial models, 3-OH-NHMC, was also identified and characterized in rat liver microsomes by analytical (HPLC) and spectral (UV and NMR) comparisons with a reference standard. The two metabolites, 3-OH-NHMC and 3-OH-carbazole, were shown to be cytotoxic to cultured rat hepatocytes as assessed by lactate dehydrogenase (LDH) leakage and neutral red (NR) uptake. These studies demonstrate the prospective potential of microbial models for predicting the formation of metabolites from drugs and other xenobiotics in mammalian systems.

Animals↗

PubMed1992

Some properties of receptive fields of olfactory mitral/tufted cells in the frog.

1. Different regions of the frog's olfactory epithelium were stimulated with nine glass micropipettes either individually or simultaneously in different combinations. The stimulus was a positive electrical pulse (4 s) consisting of a progressive increase, a plateau, and a progressive decrease in current intensity. Extra- and intracellular recordings were made from olfactory bulb mitral/tufted cells. Some of these cells were identified by intracellular injection of Lucifer yellow. 2. The action potential response patterns of mitral/tufted cells during the different phases of the stimulation were coded according to whether the activity was increased or decreased compared with its spontaneous level just before stimulation. Neural responses were classified into 11 types: individual neurons responded with different response types to stimuli delivered at different epithelial sites. On the basis of these response types, it was found that neurons could be classified into two groups. All response types in one group included an initial phase of increased discharge (excitation), whereas all types in the other group included an initial phase of decreased activity (suppression). Neurons that displayed response types belonging to one group never displayed those of the other group. It was thus concluded that a given neuron responded either always with an increased activity or always with a decreased activity, whatever the location of the stimulus. 3. The receptive field of a mitral/tufted cell appeared to be homogenous and not divided into areas of different properties, at least under the present experimental conditions. The extent of a receptive field was estimated by determining the number of effective epithelial sites (where an electrical stimulus evoked a response from a bulbar neuron).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1992

[Condylar displacement and mandibular bending deformation due to bite force].

The purpose of this study was to investigate the influence of the difference of the biting pivot positions, vertical dimensions and mandibular positions on the condylar displacement during clenching. The condylar displacement was measured by the Pantograph using the point of condyle on the Kinematic Axis as the representative and the Path of the Kinematic Axis (PKA) as the standard for the judgement of the displacement. The bending deformation of the mandible was also measured by a multi-vision and image analyzing system in order to correct its influence on the condylar displacement measured. The results were as follows: 1. The direction and magnitude of the condylar displacement changed with the biting pivot position. The bilateral condyles moved upwards deviating from the PKA when clenching on the bilateral 2nd-molar or the bi-or unilateral canine teeth; Whereas the biting-side condyle moved downwards and the idling condyle either moved upwards deviating from the PKA or backwards along the PKA when clenching on the unilateral 2nd-molar. 2. The displacement of the idling condyle was multi-directional when clenching on the habitual closure whereas it was unidirectional and of a smaller magnitude when clenching on the most retruded closure. 3. When clenching on the unilateral 2nd-molar, the mandible on the non-pivot side had an inward and upward bending deformation and the arch width decreased. It can be inferred that the actual idling condylar displacement was more inward and upward than that measured by the Pantograph.

Adult↗

PubMed1991

[Relationship between the bacterial resistance induced by rifamdin and the RNA polymerase].

The results of our experiment in vitro showed that the activity of standard RNA polymerase decreased while the concentration of RFD and RFP increased, indicating that the target site of action of RFD was similar to that of RFP on RNA polymerase. Incorporation of [3H] UR into the RNA of sensitive cells of S. sureus and E. coli was strongly inhibited by RFD, but RFD did not affect the resistant strains. In purified DNA-dependent RNA polymerase of sensitive and resistant strains, the enzyme activity of sensitive E. coli a S. aureus strains was inhibited by RFD, but RFD did not inhibit that of the resistant strains (except the P. vulgaris). It can be concluded that a decreased susceptibility of RNA polymerase to RFD as well as a decreased permeability of bacterial envelope may induce bacterial resistance to the drug.

DNA-Directed RNA Polymerases↗

PubMed1990

[Inhibitory effect of liuwei dihuang decoction on induced mutation and spontaneous tumor].

Anti-mutagenic activity was evaluated with micronuclear test. It appeared to be same between the result of mice treated with 10 g/kg Liuwei Dihuang decoction (LWDHd) for 3 days and that with 34.5 g/kg for 10 days. All the permillages of micronuclear appearance of treated groups were less than that of controls. The intercept (A) value of dose-effect curve were 12.7 and 9.4 as treated with cyclophosphamide (Cy) alone, but 1.2 and 3.2 as orally administered with LWDHd before injecting Cy. It showed that LWDHd could inhibite mutagenic activity of Cy. The affection of LWDHd on spontaneous tumorigenesis was observed in LACA mice. The tumor incidence rate was 9.0% in the control mice observed for 60 weeks, but 5.0% in the animal feeding LWDHd in food. The tumor incidence rate of big dose group was 1.0% and the difference was significant between it and that of the control (P less than 0.01).

Animals↗

PubMedDate not supplied

Identification and boundary extraction of blobs in complex imagery.

Automated identification and boundary extraction of blobs in "real world" imagery is a difficult task because the boundaries are so irregular that there is often insufficient a priori information describing these boundaries and traditional methods fail. This paper has proposed a progressive segmentation approach and a boundary estimation method to identify the blobs and to yield an accurate description of its boundary. The multiresolution image processing technique is incorporated into the whole work. This work has been applied to the problem of identifying and extracting the boundaries of major vessels (e.g., the aorta) in Magnetic Resonance (MR) imagery and the results are satisfactory. A Laplacian of Gaussian (LOG) operator is utilized as a spot detector to locate the approximate position of the blob of interest. A subimage centered on this approximate position is extracted to eliminate unwanted portions of the image and facilitate further processing. A histogram pyramid is created for the subimage histogram for automated determination of the threshold in the noisy histogram. A shrink-expand operation is then employed to reduced noise and undesired structures in the subimage. The rough and irregular boundary of the blob of interest obtained by thresholding is reparameterized into polar coordinates to create a Fourier descriptor representation of the boundary. Then, the discrete Fourier transform is applied to the reparameterized 1-D discrete curve to permit appropriate smoothing, as required, in frequency space. Finally, the boundary estimation is completed by taking the inverse Fourier transform to reconstruct the boundary of interest.

Aorta↗