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Biomedical subjects

W Chen

Publications and source records attributed to W Chen.

At least 1,153 records · Page 64Linked to original sources
PubMed1990

Pneumonia in mice produced by cell-free extract of cultures of Bordetella parapertussis.

A single dose of culture fluid of Bordetella parapertussis freed from cells (CFCF) given intranasally to four-week-old mice free from intercurrent respiratory disease produced a subacute bronchopneumonia, which was similar to that induced by whole cells of ovine isolates of B parapertussis, except that the lesions were less severe and less extensive. From eight hours to 17 days after inoculation, the mice exhibited marked infiltration of neutrophils and macrophages into the alveolar septa, bronchiolar and alveolar spaces, and hyperplasia of peribronchiolar and perivascular lymphoid tissue. Electron microscopy showed damage to ciliated cells, type 1 pneumocytes and alveolar macrophages. These results suggest that extracellular toxic substance(s) produced by ovine isolates of B parapertussis might be involved in the initiation and development of lesions in ovine chronic non-progressive pneumonia.

Animals↗
PubMed1989

Isolation, culture and main characteristics of mouse fat-storing cells: interaction with viruses.

Fat-storing cells were isolated from 15-day-old mouse sinusoidal cell cultures (Kupffer or endothelial cells), where they had multiplied abundantly; they were then purified by a negative selection method based on the fact that they do not possess Fc receptors, as do both other types of cells. The fat-storing cells, which could be subcultured for at least 10 passages, have the main morphological characteristics already described in vivo, in particular, the rough endoplasmic reticulum and the lipid droplets, which become less and less apparent as the number of passages increases. Subcultured fat-storing cells, almost devoid of lipid droplets and vitamin A, were able to take up retinol, as the appearance of a typical autofluorescence indicated; the number of lipid droplets increased concomitantly. Furthermore, the cultured fat-storing cells were able to internalize one-micron-sized latex beads by phagocytosis. Infection of fat-storing cells with mouse hepatitis virus 3, ectromelia or Sindbis virus led to multiplication of the virus particles. There was a direct relation between the multiplication of mouse hepatitis virus 3 in cultured fat-storing cells and the susceptibility of the animals to the virus. In the case of Sindbis virus, interferon is produced, its production being independent of the presence of vitamin A.

Animals↗
PubMed1989

Yeast upstream activator protein GCN4 can stimulate transcription when its binding site replaces the TATA element.

We replaced the required TATA element of a yeast gal-his3 promoter by a binding site for GCN4, a protein that normally activates transcription when bound upstream of a TATA element. Surprisingly, GCN4 efficiently activates his3 transcription from wild-type initiation sites, though in a pattern associated with constitutive his3 transcription rather than GCN4 upstream activation through a TATA element. Transcriptional stimulation by GCN4 requires both the DNA-binding domain and the acidic activation function but is not affected by changing the spacing or helical relationship between the GCN4 binding site and the mRNA start sites. GCN4 is not sufficient for this TATA-independent activation; a sequence in the gal fragment distinct from the GAL4 binding sites is also required. Thus, GCN4 functions both when bound upstream of a TATA element and also when bound at the position of a TATA element. In the latter case, we suggest the possibility that GCN4 might be able to stimulate transcription by an alternate mechanism that does not involve a conventional TATA-binding transcription factor.

Bacterial Proteins↗
PubMed1989

Localized 13C-[1H] NMR of rat liver in vivo using surface-spoiling gradients.

An NMR spectroscopy localization method that employs an inhomogeneous surface-spoiling magnetic field gradient has been applied to detect the 13C-[1H] signals from deep-lying liver tissue of rat in vivo. The method requires small gradient driving currents (less than 1 amp) and short gradient periods (approximately 0.5-1.6 ms). Thus, it is not likely to suffer from induced eddy currents and can detect short T2 resonances. We demonstrate that by employing a pulsed surface-spoiling gradient one can eliminate "contaminating" signals from the surface-lying tissues (muscle, fat and skin) while still maintaining the resonance linewidth resolution for the deep-lying tissue of interest (liver). The feasibility of using this localization approach to trace glucose conversion into glycogen is shown.

Animals↗
PubMed1989

Respiratory tract-associated lymphoid tissue in conventionally raised sheep.

The distribution and morphological features of respiratory tract-associated lymphoid tissue was investigated in 20 clinically healthy sheep aged from 6 months to 9 years. Five different forms of lymphoid tissue were identified, but their distribution varied between regions of the respiratory tract and between individuals. Scattered lymphoid cells were the most predominant form. Dense lymphoid aggregations were frequently seen in the pharyngeal tonsil and bronchioles. They were less common in the mid-nasopharynx and about the opening of the auditory tube, occasionally seen in the anterior nasopharynx, trachea and bronchus and rarely found in the regions of the nasal conchae, nostril, nasal vestibule and epiglottis. Nodular lymphoid aggregations with morphologically distinct lympho-epithelium were seen only in the pharyngeal tonsil and opening of the auditory tube region. Small numbers of intra-epithelial lymphoid cells were always present throughout the mucosa, but intraluminal lymphocytes were observed mainly in the regions of pharyngeal tonsil, trachea, bronchi and large bronchioles. The respiratory tract-associated lymphoid tissue is less developed in sheep than in most other species studied, except perhaps cattle.

Animals↗
PubMed1989

Rec-assay of human bile for mutagenicity and co-mutagenicity.

Spore rec-assay of human bile was conducted by the Bacillus subtilis test system to examine possible mutagenicity and co-mutagenicity. Of 26 samples examined, 8 (30.8%) showed mutagenic activity and 23 (88.5%) enhanced the mutagenic activity of mitomycin C.

Bacillus subtilis↗
PubMed1989

[Scanning electron microscopic observation of the nasal mucosa microvasculature].

The normal microvasculature of a rat nasal mucosa was investigated in microcorrosion casts viewed under a scanning electron microscope. The nasal mucosa microvasculature was composed of arterioles, venules, capillaries and cavernous sinuses. Both arterioles and venules ran parallel to the long axis of the nasal concha. The capillaries and cavernous sinuses were particularly abundant and interconnected by means of numerous short anastomoses to form a rich dense network. A characteristic feature of the nasal mucosa vasculature was that the capillaries possessed a fenestrated structure, the venules and arterioles were porous, and the surface of cavernous sinuses formed a three dimensional lace-work structure.

Animals↗