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Biomedical subjects

W C Li

Publications and source records attributed to W C Li.

35 records · Page 2Linked to original sources
PubMed1994

The two duplicated insecticyanin genes, ins-a and ins-b are differentially expressed in the tobacco hornworm, Manduca sexta.

Two gene-specific probes were generated from the unique sequences in the 3' non-coding regions of the two insecticyanin genes, ins-a and ins-b to study the developmental expression of these genes in Manduca sexta. Both genes were initially transcribed in the freshly hatched first instar larvae and then expressed in the epidermis and to a lesser degree in the fat body during every larval feeding stage. In the epidermis of the 4th and 5th instar larvae, both mRNAs appeared shortly before ecdysis and accumulated to maximal levels within a day. As the larval epidermis became pupally committed on day 3 of the 5th (final) instar, INS-a mRNA quickly decreased, whereas INS-b mRNA showed a second peak of accumulation. In the fat body, both genes showed a similar expression pattern within the 4th instar to that of the epidermis except that levels were lower and ins-b mRNA dominated. In the final instar, only ins-b mRNA was present in significant amount. These findings not only reveal that the two duplicated insecticyanin genes have diverged in their expression pattern but also demonstrate, for the first time, that fat body also expresses insecticyanin genes.

Animals↗
PubMed1994

The redox active components H2O2 and N-acetyl-L-cysteine regulate expression of c-jun and c-fos in lens systems.

Hydrogen peroxide (H2O2) is implicated in human cataract development. At the molecular level H2O2 has been observed to cause damage to DNA, protein and lipid. It is now demonstrated, for the first time in a lens system, that H2O2 at concentrations found in cataract patients induces expression of both c-jun and c-fos. At optimal concentrations of H2O2, mRNA accumulation of c-jun and c-fos in the rat lenses is induced 20- and 18-fold above normal levels respectively, but with distinct kinetics. This induction occurs at the transcriptional level. H2O2 also induces transactivation by activating protein-1 (AP-1) in rabbit lens epithelial cells. The antioxidant N-acetyl-cysteine (NAC) has a dual effect on the induction of c-jun and c-fos. Preincubation of rat lenses with 5 mM NAC inhibits the induction by H2O2, while 30 mM and 50 mM NAC induce expression of these genes and mask the H2O2 effect. H7 (50 microM), genistein (2 microM) and okadaic acid (20 nM), all block the induction of c-jun and c-fos mRNA accumulation in the H2O2-treated rat lenses. These results suggest that H2O2 activates protein kinase and phosphatase dependent signal transduction pathways to induce c-jun and c-fos expression which may regulate lens crystallin genes and other genes containing AP-1 binding sites.

Acetylcysteine↗
PubMed1991

Motorcycle licensure, ownership, and injury crash involvement.

The interrelationships among motorcycle licensure, ownership, and injury crash involvement were investigated in a sample of 2,723 motorcycle drivers severely or fatally injured in California in 1985-86. Owners of motorcycles in such crashes ("driver-owners") were less likely to have valid licenses than a random sample of motorcycle owners who had not been in crashes (42 vs. 57 percent). Thirty-three percent of the crash-involved drivers had valid motorcycle driver's licenses; 39 percent were operating motorcycles they did not own ("driver-nonowners"). Driver-nonowners were less likely to be validly licensed than driver-owners (20 percent vs. 44 percent). The licensing rate of crash-involved driver-nonowners was 15 percent if the owner was also unlicensed. Rates of valid licensure were lowest among the youngest drivers. Virtually no crash-involved driver-nonowners under age 21 were licensed in cases in which the owner was also young and unlicensed.

Accidents, Traffic↗
PubMed1988

Clear cell lymphoma: a clinicopathological study of four cases.

Four cases of clear cell lymphoma were studied by means of light and electron microscopy, enzyme-histochemistry, and E- and EAC-rosette formation. On light microscopic examination the tumors were seen to be composed mainly of round, oval, or slight irregular cells with water-clear, abundant cytoplasm. The neoplastic cells has round, oval, or convoluted nuclei with fine, evenly dispersed chromatin and one or more small but distinct nucleoli. On electron microscopic examination the clear cell lymphoma were characterized by lymphoid cells with striking electron lucent cytoplasm with few organelles. According to E-rosette test and enzyme-histochemical findings, the investigators proposed that the clear cell lymphoma may be derived from T-cell lineages. Differentiated diagnoses of clear cell lymphoma from B-immunoblastic sarcoma, pleomorphic cell lymphoma, clear cell sarcoma, and clear carcinomas derived from lung, ovary, or kidney were discussed.

Adenocarcinoma↗
PubMed1988

Histochemistry and electron microscopy in the diagnosis of small mucous cells in carcinoma of the stomach.

One hundred and two cases of poorly differentiated adenocarcinoma were obtained from 71 surgical and 31 biopsy specimens of the stomach. These tumours produced both intracellular and extracellular mucins, which were demonstrated to be neutral mucins, N-acetyl sialomucins, sulphomucins and O-acetyl sialomucins. The majority of tumours (85.3%) secreted two or more kinds of mucins simultaneously, but only a small proportion (14.7%) produced a single kind of mucin. Ultrastructurally, three types of mucin granules were identified; these differed in shape and density. Tumour cells containing intracellular mucins or mucin granules were designated as mucous cancer cells and further subdivided into small, large and goblet mucous cells; tumour cells having neither mucins nor glandular differentiation were designated as undifferentiated cancer cells. These histochemical distinctions, supported by the electron microscopical observations, may be useful to demonstrate early malignant foci in gastric biopsies.

Adenocarcinoma↗
PubMed1987

Response of the wild type and low xanthine dehydrogenase strains of Drosophila melanogaster to adenine resistance selection.

Survival rates of two Drosophila melanogaster strains, the Oregon R Wild Type (WT), and a mutant that was Low Xanthine Dehydrogenase (LXD), grown for six generations in control and in adenine-supplemented media, were determined. Although adenine was toxic to both strains, it was less toxic to the LXD strain. Uric acid levels indicated that WT Drosophila melanogaster was less able to metabolize adenine through the detoxification pathway. Male flies of both strains appeared to be more susceptible to adenine toxicity than were female. The results demonstrate that the adenine resistant strain may possess an enzyme pattern to minimize the toxic effect of adenine.

Adenine↗
PubMed1986

T-cell lymphoma: a morphological, histochemical and immunological study of nine Chinese cases.

Nine cases of T-cell lymphoma presenting in the Guizhou province of China between 1982 and 1984 are reviewed. Seven of the patients were male; seven patients have died, the mean survival period being 22 months. The clinical features resembled those reported in Japanese cases, but skin lesions were absent. Histologically three cases were classified as of lymphoblastic type, three as pleomorphic cell type, two as clear cell type and one as immunoblastic-lymphadenopathy-like T-cell type.

Adolescent↗
PubMedDate not supplied

Histamine excites rat cerebellar granule cells in vitro through H1 and H2 receptors.

The effects of histamine on the firing of cerebellar granule cells were investigated in vitro. Histamine predominantly produced excitatory (117/123, 95.1%) and in a few cases inhibitory (6/123, 4.9%) responses in granule cells. The histamine-induced excitation was not blocked by perfusing the slice with low Ca2+/high Mg2+ medium, supporting a direct postsynaptic action of histamine. The H1 receptor antagonists triprolidine and chlorpheniramine significantly diminished the histamine-induced excitation, but the H2 receptor antagonist ranitidine did not significantly reduce the excitation. On the other hand, the H2 receptor agonist dimaprit could elicit a weak excitation of granule cells. This dimaprit-induced excitation was blocked by ranitidine but not triprolidine. These results reveal that the excitatory effect of histamine on cerebellar granule cells is mediated by both H1 and H2 receptors with a predominant contribution of H1 receptors. The relevance of these findings to the possible function of the hypothalamocerebellar histaminergic fibers in cerebellum is discussed.

Animals↗
PubMedDate not supplied

Dual actions of isthmic input to tectal neurons in a reptile, Gekko gekko.

We analyzed postsynaptic potentials and dye-labeled morphology of tectal neurons responding to electrical stimulation of the optic nerve and of the nucleus isthmi in a reptile, Gekko gekko, in order to compare with previously reported interactions between the optic tectum and the nucleus isthmi in amphibians and birds. The results indicate that isthmic stimulation exerts inhibitory and excitatory actions on tectal cells, similar to dual isthmotectal actions in amphibians. It appears that dual actions of the isthmotectal pathway in amphibians and reptiles are shared by two subdivisions of the nucleus isthmi in birds. The morphology of tectal cells responding to isthmic stimulation is generally similar to that of tectoisthmic projecting neurons, but they differ particularly in that some tectoisthmic cells bear numerous varicosities whereas cells receiving isthmic afferents do not. Thus, it is likely that at least some tectoisthmic cells may not be in the population of tectal cells that can be affected by isthmic stimulation. Forty-four percent of injections resulted in dye-coupled labeling, suggesting extensive electrical connections between tectal cells in reptiles.

Animals↗
PubMedDate not supplied

Characterization of group D1 non-typhoid Salmonella isolates by serotyping and pulsed field gel electrophoresis.

Non-typhoid salmonella infection is not uncommon in immunocompetent patients in Taiwan. Bacterial factors may play an important role in the pathogenesis of such infections. In a previous study, Salmonella group D1 was found to have the tendency to cause bacteremia with a higher frequency than other serotypes. In the present study, we prospectively collected 94 Salmonella group D1 isolates for serotyping and molecular typing. Salmonella panama and Salmonella dublin seemed more invasive than other serotypes. Pulsed field gel electrophoresis was also done to characterize of Salmonella enteritidis and Salmonella dublin. PFGE type "a" of Salmonella dublin appeared to be more invasive than the other two PFGE types. All six Salmonella dublin isolates were Vi antigen negative. Further study using a larger number of isolates is needed to identify the tendency to invade blood stream of Salmonella dublin and Salmonella panama.

Adult↗
PubMedDate not supplied

Genetic analysis of the nitrogen fixation system in Klebsiella pneumoniae.

Fine structure mapping of nif mutations of Klebsiella pneumoniae was accomplished by means of Pl-transductional crosses and the plasmid R144 drd mediated conjugations. The physical distance between nif mutations based on the percentage of co-transduction with hisD of the nif mutations was estimated. The maximal distance between two mutations was calculated about 3 Kb, and the average distance between different nif mutations was about 1 to 2 Kb. So no "silent region" was shown within the nif cluster nearby the histidine operon. Several hisD-unlinked nif mutants were isolated and investigated genetically and biochemically. They all differed from the glutamineless mutants, one of these mutants was tentatively assigned as a sort of N-assimilation mutant with little activity of glutamate synthetase. It differed from the known N-assimilation mutants in its absence of nitrogenase activity. Since the wild type hisD-linked nif genes carried by the plasmid RP4 failed to complement the defects of the hisD-unlinked nif genes in the recipient cells but they were effective to facilitate E. coli in acquiring the ability to fix nitrogen, which indicates that the hisD-unlinked nif genes necessary for the functioning of the hisD-linked nif genes are present in E. coli.

Chromosome Mapping↗