Biomedical subjects

C M Luo

Publications and source records attributed to C M Luo.

7 recordsLinked to original sources

PubMed1997

Inactivation of p53 results in high rates of homologous recombination.

Using a plasmid substrate which integrates into the genome, we determined that the rate of homologous recombination was suppressed by p53. Human tumor cell lines, mutant or null for p53 had recombination rates 10000-times greater than primary fibroblasts. When isogenic cell pairs from tumor cells or primary fibroblasts were compared, differing only in one genetic change which inactivated p53, the recombination rate increased > 100-fold. Functional inactivation of p53 by dominant mutant p53, by large T antigen of SV40 virus, by E6 protein of human papilloma virus, or by genetic deletion led to the same result. Our results suggest that p53 suppresses spontaneous homologous recombination, and that p53 is not required for recombination to proceed. The mechanism of recombination suppression may be related to the reported association of p53 with Rad 51, but the functional consequences of this association are not yet established. It is suggested that suppression of homologous recombination is the means by which p53 maintains genetic stability.

Blotting, Western↗

PubMed1996

High frequency and error-prone DNA recombination in ataxia telangiectasia cell lines.

The only specific DNA repair defect found in ataxia telangiectasia (A-T) cells is mis-repair of cleaved DNA. In this report we measured DNA recombination, given its role in DNA repair and genetic instability. Using plasmids containing selectable reporter genes, we found a higher frequency of both chromosomal recombination (>100 times) and extra-chromosomal recombination (27 times) in SV40-transformed A-T cell lines compared with in an SV40-transformed normal fibroblast cell line. Southern analysis of single A-T colonies exhibiting post-integration recombination revealed that 24/27 had undergone aberrant rearrangements; recombination in normal fibroblast colonies was achieved by gene conversion in 8/11 clones and 10/11 clones showed unchanged copies of the plasmid. Using co-transfection of two integrating plasmids, each containing a separate deletion in the xgprt reporter gene, the 27 times difference in extra-chromosomal recombination was found when the plasmids were cleaved at a distance from the reporter gene. When the plasmids were cleaved within the reporter gene, the co-transfection frequency was reduced in A-T, but was increased in normal cells. We conclude that A-T cell lines have not only a high frequency chromosomal and extra-chromosomal recombination, but also exhibit error-prone recombination of cleaved DNA.

Ataxia Telangiectasia↗

PubMed1996

[The clinical research of the tooth acid erosion disease in workers related to acid jobs]

Through investigation into 1671 workers who do six acid related jobs in fourteen factories,and 501 workers who work in non-acid condition in contrast.The paper has worked out the criteria of diagnosing occupational acid erosion disease,including the classified criteria of diagnosing single tooth acid erosion disease and the criteria of diagnosing different degrees of the tooth acid erosion disease in the oral cavity.It has also been found out that these are close relationships between the rate of suffering the occupational tooth acid erosion disease and the degree of the erosion,on the one hand and density of acid fog in the air and the types of acid workers are exposed ton and the length of the years working in such environment.

Journal Article↗

PubMed1995

Microcomputer system for automatic identification of the Cryptococcus neoformans and its clinical application.

In this study, microcomputer image processing and pattern recognition technology, and the knowledge of morphology and optical characteristics of Cryptococcus neoformans were used for identification of Cryptococcus neoformans. Four groups of mice were lethally infected with standard strain, Wuhan strain, American B-2643 strain and Var. Shanghainesis of the Cryptococcus neoformans. The samples collected included mice brain, lung, kidney, liver, small intestine tissue and were observed under a light microscope. More than 600 images of the fungus were input into a microcomputer. A system of computer for automatic identification of the Cryptococcus neoformans was developed. The technique involved image preprocessing, image segmenting, coding of line-length on the edge, curve fitting, extracting of image feature, building of image library and feature data bank etc.. And then, 768 images of the clinical samples and other fungus samples whose morphological features tend to be confused with Cryptococcus neoformans were input into microcomputer and subjected to automatic identification. The Cryptococcus neoformans was accurately identified within 15 min, and the consistency rate with results of routine culture was 98%.

Animals↗

PubMed1995

Carbachol, glycine and gamma aminobutyric acid also activate cardiovascular neurons of pontomedulla responsive to glutamate.

Thirty-three cats under intraperitoneal chloralose (40 mg/kg) and urethane (400 mg/kg) anesthesia were used to explore the effect of microinjections (100 nl) of carbachol (CCh, 0.5 M), a cholinergic analogue, glycine (Gly, 1 M) and gamma aminobutyric acid (GABA, 0.4 M) on the cardiovascular-reactive sites in the pontomedulla that responded to microinjection of monosodium glutamate (Glu, 0.25 M, 100 nl) resulting in changes of systemic arterial pressure (SAP). Brain sites under exploration included gigantocellular tegmental field and lateral tegmental field (FTG-FTL), the dorsomedial (DM) and ventrolateral (VLM) medulla which produced pressor responses; caudal VLM (CVLM) and paramedian reticular nucleus (PRN) which produced depressor responses. It was found that CCh produced significant fall of SAP in DM and VLM while the rise of SAP in the same site by Glu. CCh produced SAP decrease in CVLM similar to Glu. GABA significantly caused a slight to moderate increase of SAP in FTG-FTL, DM and VLM, and decrease of SAP in CVLM, all in direction similar to that of Glu. Gly produced significant and marked increase of SAP in DM and VLM similar to Glu both in magnitude and duration. Gly produced increase of SAP in CVLM but the fall of SAP by Glu. PRN was relatively non-reactive except a few microinjections of CCh which produced hypotension. In conclusion, the cardiovascular-reactive sites in the pontomedulla that respond to Glu may also react to other chemicals or neurotransmitters. It is highly possible that multiple receptors of different nature co-exist in neurons of some cardiovascular regions in the pontomedulla.

Animals↗

PubMed1988

[Growth capability of epithelial cell line of human poorly differentiated nasopharyngeal carcinoma and its response to Chinese medicinal herbs and marine drugs].

By 3H-TdR incorporation, dye exclusion and cell colony-forming tests, the capability of short-term in vitro growth of the epithelial cell line of human poorly differentiated nasopharyngeal carcinoma (CNE-2Z) was assayed. At the same time, its response to 54 kinds of Chinese medicinal herbs and marine drugs was studied. The results showed that the 3H-TdR incorporation rate of cells was 1.8 +/- 0.02%, reproduction rate was 60.9 +/- 13.0% and colony-forming rate, 40.8 +/- 3.5%. As to the ratios of the three cell growth indexes and response to medicines, the Chinese medicinal herbs and marine drugs causing the reduction of colony-forming and cell survival ratios were predominant (64.8% and 40.7%). The results indicate that the majority of drugs possess the cytotoxic and inhibitory effect on cell reproduction to different degrees. The composite cell response to every kind of drug could be divided into 6 types: descending, ascending, peaked, valley-like, depressed and stable. The depressing type drugs might inhibit or arrest the cell growth of nasopharyngeal carcinoma and are worthy of further study.

Cell Division↗

PubMed1985

Effects of cadmium on cadmium smelter workers.

The effects of cadmium on 65 workers in a cadmium-refining plant in the People's Republic of China were investigated. The average airborne cadmium oxide concentrations ranged from 0.004 to 0.187 mg/m3 at most worksites. Except for some vague symptoms and reports of anosmia, no significant abnormalities were found in the clinical examinations. The level of cadmium in the blood and urine was increased in the majority of the cadmium-exposed subjects. Nine cases (13.8%) with suspected or mild renal tubular damage were found in this study.

Adolescent↗