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Biomedical subjects

M Lui

Publications and source records attributed to M Lui.

26 records · Page 2Linked to original sources
PubMed1989

Cytogenetics of undifferentiated nasopharyngeal carcinoma xenografts from southern Chinese.

Three undifferentiated nasopharyngeal carcinoma (NPC) tumour lines were successfully established from fresh biopsy material injected s.c. into athymic mice and passaged for many generations. These xenografts were found to be free of infiltrating lymphoid cells and remained undifferentiated up to passage 30. They were designated NPC/HK2117 (Xeno-1), NPC/HK1915 (Xeno-2) and NPC/HK1530 (Xeno-3), respectively. Passage 16 from Xeno-1, passage 1 from Xeno-2 and passage 14 from Xeno-3 were studied cytogenetically using G-banding with the trypsin-Giemsa method. Two xenografts were hyperdiploid with chromosome modal numbers ranging from 49 to 76, and one was hypodiploid with modal numbers ranging from 28 to 38. Five marker chromosomes have been identified with involvement of chromosomes 1, 3, 11, 12 and 17. Marker chromosomes derived from chromosomes 12q, 1q and 3q were consistent in one of the 2 xenografts successfully G-banded, and chromosomes 12, 11 and 17 were consistent in another. Three out of the 6 markers involve 12q13----qter. An abnormal chromosome 3 with most of the p arm deleted was also observed.

Animals↗
PubMed1980

Establishment of a cell line (NPC/HK1) from a differentiated squamous carcinoma of the nasopharynx.

A long-term cell culture epithelioid cell line was established from a recurrent squamous carcinoma of the nasopharynx of a Chinese male 17 1/2 years after radiation therapy. The cell line, designated NPC/HK1, has been passed 72 times over a period 1 year. The cells have been shown by light and electron microscopies to be of the squamous epithelial type. When they were transplanted subcutaneously into the back of athymic nude BALB/c (nu/nu) mice, tumors developed at the sites of inoculation, which on histological examination were shown to be well-differentiated squamous carcinomas, similar in morphology to the recurrent human tumor from which they were derived. Karyotypic analysis of cells from the cell line demonstrates an aneuploid human type with a modal chromosome number of 74 with both numerical and structural aberrations. Viral particles or Epstein-Barr viral nuclear antigen (EBNA) has not been demonstrated in the cells from the primary culture or several of the subcultures tested. The presence of EBNA in touch smears prepared from the biopsy tissue was inconclusive. Infection of the subcultured cells with EBV from P3HR1 and B95-8 cells was unsuccessful.

Adult↗
PubMed1978

Partial reactions of aminoacyl-tRNA synthetases as functions of pH.

The effect of pH on the properties of the partial reactions of arginyl-tRNA synthetase of E. coli has been investigated. V max of pyrophosphorolysis of arginyl adenylate has a pH optimum at pH 6.1, whereas V max of the transfer of arginine to tRNA has a pH optimum of 8.2. These values correlate with the pH optima of the ATP:PPi exchange and the overall esterification reaction, respectively. Only the pyrophosphorolysis reaction requires a divalent cation; transfer proceeds in the presence of EDTA. Inorganic pyrophosphate inhibits the transfer reaction to an extent independent of the concentration of tRNA; the maximum inhibition is a function of pH, corresponding to the relative rate of pyrophosphorolysis of the common intermediate compared with the rate of transfer. These results show that different groups on the enzyme participate in the rate-limiting steps of the two partial reactions and that these partial reactions have properties consistent with their participation in the overall esterification of arginine with tRNA.

Amino Acyl-tRNA Synthetases↗
PubMed1977

Possible transformation of nasopharyngeal epithelial cells in culture with Epstein-Barr virus from B95-8 cells.

Explants of fresh biopsy specimens from non-neoplastic nasopharyngeal (NP) mucosa, nasopharyngeal carcinoma (NPC), other tumours (OT) of the head and neck and freshly removed tonsils were treated with an Epstein-Barr virus (EBV) preparation from B95-8 cells and cultured. The mainly epitheloid outgrowths from these infected explants were then compared with those from their respective uninfected controls at 14 days. Growth stimulation occurred with a significantly higher frequency, and the degree of stimulation was generally higher with the infected NP explants than those of the similarly infected explants of other origins. Furthermore, after treatment with the virus preparation, several of the outgrowths from the NP explants showed growth characteristics and cellular morphology typical of those of transformed cells. Light microscopy has shown the changed NP cells to have epithelial characteristics. This is now being verified by electron microscopy, which has so far shown the presence of keratin fibrils and desmosomes in one specimen examined. They are also being examined for the presence of EBV-DNA and EBNA, and other features of transformation, including malignant tendency, by passage through athymic nude mice.

Cell Division↗