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Biomedical subjects

E C Chew

Publications and source records attributed to E C Chew.

68 records · Page 4Linked to original sources
PubMedDate not supplied

Fine structural observation of a nucleolar-nuclear matrix-lamina-intermediate filament system in transformed cells.

The nuclear matrix is a nonchromatin structure of the nucleus normally concealed by a much larger mass of chromatin. Several methods have been developed to remove chromatin from nucleus while preserving the underlying matrix architecture to some degree. The present study showed that after extraction of PtK2 cells and cervical carcinoma cells (CC3) with Triton X-100, ammonium sulfate and DNase, the nucleolar-nuclear matrix-intermediate filament (Nu-Nm-L-IF) network remained. The nucleolus was oval in shape and appeared as a fibrillar mass with an accentric dense fibrillar centre. This nucleolar skeleton was in direct connection with the nuclear matrix which in turn is connected with cytoplasmic intermediate filaments by lamins. It is concluded from these observations that the Nu-NM-L-IF system forms a continuous system which plays an important role in the maintenance of the nucleolar, nuclear and cytoplasmic integrity and cellular function.

Animals↗
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Electron microscopic analysis of the relationship between nuclear matrix stability and cell differentiation.

Two cell lines, the less differentiated CC2/CUHK2 and the more differentiated CC3/CUHKE3, were used to study the difference in nuclear matrix stability against DNase 1 digestion. The nuclear matrix was almost totally extracted when the CC3/CUHK3 cells were digested with 100 micrograms/ml DNase 1, while that of the CC2/CUHK2 cells was still present even when 200 micrograms/ml DNase 1 was used. It is suggested that more differentiated cells have a less stable nuclear matrix while the less differentiated ones have a more stable nuclear matrix. The same phenomenon was also observed in normal human and rat cervical epithelia. The nuclear matrix of the poorly differentiated basal cells was more stable than that of the more differentiated superficial cells. This cell differentiation stage dependent stability of the nuclear matrix is probably related to the nuclear activity and gene expression.

Animals↗
PubMedDate not supplied

The growth and behaviour of pig retinal pigment epithelial cells in culture.

The retinal pigment epithelium contains melanin and lipofuscin. It is believed that in the in vivo system, the incomplete degradation of phagocytosed outer segment discs leads to the formation of lipofuscin. Our results showed that pig RPE cells can be successfully cultured using standard culture techniques without addition of specific growth factors. In this system, the autofluorescent material is formed mainly from the degradation of pigment granules. This culture system may provide an excellent model for studying of diseases related to the retina.

Animals↗
PubMedDate not supplied

A quantitative study of the interphasic nucleolar organizer regions in two human cervical carcinoma cell lines.

We have studied the relationship between interphase nucleolar organizer regions (NORs) distribution and nucleolar size in cancer cells under prolonged culture. Six morphometric parameters (NUCLEAR SIZE, NOR NUMB, AREA SUM, MEAN AREA, SIZE RATIO and SIZE RATIO MEAN) of AgNORs in cancer cells were analyzed by an image analyzing system. The results show that the parameters NORN NUMB, AREA SUM and NUCLEAR SIZE demonstrate the most consistent changes in the two cervical carcinoma cell lines studied. These three parameters of AgNORs appear to be correlated with the degree of "dedifferentiation" that occurred in tumor cells under prolonged culture.

Cell Division↗
PubMedDate not supplied

Microwave fixation of nuclear matrix in tumor cells.

Microwave irradiation provides good fixation of human and animal tissues for light and electron microscopy. In this study, microwave irradiation was used for the fixation of cytoplasmic and nuclear matrix in tumor cells. The nuclear matrix appears well preserved and exhibits a network formed by thick and thin filaments. Hence microwave fixation can be used as a quick and effective method for the study of the morphology of nuclear matrix.

Animals↗
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Fine structural observations on the human sperm nuclear matrix.

The nucleus of the mammalian sperm is formed after a series of morphological and biochemical changes during spermatogenesis. The human sperm nucleus, after sequential extraction with detergents, nuclease and ammonium sulfate, consists of a fibroskeletal structure which maintains the original nuclear shape. The chromatin-depleted skeleton is formed by thick and thin fibers as well as electron-dense patches of different sizes. These highly branched matrix fibers had average diameters of 35 and 12 nm. Polarization of the fibroskeletal structure is apparent and can be used as a good model to study the function of nuclear matrix in nuclear compartmentation in germ cells.

Chromatin↗
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Microwave-enhanced immunohistochemical staining of a formalin-sensitive antigen-laminin receptor.

Many potentially useful antigens have been difficult to detect in formalin-fixed, paraffin-embedded tissues. Recently a number of pathological and research laboratories have demonstrated that some antigens masked by formalin fixation could be restored to detectability by microwave heating. Previously, we were unable to demonstrate laminin receptor in cells processed by the routine fixation. Our results showed that microwave heating together with trypsin produced the best immunohistochemical staining for this receptor. Nevertheless, no significance was found in the levels of 67 kD LR in high and low metastatic tumor cell lines.

Adenocarcinoma↗
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The association of HPV 16 DNA with specific nuclear matrix proteins of normal and cervical carcinoma cell.

Human papillomavirus type 16 (HPV 16) has been found to be integrated into the DNA of epithelial cells in most cervical cancers. The HPV16 DNA is bound to different nuclear matrix proteins in normal and cervical carcinoma cells. It has high affinity, for acidic proteins in cancer cells. The molecular weights of the acidic proteins are 200 kD, 186 kD and 67 kD. On the other hand, the viral DNA seemed to bind to higher molecular weight basic nuclear matrix proteins (250 kD, 150 kD) of normal cells. Further investigation of the functional roles of these nuclear matrix proteins may provide insight into the process of carcinogenesis of the cervix.

DNA, Viral↗
PubMedDate not supplied

Expression of nm23-H1 in human meningioma cells.

The expression of nm23-H1 has been demonstrated to be highly correlated with the metastatic potential of various tumors. In the present investigation, meningiomas of different pathological grades were used to study on their nm23-H1 expression. Immunohistochemistry showed that nm23-H1 was expressed mainly in the cytoplasm especially in the perinuclear region in explants under short-term culture. Western-blotting demonstrated the specific expression of nm23 protein in all tumor samples. The expression was also found to be sex-dependent on tumor progression in female, but not in male patients. RT-PCR results confirmed nm23-H1 expression was higher in benign tumors than in their normal counterpart. Our observations thus suggest that nm23-H1 may play an important role in the progression of meningiomas in female patients.

Adult↗
PubMedDate not supplied

Electrophoretic analysis of nuclear matrix proteins in human hepatocellular carcinoma.

The nuclear matrix is the non-chromatin skeleton of the nucleus. This structure contributes to the shape of the nucleus and regulates various nuclear functions. In this study, nuclear matrix proteins of human normal liver, a liver cancer cell line, HepG2, and hepatocellular carcinomas (HCC) were investigated. Using high resolution two-dimensional polyacrylamide gel electrophoresis, the nuclear matrix proteins of 3 normal liver and 14 HCC were compared and contrasted. A high degree of similarity between normal liver, HepG2, and HCC nuclear matrix protein patterns was found. Two HCC specific nuclear matrix proteins were identified. Among these, one protein (HCC-1, Mr 62 kd, pI 5.3) appeared in all tumor samples and HCC-2 (Mr 33.25, pI 5.3-5.5) was present in 9/11 tumors, but absent in normal liver and HepG2. Our results indicate the presence of HCC specific nuclear matrix proteins. These matrix proteins may be used as markers for HCC.

Antigens, Nuclear↗
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Effect of glucocorticoid hormone on nuclear matrix in cervical cancer cells in vitro.

Human papillomavirus (HPV) is one of the crucial factors in cervical carcinogenesis. High risk HPV16 prototype has been demonstrated in association with the nuclear matrix in a cervical carcinoma cell line(1,2). Nuclear matrix (NM) has been established as playing an important role in various nuclear activities as well as carcinogenic processes. Dexamethasone (DEX) (glucocorticoid hormone) inhibited the growth of CC2/CUHK2 cervical carcinoma cells with concurrent induction of epithelial cell differentiation. 2D- PAGE (IEF and NEPHGE) revealed alternations in NM protein composition. Further demonstration of changes in NM was evidenced by NuMA (a novel NM protein) labelling. The HPV16 E7 oncoprotein was shown to be reduced in total cellular protein as well as in NM protein fractions in response to DEX treatment, and this suppressed expression was confirmed by RT-PCR. Thus, it is suggested that dexamethasone can down-regulate the growth of cervical cancer cells and its induced changes in NM may be a cause of this suppression.

Carcinoma↗
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Nuclear matrix of human ovarian cancer cells in vitro.

The epithelial neoplasia constitute 60% of all primary tumors of the ovary and 90% of these are malignant. Nuclear matrix has been found to be involved in normal and abnormal nuclear activities. Previously, we have identified tumor-associated nuclear matrix proteins in cancers of human liver, nasopharynx and cervix. In this study, we compared nuclear matrices of immortalized ovarian and cancer cell lines by morphometric and 2-D gel electrophoresis analysis.

Electrophoresis, Gel, Two-Dimensional↗
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Association of EGFR gene fragments with nuclear matrices in glioblastoma cell lines.

The association of epidermal growth factor receptor DNA fragments with nuclear matrix in glioblastoma cell lines was investigated. Two different DNA fragments (primer I-III, 940 bp and primer IV-V, 110 bp) were amplified in both genomic DNA and nuclear matrix-associated DNA. It was found that the 110 bp DNA fragment (primer IV-V) from a non-encoding region was more closely associated with the nuclear matrices of cell line U343, U373, A172, and T98 than with U87. The other DNA fragment (primer I-III) was found in both the genomic DNA and NM DNA from cell line of U343 and U87. Another long DNA fragment (primer I-II, 1015 bp) was not detected in the DNA of all cell lines. Our findings suggest that the attachment of the 110 bp DNA fragments to nuclear matrix may contribute to the growth and malignancy of glioblastoma.

DNA Fragmentation↗