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Biomedical subjects

M S Lakshmi

Publications and source records attributed to M S Lakshmi.

At least 19 recordsLinked to original sources
PubMed1992

Image processing for cell cycle analysis and discrimination in metastatic variant cell lines of the B16 murine melanoma.

Computer-based image analysis offers a wide range of techniques which can be used to make objective and reproducible detection and measurement of subvisual features of microscopic images of cells. We describe here a prototype imaging system for specimen analysis. Using this system, studies have been carried out on the low metastasis variant F1 and high metastasis variant BL6 of the B16 murine melanoma. Cell cycle analyses have been carried out based on the measurement of integrated nuclear density, nuclear area and nucleocytoplasmic ratio of cells stained using standard procedures. It has been possible to discriminate between the two cell populations on the basis of ploidy. The two cell lines had a similar proportion of cells in the S-phase.

Animals↗
PubMed1988

Spontaneous sister chromatid exchange in metastatic variants of the murine B16 melanoma and human astrocytomas in culture.

Three metastatic variants, BL6 (high metastasis), F1 (nonmalignant) and F10 (intermediate malignancy) of the B16 murine melanoma, and a pulmonary metastatic line BL6-ML8 of the BL6 primary tumour have been examined for spontaneous sister chromatid exchange (SCE). Two human astrocytoma cell lines were also examined. SCE was encountered in 29 and 13% of second division metaphases of BL6 and F10. In contrast, only 3% of second division metaphases of the F1 showed SCE. In BL6-ML8, 40% of the metaphases showed SCE. Approximately 2-4% of the human astrocytoma second division cells showed SCE. The variant lines were karyotypically heterogeneous. The pattern of cell distribution according to chromosome number showed an overall similar profile in the melanoma variants. However, the metastatic BL6-ML lines showed a marked shift to a hypertriploid state. SCEs occurred with higher frequency in this hypertriploid subpopulation of BL6 and F10 cells than in F1. SCE incidence in the hypertriploid subpopulation was twofold higher in the metastatic line than in the primary BL6 line. The number of SCEs per chromosome was twice as high in F10, BL6 and BL6-ML8 as in the F1 cells. This hypertriploid subpopulation showed a marked increase of SCEs on exposure to mitomycin C and ethyl methane sulphonate, indicating their mutability. It is suggested that the parallelism between SCE and metastatic potential may be relevant in the context of the generation of the metastatic phenotype.

Animals↗
PubMed1985

Antigenic heterogeneity of metastasizing and nonmetastasizing forms of hamster lymphosarcoma: comparison of primary tumor and spontaneous liver metastases.

Antisera were raised in rabbits against nonmetastasizing (NML) and metastasizing (ML) forms of hamster lymphosarcoma and were purified against normal hamster tissues. Immunoglobulins from the purified antisera were precipitated with 1.6 M ammonium sulfate, radioiodinated and IgG separated by Sephadex G-200 gel filtration. 125I-IgG preparations were analyzed by a direct cell binding assay and by a complement-dependent cytotoxicity test, employing single cell suspensions from primary lymphosarcoma. In some experiments, 125I-IgG was also tested against ML cells obtained from primary tumor (1 degree) and its liver metastasis (2 degrees). NML induced greater anti-tumor antibody production than ML, suggesting greater antigenicity of the non-metastasizing tumor. The two lymphosarcomas appeared to share some common tumor-associated antigens since antibody to one tumor type was either completely or partially absorbed by tumor cells of the other type. Anti-ML 125I-IgG proved up to 2-5 times more cytotoxic for ML 1 degree than 2 degrees cells. Although both tumors were highly tumorigenic in hamsters, only ML gave rise to distant metastases, predominantly in the liver.

Animals↗
PubMed1983

Isoelectric characteristics and the secondary structure of some nucleic acids.

The isoelectric characteristics of some nucleic acid preparations from rat liver have been examined. 10S and 4S RNA species and SV-DNA were found to have isoelectric points of 5.2, 6.0-6.7, and 4.35 respectively. The molecular charge ratios (net negative charge/nucleotide) were calculated. Using SV-DNA as a standard, these isoelectric characteristics and charge ratios have been interpreted as indicating that the 10S and 4S RNAs have 35 and 56% of the molecules involved in secondary structure.

DNA, Viral↗
PubMed1983

The membrane external proteins of human astrocytomas in culture.

The cell surface proteins of some human astrocytomas have been investigated. Cell cultures were initiated from the tumours and surface proteins labelled with radioiodine in monolayer cultures. Normal glial and astrocytoma cells were found to possess a common surface protein pattern. In the molecular weight (MW) range of 225,000-75,000 daltons, the protein profile contained 6 well-defined peaks. The 195,000-dalton component (pb) was found liable to resolve into pb and a forerunning component pb'. Component pd (130,000 daltons) similarly showed resolution into subcomponents in 5 out of 9 tumours. The remaining components appeared more homogeneous in electrophoresis. There were also significant quantitative changes in the expression of the various components of the astrocytomas as compared with the normal glial cell line. Component pa was found to be reduced by greater than 70% in 7 out of 9 astrocytomas. The levels of 225,000-dalton proteins were found to be directly proportional to the survival times of the patients. Components pc appeared to be amplified by a factor of 1.6-3.5 in all the astrocytomas as compared with the normal glial line. Increased incorporation of radioiodine was also seen in 7 out of 9 tumours in components with MW of less than 75,000 daltons. The possible significance of the differential expression of the surface components is discussed. It is suggested that some of these changes, especially in component pa, may be associated with the malignant state.

Astrocytoma↗
PubMed1982

Antigenic differences between a primary hamster lymphosarcoma and its liver metastases.

An antiserum was raised in rabbits against a primary metastasizing lymphosarcoma (ML) of the hamster. This was made tumor-specific by absorption with normal hamster tissue extracts. Immunoglobulin-G was prepared and tested for its cytotoxicity towards cells derived from the primary tumor and its liver metastases. The ML-specific IgG was found to be 2--5 times more cytotoxic for cells derived from the primary tumor compared to cells obtained from liver metastases.

Animals↗
PubMed1982

The role of cell surface proteins in the induction of histogenetic differentiative responses by some human breast tumours and hamster tumors implanted into chick embryos.

Cells of human breast tumours and fibrocystic hyperplasia grown in culture, and three hamster tumours were implanted between the cell layers of 18-hour-old chick blastoderm. Their ability to induce histogenetic responses in the ectodermal and endodermal embryonic tissues was investigated. The surface proteins of these tumour cells were labelled by lactoperoxidase-catalysed radioiodination. It is shown that the ability to induce the histogenetic effects may be related to the expression of 265K (K = 10(3) daltons) and 233K proteins on the surface of human tumour cells and of 115K proteins on the hamster tumour cells. The antiproteinase, aprotinin, inhibits the induction of the histogenetic responses by and apparently also prevents the deletion of 115K proteins from the hamster tumour cells. It is therefore suggested that cell surface proteins are involved in the complex processes of interaction between embryonic and tumour cells and in the recognition by the embryonic cells of the tumour cells implanted into their midst.

Animals↗
PubMed1981

Membrane surface properties of normal and malignant cells: partition in aqueous two-polymer phase systems.

The partition of normal and malignantly transformed fibroblast lines and cell lines initiated from malignant human astrocytomas and a benign ganglioneuroma has been examined in aqueous dextran-polyethylene glycol phase system containing phosphate buffer with a low phosphate/sodium chloride ratio. The malignant astrocytomas showed a significantly lower partition coefficient as compared with the benign ganglioneuroma. Treatment of astrocytoma cells with dexamethasone caused an increase in the partitioning of the cell population. No differences were found in the partition behaviour of normal BHK-21 cells and their malignant transformants, the TRES fibrosarcoma cells. Polyoma and simian virus-transformed 3T3 fibroblasts showed partition ratios similar to the untransformed cells. Dexamethasone pre-treatment had no effect on the partition behaviour of these cells. The significance of these observations has been discussed in relation to the surface hydrophobicity and the neoplastic state.

Animals↗
PubMed1979

Differences in the surface components of normal and SV-40 transformed 3T3 mouse fibroblasts.

The differences in the surface components of 3T3 mouse fibroblasts and those transformed by Simian virus 40 have been examined using the isoelectric equilibrium method. The net negative surface charge density of the transformed cells appears to be marginally lower than that of the untransformed cell. Chemical modification studies of the surface groups have indicated that about 30% more cationic groups are present on the transformed cells, suggesting the occurrence of some additional basic material not detectable on the surface of normal cells. These basic groups show a modulation of ionisation characteristics in the presence of carboxylic groups. This may indicate a distribution of the cationic extra material in the vicinity of acidic glycoprotein components of the surface. This investigation has also revealed the occurrence of unidentified anionic groups which ionise at high pH, which appear to be thiol groups.

Anions↗
PubMed1977

Does dexamethasone inhibit the growth of human gliomas?

Dexamethasone (10-(4)M) was shown to inhibit the growth of human gliomas in culture. This was indicated by the inhibition of incorporation of radioactively labeled thymidine into the deoxyribonucleic acid (DNA) of the cells, and by the increase in the generation time of cells exposed to the drug in vitro. On the other hand, tumors obtained from patients who had received dexamethasone before craniotomy grew considerably faster in vitro than tumors from patients who had not been given the drug before operation.

Astrocytoma↗
PubMed1975

Tumour-associated surface antigen(s) in human astrocytomas.

The cytotoxic properties of a hetero-antiserum have been used to demonstrate surface antigen(s) common to seven human astrocytomas. This has been designated human astrocytoma-associated antigen (HAAA). Tissue cultures of astrocytomas were prepared. A rabbit antiserum was raised to one of these and its antibody activity on the original tumour cells assayed by dye exclusion cytotoxicity testing. After repeated absorption with associated antigen(s). In a series of absorption experiments, HAAA was detected in six other human astrocytoma cultures, but not found in a series of other human tumours and tissues tested. Homogenates of two original astrocytomas absorbed out HAAA activity in a similar way indicating the presence of the antigen(s) in vivo. The significance of this HAAA is discussed.

Antigens, Neoplasm↗