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Biomedical subjects

R Rajaraman

Publications and source records attributed to R Rajaraman.

At least 37 records · Page 2Linked to original sources
PubMed1983

Exogenous fibronectin requirement for adhesion by neoplastic human cells.

We have studied the effect of serum, plasma and plasma fibronectin on the spreading behavior of several normal and neoplastic human cells using a quantitative spreading assay. Normal human cells are rich in surface fibronectin and are able to spread in the absence of serum or exogenous fibronectin. Virus-transformed cells and cells of neoplastic origin have reduced or no recognizable surface fibronectin and are dependent on serum or plasma for spreading. In agreement with previous studies on rodent cells, fibronectin appears to be the major factor responsible for this effect. Neoplastic cells can spread on fibronectin-coated substrata or can recruit fibronectin directly from the medium. The capacity of transformed cells to recruit fibronectin from the medium correlates with the presence of intercellular fibronectin as seen by the immunofluorescence technique on monolayer cultures. Our results are in keeping with the concept that neoplastic cells may be dependent on extracellular fibronectin for adherence in vivo and that this dependency may vary between different cell types.

Animals↗
PubMed1982

Novel vesicular extrusions during cell spreading.

During the late stages of cell spreading in vitro, the cells extrude a vesicular material into the medium. This phenomenon was observed in human glia and glioma cells as well as in human diploid fibroblasts MRC-5 and WI-38 cells. This extrusion of vesicular material is inhibited by cytochalasin-B and colcemid suggesting the involvement of microfilaments and microtubules and the active nature of this event. It appears that the cells may be excreting damaged surface components by a mechanism similar to patching, capping and endocytosis.

Cell Line↗
PubMed1982

Macrophage migration inhibition factor (MIF): reducing the variables.

While the phenomenon of macrophage migration inhibition is a useful indicator of lymphokine release, it may be caused by other substances, it is subject to considerable variability, and it may be masked by the concomitant presence of substances stimulating migration. We have investigated certain aspects of the lymphokine macrophage interaction in order to circumvent these problems. Cells from the murine macrophage cell line RAW 264-7 migrated with less variability than fresh guinea pig peritoneal macrophages and were more sensitive target cells for human macrophage migration inhibition factor (MIF). Assays were performed with serum-free and endotoxin-free medium and in all cases in the presence and absence of L-fucose. This added specificity to the assay in that biological MIF activity was invariably blocked by L-fucose whereas migration inhibition produced by antigen complexed antibody, endotoxin, and periodate was not affected by L-fucose. It was also possible to demonstrate MIF activity in mixtures of MIF and migration stimulation factor by using L-fucose. We suggest that MIF activity is determined with less variability by using a macrophage cell line as indicator cells and performing the assays in the presence and absence of L-fucose.

Animals↗
PubMed1982

Fibronectin distribution pattern and the three-dimensional growth behavior of mammalian cells under anchorage-independent conditions.

Several types of normal diploid cells, established "normal" cells, and transformed cells of human and rodent origin have been studied with reference to cell surface fibronectin distribution and their anchorage-independent growth behavior. All cell types that showed intercellular and fibrillar surface fibronectin were anchorage-dependent for growth. Lack of surface fibrillar fibronectin in spontaneously or virus-transformed cells and cells of neoplastic origin was accompanied by anchorage-independent growth potential. The degree of three-dimensional organization of cells under anchorage-independent growth conditions was dependent on the amount of intercellular fibronectin. The significance of these observations to in vivo tumor growth is discussed.

Animals↗
PubMed1980

Morphological reverse transformation of Chinese hamster ovary (CHO) cells and surface fibronectin.

Alterations in the distribution of surface fibronectin during reverse transformation of chinese hamster ovary (CHO) cells induced by dibutyryl adenosine cyclic monophosphate (dbcAMP) and theophylline was examined by indirect immunofluorescence. dbcAMP-induced reverse transformation was not followed by any significant increase in surface fibronectin up to 48 hrs after treatment. Reverse transformation induced by theophylliner by itself or in combination with dbcAMP is followed several hours later by a phenomenal increase in fibrillar surface fibronectin, which is largely persistent even in the presence of cytochalasin-B or colcemid but is sensitive to the presence of cycloheximide. It appears that reverse transformation consists at least of two steps: (a) morphological reversion to normal phenotype and (b) modulation of cell membrane properties or components favouring retention of fibronectin in the cell surface.

Animals↗
PubMed1978

Cellular immunity to a lung homogenate in asymptomatic cigarette smokers.

Leucocyte migration in the presence and absence of a soluble lung homogenate has been studied in a group of asymptomatic cigarette smokers. Results were expressed as migration indices. Controls consisted of age-matched subjects who had never smoked and had no past history of any pulmonary disease. The migration indices, the number of pack-years smoked and the results of pulmonary function studies were tested for correlation. The mean leucocyte migration index of the test group of sixteen smokers was significantly less than was that of the control group (P less than 0.001). Inhibition of leucocyte migration in the presence of the lung homogenate was not observed in any of the control subjects. Six of the sixteen asymptomatic cigarette smokers, however, were identified by inhibition of leucocyte migration in the presence of the lung homogenate. The number of pack-years which had been smoked did not correlate with the migration indices (r = -0.06); however, inhibition of leucocyte migration was not observed in subjects who had smoked less than 6 pack-years.

Adult↗
PubMed1977

Interaction of living cells with polyionenes and polyionene-coated surfaces.

Polyionenes have been shown recently (A. Rembaum, Appl. Polym. Symp. No. 22, 299, 1973) to produce the following biological effects: 1) bactericidal action, 2) formation of insoluble complexes with DNA and heparin, 3) neuromuscular blocking action, 4) cell aggregation and lysis, and (5) cell adhesion. In present study, polyionenes of various structures (mainly I3, 3, I6, 10) were used as molecular probes to gain an understanding of the cell surface phenomena of adhesion on glass- and polyionenes-treated surfaces. Since tumor cells show different durface cell properties, including an increase in the anodic mobility, they bind preferentially to polyionene-treated surfaces. Normal human diploid WI-38 cells were found to adhere at a lower rate than SV-transformed WI-38 cells. However, cell spreading was accelerated in both cases. A study of the interaction of polyionenes in solution in vitro and in vivo and polyionenes covalently bound to polymeric microspheres with leukemic murine EL4 cells and normal thymocytes showed specific cytotoxity towards the leukemic cells.

Animals↗
PubMed1977

Migration inhibition produced by sodium periodate oxidation of the macrophage membrane, and reversal by sodium borohydride.

Guinea pig peritoneal exudate cells were harvested 3 to 4 days after the intraperitoneal injection of Marcol oil. The washed cells were exposed to various concentrations of sodium periodate in phosphate-buffered saline (PBS) at pH 7.4 for 10 min at +4 degrees C. The cells were then used in the in vitro migration assay, and migration was consistently inhibited at concentrations from 10(-3) to 10(-5) M. The viability of the macrophages was not affected by this treatment. Sodium borohydride (10(-3) to 10(-5) M) in PBS for 10 min at pH 7.4 reversed the periodate effect. Experiments with purified macrophages showed that sodium periodate has a direct effect on macrophage function rather than an indirect effect via the potentiation of migration inhibition factor. In support of this, the in vitro spreading of macrophages on glass substrate for 1 h has been shown to be inhibited. This spreading inhibition can also be reversed by treatment with sodium borohydride. These results provide a new approach to understanding the biological significance and role of macrophage migration inhibition.

Animals↗
PubMed1976

E rosette formation by human t lymphocytes: a spontaneous cell mediated cytotoxic phenomenon.

The nature and significance of spontaneous association between unsensitized human T lymphocytes and sheep erythrocytes has been studied in relation to a possible cytotoxic reaction. Human lymphocytes and 51Cr labelled sheep erythrocytes when mixed in ratios of 5 or 10:1 released 70-100% of 51Cr into the supernatants. This suggests that E rosette formation may be the first step in a spontaneous T cell mediated cytotoxic reaction to sheep erythrocytes.

Animals↗