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J G Dickson

Publications and source records attributed to J G Dickson.

30 records · Page 2Linked to original sources
PubMed1984

Quantitative evaluation of neurite outgrowth in cultures of human foetal brain and dorsal root ganglion cells using an enzyme-linked immunoadsorbent assay for human neurofilament protein.

An enzyme-linked immunoadsorbent assay has been developed to evaluate comparative levels of neurofilament protein in developing primary cultures of human foetal dorsal root ganglion and brain tissue. The quantitative parameters of the assay, relating linearity of response with varying levels of neurofilament protein, were verified by comparing the relative binding of human species-specific (BF10) and cross-species-reactive (RT97) monoclonal antibodies to mixtures of human and baboon spinal cord homogenates that had been passively adsorbed onto microtitre wells. In human neural cultures, the localisation of neurofilament protein to growing neurites was determined by indirect immunofluorescence staining with anti-neurofilament antibodies and, using the immunoadsorbent assay, a time-dependent increase in the level of neurofilament protein was detected that correlated with the morphological time course of neurite development. In the case of dorsal root ganglion cells over 6 days in vitro, a seven- to ninefold greater increase in neurofilament protein levels was observed in cultures treated with nerve growth factor when compared with control unstimulated preparations. The quantitative responsiveness of dorsal root ganglion neurones to nerve growth factor detected by the neurofilament assay indicates its potential usefulness in the identification and analysis of neurotrophic and neurotoxic factors or cellular interactions operating in vitro.

Antibodies, Monoclonal↗
PubMed1983

Expression of human neuronal antigens in a mouse neuroblastoma x human dorsal root ganglion cell hybrid.

Clonal mouse neuroblastoma cells were fused with cells from human foetal dorsal root ganglia and several continuously-growing hybrid clones isolated. One hybrid cell line (F2.1D1) containing a number of human chromosomes, was shown to retain the ability to extend neurites in response to dibutyryl cyclic AMP and to express various antigens characteristic of human foetal dorsal root ganglion neurons. The X-chromosome-controlled 12E7 antigen, human Thy-1 and the neuron-specific F12.A2B5 antigen were identified as surface components of the hybrid cells. None of these antigens were detected in the parental neuroblastoma cell line. In addition, using a species-specific monoclonal antibody, the hybrid cells were shown to synthesize human neurofilament protein. This is the first demonstration of the continued expression of a human species- and neuron-specific gene product in a human-mouse somatic cell hybrid.

12E7 Antigen↗
PubMed1983

Identification of cell-surface antigens present exclusively on a sub-population of astrocytes in human foetal brain cultures.

We have examined two monoclonal antibodies (McAbs; coded MI/N1 and 308) raised to human neuroblastoma cells for cell-type-specific reactivity in cultures of human neural tissues and in frozen sections of intact primate spinal cord. In dual-label immunofluorescence assays using established cell-type antigenic markers as positive controls, the reactivity patterns obtained with both McAbs MI/N1 and 308 were consistent with the detection of astrocyte-specific cell-surface antigens. No reactivity of the antibodies with other human neural cell-types, or with human muscle cells was detected. In cultures of human foetal brain a sub-population of astrocytic cells remained unlabeled by antibodies MI/N1 and 308. The significance of the latter observation has not yet been defined but may represent a developmental or functional division within the astrocytic cell lineage.

Antibodies, Monoclonal↗
PubMed1982

Reorganization of porcine thyroid cells into functional follicles in a chemically defined, serum- and thyrotropin-free medium.

In the serum-free, chemically defined medium NCTC 109, freshly isolated porcine thyroid cells aggregate and form functional follicles in culture even in the absence of thyrotropin. The follicular pattern observed under light and electron microscopy express the main morphological characteristics of in vivo thyroid cells. Follicles are large, replete with dense colloid, and the apical pole of cells is characterized by well-developed microvilli and the presence of aminopeptidase N. The index of iodide transport activity (125I-C/M ratio) decreases vs. days of culture to a resting value of about 1 or 2 at day 2. Addition of thyrotropin (200 microU/ml final concentration) at day 4 is followed by a 10-fold increase in iodide transport activity within 24 h and a 40-fold increase 4 d later. Incorporation and organification of iodide are dose dependent between 0 and 250 microU/ml thyrotropin; highest concentrations (4,000--16,000 muU/ml) are significantly inhibitory. In the absence of thyrotropin each cell synthesizes 8.2 pg thyroglobulin/d. Acute stimulation by thyrotropin at day 4 resulted in a slight decrease in the quantity of thyroglobulin present in the cell layer but in an increase in the total amount of thyroglobulin recovered in both cells and medium, reaching 34.3 pg/cell/d. The protein exported into the medium is thyroglobulin, as shown by SDS PAGE and immunological properties. Here we demonstrate that porcine thyroid cells can be maintained in culture as resting, highly differentiated, follicular-associated cells, sensitive to acute stimulation by thyrotropin.

Animals↗
PubMed1981

Follicle formation and iodide metabolism in cultures of human thyroid cells.

Primary cultures were initiated using thyroid tissue obtained at operation from patients with Graves's disease. The in-vitro conditions which permitted the formation of functional follicular structures in both primary cultures and derived sub-cultures were examined. In both situations, culture without the addition of calf serum to the medium resulted in the formation of follicles in response to thyrotrophin. In primary cultures the response to stimulation by exogenous thyrotrophin was variable. However, cells derived from long-term primary monolayers responded to thyrotrophin stimulation in a more predictable manner. In sub-cultures, the ability of cells to concentrate and organify iodide was augmented in a dose-dependent fashion in response to thyrotrophin (0 to 0.2 mu./ml); maximal values of 20 to 80 times those of control cultures being obtained. While follicular structure was maintained at higher hormone concentrations iodide-trapping capacity declined. Similar effects were produced by both low and high purity thyrotrophin and by dibutyryl cyclic AMP. Thyroid cells from two patients with a genetic defect of iodide organification exhibited the same lesion in vitro.

Cells, Cultured↗
PubMed1979

The association of actin with a thyroid lysosomal fraction.

A lysosome-enriched fraction was prepared from bovine thyroid tissue using sucrose gradient centrifugation. An inhibitor of DNAase I was found to co-sediment and co-purify with the lysosomal fraction. This inhibitory activity is blocked by heavy meromyosin in the absence of ATP, and a component of 42000 molecular weight can be isolated by affinity chromatography on DNAase I linked to Sepharose. These results are consistent with the presence of an actin-like protein in a lysosome-enriched preparation from bovine thyroid tissue. Also, an increase in the level of membrane-associated actin is observed in response to thyrotropin stimulation of the thyroid tissue

Actins↗