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Biomedical subjects

A G Walker

Publications and source records attributed to A G Walker.

10 recordsLinked to original sources

Methods for the estimation of the number and quality of animal cells immobilized in carbohydrate gels.

Rapid and reliable methods for the determination of survival, proliferation, and metabolic activity of immobilized cells in gels are described. The first method is based on an MTT assay that measures qualitatively and quantitatively the metabolic activity of the cells. The second method determines cell number by measuring the amount of DNA available for Feulgen staining. In the third method, two fluorescent dyes are used to differentially stain viable and dead cells. The fourth method involves the use of glutaraldehyde to protect the cells when melting the gel to facilitate hemocytometric count. The presented techniques should help to test the efficiency of the immobilization procedures and to monitor the growth and survival of immobilized cells.

Animals

The rapid and sensitive enumeration of antibody-secreting cells using immunogold/silver staining (SIG-blot assay).

A simple and robust method has been developed for the enumeration of antibody-secreting cells. Secretion is assessed on the surface of 96-well microtitre plates using immunogold/silver staining techniques. The method is sufficiently straightforward to allow, for the first time, assessment of secretory cells in the clinical laboratory. This approach has great potential for enumerating cells that secrete other products, such as the interleukins.

Animals

Immunocytochemical demonstration of glial-neuronal interactions and myelinogenesis in subcultures of rat brain cells.

Subcultures have been established from primary rat brain cell cultures and have been characterised with a range of cell-specific immunocytochemical markers. The subcultures are mainly composed of fibrous astrocytes, oligodendrocytes and neurones. The cells do not divide to any great extent giving a system where it is possible to follow culture development at the cellular level for a number of weeks. During this time oligodendrocytes colonise subpopulations of neurones, differentiate further showing the presence of myelin basic protein and elaborate myelin-like membrane; the fibrous astrocytes remain scattered uniformly throughout the cultures. Radially oriented processes emerge from the oligodendrocyte-neurone aggregates which subsequently coalesce to form fascicles that link the clusters of cells together. These fascicles react with antibodies for both neurofilament protein and myelin basic protein. The subcultures provide a straightforward system that is composed of cells derived entirely from the CNS, is free from mitotic inhibitors and yet retains a sufficiently low cell density to allow immunocytochemical identification of the cell types present. The subcultures should be useful for the study of trophic interactions between oligodendrocytes and neurones as well as the early events associated with myelinogenesis.

Animals

Antenatal diagnosis of urinary tract abnormalities: correlation of ultrasound appearance with postnatal diagnosis.

A review was made of the natural history of the urinary tract abnormalities diagnosed antenatally in 18 fetuses in order to correlate the ultrasound appearance with subsequent postnatal diagnosis and prognosis. Unilateral disease, both obstruction and multicystic renal disease, was associated with a good prognosis. Bilateral dysplastic kidneys had a very poor prognosis. The antenatal ultrasound demonstration of bladder distention and/or hydronephrosis, however, does not always signify true obstruction of the urinary tract. This is important in view of the recent introduction of in utero interventions to preserve renal function and prevent pulmonary hypoplasia.

Dilatation, Pathologic

Immunocytochemical characterisation of cell cultures grown from dissociated 1-2-day post-natal rat cerebral tissue. A developmental study.

A range of cell-specific markers have been employed with immunocytochemical methods to characterise and quantitate the cell types present in mixed brain cell cultures derived from dissociated 1-2-day post-natal rat cerebral hemispheres and grown in the presence of FCS. Protoplasmic astrocytes (GFAP+, A2B5-) were the major cell type to develop in culture, a confluent monolayer forming in 5-8 days. A population of smaller round cells of oligodendrocyte-like morphology appeared on this astrocyte layer. Greater than 70% of these smaller cells were GC- and thus were not oligodendrocytes. The GC- cells were A2B5+ and, in early cultures, may therefore be progenitor glial cells. Examination of GFAP and A2B5 co-expression by these smaller cells was difficult due to the dense underlying GFAP+ astrocyte layer. In less dense areas of older cultures these smaller cells with processes were GFAP+ and A2B5+: these are Type 2, fibrous astrocytes. GC+ oligodendrocytes, comprising 5-10% of the total identified cell population, were initially distributed over the astrocyte monolayer; in older cultures (after about 8 days) GC+ cells were observed in clumps over places where NF+ cells were identifiable. Such GC+ cells mostly became MBP+. Neurones accounted for about 6% of the identifiable cells in early cultures but a lower percentage in older cultures. Minor populations of ependymal cells and macrophages were present; cells displaying fibronectin, fibroblasts, were rarely identified. Use of horse serum in place of FCS gave lower yields of GC+ cells in cultures, slowed down astrocyte development, and resulted in the formation of trunks of GFAP+ cells throughout cultures. Other sera gave lower numbers of GC+ cells.

Animals