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N A Lytton

Publications and source records attributed to N A Lytton.

7 recordsLinked to original sources
PubMed1987

Calcium-induced changes in cytoskeleton and motility of cultured human keratinocytes.

In normal epidermis keratinocytes migrate upward from the basal layer as they undergo terminal differentiation, yet they also have the capacity for lateral movement during wound healing. The purpose of our experiments was to investigate these two types of movement by manipulating the calcium ion concentration of the medium so that keratinocytes formed monolayers (0.1 mM calcium) or stratified sheets (2.0 mM calcium). Time-lapse video recording indicated that keratinocytes in low-calcium medium were laterally more motile than keratinocytes in normal medium. This was consistent with the ultrastructural appearance of the cells and the lack of desmosomal junctions, determined by scanning and transmission electron microscopy. During calcium-induced stratification keratinocytes moved upward from the basal layer by gliding over their neighbors and forming contacts with other suprabasal cells. Keratinocytes in low-calcium medium migrated into wounds made in the cultures, a process which was inhibited by monensin; however, stratified keratinocytes in normal medium did not enter wounds. Cytochalasin D caused rapid cell rounding and disruption of actin filaments in keratinocytes grown in low-calcium but not in normal medium, indicating more rapid treadmilling of actin and consistent with the greater motility of keratinocytes in low-calcium medium. Our results suggest that desmosome formation may place constraints on the movement of individual keratinocytes and that the actomyosin cytoskeleton is involved in lateral migration.

Actins↗
PubMed1984

Immunofluorescence distribution of alpha tubulin, beta tubulin and microtubule-associated protein 2 during in vitro maturation of cerebellar granule cell neurones.

In vivo developmental immunocytochemical studies have recently shown that granule cell axons (parallel fibres) undergo progressive modification of alpha tubulin as they form permanent synapses, a change that is not observed in other microtubule-containing structures (e.g. Purkinje cell dendrites). In this study we have used primary cultures of young rat cerebellum enriched in granule cells to follow maturation of their axons under defined in vitro conditions. Our results show that alpha tubulin is not modified in culture as assessed by immunofluorescence using monoclonal antibodies that recognise different forms of alpha tubulin. We have also confirmed in vivo data showing that microtubule-associated protein 2 is absent from granule cell axons at all developmental stages in vitro. The distribution of axonal cytoskeletal proteins is compared and contrasted during in vivo and in vitro maturation, and considered in relation to differences between the two systems.

Animals↗
PubMed1984

Immunocytochemical demonstration of alpha-tubulin modification during axonal maturation in the cerebellar cortex.

Previous light microscopic immunocytochemical studies using two monoclonal antibodies that recognise alpha-tubulin (YOL/34 and YL1/2) but differ in their isotypic specificity have shown that the unmyelinated parallel fiber axons in the cerebellar cortex are labeled with only one of the antibodies (YOL/34). We now show that at 10 d postnatally the parallel fibers are labeled with both antibodies, and that during development YL1/2 (but not YOL/34) immunoreactivity disappears progressively from parallel fibers in the lower regions of the molecular layer upwards towards the external germinal layer. By approximately 28 d postnatally, the differential staining pattern of parallel fibers by the antibodies is established throughout the molecular layer. The time course, light microscopic, and ultrastructural staining distribution corresponds to a progressive change in alpha-tubulin immunoreactivity as the parallel fibers form synaptic contacts. This modification of alpha-tubulin (which was not observed in Purkinje cell dendrites or Bergmann glia) may be related to the formation of a basic isotype of alpha-tubulin within parallel fiber axons at maturation.

Animals↗
PubMed1983

Immunocytochemical evidence for tubulin in the presynaptic terminal of synaptosomes.

Ultrastructural studies of intact tissue rarely show presynaptic microtubules, and immunocytochemical studies on tissue sections have previously been unable to demonstrate tubulin in the nerve terminal. In contrast, a microtubular coil can be readily detected in the presynaptic nerve terminal of synaptosomes. We have developed an immunocytochemical procedure on the synaptosome preparation and demonstrated, using monoclonal antibodies, that in the presynaptic terminal alpha and beta tubulin subunits are specifically restricted to the equatorial microtubular coil.

Animals↗
PubMed1983

Axonal sub-populations in the central nervous system demonstrated using monoclonal antibodies against alpha-tubulin.

Using two monoclonal antibodies that specifically recognise alpha-tubulin we describe differences in their light and electron microscopic immunoperoxidase staining of axons in cerebellum, hippocampus, and cerebral cortex. In the molecular layer of the cerebellar cortex at the light microscopic level, one of the antibodies (YOL/34) labelled parallel fibre axons (in an identical manner to a beta-tubulin monoclonal antibody) while the other antibody (YL1/2) failed to label them. Extending these studies to the electron microscopic level in the cerebellum we have determined the sub-cellular localisation of alpha-tubulin in microtubules and the postsynaptic density, and also demonstrated a sub-population of parallel fibres and myelinated axons labelled with antibody YL1/2. The monoclonal antibodies were further characterised using immunoblotting against alpha-tubulin separated by isoelectric focusing gels. The results suggest that the contrasting staining patterns between the alpha-tubulin antibodies may reflect axonal sub-populations containing different isotypes of alpha-tubulin.

Animals↗