Biomedical subjects

R D Hadley

Publications and source records attributed to R D Hadley.

At least 19 recordsLinked to original sources

PubMed1991

Laminin-like immunoreactivity in the snail Helisoma: involvement of approximately 300 kD extracellular matrix protein in promoting outgrowth from identified neurons.

Polyclonal antibodies directed against laminin (LM), and against the A and B chains of reduced LM were used to identify antigenically related proteins in the extracellular matrix (ECM) of the snail Helisoma trivolvis. Immunofluorescence of snail central ganglionic rings using either the anti-LM or anti-B chain antibodies labeled the ECM within ganglionic sheaths as well as basal laminae surrounding the ganglia. Both the anti-LM and anti-B chain antibodies recognized a prominent, approximately 300-kD protein on immunoblots of a snail central ganglion preparation enriched in ECM components. The anti-A chain antibody failed to label any structures in sections of snail ganglia or to recognize any proteins on immunoblots of ganglionic ECM. A polyclonal antibody was raised against the approximately 300-kD snail protein. Immunofluorescence of snail ganglia with the anti- approximately 300-kD antibody gave a distribution of labeled structures comparable to that obtained with the anti-LM antibody. Immunofluorescent labeling of sections of snail muscle and salivary gland with the anti- approximately 300-kD antibody revealed a distribution of reactive protein characteristic of an ECM component. Probing immunoblots of ganglionic ECM with the anti- approximately 300-kD antibody revealed the recognition of the same approximately 300-kD protein as identified by the anti-LM antibodies. Media conditioned by Helisoma central ganglionic rings (CM) contains an unidentified neurite outgrowth promoting factor (NOPF). Immunoblots of CM probed with the anti-B chain and anti- approximately 300-kD antibodies reveal the recognition of a soluble approximately 300-kD protein similar to the approximately 300-kD protein identified in snail ECM. The ganglionic ECM preparation containing the approximately 300-kD protein supported outgrowth from cultured snail buccal neurons B5, and addition of anti- approximately 300-kD Fab fragments to CM abolished its outgrowth promoting activity. These results suggest that the approximately 300-kD ECM protein may be the NOPF in CM and/or functions in promoting neurite outgrowth.

Animals↗

PubMed1990

Innervation and geometry of rabbit ciliary ganglion cells after preganglionic nerve regeneration.

Previous studies have shown a consistent relationship between the dendritic complexity of autonomic neurons and the number of preganglionic axons that innervate them. This relationship is established postnatally, probably through mitigation of preganglionic competition on neurons with increasing dendritic complexity. The present study examines whether a similar relationship between neuronal geometry and the number of axons that innervate rabbit ciliary ganglion neurons is established when the preganglionic nerve is interrupted and then allowed to regenerate. Such a pattern would indicate that the mechanisms responsible for establishing the relationship between innervation and postsynaptic geometry in neonates persist in the adult animal. Ganglion cells were fully reinnervated by about 8 weeks after preganglionic nerve crush. On average, the number of inputs to reinnervated neurons was similar to normal (range = 1 to 4 inputs/cell, mean = 2.1). The number of inputs that cells received was related to their dendritic complexity. Neurons that received a single input had very simple dendritic arbors, or lacked dendrites altogether, whereas neurons that received 2 or more inputs had considerably more complex arbors. The correlation between dendritic complexity and innervation suggests that the geometry of postsynaptic neurons continues to influence the number of inputs each ganglion cell receives in maturity. As a corollary, changes in the dendritic arbors of adult neurons would presumably influence the arrangement of their synaptic inputs.

Action Potentials↗

PubMed1986

Dynamic changes in the dendritic geometry of individual neurons visualized over periods of up to three months in the superior cervical ganglion of living mice.

We describe a means of visualizing the same neuron in the superior cervical ganglion of young adult mice over intervals of up to 3 months. The dendrites of these neurons change during this interval; some branches retract, others elongate, and still others appear to form de novo. Thus, neuronal dendrites in this part of the nervous system are subject to continual change beyond what is usually considered the developmental period. The remodeling of postsynaptic processes further implies that the synaptic connections made onto these cells undergo substantial rearrangement well into adulthood.

Animals↗

PubMed1985

Formation of electrical synapses between isolated, cultured Helisoma neurons requires mutual neurite elongation.

Our previous experiments have suggested the hypothesis that conjoint active neuronal outgrowth may be necessary for formation of new electrical synapses between identified neurons of adult Helisoma buccal ganglia. This growth dependence hypothesis now has been tested by examining the responses of individual pairs of neurons in isolation from the influences of the ganglionic environment. Isolated cell culture of identified neurons (neuron 5) showed that: (i) neurons growing in cell culture undergo a predictable sequence of morphological changes culminating in a stable morphological state (i.e., growth stops); (ii) contact between actively growing neurons in cell culture results in the formation of electrical connections, just as in ganglia; and (iii) when an actively growing neuron encounters a neuron that is morphologically stable, electrical connections do not form or are very weak, even though strong connections are made between pairs of actively growing neurons in the same culture. These results establish that processes closely associated with growth are required for formation of electrical synapses between these neurons.

Animals↗

PubMed1978