Elucidation of the Retinoid Signalling Pathway Involved in Axon Guidance in Lymnaea stagnalis and Xenopus laevis

The vitamin A metabolite, retinoic acid (RA), is known to play a crucial role in several developmental processes including axial patterning and differentiation. More recently, RA has been implicated in the regenerative process acting through its classical signaling pathway, the nuclear receptors, retinoic acid receptor (RAR) and retinoid X receptor (RXR), to mediate gene transcription. Moreover, RA has been shown to act as a guidance molecule for growth cones of regenerating motorneurons of the pond snail, Lymnaea stagnalis. Our lab has recently shown that RA can induce this morphological response independent of nuclear transcription, however, the role of the retinoid receptors in RA-induced chemoattraction is still unknown. Here, I show that the retinoid receptors, RXR and RAR, may mediate the growth cones response to the metabolically active retinoic acid isomers, all-trans and 9-cis RA, in Lymnaea stagnalis. Data presented here show that both an RXR and RAR antagonist can block growth cone turning in response to application of both isomers. Because no prior investigations have shown growth cone turning of individual vertebrate neurons, I aimed to show that both retinoic acid isomers were capable of inducing growth cone turning of embryonic spinal cord neurons in the frog, Xenopus laevis. For the first time in Xenopus, I showed that both all-trans and 9-cis RA were able to induce significantly more neurite outgrowth from cultured embryonic spinal cord neurons and induce positive growth cone turning of individual growth cones. In addition, I showed that the presence of the RXR antagonist, HX531, blocked 9-cis RA-induced growth cone turning and the RARβ antagonist, LE135, blocked all-trans RA-induced growth cone turning in this species. Evidence provided here shows for the first time, conservation of retinoic acid-induced growth cone turning in a vertebrate model system. In addition, these data show that the receptors involved in this morphological response may be the same in vertebrates and invertebrates.

Memo regarding the drainage of marsh lands

Memo regarding the drainage of marsh lands (1 page, handwritten), Jan. 15, 1855.

Memorandum respecting the marsh drainage

Memorandum respecting the marsh drainage (2 ½ pages, handwritten), July 7, 1855.

Report by Jacob Misner on setting contracts for deepening and clearing ditches and estimates of quantities and costs of marsh drainage

Report by Jacob Misner on setting contracts for deepening and clearing ditches and estimates of quantities and costs of marsh drainage (3 ½ pages, handwritten). This is marked as a copy, July 14, 1855.

Estimate of amount of excavation done by A. Cook on the ditch for marsh lands drainage

Estimate of amount of excavation done by A. Cook on the ditch for marsh lands drainage, Aug. 29, 1855.

Estimate of work done on marsh drainage by A. Cook, signed by S.D. Woodruff

Estimate of work done on marsh drainage by A. Cook, signed by S.D. Woodruff, Aug. 31, 1855.

Estimate of work done on marsh lands drainage by Alexander Cook, signed by S.D. Woodruff

Estimate of work done on marsh lands drainage by Alexander Cook, signed by S.D. Woodruff, Nov. 10, 1855.

Estimate of work done on marsh lands drainage by A. Cook and A. Mains and an estimate of time on the marsh lands survey from September to November

Estimate of work done on marsh lands drainage by A. Cook and A. Mains and an estimate of time on the marsh lands survey from September to November by Fred Holmes, Thomas Baird and Joseph Simpson. This is signed by S.D. Woodruff, Nov. 29, 1855.

Estimate of work done on marsh lands drainage by Alexander Cook and Andrew Mains

Estimate of work done on marsh lands drainage by Alexander Cook and Andrew Mains. This is signed by S.D. Woodruff. Also on this sheet is pay roll for engineer services for the months of September, October and November, 1855. This was paid to Frederick Holmes, Thomas Baird, Joseph Simpson and Len [illegible name], Nov.30, 1855.

Estimates for marsh drainage sent to Dexter Deverardo from S.D. Woodruff for Alexander Cook and Andrew Mains

Estimates for marsh drainage sent to Dexter Deverardo from S.D. Woodruff for Alexander Cook and Andrew Mains, Nov. 30, 1855.

Estimate of work done on marsh drainage by Alexander Cook and Andrew Mains

Estimate of work done on marsh drainage by Alexander Cook and Andrew Mains, Nov. 1855.

Engineer estimate (5 ½ pages, handwritten) in the marsh lands drainage presented to the Chamber and Councilors of the County of Welland in council assembled

Engineer estimate (5 ½ pages, handwritten) in the marsh lands drainage presented to the Chamber and Councilors of the County of Welland in council assembled. This report is signed by S.D. Woodruff, June 20, 1857.

Estimate from the County of Welland to S.D. Woodruff for engineering services in marsh lands drainage for 1 year

Estimate from the County of Welland to S.D. Woodruff for engineering services in marsh lands drainage for 1 year, Dec. 1857.

Engineer services in the marsh lands drainage to the 28th of April inclusive to Frederick Holmes, Louis Clement and Thomas Baird

Engineer services in the marsh lands drainage to the 28th of April inclusive to Frederick Holmes, Louis Clement and Thomas Baird. Signed by S.D. Woodruff, April 28, 1855.