|Dr Ann E. Sefton||Professor from 1992 (in-charge) (0.2)
Associate Dean, Curric., Fac. Med.
|Dr Ann Goodchild||Research Assistant, Grade 2
(with Paul Martin)
|Paul Armson||PhD student (0.25)||1991-|
|Krystel Huxlin||PhD student
Fac. Med. Award
|Amanda Johnston||BSc(Med) (Supervisor:
Bogdan Dreher, Anat. & Histol.)
|Nick Barrett||BSc(Med) (Assoc. Supervisor:
Brendan O'Sullivan, RPAH)
|Dr Tom Fitzgibbon||Dept of Clinical Ophthalmology (0.2)||1990-|
Current effective full-time personnel = 1.4
The research of the Laboratory is principally directed towards understanding the phenomena taking place during development and regeneration of the visual system in mammals. In collaboration with Paul Martin's group, the Laboratory is also studying the structure and function of the visual pathway in adult primates.
The role of trophic factors in the survival of injured adult neurons
Neurons in the adult mammalian central nervous system degenerate following traumatic lesions such as axotomy. Whether their survival depends on the availability of a developmentally regulated trophic factor produced by their target cells is not known. Experiments were continued to test this hypothesis by applying the 480 kDa superior collicular chondroitin sulfate proteoglycan, purified in the Laboratory of Max Bennett, to adult rat retinal ganglion cells following their axotomy. When injected intraocularly for two weeks following intraorbital section of the optic nerve (which destroys 80% of retinal ganglion cells within two weeks), this proteoglycan prevented the degeneration of 64% of the injured retinal ganglion cells. This saving effect was larger than that of any other known trophic factor tested in the same system. Our results indicate that adult rat retinal ganglion cells may revert to a 'development-like' state following axotomy. This would include a renewed dependence on target-derived trophic factors for survival.
Glial response to axotomy and the application of trophic factor
This project was undertaken in collaboration with Zofia and Bogdan Dreher from the Dept of Anatomy. It has been postulated that the major reason for the lack of regeneration following a lesion in the mature mammalian central nervous system is that its glial environment becomes inhibitory to axonal regrowth as a result of the injury. Part of this inhibitory glial response consists of an astrogliosis in which astrocytes hypertrophy, multiply and express high levels of GFAP. The aim of this study was to characterize the glial response to section of the optic nerve, intraocular penetrations (the method of choice for intraocular injection of therapeutic substances) and intraocular injections using a battery of antibodies recognizing proteins specific to the two types of macroglia in the rat retina - astrocytes and Müller cells. The findings were rather startling: in the retina, unlike the rest of the brain, there was no astrogliosis in response to the Wallerian degeneration of retinal ganglion cells or intraocular penetrations. When collicular proteoglycan was injected into the eyes, however, the expression of GFAP in astrocytes decreased markedly so that the cells were no longer visible. Rather than astrocytes being stimulated by injury, it was the Müller cells that increased their expression of GFAP and a range of other proteins. The responses of Müller cells were stronger following intraocular injections of collicular proteoglycan than as a result of the Wallerian degeneration of 80% of retinal ganglion cells. It was concluded that the retina is a unique region of the central nervous system in terms of its glial response to injury. Müller cells, rather than astrocytes, became reactive in response to changes in their immediate environment.
Neuronal response to axotomy and the application of trophic factor
In collaboration with Zofia Dreher, Bogdan Dreher and Max Bennett, the reaction of retinal neurons and glia were assessed after section of the optic nerve followed by the intraocular injection of the collicular chondroitin sulfate proteoglycan which was shown to rescue a significant proportion of adult retinal ganglion cells from axotomy-induced cell death. A battery of antibodies were used to monitor the levels of various intracellular proteins such as protein kinase C, the calcium binding proteins calbindin and parvalbumin, and neurofilaments. Protein kinase C is thought the be involved in the pathway controlling cell death while a failure of intracellular calcium regulation (which involves the use of calcium binding proteins) has been demonstrated to kill neurons. The aim was thus to determine how the levels of such molecules change in retinal neurons (particularly retinal ganglion cells) following axotomy and the injection of collicular proteoglycan. This may enable us to predict how well equipped retinal ganglion cells are to survive axotomy and which intracellular pathway the trophic collicular proteoglycan is activating to rescue them. This study is still ongoing.
The identification of neurons exhibiting NADPH-diaphorase activity in the normal adult rat retina
NADPH-diaphorase is an enzyme that has been co-localized with nitric oxide synthase. It was found in our laboratory that using better controlled fixation parameters, this enzyme could be detected in many more retinal cells than was previously published. NADPH-diaphorase was identified in ganglion cells, displaced amacrine cells, amacrine cells in the inner nuclear layer, photoreceptors and Müller cells of the normal adult rat retina. This was also the first time that a glial cell was found to contain a constitutive form of nitric oxide synthase. These results have important implications for the role of nitric oxide in normal retinal function, suggesting that this molecule may act as a neuromodulator in the light transmission pathway. In addition, given the reactivity of Müller cells following damage to the retina or optic nerve, nitric oxide may also play a role in retinal pathology.
Changes in the expression of NADPH-diaphorase in the adult rat retina following axotomy
This project was carried out in collaboration with Max Bennett. One hypothesis as to the mechanism of neuronal cell death following axotomy in the central nervous system is that microglial cells which invade the injury site and phagocytose debris from dead cells, also produce nitric oxide to kill live but inactive neurons. Astrocytes in the brain have also been shown to express inducible nitric oxide synthase after cerebral damage such as that resulting from stab wounds or ischaemia. In addition, previous results from this Lab have suggested that retinal Müller cells normally expressed NADPH-diaphorase. Therefore, it was of interest to determine whether any of these cell types express NADPH-diaphorase in the retina following section of the optic nerve and thus, whether they could contribute to the massive ganglion cell death which occurs within two weeks of axotomy. It was found that two weeks following section of the optic nerve, no microglia or astrocytes were labelled for NADPH-diaphorase. However, there was an increase in the staining of Müller cells. Therefore, in the retina, it is unlikely that astrocytes and microglia use nitric oxide to kill injured retinal ganglion cells following axotomy. It is also uncertain whether nitric oxide acts as a toxic molecule in the retina since injections of L-NAME, an inhibitor of nitric oxide synthase, did not result in the rescue of retinal ganglion cells following axotomy. Preliminary results suggest that the injection of collicular proteoglycan caused an increase in the expression of NADPH-diaphorase in the retina, both in Müller cells and a neuronal population in the ganglion cell layer, suggesting that in this situation, rather than being toxic to injured neurons, nitric oxide may actually contribute to their survival.
Collaborative work with Paul Martin will continue in studies of the visual system of the marmoset. In addition, a new collaboration with Max Bennett will commence with studies of cells of the developing rat lateral geniculate nucleus. The effects of nitric oxide on synaptic interactions will be investigated using patch clamp techniques. The regenerative effects in vivo of the retinal ganglion cell neurotrophic factor will be investigated further in adult animals after lesions to the optic nerve and a parallel study on the effects of lesions on the classes of retinal ganglion cells in the rat will be concluded. The potential trophic factor extracted from the thalamus will be further investigated and studies will continue on the effect of potential growth factors on retinal ganglion cells by studying calcium activation. A study of the thalamic reticular nucleus in the cat is being prepared for publication.
The Laboratory work area comprises rooms 425, 426, 427 and 431 of the Anderson Stuart building. Dr Sefton's office is room 429 and other personnel occupy room 430. Equipment includes: high quality light (transmission and fluorescent) and dissecting microscopes; Imagellan image analysis systems; photomicrography; facilities for immunohistochemistry, histochemistry and various neuroanatomical tracing techniques; laminar flow cabinet; incubator; surgical, anaesthetic and some electrophysiological equipment; Macintosh personal computers and accessories.
MOST RECENT TOTAL ANNUAL CITATIONS (for 1993): 81
|NHMRC||The visual system in dichromatic and
trichromatic marmoset monkeys
(*Lab's share annually (30% = $18,400)
Total for 1994: $18,400
Total for 1995: $18,400
Sefton A Jervie (1990) Selection of medical students. Medical Journal of Australia, 153, 440-441
Sefton A Jervie (1991) Selection of medical students. The Sydney experience. Radius Annual, 1, 18-19
Sefton A Jervie (1992) A graduate degree for medicine at the University of Sydney. New Doctor, 57, 21-22
Armstrong R, Sefton A Jervie (1992) Selection process into medicine. The Crossexaminer, 1, 11-13
Sefton A Jervie (1993) Decision-making for major educational change: A four year postgraduate medical curriculum at the University of Sydney. ANZAME Bulletin, 20, 3-10
Sefton A Jervie (1993) Why change medical education to a four-year postgraduate programme? Ulitarra, 4, 86-92
Geffen L, Saunders N, Sefton A Jervie (1994) Australian graduate medical schools: A progress report. Medical Journal of Australia, 160, 393-394
Sefton A Jervie (1995) Medical education in a time of change: A view from the University of Sydney. Medical Education (in press)
Sefton A Jervie (1995) Educating the health workforce in customer focus. Proceedings of the Customer Focus Conference (in press)
Sefton A Jervie, Cheng N, Thong IG, eds (1992) The Centenary Book of the Sydney University Medical Society, Hale and Iremonger, Sydney, 224pp. (Includes contributions to Chapters 2, 4, 5 and 7).
Chapters in Books
Sefton A Jervie (1991) Experiments in neuroscience. A Sourcebook of Practical Experiments in Physiology requiring Minimal Equipment, International Union of Physiological Sciences, ed, World Scientific, Singapore, 47-74
Sefton A Jervie (1992) Whither practical classes? Advances in Physiological Sciences, Manchanda SK, Selvamurthy W, Mohan Kumar V, eds, M/S Macmillan India, New Delhi, 24-30
Hayes SC, Farnill D, Sefton A Jervie (1994) Improving the English communication skills of preclinical medical students. Annals of Community-oriented Education, Engel C, Schmidt H, Vluggen PI, eds, 7, 317-328
Conference Abstract and Presentation
Sefton A Jervie, Somjen, G (1994) Workshop on Teaching, International Union of Physiology Sciences, Advances in Physiology Education, 11, S70-S77, Inverness (Jul 93)
|Med 3||Sc 3||Total|
|Practical classes (no.)||10||(10)||2||(4)||14|
Total formal contact teaching time = 64 h
Service to University and Department