Remak, father and son

Robert Remak (1815-1865): discoverer of the fungal character of dermatophytoses

Robert Remak was the first scientist to undertake successful research on fungal skin infections. A neurologist, physiologist, and embryologist, Remak was the first to observe the fungal changes causing the disease of favus; however, he gave credit for the discovery to Professor Johann Schönlein and denied all attempts by others to credit him with the discovery by calling them a mistake. He named the disease Achorion schönleinii; however, over time, the name was changed to Trichophyton schoenleinii. Remak also described axial fibers encased in a medullary sheath and was the first to recognize nonmyelated (sympathetic) nerve fibers, today called fibers of Remak. He demonstrated the existence of the medullary nerve sheath and its production in the process of structured cell division. Remak also was the first to demonstrate that the cerebral cortex consists of six layers and to assert that there are three germ layers in the early embryo and not four.

A bird's eye view of enteric nervous system development: lessons from the avian embryo

The avian embryo has been an important model system for studying enteric nervous system (ENS) development for over 50 y. Since the initial demonstration in chick embryos that the ENS is derived from the neural crest, investigators have used the avian model to reveal the cellular origins and migratory pathways of enteric neural crest-derived cells, with more recent work focusing on the molecular mechanisms regulating ENS development. Seminal contributions have been made in this field by researchers who have taken advantage of the strengths of the avian model system. These strengths include in vivo accessibility throughout development, ability to generate quail-chick chimeras, and the capacity to modulate gene expression in vivo in a spatially and temporally targeted manner. The recent availability of the chicken genome further enhances this model system, allowing investigators to combine classic embryologic methods with current genetic techniques. The strengths and versatility of the avian embryo continue to make it a valuable experimental system for studying the development of the ENS.

Mismatch between electrophysiologically defined and ventriculography based theoretical targets for posteroventral pallidotomy in Parkinson's disease

OBJECTIVES

Over the past few years many reports have shown that posteroventral pallidotomy is an effective method for treating advanced cases of Parkinson's disease. The main differences with earlier descriptions were the use of standardised evaluation with new high resolution MRI studies and of single cell microrecording which can electrophysiologically define the sensorimotor portion of the internal globus pallidus (GPi). The present study was performed on a consecutive series of 40 patients with Parkinson's disease who underwent posteroventral pallidotomy to determine localisation discrepancies between the ventriculography based theoretical and the electrophysiologically defined target for posteroventral pallidotomy.

METHODS

The tentative location of the posteroventral GPi portion was defined according to the proportional Talairach system. Single cell recording was performed in all patients. The definitive target was chosen according to the feasibility of recording single cells with GPi cell features, including the presence of motor drive and correct identification of the internal capsule and of the optic tract by activity recording and microstimulation.

RESULTS

In all 40 patients the electrophysiologically defined sensorimotor portion of the GPi was lesioned, with significantly improved cardinal Parkinson's disease symptoms as well as levodopa induced dyskinesias, without damage to the internal capsule or optic tract. Significant differences between the localisation of the ventriculography based theoretical versus electrophysiological target were found in depth (p<0.0008) and posteriority (p<0.04). No significant differences were found in laterality between both approaches. Difference ranges were 8 mm for laterality, 6.5 mm for depth, and 10 mm for posteriority.

CONCLUSIONS

Electrophysiologically defined lesion of GPi for posteroventral pallidotomy, shown to be effective for treating Parkinson's disease, is located at a significantly different site from the ventriculography based theoretical target.