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J Meek

Publications and source records attributed to J Meek.

4 recordsLinked to original sources
PubMed1978

A Golgi study of goldfish optic tectum.

A study of goldfish optic tectum was performed with rapid-Golgi, Golgi-Kopsch and a modified Golgi-Cox impregnation which proved quite suitable to impregnate cells in the middle tectal layers and to study more closely axonal properties. Fifteen cell types are distinguished, based upon the position of dendritic trees and axonal properties. Two cell types are found with dendrites in the marginal layer: type I with an axon terminating in the central gray layer and type II without an impregnated axon. Three cell types (III, IV and V) have dendrites in a single, specific tectal layer and an axon terminating within the tectum. Five cell types (VI-X) have dendrites in two horizontal planes. Two of them have myelinated axons leaving the tectum, whereas the axons of the remaining three types project to different tectal layers. While these first ten cell types have dendrites almost exclusively in the superficial half of the tectum, the remaining five types have dendrites in deeper layers too. This especially holds for the most conspicuous tectal cells (types XII and XIII), which have dendritic trees branching at three or more horizontal levels and a myelinated axon leaving the tectum, with sometimes a very peculiar course (XIII1). Also type XI has three or more dendritic trees, but its axon was not found. The numerous cells with cell bodies in the deepest tectal layer (type XIV) have dendrites and axonal terminations anywhere in the tectum, except in the most superficial and the deepest layer. However, most dendrites occur in the optic layers, whereas the axons, always originating from the dendritic shaft in the superficial tectal half, generally terminate in the middle tectal layers. Type XV cells have their soma in the deepest tectal layer as well, but their dendrites do not reach the optic layers. Per tectal lobe the following numbers are estimated: type I : 5,000-20,000 neurons; Type III : 2,500-10,000; types IV--XIII : each 500-2,000 and type XIV : 1,000,000-2,000,000. The total number of myelinated tectal efferents is estimated at 2,000-8,000. Comparison with other Golgi studies in teleosts leads to the conclusion that the tecta of these species of fish are basically similar.

Animals↗
PubMed1978

Myelin impregnation: an improved Golgi-Cox modification.

Optic tecta of goldfish were coated with egg yolk and immersed for only one week in one of the following impregnation fluids: a) Solution A + B; A = 1 g K2Cr2O7 and 1 g HgCl2 boiled for 15 min in 85 ml distilled water and allowed to cool; B = 0.8 g K2Cr2O4 and 0.5 g KWO4 dissolved in 20 ml distilled water. b) Solution A + B two volumes diluted with boiled distilled water. c) Solution A + B four volumes diluted with boiled distilled water. Each tectum was immersed 6 hr in 100 ml distilled water containing 0.5 g LiOH and 15 g KNO3, washed 18 hr in 500 ml 0.2% acetic acid, dehydrated with ethanol, and embedded in low viscosity nitro cellulose. Sections were cut at 100 micron with a rotary microtome after clearing with cedarwood oil. Methods b) and c) have two advantages compared with method a), the original Golgi-Cox method. First, more cells are impregnated, especially in the layers extending 200-400 micron below the surface, and dendrites as well as unmyelinated axons are well impregnated. Second, myelin sheaths are impregnated and can be recognized by their peculiar chain-like appearance. The described Golgi-Cox modification offers an appropriate method to study the morphology of superficially located nervous tissue.

Animals↗