Histochemical localization of aluminum in the rabbit CNS.

Aluminum was observed in the nucleolus, interchromatin granules, rough endoplasmic reticulum, free ribosomes, euchromatin, and the heterochromatin of the neuron. The association of aluminum with the first four r-RNA-containing cellular components and with the last two DNA-containing chromatins suggests the association of aluminum with the nucleic acids. The aluminum may interfere with the normal mechanism of the protein synthesis of r-RNA and of the transcription or gene modulation of DNA. Aluminum was also observed in the astrocytic process and in the nuclei of endothelial cells, pericytes, and the muscle cells of the blood vessels. The detection of aluminum in the pyrimidal cells of the cerebral cortex and hippocampus and in the spinal cord neurons, was observed 1 h after i.v. injection, indicating a rapid entry of aluminum from the injection site through the blood-brain barrier (BBB) to the neurons. Using Morin stain, pyramidal neurons of the cerebral cortex and hippocampus, motoneurons of spinal cord, ganglion cells, and bipolar cells of retina and Purkinje cells of cerebellum, exhibited yellow fluorescence, with peak intensity at 560 nm. Tangles were observed in these six types of neurons. The granule cells of hippocampus and cerebellum and the photoreceptors of the retina exhibited green fluorescence with the peak intensity at 490-500 nm. Tangles were not observed in these three types of neurons.

Neurofibrillar changes in goldfish (Carassius auratus L.) brain in relation to environmental temperature.

Neurofibrillar changes occur in the brains of goldfish, Carassius auratus L., maintained at 5 degrees C for 177 days or more under a 12-hour photoperiod. In paraffin sections impregnated by the silver method of Holmes, the light microscopic appearance of the neurofibrillary change was evidenced by black rings 1 micrometer to 2 micrometer in outside diameter. A quantitative study showed the mean number of rings to be: optic tectum layer 3, 1.34 X 10(2)/mm(3), layer 5, 1.14 X 10(2)/MM(3), nucleus prerotundus 4.63 X 10(2)/mm(3), olfactory bulbs, 6.2 X 10(2)/mm3. In the brains of fish kept at 15 degrees C a few rings are found only in some olfactory bulbs and not in any other region of the brain. The brain wet weight also changes and was found to be significantly (p less than 0.01) less in 5 degrees C than in 15 degrees C fish, the mean values being 0.1588 g and 0.2091 g respectively. The significance of the observed changes is discussed. It is suggested that the smaller brain wet weight may reflect a change in the vasculature of the brain and be related to the acclimation process. It is hypothesized that the rings are a morphological expression of a physiological change caused by prolonged exposure to low temperatures; a neuronal response reflecting either early degeneration or a functional adaptation which may involve an alteration in axoplasmic transport. It is suggested that this system is a useful model for the study of relationships between neurofibrillar disturbances and neuronal function.

A silver impregnation method for nervous tissue suitable for routine use with mounted sections.

A simple, reliable silver impregnation method for nervous tissue is described for tissues fixed in various fixatives including formalin, Bouin, and Susa. Sections are impregnated in a solution containing 1 g Protargol, 2 ml of a 1% Cu(NO3)2 solution, 2 ml of a 1% AgNO3 solution, and 2-4 drops 30% H2O2 in 100 ml distilled water. Sections are impregnated 2-5 days at 37 C and thereafter reduced in a hydroquinone-formalin solution. This is followed by gold toning and subsequent reduction, dehydration and mounting. This method has been found to be very reliable and selective.

Innervation of the hamster Harderian gland.

Harderian glands of male and female hamsters have nerve endings associated with the secretory cells, myoepithelial cells, and the blood vessels. The nerve endings adjacent to the myoepithelial cells also have myoneural junctions.

Axonal outgrowth and cell migration in vitro from nervous system of cockroach embryos.

Brain and ganglia of embryonic Periplaneta americana were grown for 2 to 3 weeks in a chemically defined medium. Nerve fibers sprouted vigorously from intact brains and ganglia, interconnecting nerve cultures, and adjacent cultures of the digestive tract, Glia, tracheal, and nerve cells were present in large numbers in the migratory zone surrounding the explants.