Brain hypoxia studied in mouse central nervous system cultures. I. Sequential cellular changes

Heavily myelinated cultures of newborn mouse cerebellum were exposed to hypoxia and studied by electron microscopy. The cultures were placed in an incubating medium deprived of oxygen (95 to 97 per cent deprivation) for 7 to 60 minutes and fixed immediately for electron microscopy. The amount of oxygen present in the medium and time course of hypoxia were constantly monitored and recorded by an oxygen probe of polarographic oxygen sensor type and a recorder. In contrast to previous in vivo studies, this in vitro model of hypoxic cell injury has provided accurate information concerning the relationship between degree of hypoxia and cell lesion. Hypoxia affected neurons which showed "swelling" and disorganization of cristae in mitochondria and reduced cytoplasmic matrix density due to the dispersion of polysomes. A small population of neurons with an increased cytoplasmic density and "swollen" mitochondria was also noted. Clearing and degeneration of presynaptic terminals and postsynaptic dendrites were observed. After a longer period of hypoxia most neurons showed an extensive degenerative change consisting of rarefaction of cytoplasm and loss of cytoplasmic organelles. In contrast to neuronal changes, no structural alteration was observed in astrocytes and oligodendrocytes.

Nuroaxonal degeneration induced by sodium diethyldithiocarbamate in cultures of central nervous tissue

Well myelinated cultures of newborn mouse cerebellum, exposed to varying concentrations of sodium diethyldithiocarbamate (DDC), a heavy metal chelating agent, were examined by light and electron microscopy. DDC treatment of cultures for 24-48 hours produced swellings of axons and presynaptic endings, the morphological features characteristic of dystrophic axons. The axonal swellings contained an increased amount of endoplasmic reticulum, mitochondria and dense bodies. A continued exposure to DDC induced an extensive degeneration of axons and ensheathing myelin. Glial cells, on the other hand, were structurally intact even after a long-term exposure to DDC. It is suggested that DDC produces in myelinated CNS cultures an initial enlargement of axons and presynaptic endings and then continues to induce Wallerian degeneration in axons.

The neurotoxic effects of triethyltin (TET) sulfate on myelinating cultures of mouse spinal cord

Well myelinated cultures of mouse spinal cord, exposed to varying concentrations of triethyltin sulfate, were examined at different time intervals by light and electron microscopy. At a high concentration of TET (10(-6)M) for 1-2 hours, the myelin sheaths and cells showed marked degenerative changes. At lower concentrations of TET (10(-7)-10(-9) M) intramyelinic and other types of vacuole formation were seen; however, these lesions were always accompanied by changes in the perikarya, dendrites and axons of neurons and in the astrocytes. Also, there was an apparent increased number of neurofilaments and neurotubules in many axons. The findings are discussed in relation to the lesions induced in the experimental animal by alkyl tin intoxication.

Measurement of protein in cultures of nervous tissue grown on collagen substrate

The microchemical method of Bonting & Jones was found to detect the amount of protein present in tissue culture explants without measuring protein of collagen substrate. The protein contents of chick spinal cord explants at different points during a 1-month culture period were studied using this method.

Effects of the cholesterol biosynthesis inhibitor ay9944 on organotypic cultures ofmouse spinal cord. Retarded myelinogenesis and induction of cytoplasmic inclusions

Young cultures of fetal mouse spinal cord were exposed to nutrient medium containingAY9944 [trans-1,4-bis(2-chlorobenzylaminomethyl)cyclohexane dihydrochloride], apotent cholesterol biosynthesis inhibitor, and their reactions were studied by light and electron microscopy. AY9944 treatment for 4 to 7 days retarded cultures revealed anaccumulation of numerous intracytoplasmic inclusions in perikarya of neurons, astrocytes,and oligodendrocytes. These inclusions were also found in dendritic processes, myelinated axons, and presynaptic terminals. These inclusions were composed of concentric lamellar structures or of reticular internal structures. Although considerable improvement of myelination and diminution of cytoplasmic inclusions were noted following the removal of the inhibitor and the restitution in normal nutrient medium, a complete recovery oflesions was not observed during the 3-week restitution period in vitro.

Increased activity of choline acetyltransferase and acetylcholinesterase in developing cultures of chick spinal cord: a correlation with morphological development

Explants of 10-12-day-old embryonic chick spinal cord were cultured for up to 20 days by the "coverslip-roller" method. Morphological development of neurons as shown by the presence of mature neurons, myelinated axons and synaptic structures, was demonstrated by light and electron microscopy. Two important enzymes associated with acetylcholine transmitter metabolism, choline acetyltransferase (ChAc) and acetylcholinesterase (AChE), were assayed in cultures at selected time intervals. The activity of ChAc and AChE exhibited an increase of 60 per cent and 80 per cent, respectively, over a 20-day period. It is concluded that organotypic cultures of embryonic chick spinal cord show differentiation not only in morphological aspects, but also in biochemical terms through progressive development of ChAc and AChE.

Neurotrophic effect on isolated chick embryo muscle in culture

Acetylcholinesterase activity in cultures of dissociated skeletal muscle prepared from the thigh muscle of the 10-day-old chick embryo was increased by the presence of innervating spinal cord explants, spinal cord explants in a parabiotic environment, and by media containing brain-spinal cord extract.