Chick Embryo Cerebral Hemispheres Research Articles

Compartmentation of the S-adenosylmethionine pool in developing chick embryo cerebral hemispheres, as demonstrated by a fingerprint study of 18 S ribosomal RNA

Compartmentation of the S-adenosylmethionine pool in developing chick embryo cerebral hemispheres, as demonstrated by a fingerprint study of 18 S ribosomal RNA

Differentiation of chick embryo cerebral hemispheres: a critical evaluation of a bulk preparation of neuroblasts and spongioblasts.

Abstract— A critical evaluation of a previously described method of bulk preparation of neuroblasts and spongioblasts from chick embryo cerebral hemispheres furnished the following results. A major loss of total RNA occurs during the preparation of the cell fractions. The loss occurred mainly during the dissociation of the tissue and the following centrifugations. The missing RNA's were found in the supernatants after cell centrifugation at low speed. There was a selective loss of transfer RNA amounting to 70–80 per cent relative to ribosomal RNA. The relative proportions of the 29, 18 and 5s ribosomal RNA's were constant, but there was a decrease in their proportion relative to heavy‐molecular weight, rapidly‐labelled nuclear RNA. The ribosomal RNA's in the low‐speed supernatant could be resedimented at 35,000 g whereas most transfer RNA could not. The results are consistent with a loss of fragments of cytoplasm containing ribosomes and with additional extraction of transfer RNA during the preparation.

Glycolytic substrate utilization and energy consumption in the cerebral hemispheres of the chick embryo during the period of EEG development.

Abstract— The glycolytic substrate utilization and energy consumption of chick embryo hemispheres aged 15 and 19 days, respectively, were studied by converting the heads into a closed system. After transforming the brain into a closed system by decapitation, spontaneous bio‐electrical potential changes, as indicated by EEG measurements, stayed normal in the hemispheres until at least 30 s after the procedure. Although the two developmental stages studied represented the start and the final phase of functional development, no changes in carbohydrate utilization and energy consumption were observed when comparing hemispheres of the two stages mentioned. The utilization of substrates other than glucose during embryological development is discussed. The disappearance of the EEG is not related to the overall depletion of high energy phosphates in the hemispheres since ATP is still present at nearly its original level after 2 min of ischaemia, despite the low level of P‐creatine occurring at 30 s after decapitation. A compartmentation of the major pools of P‐creatine and ATP is suggested.

Hydrocortisone as a possible inductor of Na +−K +-ATPase in the chick embryo cerebral hemispheres

Changes evoked by hydrocortisome administration in the Na +−K +-stimulated ATPase of the chick embryo cerebral hemispheres were investigated. The Na +−K +-stimulated ATPase activity in the homogenates of intact chick embryos was not detectable on day 13, but a rapid increase after this day was observed. The Mg 2+-dependent ATPase activity rose gradually but significantly till day 21 of incubation. Hydrocortisone (20 μg per egg) was found to induce the Na +−K +-stimulated ATPase activity but had no effect on the Mg 2+-dependent ATPase activity of the chick embryo cerebral hemispheres. Different sensitivity of the tissue to the hormone was observed before and after day 13 of incubation. Similar changes in the enzyme activity were demonstrated in the microsomal fraction isolated from the hemisphere homogenates and were correlated with the concentraion of sodium and potassium in the hemispheres. Sensitivity of the Na +−K +-stimulated ATPase increase to actinomycin D and cycloheximide was observed.

Cultivation and growth of dissociated neurons from chick embryo cerebral cortex in the presence of different substrates.

Dissociated cells from 7-day old chick embryo cerebral hemispheres were cultivated for one month in Rose chambers. Four different culture conditions were employed in the composition of the matrix on which the cells were cultivated: collagen alone, collagen plus embryonic extract, collagen plus plasma and collagen plus plasma and embryonic extract. Within the first 48 hours of cultivation the cells formed processes under all four culture conditions. In the presence of plasma the dissociated cells remained well isolated; in the other culture conditions many cells reassociated into clumps. After 2–3 weeks in cultures on collagen or collagen plus embryonic extract many polygonal cells developed and formed a layer upon which typical neurons and oligodendrocyte-like cells were observed. After 3 weeks the polygonal cells began to transform into astrocyte-like cells. In the presence of plasma the cell bodies of the neuroblasts remained small and round. The processes developed generally consisted of one long and many short thick fibres; all processes had a bulbous appearance. In 3–4-weeks old cultures the cells which remained viable, were morphologically unchanged. The differences in the morphological aspects of the cells cultivated on plasma and those cultivated on collagen alone or with embryonic extract are discussed.

Dissociation, fractionation, and culture of embryonic brain cells

Cell suspensions from 11-day chick embryo cerebral hemispheres were prepared by mechanical dissociation and cultured in a modified plasma clot system. Three distinct cell types are recognized: large cells (A), with the morphological characters of adult neurons, small cells (B) also presumably neuronal in character and thin, spread-out cells (C) which are epithelial. The neuronal-like elements, A and B, do not divide and have little mobility in culture: they grow very early, complexe processes which establish physical contact with one another and with other cell bodies. The epithelial cells, C, grow in culture even on uncoated glass surfaces, are very mobile, proliferate actively and can be propagated over a period of months. The A and C type cells have been fractionated from the harvested suspension by differential floation and selective glass attachment techniques to produce over 90% pure populations. The purification of the B type cells has not yet been achieved, due to their high and specific adhesiveness, both in suspension and in culture, to the C cells.

Differentiating cells of chick embryo hemispheres: Characterization and quantitative evaluation of the cell types and bulk preparation of enriched fractions

A method of fractionation of neuroblasts and spongioblasts perikarya from developing chick embryo cerebral hemispheres is described. The tissue, treated by a mixture of acetone-glycerol-water is dissociated through a nylon sieve. Differential centrifugation on sucrose 1.3 M and 1.8 M has been used to obtain fractions enriched in neuroblasts (80% purity) and spongioblasts (90% purity). The duration of the whole operation is two hours.