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S Fedoroff

Publications and source records attributed to S Fedoroff.

At least 55 records · Page 3Linked to original sources
PubMed1986

Spectrin does not redistribute with actin during dBcAMP-induced changes in astrocytes in vitro.

Cells of the astrocyte lineage obtained from mouse neopallium and grown in colony culture have been investigated for a correlation between distributions of F-actin and the common subunit of an erythrocyte actin binding protein, alpha-spectrin (brain fodrin). The cells of the astrocyte lineage at the astroblast stage have F-actin organized in the form of prominent, linearly arranged microfilament bundles. We have demonstrated that spectrin in these cells forms a fine reticulum lining the cell cortex. During the dibutyryl cyclic (dBcAMP)-induced transition from astroblasts to reactive astrocytes, actin-containing microfilaments undergo the dramatic rearrangement from a predominantly linear to a predominantly circumferential spatial organization. remains in the form of a fine reticulum lining the cellular cortex. These remains in the form of a fine reticulum lining the cellular cortex. These findings support the recent notion that spectrin in non-erythroid cells is not essential for maintaining the organization and plasma membrane membrane anchorage of the prominent microfilament bundles.

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PubMed1985

Assembly of glial intermediate filament protein is initiated in the centriolar region.

Assembly of glial intermediate filament protein (GFP) into intermediate filaments (IF) was first detected by immunofluorescence in the perinuclear region of astrocytes differentiating in colony cultures before the rest of the cytoplasm was labeled. Double labeling with antisera specific for centrioles indicated that this site corresponds to the centriolar region. These studies suggest that the centriolar region plays an important role in the assembly of some types of IF as well as microtubules.

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PubMed1985

Development of mouse spinal cord in tissue culture: IV. Effects of embryonic extracts on neuron formation and migration.

Possible influences upon patterns of neurogenesis expressed in vitro were examined quantitatively by the use of microfragment cultures of embryonic day 10 mouse neural tube. Crude extracts were prepared either from whole embryos (day 13 or 15 of gestation) or from embryonic brains (day 18 of gestation) and added to the culture medium for the first 10 days of culturing. Neuronal outgrowth zones surrounding individual microfragments were reduced in area (indicating restricted neuronal migration) and in number of neurons present (indicating restricted production of neurons) following treatment with either of the extracts. The severity of reductions observed were related to the developmental age of embryonic tissue used for preparing the extract, as greatest reduction resulted from addition of embryonic day 18 brain extracts and to concentration employed, higher doses further restricting neuronal outgrowth. By increasing the concentrations of extract the proportional number of large-sized neurons forming the outgrowth zones became greater relative to the small neuron contribution, indicating an enhanced survival for this neuronal population. The formation and migration of astroglial precursor cells was not affected by the addition of any of the extracts. The number of neurons remaining within the original portions of neural tube microfragments was not significantly altered following culturing in the presence of embryonic extract. This suggested that the reduction in neuron number in the outgrowth zone actually reflected a decreased neuron production and was not simply the result of a retention of neurons within the remaining portion of the microfragment. The results suggest the presence of substances within mouse embryos that have regulatory effects on aspects of development of the central nervous system. Indications are that survival and maturation of postmitotic neuroblasts are promoted in vitro while the formation of additional neuronal progenitor cells may be partially inhibited by the addition of embryonic mouse extracts to the medium. We propose that an endogenous negative feedback mechanism may be involved in the coordination of patterns of neurogenesis.

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PubMed1984

Astrocyte cell lineage. V. Similarity of astrocytes that form in the presence of dBcAMP in cultures to reactive astrocytes in vivo.

The relationship between astrocytes forming in the presence of dibutyryl cyclic AMP (dBcAMP) in culture and reactive astrocytes responding to a cerebral cortex stab wound was investigated using computerized image analysis (Zeiss IBAS 1) and immunocytochemical staining. The diameters of the nuclei of astrocytes in primary cultures of newborn mouse neopallial cells were compared to those of the nuclei of normal and reactive astrocytes in histological sections of mouse cerebral cortex. We found that the nuclei of astrocytes that formed in the presence of dBcAMP in cultures are significantly larger than those of spontaneously occurring small stellate astrocytes in culture and of normal astrocytes of the cerebral cortex in vivo but corresponded more closely to the nuclei of reactive astrocytes in the area surrounding a stab wound in the cerebral cortex. Large stellate cells formed in the presence of dBcAMP had vimentin and an increase in GFP-containing intermediate filaments. Formation of reactive astrocytes in vivo is also associated with an increase in both vimentin and GFP-containing intermediate filaments. These observations indicate a closer relationship of astrocytes formed in the presence of dBcAMP in cultures to the reactive astrocytes in the cerebral cortex than to normal astrocytes. We propose, therefore, that the large stellate astrocytes that form in the presence of dBcAMP be referred to as reactive astrocytes in culture.

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PubMed1984

Astrocyte cell lineage. III. The morphology of differentiating mouse astrocytes in colony culture.

Disaggregated cells of newborn DBA/1J mouse neopallium were grown in colony cultures, and colonies of cells at various stages of differentiation along the astrocyte cell lineage were examined after 3 days, 1, 2 and 4 weeks by electron microscopy and by NBD-phallacidin which demonstrates the distribution of microfilaments. The earliest astrocyte precursor cells or glioblasts are closely apposed epithelial cells that rarely have junctions. Their scanty cytoplasm contains many free ribosomes but few microfilaments. The cells in the next stages of astrocyte lineage or proastroblasts are flat and are separated from each other to a variable degree. They have intercellular junctions associated with microfilaments and contain singly dispersed intermediate filaments. The proastroblasts gradually differentiate into astroblasts which have a similar morphology except that in addition to the singly distributed intermediate filaments they also contain intermediate filaments arranged into bundles of various sizes. The mature fibrous astrocytes have well-defined processes and distinct perikarya. They form from astroblasts in culture and also contain numerous bundles of intermediate filaments. The dibutyryl-cyclic AMP (dBcAMP)-induced astrocytes in culture in contrast are large stellate cells similar to reactive astrocytes found around sites of injury in the brain. On the basis of these and previous immunocytochemical studies of the formation and distribution of intermediate filaments in the cytoplasm of differentiating astrocytes, criteria are proposed for identification of different cells along the astrocyte lineage.

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PubMed1984

Astrocyte cell lineage. IV. Changes in the organization of microfilaments and adhesion patterns during astrocyte differentiation in culture.

The organization of microfilaments using NBD-phallacidin and cell adhesion to substratum by surface reflection interference microscopy was examined during differentiation of astrocytes in colony cultures and correlated with motile behaviour of cells. Disaggregated cells from neopallium of 12-day-old or newborn DBA/1J mouse embryos were used to establish colonies and astrocyte precursor cells at various stages of differentiation along the astrocyte lineage were examined after 3 days, 1, 2 and 4 weeks in culture. The earliest astrocyte precursor cells, the glioblasts, are stationary and form epithelial-type colonies which adhere to the substratum primarily around the edge where large microfilament bundles are found. Bundles of microfilaments are also present around the apical ends of closely packed cells. As the epithelial cells start to separate and transform into flat proastroblasts, adherens-type junctions which have a zig-zag appearance and are associated with microfilaments form between adjacent cells. In the highly motile astroblasts these junctional regions break down into multiple smaller regions where the separated cells remain in contact through fine processes. The astroblasts also have stress fibres, focal contacts with substratum, foci from which microfilament bundles radiate and a complex pattern of fine, circumferentially oriented bundles of microfilaments. This elaborate organization of microfilaments disappears as the motile astroblasts differentiate into stationary fibrous astrocytes that have little polymerized actin and lack focal contacts. These results show that stationary astrocyte precursor cells in vitro go through a highly motile stage having a characteristic distribution of microfilaments and focal contacts before becoming stationary again. We consider that the motile stage could correspond to the stage in vivo when astrocyte precursor cells migrate from the ventricular and subventricular regions to take up position in different parts of the developing brain.

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PubMed1984

Isolation and transplantation of oligodendrocyte precursor cells.

Newborn DBA/1J mouse neopallium was disaggregated and grown in high cell densities in tissue culture. In culture, the oligodendrocyte cell precursors are recognized as small refractile cells which use astrocyte precursor cells as a substratum. Using metrizamide density gradients, the oligodendrocyte precursor cells were separated from the astroblasts after 7 days in culture and then transplanted into the cerebellums of neonatal mice. The differentiation of the cultured oligodendrocyte precursors was analyzed in the transplants by nuclear morphometry, light and electron microscopy and immunocytochemistry. Analysis of the experiments indicated that the oligodendrocyte precursor cells, initially grown in culture, differentiated and myelinated host neuronal processes after transplantation. Moreover, the ultrastructure of the transplanted oligodendrocytes resembled mature oligodendrocytes in situ.

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PubMed1983

Temporal relationship between the appearance of vimentin and neural tube development.

Intermediate filaments of the vimentin type that were initially identified within mesodermally derived cells have recently been demonstrated within several immature cell types derived from neuroectoderm, such as astroblasts and early stage neuroblasts. The objective of the present study was to determine the earliest developmental stage at which vimentin could be detected in the mouse neural tube. Vimentin was not detectable in the newly formed neural tube in E8 embryos. In the E9 neural tube the first positively labeled processes were observed in the ventrolateral region of the cervical neural tube with the processes having the distribution and appearance of those of radial glial cells. Between E9 and E10 there was a significant increase in the vimentin content of the neural tube as labeled filamentous bundles were observed throughout the ventricular cell layer and in the forming mantle layer. The distribution of labeled filaments in the E11 neural tube was similar to that of the E10 tissue although staining intensity was greater in the mantle layer in the E11 tissue. This work identifies the temporal relationship between the appearance of vimentin and neural tube development.

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PubMed1983

Fibrous astrocytes and reactive astrocyte-like cells in transplants of cultured astrocyte precursor cells.

Mouse neopallium was disaggregated at 3 developmental stages (E15, E18, PO) and grown in colony cultures for 7 days. On the seventh day of culturing the colonies of cells were transplanted into the cerebellums of neonatal mice. After 3 weeks the astrocytes within the transplants were identified with GFAP immunoperoxidase staining and by morphometric nuclear measurements of the GFAP positive cells. Cultures of E15 and E18 disaggregated neopallium gave rise to typical fibrous astrocytes in the transplants which were similar to fibrous astrocytes in the cerebral white matter of adult mice. Cultures of PO disaggregated neopallium gave rise to reactive astrocyte-like cells in the transplants which stained intensely for GFAP and had nuclei significantly larger than the astrocytes in the cerebral white matter of adult mice and in transplants of the E15 and E18 cultures.

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PubMed1983

Astrocyte cell lineage. II. Mouse fibrous astrocytes and reactive astrocytes in cultures have vimentin- and GFP-containing intermediate filaments.

When cells from mouse neopallium are grown in colony cultures for 10-12 days, small cells with many processes, resembling normal fibrous astrocytes, form on top of the astrocyte precursor cells independently of the presence of dBcAMP in the culture medium. These cells are distinctly different from the much larger, previously described reactive astrocytes which also form in colony cultures and whose maturation is greatly enhanced by the presence of dBcAMP in the culture medium. Immunofluorescence studies showed that both vimentin-containing and glial filament protein (GFP)-containing intermediate filaments (IF) are present in the small normal fibrous astrocytes as well as in the larger reactive astrocytes. The vimentin-containing IF are assembled first in astrocyte precursor cells, whereas GFP-containing IF are assembled later toward the final stages of astrocyte differentiation both in vivo and in vitro. Thus in respect to the expression of the two types of IF, astrocyte differentiation in vitro closely resembles that in vivo. Parallel studies by electron microscopy showed that the vimentin-positive but GFP-negative astrocyte precursor cells contain single IF or small groups of IF, whereas in the more differentiated normal fibrous astrocytes and reactive astrocytes which are also GFP-positive, additional IF arranged in large bundles are present.

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PubMed1982

The development of mouse spinal cord in tissue culture. II. Development of neuronal precursor cells.

Neural tubes of mouse embryos at Theiler Stages 14, 15, and 16 were grown in cultures for 21 d with 0.5 MicroCi/ml tritiated thymidine or cold growth medium. It was found that 50 to 60% of the neurons formed in the outgrowth zone were labeled, indicating that they formed from precursor cells that proliferated in the cultures. The unlabeled neurons must have formed from cells that were already postmitotic when the cultures were started. By comparing the total number of neurons per neuromere formed in vivo and in vitro, it seems that the postmitotic precursor cells survive better in cultures and only a small percentage of proliferative precursor cells in cultures enter the postmitotic stage and form neurons.

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PubMed1982

The development of chick spinal cord in tissue culture. III. Neuronal precursor cells in culture.

On culturing fragments of neural tube of Hamilton and Hamburger (H & H) Stage 10 chick embryos, large multipolar neurons developed. The aim of this investigation was to determine whether these neurons in culture developed from dividing neuronal precursor cells, from postmitotic precursor cells, or both. Of the neurons formed during the 20 d of culturing in the presence of [3H]thymidine, 26% were unlabeled, indicating that they originated from cells that were already postmitotic at the time of explantation. By labeling cells of the neural tube in vivo and determining the total number of cells in the neural tube, we estimated that the neural tube of chick embryos of H & H Stage 10 contained approximately 1000 (3.3%) postmitotic cells. By estimating the total number of neurons that formed in 20-d cultures and the percentage of labeled and unlabeled neurons, we concluded that the postmitotic neuronal precursor cells survived well in cultures and proceeded on their predetermined path of differentiation. By considering the number of neurons found in the spinal cord in vivo and the number of labeled neurons found in cultures, we concluded that only a relatively small fraction of the dividing neuronal precursor cells entered the postmitotic stages of differentiation and formed neurons in cultures. The majority of cells that did this, entered the postmitotic stage of differentiation during the first 5 d in culture.

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PubMed1982

Isolation and identification of neuroblast precursor cells from mouse neopallium.

In this paper we describe the isolation of mouse neopallial neuroblast precursors using colony cultures and density gradients. The differentiation of neuroblast precursors was studied in tissue culture and after transplantation to the cerebellums of neonatal mice. In culture, survival of these cells is dependent on astroblasts, and their differentiation is incomplete. In the cerebellum, however, the cells give rise to neurons that correspond closely to the pyramidal cells and interneurons of mouse cerebral cortex according to morphometric measurements.

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PubMed1981

Astrocyte cell lineage. I. Astrocyte progenitor cells in mouse neopallium.

The astrocyte cell lineage during postnatal development of the neopallium of Swiss mice was studied, using a colony culture assay method in which dissociated neopallial cells form discrete colonies in culture. It was found that immature epithelial-like cells that from type A colonies in culture come primarily from the subventricular zone but also from other regions of the neopallium. In culture, cells of type A colonies from type C colonies consisting of cells, which although still epithelial like, differ morphologically from the type A colony-forming cells. In the presence of dibutyryl cyclic adenosine monophosphate (dBcAMP) the type C colonies form cells rich in glial fibrillary acidic protein (GFAP) and stainable with Cajal's gold chloride sublimate, a stain specific for astrocytes. Therefore, it is proposed that type A colony-forming cells are astrocyte progenitor cells resembling the "pale" cells found in the subventricular zone (Blakemore and Jolly, '72), the "large glioblasts" (Sturrock, '76) and the free subependymal cells (Privat, '70; Paterson et at., '73) in the corpus callosum. The sequence of the lineage, i.e., cells forming type A colonies give rise to cells forming type C colonies which eventually differentiate into astrocytes, takes place in situ as well as in culture. As postnatal development of the neopallium progresses the number of colony-forming cells decreases in the subventricular zone and in other parts of the neopallium. The astrocyte progenitor cells migrate from the subventricular zone to other parts of the neopallium and progress through the lineage of differentiation in all regions of the neopallium.

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PubMed1979

The development of mouse spinal cord in tissue culture. I. Cultures of whole mouse embryos and spinal-cord primordia.

Whole mouse embryos were grown in vitro from Theiler stage 12 (1 to 7 somites) to Theiler stages 15 and 16 (25 to 35 somites). This procedure gives experimental access to precisely staged embryos during the early period of neurogenesis. To follow the further development of neurons in vitro, fragments of spinal primordia were set up from these cultured embryos. In such cultures, the proliferation of precursor cells, the formation of postmitotic cells, and, finally, the cytodifferentiation of neurons were observed.

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