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Results for “Cell Differentiation/physiology”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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30 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

A morphometric analysis of cellular differentiation in caps of primary and lateral roots of Helianthus annuus

In order to determine if patterns of cell differentiation are similar in primary and lateral roots, I performed a morphometric analysis of the ultrastructure of calyptrogen, columella, and peripheral cells in primary and lateral roots of Helianthus annuus. Each cell type is characterized by a unique ultrastructure, and the ultrastructural changes characteristic of cellular differentiation in root caps are organelle specific. No major structural differences exist in the structures of the composite cell types, or in patterns of cell differentiation in caps of primary vs. lateral roots.

Non-NASA Center↗
NASA NTRS1985

Changes in the distribution of plastids and endoplasmic reticulum during cellular differentiation in root caps of Zea mays

In calyptrogen cells of Zea mays, proplastids are distributed randomly throughout the cell, and the endoplasmic reticulum (ER) is distributed parallel to the cell walls. The differentiation of calyptrogen cells into columella statocytes is characterized by the following sequential events: (1) formation of ER complexes at the distal and proximal ends of the cell, (2) differentiation of proplastids into amyloplasts, (3) sedimentation of amyloplasts onto the distal ER complex, (4) breakdown of the distal ER complex and sedimentation of amyloplasts to the bottom of the cell, and (5) formation of sheets of ER parallel to the longitudinal cell walls. Columella statocytes located in the centre of the cap each possess 4530 +/- 780 micrometers2 of ER surface area, an increase of 670 per cent over that of calyptrogen cells. The differentiation of peripheral cells correlates positively with (1) the ER becoming arranged in concentric sheets, (2) amyloplasts and ER becoming randomly distributed, and (3) a 280 per cent increase in ER surface area over that of columella statocytes. These results are discussed relative to graviperception and mucilage secretion, which are functions of columella and peripheral cells, respectively.

NASA Discipline Number 40-10↗
NASA NTRS1987

The structure of the stem endodermis in etiolated pea seedlings

Differentiation of the endodermis was examined in third internodes of etiolated Pisum sativum L. cv. Alaska seedlings. The endodermis in young internodes contains large, sedimented amyloplasts; in older internodes, a casparian strip differentiates and the endodermis becomes depleted of starch except for the proximal region of the stem, which retains sedimented amyloplasts and remains graviresponsive. Sedimentation occurs in the hook but does not occur consistently until cells reach the base of the hook, where the axis becomes vertical, rapid cell elongation starts, and amyloplast diameter increases substantially. Contact between endoplasmic reticulum and amyloplasts was observed. Endoplasmic reticulum is not distributed polarly with respect to gravity. No symplastic or apoplastic blockages exist in the endodermis at the level of the stem where lateral gradients may be established during tropic curvature.

Non-NASA Center↗
NASA NTRS1987

Influence of microgravity on cellular differentiation in root caps of Zea mays

We launched imbibed seeds of Zea mays into outer space aboard the space shuttle Columbia to determine the influence of microgravity on cellular differentiation in root caps. The influence of microgravity varied with different stages of cellular differentiation. Overall, microgravity tended to 1) increase relative volumes of hyaloplasm and lipid bodies, 2) decrease the relative volumes of plastids, mitochondria, dictyosomes, and the vacuome, and 3) exert no influence on the relative volume of nuclei in cells comprising the root cap. The reduced allocation of dictyosomal volume in peripheral cells of flight-grown seedlings correlated positively with their secretion of significantly less mucilage than peripheral cells of Earth-grown seedlings. These results indicate that 1) microgravity alters the patterns of cellular differentiation and structures of all cell types comprising the root cap, and 2) the influence of microgravity on cellular differentiation in root caps of Zea mays is organelle specific.

NASA Program Space Biology↗
NASA NTRS1992

Endochondral bone formation in embryonic mouse pre-metatarsals

Long term exposure to a reduced gravitational environment has a deleterious effect on bone. The developmental events which occur prior to initial bone deposition will provide insight into the regulation of mature bone physiology. We have characterized a system in which the events preceding bone formation take place in an isolated in vitro organ culture environment. We show that cultured pre-metatarsal tissue parallels development of pre-metatarsal tissue in the embryo. Both undergo mesenchyme differentiation and morphogenesis to form a cartilage rod, which resembles the future bone, followed by terminal chondrocyte differentiation in a definite morphogenetic pattern. These sequential steps occur prior to osteoblast maturation and bone matrix deposition in the developing organism. Alkaline phosphatase (ALP) activity is a distinctive enzymatic marker for mineralizing tissues. We have measured this activity throughout pre-metatarsal development and show (a) where in the tissue it is predominantly found, and (b) that this is indeed the mineralizing isoform of the enzyme.

NASA Discipline Number 93-10↗
NASA NTRS2000

atonal regulates neurite arborization but does not act as a proneural gene in the Drosophila brain

Drosophila atonal (ato) is the proneural gene of the chordotonal organs (CHOs) in the peripheral nervous system (PNS) and the larval and adult photoreceptor organs. Here, we show that ato is expressed at multiple stages during the development of a lineage of central brain neurons that innervate the optic lobes and are required for eclosion. A novel fate mapping approach shows that ato is expressed in the embryonic precursors of these neurons and that its expression is reactivated in third instar larvae (L3). In contrast to its function in the PNS, ato does not act as a proneural gene in the embryonic brain. Instead, ato performs a novel function, regulating arborization during larval and pupal development by interacting with Notch.

NASA Discipline Developmental Biology↗
NASA NTRS2000

Effects of hindlimb unloading on neuromuscular development of neonatal rats

We hypothesized that hindlimb suspension unloading of 8-day-old neonatal rats would disrupt the normal development of muscle fiber types and the motor innervation of the antigravity (weightbearing) soleus muscles but not extensor digitorum longus (EDL) muscles. Five rats were suspended 4.5 h and returned 1.5 h to the dam for nursing on a 24 h cycle for 9 days. To control for isolation from the dam, the remaining five littermates were removed on the same schedule but not suspended. Another litter of 10 rats housed in the same room provided a vivarium control. Fibers were typed by myofibrillar ATPase histochemistry and immunostaining for embryonic, slow, fast IIA and fast IIB isomyosins. The percentage of multiple innervation and the complexity of singly-innervated motor terminal endings were assessed in silver/cholinesterase stained sections. Unique to the soleus, unloading accelerated production of fast IIA myosin, delayed expression of slow myosin and retarded increases in standardized muscle weight and fiber size. Loss of multiple innervation was not delayed. However, fewer than normal motor nerve endings achieved complexity. Suspended rats continued unloaded hindlimb movements. These findings suggest that motor neurons resolve multiple innervation through nerve impulse activity, whereas the postsynaptic element (muscle fiber) controls endplate size, which regulates motor terminal arborization. Unexpectedly, in the EDL of unloaded rats, transition from embryonic to fast myosin expression was retarded. Suspension-related foot drop, which stretches and chronically loads EDL, may have prevented fast fiber differentiation. These results demonstrate that neuromuscular development of both weightbearing and non-weightbearing muscles in rats is dependent upon and modulated by hindlimb loading.

Non-NASA Center↗
NASA NTRS1999

Differential expression of human lysyl hydroxylase genes, lysine hydroxylation, and cross-linking of type I collagen during osteoblastic differentiation in vitro

The pattern of lysyl hydroxylation in the nontriple helical domains of collagen is critical in determining the cross-linking pathways that are tissue specific. We hypothesized that the tissue specificity of type I collagen cross-linking is, in part, due to the differential expression of lysyl hydroxylase genes (Procollagen-lysine,2-oxyglutarate,5-dioxygenase 1, 2, and 3 [PLOD1, PLOD2, and PLOD3]). In this study, we have examined the expression patterns of these three genes during the course of in vitro differentiation of human osteoprogenitor cells (bone marrow stromal cells [BMSCs]) and normal skin fibroblasts (NSFs). In addition, using the medium and cell layer/matrix fractions in these cultures, lysine hydroxylation of type I collagen alpha chains and collagen cross-linking chemistries have been characterized. High levels of PLOD1 and PLOD3 genes were expressed in both BMSCs and NSFs, and the expression levels did not change in the course of differentiation. In contrast to the PLOD1 and PLOD3 genes, both cell types showed low PLOD2 gene expression in undifferentiated and early differentiated conditions. However, fully differentiated BMSCs, but not NSFs, exhibited a significantly elevated level (6-fold increase) of PLOD2 mRNA. This increase coincided with the onset of matrix mineralization and with the increase in lysyl hydroxylation in the nontriple helical domains of alpha chains of type I collagen molecule. Furthermore, the collagen cross-links that are derived from the nontriple helical hydroxylysine-aldehyde were found only in fully differentiated BMSC cultures. The data suggests that PLOD2 expression is associated with lysine hydroxylation in the nontriple helical domains of collagen and, thus, could be partially responsible for the tissue-specific collagen cross-linking pattern.

NASA Discipline Musculoskeletal↗
NASA NTRS1997

Interactions between integrin receptors and fibronectin are required for calvarial osteoblast differentiation in vitro

We previously showed that anti-fibronectin antibodies or soluble fibronectin fragments containing the central cell-binding domain inhibit formation of mineralized nodules by fetal calvarial osteoblasts in vitro. These findings suggest a critical role for fibronectin in osteoblast differentiation and morphogenesis. In this study we tested the hypothesis that fibronectin's effects on osteogenesis are mediated via direct interactions with integrin receptors for fibronectin on osteoblasts. Immunocytochemical analysis identified the integrin fibronectin receptor alpha5ss1 in fetal rat calvarial tissue and in cultured osteoblasts at all stages of differentiation. Three other integrins, alpha3ss1, alpha8ss1 and alphavss3, which can bind fibronectin, as well as other matrix components, were also identified in tissue and at all stages of cell culture. Immunoprecipitation data showed that alpha5ss1 levels are constant throughout osteoblast differentiation whereas levels of alpha3ss1 and alpha8ss1 decline in mature mineralized cultures. To determine whether integrin fibronectin receptors are required for osteoblast formation of mineralized nodules, we examined the extent of nodule formation in the presence and absence of function-perturbing anti-integrin antibodies. The antibodies were present continuously in cultures beginning at confluence (day 3), and nodule formation was measured at days 10 and 20. An anti-alpha5 integrin subunit antibody reduced nodule formation to less than 5% of control values at both time points. Inhibition of nodule formation was reversible and did not affect cell attachment and viability. Function-perturbing antibodies against alpha3ss1 and alpha8ss1 also reduced nodule formation, to less than 20% of control values. In contrast, function-perturbing antibodies to alphavss3 and alphavss5 did not affect nodule formation, indicating that the inhibitions noted were indeed specific. To determine the effect of antibody treatment on gene expression, steady-state mRNA expression was examined and found to be suppressed for osteoblast markers alkaline phosphatase and osteocalcin. Together, these results indicate that direct osteoblast interactions with the extracellular matrix are mediated by a select group of integrin receptors that includes alpha5ss1, alpha3ss1 and alpha8ss1. We further conclude that the specific alpha5ss1 fibronectin receptor mediates critical interactions between osteoblasts and fibronectin required for both bone morphogenesis and osteoblast differentiation.

NASA Center ARC↗
NASA NTRS1993

Studies of chondrogenesis in rotating systems

A great deal of energy has been exerted over the years researching methods for regenerating and repairing bone and cartilage. Several techniques, especially bone implants and grafts, show great promise for providing a remedy for many skeletal disorders and chondrodystrophies. The bioreactor (rotating-wall vessel, RWV) is a cell culture system that creates a nurturing environment conducive to cell aggregation. Chondrocyte cultures have been studied as implants for repair and replacement of damaged and missing bone and cartilage since 1965 [Chesterman and Smith, J Bone Joint Surg 50B:184-197, 1965]. The ability to use large, tissue-like cartilage aggregates grown in the RWV would be of great clinical significance in treating skeletal disorders. In addition, the RWV may provide a superior method for studying chondrogenesis and chondrogenic mutations. Because the RWV is also reported to simulate many of the conditions of microgravity it is a very useful ground-based tool for studying how cell systems will react to microgravity.

Non-NASA Center↗
NASA NTRS1993

Utilization of microgravity bioreactors for differentiation of mammalian skeletal tissue

Bioreactor cell and tissue culture vessels can be used to study bone development in a simulated microgravity environment. These vessels will also provide an advantageous, low maintenance culture system on space station Freedom. Although many types of cells and tissues can potentially utilize this system, our particular interest is in developing bone tissue. We have characterized an organ culture system utilizing embryonic mouse pre-metatarsal mesenchyme, documenting morphogenesis and differentiation as cartilage rods are formed, with subsequent terminal chondrocyte differentiation to hypertrophied cells. Further development to form bone tissue is achieved by supplementation of the culture medium. Research using pre-metatarsal tissue, combined with the bioreactor culture hardware, could give insight into the advantages and/or disadvantages of conditions experienced in microgravity. Studies such as these have the potential to enhance understanding of bone development and adult bone physiology, and may help define the processes of bone demineralization experienced in space and in pathological conditions here on earth.

Non-NASA Center↗