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Page 173 of 547-
Cerebellar Cells Self-Assemble into Functional Organoids on Synthetic, Chemically Crosslinked ECM-Mimicking Peptide Hydrogels.
Hydrogel-supported neural cell cultures are more in vivo-relevant compared to monolayers formed on glass or plastic substrates. However, there is a lack of synthetic microenvironment available for obtaining standardized and easily reproducible cultures characterized by tissue-mimicking cell composition, cell-cell interactions, and functional networks. Synthetic peptides representing the biological properties of the extracellular matrix (ECM) proteins have been reported to promote the adhesion-driven differentiation and functional maturation of neural cells. Thus, such peptides can serve as building blocks for engineering a standardized, all-synthetic environment. In this study, we have compared the effect of two chemically crosslinked hydrogel compositions on primary cerebellar cells: collagen-like peptide (CLP), and CLP with an integrin-binding motif arginine-glycine-aspartate (CLP-RGD), both conjugated to polyethylene glycol molecular templates (PEG-CLP and PEG-CLP-RGD, respectively) and fabricated as self-supporting membranes. Both compositions promoted a spontaneous organization of primary cerebellar cells into tissue-like clusters with fast-rising Ca2+ signals in soma, reflecting action potential generation. Notably, neurons on PEG-CLP-RGD had more neurites and better synaptic efficiency compared to PEG-CLP. For comparison, poly-L-lysine-coated glass and plastic surfaces did not induce formation of such spontaneously active networks. Additionally, contrary to the hydrogel membranes, glass substrates functionalized with PEG-CLP and PEG-CLP-RGD did not sufficiently support cell attachment and, subsequently, did not promote functional cluster formation. These results indicate that not only chemical composition but also the hydrogel structure and viscoelasticity are essential for bioactive signaling. The synthetic strategy based on ECM-mimicking, multifunctional blocks in registry with chemical crosslinking for obtaining tissue-like mechanical properties is promising for the development of fast and well standardized functional in vitro neural models and new regenerative therapies.
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[The structure of stratified bodies in the axoplasm of dissected fibers of the optic nerve situated distally from the lesion].
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[The peroxisomes of Triturus cristatus (amphibian, urodele) adrenal cortex cells: peroxisome number as a function of steroidogenic activity].
Peroxisomes are scarce in the poorly active interrenal cells of hypophysectomized animals; their number increases drastically in cells which are stimulated by corticotrophic factors. A precise correlation appears thus to exist between the steroidogenic activity of the interrenal cells and the number of peroxisomes in these cells.
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Control of protein synthesis in anterior pituitary gland.
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Ultrastructure of neurosecretosomes sedimented in the nuclear fraction from the posterior pituitary of the rat.
Subcellular fractions of the posterior pituitary of the rat were isolated by differential and density gradient centrifugation, and microsamples prepared for electron miscroscopy by KMnO4 or glutaraldehyde-OsO4 fixation. The nuclear fraction, P1 (1000 g x 7 min), was the main neurosecretosome (NSS) fraction and contained nuclei and mitochondria in addition to NSS (60%). The crude mitochondrial fraction, P2 (10,000 g x 20 min), contained free mitochondria (70%), NSS, unidentified membrane particles, fat droplets derived from pituicytes, neurosecretory granules (NSG) and synaptosomes, identified by the presence of synaptic membrane thickenings. Fraction P3 (32,900 g x 20 min) contained mainly free NSG, while fraction P4 (118,000 g x 30 min) had a high microsome content.
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The adsorptive and transport capacity of tanycytes during the perinatal period of the rat.
Transport of ferritin and horseradish peroxidase from the 3rd ventricle to the median eminence was examined in rats during the perinatal life, the time when functional interrelations between hypothalamus and hypophysis are established. Protein tracers injected into the lateral ventricle are adsorbed on the apical surface of the tanycyte, mainly on its protrusions or in indentations. On the 18th day of prenatal life a few small bleblike protrusions are observed. After birth microvilli appear. In time their concentration increases to result in an increase of adsorbed substances. They are taken up by smooth and coated pinocytotic vesicles and transported to the basal portion of the cell or to the intercellular space bypassing junctional complexes. In addition to pinocytotic vesicles protein tracers fill channels of smooth ER or Golgi complex and multivesicular bodies illustrating a process probably involved in metabolic or secretory processes.
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Light and electron microscopical investigations on the tanycyte differentiation during the perinatal period in the rat.
The differentiation of tanycytes was studied light and electron microscopically during the perinatal period in rats, the time when functional connections between hypothalamus and hypophysis are established. The 3rd ventricle is slit-like between 16 and 18 days of the prenatal period. Its wall is formed by intensively proliferating matrix cells with apical processes, ovoid perikarya and a basal process. The ventral region of the 3rd ventricle becomes funnel-shaped on the 20th day of the prenatal period. As the cells differentiate, the apical process becomes shorter and broader. Moreover, on day 20 of prenatal life cells without apical processes appear. Their number increases during the postnatal period. The concentration of endoplasmic reticulum, mitochondria, polysomes, lipid droplets, dense bodies (lysosomes), lamellated and multivesicular bodies increases. Initially the cells are similar but from the 3rd day of postnatal life differentiation occurs in different regions of the infundibular recess. After the 5th day, there are no marked changes in the structure and distribution of these cells.
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Ultrastructure of the adenohypophysis in the domestic pig (Sus scrofa domestica). Part I: Cells of the pars anterior.
In the hypophyses of 46-79 days old pig embryos three groups of cells were separated; one group constitute non-differentiated cells, second, cells becoming differentiated, and third, seven types of differentiated cells. Probably three of these types are equivalent to the secretory cells STH, TSH, and FSH, and one type of them--to the cells described in the hypophysis of adult vertebrates as stellate cells or follicular cells. Possibly only one type of the differentiated cells has the ability to liberate a secretion into the intercellular space; however, the type of a hormone produced by these cells has not been described yet. It seems that in the studied stages of development of the hypophysis production and accumulation of hormones takes place in secretory cells, while the secretion of these hormones begins later than in periods of development investigated by us.
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Effect ofprostaglandins E1 and E2 on hypothalamoneurohypophyseal--Neurosecretory systems of rats: a histochemical study.
PGE2 increases NSM in the neurosecretory neurons and posterior pituitary store of HNNS. It stimulates acid phosphatase and TPPase activities in HT, indicating increased synthesis of NSM. PGE2 also increases AChE and BuChE activities. PGE1 shows very little effect on NSM distribution and enzyme activities. It is concluded that PGE2 causes increased HNNS activity by stimulating AChE-mediated and Ca2+-dependent "stimulation secretion coupling mechanism".
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Identification and morphometric evaluation of the synapses of optic nerve afferents in the optic tectum of the axolotl (Ambystoma mexicanum).
Ther terminals of retinal afferents in the tectum of the axolotl have been identified ultrastructurally using techniques of horseradish peroxidase-filling and degeneration. The mitochondria in filled structures show a characteristic electron-lucent matrix. After both eyes have been removed, terminals with light mitochondria disappear from the area known to receive an optic input. In this area the presence of light mitochondria is almost always diagnostic of the retinal origin of a bouton. The synapses are similar to those assumed to be of retinal origin in other vertebrates. Detailed morphometric analysis has been carried out on identified optic synapses in the optic tectum of the axolotl.