scholarly journals Progressive and spatially differentiated stability of microtubules in developing neuronal cells.

1989 ◽  
Vol 109 (1) ◽  
pp. 253-263 ◽  
Author(s):  
S S Lim ◽  
P J Sammak ◽  
G G Borisy
Keyword(s):  
Cell Body ◽  
Growth Cone ◽  
Cellular Differentiation ◽  
Progressive Increase ◽  
Fluorescence Recovery ◽  
Plastic Properties ◽  
Intracellular Location ◽  
Laser Microbeam ◽  
Neuronal Cytoskeleton ◽  
The Stability

The establishment of neural circuits requires both stable and plastic properties in the neuronal cytoskeleton. In this study we show that properties of stability and lability reside in microtubules and these are governed by cellular differentiation and intracellular location. After culture for 3, 7, and 14 d in nerve growth factor-containing medium, PC-12 cells were microinjected with X-rhodamine-labeled tubulin. 8-24 h later, cells were photobleached with a laser microbeam at the cell body, neurite shaft, and growth cone. Replacement of fluorescence in bleached zones was monitored by digital video microscopy. In 3-d cultures, fluorescence recovery in all regions occurred by 26 +/- 17 min. Similarly, in older cultures, complete fluorescence recovery at the cell body and growth cone occurred by 10-30 min. However, in neurite shafts, fluorescence recovery was markedly slower (71 +/- 48 min for 7-d and 201 +/- 94 min for 14-d cultures). This progressive increase in the stability of microtubules in the neurite shafts correlated with an increase of acetylated microtubules. Acetylated microtubules were present specifically in the neurite shaft and not in the regions of fast microtubule turnover, the cell body and growth cone. During the recovery of fluorescence, bleached zones did not move with respect to the cell body. We conclude that the microtubule component of the neuronal cytoskeleton is differentially dynamic but stationary.

Translocation of the neuronal cytoskeleton and axonal locomotion

1982 ◽  
Vol 299 (1095) ◽  
pp. 313-327 ◽  
Keyword(s):  
Plasma Membrane ◽  
Axonal Transport ◽  
Cell Body ◽  
Cytoskeletal Proteins ◽  
The Other ◽  
Current Understanding ◽  
Axonal Elongation ◽  
Neuronal Cytoskeleton ◽  
Other Hand ◽  
Neuron Cell Body

Recent studies of axonal transport indicate that cytoskeletal proteins are assembled into polymers in the neuron cell body and that these polymers move from the cell body toward the end of the axon. On the other hand, membranous elements appear to be inserted into the axonal plasma membrane preferentially at the end of the axon. These new observations are explored in relation to our current understanding of axonal elongation.

scholarly journals Evidence that calcium may control neurite outgrowth by regulating the stability of actin filaments.

1989 ◽  
Vol 109 (3) ◽  
pp. 1229-1243 ◽  
Author(s):  
K L Lankford ◽  
P C Letourneau
Keyword(s):  
Neurite Outgrowth ◽  
Growth Cone ◽  
Actin Filaments ◽  
Monovalent Cation ◽  
Stabilizing Agent ◽  
Growth Cone Collapse ◽  
Neurite Retraction ◽  
Calcium Removal ◽  
The Stability ◽  
Triton X

We investigated the effects of calcium removal and calcium ionophores on the behavior and ultrastructure of cultured chick dorsal root ganglia (DRG) neurons to identify possible mechanisms by which calcium might regulate neurite outgrowth. Both calcium removal and the addition of calcium ionophores A23187 or ionomycin blocked outgrowth in previously elongating neurites, although in the case of calcium ionophores, changes in growth cone shape and retraction of neurites were also observed. Treatment with calcium ionophores significantly increased growth cone calcium. The ability of the microtubule stabilizing agent taxol to block A23187-induced neurite retraction and the ability of the actin stabilizing agent phalloidin to reverse both A23187-induced growth cone collapse and neurite retraction suggested that calcium acted on the cytoskeleton. Whole mount electron micrographs revealed an apparent disruption of actin filaments in the periphery (but not filopodia) of growth cones that were exposed to calcium ionophores in medium with normal calcium concentrations. This effect was not seen in cells treated with calcium ionophores in calcium-free medium or cells treated with the monovalent cation ionophore monensin, indicating that these effects were calcium specific. Ultrastructure of Triton X-100 extracted whole mounts further indicated that both microtubules and microfilaments may be more stable or extraction resistant after treatments which lower intracellular calcium. Taken together, the data suggest that calcium may control neurite elongation at least in part by regulating actin filament stability, and support a model for neurite outgrowth involving a balance between assembly and disassembly of the cytoskeleton.

FLAXSIBILITY OF POTATO VARIETIES IN THE URALS STEPPE ZONE

2016 ◽  
Vol 1 (3) ◽  
pp. 20-22 ◽  
Author(s):  
Аминова ◽  
Evgeniya Aminova ◽  
Мушинский ◽  
Aleksandr Mushinskiy ◽  
Герасимова ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Regression Coefficient ◽  
Factor Model ◽  
Steppe Zone ◽  
Progressive Increase ◽  
The Urals ◽  
Potato Varieties ◽  
Ecological Flexibility ◽  
Growing Conditions ◽  
The Stability

The purpose of research is to identify potato varieties with high ecological flexibility and stability in the conditions of steppe zone of the Urals. The experience was laid by one-factor circuit in 3-fold repetition. The studies were conducted for middle and middle-early varieties of potatoes domestic and foreign selection. We define the parameters of their ecological plasticity and stability analysis using two-factor model (conditions and years). In 3-year data were allocated potato varieties – Artemis (58.9 t/ha), Aerrow (51.6 t/ha), Riviera (51.1 t/ha), Romano (55.2 t/ha). The regression coefficient ranged from 0.54 to 2.59, the stability coefficients vary from 0.20 to 49.04. It was found that the regression coefficient is significantly greater than one, indicating that the progressive increase in yield under the influence of improved growing conditions in such varieties as: Rainbow (Ri 2.19), Sail (Ri 2.59), Memory Kovalenko (Ri 2.41) Tarasov (Ri 2.05), Karatop (Ri 2.19) – varieties of intensive type. Revealed grade plastic – Nevsky, Spiridon, Romano, Aerrow, Scarlett Red, Riviera, Curator (Ri=0.70-1.08).

scholarly journals A cytochemical study of lectin receptors on isolated chick neural retina neurons in vitro

1982 ◽  
Vol 53 (1) ◽  
pp. 1-20
Author(s):  
J.A. Bee
Keyword(s):  
Sialic Acid ◽  
Cell Body ◽  
Growth Cone ◽  
Ricinus Communis ◽  
Lectin Binding ◽  
Neuronal Cell ◽  
Cytochemical Study ◽  
Lectin Receptors ◽  
Dolichos Biflorus ◽  
Dolichos Biflorus Agglutinin

The cell body, neurite and growth cone of isolated retinal neurons have been compared on the basis of their ability to bind a number of fluorescently labelled lectins, each possessing a unique carbohydrate specificity. The susceptibility of the respective binding patterns following pretreatment of these fixed cells with either neuraminidase or trypsin was also investigated. Neuronal cell bodies displayed the most intense binding of each lectin, with localization of limulin binding (specific for sialic acid) predominantly to the neurite hillock, the point on the cell body from which the neurite projects. Limulin binding was almost totally abolished by pretreatment with either neuraminidase or trypsin. In contrast to the cell body, limulin binding to the neurite or growth cone was not detected. These regions of the cell apparently possessed sialic acid, however, since pretreatment with neuraminidase reduced wheat germ agglutinin binding (to N-acetylglucosamine) and markedly enhanced Dolichos biflorus agglutinin binding (to N-acetylgalactosamine) to both the neurite and growth cone. The initially low binding of Dolichos biflorus agglutinin to the neurite and growth cone was slightly enhanced by pretreatment with trypsin. Uniformly low levels of binding of either Ricinus communis agglutinin 60 (galactose, N-acetylgalactosamine) or R. communis agglutinin 120 (galactose) was observed over the entire neuron. R. communis agglutinin 120 binding was not enhanced by pretreatment with neuraminidase. Receptors for either concanavalin A (mannose, glucose) or Ulex europaeus agglutinin I (fucose) were abundant over the entire nerve cell with the former exhibiting more marked trypsin sensitivity. From these data, it is apparent that the repertoire of lectin binding sites of the neurite and growth cone of these differentiating nerve cells differs markedly from that of the cell body, which itself demonstrates some degree of regionalization.

scholarly journals Use of reinforced earth to improve the stability of railway sleepers

2018 ◽  
Vol 149 ◽  
pp. 02070
Author(s):  
Souad Atoub ◽  
Riad Benzaid ◽  
Mustapha Tekkouk
Keyword(s):  
Industrial Development ◽  
Progressive Increase ◽  
Soil Reinforcement ◽  
Cohesionless Soil ◽  
Vertical Loading ◽  
Railway Infrastructure ◽  
Reinforced Earth ◽  
Long Time ◽  
Real Size ◽  
The Stability

Soil reinforcement with inclusion has been used since the dawn of time, however, decisive progress in this area dates back only a few decades, When the techniques of soil reinforcement are passed to an industrial development with metallic inclusions then geosynthetic and for applications as well in embankments as in cuttings. Reinforced earth is one of the most used methods for soil strengthening. It is a relatively recent technique whose principle consists in associating with a cohesionless soil tensile reinforcements, which thus give the material an anisotropic cohesion in the direction of the reinforcements. Among the areas where the reinforced earth is currently experiencing a remarkable expansion, railway infrastructure, traditional means for the transport of passengers and goods, and which has never ceased to be the subject of technical progress. This progress based for a long time on the empiricism, allowed the progressive increase, as well speeds as tonnage by axle. However, the railway remains a privileged place of deformation under the effect of the repetitive application of loads. These deformations are largely related to the problem of ballast settlement, a problem whose causes are diverse and that we will try to study in the laboratory on a physical model in real size. The present work consists in experimentally analyzing the load-settlement relationships that exist during the introduction of stainless steel reinforcement into an unstable rail ballast under static vertical loading and to establish the conditions that lead to the reduction of recorded settlements in order to improve the stability of railway sleepers.

scholarly journals Myosin 1b promotes axon formation by regulating actin wave propagation and growth cone dynamics

2018 ◽  
Vol 217 (6) ◽  
pp. 2033-2046 ◽  
Author(s):  
Olga Iuliano ◽  
Azumi Yoshimura ◽  
Marie-Thérèse Prospéri ◽  
René Martin ◽  
Hans-Joachim Knölker ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Symmetry Breaking ◽  
Motor Activity ◽  
Actin Cytoskeleton ◽  
Growth Cone ◽  
Growth Cones ◽  
Actin Network ◽  
Mechanical Control ◽  
Actin Waves ◽  
The Stability

Single-headed myosin 1 has been identified in neurons, but its function in these cells is still unclear. We demonstrate that depletion of myosin 1b (Myo1b), inhibition of its motor activity, or its binding to phosphoinositides impairs the formation of the axon, whereas overexpression of Myo1b increases the number of axon-like structures. Myo1b is associated with growth cones and actin waves, two major contributors to neuronal symmetry breaking. We show that Myo1b controls the dynamics of the growth cones and the anterograde propagation of the actin waves. By coupling the membrane to the actin cytoskeleton, Myo1b regulates the size of the actin network as well as the stability and size of filopodia in the growth cones. Our data provide the first evidence that a myosin 1 plays a major role in neuronal symmetry breaking and argue for a mechanical control of the actin cytoskeleton both in actin waves and in the growth cones by this myosin.

The stability of milk protein to heat: II. Effect on heat stability of ageing milk at different temperatures

1966 ◽  
Vol 33 (1) ◽  
pp. 83-91 ◽  
Author(s):  
D. T. Davies ◽  
J. C. D. White
Keyword(s):  
Milk Protein ◽  
Heat Stability ◽  
Subclinical Mastitis ◽  
Progressive Increase ◽  
Common Occurrence ◽  
Coagulation Time ◽  
Rate Of Increase ◽  
Different Temperatures ◽  
Significant Change ◽  
The Stability

SummaryThe effect on heat stability as measured by coagulation time, of storing separated milk at 20, 4 and −20 °C has been examined. Milk with a good coagulation (initial clots large) could be stored for at least 30 h at 20 °C, 1 week at 4 °C and 1 month at −20 °C with no significant change in coagulation time. With milks giving a poor coagulation (initial clots small), a common occurrence during storage at 20 °C was a marked progressive increase in coagulation time; the rate of increase was reduced by storage at 4 °C. The increase in coagulation time of these labile milks, which are usually obtained from cows with subclinical mastitis, may occur to the same extent in darkness as in light, may be enhanced by exposure to light or may occur only when the milk is exposed to light. From these results, together with others reported by Davies & White (1966) and White & Davies (1966) it is concluded that, in studying heat stability, milks giving a good coagulation should be regarded as in a different class from milks giving a poor coagulation.

scholarly journals Dynamics of Axonal Microtubules Regulate the Topology of New Membrane Insertion into the Growing Neurites

1998 ◽  
Vol 143 (4) ◽  
pp. 1077-1086 ◽  
Author(s):  
Stanislav Zakharenko ◽  
Sergey Popov
Keyword(s):  
Plasma Membrane ◽  
Cell Body ◽  
Growth Cone ◽  
Dynamic Instability ◽  
Drug Application ◽  
Culture Cell ◽  
Membrane Material ◽  
Cellular Mechanisms ◽  
Neuronal Processes ◽  
Necessary And Sufficient

Nerve growth depends on the delivery of cell body–synthesized material to the growing neuronal processes. The cellular mechanisms that determine the topology of new membrane addition to the axon are not known. Here we describe a technique to visualize the transport and sites of exocytosis of cell body– derived vesicles in growing axons. We found that in Xenopus embryo neurons in culture, cell body–derived vesicles were rapidly transported all the way down to the growth cone region, where they fused with the plasma membrane. Suppression of microtubule (MT) dynamic instability did not interfere with the delivery of new membrane material to the growth cone region; however, the insertion of vesicles into the plasma membrane was dramatically inhibited. Local disassembly of MTs by focal application of nocodazole to the middle axonal segment resulted in the addition of new membrane at the site of drug application. Our results suggest that the local destabilization of axonal MTs is necessary and sufficient for the delivery of membrane material to specific neuronal sites.

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