scholarly journals Dynamic organization of ATP and birefringent fibrils during free locomotion and galvanotaxis in the plasmodium of Physarum polycephalum.

1990 ◽  
Vol 110 (4) ◽  
pp. 1097-1102 ◽  
Author(s):  
T Ueda ◽  
T Nakagaki ◽  
T Yamada
Keyword(s):  
Scaling Law ◽  
Directed Migration ◽  
Advancing Front ◽  
Atp Concentration ◽  
Dc Electric Field ◽  
A Cell ◽  
Birefringent Fibrils ◽  
Ameboid Cell ◽  
Plasmodium Of Physarum Polycephalum ◽  
Dynamic Organization

Directed migration by a cell is a good phenomenon for studying intracellular coordination. Dynamic organization of both ATP and birefringent fibrils throughout the cell was studied in the multinuclear ameboid cell of the Physarum plasmodium during free locomotion and galvanotaxis. In a directionally migrating plasmodium, waves of ATP as well as thickness oscillations propagated from just inside the advancing front to the rear, and ATP concentration was high at the front on the average. In a DC electric field, locomotion was inhibited more strongly, ATP concentration decreased more, and birefringent fibrils were formed more abundantly at the anodal than at the cathodal side. Inside the cell there were a few undulations in the distributions of ATP and birefringent fibrils. In short, birefringent fibrils become abundant where ATP concentration decreases. The possible mechanism of the coordination in the directed migration and the implications of the scaling law are discussed.

What Determines the Intracellular ATP Concentration

2002 ◽  
Vol 22 (5-6) ◽  
pp. 501-511 ◽  
Author(s):  
Fazoil I. Ataullakhanov ◽  
Victor M. Vitvitsky
Keyword(s):  
Energy Charge ◽  
Lipid Synthesis ◽  
Intracellular Atp ◽  
Atp Concentration ◽  
Polysaccharide Synthesis ◽  
Additional Control ◽  
Adenylate Pool ◽  
A Cell ◽  
Energy Consuming ◽  
The Individual

Analysis is made of the mechanisms that control the intracellular ATP level. The balance between energy production and expenditure determines the energy charge of the cell and the ratio of [ATP] to the adenylate pool. The absolute ATP concentration is determined by the adenylate pool, which, in its turn, depends on the balance between the rates of AMP synthesis and degradation. Experimental data are discussed that demonstrate an increase in the adenylate pool in response to activation of energy-consuming processes. A hypothesis is proposed according to which variation in the adenylate pool and absolute ATP concentration affords a cell the possibility of additional control over processes fulfilling useful work. A mechanism involved in this regulation is described using human erythrocytes as an example. The hypothesis explains why different metabolic pathways (protein and DNA syntheses, polysaccharide synthesis, and lipid synthesis) use different trinucleotides (GTP, UTP, and CTP, respectively) as an energy source. This allows the cell to independently control these metabolic processes by varying the individual nucleotide pools.

scholarly journals Actin polymerization downstream of integrins: signaling pathways and mechanotransduction

2020 ◽  
Vol 477 (1) ◽  
pp. 1-21 ◽  
Author(s):  
Stéphane Romero ◽  
Christophe Le Clainche ◽  
Alexis M. Gautreau
Keyword(s):  
Actin Cytoskeleton ◽  
Signaling Pathways ◽  
Actin Polymerization ◽  
Cell Attachment ◽  
Direct Interaction ◽  
Directed Migration ◽  
A Cell ◽  
Migration Of Cells ◽  
Intense Research ◽  
Surrounding Extracellular Matrix

A cell constantly adapts to its environment. Cell decisions to survive, to proliferate or to migrate are dictated not only by soluble growth factors, but also through the direct interaction of the cell with the surrounding extracellular matrix (ECM). Integrins and their connections to the actin cytoskeleton are crucial for monitoring cell attachment and the physical properties of the substratum. Cell adhesion dynamics are modulated in complex ways by the polymerization of branched and linear actin arrays, which in turn reinforce ECM-cytoskeleton connection. This review describes the major actin regulators, Ena/VASP proteins, formins and Arp2/3 complexes, in the context of signaling pathways downstream of integrins. We focus on the specific signaling pathways that transduce the rigidity of the substrate and which control durotaxis, i.e. directed migration of cells towards increased ECM rigidity. By doing so, we highlight several recent findings on mechanotransduction and put them into a broad integrative perspective that is the result of decades of intense research on the actin cytoskeleton and its regulation.

scholarly journals Scaling law for a low-pressure gas breakdown in a homogeneous DC electric field

JETP Letters ◽  
2000 ◽  
Vol 72 (2) ◽  
pp. 34-37 ◽  
Author(s):  
V. A. Lisovsky ◽  
S. D. Yakovin
Keyword(s):  
Electric Field ◽  
Scaling Law ◽  
Low Pressure ◽  
Dc Electric Field ◽  
Gas Breakdown

ALONG THE EVOLUTION PROCESS KLEIBER'S 3/4 LAW MAKES WAY FOR RUBNER'S SURFACE LAW: A FRACTAL APPROACH

Fractals ◽  
2019 ◽  
Vol 27 (02) ◽  
pp. 1950015 ◽  
Author(s):  
XIAO-XIA LI ◽  
JI-HUAN HE
Keyword(s):  
Metabolic Rate ◽  
Body Mass ◽  
Basal Metabolic Rate ◽  
Fractal Theory ◽  
Scaling Law ◽  
Evolution Process ◽  
Fractal Approach ◽  
Biologically Relevant ◽  
A Cell ◽  
Scaling Index

Rubner 1880 surface law reveals that the basal metabolic rate scales with body mass raised to the power of 2/3, which is geometrically correct and biologically relevant. However, Kleiber 1932 scaling law experimentally found that the scaling index was 3/4 instead of 2/3. There is no theory that can explain the Kleiber's data, explanations in Science in 1997 and later in Nature in 2002 for 3/4 scaling law for all life were apparently wrong. Here we show that Rubner's surface law was approximately correct, and it requires modification due to the fact that a cell is porous. Using fractal theory, the scaling index is about 0.7, 0.73, and 0.83, respectively, for inactive, active and motion statuses, and Kleiber's exponent can be fully explained by Rubner's law.

Effect of Niacin on Mitochondria of Allium Cepa Root Cells

1967 ◽  
Vol 25 ◽  
pp. 78-79
Author(s):  
M. Arif Hayat
Keyword(s):  
Nicotinamide Adenine Dinucleotide ◽  
Hydrogen Transfer ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Nicotinamide Adenine ◽  
Root Tips ◽  
Root Cells ◽  
Transfer Processes ◽  
Standard Procedures ◽  
A Cell ◽  
Critical Interest

Although it is recognized that niacin (pyridine-3-carboxylic acid), incorporated as the amide in nicotinamide adenine dinucleotide (NAD) or in nicotinamide adenine dinucleotide phosphate (NADP), is a cofactor in hydrogen transfer in numerous enzyme reactions in all organisms studied, virtually no information is available on the effect of this vitamin on a cell at the submicroscopic level. Since mitochondria act as sites for many hydrogen transfer processes, the possible response of mitochondria to niacin treatment is, therefore, of critical interest.Onion bulbs were placed on vials filled with double distilled water in the dark at 25°C. After two days the bulbs and newly developed root system were transferred to vials containing 0.1% niacin. Root tips were collected at ¼, ½, 1, 2, 4, and 8 hr. intervals after treatment. The tissues were fixed in glutaraldehyde-OsO4 as well as in 2% KMnO4 according to standard procedures. In both cases, the tissues were dehydrated in an acetone series and embedded in Reynolds' lead citrate for 3-10 minutes.

Ultrastructure of melanocyte-keratinocyte interactions and pigment transfer in vitro

1978 ◽  
Vol 36 (2) ◽  
pp. 650-651
Author(s):  
Raul I. Garcia ◽  
Evelyn A. Flynn ◽  
George Szabo
Keyword(s):  
Direct Injection ◽  
Skin Pigmentation ◽  
Freeze Fracture ◽  
Pigment Granule ◽  
Time Lapse ◽  
Ultrastructural Level ◽  
Lanthanum Tracer ◽  
A Cell

Skin pigmentation in mammals involves the interaction of epidermal melanocytes and keratinocytes in the structural and functional unit known as the Epidermal Melanin Unit. Melanocytes(M) synthesize melanin within specialized membrane-bound organelles, the melanosome or pigment granule. These are subsequently transferred by way of M dendrites to keratinocytes(K) by a mechanism still to be clearly defined. Three different, though not necessarily mutually exclusive, mechanisms of melanosome transfer have been proposed: cytophagocytosis by K of M dendrite tips containing melanosomes, direct injection of melanosomes into the K cytoplasm through a cell-to-cell pore or communicating channel formed by localized fusion of M and K cell membranes, release of melanosomes into the extracellular space(ECS) by exocytosis followed by K uptake using conventional phagocytosis. Variability in methods of transfer has been noted both in vivo and in vitro and there is evidence in support of each transfer mechanism. We Have previously studied M-K interactions in vitro using time-lapse cinemicrography and in vivo at the ultrastructural level using lanthanum tracer and freeze-fracture.

Dendritic cells of the human epidermis: immuno-electron microscopic studies of la antigen reactivity

1978 ◽  
Vol 36 (2) ◽  
pp. 644-645
Author(s):  
G. Rowden ◽  
M. G. Lewis ◽  
T. M. Phillips
Keyword(s):  
Dendritic Cells ◽  
Langerhans Cells ◽  
Cell Types ◽  
Cell Type ◽  
Electron Microscopic ◽  
La Antigen ◽  
Microscopic Studies ◽  
A Cell ◽  
C3 Receptors ◽  
Antigen Reactivity

Langerhans cells of mammalian stratified squamous epithelial have proven to be an enigma since their discovery in 1868. These dendritic suprabasal cells have been considered as related to melanocytes either as effete cells, or as post divisional products. Although grafting experiments seemed to demonstrate the independence of the cell types, much confusion still exists. The presence in the epidermis of a cell type with morphological features seemingly shared by melanocytes and Langerhans cells has been especially troublesome. This so called "indeterminate", or " -dendritic cell" lacks both Langerhans cells granules and melanosomes, yet it is clearly not a keratinocyte. Suggestions have been made that it is related to either Langerhans cells or melanocyte. Recent studies have unequivocally demonstrated that Langerhans cells are independent cells with immune function. They display Fc and C3 receptors on their surface as well as la (immune region associated) antigens.

Presence of antibody in virus-infected brain cells of SSPE ferrets

1983 ◽  
Vol 41 ◽  
pp. 804-805
Author(s):  
Hannah R. Brown ◽  
Tammy L. Donato ◽  
Halldor Thormar
Keyword(s):  
Measles Virus ◽  
Plasma Cells ◽  
Subacute Sclerosing Panencephalitis ◽  
Protein A ◽  
Neutralizing Antibody ◽  
Brain Cells ◽  
Antibody Titers ◽  
A Cell ◽  
The Central Nervous System ◽  
The Brain

Measles virus specific immunoglobulin G (IgG) has been found in the brains of patients with subacute sclerosing panencephalitis (SSPE), a slowly progressing disease of the central nervous system (CNS) in children. IgG/albumin ratios indicate that the antibodies are synthesized within the CNS. Using the ferret as an animal model to study the disease, we have been attempting to localize the Ig's in the brains of animals inoculated with a cell associated strain of SSPE. In an earlier report, preliminary results using Protein A conjugated to horseradish peroxidase (PrAPx) (Dynatech Diagnostics Inc., South Windham, ME.) to detect antibodies revealed the presence of immunoglobulin mainly in antibody-producing plasma cells in inflammatory lesions and not in infected brain cells.In the present experiment we studied the brain of an SSPE ferret with neutralizing antibody titers of 1:1024 in serum and 1:512 in CSF at time of sacrifice 7 months after i.c. inoculation with SSPE measles virus-infected cells. The animal was perfused with saline and portions of the brain and spinal cord were immersed in periodate-lysine-paraformaldehyde (P-L-P) fixative. The ferret was not perfused with fixative because parts of the brain were used for virus isolation.

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