scholarly journals Specific features of glycogen metabolism in the liver

1998 ◽  
Vol 336 (1) ◽  
pp. 19-31 ◽  
Author(s):  
Mathieu BOLLEN ◽  
Stefaan KEPPENS ◽  
Willy STALMANS
Keyword(s):  
Glycogen Synthesis ◽  
Glycogen Metabolism ◽  
Cell Types ◽  
Hepatic Glycogen ◽  
Metabolizing Enzymes ◽  
Extrahepatic Tissues ◽  
Glycogen Deposition ◽  
Parenchymal Cells ◽  
Different Cell Types

Although the general pathways of glycogen synthesis and glycogenolysis are identical in all tissues, the enzymes involved are uniquely adapted to the specific role of glycogen in different cell types. In liver, where glycogen is stored as a reserve of glucose for extrahepatic tissues, the glycogen-metabolizing enzymes have properties that enable the liver to act as a sensor of blood glucose and to store or mobilize glycogen according to the peripheral needs. The prime effector of hepatic glycogen deposition is glucose, which blocks glycogenolysis and promotes glycogen synthesis in various ways. Other glycogenic stimuli for the liver are insulin, glucocorticoids, parasympathetic (vagus) nerve impulses and gluconeogenic precursors such as fructose and amino acids. The phosphorolysis of glycogen is mainly mediated by glucagon and by the orthosympathetic neurotransmitters noradrenaline and ATP. Many glycogenolytic stimuli, e.g. adenosine, nucleotides and NO, also act indirectly, via secretion of eicosanoids from non-parenchymal cells. Effectors often initiate glycogenolysis cooperatively through different mechanisms.

scholarly journals Glycogen synthesis in the perfused liver of the starved rat

1972 ◽  
Vol 129 (3) ◽  
pp. 529-538 ◽  
Author(s):  
D. A. Hems ◽  
P. D. Whitton ◽  
E. A. Taylor
Keyword(s):  
Time Course ◽  
Sequential Sampling ◽  
Glycogen Synthesis ◽  
Lateral Lobe ◽  
Hepatic Glycogen ◽  
Perfused Liver ◽  
Glycogen Deposition ◽  
Glucose Dependence

1. In the isolated perfused liver from 48h-starved rats, glycogen synthesis was followed by sequential sampling of the two major lobes. 2. The fastest observed rates of glycogen deposition (0.68–0.82μmol of glucose/min per g fresh liver) were obtained in the left lateral lobe, when glucose in the medium was 25–30mm and when gluconeogenic substrates were present (pyruvate, glycerol and serine: each initially 5mm). In this situation there was no net disappearance of glucose from the perfusion medium, although 14C from [U-14C]glucose was incorporated into glycogen. There was no requirement for added hormones. 3. In the absence of gluconeogenic precursors, glycogen synthesis from glucose (30mm) was 0–0.4μmol/min per g. 4. When livers were perfused with gluconeogenic precursors alone, no glycogen was deposited. The total amount of glucose formed was similar to the amount converted into glycogen when 30mm-glucose was also present. 5. The time-course, maximal rates and glucose dependence of hepatic glycogen deposition in the perfused liver resembled those found in vivo in 48h-starved rats, during infusion of glucose. 6. In the perfused liver, added insulin or sodium oleate did not significantly affect glycogen synthesis in optimum conditions. In suboptimum conditions (i.e. glucose less than 25mm, or with gluconeogenic precursors absent) insulin caused a moderate acceleration of glycogen deposition. 7. These results suggest that on re-feeding after starvation in the rat, hepatic glycogen deposition could be initially the result of continued gluconeogenesis, even after the ingestion of glucose. This conclusion is discussed, particularly in connexion with the role of hepatic glucokinase, and the involvement of the liver in the glucose intolerance of starvation.

Molecular morphology of hepatic glycogen metabolism

1991 ◽  
Vol 49 ◽  
pp. 48-49
Author(s):  
Robert R. Cardell
Keyword(s):  
Phosphoenolpyruvate Carboxykinase ◽  
Smooth Endoplasmic Reticulum ◽  
Glycogen Synthesis ◽  
Glycogen Metabolism ◽  
Hepatic Glycogen ◽  
Hepatic Gluconeogenesis ◽  
Morphological Aspects ◽  
Molecular Morphology

For over two decades we have studied morphological aspects of hepatic glycogen metabolism, particularly the role of smooth endoplasmic reticulum in this process. Recently investigators have emphasized the role of hepatic gluconeogenesis (formation of glucose from non-carbohydrate precursors) in glycogen synthesis. To contribute new morphological information to this discussion we have developed probes for the detection of the relevant gluconeogenic enzymes by immunocytochemistry and the expression of the genes for the enzymes by in situ hybridization histochemistry. In this report we present: our work on the expression of a gene for the major rate limiting enzyme in hepatic gluconeogenesis, phosphoenolpyruvate carboxykinase (PEPCK).

Morphometric analysis and autoradiography of the smooth endoplasmic reticulum during glycogen deposition in the fetal mouse hepatocyte

1990 ◽  
Vol 48 (3) ◽  
pp. 544-545
Author(s):  
Joanette Shockey Breslin ◽  
Robert R. Cardell
Keyword(s):  
Endoplasmic Reticulum ◽  
Morphometric Analysis ◽  
Smooth Endoplasmic Reticulum ◽  
Glycogen Synthesis ◽  
Glycogen Metabolism ◽  
Hepatic Glycogen ◽  
Thin Sections ◽  
Glycogen Accumulation ◽  
Fetal Mouse ◽  
Glycogen Deposition

Analyses of adult hepatic glycogen deposition by numerous investigators have determined that the smooth endoplasmic reticulum (SER) proliferates immediately prior to glycogen deposition and during the early stages of glycogen accumulation, then decreases as glycogen levels reach their maximum, suggesting that SER participates in adult hepatic glycogen metabolism. Less is known regarding fetal hepatic glycogen synthesis and the participation of the fetal SER. The studies described here test the hypothesis that the SER functions in the synthesis of fetal hepatic glycogen. Quantitative analysis of SER and glycogen levels during hepatic glycogen synthesis tests the existence of a correlation between glycogen and SER. Newly deposited labeled glycogen is localized via autoradiography and the extent of association between labeled glycogen and SER quantified, establishing whether glycogen is necessarily deposited near membranes of SER.Fetal mouse livers were harvested at daily intervals between days 14 and 19 of gestation, immersion fixed in 2% glutaraldehyde, 2% paraformaldehyde, post-fixed in 1 % OsO4 dehydrated in EtOH and embedded in Epon 812. Semi-thin (0.5μm) and ultra-thin sections (60 nm) were prepared for morphometric analysis.2

Role of Transcriptional Read-Through in PRE Activity in Drosophila melanogaster

Acta Naturae ◽  
2016 ◽  
Vol 8 (2) ◽  
pp. 79-86 ◽  
Author(s):  
P. V. Elizar’ev ◽  
D. V. Lomaev ◽  
D. A. Chetverina ◽  
P. G. Georgiev ◽  
M. M. Erokhin
Keyword(s):  
Dna Sequences ◽  
Cell Types ◽  
Transcription Terminator ◽  
Response Elements ◽  
Polycomb Response Elements ◽  
The Individual ◽  
Multicellular Organisms ◽  
Different Cell Types ◽  
Main Factor

Maintenance of the individual patterns of gene expression in different cell types is required for the differentiation and development of multicellular organisms. Expression of many genes is controlled by Polycomb (PcG) and Trithorax (TrxG) group proteins that act through association with chromatin. PcG/TrxG are assembled on the DNA sequences termed PREs (Polycomb Response Elements), the activity of which can be modulated and switched from repression to activation. In this study, we analyzed the influence of transcriptional read-through on PRE activity switch mediated by the yeast activator GAL4. We show that a transcription terminator inserted between the promoter and PRE doesnt prevent switching of PRE activity from repression to activation. We demonstrate that, independently of PRE orientation, high levels of transcription fail to dislodge PcG/TrxG proteins from PRE in the absence of a terminator. Thus, transcription is not the main factor required for PRE activity switch.

scholarly journals Glycogen synthesis in the perfused liver of adrenalectomized rats

1976 ◽  
Vol 156 (3) ◽  
pp. 585-592 ◽  
Author(s):  
P D Whitton ◽  
D A Hems
Keyword(s):  
Intact Animal ◽  
Glycogen Synthesis ◽  
Hepatic Metabolism ◽  
Hepatic Glycogen ◽  
Perfused Liver ◽  
Short Term ◽  
Glycogen Accumulation ◽  
Glycogen Deposition ◽  
Adrenalectomized Rats

1. A total loss of capacity for net glycogen synthesis was observed in experiments with the perfused liver of starved adrenalectomized rats. 2. This lesion was corrected by insulin or cortisol in vivo (over 2-5h), but not by any agent tested in perfusion. 3. The activity of glycogen synthetase a, and its increase during perfusion, in the presence of glucose plus glucogenic substrates, were proportional to the rate of net glycogen accumulation. 4. This complete inherent loss of capacity for glycogen synthesis after adrenalectomy is greater than any defect in hepatic metabolism yet reported in this situation, and is not explicable by a decrease in the rate of gluconegenesis (which supports glycogen synthesis in the liver of starved rats). The short-term (2-5h) stimulatory effect of glucocorticoids in the intact animal, on hepatic glycogen deposition, may be mediated partly through insulin action, although neither insulin or cortisol appear to act directly on the liver to stimulate glycogen synthesis.

An Overview of the Latest Applications of Platelet-Derived Microparticles and Nanoparticles in Medical Technology 2010-2020

2021 ◽  
Vol 21 ◽  
Author(s):  
Tahereh Zadeh Mehrizi
Keyword(s):  
Drug Delivery ◽  
Cell Types ◽  
Current Status ◽  
Target Cells ◽  
Interesting Point ◽  
Large Size ◽  
Review Study ◽  
Cellular Pathways ◽  
Different Cell Types

: Today, Platelets and platelet-derived nanoparticles and microparticles have found many applications in nanomedical technology. The results of our review study show that no article has been published in this field to review the current status of applications of these platelet derivatives so far. Therefore, in present study, our goal is to compare the applications of platelet derivatives and review their latest status between 2010 and 2020 to present the latest findings to researchers. A very interesting point about the role of platelet derivatives is the presence of molecules on their surface which makes them capable of hiding from the immune system, reaching different target cells, and specifically attaching to different cell types. According to the results of this study, most of their applications include drug delivery, diagnosis of various diseases, and tissue engineering. However, their application in drug delivery is limited due to heterogeneity, large size, and the possibility of interference with cellular pathways in microparticles derived from other cells. On the other hand, platelet nanoparticles are more controllable and have been widely used for drug delivery in treatment of cancer, atherosclerosis, thrombosis, infectious diseases, repair of damaged tissue, and photothermal therapy. The results of this study show that platelet nanoparticles are more controllable than platelet microparticles and have a higher potential for use in medicine.

Measurements of cell adhesion

Development ◽  
1973 ◽  
Vol 30 (2) ◽  
pp. 499-509
Author(s):  
Janet E. Hornby
Keyword(s):  
Cell Types ◽  
Random Motion ◽  
Chick Embryos ◽  
Collision Efficiency ◽  
20 Nm ◽  
Kidney Liver ◽  
Different Cell Types ◽  
Laminar Shear ◽  
Lyophobic Sols

Cell suspensions were prepared from the kidney, liver and heart of chick embryos of 5 or 8 days of incubation, and from the limb-buds of chick embryos of 5, 6, 7, 8 or 9 days of incubation. When these suspensions were aggregated under laminar shear in a Couette viscometer or random motion in a reciprocating shaker they obeyed the theoretical relationships derived for flocculating lyophobic sols. The values of the collision efficiency found for the different cell types under given conditions were used to calculate the force of interaction between cells of each type. The force of interaction ranged between 9 × 10−11 N (8-day heart) and 3 × 10−9 N (8-day liver). The forces of interaction between cells appear to be responsible for aligning the membranes of adjacent cells with a 10–20 nm gap. It is possible to arrange the cell types in a hierarchy based on the forces of interaction between them. The possible role of these forces in cell specificity is considered.

scholarly journals Precancerous niche (PCN), a product of fibrosis with remodeling by incessant chronic inflammation

4open ◽  
2019 ◽  
Vol 2 ◽  
pp. 11 ◽  
Author(s):  
Björn L.D.M. Brücher ◽  
Ijaz S. Jamall
Keyword(s):  
Extracellular Matrix ◽  
Chronic Inflammation ◽  
Genetic Material ◽  
Cell Communication ◽  
Cell Types ◽  
Complex Signaling ◽  
Different Cell Types ◽  
Multiple Signaling ◽  
Extracellular Environment

Fibroblasts are actively involved in the creation of the stroma and the extracellular matrix which are important for cell adhesion, cell–cell communication, and tissue metabolism. The role of fibrosis in carcinogenesis can be examined by analogy to tissues of various cancers. The orchestration of letters in the interplay of manifold components with signaling and crosstalk is incompletely understood but available evidence suggests a hitherto underappreciated role for fibrosis in carcinogenesis. Complex signaling and crosstalk by pathogenic stimuli evoke persistent subclinical inflammation, which in turn, results in a cascade of different cell types, ubiquitous proteins and their corresponding enzymes, cytokine releases, and multiple signaling pathways promoting the onset of fibrosis. There is considerable evidence that the body's attempt to resolve such a modified extracellular environment leads to further disruption of homeostasis and the genesis of the precancerous niche as part of the six-step process that describes carcinogenesis. The precancerous niche is formed and can be understood to develop as a result of (1) pathogenic stimulus, (2) chronic inflammation, and (3) fibrosis with alterations of the extracellular matrix, stromal rigidity, and mechano-transduction. This is why carcinogenesis is not just a process of aberrant cell growth with damaged genetic material but the role of the PCN in its entirety reveals how carcinogenesis can occur without invoking the need for somatic mutations.

scholarly journals Pancreatic α and β cells are globally phase-locked

2020 ◽  
Author(s):  
Huixia Ren ◽  
Yanjun Li ◽  
Chengsheng Han ◽  
Yi Yu ◽  
Bowen Shi ◽  
...  
Keyword(s):  
Islet Cells ◽  
Cell Types ◽  
Phase Oscillators ◽  
Β Cells ◽  
Oscillation Modes ◽  
Different Types ◽  
Glucagon And Insulin ◽  
Different Cell Types

ABSTRACTThe Ca2+ modulated pulsatile secretions of glucagon and insulin by pancreatic α and β cells play a key role in glucose metabolism and homeostasis. However, how different types of islet cells couple and coordinate via paracrine interactions to produce various Ca2+ oscillation patterns are still elusive. By designing a microfluidic device to facilitate long-term recording of islet Ca2+ activity at single cell level and simultaneously identifying different cell types in live islet imaging, we show heterogeneous but intrinsic Ca2+ oscillation patterns of islets upon glucose stimulation. The α and β cells oscillate in antiphase and are globally phase locked to various phase delays, causing fast, slow or mixed oscillations. A mathematical model of coupled phase oscillators quantitatively agrees with experiments and reveals the essential role of paracrine regulations in tuning the oscillation modes. Our study highlights the importance of cell-cell interactions to generate stable but tunable islet oscillation patterns.

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