A special pattern of the smooth endoplasmic reticulum in the kidney of the snail Cryptomphalus aspersa

1976 ◽  
Vol 22 (3) ◽  
pp. 617-622
Author(s):  
R. Paniagua ◽  
J.J. Vazquez
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Membrane ◽  
Smooth Endoplasmic Reticulum ◽  
Glycogen Metabolism ◽  
Alpha Particles ◽  
Structural Pattern ◽  
Dark Cells ◽  
Beta Particles ◽  
Special Pattern

A special structural pattern of the smooth endoplasmic reticulum (SER) has been observed in the kidney of the snail Cryptomphalus aspersa. Two types of cells (clear and dark) cover the foldings of the renal sac; the dark cells are by far the most numerous. A cisterna of SER enveloping the nucleus appears invariably in both types of cells, with no disruptions, or small ones (from 50 to 90 nm) along its profile. The layer of cytoplasm lodged between the external nuclear membrane and this cisterna is found invariably to be from 0-20 to 0-25 mum in width. Glycogen is abundant in the cytoplasm as alpha particles, and also in the nucleus, but as beta particles. It is noteworthy that absolutely no glycogen is present in the layer of cytoplasm lodged between the nuclear membrane and the surrounding SER envelope. Long profiles of SER are also observed closely approaching and parallel to the plasma membrane of the dark cells. Considering the role of SER in glycogen metabolism in the kidney of the snail, the possible function of these cisternae as a support system ofr enzymes involved in the metabolism of glucides is discussed.

scholarly journals Role of p97 and Syntaxin 5 in the Assembly of Transitional Endoplasmic Reticulum

2000 ◽  
Vol 11 (8) ◽  
pp. 2529-2542 ◽  
Author(s):  
Line Roy ◽  
John J.M. Bergeron ◽  
Christine Lavoie ◽  
Rob Hendriks ◽  
Jennifer Gushue ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Secretory Pathway ◽  
Atp Hydrolysis ◽  
Smooth Endoplasmic Reticulum ◽  
Atp Depletion ◽  
Low Density ◽  
Transitional Endoplasmic Reticulum ◽  
Membrane Compartment ◽  
A Cell

Transitional endoplasmic reticulum (tER) consists of confluent rough and smooth endoplasmic reticulum (ER) domains. In a cell-free incubation system, low-density microsomes (1.17 g cc− 1) isolated from rat liver homogenates reconstitute tER by Mg2+GTP- and Mg2+ATP-hydrolysis–dependent membrane fusion. The ATPases associated with different cellular activities protein p97 has been identified as the relevant ATPase. The ATP depletion by hexokinase or treatment with either N-ethylmaleimide or anti-p97 prevented assembly of the smooth ER domain of tER. High-salt washing of low-density microsomes inhibited assembly of the smooth ER domain of tER, whereas the readdition of purified p97 with associated p47 promoted reconstitution. The t-SNARE syntaxin 5 was observed within the smooth ER domain of tER, and antisyntaxin 5 abrogated formation of this same membrane compartment. Thus, p97 and syntaxin 5 regulate assembly of the smooth ER domain of tER and hence one of the earliest membrane differentiated components of the secretory pathway.

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).

Liver alterations as a result of the 90-day continuous feeding of 2,3,7,8-tetrachlorodibenzo-p-dioxin

1986 ◽  
Vol 44 ◽  
pp. 364-365
Author(s):  
J.N. Turner ◽  
D.N. Collins
Keyword(s):  
Endoplasmic Reticulum ◽  
Smooth Endoplasmic Reticulum ◽  
Complex Mixture ◽  
Environmental Toxins ◽  
Bile Canaliculi ◽  
Cytoplasmic Vacuoles ◽  
Continuous Feeding ◽  
Tetrachlorodibenzo P Dioxin ◽  
Dose Levels

Chlorinated hydrocarbons are a highly toxic, ubiquitous class of environmental toxins of which 2,3,7,8- tetrachlorodibenzo-p-dioxin (TCDD) is the most toxic. PCB pyrolysates contain a complex mixture of these chemicals and have been shown to produce extensive alterations in the liver of guinea pig hepatocytes, including proliferated smooth endoplasmic reticulum (SER), concentric membrane arrays (CMA) which are a condensation of proliferated SER, and cytoplasmic vacuoles. A mechanism of membrane excretion into the bile canaliculi and sinusoids has been proposed to account for these alterations and their relationship to each other. This report demonstrates the proposed mechanism for a purified compound (TCDD) fed continuously for 90 days and further elucidates the role of the cytoplasmic vacuoles which are observed for dose levels at which no other alteration is present.

scholarly journals Association of glycogen synthase phosphatase and phosphorylase phosphatase activities with membranes of hepatic smooth endoplasmic reticulum.

1979 ◽  
Vol 83 (2) ◽  
pp. 348-356 ◽  
Author(s):  
R N Margolis ◽  
R R Cardell ◽  
R T Curnow
Keyword(s):  
Endoplasmic Reticulum ◽  
Glycogen Synthase ◽  
Close Contact ◽  
Smooth Endoplasmic Reticulum ◽  
Glycogen Synthesis ◽  
Glycogen Metabolism ◽  
Hepatic Glycogen ◽  
Phosphatase Activities ◽  
Regulatory Enzymes ◽  
Glycogen Particles

A detailed investigation was conducted to determine the precise subcellular localization of the rate-limiting enzymes of hepatic glycogen metabolism (glycogen synthase and phosphorylase) and their regulatory enzymes (synthase phosphatase and phosphorylase phosphatase). Rat liver was homogenized and fractionated to produce soluble, rough and smooth microsomal fractions. Enzyme assays of the fractions were performed, and the results showed that glycogen synthase and phosphorylase were located in the soluble fraction of the livers. Synthase phosphatase and phosphorylase phosphatase activities were also present in soluble fractions, but were clearly identified in both rough and smooth microsomal fractions. It is suggested that the location of smooth endoplasmic reticulum (SER) within the cytosome forms a microenvironment within hepatocytes that establishes conditions necessary for glycogen synthesis (and degradation). Thus the location of SER in the cell determines regions of the hepatocyte that are rich in glycogen particles. Furthermore, the demonstration of the association of synthase phosphatase and phosphorylase phosphatase with membranes of SER may account for the close morphological association of SER with glycogen particles (i.e., disposition of SER membranes brings the membrane-bound regulatory enzymes in close contact with their substrates).

The submicrosomal distribution of dolichol and dolichol phosphokinase activity in rat liver

1982 ◽  
Vol 60 (1) ◽  
pp. 36-41 ◽  
Author(s):  
Jack W. Rip ◽  
Kenneth K. Carroll
Keyword(s):  
High Pressure ◽  
Endoplasmic Reticulum ◽  
Rat Liver ◽  
Smooth Endoplasmic Reticulum ◽  
Glycoprotein Synthesis ◽  
Dolichyl Phosphate ◽  
Glycoprotein Processing ◽  
Specific Activities ◽  
High Concentrations

Microsomes were isolated from rat liver and fractionated into Golgi, smooth endoplasmic reticulum (SER), and rough endoplasmic reticulum (RER) components, and the purity of these fractions was determined. The dolichol content of each of the three fractions was estimated, using high-pressure liquid chromatography. Although highest concentrations (1940 ng/mg protein) were found in Golgi, the RER contained the largest absolute amounts. The presence of large quantities of dolichol in RER is consistent with the role of dolichol as an intermediate in asparagine-linked glycoprotein synthesis. RER and SER fractions contained high specific activities for dolichol phosphokinase, while the activity in Golgi was quite low. High concentrations of dolichol in Golgi and high dolichol phosphokinase activity in SER suggest that dolichol (and dolichyl phosphate) may be utilized in Golgi for glycoprotein processing and in the transmembrane movement of sugars such as galactose.

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

scholarly journals FINE STRUCTURAL LOCALIZATION OF ACYLTRANSFERASE ACTIVITY IN RAT HEPATOCYTES

1972 ◽  
Vol 20 (12) ◽  
pp. 1031-1040 ◽  
Author(s):  
FRANCINE M. BENES ◽  
JOAN A. HIGGINS ◽  
RUSSELL J. BARRNETT
Keyword(s):  
Heavy Metal ◽  
Endoplasmic Reticulum ◽  
Smooth Endoplasmic Reticulum ◽  
Rat Hepatocytes ◽  
Potassium Ferricyanide ◽  
Potassium Ferrocyanide ◽  
Significant Extent ◽  
Acyltransferase Activity ◽  
Structural Localization

A method for the fine structural localization of acyltransferases catalyzing the transfer of acyl groups from palmityl-coenzyme A (CoA) to α-glycerophosphate based on the formation of a heavy metal precipitate at the site of CoA release is described. In this method CoA released through the action of the enzyme is oxidized by potassium ferricyanide, which is reduced to potassium ferrocyanide and precipitates in the presence of cupric ions. Acyltransferase activity was found to survive both fixation in glutaraldehyde and incubation in the presence of the capture reagent system used for cytochemistry. Reaction product marking the enzyme activity was located within the cisternae of the rough endoplasmic reticulum and to lesser, but significant extent, within the membranous envelope of the smooth endoplasmic reticulum. Reaction product was not associated to any significant extent with other membranous organelles. The significance of these observations in terms of the role of acyltransferases in liver function is discussed.

scholarly journals Macroautophagy Involved in Testosterone Synthesis in Leydig Cells of Male Dairy Goats (Capra Hircus)

2021 ◽  
Author(s):  
Hong Chen ◽  
Kexin Chen ◽  
Fange Zhao ◽  
Yihan Guo ◽  
Yue Liang ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Leydig Cells ◽  
Smooth Endoplasmic Reticulum ◽  
Capra Hircus ◽  
Dairy Goats ◽  
Serum Luteinizing Hormone ◽  
Ultrastructural Characteristics ◽  
Autophagy Activity ◽  
Testosterone Synthesis

Abstract Background Testosterone is an important steroid hormone that is indispensable for male sexual development and the reproductive system. Leydig cells (LCs), where autophagy extremely active, reside in the testicular interstitium and are the major sites of testosterone production. However, the ultrastructural characteristics and the functional role of autophagy in LCs of livestock remain unknown. This study was to investigate the role of autophagy in LCs testosterone synthesis of dairy goats at juvenile, pubertal, and adult stages. Results In the present study, morphological results showed that the steroidogenic activity and ultrastructure of the LCs were altered with increasing age. Serum luteinizing hormone and testosterone levels were significantly elevated with sexual maturation. Organelles involved in testosterone synthesis, e.g., smooth endoplasmic reticulum, mitochondria, and lipid droplets, were abundantly distributed within the cytoplasm of LCs in adult testes. However, further studies demonstrated that selective autophagy (including lipophagy and mitophagy) did not participate in the synthesis of testosterone in LCs. In contrast, the autophagy activity was enhanced in the testes at puberty and adulthood compared to that at the juvenile stage. Moreover, a number of different autophagosomes, including phagophores and autolysosomes, were observed within the cytoplasm of LCs. Conclusions Together, our results reveal that macroautophagy is involved in testosterone synthesis mainly through degrading mitochondria and endoplasmic reticulum in the LCs of dairy goats.

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