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.

Morphological and biochemical analyses of changes in rat hepatocytes related to wine and ethanol consumption

1984 ◽  
Vol 42 ◽  
pp. 232-233
Author(s):  
S.M. Geyer ◽  
C.L. Mendenhall ◽  
J.T. Hung ◽  
E.L. Cardell ◽  
R.L. Drake ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Enzyme Activity ◽  
Malic Enzyme ◽  
Smooth Endoplasmic Reticulum ◽  
Rat Hepatocytes ◽  
Mature Male ◽  
Treatment Groups ◽  
Malic Enzyme Activity ◽  
Biochemical Analyses

Thirty-three mature male Holtzman rats were randomly placed in 3 treatment groups: Controls (C); Ethanolics (E); and Wine drinkers (W). The animals were fed synthetic diets (Lieber type) with ethanol or wine substituted isocalorically for carbohydrates in the diet of E and W groups, respectively. W received a volume of wine which provided the same gram quantity of alcohol consumed by E. The animals were sacrificed by decapitation after 6 weeks and the livers processed for quantitative triglycerides (T3), proteins, malic enzyme activity (MEA), light microscopy (LM) and electron microscopy (EM). Morphometric analysis of randomly selected LM and EM micrographs was performed to determine organellar changes in centrilobular (CV) and periportal (PV) regions of the liver. This analysis (Table 1) showed that hepatocytes from E were larger than those in C and W groups. Smooth endoplasmic reticulum decreased in E and increased in W compared to C values.

scholarly journals DIFFERENTIATION OF ENDOPLASMIC RETICULUM IN HEPATOCYTES

1971 ◽  
Vol 49 (2) ◽  
pp. 264-287 ◽  
Author(s):  
A. Leskes ◽  
P. Siekevitz ◽  
G. E. Palade
Keyword(s):  
Endoplasmic Reticulum ◽  
Phosphatase Activity ◽  
Rough Endoplasmic Reticulum ◽  
Specific Activity ◽  
Smooth Endoplasmic Reticulum ◽  
Rat Hepatocytes ◽  
Adult Level ◽  
Enzyme Specific Activity ◽  
Cytochemical Reaction ◽  
And Control

The distribution of glucose-6-phosphatase activity in rat hepatocytes during a period of rapid endoplasmic reticulum differentiation (4 days before birth-1 day after birth) was studied by electron microscope cytochemistry. Techniques were devised to insure adequate morphological preservation, retain glucose-6-phosphatase activity, and control some other possible artifacts. At all stages examined the lead phosphate deposited by the cytochemical reaction is localized to the endoplasmic reticulum and the nuclear envelope. At 4 days before birth, when the enzyme specific activity is only a few per cent of the adult level, the lead deposit is present in only a few hepatocytes. In these cells a light deposit is seen throughout the entire rough-surfaced endoplasmic reticulum. At birth, when the specific activity of glucose-6-phosphatase is approximately equal to that of the adult, nearly all cells show a positive reaction for the enzyme and, again, the deposit is evenly distributed throughout the entire endoplasmic reticulum. By 24 hr postparturition all of the rough endoplasmic reticulum, and in addition the newly formed smooth endoplasmic reticulum, contains heavy lead deposits; enzyme activity at this stage is 250% of the adult level. These findings indicate that glucose-6-phosphatase develops simultaneously within all of the rough endoplasmic reticulum membranes of a given cell, although asynchronously in the hepatocyte population as a whole. In addition, the enzyme appears throughout the entire smooth endoplasmic reticulum as the membranes form during the first 24 hr after birth. The results suggest a lack of differentiation within the endoplasmic reticulum with respect to the distribution of glucose-6-phosphatase at the present level of resolution.

Biogenesis of Smooth Endoplasmic Reticulum in Hepatocytes of Phenobarbital Treated Rats

1974 ◽  
Vol 32 ◽  
pp. 308-309
Author(s):  
Joan A. Higgins
Keyword(s):  
Endoplasmic Reticulum ◽  
Rough Endoplasmic Reticulum ◽  
Specific Activity ◽  
Smooth Endoplasmic Reticulum ◽  
Rat Hepatocytes ◽  
Membrane Formation ◽  
Drug Detoxification ◽  
Marked Proliferation

In response to intraperitoneal injections of phenobarbital there is a marked proliferation of smooth endoplasmic reticulum membranes (s.e.r.) of rat hepatocytes, with little change in other membranous organelles. This increased membrane formation is accompanied by a rise in the specific activity of the enzymes involved in drug detoxification initially in the rough endoplasmic reticulum (r.e.r.) followed by a rise in the s.e.r. There is also an increased accumulation of glycerophospholipid in the newly formed s.e.r.

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.

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 STUDIES ON THE BIOGENESIS OF SMOOTH ENDOPLASMIC RETICULUM MEMBRANES IN LIVERS OF PHENOBARBITAL-TREATED RATS

1972 ◽  
Vol 55 (2) ◽  
pp. 282-298 ◽  
Author(s):  
Joan A. Higgins ◽  
Russell J. Barrnett
Keyword(s):  
Endoplasmic Reticulum ◽  
Rat Liver ◽  
Specific Activity ◽  
Smooth Endoplasmic Reticulum ◽  
Normal Liver ◽  
Subsequent Treatment ◽  
Cell Fractionation ◽  
Acyltransferase Activity ◽  
Normal Rat

The localization of acyltransferases involved in acylation of α-glycerophosphate, during phenobarbital induced proliferation of smooth endoplasmic reticulum (ser) membranes, has been investigated using cytochemical and cell fractionation techniques. In cytochemical studies of normal rat liver, reaction product marking acyltransferase activity was associated to the greatest extent with the rough endoplasmic reticulum (rer) membranes and to a lesser extent with ser membranes. In liver from phenobarbital-treated rats, reaction product was largely restricted to ser membranes. The specific activity of the acyltransferases of rough microsomes from normal rat liver was higher than that of the smooth microsomes. On injection of phenobarbital, this fell rapidly after three injections to a low level, at which it remained during subsequent treatment. The specific activity of the smooth microsomes, on injection of phenobarbital, rose to a peak 12 hr after the first injection, after which it fell to a level at an activity above that of smooth microsomes of normal liver. A mechanism is postulated for the biogenesis of smooth membranes in which the phospholipid is synthesized in situ and the protein is synthesized in the rer and moves to the site of newly synthesized phospholipid, where it is inserted to produce a whole membrane.

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.

scholarly journals Effect of insulin on ultrastructure and glycogenesis in primary cultures of adult rat hepatocytes

1977 ◽  
Vol 74 (3) ◽  
pp. 878-900 ◽  
Author(s):  
D Bernaert ◽  
JC Wanson ◽  
P Drochmans ◽  
A Popowski
Keyword(s):  
Endoplasmic Reticulum ◽  
Smooth Endoplasmic Reticulum ◽  
Primary Cultures ◽  
Active Form ◽  
Rat Hepatocytes ◽  
High Concentration ◽  
Trophic Effect ◽  
Adult Rat ◽  
Glycogenosis Type ◽  
High Concentrations

Insulin in the presence of high concentrations of glucose has a beneficial trophic effect on the development of primary cultures of hepatocytes. Compared to the situation observed in hormone-free control cultures, the flattening of the reaggregated hepatocytes is enhanced, and the reconstituted cell trabeculae are enlarged and tend to form a confluent monolayer after 3 days; the survival time is prolonged from 3 to 5 or 6 days. Ultrastructural modifications are also initiated by insulin; numerous glycogen particles appear after 24 h, in between the cisternae of the proliferated smooth endoplasmic reticulum. After 48 h, large amounts of glycogen are stored, and numerous polysomes are present. A small number of cells showed an increased synthesis of lipid droplets in the lumen of the smooth endoplasmic reticulum and form liposomes at the same time. After 72 h, cytolysomes filled with glycogen develop, simulating glycogenosis type II. Simultaneously, microtubules and microfilaments, closely related to numerous polysomes, appear in cytoplasmic extensions constituting undulating membranes. The biochemical data demonstrate that, in the absence of insulin, a high concentration of glucose stimulates glycogenesis and hinders glycogenolysis. This effect of glucose on polysaccharide synthesis is progressively lost. The addition of insulin to the culture induces after 48 and 72 h, a three- to fivefold increase of the glucose incorporation into glycogen, as compared to the controls. The presence of insulin is required to maintain the hepatocyte's capacity to store glycogen. Glycogen synthetase is converted into its active form under the influence of glucose. Insulin increases the rate of activation.

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