scholarly journals METABOLIC AND ULTRASTRUCTURAL CHANGES INDUCED IN ADIPOSE TISSUE BY INSULIN

1960 ◽  
Vol 8 (1) ◽  
pp. 83-101 ◽  
Author(s):  
Russell J. Barrnett ◽  
Eric G. Ball
Keyword(s):  
Adipose Tissue ◽  
Plasma Membrane ◽  
Plasma Membranes ◽  
Morphological Changes ◽  
Ultrastructural Changes ◽  
Cytoplasmic Matrix ◽  
Smooth Membrane ◽  
Metabolic Action ◽  
Rat Adipose Tissue

The addition in vitro of insulin to rat adipose tissue (epididymal) produces marked metabolic changes which may be followed by measurement of the net gas exchange of the tissue. Using this method to monitor the metabolic action of insulin, concomitant observations with the electron microscope on the tissue have been made. These reveal that pronounced morphological changes are induced by insulin. The plasma membranes of the adipose cells become invaginated at many sites to form minute finger-like indentations. Numerous tiny, membrane-bounded vesicles are also present and arranged in relationship to the plasma membrane in such a way as to suggest that their formation occurred when a recessed fold was pinched off. Deeper in the cytoplasm, especially in specimens that had been incubated a longer time, numerous large, smooth, membrane-limited vesicles are seen. Finally, in these incubated specimens the cytoplasmic matrix has lost much of its granular nature, small lipid droplets are frequently found in the cytoplasm and suggestive changes have occurred in mitochondria. In control specimens, incubated without insulin for identical periods of time, indentations and vesicles in the plasma membrane are sparse at best and no vesicles or membrane-bound spaces appear deeper in the cytoplasm. The metabolic and morphologic changes induced by insulin seem to be interdependent events. Both changes appear to be initiated rapidly and concomitantly in the tissue. Both processes are initiated by insulin at concentrations considered to be physiological, 0.004 µg. (100 µunits) per ml. Insulin treated with alkali fails to initiate either process. It is concluded that insulin initiates pinocytosis in rat adipose tissue and the possible significance of this process in the mode of action of insulin is discussed.

scholarly journals Effects of Prolactin in Vitro on Fatty Acid Synthesis in Rat Adipose Tissue

1959 ◽  
Vol 234 (12) ◽  
pp. 3111-3114 ◽  
Author(s):  
Albert I. Winegrad ◽  
Walter N. Shaw ◽  
Francis D.W. Lukens ◽  
William C. Stadie
Keyword(s):  
Adipose Tissue ◽  
Fatty Acid ◽  
Fatty Acid Synthesis ◽  
Acid Synthesis ◽  
Rat Adipose Tissue

scholarly journals Galanin inhibits leptin expression and secretion in rat adipose tissue and 3T3-L1 adipocytes

2004 ◽  
Vol 33 (1) ◽  
pp. 11-19 ◽  
Author(s):  
RY Li ◽  
HD Song ◽  
WJ Shi ◽  
SM Hu ◽  
YS Yang ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Mrna Expression ◽  
Vital Role ◽  
Dependent Manner ◽  
Protein Levels ◽  
Orexigenic Peptide ◽  
Fat Depot ◽  
Rat Adipose Tissue ◽  
Leptin Expression

In addition to serving as a fat depot, adipose tissue is also considered as an important endocrine organ that synthesizes and secretes a number of factors. Leptin is an adipocyte-derived hormone that plays a vital role in energy balance. Expression of leptin is regulated by dietary status and hormones. In the present study, we report that galanin, an orexigenic peptide, inhibits leptin expression and secretion in rat adipose tissue and in 3T3-L1 adipocytes. Treatment with galanin (25 micro g/animal) induced approximately 46% down-regulation of leptin secretion at 15 min, followed by 40, 37 and 47% decreases in leptin secretion at 1, 2 and 4 h respectively. Although Northern blot analysis of adipose tissue from the same animals showed that leptin mRNA expression in adipose tissue was unaffected by galanin treatment for 2 h, galanin treatment for 4 h led to decline of leptin mRNA expression in a dose-dependent manner. Meanwhile, treating the rats with galanin had no effect on leptin mRNA expression in the hypothalamus. The inhibitory action of the galanin on leptin mRNA and protein levels was also observed in vitro. When incubated with 10 nM galanin for 48 h, leptin mRNA expression and protein secretion also decreased in 3T3-L1 adipocytes. On the other hand, galanin was found not only to express in rat adipose tissue, but also to increase about 8-fold after fasting. Based on these data, we speculate that increased galanin expression in rat adipose tissue after fasting may be involved in reducing leptin expression and secretion in fasting rats.

Effects of hormones on cyclic AMP release from rat adipose tissue in vitro

FEBS Letters ◽  
1974 ◽  
Vol 49 (1) ◽  
pp. 65-69 ◽  
Author(s):  
P. Zumstein ◽  
J. Zapf ◽  
E.R. Froesch
Keyword(s):  
Adipose Tissue ◽  
Cyclic Amp ◽  
Adipose Tissue In Vitro ◽  
Rat Adipose Tissue

scholarly journals Surface membrane vesicles from mononuclear cells stimulate erythroid stem cells to proliferate in culture

Blood ◽  
1982 ◽  
Vol 60 (3) ◽  
pp. 583-594 ◽  
Author(s):  
N Dainiak ◽  
CM Cohen
Keyword(s):  
Plasma Membrane ◽  
Plasma Membranes ◽  
Mononuclear Cells ◽  
Surface Membrane ◽  
Freeze Fracture ◽  
Membrane Vesicles ◽  
Cell Types ◽  
Target Cells ◽  
Freeze Fracture Electron Microscopy

Abstract In order to examine the contribution of cell surface materials to erythroid burst-promoting activity (BPA), we separated media conditioned by a variety of human cell types into pellets and supernatants by centrifugation. When added to serum-restricted cultures of nonadherent human marrow cells, pellets contained about half of the total stimulatory activity. Freeze-fracture electron microscopy of the pellets revealed the presence of unilamellar membrane vesicles ranging from 0.10 to 0.40 microM in diameter. The amount of BPA in culture increased with added vesicle concentration in a saturable fashion. Preparation of leukocyte conditioned medium (LCM) from 125I-wheat germ agglutinin labeled cells and studies comparing the glycoprotein composition of vesicles with that of leukocyte plasma membranes suggest that LCM-derived vesicles are of plasma membrane origin. Moreover, partially purified leukocyte plasma membrane preparations also contained BPA. While disruption of vesicles by freezing/thawing and hypotonic lysis did not alter BPA, heat, trypsin, or pronase treatment removed greater than 65% of BPA, implying that vesicle surface rather than intravesicular molecules express BPA. Results of BPA assays performed in two-layer clots indicated that proximity to target cells is required for vesicle BPA expression. We conclude that membrane vesicles spontaneously shed from cell surfaces may be important regulators of erythroid burst proliferation in vitro.

Metabolic influences on enzymes of glycogen synthesis and breakdown in adipose tissue

1964 ◽  
Vol 207 (6) ◽  
pp. 1215-1220 ◽  
Author(s):  
Alisa Gutman ◽  
Eleazar Shafrir
Keyword(s):  
Adipose Tissue ◽  
Protein Content ◽  
Glycogen Synthesis ◽  
Total Activity ◽  
Epididymal Adipose Tissue ◽  
Control Value ◽  
Prolonged Fast ◽  
Rat Adipose Tissue

Rat adipose tissue from different body sites was shown to contain uridine diphosphoglucose (UDPG)-transglucosylase activity, which on the basis of protein content was comparable to or higher than that reported for muscle or liver. In epididymal adipose tissue, the activity of UDPG-glycogen transglucosylase and phosphorylase, as well as the content of glycogen per wet weight, decreased with increasing age of the animals in parallel with the decrease of tissue protein content. On prolonged fast the activity of UDPG-glycogen transglucosylase and phosphorylase per milligram protein dropped by 25–50% of the control value. On refeeding, the extent of changes was variable but, in general, at 24 hr control or higher levels of activity were reached and at 48 hr the activities were elevated. The ratio of glucose 6-phosphate independent activity of UDPG-glycogen transglucosylase to total activity was not affected by fasting and refeeding or by the administration of glucose with insulin. In adrenalectomized rats, with high adipose tissue glycogen, no change in UDPG-glycogen transglucosylase was found, whereas the levels of phosphorylase were elevated. Epinephrine in vivo and in vitro did not affect the activity of UDPG-glycogen transglucosylase of adipose tissue.

scholarly journals Properties of phosphatidate phosphohydrolase in rat adipose tissue

1994 ◽  
Vol 301 (3) ◽  
pp. 793-799 ◽  
Author(s):  
S C Jamdar ◽  
W F Cao
Keyword(s):  
Adipose Tissue ◽  
Plasma Membranes ◽  
Lipid A ◽  
Mesangial Cell ◽  
Intraperitoneal Administration ◽  
Subcellular Fractions ◽  
Phosphatidate Phosphohydrolase ◽  
Membrane Bound ◽  
Rat Adipose Tissue ◽  
Triton X

Previously we have identified the presence of two different phosphatidate phosphohydrolase (PPH) activities in rat adipose tissue, based on Mg(2+)-dependency. In the present investigation, we have further characterized these isoenzymes, using both aqueous dispersed and membrane-bound phosphatidate as substrates and differentiated these activities on the basis of both Mg(2+)-dependency and N-ethylmaleimide (NEM)-sensitivity. These two distinguishing criteria gave identical estimates of PPH activities present in the different subcellular fractions. The microsomal and cytosol fractions contained mainly the Mg(2+)-dependent (NEM-sensitive) form, which was inhibited by various thiol reagents, was inactivated by heating at 55 degrees C for 20 min, and was decreased significantly within 2 h after intraperitoneal administration of cystamine (200 mg/kg). Such treatments had no effects on the Mg(2+)-independent (NEM-insensitive) form of PPH, which was mainly located in the plasma membranes, mitochondrial and microsomal fractions. Addition of Lipid A and guanosine 5′-[gamma-thio]triphosphate to the assay mixture had no effect on the PPH activities. The Mg(2+)-independent PPH form, which was thermostable in the intact subcellular fractions, became thermolabile when these fractions were disrupted in the presence of Triton X-100. The present studies demonstrate that: (1) the thermostability is not a satisfactory index to differentiate these isoenzymes; (2) the thiol/disulphide exchange may be involved in the regulation of Mg(2+)-dependent PPH activity; and (3) the PPH isoenzymes do not seem to be under G-protein control in adipose tissue, as reported previously in the mesangial cell line.

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