Lipoproteins and Lipoprotein Lipase

Hamosh, Margit; Hamosh, Paul

doi:10.1002/cphy.cp030112

Cited by 8 publications

(9 citation statements)

References 347 publications

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“…The difference between the results may also partly be due to our use of diluted fat cell suspensions (1 -2% v/v) instead of dense cell concentrations (10% v/v or higher) because the accumulation of endogenous metabolites may inhibit the lipolytic action of catecholamines (Kather, 1990). Finally, only subcutaneous adipocytes have previously been studied in man (Hollenga et al, 1991;Langin et al, 1991), although these cells have a lower metabolic activity, including lipolysis (Hamosh et al, 1963;Fessler & Beck, 1965;Ostman et al, 1979) and PI/P2-receptor sensitivity (Hellmer et al, 1992), than omental fat cells. In agreement with this, our present data show that the P3-receptor agonistic effects of CGP 12177 are more pronounced in omental fat cells.…”

Section: Discussionmentioning

confidence: 99%

Evidence for a functional β₃‐adrenoceptor in man

Lönnqvist

Krief

Strosberg

et al. 1993

British J Pharmacology

152

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1. The existence of a functional beta 3-adrenoceptor in man was investigated by studying the lipolytic action of selective beta-adrenoceptor agents in isolated white omental and subcutaneous fat cells. 2. The non-selective beta 1/beta 2-adrenoceptor antagonist, CGP 12177 was lipolytic in both omental and subcutaneous fat cells. The intrinsic activity relative to isoprenaline was greater in omental than in subcutaneous cells. 3. Addition of the beta 2-adrenoceptor antagonist, ICI 118,551 and the beta 1-adrenoceptor antagonist CGP 20712A in combination or the non-selective beta-adrenoceptor antagonist propranolol alone (all 10(-7) M), induced a rightward shift of the dose-response curves for isoprenaline- and BRL37344-stimulated lipolysis of about 4 and 2 log-units, respectively. However, the antagonists did not alter lipolysis induced by CGP12177. 4. Several concentrations of beta-adrenoceptor antagonists were used to determine the pA2 values by Schild analysis. The values for CGP 20712A and ICI 118,551 (6.63 +/- 0.20 and 6.25 +/- 0.12) as antagonists of the lipolytic effects of CGP 12177 were over 2 units lower than the pA2 value for CGP 20712A against the response to the selective beta 1-agonist dobutamine (8.58 +/- 0.23) and the pA2 value for ICI 118,551 against the response to the selective beta 2-agonist terbutaline (9.15 +/- 0.26). 5. beta 3-Adrenoceptor mRNA expression, investigated with a polymerase chain reaction assay, was demonstrated in both types of adipocytes in the same cell preparations that had a lipolytic response to CGP 12177. 6. In conclusion, human white fat cells express an atypical beta-adrenoceptor in addition to beta 1- and beta 2-adrenoceptors. This receptor is stimulated more selectively by the beta1/beta2-antagonist CGP 12177 than by BRL 37344 and is poorly sensitive to blockade by selective beta1- and beta2-antagonists. On the basis of the pharmacological properties and the mRNA analyses, we suggest that this atypical receptor corresponds to the beta 3-adrenoceptor subtype.

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Section: Discussionmentioning

confidence: 99%

Evidence for a functional β₃‐adrenoceptor in man

Lönnqvist

Krief

Strosberg

et al. 1993

British J Pharmacology

152

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“…LPL is a membrane-bound enzyme found in the capillary lumen in many tissues that hydrolyzes triglycerides circulating in the blood, freeing up fatty acids that can be taken in by cells. The circulating triglycerides are directed to specific tissues by changes in LPL activity (Hamosh and Hamosh 1985;Herzberg 1991). LPL activity in tissues depends on the physiological state of the animal.…”

Section: Physiological and Biochemical Zoologymentioning

confidence: 99%

Physiology and Behavior Influence Lactation Efficiency in Northern Elephant Seals (Mirounga angustirostris)

McDonald

Crocker

2006

Physiological and Biochemical Zoology

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The efficiency with which mothers convert acquired energy into milk is a key determinant of the magnitude of parental in vestment in mammals; however, the mech~isms underlying lactation efficiency are poorly understood. Investigations on northern elephant seals have shown lactation efficiency, mea sured as the proportion of total energy expenditure that goes to the pup as milk, increases with age. In a cross-sectional study the physiological and behavioral determinants of lactation ef ficiency were investigated in eight young and seven prime (older) elephant seals by conducting behavioral observations and collecting milk, blood, and tissue on days 3 and 22 of lactation. Milk composition, circulating fatty acid and triglyc eride concentrations, and mammary and blubber lipoprotein lipase activity were determined. Prime females had significantly greater percent milk fat and circulating fatty acids on day 3 than did young females, but these differences disappeared by day 22. The ability for prime females to produce higher-energy milk early in lactation may allow them to increase lactation efficiency by increasing the rate of energy transfer. In addition, prime females spent significantly more time resting. A com bination of reduced activity and more rapid energy delivery likely explains the increase in lactation efficiency with age found in a previous study.

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“…In order to further characterize the nature of the membrane-bound material, we made the primary assumption that the material we observed in animal after animal (six calves and ten goats) in the majority of the intravascular macrophages was indeed a lipoprotein. The lipoproteins are generally divided into four categories: chylomicrons, very-low-density lipoproteins (VLDL), low-density lipoproteins (LDL), and high-density lipoproteins (HDL) (Hamosh and Hamosh, 1985). In cattle and sheep, serum HDL is the predominant lipoprotein; it carries 57-60% of serum lipids, transporting not only the lipids used in energy metabolism but also those used as a substrate for milk secretion (Evans et al, 1961;Cross et al, 1983).…”

Section: Introductionmentioning

confidence: 99%

Morphology of pulmonary intravascular macrophages (PIMs) in ruminants: Ultrastructural and cytochemical behavior of dense surface coat

et al. 1989

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Recent studies have indicated that pulmonary intravascular macrophages (PIMs) are a resident cell population which in structure and function resemble mature macrophages of the mononuclear phagocyte system (MPS) in various domestic species, particularly the ruminants. The ultrastructural features of PIMs of the goat and calf lungs were studied by using vascular perfusion and direct airway instillation of fixatives. Staining with tannic acid as a component of paraformaldehyde-glutaraldehydebased fixative revealed the presence of an electron-dense coat on the surface of the cell membrane of the PIMs. The surface coat disappeared after heparin infusion and after enzymatic digestion with lipolytic lipase, suggesting that the surface coat was predominantly lipoprotein in nature. The lipoprotein coat was organized in the form of a linear chain of spherical globules with a consistent periodicity created by the intervening translucent space between individual globules. The surface coat was separated from the outerleaflet of the cell membrane by an empty space measuring 35-39 nm in width. P I M s possessed a significant number of coated pits and coated vesicles, the cell organelles of receptor-mediated endocytosis of lipoproteins. In concurrence with the coated pits and vesicles, microtubules, multivesicular bodies, and lipoprotein-positive vesicles were also observed. It is conceivable that PIMs are involved in lipid metabolism and are the major source of vasoactive substances, which significantly influence both the dynamics of pulmonary circulation and the surfactant turnover of the ruminant lung.

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Lipoproteins and Lipoprotein Lipase

Abstract: The sections in this article are: History Lipoproteins Chylomicrons Very‐Low‐Density Lipoproteins Low‐Density Lipoproteins High‐Density Lipoproteins Lipoprotein Lipase History of Lipoprotein Lipase … Show more

Cited by 8 publications

References 347 publications

Evidence for a functional β₃‐adrenoceptor in man

Evidence for a functional β₃‐adrenoceptor in man

Physiology and Behavior Influence Lactation Efficiency in Northern Elephant Seals (Mirounga angustirostris)

Morphology of pulmonary intravascular macrophages (PIMs) in ruminants: Ultrastructural and cytochemical behavior of dense surface coat

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Lipoproteins and Lipoprotein Lipase

Abstract: The sections in this article are: History Lipoproteins Chylomicrons Very‐Low‐Density Lipoproteins Low‐Density Lipoproteins High‐Density Lipoproteins Lipoprotein Lipase History of Lipoprotein Lipase … Show more

Cited by 8 publications

References 347 publications

Evidence for a functional β3‐adrenoceptor in man

Evidence for a functional β3‐adrenoceptor in man

Physiology and Behavior Influence Lactation Efficiency in Northern Elephant Seals (Mirounga angustirostris)

Morphology of pulmonary intravascular macrophages (PIMs) in ruminants: Ultrastructural and cytochemical behavior of dense surface coat

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Evidence for a functional β₃‐adrenoceptor in man

Evidence for a functional β₃‐adrenoceptor in man