Perfused Adipose Tissue Research Articles

Determining Contrast Medium Dose and Rate on Basis of Lean Body Weight: Does This Strategy Improve Patient-to-Patient Uniformity of Hepatic Enhancement during Multi–Detector Row CT?

To prospectively evaluate the use of lean body weight (LBW) as the main determinant of the volume and rate of contrast material administration during multi-detector row computed tomography of the liver. This HIPAA-compliant study had institutional review board approval. All patients gave written informed consent. Four protocols were compared. Standard protocol involved 125 mL of iopamidol injected at 4 mL/sec. Total body weight (TBW) protocol involved 0.7 g iodine per kilogram of TBW. Calculated LBW and measured LBW protocols involved 0.86 g of iodine per kilogram and 0.92 g of iodine per kilogram calculated or measured LBW for men and women, respectively. Injection rate used for the three experimental protocols was determined proportionally on the basis of the calculated volume of contrast material. Postcontrast attenuation measurements during portal venous phase were obtained in liver, portal vein, and aorta for each group and were summed for each patient. Patient-to-patient enhancement variability in same group was measured with Levene test. Two-tailed t test was used to compare the three experimental protocols with the standard protocol. Data analysis was performed in 101 patients (25 or 26 patients per group), including 56 men and 45 women (mean age, 53 years). Average summed attenuation values for standard, TBW, calculated LBW, and measured LBW protocols were 419 HU +/- 50 (standard deviation), 443 HU +/- 51, 433 HU +/- 50, and 426 HU +/- 33, respectively (P = not significant for all). Levene test results for summed attenuation data for standard, TBW, calculated LBW, and measured LBW protocols were 40 +/- 29, 38 +/- 33 (P = .83), 35 +/- 35 (P = .56), and 26 +/- 19 (P = .05), respectively. By excluding highly variable but poorly perfused adipose tissue from calculation of contrast medium dose, the measured LBW protocol may lessen patient-to-patient enhancement variability while maintaining satisfactory hepatic and vascular enhancement.

An in situ perfusion protocol of rat epididymal adipose tissue useful in metabolic studies

Experimental approaches involving the perfusion of tissues and organs offer the advantage of improved physiological relevance over the use of isolated tissues or cells while at the same time being much more controlled and tissue-specific than studies in vivo. Nevertheless, there have been few metabolic studies performed in perfused white adipose tissue, largely because of the difficulty of the surgical technique involved. Although some methods have been described, they are difficult to use as perfusion protocols and their reproducibility is poor. We have modified a rat perfusion method, based on a modification of the Ho and Meng technique, for use with epididymal white adipose tissue (eWAT), and we present it here as a protocol to be reproduced. We also offer surgical solutions for the most common variants of vessel distributions in rats. Using the protocol described here, the perfused adipose tissue is viable and metabolically active, as indicated by the maintenance of tissue ATP levels and adiponectin secretion and by endogenous lipolysis regulation. Moreover, there is a high level of lipoprotein lipase activity in the endothelium of the tissue, which is heparin-releasable. Thus, this method is a useful and reproducible tool that allows the perfusion of eWAT for use in metabolic studies.

Restricted passage of insulin across capillary endothelium in perfused rat adipose tissue.

Passage of insulin across capillary endothelium was monitored in perfused rat parametrial adipose tissue by the effect of intra-arterially infused insulin on oxidation of [U-14C]glucose to CO2. Glucose oxidation was constant at 34 nmol C.g-1.min-1 for 90 min in tissues perfused with 0 or 50 microU/ml. The rate of oxidation was doubled in 90 min at 100 microU/ml and maximal (4 X control) in 40 min at 200 microU/ml and in 20-30 min at 500 microU/ml. The slow decline in oxidation rate when insulin infusion was stopped suggested that insulin was sequestered in the tissue. Although half-maximal response to insulin occurred in perfused tissues at 100 microU/ml, it occurred at 8 microU/ml in incubated adipocytes and at 30 microU/ml in incubated tissue. In addition, the time required for maximal response to insulin was longer in perfused adipose tissue than in incubated cells and tissues. The data indicate that transfer of insulin from blood to parenchymal cells in perfused tissue was restricted. The minimal amount of insulin needed for a response by adipocytes in perfused tissue was estimated to be less than 1% of that in blood. Our findings are consistent with the concept that insulin is transferred across capillary endothelium by a receptor-mediated process.

Uptake of blood triglyceride by various tissues.

AbstractTriglycerides are transported in the blood in chylomicrons and very low density lipoproteins. Electron microscopic studies indicate that these particles, which range in diameter from 0.03–0.6 μ, cannot cross the capillary endothelium in most tissues. There is now considerable evidence that the triglycerides are hydrolyzed to free fatty acids (FFA) during uptake and that this process is catalyzed by lipoprotein lipase. The enzyme is found in nearly all tissues that utilize circulating triglyceride, and the level of activity, in individual tissues, varies with nutritional and physiological states that affect triglyceride uptake, such as fasting, diabetes and pregnancy. Studies in perfused adipose tissue with doubly labeled chylomicrons showed that hydrolysis occurs outside of the blood stream. Two‐thirds of the fatty acids are incorporated into tissue triglyceride and the rest are release as FFA, with glycerol, to the blood. Infusion of heparin causes immediate release of lipoprotein lipase activity to the blood and decreases the amount of chylomicron‐triglyceride hydrolyzed by the tissue. Electron microscopic cytochemical studies showed that hydrolysis of blood glycerides by lipoprotein lipase in adipose tissue occurs within the capillary endothelial cells and in the subendothelial space near the pericytes, but not in the capillary lumen or near the fat cells. The results indicate that the fatty acids of chylomicrons cross the capillary endothelium as glycerides and FFA, within a membrane‐bounded system, and cross the extravascular space to the fat cells as FFA.

FFA-3H uptake by perfused adipose tissue: electron microscopic autoradiographic study.

FFA-3H uptake by perfused adipose tissue: electron microscopic autoradiographic study.

METABOLISM OF CHYLOMICRONS AND TRIGLYCERIDE EMULSIONS BY PERFUSED RAT ADIPOSE TISSUE.

The uptake and metabolism of chylomicrons and artificial emulsions of triglycerides by adipose tissue has been studied in the perfused parametrial fat body of the rat. The triglyceride preparations were labeled with either glyceryl-C14 or with glyceryl-C14 and palmitate-H3. The uptake of both chylomicrons and emulsions was proportional to the blood triglyceride concentration and to the duration of infusion; the uptake of chylomicron triglycerides was about 40% greater than that of the artificial emulsion. About two-thirds of the triglycerides removed were hydrolyzed to glycerol and fatty acids and the rest was retained, without being hydrolyzed, in the fat cells. The uptake and metabolism of triglycerides was greatly reduced when the fat donors were deprived of food for 2 days. About 70% of the fatty acids cleaved from blood triglycerides were incorporated into tissue lipids, whereas less than 15% of those infused as free fatty acids were esterified by the perfused adipose tissue. Labeled glycerol was released to the venous blood for several minutes after the blood stream had been flushed of labeled triglycerides. The findings suggest that a major part of the hydrolysis of blood triglycerides occurred after the triglycerides had been removed from the blood stream.

PERFUSION OF RAT ADIPOSE TISSUE.

A technique is described for perfusing the parametrial fat pad of the rat. The rate of flow through the tissue was dependent on temperature, pressure, and the protein composition of the perfusing fluid. The latter also had a pronounced effect on the rate of edema formation in the tissue. The rate of fatty acid release by perfused adipose tissue was affected by the nutritional state of the fat donor and by the composition of the perfusing fluid. Tissue from fed rats did not release fatty acids. Adipose tissue from fasted rats released fatty acids when the tissue was perfused with diluted blood (1.10) or 4% albumin solution but not when perfused with 8% albumin. Perfused tissue released fatty acids at a much faster rate than did incubated tissue. Diluted blood and serum inhibited the release of fatty acids by incubated adipose tissue.

Effect of Hydrocortisone, Corticosterone, and Cortisone on Visceral and Total Body Fat in Albino Mice

Effect of Hydrocortisone, Corticosterone, and Cortisone on Visceral and Total Body Fat in Albino Mice