Variations in 35SO4 incorporation into glycosaminoglycans along canine coronary arteries. A possible index of artery wall stress.
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Focal areas of accentuated wall stress along the course of canine coronary arteries may be revealed by the level of 35SO4 incorporation into glycosaminoglycans (GAG). In the anterior descending artery, 35SO4 incorporation in higher in the proximal than in the distal region and may be extraordinarily high as the vessel enters a proximally located muscle bridge and at the takeoff region of multidirectional branches. In the circumflex artery, the incorporation also is higher in the proximal than in the distal region and is high at the genu where the posterior descending artery forms. There are differences in uptake of 35SO4 in vessels even when the arteries arise from the same vascular bed.this was shown by the higher incorporation in the left coronary artery than in the right coronary artery. A general anatomical agreement exists between these sites of high 35SO4 incorporation and previously described locations of interval elastic disruption ans proliferation of intimal connective tissue in the dog. (+info)
Measurement of myocardial glucose uptake in patients with ischemic cardiomyopathy: application of a new quantitative method using regional tracer kinetic information.
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Quantification of myocardial glucose uptake (MGU) by 18F-fluoro-2-deoxyglucose (FDG) using PET may be inaccurate, because the correction factor that relates myocardial FDG uptake to MGU, the lumped constant (LC), is not a true constant. Recent studies have shown that analysis of FDG time-activity curves allows determination of individual LCs and that variable LCs yield accurate determination of MGU. We compared the magnitude of the LC in different regions of the heart in patients with ischemic cardiomyopathy. METHODS: Twenty patients with ischemic cardiomyopathy and an average ejection fraction of 33% underwent dynamic 13N-ammonia and FDG PET. We determined myocardial perfusion and MGU in 177 regions classified as control (71 regions), mismatch (50 regions) and match (56 regions), according to findings on PET and echocardiography. Regional MGU was calculated with both regional LCs and a fixed LC of 0.67. RESULTS: All results were expressed as mean +/- SD. Myocardial perfusion was highest in control regions (0.52+/-0.18 mL/g/min), reduced in mismatch regions (0.43+/-0.19 mL/g/min; P < 0.05 versus control) and severely reduced in match regions (0.28+/-0.17 mL/g/min; P < 0.001 versus control and mismatch). Regional LCs ranged from 0.45 to 1.30 and differed between patients (P < 0.001). Regional LCs were similar in regions diagnosed as control (0.78+/-0.23), mismatch (0.80+/-0.24) and match (0.72+/-0.21). MGU (micromol/g/min) calculated by regional LCs was similar in control (0.52+/-0.16) and mismatch (0.49+/-0.19) regions and decreased in match regions (0.31+/-0.12, P < 0.001). The agreement between MGU calculated with variable and fixed LCs was poor. CONCLUSION: The LC used in the calculation of MGU was not affected by regional differences in the metabolic state of the myocardium. However, the LC varied substantially between patients in control, mismatch and match regions. These findings indicate that quantitative measurements of MGU using a fixed LC must be interpreted with caution. (+info)
A novel potential application for 99mTc-HMPAO: endothelial cell labeling for in vitro investigation of cell-biomaterial interactions.
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Good adherence of endothelial cells (ECs) seeded on vascular prostheses and cell retention under flow conditions are important factors to consider in the use of functionalized prostheses in vascular surgery. Because 111In-oxine radiolabeling presents disadvantages, we wondered whether, because of its well-known physical properties, 99mTc-hexamethyl propyleneamine oxime (HMPAO or exametazime) could be used. METHODS: The cytotoxicity of unlabeled HMPAO and 99mTc-HMPAO at increasing concentrations and activities was tested on monolayers of the EC line EA-hy-926. The influence of temperature and time on tracer incorporation into cells was also tested. The optimal labeling conditions were applied to evaluate the retention of ECs seeded on polyester grafts under flow conditions by gamma camera detection. RESULTS: The activity of 10 MBq/10(6) cells corresponding to 4.5 microg/10(6) cells of unlabeled HMPAO, applied for 3 h at 37 degrees C (cellular uptake = 18%), was the best compromise between the maintenance of cell viability and metabolic activity and efficient detection by the gamma camera. Spontaneous leakage was observed and analyzed by high-performance liquid chromatography. A cell loss of 13% after 180-min exposure to shear stress was obtained. CONCLUSION: Our data thus indicate the feasibility of using such a radiolabeling technique to investigate EC-biomaterial interactions. (+info)
PET imaging of adrenal cortical tumors with the 11beta-hydroxylase tracer 11C-metomidate.
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The purpose of the study was to evaluate PET with the tracer 11C-metomidate as a method to identify adrenal cortical lesions. METHODS: PET with 11C-metomidate was performed in 15 patients with unilateral adrenal mass confirmed by CT. All patients subsequently underwent surgery, except 2 who underwent biopsy only. The lesions were histopathologically examined and diagnosed as adrenal cortical adenoma (n = 6; 3 nonfunctioning), adrenocortical carcinoma (n = 2), and nodular hyperplasia (n = 1). The remaining were noncortical lesions, including 1 pheochromocytoma, 1 myelolipoma, 2 adrenal cysts, and 2 metastases. RESULTS: All cortical lesions were easily identified because of exceedingly high uptake of 11C-metomidate, whereas the noncortical lesions showed very low uptake. High uptake was also seen in normal adrenal glands and in the stomach. The uptake was intermediate in the liver and low in other abdominal organs. Images obtained immediately after tracer injection displayed high uptake in the renal cortex and spleen. The tracer uptake in the cortical lesions increased throughout the examination. For quantitative evaluation of tracer binding in individual lesions, a model with the splenic radioactivity concentration assigned to represent nonspecific uptake was applied. Values derived with this method, however, did show the same specificity as the simpler standardized uptake value concept, with similar difference observed for cortical versus noncortical lesions. CONCLUSION: PET with 11C-metomidate has the potential to be an attractive method for the characterization of adrenal masses with the ability to discriminate lesions of adrenal cortical origin from noncortical lesions. (+info)
Whole-cell versus total RNA extraction for analysis of microbial community structure with 16S rRNA-targeted oligonucleotide probes in salt marsh sediments.
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rRNA-targeted oligonucleotide probes have become powerful tools for describing microbial communities, but their use in sediments remains difficult. Here we describe a simple technique involving homogenization, detergents, and dispersants that allows the quantitative extraction of cells from formalin-preserved salt marsh sediments. Resulting cell extracts are amenable to membrane blotting and hybridization protocols. Using this procedure, the efficiency of cell extraction was high (95.7% +/- 3.7% [mean +/- standard deviation]) relative to direct DAPI (4',6'-diamidino-2-phenylindole) epifluorescence cell counts for a variety of salt marsh sediments. To test the hypothesis that cells were extracted without phylogenetic bias, the relative abundance (depth distribution) of five major divisions of the gram-negative mesophilic sulfate-reducing delta proteobacteria were determined in sediments maintained in a tidal mesocosm system. A suite of six 16S rRNA-targeted oligonucleotide probes were utilized. The apparent structure of sulfate-reducing bacteria communities determined from whole-cell and RNA extracts were consistent with each other (r(2) = 0.60), indicating that the whole-cell extraction and RNA extraction hybridization approaches for describing sediment microbial communities are equally robust. However, the variability associated with both methods was high and appeared to be a result of the natural heterogeneity of sediment microbial communities and methodological artifacts. The relative distribution of sulfate-reducing bacteria was similar to that observed in natural marsh systems, providing preliminary evidence that the mesocosm systems accurately simulate native marsh systems. (+info)
Meal fatty acid uptake in human adipose tissue: technical and experimental design issues.
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The adipose tissue uptake of dietary fat has been studied using fatty acid radiotracers incorporated into a meal, followed by adipose tissue biopsies. A number of experimental design issues, including the use of isotopic tracers to measure meal fatty acid oxidation and plasma appearance of tracer, as well as the heterogeneity of adipose tissue fatty acid uptake, have been addressed. We examined these questions in a study of 24 volunteers (12 men and 12 women) who consumed a meal containing [(3)H]triolein and [(14)C]triolein. Slight differences in the purity of [(3)H]triolein vs. [(14)C]triolein were found, which could affect the apparent adipose tissue uptake of meal fatty acids. The adipose tissue triglyceride specific activity from bilateral biopsy sites agreed well, implying that a unilateral biopsy is satisfactory for measuring tracer uptake. Meal fatty acid oxidation measured using [(3)H]triolein and [(14)C]triolein was well correlated (r = 0.79, P < 0.0001). The peak tracer appearance in plasma chylomicrons occurred 1 h after the ingestion of a second, unlabeled meal. Our findings have implications for the experimental design of future meal fatty acid tracer/adipose tissue biopsy studies. (+info)
Spontaneous reversal of portal blood flow: the case for and against its occurrence in patients with cirrhosis of the liver.
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Because of its presumed serious clinical significance, we made an analysis of the evidence for and against the occurrence of spontaneous reversal of portal flow in cirrhosis of the liver. We examined the evidence obtained from manometric studies, radioactive tracer studies, radiologic studies, and actual measurements of magnitude and direction of portal blood flow. Concerning manometric studies, we introduced a physical analysis, based on first principles, which demonstrates that the occluded portal pressures cannot be used to construct a hydraulic gradient for portal flow. Similarly, we examined the weakness of the evidence derived from radioactive tracer and radiologic studies and, in the latter, the drastically opposite results reported by different investigators. Finally, we found that actual measurements of magnitude and direction of portal flow provide impressive evidence against the occurrence of spontaneous reversal of portal flow in cirrhosis. We conclude that unless new and convincing evidence is provided, it may not serve the best interests of medicine and of our patients to continue accepting spontaneous reversal of portal flow in cirrhosis as if it were a proven phenomenon. (+info)
Transgalactooligosaccharides stimulate calcium absorption in postmenopausal women.
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The aim of this study was to investigate whether a product rich in transgalactooligosaccharides (TOS, Elix'or) stimulates true Ca absorption in postmenopausal women. The study was a double-blind, randomized crossover study, consisting of two 9-d treatment periods separated by a 19-d washout period. During the treatment periods, 12 subjects drank 200 mL yogurt drink twice (at breakfast and lunch) containing either TOS (20 g/d) or the reference substance, sucrose. On d 8 of each treatment period, (44)Ca and (48)Ca were administered orally and intravenously, respectively. Before and during the 36 h after isotope administration, urine was collected and the ratios of isotopes present were measured by inductively coupled plasma mass spectrometry (ICP-MS). From the isotope enrichments, true calcium absorption was calculated. TOS increased true calcium absorption 16%, from (mean +/- SD) 20.6 +/- 7.0% during the reference treatment to 23.9 +/- 6.9% during the TOS treatment (P: = 0.04, one-sided). In conclusion, in this study in postmenopausal women, greater Ca absorption was observed after consumption of a product rich in TOS (Elix'or) compared with the reference treatment. This increase in Ca absorption was likely due solely to TOS. The increased Ca absorption was not accompanied by increased urinary Ca excretion, meaning that TOS also may indirectly increase the uptake of Ca by bones and/or inhibit bone resorption. (+info)