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At least 19 recordsLinked to original sources
PubMed1979

Polyglutaraldehyde: a new reagent for coupling proteins to microspheres and for labeling cell-surface receptions. II. Simplified labeling method by means of non-magnetic and magnetic polyglutaraldehyde microspheres.

Procedures were developed for the synthesis of a new immunoreagent in form of polyglutaraldehyde (PGL) microspheres in sizes ranging from about 50 nm to 1.5 micron. Addition of fluorochromes during synthesis yielded microspheres of high fluorescence intensity. By carrying out the polymerization of glutaraldehyde in presence of iron oxide, magnetic PGL microspheres were produced. Antibody conjugates obtained by interaction of PGL microspheres with immunoglobulins were used to label human red blood cells (RBC) and lymphocytes. A simple method for the separation of magnetically labeled human RBC from unlabeled cells was demonstrated.

Aldehydes↗
PubMed1978

The effect of ergotamine on tissue blood flow and the arteriovenous shunting of radioactive microspheres in the head.

1 The radioactive microsphere method was used to study the effects of ergotamine (5, 10 and 20 mug/kg, i.v.) on systemic and regional haemodynamic variables in chloralose-urethane anaesthetized cats. The influence of the drug was also studied on the number of 15 mum microspheres escaping entrapment in the head to emerge in the left external jugular vein.2 Ergotamine decreased the heart rate and cardiac output. Since arterial blood pressure remained unchanged, calculated total peripheral resistance increased.3 The regional distribution of cardiac output obtained with 15 mum microspheres agreed well with previous studies in cats where 25 mum spheres were used. The most pronounced difference was that in the present investigation more microspheres, apparently escaping through arteriovenous anastomoses (AVAs), were detected in the lungs than when larger spheres had been used.4 Coronary blood flow decreased, while uterine blood flow was increased by the drug. The microsphere content of the lungs, which receive the spheres not only via bronchial arteries but also via AVAs, was greatly reduced by all doses of ergotamine. Ergotamine did not influence tissue blood flow to other major organs such as the brain, kidneys, skin, liver, skeletal muscle or the gastrointestinal tract.5 In the 16 experiments, 0.46 +/- 0.05 (s.e. mean)% of the total microspheres injected (equivalent to 11.7 +/- 1.4% of microspheres detected in the left-side of the head) appeared within 2 min of microsphere injection into the left external jugular vein. The highest dose of ergotamine significantly reduced the shunting of the microspheres in the head.6 Since 15 mum microspheres are only likely to reach the lungs by passing into the venous circulation through large glomus-type AVAs, we conclude that ergotamine reduces the fraction of microspheres appearing in the lungs by causing strong vasoconstriction in the AVAs in the head.7 In conformity with the closure of head AVAs is the finding that ergotamine reduced the jugular venous Po(2) and O(2) saturation thereby increasing the A-V O(2) saturation difference.8 It is quite possible that decreased A-V shunting may be the prominent mechanism of the antimigraine action of the drug, since sudden opening of AVA's has been implicated in the pathophysiology of migraine-syndrome.

Animals↗
PubMedDate not supplied

The measurement of glomerular blood flow in the rat kidney: influence of microsphere size.

1. Radioactively labelled microspheres were used to determine glomerular blood flow in glomerular populations with distinct vascular characteristics. Two batches of microspheres (15 +/- 5.0 micrometer diameter and 7.0--10 micrometer diameter) were utilized. 2. The results show that the larger microspheres overestimate the superficial glomerular blood flow (414 +/- 61 nl/min, mean +/- s.e.m.) and underestimate the deep glomerular blood flow (98 +/- 10 nl/min), when compared with the data obtained with 7.0--10 micrometer diameter microspheres (317 +/- 30 nl/min and 209 +/- 23 nl/min, respectively). 3. The rheological artefact associated with the use of larger microspheres is confirmed by finding an uneven size distribution of microspheres lodged in the glomeruli. In each of three experiments, the mean diameter of 200 microspheres lodged in the superficial glomeruli (16.43 +/- 0.27 micrometer, 15.87 +/- 0.23 micrometer and 16.58 +/- 0.27 micrometer) was significantly greater than that found in the deep glomeruli (15.36 +/- 0.15 micrometer, 15.25 +/- 0.21 micrometer and 15.73 +/- 0.24 micrometer; P less than 0.01, less than 0.05 and less than 0.01, respectively). No such difference was detected when the 7.0--10 micrometer spheres were used. 4. Glomerular blood flow can be measured at all depths of the rat's cortex and the demonstrated rheological artefact associated with use of the larger spheres is circumvented with the use of 7.0--10 micrometer microspheres.

Animals↗
PubMedDate not supplied

Diameter of arterial microvessels trapping 8--10 micron, 15 micron and 25 micron microspheres as determined by vital microscopy of the hamster cheek pouch.

An assumption inherent in the use of microsphere methodology for measuring regional blood flow is that microspheres are removed from the circulation by impacting in arterial vessels of approximately their own diameter. We investigated the in vivo relationship between the diameter of varying size microspheres and the calibre of trapping microvessels within the hamster cheek pouch. Intracardiac injection of 8-10, 15 +/- 5, 25 +/- 5 micron carbonized microspheres with diversion of the cardiac output into the bracheocephalic trunk provided direct, in vivo visualization of the impaction sites of these various size microspheres within the cheek pouch microvasculature. Fifteen micron microspheres usually impacted at the orifice or neck of small arterioles and protruded into the lumen of the parent vessel. Eight to ten micron microspheres lodged in vessels with a mean diameter of 11.5 +/- SD 3.4 micron indicating that they usually impacted primarily in terminal arterioles.

Animals↗
PubMed1978

Quantitation of collateral and ischemic flows with microspheres and diffusible indicator.

Flow to myocardium following coronary occlusion may not originate solely from collateral channels. Some flow might be derived from overlapping coronary arteries which also perfuse tissue within the territory of the obstructed vessel prior to occlusion. Left atrial microsphere injection during perfusion of the left anterior descending (LAD) artery from a special reservoir containing microsphere-free blood and again after LAD occlusion permitted measurement of noncollateral overlap and total ischemic LAD (TIF) flows, respectively, and mathematical derivation of true collateral flow (TCF). Whereas TIF averaged 0.25 +/- 0.03 ml/min per g, TCF was 0.14 +/- 0.03 ml/min per g, only 50.6% of TIF. The remainder of the TIF represented either inadvertant inclusion of normally perfused tissue with the ischemic LAD myocardium or actual overlap of LAD and left circumflex circulations. 86RbCl was injected simultaneously with the microspheres following coronary occlusion. 86Rb and microsphere densities in the whole heart and ischemic area were closely correlated, although microsphere distribution tended to be more heterogeneous. No segment of ischemic myocardium containing 86Rb was free of microspheres. Therefore, the geometry of undeveloped collateral channels is adequate to permit passage of 15-micron particles. Absolute 86Rb flows were consistently less than microsphere flows.

Animals↗
PubMed1975

Comparison of gastric mucosal blood flow as determined by aminopyrine clearance and gamma-labeled microspheres.

Gastric mucosal blood flow was simultaneously determined by aminopyrine clearance and gamma-labeled microspheres (15 +/- 5 mu in diameter) in anesthetized dogs prepared with a chambered segment of stomach greater curvature. Paired flow measurements were made in 11 dogs (n = 28) secreting in response to intravenous histamine (1mug per kg per min), in 11 (n = 21) nonsecreting dogs given intravenous isoproterenol (0.5 or 1.0 mug per kg per min), and in 9 (n = 10) dogs given no drugs to stimulate secretion or blood flow (resting dogs). Eight additional injections were done in dogs receiving various combinations of isoproterenol and histamine. Isotonic HCl was maintained on the mucosal surface during all experiments. Regression analysis demonstrated a highly significant linear correlation between clearance and microsphere-measured flow in the histamine (P less than 0.001, r = 0.96) and isoproterenol (P less than 0.001, r = 0.78) experiments, with clearance averaging 83% of microsphere flow during histamine stimulation but only 25% during isoproterenol. The relationship between clearance and microsphere flow was not significantly different for the resting and isoproterenol experiments. Mucosal perfusion measured by microspheres was about 5 times the resting value for both histamine and isoproterenol-stimulated dogs. Perfusion calculated from aminopyrine clearance averaged 46, 38, and 90% of the microsphere value in the resting, isoproterenol, and histamine experiments, respectively. Pooled data from secreting dogs demonstrated a fairly constant ratio of microsphere-measured flow to clearance (1.25 +/- 0.06 mean +/- SEM), regardless of the secretory rate. Our results indicate that aminopyrine clearance reflects only a small fraction of mucosal blood flow in the nonsecreting stomach, even in the presence of exogenous acid.

Aminopyrine↗
PubMed1979

Aldocyanoin microspheres: partial amino acid analysis of the microparticulates formed from simple reactants under various conditions.

The work of Kenyon and Nissenbaum on aldocyanoin microspheres was repeated and extended. It was determined that the microspheres contained amino acids and that specific amino acids could be incorporated into the microspheres by adding the requisite aldehyde or ketone precursor to the model mixture. Microsphere formation was found to be dependent on the availability of oxygen. Under anaerobic conditions of synthesis, no microspheres formed in the time allotted and the amino acid composition of the macromolecular material was simple. Microparticulate material synthesized by C. Folsome using a quenched spark technique was analyzed and found to contain amino acids that had a qualitative composition similar to both a Miller-Urey discharge and the Kenyon-Nissenbaum microspheres.

Aerobiosis↗
PubMed1978

Regional blood flows measured in conscious rats by combined Fick and microsphere methods.

Regional blood flow measurements made by the radioactive microsphere technique were studied in conscious rats. A femoral arterial reference sample blood flow was measured directly, and at the same time indirectly by the combined use of direct Fick cardiac output and microsphere techniques. A significant correlation (r = .81, P less than .01) was obtained between direct and indirect blood flow values when 200--400 microspheres were trapped in the reference sample. When 100--200 microspheres were trapped, regional blood flow was 32% below true flow (P less than .01); and cardiac output, calculated by the reference sample method, was 57% greater than Fick cardiac output (P less than .01). When three consecutive Fick determinations and microsphere injections (20,000 per injection, 15 micrometer diam) were made in conscious rats, significant correlations were obtained among the first, second, and third regional blood flow measurements (r = .95, P less than .01). The results have demonstrated that cardiac output and reference blood flow can be measured with accuracy and precision in the conscious rat by the radioactive microsphere procedure.

Animals↗
PubMed1979

Albumin microspheres as carrier of an inhibitor of leukocyte elastase: potential therapeutic agent for emphysema.

Methods are described for the covalent attachment of succinoyl-Ala-Ala-Pro-ValCH2Cl, an active site-directed inhibitor of human leukocyte elastase (EC 3.4.21.11), to microspheres of human albumin. The insertion of side arms of various lengths revealed that maximum inhibition of this enzyme was obtained when the spacer arm was at least 24.3 A in length. Approximately 30 molecules of the inhibitor could be attached to each molecule of albumin. Such derivatized microspheres were capable of inhibiting approximately one mole of elastase per mole of albumin, which is comparable to the inhibitory activity of alpha 1-antitrypsin. Experiments in vivo in which rats were injected intravenously with radiolabeled microspheres to which the inhibitor had been attached showed a rapid and exclusive uptake by the lungs. About 40--50% of the injected microspheres subsequently remained in the lungs with a half-life of approximately 17 days. These derivatized microspheres thus appear to offer promise as a therapeutic agent for emphysema.

Albumins↗
PubMed1978

Comparison of microspheres and 86Rb+ as tracers of the distribution of cardiac output in rats indicates invalidity of 86Rb+-based measurements.

The technique of using gamma-labeled plastic microspheres (15 +/- 5 micrometer) to measure cardiac output (CO) and its fractional distribution (FD) to individual tissues and organs was judged by various criteria to give valid data when applied to barbital-sedated warm-acclimated or cold-acclimated (CA) white rats, which were either resting or responding calorigenically to infused noradrenaline (NA). The FD of CO to each of 16 tissues or organs of CA rats at rest or responding to NA was then estimated both with 86Rb+ and with microspheres, the two tracers being injected simultaneously. For only seven of the tissues examined in resting rats and only one in NA-infused rats was the FD of CO estimated with 86Rb+ not significantly different from that estimated with microspheres. 86Rb+ to microsphere ratios of the FD of CO to individual tissues ranged from 3.5 and 3.0 for liver and skeletal muscle, respectively, down to 0.09 and 0.07 for brown adipose tissue (BAT) and brain. Since microsphere-based estimates of blood flow to the interscapular BAT of CA rats responding to NA were corroborated by direct measurements of venous efflux from the tissue, it is unequivocal that the 86Rb+-based estimate of the fraction of CO directed to interscapular BAT was highly erroneous. When considered along with data from the literature, the present findings support a conclusion that the uptake of 86Rb+ by a tissue frequently does not provide a valid measure of the FD of CO to the tissue. Some of the factors that are likely responsible for this situation are discussed, and it is suggested that only by a fortuitous combination of circumstances does the uptake of 86Rb+ by a tissue sometimes match the FD of CO to the tissue.

Adipose Tissue, Brown↗
PubMed1977

Cardiovascular effects of radioactive microsphere suspensions and Tween 80 solutions.

The cardiovascular effects of two concentrations of Tween 80 (polyoxyethylene sorbitan mono-oleate), a surface-active agent commonly used to prevent aggregation of radionuclide-labeled microspheres, were examined in conscious dogs. Two types of adverse reactions were noted. The first (Type A) consisted of reductions in cardiac dimensions as well as hypotension and tachycardia. The second (Type B) was less severe and involved only a decrease in cardiac dimensions with no change in left ventricular systolic pressure or heart rate. A 10% dextran solution with .05 +/- .02% Tween 80 injected into the left atrium caused systemic and/or cardiac alterations in all four dogs studied. Administration of a lower concentration of Tween 80 (0.01 +/- 0.005%), which was the minimum concentration necessary to prevent aggregation of microspheres, induced adverse reactions in 6 of 41 dogs studied. Subsequent administration of this concentration of Tween 80 on the same day rarely induced adverse reactions. Thus, care must be exercised in application of microsphere techniques to organ blood flow measurements when Tween 80 is used to prevent microsphere aggregation, since this surface-active agent causes profound alterations in cardiac dynamics in concentrations normally employed in experiments involving microsphere techniques.

Animals↗
PubMed1978

Dextran as a radioactive microsphere suspending agent: severe hypotensive effect in rat.

The effects of different commercially available radioactive microsphere suspending solutions were studied on the cardiovascular hemodynamics of male, Sprague-Dawley rats. Single left ventricular injections of carbonized radioactive microspheres (15 +/- 5 micron diam) totaling 850,000 spheres, suspended in 10% dextran (mol wt, 73,000) solution with Tween, caused reductions in arterial pressure (control, 101; postinjection, 74 mmHg; P less than 0.001), with no change in heart rate. Identical injections made with isotonic saline solution plus Tween had no effect on either heart rate or arterial pressure. Independent studies were conducted to examine the effects of 1-ml injections of four suspending solutions without microspheres on the cardiovascular hemodynamics of rats. Isotonic saline had no hemodynamic effect, and isotonic saline plus Tween decreased only heart rate. Ten percent dextran soluton with Tween decreased arterial pressure, heart rate, peak left ventricular systolic pressure, and left ventricular end-diastolic pressure. Similar changes occurred when dextran solution without Tween was administered. These data demonstrate that 10% dextran solution used as a microsphere suspending agent induces a severe hypotensive response in rats. Furthermore, injections of up to 850,000 microspheres in isotonic saline solution do not alter arterial pressure in the rat.

Animals↗
PubMed1979

Shunting of microspheres across the canine coronary circulation.

Coronary shunting of 9 +/-1 micrometer and 25 +/- 5 micrometer radiolabeled microspheres was examined in anesthetized, open-chest dogs, whose left common coronary arteries were perfused at controlled pressures. Shunting was estimated from the difference in radioactivity between perfusion line and coronary sinus blood samples during selective elevations of coronary perfusion pressure (CPP), left ventricular afterload, and inspired oxygen. A linear relationship was found between coronary shunting of 9-micrometer microspheres and CPP over the range 100-200 mmHg. According to regression analysis, percent shunt flow was 4.0% at control CPP (100 mmHg) and 10.0% at CPP of 200 mmHg. No shunting of 25-micrometer microspheres occurred at any CPP. Raising afterload did not affect shunting at control CPP but attenuated the increase in shunting at elevated CPP. Changing inspired gas from room air to 100% oxygen did not influence shunting at control or elevated CPP. Raising CPP to 150 and 200 mmHg also released 2.5% and 5.9% of pretrapped 9-micrometer microspheres, respectively. This study demonstrates that vessels permitting passage of microspheres across coronary circulation are sensitive to elevated perfusion pressure.

Animals↗
PubMed1978

Diameter of afferent arterioles during autoregulation estimated from microsphere data in the dog kidney.

Afferent arteiolar diameters, relative flow distribution, and flow conductance factors are estimated by nonlinear regression analysis of the sieving effect on microspheres in different vascular structures of the dog renal cortex. The data presented are from experiments in which microspheres of 10-30 microgram were injected into the abdominal aorta during normotension and after lowering the blood pressure to the lower limit of autoregulation. Microscopic examination of the spheres trapped in the glomeruli and the renal arteries showed an increasing exclusion of microspheres greater than 15 micrometer from the afferent arterioles during normotension. This effect was most pronounced for the deeper cortical layers and can be explained mainly as geometrical exclusion of spheres from afferent arterioles. During hypotension, progressively larger microspheres entered glomeruli and afferent arterioles, presumably due to vasodilation of the vessels. There was a significant redistribution of microspheres larger than 15 micrometer from the outer to the inner cortex during hypotension without a corresponding redistribution of smaller spheres or the estimated blood flow. Approximately the same degree of dilation of afferent arterioles was observed during autoregulatory hypotension in three cortical layers.

Animals↗
PubMed1977

[Estimation of regional circulation in rats: results obtained by using 15 and 50 micron diameter microspheres and rubidium].

Radioactive microspheres, 15 or 50 micron in diameter, were used to estimate the distrubtion of cardiac output and the degree of shunting of microspheres through the systemic and pulmonary circulations in anaesthetized rats. Extraction of 15 micron spheres by the pulmonary capillaries was nearly 100% and the amounts of microspheres per gram of lung tissue were not significantly different in the various lobes of lung. After injection into the left ventricle, the proportion of microspheres shunted to the lungs was almost identical using 15 or 50 micron spheres. Similar results were observed after injection into the internal of external carotid artery. The distribution of cardiac output showed a significant difference between 15 and 50 micron spheres, the proportion of 50 micron spheres found in the stomach being higher, which suggests the existence in this organ of arteriovenous shunts larger than 15 micron. The rubidium method yielded higher fractions of cardiac output in the liver (hepatic artery), lung and skin whereas the microspheres distribution to the heart, spleen and digestive tract exceeded that of rubidium. The origins of these differences are discussed.

Animals↗
PubMed1979

Observations on the validity of using "NEN-TRAC" microspheres for measuring organ blood flow.

"NEN-TRAC" brand of radioactive microsphere, 15 micron in diameter, have recently become available and therefore organ blood flow (Q) values obtained using these have been compared with values simultaneously obtained with the well-established "TRACER" brand of microspheres. For all major tissues of the body of two conscious sheep, there was excellent agreement between Q values obtained using NEN-TRAC Ce-141 and TRACER Sr-85 in one sheep, and between Q values obtained using NEN-TRAC Ce-141 and Sn-113 and TRACER Cr-51, Sr-85 and Nb-95 in a second sheep. It is concluded that NEN-TRAC microspheres satisfy the major validation tests to which TRACER microspheres have been previously subjected, and therefore it is valid to proceed with use of the new product.

Animals↗